Jiguang He

Performance Analysis of OSTBC Transmission in Lossy Forward MIMO Relay Networks

We analyze the outage probability for the orthogonal space-time block code based multiple-input multiple-output (MIMO) relay networks, composed of one source, one relay, and a single destination. The relay forwards the decoded and interleaved information sequence even though the information part may contain error(s), according to the lossy forward strategy. In spatially independent MIMO channels, we find that the diversity order of the relay network can be interpreted and formulated by the well-known max-flow min-cut theorem. Moreover, we extend the analysis to the case of spatially correlated MIMO channels. Approximated explicit expressions for the outage probabilities are obtained in high signal-to-noise ratio regime.

Transmission of correlated sources over non-orthogonal Gaussian MACs

We investigate the transmission of multiple correlated binary sources to a single destination over non-orthogonal Gaussian multiple access channels (MACs). By considering a binary codebook, we derive the admissible rate regions of the two-source Gaussian MAC. It is demonstrated that the admissible rate region increases as the correlation between the sources increases. Furthermore, we develop an iterative joint source channel decoding scheme based on systematic irregular low-density parity-check codes by exploiting the correlation between the two sources. The constituent decoders corresponding to each source are implemented in parallel via local iterations, exchanging extrinsic information with each other during the global iterations. Simulation results are provided to verify the performance improvement of the transmission of correlated sources compared to its independent sources counterpart.

Minimum power based relay selection for orthogonal multiple access relay networks

We analyze the performance of a multi-source multi-helper transmission with lossy forward (LF) relaying. In LF, estimates at the relay are encoded and forwarded to the destination for improving the reliability of the received sequence transmitted from the multiple source nodes. Unlike the conventional decode-and-forward (DF) relaying, LF sends the data even in the case where decoding is not error-free. We extend the results of the channel with multiple sources and a single helper to perform relay selection by utilizing the union of rate regions. A power minimization problem is formulated using the above strategy and solved by exploiting the successive convex approximation (SCA) technique. Numerical results are presented to show that the proposed relay selection method achieves the same performance as the exhaustive search.

Performance Improvement of Joint Source-Channel Coding With Unequal Power Allocation

We develop a joint source-channel coding (JSCC) scheme based on an unequal power allocation strategy, in which different levels of power are allocated according to a priori probability distribution of the information bits. Two protograph low-density parity-check codes are used as the source code and the channel code, respectively, in the proposed JSCC scheme. With fixed row weight and row element alphabet, optimization on the source code is conducted via random search to obtain a best-found base matrix with the lowest decoding threshold among all the searched base matrices. Simulation results show that the new JSCC scheme outperforms the traditional equal power allocation-based JSCC by exploiting the source statistics at the decoder. Moreover, theoretical threshold analysis is in agreement with the practical simulation results.

Fading Correlations for Wireless Cooperative Communications: Diversity and Coding Gains

We theoretically analyze outage probabilities of the lossy-forward (LF), decode-and-forward (DF), and adaptive decode-and-forward (ADF) relaying techniques, with the aim of characterizing the impact of the spatial and temporal correlations of the fading variations. First, the exact outage probability expressions are analytically obtained for LF, DF, and ADF relaying assuming each link suffers from statistically independent Rayleigh fading. Then, approximated, yet accurate closed-form expressions of the outage probabilities for the relaying schemes are derived. Based on the expressions, diversity and coding gains are found. The mathematical methodology for the derivation of the explicit outage probability is further extended to the case, where the account is taken of the spatial and temporal correlations of the fading variations. The diversity gains with LF, DF, and ADF are then derived in the presence of the correlations. It is found out that the three techniques can achieve full diversity, as long as the fading variations are not fully correlated. We then investigate the optimal relay location and the optimal power allocation for the three relaying techniques. It is shown that the optimal solutions can be obtained under the framework of convex optimization. It is revealed that in correlated fading, the relay should move close to the destination or allocate more transmit power to the relay for achieving lower outage probabilities, compared with the case in independent fading.

Performance analysis for multi-source multi-relay transmission over κ-μ fading channels

We derive the outage probability of a multi-source multi-relay transmission system, where all the links experience κ-μ fading variations. The source-relay links are assumed to be non-orthogonal multiple access channels (MACs). Two transmission schemes are considered for relay-destination transmission, i.e., non-orthogonal maximum ratio transmission (MRT) and orthogonal transmission with joint-decoding (JD) at the destination. The outage probability is formulated by taking into consideration the different decoding results at the relays. It is found that, with or without the impact of line-of-sight (LOS) component or the number of multipath clusters in channels, the outage performance of the system with JD is superior to that with MRT. Furthermore, we investigate the impact of the geometric gain based relay location and power allocation for relays on the performance.