Compressed preamble for a wireless communication system

• US 9,954,703 B2
• Filed: 06/11/2015
• Issued: 04/24/2018
• Est. Priority Date: 06/11/2014
• Status: Active Grant

• Current Assignee: NXP USA, Inc. (NXP Semiconductors NV)
• Original Assignee: Marvell World Trade Limited (Marvell Technology Group Limited)
• Inventors: Zhang, Hongyuan, Zheng, Xiayu, Cao, Rui, Xu, Mingguang, Srinivasa, Sudhir, Huang, Jie
• Primary Examiner(s): Jagannathan, Melanie
• Application Number:
  US14/737,273
• Publication Number:
  US 20150365266A1
• Time in Patent Office: 1,048 Days
• CPC Class Codes: H04B 7/066 Combined feedback for a number of channels, e.g. over several subcarriers like in orthogonal frequency division multiplexing [OFDM]
• CPC Class Codes: H04L 1/0009 by adapting the channel coding H04L1/1812 takes precedence
• CPC Class Codes: H04L 1/0057 Block codes H04L1/0061, H04L1/0064 take precedence
• CPC Class Codes: H04L 27/2602 Signal structure
• CPC Class Codes: H04L 27/26025 Numerology, i.e. varying one or more of symbol duration, subcarrier spacing, Fourier transform size, sampling rate or down-clocking allocating sub-channels of the transmission path H04L5/003
• CPC Class Codes: H04L 27/2603 Signal structure ensuring backward compatibility with legacy system
• CPC Class Codes: H04L 27/26035 Maintenance of orthogonality, e.g. for signals exchanged between cells or users, or by using covering codes or sequences using different training sequence per antenna H04B7/0684; code allocation H04J13/16
• CPC Class Codes: H04L 27/2605 Symbol extensions, e.g. Zero Tail, Unique Word [UW]
• CPC Class Codes: H04L 27/2627 Modulators
• CPC Class Codes: H04L 27/2634 Inverse fast Fourier transform [IFFT] or inverse discrete Fourier transform [IDFT] modulators in combination with other circuits for modulation
• 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

Abstract

One or more long OFDM symbols for a data portion of a data unit data are generated. Each of the one or more long OFDM symbols is generated with a first number of OFDM tones. One or more short OFDM symbols for one or more long training fields of a preamble of the data unit are generated. Each of the one or more short OFDM symbols is generated with a second number of OFDM that is a fraction 1/N of the first number of OFDM tones, wherein N is a positive integer greater than one. The data unit is generated. Generating the data unit includes generating the preamble to include the one or more short OFDM symbols corresponding to the one or more training fields of the preamble and generating the data portion to include the one or more long OFDM symbols.

Claims

1. A method for generating a physical layer (PHY) data unit for transmission via a communication channel, the method comprising:

generating, at a communication device, one or more long orthogonal frequency division multiplexing (OFDM) symbols for a data portion of the PHY data unit, wherein each of the one or more long OFDM symbols is generated with a first number of OFDM tones;

generating, at the communication device, one or more short OFDM symbols for one or more long training fields of a preamble of the PHY data unit, wherein each of the one or more short OFDM symbols is generated with a second number of OFDM tones, wherein multiple sets of N zero OFDM tones are respectively included between pairs of non-zero OFDM tones in the one or more short OFDM symbols, wherein N is a positive integer greater than one, and wherein the one or more long training fields are for a receiver device to generate an estimate of a communication channel; and

generating, at the communication device, the PHY data unit, including (i) generating the preamble to include the one or more short OFDM symbols corresponding to the one or more training fields of the preamble, and (ii) generating the data portion to include the one or more long OFDM symbols.

2. The method of claim 1, wherein generating a short OFDM symbol of the one or more short OFDM symbols includes:

converting, at the communication device, a frequency domain sequence corresponding to the short OFDM symbol to a time-domain sequence using an Inverse Discrete Fourier Transform (IDFT) of a first size corresponding to the first number of tones, the frequency domain sequence including multiple sets of N zero OFDM tones respectively included between pairs of non-zero OFDM tones, and

truncating, at the communication device, the time-domain sequence to a number of samples corresponding to the first size divided by N.

