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A digital modulation scheme, OFDM, multiplexes many orthogonaly arranged sub-carriers and use spectrum efficiently. However, its performance is degraded under environments with severe multipath fading. The use of a previously reported, iterative detection of pre-coded OFDM scheme is proposed. Furthermore, the results of a computer simulation confirmed good performance. We present our analysis of the performance of iterative detection of pre-coded OFDM combined with convolutional code. The results of the simulation show that our scheme, performed better under severe fading than the conventional scheme did.

Objective: We previously showed that chronic renal failure (CRF) enlarges infarct size after ischemia/reperfusion (I/R) through impairment of reperfusion-induced Akt activation. Here we examined molecular mechanisms by which CRF impairs Akt activation, focusing on interplay between two phosphorylation sites in Akt, Thr308 and Ser473. Methods and results: Rats received 5/6 nephrectomy (SNx) or a sham operation (Sham). Development of CRF in SNx was confirmed by a 2.2-fold increase in serum creatinine level at 4 weeks after the operation. Infarct size after 20-min coronary occlusion/2-hr reperfusion was larger in SNx than in Sham (53.2±5.8 vs. 41.1±2.4% of risk area, p Conclusion: Insufficient activation of Akt by its intramolecular interplay between Thr308 and Ser473 phosphorylation due to down-regulated B55α contributes to increased myocardial susceptibility to I/R injury in CRF.

Background: Comorbid acute kidney injury (AKI) predicts poor prognosis in patients with acute myocardial infarction (MI). Although type 2 diabetes (T2D) is a well-known risk factor of AKI after MI, the mechanism of the increased risk remains unclear. Here we hypothesized that T2D increases AKI after MI via toll-like receptor (TLR)-mediated inflammation. Methods and Results: OLETF, a rat model of obese T2D, and LETO, non-diabetic controls, at 25-30 weeks of age were randomized into sham and permanent coronary ligation (MI) groups. At baseline, body weight (617±23 vs. 537±13 g), fasting plasma glucose (267±32 vs. 153±15 mg/dl) and urinary protein level (6.4 vs. 0.6 g/gCr), but not serum creatinine, were significantly higher in OLETF than in LETO. Histologically, glomerular size was increased by 17% without mesangial proliferation in OLETF compared to that in LETO, indicating that OLETF developed early-stage nephropathy by this age. At 12 h after MI, mRNA levels of TLR2, TLR4, IL-6 and TNF-α in the kidney were increased by 1.6-, 1.2-, 2.6-, 1.5-fold, respectively, in OLETF but not in LETO. Furthermore, immunoblot analyses showed that phosphorylation levels of p38 MAPK and JNK, downstream mediators of the TLR signal, were significantly elevated by MI in OLETF. Histological abnormalities in the kidney or increase in serum creatinine were not detected in either LETO or OLETF 12 h after MI. However, in immunohistochemical analyses, areas positive for neutrophil gelatinase-associated lipocalin (NGAL) and kidney injury molecule-1 (KIM-1) were significantly increased by 4.0- and 5.3-fold, respectively, and NGAL mRNA level was increased by 1.8-fold after MI in OLETF but not in LETO. In sham-operated LETO and OLETF, areas positive for NGAL and KIM-1 were barely detected. Infarct sizes were similar and cardiac BNP mRNA levels in the non-infarcted left ventricle were equally elevated at 12 h after MI in LETO and OLETF, suggesting that MI-induced cardiac loads were comparable in the two groups. However, mortality at 48 h after MI was significantly higher in OLETF than in LETO (68% vs. 18%, P Conclusion: The results suggest that AKI after MI is enhanced in T2D via TLR-mediated inflammation. The cardio-renal interaction may underlie increased post-MI mortality in T2D.

In this paper, the positioning system using a direct sequence spread spectrum (DS/SS) inter-vehicle communication (IVC) scheme based on location oriented pseudo noise (PN) code allocation is considered. DS/SS-IVC scheme based on location oriented PN code allocation has a superiority in terms of that the interference of hidden terminal can mitigate. In this scheme, each vehicle determine the PN code based on the location that is estimated by GPS. However, in actuality, this location information is not perfect and this error cause a degradation of communication performance. In order to solve this problem, the positioning system of DS/SS-IVC scheme is studied in this paper. The successive interference cancellation (SIC) scheme, slotted ALOHA scheme with code sensing are applied so as to improve the positioning accuracy. Furthermore, the elimination of ranging data that have large ranging error is also proposed in this paper. By applying these schemes, the positioning accuracy can be improved.

