Performance analysis of resource sharing policies in CDMA networks

We consider an interference‐limited code division multiple access (CDMA) network, in which some of the service classes are explicit rate controlled. Such rate‐controlled service classes include adaptive ones whose holding time does not depend on the sending rate, while the holding time of elastic services becomes longer when their sending rate is slowed down. We develop a Markov model that allows us to study the impact of employing service differentiation (prioritization) during admission control and rate control on the classwise blocking probabilities and throughputs. The admission control takes into account the interference from adjacent cells as a log‐normally distributed random variable and employs service class and state‐dependent (soft) blocking in addition to hard blocking. The state‐dependent rate control algorithm takes into account the minimum and maximum requested rates of admitted sessions in a fairness policy‐dependent manner. Our conclusion is that work conserving bandwidth sharing policies may have a major impact on the moments of the time spent in the system by elastic services, but only a minor one on the classwise blocking probabilities. When the admission control algorithm takes into account the neighbour cell caused interference, the blocking probability of all classes increases somewhat, but the throughput of the accepted sessions increases. Blocking prioritization in the soft blocking model affects the classwise total blocking probabilities but has little impact on the throughput of adaptive and elastic traffic. Copyright © 2006 John Wiley & Sons, Ltd.     

WSN中能量有效分簇多跳路由算法

针对现有无线传感器网络(WSN)分簇路由算法存在的能耗不均衡问题,提出一种能量有效分簇多跳路由算法,该算法包括两个方面:一是选举簇首时引入簇内平均剩余能量因子,根据上一轮结束后簇内各节点剩余能量和簇内节点的平均剩余能量的比值更新簇首在所有节点中所占的百分比;二是要求簇首根据MTE多跳路由协议与基站通信,从而均衡WSN整...     

认知无线多跳网中保证信干噪比的频谱分配算法

为解决无线多跳网络在固定频谱分配方式下所固有的信道冲突等问题,利用认知无线电的动态频谱分配技术,提出了一种适用于次用户组成的无线多跳网络的、underlay方式下的全分布式频谱分配算法。该算法将频谱分配问题建模成静态非合作博弈,证明了纳什均衡点的存在,并给出了一种求解纳什均衡点的迭代算法。大量仿真实验证明,该算法能实现信道与功率的联合分配,在满足主用户干扰功率限制的同时,保证次用户接收信干噪比要求。     

多跳无线网网络拓扑控制优化目标研究

研究了多跳无线网中网络性能与网络拓扑结构关系的问题。数值计算结果表明网络节点只与“最邻近”的节点建立链路时形成的拓扑结构节点的吞吐量最大,这样的拓扑结构同时能满足网络的低功耗、低截获概率和可靠性要求。计算机仿真结果验证了上述结论。因而,网络拓扑控制的目标就转化为节点在邻节点中选择“最邻近”节点,继而建立逻辑链路的问题。     

认知无线多跳网中结合QoS查找的跨层多信道MAC协议

针对认知无线多跳网中频谱资源具有较大时变性及差异性的问题,设计了一种结合QoS查找的跨层多信道MAC协议。该协议将按需QoS查找与动态频谱分配跨层相结合,仅让参与传输的节点执行频谱分配并按QoS要求获取频谱资源。此外,协议使用频分双工收发机实现了对公共控制信道的不间断监听,并设计了一套支持不同数量收发机节点间混合通信的接入算法。大量仿真结果表明,该协议能有效保证对端到端传输的QoS要求的满足,并显著提高端到端吞吐量及时延。     

Dynamic spectrum sharing in cognitive radio networks using truthful mechanisms and virtual currency