3. The method of claim 2, further comprising boosting, at the communication device, power of non-zero OFDM tones used to transmit the training sequence.

4. The method of claim 3, wherein boosting the power of non-zero OFDM tones used to transmit the training sequence comprises scaling the power by a scaling factor that corresponds to a square root of a ratio of a number of non-zero OFDM tones in each of the one or more long OFDM symbols to a number of non-zero OFDM tones in each of the one or more short OFDM symbols.

5. The method of claim 1, wherein:

generating the one or more long OFDM symbols comprises generating the one or more long OFDM symbols using an Inverse Discrete Fourier Transform (IDFT) of a first size corresponding to the first number of tones, and

generating the one or more short OFDM symbols comprises generating the one or more short OFDM symbols using an IDFT of a second size corresponding to the second number of tones.

6. The method of claim 1, wherein:

N is 4 when a first compression mode is used to generate the one or more short OFDM symbols, and

N is 2 when a second compression mode is used to generate the one or more short OFDM symbols.

7. The method of claim 1, wherein generating a short OFDM symbol of the one or more short OFDM symbols includes:

receiving a training sequence corresponding to the short OFDM symbol, wherein the training sequence has a size corresponding to a number of non-zero tones in a long OFDM symbol divided by N, and

up-sampling, at the communication device, the training sequence by a factor N.

8. An apparatus, comprising:

a network interface device having one or more integrated circuits configured to;

generate one or more long orthogonal frequency division multiplexing (OFDM) symbols for a data portion of a physical layer (PHY) data unit, wherein the one or more long OFDM symbols are generated with a first number of OFDM tones;

generate one or more short OFDM symbols for one or more long training fields of a preamble of the PHY data unit, wherein the one or more long OFDM symbols are generated with a second number of OFDM tones, wherein multiple sets of N zero OFDM tones are respectively included between pairs of non-zero OFDM tones in the one or more short OFDM symbols, wherein N is a positive integer greater than one, and wherein the one or more long training fields are for a receiver device to generate an estimate of a communication channel; and

generate the PHY data unit, including (i) generating the preamble to include the one or more short OFDM symbols corresponding to the one or more training fields of the preamble and (ii) generating the data portion to include the one or more long OFDM symbols.

9. The apparatus of claim 8, wherein the one or more integrated circuits are configured to generate a short OFDM symbol of the one or more short OFDM symbols at least by:

converting a frequency domain sequence to a time-domain sequence using an Inverse Discrete Fourier Transform (IDFT) of a first size corresponding to the first number of tones, the frequency domain sequence including multiple sets of N zero OFDM tones respectively included between pairs of non-zero OFDM tones, and

truncating the time-domain sequence to a number of samples corresponding to the first size divided by N.

10. The apparatus of claim 9, wherein the one or more integrated circuits are further configured to boost power of non-zero OFDM tones used to transmit the training sequence.

11. The apparatus of claim 10, wherein the one or more integrated circuits are configured to boost the power of non-zero OFDM tones used to transmit the training sequence comprise at least by scaling the power by a scaling factor that corresponds to a square root of a ratio of a number of non-zero OFDM tones in each of the one or more long OFDM symbols to a number of non-zero OFDM tones in each of the one or more short OFDM symbols.

12. The apparatus of claim 8, wherein the one or more integrated circuits are configured to:

generate the one or more long OFDM symbols using an Inverse Discrete Fourier Transform (IDFT) of a first size corresponding to the first number of tones, and

generate the one or more short OFDM symbols using an IDFT of a second size corresponding to the second number of tones.

13. The apparatus of claim 8, wherein:

N is 4 when a first compression mode is used to generate the one or more short OFDM symbols, and

N is 2 when a second compression mode is used to generate the one or more short OFDM symbols.

14. The apparatus of claim 8, wherein the one or more integrated circuits are configured to generate a short OFDM symbol of the one or more short OFDM symbols at least by:

receiving a training sequence corresponding to the short OFDM symbol, wherein the training sequence has a size corresponding to a number of non-zero tones in a long OFDM symbol divided by N, and

up-sampling the training sequence by a factor N.