Unequal error protection polar codes for low latency communications
Methods, systems, and devices for wireless communications are described. Polar coding involves assigning bits to different bit-channels, and encoding the bits such that certain bit-channels (e.g., polar channels) are polarized to increased reliability, while other bit-channels are polarized to decreased reliability. To ensure that polar codes for extended reality (XR) and video applications have increased reliability for the aspects of an XR stream or video code that are most important, the information bits of a stream may be sorted based on priority or importance. Then the sorted information bits may be mapped to the most reliable bit-channels of a polar encoder. Any errors in the transmission may therefore be most likely to occur in the less important bits. Accordingly, in the case of XR, the information bits that are most important to user experience/perception are the most likely to be successfully received and decoded at the receiver.
1 . A first wireless communications device for wireless communications, comprising:
one or more memories storing processor-executable code; and
one or more processors coupled with the one or more memories and individually or collectively operable to execute the code to cause the first wireless communications device to:
receive a plurality of information bits for transmission to a second wireless communications device, wherein the plurality of information bits comprises a stream of video data;
map the plurality of information bits to a plurality of bit-channels of a polar encoder based at least in part on respective priorities of the plurality of information bits and based at least in part on respective channel qualities of the plurality of bit-channels;
encode the plurality of information bits using the polar encoder in accordance with the mapping to generate a codeword; and
transmit the codeword to the second wireless communications device.
2 . The first wireless communications device of claim 1 , wherein, to map the plurality of information bits to the plurality of bit-channels, the one or more processors are individually or collectively operable to execute the code to cause the first wireless communications device to:
map the plurality of information bits to a first subset of bit-channels of the plurality of bit-channels, the first subset of bit-channels comprising information bit-channels, wherein a second subset of bit-channels of the plurality of bit-channels comprises frozen bit-channels.
3 . The first wireless communications device of claim 2 , wherein the one or more processors are individually or collectively further operable to execute the code to cause the first wireless communications device to:
determine the first subset of bit-channels from the plurality of bit-channels based at least in part on a cost-function that reduces bit error rate.
4 . The first wireless communications device of claim 2 , wherein the one or more processors are individually or collectively further operable to execute the code to cause the first wireless communications device to:
determine the first subset of bit-channels from the plurality of bit-channels based at least in part on an error probability rate associated with each of the plurality of bit-channels and respective quantities of subsequently indexed bit-channels of the first subset of bit-channels.
5 . The first wireless communications device of claim 2 , wherein the one or more processors are individually or collectively further operable to execute the code to cause the first wireless communications device to:
determine respective channel qualities of the first subset of bit-channels, each respective channel quality based at least in part on a respective error probability for a respective bit-channel of the first subset of bit-channels and respective error probability rates associated with previously indexed bit-channels of the first subset of bit-channels.
6 . The first wireless communications device of claim 2 , wherein a ratio between a first quantity of bit-channels of the first subset of bit-channels and a second quantity of bit-channels of the second subset of bit-channels is based at least in part on a channel capacity of a communication channel between the first wireless communications device and the second wireless communications device.
7 . The first wireless communications device of claim 1 , wherein the one or more processors are individually or collectively further operable to execute the code to cause the first wireless communications device to:
determine the respective priorities of the plurality of information bits based at least in part on an information type associated with each information bit of the plurality of information bits.
8 . The first wireless communications device of claim 1 , wherein the one or more processors are individually or collectively further operable to execute the code to cause the first wireless communications device to:
determine the respective priorities of the plurality of information bits based at least in part on respective frequencies associated with the plurality of information bits.
9 . The first wireless communications device of claim 1 , wherein the one or more processors are individually or collectively further operable to execute the code to cause the first wireless communications device to:
determine the respective priorities of the plurality of information bits based at least in part on a first subset of the plurality of information bits being associated with direct current aspects of the stream of video data and a second subset of the plurality of information bits being associated with alternating current aspects of the stream of video data.
10 . The first wireless communications device of claim 1 , wherein the one or more processors are individually or collectively further operable to execute the code to cause the first wireless communications device to:
determine the respective priorities of the plurality of information bits based at least in part on identifying a most significant bit of the plurality of information bits and a least significant bit of the plurality of information bits.
11 . The first wireless communications device of claim 1 , wherein the one or more processors are individually or collectively further operable to execute the code to cause the first wireless communications device to:
append a set of cyclic redundancy check bits to the plurality of information bits.
12 . The first wireless communications device of claim 1 , wherein the one or more processors are individually or collectively further operable to execute the code to cause the first wireless communications device to:
communicate an indication of the mapping with the second wireless communications device.
13 . The first wireless communications device of claim 1 , wherein the stream of video data comprises a stream of extended reality video data.
