WO1993009629A1

WO1993009629A1 - Method and apparatus for reserving a communication path in a telepoint communications system

Info

Publication number: WO1993009629A1
Application number: PCT/US1992/008250
Authority: WO
Inventors: Robert W. Furtaw; Richard A. Comroe
Original assignee: Motorola, Inc.
Priority date: 1991-11-04
Filing date: 1992-09-30
Publication date: 1993-05-13
Also published as: MX9206337A

Abstract

A telepoint communications system (200) employs a method (621-633) of selectively changing the service state of a communication path. The telepoint system (200) includes a base unit (201) and at least one handset (210). The base unit (201) is coupled to a public switched telephone network (PSTN, 206) via at least one wireline (202), and is able to communicate with the handsets (210-220) via at least one radio frequency (RF) channel. The method includes the step of, at the handset (210), receiving (605) a PSTN access number from the base unit (201). The handset (210) might then signal (617), to the base unit (201), a service request (416) to change the service state for the PSTN wireline associated with the PSTN access number. The base unit (201) might, after receiving the request signal, alter the service state (508) of the PSTN wireline.

Description

f METHOD AND APPARATUS FOR

RESERVING A COMMUNICATION PATH IN A TELEPOINT * 5 COMMUNICATIONS SYSTEM

Technical Field

This i nvention relates generally to telepoint 10 communication systems, and more particularly to a method of reserving a communication path in a such a system.

Background of the Invention

15 Cordless telephone systems, such as system 100 shown in

FIG. 1 , are well known in the art. The base unit 102 terminates a phone line 104 with an associated public switched telephone network (PSTN, 106) access number. When calls are placed to this telephone number, the base unit 102 signals the handset

20 101 , then relays the call via an RF channel of a predetermined frequency. Similarly, the handset 101 may initiate a call by signalling to the base unit, on the same RF channel, and the communication is relayed in the other direction. This type of two-way communication, using a single RF channel and an

25 associated PSTN wireline, is well known in the art.

So-called telepoint communications systems, by contrast, employ strategically placed base units to provide one-way telecommunications coverage to locations of high pedestrian traffic, such as railway stations, airports, and other public

30 complexes. Each base unit communicates with, but is not paired directly with any one of, a plurality of telepoint handsets. The telepoint handsets may initiate, but not receive, a call whenever

_; the handset is located within a coverage area of a telepoint base unit. These non-paired telepoint base units function quite like a bank of wired pay phones. Each base unit terminates a plurality of phone lines, where each phone line may be associated with a specific phone number.

In the case of pay phones, each individual pay phone instrument is typically marked with and identified by its associated telephone number. When using a pay phone, a user can make note of its telephone number, relay the telephone number to a called party, and after his call is terminated, receive a return call through the same pay phone. in the case of telepoint systems, however, a user may initiate calls without even seeing the base unit. Further, even if the user knew the phone number of the wireline for a given call, the user would have no way of reserving the wireline for a return call. Upon terminating a telepoint system call, another telepoint user could initiate a call on the previously used wireline, without the knowledge of the waiting user.

Accordingly, a need exists for a method of selectively being able to receive inbound telephone calls on a handset in a telepoint communications system.

Summary of the Invention

The present invention encompasses a method of selectively changing the service state of a communication path in a telepoint communications system. The telepoint system includes a base unit and at least one handset. The base unit is coupled to a public switched telephone network (PSTN) via at least one wireline, and is able to communicate with the handsets via at least one radio frequency (RF) channel. Each wireline is associated with, and coupled to, one of the RF channels. The method includes the step of, at the^" handset, receiving a PSTN access number from the base unit. The handset might then signal, to the base unit, a service request to change the service state for the PSTN wireline associated with the PSTN access number. The base unit might, after receiving the request signal from the handset, alter the service state of the PSTN wireline.

Brief Description of the Drawings

FIG. 1 shows a cordless phone handset and paired base unit which is known in the art. FIG. 2 shows cordless phone system including several handsets and a multi-line base unit, which system may employ the present invention.

