352 research outputs found
Exact performance analysis of dual-hop semi-blind AF relaying over arbitrary nakagami-m fading channels
Relay transmission is promising for future wireless systems due to its significant cooperative diversity gain. The performance of dual-hop semi-blind amplify-and-forward (AF) relaying systems was extensively investigated, for transmissions over Rayleigh fading channels or Nakagami-m fading channels with integer fading parameter. For the general Nakagami-m fading with arbitrary m values, the exact closed-form system performance analysis is more challenging. In this paper, we explicitly derive the moment generation function (MGF), probability density function (PDF) and moments of the end-to-end signal-to-noise ratio (SNR) over arbitrary Nakagami-m fading channels with semi-blind AF relay. With these results, the system performance evaluation in terms of outage probability, average symbol error probability, ergodic capacity and diversity order, is conducted. The analysis developed in this paper applies to any semi-blind AF relaying systems with fixed relay gain, and two major strategies for computing the relay gain are compared in terms of system performance. All analytical results are corroborated by simulation results and they are shown to be efficient tools to evaluate system performance. © 2011 IEEE.published_or_final_versio
A novel equivalent definition of modified Bessel functions for performance analysis of multi-hop wireless communication systems
A statistical model is derived for the equivalent signal-to-noise ratio of the Source-to-Relay-to-Destination (S-R-D) link for Amplify-and-Forward (AF) relaying systems that are subject to block Rayleigh-fading. The probability density function and the cumulated density function of the S-R-D link SNR involve modified Bessel functions of the second kind. Using fractional-calculus mathematics, a novel approach is introduced to rewrite those Bessel functions (and the statistical model of the S-R-D link SNR) in series form using simple elementary functions. Moreover, a statistical characterization of the total receive-SNR at the destination, corresponding to the S-R-D and the S-D link SNR, is provided for a more general relaying scenario in which the destination receives signals from both the relay and the source and processes them using maximum ratio combining (MRC). Using the novel statistical model for the total receive SNR at the destination, accurate and simple analytical expressions for the outage probability, the bit error probability, and the ergodic capacity are obtained. The analytical results presented in this paper provide a theoretical framework to analyze the performance of the AF cooperative systems with an MRC receiver
Exact Outage Probability of Dual-Hop CSI-Assisted AF Relaying over Nakagami-m Fading Channels
published_or_final_versio
A Unified Framework for Multi-Hop Wireless Relaying with Hardware Impairments
Relaying increases the coverage area and reliability of wireless
communications systems by mitigating the fading effect on the received signal.
Most technical contributions in the context of these systems assume ideal
hardware (ID) by neglecting the non-idealities of the transceivers, which
include phase noise, in-phase/quadrature mismatch and high power amplifier
nonlinearities. These non-idealities create distortion on the received signal
by causing variations in the phase and attenuating the amplitude. The resulting
deterioration of the performance of wireless communication systems is further
magnified as the frequency of transmission increases. In this paper, we
investigate the aggregate impact of hardware impairments (HI) on the general
multi-hop relay system using amplify-and-forward (AF) and decode-and-forward
(DF) relaying techniques over a general H-fading model. H-fading model includes
free space optics, radio frequency, millimeter wave, Terahertz, and underwater
fading models. Closed-form expressions of outage probability, bit error
probability and ergodic capacity are derived in terms of H-functions. Following
an asymptotic analysis at high signal-to-noise ratio (SNR), practical
optimization problems have been formulated with the objective of finding the
optimal level of HI subject to the limitation on the total HI level. The
analytical solution has been derived for the Nakagami-m fading channel which is
a special case of H-fading for AF and DF relaying techniques. The overall
instantaneous signal-to-noise-plus-distortion ratio has been demonstrated to
reach a ceiling at high SNRs which has a reciprocal proportion to the HI level
of all hops transceivers on the contrary to the ID.Comment: 16 pages, 10 figures, journal pape
Differential Modulation and Non-Coherent Detection in Wireless Relay Networks
The technique of cooperative communications is finding its way in the next
generations of many wireless communication applications. Due to the distributed
nature of cooperative networks, acquiring fading channels information for
coherent detection is more challenging than in the traditional point-to-point
communications. To bypass the requirement of channel information, differential
modulation together with non-coherent detection can be deployed. This thesis is
concerned with various issues related to differential modulation and
non-coherent detection in cooperative networks. Specifically, the thesis
examines the behaviour and robustness of non-coherent detection in mobile
environments (i.e., time-varying channels). The amount of channel variation is
related to the normalized Doppler shift which is a function of user's mobility.
The Doppler shift is used to distinguish between slow time-varying
(slow-fading) and rapid time-varying (fast-fading) channels. The performance of
several important relay topologies, including single-branch and multi-branch
dual-hop relaying with/without a direct link that employ amplify-and-forward
relaying and two-symbol non-coherent detection, is analyzed. For this purpose,
a time-series model is developed for characterizing the time-varying nature of
the cascaded channel encountered in amplify-and-forward relaying.Comment: PhD Dissertatio
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