14 . A second wireless communications device for wireless communications, comprising:
one or more memories storing processor-executable code; and
one or more processors coupled with the one or more memories and individually or collectively operable to execute the code to cause the apparatus second wireless communications device to
receive a codeword from a first wireless communications device;
decode the codeword using a polar decoder to generate a plurality of information bits, the plurality of information bits ordered in accordance with a plurality of bit-channels of the polar decoder, wherein the plurality of information bits comprises a stream of video data;
reorder the plurality of information bits based at least in part on a mapping of the plurality of information bits to the plurality of bit-channels, the mapping based at least in part on respective priorities of the plurality of information bits and based at least in part on respective channel qualities of the plurality of bit-channels.
15 . The second wireless communications device of claim 14 , wherein the one or more processors are individually or collectively further operable to execute the code to cause the second wireless communications device to:
communicate an indication of the mapping with the first wireless communications device.
16 . The second wireless communications device of claim 14 , wherein the plurality of bit-channels comprises a first subset of bit-channels comprising information bit-channels and a second subset of bit-channels of the plurality of bit-channels comprises frozen bit-channels.
17 . The second wireless communications device of claim 16 , wherein the first subset of bit-channels from the plurality of bit-channels are based at least in part on a cost-function that reduces bit error rate.
18 . The second wireless communications device of claim 16 , wherein the first subset of bit-channels from the plurality of bit-channels is based at least in part on an error probability rate associated with each of the plurality of bit-channels and respective quantities of subsequently indexed bit-channels of the first subset of bit-channels.
19 . The second wireless communications device of claim 16 , wherein each respective channel quality of the first subset of bit-channels is based at least in part on a respective error probability for a respective bit-channel of the first subset of bit-channels and respective error probability rates associated with previously indexed bit-channels of the first subset of bit-channels.
20 . The second wireless communications device of claim 16 , wherein a ratio between a first quantity of bit-channels of the first subset of bit-channels and a second quantity of bit-channels of the second subset of bit-channels is based at least in part on a channel capacity of a communication channel between the first wireless communications device and the second wireless communications device.
21 . A method for wireless communications at a first wireless communications device, comprising:
receiving a plurality of information bits for transmission to a second wireless communications device, wherein the plurality of information bits comprises a stream of video data;
mapping the plurality of information bits to a plurality of bit-channels of a polar encoder based at least in part on respective priorities of the plurality of information bits and based at least in part on respective channel qualities of the plurality of bit-channels;
encoding the plurality of information bits using the polar encoder in accordance with the mapping to generate a codeword; and
transmitting the codeword to the second wireless communications device.
22 . The method of claim 21 , wherein mapping the plurality of information bits to the plurality of bit-channels comprises:
mapping the plurality of information bits to a first subset of bit-channels of the plurality of bit-channels, the first subset of bit-channels comprising information bit-channels, wherein a second subset of bit-channels of the plurality of bit-channels comprises frozen bit-channels.
23 . The method of claim 22 , further comprising:
determining the first subset of bit-channels from the plurality of bit-channels based at least in part on a cost-function that reduces bit error rate.
24 . The method of claim 22 , further comprising:
determining the first subset of bit-channels from the plurality of bit-channels based at least in part on an error probability rate associated with each of the plurality of bit-channels and respective quantities of subsequently indexed bit-channels of the first subset of bit-channels.
25 . The method of claim 22 , further comprising:
determining respective channel qualities of the first subset of bit-channels, each respective channel quality based at least in part on a respective error probability for a respective bit-channel of the first subset of bit-channels and respective error probability rates associated with previously indexed bit-channels of the first subset of bit-channels.
26 . The method of claim 22 , wherein a ratio between a first quantity of bit-channels of the first subset of bit-channels and a second quantity of bit-channels of the second subset of bit-channels is based at least in part on a channel capacity of a communication channel between the first wireless communications device and the second wireless communications device.
27 . The method of claim 21 , further comprising:
determining the respective priorities of the plurality of information bits based at least in part on an information type associated with each information bit of the plurality of information bits.
28 . The method of claim 21 , further comprising:
determining the respective priorities of the plurality of information bits based at least in part on respective frequencies associated with the plurality of information bits.
29 . The method of claim 21 , further comprising:
determining the respective priorities of the plurality of information bits based at least in part on a first subset of the plurality of information bits being associated with direct current aspects of the stream of video data and a second subset of the plurality of information bits being associated with alternating current aspects of the stream of video data.
30 . A method for wireless communications at a second wireless communications device, comprising:
receiving a codeword from a first wireless communications device;
decoding the codeword using a polar decoder to generate a plurality of information bits, the plurality of information bits ordered in accordance with a plurality of bit-channels of the polar decoder, wherein the plurality of information bits comprises a stream of video data;
reordering the plurality of information bits based at least in part on a mapping of the plurality of information bits to the plurality of bit-channels, the mapping based at least in part on respective priorities of the plurality of information bits and based at least in part on respective channel qualities of the plurality of bit-channels.