CAPACITY ENHANCEMENT IN CELLULAR SYSTEM - A REVIEWto enhance the capacity of cellular system have...

International Journal of Network and Mobile TechnologiesVolume 2 • Number 2 • July-December 2011 • pp. 91-106

CAPACITY ENHANCEMENT IN CELLULAR SYSTEM - A REVIEWBharat Bhushan1, Ajay Kaushik2 & Amit Kumar Garg3

1Research Scholar,Maharishi Markendeshwar University, Mullana, (India), (E-mail: aitbharat@ gmail.com).2Lecturer ECE Department, Maharishi Markendeshwar University, Mullana, (India), (E-mail: [email protected].).3Professor & H.O.D. ECE Department Maharishi Markendeshwar University, Mullana, (India), (E-mail: [email protected].).

Abstract: Cellular communication has a tremendous growth in recent years. Capacity enhancementbecomes an important topic of discussion. Both researchers and academicians have been recognized theneed of capacity enhancement of cellular system in a sustained manner. In this paper, various techniquesto enhance the capacity of cellular system have been discussed. The various performance metrics like cellplanning, frequency reuse, cell splitting, cell sectoring, Handoff Strategy, propagation factors are exploredto capacity enhancement to fulfill the demand of users.

1. INTRODUCTIONA Cellular Telephone system provides a wirelessconnection to the PSTN for any user location withinradio range of system. Cellular system accommo-dates a large numbers of users over a largegeographical area, with in a limited frequencyspectrum. Cellular system provides high qualityservice than landline phones. The objective ofefficient system is to provide good speech quality,compatibility with ISDN, efficient use of bandwidth;and support for Handoff etc, with low cost. Digitalsystems are used in the cellular communicationsystem to transmit both voice and data using singletechnology. Various algorithms are developed forefficient speech compression to make small band-width operated system. The encryption is also donefor the security purpose.

Figure 1: Cell Division using Frequencies Reuse [15].

Figure 1 shows the cellular system geographicalarea is divided into cells. Each cell uses the differentfrequency to avoid inference. Cellular system isbased on the concept of low power transmitter andsmall cells. The distance between cells using samefrequency kept at sufficient distance to preventinterference. The reuse of frequency increases theoverall capacity of system in term of possiblenumber of users. The cells are usually circular; butare modeled as Hexagonal Usually seven cells areused in a cluster with an efficient distance withdifferent frequency as in Figure 1. A number ofchannels in each cell are reserved for signalinginformation the cells are usually roughly circular,but are easier to model as hexagons. There is anapproximate two-cell buffer between cells using thesame set of frequencies, giving good separation andminimizing interference. In areas that are denselypopulated with users, the transmitted power isreduced and the cells are smaller. At the centre ofeach cell is a base station consisting of a computer-controlled transceiver connected to an antenna,which communicates with all of the mobile devicesin the cell. In a small system, all of the base stationsare connected to a single mobile telephone switchingoffice (MTSO) or mobile switching centre (MSC).In larger systems, several MTSOs may be required,all of which will be connected to a second levelMTSO, and so on MTSOs are connected to at leastone exchange in the Public Switched TelephoneSystem (PSTN). MTSOs communicate with eachother via the PSTN using a packet switching networkas shown in Figure 2.

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92 International Journal of Network and Mobile Technologies

Figure 2: Cellular Operating System [16].

At any given time, each mobile device is underthe control of the base station for whatever cell ithappens to be in. When the device leaves the cell,the base station detects the fact that the receivedsignal strength is fading and asks the surroundingbase stations to report the power levels they arereceiving from the device. Control is transferredto the cell whose base station is receiving thestrongest signal, and a message is sent to the deviceinforming it that it is now under the control of adifferent base station and must switch to a newchannel. This process is called handoff, and takesapproximately 300 milliseconds.

Figure 3: Graph Showing Subscribers Growth [17].

Figure 3 shows tremendous growth in thedemand of wireless subscriber, so our resourcesare getting limited. Frequency spectrum is limited.So to fulfill this demand, the different techniqueshave been used to enhance the capacity. Theconstraints like path loss reduction, frequencyanalysis, algorithms, quality of service, cell planning,Handoff, propa-gation factors effect are studied.The remaining part of this paper is organized asfollows. In Section 2 various Techniques to Enhancethe Capacity efficiency is presented in Section 3.In Section 4 conclusion and future scope isdiscussed.

2. TECHNIQUES TO ENHANCE THECAPACITY

1. Cellular Planning: Radio coverage associatedwith fixed-location cellular system that is inter-connected with other cells. To provide radiocoverage to a larger geographical area. The cell’sare often ally hexagonal block and a group of cellis are called cluster. Cell planning means to celldimensioning and base station placement. But it istough practice. Many other constraints like location,power, antenna height and tilting, path loss,switching etc. affect the efficiency. So here differentmethod of cell planning with constraints isdiscussed.

Capacity Enhancement in Cellular System - A Review 93

Chamaret B. et al. [1] proposed that due toincrease in demand radio network planning andoptimization becomes a problem. So a mathematicalmodel was proposed to discuss the Base-Stationlocation, transmitted power, antenna heightdiagram and tilting. The objective of paper toachieve large coverage of traffic demand area(TDA) a large Base-Station set is needed and toachieve low cost network. A Base-Station set assmall as possible is also needed. This creates aconflict. A model addressing to this conflict hasbeen proposed. To keep the idea of number ofrequired Base-Station (BS) to minimal level with alarge coverage of TDA is done by minimizing theno. of cells that cover any point of TDA. Anexperiment was performed in test area of 73 × 76km2 was considered. Test area was divided in to150 equal strips. At each potential site BS with anantenna height of 30m was located and a cellaccording to a maximum path loss 110db at 900MHz is computed with a multiple diffractionpropagation model with SUN SPARC 10. Hecnce itwas concluded that the mean coverage per BS whichis the relative coverage of the selected networkdivided by the number of selected BS. Thisprovides an idea of efficiency of the radio network.Inverse of it, if the radio network cost was consideredproportional to the number of BS represents theevolution of coverage cost of an area unit.

Margaret H. Wright et al. [2] elaborated in thispaper to predict quantative measurement of systemperformance as a function of the system parameterand to optimize predicted overall performanceby choosing the best value for the parameterthat can be controlled by provider or maintainer.Direct methods are suited to find the optimalplacement of base station, since they require onlythe value of the function to be optimized.In numerical testing they proposed the customizevariant of Nelder-Mead method”, a simplexmethod to be reasonably efficient and reliable atfinding local optima. The Nelder-Mead method isconceptually simple, The NM method attempts tominimize a scalar value non-linear function of n realvariable using only function values, without andderivation information Many of most well knowndirect search method including NM maintain at eachstep a non-degenerate simplex, geometricallydefined by (n + 1) vertices. It was concluded thatN-M method is highly effective for the base stationoptimization.

