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Telecommunication Networks and Applications Conference (ATNAC), 2009 Australasian

Date 10-12 Nov. 2009

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Displaying Results 1 - 25 of 27
  • [Title page]

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  • [Copyright notice]

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  • Table of content

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  • An adaptive dual-antenna TD-SCDMA receiver blind algorithm based on MSNR

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (453 KB) |  | HTML iconHTML  

    In this paper, a dual-antenna receiver adaptive algorithm AMSNR in TD-SCDMA terminal is proposed. The dual-antenna receiver combines the received signal from different antennas with optimized weights according to the Maximum Signal-to-Noise Ratio (MSNR) criteria. Simulation results show that this algorithm can achieve better performance than conventional receiver with single antenna, and comparing to Space Time Joint Detection (ST-JD), the presented algorithm can decrease the computation complexity greatly. View full abstract»

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  • Iterative MIMO-OFDM detection under nonlinear channel distortions

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (437 KB) |  | HTML iconHTML  

    In this study, we investigate the practical effect of nonlinear channel distortion on Alamouti space-time coded MIMO-OFDM signals. In particular, we consider a slow fading environment under which the performance of an iterative nonlinear distortion cancellation algorithm is studied. Furthermore, an adaptive MIMO-OFDM system is also proposed in conjunction with iterative noise cancellation to combat the nonlinear channel distortion effects on MIMO-OFDM signals. View full abstract»

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  • QAM modulations over wavelet based OFDM channel for facial expression recognition

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1078 KB) |  | HTML iconHTML  

    Facial expression recognition (FER) has attracted significant interest in the scientific community due to its importance for human centred interfaces. This study compare the effect of different modulation for person-independent facial expression recognition from face images. The image is transmitted based on wavelet based OFDM channel. Then, the higher order local autocorrelation (HLAC) is used for feature extraction and the features are classified using the naive Bayesian (NB) classifier. Six different facial expressions are considered. Experiments carried out on Cohn-Kanade database shows comparable performance between different modulation in received images based on classification accuracy. BER performance is also included to observe when FER is applied to the wavelet based OFDM channel in two different QAM modulations, 4- and 16-QAMs. It is shown that the biorthogonal wavelet family of bior5.5 of 4-QAM outperforms db2 of 4-QAM. When the system uses 16-QAM, the BER result also shows that bior5.5 is better than db2. View full abstract»

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  • Performance evaluation of multiple-antenna DS-CDMA wireless communication systems with different diversity combining methods

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (477 KB) |  | HTML iconHTML  

    The effects of multipath fading and additive white Gaussian noise (AWGN) on the bit error rate (BER) performance of direct-sequence code-division multiple-access (DS-CDMA) systems is studied in this paper. The expression for the conditional BER, conditioned on a given level of fading is derived and then the unconditional BER is evaluated. The BER performance results of the system are evaluated in a fading channel for different magnitude of fading. The proposed approach is also extended to estimate the BER performance of the CDMA system having multiple receiving antennas. The effectiveness of the selection method and maximal ratio combining (MRC) method as diversity combining schemes are investigated and compared. To enhance the system performance channel coding is also applied to the system. View full abstract»

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  • Is broadband over power-lines dead?

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (941 KB) |  | HTML iconHTML  

    Recently there has been a significant amount of publicity about high levels of radiation from power lines using Broadband communications over Power Lines (BPL). Specific interference problems, or experimental measurements are typically cited. For smart grid, smart metering and advanced metering infrastructure applications, low data rate Power Line Communications (PLC) will be required. This paper describes a Matlab® program for calculating the radiation and resistive losses for power lines from BPL and PLC signals. Results are presented for Single Wire Earth Return (SWER) lines, for three phase overhead lines using typical conductors mounted on crossarms and for bundled aerial conductors. These results show that depending on the cable and signal frequency, BPL and PLC can be achieved without causing significant interference. View full abstract»

