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Cooperative Fading Regions for Decode and Forward Relaying

IEEE TRANSACTIONS ON INFORMATION THEORY 2008年第11期54卷 4908-4924页

作者： Savazzi, Stefano Spagnolini, Umberto Politecn Milan Dipartimento Elettron & Informaz I-20133 Milan Italy

Cooperative transmission protocols over fading channels are based on a number of relaying nodes to form virtual multi-antenna transmissions. Diversity provided by these techniques has been widely analyzed for the Rayleigh fading case. However, short range or fixed wireless communications often experience propagation environments where the fading envelope distribution is meaningfully different from Rayleigh. The main focus in this paper is to investigate the impact of fading distribution on performances of collaborative communication. Cooperative protocols are compared to co-located multi-antenna systems by introducing the concept of cooperative fading region. This is the collection of fading distributions for which relayed transmission can be regarded as a competitive option (in terms of performances) compared to multi-antenna direct (noncooperative) transmission. The analysis is dealt with by adopting the information theoretic outage probability as the performance metric. Cooperative link performances at high SNR are conveniently expressed here in terms of diversity and coding gain as outage parameters that are provided by the fading statistics of the channels involved in collaborative transmission. Advantages of cooperative transmission compared to multi-antenna are related to the propagation environment so that the analysis can be used in network design.

关键词： Cooperative diversity cooperative transmissions decode and forward relaying distributed space-time coding fading channels

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distributed space-time Continuous Phase Modulation Code Design

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IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS 2008年第11期7卷 4455-4461页

作者： Silvester, Anna-Marie Lampe, Lutz Schober, Robert Univ British Columbia Dept Elect & Comp Engn Vancouver BC V6T 1Z4 Canada

In this paper, distributed space-time (ST) codes for continuous-phase modulation (CPM) are introduced. The distributed ST codes are designed to operate in wireless networks containing a large set of nodes N, of which only a small a priori unknown subset S C N will be active at any time. Under the proposed scheme, a relay node transmits a signal which is the product of a diagonal block-based ST code (optimized specifically for ST-CPM transmission) and a signature vector of length N. uniquely assigned to each node in the network. An efficient method is presented for the design and optimization of appropriate signature vector sets, assuming a quasi-static, frequency nonselective fading channel model. If a properly designed signature vector set is employed it is shown that a diversity order of d = min{N-S, N-c} an be achieved, where NS is the number of active relay nodes. The decoding complexity of the proposed scheme is shown to be independent of the number of active relay nodes, and non-coherent receiver implementations, which do not require channel estimation, are applicable. Compared to distributed ST transmission with linear modulation, distributed ST-CPM can considerably reduce the energy consumption at the transmitter due to the constant envelope of the transmit signal. At the same time, the additional energy consumption due to more complex receiver processing can be kept low. Therefore, the proposed distributed ST-CPM scheme is particularly apt for energy-efficient cooperative transmission in wireless networks.

关键词： distributed space-time coding continuous-phase modulation wireless networks relaying ad hoc and sensor networks co-operative diversity

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Performance analysis of a multihop relay network using distributed Alamouti code

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WIRELESS NETWORKS 2015年第1期21卷 217-226页

作者： Aydin, Ibrahim Aygolu, Umit Sakarya Univ Dept Elect & Elect Engn TR-54187 Esentepe Sakarya Turkey Istanbul Tech Univ Fac Elect & Elect Engn TR-34469 Istanbul Turkey

In this paper, we apply the classical Alamouti coding technique in a distributed and cascaded fashion to multihop relay networks where relays perform the decode-and-forward (DF) protocol at each relay stage. The considered system consists of two antennas at the source, two single-antenna relays at each relay stage and one antenna at the destination. The source transmits at each coding step two symbols according to the Alamouti code, to the first relay stage where each relay decodes the two symbols independently. The two relays of each relay stage behave like the two antennas of the source and transmit the two estimated symbols to the next relay stage until the destination using distributed Alamouti code. We obtain a closed form expression for the outage probability of the N-hop relay network and derive a tight analytical upper bound for the bit error probability at the destination, by considering the two-hop case firstly and then generalizing for the N-hop networks. We also show that DF protocol provides better bit error performance compared to the amplify-and-forward protocol previously considered in the literature for N-hop relay networks.

