IEEE 802.

11 Protocol
 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
 Throughput Formula
 Throughput without
Error

• Where,
– (Distributed Interframe Space)
– Backoff Time
– Data Frame Transmission
– SIFS (Short Interframe Space)
– Acknowledgment Frame Transmission
 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
 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
 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
 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
 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)
 Solution
 Throughput without
• Formula
Error
 Components of • Given Parameters
Throughput Calculation – Payload size : 256 bytes
 Timing delay of data – Short Interframe Space : 160µs
transmission – Slot time : 52 µs
 Question – Minimum contention window size : 15
 Solution – Duration for preamble and header : 560 µs
– Duration of a symbol : 40 µs
– Header size : 36 bytes (long header)
• Missing parameters
 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 :
 Solution
 Throughput without
Error • Transmission Time of Data Frame :
 Components of
Throughput Calculation
 Timing delay of data
transmission
 Question
 Solution
 Solution
 Throughput without
Error • Transmission Time of ACK Frame :
 Components of
Throughput Calculation
 Timing delay of data • Throughput Calculation
transmission
 Question
 Solution

TP
 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
 Throughput with Packet
delivery considering packet losses and
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
 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

{
( 𝐶 𝑊 𝑚𝑖𝑛 +1 ) × 2 𝑗 − 1 − 1
× 𝑇 𝑠𝑙𝑜𝑡 , 1≤ 𝑗 ≤ 𝑡h𝑟𝑒𝑠h𝑜𝑙𝑑
𝑇 𝑏𝑜 ( j )= 2
𝐶 𝑊 𝑚𝑎𝑥
× 𝑇 𝑠𝑙𝑜𝑡 , 𝑗 > 𝑡h𝑟𝑒𝑠h𝑜𝑙𝑑
2
 Throughput with Packet Error Rate (PER)
 Throughput without
Error • Threshold and Parameters
 Components of – Threshold is the maximum number of backoff stages,
Throughput Calculation
 Timing delay of data
typically chosen as 6
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
 Throughput with Packet Error Rate (PER)
 Throughput without
Error • Calculation of 𝛼:
 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
 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
 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 PER=0.5, iterate to j=15
transmission for convergence
 Throughput with Packet
Error Rate (PER) j
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 for Different Iterations
 Solution
 Throughput without
Error • Throughput calculation
 Components of
Throughput Calculation
 Timing delay of data • Where:
transmission
 Throughput with Packet
Error Rate (PER)
 Solution
 Throughput without
Error • Compute the throughput
 Components of
Throughput Calculation
 Timing delay of data
transmission
 Throughput with Packet
Error Rate (PER)
 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
 Throughput with Packet
• These models help in designing and optimizing
Error Rate (PER) wireless communication systems by accounting for
 Path Loss Models for
IEEE 802.11ah
factors such as distance, frequency, and the
environment
 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
 Throughput with Packet
• Macro Development (AP at 15 meters height)
Error Rate (PER)
 Path Loss Models for • Accounts for greater height and frequence impact
IEEE 802.11ah
– Outdoor Path Loss • Pico Deployment (AP at 2 meters height)
Model

• Includes higher fixed loss due to closer proximity to obstacles

 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
 Throughput with Packet
• It typically employs a two-slope approach with a
Error Rate (PER) breakpoint distance to represent different loss rates
 Path Loss Models for
IEEE 802.11ah
for short and long distances from the transmitter.
– 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.
 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
 References
Text Book:
1. Sudhir Kumar, Fundamentals of Internet of Things, 1 st edition, CRC
Press, Taylor & Francis Group, 2022
Page No:42-45