IEEE 802.11 DCF is the MAC protocol currently used in wireless LANs. 802.11
DCF is inefficient due to two types of overhead; channel idle time and
collision time. This paper presents the design and performance evaluation of an
efficient MAC protocol for wireless networks, called Token-DCF. Token-DCF
decreases both idle time and collision time. In Token-DCF, each station keeps
track of neighboring links' queue length by overhearing of transmitted packets
on the wireless medium. The result is then used to assign privileges to the
network stations.

Real-time applications are performance critical applications that require
bounded service latency. In multi-hop wireless ad-hoc and sensor networks,
communication delays are dominant over processing delays. Therefore, to enable
real-time applications in such networks, the communication latency must be
bounded. In this paper, we derive expressions of real-time capacity that
characterize the ability of a network to deliver data on time as well as
develop network protocols that achieve this capacity.

We consider the adaptive shortest-path routing problem in wireless networks
under unknown and stochastically varying link states. In this problem, we aim
to optimize the quality of communication between a source and a destination
through adaptive path selection. Due to the randomness and uncertainties in the
network dynamics, the quality of each link varies over time according to a
stochastic process with unknown distributions. After a path is selected for
communication, the aggregated quality of all links on this path (e.g., total
path delay) is observed.

Major wireless operators are nowadays facing network capacity issues in
striving to meet the growing demands of mobile users. At the same time,
3G-enabled devices increasingly benefit from ad hoc radio connectivity (e.g.,
Wi-Fi). In this context of hybrid connectivity, we propose Push-and-track, a
content dissemina- tion framework that harnesses ad hoc communication
opportunities to minimize the load on the wireless infrastructure while
guaranteeing tight delivery delays.

This dissertation is a study on the design and analysis of novel, optimal
routing and rate control algorithms in wireless, mobile communication networks.
Congestion control and routing algorithms upto now have been designed and
optimized for wired or wireless mesh networks.

We develop an approximate analytical technique for evaluating the performance
of multi-hop networks based on beacon-less CSMA/CA as standardised in IEEE
802.15.4, a popular standard for wireless sensor networks. The network
comprises sensor nodes, which generate measurement packets, and relay nodes
which only forward packets. We consider a detailed stochastic process at each
node, and analyse this process taking into account the interaction with
neighbouring nodes via certain unknown variables (e.g., channel sensing rates,
collision probabilities, etc.).

This paper attempts to answer a question: for a given traversal area, how to
quantify the geometric impact of anchor placement on localization performance.
We present a theoretical framework for quantifying the anchor placement impact.
An experimental study, as well as the field test using a UWB ranging
technology, is presented. These experimental results validate the theoretical
analysis. As a byproduct, we propose a two-phase localization method (TPLM) and
show that TPLM outperforms the least-square method in localization accuracy by
a huge margin.

In this paper we present a model for the lifetime of wireless sensor
networks. The model takes into consideration several parameters such as the
total number of sensors, network size, percentage of sink nodes, location of
sensors, the mobility of sensors, and power consumption. A definition of the
life time of the network based on three different criteria is introduced;
percentage of available power to total power, percentage of alive sensors to
total sensors, and percentage of alive sink sensors to total sink sensors. A
Matlab based simulator is developed for the introduced model.

Cognitive radio (CR) is a new paradigm that utilizes the available spectrum
band. The key characteristic of CR system is to sense the electromagnetic
environment to adapt their operation and dynamically vary its radio operating
parameters. The technique of dynamically accessing the unused spectrum band is
known as Dynamic Spectrum Access (DSA). The dynamic spectrum access technology
helps to minimize unused spectrum bands. In this paper, main functions of
Cognitive Radio (CR) i.e. spectrum sensing, spectrum management, spectrum
mobility and spectrum sharing are discussed.

In this paper we propose a new routing protocol with low energy consumption
for wireless sensor networks based on the clustering approach. Our protocol is
based on a strategy which aims at providing a more equitable exploitation of
the selected nodes (cluster-heads) energy by distributing their load of the
managed sensors during the clustering process. In order to save the energy
dissipated while transmitting sensed data to the base station, the multi-hops
routing strategy is used to arrange the communication of the data between
cluster-heads nodes.

A wireless network is realized by mobile devices which communicate over radio
channels. Since, experiments of real life problem with real devices are very
difficult, simulation is used very often. Among many other important properties
that have to be defined for simulative experiments, the mobility model and the
radio propagation model have to be selected carefully. Both have strong impact
on the performance of mobile wireless networks, e.g., the performance of
routing protocols varies with these models. There are many mobility and radio
propagation models proposed in literature.

In this paper, the performance of high speed optical fiber based network is
analysed by using dispersion compensating module (DCM). The optimal operating
condition of the DCM is obtained by considering dispersion management
configurations for the symmetrical system i.e Pre-compensation &
Post-compensation. The dispersion compensating fiber (DCF) is tested for a
single span, single channel system operating at a speed of 10 Gb/s with a
transmitting wavelength of 1550 nm, over 120 km single mode fibre by using the
compensating fiber for 24 km,30km and 35Km.

The concepts of MIMO MC-CDMA are not new but the new technologies to improve
their functioning are an emerging area of research. In general, most mobile
communication systems transmit bits of information in the radio space to the
receiver. The radio channels in mobile radio systems are usually multipath
fading channels, which cause inter-symbol interference (ISI) in the received
signal. To remove ISI from the signal, there is a need of strong equalizer. In
this thesis we have focused on simulating the MIMO MC-CDMA systems in MATLAB
and designed the channel estimation for them.

Modern radio communication is faced with a problem about how to distribute
restricted frequency to users in a certain space. Since our task is to minimize
the number of repeaters, a natural idea is enlarging coverage area. However,
coverage has restrictions. First, service area has to be divided economically
as repeater's coverage is limited. In this paper, our fundamental method is to
adopt seamless cellular network division.

