Dynamic Channel Allocation Scheme Research Articles

Dynamic Channel Allocation in Wireless Networks Using Adaptive Learning Automata

Single-channel based wireless networks have limited bandwidth and throughput and the bandwidth utilization decreases with increased number of users. To mitigate this problem, simultaneous transmission on multiple channels is considered as an option. In this paper, we propose a distributed dynamic channel allocation scheme using adaptive learning automata for wireless networks whose nodes are equipped with single-radio interfaces. The proposed scheme, Adaptive Pursuit learning automata runs periodically on the nodes, and adaptively finds the suitable channel allocation in order to attain a desired performance. A novel performance index, which takes into account the throughput and the energy consumption, is considered. The proposed learning scheme adapts the probabilities of selecting each channel as a function of the error in the performance index at each step. The extensive simulation results in static and mobile environments provide that the proposed channel allocation schemes in the multiple channel wireless networks significantly improves the throughput, drop rate, energy consumption per packet and fairness index—compared to the 802.11 single-channel, and 802.11 with randomly allocated multiple channels. Also, it was demonstrated that the Adaptive Pursuit Reward-Only (PRO) scheme guarantees updating the probability of the channel selection for all the links—even the links whose current channel allocations do not provide a satisfactory performance—thereby reducing the frequent channel switching of the links that cannot achieve the desired performance.

상향링크 셀룰러 시스템에서 그룹 탐색 기반의 분산동적채널할당 방법

주파수 재사용률 1을 사용하는 상향링크 셀룰러 시스템의 동적채널할당 (DCA : Dynamic Channel Allocation) 방법에서는 신규호가 채널 할당을 요구할 때 신규호의 SINR (Signal to Interference and Noise Ratio)이 요구된 SINR 보다 작거나 할당할 채널이 부족한 경우에 신규호 차단이 발생한다. 이러한 차단된 신규호에 대한 추가적인 채널할당을 위하여 인접한 셀에서 채널을 가져오게 된다. 이 경우에 동일 채널 간섭 (CCI: Co-Channel Interference)이 발생하게 되고 이로 인해 기존 호의 SINR이 저하되어 기존 호에 대한 채널 재할당을 해야 하는 경우가 생기게 된다. 따라서 신규호 블록율이 증가할수록 인접한 셀에서 채널을 가져오는 경우의 수를 증가시킴으로써 채널 재할당 과정은 복잡한 연산과정이 필요한 NP-hard 문제가 된다. 그 문제를 해결하기 위하여 본 논문에서는 차단된 신규호를 감소시킴으로써 추가적인 채널할당을 위하여 인접한 셀에서 채널을 가져오는 횟수를 감소시키고 그 결과로 채널 재할당 횟수가 감소되어 복잡한 연산과정을 피할 수 있는 Group Search-based DCA 방법을 제안한다. 제안한 방법은 신규호의 차단율을 감소시키기 위하여 신규호에 대한 채널할당시 단말이 속해 있는 셀뿐만 아니라 그 주변의 셀까지를 한 그룹으로 묶어서 채널 탐색 범위를 확장하는 방법을 사용한다. 시뮬레이션 결과에서 제안한 Group Search-based DCA가 탐색 범위를 단말이 속한 셀로 한정하는 Single Search-based DCA보다 신규호 차단률과 시스템 수율 성능을 향상시킴을 확인할 수 있었다. In DCA (Dynamic Channel Allocation) scheme of uplink cellular system appling a frequency reuse factor of one, when a new call requests a channel, the new call will be blocked if its SINR (Carrier to Noise and Interference Ratio) is less than the required SINR or there is no available channel. The additional channel allocation for the blocked new call can be performed with channel borrowing in the adjacent cells. The channel borrowing causes the CCI (Co-Channel Interference), thus the SINR of the existing calls is deteriorated and the channel reallocation for the existing calls is required. As a result, the channel borrowing leads to a complex calculation so that it is a NP-hard problem. Therefore, to overcome the problem, we propose a novel Group Search-based DCA scheme which decreases the number of the blocked new calls and then reduces the number of the channel reallocation by the channel borrowing for the blocked new calls. The proposed scheme searches the all channels in a group of the adjacent cells and home cell at the same time in order to minimizes the number of the blocked new calls. The simulation results show that proposed Group Search-based DCA scheme provides better new call blocking probability and system throughput than the existing Single Search-based DCA scheme which searches only the channels in home cell.

