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1.
To provide an acceptable call blocking probability in circuit-switched cellular networks, such as the Advanced Mobile Phone
System (AMPS) networks, a significant fraction of the channel capacity in each cell is normally unused. This “free” capacity
can be effectively used for packet data transmissions that yield to voice traffic when necessary. Cellular Digital Packet
Data (CDPD) is a packet-switched data service which may share radio channels with the AMPS service on a secondary basis to
tap this “free” capacity. The length of time that a CDPD stream can occupy a channel is greatly influenced by the channel
assignment strategies of both the AMPS and the CDPD systems. This paper investigates these channel assignment strategies and
their effects on the CDPD channel holding times, in comparison with the optimal channel assignment strategy that interrupts
the CDPD service only when a new AMPS call finds no other idle channels in the cell site. One such optimal strategy is the
cooperative strategy in which the CDPD and AMPS networks actively communicate with each other. It is shown that other optimal
strategies exist without the need of communications between the two systems. The effects of AMPS traffic levels, number of
channels, and number of CDPD streams at the cell site on the CDPD channel holding time and channel utilization are also considered.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
2.
To provide an acceptable call blocking probability in circuit-switched cellular networks, such as the Advanced Mobile Phone
System (AMPS) networks, a significant fraction of the channel capacity in each cell is normally unused. This “free” capacity
can be effectively used for packet data transmissions that yield to voice traffic when necessary. Cellular Digital Packet
Data (CDPD) is a packet-switched data service which may share radio channels with the AMPS service on a secondary basis to
tap this “free” capacity. The length of time that a CDPD stream can occupy a channel is greatly influenced by the channel
assignment strategies of both the AMPS and the CDPD systems. This paper investigates these channel assignment strategies and
their effects on the CDPD channel holding times, in comparison with the optimal channel assignment strategy that interrupts
the CDPD service only when a new AMPS call finds no other idle channels in the cell site. One such optimal strategy is the
cooperative strategy in which the CDPD and AMPS networks actively communicate with each other. It is shown that other optimal
strategies exist without the need of communications between the two systems. The effects of AMPS traffic levels, number of
channels, and number of CDPD streams at the cell site on the CDPD channel holding time and channel utilization are also considered.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
3.
Jintao Xiong Weibo Gong Chunming Qiao 《Lightwave Technology, Journal of》2003,21(6):1421-1434
We propose a rational approximation (RA)-based algorithm to perform the blocking analysis of circuit-switched all-optical networks. Our algorithm can be applied to large networks with various topologies and routing and wavelength assignment algorithms. It can be applied to optical networks with either full, sparse, or no wavelength conversion. We also propose fixed-path wavelength assignment algorithms for networks with balanced and unbalanced traffic. 相似文献
4.
The wireless mesh network is a new emerging broadband technology providing the last-mile Internet access for mobile users by exploiting the advantage of multiple radios and multiple channels. The throughput improvement of the network relies heavily on the utilizing the orthogonal channels. However, an improper channel assignment scheme may lead to network partition or links failure. In this paper we consider the assignment strategy with topology preservation by organizing the mesh nodes with available channels, and aim at minimizing the co-channel interference in the network. The channel assignment with the topology preservation is proved to be NP-hard and to find the optimized solution in polynomial time is impossible. We have formulated a channel assignment algorithm named as DPSO-CA which is based on the discrete particle swarm optimization and can be used to find the approximate optimized solution. We have shown that our algorithm can be easily extended to the case with uneven traffic load in the network. The impact of radio utilization during the channel assignment process is discussed too. Extensive simulation results have demonstrated that our algorithm has good performance in both dense and sparse networks compared with related works. 相似文献
5.
