OFDMA with adaptive subcarrier-cluster configuration and selective loading
A method and apparatus for allocating subcarriers in an orthogonal frequency division multiple access (OFDMA) system is described. In one embodiment, the method comprises allocating at least one diversity cluster of subcarriers to a first subscriber and allocating at least one coherence cluster to a second subscriber.
1. A method, comprising:
transmitting, at a first time by a base station, at least a first pilot symbol to a subscriber unit for measuring the at least a first pilot symbol and obtaining first channel and interference information for a plurality of orthogonal frequency division multiple access (OFDMA) subcarriers;
receiving, by the base station from the subscriber unit, after the transmitting of the at least first pilot symbol to the subscriber unit, first feedback of channel and interference information relating to at least one subset of OFDMA subcarriers of the plurality of OFDMA subcarriers, the receiving of the first feedback of channel and interference information includes receiving a first indication of a modulation and coding rate associated with a first OFDMA subcarrier of the at least one subset of OFDMA subcarriers of the plurality of OFDMA subcarriers and a second indication of a modulation and coding rate associated with a second OFDMA subcarrier of the at least one subset of OFDMA subcarriers of the plurality of OFDMA subcarriers;
transmitting, by the base station to the subscriber unit, a first allocation of OFDMA subcarriers of the plurality of OFDMA subcarriers selected by the base station for use by the subscriber unit, after, and based on at least the receiving of the first feedback of channel and interference information;
transmitting, at a second time after the first time, by the base station, at least a second pilot symbol to the subscriber unit for measuring the at least second pilot symbol and obtaining second channel and interference information for the plurality of OFDMA subcarriers;
receiving, by the base station from the subscriber unit, after the transmitting of the at least second pilot symbol to the subscriber unit, second feedback of channel and interference information relating to the at least one subset of OFDMA subcarriers of the plurality of OFDMA subcarriers, the receiving of the second feedback of channel and interference information includes receiving a third indication of a modulation and coding rate associated with the first OFDMA subcarrier of the at least one subset of OFDMA subcarriers of the plurality of OFDMA subcarriers and a fourth indication of a modulation and coding rate associated with the second OFDMA subcarrier of the at least one subset of OFDMA subcarriers of the plurality of OFDMA subcarriers; and
transmitting, by the base station to the subscriber unit, a second allocation of OFDMA subcarriers of the plurality of OFDMA subcarriers selected by the base station for use by the subscriber unit, after, and based on at least the receiving of the second feedback of channel and interference information.
2. The method of claim 1 , further comprising transmitting, by the base station to the subscriber unit, a retraining request, the second feedback of channel and interference information being received after the transmitting of the retraining request.
3. The method of claim 1 , wherein at least one OFDMA subcarrier of the first allocation of OFDMA subcarriers of the plurality of OFDMA subcarriers is non-contiguous with other OFDMA subcarriers of the first avocation of OFDMA subcarriers of the plurality of OFDMA subcarriers.
4. The method of claim 1 , wherein the first, second, third, and fourth indications of modulation and coding rates associated with the first and second OFDMA subcarriers of the at least one subset of OFDMA subcarriers of the plurality of OFDMA subcarriers include a signal-to-interference-plus-noise ratio (SINR) index.
5. The method of claim 1 , wherein the receiving of the first feedback of channel and interference information and the second feedback of channel and interference information from the subscriber unit occurs on all OFDMA subcarriers of the plurality of OFDMA subcarriers.
6. The method of claim 1 , wherein the second allocation of OFDMA subcarriers of the plurality of OFDMA subcarriers is different from the first allocation of OFDMA subcarriers of the plurality of OFDMA subcarriers.
7. The method of claim 1 , wherein each of the first and second pilot symbols occupies an entire orthogonal frequency division multiplexing (OFDM) frequency bandwidth.