关键词： Wireless communications Cooperative diversity Multihop relay networks distributed space-time coding

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Training and Decodings for Cooperative Network with Multiple Relays and Receive Antennas

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IEEE TRANSACTIONS ON COMMUNICATIONS 2012年第6期60卷 1534-1544页

作者： Sun, Sun Jing, Yindi Univ Alberta Dept Elect & Comp Engn Edmonton AB T6G 2V4 Canada

In this paper, channel training and coherent decodings under channel estimation error are investigated for relay networks with one single-antenna transmitter, R single-antenna relays, and one R-antenna receiver. A two-stage training scheme is proposed to estimate both the relay-receiver and the transmitter-relay channels at the receiver, which are commonly required in amplify-and-forward (AF) relay networks. We use distributed space-time coding (DSTC) for data transmission and investigate the effect of channel estimation errors on network performance. Two coherent decodings are considered: mismatched decoding in which channel estimations are treated as if perfect, and matched decoding in which estimation error is taken into consideration. We show that for full diversity, with mismatched decoding, at least 3R symbol intervals are required for training;while with matched decoding, R+2 symbol intervals for training are enough. The complexities of the decoding schemes are investigated. To achieve a balance between performance and complexity, an adaptive decoding scheme is proposed. Simulated error rates are shown to justify the analytical results.

关键词： MIMO relay network channel training LMMSE estimation diversity distributed space-time coding

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Channel and delay estimation algorithm for asynchronous cooperative diversity

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WIRELESS PERSONAL COMMUNICATIONS 2006年第3-4期37卷 361-369页

作者： Tourki, Kamel Deneire, Luc Lab 13S F-06903 Sophia Antipolis France

Wireless Mobile Communications rely on a host of techniques, all related to one goal, sending the most possible information accross a link or a network. In recent years, both spatial and multiuser diversity have proven to be key techniques to achieve this goal. These two diversity dimensions can be exploited by the use of multiple antennas and/or the use of multiple terminals sending at the same time/frequency/code, these terminals can be seen as a multiple antenna emitter. This transmission diversity can be achieved with cooperative space-time encoded transmissions. One of the practical problems with this sort of array of transmitters is that the emitters will be asynchronous to some extent, hence the need for systems that can deal with asynchronicity, both from a signal design point of view and from a signal processing point of view. Having tackled the signal design previously, we take a look at the signal processing aspect and present a channel and delay estimation algorithm for asynchronous cooperative diversity in Block-Flat-Fading channel. The signal design is based on a precoding frame-based scheme with packet-wise encoding. This precoding is based on the addition of a cyclic prefix, implemented as a training sequence. The signal processing takes advantage of the known symbols offered by this cyclic prefix/training sequence and we show that it enables best synchronization and channel estimation which reaches the Cramer-Rao Bound. The BER performances are the same as synchronous MRC case, with full diversity order.

关键词： cooperative diversity synchronization distributed space-time coding cyclic prefix time reverse Rayleigh block-flat-fading channel

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Using orthogonal and quasi-orthogronal designs in wireless relay networks

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IEEE TRANSACTIONS ON INFORMATION THEORY 2007年第11期53卷 4106-4118页

作者： Jing, Yindi Jafarkhani, Hamid Univ Calif Irvine Dept Elect Engn & Comp Sci Irvine CA 92697 USA

distributed space-time coding was proposed to achieve cooperative diversity in wireless relay networks without channel information at the relays. Using this scheme, antennas of the distributive relays work as transmit antennas of the sender and generate a space-time code at the receiver. It achieves the maximal diversity when the transmit power is infinitely large. This paper is on the design of practical distributed space-time codes (DSTCs). We use orthogonal and quasi-orthogonal designs which are originally used in the design of space-time codes for multiple-antenna systems. It is well known that orthogonal space-time codes have full diversity and linear decoding complexity. They are particularly suitable for transmissions in the network setting using distributed space-time coding since their "scale-free" property leads to good performance. Our simulations show that they achieve lower error rates than the random code. We also compare distributed space-time coding to selection decode-and-forward using the same orthogonal designs. Simulations show that distributed space-time coding achieves higher diversity than selection decode-and-forward (DF) when there is more than one relay. We also generalize the distributed space-time coding scheme to wireless relay networks with channel information at the relays. Although our analysis and simulations show that there is no improvement in the diversity, in some networks, having channel information at the relays saves both the transmission power and the transmission time.

关键词： relay network distributed space-time coding orthogonal and quasi-orthogonal designs diversity coding gain pairwise error probability (PEP)

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Cooperative Transmission for Wireless Relay Networks Using Limited Feedback

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IEEE TRANSACTIONS ON SIGNAL PROCESSING 2010年第7期58卷 3828-3841页

作者： Paredes, Javier M. Khalaj, Babak H. Gershman, Alex B. Tech Univ Darmstadt Commun Syst Grp D-64283 Darmstadt Germany Sharif Univ Technol Dept Elect Engn Tehran Iran Sharif Univ Technol ACRI Tehran Iran

To achieve the available performance gains in half-duplex wireless relay networks, several cooperative schemes have been earlier proposed using either distributed space-time coding or distributed beamforming for the transmitter without and with channel state information (CSI), respectively. However, these schemes typically have rather high implementation and/or decoding complexities, especially when the number of relays is high. In this paper, we propose a simple low-rate feedback-based approach to achieve maximum diversity with a low decoding and implementation complexity. To further improve the performance of the proposed scheme, the knowledge of the second-order channel statistics is exploited to design long-term power loading through maximizing the receiver signal-to-noise ratio (SNR) with appropriate constraints. This maximization problem is approximated by a convex feasibility problem whose solution is shown to be close to the optimal one in terms of the error probability. Subsequently, to provide robustness against feedback errors and further decrease the feedback rate, an extended version of the distributed Alamouti code is proposed. It is also shown that our scheme can be generalized to the differential transmission case, where it can be applied to wireless relay networks with no CSI available at the receiver.

