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A new vertical transition between a substrate integrated waveguide in a low-temperature co-fired ceramic substrate and an air-filled standard waveguide is proposed in this paper. A rectangular cavity resonator with closely spaced metallic vias is designed to connect the substrate integrated waveguide to the standard air-filled waveguide. Physical characteristics of an air-filled WR-22 to WR-22 transition are compared with those of the proposed transition. Simulation and experiment demonstrate that the proposed transition shows a -1.3 dB insertion loss and 6.2 GHz bandwidth with a 10 dB return loss for the backto- back module. A 40 GHz low-temperature co-fired ceramic module with the proposed vertical transition is also implemented. The implemented module is very compact, measuring 57 mm × 28 mm × 3.3 mm. [ABSTRACT FROM AUTHOR]

Ethernet ring protection (ERP) technology, which is defined in ITU-T Recommendation G.8032, has been developed to provide carrier grade recovery for Ethernet ring networks. However, the filtering database (FDB) flush method adopted in the current ERP standard has the drawback of introducing a large amount of transient traffic overshoot caused by flooded Ethernet frames right after protection switching. This traffic overshooting is especially critical when a ring provides services to a large number of clients. According to our experimental results, the traditional FDB flush requires a link capacity about sixteen times greater than the steady state traffic bandwidth. This paper introduces four flush optimization schemes to resolve this issue and investigates how the proposed schemes deal with the transient traffic overshoot on a multi-ring network under failure conditions. With a network simulator, we evaluate the performance of the proposed schemes and compare them to the conventional FDB flush scheme. Among the proposed methods, the extended FDB advertisement method shows the fastest and most stable protection switching performance. [ABSTRACT FROM AUTHOR]

In this paper, an ultra-wideband internal antenna for use in mobile applications is proposed. The proposed antenna has symmetrical bi-arm structures printed on the top and bottom of the substrate, and it occupies a compact area of 10 mm × 10 mm × 1 mm. The designed antenna has an impedance bandwidth from 3 GHz to 12 GHz and near omnidirectional radiation patterns over the frequency band of interest. The group delay between two antennas fabricated using the proposed design is less than 0.8 ns, and the maximum gain variation is about 3.16 dB. [ABSTRACT FROM AUTHOR]

Ultra-wideband (UWB) systems have witnessed a debate over whether they may cause interference to other existing and future narrowband systems sharing their band of operation. The detect and avoid (DAA) mechanism was developed as a solution to reduce interference to narrowband systems in order to ease regulatory concerns. It works by adaptively reducing the transmitted power at the overlapping bands upon detecting an active narrowband link. However, employing DAA degrades the performance of UWB transmissions. In this paper, we present the Korean UWB regulations as an example of regulations that require DAA in certain bands. We investigate DAA's impact on performance and propose a method to mitigate it, which provides UWB with the more efficient support of the DAA mechanism and enables it to avoid a larger number of narrowband users while sustaining the data rate. Results show significant improvement in performance with the application of our technique compared to conventional performance. [ABSTRACT FROM AUTHOR]

The design of a dual and triple-band planar inverted-F antenna (PIFA) is proposed for WLAN 802.11 a/b/g applications. Dual-band operation is achieved by simply truncating one of the top rectangular radiating plate's corners, and wide bandwidth for the upper-band is obtained by applying an additional small rectangular slit. By further extending the slit length, a triple-band operation can also be achieved with a maximum gain of around 5 dBi. Simulated results are provided to validate the measured results. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 2159–2162, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22682 [ABSTRACT FROM AUTHOR]

A rapid control method is proposed to improve the transmission properties of a synchronized QoS ad hoc network (synchronized QoS network). The synchronized QoS network has already been proposed to assure transmission bandwidth in ad hoc networks. However, the VC (virtual circuit) establish time and the VC breakage interval both expand in this network. Furthermore, the rate of successful communication deteriorates in relation to network topology changes. These problems become serious when a synchronized QoS network is applied to the multirobot rescue systems operating in urban disaster areas. The rapid control method modifies the frame structure of the conventional synchronized QoS network. This method accelerates control packet transmission and therefore improves the VC establish time, VC breakage interval, and the rate of successful communications. These improvements are confirmed by computer simulations in which a reconnaissance into distant space by a multirobot rescue system is simulated. © 2006 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 89(9): 51–59, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.20278 [ABSTRACT FROM AUTHOR]

