Padding for orthogonal frequency division multiplexing (OFDM) symbols in a wireless communication system

• US 10,116,477 B2
• Filed: 09/18/2017
• Issued: 10/30/2018
• 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): Huang, David S
• Application Number:
  US15/706,971
• Publication Number:
  US 20180006860A1
• Time in Patent Office: 407 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

A boundary within a last orthogonal frequency division multiplexing (OFDM) symbol of a PHY data unit is determined. Pre-encoder padding bits are added to a set of information bits to generate a set of padded information bits such that the set of padded information bits, after being encoded, fill one or more OFDM symbols up to the boundary within the last OFDM symbol. The set of padded information bits are encoded to generate a set of coded bits. A PHY preamble is generated to include a subfield that indicates the boundary. The one or more OFDM symbols are generated to include (i) the set of coded information bits in the one or more OFDM symbols up to the boundary to allow a receiving device to stop decoding the one or more OFDM symbols at the boundary, and (ii) post-encoder padding bits in the last OFDM symbol following the boundary.

Claims

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

receiving, at a communication device, a set of information bits to be included in a data portion of the PHY data unit;

determining, at the communication device, a boundary within a last orthogonal frequency division multiplexing (OFDM) symbol, the last OFDM symbol among one or more OFDM symbols of the data portion of the PHY data unit;

adding, at the communication device, a number of pre-encoder padding bits to the set of information bits to generate a set of padded information bits, wherein the number of pre-encoder padding bits is determined such that the set of padded information bits, after being encoded, fill the one or more OFDM symbols up to the boundary within the last OFDM symbol;

encoding, at the communication device, the set of padded information bits to generate a set of coded bits;

generating, at the communication device, a PHY preamble to include a subfield that indicates the boundary;

generating, at the communication device, the one or more OFDM symbols to include (i) the set of coded information bits in the one or more OFDM symbols up to the boundary within the last OFDM symbol to allow a receiving device to stop decoding the one or more OFDM symbols at the boundary, and (ii) post-encoder padding bits in the last OFDM symbol following the boundary; and

generating, at the communication device, the PHY data unit to include the PHY preamble and the one or more OFDM symbols of the data portion.

2. The method of claim 1, wherein:

the method further comprises determining, at the communication device, an excess number of information bits that do not fit in a respective maximum integer number of OFDM symbols that can be entirely filled by the set of information bits after being encoded; and

determining the boundary comprises determining the boundary based at least in part on the determined number of excess information bits.

3. The method of claim 1, wherein:

generating the PHY preamble includes generating the PHY preamble to include a signal field, the signal field including the subfield that indicates the boundary.

4. The method of claim 3, wherein:

the signal field is a high efficiency signal field A (HE-SIGA).

5. The method of claim 1, wherein:

generating the PHY preamble includes setting a value of the subfield that indicates the boundary to an integer selected from a set of integers consisting of 1, 2, 3, and 4.

6. The method of claim 1, wherein:

generating the PHY data unit further comprises including an extension field after the data portion of the PHY data unit; and

a duration of the extension field is determined based on the boundary.

7. The method of claim 6, wherein:

generating the PHY preamble comprises generating the PHY preamble to include another subfield that indicates the PHY data unit includes the extension field.

8. The method of claim 1, further comprising:

generating, at the communication device, the post-encoder padding bits includes repeating a subset of the coded bits multiple times.

