IEEE 802.

11 Protocol

by
Dr M Rajasekhara Babu
School of
Computer Science and Engineering

Vellore-632014, Tamil Nadu, India

 Outline

Session Objectives & Session Plan

Throughput without Error

Throughput with Packet Error Rate (PER) and Path Loss

Models for IEEE 802.11ah

Summary, References

Dr M Rajasekhara Babu, Professor; School of C.S.E, Vellore Institute of Technology (VIT)-Vellore; 26-Aug-24 11:28 PM Slide. 2
 Objectives & Teaching Learning Material

To provide knowledge on Throughput without Error

To understand about Throughput with Packet Error

Rate (PER) and Path Loss Models for IEEE 802.11ah

Dr M Rajasekhara Babu, Professor; School of C.S.E, Vellore Institute of Technology (VIT)-Vellore; 26-Aug-24 11:28 PM Slide. 3
 Session Plan
Skill and
Time Learning Aid and Typical Student
Content Faculty Approach Competency
(in min) Methodology Activity
Developed
Quiz Questions Answers Knowledge
05 Re-Cap
Presentation Organizes Identifies Evaluation

10 Introduction Explains Presentations Observes Knowledge

20 Throughput without Error Explains Presentation Listens Application

Throughput with Packet Error

10 Rate (PER) and Path Loss Explains Presentation Observes Knowledge
Models for IEEE 802.11ah
Conclusion and Listens Comprehen
05 Summary Facilitates
Summary with quiz Participates sion
Dr M Rajasekhara Babu, Professor; School of C.S.E, Vellore Institute of Technology (VIT)-Vellore; 26-Aug-24 11:28 PM Slide. 4
 Throughput without Error
 Throughput without
Error • Is the rate at which data is successfully transmitted
over a network or communication channel
• Is measured in bits per second (bps) or megabits per
second (Mbps)
• It reflects the efficiency and performance of the
transmission protocol
• The formula for throughput without error:
– divides the total amount of data transmitted by the total
time taken for the transmission cycle, including all
necessary wait and transmission times

Dr M Rajasekhara Babu, Professor; School of C.S.E, Vellore Institute of Technology (VIT)-Vellore; 26-Aug-24 11:28 PM Slide. 5
 Throughput Formula
 Throughput without
Error

• Where,
– (Distributed Interframe Space)
– Backoff Time
– Data Frame Transmission
– SIFS (Short Interframe Space)
– Acknowledgment Frame Transmission

Dr M Rajasekhara Babu, Professor; School of C.S.E, Vellore Institute of Technology (VIT)-Vellore; 26-Aug-24 11:28 PM Slide. 6
 Components of Throughput Calculation
 Throughput without
Error • Payload Size
 Components of – The amount of actual data being transmitted, excluding
Throughput Calculation
headers and control information
• Interframe Spaces
– SIFS (Short Interframe Space)
• A brief time period required between different types of frames,
such as data and acknowledgment frames, to ensure proper
reception and processing
– DIFS (Distributed Interframe Space)
• Time interval that a device must wait before attempting to
access the medium after a data transmission
• It is calculated as the sum of Short Interframe Space (SIFS)
and twice the Slot Time
Dr M Rajasekhara Babu, Professor; School of C.S.E, Vellore Institute of Technology (VIT)-Vellore; 26-Aug-24 11:28 PM Slide. 7
 Components of Throughput Calculation
 Throughput without
Error • Backoff Time
 Components of – The time a device waits before attempting to retransmit
Throughput Calculation
after a collision or when the medium is busy. This time is
determined by a uniform distribution within the contention
window size
• Transmission Time
– Data Frame Transmission
• Includes the time required for the preamble, header, and
payload data. The number of symbols needed is calculated
based on the payload and header size.
– Acknowledgment Frame Transmission
• Time required to send an acknowledgment frame, including
preamble and header, with a fixed number of symbols
Dr M Rajasekhara Babu, Professor; School of C.S.E, Vellore Institute of Technology (VIT)-Vellore; 26-Aug-24 11:28 PM Slide. 8
 Components of Throughput Calculation
 Throughput without
Error • Error-Free Assumptions
 Components of – The throughput calculation assumes an error-free
Throughput Calculation
scenario where there are no retransmissions or data
losses
– This simplifies the model by not accounting for
retransmission delays or error recovery processes

Dr M Rajasekhara Babu, Professor; School of C.S.E, Vellore Institute of Technology (VIT)-Vellore; 26-Aug-24 11:28 PM Slide. 9
 Timing delay of data transmission
 Throughput without
Error
Different delays
 Components of
Throughput Calculation Source Router Router Destination
 Timing delay of data
transmission
Propagation delay

Processing delay Transmission delay

Queueing delay

Dr M Rajasekhara Babu, Professor; School of C.S.E, Vellore Institute of Technology (VIT)-Vellore; 26-Aug-24 11:28 PM Slide. 10
 Question
 Throughput without
Error • Determine the throughput in an error-free scenario
 Components of for a protocol with a payload size of 256 bytes,
Throughput Calculation
 Timing delay of data given the following parameters
transmission – Short Interframe Space : 160µs
 Question
– Slot time : 52 µs
– Minimum contention window size : 15
– Duration for preamble and header : 560 µs
– Duration of a symbol : 40 µs
– Header size : 36 bytes (long header)