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  • Analysis of network connectivity: Wildlife and Sensor Network

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (531 KB) |  | HTML iconHTML  

    Connectivity Maintenance for mobile nodes is an important issue in Ad-hoc Wireless Sensor Network application like Wildlife Monitoring wherein data needs to be constantly captured and analysed to track and study animals. The random nature of the animal movement makes the task of tracking quite challenging. The work presented here attempts at addressing and analysing the issue of node connectivity as the network situation changes from dense to sparse and vice versa. Here we are looking at establishing Hand-Off to provide connectivity via next hop nodes and analyse its effect on the duration of connectivity. This is done by determining the transmitting radius of the nodes for maximum coverage, based on the maximum velocity of the animal carrying the node. To over-come the problem of network holes formed due to dynamically varying node densities in the network, we establish an adaptive and energy efficient sampling scheme. Preliminary modelling results reflects that the duration of connectivity hyperbolically reduces with reduction in the overlap of mobile and receiving node, and that the mobile node is able to quickly adapt itself by predicting the values for the next hop node with a small number of sample inputs. View full abstract»

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  • Staged request routing for reduced carbon footprints of large scale server systems

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (468 KB) |  | HTML iconHTML  

    The power consumption of server systems used as part of online services is an important problem as these have become major energy users. Generally, such systems are dimensioned for peak loads and typically have average utilisations of 20-30%. This paper introduces a simple routing mechanism that uses overflow techniques to assign requests to these servers. As these mechanisms employ a staged process, idle systems can be suspended. For a rising number of servers, this yields a load proportional power profile. Request distribution is implemented by a router device; servers report their utilisation to the router. Idle systems suspend their operation; suspended systems are returned to the active state by the Wake-on-LAN function. The system design, performance models and initial results are presented. View full abstract»

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  • Performance evaluation of next generation WiMedia UWB system

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1335 KB) |  | HTML iconHTML  

    WiMedia ultra-wideband (UWB) system has been given much attention because of its outstanding features including low cost, low power consumption, and high transmission capability. Its data rate up to 480 Mbps is enabled through dual carrier modulation (DCM) which uses two differently mapped 16 quadrature amplitude modulation (QAM) constellations to acquire frequency diversity. On the other hand, recently WiMedia UWB considered a new version of DCM to meet the increasing requirement for higher speed transmission. However, there are no related research articles in the literature. In this paper, we propose two constellation mapping rules for M-ary QAM based DCM (M-DCM) and evaluate their bit error rate (BER) performances in case of M = 256. Simulation results show the possibility and suitability of 256-DCM for the next generation WiMedia UWB system. View full abstract»

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  • The analytical method of Genetic Algorithm -Aided Iterative Joint Channel Estimation and Multi-User Detection

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (600 KB) |  | HTML iconHTML  

    This is a recent research on Space-Division-Multiple-Access-Orthogonal frequency Division Multiplexing (SDMA-OFDM) for channel estimation based on iterative joint channel estimation and a new Genetic Algorithm (GA). Assisted iterative joint channel estimation and Multi-User Detection (MUD) is the most recent approach for MTMO SDMA-OFDM systems and GA-aided MUD techniques for providing the best capacity of ¿soft¿ outputs of the Generic Algorithm. These are the key technology in wireless communication. The main focus of this research is based on the Uniform Cross-over technique used for mutating the symbol chromosomes to obtain an initial Frequency Domain-CHannel Transfer Function (FD-CHTF). Based on the analysis of the Genetic Algorithm -Aided Iterative Joint Channel Estimation and Multi-User Detection (GA-JCEMUD) on individual-based or population-based on soft output single application an increase in number of users is obtained couple with resolve in the Multi-User Interference through perturbation technique in the SDMA-OFDM system. Finally, a range of simulation results are provided to demonstrate the improvement of the performance. View full abstract»