8. A base station, comprising:
a transceiver configured to:
transmit, at a first time, at least a first pilot symbol to a subscriber unit for measuring the at least a first pilot symbol and obtaining first channel and interference information for a plurality of orthogonal frequency division multiple access (OFDMA) subcarriers;
receive, from the subscriber unit, after the transmitting of the at least first pilot symbol to the subscriber unit, first feedback of channel and interference information relating to at least one subset of OFDMA subcarriers of the plurality of OFDMA subcarriers, the receiving of the first feedback of channel and interference information includes receiving a first indication of a modulation and coding rate associated with a first OFDMA subcarrier of the at least one subset of OFDMA subcarriers of the plurality of OFDMA subcarriers and a second indication of a modulation and coding rate associated with a second OFDMA subcarrier of the at least one subset of OFDMA subcarriers of the plurality of OFDMA subcarriers;
transmit, to the subscriber unit, a first allocation of OFDMA subcarriers of the plurality of OFDMA subcarriers selected by the base station for use by the subscriber unit, after, and based on at least the receipt of the first feedback of channel and interference information;
transmit, at a second time after the first time, at least a second pilot symbol to the subscriber unit for measuring the at least second pilot symbol and obtaining second channel and interference information for the plurality of OFDMA subcarriers;
receive, from the subscriber unit, after the transmission of the at least second pilot symbol to the subscriber unit, second feedback of channel and interference information relating to the at least one subset of OFDMA subcarriers of the plurality of OFDMA subcarriers, the receipt of the second feedback of channel and interference information includes receiving a third indication of a modulation and coding rate associated with the first OFDMA subcarrier of the at least one subset of OFDMA subcarriers of the plurality of OFDMA subcarriers and a fourth indication of a modulation and coding rate associated with the second subcarrier of the at least one subset of OFDMA subcarriers of the plurality of OFDMA subcarriers: and
transmit, to the subscriber unit, a second allocation of OFDMA subcarriers of the plurality of OFDMA subcarriers selected by the base station for use by the subscriber unit, after, and based on at least the receipt of the second feedback of channel and interference information.
9. The base station of claim 8 , wherein the transceiver is further configured to transmit, to the subscriber unit, a retraining request, the receipt of the second feedback of channel and interference information occurring after the transmission of the retraining request.
10. The base station of claim 8 , wherein at least one OFDMA subcarrier of the first allocation of OFDMA subcarriers of the plurality of OFDMA subcarriers is non-contiguous with other OFDMA subcarriers of the first allocation of OFDMA subcarriers of the plurality of OFDMA subcarriers.
11. The base station of claim 8 , wherein the first, second, third, and fourth indications of modulation and coding rates associated with the first and second OFDMA subcarriers of the at least one subset of OFDMA subcarriers of the plurality of OFDMA subcarriers include a signal-to-interference-plus-noise ratio (SINR) index.
12. The base station of claim 8 , wherein the receipt of the first feedback of channel and interference information and the second feedback of channel and interference information from the subscriber unit occurs on all OFDMA subcarriers of the plurality of OFDMA subcarriers.
13. The base station of claim 8 , wherein the second allocation of OFDMA subcarriers of the plurality of OFDMA subcarriers is different from the first allocation of OFDMA subcarriers of the plurality of OFDMA subcarriers.
14. The base station of claim 8 , wherein each of the first and second pilot symbols occupies an entire orthogonal frequency division multiplexing (OFDM) frequency bandwidth.
15. A method for a wireless system employing orthogonal frequency division multiple access (OFDMA) at least on a downlink, the method comprising:
providing, at a first step by a base station, a first pilot symbol using a plurality of OFDMA subcarriers to a subscriber unit;
receiving, at a second step by the base station from the subscriber unit, first feedback information as to a plurality of dusters, each of which includes at least two OFDMA subcarriers of the plurality of OFDMA subcarriers;
providing, at a third step by the base station, first allocation information as to a first plurality of OFDMA subcarriers to the subscriber unit for use by the subscriber unit;
providing, at a fourth step by the base station, a second pilot symbol using a plurality of OFDMA subcarriers to the subscriber unit;
receiving, at a fifth step by the base station, from the subscriber unit, second feedback information as to the plurality of clusters;
providing, at a sixth step by the base station, second allocation information as to a second plurality of OFDMA subcarriers to the subscriber unit for use by the subscriber unit;
the first feedback information including indices relating to a first modulation and coding rate respectively for each cluster of the plurality of clusters; and
the second feedback information including indices relating to a second modulation and coding rate respectively for each duster of the plurality of dusters.
