Ryuhei Funada

Beam Codebook Based Beamforming Protocol for Multi-Gbps Millimeter-Wave WPAN Systems

In this paper, we propose a feasible beamforming (BF) scheme realized in media access control (MAC) layer following the guidelines of the IEEE 802.15.3c criteria for millimeter-wave 60GHz wireless personal area networks (60GHz WPANs). The proposed BF targets to minimize the BF set-up time and mitigates the high path loss of 60GHz WPAN systems. It is based on designed multi-resolution codebooks, which generate three kinds of patterns of different half power beam widths (HPBWs): quasi-omni pattern, sector and beam. These three kinds of patterns are employed in the three stages of the BF protocol, namely device-to-device (DEV-to-DEV) linking, sector-level searching and beam-level searching. All the three stages can be completed within one superframe, which minimizes the potential interference to other systems during BF set-up period. In this paper, we show some example codebooks and provide the details of BF procedure. Simulation results show that the setup time of the proposed BF protocol is as small as 2% when compared to the exhaustive searching protocol. The proposed BF is a complete design, it re-uses commands specified in IEEE 802.15.3c, completely compliant to the standard; It has thus been adopted by IEEE 802.15.3c as an optional functionality to realize Giga-bit-per-second (Gbps) communication in WPAN Systems.

A Virtual Time-Slot Allocation Throughput Enhancement Scheme with Multiple Modulations for a Multi-Gbps Millimeter-Wave WPAN System

This paper proposes a Virtual Time-slot Allocation (VTSA) throughput enhancement scheme with multiple modulation methods to realize a multi-Gbps time division multiple access (TDMA) wireless personal area network (WPAN) system in a realistic millimeter-wave residential multipath environment. The VTSA scheme allows multiple communication links in the network to simultaneously use the same time-slot, thus increases system throughput. Additionally, by coupling to higher-order modulation schemes, higher data rate can be achieved. The combination of both is found to be capable of realizing a multi-Gbps WPAN system. However, the employment of the VTSA scheme causes the generation of co-channel interference (CCI) in the system, and CCI is found to affect the modulation schemes differently. This paper investigates the tradeoff parameters between varying CCI due to the employment of the VTSA scheme, and the higher-order modulations applied. As a result, it is found that the VTSA scheme is capable of increasing 30% of the system throughput. It is also found that in low CCI environment, 16QAM offers the highest achievable system throughput, whereas when CCI becomes higher, the more-robust BPSK offers the highest throughput.

A Multi-Gbps Millimeter-Wave WPAN System Based on STDMA with Heuristic Scheduling

This paper proposes a spatial time-division multiple access (STDMA) throughput enhancement scheme for a multi-Gbps millimeter-wave (mmWave) wireless personal area network (WPAN) system. The system design includes in the medium access control (MAC) layer, an interference-monitoring mechanism and a heuristic TDMA time-slot scheduling engine, and in the physical (PHY) layer, a Reed-Solomon (RS) coded phase-shift keying (PSK) system with selective Rake reception over a realistic 60GHz multipath propagation channel. The theoretical analysis of the throughput and error performance is verified by Monte Carlo simulations. Firstly, it is found that the proposed STDMA scheme is capable of improving system throughput as much as 100%. Secondly, the co-channel interference (CCI) in a communication link has to be controlled at/below -15dB in order to achieve the optimum system throughput. Lastly, different tolerable CCI levels to meet respective application requirements are determined.

Physical layer design and performance analysis on multi-Gbps millimeter-wave WLAN system

60 GHz millimeter wave technology has become an attractive solution for wireless communication in the most recent market. In the draft of IEEE 802.11ad standard, two modulation schemes are being considered in the design of physical (PHY) layer, namely, Single-Carrier (SC), and Orthogonal Frequency Division Multiplexing (OFDM). In this paper, the error performances of both coded modulation schemes under different channel models with hardware impairment are investigated. This hardware impairment includes non-linear distortion induced by 60 GHz power amplifier (PA) and phase noise of 60 GHz Phased Locked Loop (PLL) circuit. The channel models include Line-of-Sight (LOS) and Non-Line-of-Sight (NLOS) conference room models. Simulation results demonstrate that OFDM requires a much higher back-off power than SC to achieve the system requirement. In a realistic 60GHz channel based on measurements provided by 802.11ad, OFDM has gained better performance than SC with hardware impairment under NLOS situation using directional antennae.

