lots) 1 superframe (20.48 ms) Pilot Payload burst (138 NCP-SC blocks) Reserved 102.4 us TTI (150 NCP-SC blocks) NCP-SC block (0.67 us) 480 data symbols 32 null symbols Figure 11.36 NCP-SC frame structure. Connected beam Candidate beams Figure 11.37 Image of the current candidate beams while connected. Beam tracking is achieved with two phases of beam selection: an initial beam search- ing phase and a beam tracking phase. Figure 11.37 shows an image which indicates the current candidate beams while connected. The beam is selected by using the 4 row by 16 column array of patch antennas that feeds the lens. In the initial beam searching phase, the AP samples all available beams by transmit- ting a TTI-length pilot signal and listening for a TTI-length interval on each candidate beam. Each pilot transmission contains information indicating when the AP will attempt reception on each beam. Specifically, the AP will utilize 64 TTIs to transmit the pilot sig- nal on each beam and will also utilize an additional 64 TTIs as it sequentially listens on all 64 candidate beams in the initial beam searching phase. The UD detects a subset of the candidate beams, synchronizes to the frame, measures their signal-to-noise ratios (SNRs) and sends a measurement report with this information back to the AP at the 11 Measurements time that corresponds to the beam with the best SNR. Upon reception of this report, the AP will transition to the tracking phase by updating the candidate beam list to contain the best beam and all surrounding beams. The candidate beam set is transmitted every superframe or 20.48 ms, where a superframe consists of 200 TTIs, each exactly 102.4 us. The AP averages over five superframes before making the beam selection decision (i.e. the beam used for the payload data). Thus, the beam update interval is 102.4 ms. After establishing the connection, the phase changes to the beam tracking phase, and the pilot signal is transmitted from seven candidate beams: the selected beam used for the payload and its six neighbor