This study presents an over-the-air (OTA) demonstration of quantum-annealing-aided multi-user detection (QA-aided MUD). QA-aided MUD is a quantum–digital hybrid method that combines iterative multi-user detection (MUD) and quantum annealing (QA). We apply it to multi-input multi-output (MIMO) systems with orthogonal frequency division multiplexing (OFDM) transmission and least squares (LS) channel estimation. The OTA experiments in an outdoor environment demonstrate that QA-aided MUD can successfully detect transmitted signals from eight user equipments.

We present performance evaluation of quantum-annealing-aided multi-user detection (QA-aided MUD) in over-loaded and fully loaded multi-input multi-output systems with orthogonal frequency division multiplexing (MIMO-OFDM). QAaided MUD is a method of iterative multi-user detection (MUD) accelerated by using QA. We previously applied this method to single-input single-output (SISO) single-carrier non-orthogonal multiple access (SC-NOMA) and demonstrated that it achieves error rate and convergence performance comparable to the conventional iterative MUD based on the MAP algorithm. In this study, we have newly developed QA-aided MUD for MIMO-OFDM and conducted performance evaluation under the 3GPP UMa channel model by employing the D-Wave qquantum annealer and other digital annealing techniques. The evaluation results show that the block error rate (BLER) obtained by QA-aided MUD outperforms that of conventional low-complexity MUDs, particularly in overloaded scenarios. It is also observed that the annealing parameters significantly impact BLER in some conditions. Additionally, we present bit error rate (BER) analysis using a few instances, employing both the D-Wave quantum annealer and other digital annealing techniques. The results demonstrate that QA-aided MUD with each annealing technique avoids the error floor and can achieve error-free performance. Finally, we discuss future perspectives by evaluating the computational complexity and computation time of QA-aided MUD.

Camera-assisted prediction-based handover has been implemented in a proactive manner for an indoor dynamic 60 GHz radio channel. Here, our proposed deep learning model is utilized to forecast the decline in signal quality caused by blockage. The predictive model shows equivalent accuracy and faster training time in comparison with models using state-of-the-art deep learning architectures of ResNet-18 and ResNet-50, owing to its suitability to the data obtained in the proposed handover experiment. Accordingly, a proactive physical layer handover method is proposed, which is based on the link quality prediction. This method outperforms handover in a reactive man-ner, as evidenced by longer connected duration, demonstrating its feasibility of malntaining a seamless connection.

LPWA (Low Power Wide Area) is expected to be a communication technology suitable for the Internet of Things (loT) because of its features. Since LoRa communication has a trade-off between communication range and transmission rate, performance is inherently varied depending on the surrounding environment. Therefore, to achieve stable and efficient communication performance, it is necessary to set appropriate parameters for LoRa depending on the communication environment between the base station and the terminal. We here propose a method for dynamic control of parameter settings based on reception statistics of beacons. The effectiveness of the proposed method is evaluated from the real experiments.

This paper reports on work in progress on a self-interference (SI) suppression method for in-band full-duplex (IBFD) relaying. We propose to implement the two-stage SI suppression method where feedforward linear finite impulse response (FIR) filters are designed in the digital domain considering the processing delay and error vector magnitude (EVM). While the analog SI cancellation (ASIC) filter coefficient is determined based on the least square (LS) estimator, the digital SI cancellation (DSIC) filter is designed by optimizing the estimation error as well as the filter length. Simulation results show that the proposed method can significantly suppress SI while reducing the processing delay at the relay.

Low-power wide-area (LPWA) is a major communicaiton technology used in the Internet of Things (Io‘I’), Major sensor networks are constructed using original protocols specific to each LPWA standard and cannot communicate directly with devices connected to the Internet. To enhance the convenience of devices using LPWA, it is necessary to improve their interop-erability with Internet applications with TCP/IP. Previous study have enabled Single-hop TCP/IP communication over Private LoRa. In this study, we construct a multi-hop environment for TCP/IP communication over Private LoRa, and evaluate its performance using both UDP and TCP communication. Previous research has enabled one-to-one communication using UDP and TCP over a Private LoRa interface, an LPWA technology. This study leverages the characteristics of LPWA for ultra-Iong-distance transmission and implements TCP/IP communication in a multi-hop environment. This paper evaluates the performance of UDP and TCP on actual devices.

