MIMO TRANSMITTER AND METHOD FOR TRANSMITTING AN OFDM SYMBOL IN ACCORDANCE WITH AN IEEE 802.11 COMMUNICATION STANDARD OVER A PLURALITY OF SPATIAL CHANNELS

• US 20090252257A1
• Filed: 06/11/2009
• Published: 10/08/2009
• Est. Priority Date: 08/08/2003
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Intel Corporation
• Inventors: Ho, Minnie, Jacobsen, Eric A., Maltsev, Alexander A., Sandhu, Sumeet, Sadowsky, John, Sadri, Ali S.
• Granted Patent: US 7,822,135 B2
• Time in Patent Office: Days
• US Class Current: 375/299
• CPC Class Codes: H04B 7/0408 using two or more beams, i.e. beam diversity
• CPC Class Codes: H04W 16/28 using beam steering
• CPC Class Codes: H04W 74/02 Hybrid access

Abstract

A multiple-input-multiple output (MIMO) transmitter for transmitting an orthogonal frequency division multiplexed (OFDM) symbol over a plurality of spatial channels using a plurality of antennas is described. The transmitter includes encoding circuitry to encode blocks of input bits in accordance with a variable encoding rate to generate blocks of encoded bits and a spatial-frequency parser to parse the blocks of encoded bits into spatial-frequency groups. The transmitter also includes subcarrier modulators to modulate each spatial-frequency group of encoded bits on one of the OFDM subcarriers to generate symbol-modulated subcarriers. Spatial-frequency groups having a greater number of encoded bits are modulated at higher-order modulation levels and spatial-frequency groups having a lesser number of encoded bits are modulated at lower-order modulation orders.

Claims

1. A multiple-input-multiple output (MIMO) transmitter for transmitting an orthogonal frequency division multiplexed (OFDM) symbol over a plurality of spatial channels using a plurality of antennas comprising:

encoding circuitry to encode blocks of input bits in accordance with a variable encoding rate to generate blocks of encoded bits;

a spatial-frequency parser to parse the blocks of encoded bits into spatial-frequency groups;

subcarrier modulators to modulate each spatial-frequency group of encoded bits on one of the OFDM subcarriers to generate symbol-modulated subcarriers, wherein spatial-frequency groups having a greater number of encoded bits are modulated at higher-order modulation levels and spatial-frequency groups having a lesser number of encoded bits are modulated at lower-order modulation orders; and

circuitry to combine the symbol-modulated subcarriers and generate signals for transmission through each of the spatial channels, the spatial channels being non-orthogonal and having different multipath characteristics,

wherein the spatial-frequency subcarrier modulation assignments are determined from channel characteristics of the subcarriers for the spatial channels.

2. The transmitter of claim 1 wherein each spatial-frequency group is associated with a spatial component and a frequency component of the OFDM symbol, the spatial component being associated with one of the spatial channels, the frequency component being associated with one of a plurality of OFDM subcarriers,

wherein a number of encoded bits in each block encoded by the encoding circuitry is based on the variable encoding rate which is determined for each block of encoded bits based on the spatial-frequency subcarrier modulation assignments, and

wherein the spatial-frequency parser is configured to parse each block of encoded bits based on the spatial-frequency subcarrier modulation assignments associated with a particular one of the OFDM subcarriers of a particular one of the spatial channels.

3. The transmitter of claim 2 wherein the circuitry to combine the symbol-modulated subcarriers is configured to combine separate sets of symbol-modulated subcarriers for transmission through each spatial channel to allow different data to be transmitted through each spatial channel.

4. The transmitter of claim of claim 3 wherein the OFDM symbol is configured for transmission in accordance with an IEEE 802.11 communication standard,

wherein up to four spatial channels utilize a single 20 MHz channel in which each spatial channel utilizes a same set of OFDM subcarriers.

5. The transmitter of claim of claim 3 wherein the OFDM symbol is configured for transmission in accordance with an IEEE 802.11 communication standard,

wherein up to four spatial channels utilize two 20 MHz channels to provide a 40 MHz wideband channel in which some of the spatial channels utilizes a same set of OFDM subcarriers.

6. The transmitter of claim 2 wherein the circuitry to combine the symbol-modulated subcarriers is configured to combine corresponding symbol-modulated subcarriers associated with the spatial component, wherein the same data is transmitted through each spatial channel.

7. The transmitter of claim of claim 6 wherein the OFDM symbol is configured for transmission in accordance with an IEEE 802.11 communication standard,

wherein up to four spatial channels utilize a single 20 MHz channel in which each spatial channel utilizes a same set of OFDM subcarriers.

8. The transmitter of claim of claim 6 wherein the OFDM symbol is configured for transmission in accordance with an IEEE 802.11 communication standard,

wherein up to four spatial channels utilize two 20 MHz channels to provide a 40 MHz wideband channel in which some of the spatial channels utilizes a same set of OFDM subcarriers.

