## 3 Proposed EP-MAC Protocol Design
### Reservation of Slot and Data Transmission  
At the beginning of each frame the nodes that belong to the same virtual cluster will be synchronized with each other. After synchronization the reservation slot will be used for transmission agreement purpose between nodes. The node that has data to send will contend with other intended sender in a slotted CSMA/CA fashion. And the reservation will be done using the exchange of RTS/CTS technique used in IEEE 802.11 with slight amendment. The amendment is that the CTS message will be accompanied with the data slot number. And that particular couple of nodes who exchange the RTS, CTS successfully will use that data slot. The first couple of nodes who successfully exchange RTS/CTS will get data slot number 1. Data slot number will be sent by the receiver with the CTS. The transmission which involves one node as sender or receiver of the previous successful pair will get priority for the next slot. Priority can be controlled by changing contention window size as described in Section 3.6. Consecutive slot assignment of a node will minimize the on off radio of the node. Now the next couple of nodes who successfully transfer RTS/CTS will be given either data slot number 1 or slot number 2 depending on the mutual exclusiveness of the two transmission links. In fact the receiver, _i.e._, the node sending CTS will decide the slot number by looking at the sets of links created in the way described in Section 3.3 of the paper. In each data slot more than one communication is possible at a time. Which couple of nodes are allowed to communicate simultaneously, it can be found in the neighbors list table. So, the second couple will get the same slot as the previous couple or a new slot depending on the status of the mutually exclusiveness state of the two links in the neighboring list. Thus for the ith couple it can get any slot previously chosen by another couple or a new slot. But if one node is in common with in two transmissions either as sender or receiver in that case the transmissions will never be given the same slot at a time. For bursty traffic of large message, more than one consecutive data slot can be assigned to a particular link, if sender node of the link asks for more than one data slots during RTS. In that case receiver replies CTS with mentioning id of some consecutive slots. But during huge traffic this consecutive slot allocation to a particular node will be impractical and also it will promote unfairness. So during heavy traffic the ith slot can be given to every frame to that particular couple of node. Sothat RTS/ CTS exchange will be minimized for that particular couple. When a sensor node successfully exchanges RTS/CTS with another node then they wait for the time to see where one of them can successfully send a RTS or receive a RTS. If so then the node will be given consecutive data slot. If the next successful RTS is directed to other node then the previous couple will go to sleep with an agreement to wake up at the beginning of their designated data slot. There will be no wastage of the radio/energy due to the multiple on-off. Because the node intended to send multiple data to different nodes usually will do it in the consecutive time slots. The nodes who have failed to reserve any slot during reservation period will go to sleep until the beginning of the next frame. The nodes that successfully reserved slots will perform data transmission during this phase. Since this phase is in fact TDMA, so without any RTS or CTS data will be transmitted between nodes. In this transmission procedure the sensor nodes can save more energy because when a node wakes up it has a guaranteed data slot and thus performs transmission. The protocol ensures throughput maximization and best channel utilization because simultaneous transmission facilities among the neighbors are allowed. Another advantage is the bandwidth reuse.