Formal analysis techniques are widely used today in order to verify and
analyze communication protocols. In this work, we launch a quantitative
verification analysis for the low- cost Radio Frequency Identification (RFID)
protocol proposed by Song and Mitchell. The analysis exploits a Discrete-Time
Markov Chain (DTMC) using the well-known PRISM model checker. We have managed
to represent up to 100 RFID tags communicating with a reader and quantify each
RFID session according to the protocol's computation and transmission cost
requirements.

Powerful spectrum sensing schemes enable cognitive radios (CRs) to find
transmission opportunities in spectral resources allocated exclusively to the
primary users. In this paper, maximizing the average throughput of a secondary
user by optimizing its spectrum sensing time is formulated assuming that a
prior knowledge of the presence and absence probabilities of the primary users
is available.

This paper aims to reduce the prebuffering requirements, while maintaining
continuity, for video streaming. Current approaches do this by making use of
adaptive media playout (AMP) to reduce the playout rate. However, this
introduces playout distortion to the viewers and increases the viewing latency.
We approach this by proposing a frame rate optimization framework that adjusts
both the encoder frame generation rate and the decoder playout frame rate.
Firstly, we model this problem as the joint adjustment of the encoder frame
generation interval and the decoder playout frame interval.

Recently mobile agents are used to discover services in mobile ad-hoc network
(MANET) where agents travel through the network, collecting and sometimes
spreading the dynamically changing service information. But it is important to
investigate how reliable the agents are for this application as the
dependability issues(reliability and availability) of MANET are highly affected
by its dynamic nature.The complexity of underlying MANET makes it hard to
obtain the route reliability of the mobile agent systems (MAS); instead we
estimate it using Monte Carlo simulation.

"Web Of Things" evolved from "Internet Of Things". Lot of research has been
done in designing architecture for "Web Of Things". Two main architectures are
Smart gateway based architecture and embedded Web Server based architecture.
These architectures address some of the basic and essential issues relating to
Service Oriented Architecture for "Web Of Things".

The goal of this research report is to present OSERENA "Optimized SchEduling
RoutEr Node Activity", a distributed coloring algorithm optimized for dense
wireless networks. Network density has an extremely reduced impact on the size
of the messages exchanged to color the network. Furthermore, the number of
colors used to color the network is not impacted by this optimization. We
describe in this research report the properties of the algorithm and prove its
correctness and termination. Simulation results point out the considerable
gains in bandwidth.

Statistical network calculus is the probabilistic extension of network
calculus, which uses a simple envelope approach to describe arrival traffic and
service available for the arrival traffic in a node. One of the key features of
network calculus is the possibility to describe the service available in a
network using a network service envelope constructed from the service envelopes
of the individual nodes constituting the network.

The Wireless Sensors Network (WSN) is an emergent technology resulting from
progress of various fields. Many applications of networks WSN are born. One of
the applications which have an operational effectiveness relates to the field
of health and allows a medical remote support. Miniature wireless sensors,
strategically placed on the human body, create a Wireless Body Sensor Network
(WBSN) which allows supervising various essential biological signals (rate of
heartbeat, pressure, etc). The sensitivity of medical information requires
mechanisms of safety.

Industry experience indicates that the ability to incrementally expand data
centers is essential. However, existing high-bandwidth network designs have
rigid structure that interferes with incremental expansion. We present
Jellyfish, a high-capacity network interconnect, which, by adopting a random
graph topology, yields itself naturally to incremental expansion.

Cognitive Radio (CR) aims to increase the spectrum utilization by allowing
secondary users (SU) to access unused licensed spectrum bands. To maximize the
throughput given limited sensing capability, SUs need to strike a balance
between sensing the channels that are not heavily used by primary users (PU)
and avoiding collisions with other SUs. To randomize sensing decisions without
resorting to multiuser sensing policies, it is proposed to exploit the
spatially-variant fading channel conditions on different links by adapting the
reward to the channel state information (CSI).

One of the most important problems in wireless sensor network is to develop a
routing protocol that has energy efficiency. Since the power of the sensor
Nodes are limited, conserving energy and network life is a critical issue in
wireless sensor network. Clustering is one of the known methods widely used to
face these challenges. In this paper, a cluster based communication protocol
with considering the low energy consumption in wireless sensor networks, is
introduced which balances the energy load among sensor nodes.

The recursive least-squares (RLS) algorithm has well-documented merits for
reducing complexity and storage requirements, when it comes to online
estimation of stationary signals as well as for tracking slowly-varying
nonstationary processes. In this paper, a distributed recursive least-squares
(D-RLS) algorithm is developed for cooperative estimation using ad hoc wireless
sensor networks. Distributed iterations are obtained by minimizing a separable
reformulation of the exponentially-weighted least-squares cost, using the
alternating-minimization algorithm.

To cope with the increasing demand of wireless communication services
multi-carrier systems are being used. Radio resources are very limited and
efficient usages of these resources are inevitable to get optimum performance
of the system. Paging channel is a low-bandwidth channel and one of the most
important channels on which system performance depends significantly. Therefore
it is vulnerable to even moderate overloads.

In this paper, we analyze the numerical stability of the popular Longley-Rice
Irregular Terrain Model (ITM). This model is widely used to plan wireless
networks and in simulation-validated research and hence its stability is of
fundamental importance to the correctness of a large amount of work. We take a
systematic approach by first porting the reference ITM implementation to a
multiprecision framework and then generating loss predictions along many random
paths using real terrain data.

In this paper we present a cooperative medium access control (MAC) protocol
that is designed for a physical layer that can decode interfering transmissions
in distributed wireless networks. The proposed protocol pro-actively enforces
two independent packet transmissions to interfere in a controlled and
cooperative manner. The protocol ensures that when a node desires to transmit a
unicast packet, regardless of the destination, it coordinates with minimal
overhead with relay nodes in order to concurrently transmit over the wireless
channel with a third node.

