U.S. patent application number 13/572754 was filed with the patent office on 2012-12-06 for codes and preambles for single carrier and ofdm transmissions.
This patent application is currently assigned to QUALCOMM Incorporated. Invention is credited to Ismail Lakkis.
Application Number | 20120311410 13/572754 |
Document ID | / |
Family ID | 42075805 |
Filed Date | 2012-12-06 |
United States Patent
Application |
20120311410 |
Kind Code |
A1 |
Lakkis; Ismail |
December 6, 2012 |
CODES AND PREAMBLES FOR SINGLE CARRIER AND OFDM TRANSMISSIONS
Abstract
Certain aspects of the present disclosure relate to a method for
generating a frame structure suitable for use in both single
carrier (SC) and Orthogonal Frequency Division Multiplexing (OFDM)
transmission modes, while ensuring accurate channel estimation at a
receiver.
Inventors: |
Lakkis; Ismail; (San Diego,
CA) |
Assignee: |
QUALCOMM Incorporated
San Diego
CA
|
Family ID: |
42075805 |
Appl. No.: |
13/572754 |
Filed: |
August 13, 2012 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
12572876 |
Oct 2, 2009 |
|
|
|
13572754 |
|
|
|
|
61103503 |
Oct 7, 2008 |
|
|
|
Current U.S.
Class: |
714/783 ;
714/E11.001 |
Current CPC
Class: |
H04J 13/0014 20130101;
H04J 13/10 20130101; H04L 25/0202 20130101; H04L 27/0008
20130101 |
Class at
Publication: |
714/783 ;
714/E11.001 |
International
Class: |
H03M 13/00 20060101
H03M013/00 |
Claims
1. A method for wireless communications, comprising: receiving a
channel estimation (CE) field transmitted over a wireless channel,
wherein the CE field was constructed by using a pair of Golay
complementary codes; processing the received CE field by using a
matched filter associated with the pair of Golay complementary
codes to obtain a first filter output and a second filter output;
and estimating the wireless channel by combining the first and
second filter outputs.
2. The method of claim 1, wherein estimating the wireless channel
comprises: combining a fast Fourier transform (FFT) of the first
filter output and a FFT of the second filter output.
3. An apparatus for wireless communications, comprising: a receiver
configured to receive a channel estimation (CE) field transmitted
over a wireless channel, wherein the CE field was constructed by
using a pair of Golay complementary codes; a processor configured
to process the received CE field by using a matched filter
associated with the pair of Golay complementary codes to obtain a
first filter output and a second filter output; and an estimator
configured to estimate the wireless channel by combining the first
and second filter outputs.
4. The apparatus of claim 3, wherein the estimator is also
configured to combine a fast Fourier transform (FFT) of the first
filter output and a FFT of the second filter output.
5. An apparatus for wireless communications, comprising: means for
receiving a channel estimation (CE) field transmitted over a
wireless channel, wherein the CE field was constructed by using a
pair of Golay complementary codes; means for processing the
received CE field by using a matched filter associated with the
pair of Golay complementary codes to obtain a first filter output
and a second filter output; and means for estimating the wireless
channel by combining the first and second filter outputs.
6. The apparatus of claim 5, wherein the means for estimating the
wireless channel comprises: means for combining a fast Fourier
transform (FFT) of the first filter output and a FFT of the second
filter output.
7. A computer-program product for wireless communications,
comprising a computer-readable medium comprising instructions
executable to: receive a channel estimation (CE) field transmitted
over a wireless channel, wherein the CE field was constructed by
using a pair of Golay complementary codes; process the received CE
field by using a matched filter associated with the pair of Golay
complementary codes to obtain a first filter output and a second
filter output; and estimate the wireless channel by combining the
first and second filter outputs.
8. A wireless node, comprising: at least one antenna; a receiver
configured to receive via the at least one antenna a channel
estimation (CE) field transmitted over a wireless channel, wherein
the CE field was constructed by using a pair of Golay complementary
codes; a processor configured to process the received CE field by
using a matched filter associated with the pair of Golay
complementary codes to obtain a first filter output and a second
filter output; and an estimator configured to estimate the wireless
channel by combining the first and second filter outputs.
Description
CLAIM OF PRIORITY UNDER 35 U.S.C. .sctn.119
[0001] The present application for patent is a Divisional of U.S.
patent application Ser. No. 12/572,876 entitled "CODES AND
PREAMBLES FOR SINGLE CARRIER AND OFDM TRANSMISSIONS," filed Oct. 2,
2009, which claims benefit of Provisional Application Ser. No.
61/103,503 filed Oct. 7, 2008, and assigned to the assignee hereof
and hereby expressly incorporated by reference herein.
BACKGROUND
[0002] 1. Field
[0003] Certain aspects of the present disclosure generally relate
to wireless communications and, more particularly, to generation of
extended Golay codes and usage in different fields of a packet for
single carrier and Orthogonal Frequency Division Multiplexing
(OFDM) transmissions.
[0004] 2. Background
[0005] Millimeter wave communications represent communications
where a carrier frequency of approximately 60 GHz is utilized. A
dual-mode millimeter-wave Physical Layer (PHY) can support a single
carrier (SC) modulation and an Orthogonal Frequency Division
Multiplexing (OFDM) modulation by employing a common mode (CM)
transmission.
[0006] The CM represents a single-carrier mode used by both SC and
OFDM based devices for beaconing, network-control signaling, and
base-rate data communications. The CM can be typically employed for
interoperability between different devices and different networks.
However, a frame structure of the SC transmission mode is
substantially different from a frame structure of the OFDM
transmission mode, which limits the level of interoperability
between the SC and OFDM devices and networks.
[0007] The present disclosure proposes generation of a frame
structure suitable for use by both SC-modulated and OFDM-modulated
transmission signals, while ensuring accurate channel estimation at
a receiver side.
SUMMARY
[0008] Certain aspects provide a method for wireless
communications. The method generally includes obtaining at least
one extended Golay code of at least length 2.sup.m+2.sup.n, wherein
the at least one extended Golay code comprises at least a first
Golay code of length 2.sup.m and a second Golay code of length
2.sup.n, and generating a packet using the at least one extended
Golay code.
