Learning to Share

When we were young, we were taught to share our belongings. Although sharing was difficult for some children, most of us adapted to the courteous expectations of our parents and teachers.

Like toddlers and their toys, some wireless carriers have had a hard time letting go of their cell sites. Slowly but surely, however, they are learning to share --whether it is on their own accord, or by local communities.

At last count, there were more cell sites in the United States than McDonald's, Burger King and Wendy's restaurants in the world. Unfortunately, zoning boards aren't as accepting of cell towers as they are restaurants. Sometimes communities can hold up a site's approval for months, delaying your network build-out and causing you to miss out on potential customers.

Several carriers have found a solution to zoning battles through co-location. Co-location is nothing new, but its acceptance in the wireless industry by some carriers is. The number of cell sites grew three times as fast in 1997 as in 1996, indicating that although carriers are well aware of the benefits of co-location, they are just starting to do it. Traditionally, wary cellular and PCS providers have eyed each other with distrust and have been reluctant to try it at all, said Ron Gibbs, Lodestar Towers president & CEO.

"The high cost of building out their infrastructure has caused carriers to re-conclude that co-location is not only a viable economic option, but it can also accelerate their build-out schedule," he said.

As PCS builds out nationwide, operators are accepting the concept of co-location, agreed Mark Van Dyke, BellSouth Mobility DCS senior manager of real estate & tower attachment. Not only can they save money, but carriers also understand that with new competition, co-location is the only way to get into some communities. If a PCS company is the third or fourth carrier coming into a market occupied by two cellular incumbents and one additional PCS carrier, Van Dyke said, that company probably would share a site rather than risk not building out its network in that area.

Sue Smith, TWS vice president of engineering, said carriers' main objection to co-location is usually political. Carriers worry about who owns the site and who is responsible if it goes down. Early on, some even thought that if they owned a site, they could block competitors from getting coverage in an area, she said.

"We are pleased to see some of the carriers coming away from that, because the competitor is going to get there no matter what," she said. "It is just going to be three months later, and they are going to build another tower. But they are going to get there."

In some communities, citizens require co-location efforts before they will even consider zoning approval. According to Public Technologies, tower applicants in Palm Beach County, FL, must send a certified-mail announcement that expresses their siting needs or sharing capabilities to all other tower users in the area. You cannot be denied or deny space on a tower unless mechanical, structural or regulatory factors prevent sharing. In these cases, sharing space with competitors is better than not being able to obtain the site you need to expand your customer base.

BellSouth Mobility DCS and 360 Degrees Communications are two carriers that have embraced co-location. Both lease space on their towers to other carriers as well as rent space from their competitors. Both are realizing financial benefits. They have saved money in construction costs by sharing space on competitors' towers, and they have generated revenue to help cover costs of new construction by leasing their own towers to other carriers.

BellSouth Mobility DCS has co-located and has allowed co-location on its sites since its initial deployment in 1995. Close to 60% of the company-owned towers have other carriers co-located on them, and in some markets, between 75% and 95% of its towers support multiple users. Similarly, 360 Degrees announced plans last December to lease space on many of its cellular towers. The company, which owns 1,800 cell sites, was involved in site sharing on a reciprocal basis prior to the announcement.

"We feel like we are being good corporate citizens by co-locating," Van Dyke said. "We were open-minded when we sought to build out sites. If I let a carrier on my site, I know I can go back to that carrier when I need to, so it has accelerated our network deployment."

AVOIDING INTERFERENCE It is possible to have many users on the same tower if you have the right technology. For instance, in Florida, Lodestar has a 480-foot tower with four PCS carriers, one cellular carrier, two electronic news-gathering dishes, four microwave dishes, two low-power FM stations, two low-power TV stations, 65 channels of SMR, 10 to 20 UHF channels, and 10 to 20 VHF channels. UNIsite, a build-to-suit company, has seven operators on a 150-foot monopole in Illinois. Both vendors have had few problems with combining so many carriers on one tower.

