Abstract: This paper describes a feasibility study that is
included with the research, development and testing of a micro
communications sonobuoy deployable by Maritime Fixed wing
Unmanned Aerial Vehicles (M-UAV) and rotor wing Quad Copters
which are both currently being developed by the University of
Adelaide. The micro communications sonobuoy is developed to act
as a seamless communication relay between an Autonomous
Underwater Vehicle (AUV) and an above water human operator
some distance away. Development of such a device would eliminate
the requirement of physical communication tethers attached to
submersible vehicles for control and data retrieval.
Abstract: The fault current levels through the electric devices
have a significant impact on failure probability. New fault current
results in exceeding the rated capacity of circuit breaker and switching
equipments and changes operation characteristic of overcurrent relay.
In order to solve these problems, SFCL (Superconducting Fault
Current Limiter) has rising as one of new alternatives so as to improve
these problems. A fault current reduction differs depending on
installed location. Therefore, a location of SFCL is very important.
Also, SFCL decreases the fault current, and it prevents surrounding
protective devices to be exposed to fault current, it then will bring a
change of reliability. In this paper, we propose method which
determines the optimal location when SFCL is installed in power
system. In addition, the reliability about the power system which
SFCL was installed is evaluated. The efficiency and effectiveness of
this method are also shown by numerical examples and the reliability
indices are evaluated in this study at each load points. These results
show a reliability change of a system when SFCL was installed.
Abstract: In this paper we study the resource allocation problem
for an OFDMA based cooperative two-way relaying (TWR) network.
We focus on amplify and forward (AF) analog network coding
(ANC) protocol. An optimization problem for two basic resources
namely, sub-carrier and power is formulated for multi-user TWR
networks. A joint optimal optimization problem is investigated and
two-step low complexity sub-optimal resource allocation algorithm is
proposed for multi-user TWR networks with ANC protocol. The
proposed algorithm has been evaluated in term of total achievable
system sum-rate and achievable individual sum-rate for each userpair.
The good tradeoff between system sum-rate and fairness is
observed in the two-step proportional resource allocation scheme.
Abstract: In this paper, a reliable cooperative multipath routing
algorithm is proposed for data forwarding in wireless sensor networks
(WSNs). In this algorithm, data packets are forwarded towards the
base station (BS) through a number of paths, using a set of relay
nodes. In addition, the Rayleigh fading model is used to calculate
the evaluation metric of links. Here, the quality of reliability is
guaranteed by selecting optimal relay set with which the probability
of correct packet reception at the BS will exceed a predefined
threshold. Therefore, the proposed scheme ensures reliable packet
transmission to the BS. Furthermore, in the proposed algorithm,
energy efficiency is achieved by energy balancing (i.e. minimizing
the energy consumption of the bottleneck node of the routing path)
at the same time. This work also demonstrates that the proposed
algorithm outperforms existing algorithms in extending longevity of
the network, with respect to the quality of reliability. Given this, the
obtained results make possible reliable path selection with minimum
energy consumption in real time.
Abstract: Delay-Tolerant Networks (DTNs) are sparse, wireless
networks where disconnections are common due to host mobility and
low node density. The Message Ferrying (MF) scheme is a mobilityassisted
paradigm to improve connectivity in DTN-like networks. A
ferry or message ferry is a special node in the network which has
a per-determined route in the deployed area and relays messages
between mobile hosts (MHs) which are intermittently connected.
Increased contact opportunities among mobile hosts and the ferry
improve the performance of the network, both in terms of message
delivery ratio and average end-end delay. However, due to the inherent
mobility of mobile hosts and pre-determined periodicity of the
message ferry, mobile hosts may often -miss- contact opportunities
with a ferry. In this paper, we propose the combination of stationary
ferry access points (FAPs) with MF routing to increase contact
opportunities between mobile hosts and the MF and consequently
improve the performance of the DTN. We also propose several
placement models for deploying FAPs on MF routes. We evaluate the
performance of the FAP placement models through comprehensive
simulation. Our findings show that FAPs do improve the performance
of MF-assisted DTNs and symmetric placement of FAPs outperforms
other placement strategies.
