11.3 Covering Tunnels with Antennas
For a short tunnel of a few hundred meters where you have line of sight from one end to the other the preferred coverage system in a tunnel will often be yagi antennas at the end of the tunnel beaming through the tunnel as well as covering the HO zone to the tunnel. This is a fast and relatively inexpensive solution (See Section 11.11.4 & Figure 11.28). Often these solutions will be operating on the nearby macro cell via a repeater system and thus not even require a dedicated base station.
Although antennas inside the tunnel, even for large tunnels, feeding sections of the tunnel to provide end to end coverage (as illustrated in Figure 11.5) are a viable solution there are some pitfalls that are to be avoided. Let us have a look on some of the common issues that one needs to consider carefully.