[0009] Certain aspects provide an apparatus for wireless
communications. The apparatus generally includes a module
configured to obtain at least one extended Golay code of at least
length 2.sup.m+2.sup.n, wherein the at least one extended Golay
code comprises at least a first Golay code of length 2.sup.m and a
second Golay code of length 2.sup.n, and a generator configured to
generate a packet using the at least one extended Golay code.
[0010] Certain aspects provide an apparatus for wireless
communications. The apparatus generally includes means for
obtaining at least one extended Golay code of at least length
2.sup.m+2.sup.n, wherein the at least one extended Golay code
comprises at least a first Golay code of length r and a second
Golay code of length 2.sup.n, and means for generating a packet
using the at least one extended Golay code.
[0011] Certain aspects provide a computer-program product for
wireless communications. The computer-program product includes a
computer-readable medium comprising instructions executable to
obtain at least one extended Golay code of at least length
2.sup.m+2.sup.n, wherein the at least one extended Golay code
comprises at least a first Golay code of length 2.sup.m and a
second Golay code of length 2.sup.n, and generate a packet using
the at least one extended Golay code.
[0012] Certain aspects provide a wireless node. The wireless node
generally includes at least one antenna, a module configured to
obtain at least one extended Golay code of at least length
2.sup.m+2.sup.n, wherein the at least one extended Golay code
comprises at least a first Golay code of length 2.sup.m and a
second Golay code of length 2.sup.n, a generator configured to
generate a packet using the at least one extended Golay code, and a
transmitter configured to transmit the generated packet via the at
least one antenna.
[0013] Certain aspects provide a method for wireless
communications. The method generally includes generating a preamble
comprising a channel estimation (CE) field, wherein the CE field
comprises a pattern being defined from a pair of Golay
complementary codes, pre-pending the preamble to a data payload,
and transmitting a packet having the preamble and the data payload
therein.
[0014] Certain aspects provide an apparatus for wireless
communications. The apparatus generally includes a generator
configured to generate a preamble comprising a channel estimation
(CE) field, wherein the CE field comprises a pattern being defined
from a pair of Golay complementary codes, a circuit configured to
pre-pend the preamble to a data payload, and a transmitter
configured to transmit a packet having the preamble and the data
payload therein.
[0015] Certain aspects provide an apparatus for wireless
communications. The apparatus generally includes means for
generating a preamble comprising a channel estimation (CE) field,
wherein the CE field comprises a pattern being defined from a pair
of Golay complementary codes, means for pre-pending the preamble to
a data payload, and means for transmitting a packet having the
preamble and the data payload therein.
[0016] Certain aspects provide a computer-program product for
wireless communications. The computer-program product includes a
computer-readable medium comprising instructions executable to
generate a preamble comprising a channel estimation (CE) field,
wherein the CE field comprises a pattern being defined from a pair
of Golay complementary codes, pre-pend the preamble to a data
payload, and transmit a packet having the preamble and the data
payload therein.
[0017] Certain aspects provide a wireless node. The wireless node
generally includes at least one antenna, a generator configured to
generate a preamble comprising a channel estimation (CE) field,
wherein the CE field comprises a pattern being defined from a pair
of Golay complementary codes, a circuit configured to pre-pend the
preamble to a data payload, and a transmitter configured to
transmit via the at least one antenna a packet having the preamble
and the data payload therein.
[0018] Certain aspects provide a method for wireless
communications. The method generally includes receiving a channel
estimation (CE) field transmitted over a wireless channel, wherein
the CE field was constructed by using a pair of Golay complementary
codes, processing the received CE field by using a matched filter
associated with the pair of Golay complementary codes to obtain a
first filter output and a second filter output, and estimating the
wireless channel by combining the first and second filter
outputs.
[0019] Certain aspects provide an apparatus for wireless
communications. The apparatus generally includes a receiver
configured to receive a channel estimation (CE) field transmitted
over a wireless channel, wherein the CE field was constructed by
using a pair of Golay complementary codes, a processor configured
to process the received CE field by using a matched filter
associated with the pair of Golay complementary codes to obtain a
first filter output and a second filter output, and an estimator
configured to estimate the wireless channel by combining the first
and second filter outputs.
[0020] Certain aspects provide an apparatus for wireless
communications. The apparatus generally includes means for
receiving a channel estimation (CE) field transmitted over a
wireless channel, wherein the CE field was constructed by using a
pair of Golay complementary codes, means for processing the
received CE field by using a matched filter associated with the
pair of Golay complementary codes to obtain a first filter output
and a second filter output, and means for estimating the wireless
channel by combining the first and second filter outputs.
[0021] Certain aspects provide a computer-program product for
wireless communications. The computer-program product includes a
computer-readable medium comprising instructions executable to
receive a channel estimation (CE) field transmitted over a wireless
channel, wherein the CE field was constructed by using a pair of
Golay complementary codes, process the received CE field by using a
matched filter associated with the pair of Golay complementary
codes to obtain a first filter output and a second filter output,
and estimate the wireless channel by combining the first and second
filter outputs.
[0022] Certain aspects provide a wireless node. The wireless node
generally includes at least one antenna, a receiver configured to
receive via the at least one antenna a channel estimation (CE)
field transmitted over a wireless channel, wherein the CE field was
constructed by using a pair of Golay complementary codes, a
processor configured to process the received CE field by using a
matched filter associated with the pair of Golay complementary
codes to obtain a first filter output and a second filter output,
and an estimator configured to estimate the wireless channel by
combining the first and second filter outputs.
BRIEF DESCRIPTION OF THE DRAWINGS
[0023] So that the manner in which the above-recited features of
the present disclosure can be understood in detail, a more
particular description, briefly summarized above, may be had by
reference to aspects, some of which are illustrated in the appended
drawings. It is to be noted, however, that the appended drawings
illustrate only certain typical aspects of this disclosure and are
therefore not to be considered limiting of its scope, for the
description may admit to other equally effective aspects.
[0024] FIG. 1 illustrates an example wireless communication system,
in accordance with certain aspects of the present disclosure.
[0025] FIG. 2 illustrates various components that may be utilized
in a wireless device in accordance with certain aspects of the
present disclosure.
