ntation between the relative and absolute timing requirements. When a cell site is required to be within 3 us of any other radio, this is implemented by ensuring that every radio is within +1.5 us of a common reference time (UTC). This is an abso- lute requirement because every radio is measured against a fixed, external yardstick. However, when there is a relative requirement between two radios, then it simply means that radio 1 and radio 2, cooperating to deliver a service to their connected UEs, need to agree with each other to within the relative time limit. It does not mean that a radio on one side of the country needs to be aligned within that same relative time limit with every other radio in the network or some external measure such as UTC. As these two radios are close to each other, both of their timing signals probably come from a com- mon master source that is relatively close by-as shown in Figure 10-32. Mostly, these devices are connected to the same segment of the front-haul or mid-haul network, SO getting them within a rel- ative time budget of 260 ns or even 130 ns of each other is much easier to achieve than trying to synchronize the whole network to this required level of accuracy. There is further discussion on this topic in the section "Relative Versus Absolute Timing" in Chapter 11. Common master clock T-BC, T-BC /T-TSC End application Relative TE TBC/T-TSC End application Figure 10-32 Relative Time Budget with Respect to Common T-BC Remember that the relative time budget is an important part of timing the CRAN, but the absolute limit still applies. The nodes need to be simultaneously within their corresponding limits for both absolute and relative time. This section covered the details of the timing requirements in the 5G NR architecture and showed that the complexity really arises when discussing timing for the evolution of the 5G disaggregated CRAN. Timing the DRAN is much more straightforward for the network engineer, but it is clear that most attention on delivering accurate time will n