Abstract The Advanced Television Systems Committee (ATSC) finalized its next‐generation digital terrestrial broadcast standard in 2016, known as ATSC 3.0. In order to enhance spectral efficiency, the standard employs two‐dimensional non‐uniform constellations (2D‐NUCs) for signal mapping. As a result, a 2D demapper, with computational complexity much higher than one‐dimensional (1D) demappers, has to be designed for the receiver. In this paper, a suboptimal low‐complexity 2D‐demapping method is proposed for ATSC 3.0. The proposed method takes advantage of the 2D‐NUC's feature that constellation points with same most significant bits tend to locate in the same subregion. Simulation results show that compared with the conventional Max‐Log‐MAP 2D demapping, the proposed method achieves at least complexity reduction with negligible performance loss. Moreover, compared with another 2D demapper specially designed for ATSC 3.0, the proposed method dispenses with high‐complexity exponential and logarithmic operations at a small performance cost of at most 0.14 dB.

Long‐term evolution (LTE) standard employs orthogonal frequency division multiplexing (OFDM) for downlink (DL) data transmission. As pilot subcarriers are non‐uniformly and sparsely spaced in the OFDM DL transmission, more complicated channel estimation methods may have to be adopted in the mobile devices to ensure adequate performance. An iterative approach is proposed for the channel estimation task, in which an inverse fast Fourier transform and fast Fourier transform pair is iteratively used to smooth channel estimates provided by decision feedback. The performance of this approach is compared with two two‐dimensional interpolation methods and one discrete Fourier transform‐based estimation method that have been proposed for the LTE DL transmission. Simulation results show that the performance of the proposed method surpasses all the other methods except at high signal‐to‐noise ratio, and moreover, not a single estimation method consistently performs better than the proposed method for all the channel models considered. Thus, the proposed method is the best among the considered methods for LTE DL transmission.

The combined application of diversity and error-correction coding for combating multitone jamming (MTJ) in fast frequency-hopping/M-ary frequency-shift-keying (FFH/MFSK) systems over Rayleigh fading channels is investigated. A log-likelihood-combining metric which requires only easy-to-obtain system parameters for its computation is proposed. In addition, four soft-decision coding schemes which employ the proposed diversity-combining metric as decoding metric are considered. An upper bound on the bit error rate of the proposed metric is derived. Simulation results show that the proposed metric outperforms robust metrics. Moreover, the improvement is most substantial for low signal-to-jamming ratio (SJR). Performances of convolutional codes and turbo codes together with either bit-interleaving or symbol-interleaving are examined. Upper bounds are derived for the bit error rates of the convolutional coding schemes, and simulations are performed for all coding schemes. The results show that significant performance improvement can be achieved in difficult transmission conditions by changing the interleaving method from bit-interleaving to symbol-interleaving, but without changing the code. In particular, the symbol-interleaved turbo coding scheme is the best among the four for maintaining system performance at an acceptable level for most situations.

The effects of bit-interleaving on the performance of convolutional codes and turbo codes in fast frequency- hop/spread-spectrum multiple-access systems with M-FSK modulation are investigated. It is observed that bit-interleaving induces two counter-acting forces on decoder performance. On the one hand, bit-interleaving disperses consecutive error bits caused by a noisy M-ary signal and makes the errors more correctable. On the other hand, the same measure makes it difficult for the decoder to make use of the bit dependency information. Both theoretical upper bounds and simulation results show that bit- interleaving degrades the performance of soft-decision decoded convolutional codes and turbo codes.

A fully connected frequency-hop packet radio network is considered. Four packet-combining techniques are presented, which significantly reduce the packet-error rate. An analytical model is used to offer insight into how system dynamics are affected by the error-control method and retransmission backoff policy. It is shown that enhancing the error-control method increases the maximum throughput of the network and alleviates the stability problem, but does not solve the problem. On the other hand, a good choice of retransmission backoff policy solves the stability problem, but does not alter the maximum throughput. These results suggest that in order to construct a stable network with large throughput, a good error-control method and retransmission backoff policy are both necessary.

A fully connected radio network is considered in which packets are sent using Reed-Solomon error-control coding, slow frequency-hop (FH) modulation, and generalized retransmission backoff policy. An easy-to-use analytical method for finite population FH networks is developed which offers insight into how system dynamics is affected by the number of users and the input rate. The performance of several retransmission backoff policies is examined. It is shown that the performance of exponential backoff policy with small minimum retransmission probability is not too far away from the optimum, when the code-block length is small and the number of users is not unreasonably large. It is also shown that packet rejection after a certain number of unsuccessful transmissions can stabilize some networks as one would expect, but may destabilize some others contrarily. Finally, the accuracy of the method is verified by extensive simulation results.

The minimum average error probability achievable by block codes on the two-user multiple-access channel is investigated. A new exponential upper bound is found which can be achieved universally for all discrete memoryless multiple-access channels with given input and output alphabets. It is shown that the exponent of this bound is greater than or equal to those of previously known bounds. Moreover, examples are given where the new exponent is strictly larger.