Networks :: Wireless Networks jamie@drfrostmaths.com www.drfrostmaths.com @DrFrostMaths Last modified: 26th August 2019

www.drfrostmaths.com ? Everything is completely free. Why not register? Registering on the DrFrostMaths platform allows you to save all the code and progress in the various Computer Science mini-tasks. It also gives you access to the maths platform allowing you to practise GCSE and A Level questions from Edexcel, OCR and AQA. With Computer Science questions by: Your code on any mini-tasks will be preserved. Note: The Tiffin/DFM Computer Science course uses JavaScript as its core language. Most code examples are therefore in JavaScript. Using these slides: Green question boxes can be clicked while in Presentation mode to reveal. Slides are intentionally designed to double up as revision notes for students, while being optimised for classroom usage. The Mini-Tasks on the DFM platform are purposely ordered to correspond to these slides, giving your flexibility over your lesson structure. ?

Learning Objectives Directly from the OCR specification: This stuff here.

INTRO :: Wired vs Wireless Router Recall that a router is a device that allows a network (e.g. a LAN) to access other networks (often the internet). Router In a wired network, all devices are connected by physical wires. …while in a wireless network, only the connection of the router to the internet is necessarily wired The Internet

Advantages of wireless networks Disadvantages ? ? No installation of physical wiring necessarily required. Devices can physically move around within the network. Limited range of signal (and affected by walls, etc) and connection less reliable. Can be interference from other wireless networks. Less secure than wired networks. Fun Fact: The ‘Fi’ in the term ‘Wi Fi’ (i.e. the radio technology used for wireless LANs) is not short for anything. One of the founding members of the WiFi Alliance has stated that it was just a pun on the term ‘hi fi’.

Dr Frost’s home wireless router I am able to access my wireless router’s settings from a browser by going to dsldevice.lan Let’s explore… These are devices on my network right now. We will see later that there are two different ‘frequency bands’ used for WiFi. Here are all the devices on my network in each… We will see that MAC addresses are a permanent identifier for devices within a LAN (but are not visible outside of it), whereas IP addresses are an identifier for the device on the internet (e.g. so that external services can connect to it) Ethernet is a wired technology. There are no devices plugged directly into the router.

Dr Frost’s home wireless router We will see that each of the 2.4 GHz and 5 GHz frequency bands are subsequently broken up into different ‘channels’. Changing the channel can reduce interference if lots of wireless networks nearby are using the same channel. This is the MAC address for the router itself.

Increasing wavelength How does wireless transmission occur? Increasing wavelength Gamma rays Ultra- violet X rays Infrared Microwaves Radio Frequency (Hz) 10 20 10 18 10 16 10 14 10 12 10 10 10 8 10 6 10 4 Visible Light 5 GHz 2.4 GHz Wireless communication uses radio waves for data transmission. Their low wavelength means the waves can travel greater distances and pass through walls. Wi-Fi® is a protocol/standard used for wireless communication. It uses two ‘bands’ of the radio frequency spectrum, 5 GHz (=5000 Hz) and 2.4 GHz… ! The frequency of a wave (measured in Hz) is the number of wave oscillations per second. If the frequency doubles, the wavelength halves.

Wireless radio bands ? ? 1 5 9 2 6 10 3 7 11 4 8 2.4 GHz 2.42 GHz Each of 2.4 GHz and 5 GHz bands are divided up into different channels (my wireless router used Channel 11), each which spans a frequency range. Notice that the channels overlap. Using non-overlapping channels can avoid interference of signals. Advantages of 2.4 GHz Advantages of 5 GHz ? ? Lower bandwidth means a greater range and waves pass through walls/objects more easily. Faster communication over a short distance. More non-overlapping channels, so less interference between devices.

Example Exam Question ?

WAPs vs hotspots vs dongles vs routers Some devices (e.g. older laptops/PCs) don’t have inbuilt wireless connectivity, possibly only allowing a wired ethernet connection. WiFi dongles are typically USB (to give wireless connectivity to a machine) or HDMI (particularly for streaming video content to a TV). However, most modern TVs now have inbuilt WiFi. Here’s my TV as seen on my router’s admin controls, along with its MAC address (top) and IP address (bottom). It’s currently off. The TV has inbuilt WiFi so doesn’t require a dongle. There’s a PS4 too! Notice by the way that the MAC addresses are completely different, whereas the IP addresses are quite similar. We’ll see the reason for this when we cover network protocols.

WAPs vs hotspots vs dongles vs routers The router acts as a hub that sets up a local area network and manages all of the devices and communication in it (as well as providing access to the internet). An access point, on the other hand, is a sub-device within the local area network that provides another location for devices to connect from and enables more devices to be on the network. Internet WAP Router WAP You will see these attached to walls/ceilings around your school. These are WAPs (Wireless Access Points), designed to allow your devices to connect to the school’s LAN; it is the school’s router elsewhere that subsequently gives you access to the internet.

WAPs vs hotspots vs dongles vs routers A hotspot is a physical location (e.g. a school, coffee shop) where devices can access a WiFi network. The Wireless Access Points meanwhile are the network devices within the hotspot that enables phones/computers to access the wireless network. Internet WAP Router WAP Tiffin School hotspot