WO2001033892A1

WO2001033892A1 - Call notification delivered by an alternate network

Info

Publication number: WO2001033892A1
Application number: PCT/US2000/025324
Authority: WO
Inventors: Nils Rydbeck
Original assignee: Ericsson Inc.
Priority date: 1999-10-29
Filing date: 2000-09-14
Publication date: 2001-05-10
Also published as: AU7381500A

Abstract

In response to receiving a request to establish contact with the wireless commutations mobile station, a wireless communications network attempts to page the mobile station for a given time period, and if unsuccessfull, contacts a separate alternate network. The first network transfers the request and the identification of the mobile station to the alternate network, and the alternate network attempts to establish contact with the mobile station through its own page attempt. The two networks service geographic areas that at least partially overlap, with the alternate network's area preferably completely overlapping the first network's service area. Preferably, the alternate network transmits its page attempt at a higher power link margin and uses short message service to notify the mobile station that it was being paged by the first network.

Description

CALL NOTIFICATION DELIVERED BY AN ALTERNATE NETWORK

Background of the Invention

The present invention is directed to a wireless communications system and, more particularly, a primary wireless communication network coupled to an alternate communication network for contacting disadvantaged users.

A fundamental limitation of many wireless communication networks is an inability to provide service to disadvantaged users who fall below the link margin of the wireless communication network. Link margin refers to the signal strength that the network provides above the strength needed to maintain line of sight communication. By way of example, a hypothetical network may provide a link margin of +20dB. This network would be able to reach a mobile user who is inside a building with 15dB of shielding loss, and provide that user with a signal strength that is 5dB above the minimum required for a useful link. If the same hypothetical user were to go deeper into the building, say to a point that provided 25dB shielding loss, the network would no longer be able to reach the user because the signal strength would have fallen to 5dB below the minimum useful level.

The hypothetical user would undoubtedly wish to receive an incoming call, or, if this were not possible, at least receive some notification that an attempt had been made to reach them. This is especially important as often times the user is not aware that they have entered a location where they can not be accessed. Several systems have combined call setup/paging and high penetration capability. Unfortunately, this requires that the call paging equipment have specialized high penetration capability as well. Conversely, the high penetration equipment must be able to provide for call setup. Additionally, when the link conditions cause the cellular page to fail, the problem is not solved merely by

escalating the link margin during the paging process because the mobile station may lack means to engage in a call even after having been made aware of the

need to do so.

By having separate primary cellular and alternate networks, each can be

optimized to more effectively accomplish their principle task. For instance, at the

physical layer, the alternate network may have more RF transmission power, different antenna patterns to reach long distances in marine or maritime regions, and include different channel codes so as to emphasize the delivery of short alphanumeric messages. At the data link control layer, the alternate network may

have different or adaptive time-out parameters for retry, a different ARQ scheme,

and so forth.

Thus, there is a need for a method of notification of failed pages by use of a separate alternate network, which may be an overlay to the primary cellular

network. This enables both networks to be optimized for their principle tasks by

recognizing the utility that comes from providing functional, logical separation

between the networks.

Summary of the Invention

The present invention provides a method of contacting a mobile station through an alternate network. After a first network has unsuccessfully attempted

to contact the mobile station, a second alternate network attempts contact. The

second network is independent from the first, but covers at least some of the same geographic region. The second network has different criteria for contacting the mobile station than the first network, such as through higher link margins, higher power levels, different antenna patterns, or the like.

A cellular network receives an incoming request to establish a call with a

mobile station. The cellular network pages the mobile station through the cellular network. When the mobile station does not respond to the paging attempts, an

alternate network is notified to contact the mobile station. Preferably, the alternate network receives the mobile station address from the cellular network, and may also receive an alphanumeric text message that is to be forwarded to the mobile station. After notifying the alternate network, the cellular network may continue

trying to contact the mobile station, or may stop. In one embodiment, the

alternate network is a high penetration network and transmits signals to the mobile station at a higher power link margin than the cellular network.

