Co-channel interference analysis of shadowed Rician channels

This paper presents an exact analysis of co-channel interference (CCI) in a shadowed-Nakagami (desired)/shadowed-Rician (interfering) channel. Because a Rician distribution can be closely approximated by a Nakagami distribution (Nakagami 1960), the proposed analysis can be viewed as a close approximation of a shadowed-Rician (desired)/shadowed-Rician (interfering) model. The model provided in this paper includes many flexibilities-different Rice factors, different shadowing spreads, and different transmitted powers for desired and interfering signals. Therefore, it is a powerful tool for determining cell sizes and power levels in mixed micro/macro cellular systems     

Trellis coded modulation schemes for shadowed Rician fading channels

The Canadian mobile satellite (MSAT) channel has been modelled as the sum of lognormal and Rayleigh components to represent foliage attenuation and multipath fading, respectively. The paper derives a Chernoff based error bound on the performance of trellis coded modulation (TCM) schemes operating on this channel.<>     

Effects of Rician faded and log-normal shadowed signals on spectrumefficiency in microcellular radio

An assessment of spectrum efficiency for a microcellular land mobile radio system is presented by considering the desired signal as (fast) Rician fading with (slow) log-normal shadowing and cochannel interfering signals as uncorrelated (fast) Rayleigh fading superimposed over (slow) log-normal shadowing. Spectrum efficiency is defined in terms of reuse distance, i.e., cluster size, traffic intensity, bandwidth of the system, and area of a cell by considering cochannel interference probability. The expression for cochannel interference probability is derived using appropriate path-loss law for microcells for four different cases: Rician plus log-normal desired signal and Rayleigh plus log-normal interfering signals; Rician desired signal and Rayleigh fading plus log-normal shadowing interfering signals; Rician desired signal and Rayleigh interfering signals; and both desired and interfering signals as Rician fading. The performance of a microcellular system is compared with that of a conventional macrocellular system     

Distribution of SIR and performance of DS-CDMA systems inlognormally shadowed Rician channels

New closed form expressions for the probability density function and the cumulative distribution function of the ratio of L_S Rician signals to L_I Rician interferers, so-called signal-to-interference (SIR) power ratio, are derived. These SIR distributions are then used to evaluate the error probability and capture probability of direct sequence code division multiple access systems operating in Rician faded channels with lognormal shadowing. The influence of various system parameters such as the Rice K factor, shadowing spread, number of interferers, and spread spectrum processing gain on the system performance are analyzed and discussed     

Two-stage Doppler-phasor-corrected TCM/DMPSK for shadowed mobilesatellite channels

A two-stage Doppler-phasor correction algorithm for mobile satellite, DSP-based modems is presented. The modulation considered is trellis-coded, differential phase-shift keying (DPSK) involving eight signal points. The Doppler phasor rather than the Doppler frequency is corrected as it leads to easy realization in DSP-based software. The Doppler phasor correction algorithm that is presented has a setup mode where the data are known and a data mode where the data are unknown. As such, it is intended for stream data or digital speech transmission. Both computer simulation and analytical techniques are used in the performance analysis     

Trellis coded MDPSK in correlated and shadowed Rician fadingchannels

The performance of trellis-coded multilevel differential phase-shift keying (TC-MDPSK) signals in correlated and shadowed Rician fading channels is evaluated. The pairwise error probabilities of the TC-MDPSK signals in the channels are calculated directly and approximated asymptotically. The asymptotic expression can be put into a product form and used in a transfer function approach to estimate the error performance of TC-MDPSK. The bit error rate of TC-MDPSK is estimated by using a truncated form of the union bound and by an asymptotic expression. In the two examples considered, these formulas show fairly good agreement in both correlated and shadowed Rician channels and are at least 2-dB tighter in signal-to-noise ratio than the Chernoff bound in the correlated Rician channels. Asymptotic expressions for the error probability of uncoded MDPSK in both correlated and shadowed Rician channels are also obtained     

SER and throughput analysis of space–time analog network coded relaying system over shadowed Rician fading channels

Wireless Networks - This research article presents an innovative approach based on analog network coding (ANC) in conjunction with space time block coding (STBC) which is termed as space time...     

