Multiplex communications – Communication techniques for information carried in plural... – Combining or distributing information via code word channels
Reexamination Certificate
2000-02-14
2001-10-16
Chin, Wellington (Department: 2664)
Multiplex communications
Communication techniques for information carried in plural...
Combining or distributing information via code word channels
C370S320000, C370S335000, C370S441000, C370S342000
Reexamination Certificate
active
06304581
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to the field of communications and communication systems, more particularly, to a code division multiple access (CDMA) communication system.
Orthogonal transmit diversity (OTD) is a feature of a CDMA communication system implemented for improving performance of a communication link between a base station and a mobile station. The commonly known IS-2000 standard provides a detailed description for implementation and use of an OTD feature in a CDMA communication system. A copy of the IS-2000 standard may be obtained by contacting Telecommunications Industry Association, 2500 Wilson Blvd., Suite 300, Arlington, Va. 22201 USA, or visiting a world web site on the internet located at http://www.tiaonline.org/, which incorporated by reference herein. The OTD feature is applicable for both single carrier CDMA system and multi-carriers (MC) CDMA system.
Generally speaking, information data in a CDMA system is coded according to a coding rate. For example, coding rates of ⅓, {fraction (
1
/
2
)} and ¼ are commonly used in CDMA systems operating according to IS-2000 standards; other coding rates are also available. For example, when the information data is coded according to a ⅓ coding rate, the encoder produces 3 data symbols for every input information data bit, similarly for other encoding rates. One ordinary skilled in the art may appreciate that data symbol and data bit are interchangeable terms. After the information data has been encoded, the encoded symbols are transmitted to a receiving unit for decoding and recovery of the information data bits. The transmission of data normally takes place over a channel with varying propagation characteristics. As a result, if the encoded symbols are transmitted sequentially from a transmitting source such that all or most of the encoded symbols experience the same or similar propagation characteristics in the transmission channel, the information data may not be decoded or recovered at the receiver due to severe degradation in the received signal energy of all or most of the encoded symbols.
The OTD provides a method for transmission of encoded symbols such that, as much as possible, each encoded data symbol of an information data bit experiences a propagation characteristics independent of other encoded symbols of the same information data bit. As such, the possibility of degrading all or most of the encoded data symbols of the same information data bit due to a varying propagation channel characteristics is spread and minimized. A system implementing the OTD feature transmits encoded data symbols of an information data bit from at least two transmit antennas, such that one encoded symbol is transmitted from one antenna and another encoded symbol from another antenna. The encoded symbols transmitted from each antenna are spread using an orthogonal Walsh code different than the Walsh code used for the encoded symbols transmitted from the other antenna. A mobile station, or a remote receiving unit, receiving both signals obtains a reception diversity improvement by allowing the decoder to process a group of symbols that have faded independently. In order to ensure that coded symbols from the same information data bit fade independently in transmission, use of two parallel interleavers in the transmitter may be required according to the description provided in the earlier versions of IS-2000 standard and related literatures. Referring to
FIG. 1
, a CDMA communication system transmitter block diagram
100
is shown. Raw information data bits are added with CRC bits and some other tail data bits in a block
101
to produce information data bits
102
. Information data bits
102
are fed to a channel encoder
103
for encoding according to an encoding rate to produce encoded symbols
104
. In case of implementing an OTD feature, the encoded symbols
104
are fed to an OTD interleaver
105
; otherwise, the encoded symbols
104
are fed to a single interleaver before further processing of the transmit signal. After interleaving, interleaved symbols
106
are produced. Interleaved symbols
106
pass through a transmit signal processing block
107
which may include long code masking, power control operation and power control puncturing operations; such operations are well known in the art and more specifically explained in the IS-2000 standard. Block
107
produces data symbols
108
which pass through a data splitter
109
to produce two streams of data symbols
110
and
111
. The data symbols
110
and
111
are modulated independently in QPSK modulators
112
and
113
and up-converted to an appropriate carrier frequency before transmission from antennas
114
and
115
. On a receiving end both signals transmitted from antennas
114
and
115
are demodulated, decoded and combined to recover the information data bits.
The OTD interleaver
105
requires at least two data block interleavers
120
and
121
. The information data bits
102
are normally transmitted in a block of data format, as such, the encoded symbols are also in a block of encoded symbols format. Normally, a block of information data bits is set to occupy a predefined time frame. The number of information data bits in a time frame varies depending on the information data bit rate. Time frames of 5, 10, 20, 40 and 80 mSec. are possible. The information data rate also may vary from 9.6 kbps up to 460.8 kbps. Calculating the number of information data bits or encoded symbols in a time frame is well known by one ordinary skilled in the art. Similarly, the number of encoded symbols depends on the encoding rate and the number of information data bits in a time frame. For example, one block of encoded symbols
104
in a 20 mSec time frame may include 384 encoded symbols for an information data bit rate 9.6 Kbps in a 20 mSec time frame using an encoding rate of ½.
A block of encoded symbols
104
are de-muxed in a de-mux block
122
to produce two halves, blocks of symbols
123
and
124
which have the same time frame and equal to the time frame of the block of encoded symbols
104
. The number of symbols in each block of symbols
123
and
124
is equal to one half of the encoded symbols in the block of encoded symbols
104
. Two data block interleavers
120
and
121
according to a prior art provide the interleaving functions for interleaving each block of symbols
123
and
124
. If the number of encoded symbols in the block of encoded symbols
104
is equal to “N”, the number of symbols in each block
123
and
124
is equal to “N/2”. As a result, the interleavers
120
and
121
perform interleaving functions for “N/2” symbols. The operation of interleaving is according to a known and predetermined algorithm. Such algorithm often may be governed by a mathematical relationship mapping the input to output symbols. The interleavers
120
and
121
then output interleaved symbols
125
and
126
of block of encoded symbols
123
and
124
. The OTD interleaver
105
may additionally for improving performance may include a circular shift operation
127
shifting data symbols by a predetermined number. The circular shift function
127
shifts the data symbols of, in this case, the interleaved symbols
126
to produce data symbols
128
. Data symbols
128
and
125
are muxed in a mux-ing block
129
to produce interleaved symbols
106
.
Referring to
FIG. 2
, a case of multi-carrier (MC) CDMA communication system, the OTD MC interleaver
201
may be used. Interleaver
201
inputs encoded symbols
104
and outputs interleaved symbols
106
according to its internal OTD operations. A block of input encoded symbols is de-muxed into three blocks
202
,
203
and
204
in a demux-ing block
205
for multi-carrier CDMA system with three CDMA carriers. Each block of symbols
202
,
203
and
204
pass through an interleaver block respectively shown as interleaver blocks
206
,
207
and
208
to produce interleaved blocks of symbols
209
,
210
and
211
respectively. Interleaved symbols
210
and
208
pass throug
Chen Jiangnan
Jalloul Louay
Chin Wellington
Duong Frank
Haas Kenneth A.
Motorola Inc.
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