Elaboración del Manual de Calidad

The set of physical parameters such as transmission power, distance and antenna orientation are fixed based on evaluation presented in Section 5.5.1 and listed in Table 5.6. The set of network parameters parameters are validated in this section. The results will be able to define the PHY parameters for the network performance. As setup section 5.4.3, the same scenarios are used to evaluate the set of network parameters. Data rate is swept from the minimum of 2 Kbps till 150 Kbps, and the corresponding paket delivery ratio is measured. The packet delivery ratio will indicate how many packets succeed in reaching the receiver. Upon varying the transmission rate, the effect of the physical medium on data communication can be fixed. Different packet size will help in identifying the number of retransmission in case of higher packet lengths. No MAC is used, hence until the packet is received at the receiver, the retransmission will be carried out. Upon exceeding the maximum number of retransmissions, the node will ignore the packet. However, in this experiment, as soon a packet fails, it is considered as a dropped packet. Results for different Scenarios are discussed in the following subsections. SC1 Transmission power, distance and orientation are listed in table 5.6. The packet length is fixed for each iteration of the measurement. In Scenario 1, as the packet length increases, even in the higher data rates, the packet delivery ratio is decreased. This indicates that the higher packet length, will make the node to communicate for a longer time. However, the failure of the packet can occur if the frame is corrupted due to very low RSSI. It is also conversely found that the higher data rates will not increase the packet delivery ratio, in case of higher packet length. For a fixed packet length, the PDR increases as the data rate increases. An important observation is that the PDR is almost constant at higher data rates for a fixed packet length. SC2In Scenario 2, as the packet length increases, even in the higher data rates, the packet delivery ratio is decreased. This behaviour is similar to that of the Scenario 1. The data rate is directly proportional to the packet delivery ratio, however it changes with that of the packet length. The packet length decreases the PDR in lower data rates and PDR increases as the data rate is increases. This indicates that the higher packet length, higher data rates is required to maintain the reliability of the network. The performance can be related to that of the SC1, since the Scenario is partially inside the

0 50 100 150 55 60 65 70 75 80 85 90 95 100 Tx rate Kbps

Packet delivery ratio %

Tx rate vs PDR (fixed packet length)

packet legnth (PL) 5 bytes PL 20 bytes PL 40 bytes PL 60 bytes PL 80 bytes PL 100 bytes

Figure 5.23: Tx Rate vs Packet delivery ratio evaluated with fixed packet length. Measured in SC1 flesh. 0 50 100 150 60 65 70 75 80 85 90 95 100 Tx rate Kbps

Packet delivery ratio %

Tx rate vs PDR (fixed packet length)

packet legnth (PL) 5 bytes PL 20 bytes PL 40 bytes PL 60 bytes PL 80 bytes PL 100 bytes

Figure 5.24: Tx Rate vs Packet delivery ratio evaluated with fixed packet length. Measured in SC2

SC3In Scenario 3, the behaviour of the network totally differs than that of the implanted nodes.

CHAPTER 5. CHARACTERISATION OF PHY LAYER OF AN IMPLANATABLE SENSOR NODE

The implications are similar to that of the data communication in the free space. It also important to notice that the distance in the SC3 validation is higher than that of the previous Scenarios. The dependency of the data rate and packet delivery ratio still is linearly proportionate. For higher packet length, the packet delivery ratio is lower in lower data rates. The analysis of the

0 50 100 150 80 82 84 86 88 90 92 94 96 98 100 Tx rate Kbps

Packet delivery ratio %

Tx rate vs PDR (fixed packet length)

packet legnth (PL) 5 bytes PL 20 bytes PL 40 bytes PL 60 bytes PL 80 bytes PL 100 bytes

Figure 5.25: Tx Rate vs Packet delivery ratio evaluated with fixed packet length. Measured in SC3

experimental results were studied and the results are explained. The selection of parameters for the next set of experiments are fixed as shown in table 5.7. The table indicates the values of the data rate and the packet length. The choice of the value is based on the results from the previous experiments. Small packet length with twice the data rate will have better performance in all the Scenarios. Thus in order to verify the network performance, the most suited parameters are chosen which is twice the packet length. In this scenario, the node can also send packets much faster, which will also reduce the congestion in the network and increase the reliability. Higher packet length resulting in lower packet delivery ratio is not a suitable candidate for the in-body sensor network.

Parameter Value Packet length 20 bytes

Data rate 40 Kbps

Table 5.7: Optimum parameters from hardware evaluation

5.6

Conclusion

from

characterization

of

implantable