Multicarrier communication system and methods for link adaptation using uniform bit loading and subcarrier puncturing

• US 20050152466A1
• Filed: 06/07/2004
• Published: 07/14/2005
• Est. Priority Date: 01/12/2004
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Intel Corporation
• Inventors: Pudeyev, Andrey V., Maltsev, Alexander A., Davydov, Alexei V., Rubtsov, Alexey E., Sadri, Ali S.
• Granted Patent: US 7,570,953 B2
• Time in Patent Office: Days
• US Class Current: 375/260
• 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 5/0007 the frequencies being orthogonal, e.g. OFDM(A), DMT
• CPC Class Codes: H04L 5/0023 Time-frequency-space
• CPC Class Codes: H04L 5/0042 intra-user or intra-terminal allocation
• CPC Class Codes: H04L 5/0046 Determination of how many bits are transmitted on different sub-channels
• CPC Class Codes: H04L 5/0053 Allocation of signaling, i.e. of overhead other than pilot signals
• CPC Class Codes: H04L 5/006 Quality of the received signal, e.g. BER, SNR, water filling
• CPC Class Codes: H04L 5/0085 when channel conditions change
• CPC Class Codes: H04L 5/0096 Indication of changes in allocation
• CPC Class Codes: H04W 52/34 TPC management, i.e. sharing limited amount of power among users or channels or data types, e.g. cell loading
• CPC Class Codes: H04W 52/42 in systems with time, space, frequency or polarisation diversity

Abstract

A method for selecting transmission parameters of a multicarrier communication channel comprises setting a power level for active subcarriers of a multicarrier communication channel based on a number of the active subcarriers to achieve a highest channel capacity.

Claims

1. A method comprising:

setting a power level for active subcarriers of a multicarrier communication channel based on a number of the active subcarriers;

calculating a channel capacity based on the power level and an effective subcarrier noise power for each active subcarrier; and

decreasing the number active subcarriers in the set and re-performing the setting and calculating to determine a final set of active subcarriers that provide a highest calculated channel capacity.

2. The method of claim 1 wherein setting the power level further comprises increasing the power level of each active subcarrier after removing one or more subcarriers from the active set.

3. The method of claim 2 further comprising sorting the subcarriers based on an effective subcarrier noise power, and

wherein decreasing the number of active subcarriers in the set comprises removing one of the subcarriers having the next greatest effective subcarrier noise power from the set of active subcarriers prior to resetting the power levels of the remaining subcarriers and recalculating the channel capacity.

4. The method of claim 3 further comprising initially selecting subcarriers for the active set having an effective subcarrier noise power below a predetermined threshold.

5. The method of claim 2 further comprising initially selecting substantially all subcarriers to be in the set of active subcarriers.

6. The method of claim 2 wherein setting comprises setting the power level of each subcarrier of the active set to a total transmit power divided by the number of the active subcarriers, the total transmit power being an actual transmit power level used for transmitting a current packet.

7. The method of claim 2 wherein setting comprises setting the power level of each subcarrier of the active set based on a transmitter power budget divided by the number of the active subcarriers, the transmitter power budget being an available transmitter power of a transmitting station.

8. The method of claim 2 wherein setting comprises setting the power level of each subcarrier of the active set based on a maximum power spectral density, wherein the maximum power spectral density is predetermined by a regulating authority.

9. The method of claim 1 wherein calculating the channel capacity comprises summing individual subcarrier capacities of each subcarrier in the active set,

wherein the individual subcarrier capacities are calculated based on the set power level divided by an effective subcarrier noise power for an associated subcarrier of the active set.

10. The method of claim 1 further comprising selecting at least one of a modulation level and coding rate for the active subcarriers based on the calculated channel capacity.

11. The method of claim 10 wherein selecting the at least one of the modulation level and the coding rate comprises:

calculating a mean effective subcarrier capacity based on effective subcarrier capacities for the active subcarriers; and

selecting a modulation level and coding rate combination for the subcarriers of the active set that provides a data rate per subcarrier close to the mean effective subcarrier capacity.

