Following our recent Wi-Fi survey of Melbourne CBD, NetWireless detected and mapped over 35,000 individual access points from cafes, shopping centres, tourism and government sectors throughout the city and detected over 60,000 separate Wi-Fi networks. Although, this study had limitations we could gain significant insights about Melbourne’s Wi-Fi network.
Our previous blog piece highlighted that 23% of Melbourne CBD’s Wi-Fi networks are unsecured; a major concern for security! So, it was even more shocking to identify that Melbournians are happy with:
- slow network speeds
- unexplained packet/data losses
- broken signals causing screen jitters
- overall cumbersome user experience leading to lower productivity in the workplace.
From the snapshot of data sourced we can see that Melbourne’s CBD network is overcrowded, with access points deployed over the top of each other. Within such proximity, the Wi-Fi signal is extremely prone to interference resulting in networks having significantly reduce performance.
Density of Access Points is a Big Problem
On average, in Melbourne CBD an individual Access Point has been detected every 38 SQM*, which is often the case with unregulated deployment. Basically, you have a lot of Access Points working over the top of each other, causing significant adjacent interference between different networks and interacting devices. The location of an Access Point is a vital consideration in reducing interference across a network. If there is over deployment, by simply adding more Access Points to solve an underperforming network you will inherently make the situation a lot worse.
Further to this, non-Wi-Fi interference can also be problematic. To reduce dead spots, carefully place Access Points in a 1m clear zone away from materials and items that obstruct signal.
Bandwidth Strategy to Reduce Congestion
A congested network will reduce performance as throughput will be delayed and drop outs of information more likely (known as co-channel interference). You can implement numerous techniques in high density environments to reduce congestion, one of which is to increase the bandwidth.
Wider bandwidths allow for a higher data rate (the speed at which the client devices are able to communicate with Access Points) whilst lower bandwidth reduces the ability to have additional devices on the network. Be conscience that increasing bandwidth will create fewer non-overlapping channels. Figure 1 highlights the bandwidth selection within Melbourne CBD.
Figure 1. Bandwidth utilization across the Melbourne CBD from NetWireless subset of data.
Most networks in Melbourne CBD function on 20Mz of bandwidth which is usually associated with the 2GHZ wavelength. This is expected as most devices are supported on the 20Mz/2GHZ. In dense environments, 20Mz should be used on the 2Ghz frequency to reduce co-channel interference.
Usually associated with the 5Ghz Wavelength are 33% of devices functioning on the 40Mz or wider bandwidth range. In fact, 15% are functioning on the 80, 80+80 or 160Mz bandwidth. 5Ghz frequencies offer more bandwidth, channel selection but require higher density of Access Points.
- It is not a good idea to run 40Mz on the 2.4Ghz as this will create overlapping channels and increase co-channel interference.
- Using 20Mz on 2.4GHZ provides 3 non-overlapping channels (1,6, and 11) and these are the standard recommendations which is why many wireless routers will automatically select these channels. However, be cautious of neighbouring networks all doing the same.
- The 160Mz range will allow only 2 channels to be available and should only be an option in very small, well-designed environments with little or no neighbouring interference.
- Access Points and client devices must support the chosen bandwidth
If you’ve extended the bandwidth and the problem is worsening for your network from the creation of overlapping channels and yet your client density is still increasing then it’s time to review the channel selection.
Channel Selection Strategy to Reduce Congestion
In the 2Ghz frequency most channel selection is on the 1,6, and 11 as expected with least utilization on channel 12. In the 5Ghz range channel 36 is most utilised and channel 120 least used.
Figure 3. 5Ghz Wi-Fi Network channel selection within our subset of data collected from Melbourne CBD.
Some networks have been intentionally diverted to less congested channels (even though frequencies overlap). This is possible by recording SSID data to identify the ideal channel selection for you network.
- Avoid placing a neighbouring Access Point on an adjacent channel. Although not always possible, it is good practice.
- Strategising to select channels that reduce adjacent interference will see improved network speeds.
- If you’re on the 2GHz frequency, it may also be worth considering transferring from 2GHZ to a 5GHZ network as it provides far greater channel selection. With more channel choice comes the obvious benefit of reducing adjacent interference. Access points located next to one another can be placed on different channels to reduce interference. However, the downside to this decision is that access points need to be in a higher density to counteract the shorter travelling distance of the 5Ghz frequency.
Ensuring your equipment can simultaneously run across both Wi-Fi frequencies (2.4Ghz and 5Ghz) would be the goal in micro-managing your network to its ultimate performance.
The Wi-Fi standard Deployed Matters
Each Wi-Fi standard protocol deployed will define what capabilities are available on your network including the frequency range, bandwidth capabilities, data rate and available channels. Figure 4 represents protocols deployed within Melbourne CBD. As you can see there is a range from old legacy systems to the most advanced currently available Wi-Fi standard in Australia.
Ten percent of networks detected were on the most advanced protocol for wireless environments. The 802.11ac protocol enables 24 channels in 5Ghz range and 1.3Gps data rate. It is highly advisable for networks functioning on older 802.11 protocols to consider upgrading their network protocol.
- Only one 802.11n standard can work on the 2Ghz in the same location before there is significant interference.
Are you experiencing a slow network but are not happy about your situation? NetWireless can complete a site survey using reputable equipment by Ekahau to identify any network issues.
NetWireless is a multi-disciplinary IT network and management company specialising in Wi-Fi design, deployment, security and managed services. Speak to our technical consultants today (CALL 1300 324 844) to ensure your Wi-Fi infrastructure will meet your needs.
* The total survey distance was 64km, but our covered area, was close to 45km (due to riding on both sides of the street and crossing the same intersection up to 4 times). Based on 45km survey area; On average one access point is detected every 38SQM. What our survey does not pick up, and can be more interesting, is Access Points in the middle of office buildings, or potentially above the 6th floor of a skyscraper. If we estimate that there is one wireless Access Point per 38SQM and compare this to ‘Melbourne City Councils CLUE 2015 Report – Docklands, Melbourne & Southbank’. The total combined floor space of Melbourne CBD (office, residential, retail, entertainment and carpark space) would equal 20,740,800 SQM which could mean that there are up to 545,810 Wireless Access Points potentially located within Melbourne CBD. To put in perspective, Bryce managed to survey 2,100,000SQM. Not bad effort, but just over 10%.