Full-duplex cellular (FDC), which incorporates inband full-duplex (IBFD) into a cellular system, is a candidate scheme to enhance the spectral efficiency of the mobile communication system. To realize FDC, it is necessary to reduce self-interference (SI) and control inter-user interference (IUI) by appropriate user scheduling. Many researchers have studied various technologies to overcome them, but there are few studies to demonstrate the effectiveness of IBFD with actual equipment, which works in real time. In this paper, we develop a 5G-based real-time FDC prototype, which has functions of digital SI cancellation, collecting IUI information, and flexibly changing user scheduling in real time. In addition, this system can transmit and receive arbitrary data using 5G signals even in FD operation. We evaluate its fundamental effectiveness by experiment and show that IBFD can nearly double the UL and DL throughput.

In this paper, we developed and demonstrated a highly spectral-efficient private 5G standalone system using open-source 5G software and software-defined radio. We introduced an innovative waveform shaping technique for downlink (DL) transmissions and a dynamic bandwidth adaptation scheduler for uplink (UL) communications within the 5G base station. These methods substantially reduce out-of-band emissions (OOBE), making high-speed transmission possible even under stringent interference requirements, with only a minimal 18% throughput reduction and no need for device modifications. Notably, our developed prototype ensures complete compatibility with existing 5G systems, allowing commercial off-the-shelf devices, such as smartphones, to connect seamlessly. Experiments in an anechoic chamber using a smartphone have shown that high-data-rate transmission (240.5 Mbps at DL and 43.9 Mbps at UL) can be achieved while suppressing OOBE by 25dB at DL and 11dB at UL.

In-band full-duplex (IBFD) is gaining attention due to its improved spectral utilization efficiency towards 6G. A dynamic full-duplex cellular (DDC) system has been proposed to gradually introduce IBFD into the current time-division duplex-based 5G system. In addition, the DDC system with transmission (Tx) and reception (Rx) separation has been proposed to reduce self-interference at base stations. However, previous studies have not considered a multi-cell environment. In this study, we propose a DDC system with separated and distributed Rx antennas for a multi-cell environment equipped with directional antennas to reduce inter-cell interference.

In this paper, we show that there is an excellent possibility that 5G can be operated as a spectrum-sharing system in the 15 GHz band of the frequency range 3 (FR3). First, we consider how much spectrum resource can be secured in the 15 GHz band and show that it can ensure a 550 MHz bandwidth in many places and a 190–510 MHz bandwidth in urban areas. Next, we propose a phase noise model for the 15 GHz band, evaluate the block error rate characteristics of various sub carrier spacings (SCSs) using link-level simulation, and show no effect of phase noise if the SCS is 30 kHz or more. Finally, the interference immunity of the 5G new radio is evaluated, and it is found that the required SIR is approximately 10 dB and that each 5G base station could achieve coverage of approximately 700 m in radius.

Toward 6G, cell-free networks (CFN) are attracting attention as a solution to the problem of poor communication quality at the cell edge. In CFN, many access points are densely deployed and cooperatively operated as distributed MIMO systems. In uplink communication in CFN, transmit power control (TPC) is required to mitigate interference and ensure fairness between users. In this paper, we propose an open-loop TPC algorithm for CFN and evaluate its performance by computer simulation. As a result, an improvement of 55.0% in the fifth percentile spectral efficiency is achieved compared to the case without TPC while maintaining a higher average spectral efficiency.

The increasing demand for faster and more efficient communication technologies has highlighted the in-band full-duplex (IBFD) cellular system as a key advancement for the upcoming 6th-generation mobile communication (6G) systems. Due to the limited availability and high demand for frequency resources, maximizing the utilization of existing frequencies is crucial. The dynamic full-duplex cellular (DDC) system addresses this challenge by introducing IBFD, which simultaneously transmits and receives signals on the same in-band frequency, thereby having the potential to double the spectrum efficiency. However, existing studies on the DDC system have been evaluated using system-level simulations that simplify physical layer processing and focus solely on the MAC layer scheduler, leaving their practical applicability to actual 5G systems undetermined. To address this gap, we present a DDC system emulator developed using OpenAirInterface (OAI), which emulates the complete 5G system from the physical layer to the 5G core network. We propose higher-layer signaling to facilitate IBFD transmission within the DDC system and create a single-cell emulator to evaluate its applicability for future cellular systems beyond 5G. Our results indicate that the DDC system can enhance spectral efficiency while maintaining compatibility with existing 5G infrastructure, paving the way for future 6G implementations. Specifically, our evaluation example shows a 19% increase in downlink throughput, underscoring the practical advantages of the DDC system.

This study proposes a heterogeneous in-band full-duplex (Het-IBFD) system for the simultaneous transmission of the Wi-SUN field area network (Wi-SUN FAN) 1.1 signal using IEEE 802.15.4-2020-compliant orthogonal frequency division multiplexing (OFDM) and reception of the Wi-SUN FAN 1.0 signal using IEEE 802.15.4g-compliant frequency-shift keying (FSK). Furthermore, we propose a simple and highly accurate digital self-interference (SI) canceller to realize the proposed system, focusing on the difference between the spectrum of the IEEE 802.15.4g FSK and IEEE 802.15.4-2020 OFDM. The proposed Het-IBFD system using the proposed digital SI canceler is evaluated using computer simulations under the conditions of one-path Rayleigh fading for the desired communication channel and Rice fading for the SI channel. If no quantization noise effect is considered and the Rice factor is 5 dB, the communication quality of the FSK in Het-IBFD can achieve the required packet error rate (PER) of the wireless smart ubiquitous network (Wi-SUN) system. This is realized using the proposed digital SI canceller when the sum of the pathloss and antenna/analog SI cancelation level is more than 39 dB. If the quantization noise effect is considered with the 12-bit acrlong ADC and the Rice factor is 20 dB, the communication quality of the FSK in Het-IBFD can achieve the required PER of the Wi-SUN system using the proposed digital SI canceller when the sum of the pathloss and antenna/analog SI cancelation level is more than 52 dB.

This paper first summarizes the specifications of standardized wireless personal area networks (WPANs) and wireless local-area networks (WLANs) using the 60 GHz band, for example IEEE 802.15.3c and 802.11ad standards, and the significance of the standardization, together with the standardization transition of third-generation partnership project (3GPP)-based public wireless communication systems and other radio systems in the 2010s. The concept of a virtual community network (VCN) using a millimeter-wave wireless communication system in the 6G era is then proposed based on the 3GPP-based orthogonal frequency-division multiple access (OFDMA) system. Moreover, by using a latest propagation characteristics model of the 60-GHz propagation characteristics in 3GPP, we evaluated the block error rate (BLER) performance of the proposed VCN by changing the parameters of the physical layer such as the subcarrier spacing (SCS) through computer simulation. The results showed that a transmission distance of 5 m per terminal could be achieved even with a low-gain antenna, demonstrating the feasibility of a VCN based on the high-density installation of many terminals in a room.

