Grade-of-service differentiated static resource allocation schemes in WDM networks

This paper presents a study on the Grade-of-Service (GoS) differentiation of static resource allocation in lightpath routed WDM networks, where lightpath requests between node pairs are given. Each request is associated with a service grade. The goal is to maintain certain service levels for the requests of all grades. The service levels are measured in terms of their acceptance ratios. We solve this network optimization problem by adopting a penalty-based framework, in which network design and operation goals can be evaluated based on cost/revenue. We propose a static GoS differentiation model as one minimizing the total rejection and cost penalty, in which the rejection penalty reflects the revenue of accepting a request, and the cost penalty reflects the resource consumption of providing a lightpath to a request. Then, a solution based on the Lagrangian relaxation and subgradient methods is used to solve the proposed optimization problem. Three different application scenarios are presented: static GoS differentiation of requests between the same node pair, static GoS differentiation of requests between different node pairs, and an integration of static GoS differentiation into the network profit objective. The fairness issues and the impact of relative penalty factors are discussed to provide guidelines for network planning.     

WDM网状网中考虑传输损伤的动态波带交换算法

针对光信号在传输中受到的自发辐射噪声和偏振模色散两种损伤,提出一种考虑信号质量限制的动态波带交换(DWS-SQC)算法.该算法在保证信号传输质量要求前提下,最小化可选路径端12占用数和减少路径所经总链路数.不同负载动态业务下的仿真研究表明:DWS-SQC既考虑了网络中信号损伤的影响,又有利于网络负载均衡和提高全网端口利用率,可以降低全网阻塞率.     

Path selection methods with multiple constraints in service-guaranteed WDM networks

We propose a new approach to constraint-based path selection for dynamic routing and wavelength allocation in optical networks based on WDM. Our approach considers service-specific path quality attributes, such as physical layer impairments, reliability, policy, and traffic conditions, and uses a flooding-based transfer of path information messages from source to destination to find multiple feasible paths. It is fully decentralized, as it uses local network state information. To better understand how multiple constraints impact the efficiency of wavelength routing, and consequently provision the service guarantees, we specifically focus on electronic regenerators that, while being widely considered as the basic building blocks for optical switching nodes, are likely to impose conflicting constraints on routing. For example, electronic regenerators extend the optical reach and could perform wavelength shifting, but also induce impairments, such as delays and operational costs. The question for constraint-based routing is how to account for these conflicting effects. To validate the network modeling, a wide range of networking scenarios are simulated, such as ring, mesh and interconnections of all-optical networks with electronic gateways. For all these scenarios, our approach is shown to efficiently accommodate multiple, conflicting routing metrics related to different services and network architectures.     

Dynamic resource allocation in ATM networks

This article investigates resource allocation in ATM networks and emphasizes bandwidth allocation. Resource allocation methods are categorized, and static and dynamic allocation strategies are compared. Dynamic allocation uses actual traffic behavior, while static allocation uses only the reference traffic condition given a priori. Examples of dynamic allocation strategies are available bit rate flow control, dynamic connection admission control, and dynamic VP bandwidth control. Dynamic resource allocation is shown to be promising for situations where the a priori reference model is unclear     

Quick resource allocation in heterogeneous networks

Wireless Networks - In this paper, an innovative technique is given to reduce the implementation time taken for doing the seamless communication in heterogeneous networks. When a new user arrives...     

Wavelength assignment for multicast in all-optical WDM networks with splitting constraints

Multicast is an important application in all-optical WDM networks. The wavelength assignment problem for WDM multicast is to assign a set of wavelengths to the links of a given multicast tree. In an all-optical WDM network without wavelength conversions, wavelength assignment is the key to guarantee the quality of service and to reduce communication costs. In this paper, we study wavelength assignment for WDM multicast with two criteria, to cover the maximum number of destinations, and to minimize the wavelength costs. The computational complexity of the problem is studied. Three heuristic algorithms are proposed and the worst-case approximation ratios for some heuristic algorithms are given. We also derive a lower bound of the minimum total wavelength cost and an upper bound of the maximum number of reached destinations. The efficiency of the proposed heuristic algorithms and the effectiveness of the derived bounds are verified by the simulation results.     

