In order to exploit the information about the actual channel status, we define the probability of contention failure,, to be the probability that a request slot transmitted by the SS of interest fails (collisions), and the utilization factor of contention period,, to be the average utilization rate of contention periods.
The possible reason behind this is, when the number of transmission attempts are low, the probability of contention failures is not large enough to penalize a channel with low PU activity from getting selected; therefore, most SU select those ending up with higher collisions.
Since the probability of a contention failure is defined as the probability that a transmitted request encounters a collision, this yields.
Finally, channels C 3 and C 4 have values 6 and 8, respectively, and they are common to both nodes N 1 and N 2. Going on this manner, CCL of the N 1 N 2 pair would include channels C 3 and C 4 in the same order, because, as mentioned, we give higher priority to those channels that are 'less common' throughout the network, so as to increase the probability of winning contentions.
Notations and variables Meaning and explanation Number of estimated active connections Probability of a contention failure Transmission probability Utilization factor of contention period Optimal value of parameter p Initial backoff window size Maximum backoff window size Maximum number of backoff stages Average contention window size Optimal contention window size.
To find this channel set, we have to calculate the probability of winning the contention on a given idle channel i.
Heusse et al. [16] theoretically analyzed the performance anomaly of 802.11b [17] by deriving expressions for throughput, probability of collision, and contention time.
Equation 2 gives the probability of winning the contention conditioned on, the backoff time τ of SU j, the number of other SUs trying to access channel i which is r and the given SU j is trying to transmit on channel i.
Because the packet transmission probability adopted by DB at the high network density can reduce the high degree of contention, DB's probability of single hop broadcast failure was low.
In cases of small busyness probability, (light contention) is a suitable and tight approximation for ; thus, a linear equation with least difficulty in computations is obtained.
Decreasing the access probability substantially reduces the occurrence of collisions, since the probability of simultaneous access of chunks in contention reduces (see Section 4.3).
