WO2008106797A1 - Methods and systems for wireless networks with relays - Google Patents

Abstract

Methods and systems are provided for use with wireless networks having one or more cell in which each cell includes a base station (BS), at least one relay station (RS) and at least one mobile station (MS). The at least one relay station can be used as an intermediate station for providing comm.unicat.ion between the BS and MS. Methods are provided for allocating OFDM resources for communicating between the BS, RS and/or MS. In some embodiments on the invention, the methods are consistent and/or can ba used in conjunction with existing standards such as 802.16e.

Description

Methods and Systems for Wireless Networks with Relays

Related Applications

This application claims the benefit of U.S.

Provisional Patent Application No. 60/892,574 filed on March 2, 2007, U.S. Provisional Patent Application No. 60/892,577 filed on March 2, 2007 and U.S. Provisional Patent Application No. 60/949,744 filed on July 13, 2007, which are all hereby incorporated by reference in their entirety.

Field of the Invention The invention relates to the field of wireless communications, more specifically to systems and methods for supporting Orthogonal Frequency Division Multiplexed (OFDM) communication using relays.

Background of the Invention Orthogonal frequency division multiplexing (OFDM) is a form of multiplexing that distributes data over a number of carriers that have a very precise spacing in the frequency domain. The precise spacing of the carriers provides several benefits such as high spectral efficiency, resiliency to radio frequency interference and lower multi-path distortion. Due to its beneficial properties and superior performance in multi- path fading wireless channels, OFDM has been identified as a useful technique in the area of high data-rate wireless communication, for example wireless metropolitan area networks (MAN) . Wireless MAN are networks to be implemented over an air interface for fixed, portable, and mobile broadband access systems.

In some wireless networks, a mobile station (MS) in a given cell is only served by its serving base station (BS) . One drawback of such wireless networks is that MSs near an edge of the given cell suffer performance loss due to interference from other cells in cellular networks and propagation loss in non-cellular networks which results in limited data rates and gaps in coverage of the given cell.

While soft hand off can be used in cellular networks to improve performance to some extent for MSs at the cell edge, the improved performance comes at the cost of additional system complexity and a spectrum efficiency penalty.

One way to improve the performance is to introduce a fixed relay station (RS) into wireless networks. The use of an RS may provide a) enhanced system capacity, b) enhanced data rate and cell coverage, c) reduced MS transmit power requirements and d) allow less expensive power amplification.

Summary of the Invention

According to an aspect of the invention there is provided a method for managing a transmission resource including a dedicated transmission resource portion and a non- dedicated transmission resource portion in a network including a base station and at least one relay, the method comprising: managing the dedicated transmission resource portion in at least one of a centralized manner and a distributed manner; each of the at least one relays managing the non-dedicated transmission resource portion in a distributed manner.

In some embodiments managing a transmission resource comprises at least one ofs managing transmission resources in a downlink direction from the base station to the at least one relay station; and managing transmission resources in an uplink direction from at least one relay station to the base station. In some embodiments the base station managing the dedicated transmission resource portion in a centralized manner and each of the at least one relays managing non-dedicated transmission resources in a distributed manner is in response to: a mobile station sending a request to the base station for a transmission resource assignment on a path between the mobile station and the base sbation.

In some embodiments the base station managing the dedicated transmission resource portion in a centralized manner comprises for a path between the base station and an end of path relay comprising N relays and N associated links, N>=1: assigning a maximum capacity for the transmission resource for each link in the path; and for each link in the path, assigning less than the maximum capacity for the link as the dedicated transmission resource portion.

In some embodiments the method further comprises the base station transmitting at least one of: an assignment of the dedicated transmission resource portion for a link between the base station and at least one relay one hop away from the base station along the path; an assignment of the dedicated transmission resource portion for a link between a relay that is more than one hop away from the base station along the path and at least one subordinate relay along the path.

In some embodiments the base station transmitting an assignment of the dedicated transmission resource portion comprises: the base station transmitting an indication of an amount of transmission resource to be used as the dedicated resource portion to a subordinate relay.

In some embodiments the method further comprises: the subordinate relay transmitting an indication of an amount of transmission resource and a particular location within the transmission resource to be used as the dedicated transmission resource portion to a one hop away subordinate relay.

In some embodiments the bass station transmitting an assignment of the dedicated transmission resource portion comprises: the base station transmitting an indication of an amount of transmission resource and a particular location within the transmission resource to be used as the dedicated transmission resource portion to a subordinate relay.

In some embodiments the base station managing the dedicated transmission resource portion in a centralized manner comprises for a path between the base station and an end of path relay comprising N relays and N associated links, N>=1: assigning a maximum capacity for the transmission resource for each link along the path; and for the link of a relay one hop away from the base station along the path, assigning less than the maximum capacity as the dedicated transmission resource portion.

In some embodiments the method further comprises the base station transmitting: the assignment of the dedicated resource portion for the link of the relay one hop away from the base station along the path.

In some embodiments the base station transmitting an assignment of the dedicated transmission resource portion comprises: the base station transmitting an indication of an amount of transmission resource to be used as the dedicated transmission resource portion to a subordinate relay.

In some embodiments the base station transmitting an assignment of the dedicated transmission resource port-ion comprises: the base station transmitting an indication of an amount of transmission resource and a particular location within the transmission resource to be used as the dedicated transmission resource portion to a subordinate relay.

In some embodiments the method further comprises: for a relay having a link with a subordinate relay that is more than one hop away from the base station along the path and having an assigned maximum capacity, assigning less than the maximum capacity as a dedicated transmission resource.

In some embodiments the method further comprises the relay transmitting: the assignment of the dedicated transmission resource for the relay having the link with the subordinate relay that is more than one hop away from the base station along the path.

In some embodiments the method further comprises: the relay transmitting an indication of an amount of transmission resource and a particular location within the transmission resource to be used as the dedicated transmission resource portion to the subordinate relay that is more than one hop away from the base station along the path.

In some embodiments transmitting the assignment comprises transmitting a media access control (MAC) layer information element (IE) .

In some embodiments the method further comprises: a relay along the path sending a request to the base station for a dedicated transmission resource assignment for a link between the relay sending the request and the base station.

In some embodiments the method further comprises: the base station receiving a request for a dedicated transmission resource assignment; the base station considering the request before allocating the dedicated transmission resource. In some embodiments each of the at least one relays managing the non-dedicated transmission resource portion in a distributed manner comprises: a relay along the path assigning a non-dedicated portion of the transmission resource to at least one link between the relay assigning the non-dedicated portion of the transmission resource and a subordinate relay along the path.

In some embodiments the method further comprises the relay transmitting: an assignment of the non-dedicated transmission resource portion the subordinate relay along the path.

In some embodiments the marhod further comprises: the relay transmitting an indication of at least one of: an amount: of transmission resource; and a particular location within the transmission resource to be used as the non-dedicated transmission resource portion to the subordinate relay along the path.

In some embodiments the method further comprises: a relay along the path determining for what purpose the dedicated transmission resource is used in a link to a subordinate relay.

In some embodiments a purpose for which the dedicated transmission resource is used is for a delay sensitive service flow.

In some embodiments the method further comprises when using a HARQ (hybrid automatic repeat request) retransmission scheme, performing either one of: a) transmitting a first transmission on the dedicated resource and retransmitting a portion of or all of the first transmission on an additional, dynamically assigned resource; and b) controlling a first transmission and subsequent retransmissions on the dedicated resource by including an additional dedicated control channel to transmit information regarding whether a given transmission is the first transmission or a subsequent retransmission.

In some embodiments retransmitting a portion of or all of the first transmission on an additional, dynamically assigned resource comprises: transmitting an indication of an amount of transmission resource and/or a particular location within the transmission resource to be used as a HARQ retransmission resource to a subordinate relay.

In some embodiments transmitting the indication of an amount of transmission resource and/or a particular location within the transmission resource to be used as a HARQ retransmission resource to a subordinate relay comprises transmitting a media access control (MAC) layer information element (IE) containing the indication.

According to another aspect of he invention, there is provided a method for reporting information on a dedicated resource from a relay to a superodinate relay or a base station comprising: transmitting a, type of reporting information_/ transmitting a value associated with the type of reporting information that further defines the reporting information.

In some embodiments transmitting a type of reporting information comprises transmitting an indication of at least one of the following types of information: channel quality; closed loop MIMO related feedback; uplink bandwidth request; flow control; uplink HARQ control; and fast base station selection.

In some embodiments transmitting the type of reporting information comprises transmitting a first number of bits used to identify the type; and transmitting the value associated with the type comprises transmitting a second number of bits used to identify the value. In some embodiments the first number of bits is 3 and the second number of bits is either 3 or 6.

According to yet another aspect of the invention, there is provided a method for requesting a dedicated channel transmission resource for a link between a base station and a relay in an uplink direction from the relay to the base station or for a link between a relay and a superordinate relay in an uplink direction from the relay to the superordinate relay, the method comprising: sending a message requesting a dedicated channel transmission resource; receiving an assignment of the dedicated channel transmission resource.