Brief Description of the Drawings FIGURE 1 is a schematic diagram illustrating a wireless communications

network in accordance with the present invention;

FIGURE 2 is a schematic diagram illustrating the components of a mobile

station;

FIGURE 3 illustrates a High-Penetration Short Message Service network;

FIGURE 4 is a schematic illustration of the information exchange taken

between the cellular network and HP-SMS network for contacting the mobile

station; and

FIGURE 5 is a flowchart illustrating the process of contacting the mobile

station in accordance with the present invention. Detailed Description of the Preferred Embodiment(s)

Referring now to the drawings, the method of paging a mobile station according to the present invention will be described. The invention provides for paging of a mobile station 20 through a wireless communication network 10. If the paging fails to successfully contact the mobile station 20, the wireless communication network 10 contacts an alternate network 100, such as a high- penetration short message service (HP-SMS) to attempt a message delivery to the mobile station 20. Because the two networks 10, 100 are independent, each may be designed to optimize their principle tasks. A conventional wireless communications network is illustrated schematically in Figure 1 and indicated generally by the numeral 10. The network 10 typically includes a plurality of base stations 12 which are connected via a mobile services switching center (MSC) 14 to a terrestrial communications network such as the Public Switched Telephone Network (PSTN) 18. Each base station 12 is located in, and provides service to, a geographic region referred to as a cell. In general, there is one base station 12 for each cell within a given system. Within each cell, there may be a plurality of mobile stations 20 that communicate via radio link with the base station 12. The base station 12 allows the user of the mobile station 20 to communicate with other mobile stations 20, or with users connected to the PSTN 18. The MSC 14 routes calls to and from the mobile station 20 through the appropriate base station 12. Information concerning the location and activity status of the mobile station 20 may be stored in a Home Location Register (HLR) 21 and a Visitor Location Register (VLR) 22, which are connected to the MSC 14. Figure 2 is a block diagram of a typical mobile station 20. The disclosed embodiment of the mobile communication device is a fully functional cellular telephone, such as an ANSI-136 compliant cellular telephone, capable of transmitting and receiving digital signals. The mobile station 20 may also be able to monitor two or more control channels for monitoring separate networks, such as that disclosed in U.S. Patent Application Serial No. 09/193,261 filed November 18, 1998 entitled "Method for Switching Between Regular and Robust Services," which is incorporated herein by reference. The mobile station 20 includes a main processor 22 for controlling the overall operation of the mobile station 20 and a memory 24 for storing control programs and data used by the mobile station 20 during operation. Input/output circuits 26 interface the main processor 22 with a keypad 28, a display 30, audio processing circuits 32, receiver 38, transmitter 40, and an optional GPS receiver 50. The keypad 28 allows the operator to dial numbers, enter commands, and select options. The display 30 allows the operator to see dialed digits, stored information, and call status information. The audio processing circuits 32 provide basic analog audio outputs to a speaker 34 and accept analog audio inputs from a microphone 36. The receiver 38 and transmitter 40 receive and transmit signals using a shared antenna 44. The optional GPS receiver 50 enables the mobile station 20 to determine its current location based on positioning signals transmitted by a GPS satellite.

The mobile station 20 registers with the servicing MSC 14 when it is powered on, and preferably at periodic intervals, so that the servicing MSC 14 can keep track of the location of the mobile station 20. The VLR 22 contains the relevant data on visiting mobile stations while they are located within the servicing MSC region The mobile station 20 also registers when it travels between two different service areas As part of this registration procedure, the mobile station 20 typically transmits its Mobile Identification Number (MIN) and its Electronic Serial Number (ESN) to the MSC 14 The MSC 14 verifies that the MIN/ESN combination does in fact belong to a valid subscriber by referencing the appropriate HLR 21 In addition, it is customary for the servicing MSC 14 to update the HLR 21 of the subscriber's home system with the location of the mobile station 20 when the mobile station 20 registers with the MSC 14 When an MSC 14 receives a call addressed to a subscriber that is not currently in that MSC's service area, the MSC 14 will query the HLR 21 for the subscriber's location so that the call can be forwarded to the MSC 14 currently servicing the subscriber

