**6.1. Conclusion**

94 Wireless Sensor Networks – Technology and Protocols

situations, such as the switching detection error.

solid line represents the actual display.

From these expressions, it could be found that with the increase in the length L, the ratio of the PFs to RFs increases, which means that more frames should be encoded and transmitted. In other words, the triangle will be enlarged and finally all the frames at the same time

In order to overcome this problem, the N(p, f, s) should be fed back periodically, which is able to divide a large triangle into many smaller triangles as shown in Fig. 16. In the UDMVT, the N(p, f, s) is fed back periodically at the end of the triangle. The fed back N(p, f, s) from the end of the previous triangle is used to predict the next triangle. Therefore, only potential frames are transmitted each time and the transmission bitrate is reduced. N(f, p, s) should be detected at client and fed back periodically. At the server, N(p, f, s) is used to divide the frames into PFs and RFs. The transmission bitrate can be reduce by only transmitting the PFs and ignore the RFs. Although the transmission of RFs is unnecessary, encoding and transmitting the RFs can work as a kind of insurance against some special

**Figure 16.** The triangles of the potential frames. Dotted line represents the possible display path while

(a) k = 1 (b) k = 2

instant are involved into the triangle, which is also shown in Fig. 15.

In this paper, at first, we analyzed the conventional non-aggregation, full aggregation, and our proposed partial aggregation with Markovian chain. The analytical result showed that, conventional method suffers large energy consumption with the highest accuracy, while full aggregation suffers long transmission delay, with the least accuracy. However, our proposed partial aggregation has the energy, delay and data accuracy between nonaggregation and full aggregation. When the random pushing rate becomes larger, the partial aggregation tends to non-aggregation and it tends to full aggregation with large random pushing rate. Hence, we find that the partial aggregation can trade off energy, delay and accuracy according to different applications. Secondly, we discussed the tradeoffs among data accuracy, transmission delay and energy consumption with different significances according to different applications by proposing tradeoff index (TOI). From the results, we find that non-aggregation has the best TOI for low event generation rate, that the partial aggregation does for moderate event generation rate, and that the full aggregation does for large event generation rate. At last, we discussed multiview multi-robot sensor network from the viewpoint of potential applications, existing schemes and our proposed UDMVT.
