Digital communications system

• US 20030109253A1
• Filed: 10/07/2002
• Published: 06/12/2003
• Est. Priority Date: 01/18/2000
• Status: Active Grant

• Current Assignee: Motorola Solutions, Inc.
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Phillips, Christopher Frank, Fenton, Shaun Richard
• Granted Patent: US 7,499,707 B2
• Time in Patent Office: Days
• US Class Current: 455/422.1
• CPC Class Codes: H04B 7/2621 using frequency division multiple access [FDMA] H04B7/2615 takes precedence

Abstract

In FDMA communications between two or more primary radios (41, 42; 141, 142), use is made of a quiescent period in the primary communication. The quiescent period is used by secondary radios (43, 44; 143, 144) to communicate with each other. The quiescent period may be a transmit interrupt (TI) frame, normally provided in a DIIS protocol in order to permit return signalling from a called radio (43, 44). The secondary radios (43, 44) may signal to each other during the TI frame. Alternatively, the quiescent period may be a gap in channel activity, in which case regulated access telegrams (96) are transmitted by either a calling primary device (141), or a “last to call” primary device (141), or a base station (141), the regulated access telegrams determining a reservation window period during which secondary devices (143, 144) may signal to one another.

Claims

1. A method of performing Frequency Division Multiplex Access (FDMA) communications including the steps of arranging two or more primary devices (41, 42;

141, 142) to be in two-way primary communication with one another over a signal channel, and performing two-way signalling communication over said channel between two or more secondary devices (43, 44;

143, 144) not involved in same primary communication, utilising a quiescent period (32;

97) in said primary communication.

2. A method as claimed in claim 1, wherein DIIS protocol is used having at least two signalling frames (32) each interleaved between payload frames (31) and each said signalling frame (TI frame) is used as said quiescent period.

3. A method as claimed in claim 1 or 2, wherein:

a first secondary device (43) transmits a signal in one signalling frame to a second secondary device (44);

said second secondary device transmits an acknowledgement signal to said first secondary device in a subsequent signalling frame; and

if said first secondary device does not receive said acknowledgement signal within a predetermined time then said first secondary device re-transmits said signal in another signalling frame until said acknowledgement signal is received by said first secondary device or until said signal has been transmitted by said first secondary device a predetermined maximum number of times.

4. A method as claimed in claim 1 or 2, wherein a first secondary device (43) transmits a signal a predetermined number of times in different signalling frames to a second secondary device (44).

5. A method as claimed in claim 3 or 4, wherein the signal transmitted by said first secondary device and the acknowledgement signal transmitted by said second secondary device are each one slot in length and said signalling frame is two slots in length.

6. A method as claimed in claim 5, wherein said slot is 20 ms in length.

7. A method as claimed in claim 1, wherein said quiescent period is a gap in channel activity and regulated access telegrams (96) are transmitted in said gap by one of a calling primary device, a last to call primary device, and a base station for substantially determining a reservation window period for said secondary devices to signal to one another.

8. A method as claimed in claim 7, wherein a calling secondary device (43) determines that the reservation window period is either sufficiently long to enable completion of signalling between secondary devices or that said signalling will be completed within a predetermined maximum time after said reservation window.

9. A system performing Frequency Division Multiplex Access (FDMA) communications including two or more primary devices (41, 42;

141, 142) arranged to be in two-way primary communication with one another over a signal channel, and two or more secondary devices (43, 44;

143, 144), not involved in said primary communication, having means arranged to utilise a quiescent period (32;

97) in said primary communication.

10. A system as claimed in claim 9, wherein a DIIS protocol is used having at least two signalling frames (32), each interleaved between payload frames (31) and each said signalling frame is used as said quiescent period.

11. A system as claimed in claim 9 or 10, wherein:

a first secondary device (43) has means for transmitting a signal in one signalling frame to a second secondary device (44);

said second secondary device has means for transmitting an acknowledgement signal to said first secondary device in a subsequent signalling frame; and

if said first secondary device does not receive said acknowledgement signal within a predetermined time, then said first secondary device means for transmitting is arranged to re-transmit said signal in another signalling frame until said acknowledgement signal is received by said first secondary device or until said signal has been transmitted by said first secondary device a predetermined maximum number of times.

12. A system as claimed in claim 9 or 10, wherein a first secondary device (43) has means for transmitting a signal a predetermined number of times in different signalling frames to a second secondary device (44).

13. A system as claimed in any of claims 9-12, wherein the signal transmitted by the first secondary device and the acknowledgement signal transmitted by the second secondary device are each one slot in length and said signalling frame is two slots in length.

14. A system as claimed in claim 9, wherein said quiescent period is a gap in channel activity and one of a calling primary device, a last to call primary device, and a base station are arranged to transmit regulated access telegrams in said gap, whereby said regulated access telegram determines a reservation window period for said secondary devices to signal to one another.

15. A system as claimed in any of claims 9-14, wherein a calling secondary device has means for determining that the reservation window period is either sufficiently long to enable completion of signalling between secondary devices or that said signalling will be completed within a predetermined time after said reservation window.