MIMO systems having a channel decoder matched to a MIMO detector
View Patent ↗A method and apparatus for reducing the number of erred bits in the decoded signal by using a channel decoder whose transfer characteristic is matched to the transfer characteristic of the MIMO detector. This means that the curve of the transfer characteristic of the MIMO detector is 1) above the curve of the reflected transpose of the transfer characteristic of the channel decoder for about 95% of the curve, and 2) close to the reflected transpose of the curve of the transfer characteristic of the channel decoder. Particularly, an LDPCC decoder can be used as the channel decoder and can be matched to the MIMO detector by matching 1) the transfer characteristic of the LDPCC decoder's CND to 2) the transfer characteristic of a combination of the MIMO detector and the LDPCC VND. Furthermore, the LDPCC can be similarly matched to any appropriate detector in addition to or instead of the MIMO detector. Additionally, a receiver can re-match the transfer characteristics of the detector and the channel decoder when the channel characteristics and/or SNR of the received signals change.
1. A receiver of a wireless communication device comprising:
a detector;
a channel decoder for receiving an output of the detector; and
wherein a curve of the transfer characteristic of the detector is:
above a curve of a reflected transpose of the curve of the transfer characteristic of the channel decoder for about 95% of the curve; and
within a threshold difference of the reflected transpose of the curve of the transfer characteristic of the channel decoder.
2. The invention of claim 1 , wherein when the curve of the transfer characteristic of the detector and the curve of the reflected transpose of the curve of the transfer characteristic of the channel decoder are plotted on a scale of 0 to 1, then the threshold difference is 0.05.
3. The invention of claim 1 , wherein the detector is a MIMO detector.
4. A receiver of a wireless communication device comprising:
a detector; and
a low density parity check code channel decoder having a variable node decoder and a check node decoder; and
wherein a transfer characteristic of a combination of the detector and the variable node decoder is:
above a curve of a reflected transpose of the curve of the transfer characteristic of the check node decoder for about 95% of the curve; and
within a threshold difference of the reflected transpose of the curve of the transfer characteristic of the check node decoder.
5. The invention of claim 4 , wherein when the curve of the transfer characteristic of the detector and the curve of the reflected transpose of the curve of the transfer characteristic of the channel decoder are plotted on a scale of 0 to 1, then the threshold difference is 0.05.
6. The invention of claim 4 , wherein the detector is a MIMO detector.
7. A method for use in a receiver of a wireless communication device, the receiver having a detector, the method comprising the steps of:
dynamically selecting a channel decoder based on the detector's transfer characteristic, wherein the selecting step is performed responsive to the channel characteristics of signals received at the receiver changing by a channel characteristic threshold between a first and a second time period; and
wherein the channel decoder is a low density parity check code channel decoder having a variable node decoder and a check node decoder; and
the selecting step further comprising:
selecting a degree of the check node decoder and degrees of the variable node decoder; and
selecting a channel decoder such that a curve of transfer characteristic of the detector is:
above a curve of a reflected transpose of the curve of the transfer characteristic of the channel decoder for about 95% of the curve; and
within a threshold difference of the reflected transpose of the curve of the transfer characteristic of the channel decoder.
8. The invention of claim 7 , wherein the selecting step comprises selecting a degree of the check node decoder and degrees of the variable node decoder such that a curve of transfer characteristic of a combination of the detector and the variable node decoder is:
above a curve of a reflected transpose of the curve of the transfer characteristic of the check node decoder for about 95% of the curve; and
within a threshold difference of the reflected transpose of the curve of the transfer characteristic of the check node decoder.
9. The invention of claim 8 , wherein when the curve of the transfer characteristic of the detector and the curve of the reflected transpose of the curve of the transfer characteristic of the channel decoder are plotted on a scale of 0 to 1, then the threshold difference is 0.05.
10. The invention of claim 7 , wherein the detector is a MIMO detector.
11. The invention of claim 7 , wherein when the curve of the transfer characteristic of the detector and the curve of the reflected transpose of the curve of the transfer characteristic of the channel decoder are plotted on a scale of 0 to 1, then the threshold difference is 0.05.
12. A transmitter of a wireless communication device for transmitting an encoded signal to a receiver having a detector, the transmitter comprising:
an encoder adapted to:
encode a signal using a first channel code responsive to an indication that the detector has a first transfer characteristic; and
encode the signal using a second channel code, different from the first channel code, responsive to an indication that the detector has a second transfer characteristic, the second transfer characteristic being different than the first transfer characteristic.
13. The invention of claim 12 , wherein:
the first channel code is decodable by a first channel decoder, wherein a curve of the transfer characteristic of the detector is:
above a curve of a reflected transpose of the curve of the transfer characteristic of the first channel decoder for about 95% of the curve; and
within a threshold difference of the reflected transpose of the curve of the transfer characteristic of the first channel decoder; and
the second channel code is decodable by a second channel decoder, wherein a curve of the transfer characteristic of the detector is:
above a curve of a reflected transpose of the curve of the transfer characteristic of the second channel decoder for about 95% of the curve; and
within a threshold difference of the reflected transpose of the curve of the transfer characteristic of the second channel decoder.
14. A method for use in a transmitter of a wireless communication system having a receiver having a detector, the method comprising the steps of:
transmitting a first signal encoded with a first channel code responsive to an indication that the detector has a first transfer characteristic; and
transmitting a second signal using a second channel code, different from the first channel code, responsive to an indication that the detector has a second transfer characteristic, the second transfer characteristic being different than the first transfer characteristic.
15. The invention of claim 14 , wherein:
the first channel code is decodable by a first channel decoder, wherein a curve of the transfer characteristic of the detector is:
above a curve of a reflected transpose of the curve of the transfer characteristic of the first channel decoder for about 95% of the curve; and
within a threshold difference of the reflected transpose of the curve of the transfer characteristic of the first channel decoder; and
the second channel code is decodable by a second channel decoder, wherein the curve of the transfer characteristic of the detector is:
above a curve of a reflected transpose of the curve of the transfer characteristic of the second channel decoder for about 95% of the curve; and
within a threshold difference of the reflected transpose of the curve of the transfer characteristic of the second channel decoder.