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Performance of cooperative relaying employing infrastructure based fixed relays having multiple antennas have been investigated. Here, relay performs selection combining and destination performs MRC combining of signals. Outage and bit error rate (BER) performance of such relay network in terms of relay positioning and number of antenna elements, in Nakagami-n fading channel, have been presented....
In this paper, two classes of cooperative protocols for wireless relay networks are considered. Both classes of protocols consist of two transmission phases: broadcasting phase and cooperating phase. Protocol I - In the broadcasting phase, the source only broadcasts to all potential relays; during the cooperating phase, only the relays communicate with the destination. Protocol II - During the broadcasting...
In this paper, we propose and investigate a decentralized adaptive transmission technique for cooperative wireless communications. A number of relays adaptively switch between two transmission modes: Alamouti diversity and spatial multiplexing. The relays may exploit Amplify-and-Forward (AF) or Decode-and-Forward (DF) transmission technique. The performances of the decentralized adaptive transmission...
This paper proposes a new combinational technology which is feasible to apply physical-layer network coding (PNC) to wireless fading channel. The key step of PNC is that sources broadcast signals simultaneously without orthogonal scheduling. Naturally, the signals overlap in the free space at the receivers. Since the signals from different sources are mutual independent, rooted on this rational assumption,...
In cooperative automatic repeat request (ARQ), the retransmission can be done by the source or by a selected relay. We consider opportunisitic amplify and forward (AF) relaying. The selected relay offers the highest instantaneous signal to noise ratio (SNR) of the relaying link (source-relay-destination). We investigate the optimal combination of source and relays transmission for a destination using...
This paper investigates the diversity performance of wireless relay networks with multiple parallel relays communicating with the destination over orthogonal channels. The networks under consideration employ two signal-to-noise ratio (SNR) thresholds and multiple hard-decision detections (HDD) at the destination. One SNR threshold is used to select transmitting relays in the second phase: a relay...
In this paper, we provide a survey of cooperative automatic repeat request (ARQ) protocols for multi-relay systems operating over multiple-input-multiple-output (MIMO) broadband channels. We study three main operating modes: amplify-and-forward (AF), decode-and-forward (DF), and positive/negative acknowledgment (ACK/NACK)-aided DF. We describe efficient minimum mean square error (MMSE) frequency domain...
We derive new exact closed-form expressions for the symbol error rate (SER) of cooperative selection diversity (CSD) with amplify-and-forward (AF) transmission using channel-state-information (CSI)-based gain relaying. We consider the general fading condition of independent but not necessarily identically distributed (i.n.d.) Nakagami-m fading. We also present a closed-form expression for i.n.d. Rayleigh...
Cooperative communication has been widely investigated to improve performance of wireless networks. In cooperative wireless system, various MIMO scheme such as OSTBC, CDD and V-BLAST can be easily applied and obtain diversity or multiplexing gain. These schemes cannot obtain diversity and multiplexing gain simultaneously. To guarantee both high throughput and reliable transmission, hybrid STBC can...
Spectrum efficient multiple relay selection strategy for two-hop cooperative decode-and-forward relay networks is proposed for the case when the sum power among all relay nodes is limited. Based on the outage-multiplexing tradeoff (OMT), the number of active relay nodes is maximized so that the resulting sum-relay capacity is maximized while each relay outage capacity remains greater than or equal...
In this paper, three cooperative relaying schemes are proposed for relay networks comprised of two source terminals and multiple relays, each with single antenna. The new relaying schemes, corresponding to the maximum ratio combining of the downlink and uplink channels, phase rotation of the received signals at relays, and the channel gain equalization, are designed based on the maximization of the...
Distributed orthogonal space-time block code (DOSTBC) designs have the potential to achieve significant diversity gain in relay networks but such designs do not use any channel information at the transmitter to optimize the system performance. When channel information is available fully or partially at the relays, transmit beamforming can be employed to enhance the performance of the wireless relay...
In this work, a novel two-level rate superposition coding relaying (SC-relaying) strategy is investigated. In this SC-relaying strategy, the channel state feedback of relay-to-source is introduced under a long term power constraint at source. For the SC-relaying strategy, the source power SNR exponent constraints are first obtained. And then, by using the power SNR exponent constraints, the optimizing...
Traditional routing strategies for multi-hop wireless networks forward packets by selecting at the sender side the next hop for each packet. Recently, such a paradigm has been called into question by a new approach, namely the opportunistic routing. It exploits the broadcast nature of wireless transmissions to take advantage from spatial diversity by routing the packets according to the propagation...
The mobile communication systems services are shifting from voice conversation to data transmission through the Internet. The information transferred over the Internet is becoming increasingly rich, there will be a demand of peak data transmission rates of around 100 Mbps-1Gbps even in mobile communications systems. However, as the data transmission rate becomes higher, the peak transmit power becomes...
We investigate the symbol error rate (SER) and outage probability of the cooperative transmission with the decode-and-forward relay protocol over dissimilar Rayleigh fading channels. The technique of orthogonal space-time block coding (STBC) is applied at the links of source-relay, source-destination and relay-destination. Closed-form expressions of outage probability and SER are derived, respectively...
An adaptive relay allocation scheme for multi-user cooperative communication systems with amplify-and-forward (AF) relays is investigated. We consider maximizing system capacity while guaranteeing the QoS (Quality of Service) of each user. Proposed relay allocation scheme uses space-time coding technique. It performs well in allocating relay nodes to multiple source-destination pairs. The proposed...
This paper proposes a cooperative diversity protocol with truncated automatic repeat request (ARQ) for multicast transmission. The proposed method employs SNR threshold-based selective relaying for distributed space time block coding for retransmission. Numerical results will show that the proposed method with optimal SNR threshold improves the error and throughput performance remarkably.
Cooperative diversity has been recently proposed as a way to form virtual antenna arrays that provide dramatic gains in slow fading wireless environments. In a multiple-relay network, the opportunistic relay selection scheme has been shown to outperform any other strategy that involves the conventional all-participate scheme. The opportunistic relay selection scheme generally supposes the existence...
In this paper, we consider a general two-hop relay network and propose a distributed turbo coding with selective relaying (DTC-SR) scheme to improve the performance of relayed transmission. In the proposed scheme, each relay adaptively selects an amplify and forward (AAF) or a decode and forward (DAF) protocol based on whether it can decode correctly or not. Among all the relays, a single relay, which...
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