共查询到20条相似文献,搜索用时 15 毫秒
1.
As the use of mobile communications systems grows, the need arises for new and more efficient channel allocation techniques. The total number of available channels on a real-world network is in fact a scarce resource, and many assignment heuristics suffer from a clear lack of flexibility (this is the case of Fixed Channel Allocation), or from high computational and communication complexity (as with channel borrowing techniques). Performance can be improved by representing the system with an objective function whose minimum is associated with a good configuration; the various constraints appear as penalty terms in the function. The problem is thus reduced to the search for a minimum, that is often performed via heuristic algorithms like Hopfield neural networks, simulated annealing or reinforcement learning. These strategies usually require a central process to have global information and decide for all cells. We consider an objective-function formulation of the channel assignment problem that has been previously solved by search heuristics; we prove that the search time for the global minimum of the objective function is O(nlogn), and therefore there is no need for search techniques. Finally we show that the algorithm that arises from this formulation can be modified so that global knowledge and synchronization are no longer required, and we give its distributed version. By simulating a cellular network with mobile hosts on a hexagonal cell pattern with uniform call distribution, we show that our technique actually performs better than the best known algorithms. 相似文献
2.
The conventional approach of hybrid channel assignment strategy in cellular networks is rather inefficient due to the fact that it does not take advantage of the FCA scheme to the extreme. In this paper, we divide a cell into two parts: inner cell region and outer cell region, and apply the dynamic channel assignment and the fixed channel assignment schemes to the inner region and out region, respectively, in an attempt to fully utilize the strengths of the channel assignment schemes. In the performance evaluation, we demonstrate that the channel reuse efficiency has been improved compared to the FCA and DCA schemes. We also calculate the probability of an intracell handoff due to the use of the space partitioning. The proposed scheme can be adapted to a multi-tier structure with high/low speed mobile users, and hot spots. 相似文献
3.
4.
A mathematical model that predicts the dynamic flows in cellular mobile networks that allocate channels using the Borrowing Channel Assignment (BCA) scheme is described in this paper. Two types of handoff procedures – the prioritized and non-prioritized schemes – will be considered in the model. Discrete event simulations were performed and the results were found to be comparable to the results obtained using the mathematical model. Application to comparative study of the dynamic behaviours of the BCA and the Fixed Channel Assignment (FCA) schemes is also presented. 相似文献
5.
6.
7.
8.
We define a cellular assignment graph to model the channel assignment problem in a cellular network where overlapping cell segments are included in the model. Our main result is the Capacity-Demand Theorem which shows a channel assignment function is always possible unless there is a connected subregion of cells and overlap segments containing more channel requests then the total capacity of all transceivers within or on the boundary of the subregion and covering any part of the subregion with an overlapping segment. We further describe the simplicity and regularity of our proposed cellular assignment graphs and their accessibility for simulation and theoretical investigation without artifacts from the overall geographical region boundaries. 相似文献
9.
该文根据无线Mesh网络流量呈现树状拓扑汇聚的特点提出基于拓扑分割的信道分配策略。依据无线干扰对不同链路的影响程度,把无线干扰分类为有确定方向的纵向干扰和横向干扰;提出沿着纵向干扰方向逐跳分割网络拓扑算法;提出最少信道隔离纵向干扰和为吞吐量最小的子拓扑增加信道的子拓扑间信道分配策略;提出横向干扰分块的子拓扑内信道使用方法;理论分析子拓扑内的冲突域及网络性能瓶颈,仿真研究子拓扑的吞吐性能及信道分配顺序。仿真结果表明,隔离纵向干扰和增加信道的分配策略能够有效保证和提升网络吞吐量,横向干扰分块的方法优于802.11s中定义的公共信道框架多信道机制。 相似文献
10.
11.
本文提出一种新的动态信道分配策略,称之为分级紧致的动态信道分配(CCDCA),所谓分级就是基于引入的"冷态"和"热态"的概念,将小区所处的状态分为冷态与热态;所谓紧致就是对处于不同状态的小区给出不同的紧致模型.该策略在对"热态"的处理过程中利用了"冷态"的先验信息,有机地结合了局部信息与整体信息,同时能保证小区间有较小的服务偏差,提高了整个系统的服务质量.文中还从理论上给出了冷、热态阈值的分析模型,计算出了模型的主要参数,该模型也可以用来分析系统性能.仿真结果证明该方案有较小的呼阻率和较高的频谱利用率,所提出的模型比较接近实际系统. 相似文献
12.
13.