In cognitive radio networks, there are scenarios where secondary users (SUs) utilize opportunistically the spectrum originally allocated to primary users (PUs). The spectrum resources available to SUs fluctuates over time due to PUs activity, SUs mobility and competition between SUs. In order to utilize these resources efficiently spectrum sharing techniques need to be implemented. In this paper we present an approach based on game-theoretical mechanism design for dynamic spectrum sharing. Each time a channel is not been used by any PU, it is allocated to SUs by a central spectrum manager based on the valuations of the channel reported by all SUs willing to use it. When an SU detects a free channel, it estimates its capacity according to local information and sends the valuation of it to the spectrum manager. The manager calculates a conflict-free allocation by implementing a truthful mechanism. The SUs have to pay for the allocation an amount which depends on the set of valuations. The objective is not to trade with the spectrum, but to share it according to certain criteria. For this, a virtual currency is defined and therefore monetary payments are not necessary. The spectrum manager records the credit of each SU and redistributes the payments to them after each spectrum allocation. The mechanism restricts the chances of each SU to be granted the channel depending on its credit availability. This credit restriction provides an incentive to SUs to behave as benefit maximizers. If the mechanism is truthful, their best strategy is to communicate the true valuation of the channel to the manager, what makes possible to implement the desired spectrum sharing criteria. We propose and evaluate an implementation of this idea by using two simple mechanisms which are proved to be truthful, and that are tractable and approximately efficient. We show the flexibility of these approach by illustrating how these mechanisms can be modified to achieve different sharing objectives which are trade-offs between efficiency and fairness. We also investigate how the credit restriction and redistribution affects the truthfulness of these mechanisms.     

MrFair: Misbehavior-resistant fair scheduling in wireless mesh networks

It is a critical issue to ensure that nodes and/or flows have fair access to the network bandwidth in wireless mesh networks (WMNs). However, current WMNs based on IEEE 802.11 exhibit severe unfairness. Several scheduling schemes have been proposed to ensure fairness in WMNs. Unfortunately, all of them implicitly trust nodes in the network, and thus are vulnerable to the misbehavior of nodes participating in scheduling. In this paper, we address the threats to fair scheduling in WMNs resulting from node misbehavior and present a generic verification framework to detect such misbehavior. Moreover, we develop two verification schemes based on this framework for distributed and centralized authentication environments, respectively. We validate our approach by extending an existing fair scheduling scheme and evaluating it through simulation. The results show that our approach improves misbehavior detection with light performance overhead.     

Energy balanced data propagation in wireless sensor networks

We study the problem of energy-balanced data propagation in wireless sensor networks. The energy balance property guarantees that the average per sensor energy dissipation is the same for all sensors in the network, during the entire execution of the data propagation protocol. This property is important since it prolongs the network’:s lifetime by avoiding early energy depletion of sensors. We propose a new algorithm that in each step decides whether to propagate data one-hop towards the final destination (the sink), or to send data directly to the sink. This randomized choice balances the (cheap) one-hop transimssions with the direct transimissions to the sink, which are more expensive but “bypass” the sensors lying close to the sink. Note that, in most protocols, these close to the sink sensors tend to be overused and die out early. By a detailed analysis we precisely estimate the probabilities for each propagation choice in order to guarantee energy balance. The needed estimation can easily be performed by current sensors using simple to obtain information. Under some assumptions, we also derive a closed form for these probabilities. The fact (shown by our analysis) that direct (expensive) transmissions to the sink are needed only rarely, shows that our protocol, besides energy-balanced, is also energy efficient. This work has been partially supported by the IST/FET/GC Programme of the European Union under contract numbers IST-2001-33135 (CRESCCO) and 6FP 001907 (DELIS). A perliminary version of the work appeared in WMAN 2004 [11]. Charilaos Efthymiou graduated form the Computer Engineering and Informatics Department (CEID) of the University of Patras, Greece. He received his MSc from the same department with advisor in S. Nikoletseas. He currently continuous his Ph.D studies in CEID with advisor L. Kirousis. His research interest include Probabilistic Techniques and Random Graphs, Randomized Algorithms in Computationally Hard Problems, Stochastic Processes and its Applications to Computer Science. Dr. Sotiris Nikoletseas is currently a Senior Researcher and Managing Director of Research Unit 1 (“Foundations of Computer Science, Relevant Technologies and Applications”) at the Computer Technology Institute (CTI), Patras, Greece and also a Lecturer at the Computer Engineering and Informatics Department of Patras University, Greece. His research interests include Probabilistic Techniques and Random Graphs, Average Case Analysis of Graph Algorithms and Randomized Algorithms, Fundamental Issues in Parallel and Distributed Computing, Approximate Solutions to Computationally Hard Problems. He has published scientific articles in major international conferences and journals and has co-authored (with Paul Spirakis) a book on Probabilistic Techniques. He has been invited speaker in important international scientific events and Universities. He has been a referee for the Theoretical Computer Science (TCS) Journal and important international conferences (ESA, ICALP). He has participated in many EU funded R&D projects (ESPRIT/ALCOM-IT, ESPRIT/GEPPCOM). He currently participates in 6 Fifth Framework projects: ALCOM-FT, ASPIS, UNIVERSAL, EICSTES (IST), ARACNE, AMORE (IMPROVING). Jose Rolim is Full Professor at the Department of Computer Science of the University of Geneva where he leads the Theoretical Computer Science and Sensor Lab (TCSensor Lab). He received his Ph.D. degree in Computer Science at the University of California, Los Angeles working together with Prof. S. Greibach. He has published several articles on the areas of distributed systems, randomization and computational complexity and leads two major projects on the area of Power Aware Computing and Games and Complexity, financed by the Swiss National Science Foundation. Prof. Rolim participates in the editorial board of several journals and conferences and he is the Steering Committee Chair and General Chair of the IEEE Distributed Computing Conference in Sensor Systems.     

