Probabilistic amplitude shaping
This disclosure provides methods, devices and systems for encoding data for wireless communication to achieve a desired amplitude distribution. Some implementations more specifically relate to performing an encoding operation to shape the amplitudes of the resultant symbols such that the amplitudes have a non-uniform distribution. In some implementations of the non-uniform distribution, the probabilities associated with the respective amplitudes generally increase with decreasing amplitude. Some implementations enable the tracking of MPDU boundaries to facilitate successful decoding by a receiving device. Additionally or alternatively, some implementations enable the determination of a packet length after performing the amplitude shaping, which enables a transmitting device to determine the number of padding bits to add to the payload and to signal the packet length to a receiving device so that the receiving device may determine the duration of the packet.
1. A method for wireless communication by a wireless communication device, the method comprising:
performing an amplitude-shaping encoding operation on information bits of an information block, the information block including information bits from a plurality of medium access control (MAC) protocol data units (MPDUs) and further including a plurality of predetermined sequences of bits, each predetermined sequence of bits being located between bits of a respective pair of adjacent MPDUs in the information block, the amplitude-shaping encoding operation not being performed on the predetermined sequences of bits; and
transmitting a wireless packet that includes a plurality of symbols that represent the amplitude-shaped information bits and the predetermined sequences of bits, the predetermined sequences of bits indicating respective boundaries between the plurality of MPDUs.
2. The method of claim 1 , further comprising performing a systematic encoding operation on the amplitude-shaped information bits and the predetermined sequences of bits, wherein the plurality of symbols represent the systematically-encoded bits.
3. The method of claim 1 , wherein the amplitude-shaping encoding operation has an intrinsically-variable coding rate.
4. The method of claim 1 , wherein the amplitude-deshaping decoding operation has an intrinsically-variable decoding rate.
5. The method of claim 1 , further comprising performing a systematic encoding operation on the amplitude-shaped information bits, wherein the plurality of symbols represent the systematically-encoded bits.
6. A method for wireless communication by a wireless communication device, the method comprising:
receiving a wireless packet that includes a plurality of symbols that represent amplitude-shaped information bits and predetermined sequences of bits, the predetermined sequences of bits indicating respective boundaries between a plurality of medium access control (MAC) protocol data units (MPDUs);
performing an amplitude-deshaping decoding operation on the amplitude-shaped information bits, the amplitude-deshaping decoding operation not being performed on the predetermined sequences of bits; and
reassembling the amplitude-deshaped information bits into the plurality of MPDUs in accordance with the boundaries indicated by the predetermined sequences of bits.
7. The method of claim 6 , further comprising, prior to the performance of the amplitude-deshaping decoding operation, performing a systematic decoding operation on the amplitude-shaped information bits and the predetermined sequences of bits, wherein the amplitude-deshaping decoding operation is performed on the systematically-decoded amplitude-shaped information bits.
8. A method for wireless communication by a wireless communication device, the method comprising:
performing an amplitude-shaping encoding operation on information bits of an information block, the information block including information bits from a plurality of medium access control (MAC) protocol data units (MPDUs), the performance of the amplitude-shaping encoding operation including adjusting a coding rate of the amplitude-shaping encoding operation in accordance with a number of amplitude-shaped information bits generated by the amplitude-shaping encoding operation such that a length associated with a resultant wireless packet can be determined; and
transmitting the resultant wireless packet, the wireless packet including a plurality of symbols that represent the amplitude-shaped information bits, the wireless packet further including an indication of the length.
9. The method of claim 8 , wherein the adjustment of the coding rate of the amplitude-shaping encoding operation comprises adjusting the coding rate of the amplitude-shaping encoding operation on a code-block basis, a group-of-code-blocks basis, or an MPDU basis, in accordance with the number of amplitude-shaped information bits generated by the amplitude-shaping encoding operation.
10. The method of claim 8 , further comprising:
monitoring, during or after the amplitude-shaping encoding operation, the number of amplitude-shaped information bits generated by the amplitude-shaping encoding operation; and
determining whether the number of amplitude-shaped information bits satisfies a threshold, wherein the adjustment of the coding rate of the amplitude-shaping encoding operation is responsive to the determination.
11. The method of claim 8 , further comprising:
monitoring the number of amplitude-shaped bits generated by the amplitude-shaping encoding operation;
monitoring a number of information bits input to the amplitude-shaping encoding operation;
determining whether a difference between the number of amplitude-shaped bits generated by the amplitude-shaping encoding operation and the number of information bits input to the amplitude-shaping encoding operation satisfies a threshold, wherein the adjustment of the coding rate of the amplitude-shaping encoding operation is responsive to the determination.
12. The method of claim 11 , wherein the adjustment comprises stopping the amplitude-shaping encoding operation responsive to determining that the difference is greater than the threshold.
13. The method of claim 11 , wherein the adjustment comprises repeating one or more of the amplitude-shaped information bits responsive to determining that the difference is less than a threshold.
14. The method of claim 8 , wherein the adjustment of the coding rate of the amplitude-shaping encoding operation comprises changing a probability mass function associated with the amplitude-shaping encoding operation.
15. The method of claim 14 , wherein the amplitude-shaping encoding operation comprises a prefix encoding operation and changing the probability mass function associated with the amplitude-shaping encoding operation comprises switching from using a first look-up table associated a first probability mass function to a second look-up table associated with a second probability mass function to perform the prefix encoding operation.
16. A method for wireless communication by a wireless communication device, the method comprising:
receiving a wireless packet that includes a plurality of symbols that represent amplitude-shaped information bits associated with a plurality of medium access control (MAC) protocol data units (MPDUs), the wireless packet further including an indication of a length associated with the wireless packet;
performing an amplitude-deshaping decoding operation on the amplitude-shaped information bits, the performance of the amplitude-deshaping decoding operation including adjusting a decoding rate of the amplitude-deshaping decoding operation in accordance with the indicated length; and
reassembling the amplitude-deshaped information bits into the plurality of MPDUs.
17. The method of claim 16 , further comprising, prior to the performance of the amplitude-deshaping decoding operation, performing a systematic decoding operation on the amplitude-shaped information bits, wherein the amplitude-deshaping decoding operation is performed on the systematically-decoded amplitude-shaped information bits.
18. The method of claim 16 , wherein the adjustment of the decoding rate of the amplitude-deshaping decoding operation includes determining an effective coding rate of the amplitude-shaped bits, wherein the decoding rate is adjusted in accordance with the effective coding rate.