Throughput limitation of wireless networks imposes many practical problems as a result of wireless media broadcast nature. The solutions of the problem are mainly categorized in two groups; the use of multiple orthogonal channels and network coding (NC). The networks with multiple orthogonal channels and possibly multiple interfaces can mitigate co-channel interference among nodes. However, efficient assignment of channels to the available network interfaces is a major problem for network designers. Existing heuristic and theoretical work unanimously focused on joint design of channel assignment with the conventional transport/IP/MAC architecture. Furthermore, NC has been a prominent approach to improve the throughput of unicast traffic in wireless multi-hop networks through opportunistic NC. In this paper we seek a collaboration scheme for NC in multi-channel/interface wireless networks, i.e., the integration of NC, routing and channel assignment problem. First, we extend the NC for multiple unicast sessions to involve both COPE-type and a new proposed scheme named as Star-NC. Then, we propose an analytical framework that jointly optimizes the problem of routing, channel assignment and NC. Our theoretical formulation via a linear programming provides a method for finding source–destination routes and utilizing the best choices of different NC schemes to maximize the aggregate throughput. Through this LP, we propose a novel channel assignment algorithm that is aware of both coding opportunities and co-channel interference. Finally, we evaluate our model for various networks, traffic models, routing and coding strategies over coding-oblivious routing. 相似文献
6.
《Photonics Technology Letters, IEEE》2008,20(21):1787-1789
7.
McEliece R.J. Sivarajan K.N. 《IEEE transactions on information theory / Professional Technical Group on Information Theory》1994,40(1):21-34
Studies the performance of channel assignment algorithms for “channelized” (e.g., FDMA or TDMA) cellular telephone systems, via mathematical models, each of which is characterized by a pair (H,p), where H is a hypergraph describing the channel reuse restrictions, and p is a probability vector describing the variation of traffic intensity from cell to cell. For a given channel assignment algorithm, the authors define T(r) to be the amount of carried traffic, as a function of the offered traffic, where both r and T(r) are measured in Erlangs per channel. They show that for a given H and p, there exists a function TH,p(r), which can be computed by linear programming, such that for every channel assignment algorithm, T(r)⩽TH,p(r). Moreover, they show that there exist channel assignment algorithms whose performance approaches TH,p (r) arbitrarily closely as the number of channels increases. As a corollary, they show that for a given (H,p) there is a number r0 , which also can be computed by linear programming, such that if the offered traffic exceeds r0, then for any channel assignment algorithm, a positive fraction of all call requests must be blocked, whereas if the offered traffic is less than r0, all call requests can be honored, if the number of channels is sufficiently large. The authors call r0, whose units are Erlangs per channel, the capacity of the cellular system 相似文献
8.
A promising approach for implementing channel assignment and control in cellular mobile telephone networks is the virtually
fixed channel assignment (VFCA) scheme. In VFCA channels are allocated to cells according to the fixed channel assignment
(FCA) scheme, but cells are allowed to borrow channels from one another. As such, VFCA maintains the efficiency of FCA, but
adds the flexibility lacking in FCA. One feature of a VFCA network is that, to prevent co-channel interference, it requires
several channels to be locked to serve a single call that borrows a channel. This feature raises the concern that VFCA may
lead to chain reaction in channel borrowing among cells and cause the network performance to degrade, especially under heavy
traffic conditions. In this paper, we propose the virtually fixed channel assignment with recall (VFCAWR) scheme: The network
is implemented according to VFCA, but a cell can recall a locked channel to service an arriving handoff call, which occurs
when a mobile unit crosses the boundary of its cell. We model the network as a three-dimensional Markov chain and derive its
steady-state performance. Through modification of this basic model, we evaluate two dynamic channel assignment strategies,
the virtual channel reservation (VCR) strategy and the linear switch-over (LSO) strategy, which exploit the unique borrowing/recall
capability of VFCAWR to reduce the weighted cost of blocking fresh and handoff calls by reserving several virtual channels
(the channels that may be borrowed from adjacent cells when necessary) for handoff calls. We validate the analytical models
by simulation; the simulation test cases show that our models accurately predict the system performance measures of interest.