Abstract: In this paper, we study the cooperative communications where multiple cognitive radio (CR) transmit-receive pairs competitive maximize their own throughputs. In CR networks, the influences of primary users and the spectrum availability are usually different among CR users. Due to the existence of multiple relay nodes and the different spectrum availability, each CR transmit-receive pair should not only select the relay node but also choose the appropriate channel. For this distributed problem, we propose a game theoretic framework to formulate this problem and we apply a regret-matching learning algorithm which is leading to correlated equilibrium. We further formulate a modified regret-matching learning algorithm which is fully distributed and only use the local information of each CR transmit-receive pair. This modified algorithm is more practical and suitable for the cooperative communications in CR network. Simulation results show the algorithm convergence and the modified learning algorithm can achieve comparable performance to the original regretmatching learning algorithm.
Abstract: In this paper, we proposed a new routing protocol for
Unmanned Aerial Vehicles (UAVs) that equipped with directional
antenna. We named this protocol Directional Optimized Link State
Routing Protocol (DOLSR). This protocol is based on the well
known protocol that is called Optimized Link State Routing Protocol
(OLSR). We focused in our protocol on the multipoint relay (MPR)
concept which is the most important feature of this protocol. We
developed a heuristic that allows DOLSR protocol to minimize
the number of the multipoint relays. With this new protocol the
number of overhead packets will be reduced and the End-to-End
delay of the network will also be minimized. We showed through
simulation that our protocol outperformed Optimized Link State
Routing Protocol, Dynamic Source Routing (DSR) protocol and Ad-
Hoc On demand Distance Vector (AODV) routing protocol in
reducing the End-to-End delay and enhancing the overall
throughput. Our evaluation of the previous protocols was based
on the OPNET network simulation tool.
Abstract: This paper presents the impact study of GTO Controlled Series Capacitor (GCSC) parameters on measured impedance (Zseen) by MHO distance relays for single transmission line high voltage 220 kV in the presence of single phase to earth fault with fault resistance (RF). The study deals with a 220 kV single electrical transmission line of Eastern Algerian transmission networks at Group Sonelgaz (Algerian Company of Electrical and Gas) compensated by series Flexible AC Transmission System (FACTS) i.e. GCSC connected at midpoint of the transmission line. The transmitted active and reactive powers are controlled by three GCSC-s. The effects of maximum reactive power injected as well as injected maximum voltage by GCSC on distance relays measured impedance is treated. The simulations results investigate the effects of GCSC injected parameters: variable reactance (XGCSC), variable voltage (VGCSC) and reactive power injected (QGCSC) on measured resistance and reactance in the presence of earth fault with resistance fault varied between 5 to 50 Ω for three cases study.
Abstract: We consider a two-way relay network where two sources exchange information. A relay helps the two sources exchange information using the decode-and-XOR-forward protocol. We investigate the power minimization problem with minimum rate constraints. The system needs two time slots and in each time slot the required rate pair should be achievable. The power consumption is minimized in each time slot and we obtained the closed form solution. The simulation results confirm that the proposed power allocation scheme consumes lower total power than the conventional schemes.
Abstract: WIMAX relay station mesh network has been approved by IEEE 802.16j as a standard to provide a highly data rate transmission, the RS was implemented to extend the coverage zone of the BS, for instance the MSs previously were out of the coverage of the BS they become in the coverage of the RS, therefore these MSs can have Admission control from the BS through the RS. This paper describe a problem in the mesh network Relay station, for instance the problem of how to serve the mobile stations (MSs) which are out of the Relay station coverage. This paper also proposed a solution for mobile stations out of the coverage of the WIMAX Relay stations mesh Network. Therefore Ad-hoc network defined as a solution by using its admission control schema and apply it on the mobiles inside and outside the Relay station coverage.
