 | wireless head | WiFi experts |
| wireless head | WiFi experts |
The first task in designing an office WiFi solution is to understand your requirements.
An important term we use below is 'access point' (AP). This is a device that provides WiFi. Almost always, multiple APs are used in a WiFi solution.
There are five important factors for understanding office WiFi requirements:-
The more capable a WiFi solution is for each of these five factors, the more expensive it will be. Therefore, the correct understanding of requirements is essential to getting a capable solution while keeping costs to a minimum. In short, an appropriate solution.
If your office must handle large uploads and downloads, or video streaming, or video conferencing, then your APs should support higher aggregate throughput than otherwise. Content creators, for example, tend to have higher throughput requirements than normal to minimise wait times when uploading and downloading. Video streaming requires high throughput which is also time sensitive. Video conferencing has a higher-than-normal throughput requirement and is still more time sensitive, as noted below. These three use cases can add a substantial throughput load to WiFi.
If your office WiFi must provide WiFi calling (also known as voice over WiFi) then low latency WiFi is essential. Video conferencing includes voice and video. It combines a low latency requirement so that interactive conversations flow naturally, with a higher-than-normal throughput requirement noted above. Low latency WiFi requires selecting APs that have good support for it, their correct configuration, and the optimal number and location of APs. Support for low latency is a difficult WiFi requirement that is becoming more common. Low latency requirements have been addressed in WiFi 5 and WiFi 6 and will be addressed again in WiFi 7.
The more WiFi connected devices there are in an area, the harder an AP serving that area must work to support them. Increasing the density of connected devices will eventually experience two fundamental limitations:-
Concerning the first limitation. Higher levels of workload will need APs with more powerful processors. In extreme cases it may not be possible for one AP to support all the connected devices, even though it is able to cover the area. This is likely in areas like venues, where devices are close together and make heavy use of WiFi. The answer is of course multiple APs to cover such an area.
Concerning the second limitation. Like the number of trains per minute is limited by the amount of time available on their train track, the amount of WiFi that can be sent is limited by the amount of time available on the spectrum it can use. The answer for trains is to increase the speed of the trains so they are on the track for less time or increase the numbers of tracks. The answer for WiFi is similar, send the data more quickly or use more spectrum. However, WiFi has a harder limitation, the total amount of spectrum available has a reachable limit.
If your office WiFi is sufficiently critical, then some amount of over provisioning of WiFi service should be considered. Over provision is where an area is served by more than the minimum number of APs required. Over provisioning has three main benefits:-
If a design must handle large changes in the density of connected devices, such as guests in a seminar, the extra APs required will likely result in over provision of APs when that high load is not present.
There are many features that add value to the basic WiFi service provided by an AP. Perhaps the most common is a simple security feature, blocking access to anything other than the Internet. An advanced version of this enforces more complex security requirements, for example filtering out traffic to known threats on the Internet. Voucher systems improve flexibility by providing access control of connected devices with individual passwords valid for specific time windows. Added Bluetooth radios can have multiple uses, such as location tracking and device management. WiFi traffic capture can provide detailed information about specific devices and how the network is performing. Spectrum capture can help identify problems at a more fundamental level, such as interference. Alternate directional antennas can be used to enable better control of coverage.
Other than the requirements factors, there are many environmental factors that can affect a WiFi design. The simplest to understand is that the range of WiFi can be strongly limited by walls in a building. Other factors include interference from electrical devices and neighbouring WiFi. There are also problems created by weather and military satellites.
Typical office use of WiFi is not very demanding. Nonetheless, office WiFi can easily provide poor service if clumsily designed or misconfigured. Many non-obvious environmental factors can create difficulties too. Probably the most sustained competition between WiFi equipment makers has been for office WiFi, so that equipment is now excellent value. Although the demands on office WiFi have risen strongly over time, the equipment capability has more than kept pace. Consequently, the most important factor for good office WiFi is the WiFi design and configuration, not the access point selection. Select a good WiFi specialist by listening to them explain what in your environment might create difficulties. It is very unlikely that there will be none or few. For help in this see the 'Office WiFi use cases' section below
Generally, equipment makers sell access points that support all WiFi specifications up to the latest. Although they do not necessarily implement all the features. They also sell their previous generation access points. Obviously, the newer equipment is more expensive. Both access point and client devices must support the same WiFi specification to take full advantage of its advances. In an office there is usually a wide diversity of equipment supporting different specifications. Early in the life of a WiFi specification client devices that support it usually arrive in the office before the access points that do. Within two years a significant proportion of client devices will be using a the latest specification.
Some early tests of consumer equipment showed WiFi 6 to be no better than WiFi 5. This was because WiFi technology is now so complex that it takes a while to perfect it, combined with the pressure to be first to market. Further, while the latest WiFi specification always appears to be the best choice, it is worth noting that most of its advantages are for special use cases rather than the typical office WiFi use case. If you regularly upgrade access point and client device firmware, as you should, the full expected performance uplift of a new WiFi specification will eventually appear. If you are more of a get it and forget it type, you may be better to wait until the latest WiFi specification has been in products for a while.
