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This paper analyzes the outage probability of cooperative communications over asymmetric fading environments. This work investigates the scenario where cooperative nodes are located at different geographical locations. Some cooperative nodes experience line of sight (LOS) signals and some nodes may experience non-LOS (NLOS) signals. As a result, signals in different links are affected by different...
Cooperative diversity is an attractive way to combat fading in wireless networks,. Conventionally, the outage probability, which measures robustness of the transmission to fading in cooperative communication, is deduced on the condition that the signal-to-noise ratio (SNR) is very high. However, the result is only an approximation. In this paper, proposed a new way to deduce the accurate outage probability...
Relay networks achieve high performance by utilizing cooperation between nodes which can classified as multi-hop networks and cooperative MIMO relaying networks. Cooperative diversity is a transmission technique to overcome fading, multipath and inter-channel interference. As an important part of "spatial diversity" systems, cooperative diversity involving multi hop data relays is a solution...
A cognitive radio should be capable of finding the best spectrum band for communication depending on primary transmissions, the ambient noise level and interference. The first step in achieving this goal is to sense the existence of primary and secondary transmitters in various channels. In addition to the problem of signal detection, there is a need to distinguish between different signals at very...
A data and channel aided maximum likelihood (DCA-ML) symbol timing estimator for cooperative communications operating in flat fading channels is presented. The performance of the estimator is evaluated in terms of bit-error-rate (BER) and estimator variance. The BER performance is evaluated in various fading conditions and compared to a non-data-aided near maximum likelihood (NDA-NML) timing estimator...
Joint decoding at the base stations is investigated as a means to improve the uplink/downlink throughput of current cellular systems over fading channels. In this paper, the multi-cell relay-assisted time-division uplink system, i.e. one active user per time slot per cell with a relay serving that user, is studied. A linear mesh network is considered in which a single user per-cell communicates to...
Multiple-input multiple-output (MIMO) systems exploit transmit diversity to combat the effect of fading channels. Recently, a new paradigm known as cooperative communication was proposed that achieves the same transmit diversity as the MIMO system. However unlikely MIMO system which requires multiple antennas, cooperative communications use the scheme of sharing single antenna to generate a virtual...
We consider a source-destination pair assisted by multiple decode-and-forward relays without channel state information at transmitter (CSIT). We investigate three schemes exploiting spatial diversity including multiple-relay cooperation (MR-Coop), conventional multiple-relay relaying (MR-Relay), and multiple-input-single-output (MISO). The total power is equally allocated to transmission partners...
Cooperative communication represents a new class of diversity techniques in which multiple nodes each with a single antenna cooperate to generate a virtual multiple-antenna transmission system and thus offer the benefits of spatial diversity. This paper proposes suitable array codes used as low-density parity-check (LDPC) codes to be applied in the cooperative amplify-and-forward (AF) network. A mathematical...
The quality of service (QoS) support in wireless local area networks (WLANs) faces a big challenge due to time-correlated fading channel. Conventional automatic repeat reQuest (ARQ) schemes based on time diversity may result in consecutive retransmission failures degrading QoS severely. This paper proposes a novel Differentiated cooperative medium access control (MAC) protocol, called DC-MAC, to enhance...
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