The number of contending neighbors of a node in a multihop ad hoc network has
to be adjusted while analyzing the performance of the network such as computing
the end-to-end delays along a path from a given source to a destination. In
this paper, we describe a method to adjust the number of contending neighbors
of a node in a multihop wireless ad hoc network. Our method is based on the
minimum number of neighbors that has to be common between two consecutive nodes
along a path. We derive an analytical expression for the adjustment factor.

We construct a simple network model to provide insight into network design
strategies. We show that the model can be used to address various approaches to
network coding, MAC, and multi-packet reception so that their effects on
network throughput can be evaluated. We consider several topology components
which exhibit the same non-monotonic saturation behavior found within the Katti
et. al. COPE experiments. We further show that fairness allocation by the MAC
can seriously impact performance and cause this non-monotonic saturation.

Vehicular Ad Hoc Networks (VANET) is a subclass of Mobile ad hoc networks
which provides a distinguished approach for Intelligent Transport System (ITS).
The survey of routing protocols in VANET is important and necessary for smart
ITS. This paper discusses the advantages / disadvantages and the applications
of various routing protocols for vehicular ad hoc networks. It explores the
motivation behind the designed, and traces the evolution of these routing
protocols. F inally the paper concludes by a tabular comparison of the various
routing protocols for VANET.

Common WLAN pathologies include low signal-to-noise ratio, congestion, hidden
terminals or interference from non-802.11 devices and phenomena. Prior work has
focused on the detection and diagnosis of such problems using layer-2
information from 802.11 devices and special-purpose access points and monitors,
which may not be generally available. Here, we investigate a userlevel
approach: is it possible to detect and diagnose 802.11 pathologies with
strictly user-level active probing, without any cooperation from, and without
any visibility in, layer-2 devices?

The performances of the routing protocols are important since they compute
the primary path between source and destination. In addition, routing protocols
need to detect failure within a short period of time when nodes move to start
updating the routing table in order to find a new primary path to the
destination. Meantime, loss of packets and end-to- end delays will increase
thereby reducing throughput and degrading the performance of the network.

Wireless sensor networks (WSNs) suffers from the hot spot problem where the
sensor nodes closest to the base station are need to relay more packet than the
nodes farther away from the base station. Thus, lifetime of sensory network
depends on these closest nodes. Clustering methods are used to extend the
lifetime of a wireless sensor network.

In this paper, we consider resource allocation in the the fourth generation
(4G) cellular uplink. Our focus is on 4G cellular systems that conform to the
3GPP LTE standard and its enhancements, which are expected to be the
predominant 4G cellular systems. In order to cater to an ever-increasing user
traffic, the 4G uplink allows for precoded multi-stream (precoded MIMO)
transmission from each scheduled user and also allows multi-user (MU)
scheduling wherein multiple users can be assigned the same time-frequency
resource.

We design a cross-layer approach to aid in develop- ing a cooperative
solution using multi-packet reception (MPR), network coding (NC), and medium
access (MAC). We construct a model for the behavior of the IEEE 802.11 MAC
protocol and apply it to key small canonical topology components and their
larger counterparts. The results obtained from this model match the available
experimental results with fidelity.

The issue of mobility is important in wireless network because internet
connectivity can only be effective if it's available during the movement of
node. To enhance mobility, wireless access systems are designed such as IEEE
802.16e to operate on the move without any disruption of services. In this
paper we are analyzing the impact of mobility on the QoS parameters
(Throughput, Average Jitter and Average end to end Delay) of a mobile WiMAX
network (IEEE 802.16e) with CBR application.

Ad-hoc routing protocols use a number of algorithms for route discovery. Some
use flooding in which a route request packet (RREQ) is broadcasted from a
source node to other nodes in the network. This often leads to unnecessary
retransmissions, causing congestion and packet collisions in the network, a
phenomenon called a broadcast storm. This paper presents a RREQ message
forwarding scheme for AODV that reduces routing overheads. This has been called
AODV_EXT. Its performance is compared to that of AODV, DSDV, DSR and OLSR
protocols.

To achieve the requirement of high data rate, low latency, user fairness for
next generation wireless networks, proper designing of cross-layer optimized
dynamic resource allocation algorithm is prerequisite. In this paper, we
propose a dynamic resource allocation scheme in Orthogonal Frequency Division
Multiple Access (OFDMA) systems to optimize the non real-time (NRT) traffic,
which requires allocation of minimum quantum of data within a predefined time
that does not incur packet loss.

Business relationships between autonomous systems (AS) are crucial for
Internet routing. Existing algorithms used heuristics to infer AS relationships
from AS topology data. In this paper we propose a different approach to infer
AS relationships from more informative data sources, namely the BGP Community
and Local Preference attributes. These data contain rich information on AS
routing policies and therefore closely reflect AS relationships. We accumulate
the BGP data from RouteViews, RIPE RIS and route servers in August 2010 and
February 2011.

There is a trend of applying machine learning algorithms to cognitive radio.
One fundamental open problem is to determine how and where these algorithms are
useful in a cognitive radio network. In radar and sensing signal processing,
the control of degrees of freedom (DOF)---or dimensionality---is the first
step, called pre-processing. In this paper, the combination of dimensionality
reduction with SVM is proposed apart from only applying SVM for classification
in cognitive radio. Measured Wi-Fi signals with high signal to noise ratio
(SNR) are employed to the experiments.

Relay-assisted cooperative wireless communication has been shown to have
significant performance gains over the legacy direct transmission scheme.
Compared with single relay based cooperation schemes, utilizing multiple relays
further improves the reliability and rate of transmissions. Distributed
space-time coding (DSTC), as one of the schemes to utilize multiple relays,
requires tight coordination between relays and does not perform well in a
distributed environment with mobility.