Ant Colony Optimization Algorithm for Centralized Dynamic Channel Allocation in Multi-Cell OFDMA Systems

The dynamic channel allocation (DCA) scheme in multi-cell systems causes serious inter-cell interference (ICI) problem to some existing calls when channels for new calls are allocated. Such a problem can be addressed by advanced centralized DCA design that is able to minimize ICI. Thus, in this paper, a centralized DCA is developed for the downlink of multi-cell orthogonal frequency division multiple access (OFDMA) systems with full spectral reuse. However, in practice, as the search space of channel assignment for centralized DCA scheme in multi-cell systems grows exponentially with the increase of the number of required calls, channels, and cells, it becomes an NP-hard problem and is currently too complicated to find an optimum channel allocation. In this paper, we propose an ant colony optimization (ACO) based DCA scheme using a low-complexity ACO algorithm which is a kind of heuristic algorithm in order to solve the aforementioned problem. Simulation results demonstrate significant performance improvements compared to the existing schemes in terms of the grade of service (GoS) performance and the forced termination probability of existing calls without degrading the system performance of the average throughput.

Supporting Asymmetric Traffic in a TDD/CDMA Cellular Network via Interference-Aware Dynamic Channel Allocation and Space–Time LMMSE Joint Detection

In a time-division duplexing (TDD)/code-division multiple-access (CDMA) cellular network with asymmetric data traffic, dynamic channel allocation (DCA) enhances resource utilization compared with fixed channel allocation (FCA). However, it also induces base-to-base and mobile-to-mobile crossed-slot intercell interference, which can severely degrade system performance. To deal with this problem, a decentralized scheme is proposed, which combines an interference-aware DCA algorithm with space-time linear minimum-mean-square-error (LMMSE) joint detection at the base and mobile stations. The former assigns active links to timeslots in a way that crossed-slot interference is mitigated, while the latter suppresses the remaining intercell interference (along with intersymbol and intracell interference), exploiting its spatio-temporal autocorrelation statistics. The performance of this scheme is evaluated in terms of downlink and uplink signal-to-interference-plus-noise ratio (SINR) outage and average throughput via analytical approximations and Monte Carlo simulations, and it is compared with that of benchmark random DCA (RDCA) and FCA schemes. The cases of single- and dual-antenna reception with perfect and imperfect channel state information are examined. It is shown that the proposed scheme achieves higher average throughput than FCA (particularly for dual-antenna reception) as well as RDCA (for heavy traffic loads). These throughput gains are more significant in uplink than in downlink.

Performance analysis of a threshold based distributed channel allocation algorithm for cellular networks

Rapid advances of the handheld devices and the emergence of the demanding wireless applications require the cellular networks to support the demanding user needs more effectively. The cellular networks are expected to provide these services under a limited bandwidth. Efficient management of the wireless channels by effective channel allocation algorithms is crucial for the performance of any cellular system. To provide a better channel usage performance, dynamic channel allocation schemes have been proposed. Among these schemes, distributed dynamic channel allocation approaches showed good performance results. The two important issues that must be carefully addressed in such algorithms are the efficient co-channel interference avoidance and messaging overhead reduction. In this paper, we focus on our new distributed channel allocation algorithm and evaluate its performance through extensive simulation studies. The performance evaluation results obtained under different traffic load and user mobility conditions, show that the proposed algorithm outperforms other algorithms recently proposed in the literature.