This paper shows demonstration on coherent joint transmission (CJT) in down link (DL) with multiple distributed units (DUs), among which phase synchronization is established by Wireless two-way interferometry (Wi-Wi) that provides precise synchronization on carrier phase wirelessly and continuously in the manner of two-way phase transfer measured at intermediate frequency band by small-size and low-power consumption devices. It has been demonstrated through experiment conducted in a test field with 4 DUs that the proposed method brings comparable gain in CJT with ideal case; the loss relative to the gain by ideal CJT was 1.31 dB at 99% probability although the loss for the method without phase synchronization (only timing and frequency are synchronized) was more than 20 dB.

The emerging in-band full-duplex (IBFD) system is a promising technique to enhance spectral efficiency and reduce latency in the beyond 5G systems. However, effectively mitigating self-interference (SI) is crucial for leveraging IBFD advantages. This paper presents a dual-stage approach to suppress SI, constructing feedforward linear finite impulse response (FIR) filters in the digital domain by carefully considering processing delays and error vector magnitude (EVM). In this sense, the analog self-interference cancellation (ASIC) filter coefficient is first calculated through the least squares (LS) estimator, whereas the digital self-interference cancellation (DSIC) filter is obtained by optimizing both the estimation error and filter length using the dual gradient descent method. The simulation results validate the effectiveness of this method in mitigating SI while reducing the processing delay at the relay.

Low-power wide-area (LPWA) is a major communication technology used in the Internet of Things (IoT). However, since LPWA does not conform to the TCP/IP protocol stack and employs its own unique protocol, sensors equipped with LPWA I/F face difficulty when connecting directly to the Internet. In a previous study, to extend general TCP/IP communication on LPWA networks, we constructed a TCP/IP network over Private LoRa, but it was found that TCP communication performance using LoRa devices was significantly degraded due to the characteristics of LPWA such as the low transmission rate. In the present study, to improve the performance of TCP communication using the Private LoRa interface, we propose a transmission control method that avoids collisions by modifying the advertised window size on IP2LoRa and demonstrate the effectiveness of the proposed method using TCP flow analysis.

Direction of arrival (DOA) estimation is a crucially important task of signal processing for audio applications. Infrasound might form Lamb or acoustic gravity waves and accordingly propagate at a speed that is different from the general speed. Therefore, conventional DOA methods that require a presumed sound speed are not applicable. As described herein, a newly proposed algorithm can estimate DOA and sound speed simultaneously. The algorithm, which is based on arrival time differences measured using a non-uniform sensor array, obtains estimates by nonlinear optimization with a constraint. Comparisons with conventional methods through computer simulations showed superior performance of the proposed algorithm in some conditions, such as a case where sound speeds differ from the assumed ones.

A new method to realize computation of the log-likelihood ratio (LLR) in multi-user detection (MUD) by quantum annealing (QA) is proposed herein. One metaheuristic algorithm for solving combinatorial optimization problems is QA. Recently, QA has been applied in various fields to hasten computations. This study specifically examines the application of QA in up-link non-orthogonal multiple access (UL-NOMA) that employs iterative MUD. Our proposed method, QA-aided MUD, uses QA to calculate LLR in iterative MUD. We tested QA-aided MUD with a D-Wave quantum annealer. The error rate analysis demonstrates that QA-aided MUD has comparable performance to that of conventional MUD method. Furthermore, when the annealing time was set to 20 µs, we demonstrated than that the total computation time is 1/10 of the computation time necessary when using a digital computer. We also evaluated the convergence behavior of QA-aided MUD through evolution of mutual information. The results indicate that QA-assisted MUD has almost identical convergence performance to that of the conventional MUD method for LLR calculations.

