Co-channel Interference Model Research Articles

Modeling of co-channel interference in bluetooth low energy based on measurement data

The intense use of the 2.4 GHz ISM band by several wireless technologies has resulted in increased co-channel interference between networks operating in this frequency band. The aim of this paper is to investigate modeling techniques of co-channel interference affecting bluetooth low energy devices. The models are derived from recorded interference. Two types of models are introduced: a time domain model utilizing IQ data as reference and a spectrum-based model in which the reference signal is captured in frequency domain by a real-time spectrum analyzer. The recorded interference is also used as a reference to analyze the accuracy of proposed models. The proposed IQ-based model shows a degradation in performance for the environments with dominant bluetooth interfering signals. The frequency-based model not only addresses this problem, but also results in a huge data decimation in recording the interference.

Modeling and Analysis of Co-Channel Interference for IEEE 802.11 Wireless Local Area Network

With emerging network technologies, internet is used to provide backbone support for communication with each other. In this highly dynamic wireless environment Co-channel interference (CCI) create a constraint in terms of congestion. To maintain quality of service (QoS) in IEEE 802.11, WLAN performance analysis of CCI is necessary. In this paper, we present an analytical model for performance evaluations of the CCI effect in multi access point (AP) WLAN. The AP regions are overlapped to produce CCI effect which forces the network for retransmission of lost data results in congestion in the network. Various performance measures of the proposed scheme such as response time, queue length, probability of loss etc with respect to CCI factor is determined. Computational aspects of the proposed model in terms of graphs are presented.

Spectral Efficiency of Distributed Large-Scale MIMO Systems With ZF Receivers

Distributed multiple-input multiple-output (D-MIMO) is a promising technique for next-generation wireless networks, which offers a remarkable spectral efficiency gain over the conventional colocated MIMO (C-MIMO). In contrast to C-MIMO, which can be regarded as a special case of D-MIMO, performance analysis of D-MIMO is a challenging problem. This is because radio channels between a user and the distributed radio ports (RPs) are characterized by nonidentical path-loss and shadowing effects that render the classical analytical methods nontractable. In this paper, new accurate expressions for the uplink spectral efficiency of D-MIMO and C-MIMO systems are presented and compared for given large-scale coefficients. We further consider the uplink spectral efficiency for a single-cell distributed large-scale MIMO (D-LMIMO) system with linear zero-forcing (ZF) receivers that account for path loss along with shadow fading and multipath fading effects. Exact expressions for the average spectral efficiency over shadow fading in the asymptotically very large number of RPs antenna regime is explicitly derived, and a tight closed-form lower bound on the asymptotic spectral efficiency is presented. We demonstrate that, the transmit power of each user in D-LMIMO can be scaled down proportionally to the inverse of the number of RP antennas with no performance reduction. Moreover, we study the spectral efficiency of a D-MIMO in a multicell environment taking into account accurate cochannel interference (CCI) models. These expressions provide meaningful insights into the impact of signal-to-noise ratio (SNR), RPs and user positions, number of RPs antennas, shadow fading, and out-of-cell interference on the spectral efficiency of D-MIMO over practical scenarios. Finally, numerical results are validated by simulation to confirm our analysis.

A novel interference modeling scheme in cognitive networks

In this paper, we propose a mathematical model of aggregate co-channel interference over Rayleigh fading in cognitive networks. Unlike the statistical models in the literature that aim at finding the bound or approximation of the interference, the proposed model gives an accurate expression of probability density function (PDF), cumulative distribution function (CDF) and mean and variance of the interference, which takes into account a number of factors, such as spectrum sensing scheme, and spatial distribution of the secondary users (SUs). In particular, we focus on a more general spatial structure where there are two roles of primary users (PUs) and the interfering SUs distributed in the two-dimensional space. The framework developed in this paper is easy to be applied in power control, error evaluation and other applications.

