Effect Of Co-channel Interference Research Articles

Beamforming in Dual-Hop AF Relaying with Imperfect CSI and Co-channel Interference

This letter studies the joint effects of imperfect channel state information (CSI) and co-channel interference (CCI) on a dual-hop variable gain amplify-and-forward (AF) relay network with beamforming. The source and destination are both equipped with multiple antenna, while the relay has a single antenna. Specifically, the analytical expressions for the outage probability and average symbol error rate of the considered AF relaying are derived. Moreover, the asymptotic analysis at high SNR is also presented to reveal the diversity order and array gain of the relay system. Finally, computer simulations are given to confirm the validity of the proposed theoretical analysis and quantify the combined influence of imperfect CSI and CCI on the system performance.

Differential Maximum Ratio Combining (MRC)-Based Throughput Analysis on Dual-Fading Models of Slotted-Aloha CDMA Systems

In this paper we investigate throughputs of Slotted-ALOHA code division multiple access systems with differential detection upon L-branch antenna by means of maximum ratio combining (MRC) diversity technique. We investigate the effects of co-channel interference by employing two different fading models (i.e. between the desired signals and its interferences.) We consider systems under Nakagami/Nakagami and Rician/Nakagami fading environments. The purpose of employing MRC diversity and differential phase shift keying with L-branch antenna is to overcome multipath fading interference in order to enhance the performance of the systems. Our research indicates that the implementation of L-branch antenna in the receiver have reasonably increased the throughputs of the systems. Furthermore, we also investigate the inverse relation between interference signal and the throughputs of the systems. We further point out that the value of Nakagami fading parameter M and Rician factor K are proportional to the achievable throughputs of the systems.

Performance Study and Optimization of Cooperative Diversity Networks with Co-Channel Interference

In this paper, we investigate the effect of co-channel interference on the performance of cooperative diversity networks with amplify-and-forward (AF) relaying. We consider both conventional and opportunistic relaying. First, we obtain a tight upper-bound for the equivalent signal-to-interference-plus-noise ratio (SINR) at the destination. Subsequently, the cumulative distribution function (CDF), probability density function (PDF) and moment generating function (MGF) of the effective SINR are determined based on the upper-bound. Expressions for the error probabilities in both conventional and opportunistic relaying are derived utilizing the statistical characterization of the effective SINR. We also derive an approximate PDF of the equivalent instantaneous SINR at the destination. This leads to a simple and general asymptotic error probability expression which facilitates better insight into the effect of different system parameters on the error probability. Furthermore, we investigate the problem of optimum resource allocation in the network aiming at improving performance in the presence of resource constraints. We present numerical results that illustrate the excellent match between the analytical results and the simulation results, and the performance enhancement resulting from the proposed optimal resource allocation.

Toward an Access Infrastructure for Mobile Cloud

The provision of mobile cloud service calls for a wireless access infrastructure that offers high bandwidth to mobile users. Among all enabling technologies, wireless mesh networks (WMNs) have the advantage of low deployment cost and widely available user equipments. To provide more bandwidth, access points in WMNs are commonly equipped with multiple wireless interfaces (radios) that can operate on multiple non-overlapping channels in parallel. The objective of channel assignments in a multi-channel, multi-radio MWN is to reduce co-channel interference experienced by links so as to increase network capacity while maintaining network connectivity. Prior studies addressing this issue majorly considered effects of co-channel interference at the link layer. In this study, the authors consider co-channel interference at the physical layer. Furthermore, most existing methods are based on heuristic or game theory. This study applies simulated annealing technique to the channel allocation problem. The objective function for this approach is defined as the total signal-to-interference radio (SIR) experienced by each link. To maintain network connectivity, the proposed approach limits the set of assigned channels for each radio. Experimental results show that, compared with traditional heuristic-based and game-theoretic approaches, the proposed simulated annealing algorithm results in more operative links.

Frequency and Subcarrier Reuse Partitioning for FH-OFDMA Cellular Systems

One of the most serious factors constraining the next generation cellular mobile consumer communication systems will be the severe co-channel interference experienced at the cell edge. Such a capacity-degrading impairment combined with the limited available spectrum resource makes it essential to develop more spectrally efficient solutions to enhance the system performance and enrich the mobile user's application services. This paper proposes a unique hybrid method of frequency hopping (FH) and subcarrier-reuse-partitioning that can maximize the system capacity by efficiently utilizing the available spectrum while at the same time reduce the co-channel interference effect. The main feature of the proposed method is that it applies an optimal combination of different frequency reuse factors (FRF) and FH-subcarrier allocation patterns into the partitioned cell regions. From the simulation results, it is shown that the proposed method can achieve the optimum number of subcarrier subsets according to the frequency-reuse distance and results in better performance than the fixed FRF methods, for a given partitioning arrangement. The results are presented in the context of both blocking probability and BER performances. It will also be shown how the proposed scheme is well suited to FH-OFDMA based cellular systems aiming at low co-channel interference performance and optimized number of subcarriers.

