Multiple Access Protocols in Networking

There are three types of Multiple Access Protocols
1 Random Access Protocols

• ALOHA
• CSMA (Carrier Sense Multiple Access)
• CSMA/CD (Carrier Sense Multiple Access with Collision Detection)
• CSMA/CA (Carrier Sense Multiple Access with Collision Avoidance)

2 Controlled Access Protocols

• Reservation 
• Polling
• Token Passing

3 Channelization Protocols

• FDMA (Frequency Division Multiple Access)
• TDMA (Time-Division Multiple Access)
• CDMA (Code Division Multiple Access)

1 Random Access Protocols

↪ ALOHA : - Whenever a user has a frame to send, it simply transmits the frame. If collision occurs, it waits for a random period of time and re-sends it again. Sender can always find out if its frame was destroyed by listening to channel. For a LAN, feedback is immediate, while for a satellite there is a long delay of 270 ms before sender knows.

↪ CSMA : - A user wishing to transmit first listens to the medium to see if another transmission is in progress (carrier sense) Detection or sensing delay is determined by receiver hardware: a small detection time means that a user can detect a free channel rapidly.

↪ CSMA/CA : -  Carrier-sense multiple access with collision avoidance (CSMA/CA) in computer networking, is a network multiple access method in which carrier sensing is used, but nodes attempt to avoid collisions by transmitting only when the channel is sensed to be "idle".

↪ CSMA/CD : - Carrier-sense multiple access with collision detection (CSMA/CD) is a media access control method used most notably in early Ethernet technology for local area networking.

2 Controlled Access Protocols

 ↪ Reservation : - In the reservation method, a station needs to make a reservation before sending data. Time is divided into intervals. In each interval, a reservation frame precedes the data frames sent in that interval.

 ↪ Polling : - Polling works with topologies in which one device is designated as a primary station and the other devices are secondary stations. All data exchanges must be made through the primary device even when the ultimate destination is a secondary device.

 ↪ Token Passing : - In the token-passing method, the stations in a network are organized in a logical ring. In other words, for each station, there is a predecessor and a successor. The predecessor is the station which is logically before the station in the ring; the successor is the station which is after the station in the ring.

3 Channelization Protocols

 ↪ FDMA : - Frequency division multiple access or FDMA is a channel access method used in multiple-access protocols as a channelization protocol. FDMA gives users an individual allocation of one or several frequency bands, or channels.

 ↪ TDMA : - Time-division multiple access (TDMA) is a channel access method for shared-medium networks. It allows several users to share the same frequency channel by dividing the signal into different time slots.

 ↪CDMA : - Code-division multiple access (CDMA) is a channel access method used by various radio communication technologies. CDMA is an example of multiple access, where several transmitters can send information simultaneously over a single communication channel. CDMA is used as the access method in many mobile phone standards.