A New Joint Source-Channel Coding for Short-Packet Communications

In this paper, we propose a new joint source-channel coding (JSCC) for short-packet communications, especially for the uplink from the sensor to the base station. At the transmitter, the sensing information is first encoded by a two-stage description, referred to as classified enumerative (CE) coding, and then encoded by a random multiple-rate code. The two-stage CE coding describes a binary sequence by its type class indicator and its rank in the associated type class, which can approach the entropy for biased sources. The random multiple rate coding transforms the variable-length output of the CE coding into a fixed-length channel input, allocating lower energy to lower-rate component codes. At the receiver, the sensing information can be recovered by a trial-and-error (for type classes) decoding either serially or parallelly. The serial decoding has a low implementation complexity, while the parallel decoding has a low decoding delay. To alleviate the mis-correction probability and stop the decoding earlier, we turn to the cyclic redundancy check (CRC) coding. To predict the performance of the proposed JSCC scheme, we present the weighted random-coding union (RCU) bounds based on the conventional RCU bound. The proposed JSCC scheme is universal in the sense that it does not require knowledge of source statistics. Simulation results show that the performance matches well with the presented bounds, validating our analysis. Simulation results also show that the proposed JSCC scheme can outperform the double polar JSCC scheme (exhibiting a coding gain of up to 0.3 dB) and can approach the JSCC bounds (exhibiting a gap of less than 0.5 dB).