Dynamic channel assignment with queuing in highway microcells

The effect of queuing on an ordered dynamic channel assignment with reassignment (QODCAR) scheme in a highway microcellular environment are studied. Results show that queuing improves channel use by approximately 9-43%, and significantly lowers the probability of call failure.<>     

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.     

阴影衰落信道下多波束卫星移动通信系统的动态信道分配策略

针对已有动态信道分配策略在阴影衰落环境中性能损失较大的问题,对卫星移动通信系统的阴影衰落信道模型进行分析,提出了一种动态信道分配策略。该策略结合用户的运动状态,通过在用户的预测运动轨迹上选取抽样点,将这些抽样点的平均干扰作为信道分配的指标,并采用链路质量约束避免了流量较大时的性能恶化。仿真结果表明提出的动态信道策略可在不增大阻塞率的前提下,在中低流量时将用户平均信噪比提高约0.5 dB。该策略可以应用于阴影衰落信道下的地面移动卫星通信系统,以提高用户的平均链路性能。     

A pilot-based dynamic channel assignment scheme for wireless access TDMA/FDMA systems

We propose a control architecture for implementing a dynamic channel assignment (DCA) algorithm which optimizes two-way channel quality in a TDMA portable radio system. Computer simulations are used to evaluate the performance of this DCA method. A common control frequency, which is frame-synchronized among base stations, provides (1) beacons for portables to locate base stations and obtain DCA information, (2) broadcast channels for system and alerting information, and (3) pilot signals to permit portables to evaluate downlink interference. This allows low-complexity radio ports and portables to mutually select channels to avoid interference and avoid creating excessive interference. Results from computer simulations demonstrate the good spectrum efficiency of this method and its potential for handling nonuniform traffic demand. This work is targeted toward understanding the implications to local exchange networks of wireless system alternatives that could provide access to those networks.A preliminary work with the same title was presented at the Second International Conference on Universal Personal Communications, October 12–15, 1993, Ottawa, Canada.     

Distributed dynamic channel allocation algorithms in microcells under light traffic loading

We consider distributed dynamic channel allocation (DCA) algorithms for wireless cellular networks. Two algorithm extremes are the baseline of our investigation: Theaggressive type algorithms, where channel assignments of ongoing calls may be reconfigured to make room for a new access request; and thetimid one, where reconfigurations are not permitted. While, generally, analyses of DCA algorithms appear very difficult, we show here that a light traffic analysis can be tractable. For that realm, we derive performance expressions showing significant reductions in access blocking probability when an aggressive, rather than the timid, access algorithms is used. The relative efficacy of various algorithms that we present can be analytically probed in this range. Certain aggressive algorithms are observed to attain the best performance possible therein. The advantage over timid is particularly substantial for planar cellular arrays. These results hint that there may be significant channel savings, associated with the type of aggressive algorithms described here, in the important, yet much more difficult to analyze, operating realm where the blocking, but not necessarily the loading, is low; and lead us to devise a family of hybrid DCA algorithms that are both stable and low blocking.     

Handoff prioritisation with implicit channel reservation indistributed dynamic channel assignment algorithms

A new distributed dynamic channel assignment scheme with implicit channel reservation for handoff prioritisation is proposed. This scheme reduces the degree of computation and communications among base stations required for channel reservation and achieves a capacity similar to that of the maximum packing algorithm. For 40 total channels, the proposed algorithm achieves a 116% capacity increase relative to the nonprioritised fixed channel assignment (FCA) scheme and 93% relative to FCA with optimum channel reservation     

A compact dynamic channel assignment scheme based on Hopfield networks for cellular radio systems

In this paper, a new channel assignment strategy named compact dynamic channel assignment (CDCA) is proposed. The CDCA differs from other strategies by consistently keeping the system in the utmost optimal state, and thus the scheme allows to determine a call succeeding or failing by local information instead of that of the whole network. It employs Hopfield neural networks for optimization which avoids the complicated assessment of channel compactness and guarantees optimum solutions for every assignment. A scheme based on Hopfield neural network is considered before; however, unlike others, in this algorithm an energy function is derived in such a way that for a neuron, the more a channel is currently being allocated in other cells, the more excitation the neuron will acquire, so as to guarantee each cluster using channels as few as possible. Performance measures in terms of the blocking probability, convergence rate and convergence time are obtained to assess the viability of the proposed scheme. Results presented show that the approach significantly reduces stringent requirements of searching space and convergence time. The algorithm is simple and straightforward, hence the efficient algorithm makes the real‐time implementation of channel assignment based on neural network feasibility. Copyright © 2008 John Wiley & Sons, Ltd.     

