Long training field (LTF) for use within single user, multiple user, multiple access, and/or MIMO wireless communications

• US 8,879,472 B2
• Filed: 04/23/2012
• Issued: 11/04/2014
• Est. Priority Date: 04/24/2011
• Status: Active Grant

• Current Assignee: Avago Technologies International Sales Pte Limited (Broadcom, Inc.)
• Original Assignee: Broadcom Corporation (Broadcom, Inc.)
• Inventors: Porat, Ron
• Primary Examiner(s): Elliott, IV, Benjamin H
• Assistant Examiner(s): Nowlin, Eric
• Application Number:
  US13/454,010
• Publication Number:
  US 20120269124A1
• Time in Patent Office: 925 Days
• Field of Search: 370320-329, 370470-474, 370/491, 370/500, 370/509, 370513-515, 370/338, 370/465
• US Class Current: 370/328
• CPC Class Codes: H04L 27/2602 Signal structure
• 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 27/2613 Structure of the reference signals
• CPC Class Codes: H04L 27/2618 Reduction thereof using auxiliary subcarriers
• CPC Class Codes: H04L 27/2666 Acquisition of further OFDM parameters, e.g. bandwidth, subcarrier spacing, or guard interval length
• CPC Class Codes: H04W 52/18 TPC being performed according to specific parameters
• CPC Class Codes: H04W 72/542 using measured or perceived quality
• CPC Class Codes: H04W 84/12 WLAN [Wireless Local Area Networks]

Abstract

Long training field (LTF) for use within single user, multiple user, multiple access, and/or MIMO wireless communications. Classification of a signal may be performed using one or more LTF'"'"'s therein. While such one or more LTF'"'"'s may also be employed for performing functions such as channel estimation, channel characterization, etc., one or more particular characteristics of an LTF extracted from a received signal may also be employed to classify the signal as corresponding to one of a number of possible signal types. For example, such LTF-based classification may be used to classify the respective channel bandwidths associated with the signal (e.g., as being either 1 MHz or 2 MHz channel bandwidth). Generally, one or more LTF fields within one or more signals are employed for any of a number of additional uses beyond or in addition to such functions as channel estimation, channel characterization, etc.

Claims

1. An apparatus comprising:

a communication interface configured to support communications with at least one additional apparatus in accordance with a plurality of channel bandwidths; and

a processor configured to;

extract a long training field (LTF) sequence from a packet; and

classify the packet as one of a plurality of packet types based on frequency domain cross-correlation processing of the LTF sequence with each of a plurality of predetermined LTF sequences, wherein;

a first of the plurality of predetermined LTF sequences is used for classification of the packet in accordance with a first of the plurality of channel bandwidths;

a second of the plurality of predetermined LTF sequences is used for classification of the packet in accordance with a second of the plurality of channel bandwidths; and

the LTF sequence or at least one of the plurality of predetermined LTF sequences being [0 0 0 1 −

1 1 −

1 −

1 1 −

1 1 1 −

1 1 1 1 0 −

1 −

1 −

1 1 −

1 −

1 −

1 1 −

1 1 1 1 −

1 0 0].

2. The apparatus of claim 1, wherein:

a first of the plurality of predetermined LTF sequences being a 32 fast Fourier transform (FFT) LTF sequence; and

a second of the plurality of predetermined LTF sequences being a 64 FFT LTF sequence.

3. The apparatus of claim 1, wherein a first of the plurality of predetermined LTF sequences being orthogonal to a second of the plurality of predetermined LTF sequences such that the first of the plurality of predetermined LTF sequences having zero cross-correlation with the second of the plurality of predetermined LTF sequences or a cross-correlation less than a threshold.

4. The apparatus of claim 1, wherein:

a short training field (STF) within the packet and at least one of the plurality of predetermined LTF sequences having a negative cross-correlation greater than a first threshold; and

the STF within the packet and each of the plurality of predetermined LTF sequences respectively having a respective peak to average power ratio (PAPR) less than a second threshold.

5. The apparatus of 1 further comprising:

a wireless station (STA), wherein the at least one additional apparatus is an access point (AP).

