The 802.11 wireless-local-area-network (WLAN) market continues to enjoy exceptional growth. According to IC Insights (www.icinsights.com), this year's 802.11 silicon shipments are projected to reach 35 million chips. That number translates into 80% growth for 2003 alone. As this trend continues, radio density will dramatically increase in multiple environments: enterprises, public hot spots, and—eventually—home-entertainment systems.

This radio-density explosion will be a mixed blessing, however. Today, every cell in an 802.11 WLAN is actually a shared network equivalent to the early days of wired-Ethernet LANs. In addition, factor in the limited number of radio-frequency (RF) channels combined with large coverage zones. These elements limit the number of shared networks that can be deployed in any given space.

Some people think that these problems could be solved with better network management or more sophisticated site surveys. Other individuals believe that these issues can be mitigated with tools that manually measure and configure the RF environment. But these proposed solutions are work intensive and expensive. Plus, their static factors make them problematic as the number of WLAN users increases.

Once they become operational, 802.11 WLANs constantly change. As more end stations are added, WLANs must rearrange themselves or expand for better performance and routine fault management. As the network grows in size and complexity, each of these tasks becomes geometrically more difficult. The necessity to automate some or all of the daily-operations management becomes increasingly important.

Remember that the environment is subject to constant change. People and devices move, furniture and partitions are re-arranged, or a variety of bandwidth-demanding applications is added. The image of a team of WLAN managers following users around in order to readjust and fine tune network operation is logistically unsound and economically doomed.

The ideal solution is a completely automated, self-organizing WLAN system. It should monitor, configure, and optimize the RF domain wherever and whenever it's needed. To be truly automated, however, the RF control system must address certain requirements. Installation, for example, must be simple plug and play. All changes must be self compensating.

In addition, the load must be dynamically and optimally distributed across available bandwidth. When it's possible, roaming must be at the maximum data rate. Fault handling and failover have to be automatic and predictable. Lastly, the network's adaptation behavior must always be stable and deterministic—not unpredictable and oscillating.

The control system should be continuously running so that it rapidly adapts to changes without user intervention. To allow for installation in a variety of devices (clients, access points, and switches), the control system must be lightweight and computationally efficient. It also must be able to work across multiple network architectures.

When it comes to purchasing an 802.11 network, many users find that the cost of installation is the number one stumbling block. Compared to the cost of purchasing the WLAN hardware, it typically costs more to survey the site; develop an engineering plan; hire consultants; simulate the environment; install the equipment and software; and follow up with tuning. After the initial installation is complete, thousands of dollars may still be needed to manually reoptimize placement and reconfigure channel maps.

In future environments, such as home entertainment, planning won't be an option at any level. Consumers won't tolerate anything less than being able to plug in devices wherever they want them. This means that the networks must eliminate configuration limitations so 802.11-based products can be installed without any special skills. For these goals to be reached, a continuously running automatic system must gain control over several elements. For instance, the self-organizing WLAN network must control frequency/channel selection and transmit power control.

A self-organizing network should constantly evaluate and recompute optimal channel allocations for the entire network. It doesn't matter if this evaluation is done at initial startup or on an ongoing basis. The vital point is that this allocation should be handled automatically. Otherwise, the WLAN will need reconfiguration every time a change is made to either the network settings or the RF environment.

Upon closer inspection, this problem reveals other dark sides as well. The elements of channel selection and transmit power control are highly interdependent. If both elements aren't simultaneously coordinated, the physical placement of the APs is restricted. For example, say the transmit power isn't controlled. By default, all of the cells would operate at full power. The APs would then have to be spaced very far apart to avoid co-channel interference. If they're placed far enough apart, it's safe to say that two APs—on the same frequency—won't create overlapping coverage zones.

If two APs on the same channel do have overlapping coverage zones, they create a large shared collision domain. This domain diminishes bandwidth (FIG. 1). For the users within it, traffic from either cell adversely impacts the performance of the conjoined overlapping cells. Essentially, access points on the same frequency are competing with one another to serve the users in the shared-collision domain.

This condition of conjoined overlapping cells occurs in WLAN installations that have reached "ChannelMax." This state is reached when all of the available non-overlapping channels have been allocated in a given space. In a typical 200-by-200-ft. office space with 802.11-based APs supporting eight channels, ChannelMax is reached when only eight APs are installed (FIG. 2). In this example, adding more APs beyond ChannelMax doesn't increase available bandwidth. Instead, it creates more shared collision domains. The available bandwidth is therefore reduced.