## 6 Discussion  
This interference investigation provides insights and guidelines for BSN deployment configurations, such as the maximum traffic load of a BSN and the maximum BSN density, to meet the reliable communication requirements. For instance, in the moderate scenario, given the reliability requirement (PER is less than 0.05) and the reliability level (at least 90% of the data packets are transmitted reliably), the duty cycle of a BSN should be less than 10% (obtained from Table 3). Conversely, given that the duty cycle of a BSN is 10% and the reliability level is 90%, the maximum number of BSNs that can be accommodated on one channel is around 16 in the off-peak scenario (also obtained from Table 3). In addition, given the BSN density and transmission power, there is a maximum traffic load (duty cycle) for each BSN. For example, from Figure 4, given the reliability requirement (PER is less than 0.1), the maximum duty cycle of a BSN is around 30% with a transmission power of 0 dBm, while the maximum duty cycle of a BSN is around 20% with a transmission power of \(-10\) dBm. Also from \begin{table}
\begin{tabular}{|c|c|c|c|c|} \hline Parameter & Path & Path & Path & Path \\  & loss 1 & loss 2 & loss 3 & loss 4 \\ \hline \(d_{\text{0}}\) (cm) & 10 & 10 & 10 & 10 \\ \hline \(\Omega_{\text{l}}(d_{\text{0}})\) (dB) & 32.2 & 41.2 & 35.7 & 35.2 \\ \hline \(\sigma\) (dB) & 4.1 & 6.1 & 6.2 & 6.1 \\ \hline \(\gamma_{\text{on-body}}\) & 3.35 & 3.23 & 3.38 & 3.11 \\ \hline \end{tabular}
\end{table} 
Table 4: The parameter settings of the path loss model in case study. Figure 5: Average PER for different on-body path loss model. Figure 4, we know that when the transmission power is low, the main reason for erroneous or lost packet reception is the radio signal blockage by the human body rather than inter-user interference. Thus a minimum transmission power has to be ensured to avoid packet loss by blockage of human body. This is under the assumption that intra-BSN communication in a BSN is coordinated by the coordinator of the BSN following a centralized MAC. There are cases that BSNs employ a distributed MAC without a coordinator. As long as there is only one sensor node transmitting in a BSN at a time, the analysis results in the paper work. For the distributed intra-BSN MAC cases, we would suggest CSMA/CA for the interference mitigation scheme. The cases of multi-channel scenarios actually could be obtained easily from the single channel case by just considering the same number of networks on a single channel. Inter-user interference could be determined by a number of factors including distance between BSNs, human effects, and environmental effects. It is difficult to evaluate the performance of BSNs without specific application settings. According to our experimental experiences, when the experimental environment changes, the performance of a BSN could be 23% worse than the studied case. In addition, the investigation provides implications on mitigation schemes for inter-user interference in BSNs when the multitude of operating scenarios is predetermined. For instance, we may reduce the probability of overlapping transmission to improve the SINR. To achieve this goal, transmissions of neighboring BSNs can be rescheduled to avoid overlapping transmissions when the BSN density is low. Moreover, when the BSN density is high, exceeding the maximum number of BSNs that can be accommodated, a channel switching scheme can be incorporated to reduce the congestion level of the current channel. In addition, each BSN is able to select its transmission power adaptively according to its surrounding environment and performance requirement. The BSN with higher priority use higher transmission power to ensure its reliable transmission. In the future work, we proposed a lightweight and distributed inter-user interference mitigation scheme, that can be easily integrated with the IEEE 802.15.4 protocol stack.