无线 Mesh 网络部分重叠信道分配综述

无线Mesh网络面临的主要挑战是由共信道干扰导致的网络容量下降问题,仔细规划部分重叠信道的使用能减少甚至消除共信道干扰。在介绍部分重叠信道基本概念的基础上,重点从单播和多播2个角度对国内外部分重叠信道分配研究领域的成果进行了分类总结与分析;深入剖析部分重叠信道分配中的难点与挑战,并展望了未来的研究方向,以期促进无线Mesh网络向“最后一公里”接入的理想解决方案演进。     

Two‐stage channel assignment scheme in wireless networks

This paper presents a new channel assignment scheme that efficiently improves the spatial frequency–spectrum reuse in a wireless network with heterogeneous demands, in which the cells are partitioned into a lot of clusters. Since the channel demands of each cell are different, this scheme adopts two stages to effectively assign channels. In the first stage, the cluster‐based scheme allocates a number of channels to the cells of each cluster for satisfying the requirement of co‐channel reuse. The channel demand of majority cells will be satisfied in this stage. In the second stage, when the channel requirement of most cells has been fulfilled, the tree‐based assignment scheme allocates channels for the minority cells, which are still lacking of channels. Simulation results showed that the proposed scheme is superior to the previous schemes. Copyright © 2005 John Wiley & Sons, Ltd.     

Tree‐based channel assignment schemes for multi‐channel wireless sensor networks

Many sensor node platforms used for establishing wireless sensor networks (WSNs) can support multiple radio channels for wireless communication. Therefore, rather than using a single radio channel for whole network, multiple channels can be utilized in a sensor network simultaneously to decrease overall network interference, which may help increase the aggregate network throughput and decrease packet collisions and delays. This method, however, requires appropriate schemes to be used for assigning channels to nodes for multi‐channel communication in the network. Because data generated by sensor nodes are usually delivered to the sink node using routing trees, a tree‐based channel assignment scheme is a natural approach for assigning channels in a WSN. We present two fast tree‐based channel assignment schemes (called bottom up channel assignment and neighbor count‐based channel assignment) for multi‐channel WSNs. We also propose a new interference metric that is used by our algorithms in making decisions. We validated and evaluated our proposed schemes via extensive simulation experiments. Our simulation results show that our algorithms can decrease interference in a network, thereby increasing performance, and that our algorithms are good alternatives for static channel assignment in WSNs. Copyright © 2015 John Wiley & Sons, Ltd.     

基于最大化网络吞吐量的WMN信道分配算法

为了解决无线Mesh网络中的信道分配问题,提出了一种基于博弈论的信道分配算法.该算法将网络中每一个节点模型化为一个博弈者,每个博弈者的策略为信道的分配方案,并将整个网络的吞吐量作为效用函数的目标,效用函数的物理意义则是在给定流量需求矩阵下传输的成功率.博弈者通过相互博弈来优化收益函数以最大化网络吞吐量.通过NS2.34仿真分析得出,GBCA算法在收敛性、丢包率和吞吐量上都要优于当前的算法.     

Joint processing of topology control and channel assignment in wireless ad hoc networks

Network topology construction and its channel assignment for each node in the constructed network topology are two main problems in the initialization of topology building. Topology control is an effective way to solve the problem of topology building. To investigate the joint effect of topology control and channel assignment, we propose a joint processing scheme composed of a k‐Neighbor topology control algorithm and a greedy channel assignment (GCA) algorithm in this paper. Based on this joint processing scheme, the relationships between the energy consumption, the total required channel number and the network connectivity are discussed. We also discuss the impact of some parameters on the performance of networks in terms of the path loss factor, node density, maximum node degree, etc. Our main contributions in this paper is that we find that topology control has a good effect on improving the performance of channel assignment, and the proposed joint processing scheme can reduce the required channel number effectively, compared with its theoretical upper bound. In particular, if the node degree in a network is not more than k, various simulations indicate that the required channel number is not more than 2k + 1. Copyright © 2008 John Wiley & Sons, Ltd.     

A dynamic channel assignment scheme for clustered multihop cellular networks

Whereas cellular systems have traditionally adopted single‐hop transmissions between the mobile station (MS) and the base station (BS), researchers expect multihop transmission to be utilised in the future. Cellular systems present several challenges, such as channel assignment, which are exacerbated by multimedia service traffic and an increasing number of subscribers. Recently, a clustered multihop cellular network (cMCN) architecture that complements traditional cellular systems has been proposed and studied using fixed channel assignment (FCA). However, the performance of FCA is limited when the traffic pattern varies in a service area. This paper proposes the use of dedicated information ports (DIPs) as clusterheads in cMCN, followed by a multihop dynamic channel assignment (mDCA) scheme. The mDCA works by assigning channels based on information about interference in surrounding cells. Two different channel searching strategies are developed and evaluated. Through computer simulation, we show that the proposed mDCA is able to achieve a significantly improved capacity which is maintained when the number of system channels is increased. Finally, issues regarding the implementation of the mDCA and future work on this topic are discussed. Copyright © 2007 John Wiley & Sons, Ltd.     

