Apparatus and methods for communicating using symbol-modulated subcarriers

• US 7,321,614 B2
• Filed: 09/29/2003
• Issued: 01/22/2008
• Est. Priority Date: 08/08/2003
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Intel Corporation
• Inventors: Jacobsen, Eric A., Stephens, Adrian P
• Primary Examiner(s): Kumar; Pankaj
• Application Number:
  US10/675,892
• Publication Number:
  US 20050068916A1
• Time in Patent Office: 1,576 Days
• Field of Search: 375/224, 375/225, 375/228, 375/295, 375/221, 375/219, 375/140, 375/146, 375/147, 341/173, 455/17, 455/7, 455/39, 455/59, 455/91, 455/102, 455/126, 455/127.1, 455/127.2, 455/115.1, 455/115.3, 455/115.4, 322/185, 340/870.18, 340/870.01, 370/203, 370/204, 370/241, 370/310, 370/431, 370/464, 370/527, 370/522, 370/498, 370/208
• US Class Current: 375/221
• CPC Class Codes: H04L 1/0001 Systems modifying transmission characteristics according to link quality, e.g. power backoff adaptive data allocation for multicarrier modulation H04L5/0044; controlling transmission power for radio systems H04W52/04
• CPC Class Codes: H04L 1/0003 by switching between different modulation schemes
• CPC Class Codes: H04L 1/0007 by modifying the frame length
• CPC Class Codes: H04L 1/0009 by adapting the channel coding H04L1/1812 takes precedence
• CPC Class Codes: H04L 1/0015 characterised by the adaptation strategy
• CPC Class Codes: H04L 1/0017 where the mode-switching is based on Quality of Service requirement
• CPC Class Codes: H04L 1/004 by using forward error control H04L1/0618 takes precedence; coding, decoding or code conversion, for error detection or correction H03M13/00
• CPC Class Codes: H04L 1/0071 Use of interleaving interleaving per se H03M13/27
• CPC Class Codes: H04L 1/1854 Scheduling and prioritising arrangements
• CPC Class Codes: H04L 1/188 Time-out mechanisms
• CPC Class Codes: H04L 5/0007 the frequencies being orthogonal, e.g. OFDM(A), DMT
• CPC Class Codes: H04L 5/0046 Determination of how many bits are transmitted on different sub-channels
• CPC Class Codes: H04L 5/006 Quality of the received signal, e.g. BER, SNR, water filling
• CPC Class Codes: H04W 24/10 Scheduling measurement reports ; Arrangements for measurement reports
• CPC Class Codes: H04W 52/20 using error rate
• CPC Class Codes: H04W 52/243 taking into account interferences
• CPC Class Codes: H04W 52/265 taking into account the quality of service QoS
• CPC Class Codes: H04W 52/367 Power values between minimum and maximum limits, e.g. dynamic range
• CPC Class Codes: H04W 52/42 in systems with time, space, frequency or polarisation diversity
• CPC Class Codes: H04W 84/12 WLAN [Wireless Local Area Networks]

Abstract

Apparatus and methods for selecting a transmit power level and subcarrier modulation assignments based on measured channel conditions to achieve a performance level for communications over a symbol-modulated subcarrier communication channel are provided. In some embodiments, the transmit power level may be changed depending on whether a desired packet error rate and/or a desired link data rate can be achieved based on selected subcarrier modulation assignments and a selected transmit power level.

Claims

1. A method comprising:

selecting a transmit power level and subcarrier modulation assignments based on measured channel conditions to achieve a performance level for communications over a symbol-modulated subcarrier communication channel;

determining at least one of a desired packet error rate and a desired link data rate based on the performance level desired for an application and a data type; and

determining whether to change the transmit power level depending on whether the at least one of the desired packet error rate and the desired link data rate can be achieved based on the selected subcarrier modulation assignments and the selected transmit power level.

2. The method of claim 1 further comprising generating at least one of an estimated packet error rate and an estimated link data rate for the channel based on the selected subcarrier modulation assignments and the selected transmit power level, and

wherein the determining whether to change the transmit power level is based on a comparison between the at least one of the estimated packet error rate and link data rate, and the at least one of the desired packet error rate and the desired link data rate.

3. The method of claim 2 wherein the selecting the subcarrier modulation assignments and the generating the at least one of the estimated packet error rate and the estimated link data rate are performed by a receiving station, and

wherein the method further comprises requesting, by the receiving station, a transmitting station to change the transmit power level based on the desired packet error rate and the desired link data rate.

