Abstract
The outage probability is an important performance measure for cooperative diversity schemes. However, in mobile environments, the outage probability does not completely describe the behavior of cooperative diversity schemes since the mobility of the involved nodes introduces variations in the channel gains. As a result, the capacity outage events are correlated in time and second-order statistical parameters of the achievable information-theoretic capacity such as the average capacity outage rate (AOR) and the average capacity outage duration (AOD) are required to obtain a more complete description of the properties of cooperative diversity protocols. In this paper, assuming slow Rayleigh fading, we derive exact expressions for the AOR and the AOD of three well-known cooperative diversity protocols: variable-gain amplify-and-forward, decode-and-forward, and selection decode-and-forward relaying. Furthermore, we develop asymptotically tight high signal-to-noise ratio (SNR) approximations, which offer important insights into the influence of various system and channel parameters on the AOR and AOD. In particular, we show that on a double-logarithmic scale, similar to the outage probability, the AOR asymptotically decays with the SNR with a slope that depends on the diversity gain of the cooperative protocol, whereas the AOD asymptotically decays with a slope of -1/2 independent of the diversity gain.
Highlights
T HE capacity outage probability (OP) is an important performance measure in wireless communication systems with delay constraints operating over slow fading channels [1], [2]
Cooperative diversity is an efficient means to improve the OP of wireless systems by exploiting spatially distributed nodes to effectively synthesize a virtual array that emulates the operation of a multiantenna transceiver [5]–[19]
We present an analytical framework for calculation of the average capacity outage rate (AOR) and average capacity outage duration (AOD) of cooperative diversity systems with mobile nodes
Summary
T HE capacity outage probability (OP) is an important performance measure in wireless communication systems with delay constraints operating over slow fading channels [1], [2]. We present an analytical framework for calculation of the AOR and AOD of cooperative diversity systems with mobile nodes. We derive exact expressions for both parameters for cooperative diversity systems employing the aforementioned AF, DF, and SR protocols, respectively, which are assumed to operate over slowly time-varying Rayleigh fading channels. These approximations provide significant insight into the dependence of the AOR and AOD on various system and channel parameters such as the Doppler frequency and the data rate This insight facilitates the design of cooperative diversity systems and the comparison of different protocols.
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