## 4 The Proposed Method: SLP-E
### Protocol Execution Phase
#### 4.2.1 Scenario-1  
A sensor node changes into a source node after detecting an asset and begins transmitting packets to the base station using the proposed SLP-E technique. The following five phases of the routing protocol in this instance are described as follows:  
* _Phase-1_: To generate a reverse random walk named a backward random walk (BRW), upon detecting an asset within its sensing range, a source node conducts a check of its location in relation to the base station (BS). If the distance between the source node and the BS is determined to be less than or equal to one-fourth of the network radius measured from the BS's position, it identifies itself as being in scenario-1. Subsequently, the source node examines the details of its neighboring nodes, which are categorized into lower neighbors, equal neighbors, and distant or far-away neighbors (the specifics of these neighbor nodes are provided in Section 4.1). From this analysis, the source node establishes the farther neighbors as its forwarding set, and among these farther neighbors, it selects the node with the highest energy to forward the packet. The packets are sent in the opposite direction using the farther neighbor set, away from the base station position. The source determines each packet's hop count to travel in this direction, and this value is chosen randomly between one-third and two-thirds of the network radius (both these values are measured in terms of hops; mathematical analysis that shows the way of calculating the number of hops in each phase is delivered in Section 6.1). We choose these restrictions so that the packet can only travel a certain range (measured in hops). By doing this, when the source node is close to the base station, the packet is prevented from reaching the network boundary. No matter where the source node is in the network, this results in energy conservation, packet delay reduction, and the balance of network lifetime (NLT) and safety period. The hop count number is reduced by one count once this packet is received by a neighbor node, and the neighbor node with the highest residual energy is the one chosen from the list of neighbors to relay this packet. This process continues as long as the hop count value in the packet is non-zero. When the hop count value in the packet is zero, phase-2 of the routing process begins. The phantom node (PN) is the node at which the BRW terminates. * _Phase-2_: In this phase, the packets are relayed in either a clockwise or anti-clockwise direction. The phantom node decides whether to send the packets in an anti-clockwise or clockwise direction with a coin toss experiment and relays the packets to a neighbor that is in an equal neighbor set. This procedure of transmitting is repeated for \(H\) hops, where \(H\) is a random number selected between \(45^{\circ}/\theta\) and \(180^{\circ}/\theta\), where \(\theta\) is the hop size in an annular walk and its corresponding number is determined utilizing Equation (4). The virtual source (VS) refers to the node where the transmission process ends in this phase. * _Phase-3_: From the virtual source, the packets travel in an inward direction towards the BS for certain hops. In this phase, the packets are forwarded to at least two hops in the inward direction from the VS, and the maximum distance they travel is up to the boundary of the inner circle (see Figure 1). The inward walk lower limit in this phase is two hops from the VS, and the upper limit is the boundary of the inner circle (with pink color). Intermediate node-1 (IN1) is found randomly between those set limits. Unlike in the existing solutions where packets are sent directly to the BS through min-hop routing (shortest path routing), in this phase, one additional intermediate node (IN1) is chosen randomly between two nodes away from the VS and the boundary of the inner circle which is showing the threshold value. This improves the routing path's randomness and diversity.