In some embodiments the relay sending a message comprises: sanding the message in the form of a media access control (MAC) layer header.

In some embodiments receiving an assignment comprises: receiving an assignment in the form of a media access control (MAC) layer information element (IE) .

In some embodiments a message having substantially the same format as the message used for requesting the dedicated channel transmission resource is used for each of: acknowledging the assignment of the dedicated channel transmission resource; and sending a HARQ retransmission request.

In some embodiments sending the message indicating a request for the dedicated channel transmission resource comprises: sending a request type that indicates that che request for the transmission resource is one of incremental, aggregate, or transmission rate based.

According to still a further aspect of the invention, there is provided a method for requesting a dedicated channel transmission resource for a link between a base station and a relay in an uplink direction from the relay to the base station or for a link between a relay and a superordinate relay in an uplink direction from the relay to the superordinate relay, the method comprising: receiving a message indicating a request for a dedicated channel transmission resource; determining an allocation for the dedicated channel transmission resource based at least in part on the message; sending an assignment of the dedicated channel transmission resource.

In some embodiments receiving a message comprises: receiving the message in the form of a media access control (MAC) layer header.

In some embodiments sending an assignment comprises: sending an assignment in the form of a, media access control (MAC) layer information element (IS) .

In some embodiments sending an assignment of the dedicated channel transmission resource comprises: in a centralized management scheme, the base station sending an assignment of the dedicated channel transmission resource to all subordinate relays; and in a distributed management scheme, the base acation sending an assignment of the dedicated channel transmission resource to relays one hop away from the base station and the superordinate relay sending an assignment of the dedicated channel transmission resource to relays one hop away from the superordinate relay.

In some embodiments at least one of size of an allocated dedicated channel transmission resource and allocation interval of an allocated dedicated channel transmission resource can be increased or decreased based on at least one of traffic load and channel conditions. ■ In some embodiments the traffic load and/or channel conditions are calculated at least one of: periodically; and in response to specific events.

Other aspects of the invention include a base station relay, and/or mobile station each adapted to perform methods described above.

Other aspects and features of the present invenbion will become apparent to those ordinarily skilled in the art upon review of the following description of specific embodiments of the invention in conjunction with the accompanying figures.

Brief Description of the Drawings

Embodiments of the invention will now be described with reference to the attached drawings in which:

Figure 1 is a block diagram of an example of a network including a base station, relay stations and mobile stations,-

Figure 2 is a flow chart for a method of management of transmission resources according to an embodiment of the invention;

Figure 3 is a flow chart of another method of management of transmission resources according to an embodiment of the invention;

Figure 4A is a block diagram of another example of a network including a base station, relay stations and mobile stations; Figure 43 is a schematic diagram illustrating a transmission resource allocated to links of the network of Figure 4A;

Figure 5A is a block diagram of another example of a network including a base station, relay stations and mobile stations;

Figure 5B is a schematic diagram illustrating a transmission resource allocated to links of the network of Figure 5A before and after a request for additional transmission resource is requested for a service flow;

Figure 6A is a block diagram of an example of a network including a serving base station, a target base station, relay stations and a moving relay station being handed off from the serving base station to the target base station;

Figure 6B is a schematic diagram illustrating a transmission resource allocated to links of the network of Figure 6A before and after a handoff occurs;

Figure 7 is a flow chart for a method of requesting and allocating a dedicated transmission resource according to an embodiment of the invention;

Figure 8 is a block diagram of a cellular communication system;

Figure 9 is a block diagram of an example base station that might be used to implement some embodiments of the present invention;

Figure 10 is a block diagram of an example wireless terminal that might be used to implement some embodiments of the present invention; Figure 11 is a block diagram of a logical breakdown of an example OFDM transmitter architecture that might be used to implement some embodiments of the present invention; and

Figure 12 is a block diagram of a logical breakdown of an example OFDM receiver architecture that might be used to implement some embodiments of the present invention.

Detailed Description of the Embodiments of the Invention

In accordance with embodiments of the invention, various physical layer designs and procedures are provided for enabling relay based communications that may find applications in an IEEE 802.16 based network. The concepts described herein are not, however, limited in this regard and may be applicable to any OFDM based systems, such as 3GPP and 3GPP2 evolutions.

Figure 1 shows an example of a wireless system, for example an OFDM network: that includes relays. Shown is a base station (BS) 130 that is in communication with one or more mobile stations (MS), only one shown MS-I 132, and one or more first tier relay stations (RS), only one shown RS-I 138. Some of the first tier (one hop away from BS) relay stations are in communication with one or more second tier (two hops away from BS) relay stations. RS and MS the same number of hops away from the BS are said to be in the same tier. In the illustrated example RS-I 138 is in communication over a communication link with second tier RS-2 140. Each relay station can serve one or more mobile stations. For example,

RS-I 138 is in communication over a communication link with MS- 2 134, and RS-2 140 is in communication over a communication link with MS-3 136. in the particular example, there is a two- tier relay structure, such that there is a maximum of three hops to reach a mobile station. Larger numbers of hops are contemplated. Furthermore, the specific network of Figure 1 is to be considered only an example. More generally, an arbitrary arrangement of base stations, relay stations, and mobile stations is contemplated. The mobile stations will change over time due to their mobility. Some embodiments support only fixed relays; others support mobile relays, while further embodiments support both fixed and mobile relays.

For a network topology utilizing relays, traffic flow is not necessarily evenly distributed on all links. Usually a first hop is a bottleneck for traffic flow. Ideally, traffic flow should be managed at each relay so that the input data rate and output data rate are substantially equal . A fully centralized resource management scheme,, in which the base station handles all aspects of resource management, can handle the above, but incurs significant delay, overhead and multi-hop relay base station (MR-BS) complexity. A fully distributed resource management scheme, in which resource management: tasks are distributed amongst the base station and relays may cause significant data dropping due to the lack of a global view.

Described herein are embodiments of an inventive scheme for combining aspects of centralized and distributed resource management. For example, a method for managing transmission resources including a dedicated transmission resource portion and a non-dedicated transmission resource portion in a system having a base station and at least one relay station in which the base station the base station manages the dedicated transmission resource portion in a centralized manner and/or a. distributed manner and each of che at least one relays manages the non-dedicated transmission resource portion in a distributed manner.

In the inventive resource management scheme, be it centralized or distributed, management of transmission resource allocation may be performed for one or both of uplink (UL) and downlink (DL) . UL is transmitting in a direction from a mobile station or relay station to a superordinate station, a superordinate station being defined as a relay one or more hops closer to the base station, or the base station itself. DL is transmitting in a direction from a base station or relay to a subordinate station, a subordinate relay being defined as a relay in a tier one hop further away from the base station than a relay of a given tier. A further task in the management of transmission resource allocation may include dedicating a portion of a transmission resource to a particular type of service .

Embodiments of the present invention include methods fcr a base station to dedicate transmission resources for at least one relay one hop away, and ir. some cases for relays one or more subsequent hops away. In addition, transmission resources that are not dedicated, may be shared amongst subordinate relays.

Embodiments of the inventive resource management, scheme may result in one or more of: a reduction in delay for certain service flows, a reduction in the buffer size of an RS node, a reduction in the packet drop rate, and a reduction in the amount of signalling overhead.

In some embodiments, allocating a dedicated transmission resource involves three steps: 1) determining a maximum allowed amount of transmisβion resource on each link, 2) assigning a dedicated resource that is at least a portion of the maximum allowed amount of the transmission resource on each link; and 3) sharing the portion of the maximum allowed amount of the transmission resource on each link that is not assigned as a dedicated resource to one or more relays or mobile stations one hop further away in the direction of a greater number of hops away. 1-) Determining a Maximum Allowed Amount of Transmission Resource on each Link

Λ transmission resource available to a relay is divided amongst the links between the relay and each of the one hop away subordinate relays being served by the relay. This provides a maximum amount of the transmission resource for each link, referred to hereafter as an R-link resource cap. The division amongst the links is implementation specific and as such the transmission resource can be divided amongst the subordinate relays in any desired manner. When allocating the transmission resource, an aggregate of the R-link resource cap allocated to each subordinate relay/mobile station being served by a relay/base station is not to exceed the R-link resource cap allocated to the serving relay/base station.

Tn a centralized management scheme, the base station performs this task for each relay in each tier.

In a distributed management scheme, the base station performs this task for the relays one hop away from the base station and the relays on each tier perform a similar task for subordinate relays one hop away.

2) Assigning a. Dedicated Resource

For each link, an amount of the transmission resource less than the R-link resource cap for that link is assigned as a dedicated UL transmission resource (UL DCH) to the link for a given service. In some embodiments, the given service is a delay sensitive service, one particular example of which is voice.

