An improved handover algorithm based on signal strength plus distance for interoperability in mobile cellular networks

In future generation mobile cellular systems, position location of mobile terminal is expected to be available. In this paper, we propose an initiation algorithm for intersystem handover based on the combination of position location of mobile terminal and the absolute signal strength thresholds. Global System for Mobile communication (GSM) and Universal Mobile Telecommunication Systems (UMTS) networks are considered for interworking. The proposed algorithm reduces the handover rate by around 50% and thus improves the network resource efficiency as compared to that based on signal strength thresholds only.     

A distributed laxity-based priority scheduling scheme for time-sensitive traffic in mobile ad hoc networks

Characteristics of Mobile Ad hoc Networks such as shared broadcast channel, bandwidth and battery power limitations, highly dynamic topology, and location dependent errors, make provisioning of quality of service (QoS) in such networks very difficult. The Medium Access Control (MAC) layer plays a very important role as far as QoS is concerned. The MAC layer is responsible for selecting the next packet to be transmitted and the timing of its transmission. We have proposed a new MAC layer protocol that includes a laxity-based priority scheduling scheme and an associated back-off scheme, for supporting time-sensitive traffic. In the proposed scheduling scheme, we select the next packet to be transmitted, based on its priority value which takes into consideration the uniform laxity budget of the packet, the current packet delivery ratio of the flow to which the packet belongs, and the packet delivery ratio desired by the user. The back-off mechanism devised by us grants a node access to the channel, based on the rank of its highest priority packet in comparison to other such packets queued at nodes in the neighborhood of the current node. We have studied the performance of our protocol that combines a packet scheduling scheme and a channel access scheme through simulation experiments, and the simulation results show that our protocol exhibits a significant improvement in packet delivery ratio under bounded end-to-end delay requirements, compared to the existing 802.11 DCF and the Distributed Priority Scheduling scheme proposed recently in [ACM Wireless Networks Journal 8 (5) (2002) 455–466; Proceedings of ACM MOBICOM '01, July 2001, pp. 200–209].     

IFQ:一种新的ATM网络业务调度算法

本文提出了插空公平公队列（ＩＦＱ）调度算法。由于该方法考虑了ＡＴＭ网络中不同种类连接的特性,能充分利用网络资源。理论分析和仿真实验表明,ＩＦＱ算法能为Ｇ连接提供预约带宽保证和确定的时延上界,满足业务的实时传输要求。同时ＩＦＱ调度算法还具有连接独立性特点,能灵活地分配带宽资源。     

Automated design algorithms for tactical wireless networks

To guide users who attempt to deploy wireless networks in military applications, there is an evolving need for developing systematic methodologies to analyze/predict the performance of mobile ad hoc networks (MANETs). In addition, the advance in cognitive networking research provides opportunities for exploiting unused spectrum to optimize throughput of MANETs. However, with the increasing number of parameters/constraints, there is even a more demanding need to develop automated methodologies to design/tune such networks.In this work, we study the concepts and challenges for automatic design/re-configuration of cognitive MANETs, in addition to proposing design automation algorithms. The paper is divided into two parts. In the first part, we describe the design objectives, imposed constraints, and involved parameters in MANET design. We discuss how cognitive techniques can be employed to exploit the unused spectrum in military architectures. We then discuss the challenges that face the design/re-configuration of a cognitive network and their implications at different network layers. We also describe possible implementation options for designing MANETs that employ cognitive features at all layers. In the second part of this work, we propose design automation algorithms for optimally setting parameters to achieve a desired objective and satisfy certain constraints. Despite providing the optimal configuration, the simple approach of testing all possible combinations of parameter settings has significant time complexity (the COMB approach). Thus, we propose a novel heuristic (Sequential Parameter Optimization or SEPO) for searching through the possible parameter settings and selecting the best design options. SEPO is efficient in terms of both convergence speed and parameter tuning. We also discuss the foundation for using supervised learning to speed up the design (search) process. By evaluating realistic design of military-like scenarios that require optimizing a diverse set of metrics, we show that SEPO generates comparable results to the optimal, straightforward (slow-converging) COMB approach that is based on exhaustive search.     