Minseok Jeong et al. [5] explained path lossmodels. In the mobile communication path loss isthe main constraints for the system efficiency. Mainmodels are Okumura–Hata Model, Cost-231 Hata,ITU-R model studied. The problem of model is thatthe predicted expressions were based on qualitativepropagation environments such as urban, suburbanand open area. From these models the Cost 231-Walfisch-ikegami model was a result of effort touse a quantative description of propagationenviroment. In addition to height of Transmittingand Receiving antenna, the quassi-uniform buildingheight and the width of street are considered.Objective was to compare the Okumura Hata andCost-231 model. It was concluded that Cost-231 isextension of Okumura Hata Model to cover thefrequency up to 2000 M Hz. and Cost 231-Hata isclose to Okumura when building group Height is about half of street width. Also at the frequency morethan 2000 MHz ITU-R are based on Okumura,suburban area.

Samuel Pierre et al. [6] proposed this paper forcell assignment to switches with the Taboo SearchAlgorithm. Thus, the problem of cell assignmentcould be summarized as follows: for a set of cellsand switches (whose positions are known), assignthe cells to the switches in a way that minimizesthe cost function. The cost function integrates acomponent of link cost and a component of handoffcost. The assignment must take into account theswitch’s capacity constraints that make themcapable to host only a limited number of calls. Thepressure to reduce costs adds new urgency to thesearch for optimized or quasi-optimized networkdesigns which can minimize the number and costof required facilities. Two types of Handoffdiscussed simple handoff and complex handoff.

In this paper a heuristic approach has beendiscussed based on taboo search to solve theproblem of assigning cells to switches in cellularmobile networks. The implementation of thatapproach was consisted of defining a series ofmoves for short-term and middle-term memorycomponents. These moves allow for improving thecost of a solution or re-establishing its feasibility.This has led them to define a gain structure withupdate procedures to efficiently choose at eachiteration, the best solution in the current neighbor-hood. The implementation of long-term andmiddle-term memory components has required achoice for intensification areas and a definition of


a diversification policy. On comparing withsimulated annealing (SA) it was proposed that TSalgorithm performance is better than the SAalgorithm. In particular, for large-size problems,TS founds solutions that are twice as good as thoseof SA.

Shine-Ming Tsai£ et al. [7] proposed a HCNchannel assignment scheme called repacking ondemand (RoD). RoD was originally proposed forwireless local loop networks. They expend thiswork to accommodate mobile HCN. A simulationmodel is proposed to study the performance ofHCN with RoD and some previously proposedschemes. The important issues is capacity planning.Especially when the number of cellular subscribersgrows rapidly, it was required that the cellularservice provider increases its network capacityeffectively. One possible solution was to deploy thehierarchical cellular network (HCN) the HCNconsists of two types of base stations (BSs): microBSs and macro BSs. A micro BS with low powertransceivers provides small radio coverage(referred to as micro cell), and a macro BS withhigh power transceivers provides large radiocoverage (referred to as macro cell). The micro cellscover mobile subscribers (MSs) in heavy telegraphicareas. A macro cell is overlaid with several microcells to cover all MSs in these micro cells.

A basic scheme called no repacking (NR). Inthis scheme, when a call attempt (either a new callor a handoff call) for an MS arrives, the HCN firsttries to allocate a channel in the micro cell of theMS. If no idle channel is available in this micro cell,the call attempt over-flows to the correspondingmacro cell. If the macro cell has no idle channel,the call attempt is rejected. Call blockings and force-terminations of NR can be reduced by repackingtechniques. If a call attempt for a micro cell BSi thathas no idle channel. In NR this call attempt is servedby the corresponding macro cell. If radio channelsare available in later, this call can be transferredfrom the macro cell to again. The process ofswitching a call from the macro cell to micro cell iscalled repacking. Repacking increases the numberof idle channels in a macro cell so that more macrocell channels can be shared by the call attemptswhere no channels are available in the micro cells.The study develops a simulation model toinvestigate the performance (i.e. the call blocking,force-termination, and incompletion) for NR, AR,and RoD. System Parameters, Traffic Parameter,

Mobile Parameter are discussed in this paper.It was concluded that on increasing the Macrochannel C significantly improves the Probability ofBlocking, Probability of force-termination, Probabilityof new call.

M.Al.-Akaidi et al. [9] explained HCS which usedfor the multimedia traffic in 3-G system.In this type of network an efficient cell assignmentscheme is required to improve Quality of Service(QoS) of the system in terms of droppingprobability blocking probability and channelutilization. In this a new channel assignment schemewhich exploits the delay insensitive property of nonreal-time data service to admit user to preferredcell layer. This scheme is anticipated to improvethe QoS of real time voice user for both blockingprobability and channel utilization parameter.

Problem is to provide efficient cell planningtechnique to improve quality of service (QoS) ofthe system in terms of dropping probability.So objective is to design of wireless network usingHierarchical (multi-tier) cellular structure (HCS) toprovide high coverage and capacity. HCS has twolayers i.e. over flow scheme and speed–sensitiveassignment Speed sensitive assignment scheme isrequired to classify according to their speed inmacro cell and micro cell. It was concluded thatincrease in outage as the data service wereintroduced and there is an increase in the trafficoffered to each micro cell.

Stuart Allen et al. [10] presented a paper for 3gnetwork deployment. The location and configu-rationof transmission of infrastructure problem hasmentioned. A cell planning is a challenging due toinherent complexity, which stems from requirementconcerning radio modeling and optimization.Factor, cell coverage, service quality and capacityare interdependent with the call planning. So theCDS Smartplan optimization tool for automatic CellPlanning. This is an optimization engine which iscapable of finding highly efficient cell plans. Goalis to steer the network configuration towardsachieve the best key performance indicators (KPI).These KPI could be set to represent coverage,traffic, cost, dominance/interference or any othervariables in any combination to cover 95% coverage;site cost to be minimized; cell isolation to beoptimized. The required coverage 95% was achievedon different KPI structure.

