Ryota Kimura

A design of single carrier based PHY for IEEE 802.15.3c standard

This paper proposes an air interface for ultra high-speed millimeter wave (60 GHz) systems which have been under standardization process at IEEE 802.15.3c: the proposed channel plan permits ease of portable device implementation employing the major crystal oscillator used in CDMA cellar phones. The proposed transmission modes offer much greater scalability, covering from several tens Mbps to over 4 Gbps. The proposed preamble employs Golay codes, providing sufficient robustness against wireless environment being subject to the characteristics of millimeter wave with reduced hardware complexity. Common mode is a novel technique to communicate with single carrier (SC) and OFDM camps with multi rates up to around 1.5 Gbps. This technique gives the proposed systems easy expandability from SC to OFDM or other SCs and vice versa.

Hardware Impairments on LDPC Coded SC-FDE and OFDM in Multi-Gbps WPAN (IEEE 802.15.3c)

The multi-Gbps wireless personal area network (WPAN) using 60-GHz is being standardized in the task group of IEEE 802.15.3c. In the physical (PHY) layer design, there are two competitive techniques, one is orthogonal frequency division multiplexing (OFDM) and the other is single-carrier frequency-domain equalization (SC-FDE), a.k.a., single-carrier block transmission (SCBT). This paper compared the performance of low-density parity-check (LDPC) coded OFDM and SC-FDE under hardware impairments including analog-to-digital converter (ADC) resolution, non-linear distortion induced by 60- GHz power amplifier (PA), and phase noise of 60-GHz PLL circuits. The simulation results show that SC-FDE has much better performance than OFDM under hardware impairments of 60-GHz devices and circuits.

Golay sequence aided channel estimation for millimeter-wave WPAN systems

In order to design a simple and highly accurate channel estimator for wireless personal area network systems, this paper proposes Golay sequence aided channel estimation. To evaluate the performance of proposed channel estimation, bit error rate performance of single-carrier transmission with frequency-domain equalization has been analyzed by computer simulation. When 8PSK modulation and Reed-Solomon coding RS(255, 239) as forward error correction are used, the proposed Golay sequence aided channel estimation works very well in millimeter-wave and non line-of-sight fading environments with a 1.8 dB degradation of Eb/N0 at 10-6 of bit error rate against the ideal channel estimation, which is practically acceptable. Moreover, comparing with Chu sequence aided channel estimation, the proposed Golay sequence aided channel estimation improves 0.4 dB of Eb/N0 at the bit error rate while achieving much less hardware than Chu sequence aided one, which is very important for mobile terminal applications.

Performance Evaluation of Time Alignment Control under High-Mobility Environment for Dynamic Parameter Controlled OF/TDMA

This paper proposes a time alignment control (TAC) for reducing an influence of multiple access interference (MAI) due to propagation delays (PDs) in uplink transmission from multiple mobile stations (MSs) to an access point (AP) for an orthogonal frequency division multiple access (OFDMA) based mobile communication system. In addition, this paper presents our evaluation of the proposed TAC as applied to dynamic parameter control orthogonal frequency and time division multiple access (DPC-OF/TDMA) which has been suggested for use in new generation mobile communication system. This paper also proposes several formats for an activation slot (ACTS) in which the GIs are lengthened in order to avoid the MAI because the TAC cannot be performed yet in an initial registration of the MSs. Computer simulation elucidates that lengthening the GIs of data symbols in the ACTS adequately to compensate a maximum delay improves the transmission performance of the ACTS at the initial registration without PDs compensation. The simulation also elucidates that the proposed TAC is performed to reduce the influence of the MAI effectively and that updating the estimates of the PDs every certain period is needed to compensate the PDs accurately under high-mobility environment.

Adjacent channel interference resistance of a multi-Gbps millimeter-wave WPAN system

This paper investigates the adjacent channel interference (ACI) resistance of a multi-Gbps single carrier wireless personal area network (WPAN) operating in the 60 GHz millimeter-wave band. The significance of performance degradation due to ACI is investigated corresponding to varying factors such as types of modulation and radio frequency (RF) hardware impairments. The level of modulation scheme is found to change the system resistance against ACI considerably. RF hardware impairments such as power amplifier (PA) non-linearity and phase-locked loop (PLL) phase noise are also major factors affecting ACI generation. The tolerable ACI for WPAN system design is defined as the ACI that causes 0.5 dB degradation in required signal to noise ratio (SNR) at bit error rate (BER)=10-6. It is found that for a system employing pi/2 binary phase shift keying (BPSK) with PA output backoff (OBO)=3 dB, ACI=13.5 dB causes 0.5 dB BER degradation. For systems employing quadrature phase shift keying (QPSK) modulation, the tolerable ACI with PA OBO=3 dB and 5 dB are observed at 9 dB and 15 dB, respectively. For modulation schemes with higher levels such as the 16-quadrature amplitude modulation (QAM) system with PA OBO=3 dB and 5 dB, the tolerable ACI of 1 dB and 5 dB are observed. Next, the maximum ACI resistance is defined as the tolerable ACI by the system before the BER performance degrades and saturates towards 0.5. The performance of pi/2-BPSK system with PA OBO=3 dB has maximum resistance against ACI up to 25 dB before the BER saturates towards 0.5. Similar performance can be observed in QPSK system, but with PA OBO increased to 5 dB. Systems with 16-QAM are found to saturate to BER=0.5 beyond ACI=10 dB. Additionally, the presence of PLL phase noise is found to severely compromise the system performance particularly those with higher modulation levels. ACI as low as 0 dB is found to cause error floor to 16-QAM systems.