9. An apparatus, comprising:

a network interface device having one or more integrated circuit (IC) devices configured to;

receive a set of information bits to be included in a data portion of a physical layer (PHY) data unit,

determine a boundary within a last orthogonal frequency division multiplexing (OFDM) symbol, the last OFDM symbol among one or more OFDM symbols of the data portion of the PHY data unit,

add a number of pre-encoder padding bits to the set of information bits to generate a set of padded information bits, wherein the number of pre-encoder padding bits is determined such that the set of padded information bits, after being encoded, fill the one or more OFDM symbols up to the boundary within the last OFDM symbol,

encode the set of padded information bits to generate a set of coded bits,

generate a PHY preamble to include a subfield that indicates the boundary,

generate the one or more OFDM symbols to include (i) the set of coded information bits in the one or more OFDM symbols up to the boundary within the last OFDM symbol to allow a receiving device to stop decoding the one or more OFDM symbols at the boundary, and (ii) post-encoder padding bits in the last OFDM symbol following the boundary, and

generate the PHY data unit to include the PHY preamble and the one or more OFDM symbols of the data portion.

10. The apparatus of claim 9, wherein the one or more IC devices are further configured to:

determine an excess number of information bits that do not fit in a respective maximum integer number of OFDM symbols that can be entirely filled by the set of information bits after being encoded; and

determine the boundary based at least in part on the determined number of excess information bits.

11. The apparatus of claim 9, wherein the one or more IC devices are further configured to:

generate the PHY preamble to include a signal field, the signal field including the subfield that indicates the boundary.

12. The apparatus of claim 11, wherein:

the signal field is a high efficiency signal field A (HE-SIGA).

13. The apparatus of claim 9, wherein the one or more IC devices are further configured to:

set a value of the subfield that indicates the boundary to an integer selected from a set of integers consisting of 1, 2, 3, and 4.

14. The apparatus of claim 9, wherein the one or more IC devices are further configured to:

include an extension field after the data portion of the PHY data unit; and

determine a duration of the extension field based on the boundary.

15. The apparatus of claim 14, wherein the one or more IC devices are further configured to:

generate the PHY preamble to include another subfield that indicates the PHY data unit includes the extension field.

16. The apparatus of claim 9, wherein the one or more IC devices are further configured to:

generate the post-encoder padding bits at least by repeating a subset of the coded bits multiple times.

17. The apparatus of claim 9, wherein the network interface device comprises:

a media access control (MAC) processing unit implemented on the one or more IC devices; and

a PHY processing unit implemented on the one or more IC devices and coupled to the MAC processing unit;

wherein the PHY processing unit is configured to;

add the number of pre-encoder padding bits to the set of information bits,

encode the set of padded information bits to generate the set of coded bits,

generate the PHY preamble to include a subfield that indicates the boundary,

generate the one or more OFDM symbols to include (i) the set of coded information bits in the one or more OFDM symbols up to the boundary within the last OFDM symbol to allow a receiving device to stop decoding the one or more OFDM symbols at the boundary, and (ii) the post-encoder padding bits in the last OFDM symbol following the boundary, and

generate the PHY data unit to include the PHY preamble and the one or more OFDM symbols of the data portion.

18. The apparatus of claim 17, wherein the PHY processing unit comprises:

a pre-encoder padding unit implemented on the one or more IC devices, the pre-encoder padding unit configured to generate the pre-encoder padding bits, and to add the pre-encoder padding bits to the set of information bits;

one or more encoders implemented on the one or more IC devices, the one or more encoders configured to encode the set of padded information bits to generate the set of coded bits; and

a post-encoder padding unit implemented on the one or more IC devices, the post-encoder padding unit configured to generate the post-encoder padding bits, and to append the post-encoder padding bits to the set of coded bits.

19. The apparatus of claim 17, wherein the PHY processing unit further comprises:

one or more constellation mappers implemented on the one or more IC devices, the one or more constellation mappers configured to map subsets of i) the set of coded information bits, and ii) the post-encoder padding bits, to constellation points; and

one or more inverse fast Fourier transform (IFFT) calculation units implemented on the one or more IC devices, the one or more IFFT calculation units configured to convert constellation points to time-domain signals corresponding to OFDM symbols.

20. The apparatus of claim 17, wherein the PHY processing unit comprises:

one or more transceivers implemented on the one or more IC devices.

21. The apparatus of claim 20, further comprising:

one or more antennas coupled to the one or more transceivers.