FIG. 3 shows a timing diagram illustrating communication signals which may be exchanged between a handset and a base unit, in accordance with the present invention.

FIG. 4 shows a cordless phone handset, in accordance with one embodiment of the present invention.

FIG. 5 shows a portion of a base unit memory device, which may include information for carrying out the present invention. FIG. 6A shows a flow diagram depicting the handset operation, in accordance with one embodiment of the present invention.

FIG. 6B shows a flow diagram depicting the line-reserve operation, in accordance with the present invention. FIG. 7 shows a flow diagram depiction the base unit operation, in accordance with the present invention.

FIG. 8A shows a simplified block diagram of a base unit, in accordance with the present invention.

FIG. 8B shows a simplified block diagram of a handset, in accordance with the present invention.

Description of a Preferred Embodiment

FIG. 2 illustrates a simplified graphical representation of a telepoint communications system 200. The system 200 includes base unit 201 and cordless handsets 210-220. The handsets 210-220 may be identical to the handset (101 ) shown in FIG. 1. Each of these handsets 210-220 may have private base units e.g., base unit 102, located elsewhere. When they are away from the coverage area of their private base unit 102, they may initiate calls through a public base unit 201 , via any of the phone lines 202-208 terminating at the base unit 201 , which phone lines, or wirelines, are further coupled to PSTN 206.

There is no predetermined pairing between wirelines 202- 208 attached to a public base unit 201 and cordless handsets 210-220. The base unit 201 may serve any cordless handsets (within its coverage area) wishing to initiate calls, up to the limit of the number of attached phone lines 202-208 on a first- come first-serve basis. While four wirelines 202-208 are shown, the public base unit 201 may terminate any number of phone lines. In the preferred embodiment, the contemplated base unit 201 can terminate any number from one to the maximum number of allowable radio frequency (RF) channels presently available for cordless phone use. Accommodating such a number of channels typically, involves including circuitry within the base unit 201 for each wireline- RF channel pair. Though the present invention is described using RF channels, it is anticipated that any type of communication schemes may be employed, including TDM, FDM, etc.

The base unit 201 makes its presence known to the handsets 210-220 within its coverage area, by periodically transmitting signals (e.g. signals 402-408 in FIG. 3, later described) on each RF channel assigned for that system. The signal on each RF channel includes the PSTN access number (or simply that portion which distinguishes it from the other wirelines for that system) of the associated wireline / RF channel pair. In the embodiment shown in FIG. 2, signal 400 shown in FIG.3 would be transmitted on each of the four RF channels from the base unit 201 , each channel identifying the phone number for its associated wireline 202-208.

The handsets 210-220 locate a base unit by scanning for these periodically transmitted signals 402-408 on base transmit channels, the particular frequency of which are preferably known by the handset, but which might be identified by scanning an entire frequency range. Upon finding a channel with these signals, the handset remains on that channel for as long as these signals remain present. Also, the handset temporarily saves the phone number contained within these messages.

FIG. 4 illustrates a cordless phone handset 300 which may employ the invention. The handset includes a speaker 302 and microphone 310, keypad 308, display 304, and function keys 306. In the preferred embodiment, one of the function keys 306 is provided to display the PSTN access number, while another is provided to select/de-seiect the line-reserve feature, as later described. Typical handset signals 412 are shown in FIG. 3, which signals convey control and voice data to the handset. Keypad 308 may be used to enter the digits of the desired phone number, which digits are also echoed on display 304 for the operator's feedback . When the user wants to know the phone number of the line being used by the^' base unit (during a call), the user depresses an appropriate function key 306. This causes the associated phone number of the phone line being utilized to be displayed on the handset display 304. (This number was received from the messages 402-408 transmitted by the base unit 201 , and which were received by the handset prior to the call initiation. The user may then announce the number to the called party.)

