We describe a simplified receiver structure having several receiving antennas (i.e., an adaptive array antenna system) and using time-division-multiplexing (TDM) signal processing. Three simplified receiver structures were investigated for use in the antenna system. To confirm the feasibility of using a TDM receiver, both a TDM receiver and a conventional adaptive array receiver were constructed for testing. In our proposed system, several repetitions of the constant modulus algorithm (CMA) are used to reduce co-channel interference (CCI). The frame format used for both receivers was the same as that of the personal handy phone system in Japan. The laboratory testing was done using a fading simulator to enable measurement of the bit error rate. The results are very promising and show the feasibility of the TDM receiver.

An implantable WBAN path-loss model for a capsule endoscopy which is used for examining digestive organs, is developed by conducting simulations and experiments. First, we performed FDTD simulations on implant WBAN propagation by using a numerical human model. Second, we performed FDTD simulations on a vessel that represents the human body. Third, we performed experiments using a vessel of the same dimensions as that used in the simulations. On the basis of the results of these simulations and experiments, we proposed the gradient and intercept parameters of the simple path-loss in-body propagation model.

This letter presents a performance evaluation of wireless communications applicable into a capsule endoscope. A numerical model to describe the received signal strength (RSS) radiated from a capsule-sized signal generator is derived through measurements in which a liquid phantom is used that has electrical constants equivalent to human tissue specified by IEC 62209-1. By introducing this model and taking into account the characteristics of its direction pattern of the capsule and propagation distance between the implanted capsule and on-body antenna, a cumulative distribution function (CDF) of the received SNR is evaluated. Then, simulation results related to the error ratio in the wireless channel are obtained. These results show that the frequencies of 611 MHz or lesser would be useful for the capsule endoscope applications from the view point of error rate performance. Further, we show that the use of antenna diversity brings additional gain to this application.

A system combining multicarrier modulation and adaptive modulation in which a suitable level of quadrature amplitude modulation (QAM) is selected for each subcarrier and time-slot, is proposed for high-bit-rate and high-quality digital land mobile communications. The advantages of the system are a mode in which information cannot be transmitted under adverse propagation conditions and a buffer memory to limit a transmission delay time. If the allowable delay time is small, such as in voice and video transmissions, the system tends to have a poor bit error rate (BER) because of the forcible QAM-level selection. Our new selection scheme improves the BER for small transmission delay time. Suitable distribution of the delay time among subcarriers is obtained by using the scheme where the QAM-level of each subcarrier is chosen collectively using the number of data bits stored in memory. Computer simulation of the systems BER performance showed that the system could provide a noticeable BER improvement over frequency-selective fading channels as well as flat Rayleigh fading channels. The QAM-level selection scheme was also effective for a low maximum Doppler frequency and a small memory size. The system could thus attain about 25-fold improvement in BER at Es/N030 dB compared to the multicarrier/16QAM system. It also attained about 60-fold and 3. 5-fold improvement in BER at fd=10Hz compared with the system with multicarrier/16QAM and without the QAM-level selection scheme, respectively.

This paper gives laboratory as well as the results of field experiment and describes the implementation of a system developed to evaluate and demonstrate multimedia multimode time division multiple access (MTDMA). The equipment has been developed with the radio transmission technology for future public land mobile telecommunication systems (FPLMTS/IMT-2000) in mind. To meet FPLMTS/IMT-2000 requirements the system employs the following techniques: a hybrid multiplex modulation system consisting of quadrature phase shift keying (QPSK) and 16-ary quadrature amplitude modulation (16QAM), a high data transmission bit rate of 2 Mbit/sec for QPSK, 4 Mbit/sec for 16QAM, and diversity combining and adaptive equalization technique. For the diversity adaptive equalization technique, we used a decision feedback equalizer (DFE) consisting of one feedback (FB) transversal filter and two feed-forward transversal (FF) filters. The output signals from two branches of space diversity reception antennas are then fed to the two FF filters of the DFE. For middle-speed mobile radio communication for a micro-cellular pedestrian environment, a QPSK modulation system is selected to obtain wide coverage, while for a pico-cellular indoor office environment, the delay spread is small, and a 16QAM modulation system is selected to achieve a high bit rate. The results given here of laboratory and field experiments show the technical feasibility of MTDMA for future public land mobile telecommunication systems.

A slow frequency-hopping/16-ary quadrature amplitude modulation (slow-FH/16QAM) system based on time-division-multiple-access (TDMA) is appropriate for third-generation land mobile cellular communications because of its high immunity to interference. The system uses 16QAM for high spectral efficiency and slow-FH and forward-error-correction (FEC) for high-quality transmission. To reduce sensitivity to interference, the system uses an improved decoding scheme based on a minimum Euclidean-distance which is effective when the interference level is dispersed by FH. The bit error rate (BER) of the system due to interference has been evaluated in a previous study, both theoretically and by computer simulation. Although computer-simulated results showed that the system improved the BER, the hardware feasibility was not considered. This paper presents a hardware implementation of the system and the results of experimental transmission using equipment we developed to verify the system and to confirm the BER performance. The laboratory experimental results indicated that the system could provide high-quality transmission over a channel that has frequency-selective fading and co-channel interference. This system provided an Eb/N0 of 9 dB with space diversity and one of 15 dB without it, when BER=10-3 and fd=120 Hz. Field experiments were also conducted in a suburban area of Tokyo to demonstrate the BER performance. The results meant that the system could lower sensitivity to vehicle velocity more than a system without FH and that the BER performance of the system was improved notably against that of a system without FH, especially at low vehicle velocity.

