# Exploiting Outage and Error Probability
## 2 Related Work
The opportunistic routing scheme selects the multiple nodes as a forwarding set and let any of those nodes, overhearing the data to forward the data to destination. A data packet is useful only if it arrives at the destination before a certain expiration time. In [23], the authors design an algorithm to minimize the probability of collision. Cooperative data transmission, optimal allocation of power and selection of route is considered in the proposed algorithm. The relaying technique used is incremental decode and forward. In this technique, the source node transmits its data via direct path, if the destination node is not able to detect the data packet, the relay node forwards the data packet to the destination node. Collision aware routing algorithm is also proposed which minimizes the probability of collision in the network. This algorithm consists of following steps. In first step each node computes the probability of collision when a signal is transmitted from one node to another. In second step, the Bellman-Ford algorithm is used to find the route that causes minimum collision. In third step the optimal power that is calculated by using Langrage Multipliers method is assigned to all nodes. Energy efficient cooperative routing in terrestrial WSN has been investigated in [24], where N numbers of sensor nodes are randomly deployed in two dimensional (2D) field to monitor a geographical area. The protocol utilizes decode and forward relaying technique to satisfy the prescribed SNR constraint at receiver node. It also utilizes the Bellman-Ford algorithm by assigning the required transmission power as link cost metric and invokes the multi-parametric programming theory to make their proposed framework tractable. This increases the transmission diversity and lowers the transmission power by employing the minimum power relaying policy. However, the trade-off between transmission power and reliability still exists in dense networks. A clustered WSN is considered in [25] where sensor nodes relay data packets in each cluster to neighbor clusters via cooperative communication. Sensor nodes in the same cluster have very short distance with each other. while the distance between the adjacent clusters is very large as compared to the distance between nodes within the cluster. This scheme functions in two phases: In first Phase nodes in a cluster transmit data packets to the cluster head. Then cluster head (Source node) broadcasts the packet with certain energy to the nodes within the same cluster. In second phase the sensor nodes that decode the packet correctly and the cluster head will transmit the packet to the receiving node. Cluster head is shown that it can adjust its power level for communication within the cluster in order to control the overall number of cooperators such that the overall energy consumption is minimized. In [26], Energy Efficient Cooperative Communication (EECC) scheme is proposed which is not basically a routing protocol but it helps to minimize packet loss and improves the transmission performance. At each hop between source and sink, cooperative relaying based communication is performed. In case a node does not receive a data packet, nearby nodes which have overheard the packet successfully will cooperate reactively and the best relay is selected out of them to participate in the transmission. This scheme minimizes retransmissions and provides better results in denser networks. Table 1 shows the comparison of techniques discussed in related work.