Each mobile station 20 scans the control channels for the presence of a paging request addressed to the mobile station 20 When the servicing MSC 14 receives a request to contact a mobile station 20, a paging request is transmitted by the nearest base station 12 The paging request is broadcast over a control channel and includes digital control channel location information The paging request is transmitted from the base station 12 at a limited power level The link margin at the power level may be inadequate for successfully contacting the mobile station 20 due to impairments including fading of signal amplitude, Doppler shifts, phase variations, signal shadowing or blockage, implementation losses, and anomalies in the antenna radiation pattern Increasing the signal power of the paging request to increase the link margin is often unproductive The base stations 12 often are not equipped to handle higher power levels with the existing equipment and would require expensive alterations Increased transmission power also makes it difficult to control co-channel interference, especially in

TDMA systems with narrow re-use margins Additionally, increased power is

practical in only one direction, from the base station 12 to the mobile station 20 because the mobile station 20 remains power limited

The cellular network 10 may be equipped with a high-penetration short message service such as that disclosed in U S Patent No 5,884, 170 to Valentine

et al , and pending U S Patent Applications Serial Nos 08/931 ,625 (filed September 16, 1997), 08/989,088 (filed December 1 1 , 1997), and 08/559,692 (filed November 15, 1995), each of which is incorporated by reference in their

entirety These networks provide for a hybrid system having a combined high penetration system included with the paging abilities

Figure 3 illustrates a high-penetration short message service network (HP-

SMS) 100 connected to the wireless communications network 10 The present invention also includes other alternate networks 100 that service the geographic area common with the wireless communications network 10, and may include

networks having higher power levels, link margins, more robust channel codes, narrower antenna patterns, etc that have a different expectation of reaching the

mobile station 20 for whatever reason The HP-SMS network 100 includes a control module 1 10 in

communication with the wireless communications network 10 The HP-SMS and

cellular network 10 may be connected via a wireline link or via radio transmissions, or any other known technique IN the HP-SMS network 100 shown in Figure 3, one or more satellites 1 12 serve as relays or transponders between one or more earth stations 1 14 and the mobile stations 20. The satellite conveys radiotelephone communications over duplex links 122 to mobile stations 20 and an earth station 1 14. The earth station 1 14 in turn is connected to the PSTN 18,

allowing communications between satellite radiotelephones, and communications between satellite radio telephones and conventional terrestrial cellular

radiotelephones or landline telephones. The HP-SMS network 100 may utilize a

single antenna beam 120 covering the entire area served by the HP-SMS network 100, or, as shown, the satellite 1 12 may be designed such that it produces

multiple minimally-overlapping beams 120, each serving distinct geographical coverage areas 124 in the HP-SMS network's service region. The HP-SMS

network 100 may also include, or instead be, a terrestrial-based system.

The HP-SMS network 100 preferably provides for a stronger transmission power than that of the cellular network 10. This allows for contacting mobile

stations 20 that are otherwise non-accessible by paging attempts from the normal

cellular network 10. Additionally, the HP-SMS network 100 may transmit the

signal over different channels, such as broadcast channels designated for the transmission of alphanumeric data such as that provided by short message service. In most networks, a short message supplied to the mobile station 20 will

be limited to about 200 alphanumeric characters. The cellular network 10 and alternate network 100 are separate and

