U.S. patent application number 11/056154 was filed with the patent office on 2005-09-15 for encoding system and method for a transmitter in wireless communications.
This patent application is currently assigned to Broadcom Corporation. Invention is credited to Hansen, Christopher J., Moorti, Rajendra T., Trachewsky, Jason Alexander.
Application Number | 20050204258 11/056154 |
Document ID | / |
Family ID | 34923503 |
Filed Date | 2005-09-15 |
United States Patent
Application |
20050204258 |
Kind Code |
A1 |
Hansen, Christopher J. ; et
al. |
September 15, 2005 |
Encoding system and method for a transmitter in wireless
communications
Abstract
Method and system encodes a signal according to a code rate that
includes a ratio of uncoded bits to coded bits. An outer encoder
encodes the signal into code words. An interleaver converts the
code words into a byte sequence for wireless transmission. An inner
encoder executes a convolutional code to generate an encoded
signal. The encoded signal is transmitted over a plurality of
subcarriers associated with a wide bandwidth channel having a
spectral efficiency associated with the code rate. The outer
encoder includes a Reed-Solomon encoder having a rate that
increases the code rate of uncoded bits to coded bits.
Inventors: |
Hansen, Christopher J.;
(Sunnyvale, CA) ; Trachewsky, Jason Alexander;
(Menlo Park, CA) ; Moorti, Rajendra T.; (Mountain
View, CA) |
Correspondence
Address: |
SQUIRE, SANDERS & DEMPSEY L.L.P.
14TH FLOOR
8000 TOWERS CRESCENT
TYSONS CORNER
VA
22182
US
|
Assignee: |
Broadcom Corporation
|
Family ID: |
34923503 |
Appl. No.: |
11/056154 |
Filed: |
February 14, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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60544605 |
Feb 13, 2004 |
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60545854 |
Feb 19, 2004 |
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60568914 |
May 7, 2004 |
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60573781 |
May 24, 2004 |
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Current U.S.
Class: |
714/755 |
Current CPC
Class: |
H03M 13/2906 20130101;
H03M 13/6362 20130101; H04W 84/12 20130101; H03M 13/27 20130101;
H03M 13/2936 20130101; H03M 13/1102 20130101; H04B 7/0689 20130101;
H03M 13/2966 20130101; H03M 13/1515 20130101 |
Class at
Publication: |
714/755 |
International
Class: |
H04B 001/69; H04B
001/707; H04B 001/713; H03M 013/00 |
Claims
What is claimed is:
1. A system for generating a signal for wireless communication, the
system comprising: an outer encoder to execute outer encoding
having a first rate on a signal to generate at least one code word;
an interleaver to interleave said at least one code word into a
byte sequence; an inner encoder to execute convolutional encoding
having a second rate on said byte sequence to generate an encoded
signal, wherein said first rate and said second rate produce an
overall coding rate corresponding with a spectral efficiency.
2. The system of claim 1, wherein said overall coding rate
comprises a ratio of uncoded bits in said signal to coded bits in
said encoded signal.
3. The system of claim 1, wherein said outer encoder includes a
Reed-Solomon encoder.
4. The system of claim 1, wherein said outer encoding includes
Reed-Solomon encoding.
5. The system of claim 1, further comprising a plurality of
subcarriers to transmit said encoded signal over a wide bandwidth
channel corresponding to said spectral efficiency.
6. The system of claim 5, wherein said wide bandwidth channel
includes a bandwidth of approximately 40 MHz.
7. The system of claim 1, wherein said inner encoder punctures said
convolutional encoding to generate said encoded signal.
8. The system of claim 7, wherein said inner encoder punctures at a
7/8 puncture rate.
9. A method for generating a signal for wireless communication, the
method comprising: executing an outer encoding process on a signal,
wherein said outer encoding process has a first rate; generating at
least one code word from said outer encoding; interleaving said at
least one code word into a byte sequence; and convolutionally
encoding said byte sequence according to a second rate, wherein
said convolutionally encoding includes generating an encoded signal
according to an overall coding rate produced by said first rate and
said second rate, wherein said overall coding rate corresponds to a
spectral efficiency.
10. The method of claim 9, wherein said executing said outer
encoding process comprises using a Reed-Solomon encoding
process.
11. The method of claim 9, wherein said convolutionally encoding
comprises puncturing said byte sequence.
12. The method of claim 9, wherein said interleaving comprises
converting said at least one code word into bytes within said byte
sequence.
