The Fundamental Law of Science and Technology and the Basic Plan of Science and Technology were established in Japan in 1995 and 1996, respectively and the second Basic Plan for Science and Technology R&D was established in April, 2001. In addition, as a part of Japanese government administrative reform, the Council for Science and Technology Policy was organized in the Cabinet Office and the most of the national research laboratories including the Communications Research Laboratory (CRL) have been restructured to the Independent Administrative Institution (IAI). This paper introduces first the relationship between the info-communications R&D and the national science and technology policy in Japan. Second, the R&D of CRL, IAI is introduced. Third, as a typical example of the wireless communications R&D, the research of wireless communication in CRL is shown in more detail in terms of terrestrial wireless/mobile communication system and satellite communication system. Finally the future prospect of such an R&D is shown briefly.

We report our studies on the spectral sensitivity of superconducting NbN thin-film single-photon detectors (SPD's) capable of GHz counting rates of visible and near-infrared photons. In particular, it has been shown that a NbN SPD is sensitive to 1.55-µm wavelength radiation and can be used for quantum communication. Our SPD's exhibit experimentally measured intrinsic quantum efficiencies from 20% at 800 nm up to 1% at 1.55-µm wavelength. The devices demonstrate picosecond response time (<100 ps, limited by our readout system) and negligibly low dark counts. Spectral dependencies of photon counting of continuous-wave, 0.4-µm to 3.5-µm radiation, and 0.63-µm, 1.33-µm, and 1.55-µm laser-pulsed radiations are presented for the single-stripe-type and meander-type devices.

This paper proposes list Viterbi equalizers (LVEs) that use two kinds of metric criteria for wide-spread time-dispersive channels to achieve a good trade-off between complexity and bit error rate (BER) performance. For Viterbi equalization employing a state-reduction algorithm, the modified metric criterion proposed by Ungerboeck is not always equivalent to the squared Euclidean distance metric criterion. This paper proposes the following two schemes for the LVE: (1) to combine two kinds of metric criteria like combining diversity; (2) to select the metric criterion like selection diversity according to the channel impulse response. Finally, computer simulation shows that the proposed schemes improve BER performance on wide-spread frequency selective fading channels, even if the proposed schemes have smaller complexity than the conventional one.

A multiphase low-jitter delay-locked loop (DLL) with harmonic-lock prevention, targeted at a gigabit parallel link interface, is delineated. A three-input four-state dynamic phase detector (PD) is proposed to obviate harmonic locking. Employing a low-jitter delay element and a new type of PD, the DLL is compact and feasible in its nature. The DLL is designed using a 0.35 µm 2P4M CMOS process with 3.3 V supply. Experimental results show that the circuit avoids false locking.

This paper proposes an extension of a conventional current conveyor (CC) concept and its applications. A relaxation of the definition of a conventional CC makes a CC simple. A novel current conveyor named extended current conveyor (ECC) is introduced. An ECC keeps the most significant feature of a CC, i.e., a CC is combination of a VCVS and a CCCS. On the other hand, the other conditions are relaxed. All terminals of the ECC are allowed to have offset voltage and offset current. An ECC usually has a simple structure with a small number of MOSFETs thanks to the relaxation of the conditions. Some circuit configurations for the ECC which have various characteristics are shown. An NIC and OTAs are realized using ECCs. Validity of an ECC is confirmed through HSPICE simulation.

In this report, we propose a new bilateral floating resistor circuit having both positive and negative resistance values. The equivalent resistance of this floating resistor in CMOS technology can be changed by using controlled-voltages, which is an advantage over polysilicon or diffused resistor in the integrated circuit. Moreover the characteristics of the proposed circuit are independent of the threshold voltage. We have simulated the proposed circuit by using HSPICE. Finally, we have confirmed that the proposed circuit is useful as an analog component.