S.M. Allen et al. [12] described the AutomatedCell Planning Technique for the improvements of


network quality and cost. This paper describe anoptimization algorithm for cell planning based onsimulated annealing which is used to investigatethe effect of several strategies for planning, thestaged rollout of cellular network. The objective ofthis paper is to reducing the cost of networkinfrastructure maximizing the coverage maximizingthe traffic capacity of network and keepinginterfaces below acceptable levels. Each potentialcell plan is devalued by considering of large no. ofreception test points (RTP) distributed over networkarea. Each RTP has associated signal and trafficrequirement that are used to calculate the coverage,traffic capacity and potential interface of cell plan.

The optimization algorithm used is based onSimulated Annealing, an iteration process thatinvolve making small changes to network at eachstep like adding site changing the power of singlesector, moving site. The resulting cell planning ateach iteration is evaluavated and either acceptedor system based on assessment of network Simulatedannealing uses a probabilistic mechanism to avoidthe algorithm convert to solution which are locallybut not globally optimal.

In this paper site selection, site configuration,downlink field strength, optimization algorithm,coast function Neighborhood etc was studied.It was concluded that increase of traffic anddecrease in cost with this algorithm.

T Reza et al. [28] presented a new cell planningis based on active contour theory. The structure ofproposed method lets several parameters be appliedin cellular mobile communication network designsimultaneously. In this paper iterative optimizationalgorithm is proposed to optimize the parameterset of contour. The optimization criteria include themaximum overlap coverage area as well as minimumnumber of cell and Cell overlaps. Active ContourTheory is an Image Processing and Machine Visionalgorithm to extract the minimum area surroundingcontour for a two dimensional object. The mainthing is to shrink and expand the outer contour ofobject in any iteration. The ides is also known assnake theory or gradient vector Flow (Guf)optimization algorithm. In this no. of base stationis initialize in first stage based on the dimension ofarea and the cell radius. In next stage the locationof base station are initialized based on the greedyalgorithm. The location of base station are tunedusing net stage and the fitness function is calculationfor all cells in area. If the requirements are not met,

the number of based station is checked andcorrected based on overlap of neighbor cells andcorrected based on overlap of neighbor cells andthe coverage of each cell. For optimization the cellradius a gradient based approach has beendeployed to adjust the cell radius. It was concluded99.23% and 97.23% overall coverage in uniform andnon-uniform traffic situation respectively revealinga great improvements with respect to geneticalgorithm.

2. Frequency Reuse: It is a technique of reusefrequency and channel in communication systemto improve the capacity and efficiency. Frequencyreuse means that frequency allocated to cell arereused in regular pattern of cells is called cluster.Each cell is designed to use radio frequency onlywith in its boundaries, the same frequency can bereuse in another cell not far away withoutinterference. These cells are called co-channels. Sodifferent method is used to maximize the trafficload. These are discussed here.

Antonio Capone et al. [3] proposed the planningof reuse of available frequency in efficient way.In this paper author proposed the Tabu SearchAlgorithm. Its objective is to maximize the sum oftraffic load offered by the region in which the ratiobetween the received power and the sum of powerreceived from interfering transmission is abovethreshold valuve. In this paper they present analgorithm based on Tabu Search Technique to solvethe problem In this model Channel AssignmentProblem (CAP) is given narrowband cellularnetwork. Proposed model describe the CAPproblem in narrowband cellular network whichaccounts for the cumulative effect of interferes. INthis model the service area was portioned intoregion and propagation characteristics are assignedby means of levels received in each region byconsider B.S. Their objective is to keep the longterm C/I above capture ratio through out servicearea. Here TS approach is used. The ability ofreceiver to detect signal in the presence of inter-ference noise is known as Capture Effect. It is basedon load search and initiation procedure the basicmoves are defined as the swaps of used frequencywith a used one for one B.S. At each iteration itassociated with the current solution the followingattributes; the BS and the couple of frequenciesinvolved. The adopted algorithms have beendeveloped using C++ languages and SUN Sparc 10workstation have been used to obtain numericalresults. Hence it was estimate that the tuning of ‘T’


(iteration) may be a key issue for the efficiency ofalgorithm. So they used TS approach. The resultare equal very close to the maximum valueachievable with fixed TS.

Klas Johansson et al. [18] has explained twocapacity expansion strategies as Multi-accessnetwork and hierarchical cell structure. Cost canbe minimized for a cell structure; cost can beminimized for asset of available radio accesstechnologies given heterogeneous requirement onarea coverage, capacity and quality of service.In this paper they quantify the infrastructure costfor a multi-access network composed of macrocellular HSPDA base station and IEEE 802.11WLAN access point. The network is dimensionedfor an urban environment using stochastic model forhetero-geneous traffic density.

This paper treats cost efficient deploymentstrategies for network composed of HSPDA macrocellular base station (BS) and IEEE-802.11g accesspoint (A.P). These represent system with long rangefor wide area coverage and low cost, short rangeaccess point suitable for hot spot.

Two problem had addressed first is the tradeoffbetween no. of macro cellular BS and comple-mentary WLAN APs needed another is to findparameter which is most important to improvementin each system in order to reduce the cost. Theobjective is to contribute to a better understandingof the role of multi-access as capacity expansionstrategy and for this reason a stochastic spatialdistribution of traffic is assumed.

A macroscopic model is used to capture keytechnical and economical parameter that influencethe infrastructure cost for a typical mobile networkdimensioning and capacity analysis like interference,propagation etc. This explains how operator couldexploit WLAN in the short run instead of buildinga dense macro cell network if traffic suddenlyincreases. There is fulfillment during transitionperiod increasing capacity from 5 to 10 Mbp/km2

with WLAN instead of deploying more macro sites,as increases the cost. In long run increasing capacityin macro cell is more cost efficient. A graph showsthat decrease in cost coefficient of HSPDA, 802.11.Increase in HSPDA BS capacity and AP coverage in802.11.

Mohmoud Al-Ayyoub et al. [33] explained the selfmanagement technology. As the cellular networktechnology that allows an operator to fully use all

its licensed spectrum in every base station are veryattractive. These co-channel frequency reuse amongneighbor base station increases interference inoverlapping cell-edge area and degrade thenperformance. Solution to this problem is proposedto configure the base station to use different partsof spectrum to serve edge user. Such fractionalfrequency reuse and associated intercell interferencecoordination (ICIC). Self management technologyare fully automated in task of managing (configure,monitoring, optimization) a cellular network areemerging as an important tool in reducing serviceprovider OPEX and CAPEX and has distinguishfeature of LTE. Main objective of LTE are computationefficiency controlled cascading and stability andoptionally of solution. But reality this is not possibleto achieve all. Method is Spectrum is divided intoa set of orthogonal Channels ‘k’.

