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Showing papers on "Channel allocation schemes published in 2002"


Patent
06 May 2002
TL;DR: In this paper, a method and system for dynamically selecting a communication channel between an access point (AP) and a plurality of stations (STAs) in an IEEE 802.11 wireless local area network (WLAN) is presented.
Abstract: Disclosed is a method and system for dynamically selecting a communication channel between an access point (AP) and a plurality of stations (STAs) in an IEEE 802.11 wireless local area network (WLAN). The method includes the steps of: determining whether a new channel to be used by the plurality of STAs is needed; measuring the channel quality of a plurality of frequency channels by at least one of the plurality of STAs; reporting the quality of the plurality of frequency channels in terms of a received signal strength indication (RSSI), Clear Channel Assessment (CCA) busy periods and periodicity; and, selecting one of the candidate channels based on the channel quality report for use in communication between the AP and the plurality of STAs.

349 citations


Patent
10 May 2002
TL;DR: In this article, a single mode mobile terminal is used to support mobile assisted signal strength measurement operations in both a fixed frequency reuse based communication network and an adaptive channel allocation-based communication network.
Abstract: Communication systems and methods are provided allowing a single mode mobile terminal to support mobile assisted signal strength measurement operations in both a fixed frequency reuse based communication network and an adaptive channel allocation based communication network. Candidate base station signal strength measurements are requested by a fixed frequency reuse type network, measured by the mobile terminal and provided to the fixed frequency reuse type network which is seeking to identify a strongest signal for mobile assisted handover operations. In addition, interference signal strength measurements are requested by an adaptive channel allocation type network, measured by the mobile terminal and provided to the adaptive channel allocation type network by the mobile terminal. No redundant circuitry is required in the mobile terminal. Instead, the mobile terminal executes the same operations using the same hardware regardless of whether the requested measurement is of a candidate signal strength or an interference signal.

272 citations


Proceedings ArticleDOI
06 Nov 2002
TL;DR: An approach of optimizing AP placement and channel assignment in WLAN by formulating an optimal integer linear programming (ILP) problem to minimize the maximum of channel utilization, which qualitatively represents congestion at the hot spot in Wlan service areas is proposed.
Abstract: The design of a wireless local area network (WLAN) has an important issue of determining the optimal placement of access points (AP) and assignment of channels to them. WLAN services in the outdoor as well as indoor environments should be designed in order to achieve the maximum coverage and throughput. To provide the maximum coverage for WLAN service areas, AP should be installed such that the sum of signal measured at each traffic demand point is maximized. However, as users connected to an AP share wireless channel bandwidth with others in the same AP, AP placement should be carefully decided to maximize the throughput by considering load balancing among AP and channel interference for the user traffic demand. In this paper, therefore, we propose an approach of optimizing AP placement and channel assignment in WLAN by formulating an optimal integer linear programming (ILP) problem. The optimization objective is to minimize the maximum of channel utilization, which qualitatively represents congestion at the hot spot in WLAN service areas. It is seen from the simulation results that the proposed method finds the optimal AP placement and channels which minimize the maximum of channel utilization.

269 citations


Proceedings ArticleDOI
07 Aug 2002
TL;DR: This work proposes a priority-based fair medium access control protocol by modifying the distributed coordination function (DCF) of the IEEE 802.11 MAC, and approximations to the optimal contention window sizes, which are based on a theoretical analysis, are evaluated numerically and shown to work well under different network configurations and traffic scenarios.
Abstract: Fair allocation of bandwidth and maximization of channel utilization are two important issues when designing a contention-based wireless medium access control (MAC) protocol. However, achieving both design goals at the same time is very difficult, and has not yet been addressed elsewhere. We study this challenging problem, particularly for data communications in IEEE 802.11 wireless local area networks (WLANs). We propose a priority-based fair medium access control (P-MAC) protocol by modifying the distributed coordination function (DCF) of the IEEE 802.11 MAC. The key idea is that the contention window size for each wireless station is properly selected to reflect: (1) the relative weights among data traffic flows, so as to achieve the weighted fairness; (2) the number of stations contending for the wireless medium, so as to maximize the aggregate throughput. In P-MAC, our approximations to the optimal contention window sizes, which are based on a theoretical analysis, are evaluated numerically and shown to work well under different network configurations and traffic scenarios. Moreover, simulation results show that, with few changes to the original DCF, P-MAC performs significantly better in terms of both fairness and throughput.

