l-13 Rel-8 Cat-4 (1.4 MHz LTE-M) (200 kHz NB-LTE) Downlink peak rate 150 Mbps 1 Mbps 128 kbps Uplink peak rate 50 Mbps 1 Mbps 128 kbps Max number of downlink spatial layers Number of UE RF receiver chains Duplex mode Full duplex Half duplex (opt) Half duplex (opt) UE RX/TX bandwidth 20 MHz 1.4 MHz 200 kHz Maximum UE transmit power 23 dBm ~~20 dBm 23 dBm Modem complexity 20' % LTE Small Cell Optimization 3.3 Enhanced CoMP Release 11 defined the use of Co-operative Multipoint Transmission (CoMP) as covered in Chapter 2. The work in Release 11 focused for the case of ideal backhaul since non-ideal backhaul limits the gains achievable with CoMP to a large extend, making solutions relying on joint transmission rather impractical. Release 12 work with Enhanced CoMP was focusing on the support of scheduler coordi- nation with the non-ideal backhaul, not impacting the UE side at all. The study done in 3GPP concluded that significant gains are hard to find with such operation, as reported in [5] and also as shown in Figure 3.4, where only one result presented from different companies was showing any improvement in the total cell capacity and other results indicated rather loss of capacity. Thus, it was not considered reasonable to add new network elements but rather 3GPP agreed in introducing the following enhancements for the X2-interface application protocol (X2AP) to facilitate further scheduler coordination. The study also found, as expected, that the backhaul latency has major impact for the gain potential. While with 5 ms backhaul latency, the median results from different companies, as shown in [5] gives some gain, with the 50 ms backhaul latency, there is rather loss than performance gain from the scheduler coordination. The actual specification work was also divided into two different Releases due to the time limitations in Release 12 finalization. Release 12 enhanced CoMP was completed finally covering the following enhancements: CoMP hypotheses, which covers hypothetical resource allocation including benefit me