4. The method of claim 3 further comprising:

refraining, at the transmitting station, from increasing the transmit power level based on at least one of either network considerations, interference considerations or power consumption considerations;

reselecting the subcarrier modulation assignments to achieve a quality of service level; and

communicating the re-selected selecting subcarrier modulation assignments to the receiving station.

5. The method of claim 1, wherein the determining the at least one of the desired packet error rate and the desired link data rate is based on whether the data type comprises voice, audio, video, gaming, internet protocol, file transfer or email data.

6. The method of claim 5 wherein the determining the at least one of the desired packet error rate and the desired link data rate further comprises determining the desired packet error rate and the desired link data rate based on a desired quality of service level for the application using data of the data type.

7. The method of claim 1 further comprising:

decreasing the transmit power level to less than a maximum power level for an application that meets a predetermined quality of service level with data having at least one of a low desired data rate or a high permitted packet error rate; and

communicating at the decreased transmit power level at either a lowered link data rate selected to substantially achieve the desired packet error rate, or at an increased packet error rate selected to substantially achieve the desired link data rate.

8. The method of claim 1 further comprising:

measuring channel conditions of at least one other communication channel; and

refraining from increasing the transmit power level when an increased transmit power level would cause an unacceptable level of interference with other communication devices based on the measured channel conditions of the at least one other communication channel.

9. The method of claim 1 further comprising increasing the transmit power level to achieve at least one of a decreased the packet error rate or an increased the link data rate to substantially meet a quality of service level for the application and the data type.

10. The method of claim 1 further comprising:

refraining from increasing the transmit power level; and

either communicating at a lowered link data rate selected to substantially achieve the desired packet error rate, or communicating at a reduced packet error rate selected to substantially achieve the desired link data rate.

11. A method comprising selecting a transmit power level and subcarrier modulation assignments based on measured channel conditions to achieve a performance level for communications over a symbol-modulated subcarrier communication channel,

wherein the communication channel comprises a plurality of individual symbol-modulated subcarriers, and wherein the selecting comprises selecting modulation rates for the individual subcarriers based on the measured channel conditions,

wherein the selecting the subcarrier modulation assignments comprises selecting the subcarrier modulation assignments for the individual subcarriers based on a received signal, and

wherein the method further comprises receiving data packets comprising data and training symbols modulated in accordance with the selected subcarrier modulation assignments over the plurality of subcarriers, the data packets transmitted at the selected transmit power level.

12. The method of claim 11 wherein the selecting the subcarrier modulation assignments comprises selecting one of no modulation, BPSK modulation, QPSK modulation, 8-PSK modulation, 16-QAM, 32-QAM, 64-QAM, 128-QAM and 256-QAM for the individual subcarriers of the communication channel.

13. A method comprising:

receiving a communication signal transmitted at a predetermined transmit power level carrying packets in a burst of predetermined size;

evaluating based on characteristics of the received communication signal for various packet error rates, various subcarrier modulation assignments and fragment sizes to determine potential link data rates; and

selecting one of the subcarrier modulation assignments and fragment sizes based on the potential link data rate to achieve a desired link data rate.

14. The method of claim 13 wherein:

the receiving the communication signal comprises receiving the communication signal transmitted at the predetermined transmit power level carrying packets having one of either a requested or a predetermined burst size; and

the evaluating comprises evaluating the various subcarrier modulation assignments and fragment sizes based on measured conditions of a communication channel through which the communication signal is received.

15. The method of claim 13 wherein:

the evaluating further comprises estimating a duration of a data burst and a number of bytes expected to be received without error to determine an estimated link data rate, and

wherein the selecting further comprises selecting a combination of packet error rate and fragment size to achieve a highest link data rate.

16. The method of claim 13 further comprising:

transmitting the selected subcarrier modulation assignments, the selected fragment size and an expected packet error rate to a transmitting station; and

receiving subsequent communications from the transmitting station in accordance with the selections.

17. The method of claim 13 wherein the communication signal is received through a communication channel comprising a plurality of individual symbol-modulated subcarriers, and wherein the selecting comprises selecting modulation rates for the individual subcarriers based on the measured conditions of the communication channel.

18. The method of claim 17 wherein the selecting the subcarrier modulation assignments comprises selecting at least one of no modulation, BPSK modulation, QPSK modulation, 8-PSK modulation, 16-QAM, 32-QAM, 64-QAM, 128-QAM and 256-QAM for the individual subcarriers of the communication channel,

wherein individual subcarriers having a better channel response are assigned higher-order modulation assignments having more bits per symbol, and

wherein subcarriers having a worse channel response are assigned lower-order modulation assignments having less bits per symbol.

