Wireless Limitations

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Limitations of wireless networking


While wireless technology is undoubtedly an appropriate technology for many applications, it should not be regarded as a ubiquitous solution for every networking environment – despite great advances in recent years, the concept of the "wireless building" is still some way off. For any application where mobility is not critical, a hard-wired connection will provide a faster, more reliable and more cost-effective solution.

Near-ubiquitous availability of wireless services and the proliferation of wireless-equipped laptops have resulted in some misconceptions about the role of this technology. Wireless is not the solution to every connectivity problem.  Information Services needs to ensure that the expectations of users are managed appropriately.

It is easy to see wireless networking as a direct replacement for wired networks, on grounds of cost per connection, ease of installation, convenience of use and the desirability of the technology. However, this would be to mistake the level of development of the technology, its reliability, and therefore its appropriate role in a campus environment.

Wireless network technology has a much smaller effective data throughput than the wired equivalent currently deployed, and this situation is likely to be the case for some time.  While the technology has advanced greatly, real-world deployment of some of the advances is still some time away.

The wireless network should not be considered a like-for-like replacement for the conventional University wired network. It is intended to facilitate short-duration connection to the network from convenient locations without being inhibited by cabling and the need to find a physical network point.

In particular, in most cases it is unsuitable for replacing a normal wired office connection, typically in operation for most of the business day, for various reasons:

  • Currently-implemented wireless technology does not provide the same bandwidth guarantees as a wired connection; in fact the bandwidth is substantially more limited than a wired connection, and is additionally shared with other users who are connected to the same access point. The theoretical aggregate bandwidth available for all users connected to a single access point is substantially less than that available to a single user connected via the wired network;
  • Wireless networks are subject to interference from any electromagnetic sources, and the signal strength is greatly reduced by many building materials or any water-containing object (e.g. a class full of students). The presence in the vicinity of items such as microwave ovens, DECT phones, wire-framed door glass, people, machinery, and many other things in the local environment will dramatically reduce the throughput and reliability of the installation; such interference may come and go depending on the operation and movement of objects, and a measurement of interference at one time says nothing about the level of interference at another time;
  • For authentication purposes, wireless network traffic passes through one of a number of gateway devices, and these may cause congestion problems or even failure under error conditions or high or malicious traffic; the actions of a few can potentially affect the network connections of many;
  • Traffic from the wireless network is firewalled - not all campus services may be available to wireless users. This is necessary so that for example, bandwidth-hungry applications such as streaming video are tightly controlled, to ensure that no one user can inadvertently saturate the shared network, to the detriment of other users in the vicinity.

Regarding use of the wireless network for bulk teaching purposes, it should be remembered that by its nature, a single access point cannot be expected to provide sustained and reliable service for large amounts of traffic. Typically, an access point can reasonably support around 25 or so users with a 'bursty' traffic profile (e.g., opening typical web pages, reading email). Performance of wireless in a particular area will decrease dramatically as the number of users increases, or if those users maintain sustained flows of traffic for a period of time (for example, at initial network logon, while transferring large files or web pages with large images, or streaming audio or video content).

Information Services is always ready to offer advice to teaching staff at any time, but preferably, well in advance of any potential usage, so that operational advice can be provided, or any additional service provision made, in order to try and minimise potential problems. It is not always possible to mitigate problems by the installation of additional access points.

In deploying wireless networks, IT Services follows best practice advice and guidelines from many sources, the foremost of which is the JANET Wireless Advisory Group. The group has issued a number of documents relating to wireless networking, both technical and non-technical, drawn from experience in the academic community.