Search

In this paper, for an interference alignment (IA) based network, a time splitting scheme for transmitting training and data symbols is optimized. The time allocated for transmitting training symbol will affect the precision of channel estimation (CE) and thus the achievable rate as well as the duration for data symbol transmission. With the least square (LS) and relaxed minimum mean square error (RMMSE) CE algorithm, the lower bounds of achievable rate are carefully derived, respectively. Then we formulate an optimization problem to maximize the lower bounds of achievable rate by optimizing the time splitting factor (TSF). The existence of optimum is first proved. Then, regarding the complexity of solution, Taylor expansion is adopted to find the approximated optimal TSF. Numerical results are presented to show the optimal TSF can achieve larger lower bound of achievable rate over other fixed TSFs due to its adaptivity to the channel characteristics and its statistics of CE errors. Numerical results also validate that the approximation just brings out some small and acceptable errors on the system rate. In addition, RMMSE CE algorithm shows better performance than LS CE because RMMSE considers noise statistics as modification. [ABSTRACT FROM AUTHOR]

Classical Turbo code suffers from high error floor due to its small Minimum Hamming Distance (MHD). Newly-proposed 3D-Turbo code can effectively increase the MHD and achieve a lower error floor by adding a rate-1 post encoder. In 3D-Turbo codes, part of the parity bits from the classical Turbo encoder are further encoded through the post encoder. In this paper, a novel Bit-Interleaved Coded Modulation (BICM) system is proposed by combining rotated mapping Quadrature Amplitude Modulation (QAM) and 3D-Turbo code to improve the Bit Error Rate (BER) performance of 3D-Turbo code over Raleigh fading channel. A key-bit protection scheme and a Two-Dimension (2D) iterative soft demodulating-decoding algorithm are developed for the proposed BICM system. Simulation results show that the proposed system can obtain about 0.8-1.0dB gain at BER of 10~6, compared with the existing BICM system with Gray mapping QAM. [ABSTRACT FROM AUTHOR]