Low bandwidth PHY for WLAN

• US 8,902,869 B2
• Filed: 06/12/2012
• Issued: 12/02/2014
• Est. Priority Date: 06/15/2011
• Status: Active Grant

• Current Assignee: NXP USA, Inc. (NXP Semiconductors NV)
• Original Assignee: Marvell World Trade Limited (Marvell Technology Group Limited)
• Inventors: Zhang, Hongyuan, Banerjea, Raja, Srinivasa, Sudhir
• Primary Examiner(s): Pham, Chi
• Assistant Examiner(s): Rivas, Raul
• Application Number:
  US13/494,527
• Publication Number:
  US 20120320890A1
• Time in Patent Office: 903 Days
• Field of Search: None
• US Class Current: 370/338
• CPC Class Codes: H04L 1/0025 Transmission of mode-switching indication
• 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 1/0043 Realisations of complexity reduction techniques, e.g. use of look-up tables
• CPC Class Codes: H04L 1/0057 Block codes H04L1/0061, H04L1/0064 take precedence
• CPC Class Codes: H04L 1/0061 Error detection codes
• CPC Class Codes: H04L 1/08 by repeating transmission, e.g. Verdan system H04L1/1858 and H04L1/189 take precedence
• CPC Class Codes: H04L 27/2602 Signal structure
• CPC Class Codes: H04L 27/2613 Structure of the reference signals
• CPC Class Codes: H04L 27/26132 using repetition
• CPC Class Codes: H04L 27/26136 Pilot sequence conveying additional information
• CPC Class Codes: H04L 7/048 using the properties of error detecting or error correcting codes, e.g. parity as synchronisation signal

Abstract

A method, in a communication system utilizing channels for transmitting first PHY mode data units, includes generating first and second data units conforming to first and second PHY modes, respectively, causing the first data unit to be transmitted via a channel, determining a frequency band for transmitting the second data unit, and causing the second data unit to be transmitted via the frequency band. Generating the first and second data units includes generating first and second series of OFDM symbols, respectively. At least a portion of the second OFDM symbols includes more upper-edge than lower-edge guard tones, or vice versa. The frequency band has a bandwidth equal to the channel bandwidth divided by n≧2, and either a lowest or highest sub-band of one or more channels is excluded from the frequency band when the second OFDM symbols include more upper-edge or more lower-edge guard tones, respectively.

Claims

1. A method, in a communication system, of generating and causing to be transmitted data units conforming to a first physical layer (PHY) mode and data units conforming to a second PHY mode different than the first PHY mode, wherein the communication system utilizes a plurality of channels for transmitting data units conforming to the first PHY mode, and wherein each channel of the plurality of channels has a first bandwidth, the method comprising:

generating a first data unit conforming to the first PHY mode, wherein generating the first data unit includes generating a first series of orthogonal frequency division multiplexing (OFDM) symbols;

causing the first data unit to be transmitted via a channel of the plurality of channels;

generating a second data unit conforming to the second PHY mode, wherein

generating the second data unit includes generating a second series of OFDM symbols, and

at least a portion of the second series of OFDM symbols includes one of (i) more upper-edge guard tones than lower-edge guard tones, or (ii) more lower-edge guard tones than upper-edge guard tones;

determining a frequency band for transmitting the second data unit, wherein

the frequency band has a second bandwidth equal to the first bandwidth divided by an integer n, wherein n≧

2,

determining the frequency band for transmitting the second data unit includes excluding one of (i) a lowest sub-band of each of one or more channels in the plurality of channels when the portion of the second series of OFDM symbols includes more upper-edge guard tones than lower-edge guard tones or (ii) a highest sub-band of each of the one or more channels in the plurality of channels when the portion of the second series of OFDM symbols includes more lower-edge guard tones than upper-edge guard tones, and

each sub-band of each channel in the plurality of channels has the second bandwidth; and

causing the second data unit to be transmitted via the determined frequency band.

2. A method according to claim 1, wherein the integer n is equal to 2.

3. A method according to claim 2, wherein:

generating the first series of OFDM symbols includes utilizing a 64-point inverse fast Fourier transform (IDFT); and

generating the second series of OFDM symbols includes utilizing a 32-point IDFT.

4. A method according to claim 2, wherein:

generating the first series of OFDM symbols includes utilizing a 64-point inverse fast Fourier transform (IDFT); and

generating the second series of OFDM symbols includes utilizing a 64-point IDFT with at least one half of a total number of generated tones set equal to zero.

5. A method according to claim 1, wherein:

generating the first series of OFDM symbols includes utilizing a first clock rate; and

generating the second series of OFDM symbols includes utilizing the first clock rate.

6. A method according to claim 1, wherein the first PHY mode corresponds to a first data throughput and the second PHY mode corresponds to a second data throughput lower than the first data throughput.

7. A method according to claim 1, wherein the portion of the second series of OFDM symbols includes a data portion of the second series of OFDM symbols.

8. A method according to claim 1, wherein:

the portion of the second series of OFDM symbols includes more lower-edge guard tones than upper-edge guard tones; and

determining the frequency band for transmitting the second data unit includes excluding the highest sub-band of the one or more channels in the plurality of channels.