Currently, orthogonal frequency division multiplexing (OFDM), standardized in IEEE 802.15.4, has attracted attention as a transmission scheme for higher data rates, long-distance transmissions, and mobile communications for the expansion of Internet of Things (IoT) applications as well as for legacy IoT applications, such as smart metering systems and home-area networks. In particular, receiving schemes using IEEE 802.15.4-based OFDM have been actively examined to realize mobile communication. Previous studies used the long training field (LTF) and pilot subcarriers for channel estimation of multipath fading, achieving mobile communication with data rates of 100 Kb/s or above at moving speeds of up to 40 km/h in an urban environment. In a previous study, channel estimates were obtained by repeating channel estimates from the LTF and pilot subcarriers in the time domain and by interpolating the estimates in the frequency domain. This study proposes a receiving scheme for IEEE 802.15.4 OFDM aimed at high-speed mobile IoT communication systems. In the time axis direction, the proposed scheme obtains channel estimates in the same manner as previous schemes. However, in the frequency axis, the proposed scheme obtains the channel estimates by copying estimates of neighboring subcarriers according to the coherence bandwidth of the multipath fading channel to update the channel estimates frequently. Computer simulation results show that the proposed scheme, including delay spread estimation can achieve mobile communication with a data rate of 100 Kb/s at moving speed of 200 km/h in the urban environment.

In-band full-duplex (IBFD) is a technique for transmitting and receiving signals simultaneously using the same frequency and time slot. Ideally, by adopting IBFD, the frequency utilization efficiency can be twice than that of the half-duplex. In this study, we focus on a full-duplex cellular (FDC) system, where the base station (BS) allows for the superimposition of downlink (DL) communications with other user equipment (UE) on the uplink (UL) communications and the superimposition of UL communications with other UE on DL communications by applying IBFD. The BS needs to identify the UE whose signals do not degrade DL communication quality in the FDC. Moreover, self-interference (SI) of the BS (i.e., interference when the transmitted signal interferes with its own received signal in IBFD) should not degrade the UL communication quality. This paper summarizes the system configuration and research and development items on the dynamic-duplex cellular system that is generally operated in half-duplex. It adaptively performs IBFD only for UEs whose signal does not interfere with other users. In addition, this paper summarizes the development of a monitoring system for the interference from UEs and the development of digital and analog SI canceller applicable to a BS. The developed BS can reduce SI by more than 35 dB in the RF and more than 20 dB in the digital parts.

Full-duplex cellular (FDC) system, which introduces in-band full-duplex (IBFD) to the cellular system, has been paid attention to for increasing spectral efficiency in 5G and 6G systems. IBFD causes new interferences, such as self-interference (SI), because uplink (UL) and downlink (DL) communications are performed simultaneously on the same frequency resources; however, if the new interferences problem can be overcome, IBFD can ideally improve spectral efficiency up to twice that of half-duplex (HD) system. Many SI cancellations have been proposed; however, to the best of our knowledge, there has been no study of digital SI cancellation for application of IBFD to the 5G system by taking into account the 5G signal configuration and the impact on the performance of low-density parity-check (LDPC) code. In this paper, we propose a digital SI cancellation for applying to the 5G-based orthogonal frequency division multiplexing (OFDM) signal. First, we propose a demodulation reference signal (DMRS) configuration to improve the estimation accuracy of the SI channel. Second, the noise power estimation scheme using the proposed DMRS configuration is also proposed for decoding 5G adopted LDPC. Finally, the proposed scheme is evaluated by computer simulations, and we found that the communication quality in IBFD operation becomes equivalent to that in HD operation by applying the proposed digital SI cancellation.

The Internet of Things (IoT) has been increasingly realizing communication among diverse devices, in addition to sensors and meters. IoT is equipped with communication functions and entails interconnection via the Internet to collect and use various data. Wireless smart ubiquitous network (Wi-SUN) conforms to the international standard IEEE 802.15.4, and it has therefore been considered a wireless communication standard for IoT. The Wi-SUN uses frequency-shift keying (FSK), standardized in IEEE 802.15.4, and achieves a typical data rate of 100 kbps. However, when Wi-SUN is used in other IoT applications to realize smart cities and smart factories, communications with higher data transmission rates and longer distances are required. Orthogonal frequency division multiplexing (OFDM), standardized in IEEE 802.15.4, has been used as a transmission method to satisfy the associated requirements. In this study, the fundamental transmission characteristics of IEEE 802.15.4 OFDM were first evaluated through computer simulations and laboratory experiments by employing developed evaluation boards. Next, the outdoor transmission performance of IEEE 802.15.4 OFDM was evaluated using the developed evaluation boards. Experimental results indicate that IEEE 802.15.4 OFDM can yield the same transmission distance as that of FSK using a smaller transmit power to achieve the packet error rate (PER) smaller than 10%.

In-band full-duplex (IBFD), which ideally leads to a doubling of spectral efficiency, has been attracting much attention as a promising technology for the beyond 5G and 6G cellular systems. As a method for introducing IBFD to cellular systems, the dynamic duplex cellular (DDC) system has been proposed. In the DDC system, IBFD is applied if it does not degrade the quality of existing half-duplex (HD) communications. However, the conventional DDC system has not established sufficient improvement of user throughput due to the residual self-interference (SI) at the base station (BS). In this paper, we propose a DDC system with distributed receive-only base stations based on the concept of distributed antenna systems to reduce the impact of the SI. In the proposed system, the radio unit (RU) of the BS is separated into transmit-only RU (TRU) and receive-only RU (RRU), and the TRU and multiple RRUs are spatially distributed in the cell. The effectiveness by the proposed system is evaluated by computer simulation in the single-cell environment.

Wireless technology that can conFigure wide-area IoT systems with high data rates is required toward 6G. To further expand area coverage, it is necessary to improve the data rate of the conventional machine type communications (MTC) such as LTE-M and mMTC at the edge of the coverage area. In this paper, we propose an orthogonal frequency division multiplexing (OFDM) with symbol-edges truncating transmission (STTOFDM) for data rate enhancement. In the proposed STT-OFDM scheme, only a part of the cyclic prefix (CP)-OFDM symbols, which is the legacy communication scheme adopted to 4G and 5G, is transmitted. On the receiver side, zeros are inserted where the no transmission took place at the transmitter side before normal OFDM demodulation is performed. The energy per one-symbol transmission is expected to be reduced by the proposed STTOFDM. We evaluate the achievable throughput and show the usefulness of the proposed STT-OFDM scheme. The proposed STT-OFDM can improve the throughput of the CP-OFDM by about 1.5 times even in low SNR environments.