The wiretap channel is a setting where one aims to obtain information-theoretic security of communicated data under the sole assumption that the channel from a sender Alice to an eavesdropper Eve is “noisier” than that from Alice to a receiver Bob. However, in practice, the difference between the two channels in terms of noise may be much smaller because of the wide spread application of high-performance communication technologies. Thus, establishing a wiretap channel over real channels is a challenging task. In this paper, we report a wiretap channel in the form of a “protocol” (a so-called virtual wiretap channel) realized by using a highly precise wireless clock-synchronization technology called the wireless two-way interferometry (abbreviated as Wi-Wi). Wi-Wi technology has already been implemented in wireless communication devices, and it measures the clock time difference and signal propagation time in a situation where the precisions of both values are mutually affected. That is, Alice or Bob can induce a noise on Eve's clock time difference measurement by physically introducing noise in the signal propagation time between Alice and Bob. We analyzed the proposed wiretap channel referred to as the Wi-Wi wiretap channel experimentally, and estimated its parameters (e.g., the error probabilities). We confirmed that the Wi-Wi wiretap channel works well as a virtual wiretap channel by simulating and experimentally demonstrating a well-known, provably secure, optimal wiretap code over it. The results show that Wi-Wi wiretap channel can serve as a physical layer security, useful for synchronized Internet of Things (IoT) devises.

Deep learning is applied to predict received power in a 60 GHz band propagation model from time-series images. Both three-dimensional (3D) convolutional neural network (CNN) and the combination with long short-term memory (CNN+LSTM) are used to construct predictive models. The CNN and CNN+LSTM models are evaluated to predict the received power up to 2 seconds ahead with root-mean-square errors of 2.81 dB and 2.27 dB, respectively. In addition, Kirchhoff approximation (KA) is applied as an efficient data generator to calculate the received power analytically for the corresponding propagation model. The calculated received power values are compared with measured results to validate the formulation.

Low-power wide-area (LPWA) is a major communication technology used in the Internet of Things (IoT). However, since LPWA does not conform to the TCP/IP protocol stack and employs its own unique protocol, it is difficult for sensors equipped with LPWA I/F to connect to the Internet directly. In the present study, to realize general TCP/IP communication on LPWA networks, we construct a TCP/IP network over Private LoRa, and evaluate its communication performance. Moreover, we verify the feasibility of TCP/IP communication over LoRa by using a popular Internet application.

Device-to-Device (D2D) communications in this paper refer to autonomous direct communications among end devices without central control. Wireless networks based on autonomous D2D communications are of resiliency feature. We developed a lifelog gathering system using such autonomous D2D communications towards elderly health monitoring in depopulated area, where creating wireless networks with coverage over entire area is costly. The developed system consists of three types of terminals, i.e., sensing terminal (s-terminal), delivering terminal (d-terminal), and gathering terminal (g-terminal). The s-terminal collects lifelog at objective’s house. The d-terminal can be placed in a moving car and it receives lifelog data when running within communication range of the objective’s house. Moreover, the lifelog is forwarded to the g-terminal when the d-terminal enters the communication range of facilities where the g-terminal is in operation. We conducted field experiments in a mountainous village. The measured results show that the developed system can successfully gather lifelog data even under non line-of-sight environments. Examples of observation from the gathered lifelog data are also presented.

It is expected that IEEE 802.11ad is used as intra-vehicle communications for high-speed transmission. Currently, since motion detection by frequency modulated continuous wave (FMCW) signals in mmW has been available, issues on interference between IEEE 802.11ad and FMCW signals have been raised. To solve the issues, an interference mitigation method applicable into IEEE 802.11ad against FMCW signals has been proposed. In this method, FMCW signals are detected by summation of the energy in frequency domain of interfered received signals. Interference suppression is achieved by nulling the frequencies where it is determined that FMCW signals are detected. The method does not require any changes of IEEE 802.11ad specifications. Simulation results show that significant improvement on BER has been achieved by introducing the method over SIR range from 0 dB to 8 dB. Experiment on the method has been conducted to evaluate performance of the method in a vehicle. The results obtained by the experiment have shown that the method successfully suppresses FMCW signals.

IEEE 802.11ad is expected to be used as in-vehicle communications for high-speed transmission. Recently, radar systems using frequency modulated continuous wave (FMCW) signals in the 60 GHz band have been investigated for a child presence detection in a vehicle. Therefore, there is a concern that the in-vehicle radio communication system could be interfered with by the radar system. In this paper, transmission experiment of IEEE 802.11ad signals with existence of FMCW signals was conducted in a vehicle since the impact of the mutual interference has not been clarified. The results show that if the transmit antenna and the receive antenna face each other, the stable communication can be established in a vehicle even if the FMCW signal interferes. In addition, stable communications are confirmed by using reflection from the vehicle body as long as received signal power is beyond -33 dBm.