200 citations


Patent
14 Mar 2002
TL;DR: In this paper, a channel map is created and maintained at each mobile station of the ad hoc network, and any of the mobile stations is selectable to form a DFS owner that defines the channel frequency to be used upon which to define a communication channel for communications in the network.
Abstract: An assembly, and an associated method, for an ad hoc network, such as an independent basic service set defined in an IEEE 802.11 protocol specification. A channel map is created and maintained at each mobile station of the ad hoc network. The channel map is populated with channel characteristic indicia of channel frequencies that might be available upon which to be used in the ad hoc network to effectuate communications between the mobile stations. Information related to the channel map created and maintained at each of the mobile stations is exchanged, and any of the mobile stations is selectable to form a DFS owner that defines the channel frequency to be used upon which to define a communication channel for communications in the network.

138 citations


Journal ArticleDOI
TL;DR: This paper shows how to minimize the average response time given multiple broadcast channels by optimally partitioning data among them and offers an approximation algorithm that is less complex than the optimal and shows that its performance is near-optimal for a wide range of parameters.
Abstract: Broadcast is a scalable way of disseminating data because broadcasting an item satisfies all outstanding client requests for it. However, because the transmission medium is shared, individual requests may have high response times. In this paper, we show how to minimize the average response time given multiple broadcast channels by optimally partitioning data among them. We also offer an approximation algorithm that is less complex than the optimal and show that its performance is near-optimal for a wide range of parameters. Finally, we briefly discuss the extensibility of our work with two simple, yet seldom researched extensions, namely, handling varying sized items and generating single channel schedules.

134 citations


Patent
08 May 2002
TL;DR: In this paper, a channel swapping mechanism was proposed to improve the dynamic frequency selection (DFS) algorithm used in wireless LANs by adding a swapping mechanism to avoid the problem of sub-optimal channel selection.
Abstract: The present invention enhances the dynamic frequency selection 9DFS) algorithms used in Wireless LANs by adding a channel swapping mechanism. The aim of the traditional DFS algorithm is to dynamically select channels in a wireless LAN in such a way that the best performance is achieved. However, not always the optimal channel selection is achieved. This invention describes an addition to the DFS algorithm in such a way that two APs can decide to swap channels instead of one AP switching to another channel. To avoid the problem of sub-optimal channel selection, a requesting AP sends Swap Requests to other APs in order to sense the willingness of other APs to swap channels with the requesting AP.

127 citations


Proceedings ArticleDOI
10 Dec 2002
TL;DR: A novel cross layer design concept that could improve the network throughput significantly for mobile ad hoc networks by utilizing channel reservation control packets employed at the MAC layer for exchanging timely channel estimation information to enable an adaptive selection of a spectrally efficient transmission rate.
Abstract: We propose a novel cross layer design concept that could improve the network throughput significantly for mobile ad hoc networks. The channel reservation control packets employed at the MAC layer can be utilized at the physical layer for exchanging timely channel estimation information to enable an adaptive selection of a spectrally efficient transmission rate. In particular, the size of a digital constellation can be varied dynamically based on the channel condition estimated at the receiver which can be relayed to the transmitter via the control packets. In addition, this channel adaptive information gathered at the MAC layer can be communicated to the routing layer via different routing metrics for optimal route selection. We have examined the performance improvement at the network layer due to cross layer communications. For this, we present a simple cross layer design implemented with minor modifications on the IEEE 802.11 standard and the dynamic source routing (DSR) protocol. We demonstrate that the network throughput is significantly increased, as much as 50% to 100%, in low mobility scenarios simulated using ns-2.

104 citations


Proceedings ArticleDOI
07 Aug 2002
TL;DR: The spectrum utilization, blocking probability and forced termination probability for these two different channel access schemes are compared.
Abstract: Spectrum for mobile networks is becoming scarce and on the other hand plenty of sporadically used frequencies exist. The spectrum utilization of such spectra is very low, which is a reason to think about a way to make them available for commercial purpose without a drawback for the license owners. We recommend a strategy called spectrum pooling which is based on this idea. The notion spectrum pool was first mentioned by Mitola III (see Proc. IEEE International Workshop on Mobile Multimedia Communications, p.3-10, 1999). In a spectrum pooling system the license owner of the spectrum allows priorly specified candidate renters to use his spectrum until he needs his spectrum himself. The renters of the spectrum may be treated in two different ways. One way is that communication processes of spectrum renters can persist as long as there are channels for the processes of the license owners. The other way is that the owner has no knowledge whether the channels are occupied by renters or not and treat the channels used by renters like free channels. In both cases the renters have to measure the interference level in the channel after dedicated time intervals and have to leave the channel within the time interval T/sub p/ as soon as the interference exceeds a prior specified threshold. We compare the spectrum utilization, blocking probability and forced termination probability for these two different channel access schemes.