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 dynamic channel assignment for in-building microsystems

Several fully distributed measurement-based dynamic channel assignment (DCA) schemes are compared for the large-scale uncoordinated deployment of in-building microsystems: DCA based on the first quality of service (DCA-FQZOS) channel selection, DCA based on best QOS channel selection (DCA-BQOS), DCA-WO (channel) (DCA with weighted channel orderings), and DCA-WO (carrier) (DCA with weighted carrier orderings). The DCA schemes are evaluated in terms of their blocking probabilities and algorithm processing delay. We also investigate how the DCA performance depends on the number of radio ports per base station, asynchronous time-slot transmission, and propagation conditions. Of the proposed DCA schemes, the simulation results show that there are tradeoffs in selecting a DCA scheme. Finally, a new scheme called DCA with limited selection weighted ordering (DCA-LSWO) is proposed that combines some previous strategies to improve performance for in-building microsystems     

Improved channel assignment scheme with access control for thecommon packet channel in WCDMA systems

We propose a channel assignment scheme with access control for obtaining better system performance within the common packet channel (CPCH) access procedure of wideband code-division multiple-access (WCDMA) systems. The proposed scheme is analyzed taking multiple access interference into consideration and is compared with other schemes in the 3rd Generation Partnership Project (3GPP): the basic scheme, the channel monitoring scheme, and the channel assignment scheme without access control. The results show that the proposed scheme provides high throughput, even under high-loading conditions, since the access control algorithm based on channel load prohibits excessive interference     

TDMA-based adaptive modulation with dynamic channel assignment forhigh-capacity communication systems

This paper proposes a time-division multiple-access (TDMA)-based adaptive modulation scheme with dynamic channel assignment (AMDCA) to achieve high-capacity communication systems under dynamically changing propagation path and traffic conditions. The proposed method measures the received carrier-to-noise plus interference power ratio (C/(N+I)) of each TDMA slot to search available slots as well as to find out the optimum modulation parameters for each terminal, thereby effectively combining the effect of mitigating both spatially distributed electric field strength variation by the slow adaptive modulation and spatially and temporally distributed traffic variation by the dynamic channel assignment (DCA). Computer simulation confirms that the proposed AMDCA system can achieve approximately three times higher system capacity than the conventional fixed channel assignment (FCA) using QPSK     

Distributed arbitration scheme for on-chip CDMA bus with dynamic codeword assignment

Several code-division multiple access (CDMA)-based interconnect schemes have been recently proposed as alternatives to the conventional time-division multiplexing bus in multicore systems-on-chip. CDMA systems with a dynamic assignment of spreading codewords are particularly attractive because of their potential for higher bandwidth efficiency compared with the systems in which the codewords are statically assigned to processing elements. In this paper, we propose a novel distributed arbitration scheme for dynamic CDMA-bus-based systems, which solves the complexity and scalability issues associated with commonly used centralized arbitration schemes. The proposed arbitration unit is decomposed into multiple simple arbitration elements, which are connected in a ring. The arbitration ring implements a token-passing algorithm, which both resolves destination conflicts and assigns the codewords to processing elements. Simulation results show that the throughput reduction in an optimally configured dynamic CDMA bus due to arbitration-related overheads does not exceed 5%.     

An efficient borrowing channel assignment scheme for cellularmobile systems

In this paper, we propose a new efficient borrowing channel assignment (BCA) scheme, which consists of two phases. The first ordinary channel allocation phase borrows a channel from neighboring cells by an impact-based borrowing strategy. The second channel reallocation phase has a reallocation procedure for locked-channel utilization and a reallocation procedure for efficient channel reuse. Simulation results show that in both uniform and nonuniform traffic cases, our schemes significantly reduce the system blocking probability over the other existing schemes. Furthermore, one of our schemes has a much smaller number of reallocations than other compared schemes     