When the user wishes to- terminate the call, but reserve the base unit channel, an appropriate function key is activated on the handset 306. In^" the preferred embodiment, such a keystroke causes a different set of signals to be transmitted to the base unit 201 , which instructs., the base unit 201 to terminate the call, but continue transmitting on the channel 414. Line-reservation by the base unit 201 may remain active as long as the handset continues transmitting a reservation signal such as that shown in FIG. 3 (416). This may continue until one of several conditions occur. The user may explicitly cancel the line-reserve feature (hereafter "reservation") by activating an appropriate one of the function keys 306 on the handset 304. Also, the user may initiate a new call to the base unit 412, or answer a received call for which the line was reserved, either of which might automatically cancel the reservation. Further, the user might take the handset out of the range of the base unit, which may result in cancellation of the line-reserve feature. Additionally, in a preferred embodiment, the base unit may cancel the reservation after a predetermined time has elapsed, thereby preventing handset operators from abusing the privilege and reducing the number of available PSTN lines for other calls. FIG. 5 represents a portion of a memory device coupled to a microprocessor in the base unit, which components are later described, for a telepoint communications system having 100 wirelines and associated RF channels. The wireline identification (ID) is shown in field 502. The last 4 digits of the PSTN access number are shown in field 504 (the area code and exchange could, for example, be common for all; this information being stored in a separate memory device). Field 506 contains the RF channel frequency information (which may be represented by 25 kHz increments from a predetermined base frequency for that telepoint system, as shown). Field 508 contains the wireline status code in effect for the wireline identified in the accompanying memory location of field 502. These codes may be, for example, "B^M to represent a busy condition; "R" to represent a reserved condition; and "I" to represent an idle condition. Using the example shown in data base 500, the wireline having ID number 001 is in a "reserved" state, while the wireline having ID number 100 is in a "busy" state. The format of the status codes are not important; it is only important that they somehow distinguish between a busy, idle, or reserved wireline

FIG. 6A shows a simplified flow diagram 600 which depicts the handset operation for the telepoint system in accordance of one embodiment of the present invention. The operation begins when the handset scans (601) for an available channel. This operation may include a discrete frequency scan from a list of predetermined frequencies stored in the handset, or a spectral scan within a range of potential available frequencies for that telepoint system. The scan operation continues until an identified channel becomes available (603). Once a channel becomes available, the handset receives and saves (605) the PSTN access number for the wireline associated with the particular channel (e.g., automatically). The PSTN access number (P.A.N.) is sent in the outbound words for that RF channel, as later described. The handset then remains idle (607) until an outbound call is initiated by the handset operator. Once a call is initiated, the handset then displays (609) the saved PSTN access number and transmits the call in accordance with the signalling shown in FIG. 3. The handset then continues, in known fashion, until a call disconnect is detected (611), or the line-reserve feature is selected (617). If neither a call disconnect is detected (611), or the line-reserve function selected (617), transmission signalling continues, while displaying (609) the PSTN access number, as shown. Upon detection (611) of a call disconnect, the call is terminated (613) and the routine is exited (615).

When the line-reserve feature is selected (617), the handset transmits (621) a reservation signal and continues to monitor the RF channel. Though not described in detail below, the base unit responds to this request by changing the status of the wireline from busy ("B") to reserved ("R"). Once the channel is lost (623), the routine is exited (615). (Note: "lost" is defined, in a preferred embodiment, as a condition where the received signal strength (RSS) falls below a predetermined threshold for a predetermined amount of time, or some other unexpected failure of the system, or its related components). While the channel is still available, the handset looks for the line-reserve to be de¬ selected (625), e.g. invoked by a second function key on the handset. Once this feature is selected by the operator, the handset transmits a terminate reservation signal (629) before exiting the routine (615). Until the line-reserve feature is de¬ selected (625) the handset looks for an incoming call until one is detected (627). If an incoming call is not detected, the handset continues to transmit the reservation signal and monitor the assigned RF channel (621). Once an incoming call is detected, the handset rings (631), and the operator is given the option of answering the telephone (633). A ring timer is then initiated, which timer is set to a predetermined amount of time to prevent prolonged ringing of the handset. During this time, the handset continues to ring. (631), or in the alternative, the call may be transferred, e.g., to another predetermined wireline or handset. Once the handset is answered, or the timer expires, the handset is engaged in the call by transmitting the appropriate signals to the base unit (609), and continues in the same manner as if the call was initiated by the handset operator.