In a centralized management scheme, the base station manages the R-link resource cap for each of the links of each tier and assigns the dedicated resource by sending a •transmission resource allocation message to the RSs one or more hops away,

In a distributed management scheme, the base station manages the R-link resource cap for each of the links between the base station and relays one hop away. Relays on each tier perform a similar task for subordinate relays one hop further away.

In some embodiments, the dedicated resource allocation may include periodic granting of UL transmission resource and polling from the relay to subordinate relays one or more hops further away.

3) Sharing of Non-Dedicated Resource

Once dedicated transmission resources are allocated, in either a centralized or distributed manner, relays on each tier may perform resource management for non-dedicated resources of the transmission resource of a given link on a per-frame basis for each of its one hop subordinate relays. In some embodiments, the resource management performed by the relays enables dynamic and/or short-term allocation of the transmission resources. The non-dedicared portion of the transmission resource of the given link, i.e. the difference between the maximum amount of the transmission resource and the R-link resource cap of the given link, is shared among one or more of the one hop away subordinate relays being served by the given relay.

In some embodiments, a relay along the path assigns a non-dedicated portion of the transmission resource to ar least one link between the relay assigning the non-dedicated portion of the transmission resource and a subordinate relay along the path. The relay transmits the assignment of the non-dedicaced transmission resource portion the subordinate relay along the path. In some embodiments, the relay transmits an indication of an amount of transmission resource and/or a particular location within che transmission resource to be used as the non- dedicated transmission resource portion to the subordinate relay along the path.

In some embodiments, a relay along the path determines for what purpose the dedicated transmission resource is used in a link to a subordinate relay. For example, the dedicated transmission resource may be used for a delay sensitive service flow. The usage of the dedicated transmission resource is implementation specific and may be allocated by the relay for any desired type of service. In some embodiments, the determination of the purpose of use of the dedicated transmission resource occurring in a distributed manner by the relays is performed in conjunction with the allocation of the size and/or location of the dedicated resource, which is performed in either a centralized or distributed manner.

The assignment to each link is restricted by the R- link resource cap for that link. The superodinate relay controls that the R-link resource cap for that link is not exceeded.

The dedicated traffic resource is allocated or updated in response to any number of events. A. list of events includes, but is not limited to, when a service flow is granted, closed or handed off, upon entry into the network of a new relay, or when a new mobile station enters a network via an access relay.

Dedicated traffic resource assignment

The second step described above, "Assigning a Dedicated Resource" can be implemented in a number of ways. In some implementations, a base station directly sends the dedicated traffic channel assignment to the impacted relay. In some embodiments, the assignment is sent using an information elements (IE) format, an example of which will be described in further detail below. In some embodiments, the assignment is sent using a unicast message. These are particular examples of how the resource assignment mat be sent, however, other implementation specific implementations are contemplated. This is considered to be a centralized resource management scheme. Such a process may, for example, be triggered by a mobile station initially accessing a network. As part of the access process the base station allocates dedicated resources in appropriate network links to accommodate the mobile station.

In some embodiments, the base station transmits an assignment of a dedicated transmission resource portion. In some embodiments, the base station transmits an indication of an amount of transmission resource and/or a particular location within the transmission resource to be used as a dedicated transmission resource portion to a subordinate relay. In some implementations, a base station instructs one hop away subordinate relays about the dedicated resource allocation. Each relay then assigns resources to subordinate relays one hop away. The subordinate relays one hop away perform the same function for subordinate relays a further hop away, and so on. This is a distributed resource management scheme. Such a process may, for example, be triggered by a mobile station initially accessing a network. As part of the access process the base station allocates dedicated resources to a relay one hop away and subsequent relays along a path to the mobile station allocate dedicated resources to accommodate the mobile station. In some implementations, a relay proposes a preferred dedicated resource assignment to the base station to suit the needs of the relay. The base station still makes the ultimate decision regarding the dedicated resource allocation, but may rake into consideration the relay's proposal. The base station responds to the relay by providing the dedicated resource allocation. In such an implementation, sending the allocation information to the relay in response to the proposed request can be performed in either a centralized or distributed manner as discussed above.

In some embodiments, the base station transmits an indication of an amount of transmission resource to be used as the dedicated resource to a subordinate relay. In some embodiments, the subordinate relay transmits an indication of an amount of transmission resource and/or a particular location within the transmission resource to be used as the dedicated transmission resource portion to a one hop away subordinate relay.

A method for implementing of a management scheme according to embodiments of the invention, in particular based on a centralized scheme for assigning dedicated transmission resources, will now be described with reference to Figure 2. A first step 2-1 involves a base station assigning a maximum capacity for the transmission resource for each link in the path. A second step 2-2 involves, foe each link in the path, the base station assigning less than the maximum capacity for the link as a dedicated transmission resource. A third step 2-3 involves the base station transmitting an assignment of the dedicated transmission resource for a link between the base station and at least one relay one hop away from the base station along the path. A fourth step 2-4 involves the base station transmitting an assignment of the dedicated transmission resource for a link between a relay that is more than one hop away from the base station along the path and at least one subordinate relay along the path. A fifth step 2-5 involves a relay along the path assigning a non-dedicated portion of the transmission resource to at least one link between the relay and a subordinate relay along the path.

A method for implementing of a management scheme according to embodiments of rhe invention, in particular based on a distributed scheme for assigning dedicated transmission resources, will now be described with reference to Figure 3. A first step 3-1 involves the base station assigning a maximum capacity for the transmission resource for each link along the path. A second step 3-2 involves for the link, of a relay one hop away from the base station along the path, the base station assigning less than the maximum capacity as a dedicated transmission resource. A third step 3-3 involves the base station transmitting the assignment of the dedicated resource for the link of the relay one hop away from the base station along the path. A fourth step 3-4 involves for a relay having a link with a subordinate relay that is more than one hop away from the base station along the path and having an assigned maximum capacity, the relay assigning less than the maximum capacity as a dedicated transmission resource. A fifth step 3-5 involves the relay transmitting the assignment of the dedicated transmission resource for the relay having the link with the subordinate relay that is more than one hop away from the base station along the path. Steps 3-4 and 3-5 may be repeated at each tier of the network such that all the links in a path between the base station and the last relay in the path are updated accordingly. A sixth step 3-6 involves a relay along the path assigning a non-dedicated portion of the transmission resource to at least one link between the relay and a subordinate relay along the path. In some embodiments, the base .station managing a dedicated transmission resource portion of the transmission resource in a centralized manner and each of the at least one relays managing non-dedicated transmission resources in a distributed manner is in response to a mobile station sending a request to the base station for a transmission resource assignment on a path between the mobile station and the base station.

While the above examples are described as updating the dedicated transmission resource of a particular path, updating multiple paths simultaneously is also contemplated.

An illustrative example of a management scheme according to embodiments of the invention will now be described with reference to Figures 4A and 4B, Figure 4A includes an example of a portion of a network similar to Figure 1, but with a greater number of relays. A multi-hop relay base 3tation MR- BS 210 is shown in communication with relays Rl 220, R2 221 and R3 222, that are one hop away from MR-BS 210. Rl 220 is in communication with RIi 230 and R12 231. RlI 230 and R12 231 are in communication with mobile stations Ml 240 and M2 241, respectively. R2 is in communication with R21 232. R21 232 is in communication with R3 242. R3 is in communication with R31 233. R31 233 is in communication with RA 243 and R5 244.

Figure 4B illustrates the transmission resources allocated for DL signalling between MR-BS 210 and the relays one hop away Rl 220, R2 221, R3 222 from MR-BS 210 and between the relays one hop away Rl 220, R2 221, R3 222 from MR-BS 210 and the relays two hops away RIl 230, R12 231, R21 232, R31 233 from MR-BS 210, as columns connecting the blocks representing the base station and relays. Column 211 between MR-BS 210 and Rl 220 represents an entire resource allocated for DL signalling between these two nodes. The shaded portion of column 211, Indicated at 212, represents a portion of the resource dedicated for at least one particular type of service. The unshaded portion of column 211, indicated at 213, represents a portion of the resource that is not dedicated and is available for other types of services. Column 221 between R1 220 and R11 230 represents an entire resource allocated for DL signalling between these two nodes. Column 224 between R1 220 and R12 231 represents the entire resource allocated for DL signalling between these two nodes. In the example of Figure 4B, the dedicated resource, column 212, is split into equal portions and allocated as a dedicated resource 222 between R1 220 and R11 230 and as a dedicated resource 225 between Rl 220 and R12 231. The non-dedicated resource 213 is split into equal portions and allocated as non-dedicated resource 223 between R1 220 and R11 230 and as non-dedicated resource 226 between R1 220 and R12 231, respectively. In Figure 4B, the dedicated resource 212 and the non-dedicated resource 213 are equally divided for the links between R1 220 and RlI 230 and between R1 220 and R12 230, however the allocation of the dedicated resource portion and the non-dedicated resource portion is implementation specific and can be allocated in any manner that reflects the needs of the links involved. Similar allocations of resources are illustrated for tile links between NR-BS 210 and R2 221, between R2 221 and R21 232, between MR-BS 210 and R3 222, and between R3 222 and R31 233.