A Distributed Dynamic Channel Allocation Scheme in Cellular Communication Networks

This article presents a description and performance evaluation of an efficient distributed dynamic channels allocation (DDCA) scheme, which can be used for channel allocation in cellular communication networks (CCNs), such as the global system for mobile communication (GSM). The scheme utilizes a well-known distributed artificial intelligence (DAI) algorithm, namely, the asynchronous weak-commitment (AWC) algorithm, in which a complete solution is established by extensive communication among a group of neighbouring collaborative cells forming a pattern, where each cell in the pattern uses a unique set of channels. To minimize communication overhead among cells, a token-based mechanism was introduced. The scheme achieved excellent average allocation efficiencies of over 85% for a number of simulations.

Traffic Model and Performance Analysis of Cellular Mobile Systems for General Distributed Handoff Traffic and Dynamic Channel Allocation

An analytical model for channelized cellular mobile circuit-switched systems that support general arbitrary distributed handoff traffic has been proposed. The model is applicable for a dynamic channel allocation scheme. A 2-D Markov chain is developed, which can be used to compute congestion for all kinds of traffic streams. The proposed model is not restricted by a limited range of user mobility and can be reduced to predict congestion for Poisson-distributed handoff traffic and fixed channel allocation scheme.

Optimal channel allocation algorithm with efficient channel reservation for cellular networks

Today, there is a rapid growth of mobile users. As the available frequency spectrum is limited, it must be efficiently utilised. This paper proposes a dynamic channel allocation scheme with efficient channel reservation for handoff calls. The proposed algorithm deals with both originating calls and handoff calls. In the proposed algorithm, we reserve some channels for handoff calls. Later, it increments or decrements, the reserved channels dynamically based on the traffic. Quality of Service (QoS) may be improved further by reserving the channels for handoff calls based on the user mobility and type of cell. The reservation factor, which varies the number of reserved channels, is based on both the blocking probability and the dropping probability. The results indicate clearly that the proposed channel allocation scheme exhibits better performance by considering the above said user mobility and type of cells. Also, it reduces the call dropping rate than the existing channel allocation schemes.

On the Effect of User Mobility in Mobile Radio Systems With Distributed DCA

In this paper, the impact of user mobility and the handover process on the performance of interference adaptive (IA) dynamic channel allocation (DCA) schemes is investigated. Among the hundreds of papers that can be found in the literature dealing with DCA (IEEE Pers. Commun., vol. 3, no. 3, p. 10, Jun. 1996), only very few analyze their performance by taking into proper consideration all the aspects related to user mobility: the speed of mobiles, the handover process, the radio channel fluctuations, and the forced terminations. The results we show in this paper have been achieved by means of a simulation tool that takes propagation, mobility, handover, power control, directed retry (DR), interference, traffic, and channel allocation into account. Moreover, some simplified analytical descriptions are given to discuss the behavior of the blocking probability when varying the speed of users. We compare the performance of well-known totally distributed IA-DCA schemes (least interference algorithm and least interference and threshold algorithm) ( IEEE J. Sel. Areas Commun., vol. 14, no. 5, p. 698, May 1996) to that of a partially distributed algorithm. The comparison to fixed channel allocation is also considered, and the role of DR is emphasized. To emphasize the role played by the speed of the terminals, two different mobility models are considered; the numerical results show that the satisfaction probability changes when taking user mobility into account, whereas the blocking probability is scarcely affected by the mobile speed; the latter statement is compared to previous results from the literature, and it is in good agreement

Dynamic guard channel allocation scheme for calls in WONs

Future wireless networks will provide ubiquitous communication services to a large number of mobile users. The design of such networks is based on heterogeneous wireless overlay networks that allow efficient use of the limited available spectrum, and also cover different ranges of coverage areas. A dynamic guard channel allocation scheme for calls in wireless overlay networks is developed. The new scheme considers the mobility, current location of mobile terminals, and bandwidth status in allocating bandwidth for new calls in order to guarantee the quality of service for all calls.