FIG. 7 shows a simplified flow diagram (700) depicting the base unit operation corresponding to a specific radio frequency (RF) channel, and its associated PSTN wireline. It is assumed that the logic flow described herein with respect to one RF channel is substantially replicated for each RF channel in the system. The routine begins, initially, with the channel status of the associated wireline (e.g., from data base 500) being in the "idle" state. The base unit men scans (702) its corresponding RF channel frequency for a handset transmission. During this scanning period, the base unit transmits messages (e.g., periodically) identifying the channel state as being idle, and containing the associated, PSTN access number (PAN) of the corresponding wireline. In a preferred embodiment, the PAN is determined by accessing the database 500 (i.e., field 504 in FIG.

5).

If a call from the handset is detected (704), the base unit determines (708) whether or not the associated wireline is available. This is accomplished by retrieving a portion of the data base 500 shown in FIG. 5 (field 508 containing the status code of the associated wireline). If the wireline is not available (i.e., field 508 has a status code other than "I"), the base unit issues (710) a busy signal on the channel attempting to make the call. If the wireline is available, the base unit updates (712) the billing file, which may be held in a data base separate from data base 500. The base unit then updates (716) the wireline status code to a busy state ("B"), such as that entered in field 508 for wireline ID number 002, shown in FIG. 5. The call is then patched (718), i.e., a connection is made between the RF section of the base unit and the PSTN wireline by the base unit, via a PSTN interface, as later described. The call continues until a disconnect or reservation-end signal has been received (720). Upon receipt of a disconnect or reservation-end signal, the base unit updates the status code for the wireline, as appropriate (i.e., alters the state from "R" to "I" if reservation-end is received, or if handset goes out of range). The base unit then terminates the current call (722) and the routine is exited (726).

Returning to the point where the base unit looks for a handset call (704), if no handset call is received, the base unit then checks for an call from the PSTN (706). If the received signal does not indicate an PSTN call, the base unit continues to scan the RF channel (702). If a PSTN call is detected, i.e., the associated wireline receives a call-ringing signal, the base unit determines whether or not that particular wireline has been reserved (714) by any of the handsets in the system. That is, the base unit retrieves the status code (field 508) for the particular wireline holding the PSTN call, and looks for a status code of "R". If that particular wireline has been reserved, the wireline status is updated (716) to a busy state, ("B") just as in the case of the handset call. From this point, the call is processed in an identical manner as in the case of the outbound call. If the wireline has not been reserved, i.e., status code is "I" or "B", then the base unit ignores the ringing signal on the wireline (724), and the routine is exited (726).

FIG. 8A shows a simplified block diagram of a base unit 800 which may be used to employ the present invention. The base unit 800 includes an antenna 801 for transmitting/receiving communication signals to/from the handset, which handset is later described. The base unit 800 further includes transmit circuitry 803, receive circuitry 805, memory device 807, and digital processor 811. Lastly, the base unit 800 might include a PSTN interface to couple the RF section (803, 805) to PSTN wirelines 813. FIG. 8B shows a simplified block diagram of a handset 850 which may employ the present invention. The handset includes an antenna 815 for transmitting/receiving communication signals to/from the base unit 800. Further, each handset includes transmit circuitry 817, receive circuitry 819, memory device 825, keypad 829, display device 831 , and digital processor 827.

Lastly the handset includes a microphone 821 , and a speaker 823.