Analsysis on Co-channel Interference of Human Body Communication Supporting IEEE 802.15.6 BAN Standard

Human body communication (HBC) is being recognized as a new communication technology for mobile and wearable devices in a body area network (BAN). This paper presents co-channel interference experienced by HBC supporting the physical layer in the IEEE 802.15.6 BAN standard. To analyze the co-channel interference, a co-channel interference model is introduced, and spacedomain and time-domain parameters representing an interference environment are generated using the cochannel interference model. A new signal-to-interference ratio (SIR) parameter depending on the peak amplitudes of the data signals causing co-channel interference is defined; co-channel interference can be easily analyzed and modelled using the newly defined SIR. The BER degradation model derived using the co-channel interference model and SIR in this paper can be effectively used to estimate the performance.

Co-Channel Interference Modeling in Cognitive Wireless Networks

Cognitive radio is a promising technology for sharing the underutilized frequency bands that have been licensed to primary users. However, due to the uncertainty in detecting the existence of the primary user, the secondary user may interfere with the primary users when both primary and secondary users are active simultaneously. Therefore, understanding the interference and its consequences on the cognitive network is critical. Unlike the statistical models previously reported in the literature that aim at approximation of the interference, based on the solid mathematical analysis, we propose an accurate model for describing the co-channel interference with probability density function, cumulative distribution function, mean, and variance of the interference suffered by the primary users. The proposed model not only takes into account a number of factors, such as the spectrum-sensing scheme, the spatial distribution of secondary users, and the channel conditions, including shadowing and Nakagami fading, but also gives an exact mathematical expression of the influences from these factors. The developed framework supports practical applications such as evaluating the cognitive network of any spatial shape and density of the secondary users and the methods of power control and spectrum sensing used by the secondary users. Simulation results are provided to verify the effectiveness of the analytical model.

Interference coordination for secrecy enhancement in random wireless networks

The co-channel interference modeling is vital for evaluating the secrecy performance in random wireless networks, where the legitimate nodes and eavesdroppers are randomly distributed. In this paper, a new interference model is proposed from the user-dominant perspective. The model can provide a better analytical assessment of secrecy performance with interference coordination for the presence of eavesdroppers. The typical legitimate is assumed to be located at the origin, and chooses the closest base station (BS) as its serving BS. The field of interferers is obtained by excluding the desired BSs (including the serving BS and its cooperative BS(s)). In contract with the exiting interference model, it is assumed that desired BSs and interferers belong to the same Poisson Point Process (PPP), and eavesdroppers are distributed according to another independent PPP. Based on this model, the average secrecy transmission capacity is derived in simply analytical forms with interference coordination. Analysis and simulation results show that the secrecy performance can be significantly enhanced by exploiting interference coordination. Furthermore, the average secrecy transmission capacity increases with increasing number of cooperative BSs.

Study on downlink spectral efficiency in orthogonal frequency division multiple access systems

In previous studies on the capacity of orthogonal frequency division multiple access (OFDMA) systems, it is usually assumed that co-channel interference (CCI) from adjacent cells is a Gaussian-distributed random variable. However, very-little work shows that the Gaussian assumption does not hold true in OFDMA systems. In this paper, the statistical property of CCI in downlink OFDMA systems is studied, and spectral efficiency of downlink OFDMA system is analyzed based on the derived statistical model. First, the probability density function (PDF) of CCI in downlink OFDMA cellular systems is studied with the considerations of path loss, multipath fading and Gaussian-like transmit signals. Moreover, some closed-form expressions of the PDF are obtained for special cases. The derived results show that the PDFs of CCI are with a heavy tail, and significantly deviate from the Gaussian distribution. Then, based on the derived statistical properties of CCI, the downlink spectral efficiency is derived. Numerical and simulation results justify the derived statistical CCI model and spectral efficiency.