98 citations


Proceedings ArticleDOI
07 Nov 2002
TL;DR: This work proposes an algorithm to allocate channels to users based on their spatial separability properties, while appropriately adjusting beamforming weights and transmission rates for each user in a channel in the context of orthogonal frequency division multiplexing (OFDM).
Abstract: The increasing popularity of wireless broadband access in local and wide area networks is the main expression of the need for flexible and ubiquitous wireless connectivity. In order to satisfy user resource requirements in the presence of volatility of the wireless medium, sophisticated multiple access and adaptation techniques are required, which alleviate channel impairments and increase system throughput. The use of multiple antennas at the base station allows intra-cell channel reuse by multiple spatially separable users through space division multiple access (SDMA) and hence enhances cell capacity. However, the employment of antennas in the physical layer raises significant issues in the medium access control (MAC) layer. We investigate the impact of antenna arrays on MAC layer channel allocation in the context of orthogonal frequency division multiplexing (OFDM), which is the predominantly proposed signaling scheme for wireless broadband access. We propose an algorithm to allocate channels to users based on their spatial separability properties, while appropriately adjusting beamforming weights and transmission rates for each user in a channel. The unified consideration of such adaptive techniques yields significant throughput benefits.

96 citations


Journal ArticleDOI
10 Dec 2002
TL;DR: The optimal transmit power allocation scheme to improve bit-error rate (BER) performance in a multicarrier system with diversity reception is developed andumerical results show that the optimal and suboptimal power allocation schemes significantly outperform the equalPower allocation scheme.
Abstract: In a multicarrier system, transmit power allocation over different subchannels is an effective means of improving the performance We develop the optimal transmit power allocation scheme to improve bit-error rate (BER) performance in a multicarrier system with diversity reception A simple suboptimal scheme is also derived from the optimal one, and an asymptotic case referred to as the equal-signal-to-noise ratio scheme is discussed Numerical results show that the optimal and suboptimal power allocation schemes significantly outperform the equal power allocation scheme The effects of the modulation level, the number of receiving antennas, and the number of subchannels on the BER performance are also investigated

Proceedings ArticleDOI
07 Nov 2002
TL;DR: An analytical model for cellular networks with a combined adaptive bandwidth allocation and traffic-restriction mechanism is developed and two important quality-of-service (QoS) metrics, degradation ratio and upgrade/degrade frequency are derived.
Abstract: An analytical model is developed for cellular networks with a combined adaptive bandwidth allocation and traffic-restriction mechanism. Instead of focusing only on the bandwidth utilization and forced-termination probability, we derive two important quality-of-service (QoS) metrics, degradation ratio and upgrade/degrade frequency. We show numerically that these two metrics must be taken into account in order to support the QoS specified by each client. The effects of system loads and clients' mobility on system performance are also investigated. Even under the various distributions of mobility, the simulation results are shown to match our analytical results, implying the applicability of our analytical model to more general cases.

Journal ArticleDOI
TL;DR: It is shown that with the proposed algorithms, the RWA problem with tunnel allocation in the optical networks containing MG-OXCs can be solved effectively and that DTA is outperformed by CB-STA in the same network environment due to a well-disciplined approach for allocating tunnels with CB- STA.
Abstract: We propose a novel switching architecture of multigranularity optical cross-connects (MG-OXCs) for dealing with multigranularity traffic in the optical domain. MG-OXCs can cooperate with the generalized multiprotocol label switching (MPLS) control plane, which provides the advantages of cost reduction, better scalability in physical size, and unified traffic management. Detailed discussions are provided on the characteristics and implementation issues for the switching architecture. Based on the proposed MG-OXCs, two routing and wavelength assignment (RWA) with tunnel allocation algorithms are presented: dynamic tunnel allocation (DTA) and capacity-balanced static tunnel allocation (CB-STA). In the former, we use fixed alternate routing with k-shortest paths to inspect network resources along each alternate path for dynamically setting up lightpaths. For the latter, fiber and waveband tunnels are allocated into networks at the planning stage (or off-line) according to weighted network link-state (W-NLS). We will show that with the proposed algorithms, the RWA problem with tunnel allocation in the optical networks containing MG-OXCs can be solved effectively. Simulation is conducted on networks with different percentages of switching capacity and traffic load. The simulation results show that DTA is outperformed by CB-STA in the same network environment due to a well-disciplined approach for allocating tunnels with CB-STA.. We also find that the mix of the two approaches yields the best performance given the same network environment apparatus.