13. The method of claim 9, further comprising transmitting said
encoded signal over a plurality of subcarriers for a wide bandwidth
channel corresponding to said spectral efficiency.
14. A device to generate a signal for wireless communication, the
device configured to: execute an outer encoding process on a
signal, wherein said outer encoding process has a first rate;
generate at least one code word from said outer encoding;
interleave said at least one code word into a byte sequence; and
convolutionally encode said byte sequence according to a second
rate to generate an encoded signal according to an overall coding
rate produced by said first rate and said second rate, wherein said
overall coding rate corresponds to a spectral efficiency.
15. The device of claim 14, said device further configured to use
an outer encoder for said outer encoding process.
16. The device of claim 15, wherein said outer encoder is
configured to use a Reed-Solomon encoding process for said outer
encoding process.
17. The device of claim 14, said device further configured to use
an inner encoder to convolutionally encode said byte sequence.
18. The device of claim 17, wherein said inner encoder is
configured to puncture said byte sequence to generate said encoded
signal.
19. A method for encoding a signal for wireless transmission, the
method comprising: generating a code word from a signal using a
Reed-Solomon encoding process, wherein said Reed-Solomon encoding
process has a first rate; and generating an encoded signal from
said code word using a convolutional encoding process having a
second rate, wherein said first rate and said second rate produce
an overall coding rate applicable having a spectral efficiency for
a wide bandwidth transmission.
20. The method of claim 19, further comprising converting said code
word to a byte sequence.
21. The method of claim 19, further comprising transmitting said
encoded signal within a channel suitable for said wide bandwidth
transmission.
22. The method of claim 20, further comprising puncturing said byte
sequence.
23. A system for encoding a signal, the signal comprising: first
generating means for generating a code word from a signal using a
Reed-Solomon encoding process, wherein said Reed-Solomon encoding
process has a first rate; and second generating means for
generating an encoded signal from said code word using a
convolutional encoding process having a second rate, wherein said
first rate and said second rate produce an overall coding rate
having a spectral efficiency applicable for a wide bandwidth
transmission.
24. The system of claim 23, further comprising transmitting means
for comprising transmitting said encoded signal within a channel
suitable for said wide bandwidth transmission.
25. The system of claim 23, further comprising converting means for
converting said code word to a byte sequence.
26. The system of claim 25, further comprising puncturing means for
puncturing said byte sequence.
27. A system for generating a signal for wireless communication,
the system comprising: executing means for executing an outer
encoding process on a signal, wherein said outer encoding process
has a first rate; generating means for generating at least one code
word from said outer encoding; interleaving means for interleaving
said at least one code word into a byte sequence; and encoding
means for convolutional encoding said byte sequence, wherein said
convolutional encoding has a second rate to generate an encoded
signal according to an overall coding rate produced by said first
rate and said second rate, wherein said overall coding rate
corresponds to a spectral efficiency.
Description
[0001] This patent application claims priority under 35 USC .sctn.
119 to the following co-pending patent applications: U.S.
Provisional Patent Application Ser. No. 60/544,605, filed Feb. 13,
2004; U.S. Provisional Patent Application Ser. No. 60/545,854,
filed Feb. 19, 2004; U.S. Provisional Patent Application Ser. No.
60/568,914, filed May 7, 2004; and U.S. Provisional Patent
Application Ser. No. 60/573,781, filed May 24, 2004.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] This invention relates generally to wireless communication
systems and more particularly to a transmitter transmitting at
improved data rates with such wireless communication systems and
methods of encoding signals to achieve the data rate.
[0004] 2. Description of the Related Art
[0005] Wireless and wire lined communications may occur between
wireless or wire lined communication devices according to various
standards or protocols. Communication systems and networks may
include national or international cellular telephone systems, the
Internet, point-to-point or in-home wireless networks and the like.
A communication system is constructed, and may operate in
accordance with the standard. For example, wireless communication
systems may operate in accordance with one or more standards
including, but not limited to, IEEE 802.11, Bluetooth, advanced
mobile phone services (AMPS), digital AMPS, global system for
mobile communications (GSM), code division multiple access (CDMA),
local multi-point distribution systems (LMDS),
multi-channel-multi-point distribution systems (MMDS), and the
like.