无线网络中兼顾业务类型及公平性的无线资源共享问题研究

基于图染色理论提出了2种无线网络中的无线资源共享算法C_TDRS和S_TDGRS.这2种算法分别从子信道和业务流角度考虑,以尽力满足业务需求为目标,兼顾了业务类型和资源共享的公平性.仿真结果表明,2种算法的共享结果在系统吞吐率和比例公平方面比现有算法更接近最优值,并且S_TDGRS算法对2个指标有很好的折衷.     

Addressing the interdependence in providing fair and efficient bandwidth distribution in hybrid optical‐wireless networks

The convergence of optical and wireless technologies may offer a compelling network access infrastructure because these technologies combine major benefits such as large coverage in the wireless part and huge bandwidth in the optical part of the converged access network. The convergence of the passive optical networks with 4G wireless standards, such as the Worldwide Interoperability for Microwave Access and the Long Term Evolution, constitutes a quite attractive solution to meet the challenges of the modern bandwidth‐hungry access networks. One of the most important objective a modern access network has to address is the adequate bandwidth distribution to the final users. In addition, several other aims are emerged towards this goal, such as fairness and quality of service provisioning. The adversity of designing an efficient bandwidth distribution scheme for hybrid optical‐wireless access networks lies in the interdependence of both domains: the bandwidth distribution in the wireless domain depends on the optical transmission grant opportunities, while the bandwidth coordinator in the optical part has to be aware of the mobile user heterogeneity in the wireless domain. Moreover, the bandwidth decision‐making module in both networks has to be aware of providing a fair allocation independently of the number of mobile users or the traffic requests in the network. In this work, we endeavor to address the aforementioned challenges. A novel, fair, and efficient bandwidth distribution scheme is proposed for hybrid optical‐wireless access networks. By using weighted fairness provisioning techniques, the proposed scheme intends to alleviate the interdependence of the two domains, offering a fair and efficient bandwidth distribution to the mobile users. The weights are properly defined, by utilizing suitable optimization techniques such as the Lagrange multiplies, so as to incorporate the underlying features of each traffic requests, such as the population density and the propagation delay. Extensive simulation results indicate the capability of the proposed scheme, compared with other competitive allocation schemes, in provisioning a more efficient and fair bandwidth distribution in terms of latency, throughput, and packet drop ratio. Copyright © 2015 John Wiley & Sons, Ltd.     

Performance analysis of handover delay and buffer capacity in mobile OpenFlow‐based networks

Software‐defined networking (SDN) is a network concept that brings significant benefits for the mobile cellular operators. In an SDN‐based core network, the average service time of an OpenFlow switch is highly influenced by the total capacity and type of the output buffer, which is used for temporary storage of the incoming packets. In this work, the main goal is to model the handover delay due to the exchange of OpenFlow‐related messages in mobile SDN networks. The handover delay is defined as the overall delay experienced by the mobile node within the handover procedure, when reestablishing an ongoing session from the switch in the source eNodeB to the switch in the destination eNodeB. We propose a new analytical model, and we compare two systems with different SDN switch designs that model a continuous time Markov process by using quasi‐birth–death processes: (1) single shared buffer without priority (model SFB), used for all output ports for both control and user traffic, and (2) two isolated buffers with priority (model priority finite buffering [PFB]), one for control and the other for user plane traffic, where the control traffic is always prioritized. The two proposed systems are compared in terms of total handover delay and minimal buffer capacity needed to satisfy a certain packet error ratio imposed by the link. The mathematical modeling is verified via extensive simulations. In terms of handover delay, the results show that the model PFB outperforms the model SFB, especially for networks with high number of users and high probability of packet‐in messages. As for the buffer dimensioning analysis, for lower arrival rates, low number of users, and low probability of packet‐in messages, the model SFB has the advantage of requiring a smaller buffer size.     

