Up until now, the only concern has been the requirement to deliver the "traditional" +1.1 us phase alignment to the radio equipment, either at the combined DU/RU site in the DRAN or at the DU/BBU site in the CRAN. Currently, there is a new range of requirements from some of the radio coordination techniques and new services defined in the later releases of the 3GPP specifications. Tables 10-13 and 10-19 in Chapter 10 summarize these requirements for both LTE-A and 5G New Radio (NR), respectively. However, these new requirements are relative requirements (as opposed to absolute). Absolute tim- ing requirements, such as the +1.1/1.5 us for TDD radios, means that every piece of radio equip- ment must be aligned to within +1.5 us of some absolute time standard, which has been agreed is UTC. By this method, every cell site on the network will be within 3 us of any of its neighbors, and the whole network will be within +1.5 us of UTC. A relative requirement is only between two or more pieces of equipment, such as an RU and a DU, and says very little about the phase alignment compared to an RU on the other side of the country. So, when two RUs are coordinating with each other to deliver a combined data stream to a UE vis- ible to both, these devices have to be closely aligned in phase relative to each other. This might be a value of +130 ns or even +65 ns, which sound like very, very small numbers. Note that the relative requirement does not override the absolute +1.5-us phase alignment to UTC. Both constraints must apply simultaneously; the RU must be within the +1.5 us for the TDD radio and it must also be within the required relative alignment to the other RU it is coordinating with. However, recognize that these relative requirements are between devices that are close together (less than 20 km or so) and, in many cases, either directly connected with each other or are only one or two hops apart. It is not like the timing solution must deliver around +130 ns of accuracy across the whole network or the whole country. 