[0006] Wireless local area networks (WLAN) that may use IEEE
802.11, 802.11a, 802.11b, or 802.11g that employ single input,
single output (SISO) wireless communications. Other types of
communications include multiple input, single output (MISO), single
input, multiple output (SIMO), and multiple input, multiple output
(MIMO). With the various types of wireless communications, it may
be desirable to use the various types of wireless communications to
enhance data throughput within a WLAN.
[0007] For example, improved data rates may be achieved with MIMO
communications in comparison to SISO communications. Most WLAN,
however, include legacy wireless communication devices that are
devices compliant with an older version of a wireless communication
standard. Thus, a transmitter capable of MIMO wireless
communications also may be backward compatible with legacy devices
to function in a majority of existing WLANs. One factor for
backward compatibility is that transmitters, receivers, and the
like assume all signals within a system are valid.
BRIEF SUMMARY OF THE INVENTION
[0008] A system for generating a signal for wireless communication
is disclosed. The system includes an outer encoder to execute outer
encoding having a first rate on a signal to generate at least one
code word. The system also includes an interleaver to interleave
the at least one code word into a byte sequence. The system also
includes an inner encoder to execute convolutional encoding having
a second rate on the byte sequence to generate an encoded signal.
The first rate and the second rate produce an overall coding rate
corresponding with a spectral efficiency.
[0009] A method for generating a signal for wireless communication
also is disclosed. The method includes executing an outer encoding
process on a signal. The outer encoding process has a first rate.
The method also includes generating at least one code word from the
outer encoding. The method also includes interleaving the at least
one code word into a byte sequence. The method also includes
convolutionally encoding the byte sequence according to a second
rate. The convolutionally encoding includes generating an encoded
signal according to an overall coding rate produced by the first
rate and the second rate. The overall coding rate corresponds to a
spectral efficiency.
[0010] A method for encoding a signal for wireless transmission
also is disclosed. The method includes generating a code word from
a signal using a Reed-Solomon encoding process. The Reed-Solomon
encoding process has a first rate. The method also includes
generating an encoded signal from said code word using a
convolutional encoding process having a second rate. The first rate
and the second rate produce an overall coding rate having a
spectral efficiency applicable for a wide bandwidth
transmission.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] For proper understanding of the present invention, reference
should be made to the accompanying drawings:
[0012] FIG. 1 illustrates a wireless communication system in
accordance with the present invention;
[0013] FIG. 2 illustrates a wireless communication device in
accordance with the present invention;
[0014] FIG. 3 illustrates an encoding system in accordance with the
present invention;
[0015] FIG. 4 illustrates a transmitter in accordance with the
present invention; and
[0016] FIG. 5 illustrates a flowchart for encoding data in
accordance with the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0017] Reference will now be made to the following detailed
description of the preferred embodiments of the present invention.
Examples of preferred embodiments may be illustrated by the
accompanying drawings.
[0018] FIG. 1 depicts a communication system 10 according to the
present invention. Communication system 10 may be a wireless
communication system having networks supported by various wireless
communication standards or protocols. Communication system 10
includes base stations 12, 14 and 16. Base stations 12, 14 and 16
may provide access for wireless devices and components to
communication system 10. Communication system 10 may provide
services and content to the devices and components via base
stations 12, 14 and 16.
[0019] Communication system 10 also may include wide area networks
(WANs), local area networks (LANs), wireless local area networks
(WLANs), ad-hoc networks, virtual networks, and the like to
facilitate the exchange of information or data. For example,
network 20 may be coupled to base stations 12, 14 and 16 and
support communications with communication system 10.
[0020] Communication system 10 may forward data or information in
the form of signals, either analog or digital. Wireless devices
within the individual base stations may register with the base
stations and receive services or communications within
communication system 10. The wireless devices may exchange data or
information via an allocated channel. Network 20 may set up LANs to
support the channel. To support the wireless communication,
communication system 10 and its applicable networks may use a
standard of protocol for wireless communications. For example, the
IEEE 802.11 specification may be used. The IEEE 802.11
specification has evolved from IEEE 802.11 to IEEE 802.11b to IEEE
802.11a and to IEEE 802.11g. Wireless communication devices that
are compliant with IEEE 802.11b (standard 11b) may exist in the
same wireless local area network as IEEE 802.11g (standard 11g)
compliant wireless communication devices. Further, IEEE 802.11a
(standard 11a) compliant wireless communication devices may reside
in the WLAN as standard 11g compliant wireless communication
devices.