It is controversial whether treatment with an angiotensin II receptor blocker (ARB) or a calcium channel blocker (CCB) improves prognosis of hemodialysis (HD) patients. This study was designed as a multicenter prospective cohort study. HD patients (n = 1071) were enrolled from 22 institutes in January 2009 and followed up for 3 years. Patients with missing data, kidney transplantation or retraction of consent during the follow-up period (n = 204) were excluded, and 867 patients contributed to analysis of mortality. Propensity score (PS) for use of ARB and that for CCB was calculated using a multiple logistic regression model. ARB and CCB were prescribed in 45.6 and 54.7 % of patients at enrollment. During the 3-year follow-up period, all-cause mortality and cardiovascular mortality rates were 18.8 and 5.1 %, respectively. Kaplan–Meier curves showed that all-cause and cardiovascular mortality rates were lower in the ARB group than in the non-ARB group, though the mortality rates were similar in the CCB group and non-CCB group. In PS-stratified Cox regression analysis, ARB treatment was associated with 34 and 45 % reduction of all-cause death and cardiovascular death, respectively. In PS matching analysis, ARB treatment was associated with a significant reduction (46 % reduction) in the risk of all-cause death. A significant impact of CCB treatment on all-cause or cardiovascular mortality was not detected in PS analysis. The use of an ARB, but not a CCB, is associated with reduced all-cause and cardiovascular mortalities in patients on HD.

In MIMO(Multiple-Input Multiple Output)-OFDM(Orthogonal Frequency Division Multiplexing) systems, ICI(Inter-Carrier Interference) is generated by Doppler-spread in mobile reception of OFDM signals. The MIMO-ICI canceller with complexity reduction has been proposed. It is possible to reduce the complex. However, reception characteristics are deteriorated than the ordinary MIMO-ICI canceller. In this paper, the improving scheme of the conventional MIMO-ICI canceller with complexity reduction is proposed. In the proposed scheme, the iterative detection is adopted. As the results of computer simulations, the proposed scheme can improve reception characteristics with complexity reduction.

One of the major factors of performance degradation in OFDM systems is influence of additive impulsive noise. Especially, reception characteristic is extremely degraded under multi-path channel. Many efficient impulsive noise reduction schemes are proposed for low order modulation such as QPSK, 16QAM. However, in higher order modulation as 64QAM, reception characteristics are degraded because constellation is dense. In this paper, efficient impulsive noise reduction scheme is proposed for OFDM transmission using higher order modulation such as 64QAM.

In previous study, the IVC(Inter Vehicle Communication) system using the UWB(Ultra Wideband) radar was proposed. Proposed system able to simultaneously perform ranging and communication in same packet structure and transceiver. However, vehicle information to be transmitted is not determined, ranging accuracy of radar system and communication system have not been evaluated. In this paper, transmitted data is vehicle ID and transmission time of signal, ranging accuracy of radar system and communication system are evaluated.

Background Fatty acid-binding protein 4 (FABP4) is expressed in both adipocytes and macrophages. Recent studies have shown secretion of FABP4 from adipocytes and association of elevated serum FABP4 level with obesity, insulin resistance, hypertension, and atherosclerosis. However, little is known about role of FABP4 in cardiac function. Methods From the database of the Tanno-Sobetsu Study, data for 190 subjects (male/female: 82/108) who were not treated with any medication and underwent echocardiography in 2011 or 2012 were retrieved for analyses of relationships between serum FABP4 concentration, metabolic markers and parameters of echocardiography. Results Serum FABP4 level was positively correlated with age, body mass index (BMI), blood pressure (BP), LDL cholesterol, HOMA-R and mean left ventricular (LV) wall thickness (LVWT, males: r = 0.315, females: r = 0.401, p

In the current inter-vehicle communication (IVC) systems such as IEEE802.11p, the CSMA/CA scheme for the MAC scheme and the OFDM for the modulation scheme are most commonly used for the media access scheme and the modulation scheme respectively. These systems are assumed to be used in the application such as safety driving assistance, reducing traffic congestions and so on. On the other hand, since the required application in ITS must cover various field, development of the inter-vehicle communication scheme that has different characteristics from IEEE802.11p for high speed and large capacity data transmission is required for new applications such short range ad hoc network without base stations. In this paper, a new DS-CDMA IVC system using successive interference canceller (SIC) is proposed and its performance is compared with the CSMA/OFDM IVC. As the result of simulation, in the broad cast based wide range IVC, the CSMA/OFDM system can achieve better packet error rate (PER) performance than the proposed DS-CDMA IVC system. On the other hand, it was confirmed that the proposed DS-CDMA IVC system has better packet error rate performance with short latencies in the short range IVC where many short packets are exchange between vehicles.