[0026] FIG. 3 illustrates an example transmitter that may be used
within a wireless communication system in accordance with certain
aspects of the present disclosure.
[0027] FIG. 4 illustrates an example receiver that may be used
within a wireless communication system in accordance with certain
aspects of the present disclosure.
[0028] FIG. 5 illustrates an example of extended Golay matched
filter that may be used within the receiver from FIG. 4 in
accordance with certain aspects of the present disclosure.
[0029] FIG. 6 illustrates another example of extended Golay matched
filter that may be used within the receiver from FIG. 4 in
accordance with certain aspects of the present disclosure.
[0030] FIG. 7 illustrates example operations for designing extended
Golay codes for usage within a transmission packet in accordance
with certain aspects of the present disclosure.
[0031] FIG. 7A illustrates example components capable of performing
the operations illustrated in FIG. 7.
[0032] FIG. 8 illustrates an example of standard frame format for a
millimeter wave communication system in accordance with certain
aspects of the present disclosure.
[0033] FIG. 9 illustrates an example of channel estimation (CE)
field that may be used within a preamble of the frame in accordance
with certain aspects of the present disclosure.
[0034] FIG. 10 illustrates an example circuitry for processing of
the CE field that may be used within the receiver from FIG. 4 in
accordance with certain aspects of the present disclosure.
[0035] FIG. 11 illustrates an example of long CE field in
accordance with certain aspects of the present disclosure.
[0036] FIG. 12 illustrates an example of preamble format with a
short CE field in accordance with certain aspects of the present
disclosure.
[0037] FIG. 13 illustrates another example of preamble format with
a short CE field in accordance with certain aspects of the present
disclosure.
[0038] FIG. 14 illustrates an example of Kronecker code with a
centered tap in accordance with certain aspects of the present
disclosure.
[0039] FIG. 15 illustrates an example of channel estimate for a
single path in accordance with certain aspects of the present
disclosure.
[0040] FIG. 16 illustrates an example of preamble structure for an
Orthogonal Frequency Division Multiplexing (OFDM) transmission mode
that may be also used for a Single Carrier (SC) transmission mode
in accordance with certain aspects of the present disclosure.
[0041] FIG. 17 illustrates example operations for designing a
preamble structure within a transmission frame in accordance with
certain aspects of the present disclosure.
[0042] FIG. 17A illustrates example components capable of
performing the operations illustrated in FIG. 17.
[0043] FIG. 18 illustrates example operations for processing of a
received CE sequence to obtain channel estimates in accordance with
certain aspects of the present disclosure.
[0044] FIG. 18A illustrates example components capable of
performing the operations illustrated in FIG. 18.
DETAILED DESCRIPTION
[0045] Various aspects of the disclosure are described more fully
hereinafter with reference to the accompanying drawings. This
disclosure may, however, be embodied in many different forms and
should not be construed as limited to any specific structure or
function presented throughout this disclosure. Rather, these
aspects are provided so that this disclosure will be thorough and
complete, and will fully convey the scope of the disclosure to
those skilled in the art. Based on the teachings herein one skilled
in the art should appreciate that the scope of the disclosure is
intended to cover any aspect of the disclosure disclosed herein,
whether implemented independently of or combined with any other
aspect of the disclosure. For example, an apparatus may be
implemented or a method may be practiced using any number of the
aspects set forth herein. In addition, the scope of the disclosure
is intended to cover such an apparatus or method which is practiced
using other structure, functionality, or structure and
functionality in addition to or other than the various aspects of
the disclosure set forth herein. It should be understood that any
aspect of the disclosure disclosed herein may be embodied by one or
more elements of a claim.
[0046] The word "exemplary" is used herein to mean "serving as an
example, instance, or illustration." Any aspect described herein as
"exemplary" is not necessarily to be construed as preferred or
advantageous over other aspects.
[0047] The teachings herein may be incorporated into (e.g.,
implemented within or performed by) a variety of wired or wireless
apparatuses (e.g., nodes). In some aspects, a wireless node
implemented in accordance with the teachings herein may comprise an
access point or an access terminal or a piconet controller or other
type of wireless device.
[0048] An access point ("AP") may comprise, be implemented as, or
known as NodeB, Radio Network Controller ("RNC"), eNodeB, Base
Station Controller ("BSC"), Base Transceiver Station ("BTS"), Base
Station ("BS"), Transceiver Function ("TF"), Radio Router, Radio
Transceiver, Basic Service Set ("BSS"), Extended Service Set
("ESS"), Radio Base Station ("RBS"), or some other terminology.
[0049] An access terminal ("AT") may comprise, be implemented as,
or known as an access terminal, a subscriber station, a subscriber
unit, a mobile station, a remote station, a remote terminal, a user
terminal, a user agent, a user device, user equipment, or some
other terminology. In some implementations, an access terminal may
comprise a cellular telephone, a cordless telephone, a Session
Initiation Protocol ("SIP") phone, a wireless local loop ("WLL")
station, a personal digital assistant ("PDA"), a handheld device
having wireless connection capability, or some other suitable
processing device connected to a wireless modem. Accordingly, one
or more aspects taught herein may be incorporated into a phone
(e.g., a cellular phone or smart phone), a computer (e.g., a
laptop), a portable communication device, a portable computing
device (e.g., a personal data assistant), an entertainment device
(e.g., a music or video device, or a satellite radio), a global
positioning system device, or any other suitable device that is
configured to communicate via a wireless or wired medium.
[0050] Although particular aspects are described herein, many
variations and permutations of these aspects fall within the scope
of the disclosure. Although some benefits and advantages of the
preferred aspects are mentioned, the scope of the disclosure is not
intended to be limited to particular benefits, uses, or objectives.
Rather, aspects of the disclosure are intended to be broadly
applicable to different wireless technologies, system
configurations, networks, and transmission protocols, some of which
are illustrated by way of example in the figures and in the
following description of the preferred aspects. The detailed
description and drawings are merely illustrative of the disclosure
rather than limiting, the scope of the disclosure being defined by
the appended claims and equivalents thereof.