[0021] These different standards may operate within different
frequency ranges, such as 5 to 6 gigahertz (GHz) or 2.4 GHz. For
example, standard 11a may operate within the higher frequency
range. One feature of standard 11a is that portions of the spectrum
from between 5 to 6 GHz may be allocated to a channel. The channel
may be 20 megahertz (MHz) wide within the frequency band. Standard
11a also may use orthogonal frequency division multiplexing (OFDM).
OFDM may be implemented over sub-carriers that represent lines, or
values, within the frequency domain of the 20 MHz channels. A
wireless signal may be transmitted over many different sub-carriers
within the channel. The sub-carriers are orthogonal to each other
so that information may be extracted off each sub-carrier about the
signal without appreciable interference.
[0022] Legacy devices may exist within communication system 10.
Legacy devices are those devices compliant with earlier versions of
the wireless standard, but reside in the same WLAN as devices
compliant with a current or later version of the standard. A
mechanism may be employed to ensure that legacy devices know when
the newer version devices are utilized in a wireless channel to
avoid interference or collisions.
[0023] Thus, newer devices or components within communication
system 10 may use current standards that have backward
compatibility with already installed equipment. The devices and
components may be adaptable to legacy standards and current
standards when transmitting information within communication system
10. Legacy devices or components may be kept off the air or off the
network so as to not interfere or collide with information or data
that they are not familiar with. For example, if a legacy device
receives a signal or information supported by standard 11n, then
the device should forward the information or signal to the
appropriate destination without modifying or terminating the signal
or its data. Further, a received signal may not react to the legacy
device as if the legacy device is a device compatible with a new or
current standard.
[0024] Communication system 10 may operate according to the IEEE
802.11n (standard 11n) protocol for wireless communications.
Alternatively, communication system 10 may operate under a variety
of standards or protocols, such as standard 11a, standard 11g and
standard 11n and may include legacy devices or components. For
example, certain components may comply with standard 11a while
newer components may comply with standard 11n. Standard 11n may
occupy the 5 to 6 GHz band, or, alternatively, standard 11n may
occupy the 2.4 GHz band. Standard 11n may be considered an
extension of standard 11a. Standard 11n devices and components may
operate with a data rate that exceeds 100 Mbps. The devices and
components within communication system 10 may know the physical
layer rate for standard 11n devices and components may be greater
than those of previous standards.
[0025] Bandwidth for wireless channels under standard 11n may be 20
MHz or 40 MHz. Thus, standard 11n may implement wider bands than
previous standards, such as standard 11a. For example, standard 11n
may put two 20 MHz bands together as a 40 MHz band and may send
twice as much data as previous standards. Moreover, information or
data may be filled in a gap between the two 20 MHz bands. The gap
results due to falloff between the two bands. By filling in the
gap, data or information may be sent according to standard 11n at a
rate twice as much as previous standards, if not more.
[0026] Communication system 10 also may include a multiple input,
multiple output (MIMO) structure. MIMO structures may be
implemented in communication system 10 to improve the robustness of
wireless communications. To better improve robustness,
communication system 10 also may set the number of data streams to
be less than the number of transmitters of a wireless device.
[0027] Communication system 10 may resolve the issue of signals
generated by legacy devices or components and having the signals
operate within a MIMO system using multiple antennas. For example,
communication system 10 may determine how the standard 11a signals
will work within the wider bandwidth of the channels for standard
11n. Communication system 10 may increase the probability of
reception of signals transmitting large amounts of data under
current standards or protocols. Further, it may be presumed that
all the devices and components within communication system 10 may
receive all transmitted signals, no matter what format, protocol or
standard is used.
[0028] FIG. 2 depicts a wireless communication device 200 according
to the present invention. Wireless device 200 includes host device
18 and an associated radio 60. For cellular telephone hosts, radio
60 may be a built-in component. For personal digital assistants
hosts, laptop hosts, personal computer hosts and the like, radio 60
may be built-in or an externally coupled component.
[0029] Host device 18 may include processing module 50, memory 52,
radio interface 54, input interface 58 and output interface 56.
Processing module 50 and memory 52 may execute instructions that
are done by host device 18. For example, for a cellular telephone
host device, processing module 50 may perform the corresponding
communication functions in accordance with a particular cellular
telephone standard, such as standard 11n.
[0030] Radio interface 54 may allow data to be received from and
sent to radio 60. For data received from radio 60, such as inbound
data, radio interface 54 provides the data to processing module 50
for further processing or routing to the output interface 56.
