Wireless Device-to-Device Communications and Networks by Song Lingyang & Niyato Dusit & Han Zhu & Hossain Ekram

Author:Song, Lingyang & Niyato, Dusit & Han, Zhu & Hossain, Ekram [Song, Lingyang]
Language: eng
Format: azw3
Publisher: Cambridge University Press
Published: 2015-02-27T16:00:00+00:00

(7.1)

In other words, the user whose transmission yields the largest utility will be scheduled to transmit. With this scheduling policy, the system throughput will be maximized, since the scheduling algorithm favors those users whose channel quality is good in the long run. For example, if there are users 1 and 2, the channel quality of each of these users could be good or bad. If the probabilities of good channel quality of users 1 and 2 are 0.8 and 0.1, respectively, the probabilities that users 1 and 2 will be scheduled to transmit their packets are 0.85 and 0.15, respectively. This is based on the assumption that, if both users have good or bad channel quality, they will be randomly scheduled for transmission with equal probability. The probabilities that the users will be scheduled for transmission can be calculated as follows. The probability that both users have good channel quality is and each user has an equal chance to transmit with probability 0.04. The probability that user 1 has good channel quality while user 2 has bad channel quality is . User 1 will always be scheduled for transmission in this case. The probability that user 1 has bad channel quality while user 2 has good channel quality is . User 2 will always be scheduled for transmission in this case. Finally, the probability that users 1 and 2 have bad channel quality is , and each user has an equal chance to transmit with probability . Clearly, the fairness of this scheduling policy is poor, since user 2 will have much less opportunity to transmit its packet. Therefore, the optimization problem can be extended to include a constraint on the minimum transmission requirement as follows:

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