METHOD AND SYSTEM FOR PROVIDING SCRAMBLED CODED MULTIPLE ACCESS (SCMA)
A multiple access scheme is described. A first bit stream is scrambled from a first terminal according to a first scrambling signature. A second bit stream is scrambled from a second terminal according to a second scrambling signature, wherein the first bit stream and the second bit stream are encoded using a low rate code. The first scrambling signature and the second scrambling signature are assigned, respectively, to the first terminal and the second terminal to provide a multiple access scheme.
1 . A method comprising:
scrambling a first bit stream from a first terminal according to a first scrambling signature; and
scrambling a second bit stream from a second terminal according to a second scrambling signature,
wherein the first bit stream and the second bit stream are encoded using a low rate code, the first scrambling signature and the second scrambling signature being assigned, respectively, to the first terminal and the second terminal to provide a multiple access scheme.
2 . A method according to claim 1 , further comprising:
generating an output data stream that includes the encoded bit streams and one or more pilot symbols for synchronization.
3 . A method according to claim 1 , further comprising:
encoding each of the bit streams to output a composite signal using turbo code encoding, wherein the encoding utilizes constituent encoding having a transfer function:
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4 . A method according to claim 1 , wherein the bit streams are encoded by a plurality of constituent encoders utilizing identical transfer functions.
5 . A method according to claim 1 , wherein the low code rate includes rate 1/14, rate 1/12, rate 1/10, rate 1/8, rate 1/6, or rate 1/4.
6 . A method according to claim 1 , wherein the scrambling signatures include Gold sequences.
7 . An apparatus comprising:
a plurality of encoders, each encoder being configured to encode a first data stream from a first terminal and a second data stream from a second terminal using a low code rate;
a first scrambler configured to scramble the first encoded bit stream according to a first scrambling signature; and
a second scrambler configured to scramble the second encoded bit stream according to a second scrambling signature,
wherein the first scrambling signature and the second scrambling signature are assigned, respectively, to the first terminal and the second terminal to provide a multiple access scheme.
8 . An apparatus according to claim 7 , wherein an output data stream is generated, the output data stream includes the encoded bit streams and one or more pilot symbols for synchronization.
9 . An apparatus according to claim 7 , wherein each encoder is configured to encode each of the bit streams to output a composite signal using turbo code encoding, wherein the encoding utilizes constituent encoding having a transfer function:
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10 . An apparatus according to claim 7 , wherein the encoders include a plurality of constituent encoders utilizing identical transfer functions.
11 . An apparatus according to claim 7 , wherein the low code rate includes rate 1/14, rate 1/12, rate 1/10, rate 1/8, rate 1/6, or rate 1/4.
12 . An apparatus according to claim 7 , wherein the scrambling signatures include Gold sequences.
13 . A method comprising:
applying joint detection and interference cancellation on a received composite signal, wherein the composite signal includes one or more encoded bit streams having a low code rate;
estimating the encoded bit streams;
descrambling the estimated bit streams;
decoding the descrambled bit streams;
modifying the composite signal based on the decoded bit stream; and
iteratively decoding bit streams of the modified composite signal.
14 . A method according to claim 13 , wherein the received composite signal includes one or more pilot signals for synchronization, the method further comprising:
performing synchronization based on the pilot signals.
15 . A method according to claim 13 , wherein the decoding is based on a turbo code utilizing constituent encoding having a transfer function,
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16 . A method according to claim 13 , wherein the low code rate includes rate 1/14, rate 1/12, rate 1/10, rate 1/8, rate 1/6, or rate 1/4.
17 . A method according to claim 13 , wherein the scrambling signatures include Gold sequences.
18 . A system comprising:
a joint detector and interference canceller configured to detect and cancel interference from a received composite signal, wherein the composite signal includes one or more encoded bit streams having a low code rate;
a demodulator configured to estimate the encoded bit streams;
a plurality of descramblers configured to descramble the estimated bit streams;
a plurality of decoders configured to decode the bit streams; and
a plurality of scramblers configured to re-scramble the decoded bit streams, wherein the joint detector and interference canceller is further configured to modify the composite signal for subsequent iterative decoding by the decoders.
19 . A system according to claim 18 , wherein the received composite signal includes one or more pilot signals for synchronization.
20 . A system according to claim 18 , wherein the decoding by the decoders is based on a turbo code utilizing constituent encoding having a transfer function,
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21 . A system according to claim 18 , wherein the low code rate includes rate 1/14, rate 1/12, rate 1/10, rate 1/8, rate 1/6, or rate 1/4.
22 . A system according to claim 18 , wherein the scrambling signatures include Gold sequences.
23 . A system according to claim 18 , wherein the composite signal represents a plurality of bit streams corresponding to a plurality of satellite terminals.