40 Gbit/s optical transceiver using a novel OTDM MUX module has been developed. OTDM (Optical-Time-Division-Multiplexing) MUX module, the core component of the transmitter, consisted of a optical splitter, two electro-absorption (EA) modulators and a combiner in a sealed small package. As the split optical paths run through the "air" in the module, greatly stable optical phase relation between bit-interleaved pulses could be maintained. With the OTDM MUX module, the selection between conventional Return-to-Zero (conventional-RZ) format and carrier-suppressed RZ (CS-RZ) format is performed by slightly changing the wavelength of laser-diode. In a receiver, 40 Gbit/s optical data train is optically demultiplexed to 10 Gbit/s optical train, before detected by the O/E receiver for 10 Gbit/s RZ format. Back-to-back MUX-DEMUX evaluations of the transceiver exhibited good sensitivities of under -30 dBm measured at 40 Gbit/s optical input to achieve the bit-error-rate (BER) of 10-9. Another unique feature of the transceiver system was a spectrum switch capability. The stable RZ and CS-RZ multiplexing operation was confirmed in the experiment. Once we adjust the 40 Gbit/s optical signal to CS-RZ format, the optical spectrum would maintain its CS spectrum shape for a long time to the benefit of the stable long transmission characteristics. In the recirculating loop experiment employing the OTDM MUX transceiver, the larger power margin was successfully observed with CS-RZ format than with conventional-RZ format, indicating that proper encoding of conventional-RZ and CS-RZ was realized with this prototype transceiver. In the case of CS-RZ format, the error free (BER < 10-9) transmission over 720 km was achieved with the long repeater amplifier span of 120 km.

In this paper, we propose a method of unicast and broadcast packet sharing for the orthogonal frequency division multiplexing (OFDM) multi-base station (BS) indoor wireless communication system using an adaptive array antenna on mobile terminals. The adaptive array antenna placed on the mobile terminal allows quality improvement due to the diversity effect when the data transmitted from all BSs are the same, and provides capacity improvement by channel sharing when the data from each BS are different. In the proposed sharing method, unicast packets are transmitted independently from multiple BSs in order to increase the communication capacity, and broadcast packets are transmitted simultaneously with other BSs in order to enhance the communication quality without retransmission. Furthermore, by modifying the packet assignment procedure, we confirm that quality can be improved for unicast packets in a low traffic environment.

We introduce PC Linux cluster computing techniques to an Evolutionary Graph Generation (EGG) system, and successfully implement the parallel version of the EGG system, called PEGG. Our survey satisfactorily shows that the parallel evolutionary approach meets our expectation that the final solutions obtained from PEGG will be as good as or better than those obtained from EGG, and that PEGG can ultimately improve the speed of evolution.

In this paper, we propose a novel electronic bearer check system (EBC). This system allows the consumer to pay any amount of money below an upper-boundary on the Internet within an expiration period. During each transaction, the consumer does not need to contact the bank's server. Furthermore, this electronic bearer check can be transferred to any third party. The off-line characteristic of our system is very convenient for the consumer. Moreover, the double spending and double depositing problem will not occur in this system. More importantly, the framework of this system provides anonymity to protect customer privacy.

An efficient construction of a permutation network has been proposed by Waksman. However, his construction is only for permutation networks with 2k inputs. This paper provides a construction of permutation networks with arbitrary number of inputs that is an extension of Waksman's construction. By applying our construction to Abe's Mix-net, we can improve the efficiency of the Mix-net.

Anonymous communication essentially involves two difficulties; 1) How does the sender send a message anonymously? 2) How does the receiver send a reply to the anonymous sender? In this paper, we propose an anonymous communication method named Rivulet that overcomes both of the difficulties by using group communication. Moreover, anonymous communication holds two dilemmas; 1) Strong anonymity or good performance? 2) Protect the privacy or promote the crime? Rivulet provides a solution for the former dilemma. The latter one is hard and important problem for all privacy protection schemes, therefore, we have to keep discussing this dilemma.

A 2D photonic crystal surface-emitting laser using a triangular lattice is developed, and current-injected lasing oscillation is demonstrated. From consideration of the Bragg diffraction condition in the 2D triangular-lattice structure, it is shown that the 2D coupling phenomenon occurs in the structure. As a result of the 2D periodicity of the structure, the longitudinal mode and lateral mode can be controlled, and stable single-mode oscillation is possible over a large 2D area. The lasing mode of the structure is analyzed by calculating the photonic band diagram by the 2D plane-wave expansion method, and we show that four band edges at which the lasing oscillation can occur exist at the Γ point. Current-injected lasing oscillation is successfully demonstrated at room temperature under pulsed conditions. The threshold current density is 3.2 kA/cm2 and the lasing wavelength is 1.285 µm. From the near-field and far-field patterns, it is shown that large-area 2D (diameter 480 µm) lasing oscillation occurs in the device and the divergence angle is very narrow (less than 1.8). We also demonstrate the correspondence between the measured lasing wavelengths and calculated band diagram by comparing the polarization characteristics with the calculated distribution of the electromagnetic field. The results indicate that 2D coherent lasing oscillation occurs due to the multi-directional coupling effect in the 2D photonic crystal. Finally, we show that the polarization patterns of the lasers can be controlled by introducing artificial lattice defects from the theoretical calculation.

