The open nature of wireless communications renders unmanned aerial vehicle (UAV) communications vulnerable to impersonation attacks, under which malicious UAVs can impersonate authorized ones with stolen digital certificates. Traditional fingerprint-based UAV authentication approaches rely on a single modality of sensory data gathered from a single layer of the network model, resulting in unreliable authentication experiences, particularly when UAVs are mobile and in an openworld environment. To transcend these limitations, this paper proposes SecureLink, a UAV authentication system that is among the first to employ cross-layer information for enhancing the efficiency and reliability of UAV authentication. Instead of using single modalities, SecureLink fuses physical-layer radio frequency (RF) fingerprints and application-layer micro-electromechanical system (MEMS) fingerprints into reliable UAV identifiers via multimodal fusion. SecureLink first aligns fingerprints from channel state information measurements and telemetry data, such as feedback readings of onboard accelerometers, gyroscopes, and barometers. Then, an attention-based neural network is devised for in-depth feature fusion. Next, the fused features are trained by a multi-similarity loss and fed into a one-class support vector machine for open-world authentication. We extensively implement our SecureLink using three different types of UAVs and evaluate it in different environments. With only six additional data frames, SecureLink achieves a closed-world accuracy of 98.61% and an open-world accuracy of 97.54% with two impersonating UAVs, outperforming the existing approaches in authentication robustness and communication overheads. Finally, our datasets collected from these experiments are available on GitHub: https://github.com/PhyGroup/SecureLink_data.

This article investigates the uplink of a reconfigurable intelligent surface (RIS)-assisted wireless communication system. In this uplink, the RIS is powered by the energy harvested from ambient energy sources, and assists multiple users in uploading data to a multi-antenna base station (BS). A hybrid architecture is proposed for the RIS, so that each reflecting unit (RU) at the RIS is enabled to select its working mode among passive, active and deactivated modes. In this way, the RIS can schedule the energy in a fined-grained manner. Meanwhile, a new protocol is proposed to enable the RIS to schedule the harvested energy with a forward-looking approach. Under the hybrid RIS architecture and the newly proposed protocol, an optimisation problem is formulated to jointly optimise the working modes of RUs, the amplitude coefficient of active RUs, the receive beamforming at the BS, the power allocation at the users, with the goal to maximize the long-term system throughput by considering a minimum-rate-requirements constraint at each user and an energy scheduling constraint at the RIS. The formulated problem is an intractable dynamic and mixed-integer nonlinear programming. To solve this problem, a hierarchical deep reinforcement learning based framework is proposed. Simulation results show that, by using hybrid RISs, our self-powered wireless system can achieve up to 12 (5) times of the throughput than the throughput achieved by a self-powered wireless system with just active (passive) RISs and myopic energy scheduling.

In this article, we propose an event-triggeredH∞filtering algorithm based on hysteresis quantized measurements for accurate state estimation in networked mass-switching autonomous marine vehicles (AMVs). The proposed method addresses several critical challenges in networked AMV filtering, including limited communication bandwidth, constrained energy resources, and signal transmission delays. A dynamic model is first established to capture the parameter variations caused by mass changes in AMVs. To alleviate bandwidth limitations and reduce signal chattering, a hysteresis-based quantization scheme is introduced. Furthermore, an energy-efficient event-triggered mechanism is designed to be both energy-efficient and capable of preventing excessively long periods without triggering, thereby reducing the frequency of data transmission. To facilitate rigorous stability analysis, a novel augmented Lyapunov-Krasovskii functional is constructed, and Wirtinger-based inequalities are employed to handle the time-delay-dependent integral terms. Based on this, a co-design strategy is also developed to jointly solve both the filter and the event-triggering mechanism. Simulation results demonstrate that the proposed method achieves accurate state estimation for networked mass-switching AMVs while reducing the transmission rate by 75%, significantly outperforming conventional logarithmic quantizers in suppressing chattering.

