蜂窝移动通信中一种分级紧致的动态信道分配方案

本文提出一种分级紧致的动态信道分配（CCDCA）方案。文中首先根据信道使用情况与业务量的关系，将小区分成“冷态”和“热态”，并给出了相应的阈值，然后在对“热态”的处理过程中利用“冷态”的先验信息，对不同状态的小区给出了不同的紧致措施。该方案还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。文中还根据冷、热态的特点构造了一个二维马尔科夫链模型，计算出了模型的主要参数；其思想可用于分析多种信道分配问题。仿真结果证明CCDCA方案有较小的呼阻率和较高的频谱利用率。     

A channel assignment algorithm via conflict shifting for distributed cognitive networks

Channel assignment is a challenge for distributed cognitive networks due to spectrum mobility and lack of centralized entity. We present a dynamic and efficient algorithm via conflict shifting, referred as Shifting-based Channel Assignment (SCA). In this algorithm, the system was modeled with a conflict graph, and users cannot assign the channels that primary users (legacy users) and neighbors already occupied. In order to eliminate the conflicts between neighbors efficiently, secondary users (unlicensed users) try to transfer them through a straight path to the boundary, where conflicts are easier to solve as there are less neighbors for boundary users. Actions in one shift are executed in slots, and users act in a synchronous and separated manner. As a result, some of the conflicting channels are avoid from directly abandoned, and for this, utility of the entire network can be improved. Simulation results show that the proposed algorithm can provide similar utility performance while obviously reducing the communication cost than bargaining-base algorithms. In small scale networks with low user mobility (under 20%), it reduces 50% of the communication overhead than the later.     

Channel assignment in cellular radio using genetic algorithms

The channel assignment problem has become increasingly important in mobile telephone communication. Since the usable range of the frequency spectrum is limited, the optimal assignment problem of channels has become increasingly important. Recently Genetic Algorithms (GAs) have been proposed as new computational tools for solving optimization problems. GAs are more attractive than other optimization techniques, such as neural networks or simulated annealing, since GAs are generally good at finding an acceptably good global optimal solution to a problem very quickly. In this paper, a new channel assignment algorithm using GAs is proposed. The channel assignment problem is formulated as an energy minimization problem that is implemented by GAs. Appropriate GAs operators such as reproduction, crossover and mutation are developed and tested. In this algorithm, the cell frequency is not fixed before the assignment procedures as in the previously reported channel assignment algorithm using neural networks. The average generation numbers and the convergence rates of GAs are shown as a simulation result. When the number of cells in one cluster are increased, the generation numbers are increased and the convergence rates are decreased. On the other hand, with the increased minimal frequency interval, the generation numbers are decreased and the convergence rates are increased. The comparison of the various crossover and mutation techniques in a simulation shows that the combination of two points crossover and selective mutation technique provides better results. All three constraints are also considered for the channel assignments: the co-channel constraint, the adjacent channel constraint and the co-site channel constraint. The goal of this paper is the assignment of the channel frequencies which satisfied these constraints with the lower bound number of channels.     

3D placement of unmanned aerial vehicles and partially overlapped channel assignment for throughput maximization

This paper investigates a wireless system with multi-Unmanned Aerial Vehicles (UAVs) for improving the overall throughput. In contrast to previous studies that optimize the locations of UAVs and channel assignment separately, this paper considers the two issues jointly by exploiting Partially Overlapped Channels (POCs). The optimization problem of maximizing network throughput is formulated as a non-convex and non-linear problem. In order to find a practical solution, the problem is decomposed into two subproblems, which are iteratively optimized. First, the optimal locations of UAVs are determined under a fixed channel assignment scheme by solving the mixed-integer second-order cone problem. Second, an efficient POC allocation scheme is determined via the proposed channel assignment algorithm. Simulation results show that the proposed approach not only significantly improves system throughput and service reliability compared with the cases in which only orthogonal channels and stationary UAVs are considered, but also achieves similar performance using the exhaustive search algorithm with lower time complexity.     

Protocols and architectures for channel assignment in wireless mesh networks

The use of multiple channels can substantially improve the performance of wireless mesh networks. Considering that the IEEE PHY specification permits the simultaneous operation of three non-overlapping channels in the 2.4 GHz band and 12 non-overlapping channels in the 5 GHz band, a major challenge in wireless mesh networks is how to efficiently assign these available channels in order to optimize the network performance. We survey and classify the current techniques proposed to solve this problem in both single-radio and multi-radio wireless mesh networks. This paper also discusses the issues in the design of multi-channel protocols and architectures.     

