Every day non-technical people around the world effortlessly install home wireless networks without ever worrying about an RF site survey. At the same time, experienced service provider and enterprise IT administrators battle with RF site surveys before they can deploy wireless networks that span larger spaces. Why?
The answer is simple: 802.11 access points (APs) interfere with each other, so a site survey is required to keep the APs far enough apart to avoid interference yet close enough to provide coverage. Most homes require only a single AP and thus avoid interference. However, most offices and other commercial spaces require multiple APs to assure adequate coverage, thus mandating extensive — and expensive — site surveys to resolve interference issues. It takes RF expertise to build a functional wireless LAN across a large space while minimizing interference/coverage trade-offs inherent in multi-AP installations.
The interference issue and correlated site survey have hampered the growth of 802.11 in large-scale networks. Not only does interference create installation hurdles but the dynamic nature of RF coverage also can wreak havoc with the wireless network, even after a thorough site survey. Common events, such as opening an elevator door or installing a new metal filing cabinet or a display case, can change the RF domain sufficiently to alter the delicate balance between coverage and interference. This issue, coupled with the lack of RF expertise among most enterprise and service provider IT staffs, can cause operational costs to skyrocket when trying to control and manage a WLAN.
So why aren’t there solutions that overcome the interference issue and still create a WLAN that provides scalable coverage? Unfortunately, vendors face a dilemma; they either must comply with the 802.11 specifications and endure the multi-AP interference issues or they must develop their own proprietary solutions. So far, vendors have chosen to comply due to the market appeal of 802.11.
However, there is a way to provide scalable wireless coverage without interference and still maintain compatibility with 802.11. The first step is to rethink how to scale coverage areas. Instead of deploying multiple APs and dealing with interference, IT administrators can deploy a single AP that has antennas that connect over the Ethernet network. With this approach, multi-AP interference virtually is eliminated because there is only one AP. The benefit is scalable wireless coverage that doesn’t require the traditional site survey. Since there is no interference, these “packet antennas” can be placed wherever coverage is required and as close together as desired, providing an 802.11-compliant interface to the wireless clients. In essence, an AP changes from a small device with two antennas to a central wireless controller with packet antennas throughout the space.
Finally, WLANs of all sizes can be installed as easily as home networks. Wireless coverage can be established wherever required without worrying about interference, RF channel management or AP placement. Wireless networks can be deployed and scaled to provide uniform coverage by people with no RF expertise.
In addition to making large WLANs easier and cheaper to install, this packet antenna architecture offers several other key benefits.
Since the packet antennas are completely unmanaged devices, the configuration, management, and security of the entire WLAN are combined into a single platform. This approach minimizes the operational issues of maintaining a wireless LAN. The entire WLAN can carry mission-critical traffic because the centralized AP can be configured with fault tolerance and redundancy.
Without worries about channel interference, the packet antennas can be placed as close together as desired to enable several solutions impossible in multi-AP environments. First, dense wireless coverage can be provided with true redundancy — if a packet antenna fails, coverage is maintained by the dense array of packet antennas. Also, since each packet antenna provides a full 802.11 coverage cell, the capacity of the wireless network can scale to meet the performance needs of the network. In addition to all of this, the single AP overcomes the client mobility issues inherent in multi-AP installations. The client has to associate only once to the single AP, and as that client mobilizes throughout the network, it never has to re-associate or re-authenticate. Not only does this provide better end user performance, it eliminates the handoffs that technically hamper the adoption of latency-sensitive applications, such as voice over WLANs.
Large wireless LANs for enterprises and hotspots show a tremendous amount of potential, but much of that is locked behind basic technical issues. Like the early days of Ethernet, wireless still is a complex technology. In addition, just like Ethernet, a slight modification of the architecture perspective can open up a whole new world of simplicity and scalability. With a wireless architecture based on packet antennas and a central access point, wireless LANs can overcome the issues that plague rapid enterprise and hotspot adoption.
Harry Bims is founder and CTO of AirFlow Networks. He can be reached at hbims@airflownetworks.com.