Radio communication systems using the frequency-shift keying (FSK) scheme standardized by the IEEE 802.15.4g standard can realize low-power consumption and highly reliable communications and are mainly adopted for smart metering as part of the Internet of Things (IoT). However, smart metering has recently broadened its application expectations, with broadband and long-distance communications now required. To fulfill these requirements, orthogonal frequency-division multiplexing (OFDM) has been incorporated into the IEEE 802.15.4g and 802.15.4x standards. However, comprehensive transmission performance analysis of OFDM under static and multipath fading environments has not been conducted. In this article, we first evaluated the packet error rate (PER) of OFDM assuming fixed communications using computer simulations. We then evaluated the transmission distance of OFDM and showed that OFDM can communicate at transmission distances up to 3.0 times longer than those specified in IEEE 802.15.4g FSK. Next, the PER in a mobile communication environment was evaluated using computer simulations. When only the long training field (LTF) was used to estimate multipath radio channels, the required PER of 10% was not achieved, even in a mobile communication environment at a speed of several km/h. To solve this problem, we proposed a receiving scheme which included a new channel estimation scheme. This scheme successively utilized not only the LTF but also pilot signals inserted into the transmitter to estimate radio propagation characteristics. Computer simulation results showed that the required PER was achieved even in a mobile communication environment at 30–40 km/h by using the proposed scheme.

In-band full-duplex (IBFD) systems are attracting attention as a key technology for ideally doubling channel capacity for beyond 5G and 6G. First, we propose an analytical model of the effect of$N$-bit analog-to-digital converter (A/D) quantization noise on channel capacity quasi-upper limit of the desired signal at the base station of the IBFD systems. We derive averaged and peak powers of input signal to$N$-bit A/D and quantization noise power of$N$-bit A/D to formulate uplink (UL) channel capacity quasi-upper limit. Numerical analysis results by the proposed analytical model show that the UL channel capacity quasi-upper limit degrades by 16% and 80% in the 12- and 8-bit A/D, respectively. Second, we propose digital signal-processing (DSP)-assisted dual- and quad-A/Ds to reduce the quantization noise effect in IBFD systems. When A/D resolution bit is 8-bit, the proposed DSP-assisted dual- and quad-A/Ds improve the UL channel capacity quasi-upper limit by up to 92.3 and 192%, respectively, compared to conventional A/D for peak-to-average power ratio condition of 15 dB and analog self-interference (SI) cancellation capability of 30 dB. The proposed dual- and quad-A/Ds can reduce the burden on the analog SI cancellation circuitry by 6 and 12 dB, respectively.

Currently, in-band full-duplex (IBFD) has attracted much attention and has been researched for the beyond 5G systems. IBFD enables simultaneous operation of downlink (DL) and uplink (UL) communications at the same frequency and ideally doubles spectrum efficiency compared with the conventional half-duplex. In recent years, the dynamic-duplex cellular (DDC) system has been proposed to flexibly expand the system capacity with IBFD. However, previous studies of the DDC system were based on the LTE (Long-Term Evolution) system in the sub-6 GHz band. In this paper, we propose a 5G new radio-based DDC system to add UL communications to the DL subframes by considering the antenna directivity in the super high frequency (SHF) band.

The full-scale operation of the 5th generation mobile communication (5G) system was started in several countries. In Japan, in addition to the 5G nationwide public network service provided by telecommunications carriers, the local 5G (i.e., a private 5G network self-operated by various entities to flexibly configure and use a dedicated network within their buildings or premises) is attracting attention. As the local 5G systems become more widespread in the future, many local 5G systems will need to coexist in nearby areas. Therefore, estimating operational area of local 5G systems and avoiding interference between them will be important. Conventionally, the free-space propagation (FS) and the extended-Hata (EH) models are well-known as radio propagation estimation methods. However, they have problems to calculate the radio protection area from the interference and cause wasteful protection area setting or the lack of the radio protection. In this paper, we propose two novel methods for estimating the radio protection area to achieve both high spectrum efficiency and interference protection. In the proposed methods, the effect of single-knife edge diffraction is considered to the conventional models. The proposed methods are evaluated by using measurement results of actual radio propagation experiments in the campus field of Kyoto University.

In recent years, the Wi-SUN field area network (FAN), a wireless multi-hop communication standard, has emerged in smart city infrastructures. Wi-SUN FAN adopts the Internet protocol version 6 (IPv6) routing protocol for low power and lossy networks (RPL) as its routing protocol in the network layer. RPL is originally developed for fixed nodes, such as smart metering devices. Nevertheless, as smart city infrastructures develop, mobile nodes' deployment becomes inevitable, and the Wi-SUN FAN needs to support the routing of mobile nodes. This paper evaluates the delivery rate of data packets from a mobile node to the network's gateway under RPL by computer simulations. The results specify that the slow parent handover deteriorates the delivery rate. Then, we propose a routing algorithm that considers the mobile node's movement to achieve reliable mobile communication in the Wi-SUN FAN. The computer simulation results show that the proposed routing algorithm increases the delivery rate by up to 80.7% compared to the original RPL.

To improve the spectral efficiency of the 5th generation mobile communication system (5G) and beyond, the universal time-domain windowed orthogonal frequency division multiplexing (UTW-OFDM) has been proposed. Particularly, the simplified UTW-OFDM is highly compatible with the conventional cyclic-prefix-based OFDM (CP-OFDM). It can strongly suppress out-of-band emission (OOBE) with a simple configuration of multiplying a time window with a long transition length. However, in the simplified UTW-OFDM, multiplication of the time window causes inter-carrier interference (ICI), which degrades the communication quality, especially for higher-order modulation schemes such as 64QAM. In this paper, firstly, we investigate the applicability of the simplified UTW-OFDM to 5G. Next, an ICI canceller is proposed for the simplified UTW-OFDM-applied 5G system to improve the communication quality. In the proposed method, an optimal ICI cancellation weight is designed by taking the noise enhancement suppression into account. The proposed method improves communication quality while achieving stronger OOBE suppression. In the case of 64QAM, the simplified UTW-OFDM can suppress the PSD at the channel edge by up to 45.0 dB compared to that of CP-OFDM.

