Hideyuki Shinonaga

Proposed relay method with P-MP structure of IEEE 802.16-2004

This paper presents a relay method with a P-MP (point to multipoint) structure by extending the IEEE 802.16-2004 standard in order to expand the coverage area (2004). In the proposed relay method, a RS (relay station) sends a polling message for the SSs (subscriber station) assigned to the former to forward uplink data in terms of the contention opportunities in the uplink subframe, and obtains a contention request period to communicate between the RS and these SSs. The feature of the proposed relay method is that it can be applied to TDD (time division duplex) and FDD (frequency division duplex), and both BS (base station) and RS operating at the same and at different carrier frequencies respectively. In this paper, we evaluated the basic characteristics of the proposed relay method in terms of throughput and delay time through computer simulations. We show that the introduction of the proposed relay method is effective in expanding the coverage area, and that the proposed relay method has an effect on the increase of the system throughput without affecting the delay time by adjusting the time interval parameter for BW requests of SSs assigned to the RS correctly

Long-range oversea wireless network using 2.4 GHz wireless LAN installation and performance

High-quality 2.4 GHz wireless LAN over long-range oversea paths was installed using a space diversity technique. The installed network consists of five wireless links, including a long-range 11.3 km link. To lower the adverse affect of fluctuation in the tidal level, two wireless LAN devices with different antenna heights were installed at one side of the longest link. The antenna heights were suitably determined on the basis of link profile and gained data at the deployment of the equipment. The measured performance indicates that the link with space diversity achieves 100% operating rate in a measured period of time, while the link without space diversity achieves an approximately 90% operating rate in the same time. This method effectively improves the quality of conventional wireless LAN systems.

Simulation evaluation on area extension and system capacity of CDMA packet communication system utilizing multihop connection

The objective of this study is to evaluate effectiveness of multihopping technique applied to CDMA packet communication system. The system model is designed so that mobile stations that have no direct connectivity to any base station setup multi-hopped paths by way of neighbor mobile stations. Two policies are addressed in selecting relay stations based on battery usage, minimized usage on relay station and minimized usage on all stations along multihopped path. With these conditions, system characteristic is evaluated in terms of system capacity and coverage area extension. The result of computer simulation shows that multihopping technique does extend the coverage area with effectively equal performance to the conventional single hop system when the system load is relatively light.

Adaptive media switching for future vehicle-to-vehicle communication

Vehicle-to-vehicle (peer-to-peer) communication is expected to play an important role in ITS (intelligent transport systems). This paper proposes an adaptive media switching method for future vehicle-to-vehicle communication. Our method adopts an approach to select the most suitable radio communication media from several possible types based on the vehicle locations, available media and communication quality. Before the network configuration of inter-vehicle and roadside-vehicle communication changes, the vehicle detects it and then initiates the media reselection. During such media switching, our proposed HTTP-based session layer mobility avoids any interruption of communication. We conducted field tests using several experimental vehicles. The results verify that our proposed method is effective in selecting the most suitable media, and disconnection of communication during the media switching is also avoided

Performances of beamforming in downlink with smart antenna testbed

This paper describes field trials with a smart antenna testbed system for IMT-2000 to evaluate the beamforming performance in the downlink. In the testbed system, a method to fit the transmit beam pattern to the virtual beam pattern, which is formed virtually for the downlink beamforming with correlation matrices measured in the uplink, was employed as the criterion of the downlink beamforming. Also, in consideration of the difference of antenna element radiation characteristics in uplink and downlink frequencies, the transmit and receive beam pattern calibration (TR-BPCal) algorithm was employed. The results of field trials confirmed the downlink beam/null-steering to the desired/undesired user, the transmit power reduction in the base transceiver station due to the null-steering to the interference signal and an improvement of the reduction when using the TR-BPCal algorithm.

A Study on Symbol and Sub-Carrier Mapping Techniques for MC-CDMA based on LDPC Code with Progressively Increased Column-Weight

This paper proposes a symbol mapping scheme on sub-carriers in use of MC-CDMA (multi carrier-code division multiple access) and LDPC (low-density parity-check) codes. Aiming at high spectrum efficiency, 16QAM modulation and LDPC codes with the PICW (progressively increased column-weight) are used here. The PICW-LDPC code is proposed in our previous studies and is proved to have better decoding performance as rate-compatible LDPC codes. By adopting the proposed symbol mapping method, the FER (frame error rate) performance of the PICW-LDPC code is improved, the required Es/N0 is reduced by 0.12 dB in an AWGN channel. In order to improve FER performance in the multi-path channel, the proposed sub-carrier mapping is further applied, and the required Es/N0 can also be reduced by 2.32 dB

Large-scale CFO-SS (high-speed, long-range 2.4 GHz wireless LAN) network for educational Internet access

A 2.4 GHz wireless LAN network interconnecting schools and educational facilities is constructed employing CFO-SS (carrier frequency offset-spread spectrum) systems. The CFO-SS system provides high-speed (10 or 18 Mbit/s) and long-range transmission without reducing the transmission speed. Parameters of CFO-SS links such as radio channels, antenna polarizations and access modes are selected by considering the CFO-SS network architecture. Changing a radio channel by a network management software, CFO-SS keeps the link quality at a predetermined level under interference from other existing systems using the 2.4 GHz band. The throughput performance is improved with a window control protocol of CFO-SS.

On symbol timing for OFDM based mobile communications systems

This paper deals with symbol timing synchronization issue for broadband OFDM based mobile communication system. A symbol timing approach using adaptive threshold is proposed. Several OFDM training symbol formats and the corresponding timing metrics are evaluated. Simulations am carried out using Rayleigh fading model at 5 GHz band, with the velocity being 100 km/h and 150 km/h. The performances of the simulation results demonstrate that the proposed symbol timing method is feasible for mobile telecommunications.

High speed wireless access system using 4.9 GHz band

At present, wireless access systems in the 5 GHz band, specified by the MMAC-PC (Multimedia Mobile Access Communication systems Promotion Council), are allocated frequencies from 5.15 to 5.25 GHz, and only for indoor use in Japan. Outdoor wireless access systems in the 5 GHz band are currently under consideration. This paper presents a high speed wireless access system developed for operating on 4.9 GHz band (4.9 to 5.0 GHz). The composition of equipment and OFDM modem technology are discussed. Furthermore, the throughput characteristic of equipment and HDTV (high definition television) image transmission experiment results are described.