Output interface 56 may provide connectivity to an output display
device such as a display, monitor, speakers and the like, such that
the received data may be displayed. Radio interface 54 also may
provide data from the processing module 50 to radio 60. Processing
module 50 may receive the outbound data from an input device such
as a keyboard, keypad, microphone an the like, via input interface
58 or may generate the data itself. For data received via input
interface 58, processing module 50 may perform a corresponding host
function on the data or route it to radio 60 via the radio
interface 54.
[0031] Radio 60 may include a host interface 62, a baseband
processing module 64, memory 66, a plurality of radio frequency
(RF) transmitters 68-72, a transmit/receive (T/R) module 74, a
plurality of antennas 82-86, a plurality of RF receivers 76-80, and
a local oscillation module 100. Baseband processing module 64, in
combination with operational instructions stored in memory 66, may
execute digital receiver functions and digital transmitter
functions, respectively. Baseband processing modules 64 may be
implemented using one or more processing devices. Memory 66 may be
a single memory device or a plurality of memory devices. When
processing module 64 implements one or more of its functions via a
state machine, analog circuitry, digital circuitry, or logic
circuitry, memory 66 storing the corresponding operational
instructions is embedded with the circuitry comprising the state
machine, analog circuitry, digital circuitry, or logic
circuitry.
[0032] Radio 60 may receive outbound data 88 from host device 18
via host interface 62. Baseband processing module 64 receives
outbound data 88 and, based on a mode selection signal 102,
produces one or more outbound symbol streams 90. Mode selection
signal 102 may indicate a particular mode.
[0033] Baseband processing module 64, based on mode selection
signal 102, may produce one or more outbound symbol streams 90 from
output data 88. For example, if mode selection signal 102 indicates
that a single transmit antenna is being utilized for the particular
mode that has been selected, baseband processing module 64 may
produce a single outbound symbol stream 90. Alternatively, if mode
selection signal 102 indicates 2, 3 or 4 antennas, baseband
processing module 64 may produce 2, 3 or 4 outbound symbol streams
90 corresponding to the number of antennas from output data 88.
[0034] Depending on the number of outbound streams 90 produced by
baseband module 64, a corresponding number of the RF transmitters
68-72 may be enabled to convert outbound symbol streams 90 into
outbound RF signals 92. Transmit/receive (T/R) module 74 may
receive outbound RF signals 92 and provides each outbound RF signal
to a corresponding antenna 82-86.
[0035] When radio 60 is in a receive mode, T/R module 74 may
receive one or more inbound RF signals via antennas 82-86. T/R
module 74 provides inbound RF signals 94 to one or more RF
receivers 76-80. RF receivers 76-80 may convert inbound RF signals
94 into a corresponding number of inbound symbol streams 96. The
number of inbound symbol streams 96 may correspond to the
particular mode in which the data was received. Baseband processing
module 60 may receive inbound symbol streams 90 and converts them
into inbound data 98, which are provided to the host device 18 via
the host interface 62.
[0036] FIG. 3 depicts an encoding system 300 for use with wireless
communications according to the present invention. Encoding system
300 may be coupled to a transceiver to code signals for
transmission within a wireless network or system. Alternatively,
encoding system 300 may be coupled to other devices or components
for wireless communications. Further, encoding system 300 may be
within the transceiver. Encoding system 300 also may operate or
encode according to an applicable wireless communication standard
or protocol. For example, encoding system 300 may operate according
to standard 11n, so that encoded signals are formatted to take
advantage of the improvements of standard 11n over legacy
standards.
[0037] Encoding system 300 may include outer encoder 302,
interleaver 304 and inner encoder 306. Encoding system 300 receives
data or information as signal 310 at outer encoder 302. Inner
encoder 306 outputs coded signal 312. A code rate may be determined
by comparing signal 310 with coded signal 312. The code rate also
may be referred to as an overall coding rate. For example, a code
rate may be the ratio of uncoded bits in signal 310 to the coded
bits in coded signal 312. For example, the code rate may be the
ratio of the data rate to the coded data rate, or data rate/coded
data rate. Encoding system 300 may improve the code rate over
legacy systems so as to comply with standard 11n.
[0038] The overall code rate may correspond to a specified spectral
efficiency. The specified spectral efficiency may be known as a
high spectral efficiency. The spectral efficiency may be the ratio
of the data rate to the signal bandwidth. For example, a code rate
may be 0.8 or higher to support a high spectral efficiency
corresponding with the larger signal bandwidth of standard 11n.
