Performance Analysis of a DS-CDMA Cellular System with Cell Splitting into Macrocell and Microcell Architecture (original) (raw)

Reverse link capacity analysis of a CDMA cellular system with mixed cell sizes

IEEE Transactions on Vehicular Technology, 2000

The demands for mobile communication services are growing rapidly. In heavily populated areas, cell splits are unavoidable to increase the capacity of the cellular system. Cell splitting makes a cellular system have mixed cell sizes. For cell planning, it is necessary to analyze the reverse link capacity of a code-division multiple-access (CDMA) cellular system with mixed cell sizes. In this paper, we propose a method to calculate the reverse link capacity of a CDMA cellular system with mixed cell sizes. When a macro cell is split into three micro cells, as an example, we calculate the reverse link capacities for the three micro cells and the neighboring macro cells. The results show that as the radius of a micro cell decreases, the reverse link capacity of the micro cell increases, while those of the neighboring macro cells decrease.

Capacity evaluation for CDMA cellular systems

Proceedings IEEE INFOCOM 2001. Conference on Computer Communications. Twentieth Annual Joint Conference of the IEEE Computer and Communications Society (Cat. No.01CH37213)

In this paper, we find bounds and approximations for the capacity of mobile cellular communication networks based on Code Division Multiple Access (CDMA). We develop efficient analytic techniques for capacity calculations of CDMA cellular networks. Each cell is modeled as an independent Å ½ queue and traffic capacity assessed based on the maximum Erlang traffic that leads to acceptable link quality with high probability. Subsequently, approximations and bounds for the outage probability and hence traffic capacity are obtained using Asymptotic Expansions and Large Deviations Theory. Numerical examples, considering uniform and Normalized Truncated Gaussian user density in the system are evaluated. The propagation model we consider takes care of distance and lognormal shadowing losses.

Effects of interference on capacity in multi-cell CDMA networks

Journal of Systemics, Cybernetics …, 2006

An overwhelming number of models in the literature use average interference for calculation of capacity of a CDMA network. In this paper, we calculate the actual per-user interference and analyze the effect of user-distribution on the capacity of a CDMA network. We show that even though the capacity obtained using average interference is a good approximation to the capacity calculated using actual interference for a uniform user distribution, the deviation can be tremendously large for nonuniform user distributions. We also present an analytical model for approximating the user distributions using 2-dimensional Gaussian distributions by determining the means and the standard deviations of the distributions for every cell. This allows us to calculate the inter-cell interference and the reverse-link capacity of the network. We compare our model with simulation results and show that it is fast and accurate enough to be used efficiently in the planning process of large CDMA networks.

Interference-based capacity analysis in CDMA cellular systems

2003 IEEE Wireless Communications and Networking, 2003. WCNC 2003.

In multiple cellular CDMA systems, the channel capacity heavily depends upon the interference caused by the signal power of other users. In this paper, we exactly quantify the cell capacity by focusing on not only the number of users but also the location of active users. To inspect the effect of multicell CDMA environments, we model three 1/6 cells divided by 60 • sector antennas and analyze the increased interference when a user is added to the unit of cell. Based on the capacity analysis, we propose a new call admission control scheme that uses the location information of users. Whenever a new user arrives, our scheme checks whether the admittance of that user can occur within the cell capacity. If the user is far away from the base station, it will have less chance of acceptance because it creates more interference, resulting in reduced capacity. Our scheme allows more users to enter the network if they generate less interference. Therefore it has the effect of increased system capacity without sacrificing the QoS of all the other active users. Through simulations we show that the performance is improved by 10 to 20% in terms of the number of active users that can be accomodated.

Outage and capacity analysis of cellular CDMA with admission control

2002

We analyze the outage and capacity performance of an interference based admission control strategy in cellular CDMA systems. Most approaches to estimate the outage probability and the system capacity of CDMA systems in the literature do not take interference based admission control into account. In this paper, we present an analytical model to evaluate the outage probability and the capacity on the reverse link of cellular CDMA systems with interference based admission control. We make two main approximations in the outage analysis -one based on the central limit theorem (CLT) and the other based on the Chernoff bound (CB). We also obtain an improved approximation to the outage probability using Edgeworth expansion. It is shown that the considered admission control policy results in increased system capacity compared to that with no admission control, by about 30% for an outage probability of 0.01.

