Method and apparatus providing decentralized, goal-orientated adaptive learning in an adaptive orthogonal frequency division multiplex communication system

• US 20050128935A1
• Filed: 12/10/2003
• Published: 06/16/2005
• Est. Priority Date: 12/10/2003
• Status: Active Grant

• Current Assignee: Conversant Wireless Licensing S.à.r.l. (f/k/a Core Wireless Licensing S.a.r.l.) (MOSAID Technologies Inc. (f/k/a Conversant Intellectual Property Management))
• Original Assignee: Nokia Corporation
• Inventors: Stolpman, Victor J., Tang, Clive K.
• Granted Patent: US 7,016,297 B2
• Time in Patent Office: Days
• US Class Current: 370/208
• CPC Class Codes: H04L 1/0003 by switching between different modulation schemes
• CPC Class Codes: H04L 1/0009 by adapting the channel coding H04L1/1812 takes precedence
• CPC Class Codes: H04L 1/0021 in which the algorithm uses adaptive thresholds
• CPC Class Codes: H04L 27/2601 Multicarrier modulation systems

Abstract

Disclosed is an OFDM communications system and a method of operating the OFDM communications system. The system includes an OFDM transmitter for transmitting data over a plurality of OFDM sub-channels, where the OFDM transmitter has a plurality of modulators of different types. The system further includes an OFDM receiver for receiving the data from the plurality of OFDM sub-channels, where the OFDM receiver has a plurality of corresponding demodulators of the different types. The system further includes, in accordance with this invention, an adaptive learning automata that contains a group or team of independent, decentralized automaton operating in accordance with a game theory-based approach. Each of the plurality of automaton are responsible for managing one MCS switching threshold value so as to maximize at least one selected performance criterion. The OFDM transmitter is responsive to the MCS switching thresholds for selecting an appropriate one or ones of said modulators for modulating the data for various ones of the sub-channels.

Claims

1. A method for operating an orthogonal frequency duplex multiplexing (OFDM) communications system, comprising:

when transmitting data over a plurality of OFDM sub-channels from an OFDM transmitter to an OFDM receiver through a channel,

operating a co-operative adaptive learning automata comprised of a plurality of automaton to adjust values of modulation coding scheme (MCS) switching thresholds so as to maximize at least one selected performance criterion;

based on the values of the switching thresholds, selecting a MCS and modulating data with the selected MCS; and

transmitting the modulated data over at least some of the sub-channels.

2. A method as in claim 1, further comprising:

receiving the data at the OFDM receiver; and

demodulating the received data using a demodulator that corresponds to the selected MCS.

3. A method as in claim 2, where the plurality of automata are located at the OFDM transmitter, and where feedback information that is indicative of the at least one selected performance criterion is signaled from the OFDM receiver to the OFDM transmitter, and where information indicative of the selected MCS is signaled from the OFDM transmitter to the OFDM receiver.

4. A method as in claim 2, where the plurality of automata are located at the OFDM receiver, and where information that is indicative of the selected MCS is signaled from the OFDM receiver to the OFDM transmitter.

5. A method as in claim 1, where the selected performance criterion comprises data throughput.

6. A method as in claim 1, where the OFDM communications system operates by loading a plurality of data packets across the plurality of sub-carriers so that the plurality of data packets are loaded into one OFDM symbol.

7. A method as in claim 1, where the OFDM communications system operates by loading each sub-carrier with a data packet so that each data packet is spread across a plurality of OFDM symbols.

8. A method as in claim 1, further comprising a step of initializing the automata by:

partitioning the switching thresholds into a pre-defined set of combinations to cover all or substantially all of a range of operating signal-to-noise ratios (SNRs);

assigning a particular switching threshold to a particular one of the plurality of automaton;

initializing an internal probability vector of each of the plurality of automaton such that the probabilities of choosing a particular action are the same;

mapping each particular action of each of the plurality of automaton to a unique switching threshold value; and

selecting an action at random.

9. A method as in claim 8, where for a mode 1 operation where the OFDM communications system operates by loading a plurality of data packets across the plurality of sub-carriers so that the plurality of data packets are loaded into one OFDM symbol, further comprising:

based on selected switching threshold values, determining what MCS to use in each of the sub-carriers, thereby determining how many data packets an OFDM symbol can carry;

loading the sub-carriers with the data packets;

transmitting the OFDM symbol from the OFDM transmitter;

receiving the OFDM symbol at the OFDM receiver and determining a packet error rate (PER) to determine data throughput (TP), TP=(1-PER)*PPS, where PPS=packets-per-symbol;

based on the data throughput, updating the internal probability vector of each automaton such that only if the selected action has resulted in good throughput performance the selection probability of the selected action is increased, thereby updating the switching threshold values;

in each of the plurality of automaton selecting another action at random using the updated automaton internal probability vector; and

at the next OFDM symbol, assigning MCSs to the sub-carriers according to the updated switching threshold values, loading new data packets to the sub-carriers accordingly, and transmitting the next OFDM symbol.

