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The wireless edge of the network has become ubiquitous, and so too have our expectations of a reliable and secure connection. As we have become used to the convenience of connecting wherever and however we want, we tolerate the flaws in a typical Wi-Fi connection – pauses in downloads, occasional drop-outs where we must re-connect, and lengthy waits as we try to join a public Wi-Fi network. For our personal browsing, we make a conscious compromise between convenience and reliability because apart from being frustrating at times, no real harm is done. But in a business environment, reliable wireless connectivity can’t be a compromise for critical operations, especially where it can be the difference between life and death.

Why multi-channel is not always the best choice

Most Wi-Fi networks operate on a multi-channel architecture (aka “micro-cell”), where each wireless access point (AP) connects to a mobile client using one of several radio channels. To achieve optimal throughput to each client, it’s important to have good signal strength but minimal radio interference by ensuring that the APs are not too close, and the same radio channels do not overlap (called “co-channel interference”). However, this can be difficult when there may be physical layout constraints, and there are only a few channels to choose from – and even harder in a multi-tenancy building when your neighbour chooses the same channels as you! To assist with this, tools are used to survey the physical site to plan the channel map for the optimal experience, but these tools can be expensive and time consuming to use effectively. This is how typical Wi-Fi networks are designed, and why they occasionally exhibit reliability glitches.

Some years ago, an alternative architecture was proposed that utilised the same radio channel for all APs in the network. In this model, placement of the APs was no longer critical because they all used the same channel, so interference was not an issue. If coverage was poor in one location, then additional APs could be easily deployed without worrying about introducing bandwidth-destroying interference. Although the single-channel architecture solved one of the biggest challenges of Wi-Fi network design, it too had some limitations, the main one being that its total network throughput was usually lower than multi-channel.

Since then, multi-channel Wi-Fi has become the predominant architecture and most of the time, it does a great job. However, there are some situations where multi-channel is not the best choice, and alternative solutions can provide a better experience. Applications of this type usually fall into three categories:

  1. Dynamic physical environments, like warehouses, where radio coverage is continuously being changed as objects are moved and removed. This makes multi-channel planning almost impossible, so the work-around is to deploy more APs. Unfortunately, this not only increases cost, but it introduces more radio interference, which reduces data throughput.
  2. Environments that must have reliable connectivity to mobile devices, like hospitals, where even a momentary loss of data connectivity can have a serious effect. As a wireless client moves, its connection will “roam” to another AP when it perceives a significantly more attractive signal. Unfortunately, this roaming process can sometimes be slow and disruptive as security credentials must be established or re-negotiated. Often this can manifest as an annoying lag on a VoIP call, or random artefacts in video. One solution is to use only wireless clients that support “fast-roaming” protocols, or intelligent bridging devices that handle the roaming on behalf of the client. Both these solutions add complexity and cost.
  3. Environments where there are many roaming wireless users, like schools, hospitals, public venues, etc. Multi-channel struggles to cope in these situations because only one client can talk to an AP at a time. So, having more clients associated with an AP means there is less time for each client to talk, so the effective bandwidth to each client is reduced. Adding more APs doesn’t always help because co-channel interference increases, which also reduces bandwidth.
What’s needed is a cost-effective Wi-Fi solution that combines the best features of both architectures: multi-channel’s throughput with single-channel’s easy deployment and reliable, seamless roaming connectivity. Luckily, there is a solution that allows the user to select multi-channel, single channel or both, for the optimal Wi-Fi experience. Previously, users had to choose one architecture or another, and where it was desirable to run both multi-channel and single-channel systems on premises, they had to manage two different networks with different tools. Administration efforts were increased because firmware updates had to be applied twice, and engineers had two different systems to learn and maintain.

What does Allied Telesis have?

Now, with the new Hybrid Wireless solution from Allied Telesis, a Wi-Fi network can be deployed with a mix of channel architectures and administered using the same management tool. Using the name “Channel Blanket” for the single-channel architecture, the Hybrid Wireless APs can offer both multi-channel and Channel Blanket at the same time! Operating at the fastest Wi-Fi speeds available today, they are the ideal choice for reliable Wi-Fi in the challenging environments described above:
  1. In a dynamic environment, Channel Blanket APs can be deployed in greater numbers than multi-channel APs because their single radio channel does not introduce interference. If greater bandwidth is required then the APs can be configured to support up to 3 blankets concurrently, which significantly increases capacity in dense AP environments.
  2. Channel Blanket has the advantage in an environment that requires reliable roaming too. With single-channel, all APs in the network appear as if they are a single AP, so the mobile client only sees that it is connected to one large AP. When the client moves, the Wi-Fi controller assigns it to a new AP, so the client is unaware of the “roam” and needs no special features to support it (e.g. fast-roaming protocols). Not only does this simplify the client, but it means the Wi-Fi connection is not interrupted by the move, and no latency is introduced, or data lost. Note that although new standards have been ratified to facilitate better roaming (e.g. IEEE802.11k/v/r), only high-end, modern wireless clients support these standards (e.g. iPhone6 with iOS7 and later). Clients that do not support these standards will still experience some disruption or data loss when roaming on multi-channel wireless networks.
  3. In an environment with a high client density, Channel Blanket can increase the available bandwidth by enabling more APs to be installed in the same area without introducing co-channel interference. Although this is possible with multi-channel too, Channel Blanket solutions require no channel planning so installation and management is much easier.
Until now, customers that required industrial-grade Wi-Fi, high-density coverage or seamless roaming had to make a choice between multi-channel and single-channel architectures. With multi-channel, high client density is difficult to achieve, and you risk having wireless clients that do not support fast roaming protocols; with single-channel you risk using an “unconventional” solution requiring disparate management tools. To mitigate these risks, customers wanted to use both architectures together, but until now, this required two different wireless systems or many complex work-arounds, which were cost prohibitive.

Conclusion

The new Allied Telesis Hybrid Wireless solution uniquely enables customers to configure both architectures simultaneously on the same hardware to best suit their specific application. Customers now have the flexibility to configure their wireless LAN to provide multi-channel coverage for some clients and Channel Blanket for others – useful when some clients want the best bandwidth, and others need seamless roaming for non-stop connectivity. Combined with our innovative Autonomous Wireless Controller (AWC), which is a unified, easy-to-use management tool that continually tunes the APs for optimal coverage, the Hybrid Wireless solution is an effective alternative to the compromises and work-arounds of multi-channel Wi-Fi. To find out more about Hybrid Wireless and how you can have a no-compromise Wi-Fi experience with reduced administration effort at a reasonable cost, contact Allied Telesis.