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COE Chapter 12: multiple Access - Coggle Diagram

- - - - When nodes or stations are connected to a common link, called a multipoint or broadcast link, --> need a multiple access protocol to coordinate the access to the link.
        
        Medium access methods can be categorized as:
        
        Random Access
        
        Each station has a right the the medium without being controlled by any other station.
        
        If more than one station tries to send, there will be an access conflict (collision), the frames will be either destroyed or modified.
        
        MA: Aloha
        
        designed to be used on a radio local are network (LAN) with a data rate of 9600 bps. Each station send the frame whenever it has one ready. Since there is one channel to share, there is possibilty of collision.
        
        3 more items...
        
        CSMA
        
        Chance of collision can decrease if a station senses the medium before trying to use it.
        
        Can not eliminate collision, the possibility of collision exists because of propagation delay.
        
        Controlled Access
        
        the stations consult one another to find which station has the right to send frame. A station can't send unless authorized by other stations.
        
        Three main methods are:
        
        Reservation
        
        polling
        
        Token passing
        
        Channelized
        
        The avilinle bandwidth of a link is shared in time, frequency, or through code, among different stations.
        
        3 channelization protocols are:
        
        FDMA (Frequency-division multiple access)
        
        TDMA (Time-division MA)
        
        CDMA (Code-division MA)
        
        FDMA, the bandwidth is divided into bands; each band is reserved for the use of specific station.
        
        TDMA, Bandwidth is time-shared; each station allocated a time slot to send data.
        
        CDMA, Bandwidth is no divided, yet data from all inputs are transmitted simultaneously. Uses the entire bandwidth of the channel. One type of CDMA, uses encoding schemes for data bits (1s and 0s) for different users.