The example above is described with reference to DL signalling, however, it is to be understood that the same concept applies to UL signalling as well.

An example of how a delay sensitive service flow associated with a mobile station is allocated a dedicated resource channel will now be described with reference to Figures 5A and 5B. Figure 5A(i) illustrates a portion of a network representing a signal path between MR-BS 310 and a mobile station MS 340, via a first relay RSl 320 and a second relay RS2 330 , prior to MS 340 requesting a dedicated resource for ^"Che delay sensitive service flow. Column 312 between MR-BS 310 and RSl 320 represents an entire resource allocated for UL signalling between these two nodes. The shaded portion of column 312, indicated as 313, represents a portion of the resource for existing dedicated resources. The unshaded portion of column 312, indicated as 314, represents a non-dedicated resource available for other types of services. Column 322 between RSl 320 and RS2 330 represents an entire resource allocated for UL signalling between these two nodes. The shaded portion of column 322, indicated as 323, represents a portion of the resource for existing dedicated resources. The unshaded portion of column 322, indicated as 324, represents a non- dedicated resource available for other types of services.

Figure 5B is a signal flow diagram that illustrates signal flows between the nodes in the network, A first signal flow 350 is a request from MS 340 to MR-BS 310 to add a delay sensitive flow. A second signal flow 355 is a message from MR- BS 310 to RSl 320 that informs R51 320 of an increase to the currently allotted dedicated resource between MR-BS 310 and RSl 320 by a specified amount to accommodate the delay sensitive flow requested by MS 340. A third signal flow 360 is a message from MR-BS 310 to instruct RSl 320 to update the currently allotted dedicated resource between MSl 320 and RS2 330. A fourth signal flow 365 is a message from RSl 320 to RS2 330 to inform RS2 330 of an increase in the currently allotted dedicated resource from RSl 320 to RS2 330 by a specified amount to accommodate the dedicated resource requested by MS 340. With an increase in size of the dedicated resource channel along a signal path between MS 340 and MR-BS 310, UL signalling between MS 340 and MR-BS 310 can be accommodated. As described above, the non-dedicated transmission resources can be allocated by the relays. For example, if an additional subordinate relay RS3 was in communication with RSl 320, RSl may divide up the non-dedicated resource 314 for use by RS2 330 and RS3, and send signalling messages to RS2 330 and RS3 as to the amount and/or location of the non-dedicated transmission resource each relay is allocated.

Figure 5A(ii) illustrates the same portion of the network as Figure 5A(D after MS 340 has been granted a dedicated resource for the delay sensitive service flow. In particular_/ it can be seen that dedicated resource channel 315 between MR-BS 310 and RSl 320 has increased in size in response to signalling message 355 from MR-BS 310 to RSl 320 and dedicated resource channel 325 between RSl 320 and RS2 330 has increased in size in response to signalling message 360 from RS12 320 to RS2 330.

The example above is described with reference to UL signalling, however, it is to be understood that the same concept applies to DL signalling as well.

An example of how a delay sensitive service flow for a relay station moving from a first cell being served by a serving base station to a second cell being served by a target base station is allocated a dedicated resource channel will now be described with reference to Figures 6A and 6B. Figure 6A(i) illustrates a portion of a network representing a signal path between a serving MR-BS 410 and a mobile relay station MRS 420 in a first cell and a portion of a network representing a signal path between a target MR-BS 430 and a relay station RS2 450, via relay RSl 440, prior to a handoff of MSR 420 from serving MR-BS 410 to target MR-BS 430. Column 412 between serving MR-BS 410 and MRS 420 represents an entire resource allocated for UL signalling between these two nodes, including shaded portion 413 representing a portion of the resource dedicated for particular services. Column 432 between target MR-BS 430 and RSl 440 represents an entire resource allocated for UL signalling between these two nodes, including shaded portion 433 representing a portion of the resource dedicated for particular services. Column 442 between RSl 440 and RS2 450 represents an entire resource allocated for UL signalling between these two nodes, including shaded portion 443 representing a portion of the resource dedicated for particular services.

Figure 6β is a signal flow diagram that illustrates signal flows between the nodes. A first signal flow 460 represents signalling involved for handoff of MRS 420 from serving MR-BS 410 to target MR-BS 430. A second signal flow 455 is a message sent from target MR-BS 430 to RSl 440 that informs RSl 440 of an increase to the currently allotted dedicated resource between target MR-BS 430 and RSl 440 by a specified amount to accommodate a dedicated resource used by MRS 420. A third signal flow 470 is a message from target MR-BS 430 to RSl 440 to inform RS2 450 of an increase in the currently allotted dedicated resource from RSl 440 to RS2 450 by a specified amount to accommodate dedicated resource used by MRS 420. A fourth signal flow 475 is a message from RSl 440 to RS2 450 to inform RS2 450 of an increase in the currently allotted dedicated resource from RSl 440 to RS2 450 by a specified amount to accommodate dedicated resource used by MRS 420. With an increase in size of the dedicated resource channel along the signal path between target MR-BS 430 and MRS 420 UL signalling between MRS 420 and target MR-BS 430 can be accommodated.

Figure 6A(ii) illustrates the same portions of the networks as Figure 6A(i) after MRS 420 has completed handoff from serving MR-BS 410 to target MR-BS 430 and MRS 420 has been granted a UL dedicated resource. In particular, it can be seen that dedicated resource 435 between target MR-BS 430 and RSl 440 has increased in response to the signalling message 465 and dedicated resource 445 between RSl 440 and RS2 450 has increased in response to the signalling message 475 from RSl 440 to RS2 450.

The example above is described with reference to UL signalling, however, it is to be understood that the same concept applies to DL signalling as well.

Sending messages from the MR-BS to subordinate relays or relays to subordinate relays can be performed in many different ways. Some of these ways will be discussed in further detail below. A particular example is a UL DCH assignment IE.

Uplink Dedicated Channel (UL DCH) allocation

The following are descriptions of how UL transmission resource assignments may be made in a distributed management scheme and in a centralized management scheme.

Distributed Management Scheme

Following network entry and initialization, a relay is assigned a dedicated relay uplink channel (RS UL DCH) by a superordinate station, be that a base station or a superordinate relay, depending on where the relay accesses the network, if for some reason the relay is not allocated a RS UL DCH, it may request one. In some embodiments the superordinate station transmits the assignment in the form of an RS UL DCH assignment information element (IE) in an R-MAP message and the assigned transmission resource is available to the relay starting in a next frame after being received. The R-MAP message is a message that defines the usage of downlink and uplink intervals on the relay link. - 2? -

The size of the dedicated RS UL DCH is large enough for management messages to be sent by the relay. The size of the dedicated RS LJL DCH and/or the allocation interval of the dedicated RS UL DCH can be increased or decreased based on traffic load and/or channel conditions. The traffic load may be calculated periodically and/or in response to specific events.

When a mobile station being served by a relay adjusts its service flow requirements, it impacts the bandwidth requirements on all dedicated RS UL DCHs in links along the path to the base station. The service flow requirements are communicated to the base station via a control message. In response, the base station may adjust the dedicated RS UL DCH of a relay one hop away from the base station along the path between the base station and the mobile station. In some embodiments, the base station sends a new RS UL DCH assignment using a RS UL DCH assignment IE. In some embodiments, the RS UL DCH assignment IE includes RS UL DCH size adjustments and a connection identifier (CID) of the service flow between the base station and mobile station of the updated service flow. Each relay along the path then determines whether it needs to adjust the size of the RS UL DCH for the next hop along the path to the mobile station, for example from relay to next hop relay or relay to mobile station.

In some embodiments, any. and all dedicated channel resources are allocated before non-dedicated UL resources are allocated.

Centralized Management Scheme

In a centralized management scheme, the operation is similar to the distributed management scheme, except that the bass station is responsible for assigning the dedicate uplink channel for each hop along the path, instead of only the first hop along the path and allowing the relays on each subsequent hop to allocate the UL DCH.

In some embodiments the base station transmits the assignment in the form of an RS UL DCH assignment information element (IE) in an R-MAP message and the assigned transmission resource is available to the relay starting in a next frame after being received.

The Size of the dedicated UL DCH is large enough for management messages to be sent by the relay. The size of the dedicated RS UL DCH and/or the allocation interval of the dedicated RS UL DCH can be increased or decreased based or. traffic load and/or channel conditions. For example, with respect to the channel conditions, quality of the channel over time may improve or deteriorate. As a result, each subchannel may carry a greater or leaser number of bits, respectively. Hence, adjustment to the total number of allocated subchannels and/or allocation interval may be performed to maintain the same throughput. The traffic load and/or channel conditions may be calculated periodically and/or in response to specific events .

When a mobile station adjusts its service flow requirements, it impacts the bandwidth requirements on all dedicated relay uplink channels along the path to the base station. The service flow requirements are communicated to the base station via a control mesgage. In response, the base station may adjust the dedicated RS UL DCH cf each relay along the path between the base station and the mobile station. In some embodiments, the base station sends a new RS UL DCH assignment using a RS UL DCH assignment IE.

