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.

Base station apparatus of mobile communication system

Abstract: A base station including a transmitting and receiving amplifier for amplifying CDMA signals exchanged with a mobile station; a radio stage connected to the transmitting and receiving amplifier for carrying out D/A conversion of a transmitted signal that undergoes baseband spreading, followed by quadrature modulation, and for carrying out quasi-coherent detection of a received signal, followed by A/D conversion; a baseband signal processor connected with the radio stage for carrying out baseband signal processing of the transmitted signal and the received signal; a transmission interface connected with the baseband signal processor for implementing interface with external channels; and a base station controller for carrying out control such as management of radio channels and establishment and release of the radio channels. The base station communicates with the external channels using ATM cells, and with the mobile stations using the CDMA signals by mapping a plurality of logical channels into a plurality of physical channels. The CDMA signals are spreading using two types of spreading code sequences, that is, a short code and a long code.

IDMA vs. CDMA: Analysis and Comparison of Two Multiple Access Schemes

Abstract: This article presents comprehensive comparisons of interleave division multiple access (IDMA) and direct sequence code division multiple access (DS-CDMA) in terms of performance and complexity assuming iterative multiuser detection. IDMA can be seen as a special case of DS-CDMA with spreading gain of one using very low rate code and user-specific interleavers for user separation. We focus on three suboptimum linear detectors: minimum mean square error (MMSE), rake (or matched filter), and soft-rake detectors from practical concerns. We analytically prove that the three detectors are equivalent for asynchronous users of IDMA on frequency flat channels for complex modulation alphabets. Such equivalence has been shown only for binary phase shift keying (BPSK) in the literature. The equivalence guarantees the MMSE solution for IDMA without computationally expensive matrix inversions or matrix-vector multiplications. This is generally not the case for DS-CDMA since DS-CDMA is sensitive to user asynchronism. We also discuss complexity aspects when the MMSE detector is used where we focus on essential differences in complexity between IDMA and DS-CDMA, instead of discussing particular complexity reduction techniques. Computer simulations are performed in various scenarios and the performance is analyzed by bit error rate simulations as well as by extrinsic information transfer (EXIT) charts. The analysis reveals the advantages of IDMA over DS-CDMA in terms of performance and complexity under practical considerations, particularly in highly user loaded scenarios.

Method and apparatus for video encoding and decoding using adaptive interpolation

Abstract: A method and apparatus is disclosed herein for video encoding and/or decoding using adaptive interpolation is described. In one embodiment, the decoding method comprises decoding a reference index; decoding a motion vector; selecting a reference frame according to the reference index; selecting a filter according to the reference index; and filtering a set of samples of the reference frame using the filter to obtain the predicted block, wherein the set of samples of the reference frame is determined by the motion vector.

From Mobile Phones to Personal Wellness Dashboards

Abstract: The paradigm of wellness mobiles will enable health-care professionals to have access to comprehensive real-time patient data at the point of care and anywhere there is cellular network coverage. More importantly, users can continuously and frequently track their health on the go and receive real-time user assistance when needed to alter their lifestyles. Recently, there has been a growing interest in developing proactive wellness products and health-related smartphone applications. However, developing quantifiable measures of wellness for continuous tracking and designing compliant-monitoring systems is quite challenging. This article motivates future research in this emerging field by presenting a ringside view of the recent developments and trends favoring this technology and the challenges facing the next generation of telemedicine.

Energy-efficient CPU scheduling for multimedia applications

Abstract: This article presents the design, implementation, and evaluation of EScheduler, an energy-efficient soft real-time CPU scheduler for multimedia applications running on a mobile device. EScheduler seeks to minimize the total energy consumed by the device while meeting multimedia timing requirements. To achieve this goal, EScheduler integrates dynamic voltage scaling into the traditional soft real-time CPU scheduling: It decides at what CPU speed to execute applications in addition to when to execute what applications. EScheduler makes these scheduling decisions based on the probability distribution of cycle demand of multimedia applications and obtains their demand distribution via online profiling.We have implemented EScheduler in the Linux kernel and evaluated it on a laptop with a variable-speed CPU and typical multimedia codecs. Our experimental results show four findings: first, the cycle demand distribution of our studied codecs is stable or changes slowly. This stability implies the feasibility to perform our proposed energy-efficient scheduling with low overhead. Second, EScheduler delivers soft performance guarantees to these codecs by bounding their deadline miss ratio under the application-specific performance requirements. Third, EScheduler reduces the total energy of the laptop by 14.4p to 37.2p relative to the scheduling algorithm without voltage scaling and by 2p to 10.5p relative to voltage scaling algorithms without considering the demand distribution. Finally, EScheduler saves energy by 2p to 5p by explicitly considering the discrete CPU speeds and the corresponding total power of the whole laptop, rather than assuming continuous speeds and cubic speed-power relationship.