A decode and forward protocol based Trellis Coded Modulation (TCM) scheme for the half-duplex relay channel, in a Rayleigh fading environment, is presented. The proposed scheme can achieve any spectral efficiency greater than or equal to one bit per channel use (bpcu). A near-ML decoder for the suggested TCM scheme is proposed. It is shown that the high SNR performance of this near-ML decoder approaches the performance of the optimal ML decoder. The high SNR performance of this near-ML decoder is independent of the strength of the Source-Relay link and approaches the performance of the optimal ML decoder with an ideal Source-Relay link. Based on the derived Pair-wise Error Probability (PEP) bounds, design criteria to maximize the diversity and coding gains are obtained. Simulation results show a large gain in SNR for the proposed TCM scheme over uncoded communication as well as the direct transmission without the relay. Also, it is shown that even for the uncoded transmission scheme, the choice of the labelling scheme (mapping from bits to complex symbols) used at the source and the relay significantly impacts the BER vs SNR performance. We provide a good labelling scheme for @math -PSK signal set, where @math is an integer.
Achievable rates and upper bounds on the capacity for the discrete memoryless relay channel for the full-duplex and the more practical half-duplex relay channel were obtained in @cite_19 , @cite_14 . These results were extended for the half duplex Gaussian relay channel in @cite_8 . Optimal power allocation strategies to maximize the achievable rate for the Rayleigh fading relay channel were investigated in @cite_20 . Several protocols like Amplify and Forward (AF), Decode and Forward (DF), Compress and Forward (CF) were proposed @cite_6 . Power allocation strategies for the Non Orthogonal DF (NODF) protocol were discussed in @cite_21 . Non-orthogonal relay protocols offer higher spectral efficiency when compared with orthogonal relay protocols @cite_11 , @cite_2 , @cite_0 . Hence, the proposed TCM scheme in this paper is based on the NODF protocol.
@cite_14 @cite_8 @cite_21 @cite_6 @cite_0 @cite_19 @cite_2 @cite_20 @cite_11
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We consider the communication problem in a multi-hop relay network where the intermediate relay nodes cannot transmit and receive at the same time. The motivation for this assumption comes from the fact that current radios operate in TDD mode when the transmitting and receiving frequencies are the same. We label such a node radio as a cheap radio and the corresponding node of the network as a cheap node. In this paper we derive the capacities of the degraded cheap relay channel and the multi-hop net- work with cheap nodes. The proof of the achievability parts in coding theorems are presented based on the jointly typical sequences, while the proof of the con- verses are derived from the direct application of the upper bounds derived in (7). A relay channel consists of an input x_ l , a relay output y_ 1 , a channel output y , and a relay sender x_ 2 (whose transmission is allowed to depend on the past symbols y_ 1 . The dependence of the received symbols upon the inputs is given by p(y,y_ 1 |x_ 1 ,x_ 2 ) . The channel is assumed to be memoryless. In this paper the following capacity theorems are proved. 1)If y is a degraded form of y_ 1 , then C : = : !_ p(x_ 1 ,x_ 2 ) , I(X_ 1 ,X_ 2 ;Y), I(X_ 1 ; Y_ 1 |X_ 2 ) . 2)If y_ 1 is a degraded form of y , then C : = : !_ p(x_ 1 ) x_ 2 I(X_ 1 ;Y|x_ 2 ) . 3)If p(y,y_ 1 |x_ 1 ,x_ 2 ) is an arbitrary relay channel with feedback from (y,y_ 1 ) to both x_ 1 x_ 2 , then C : = : p(x_ 1 ,x_ 2 ) , I(X_ 1 ,X_ 2 ;Y),I ,(X_ 1 ;Y,Y_ 1 |X_ 2 ) . 4)For a general relay channel, C : : p(x_ 1 ,x_ 2 ) , I ,(X_ 1 , X_ 2 ;Y),I(X_ 1 ;Y,Y_ 1 |X_ 2 ) . Superposition block Markov encoding is used to show achievability of C , and converses are established. The capacities of the Gaussian relay channel and certain discrete relay channels are evaluated. Finally, an achievable lower bound to the capacity of the general relay channel is established. We propose novel cooperative transmission protocols for delay-limited coherent fading channels consisting of N (half-duplex and single-antenna) partners and one cell site. In our work, we differentiate between the relay, cooperative broadcast (down-link), and cooperative multiple-access (CMA) (up-link) channels. The proposed protocols are evaluated using Zheng-Tse diversity-multiplexing tradeoff. For the relay channel, we investigate two classes of cooperation schemes; namely, amplify and forward (AF) protocols and decode and forward (DF) protocols. For the first class, we establish an upper bound on the achievable diversity-multiplexing tradeoff with a single relay. We then construct a new AF protocol that achieves this upper bound. The proposed algorithm is then extended to the general case with (N-1) relays where it is shown to outperform the space-time coded protocol of Laneman and Wornell without requiring decoding encoding at the relays. For the class of DF protocols, we develop a dynamic decode and forward (DDF) protocol that achieves the optimal tradeoff for multiplexing gains 0lesrles1 N. Furthermore, with a single relay, the DDF protocol is shown to dominate the class of AF protocols for all multiplexing gains. The superiority of the DDF protocol is shown to be more significant in the cooperative broadcast channel. The situation is reversed in the CMA channel where we propose a new AF protocol that achieves the optimal tradeoff for all multiplexing gains. A distinguishing feature of the proposed protocols in the three scenarios is that they do not rely on orthogonal subspaces, allowing for a more efficient use of resources. In fact, using our results one can argue that the suboptimality of previously proposed protocols stems from their use of orthogonal subspaces rather than the half-duplex constraint. We consider three-node wireless relay channels in a Rayleigh-fading environment. Assuming transmitter channel state information (CSI), we study upper bounds and lower bounds on the outage capacity and the ergodic capacity. Our studies take into account practical constraints on the transmission reception duplexing at the relay node and on the synchronization between the source node and the relay node. We also explore power allocation. Compared to the direct transmission and traditional multihop protocols, our results reveal that optimum relay channel signaling can significantly outperform multihop protocols, and that power allocation has a significant impact on the performance. Cooperative diversity is a transmission technique, where multiple terminals pool their resources to form a virtual antenna array that realizes spatial diversity gain in a distributed fashion. In this paper, we examine the basic building block of cooperative diversity systems, a simple fading relay channel where the source, destination, and relay terminals are each equipped with single antenna transceivers. We consider three different time-division multiple-access-based cooperative protocols that vary the degree of broadcasting and receive collision. The relay terminal operates in either the amplify-and-forward (AF) or decode-and-forward (DF) modes. For each protocol, we study the ergodic and outage capacity behavior (assuming Gaussian code books) under the AF and DF modes of relaying. We analyze the spatial diversity performance of the various protocols and find that full spatial diversity (second-order in this case) is achieved by certain protocols provided that appropriate power control is employed. Our analysis unifies previous results reported in the literature and establishes the superiority (both from a capacity, as well as a diversity point-of-view) of a new protocol proposed in this paper. The second part of the paper is devoted to (distributed) space-time code design for fading relay channels operating in the AF mode. We show that the corresponding code design criteria consist of the traditional rank and determinant criteria for the case of colocated antennas, as well as appropriate power control rules. Consequently space-time codes designed for the case of colocated multiantenna channels can be used to realize cooperative diversity provided that appropriate power control is employed.