  This paper presents, a Group Based Optimal Retransmission Medium Access
(GORMA) Protocol is designed that combines protocol of Collision Avoidance (CA)
and energy management for low-cost, short-range, low-data rate and low-energy
sensor nodes applications in environment monitoring, agriculture, industrial
plants etc. In this paper, the GORMA protocol focuses on efficient MAC protocol
to provide autonomous Quality of Service (QoS) to the sensor nodes in one-hop
QoS retransmission group and two QoS groups in WSNs where the source nodes do
not have receiver circuits. Hence, they can only transmit data to a sink node,
but cannot receive acknowledgement control signals from the sink node. The
proposed protocol GORMA provides QoS to the nodes which work independently on
predefined time by allowing them to transmit each packet an optimal number of
times within a given period. Our simulation results shows that the performance
of GORMA protocol, which maximize the delivery probability of one-hop QoS group
and two QoS groups and minimize the energy consumption.
