# Towards Efficient Wireless Body Area Network Using Two-Way Relay Cooperation
## 6 Joint Network-Channel Coding over Cooperative Link
### Simulation and Performance Evaluation  
The range of efficient data transmission is increased using multiple channel coding schemes. As complexity is a major issue in WBAN, simple coding schemes are employed to increase the efficient hop-length and improve reliability. Convolutional codes with code rates of 1/2 and 1/3 and BCH codes with error correction capability of 2 and 4 are studied and analyzed. The simulation results for convolutional codes with \(R=1/2\) and BCH codes with \(t=2\) are shown in Figure 14 for in-body communication and Figure 15 for on-body communication. An extended hop length of 7.5-10% in one-way relay communication and 5-7.5% in two-way relay cooperation for in-body, 8.5-14% for one-way relay communication and 5.5-8.5% for two-way relay cooperation in on-body LOS scenario and 5-7% for one-way relay communication and 3.5-5% for two-way relay cooperation in the case of on-body NLOS is achieved for cooperative communication in the simplest case i.e., convolutional code with code rate 1/2 and BCH codes with error correction capability of 2. Both codes almost result in the same improvement in link length. However, the degradation in case of BCH is more rapid compared to convolutional code. As the code rate in convolutional codes and error correcting capability in BCH codes increases, the length of link with efficient transmission also increases as depicted by Figures 16 and 17. The maximum extension in hop length is achieved for convolutional codes with a rate of 1/3 but that also means a large overhead i.e., three bits to be transmitted for a single data bit. The EE of the JNC coded links also depends on the packet size transmitted over the link. The EE results for packet sizes of 500 and 2000 bits show an increase in efficiency for larger data packet i.e., approximately 18-20% improvement in direct link and 11-13% in cooperative link. Similar results are achieved for the EE for BCH coded data for both in-body communication and on-body communication. The improved efficiency is observed at lower link lengths, but smaller packets provide greater hop extension and gradual decay for larger link distances. Figure 14: Energy efficiency for joint network channel (JNC) coded data, convolutional \(R=1/2\), BCH \(t=2\) (in-body communication). Figure 15: Energy efficiency for JNC coded data, convolutional \(R=1/2\), BCH \(t=2\) (on-body communication). (**a**) energy efficiency for JNC coded data, convolutional \(R=1/2\), BCH \(t=2\) (on-body LOS communication); (**b**) energy efficiency for JNC coded data, convolutional \(R=1/2\), BCH \(t=2\) (on-body NLOS communication). Asymmetrical Links and Larger Packets  
Despite the coding overhead, JNC coding provides an edge in case of asymmetrical links. The communication link gives maximum efficiency if the relay node is placed at equal distance from both source and destination nodes. Change in position of relay node deteriorates the performance of the system and minimizes the efficient length of the link. For example, in the case of in-body cooperation, a 20-35% decrement in efficient transmission length occurs, but if this link is coded, a compensation of 5-10% can be achieved. Similar to Figures 8 and 9, it is observed that larger packet sizes improve the EE at the cost of effective link length. For in-body communication link, approximately 7.5% decrement in effective link length is observed for a packet size of 2000 bits compared to 500 bits. Almost 13-18% improvement in efficient link length can be achieved with JNC coding. This is also true for on-body communication. Figure 16: Energy efficiency for JNC coded data, convolutional \(R=1/3\), BCH \(t=4\) (in-body communication). Figure 17: Energy efficiency for JNC coded data, convolutional \(R=1/3\), BCH \(t=4\) (on-body communication). (**a**) energy efficiency for JNC coded data, convolutional \(R=1/3\), BCH \(t=4\) (on-body LOS communication); (**b**) energy efficiency for JNC coded data, convolutional \(R=1/3\), BCH \(t=4\) (on-body NLOS communication).