Medium access control protocols can be classified as random access, controlled access, or channelization protocols. Random access protocols have no central control and stations decide independently when to transmit. Common random access protocols include ALOHA, CSMA, CSMA/CD, and CSMA/CA. Controlled access protocols require stations to get permission before transmitting, using methods like reservation, polling, or token passing. Channelization protocols divide the channel bandwidth by frequency (FDMA), time (TDMA), or code (CDMA).

1. {
M.A.C
Medium Access Control

2.  Random-access protocols
 Controlled-access protocols
 Channelization protocols
Classification of multiple-
access protocols

3.  Random access or contention methods, no
station is superior to another station and none
is assigned control over another. At each
instance, a station that has data to send uses a
procedure defined by the protocol to make a
decision or whether or not to send. This
decision depends on the state of the medium
(idle or busy)
What is Random-access
protocols?

4.  ALOHA
 CSMA
 CSMA/CD
 CSMA/CA
Type of Random-access
protocols

5.  was developed at the University of Hawaii in
early 1970.
 Designed for a radio (wireless) LAN.
 The medium is shared between the stations.
When a station sends data, another station may
attempt to do so at the same time. The data from
the two stations collide and become garbled.
ALOHA

6. Frame in pure ALOHA
network

7. Procedure for pure ALOHA
protocol

8.  Minimize the change of collision.
 Increase the performance.
 CSMA is based on the principle
”sense before transmit” or “Listen before talk”.
CSMA

9. Space/Time model of a collision in CSMA

10.  Carrier sense multiple access with collision
detection (CSMA/CD) algorithm to handle the
collision.
CSMA/CD

11. Collision of the first bits in CSMA/CD

12.  Carrier sense multiple access with collision
avoidance (CSMA/CA).
 Was invented for wireless network.
CSMA/CA

13.  In controlled access, the stations consult on
another to find which station has the right to
send. A station cannot send unless it has been
authorized by other stations.
What is Controlled-access
protocols

14.  Reservation
 Polling
 Token passing
Type of Controlled-access
protocols

15.  Time is divided into intervals.
 A station needs to make a reservation before
sending data.
Reservation

16. Reservation access method

17.  Works with topologies.
 One device is designated as a primary station.
 Other device is are secondary stations.
 All exchange must be made through the
primary device.
Polling

18. Select and poll function in polling-access method

19.  The stations in a network are organized in a
logical ring.
 Predecessor: station which is logically before
the station in the ring.
 Successor: station which is after the station in
the ring.
Token Passing

20. Example token passing

21.  Channelization(channel partition) is a multiple-
access method in which the available
bandwidth of a link is shared in time
What is Channelization
protocols

22.  FDMA
 TDMA
 CDMA
Type of Channelization
protocols

23.  Available bandwidth is divided into frequency
bands.
 Each station is allocated a band to send its data.
FDMA (Frequency-division multiple access)

24. FDMA

25.  Station share the bandwidth of the channel in
time.
 Each station is allocated a time slot during
which it can send data.
 Each station transmits its data in its assigned
time slot.
TDMA (Time-Division Multiple Access)

26. TDMA

27.  Was conceived several decades ago.
 Recent advance in electronic technology have
finally made its implementation possible.
 CDMA differ from FDMA and TDMA.
 There no timesharing
CDMA (Code-Division Multiple Access)

28. CDMA