Robert Mawrey, UNIsite vice president of systems & technology, said some radio engineers only use intermodulation analysis to manage spacing between antennas. More can be done, however, he said, to predict interference problems. For years wireless carriers have put 20 feet or more between antennas because they really didn't know how much was needed. Actual antenna spacing requirements can be estimated using comprehensive interference analysis techniques. The interference analysis should include investigation of intermodulation and harmonics, noise, desensitization, antenna coupling and equipment characteristics, he said.

"Twenty feet is often very conservative and convenient," Mawrey said. "The real trick is to figure out how much spacing is needed between the carriers on the tower so you don't waste space and put up a lot more towers."

UNIsite has been able to place some carriers only five feet away from one another, and Mawrey said one foot of vertical spacing is often sufficient to prevent interference among systems. The company uses its software, UNIstar, to predict RF interference between arrays of antennas on a particular tower. The UNIstar software enables UNIsite to create a model of the antenna site by entering all the information about each carrier's radio equipment, cables, antennas and proposed frequencies into a database. The software analyzes any interference problems among different carriers' systems. It shows which carriers will have problems interacting and the type of interactions that can occur. With that knowledge, the RF engineer can modify the equipment configuration or the antenna placement.

NO BARRIERS It also is possible to combine technologies without any space in between carriers. Using certain technology, a carrier can be put at the same elevation as others using filters to avoid interference. TWS offers SpectraShare PCS Antenna Combiner, which allows up to six PCS service providers to share the same antennas, head frame and cable run. The SpectraShare combiner supports all PCS air interface standards (CDMA, TDMA and GSM) simultaneously. It is located at the base of the tower and provides an interface between each base transceiver station and the common antenna array. On the transmit, it takes all of the signals, combines them and puts them onto the antenna. It also takes the receive signal from the antenna and splits it up among all of the operators. TWS developed SpectraShare for areas where you can't have separate head frames because there isn't enough height on the site, or where a flagpole stealth tower is being used that is too thin to put on extra head frames.

"In that situation, normally you can only have one operator," Smith said. "If a second operator wanted to go on that site, we could use the combiner. It accommodates anywhere from two to six players in any band and any technology."

Terry Peters, UNIsite vice president of sales & marketing, said his company installs multiuser stealth flagpoles. One 3-operator tower in Cleveland looks just like a flagpole, but the antenna array is inside the pole. UNIsite is working with Stealth Technologies to develop a 6-operator flagpole that will be 150 feet with all the antennas inside the tower.

While SpectraShare combines PCS carriers in the A-F bands, crossband couplers can combine a PCS carrier with cellular carriers on the same tower. This technology also reduces the number of cable runs on a tower or building, explained Andy Singer, director of technical marketing at Celwave, which makes antennas, cables, crossband couplers, filters and combiners for co-location. Couplers make it possible for a cellular and a PCS carrier to be at the same elevation on a tower. Paired with dual-band antennas or separate antennas, they combine cellular and PCS carriers onto one cable. The couplers are basically two filters. One is placed at the top of the tower and the other at the bottom. The PCS and cellular transmissions are put through the crossband couplers at the bottom of the tower and combined into one cable feed. At the top, the other half of the crossband coupler splits the signals into specific bands, and the cellular and PCS signals go to separate antennas.

Additionally, antennas are available to combine cellular and PCS under one radome. These dual-band antennas have been tried on a number of systems, Singer said. Two separate dual-band antennas can be mounted under one radome so it looks like one antenna instead of two to the untrained eye. For instance, Lodestar uses combining technology to maximize the amount of carriers it can fit on its towers. In Florida, the company uses splitters and cross-band couplers to compress 240 wireless channels into one space from three transmit lines and one common receiver system.

With the right mix of technology, co-location won't disrupt your network. Sharing space with your competitors may be the only way to get into some communities. If you try it, not only will you be invited to play, but you will make more friends in the process.

Last month, PCIA won the approval of the U.S. Department of Justice to move forward with the launch of its Collocation Clearinghouse (CC).

