NTT DoCoMo

About: NTT DoCoMo is a based out in . It is known for research contribution in the topics: Base station & Mobile station. The organization has 4032 authors who have published 8655 publications receiving 160533 citations.

Performance and design of SIC receiver for downlink NOMA with open-loop SU-MIMO

Abstract: This paper investigates the performance and design of successive interference cancellation (SIC) receiver for downlink non-orthogonal multiple access (NOMA) combined with 2-by-2 open-loop single-user (SU)-MIMO. Compared to NOMA with 1-by-2 SIMO (Single Input Multiple Output), for NOMA with 2-by-2 SU-MIMO we have to deal with both inter-user and interstream interference at the receiver of each user. Therefore, we introduce different weight generation schemes for both before SIC and after SIC according to the transmission rank combination between the user equipment (UEs), while taking into account inter-user interference. In addition, we compare the performance of different SIC receivers; specifically, codeword level SIC (CWIC), symbol level SIC (SLIC), and ideal SIC. Assuming LTE (Long Term Evolution) Transmission Mode 3 (TM3), link-level simulations are conducted under different allocated transmit powers, rank combinations, and modulation and coding schemes (MCS). The link-level simulation results showed that the CWIC receiver achieves higher performance compared to SLIC and achieves almost the same performance compared to ideal SIC when the power ratio of cell-center UE is below 0.35, and the MCS of cell-center UE and cell-edge UE are 16QAM (R = 0.49) and QPSK (R = 0.49), respectively.

Linear power amplification method and linear power amplifier

Abstract: A combined signal of a digital pilot signal and a digital transmission signal is applied to a digital predistorter ( 20 ), wherein it is added with odd-order distortions based on a power series model to generate a predistorted signal, then the predistorted signal is converted by a DA converter ( 31 ) to an analog signal, then the analog signal is upconverted by a frequency upconverting part ( 33 ) to a send frequency band, and the upconverted signal is output after being amplified by a power amplifier ( 37 ). A pilot signal component is extracted from the power amplifier output, then odd-order distortion components of the power series model are extracted by a digital predistorter control part ( 50 ) from the pilot signal component, and the odd-order distortions in the digital predistorter ( 20 ) are controlled to decrease the levels of the distortion components.

Prototype of pedestrian-to-vehicle communication system for the prevention of pedestrian accidents using both 3G wireless and WLAN communication

Abstract: For the realization of a safe road traffic environment a wireless communication system which makes an information network between pedestrians and vehicles has been needed. A prototype of pedestrian-to-vehicle communication system was developed by using a cellular phone and a car navigation system equipped with GPS and wireless communication function. By interoperation of 3G wireless network and wireless LAN, it was possible to communicate in a wide area and with little delay time in a local area. The system can exchange the necessary information between pedestrians and vehicles, inform of the location of the ones that have an accident risk, and give an alarm by employing the developed algorithm for estimating the collision risk between each pedestrian and vehicle. The effectiveness of the system was shown by simulation of traffic situations.

Enhancing user fairness in non-orthogonal access with successive interference cancellation for cellular downlink

Abstract: Aiming at a better tradeoff between the system frequency efficiency measured by the mean user throughput and the user fairness measured by the cell-edge user throughput, we propose applying fractional frequency reuse (FFR) and weighted proportional fair (PF)-based multiuser scheduling to non-orthogonal access with a successive interference canceller (SIC) in the cellular downlink. We also propose a frequency block access policy for cell-interior and cell-edge user groups in FFR, which are appropriate for non-orthogonal access with the SIC. The optimum power is allocated to the non-orthogonally multiplexed users in conjunction with the weighted multiuser PF scheduler. Extensive simulation results show that the proposed non-orthogonal access scheme with the SIC significantly enhances the system frequency efficiency and user fairness at the same time compared to orthogonal access, which is widely used in 3.9 and 4G mobile communication systems.