An important new capability was introduced in WiFi 5. That was to support concurrent data exchange from access points to client devices, in other words, an access point can send data to more than one client device at the same time. WiFi 6 significantly improved on WiFi 5 by making concurrent data exchange work in both directions. Obviously, concurrency increases the amount of data that can be exchanged in an amount of time, i.e. throughput, so for the same amount of data more time becomes available on WiFi. This is very useful for high data usage, such as by many users in the high density of users use case, and in the video streaming use case, both of which are constrained by the limited amount of time available on WiFi. Concurrency also helps VoWiFi, because making more time available on WiFi should reduce the wait time for data transfer, meaning less of the delay that diminishes the VoWiFi experience. If you use media streaming, especially video, or use VoWiFi, then WiFi 6 has an important advantage.
So far, each new WiFi specification has introduced higher data transfer data rates. Like concurrency, this improves throughput which benefits the same use cases.
Another feature of WiFi 6 improves channel reuse that occurs within a small enough area to create a problem called co-channel contention. This feature will be less of an advantage for equipment that can use the extra spectrum recently made available for WiFi, discussed in the 'Spectrum' section below. If you can't wait for equipment that supports the extra spectrum, and you have co-channel contention, then this is an important advantage
In 2020 extra radio spectrum was made available to WiFi. While there is more of it, there is still fixed amount of spectrum available for use by WiFi. For office WiFi deployments, the main advantages of the extra spectrum are the same as concurrent data exchange discussed above. However, it provides a superior solution to co-channel contention than the new feature of WiFi 6. The extra channels could instead be combined into wider channels for higher throughput scenarios, such as in the streaming video use case and in the high user density use case. Another way of looking at this, is that more transfer time becomes available on access points because data can be spread over more access points on the extra channels. This improves VoWiFi because if more time is available on spectrum it should reduce the time wait for transfer (i.e. reduce latency) which benefits VoWiFi
It is useful to understand the typical office WiFi use case, and a few special use cases. This will help you to discuss your requirements with a specialist on a level that leads to an appropriate design and simultaneously check your specialist really knows their subject
The typical office WiFi use case is dominated in volume by web then email traffic, although if media streaming (such as video or music) is allowed that can be the second highest. The highest traffic by number of requests (i.e. sessions) will be DNS traffic, it is latency sensitive but relatively low volume traffic. Web protocols and ports are used by many applications to communicate with servers, therefore much of the web traffic will be due to other kinds of activity than viewing web sites. For example, anti-virus programs getting threat signatures, data backup and file synchronisation programs, file downloads, app updates, and video and voice conferencing. Taken as a whole, office WiFi network traffic mainly comprises short low volume data exchanges. Occasionally there are medium sized exchanges, but they are usually short lived. Large distinct data exchanges are infrequent. The combined traffic forms waves of rising and falling but modest volume that correlate with things like lunch breaks and shift changes, repeating daily and weekly in a predictable way
One common special use case is streaming music/voice/video; these tend to be used more extensively in creative industries. Music and voice (such as podcasts) require little data, although people are intolerant of interruptions in streaming, especially for voice, so low latency is very important for this special use case. Some streaming applications try to ensure good service by downloading a large chunk of data at the beginning, causing a spike in data transfer. This is typical behaviour of Spotify, for example. Video requires much more data than music and voice and so more time on WiFi to transfer it. The amount of time available on WiFi is a limited resource. Streaming multiple videos simultaneously can quickly consume all available time resulting in a degraded WiFi experience. Video players like YouTube usually buffer just ahead of the current play point. This behaviour reduces wasted data transfer because it is common for video streams to be terminated before they complete. This behaviour also makes the video data transfer pattern less spikey than music and voice and so easier to manage, except when there are multiple concurrent streams
Another special use case that is increasingly being incorporated into the typical use case, is voice calls over WiFi instead of mobile networks; this has become known as voice-over-WiFi (VoWiFi) or WiFi calling. Obviously, transfer delays must be minimised, otherwise it creates awkward conversations like those you have probably seen in live interviews held between people in different continents, or worse with pauses and lost or garbled parts within speech. In fact, people are at their most intolerant of glitches in conversation. In recent years VoWiFi has become a common feature of smartphones, although it is usually disabled by default, probably because it does not perform well on typical WiFi networks. So, although VoWiFi data throughput is low, by some measures it is the most demanding use case, requiring careful equipment selection and configuration. This use case is especially valuable if mobile phone reception is poor in a building
A less common special use case is a high density of users in an area; this creates three important difficulties. Firstly, managing many client devices is a bigger administrative task for an access point, requiring more processing power and so more expensive access points. Secondly, if many access points are used to manage the users, all available channels may be used, forcing channel reuse. In a small enough area channel reuse can lead to a problem known as co-channel contention which degrades WiFi performance. Thirdly, more users transfer more data, which uses more time on WiFi, which as noted above is a limited resource. This use case is common in places like stadiums, venues, and lecture theatres but is becoming more common in offices that have rooms for training/seminars/press conferences. Anywhere really where a lot of users are close together and using WiFi
Finally, a recently increased use case, video conferencing. Video conferencing is a difficult use case because it combines the moderately high data volumes of low-quality video with the low delay requirements of VoWiFi. Consequently, it is important that the algorithms that prioritise voice over video work well, which is mostly dependent on how much has been spent on developing them and so effects the price of the equipment. Good modern access points and good client devices can manage this well, but we should not expect great results from low-cost equipment installed without care for this use case, especially if there are many users of access points
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