基于排队模型的无线Mesh网延时分析与优化

在提供无线接入的网格网中,不同用户因所处地理位置的不同所获得的服务质量（吞吐量、延时）会有较大程度的差异。文中使用排队网络对Mesh网建立模型,从理论上分析了非饱和流量的情况下不同用户获得的延时的差异。分析发现,通过设置多个缓冲区并调度不同数据流在中间节点上的优先级别,可以使不同用户的延时趋于均匀从而保证网络的公平性。把优先级的分配问题归结为一个以公平性为目标的组合优化问题并提供了解法。使用Lorenz曲线来度量公平性,仿真结果表明,使用优化的调度算法可以获得更好的网络公平性。     

Analytical modeling and resource planning for cognitive radio systems

Cognitive radio heralds the next step in the evolution of wireless communications. In this paper, an analytical model for infrastructure based cognitive radio systems is proposed, and its performance is evaluated under bursty traffic scenarios in a multiple cell environment. Performance metrics like probabilities of dropping and blocking for primary and secondary users as well as forced termination and forced frequency handoff for secondary users are investigated, and the analytical model is verified with simulations. In addition to the analytical model, a new resource planning method is proposed to compensate for uneven traffic load distribution. The proposed method considers offered traffic, hop count to the heavily loaded cell, and velocity of mobile users during resource planning and performs better in terms of probability of blocking, dropping, and forced termination. The proposed method is promising in balancing the system performance measures, yet there is room for further improvement for finding a closed formula for the proposed analytical model. Copyright © 2010 John Wiley & Sons, Ltd.     

Efficient delay based scheduling with fairness in multi-hop wireless mesh networks

Some scheduling algorithms have been designed to improve the performance of multi-hop wireless mesh networks (WMNs) recently. However the end-to-end delay is seldom considered as the complexity of multi-hop topology and open wireless shared channel. This article proposes an efficient delay based scheduling algorithm with the concept of buffer-data- hops. Considering the demand satisfaction factor (DSF), the proposed algorithm can also achieve a good fairness performance. Moreover, with the interference-based network model, the scheduling algorithm can maximize the spatial reuse, compared to those graph-based scheduling algorithms. Detailed theoretical analysis shows that the algorithm can minimize the end-to-end delay and make a fair scheduling to all the links.     

Cross-layer radio resource allocation in packet CDMA wireless mobile networks

An efficient radio resource allocation scheme is crucial for guaranteeing the quality of service (QoS) requirements and fully utilizing the scarce radio resources in wireless mobile networks. Most of previous studies of radio resource allocation in traditional wireless networks concentrates on network layer connection blocking probability QoS. In this paper, we show that physical layer techniques and QoS have significant impacts on network layer QoS. We use a concept of cross-layer effective bandwidth to measure the unified radio resource usage taking into account both physical layer linear minimum-mean square error (LMMSE) receivers and varying statistical characteristics of the packet traffic in code devision multiple access (CDMA) networks. We demonstrate the similarity between traditional circuit-switched networks and packet CDMA networks, which enables rich theories developed in traditional wireless mobile networks to be used in packet CDMA networks. Moreover, since both physical layer signal-to-interference ratio (SIR) QoS and network layer connection blocking probability QoS are considered simultaneously, we can explore the tradeoff between physical layer QoS and network layer QoS in packet CDMA networks. This work is supported by Natural Science and Engineering Research Council of Canada. Please address all correspondence to Professor Vikram Krishnamurthy at the above address. Fei Yu received the Ph.D. degree in electrical engineering from the University of British Columbia in 2003. From 2002 to 2004, he was with Ericsson (in Lund, Sweden), where he worked on the research and development of dual mode UMTS/GPRS handsets. From 2005, he has been working in Silicon Valley at a start-up, where he conducts research and development in the areas of advanced wireless communication technologies and new standards. After completing the PhD, he has been a research associate in the Department of Electrical and Computer Engineering at the University of British Columbia. His research interests include cross-layer optimization, QoS provisioning and security in wireless networks. Vikram Krishnamurthy (S’90-M’91-SM’99-F’05) was born in 1966. He received his bachelor’s degree from the University of Auckland, New Zealand in 1988, and Ph.D. from the Australian National University, Canberra, in 1992. Since 2002, he has been a professor and Canada Research Chair at the Department of Electrical Engineering, University of British Columbia, Vancouver, Canada. Prior to this he was a chaired professor at the Department of Electrical and Electronic Engineering, University of Melbourne, Australia. His research interests span several areas including ion channels and nanobiology, stochastic scheduling and control, statistical signal processing and wireless telecommunications. Dr. Krishnamurthy has served as associate editor for IEEE Transactions on Signal Processing, IEEE Transactions Aerospace and Electronic Systems, IEEE Transactions Nanobioscience, IEEE Transactions Circuits and Systems II, Systems and Control Letters and European Journal of Applied Signal Processing. He was guest editor of a special issue of IEEE Transactions on NanoBioScience, March 2005 on bio-nanotubes.     