Joint Statistics of Radio Frequency Interference in Multiantenna Receivers

Many wireless data communications systems, such as LTE, Wi-Fi, and Wimax, have become or are rapidly becoming interference limited due to radio frequency interference (RFI) generated by both human-made and natural sources. Human-made sources of RFI include uncoordinated devices operating in the same frequency band, devices communicating in adjacent frequency bands, and computational platform subsystems radiating clock frequencies and their harmonics. Additive RFI for these wireless systems has predominantly non-Gaussian statistics, and is well modeled by the Middleton Class A distribution for centralized networks, and the symmetric alpha stable distribution for decentralized networks. Our primary contribution is the derivation of joint spatial statistical models of RFI generated from uncoordinated interfering sources randomly distributed around a multiantenna receiver. The derivation is based on statistical-physical interference generation and propagation mechanisms. Prior results on joint statistics of multiantenna interference model either spatially independent or spatially isotropic interference, and do not provide a statistical-physical derivation for certain network environments. Our proposed joint spatial statistical model captures a continuum between spatially independent and spatially isotropic statistics, and hence includes many previous results as special cases. Practical applications include co-channel interference modeling for various wireless network environments, including wireless ad hoc, cellular, local area, and femtocell networks.

CELLULAR SYSTEM INFORMATION CAPACITY CHANGE AT HIGHER FREQUENCIES DUE TO PROPAGATION LOSS AND SYSTEM PARAMETERS

In this paper, mathematical analysis supported by computer simulation is used to study cellular system information capacity change due to propagation loss and system parameters (such as path loss exponent, shadowing and antenna height) at microwave carrier frequencies greater than 2 GHz and smaller cell size radius. An improved co-channel interference model, which includes the second tier co-channel interfering cells is used for the analysis. The system performance is measured in terms of the uplink information capacity of a time-division multiple access (TDMA) based cellular wireless system. The analysis and simulation results show that the second tier co-channel interfering cells become active at higher microwave carrier frequencies and smaller cell size radius. The results show that for both distance-dependent: path loss, shadowing and effective road height the uplink information capacity of the cellular wireless system decreases as carrier frequency increases and cell size radius R decreases. For example at a carrier frequency fc = 15.75 GHz, basic path loss exponent α = 2 and cell size radius R = 100, 500 and 1000m the decrease in information capacity was 20, 5.29 and 2.68%.

Capacity Analysis of a Multi-Cell Multi-Antenna Cooperative Cellular Network with Co-Channel Interference

Characterization and modeling of co-channel interference is critical for the design and performance evaluation of realistic multi-cell cellular networks. In this paper, based on alpha stable processes, an analytical co-channel interference model is proposed for multi-cell multiple-input multi-output (MIMO) cellular networks. The impact of different channel parameters on the new interference model is analyzed numerically. Furthermore, the exact normalized downlink average capacity is derived for a multi-cell MIMO cellular network with co-channel interference. Moreover, the closed-form normalized downlink average capacity is derived for cell-edge users in the multi-cell multiple-input single-output (MISO) cooperative cellular network with co-channel interference. From the new co-channel interference model and capacity, the impact of cooperative antennas and base stations on cell-edge user performance in the multi-cell multi-antenna cellular network is investigated by numerical methods. Numerical results show that cooperative transmission can improve the capacity performance of multi-cell multi-antenna cooperative cellular networks, especially in a scenario with a high density of interfering base stations. The capacity performance gain is degraded with the increased number of cooperative antennas or base stations.