Patent
14 Jun 2002
TL;DR: In this paper, a cellular radio system consisting of at least one base station and at most one terminal communicating over a radio connection with a base station is considered, and a controller is arranged to form a priority list for each terminal group of the radio channels in the cellular radio network.
Abstract: A cellular radio system comprising at least one base station and at least one terminal communicating over a radio connection with a base station and a controller for carrying out dynamic channel allocation in a cellular radio network The controller included in the cellular radio system is arranged to group said one or more terminals communicating over a radio connection with the base station of the cellular radio system into one or more terminal groups, and the controller is arranged to form a priority list for each terminal group of the radio channels in the cellular radio network from the highest quality channels as regards the terminal group, and to allocate one or more radio channels from the channels on the priority list to the terminal if need be

Patent
Chiu Y. Ngo1
23 Aug 2002
TL;DR: In this paper, a method and system for dynamically selecting a communication channel between an access point (AP) and a plurality of mobile terminals (MTs) in a wireless local area network (WLAN), the method having the steps of measuring a channel quality of a pluralityof frequency channels, reporting to the AP from the plurality of MTs of the candidate channels including a received signal strength indication (RSSI) of all channels measured and, selecting one of the channels based on the channel quality report for use in communication between the AP and the MTs.
Abstract: Disclosed is a method and system for dynamically selecting a communication channel between an access point (AP) and a plurality of mobile terminals (MTs) in a wireless local area network (WLAN), the method having the steps of (a) measuring a channel quality of a plurality of frequency channels, (b) reporting to the AP from the plurality of MTs of the candidate channels including a received signal strength indication (RSSI) of all channels measured and, (c) selecting one of the channels based on the channel quality report for use in communication between the AP and the plurality of MTs.

Journal ArticleDOI
TL;DR: In this paper, a closed-form solution to the blocking and dropping probability in wireless cellular networks with handoff is presented, and performance measures of interest are explicitly given, including failure and repair of channels and performance analysis for cellular systems.

Patent
06 Jun 2002
TL;DR: In this paper, the authors propose a method for transmitting information using an allocated channel over a plurality of frames by a single channel allocation request, where the allocated channel is released when transmission is terminated or when a communication apparatus is disconnected from a network.
Abstract: In a wireless communication system with a periodical frame structure, as a method for transmitting information using an allocated channel over a plurality of frames by a single channel allocation request, an allocated channel is released when transmission is terminated or when a communication apparatus is disconnected from a network, and a channel can be allocated over a plurality of continuous frames.

Proceedings ArticleDOI
D. Gerakoulis1, P. Salmi
21 May 2002
TL;DR: The orthogonal frequency division multiplexing (OFDM) technique introduced here, termed interference suppressing OFDM (IS-OFDM), is a point-to-point physical link system for ultra wide bandwidth (UWB) radio channels which has the capability of suppressing narrow-band interference.
Abstract: The orthogonal frequency division multiplexing (OFDM) technique introduced here, termed interference suppressing OFDM (IS-OFDM), is a point-to-point physical link system for ultra wide bandwidth (UWB) radio channels which has the capability of suppressing narrow-band interference. System performance evaluation has been provided in the presence of narrow band interference, inter-symbol/inter-channel interference, or frequency selective fading. BER performance of the IS-OFDM is compared with an equivalent ordinary OFDM system. As shown, the IS-OFDM in a narrow band interference channel has a significant advantage over the ordinary OFDM which exhibits an error floor for every narrow band interference to signal ratio. Also, in an UWB indoor multipath channel the IS-OFDM has a significant advantage over the ordinary OFDM which, as shown, does not offer an acceptable performance for this type of channel.

