Channel assignment for cellular radio using extended dynamic programming

The channel assignment is an important aspect of cellular radio networks. Because of the limitations on the frequency spectrum, the optimal or near-optimal channel assignment has become an essential part of the network operations of wireless personal communication systems. We formulate a new strategy for the channel assignment problem in agreement with the electromagnetic compatibility constraints. We introduce and formulate the extended dynamic programming (EDP), as an extension of dynamic programming for solving the channel assignment problem in a cellular system. Using EDP an algorithm is developed for fixed channel assignment problem and it is tested and compared with other existing methods by solving different problems. In agreement with electromagnetic compatibility constraints, solution strategy based on EDP algorithm finds many valid solutions with minimum possible bandwidth.     

An efficient heuristic algorithm for channel assignment problem incellular radio networks

This paper presents an efficient heuristic algorithm for the channel assignment problem in cellular radio networks. The task is to find channel assignment with minimum frequency bandwidth necessary to satisfy given demands from different nodes in a cellular network. At the same time the interference among calls within the same cell and from different neighboring cells are to be avoided, where interference is specified as the minimum frequency distance to be maintained between channels assigned to a pair of nodes. The simplest version of this problem, where only cochannel interferences are considered, is NP-complete. The proposed algorithm could generate a population of random valid solutions of the problem very fast. The best among them is the optimum or very near to optimum solution. For all problems with known optimal solutions, the algorithm could find them. A statistical estimation of the performance of the proposed algorithm is done. Comparison with other methods show that our algorithm works better than the algorithms that we have investigated     

ATMAC: adaptive token‐based medium access control protocol for cognitive radio wireless mesh network

In next generation wireless communication, cognitive radio technology facilitates to utilize underutilized licensed frequency bands that help to enhance the spectrum utilization. Cognitive radio wireless mesh network (CRWMN) is a promising and reliable technology to experience high throughput with low cost. Existing IEEE 802.11 based medium access control (MAC) protocols offer high data rates with decreasing efficiency at the MAC layer. Hence, most of the researchers applied aggregation mechanisms to provide the solution to bandwidth craving applications. In CRWMN, MAC design is significant because stability, efficient resource utilization, and scalability are predominating problems; however, the specified MAC issues are not yet resolved. The proposed MAC is novel, which aims to ensure reliability and scalability for CRWMN. The common control channel is used to exchange handshaking frames between the transmitter and receiver. It helps us to schedule the data transmission as well as reserve the channel in a discrete time interval. It introduces a token‐based channel accessing mechanism with resource‐aware channel assignment, which resolves the problems of efficiency and stability. The proposed MAC simulated using the network simulator (ns‐2), and the simulation results demonstrate that the proposed protocol improved the performance compared with the existing protocols.     

Graph theoretical considerations of channel offset systems in acellular mobile system

The problem of assigning channels in a channel-offset-type of cellular mobile radio communication system is formulated as a problem of assigning channels to the vertices of a network. It is shown that the assignment problem in a network is a generalized graph coloring problem. When the interchannel interference function is a rational number, the optimal channel offset scheme is obtained. and upper and lower bounds of the minimum total bandwidth in a channel-offset scheme are derived. These factors give basic and useful knowledge for designing a channel-offset system of a cellular mobile system, and they are useful not only for a fixed channel assignment but also for a dynamic channel assignment and rearrangement     

认知无线网络中一种基于蚁群优化的频谱分配算法

针对认知无线电中的频谱分配问题,该文提出一种基于蚁群优化的频谱分配方法。该方法在授权用户和认知用户共存的认知网络模型中,通过蚁群访问各个认知节点,并释放信息素,从而实现概率型的全局搜索的并行频谱分配算法。与传统的频谱分配方式比较,该算法能够进行增强型学习积累,快速收敛到最优路径,从而获得了最优的平均信道效益。文中对该算法进行了分析和说明,并通过仿真证明了算法的有效性和稳定性。     

