Masayuki Fujise

Energy management in the IEEE 802.16e MAC

Energy management is an important component for the emerging standard IEEE 802.16e supporting mobility. In this paper, we characterize the standardized sleep mode in IEEE 802.16e. The comparison between our result and the simulation shows that our analytical model is accurate in evaluating the energy consumption and hence provides a potential guidance in efficiently managing energy.

Pattern reconfigurable leaky-wave antenna design by FDTD method and Floquet's Theorem

A pattern reconfigurable millimeter-wave coplanar waveguide leaky-wave antenna is designed by using the finite-difference time-domain (FDTD) method combined with Floquets theorem and the simple linear interpolation technique. The concept of equivalent period is presented for mixed-periodic structures. The novel design process results in a reduction in the design time compared with that of the traditional FDTD method.

An improvement for authentication protocol in third-generation wireless networks

An improvement for the mutual authentication in the third-generation mobile networks is proposed to address the potentially long delay in waiting for authentication vector (AV) when SGSN and HLR/AuC are located far away from each other, or when the two entities are operated by different operators, or when the mobile terminal (MT) call/mobility activity is frequent. In the 3GPP Technical Specification TS33.102, the probability that an action triggering authentication and key agreement (AKA) has to wait for an AV is fixed as high as 20%. Our proposed scheme is able to achieve this probability smaller than 2% with negligible increased signaling overhead and low storage cost

Carrier-to-noise ratio and sidelobe level in a two-laser model optically controlled array antenna using Fourier optics

The carrier-to-noise ratio of the microwave signal and the reduction of the antenna sidelobe are discussed for an optically controlled array antenna whose microwave aperture distribution is generated and controlled using Fourier transform and optical/electrical conversion. A two-laser model using two laser diodes whose frequency difference is set to the desired microwave frequency is proposed and compared with a single-laser model using an external modulator. The two-laser model seems to be favorable from the viewpoint of available laser diode output power. The required laser output for the two-laser model can be about 10 dB less than that for the single-laser model. Moreover, relationships between the antenna radiation characteristics and the aperture size of an image mask are investigated. It is clarified that the sidelobe level can be reduced about 20 dB without changing the gain and beamwidth by using a reference optical beam with a tapered amplitude distribution. >

Design of low-profile microstrip antenna with enhanced bandwidth and reduced size

An effective technique is presented to enhance the bandwidth and reduce the size of an ultralow-profile microstrip antenna. By loading multicouple staggered slots on the patch and using inset feed structure, two TM10 modes can be excited at two close frequencies and matched well simultaneously. Designs based on the structures with four-, five-, and six-couple staggered slots have been made to demonstrate the effective technique. To the best designed results, the presented ultralow-profile microstrip antenna obtains a bandwidth enhancement of about two times and a size reduction of about 60% compared with the ordinary one. The technique is suitable for radio-frequency front-end antenna integration and package in microwave and millimeter-wave bands

Feed circuits of double-layered self-diplexing antenna for mobile satellite communications

An analysis of feed circuits for a double-layered self-diplexing antenna for mobile satellite communications is presented. It is possible to reduce the weight of the diplexer for a self-diplexing antenna by getting large internal isolation between transmitting and receiving. The internal isolation is shown to be heavily dependent on the configuration and errors of the feed circuits of the antenna. The feed circuits of two- and four-point feeds for the antenna are discussed, using the cavity model of microstrip elements, and an error analysis of the feed circuit is carried out. >

Optical Single-Sideband Modulation at 60 GHz Using Electro-Absorption Modulators

With standard fiber and conventional optical double-sideband modulations, the fiber transmission distances of millimeter-wave signals are severely limited under several kilometers due to dispersion-induced signal fading. This limitation could be minimized by employing optical single-sideband (OSSB) modulation. This paper presents experiment of optical single-sideband modulation at 60 GHz, using two individual electro-absorption modulators in parallel. Stabilizing the achieved OSSB spectrum is also discussed.

Location Management Congestion Problem in Wireless Networks

We propose and study the location management congestion problem arising in the group mobility scenarios. In the hot-spot locations, e.g., supermarket, bus interchange, or public transportation systems, a large number of travelers move into the same area concurrently and trigger the location update (LU) procedure simultaneously to register their new locations. However, due to the limited bandwidth in a base station, only a small part of the LU requests has the opportunity to capture a radio channel and succeeds in refreshing the new information to the corresponding database in the wireless networks. The remaining mobile terminals (MTs) are unable to obtain a radio channel, and consequently, the LU requests are rejected. A significant consequence of a failed LU is the out-of-date location identity in the network databases and, thereafter, the incapability in establishing the valid route for the potential call connection request, which will seriously degrade the network quality-of-service (QoS). We develop a queueing model to characterize the congestion issue and propose a buffer scheme to eliminate this problem. The consequence of the LU failure on the MTs call activity is also investigated. The comparison demonstrates the high efficiency of the proposed approach in decreasing the LU failure as well as the resulting call blocking probability. The analytical model has been validated by the discrete event simulation

Security Management in the Next Generation Wireless Networks

In this paper, we make an introduction to the security management in the next generation wireless mobile net- works, including the access security mechanisms in the circuited-switched domain, packet-switched domain and emerging IP multimedia subsystem domain. Several re- search challenges are identified, including security architecture with network heterogeneity, energy-security trade- offs and mobility-security interaction. The identified is- sues can serve as the potential guidance for further study to satisfy higher security requirement and lower introduced overhead.

Performance Analysis of Wireless Networks Over Rayleigh Fading Channel

Employing a cross-layer approach, the explicit relationships between the fading channel characteristics and the significant teletraffic variables as well as the performance metrics in wireless network evaluation are formulated. In particular, the channel holding time, handoff probability, handoff call arrival rate, call blocking probability, call completion probability, and forced termination probability are developed, taking into account the carrier frequency (or equivalently wavelength), maximum Doppler frequency, and fade margin. In addition, the set of formulas are derived with the generalized assumptions for the call holding time and cell residence time. The analytical model has been validated by the simulation with the conventional exponential model and, additionally, the relaxed models for call holding time and cell residence time, e.g., Erlang and hyper-Erlang. The comparison demonstrates that the traditional result without considering the fading channel characteristics leads to substantially overestimated call blocking probability and call completion probability. The methodology presented in this paper provides a feasible manner for the wireless network cross-layer design and optimization