One of the key requirements in our recent Sandman Signature Hotel project was to deliver a WiFi network that could guarantee 100% wireless network coverage for guests and staff at the 170 room hotel.
Hotel wireless networks are typically considered to be high density environments where the number of client devices and required application throughput exceed the available capacity of a traditional “coverage-oriented” Wi-Fi network design.
If you’re considering installing a wireless network into a hotel environment, even a well-designed network that provides coverage at good signal strength and SNR (signal-to-noise ratio) will be insufficient to ensure high performance due to inadequate capacity.
The bottleneck in the system is air.
The unavoidable fact is that Wi-Fi relies on air to carry signals and air is a shared medium. This means that clients and access points must contend for “available airtime” to transmit data.
The objective then, when you need to achieve 100% true WiFi coverage, is to segment clients into the smallest possible collision domains (different radio frequencies) while maximizing the use of available spectral capacity.
Having achieved this with the Sandman Hotels project successfully, we thought we’d share our 5 Key Principles to help you achieve true 100% “coverage” for your own hotel.
#1. Coverage Does Not Guarantee Capacity
There is a substantial difference between Wi-Fi networks designed for “coverage” versus those designed for capacity. Coverage indicates signal strength but capacity covers the amount of signals that can be transmitted through the air.
Whilst signal coverage from access points in dense environments like hotels may be strong, crammed airspace leads to less available airtime for devices. This leads to slower connections and more unpleasant user experiences.
To meet performance and capacity needs of a truly satisfactory wireless network experience, the following additional items should be considered:
- Design the network to make maximum use of available spectral capacity
- Take steps to reduce co-channel interference
- Encourage devices to use the 5GHz band frequency instead of the more crowded 2.4 GHz frequency with intelligent Band Steering techniques.
- Distribute wireless users between available Access Points with load balancing
#2. Identify Client Device Capabilities
It almost goes without saying that before you start upgrading your network, you should conduct a requirements gathering exercise.
With a thorough understanding of user needs, you can begin to design a solution that fits with your business objectives. Through the process of requirements gathering, you can identify network design objectives so that the WiFi network will align with business targets and meet desired performance levels.
To gather requirements:
- Identify the client device types and their wireless capabilities
- Get an accurate count of how many devices will need supporting
- Determine data rates and frequency bands
- Calculate the maximum throughput that each device on the network can achieve
#3. Estimate Data Throughput Required by Applications on the Network
The table below from the Cisco Wireless LAN Guide lists typical bandwidth requirements for common applications.
Once the client device and application requirements have been identified, you can forecast the required access point radio capacity and subsequently estimate the number of APs required to fulfil 100% WiFi coverage.
#4. Estimate Network Load (Airtime)
Aerohive give an excellent formula to help you calculate estimated load in their Hi Density Wireless Whitepaper.
First, determine how much airtime the target application will consume when used on each device type by dividing the required throughput by the maximum TCP or UDP throughput the device is capable of achieving.
Second, multiply the total client device quantity for each device type by the required airtime per client device to determine the number of AP radios required to support those devices in the environment.
Finally, to forecast the aggregate required AP capacity, add the number of AP radios required to support each device type at the target application throughput level together to determine the total number of AP radios required. Adjust the number of radios if only a percentage of clients will be connected to and transmitting on the WLAN concurrently. If all client devices will be online concurrently, then no adjustment is necessary. Since most deployments utilize dual-radio APs, divide the adjusted number of AP radios by two to forecast the number of dual-radio access points required to support the identified devices and applications. If a fractional number results, round up.
The example cited in the whitepaper above is this:
A 1-Mbps standard definition TCP video application running on an Apple iPad 2 that is capable of achieving a maximum 30 Mbps of TCP throughput yields an airtime consumption of 3.33% per device on a particular channel. This means that every iPad 2 device running the video application requires 3.33% of the capacity of a single access point radio (assuming no outside noise or interference).
Perform this calculation separately for every device and application type that will be supported in the environment.
Then, if there are 40 total Apple iPads, and each one consumes 3.33% airtime, then a total of 1.33 AP radios are required to support all 40 devices concurrently (40 x 3.33%). Perform this calculation individually for every device type that will be supported in the environment.
Remember, the calculations are only estimates, and the final scenario will likely be different. The process however, is a useful tool in helping you design an appropriate, fit-for-purpose wireless network.
#5. Make Full Use of 5GHz Frequency Band
As wireless devices roam throughout your hotel, there needs to be seamless overlap between access points to ensure network connectivity remains constant.
All points of access that operate on the same frequency will contend for available airtime. In high density environments like hotels, merely having multiple access points on the same frequency with overlapping signal fields will not increase capacity or performance.
In fact, it has the opposite effect as it creates more competition for airtime and reduces performance. This is known as co-channel interference.
Therefore it is critical that WiFi cells operate on diffferent frequencies to reduce interference.
#6. Ensure Wireless Signals are Strong Throughout the Hotel
Wi-Fi clients achieve the highest data rates when they reside within an area of strong signal strength from the access point with minimal interference.
In the pursuit of good signals, most manufacturers advise trying to achieve a consistent signal strength of -65 to -67 dBm with an SNR of 25-30 dB.
Therefore, hotel networks should be designed in a way that allows them to maintain signals to at least two APs on non-overlapping channels (for roaming purposes), high SNR, and are able to maintain high data rates.
Closing Notes
You can’t ignore the widespread adoption of wireless devices and the expectations of users.
The only way to ensure a good customer experience in a high density environment like a hotel is to use expert design principles that put network planning and user experience at the very forefront of the project.
As well as expert design, the technological solution you employ must also be fit for purpose and best in class to meet the needs of the network. Therefore, to deliver a truly 100% wireless coverage, you need to follow a strict process of gathering requirements, expert design, detailed configuration and continual optimisation and maintenance.
Documents used in the production of this information:
