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There's a lull right now in Wi-Fi related news, so let's open the floor to questions: Any nagging questions on Wi-Fi, cell data, WiMax, Google Android, or other wireless data technologies and services? Post your questions in the comments, and I'll try to answer them with the help of other experts in the field as needed.
Q from Andrew (see comments) about cellular networks: The answer you seek would fill volumes. Fundamentally, GSM and CDMA employ different ways of reserving frequencies for users on the network, but both specifications do reserve spectrum. There is no intentional contention, in which manner GSM and CDMA (and their third-generation flavors HSPA and EVDO) are akin to WiMax, which uses OFDMA to reserve data slots (either by time or frequency). GSM uses time division multiple access (TDMA) or multiplexing to reserve periods of time for each receiver; CDMA's very definition is code division multiple access, which assigns unique codes which allow multiple transmissions over the same frequency at the same time. See also reply from George Bednyakov in the comments.
Q from Piet: "I'm from Europe, but I was curious how widely spread free outdoor Wi-FI is in the US?": It varies tremendously from city to city. There are at least hundreds, perhaps over 1,000 hotzones in limited areas, such as downtowns, parks, or public squares across hundreds of cities. Often, a city or a chamber of commerce sponsors such areas. Most of these offer entirely free access or access for a limited period of time or at a restricted speed. Larger, city-wide deployments that are free are pretty scarce, as are city-wide deployments of all kinds. Notably, anywhere MetroFi has a network, they push the free, ad-supported option. Some other metro-scale Wi-Fi firms offer limited free service, too, but that's rare.
Q from Steve about Rhode Island's state-wide wireless initiative: The project stalled in spring 2007 when the state assembly declined to provide a $28m loan guarantee for building the network further. Many lessons were learned, the group behind the project notes, and it's not necessarily dead in the water. Steve asked specific questions about technology, frequencies, and so forth, but my understanding is that in the pilot stage, everything was malleable for testing purposes; no firm decisions about a precise set of deployment hardware or licenses had been decided, as far as I know.
Q. from "toukoob" (see comments) about the security of data transferred over EDGE by and to an iPhone: EDGE is generally considered secure, although experts I've spoken to say that it's crackable with some real effort. So your neighbor or a committed cracker won't have the horsepower, but an industrial spy or a government agent would likely have a portable system that would given some amount of time. You can't break EDGE generically, but could capture and crack data from a particular phone at a particular time. I would love it if Apple and/or AT&T would offer a persistent VPN connection that worked regardless of the medium. NetMotion Wireless and other firms have had such systems for years that work on laptops and handhelds, and they simply require some basic client software and a server on the remote end, as well as an approach to IP address assignment that AT&T could easily manage.
Q. from Edwin (see comments) on current municipal Wi-Fi projects in some form: The best source of information about what's happening in city-wide Wi-Fi is MuniWireless. Now, the company and staff benefit from the municipal Wi-Fi industry by accepting advertising, running conferences, and selling reports and advice. However, in my experience over several years now with Esme Vos, the founder, and other staff writers and producers, I've never found a bias in the presentation of the facts they gather. MuniWireless is definitely a proponent of the notion of wide-scale, wide-area networking at low cost over wireless, but they're also good reporters. One measure of this is that their most recent report showed a huge decline in projected spending over previous estimates, but a big uptick over current year spending. They covered that decline in the estimate quite well.
Utility poles and Wi-Fi: As part of a new series of frequently asked question (FAQ) responses, I respond to a question from a colleague who asked:
"Why are utility poles the key to WiFi network deployment? Because they're tall and everywhere?" (Send your questions that you want the inside FAQ on to firstname.lastname@example.org.)
Answer: Sort of. It's the odd convergence of three separate problems with deploying Wi-Fi across a city that make utility poles have so much importance: real estate, electricity, and height.
Wireless technology is all about location, location, location, just like the old joke. I have been told that at companies like Starbucks and Barnes and Noble, the people who sort out where to next locate a store are among the most important in the firm. Likewise, knowing the placement assets in a city or county, which often largely involve utility poles, becomes one of the most important factors in rolling out a Wi-Fi network.
Who owns the pole is also important. In most cases, a utility owns most or all poles in a city; there are exceptions. But it's not always the case that a municipality controls the utility. Even when a utility is public, not private, it may have its own agenda and be a separate political entity that a government that wants to faciliate the deployment of Wi-Fi can't control.