Design guidelines for wireless sensor networks: communication, clustering and aggregation

When sensor nodes are organized in clusters, they could use either single hop or multi-hop mode of communication to send their data to their respective cluster heads. We present a systematic cost-based analysis of both the modes, and provide results that could serve as guidelines to decide which mode should be used for given settings. We determine closed form expressions for the required number of cluster heads and the required battery energy of nodes for both the modes. We also propose a hybrid communication mode which is a combination of single hop and multi-hop modes, and which is more cost-effective than either of the two modes. Our problem formulation also allows for the application to be taken into account in the overall design problem through a data aggregation model.     

A method to enhance lifetime in data aggregation for multi-hop wireless sensor networks

Wireless Sensor Networks nowadays find wide variety of applications especially in real time. Innovative methods of energy efficient protocols and transmission reduction techniques keep improving to enhance the lifetime of the sensor nodes as they are powered by non-rechargeable batteries. Multi hop transmission and data aggregation are major techniques to reduce the power spent by the sensor node. In this paper, we propose a new ribbon structure for the existing multi hop WSN topologies with modified media access control mechanism called co-operative MAC. The ribbon structure is proposed to reap benefits of PEGASIS and APTEEN protocols. The low power consumption as in PEGASIS is maintained but the number of data packets transmitted is reduced by half. In the proposed scheme, only one of the two nodes along the parallel path involves in data transmission alternating roles in every cycle of aggregation. However, for values sensed above threshold, the inactive node interferes with normal cycle and gets its data transmitted to the sink node. This algorithm is compared with cluster based and chain based protocols and the simulation results show significant energy savings.     

New coalition formation game for spectrum sharing in cognitive radio networks

In cognitive radio networks, Secondary Users (SUs) can access the spectrum simultaneously with the Primary Users (PUs) in underlay mode. In this case, interference caused to the licensed users has to be effectively controlled. The SUs have to make spectrum access decisions in order to enhance their quality of service, but without causing harmful interference to the coexisting PUs. In this paper, we propose a cooperative spectrum decision, which enables the SUs to share the spectrum with the PUs more efficiently. Our approach is based on a new coalitional game in which the coalition value is a function of the SUs' spectral efficiencies, the inter‐SUs interference, and the interference caused to the PUs. By applying new Enter and Leave rules, we obtain a stable coalition structure. Simulation results show that the SUs' spectral efficiencies are considerably increased and that the interference caused to the coexisting PU is reduced by about 7.5% as compared to an opportunistic spectrum access scheme. Moreover, the proposed coalitional game results in a more balanced spectrum sharing in the network. Copyright © 2014 John Wiley & Sons, Ltd.     

Optimal spectrum utilisation in cognitive radio networks based on processor sharing techniques

Cognitive radio networks have achieved higher efficiency in terms of spectrum usage; however they do not readily solve any competition for access among secondary users. Optimisation is applied to an underlay network to obtain the optimal solution for at least two secondary users operating simultaneously on the same channel. Performance measures are used as the target for optimisation. However, the objective function is difficult to obtain in closed form. For the performance measures, queueing theory, particularly weighted processor sharing techniques are employed to model the system dynamics and behaviour. Transmission power and the interference temperature limit are used to allocate weights to the secondary users. Queue length and waiting time functions obtained from the queuing models are used for optimisation. After establishing that the objective function can be considered to be pseudo‐convex, convex programming is then deployed to obtain the optimised solution. The results suggest that there is indeed an improvement in network performance after optimisation. The immediate benefits of such a system are firstly improved spectrum utilisation through adding multiple secondary users and secondly, through optimisation, higher performance that can be achieved by the secondary users.