Abstract: The wireless adhoc network is comprised of wireless
node which can move freely and are connected among themselves
without central infrastructure. Due to the limited transmission range
of wireless interfaces, in most cases communication has to be relayed
over intermediate nodes. Thus, in such multihop network each node
(also called router) is independent, self-reliant and capable to route
the messages over the dynamic network topology. Various protocols
are reported in this field and it is very difficult to decide the best one.
A key issue in deciding which type of routing protocol is best for
adhoc networks is the communication overhead incurred by the
protocol. In this paper STAR a table driven and DSR on demand
protocols based on IEEE 802.11 are analyzed for their performance
on different performance measuring metrics versus varying traffic
CBR load using QualNet 5.0.2 network simulator.
Abstract: This paper presents a new approach for setting
frequency relays based on the dynamic of power system. A
simplified model of the power system based on the load-frequency
control loop will be developed to be used instead of the complete
model of the power system. The effects of the equipments and their
responses on the frequency variations of the power plant will be
investigated and then a method for adaptive settings of frequency
relays will be explained. The proposed method will be investigated
by analyzing a simplified model of a power plant by MATLAB
software.
Abstract: Protective relays are components of a protection system
in a power system domain that provides decision making element for
correct protection and fault clearing operations. Failure of the
protection devices may reduce the integrity and reliability of the power
system protection that will impact the overall performance of the
power system. Hence it is imperative for power utilities to assess the
reliability of protective relays to assure it will perform its intended
function without failure. This paper will discuss the application of
reliability analysis using statistical method called Life Data Analysis
in Tenaga Nasional Berhad (TNB), a government linked power utility
company in Malaysia, namely Transmission Division, to assess and
evaluate the reliability of numerical overcurrent protective relays from
two different manufacturers.
Abstract: Directional over current relays (DOCR) are commonly used in power system protection as a primary protection in distribution and sub-transmission electrical systems and as a secondary protection in transmission systems. Coordination of protective relays is necessary to obtain selective tripping. In this paper, an approach for efficiency reduction of DOCRs nonlinear optimum coordination (OC) is proposed. This was achieved by modifying the objective function and relaxing several constraints depending on the four constraints classification, non-valid, redundant, pre-obtained and valid constraints. According to this classification, the far end fault effect on the objective function and constraints, and in consequently on relay operating time, was studied. The study was carried out, firstly by taking into account the near-end and far-end faults in DOCRs coordination problem formulation; and then faults very close to the primary relays (nearend faults). The optimal coordination (OC) was achieved by simultaneously optimizing all variables (TDS and Ip) in nonlinear environment by using of Genetic algorithm nonlinear programming techniques. The results application of the above two approaches on 6-bus and 26-bus system verify that the far-end faults consideration on OC problem formulation don-t lose the optimality.
Abstract: Overcurrent (OC) relays are the major protection
devices in a distribution system. The operating time of the OC relays
are to be coordinated properly to avoid the mal-operation of the
backup relays. The OC relay time coordination in ring fed
distribution networks is a highly constrained optimization problem
which can be stated as a linear programming problem (LPP). The
purpose is to find an optimum relay setting to minimize the time of
operation of relays and at the same time, to keep the relays properly
coordinated to avoid the mal-operation of relays.
This paper presents two phase simplex method for optimum time
coordination of OC relays. The method is based on the simplex
algorithm which is used to find optimum solution of LPP. The
method introduces artificial variables to get an initial basic feasible
solution (IBFS). Artificial variables are removed using iterative
process of first phase which minimizes the auxiliary objective
function. The second phase minimizes the original objective function
and gives the optimum time coordination of OC relays.
