Reservation systems Reservation systems Single server/channel shared by multiple users Only one user can use the channel at a time Need to coordinate between users 。Polling station Polls the users to see if they have anything to send One cycle R1 D1 R2 D2 R3 D3 R1 D1 R2 D2 Transmission interval Reservation interval,no transmission Weigiang Sun Communication NetworksWeiqiang Sun Communication Networks Reservation systems • Reservation systems – Single server/channel shared by multiple users – Only one user can use the channel at a time – Need to coordinate between users • Polling station – Polls the users to see if they have anything to send 2 R1 D1 R2 D2 R3 D3 R1 D1 R2 D2 Reservation interval, no transmission Transmission interval One cycle