This paper proposes a new algorithm, TBRA (Termites- Based Routing Algorithm), for use in three- dimensional mobile wireless sensor networks. The TBRA is a routing selection strategy based on the concept of the ant colony optimization algorithm. It is difficult to establish and maintain optimal routes in a 3D space because the RSSI, energy of sensor nodes, vary with time. This routing selection strategy can be used for various traffic conditions by measuring and counting the average energy of nodes, RSSI value. The main contribution of this study combines ACO algorithm and Durkin's propagation model to derive an efficient routing scheme for wireless sensor networks in a 3D space.

In dense sensor networks, there are a large number of low-power, short-lived, low cost and unreliable sensors. A major challenge in constructing dense sensor networks is to prolong network lifetime as well as to keep low sensing coverage loss ratio. To prolong network lifetime, it is necessary to turn off redundant nodes to save energy. Moreover, to obtain low sensing coverage loss ratio is an important issue in dense sensor networks. We propose a cluster-based algorithm that can present a flexible, adjustable and energy-efficient scheme to identify redundant nodes for different requirements of network lifetime and low sensing coverage loss ratio. This algorithm needs without additional GPS and directional antennas support to identify redundant nodes. Our simulation results show that the cluster-based algorithm could save energy consumption under the process of determining redundant nodes for prolonging network lifetime, and achieve low sensing coverage loss ratio.

Wireless multihop access networks, where clients can access the Internet through Internet gateways by direct or multihop transmissions, are potential for future wireless data services and vehicular network applications. In the context of multihop transmissions, less number of gateways is required for Internet access while a certain level of Internet connectivity still holds. In this paper, we investigate the Internet connectivity, which is the probability that all clients are Internet-reachable, in one-dimensional multihop wireless access networks. We show the relationship between the Internet connectivity and the deployment of Internet gateways. These results are useful for network operators and service providers to deploy Internet gateways, manage clients, design protocols and develop wireless-based software for future mobile network applications.

With the advance of wireless technologies, wireless mesh backhaul networks (WMBNs) are emerging an alternative to conventional wired backbones for metropolitan areas. As real-time applications (e.g., voice over IP and video streaming) rapidly grow, provisioning quality-of-service (QoS) guarantees is one of the most important issues for WMBNs. In this paper the QoS problem for routing and scheduling in TDMA-based WMBNs was considered. An integrated routing and scheduling mechanism was proposed to provides QoS guarantees to real-time services with unrestricted topologies for TDMA-based WMBNs. A linear programming optimization is devised to solve the amount of non-collision bandwidth for a path according to the available resource and the interference. A simulation model is developed to investigate the performance of the proposed mechanism. Through the developed simulation, a series of experiments are conducted to show the capabilities of the proposed mechanism.

In this paper, we study the performance of radio resource allocation for cellular networks where real-time (RT) and non-real-time (NRT) data traffic are considered in addition to voice traffic. To guarantee the performance of voice traffic, preemptive priority is used so that voice calls can preempt data packets and RT data traffic preempts NRT data traffic. By reserving channels specifically for RT data, the packet loss probability and mean queueing delay can be reduced, meanwhile, the performance of NRT data can also be improved. This is achieved at the expense of increasing voice blocking probability. Thus, the number of reserved channels can be adjusted to control the voice blocking probability while improving the performance of data traffic. Besides, the packet loss probability of RT traffic is smaller for smaller RT traffic ratio. On the contrary, the smaller the RT traffic ratio, the larger the queueing delay.

The paper proposes mobility-aided resource reservation (MARR) with admission control (AC) to provide better usage of scarce resources in wireless broadband networks. The area of a cell is divided into an outer ring and an inner ring. A target cell is predicted by extrapolating the trajectory of each MS. In order to reduce signaling overhead, bandwidth is reserved only in the target cell as MSs move into the outer ring and leave the serving base station (BS). The amount of bandwidth to be reserved is dynamically adjusted according to the instantaneous variation of mobility ratio, location, and direction of an MS. Two scenarios of the MARR scheme are investigated by OPNET simulation and compared by considering the mobility ratio threshold in the calculation of the direction weighting. Simulation results show that employing the MARR scheme can indeed reduce connection dropping probability, and make better bandwidth utilization when appropriate parameters are chosen.

