# Tag-to-Tag Interference Suppression Technique Based on Time Division for RFID
## 5 Computer Simulations
### Many Tags with Random Time Slots  
Finally, in order to illustrate the interference-suppression performance of the proposed RFID system compared to the conventional system and an anti-collision RFID system based on the gold-code sequence, we present simulation results based on the use of a large number of tags with random time slots in a reader interrogation zone. Figure 11: FER curves of the proposed and conventional systems with a frame length of 512 bits (distances of 1.5, 1.8, 2.1 and 2.5 m). Figure 10: FER curves of the proposed and conventional systems with a frame length of 144 bits (distances of 1.5, 1.8, 2.1 and 2.5 m). Figure 12 shows BER curves (at a distance of 0.8 m) for different SNR values with the proposed RFID system, the conventional system without the anti-collision technique in the presence of 250 interference tags (30 tags at distances ranging from 1.5 m to 4 m, 80 tags at distances ranging from 4 m to 7 m, and 140 tags at distances ranging from 7 m to 10 m) in an interrogation zone. In Figure 12, we observe that the proposed RFID system has a much better performance than the conventional system, because the BER curve of the proposed system is much lower than that of the conventional system. In Figure 13, we consider four tags of interest, which have different distances (0.5, 0.6, 0.7 and 0.8 m) and unique time slots in the presence of 510 interference tags (60 tags at distances ranging from 1.5 m to 4 m, 150 tags at distances ranging from 4 m to 7 m, and 300 tags at distances ranging from 7 m to 10 m) in an interrogation zone. In Figures 13 and 14, we compare the performance of the proposed RFID system to the conventional system and an anti-collision RFID system based on the gold-code sequence. From both figures, we observe that the proposed RFID system works properly in the interference environment for all cases and it has better performance than that of the gold-code anti-collision RFID system, while the conventional system without the anti-collision technique has high BERs for all SNRs in all cases. The SNR analyses for results of Figures 13 and 14 are shown in Tables 1 and 2, respectively. For these analyses, we consider the data reliability rates at 90%, 95%, 97%, and 99% at different distances and we indicate the minimum SNRs for achieving the considered data reliability rates in Tables 1 and 2 for Figures 13 and 14, respectively, for the proposed RFID systems, the gold-code anti-collision RFID system, and the conventional system. From both Tables, we observe that the required minimum SNRs for achieving all reliability rates for the proposed RFID system are lower than them of the gold-code anti-collision RFID system in both cases, while the conventional system does not make the considered data reliability rates for all SNRs in both cases. Figure 12: BER curves of the proposed and conventional systems at a distance of 0.8 m in the presence of 250 interference tags. Figure 14: BER curves of the proposed system, conventional system without anti-collision technique, and anti-collision system based on gold-code systems, for four tags of interest with different distances in the presence of 270 interference tags.