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, mobile station, and method

Abstract: A single carrier scheme is used in an uplink in the mobile communication system. A base station used in the mobile communication system includes: means configured to perform communication with a mobile station that uses the whole or a part of a system frequency band; storage means configured to store correspondence relationship between radio parameters including a bandwidth, a modulation scheme and a channel coding rate of the uplink and filter parameters including at least a roll-off factor of a band limitation filter; and determination means configured to determine radio parameters and filter parameters for each mobile station based on the correspondence relationship according to channel state of the uplink. The radio parameters and the filter parameters determined in the determination means are reported to the mobile station.

Device management apparatus, device, and device management method

Abstract: A device management apparatus includes a device configuration information holding unit, a subscriber information holding unit, a security policy holding unit, a module state holding unit, and a device diagnosis unit. The security policy holding unit holds a security policy set based on the configuration based on the configuration information or the subscriber information. The device diagnosis unit examines the security policy and the module state information to make a diagnosis of a configuration of the device.

Base station connection method, radio network controller, and mobile station

Abstract: A method for connecting the radio link between a mobile station and a base station is provided to improve quality of received signals at the base station and the mobile station. A radio network controller (RNC) monitors the difference between the reception power of signals from the source base station BS1 and the destination base station BS2. If the base station BS2 is incapable of directional beam signal transmission and reception, and when the reception power difference becomes smaller than a first handover threshold, the radio network controller adds the base station BS2 as a radio link connection destination of the mobile station. If the base station BS2 is capable of directional beam signal transmission and reception, and when the reception power difference becomes smaller than a second handover threshold, which is larger than the first handover threshold, the radio network controller adds the base station BS2 as a radio link connection destination of the mobile station.

Downlink SINR distribution in a heterogeneous cellular wireless network with biased cell association

Abstract: For an arbitrarily-located user terminal (UE) in a multi-tier heterogeneous cellular wireless network, the joint distribution of the downlink SINR at the UE from the candidate serving base stations (BSs) in the accessible tiers of the network has been derived in closed form for the cases where the candidate serving BS from each accessible tier is chosen as either the one nearest to the UE [1] or the one that is received strongest (equivalently, with maximum SINR) at the UE [2], when the locations of the BSs in the tiers are modeled by independent Poisson Point Processes, and the fading on all links is assumed independent identically distributed (iid) and Rayleigh. The actual serving BS for the UE is chosen as the nearest/strongest/max-SINR candidate serving BS after imposing selection bias across the tiers. The above joint distributions can be used to yield the distribution of the actual SINR at the UE (i.e., when receiving from this serving BS) when no selection bias exists across tiers. However, for the practically important case of selection bias, analytical calculation of the distribution of the actual SINR presents significant challenges. This work derives and summarizes the distribution of actual downlink SINR for all the above criteria for selection of the serving BS accounting for selection bias. We then explore some implications of these results for design and operation of a heterogeneous network.

Investigation of optimum pilot channel structure for VSF-OFCDM broadband wireless access in forward link

Abstract: This paper clarifies the optimum pilot channel structure in the broadband forward link for variable spreading factor-orthogonal frequency and code division multiplexing (VSF-OFCDM) wireless access using two-dimensional spreading while taking into account the following factors that affect radio link performance: (1) channel estimation accuracy for coherent detection, (2) the accuracy of the signal-to-interference power ratio (SIR) measurement for adaptive modulation and channel coding and the reliability information of the received signals, (3) the configuration of simultaneously multiplexed orthogonal pilot patterns, and (4) the impact on cell search, as well as flexibility in allocating transmission power resources. We show that although the time-multiplexed and code-multiplexed structure achieves almost the same channel estimation accuracy, the code-multiplexed structure is more advantageous due to flexible multiplexing of the orthogonal pilot patterns within one sub-carrier resulting from the accommodation of numerous OFCDM symbols in a frame. Assuming the use of an adaptive antenna array beam-forming transmitter where many orthogonal pilot patterns are required, we clarify that the cod-multiplexed structure achieves more accurate SIR measurement compared to the time-multiplexed structure. Meanwhile, the time-multiplexed structure is advantageous in that it does not require an exclusive synchronization channel for cell search. Consequently, we elucidate that the code-multiplexed structure is overall slightly superior to the time-multiplexed structure because the code-multiplexed pilot channel structure is advantageous in that it can flexibly share transmission power resources among other physical channels, thereby resulting in increasing the number of orthogonal pilot patterns and increasing the number of simultaneous packet channels despite obtaining almost the identical merits of the time-multiplexed structure from the viewpoint of radio link performance.