In this paper, we propose a novel uplink non-orthogonal multiple access (UL-NOMA) for massive communications under the number of user equipments (UEs) that send signals simultaneously is larger than the number of receive antennas. The base station (BS) separates the superimposed signals through minimum mean square error (MMSE) spatial filtering with successive interference cancellation (SIC). In order to improve the signal separation performance, frequency domain-space time block coding (FD-STBC) is adopted as transmit diversity in the uplink. As FD-STBC, we examine two ways of transmit power allocation method for each UE. The proposed methods are evaluated by computer simulations and also experiments, which were performed under condition when up to 6 UEs transmit signals simultaneously. Performance evaluation is given by packet error rate (PER) by sending 16 bytes a packet as the signal. The results of the computer simulation and the experiments show good agreement, and the experimental results with the power difference for each UE, show that PER is less than 10% in single transmission without repetition when the number of UEs is up to 6. These are the results when the overloaded ratio, which is the ratio of the number of UEs to the number of the receive antennas, is up to 300%. And these results showed that it is effective to make a power difference for each UE.

This paper gives evaluation on MIMO communications by RF signals in seawater thorough analysis on channel capacity, simulations, and experiment in shallow water. The analysis on channel capacity reveals that near-bound capacity in MIMO communications is achieved by interference cancellation based on ZF by setting antenna spacing of more than a half of wavelength in seawater. Simulation results show that expected bitrate reaches at more than 10 bps/Hz and 20 bps/Hz by employing 2x2 and 4x4 MIMO communications, respectively, with 64QAM in frequency band of 10 MHz. Experiment in shallow water has been conducted on 2x2 MIMO communications with 64QAM, and 10-Mbps data transmission has been achieved, which is expected bitrate in wireless communications in seawater by RF signals.

Deployment of global navigation satellite system (GNSS) buoy system as an array in a wide ocean is expected as a powerful tool for monitoring tsunami and ocean bottom crustal deformation in the region [1]. IoT non-terrestrial network (NTN) [2] is crucial to realize the system since the buoys are deployed in the ocean. In the GNSS buoy array, although data size sent from each buoy is small, it requires to accommodate more than 10 buoys while the satellite link in available. In this case, grant-free access, which brings advantages of low latency and small signaling overhead, is expected. In this work, the use of uplink based on non-orthogonal multiple access (UL-NOMA) [3] is evaluated as grant-free access in the GNSS buoy array. We propose a method of generating a low-density signature of NOMA by buoy's location (latitude and longitude) for reducing the signaling overhead and latency.

In wireless communication for Internet-of-Things (IoT), a base station (BS) is required to efficiently accommodate radio signals transmitted from massive IoT devices. We have developed and demonstrated an uplink non-orthogonal multiple access (UL-NOMA) system, in which signals from the devices are multiplexed in the power domain without any spatial multiplexing or spreading. In the UL-NOMA strategy, precise transmit power control (TPC) methods are required to compensate for various fading fluctuation. For example, NOMA that multiplex devices' signals in the power domain utilize the difference of received signal power at BS to successfully achieve successive interference cancellation (SIC). To maintain the difference of received power at BS, the implementation of precise TPC is crucial. In the paper, a prediction method on the future fading condition from current conditions is useful to realize precise TPC in UL-NOMA in the power domain. The prediction method at IoT device side with the autoregressive (AR) model is proposed which utilizes received OFDM signals in the downlink. The proposed TPC is evaluated by computer simulations. Simulation results show that TPC with the proposed fading prediction improves the signal separation success rate of UL-NOMA with SIC. The ratio that the signals of all devices in multiplexing 5 devices are separated is improved from 39% to 66%.

