urse, using a single centralized GNSS receiver and GM with PTP can take the whole site off the air (except for what an overlapping macro cell could service) should it ever fail. On the other hand, a macro cell on a mountaintop going offline (by losing its timing signal) might take down every subscriber in the valley below, SO redundancy is a more important consideration. An advantage to these high locations is that GNSS signals are generally coming from well above the horizon, SO a shielded antenna that blocks signals from below the horizon greatly reduces the risk of jamming. Any possibility of short-term jamming can be handled by robust holdover performance. For holdover, the small cell is probably going to be quite poor in holdover performance, SO that it needs assistance from the transport network to maintain an accurate timing signal. It makes sense to provide resilience should the local GNSS receiver fail or get jammed. This requires putting another receiver at an alternative location and bringing a backup source of timing into the local campus from there. The alternative site should be out of range of a local jammer, at least 2-3 km away for urban sites or 5-10 km in more suburban or rural settings. Transport capabilities are also an important consideration. If the transport network is not timing- aware, then placing a GNSS receiver without a form of backup is the best worst option. For the ex- ample mountaintop deployment, it is very unlikely that such a site would be well-served by fiber links, and it might be reachable only by microwave. Providing a timing solution over the transport might require modification of that microwave equipment. As previously discussed, for many loca- tions, that might be neither necessary nor cost efficient. 11.1.1 Redundancy In the section on small cells and macro cells, one aspect to consider in the design of a timing solu- tion is redundancy and resilience. Given the deployment location and type, sometimes redundancy can be improved without spending a lot of money. For exa