Special Issue on Next Generation Wireless Technologies

The next generation wireless networks are expected to converge into a ubiquitous architecture, which includes high-speed cellular networks, wireless local area networks (WLANs), mobile ad hoc networks, peer-to-peer networks, wireless metropolitan area networks (WMANs), etc. The increasing demand of wireless multimedia services has motivated the development of broad wireless access in the heterogeneous wireless networks. Mobile subscribers can enjoy the high bit rate, low cost, ubiquitous coverage, and secure connection. For the next generation wireless networks, further extensive investigation, experimentation and development are necessary, such as capacity analysis/ enhancement, quality-of-service (QoS) support, power saving, wireless routing, security, and mobility management. This special issue presents recent cutting edge research and state-of-the-art technology. The accepted eight papers are selected from the 2nd International Conference on Broadband Networks (BroadNets’05, held in Boston, MA, Oct. 3–7, 2005), the 2nd International Conference on Quality of Service for Heterogeneous Wired/Wireless Networks (QShine’05, held in Orlando, FL, Aug. 22–24, 2005), and the 11th Mobile Computing Workshop (held in Taiwan, Mar. 31, 2005). These papers are timely and valuable for future analysis, implementation and experiments of heterogeneous broadband wireless networks. In the first paper “Dynamic power saving mechanism for 3G UMTS system,” Yang investigates a power saving mechanism for Universal Mobile Telecommunications System (UMTS). Analytic and simulation models are proposed to study the two control parameters: discontinuous reception (DRX) cycle and the inactivity timer threshold. Optimal values of the two parameters in terms of maximum power saving are obtained. A dynamic algorithm is also proposed to enhance the performance of DRX. In the second paper “Predictive dynamic channel allocation scheme for improving power saving and mobility in BWA networks,” Chen and Tan propose a signal-aware dynamic channel allocation (SDCA) to improve the channel utilization as well as to reduce the probability of out-ofservice for IEEE 802.16 networks. The SDCA not only increases the capacity of the system but saves the overall power consumption of the system well. A location prediction scheme is presented to prevent the out-of-service effect on mobile subscriber stations due to user mobility. In the third paper “Queue analysis and multiplexing of heavy-tailed traffic in wireless packet data networks,” Teymori and Zhuang investigate the queuing behavior of self-similar traffic flows for data applications in a packetswitching single-server wireless network. Close-form expressions are derived for the relation among the traffic parameters, the channel working state probability, the server capacity, and the queue distribution for an infinite Mobile Netw Appl (2007) 12:1–3 DOI 10.1007/s11036-006-0001-1

Predictive Dynamic Channel Allocation Scheme for Improving Power Saving and Mobility in BWA Networks

The radio spectrum of IEEE 802.16 medium access control (MAC) protocol ranges from 2-66 GHz, which is one of potential solutions for broadband wireless access (BWA) or beyond third generation (B3G)...

Ultimate Dynamic Spectrum Allocation via User-Central Wireless Systems

Current wireless systems are called vendor-central systems because, users should subscribe to a service provider (vendor) and receive the service through the spectrum assigned to that vendor at all times. Vendorcentral systems suffer from low utility performance defined in terms of spectrum efficiency, blocking rate, and revenue. Variety dynamic channel allocation schemes have been proposed to address the weak utility performance of vendor-central systems.In this work, a futuristic user-central wireless system architecture that leads to an ultimate freedom in channel allocation will be introduced. This architecture is implemented based on the capabilities of cognitive radios. In user-central systems, a user has the freedom of receiving the service through an optimum vendor at any time instance and geographical location. The optimum vendor is selected by an intelligent mobile based on parameters such as the vendor signal power, channel availability, congestion rate, cost-per-second, and quality-of-service. We propose that vendors form a vendor area network (VAN) controlled by an inter-vendor mobile registration center (MRC). This paper discusses the system’s structure, call procedure, and utility performance benefits attained by this system.

