Algorithm 4. PDACAS_CellHeader_Aggregate.

Input:

None

Output:

An intermediate aggregation result Dj

Method:

1. Broadcasts the ordered ID set Sj to all the sensor nodes in the cell;

2. Dj = 0;

3. Initiates a p-bit bitmap BITj, with each bit to be 0;

4. Sends Dj and BITj to the head node in Sj;

5. Waits for Dj and BITj to traverse the one-way circulation list of sensor nodes two times;

6. receives Dj;

7. Sends Dj to the sink.