A multistage self-organizing algorithm combined transiently chaotic neural network for cellular channel assignment

In this paper, a new multistage self-organizing channel assignment algorithm with a transiently chaotic neural network (MSSO-TCNN) is proposed as an optimization algorithm. The algorithm is used for assigning channels in cellular mobile networks to cells in the frequency domain. The MSSO-TCNN consists of a progressively initial channel assignment stage and the TCNN assignment stage. According to the difficulty measure of each cell, the first stage is executed to assign channels cell by cell inspired by the mechanism of bristle. If the optimum assignment solution is not obtained in the first stage, the TCNN stage is then applied to continue the channel assignment until the optimum assignment is made or a maximum number of iterations is reached. A salient feature of the TCNN model is that chaotic neurodynamics are temporarily generated for searching and self-organizing in order to escape local minima. Therefore, the neural network gradually approaches, through transient chaos, a dynamical structure similar to conventional models such as the Hopfield neural network and converges to a stable equilibrium point. A variety of testing problems are used to compare the performance of the MSSO-TCNN against existing heuristic approaches. Simulation results show that the MSSO-TCNN improves performance substantially through solving well-known benchmark problems within comparable numbers of iterations to most existing algorithms.     

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.     

Channel Assignment Strategies for Multiradio Wireless Mesh Networks: Issues and Solutions

Next-generation wireless mobile communications will be driven by converged networks that integrate disparate technologies and services. The wireless mesh network is envisaged to be one of the key components in the converged networks of the future, providing flexible high- bandwidth wireless backhaul over large geographical areas. While single radio mesh nodes operating on a single channel suffer from capacity constraints, equipping mesh routers with multiple radios using multiple nonoverlap- ping channels can significantly alleviate the capacity problem and increase the aggregate bandwidth available to the network. However, the assignment of channels to the radio interfaces poses significant challenges. The goal of channel assignment algorithms in multiradio mesh networks is to minimize interference while improving the aggregate network capacity and maintaining the connectivity of the network. In this article we examine the unique constraints of channel assignment in wireless mesh networks and identify the key factors governing assignment schemes, with particular reference to interference, traffic patterns, and multipath connectivity. After presenting a taxonomy of existing channel assignment algorithms for WMNs, we describe a new channel assignment scheme called MesTiC, which incorporates the mesh traffic pattern together with connectivity issues in order to minimize interference in multi- radio mesh networks.     

Design of logical topology with K‐connected constraints and channel assignment for multi‐radio wireless mesh networks

In multi‐radio multi‐channel wireless mesh networks, the design of logical topology is different from that in single channel wireless mesh networks. The same channel assignment algorithm used for various logical topologies will lead to diverse network performance. In this paper, we study the relationship between k ‐connected logical topology and the maximum number of assigned channels. Meanwhile, we analyze the issues affecting channel assignment performance, and present the lower and upper bounds of the maximum allowable number of assigned channels for k ‐connected logical topology. We then develop a k ‐connected logical topology design algorithm based on shortest disjoint paths and minimum interference disjoint paths for each node‐pair. In addition, we propose a static channel assignment algorithm according to minimum spanning tree search. Extensive simulations show that our proposed algorithm achieves higher throughput and lower end‐to‐end delay than fault tolerant topology control algorithms, which validates the involved trade‐off between path length and nodal interference. Moreover, numerical results demonstrate that our proposed channel assignment further improves network performance under the context of limited radio interfaces. Copyright © 2014 John Wiley & Sons, Ltd.     