Resource allocation strategies for survivability in WDM optical networks

WDM optical networks are high speed networks and provide enormous capacity. Survivability is very important issue in these networks. Survivability requires resources for handling the failures. So, efficient resource allocation strategy is required for survivability. In this paper, we have presented two resource allocation strategies for survivability. These strategies reserve the resources for the primary lightpaths and backup lightpaths. Then extensive simulations are done on different networks to evaluate the performance in terms of blocking probability. The results show that the second strategy performs better than first strategy.     

Survivable lightpath provisioning in WDM mesh networks under shared path protection and signal quality constraints

This paper addresses the problem of survivable lightpath provisioning in wavelength-division-multiplexing (WDM) mesh networks, taking into consideration optical-layer protection and some realistic optical signal quality constraints. The investigated networks use sparsely placed optical-electrical-optical (O/E/O) modules for regeneration and wavelength conversion. Given a fixed network topology with a number of sparsely placed O/E/O modules and a set of connection requests, a pair of link-disjoint lightpaths is established for each connection. Due to physical impairments and wavelength continuity, both the working and protection lightpaths need to be regenerated at some intermediate nodes to overcome signal quality degradation and wavelength contention. In the present paper, resource-efficient provisioning solutions are achieved with the objective of maximizing resource sharing. The authors propose a resource-sharing scheme that supports three kinds of resource-sharing scenarios, including a conventional wavelength-link sharing scenario, which shares wavelength links between protection lightpaths, and two new scenarios, which share O/E/O modules between protection lightpaths and between working and protection lightpaths. An integer linear programming (ILP)-based solution approach is used to find optimal solutions. The authors also propose a local optimization heuristic approach and a tabu search heuristic approach to solve this problem for real-world, large mesh networks. Numerical results show that our solution approaches work well under a variety of network settings and achieves a high level of resource-sharing rates (over 60% for O/E/O modules and over 30% for wavelength links), which translate into great savings in network costs.     

Adaptive resource allocation in multiuser OFDM systems with proportional rate constraints

Multiuser orthogonal frequency division multiplexing (MU-OFDM) is a promising technique for achieving high downlink capacities in future cellular and wireless local area network (LAN) systems. The sum capacity of MU-OFDM is maximized when each subchannel is assigned to the user with the best channel-to-noise ratio for that subchannel, with power subsequently distributed by water-filling. However, fairness among the users cannot generally be achieved with such a scheme. In this paper, a set of proportional fairness constraints is imposed to assure that each user can achieve a required data rate, as in a system with quality of service guarantees. Since the optimal solution to the constrained fairness problem is extremely computationally complex to obtain, a low-complexity suboptimal algorithm that separates subchannel allocation and power allocation is proposed. In the proposed algorithm, subchannel allocation is first performed by assuming an equal power distribution. An optimal power allocation algorithm then maximizes the sum capacity while maintaining proportional fairness. The proposed algorithm is shown to achieve about 95% of the optimal capacity in a two-user system, while reducing the complexity from exponential to linear in the number of subchannels. It is also shown that with the proposed resource allocation algorithm, the sum capacity is distributed more fairly and flexibly among users than the sum capacity maximization method.     

Dynamic load balancing in WDM packet networks with and without wavelength constraints

We develop load balancing algorithms for WDM-based packet networks where the average traffic between nodes is dynamically changing. In WDM-based packet networks, routers are connected to each other using wavelengths (lightpaths) to form a logical network topology. The logical topology may be reconfigured by rearranging the lightpaths connecting the routers. Our algorithms reconfigure the logical topology to minimize the maximum link load. In this paper, we develop iterative reconfiguration algorithms for load balancing that track rapid changes in the traffic pattern. At each reconfiguration step, our algorithms make only a small change to the network topology hence minimizing the disruption to the network. We study the performance of our algorithms under several dynamic traffic scenarios and show that our algorithms perform near optimally. We further show that these large reconfiguration gains are achievable in systems with a limited number of wavelengths.     

