A school’s guide to wireless networking
INTRODUCTION
Wireless networks in schools need to be fast, easy to access and secure. They need to have excellent coverage, sufficient density and be able to handle high peaks. This guide provides key information that will aid you in making an informed decision when purchasing a wireless network for your school. It will explain the basics of wireless networking, describe the types of wireless networks available, provide you with a list of things to consider about your network, outline the types of survey that can be carried out and provide you with knowledge of key terminology.
Contents
WHAT IS A WIRELESS NETWORK?
A wireless network (often referred to as WiFi) is an extension of the Local Area Network. It allows devices to connect to the network without being ‘plugged in’. Most of the devices we use today from new laptops and tablets to mobile phones rely on a wireless network to access data. From a management perspective there are lots of considerations when designing a wireless network but from a user perspective we mostly care about one thing; connectivity.
HOW DOES WIFI ACTUALLY WORK?
WiFi works by transmitting packets of data using electromagnetic radio waves, back and forth between a device and an access point (AP), which is networked to your Local Area Network. Radio waves can pass through solid structures but the transparency is affected by the material and the thickness. Depending on the wireless standard your network operates on, the radio waves will in the 2.4GHz or 5GHz bands.
Controller
Manages your access points, connection, authentication, guest portal and more.
Access Point
Provides the wireless signal to connect devices to the network.
Switch
Connects the access points to the Local Area Network (LAN) and powers the AP using Power Over Ethernet (PoE).
Cabling
The physical connection between the switch and the AP and a crucial consideration as wireless networks get faster.
Controller based
Probably the most common type of wireless network in schools. The controller allows for centralised advanced management of the entire network, in regards to authentication, guest portals, VLANs and more.
Cloud based
Instead of buying a controller you pay a subscription to a cloud service. Your network is managed from the cloud, simplifying management and administration. It also allows for remote management across multiple sites.
No controller
In smaller networks the access points take on the role of controller to reduce costs and complexity. These are ideal in smaller installations with a limited number of users and APs.
WHAT ARE YOU GOING TO USE IT FOR?
It may seem obvious, but this is the first at most important question any wireless networking company will ask you. It will define the solution that is proposed. For example, a WiFi network that will only be used for staff smartphones is fairly straight forward, but a network that is required to handle 30 laptops downloading and uploading content simultaneously requires a more powerful solution. In order to have a truly effective wireless network, you need to have considered every possible use in every possible location.
COVERAGE AREA
Besides the obvious locations for access points, such as classrooms and offices, you may need to consider more obscure locations where users may require an internet connection to conduct things like electronic registers, such as the changing rooms or playing fields. As well as this, you should consider areas you may not require coverage, such as the toilets and stairwells.
COVERAGE VS. DENSITY
It is natural to believe you want the best possible coverage, but you should also give careful consideration to density. A high density wireless network, that can handle the throughput from a classroom full of devices, requires a different surveying approach. You should be aware of which areas in your school require higher density. For example, a classroom with 30 devices does not require a survey to determine that it needs a dedicated AP.
INFRASTRUCTURE
A wireless network is more than just APs. You must also consider the additional infrastructure. Each access point will need its own IP address and a cable with sufficient bandwidth that connects to its own port on a Power Over Ethernet (PoE) switch. Any trunk links and backbones will also need to have sufficient bandwidth to avoid bottlenecks.
WHAT IS A WIRELESS SURVEY?
A wireless survey is the process of an engineer visiting a site and carrying out a series of tasks in order to aid them in designing a WiFi network or part of it.
The type of survey required depends on the nature of the site and the application of the network. There are three types of wireless surveys that can be conducted; active, passive and predictive. Knowing the differences between them can help you ensure your school is surveyed correctly.
ACTIVE SURVEYS
WHAT?
Active surveys take place on an live wireless network. They use the existing APs to create a heatmap of the current WiFi coverage whilst measuring things like round-trip time, throughput rates, packet loss and bandwidth. Specialist software performs a series of tasks such as sending/receiving large files and ping tests. The results are then displayed in a report with detailed heatmaps.
WHY?
Active surveys are used in order to troubleshoot problems or upgrade existing networks. The survey’s results will reveal gaps in coverage that can then be accounted for in the next step, the design phase. They can also be used as post-installation surveys to ensure everything is working as intended.
PASSIVE SURVEYS
WHAT?
A network engineer makes use of an AP and a wireless device, typically a laptop, to generate data about the Radio Frequency (RF) environment. Intelligent software uses these results, along with a schematic of the area, to suggest a network design. The engineer can then edit this design to match certain criteria, for example included higher density for classrooms that will be using a large number of devices.