Evaluation of the Effects of Co-Channel Interference on the Bit Error Rate of Wireless Networks with Error Correcting Codes in Fading Channels

This paper presents a performance analysis of wireless networks using error correcting codes on channels with Rayleigh fading in the presence of co-channel interference. The performance is evaluated in terms of the average bit error rate (BER) using TCM (Trellis-Coded Modulation) and TTCM (Turbo Trellis-Coded Modulation) schemes for QAM modulations. The effects of co-channel interference are evaluated through Monte Carlo simulation in scenarios where the system is affected by a dominant interfering synchronous and similar to the target user. For each coded-modulation schemes, the results show that there are BER floors, which vary according to the signal-interference (S/I).

Single-carrier frequency domain adaptive antenna array for uplink multi-user MIMO transmission in a cellular system

In this paper, single-carrier frequency domain adaptive antenna array (SC-FDAAA) for the uplink multi-user multiple-input multiple-output (MIMO) transmission in a cellular system is studied. By employing AAA weight control in frequency domain, the base station (BS) can suppress the multi-user interference (MUI) and therefore realize multi-user SC transmission. In addition, channel frequency selectivity can be exploited to obtain the frequency diversity (or the multi-path diversity). The frequency domain signal-to-interference-plus-noise-ratio (SINR) after weight control is investigated and the computational complexity of the proposed receiver is analyzed. In numerical simulations, cellular structure using the frequency reuse is assumed, and the effect of co-channel interference (CCI) is considered. The performance of the SC uplink multi-user MIMO transmission using SC-FDAAA is testified and compared with other multi-user detection schemes. The link capacity (maximum number of users/cell) and cellular link capacity (link capacity/frequency reuse factor) are also be evaluated.

Regenerative Cooperative Diversity Networks With Co-channel Interference: Performance Analysis and Optimal Energy Allocation

A study of the effects of co-channel interference on a multirelay system with decode-and-forward (DF) protocol is presented. Orthogonal relaying is considered, and all relays that correctly decode the message in the broadcasting phase participate in the adaptive relaying phase. First, the effective signal-to-interference-plus-noise ratio (SINR) at the receiver is derived. Then, considering outage as the performance metric, we obtain exact closed-form expression for the outage probability. Simple and general asymptotic expressions for the outage probability, which explicitly show the coding and the diversity gains, are also derived and discussed. Furthermore, we present optimal energy-allocation schemes for minimizing outage under different resource constraints. Monte Carlo simulations are further provided to confirm the analytical results and illustrate the outage performance for different interference conditions and optimization schemes.

On the Performance of Dual-Hop Systems with Multiple Antennas: Effects of Spatial Correlation, Keyhole, and Co-Channel Interference

In this paper, taking into account realistic propagation conditions, namely, spatial correlation, keyhole channels, and unequal-power co-channel interference, we investigate the performance of a wireless relay network where all the nodes are equipped with multiple antennas. Considering channel state information assisted amplify-and-forward protocol, we present analytical expressions for the symbol error rate (SER) and outage probability. More specifically, we first derive the SER expressions of a relay system with orthogonal space-time block coding (OSTBC) over correlated/keyhole fading channels. We also analyze the outage probability of interference corrupted relay systems with maximal ratio combing (MRC) at the receiver as well as multiple-input multiple-output MRC (MIMO MRC). Numerical results are given to illustrate and verify the analytical results.

Dual-hop amplify-and-forward relaying in the presence of co-channel interference: performance study and system optimisation

In this study, the authors investigate the effect of co-channel interference on the performance of dual-hop communications with amplify-and-forward relaying. First, the exact equivalent signal-to-interference-plus-noise ratio (SINR) at the destination is formulated and upper bounded. Then, the cumulative distribution function, probability density function (PDF) and moment generating function of the upper bounded SINR are determined. Further, expressions for the error and the outage probabilities are obtained. Moreover, an approximate PDF of the dual-hop link's instantaneous SINR is derived. In particular, simple expressions for the error and outage probabilities are presented and discussed. Numerical and simulation results are provided and confirm the tightness of the presented asymptotic expressions. Besides, optimisation of the power allocation and relay positioning are addressed. Specifically, the authors study adaptive power allocation with fixed relay location, optimal relay location with fixed power allocation, and joint optimisation of the power allocation and relay location under total transmit power constraint, in order to minimise the asymptotic average error probability and outage probability. Results show that optimum power allocation, optimum relay location and joint optimisation significantly improve the system performance in terms of error and outage probabilities compared to uniform power allocation and mid-point distance location of the relay node.