To understand the operation of the base unit 800 and the handset 850, consider a telephone call originating from the handset 850 out to a PSTN wireline, in accordance with the flow diagram of FIGs. 6A and 7. Upon switching on the handset 850, the receive circuitry 819, in concert with antenna 815, attempt to acquire an RF channel which is available for communication. If an RF channel is not available within a predetermined time, or there are no available wirelines, the handset might, for example, emit a busy tone. If a channel is available, the handset might, for example, illuminate an indicator light to show the operator that the phone is ready for use. The call may be initiated by pressing a sequence of keys on keypad 829, which sequence is processed in processor 827. In the alternative, a telephone number may be retrieved from memory device 825, and processed in a similar manner. Once the telephone number has been entered, the transmit circuitry 817 transmits the appropriate signals via antenna 815, which signals are received by the antenna 801 of the base unit 800. The receiver circuitry 805 of the base unit 800 then demodulates the transmitted information and presents it to the PSTN interface 809. If these are voice signals, the signals are simply passed on to the appropriate PSTN wireline 813 associated with the RF channel transmitting the data. If the information includes a line-reservation signal, telephone number, or other predetermined feature sequence, the processor 811 processes the information, and may use memory 807 to do so. The response communication signals from the landline telephone are then transmitted via the wireline 813, passed on through the PSTN interface 809, and transmitted via transmit circuitry 803 and antenna 801. The signals are then received at the handset 850 using antenna 815 and receive circuitry 819. The signals are then passed on to the speaker 823 which emits the voice of the landline party. In the preferred embodiment of the present invention, data base 500 shown in FIG. 5 may be stored in memory device 807 of the base unit 800. Similarly, line-reserve (e.g., select and de¬ select) function keys would be included on the keypad 829 of the base unit 850. Lastly, the PSTN access number could be displayed using display device 831 on the handset 850. The foregoing scenario and implementations, merely represent one particular embodiment of the present invention.

What is claimed is:

Claims

1 ) In a telepoint communications system which includes a base unit and at least one handset, the base unit being coupled to a public switched telephone network (PSTN) via at least one wireline, the base unit further communicating with the at least one handset via at least one radio frequency (RF) channel, each wireline being associated with one of the- RF channels and having at least two service states, a method of selectively changing the service state of a first wireline, the method comprising the steps of:

at the handset: receiving, from the base unit, a PSTN access number corresponding to the first wireline, via a first RF channel, said first RF channel being coupled to the first wireline;

signalling, to the base unit via said first RF channel, a service request for the first wireline;

at the base unit; receiving said service request; and

altering, responsive to said step of receiving, the service state of the first wireline from a first state to a second state.

2) A method in accordance with claim 1 , further comprising the step of, at the handset, searching a set of RF channels until said first RF channel is identified.

3) A method in accordance with claim 2, wherein said step of searching further comprises the step of scanning a predetermined list of RF channel frequencies.

4) A method in accordance with claim 1 , wherein said step of altering further comprises the step of changing the service state from a busy state to a reserved state.

5) A method in accordance with claim 1, wherein said step of altering further comprises the step of changing the service state from a reserved state to an idle state.

6) A method in accordance with claim 1 , wherein said step of altering further comprises the step of changing the service state from a reserved state to a busy state.

7) In a handset used in a telepoint communications system which includes a base unit coupled to a PSTN via at least one wireline, the base unit further communicating with the handset via at least one RF channel, each RF channel being associated with one of the wirelines, each of the wirelines having at least two service states, a method of selectively reserving a first wireline, the method comprising the steps of:

searching a set of RF channels until a first RF channel, associated with the first wireline, is identified;

receiving, from the base unit, a PSTN access number corresponding to the first wireline; and

signalling, to the base unit, a first service request to reserve the first wireline.

8) A method in accordance with claim 7, further comprising the step of initiating a communication on said first RF channel.

9) A method in accordance with claim 7, wherein said step of searching further comprises the step of scanning a predetermined list of RF channels.

10) A method in accordance with claim 7, further comprising the step of signalling, to the base unit, a second service request to relinquish said reserved wireline.