WHY?
Passive surveys are the best option for new networks that will be required to cover a large area. Unlike active surveys, they do not require the presence of an existing network in order to be carried out, therefore they are ideal for new builds or refurbishments.
PREDICTIVE SURVEYS
WHAT?
Predictive surveys are carried out by using a plan of the premises and applying simulation tools. Intelligent software accounts for signal loss and reflections from walls or large objects and uses ‘virtual access points’ to create a design that maximizes coverage.
WHY?
Predictive surveys are usually conducted when carrying out a physical survey is not a viable option; this could be due to strict time or budget constraints. Predictive surveys can be carried out remotely and are therefore usually the cheapest option. With smaller locations, a predictive survey is often all you’ll need.
POST INSTALLATION SURVEY
After a new wireless network has been installed, it is highly recommended that a post installation survey is carried out. It ensures that the network is working as intended, and if it isn’t it will troubleshoot problems that you may be experiencing. It is especially crucial if there have been changes to the site in question, for example large furniture has been installed since the original survey took place. Post installation surveys are conducted as active surveys.
802.11ac
A wireless standard that uses up to 8 MIMO spatial streams to achieve up to 1.3Gbps.
802.11ac Wave 2
An evolution of 802.11ac that uses MU-MIMO to increase theoretical speeds to 2.3Gbps.
802.11n
A wireless standard that uses up to 4 MIMO spatial streams to achieve up to 450Mbps.
AP
Access Point. Hardware that allows devices to connect to the network wirelessly through the use of electromagnetic waves.
Bandwidth
The maximum amount of data that can be carried from one point to another in a given time period. Different to throughput.
Beamforming
A technology that allows APs to dynamically focus their power in the directions of devices that are connected to it.
Bonjour
Technology found on all Apple devices that actively searches for other Apple devices to connect to. Designed for ease of use in home environments, but can cause problems with multiples of devices on a corporate / academic network.
BYOD
Bring Your Own Device. The use of personal devices on an organisations network.
Channel
A pre-defined radio frequency used by an access points.
Controller
A wireless controller is used to manage a large number or access points. It unifies configuration, authentication and deployment into one device.
Coverage
The physical area that the wireless signal covers.
CSMA-CA
Carrier-Sense Multiple Access with Collision Avoidance. The methodology that most wireless devices use to avoid multiple devices transmitting at once. APs and devices are only able to ‘listen’ to one transmission on a given stream at a time. Therefore, each device senses the carrier to check if it is clear and will only transmit if it is. If two devices do sense and therefore transmit at exactly the same time a collision occurs, the device detects this and tries again after a random delay timer.
Density
Used as a term referring to the higher population of devices in any one given space. E.g. A classroom with 30+ wireless devices requires its own access point for best throughput.
DHCP
Dynamic Host Configuration Protocol. A protocol that enables dynamic IP address allocation and configuration on the Local Area Network (LAN).
Directional antenna
An antenna connected to an access point that transmits and receives in a given direction. I.e. It’s a bit like a wireless version of a torch beam shinning down a corridor, rather than a general pendant style light bulb providing light in an area.
DNS
Domain Name Service. A service that translates a text URL into the numerical IP address for the requested server.
Dual-band
Wireless networking devices that support both 2.4GHz and 5GHz frequency bands.
Guest portal
Web-based access/login for guests on the wireless network. Managed by the controller. The user enters a username and password before being granted access to the network.
Mesh
A network of APs that aren’t cabled to the LAN, but instead repeat the signal from a neighbouring AP.
MIMO
Multiple Input Multiple Output. Utilizing multiple antennas from both an AP and a device to create multiple spatial streams, increasing throughput.
MU-MIMO
Multiple User Multiple Input, Multiple Output. The practice of devices sharing multiple spatial streams, enabling APs to communicate with multiple devices simultaneously.
Omni-directional antenna
An antenna connected to an access point that transmits and receives in all directions, forming a donut shape of coverage around the AP.
Overlap
The shared coverage space between two APs. The controller will assign channels to each AP to ensure overlapping APs are not transmitting on the same radio frequency.
PoE
Power over Ethernet. Power delivered to devices across the copper data cabling to power devices. Removes the need for a separate power cable for devices.
Radius Server
A user authentication service for use with systems like Windows Active Directory.
RF environment
Radio Frequency Environment. How electromagnetic waves react to a given physical space.
Spatial Stream
A stream of data transmitting to and from a single device antenna and an AP antenna.
Throughput
The actual amount of data that is being carried from one point to another in a given time period. Different to bandwidth.
VLAN
Virtual Local Area Network. Segmentation of users types/devices within a local area network.
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