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.

Communication control system, communication control method, base station device and mobile terminal device

Abstract: In packet communications between a mobile terminal and a base station, the mobile terminal checks a priority level of a traffic and judges a type of the traffic, and transmits a reservation signal for a transmission request to the base station when the type of the traffic is a high priority level or realtime type, and does not transmits it when the type of the traffic is a low priority level or non-realtime type, while the base station determines a resource amount to be reserved for packet transmission according to a resource utilization state and the reservation signal for the traffic of the high priority level or realtime type, or an average transmission interval or transmission rate for the traffic of the low priority level or non-realtime type according to margins in remaining resources, and notifies the resource amount or the average transmission interval or transmission rate to the mobile terminal.

Power mode aware packet communication method and apparatus

Abstract: Packet communication method and system in which a packet destined for a terminal is provided service according to a service table indexed by packet classification and the terminal's power mode. The service table may specify for a connection a predetermined quality of service or discarding the packet. For a power mode having an alerting mechanism, the service may include alerting the terminal. For a multicast or broadcast packet, as each terminal may be in a different power mode, the associated service in the service table may therefore be different for each terminal. In that case, the packet is provided with service so that any given terminal is provided with at least the quality of service specified in the service table. Thus, a multicast or broadcast packet is discarded when the service specified for all terminals is 'discard'. Each terminal is alerted, however, if the associated service includes alerting the terminal.

Cholesky Factorization With Symmetric Permutation Applied to Detecting and Precoding Spatially Multiplexed Data Streams

Abstract: We study computationally efficient spatial multiplexing transmission techniques aiming at high spectral efficiency. Two nonlinear transmission schemes based on the minimum mean-squared error criterion are considered in this paper: a detection scheme also known as V-BLAST and a precoding scheme called Tomlinson-Harashima precoding. The nonlinear techniques are known to be more powerful than simple linear filters, however, a large complexity overhead results. Initial proposals for the nonlinear schemes require the complexity proportional to N4 if the number of data streams is denoted by N. We propose to apply Cholesky factorization with symmetric permutation for finding a very simple and efficient algorithm that reduces the complexity by a factor of N. We conclude that the large performance advantage of the nonlinear detection and precoding schemes against their simple linear alternatives can be obtained without complexity overhead

Joint Frame Synchronization and Frequency Offset Estimationin OFDM Systems

Abstract: A new joint frame synchronization and carrier frequency offset estimation scheme in orthogonal frequency division multiplexing (OFDM) systems is proposed in this paper, where both frame synchronization and carrier frequency offset estimation can be performed by using only ONE training symbol. Frame synchronization and carrier frequency offset acquisition are performed simultaneously in the proposed scheme. Reliable frame synchronization is obtained in the proposed scheme even in low SNR. The maximum carrier frequency offset acquisition range of the proposed scheme can be up to one half of the total signal bandwidth. The same training symbol can also be utilized to carrier frequency offset Fine Adjustment, which estimates the remaining carrier frequency offset after acquisition with higher accuracy. The performance comparison of the proposed Fine Adjustment algorithm and Schmidl's algorithm by using computer simulation illustrates and verify the superior performance of the proposed algorithm with regard to estimation accuracy.

Radio communication system, radio base station apparatus, user terminal and radio communication method

Abstract: To reduce overhead of CSI feedback without decreasing throughput in applying CoMP transmission, a radio communication method of the invention is characterized by including, in a user terminal measuring quality information for each of cells to perform Coordinated Multi-Point transmission, and notifying a radio base station apparatus of the quality information, in the radio base station apparatus calculating a quality difference between the cells to perform Coordinated Multi-Point transmission, by using the quality information for each the cells from the user terminal, determining granularity of inter-cell channel state information for each of the cells based on the quality difference, and notifying the user terminal of the granularity, and, in that the user terminal generating inter-cell channel state information for each of the cells according to the granularity from the radio base station apparatus, and transmitting the inter-cell channel state information for each of the cells to radio base station apparatuses of cells to perform Coordinated Multi-Point transmission