An Example Wireless Communication System
[0051] The techniques described herein may be used for various
broadband wireless communication systems, including communication
systems that are based on a single carrier transmission. Aspects
disclosed herein may be advantageous to systems employing Ultra
Wide Band (UWB) signals including millimeter-wave signals. However,
the present disclosure is not intended to be limited to such
systems, as other coded signals may benefit from similar
advantages.
[0052] FIG. 1 illustrates an example of a wireless communication
system 100 in which aspects of the present disclosure may be
employed. The wireless communication system 100 may be a broadband
wireless communication system. The wireless communication system
100 may provide communication for a number of cells 102, each of
which is serviced by a base station 104. A base station 104 may be
a fixed station that communicates with user terminals 106. The base
station 104 may alternatively be referred to as an access point, a
Node B or some other terminology. A cell 102 within the wireless
communication system 100 may be a piconet comprising a collection
of one or more logically associated devices that share a single
identifier with a common coordinator, such as, for example, a
piconet controller.
[0053] FIG. 1 depicts various user terminals 106 dispersed
throughout the system 100. The user terminals 106 may be fixed
(i.e., stationary) or mobile. The user terminals 106 may
alternatively be referred to as remote stations, access terminals,
terminals, subscriber units, mobile stations, stations, user
equipment, etc. The user terminals 106 may be wireless devices,
such as cellular phones, personal digital assistants (PDAs),
handheld devices, wireless modems, laptop computers, personal
computers, etc.
[0054] A variety of algorithms and methods may be used for
transmissions in the wireless communication system 100 between the
base stations 104 and the user terminals 106. For example, signals
may be sent and received between the base stations 104 and the user
terminals 106 in accordance with UWB techniques. If this is the
case, the wireless communication system 100 may be referred to as
an UWB system.
[0055] A communication link that facilitates transmission from a
base station 104 to a user terminal 106 may be referred to as a
downlink (DL) 108, and a communication link that facilitates
transmission from a user terminal 106 to a base station 104 may be
referred to as an uplink (UL) 110. Alternatively, a downlink 108
may be referred to as a forward link or a forward channel, and an
uplink 110 may be referred to as a reverse link or a reverse
channel.
[0056] A cell 102 may be divided into multiple sectors 112. A
sector 112 is a physical coverage area within a cell 102. Base
stations 104 within a wireless communication system 100 may utilize
antennas that concentrate the flow of power within a particular
sector 112 of the cell 102. Such antennas may be referred to as
directional antennas.
[0057] FIG. 2 illustrates various components that may be utilized
in a wireless device 202 that may be employed within the wireless
communication system 100. The wireless device 202 is an example of
a device that may be configured to implement the various methods
described herein. The wireless device 202 may be a base station 104
or a user terminal 106.
[0058] The wireless device 202 may include a processor 204 which
controls operation of the wireless device 202. The processor 204
may also be referred to as a central processing unit (CPU). Memory
206, which may include both read-only memory (ROM) and random
access memory (RAM), provides instructions and data to the
processor 204. A portion of the memory 206 may also include
non-volatile random access memory (NVRAM). The processor 204
typically performs logical and arithmetic operations based on
program instructions stored within the memory 206. The instructions
in the memory 206 may be executable to implement the methods
described herein.
[0059] The wireless device 202 may also include a housing 208 that
may include a transmitter 210 and a receiver 212 to allow
transmission and reception of data between the wireless device 202
and a remote location. The transmitter 210 and receiver 212 may be
combined into a transceiver 214. An antenna 216 may be attached to
the housing 208 and electrically coupled to the transceiver 214.
The wireless device 202 may also include (not shown) multiple
transmitters, multiple receivers, multiple transceivers, and/or
multiple antennas.
[0060] The wireless device 202 may also include a signal detector
218 that may be used in an effort to detect and quantify the level
of signals received by the transceiver 214. The signal detector 218
may detect such signals as total energy, energy per subcarrier per
symbol, power spectral density and other signals. The wireless
device 202 may also include a digital signal processor (DSP) 220
for use in processing signals.
[0061] The various components of the wireless device 202 may be
coupled together by a bus system 222, which may include a power
bus, a control signal bus, and a status signal bus in addition to a
data bus.
[0062] FIG. 3 illustrates an example of a transmitter 302 that may
be used within a wireless communication system 100 that utilizes a
single-carrier (SC), an Orthogonal Frequency Division Multiplexing
(OFDM) or some other transmission technique. Portions of the
transmitter 302 may be implemented in the transmitter 210 of a
wireless device 202. The transmitter 302 may be implemented in a
base station 104 for transmitting data 304 to a user terminal 106.
The transmitter 302 may also be implemented in a user terminal 106
for transmitting data 304 to a base station 104 on an uplink
110.
[0063] Data 304 to be transmitted are shown being provided as input
to a mapper 306. The mapper 306 may map the data stream 304 onto
constellation points. The mapping may be done using some modulation
constellation, such as binary phase-shift keying (BPSK), quadrature
phase-shift keying (QPSK), 8 phase-shift keying (8PSK), quadrature
amplitude modulation (QAM), etc. Thus, the mapper 306 may output a
symbol stream 308, which may represent an input into a preamble
insertion unit 310.
[0064] The preamble insertion unit 310 may be configured for
inserting a preamble sequence at the beginning of the input symbol
stream 308, and may generate a corresponding data stream 312. The
preamble may be known at the receiver and may be utilized for time
and frequency synchronization, channel estimation, equalization and
channel decoding. The output 312 of the preamble insertion unit 310
may then be up-converted to a desired transmit frequency band by a
radio frequency (RF) front end 314. An antenna 316 may then
transmit a resulting signal 318 over a wireless channel.
[0065] FIG. 4 illustrates an example of a receiver 402 that may be
used within a wireless device 202 that utilizes a single-carrier or
some other transmission technique. Portions of the receiver 402 may
be implemented in the receiver 212 of a wireless device 202. The
receiver 402 may be implemented in a user terminal 106 for
receiving data 404 from a base station 104 on a downlink 108. The
receiver 402 may also be implemented in a base station 104 for
receiving data 404 from a user terminal 106 on an uplink 110.