Abstract: This paper addresses the problems encountered by conventional distance relays when protecting double-circuit transmission lines. The problems arise principally as a result of the mutual coupling between the two circuits under different fault conditions; this mutual coupling is highly nonlinear in nature. An adaptive protection scheme is proposed for such lines based on application of artificial neural network (ANN). ANN has the ability to classify the nonlinear relationship between measured signals by identifying different patterns of the associated signals. One of the key points of the present work is that only current signals measured at local end have been used to detect and classify the faults in the double circuit transmission line with double end infeed. The adaptive protection scheme is tested under a specific fault type, but varying fault location, fault resistance, fault inception angle and with remote end infeed. An improved performance is experienced once the neural network is trained adequately, which performs precisely when faced with different system parameters and conditions. The entire test results clearly show that the fault is detected and classified within a quarter cycle; thus the proposed adaptive protection technique is well suited for double circuit transmission line fault detection & classification. Results of performance studies show that the proposed neural network-based module can improve the performance of conventional fault selection algorithms.
Abstract: This paper presents the development of adaptive
distance relay for protection of parallel transmission line with mutual
coupling. The proposed adaptive relay, automatically adjusts its
operation based on the acquisition of the data from distance relay of
adjacent line and status of adjacent line from line circuit breaker IED
(Intelligent Electronic Device). The zero sequence current of the
adjacent parallel transmission line is used to compute zero sequence
current ratio and the mutual coupling effect is fully compensated.
The relay adapts to changing circumstances, like failure in
communication from other relays and non - availability of adjacent
transmission line. The performance of the proposed adaptive relay is
tested using steady state and dynamic test procedures. The fault
transients are obtained by simulating a realistic parallel transmission
line system with mutual coupling effect in PSCAD. The evaluation
test results show the efficacy of adaptive distance relay over the
conventional distance relay.
Abstract: Cellular networks provide voice and data services to the users with mobility. To deliver services to the mobile users, the cellular network is capable of tracking the locations of the users, and allowing user movement during the conversations. These capabilities are achieved by the location management. Location management in mobile communication systems is concerned with those network functions necessary to allow the users to be reached wherever they are in the network coverage area. In a cellular network, a service coverage area is divided into smaller areas of hexagonal shape, referred to as cells. The cellular concept was introduced to reuse the radio frequency. Continued expansion of cellular networks, coupled with an increasingly restricted mobile spectrum, has established the reduction of communication overhead as a highly important issue. Much of this traffic is used in determining the precise location of individual users when relaying calls, with the field of location management aiming to reduce this overhead through prediction of user location. This paper describes and compares various location management schemes in the cellular networks.
Abstract: In this paper, we provide complete end-to-end delay analyses including the relay nodes for instant messages. Message Session Relay Protocol (MSRP) is used to provide congestion control for large messages in the Instant Messaging (IM) service. Large messages are broken into several chunks. These chunks may traverse through a maximum number of two relay nodes before reaching destination according to the IETF specification of the MSRP relay extensions. We discuss the current solutions of sending large instant messages and introduce a proposal to reduce message flows in the IM service. We consider virtual traffic parameter i.e., the relay nodes are stateless non-blocking for scalability purpose. This type of relay node is also assumed to have input rate at constant bit rate. We provide a new scheduling policy that schedules chunks according to their previous node?s delivery time stamp tags. Validation and analysis is shown for such scheduling policy. The performance analysis with the model introduced in this paper is simple and straight forward, which lead to reduced message flows in the IM service.
Abstract: This paper presents the impact study of apparent
reactance injected by series Flexible AC Transmission System
(FACTS) i.e. Thyristor Controlled Series Reactor (TCSR) on the
measured impedance of a 400 kV single electrical transmission line
in the presence of phase to earth fault with fault resistance. The study
deals with an electrical transmission line of Eastern Algerian
transmission networks at Group Sonelgaz (Algerian Company of
Electrical and Gas) compensated by TCSR connected at midpoint of
the line. This compensator used to inject active and reactive powers
is controlled by three TCSR-s. The simulations results investigate the
impacts of the TCSR on the parameters of short circuit calculation
and parameters of measured impedance by distance relay in the
presence of earth fault for three cases study.