Takeo Ohseki

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In this paper, we propose a burst construction and packet mapping scheme in the orthogonal frequency-division multiple access (OFDMA) downlinks of IEEE 802.16 systems. In the standard of the systems, there are some restrictions on the usage of downlink radio resources and they are defined in the physical layer (PHY) specification. One of the main(More)
This paper presents novel broadcast methods for an inter-vehicle communications system for ITS. During inter-vehicle communications, it is essential that emergency information be broadcast to surrounding vehicles. Emergency information such as emergency-vehicle-approach information and traffic accident information are needed by vehicles in a particular(More)
In this paper, we present a multihop mobile communications system utilizing fixed relay stations to enhance the coverage of the service area. A multihop mobile communications system was originally proposed as a system in which only mobile stations relay communication between other mobile stations and a base station to solve the problem of poor coverage(More)
Due to the recent mobile traffic explosion, especially in hotspots where a lot of traffic is generated in a limited space, an imbalance in the traffic load among cells occurs. Such traffic load imbalance requires the deployment of many base stations (BSs) in the hotspots. This results in the inefficient operation of cellular systems. In order to overcome(More)
In this paper, a fast outer-loop link adaptation (OLLA) scheme is proposed to realize low-latency transmission. OLLA generally compensates for the estimated signal-to-interference-plus-noise ratio (SINR) that is used to optimize the selection of a modulation and coding scheme (MCS) based on the reception of a positive acknowledgement (ACK) or a negative(More)
In 3GPP Release 12, 256QAM (Quadrature amplitude modulation) is expected to be adopted in downlinks of the LTE-Advanced standard as a new modulation order for the purpose of further enhancement in frequency efficiency. However, if a UE (user equipment) is configured to be able to select 256QAM in downlink transmission, the UE cannot select several MCSs(More)
To meet the strong demand for broadband multimedia services by both nomadic and mobile users, it is important to increase the bit rate of future mobile communications systems. To enhance system capacity, novel technologies or new concepts for improving bandwidth efficiency are indispensable. In this paper, an adaptive downlink modulation using OFDM and(More)
This paper proposes a multihop mobile communications system using an MC-CDMA transmission technique in the forward links. In the system, it is assumed henceforth that each mobile station has a relaying function where a frequency band is used both in the 1st and 2nd hops. Then, we examined a radio resource allocation method in the forward links. In this(More)
In IEEE 802.16 uplinks, the permutation of data on a frequency domain is performed when logical subchannels are transformed to physical subchannels to scatter deterioration of the radio propagation environment via inter-cell interference. However, it is ideal from the viewpoint of evading interference to completely divide the radio resource between the(More)