In some embodiments, any and all dedicated channel resources are allocated before non-dedicated UL resources are allocated. A method will now be described for the request and allocation of a UL dedicated channel with reference to Figure 7. A first step 7-X involves a relay sanding a message requesting a dedicated channel transmission resource. A second step 7-2 involves a base station receiving a message indicating a request for a dedicated channel transmission resource. A third step 7-3 involves the base station determining an allocation for the dedicated channel transmission resource based at least in part on the message. A fourth step 7-4 involves the base station sending an assignment of the dedicated channel transmission resource. A fifth step 7-5 involves the relay receiving an assignment of the dedicated channel transmission resource.

In step 7-1, the relay may send the message in the form of a media access control (MAC) layer header, in step 7-4 the base station may send the assignment of the dedicated channel transmission resource in the form of a media access control (MAC) layer information element (IE) . If the relay requesting the dedicated channel is one or more hops away from the base station, the IE is forwarded via one or more superordinate relays to the relay making the request .

HARQ operation on dedicated traffic resource

Using HARQ transmissions allows more than one transmission of a packet or portions of a packet to ensure that a receiver properly receives the packet. Embodiments of the present invention enable additional transmission resources to be allocated for HARQ retransmissions as necessary.

The HARQ used on the RS UL DCH is a negative acknowledgement (NAK) - based HARQ and a hop-by-hop HARQ, which means that is the packet is not forwarded onto a relay one hop away until the entire message has been received and acknowledged at a relay receiving the message. In some embodiments, a RS UL DCH assignment IE is configured for use with in HARQ operation on the RS UL DCH.

The dedicated resource is always used for a first transmission. In some embodiments, sequential retransmissions are transmitted on additional dynamically assigned resources without a specific request for additional bandwidth from the node transmitting the sequential retransmissions. For example, an access relay that is providing service to a mobile station or a sυperordinate relay that is providing service to a relay, assigns an appropriate transmission resource if a negative acknowledgement (NAK) is issued by the access relay, or the superordinace relay, in response to the packet not being properly received.

In some embodiments, the dedicated traffic resource utilization is fully controlled by the relay that is sending rhe retransmissions. In addition to transmitting a first or subsequent transmission, the relay utilizes an assigned dedicated control channel to indicate to the superordmate or base station, if the transmission is a first or subsequent retransmission.

Packets from multiple MSs/RSs are multiplexed and transmitted through the RS UL DCH on one or more resource blocks. Each DCH resource block can be used for transmitting a single HARQ burst at a time. For allocation of a new DCH resource block a number of DCH HARQ channel identifiers (ACID) are also assigned. Implicit sequential cycling of DCH ACID is used for each occurrence of the periodically assigned resource. The first transmission after enabling HARQ is always HARQ channel 0, therefore the DCH ACID is 0. The DCH ACID is incremented by 1 for each periodic transmission and reset to 0 when a maximum DCH ACID number is reached. In some embodiments, sequential retransmissions are transmitted using an additional resource to that of the existing dedicated resources on RS UL DCH. In some embodiments, the additional resource is allocated in an information element sent by a superordinate relay or the base station. When using the dedicated resource, the retransmission is sent using the same HARQ channel and is sent on the next occurrence of the same HARQ channel after the NAK signal. Thus, the dedicated resource allocation may minimize signalling overhead for the retransmissions. When using the additional resource; a one time additional resource is allocated to the HARQ channel that requires transmission. In such a case, the number of the DCH ACID shall be large enough to allow the maximum number of retransmission attempts before the DCH ACID wraps around to a value equal to the starting value.

In some embodiments, for example in the case of a centralized resource management schema, the intermediate RS may also generate a RS UL DCH header with a HARQ retransmission request, so that the base station can allocate resources for the retransmission.

Included below is an example of a format of a UL DCH assignment IE for use in relation to allocating the OL DCH.

RS_UL_DCH assignment IE format

The "HARQ type" field in the IE described above indicates that the assignment may be one of four types, in particular, Disabled (no HARQ) , HARQ Chase, HARQ CTC IR, or HARQ CC IR. Subsequent fields of the IE indicate information relevant to these assignments.

The "Assignment type" field in the IE described above indicates that the assignment may be one of four types, in particular, an incremental assignment (add the specified resource to UL DCH) , an aggregate assignment (an aggregate assignment with no resource indicates all UL DCH removal), a removal of an assignment (remove the specified resource from UL DCH) or Tx profile and settings assignment:. Subsequent fields of the IE indicate how these assignments may be made.

This is a specific example of a UL DCH assignment IE and is not intended to limit the scope of the invention. In some embodiments, the IE may not include all of the features included above and/or may include additional features not specifically disclosed herein. More generally, the number of bits in each field, the overall size of the IE and the functions/content of the IE are implementation specific.

Included below is an example of a format of a UL DCH HARQ retransmit IE for use in relation to allocating the UL DCH.

RS UL DCH HARQ RETX IE format

The "HARQ Control" filed indicated whether the HARQ control is asynchronous or synchronous. The "Retransmission Type" field indicates that the retransmission type may be one of two types, in particular, that HARQ retransmission is to occur in an allocated dedicated UL_DCH or that HARQ retransmission is to occur in a resource assigned in this IE. If the latter type is selected, subsequent fields of the IE indicate wherein the IE these assignments may be made.

This is a specific example of a UL OCH HARQ retransmit IE and is not intended to limit the scope of the invention. In some embodiments, the IE may not include all of the features included above and/or may include additional features not specifically disclosed herein. More generally, the number of bits in each field, the overall size of the IE and the functions/content of the IE are implementation specific.

Relay uplink dedicated channel (RS UL DCH) signalling header

In some embodiments, the relay requests a dedicated uplink transmission resource for signalling and data transmissions instead of an explicit BW request and allocation for each transmission. The allocated dedicated uplink channel is implemented by the relay after receiving a resource allocation message. In some embodiments, the resource allocation message as received as an RS UL DCH assignment IE. A3 the resource assignment is a periodic allocation of uplink bandwidth, no subsequent periodic UL-MAP IE is needed in a UL- MAP message or R-MAP message for allocating UL bandwidth.

In some embodiments, for a rate based UL DCH request, a relay specifies an average required data rate without specifying an allocation frequency. The base station or one hop away superordinate relay determines a specific BW size and frequency configuration in response tα the rate based request from the relay.

In some embodiments, the relay requests a dedicated uplink resource by specifying the dedicated channel request through a signalling header. The relay confirms the successful reception of the resource allocation by sending a DCH assignment acknowledgement.

In some embodiments, the request is transmitted by the relay in the format of a media access control (MAC) layer header.

In some embodiments, the MAC layer header may also be used to acknowledge the DCH assignment and be used for transmitting a HARQ retransmission request.

Included below is a particular example of a format of a signalling header for use in relation to requesting UL DCH, acknowledging receipt of allocation of the UL DCH and requesting HARQ retransmissions.

RS uX_DCH signalling header

This is a specific example of a signalling header and s not intended to milit the scope of the invention. In some embodiments, the header may not include the features of acknowledging receipt of allocation of the UL DCH and/or requesting HARQ retransmissions ar.d/or may include additional features not specifically disclosed herein. More generally, the number of bits in aach field, the overall size of the header and the functions/content in the header are implementation specific.

In some embodiments of the present invention there is provided a Relay Station Dedicated Control Block (RS DCB) that may be used for BW request. As such the RS DBC is another manner in which a relay may request a dedicated channel .

More generally, the RS DCB enables a relay to report information either regularly required or that is urgently needed by superordinate relays, Other types of information that may be included in the RS DBC besides bandwidth request information include, but are not limited to, channel quality information, close loop MIMO related feedback information, Quality of service (QoS) and resource information, up link (UL) HARQ control information (if an UL dedicated traffic resource is also allocated) , flow control information, and fast base station selection (FBSS) information.

In some embodiments the RS DBC is 9 bits long. In some embodiments the RS Dae is 6 bits long. The RS DCB is implementation specific, and as such may have a length other than 6 or 9 bits.

The RS DCB shall include type identity (TID) information and corresponding value information. The TID information is included in a Type field. In some embodiments, the type field is 3 bits long enabling up to 8 different types. In some embodiments, the corresponding value information is .included in a Value fiald. In some embodiments, the type field is 3 bits long enabling up to θ different types. In some embodiments, the type field is 6 bits long enabling up to 64 different types.

The following is a particular design example for a RS DCB chat is 9 bits in length, 3 bits for a type field and 6 bits for a value field.

The following is a particular design example for a RS DCB that is 6 bits in length, 3 bits for a type field and 3 bits for a value field.

The following is a particular design example for encoding a RS DCB that is 6 bits in length.

The encoding values described above are for a particular example, but more generally, the encoding values are implementation specific.