Electricity is a related issue. With the exception of a handful of networks, such as the one in St. Louis Park, Minn., Wi-Fi nodes and backhaul radios need juice. St. Louis Park went with installing new, tall poles that use solar power and batteries. Even they had problems--residents complained about aesthetics, which led to a delay, a redesign, and additional cost.
In many cases, utility poles lack enough power to add additional devices, or, if they're used for street lights, may have power supplied only part of the day. This burned Toronto's nascent network initially, and has led to a delay and possibly the end of an attempt for service in St. Louis, Mo. In St. Louis, power is "bank switched" for lights, making it a large issue to figure out how to provide power to Wi-Fi without turning on the lamps.
Utility poles may also be in too poor a condition or overloaded (either with equipment, weight, or electrical requirements), with extensions already added, to allow another device to be placed on it. However, the Telecom Act of 1996 requires that utilities make nondiscriminatorily priced access available to poles for certain kinds of services. I haven't seen a Wi-Fi provider yet challenge a utility on the basis of failure to provide pole access. It's unclear whether Wi-Fi, as an information service, qualifies. Wi-Fi that carries VoIP or other telephony signals as a fundamental purpose of the network might.
Poles aren't all the same: each is an individual, and some cities are finding that hundreds of thousands to many millions of dollars might be required to upgrade the pole infrastructure to support modern devices being placed on them. Tacoma Power, for instance, did a massive overhaul a decade ago before installing a new fiber-optic network for electrical system monitoring, cable television, and broadband.
Of all the utilities in the U.S., Southern California Edison Company has had the worst public face on this issue, delaying networks all across its territory by initially refusing to allow any Wi-Fi nodes without tons of study, and fees the same as cell carriers--$2,000 a month per pole. (Cell equipment is generally larger and more power hungry.) They relented since this article in the L.A. Times was published in July 2006, but not to wholesale availability. Its neighbor to the north, PG&E, has apparently no problem in providing pole access on similarly aged infrastructure.
Now for height, you have a mix of opinions based on which kind of equipment is deployed on a network. The split is typically between the mesh-cluster approach and the router-backhaul approach. The former, represented mostly and predominantly by Tropos Networks, involves building city-wide networks as clusters of Wi-Fi mesh access points, typically 4 to 6 in a pod. Each cluster has a separate backhaul radio that aggregates the traffic from the cluster to a remote point, which is turn is hooked via fiber optic or licensed wireless to central points of presence.
In this model, you want nodes to be lower, because your goal is to push access to the street and ground floors, and to allow the nodes to have as much line of site to each other as possible. Tropos and most other metro-scale vendors use omnidirectional antennas on their public Wi-Fi nodes, and that means that signals drop in strength rapidly. A node mounted 20 feet off the ground has enormously less energy when hitting a ground-floor apartment or iPhone user walking by then if it's 10 feet off the ground. The backhaul radio needs to be placed higher for line of site on its point-to-point connection.
In the other model, pursued by most other vendors (Strix Systems, SkyPilot Networks, BelAir Networks, and equipment from Motorola and Cisco), there's little or no mesh. Each Wi-Fi node has at least one 5 GHz or other backhaul radio. This means the Wi-Fi node has to be located where it can most effectively reach the most users, but high enough to get a good line of site to an aggregation point. With multiple backhaul radios, switching can be used, too, so that the optimal path is used to ensure the greatest amount of data is sent as efficiently as possible.
Praise the humble utility pole: It's the linchpin and the albatross in so many metro-scale wireless plans.
Update: A spokesperson from Solis Energy wrote in to note that I didn't mention solar-powered solutions in context of utility poles, and she's write. Solis Energy is one of several firms now offering a variety of self-containing solar/battery systems designed to unhook devices like Wi-Fi nodes from the needs of the grid, and, by extension, from the limitations and restrictions of using utility poles. Solar-plus-batteries are also solutions for places that are completely off the grid, such as rural areas and developing nations, or where the cost of accessing the grid is far higher than a self-contained system.
The mesh-networking firm Meraki Networks announced a solar-powered kit for their outdoor nodes that should run a few hundred dollars when it ships in December, the new availability date. They built the unit in house to work closely with their mesh router to keep power requirements very low, as well as provide direct reporting of energy use and other conditions. Read my interview with the firm's head on the solar and outdoor routers.