In this paper, we propose a demodulation method using maximum likelihood sequence estimation (MLSE) after coherent detection for partial response signaling single sideband (SSB) signals and present the bit error rate performance achieved by this configuration. Coherent detection is implemented by a pilot carrier method. The power of the pilot carrier inserted in the SSB modulated wave and the noise bandwidth of the phase locked loop (PLL) that extracts the base carrier cause the degradation in the power efficiency of the SSB signal. We then evaluate the equivalent carrier-to-noise power ratio (CNR) degradation of the pilot carrier method. The partial response demodulated signal can be MLSE decoded since the signal is time correlated. From the characteristics of an SSB demodulated signal, first-order MLSE decoding using only the in-phase channel generally results. Here, we also study a complex MLSE decoding method that considers the quadrature channel. Based on this configuration, we show that the SSB signal power efficiency was improved by about 5 dB compared to the conventional coherent detection and instantaneous identification and demodulation method. © 2004 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 88(4): 44–53, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.20167 [ABSTRACT FROM AUTHOR]

In order to realize beam forming with an identical radiation characteristic over a wide bandwidth, this paper describes a method of design for two-dimensional FIR fan filters with wedge-shaped transition regions. In order to provide excellent amplitude approximations in a wide range from low to high frequencies with different transition range widths, a method based on the two-dimensional Fourier series approximation is used. The approximate amplitude characteristic of the target fan filter for which the widths of the passband and the transition band are specified in proportion to the frequency from the origin is greatly degraded at low frequencies near the origin. To reduce this degradation, the target amplitude characteristic at low frequencies of the fan filter is replaced with a rectangular cross-sectional shape. The width of the rectangular amplitude characteristic is set such that the amplitude of the designed result takes the specified value on the center line. Design examples are given for an axially symmetric fan filter and a diagonally symmetric fan filter. Further, the characteristics of the beam formers using these filters are derived and the effectiveness of the method is demonstrated. © 2002 Wiley Periodicals, Inc. Electron Comm Jpn Pt 3, 85(7): 38–49, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecjc.1106 [ABSTRACT FROM AUTHOR]

In data transmission on a broadband network, such as an ATM network, rate-based congestion control is considered effective in preventing data loss caused by buffer overflow at a relay node and in achieving high throughput. Under this control, the sender node dynamically changes the transmission rate according to the network condition. However as the network grows, the delay for inquiry to the network condition increases so that it becomes hard to control congestion adequately. One of the solutions to that problem is to divide the network into several logical blocks and then to install virtual end systems at the block boundaries. When congestion control is carried out at each block, the delay for inquiry is decreased and the queue length of each node is kept low. As a result, cell discard caused by buffer overflow is reduced. In this paper, we build a queuing network model and then analyze it approximately to evaluate the effect of the virtual end systems. We investigate the influence of delay between the two ends and the locations of the virtual end systems in the network and then find some situations in which the virtual end systems do not work efficiently. The result shows that it is not sufficient simply to increase the number of virtual end systems and/or to consider their locations. The virtual end system should report its rate reduction to the sender node and should reduce its rate reduction ratio to serve more cells in its buffer. © 1999 Scripta Technica, Electron Comm Jpn Pt 1, 82(6): 8–17, 1999 [ABSTRACT FROM AUTHOR]

Video traffic is expected to become increasingly important with the large scale deployment of broadband ISDN. In the literature, it is suggested that smoothing variable bit rate (VBR) video traffic before transmitting it onto the network would help reduce the probability of cell loss. In this paper we show why deterministic smoothing at the source approximates the minimum achievable loss over the network end-to-end of all possible smoothing schemes. Furthermore, we develop a powerful yet simple analytical technique that can efficiently calculate the loss probability at any point in a network carrying video traffic. We validate our analytical results using traces of actual video segments. The results can be used for admission control and traffic management. We find that in the case of highly correlated traffic such as motion JPEG video, the way to control loss is to ensure that the fraction of time the arrival process exceeds the service process is small. We also find that for such sources increasing the buffer size only marginally decreases the loss. [ABSTRACT FROM AUTHOR]

A V dipole antenna with multiple stub loading is proposed as a traveling wave antenna with a wide bandwidth in both the gain and input impedance. It is considered that the present antenna is essentially a tapered transmission line loaded with open stubs. Then the operating principle is studied by reducing the structure to an equivalent nonuniform transmission line. It is found from the relationship between the equivalent distributed parameters and the stub that the dipole-type stub array with its stub length reduced gradually from a hail wavelength to a quartet wavelength is a basic structure for the broadband nature by the decaying traveling wave. Based on this concept, an actual stub-loaded V dipole antenna was characterized numerically. It is demonstrated that uniform characteristics of an input admittance of 5 mS, a gain of 8 dB and a front-to-back ratio of 10 dB are obtained over ±30 percent around the center frequency in the case of a V dipole with an included angle of 30°. This antenna was fabricated and the validity of the present theory was confirmed because the theoretical and experimental results agreed well. [ABSTRACT FROM AUTHOR]

Focuses on the interconnection of the broadband interconnection networks. Functionality of the fabric beyond conventional connectivity.