Cellular System Information Capacity Change at Higher Frequencies Due to Propagation Loss and System Parameters (original) (raw)
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Minimum Cell Size for Information Capacity Increase in Cellular Wireless Network
… Conference (VTC Spring), …
An information capacity-cost analysis is used to find a minimum cell size for information capacity increase in cellular wireless network, thus a theoretical limit to cell size reduction. The results show that as the cell size radius R reduces to 300 m and less, the proposed interference model show a 5.76-18.89 % decrease in the information capacity per unit cost (£, $, etc) at microwave carrier frequencies f c > 3.35 GHz. This result illustrates that there is a theoretical limit to cell size reduction in relation to information capacity performance and cost. An inductive approach is used to generate a formula for calculating the number of co-channel interfering cells N n in a cellular wireless site layout. Such a formula allows one to calculate the number of co-channel interfering cells in subsequent tiers of a cellular wireless site layout. The geometric derivation shows that the number of co-channel interfering cell N n in a subsequent tier is the product of the number of co-channel interfering cells in the first tier N I and the tier number n. Thus, the number of co-channel interfering cell in a subsequent tier N n = N I × n. This formula enables subsequent tier co-channel interference to be included in the information capacity analysis of future and emerging, and finding the minimum cell size for information capacity increase in a cellular wireless communication system.
A Comparative Capacity/Coverage Analysis for CDMA Cell in Different Propagation Environments
Wireless Personal Communications, 2000
In the design of cells in mobile communication systems, path loss prediction models play an important role and have been the subject of the study for some time (M.F. Ibrahim and J.D. Parsons, IEE Proceedings, Vol. 130, No. 5, 1983). This paper presents the analysis of two main factors that affect the capacity bounds in a UMTS cell for different propagation models. These are the (i) interference levels at Node B, which increases with the number of active users, and (ii) the limited sending power of the user equipment (UE) which may not be able to send signals with enough power to reach Node B with the required received power level due to path loss. The aim of this paper is to analyse the capacity/coverage of the uplink of UMTS system in different propagation environments (free space, suburban, urban, dense urban, rural) and derive the capacity bounds for the UMTS cell. The capacity bounds have been extracted based on the extended COST-231 Hata model (http://cost.cordis.lu/src/whatiscost.cfm). COST-231 Hata is an extension of the Okumura-Hata model which covers the higher frequencies (G.L. Stüber, "Principles of Mobile Communications," Kluwer, 1996) necessary for WCDMA. The basic model describes the propagation loss in an urban environment, but a number of correction factors can be applied to extend its application to a broader range of environments. The analysis takes into account a number of capacity influencing factors such as the CDMA code non-orthogonality, the inter-cell interference, imperfect power control, and different service specific factors. The simulation results show the effect of different system and varying environmental parameters upon the system's capacity in different environments. The results clearly demonstrate that it is too optimistic to rely on studies based on free space assumptions.
Sensitivity Analysis of Conditional Co-Channel Interference in Cellular FDMA/TDMA Systems
Multiaccess, Mobility and Teletraffic for Wireless Communications: Volume 3, 1999
ABSTRACT Co-channel interference (CCI) is the most severe capacity limiting source in cellular FDMA/TDMA systems. Probability of CCI depends on several factors including cluster size, path loss, slow and fast fading, cell geometry, network load, CCI protection ratio etc. The effects of these parameters to the conditional CCI probabilities (outages) are studied in this paper. Fast fading is modeled as a Rayleigh distributed random variable. Lognormal shadowing models the slow fading. Shadowing may be correlated or uncorrelated. Two different lognormal sum approximations, namely Fenton-Wilkinson (FW) and modified Schwartz-Yeh (SY) approaches are used in the calculations. Cell geometries are based on the conditional worst and average case macrocell scenarios. The results show that the CCI probability is most sensitive to path loss variations. Very high variance lognormal fading causes high outages even at short distances from a mobile station (MS) to the base station (BS). Correlations between the desired signal and the joint interfering signal have more impact on the system performance than correlations between individual interference components.
Information theoretic capacity of cellular multiple access channel with shadow fading
IEEE Transactions on Communications, 2010
I. INTRODUCTION In the past, wireless systems were designed to accommodate a large number of voice and/or low data rate users. With the emergence and continuous growth of wireless data services, the value of a wireless network is not only defined by how many users it can support, but also by its ability to support high data capacity at localized spots. Shannon developed a mathematical theory for the single-link channel capacity in [1] providing the framework for studying performance limits in communication. Shannon's work gave birth to the field of information theory. In information theoretic literature different approaches have been reported to determine maximum data rate and the means to achieve this under various assumptions and constraints. Despite the work in this field, the first important attempt to study the capacity of a cellular system was carried out in the previous decade by Wyner [2]. Wyner's model studies the uplink channel and although it considers a very crude approximation of path loss with no path loss variability across the cell, it manages to provide an insight into the cooperation of the base stations and the benefits that can be achieved through that process. Fading was incorporated in Wyner's model by Somekh and Shamai in [3]. They maintained the assumption of a hyper-receiver with delay-less access to all cell-site receivers and assumed the same interference pattern as Wyner's. They used a "raster-scan" method to transform the two-dimensional system into an equivalent linear system in order to arrange the fading coefficients and the system's path gains in the channel matrix. Their results showed that for a certain range of relatively high inter-cell interference, the fading improves the system performance as compared to the case when there is no fading.