Optimal resource allocation in multiservice CDMA networks

This paper addresses the problem of dynamic resource allocation in a multiservice direct-sequence code-division multiple-access (DS-CDMA) wireless network supporting real-time (RT) and nonreal-time (NRT) communication services. For RT users, a simple transmission power allocation strategy is assumed that maximizes the amount of capacity available to NRT users without violating quality of service requirements of RT users. For NRT users, a joint transmission power and spreading gain (transmission rate) allocation strategy, obtained via the solution of a constrained optimization problem, is provided. The solution maximizes the aggregate NRT throughput, subject to peak transmission power constraints and the capacity constraint imposed by RT users. The optimization problem is solved in a closed form, and the resulting resource allocation strategy is simple to implement as a hybrid CDMA/time-division multiple-access strategy. Numerical results are presented showing that the optimal resource allocation strategy can offer substantial performance gains over other conventional resource allocation strategies for DS-CDMA networks.     

Prioritized resource allocation for stressed networks

Overloads that occur during times of network stress result in blocked access to all users, independent of importance. These overloads can occur because of degraded resource availability or abnormally high demand. Public broadband networks must dynamically recognize some multimedia connections as having greater importance than others and allocate resources accordingly. A new approach to connection admission control is proposed that uses an upper limit policy to optimize the admission of connections based on the weighted sum of blocking across traffic classes. This results in a simple algorithm suitable for multimedia and packet networks. This work is also the first to demonstrate that the use of an upper limit policy is superior to traditional approaches of adding extra capacity or partitioning capacity, both in terms of the amount of resources required and sensitivity to load variations. An upper limit policy can also be deployed much faster when a large overload occurs from a disaster event     

Dynamic resource allocation for quality of service on a PON withhome networks

Earlier efforts on optical access concentrated on the design of PONs for the collection and distribution portion of the access network. A possible evolution scenario for these types of access networks could be the SuperPON system. The SuperPON system exploits all possible upgrades of an FSAN APON system. In these networks the optical hardware is very simple, but a media access control protocol is needed for upstream traffic control. Even so, the role of communications is already well established in the office environment, thanks to networking innovations such as the Ethernet LAN. With the development of cheap, affordable broadband communications and the increasing complexity of consumer goods, it seems natural to extend the network into homes. As home area network application ever increases, we consider connectivity between the access network and the home network, which generates multiple traffic, in order to design a MAC protocol over the SuperPON access network with home networks. Global FIFO is quite simple, and allows dynamic upstream bandwidth allocation on the basis of a request-and-permit mechanism on the APON architecture. It has good bandwidth efficiency; however, being cell-based, it does not consider multiple traffic types from home networks. In this article we describe and analyze a new dynamic MAC resource allocation algorithm called multiple queue-FIFO that can achieve good performance under the SuperPON access network in the home network environment     

Cross-layer resource allocation over wireless relay networks for quality of service provisioning

The authors propose a physical-datalink cross-layer resource allocation scheme over wireless relay networks for quality-of-service (QoS) guarantees. By integrating information theory with the concept of effective capacity, the proposed scheme aims at maximizing the relay network throughput subject to a given delay QoS constraint. This delay constraint is characterized by the so-called QoS exponent thetas, which is the only requested information exchanged between the physical layer and the datalink layer in our cross-layer design based scheme. Over both amplify-and-forwards (AF) and decode-and-forward (DF) relay networks; the authors develop the associated dynamic resource allocation algorithms for wireless multimedia communications. Over DF relay network, the authors also study a fixed power allocation scheme to provide QoS guarantees. The simulations and numerical results verify that our proposed cross-layer resource allocation can efficiently support diverse QoS requirements over wireless relay networks. Both AF and DF relays show significant superiorities over direct transmissions when the delay QoS constraints are stringent. On the other hand, the results demonstrate the importance of deploying the dynamic resource allocation for stringent delay QoS guarantees.     

Dynamic resource allocation in mobile heterogeneous cellular networks

User mobility is a challenging issue in macro and femto cellular networks for the fifth-generation and newer mobile communications due to the time-varying interference and topology experienced. In this paper, we consider an OFDMA-based two-tier network with one macro cell and several femto cells, wherein each macro user and/or femto user can leave or enter its serving cell frequently, referred to as user mobility. A resource allocation problem with different rate requirements of mobile users is then formulated. Assuming well knowledge of the user locations and the channel state information, we propose a dynamic algorithm with static and dynamic parts for a better trade-of between computational complexity and system throughput. The static algorithm, named interference weighted cluster algorithm in this paper, is based on the graph theory to cluster the femtocells by minimizing the interference between clusters, while the dynamic algorithm is to deal with the user mobility by sharing the resource blocks under the constraints of rate requirements. Numerical results are demonstrated to show the effectiveness of the proposed dynamic resource allocation algorithm in terms of capacity, computational time, and outage probability.