preferably do not share any components. While the networks 10,100 overlay for

at least some geographic area, each can be constructed to best perform specific functions, without requiring exotic alterations that allow for a single hybrid system to perform both tasks. By way of example, the alternate network 100 may have more RF transmission power, different antenna patterns to reach long distances, and different channel codes so as to emphasize the delivery of short alphanumeric messages. Additionally, the alternate network 100 may provide for different re-attempt parameters, ARQ scheme, etc. Figure 4 illustrates the process taken between the cellular network 10 and the alternate network 100 to contact a mobile station 20. Initially, the cellular network 10 receives a request for a call to the mobile station 20. The request is processed through the MSC 14 which forwards the request to the nearest base station 12. The base station 12 transmits a paging request to the mobile station 20 attempting to establish a call set-up. The duration of the paging attempts by the base station 12 is preferably limited to a predetermined duration without successfully contacting the mobile station 20. If the page is answered by the mobile station 20, the call will be processed in the conventional manner well known in the art. If the page is not answered during the provided duration, the cellular network 10 accesses the HLR 21 of the mobile station 20 to determine whether the user subscribes to alternate service. Alternatively, the cellular network 10 may query the requesting party whether they choose to attempt to reach the mobile station via the alternate network 100. If either condition is positive, the cellular network 10 sends a notification request to the alternate network 100. The notification request should include at a minimum the identification of the mobile station 20 and optionally any desired message, such as the identity of the requester. Additionally, a more thorough alphanumeric message may be input by the requesting party through a mobile terminal, a standard telephone, a computer terminal, or equivalent device, or the message may be input by calling an operator at a service center who inputs the message into the network 10. The request may also include a query from the cellular network 10 to check the equipment as desired by the cellular network administrator. The alternate network 100 then transmits a message attempting to contact the mobile station 20. One method of determining whether the mobile station 20 has received the message is through a one-bit acknowledgement sent by the mobile station 20 that is expanded to many bits by way of a channel code such as that described in U.S. Patent No. 5,918,174, and U.S. Patent Application No. 08/989,088, filed December 11 , 1997, both herein incorporated by reference in their entirety.

If the message is received by the mobile station 20, a verification response is sent to the cellular network 10, after which billing information will be sent from the alternate network 100 to the cellular network 10. If the message is not received by the mobile station 20, the message may be repeatedly sent. After a predetermined time or number of attempts, the alternate network 100 may notify the cellular network 10 of the failed attempt.

In one optional embodiment, the alternate network service may be established as a separate option for subscribers to the cellular network 10, or the requestor attempting to contact the mobile station 20. Within this option, if neither the requesting or requestor party subscribe to the alternate network service, the cellular network 10 will not contact the alternate network 100 and the attempt to contact the mobile station 20 will be limited to the cellular network. Alternatively, the alternate network service may be an option available for every subscriber within the cellular network 10 and the contact attempt will be automatically forwarded to the alternate network 100 without the requestor or requesting party knowledge.

In another embodiment, if the original paging attempt is unsuccessful, the cellular network 10 may notify the requesting party and query whether they desire to use the alternate network 100. Within each embodiment, billing amounts and information may be established.

Figure 5 illustrates the logical progression of attempting to contact the mobile station 20. The cellular network 10 receives a request to contact a mobile station (block 202). The MSC 14 will determine the location of the mobile station 20 and then process the call through the closest base station 12. The base station 12 pages the mobile station (block 204) for a given time period or a given number of attempts. The time period may be one continuous length of constant paging, or may be spread out over a length of time such as paging for thirty- seconds, and then waiting ten minutes, and then again paging. Various paging routines are possible depending upon the parameters of the cellular network 10 (block 206). If the page is answered, the call is processed in accordance with a conventional format (block 210). If the page is not answered, the cellular network 10 sends a notification request to the alternate network 100 containing the identification of the requesting and requestor parties, and any other desired information (block 212).

After notifying the alternate network 100, the cellular network 10 may also continue paging the mobile station 20. The cellular network 10 may have a standard link margin strength, or may include a HP component.

π The alternate network 100 receives the request from the cellular network 10 and begins paging the mobile station (block 214). If the page is answered (block 216), the relevant information transferred from the cellular network 10 is communicated to the mobile station (block 222). Alternatively, the page may contain all the needed information thereby eliminating the need to transfer any additional information. The alternate network 100 will contact the cellular network 10 indicating that the page was successful and billing information will be distributed as necessary (block 224). If the alternate network 100 cannot immediately contact the mobile station, it may continue trying over a predefined period of time (block 218). Alternatively, the message may be queued and the attempt tried again at a later time. If the alternate network 100 cannot successfully contact the mobile station after the predefined time period, the alternate network will notify the cellular network 10 of the unresponsive page (block 220). The mobile terminal 20 may also be equipped with a call "answering service" in which an indicator will notify the user that a party is attempting contact. Upon noticing that the indicator is activated, the user contacts a voice mail or other like account to receive the message.