Fatty acid-binding protein 4 (FABP4) is expressed in adipocytes, and elevated plasma FABP4 level is associated with obesity-mediated metabolic phenotype. Postprandial regulation and secretory signaling of FABP4 has been investigated.Time courses of FABP4 levels were examined during an oral glucose tolerance test (OGTT; n=53) or a high-fat test meal eating (n=35). Effects of activators and inhibitors of adenyl cyclase (AC)-protein kinase A (PKA) signaling and guanylyl cyclase (GC)-protein kinase G (PKG) signaling on FABP4 secretion from mouse 3T3-L1 adipocytes were investigated.FABP4 level significantly declined after the OGTT or a high-fat meal eating, while insulin level was increased. Treatment with low and high glucose concentration or palmitate for 2 h did not affect FABP4 secretion from 3T3-L1 adipocytes. FABP4 secretion was increased by stimulation of lipolysis using isoproterenol, a β3 -adrenoceptor agonist (CL316243), forskolin, dibutyryl-cAMP and atrial natriuretic peptide, and the induced FABP4 secretion was suppressed by insulin or an inhibitor of PKA (H-89), PKG (KT5823) or hormone sensitive lipase (CAY10499).FABP4 is secreted from adipocytes in association with lipolysis regulated by AC-PKA- and GC-PKG-mediated signal pathways. Plasma FABP4 level declines postprandially, and suppression of FABP4 secretion by insulin-induced anti-lipolytic signaling may be involved in this decline in FABP4 level.

In order to improve performance of high-speed power line communication (PLC) using OFDM (Orthogonal Frequency Division Multiplexing), compensation of the influence of additive impulsive noise is required. In this paper, the scheme to make precise channel estimation under impulsive power line channel is proposed. Although many schemes to improve influence of the additive impulsive noise are proposed, they usually require precise estimation of the PLC channel transfer function. We have already proposed the scheme for channel estimation under these situations using the pilot symbols inserted in two successive OFDM symbols. However, data transmission performance slightly degrades because two successive pilot symbols are inserted. In this paper, the scheme to estimate channel transfer function using only one OFDM symbol is proposed. As the result of computer simulation, possibility of precise channel estimation was confirmed under existence of class A impulsive noise.

Gastric PCO2 monitoring during canine hemorrhagic shock encountered occasional baseline drift to higher direction when conventional PCO2 sensor was used. As a result of chemical analysis of gastric juice of dogs and human, hydrogen sulfide and acetic acid were identified as causative compounds. It was speculated that these weak acid molecules would permeate gas-permeable silicone membrane to be accumulated in the inner solution of Severinghaus-type PCO2 sensors. In order to prevent this phenomenon, double-membrane type PCO2 sensor was constructed. In this sensor, acid-neutralizing solution was installed between the inner and the outer membranes in order to dissociate weak acid molecules into corresponding ions, which can not diffuse into the inner silicone membrane. In addition, Cu2O particles were mixed in the inner silicone membrane to trap hydrogen sulfide in this membrane. It was confirmed by experiments in vitro that the readings of improved gastric PCO2 sensors were not affected by acetic acid or hydrogen sulfide. As a result of a preliminary clinical evaluation, continuous monitoring of gastric PCO2 was carried out for 72 h without detectable baseline drift or the change of sensitivity.

The inter-vehicle communication (IVC) systems based on CSMA/OFDM scheme such as IEEE802.11p or ARIB STD-T109 in Japan are widely developed because autonomous distributed networks are easily made by using the Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) MAC protocol. However, the hidden terminals in CSMA networks cause the performance degradation. In our previous study, a new IVC scheme using Code Division Multiple Access (CDMA) had been proposed to mitigate the impact of hidden terminals and evaluated the performance in the simple straight road model. However, performances of both IVC schemes are not evaluated in the urban area road model assuming multipath fading. In this paper, performances of the DS-CDMA IVC scheme and CSMA/OFDM IVC scheme are evaluated in urban area road model. As the results of simulations, it was confirmed that the PER (Packet Error Rate) performances of CSMA/OFDM IVC can be made better than the DS-CDMA. On the other hand, DS-CDMA shows the possibility that it is able to achieve a low delay communication as compared with CSMA/OFDM.