We study the power-aware buffering problem in battery-powered sensor
networks, focusing on the fixed-size and fixed-interval buffering schemes. The
main motivation is to address the yet poorly understood size variation-induced
effect on power-aware buffering schemes. Our theoretical analysis elucidates
the fundamental differences between the fixed-size and fixed-interval buffering
schemes in the presence of data size variation.

The key parameters that need to be addressed while designing protocols for
sensor networks are its energy awareness and computational feasibility in
resource constrained sensor nodes. Variation in the distances of nodes from the
Base Station and differences in inter-nodal distances are primary factors
causing unequal energy dissipation among the nodes.

We present a novel feedback protocol for wireless broadcast networks that
utilize linear network coding. We consider transmission of packets from one
source to many receivers over a single-hop broadcast erasure channel, but the
proposed scheme is applicable to more general lossy networks. Our method
utilizes a predictive model to request feedback only when the probability that
all receivers have completed decoding is significant.

The interference imposes a significant negative impact on the performance of
wireless networks. With the continuous deployment of larger and more
sophisticated wireless networks, reducing interference in such networks is
quickly being focused upon as a problem in today's world. In this paper we
analyze the interference reduction problem from a graph theoretical viewpoint.
A graph coloring methods are exploited to model the interference reduction
problem.

Detecting misbehavior (such as transmissions of false information) in
vehicular ad hoc networks (VANETs) is very important problem with wide range of
implications including safety related and congestion avoidance applications. We
discuss several limitations of existing misbehavior detection schemes (MDS)
designed for VANETs. Most MDS are concerned with detection of malicious nodes.
In most situations, vehicles would send wrong information because of selfish
reasons of their owners, e.g. for gaining access to a particular lane.

Wireless sensor networks (WSNs) became one of the high-technology domains
during the last years. Real-time applications for them make it necessary to
provide the guaranteed Quality of Service (QoS). The main contributions of the
paper are a service framework and a guaranteed QoS model that are suitable for
the WSNs with some characteristics of the distribution, multi-hop, etc. To do
it, we develop a sensor node model based on virtual buffer sharing and present
a two-layer scheduling model by arrival curves and service curves in the
network calculus.

Performance and reliability of content access in mobile networks is
conditioned by the number and location of content replicas deployed at the
network nodes. Location theory has been the traditional, centralized approach
to study content replication: computing the number and placement of replicas in
a static network can be cast as a facility location problem. The endeavor of
this work is to design a practical solution to the above joint optimization
problem that is suitable for mobile wireless environments.

We design a cross-layer approach to optimize the joint use of multi-packet
reception and network coding, in order to relieve congestion. We construct a
model for the behavior of the 802.11 MAC and apply it to several key canonical
topology components and their extensions to any number of nodes. The results
obtained from this model match the available experimental results, which are
for routing and opportunistic network coding, with fidelity.

In this paper, we provide a matrix-analytic solution for randomized load
balancing models (also known as \emph{supermarket models}) with phase-type (PH)
service times. Generalizing the service times to the phase-type distribution
makes the analysis of the supermarket models more difficult and challenging
than that of the exponential service time case which has been extensively
discussed in the literature.

This paper discusses an efficient approach to design and implement a highly
available peer- to-peer system irrespective of peer timing and churn. Although
peers in P2P system join or leave at whim, it has been found that most of the
peers follow diurnal pattern of availability governed by the time of day
effect. When considering a global P2P system, the cyclic behavior of peers
situated on diff?erent time zones can be found complementary of one another.
Our approach utilizes the diurnal pattern of globally dispersed peers to
develop a grouping strategy.

In operational networks, nodes are connected via multiple links for load
sharing and redundancy. This is done to make sure that a failure of a link does
not disconnect or isolate some parts of the network. However, link failures
have an effect on routing, as the routers find alternate paths for the traffic
originally flowing through the link which has failed. This effect is severe in
case of failure of a critical link in the network, such as backbone links or
the links carrying higher traffic loads.

One unfortunate consequence of the success story of wireless sensor networks
(WSNs) in separate research communities is an ever-growing gap between theory
and practice. Even though there is a increasing number of algorithmic methods
for WSNs, the vast majority has never been tried in practice; conversely, many
practical challenges are still awaiting efficient algorithmic solutions. The
main cause for this discrepancy is the fact that programming sensor nodes still
happens at a very technical level.

Access networks, in particular, Digital Subscriber Line (DSL) equipment, are
a significant source of energy consumption for wireline operators. Replacing
large monolithic DSLAMs with smaller remote DSLAM units closer to customers can
reduce the energy consumption as well as increase the reach of the access
network. This paper attempts to formalize the design and optimization of the
"last mile" wireline access network with energy as one of the costs to be
minimized. In particular, the placement of remote DSLAM units needs to be
optimized. We propose solutions for two scenarios.

When data productions and consumptions are heavily unbalanced and when the
origins of data queries are spatially and temporally distributed, the so called
in-network data storage paradigm supersedes the conventional data collection
paradigm in wireless sensor networks (WSNs). In this paper, we first introduce
geometric quorum systems (along with their metrics) to incarnate the idea of
in-network data storage. These quorum systems are "geometric" because curves
(rather than discrete node sets) are used to form quorums.

The problem of packet scheduling for traffic streams with target outflow
profiles traversing input queued switches is formulated in this paper. Target
outflow profiles specify the desirable inter-departure times of packets leaving
the switch from each traffic stream. The goal of the switch scheduler is to
dynamically select service configurations of the switch, so that actual outflow
streams ("pulled" through the switch) adhere to their desired target profiles
as accurately as possible.

