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.

Selection of a target network for a seamless handover from a plurality of wireless networks

Abstract: Method and device for deciding a handover of a communication link between a mobile device and a current network to one of a number of available networks, including determining network parameters for each if the available networks and determining a set of candidate networks basically suitable for handling the communication with the mobile device. From the set of candidate networks a target network is selected, based on a comparison of link parameters describing a communication link between the mobile device and each candidate network. A handover is then performed to the selected target network. The invention enables a seamless inter-network handover and avoids significant degradation of service or service termination.

Scalability and robustness analysis of mobile IPv6, fast mobile IPv6, hierarchical mobile IPv6, and hybrid IPv6 mobility protocols using a large-scale simulation

Abstract: Fast mobile IPv6 (FMIP) and hierarchical mobile IPv6 (HMIP) are enhancements to the standard mobile IPv6 (SMIP) protocol for reducing handover latency and data loss, and for localized mobility management. In this paper, we present scalability and robustness analysis of the three protocols and two hybrid protocols of FMIP and HMIP, using a large-scale simulation. The simulation results indicate that FMIP achieves the best handover performance. HMIP incurs considerably less per-handover signaling overhead than FMIP on the wireless link, but HMIP data traffic has a fixed and permanent overhead even after handover. Hybrid protocols achieve FMIP-like handover performance and improve handover signaling overhead but cannot remove tunneling overhead. Hybrid protocols are also more robust to access router and home agent failures.

CDMA communication method and group spreading modulator

Abstract: A CDMA communication method capable of providing a multi-rate user with high quality transmission using a spreading sequence selected from sequences which consist of multilayer sequences arranged in a hierarchical tree structure. A higher level sequence C16(1) and its inverted sequence C ¯ 16(1) are included in its lower level sequences {C32(1), C32(2)} and {C64(1), C64(2), C64(3), C64(4)}, for example, and a sequence from a higher level is selected to transmit a higher rate data: The C16(1) is used to transmit data whose peak rate is twice the peak rate of the data transmitted using its lower level sequences {C32(1), C32 (2)}, and four times (= 22) that of the data transmitted using the sequences {C64(1), C64(2), C64(3), C64(4)}. The C16(1), however, cannot be selected if any one of its lower level sequences {C32(1), C32(2)} and {C64(1), C64(2), C64(3), C64(4)} are already being used. This makes it possible for all the spreading sequences of simultaneous multi-rate users to be orthogonal at any transmission rate.

Analytical Modeling of Heterogeneous Cellular Networks: Geometry, Coverage, and Capacity

Abstract: This self-contained introduction shows how stochastic geometry techniques can be used for studying the behaviour of heterogeneous cellular networks (HCNs). The unified treatment of analytic results and approaches, collected for the first time in a single volume, includes the mathematical tools and techniques used to derive them. A single canonical problem formulation encompassing the analytic derivation of Signal to Interference plus Noise Ratio (SINR) distribution in the most widely-used deployment scenarios is presented, together with applications to systems based on the 3GPP-LTE standard, and with implications of these analyses on the design of HCNs. An outline of the different releases of the LTE standard and the features relevant to HCNs is also provided. A valuable reference for industry practitioners looking to improve the speed and efficiency of their network design and optimization workflow, and for graduate students and researchers seeking tractable analytical results for performance metrics in wireless HCNs.