10. A method as in claim 8, where for a mode 2 operation where the OFDM communications system operates by loading each sub-carrier with a data packet so that each data packet is spread across a plurality of OFDM symbols, further comprising:

based on selected switching threshold values, determining what MCS to use in each of the sub-carriers, and loading each sub-carrier with a symbol from an assigned data packet;

transmitting a frame of OFDM symbols from the OFDM transmitter;

receiving the frame of OFDM symbols at the OFDM receiver and determining a packet error rate (PER) to determine data throughput (TP), TP=(1-PER)*PPF, where PPF=packets-per-frame, or TP=(1-PER)*PPS, where PPS=packets-per-symbol;

based on the data throughput, updating the internal probability vector of each automaton such that only if the selected action has resulted in good throughput performance the selection probability of the selected action is increased, thereby updating the switching threshold values;

in each of the plurality of automaton selecting another action at random using the updated automaton internal probability vector; and

at the first OFDM symbol of the next frame, assigning MCSs to the sub-carriers according to the updated switching threshold values, loading a new frame of data packets to the sub-carriers accordingly, and transmitting the next frame of OFDM symbols.

11. A method as in-claim 9, where loading the sub-channels further comprises disabling a sub-channel and not loading a data packet if the sub-channel condition is poor.

12. A method as in claim 10, where loading the sub-channels further comprises disabling a sub-channel and not loading a data packet if the sub-channel condition is poor.

13. A method as in claim 9, where one automaton learning trial is performed per OFDM symbol.

14. A method as in claim 10, where one automaton learning trial is performed per OFDM frame.

15. A method as in claim 8, where for a mode 1 operation where the OFDM communications system operates by loading a plurality of data packets across the plurality of sub-carriers so that the plurality of data packets are loaded into one OFDM symbol, further comprising:

based on selected switching threshold values, determining what MCS to use in each of the sub-carriers, thereby determining how many data packets an OFDM symbol can carry;

loading the sub-carriers with the data packets;

transmitting the OFDM symbol from the OFDM transmitter;

receiving the OFDM symbol at the OFDM receiver and determining a packet error rate (PER) to determine data throughput (TP) in accordance with;

TP=(1-PER)*PPS, where PPS=packet-per-symbol;

based on the data TP, updating the internal probability vector of each automaton such that only if the selected action has resulted in good throughput performance the selection probability of the selected action is increased, thereby updating the switching threshold values, where the automaton internal probability vector is updated for each packet received in an OFDM symbol;

in each of the plurality of automaton selecting another action at random using the updated automaton internal probability vector; and

at the next OFDM symbol, assigning MCSs to the sub-carriers according to the updated switching threshold values, loading new data packets to the sub-carriers accordingly, and transmitting the next OFDM symbol.

16. A method as in claim 8, where for a mode 2 operation where the OFDM communications system operates by loading each sub-carrier with a data packet so that each data packet is spread across a plurality of OFDM symbols, further comprising:

based on selected switching threshold values, determining what MCS to use in each of the sub-carriers, and loading each sub-carrier with a symbol from an assigned data packet;

transmitting a frame of OFDM symbols from the OFDM transmitter;

receiving the frame of OFDM symbols at the OFDM receiver and determining a packet error rate (PER) to determine data throughput (TP), where the PER and TP are determined only for those packets (active packets) in an active SNR region defined as a SNR range covered by the available combinations of switching thresholds, and where PER and TP are determined in accordance with;

TP=(1-PER)*PPF, where PPF=packets-per-frame, or TP=(1-PER)*PPS, where PPS=packets-per-symbol;

based on the data throughput for active packets only, updating the internal probability vectors of selected ones of the plurality of automaton such that only if the selected action has resulted in good throughput performance the selection probability of the selected action is increased, thereby updating the switching threshold values, where the automaton internal probability vector is updated for each active packet received in a OFDM frame;

in each of the plurality of automaton selecting another action at random using the updated automaton internal probability vector; and

at the first OFDM symbol of the next frame, assigning MCSs to the sub-carriers according to the updated switching threshold values, loading a new frame of data packets to the sub-carriers accordingly, and transmitting the next frame of OFDM symbols.

