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.

A matched filter approximation for SC/MMSE iterative equalizers

Abstract: This letter proposes a new iterative ISI equalization algorithm that offers low computational complexity: order L/sup 2/ with channel memory length L. The proposed algorithm is an extension of Reynolds and Wang's SC/MMSE (soft canceler followed by MMSE filter) equalizer: approximations are used properly to reduce the computational complexity. It is shown that the approximations used in the proposed algorithm do not cause any serious performance degradations from the trellis-based iterative equalization algorithms.

Cross-Layer Design for Power Efficiency and QoS Provisioning in Multi-Hop Wireless Networks

Abstract: In recent years, it has become common consensus that independent consideration of communication layers often turns out to be inadequate in terms of providing the desired quality of service (QoS) and power efficiency in wireless networks. The need for a synergistic, cross-layer design framework has already been identified. In that respect, our work constitutes an important step towards a better understanding of the cross-layer paradigm by simultaneously targeting both the power efficiency and the end-to-end QoS in multi-hop wireless networks. More specifically, we address the joint problem of power control and scheduling with the objective of minimizing the total transmit power subject to the end-to-end bandwidth guarantees and the bit error rate constraints of each communication session. After identifying the inherent difficulty of the problem, we propose two classes of heuristic algorithms that rely on graph theory principles as well as on derived metrics such as effective interference. The first heuristic follows a top-down design strategy by solving the schedule feasibility problem as the initial step and then targeting the total power efficiency. On the other hand, the second heuristic follows a bottom-up approach that schedules one wireless link at a time by greedily filling up the available time slots. The simulation results reveal valuable insights about the performance of each strategy. The top-down design strategy turns out to address power efficiency issues better, whereas the bottom-up design strategy with a properly selected cost function for link scheduling shows better performance in finding a feasible solution, namely one that satisfies both the QoS and the transmit power constraints. Our results also illustrate the impact of routing decisions on the feasibility and the power efficiency of multi-hop wireless networks through employing different routing criteria in the experiments

Handover processing method, eNB and network communication system thereof

Abstract: Embodiments of the present invention includes a handover processing method, a source eNB, a neighboring eNB and a network communication system. In one embodiment of the handover processing method, a source eNB selects a target eNB from neighboring eNBs that can accept a handover request from a mobile terminal, and notifies a selection result to the mobile terminal; if handover information corresponding to the mobile terminal is received by an neighboring eNB that can accept the handover request of the mobile terminal within a preset handover waiting time, the neighboring eNB determines that it is a target eNB and cooperates with the mobile terminal to perform a handover; otherwise, the neighboring eNB determines that it is a prepared eNB and reduces its resources reserved for the mobile terminal. The present invention can effectively improve the successful handover probability.

Image and video compression using sparse orthonormal transforms

Abstract: A method and apparatus is disclosed herein for performing compression with sparse orthonormal transforms. In one embodiment, the method comprises receiving a block of data; classifying the block of data based on directional structure; selecting one of a plurality of available directional, orthonormal transforms to apply to the block based on results of classifying the block; and applying the selected transform to the block to generate a plurality of coefficients, thereby producing a compressed version of the block.

Cell search method and apparatus for mobile station in mobile communication system

Abstract: The present invention reduces the time required for cell search and increase the accuracy of the cell search by determining, during selection of frame boundaries and a scramble code, whether or not the selection results are correct. A mobile station causes descramblers to descramble a received signal with eight scramble codes. Then, correlators calculate the phases of the scramble codes on the basis of frame boundaries, and despreads the signal with a spreading code for a CPICH. The mobile station performs this operation over a plurality of symbols, and causes averaging process sections to average the results. Then, a peak detector selects a scramble code with which an average correlation coefficient is largest. This maximum average correlation coefficient is output to a detection results judging section, which then calculates the ratio of this value to a reference value calculated inside the mobile station, thereby judging detection results.