一种基于帧的快速包调度算法

本文提出了基于帧的近似排序包调度新算法（FASFQ）,该算法用帧排序代替传统的包排序来处理G连接（预约带宽的连接）数据,并在帧与帧之间的空隙传送E型（best offort型）数据。理论分析和实验结果都表明,FASFQ算法与传统算法相比,在大大降低了排序复杂的同时,还能为G连接提供预约带宽,保证连接的独立性和公平性,避免E连接对G连接的冲击。     

A distributed link scheduling algorithm for CDMA packet radio networks

A distributed algorithm for the conflict-free channel allocation in CDMA (code division multiple access) networks is presented. Dynamic adjustment to topological changes is also considered. Though the schedules produced by our algorithm are not optimal with respect to link schedule length, the algorithm is simple and practical. The link schedule length minimization problem is NP-complete. Here the length of a link schedule is the number of time slots it uses. The algorithm guarantees a bound 2 — 1 time slots on the TDMA cycle length, where is the maximum degree of a station (i.e., maximum number of stations that a station can reach by radio links) in the network. The message complexity of a station isO().     

Optimal dynamic spectrum allocation-assisted latency minimization for multiuser mobile edge computing

Mobile Edge Computing (MEC) has been envisioned as an efficient solution to provide computation-intensive yet latency-sensitive services for wireless devices. In this paper, we investigate the optimal dynamic spectrum allocation-assisted multiuser computation offloading in MEC for overall latency minimization. Specifically, we first focus on a static multiuser computation offloading scenario and jointly optimize users' offloading decisions, transmission durations, and Edge Servers' (ESs) resource allocations. Owing to the nonconvexity of our joint optimization problem, we identify its layered structure and decompose it into two problems: a subproblem and a top problem. For the subproblem, we propose a bisection search-based algorithm to efficiently find the optimal users' offloading decisions and ESs’ resource allocations under a given transmission duration. Second, we use a linear search-based algorithm for solving the top problem to obtain the optimal transmission duration based on the result of the subproblem. Further, after solving the static scenario, we consider a dynamic scenario of multiuser computation offloading with time-varying channels and workload. To efficiently address this dynamic scenario, we propose a deep reinforcement learning-based online algorithm to determine the near-optimal transmission duration in a real-time manner. Numerical results are provided to validate our proposed algorithms for minimizing the overall latency in both static and dynamic offloading scenarios. We also demonstrate the advantages of our proposed algorithms compared to the conventional multiuser computation offloading schemes.     

An efficient and flexible MPLS signaling framework for mobile networks

Multiprotocol Label Switching (MPLS) has gained momentum in recent years as an effective tool to provide Quality of Service (QoS) in a variety of networks. This has in turn created active interest in the area of recovery in MPLS based networks. A number of recovery schemes for MPLS domains have been proposed in recent years. However, the current schemes lack support for recovery in dynamic network topologies. In this paper, a new flexible signaling protocol for LSP rerouting in dynamic network environments is introduced. The signaling protocol recovers from node and link failures reactively, taking a local approach to LSP reestablishment. The performance of the signaling protocol is evaluated through simulations. Results indicate that the protocol can effectively and efficiently handle rerouting in dynamic networks with a low protocol signaling overhead as compared to contemporary MPLS rerouting protocols. This would enable the MPLS based IP-QoS support mechanisms to extend to dynamic network topologies. A preliminary version of this work was presented at the 2004 IEEE International Conference on Communications, Paris. Ramprasad Nagarajan has received his B.E. degree in Electronics and Telecommunications from Pune University, India in 1999. He received his M.S. degree in Electrical and Computer Engineering from the Ohio State University, Columbus, OH in 2004. Currently, he is a Wireless Network Engineer in Nortel Networks, specializing in the area of network architecture and design of wireless packet core networks. Ramprasad’s current research interests include the study of wireless network evolution trends, next generation wireless networks, network capacity planning, performance analysis, and optimization. He is a member of the IEEE. Eylem Ekici has received his B.S. and M.S. degrees in Computer Engineering from Bogazici University, Istanbul, Turkey, in 1997 and 1998, respectively. He received his Ph.D. degree in Electrical and Computer Engineering from Georgia Institute of Technology, Atlanta, GA, in 2002. Currently, he is an assistant professor in the Department of Electrical and Computer Engineering of the Ohio State University, Columbus, OH. Dr. Ekici’s current research interests include wireless sensor networks, vehicular communication systems, next generation wireless systems, and space-based networks, with a focus on routing and medium access control protocols, resource management, and analysis of network architectures and protocols. He also conducts research on interfacing of dissimilar networks.     

