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     

Partially overlapping channel assignment for WLANs using SINR interference model

The use of multiple channels in 802.11 wireless local area networks can improve network performance. Many efforts have been done to better exploit multiple non‐overlapped channels. However, the number of orthogonal channels in the Institute of Electrical and Electronics Engineers 802.11 standards is very much limited. Recent studies indicate that we can improve the full‐range channel utilization and the network throughput by properly utilizing the partially overlapping channels. However, little work was focused on channel assignment for partially overlapping channels. In this paper, we investigate the problem of partially overlapping channel assignment to improve the performance of 802.11 wireless networks based on the Signal to Interference–Noise Ratio interference model. Using the Signal to Interference–Noise Ratio model, we deduce a direct relationship between maximizing system throughput and minimizing total interference when partially overlapping channels are employed. After that, we propose a greedy method to minimize the total interference for throughput maximization. We evaluate our algorithm through extensive simulations and compare its performances with those of the state‐of‐the‐art. Copyright © 2013 John Wiley & Sons, Ltd.     

MIMO干扰信道下的协作干扰对齐优化算法

干扰对齐是将来自其他发射机的干扰信号对准到同一信号子空间,从而减少对期望信号的干扰的一种传输技术,近年来得到了广泛的关注.本文为K用户多输入多输出(MIMO)干扰信道系统提出了一种协作干扰对齐优化算法.通过对信道的奇异值分解,基于矩阵弦距离,不仅选出一组最好的特征子信道来传输信号,而且还选取一组有利于有用信号远离干扰信号的预编码矩阵,这样,可以最大化减少干扰对有用信号的影响.另外,本文还根据得出的预编码矩阵来计算和优化干扰抑制矩阵.本文算法在没有用迭代的基础上来计算预编码矩阵和干扰抑制矩阵,这样不仅使整个系统的复杂度大大降低,进一步,仿真结果显示容量和能量效率较其他算法有明显改进,这也正是最近受到广泛瞩目的绿色通信所要求的.     

Sequential algorithm for channel equalisation employing a stack

A sequential algorithm based on a stack, and applicable to the problem of recovering digital data after degradation by intersymbol interference and additive noise, is described. Results are presented showing a tradeoff between performance and equipment complexity, with performance asymptotic to the maximum-likelihood-sequence (Viterbi) estimate when the storage is large.     

Sequential signalling under a peak power constraint

The error exponent for sequential signaling over the additive-Gaussian-white-noise channel subject to a peak power constraint is derived. This exponent is maximum under the assumption that information is transmitted in blocks.     

Optimal power allocation for cognitive radio under interference outage constraint

Cognitive radio is able to share the spectrum with primary licensed user, which greatly improves the spectrum efficiency. We study the optimal power allocation for cognitive radio to maximize its ergodic capacity under interference outage constraint. An optimal power allocation scheme for the secondary user with complete channel state information is proposed and its approximation is presented in closed form in Rayleigh fading channels. When the complete channel state information is not available, a more practical transmitter-side joint access ratio and transmit power constraint is proposed. The new constraint guarantees the same impact on interference outage probability at primary user receiver. Both the optimal power allocation and transmit rate under the new constraint are presented in closed form. Simulation results evaluate the performance of proposed power allocation schemes and verify our analysis.     

基于干扰感知的多接口无线Mesh网络信道分配算法

针对无线Mesh网络因受部署在本地的其他网络干扰而导致的传输能力下降的问题,设计了一种基于干扰感知的多接口动态信道分配算法予以克服。同时采用链接重建的方法避免传输中的数据流因信道改变而被破坏的问题。通过实验仿真,证明在复杂电磁环境下,该算法能有效降低网络干扰,保证网络服务质量。     

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.     

一种基于二次约束的零陷加宽算法

本文提出了一种基于二次约束的零陷加宽有效算法.该方法在Capon波束形成器的基础上,通过对干扰积分矩阵进行二次方约束和优化选取约束参数的方法控制零陷的深度和宽度;采用拉格朗日乘子法解决了二次方优化问题,精确计算了影响算法性能的拉格朗日乘子的取值范围,从而达到抑制运动干扰的目的.仿真结果验证了该方法的有效性,与现有的算法相比,在旁瓣抑制和输出信干噪比方面有一定优势.     

