## 4 EMOR Protocol Design for WSN in NAN
### Probe Message Forwarding Mechanism in Data Collection Scope  
All sensor nodes within long radio range \(R_{l}\) which received the broadcast message from the mobile sink, need to send a data set comprising of information such as source ID, status transition frequency, working-sleeping schedule and all neighbor IDs to the mobile sink node during the data collection period. The format of probe message being forwarded to the mobile sink can be seen from Table 1.  
The length of the probe message is 120 bits in which the source ID occupies 10 bits, working-sleeping schedule occupies 15 bits, status transition frequency and neighbor IDs have 10 bits each, sink ID has 10 bits, forwarders ID has 60 bits and EOH contains 5 bits. The \"Source ID\" represents the ID of the node sending the message to the mobile sink. The \"Working-Sleeping Schedule\" represents the information about whole working time and whole sleeping time of the respective node. \"Status Transition Frequency\" provides information about the transitions from working mode to sleeping mode and vice versa of the sensor node. \"Neighbor IDs\" includes the ID list of neighboring nodes to the source node. If there is no neighbor or all neighboring nodes are in sleeping mode, the \"Neighbor IDs\" field remains empty. Moreover, the \"Sink ID\" is related to mobile sink's SID and is used to indicate that the probe message being forwarded from the sensor node is specifically targeted for the desired sink node in case of multiple mobile sinks present in the network. \"Forwarders ID\" stores the IDs of nodes which have already forwarded this probe message to the mobile sink. This field is updated \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline \multirow{2}{*}{**Fields**} & **Source** & **Working-Sleeping** & \begin{tabular}{c} **Status** \\ **Schedule** \\ \end{tabular} & \begin{tabular}{c} **Neighbor** \\ **Transition** \\ **Frequency** \\ \end{tabular} & \begin{tabular}{c} **Sink** \\ **IDs** \\ \end{tabular} & \
\begin{tabular}{c} **Forwarders** \\ **ID** \\ \end{tabular} &
\begin{tabular}{c} **Expected** \\ **Optimal Hops** \\ **(EOH)** \\ \end{tabular} \\ \hline Length (bits) & 10 & 15 & 10 & 10 & 10 & 60 & 5 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Format of probe message in data collection scope. when a new node forwards this probe message to the mobile sink and adds its ID in the forwarders ID list. Likewise, \"EOH\" field stores the value of expected optimal hops needed for the source ID message to reach the sink node. As this probe message can be generated by any sensor node within the radio range \(R_{l}\) of the mobile sink, so it's quite probable that different working-sleeping schedules and status transition frequencies of sensor nodes can lead to inefficient probe message forwarding. Therefore, only the nodes that have received the probe message can participate in this forwarding mechanism. For example, for an intermediate node \(V_{S}\) receiving the probe message from one of its neighbors \(V_{r}\) as shown in Figure 3, the first step would be to check its own ID in the \"Forwarders ID\" field. If the probe message was not forwarded by this node \(V_{S}\), it will add its ID to \"Forwarders ID\" field, determine the total number of forwarders (TNF) for this probe message and then calculate (EOH-TNF). Now it will check the \"Neighbor IDs\" field and see which neighbor's EOH is closest to (EOH-TNF) as an optimal forwarder. Since the asynchronous working-sleeping cycle strategy is used in sensor nodes, if any sensor node \(V_{S}\) receives the probe message from its surrounding node \(V_{r}\), it will forward the probe message to one of its neighbors only if that neighbor node is in working mode. Likewise, it will not forward the probe message if there is no neighboring node or the neighbor is in sleeping mode. The probe message receiving and forwarding mechanism based on asynchronous working-sleeping cycle of nodes is depicted in Figure 3. Algorithm 1 provides the details about probe message forwarding mechanism.