A physical channel is used to trnamsit the RS DCB. In some embodiments, for a 6 bit DCB, an enhanced fast feedback channel (6 bit payload/48 sub-carriers) as defined in IEEE802.16e is used as the physical channel for transmitting the RS DCB.

In some embodiments, for a 9 bit DCB, three 3 bit feedback channels as defined in IEEE802.16e are used as the physical channel for transmitting the RS DCB. More generally, as the physical channel used to implement RS DCB is implementation specific, any manner of channel allowing transmission of a number of bits used for the RS DCB can be used as ths physical channel.

RS_Preamble

In systems that do not use relay stations, the BS transmits a preamble that is used by mobile stations to measure radio propagation environment and enable MS cell selection. In 802.16e_r this preamble is transmitted at the start of every DL sub-frame. When relay stations are present, they also transmit such a preamble in a similar manner so that MS cell selection can be performed as before. This preamble is referred to as a "normal preamble". A problem with this approach is that an RS needs to be able to look at a received preamble and transmit a preamble at the same time. An embodiment of the invention provides a method of a preamble transmission by the RS that enables RS radio environment measurement without interrupting MS cell selection.

In some implementations of the invention, a new preamble, referred to as an RS_preamble since it is transmitted by the RS only and not the BS, is transmitted in every Nth frame, where N ≥ 1, once the RS enters the network. In some embodiments, the RS_preamble is transmitted in addition to the normal preamble. In some embodiments, frames are as defined in 802.16e, but other frame definitions are contemplated.

In some embodiments, the RS_preamble is transmitted within a UL sub-frame for TDD implementations or a UL sub-frame for FDD implementations. Note this is in contrast to the normal preamble that is transmitted during the DL sub-frame. A pseudo-random noise (PN) sequence for each respective RS preamble may be the same as that of an assigned normal preamble or the PN sequence may be different.

The RS' s transmission and receiving of this RS_preamble is synchronized so that at each RS_preamble transmission time, RSs that need to listen to preambles are not transmitting preambles at the same time as they are receiving the preambles. For example, first tier RSs can simultaneously transmit their preambles during a first preamble transmission period, and second tier RSs can monitor these; similarly, second tier RSs can simultaneously transmit their preambles during a second preamble transmission period, and first and/or third tier RSs when present can monitor these. In a particular example, first tier RSs transmit their preamble during odd UL sub-frames or UL frames, and second tier RSs transmit their RS_preamble during even UL sub-frames or UL frames.

In some embodiments RS_preamble reuse within a cell is employed. In some embodiments, the RS_preamble is transmitted out of band.

In some embodiments, for the multiple carrier/multiple channel case a common channel is defined as a primary channel for transmitting an RS_preamble for each respective RS to determine a radio environment measurement. The radio environment measurements are used, for example, to establish topology, for interference avoidance, for carrier or channel assignment and/or for zone configuration.

Description of Example BS and MS

For the purpose of providing context for embodiments of the invention for use in a communication system, Figure 8 shows a base station controller (BSC) 10 which controls wireless communications within multiple cells 12, which cells are served by corresponding base stations (BS) 14. In general, each base station 14 facilitates communications using OfDM with mobile and/or wireless terminals 16, which are within the cell 12 associated with the corresponding base station 14. The movement of the mobile terminals 16 in relation to the base stations 14 results in significant fluctuation in channel conditions. As illustrated, the base stations 14 and mobile terminals 16 may include multiple antennas to provide spatial diversity for communications. Also shown are relay stations 17. A high level overview of the mobile terminals 16 and base stations 14 upon which aspects of the present invention are implemented is provided prior to delving into the structural and functional details of the preferred embodiments. With reference to Figure 9, a base station 14 is illustrated. The base station 14 generally includes a control system 20, a baseband processor 22, transmit circuitry 24, receive circuitry 26, multiple antennas 28, and a network interface 30. The receive circuitry 26 receives radio frequency signals bearing information from one or more remote transmitters provided by mobile terminals 16 (illustrated in Figure 8). A low noise amplifier and a filter (not shown) may co-operate to amplify and remove broadband interference from the signal for processing. Downconversion and digitization circuitry (not shown) will then downconvert the filtered, received signal to an intermediate or baseband frequency signal, which is then digitized into one or more digital streams.

The baseband processor 22 processes the digitised received signal to extract the information or data bits conveyed in the received signal. This processing typically comprises demodulation, decoding, and error correction operations. As such, the baseband processor 22 is generally implemented in one or more digital signal processors (DSPs) or application-specific integrated circuits (ASICs) . The received information is then sent across a wireless network via the network interface 30 or transmitted to another mobile terminal 16 serviced by the base station 14.

On the transmit side, the baseband processor 22 receives digitized data, which may represent voice, data, or control information, from the network interface 30 under the control of control system 20, and encodes the data for transmission. The encoded data is output to the transmit circuitry 24, where it is modulated by a carrier signal having a desired transmit frequency or frequencies. A power amplifier (not shown) will amplify the modulated carrier signal to a level appropriate for transmission, and deliver the modulated carrier signal to the antennas 28 through a matching network (not shown) . Various modulation and processing techniques available to those skilled in the art are used for signal transmission between the base station and the mobile terminal.

With reference to Figure 10, a mobile terminal 16 configured according to one embodiment of the present invention is illustrated. In some embodiments, a relay may have similar compenents as described below. Similarly to the base station 14, the mobile terminal 16 will include a control system 32, a baseband processor 34, transmit circuitry 36, receive circuitry 38, multiple antennas 40, and user interface circuitry 42. The receive circuitry 38 receives radio frequency signals bearing information from one or more base stations 14. A low noise amplifier and a filter (not shown) may co-operate to amplify and remove broadband interference from the signal for processing. Downconversion and digitization circuitry (not shown) will then downconvert the filtered, received signal to an intermediate or baseband frequency signal, which is then digitized into one or more digiral streams.

The baseband processor 34 processes the digitized received signal to extract the information or data bits conveyed in the received signal. This processing typically comprises demodulation, decoding, and error correction operations. The baseband processor 34 is generally implemented in one or more digital signal processors (DSPs) and application specific integrated circuits (ASICs) .

For transmission, the baseband processor 34 receives digitized data, which may represent voice, data, or control information, from the control system 32, which it encodes for transmission. The encoded data is output to the transmit circuitry 36, where it is used by a modulator to modulate a carrier signal that is at a desired transmit frequency or frequencies. A power amplifier (not shown) will amplify the modulated carrier signal to a level appropriate for transmission, and deliver the modulated carrier signal to the antennas 40 through a matching network {not shown). Various modulation and processing techniques available to those skilled in the art are used for signal transmission between the mobile terminal and the base station.

In OFDM modulation, the transmission band is divided into multiple, orthogonal carrier waves. Each carrier wave is modulated according to the digital data to be transmitted. Because OFDM divides the transmission band into multiple carriers, the bandwidth per carrier decreases and the modulation time per carrier increases. Since the multiple carriers are transmitced in parallel, the transmission rate for the digital data, or symbols, on any given carrier is lower than when a single carrier is used.

OFDM modulation utilizes the performance of an

Inverse Fast Fourier Transform (IFFT) on the information to be transmitted. For demodulation, the performance of a Fast Fourier Transform (FFT) on the received signal recovers the transmitted informacion. In practice, the IFFT and FFT are provided by digital signal processing carrying out an Inverse Discrete Fourier Transform (IDFT) and Discrete Fourier Transform (DFT), respectively. Accordingly, the characterizing feature of OFDM modulation is that orthogonal carrier waves are generated for multiple bands within a transmission channel. The modulated signals are digital signals having a relatively low transmission rate and capable of staying within their respective bands. The individual carrier waves are not modulated directly by the digital signals. Instead, all carrier waves are modulated at once by IFFT processing.

In operation, OFDM is preferably used for at least down-link transmission from the base stations 14 to the mobile terminals 16. Each base station 14 is equipped with "n" transmit antennas 28, and each mobile terminal 16 is equipped with ^v\m" receive antennas 40. Notably, the respective antennas can be used for reception and transmission using appropriate duplδxers or switches and are so labelled only for clarity.

With reference to Figure 11, a logical OFDM transmission architecture will be described. initially, the base station controller 10 will send data to be transmitted to various mobile terminals 16 to the base stacion 14. The base station 14 may use the channel quality indicators [CQIs) associated with the mobile terminals to schedule the data for transmission as well as select appropriate coding and modulation for transmitting the scheduled data. The CQIs may be directly from the mobile terminals 16 or determined at the base station 14 based on information provided by the mobile terminals 16. In either case, the CQI for each mobile terminal 16 is a function of the degree to which the channel amplitude (or response) varies across the OFDM frequency band.