Preamble Design for Millimeter-Wave Single Carrier WPANs

In this paper we present preamble design for millimeter-wave single carrier wireless personal area networks. Several factors are considered for a successful preamble design, such as sequence complexity, operation range, associated delay, robustness to frequency offset. Complementary Golay sequences are selected, which combine flexibility and performance. Simula- tion results indicate at optimum threshold level, it is possible to reduce both false alarm probability and miss detection probability less than 10 �3 in non-line-of-sight channels.

Operation Range Estimation of Reed-Solomon Coded SC-FDE System in 60-GHz WPANs

60-GHz band is a popular choice of industry for next generation wireless personal area networks, which will enable data rates in the order of Gbps. Single-carrier frequency domain equalization (SC-FDE) systems are proposed to obtain such high data rates in low-power and low-cost consumer products. In this paper, we are suggesting to use simple zero- forcing equalization to reduce the complexity requirement. We test system performance through simulations and find associated range of the WPAN. Our simulations take into account non-line- of-sight (NLOS) multipath channel model, channel estimation errors and RF impairments of phase noise and power amplifier distortion, to obtain realistic results. Our results show zero- forcing equalization can be employed in applications robust to delay such as file transfer between PCs and peripherals up to 4 meters. This result encourages the usage of 60-GHz band in low-power devices such as cellular phones and cameras. For applications which are sensitive to delay such as video streaming, more complex MMSE equalizer is required.

Constructing Network Slices with Locator/ID Split and Locator Division for 5G Core Network

The 5G core network will employ network slices, logical networks over physical infrastructure, each of which provides a specific service. There are two typical methods for network slicing: the hop- by-hop method using SDN and the edge-overlay method using Layer 2 over Layer 3 (L2 over L3) tunneling. In the hop-by-hop method, migration from the existing infrastructure is difficult and the SDN controller will become a single point of failure. In the edge-overlay method, tunneling causes header overhead and throughput degradation. This paper proposes a network slicing method without using SDN nor tunneling for the 5G core network using IPv6. In the proposed method, the lower 64-bit part of an IPv6 address (the node identifier) identifies a node and the upper 64-bit part (the locator) specifies the subnet to which the node is attached. This approach is suitable to support mobility management without tunneling such as MocLis. The slice identifier and the subnet number in the slice are embedded within the locator. Thus, the proposed method avoids the problems of system migration, a single point of failure, header overhead, and throughput degradation. In the proof of concept prototype, a Docker container is used as a virtual node in a network slice and a MPLS label-switched path is used as a virtual link between virtual nodes. TCP Throughput evaluation shows that the proposed method is superior to the edge-overlay method.

Channel estimation with scattered pilots in GFDM with multiple subcarrier bandwidths

This paper proposes a channel estimation scheme with scattered pilots in generalized frequency division multiplexing (GFDM) with multiple subcarrier bandwidths. In the proposed scheme, the pilot symbols are assigned to narrow bandwidth subcarriers. Thus, it is possible to avoid inter-subsymbol interference that is inevitable in GFDM with unified bandwidth subcarriers. On a GSM-TU channel, the mean square error (MSE) of the proposed GFDM is equivalent to that of the OFDM and bit error rate (BER) performance for QPSK symbols is about 1dB better than that of the conventional GFDM at a BER of 10−3.

GFDM with Different Subcarrier Bandwidths

This paper proposes a generalized frequency division multiplexing (GFDM) modulation scheme that transmits a signal with different subcarrier bandwidths. In a receiver, the GFDM signal is demodulated by using a zero forcing (ZF) algorithm or a minimum mean square error (MMSE) algorithm and the BER performance of these algorithms is related to the condition number of a modulation matrix. This matrix can be optimized by adjusting the roll-off factor of subcarrier filters. It is shown that the performance of the proposed GFDM is about 0.02 dB better than that with a roll-off factor of 0 at a BER of 10^(-3) on an AWGN channel. On the other hand, on the multipath fading channels, the BER performance improves as the subcarrier bandwidth increases because of frequency diversity.