Most municipal networks that are being bid out combine several kinds of networks and several kinds of services: The coverage and criticism of municipally authorized and bid networks often focuses strictly on Wi-Fi. That's just one element. Most municipal networks comprise six separate components.

Wi-Fi for mobility. This is the typical form of outdoor Wi-Fi that's well characterized and currently employed in networks as large as several hundred scale miles. This is also the form in greatest competition with cellular 3G because outdoor Wi-Fi typically offers much greater upload and some greater download speeds unless heavily loaded with users. Wi-Fi can be cheaply deployed in rural areas--think the giant networks in Oklahoma, New Mexico, and Oregon--where 3G isn't a sensible investment for cell carriers. In urban environments, mobile Wi-Fi will work, but may have competition and interference.

Wi-Fi for residences. This is the riskiest part of metro-scale wireless: having signals strong enough from the least number of outdoor Wi-Fi mesh nodes or access points--least number to keep costs at their lowest--to reach weakly enough into single-floor and multi-floor residences that they don't interfere (much) with existing networks and yet can be picked up with high-gain adapters or bridges.

Intra-node networks. All mesh networks use some form of communication among nodes to achieve the mesh advantage. This type of communications can be in the same band and channel (Tropos, one kind of BelAir router) or in 5 GHz (more common). The former saves cost; the latter reduces contention, reuses spectrum, and has a greater backhaul pool available, but requires one 5 GHz radio for every 2.4 GHz radio, keeping costs much higher.

Back-haul networks. Moving data from mesh clusters into higher-capacity point-to-multipoint connections is a clearly different form of network. WiMax should play a big part here, as it will in EarthLink deployments in which Motorola Canopy base stations--which are very WiMax like and will eventually go through certification—form the aggregated backhaul. These networks are subversive: In most municipal deployments, cities will turn over intra-building data networking to the muni-scale provider who will use WiMax or fiber to link those facilities together. Philly estimates 300 to 500 buildings will add better networking or replace wired leased lines with Canopy connections.

Aggregation. The back-haul networking will reach aggregation points which will comprise either or both fiber optic lines and high-frequency, short-range, very high speed microwave links.

Backbone. The network operation center where traffic is exchanged across the network, to local servers, and to peering points that join to the Internet.

Now the first four functions can be in a single device, of course. But it's good to think about all this entails.

• The service side is equally broad, and can include:
• Non-subscriber mobile access
• Subscriber mobile access
• Fixed residential access
• Mobile city workers
• Mobile public safety workers (often, however, on a separate frequency band)
• Fixed business broadband (WiMax like)
• Fixed municipal broadband (WiMax like)
• Fixed smart devices (parking meters, utility meters)
• Mobile city assets (vehicles and equipment tracking)
• Fixed or mobile sensors
• Commuter bus, train, ferry access
• College campus access (for all purposes)
• Indoor municipal building service for city workers

The RFP released from Houston, Texas, today for a citywide network defines these into three categories: public service (municipal non-emergency purposes), public access, and public safety.

Most of the above are on the plate for every single serious urban municipal broadband RFP, which is one reason why fiber--despite its expense--is often cited as a reasonable part of a broadband plan. If not to the home or node, at least a fiber ring to deal with local backhaul and municipal needs.