12. The method of claim 11 wherein selecting the at least one of the modulation level and the coding rate further comprises:

calculating a subcarrier signal-to-noise ratio for each active subcarrier based on the selected power level and the effective subcarrier noise power for an associated subcarrier; and

calculating an effective subcarrier capacity for each active subcarrier based on the calculated subcarrier signal-to-noise ratio for an associated subcarrier.

13. The method of claim 11 wherein selecting the modulation level and the coding rate for the subcarriers of the active set comprises determining:

a first modulation level and first coding rate that provides an upper data rate at least slightly greater than the mean effective subcarrier capacity;

a second modulation level and second coding rate that provides a lower data rate at least slightly less than the mean effective subcarrier capacity;

calculating a first number of the active subcarriers with capacities higher than the upper data rate;

calculating a second number of the active subcarriers with capacities lower than the lower data rate;

selecting the first modulation level and the first coding rate associated with the upper data rate when a difference between the first and second numbers is greater than a predetermined percentage of the active subcarriers; and

selecting the second modulation level and the second coding rate associated with the lower data rate when a difference between the first and second numbers is less than or equal to a predetermined percentage of the active subcarriers.

14. The method of claim 1 further comprising determining channel state information for the multicarrier communication channel, the channel state information comprising at least an effective subcarrier noise power for either individual subcarriers or groups of subcarriers.

15. The method of claim 10 further comprising sending the selected set of active subcarriers, the selected power level, the selected modulation level and the selected coding rate to a transmitting station for use in transmitting a next packet.

16. The method of claim 15 further comprising receiving the next packet from a transmitting station, the next packet having been transmitted using the selected active set of subcarriers in accordance with the selected power level, the selected modulation level and the selected coding rate.

17. The method of claim 1 wherein the multicarrier communication channel comprises either a standard-throughput channel or a high-throughput communication channel, the standard-throughput channel comprising one subchannel, the high-throughput channel comprising a combination of one or more subchannels and one or more spatial channels associated with each subchannel.

18. The method of claim 17 wherein the high-throughput communication channel comprises one of:

a wideband channel having up to four frequency separated subchannels;

a multiple-input-multiple-output (MIMO) channel comprising a single subchannel having up to four spatial subchannels; and

a wideband-MIMO channel comprising two or more frequency separated subchannels, each subchannel having two or more spatial channels.

19. The method of claim 17 wherein when the multicarrier communication channel is a high-throughput communication channel, the one or more spatial channels and the one or more subchannels are provided by one or more transmit antennas of a transmitting station.

20. The method of claim 17 wherein the subcarriers of an associated subchannel have a null at substantially a center frequency of the other subcarriers to achieve substantial orthogonality between the subcarriers of the associated subchannel.

21. A multicarrier communication station comprising:

radio frequency circuitry to communicate radio frequency signals over a multicarrier communication channel; and

subcarrier selection circuitry to select a set of active subcarriers of the multicarrier communication channel by decreasing a number of the active subcarriers in the set and increasing a power level of remaining active subcarriers to achieve a highest channel capacity.

22. The communication station of claim 21 wherein the subcarrier selection circuitry sets the power level for active subcarriers based on a number of the active subcarriers, calculates a channel capacity based on the power level and an effective subcarrier noise power for each active subcarrier, removes an active subcarrier from the set, increases the power level of the remaining active subcarriers and recalculates the channel capacity to determine a final set of active subcarriers that provide the highest calculated channel capacity.

23. The communication station of claim 21 wherein the subcarrier selection circuitry sorts the subcarriers based on an effective subcarrier noise power, and removes one of the subcarriers having the next greatest effective subcarrier noise power from the set of active subcarriers prior to the increase of the power levels of the remaining subcarriers and the recalculation of the channel capacity.

24. The communication station of claim 23 wherein the subcarrier selection circuitry initially selects subcarriers for the active set having an effective subcarrier noise power below a predetermined threshold.

25. The communication station of claim 22 wherein the subcarrier selection circuitry initially selects substantially all subcarriers to be in the set of active subcarriers.

26. The communication station of claim 22 wherein the subcarrier selection circuitry sets the power level of each subcarrier of the active set to a total transmit power divided by the number of the active subcarriers, the total transmit power being an actual transmit power level used for transmitting a current packet to the communication station a service field of a current packet.