Compound statistical models for shadowed fading channels

The commonly used distribution for shadowed fading channels, the Nakagami-lognormal distribution, arises by compounding the Nakagami and log-normal distributions. This distribution, however, does not have a closed form and recently this led Shankar [Outage probabilities in shadowed fading channels using a compound statistical model. IEE Proc Commun 2005; 152:828–32; Error rates in generalized shadowed fading channels. Wireless Personal Commun 2004; 28:233–8; A compound scattering pdf for the ultrasonic echo envelope and its relationship to K and Nakagami distributions. IEEE Trans Ultrason Ferroelectr Frequency Control 2003; 50:339–43.] to propose an alternative form obtained by compounding the Nakagami and gamma distributions. In this note, we derive a comprehensive collection of models for shadowed fading channels obtained by compounding the Nakagami distribution with 16 flexible families. The calculations involve use of several special functions and their properties. We feel that this work could serve as a useful reference for statistical modeling of shadowed fading channels.     

Spread-spectrum path diversity in a shadowed Rician fadingland-mobile satellite channel

The effects of two types of path diversity techniques, namely selection diversity and maximal ratio combining, on the bit error probability are investigated for direct-sequence spread-spectrum (DS/SS) transmission in a land mobile satellite channel using coherent binary phase-shift keying (BPSK) modulation. It is assumed that the channel consists of a log-normally shadowed line-of-sight signal plus Rayleigh distributed multipath signals. The bit error probability is evaluated for light, average, and heavy shadowing. The performance is also measured in terms of the outage probability     

Outage probability for lognormal-shadowed Rician channels

A new general outage probability expression for a Rician signal received among L Rician interferers is derived. This result is shown to cover previous published expressions involving Rayleigh signal/interferers as special cases. A new method is then applied to further extend the result to include the effect of lognormal shadowing on the outage probability (for microcellular mobile radio systems in Rician/Rician fading environments). New Rician/Rician outage probability curves against the normalized reuse distance and cluster size with and without lognormal shadowing effect are presented and discussed     

Multiple-frequency slotted ALOHA in a shadowed and Rician faded radio environment

A multiple-frequency channel is proposed to enhance the capacity of slotted ALOHA radio networks. The throughput is derived considering each packet being frequency assigned randomly in an uncorrelated shadowing and fading channel. Poisson and binomial distributions are assumed for the packet arrival models for an infinite and a finite number of users, respectively.<>     

Direct-sequence spread spectrum in a shadowed Rician fading andland-mobile satellite channel

The performance of a direct-sequence spread-spectrum land-mobile satellite transmission system, using binary phase-shift keying (BPSK) modulation, is analysed. The satellite channel is modeled as having Rician fading characteristics. The bit-error probability is evaluated, considering both the envelope and the phase variation. Assuming a Gaussian approximation for the interference, numerical results are obtained for both spread-spectrum and narrowband land-mobile satellite communication systems with BPSK modulation. A comparison of the two systems is made for light, average, and heavy shadowing     

Monotonicity results for coherent MIMO Rician channels

The dependence of the Gaussian input information rate on the line-of-sight (LOS) matrix in multiple-input multiple-output (MIMO) coherent Rician fading channels is explored. It is proved that the outage probability and the mutual information induced by a multivariate circularly symmetric Gaussian input with any covariance matrix are monotonic in the LOS matrix D, or more precisely, monotonic in D/sup /spl dagger//D in the sense of the Loewner partial order. Conversely, it is also demonstrated that this ordering on the LOS matrices is a necessary condition for the uniform monotonicity over all input covariance matrices. This result is subsequently applied to prove the monotonicity of the isotropic Gaussian input information rate and channel capacity in the singular values of the LOS matrix. Extensions to multiple-access channels (MAC) are also provided.     

Multitone jamming of FH/BFSK in Rician channels

A new bit error rate (BER) expression for a noncoherent frequency-hopped binary-frequency-shift-keying (FH/BFSK) receiver in Rician channels, subjected to independent multitone and wideband noise interference, is derived. Unlike previously published analyzes, we combine the signal and jammer multipath components, the additive white Gaussian noise (AWGN), and other wideband interference as a single Gaussian process. This method leads to a BER expression which consists of only a single rather than a triple integral requiring numerical computation. We also present a new derivation of the probability density function (PDF) of the ratio of two Rician random variables, used in a previously published approximate BER analysis     