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  • A new cooperative communication for orthogonal frequency and code division multiple access

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (498 KB) |  | HTML iconHTML  

    Orthogonal frequency and code division multiplexing (OFCDM) has been spotlighted as a next generation communication system. Cooperative OFCDM relaying system has advantages that provide the high reliability while maintaining high data rate because of getting the frequency diversity and the spatial diversity. However, this system decreases a throughput performance when it employs many relays. Therefore, in this letter, we present that the proposed system combines CDD due to complement throughput performance problem. In addition to that, the proposed system based on orthogonal frequency and code division multiple access (OFCDMA) which efficiently communicates each other through assigning the subcarrier and the channel code according to channel state or other environments. View full abstract»

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  • New transmission scheme with hierarchical modulation in dual-hop wireless relaying systems

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (610 KB) |  | HTML iconHTML  

    Dual-hop transmission is a technique by which the channel from the source to the destination is split into two possibly shorter links using other nodes. The source transmits signals to the destination via a group of nodes that act as relays. It is an effective technique when the direct link between the source and the destination is in deep fading, severe shadowing, or non-line-of-sight (NLOS) environment. In this network, the reliability of the communications is improved whereas the throughput might go down since the transmission is performed by two times. In this paper, we propose a scheme that uses hierarchical modulation at the source and selective modulation based on cyclic redundancy check (CRC) code at the relays. Simulation results show that our scheme outperforms conventional schemes in terms of the bit error rate (BER) and throughput performances. View full abstract»

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  • The effect of traffic distribution and transport protocol on WLAN performance

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (465 KB) |  | HTML iconHTML  

    Because the statistics of traffic load strongly impact on the queuing and blocking performance of a network, the choice of traffic distribution and transport protocol greatly influences WLAN performance. In this paper we examine the effect of traffic arrival distributions and transport protocols on WLAN performance. In particular, we analyze (by simulation) the effect of four diverse traffic models (Exponential, Pareto, Poisson, and CBR) on the performance of a typical IEEE 802.11 ad hoc network for TCP and UDP. Results obtained show that the network performance for Poisson is almost independent of traffic load for TCP and UDP but not for CBR. However, for both the Pareto and Exponential the network performance is almost independent of load for TCP, but is sensitive to UDP. The network achieves best and worst throughput performance for CBR and Poisson, respectively. Our findings reported in this paper provide some insight into the impact of the choice of traffic models and transport protocols on WLAN performance. View full abstract»

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  • Estimation by cross-correlation of the number of nodes in underwater networks

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (444 KB) |  | HTML iconHTML  

    Knowledge of the number of nodes in a network is very useful in practical network operations. To date techniques employed to estimate the number of nodes in a network have been based on some aspect of the communications protocol(s) in use. Unfortunately, underwater networks have properties such as long propagation delay, high absorption, and dispersion that limit protocol-based techniques for estimating the number of nodes in a network. This paper investigates the estimation of the number of signal sources (N) in a region of interest through the cross-correlation of the acoustic signals received at two nodes. It is shown that the N can be expressed as a function of the mean and the standard deviation of the cross-correlation function. On the assumption that the signal sources are nodes in an underwater network, this method can be used to estimate the number of network nodes. View full abstract»

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  • On network traffic concentration and updating interval for proactive recovery method against large-scale network failures

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (576 KB) |  | HTML iconHTML  

    Proactive recovery methods from network failures, based on multiple routing configurations, are effective for quick failure recovery, as compared with reactive recovery methods. However, there are two major problems, especially when we consider recovering from large-scale network failures: updating interval for recalculation of routing configurations against network growth, and network traffic concentration on specific nodes and links after recovering failures. In this paper, we first propose a light-weight and distributed algorithm for updating routing configurations when new nodes and links join the network, which does not need overall recalculation. We then evaluate the proactive recovery method for large-scale network failures, with proposed algorithm from the viewpoint of above two problems. Through numerical evaluation results, we find that to maintain the recovery performance, we should recalculate the routing configurations when the network grows by roughly 5-10%. We also present that the degree of network traffic concentration decreases when we employ a hop-by-hop selection mechanism of routing configuration. View full abstract»

