---
title: "Channel performance measures"
subject: "Data Communication"
chapter: 1
key: "semester_5/data_communication:channel-performance-measures"
source: https://www.bctengineer.com/q/semester_5/data_communication/channel-performance-measures
site: BCT Engineering
---

# Channel performance measures

Data Communication · Chapter 1: Introduction

- Asked in: 2078 Bhadra, 8 marks; 2075 Asoj, 4 marks; 2072 Chaitra, 4 marks; 2072 Kartik, 2 marks; 2070 Chaitra, 5 marks; 2070 Asar, 4 marks (asked 6 times)
- Video: [Network Performance](https://www.youtube.com/watch?v=5AVuUgEJu1E) — Neso Academy
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_5/data_communication/channel-performance-measures
- Whole chapter: https://www.bctengineer.com/md/semester_5/data_communication/chapter-1

## Question

Describe the measures (parameters) used to characterize the performance of a channel, such as bandwidth, throughput, latency, jitter and bit error rate.

## Short answer

Performance is characterized by bandwidth (Hz or bps), throughput (actual delivered bps), latency (propagation + transmission + queuing + processing), jitter (delay variation), and bit error rate (BER = erroneous bits / total bits).

## Answer

The performance of a channel is judged by how fast, how reliably and how promptly it carries data. The main measures are:

#### 1. Bandwidth
The range of frequencies the channel passes, in Hz (analog sense). In the digital sense it is the maximum bit rate of the link, in bps. Higher bandwidth allows a higher data rate (Nyquist: C = 2B log₂L).

#### 2. Throughput
The actual number of bits successfully delivered per second. It is always less than or equal to the bandwidth because of delays, errors, retransmissions and protocol overhead. Example: a 10 Mbps link may give only 6 Mbps throughput.

#### 3. Latency (delay)
The time for a message to travel from source to destination:

Latency = propagation time + transmission time + queuing time + processing time

- Propagation time = distance / propagation speed
- Transmission time = message size / bandwidth

#### 4. Jitter
The variation in delay of successive packets. If packets arrive at uneven intervals, real-time voice and video break up. Buffers at the receiver reduce jitter.

#### 5. Bit error rate (BER)
BER = number of erroneous bits / total bits transmitted. It depends on the signal-to-noise ratio and the modulation used. Example: 1 error in 10⁶ bits gives BER = 10⁻⁶.

#### 6. Others
- **Bandwidth-delay product** = bandwidth × round-trip delay: the number of bits that can be "in flight" on the link.
- **Signal-to-noise ratio (SNR)**: signal power / noise power; sets the Shannon capacity.

| Measure | Unit | Meaning |
|---|---|---|
| Bandwidth | Hz / bps | Capacity of channel |
| Throughput | bps | Actual delivered rate |
| Latency | s / ms | End-to-end delay |
| Jitter | ms | Delay variation |
| BER | none | Reliability |

## Check yourself

The answer's key points as multiple-choice questions, with the correct option and why.

1. How does throughput relate to bandwidth?
   A. Throughput is the actual delivered rate and is at most the bandwidth
   B. Throughput is always greater than bandwidth
   C. Throughput always equals bandwidth
   D. Throughput is the variation in delay
   Answer: A. Delays, errors, retransmissions and overhead make the delivered rate lower than the link capacity. (Key point: Throughput vs bandwidth)

2. Which expression gives latency?
   A. Propagation time only
   B. Propagation + transmission + queuing + processing time
   C. Message size / bandwidth only
   D. Bandwidth x round-trip delay
   Answer: B. Latency is the sum of four delays; transmission time alone is message size / bandwidth. (Key point: Latency components)

3. What is jitter and why does it matter?
   A. Fraction of bits received in error; it corrupts files
   B. Total end-to-end delay; it limits bandwidth
   C. Variation in delay of successive packets; it breaks up real-time voice and video
   D. Actual bits per second delivered; it lowers capacity
   Answer: C. Uneven packet arrival harms real-time media, and receiver buffers reduce it. (Key point: Jitter)

4. 1 error in 10^6 bits transmitted gives what BER?
   A. 10^6
   B. 10^-3
   C. 1
   D. 10^-6
   Answer: D. BER = erroneous bits / total bits = 1/10^6 = 10^-6. (Key point: Bit error rate)

## Related in Data Communication

- [Define throughput and latency](https://www.bctengineer.com/question.md?key=semester_5%2Fdata_communication%3Athroughput-latency-define) — Data Communication, chapter 1
- [Trellis decoding of 1/2 rate conv. code (3-bit errors)](https://www.bctengineer.com/question.md?key=semester_5%2Fdata_communication%3Aconv-trellis-3bit) — Data Communication, chapter 8, asked 2×
- [Trellis decoding of 1/2 rate conv. code (2-bit errors)](https://www.bctengineer.com/question.md?key=semester_5%2Fdata_communication%3Aconv-trellis-2bit) — Data Communication, chapter 8, asked 2×

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- [T1 and E1 bit rate and bandwidth; DPCM encoder](https://www.bctengineer.com/question.md?key=semester_6%2Fcommunication_systems%3At1-e1-bitrate-dpcm) — Communication Systems, chapter 5
- [TDM of 24 voice signals: PAM bandwidth and PCM sampling rate](https://www.bctengineer.com/question.md?key=semester_6%2Fcommunication_systems%3Atdm-24-voice-pam-pcm) — Communication Systems, chapter 5
- [PCM: minimum channel bandwidth numerical](https://www.bctengineer.com/question.md?key=semester_6%2Fcommunication_systems%3Apcm-bandwidth-3khz-0-5pct) — Communication Systems, chapter 4
- [PCM 7-bit at 50 Mbps: maximum message bandwidth](https://www.bctengineer.com/question.md?key=semester_6%2Fcommunication_systems%3Apcm-7bit-50mbps-bandwidth) — Communication Systems, chapter 4