 NDL symb X NRB SC resource elements, corresponding to one slot in the time domain and 180 kHz in the frequency domain [11]. In the frequency domain, the number of resource blocks, NRB, can range from NRB-min = 6 to NRB-max 110. In addition there is also a reduced sub-carrier spacing Aflow = 7.5 kHz, only for MBMS-dedicated cell. In the case of 15 kHz sub-carrier spacing there are two cyclic-prefix lengths, corresponding to seven (normal cyclic prefix) and six (extended cyclic prefix) OFDM symbols per slot shown in Equations (3.2) and (3.3) respectively. NormalcyclicprefixTcp = 160xTs(OFDMsymbol#0 TCP = 144xTs(OFDMsymbol# 1to#6) [14] (3.2) Extendedcyclicprefix TCP-e = 512xTs(OFDMsymbol# OtoOFDMsymbol#5 (3.3) where Ts = 1/(2048xA )) [14]. 3.5.3.1 LTE Downlink Numerology Table 3.2 provides an example of downlink sub-frame numerology for different spectrum allocations. LTE supports a wide range of channel bandwidths (e.g., 1.4/3/5/10/15/20 MHz etc.) but 5, 10, and 20 MHz are the expected ones to be supported at large. Each sub-frame is comprised of two slots of length 0.5ms (either 6 or 7 OFDM symbols depending on the cyclic prefix length). For normal cyclic prefix, within each slot, reference symbols for antenna ports9 0 and 1 are located in the first and fifth OFDM symbols, while reference symbols for antenna ports 2 and 3 are located in the second OFDM symbol [11]. 9 An antenna port is defined by a reference signal, unique within the cell. The number of downlink antenna ports equals 1, 2, or 4 and the antenna port number p should fulfil p = 0, E {0,1} and p e {0, 1, 2, 3} respectively. Next Generation Mobile Communications Ecosystem One downlink slot Tslot Nsymm OFDM symbols k = NRB NRB - 1 SC - Resource block NDL symb X N resource elements Resource element (k, /) / = Nsymb 1 2009 3GPP [13] 3.6 Downlink Resource Grid. Reproduced with permission from C Figure 3.2 Typical parameters for downlink transmission scheme Table Transmission BW (MHz) 1.0 ms Subframe duration 15 kHz 15.36 23.04 30.72 Subcarrier spacing Samp