Peter Han Joo Chong 《中国电子科技》2008,6(3):257-263
In this paper, we propose a clustered multihop cellular network (cMCN) architecture and study its performance using fixed channel assignment (FCA) scheme for uplink transmission. The proposed cMCN using FCA can be applied with some reuse factors. An analytical model based on Markov chain is developed to analyze its performance and validated through computer simulation. And then, we implement direct peer-to-peer communication (DC) in cMCN by considering more reasonable conditions in practice. DC means that two calls communicate directly instead of going through base stations. The results show that cMCN with FCA can reduce the call blocking probability significantly as compared with the traditional single-hop cellular networks with FCA and can be further reduced by using DC. 相似文献
14.
在对信道分配问题分析的基础上,给出数学模型,将此问题转化为带约束的优化问题,并通过设计遗传算法的个体编码方式,适应度函数、遗传算子实现了移动通信中的信道分配问题的优化。 相似文献
15.
In cellular communications, one of the main research issues is how to achieve optimum system capacity with limited frequency
spectrum. For many years, researchers have proposed and studied many dynamic channel assignment (DCA) schemes to increase
the capacity of cellular systems. Another proposed technique, Reuse Partitioning (RP), is used to achieve higher capacity
by reducing the overall reuse distance. In convention, when RP is exploited in network-based DCA, a portion of channels will
be assigned permanently to each partitioned region. However, the number of channels assigned to each region may not be~optimum
due to factors like the uneven and time-varying traffics. In this paper, a new network-based DCA scheme is proposed with the
flexible use of RP technique, named as flexible dynamic reuse partitioning with interference information (FDRP-WI). In this
scheme, channels are open to all incoming calls and no channel pre-allocation for each region is required. As long as the
channel assignment satisfies the co-channel interference constraints, any user from any region can use any channel. The scheme
aims to minimize the effect of assigned channels on the availability of channels for use in the interfering cells and to reduce
overall reuse distance. Both FDRP-WI with stationary users and mobile users are investigated. Simulation results have confirmed
the effectiveness of FDRP-WI scheme. In the case with stationary users, FDRP-WI exhibits outstanding performance in improving
the system capacity under both uniform and non-uniform traffic distributions. Under the uniform traffic case, the scheme can
provide over 100% capacity improvement as compared to conventional fixed channel assignment scheme with 70 system channels
at 1% blocking probability. In the case with mobile users, the impact of mobility on the new call probability, P
b, and the call dropping probability, P
d, is evaluated. The effect on system capacity of reserving some channels for handoff calls is first studied. Then, we propose
a new handoff scheme, called “Reverse Overflow” (RO), to improve the utilization of channels with smaller reuse distances
under mobile environment. Simulation results show that, with RO handoff, the system capacity of FDRP-WI is effectively improved
at the expense of higher handoff rates in the cellular system. 相似文献
16.
17.
基于混沌神经网络的移动通信信道分配方法研究 总被引:2,自引:0,他引:2
该文应用混沌神经网络求解信道分配问题,给出了信道分配的能量函数表达式和混沌神经网络模型,研究了判别混沌神经网络混沌特性的Lyapunov指数法,讨论了网络模型参数对网络混沌特性的影响,提出了基于混沌神经网络的信道分配算法.仿真结果表明,混沌神经网络具有复杂的瞬态混沌特性,它比Hopfield网络具有更强的搜索全局最优解的能力,和更快的收敛速度. 相似文献
18.
Kotrotsos S. Kotsakis G. Demestichas P. Tzifa E. Demesticha V. Anagnostou M. 《Wireless Personal Communications》2001,18(3):289-317
The frequency assignment problem will maintain its importance for several years, since future versions of legacy cellular systems, e.g., those of GSM, will continue to exist. This paper elaborates on an interference-oriented version of the frequency assignment problem. The objective function is associated with the interference levels that are imposed by the frequency allocation, while the constraints are related to the allocation of the frequencies required in each cell and the prevention of some unacceptable interference situations. The problem is formally stated, mathematically formulated and solved by means of computationally efficient heuristics. Finally, results are obtained and concluding remarks are made. 相似文献
19.
20.
本文介绍了蜂窝移动通信系统中一种新的动态信道指配策略──基于紧凑模式的信道借用指配策略(CPCB).这种策略不仅具有基于紧凑模式的动态信道指配的优点,而且具有固定信道指配策略中信道借用的优点.作者将新算法在一种普遍采用的49个蜂窝的蜂窝通信网络上进行了仿真,分别对几种均匀和非均匀模式的业务分布情况进行了比较,结果表明:CPCB的系统平均阻塞率低于FCA、BDCL、基于CP的DCA和CPMCB等,而且随着负载的增加,其系统平均阻塞率的增长速率也明显低于上述各种策略. 相似文献