na known as controlled reception pattern antennas (CRPA), which use adaptive antenna techniques to accept signals from the direction of the satel- lites and ignore the jamming signal. These devices are still high-end units with primarily milit- ary applications, but antenna design is a very important factor for the resilience of a GNSS receiver. Implement multiband, multi-constellation receivers and use any available augmentation signals (see Chapter 3). For example, Galileo had an extended outage during July 2019, and even GPS had an "anomaly" on January 25-26, 2016 due to an error in a data upload. Having a receiver that can survive outages or instability in a whole system is a clear advantage. Happily, most receivers produced in recent years have multi-constellation capability, SO be sure to activate the feature and make sure that the antenna systems and radio filters allow reception of the desired signal bands. Use a remote source of frequency, phase, and time, such as PTP with SyncE. This will help the cell site survive a local GNSS outage. If the transport connected to the cell site has PTP-un- aware elements in it, then using APTS is an obvious solution (see the section "Assisted Partial Timing Support with G.8275.2" later in the chapter). Engineers understand that a major outage of GNSS-based systems is not a matter of "if" but a mat- ter of "when." For example, one risk that is increasing up until a predicted maximum in 2025-2026 is the worsening space weather resulting from the next peak in the solar cycles. Whatever the cause, at some point there will be a widespread outage. PTP and SyncE Redundancy It is obvious that any timing solution should not rely on a single point of failure, and this certainly applies to the reference sources of frequency, phase, and time. One common oversight that many engineers have is to focus more on the resilience of the PTP signal and not take full advantage of what SyncE can do to build a robust and accurate timing solution. It is vital to have multiple sources of PTP av