Numerical and simulation results also show that both dynamic strategies outperform conventional channel reservation schemes
based on fixed channel assignment and hybrid channel assignment.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
9.
The bandwidth of a wavelength channel in WDM optical networks is very high compared to the user’s requirements for various
applications. Therefore, there is a scope for better utilization of channel bandwidth by traffic grooming, in which several
user’s channels are multiplexed for transmission over a single channel. Several research works have been reported on traffic
grooming routing and wavelength assignment (GRWA) for static and dynamic traffic pattern under centralized environment. Distributed
dynamic grooming routing and wavelength assignment (DDGRWA) is a new and quite unexplored area in WDM optical mesh networks.
This article introduces the concept of distributed traffic grooming in WDM mesh networks which also includes virtual topology
construction, reconfiguration, routing and wavelength assignment in the distributed environment assuming incoming traffic
to be dynamic in nature. We have also presented simulation results of our algorithm on dynamically generated traffic under
various network topologies. 相似文献
10.
Considers routing connections in a reconfigurable optical network using WDM. Each connection between a pair of nodes in the network is assigned a path through the network and a wavelength on that path, such that connections whose paths share a common link in the network are assigned different wavelengths. The authors derive an upper bound on the carried traffic of connections (or equivalently, a lower bound on the blocking probability) for any routing and wavelength assignment (RWA) algorithm in such a network. The bound scales with the number of wavelengths and is achieved asymptotically (when a large number of wavelengths is available) by a fixed RWA algorithm. The bound can be used as a metric against which the performance of different RWA algorithms can be compared for networks of moderate size. The authors illustrate this by comparing the performance of a simple shortest-path RWA (SP-RWA) algorithm via simulation relative to the bound. They also derive a similar bound for optical networks using dynamic wavelength converters, which are equivalent to circuit-switched telephone networks, and compare the two cases. Finally, they quantify the amount of wavelength reuse achievable in large networks using the SP-RWA via simulation as a function of the number of wavelengths, number of edges, and number of nodes for randomly constructed networks as well as de Bruijn networks. They also quantify the difference in wavelength reuse between two different optical node architectures 相似文献
11.
12.
In wireless cellular networks or in other networks with single-hop communication, the fundamental access control problem pertains to access point (AP) selection and channel allocation for each user. For users in the coverage area of one AP, this involves only channel allocation. However, users that belong in the intersection of coverage areas of more than one AP can select the appropriate AP to establish connection and implicitly affect the channel assignment procedure. We address the joint problem of AP selection and channel assignment with the objective to satisfy a given user load vector with the minimum number of channels. Our major finding is that the joint problem reduces to plain channel allocation in a cellular network that emerges from the original one after executing an iterative and provably convergent clique load balancing algorithm. For linear cellular networks, our approach leads to minimum number of required channels to serve a given load vector. For 2D cellular networks, the same approach leads to a heuristic algorithm with a suboptimal solution due to the fact that clique loads cannot be balanced. Numerical results demonstrate the performance benefits of our approach in terms of blocking probability in a dynamic scenario with time-varying number of connection requests. The presented approach constitutes the basis for addressing more composite resource allocation problems in different context. 相似文献
13.
Efficient management of wireless channels is critical for the performance of cellular systems. Resource planning represents the allocations of system channels into cells. Accordingly, channel assignment strategies respond for using the allocated channels of cells to provide communication services in cells. However, a cellular system that experiences the varying of traffic distributions and the mobile service stations (MSSs) failing to provide communication services or recovered from failures will lessen the utilization of channels to provide communication services. In this paper, we present a distributed fault-tolerant resource planning scheme that can adaptively allocate channels to cells according to above variations in cellular systems. When the MSS of a cell fails to provide communications, its allocated channels can be reallocated to other non-failed MSSs. Our scheme has the advantages of low message overhead and low time delay. Moreover, freedom from deadlock is ensured. Simulation results, which are observed from reducing the overall average call blocking probability and the message overhead with and without applying our resource planning scheme to various channel assignment strategies, demonstrate that our algorithm is very efficient. 相似文献
14.
