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An OFDM transmission is robust to the multipath delay due to the addition of a cyclic prefix (CP). However, it will suffer from an inter-block-interference (IBI) under a severe long delay multipath channel whose channel impulse response (CIR) is longer than that of the CP. Since extending the CP leads to the loss of spectrum efficiency, some compensation scheme is needed to cope with the interference. The iterative interference cancellation with a channel code is effective even such a severe multipath channel because more reliable symbols can be obtained. Whereas a convolutional code has been mainly examined in the previous work, this paper considers a LDPC code. In the simulation, the performance of LDPC coded MIMO-OFDM systems with the iterative cancellation receiver is evaluated under such a severe long delay multipath channel in terms of bit-error-rate (BER) and block-error-rate (BLER). The results show that the performance can be improved by a few iterations.

This paper discusses a reliable wireless connection for factory through a distributed antenna system in 920MHz. In this paper, a base station that combines multiple destination nodes installed in a factory and mobile nodes are assumed. In a proposed system, multiple TXs and RXs for a base station are assumed to be fed through a single fiber with Wavelength Division Multiplexing(WDM) or Time Division Multiplexing(TDM) technique with a concept of radio over fiber(RoF). Diversity combining technique are investigated for multiple antenna reception through measurement campaigns in a laboratory room that mimics a factory environment.

This paper discusses a coexisting signal detection technique for sharing the spectrum of an Ultra Wideband (UWB) radio with other radio systems. In some countries' regulations, the Detection and Avoidance technique is required to be implemented in UWB systems so they do not interfere with other radio systems. In most interference avoidance techniques it is necessary to detect emissions of the interfering system and the interfering bands. In this paper, correlation detection is applied for interfering signal detection without band pass filters. In the detector, a Chirp-UWB is prepared as a template waveform. The signal received before UWB communications is correlated with the Chirp-UWB template waveform, and is then integrated. The integral period is decided from the sweep function of the Chirp-UWB and the interfering bands. Therefore the detection technique can detect arbitrary frequency band signals by modifying the integral period. The sweep function of the Chirp-UWB also improves the detection performance. A sine function is adopted for the sweep function of the chirp. The miss Detection Error Rate and False Alarm Rate are evaluated to show the effectiveness of the proposed interference detection technique.

This paper proposes a joint source-channel coding technology to transmit periodic vital information such as an electrocardiogram. There is an urgent need for a ubiquitous medical treatment space in which personalized medical treatment is automatically provided based on measured vital information. To realize such treatment and reduce the constraints on the patient, wireless transmission of vital information from a sensor device to a data aggregator is essential. However, the vital information has to be correctly conveyed through wireless channels. In addition, sensor devices are constrained by their battery power. Thus, a coding technique that provides robustness to noise, channel efficiency and low power consumption at encoding is essential. This paper presents a coding method that uses correlation of periodic vital information in the time domain, and provides a decoding scheme that uses the correlation as side information in a maximum a posteriori probability algorithm. Our results show that the proposed method provides better performance in terms of mean squared error after decoding in comparison to differential pulse-code modulation, and the uncoded case.

In March, 2007, IEEE802.15.4a was standardized as a low-rate and low-power UWB system for sensor networks. In general, detection of the IEEE802.15.4a signal is considered to be difficult because of its low transmitting power density and low duty cycle. However, if detecting of the IEEE802.15.4a signal is available, it is possible to avoid interference issues both among the IEEE802.15.4a systems and between the 15.4a and other UWB systems. This letter proposes a simple detection method using non-coherent detectors. The possibility of detecting of the IEEE802.15.4a signal by proposal detection method was examined. By conducting experiments with an emulated 15.4a RF signal, the signal detection probability was examined, and 15.4a signal from the range of about 11 meters in the radius could be detected. From this observation, the CSMA/CA method with detecting the signal in 15.4a system may be applied for alternative access method for 15.4a systems.

Recently, the sensor network technology attracts a great deal of attention achieving a safe and comfortable ubiquitous society. The sensor networks are already used in environment and disaster monitoring, medical care, logistics and transportation.This paper aimed to understand the outline of the sensor network technology centering on the wireless sensor network technology.

In multiple-input multiple-output (MIMO) eigenbeam space-division multiplexing (E-SDM), increased phase angle variation velocities have been reported because the transmission and reception weights become increasingly sensitive to smaller gaps between eigenvalues. In this paper, the effects of close eigenvalues were evaluated based on the number of antenna elements and spatial correlations. The evaluation is executed using the ITU-R M.2135-1 time variant channel model. As a result, it is clarified that there is a good possibility of improved communication performance in MIMO E-SDM based on adaptive control of the channel estimation time period using the eigenvalue gap as an input parameter.

This paper presents the Bit Error Rate characteristics of Ultra Wide Band signals made by using the low pulse duty factor and spreading code in the body surface channel, body to external channel as well as multiuser multipath channel. Additionally, this paper presents the distance-mean transmitting power performances, yielded from the BER characteristics results in the body surface channel and body to external channel. From the results, it was found that the spreading code increases the time resolution of separating paths in using RAKE receiver and decreases the multiuser interference in multipath channel.

Wavelet packet modulation (WPM) using the discrete wavelet transform is a multiplexing transmission method in which data is assigned to wavelet subbands having different time and frequency resolutions. The WPM keeps data transmission throughput even in tone and impulse interference environments that cannot be achieved with conventional multiplexing methods such as TDM (Time division multiplexing) or OFDM (Orthogonal frequency division multiplexing). In this paper, we propose an effective multicarrier transmission method of WPM for wireless mobile communications. First, the transmission characteristics of WPM in fading environments are minutely investigated. Then, taking the advantage of the WPM and the OFDM that has an equalizing technique in multipath fading environments, we propose a multimode transmission method using them. The adaptive transmission in those fading and interference environments is achieved by using the multimode transmission. Their transmission performances are evaluated by computer simulations.

Multiple block coded modulations lMBCMr are studied. One characteristic of the studied MBCM schemes is that they have both a block and a trellis structure. A general rule for deriving branch variables so as to establish a decoding trellis is presented. Examples of MBCM schemes employing 8dPSK and 16dPSK constellations are given. Two different methods using these schemes are proposed for producing unequal error protection. Computer simulations are done to show the UEP ability.

Pilot symbol-assisted modulation (PSAM) has been proposed to overcome the Rayleigh fading. However, as the fading rate becomes more rapid, it is difficult to provide an exact interpolation with conventional PSAM. To compensate for the fast Rayleigh fading, a PSAM which calculates in the frequency domain rather than the time domain as in conventional PSAM is proposed. Although this PSAM scheme only needs the zero interpolation for fading estimation, it provides a very accurate estimate even in relatively fast Rayleigh fading environments. We introduce this PSAM using fast Fourier transform (FFT) and apply it to 16QAM and then show some results of computer simulations.

A two-symbols/branch scheme of multiple block coded modulation (MBCM) is investigated under fading channels. Compared with a conventional scheme of block coded modulation (BCM), this two-symbols/branch MBCM scheme greatly increases the minimum squared Euclidean distance (MSED), minimum symbol distance (MSD), and minimum product distance (MPD). These three distances determine the bit-error-rate (BER) performance under either Gaussian or fading channels. A pilot symbol assisted fading compensation, as well as the techniques of symbol interleaving and branch weighting, are employed to combat the effect of channel fading. Through computer simulations, it is shown that large coding gains are obtained under both Rayleigh and Rician fading channels.