Proceedings ArticleDOI
07 Aug 2002
TL;DR: This paper proposes an adaptive bandwidth allocation scheme, which is capable of providing QoS guarantees, ensuring long-term fairness, and achieving high bandwidth utilization, using a finite-state Markov channel model.
Abstract: In this paper we propose a general utility-oriented adaptive quality of service (QoS) model for wireless networks and establish a framework for formulating the bandwidth allocation problem for users with time-varying links. For slow link variations, it is inadequate to only employ low-level adaptive mechanisms at the symbol or packet level, such as error correction coding or swapping packet transmission opportunities. To improve bandwidth utilization and satisfy users' QoS requirements, high-level adaptive mechanisms working at larger time scale are needed. We propose an adaptive bandwidth allocation scheme, which is capable of providing QoS guarantees, ensuring long-term fairness, and achieving high bandwidth utilization. A finite-state Markov channel model (FSMC) is used to model wireless links.

Proceedings ArticleDOI
01 Jul 2002
TL;DR: An analytical model for a GSM-based cellular mobile network that applies an intelligent under-overlay (IUO) scheme to increase capacity by increasing frequency reuse while maintaining service quality is presented.
Abstract: The paper presents an analytical model for a GSM-based cellular mobile network that applies an intelligent under-overlay (IUO) scheme to increase capacity by increasing frequency reuse while maintaining service quality. The IUO is a multi-layer cell structure that is based on dividing the frequency band into super layer and regular layer frequency groups. The super frequencies (channels) can be used by mobile stations with good C/I (carrier/interferer) ratio, while the regular frequencies can be used over the whole cell. The use of IUO is expected to provide up to 40% gain of capacity (see Nokia Telecommunications, www.nokia.com). We study the effect of various parameters on the performance of networks using IUO and provide practical planning support based on the analytical results. The considered parameters include network parameters, like super area coverage, and mobile user mobility parameters, like moving mobile ratio and average mobile speed.

Proceedings ArticleDOI
07 Oct 2002
TL;DR: This paper proposes a new WLAN design approach that focuses on assuring sufficient data rate capacity to meet expected user demand in the coverage area, while still satisfying signal coverage and interference level requirements.
Abstract: An important issue in the widespread deployment of infrastructure based wireless local area networks (WLANs) is the network design. In this paper, we propose a new WLAN design approach that focuses on assuring sufficient data rate capacity to meet expected user demand in the coverage area, while still satisfying signal coverage and interference level requirements. Noting the low cost of WLAN access points, we formulate a novel mathematical network design model within the framework of constraint satisfaction problems. Our model is termed the capacity based WLAN constraint satisfaction problem (Cap-WLAN CSP). The solution of the Cap-WLAN CSP model yields a network design based on data rate demand by providing the access point locations, the frequency channel allocation, and power levels required for the WLAN to meet expected user demands. Our numerical results illustrate that the capacity based approach is more appropriate for the design of WLAN systems than those of traditional coverage based designs.

Journal ArticleDOI
TL;DR: A general algorithm is developed that guarantees relaxed mutual exclusion for a single resource and proves necessary and sufficient conditions for the information structure and can be used to design more efficient distributed channel allocation algorithms.
Abstract: Distributed dynamic channel allocation (DDCA) is a fundamental resource management problem in mobile cellular networks. It has a flavor of distributed mutual exclusion but is not exactly a mutual exclusion problem. We establish the exact relationship between the two problems. Specifically, we introduce the problem of relaxed mutual exclusion to model one important aspect of the DDCA problem. We develop a general algorithm that guarantees relaxed mutual exclusion for a single resource and prove necessary and sufficient conditions for the information structure. Considering distributed dynamic channel allocation as a special case of relaxed mutual exclusion, we apply and extend the algorithm to further address the issues that arise in distributed channel allocation such as deadlock resolution, dealing with multiple channels, design of efficient information structures, and channel selection strategies. Based on these results, we propose an example distributed channel allocation scheme using one of the information structures proposed. Analysis and simulation results are provided and show that the results of this research can be used to design more efficient distributed channel allocation algorithms.

