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:
encoding, by an encoder of first data communications terminal, a first bit stream using a low rate forward error correction (FEC) code to generate a first encoded data stream;
encoding, by an encoder of a second data communications terminal, a second bit stream using the low rate FEC code to generate a second encoded data stream;
scrambling, by a scrambler of the first data communications terminal, the first encoded data stream based on a first scrambling signature; and
scrambling, by a scrambler of the second data communications terminal, the second encoded data stream based on a second scrambling signature;
modulating, by a modulator of the first data communications terminal, the scrambled first encoded data stream to generate a first modulated data signal for transmission over a wireless data communications channel; and
modulating, by a modulator of the second data communications terminal, the scrambled second encoded data stream to generate a second modulated data signal for transmission over the wireless data communications channel; and
wherein the low rate FEC code is of a rate less than ⅓, and
wherein the first scrambling signature and the second scrambling signature are assigned, respectively, to the first terminal and the second terminal to distinguish the first encoded data stream from the second encoded data stream as respectively originating from the first terminal and the second terminal in a multiple access scheme, where the first encoded data stream and the second encoded data stream are configured to simultaneously share the wireless data communications channel and to be decoded by a receiving data communications terminal via a joint detection/interference cancellation process.
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 , wherein the encoding of each of the first and second bit streams comprises a turbo code encoding, which 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 rate of the low rate FEC code is 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. A data communications terminal comprising:
an encoder configured to encode a bit stream of the data communications terminal using a low rate forward error correction (FEC) code to generate an encoded data stream, wherein the low rate FEC code is of a rate less than ⅓;
a scrambler configured to scramble the encoded data stream based on a scrambling signature; and
a modulator configured to modulate the scrambled encoded data stream to generate a modulated data signal for transmission over a wireless data communications channel; and
wherein the scrambling signature is configured to distinguish the encoded data stream from a further encoded data stream of a further data communications terminal, and to distinguish the encoded data stream as originating from the data communications terminal in a multiple access scheme, where the encoded data stream is configured to simultaneously share the wireless data communications channel with the further encoded data stream and to be decoded by a receiving data communications terminal via a joint detection/interference cancellation process.
8. The data communications terminal according to claim 7 , wherein the data communications terminal is configured to generate an output data stream that includes the encoded data stream and one or more pilot symbols for synchronization.
9. The data communications terminal according to claim 7 , wherein the encoding of the bit stream comprises a turbo code encoding, which utilizes constituent encoding having a transfer function:
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10. The data communications terminal according to claim 7 , wherein the bit streams are encoded by a plurality of constituent encoders utilizing identical transfer functions.
11. The data communications terminal according to claim 7 , wherein the rate of the low rate FEC code is rate 1/14, rate 1/12, rate 1/10, rate 1/8, rate 1/6, or rate 1/4.
12. The data communications terminal according to claim 7 , wherein the scrambling signature includes a Gold sequence.
13. A data communications system comprising:
a first data communications terminal comprising an encoder configured to encode a first bit stream of the first data communications terminal using a low rate forward error correction (FEC) code to generate a first encoded data stream, a scrambler configured to scramble the first encoded data stream based on a first scrambling signature, and a modulator configured to modulate the scrambled first encoded data stream to generate a first modulated data signal for transmission over a wireless data communications channel; and
a second data communications terminal comprising an encoder configured to encode a second bit stream of the second data communications terminal using a low rate forward error correction (FEC) code to generate a second encoded data stream, a scrambler configured to scramble the second encoded data stream based on a second scrambling signature, and a modulator configured to modulate the scrambled second encoded data stream to generate a second modulated data signal for transmission over the wireless data communications channel; and
wherein the low rate FEC code is of a rate less than ⅓, and
wherein the first scrambling signature and the second scrambling signature are assigned, respectively, to the first terminal and the second terminal to distinguish the first encoded data stream from the second encoded data stream as respectively originating from the first terminal and the second terminal in a multiple access scheme, where the first encoded data stream and the second encoded data stream are configured to simultaneously share the wireless data communications channel and to be decoded by a receiving data communications terminal via a joint detection/interference cancellation process.
14. The data communications system according to claim 13 , wherein the encoding of each of the first and second bit streams comprises a turbo code encoding, which utilizes constituent encoding having a transfer function:
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