This document summarizes multiple access protocols used in computer networks. It describes random access protocols like ALOHA, CSMA, CSMA/CD, and CSMA/CA that allow nodes to transmit without coordination. It also covers controlled access protocols like reservation, polling, and token passing that coordinate transmissions between nodes to avoid collisions. Finally, it discusses channelization protocols including FDMA, TDMA, and CDMA that divide the available bandwidth between nodes in different ways.

1. ATAL BIHARI VAJPAYEE UNIVERSITY
BILASPUR (C.G)
DEPARTMENT OF COMPUTER SCIENCE AND APPLICATION
TOPIC : MULTIPLE ACCESS PROTOCOL
PRESENTED BY : PRAVIN BHARGAV AND SURYKANT RATREY
SUBMITTED TO MISS ANKITA JAISWAL
SUBJECT : COMPUTER NETWORK

2. PRAVIN
BHARGAV
SURYAKANT
RATRE
 Random Access Protocol
ALOHA
CSMA
CSMA/CD
CSMA/CA
 Controlled Access Protocol
 Channelization Protocol

3. The data link layer is used in a computer network to
transmit the data between two devices or nodes . It is
responsible to flow control and the error control in the
data link control . It is also the second last layer of Open
System Interconnection(OSI)Model.
Data Link Layer

5. Data Link
Control
A data link control is a reliable channel for transmitting
the data over a dedicated link using various techniques
such as framing , error control and flow control of data
packets in the computer network.

6. Multiple
Access
Protocol
The multiple access
protocol is used for
decrease the collision
if there is no dedicated
link present
For example
A teacher
gives a
question to
students then
All students
are give their
answer at the
same time
Then teacher
will be
manage to all
students.

7. Multiple
Access
Protocols
Random
Access
Protocols
Controlled
Access
Protocols
Channelization
Protocols
Multiple Access Protocols can
be subdivided further as :

8. 1.Random Access
Protocol
In this ,all station have same priority in which no one station have more
priority more than other station . Any station can send the data
depending apon the medium’s situation (idol or busy).

9. Random access protocols are further subdivided as:
Random
Access
Protocols
Aloha
CSMA
CSMA/CD
CSMA/CA

10. (A) ALOHA
It is designed for wireless LAN (Local Area Network) but can also be
used in a shared medium to transmit data. Using this method, any
station can transmit data across a network simultaneously when a
data frameset is available for transmission.

11. Pure
Aloha:
The station can transmit data at any time is called the pure
aloha .When two or more station transmit the data
simultaneously, there is a chance of collision and the
frames are destroyed. In pure aloha the sender will except
acknowledgement from the receiver if that is not received
so the sender assums that the frame has been destroyed.
After the collision the station waits for random amount of
times.

12. Slotted
Aloha:

13. Carrier Sense Multiple Access is used for when two or
more stations start sending their signals over the data link
layer. Carrier sense multiple access requires that each
stations first check the state of the medium before
sending.

14. CSMA
1-Persistent
Non-Persistent
P-Persistent

15. Non-
Persistent:
It first assesses the channel before transmitting data; if the
channel is idle, the node transmits data right away. If not, the
station must wait for an arbitrary amount of time (not
continuously), and when it discovers the channel is empty, it
sends the frames.

16. 1-
Persistent:
It senses the shared channel first and delivers
the data right away if the channel is idle. If not,
it must wait and continuously track for the
channel to become idle and then broadcast the
frame without condition as soon as it does. It
is an aggressive transmission algorithm.

17. P-Persistent:
It consists of the 1-Persistent and Non-
Persistent modes combined. Each node
observes the channel in the P-Persistent mode,
and if the channel is idle, it sends a frame with
a P probability. If the data is not transferred,
the frame restarts with the following time slot
after waiting for a (q = 1-p probability) random
period.

18. CSMA/CD
Carrier Sense Multiple Access /Collision Detection is a media
access control mathod. CSMA/CD is one such technique where
the different stations have to follow this protocol and detect the
collision. This protocol decides which station will transmit when
so that data reaches the destination without corruption.

19. CSMA/CA
It is a Carrier Sense Multiple Access /Collision Avoidence in
this when the station send the data and sender receive the
acknowledgment that means the data has successfully
transmitted if the occur will be come then there will be use of
the INTERFRAME SPACE mathod there are if the station is idol
but yet station does not send the data that will be wait.

20. Controlled Access Protocol :-
In the controlled access protocols all stations need to
consult each other to find out which station has the right
to send the data .It grant permission to send only one
node at a time simultaneously to avoid collisions .

21. Types of Controlled Access Protocols
Controlled
Access
Protocols
Reservation
Polling
Token
Passing

22. 1. Reservation :-
In Reservation a station
need to create a reservation
before sending the data.

23. We divide a time into intervals.
In each interval, reservation frame for
goes the data frame sent in that
interval.
Reservation time.
Data transmission period of variable
frames.

25. 2. Polling
In this one station act as primary station any other as
secondary station. And work on round robin technique.

28. 3. Token Passing :-
In token passing scheme the station are
connected logically to each other and access to
stations are governed by token.

30. Channelization
Available bandwidth of a link is shared in time,
frequency or through code among different
stations.

31. Techniques of channelization
FDMA
FDMA
CDMA
TDMA

32. FREQUENCY
DIVISION
MULTIPLE ACCESS
In this protocol the available bandwidth is divided into
frequency bands . Each station is allocated to send its
data.

34. TIME DIVISION
MULTIPLE
ACCESS
In this protocol , the stations share
the bandwidth of the channel in
time interval . Each station is
allocated a time slot during which
it can send the data.

36. CDMA
It stands for code division multiple access , by this
technique station can access the entire bandwidth of
link anytime here every station is assigned a code

37. Code
Properties :-
1. We multiply each code by another we get 0.
2. If we multiply code by itself we get station ‘s number.

39. Coding method (Walsh Table)
W1 = [+1]
W2n = [Wn ] [Wn]
[Wn] [Wn]’ [Wn]’ is compliment of Wn.
2n => no.of station.
Example :- If we have two station which share a link.
W2x1 = [W1] [W1]
[W1] [W1]’
W2 = [+1] [+1]
[+1] [-1]
Code for station 1 -> +1 +1
Code for station 2 -> +1 -1

40. A 0 bit is represent by -1
A 1 bit is represent by +1
Data bit 0 -> -1
Data bit 1
-> +1
Silence
-> 0