1,139 research outputs found
Outage rates and outage durations of opportunistic relaying systems
Opportunistic relaying is a simple yet efficient cooperation scheme that
achieves full diversity and preserves the spectral efficiency among the
spatially distributed stations. However, the stations' mobility causes temporal
correlation of the system's capacity outage events, which gives rise to its
important second-order outage statistical parameters, such as the average
outage rate (AOR) and the average outage duration (AOD). This letter presents
exact analytical expressions for the AOR and the AOD of an opportunistic
relaying system, which employs a mobile source and a mobile destination
(without a direct path), and an arbitrary number of (fixed-gain
amplify-and-forward or decode-and-forward) mobile relays in Rayleigh fading
environment
A Simple Cooperative Diversity Method Based on Network Path Selection
Cooperative diversity has been recently proposed as a way to form virtual
antenna arrays that provide dramatic gains in slow fading wireless
environments. However most of the proposed solutions require distributed
space-time coding algorithms, the careful design of which is left for future
investigation if there is more than one cooperative relay. We propose a novel
scheme, that alleviates these problems and provides diversity gains on the
order of the number of relays in the network. Our scheme first selects the best
relay from a set of M available relays and then uses this best relay for
cooperation between the source and the destination. We develop and analyze a
distributed method to select the best relay that requires no topology
information and is based on local measurements of the instantaneous channel
conditions. This method also requires no explicit communication among the
relays. The success (or failure) to select the best available path depends on
the statistics of the wireless channel, and a methodology to evaluate
performance for any kind of wireless channel statistics, is provided.
Information theoretic analysis of outage probability shows that our scheme
achieves the same diversity-multiplexing tradeoff as achieved by more complex
protocols, where coordination and distributed space-time coding for M nodes is
required, such as those proposed in [7]. The simplicity of the technique,
allows for immediate implementation in existing radio hardware and its adoption
could provide for improved flexibility, reliability and efficiency in future 4G
wireless systems.Comment: To appear, IEEE JSAC, special issue on 4
Outage Analysis of Hybrid Satellite-Terrestrial Cooperative Network with Best Relay Selection
In this paper, we study the performance of a downlink hybrid satellite-terrestrial cooperative network. The decode-andforward scheme is used and a selection of the best relay terminal is implemented. In this proposed system, a two time-slot scenario is considered. The first time slot is used by the satellite for broadcasting the information to the terrestrial relays and the destination. In the second time slot, only the best relay which provides the maximal received signal-to-noise (SNR) ratio at the
destination is selected for forwarding the information. Then, both signals are combined using the maximum ratio combining (MRC) technique. The analytical expression of the outage probabiliy is evaluated and is then verified with the simulation. The results show that our analytical expression matched well to the simulation results at the high SNR regime
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