The presence of a jammer in an Internet of Things (IoT) network severely degrades all communication efforts between adjacent wireless devices. The situation is getting worse due to retransmission attempts made by affected devices. Therefore, jammers must be detected or localized quickly to activate a series of corrective countermeasures so as to ensure the robust operation of the IoT network. This article proposes a novel metric called the number of jammed slots (NJSs). It can detect and localize both reactive and proactive jammers that follow arbitrary jamming attack patterns. NJS is applicable to all communication paradigms, such as unicast, broadcast, and multicast. In NJS, the wireless medium status is monitored by IoT devices and summarized reports are sent to a central node. Then, the central node determines the jamming duration, the affected nodes, and the approximate location of the jammer(s). Also, the specificity, precision, and accuracy of NJS are at least 48%, 19%, and 20% better than the other state-of-the-art statistical methods, respectively. In addition, in terms of the detection time, NJS is four times faster when detecting an active jammer in the network. It can also localize the jammer with less jammer localization errors.

Drone communications make use of line-of-sight coverage of drones to realise services that ground devices may not support. Many relevant applications such as video capture by drones and drone traffic management, require group communications between drones to efficiently disseminate data. In this paper, we study high-performance yet resource-efficient multicasting between drones that may change their locations in order to fulfill their missions. This is achieved by proposing novel trajectories for mobile drones to seamlessly transit, with controlled travel distances and traffic overheads, in a multicasting environment. The presented efficient transition via trajectory adjustment (ETTA) algorithm is developed based on our analysis of the condition that determines when a straight-line trajectory between the origin and destination of a drone is not seamless. The algorithm then proposes the trajectory adjustment schemes that form a new interference-controlled and travel-distance-controlled trajectory to replace an interrupted straight-line trajectory. Our NS2 simulation results demonstrate that ETTA, as compared to other mobile multicasts, can achieve guaranteed performance in a multicast with heavier traffic loads.

An active jammer could severely degrade the communication quality for wireless networks. Since all wireless nodes openly access the shared media, the harsh effects are exaggerated by retransmission attempts of affected devices. Fast and precise detection of the jammer is of vital importance for heterogeneous wireless environments such as the Internet of things (IoT). It could activate a series of corrective countermeasures to ensure the robust operation of the network. In this paper, we propose a local, straightforward, and numerical metric called the number of jammed slots (NJS), by which we can quickly detect the presence of a jammer and identify the jammed nodes at the software level in broadcast networks. NJS calculation is carried out by a central node which collects the MAC-layer statuses of all wireless nodes in a periodical fashion. Our simulation results indicate that NJS outperforms current detection methods in terms of accuracy and precision.

The trustworthiness of vehicle messages is a major focus in intelligent transportation research. Existing studies focus on enhancing the accuracy of vehicle trustworthiness evaluation, overlooking that the transmission performance may affect the quality of vehicle messages, which are essential for implementing trustworthiness evaluation. This paper studies a novel vehicle message scheduling scheme to regulate vehicles’ transmissions so that incident messages for any part of the road can be reliably and accurately sent to a roadside unit. Through strategically scheduling vehicle transmissions to avoid interference between vehicles while guaranteeing sufficient numbers of vehicles transmitting their sensor data, vehicle messages can reliably yet timely arrive at Road Side Units (RSUs) without missing reporting an event on the road.

Wireless mesh networks (WMNs) connect to the Internet via access gateways. This paper studies multi-source video multicast in Internet-connected WMNs. The focus is on the design of a shareable integrated multicast that allows the multicasts of video sources to employ common Internet shortcuts or WMN paths to avoid potentially high WMN overheads and excessive Internet usage. Several algorithms are described that together form a video multicast framework running a controlled number of shareable multicasts under the constraint of Internet availability. These algorithms are the resource-efficient source group algorithm, the efficient integrated architecture algorithm, and the interference-controlled multicasting tree algorithm. These algorithms represent different approaches to overcoming various costs arising from multi-source video multicast, enabling multiple video sources to distribute delay, and throughput-guaranteed videos to receivers across large-scale areas. Simulation results are presented that quantify the performance gains that can be achieved.