Patent
15 Apr 2002
TL;DR: In this paper, a wireless digital communication method for communicating between a base station (12) and a plurality of user equipment mobile terminals (UEs 30) employs adaptive modulation and coding to achieve improved radio resource utilization and provide optimum data rates for user services.
Abstract: A wireless digital communication method for communicating between a base station (12) and a plurality of user equipment mobile terminals (UEs 30) and employs adaptive modulation and coding to achieve improved radio resource utilization and provide optimum data rates for user services Blocks of downlink (DL) data are received by the base station which requests downlink DL channel quality measurements only from those mobile terminals (30) with pending downlink transmissions The UEs respond to the request by measuring and reporting DL Channel quality to the base station, which then allocates resources such that the UEs will make best use of radio resources The base station notifies the UEs of the physical channel allocation indicating the modulation/coding rate and allocated slots followed by transmission of blocks of downlink data which are transmitted to the UEs

Journal ArticleDOI
TL;DR: The results obtained from the experimental model show that the proposed scheme restricts the delay of both periodic and time-critical data to a pre-specified bound, and the proposed bandwidth allocation scheme also fully utilized the bandwidth resource of the network system.
Abstract: This paper presents a method for implementing a bandwidth allocation scheme on Profibus that operates on a token-passing discipline basis. In order to implement the bandwidth allocation scheme, this study incorporates the following additional functions to the fieldbus datalink layer (FDL) protocol of Profibus. First, the medium bandwidth of the network system is separated into both periodic and time-available intervals, and, second, node timers are synchronized over a local link. The validity of this bandwidth allocation scheme is determined using an experimental model of a network system. The results obtained from the experimental model show that the proposed scheme restricts the delay of both periodic and time-critical data to a pre-specified bound. The proposed bandwidth allocation scheme also fully utilized the bandwidth resource of the network system.

Journal ArticleDOI
TL;DR: The proposed MPr scheme is adaptive in that it can dynamically adjust the number of reserved channels for the handoff according to the periodical measurement of the traffic status within a local cell, thus completely eliminating the signaling overhead for status information exchange among cells mandated in most existing channel allocation schemes.
Abstract: This paper presents a new adaptive bandwidth allocation scheme to prevent handoff failure in wireless cellular networks, known as the measurement-based preassignment (MPr) technique. This technique is particularly useful in micro/pico cellular networks which offers quality-of-service (QoS) guarantee against call dropping. The proposed MPr scheme distinguishes itself from the well-known guarded channel (GC) based schemes in that it allows the handoff calls to utilize a prereserved channel pool before competing for the shared channels with new call arrivals. The key advantage of the proposed MPr scheme is that it enables easy derivation of the number of channels that needs to be reserved for handoff based on a predetermined handoff dropping probability, without the need for solving the often complex Markov chain required in GC schemes, thus, making the proposed MPr scheme simple and efficient for implementation. This is essential in handling multiple traffic types with potentially different QoS requirements. In addition, the MPr scheme is adaptive in that it can dynamically adjust the number of reserved channels for the handoff according to the periodical measurement of the traffic status within a local cell, thus completely eliminating the signaling overhead for status information exchange among cells mandated in most existing channel allocation schemes. Numerical results and comparisons are given to illustrate the tradeoff.

Journal ArticleDOI
TL;DR: The method proposed to solve the frequency-assignment problem is an approximate nondeterministic tree search (ANTS) algorithm, which is a metaheuristic algorithm based on a computational paradigm inspired by the way real ant colonies function.
Abstract: The frequency-assignment problem is concerned with the assignment of discrete channels to the transmitters of a radio network. Separation of the frequencies assigned to transmitters is necessary to avoid interference. However, unnecessary separation causes an excess requirement for spectrum, the cost of which may be very high. The aim of the work is to minimize the frequency spectrum required for a given level of reception quality over the network. In contrast to the majority of the work presented in the literature, the model chosen to formalize the problem takes multiple interference into consideration. This should provide a better approximation of reality. The method proposed to solve this problem is an approximate nondeterministic tree search (ANTS) algorithm, which is a metaheuristic algorithm based on a computational paradigm inspired by the way real ant colonies function.

