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.

Mobile streaming media CDN enabled by dynamic SMIL

Abstract: In this paper, we present a mobile streaming media CDN (Content Delivery Network) architecture in which content segmentation, request routing, pre-fetch scheduling, and session handoff are controlled by SMIL (Synchronized Multimedia Integrated Language) modification. In this architecture, mobile clients simply follow modified SMIL files downloaded from a streaming portal server; these modifications enable multimedia content to be delivered to the mobile clients from the best surrogates in the CDN. The key components of this architecture are 1) content segmentation with SMIL modification, 2) on-demand rewriting of URLs in SMIL, 3) pre-fetch scheduling based on timing information derived from SMIL, 4) SMIL updates by SOAP (Simple Object Access Protocol) messaging for session handoffs due to clients mobility. We also introduce QoS control with a network agent called an "RTP monitoring agent" to enable appropriate control of media quality based on both network congestion and radio link conditions. The current status of our prototyping on a mobile QoS testbed "MOBIQ" is reported in this paper. We are currently designing the SOAP-based APIs (Application Programmable Interfaces) needed for the mobile streaming media CDN and building the CDN over the current testbed.

Variable spreading factor-OFCDM with two dimensional spreading that prioritizes time domain spreading for forward link broadband wireless access

Abstract: This paper proposes the optimum design for adaptively controlling the spreading factor in orthogonal frequency and code division multiplexing (OFCDM) with two-dimensional spreading according to the cell configuration, channel load, and propagation channel conditions, assuming the adaptive modulation and channel coding (AMC) scheme employing QPSK and 16QAM data modulation. Furthermore, we propose a two-dimensional channelization code assignment scheme to achieve skillfully orthogonal multiplexing of multiple physical channels. Computer simulation results elucidate that bit-interleaving in the frequency domain is superior to chip-interleaving especially for a full channel load because bit-interleaving exhibits a large randomization effect of burst errors, while still maintaining code orthogonality. In time domain spreading, the optimum spreading factor, except for an extremely high mobility case such as for the fading maximum Doppler frequency f/sub D/ = 1500 Hz, becomes SF/sub Time/ = 16, and it should be decreased to SF/sub Time/ = 8 for such a very fast fading environment using 16QAM modulation. When the channel load is light such as C/sub mux//SF = 0.25 (C/sub mux/ and SF denote the number of multiplexed codes and total spreading factor, respectively), the required average received signal energy per symbol-to-background noise power spectrum density ratio (E/sub s//N/sub 0/) is reduced as the spreading factor in the frequency domain is increased up to say SF/sub Freq/ = 32 for QPSK and 16QAM modulation, respectively (Note that, nevertheless, 16QAm modulation under such a lighter channel load condition is replaced by QPSK modulation together with two fold the channel load as 16QAM to achieve the same information bit rate). Meanwhile, when the channel load is close to full such as when C/sub mux//SF = 0.94, the optimum spreading factor in the frequency domain is SF/sub Freq/ = 1 for 16QAM modulation and SF/sub Freq/ = 1 to 8 for QPSK modulation according to the delay spread. Consequently, by setting several combinations of spreading factors in the time and frequency domains, the near maximum link capacity is achieved both in cellular and hot-spot cell configurations assuming various channel conditions.

Client apparatus, device verification apparatus, and verification method

Abstract: A client apparatus for utilizing services by executing service programs includes a policy holding unit, a verification unit, a verification result holding unit, and a verification result notification unit. The policy holding unit holds a service-specific verification policy pre-checked by a device verification apparatus. The verification unit verifies an operation and configuration of the client apparatus itself by using the verification policy when the service program is executed. The verification result notification unit notifies the verification result to the device verification apparatus, which requests the verification result.

1.3 Evolution of 5G mobile technology toward 1 2020 and beyond

Abstract: Recently, LTE has become the mainstream of mobile technologies, and global expectations for 5G toward 2020 and beyond are rapidly growing. It is expected that 5G will cover a wide variety of use cases and a wide range of frequency bands. Today, some promising technologies are emerging, especially those using new technology combinations. Through such combinations, things which were considered impossible today will be achieved in the 5G era. Together, let us envision a new world: Wider coverage cellular systems even at higher frequencies, and single-RAT 5G system which covers all 5G use cases and spectrum bands.

Control method of searching neighboring cells, mobile station, and mobile communication system

Abstract: A control method of searching for a neighboring cell of a mobile station communicating with a base station is provided in a direct sequence CDMA mobile communication system which transmits information by carrying out double modulation using a first spreading code group and a second spreading code. The first spreading code group includes spreading codes that have a same repetition period as an information symbol period and are used in common by the base stations, and the second spreading code has a repetition period longer than the information symbol period. The base stations are assigned different second spreading codes. The control method stores at least one second spreading code and its phase into a first table, which second spreading code corresponds to a perch channel whose second spreading code and phase are known; stores a second spreading code used by a neighboring base station into a second table; searches for a perch channel whose second spreading code and phase are unknown; and searches for a perch channel whose second spreading code and phase are known. The neighboring cell search method can save the power consumption and time required for the mobile station to carry out the cell search with preventing an increase in the total cost of the system.