The present invention may, of course, be carried out in other specific ways than those herein set forth without departing from the spirit and essential characteristics of the invention. For clarity, the present discussion will assume that the mobile station 20 is a cellular telephone. However, it is to be understood that other wireless communications mobile stations, such as personal communications assistants, pagers, and the like, are also within the scope of the present invention. Additionally, the cellular network 10 and alternate network 100 may transmit signals to and from the mobile stations 20 via antennas, satellites 112, or a combination of both. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive, and all changes coming within the meaning and equivalency range of the appended claims are intended to be embraced therein.

Claims

ClaimsWhat is claimed is:

1. A method for processing a request to establish a cellular telephone call comprising the steps of: receiving an incoming request to establish a call with a mobile station over a cellular network; paging the mobile station by the cellular network, in response to the incoming request; and notifying an alternate network to contact the mobile station when the mobile station does not respond to the paging by the cellular network.

2. The method of claim 1 , wherein the alternate network receives the mobile station address from the cellular network for contacting the mobile station.

3. The method of claim 2, further including the alternate network receiving an alphanumeric text message from the cellular network that is forwarded to the mobile station.

4. The method of claim 1 , wherein paging the mobile station by the cellular network continues for a predetermined time period prior to notifying the alternate network.

5. The method of claim 1 , further including the cellular network determining whether the mobile station subscribes to paging by the alternate network prior to notifying the alternate network.

6. The method of claim 1 , further including the cellular network determining whether the requestor subscribes to paging by the alternate network prior to notifying the alternate network.

7. The method of claim 1 , wherein the alternate network is a high penetration network and transmits signals to the mobile station at a higher power link margin than the cellular network.

8. The method of claim 7, wherein the alternate network includes a short message service.

9. The method of claim 7, wherein the alternate network transmits signals at a higher power level than the cellular network.

10. The method of claim 7, wherein the alternate network transmits signals using a robust channel coding scheme than said cellular network.

11. The method of claim 7, wherein the alternate network transmits signals over a narrower antenna pattern than the cellular network.

12. The method of claim 1 , wherein the alternate network is capable of transmitting signals to the entire geographic area covered by the cellular network.

13. A method of contacting a wireless communications device comprising: receiving a request at a wireless communications network to contact the wireless communications device, the request including an identification number of the wireless communications device; paging the wireless communications device through the wireless communications network for a predetermined time period at a first transmission power; relaying the request and identification number to an alternate network to begin paging the wireless communications device at a second transmission power; and continuing paging the wireless communications device through the alternate network.

14. The method of claim 13, further including the wireless communications network continuing to page the wireless communications device for a second predetermined time.

15. The method of claim 13, wherein the wireless communications device receives notification from the alternate network that the wireless communications device has been successfully contacted.

16. The method of claim 15, further including receiving billing information from the alternate network.

17. The method of claim 13, wherein the wireless communications network is independent from the alternate network and wherein the wireless communications network and the alternate network service geographic areas that at least partially overlap.

18. The method of claim 17, wherein the geographic area serviced by said alternate network entirely covers the geographic area serviced by said wireless communications network.

19. The method of claim 13, wherein the alternate network is a high- penetration short message service.

20. The method of claim 19, wherein the high-penetration short message service transmits signals at a higher link margin than the wireless communications network.

21. The method of claim 20, wherein the high-penetration short message service transmits signals at a higher power level than the wireless communications network.

22. A method of contacting a mobile terminal comprising the steps of: transmitting a first paging request to the mobile terminal through a first network at a first link margin; and transmitting a second paging request to the mobile terminal through a second network at a second link margin in response to said first paging attempt being unsuccessful.

23. The method of claim 22, wherein the second paging request has a higher power level than the first paging request.

24. The method of claim 22, wherein the second network transmits signals using a more robust channel code than the first network.

25. The method of claim 22, wherein the second network has a narrower antenna pattern than the first network.