Prioritized channel assignment in a cellular radio network

Dimensioning procedures for prioritized channel assignment in a cellular radio network are considered. Under the cutoff priority discipline, the prioritized channel assignment procedures for a single cell and multicell system are formulated as nonlinear discrete capacity allocation problems. Exact incremental algorithms which efficiently solve the proposed problems are devised. They are based on the properties of the blocking probabilities of new calls and handoff calls. Given the number of available frequency channels together with the arrival rates and the grade of service (GOS) for both types of calls in each cell, algorithm SP1 generates an optimal channel assignment which ensures priority for handoff calls. Given the arrival rates and distinct GOSs for new and handoff calls, algorithm SP2 finds the minimum number of channels required in each cell. Algorithm MP extends algorithm SP1 to a multicell system and provides the prioritized channel assignment for all calls in the system. The algorithms are very fast and are appropriate for the fair allocation of frequency channels among cells     

Channel assignment using genetic algorithm based on geometric symmetry

The paper deals with the channel assignment problem in a hexagonal cellular network with two-band buffering, where channel interference does not extend beyond two cells. Here, for cellular networks with homogeneous demands, we find some lower bounds on the minimum bandwidth required for various relative values of s/sub 0/, s/sub 1/, and s/sub 2/, the minimum frequency separations to avoid interference for calls in the same cell, or in cells at distances of one and two, respectively. We then present an algorithm for solving the channel assignment problem in its general form using the elitist model of genetic algorithm (EGA). We next apply this technique to the special case of hexagonal cellular networks with two-band buffering. For homogeneous demands, we apply EGA for assigning channels to a small subset of nodes and then extend it for the entire cellular network, which ensures faster convergence. Moreover, we show that our approach is also applicable to cases of nonhomogeneous demands. Application of our proposed methodology to well-known benchmark problems generates optimal results within a reasonable computing time.     

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.     

蜂窝移动通信系统中的一种新的优化信道分配模型

本文提出了一种新的蜂窝移动通信系统最优信道分配模型.首先根据信道分配的特点构造了一种信道分配方程模型;进而建立了信道分配最优模型,利用Pontryain最小值原理获得了模型的最优解;给出的仿真结果验证了分析结论的正确性.该模型可以用来有效地研究信道分配问题的宏观性能,并提供了一种高效、快速的算法.     

Efficient radio resource management for wireless multimedia communications: a multidimensional QoS-based packet scheduler

Future wireless multimedia systems will support a variety of services with diverse range of capabilities and bit rates. For these systems, it is highly desired for real-time conversational and non-real-time services to efficiently share the available channels and bandwidth in an optimized way. The partitioned resource shaping with either fixed or a slow changing dynamic, proposed for conventional packet scheduling techniques, proves difficult and inefficient under fast-changing dynamics of radio channel and traffic. By taking into account almost all the aspects (dimensions) of quality-of-service (QoS) provisioning, the proposed unified fast dynamic multidimensional QoS-based packet scheduler (MQPS) in this paper elegantly and efficiently encapsulates features of many possible packet scheduling strategies. MQPS applies an optimization and tuning mechanism to packet scheduling weights to adopt the most appropriate packet scheduling and channel assignment strategy in response to the varying traffic and radio channel conditions. As an example, the technique is applied to a high-speed downlink packet access (HSDPA) system. It is shown that MQPS provides significantly better performance than existing techniques by satisfying all the requirements of a successful QoS provisioning to maximum possible level simultaneously.     

Joint Optimal Access Point Selection and Channel Assignment in Wireless Networks

In wireless cellular networks or in other networks with single-hop communication, the fundamental access control problem pertains to access point (AP) selection and channel allocation for each user. For users in the coverage area of one AP, this involves only channel allocation. However, users that belong in the intersection of coverage areas of more than one AP can select the appropriate AP to establish connection and implicitly affect the channel assignment procedure. We address the joint problem of AP selection and channel assignment with the objective to satisfy a given user load vector with the minimum number of channels. Our major finding is that the joint problem reduces to plain channel allocation in a cellular network that emerges from the original one after executing an iterative and provably convergent clique load balancing algorithm. For linear cellular networks, our approach leads to minimum number of required channels to serve a given load vector. For 2D cellular networks, the same approach leads to a heuristic algorithm with a suboptimal solution due to the fact that clique loads cannot be balanced. Numerical results demonstrate the performance benefits of our approach in terms of blocking probability in a dynamic scenario with time-varying number of connection requests. The presented approach constitutes the basis for addressing more composite resource allocation problems in different context.     

