ITU‐T's Technical Reports and Specifications 621 Infrastructure sharing has the potential to (GSMA, 2008): Lead to faster and wider roll‐out of coverage into new and currently underserved geographical areas. Reduce the number of antenna sites. Reduce the energy and carbon footprint of mobile networks. Reduce the environmental impact of mobile infrastructure on landscape. Reduce costs for operators. Optimize the use of the RF spectrum and increase data speeds through active sharing of the frequencies. In some cases, site sharing increases competition by giving operators access to key sites necessary to compete on quality of service and coverage, thus sharing improves roaming. Governments may also consider positive incentives to roll out into underserved areas. In both passive and active sharing, it is necessary to consider the possible effects on RF exposure levels and compliance boundaries. As discussed in section 7.2, antennas that are close together or operating at higher powers may have overlapping compliance zones leading to a combined zone that is larger than the individual antenna zones. Antennas that are shared by more than one operator may have higher combined transmitter powers. Nearby residents may think that a higher number of antennas in the surrounding areas will lead to higher exposure levels at the ground level in publicly accessible areas. Measurements undertaken in Germany demonstrated that neither distance to the antenna nor the number of visible antennas were accurate indicators of RF exposure. Instead, the orientation of the antenna’s main lobe constitutes the main factor influencing exposure (Bornkessel et al., 2007). 7.4 Location of antennas and access restrictions Wireless communication antennas should be positioned so that locations where the public exposure limits may be exceeded are not reasonably accessible to the general public. This can be achieved by selecting the location of the antenna or by the use of barriers to restrict access. Low power antenna installations and wireless access points have no or limited positioning requirements. In addition, simple guidance may be provided by the operator or equipment manufacturer. Higher power antennas are generally mounted above head height (sometimes on a short antenna mounting pole) or on the outer surface of buildings where it is not possible for the public to access areas in front of the antennas. Such antennas have directive antenna patterns that substantially decrease the exposure to directions above the horizon and to the ground near the antenna tower. When locating antennas, an assessment of the size of the EMF compliance zone should be conducted to determine whether the compliance zones could reach adjacent buildings. This could require a change in antenna position or reduction in transmitter power in order to ensure compliance with the EMF limits (Recommendation ITU‐T K.70, 2007).