Optimized priority based energy efficient routing algorithm for mobile ad hoc networks

Recently more and more research interest focuses on the energy efficient routing in mobile ad hoc networks and many related routing algorithms are reported. In this paper, a new optimized priority based energy efficient routing algorithm is presented and priority is added to the existing routing algorithm according to the residual energy proportion of the nodes. Lower residual energy means lower priority and the nodes with lower priority are less likely to forward packets to other nodes. The algorithm needs no global information of the networks and only a little modification is needed to the existing algorithm, so it is practical to be implemented. The algorithm can improve the performance of routing discovery, routing maintenance and cache management at the same time. Some optimization strategy is taken to reduce the network overhead and the lifetime of the network is much longer and the network with our algorithm can transfer much more effective data. Simulation with NS-2 is done and satisfying results are obtained with this algorithm. The results show that the algorithm is efficient.     

An optimal scheduling algorithm for testing interconnect using boundary scan

Systems will soon be built with ICs that conform with the IEEE 1149.1 boundary scan architecture. Due to the hierarchical nature of such systems, they may contain many boundary scan chains. These chains can be used to test the system, subsystem, and board interconnect. To reduce test time, the application of test vectors to these scan chains must be carefully scheduled. This article deals with problems related to finding an optimal schedule for testing interconnect. This problem is modeled using a directed graph. The following results are obtained: (1) upper and lower bounds on interconnect test time; (2) necessary and sufficient conditions for obtaining an optimal schedule when the graph is acyclic; (3) sufficient condition for obtaining an optimal schedule when the graph is cyclic; and (4) an algorithm for constructing an optimal schedule for any graph.This work was supported by Defense Advanced Research Projects Agency and monitored by the Office of Naval Research under contract No. N00014-87-K-0861. The views and conclusions contained in this document are those of the authors and should not be interpreted as necessarily representing the official policies, either expressed or implied, of the Defense Advanced Research Projects Agency or the U.S. Government.     

一种保留图像边缘信息的图像复原方法

针对图像复原的同时要求保留图像边缘信息的矛盾,利用图像的梯度模,提出了一种保留图像边缘信息的图像复原方法。本方法对图像修复的同时,具有保护图像边缘的作用。实验表明本方法在去除噪声和信噪比上取得了较好的效果。     

Joint Optimization of Trajectory and Task Offloading for Cellular-Connected Multi-UAV Mobile Edge Computing

Since the computing capacity and battery energy of unmanned aerial vehicle(UAV)are constrained,UAV as aerial user is hard to handle the high computational complexity and time-sensitive applications.This paper investigates a cellular-connected multi-UAV network supported by mobile edge computing.Multiple UAVs carrying tasksfly from a given initial position toa termination position within a specified time.To handle the large number of tasks carried by UAVs,we propose a energy cost of all UAVs based problem to determine how many tasks should be offloaded to high-altitude balloons(HABs)for computing,where UAV-HAB association,the trajectory of UAV,and calculation task splitting are jointly optimized.However,the formulated problem has nonconvex structure.Hence,an efficient iterative algorithm by applying successive convex approximation and the block coordinate descent methods is put forward.Specifically,in each iteration,the UAV-HAB association,calculation task splitting,and UAV trajec-tory are alternately optimized.Especially,for the nonconvex UAV trajectory optimization problem,an approximate convex optimization problem is settled.The numerical results indicate that the scheme of this paper proposed is guaranteed to converge and also significantly reduces the entire power consumption of all UAVs compared to the benchmark schemes.     

Edge computing technologies for Internet of Things: a primer

With the rapid development of mobile internet and Internet of Things applications, the conventional centralized cloud computing is encountering severe challenges, such as high latency, low Spectral Efficiency (SE), and non-adaptive machine type of communication. Motivated to solve these challenges, a new technology is driving a trend that shifts the function of centralized cloud computing to edge devices of networks. Several edge computing technologies originating from different backgrounds to decrease latency, improve SE, and support the massive machine type of communication have been emerging. This paper comprehensively presents a tutorial on three typical edge computing technologies, namely mobile edge computing, cloudlets, and fog computing. In particular, the standardization efforts, principles, architectures, and applications of these three technologies are summarized and compared. From the viewpoint of radio access network, the differences between mobile edge computing and fog computing are highlighted, and the characteristics of fog computing-based radio access network are discussed. Finally, open issues and future research directions are identified as well.     

