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The performance of non-preemptive M/M/l queuing system with two priority is newly proposed. Though this kind of queuing system is researched by many scholars, the performance indexes are often approximate. The complementary variable method is also used to make vector Markov process and analyze the state-change equations of the queuing system. With Rouche theorem to analyze the coefficient of the generating...
Consider a group of peers, an ideal random peer sampling service should return a peer, which is an unbiased independent random sample of the group. This paper focuses on peer sampling service based on view shuffling (aka gossip-based peer sampling), where each peer is equipped with a local view of size c. This view should correspond to a uniform random sample of size c of the whole system in order...
Awerbuch and Scheideler have shown that peer-to-peer overlays networks can survive Byzantine attacks only if malicious nodes are not able to predict what will be the topology of the network for a given sequence of join and leave operations. In this paper we investigate adversarial strategies by following specific protocols. Our analysis demonstrates first that an adversary can very quickly subvert...
In this paper we study the overhead introduced by secure functions in considering two models of non-repudiation protocols. The models are specified using the Markovian process algebra PEPA. The basic model suffers from the well known state space explosion problem when tackled using Markov chain analysis. Following previous study of performance modelling on security protocols, mean value analysis and...
The popularity of P2P networks makes them an attractive target for hackers. Potential vulnerabilities in the software used in P2P networking represent a big threat for users and the whole community. To prevent and mitigate the risks, intrusion detection techniques have been traditionally applied. In this work in progress, a Markov based technique is applied to the detection of anomalies in the usage...
A key challenge of message forwarding in delay tolerant networks (DTNs) is to increase delivery rate and decrease delay and cost. When information for future connectivity is not available, opportunistic routing is preferred in DTNs in which messages are forwarded opportunistic (non-deterministically) to nodes with higher delivery probabilities. Many real objects have non-deterministic but cyclic motions;...
We provide a simple physical interpretation, in the context of the second law of thermodynamics, to the information inequality (a.k.a. the Gibbs' inequality, which is also equivalent to the log-sum inequality), asserting that the relative entropy between two probability distributions cannot be negative. Since this inequality stands at the basis of the data processing theorem (DPT), and the DPT in...
Every health care system employs a set of protocols to manage and reduce the impact of infectious disease whenever it appears within the population. Although a great deal of research has been conducted to determine when an outbreak is occurring, research pertaining to whether the response policies are effective is not easily located. Much of the difficulty lies in selecting an appropriate modelling...
Based on the standardized IEEE 802.11 Distributed Coordination Function (DCF) protocol, this paper proposes a new backoff algorithm, called Smart Exponential-Threshold-Linear (SETL) Backoff Algorithm to enhance the system performance of contention-based wireless networks. As we know, the smaller contention window (CW) will increase the collision probability, but the larger CW will delay the transmission...
Generative models are created to be used in the design and performance assessment of high layer wireless communication protocols and some error control strategies. Generative models can replace real digital wireless channels to significantly reduce the time and complexity of system simulation. The errors occurring in digital wireless channels are not independent but form clusters or bursts. Generative...
IEEE 802.11 wireless network supports multiple link rates at the physical layer. Each link rate is associated with a certain required Signal-to-Interference-and-Noise Ratio (SINR) threshold for successfully decoding received packets. Suppose constant noise and no power adjustment strategy exists, apparently SINR is solely affected by the accumulated interference power level 1. The method of selecting...
Accurate modelling of primary system activity is key to reliable performance evaluation of dynamic spectrum access (DSA) technologies. Measurements on spectrum use show that in some cases the lengths of the vacant periods in a given frequency band can be correlated, a feature commonly used semi-Markov ON/OFF-models cannot reproduce. In this paper we study the stochastic properties of a simple primary...
This paper addresses the design and performance evaluation of relay strategies for opportunistic Delay Tolerant Networks (DTNs) augmented with throwboxes. By opportunistic we mean that a node does not have any knowledge regarding its past and future contact opportunities with the other nodes. We consider a network model composed of both mobile relay nodes and throwboxes, where throwboxes are stationary...
In wireless LANs, throughput is one of, if not the most, important performance metric. This metric becomes more critical at the bottleneck area of the network, which is normally the area around the access point (AP). In this paper, we propose SI-CCMAC, a sender initiating concurrent cooperative MAC for wireless LANs. It is designed to improve the throughput performance in the region near the AP through...
In the multi-agent systems, the resources for the task and the ability of each single agent may be limited. An agent cannot do the whole task by itself, it need the help of other agents. So, the task needs to be decomposed into several subtasks. Some of the subtasks will be carried out locally by the original agent, while others need to be done non-locally with other agents. So, during the negotiation...
Recent studies have been conducted to indicate the ineffective usage of licensed bands due to the static spectrum allocation. In order to improve the spectrum utilization, the cognitive radio (CR) is therefore suggested to dynamically exploit the opportunistic primary frequency spectrums. How to provide efficient spectrum handoff has been considered a crucial issue in the CR networks. Existing spectrum...
We consider the problem of communication for a network composed of two half-duplex relays. A Successive relaying protocol in which the relays transmit their received messages successively to the destination is studied. A non-cooperative coding based on dirty paper coding (DPC) and a cooperative coding based on block Markov encoding (BME) are proposed and the optimum input distribution for the degraded...
A single queue incorporating a retransmission protocol is investigated, assuming that the sequence of per effort success probabilities in the Automatic Retransmission reQuest (ARQ) chain is a priori defined and no channel state information at the transmitter is available. A Markov Decision Problem with an average cost criterion is formulated where the possible actions are to either continue the retransmission...
Congestion control in packet-based networks is often realized by feedback protocols. In this paper we assess their performance under a back-pressure mechanism that has been proposed and standardized for Ethernet metropolitan networks. In such a mechanism the service rate of an upstream queue is reduced when the downstream queue is congested, in order to protect the downstream queue. We study a Markovian...
In all-IP wireless networks, groups of cells are served by IP access gateways. When users move between regions served by different gateways, IP and application layer mobility signaling is triggered. The key performance indicator to assess a given mobility protocol is the mean number of gateway handoffs. In this paper, we propose a new fundamental approach, which majorly extends past work in cellular...
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