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16
Investigations into cochannel interference in microcellular mobile radio systems
 IEEE Trans. Veh. Technol
, 1992
"... AbstractA microcell interference model termed the Nakagami m,/m, is introduced in this paper. The desired signal as well as the cochannel interferers are assumed to have Nakagami statistics but with different amounts of fading. A special case of this model is obtained when the desired signal has Na ..."
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AbstractA microcell interference model termed the Nakagami m,/m, is introduced in this paper. The desired signal as well as the cochannel interferers are assumed to have Nakagami statistics but with different amounts of fading. A special case of this model is obtained when the desired signal has Nakagami statistics while the cochannel interferers are subject to Rayleigh fading. The probability density function of the signaltointerference ratio in the Nakagami m,/m, model is derived. This model is also compared with a Rician/Rayleigh microcellular model. The Nakagami m,/m, model is chosen to investigate the microcellular systems because Nakagami distributions fit experimental data better than either Rayleigh or Rician distributions in many cases. Expressions for the outage probabilities in microcell systems are derived. Numerical results show that, compared to medium/large cell systems, the microcellular systems have a lower outage probability. The impact of diversity on the microcellular system is also studied. Both signaltonoise plus interference ratio selection diversity and signalplusinterference selection diversity are investigated and an improvement to the outage probability due to diversity is observed. I.
Optimal Power Control in Interference Limited Fading Wireless Channels with Outage Probability Specifications
, 2000
"... We propose a new method of power control for interference limited wireless networks with Rayleigh fading of both the desired and interference signals. Our method explictly takes into account the statistical variation of both the received signal and interference power, and optimally allocates powe ..."
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Cited by 16 (2 self)
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We propose a new method of power control for interference limited wireless networks with Rayleigh fading of both the desired and interference signals. Our method explictly takes into account the statistical variation of both the received signal and interference power, and optimally allocates power subject to constraints on the probability of fading induced outage for each transmitter/receiver pair. We establish several results for this type of problem. For the case
The multiplydetected macrodiversity scheme for wireless cellular systems
 IEEE Trans. Veh. Tech
, 1998
"... Abstract—In this paper, the multiplydetected macrodiversity (MDM) scheme is proposed for wireless cellular systems. As opposed to the traditional macrodiversity schemes, in which at any time a signal from only one base station is selected, in the MDM scheme there is no selection, but all the receiv ..."
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Abstract—In this paper, the multiplydetected macrodiversity (MDM) scheme is proposed for wireless cellular systems. As opposed to the traditional macrodiversity schemes, in which at any time a signal from only one base station is selected, in the MDM scheme there is no selection, but all the received signals are detected, and a maximumlikelihood decision algorithm is employed to maximize the probability of correct decision. We study the performance of the MDM scheme and compare it with the performance of the traditional selectionbased macrodiversity schemes. Depending on the propagation parameters, our results show that through the use of the MDM scheme, significant improvement in the biterror rate (BER) can be achieved. For instance, if the outage probability is defined as BER above 100R, the outage is eliminated at least 45 % of the time as compared with signaltointerference (S/I) diversity, for a propagation attenuation exponent of 4.0 and shadowing standard deviation of 4.0 dB. Furthermore, as compared with the (S/I) diversity, the MDM scheme reduces, on the average, the BER at least two orders of magnitude throughout more than 60 % of the cell area for a propagation attenuation exponent of 3.5, shadowing standard deviation of 4.0 dB, and system loading of less than 50%. Index Terms—Cellular systems, diversity techniques, macrodiversity, macroscopic diversity, maximum likelihood. I.
Novel Adaptive Array Algorithms and Their Impact on Cellular System Capacity
 Cellular System Capacity, Doctoral Dissertation, Virginia Polytechnic Institute and State Univ
, 1997
"... This report focuses on the application of adaptive arrays to the Advanced Mobile Phone Service (AMPS) and Code Division Multiple Access (CDMA) cellular systems. Adaptive arrays have been proposed as early as in the 1960s to improve the signal quality, but most of its applications were restricted ..."