Dr M Rajasekhara Babu, Professor; School of C.S.E, Vellore Institute of Technology (VIT)-Vellore; 26-Aug-24 11:28 PM Slide. 11
 Solution
 Throughput without
• Formula
Error
 Components of • Given Parameters
Throughput Calculation – Payload size (𝐿 ): 256 bytes
 Timing delay of data – Short Interframe Space (𝑇 ): 160µs
transmission – Slot time (𝑇 ): 52 µs
 Question – Minimum contention window size (𝐶𝑊 ): 15
 Solution – Duration for preamble and header (𝑇 ): 560 µs
– Duration of a symbol (𝑇 ): 40 µs
– Header size (𝐿 ): 36 bytes (long header)
• Missing parameters
– 𝑇
– 𝑇
– 𝑇
– 𝑇

Dr M Rajasekhara Babu, Professor; School of C.S.E, Vellore Institute of Technology (VIT)-Vellore; 26-Aug-24 11:28 PM Slide. 12
 Solution
 Throughput without
Error • Data Interframe Spacing Calculation:
 Components of
Throughput Calculation
 Timing delay of data
– Substituting the given values
transmission
 Question
 Solution

• Backoff Time :
µs

Dr M Rajasekhara Babu, Professor; School of C.S.E, Vellore Institute of Technology (VIT)-Vellore; 26-Aug-24 11:28 PM Slide. 13
 Solution
 Throughput without
Error • Transmission Time of Data Frame :
 Components of
Throughput Calculation
 Timing delay of data
transmission
 Question
 Solution

Dr M Rajasekhara Babu, Professor; School of C.S.E, Vellore Institute of Technology (VIT)-Vellore; 26-Aug-24 11:28 PM Slide. 14
 Solution
 Throughput without
Error • Transmission Time of ACK Frame :
 Components of
Throughput Calculation
 Timing delay of data
transmission • Throughput Calculation
 Question
 Solution

TP
Dr M Rajasekhara Babu, Professor; School of C.S.E, Vellore Institute of Technology (VIT)-Vellore; 26-Aug-24 11:28 PM Slide. 15
 Throughput with Packet Error Rate (PER)
 Throughput without
Error • It measures effective data transfer rate when errors
 Components of are present
Throughput Calculation
 Timing delay of data • It accounts for the actual rate of successful data
transmission
delivery considering packet losses and
 Throughput with Packet
Error Rate (PER) retransmissions
• This metric helps understand the impact of packet
errors on transmission efficiency
• It is essential for optimizing network performance
under real-world conditions with errors

Dr M Rajasekhara Babu, Professor; School of C.S.E, Vellore Institute of Technology (VIT)-Vellore; 26-Aug-24 11:28 PM Slide. 16
 Throughput with Packet Error Rate (PER)
 Throughput without
Error • Error Impact on Throughput
 Components of – When errors occur, retransmission and back-off time
Throughput Calculation
 Timing delay of data
increase exponentially
transmission • Adjusted Throughput Calculation
 Throughput with Packet
Error Rate (PER) – Adjust the numerator of the throughput formula by
multiplying with (1 - PER)
• Backoff Interval Calculation

Dr M Rajasekhara Babu, Professor; School of C.S.E, Vellore Institute of Technology (VIT)-Vellore; 26-Aug-24 11:28 PM Slide. 17
 Throughput with Packet Error Rate (PER)
 Throughput without
Error • Threshold and Parameters
 Components of – Threshold is the maximum number of backoff stages,
Throughput Calculation
typically chosen as 6
 Timing delay of data
transmission – Example parameters:
 Throughput with Packet – =1023
Error Rate (PER)
– =15
– threshold=6threshold=6 because
• Iteration for Convergence
– Iterations continue until the convergence of or
until
– Typically, 6 to 10 iterations are sufficient for PER in the
range of 0.1 to 0.2
Dr M Rajasekhara Babu, Professor; School of C.S.E, Vellore Institute of Technology (VIT)-Vellore; 26-Aug-24 11:28 PM Slide. 18
 Throughput with Packet Error Rate (PER)
 Throughput without
Error • Calculation of :
 Components of –
Throughput Calculation
 Timing delay of data • For
transmission • For
 Throughput with Packet • For
Error Rate (PER)
• For
• And so on
• Exponential Growth
– approximately doubles for each retransmission until
is reached

Dr M Rajasekhara Babu, Professor; School of C.S.E, Vellore Institute of Technology (VIT)-Vellore; 26-Aug-24 11:28 PM Slide. 19
 Question
 Throughput without
Error • Determine the throughput in an error-prone scenario
 Components of with a Packet Error Rate (PER) of 0.1, given a
Throughput Calculation
 Timing delay of data payload size of 256 bytes. Use the provided back-
transmission off times and probabilities for different iterations,
 Throughput with Packet
Error Rate (PER)
and compute the throughput based on the provided
formula and values

