Single frequency network (SFN) for broadcast/multicast application on a spotbeam satellite
Systems and methods operating a spotbeam satellite network to provide single frequency network broadcast and multicast services. One example embodiment provides a satellite broadcast system. The system includes an electronic processor communicatively coupled to a satellite and a user equipment. The electronic processor is configured to receive a plurality of bearer signals, each bearing identical broadcast program information. The electronic processor is configured to, for each of the plurality of bearer signals, generate one of a plurality of spotbeams for transmission by the satellite within a coverage area. The user equipment is configured to receive the bearer signals from a plurality of adjacent spotbeams of the plurality of spotbeams. The user equipment is configured to constructively utilize the bearer signals received from the plurality of adjacent spotbeams to decode the program information.
1. A method for operating a satellite network to broadcast a plurality of spotbeams within a coverage area, the method comprising:
receiving, with a user equipment, bearer signals from a plurality of adjacent spotbeams of the plurality of spotbeams, wherein each of the plurality of spotbeams carries a bearer signal bearing identical broadcast program information; and
constructively utilizing, with the user equipment, the bearer signals received from the plurality of adjacent spotbeams to decode the identical broadcast program information;
wherein the bearer signals transmitted in each spotbeam of the plurality of adjacent spotbeams are transmitted with a differential delay with respect to the bearer signals of each of the other spotbeams of the plurality of adjacent spotbeams, and
wherein the choice of the differential delay is optimized relative to constraints that include at least one selected from a group consisting of: a maximization of a received signal to noise and interference ratio; a minimization of user equipment implementation complexity; and a minimization of difference from existing terrestrial broadcast/multicast standards.
2. The method of claim 1 , wherein
the plurality of adjacent spotbeams are part of a cluster of adjacent spotbeams; and
the bearer signals transmitted in each spotbeam of the cluster are transmitted with a differential delay with respect to the bearer signals of each of the other spotbeams of the cluster.
3. The method of claim 2 , wherein the differential delay of the bearer signals for each pair of beams within the cluster is unique throughout the coverage area.
4. The method of claim 2 , wherein
each differential delay within a set of differential delays for the cluster is unique within the cluster;
the plurality of spotbeams comprises the cluster and a second cluster; and
the plurality of spotbeams of the second cluster are transmitted using a second set of differential delays, which are identical to the set of differential delays for the cluster.
5. The method of claim 2 , wherein a quantity of spotbeams making up the cluster is dependent on a spatial selectivity of the plurality of spotbeams.
6. The method of claim 5 , where a criterion for including a spotbeam in the cluster is that including the spotbeam would cause at least a 1 dB increase in a signal-to-noise-and-interference ratio at the user equipment.
7. The method of claim 2 , where the differential delay are introduced in a ground-based beam former.
8. The method of claim 1 , wherein constructively utilizing the bearer signals includes introducing frequency redundancy in a transmitted signal such that demodulation with acceptable quality is possible even when the received signal amplitudes are relatively low in certain segments of a frequency band of the transmitted signal.
9. The method of claim 8 , wherein the frequency redundancy is introduced by frequency hopping across the transmitted signal bandwidth resource blocks carrying segments of the transmitted information stream and applying error correction to recover the resource blocks containing errors.
10. A satellite broadcast system, the system comprising:
an electronic processor communicatively coupled to a satellite and configured to
receive a plurality of bearer signals, each bearing identical broadcast program information;
for each of the plurality of bearer signals, generate one of a plurality of spotbeams for transmission by the satellite within a coverage area; and
introduce into a bearer signal of each spotbeam of the plurality of spotbeams a differential delay with respect to a bearer signal of each of the other spotbeams of the plurality of spotbeams, wherein the differential delays are determined relative to constraints that include at least one selected from a group consisting of: a maximization of a received signal to noise and interference ratio; a minimization of user equipment implementation complexity; and a minimization of difference from existing terrestrial broadcast/multicast standards; and
a user equipment configured to
receive the plurality of bearer signals from a plurality of adjacent spotbeams of the plurality of spotbeams; and
constructively utilize the plurality of bearer signals received from the plurality of adjacent spotbeams to decode the identical broadcast program information.
11. The system of claim 10 , wherein
the plurality of adjacent spotbeams are part of a cluster of adjacent spotbeams; and
the electronic processor is further configured to introduce into a bearer signal of each spotbeam of the cluster a differential delay with respect to a bearer signal of each of the other spotbeams of the cluster.
12. The system of claim 11 , wherein the differential delay of the plurality of bearer signals for each pair of beams within the cluster is unique throughout the coverage area.
13. The system of claim 11 , wherein
each differential delay within a set of differential delays for the cluster is unique within the cluster;
the plurality of spotbeams comprises the cluster and a second cluster; and
the electronic processor is further configured to introduce into the plurality of spotbeams of the second cluster a second set of differential delays, which are identical to the set of differential delays for the cluster.
14. The system of claim 11 , wherein the electronic processor is further configured to determine the quantity of spotbeams making up the cluster based on a spatial selectivity of the plurality of spotbeams.
15. The system of claim 14 , wherein the electronic processor is further configured to include a spotbeam in the cluster when including the spotbeam would cause at least a 1 dB increase in the signal-to-noise-and-interference ratio at the user equipment.
16. The system of claim 11 , where the electronic processor is included in a ground-based beam former.
17. The system of claim 10 , wherein the user equipment is configured to constructively utilize the plurality of bearer signals by introducing frequency redundancy in a transmitted signal such that demodulation with acceptable quality is possible even when the received signal amplitudes are relatively low in certain segments of a frequency band of the transmitted signal.
18. The system of claim 17 , wherein the frequency redundancy is introduced by frequency hopping across the transmitted signal bandwidth resource blocks carrying segments of the transmitted information stream and applying error correction to recover the resource blocks containing errors.