e most important requirement is to ensure that exactly the same OFDM waveform is transmitted from all involved cells. This requires an accurate time synchronization among the cells; the allocation of the same time-frequency resource blocks for the MBMS transmission in all cells, including the same transport format (i.e., modulation and coding scheme); and the identical mapping of user data packets into RBs [14]. The method used for time synchronization is not the subject of the 3GPP stan- dardization, and it is left for vendor selection to choose a method from the avail- able legacy solutions, such as IEEE 1588 [9] or GPS-based solutions. The uniform allocation of time-frequency RBs and MCS in all cells involved in the MBSFN transmission is performed by a central coordination entity, called multicast/broad- cast coordination entity (MCE). The MCE would typically be a separate physical © 2009 by Taylor & Francis Group, LLC Architecture and Protocol Support for RRM Single cell transmission eNode B BM-SC transmission IP multicast capable transport eNode B eNode Control plane interface BM-SC: Broadcast Multicast Service Center User plane interface Figure 4.17 The E-UTRAN MBMS architecture. node, part of the evolved universal terrestrial radio access network (E-UTRAN) and responsible for a certain set of eNode Bs. See Figure 4.17 for a complete picture of the E-UTRAN MBMS architecture. The MCE would typically allocate time-frequency RBs in a periodic pattern at the start of the session, which would remain static (semistatic) throughout the lifetime of the MBMS session. The details of the MCE-eNode B resource con- figuration signaling has not been settled in 3GPP at the time of writing. When allocating the time-frequency resources to the MBMS transmission, the MCE may consider maintaining a guard zone around the border region of the MBMS area, where the same resource cannot be used in neighbor cells in order to avoid unicast traffic interfering with the MBMS transmission. Finally, the identical mapping of user data int