Scheduled data 44, which is a stream of bits, is scrambled in a manner reducing the peak-to-average power ratio associated with the data using data scrambling logic 46. A cyclic redundancy check (CRC) for the scrambled data is determined and appended to the scrambled data using CRC adding logic 48. Next, channel coding is performed using channel encoder logic 50 to effectively add redundancy to the data to facilitate recovery and error correction at the mobile terminal 16. Again, the channel coding for a particular mobile terminal 16 is based on the CQI. in some implementations, the channel encoder logic 50 uses known Turbo encoding techniques . The encoded data is then processed by rate matching logic 52 to compensate for the data expansion associated with encoding.

Bit interleaver logic 54 systematically reorders the bits in the encoded data to minimize the loss of consecutive data bits. The resultant data bits are systematically mapped into corresponding symbols depending on the chosen baseband modulation by mapping logic 56. Preferably, Quadrature Amplitude Modulation (QAM) or Quadrature Phase Shift Key [QPSK) modulation is used. The degree of modulation is preferably chosen based on the CQI for the particular mobile terminal. The symbols may be systematically reordered to further bolster the immunity of the transmitted signal to periodic data loss caused by frequency selective fading using symbol interleaver logic 59.

At this poinC_/ groups of bits have been mapped into symbols representing locations in an amplitude and phase constellation. When spatial diversity is desired, blocks of symbols are then processed by space-time block code (STC) encoder logic 60, which modifies the symbols in a fashion making the transmitted signals more resistant to interference and more readily decoded at a mobile terminal 16. The STC encoder logic 60 will process the incoming symbols and provide "n" outputs corresponding to the number of transmit antennas 28 for the bass station 14. The control system 20 and/or baseband processor 22 as described above with respect to Figure 9 will provide a mapping control signal to control STC encoding. At this point, assume the symbols for the ^ssn" outputs are representative of the data to be transmitted and capable of being recovered by the mobile terminal 16.

For the present example, assume the base station 14 has two antennas 28 (n=2) and the STC encoder logic 60 provides two output streams of symbols. Accordingly, each of the symbol streams output by the STC encoder logic 60 is sent to a corresponding ΪFFT processor 62, illustrated separately for ease of understanding. Those skilled in the art will recognize that one or more processors may be used to provide such digital signal processing, alone or in combination with other processing described herein. The IFFT processors 62 will preferably operate on the respective symbols to provide an inverse Fourier Transform. The output of the IFFT processors 62 provides symbols in the time domain. The time domain symbols are grouped .into frames, which are associated with a prefix by prefix insertion logic 64. Each pf the resultant signals is up-converted in the digital domain to an intermediate frequency and converted to an analog signal via the corresponding digital up-conversion (DUC) and digital-to- analog (D/A) conversion circuitry 66. The resultant (analog) signals are then simultaneously modulated at the desired RF frequency, amplified, and transmibted via the RF circuitry 68 and antennas 28, Notably, pilot signals known by the intended mobile terminal 16 are scattered among the sub-carriers. The mobile terminal 16, which is discussed in detail below, will use the pilot signals for channel estimation.

Reference is now made to Figure 12 to illustrate reception of the transmitted signals by a mobile terminal 16. Upon arrival of the transmitted signals at each of the antennas 40 of the mobile terminal 16, the respective signals are demodulated and amplified by corresponding RF circuitry 70. For the sake of conciseness and clarity, only ons of the two receive paths is described and illustrated in detail. Analog- to-digital (A/D) converter and down-conversion circuitry 72 digitizes and downconverts the analog signal for digital processing. The resultant digitized signal may be used by automatic gain control circuitry (AGC) 74 to control the gain of the amplifiers in the RP circuitry 70 based on the received signal level.

Initially, the digitized signal is provided to synchronization logic 76, which includes coarse synchronization logic 78, which buffers several OFDM symbols and calculates an auto-correlation between the two successive OFDM symbols. A resultant time index corresponding to the maximum of the correlation result determines a fine synchronization search window, which is used by fine synchronization logic 80 to determine a precise framing starting position based en the headers. The output of the fine synchronization logic 80 facilitates frame acquisition by frame alignment logic B4. Proper framing alignment is important so that subsequent FFT processing provides an accurate conversion from the time domain to the frequency domain. The fine synchronization algorithm is based on the correlation between the received pilot signals carried by the headers and. a local copy of the known pilot data. Once frame alignment acquisition occurs, the prefix of the OFDM symbol is removed with prefix removal logic QS and resultant samples are sent to frequency offset correction logic 88, which compensates for the system frequency offset caused by the unmatched local oscillators in the transmitter and the receiver. Preferably, the synchronization logic 76 includes frequency offset and clock, estimation logic 82, which is based on the headers to help estimate such effects on the transmitted signal and provide those estimations to the correction logic 88 to properly process OFDM symbols.

At this point, the OFDM symbols in the time domain are ready for conversion to the frequency domain using FFT processing logic 90. The results are frequency domain symbols, which are sent to processing logic 92. The processing logic 92 extracts the scattered pilot signal using scattered pilot extraction logic 94, determines a channel estimate based on the extracted pilot signal using channel estimation logic 96, and provides channel responses for all sub-carriers using channel reconstruction logic 98. in order to determine a channel response for each of the sub-carriers, the pilot signal is essentially multiple pilot symbols that are scattered among the data symbols throughout the OFDM sub-carriers in a known pattern in both time and frequency. Examples of scattering of pilot symbols among available sub-carriers over a given time and frequency plot in an OFDM environment are found in PCT Patent Application No. PCT/CA2005/000387 filed March 15, 2005 assigned to the same assignee of the present application. Continuing with Figure 12, the processing logic compares the received pilot symbols with the pilot symbols that are expected in certain sub-carriers at certain times to determine a channel response for the sub-carriers in which pilot symbols were transmitted. The results are interpolated to estimate a channel response for most, if not all, of the remaining sub- carriers for which pilot symbols were not provided. The actual and interpolated channel responses are used to estimate an overall channel response, which includes the channel responses for most, if noc all, of the sub-carriers in the OFDM channel.

The frequency domain symbols and channel reconstruction information, which are derived from the channel responses for each receive path are provided to an STC decoder 100, which provides STC decoding on both received paths to recover the transmitted symbols. The channel reconstruction information provides equalization information to the STC decoder 100 sufficient to remove the effects of the transmission channel when processing the respective frequency domain symbols

The recovered symbols are placed back in order using symbol de-interleaver logic 102, which corresponds to the symbol interleave:.- logic 5S of the transmitter. The de- interleaved symbols are then demodulated or de-mapped to a corresponding bitstream using de-mapping logic 104. The bits are then de-interleaved using bit de-interleaver logic 106, which corresponds no the bit interleaver logic 54 of the transmitter architecture. The de-interleaved bits are then processed by rate de-inatching logic 108 and presented to channel decoder logic 110 to recover the initially scrambled data and the CRC checksum. Accordingly, CRC logic 112 removes the CRC checksum, checks the scrambled data in traditional fashion, and provides it to the de-scrambling logic 114 for de- scrambling using the known base station de-scrambling code to recover the originally transmitted data 116.

In parallel to recovering the data 116, a CQI, or at laast information sufficient to create a CQI at the base station 14, is determined and transmitted to the base station 14. As noted above, the CQI may be a function of the carrier- to-interference ratio (CR) , as well as the degree to which the channel response varies across the various sub-carriers in the OFDM frequency band. The channel gain for each sub-carrier in the OFDM frequency band being used to transmit information is compared relative to one another to determine the degree to which the channel gain varies across the OFDM frequency band. Although numerous techniques are available to measure the degree of variation, one technique is to calculate the standard deviation of the channel gain for each sub-carrier throughout the OPDM frequency band being used to transmit data.

Figures 8 to 12 each provide a specific example of a communication system or elements of a communication system that could be used to implement embodiments of the invention. IN some embodiments a relay may have particular elements found in either the base station or mobile station to enable communication between the bases station and mobile station and or other relay stations. It is to be understood that embodiments of the invention can be implemented with communications systems having architectures that are different than the specific example, but that operate in a manner consistent with the implementation of the embodiments as described herein.

For multi-hop implementations such as described previously, each relay node will include some transmitting functionality and some receiving functionality. For example, a relay station may include components of the example OFDM transmitter architecture and the example OFDM receiver architecture.

Numerous modifications and variations of the present invention are possible in light of the above teachings, it is therefore to be understood that within the scope of the appended claims, the invention may be practised otherwise than as specifically described herein.

Claims

CLAIMS :

1. A method for managing a transmission resource including a dedicated transmission resource portion and a non- dedicated transmission resource portion in a network including a base station and at least one relay, the method comprising:

managing the dedicated transmission resource portion in at least one of a centralized manner and a distributed manner;

each of the at least one relays managing the non- dedicated transmission resource portion in a distributed manner.

2. The method of claim 1, wherein managing a transmission resource comprises at least or.e of:

managing transmission resources in a downlink direction from the base station to the at least one relay station; and

managing transmission resources in an uplink direction from at least one relay station to the base station.

3. The method of claim 1, wherein the base station managing the dedicated transmission resource portion in a centralized manner and each of the at least one relays managing non-dedicated transmission resources in a distributed manner is in response to:

a mobile station sending a request to the base station for a transmission resource assignment on a path between the mobile station and the base station.