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.     

认知无线多跳网中保证信干噪比的频谱分配算法

为解决无线多跳网络在固定频谱分配方式下所固有的信道冲突等问题,利用认知无线电的动态频谱分配技术,提出了一种适用于次用户组成的无线多跳网络的、underlay方式下的全分布式频谱分配算法。该算法将频谱分配问题建模成静态非合作博弈,证明了纳什均衡点的存在,并给出了一种求解纳什均衡点的迭代算法。大量仿真实验证明,该算法能实现信道与功率的联合分配,在满足主用户干扰功率限制的同时,保证次用户接收信干噪比要求。     

Joint Optimization for Congestion Avoidance in Cognitive Radio WMNs under SINR Model

Due to limited spectrum resources and differences in link loads, network congestion is one of the key issues in cognitive radio wireless mesh networks. In this letter, a congestion avoidance model with power control, channel allocation, and routing under the signal‐to‐interference‐and‐noise ratio is presented. As a contribution, a nested optimization scheme combined with a genetic algorithm and linear programming solver is proposed. Extensive simulation results are presented to demonstrate the effectiveness of our algorithm.     

An efficient channel assignment algorithm for multicast wireless mesh networks

Multicast can enhance the performance of wireless mesh networks (WMNs) effectively, which has attracted great attentions in recent years. However, multicast communication in WMNs requires efficient channel assignment strategy to reduce the total network interference and maximize the network throughput. In this paper, the concept of local multicast is proposed to measure interference and solve hidden channel problem in multicast communication. Basing on the concept, we propose a channel assignment algorithm considering the interference of local multicast and forwarding weight of each node (LMFW). The algorithm fully considers partially overlapped channels and orthogonal channels to improve the network performance. Simulations show that the proposed algorithm can reduce interference and improve network capacity of WMNs.     

基于最大流的无线mesh网络负载均衡信道分配算法

针对无线mesh网络中各信道间的干扰情况及流量负载均衡问题,定义了负载均衡的目标优化函数,设计一种基于最大流的负载均衡信道分配算法。该算法优先考虑为负载量比较大的链路分配更多的带宽,使得一些关键链路能够承受较大的流量负载,实现各信道的负载均衡,减少网络拥塞,降低分组丢失率和延迟。实验结果表明,该算法较好地平衡了网络负载,在网络业务较重的情况下还能获得较好的网络性能。     

A topology preserving cluster‐based channel assignment for wireless mesh networks

Wireless Mesh Networks (WMN) with multiple radios and multiple channels are expected to resolve the capacity limitation problem of simpler wireless networks. However, optimal WMN channel assignment (CA) is NP complete, and it requires an optimal mapping of available channels to interfaces mounted over mesh routers. Acceptable solutions to CA must minimize network interference and maximize available network throughput. In this paper, we propose a CA solution called as cluster‐based channel assignment (CBCA). CBCA aims at minimizing co‐channel interference yet retaining topology through non‐default CA. Topology preservation is important because it avoids network partitions and is compatible with single‐interface routers in the network. A ‘non‐default’ CA solution is desired because it uses interfaces over different channels and reduces medium contention among neighbors. To the best of our knowledge, CBCA is a unique cluster‐based CA algorithm that addresses topology preservation using a non‐default channel approach. The main advantage of CBCA is it runs in a distributed manner by allowing cluster heads to perform CA independently. CBCA runs in three stages, where first the WMN nodes are partitioned into clusters. The second stage performs binding of interfaces to neighbors and third stage performs CA. The proposed algorithm improves over previous work because it retains network topology and minimizes network interference, which in turn improves available network throughput. Further, when compared with two other CBCA algorithms, CBCA provides better performance in terms of improved network interference, throughput, delay, and packet delivery ratios when tested upon network topologies with various network densities and traffic loads. Copyright © 2014 John Wiley & Sons, Ltd.     

利用部分重叠信道的多无人机自主协同优化抗干扰

针对多无人机通信网络抗干扰中的功率和信道联合优化问题,考虑多无人机通信网络中的部分重叠信道切换、外部恶意干扰与网络内部互扰问题,通过构建Stackelberg博弈抗干扰模型,设计无人机用户和干扰机的效用函数,并提出了基于次梯度迭代的算法求解博弈的均衡解,获得无人机用户在干扰条件下的部分重叠信道选择和功率选择联合优化结果。仿真结果表明,所提算法能使多无人机用户获得良好的信道选择和传输功率策略,优化多无人机通信网络抗干扰性能。     

Optimal radio channel assignment through a new binary dynamic simulated annealing algorithm

The radio channel assignment problem (CAP) is classified as an NP-complete binary optimization problem, which creates the need for faster, yet optimal optimization algorithms to reduce the time of computation when solving such a complex problem. Simulated annealing (SA), a powerful optimal combinatorial search algorithm, was found to be very suitable for CAP. This paper extends the standard capabilities of SA and proposes a new CAP-oriented, quicker binary SA, the binary dynamic SA (BDSA) algorithm, as part of a newly proposed radio channel assignment approach. Simulation results proved that the proposed BDSA has very fast convergence as a stand-alone algorithm and even faster convergence with the newly proposed radio channel assignment approach. © 1998 John Wiley & Sons, Ltd.     