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This report focuses on the application of adaptive arrays to the Advanced Mobile Phone Service (AMPS) and Code Division Multiple Access (CDMA) cellular systems. Adaptive arrays have been proposed as early as in the 1960s to improve the signal quality, but most of its applications were restricted to defense purposes. Recently, there has been a surge in interest of applying adaptive arrays for cellular systems. This work introduces new blind adaptive array algorithms for AMPS and CDMA signals. The theoretical capacity limit using an adaptive array at the base station for an AMPS cellular system is derived in this work. One of the significant contributions in this research is a macrocell channel model which provides angleofarrival (AOA) statistics of the multipath components. Practical issues involved in the implementation of an adaptive array are addressed and the author's implementation of an 8element adaptive array operating at 2.05 GHz is explained. This research also analyzes the capacity that can be o#ered by an adaptive array in a system where CDMA users coexist with existing AMPS users. A novel cellular CDMA system which exploits adaptive arrays is introduced and the capacity o#ered by this system is compared with existing and other systems exploiting spatial dimension.
Interference in Cellular Networks: Sum of Lognormals Modeling
, 2007
"... ii We examine the existing methods for evaluating the distribution of the sum of lognormal random variables, focusing on closedform results. We find that there are no results in literature that are both simple and accurate. We then derive a new closedform expression for the lower tail of the distr ..."
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ii We examine the existing methods for evaluating the distribution of the sum of lognormal random variables, focusing on closedform results. We find that there are no results in literature that are both simple and accurate. We then derive a new closedform expression for the lower tail of the distribution, and use it to construct a new method using a powerlognormal distribution. We apply both basic momentmatching and our new method the problem of the total interference power in a cellular system. For both methods, we derive equations that find the interference distribution essentially in closed form, using minimal numerical integration. We apply both methods to the uplink and downlink in systems with and without power control, for various cellular layouts, channel models and user activity probability. We compare distributions obtained by MonteCarlo simulation directly with those obtained by our method, and find very good matches in many useful cases. iii Acknowledgements
Analytical modeling of interference in cellular fixed relay networks
 IEEE Canadian Conference on Electrical and Computer Engineering (CCECE
, 2006
"... We develop a simple yet accurate analysis of the interference distribution in a cellular system, with particular emphasis on a twohop fixed relay network, though the analysis may apply to much wider contexts. Similar analyses have already been proposed, but suffer from being too specific in their a ..."
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We develop a simple yet accurate analysis of the interference distribution in a cellular system, with particular emphasis on a twohop fixed relay network, though the analysis may apply to much wider contexts. Similar analyses have already been proposed, but suffer from being too specific in their assumptions, are analytically difficult, consider only the uplink, and are not necessarily validated. We provide a simple closedform solution for a wide variety of cases and validate all our theoretical curves directly by MonteCarlo simulations of the exact same models. Our method is flexible for many channel and system parameters, and for arbitrary cellular layouts, thus it can readily be applied to a twohop relay context.
Analysis of DVBH Network Coverage With the Application of Transmit Diversity
 IEEE Trans. on Broadcasting
, 2008
"... Abstract—This paper investigates the effects of the Cyclic Delay Diversity (CDD) transmit diversity scheme on DVBH networks. Transmit diversity improves reception and Quality of Service (QoS) in areas of poor coverage such as sparsely populated or obscured locations. The technique not only provides ..."