9. A method according to claim 1, wherein the one or more channels in the plurality of channels include all channels in the plurality of channels.

10. An apparatus comprising:

a network interface configured to

generate a first data unit conforming to a first PHY mode at least in part by generating a first series of orthogonal frequency division multiplexing (OFDM) symbols,

cause the first data unit to be transmitted via a channel of a plurality of channels each having a first bandwidth,

generate a second data unit conforming to a second PHY mode different than the first PHY mode at least in part by generating a second series of OFDM symbols, wherein

at least a portion of the second series of OFDM symbols includes one of (i) more upper-edge guard tones than lower-edge guard tones, or (ii) more lower-edge guard tones than upper-edge guard tones,

determine a frequency band for transmitting the second data unit, wherein

the frequency band has a second bandwidth equal to the first bandwidth divided by an integer n, wherein n≧

2,

the network interface is configured to determine the frequency band for transmitting the second data unit at least in part by excluding one of (i) a lowest sub-band of each of one or more channels in the plurality of channels when the portion of the second series of OFDM symbols includes more upper-edge guard tones than lower-edge guard tones or (ii) a highest sub-band of each of the one or more channels in the plurality of channels when the portion of the second series of OFDM symbols includes more lower-edge guard tones than upper-edge guard tones, and

each sub-band of each channel in the plurality of channels has the second bandwidth, and

cause the second data unit to be transmitted via the determined frequency band.

11. An apparatus according to claim 10, wherein the integer n is equal to 2.

12. An apparatus according to claim 11, wherein the network interface is configured to

generate the first series of OFDM symbols at least in part by utilizing a 64-point inverse fast Fourier transform (IDFT), and

generate the second series of OFDM symbols at least in part by utilizing a 32-point IDFT.

13. An apparatus according to claim 11, wherein the network interface is configured to

generate the first series of OFDM symbols at least in part by utilizing a 64-point inverse fast Fourier transform (IDFT), and

generate the second series of OFDM symbols at least in part by utilizing a 64-point IDFT with at least one half of a total number of generated tones set equal to zero.

14. An apparatus according to claim 10, wherein the network interface is configured to

generate the first series of OFDM symbols at leas n part by utilizing a first clock rate, and

generate the second series of OFDM symbols at least in part by utilizing the first clock rate.

15. An apparatus according to claim 10, wherein the first PHY mode corresponds to a first data throughput and the second PHY mode corresponds to a second data throughput lower than the first data throughput.

16. An apparatus according to claim 10, wherein the portion of the second series of OFDM symbols includes a data portion of the second series of OFDM symbols.

17. An apparatus according to claim 10, wherein:

the portion of the second series of OFDM symbols includes more lower-edge guard tones than upper-edge guard tones, and

the network interface is configured to determine the frequency band for transmitting the second data unit at least in part by excluding the highest sub-band of the one or more channels in the plurality of channels.

18. An apparatus according to claim 10, wherein the one or more channels in the plurality of channels include all channels in the plurality of channels.

19. A method, in a communication system, of generating and causing to be transmitted data units conforming to a first physical layer (PHY) mode and data units conforming to a second PHY mode different than the first PHY mode, wherein the communication system utilizes a plurality of channels for transmitting data units conforming to the first PHY mode, and wherein each channel of the plurality of channels has a first bandwidth, the method comprising:

generating a first data unit conforming to the first PHY mode, wherein generating the first data unit includes generating a first series of orthogonal frequency division multiplexing (OFDM) symbols utilizing a clock rate;

causing the first data unit to be transmitted via a channel of the plurality of channels;

generating a second data unit conforming to the second PHY mode, wherein

generating the second data unit includes generating a second series of OFDM symbols utilizing the clock rate, and

at least a data portion of the second series of OFDM symbols includes more lower-edge guard tones than upper-edge guard tones;

determining a frequency band for transmitting the second data unit, wherein

the frequency band has a second bandwidth equal to half the first bandwidth, and

determining the frequency band for transmitting the second data unit includes excluding an upper sideband of each of one or more channels in the plurality of channels; and

causing the second data unit to be transmitted via the determined frequency band.

20. An apparatus comprising:

a network interface configured to

generate a first data unit conforming to a first PHY mode at least in part by generating a first series of orthogonal frequency division multiplexing (OFDM) symbols utilizing a clock rate,

cause the first data unit to be transmitted via a channel of a plurality of channels each having a first bandwidth,

generate a second data unit conforming to a second PHY mode different than the first PHY mode at least in part by generating a second series of OFDM symbols utilizing the clock rate, wherein at least a data portion of the second series of OFDM symbols includes more lower-edge guard tones than upper-edge guard tones.

determine a frequency band for transmitting the second data unit, wherein

the frequency band has a second bandwidth equal to half the first bandwidth, and

the network interface is configured to determine the frequency band for transmitting the second data unit at least in part by excluding an upper sideband of each of one or more channels in the plurality of channels, and

cause the second data unit to be transmitted via the determined frequency band.