Employing energy harvesting (EH) at a relay node with simultaneous wireless information and energy transfer (SWIET) is promising to prolong the lifetime of energy-constrained relay systems. In this paper, we investigate the optimal resource allocation in an orthogonal-frequency-division multiplexing (OFDM) decode-and-forward (DF) relay system that implements SWIET at the source-to-relay link in order to maximize the end-to-end achievable rate. We first propose an optimal energy-transfer power allocation (EPA) policy which can utilize the frequency diversity provided by OFDM modulation. We then validate that the ordered-SNR subcarrier pairing is globally optimum. To optimize EH time and information-transmission power allocation (IPA), we formulate the involved problem as a non-convex programming problem, and then transform it into a quasi-convex optimization problem. By solving this quasi-convex optimization problem with the bisection search method, we propose an algorithm which can jointly optimize the EH time and IPA. By analytical analysis, we validate that our proposed resource allocation scheme has much lower computational complexity than the peer studies in the literature. Finally, our simulations demonstrate the optimality of our proposed resource allocation scheme.

Devices in wireless mesh networks can operate on multiple channels and automatically adjust their transmission rates for the occupied channels. This paper shows how to improve performance-guaranteed multicasting transmission coverage for wireless multi-hop mesh networks by exploring the transmission opportunity offered by multiple rates (MR) and multiple channels (MC). We investigate the characteristics and behavior of transmissions with different rates in wireless multi-hop mesh networks. We then propose parallel low-rate transmissions and alternative rate transmissions to explore the advantages of MRMC under the constraint of limited channel resources. A novel link-controlled multi-rate multi-channel multicast algorithm is also designed to extend wireless multicast coverage with high throughput. Our NS2 simulation results demonstrate the improved multicast quality of LC-MRMC in much larger wireless areas as compared to current studies.

One of the main challenges towards reliable multicast transmissions over wireless networks is the dynamics of the wireless links (e.g. wireless errors, fading, interference, collisions, etc.) that can cause retransmissions overhead over the limited available bandwidth. To this end this paper considers the scenario of wireless multicast networks where network coding is applied to improve network throughput. We first propose a novel cross-layer optimisation framework for network topology design in order to optimise the wireless multicast rate, data flow of the wireless links, energy supply and node lifetime. The performance of the proposed solution is evaluated and compared against other solutions from the literature in terms of system throughput, total energy, and network lifetime. The results show that the proposed cross-layer design outperforms the other schemes involved, reaching up to 50% increase in the system throughput.

This paper considers relay positioning in wireless butterfly networks consisting of two source nodes, a relay node and two destination nodes. The relay-assisted data transmission from two source nodes to two destination nodes is carried out based on either physical-layer network coding (PLNC) or analog network coding (ANC) techniques. The reliability of communications in wireless network-coded butterfly networks (WNCBNs) is assured by applying hybrid automatic repeat request protocol with incremental redundancy (HARQ-IR). In this paper, we first evaluate the total energy consumption (EC) of both PLNC and ANC schemes in WNCBNs. Based on the derived EC, we develop algorithms that optimize the location of the relay node for PLNC and ANC schemes in order to minimize the total EC for a green communication system subject to node location and power allocation constraints. Finally, simulation results are provided which identify the optimized relay locations for various scenarios of node location and power allocation in the WNCBN.

Wireless transmission resources are limited for high performance wireless multimedia applications. This paper theoretically studies a new capacity aggregation policy in both single-hop and multi-hop wireless networks with the motivation of ameliorating the trade-off between limited channel resources and multiple flow transmission. The capacity aggregation policy aggregates residual channel capacity that remains unused by the previous flow scheduling policy in order to future increase the number of performance guaranteed multimedia flows. We then proposed a novel efficient multi-flow multicasting algorithm to apply the policies of flow scheduling and capacity aggregation to practical multimedia multicasting so as to quickly and reliably admit extra multicasting traffic in a wireless network. Finally, we use NS2 simulations to evaluate the studied policy and the EMMT algorithm. Our simulation results prove the effectiveness of our schemes in improving the ability of networks to admit more multimedia flows.