The 5G will not only offer high speed and greater capacity communication but also support the IoT. To support IoT, it is important that next generation NodeB (gNB) will be able to deal with massive uplink signals transmitted from IoT devices. Non-orthogonal multiple access (NOMA) is one of the effective methods to handle massive signals from the IoT devices. However, when NOMA is used for downlink, it is necessary to perform signal separation on the user equipment (UE), which suffers from heavy load on UE. We consider that it is better to employ orthogonal multiple access (OMA) for downlink to prevent too much computational cost and power consumption for UE. Hence, we have studied a system that uses NOMA for uplink and OMA for downlink. The feature of our system is that single carrier is used for uplink to reduce peak to average power ratio (PAPR). Although the single carrier transmission with NOMA will be in demand in the future, most of the research is computer simulation. In this paper, we demonstrated and evaluated our system using hardware. We measured the performance difference between uplink using NOMA and downlink using OMA in terms of packet error rate (PER) to obtain tips to improve uplink performance. From the result, we confirmed that uplink NOMA could be performed well in hardware. However, to improve reliability, it is necessary for the system to incorporate some techniques such as diversity with uplink NOMA. Without the techniques, the uplink with NOMA is less reliable than downlink with OMA so far.

Decentralized synchronization among peer devices (PDs) for distributed device-to-device (D2D) wireless networks has been explored by many researches. A general way of performing decentralized synchronization is based on pulse-coupled methods. In which, all PDs are equal and each PD sends and receives synchronization packets as well as adjusts own clock accordingly to achieve mutual synchronization. A newly published standard of IEEE STD 802.15.8 (STD-15.8) provides a systematic process to achieve synchronization for distributed D2D. However, we find that the synchronization process of STD-15.8 may results in separated synchronization clusters. To solve this problem, we propose additional procedures to that of STD-15.8. Then, we conduct step-by-step simulations to reflect the lower MAC functions of real transceivers by employing multiagent model. The simulation results verify the effectiveness of our proposal on improving synchronization.

In this paper, we consider boolean network tomography to identify link failures in a network. In boolean network tomography, the relationship between end-to-end measurements and link states are represented with a system of boolean equations, and failure links are identified by solving the equations. In order to establish measurement paths efficiently, we propose an adaptive boolean network tomography scheme, where measurement paths are established sequentially according to a candidate set of failure links. Here, to derive the candidate set, we extend CBP (Combinatorial Basis Pursuit), a representative decoding algorithm in Combinatorial Group Testing, and utilize its property that it can identify failure links without false negative errors. We evaluate the performance of the proposed scheme in terms of the number of measurement paths and compare it with a non-adaptive boolean network tomography scheme. Furthermore, we propose mobility-assisted boolean network tomography, which can improve the ambiguity problem in boolean network tomography.

Millimeter-wave radios have great potential of spatial interference management through its physically small but possibly electrically large antenna aperture. It is expected that the interference management becomes a major challenge after massive deployment of millimeter-wave devices. This paper therefore discusses design guidelines and an influential radio link property of two beamforming schemes for spatial coexistence at 60 GHz; conventional gain focusing and the interference alignment. The guideline is derived from an example of distributed channels in a small room. The investigation shows that, under a moderate receive signal-to-noise ratio, 1) having 2λ2antenna apertures at the Tx and Rx realizes 3 to 7 bit/s/Hz under the presence of mutual interference, 2) the gain focusing is as robust as the interference alignment, and finally, 3) inter-link correlation is a primary bottleneck in the interference alignment.

Visualization of stomach and small intestine, nowadays can be done with wireless capsule endoscopy. However, the limitation of bandwidth at low frequencies such as Industrial, Scientific and Medical (ISM) band and Medical Implant Communication Service (MICS) band do not provide high resolution images. One of the possible frequency band to have clear images from digestive organs is the use of Ultra Wideband (UWB) at frequency of 3.1-10.6 GHz. To have high resolution wireless endoscopy at higher frame rate, we need to investigate the antenna, path-loss model and radio channel behavior at available higher frequency band such as UWB band. This paper discusses on UWB antennas and propagation for digestive organs implanted device.