Further according to the example, coding system 300 may include a
code rate of 0.8 at 100 megabits/second for a channel having a 40
MHz bandwidth. Constraints applied by standard 11n may warrant a
high code rate to increase the ratio of uncoded bits to coded bits
over legacy standards. Thus, outer encoder 302, interleaver 304 and
inner encoder 306 may operate according to the constraints and a
target code rate of 0.8.
[0039] Encoding system 300 may code bits to improve performance
over a system of uncoded bits. A tradeoff, however, may exist
between performance and complexity of encoding system 300. Thus, if
encoding system 300 becomes too complex, any benefit from improved
performance may be offset by higher costs in constructing and
implementing encoding system 300.
[0040] Outer encoder 302 may include a Reed-Solomon (R-S) encoder.
An R-S encoder may be applicable for coding longer frames. When
encoding, encoding system 300 may forward longer frames with an
increased probability of being received correctly. Outer encoder
302 may implement the R-S encoder even if the applicable wireless
standard uses short frames. Further, outer encoder 302 may be
separable from any convolutional coding, such as that done by inner
encoder 306. Outer encoder 302 may receive data or information as
bits or bytes and then codes the bits or bytes for interleaver 304.
For example, outer encoder 302 may generate 2-5 code words
comprised of bytes. In the example, a code word 320 may include
about 255 bytes with about 239 information bytes. Thus, codeword
320 also may include about 16 redundant bytes.
[0041] Interleaver 304 receives code word 320 to perform
interleaving on the bytes in code word 320, and to generate bits or
bytes 330. Interleaver 304 may be a byte interleaver to interleave
one sequence of bytes into a new sequence of bytes before entering
outer encoder 306. Interleaver 304 may reduce an error rate of
encoding system 300 by resolving errors before the errors arrive at
inner encoder 306. Bit or byte errors from outer encoder 302 may be
randomly generated, but also may occur in bursts. Interleaver 304
may operate according to a specified rate or operator.
[0042] Inner encoder 306 receives bits or bytes 330 and performs
convolutional coding to generate coded signal 312. Inner encoder
306 may be a convolutional encoder that in conjunction with outer
encoder 302 establishes the desired code rate. For example, inner
encoder 306 and outer encoder 302 may work together to develop a
code rate of about 0.8. Inner encoder 306 and outer encoder 302,
however, may be separable from each other. Thus, outer encoder 302
and its encoding schemes may be removed or changed within encoding
system 300 without impacting inner encoder 306, or its
convolutional code. Thus, modularity between the encoding schemes
may exist to improve performance without increased complexity to
existing systems, or the need of new code or devices for encoding
system 300.
[0043] Further, the convolutional code of inner encoder 306 may be
punctured at 7/8s on a binary convolutional code. The coding rate
of inner encoder 306 may generate a code rate of 0.8 for encoding
system 300, when combined with the code rate of outer encoder 302.
Referring back to the R-S encoder, examples of the R-S code may
have a rate that is multiplied by the code rate of a 7/8s
convolutional code to achieve a code rate 0.8. Further, inner
encoder 306 may be a convolutional encoder operable with legacy
standards, such as standard 11a.
[0044] Coded signal 312 may include frame 332. Frame 332 may be one
of many frames within coded signal 332. Frame 332 includes
preamble, or header, field 334 and data field 336. Preamble field
334 may be referred to as a preamble. Preamble field 334 may
include data or information regarding frame 332 or coded signal
312. The information may include, but is not limited to, length of
frame 332. Alternatively, preamble field 334 may include
information regarding code words from outer encoder 302 or
information about coded signal 312. Preamble field 334, however, is
not so large as to make frame 332 unreadable or unusable. Preamble
field 334 also may include short and long training fields.
[0045] With regard to inner encoder 306, it may be the same
convolutional encoder as used in conjunction with standard 11a.
Puncturing of the convolutional code according to standard 11a may
also be 2/3 and 3/4. Options may be added for these codes, such as
a 256 state code or new puncturings for rates of 4/5, 5/6 and 7/8,
as discussed above. Thus, inner encoder 306 may be an encoder
having the above puncture rates. Moreover, the options listed above
may be combined, if desired.
