Multiple Access Point Architectures and Wi-Fi Whole Home Coverage
As mentioned in a previous blog post on AP Coordination by my colleague Neeharika Allanki, homes sizes are growing and the number of client devices in a home network are increasing exponentially. There is a need for not only consistent performance in terms of throughput and connectivity, but also Wi-Fi coverage throughout the home. Consumers often need more than one Wi-Fi Access Point (AP) in the home network to provide that coverage.
Many houses in the world do not have existing wires that can be used to network these APs together, and so one of the easiest and most cost effective ways to provide whole home Wi-Fi coverage is by using Wi-Fi itself to connect together the APs in the home. The technologies available today that can do this are Mesh APs (MAPs), Repeaters or Extenders.
Wireless repeaters and extenders have been around for years due to consumers seeing the need to expand Wi-Fi coverage in their homes. While some form of wireless mesh networking has been around for more than ten years, until recently there were not products designed for the home that used mesh to connect multiple APs. In the past year, there has been a dizzying array of product announcements and introductions for home Wi-Fi coverage, with many of them using mesh networking.
Mesh Access points (MAPs) are quickly gaining traction in home networks mainly due to ease of installation (even over Repeaters/Extenders) and the promise of high throughput with whole home coverage. A mesh AP network can be defined as a self-healing, self-forming, and self-optimizing network of MAPs. Each MAP can communicate with others using smart routing protocols and thereby choose an optimal path in order to relay the data from one point to another.
As mentioned before in our AP Coordination blog, client steering (moving Wi-Fi clients to the best AP in each location) and band steering (moving and keeping Wi-Fi clients on the best band: 2.4 GHz or 5 GHz) are very important in any multi-AP solution, such as mesh or an AP + repeaters/extenders network. This is needed to ensure that each mobile client stays connected to the best AP for its current location. Without client steering, Wi-Fi clients may show connectivity to Wi-Fi, but throughput may suffer tremendously. This often shows up as the dreaded “Buffering…” message when streaming a video or a slow progress bar when loading a web page. In a fully wireless multiple AP solution, client steering and band steering is even more critical due to the throughput and latency penalty when traffic is repeated over Wi-Fi from one AP to another. As MAPs communicate with each other to form the mesh network, they implement some form of AP Coordination, and it is usually proprietary in nature.
CableLabs recently tested mesh networking solutions and AP + repeater solutions consisting of 3 APs in a 5000+ sq. ft. test house. We performed throughput, jitter, latency and coverage testing at more than twenty locations in and around the house. We found that we were able to run two streaming videos, at HD bitrates (~20Mbps), to video clients in the home while also delivering over 50Mbps to our test client. Both mesh and AP + repeater solutions were able to handle this video throughput, as well as deliver over 50Mbps throughput throughout the house and even to some areas 20’ outside the house. This is excellent news for consumers whose access to the Internet is wireless and who want that access everywhere in their homes.
CableLabs is working with vendors to define a standardized AP Coordination Protocol that would allow all APs in a home network to share information to allow them to make client steering decisions, along with other network maintenance tasks.
AP Coordination in Home Networks
Multiple Access Points Can Improve Home Wi-Fi Coverage: The Secret Sauce is AP Coordination
Before we address AP Co-ordination in Home Networks, it is important to note that average home sizes have been increasing at a steady pace in the past four decades as seen from the figure below.
Increasing Home Size
As consumers, we expect our home Wi-Fi network to be ubiquitous, providing reliable connection speeds wherever we are in the home. A single AP may not be capable of providing whole home coverage, especially in larger sized homes. In a recent blog post, my colleague Vikas Sarawat described how a range of multi-access point architectures have emerged to solve this coverage gap. These architectures solve the whole home coverage problems but there are other gaps that need to be addressed in order to have an overall positive Wi-Fi experience.
Single AP vs. Multiple AP Architecture
For example, most consumer grade access point solutions currently lack a centralized Wireless LAN controller (WLC). In general, a WLC acts as a commander-in-chief which manages and controls all the APs that it serves and thereby leads to network optimization.
In the absence of a centralized WLC, multiple APs do not communicate with each other. In fact, they can at times treat each other as rogue APs that are not even operating on the same network.
Hence, there needs to be some sort of a direct communication protocol between these multiple APs in-order to provide a good Wi-Fi experience to the consumers. Although AP co-ordination has been a topic of research in a controller-based architecture ecosystem (e.g., for enterprise and community Wi-Fi environments) for some years, historically, the residential consumer premise equipment vendors have not paid much attention to coordination since most homes only had a single AP. To address this shortcoming, CableLabs is actively working on defining and standardizing the AP coordination protocols.
Our goal is to have a lightweight AP co-ordination solution that provides the following two benefits:
Optimal AP selection: When there are multiple APs available, many clients rely solely on signal strength to decide which AP to connect to, but it might not always be optimal concerning throughput for the client.
There are often conditions where a lower received signal strength indicator (RSSI) from the gateway AP may provide better throughput than a stronger RSSI from the repeater. The client cannot determine which is the best connection on its own – the infrastructure must inform it. Choosing the best point of attachment in each location is a decision that warrants information and intelligence on the client-side, the network-side, or possibly both.
Client Steering: APs also need to decide when and how to steer clients to the best AP based on network conditions (e.g., load, bands). This is especially important since many clients prefer to stay associated with one Wi-Fi network even though another Wi-Fi network with “better” connectivity is available. This is commonly referred to as the "sticky client" issue.
With AP co-ordination, the APs can exchange information on how best to get rid of the sticky client problem in a standard fashion. A partial solution has been defined in the IEEE 802.11k and 802.11v standard but not many APs or clients implement them yet.
While the IEEE 802.11k defines methods of retrieving information from clients in the form of neighbor requests and reports, the IEEE 802.11v standard provides the AP with the ability to configure client stations wirelessly in the form of the BSS Transition Management (BTM) feature.
To summarize, AP coordination is an important topic of research, particularly within the home networks where there is no WLC. CableLabs is actively engaging with the vendor community to develop a standard way of implementing in-home AP coordination protocols which we plan on submitting to the standards bodies such as WFA and WBA in the near future.