This paper presents a performance evaluation on path diversity introduced in a wireless network established by unmanned aerial vehicles or unmanned aircrafts (UAs). One of usage scenarios of the wireless network established by UAs is establishment of a temporal communications instead of disrupted terrestrial networks due to a massive disaster. In order to evaluate system performance based on this usage scenario, we have conducted the following simulations; first, radio propagation characteristics between UAs flying over different two conditions have been simulated, after that, system simulations have been carried out over radio channels derived by simulations. Results regarding radio propagation reveal that characteristics including path loss and RMS delay are highly depend on not only altitude of the deployed UAs, but also its polarization of radio signal. System simulations based on the channel impulse responses obtained by propagation simulations, in which IEEE802.11g is utilized as specifications of the radio system, show that path diversity introduced by deploying multiple UAs brings remarkable improvement on achievable throughputs.

This paper proposes a relaying protocol which combines a network coding with a mobility of small unmanned aircraft (UA) for wireless relay networks. We consider the scenario where the UA circles above around the networks automatically and bridges the signals between ground access points (GAPs) of the distant networks. Such wireless relay networks using UA can be considered particularly useful for emergencies e.g., when the communication networks are partially or completely interrupted after the disaster or power failure. The proposed protocol using network coding and UA can provide a significant diversity gain in contrast to conventional relay protocol. In this paper, simulation results are presented to demonstrate the reliability of the proposed protocol. The bit error rate of the proposed protocol can be lower than that of the conventional relay protocol. This paper also reveals that the diversity gain can be achieved by the proposed protocol.

This paper presents a performance evaluation of 60 GHz high-speed radio systems under an application scenario related to a medical operation. The evaluation is based on the following specifications: IEEE 802.15.3c and IEEE 802.11ad, which have been designed to provide data rates of multi-Gbps at physical layer. First, by using measured power delay profiles (PDPs) in hospital environments, both inter-symbol-interference (ISI) and channel capacity are calculated. Then, system simulations are carried out in order to show achievable throughputs. The results reveal that OFDM systems provide the required throughput for the application scenario in all the measured PDPs. On the other hand, the single carrier (SC) systems without any equalization are limited to 85 % of the measured PDPs where the required throughput is achieved. Also, it is shown that the calculated channel capacity for each measured PDP reveals the similar trend with the available throughputs obtained from the system simulations.

Wireless Body Area Network (WBAN) has drawn considerable attention as a means to gather vital data from on-body sensors. In WBAN, however, a star network topology is mainly supported, connecting a central coordinator to vital sensor nodes put on different positions of a human body, so the links between the coordinator and the sensor nodes are often blocked by parts of the human body when the man takes different postures and motions. Therefore, to support real-time vital data gathering in WBANs, a scheme for mitigating such link blockings is essential. This paper proposes a cooperative scheme for ensuring reliable data transmission in a WBAN. For each sensor node on a human body, the proposed scheme autonomously assigns a sensor node as a cooperator out of other sensor nodes and the cooperator retransmits packets from the sensor node for a coordinator instead of the sensor node when the direct link between them is blocked. After presenting the cooperator selection algorithm, using the Received Signal Strength Indication (RSSI) data obtained from the experiment in an anechoic chamber, the paper evaluates the performance of the proposed scheme in terms of average and worst outage rates.

This letter presents radio channel measurements and modeling results for the feasibility study of 60 GHz high-speed radio systems in hospital environments. Two possible applications of those systems are considered: real-time video streaming for angiography and for ultrasonic inspection. Channel modeling was performed for the path loss and multipath characteristics of the propagation channel, i.e., the delay spreads. Results revealed generally lower path loss and delay spread values compared to regular indoor office and residential environments. The results indicate that the 60 GHz radio systems operating in hospital environments can provide better signal quality and wider coverage than those operated in regular indoor environments, though increased interference with neighboring cells might be an unfortunate consequence.

This report describes results from 60 GHz channel measurements and modelling in a shielded room. Final goal of this work is to investigate potential and feasibility of 60 GHz radios for very-high-data-rate short-range communications in medical applications. The measurement in a shielded room is meaningful for studying propagation characteristics in medical applications, since real surgery rooms are typically shielded. One particular usage scenario, i.e., real-time video streaming for ultrasonic imaging, was considered, where the antenna settings were adjusted to the usage scenario accordingly. Link budget and delay domain multipath characteristics were analyzed and modelled. Finally, model parameters that fit the measured power delay profiles were given.

