Baud rate is the number of signal changes, or symbols, transmitted per second. It measures how often the state of the medium changes — its voltage, frequency, phase or amplitude — not how much data those changes carry. It is measured in baud.

Bit rate is the number of bits transmitted per second, measured in bits per second (bps) and its multiples such as kbps, Mbps and Gbps. It measures the actual quantity of data moved per second.

Define bandwidth in the context of data transmission.

Bandwidth is the range of frequencies a transmission medium can carry, measured in hertz. In everyday network use the term is also used to mean the maximum amount of data a link can carry per second, because the two are directly related.

Latency is the time delay between the moment a signal or data is sent and the moment it arrives or is acted upon at the destination. It is measured in units of time, usually milliseconds.

Define protocol in the context of networking.

A protocol is an agreed set of rules governing communication between devices. It defines things such as the format of the data, the order in which messages are exchanged, how errors are detected and handled, and the speed and timing of transmission, so that devices from different manufacturers can communicate successfully.

How does baud rate differ from bit rate?

Baud rate counts signal changes per second; bit rate counts bits per second. They are equal only when each signal change carries exactly one bit. If the encoding scheme uses more than two distinguishable states, each signal change carries more than one bit and the bit rate is a multiple of the baud rate.

AQA A-Level Computer Science 7517

Fundamentals of Programming

Topic overview Data types Programming concepts and program structure Arithmetic operations Relational Operations, Constants and Variables Boolean operations String-handling operations Random numbers and exception handling Subroutines, parameters and return values Variable scope and stack frames Recursive techniques Programming paradigms and the procedural approach Classes, Objects, Inheritance and Polymorphism Aggregation, Composition, Class Diagrams and Design Principles

Fundamentals of Data Structures

Topic overview Data Structures and Abstract Data Types Static and Dynamic Data Structures Queues and Linear Queues Circular and Priority Queues Stacks Graphs Trees Hash tables Dictionaries Vectors and Their Notation Vector Arithmetic and Geometry

Fundamentals of Algorithms

Topic overview Graph traversal Tree traversal Reverse Polish notation Searching algorithms Sorting algorithms Optimisation algorithms

Theory of Computation

Topic overview Logic Problems and Algorithm Constructs Pseudo-Code, Hand-Tracing and Program Correctness Representational Abstraction, Generalisation and Information Hiding Procedural and Functional Abstraction Data Abstraction and Problem Reduction Decomposition and Composition Automation and Finite State Machines Sets and Set Notation Subsets and Set Operations Regular expressions and regular languages Backus-Naur Form and syntax diagrams Comparing Algorithms and Functions Order of complexity and Big-O notation Limits of computation, tractability and heuristics Computable problems and the Halting problem Turing machines

Fundamentals of Data Representation

Topic overview Number systems and the sets of numbers Number bases: decimal, binary and hexadecimal Bits, bytes and units of information Unsigned binary and binary arithmetic Signed binary using two's complement Fixed point and floating point representation Normalisation of floating point numbers Rounding errors, accuracy, range and precision Character coding systems Error checking and correction Bit patterns, analogue and digital Bitmapped graphics Vector graphics Digital representation of sound MIDI and Data Compression Encryption

Fundamentals of Computer Systems

Topic overview Hardware, Software and Its Classification System Software and the Operating System Translators and the Role of the Operating System Classification of programming languages Types of program translator Logic Gates and Their Truth Tables Logic Circuits and D-Type Flip-Flops Half-Adders and Full Adders Boolean algebra

Fundamentals of Computer Organisation and Architecture

Topic overview Internal components, buses and von Neumann and Harvard architectures The Stored Program Concept and the Processor The Fetch-Execute cycle The processor instruction set Addressing modes Machine-Code Operations Shifts, Halting and Assembly Language Programs Interrupts Factors affecting processor performance Input and output devices Secondary storage devices

Fundamentals of Communication and Networking

Topic overview Communication methods Communication basics Network Topology and Types of Networking Wireless networking The Internet and Packet Switching Routing, URLs and Domain Names Firewalls, Worms, Trojans and Viruses Encryption, Digital Signatures and Certificates TCP/IP Standard application layer protocols IP Address Structure and Subnet Masking IP Standards and Public and Private Addresses DHCP and Network Address Translation Client server model Thin- versus thick-client computing

Consequences of Uses of Computing

Topic overview The Four Kinds of Issue in Computing Legislation, Ethical Dilemmas and Case Studies

Systematic Approach to Problem Solving

Topic overview Analysis, Design and Implementation Testing and Evaluation

Fundamentals of Databases

Topic overview Conceptual data models and entity relationship modelling Relational databases Database design and normalisation techniques Structured Query Language (SQL)Client server databases

Big Data

Topic overview Volume, Velocity and Variety Why Big Data Resists Analysis Distributed Processing and Functional Programming Fact-Based Models and Graph Schemas

Fundamentals of Functional Programming

Topic overview Function Types, First-Class Objects and Function Application Partial Function Application and Composition Writing functional programs Lists in functional programming

Fundamentals of Communication and Networking

Communication basics

2 things to know
Paper 2

Overview

Recall questions on baud rate, bit rate, bandwidth, latency and protocol, and on why the bit rate can exceed the baud rate.

What you need to know

Answer each one before you reveal it.

Your recallNot started

Numbers

Explain how the bit rate can be higher than the baud rate.

Numbers

A student says a fibre link 'has more bandwidth so the data arrives sooner'. What is wrong with that?

Questions from this subtopic

Each one with the model answer underneath.

1
Define baud rate.
Model answer
Baud rate is the number of signal changes, or symbols, transmitted per second. It measures how often the state of the medium changes — its voltage, frequency, phase or amplitude — not how much data those changes carry. It is measured in baud.
2
Define bit rate.
Model answer
Bit rate is the number of bits transmitted per second, measured in bits per second (bps) and its multiples such as kbps, Mbps and Gbps. It measures the actual quantity of data moved per second.
3
Define bandwidth in the context of data transmission.
Model answer
Bandwidth is the range of frequencies a transmission medium can carry, measured in hertz. In everyday network use the term is also used to mean the maximum amount of data a link can carry per second, because the two are directly related.
4
Define latency.
Model answer
Latency is the time delay between the moment a signal or data is sent and the moment it arrives or is acted upon at the destination. It is measured in units of time, usually milliseconds.
5
Define protocol in the context of networking.
Model answer
A protocol is an agreed set of rules governing communication between devices. It defines things such as the format of the data, the order in which messages are exchanged, how errors are detected and handled, and the speed and timing of transmission, so that devices from different manufacturers can communicate successfully.
6
How does baud rate differ from bit rate?
Model answer
Baud rate counts signal changes per second; bit rate counts bits per second. They are equal only when each signal change carries exactly one bit. If the encoding scheme uses more than two distinguishable states, each signal change carries more than one bit and the bit rate is a multiple of the baud rate.

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