共查询到20条相似文献,搜索用时 93 毫秒
1.
本文对复制理论在编码与扩频序列设计中的应用等问题进行了深入的研究.第二部分简要介绍了信号的复制理论.在第三部分提出了一种新的OVSF码的设计算法,从而在理论上解释了OVSF码的生成过程,即OVSF码可以通过复制信息的变化,利用复制方法得到.在第四部分里,我们利用m序列所具有的移位可加性,提出了一个在不知道本原多项式情况下生成GF(2)上全部n级m序列的算法,丰富了扩频序列设计方法. 相似文献
2.
本文在介绍了OVSF码生成算法及属性的基础上,详细讨论了目前国际上较成熟的几种动态OVSF码分配算法,并对各算法的产生背景及特性进行了比较分析。 相似文献
3.
OVSF码是广泛用于第三代移动通信的信道化码。本文简要介绍了OVSF码的生成原理,提出了一种适用于WCDMA系统的OVSF码产生算法并用FPGA实现之。该方法实现简单,占用极小的系统资源,具有较强的实用价值。 相似文献
4.
介绍了现有的两种OVSF多码分配算法,并通过计算机仿真考察了它们在吞吐量、和阻塞率等指标上的性能。仿真结果表明,快速算法和传输所专利算法在吞吐量和阻塞率上的表现一样,但是快速算法更加快速、简单。因此快速算法可广泛应用于以OVSF码作为信道化码的各种DS-CDMA系统中。 相似文献
5.
WCDMA系统的信道码分配策略 总被引:1,自引:0,他引:1
第三代移动通信系统WCDMA支持多业务、多QoS的传输,能更好地利用信道码的分配策略。3GPPWCD-MA标准采用的正交可变长扩频码(OVSF)支持变速率业务,举例说明了一种可行的信道码动态分配方案。 相似文献
6.
提出1种为每类呼叫预留资源的信道化码分配算法。将新算法与已有的单一分区法、混合分区法1、混合分区法2等保留算法进行比较,计算机仿真表明,分区借码法在公平性和码阻塞率方面最好,是公平和吞吐量最好的保留算法。该算法简单、有效和公平,可应用于以OVSF码作为信道化码的各种DS-CDMA系统。 相似文献
7.
8.
9.
随着移动通信技术的发展,多媒体信息的传输是必然的趋势。WCDMA是第三代移动通信IMT 2000中的主流技术,他支持多媒体从低速率到高速率的多种业务。每种业务有不同的地址码,为了防止各种数据业务的干扰,地址码必须具有正交的特性。由于速率不同,而扩频后的带宽是固定的,为了满足信道的传输,就采用了不同长度的正交码(OVSF)。介绍了OVSF码在WCDMA中的使用,并讨论了OVSF码在WCDMA下行链路分配的几种算法,容量门限法更接近实际情形,能有效降低码阻塞率,保证实时传输。 相似文献
10.
11.
Scheduling algorithms for shared fiber-delay-line optical packet Switches-part I: the single-stage case 总被引:1,自引:0,他引:1
In all-optical packet switching, packets may arrive at an optical switch in an uncoordinated fashion. When contention occurs, fiber delay lines (FDLs) are needed to delay (buffer) the packets that have lost the contention to some future time slots for the desired output ports. There have been several optical-buffered switch architectures and FDL assignment algorithms proposed in the literature. However, most of them either have high implementation complexity or fail to schedule in advance departure time for the delayed packets. This paper studies the packet scheduling algorithms for the single-stage shared-FDL optical packet switch. Three new FDL assignment algorithms are proposed, namely sequential FDL assignment (SEFA), multicell FDL assignment (MUFA), and parallel iterative FDL assignment (PIFA) algorithms for the switch. The proposed algorithms can make FDLs and output-port reservation so as to schedule departure time for packets. Owing to FDL and/or output-port conflicts, the packets that fail to be scheduled are discarded before entering the switch so that they do not occupy any FDL resources. It is shown by simulation that with these algorithms, the optical-buffered switch can achieve a loss rate of /spl sim/10/sup -7/ even at the load of 0.9. These algorithms are extended to the three-stage Clos-Network optical packet switches in the companion paper. 相似文献
12.