17. An orthogonal frequency duplex multiplexing (OFDM) communications system, comprising:

an OFDM transmitter for transmitting data over a plurality of OFDM sub-channels, said OFDM transmitter comprising a plurality of modulators of different types;

an OFDM receiver for receiving the data from the plurality of OFDM sub-channels, said OFDM receiver comprising a plurality of corresponding demodulators of the different types; and

an adaptive learning automata comprised of a group of independent, decentralized automaton operating in accordance with a game theory-based approach, each of the plurality of automaton being responsible for managing one modulation coding scheme (MCS) switching threshold value so as to maximize at least one selected performance criterion, said OFDM transmitter being responsive to the MCS switching thresholds for selecting an appropriate one or ones of said modulators for modulating the data for various ones of the sub-channels.

18. An OFDM communications system as in claim 17, where said OFDM receiver demodulates the received data using one or more demodulators that correspond to the selected modulators.

19. An OFDM communications system as in claim 18, where the group of automaton is located at the OFDM transmitter, and where feedback information that is indicative of the at least one selected performance criterion is signaled from the OFDM receiver to the OFDM transmitter, and where information indicative of the selected MCS is signaled from the OFDM transmitter to the OFDM receiver.

20. An OFDM communications system as in claim 18, where the group of automaton is located at the OFDM receiver, and where information that is indicative of the selected MCS is signaled from the OFDM receiver to the OFDM transmitter.

21. An OFDM communications system as in claim 17, where the selected performance criterion comprises data throughput.

22. An OFDM communications system as in claim 17, where the OFDM communications system operates by loading a plurality of data packets across the plurality of sub-carriers so that the plurality of data packets are loaded into one OFDM symbol.

23. An OFDM communications system as in claim 17, where the OFDM communications system operates by loading each sub-carrier with a data packet so that each data packet is spread across a plurality of OFDM symbols.

24. An OFDM communications system as in claim 17, further comprising means for initializing the group of automaton by partitioning the switching thresholds into a pre-defined set of combinations to cover all or substantially all of a range of operating signal-to-noise ratios (SNRs);

assigning one switching threshold to one of automaton of the group;

initializing an internal probability vector of each automaton such that the probabilities of choosing a particular action are the same;

mapping each particular action of each automaton to a unique switching threshold value; and

selecting an action at random with each automaton.

25. An OFDM communications system as in claim 24, where for a mode 1 operation the OFDM communications system operates by loading a plurality of data packets across the plurality of sub-carriers so that the plurality of data packets are loaded into one OFDM symbol, and further comprising means, responsive to selected switching threshold values, for determining what MCS to use in each of the sub-carriers, thereby determining how many data packets an OFDM symbol can carry;

for loading the sub-carriers with the data packets;

for transmitting the OFDM symbol from the OFDM transmitter;

for receiving the OFDM symbol at the OFDM receiver and determining a packet error rate (PER) to determine data throughput; and

means, responsive to the determined data throughput, for updating the internal probability vector of an automaton that made a switching threshold decision such that only if the selected action has resulted in good throughput performance the selection probability of the selected action is increased, thereby updating the switching threshold values, and for selecting another action at random using the updated automaton internal probability vector and, at the next OFDM symbol, assigning MCSs to the sub-carriers according to the updated switching threshold values, loading new data packets to the sub-carriers accordingly, and transmitting the next OFDM symbol.

26. An OFDM communications system as in claim 24, where for a mode 2 operation the OFDM communications system operates by loading each sub-carrier with a data packet so that each data packet is spread across a plurality of OFDM symbols, and further comprising means, responsive to selected switching threshold values, for determining what MCS to use in each of the sub-carriers, and loading each sub-carrier with a symbol from an assigned data packet;

for transmitting a frame of OFDM symbols from the OFDM transmitter;

for receiving the frame of OFDM symbols at the OFDM receiver and determining a packet error rate (PER) to determine data throughput; and

means, responsive to the determined data throughput, for updating the internal probability vector of an automaton that made a switching threshold decision such that only if the selected action has resulted in good throughput performance the selection probability of the selected action is increased, thereby updating the switching threshold values;

for selecting another action at random using the updated automaton internal probability vector and, at the first OFDM symbol of the next frame, for assigning MCSs to the sub-carriers according to the updated switching threshold values, loading a new frame of data packets to the sub-carriers accordingly, and transmitting the next frame of OFDM symbols.

27. An OFDM communications system as in claim 25, where loading the sub-channels further comprises disabling a sub-channel and not loading a data packet if the sub-channel condition is poor.

28. An OFDM communications system as in claim 26, where loading the sub-channels further comprises disabling a sub-channel and not loading a data packet if the sub-channel condition is poor.

29. An OFDM communications system as in claim 25, where one automaton learning trial is performed per OFDM symbol.

30. An OFDM communications system as in claim 26, where one automaton learning trial is performed per OFDM frame.