Delay and jitter analysis of Generalized TDMA with General Traffic ( K. Khan and H. Peyravi) The
TDMA (Time-Division Multiple Access) protocol with its variants
has been widely used and extensively researched in various
wire-line and wireless communication networks. Major medium access
control (MAC) protocols (e.g., random access, fixed and demand
assignment protocols),
time slot interchange switches, and multiplexers are based on TDMA. The
next generation of wireless networks are expected to support multimedia
and real-time applications with quality of service (QoS) guaranteed.
The General Packet Radio Service (GPRS) that allows continuous wireless
connection to data networks is based on TDMA is such an example. The
GPRS technology allows mobile phones to be used for sending and
receiving data over an Internet Protocol (IP)-based network.
Most previously performance analyses of TDMA have been based on the
assumption of symmetric and predictable traffic distributions. It has
been assumed that either the message inter-arrival time is exponentially
distributed and/or the message length is geometrically distributed.
While these assumptions provides analytical simplicity to estimate
different performance metrics of a communication channel, they may not
realistically reflect the behavior of modern traffic which are either
correlated and/or bursty in nature. In this research project, first we
relax the above assumptions and present a delay and jitter
performance analysis of a generalized TDMA for a general traffic.
Second, we present the analysis for two resource allocation
models, namely consecutive and interleaved slot assignment schemes within a frame time.
Fault tolerant routing in wireless mesh networks (Y. Drabu and H. Peyravi)
Multi-hop Wireless mesh networks (WMNs) are emerging as a viable alternative solution for cost effective access networks. WMNs
can fill the capacity and coverage limitation of traditional cellular,
point-to-point wireless systems. In contrast to traditional cellular
system, WMNs need only one access point to the wired network, while
other access points share a connection over the air. Wireless mesh
networks combine several existing technologies and concepts from
cellular, ad hoc, and sensor networks to improve network coverage, easy
of deployment and better throughput.
In this project, we propose and design a fault-tolerant WMN based on a hexagonal topology
with multi-radio and directional vectorized antennas. For this model,
we introduce an addressing and routing scheme that simplifies the
network operations. Further, we extend the routing approach to cope
with one or multiple network link failure, as link failure is common in
wireless networks. To address this, we exploit the regularity and
multipath characteristics of an augmented tri-sectionized hexagonal
system to route around link or node failures.
MAC layer misbehavior in wireless networks (J. Hoblos and H. Peyravi)
In
wireless networks such as IEEE 802.11, the nodes contend to
access the medium through a loosely distributed coordination via
contention ( e.g., CSMA/CA) . In these networks the access fairness is
provisioned through a uniform random access mechanism that
is maintained by an exponential or uniform back-off algorithm.
However, nodes can easily gain more access to the
medium by manipulating their internal back-off algorithm. A
selfish node can reduce its contention window and gain better
throughput while other nodes can suffer from media access and
hence degradation in their throughput. This misbehavior cannot easily
be detected if the base station simply collects samples of back
of values. In fact a selfish node can reduces its contention
window in an statistical manner and in short run while maintaining the
statistical characteristics of its back-off values without being
detected in a long term. In this project, we are investigating
several statistical techniques to identify a selfish node.
Optimal gateway placement in wireless mesh networks (Y. Drabu and H. Peyravi) The placement of gateways
in wireless mesh networks has a critical impact
on the overall performance in terms of throughput and capacity. Finding
optimal
locations through search space not only is computationally
intractable,but also infeasible due to the dynamic nature of the
traffic flows. In
this project, we consider the problem of optimally placing a given
number of gateway routers in a wireless mesh with the objective to
minimize the
transmission blocking probability. We are investigating the
performance of spacing the gateways uniformly for an end-to-end
performance with uniform loads that are independently
distributed across the network. Through simulation and analysis, we
are investigating the performance gains one can achieve by
different
placement policies such as uniform placement, random placement, and
hot-spot placement for uniform and non-uniform traffic models. For
nonuniform link load, we provide a dynamic programming algorithm
for
the optimal placement and compare the performance with random and
uniform placement. We are also investigating the effect of
different traffic models and applications on the placement algorithms.
Dynamic bandwidth management in IP networks (Y. Drabu and H. Peyravi) While
a significant portion of Internet traffic is still best effort,
emerging applications with different quality of service(QoS)
requirements (e.g., multimedia) are evolving at a faster pace and
require more than best-effort services. The Integrated Services
(IntServ) model attempts to achieve an end-to-end per flow QoS through
RSVP, however it lacks scalability. The differentiated services
(DiffServ) model, on the other hand, attempts to classify packets based
on their QoS requirements to receive different services, and it is the
focus of recent IETF activity. To ensure QoS, the admission control
policy and the packet scheduler should work in tandem to i) control the
misbehaved traffic through policing, shaping, metering, pricing
techniques, and ii) contain the delay, delay variation, packet loss
rate, and bandwidth loss through robust packet scheduling policies. In
this project, we investigate an adaptive admission control that reduces
bandwidth loss when the traffic is light and enforces a stringent
traffic regulation when the traffic load is high. A similar mechanism
is used for the packet scheduler that maintains the QoS metrics
adaptively within their limited boundaries. Internet2 traffic traces
and Opnet synthetic traffic are being used to evaluate the performance
of the algorithms.
Traffic Management and QoS Provisioning in
IP Networks(Y. Drabu, K. Khan and H. Peyravi)
The objective of this work is to investigate the impact
of self-similar traffic on the performance of output buffers in
switches and routers. It is a known fact that the superposition of
independent alternating renewal processes (flows) can show self-similar
characteristics. Since analytical and empirical studies have shown that
self-similar traffic can have a detrimental impact on the QoS, finding
an effective buffer management algorithm that can manage self-similar
traffic has become an important problem in traffic engineering. Optimal
resource allocation is directly affected by optimal buffer size and
buffer management policy, bandwidth assignment and traffic management.
In this project we study the effect of self-similar and bursty traffic
on the triggered threshold buffer management algorithms. Besides the
second-order self-similar traffic, we are investigating the effects of
fractional Brownian motion on active queue management schemes.
Recent Publications:
Y. Drabu and H. Peyravi. Fault Tolerant Routing in Tri-Sector Wireless
Cellular Mesh Networks. In Proceedings Parallel and Distributed
Computer Systems (PDCS), pages 209-216, San Francisco, USA, September
2006.
M.
K. Khan and H. Peyravi. Delay and jitter analysis of generalized
demand-assignment multiple access (DAMA) protocols with general
traffic. In HICSS ’05: Proceedings of the 38th Annual Hawaii
International Conference on System Sciences (HICSS’05) - Track 9, page
304.1, Washington, DC, USA, January 2005. IEEE Computer Society.
Y.
Drabu and H. Peyravi. An adaptive bandwidth control algorithm for IP
routers. In Proceedings International Conference on Communications in
Computing (CIC), pages 311–317, Las Vegas, USA, June 2004.