This paper discusses the IVC (Inter Vehicle Communication) system using the UWB (Ultra Wideband) radar. DSUWB (Direct Sequence - UWB) signal is used for this IVC system because it has CDMA (Code Division Multiple Access) Capability. However, there is the near-far problem due to difference of signal power from each vehicles, it becomes the cause of degradation of communication characteristics and detection accuracy of the signal. In this paper, we propose the iterative detection system using the SIC (Successive Interference Cancellation) to improve detection rate of the signal and the bit error rate (BER) performance. The signals except the desired signal detected by the SIC is subtracted from the original received signal. As the result, the performance was improved.

In this paper, the pedestrian positioning system based on UWB(Ultra Wide Band) ranging is proposed and its basic characteristic is analyzed. In the safety driving systems, protection of pedestrians is one of the most important topics. In the proposed system, the movements of pedestrians are monitored by the base stations placed at the road sides and the information of dangerous situation against the approaching vehicles is informed using DSRC(Dedicated Short Range Communication). By using UWB, precise positioning against many pedestrians is expected to be archived. In this paper, positioning performance against pedestrians is evaluated by computer simulation assuming the operation at the crossings. As the result, it was confirmed that the proposed UWB ranging scheme can achieve the sufficient precision and can trace the movement of the pedestrian in detail. Moreover, the possibility of successful ranging is also evaluated and the scheme of packet transmission to increase the successful transmission based on the slotted ALOHA scheme is proposed.

This paper discusses the multipath compensation technique for pulse based UWB systems. The RAKE reception is common technique as the multipath compensation technique. The multi-carrier pulse is possible to control the power spectrum density in the frequency domain. In this paper, the iterative RAKE reception by using the multi-carrier pulse is proposed to obtain better reception performance. The root mean square error (MSE) between the ideal received signal and approximated multi-carrier pulse is evaluated. The error becomes smaller by using proposed RAKE reception technique, because the correlation of the template pulse in each RAKE finger can be reduced by the iterative RAKE and the frequency selective fading can be compensated by using the multi-carrier pulse. The bit error rate (BER) performances are also evaluated to show the effectiveness of the proposed RAKE reception.

In Japanese Digital Terrestrial Television Broadcasting (DTTB), the identification of multi-path is important to improve its reception characteristics. In order to enhance the resolution of the delay profile, it is effective that continuous multiple channel transfer functions are connected and the frequency bandwidth is extended. However, the guard band is existing between each channel and the transfer function is not obtained directly. The phases of each channel are not synchronized because the each channel is broadcasting independently. In this paper, the scheme to connect multiple channel transfer functions is proposed. In the proposed scheme, interpolation of guard band by using the linear prediction filter based on the RLS(Recursive Least Square) algorithm and compensation of phase between adjacent channels are performed. As the result, it was conformed that resolution enhancement of the delay profile is possible. It is possible to improve the time resolution of the delay profile that has 0.024[μs].

OFDM (Orthogonal Frequency Division Multiplexing) is the modulation scheme that is widely used in broadband power line communication (PLC). In OFDM transmission, influence of the additive impulsive noise appears on every subcarriers that are the outputs of the DFT in the receiver because of the broad band spectrum of the impulsive noise. As the result, it causes significant degradation of the performance of OFDM transmission. Therefore, an appropriate measure to reduce the influence of impulsive noise is required and many schemes for impulsive noise reduction are proposed. In order to reduce the influence of the impulsive noise effectively from the received signal, precise estimation of transmission channel is necessary. However, the pilot symbols for channel estimation are also affected by impulsive noise and the scheme to estimate transmission channel under impulsive noise channel is required. In this paper, a channel estimation scheme for OFDM transmission under the class A impulsive noise channel using the pilot symbols is proposed. In the proposed scheme, channel estimation and reduction of impulsive noise is iteratively applied in order to increase the precision of channel estimation. As the results of simulation, the precision of channel estimation was improved and the bit error performance almost equivalent to the ideal channel estimation case could be achieved for data symbols.

