# A Novel Bitrate Adaptation Method for Heterogeneous Wireless Body Area Networks
## 5 Simulation Studies and Analysis of the Obtained Results  
To reliably determine the usefulness of the analyzed methods dedicated for WBANs operating in variable propagation conditions, a scenario representing a movement along an L-shaped corridor with both LOS and NLOS conditions was analyzed. The initial parameters of the WBAN included the transmitted signal power, the number of network nodes, and the duration of a single time slot. In addition, the initial throughputs for the NB interface and the number of available thresholds (an important parameter of known methods for adaptive data stream allocation, i.e., ARF, ALBS, LA) were set. As it was previously mentioned, for the UWB interface, there were only two bitrates available.  
It was decided to determine the optimal value, in terms of the cumulative RMS value of the network throughput, of the bitrate threshold number that should be used to maximize the efficiency of the analyzed algorithms (besides the AMASD, which smoothly changes the bitrate in a determined range).  
The impact of the number of threshold values on the efficiency of the methods was analyzed for the same data set, and the results were averaged for all montage locations of the MN. It must be noted that if the RMS value was closer to 0, the available algorithm used the resources more efficiently. To avoid a random factor, the probability of receiving the packet, \(P_{REC}(P_{0})\), was calculated, as in (15). In Figure 7, the results of the analyzed methods' effectiveness as a function of the deterministic number of threshold values are presented.  
Based on the results, it was determined that the value of 6 available thresholds for bitrate adaptation is the optimal value for all algorithms, considering the smallest, cumulative RMS. It is also worth noting that the number of thresholds greater than 6 does not significantly increase the effectiveness of resource usage and even worsens it. This is due to too many changes in the data rates, which leads to an increased inertia of selected methods (through a slow bitrate change) and, consequentially. a packet's loss at the sudden change of the parameters, e.g., due to the change in the LOS/NLOS conditions.  
Due to the non-deterministic nature of the developed propagation model (13), radio distance measurements (Table 2), detection of the LOS conditions (Table 3), LQI (14), probability of packet reception (16), and the user's motion with the MN, all scenarios were analyzed for 10 user walks, and for each MN montage location, for a time of about 6 min, which corresponds to about 9000 user data transmissions in 20 ms time slots. The time interval between the start of two successive slots to send user data was 40 ms. Such a number of transmissions enables a reliable assessment of the analyzed methods' usefulness for adaptive data stream allocation in WBANs. In Table 4, the chosen parameters of the WBAN heterogeneous simulator are presented.  
In addition to the values presented in Table 4, the results of other measurements, like the propagation model parameters, the RDMs error, etc., were also investigated. It is worth noting that the transmitted signal power in both RIs are adjusted in such a way that along the signal propagation path (along the corridor) there are changes in the received signal power, forcing the calculation of the probability of receiving the packet, \(P_{REC}(P_{0})\), using the linear functions,\(f_{1}(P_{0})\),\(f_{2}(P_{0})\), according to the expression (16). This highlights the reasonability of using methods for adaptive data streams allocation by rate adaptation and differences in their operation.