[0066] When a signal 404 is received by an antenna 406, it may be
down-converted to a baseband signal 410 by an RF front end 408. A
frame format of the received signal for single-carrier data
communications typically comprises a preamble followed by a data
portion. A portion of the preamble 412 may be used for channel
estimation by unit 416. Received data 414 may be processed by an
equalization unit 420 employing previously computed channel
estimates 418.
[0067] A demapper 424 may input an equalized data stream 422 and
may perform the inverse of the symbol mapping operation that was
performed by the mapper 306 from FIG. 3 thereby outputting a data
stream 426. Ideally, this data stream 426 corresponds to the data
304 that was provided as input to the transmitter 302, as
illustrated in FIG. 3.
[0068] Aspects disclosed herein may be advantageous to wireless
systems employing SC and OFDM signals used in 60 GHz millimeter
wave systems, such as systems defined by the IEEE 802.15.3c
protocol and Very High Throughput 60 (VHT60) protocol. However, the
present disclosure is not intended to be limited to such systems,
as other applications may benefit for similar advantages.
Design of Extended Golay Codes
[0069] The present disclosure relates to generation of Golay codes
and extended Golay codes and its usage in the different fields of a
packet for SC-based and OFDM-based transmissions. A pair of Golay
complementary codes of length N may be specified by a delay vector
D=[D.sub.0 D.sub.1 . . . D.sub.M-1] and a seed vector W=[W.sub.0
W.sub.1 . . . W.sub.M-1], where N=2.sup.M. The elements of D may
all be distinct and may be chosen from the set of values 2.sup.0,
2.sup.1, . . . , 2.sup.M-1. The elements of W may be binary values,
i.e., +1 or -1, or quadric-phase values, i.e., +1, -1, +j, -j, or
complex multilevel values.
[0070] In one aspect of the present disclosure, an extended Golay
code of length 2.sup.m+2.sup.n may be obtained by attaching a first
Golay code of length 2.sup.m to a second Golay code of length
2.sup.n. The first Golay code may be pre-pended to the second Golay
code or the second Golay code may be appended to the first Golay
code.
[0071] In one example, a pair of Golay complementary codes may be
of length 8 chips and denoted as a.sup.(1) and b.sup.(1), while
another pair of Golay complementary codes may be of length 16 chips
and denoted as a.sup.(2) and b.sup.(2). Then, a pair of
complementary Golay codes a.sup.(3) and b.sup.(3) of length 24
chips may be constructed in many different ways. For example, the
Golay code a.sup.(3)may be constructed by appending the Golay code
a.sup.(1) to the Golay code a.sup.(2), and the Golay code b.sup.(3)
may be constructed by appending the Golay code b.sup.(1) to the
Golay code b.sup.(2). Another set of extended complementary Golay
codes may be constructed by appending a.sup.(1) to b.sup.(2) and
b.sup.(1) to a.sup.(2).
[0072] It should be also noted that an extended Golay code of any
even length may be obtained by using the proposed method and by
appending a first Golay code to another extended Golay code. Also,
an extended Golay code may be obtained by attaching more than two
Golay codes. For example, a Golay code of length 26 chips may be
obtained by attaching three Golay codes of length 16, 8, and 2
respectively to each other.
[0073] FIG. 5 illustrates an extended Golay matched filter 400 that
may be used within the receiver 402 from FIG. 4 in accordance with
certain aspects of the present disclosure. The filter 500 may be
applied to perform matched filtering to the received extended Golay
codes a.sup.(3)=[a.sup.(1) a.sup.(2)] and b.sup.(3)=[b.sup.(1)
b.sup.(2)] previously transmitted over a wireless channel. A Golay
matched filter 502 may be matched to complementary Golay codes
(a.sup.(1),b.sup.(1)) and a Golay matched filter 504 may be matched
to complementary Golay codes (a.sup.(2), b.sup.(2)). An extended
Golay code 514 (i.e., the code a.sup.(3)=[a.sup.(1) a.sup.(2)]) may
be obtained at the receiver 402 by combining matched filter outputs
506 and 510, while an extended Golay code 516 (i.e., the code
b.sup.(3)=[b.sup.(1) b.sup.(2)]) may be obtained by combining
matched filter outputs 508 and 512.
[0074] Instead of being the received signal that comprises the
extended Golay codes transmitted over the wireless channel, an
input signal 501 may be a Dirac function or a Kronecker code. By
exciting the extended Golay matched filter 500 with the Dirac or
the Kronecker pulse signal, the filter 500 may be configured to be
a generator of the extended Golay code sequences 514 and 516 for
transmission, and it may be utilized within the transmitter 302
from FIG. 3.
[0075] FIG. 6 illustrates another example of extended Golay matched
filter 600 that may be used within the receiver 402 from FIG. 4 in
accordance with certain aspects of the present disclosure. An
obtained extended Golay code sequence 610 may correspond to the
extended Golay code a.sup.(3)=[a.sup.(1) a.sup.(2)], and another
obtained extended Golay code sequence 612 may correspond to the
extended Golay code b.sup.(3)=[b.sup.(1) b.sup.(2)]. The sequence
610 may be obtained by combining branch a outputs 602 and 606 of
two Golay matched filters that are matched to two pairs of
complementary Golay codes (a.sup.(1), b.sup.(1)) and (a.sup.(2),
b.sup.(2)), and the sequence 612 may be obtained by combining
branch b outputs 604 and 608 of the same two Golay matched
filters.
[0076] Similarly as for the filter 500 from FIG. 5, the extended
Golay matched filter 600 may be excited at an input 601 by the
Dirac function or the Kronecker code. In this aspect of the present
disclosure, the filter 600 may be configured as a generator of the
extended Golay code sequences 610 and 612 for transmission, and it
may be utilized within the transmitter 302 from FIG. 3.
[0077] A packet for transmission may comprise a preamble and a data
payload, and may be constructed by using the extended Golay codes.
The extended Golay codes may be utilized in any of the fields of
the preamble or in all fields of the preamble. The extended Golay
codes may be also used as spreading codes for at least a header or
the data payload of the transmission packet. Furthermore, the
extended Golay codes may be inserted in the header and/or in the
payload to enable frequency domain processing at a receiver.
