## 9 Performance Evaluation
### Transmission Rate Privacy  
To handle this issue, we have adopted two threshold values: R\({}_{\text{min}}\) and R\({}_{\text{max}}\) where the sensor needs to keep its message transmission rate between these two values. The sensor needs to send real message at the end of subinterval time slot. If it does not have a real message, then it needs to send a fake message only if that time slot is scheduled to send a fake message according to ECAT protocol, otherwise no  
Figure 26: The average fake messages in a busy network with 70% of the slots occupied by real messages. The reduction of fake messages transmission in ECAT is about 88% compared to SGAT. transmission will happen and the slot remains idle. Ideally, the sensor has a real message at the subinterval so it does not need to waste a slot by sending a fake message. The sensor can use this facility to control the threshold data rate. For instance, if the rate is high (such as in areas nearby the BS), it can replace fake messages with real messages which is a double fold beneficial. If all the fake messages are already replaced and still there is real messages above the threshold, then the sensor is required to queue the messages and delay the transmission to maintain same average message rate between \(R_{min}\) and \(R_{max}\). In contrast, if the message rate is low (as in the periphery sensors), then the sensor can transmit more fake messages during idle slots. We have simulated the network in Figure 15 for ECAT and assigned the \(R_{min}\) to be _thirteen_ messages for two consecutive (\(\overline{\omega}\)) intervals (a total of 20 subintervals). We have assigned the R\({}_{\max}\) to be 13 messages during this period, which is seven less than the total number of subintervals. That means we allow up to 13 real and fake messages during these two consecutive (\(\overline{\omega}\)) intervals. Figure 27 exhibits the output of the simulation for four different individual transmissions. For instance, the first transmission shows, 14 real messages (blue bar), 2 fake messages (light blue bar), and _four_ idle slots (green bar). The total real and fake messages is 16 (_orange bar_) which is above the assigned threshold, _thirteen_, by _three_ messages, which is expressed by the brown bar. The SN will cancel _three_ fake messages out of the _four_. In some worse cases, the sensors would need to queue the messages for next slots. For instance, if there is 15 real messages during this time, the system send only 13 messages and queue 2 messages for the next period. Ultimately, the overall message rate during T\({}_{\text{art}}\) will be within the assigned thresholds. Figure 27: The simulation shows the total real messages, fake messages and idle slots. The threshold rate is _thirteen_ messages over \(T_{\text{art}}\) period. For instance, the first transmission shows total of _sixteen_ messages, which is _three_ above the threshold value. The sensor will cancel three fake messages. The third set shows the number of transmissions at the threshold. We have simulated this approach extensively for (500), (1000), (1500) and (2000) transmissions as exhibited in Figure 28. The first, third and fifth bar sets show the total amount of fake messages needed to be replaced with real messages to maintain \(R_{min}\) for the thresholds of th = 10, th = 11 and th = 12 consecutively. For instance, a threshold of 10 means that the maximum number of messages transmitted should be 10 (out of 20 in our simulation). The second, fourth and sixth bar sets also show the number of messages which needed to be queued for the three consecutive threshold values. Therefore, if we have real messages above the number of scheduled fake messages, then we have to queue the messages for the next period of T\({}_{\text{art}}\). Overall, this simulation exhibits a great preference since we always would like to reduce the amount of fake messages and keep the bandwidth busy with real messages whenever it is possible. In addition, the simulation exhibits very small messages need to be queued (delayed).