Microdiversity on Rician fading channels

The performance of an L-branch equal gain (EG) combiner on slow and nonselective Rician fading channels is analyzed. Two performance criteria are considered; the probability distribution of signal-to-noise power ratio (SNR) at the output of the EG combiner and the average bit error rate (BER). Matched filter receivers are considered for two binary modulation formats, coherent phase shift keying (CPSK) and noncoherent frequency shift keying (NCFSK). Results using both maximal ratio combining (MRC) and selection diversity combining (SC) are presented for comparison. Our results show that from a feasibility and practical tradeoffs point of view, the performance of an EG combiner may be as good as that of a MR combiner. The effects of gain unbalance between branches of the EG combiner on the probability distribution of SNR and on the bit error rates are also investigated. The Rician fading model may be used to model bath the microcellular environment and the mobile satellite fading channel. Hence, the results of this paper may be useful in both of these areas. Furthermore, in the development of the analysis, we present an efficient method for computing the distribution of sums of Rician random variables. This may be useful for other problems involving Rician fading. The suitability of modeling a Rician fading environment by a properly chosen Nakagami model is examined. A formula for determining the corresponding values of Rician parameter K and Nakagami parameter m is also assessed     

Capacity of MIMO Rician channels

This paper presents exact results on the capacity of multiple-input-multiple-output (MIMO) Rician channels when perfect channel state information (CSI) is assumed at the receiver but the transmitter has neither instantaneous nor statistical CSI. It first derives the exact expression for the average mutual information (MI) rate of MIMO Rician fading channels when the fading coefficients are independent but not necessarily identically distributed. The results for the independent and identically distributed (i.i.d.) MIMO Rician and Rayleigh fading channels are also obtained as special cases. These results are derived using a different approach than the one used by Telatar for the i.i.d. Rayleigh case. The complementary cumulative distribution function (CCDF) of the MI is also obtained using a Gaussian approximation. The CDF of MI can serve as an upper bound to the outage probability of nonergodic MIMO Rician channels. Numerical results confirm that for a fixed channel gain, a strong tine-of-sight component decreases the channel capacity due to the lack of scattering.     

A class of generalized models for shadowed fading channels

The commonly used models for shadowed fading channels arise by compounding the Nakagami distribution with others such as the log-normal and gamma distributions. A distribution that is more flexible than the Nakagami distribution is the well known Weibull distribution. In this paper, we derive a collection of generalized models for shadowed fading channels by compounding the Weibull distribution with other distributions belong to some fifteen flexible families. We also illustrate the superior performance of these models over the standard Nakagami models.     

Symbol-aided plus decision-directed reception for PSK/TCMmodulation on shadowed mobile satellite fading channels

The symbol-aided (SA) synchronization concept developed by Moher and Lodge (1989) is applied to the MSAT channel modeled with a shadowed Rician process. Simulation data demonstrate that it can track the severe phase jitter encountered on the fading channel free of the false lock which plagues conventional techniques. The algorithm multiplexes known symbols into the data stream, establishing an absolute reference free of decision errors that is used to estimate the fading phase. An improvement to the SA algorithm which extracts phase information from the data-bearing symbols is proposed. It is found that the new technique is more effective for larger K. The improved algorithm is referred to as symbol-aided plus decision-directed (SADD) phase estimation. A system employing SADD phase estimation, trellis-coded modulation, interleaving, and amplitude weighting within the Viterbi decoder yielded the best BER performance on the shadowed MSAT channel considered     

Independent multitone jamming of FH/MFSK in Rician channels

We derive exact expressions of the symbol error rate (SER) performance of orthogonal, frequency-hopped, noncoherent M-ary frequency-shift-keying (FH/MFSK) receivers in the presence of independent multitone jamming (MTJ), as well as thermal and other wideband Gaussian noises. Both the signal tones and the multiple jamming tones are affected independently by Rician fading. Both the slow-hopping and fast-hopping systems are considered. In our derivation, we exploit the fact that the multipath components of the signal and jamming tones can be combined with the other Gaussian noises to form a single Gaussian process. Using this technique, we are able to obtain compact exact SER expressions which can be computed efficiently. From the computation results we provide physical explanations on the effects of several system parameters, such as jamming fraction, fading conditions and number of hops per symbol, on the SER performance of slow and fast FH/MFSK systems under independent MTJ     

Exact cochannel interference analysis for log-normal shadowedRician fading channels

An exact analytical method is presented for evaluating the probability of cochannel interference for Rician/Rayleigh faded channels with log-normal shadowing. The method requires that at least one signal (desired or interfering) be Rayleigh faded and log-normal shadowed. The Rice factor of the desired signal is shown to have a large effect on the probability of cochannel interference, while the Rice factors of the interfering signals are shown to have little effect