[0078] The extended Golay codes may be used in all fields of the
millimeter wave frame. This may include a Synchronization (SYNC)
field, a Start Frame Delimiter (SFD) field and a Channel Estimation
(CE) sequence field of the preamble. Furthermore, the extended
Golay code may be used as a cyclic prefix in a sub-block of data
for both SC and OFDM transmission modes.
[0079] In one aspect of the present disclosure, an extended Golay
code may be obtained by retrieving it from a memory. In another
aspect, the extended Golay code may be generated by using an
appropriately designed circuit. In yet another aspect, the extended
Golay code may be obtained by a device requesting it from another
device.
[0080] FIG. 7 illustrates example operations 700 for designing
extended Golay codes for usage within a transmission packet in
accordance with certain aspects of the present disclosure. At 702,
at least one extended Golay code of at least length 2.sup.m+2.sup.n
may be obtained, wherein the at least one extended Golay code may
comprise at least a first Golay code of length 2.sup.m and a second
Golay code of length 2.sup.n. At 704, a packet for transmission may
be generated using the at least one extended Golay code.
Frame and Preamble Format
[0081] FIG. 8 illustrates an example of standard frame format 800
used in millimeter wave communication systems such as the one
adopted in the IEEE 802.15.3c standard or the one adopted for the
VHT60 protocol under the IEEE 802.11 standard in accordance with
certain aspects of the present disclosure. The frame 800 may
comprise a preamble 802, a header 804 and a data payload 806.
[0082] The preamble 802 may be typically constructed from three
fields, some of which may be combined together. A Synchronization
(SYNC) field 808 may be typically used for antenna and direction
selection, Automatic Gain Control (AGC), Automatic Frequency
Control (AFC), and packet detection. A Start Frame Delimiter (SFD)
field 810 may indicate an end of the SYNC field 808. The SFD field
810 may not be a separate field, but rather a part of the SYNC
field 808 or a part of a Channel Estimation (CE) field 812. The CE
field 812 may be utilized at a receiver side to estimate multipath
channel taps.
[0083] The millimeter wave standards that define communications
based on 60 GHz carrier frequency specify a dual mode physical
layer for supporting different transmission modes and different
applications. The single carrier (SC) transmission mode typically
targets low power low cost markets. On the other hand, the OFDM
transmission mode typically targets high performance markets. The
OFDM sampling rate may be specified as 1.5 times the SC chip rate,
and the OFDM transmission mode may typically use a Fast Fourier
Transform (FFT) of size 512 chips.
[0084] The SC and OFDM transmission modes may share a unified
preamble. Alternatively, each transmission mode may have its own
preamble. It may be preferable that the SC CE field enables channel
estimation of a multipath channel that extends over at least 256
chips, whereas the OFDM CE field may enable channel estimation of a
multipath channel that extends over 512 chips matching the FFT
size. Furthermore, it may be preferable to enable time domain and
frequency domain channel estimation by using codes with perfect
autocorrelation function, i.e., a Dirac function or a Kronecker
code.
[0085] As an example, a CE field 900 illustrated in FIG. 9 may be
constructed using a length 256 Golay complementary code pair (a256,
b256). The CE field 900 may satisfy requirements for the SC-based
transmission. As illustrated in FIG. 9, a cyclic prefix 902 of
length 128 chips may be the copy of the last 128 chips of a code
904. A cyclic postfix 906 may be the copy of the first 128 chips of
the code 904. The same approach may be applied to codes 908-912.
The CE field 900 may be referred as a short CE field, and its
length may be 1024 chips.
[0086] FIG. 10 illustrates an example circuitry 1000 for processing
of a CE field (e.g., the CE field 900 from FIG. 9) in accordance
with certain aspects of the present disclosure. The circuitry 1000
may be used within the receiver 402 from FIG. 4 for obtaining
channel estimates. Once a CE field 1002 of a preamble is received,
it may be further processed in time domain. In particular, the CE
field 1002 may be input into a Golay matched filter 1004. A Golay
matched filter output 1006 (i.e., a branch that provides a Golay
code of type a) may be combined with a Golay matched filter output
1008 (i.e., with a branch that provides a Golay code of type b),
wherein the output 1008 may be taken, for example, 384 chips later
than the output 1006 by closing a switch 1010 in a determined time
instant. A combined sequence 1012 may be processed by a channel
estimation unit 1014 to obtain channel estimates 1016.
[0087] In another aspect, the CE sequence field 1002 may be
processed in frequency domain by adding the FFT of the Golay
matched filter output 1006 to the FFT of the Golay matched filter
output 1008 at a right time instant. The CE sequence field 1002 may
be used along with a SFD field of the same received preamble to
estimate multipath channels with an impulse response length of up
to 256 chips.
[0088] A longer CE field may be desired at a low signal-to-noise
ratio (SNR). In this case, the complementary Golay codes a256 and
b256 may be repeated multiple times. FIG. 11 illustrates an example
of long CE field 1100 where the repetition of two is used.
[0089] It should be noted that a Kronecker or Dirac code (sequence)
of length N may be a sequence having all zero entries except for
one of them. For example, the code [1 0 0 0] represents a Kronecker
code of length four with the first tap being non-zero. On the other
hand, a Kronecker code with a non-zero centered tap is a sequence
having all its entries set to zero except its entry number N/2
(e.g., [0 0 1 0] or [0 1 0 0] for N=4).
[0090] FIG. 12 illustrates a preamble 1200 with a short CE/SFD
field 1204 in accordance with certain aspects of the present
disclosure. The preamble 1200 may also comprise a pre-pended SYNC
field 1202. The CE/SFD field 1204 may be especially suitable for SC
transmission mode. The CE/SFD field 1204 may have the length of
only 640 chips providing a lower overhead compared to the long CE
field 1100 of length 1024 chips.
[0091] Certain aspects of the present disclosure support four
different patterns of the short CE field enabling perfect channel
estimation over duration of 256 chips with a centered tap. These
four patterns may be defined as:
[ pre a 256 b 256 post + a + b - a + b + a + b + a + b + a - b + a
+ b + a - b + a + b + a - b + a - b - a - b + a - b ] , ( 1 )
##EQU00001##
where codes a and b may refer to a Golay complementary code pair of
length 128 chips, the first 128 chips in each row of equation (1)
may act as a prefix and may be part of the SYNC field 1202, while
the last 128 chips in each row of equation (1) may act as a
postfix.