Wireless multimedia applications are major services of next generation wireless networks. This paper is one of the first to study the efficient utilization of network resources for increasing the number of concurrent multimedia flows when a channel becomes saturated. We theoretically study the flow scheduling policy with the motivation of ameliorating the trade-off between limited channel resources and multiple flow transmission. Based on the dynamic states of wireless channels and the profile of multimedia flows, the policy fully utilizes the performance gap for increasing the number of performance guaranteed multimedia flows, by scheduling multiple flows in turn without interference. We then study the policy by NS2 simulations, which prove the effectiveness of the flow scheduling policy in increasing the number of concurrent multimedia flows in both single-hop and multi-hop wireless networks.

Wireless multimedia services are major applications of next generation wireless networks. This paper is one of the first to study the efficient utilization of network resources for increasing the number of concurrent multimedia flows when a channel becomes saturated. We theoretically study the flow scheduling policy and the channel aggregation policy in both single-hop and multi-hop wireless networks with the motivation of ameliorating the trade-off between limited channel resources and multiple flow transmission. To increase the number of performance guaranteed multimedia flows, based on the dynamic states of wireless channels and the profiles of multimedia flows, the two policies fully utilize the performance gap to schedule concurrent flows for transmission in turn and aggregate multiple channels' residual capacities for useful flow transmissions. We then design a novel algorithm - efficient multi-flow multicast transmission (EMMT) - to apply the proposed policies to practical wireless multimedia multicast applications. At last, we use ns2 simulations to evaluate the studied policies and the EMMT algorithm. Our simulation results prove the effectiveness of our schemes in improving network ability to admit more multimedia flows.

This paper studies video multicasting in large-scale areas using wireless mesh networks. The focus is on the use of Internet access gateways that allow a choice of alternative routes to avoid potentially lengthy and low-capacity multihop wireless paths. A set of heuristic-based algorithms is described that together aim to maximize reliable network capacity: the two-tier integrated architecture algorithm, the weighted gateway uploading algorithm, the link-controlled routing tree algorithm, and the dynamic group management algorithm. These algorithms use different approaches to arrange nodes involved in video multicasting into a clustered and two-tier integrated architecture in which network protocols can make use of multiple gateways to improve system throughput. Simulation results are presented, showing that our multicasting algorithms can achieve up to 40 percent more throughput than other related published approaches.

Without requiring multicast support from the underlying networks, overlay multicast has the advantage of implementing inter-domain multimedia multicast communications. Usually, overlay multicast protocols employ two different topologies: r-ary tree and m-D mesh. In this paper, we study the influence of topology selection on multimedia multicast performance. We present a set of theoretical results on the worst performance, the average performance, and the performance difference along the link stress, the number of overlay hops, and the number of shortest paths for r-ary tree-based and m-d mesh-based multicast, respectively. Furthermore, through simulations in NS2, we observe and compare tree and mesh topologies along the metrics analyzed theoretically. Simulation results match our theoretical analyses. Finally we give our evaluations of and insights into these two kinds of multicast when used to transmit multimedia streams. The selection of overlay topology is application dependent. To the best of our knowledge, this is the first evaluation of multimedia multicast performances in different overlay topologies. We believe that this study is useful for protocol design of target multimedia applications and for investigating multicast functions.