This paper discusses a cooperative reception technique for Japanese digital terrestrial television broadcasting "One-segment service" using multiple terminals. In this paper, received signals and the channel information are transmitted by using one-way or two-way communication. Maximum ratio combining scheme are performed in the own terminal using the exchanged channel information. The error rate performance can be improved by using multiple receiving terminals in the One-Segment Service.

In large parking area attached to shopping malls and so on, it is difficult to find a vacant parking space. In addition, searching for parking space during long time leads to drivers stress and wasteful energy loss. In order to solve these problems, the navigation system in parking area by using ZigBee networks is proposed in this paper. The ZigBee is expected to realize low power consumption wireless system with low cost. Moreover, the ZigBee can form ad-hoc network easily and more than 65000 nodes can connect at the same time. Therefore, it is suitable for usage in the large parking area. In proposed system, the shortest route to the vacant parking space is transmitted to the own vehicle by the ZigBee ad-hoc network. Thus, the efficient guide is provided to the drivers. To show the effectiveness of the proposed parking system, the average time for arrival in the parking area is evaluated, and the performance of the vehicles that equips the ZigBee terminals is compared with the ordinary vehicles that do not equip the ZigBee terminals.

In this paper, improvement of the performance of the IVC system using the location oriented PN code allocation is studied. In this system, allocation of PN codes for each vehicle is easy. However interference problem occurs when multiple vehicles are locating in the area where the equivalent PN code is allocated. In order to mitigate the interference, MCS scheme is adopted under asynchronous transmission and time-slot allocation is adopted under synchronous transmission. In this paper, DS-CDMA scheme is evaluated by computer simulation. As the result, the effectiveness of the proposed IVC system is confirmed under several situations.

This paper discusses the IVC (Inter Vehicle Communication) system for ITS. DS-SS (Direct Sequence Spread Spectrum) is used for the IVC because it has CDMA (Code Division Multiple Access) capability. However, efficient PN code allocation scheme is a problem to solve because the vehicles communication directly without base stations. In this paper, the location oriented PN code allocation scheme is adopted for the DS-SS IVC system. The influence of the positioning error for the communication performance is evaluated. The improved performance is shown even when the positing error exists in the IVC system. To improve the performance, the positioning error correction scheme is proposed. The distance between the vehicles are estimated by using the received signal strength after de-spreading. From the simulation result, the positioning error can be mitigated by using the proposed technique.

Frequency selective fading that is caused by the multipath becomes a problem in broad band communication like a UWB (Ultra Wideband) system. This paper discusses the RAKE reception technique by using the multicarrier template waveform in the UWB-IR (Impulse Radio) system to compensate the influence of multipath. The template waveform in the UWB receiver is modified to the multicarrier pulse, because the power spectrum density can be controlled to weight for the sub-band pulses. The BER (Bit Error Rate) performance is improved, because more powerful path can be detected in each sub-band pulse of the multicarrier template waveform and the correlation values of the RAKE branches can be combined efficiently.

In this paper, an adaptive circular array antenna is applied to DS/SS (Direct Sequence / Spread Spectrum) IVC (Inter-Vehicle Communication) under shadowing environment. The DS/SS scheme is an attractive technique for the IVC system because it has advantages for CDMA (Code Division Multiple Access) capability and so on. However, the near-far problem is occurred in the DS/SS scheme. Shadowing the radio paths by large vehicles is also significant problem for the IVC system. To solve those problems, a LMS (Least Mean Square) adaptive circular array antenna is proposed. The array antenna can be controlled its directivity when the receiving vehicle knows the information of the target vehicle. The PER (Packet Error Rate) and the throughput performances are evaluated. And the performances are compared with the ordinary system by using omini-directional antenna. From the simulation results, the adaptive circular array antenna is effective for the near-far problem and influence of shadowing in the DS/SS TVC system.

This paper discusses the interfering signal detection technique for DAA (Detection And Avoidance) operation of an UWB (Ultra Wideband) systems. To detect the interfering signal, sub-band pulses of a multi-carrier type are prepared as template waveform in the detector. The received signal is correlated with the sub-band pulses and the correlation values are compared with the threshold value. The proposed detection technique is applied for the correlation detection that is often used for the demodulation scheme of the pulse-based UWB system. The DER (Detection Error Rate) and FAR (False Alarm Rate) performance are evaluated to show the effectiveness of the proposed interfering signal detection technique and the performances are compared with the ordinary scheme by using FFT. The optimum sub-band pulse width is also derived to be obtained better detection performance.