Performance analysis of a cellular network using frequency reuse partitioning

In this paper, we propose an analytical model to evaluate the performance of Frequency Reuse Partitioning (FRP) based cellular systems. In an FRP scheme, a channel with a smaller reuse factor is assigned to Mobile Stations (MSs) located near the serving Base Station (BS), whereas a channel with a larger reuse factor is assigned to MSs located near the edge of a cell. In this manner, FRP can reduce the effect of Co-Channel Interference (CCI) and improve system throughput. In order to establish an analytical model for FRP based cellular systems, we introduce a model for traffic analysis using a two dimensional Markov chain and approximate CCI levels with the power sum of multiple log-normal random components in a multi-cell environment. The performance of the FRP based system is presented in terms of channel utilization, call blocking probability, outage probability and effective throughput. The analytical results are compared with computer simulations.

Area Spectral Efficiency of Soft-Decision Space–Time–Frequency Shift-Keying-Aided Slow-Frequency-Hopping Multiple Access

Slow-frequency-hopping multiple access (SFHMA) can provide inherent frequency diversity and beneficially randomize the effects of cochannel interference. It may also be advantageously combined with our novel space-time-frequency shift keying (STFSK) scheme. The proposed system's area spectral efficiency is investigated in various cellular frequency reuse structures. Furthermore, it is compared to both classic Gaussian minimum shift keying (GMSK)-aided SFHMA and GMSK-assisted time-division/frequency-division multiple access (TD/FDMA). The more sophisticated third-generation wideband code-division multiple access (WCDMA) and the fourth-generation Long Term Evolution (LTE) systems were also included in our comparisons. We demonstrate that the area spectral efficiency of the STFSK-aided SFHMA system is higher than the GMSK-aided SFHMA and TD/FDMA systems, as well as WCDMA, but it is only 60% of the LTE system.

Multiuser Detection in Asynchronous Multibeam Communications

This paper deals with multi-user detection techniques in asynchronous multibeam satellite communications. The proposed solutions are based on successive interference cancellation architecture (SIC) and channel decoding algorithms. The aim of these detection methods is to reduce the effect of cochannel interference due to co-frequency access, and consequently, improves the capacity of the mulitbeam communications systems, by improving frequency reuse. Channel estimation allows the determination of interference coefficients, which helps their effects compensation. The developed multiuser detections techniques are iterative. Therefore, detection quality is improved from a stage to another. Moreover, a signals combining method, which is integrated into these detection solutions, enhances their capability. The proposed solutions are evaluated through computer simulations, where an asynchronous multibeam satellite link is considered over an AWGN channel. The obtained simulation results showed the robustness of these multi-user detection techniques.

Multihop Wireless Relaying Systems in the Presence of Cochannel Interferences: Performance Analysis and Design Optimization

A study of the effect of cochannel interference on the performance of multihop wireless networks with amplify-and-forward (AF) relaying is presented. Considering that transmissions are performed over Rayleigh fading channels, first, the exact end-to-end signal-to-interference-plus-noise ratio (SINR) of the communication system is formulated and upper bounded. Then, the cumulative distribution function (cdf) and probability density function (pdf) of the upper bounded end-to-end SINR are determined. Based on those results, closed-form expression for the error probability is obtained. Furthermore, an approximate expression for the pdf of the instantaneous end-to-end SINR is derived, and based on this, a simple and general asymptotic expression for the error probability is presented and discussed. In addition, the ergodic capacity of multihop wireless networks in the presence of external interference is studied. Moreover, analytical comparisons between AF and decode-and-forward (DP) multihop in terms of error probability and ergodic capacity are presented. Finally, optimization of the power allocation at the network's transmit nodes and the positioning of the relays are addressed.