16. The method according to claim 15 , wherein each of the first and second feedback information is compressed using source coding techniques and encoded using error correcting codes.
17. The method according to claim 15 , wherein the first pilot symbol and the second pilot symbol cover an entire OFDM frequency bandwidth.
18. The method according to claim 15 , wherein the first allocation information is to show that the first plurality of OFDMA subcarriers are selected from at least one duster of the plurality of dusters upon which the first feedback information is received.
19. The method according to claim 15 , wherein the second allocation information is to show that the second plurality of OFDMA subcarriers are selected from at least one duster of the plurality of dusters upon which the second feedback information is received.
20. The method according to claim 15 , wherein the plurality of OFDMA subcarriers are selected from at least one duster with good performance relative to other dusters.
21. The method according to claim 15 , wherein the fifth step is initiated by the base station and based on a request provided by the base station.
22. The method according to claim 15 , wherein the fifth step is initiated by he base station as a part of a retraining process.
23. The method according to claim 15 , wherein the first feedback information is pertinent to first channel and interference information that the subscriber unit measures based on the first pilot symbol provided by the base station, and
wherein the second feedback information is pertinent to second channel and interference information that the subscriber unit measures based on the second pilot symbol provided by the base station.
24. A base station for a wireless system employing orthogonal frequency division multiple access (OFDMA) at least on a downlink, the base station comprising:
a processor configured to:
provide a first pilot symbol using a plurality of OFDMA subcarriers to a subscriber unit, at a first step;
receive, from the subscriber unit, first feedback information as to a plurality of dusters, each of which includes at least two OFDMA subcarriers of the plurality of OFDMA subcarriers, at a second step;
provide first allocation information as to a first plurality of OFDMA subcarriers to the subscriber unit for use by the subscriber unit, at a third step;
provide a second pilot symbol using a plurality of OFDMA subcarriers to the subscriber unit, at a fourth step;
receive, from the subscriber unit, second feedback information as to the plurality of dusters, at a fifth step;
provide second allocation information as to a second plurality of OFDMA subcarriers to the subscriber unit for use by the subscriber unit, at a sixth step;
the first feedback information including indices relating to a first modulation and coding rate respectively for each duster of the plurality of dusters; and
the second feedback information including indices relating to a second modulation and coding rate respectively for each cluster of the plurality of clusters.
25. The base station according to claim 24 , wherein each of the first and second feedback information is compressed using source coding techniques and encoded using error correcting codes.
26. The base station according to claim 24 , wherein the first pilot symbol and the second pilot symbol cover an entire OFDM frequency bandwidth.
27. The base station according to claim 24 , wherein the first allocation information is to show that the first plurality of OFDMA subcarriers are selected from at least one duster of the plurality of dusters upon which the first feedback information is received.
28. The base station according to claim 24 , wherein the second allocation information is to show that the second plurality of OFDMA subcarriers are selected from at least one duster upon which the second feedback information is received.
29. The base station according to claim 24 , wherein the plurality of OFDMA subcarriers are selected from at least one duster with good performance relative to other dusters.
30. The base station according to claim 24 , wherein the fifth step is initiated by the base station and based on a request provided by the base station.
31. The base station according to claim 24 , wherein the fifth step is initiated by the base station as a part of a retraining process.
32. The base station according to claim 24 , wherein the first feedback information is pertinent to first channel and interference information that the subscriber unit measures based on the first pilot symbol provided by the base station, and
wherein the second feedback information is pertinent to second channel and interference information that the subscriber unit measures based on the second pilot symbol provided by the base station.