## 4 Implementation Details
### Generating Heterogeneous Arrivals
For FCFS, all the packets were served in the sequence they were generated in, whereas for the prioritization illustrated by Figure 6b, the packet would have to wait for transmission of one packet of \(T_{2}\). Hence, the delay advantage for the \(T_{2}\) traffic is high with only a little cost for \(T_{1}\) traffic. Figure 8: Delays for Low (CBR) and High (Poisson) Priority Traffic. (**a**) FCFS (**b**) Prioritization. Figure 6: Comparison of PDR for Prioritization without Fragmentation. Figure 2:0 Delay Comparison for with and without Prioritization (Figures 3 and 5 Combined). Similarly, Figure 9 combined the results earlier presented in Figures 4 and 6. As seen from the figure, the PDR for CBR traffic is not significantly increased, however, that of Poisson traffic is further reduced. Hence, it has been found in this section that prioritization without fragmentation provides better performance for high priority traffic when compares to FCFS. ### Prioritization using Fragmentation

Fragmentation of low priority traffic has been implemented in this experiment. Initially, the fragment size was kept as 1 B for each packet size (for example, 60 fragments would be created for a single data packet when the packet size is 60 B), and subsequently, the fragment size was increased to reach the full packet size. The rationale behind selecting 1 B as the smallest fragment size is the fact that the intended testbed is mica2 platform; mica2 notes use CC1000 radio which can transmit 1 B as the smallest unit. We first discuss the experiments for fragment size = 1 B. #### 6.3.1 Fragment Size = 1B

In this experiment, after transmitting one byte of the \(T_{1}\) data packet, the transmission is paused for the duration of \(T_{INT}\), in order to facilitate the transmission of emergency/high priority traffic. In case a packet of \(T_{2}\) is generated at any node, it would listen to the medium for \(T_{CH}\), if the channel is free it immediately transmit. In case channel is busy with some ongoing transmission of low priority packet, the node continues to listen even after \(T_{CH}\) and begins its transmission as soon as the medium gets free during \(T_{INT}\); this causes the transmission of \(T_{1}\) packet to terminate. Hence, the delay of high priority traffic is reduced as it does not need to wait for the entire packet of low priority to complete its transmission and it could instead access the channel after transmission of short fragment. The packet of \(T_{1}\) which was interrupted, shall be completely retransmitted once the channel is available. It is to be noted that the protocol in its present form, does not buffer the transmitted fragments at the receiver's end; the bytes which were previously transmitted are considered lost. The influence of applying fragmentation scheme on the delay performance of low and high priority traffic for varying packet size is shown in Figure 2:1

The effect of applying fragmentation on the PDR of low and high priority traffic has been illustrated in Figure 2:2 As expected, the PDR is much higher for CBR with fragmentation because now the packets will have to wait even longer due to the channel being interrupted during the transmission of a single packet. The delay performance for the low and high priority traffic with & without fragmentation has been shown in Figure 2:3 For the case of 'without fragmentation', complete packet is transmitted as a single unit; in other words, fragment size is kept equal to the packet size. On the other hand, fragment size is kept as 1B for the case of 'with fragmentation'. Figure 12a shows that for low priority CBR traffic, the delay increases due to fragmentation, whereas Figure 12b indicates the delay advantage for high priority Poisson traffic. Figure 2:4 PDR Comparison for with and without Prioritization (Figures 4 and 6 Combined). Figure 2:5 PDR for Prioritization using Fragmentation (Fragment Size = 1B). Figure 2:6 Comparing the Influence of Fragmentation on Delay (**a**) Low Priority Traffic (**b**) High Priority Traffic.