Multiple-QR-Decomposition Assisted Group Detection for Reduced-Complexity-and-Latency MIMO-OFDM Receivers

We propose a new multiple-QR-decomposition assisted group detection (multi-QRD-GD) algorithm for the development of reduced-complexity-and-latency multi-input multi-output (MIMO) orthogonal frequency division multiplexing (OFDM) receivers. In addition, we investigate an effect of adaptive grouping (AG) based on received signal-to-noise power ratio for multi-QRD-GD. In this paper, we describe the functions of the multi-QRD-GD algorithm and AG scheme. Then, we compare bit error rate (BER) performances of the proposed multi-QRD-GD and conventional detection algorithms by computer simulations. In addition, we compare the computational complexities of the algorithms

Selection of modulation and coding schemes of single carrier PHY for 802.11ad multi-gigabit mmWave WLAN systems

This paper presents the system design method to determine the modulation and coding schemes according to the given usage models of single carrier transmission in millimeter wave Wireless LAN systems. Various modulation and coding combinations are compared and analyzed based on the BER performance over both AWGN and fading channels. The effects of hardware impairments including power amplifier non-linear effects and phase noise, etc., are considered as well. The system design strategy provides a guideline for the selection of modulation and coding schemes in practical which can fulfill the realistic system requirements.

Performance analysis of low duty FSK system for Smart Utility Network

This paper presents the performance analysis of a realistic Smart Utility Network (SUN) system with low duty signaling design. The main focus of this paper is to evaluate the performance of the SUN system based on the specifications in an on-going industrial standardization activity, the IEEE 802.15.4g. For this purpose, a theoretical framework is constructed to model the transceiver with low duty signals over a realistic SUN channel based on actual measurements. The theoretical framework provides the models of multiple access interference (MAI) and inter-symbol interference (ISI). To align the analysis with actual industrial requirements, the developed framework is substituted with parameters from the IEEE 802.15.4g specifications. As a result, it is found that the low duty system (i.e. 0.1%) is capable of supporting up to 100 users in a single network. Additionally, by reducing the duty factor (e.g. from 1% to 0.1%), a 2-digit performance improvement (e.g. bit error rate (BER)=10–5 to BER=10–7) can be achieved as compared to the requirement of IEEE 802.15.4g specifications (i.e. BER ≈ 10–5).

Exact Error Probabilities for MRC in Frequency Selective Nakagami Fading with ISI, CCI and ACI

An exact expression of error rate is developed for maximal ratio combining (MRC) in an independent but not necessarily identically distributed frequency selective Nakagami fading channel taking into account inter-symbol, co-channel and adjacent channel interferences (ISI, CCI and ACI respectively). The characteristic function (CF) method is adopted. While accurate analysis of MRC performance cannot be seen in frequency selective channel taking ISI (and CCI) into account, such analysis for ACI has not been addressed yet. The general analysis presented in this paper solves a problem of past and present interest, which has so far been studied either approximately or in simulations. The exact method presented also lets us obtain an approximate error rate expression based on Gaussian approximation (GA) of the interferences. It is shown, especially while the channel is lightly faded, has fewer multipath components and a decaying delay profile, the GA may be substantially inaccurate at high signal-to-noise ratio.

Virtual Time-Slot Allocation Scheme for Throughput Enhancement in a Millimeter-Wave GBPS WPAN Cross Layer Design

This paper proposes the Virtual Time-slot Allocation (VTSA) scheme for throughput enhancement to realize a Gbps-order time division multiple access (TDMA) wireless personal area network (WPAN) system in a realistic millimeter-wave residential multipath environment. Conventional TDMA system allocates each time-slot to only one communication link, which is insufficient to achieve Gbps-order throughput, particularly in severe channel conditions of multipath environment. In this paper, the proposed VTSA scheme enables a single time-slot to be reused for multiple communication links simultaneously (hence the name virtual), thus significantly increases system throughput. However, this generates co-channel interference (CCI) among the communication links occupying the same time-slot. The proposed cross layer VTSA scheme is therefore designed to be able to schedule the sharing of time-slots among multiple communication links, and at the same time monitor to minimize performance degradation due to CCI. Two time-slot reuse methods are proposed and compared in this paper, namely the minimum-CCI slotting method and the random slotting method. As a result, it is found that the VTSA scheme is capable of increasing the system throughput as much as approximately 30% in the additive white Gaussian noise (AWGN), line-of-sight (LOS) and the nonline-of-sight (NLOS) multipath channel. It is also found that the minimum-CCI slotting method has 10% better performance as compared to the random slotting method.

A guard band aggregation scheme for cognitive radio using TV white space

Cognitive radio based wireless systems using TV white space have been attracting a lot of attentions. In the cognitive radio systems using TV white space, it is desirable to secure a control channel to exchange the information on the availability of white space and the frequency resource such as the frequency channel and the bandwidth. In addition, it is necessary to secure minimum frequency resource for communications if TV white space is unavailable even though TV white space is used on an opportunistic basis. In order to solve these problems, this paper proposes a guard band aggregation scheme, which aggregates the multiple guard bands between digital TV signals and uses them for a control channel and/or a communication channel. This paper shows the performance evaluation results of the digital TV signals when the guard band is used by the proposed scheme. Furthermore, it discusses the permissible transmitting power and occupied bandwidth to avoid the performance degradation of the digital TV signals.