Large-scale ad hoc sensor networks (ASN), when deployed among mobile patients, can provide a dynamic data query architecture to allow the medical specialists to monitor patients at any place. We propose a low-energy, distributed, concentric-zone-based data query mechanism that has the advantages of both proactive and reactive ad hoc routing algorithms to collect medical results from large-scale mobile patients for medical specialists. In order to secure that tree-zone-based ASN, we suggest the using of key-chain to predistribute keys in each sensor. Then we further secure data fusion based on our telemedicine hierarchical architecture. We also propose a scalable global session-key generation mechanism in our tree-zone-based sensor networks.

Initiatives to add mobility to the Internet and packet data services in third-generation (3G) cellular systems are being considered as candidate solutions for the delivery or IP data to mobile users. The Transport Control Protocol (TCP) will continue to be the most widely used transport protocol for a certain duration in 3G cellular Internet networks. Initially designed for high-speed wireline networks where random packet loss can be negligible, TCP can yield a significant throughput deterioration when applied to lossy links without modification since the primary cause of packet loss may not be network congestion. Two new types of loss can dominate TCP's performance: one is dropped packets because of route disconnection from frequent handoffs; the other is relatively high bit error rate (BER) of radio propagation channels due to multipath fading. Unlike much or the early TCP studies that largely relied on simulations, this paper presents a comprehensive analysis by modeling typical TCP congestion control algorithms. We adopt finite-state Markov channel (FSMC) model as the basis of link error definition since in typical cases it is not adequate to model a radio communication channel as a two-state Gilbert-Elliott channel when the channel quality varies dramatically. To enhance TCP performance in cellular networks, we adopt the idea of active-mobile-host to constrain the negative effect of handoff on TCP throughput in a minimized range. The accuracy of our analytical model is verified through the comparison with measurements using UCB/LBNL Network Simulator (ns-2).

We present an analytical model for a multicast-pushout write policy. The pushout scheme maintains a high switch throughput by providing an optimum balance of unicast and multicast cells in the buffer. The scheme is adaptive to changes in multicast traffic such as changing fanout sizes and input rates. We demonstrate that the model is accurate for various loads, ratios of multicast traffic and fanout sizes.

A new multi-class call admission control mechanism is proposed which is based on dynamically forming a reservation pool for handoff requests. We first develop the notion of servicing various multi-class connections based on priority determined using the combined analysis of mobile movement information and the desired QoS requirements of multimedia traffic. We also provide a practical framework for determining the occurrence time of handoff request reservations. The simulation results show that the individual QoS criteria of multi-class traffic such as the handoff call dropping probability can be achieved within a targeted objective and the new call blocking probability is constrained to be below a given level.

The low cell loss rates required from ATM switches can be achieved with shared-memory based switches using large buffers. In this paper we present a fluid flow model for replicata-at-send distinct address queue multicasting in a shared-memory switch. Due to its buffer independence the model can calculate the performance of large buffered switches. The proposed model significantly reduces computational times and produces results that closely approximate simulation. In some cases the model can produce results which are difficult to obtain via simulation, without resorting to special techniques such as importance sampling.

Replicate-at-send multicasting has the best performance of the multicasting schemes for shared-memory ATM switches. Specifically replicate-at-send-distinct address queue multicasting is the most adopted implementation because of its low hardware requirements. We present an analytical model for shared-memory switches with replicate-at-send-distinct address queue multicasting. Under various input traffic conditions the analytical model is shown to be accurate when compared to simulation results. We demonstrate that the model is accurate for a range of loads, with different ratios of multicast traffic and for a range of fanout sizes.

The importance of multicasting at the switch level is increasing with the number of applications that are demanding multicast services. We extend a fluid-flow model for unicast only shared-memory switches to include replicate-at-receive multicasting. The advantage of fluid-flow models is that they are buffer independent. This overcomes the state explosion problem experienced with Markov chain models when using large sized buffers. Our proposed model reduces the complexity of the switch so that the problem only requires the analysis of a single output queue. Under various input traffic conditions the performance of the model is compared against results obtained via simulation. With shorter computational time the proposed model produces results comparable to those from simulation.

Switching networks based on enhanced schemes of the banyan network have emerged as the transport technique for broadband integrated services digital networks (B-ISDN). Several of these incorporate multiple banyan planes. This paper examines the reliability, mean time-to-failure and availability of such a network. The network under study consists of K planes with links provided at every stage thereby allowing it to offer fault-tolerance at every stage of the network and overcoming the single-path limitation of banyan networks. A reliability model is derived using hierarchical composition. Numerical results show the effect of multiple planes on the network's reliability for various network sizes.

As the fault tolerance capability in multistage interconnection network based ATM switches is an important design consideration, many switches provide multiple paths between input and output ports. This may result in an increase of the bandwidth of the network. When the switch has no faults or few faults, the increase in bandwidth of the network can be utilized to improve the throughput of the network. We show that under no faults and for a given offered load, the throughput of the network can be improved significantly by using recirculation in a fault tolerant multistage interconnection network (MIN) based switch. Furthermore, we show using simulations that under very bursty traffic (mean burst length of 10), recirculation with fewer links provide better performance in terms of throughput and delay at a lower cost.

Shared memory ATM switches are known to provide optimal throughput-delay performance under unicast traffic. A performance evaluation by computer simulation of a generic shared memory ATM switch is done to study the effect of using thresholds for buffer space management under bursty multicast traffic. The threshold scheme assigns a different priority to unicast and multicast cells depending on whether the memory occupancy is above or below the threshold. The simulations show that the use of proposed threshold scheme results in a better throughput and cell loss rate performance under any traffic load. Cell delay is also lower for output loads under 100%.