This paper proposes an inter-user interference (IUI) reduction scheme applying successive interference cancellation (SIC) to expand the in-band full-duplex (IBFD)-applicable area in the dynamic-duplex cellular (DDC) system. If the received power of the IUI is stronger than that of the desired signal at the user equipment for downlink communication (DL-UE), the IUI component is firstly demodulated and decoded in the proposed scheme. Then, a replica signal of the IUI is generated. Finally, we can obtain the IUI-reduced desired signal by subtracting the replica signal of the IUI from the received signal. By applying the proposed scheme to the DDC system, the IBFD-applicable area can be expanded. The proposed scheme is evaluated by the link-level and the system-level simulations to show the IUI reduction and the IBFD-applicable area expansion performances. From the evaluation results, it is found that the IBFD-inapplicable area can reduce from 33.9% to 8.0%, namely the IBFD-applicable area can expand by 25.9%, by applying the proposed scheme to the DL-UE.

Wireless smart ubiquitous network (Wi-SUN) has been applied to various wireless Internet of things (IoT) networks. In Wi-SUN, IEEE 802.15.4g-based frequency shift keying (FSK) modulation is adopted as a low-power consumption physical layer. On the other hand, IEEE 802.15.4g/4x-based orthogonal frequency division multiplexing (OFDM) is one of the candidates for the next-generation physical layer of Wi-SUN to meet the increasing demand for high-speed transmission due to the diversification of applications. In the next-generation Wi-SUN, the existing FSK-based system and the new-generation OFDM-based system will be operated in the same field. In this paper, we consider the construction of an in-band full-duplex (IBFD) communication system using these heterogeneous wireless communication systems, assuming that the base station (BS) transmits the OFDM signal while receiving the FSK signal simultaneously. To realize the IBFD-based FSK and OFDM hybrid Wi-SUN base station, we propose a high-efficiency demodulation scheme based on successive interference cancellation (SIC) scheme using characteristics of the FSK spectrum and the OFDM pilot arrangement. The proposed scheme improves the self-interference (SI) channel estimation accuracy by about 20 dB and improves the bit error rate (BER) characteristics of the FSK signal in the IBFD system to the same level as the BER of the half-duplex (HD).

Wi-SUN FAN (wireless smart utility network field area network) is a technical specification of Wi-SUN that introduced multi-hop M2M (machine-to-machine) transmission for advanced smart city infrastructure. To construct a multihop network, the RPL (IPv6 routing protocol for low power and lossy networks) and the ETX (expected transmission count) are adopted as routing protocol and routing metric, respectively, in Wi-SUN FAN. The combination of the RPL and the ETX may cause a node to change its parent frequently. If a node selects a parent with lower link quality, communication reliability becomes lower. To avoid the frequent parent changing problem, parent candidates of each node should be selected appropriately. In this paper, we propose two schemes to select parent candidates for each node (i.e., optimized RSL (received signal level) threshold scheme and MAC (media access control) address filtering scheme) to stabilize the multi-hop routing construction in the Wi-SUN FAN systems. The proposed schemes are experimentally evaluated in a real field in an office building using the IoT-GWs (internet of things gateways) with Wi-SUN FAN module. By using the optimized RSL threshold scheme, the number of parent changes can be reduced by up to 96% compared to the case with unoptimized RSL threshold. Also, the number of parent changes can be reduced by up to 77% with the proposed MAC address filtering scheme compared to without the proposed scheme.

In this paper, we propose a heterogeneous wireless management scheme for a home area network (HAN) system. The HAN system integrates multiple wireless systems (e.g., the Wi-Fi operating in the 2.4 GHz-band and the Wi-SUN field area network (Wi-SUN FAN) operating in the sub-GHz-band) for the in-home health care management system. The system assumes a medical care and proactive health management, and a variety of data such as the vital data, the environment data, and the user activity data are collected to a coordinator by using IoT gateways (IoT-GWs). For the transmission scheme between the loT-GWs, we compare two schemes; the conventional FAN scheme and the proposed fast-path scheme. In the FAN scheme, all of the measured data are collected by using the Wi-SUN FAN multi-hop transmission. On the other hand, the proposed fast-path scheme uses both the Wi-Fi and the Wi-SUN FAN, and a part of the data is offloaded to the Wi-Fi from the Wi-SUN FAN. These two schemes are evaluated by computer simulations. In the case that only the vital and environmental data are collected to the coordinator, these data can be collected with the end-to-end (E2E) transmission success rate of 98 % in the proposed fast-path scheme compared with 92 % in the conventional FAN scheme.

In this paper, we propose a dependable source routing scheme for multi-hop networks based on the receiver-initiated media access control (MAC) protocol. In the proposed scheme, multiple candidates of relay terminals can be loaded in routing information, so the route is not specified uniquely. The following two effects are expected to the proposed scheme. The first is the improvement of communication reliability by avoiding disturbed link. Second is the improvement of the delay and current consumption by shortening the waiting time for communication timings. To show the effectiveness of the proposed scheme, we conduct computer simulations that suppose a multi-hop network based on the feathery receiver-initiated transmission (F-RIT) protocol in stable channel conditions. In the evaluation, the data are collected by polling communications, and the proposed scheme is applied to downlink communications. The results show the effectiveness of the proposed scheme that improves the delay by up to 41.3%and current consumption by up to 13.5% under a specific condition for the evaluation.

The wireless smart utility network (Wi-SUN) gets attention as one of the promising wireless networks for the machine-to-machine (M2M) and Internet of Things (IoT) systems. The resource-limited monitoring and management (RLMM) is a profile of the Wi-SUN for the non-Internet protocol (non-IP)-based networks in resource-poor environments. The coordinated sampled listening (CSL) is one of the IEEE 802.15.4e-based low-power media access control (MAC) protocols, and it is a candidate protocol for the RLMM systems. To construct the CSL-based RLMM systems in a variable environment, the communication characteristics should be evaluated theoretically and experimentally. In this paper, we designed a practical CSL protocol for the implementation, and a theoretical analysis scheme to evaluate communication characteristics of the practical CSL is proposed considering with the effect of Acknowledgement (ACK) frames. Furthermore, the practical CSL protocol is demonstrated experimentally using 30 actual Wi-SUN dongles in a radio anechoic chamber. The proposed theoretical analysis results agree well with not only computer simulation results but also experimental results. It means that the proposed theoretical analysis scheme has high practicality and reliability under actual environments. The experimental and theoretical results show that a high communication success rate of over 90 % can be achieved when the data generation rate is lower than 5.0 × 10−3s−1.