Application of DS-SS (Direct Sequence-Spread Spectrum) communication scheme is expected to realize efficient and reliable IVC (Inter-Vehicle Communication) system in ITS. This scheme has a lot of advantages such as robustness against additive noise and interference, possible to CDMA (Code Division Multiple Access) and so on. In this paper, the DS-SS IVC scheme based on location oriented pseudo noise (PN) code allocation scheme that makes efficient PN code allocation possible is assumed. And its performance is compared to the case of random code allocation. As the result of simulation, it was confirmed that performance of location oriented PN code and random code allocation was comparable level performance.

The performance of OFDM is improved by pre-coding data symbols in the frequency domain. However, it is not desirable that additive noise on the specific carrier whose signal-to-noise ratio is very low may degrade total system performance. Iterative detection of pre-coded OFDM has already been proposed to overcome this problem. In this paper, theoretical analysis of detection of pre-coded OFDM is performed in order to achieve optimal detection. As the result of analysis, some condition that achieves better performance has been derived.

This paper discusses a cooperative reception technique for Japanese digital terrestrial television broadcasting “One-segment service”. The Cooperative reception scheme using the scattered pilot symbol is proposed to reduce amount of exchanging information among the receivers.

One of the major factors of performance degradation in OFDM transmission is influence of additive impulsive noise. Because of wide band property of impulsive noise, it affects the symbols transmitted on many sub-carriers and bit error rate characteristic severely degrades. In this paper, an iterative scheme that reduces influence of impulsive noise by generating a replica signal of impulsive noise and reducing it from the received signal is proposed. As the result of computer simulation, good performance was confirmed.

In this paper, the measurement system for digital terrestrial television broadcasting is proposed in order to identify the reflection points of the propagation paths. The aim of identifying the reflection points is that they are used for detailed analysis of reception characteristics in the service area using the ray tracing scheme. This can be useful for designing the service area of the SFN gap filler that compensates the service area where direct signal from the main station is under shadowing. In the proposed system, the fixed directional reference antenna and the rotating antenna are used. By using time base reference obtained from the fixed directional antenna, the arrival direction and relative delay can be precisely estimated against major propagation paths and their reflection points are also estimated by using these parameters. The actual measurement was performed using the proposed measurement system and it was confirmed that precise identification of the reflection points is possible.

The interfering system detection and mitigation techniques are important topics for spectrum sharing among various radio systems. And also the interfering band estimation technique in shared wide frequency band is significant to help the interference mitigation technique. In this paper, an interfering band estimation technique is proposed. In order to detect the interfering band, the multi-band pulse consisted of the several sub-band pulses are proposed. The sub-band pulses are Gaussian enveloped pulses with different frequency sinusoidal wave. The received signal is correlated with the sub-band pulses and the interfering band is estimated from correlation values by proposed two kinds of schemes that are realizing higher estimation performance and a simpler structure. The performances are evaluated to show the effectiveness by the Root Mean Square Error (RMSE). The proposed estimation technique is simpler structure and it is achieved detecting better performance than the ordinary technique using FFT depending on the conditions.

An improvement scheme for degradation of reception characteristics of the digital terrestrial television broadcasting (DTTB) is an important issue. The degradation is caused by multipath effects, thus an analyzing technique for the channel is significant. In this paper, an analyzing technique for the channel delay profile that is obtained from the pilot symbol from the received signal is proposed. The amplitude and the delay time of paths are estimated to minimize the square error between the replica signal and the channel obtained from the received signal. Moreover, accuracy of delay time is improved by using Newton method. In the proposed scheme, the hidden path by the larger path can be found and the impulse response can be contsracted.

This paper discusses a multi-user access technique for Ultra-wideband Impulse Radio (UWB-IR) system in energy detection receiver. The UWB-IR system is modulated by On-Off shift Keying (OOK). As multi-users access scheme, the Code Division Multiple Access (CDMA) using the Optical Orthogonal Code (OOC) sequence is adopted. The integral interval and the sample energy threshold value are optimized to improve the Bit Error Rate (BER) performance. The BER performances of proposed scheme are evaluated and compared with conventional energy detection receiver in the low data rate PAN (Personal Area Network) channel. The effect of inter-user interference is improved by using proposed optimization technique.

