Umts air

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UMTS Air Interface Voice/Data Capacity - Part 1: Reverse Link Analysis
Qinqing Zhang, On-Ching Yue Bell Laboratories, Lucent Technologies Holmdel, NJ 07733 ainaing;@,lucentcom . oyue@lucent.com
there are no slots as defined in a conventional frequencydivision or time-division multiple access system. As a result, there is no hard blocking because of limited number of slots. The capacity ornumber of users supported in a CDMA system depends on system resource, such as total bandwidth, data rate, interference limits, power limits, etc. In this paper, we use the socalled "lost call held" (LCH) model as described in [2] to determine the occupancy distribution, and evaluate the capacity of UMTS/WCDMA systems based on system outage conditions. We present our analflcal and simulation models forthe reverse l n only. The analysis on the forward link is ik presented in a sequential paper [3]. In our reverse link analysis, we build an enhanced system model by considering different varying factors, such as imperfect power control, intra-cell and inter-cell interference level. Specifically, we propose a new approach to model the inter-cell interference under multiple cell condition.Furthermore, we apply different approximation methods to estimate capacity based on voice and/or data traffic loading. Finally, we derive close form expressions of Erlang capacity for a single type of traffic and mixed types of traffic. We also develop a static system level simulator to evaluate capacity and coverage for UMTS. We compare our analytical results with simulations and show that our analyticalapproach has a very good match with simulations. The paper is organized as follows. Section 2 presents the analytical models for single type of users (voice or circuit switched data users), and mixed voice and data users. System level simulation and assumptions are described in section 3. Section 4 compares our analytical ih results wt simulations. Section 5 is the conclusion.

AbstractUniversal Mobile Telecommunication Sycstem ( U M E ) can offer large voice capacity for voice service and support high-speed data for internet access and multimedia services. In this paper. we evaluate the air interface capacity for voice, data, integrated voice and data services in UMTS. We present our analytical and simulation models for the reverse link only. In our analytical model, differentvarying factors in a CDMA system are considered, such as the interference level, power control errors, soft hundof,' required signul-tointerference ratio for diferent rates, etc. We propose a new approach to model the inter-cell interjerence under multiple cell condition. Furthermore, we apply different approximation methods to calculate capacity based on voice and/or data tra#ic loading. Finally, wederive close form expressions of Erlang capacity fbr a single fYPe of trafjc and mixed types ojtraflc. We also develop a static system level simulator to evaluate capacity and coverage for UMTS. By comparing our analytical results with simulations, we show that our analytical approach has a very good match with simulations.

1

Introduction

The traditional queuing analysis has been widelyperformed for wired telephone traffic in a slotted multiple access network [l]. The capacity is limited by the availability of slots, or servers, and is a function of the probability of a user getting blocked. In CDMA spread spectrum systems, since all users occupy the same frequency spectrum and share the same time allocation,

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2

Analytical model for reverse links

Inter-cell interference modeling

The CDh4.4 system is strictly interference limited. On reverse link, many mobiles access to one base station. For one particular mobile, the total received noise plus interferencepower at...
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