Book ChapterDOI
19 May 2002
TL;DR: A new scheme that uses GPS measurements to determine when channel reservations are to be made and integrates threshold time and various features of prior schemes to minimize the effect of false reservations and to improve the channel utilization of the cellular system is proposed.
Abstract: In wireless cellular networks, in order to ensure that ongoing calls are not dropped while the owner mobile stations roam among cells, handoff calls may be admitted with a higher priority as compared with new calls. Since the wireless bandwidth is scarce and therefore precious, efficient schemes which allow a high utilization of the wireless channel, while at the same time guarantee the QoS of handoff calls are needed. In this paper, we propose a new scheme that uses GPS measurements to determine when channel reservations are to be made. It works by sending channel reservation request for a possible handoff call to a neighboring cell not only based on the position and orientation of that call's mobile station, but also depends upon the relative motion of the mobile station with respect to that target cell. The scheme integrates threshold time and various features of prior schemes to minimize the effect of false reservations and to improve the channel utilization of the cellular system. Simulation results showthat our scheme performs better in almost all typical scenarios than prior schemes.

Journal ArticleDOI
TL;DR: The results indicate that significant low denial rate, low message complexity and low acquisition time can be obtained using the algorithm presented, which is an efficient distributed algorithm for dynamic channel allocation based upon mutual exclusion model.
Abstract: Recent demand for mobile telephone service has been growing rapidly while the electro-magnetic spectrum of frequencies allocated for this purpose remains limited. Any solution to the channel assignment problem is subject to this limitation, as well as the interference constraint between adjacent channels in the spectrum. Channel allocation schemes provide a flexible and efficient access to bandwidth in wireless and mobile communication systems. In this paper, we present an efficient distributed algorithm for dynamic channel allocation based upon mutual exclusion model, where the channels are grouped by the number of cells in a cluster and each group of channels cannot be shared concurrently within the cluster. We discuss the algorithm and prove its correctness. We also show that the algorithm requires at most (worst case) O(Ng · Nn log Nn) messages, where Ng is the number of groups and Nn is the number of neighbors. This is compared to Choy's algorithm which requires O(Ng2 · Nn), where Ng is the number of groups and Nn is the number of neighboring cells in the system. We report our algorithm's performance with several channel systems using different types of call arrival patterns. Our results indicate that significant low denial rate, low message complexity and low acquisition time can be obtained using our algorithm.

Journal ArticleDOI
TL;DR: The objective in this work is to gauge how well a GA-based channel borrower performs when compared to a greedy borrowing heuristic to establish how suited GA-like (stochastic search) algorithms are for the solution of optimization problems in mobile computing environments.
Abstract: This paper highlights the potential of using genetic algorithms to solve cellular resource allocation problems The objective in this work is to gauge how well a GA-based channel borrower performs when compared to a greedy borrowing heuristic This is needed to establish how suited GA-like (stochastic search) algorithms are for the solution of optimization problems in mobile computing environments This involves the creation of a simple mobile networking resource environment and design of a GA-based channel borrower that works within this environment A simulation environment is also built to compare the performance of the GA-based channel-borrowing method with the heuristic To enhance the performance of the GA, extra attention is paid to developing an improved mutation operator The performance of the new operator is evaluated against the heuristic borrowing scheme For a real-time implementation, the GA needs to have the properties of a micro GA strategy This involves making improvements to the crossover operator and evaluation procedure so the GA can converge to a "good" solution rapidly

Journal ArticleDOI
TL;DR: This work characterize the ACCT and related performance metrics for wireless mobile networks under a newly proposed general channel allocation scheme and derives the call completion probability, the call drop probability, and the average actual call connection times for both the complete calls and the incomplete calls.
Abstract: Actual call connection time (ACCT) is the total time that a mobile user engages in communications over a wireless network during a call connection. Due to limited network resources of wireless mobile networks, a call connection may be prematurely disconnected and the ACCT for the call in general may not be the same as the requested call connection time (RCCT). The ACCT depends not only on the RCCT, but also on the network resource allocation scheme and network traffic. We characterize the ACCT and related performance metrics for wireless mobile networks under a newly proposed general channel allocation scheme. This scheme generalizes the nonprioritized scheme, the reserved channel scheme, the queueing priority scheme and the subrating scheme in such a way as to reduce the blocking probability of the handoff calls while keeping the ACCT as long as possible. Explicit formulae for the distribution and the expectation of the ACCT are obtained. The call completion probability, the call drop probability, and the average actual call connection times for both the complete calls and the incomplete calls are derived. The results can form the basis for designing better billing rate schemes by differentiating incomplete calls and complete calls.