We describe a scheme of secret communication over the Internet utilizing the potentiality of the TCP/IP protocol suite in a non-standard way. Except for the sender and the receiver of the secret communication it does not need any entities installed with special software. Moreover it does not require them to share any key beforehand. Such features of the scheme stem from the use of IP datagrams with spoofed source addresses and their related error messages for the Internet Control Message Protocol (ICMP) induced by artificial faults. Countermeasures against IP spoofing are deployed in various places since it is often used together with attacks such as distributed denial of service (DDoS) and SPAM mailing. Thus we examine the environment where the scheme works as an intention and also clarify the conditions to obsolete the scheme. Furthermore we estimate the amount of secretly communicated data by the scheme and storage requirements for the receivers and those for the observers who monitor the traffic to detect the very existence of such a secret communication. We also discuss various issues including the sender anonymity achieved by the scheme.

Very reliable mode-locked semiconductor lasers have been developed. These devices provide high signal-to-noise ratio optical clock pulses of a few picoseconds temporal width in the 1.5-micrometer wavelength region. Potential applications of these lasers for high-bit-rate optical communication systems operating at over 40 Gbps including all-optical signal processing, and for very high-speed measurement systems are described.

Teletraffic characteristics of a mobile packet communication network, which supports mobile Internet, were quantitatively evaluated by using a terminal migration model in which the cell dwell time possesses self-similarity. I used a migration model in which the migration speed of the terminal is determined by the density of the dwell terminals in a cell (determined from measured vehicular mobility characteristics). The transmission rates per terminal in a cell were estimated as teletraffic on the mobile packet communication networks using this migration model. I found that when there is self-similarity in the terminal cell dwell time, communicating terminals may be concentrated in the cell and restricted for an indefinite period of time to using only a narrow bandwidth.

Technique of Measuring 3-D velocity vector components is important for the correct diagnosis of the blood flow pattern and quantitative assessment of intratumor perfusion. However, present equipment based on ultrasonic Doppler can not provide us true 3-D velocity. To overcome the problem, we previously proposed a new method of 3-D velocity vector measurement. The method uses 2-D array probe and enable us to obtain three components of velocity vector with real time by integrating the Doppler phase shift on the each element with the relative small single aperture compared with conventional method. Basic performance of the method has been evaluated by computer simulation. In this paper, to evaluate the feasibility of the proposed method, experimental investigation using a simple ring array probe and a phantom were carried out. Three components of velocity vector for different velocity magnitude and flow direction were measured. Experimental results validated its ability of measuring 3-D velocity and its feasibility.

In this paper, a network dimensioning approach suitable to the Internet is discussed. Differently from the traditional telephone networks, it is difficult to guarantee QoS for end-users even in a statistically sense due to an essential nature of an end-to-end communication architecture in the Internet. We should therefore adopt another approach, based on the traffic measurement. In the approach, the traffic measurement is performed for monitoring the end-to-end QoS. Then, the network adaptively controls the link capacities to meet the user's QoS demands. For this purpose, the underlying network should support such a capability that the link capacities can be flexibly reused. With the WDM network as an underlying network, an example scenario for network provisioning is finally illustrated.

The frequency- and time-domain expressions are derived for the signal-to-noise power ratio (SNR) of an ideal Rake combiner output in a direct sequence spread spectrum (DS-SS) mobile communication system. The derived SNR expressions make it possible to estimate the SNR statistics after Rake combining for an arbitrary spreading chip rate in the frequency-selective multipath channel.

Low-crosstalk 1.3-µm Fabry-Perot laser diode (FP-LD) and photodiode (PD) arrays are developed. The arrays are fabricated on semi-insulating substrates and their anodes and cathodes are separated channel by channel to suppress inter-channel electrical crosstalk at high frequency. Crosstalk of less than -30 dB is achieved between neighboring LDs at 3.125 GHz. This is low enough for BER characteristics observed under asynchronous operation of a 4-channel LD array to be no worse than those under single-channel operation. Excellent uniformity of both LD and PD characteristics, high-temperature operation of the LD array, and low-voltage operation of the PD array are also attained. These arrays are suitable for low-cost high-bit-rate parallel optical communications.