Blocking probability and channel assignment in wireless networks 总被引:1,自引:0,他引:1
We consider a multi-hop wireless network with a connection-oriented traffic model and multiple transmission channels that can be spatially re-used. In such a network the blocking probability of a call that makes a channel request depends on (a) the channel assignment scheme and (b) the transmission radius of the nodes which affects the network link structure. In this work, we study these two aspects for simple wireless networks. Specifically, we develop blocking probability analysis for a wireless line and grid network and explore the tradeoff between transmission radius and blocking probability for multi-hop calls. We show that for a line network a larger transmission radius can substantially reduce the blocking probability of calls, while for a grid network with a more dense node topology using a smaller transmission radius is better. We then, investigate various channel assignment schemes and present a novel non-rearranging channel assignment algorithm for multi-hop calls in a general network. Our algorithm efficiently incorporates spatial channel re-use and significantly reduces call blocking probability when compared to other algorithms. 相似文献
15.
The limited availability of radio frequency spectrum will require future wireless systems to use more efficient and sophisticated resource allocation methods to increase network capacity. In this work, we propose a joint resource allocation algorithm (JRAA) that makes the channel base station and power assignment in a wireless network with an arbitrary number of base stations and mobiles attempting to minimize the number of channels needed to provide each user in the system with an acceptable radio connection. We compare the performance of the JRAA for both the forward (downstream) and reverse (upstream) directions, in terms of the achievable traffic capacity, with some bounds on the performance of the maximum packing (MP), clique packing (CP), and reuse partitioning (RP) techniques, which are usually used as benchmarks on the capacity that can be achieved by any traffic-adaptive dynamic channel assignment strategy, where the quality is guaranteed by the reuse distance. Those performance results verify the improvement that can be achieved by the integration of the channel base station and power assignment. Finally, several versions of the two-way channel assignment problem are studied and evaluated 相似文献
16.
Static and dynamic channel assignment using neural networks 总被引:1,自引:0,他引:1
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 相似文献
17.
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. 相似文献
18.
Chan P.T.H. Palaniswami M. Everitt D. 《Vehicular Technology, IEEE Transactions on》1994,43(2):279-288
Conventional dynamic channel assignment schemes are both time-consuming and algorithmically complex. An alternative approach, based on cascaded multilayered feedforward neural networks, is proposed and examined on two cellular systems with different configurations. Simulation results showed that the blocking performance of our multistage neural network approach can match that of an example conventional scheme with less complexity and higher computational efficiency. The example scheme considered here is the ordered channel search, which can achieve a reasonably high spectral efficiency as compared to that of an ideal dynamic channel allocation algorithm. We conclude that our neural network approach is well-suited to the dynamic channel allocation problem of future cellular or microcellular systems with decentralized control 相似文献
19.
Wavelength Selection in OBS Networks Using Traffic Engineering and Priority-Based Concepts 总被引:4,自引:0,他引:4
《Selected Areas in Communications, IEEE Journal on》2005,23(8):1658-1669
A fundamental assumption underlying most studies of optical burst switched (OBS) networks is that full wavelength conversion is available throughout the network. In practice, however, economic and technical considerations are likely to dictate a more limited and sparse deployment of wavelength converters in the optical network. Therefore, we expect wavelength assignment policies to be an important component of OBS networks. In this paper, we explain why wavelength selection schemes developed for wavelength routed (circuit-switched) networks are not appropriate for OBS. We then develop a suite of adaptive and nonadaptive policies for OBS switches. We also apply traffic engineering techniques to reduce wavelength contention through traffic isolation. Our performance study indicates that, in the absence of full conversion capabilities, intelligent choices in assigning wavelengths to bursts at the source can have a profound effect on the burst drop probability in an OBS network. 相似文献
20.
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. 相似文献