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Next, I¡¯d like to explain the first metric in priority determination. The first metric is link quality. To calculate the ETX of a link, each node should record t0, which is the time when the first hello packet is received and the number of packets it receives from the neighbor during the last w seconds. Then, according to the interval between t0 and the current time t and window w, the expected probability of successful transmission r(t) is calculated by the following Equation. The denominator is the number of hello packets that should have been received during the window, and ¥ó represents the broadcast interval of the hello packets. Count (t, t0) is the number of hello packets received during t-t0. As can be seen from the equation, there are three situations in terms of the difference between t-t0 and window time w. In SIGO, the asymmetry of the link is not considered, and only the expected probability of one-way transmission is used to calculate the link ETX. Assuming that the expected probability of a one-way transmission is r(t), then the link ETX is calculated using Equation (2). |
IEEE/ICACT20220087 Slide.13
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