The CC is designed to help carriers identify co-location possibilities in the network-deployment process and to help them document their efforts to either place new base stations on existing structures or to coordinate with other carriers to construct shared-use facilities.

"This clearinghouse will expedite the process for carriers to build out their infrastructure," said Ron Gibbs, a PCIA Board of Directors member and chairman of the group's Site Owners and Management Association. "It will indicate which sites are available in their markets instead of carriers having to recreate the whole process. With co-located sites, carriers can circumvent zoning and planning."

The CC will be a secure computerized database containing information on potential wireless communications antenna sites. When a carrier begins site acquisition/construction activity in a particular area within its licensed market, it can submit search-ring information for its proposed sites to PCIA for entry into the CC database. The search-ring information will be the latitude and longitude of the optimal site location, together with one of the several specified search radii.

The CC then will identify any instances in which one of the search rings overlaps with a search ring entered in the previous six months, and it will notify those carriers of the potential co-location possibility. PCIA would charge site owners a nominal fee per site, and the carriers also would pay to use it. All the money would go toward covering technical and administrative matters.

"Co-location is a win-win situation for everyone," said Jeff Cohen, PCIA spokesperson. "We build the infrastructure we need, and the community can have development in a reasonable way."

PCIA sought the department's approval to launch the CC to ensure participating carriers would not be in violation of federal antitrust laws. In his letter approving the CC, Assistant Attorney General Joel Klein said the exchange of broad expansion plans between rivals could raise anti-trust risks, but he noted that the CC should have no anti-competitive effects and suggested it could have a pro-competitive effect by reducing barriers to entry.

Gibbs noted there have been some concerns about the CC showing favoritism, but he said PCIA will keep the names of the site owners confidential when carriers request the information. Once the carrier chooses the site, then PCIA will divulge the owner's name and phone number so the carrier can call the site owner directly and make its own arrangements.

With Justice Department approval in hand, PCIA now will begin beta testing of the database. Those tests should be completed by early summer, and PCIA will have a formal launch soon thereafter.

There are three options for co-location. You can run an in-house leasing program, rent space from other carriers in your markets or use a third-party non-carrier that owns towers in desirable locations.

Whether you go through a third party or rent space directly from a competitor, it is important that you hire an engineering firm to conduct a structural analysis to determine whether the tower in its existing condition can hold your equipment. Not all towers were made for multiple carriers. The higher on the tower, the less capacity there is for additional equipment.

"A company wants to make sure it is placing its equipment on high-quality towers, and that the company that owns that tower will do a good job maintaining it," said Joe O'Leary, 360 Degrees vice president of operations for tower leasing. "If the conditions of the tower and the maintenance deteriorate, it will have an impact on the carrier's service."

360 Degrees requires all leasing applicants to obtain a structural analysis from the tower manufacturer or from a certified engineer. The analysis takes into consideration all things presently on the tower, plus the co-locator's equipment, to see if it can handle the capacity. If it can't, the tower can be modified and enhanced to maintain its structural integrity.

Mark Van Dyke, BellSouth Mobility DCS senior manager of real estate & tower attachment, said BellSouth Mobility DCS has chosen a combination of all three options for its network deployment.

BellSouth Mobility DCS has, in numerous cases, rebuilt its towers to accommodate co-locators, added Van Dyke. Every time a new carrier applies for permission to co-locate, BellSouth Mobility DCS and 360 Degrees run another structural analysis.

After the structural analysis, you should make sure that either your own RF engineers or a reputable engineering firm review the specifics of your equipment and that of the other parties to ensure that there will be no RF interference.

Lodestar Towers' Ron Gibbs, president & CEO, explained that his company makes sure all frequencies at the site will be compatible before it lets a carrier co-locate on one of its towers. All the carrier has to do is bring in its radio, and an engineer will conduct an intermodulation analysis to determine if there will be interference. If there is, Lodestar works with the spacing between channels and uses filters and other technologies to fit the carrier onto the tower.