Statistics of Co-Channel Interference in a Field of Poisson and Poisson-Poisson Clustered Interferers

With increasing spatial reuse of radio spectrum, co-channel interference is becoming a dominant noise source and may severely degrade the communication performance of wireless transceivers. In this paper, we consider the problem of statistical-physical modeling of co-channel interference from an annular field of Poisson or Poisson-Poisson cluster distributed interferers. Poisson and Poisson-Poisson cluster processes are commonly used to model interferer distributions in large wireless networks without and with interferer clustering, respectively. Further, by considering the interferers distributed over a parametric annular region, we derive interference statistics for finite- and infinite- area interference region with and without a guard zone around the receiver. Statistical modeling of interference is a useful tool to analyze outage probabilities in wireless networks and design interference-aware transceivers. Our contributions include: 1) developing a unified framework for deriving interference models for various wireless network environments; 2) demonstrating the applicability of the symmetric alpha stable and Gaussian mixture (with Middleton Class A as a particular form) distributions in modeling co-channel interference; and 3) deriving analytical conditions on the system model parameters for which these distributions accurately model the statistical properties of the interference. Applications include co-channel interference modeling for various wireless networks, including wireless ad hoc, cellular, local area, and femtocell networks.

Call admission control strategy for system throughput maximization considering both call- and packet-level QoSs

This letter presents a call admission control (CAC) strategy for system throughput maximization in wireless uplink systems. This strategy considers not only the call-level quality of service (QoS) (i.e., blocking probability) but also the packet-level QoS (i.e., outage probability). Using the statistical co-channel interference (CCI) model and state diagram, the outage probability and the blocking probability are investigated as a function of the relative traffic load. We formulate the CAC strategy problem based on relative traffic load, and suggest a solution. The numerical results show that maximum system throughput can be achieved by controlling the relative traffic load. In addition, we illustrate the region where system throughput is constrained by call- and packet-level QoSs. This examination shows that the call and packet-level QoSs must be considered together to achieve maximum system throughput.

Co-channel interference modeling and analysis in a poisson field of interferers in wireless communications

The paper considers interference in a wireless communication network caused by users that share the same propagation medium. Under the assumption that the interfering users are spatially Poisson distributed and under a power-law propagation loss function, it has been shown in the past that the interference instantaneous amplitude at the receiver is /spl alpha/-stable distributed. Past work has not considered the second-order statistics of the interference and has relied on the assumption that interference samples are independent. In this paper, we provide analytic expressions for the interference second-order statistics and show that depending on the properties of the users' holding times, the interference can be correlated. We provide conditions under which the interference becomes m-dependent, /spl phi/-mixing, or long-range dependent. Finally, we present some implications of our theoretical findings on signal detection.

Structured semi-blind interference rejection in dispersive multichannel systems

The impact of interference is one of the most capacity limiting factors in cellular networks today. In order to host more users in existing systems and maximize the capacity of future networks, the use of interference suppression techniques are instrumental. We propose a structured semi-blind parameter estimation procedure to support rejection of unknown cochannel interference (CCI) in systems facing multipath channels with non-negligible delay spread. Employing spatio-temporal processing, the proposed scheme exploits the temporal correlation present in the output signal from an antenna array and the training data of a desired user in order to find parameter estimates that fit the range space of a structured CCI model to the signal subspace of the interfering signals. Simulation results illustrating the behavior of a spatio-temporal receiver using the proposed scheme with respect to both signal-to-noise and signal-to-interference ratios (SNRs and SIRs) are presented. In addition, results highlighting the impact of the training sequence length as well as the impact of the channel model order of the CCI users are also included.

Performance of generalized selection combining for mobile radio communications with mixed cochannel interferers

The performance of generalized selection combining (GSC) space diversity for mobile radio systems in the presence of multiple cochannel interferers is studied. Two cochannel interference models are considered: (1) L cochannel interferers consisting of L-N Nakagami-m (1960) interferers and N Rayleigh interferers and (2) L cochannel interferers in which each interferer follows Nakagami-m distribution for a fraction of time and Rayleigh distribution for the remaining of time. The fading parameters of the Nakagami-m interferers are limited to integer values only. The desired signal is assumed to be Rayleigh faded. Also, all the desired signals and the cochannel interferers received on each branch are independent of each other. Closed-form expressions are derived for the probability density functions (PDFs) of the instantaneous signal-to-interference power ratio (SIR) at the output of the GSC for the two cochannel interference models. Using these SIR PDFs, closed-form expression for evaluating the outage probability and the average bit error probability (BEP) are subsequently derived. A differential phase-shift keying scheme is considered in the derivation. Numerical results showing the influences of various system parameters on the outage probability and the average BEP are then presented.