4. The method of any one of claims 1 to 3, wherein the base station managing the dedicated transmission resource portion in a centralized manner comprises for a path between the base station and an end of path relay comprising N relays and N associated links, N>=»1 :

assigning a maximum capacity for the transmission resource for each link, in the path; and

for each link in the path, assigning lass than the maximum capacity for the link as the dedicated transmission resource portion.

5. The method of claim 4, further comprising the base station transmitting at least one of:

an assignment of the dedicated transmission resource portion for a link between the base station and at least one relay one hop away from the base station along the path;

an assignment of the dedicated transmission resource portion for a link between a relay that is more than one hop away from the base station along the path and at least one subordinate relay along the path.

6. The method of claim 5, wherein the base station transmitting an assignment of the dedicated transmission resource portion comprises:

the base station transmitting an indication of an amount of transmission resource to be used as the dedicated resource portion to a subordinate relay.

7. The method of claim 6, further comprising:

the subordinate relay transmitting an indication of an amount of transmission resource and a particular location within the transmission resource to be used as the dedicated transmission resource portion to a one hop away subordinate relay.

8. The method of claim 5, wherein the base station transmitting an assignment of the dedicated transmission resource portion comprises:

the base station transmitting an indication of an amount of transmission resource and a particular location wichin the transmission resource to be used as the dedicated transmission resource portion to a subordinate relay.

9. The method of any one of claims 1 to 3, wherein the base station managing the dedicated transmission resource portion in a centralized manner comprises for a path between the base station and an end of path relay comprising N relays and N associated links, N>=1:

assigning a maximum capacity for the transmission resource for each link along the path; and

for the link of a relay one hop away from the base station along the path, assigning less than the maximum capacity as the dedicated transmission resource portion.

10. The method of claim 9, further comprising the base station transmitting:

the assignment of the dedicated resource portion for the link of the relay one hop away from the base station along the path.

11. The method of claim 9, wherein the base station transmitting an assignment of the dedicated transmission resource portion comprises:

the base station transmitting an indication of an amount of transmission resource to be used as the dedicated transmission resource portion to a subordinate relay.

12. The method of claim 9, wherein the base station transmit:cing an assignment of the dedicated transmission resource portion comprises:

the base station transmitting an indication of an amount of transmission resource and a particular location within the transmission resource to be used as the dedicated transmission resource portion to a subordinate relay.

13. The method of claim 10, further comprising:

for a relay having a link with a subordinate relay that is more than one hop away from the base station along the path and having an assigned maximum capacity, assigning less than "Che maximum capacity as a dedicated transmission resource.

14. The method of claim 13, further comprising the relay transmitting:

the assignment of the dedicated transmission resource for the relay having the link with the subordinate relay that is more than one hop away from the base station along the path.

15. The method of claim 14, further comprising:

the relay transmitting an indication of an amount of transmission resource and a particular location within the transmission resource to be used as the dedicated transmission resource portion to the subordinate relay that is more than one hop away from the base station along the path.

16. The method of any one of claims 4 to 8, 10 to 12, 14 and 15, wherein transmitting the assignment comprises transmitting a media access control (MAC) layer information element (IE) .

17. The method of any one of claims 1 to 16, further comprising: a relay along the path sending a request; to the base station for a dedicated transmission resource assignment for a link between the relay sending the request and the base station.

18. The method of any one of claims 1 to 17, further comprising :

the base station receiving a request for a dedicated transmission resource assignment;

the base station considering the request before allocating the dedicated transmission resource.

19. The method of any one of claims 4 to 18, wherein each of the at least one relays managing the non-dedicated transmission resource portion in a distributed manner comprises :

a relay along the path assigning a non-dedicated portion of the transmission resource to at least one link between the relay assigning the non-dedicated portion of the transmission resource and a subordinate relay along the path.

20. The method of claim 19, further comprising the relay transmitting:

an assignment of the non-dedicated transmission resource portion the subordinate relay along the path.

21. The method of claim 20, further comprising:

the relay transmitting an indication of at least one of:

an amount of transmission resource; and a particular location within the transmission resource to be used as the non-dedicaced transmission resource portion to the subordinate relay along the path.

22. The method of any one of claims 4 to 21 further comprising:

a relay along the path determining for what purpose the dedicated transmission resource is used in a link to a subordinate relay.

23. The method of claim 22 wherein a purpose for which the dedicated transmission resource is used is for a delay sensitive service flow.

24. The method of any one of claims 4 to 23, further comprising when using a HARQ (hybrid automatic repeat request) retransmission scheme, performing either one of:

a) transmitting a first transmission on the dedicated resource and retransmitting a portion of or all of the first transmission on an additional, dynamically assigned resource; and

b) controlling a first transmission and subsequent retransmissions on the dedicated resource by including an additional dedicated control channel to transmit information regarding whether a given transmission is the first transmission or a subsequent retransmission.

25. The method of claim 22, wherein retransmitting a portion of or all of the first transmission on an additional, dynamically assigned resource comprises:

transmitting an indication of an amount of transmission resource and/or a particular location within the transmission resource to be used as a HARQ retransmission resource to a subordinate relay. ^•

26. The method of claim 25 wherein transmitting the indication of an amount of transmission resource and/or a particular location within the transmission resource to be used as a HARQ retransmission resource to a subordinate relay comprises transmitting a media access control (MAC) layer information element (IE) containing the indication.

27. A method for reporting information on a dedicated resource from a relay to a superodinate relay or a base station comprising:

transmitting a type of reporting information;

transmitting a value associated with the type of reporting information that further defines the reporting information.

28. The method of claim 27, wherein transmitting a type of reporting information comprises transmitting an indication of at least one of the following types of information:

channel quality;

closed loop MIMO related feedback;

uplink bandwidth request;

flow control;

uplink HARQ control; and

fast base station selection.

29. The method of claim 26 or claim 28 wherein: transmitting the type of reporting information comprises transmitting a first number of bits used to identify the type;

transmitting the value associated with the type comprises transmitting a second number of bits used to identify the value.

30. The method of claim 29 wherein the first number of bits is 3 and the second number of bits is either 3 or 6.

31. A method for requesting a dedicated channel transmission resource for a link between a base station and a relay in an uplink direction from the relay to the base station or for a link between a relay and a superordinate relay in an uplink direction from the relay to the superordinate relay, the method comprising:

sending a message requesting a dedicated channel transmission resource;

receiving an assignment of the dedicated channel transmission resource.

32. The method of claim 31 wherein the relay sending a message comprises:

sending the message in the form of a media access control (MAC) layer header.

33. The method of claim 31 or claim 32 wherein receiving an assignment comprises:

receiving an assignment in the form of a madia access control (MAC) layer information element (IE).

34. A method for requesting a dedicated channel transmission resource for a link between a base station and a relay in an uplink direction from the relay to the base station or for a link between a relay and a superordinate relay in an uplink direction from the relay to the superordinate relay, the method comprising:

receiving a message indicating a request for a dedicated channel transmission resource;

determining an allocation for the dedicated channel transmission resource based at least in part on the message;

sending an assignment of the dedicated channel transmission resource.

35. The method of claim 34 wherein receiving a message comprises:

receiving the message in the form of a media access control {MAC) layer header.

36. The method of claim 34 or claim 35 wherein sending an assignment comprises:

sending an assignment in the form of a media access control (MAC) layer information element (IE) .

37, The method of any one of claims 34 to 36 wherein sending an assignment of the dedicated channel transmission resource comprises:

in a centralized management scheme, the base station sending an assignment of the dedicated channel transmission resource to all subordinate relays; and

in a distributed management scheme, the base station sending an assignment of the dedicated channel transmission resource to relays one hop away from the base station and the superordinate relay sending an assignment of the dedicated channel transmission resource to relays one hop away from the superordinate relay.

38. The method of any one of claims 31 to 33 wherein a message having substantially the same format as the message used for requesting the dedicated channel transmission resource is used for each of:

acknowledging the assignment of the dedicated channel transmission resource; and

sending a HARQ retransmission request.

39. The method of any one of claims 31 to 33, wherein sending the message indicating a request for the dedicated channel transmission resource comprises:

sending a request type that indicates that the request for the transiuission resource is one of incremental, aggregate, or transmission rate based.

40. The method of any or.e of claims claim 34 to 37 wherein at least one of size of an allocated dedicated channel transmission resource and allocation interval of an allocated dedicated channel transmission resource can be increased or decreased based on at least one of traffic load and channel conditions.

41. The method of claim 40 wherein the traffic load and/or channel conditions are calculated at least one of:

periodically; and

in response to specific events.

42. A base station adapted co perform the method of any one of claims 1 to 24, 34 to 37, 40 and 41.

43. A relay station adapted to perforin the method of any one of claims 1 to 33, 38 and 39.

44. A mobile station adapted to perform the method of any one of claims 3 to 21.