Abstract:
Wireless Ad hoc Network (WANET) is a decentralized setup of randomly dispersed
and mobile nodes that do not depend on a pre-existing infrastructure. These nodes tend
to contend for scarce resources (time, space, bandwidth). This contention causes interference
which is one of the most significant degradation factor in communication. Successful
communication needs an efficient Medium Access Control (MAC) protocol for
enhancing the Transmission Capacity, which is defined as the maximum permissible density
of concurrent transmissions in an area, constraint to a specified outage probability.
This objective can be achieved by managing interferers around an intended receiver to
obtain a desired threshold of signal to interference plus noise ratio (SINR). If the required
threshold is not met, an outage occurs. Existing MAC schemes like Carrier Sense
Multiple Access (CSMA), Random back off and Guard Zone-based protocols, achieve
interference mitigation through suppressing some of active nodes. This prevents nodes
from transmission in a certain space during specified time which compromises the Transmission
Capacity. Intelligent Hybrid Spread Spectrum (IHSS) MAC is one of existing
schemes which used Direct Sequence Spread Spectrum (DSSS) for network wide nodes
and Slow Frequency Hopping (SFH) to maintain orthogonality between communications
with in a zone around each receiver. Normalized outcome of IHSS MAC showed superior
performance over previous schemes.
In this research, an improved IHSS MAC scheme is proposed which enhances the
Transmission Capacity of ad hoc network where nodes are randomly distributed in space,
according to homogeneous Poisson Point Process (PPP). Proposed method employs frequency
hopping, based on assigned orthogonal codes, to minimize the effect of interference
between simultaneous transmissions. Results depict the improved outcome and
help in establishing the tradeoffs between various network parameters, as per network
designer’s requirement.
