  Quality of Service (QoS) for MANETs becomes a necessity because of its
applications in decisive situations such as battle fields, flood and earth
quake. Users belonging to diverse hierarchical category demanding various
levels of QoS use MANETs. Sometimes, even a low category user may need to send
an urgent message in time critical applications. Hence providing prioritization
based on user category and urgency of the message the user is sending becomes
necessary. In this paper we propose Enhanced MAC parameters to support Hybrid
Dynamic priority in MANETs(H-MAC). It combines both prioritization based on
user categorization and dynamic exigency. Order Statistics is used to implement
dynamic priority. We propose dynamic TXOP, Proportional AIFS and Proportional
dynamic Backoff timers based on weights and collision, to avoid packet dropping
and starvation of lower priorities. The model is simulated in ns2. We compare
our results with IEEE 802.11e and show that, 16% more throughput is achieved by
H-MAC during extensive collision. We also observe that starvation and packet
drops are reduced with proportionate bandwidth sharing compared to the existing
model.