The present article describes the experimental result of victim system detection by UWB wireless system to contribute for Japanese UWB regulatory discussion, in which a mitigation, including detect-and-avoid (DAA), technology implementation in the frequency range of 3.4 to 4.8 GHz is a major technical topic. A FPGA based MB-OFDM UWB receiver with 528 MHz sampling rate and 128 points FFT capability was prepared for this purpose and mobile WiMAX and 3GPP LTE were selected as victim systems to be detected. Various baseband victim signals generated by a vector signal generator were detected at various detect conditions and signal-to-noise ratios and time to detection was measured. In this experiment, 99% probability detection was achieved within 2.4 seconds.

In most Asian and European countries, detect-and-avoid (DAA) is required at UWB low band (3.1–4.8 GHz). In Japan, we conducted evaluation experiments on the performance of DAA until March of 2010, which was a part of a three-year campaign to provide results of literature review and technical evaluation for the purpose of accomplishing Japanese UWB regulation. In this paper, experiment results on the avoid performance are presented. Three types of victim systems, 3GPP LTE, Mobile WiMAX, and an experimental IMT Advanced Test-bed, were used in the experiments. The UWB system was built based on WiMedia specifications at the UWB low band. A notch was created in the UWB spectrum where a victim signal was going to appear. The notch was created by nullifying the related subcarriers in combination with the use of a filter or applying a window function. The interference effects of UWB to victim systems were evaluated by examining the bit error rate (BER) or packet error rate (PER) performance. Our results show that when the width and depth of the notch satisfy certain conditions, the interference level introduced by UWB can be below the permitted level in regulations.

In mobile reception of OFDM, the bit error rate characteristic is deteriorated, because the inter-carrier interference(ICI) is generated by the Doppler-spread of radio channel. The influence of ICI can be reduced by ICI canceller based on Zero-forcing equalization. In this paper, Zero-forcing ICI canceller using the linear interpolation is studied in order to reduce the complexity of the circuits. As the result of simulation, the proposed ICI canceller can achieve performance equivalent to the conventional scheme with less complexity.

In OFDM transmission, performance is degraded by the existence of time domain impulse noise because this noise has very wide bandwidth and it affects all the carriers in the OFDM symbol. Moreover, transmission characteristic is extremely degraded under multi-path channel. Such a situation frequently occurs in power-line communication (PLC) and an appropriate measure is necessary. In this paper, the scheme that reduces the influence of impulse noise under multi-path channels is proposed.

This paper discusses Inter-symbol Interference (ISI) cancellation technique and the optimized energy detection receivers in ultra-wide-band impulse radio (UWB-IR) systems. As schemes of optimizing receivers, the integration interval and the sample energy threshold value are investigated. And, ISI cancellation depends on decision feedback equalization (DFE) is used. The performances are evaluated by computer simulation in the IEEE802.15.4a channel environment. The improved BER (Bit Error Rate) performances are shown to utilize proposed energy detection scheme determined the integral interval and the sample energy threshold with the ISI cancellation technique.

In this paper, a space division DS/SS IVC(Direct Sequence / Spread Spectrum, Inter-Vehicle Communication) scheme using a circular array antenna is studied. A circular array antenna can reduce the interference between PN codes due to the congestion of many vehicles. The circular array antenna which is used in this paper has a characteristic that the directivity of the antenna can be controlled easily when a direction of target vehicle is known. The scheme to control the directivity of a circular array antenna based on the information which is exchanged between each vehicle.

The CSMA scheme that is widely adopted as a media access control in Inter-Vehicle communication systems has a hidden terminal problem. And this influence has not yet been analyzed in detail and it is necessary to know the actual influence in order to take appropriate steps against this problem. In this paper, the number of packet collisions that are caused by hidden terminals is analyzed and packet loss rate is shown quantitatively. And it is shown how this problem is improved by using spread spectrum (SS) communication scheme by computer simulation. As a result, it is confirmed that the number of packet collisions that are caused by hidden terminals occurs more than that are caused by carrier sense failures. Moreover, it is also confirmed that packet loss rate can be reduced to up to one-third of the conventional CSMA scheme by using the proposed SS scheme.

In this paper, we propose a MIMO (Multiple-Input Multiple-Output) transmission scheme using Pre-Rake filters, as well as Post-Rake filters. The Pre-Rake filter can achieve Rake diversity effect without increasing the complexity of the receiver. The reception performance of the proposed MIMO transmission scheme is evaluated. As the result, it was confirmed that the MMSEC (Minimum Mean Squared Error Combining) scheme was effective as the scheme of path combining under MIMO transmission that transmits several different symbols at the same time. In addition, it was shown that the 2 × 2 MIMO transmission system that uses 4×4 Pre/Post-Rake filters had the good performance because not only diversity effect by multiple reception antennas but also diversity effect by Pre/Post-Rake processing were achieved.