The field of mobile agent (MA) technology has been intensively researched
during the past few years, resulting in the phenomenal proliferation of
available MA platforms, all sharing several common design characteristics.
Research projects have mainly focused on identifying applications where the
employment of MAs is preferable compared to centralised or alternative
distributed computing models. Very little work has been made on examining how
MA platforms design can be optimised so as the network traffic and latency
associated with MA transfers are minimised.

Electronic collaboration among devices in a geographically localized
environment is made possible with the implementation of IEEE 802.11 based
wireless ad hoc networks. Dynamic nature of mobile ad hoc networks(MANETs) may
lead to unpredictable intervention of attacks or fault occurrence, which
consequently may partition the network, degrade its performance, violate the
QoS requirements and most importantly, affect bandwidth allocation to mobile
nodes in the network.

Virtualization technology facilitates a dynamic, demand-driven allocation and
migration of servers. This paper studies how the flexibility offered by network
virtualization can be used to improve Quality-of-Service parameters such as
latency, while taking into account allocation costs.

In this research, we study the optimization challenges of MANET and
cross-layer technique to improve its performance. We propose an adaptive
retransmission limits algorithm for IEEE 802.11 MAC to reduce the false link
failures and predict the node mobility. We implemented cross layer interaction
between physical and MAC layers. The MAC layer utilizes the physical layer
information for differentiating false link failure from true link failure.

A 60 GHz wireless Gigabit Ethernet (G.E.) communication system capable of
near gigabit data rate has been developed at IETR. The realized system covers 2
GHz available bandwidth. This paper describes the design and realization of the
overall system including the baseband (BB), intermediate frequency (IF) and
radiofrequency (RF) blocks. A differential binary shift keying (DBPSK)
modulation and a differential demodulation are adopted at IF.

A comparison of three different Optical Burst Switching (OBS) architectures
is made, in terms of performance criteria, control and hardware complexity,
fairness, resource utilization, and burst loss probability. Regarding burst
losses, we distinguish the losses due to burst contentions from those due to
contentions of Burst Control Packets (BCP).

The high-level contribution of this paper is a simulation-based analysis to
evaluate the tradeoffs between lifetime and hop count of link-disjoint,
node-disjoint and zone-disjoint multi-path routes vis-\`a-vis single-path
minimum hop routes for mobile ad hoc networks. The link-disjoint, node-disjoint
and zone-disjoint algorithms proposed in this paper can be used to arrive at
benchmarks for the time between successive multi-path route discoveries, the
number of disjoint paths per multi-path set and the hop count per multi-path
set.

Carrier Sense Multiple Access with Enhanced Collision Avoidance (CSMA/ECA) is
a distributed MAC protocol that allows collision-free access to the medium in
WLAN. The only difference between CSMA/ECA and the well-known CSMA/CA is that
the former uses a deterministic backoff after successful transmissions.
Collision-free operation is reached after a transient state during which some
collisions may occur.

A high degree of reliability for critical data transmission is required in
body sensor networks (BSNs). However, BSNs are usually vulnerable to channel
impairments due to body fading effect and RF interference, which may
potentially cause data transmission to be unreliable. In this paper, an
adaptive and flexible fault-tolerant communication scheme for BSNs, namely
AFTCS, is proposed. AFTCS adopts a channel bandwidth reservation strategy to
provide reliable data transmission when channel impairments occur.

Many localization algorithms and systems have been developed by means of
wireless sensor networks for both indoor and outdoor environments. To achieve
higher localization accuracy, extra hardware equipments are utilized by most of
the existing localization algorithms, which increase the cost and greatly limit
the range of location-based applications. In this paper we present a method
which can effectively meet different localization accuracy requirements of most
indoor and outdoor location services in realistic applications.

Even though channel assignment has been studied for years, the performance of
most IEEE 802.11-based multi-hop wireless networks such as wireless sensor
network (WSN), wireless mesh network (WMN), mobile ad hoc network (MANET) is
limited by channel interference. Properly assigning orthogonal channels to
wireless links can improve the throughput of multi-hop networks. To solve the
dynamic channel assignment problem, a routing-based channel assignment
algorithm called R-CA is proposed. R-CA can allocate channels for wireless
nodes when needed and free channels after data transmission.

A distributed data collection algorithm to accurately store and forward
information obtained by wireless sensor networks is proposed. The proposed
algorithm does not depend on the sensor network topology, routing tables, or
geographic locations of sensor nodes, but rather makes use of uniformly
distributed storage nodes. Analytical and simulation results for this algorithm
show that, with high probability, the data disseminated by the sensor nodes can
be precisely collected by querying any small set of storage nodes.

Mobile Ad Hoc Network (MANET) is a collection of nodes that can be rapidly
deployed as a multi-hop network without the aid of any centralized
administration. Misbehavior is challenged by bandwidth and energy efficient
medium access control and fair share of throughput. Node misbehavior plays an
important role in MANET. In this survey, few of the contention window
misbehavior is reviewed and compared. The contention window cheating either
minimizes the active communication of the network or reduces bandwidth
utilization of a particular node.

We consider the scheduling of arbitrary wireless links in the physical model
of interference to minimize the time for satisfying all requests. We study here
the combined problem of scheduling and power control, where we seek both an
assignment of power settings and a partition of the links so that each set
satisfies the signal-to-interference-plus-noise (SINR) constraints.

In Asynchronous Duty-Cycled Wireless Ad Hoc NETworks(ADC-WANETs), the nodes
switch between active and dormant states, and each node can determine its
active/dormant schedule independently. This complicates the Minimum-Energy
Multicasting(MEM) problem, which was primarily studied in always-active WANETs.
In this paper, we study the MEM problem in ADC-WANETs both for one-to-many
multicasting and for all-to-all multicasting. In the case of one-to-many
multicasting, we present a formalization of the Minimum-Energy Multicast Tree
Construction and Scheduling (MEMTCS) problem.