27. The communication station of claim 22 wherein the subcarrier selection circuitry sets the power level of each subcarrier of the active set based on a transmitter power budget divided by the number of the active subcarriers, the transmitter power budget being an available transmitter power of a transmitting station.

28. The communication station of claim 22 wherein the subcarrier selection circuitry sets the power level of each subcarrier of the active set based on a maximum power spectral density, wherein the maximum power spectral density is predetermined by a regulating authority.

29. The communication station of claim 21 wherein the subcarrier selection circuitry calculates the channel capacity by summing individual subcarrier capacities of each subcarrier in the active set,

wherein the subcarrier selection circuitry calculates the individual subcarrier capacities based on the set power level divided by an effective subcarrier noise power for an associated subcarrier of the active set.

30. The communication station of claim 21 further comprising modulation level and coding rate selection circuitry to select at least one of a modulation level and coding rate for the active subcarriers based on the calculated channel capacity.

31. The communication station of claim 30 wherein the modulation level and coding rate selection circuitry calculates a mean effective subcarrier capacity based on effective subcarrier capacities for the active subcarriers, and selects a modulation level and coding rate combination for the subcarriers of the active set that provides a data rate close to the mean effective subcarrier capacity.

32. The communication station of claim 31 wherein the modulation level and coding rate selection circuitry determines a first modulation level and first coding rate that provides an upper data rate at least slightly greater than the mean effective subcarrier capacity, and determines a second modulation level and second coding rate that provides a lower data rate at least slightly less than the mean effective subcarrier capacity.

33. The communication station of claim 22 wherein the radio-frequency circuitry comprises receiver circuitry to determine channel state information for the multicarrier communication channel, the channel state information comprising at least the effective subcarrier noise power for either individual subcarriers or groups of subcarriers.

34. The communication station of claim 30 wherein the radio-frequency circuitry comprises transmitter circuitry to send instructions including the selected set of active subcarriers, the selected power level, the selected modulation level and the selected coding rate to a transmitting station for use in transmitting a next packet.

35. The communication station of claim 34 wherein the radio-frequency circuitry comprises receiver circuitry to receive the next packet from the transmitting station, the next packet having been transmitted using the selected active set of subcarriers in accordance with the selected power level, the selected modulation level and the selected coding rate.

36. The communication station of claim 21 wherein the multicarrier communication channel comprises either a standard-throughput channel or a high-throughput communication channel, the standard-throughput channel comprising one subchannel, the high-throughput channel comprising a combination of one or more subchannels and one or more spatial channels associated with each subchannel.

37. A system comprising:

a substantially omnidirectional antenna;

radio-frequency circuitry coupled to the antenna to communicate radio frequency signals over a multicarrier communication channel; and

subcarrier selection circuitry to select a set of active subcarriers of the multicarrier communication channel by decreasing a number of the active subcarriers in the set and increasing a power level of remaining active subcarriers to achieve a highest channel capacity.

38. The system of claim 37 further comprising modulation level and coding rate selection circuitry to select at least one of a modulation level and coding rate for the active subcarriers based on the calculated channel capacity.

39. The system of claim 37 wherein the subcarrier selection circuitry sets the power level for active subcarriers based on a number of the active subcarriers, calculates a channel capacity based on the power level and an effective subcarrier noise power for each active subcarrier, removes an active subcarrier from the set, increases the power level of the remaining active subcarriers and recalculates the channel capacity to determine a final set of active subcarriers that provide the highest calculated channel capacity, and

wherein the modulation level and coding rate selection circuitry calculates a mean effective subcarrier capacity based on effective subcarrier capacities for the active subcarriers, and selecting a modulation level and coding rate combination for the subcarriers of the active set that provides a data rate close to the mean effective subcarrier capacity.

40. A machine-readable medium that provides instructions, which when executed by one or more processors, cause the processors to perform operations comprising:

setting a power level for active subcarriers of a multicarrier communication channel based on a number of the active subcarriers;

calculating a channel capacity based on the power level and an effective subcarrier noise power for each active subcarrier; and

decreasing the number active subcarriers in the set and re-performing the setting and calculating to determine a final set of active subcarriers that provide a highest calculated channel capacity.