Distributed Dynamic Channel Assignment for Multi-Hop DS-CDMA Virtual Cellular Network

SUMMARY In this paper, the channel segregation dynamic channel allocation (CS-DCA) scheme is applied to a multi-hop DS-CDMA virtual cellular network (VCN). After all multi-hop routes are constructed over distributed wireless ports in a virtual cell, the CS-DCA is carried out to allocate the channels to multi-hop up and down links. Each wireless port is equipped with a channel priority table. The transmit wireless port of each link initiates the CS-DCA procedure and selects a channel among available ones using its channel priority table to check. In this paper, the channel allocation failure rate is evaluated by computer simulation. It is shown that CS-DCA reduces remarkably the failure rate compared to FCA. The impact of propagation parameters on the failure rate is discussed.

A Fault-Tolerant Distributed Channel Allocation Scheme for Cellular Networks

In cellular networks, it is vital to allocate communication channels efficiently because the bandwidth allocated for cellular communication is limited. If channels are statically allocated, as is the case in current cellular networks, a cell may run out of channels when a large number of mobile hosts move to the cell. To overcome this problem, dynamic channel allocation approaches have been proposed. Under dynamic channel allocation, channels are allocated to cells on demand, thus increasing channel utilization. Such channel allocation approaches fall under two categories, namely, centralized and distributed. Centralized approaches are neither scalable nor reliable, while distributed approaches have the potential to be both reliable and scalable. In the distributed approaches, a mobile service station is responsible for allocating channels to mobile hosts in the same cell. In cellular networks, mobile service stations may fail. In addition, the network may encounter intermittent network congestion and/or link failures. It is desirable for a channel allocation algorithm to work well, even in the presence of network congestion, link failures, and/or mobile service station failures. In this paper, we present a distributed dynamic channel allocation scheme for cellular networks that is fault-tolerant. Our approach can tolerate the failure of mobile service stations, link failure, and network congestion, and make efficient reuse of channels. We also provide results of the performance evaluation of our algorithm.

Adjustable broadcast protocol for large-scale near-video-on-demand systems

Video-on-demand (VOD) is a service allowing customers to select video programs from a central server for viewing on a television or a computer screen. Traditional unicast VOD systems require huge amounts of the server network's bandwidth, so near-VOD systems using broadcast protocols have been proposed to reduce the bandwidth requirement. Although NVOD systems can service many users with less network bandwidth by broadcasting popular videos, the popularity of any given video is likely to vary widely as time goes on. However, the broadcast protocols cannot adapt to dynamic environments where the popularity distribution of videos changes, because of their fixed broadcasting schedule. We introduce a dynamic broadcast protocol called Adjustable Broadcast ( AB) based on on-line scheduling, which can adjust the number of channels being used on the fly. AB also exploits various prefetching strategies in the broadcast schedule to reduce the required bandwidth. And, we propose a dynamic channel allocation scheme using AB that minimizes the average viewer's waiting time. Using extensive simulation, we have demonstrated the effectiveness of AB and the adaptability of our dynamic channel allocation.

Using Priority, Buffering, Threshold Control, and Reservation Techniques to Improve Channel-Allocation Schemes for the GPRS System

Taking a comprehensive approach, we investigate effects on the channel allocation for the general packet radio service (GPRS) system caused by priority strategy, buffering, threshold control on the buffer, and channel reservation. Moreover, four new dynamic channel-allocation schemes based on various combinations of these techniques are proposed and analyzed using the Markov chain approach. Analytical results obtained include blocking/forced-termination/dropping probabilities, cost-function definition based on the above metrics, and (mean) delay times. Through numerical examples, we demonstrate that: 1) priority and threshold control are efficient strategies to differentiate the quality of service (QoS) between a new voice call and a handoff voice call; 2) buffering allows more admitted rates of voice calls or data packets, but increases the delay time; and 3) channel reservation may directly improve a specific service, but it degrades performance of other services much. At last, better schemes suitable for the GPRS system are suggested after a thorough comparison of system performance.