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Cited by 2 (1 self)
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Abstract—This paper investigates the effects of the Cyclic Delay Diversity (CDD) transmit diversity scheme on DVBH networks. Transmit diversity improves reception and Quality of Service (QoS) in areas of poor coverage such as sparsely populated or obscured locations. The technique not only provides robust reception in mobile environments thus improving QoS, but it also reduces network costs in terms of the transmit power, number of infrastructure elements, antenna height and the frequency reuse factor over indoor and outdoor environments. In this paper, the benefit and effectiveness of CDD transmit diversity is tackled through simulation results for comparison in several scenarios of coverage in DVBH networks. The channel model used in the simulations is based on COST207 and a basic radio planning
Bounds on the distribution of a sum of correlated lognormal random variables and their application
 IEEE Trans. Commun
, 2008
"... Abstract—The cumulative distribution function (cdf) of a sum of correlated or even independent lognormal random variables (RVs), which is of wide interest in wireless communications, remains unsolved despite long standing efforts. Several cdf approximations are thus widely used. This letter derives ..."
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Abstract—The cumulative distribution function (cdf) of a sum of correlated or even independent lognormal random variables (RVs), which is of wide interest in wireless communications, remains unsolved despite long standing efforts. Several cdf approximations are thus widely used. This letter derives bounds for the cdf of a sum of 2 or 3 arbitrarily correlated lognormal RVs and of a sum of any number of equallycorrelated lognormal RVs. The bounds are singlefold integrals of readily computable functions and extend previously known bounds for independent lognormal summands. An improved set of bounds are also derived which are expressed as 2fold integrals. For correlated lognormal fading channels, new expressions are derived for the moments of the output SNR and amount of fading for maximal ratio combining (MRC), selection combining (SC) and equal gain combining (EGC) and outage probability expressions for SC. Index Terms—Amount of fading, cochannel interference, lognormal distribution, diversity combining.
On the performance modeling of outage probability in CDMA wireless networks
 Journal of Engineering Science and Technology Review
, 2011
"... Outage probability is a key performance measure for real time traffic in wireless networks and is often considered as more critical than drop call probability. In this paper, we study the outage probability in a wireless mobile environment, where the interferers are distributed on the ground. Taking ..."
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Outage probability is a key performance measure for real time traffic in wireless networks and is often considered as more critical than drop call probability. In this paper, we study the outage probability in a wireless mobile environment, where the interferers are distributed on the ground. Taking into consideration the background noise and the cell radius, we formulate an outage probability model coupled with observed data from Airtel Nigeria formally Zain Communications Limited, a Telecommunication company operating in Nigeria and simulate the system’s performance using the Java programming language. We also present a geographical information system (GIS) solution showing the distribution of signal outages at various base stations in Akwa Ibom State (East region) of Nigeria for observed and simulated data. A performance evaluation of these data reveals that our model could greatly improve the system’s performance. The results obtained allow us to study the stability of the network and evaluate the network in a more efficient and accurate manner.
Upperbound Analysis of Cellular Channel Capacity
"... Abstract — In cellular communication systems, the same carrierfrequency is reused at spatially separated base stations (BSs) to efficiently utilize the limited bandwidth. Therefore, the channel capacity is limited by the cochannel interference (CCI) from the neighboring cochannel BSs. To reduce t ..."
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Abstract — In cellular communication systems, the same carrierfrequency is reused at spatially separated base stations (BSs) to efficiently utilize the limited bandwidth. Therefore, the channel capacity is limited by the cochannel interference (CCI) from the neighboring cochannel BSs. To reduce the CCI, it is necessary to increase the frequencyreuse factor (the number of different channel groups). However, the available bandwidth per BS becomes narrower and hence, the cellular channel capacity reduces. In this paper, we derive a simple upperbound formula for the cellular channel capacity for the given frequencyreuse factor in an interferencelimited environment assuming the worst case scenario (i.e., the mobile station of interest is located at the cell edge). Both the path loss and the lognormally distributed shadowing loss are taken into account. The derived formula predicts that the optimum frequencyreuse factor which maximizes the worst case cellular channel capacity is F=3~4 irrespective of the path loss exponent and shadowing standard deviation. This is confirmed by the computer simulation. Keywordscomponent; cellular system; channel capacity cochannel reuse; frequencyreuse factor I.