A mobile ad hoc network (MANET) is an infrastructureless and highly dynamic network. Routes in such a network may fail frequently because of node mobility or other issues. Stability therefore can be an important element in the design of routing protocols. Stable routes, also called long-lived routes, can be discovered and used to reduce the overhead resulted from route maintenance in ad hoc networks. We propose the long-lived route prediction (LRP) scheme to discover stable routes. The LRP scheme is distributed and predicts long-lived routes based on the history of link lifetime. Furthermore, we apply the LRP scheme to both the open area and urban area using simulation. Simulation results show that the LRP scheme can indeed discover stable routes to reduce route rediscovery, and can be much more efficient and scalable.

In this paper, the mobility-dependent predictive resource reservation (MDPRR) scheme is proposed to provide flexible usage of limited resource in mobile multimedia wireless networks. An admission control scheme is also considered to further guarantee the QoS of real-time traffic. The area of a cell is divided into non-handoff, pre-handoff, and handoff zones so that bandwidth is reserved in the target/sub-target cell as mobile stations move into the pre-handoff zone and leave the serving base station. The amount of bandwidth to be reserved is dynamically adjusted according to the location, the instantaneous variation of velocity and direction of mobile stations. Two scenarios of the MDPRR scheme are compared by considering the velocity threshold in the calculation of the weight of direction. The results show that employing the velocity threshold in the MDPRR scheme can indeed reduce connection dropping probability, and make better usage of the reserved bandwidth.

A frame-based packet scheduling scheme, the pinwheel scheduling (PWS) scheme, is proposed and investigated at the medium access control (MAC) layer in broadband wireless networks. The objective of the proposed scheduling scheme is to provide, respectively, low delay and low jitter for real-time traffic and short queue length for nonreal-time traffic. We have demonstrated in this paper that the proposed PWS scheme not only satisfies the packet-level QoS requirements but also has low implementation cost. As the number of constant bit rate (CBR) connections increases, variable bit rate (VBR) traffic would suffer a larger jitter, the PWS with modular strategy (PWS/MS) scheme is proposed to further enhance the PWS scheme. We also introduce two different slot-reuse strategies named real-time traffic first (RTF) and longest queue first (LQF), respectively, to improve the resource utilization. In order to demonstrate the performance of the PWS and PWS/MS schemes, comparisons are made with existing schemes such as the round-robin (RR) and weighted-round-robin (WRR) by using the OPNET software. Simulation results show that the proposed schemes are capable of maintaining the lowest delay and jitter for VBR and CBR traffic while not sacrificing the available bit rate (ABR) traffic.

We provide an extensive analysis of the MAC state operation for energy conservation and introduce both channel release and setup schemes regarding the uplink data traffic for wireless sensor networks. The introduction of a release timer has already been applied to some power saving schemes in the literature. In this paper, however, an additional release timer is used to let sink nodes go back to inactive state at time-out. Instead of using randomly distributed release timers as in the literature, we use Erlang-k distributed release timers here in order to improve the inaccuracy in the analysis. We find that a longer release time period can be a better design choice for arrival traffics with deterministic packet length.

This paper proposes the mobility-dependent resource reservation (MDRR) based admission control (AC) to provide the flexible usage of limited resource in wireless multimedia networks. The area of a cell is divided into the non-reservation pre-handoff, and handoff zones. As mobile stations move into the pre-handoff zone and is leaving the serving base station, bandwidth is reserved in the target/sub-target cell. The amount of bandwidth to be reserved is dynamically adjusted to reflect the current mobility condition of mobile stations. Performance of the proposed scheme is investigated through OPNET simulation using the 7-cell cellular network where mobile stations with random mobility and variable velocity are assumed. The results show that the proposed MDRR scheme can provide small connection dropping probability and achieve better bandwidth utilization when appropriate parameters are chosen. The fixed bandwidth reservation (FBR) scheme is compared with the MDRR scheme with non-preemption and preemption services.

Frequent handoff consumes a lot of system capability and signaling resources in a cellular system. A mobile station (MS) moving out of a cell may receive an incomplete message from a broadcast system. In this paper, we present download mechanisms in cellular systems or broadcast systems to support data users to receive the whole packet in time before moving out of the coverage area. Two download strategies: Quick Download using Multi-channel (QDM) scheme and the Quit Download (QUD) scheme are proposed in this study where the efficiencies of the two strategies are compared with the one without particular treatment. Some significant estimations such as the percentage of handoff data users having completed service before leaving the cell, the mean waiting time of non-handoff data users, and the blocking probability of data users are analyzed and compared. The numerical results show that, the QDM strategy is most efficient in reducing the handoff rate, the QUD strategy can assure the waiting time of non-handoff data users. Furthermore, these various strategies do not have serious impact on the blocking probability of data users.

