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schedule is followed by the base station as soon as it is turned on. The nodes have not yet received any sync packet from the BS, so their radios are kept on until a sync packet is received. In this way, the time schedule is being followed by the nodes. The node1 synchronizes node2 by re-transmitting a sync packet; since node2 cannot directly hear the base station.

3.1.3 能量分析——ENERGY ANALYSIS:

For energy analysis, a network of (n+1) nodes is considered so that the nodes can hear each other directly. In this circumstance, n nodes are transmitting to the base station, and in response to which received packets are conveyed to storage and analysis proposal.

“The expected energy spent in each node is the sum of the energy consumed in transmitting, receiving, sleeping and sensing states.”

Each term can be expressed as the average power in that state multiplied by the time the node is on that state [1]. Data packets are transmitted in every Tdata time interval. To enable no energy consumption due to idle listening tLP is kept large enough so that all packets generated by the nodes are received by the base station. All packets are considered broadcast packets.

Since the BS does not transmit data packets so every node will receive exactly (n-1) data packets. Only one synchronization packet is received by nodes that are originated in the base station in an interval Tdata, which is the only source of synchronization in SEA-MAC. The energy consumed by a node running SEAMAC is:

SEAMAC和其他协议的对比——COMPARISON OF SEA-MAC WITH OTHER PROTOCOLS:

By evaluating the energy consumption relation of SEAMAC with the other protocols it has been observed that:

SEAMAC saves energy by not polling the medium for possible transmissions.
SEAMAC saves energy by avoiding transmission of tone packets to wake-up nodes.
Less energy is consumed in synchronization because harmonization is initiated by the base station and one packet is enough to synchronize the entire network.
SEAMAC spends more time sleeping but since the energy consumed in sleeping time is fewer than that in any other state, it can be measured an unimportant feature.
Due to these reasons it can be said that SEAMAC outperforms the other protocols in the application of monitoring environmental variables. Some protocols attempt to combine the advantages of TDMA scheduling for power saving by periodically wanting sensing nodes become inactive. Furthermore, they are having a fixed duty cycle which is not preferable for an optimal performance for example SMAC.

Further more these protocols follow flat topologies in which inter cluster problems are absent. This topology cannot be implemented in applications where real clusters are to be formed. A significant portion of the nodes will belong to two or more virtual clusters under these protocols so energy consumption would be higher. What happens if the coordinated sleep schedules of two neighboring clusters are opposite?In such cases it is not guaranteed whether the nodes will adopt the different schedules or not. So to solve all the ambiguities it was necessary to study the performance of this scheme with different routing protocols in order to assess its performance of inter cluster communication especially for multi hop messages.

The intention of the projec