Apparatus for communicating with a fleet of vehicles

• US 4,414,661 A
• Filed: 07/02/1981
• Issued: 11/08/1983
• Est. Priority Date: 07/02/1981
• Status: Expired due to Fees

• Current Assignee: Transcom AB
• Original Assignee: Transcom AB
• Inventors: Karlstrom, Krister
• Primary Examiner(s): Olms, Douglas W.
• Application Number:
  US06/279,837
• Time in Patent Office: 859 Days
• Field of Search: 370/95, 370/85, 370/100, 370/104, 370/91, 370/110.1, 370/111, 179/2 EB, 455/33
• US Class Current: 370/332
• CPC Class Codes: H04W 56/0025 synchronizing potentially movable access points
• CPC Class Codes: H04W 74/0833 Random access procedures, e.g. with 4-step access
• CPC Class Codes: H04W 92/045 between access point and backbone network device

Abstract

A communication system is disclosed wherein plural base stations each communicate with plural associated mobile stations in a variable but well disciplined single channel time division multiplexing arrangement. Each base station communicates to and from its associated mobile stations in an associated unitary communication cycle having time segments of variable size but allotted for specific purposes. The mobile stations include clocks which are all periodically synchronized by the base station. The base station transmits cycle timing information at the beginning of each cycle so that the mobiles can determine by referring to their clocks when the various cycle segments begin and end. The number of mobile stations participating in a communication cycle with a given base station can vary as the mobiles move from the service area of one base station to the next. A particular time segment of each cycle is allocated for use by nonparticipating mobiles to transmit requests for participation in the cycles of the associated base station. The mobiles wait a random delay before transmitting their requests in order to reduce the danger of interfering transmissions of two mobiles both requesting participation in the same segment. A central traffic control center mediates the operation of the system, causing the communication cycles of adjacent base stations to occur sequentially rather than concurrently to avoid interference.

Claims

1. Apparatus for use with a fleet vehicle adapted to participate in a single frequency time division multiplexed communications systems wherein each of plural participating vehicles communicates data to a central station in a respective assigned time slot of a multiple time slot, cyclically recurring communication cycle, wherein said central station transmits synchronizing information in a predetermined time slot of each communication cycle, and wherein requests by nonparticipating fleet vehicles for participation in the communication system are communicated to the central station during another predefined time slot in the communication cycle, said apparatus comprising clock means for measuring time intervals to identifying the time slots associated with said cyclically recurring communication cycle, transceiver means for receiving said synchronizing information from said central station, means for synchronizing said clock means to said cycle in accordance with said synchronizing information, and control means responsive to said clock means and actuatable to initiate participation in said communication cycle by causing said transceiver means to transmit a request for participation in said cycle to said central station a random period after the beginning of the time slot in which said requests are to be communicated, wherein said random delay has a maximum duration which is no greater than the length of said time slot.

2. Apparatus as set forth in claim 1, wherein said control means is responsive to time slot allocation signals transmitted by said central station for thereafter causing said transceiver means to transmit standard information to said central station during its assigned time slot.

3. Apparatus as set forth in claim 2, wherein said control means causes said transceiver means to transmit said standard information to said central station only when there is a change in said information or when no other transmission has been made to said central station by that vehicle for more than a preset time period, said preset time period being substantially greater than the time from the beginning of one of said communication cycles to the beginning of the next succeeding cycle.

4. Apparatus as set forth in claim 1, wherein said control means comprises a computer programmed to control said transceiver means in accordance with timing signals provided by said clock means.

5. Apparatus as set forth in claim 1, wherein there are plural geographically spaced said central stations, each transmitting and receiving on the same frequency but in communication cycles which are spaced in time so as to be nonoverlapping, and wherein said control means includes means for automatically determining when communication with its respective central station is degraded and for then automatically requesting participation in the communication cycle of a different said central station.

6. Apparatus for communicating information between a central station and plural fleet vehicles, comprising

first communications means associated with a central station, said first communications means including a master clock, transceiver means for receiving and transmitting signals over a single frequency channel, and control means responsive to said master clock for controlling said transceiver means to establish a cyclically recurring communication cycle between said central station and said fleet vehicles, said control means causing said transceiver means to transmit synchronizing information to said fleet vehicles in first periodically occurring time slots of said communication cycle for synchronizing their operation to said communication cycle, and to receive standard information from said fleet vehicles in second periodically occurring time slots, wherein each fleet vehicle participating in said communication cycle is assigned a respective one of said time slots and wherein nonparticipating fleet vehicles request assignment of a said second time slot by transmitting a request for one of said second time slots in a third said time slot allocated for that purpose, said control means being responsive to time slot allocation requests received in said third time slots for assigning one of said second time slots to said requesting fleet vehicles and for transmitting information identifying said assigned time slots to said requesting fleet vehicles, and

a plurality of second communications means, each associated with a respective one of said fleet vehicles, each said second means including transceiver means, clock means for identifying the time slots of said cyclically recurring communication cycle, means for receiving said synchronizing information from said central station and for synchronizing said clock means to said cycle in accordance with said synchronizing information, and control means responsive to said clock means for, when seeking participation in said cycle, causing a request for participation to be transmitted a random delay after the beginning of said third time slot, said control means being respective to information transmitted from said central station which identifies the time slot assigned to said fleet vehicle for thereafter causing said transceiver means to transmit said standard data during its assigned time slot of said communication cycle.

7. Apparatus as set forth in claim 6, wherein there are plural said first communications means each associated with a respective one of plural geographically spaced said central stations, wherein said plural first means all operate on the same frequency channel, and wherein means are provided for controlling the cycle timing of said plural first communications means such that none of the said time slots associated with one of said central stations overlaps any time slots of a geographically adjacent central station.

8. Apparatus as set forth in claim 7 wherein each said second communications means includes means for determining when communication between it and the central station with which it is communicating has become degraded, and for then requesting participation in the communication cycle of a different said central station.