41. The machine-readable medium of claim 40 wherein the instructions, when further executed by one or more of the processors cause the processors to perform operations,

setting the power level further comprises increasing the power level of each active subcarrier after removing one or more subcarriers from the active set;

and

sorting the subcarriers based on an effective subcarrier noise power,

wherein decreasing the number of active subcarriers in the set comprises removing one of the subcarriers having the next greatest effective subcarrier noise power from the set of active subcarriers prior to resetting the power levels of the remaining subcarriers and recalculating the channel capacity.

42. The machine-readable medium of claim 41 wherein the instructions, when further executed by one or more of the processors cause the processors to perform operations further comprising:

selecting at least one of a modulation level and coding rate for the active subcarriers based on the calculated channel capacity,

wherein selecting the at least one of the modulation level and the coding rate comprises;

calculating a mean effective subcarrier capacity based on effective subcarrier capacities for the active subcarriers; and

selecting a modulation level and coding rate combination for the subcarriers of the active set that provides a data rate close to the mean effective subcarrier capacity.

43. A method for selecting transmission parameters of a multicarrier communication channel comprising:

setting a power level for active subcarriers of a multicarrier communication channel based on a number of the active subcarriers;

calculating a channel capacity based on the power level and an effective subcarrier noise power for each active subcarrier;

decreasing the number active subcarriers in the set and re-performing the setting and calculating to determine a final set of active subcarriers that provide a highest calculated channel capacity; and

selecting at least one of a modulation level and coding rate for the active subcarriers based on the calculated channel capacity.

44. The method of claim 43 wherein setting the power level further comprises increasing the power level of each active subcarrier after removing one or more subcarriers from the active set,

wherein selecting the at least one of the modulation level and the coding rate comprises:

calculating a mean effective subcarrier capacity based on effective subcarrier capacities for the active subcarriers; and

selecting a modulation level and coding rate combination for the subcarriers of the active set that provides a data rate per subcarrier close to the mean effective subcarrier capacity.

45. The method of claim 44 further comprising sorting the subcarriers based on an effective subcarrier noise power, and

wherein decreasing the number of active subcarriers in the set comprises removing one of the subcarriers having the next greatest effective subcarrier noise power from the set of active subcarriers prior to resetting the power levels of the remaining subcarriers and recalculating the channel capacity, and

wherein selecting the at least one of the modulation level and the coding rate further comprises:

calculating a subcarrier signal-to-noise ratio for each active subcarrier based on the selected power level and the effective subcarrier noise power for an associated subcarrier; and

calculating an effective subcarrier capacity for each active subcarrier based on the calculated subcarrier signal-to-noise ratio for an associated subcarrier.

46. A multicarrier communication station comprising:

radio frequency circuitry to communicate radio frequency signals over a multicarrier communication channel;

subcarrier selection circuitry to select a set of active subcarriers of the multicarrier communication channel by decreasing a number of the active subcarriers in the set and increasing a power level of remaining active subcarriers to achieve a highest channel capacity; and

modulation level and coding rate selection circuitry to select at least one of a modulation level and coding rate for the active subcarriers based on the calculated channel capacity.

47. The communication station of claim 46 wherein the subcarrier selection circuitry sets the power level for active subcarriers based on a number of the active subcarriers, calculates a channel capacity based on the power level and an effective subcarrier noise power for each active subcarrier, removes an active subcarrier from the set, increases the power level of the remaining active subcarriers and recalculates the channel capacity to determine a final set of active subcarriers that provide the highest calculated channel capacity, and

wherein the modulation level and coding rate selection circuitry calculates a mean effective subcarrier capacity based on effective subcarrier capacities for the active subcarriers, and selects a modulation level and coding rate combination for the subcarriers of the active set that provides a data rate close to the mean effective subcarrier capacity.

48. The communication station of claim 47 wherein the subcarrier selection circuitry sorts the subcarriers based on an effective subcarrier noise power, and removes one of the subcarriers having the next greatest effective subcarrier noise power from the set of active subcarriers prior to the increase of the power levels of the remaining subcarriers and the recalculation of the channel capacity, and

wherein the modulation level and coding rate selection circuitry determines a first modulation level and first coding rate that provides an upper data rate at least slightly greater than the mean effective subcarrier capacity, and determines a second modulation level and second coding rate that provides a lower data rate at least slightly less than the mean effective subcarrier capacity.