Turkmen Canli and Ashfaq Khokhar* Electrical and Computer Engineering Department Computer Science Department* The University of Illinois at Chicago IEEE ICC 2009 Introduction RMAC PRMAC Performance Conclusion Duty cycling Is widely used in design MAC protocols in WSNs To mitigate this energy consumption of idle listening One-hop S-MAC Multi-hop RMAC PRMAC RMAC ( routing enhanced MAC protocol ) INFOCOM 2007 SABC PION Final = C Next = A Prev = Null RTS SABC PION Final = C Next = B Prev = S RTSCTS SABC PION DATA SABC PION Final = C Next = B Prev = S RTSCTS D The DATA will be buffered DATA PION Final = C Next = A Prev = Null RTS DATA In the sleep period, single data packet is transmitted over multiple hops within one cycle. However, the protocol require new flow set up for every data packet If intermediate nodes in the flow have packets for the final destination of the flow, RMAC sets up new flow for all these packets PION PRMAC: 1 operational cycle and 4 PION packets RMAC: 3 operational cycles and 11 PION packets PION Two new fields, packetsToRecv and packetsToSend, have been added to the RMACs PION packet In the PION packet at the i th hop, these fields have the following meaning: i. packetsToSend is the number of packets node s i is planning to send to node d. ii. packetsToRecv is the number of packets node s i can receive from node s (i-1). i-1id packetsToRecvpacketsToSend i-1i PION node s (i-1) asks s i if it can receive N data packets i+1i+1 d i-1id PION i+1i+1 node s i replies to node s (i-1) that it can only receive N - x data packets node s i asks s (i+1) if it can receive M data packets M = N x + y : Interference Range r : Communication Range 1 th ACK 2 th ACK The maximum number of hops between node Y and node B is The communication latency, u, between any two nodes is computed as follows: x x x NAV policy for nodes overhearing a PION packet that are neither previous nor next hop nodes It reserves 3 time segments, for the confirmation of PION, data, and ACK segments Confirmation of PION packets: This time segment is reserved to prevent collisions during the reception of flow set up confirmation Assuming transmission of i th PION packet ends at time T i Any node that overhears this i th PION packet, reserves time segment given by equation : TiTi NAV Data Segments Assuming node B is i th node in the flow and it is going to receive N data packets time segment corresponding to j th data packet, TS(j), where, is given as follows: ACK Segments: packetsToSend (M) field of the PION packet includes the number of the data packets node B is expected to send Assuming node B is the i th hop node in the PION transmission, all ACK time segments for should be reserved N RX and N TX do not have to be equal and if N RX is bigger than N TX, N RX - N TX packets will be buffered Assume that node B is the i th hop node in the PION transmission. In order to receive j th data packet B needs to wake up at : When : sleep at ns-2 200 node randomly connected network selected 5 different source and destination node pairs and set up traffic flows Fig. 6 shows the end to end delay for chain scenario, normalized with respect to average end to end delay of RMAC We have presented PRMAC, a cross layer optimization based pipelined routing enhanced MAC protocol for wireless sensor networks Depending on traffic load, PRMAC can schedule multihop transmission of multiple packets