The wireless smart ubiquitous network (Wi-SUN) has been attracting much attention as one of the candidates of wireless sensor networks (WSNs) for the Internet-of-Things (IoT). In considering that the Wi-SUN is applied to the IoT system in the environment where the power supply cannot be easily secured, such as structure monitoring systems, it is imperative to establish the technology enabling the Wi-SUN system to operate with only a battery for a prolonged time. The key enabling technology for the low operation in the Wi-SUN system is a low-power media access control (MAC) protocol. The coordinated sampled listening (CSL) protocol is one of the standardized low-power MAC protocol. In this paper, we demonstrate the feasibility of the CSL-based protocol and verify its detailed characteristics by implementing the CSL-based protocol into the actual Wi-SUN dongles to construct the CSL-based low-power networks. The experimental and computer simulation results demonstrate the feasibility and reliability of the CSL-based protocol.

In this paper, a novel cancellation scheme named superposition cancellation technique is proposed by using a superposition modulation technique for the single carrier fullduplex (FD) system. The proposed scheme utilizes the features that a single carrier with the Nyquist filter has no inter-symbol interference (ISI) and the phase-shift keying (PSK) modulation symbol has a constant amplitude to perform the self-interference (SI) cancellation. The proposed scheme can be applied in combination with other conventional cancellation schemes. This means that the cancellation requirement for the conventional cancellation schemes can be mitigated. From the feasibility study with theoretical evaluation and computer simulations, the proposed scheme achieves about 40 dB SI cancellation.

The wireless smart ubiquitous network (Wi-SUN) field area network (FAN) attracts attention as a wireless communication standard for large-scale Internet of Things (IoT) systems. Currently, frequency shift keying (FSK) defined in IEEE 802.15.4 is adopted in the physical layer of the Wi-SUN FAN. To improve the network performance toward next-generation IoT systems, a data rate enhancement scheme for FSK has been proposed. However, there is no evaluation of data rate improvement effect by adopting the data rate enhanced FSK on the transmission characteristics of the Wi-SUN FAN. Besides, introducing the data rate enhanced FSK causes the bandwidth to increase. For multiple systems to coexist in limited frequency bands, it is necessary to achieve high spectral efficiency even when the Wi-SUN FAN adopts the data rate enhanced FSK. In this paper, we evaluate the transmission characteristics of the Wi-SUN FAN adopting the high-speed FSK of 600 kbps by computer simulations. The simulation results show that the system throughput improves by 2.5 times, but the bandwidth also increases by 2.5 times compared to the existing system. Furthermore, we propose highly-dense frequency hopping based on a novel channel arrangement scheme to improve spectral efficiency and compatibility with the existing system design while the data rate enhanced FSK is adopted. The evaluation results show that the system throughput in the proposed scheme is 2.4 times of the existing system while using less than half of the bandwidth compared to the conventional channel arrangement scheme.

IEEE 802.22 is a standardized WRAN (Wireless Regional Area Network) system that operates in TVWS (TV White Spaces) and aims to achieve an effective spectrum utilization. Since IEEE 802.22 offers excellent propagation characteristics in the UHF (Ultra High Frequency) band, it is expected to support a cost-effective wireless communication system in rural areas. To provide a long-distance wireless communication, it is important for the receiver design to compensate a multipath fading attributed to large differences in path lengths, while existing multipath fading channel profiles applicable to IEEE 802.22 has generalization and statistical limitations. To generally and stochastically reproduce the multipath propagation characteristics in an actual wide area environment, an algorithm to obtain a statistical channel model extracted from the field experiment data is required. In this study, we develop a novel channel modeling algorithm based on the conventional S-V (Saleh-Valenzuela) modeling algorithm that offers an approach to model and reproduce the multipath characteristics in an actual environment. The proposed channel modeling algorithm applies a dynamic GEV (Generalized Extreme Value) distribution fitting for the amplitude fluctuation of individual arrival cluster. We also evaluate the channel reproduction performance of the proposed algorithm by computer simulation using channel modeling factors calculated from the experiment result with a FE (Fading Emulator). As a result, by applying the proposed algorithm, the multipath fading characteristics measured in the experiment can be modeled, and its reproducibility is confirmed with regard to relative path power distribution, rms delay spread distribution, and BER characteristics.

Wireless smart utility network field area network (Wi-SUN FAN), which configures very large-scale multi-hop networks, has been standardized to promote interoperable open standards for machine-to-machine (M2M) communication. In the media access control (MAC) layer, Wi-SUN FAN adopts a carrier sense multiple access with collision avoidance (CSMA/CA) and a channel hopping (CH) to avoid interferences between devices. A channel schedule controls the operational channel of CH and it is dominant for both unicast and broadcast transmission performances. In this paper, the impact of channel schedule on the network performance is studied to enhance the unicast transmission throughput. The transmission throughput of a Wi-SUN FAN system in four multiple tandem topologies are evaluated by computer simulations in various channel schedule schemes. The simulation results show that by adopting CH and setting the broadcast interval (BI) coefficient to the optimal value that depends on the network topology, higher unicast throughput can be achieved and the transmission interval of broadcast control frames can be preserved at 131 s. In the case of a multiple tandem topology that consists of 33 devices, by adopting CH and setting the BI coefficient to be 30, the unicast throughput increases by up to 12.2% compared to the case of default parameter configuration recommended in Wi-SUN FAN standard.

Wireless Smart Utility Network Field Area Network (Wi-SUN FAN) is one of the Wi-SUN profiles that is expected to be adopted by many smart devices in advanced smart city infrastructures to provide Machine-to-Machine (M2M) communication in Low power and Lossy Networks (LLNs). The physical and data link layer of Wi-SUN FAN systems is complied with IEEE 802.15.4-2015 to perform multi-hop data transmission. Currently, the implementation of Wi-SUN FAN devices has been initiated. However, the Wi-SUN FAN devices face a serious problem of very slow network configuration. In this paper, the multi-hop network configuration time of the current Wi-SUN FAN devices is measured by the experiment to analyze the factors that cause the slow configuration. The optimization scheme to accelerate the configuration process is discussed and the instant response configuration scheme that further reduces the configuration time is proposed. In addition, the computer simulation is performed to study the trade-off relationship between the configuration time and the percentage of time used in the configuration process. Finally, the appropriate values of the configuration parameters that can complete the configuration process in each hop within 1 minute while minimally deteriorate the transmission performance in both conventional and proposed configuration schemes are determined.

The enhanced universal filtered-DFTs-OFDM (eUF-DFTs-OFDM) has been proposed for reducing the out-of-band emission (OOBE) drastically with low peak-to-average power ratio (PAPR). However, this scheme has high complexity due to the time-domain convolution of LPF. In this paper, we propose a new time-domain windowing function for the universal time-domain windowed-DFTs-OFDM (UTW-DFTs-OFDM) to reduce the OOBE with low PAPR and low implementation complexity by using a time response of the LPF for the eUF-DFTs-OFDM. The performance of the proposed time-domain window function is evaluated by simulation in terms of OOBE, PAPR, block error rate (BLER), and implementation complexity with the LTE uplink parameters. As a result, we achieve almost same performance as the eUF-DFTs-OFDM with the significant reduction of the number of multipliers used for wave-shaping.