[0092] For example, the first pattern from equation (1) can be used
to generate the CE/SFD field 1204 from FIG. 12. Then, a code 1206
may correspond to the extended Golay code [+b -a], a code 1208 may
correspond to the extended Golay code [+b +a], and a code 1210 may
correspond to the Golay code +b. Similarly, if the fourth pattern
from equation (1) is used, then the code 1206 may correspond to [-b
-a], the code 1208 may correspond to [-b +a], and the code 1210 may
correspond to -b.
[0093] FIG. 13 illustrates a preamble format 1300 with a short
CE/SFD field 1304 in accordance with certain aspects of the present
disclosure. The preamble 1300 may represent one example of the
preamble 1200 from FIG. 12. Since the last part of a SYNC field
1302 may correspond to +a128 Golay code, the first 128 chips of the
CE/SFD field 1304 may be skipped because the code +a128 in the SYNC
field 1302 may act as a part of both the SYNC and CE/SFD fields. A
long CE field may be obtained by repeating both codes 1306 and 1308
M times.
[0094] The codes 1306 and 1308 may be processed in time domain upon
reception and combined together as illustrated in FIG. 10, while
the Golay matched filter output 1008 may be taken from the b branch
256 chips later (i.e., the switch 1010 may be closed after 256
chips). Then, the Kronecker (Dirac) code with the centered tap, as
the one illustrated in FIG. 14, may be obtained.
[0095] The main channel tap for the set of patterns given by
equation (1) may be centered. If the main channel tap is required
to be the first tap, then one of the following patterns may be
utilized for the CE/SFD field 1304:
[ prefix a 256 b 256 post + a + b + a + b - a + b - a + a - b + a -
b - a - b - a ] . ( 2 ) ##EQU00002##
Again, the first Golay code +a may be part of the SYNC field 1302.
Then, the short CE/SFD field 1304 may be of length 768 chips. If
one of the patterns given by equation (2) is used for construction
of the CE field, then the channel estimate for a single path may be
obtained as the one illustrated in FIG. 15.
[0096] The extended Golay code a256 from equation (2) may be
constituted of two complementary Golay codes, whereas the extended
Golay code b256 may be constituted of the same or possibly another
two complementary Golay codes. Then, a long CE field may be
constructed by repeating the extended Golay codes a256 and b256
multiple times
[0097] Certain aspects of the present disclosure support design and
utilization of an efficient preamble structure suitable for OFDM
transmission mode that may also support the SC-based transmissions.
FIG. 16 illustrates an example of this particular preamble
structure 1600. Certain aspects of the present disclosure support
utilization of one of possible 16 patterns for a long CE/SFD field
1604 of the preamble 1600, which may enable a perfect channel
estimation of length 512 chips with a centered tap. These 16
patterns may be defined as:
[ prefix a 512 b 512 postfix - b - a + b - a - b - a - b + a - b -
a + b + b - a - b - a + b - a + b + a + b - a - b + b + a + b - a +
b + a - b + a + b + a + b - b + a + b - a + b + a + b + a - b + a +
b - b + a + b + a + b - a + b + a - b + a + b - b + a + b + a - b -
a - b + a - b + a + b + b - a + b + a - b + a + b + a + b - a + b +
b - a + b - a - b - a + b + a + b - a + b + b - a + b + a + b + a -
b + a + b - a + b + b + a - b + a + b - a + b + a + b + a - b + b +
a - b - a - b + a - b + a + b + a - b + b + a - b + a - b - a - b +
a + b + a - b - b + a - b - a - b + a + b + a - b + a - b - b - a -
b + a - b + a + b + a - b - a - b - b - a - b + a + b + a - b + a -
b - a - b - b - a - b - a + b - a - b + a - b - a - b ] . ( 3 )
##EQU00003##
[0098] In the preferred aspects of the present disclosure, the
first two patterns from equation (3) may be utilized for generation
of the long CE/SFD field 1604. In one aspect, the pattern [prefix
a512 b512 postfix] may be used for the SC-based transmission, while
the pattern [prefix b512 a512 postfix] may be used for the
OFDM-based transmission. Then, detection of a512 code versus b512
code may identify whether the received preamble is a SC preamble or
an OFDM preamble. It should be also noted that the last a128 code
of the SYNC field 1602 may act as a part of a prefix 1606 of the
CE/SFD field 1604.
[0099] Certain aspects of the present disclosure support
utilization of one of possible 16 patterns for generation of the
long CE/SFD field 1604 of the preamble 1600, which may enable a
perfect channel estimation of length 512 chips with a main tap in
the first position. These 16 patterns may be defined as:
[ a 512 prefix b 512 postfix + b - a + b + a + b - a + b - a - b -
a + b - a + b - b - a - b + a - b - a - b - a + b - a - b - a - b +
b - a + b - a - b + a - b - a - b - a + b + a - b - b - a + b - a -
b - a + b + a + b - a + b + a - b - b + a + b - a + b - a - b - a +
b + a + b + a + b + b + a + b - a + b + a + b + a - b + a + b + a +
b - b - a - b - a + b + a + b - a + b - a - b + a + b + b - a - b -
a + b - a - b + a - b - a - b + a + b - b - a + b + a + b + a - b +
a + b - a + b - a + b - b + a - b + a + b - a + b + a + b + a - b -
a + b + b + a - b + a + b + a - b - a - b + a - b - a + b - b + a -
b - a - b + a - b + a + b + a - b + a - b + b + a - b - a - b - a +
b - a - b + a - b + a - b - b + a + b + a - b + a + b - a + b + a +
b - a - b + b + a + b + a - b - a - b + a - b + a + b - a - b + b -
a - b + a - b + a + b + a - b - a - b - a - b ] . ( 4 )
##EQU00004##
[0100] FIG. 17 illustrates example operations 1700 for designing a
preamble structure within a transmission frame in accordance with
certain aspects of the present disclosure. At 1702, a preamble
comprising a CE field may be generated, wherein the CE field may
comprise a pattern being defined from a pair of Golay complementary
codes. At 1704, the preamble may be pre-pended to a data payload.
At 1706, a packet having the preamble and the data payload therein
may be transmitted over a wireless channel.