A simulation environment for GPRS traffic in an advanced travellers information system (ATIS)

General Packet Radio Service (GPRS)—a bearer service to GSM—has been deployed worldwide, and is widely considered a technology precursor to the evolving third generation (3G) wireless networks. The general conception has been that while users will be exposed to faster wide-area wireless data access, experience gained from GPRS could well prove useful for 3G, and also for systems beyond 3G deployment. In this paper, we present a comprehensive simulation study for different traffic scheduling algorithms for Quality of Service (QoS) in GPRS at the IP level. We first study the correlation between GSM and GPRS users, and show how a dynamic channel allocation scheme between GSM–GPRS can give substantially better performance than the static ones. We then extend our study by taking into account users requirements for different QoS profiles, based on seven different scheduling algorithms in GPRS. By simulating traffic related to an ATIS (Advanced Travellers Information System) at the IP level, we show how traffic scheduling algorithms perform by taking into account different performance parameters such as the average traffic, average waiting time in the scheduler, packet loss probabilities in the scheduler based on static and dynamic channel allocation schemes, packet priorities as well as average throughput per-GPRS user. The study gives a comparative analysis for various scheduling

MADF: Mobile-assisted data forwarding for wireless data networks

In a cellular network, if there are too many data users in a cell, data may suffer long delay, and system's quality-of-service (QoS) will degrade. Some traditional schemes such as dynamic channel-allocation scheme (DCA) will assign more channels to hot (or overloaded) cells through a central control system (CC) and the throughput increase will be upper bounded by the number of new channels assigned to the cell. In mobile-assisted data forwarding (MADF), we add an ad-hoc overlay to the fixed cellular infrastructure and special channels-called forwarding channels-are used to connect mobile units in a hot cell and its surrounding cold cells without going through the hot cell's base station. Thus, mobile units in a hot cell can forward data to other cold cells to achieve load balancing. Most of the forwarding-channel management work in MADF is done by mobile units themselves in order to relieve the load from the CC. The traffic increase in a certain cell will not be upper bounded by the number of forwarding channels. It can be more if the users in hot cell are significantly far away from one another and these users can use the same forwarding channels to forward data to different cold neighboring cells without interference. We find that, in a system using MADF, under a certain delay requirement, the throughput in a certain cell or for the whole network can be greatly improved.

Capacity optimizing channel allocation schemes for multi‐service cellular systems

AbstractThe trend of the wireless communication system is to provide various types of services such as voice, data and video etc. Due to the limited radio resources with international agreement, how to achieve the optimum system capacity becomes a paramount issue. In this paper, we use the idea of channel partitioning (CP) employing different reuse factors to support multiple services that require different signal‐to‐interference ratios (SIRs) in cellular systems. Two types of services are considered in this paper. Thus, we use a large reuse factor to support high SIR required service while we use a small reuse factor to support low SIR required service. From the system point of view, the average reuse factor becomes smaller and the system capacity can be improved. The system performance of CP with fixed channel allocation (FCA) scheme, namely fixed channel partitioning (FCP), is first proposed and analysed using Markov chain in a single cell model. Then a dynamic channel allocation scheme with CP called dynamic channel partitioning with interference information (DCP‐WI) is proposed and studied in the multiple‐cell model by computer simulation. The analysis and simulation results show that our proposed schemes can improve the system capacity depending on the traffic load fraction for each service. For equal arrival rate for both services, FCP and DCP‐WI provide about 33 and 60% capacity improvement respectively over a conventional FCA system using a single reuse factor to support two types of services. Copyright © 2004 John Wiley & Sons, Ltd.