In this paper, we propose an analysis scheme of the feathery receiver-initiated transmission (F-RIT) protocol for low power wireless smart utility network (Wi-SUN) system. The proposed analysis scheme is developed taking the turnaround time that deteriorates the transmission performance in implemented protocol under interference environments into account. The proposed theoretical analysis result and simulation result on the Wi-SUN Japan utility telemetering association (JUTA) profile-compliant F-RIT protocol for evaluation shows same tendency. Furthermore, the Wi-SUN JUTA profile-compliant F-RIT protocol is evaluated experimentally using actual Wi-SUN dongles. The experiments under interference environment demonstrate that the collision due to the turnaround time occurs in actual, and it is verified that the theoretical analysis by the proposed analysis scheme is efficient to evaluate the protocol generally.

IBFD (In-Band Full-Duplex) has attracted renewed attentions in recent years along with the improvement of self-interference cancellation technologies because IBFD can ideally double the system capacity. Although there have been various reports applying IBFD to the cellular system, some impair the compatibility with the conventional LTE (Long-Term Evolution) system and some are not evaluated in practical scenario such as a multi-cell environment. In this paper, we propose an advanced DDC (Dynamic-Duplex Cellular) system applying IBFD to all cells in a multi-cell environment. The proposed system suppresses inter-cell interferences among all cells and enhances the system capacity with proper scheduling and power control without information exchange among neighboring cells while maintaining compatibility with the conventional TD (Time division Duplex)-LTE system. Practicality of the proposed DDC system is also evaluated by computer simulation with regard to the enhancement of the user throughput.

Currently, the IAB (Integrated Access and Backhaul) system that offers effective relaying architecture between Donor and UEs (User Equipments) via Node has been discussed in 3GPP for various use cases including mobile relaying scenarios. For applying the IAB system to mobile systems, sub-6 GHz band is used for BL (Backhaul Link) to support wide coverage, and it is preferred to use the same frequency for both BL and AL (Access Link) due to the serious spectrum resource shortage below 6 GHz. However, since the frequency resource is divided into four links by the combination of BL/AL and UL/DL (Uplink/Downlink), system capacity of the sub-6GHz IAB system will be degraded. In this paper, we propose DDC (Dynamic full- Duplex Cellular)-IAB that applies IBFD (In-band Full-duplex) to the sub-6 GHz IAB system to enhance the system capacity. With the system level simulation in a multi-cell environment, the proposed DDC-IAB system improves UL UPT (User Perceived Throughput) between UE and Node and between UE and Donor by 90.2 % and 34.9 %, respectively, and also improves DL UPT between Donor and UE by 39.6 % compared to HD (Half-duplex)-IAB system.

The IEEE 802.22 system was standardized in 2011 as a fixed wireless communication system for regional area networks using TV white-spaces (TVWS). Due to its wide coverage area of 10-30 km, the IEEE 802.22 system is expected as a backbone wireless network system in developing countries as well as a public safety broadband communication system even in leading countries. This wide coverage enables a reduction of the number of base stations, resulting in the initial-cost saving compared to other communication systems. However, previously prototyped IEEE 802.22-based devices have not been deployed for social demonstrations, because there still have difficulties in cost and procurement due to the costly design such as FPGA-based baseband signal processing and specially customized RF components to comply with the strict spectrum limitations by some leading countries. In this paper, we prototype compact and lightweight IEEE 802.22-based radio equipment by applying mixed design using an FPGA and a DSP. Measured transmission spectrum conforms to Ofcom and FCC regulations with a transmit power of +30 dBm and +24 dBm, respectively. Also, measured receiver sensitivity achieves the requirement of the IEEE 802.22 system, and a maximal UDP throughput of 14.86 Mbit/s was obtained on the conditions of PHY mode 16 with a 6 MHz channel bandwidth and a 1/4 CP length.

In this paper, an enhanced universal filtered (UF)-DFT-spread-OFDM (eUF-DFTs-OFDM) is proposed. The conventional UF-DFTs-OFDM can drastically reduce the out-of-band emission (OOBE), which has been the problem of the conventional cyclic prefix (CP)-DFTs-OFDM. However, the conventional UF-DFTs-OFDM degrades the communication quality in long-delay multipath environment due to the frequency-domain ripples derived from extending the rise and fall time of the LPF corresponding to the guard interval (GI). On the contrary, the proposed eUF-DFTs-OFDM achieves significantly low OOBE and high communication quality even in the long-delay multi-path fading environment by applying the CP and the LPF with short rise and fall time. The advantages of the proposed eUF-DFTs-OFDM are discussed by simulating the characteristics of the OOBE, peak-to-average power ratio (PAPR) and block error rate (BLER) with the LTE uplink parameters. As a result, it is confirmed that the proposed eUF-DFTs-OFDM is capable of suppressing the OOBE at the channel edge by 40 dB compared to the conventional CP-DFTs-OFDM. Moreover, the proposed eUF-DFTs-OFDM can improve the ES/N0to achieve BLER= 10-3by about 2 dB for QPSK and 16QAM compared to the conventional UF-DFTs-OFDM. Especially for 64QAM, the proposed eUF-DFTs-OFDM can achieve BLER = 10-3at an ES/N0of 30 dB, even though BLER characteristics of the conventional UF-DFTs-OFDM results in error floor.

The 5G system requires flexible and ultrahigh-efficient spectrum usage, while spectrum efficiency is limited by using the conventional LTE and LTE-Advanced based on cyclic prefix-based orthogonal frequency division multiplexing (CP-OFDM) due to the high out-of-band emission (OOBE). Therefore, new-waveforms for reducing the OOBE are required to improve spectrum efficiency and the authors have proposed universal time-domain windowed OFDM (UTW-OFDM) as one of the new-waveforms for the 5G system. The UTW-OFDM has many advantages such as low-OOBE, low-complexity and high-compatibility with conventional CP-OFDM-based systems. In this paper, we developed a UTW converter enabling a proposed UTW-OFDM-based LTE-downlink (DL) system in real time. By applying the UTW converter to the off-the-shelf LTE-DL system, feasibility of the proposed UTW-OFDM is experimentally evaluated. The experimental results show that the UTW-OFDM suppresses power spectrum density at the channel-edge by about 20 dB and 18 dB for QPSK and 64QAM, respectively, without any throughput deterioration compared to the conventional CP-OFDM-based LTE-DL signal.