Performance issues and algorithms for dynamic channel assignment

Using dynamic channel assignment (DCA) algorithms to select communications channels as needed, time-division multiple access (TDMA) or frequency-division multiple access (FDMA) systems can serve dynamic and nonuniform traffic demands without frequency planning as long as quality is sufficient and equipment is available. Here, performance issues and algorithms for DCA in a TDMA portable radio system are considered. A fixed number of traffic servers (time slots) per radio port is assumed: therefore, the system capacity is hard-limited by the equipment availability, and the DCA efficiency is compared mainly through the signal-to-interference ratio in both the uplink and downlink directions     

Static and dynamic channel assignment using neural networks

We examine the problem of assigning calls in a cellular mobile network to channels in the frequency domain. Such assignments must be made so that interference between calls is minimized, while demands for channels are satisfied. A new nonlinear integer programming representation of the static channel assignment (SCA) problem is formulated. We then propose two different neural networks for solving this problem. The first is an improved Hopfield (1982) neural network which resolves the issues of infeasibility and poor solution quality which have plagued the reputation of the Hopfield network. The second approach is a new self-organizing neural network which is able to solve the SCA problem and many other practical optimization problems due to its generalizing ability. A variety of test problems are used to compare the performance of the neural techniques against more traditional heuristic approaches. Finally, extensions to the dynamic channel assignment problem are considered     

Greedy-based dynamic channel assignment strategy for cellularmobile networks

This letter proposes a greedy-based dynamic channel assignment (GDCA) strategy in cellular mobile communication networks. Its main feature is that it dynamically allocates the channels based on the greedy method. Instead of the regular hexagon cell shape considered by previous strategies such as BCO, BDCL, various CP-DCA, the new strategy can be applied to any irregular cell shape. In addition, it reuses channels in terms of C/I ratio criteria. By system simulation, the proposed strategy outperforms the still used FCA on call blocking probability, and even has better performance compared to BDCL and CPDCA, etc     

Multibeam cellular communication systems with dynamic channel assignment across multiple sectors

In cellular communication systems, directional multibeam antennas at cell sites can be used to reduce cochannel interference, increase frequency reuse and improve system capacity. When combined with dynamic channel assignment (DCA), additional improvement is possible. We propose a multibeam scheme using dynamic channel assignment across multiple sectors. A cell is divided into several sectors, each of which is covered by several directional beams. Specific channels are allocated to each sector as in fixed channel assignment (FCA). A channel of a sector is dynamically assigned to a wireless user who communicates through one of the several beams of the sector. The assignment is made so that constraints on the allowable cochannel interference are satisfied. Limitations due to cochannel interference are analyzed. A tractable analytical model for the proposed scheme is developed using multidimensional birth–death processes. Theoretical traffic performance characteristics such as call blocking probability, forced termination probability, handoff activity, carried traffic and channel rearrangement rate are determined. With the proposed scheme, call blocking probability can be reduced significantly for a fixed offered traffic. Alternatively, system capacity can be increased while blocking probability is maintained below the required level. Smaller forced termination probability is obtainable in comparison with corresponding FCA schemes.     

A PCE-based dynamic backup-reservation wavelength assignment scheme for WSONs

For the Destination Initialed Reservation in PCE-based Wavelength Switched Optical Networks using the distributed wavelength assignment scheme, the establishment of a lightpath might be blocked because of the contention for the same wavelength between two or more concurrent requests traversing the same links, although there might be enough wavelength resource available. In order to reduce the blocking caused by contention, in the PCE-based architecture a Dynamic Backup-reservation Wavelength Assignment (DBWA) scheme has been proposed in this paper. Considering that it is not an advisable way to reserve additional wavelength when the resource is lacking and meanwhile a lightpath with more physical hops has higher probability to collide with others, a threshold is defined to decide whether to reserve a backup wavelength or not. Simulation results show that, by setting a proper value for threshold, DBWA can reduce the contention-induced blockings efficiently in comparison with the two traditional schemes.     

一种新的基于GPON的动态带宽分配算法

为了实现吉比特无源光网络(GPON)带宽分配的公平性,降低网络的丢包率及传输延时,文章研究了GPON系统传输汇聚层的帧结构及动态带宽分配的实现方法,提出了一种新的动态带宽分配(DBA)算法--基于QoS的二层动态带宽分配算法.基本思路是根据不同等级业务的带宽需求,在PON层和ONU层分别进行带宽的合理分配.理论分析和仿真试验证明,这种算法可以提高带宽的利用率,保证不同业务的不同时延要求,并且对不同用户和不同等级的业务都具有很好的公平性.