Maximum packing channel assignment in cellular networks

We study the performance of the maximum packing channel assignment algorithm (MPA) in channelized cellular networks. MPA is a greedy algorithm, which rejects a call only when it is forced to do so, even if this involves rearrangement of channels assigned to the ongoing calls, without dropping any of them. We ignore handoffs and model the channel reuse constraints in the cellular network by a hypergraph. As the traffic and the number of channels are scaled together, we get a limiting regime where the blocking probability in the cells can be computed by solving a nonlinear optimization problem. The carried traffic in this limiting case is an upper bound on the performance of MPA for practical finite-channel systems. We show that the performance of MPA in a finite-channel cellular system can be closely approximated by considering a simple fixed-routing circuit-switched network. Thus, the finite-channel performance of MPA can be studied using methods well known in the area of circuit-switched networks. We compare the performance of MPA with other asymptotically optimal algorithms and demonstrate its optimality for low and moderate offered traffic. We envisage MPA as a practical channel assignment algorithm, for moderate size systems, and suggest approximations to reduce its complexity     

Joint relay station deployment and frequency reuse scheme for two-hop cellular networks

To fully exploit the performance benefits of relay station (RS),in the two-hop cellular networks covering hotspots,when the number of RSs is predetermined,both RS deployment and frequency reuse scheme ...     

Distributed channel assignment combined with routing over multi-radio multi-channel wireless mesh networks

In order to realize the reduction of equipment cost and the demand of higher capacity,wireless mesh network(WMN) router devices usually have several interfaces and work on multi-channels.Jointing channel allocation,interface assignment and routing can efficiently improve the network capacity.This paper presents an efficient channel assignment scheme combined with the multi-radio link quality source routing(MR-LQSR) protocol,which is called channel assignment with MR-LQSR(CA-LQSR).In this scheme,a physical interference model is established:calculated transmission time(CTT) is proposed as the metric of channel assignment,which can reflect the real network environment and channel interference best,and enhanced weighted cumulative expected transmission time(EWCETT) is proposed as the routing metric,which preserves load balancing and bandwidth of links.Meantime,the expression of EWCETT contains the value of CTT,thus the total cost time of channel assignment and routing can be reduced.Simulation results show that our method has advantage of higher throughput,lower end-to-end time delay,and less network cost over some other existing methods.     

Handover and channel assignment in mobile cellular networks

A taxonomy of channel assignment strategies is provided, and the complexity in each cellular component is discussed. Various handover scenarios and the roles of the base station and the mobile switching center are considered. Prioritization schemes are discussed, and the required intelligence distribution among the network components is defined     

一种短波跳频网的固定信道分配算法

本文基于顺序包和最大包分配算法,从需求向量为出发点,提出了一种将顺序包与最大包两种算法相结合的固定信道分配方案。研究结果表明,在分配所需要的信道数和对信道连续性的要求方面,该算法与其它算法相比具有优良的效果,并且还可用信道不连续的情形。     

最优化方法在蜂窝通信中的应用

本文研究了最优化方法在蜂窝通信系统信道复用，信道配置中的应用，通过研究共信道干扰总概率Ｐｔ与系统各参数间的关系，应用最优化方法求出使ｐｔ最小的各参数值，从而达到信道最佳复用，通过系统呼叫失败概率ｐｔ与信道配置参数间的关系，应用最优化方法求出使ｐｔ最小的信道配置参数，从而达到信道的最佳配置，文中还给出了设计实例。     

中继蜂窝网中基于功率控制的频谱分配方案

中继蜂窝网络是近年来移动通信领域的热点,为了解决传统蜂窝网络的缺点,本文提出了在中继蜂窝网中基于功率控制的频谱分配方案,通过中继方式,解决了远近效应的问题,通过频率复用可以显著的提高系统频率资源利用率和系统性能,通过采用基站功率控制技术解决了由于资源复用带来的链路干扰过大问题。     

Fairness-oriented routing algorithm joint with power control and channel assignment for multi-radio multi-channel wireless mesh networks

The multi-radio multi-channel wireless mesh network （MRMC-WMN） draws general attention because of its excellent throughput performance, robustness and relative low cost. The closed interactions among power control （PC）, channel assignment （CA） and routing is contributed to the performance of multi-radio multi-channel wireless mesh networks （MRMC-WMNs）. However, the joint PC, CA and routing （JPCR） design, desired to achieve a global optimization, was poor addressed. The authors present a routing algorithm joint with PC and CA （JPCRA） to seek the routing, power and channel scheme for each flow, which can improve the fairness performance. Firstly, considering available channels and power levels, the routing metric, called minimum flow rate, is designed based on the physical interference and Shannon channel models. The JPCRA is presented based on the genetic algorithm （GA） with simulated annealing to maximize the minimum flow rate, an non-deterministic polynomial-time hard （NP-Hard） problem. Simulations show the JPCRA obtains better fairness among different flows and higher network throughput.     