Qiu X. Chawla K. Chuang J.C.-I. Sollenberger N. 《Selected Areas in Communications, IEEE Journal on》2001,19(7):1222-1234
We propose a framework for network-assisted radio resource management in wireless data networks. This type of radio resource management techniques offer implementation and capacity benefits compared to conventional, interference-measurement based, dynamic channel assignment (DCA) algorithms. The basic idea is to use interbase signaling to shift most of the burden of the resource allocation from the air interface to the backbone infrastructure. By exchanging channel assignment as well as other relevant information in real time through the backbone network, each base can calculate the impact of a resource assignment on the system. As a result, rapid interference measurements, which are typically needed to implement DCA schemes, are replaced by a limited amount of path loss measurements and the computation of interference conditions by the base stations. This significantly reduces the measurement and over-the-air signaling requirements, and can also provide an opportunity for a better optimization of the system performance. We focus on two specific algorithms: network-assisted least-interference-based dynamic packet assignment (NA-LI-DPA) and network-assisted dynamic packet assignment with throughput optimization (NA-DPA). NA-LI-DPA closely resembles a least-interference-based dynamic channel assignment algorithm, and NA-DPA attempts to further improve the overall system throughput. The algorithms, as defined, are appropriate for a best-effort data service, where the primary goal is to provide a higher throughput. However, it will be clear from the discussion that it is also feasible to alter the algorithms to optimize performance metrics other than throughput, e.g., to ensure a certain quality of service. We show through simulation that, for a system like enhanced general packet radio service (EGPRS) system, NA-DPA can provide a throughput that is 50% higher than random packet assignment, and 25% higher than that obtained by conventional DCA algorithms 相似文献
13.
14.
In all-optical packet switching, packets may arrive at an optical switch in an uncoordinated fashion. To prevent packet loss in the switch, fiber delay lines (FDLs) are used as optical buffers to store optical packets. However, assigning FDLs to the arrival packets to achieve high throughput, low delay, and low loss rate is not a trivial task. In the authors' companion paper, several efficient scheduling algorithms were proposed for single-stage shared-FDL optical packet switches (OPSs). To further enhance the switch's scalability, this work was extended to a multistage case. In this paper, two scheduling algorithms are proposed: 1) sequential FDL assignment and 2) multicell FDL assignment algorithms for a three-stage optical Clos-Network switch (OCNS). The paper shows by simulation that a three-stage OCNS with these FDL assignment algorithms can achieve satisfactory performance. 相似文献
15.
Younghwan Yoo Sanghyun Ahn Chong Sang Kim 《Selected Areas in Communications, IEEE Journal on》2003,21(8):1263-1273
In most existing studies of wavelength-division multiplexing networks, the problems of routing and wavelength assignment are generally treated separately, since it is NP-complete to produce the optimal solutions for the two problems at the same time. The four presented adaptive routing algorithms, however, consider the availability of wavelengths during the routing process. Our algorithms favor paths with the near-maximum number of available wavelengths between two nodes, resulting in improved load balancing. Simulations show that our algorithms reduce call blocking by nearly half when compared with the least-loaded and the k-fixed routing algorithms in some small networks using the first-fit wavelength assignment policy. In addition, simulation and analysis show that the path length of our algorithms is almost the same as those of the other algorithms. 相似文献
16.
17.
18.
Channel assignment in cellular radio networks 总被引:8,自引:0,他引:8
The authors investigate algorithms based on simulated annealing to solve the channel assignment problem for cellular radio networks. The blocking probability of a network is chosen as the optimization criterion. In order to check the quality of the solutions obtained by simulated annealing, they examine some special types of networks which allow an effective calculation of optimal solutions by tailored algorithms. Their investigations show that simulated annealing is a very powerful tool for solving channel assignment problems 相似文献
19.
Routing and wavelength assignment of scheduled lightpath demands 总被引:4,自引:0,他引:4
Kuri J. Puech N. Gagnaire M. Dotaro E. Douville R. 《Selected Areas in Communications, IEEE Journal on》2003,21(8):1231-1240
We present algorithms that compute the routing and wavelength assignment (RWA) for scheduled lightpath demands in a wavelength-switching mesh network without wavelength conversion functionality. Scheduled lightpath demands are connection demands for which the setup and teardown times are known in advance. We formulate separately the routing problem and the wavelength assignment problem as spatio-temporal combinatorial optimization problems. For the former, we propose a branch and bound algorithm for exact resolution and an alternative tabu search algorithm for approximate resolution. A generalized graph coloring approach is used to solve the wavelength assignment problem. We compared the proposed algorithms to an RWA algorithm that sequentially computes the route and wavelength assignment for the scheduled lightpath demands. 相似文献
20.
Dynamic channel assignment, adapting both to traffic variations as well as to changing mobile locations, is investigated. Several ad hoc schemes of this type have been described in the literature and found to yield interesting performance improvements. However, very little is known about the performance of the optimum assignment schemes. Both upper and lower bounds for the performance of optimum algorithms within the class of reuse-type dynamic channel assignment (DCA) for a simple propagation model are established. The authors focus on the asymptotic performance, i.e., the performance in systems with large traffic loads. As a performance measure, the probability of assignment failure (intracell handoff failure) is used. Results show that the capacity one may expect to achieve with these algorithms in the asymptotic case is just above twice the capacity of a fixed channel allocation scheme 相似文献