Where WiMax rules for wireless networking

Houston is building a wireless municipal network that will provide high-speed WiMax coverage for the 640-square-mile city at a fraction of the cost of a Wi-Fi network planned just four years ago.

The $6.4 million program, paid for in part by a $5 million grant under the economic stimulus law, will provide IP network coverage for the city and eliminate the need for expensive T1 lines now connecting city facilities, enable the city to remotely manage its traffic system, allow automatic reading of water meters and have enough bandwidth left over to provide Internet access to underserved communities.

“I think the payback time is easily within 24 months,” said program manager Brian Anderson. “We are looking to reduce costs by reducing commercial expenses and using our own network. The quantifiable dollars and cents is the T1 replacement. That’s where the budget director can see a direct reduction in costs.”

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The city is using BreezeMAX Extreme tower-mounted WiMax base stations from Alvarion together with the company’s BreezeMAX subscriber devices that customers will use to connect to the base stations. The Alvaristar Management System will be used for network management. Traffic will be backhauled from the base stations to the city’s data center via a carrier-grade microwave network.

The program, which received purchase approval in August 2010 and is expected to be finished by the end of this year, is the result of some good luck and recent advances in wireless technology.

“What is available today was not available a year ago,” Anderson said. Alvarion’s BreezeMAX Extreme 802.16e base station, which provides as much as 40 megabits/sec throughput in the 3.65 GHz band in an urban environment, was released in early 2010.

Silver lining

The good luck came disguised as the failure of a deal made in 2007 with EarthLink Municipal Networks to build a Wi-Fi network for Houston. “That was fortunate,” Anderson said, because since that deal was made, WiMax has matured as a technology for wireless wide-area networking.

EarthLink had grandiose plans for building municipal Wi-Fi networks across the country on its own expense and reselling the capacity. The company made its biggest such deal in April 2007, when Houston signed a contract for $2.5 million over five years to be the lead subscriber on a $50 million municipal network that EarthLink would build and pay for. The company planned to install as many as 40 Wi-Fi access points per square mile to cover more than 600 square miles of the city.

Wi-Fi, the IEEE 802.11 family of wireless local-area network standards, is popular for public hot spots and indoor home and office networks. But it has been inadequate for coverage of an entire city. In communities with 802.11-based LANs, users have complained about spotty coverage and weak signals.

The large capital expenditures for installing the networks left EarthLink overextended. In August 2007, four months after closing the Houston deal, the company announced a layoff of nearly half of its staff and the closing of some offices. One day later, EarthLink, which had missed a deadline in Houston for securing rights to install access points on utility poles, bought its way out of the agreement with a $5 million payment to the city.

The agreement gave both sides nine months to reconsider the deal. The city began creating a business case for building its own network in 2008, and the initial WiMax effort began in 2009. Houston used some of the EarthLink settlement money to purchase three base stations for a program to provide Internet access to underserved communities. The base stations support computer centers in libraries, community centers and churches.

The release of Alvarion’s Extreme product line in 2010 improved the performance and lowered the cost of the planned infrastructure.

“It has made the expansion of the network much more affordable,” Anderson said. The original EarthLink plan called for installation of 1,400 to 2,000 Wi-Fi access points. “We are going to cover the whole city with 60 base stations.”

The $5 million federal grant from the stimulus law has allowed the city to take on the project with a capital outlay of only $1.4 million. Houston has already installed 15 base stations and plans to add at least five per month to complete the project by the end of the year.

WiMax vs. Wi-Fi

With its greater range, WiMax is better suited for wide-area networks than Wi-Fi is. The signal does not require a line-of-site path, making it suitable for urban environments and indoor coverage. WiMax also makes it easier to run multiple applications on a single system because it can prioritize network traffic for applications and users. For example, traffic signal management can be handled in near real time, while reading water meters with the same network, which only needs to happen once per 30 minutes, receives a lower priority.

However, a disadvantage of the technology is limited support for mobile traffic, said Raja Gopal, a marketing director at Alvarion. Power restrictions needed to avoid interference in the spectrum band make Houston's system a poor choice for mobile applications, he added.

The city's system operates in the shared 3.65 GHz band, which generally requires less power. In 2007, the Federal Communications Commission adopted a nonexclusive licensing scheme for the former government spectrum to facilitate rapid deployment of the band. Organizations that want a piece of the spectrum band can purchase access for a nominal registration fee, and an FCC registration database coordinate spectrum assignments to avoid interference.

That is not a problem with Houston’s plans, which call for fixed coverage with direct access provided through BreezeMAX customer premises access points that carry data to base stations. Microwave links are used to send traffic to the city data center. Because of its mobile limitations, the system is not well suited for police and emergency use. But Anderson said Houston will use a 700 MHz Long Term Evolution system for public safety data networking.

Traffic ecosystem

In addition to Internet access, one of Houston's first applications of the WiMax network will be controlling the city's traffic signals.

“We’re building an ecosystem to enable management of the traffic system,” Anderson said. That includes connecting to all 2,500 intersections with automatic traffic signals, in addition to 1,500 flashing signals in school zones. Traffic managers will be able to monitor conditions and adjust timing of the signals based on real-time data. The system also will simplify routine maintenance, as changes can be done remotely.

During holidays and vacations for schools, city employees must manually reset school zone flashers. By networking the signals, no one needs to leave the office to change the signals' timing.

The city also has networked 150,000 of the 500,000 automatic water meters, and it eventually will connect all meters to enable remote monitoring. The meters use a mobile system, and someone must drive through neighborhoods each month to pick up the readings. That's better than sending a meter reader to collect data on foot. But it still limits data collection to once a month, and starting or stopping water service in the middle of the month requires sending someone to get the reading. According to one estimate, the cost of extending an automated meter reading via a wired network would be $40 million. The WiMax network will allow the city to gather meter data with the use of inexpensive local access points.

The new system will give readings of each meter every 30 minutes. The city plans to begin a leak detection service in May. If the city observes unusually high water usage for two consecutive days, an automated phone call is made to the customer to notify of a possible leak.

Carrier cost savings

The big savings are expected to come from replacing existing links to 4,000 outlying facilities, such as water and sewage treatment plants.

“We’re looking to reduce costs by reducing commercial carrier contracts we’re using on our networks,” Anderson said. At $350 a month for a dedicated T1 line, which can provide a 1.5 megabits/sec full duplex connection, the city cannot afford to link all its facilities to the network. The WiMax network is expected to provide less expensive, faster connections to more of the facilities.

Other uses for the network could include linking to credit card pay stations for parking and offering services to other municipal and county governments in the area, Anderson said. The data center, which refreshed its Cisco Systems infrastructure in 2008, has the capacity to handle the traffic, and the carrier grade microwave link to the data center was designed to provide almost unlimited expandability.

“I think we’re just skimming the surface,” Anderson said of the uses for a municipal broadband wireless network. Because of the potential economies of such a system, “I think more applications are yet to come.”