Error Performance Evaluation of Wireless Communication Systems Using Maximal Ratio Combining with Multiple Interferers

In this paper we evaluate the error performance of wireless communication systems using M-branch maximal ratio combining (MRC) with multiple cochannel interference. Three cochannel interference models are considered: (A) L independent identically distributed (i.i.d.) Nakagami-m cochannel interferers; (B) L independent cochannel interferers consisting of L-N Nakagami-m interferers and N Rayleigh interferers; (C) L independent cochannel interferers in which each interferer follows Nakagami-m distribution for a fraction of time and Rayleigh distribution for the remaining time. In addition, the desired signal assumes Nakagami-m fading. This paper considers that an exponential correlation model is assumed for the desired signals received on each branch, while the interferers are assumed independent. Closed-form expressions are derived for the probability density functions (PDFs) of the instantaneous signal-to-interference power ratio (SIR) at the output of the MRC for the three interference models. Using these SIR PDFs, further closed-form expressions to evaluate the outage probability (OTP) and the average bit error probability (BEP) of differential phase-shift keying (DPSK) are derived. Numerical results showing the impacts of the system parameters on the OTP and the average BEP are then presented.

Availability and bit error performance of dual-polarised digital PSK-satellite systems in Ka-band

The availability of dual-polarised satellite systems in the Ka-band with different PSK-modulated signals is estimated by making use of cumulative distributions of the bit error rate. These distributions are evaluated by using an approach which combines statistical data from three years of propagation measurements with the OLYMPUS satellite at 20 and 30 GHz, and an appropriate co-channel interference model. In contrast to analogue FM systems, system simulations with QPSK, DQPSK and 8-PSK indicate no significant impact of depolarisation on the bit error performance and system availability.

Multiple chip-rate DS/CDMA system and its spreading code dependent performance analysis

The authors study a multiple chip-rate DS/CDMA system and its spreading code dependent performance. The multiple chip-rate technique is useful in some CDMA applications needing extra divisions among users in addition to code division to support variable data rate applications, such as multimedia systems. The study is applicable to both synchronous and asynchronous multiple chip-rate CDMA systems. A co-channel interference model based on correlation statistics for deriving bit error rate of a dual-chip-rate CDMA system is introduced considering various spreading codes, such as m-sequence, Gold, Gold-like, Kasami and Walsh codes. The results show that Gold code families are most suitable for the use in the dual-chip-rate CDMA system.

Cochannel interference modelling and performance analysis of microcell systems for wireless personal communications

Cochannel interference in microcell radio systems with frequency-selective fading is investigated. Two microcell cochannel interference models, the Rician/Rayleigh model and the Rician/Rayleigh-plus-lognormal model, are presented. In the first model, the desired signal within a microcell experiences Rician fading while interfering signals from cochannel cells are subject to Rayleigh fading. In the second model, the cochannel interfering signals are subject to superimposed Rayleigh fading and lognormal shadowing. Frequency-selective multipath fading is considered in both models. The probability density function of the power ratio between the desired signal and composite interferers is derived. In evaluating the composite interference, both coherent and noncoherent interference addition are considered. Using the probability density function of the signal-to-interference ratio, expressions of the system outage probability are derived. Microcell systems are compared with medium/large-cell systems in terms of the outage probability. It is shown that the former outperform the latter. The effect of frequency-selective multipath fading and that of shadowing on the outage probability are observed. The issue of cochannel reuse distance is studied and the relation between the outage probability and the reuse distance is examined. An “irreducible outage probability” due to frequency-selective multipath fading is observed.