3. Interference and capacity : Interferenceproblem are associated with the mobile communi-cation. These are due to congestion. The inter-ference occurred from clash with another mobilein the same cell due to adjacent cells. These are oftwo types: co-channel inference and adjacentchannel interference. Co-channel occurs betweentwo cells present in different clusters. Adjacentinterference occurs in between two cells in samecluster. So various techniques are used to controlthem. These techniques are discussed here.

Nasreen Badruddin et al. [11] Presented paper topresents an approach that uses relaying to increaseCDMA cellular capacity (spectral efficiency). The keyInsight is that, since the power received by themobile falls off rapidly, as a function to distance tothe base station, relaying could potentially be usedto eliminate the out-of-cell interference, thusincreasing the cellular capacity. However, as thepaper shows, achieving the increase in capacityrequire a specific relaying architecture, which cansuccessfully control the interference at the relaystations. The main challenge to increase capacityor number of user served simultaneously and toincrease the data rate capabilities to support thegrowing demand foe high data rate application.Objective is to solve the problem of “dead spots”and increase system coverage. In this paperhowever, the potential capacity gains (as measuredby the spectral efficiency) from implementingrelaying in a Code Division Multiple Access (CDMA)system are investigated. Instead of transmittingdirectly to the base station (BS), a mobile station(MS) in a CDMA system will transmit to relay


station (RS), which will then relay the signal to theBS. By placing a RS in between the MS and the BS,the transmission power is reduced due to thesmaller distance between MS-RS and RS-BScompared to MS-BS. Since a CDMA system’scapacity is interference-limited. It is hoped that byreducing the transmit power, and thus the out-of-cell interference, through relaying, the energy-per-bit to noise ratio, Eb /N0 at the BS can be increased,thereby increasing the capacity of the system. Theeffect of relaying on interference is investigated bycalculating the Eb/N0. A higher Eb /N0 at the BS canbe translated to an increase in capacity. It wasconcluded that the overall interferences experiencedby the center BS has reduced by 34%. Thus theydeduce that capacity can be increased by 51%. Theoverall decrease in interferences at BS of about 12%.Taking the inverse of new interference it can deducethat Eb/N0 at the center BS increased by 14% whichtranslate in to an increase in capacity by the samepercentage.

Hakan Bolukbasi et al. [13] proposed paper thatpresents as the demand of high data rate isincreasing so conventional cellular network withwireless fixed relay to enable multihop communi-cation is being considerate for beyond 3-G networkin order to provide high data coverage in costeffective manner.

In this paper author considered a Cellular RelayNetwork (CRN) where a large no of low complexityand low power wireless fixed relay are deployedaround the central node (BS) in each cell. Each relayand central node covers only a small area with asmall amount of power enabling the reuse offrequency time resources. Objective of this paperwas to evaluate the cell capacities in CRN whichenables to make the conventional cellular network.The paper shows that cell capacity of CRN doesn’tdepend on the cell size or the total number relaysin the cell, but it rather depends up number ofnearest relays to the central node. Pico cell networkidea is one of remedies to high data rate demandas the resources “Frequency and time” are veryscare, by splitting macro cells into much smallersize calls namely Pico cells, spectrum efficiency canbe improved significantly. Although the cost ofbase station in Pico-cellular network may be muchless than conventional base station the very factthat each Pico cell would still required the highspeed connection to the internet makes thearchitecture not as cost effective. Due to low powerfeature when there is sufficient electromagnetic

separation, it is possible to reuse the channels (timefrequency recourses) even in the same cell.

Therefore the system performance can beimproved from both reduced propagation loss andreusing the available channels. It was concludedthat use an equation which follows as cell capacityin CRN is directly proportional to the no. of rootnode. If increase the no. then the capacity of cellwould increase and accordingly either the no. ofuser in cell or the amount of bandwidth for userwould increase.

Saurbh Chhabra et al. [14] Proposed paper thatpresents the result of development of user friendlysoftware tool that can be used to calculate co-channelInterference. Both are uplink and downlink ofmobile communication due to reuse of frequenciesin spot beam or coverage cell. The cells or beamwas defined in angular domain as measured fromsatellite or the elevated platform and cells arearranged in Hexagonal Lattice and overlap to providecomplete coverage. Interference is inherentlydetrimental to a communication system. There aretwo type of interference as intrasystem andintersystem.

Out of band emission of one system thatinterferes with another system in an adjacent bandis intersystem, Co-channel interference is intra-system interference. This paper focus on co-channelinterference. So if co-channel interference iscalculated the designer will be able to manage theirlink budget calculation and optimize the design.It was concluded that for same side lobe level (db)the reuse no. increases the overall co-channelinterference; power decreases since C/I increases.Same reuse number as side lobe level of spot beamantenna pattern decreases. Thus co channelinterference is proposed to decrease.

Mark DeFaria et al. [19] illustrated that in amultihop cellular network, the physical layer ofmobile terminals is modified so that in addition isbeing able to transmit to base stations and mobileterminals are able to transmit directly to othermobile terminals. So it allows mobile terminals tolower their maximum transmission power and useother terminals as repeaters to forward their packetsto the base station. Multihop cellular networks havea higher capacity than traditional cellular networksdue to their potential of lower intercell interference.Intercell interference is lower because the maximumtransmission power of terminals is decreased. Theeffects of intercell interference in a multihop cellular


network investigated in this paper. Previoussimulation results of a one-cell system show thatthe SNIR of a multihop cellular network is slightlylower than that of a traditional cellular network.Simulations of a network with many cells show thatthe overall SNIR of a multihop cellular network isin fact higher than in a traditional cellular networkbecause of lower intercell In a multihop cellularnetwork, the physical layer of mobile terminals isto modified so that they can transmit packets notonly to base stations but to other mobile terminalsas well. Therefore, a mobile terminal would ableto decrease its maximum transmission power anduse other mobile terminals as repeaters to allow itstransmissions to reach a base station. Mobileterminals require smaller amount of transmissionpower so interference decreased. The decrease inintercell interference in a multihop cellular networkgives a potential of higher Signal to Noise andInterference Ratios (SNIR) than traditional cellularnetworks. Second the coverage in a multi hopcellular network increased because mobile terminalsthat are too far away from a base station are still isable to communicate with one by allowing trans-missions forwarded to a base station by othermobile terminals. The coverage also improved ifany mobile terminal that is caught in a deep shadowfade with respect to the base station would still beable to communicate with it by relaying its data toa nearby mobile terminal that is not caught in adeep fade. It was concluded that the multihopcellular network has a larger SNIR and smallertransmission consumption than traditional system.