This paper proposes a load balancing algorithm for a layer 2 routing (L2R) protocol of IEEE 802.15.4/4g/4e based wireless smart utility network (Wi-SUN) systems to achieve low-power consumption mesh networking. In the conventional link quality based routing method scheme discussed in IEEE 802.15.10 Draft 01, the fairness of cumulative number of sending packets has not effectively been achieved. Therefore, it may cause that many terminals send packets to a certain terminal. In the proposed method, the number of sendings is used to select the path of routing as well as link quality. The performance of the proposed routing method is evaluated by computer simulation. As the result, the proposed scheme can improve the maximum sending ratio that evaluates the cumulative number of sending packets by 59% with no degradation of the average sending times and end-to-end success rate (E2E-SR) compared with the conventional routing scheme that is one of the candidate schemes discussed in IEEE 802.15.10 Draft 01.

In this paper, we propose an enhanced universal filtered orthogonal frequency division multiplexing (eUF- OFDM) to achieve low out-of-band emission (OOBE) while maintaining high communication quality under the long-delay multipath fading environment by combinedly using a cyclic prefix (CP) and a filter with short-transition time. The proposed eUF- OFDM can suppress the OOBE at channel-edge by 25 dB compared to the conventional OFDM. Furthermore, the proposed eUFOFDM improves the signal-to-noise ratio (SNR) to achieve block-error-rate (BLER) = 10-3by 1.3 dB compared to the conventional UF-OFDM under the long- delay multipath fading mobile environment.

In this paper, a novel broadcast protocol is proposed for the receiver initiated transmission (RIT) media access control (MAC) protocol based wireless smart utility network (Wi-SUN) systems. The RIT protocol adopted by IEEE 802.15.4e achieves the low power consumption by switching the short wake-up state and the long sleep state, however, the protocol does not support broadcasting because terminals with the protocol are in the sleep state mostly. In the proposed protocol, terminals follow to adjusted periodical listening instructions that are unicasted, and the broadcasting frame transmitted at the periodical timing. Computer simulations are carried out to evaluate the required time for the layer 2 (L2) address resolution, as a typical case of the proposed broadcast protocol. The evaluation shows broadcasting is achieved by the proposed protocol and it is found that the average required time to finish the L2 address resolution is about 16s when a personal area network coordinator (PANC) performs broadcasting with repeat listen interval of 5.0s and the number of terminals is 100. Also, the evaluation results show that the proposed protocol has the flexibility that achieves broadcasting without setting parameters regardless of the number of terminals. By the proposed RIT based broadcast system, very low-power consumption internet protocol (IP) transmission in the Wi-SUN can be implemented within the permissible delay.

In this paper, the effectiveness and feasibility of the feathery receiver initiated transmission (F-RIT) protocol based wireless smart utility network (Wi-SUN) systems are proved experimentally by developing the actual modules and experimental evaluations. The experimental results show that the F-RIT based Wi-SUN systems can achieve over 90% transmission success rate under the practical automatic meter infrastructure (AMI) specified conditions. Additionally, the transmission failure factors in the experimental results are analyzed for the further improvement of the F-RIT protocol. The results of the analysis indicate that the timeout problem is the main factor of the transmission failures in the F-RIT based Wi-SUN systems.

This paper proposes novel two carrier frequency offset (CFO) estimation schemes to introduce inexpensive oscillators and operate under mobile multipath environments in wide area Wi-SUN systems based on IEEE 802.15.4g. One of the proposed schemes using a moving average low-pass filter (LPF) can compensate CFO within ±20 ppm at 920 MHz completely with simple configuration under condition of mobile and multipath fading environment. The second proposed scheme using the same LPF of the first scheme and artificially designed frequency offset can compensate larger CFO within ±30 ppm at 920 MHz.

This paper proposes a novel ultra-low-power media access control (MAC) protocol, called the feathery-receiver initiated transmission protocol (F-RIT), complied with RIT in the IEEE 802.15.4e standard (15.4e). The proposed F-RIT protocol uses compacted 15.4e MAC frames to reduce power consumption. Additionally, a simplified channel sampling process, called pre-carrier sense (Pre-CS), is introduced to the proposed F-RIT instead of carrier sense multiple access with collision avoidance (CSMA/CA) in 15.4e RIT to improve time utilization efficiency per a channel. The proposed F-RIT can improve the success rate by more than 5-fold relative to the coordinated sampled listening (CSL) protocol, another low-power-consumption protocol of 15.4e, in an environment containing 100 terminals, where each terminal transmits its signal for 100 ms, and the data transmission data occurring 0.01 s−1per a terminal.

This paper proposes an universal time-domain windowed orthogonal frequency division multiplexing (UTW-OFDM) as a novel physical layer signal format for the next generation communications systems such as the 5th generation mobile communication (5G) systems. Most of the conventional wireless communication systems such as the 4th generation mobile communication (4G) systems and WLAN are based on OFDM that has advantage in terms of spectrum efficiency in a band. However, OFDM has also drawbacks such as high out-of-band spectrum emission. Novel physical layer signal formats should be developed to overcome such drawbacks of OFDM for the 5G systems and so on. The proposed UTW-OFDM has high backward compatibility with conventional OFDM based systems such as Long term evolution (LTE) downlink and the out-of-band power emission can be reduced by over 44 dB compared to the conventional OFDM.

TV White Spaces (TVWS) technology allows wireless devices to opportunistically use locally-available TV channels enabled by a geolocation database. The UK regulator Ofcom has initiated a pilot of TVWS technology in the UK. This paper concerns a large- scale series of trials under that pilot. The purposes are to test aspects of white space technology, including the white space device and geolocation database interactions, the validity of the channel availability/powers calculations by the database and associated interference effects on primary services, and the performances of the white space devices, among others. An additional key purpose is to perform research investigations such as on aggregation of TVWS resources with conventional resources and also aggregation solely within TVWS, secondary coexistence issues and means to mitigate such issues, and primary coexistence issues under challenging deployment geometries, among others. This paper provides an update on the trials, giving an overview of their objectives and characteristics, some aspects that have been covered, and some early results and observations.

This paper performs the world's first IEEE 802.11af based Wireless Local Area Networks (WLAN) operating in TV White Space (TVWS) indoor experiment in the Ofcom TVWS pilot program of the UK. The prototype system consists of TVWS Database (WSDB), Registered Location Secure Server (RLSS), and two prototype hardware for an Access Point (AP) and a Station (STA). The developed WSDB qualified by Ofcom TVWS pilot program of the UK. The prototype hardware meets to the transmission spectrum regulation of the European Telecommunication Standards Institute (ETSI). By using the developed system, a trial indoor experiment performed in the building of the King's College London (KCL), Denmark Hill Campus in London, UK. The prototype system and the experiment results show an effectiveness of the IEEE 802.11af and indicate the way to the practical application.