6. An apparatus comprising:

a communication interface configured to support communications with at least one additional apparatus in accordance with a plurality of channel bandwidths; and

a processor configured to;

extract a long training field (LTF) sequence from a packet; and

classify the packet as one of a plurality of packet types based on comparison of at least one characteristic of the LTF with each of a plurality of characteristics respectively corresponding of a plurality of predetermined LTF sequences, wherein the LTF sequence or at least one of the plurality of predetermined LTF sequences being [0 0 0 1 −

1 1 −

1 −

1 1 −

1 1 1 −

1 1 1 1 0 −

1 −

1 −

1 1 −

1 −

1 −

1 1 −

1 1 1 1 −

1 0 0].

7. The apparatus of claim 6, wherein:

a first of the plurality of predetermined LTF sequences being a 32 fast Fourier transform (FFT) LTF sequence; and

a second of the plurality of predetermined LTF sequences being a 64 FFT LTF sequence.

8. The apparatus of claim 6, wherein a first of the plurality of predetermined LTF sequences being orthogonal to a second of the plurality of predetermined LTF sequences such that the first of the plurality of predetermined LTF sequences having zero cross-correlation with the second of the plurality of predetermined LTF sequences or a cross-correlation less than a threshold.

9. The apparatus of claim 6 further comprising:

the processor configured to classify the packet as one of the plurality of packet types based on frequency domain cross-correlation processing of the LTF sequence with each of the plurality of predetermined LTF sequences.

10. The apparatus of claim 6, wherein:

a first of the plurality of predetermined LTF sequences for classification of the packet in accordance with a first of the plurality of channel bandwidths; and

a second of the plurality of predetermined LTF sequences for classification of the packet in accordance with a second of the plurality of channel bandwidths.

11. The apparatus of claim 6, wherein:

a short training field (STF) within the packet and at least one of the plurality of predetermined LTF sequences having a negative cross-correlation greater than a first threshold; and

the STF within the packet and each of the plurality of predetermined LTF sequences respectively having a respective peak to average power ratio (PAPR) less than a second threshold.

12. The apparatus of claim 6 further comprising:

an access point (AP), and the at least one additional communication device is a wireless station (STA).

13. The apparatus of claim 6 further comprising:

a wireless station (STA), wherein the at least one additional apparatus is an access point (AP).

14. A method for execution by a communication device, the method comprising:

operating a communication interface of the communication device to support communications with at least one additional communication device in accordance with a plurality of channel bandwidths;

extracting a long training field (LTF) sequence from a packet; and

classifying the packet as one of a plurality of packet types based on comparison of at least one characteristic of the LTF with each of a plurality of characteristics respectively corresponding of a plurality of predetermined LTF sequences, wherein the LTF sequence or at least one of the plurality of predetermined LTF sequences being [0 0 0 1 −

1 1 −

1 −

1 1 −

1 1 1 −

1 1 1 1 0 −

1 −

1 −

1 1 −

1 −

1 −

1 1 −

1 1 1 1 −

1 0 0].

15. The method of claim 14, wherein:

a first of the plurality of predetermined LTF sequences being a 32 fast Fourier transform (FFT) LTF sequence; and

a second of the plurality of predetermined LTF sequences being a 64 FFT LTF sequence; and

the first of the plurality of predetermined LTF sequences being orthogonal to the second of the plurality of predetermined LTF sequences such that the first of the plurality of predetermined LTF sequences having zero cross-correlation with the second of the plurality of predetermined LTF sequences or a cross-correlation less than a threshold.

16. The method of claim 14 further comprising:

classifying the packet as one of the plurality of packet types based on frequency domain cross-correlation processing of the LTF sequence with each of the plurality of predetermined LTF sequences.

17. The method of claim 14, wherein:

a first of the plurality of predetermined LTF sequences for classification of the packet in accordance with a first of the plurality of channel bandwidths; and

a second of the plurality of predetermined LTF sequences for classification of the packet in accordance with a second of the plurality of channel bandwidths.

18. The method of claim 14, wherein:

a short training field (STF) within the packet and at least one of the plurality of predetermined LTF sequences having a negative cross-correlation greater than a first threshold; and

the STF within the packet and each of the plurality of predetermined LTF sequences respectively having a respective peak to average power ratio (PAPR) less than a second threshold.

19. The method of claim 14, wherein the communication device is an access point (AP), and the at least one additional communication device is a wireless station (STA).

20. The method of claim 14, wherein the communication device is a wireless station (STA), and the at least one additional communication device is an access point (AP).