Method for transmitting broadcast signals in a wireless communication system
A method for transmitting broadcast signals from a group of base stations to terminals of a wireless communication system. Each base station having a coverage area. The coverage areas of the base stations of the group are distributed geographically such as to serve a geographical area. Since the broadcast signals are of limited duration and are transmitted in a frequency band used by all of the base stations of the group, the base stations of the group are time-synchronized in relation to one another. The broadcast signals from the base stations of the group are time-multiplexed. In addition, the wireless communication system has multiple geographical regions. Each region includes multiple groups of base stations), and the broadcast signals of different geographical regions are time-multiplexed.
1. A method for transmitting broadcast signals by a group of base stations to terminals of a wireless communication system, each base station having a coverage zone, the coverage zones of said base stations of the group being geographically distributed so as to service a geographical zone, comprising steps of:
transmitting the broadcast signals in a same frequency band used by all the base stations of the group, the broadcast signals being of limited duration;
temporally synchronizing the base stations of the group with one another;
time-division multiplexing the broadcast signals of different base stations of the group;
wherein the wireless communication system comprises a plurality of geographical regions, each geographical region comprises a plurality of groups of base stations;
time-division multiplexing the broadcast signals of different geographical regions; and
wherein the time-division multiplexed broadcast signals are transmitted successively with no temporal overlap therebetween.
2. The method as claimed in claim 1 , further comprising step of organizing the plurality of groups of base stations of a geographical region into a plurality of respective different sets of base stations, the base stations of each group belonging to respective different sets, each set comprising a plurality of base stations belonging to respective different groups servicing respective different geographical zones; and wherein the base stations of the same set transmit the broadcast signals simultaneously.
3. The method as claimed in claim 2 , further comprising a step of geographically distributing the base stations so that adjacent base stations of different groups belong to different sets.
4. The method as claimed in claim 1 , wherein broadcast signal transmission times are predefined universal time coordinate times.
5. The method as claimed in claim 1 , wherein the broadcast signals transmitted by a group of base stations have a frequency overlap.
6. The method as claimed in claim 1 , wherein the coverage zones of adjacent base stations of a group have a geographical overlap.
7. The method as claimed in claim 1 , further comprising a step of temporally grouping the broadcast signals of different geographical regions.
8. The method as claimed in claim 1 , further comprising step of transmitting the broadcast signals of the base stations of a group in accordance with a predefined time-division multiplexing pattern repeated in accordance with a predefined repetition pattern; and wherein the broadcast signals of the base stations comprise identifiers enabling the broadcast signals within the time-division multiplexing pattern to be distinguished.
9. The method as claimed in claim 8 , wherein the broadcast signals further comprise information enabling the time-division multiplexing patterns to be distinguished within the repetition pattern.
10. The method as claimed in claim 8 , wherein a duration of the time-division multiplexing pattern is at least ten times less than a minimum duration between two repetitions of the time-division multiplexing pattern.
11. An access network of a wireless communication system, the access network comprising base stations, each base station comprising a transmitter configured to transmit broadcast signals to terminals of the wireless communication system, each base station having a coverage zone, the coverage zones of the base stations within a group being geographically distributed so as to service a geographical zone, wherein:
within the group, each base station is configured to transmit the broadcast signals in a same frequency band used by all the base stations of the group, the broadcast signals being of limited duration;
within the group, all the base stations are temporally synchronized with one another;
the broadcast signals of different base stations within the group are time-division multiplexed;
the access network comprises different geographical regions, each geographical region comprising a plurality of groups of base stations, and the broadcast signals of different geographical regions are time-division multiplexed; and
wherein time-division multiplexed broadcast signals are transmitted successively with no temporal overlap between said broadcast signals.
12. The access network as claimed in claim 11 , wherein some or all of the base stations are of half duplex type.