Md. Rezaul et al. [23] elaborated in paper thatmajor current thrust for cellular communicationsystem is improved economics through enhancecoverage early in life cycle of a network and highspectrum efficiency later in life cycle. An attractiveapproach for economical, spectrally efficient andhigh quality digital cellular and personal communi-cation serves (PCS) is the use of spread spectrummodulation with Code Division Multiple Accesstechnology. This paper deals this comparativeparametric analysis for propagation path lossconsidering macro cell region using differentmodels and contains comparatives study with realmeasurement obtained from Pacific BangladeshTelecom Limited. In cellular system reusing eachfrequency at several region of service area increasesthe capacity. Also cell corresponds to cell wherethe B.S. is placed on top of tall building or towersand transmission enough power to cover several

miles. Macrocells can be classified into differentchannel type, urban, surban, and rural. Main issueof interference into microwave system is line ofsight. Most common occurrence of this will be afrom subscriber unit located in a high rise buildingor on a balcony and in this case path loss figureapproaching free space loss. It is possible for thisthe unit is interfering signal will be strong thanaggregate power of many base station at receiver.In urban environments the probabilities of elevatedsubscriber unit is greater. Thus the impact ofsubscriber unit interference source on microwavereceiver will be more substantial than in residentialareas. Performance depends upon following factorlike Path loss variation versus distance models, HataOkumura, Walsfisch Ikegmi Models, Random slowshadowing, Random Multipath fading, IntersymbolInterference, Background Noise. It is concludedthat Walfisch –Model is more close to standardvalue as compared to Hata Models so in order tomaximizing the spectral efficiency of cellularSystem. It also advised to use Walfisch Model withapproximation factor.

Georgies S. et al. [27] analyzes a two-hop extensionto the coverage of IEEE 802.16 cell. As the naturaldegradation in cell capacity due to multihopcommunication which can be mitigated by spatialreuse, adaptive modulation and coding. Theavailable capacity can be estimated by analyzingthe random geometry related to location of BaseStation, the sponsor node and mesh subscribersituated two hops away from Base Station.

The IEEE 802.16 standard leaves undefined thecentral schedule located a B.S. Mesh networking isa part of IEEE 802.16 specification. There isnumerous application of mesh network Infra-structure relay nodes are proposed for the coverageextension. This extension is useful in case ofshadowing, are even cost efficiently in perimeterof its metropolitan network. Further in this papera scheduling strategy when exploit spatial reuse formesh node. This can apply on top of anotherscheme. The extra capacity due to capacity lossresulting from multihop communication. In thismodel adaptive modulation and coding is done byan ideal Shannon Channel. The capacity of each linkis then related to its distance, analogously toWIMAX network. It is suggested that this schemecan be used by a network operator to estimate theimpact of coverage extension in WiMax deployment.At out of perimeter nearby customer grows in no.


a new BS can be installed and SN can be moved tothe new boundary area. This area provides smoothinfrastructure expansion for cellular network.

M.Godarzvand-Chegini et al. [31] explained theinterference reduction capability of cell sectoringand power control algorithms have been consideredseparately as mean to decrease the interference inCDMA. In this paper Rota table equal sectoringmethod for CDMA in 2D urban environment (RES).In this method the equal sector of base station isrotating together to decrease the inter cell and intracell interference. Also use central power control toovercome the near far problem. Simulation resultsindicate that the proposed method considerablyincrease the CDMA capacity compared to ordinaryequal sectoring (E.S.) method. Problem discussedis to enhance the capacity limited multifading,shadowing and near far effect that cause thefluctuation of received power at the base station.Paper is focused on RES method i.e. able to rotatethe sector bases on slow variation of user distri-bution with in a cell. Methodology is used by theinterference between users is to sectoring the cellsusing directional antenna. This approach utilizespatial domain to introduction orthoganalizationto system it is fundamentally differently thanbeamforming. Beamforming method combines thereceived signals from multiple antenna in a uniqueway for each user to suppress the interference thatthe user sees. Sectoring employs directional antennas.Sectoring increases the no. user admissible in systemHowever under highly non-uniform traffic load,conventional sectoring i.e. ES method fails to bringmuch capacties. To increase the capacity of CDMAcellular system the RES is proposed to reducerejecting of call request in situation like traffic jamsand crowded hour entertainment places. It wasconclude that by simulation RES and Es method’sresult is compared. Active user in different hoursof day and night in a day off RES and ES method iscompared. In such a day assumed ,user arespending their spare time in places such as park,cinema, sport club and also gathered in twodifferent places and around different hour (around17 and 22 hours) As this time faces crises soincreasing capacity is increasing is neccesary. Byusing this method there is increase of 25% capacity.

Ihsan UlHaq et al. [34] proposed that Hand offmanagement is to ensure quality of service forwireless connection. Here by QoS mean to reducethe probability of forced termination during

handoff. This paper proposed algorithm helps insuccessful group handover and thus guarantees QoSby making the resources available in target cell. Theobjective of this article was to present a resourceallocation algorithm to prevent Cell Breathing andfacilitate Proactive for CDMA Access This enhancesthe cell capacity in terms of density of mobile stationas the MS at edge will not disconnected due to cellbreathing. To keep the interference a minimum itis important user that are far from Node-B (BTS)have to transit signal with more power than closerto Node B. It is due to user get disconnected so thearea of coverage area of cell get reduced. Thedisconnection of call at edge is called cell breathing.There are multiple user so it is called Group.In this proposed paper location information of userto allocate or free resources in target cell in advancewhile keeping the interference level with in thethreshold value. The algorithm prevents cellbreathing, resulting in increasing networkingcapacity and coverage. It was concluded thatprevention of cell breathing and enhancement incell capacity and cell remain connected to systemand thus quality of service (QoS) is maintained.

Dong Zhang et al. [35] proposed a ubiquitouswireless access network called a cellular wirelessmesh network. A cellular wireless mesh networkis organized in multi-radio, multi-channel, multi-rate and multi-hop radio cells, each served by asingle gateway. Maximum Channel Collision Timealgorithm, which derives an expression for aconservative cell capacity. In future ubiquitouswireless access networks are expected to faceincreasing demand for bandwidth. Traditionalcellular (telephone) networks will have difficultyin satisfying such increased demand, because theycannot utilize high radio frequencies such as 5-50GHz. Reason is when radio frequencies are so high,even tree leaves may absorb signals; transmissionsrequire greater reliance on line-of-sight paths andgenerally have shorter distances; and thus userpackets need to travel multiple hops before theycan reach base stations. So a cellular wireless meshnetwork (CMESH)] made up of multi-hop radiocells, each served by a single gateway. CMESH cellsare distinguished from the single-hop cells in acellular network by having multiple hops. A CMESHis deployed to provide “last-kilometer” broadbandInternet access for both residents and mobile clients.A CMESH can operate on abundant high radiofrequencies (above 5 GHz), and thus can satisfy thebandwidth required.


