 plane. The measurement should be done per traf- fic flow. The access gateway should use the sequence numbers of GTP-U packets to measure the downlink packet loss rate; UL RTWP: received total wideband power, including noise measured over the entire cell transmission bandwidth at the eNode B; UL received resource block power: total received power, including noise measured over one resource block at the eNode B; UL SIR (per UE): ratio of the received power of the reference signal trans- mitted by the UE to the total interference received by the eNode B over the UE occupied bandwidth; UL HARQ BLER: the block error ratio based on CRC check of each HARQ-level transport block; propagation delay: estimated one-way propagation delay measured during random access transmission; UE Tx time difference: time difference between the reception of the UE transmitted signal and the reference symbol transmission time instant; DL RS Tx power: downlink reference signal transmit power determined for a considered cell as the linear average over the power contributions (in [W]) of the resource elements that carry cell-specific reference signals transmit- ted by the eNode B within its operating system bandwidth. © 2009 by Taylor & Francis Group, LLC Long Term Evolution: 3GPP LTE Radio and Cellular Technology For intercell interference coordination purposes, it may be useful to measure the user plane load (e.g., in terms of number of sent user plane packets/bits per second). The definitions of such measurements and associated procedures are for further study. 4.4 User Equipment Behavior A fundamental design principle of LTE as well as its predecessors has been to allow the network to control UEs in connected mode-that is, UEs that have a radio resource control connection to the network (often casually referred to as "active" mode UEs). This design principle has been useful for protocol design and, most importantly, for radio resource management purposes because the network is in the position of making network-wide near-optimal decisions,