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  • Cooperative hybrid cyclic delay diversity scheme in dual-hop wireless networks

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (620 KB) |  | HTML iconHTML  

    Cooperative communication has been widely investigated to improve performance of wireless networks. In cooperative wireless system, various MIMO scheme such as OSTBC, CDD and V-BLAST can be easily applied and obtain diversity or multiplexing gain. These schemes cannot obtain diversity and multiplexing gain simultaneously. To guarantee both high throughput and reliable transmission, hybrid STBC can be applied. However, this typical hybrid scheme requires complex structure at the destination and generates a rate loss according to increasing the number of transmit antennas. Moreover, in cooperative wireless system, hybrid STBC is inflexible to choose relays because relays require specific STBC encoder. Therefore, in this paper, we propose the cooperative hybrid CDD scheme which can be easily applied with arbitrary number of relays without any rate loss. Furthermore, a modification is not necessary at the destination although the number of relays is changed. View full abstract»

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  • Experiences with a Generation III virtual Honeynet

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1151 KB) |  | HTML iconHTML  

    This paper proposes a methodology for establishing a virtual Honeynet on a VMware Server running Honeywall CDROM Roo. The implementation is specific to a Linux based host having a single physical network interface card. Security of virtual Honeynets is always a concern, special techniques are discussed in the paper to ensure their security and to mitigate associated risks posed to the host and virtual machines. An effort has been made to ensure that all the software (both the OS and associated tools) used for the project are either free or Open Source. Special techniques were implemented in order to enhance the data capture mechanisms on the Linux-based Honeypot to efficiently generate reports. Risk evaluation and suggestions for improvements to the methodology are proposed. View full abstract»

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  • FWM impairment in multi-wavelength optical code-division multiplexing systems

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (576 KB) |  | HTML iconHTML  

    This paper comprehensively analyzes the impact of four wave mixing (FWM) on the performance of multiwavelength optical code-division multiplexing (MW-OCDM) systems. The impact of FWM on various aspects of MW-OCDM system performance, including bit error rate (BER), the number of users, and power penalty, is quantitatively discussed with several types of optical fibers such as single mode fiber (SMF), dispersion-shifted fiber (DSF), and non-zero DSF considering different frequency spacings. We find that the operational range of optical power is strictly limited under the impact of FMW. For example, it is about 6 dB in the case of spectral amplitude encoding OCDM systems using MQC code (132, 12, 1) and SMF. Also, the impact of FWM can be relieved so as to extend the operational power range by using two dimensional (2-D) codes (especially when different time-spreading patterns are used) or increasing the frequency spacing. View full abstract»

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  • A transport layer approach for improving interactive user experience on thin clients

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1105 KB) |  | HTML iconHTML  

    Return network traffic (from servers to clients) in thin-client systems is modeled as a mixture of interactive data flows corresponding to keystrokes and bulk data flows related to screen updates. Users are very sensitive to delay and jitter of the former flows. Thus our goal is to minimize the latency of interactive data transfer without increasing latency of bulk data transfer. Through simulation experiments, we determine that the main factors causing end-to-end delay in the interactive data transfer are queuing delay in the router and buffering delay in the server. When we apply two techniques: priority queuing of interactive data flows at the router and using TCP SACK option, the average end-to-end delay can be reduced. However, several servers could take more than a second to send large bulk data flows; this delays the transmission of following interactive data flows. We then develop TCP optimization mechanisms: modifying recalculation of the retransmission timeout value and temporarily turning off the TCP SACK control, and demonstrate that they can overcome the negative effects of the existing techniques. View full abstract»

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  • Multi-level virtual ring: a foundation network architecture to support peer-to-peer application in wireless sensor network

