Shadowed Rician Research Articles

Data-Aided Fading Estimation Technique for Shadowed Mobile Satellite Fading Channels

A novel data-aided fading estimation technique that employs both pilot anddata symbols is proposed to significantly reduce the bandwidth redundancy ofthe pilot-symbol-aided (PSA) systems using receivers with low complexity andlatency in the shadowed mobile satellite fading channels. The shadowed mobilesatellite fading channels are modeled as the sum of a lognormally distributeddirect component and a Rayleigh distributed multipath component, and the PSAsystem employs 16-ary quadrature-amplitude-modulation (16QAM) fortransmission. Monte Carlo computer simulation has been used to assess thetechnique on the bit-error-rate (BER) performances of the system in the lightshadowed, the average shadowed and the heavy shadowed Rician fadingenvironments. The results have shown that the proposed technique requires avery low bandwidth redundancy to provide satisfactory BER performances, andcan substantially lower the error floors of the PSA systems.

Outage performance of cellular systems over arbitrarylognormal shadowed Rician channels

Techniques for analysing the outage performance for lognormal shadowed Rician fading channels are becoming of increasing importance as the concept of micro-cells is introduced into wireless personal communications. A general solution, however, has not yet been developed except for some special cases. The authors present an exact solution which takes the form of two-fold integrals, and is applicable to general situations without any restrictions.

Performance of MSK-CDMA System in a Shadowed Rician Fading Land-Mobile Satellite Channel

This paper investigates the bit error rate (BER) performance of direct-sequence code division multiple-access (DS-CDMA) system employing MSK modulation operating over a specular multipath channel characterized by the combined effect of Rayleigh fading and log-normal shadowing.

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.

Effect of branch correlation on a macrodiversitysystemin a shadowed Rician fading channel

The authors present an exact analysis of the co-channel interference probability of a macrodiversity cellular system with an arbitrary number of correlated branches, where the branch selection is based on local mean power. Results show that the effects of macrodiversity branch correlation cannot be ignored in the performance analysis of microcell and picocellular systems.

Performance of type-II hybrid ARQ in a shadowedRician fading LEO satellite-based spread slottedALOHA communication channel

Type-II hybrid ARQ is applied to a shadowed Rician fading low earth-orbiting (LEO) satellite-based spread slotted ALOHA communication channel. In particular it is found to be effective in combating heavy shadowing.

Incoherent estimation on co-channel interference probability for microcellular systems

Prasad and Kegel (1993) offered an approximate analysis of the co-channel interference (CCI) probability for a microcellular system that has multiple shadowed Rayleigh interfering signals and a shadowed Rician desired signal. In that analysis, coherent addition of summing multiple interfering signals was assumed. However, it has been shown that incoherent addition is a more realistic assumption (Prasad and Kegel 1991). In the present paper two approaches-approximation and exact analysis-for calculating the CCI probability under incoherent addition are given. The approximate analysis is extended from the macrocellular case. The exact analysis, newly developed in the present paper, is then used to check the accuracy of the approximation. It is shown that the results of the incoherent approximate analysis differ by an amount of 20/spl sim/30%. In addition, the authors explore the effect of correlation between the shadowing interferers. They find that in a shadowed-Rician/shadowed-Rayleigh channel, the effect of this kind of correlation increases the CCI probability for cases having a small spread in shadowing and large reuse distance. But if the spread in shadowing is large, the result can be just the opposite-this correlation yields a better performance. It is also found that in a shadowed-Rayleigh (desired)/shadowed-Rayleigh (interfering) channel, regardless of degree of spread in shadowing, this correlation seems always to improve the performance.

Channel coding for VSAT systems

Two 8-state rate 5/6 2/spl times/8PSK TCM designed for very small-aperture-terminal (VSAT) Gaussian and fading channels (GTC and FTC systems), and eventually a system with optimum performance over the mobile-satellite (MSAT) fading channel (OFT system) is obtained. The operation of these coded systems is compared with uncoded systems over Gaussian and shadowed Rician fading channels by computer simulation. For small values of bit-error probability P/sub b/, the upper bounds on P/sub b/ are analytically calculated by pair-state diagram. Finally, the OFT system is considered as inner code and after interleaving, is concatenated with an RS(31, 25) outer code. The simulation results show that this concatenated coding system has about 13 dB coding gain at P/sub b/=3/spl times/10/sup -4/ over an uncoded system with the same effective information rate (QPSK modulation) on an MSAT channel.

