Broadband multicarrier transmitter with subchannel frequency diversity for transmitting a plurality of spatial streams

• US 7,616,704 B2
• Filed: 03/08/2005
• Issued: 11/10/2009
• Est. Priority Date: 03/08/2005
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Intel Corporation
• Inventors: Li, Qinghua, Lin, Xintian E, Davydov, Alexei V
• Primary Examiner(s): Bocure; Tesfaldet
• Assistant Examiner(s): Williams; Lawrence B
• Application Number:
  US11/075,030
• Publication Number:
  US 20060203935A1
• Time in Patent Office: 1,708 Days
• Field of Search: 375/260, 375/261, 375/267, 375/298, 375/299, 455/91, 455/101, 455/102, 455/103, 455/112, 455/118, 370/57, 370/69.1, 370/120, 370/281, 370/296, 370/302, 370/343, 370/437, 370/442, 370/465, 370/478, 370/480, 370/481
• US Class Current: 375/299
• CPC Class Codes: H04B 7/0617 for beam forming
• CPC Class Codes: H04B 7/0669 using different channel coding between antennas space-time coding H04L1/0618
• CPC Class Codes: H04B 7/068 using space frequency diversity space-frequency coding H04L1/0606
• CPC Class Codes: H04L 1/0625 Transmitter arrangements
• CPC Class Codes: H04L 25/0204 of multiple channels
• CPC Class Codes: H04L 27/0008 arrangements for allowing a transmitter or receiver to use more than one type of modulation negotiating modulation type for two-way transmission paths H04L5/1453
• CPC Class Codes: H04L 27/36 Modulator circuits; Transmitter circuits
• CPC Class Codes: H04L 5/0023 Time-frequency-space
• CPC Class Codes: H04L 5/0044 allocation of payload

Abstract

A multicarrier transmitter assigns for each of a plurality of spatial channels, sets of the constellation symbols to subcarriers of each subchannel. Constellation symbol assignments to the subchannels are circularly rotated among some of the spatial channels so that subchannels use different sets of subcarriers for each spatial channel for enhanced frequency diversity.

Claims

1. A multicarrier transmitter comprising:

a modulator for each of a plurality of data streams to generate a set of constellation symbols for each of a plurality of frequency subchannels based on a number of subcarriers associated with each subchannel; and

subcarrier mapping circuitry for each of a plurality of spatial channels to assign the sets of the constellation symbols to the subcarriers of each subchannel,

wherein the subcarrier mapping circuitry is to change an order in which the constellation symbols are assigned to the subcarriers for some spatial channels without changing the number of subcarriers per spatial channel, and so that some of the subchannels use different sets of subcarriers for some spatial channels.

2. The multicarrier transmitter of claim 1 wherein the subcarrier mapping circuitry is to shift subcarrier assignments within the spatial channels of at least some but less than all spatial channels by an increasing amount for each subsequent spatial channel being assigned, the increasing amount being at least as great as a number of subcarriers comprising a first subchannel.

3. The transmitter of claim 1 wherein each subchannel comprises a subset of frequency subcarriers of a multicarrier communication channel,

wherein each subchannel is a concatenated subchannel further comprising two or more time slots, each time slot corresponding to an orthogonal frequency division multiplex access symbol time, and

wherein the subcarrier mapping circuitry is to further assign the constellation symbols of each of the subchannels to the time slots to increase time-slot diversity within an associated subchannel.

4. The transmitter of claim 3 wherein the subcarrier mapping circuitry is to assign constellation symbols of a first subchannel of a first spatial channel to a first time slot, and is to assign subsequent constellation symbols of the first subchannel of a second spatial channel to another time slot.

5. The transmitter of claim 4 further comprising data processing circuitry to determine when the multicarrier communication channel is a fast fading channel by determining when channel estimates change across time slots,

wherein the subcarrier mapping circuitry is to assign the constellation symbols of corresponding subchannel of the different spatial channels to more than one time slot.

6. The transmitter of claim 1 wherein each subcarrier has a physical index, and

wherein the subcarrier mapping circuitry is to map a logical index of subcarriers of a subchannel to one of the physical indices of the subcarriers so that subchannels use different sets of physical subcarriers in each spatial channel.

7. The transmitter of claim 1 wherein the modulators are responsive to a modulation level input to modulate the subcarriers of each spatial channel in accordance with one of a plurality of modulation levels, and

wherein the modulators are adaptable to apply a different of the modulation levels for each of the spatial channels.

8. The transmitter of claim 7 further comprising:

beamforming circuitry to apply beamformer weights in the frequency domain to the subcarriers of the spatial channels; and

a transmit antenna associated with each spatial channel,

wherein when the beamformer weights are applied to different spatial channels, subchannels of the spatial channels exhibit directivity.

9. The multicarrier transmitter of claim 1 wherein the transmitter is a WiMax multicarrier multiple-output transmitter and is part of a broadband communication station.

10. A method of transmitting multicarrier communication signals performed by a multicarrier transmitter, the method comprising:

generating a set of constellation symbols for each of a plurality of frequency subchannels based on a number of subcarriers associated with each subchannel;

assigning, for each of a plurality of spatial channels, the sets of the constellation symbols to the subcarriers of each subchannel and

modulating the assigned sets of constellation symbols for subsequent RF transmission,

wherein an order in which the constellation symbols are assigned to some spatial channels is changed without changing the number of subcarriers per spatial channel and so that some of the subchannels use different sets of subcarriers for at least some of the spatial channels.