Performance evaluation of distributed measurement-based dynamicchannel assignment in local wireless communications

The diverse environments emerging for wireless communication applications could render the centralized prediction-based channel assignment methodology, conventionally employed in cellular radio networks, impractical. The distributed measurement-based approach seems to be a more practical solution. We evaluate and compare several distributed measurement-based algorithms for dynamic channel assignment (DCA). Their performance is also compared with a centralized prediction-based algorithm. It is found that a simple aggressive algorithm with the use of a threshold, known as the least interference algorithm (LIA), performs the best     

Planning the Reassignment of Frequencies in Fiber-Wireless Access Networks

FiWi architectures have been proposed as efficient solutions to provide high bandwidth and ubiquity at access network areas. In multi-radio and multi-channel FiWi scenarios an effective frequency assignment should be done to radios so that higher throughput and low delay can be obtained and the best of such architectures is achieved. However, traffic conditions change over time meaning that radio channel reconfigurations can be done to improve network performance. In this article a methodology for FiWi frequency reassignment planning is proposed, together with two algorithms, that avoids service disruption and attempts to increase throughput, reduce delay and increase the overall QoS perceived by users. Results show that the RBR algorithm is the one able to better exploit channel reconfigurations, increasing parallel transmissions and reducing time division required by nodes at the transmission area of each other.     

QoS multicast routing in cognitive radio ad hoc networks

In this paper, we discussed the issues of QoS multicast routing in cognitive radio ad hoc networks. The problem of our concern was: given a cognitive radio ad hoc network and a QoS multicast request, how to find a multicast tree so that the total bandwidth consumption of the multicast is minimized while the QoS requirements are met. We proposed two methods to solve it. One is a two‐phase method. In this method, we first employed a minimal spanning tree‐based algorithm to construct a multicast tree and then proposed a slot assignment algorithm to assign timeslots to the tree links such that the bandwidth consumption of the tree is minimized. The other is an integrated method that considers the multicast routing together with the slot assignment. Extensive simulations were conducted to show the performance of our proposed methods. Copyright © 2011 John Wiley & Sons, Ltd.     

MR-MC无线传感器网络最小延迟数据聚集调度研究

单radio单信道无线传感器网络的最小延迟聚集调度是一个NPC问题,已提出许多解决方案。在多radio多信道网络中,节点可以同时接收多个不同节点传输的数据,降低延迟。基于上述特点,考虑树结构约束,时槽、信道和radio分配等约束条件,将多radio多信道无线传感器网络最小延迟聚集调度问题定义为一个优化问题,并分解为建立聚集树和节点调度2个子问题,针对这2个子问题分别提出启发式算法。实验结果表明,提出的算法具有良好的性能。     

Multichannel cooperative sensing for cognitive radio with users owning heterogeneous sensing ability

Multichannel cooperative sensing (MCS) is an effective method for dynamic spectrum access in cognitive radio networks. In contrast to most existing work on MCS that considered secondary users with homogeneous sensing ability, this paper studies the MCS problem for secondary users with heterogeneous sensing ability in terms of sensing accuracy. We further take into account different parameters of primary channels such as bandwidth, probability of being idle in each sensing period, and frequency selective fading at the sensing receiver. The MCS problem is formulated as a weapon target assignment problem, where more sensing resources are assigned to channels that are more valuable. This weapon target assignment problem is transformed to an integer generalized network flow problem with convex flow costs to obtain the lower bound solution, and then solved by the branch and bound algorithm with this bound to yield the exact scheme. To reduce computational complexity, a heuristic scheme is also proposed, which has approximate performance compared with the exact scheme. Finally, extensive simulation results for different scenarios illustrate the performance improvements of the proposed schemes over the existing scheme. Copyright © 2013 John Wiley & Sons, Ltd.