Underlay topology information is important to construct efficient overlay networks. To achieve end-to-end network topology inference among a group of hosts, traceroute-like tools are often used. Previously, Max-Delta has been proposed to infer a highly accurate topology with a low number of traceroutes. However, Max-Delta relies on external tools to estimate host coordinates, which incur considerable deployment overhead. In this paper, we consider novel inference schemes with no coordinate estimation. One choice is to select long paths to traceroute. That is, based on existing traceroute results, each host can estimate the distance between another host and itself. It can then select the host with the largest distance between them as the traceroute target. We call this scheme Longest-Path-First (LPF). Similarly, we can define Shortest-Path-First (SPF) inference. The intuition may indicate that LPF performs better than SPF, as longer paths often contain more underlay links and routers, and hence more undiscovered links or routers. However, our simulation results on Internet-like topologies show that SPF can achieve comparable performance with Max-Delta, while LPF performs even worse than a random inference scheme. To explain the results, we analyze the statistics of all-pairs paths between hosts. Our results show that long paths have serious overlaps on underlay links, showing much higher path stress than short paths. We also find that there exist quite a few links only appearing in short paths and seldom appearing in long paths. Therefore, with the same number of traceroutes, SPF can discover more underlay links and routers than LPF. Furthermore, as SPF prefers short paths, a traceroute in SPF sends less probing packets and consumes less network resource than that in LPF. Therefore, SPF is a highly efficient inference scheme with low deployment overhead and low measurement overhead.

In our previous work, we have analyzed the worst performance for tree-based and mesh-based multicast along the link stress, the number of overlay hops, and the number of shortest paths. In this paper, we extend our research through studying the average performance and the difference between the worst and the average performance for these metrics. We present a set of theoretical results that evaluate the average performance and the performance difference for tree-based multicast and mesh-based multicast in quantity. And also, we program NICE tree and CAN-based multicast in NS2 to evaluate our theoretical prediction and compare tree-based and mesh-based multicast. Simulation results prove our theoretical analysis. We find that tree-based multicast suits to not only real-time but also interactive streaming media applications, and mesh-based multicast holds the promise for the bottleneck-avoidance and reliable transmission in multi-source non-real-time applications.

This paper studies video multicasting in large scale areas using wireless mesh networks. The focus is on the use of Internet access gateways that allow a choice of alternative routes to avoid potentially lengthy multi-hop wireless paths with low capacity. A set of heuristic-based algorithms are described that together aim to maximize network capacity: the two-tier integrated architecture algorithm, the weighted gateway uploading algorithm, the link-controlled routing tree algorithm, and the alternative channel assignment algorithm. These algorithms use different approaches to arrange multicast group members into a clustered and two-tier integrated architecture in which network protocols can make use of multiple gateways to improve system throughput. Simulation results are used to determine the performance of the different approaches.

Wireless mesh networks hold great promise in the wireless transmission of video flows, particularly if the problem of providing sufficient network capacity can be addressed. For this reason, schemes which help to address this difficulty in capacity-limited wireless networks are of great interest. This paper presents a novel and simple algorithm, adaptive split transmission algorithm, for achieving real-time, and quality-guaranteed video transmission in wireless mesh networks. The algorithm utilizes the unused capacities of multiple channels rather than trying to transmit the flow over just one overloaded channel. The flow is efficiently split into several sub-flows in a capacity-aware manner, each sub-flow then being transmitted through different channels in parallel. The adaptive split transmission algorithm controls flows dynamically in response to changes in the states of the available channels, thereby avoiding the overloading of any one channel. We evaluate the algorithm through simulations. The results show that the adaptive split transmission algorithm achieves synchronized, quality-guaranteed, and real-time wireless video transmission. The proposed algorithm can be used for interactive real-time wireless video applications without changing current wireless hardware, MAC protocols and upper-layer protocols.

