This paper deals with network performance of 64kbit/s-based services supported in an ATM network and an ATM interworking network with 64kbit/s-based networks. It first clarifies network performance issues giving a model and objectives of study and experiment. A result of computational analysis is then presented, where a cell loss ratio of an order of 10-4 or 10-5 is obtained to give a performance equivalent to that currently used as objective values in existing networks for a 64kbit/s digital level. In order to capture the impact of cell loss and associated performance for application levels, an experimental test has been carried out using typical applications. Test results show that the cell loss ratio needs to be approximately ten times better than the bit error ratio for comparable performance for application levels. A cell loss ratio of better than 10-5, or an order of 10-6 considering an interworking situation, seems to be necessary according to the test results. It is further clarified by the test that a single cell is more valuable than a multiplexed cell for providing better cell loss resilience characteristics. Although not all applications of 64kbit/s networks have been tested, it is expected that the test results can be used as guidance for considering the support of 64 kbit/s services in an ATM and interworking networks.

Corporate information communication systems are recently orienting the integration of various kinds of communication services. A PBX and a LAN have been indispensable in the realization of these systems. Some PBXs are orienting towards distributed switching architecture, and LAN systems are increasing their scale. Both requirements can be realized by means of a high speed loop optical fiber network. An integrated LAN should satisfy the required performance as a multimedia LAN and should be provided self-healing functions which heal failures automatically, to enable continuous operation of the entire system. This paper introduces a multimedia LAN, which attaches importance to the self-healing functions, called SHM-LAN. Its system architecture and its characteristics, such as efficient channel allocation are presented. This paper also deals with the self-healing functions and some applications.

SiGe HBTs with doping level inversion, that is, a higher dopant concentration in the base than in the emitter, are realized based on the double-polysilicon self-aligned transistor scheme by means of selective epitaxy performed in a production CVD reactor. The effects of the Ge profile in the base on the transistor performance are explored. The fabricated HBT with a 12-27% graded Ge profile demonstrates a maximum cutoff frequency of 88 GHz, a maximum oscillation frequency of 65 GHz, and an ECL gate delay time of 13.8 ps.

NEXT (Near End Crosstalk loss) and FEXT (Far End Crosstalk loss) of a high speed LAN connector are analyzed using a simple coupled line model and examined experimentally. "Crosstalk Chart" is also proposed, by which, the NEXT and FEXT can be easily read off from the mutual inductance and unbalanced capacitance between pair of lines. This approach is effective for Cat.5e [1] connectors. However, for Cat.6 [2], of which transmission bandwidth is widen to 250 MHz, some additional adjustments of path pattern on the jack and terminals PCB are required. In order to assist such the adjustments, a new simple measurement technique to grasp the complex crosstalk characteristics is proposed. Two examples are introduced. One is a conventional telephone rosette, which is enhanced to be co-usable for a Cat.5e LAN connector, where only its original circuit board is reengineered. Another is a Cat.6 connector of which PCB is modified from a conventional Cat.5e connector.

The major task in compact modeling for high power devices is to predict the switching waveform accurately because it determines the energy loss of circuits. Device capacitance mainly determines the switching characteristics, which makes accurate capacitance modeling inevitable. This paper presents a newly developed compact model HiSIM-GaN [Hiroshima University STARC IGFET Model for Gallium-Nitride-based High Electron Mobility Transistors (GaN-HEMTs)], where the focus is given on the accurate modeling of the field-plate (FP), which is introduced to delocalize the electric-field peak that occurs at the electrode edge. We demonstrate that the proposed model reproduces capacitance measurements of a GaN-HEMT accurately without fitting parameters. Furthermore, the influence of the field plate on the studied circuit performance is analyzed.

This paper proposes an OFDM based adaptive modulation scheme employing variable coding rate (VCR OFDM AMS), which selects optimum modulation and coding scheme (MCS) realized by combination of several modulation schemes and coding rates. The OFDM AMS with multilevel transmit power control (OFDM AMS/MTPC) can realize high data rate transmission in the dynamic parameter controlled-orthogonal frequency and time division multiple access (DPC-OF/TDMA). The employment of OFDM AMS/MTPC, however, makes transceiver design rather complex. To solve this problem, we propose to improve throughput performances of the OFDM AMS without employment of the MTPC. The simple OFDM AMS, however, does not fully utilize transmit power for throughput improvement because there is surplus transmit power which corresponds to power margin over required signal to interference plus noise power ratio (SINR). Thus, in order to improve transmit power efficiency for throughput increase, we reduce the required SINR gaps between adjacent MCSs by introducing many coding rates. Furthermore, this paper presents an effective bit loading algorithm when multiple coding rates as well as modulation schemes are used. Computer simulation confirms that the proposed VCR OFDM AMS gives sufficient throughput performances as an alternative to the OFDM AMS/MTPC.