This paper provides channel models for wireless body area network (WBAN) in UWB frequency band, and also presents performance evaluation using the derived channel models. The channel model is given by a statistical model in which parameters are derived from actually measured channel transfer function in a hospital room environment. These models enable us to evaluate performance of UWB-based WBAN. In this paper, bit error ratio (BER) and packet error ratio (PER) are shown for UWB-based WBAN which employs a signaling scheme among OOK, BPPM, BPSK, and DPSK. The results show that both OOK and BPPM which generally uses a non-coherent receiver provide severe performance when the target PER is set to 10-2under the packet size of 128 bytes. The other signaling schemes achieve the required performance from the viewpoint of such error ratio.

Biomedical sensors can be implanted and networked in the human body for health monitor, diagnosis, treatment or as a prosthetic device. Life time and heat generated by implant due to communication and circuitry power consumption are big concerns. This paper presents a new network architecture for long range communications in the implanted sensor networks. We measured the on-body propagation around body surface and in-body propagation through tissue in the frequency ranges of 403 MHz and 2.45 GHz. We have found that the in-body path loss is more than that of on-body. To exploit the path loss difference, we propose to introduce a body surface coordinator which has more resources to the implanted sensor networks. Instead of only routing data among implants, the coordinator on the body surface can forward data from one implant to another over long distance more safely and efficiently.

Recently, UWB (ultra wide band) signal that has frequency bandwidth of 500 MHz or more is considered to be using high precision radar because of a very high resolution. The UWB is considered to have fewer influences on human being because of low transmitting power. And, MIMO (multiple-input multiple-output) radar refers to an architecture that employs multiple, spatially distributed transmitters and receivers. In this paper, sensor network made up of MIMO-UWB radar with widely separated antennas to estimate distance and to detect human being existence is studied. Detection performances are evaluated from the computer simulation by using the real propagation measurement result with the network analyzer. The positioning accuracy of the human body and the effectiveness of MIMO-UWB radar are shown.

This paper presents a performance evaluation in terms of bit error rate (BER) of a 26 GHz-band ultra-wideband (UWB) communication system through measurement-based simulation. We measured real channel responses in an office to obtain responses for use in simulations. The simulation results demonstrate that the 26-GHz-band UWB system can achieve high-speed data transmission of 500 Mbps or more, in and indoor office by using a directional antenna.

This paper presents an analysis of iterative demapping and decoding for coded M-ary bi-orthogonal keying direct sequence UWB (MBOK DS-UWB) systems via an extrinsic information transfer chart (EXIT chart). In MBOK DS-UWB systems, which have been considered a type of PHYs suitable for high-speed wireless personal area networks (WPANs) in IEEE802.15.3a, one of useful error correction techniques is iterative demapping and decoding between soft-input/soft-output (SISO) MBOK demapper and SISO channel decoder. The EXIT chart has been invented by ten Brink (1999) to allow the prediction of turbo cliff position and bit error rate after arbitrary number of iterations. Through analyses, the bit error rate performance of the iterative demapping and decoding highly depends on the UWB channel conditions in multipath fading UWB channels. We show that the use of RAKE reception is effective approach in multipath fading UWB channels for the iterative demapping and decoding via the EXIT chart.

This paper describes low-complexity rake reception and Viterbi equalization techniques for M-ary bi-orthogonal keying direct sequence UWB (MBOK DS-UWB) systems, which have been considered a type of PHY suitable for high-speed WPANs in IEEE802.15.3a. In MBOK DS-UWB systems, rake reception and equalization are essential to compensate interpulse interference generated by multipath fading. For rake reception, we derive a novel technique to reduce its implementation complexity by setting a limit on the number of delay devices. For Viterbi equalization, we provide a reduced-state sequence estimation algorithm that reduces the computation complexity for MBOK DS-UWB systems. By employing the proposed rake reception and Viterbi equalization techniques, the complexity can be reduced to less than half of ordinary rake and equalization techniques. Simulation results show that our rake reception and Viterbi equalization techniques enable almost the same performance as existing techniques despite the lower complexity.