Ultra Wideband (UWB) is an attractive technique that enable sharing spectrum with other radio systems to spread spectrum extremely wideband. However, there are potential interferences among those using in the same frequency bands and close range. This paper discusses the interference DAA (Detection And Avoidance) technique for coexisting pulse based UWB and OFDM systems. In a UWB transmitter-receiver, utilization of the OFDM signal is detected by correlating the GI (Guard Interval) signal, and the timing of GI period is also detected. The UWB signal is emitted during the GI period to mitigate the effect of interference to the OFDM signals from the UWB system. The DER (Detection Error Rate), FAR (False Alarm Rate) and BER (Bit Error Rate) performances are evaluated to show the availability of proposed DAA technique. Keywords-component; Ultra Wideband (UWB), Orhtgonal Frequency Division Multi-Plexing (OFDM), Coexistence, Interference Detect And Avoidance (DAA), Cognitive Radio, Spectrum Shareing, Guard Interval (GI) Detection.

This paper discusses a ranging technique of Ultra Wideband (UWB) system. The Energy Detection (ED) and Matched Filter (MF) are common techniques as UWB pulse detection methods in TOA (Time of Arrival) ranging system. The two-step TOA estimation is combined the ED and the MF. The two-step detection enables higher ranging accuracy than the ED with the simpler receiver structure than the MF. In this paper, the modified two-step estimation is investigated. A dual window and a sampling interval compensation technique are proposed in the ED and the MF, respectively. The performances of MAE (Mean Absolute Error) are improved in the IEEE802.15.4a system.

In this paper, two kinds of multiple-input multiple-output (MIMO) transmission schemes for UWB (ultra-wideband) wireless communication system using pre/post-rake combiners are proposed and the bit error rate (BER) performances are analyzed under high data rate wireless personal area network (WPAN) environment by computer simulation. As a result, the BER performances of the proposed multi-antenna pre/post-rake transmission schemes for UWB wireless communication system are improved as the number of fingers for pre/post-rake combining increases.

This paper discusses an interference detection technique for ultra wideband (UWB) to share the spectrum with other radio system. A detection and avoidance (DAA) technique are required in UWB system from some countries regulations. In most of interference mitigation techniques, it is required to detect existence of interfering signal and its band. However, some band pass filters are needed to detect various interfering bands detected used by the conventional energy detection. In this paper, the correlation detection is applied for the interfering signal detection without band pass filters. In UWB receiver, a chirp-UWB is prepared as a template waveform. The received signal before UWB communication is correlated with the chirp-UWB template waveform, and the signal is integrated. The integral period is decided from sweep function of the chirp-UWB depending on the interfering bands. The sweep function of the Chirp-UWB is also considered to improve the performance. The sine function is adopted for the sweep function. The miss detection error rate (DER) and false alarm rate (FAR) are evaluated to show the effectiveness of proposed interference detection technique.

Ultra-wideband (UWB) is a useful radio technique for sharing frequency bands between radio systems. It uses very short pulses to spread spectrum. However, there is a potential for interference between systems using the same frequency bands at close range. In some regulatory systems, interference detection and avoidance (DAA) techniques are required to prevent interference with existing radio systems. In this paper, the effect of interference on orthogonal frequency division multiplexing (OFDM) signals from pulse-based UWB is discussed, and an interference mitigation technique is proposed. This technique focuses on the pulse repetition cycle of UWB. The pulse repetition interval is set the same or half the period of the OFDM symbol excluding the guard interval to mitigate interference. These proposals are also made for direct sequence (DS)-UWB. Bit error rate (BER) performance is illustrated through both simulation and theoretical approximations.

This paper discusses DAA (detection and avoidance) technique for the pulse based Ultra Wideband system to share the same frequency bands with other radio systems. The MC (Multi Carrier) -CDMA modulated signal that is spread from OFDM signal is considered as the coexisting system. The interference mitigation technique is proposed focused on the pulse repetition interval of the pulse based UWB. To mitigate the effect of interference to narrower band system by the UWB system, the effective pulse repetition interval is investigated. The proposed interference mitigation technique has advantages of simple hard ware structure by only controlling the pulse repetition interval.