ed Pro, and 5G is illustrated in Figure 16.18. The practical end-to-end latency also depends on the network architecture in addition to the radio capability. The latency measurements in live networks show that the LTE latency can be below 15 ms in some networks while other networks show values in excess of 50 ms. Figure 16.19 shows latency measurements in a live network in Helsinki in Fin- land where the measurement server is also located in Helsinki. The measurements show that the practical end-to-end latency can be low if the transport network is well designed and if the content is close to the radio. When the radio latency becomes lower, it becomes even more important to optimize the other components including Multi-Access Edge Round trip time evolution LTE-Advanced Figure 16.18 Round trip time evolution. 16.3 LTE-Advanced Pro Technologies Figure 16.19 Example latency measurements in live LTE network. Ping 12 ms Ping 11 ms Ping 13 ms Ping 11 ms Ping 12 ms Ping 12 ms Computing (MEC). The MEC concept is being standardized in ETSI. In addition to low latency, MEC allows the exposure of the radio network edge to authorized third parties, which enables them to deploy innovative applications and services for mobile subscribers, enterprises, and vertical segments. A large part of the physical layer latency today is incurred by a fixed, synchronous timing relation in providing a transmission grant to the device, and acknowledging the received data. Optimizing those timing relations provides another avenue to shortening latency. Reducing latency was a major theme for LTE Releases 14 and 15, and a few rather com- prehensive enhancements were specified. Release 14 provides enhancements to uplink access delay, by allowing for UEs to skip the Physical Uplink Shared Channel (PUSCH) transmission (i.e. an empty buffer status report) unless there is no data in the buffer. Combined with semi-persistent scheduling with 1 ms periodicity, this facilitates a mode of operation where a UE is able to transmit uplink data immediately, 