Considerable Coding Gain Research Articles

Euclidean Distance-Based Weighted Prediction for Merge Mode in HEVC

Merge mode can achieve a considerable coding gain because of reducing the cost of coding motion information in video codecs. However, the simple adoption of the motion information from the neighbouring blocks may not achieve the optimal performance as the motion correlation between the pixels and the neighbouring block decreases with their distance increasing. To address this problem, the paper proposes a Euclidean distance-based weighted prediction algorithm as an additional candidate in the merge mode. First, several predicted blocks are generated by motion compensation prediction (MCP) with the motion information from available neighbouring blocks. Second, an additional predicted block is generated by a weighted average of the predicted blocks above, where the weighted coefficient is related to Euclidean distances from the neighbouring candidate to the pixel points in the current block. Finally, the best merge mode is selected by the rate distortion optimization (RDO) among the original merge candidates and the additional candidate. Experimental results show that, on the joint exploration test model 7.0 (JEM 7.0), the proposed algorithm achieves better coding performance than the original merge mode under all configurations including random access (RA), low delay B (LDB), and low delay P (LDP), with a slight coding complexity increase. Especially for the LDP configuration, the proposed method achieves 1.50% bitrate saving on average.

Robust differential modulations for asynchronous cooperative systems

Accurate channel state information and time/frequency synchronization are challenging to acquire in mobile ad hoc cooperative set-ups, where resource-constrained relaying terminals rapidly (dis)join cooperation. This paper derives low-complexity differential modulations and cooperative transmission schemes so that detection at the receiver is feasible without channel knowledge or synchronization information. A simple distributed doubly-differential (DD) time-division multiplexing (TDM) scheme using diagonal space–time (ST) unitary codes is derived to bypass multiple carrier frequency offsets (CFOs) and collect space diversity. Precoded differential orthogonal frequency division multiplexing (OFDM) transmissions are derived to additionally bypass timing offsets and collect multipath diversity using either DD diagonal or single-differential (SD) orthogonal ST block codes (OSTBCs). DD diagonal mappings suffer from considerable coding gain and signal-to-noise ratio (SNR) loss due to unitary constellation constraints and noise enhancement at the receiver. SD-OSTBCs achieve higher performance with reduced decoding complexity, at the cost of reduced CFO mitigation range. Simple and robust non-coherent selective and adaptive transmissions are also included, showing that full space and multipath diversity can still be achieved even with decoding errors at relays. Simulations corroborate theoretical claims.

TTCM assisted genetic-algorithm aided reduced-complexity multiuser detection

Turbo trellis coded modulation assisted genetic-algorithm aided reduced-complexity multiuser detection(TTCM-GA-MUD) is capable of providing a considerable coding gain of 2.9dB without any bandwidth expansion at a bit error ratio of 10E-4, while maintaining a complexity reduction factor 8.59x10E+06 compared to the optimum multiuser detector in the context of 16QAM transmissions, while supporting K=10 users.

Performance of trellis-coded direct-sequence spread spectrum with noncoherent reception in a fading environment

In this paper, we consider the performance of different coding schemes for direct-sequence spread spectrum (DS-SS) in a nonselective Rician faded channel. The Nordstrom-Robinson (NR) code, a nonlinear code that has a large distance for a given rate combined with a trellis code, is examined. A bound is developed on the error probability for this trellis-coded NR (TCNR) code with noncoherent reception over a frequency-nonselective Rayleigh or Rician fading channel with additive white Gaussian noise (AWGN). This bound is tighter than the standard union bound. Our results indicate that the standard union bound can be significantly different from the more accurate results obtained from the improved union bound. In addition, there is a considerable coding gain at high signal-to-noise ratio (SNR) for the TCNR code over the conventional DS-SS code at the same data rate.

TCM schemes with partially overlapped signal constellations

In conventional TCM schemes, for a rate of n bits per channel symbol, a 2/sup n+1/-point constellation is used. It is shown that using constellations with less than 2/sup n+1/-points, one can achieve a considerable coding gain in comparison to the traditional 2/sup n+1/-point constellation. The increase in coding gain is due to a reduction in transmitted signal energy as a result of deleting some high-power signals from the original constellation and reusing of some of the low-power signals instead.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>