[0046] Interleaver 304 may be in different states for operation
within encoding system 300. One state may be an "off" state,
wherein encoding system 300 acts as if no interleaver 304 is
present. Another state may be as an interleaver having sufficient
depth to randomize the demodulated bits over R-S code words, such
as code word 320.
[0047] Outer encoder 302 may operate or generate code words having
multiple lengths. As noted above, code word 320 may have a length
of about 255, or n, with an information sequence length of about
239 bits, or k. Thus, a correction of up to 8 byte errors may be
allowed per code word from outer encoder 302.
[0048] For an effective code rate of about 0.8, encoding system 300
may execute a coding process having a high spectral efficiency that
achieves a gain of about 4 dB, or above, over the convolutional
coding scheme alone. Further, additional components may be included
in encoding system 300 that facilitate the coding process.
Moreover, the coding processes of outer encoder 302 and inner
encoder 306 may differ from each other.
[0049] FIG. 4 depicts a block diagram of a transmitter 400
according to the present invention. Transmitter 400 includes
scrambler 472, channel encoder 474, interleaver 476, demultiplexer
470, a plurality of symbol mappers 480, 482 and 484, a plurality of
inverse fast Fourier transform (IFFT) modules 486, 488 and 490 and
encoder 492. Transmitter 400 also may include a mode manager module
475 that receives a mode selection signal and produces settings for
transmitter 400.
[0050] Scrambler 472 may add a pseudo-random sequence to outbound
data bits 488 so that the applicable data or information may appear
random. A pseudo-random sequence may be generated from a feedback
shift register having a generator polynomial to produce scrambled
data. Channel encoder 474 may receive the scrambled data and
generate a new sequence of bits having redundancy. The new sequence
may enable improved detection at a receiver. Channel encoder 474
may operate in one of a plurality of modes. These modes may
correspond to standards or protocols for wireless communications.
For example, modes may be assigned to standard 11a, standard 11g,
or standard 11n. Backward compatibility with standard 11a and
standard 11g may be achieved. Further, channel encoder 474 may be a
convolutional encoder with 64 states and a rate of 1/2. The output
of channel encoder 474, as a convolutional encoder, may be
punctured at rates of 1/2, 2/3 and 3/4. For backward compatibility
with standard 11b and the CCK modes of standard 11g, channel
encoder 474 may have the form of a CCK code as defined in standard
11b.
[0051] For improved data rates, such as those desired by standard
11n, channel encoder 474 may use the convolutional encoding, as
described above. Alternatively, channel encoder 474 may use a more
powerful code, including a convolutional code with more states, a
parallel concatenated, or turbo, code or a low-density parity check
block code. In addition, any one of these codes may be combined
with an R-S code of an outer encoder. As discussed above, the outer
encoder may be a Reed-Solomon encoder. The choice of applicable
code may be determined according to backward compatibility and
low-latency requirements.
[0052] Interleaver 476 may receive the encoded data and distribute
the data over multiple symbols. This distribution may allow
improved detection and error correction capabilities at a receiver.
Interleaver 476 may follow standard 11a or standard 11g in backward
compatible modes. For increased performance modes, such as those
associated with standard 11n, interleaver 476 may interleave data
over multiple transmit streams. Thus, these modes may be applicable
to MIMO configurations. Demultiplexer 470 may convert the
interleave stream from interleaver 476 into parallel streams for
transmission.
[0053] Symbol mappers 480, 482, and 484 may receive a corresponding
one of the parallel paths of data from demultiplexer 470.
Transmitter 400 may include any number of symbol mappers and is not
limited to the aspects shown by FIG. 4. Further, the number of
parallel data streams may vary according to the requirements of
transmitter 400. For example, the number of data streams may
correspond to a number of antennas used for transmitting. Further,
the number of symbol mappers may correspond to the number of
antennas.
[0054] Symbol mappers 480, 482 and 484 may map the bit streams, or
data streams, to quadrature amplitude modulated (QAM) symbols. The
map symbols generated by symbol mappers 480, 482 and 484 may be
provided to IFFT modules 486, 488 and 490. IFFT modules 486, 488
and 490 may be referred to as cyclic prefix addition modules. The
number of IFFT modules may correspond to the number of symbol
mappers and data streams. IFFT modules 486, 488 and 490 may perform
frequency domain to time domain conversions and may add a prefix
that allows removal of inter-symbol interference at a receiver. The
length of the IFFT and any applicable cyclic prefix may be defined.
For example, a 64 point IFFT may be used for 20 MHz channels and
128 point IFFT may be used for 40 MHz channels, used according to
standard 11n.