[0101] FIG. 18 illustrates example operations 1800 for processing
of the received CE sequence field to obtain channel estimates in
accordance with certain aspects of the present disclosure. At 1802,
the CE field may be received within the packet that was transmitted
over the wireless channel, wherein the CE field was constructed by
using a pair of Golay complementary codes. At 1804, the received CE
field may be processed by using a matched filter for the pair of
Golay complementary codes to obtain a first filter output and a
second filter output. At 1806, estimates of the wireless channel
may be obtained by combining the first and second filter
outputs.
[0102] The various operations of methods described above may be
performed by any suitable means capable of performing the
corresponding functions. The means may include various hardware
and/or software component(s) and/or module(s), including, but not
limited to a circuit, an application specific integrate circuit
(ASIC), or processor. Generally, where there are operations
illustrated in Figures, those operations may have corresponding
counterpart means-plus-function components with similar numbering.
For example, blocks 702-704, 1702-1706 and 1802-1806, illustrated
in FIGS. 7, 17 and 18 correspond to circuit blocks 702A-704A,
1702A-1706A and 1802A-1806A illustrated in FIGS. 7A, 17A and
18A.
[0103] As used herein, the term "determining" encompasses a wide
variety of actions. For example, "determining" may include
calculating, computing, processing, deriving, investigating,
looking up (e.g., looking up in a table, a database or another data
structure), ascertaining and the like. Also, "determining" may
include receiving (e.g., receiving information), accessing (e.g.,
accessing data in a memory) and the like. Also, "determining" may
include resolving, selecting, choosing, establishing and the like.
Also, "determining" may include measuring, estimating and the
like.
[0104] As used herein, a phrase referring to "at least one of" a
list of items refers to any combination of those items, including
single members. As an example, "at least one of: a, b, or c" is
intended to cover: a, b, c, a-b, a-c, b-c, and a-b-c.
[0105] The various operations of methods described above may be
performed by any suitable means capable of performing the
operations, such as various hardware and/or software component(s),
circuits, and/or module(s). Generally, any operations illustrated
in the Figures may be performed by corresponding functional means
capable of performing the operations.
[0106] The various illustrative logical blocks, modules and
circuits described in connection with the present disclosure may be
implemented or performed with a general purpose processor, a
digital signal processor (DSP), an application specific integrated
circuit (ASIC), a field programmable gate array signal (FPGA) or
other programmable logic device (PLD), discrete gate or transistor
logic, discrete hardware components or any combination thereof
designed to perform the functions described herein. A general
purpose processor may be a microprocessor, but in the alternative,
the processor may be any commercially available processor,
controller, microcontroller or state machine. A processor may also
be implemented as a combination of computing devices, e.g., a
combination of a DSP and a microprocessor, a plurality of
microprocessors, one or more microprocessors in conjunction with a
DSP core, or any other such configuration.
[0107] The steps of a method or algorithm described in connection
with the present disclosure may be embodied directly in hardware,
in a software module executed by a processor, or in a combination
of the two. A software module may reside in any form of storage
medium that is known in the art. Some examples of storage media
that may be used include random access memory (RAM), read only
memory (ROM), flash memory, EPROM memory, EEPROM memory, registers,
a hard disk, a removable disk, a CD-ROM and so forth. A software
module may comprise a single instruction, or many instructions, and
may be distributed over several different code segments, among
different programs, and across multiple storage media. A storage
medium may be coupled to a processor such that the processor can
read information from, and write information to, the storage
medium. In the alternative, the storage medium may be integral to
the processor.
[0108] The methods disclosed herein comprise one or more steps or
actions for achieving the described method. The method steps and/or
actions may be interchanged with one another without departing from
the scope of the claims. In other words, unless a specific order of
steps or actions is specified, the order and/or use of specific
steps and/or actions may be modified without departing from the
scope of the claims.
[0109] The functions described may be implemented in hardware,
software, firmware or any combination thereof. If implemented in
software, the functions may be stored as one or more instructions
on a computer-readable medium. A storage media may be any available
media that can be accessed by a computer. By way of example, and
not limitation, such computer-readable media can comprise RAM, ROM,
EEPROM, CD-ROM or other optical disk storage, magnetic disk storage
or other magnetic storage devices, or any other medium that can be
used to carry or store desired program code in the form of
instructions or data structures and that can be accessed by a
computer. Disk and disc, as used herein, include compact disc (CD),
laser disc, optical disc, digital versatile disc (DVD), floppy
disk, and Blu-ray.RTM. disc where disks usually reproduce data
magnetically, while discs reproduce data optically with lasers.
[0110] Thus, certain aspects may comprise a computer program
product for performing the operations presented herein. For
example, such a computer program product may comprise a computer
readable medium having instructions stored (and/or encoded)
thereon, the instructions being executable by one or more
processors to perform the operations described herein. For certain
aspects, the computer program product may include packaging
material.
[0111] Software or instructions may also be transmitted over a
transmission medium. For example, if the software is transmitted
from a website, server, or other remote source using a coaxial
cable, fiber optic cable, twisted pair, digital subscriber line
(DSL), or wireless technologies such as infrared, radio, and
microwave, then the coaxial cable, fiber optic cable, twisted pair,
DSL, or wireless technologies such as infrared, radio, and
microwave are included in the definition of transmission
medium.
[0112] Further, it should be appreciated that modules and/or other
appropriate means for performing the methods and techniques
described herein can be downloaded and/or otherwise obtained by a
user terminal and/or base station as applicable. For example, such
a device can be coupled to a server to facilitate the transfer of
means for performing the methods described herein. Alternatively,
various methods described herein can be provided via storage means
(e.g., RAM, ROM, a physical storage medium such as a compact disc
(CD) or floppy disk, etc.), such that a user terminal and/or base
station can obtain the various methods upon coupling or providing
the storage means to the device. Moreover, any other suitable
technique for providing the methods and techniques described herein
to a device can be utilized.
[0113] It is to be understood that the claims are not limited to
the precise configuration and components illustrated above. Various
modifications, changes and variations may be made in the
arrangement, operation and details of the methods and apparatus
described above without departing from the scope of the claims.
* * * * *