SATNAC 2008 Conference Papers
Protocols
Title: The Effects of
Distributed Packet Losses on LT Codes
Authors: Christopher
Botha (
Abstract: LT
codes are a relatively new class of codes (a sub-class of Fountain Codes) in
information theory. One application of LT codes is as a packet erasure code. LT
codes are a rateless code and are found to be more computationally efficient
than other FEC erasure codes. We investigate the effect of LT codes in the face
of distributed packet loss with the goal of obtaining results that could apply
to real-time streaming media applications. Our results in this paper show that
with the use of LT codes packet losses on a network lead to an overall
effective drop in mean throughput with no information loss. This property
coupled with computational efficiency shows promise for real-time media
streaming applications.
Title: A Multichannel
Satellite Scheduling Algorithm
Authors: John Gilmore (
Abstract: During the design process of the
South African Sumbandilasat satellite, a requirement was identified for a
store-and-forward type on-board communications payload. This will allow for
connectivity with remote rural ground stations. Due to other systems design
constraints, these communications were limited to a single, half-duplex channel
with 9600 baud capacity. This experience highlighted the requirement for a
multichannel payload, to cater for the rising need for higher bandwidth data
transfer to- and from remote parts of
Title: An Evaluation of SIP
Based Mobility in the IP Multimedia Subsystem
Authors: Richard
Good (
Abstract: Mobility will be the cornerstone of
any Next Generation Architecture. Users will expect seamless mobility across
available access networks without visible degradation of ongoing multimedia
services. The IP Multimedia Subsystem (IMS) is an IP communications framework
that provides an environment for the rapid development of innovative and
reusable services; SIP has been adopted as the signaling protocol for this
architecture. SIP is independent of the underlying transport protocols and type
of session being established making it an ideal candidate for supporting
terminal mobility in the IMS. In this paper we present two solutions for
terminal mobility in the IMS; the first uses standard SIP session
re-negotiation to transfer IMS sessions between different interfaces, this
approach involves full IMS Registration on the new interface. The second
approach maintains two active connections – the signaling remains on the
original interface while the media traffic is transferred to the new interface;
this approach requires that the terminal be under the coverage of overlapping
access networks for the duration of the session. The performance and tradeoffs
involved with these solutions are analysed. Both solutions are implemented in
the form of a practical IMS test-bed where they are subjected to realistic use
case scenarios.
Title: Cross-Layer
Optimization for Video Streaming Applications over IEEE 802.11 Mesh Networks
Authors: Nametshego
Moleme (
Abstract: In
recent years, multihop wireless mesh networks have emerged as the next
evolution in wireless network technology. The primary reason for this sudden
emergence emanates from the advantages provided by the mesh networking
technology. Wireless mesh networks provides ease of installation, cost
effective deployments, high level of scalability in a coverage area and
capacity, network flexibility and self-configuration capabilities. Furthermore,
wireless mesh networks are expected to provide seamless and ubiquitous wireless
communication. However, despite all these advantages, many research challenges
still remain in wireless mesh networks. One such challenge is the support of
real time applications such as video streaming. This paper presents a mechanism
for the transport of real-time video using a cross-layer optimization
technique. In this mechanism, rate adaptation is implemented in the data link
layer for channel error control, link stability and reliability. In the network
layer, the routing protocol is optimized for congestion control and optimal
route selection by using congestion information from the data link layer and link quality metric from the network
layer. Simulation results show that the proposed mechanism improves the
performance of multihop wireless mesh networks when UDP is used as the transport
protocol.
Title: Wise-DAD
Auto-Configuration for Wireless Multi-hop Networks
Authors: Murimo Mutanga
(
Abstract: Providing
unique IP addresses efficiently in ad-hoc networks is still an openresearch question.
Many protocols to address this problem have been proposed. Duplicate Address
Detection (DAD) is one of the most important components of IPaddress
auto-configuration protocols. DAD by
itself is not an auto configuration protocol but a means of checking for
duplicate IP addresses before an address could be assigned to a new network
node. The chance of a DAD procedure succeeding depends on the number of nodes
in the network and the number of free IP addresses remaining. As the network
size increases, the number of free IP addresses decreases hence the probability
of a failed DAD process increases. In this paper we present Wise-DAD to address
this problem. This goal was achieved by the introduction of passively updated
state information. We evaluate the performance of our solution through
simulation experiments.