[0055] Encoder 492 may receive the parallel paths of the time
domain symbols and convert them into output symbols. Encoder 492
also may be referred to as a space/time encoder. The number of
input paths to encoder 492 may equal the number of output paths.
Alternatively, the number of output paths may equal the number of
input paths plus 1. For each of the paths, encoder 492 multiplies
the input symbols with an encoding matrix having a form shown in
Equation 01 below. 1 [ C 1 C 2 C 3 C 2 M - 1 - C 2 * C 1 * C 4 C 2
M ] ( 01 )
[0056] The rows of the encoding matrix may correspond to the number
of input paths and the columns may correspond to the number of
output paths. Thus, outbound data bits 488 may be encoded and
prepared for transmission by transmitter 400, and converted to
multiple output streams. Thus, transmitter 400 may support multiple
output structures and operations.
[0057] FIG. 5 depicts a flowchart for encoding data for wireless
communications according to the present invention. The steps shown
in FIG. 5 may be used for converting outbound data into one or more
outbound data streams for multiple output transmission. Step 502
executes by receiving data bits for transmission. The bits may be
generated or created for transmission in a wireless network or
system according to a standard or protocol. For example, standard
11n may be applicable to the system or network that exchanges the
data bits. Alternatively, the applicable system or network may have
standard 11a and standard 11n devices or components. Thus, the
received bits may be received by legacy devices.
[0058] Step 504 executes by encoding the bits according to an outer
encoder, such as outer encoder 302 in FIG. 3. The outer encoder may
encode the bits or bytes according to the specified encoding
process, such as Reed-Solomon encoding. For example, the outer
encoder may be an R-S encoder. The R-S encoder may be effective in
coding longer frames. Step 504 performs the outer encoding of the
received bits. Step 506 executes by generating code words from the
outer encoder. The code words may be bytes. As discussed above, the
code words may include about 255 bytes.
[0059] Step 508 executes by interleaving the code words from bytes
into bytes or bits. Thus, the received code words from the outer
encoder may be interleaved into bits or bytes for use with multiple
data streams. Alternatively, codeword bytes may be interleaved from
one sequence of bytes into a new sequence of bytes. An interleaver,
such as interleaver 304, may be implemented. Moreover, step 508 may
be skipped if no outer encoding is performed on the received bits.
For example, the received bytes may be meant for a network or
system having only legacy devices, such as those compatible with
standard 11a. The received bytes, in this example, may not undergo
outer encoding to improve performance and to increase throughput.
Thus, step 508 may be skipped.
[0060] Step 510 executes by encoding the interleaved bytes
according to an inner encoder, such as inner encoder 306. For
example, the inner encoder may be a convolutional encoder. The
convolutional encoder may encode the bits using convolutional
coding techniques. The convolutional encoder may encode the bits to
produce a sequence of coded output. The convolutional encoder may
process multiple symbols at a time. The inner encoder also may be
specified such that if the encoder receives a number of input
streams, then an input vector length may be determined. An output
vector length also may be determined according to the number of
output streams. Thus, the received bits or bytes may be coded
according to the convolutional encoder, or the inner encoder. The
inner encoder may code to a specified rate, such as 1/2.
Alternatively, the inner encoder may code to other rates, such as
3/4, 4/5 and 7/8.
[0061] Step 512 executes by puncturing the coded bits or bytes.
Step 512 may periodically remove bits or bytes from the encoded bit
streams received from the inner encoder. Thus, the code rate may be
increased, along with the spectral efficiency corresponding to the
wider bandwidth for standard 11n. A puncture pattern may be
specified by a puncture vector parameter. A puncture vector may be
a binary column vector that indicates a bit in a corresponding
position of an input vector is sent to the output vector, or is
removed. Thus, bits in various positions may be transmitted while
bits and other positions may be removed. For example, for every 7
bits of input, the punctured code generates 8 bits of output. Thus,
the puncture rate may be 7/8. The code rate may be determined by
the puncture convolutional code rate and the code rate of the outer
encoder. As discussed above, a code rate may be equal to about 0.8
or greater.
[0062] Thus, various embodiments of an encoder system and
applicable methods for use in wireless communication systems is
disclosed. As one of average skill in the art will appreciate,
other embodiments and variations thereof may be derived from the
teaching of the present invention without deviating from the scope
of the claims and their equivalents.
* * * * *