一种基于量子细胞自动机的三维量子细胞神经网络

以量子细胞自动机为神经元,提出了一种三维的量子细胞神经网络结构;该量子细胞网络包含上下两层的量子细胞自动机阵列,并引入了A模板、B模板以及阈值的概念.以量子细胞自动机的极化率为像素值,通过选择不同的模板、阈值等参数.使得量子细胞神经网络实现了"与"、"或"、"非"操作以及边缘提取等图像处理功能,并利用MATLAB进行了仿真验证,数值仿真结果验证了其在图像处理上的有效性.与传统的细胞神经网络相比,量子细胞神经网络易于实现超大规模且具有超低功耗、超高集成度等优点.     

基于改进的遗传算法无线通信网频率指配问题研究

通过对无线通信频率指配问题的分析,结合遗传算法在频率指配领域的应用,提出了一种启发式的指配方法。该方法通过改进选择方式,自适应地调整交叉、变异概率来指配信道分配。仿真分析证明,该算法科学可行,有效地避免陷入局优解,加快了种群进化速度,减少了迭代次数,较快收敛到最优解。     

软分数频率复用

针对4G移动通信系统提出的提高频谱利用率、同频组网的需求,文章从频率复用问题入手,提出了一种软分数频率复用方案。软分数频率复用方案包括3种表现形式,在实际应用中,可以根据物理层链路增益选择适当的表现形式。文章以第2种表现形式为例介绍了采用该方案的频率复用方法。研究表明,使用软分数频率复用方案,系统的频率复用系数可以达到1/3～1。软分数频率复用方案解决了同频组网问题,并已经在上海4G实验网中得到了良好的应用。     

Efficient rate allocation,routing and channel assignment in wireless mesh networks supporting dynamic traffic flows

In this paper we address the issue of joint routing, channel re-assignment and rate allocation in multi-radio multi-channel Wireless Mesh Networks (WMNs) with the goal of optimizing the performance of the current set of flows in the WMN. The objective is to balance the instantaneous traffic in the network at the flow level, optimize link-channel assignment and allocate flow rates to achieve proportional fairness given the current traffic and network constraints, including the topology, interference characteristics, number of available channels and radios. Unlike prior work, we do not assume a priori knowledge of traffic, and instead take into account the instantaneous traffic conditions to optimize performance at the flow level, taking both throughput and fairness into account. In this work we analyze the problem and, due to its hardness, propose a fast heuristic algorithm (JRCAR) to solve it. We evaluate this algorithm through numerical experiments, including comparisons against optimal solutions. In addition, we show that JRCAR can be used in a highly responsive system in practical scenarios with time-varying traffic conditions. We implement such a system under the ns-3 simulator, where the simulation results obtained corroborate the behavior observed in the numerical experiments and show that JRCAR is effective in dynamic and practical conditions.     

移动通信网络规划中的频率优化配置软件设计

在蜂窝区移动通信网络规划中 ,许多人都习惯用等频距法或分区分组法进行小区频率配置。当各规划小区话务量分布不均匀和蜂窝小区结构不规则时 ,这种传统方法受到诸多限制。本文用动态频率分配法 ,解决了这一难题 ,并完成了程序设计。作为实例 ,最后给出了频率规划结果和各种干扰分布图。     

Fixed channel assignment in cellular radio networks using amodified genetic algorithm

With the limited frequency spectrum and an increasing demand for cellular communication services, the problem of channel assignment becomes increasingly important. However, finding a conflict-free channel assignment with the minimum channel span is NP hard. Therefore, we formulate the problem by assuming a given channel span. Our objective is to obtain a conflict-free channel assignment among the cells, which satisfies both the electromagnetic compatibility (EMC) constraints and traffic demand requirements. We propose an approach based on a modified genetic algorithm (GA). The approach consists of a genetic-fix algorithm that generates and manipulates individuals with fixed size (i.e., in binary representation, the number of ones is fixed) and a minimum-separation encoding scheme that eliminates redundant zeros in the solution representation. Using these two strategies, the search space can be reduced substantially. Simulations on the first four benchmark problems showed that this algorithm could achieve at least 80%, if not 100%, convergence to solutions within reasonable time. In the fifth benchmark problem, our algorithm found better solutions with shorter channel span than any existing algorithms. Such significant results indicate that our approach is indeed a good method for solving the channel-assignment problem     

Channel Alternation and Rotation for Trisectorized Cellular Systems

Conventional trisectored cellular systems have not taken full advantages of antenna directivities to enhance frequency reuse efficiency. A novel Channel Alternation and Rotation (CAR) scheme is proposed to coordinate channel assignments with antenna directivities. CAR employs a multi-interval cell-reuse layout. Each cell type is allocated extra channel set(s) to provide network designers the flexibility to assign channels avoiding nearest front lobe interference to enhance the carrier to interference ratio (C/I). CAR allows deployment of smaller and non-integer reuse factors based on C/I requirements, thus increasing channel capacity. Since current base station equipment is utilized, no additional costs are introduced.