关键词： Cooperative communications distributed space-time coding limited feedback wireless relay networks

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Two-Phase Bidirectional Dual-Relay Selection Strategy for Wireless Relay Networks

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Computers, Materials & Continua 2021年第10期69卷 539-553页

作者： Samer Alabed Issam Maaz Mohammad Al-Rabayah College of Engineering and Technology American University of the Middle EastKuwait

In this article,we introduce a new bi-directional dual-relay selection strategy with its bit error rate(BER)performance *** the first step of the proposed strategy,two relays out of a set of N relay-nodes are selected in a way to optimize the system performance in terms of BER,based on the suggested algorithm which checks if the selected relays using the maxmin criterion are the best *** the second step,the chosen relay-nodes perform an orthogonal space-time coding scheme using the two-phase relaying protocol to establish a bi-directional communication between the communicating terminals,leading to a significant improvement in the achievable coding and diversity *** further improve the overall system performance,the selected relay-nodes apply also a digital network coding ***,this paper discusses the analytical approximation of the BER performance of the proposed strategy,where we prove that the analytical results match almost perfectly the simulated ***,our simulation results show that the proposed strategy outperforms the current state-of-the-art ones.

关键词： Two-way wireless relay networks cooperative diversity techniques distributed space-time coding relay selection strategies network coding schemes

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distributed space-time cooperative systems with regenerative relays

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IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS 2006年第11期5卷 3130-3141页

作者： Anghel, Paul A. Leus, Geert Kaveh, Mostafa Univ Minnesota Minneapolis MN 55455 USA Tech Univ Delft Fac Elect Engn NL-2628 CD Delft Netherlands

This paper addresses some of the opportunities and the challenges in the design of multi-hop systems that utilize cooperation with one or two intermediate regenerative relays to provide high-quality communication between a source and a destination. We discuss the limitations of using a distributed Alamouti scheme in the relay channel and the additional complexity required to overcome its loss of diversity. As an alternative to the distributed Alamouti scheme, we propose. and analyze two Error Aware distributed space-time (EADST) systems built around the Alamouti code. First, using a bit error rate base relay selection approach, we design an EADST system with one and two regenerative relays that rely on feedback from the destination and we show that the proposed system improves on the distributed Alamouti scheme. In addition, we prove that the proposed one relay EADST system collects. the full diversity of the distributed MISO channel. Second, we introduce an EADST system without feedback in which the relaying energies depend on the error probabilities at the relays. Numerical results show that both EADST systems perform close to the error probability lower bound obtained by considering error-free reception at the relays.

关键词： distributed space-time coding cooperative systems regenerative relays

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Energy-Efficient Cooperative Techniques for Infrastructure-to-Vehicle Communications

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IEEE TRANSACTIONS ON INTELLIGENT TRANSPORTATION SYSTEMS 2011年第3期12卷 659-668页

作者： Tuan-Duc Nguyen Berder, Olivier Sentieys, Olivier Vietnam Natl Univ Sch Elect Engn Ho Chi Minh City Int Univ Ho Chi Minh City 70000 Vietnam Univ Rennes 1 IRISA F-35042 Rennes France

In wireless distributed networks, cooperative relay and cooperative multiple-input-multiple-output (MIMO) techniques can be used to exploit the spatial and temporal diversity gains to increase the performance or reduce the transmission energy consumption. The energy efficiency of cooperative MIMO and relay techniques is then very useful for the infrastructure-to-vehicle (I2V) and infrastructure-to-infrastructure (I2I) communications in intelligent transport system (ITS) networks, where the energy consumption of wireless nodes embedded on road infrastructure is constrained. In this paper, applications of cooperation between nodes to ITS networks are proposed, and the performance and the energy consumption of cooperative relay and cooperative MIMO are investigated and compared with the traditional multihop technique. The comparison between these cooperative techniques helps us choose the optimal cooperative strategy in terms of energy consumption for energy-constrained road infrastructure networks in ITS applications.

关键词： Cooperative multiple-input-multiple-output (MIMO) distributed space-time coding energy efficiency infrastructure-to-vehicle communications wireless communications

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