During the last year, several large metropolitan areas embarked on plans to offer large-scale municipal wireless networks, including nascent plans from Denver and San Francisco.
While these movements are in variously early stages of conception and planning—and will continue to face many legal and logistical hurdles before their launch—enterprise administrators should bank on the existence of these networks and begin to plan accordingly to mitigate the effects on performance and security in their own networks.
On its TechConnect Web site, the City of San Francisco recently released an RFI/C (Request for Information and Comment) to lay down some specifics about the citys use plan.
Particularly relevant for enterprise administrators are the defined requirements to utilize 802.11b/g for client connectivity and to provide 95 percent outdoor coverage and 90 percent indoor coverage throughout the city (the latter defined as a location with an exterior-facing wall on the first or second floor of a building).
The city also would like to explore ways to take the coverage to higher floors as well. These requirements mean that outside signals will be pouring into urban corporate office buildings, and will bleed away the ability of the corporate LAN to perform to established expectations.
Of course, San Francisco is an extremely dense Wi-Fi environment already. In a 5-minute walk around a single small block near the fringes of San Franciscos Financial District, I identified 159 distinct wireless networks consisting of 181 individual access points in the 2.4GHz spectrum alone.
The majority of these devices were deployed on channel 6, one of only three non-overlapping channels in the 802.11b/g spectrum.
Issues of interference and signal degradation are not new for wireless LAN deployments. Given the drastic shortage of non-overlapping channels in the 2.4GHz spectrum and the wide adoption of Wi-Fi technologies by businesses and individuals alike, technologies already exist to effectively manage channel allocation and cell sizes in a densely utilized RF environment.
But a ubiquitous, high-power wireless deployment blanketing the city will greatly intensify the problem.
WLAN managers should revisit their initial site surveys and access point deployment plans to help offset the effects from the outside network. Companies will likely need to reconsider access-point placement, cell sizes and channel allocations. An increased emphasis on intelligent channel management may be necessary.
Administrators should also plan to better utilize 802.11a and the relatively clean 5GHz spectrum. Although municipal networks may utilize this band for wireless mesh backhaul or inter-node communications, they likely will use highly directional antennae that are less likely to cause indoor interference.
Since the number of non-overlapping channels is much greater in 802.11a, and the number of active deployments in this spectrum are significantly lower than with 802.11b/g, there is much more room for growth with 802.11a.
Administrators must also take a closer look at their wireless security policies. A municipal wireless network implies a greater number of unauthorized clients nearby, so steps must be taken to ensure the clients cant get into the corporate network.
Conversely, administrators should take care to control whether employees in the office will be able to connect to the municipal wireless network outside.
While companies explore whether now is the time to invest in new WLAN equipment to add the latest wireless security and quality-of-service features, the wise administrator also recognizes that the changing RF landscape dictates that companies update their deployment strategies as well.
Technical Analyst Andrew Garcia can be reached at firstname.lastname@example.org.