We consider using tools like traceroute to infer the underlay topology among a group of hosts. Traditional Max-Delta inference relies on a central server and is not scalable. In this paper, we investigate a distributed inference scheme to support scalable inference. In our scheme, each host joins an overlay tree before conducting traceroute. A host then independently selects paths to traceroute and exchanges traceroute results with others through the overlay tree. As a result, each host can maintain a partially discovered topology. Furthermore, we propose several techniques to reduce the measurement cost, including (a) integrating the Doubletree algorithm to reduce measurement redundancy; (b) setting up a lookup table for routers to reduce traceroute size, and (c) conducting topology abstraction and reducing the computing frequency to reduce computational overhead. In our scheme, the computation loads for target selection are distributed to all the hosts instead of a single server, and the consumption of edge bandwidth at a host is hence limited. We have done simulations on Internet-like topologies and conducted measurements on PlanetLab. The results show that the constructed tree has a low diameter. Furthermore, the proposed improvements can efficiently reduce measurement redundancy, computational overhead and bandwidth consumption.

Without the multicast support from the underlying networks, overlay multicast has the advantage of implementing inter-domain multicast communications. Usually, overlay multicast protocols employ two different topologies: tree and m-D mesh. We propose to study the influence of topology selection to the multicast performances in this paper. We present a set of theoretic results on the metrics of the worst link stress, the worst number of overlay hops and the number of shortest paths for tree-based and M-D mesh-based multicast respectively. Then, we give our observations to these two kinds of multicast. To the best of our knowledge, we are the first to evaluate multicast performances on different overlay topologies. We hope that our results are useful for the new multicast protocol design. We hope that our results are useful for the design of new overlay multicast protocols.

Peer-to-peer networks have long being used for file sharing among the connected peers. Recently, the popular BitTorrent tool has permitted the exchange of large sized files by dividing it into fragments, and enabling the peers to exchange the fragments amongst themselves through an overlay network. Each file requires the establishment of a separate overlay among the peers. In this paper, we explore the use of proximity both in the construction of the overlay network, and the efficient exchange of the file fragments, mainly aimed at reducing the download time for the peers and reducing resource usage (esp. link bandwidth) in the underlying network. We give some analytical and simulation results to show the improvement that can be achieved using proximity.

Abstract The Knowledge Grid built on top of the peer‐to‐peer (P2P) network has been studied to implement scalable, available and sematic‐based querying. In order to improve the efficiency and scalability of querying, this paper studies the problem of multicasting queries in the Knowledge Grid. An m‐dimensional irregular mesh is a popular overlay topology of P2P networks. We present a set of novel distributed algorithms on top of an m‐dimensional irregular mesh overlay for the short delay and low network resource consumption end‐host multicast services. Our end‐host multicast fully utilizes the advantages of an m‐dimensional mesh to construct a two‐layer architecture. Compared to previous approaches, the novelty and contribution here are: (1) cluster formation that partitions the group members into clusters in the lower layer where cluster consists of a small number of members; (2) cluster core selection that searches a core with the minimum sum of overlay hops to all other cluster members for each cluster; (3) weighted shortest path tree construction that guarantees the minimum number of shortest paths to be occupied by the multicast traffic; (4) distributed multicast routing that directs the multicast messages to be efficiently distributed along the two‐layer multicast architecture in parallel, without a global control; the routing scheme enables the packets to be transmitted to the remote end hosts within short delays through some common shortest paths; and (5) multicast path maintenance that restores the normal communication once the membership alteration appears. Simulation results show that our end‐host multicast can distributively achieve a shorter delay and lower network resource consumption multicast services as compared with some well‐known end‐host multicast systems. Copyright © 2006 John Wiley & Sons, Ltd.

This paper proposes a novel and simple adaptive control algorithm for the effective delay control and resource utilization of end host multicast (EMcast) when the traffic load becomes heavy in a multigroup network with real-time flows constrained by (sigma, rho) regulators. The control algorithm is implemented at the overlay networks and provides more regulations through a novel (sigma, rho, lambda) regulator at each group end host who suffers from heavy input traffic. To our knowledge, it is the first work to incorporate traffic regulators into the end host multicast to control heavy traffic output. Our further contributions include a theoretical analysis and a set of results. We prove the existence and calculate the value of the rate threshold rho* such that for a given set of K groups, when the average rate of traffic entering the group end hosts rho macr > rho*, the ratio of the worst-case multicast delay bound of the proposed (sigma, rho, lambda) regulator over the traditional (sigma, rho) regulator is O(1/Kn) for any integer n. We also prove the efficiency of the novel algorithm and regulator in decreasing worst-case delays by conducting computer simulations.