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。     

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。     

一种基于改进遗传算法的资源分配策略

提出一种基于改进遗传算法的整体优化的动态资源分配方案。首先根据信道分配的特点构造了基因链模型,进而建立了一种整体优化模型,该算法尽量保证最大程度的紧致分配,同时针对遗传算法爬山能力差的弱点,提出一种自适应遗传方法。分析和仿真表明,该方案与现有的FCA和DCA方案相比,有较小的呼阻率和较高的频谱利用率,不论在业务量较大还是较小都能取得较好的性能指标。     

Distributed autonomous wireless channel assignment algorithm withpower control

Local autonomous dynamic channel allocation (LADCA) including power control is essential to accommodating the anticipated explosion of demand for wireless. The authors simulate call performance for users accessing channels in a regular cellular array with a base located at the center of each hexagon. The computer model includes stochastic channel demand and a propagation environment characterized by attenuation with distance as well as shadow fading. The study of LADCA shows that distributed power control and channel access can be combined in an access management policy that achieves satisfactory system capacity and provides desired call performance. The authors report: LADCA/power control is observed to be stable alleviating a major concern about users unaware of the signal to interference problems their presence on a channel might cause to others. There can be substantial inadvertent dropping of calls in progress caused by originating calls. Modeling user time dynamics is essential. LADCA contrasts very favorably with fixed channel allocation (FCA) in a comparative example     

A unified framework and algorithm for channel assignment in wireless networks

Channel assignment problems in the time, frequency and code domains have thus far been studied separately. Exploiting the similarity of constraints that characterize assignments within and across these domains, we introduce the first unified framework for the study of assignment problems. Our framework identifies eleven atomic constraints underlying most current and potential assignment problems, and characterizes a problem as a combination of these constraints. Based on this framework, we present a unified algorithm for efficient (T/F/C)DMA channel assignments to network nodes or to inter-nodal links in a (multihop) wireless network. The algorithm is parametrized to allow for tradeoff-selectable use as three different variants called RAND, MNF, and PMNF. We provide comprehensive theoretical analysis characterizing the worst-case performance of our algorithm for several classes of problems. In particular, we show that the assignments produced by the PMNF variant are proportional to the thickness of the network. For most typical multihop networks, the thickness can be bounded by a small constant, and hence this represents a significant theoretical result. We also experimentally study the relative performance of the variants for one node and one link assignment problem. We observe that the PMNF variant performs the best, and that a large percentage of unidirectional links is detrimental to the performance in general.     

A bandwidth assignment algorithm on a satellite channel for VBR traffic

Variable bit rate (VBR) video is currently by far the most interesting and challenging real-time application. A VBR encoder attempts to keep the quality of video output constant and at the same time reduces bandwidth requirements, since only a minimum amount of information has to be transferred. On the other hand, as VBR video traffic is both highly variable and delay-sensitive, high-speed networks (e.g. ATM) are generally implemented by assigning peak rate bandwidths to VBR video applications. This approach may, however, be inefficient in a satellite network based on a TDMA scheme. To overcome this problem, we have designed a demand assignment satellite bandwidth allocation algorithm in TDMA, named V2L-DA (VBR 2-Level Demand Assignment), which manages the VBR video traffic according to a dynamic bandwidth allocation algorithm. In this paper we discuss how to tune the proposed algorithm in order to optimize network utilization when MPEG-1 VBR video traffic is being transmitted. Our results indicate that most of the time only 40% of the peak rate bandwidth is needed to satisfy the VBR source, so the remaining 60% of the peak rate bandwidth can be used to transmit the datagram traffic queued in the network stations. © 1997 John Wiley & Sons, Ltd.     

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     

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.     

Fixed channel assignment algorithm for multi‐radio multi‐channel MESH networks

Recently, multi‐radio mesh technology in wireless networks has been under extensive research. This is because of its potential of overcoming the inherent wireless multi‐hop throughput, scalability and latency problems caused by the half‐duplex nature of the IEEE 802.11. The concept of deploying multiple radios in wireless network access points (APs) has shown a promising way to enhance the channel selection and the route formation while the MESH topology allows more fine‐grained interference management and topology control. Within this realm, given a set of end‐to‐end objectives, there are multiple issues that need to be identified when we consider the optimization problem for fixed multi‐channel multi‐hop wireless networks with multiple radios. This paper addresses the static channel assignment problem for multichannel multi‐radio static wireless mesh networks. We first discuss its similarities and differences with the channel assignment problem in cellular networks (WMN). Next, we present four metrics based on which mesh channel assignments can be obtained. Three of these metrics attempt to maximize simultaneous transmissions in a mesh network, either directly or indirectly. The fourth metric quantifies the ‘diversity’ of a particular assignment and can be used as a secondary criterion to the other three metrics. Related optimization models have also been developed. Copyright © 2007 John Wiley & Sons, Ltd.     

基于节点密度的混合式多信道分配算法

为了减小无线传感器网络中的同频干扰和避免网络堵塞问题,文章提出了一种基于节点密度的混合式多信道分配算法。该算法通过考虑链路干扰以及节点密度等因素,来解决局部严重同频干扰问题,实现各信道负载均衡,减少网络阻塞。仿真实验结果分析表明,该算法能有效地解决网络中同频干扰问题,较好地均衡各信道的网络负载,在数据业务较重的情况下,网络性能仍比较良好。