11. The method of claim 10 further comprising shifting subcarrier assignments of the subchannels of at least some but less than all spatial channels by an increasing amount, the increasing amount being at least as great as a number of subcarriers comprising a first subchannel.

12. The method of claim 10 wherein each subchannel comprises a subset of frequency subcarriers of a multicarrier communication channel,

wherein each subchannel is a concatenated subchannel further comprising two or more time slots, each time slot corresponding to an orthogonal frequency division multiplex access symbol time, and

wherein the assigning further comprises assigning the constellation symbols of each of the subchannels to the time slots to increase time-slot diversity within an associated subchannel.

13. The method of claim 12 further comprising:

assigning constellation symbols of a first subchannel of a first spatial channel to a first time slot; and

assigning subsequent constellation symbols of the first subchannel of a second spatial channel to another time slot.

14. The method of claim 13 further comprising:

determining when the multicarrier communication channel is a fast fading channel by determining when channel estimates change across time slots; and

assigning the constellation symbols of corresponding subchannels of the different spatial channels to more than one time slot.

15. The method of claim 10 wherein each subcarrier has a physical index, and

wherein the method further comprises mapping a logical index of subcarriers of a spatial channel to one of the physical indices of the subcarriers so that corresponding subchannels of different spatial channels use different sets of subcarriers for each spatial channel.

16. The method of claim 10 further comprising modulating the subcarriers of each spatial channel in accordance with one of a plurality of modulation levels, wherein a different of the modulation levels is applied to each of the spatial channels.

17. The method of claim 16 further comprising applying beamformer weights in the frequency domain to the subcarriers of the spatial channels, wherein when the beamformer weights are applied to the different spatial channels, subchannels within the different spatial channels exhibit directivity.

18. A system comprising:

a plurality of transmit antennas, each associated with one of a plurality of spatial channels; and

a multicarrier transmitter comprising a modulator for each of a plurality of data streams to generate a set of constellation symbols for each of a plurality of frequency subchannels based on a number of subcarriers associated with each subchannel, and subcarrier mapping circuitry for each of a plurality of spatial channels to assign the sets of the constellation symbols to the subcarriers of each subchannel,

wherein the subcarrier mapping circuitry is to change an order in which the constellation symbols are assigned to the subcarriers for some spatial channels without changing the number of subcarriers per spatial channel, and so that some of the subchannels use different sets of subcarriers for some spatial channels.

19. The system of claim 18 wherein the subcarrier mapping circuitry is to shift subcarrier assignments within the spatial channels of at least some but less than all spatial channels by an increasing amount, the increasing amount being at least as great as a number of subcarriers comprising a first subchannel,

wherein each subchannel comprises a subset of frequency subcarriers of a multicarrier communication channel,

wherein each subchannel is a concatenated subchannel further comprising two or more time slots, each time slot corresponding to an orthogonal frequency division multiplex access symbol time, and

wherein the subcarrier mapping circuitry is to further assign the constellation symbols of each of the subchannels to the time slots to increase time-slot diversity within an associated subchannel.

20. The system of claim 19 wherein the subcarrier mapping circuitry is to assign constellation symbols of a first subchannel of a first spatial channel to a first time slot, and is to assign subsequent constellation symbols of the first subchannel of a second spatial channel to another time slot, and

wherein the multicarrier transmitter further comprises data processing circuitry to determine when the multicarrier communication channel is a fast fading channel by determining when channel estimates change across time slots, and

wherein the subcarrier mapping circuitry is to assign the constellation symbols of corresponding subchannel of the different spatial channels to more than one time slot.

21. The system of claim 18 wherein each subcarrier has a physical index, and

wherein the subcarrier mapping circuitry is to map a logical index of subcarriers of a subchannel to one of the physical indices of the subcarriers so that subchannels use different sets of physical subcarriers in each spatial channel.

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

generating a set of constellation symbols for each of a plurality of frequency subchannels based on a number of subcarriers associated with each subchannel; and

assigning, for each of a plurality of spatial channels, the sets of the constellation symbols to the subcarriers of each subchannel, wherein an order in which the constellation symbols are assigned to some spatial channels is changed without changing the number of subcarriers per spatial channel and so that some of the subchannels use different sets of subcarriers for at least some of the spatial channels.

23. The computer-readable medium of claim 22 wherein the instructions, when further accessed cause the machine to perform operations further comprising shifting subcarrier assignments of the subchannels of at least some but less than all spatial channels by an increasing amount, the increasing amount being at least as great as a number of subcarriers comprising a first subchannel,

wherein each subchannel comprises a subset of frequency subcarriers of a multicarrier communication channel,

wherein each subchannel is a concatenated subchannel further comprising two or more time slots, each time slot corresponding to an orthogonal frequency division multiplex access symbol time, and

wherein the assigning further comprises assigning the constellation symbols of each of the subchannels to the time slots to increase time-slot diversity within an associated subchannel.

24. The computer-readable medium of claim 23 wherein the instructions, when further accessed cause the machine to perform operations further comprising:

assigning constellation symbols of a first subchannel of a first spatial channel to a first time slot;

assigning subsequent constellation symbols of the first subchannel of a second spatial channel to another time slot;

determining when the multicarrier communication channel is a fast fading channel by determining when channel estimates change across time slots; and

assigning the constellation symbols of corresponding subchannels of the different spatial channels to more than one time slot.