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.

Improved Recursive Maximum Expansion Scheduling Algorithms for Uplink Single Carrier FDMA System

Abstract: Single-carrier frequency division multiple access (SC-FDMA) has been selected as the uplink access scheme in the UTRA Long Term Evolution (LTE) due to its low peak-to-average power ratio properties. Nevertheless, in order to achieve such a benefit, it requires a localized allocation of the resource blocks (RBs), which naturally imposes a severe constraint on the scheduler design. In this paper, two improved recursive maximum expansion scheduling algorithms for SC-FDMA are proposed. Compared with conventional recursive maximum expansion (RME) scheme in which UE can only expand the resource allocation on neighboring RBs with the highest metrics, in proposed improved recursive maximum expansion (IRME) scheme, higher degree of freedom in RB expansion is achieved by allowing RB expansion within certain ranking threshold. Moreover, to further increase the flexibility in resource allocation, multiple surviving paths are introduced in proposed improved tree-based recursive maximum expansion (ITRME) scheme. The simulation results show that, compared with conventional RME scheme, the proposed IRME scheme can exhibit the gain about 15% in terms of spectral efficiency with a linear increase of computational complexity, and the performance can be further improved to 18% with proposed ITRME scheme if further higher complexity is permitted.

Repeating station, a communication apparatus, and a directivity control method

Abstract: A repeating station, a communication apparatus, and an antenna directivity control method are disclosed. The repeating station includes a first antenna group including at least one antenna element, a second antenna group that is different from the first antenna group, the second antenna group including two or more antenna elements adjusted so that radiation in the direction of the first antenna group is reduced, wherein the second antenna group is adjusted such that radiated power in the direction of the first antenna group is reduced.

Efficient designated confirmer signatures without random oracles or general zero-knowledge proofs

Abstract: Most prior designated confirmer signature schemes either prove security in the random oracle model (ROM) or use general zero-knowledge proofs for NP statements (making them impractical). By slightly modifying the definition of designated confirmer signatures, Goldwasser and Waisbard presented an approach in which the Confirm and ConfirmedSign protocols could be implemented without appealing to general zero-knowledge proofs for NP statements (their “Disavow” protocol still requires them). The Goldwasser-Waisbard approach could be instantiated using Cramer-Shoup, GMR, or Gennaro-Halevi-Rabin signatures. In this paper, we provide an alternate generic transformation to convert any signature scheme into a designated confirmer signature scheme, without adding random oracles. Our key technique involves the use of a signature on a commitment and a separate encryption of the random string used for commitment. By adding this “layer of indirection,” the underlying protocols in our schemes admit efficient instantiations (i.e., we can avoid appealing to general zero-knowledge proofs for NP statements) and furthermore the performance of these protocols is not tied to the choice of underlying signature scheme. We illustrate this using the Camenisch-Shoup variation on Paillier’s cryptosystem and Pedersen commitments. The confirm protocol in our resulting scheme requires 10 modular exponentiations (compared to 320 for Goldwasser-Waisbard) and our disavow protocol requires 41 modular exponentiations (compared to using a general zero-knowledge proof for Goldwasser-Waisbard). Previous schemes use the “encryption of a signature” paradigm, and thus run into problems when trying to implement the “confirm” and “disavow” protocols efficiently.

Information insertion service providing system, information insertion method, communication network, information management apparatus, and service control apparatus

Abstract: An information insertion service providing system comprises a communication network owned by a communication carrier, providing a communication service, and interconnecting an originating instrument held by an originating user of the service, a receiving instrument held by a receiving user, the information storage device, and the information processing device owned by an information insertion demander; and for reducing the load on both an information insertion demander and a receiver, the communication network has an information management station configured to receive an information insertion request from the in formation processing device, settle the insert information, based an the information insertion request and user information of the originating side and the receiving side managed by the service control station, and acquire the insert information from the information storage device, and an information transferring device configured to insert the insert information into each of the originating and receiving instruments.

Optimizing the number of dedicated pilot symbols for forward link in W-CDMA systems

Abstract: A wideband code division multiple access (W-CDMA) forward link employing both a common pilot channel (CPICH) and dedicated pilot (DP) symbols in a dedicated channel (DCH) is assumed. We optimize the number of DP symbols respectively for a low symbol rate case and a high symbol rate case in terms of the system capacity by computer simulation. It is assumed that both CPICH and DP symbols are used for channel estimation and signal-to-interference power ratio (SIR) estimation for forward link closed-loop power control by mobile stations (MSs). This paper first describes the SIR measurement method and the channel estimation method using both pilots, then demonstrates that for the 30-ksps case, one DP symbol provides the best performance, and for the 240-ksps case, the near best performance is achieved when the number of DP symbols is around eight. It is also clarified that the performance levels are mainly affected by the received signal power estimation accuracy and the overhead of the DP symbols.