     

Radio resource allocation in fixed broadband wireless networks

We consider use of fixed broadband wireless networks to provide packet services for telecommuting and Internet access. Each cell is divided into multiple sectors, each of them served by a sector antenna colocated with the base station (BS), and user terminals also use directional antennas mounted on the rooftops of homes or small offices and pointed to their respective BS antennas. To support a target data rate of 10 Mb/s, a bandwidth of several MHz is required. Since radio spectrum is expensive, the bandwidth needs to be reused very aggressively. Thus, efficient strategies for frequency reuse and managing cochannel interference are critically important. We propose several algorithms for dynamic radio-resource allocation in the fixed wireless networks. In particular, a method to be referred to as the staggered resource allocation (SRA) method uses a distributed scheduling algorithm to avoid major sources of interference while allowing concurrent packet transmission and meeting signal-to-interference objectives. The performance of the method is studied by analytic approximations and detailed simulation. Our results show that the combination of directional antennas plus the SRA method is highly effective in controlling cochannel interference. For reasonable system parameters, the SRA method delivers a throughput in excess of 30% per sector while permitting a given frequency band to be reused in every sector of every cell. It also provides satisfactory probability of successful packet transmission. In addition, a simple control mechanism can be applied in the method to improve performance for harsh radio environments     

A channel reuse strategy with adaptive channel allocation for all-optical WDM networks

The fundamental problems of WDM networks are: (1) high rate of control packet loss and (2) high propagation delay for each (re)transmission. In this paper, we minimize the station randomness to access the control architecture introducing a collisions-free access scheme. We propose a synchronous protocol according which at the end of the propagation delay each station applies a distributed algorithm for packet transmission following the data channel collisions and the receiver collisions avoidance algorithms. We introduce two data transmission stages. The time difference between them is one packet transmission time. At the end of the first stage all data channels are free and can be reused by the remaining data packets during the second stage. The proposed protocol ensures a totally collisions-free performance. The main advantage is that the data channels reuse strategy applied during the second stage provides enhanced transmission probability to the rejected packets during the first stage. This allows the data packets to try retransmission in the same cycle without requiring control packets re-coordination that increases propagation delay. Thus, we achieve large number of data packets transmission, even more than the data channels number, providing throughput improvement and delay reduction, comparing with other studies.     

WDM光网络保护中一种新的波长预留方法

研究了WDM网状网中双链路失效的保护设计问题,在双链路失效保护时采用"裁剪相继最短路"算法计算工作通路和保护通路,而预留波长时利用波长预留矩阵预留资源,并进行仿真实验.实验结果表明,基于BRM的波长预留方法与已有的两步计算法相比大大减少预留资源.     

Robust resource allocation for NOMA-assisted heterogeneous networks

As a promising technology to improve spectrum efficiency and transmission coverage, Heterogeneous Network (HetNet) has attracted the attention of many scholars in recent years. Additionally, with the introduction of the Non-Orthogonal Multiple Access (NOMA) technology, the NOMA-assisted HetNet cannot only improve the system capacity but also allow more users to utilize the same frequency band resource, which makes the NOMA-assisted HetNet a hot topic. However, traditional resource allocation schemes assume that base stations can exactly estimate direct link gains and cross-tier link gains, which is impractical for practical HetNets due to the impact of channel delays and random perturbation. To further improve energy utilization and system robustness, in this paper, we investigate a robust resource allocation problem to maximize the total Energy Efficiency (EE) of Small-Cell Users (SCUs) in NOMA-assisted HetNets under imperfect channel state information. By considering bounded channel uncertainties, the robust resource optimization problem is formulated as a mixed-integer and nonlinear programming problem under the constraints of the cross-tier interference power of macrocell users, the maximum transmit power of small base station, the Resource Block (RB) assignment, and the quality of service requirement of each SCU. The original problem is converted into an equivalent convex optimization problem by using Dinkelbach's method and the successive convex approximation method. A robust Dinkelbach-based iteration algorithm is designed by jointly optimizing the transmit power and the RB allocation. Simulation results verify that the proposed algorithm has better EE and robustness than the existing algorithms.