Stable‐path multi‐channel routing with extended level channel assignment

Wireless mesh networks (WMNs) have gained considerable popularity in recent times thanks to their self‐healing, self‐organizing, and self‐configuring nature. Because of their ability to provide high throughput and minimum packet delay, WMNs are considered to be favorable for broadband applications. For such applications, WMNs employ multiple channels, which give rise to issues like channel assignment, load balancing, and interference avoidance. Most of these issues fall into two broad categories, namely routing and channel assignment. For routing, we propose a novel proactive protocol, the stable‐path multi‐channel routing protocol (SMRP). Our proposed solution, to address channel assignment, is the extended level‐based channel assignment (ELCA) scheme. SMRP is designed to work in combination with ELCA in order to minimize interference and balance the load among the underlying nodes. Simulation results show enhanced throughput and minimal packet delay as compared with the contemporary schemes. Copyright © 2011 John Wiley & Sons, Ltd.     

Adaptive threshold control for auto-rate fallback algorithm in IEEE 802.11 multi-rate WLANs

The IEEE 802.11 standard supports multiple rates for data transmission in the physical layer. Nowadays, to improve network performance, a rate adaptation scheme called auto-rate fallback (ARF) is widely adopted in practice. However, ARF scheme suffers performance degradation in multiple contending nodes environments. In this article, we propose a novel rate adaptation scheme called ARF with adaptive threshold control. In multiple contending nodes environment, the proposed scheme can effectively mitigate the frame collision effect on rate adaptation decision by adaptively adjusting rate-up and rate-down threshold according to the current collision level. Simulation results show that the proposed scheme can achieve significantly higher throughput than the other existing rate adaptation schemes. Furthermore, the simulation results also demonstrate that the proposed scheme can effectively respond to the varying channel condition.     

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.     

Cross‐layer perspective for channel assignment in cognitive radio networks: A survey

With the advent of various emerging wireless products, the usage of limited spectrum has grown exponentially in the recent years. In the next few years, that mobile data traffic globally is expected to grow up to 50 EB/month, which is nearly a five times increase over year 2018. Therefore, it will become extremely difficult to satisfy the ever increasing demand through the current fixed spectrum assignment policy in which spectrum band is exclusively used for the particular applications, and it has also led to underutilization of a significant portion of the spectrum (like TV bands). Cognitive radio networks has emerged as a possible solution for the problem which makes dynamic spectrum access possible for unlicensed user when licensed user is not active. Among various operations of cognitive radio, channel assignment to the unlicensed user is very important. Further, wireless regional area network is one of the most important application of cognitive radio, which provides wireless broadband to the rural area using vacant TV channels. This paper discusses channel assignment techniques considering various functionalities for cognitive radio networks in respect of wireless regional area network in the existing literature. Initially, a comprehensive introduction to both cognitive radio networks and wireless regional area networks is provided, and in the end, the paper summarizes the various issues and research challenges in the channel assignment for wireless regional area networks.     

Uplink channel assignment with balanced load for code division multiple access cellular systems

In a code division multiple access (CDMA) wireless communication system, each mobile handset must be power controlled such that the power received at the base station is roughly the same. Otherwise, the interferences between mobile handsets will degrade the performance and increase the error rate. When a mobile handset uses channels from the neighbouring cells, it will raise its power to meet the threshold of signal strength. This will also increase the interference in the home cell. Therefore, we do not want a mobile handset to use channels from other cells blindly. In this paper, we propose an uplink channel assignment method based on the directed retry concept for CDMA cellular systems. The purpose is to achieve load balancing between neighbouring cells and at the same time controlling the interference levels at the base stations such that it will not affect the performance. Furthermore, priorities are given to handoff calls when assigning channels. Copyright © 2002 John Wiley & Sons, Ltd.     

Nodes organization for channel assignment with topology preservation in multi-radio wireless mesh networks

The wireless mesh network is a new emerging broadband technology providing the last-mile Internet access for mobile users by exploiting the advantage of multiple radios and multiple channels. The throughput improvement of the network relies heavily on the utilizing the orthogonal channels. However, an improper channel assignment scheme may lead to network partition or links failure. In this paper we consider the assignment strategy with topology preservation by organizing the mesh nodes with available channels, and aim at minimizing the co-channel interference in the network. The channel assignment with the topology preservation is proved to be NP-hard and to find the optimized solution in polynomial time is impossible. We have formulated a channel assignment algorithm named as DPSO-CA which is based on the discrete particle swarm optimization and can be used to find the approximate optimized solution. We have shown that our algorithm can be easily extended to the case with uneven traffic load in the network. The impact of radio utilization during the channel assignment process is discussed too. Extensive simulation results have demonstrated that our algorithm has good performance in both dense and sparse networks compared with related works.