Challenges of Bandwidth and Power Limitations in Cellular Communication: A Review
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To accommodate the current huge demand for wireless services and the anticipated future growth, there is need to review the factors affecting wireless channel capacity and techniques that can improve capacities of wireless communications. The key resources of wireless communication are available bandwidth and signal power. But these resources are limited; which in turn limit the carrying capacity of wireless system. The major reasons for their limitations are government regulations of the transmission bandwidth and the low powered devices of wireless systems. The limited wireless resources have driven operators to seek for techniques that enhance channel capacity. But each technique or method adopted comes with its own challenges. In this paper, the limiting factors affecting wireless channel capacity are discussed. In addition, various techniques developed to enhance wireless system capacity and the limitations of each of these techniques are reviewed.
Impact of Inter-Cell Interference on Capacity in the Joint Multiple Access (CDMA and SDMA) System
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Spatial filtering using smart antenna has emerged as a promising technique to improve the performance of cellular systems. Cell splitting and sectorisation in CDMA systems could result in an increase in system capacity. In this paper, we investigate the impact of inter-cell interference on reverse link capacity in a joint multiple access system arising from the combination of CDMA and SDMA systems. The system capacity of CDMA and SDMA systems is reviewed individually. The cochannel and antenna side-lobes interferences in SDMA systems due to the randomly located mobile users in a non-uniform traffic cell are studied. Therefore, the most realistic reverse link capacity improvement of the joint multiple access system is presented here by taking into consideration both intra-sector and inter-sector interferences. The results are based on the system parameters of CDMA and SDMA systems.
Capacity of TDMA digital cellular communication system
[1992 Proceedings] Vehicular Technology Society 42nd VTS Conference - Frontiers of Technology, 1992
System capacity is considered a very spficant pvameter in Mobile Communication Systems. The most important reason for changtng the current cellular system from Analog FDMA to DigitdTDMA is that many of the service areas are running out of capacity. That is because of the ever inmclliing popuIvrily of mobik lrnd portable telephones. This paper is aimed 011 evalruting the system capacity in Erlangs baed on the No& American Digital TDMA standards. The paper presenls a Monte Carlo simulation sludy o f two different frequency plans, namely, the 7-cell clus(ers with 3 sectorslccll rod the 4-4 clu!W.s with 6 scctdccU Cclls arc assumcd to bc q u a i in radius and the user density is assumed (0 be uniformly distributed among the cells. In the forward carrier (Base Stalion to Mobile Ud) a mobile unit is dowed to move uniformly in a target sector and the carrier to Co-Channel intuference ratio (U) from aII co-channel base stations is evaluated at every location of the target mob& unit. The Erlang load versus the blocking probability is evaluated. The research also sludii the effect of the TDMA lime slot assignment technique when a mobile unit requests service. The propagation path loss is assumed to be proportional to r* with log-normal shadowing.
IEEE Transactions on Wireless Communications, 2014
Small cell networks are evolving as an economically viable solution to ameliorate the capacity and coverage of state-of-the-art wireless cellular systems. Nonetheless, the dense and unplanned deployment of the small cells (e.g., femtocells, picocells) with restricted user access significantly increases the impact of interference on the overall network performance. To this end, this paper presents a novel framework to derive the statistics of the interference considering dedicated and shared spectrum access for uplink transmissions in two-tier small cell networks such as the macrocell-femtocell networks. The framework exploits the distance distributions from geometric probability theory to characterize the uplink interference while considering a traditional grid-model setup for macrocells along with the randomly deployed femtocells. The derived expressions capture the impact of path-loss, composite shadowing and fading, uniform and non-uniform traffic loads, spatial distribution of femtocells, and partial and full spectral reuse among femtocells. Considering dedicated spectrum access, first, we derive the statistics of the co-tier interference incurred at both femtocell and macrocell base stations (BSs) from a single interferer by approximating Generalized-K composite fading distribution with the tractable Gamma distribution. We then derive the distribution of the number of interferers considering partial spectral reuse and moment generating function (MGF) of the cumulative interference for both partial and full spectral reuse scenarios. Next, we derive the statistics of the crosstier interference at both femtocell and macrocell BSs considering shared spectrum access. Finally, we utilize the derived expressions to analyze the capacity in both dedicated and shared spectrum access scenarios. The derived expressions are validated by the Monte-Carlo simulations. Numerical results are generated to assess the feasibility of shared and dedicated spectrum access in femtocells under varying traffic load and spectral reuse scenarios.
Information theoretic capacity of the cellular uplink - average path loss approximation
2008
In this paper we investigate the information theoretic capacity of the uplink of a cellular system where all base station receivers jointly decode the received signals ("hyper-receiver"). Considering a distance depended power-law path loss and a more realistic Rician fading environment, we model a variable cell density network with geographically distributed user terminals. Multiple tiers of interference are considered and using an average path loss approximation model the analytical result for the per cell sum-rate capacity is found. We examine the various parameters that are affecting the capacity of the system. Especially the effect of the user distribution across the cells and the density of the cells in the cellular system is investigated. We validate the numerical solutions with Monte Carlo simulations for random fading realizations and we interpret the results for the real-world systems.