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Study on the Suppression Technology of Crossed Time Slot Interference in TD-SCDMA System

Author: JinTao
Tutor: ShiWenXiao
School: Jilin University
Course: Communication and Information System
Keywords: TD-SCDMA Crossed Time Slot Interference Dynamic Channel Allocation Cell Clusters
CLC: TN929.533
Type: Master's thesis
Year: 2009
Downloads: 184
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Abstract

1. IntroductionTD-SCDMA is an independent intellectual property rights of third-generation mobile communications (3G) standards, which is proposed by Chinese former Ministry of Information Industry Telecommunications Institute of Science and Technology (now the Datang Telecom Group) in accordance with the result of years of research. It is one of the mainstream 3G standard that is approved by International Telecommunication Union (ITU). TDD mode is used in TD-SCDMA, which is suitable for dynamic channel allocation (DCA) technology to implement.The main task of slow dynamic channel allocation techniques is to minimize the loss of the system caused by the asymmetry of services, enhance the capacity of the system, get the best spectrum efficiency through allocating the time slot of uplink and downlink reasonablely.In 3G mobile conmmunication systems, main services are multimedia data services, of which the traffic is seriously asymmetric between uplink and downlink. If the same time slot allocation approach is adopted, the cell will generate a one-way limited resources which will obviously result in loss of system capacity when the cell and its neighbour cells are at the full-load state with serious asymmetric services of uplink and downlink; If the time slot allocation is according to their own services, the one-way limited resources can cause minimum loss, but will bring crossed time slot interference in neighbour cells which makes the loss of the system capacity. Considering all the factors above, a dynamic allocation of resources is used to maximize the capacity of the system.After the study on the DCA algorithmic that is at home and abroad and the features of TD-SCDMA, the paper researches on the strategy of DCA that is suitable for TD-SCDMA. Aiming at overcoming the shortages of the current slow dynamic channel allocation algorithm in TD-SCDMA system, the paper proposes a highly efficient and practical slow dynamic channel allocation algorithm through a quantitative two-cell model which analyses crossed time slot interference on the system. The algorithm derives a multi-cell system model through the way that the hot cells are continuously derived to resolve the discriminant and expansion problem of the hot cell clusters, and increases the system capacity.2. Analyse Crossed Time Slot interferenceLiterature [67-69] have shown that crossed time slot interference especially in the base station-base station seriously affects the quality of communication, which makes crossed time slot in the uplink not work practically. Aiming at overcoming the crossed time slot interference through slow dynamic channel allocation algorithm, quantitative analysis should be taken to estimate the impact on the two-cell model to guarantee the accuracy of slow DCA algorithm.Based on the relevant research at home and abroad, this paper deduces three SNR formulas for crossed time slot interference and the same uplink or the same downlink slot interference in two-cell model with more comprehensive parameters. The paper analyses the capacity of single-cell and multi-cell system capacity through SNR. Through the above derivation, we can quantitatively analyses the impact of crossed time slot interference at a certain parameter conditions, so as to get the capacity changes of multi-cell system in TD-SCDMA and provide a more precise theoretical data for slow DCA algorithm.3. Slow DCA algorithm of TD-SCDMA systemLiterature [15] proposed a hot cell algorithm, which easily provides that cells in the 7,19,31 cell clusters obey the channel allocation of the center cell, in order to eliminate crossed time slot interference on the capacity loss of cell clusters. After the hot cell algorithm is proposed, there is not been any report of substantive breakthroughs on the slow dynamic channel allocation algorithm. Literature [38] proposed that use the condition which non-hot cell in two-cell model whether or not obey the channel allocation of the hot cell to improve the hot cell algorithm in seven-cell clusters model. But the algorithm is simply apply a two-cell model criterion directly to the multi-cell model. and the theory is incomplete. It fails to resolve the discriminant and expansion problem of the hot cell clusters.Aiming at overcoming various shortages of the current slow dynamic channel allocation algorithms, a highly efficient and practical slow dynamic channel allocation algorithm is proposed with the name of hot cell clusters derived algorithm. The algorithm derives a multi-cell system model through the way that the hot cells are continuously derived. At the same time, the criterion that non-hot cell whether or not obey the channel allocation of the hot cell through the cell derived method rational used in multi-cell system to resolve the discriminant and expansion problem of the hot cell clusters, and to improve the system capacity.Assume that there are M cells in multi-cell system. The algorithm derives a multi-cell system model through the way that the hot cells are continuously step-by-step derived. For the expanding hot cell clusters system, the Nth expansion of the cell will maximize the system capacity of the sum of N cells. Thus when the expansion is finished, we can get the maximum of the system capacity which is composed of K hot cells clusters and the edge of it. (K = <M, K value is related to the selection of the hot cell threshold. When the threshold is 0, K = M, all of the cells in the system are subject to the allocation of hot cell cluster algorithm, but it will improve computation.) As for the other cells which are neither hot cell nor hot edge cell, slot allocation can be in accordance with the service. Thus the hot cell clusters derived algorithm achieves the target that the capacity of multi-cell system is maximum.This paper uses C language to set up the simulation platform. aiming at TD-SCDMA different volume of business expectations and the ratio of business expectations business to simulate. A simulation has been conducted to compare the universality and advantages and disadvantages for no hot cell algorithm, hot cell algorithm and hot cell clusters derived algorithm. The simulation results show that, the hot cell clusters derived algorithm has better adaptability for distribution of different service model compared to the hot cell algorithm, the system resource utilization increasesed significantly.Through the algorithm description and simulation results it can be seen that the allocation of hot cell algorithm and some improved scheme of it are special cases of hot cell clusters derived algorithm. So hot cell clusters derived algorithm can highly improve capacity of the cell system whose service is changing.4.ConclusionAfter the study on the DCA algorithmic that is at home and abroad and the features of TD-SCDMA,the paper researches on the strategy of DCA that is suitable for TD-SCDMA.Excellent DCA technology especially slow DCA can effectively inhibited the loss cause by crossed time slot interference.Aiming at overcoming the shortages of the current slow dynamic channel allocation algorithm in TD-SCDMA system, the paper quantitatively analyses the impact on the system in the two-cell model, and proposes a highly efficient and practical slow dynamic channel allocation algorithm with the name of hot cell clusters derived algorithm. The algorithm derives a multi-cell system model through the way that the hot cells are continuously derived to resolve the discriminant and expansion problem of the hot cell clusters, and increases the capacity of system.The simulation results show that in the different service distribution model, hot cell clusters derived algorithm has better adaptability, improves the capacity and the performance of the system to protect the quality of service. Certainly the results of this paper are provided for the further research on the slow DCA in TD-SCDMA.

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