This paper introduces the security and trust concepts in wireless sensor
networks and explains the difference between them, stating that even though
both terms are used interchangeably when defining a secure system, they are not
the same. The difference between reputation and trust is also explained,
highlighting that reputation partially affects trust. A survey of trust and
reputation systems in various domains is conducted, with more details given to
models in ad-hoc and sensor networks as they are closely related to each other
and to our research interests.

In this paper we address the problem of prolonging the lifetime of wireless
sensor networks (WSNs) deployed to monitor an area of interest. In this
scenario, a helpful approach is to reduce coverage redundancy and therefore the
energy expenditure due to coverage. We introduce the first algorithm which
reduces coverage redundancy by means of Sensor Activation and sensing Radius
Adaptation (SARA)in a general applicative scenario with two classes of devices:
sensors that can adapt their sensing range (adjustable sensors) and sensors
that cannot (fixed sensors).

We consider in-network computation of an arbitrary function over an arbitrary
communication network. A network with capacity constraints on the links is
given. Some nodes in the network generate data, e.g., like sensor nodes in a
sensor network. An arbitrary function of this distributed data is to be
obtained at a terminal node. The structure of the function is described by a
given computation schema, which in turn is represented by a directed tree. We
design computing and communicating schemes to obtain the function at the
terminal at the maximum rate.

The OSI model, developed by ISO in 1984, attempts to summarize complicated
network cases on layers. Moreover, network troubles are expressed by taking the
model into account. However, there has been no standardization for network
troubles up to now. Network troubles have only been expressed by the name of
the related layer.

We analyze TCP-controlled bulk file transfers in a single station (STA) WLAN
with nonzero propagation delay between the file server and the WLAN. Our
approach is to model the flow of packets as a closed queueing network (BCMP
network) with 3 service centres, one each for the Access Point (AP) and the
STA, and the third for the propagation delay. The service rates of the first
two are obtained by analyzing the WLAN MAC. Simulations show a very close match
with the theory.

Rapid progress in microelectromechanical system (MEMS) and radio frequency
(RF) design has enabled the development of low-power, inexpensive, and
network-enabled microsensors. These sensor nodes are capable of capturing
various physical information, such as temperature, pressure, motion of an
object, etc as well as mapping such physical characteristics of the environment
to quantitative measurements. A typical wireless sensor network (WSN) consists
of hundreds to thousands of such sensor nodes linked by a wireless medium.

This paper presents a TDMA based energy efficient cognitive radio
multichannel medium access control (MAC) protocol called ECR-MAC for wireless
Ad Hoc Networks. ECR-MAC requires only a single half-duplex radio transceiver
on each node that integrates the spectrum sensing at physical (PHY) layer and
the packet scheduling at MAC layer. In addition to explicit frequency
negotiation which is adopted by conventional multichannel MAC protocols,
ECR-MAC introduces lightweight explicit time negotiation.

We study the problem of tracking an object moving through a network of
wireless sensors. In order to conserve energy, the sensors may be put into a
sleep mode with a timer that determines their sleep duration. It is assumed
that an asleep sensor cannot be communicated with or woken up, and hence the
sleep duration needs to be determined at the time the sensor goes to sleep
based on all the information available to the sensor. Having sleeping sensors
in the network could result in degraded tracking performance, therefore, there
is a tradeoff between energy usage and tracking performance.

In this paper an improved version of the graded precision localization
algorithm GRADELOC, called IGRADELOC is proposed. The performance of GRADELOC
is dependent on the regions formed by the overlapping radio ranges of the nodes
of the underlying sensor network. A different region pattern could
significantly alter the nature and precision of localization. In IGRADELOC, two
improvements are suggested. Firstly, modifications are proposed in the radio
range of the fixed-grid nodes, keeping in mind the actual radio range of
commonly available nodes, to allow for routing through them.

Conserving power in mobile ad-hoc and sensor networks is a big challenge.
Most of the nodes in these networks, in general, are battery powered,
therefore, an efficient power saving protocol is required to extend the
lifetime of such networks. A lot of work has been done and several protocols
have been proposed to address this problem. Gossip based protocols, which are
based on the results of percolation theory, significantly reduce power
consumption with very little implementation overhead. However, not much work
has been done to make gossiping battery aware.

Mobile ad-hoc network (MANET) is infrastructureless, self-organizable, multi
hop packet switched network. A number of routing protocols for MANETs have been
proposed in recent years. Dynamic Source Routing (DSR) protocol is one of the
most popular routing protocol for ad hoc networks. This paper presents a novel
method to enhance route maintenance part of DSR protocol. Our proposed route
maintenance significantly increases the efficiency of the protocol at the time
of route failures.

An online backup system should be quick and reliable in both saving and
restoring users’ data. To do so in a peer-to-peer implementation, data transfer
scheduling and the amount of redundancy must be chosen wisely. We formalize the
problem of exchanging multiple pieces of data with intermittently available
peers, and we show that random scheduling completes transfers nearly optimally
in terms of duration as long as the system is sufficiently large.

As many sensor network applications require deployment in remote and
hard-to-reach areas, it is critical to ensure that such networks are capable of
operating unattended for long durations. Consequently, the concept of using
nodes with energy replenishment capabilities has been gaining popularity.
However, new techniques and protocols must be developed to maximize the
performance of sensor networks with energy replenishment. Here, we analyze
limits of the performance of sensor nodes with limited energy, being
replenished at a variable rate.

It has been revealed in the literature that pure multipoint relaying (MPR)
algorithms demonstrate both simplicity and outstanding performance, as compared
to other flooding algorithms in wireless networks. One drawback of pure MPR
algorithms is that the selected forwarding set may not represent the optimum
selection. In addition, little efforts have been carried-out to investigate the
performance of such algorithms in noisy mobile ad hoc networks (MANETs)
suffering from high packet-loss and node mobility.

