Abstract-In this paper, a novel unified channel model framework is proposed for cooperative multiple-input multiple-output (MIMO) wireless channels. The proposed model framework is generic and adaptable to multiple cooperative MIMO scenarios by simply adjusting key model parameters. Based on the proposed model framework and using a typical cooperative MIMO communication environment as an example, we derive a novel geometry-based stochastic model (GBSM) applicable to multiple wireless propagation scenarios. The proposed GBSM is the first cooperative MIMO channel model that has the ability to investigate the impact of the local scattering density (LSD) on channel characteristics. From the derived GBSM, the corresponding multi-link spatial correlation functions are derived and numerically analyzed in detail.Index Terms-Cooperative MIMO channels, geometry-based stochastic model, spatial correlation, non-isotropic scattering.

The hybrid relay selection (HRS) scheme, which adaptively chooses amplify-and-forward (AF) and decode-and-forward (DF) protocols, is very effective to achieve robust performance in wireless networks. This paper analyzes the frame error rate (FER) of the HRS scheme in general cooperative wireless networks without and with utilizing error control coding at the source node. We first develop an improved signal-to-noise ratio (SNR) threshold-based FER approximation model. Then, we derive an analytical average FER expression as well as an asymptotic expression at high SNR for the HRS scheme and generalize to other relaying schemes. Simulation results are in excellent agreement with the theoretical analysis, which validates the derived FER expressions. Index TermsHybrid relay selection, frame error rate, SNR threshold-based approximation, cooperative communications.

which is then solved by a GP solver, e.g., gpcvx or MOSEK based on state-of-the-art interior-point method (IPM).An important subtlety should be noted. When all globally optimumx for (11) contains zero entries, the corresponding optimum y for (12) contains entries equal to 01. In such a case, the IPM iteratively outputs y with g 0 (y) asymptotically approaching the optimum objective value for (12), which leads to an overflow in the processor running the GP solver that implements the IPM. It is rarely known a priori if the optimum x for (11) contains zero entries. To avoid overflow, the GP solver by default adds entrywise lower-bound constraints on x, or equivalently on y before solving (12) (see [21, p. 3]). These constraints should be set to ensure that the optimum x for (11) with the extra constraints corresponds to an objective value within a prescribed small tolerance around the original optimum objective for (11). ACKNOWLEDGMENTThe authors would like to thank Prof. M. Dong and the anonymous reviewers for their precious comments and suggestions which has improved this work. REFERENCES[1] R. Cendrillon, W. Yu, M. Moonen, J. Verlinden, and T. Bostoen, "Optimal multiuser spectrum balancing for digital subscriber lines," IEEE Trans.

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In this letter, a compressed relaying scheme via Huffman and physical-layer network coding (HPNC)is proposed for two-way relay networks with correlated sources (TWRN-CS). In the HPNC scheme, both sources first transmit the correlated raw source messages to the relay simultaneously. The relay performs physical-layer network coding (PNC) on the received symbols, compresses the PNC-coded symbols using Huffman coding, and broadcasts the compressed symbols to both source nodes. Then, each source decodes the other source's messages by using its own messages as side information. Compression rate and block error rate (BLER) of the proposed scheme are analyzed. Simulation results demonstrate that the HPNC scheme can effectively improve the network throughput, and meanwhile, achieve the superior BLER performance compared with the conventional non-compressed relaying scheme in TWRN-CS. Index TermsCompression, correlated bidirectional relay networks, Huffman coding, physical-layer network coding.

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In this paper, we propose a novel multihop transmission scheme using selective network coding (NC) and differential modulation (SNC-DM) for two-way relay networks (TWRNs) when neither the source nodes nor the relay nodes know the channel state information (CSI). We first develop a bidirectional transmission scheme using NC where the information exchange in a two-way multihop relay network with the arbitrary number of hops can be completed in four transmission phases. As a result, the maximum achievable throughput does not decrease as the number of hops increases. To overcome the error propagation in the multihop transmission with decode-and-forward (DF) protocol in wireless fading channels, a selective NC scheme is proposed. In addition, we apply differential modulation in the proposed scheme to avoid channel estimation in the multihop networks. The performance of the proposed scheme is analyzed, and a closedform frame error rate (FER) expression is derived. It is shown that the proposed scheme achieves significant improvements in both FER performance and network throughput compared to the conventional multihop DF scheme in TWRNs. The analytical results are verified through numerical simulations.