A city-wide CMESH may contain thousands ofmulti-radio multi-channel, multi-rate and multi-hopcells. Each cell has a single Internet-connectedgateway and serves up to hundreds of user nodeswithin its coverage area. Small random cells arelike GSM cells, where neighboring cells use differentsets of channels to avoid inter-cell interference.Large random cells, where neighboring gatewaysare spaced. This is proposing that MaximumChannel Collision Time (MCCT) algorithm, whichderives an expression for the achievable cell capacityin a CMESH. It concluded that the conservative cellcapacity is achievable and thus its name is achievablecell capacity. The cell planning, designing methodsare proposed in these papers. These can be used asa guide line for the designing an efficient system.The principle idea for the each method is to providethe capacity enhancement.

By using relaying in CDMA uplink; capacityimprovement can be achieved through, usingcomplicated technique to mitigate the effect of largeinterference in relay system. Automated cellplanning also served 85% final traffic by usingoptimization algorithm on Simulated Annealing.In cellular relay network (CRN) has high capacitythan conventional cellular network. It transmits thehigh data rate coverage demand of system. By usingmultihop cellular network the decrease in intercellinference up to 28.7 db as compare to traditionalcellular networking also shown. The one third oftotal interference is eliminated. Average powerconsumption is also decreased up to 23 db thantraditional network. Multihop relay has betterperformance as compared to the single hop systemtransmission having cell radius more than 1.9K.M.A Heuristic cell planning proposed the 15% capacityimprovement. The capacity and coverage area upto 95% proposed to enhance by spatial reuse,adaptive modulation and coding. Using Contourbased algorithm for cell Planning the optimizationincreased up to 99.92% overall coverage. Femto CellSystem and Rotatable equal sectoring method arealso used for capacity enhancement. Also the factorslike handoff, path loss also play important role inthe cell efficiency.

4. Cell Splitting and Femto cell Strategy: It isbased on cell radius reduction cell splitting involvethe process of sub-dividing a congested cells intosmaller cells each with its own base station andcorresponding reduction in antenna size andtransmitting power. This increase the capacity ofcellular system as the increase in frequency reuse.

Folllowing methods are used to enhance capacityby using cell splitting.

X.Haung et al. [4] has represented the automaticcell planning for mobile radio network design.As there is tremendous increase in mobile serviceso the design of modern wireless communicationnetwork gets challenged with extremely limitedamount of available resources. The problem is tohow to determine the no. of cells, the optimal cellsites and parameter introduce to meet the systemrequirement while minimizing the spectral cost andfinancial cost. Its objective is to provide cell dimensio-ning, Base-Station (BS) placement and growthplanning. In this paper cell planning has proposedThree aspect are studied cell planning, Base-Station(BS) Placement and growth Planning.

Main concept was Growth Planning in whichcell splitting was done i.e. reducing the existing thecell size and adding the new cells. The problem isthen to find optimal B.S. site for new cells andoptimized dimensions of both original cells andadditional cell so that the growing demand meteffectively while offering minimum disturbance tothe exiting network structure. It was concluded thatgraph shows the coverage rate and traffic coverageis higher than threshold and financial cost gets downafter planning.

Ki-Ho et al. [20] explained in this paper a basicresources reuse scheme applied that is used forcellular network to multihop cellular network. Theyexamined the capacity gains of proposed recoursesreuse scheme through mathematical analysis basedin Shannon capacity. In multihop networks, severalimportant issues are how to increase coverage,capacity and reliability (self-heal, self-configure),while taking account into data transmission delay.By multihop relaying, can enhance SNR because ofthe path loss reduction between a Transmitter nodeand a Receiver node, and therefore we can increasedata rate.

The implementation of spatial reuse increasedShannon capacity for small ad hoc networks consistingof five nodes. In addition, two types of concurrentdata transmission show the possibility of capacityenhancement when there are two source-destinationpairs in multihop cellular networks. This wasformulate not a limited or specific spatial reusescheme, but basic spatial resource reuse schemesbased on TDMA for multihop cellular networks.Then, we analyze the cell capacity gains of the formu-lated reuse schemes through mathematical analysisusing Shannon capacity.


They assumed that nodes are distributeduniformly in cellular networks. Also, we assumethat nodes have saturated traffic. In TDMA – basedmultibased multi hop cellular network, nodes whichare away from a transmitting node may use thesame time slot. In order to formulate the distributionof nodes reusing the radio resources spatially theyassume that a node is surrounded by further sixnodes which are located at vertices of hexagramcentered at the node i.e. a cell is divided into manysmall hexagonal cells and node are located in thecenter of small hexagonal cells. Small hexagonal cellcalled “reuse region”. It was estimated an averagecell capacity when spatial reuse is implemented inmultihoped cellular networks. Graphs shoes thatadequate spatial reuse, according to size of reuseregions improves the average cell capacity.

Nagendra et al. [26] proposed that an optimizedcell planning for path loss reduction has beenproposed. A square block is considered as TrafficRequired Area (TRA) which consists of number ofbase stations (BSs) and mobile stations (MSs). Theoptimization algorithm: Tabu search, is used tooptimize the position of base stations in such a waythat the path loss (or reciprocal signal strength)between the BS and MS is minimum (or maximum).In order to accommodate large number of users,algorithm adds new BSs and also drops existingBSs. Then, the propagation path loss from a basestation to a receiver point was calculated accordingto Okumura-Hata and Walfisch-Ikegami model.These are empirical models based on the measure-ment data. In order to improve the efficiency ofthe Tabu search, intensification through dynamicTabu list and Tabu time have been used. The cellularconcept was a major breakthrough in solving theproblem of spectral congestion and user capacity.It offered very high capacity in a limited spectrumallocation without any major technological changes.

The cellular concept is a system-level idea whichcalls for replacing a single, high power transmitter(large cell) with many low power transmitters(small cells), each providing coverage to only a smallportion of the service area It was concluded thatproposed algorithm is highly effective. There isimprovement of 14% in capacity and reduction inpath loss.