The Internet infrastructure is severely stressed. Rapidly growing overhead
associated with the primary function of the Internet---routing information
packets between any two computers in the world---causes concerns among Internet
experts that the existing Internet routing architecture may not sustain even
another decade; parts of the Internet have started sinking into black holes
already.

TCP performs poorly in networks with serious packet reordering. Processing
reordered packets in the TCP layer is costly and inefficient, involving
interaction of the sender and receiver. Motivated by the interrupt coalescing
mechanism that delivers packets upward for protocol processing in blocks, we
propose a new strategy, Sorting Reordered Packets with Interrupt Coalescing
(SRPIC), to reduce packet reordering in the receiver.

In this paper we introduce WiNV - A framework for web-based interactive
scalable network visualization. WiNV enables a new class of rich and scalable
interactive cross-platform capabilities for visualizing large-scale networks
natively in a user's browser. Extensive experiments show that our system can
visualize networks that consist of tens of thousands of nodes while maintaining
fast, high-quality interaction.

We study a problem of quick detection of top-k Personalized PageRank lists.
This problem has a number of important applications such as finding local cuts
in large graphs, estimation of similarity distance and name disambiguation. In
particular, we apply our results to construct efficient algorithms for the
person name disambiguation problem. We argue that when finding top-k
Personalized PageRank lists two observations are important.

Dead Reckoning mechanism allows reducing the network utilization considerably
when used in Distributed Interactive Simulation Applications. However, this
technique often ignores available contextual information that may be
influential to the state of an entity, sacrificing remote predictive accuracy
in favor of low computational complexity. The remainder of this paper focuses
on the analysis of the Dead Reckoning Algorithms. Some contributions are
expected and overviews of the major bandwidth reduction techniques currently
investigated are discussed.

Fourth Generation (4G) Wireless System will integrate heterogeneous wireless
overlay systems i.e. interworking of WLAN/ GSM/ CDMA/ WiMAX/ LTE/ etc with
guaranteed Quality of Service (QoS) and Experience (QoE).QoS(E) vary from
network to network and is application sensitive. User needs an optimal mobility
solution while roaming in Overlaid wireless environment i.e. user could
seamlessly transfer his session/ call to a best available network bearing
guaranteed Quality of Experience.

In low power wireless sensor networks, MAC protocols usually employ periodic
sleep/wake schedule to reduce idle listening time. Even though this mechanism
is simple and efficient, it results in high end-to-end latency and low
throughput. On the other hand, the previously proposed CSMA/CA-based MAC
protocols have tried to reduce inter-node interference at the cost of increased
latency and lower network capacity.

This paper studies the problem of distributed computation over a network of
wireless sensors. While this problem applies to many emerging applications, to
keep our discussion concrete we will focus on sensor networks used for
structural health monitoring. Within this context, the heaviest computation is
to determine the singular value decomposition (SVD) to extract mode shapes
(eigenvectors) of a structure. Compared to collecting raw vibration data and
performing SVD at a central location, computing SVD within the network can
result in significantly lower energy consumption and delay.

Next generation networks (NGN) services are assumed to be a new revenue
stream for both network operators and service providers. New services
especially focused on a mobile telecommunications that would be used not only
as a communication de vice but also as a personal gateway to order or consume a
variety of services and products [1]. This type of advanced services can be
accomplished when the adaptability of the packet-networks (Internet) and the
quality of service of the circuit switched networks are combined into one
network [2].

Retransmission based on packet acknowledgement (ACK/NAK) is a fundamental
error control technique employed in IEEE 802.11-2007 unicast network. However
the 802.11-2007 standard falls short of proposing a reliable MAC-level recovery
protocol for multicast frames. In this paper we propose a latency and bandwidth
efficient coding algorithm based on the principles of network coding for
retransmitting lost packets in a singlehop wireless multicast network and
demonstrate its effectiveness over previously proposed network coding based
retransmission algorithms.

In this paper we analytically propose an alternative approach to achieve
better fairness in scheduling mechanisms which could provide better quality of
service particularly for real time application. Our proposal oppose the
allocation of the bandwidth which adopted by all previous scheduling mechanism.
It rather adopt the opposition approach be proposing the notion of
Maxmin-charge which fairly distribute the congestion. Furthermore, analytical
proposition of novel mechanism named as Just Queueing is been demonstrated.

P2P computing lifts taxing issues in various areas of computer science. The
largely used decentralized unstructured P2P systems are ad hoc in nature and
present a number of research challenges. In this paper, we provide a
comprehensive theoretical survey of various state-of-the-art search and
replication schemes in unstructured P2P networks for file-sharing applications.
The classifications of search and replication techniques and their advantages
and disadvantages are briefly explained.

This paper introduces GODDeS: a fully distributed self-organizing
decision-theoretic routing algorithm designed to effectively exploit high
quality paths in lossy ad-hoc wireless environments, typically with a large
number of nodes. The routing problem is modeled as an optimal control problem
for a decentralized Markov Decision Process, with links characterized by
locally known packet drop probabilities that either remain constant on average
or change slowly.

We consider a broad class of interference coordination and resource
allocation problems for wireless links where the goal is to maximize the sum of
functions of individual link rates. Such problems arise in the context of, for
example, fractional frequency reuse (FFR) for macro-cellular networks and
dynamic interference management in femtocells. The resulting optimization
problems are typically hard to solve optimally even using centralized
algorithms but are an essential computational step in implementing rate-fair
and queue stabilizing scheduling policies in wireless networks.

We develop a stochastic foundation for bandwidth estimation of networks with
random service, where bandwidth availability is expressed in terms of bounding
functions with a defined violation probability. Exploiting properties of a
stochastic max-plus algebra and system theory, the task of bandwidth estimation
is formulated as inferring an unknown bounding function from measurements of
probing traffic. We derive an estimation methodology that is based on iterative
constant rate probes.

