Performance evaluation of multimedia mobile communication networks based on chip-level traffic volume

提出了一种用于DS-CDMA系统的动态扩频码重新分配方案，称为RDA(Region DivisionAssignment)，通过重构码树来缓解码阻塞问题，从而有效地为所有支持的速率提供服务。我们比较了RDA与传统的OVSF码分配方案(COV)和动态OVSF码分配方案(DCA)的性能。计算机仿真结果表明，在大流量条件下，RDA的阻塞率低于DCA。仿真结果还表明，DCA算法的计算时间明显大于RDA算法。此外，RDA能够同时处理比DCA多得多的语音源。讨论了具有蜂窝结构的TDMA和W-CDMA频谱共享系统(TDMA/W-CDMA覆盖系统)的共存。在该系统中，两个系统共享相同的频段，以提高频谱效率。对存在AWGN信道的前向(下行)链路的误码率和频谱效率进行了计算。考虑到路径损耗和阴影衰落损耗，采用干扰消除(IC)的W-CDMA系统在频谱效率上与基于单一多址系统(如TDMA系统或W-CDMA系统)的频谱效率有很大差异。干扰消除可以显著提高频谱覆盖系统的误码率，通过仿真研究了新的呼叫信道限制方案(NCCL)分析模型的有效性。NCCL使用参数α限制新呼叫访问总信道，而切换呼叫不限制访问总信道。重点研究了用户移动性和参数α对与低移动性用户仿真模型匹配良好的新切换阻塞率的影响。

We proposed a dynamic reassignment scheme of spreading codes for DS-CDMA systems so called RDA (Region Division Assignment) by reconstructing the code tree to mitigate the code blocking problem in order to efficiently provide the services for all supported rates. We compare the performance of the RDA with the conventional OVSF-code assignment scheme (CONV), and the dynamic OVSF-code assignment scheme (DCA). The computer simulation results show that the blocking probability of RDA is lower than that of DCA under the heavy traffic condition. The simulation results also show that the calculation time of DCA is significantly larger than that of RDA. Furthermore, RDA is shown to be able to simultaneously handle much more voice sources than DCA.The co-existence of TDMA and W-CDMA spectrum sharing system (TDMA/W-CDMA overlaid system) with cellular architecture is discussed. In this system, both systems share the same frequency band to improve the spectrum efficiency. BER and spectrum efficiency of the system are calculated for the forward link (down-link) in the presence of AWGN channel. Taking into account the path loss and shadow fading loss, W-CDMA applying interference cancellation (IC) shows a substantial difference in spectrum efficiency than a single multiple access-based system such as TDMA system or W-CDMA system. The interference cancellation can significantly improve BER of the spectrum overlaid system.We investigate the validity of the analytical model of new call channel limiting scheme (NCCL) by means of simulation. NCCL limits new calls to access the total channels with parameter α while handover calls have no restriction to access the channels. We focus on the effects of users' mobility and the parameter α on the blocking probabilities of new and handover good match to the simulation model for low mobility users.