# Exploiting Outage and Error Probability
## 3 System Performance Analysis and Our Proposed Cooperative Routing Protocols
### System Model and Performance Analysis  
Figure 1 shows the proposed system model that consists of a Source (S), Destination (D) and Relays (R), where \(R=\{R_{1},R_{2},...R_{m}\}\). \(m\) is maximum number of relays present in the common region of S and D's transmission range which is also called cooperative region. Each node is equipped with a single omni directional antenna. This work assumes only the special case of non-Line Of Sight (LOS) communication between the nodes due to presence of fish, sea weeds, garbage, salts, etc. For non-LOS communication Rayleigh fading distribution is used. Therefore, we have assumed that each link follows Rayleigh fading as in [27; 28]. Additive White Gaussian Noise (AWGN) is also considered to add aquatic noise effect. In the proposed model, Binary Phase Shift Keying (BPSK) is used as a modulation technique, AF as a relaying technique and Maximal Ratio Combining (MRC) as a receive diversity technique. \begin{table}
\begin{tabular}{l c c c c c c c} \hline \hline
**Ref. ** & **Isoses Addressed** & **Technique** & **Relaying Technique** & **Flaw/Deficiencies** & **Achievements** & **Cost** \\ \hline
[12] WSNs & packet collision minimization, Collision caused by & Branch and bound, Mixed & Incremental decode and forward & & Minimum collision & \\  & Collision caused by & mission zone in linear programming, CSMA CA & Incremental decode and forward & only a single cost & probability, maintained total & Energy consumption \\ \hline
[13] WSNs & Dependence of the ergodic & Pareto efficient scheme, channel state information & Decode and forward & Only single relay is used & Increase in channel capacity & Overhead \\ \hline  & Overheading of acoustic & & & & & Fraction of void node & \\
[14] UWSNs & channel, Hidden & Greedy algorithm, & Decode and forward & Longer Delay, Additional & & is decreased, Reduced, Reduced & End-to-end delay, \\  & terminal problem & Opportunistic routing & & energy consumption & redundant packets & Energy consumption \\ \hline
[15] WSNs & Inefficient utilization of channel & Incremental relaying & Amplity and forward & No end-to-end delay analysis & Reduced bit error rate, & Outage increases \\ \hline  & & & & & & \\  & & & & & & High throughput & \\ \hline  & & & & & & & \\ \hline  &  
The proposed system is supposed to follow incremental relaying cooperative diversity. Communication process takes place in two phases. In the first phase, S broadcasts its signal to D and R. If signal received at destination is of sufficient quality, relays are not supposed to retransmit data to destination. On the other hand, if destination receives low quality signal, then relays retransmit the signal one by one till the desired signal quality is achieved at D or all the relays are expired. A relay performs retransmission only once. It is assumed that the channel will experience same fading affects if it performs retransmission multiple times. Therefore, to save energy, relay's transmission is restricted to single attempt. This assumption also helps to balance the load among other relay nodes. If the retransmission from 1 st relay is not successful, it will not retransmit again. Instead, it signals the other available relay to perform retransmission. This process continues till the transmission is successful or the number of available relays are finished. Quality of a signal is measured in terms of SNR threshold, \(\gamma_{0}\). The value of \(\gamma_{0}\) depends on the sensing environment. Small value of \(\gamma_{0}\) means exclusion of relays and large value of \(\gamma_{0}\) means inclusion of relays. The received signals at relays and destination are mathematically expressed as:  
\[y_{SD}(t)=h_{SD}x(t)+n_{0}(t) \tag{1}\] \[y_{SR_{i}}(t)=h_{SR_{i}}x(t)+n_{j}(t)\] (2) \[y_{R_{i}D}(t)=h_{R_{i}D}x_{s}(t)+n_{i}(t)\] (3) \[x_{s}(t)=Gy_{SR_{i}}(t) \tag{4}\]  
where i, j = 1\(\rightarrow\) m. \(h_{SD}\), \(h_{SR_{i}}\) and \(h_{R_{i}D}\) are Rayleigh fading coefficients and \(n_{0}\), \(n_{i}\) and \(n_{j}\) represent channel noises.