As wireless networks have matured, the desire of wireless service providers to establish additional cell site base stations has been driven by several factors.
One is the need to provide coverage to a geographic region where the service provider has not previously served. Also, to fill in “dead spots” or areas where existing signals are weak. Additionally, to allow for the reuse of channels or spectrum bandwidth to support a larger number of customers and to meet the higher speed requirements of emerging technologies.
The drive to meet these needs has led to a proliferation of new cell towers, indeed, a “tower industry” has arisen to meet the demand for suitable base station sites. In the early days of wireless cellular development most carriers owned their towers and allowing other users, especially competitors, on their towers was not considered. However, as the number of towers grew, the word colocation became a common term in wireless lexicon. The acceptance of wireless colocation resulted because of many reasons. One is that the wireless carriers saw an opportunity to reduce their infrastructure investment and free up cash for other uses. Another is the tower owners need to secure multiple tenants on each tower to meet return on investment goals. An increasing resistance to the construction of new towers from local groups and jurisdictions has also played a significant role in many areas.
Seeking out existing structures first when looking for new base station sites is becoming the dominant strategy. While this helps in solving the problems mentioned above, it creates new challenges. Often, the network RF design must be altered many times during the site selection process. Sometimes, the existing structures are located away from the search circle center and/or will not support the base station antennas at the height that was used for planning the system. This can result in less than the optimal coverage that is desired. The ability of existing structures to support the weight and wind loading requirements of the lines and antennas must be determined. This means that a structural analysis is required, adding to the cost of the site. When sharing a site with other emitters, interference is a consideration.
While it might seem that regulatory compliance is less complicated on a wireless colocation site, the opposite is often the case. For example, the FCC and OSHA rules regarding human exposure to non-ionizing RF energy require that all emitters, even those belonging to others, on a site be considered. FCC rules that mandate the protection of AM broadcast station patterns are another area where lack of compliance by one tenant on a site can lead to action against all colocated licensees as well as the tower owner. More local jurisdictions are requiring submission of documents to attest to the fact that the site is in compliance with all rules and regulations. Many require third party review of the compliance activities.
The drive to seek out existing structures first has produced some “outside the box” solutions that would have never been considered in early network builds. Water tanks, smoke stacks, church steeples and bell towers have become acceptable for most carriers. Many are colocating on power line towers and AM, FM and TV broadcast towers. While each of these presents its unique set of challenging considerations, they are all viable candidates for wireless colocation. With proper planning and design, all are being used successfully to support wireless base stations.
Colocating on an existing structure is a good solution for many sites; however, there are some situations where a new tower is needed. The challenge in those cases is to convince the jurisdictional authorities that no existing structure will meet the requirements and that only a new tower will work. An increasing number of zoning and planning groups are insisting that a third party assessment of the need for a new tower be submitted.