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (466 KB) |  | HTML iconHTML  

    Two main problems prevent the deployment of peer-to-peer application in a wireless sensor network: the index table, which should be distributed stored rather than uses a central server as the director; the unique node identifier, which cannot use the global addresses. This paper presents a multi-level virtual ring (MVR) structure to solve these two problems. The index table in MVR is distributed stored by using the DHT technique. MVR is constructed decentralized and runs on mobile nodes themselves, requiring no central server or interruption. Naming system in MVR uses natural names rather than global addresses to identify sensor nodes. The MVR can route directly on the name identifiers of the sensor nodes without being aware the location. Some sensor nodes are selected as the backbone nodes by the backbone selection algorithm and are placed on the different levels of the virtual rings. MVR hashes nodes' identifiers on the virtual ring, and stores them at the backbone nodes. Furthermore, MVR adopts cross-level routing to improve the routing efficiency. Experiments using ns2 simulator for up to 200 nodes show that the storage and bandwidth requirements of MVR grow slowly with the size of the network. Furthermore, MVR has demonstrated as self-administrating, fault-tolerant, and resilient under the different workloads. View full abstract»

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  • MF-TCP : Design and evaluation of TCP for message ferry delay tolerant networks

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (721 KB) |  | HTML iconHTML  

    In message ferry delay tolerant network, certain dedicated mobile nodes (message ferries) facilitate data transfer between disconnected regions of network. Message ferries travel around partitions of network, collecting data from nodes and delivering it to others. Due to high mobility of nodes and network partitioning, such a data transfer can be highly unreliable and it becomes really challenging to meet transport layer communication objectives. As we show, standard TCP performs poorly in such network because of frequent disconnections and longer propagation delays. In this paper, we present a variant of TCP (called MF-TCP) for message ferry delay tolerant networks which is designed to deal with high communication delays and significantly longer periods of disconnections. MF-TCP performs well even when intermediate nodes of TCP connections are highly mobile and round trip latency is unpredictable. Simulation results of MF-TCP show performance improvements over standard TCP in message ferry delay tolerant networks. View full abstract»

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  • Emulating radio network path losses with hardware hub

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (351 KB) |  | HTML iconHTML  

    This paper introduces a framework to emulate the path loss of radio network links in a laboratory environment. The emulator network comprises one or more multiport radio frequency (RF) hubs with variable attenuation on each port to be able to emulate the radio path loss between any two radios. The problem in this emulation approach is the determination of the appropriate port attenuation to match the multi-dimensional link losses (signal attenuations) and signal-to-interference ratios between multiple radios of a practical network. This has been structured as a constraint satisfaction problem (CSP) for both single-hub and multiple-hub emulations. We describe an algorithm based on Freuder's solution synthesis to find the solution to the CSP. Experimental results are also presented to validate the accuracy of emulation. View full abstract»

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  • Performance and scalability of M/M/c based queuing model of the SIP Proxy Server - a practical approach

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (628 KB) |  | HTML iconHTML  

    In recent years, Session Initiation Protocol (SIP) based Voice over IP (VoIP) based applications are alternative to the traditional Public Switched Telephone Networks (PSTN) because of its flexibility in the implementation of new features and services. The Session Initiation Protocol (SIP) is becoming a popular signaling protocol for Voice over IP (VoIP) based applications. The SIP Proxy server is a software application that provides call routing services by parsing and forwarding all the incoming SIP packets in an IP telephony network. The efficiency of this process can create large scale, highly reliable packet voice networks for service providers and enterprises. Since, SIP Proxy server performance can be characterized by its transaction states of each SIP session, we proposed the M/M/c performance model of the SIP Proxy Server and studied some of the key performance benchmarks such as server utilization, queue size and memory utilization. Provided the comparative results between the predicted results with the experimental results conducted in a lab environment. View full abstract»

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