In this paper the performance of an N×N internally nonblocking multi-plane ATM switch with common input and common output buffers is analyzed. Two traffic types are considered with different priorities. Two service policies are proposed to satisfy different performance requirements: one treats the high priority cells as loss-sensitive traffic, the other guarantees the delay time of high priority cells. The method of reflection is employed to evaluate the probability that a cell successfully leaves the input buffer. Performance measures such as throughput, delay and cell loss probability are then obtained. The effects of priority weights, traffic load and the buffer size on the performance of the proposed and the contrasted policies are studied. Besides, different traffic sources, such as Bernoulli and ON/OFF traffic sources, are also studied. The performance is significantly improved by adopting the multi-plane structure, and the two proposed service policies can guarantee the required quality of services as long as a high weight for high priority traffic class is given. Moreover, numerical results show that the delay time of the high priority traffic class for the two proposed service policies is insensitive to the buffer size, so that only cell loss probability is the key factor of concern for the design of the input buffer size.

Abstract By referring to the object‐oriented efforts of the Multimedia and Hypermedia information coding Expert Group (MHEG), and the augmented Petri net model, we present a formal definition of the multimedia hypermedia Petri net (MHPN) model. Through this proposed model, issues of authoring, rendering and synchronization of multimedia information (i.e. structure authoring, spatial temporal relationships, user interaction, etc.) can all be laid to rest. We have implemented a testbed system, the Petri net object information system (POIS), which offers considerable potential for the development of distributed hypermedia applications. The testbed has been implemented on an IBM‐PC486 under Windows 3.1. We are now in the process of porting the testbed model to Windows NT.

In a distributed computing environment, a testbed is built to investigate topology learning behaviors of bridges for LAN interconnection. It is flexible to configure on any networked computing facility and thus serves as an environment for rapid prototyping of bridge systems. Unlike a pure simulator, the testbed employs distributed computing in itself so that the parallelism embedded in protocols under test can be exploited as well. With modular design and unified interprocess interfacing, it can be employed to explore a variety of topology algorithms. In addition, as part of testbed functions, it can simulate network topology of interest. It also provides the challenges of distributed environments, performance reports, dynamical topology change scenarios, and a graphical user interface. By direction linking the actual code of the protocols to the testbed, the phases of design, development, and testing of new systems are fully integrated.>

This paper concerns scheduling parallel programs in multiprocessing systems. The goal is to improve the job turnaround time and speedup. As most programs are not fully parallelizable, parallel programs consisting of serial, partially parallel, and (perfectly) parallel stages, are modeled by task graphs which depict the parallelism profiles. In another perspective, the study is intended to be a queueing counterpart of Amdahl's Law. Various two-stage cases are investigated with FCFS or priority scheduling policies and the optimal strategy is determined. Results indicate that, with nonhomogeneous parallelism profiles, it would be a better processor allocation policy to give a preferential treatment to serial stages. The study might hopefully improve the design of parallel operating systems as well as parallel algorithms, databases, and parallelizing compilers.

Addition of a second bus is proposed to provide high bandwidth as well as reliable service for token-passing-bus LANs. The second bus proposed is normally used for reservation so that the token on the data bus is dynamically passed to ready users for packet transmission. Furthermore, it takes the place of the data bus when the data bus fails. A reservation token-passing protocol is used which not only is collision-free but also minimizes the token-passing delay. An analysis of this dynamic token-passing protocol includes both analytical and simulation results.>

The authors analyze the performance of interconnected CSMA/CD (carrier-sense multiple-access with collision detection) LANs. The interconnection system consists of a packet-switch node which interconnects numerous sections of local area networks operated in unslotted nonpersistent CSMA/CD mode. Each of the CSMA/CD networks has a finite number of users. The authors assume that the sections of LANs interconnected are homogeneous and they all have the same number of users attached. A detailed modeling technique of the system using continuous-time Markov chain is explored. The state-transition-rate diagrams of each of the CSMA/CD networks are investigated. The system throughput and delay are also studied. Numerical calculation and simulation of both throughput and delay are provided.>