Hệ thống 3G và mạng không dây thông minh P4

Cellular networks are typically interference limited, with co-channel interference arising from cellular frequency reuse, ultimately limiting the quality and capacity of wireless networks [280,281]. However, Adaptive Antenna Arrays (AAAs) capable of exploiting the are spatial dimension in order to mitigate this co-channel interference and thus to increase the achievable network capacity [3,6,38,242,250,282].
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Hệ thống 3G và mạng không dây thông minh P4 Third-Generation Systems and Intelligent Wireless Networking J.S. Blogh, L. Hanzo Copyright © 2002 John Wiley & Sons Ltd ISBNs: 0-470-84519-8 (Hardback); 0-470-84781-6 (Electronic)Adaptive Arrays in anFDMARDMA Cellular Network4.1IntroductionCellular networks are typically interference limited, with co-channel interference arisingfrom cellular frequency reuse, ultimately limiting the quality and capacity of wireless net-works [280,281]. However, Adaptive Antenna Arrays (AAAs) capable of exploiting the arespatial dimension in order to mitigate this co-channel interference and thus to increase theachievable network capacity [3,6,38,242,250,282]. Since AAA may receive signals with ana high gain from one direction, whilst nulling, signals arriving from other directions, it isinherently suited to a CCI-limitedcellular network. Thus a beam may be formedto commu-nicate with the desired mobile, whilst nulling interfering mobiles [6]. Assuming that eachmobile station is uniquely identifiable, it is a relatively simple task to calculate the antennaarray’s receiver weights, so as to maximise the received SINR. The use of adaptive antennaarrays in a cellular network is an area of intensive research and adaptive antenna array’shave been studied widely the context of both interference rejection and in single-cell situ- inations [ 1,15,18,261,267,268]. More recently, work has been expanded cover the analysis toand performance benefits of using base stations equipped with adaptive antenna arrays acrossthe whole of a cellular network [2,265,283]. A further approach to improving the network performance the employment of Dynamic isChannel Allocation (DCA) techniques [284-2921, which offer substantially improved call-blocking, packet dropping, and grade-of-service performance comparison to Fixed Chan- innel Allocation (FCA). A range of so-called distributed DCA algorithms were investigatedby Cheng and Chuang [290] where a given physical channel could be invoked anywhere inthe network, provided that the associated channelquality was sufficiently high. As compro-mise schemes,locally optimised distributed DCA algorithms were proposed, example, by forDelli Priscoli et al. [293,294], where the system imposed an exclusion zone for reusing agiven physical channel around locality, where it was already assigned. the In Sections 4.2.1-4.2.3 we briefly consider how an adaptive antennaarray may be mod- 193194 CHAPTER 4.NETWORKS CELLULAR ADAPTIVE ARRAYS INelled for employmentin a networklevel simulator, followed by a short overview of a varietyof channel allocation schemes in Section 4.3. This section also provides abrief performancesummary of the various channel allocation schemes based on our previous work [23,295],which suggested for the scenarios considered [23,295]that the Locally OptimisedLeast In-terference Algorithm (LOLIA) provided best overall compromise in network performance theterms. Section 4.4 presents atheoretical analysis of the performance of an adaptive antennain a cellular network. A summary several multipath propagation models given inSection of is4.5, with particular emphasis on the Geometrically Based Single-Bounce Statistical ChannelModel [296,297]. The potential methods of cellular network performance evaluation de- arescribed in Section 4.3.3.4, as are the parameters of the network simulated in later sections.Simulation results for Fixed Channel Allocation (FCA) and two Dynamic Channel Allocation(DCA) schemes using single element antennas,as well as two- and four-element adaptive an-tenna arrays for Line-Of-Sight (LOS) scenarios presented and analysed Section 4.6.2. l . are inFurthermore, simulation-specific details of the multipath model are given in Section 4.6.1,with the associated results obtained for the FCA and the LOLIA in the context of two, fourand eight element adaptive antennaarrays presented in Section 4.6.2.2. Performance resultsfor a network using power control over a multipath channel conjunction with two andfour inelement adaptive antenna arrays are provided in Section 4.6.2.3, followed by the descriptionof a network using Adaptive Quadrature Amplitude Modulation (AQAM) in Section 4.6.2.4. Performance results were also obtained for AQAM and the FCA algorithm as well asthe LOLIA, with both two- and four-element adaptive antenna arrays. Results using the‘wraparound’ technique, described Section 4.6.1, which removes the cellular edge effects inobserved at the simulation area perimete ...