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between UE signals. ose technologies will be explained below. Further, in the designing of this radio access tech-nology, based on a scenario [2] premised on its use with IoT devices, the channel bandwidth will be set at 1.08 MHz.2.1Structure of radio frameHere we discuss the structure of the radio frame for uplink data transmission from UE to BS. Figure 2 shows the basic structure of the radio frame. e time slot has a total length of 500 µs and is composed of a 250 µs reference signal and a 250 µs data signal. e reference signal is used for the purposes of identifying the UE terminals and esti-mating the channel impulse response between the UE and BS. e data signal is used to transfer data sent from UE. Transmission delay is minimized by sending a reference signal and a data signal without intermission.Here we discuss the structure of the reference signal. By using orthogonal sequences for the reference signal, even when signals are being sent by multiple UE terminals on the same time and frequency resource—in addition to identifying the sending UE—estimation of the channel impulse response necessary for the data demodulation and decoding is conducted. In the current R&D at hand, we employ the Zado-Chu sequence for the orthogonal se-quence, which is also used in LTE-A. When using this sequence, in order to estimate the channel impulse response without interference between signals from UE terminals, it is necessary to assign each UE terminal with a Zado-Chu sequence having a cyclic shi time equal to or longer than the maximum propagation delay time of valid multi-paths. Among the channel models [4] for developing the technical specications of the 5G radio access, the TDL-A channel model includes the longest delayed path in a non-line of sight environment, and the maximum delay time is ap-proximately 3.5 µs. Further, assuming the BS-UE distance of 1,153 m and urban macro cell environment, propagation delay time from UE to BS is 3.8 µs. Considering the above, it would be necessary for the orthogonal sequence cyclic shi time in the reference signal to be equal to or larger than 7.3 µs, and also considering the synchronization error between BS and UE, 18 samples equivalent to 16.7 µs are set as the cyclic shi of the orthogonal sequence. In order to accommodate simultaneous connection of 12 UEs, it would be necessary for the sequence length to be 216 or more, and in the current R&D the Zado-Chu sequence length is set at 223. As was shown in Fig. 2, a 20-length sample (equivalent to 18.5 µs) cyclic prex (CP) is added to a sequence that has been cyclically expanded to a length of 225. Figure 3 shows an example of the structure of the reference signal when cyclic shi has been applied. By assigning dierent cyclic shi numbers for each UE termi-nal, it becomes possible to identify the UE even when the BS simultaneously receives reference signals from multiple UEs. In the grant-free transmission scheme, a UE-specic cyclic shi number is assigned to each UE.Next, we discuss the structure of the data signal. Figure 4 shows the processing of information bits for the data signal in each UE terminal. Aer the information bits are scrambled, 8 bit cyclic redundancy check (CRC) encod-ing is performed. Following this, turbo encoding (coding rate: 1/2 or 1/3; constraint length: 4) is performed. Aer QPSK or 16-QAM modulation, CP is inserted and the FiF1　Outline of radio access technology that realizes simultaneous connectivity and low latencyConventional systemNew radio access systemＡＡＢＣRequestGrantDataFrequencyTimeTransmission without grant•UE Identification•Interference CancellationShortened TTI for latency reductionOne resource is shared by multiple Ues.ＡＢＣＡＢＣLatency of 10 msor more caused by transmission with grant in UL. One resource is dedicated to one UE.BSＵＥＵＥＵＥFrequencyTimeBSＵＥＵＥＵＥFiF2 Basic structure of the radio frame [3]Reference signalData signalCyclic Prefix250sGuard Time250s500s(= 1 slot duration)FiF3 Reference signal structure exampleZadoff-Chu sequenceZadoff-Chu sequence (18-sample cyclic shift)１２２３２０６２０４２２３，１16.7sDelayZadoff-Chu sequence (36-sample cyclic shift)１８８１８７２２３，１Correlation with Zadoff-Chu sequence without cyclic shiftEstimates on channel impulse responses are available without interference when these responses are terminated within 16.7 s.ＡＢＣ16.7s2 Terrestrial Communication Technology Research and Development14　　　Journal of the National Institute of Information and Communications Technology Vol. 64 No. 2 (2017)