19. An apparatus comprising:

an application controller to determine a desired performance level for an application and data type;

a physical layer to select a transmit power level and subcarrier modulation assignments for receipt of data over a communication channel at the desired performance level; and

a network controller to determine, a desired packet error rate and a link data rate based on the desired performance,

wherein the network controller is to further determine whether to change the transmit power level for subsequent communications over the communication channel depending on whether the desired packet error rate and link data rate can be achieved based on the selected subcarrier modulation assignments and the selected transmit power level.

20. The apparatus of claim 19 wherein the network controller is to estimate a packet error rate and a link data rate for the channel based on the selected subcarrier modulation assignments and the selected transmit power level,

wherein network controller is to further determine whether to change the transmit power level is based on a difference between the estimated packet error rate and link data rate, and the desired packet error rate or desired link data rate, and

wherein the network controller is to further determine the desired packet error rate and the desired link data rate based on whether the data type comprises one of voice, audio, video, gaming, internet protocol, file transfer or email data.

21. The apparatus of claim 20 wherein the communication channel comprises a plurality of individual symbol-modulated subcarriers, and wherein the network controller is to select modulation rates for the individual subcarriers based on the measured channel conditions, and

wherein the subcarrier modulation assignments comprise one of no modulation, BPSK modulation, QPSK modulation, 8-PSK modulation, 16-QAM, 32-QAM, 64-QAM, 128-QAM and 256-QAM for the individual subcarriers of the communication channel.

22. A system comprising:

a omnidirectional antenna to receive communications over a symbol-modulated subcarrier communication channel;

a physical layer coupled with the antenna to select a transmit power level and subcarrier modulation assignments based on channel conditions to achieve a performance level;

an application controller to determine the performance level based on an application and data type; and

a network controller to determine at least one of a desired packet error rate and a desired link data rate based on the performance level desired for the application and the data type,

wherein the network controller is to further determine whether to change the transmit power level for subsequent communications over the communication channel depending on whether the at least one of the desired packet error rate and the desired link data rate can be achieved based on the selected subcarrier modulation assignments and the selected transmit power level.

23. The system of claim 22 wherein:

the network controller is to instruct a transmitting station to decrease the transmit power level to less than a maximum power level for an application that meets a predetermined quality of service level with data having at least one of a low data rate data or a high packet error rate, and

the transmitting station is to communicate at the decreased transmit power level at either a lowered link data rate selected to substantially achieve the desired packet error rate, or at an increased packet error rate selected to substantially achieve the desired link data rate,

wherein the network controller is to refrain from instructing the transmitting station to increase the transmit power level when an increased transmit power level would cause an unacceptable level of interference with other communication devices based on measured channel conditions of the at least one other communication channel.

24. A computer-readable medium that stores instructions for execution by one or more processors which cause said processors to perform operations comprising:

selecting a transmit power level and subcarrier modulation assignments based on measured channel conditions to achieve a performance level for communications over a symbol-modulated subcarrier communication channel;

determining at least one of a desired packet error rate and a desired link data rate based on the performance level desired for an application and a data type;

determining whether to change the transmit power level depending on whether the at least one of the desired packet error rate and the desired link data rate can be achieved based on the selected subcarrier modulation assignments and the selected transmit power level;

generating at least one of an estimated packet error rate and an estimated link data rate for the channel based on the selected subcarrier modulation assignments and the selected transmit power level,

wherein the determining whether to change the transmit power level is based on a comparison between the at least one of the estimated packet error rate and link data rate, and the at least one of the desired packet error rate and the desired link data rate,

wherein the determining the at least one of the desired packet error rate and the desired link data rate is based on whether the data type comprises voice, audio, video, gaming, internet protocol, file transfer or email data, and

wherein the determining the at least one of the desired packet error rate and the desired link data rate further comprises determining the desired packet error rate and the desired link data rate based on a desired quality of service level for the application using data of the data type.

25. The computer-readable medium of claim 24 wherein the communication channel comprises a plurality of individual symbol-modulated subcarriers, and wherein the selecting comprises selecting modulation rates for the individual subcarriers based on the measured channel conditions, and

wherein the selecting the subcarrier modulation assignments comprises selecting one of no modulation, BPSK modulation, QPSK modulation, 8-PSK modulation, 16-QAM, 32-QAM, 64-QAM, 128-QAM and 256-QAM for the individual subcarriers of the communication channel.