An IEEE 802.11af indoor trial experiment has been conducted in the Ofcom pilot program of the United Kingdom. This paper describes an indoor propagation characterization and throughput estimation method using prototype devices based on the IEEE 802.11af standard. Since the IEEE 802.11af is recent technology for TV white space (TVWS) spectrum sharing, indoor propagation measurements at TVWS band for WLAN usage are very seldom in the previous researches. Path loss model parameters has been extracted for each line-of-sight (LoS) and non-LoS (NLoS) situation on the same floor. Also a fluctuation of measured path loss is analyzed using the log-normal and the extreme value distributions. A developed path loss model is useful for the location design of access points and the interference risk estimation for IEEE 802.11af devices. As another modeling, a throughput estimation model has been developed using the exponential distribution derived from the cumulative probability distribution (CDF) of measured throughputs. By combination of the developed path loss model and the throughput estimation model, throughput can be estimated as a function in each LoS and NLoS situation.

Demand for wireless communication has increased significantly, on the other hand, the frequency band available for wireless communication is scarce. Use of wireless communication in the TV white spaces (TVWS) has been promoted in various countries, and primary user protection is mandatory. Particularly, very strict transmit spectrum mask is configured by FCC in USA. In order to effective use of TVWS, this paper proposes a transmit power control method based on adaptive time-domain windowing processing for orthogonal frequency division multiplexing (OFDM) based wireless communication systems operating in TVWS. The proposed transmit power control scheme provides the appropriate transmit spectrum to meet the required transmit spectrum mask regulation and the maximum throughput under the given environment without any special processing at the receiver side. The proposed scheme will contribute to the realization of the wireless communication systems operating in the TVWS.

Driven by the progress of regulations of TVWS worldwide, IEEE 802.11 started a new Task Group af (TGaf) to pursue extension of traditional Wi-Fi to TV White Spaces (TVWS). Wi-Fi in TVWS offers longer distance and broader bandwidth; while maintaining the same user experience of traditional Wi-Fi systems. It is therefore regarded as one of most promising technologies to exploit the market derived from the new regulations of VHF/UHF bands. In this paper, we present the world's first prototype system of Wi-Fi in TVWS based on the TGaf draft specification. The prototype system verifies the PHY and MAC design of TGaf and the database query protocols that is needed for TVWS operation but not in the scope of TGaf. It is demonstrated that, with sufficiently defined MAC protocol and PHY that meets sharp transmission spectrum mask, the developed prototype supports video streaming on single TV channel while well coexisting with primary TV services in the vicinity.

MIMO 2-way relay network is known as a solution to realize high data rate relay networks. 2-way relaying is possible provided that interference cancellation techniques, e.g. MIMO beamforming or network coding are properly introduced. Many theoretical works on relaying using beamforming exist, but no implementation on real hardware has been reported. These works try to maximize the throughput and the relay node is not allowed to be a data source. Such relaying schemes are not suitable for our targeting networks, e.g. smart utility networks, sensor networks, etc. We implement a simple beamforming scheme that allows the relay node to be a data source. Moreover, most theoretical works assume perfect CSIT without consideration on implementation. We employ RF calibration to obtain CSIT. We evaluate the accuracy of the calibration using the channels measured in real environment, and the result confirms the validity of the method. We also present a demonstration system to show the flexibility of the implemented scheme.

In recent years, wireless mesh network functioning as backbone for other sensor network applications has been attracting much of attention. For realization of a high data rate and reliable mesh network, a synchronized mesh network technology employing OFDM as a block processing scheme has been proposed. However, the conventional scheme is not convenient as it requires network synchronization of all the nodes in the network done before starting data communication. This paper proposes a novel scalable network synchronization scheme where data transmission and network synchronization setup can be done simultaneously. The proposed algorithm is implemented in the developed 950MHz TDD MIMO two-way network prototype hardware, and its behavior is verified.

Shadowing effect caused by obstacles between transmitter and receiver always weakens the signal in wireless communications. Relay technique is proposed as a solution to the problem of shadowing. Various relaying schemes have been proposed in recent literature. However, in most of the works, performance of relaying schemes were evaluated using theoretical channel models which may be far from realistic environment. In this paper, performance of various relaying schemes are assessed by using real propagation data in a shadowing environment. MIMO wideband propagation measurements are performed in an L-shaped corridor with various positions of relay node. Using measurement data, capacity performance of well-known relaying schemes including decode-and-forward, cooperative relay and two-way relay employing network coding are evaluated. Analysis results show the benefits of relay technique against shadowing effect in a real environment as well as give directions about an optimal location to place the relay node. Furthermore, by comparing performance of different relaying schemes, the paper finds that two-way relay employing network coding has superior performance while the introduction of cooperative relay in an environment, where signal strength of direct link is extremely weak, is not efficient.

This paper develops the first prototype hardware for TDD/TDMA two-way multi-hop relay network with MIMO network coding. Since conventional wireless multi-hop relay networks have drawbacks of low data rate, TDD/TDMA two-way multi-hop relay networks have been studied as a solution to realize high data rate recently. In these networks, forward and backward streams are spatially multiplexed by using interference cancellation technology such as MIMO beamforming or MIMO network coding. In this prototype hardware, MIMO network coding and network synchronization scheme are implemented to realize such TDD/TDMA two-way multi-hop relay network in real environment. In the demonstrator using the prototype hardware, each transmitter and each receiver performs network coded broadcast (BC) and MIMO multiple access (MA) respectively. Performance of the demonstrator shows that the TDD/TDMA two-way multi-hop relay network with MIMO network coding can be realized.

This paper proposes novel time-efficient network synchronization schemes for TDD/TDMA based two-way multi-hop relay networks with block modulation. One of the proposed schemes is based on broadcast (BC) timing synchronization. Since this scheme causes network synchronization errors at each receiver, additional guard interval (GI) to compensate the error is introduced. The second proposed scheme is based on both of BC and multiple access (MA) timing synchronization. The additional GI is not required and the time-efficiency is improved because the transmit and receive timing at each node are adjusted to eliminate the network synchronization errors. The second proposed scheme achieves over 98.8% time-efficiency with arbitrary node arrangement, bandwidth, and number of hops when the number of symbols per frame is hundred.

In this paper, a neural network (NN) for peak power reduction of orthogonal frequency-division multiplexing (OFDM) signals is improved in order to suppress its computational complexity. Numerical experiments show that the proposed NN has less computational complexity than the conventional one. The number of IFFT in NN can be reduced to half, and the computational time can be suppressed by 32.7%. From the HDL simulation for FPGA implementation, hardware resouces are approximately suppressed by about 30%.