Uncoordinated
Cooperative Communications in Highly Dynamic Wireless Networks
ABSTRACT:
Cooperative
communication techniques offer significant performance benefits over
traditional methods that do not exploit the broadcast nature of wireless transmissions.
Such techniques generally require advance coordination among the participating
nodes to discover available neighbors and negotiate the cooperation strategy.
However, the associated discovery and negotiation overheads may negate much of
the cooperation benefit in mobile networks with highly dynamic or unstable
topologies (e.g. vehicular networks). This paper discusses uncoordinated cooperation
strategies, where each node overhearing a packet decides independently whether
to retransmit it, without any coordination with the transmitter, intended
receiver, or other neighbors in the vicinity. We formulate and solve the
problem of finding the optimal uncoordinated retransmission probability at every
location as a function of only a priori statistical information about
the local environment, namely the node density and radio propagation model. We
show that the solution consists of an optimal cooperation region which
we provide a constructive method to compute explicitly. Our numerical
evaluation demonstrates that uncoordinated cooperation offers a low-overhead
viable alternative, especially in high-noise (or low-power) and high node density
scenarios.
ARCHITECTURE:
EXISTING
SYSTEM:
Due to associated coordination
overheads, existing cooperative methods are suitable mostly for mesh or sensor
networks with static or relatively stable topologies. They are not useful when
the topology is very dynamic, due to either a high velocity (e.g. vehicular
networks) or a high density of the nodes (e.g. networks of mobile devices
carried by people on a busy street or conference hall). Indeed, if a network is
highly dynamic, the coordination overheads are incurred too frequently to be
practical even just to maintain an up-to-date view of the neighbor topology,
let alone up-to-date channel state information to the neighbor nodes.
PROPOSED
SYSTEM:
We consider an uncoordinated
cooperative retransmission framework, where cooperative nodes overhearing a
packet make retransmission decisions independently — with no prior
coordination or measurement of real-time channel information to other nearby
nodes, and even without being aware of their existence (apart from the
transmitter and receiver of the packet). Thus, the decisions at each node (e.g.
whether or not to retransmit an overheard packet, and the transmission power or
modulation to use) may only be based on the location of that node, the
locations of the sender and receiver, and some limited prior statistical
knowledge about the local environment, namely, the spatial distribution of the nodes
and radio propagation characteristics.
The concept of uncoordinated
probabilistic forwarding arises in many other networking contexts, such as
probabilistic flooding or gossip protocols and opportunistic forwarding in
delay-tolerant networks. It frequently leads to distributed optimization of
global performance objectives (e.g. delivery probability or latency) by tuning
the transmission probabilities at the individual nodes.
SYSTEM
REQUIREMENTS:
HARDWARE REQUIREMENTS:
•
System : Pentium IV 2.4 GHz.
•
Hard Disk :
40 GB.
•
Floppy Drive : 1.44 Mb.
•
Monitor : 15 VGA Colour.
•
Mouse :
Logitech.
•
Ram :
512 Mb.
SOFTWARE
REQUIREMENTS:
•
Operating
system : Windows XP.
•
Coding
Language
: C#.NET
REFERENCE:
Lixiang Xiong, Lavy Libman, and Guoqiang
Mao“Uncoordinated Cooperative Communications in Highly Dynamic Wireless
Networks”, IEEE JOURNAL ON SELECTED
AREAS IN COMMUNICATIONS, VOL. 30, NO. 2, FEBRUARY 2012
