Phase Error:
Sagias and Karagiannidis studied the effect of phase error on the performance of dual branch EGC receivers in correlated Nakagami-mfading channels using moment generating function (MGF) and Pad´e approximation approach [19]. Najib and Prabhu presented the error probability of EGC receiver assuming imperfect carrier recovery due to the presence of random noise in carrier recovery loops [16]. Rhodes studied the detection loss due to imperfect carrier synchronization for coher- ent phase-shift-keying (PSK) communications. This detection loss was greater for quaternary PSK (QPSK) signaling than for the binary PSK (BPSK) case. It was shown that the use of offset QPSK instead of conventional QPSK modulation for a specified value of allowable detection loss requires almost 3 dB less SNR [20]. Smadi and Prabhu developed a new method to analyze the performance of partially coherent phase shift keying systems in EGC receiver [21].
Co-channel Interference:
Beaulieu and Adnan presented the performances of QPSK in the presence of CCI in both non- fading and fading environments. Two interference models were considered, in AWGN environment and in different flat fading environments [22]. Abu-Dayya and Beauleiu derived closed form ex-
pressions for outage probability in generalized Nakagami fading environment for EGC, MRC and SC diversity combining schemes [23]. Songet.al.,presented a new outage performance analysis for EGC receiver that are limited by CCI in Rayleigh fading [24]. In [25], the performance analysis of MRC receiver with imperfect channel estimation in the presence of CCI is presented. The channel coefficients and their estimates were assumed to be complex Gaussian distributed. Closed form ex- pression for outage probability and average symbol error probability (ASEP) were presented. In [26]
the effects of imperfect channel estimation on MRC receiver are examined with multiple cochannel interferer over Rayleigh fading channels. Velkov presented the second order statistics of EGC in the presence of CCI for Rayleigh fading channels by applying the characteristic function (CF) method and the Beaulieu series [27]. Shah and Haimovich presented the performance of MRC receiver in the presence of multiple CCI sources for Rayleigh or Rician fading channel. The interfering user signal was considered as Rayleigh [28]. Rahimzadeh derived the exact closed-form expressions for the BER of BPSK in Rayleigh fading channels of MRC receiver was presented in the presence of CCI and AWGN [29]. More recently, Paris and David derived exact closed-form expressions for the outage probability of Hoyt fading channels under CCI [30]. Davidet. al. derived exact closed-form expressions for the outage probability of MRC in η−µ fading channels with antenna correlation and CCI [31]. Aalo and Zhang studied the effect of CCI on the performance of digital mobile ra- dio systems in a Nakagami fading channel. The performance of MRC diversity in the presence of multiple CCI interferes and AWGN were presented. Closed-form expressions were derived for the ABER and outage probability of both coherent BPSK systems. In [32], Leib and Pasupathy pre- sented the study of vectors perturbed by Gaussian noise. In [33] Beaulieu and Cheng derived the BER of bandlimited BPSK and CCI environment for perfect coherent detection
Fading Channels:
Karagiannidis presented a moment based approach for the performance analysis of anLbranch EGC receiver using Pad ´eapproximation method [34]. Mendeset. al., derived expressions for mo- ments and correlation coefficient of two Hoyt (Nakagami-q) signals [35]. Patel et. al., presented
the performance of EGC receiver over correlated Nakagami-mfading with arbitrarymand unequal branch SNR’s. Closed form expression for ABER for coherent binary modulation schemes were derived [36]. Zogaset. al., presented the performance of EGC receiver over Hoyt and Rician fad- ing channels using MGF and Pad ´eapproximation method. Exact closed-form expressions for the moments of the combiner output SNR were derived [37]. Karagiannidiset. al.,presented the perfor- mance of a dual branch EGC receiver over correlated Nakagami-mfading using the CF method. The performance was done for BPSK and coherent BFSK [38]. Nakagami-mdistribution is a generalized distribution of the multipath propagation [4]. It often gives the best fit to land-mobile and indoor- mobile multipath propagation. Scintillation of ionospheric radio links is modeled by Nakagami-q distribution [39]. Hoyt derived the distribution functions and the cumulative distribution functions pertaining to the modulus and angle of the normal complex variate when the mean is zero and vari- ance is different for the in phase and quadrature components of the normal complex variate [39].
In some environments, such as congested downtown areas and land-mobile satellite systems with foliage and urban shadowing, the analysis of the channel model must include both multipath and shadow fading. A relatively simple and versatile envelope distribution that generalizes multipath and shadow fading is the generalized gamma distribution (GG) [7]. In [7] Stacy introduced the GGdistribution. The author had generalized the two parameter gamma distribution which includes Rayleigh, Nakagami-m and Weibull as the special cases and Log-normal as the limiting case. In addition to the GG distribution, generalized-K(KG) distribution is also a versatile distribution for the accurate modeling of the composite propagation consisting of multipath fading superimposed by lognormal shadowing [5]. The correlated bivariate generalized-K(KG) distribution is introduced and studied in [5]. The performance analysis of MRC, EGC, and SC over bivariateKG fading channel were also presented. In the available small scale fading models such as Rayleigh, Nakagami-m, Rician and Hoyt the channel is assumed to be homogeneous. But in practice, the surfaces are ob- served to be spatially correlated, which means the channel is non-homogenous. Theη−µandκ−µ fading channels are the non-homogenous channels. Yacoub introduced the κ−µ distribution as a
generalized distribution and showed it includes the Rice and Nakagami-mdistribution as the special cases [11]. Yacoub also presented two general fading distributions, the κ−µ distribution and the η−µ distribution and proposed fading models for the distributions [12]. Yacoub introduced the symmetrical η−µ distribution as a general distribution to describe the statistical variation of the envelope in the fast fading environment [13].