Exact cochannel interference analysisfor log-normal shadowed Rician 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.

Performance of trellis coded modulation schemes on shadowed mobile satellite communication channels

The Canadian mobile satellite (MSAT) channel has been modeled as the sum of lognormal and Rayleigh components to represent foliage attenuation and multipath fading, respectively. Several authors have applied trellis coded modulation (TCM) schemes to this channel, estimating the bit error performance via computer simulation. In the present paper, analytical expressions are derived for the pairwise error probability (PEP) of TCM schemes over this channel under ideal interleaving. The analysis is applied to three detection strategies: ideal coherent detection, pilot-tone aided detection, and differential detection. The results are substantiated by means of computer simulation. In addition, first-order statistics of absolute and differential phases of a shadowed Rician process are examined. >

Spread-spectrum path diversity in a shadowed Rician fading land-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. >

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 Letter derives a Chernoff based error bound on the performance of trellis coded modulation (TCM) schemes operating on this channel.

A performance analysis of trellis-coded modulation schemes over Rician fading channels

This paper presents a saddle point approximation (SAP) method to compute the pairwise error probability (PEP) of trellis-coded modulation (TCM) schemes over Rician fading channels. The approximation is applicable under several conditions, such as finite and ideal interleaving, ideal coherent and pilot-tone aided detection, and differential detection. The accuracy of this approximation is demonstrated by comparison to the results of numerical integration. When ideal interleaving is assumed, an asymptotic approximation for the PEP of ideal coherent, pilot-tone aided or differentially detected TCM is derived. This asymptotic approximation of the PEP is in a product form and much tighter than the ordinary Chernoff bound on the PEP. Also, based on the SAP, the effect of finite interleaving depth on the error performance of TCM schemes over Rician and shadowed Rician channels is studied.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Performance comparison of different decoding strategies for a bandwidth-efficient block-coded scheme on mobile radio channels

The performance of bandwidth-efficient Reed-Solomon (RS)-coded MPSK schemes is evaluated on a shadowed Rician fading channel using different decoding strategies, namely, errors-only, errors-and-erasures, and soft-decision decoding. The lower bounds of the bit error probability are found for errors-only and for errors-and-erasures decoding. For the soft-decision decoding the upper bound of the bit error rate is derived. The error bounds are calculated and examined by simulation for some RS-coded MPSK schemes on a shadowed Rician channel. It is shown that their performance is significantly improved compared to uncoded QPSK. The amount of improvement depends on the signal-to-noise ratio (SNR), the decoding strategy, and the degree of shadowing. A comparison between different decoding techniques, for one of the RS-coded schemes, for different degrees of shadowing shows that the use of channel measurement information in the decoding process is more effective for heavy shadowed channels. >

Symbol-aided plus decision-directed reception for PSK/TCM modulation 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.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Direct-sequence spread spectrum in a shadowed Rician fading and land-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. >

Reed-Solomon codes for land mobile satellite channels

The performance of Reed-Solomon codes is determined for land mobile satellite communications where a shadowed Rician channel model is used. An effective coding/interleaving scheme is proposed which uses the multipath fading and shadowing statistics of the channel.

A new 4-state 8PSK TCM scheme for fast fading, shadowed mobile radio channels

The design of a 4-state, rate-2/3, 8PSK trellis-coded modulation (TCM) code, based on the design criteria for fading channels, is presented. To evaluate and compare the performance of this code with the other 4-state 8PSK TCM schemes presented in the literature, computer simulation is performed for a shadowed Rician fading channel. The simulation results show the superiority of the scheme for bit-error probabilities of 10/sup -3/ or less. This makes the code a suitable choice for both speech and data transmission over mobile fading channels. >