This paper proposes a novel and simple adaptive control algorithm for the effective delay control and resource utilization of EMcast when the traffic load becomes heavy in the multi-group network with real-time flows constrained by the (sigma,rho) regulators. The control algorithm is implemented at the overlay networks, and provides more regulations through a novel (sigma,rho,lambda) regulator at each group end host who suffers from heavy input traffic. To our knowledge, it is the first work to incorporate the traffic regulator into the end host multicast to control the heavy traffic output. Our further contributions include a set of theoretical analysis and results. We prove the existence and calculate the value of rate threshold rho* such that for a given set of K groups, when the average rate of traffic entering the group end hosts rholowbar > rho*, the ratio of worst-case multicast delay bound of (sigma,rho,lambda) regulator over traditional (sigma,rho) regulator is O(1/Kn) for any integer n. We also use the computer simulations to evaluate our novel algorithm and regulator that have been proved efficient in decreasing the worst-case delays

This paper presents a novel end host multicast protocol (DSM) on top of the mesh overlays for P2P networks. Unlike the previous schemes, the major feature ofDSM is that it does not need a multicast tree for routing the multicast messages. DSM can implement the scalable and efFcient multicast communications in a fully distributed way and consists of the following algorithms: I . cluster formation that forms the group into clusters and each cluster consists of a small number of members; 2. cluster core selection that selects a core for each cluster who has the minimum sum of overlay hops to all other cluster members; 3. multicast routing that includes the balanced RA routing approach which enables a cluster core to construct the connections with other cores dynamically by using the rectangle area and the balanced forwardjlooding scheme in each cluster which evenly distributes the data traf- Jic and link stress among the links in the multicast system. Simulation results show that DSM is fully distributed, scalable and efjicient as compared with some well-known end host multicast system.

We study a scalable and efficient end host multicast-DSCT (dynamic shared cluster tree) for P2P systems in this paper. In our design, we focus on making full use of underlying physical properties to improve both scalability and efficiency as data multicast in the overlay topologies of P2P systems. In this paper, we present the DSCT architecture, the dynamic scheme to select cluster cores according to the instantaneous network situations. These are all the key points to construct the basic DSCT (BDSCT) multicast. Through further studies, we provide DSCT improvement design (IDSCT) to make it more suitable for multiple-source P2P communications. Our simulation results indicate that it is possible to improve the scalability and efficiency of end host multicast in P2P systems by using our DSCT designs.

Anycasting has recently become an important research topic, especially for replicated servers. With anycasting, applications can request the "nearest" server for provision of desired (multimedia) service. In this paper, we study efficient distributed admission control (DAC) for anycast flows. We focus on algorithms that perform destination selection and efficient path establishment. Taking advantage of anycasting, our distributed algorithms differ from each other in their dependence on system status information. Performance data obtained through mathematical analysis and simulations show that, in terms of admission probabilities, DAC systems that are based on local status information have performance levels close to those that utilize global and dynamic status information. This renders our DAC algorithms useful not only for the network layer, but also for the application layer admission control for anycast flows.

Define anycast services as a group of replicated servers that may provide similar or identical services. Using anycast services can significantly simplify some applications such as to seek appropriate servers to provide quality of service and to achieve the load balance and fault-tolerance for service availability. An anycast flow is a sequence of packet that can be established between a user and any server in an anycast (replicated) service group. We study a set of efficient distributed connection setup algorithms for real-time anycast flows. Given an anycast flow between a server j and a request node s with end-to-end deadline D/sub s,j/ and minimum bandwidth requirement B/sub s,j/, our algorithms can effectively seek multiple destination connections in parallel thus the best path which satisfies the requirements of the anycast flow is chosen. The deterministic approach for worst delay bound analysis is also given.