An efficient algorithm for generalized SS/TDMA scheduling with satellite cluster and intersatellite links

We consider the satellite cluster scheduling problem, which is one of the most interesting problems in the satellite communication scheduling area. This problem is known to be NP-complete, and a couple of heuristic algorithms have been developed. In this paper, we suggest another algorithm for this problem which has the same computational complexity as the best existing one and provides much better solution quality. Extensive computational simulation results are reported.     

一种计算具有不可靠结点分布式计算网络可靠性的算法

提出了几个保持可靠性不变的缩减,结合这些缩减,利用因子分解公式建立了一个计算具有不可靠结点的分布式计算网络分布程序可靠性的有效算法,算法的时间复杂性是O(N·(V+E)),并对一些网络在Pentium 120 计算机上作了计算,结果显示用本文算法计算DPR所产生的N和所用时间比其它算法的要小得多。     

802.11 power-saving mode for mobile computing in Wi-Fi hotspots: Limitations,enhancements and open issues

Nowadays Wi-Fi is the most mature technology for wireless-Internet access. Despite the large (and ever increasing) diffusion of Wi-Fi hotspots, energy limitations of mobile devices are still an issue. To deal with this, the standard 802.11 includes a Power-Saving Mode (PSM), but not much attention has been devoted by the research community to understand its performance in depth. We think that this paper contributes to fill the gap. We focus on a typical Wi-Fi hotspot scenario, and assess the dependence of the PSM behavior on several key parameters such as the packet loss probability, the Round Trip Time, the number of users within the hotspot. We show that during traffic bursts PSM is able to save up to 90% of the energy spent when no energy management is used, and introduces a limited additional delay. Unfortunately, in the case of long inactivity periods between bursts, PSM is not the optimal solution for energy management. We thus propose a very simple Cross-Layer Energy Manager (XEM) that dynamically tunes its energy-saving strategy depending on the application behavior and key network parameters. XEM does not require any modification to the applications or to the 802.11 standard, and can thus be easily integrated in current Wi-Fi devices. Depending on the network traffic pattern, XEM reduces the energy consumption of an additional 20–96% with respect to the standard PSM. This work has been carried out while A. Passarella was with the Department of Information Engineering of the University of Pisa. Giuseppe Anastasi is an associate professor of Computer Engineering at the Department of Information Engineering of the University of Pisa, Italy. He received the Laurea (cum laude) degree in Electrical Engineering, and the Ph.D. degree in Computer Engineering, both from the University of Pisa, in 1990 and 1995, respectively. His research interests include mobile and pervasive computing, ad hoc and sensor networks, and power management. He is a co-editor of the book Advanced Lectures in Networking (LNCS 2497, Springer, 2002), and has published more than 60 papers in the area of computer networking and pervasive computing, both in international journals and conference proceedings. He is a member of the editorial board of the Journal of Ubiquitous Computing and Intelligence (JUCI), and is currently serving as Vice Program Co-Chair for the IEEE MASS 2007 conference. He has served as general chair for IEEE WoWMoM 2005, Workshops Chair for IEEE PerCom 2006 and IEEE WoWMoM 2006, and program chair for several international workshops. He has also served on the Technical Program Committee of many international conferences. He is a member of the IEEE Computer Society. Marco Conti is a research director at IIT, an institute of the Italian National Research Council (CNR). He co-authored the book “Metropolitan Area Networks” (Springer, 1997) and is co-editor of the book “Mobile Ad Hoc Networking” (IEEE-Wiley 2004). He published in journals and conference proceedings more than 180 research papers related to design, modeling, and performance evaluation of computer-network architectures and protocols. He served as TPC chair of IEEE PerCom 2006, and of the IFIP-TC6 Conferences “Networking2002” and “PWC2003”, and as TPC co-chair of ACM WoWMoM 2002, WiOpt ’04, IEEE WoWMoM2005, and ACM MobiHoc2006. He served as general co-chair of IEEE WoWMoM 2006 and as general chair of ACM REALMAN 2006. Currently, he is serving as general chair of IEEE MASS 2007. He is Associate Editor of Pervasive and Mobile Computing Journal, and he is on the editorial board of: IEEE Transactions on Mobile Computing, Ad Hoc Networks journal and Wireless Ad Hoc and Sensor Networks: An International Journal. Enrico Gregori received the Laurea in electronic engineering from the University of Pisa in 1980. In 1981 he joined the Italian National Research Council (CNR) where he is currently a CNR research director. He is currently the deputy director of the CNR institute for Informatics and Telematics (IIT). In 1986 he held a visiting position in the IBM research center in Zurich working on network software engineering and on heterogeneous networking. He has contributed to several national and international projects on computer networking. He has authored more than 100 papers in the area of computer networks and has published in international journals and conference proceedings and is co-author of the book “Metropolitan Area Networks” (Springer, London 1997). He was the General Chair of the IFIP TC6 conferences: Networking2002and PWC2003 (Personal Wireless Communications) and IEEE Pervasive Computing and Communication (PERCOM) 2006. He served as guest editor for the Networking2002 journal special issues on: Performance Evaluation, Cluster Computing and ACM/Kluwer Wireless Networks Journals. He is a member of the board of directors of the Create-Net association, an association with several Universities and research centers that is fostering research on networking at European level. He is on the editorial board of the Cluster Computing, of the Computer Networks and of the Wireless Networks Journals. His current research interests include: Ad hoc networks, Sensor networks, Wireless LANs, Quality of service in packet-switching networks, Evolution of TCP/IP protocols. Andrea Passarella is a Researcher at the IIT Institute of the National Research Council (CNR), Italy. Before joining IIT, he was a Research Associate at the Computer Laboratory of the University of Cambridge, UK. He received the Ph.D. and M.S. Degrees in Computer Engineering, both from the University of Pisa, Italy, in 2005 and 2001, respectively. His current research is mostly on opportunistic and delay-tolerant networking. More in general, he works on ad hoc and sensor networks, specifically on p2p systems, multicasting, transport protocols, and energy-efficient protocols. His research interests also include mesh networks and wireless access to the Internet. He is Co-Editor of the book “Multi-hop Ad hoc Networks: From Theory to Reality” (Nova Science, 2007). He was TPC Vice-Chair for IEEE REALMAN 2005, ACM REALMAN 2006, and IEEE MDC 2006. He served and is currently serving in the TPC of several international conferences, including IEEE PerCom 2006/07 and IEEE WoWMoM 2006/07, and workshops. He is an Associate Technical Editor for IEEE Communications Magazine. He is a member of ACM SIGMOBILE.     

