Recap-How to Design High Capacity Wi-Fi Networks
Andrew von Nagy, Wi-Fi Expert and Owner of Revolution Wi-Fi was the guest speaker at our very successful webinar on “Designing High Capacity Wi-Fi Network’s”. The webinar also featured a Demo of iBwave Wi-Fi’s Capacity Planning capabilities by Sr. Manager Technical Product Management Marc-Antoine Lamontagne. During the webinar we received a large number of questions from attendees, some of which Andrew and Marc-Antoine were was able to answer live. However, we did not have time to answer all of them. This week Marc Antoine and Vladan Jevremovic, Research Director, iBwave took some time to address some key questions asked during the webinar. Read on and let’s keep the discussion going.
1- Can you please explain the impact of deploying access points with dual 5GHz radios on the design of high capacity Wi-Fi Networks?
The first advantage of using dual 5GHz radio is to offer twice the capacity from the same access points. Since you have 2 radios running on different channels you end up with air interface available to support more users and higher throughput. This type of architecture is made possible because of the high number of non-overlapping channels available on the 5GHz band. The second advantage is to reduce the cost of the deployment for high-density environment. Since you have 2 radios in the same access point, you end up with more capacity and keep the number of access points to a minimum. You can also save on installation cost by reducing the number of cables to pull in the ceiling in order to connect all the access points. From a Design perspective, having more than one radio in the same AP will augment the number of channels being used in that location and will reduce the channels that you can use for the other APs. This will increase slightly the risk of co-channel interference (CCI) in your design and decrease the capacity available for each AP since they are sharing the same air interface. Therefore, it will be important, as you validate your network, to look at the CCI (number of access points using the same channel with overlapping coverage). This is done in iBwave Wi-Fi using the CCI map. Also, since you are increasing the density of the channel being used, it will increase the zone of transitions between APs. It will be important to look at the location of these zones to make sure they are not located in areas of high usage. This can be done in iBwave Design using the Best Channel output map.
APs with dual (or more) 5GHz radios are not yet supported out of the box with iBwave Wi-Fi. Anyhow, a simple workaround can be used by creating 2 APs with each one using a different channel. We then have a method in iBwave Design to keep the bill of material accurate. We are currently in discussion with some manufacturers to see how we could better model this type of equipment more seamlessly.
2- How 3G & LTE offloading can be implemented using Wi-Fi and how capacity has to be planned accordingly?
HetNet Capacity modeling combining 3G, 4G and Wi-Fi applications is supported with iBwave Design Enterprise. The application allows precise definition of the market share between cellular operators, technology split between 3G and 4G and finally the % of expected traffic between cellular and Wi-Fi. Based on this information, the application automatically allocates the traffic on the right network and calculates the expected load for each one. In iBwave Design, it is also possible to configure LTE services for voice over LTE and voice over Wi-Fi.
When VoLTE is selected, the traffic is automatically assigned to the 3G service for the same operator. If VoWiFi is selected, the traffic is assigned to the Wi-Fi network. This creates a complete HetNet model to validate the overall quality of experience for the users considering the offload to different network technologies. At the end, the application allows you to validate your KPIs of capacity for each network service and the expected throughput available in average for the users.
3- What main inputs are you considering for Capacity Analysis? And how it relates to the Equipment Capacity?
Equipment capacity is the maximum number of radios associated to an AP. This is specified by the manufacturer, and if the maximum number is reached, AP will decline further association requests. The manufacturer specifies this number based on their own hardware limitations. In our capacity algorithm, we calculate “airtime capacity”, as we look into files that need to be transmitted between AP and a radio. This is specified in our “user profile”, where we list applications that are likely to be used, and file size for each application. These files need to be transmitted over a user-defined period of time. The default is one hour, but it can be expressed in multiples of one hour. In our algorithm we calculate the actual air time required to transfer all files specified in a user profile, taking into account maximum throughput that each AP can achieve, which is based on radio conditions in the network (SNR, CCI, etc). We then multiply the required airtime for each user with a total number of users in AP coverage, to get the total air time needed to transmit all files for all users. Once the total required airtime reaches or exceeds the user-specified period of time, then the maximum number of users per AP has been reached, and no more users can be served with that AP. This is what we call “airtime capacity”.
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