On the capacity modeling of multi-hop cellular packet CDMA networks

2001 MILCOM Proceedings Communications for Network-Centric Operations: Creating the Information Force (Cat. No.01CH37277)

Wireless multihop networks with cellular structure have the potential to support high data rate traffic at a reasonable degree of implementation complexity. We consider a cellular network architecture composed of base stations, routers, and terminals and focus on its throughput modeling. Simply adding routers to the current cellular networks may not improve the throughput, since relaying the packets by routers may generate the same amount of interference at receivers. We derive a closed form formula for the probability density function of interference at each receiver and compare the numerical and simulation results for different path loss parameters.

Performance Study and System Capacity Analysis of a Two-Tier Cdma System

International Conference on Aerospace Sciences & Aviation Technology, 2007

One of the main factors that affects the performance of a Code Division Multiple Access (CDMA) system is the out of-cell interference. While the in-cell interference is controlled within each cell using a power control algorithm, the out of-cell interference is not and can greatly impact network coverage and the total user capacity, so that CDMA capacity is an interference limited capacity. One design technique to reduce the effect of the out of-cell interference in cellular CDMA systems is to use cells of different radii, hierarchically organized in overlapping layers, this is the multitier system. In This paper the user capacity on the reverse link direction of a certain two-tier CDMA system that consists of a small microcell embedded in a larger macrocell, i.e. a two cell system is examined. The effect of the users' mobility on the call blocking and call dropping probabilities is examined depending on the system feasibility. The simulation results show that at different call arrival rates the system capacity is increased as compared with the previous work. The dominant parameters affecting the system performance are the users' velocity and the distance between the two cells.

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.

Blocking Probability of a DS-CDMA Multi-Hop Virtual Cellular Network

IEICE Transactions on Fundamentals of Electronics, Communications and Computer Sciences, 2006

A wireless multi-hop virtual cellular network (VCN) was recently proposed to avoid the large peak transmit power, resulting from the high transmission rates expected for future mobile communication systems. In VCN, calls hop through several links to reach the central port, which is the gateway to the network. With the use of a routing algorithm based on the total uplink transmit power minimization criterion, the total transmit power of all the multi-hop links between the mobile terminal and the central port can be significantly reduced, in comparison with the present (single-hop) cellular network. In this paper, an "on-demand" channel assignment strategy, using the channel segregation dynamic channel allocation (CS-DCA) algorithm, is proposed for multi-hop DS-CDMA VCN. Computer simulation is conducted to evaluate the blocking probability performance and make a comparison between the VCN and the present cellular network.

Effects of user mobility on the capacity of a CDMA cellular network

European Transactions on Telecommunications, 1996

In the recent technical literature on cellular networks Code Division Multiple Access (CDMA) has received a large attention as a promising radio interface access technique. Many studies. are devoted to the capacity evaluation of the radio interface adopting CDMA, but seemingly none of them accounts for the variability of the user spatial density due to user mobility. This should be a concern especially in a microcellular environment, where it cannot be relied upon a significant spatial avera'ge over the radio coverage area of a Base Station. The major aim of this work is a preliminary assessment of the effects of "bursty" user mobility on the capacity of the CDMA radio interface. To this end. we introduce a user mobility model apt to describe large fluctuations of the number of users in a radio cell area. A reference model of a CDMA network is used to evaluate the effects of user mobility on the capacity for a wide range of the model parameters, by means of simulations accounting for shadowing, call attempt process, voice activity and antenna directivity and assuming perfect power control. We show that user mobility can remarkably affect the CDMA capacity, mainly because of the resulting highly bursty behaviour of self-noise. A simple traffic control scheme is devised to increase the capacity of the CDMA network, under a joint constraint on link availability, call blocking and call dropping probabilities. It is pointed out that the concepts introduced in this paper are independent of the specific CDMA implementation, i.e. they hold for any asynchronous CDMA based cellular network.