The cluster head broadcasts its status to the other sensors in the network. Each sensor selleckbio node determines to which cluster it wants to belong by choosing the cluster head that requires the minimum communication energy. Once all the nodes are organized into clusters, each cluster head creates a schedule for the nodes in its cluster. This allows the radio components of each non-cluster-head node to be turned off at all times except during its transmit time, thus minimizing the energy dissipated in the individual sensors.2.2. Cooperative CommunicationThe physical phenomena monitored by sensor networks, e.g., forest temperature, water contamination, usually yield sensed data that are strongly correlated. Data aggregation is the tool by which the correlated data size can be significantly reduced depending on the correlation factor.
Figure 2 explains the cooperative communication where the sensors at cluster 1 send the information data to the cluster head os cluster 2. At the first step, the sensors at cluster 1 send the data to their cluster head. The cluster head then aggregates the data in the second step. After the aggregation, the cluster head send the aggregated data back to all the sensors in that cluster. This is the step three in cooperative communication. At this stage, all the sensors at cluster 1 have the same information data. At the fourth step, the sensors transmit the aggregated data to the cluster 2. After receiving the data at the receiving cluster, sensors at cluster 2 transmit the received data to their cluster head locally and complete the cooperative communication.
Figure 2.Cooperative communication.3.?Error Correction Codes in Wireless Sensor NetworkError control coding (ECC) introduces redundancy into an information sequence u of length k by the addition of extra parity bits. Several different types of ECC exist, but we may loosely categorize them into two divisions: (1) block codes, which are of a fixed length nC, with nC ? k parity bits, and are decoded into one block or codeword at a time; (2) convolutional codes, which, for a rate Batimastat k/nC code, input k bits and output nC bits at each time interval, but are decoded in a continuous stream of length L >> nC. Block codes include repetition codes, Hamming codes [17], Reed Solomon codes, and BCH codes [18].
Short block codes like Hamming codes can be decoded by syndrome decoding or maximum likelihood (ML) decoding by either decoding to the nearest codeword or decoding on a trelli
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