Hanuman et al. [30] proposed that to satisfyingthe high data rate in cellular system, the cell size isreduced. So deployment of Base Station is requiredso costly approach. So in this paper femto cell has

been proposed to implement that with low cost.The femtocell are short range, low cost and lowpower base station called as home base station.Femto cell has a femto base station connected tocore network via a wired backhaul. Through wiredbackhaul a downlink and uplink data packets aredelivered to femto base station and the corenetwork co-channel interference is considerbetween BSF and BSM. So the solution to thisproblem the paper proposed a new Time DivisionDuplex frame structure called reversed pair frame.RPF consist of TDD frame with a reversed orderof downlink and uplink using the RPF and a wired–backhaul-delivered downlink data. Capacity isachieved through a simple interference mitigationprocess. In this paper performance is analyzing withthe capacity of two users than applied to multi-user.It concluded that adopting the RPF in an OFDMAfemto cell system greatly enhances the uplinkcapacity of both macro and femto cell and evendownlink capacity of them than using theconventional TDD Frame System, capacity andcoverage analysis of Femto network.

Namgeol O. et al. [32] proposed that the currentsmacro cellular system are used they have drawbackof the user far from macro cell and the user inindoor undergo poor service relative to other. Tosolve the problem macro cell are required which iscostly. So the femto cell are used Basically the Femtocell are home based station which are short rangelow cost, low power station installed by consumerfor better indoor voice and data reception. Thusthe deployment of femto cell within existing macrocell in a cellular network accommodates a largeportion of exiting traffic as well as facilitates thecapacity requirement of new applicant and services.

This paper analyzes performance of femtocellembedded HCS network adopting mare detailedradio propagation model. Considering variousenvironmental factor such as wall structure, no. ofwall, and distance between femto cell and user thispaper evaluate the overall outage problem and thedynamic range of spectral efficiency of femtocell inHCS network and required separation distancefrom macro cell for a femto cell to guarantee theminimum required spectral efficiency. In this paperSignal to Interference noise (SINR) ratio is studied.Hence proposed method represents dynamic rangeof 2-40% 2.5 and 50, 200m. In term outageprobability, average spectral efficiency, and requiredseparation from macrocell, respectively. The


evaluation results indicate that system performanceof embedded femto cells are significant affectedby surrounding environment.

Hansung et al. [36] investigated that the effectsof cell size on energy saving and system capacityand then show the effectiveness of small-cell basedfuture mobile communication systems in terms ofenergy efficiency. It implies that larger cells areneeded for energy saving when call generation rateis low. However, if the call generation rate andother situations are not changed, a small-sized celltopology has more advantages in the viewpoint ofthe energy saving and system capacity. Cell environ-ments are categorized into macro-, micro-, Pico-,and femto-cells according to their cell sizes. In orderto maintain communication coverage, a small-sizedcell-based topology requires many BSs with lowtransmit power level. On the other hand, a large-sized cell-based topology requires a few BSs witha high transmit power level. However, therelationship between energy saving and cell sizehas not been investigated yet. In this paper, weinvestigate the effect of cell size on the energysaving of MSs and BSs in terms of energy consumption,system capacity, and per-energy capacity byevaluating system-level energy efficiency. As the cellsize becomes smaller, there is significantly increaseenergy efficiency and system capacity.

5. Channel Assignment Strategies: On the basicof frequency reuse scheme different channel assign-ment strategies i.e. fixed channel and dynamicchannel assignment are used. Handoff are microcell the part of cell assignment strategies. These arediscussed here.

Jordi Perej-Romero et al. [21] proposed thatenhancement of different Radio access Technologyallocation strategies in a heterogeneous scenariowith CDMA and TDMA access technology byincluding path loss information. Cellular wirelesssystem become interference limited and conse-quently, any engineering technique developed toeither reduce interference or to improve therobustness of the system to bear interference willreadily increase network capacity and operatorrevenue. Managing interference has been topic ofinterest for many years. Interference level inpower–controlled system in related on one handto propagation losses from interference source toits target receiver and on the other hand, onpropagation losses from interference source tointerfered destination, Path loss is lead to over all

interference reduction and consequently perfor-mance and capacity improvement.

This paper focus on a heterogeneous schemewhere CDMA and TDMA access technologiescoexist and analysis different scheme for distri-bution the user between the two technologies.It was revealed that by making an appropriate useof path loss information by considering the user’san increasing order of the measured path losstowards the cell site it is possible to improve theperformance. The analysis can be used as the basicfor development of new common radio resourceManagement (CRRM) algorithm open in long andshort term. It was concluded by observing in allthe cases; the use of path loss measure by means ofallocating the users with low path loss to CDMA(LPC) outperforms the path loss unaware and LPTcase and in TDMA performance is best at less no.of user but in CDMA best performance is for addingmore user as path loss goes down. Outage alsoreduces is also shown on applying LPC or LPT.

Sedat Atmaca, Celal Ceken, and Ismail Erturk[22] considered limited bandwidth of wireless as abiggest drawback. As the demand is growing sothere is need of capacity enhancement. Multipathand co-channel interference, limited the performanceand capacity of system. These interferences arecaused by a signal from a different cell occupyingthe same frequency band. Co-channel interferenceis the interference between two signals that operateat the same frequency. In cellular communicationthe interference is usually caused by a signal froma different cell occupying the same frequency band.Directional antennas are used for capacity enhance-ment. Time Division Multiple Access (TDMA) isemployed together with Space Division MultipleAccess (SDMA) technique. In a TDMA wirelesssystem, the transmission time (frame) is dividedinto time slots assigned to the wireless terminals(WTs) and several users share the same frequencychannel simultaneously in their own slots tocommunicate. In an SDMA system, the BS does nottransmit the signal throughout the space. Itconcentrates power in the direction of the mobileunit. This reduces the power in the directions whereother terminals are present. The same principle canbe applied for reception. In order to definedirectional antenna pattern OPNET Antenna PatternEditor is used. From the graphs it is concluded thatdirectional antenna is 10 times better than the omnidirectional antenna.


Maan et al. [24] has studied the possibility ofincreasing mobile communication cell capacitythrough merging two communication systems inone cell. They supposed that the two systems musthave interference immunity from each other, sothey may work separately in the same cell and hencethe overall cell capacity would be the sum of thetwo system’s users. The two candidates, the TDMAsystem and the WCDMA system have considered.The two basic base band systems have been builtand simulated using MATLAB. Cell capacitythrough merging two communication systems inone cell. They proposed one cell model with bothTDMA and WCDMA mobile station’s transmitters,and a base station which consists of two receivers;one for WCDMA and the other for TDMA users.This simulation has concerned with the uplinksystem only. The mobile station’s transmitters andbase station receivers have been built using MATLABSIMULINK. From the simulation results, theyconcluded that the two systems can work in onecell to increase cell capacity; but with partiallysacrificing in the two systems’ BER.