Outage Probability of Decode-and-Forward Cooperative Relaying Systems with Co-Channel Interference

This paper analyzes the outage probability of multi-branch dual-hop decode-and-forward (DF) cooperative relaying systems over non-identical Nakagami/Nakagami fading channels. The paper derives an exact closed-form expression for the outage probability with maximum ratio combining considering both the effect of co-channel interference (CCI) and addictive white Gaussian noise. The results of this paper show that a DF cooperative relaying system is more vulnerable to noise than interference for low and moderate SINR, whereas it is more susceptible to interference than noise for high SINR and high diversity order. Moreover, this paper shows that the robustness of the destination against CCI is more important than that of the relay. The results of this paper are verified by Monte Carlo simulations.

Performance of Multihop Relay Systems with Co-Channel Interference in Rayleigh Fading Channels

In this letter we investigate the effect of co-channel interference on the performance of multihop transmission systems that employ amplify-and-forward relays and operate in a Rayleigh fading environment. We assume that an arbitrary number of interferers with arbitrary powers are present at each relay node and derive useful bounds for important performance measures, such as the outage probability and the average symbol error probability of various digital modulation schemes.

Performance of Adaptive MS-GSC in the Presence of Cochannel Interference

Minimum-selection generalized selection combining (MS-GSC) has been proposed as a power-saving variant of conventional generalized selection combining (GSC). Existing performance results of this scheme are limited to interference-free environments under multipath fading. This paper addresses the scenario when the received desired signal on each diversity branch is corrupted by multiple interfering signals and background noise, wherein desired and undesired signals undergo mutually independent Rayleigh fading. In the absence of perfect tracking of the instantaneous interference power on diversity branches, the adaptation thresholds that are set on the combined signal-to-noise ratio (SNR) to enhance either the spectral efficiency or power efficiency in noise-limited environments may not guarantee the target performance. This paper aims to study the effect of cochannel interference on the performance of bandwidth- and power-efficient SNR-based MS-GSC. Through the analysis, new analytical results for some important performance measures of adaptive MS-GSC schemes are presented. Numerical comparisons to clarify the impact of cochannel interference on the achieved performance of the adaptation schemes under consideration are provided.

Measurement and modeling of multiuser multiantenna system in aircraft in the presence of electromagnetic noise and interference

This article evaluates the accuracy with which the performance of a multiuser multiantenna system can be predicted with and without considering cochannel interference and noise (Gaussian, α-stable, and Cauchy) using a site-specific three-dimensional (3D) ray tracing algorithm as well as with statistical models with Gaussian and Nakagami-m channel models in small to medium sized aircraft. These models expand on previous statistical channel models such as the hyper-Rayleigh model by including the simultaneous effects of cochannel and adjacent channel interference, antenna matching, efficiency, directivity and polarization as well as (for the 3D model) site-specific multipath effects. Measurements and comparisons are made in a metallic-bodied Beech Baron BE 58P and a composite structure Rockwell T-39 Sabreliner. It was found that the 3D ray tracing model provides a mean capacity within 1% of those measured in the two aircraft in the presence of interference and noise. This was closely followed by the Nakagami-m distribution (m = 1.4), which was within 1–3% of measured capacity in the presence of interference and within 6% for a combination of interference and noise and the Gaussian model which was within 6% of measured capacity in the presence of interference and within 11% for a combination of interference and noise. The Cauchy noise degraded the capacity more than the other types of noise in the aircraft, providing a lower bound for capacity in an aircraft system. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:1137–1144, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.25939

Cochannel interference effect on BEP performance of SSC receiver in correlated Rician fading

Abstract We study the performance of dual branch switch and stay combining (SSC) diversity receivers operating over correlated Rician fading channels, in the presence of correlated Rayleigh distributed cochannel interference (CCI). Fast convergent infinite series representations for both the joint probability density function (PDF) of the SSC input signal-to-interference ratios (SIRs) and the PDF of the SSC output SIR are derived. The last one is applied to semi-analytically study the average bit error probability (ABEP) of differential binary phase shift keying (DBPSK). Furthermore, the optimum switching threshold in the sense of minimum ABEP is obtained numerically and the effects of fading severity and branch correlation on both ABEP and optimum switching threshold are investigated. Numerical and simulation results are presented to support the mathematical analysis.

Novel Anti Co-Channel Interference Scheme for Sensor Networks

With improvement of the automation level, wireless sensors are widely used, but various kinds of interference lead to problems in the application. In order to deal with co-channel interference, a throughput efficient scheme based on Extended Binary Phase Shift Keying (EBPSK) modulation is introduced in physical layer. On this basis, the corresponding transmission scheme and the important impacting filter are presented. Effects of co-channel interference on the EBPSK waveform in different cases are analyzed. Simulation results illustrate the excellent anti-interference performance of the EBPSK system itself, when the initial phase of the co-channel interference is small.