Dr M Rajasekhara Babu, Professor; School of C.S.E, Vellore Institute of Technology (VIT)-Vellore; 26-Aug-24 11:28 PM Slide. 20
 Solution
 Throughput without
Error • Recompute under PER
 Components of – Sum of the last column in Table : =441.97
Throughput Calculation
 Timing delay of data – Iterations stop at j=6j for . For
transmission PER=0.5, iterate to j=15 for convergence
 Throughput with Packet
Error Rate (PER) j 𝒃𝒐 𝒃𝒐
1 390 9×10−1 351.00
2 806 9×10−2 72.54
3 1638 9×10−3 14.74
4 3302 9×10−4 2.97
5 6630 9×10−5 0.60
6 13286 9×10−6 0.12
7 26598 9×10−7 0.024
8 26598 9×10−8 0.0024
Table of 𝛾 𝑗 ⋅ 𝑇 𝑗 for Different Iterations
Dr M Rajasekhara Babu, Professor; School of C.S.E, Vellore Institute of Technology (VIT)-Vellore; 26-Aug-24 11:28 PM Slide. 21
 Solution
 Throughput without
Error • Throughput calculation
 Components of
Throughput Calculation
 Timing delay of data
transmission • Where:
 Throughput with Packet
Error Rate (PER) –
–
–
–
–
–

Dr M Rajasekhara Babu, Professor; School of C.S.E, Vellore Institute of Technology (VIT)-Vellore; 26-Aug-24 11:28 PM Slide. 22
 Solution
 Throughput without
Error • Compute the throughput
 Components of
Throughput Calculation
 Timing delay of data
transmission
 Throughput with Packet
Error Rate (PER)

Dr M Rajasekhara Babu, Professor; School of C.S.E, Vellore Institute of Technology (VIT)-Vellore; 26-Aug-24 11:28 PM Slide. 23
 Path Loss Models for IEEE 802.11ah
 Throughput without
Error • Path loss models are used to estimate the reduction
 Components of in signal strength as it travels through different
Throughput Calculation
 Timing delay of data environments
transmission
• These models help in designing and optimizing
 Throughput with Packet
Error Rate (PER) wireless communication systems by accounting for
 Path Loss Models for factors such as distance, frequency, and the
IEEE 802.11ah
environment

Dr M Rajasekhara Babu, Professor; School of C.S.E, Vellore Institute of Technology (VIT)-Vellore; 26-Aug-24 11:28 PM Slide. 24
 Outdoor Path Loss Model
 Throughput without
Error • Is a model estimating signal loss in outdoor
 Components of environments based on distance, frequency, and
Throughput Calculation
 Timing delay of data antenna height
transmission
• Macro Development (AP at 15 meters height)
 Throughput with Packet
Error Rate (PER)
 Path Loss Models for
IEEE 802.11ah
– Outdoor Path Loss • Accounts for greater height and frequence impact
Model
• Pico Deployment (AP at 2 meters height)

• Includes higher fixed loss due to closer proximity to obstacles

Dr M Rajasekhara Babu, Professor; School of C.S.E, Vellore Institute of Technology (VIT)-Vellore; 26-Aug-24 11:28 PM Slide. 25
 Indoor Path Loss Model
 Throughput without
Error • Is a path loss model used for indoor environments
 Components of that accounts for signal attenuation due to walls,
Throughput Calculation
 Timing delay of data furniture, and other obstacles
transmission
• It typically employs a two-slope approach with a
 Throughput with Packet
Error Rate (PER) breakpoint distance to represent different loss rates
 Path Loss Models for for short and long distances from the transmitter.
IEEE 802.11ah
– Outdoor Path Loss • Two-Slope Model
Model
– Indoor Path Loss – It Uses a breakpoint distance to model different loss
Model slopes for short and long distances.

Dr M Rajasekhara Babu, Professor; School of C.S.E, Vellore Institute of Technology (VIT)-Vellore; 26-Aug-24 11:28 PM Slide. 26
 Summary
• Throughput without Error
• Components of Throughput
Calculation
• Timing delay of data transmission
• Throughput with Packet Error
Rate (PER)
• Path Loss Models for IEEE
802.11ah
– Outdoor Path Loss Model
– Indoor Path Loss Model

Dr M Rajasekhara Babu, Professor; School of C.S.E, Vellore Institute of Technology (VIT)-Vellore; 26-Aug-24 11:28 PM Slide. 27
 References
Text Book:
1. Sudhir Kumar, Fundamentals of Internet of Things, 1st edition, CRC
Press, Taylor & Francis Group, 2022
Page No:42-45

Dr M Rajasekhara Babu, Professor; School of C.S.E, Vellore Institute of Technology (VIT)-Vellore; 26-Aug-24 11:28 PM Slide. 28
 Questions ?

Dr M Rajasekhara Babu, Professor; School of C.S.E, Vellore Institute of Technology (VIT)-Vellore; 26-Aug-24 11:28 PM Slide. 29
Dr M Rajasekhara Babu, Professor; School of C.S.E, Vellore Institute of Technology (VIT)-Vellore; 26-Aug-24 11:28 PM Slide. 30