F.Thani Alami [29] discussed the admissioncontrol of a WCDMA network is a very importanttask which an operator must take into account inorder to avoid the in stability of mobile networkdue to increasing of interference level when a newmobile station appear in cell. It is based on targetload factor value fixed in dimension phase. Problemdescribed is planification and dimensioningprocesses of a WCDMA third generation multi-service network to increase the capacity. Mainobjective is studying an algorithm of admissioncontrol based on target load factor fixed in thedimensioning phase. Admission control increasesthe no. of simultaneous active user, guarantying agood quality of service and to minimize the callblocking rate.

A communication request of a new user isaccepted if it has frequency estimated less thanthreshold frequency. If estimated frequency is morethen the new call is rejected. To find value equationof load factor is used. It was concluded that withoutliberation of resource call blocking rate increasesas no. of new user increases. With the liberationdecreases with the call blocking rate of new requestin good manner.

Anupam Shukla et al. [25] described that channelsto cell in a cellular mobile communication by findingthe minimum no. of channel required obtaining an

interference free assignment. Objective is that tominimize the probability that the incoming calls areblocked, the probability that outgoing calls aredropped and also to minimize the probability thatthe carrier–to- Interference ratio of any cells belowa pre specified value.

The channel assignment scheme in general, isclassified into fixed channel assignment (FCA),Dynamic channel Assignment (DCA), HybridChannel Assignment (HCA). In FCA, a set ofchannel are permanently allocated to each cell basedon the per estimated traffic intensity. In DCA thereis no permanently allocated to each cell based onthe pre estimated traffic intensity. In DCA there isno permanent allocation of channel to cell. Thereentire set of available channel to cell is accessibleto cells and the channels are assigned on a call-by-call basis in dynamic manner. IN HCA one set ofchannels are allocated as per FCA scheme andanother set is allocated as per DCA scheme. In thispaper new algorithm by increasing the co-sitechannel interference to interference to assignminimum channel satisfy the demand constraintsand an interference free solution.

In this method Channel Separation is more forthe channels so that more channel of cells whichhave interference with the cell X can be assign andhence take minimum time for computation whencompared to other algorithm is efficient and producesresults that are very near to require bandwidth.

6. Sectoring: It is basically a technique which isused to increase the SIR without to increase incluster size. In this method cell spited is into sectorand directive antennas are used. It minimize theco-channel interference. These method are discussedhere.

Ming Zhang et al. [8] elaborated frequency reuseconcept used for the increasing the coverage area.Frequency reuse is one of the most importantconsiderations for wireless radio network planningto meet the network capacity needs and providegood grade of service.

A clover Leaf cell configuration is studied. In4 × 12 frequency review in GSM This configurationhas a unique challenge due to the fact that theantenna main beam of nearest in co-channelinterference and reduces the coverage area. Andin the conventional cell configuration dead coveragespot are found and require the use of wide beamantenna to compensate. In this paper generic cell


configuration scheme using antenna orientation atangle of 30o degree for all system is used. A novelcell configuration, Alternate Row Rotation for 4 × 12GSM reuse is proposed. In ARAR First and everyodd row of base station have antenna rotation by0° degree, i.e. 90°, 210°, 330°. Second and everyeven row of base station have antenna orientationrotation by 60° i.e. 30°, 150°, 275°. Due to the edgecoverage enhanced by neighboring sector eliminatingthe weak coverage spot issue. The configuration isbest implemented with narrow horizontal beamantenna, which reduces the co-channel interference.It has concluded that ARAR configuration resultsin better coverage and C/I.

3. DISCUSSIONThe cell planning, designing methods are proposedin these papers. These can be used as a guide linefor the designing an efficient system. The principleidea for the each method is to provide the capacityenhancement.

By using relaying in CDMA uplink; capacityimprovement can be achieved through, usingcomplicated technique to mitigate the effect of largeinterference in relay system. Automated cell planningalso served 85% final traffic by using optimizationalgorithm on Simulated Annealing [13]. In cellularrelay network (CRN) has high capacity thanconventional cellular network. It transmits the highdata rate coverage demand of system. By usingmultihop cellular network the decrease in intercellinference up to 28.7 db as compare to traditionalcellular networking also shown. The cell planning,designing methods are proposed in these papers.

By using relaying in CDMA uplink; capacityimprovement can be achieved through, usingcomplicated technique to mitigate the effect of largeinterference in relay system. Automated cellplanning also served 85% final traffic by usingoptimization algorithm on Simulated Annealing. Incellular relay network (CRN) has high capacity thanconventional cellular network. It transmits the highdata rate coverage demand of system. By usingmultihop cellular network the decrease in intercellinference up to 28.7 db as compare to traditionalcellular networking also shown. The one third oftotal interference is eliminated. Average powerconsumption is also decreased up to 23 db thantraditional network. Multihop relay has betterperformance as compared to the single hop systemtransmission having cell radius more than 1.9 K.M.

A Heuristic cell planning, Tabu Search has beenproposed with the 15% capacity improvement. Thecapacity and coverage area up to 95% proposed toenhance by spatial reuse, adaptive modulation andcoding. Using Contour based algorithm for cellPlanning the optimization increased up to 99.92%overall coverage. Femto Cell System and Rotatableequal sectoring method are also used for capacityenhancement. Also the factors like handoff, pathloss also play important role in the cell efficiency.

4. CONCLUSION AND FUTURE SCOPEThe comprehensive review shows the necessity ofoptimization and expansion of capacity to fulfill thetremendous demand of consumers. In the literaturesurvey various techniques have been studied. Thereare performance metrics like cell planning, frequencyreuse, cell splitting, cell sectoring, Handoff Strategy,propagation factors on which capacity depend. Thesemetrics are interdependent. In some technique“optimization” is discussed in literature with mainobjective function to satisfy all factors involved.Two factors, interference and handoffs are commonin all cases so these have to study properly forcellular planning. Cell Planning Method is the basicrequirement of any efficient system also it is lesscostly and more efficient than other methods. Withthe enhancement of system, quality of service (QoS)must be maintained. For the already installedsystem, the best enhancement techniques are to useoptimization algorithm, implementation of propa-gation models. These show the better efficiency andeasy to maintained.

From the comprehensive study, path lossreduction, Frequency analysis, Quality of Service,Cell Planning, Handoff, cell splitting, propagationfactors etc are concluded as performance metricshence there is a need to deep study of these forfurther capacity enhancement to fulfill the demandof users.

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