This paper proposes and analyzes the performance of a simple frequency-agile
CSMA MAC protocol. In this MAC, a node carrier-senses multiple frequency
channels simultaneously, and it takes the first opportunity to transmit on any
one of the channels when allowed by the CSMA backoff mechanism. We show that
the frequency-agile MAC can effectively 1) boost throughput and 2) remove
temporal starvation. Furthermore, the MAC can be implemented on the existing
multiple-frequency setup in Wi-Fi using multi-radio technology, and it can
co-exist with the legacy MAC using single radio.

The belief propagation (BP) algorithm is an efficient way to solve
"inference" problems in graphical models, such as Bayesian networks and Markov
random fields. The system-state probability distribution of CSMA wireless
networks is a Markov random field. An interesting question is how BP can help
the analysis and design of CSMA wireless networks. This paper explores three
such applications.

This paper is concerned with the concept of equilibrium and quality of
service (QoS) provisioning in self-configuring wireless networks with
non-cooperative radio devices (RD). In contrast with the Nash equilibrium (NE),
where RDs are interested in selfishly maximizing its QoS, we present a concept
of equilibrium, named satisfaction equilibrium (SE), where RDs are interested
only in guaranteing a minimum QoS. We provide the conditions for the existence
and the uniqueness of the SE.

The third generation partnership project (3GPP) has addressed the feasibility
of interworking and specified the interworking architecture and security
architecture for third generation (3G)-wireless local area network (WLAN), it
is developing, system architecture evolution (SAE)/ long term evolution (LTE)
architecture, for the next generation mobile communication system. To provide a
secure 3G-WLAN interworking in the SAE/LTE architecture, Extensible
authentication protocol-authentication and key agreement (EAP-AKA) is used.
However, EAP-AKA have several vulnerabilities.

We present an analytical model that enables a comparison of multiple design
options of Opportunistic Spectrum Orthogonal Frequency Division Multiple Access
(OS-OFDMA). The model considers continuous and non-continuous subchannel
allocation algorithms, as well as different ways to bond separate
non-continuous frequency bands. Different user priorities and channel dwell
times, for the Secondary Users and the Primary Users of the radio spectrum, are
studied. Further, the model allows the inclusion of different types of
Secondary User traffic.

We investigate the asymptotic behavior of the steady-state queue length
distribution under generalized max-weight scheduling in the presence of
heavy-tailed traffic. We consider a system consisting of two parallel queues,
served by a single server. One of the queues receives heavy-tailed traffic, and
the other receives light-tailed traffic. We study the class of throughput
optimal max-weight-alpha scheduling policies, and derive an exact asymptotic
characterization of the steady-state queue length distributions.

Our goal, in this paper, is to infer the topology of a network when (i) we
can send probes between sources and receivers at the edge of the network and
(ii) intermediate nodes can perform simple network coding operations, i.e.,
additions. Our key intuition is that network coding introduces
topology-dependent correlation in the observations at the receivers, which can
be exploited to infer the topology. For tree topologies, we design hierarchical
clustering algorithms, building on our prior work.

In this paper we investigate the evolution of the IPv4 and IPv6 Internet
topologies at the autonomous system (AS) level over a long period of time.We
provide abundant empirical evidence that there is a phase transition in the
growth trend of the two networks. For the IPv4 network, the phase change
occurred in 2001. Before then the network's size grew exponentially, and
thereafter it followed a linear growth. Changes are also observed around the
same time for the maximum node degree, the average node degree and the average
shortest path length.

In modern wireless networks, devices are able to set the power for each
transmission carried out. Experimental but also theoretical results indicate
that such power control can improve the network capacity significantly. We
study this problem in the physical interference model using SINR constraints.

We consider a GI/G/c/K-type retrial queueing system with constant retrial
rate. The system consists of a primary queue and an orbit queue. The primary
queue has $c$ identical servers and can accommodate the maximal number of $K$
jobs. If a newly arriving job finds the full primary queue, it joins the orbit.
The original primary jobs arrive to the system according to a renewal process.
The jobs have general i.i.d. service times. A job in front of the orbit queue
retries to enter the primary queue after an exponentially distributed time
independent of the orbit queue length.

Primary users (PU) separation concerns with the issues of distinguishing and
characterizing primary users in cognitive radio (CR) networks. We argue the
need for PU separation in the context of collaborative spectrum sensing and
monitor selection. In this paper, we model the observations of monitors as
boolean OR mixtures of underlying binary latency sources for PUs, and devise a
novel binary inference algorithm for PU separation. Simulation results show
that without prior knowledge regarding PUs' activities, the algorithm achieves
high inference accuracy.

Bandwidth allocation is a fundamental problem in communication networks. With
current network moving towards the Future Internet model, the problem is
further intensified as network traffic demanding far from exceeds network
bandwidth capability. Maintaining a certain user satisfaction degree therefore
becomes a challenge research topic. In this paper, we deal with the problem by
proposing BASMIN, a novel bandwidth allocation scheme that aims to maximize
network user's happiness. We also defined a new metric for evaluating network
user satisfaction degree: network worth.

One of the most critical tasks for network administrator is to ensure system
uptime and availability. For the network security, anomaly detection systems,
along with firewalls and intrusion prevention systems are the must-have tools.
So far in the field of network anomaly detection, people are working on two
different approaches. One is flow-based; usually rely on network elements to
make so-called flow information available for analysis. The second approach is
packet-based; which directly analyzes the data packet information for the
detection of anomalies.

Network management and security is currently one of the most vibrant research
areas, among which, research on detecting and identifying anomalies has
attracted a lot of interest. Researchers are still struggling to find an
effective and lightweight method for anomaly detection purpose. In this paper,
we propose a simple, robust method that detects network anomalous traffic data
based on flow monitoring. Our method works based on monitoring the four
predefined metrics that capture the flow statistics of the network.