The design and performance of a millimeter-wave video transmission system using 60-GHz band for indoor broadcasting-satellite (BS) signals transmission is presented. This system can transmit multiple video signals such as broadcasting signals and user-oriented signals to a television set indoors. To minimize the local oscillator's frequency offset and phase-noise effects, the system uses a remote-heterodyne scheme. Based on the concept, the system is developed to meet required carrier-to-noise-power-ratio (CNR) and 3rd-order intermodulation (IM). The BS transmission was experimentally done by using the transmitter and receiver setup. The results are very promising and show the feasibility of the system.

A new automatic-threshold-control (ATC) system for the amplitude-shift-keying (ASK) transceivers without using automatic gain control (AGC) was developed. When signal-to-noise ratio (SNR) in a transmission system fluctuates, the new system optimizes the threshold by statistic processing. In this paper, the schematic block diagram, the theory of statistical processing, and the performance estimated by numerical simulations are shown. The simulations show that under ideal conditions, the system can control the threshold voltage in a broad SNR region (wider than 20 dB). Delay of response and trapping in real situation can occur, but, the problems can be avoided by waveform shaping. It is thus concluded that the new ATC system can be applied to ASK transceivers.

In orthogonal frequency-division multiplexing (OFDM) transmission schemes, nonlinear distortion from high power amplifiers and phase noise due to oscillator instability are potentially serious problems, especially in millimeter-wave transmission systems. In this paper, we investigate and compare the combined effects on uncoded and coded OFDM signals of amplifier nonlinearity and phase noise from silicon-based devices. An analytical parametric formulation of system performance is presented. The theoretical results were in complete agreement with the computer simulation results. Total degradation was greatly reduced by applying a suppression scheme to compensate for the constant phase rotation in coded OFDM systems. In addition, the total coding gain defined for systems with different high-level M-QAM modulation was shown to increase with M.

We describe a low-cost and extremely stable millimeter-wave transmission system that uses a double-side-band (DSB) millimeter-wave self-heterodyne transmission technique. This technique allows us to use a comparatively low-cost and unstable millimeter-wave oscillator regardless of the modulation format. Furthermore, a transmission band-pass-filter (BPF) is not needed in the millimeter-wave band. The system cost can therefore be substantially reduced. We have theoretically and experimentally evaluated the carrier-to-noise power ratio (CNR) performance that can be obtained when using this technique relative to that attainable through a conventional millimeter-wave self-heterodyne technique where a single-side-band signal is transmitted. Our results show that the DSB self-heterodyne transmission technique can improve CNR by more than 3 dB.

Wireless body area network for sensing and monitoring of vital signs is the one of most rapidly growing wireless communication system and Ultra Wide-Band (UWB) is a favorable technology for wearable medical sensors. The wireless body area networks promise to revolutionize health monitoring. However, designers of such systems face a number of challenging tasks. Efficient transceiver design requires in-depth understanding of the propagation media which in this case is the human body surface. The human body is not an ideal medium for RF wave transmission; it is partially conductive and consists of materials of different dielectric constants, thickness and characteristic impedance. The results of the few measurement experiments in recent publications point to varying conclusions in the derived parameters of the channel model. As obtaining large amount of data for many scenarios and use-cases is difficult for this channel, a detailed simulation platform can be extremely beneficial in highlighting the propagation behavior of the body surface and determining the best scenarios for limited physical measurements. In this paper, an immersive visualization environment is presented, which is used as a scientific instrument that gives us the ability to observe three-dimensional RF propagation from wearable medical sensors around a human body. We have used this virtual environment to further study UWB channels over the surface of a human body. Parameters of a simple statistical path-loss model and their sensitivity to frequency and the location of the sensors on the body are discussed.

In this paper, we performed six human movement simulation by a commercial software (Poser7). We performed FDTD simulations for body area network propagation with one transmitter and six receivers. Received amplitudes were calculated for every time frame of 1/30 s interval. We also demonstrated a polarization diversity effectiveness for dynamic wearable body area network propagation.

A narrow-band digital land mobile system has been developed that operates in the frequency bands of 150 and 400 MHz, which are commonly used by transportation-related companies, local government, and public-sector organizations--and are therefore very congested. The number of users that can be accommodated in these bands is almost doubled by reducing the channel separation to 6.25 kHz, about half that of a conventional FM system. A carrier bit rate of 9.6 kbps is achieved by using π/4 shift QPSK modulation with a roll-off factor of 0.2. Laboratory and field testing showed that: (1) Without propagation delay spread, a BER of 10-2 was obtained without using space diversity. (2) With a propagation delay spread of 10 µs, a BER of 610-3 was obtained without space diversity. These measurements confirmed the technical feasibility of this narrow-band system. Its widespread implementation will help mitigate the congestion in private radio systems.

This paper introduces a state-of-art on an ultra-wideband (UWB) technology in intelligent transport systems (ITS). To examine the detection performance of a UWB short-range radar for vehicular applications, we developed a 26-GHz band short-range UWB radar system with an embedded compact MMIC-based RF module. In this paper, we briefly comment on the current regulatory environment for UWB radar systems by outlining the structure of an international organization involved in examining the regulatory status of these systems. We then describe the principles of detection and system design for impulse radar, the radar system that we developed, and a MMIC-based RF module as well as the performance of these devices. We measured their performance in a series of laboratory experiments and also measured UWB radar cross sections of an automobile. The results of our experiments suggest that our radar system is capable of detecting targets with a range resolution of around 9 cm.