Immediate neighbor scheduling (INS): An adaptive protocol for mobile ad hoc networks using direct-sequence spread-spectrum modulation

We investigate a new approach for scheduling transmissions in a mobile ad hoc network employing direct-sequence spread-spectrum (DSSS). Multiple-access interference may be better tolerated in these systems, allowing higher levels of spatial reuse and a reduction in the overhead required to schedule transmissions. We present a protocol which leverages these features of DSSS to support greater end-to-end throughput and terminal mobility rates. A protocol extension allows terminals to adjust protocol overhead in order to preserve network connectivity in sparse networks. For each transmission, terminals use a combination of common and transmitter-oriented spreading sequences in a format which allows for discovery of nearby terminals and adaptation of transmission rates to maximize throughput. The protocol does not operate over an artificial network graph, nor does it require an initialization phase or two-way exchange of information during a transmission slot. Through simulations, we evaluate the performance of the transmission scheduling protocol in a variety of static and mobile scenarios. For comparison, we also simulate a centralized transmission scheduling protocol with perfect knowledge of topology.     

SmipRef: An efficient method for multi-domain clock skew scheduling

Conventional clock skew scheduling (CSS) for sequential circuits can be solved effectively using methods including the parametric shortest path algorithm and Howard's algorithm. Nevertheless, its application is practically limited due to the difficulties in reliably implementing a large set of arbitrary dedicated clock delays for flip-flops. Thus multi-domain clock skew scheduling (MDCSS) was proposed to tackle this by constraining the total number of clock delays. However, this new problem is hard to solve optimally in general. In this paper, we propose a novel method to efficiently solve it. Under mild restrictions, the problem is transformed into a special mixed integer linear programming problem, which can be solved optimally using similar techniques for the CSS problem. Then the solution quality is further improved by a critical-cycle-oriented refinement. As a result, our method obtains optimal solutions for 88 of the 93 tests on ISCAS89 benchmarks. The experimental results on large circuits in Opencores benchmarks also demonstrate its efficiency of at least one order faster than existing algorithms. To improve the runtime performance, we also devise a graph pruning algorithm that can be applied to methods for the MDCSS problem as a preprocessing step. Its application on our method shows a speedup of 2.66X on average.