Communication system

• US 4,862,453 A
• Filed: 10/02/1987
• Issued: 08/29/1989
• Est. Priority Date: 10/03/1986
• Status: Expired due to Fees

• Current Assignee: Gec-Marconi Limited The Grove Warren Lane Stanmore Middlesex HA7 4LY England
• Original Assignee: Marconi Holdings Company Limited
• Inventors: Tolfree, Roger K., Sosin, Boleslaw M., West, Barry G.
• Primary Examiner(s): NOT, DEFINED
• Assistant Examiner(s): Scutch, III, Frank M.
• Application Number:
  US07/103,744
• Time in Patent Office: 697 Days
• Field of Search: 370/100, 370/110.1, 370/111, 370/95, 370/93, 370/79, 370/82, 370/83, 455/33, 455/56, 375/111, 375/121
• US Class Current: 370/314
• CPC Class Codes: H04W 28/06 Optimizing the usage of the radio link, e.g. header compression, information sizing , discarding information system modifying transmission characteristic according to link quality by modifying frame length H04L1/0007; dynamic adaptation of the packet size for flow control or congestion control H04L47/365
• CPC Class Codes: H04W 56/00 Synchronisation arrangements
• CPC Class Codes: H04W 74/04 Scheduled access hybrid access H04W74/02

Abstract

In a dynamic frame length slotted ALOHA system the synchronizing signals are transmitted by a base station at different frequencies (each having a period equivalent to a multiple of the time slot period). The different frequencies denote different frame lengths and the central stations detect these frequencies and select a frame length accordingly.

Claims

1. A communication system comprising:

a central station (1) having means (5,3) for transmitting synchronizing signals each defining the beginning of a time slot and means (4) for selecting the intervals between synchronising signals from different integral multiples of a time slot and for providing to said transmitting means signals corresponding to said intervals; and

a number of sub-stations (6,61) each having means (10,11,12) which is responsive to the timing of the synchronising signals and which is operative to transmit a message in a time slot selected from a number of time slots together forming a frame, the duration of said frame being determined by said synchronizing signals.

2. A communication system according to claim 1 in which the means responsive to the timing of the synchronising signal measures a time interval between two adjacent synchronising signals.

3. A communication system according to claim 2 in which the said number of time slots defines a "frame" of a length which is different from the said time interval.

4. A central station for a communication system which also includes a number of sub-stations, the central station comprising means for transmitting to each sub-station synchronising signals each defining the beginning of a time slot and means, responsive to the observed occupancy of time slots by signals received from the sub-stations, for selecting, in accordance with a predetermined algorithm, the intervals between the synchronising signals from different multiples of a time slot and for transmitting signals corresponding to said intervals to said transmitting means.

5. A sub-station for a communications system which comprises a central station according to claim 4 and at least one other sub-station, the sub-station comprising means which is responsive to the timing of synchronising signals received from the central station to determine the number of equal-length time slots to be allocated to a variable-length frame, and which is operative to transmit a message to the central station within a time slot selected from the frame.

6. A sub-station according to claim 5 in which the means responsive to the timing of the synchronising signal measures a time interval between two adjacent synchronising signals.

7. A sub-station according to claim 6 in which the said number of time slots defines a "frame" of a length which is different from the said time interval.