9. The transmitter of claim 2 further comprising circuitry to perform beamforming on the symbol-modulated subcarriers to generate beamformed signals for transmission through the spatial channels.

10. The transmitter of claim 2 wherein a request-to-send/clear-to-send (RTS/CTS) signaling structure is used to determine the channel characteristics.

11. A method performed by a multiple-input-multiple output (MIMO) transmitter for transmitting an orthogonal frequency division multiplexed (OFDM) symbol over a plurality of spatial channels using a plurality of antennas, the method comprising:

encoding blocks of input bits in accordance with a variable encoding rate to generate blocks of encoded bits;

parsing the blocks of encoded bits into spatial-frequency groups;

modulating each spatial-frequency group of encoded bits on one of the OFDM subcarriers to generate symbol-modulated subcarriers, wherein spatial-frequency groups having a greater number of encoded bits are modulated at higher-order modulation levels and spatial-frequency groups having a lesser number of encoded bits are modulated at lower-order modulation orders; and

combining the symbol-modulated subcarriers and generate signals for transmission through each of the spatial channels, the spatial channels being non-orthogonal and having different multipath characteristics,

wherein the spatial-frequency subcarrier modulation assignments are determined from channel characteristics of the subcarriers for the spatial channels.

12. The method of claim 11 wherein each spatial-frequency group is associated with a spatial component and a frequency component of the OFDM symbol, the spatial component being associated with one of the spatial channels, the frequency component being associated with one of a plurality of OFDM subcarriers,

wherein a number of encoded bits in each encoded block is based on the variable encoding rate which is determined for each block of encoded bits based on the spatial-frequency subcarrier modulation assignments, and

wherein the parsing comprises parsing each encoded block is based on the spatial-frequency subcarrier modulation assignments associated with a particular one of the OFDM subcarriers of a particular one of the spatial channels.

13. The method of claim 12 wherein the combining comprises combining separate sets of symbol-modulated subcarriers for transmission through each spatial channel to allow different data to be transmitted through each spatial channel.

14. The method of claim of claim 13 further comprising configuring the OFDM symbol for transmission in accordance with an IEEE 802.11 communication standard,

wherein up to four spatial channels utilize a single 20 MHz channel in which each spatial channel utilizes a same set of OFDM subcarriers.

15. The method of claim of claim 13 further comprising configuring the OFDM symbol for transmission in accordance with an IEEE 802.11 communication standard,

wherein up to four spatial channels utilize two 20 MHz channels to provide a 40 MHz wideband channel in which some of the spatial channels utilizes a same set of OFDM subcarriers.

16. The method of claim 12 wherein the combining comprises combining corresponding symbol-modulated subcarriers associated with the spatial component, wherein the same data is transmitted through each spatial channel.

17. The method of claim of claim 16 further comprising configuring the OFDM symbol for transmission in accordance with an IEEE 802.11 communication standard,

wherein up to four spatial channels utilize a single 20 MHz channel in which each spatial channel utilizes a same set of OFDM subcarriers.

18. The method of claim of claim 16 further comprising configuring the OFDM symbol for transmission in accordance with an IEEE 802.11 communication standard,

wherein up to four spatial channels utilize two 20 MHz channels to provide a 40 MHz wideband channel in which some of the spatial channels utilizes a same set of OFDM subcarriers.

19. The method of claim 12 further comprising performing beamforming on the symbol-modulated subcarriers to generate beamformed signals for transmission through the spatial channels.

20. The method of claim 12 further comprising using a request-to-send/clear-to-send (RTS/CTS) signaling structure to determine the channel characteristics.

21. A multiple-input-multiple output (MIMO) transmitter for transmitting an orthogonal frequency division multiplexed (OFDM) symbol in accordance with an IEEE 802.11 communication standard over a plurality of spatial channels using a plurality of antennas comprising:

encoding circuitry to encode blocks of input bits in accordance with a variable encoding rate to generate blocks of encoded bits;

a spatial-frequency parser to parse the blocks of encoded bits into spatial-frequency groups; and

subcarrier modulators to modulate each spatial-frequency group of encoded bits on one of the OFDM subcarriers to generate symbol-modulated subcarriers, wherein spatial-frequency groups having a greater number of encoded bits are modulated at higher-order modulation levels and spatial-frequency groups having a lesser number of encoded bits are modulated at lower-order modulation orders,

wherein each spatial-frequency group is associated with a spatial component and a frequency component of the OFDM symbol, the spatial component being associated with one of the spatial channels, the frequency component being associated with one of a plurality of OFDM subcarriers.

22. The transmitter of claim 21 wherein a number of encoded bits in each block encoded by the encoding circuitry is based on the variable encoding rate which is determined for each block of encoded bits based on the spatial-frequency subcarrier modulation assignments, and

wherein the spatial-frequency parser is configured to parse each block of encoded bits based on the spatial-frequency subcarrier modulation assignments associated with a particular one of the OFDM subcarriers of a particular one of the spatial channels.