Takayoshi Tashiro

Performance evaluation of mobile front-haul employing ethernet- based TDM-PON with IQ data compression [Invited]

In this paper, we experimentally and numerically evaluate the performance of a common public radio interface (CPRI) over a time division multiplexed passive optical network (TDM-PON) system for accommodating densely deployed small cells in centralized-radio-accessnetwork- based future radio access. A prototype of the CPRI over TDM-PON is developed by using Ethernet-based TDM-PON. Experimental results showed that its synchronization accuracy and latency meet the requirements of a mobile front-haul using CPRI by the implemented delay jitter reduction and low-latency bandwidth allocation techniques. An in-phase and quadrature (IQ) data compression technique is also implemented on the system to enable a higher accommodation of remote radio heads. Experiments confirmed that the compression technique meets open radio equipment interface standards in terms of latency and signal quality degradation. Numerical results showed that the technique with a 0.45 compression ratio increases the number of supportable remote radio heads from 3 to 7 for a mobile front-haul with a 100 μs latency limitation.

Mobile front-haul employing ethernet-based TDM-PON system for small cells

We develop a mobile front-haul prototype based on TDM-PON (10G-EPON). The system can accommodate 3 CPRI option-3 links and 7 compressed CPRI option-3 links with reasonable latency under 100 μs.

Transmission Performance Investigation of RF Signal in RoF-DAS Over WDM-PON With Bandpass-Sampling and Optical TDM

The radio over fiber (RoF)-distributed antenna system (DAS) over a wavelength division multiplexing-passive optical network (WDM-PON) with multiple input multiple output (MIMO) employing bandpass-sampling and optical time division multiplexing (TDM) techniques has been proposed to realize next generation broadband wireless access with higher throughput and its preliminary feasibility has been confirmed. To investigate the performance of bandpass-sampled and time domain multiplexed optical signals, and enhance the transmission performance in the wireless link of the RoF-DAS over WDM-PON, we perform two-tone signal transmission experiments with 2.4 GHz band radio frequency (RF) signals and analyze the RF carrier power, third-order intermodulation distortion (IMD) power and noise power. The analysis results confirmed that the nonlinearity of the proposed system is mainly caused by a lithium niobate-Mach-Zehnder modulator (LN-MZM) as with the other RoF systems and that the dominant noise components are the signal-spontaneous beat noise arising from the amplified spontaneous emission (ASE) of two erbium doped fiber amplifiers (EDFAs) and the signal-signal beat noise caused by the interference between the optical TDM pulses. The latter is the specific noise component in the proposed system. In addition, we clarify the principle of the signal-signal beat noise generation and report that the signal-spontaneous beat noise can be reduced by the gain optimization of the two EDFAs.

Experimental demonstration of RoF-DAS over WDM-PON with bandpass-sampling and optical TDM techniques

This paper reports the demonstration of a radio over fiber (RoF) - distributed antenna system (DAS) over a wavelength division multiplexing - passive optical network (WDM-PON) with multiple input multiple output (MIMO) by employing bandpass-sampling and optical time division multiplexing (TDM) techniques to realize next generation broadband wireless access with a gigabit-class throughput. We experimentally evaluate the performance of two optical transmissions of radio frequency (RF) signals, which are multiplexed 2.4 and 5GHz bands 802.11n RF signals in the time-domain and distributed 2.4GHz band 2×2 MIMO 802.11n RF signals with 2 channels WDM.

Small cell configurations and capacity in RoF-DAS over WDM-PON system

This paper addresses the wireless channel capacity in small cells provided by RoF-DAS over WDM-PON that can increase the capacity in a small cell with RoF entrance link and MIMO distributed antenna. Considering the SNR of the RF signal transmitted in the RoF entrance network and the interferences among wireless cells, computer simulation results show the optimized cell size to maximize the MIMO channel capacity.

Proposal of adaptive wireless cell configuration for RoF-DAS over WDM-PON system

Radio on fiber (RoF) - distributed antenna system (DAS) over wavelength division multiplexing - passive optical network (WDM-PON) with multiple - input multiple - output (MIMO) has been proposed as a next generation radio access network (RAN). This system employs optical time division multiplexing (OTDM) over one WDM channel to multiplex and transmit various types of wireless interfaces such as 3.9G, Wireless LAN and WiMAX. A combination of star and bus topologies has employed to cover a wider service area. The optical transmission loss is caused notably at remote base stations (RBSs) quipped on a WDM bus link. The loss is relatively small, but at the RBS far from the center station (CS), the RBS suffers the large accumulated loss, so the reduction of cell size provides the increasing of the number of RBSs, causes the degradation of the SNR of RoF link. This paper addresses this trade-off problem, and considers the application to the actual service area by the channel capacity investigation of RoF-DAS over WDM-PON with computer simulation. Then, this paper focuses on the flexibility of RoF-DAS over WDM-PON, considers the adaptive wireless cell configuration according to population fluctuations of day and night, or densely populated areas and sparsely populated areas, respectively.

Proposal of super low power consumption detector for emergency communication downstream system in FTTH

This paper discusses an optical access system that enables emergency voice communication when a power failure occurs in a users house, and we also propose a super low power consumption detector that consists entirely of passive devices. And we present applied techniques that comprise sub-carrier multiplexing for user multiplexing/demultiplexing and a new passive detector for signal regeneration driven solely by the transmitted optical signal power. Then we confirm the feasibility of the system experimentally by using a prototype detector that has 8-channel selectivity. We report the realization of the intended detector functions that we achieved by back-to-back simulated voice signal regeneration.

An Optical Access Network System without a Power Supply Using Blind Speech Separation and a Loopback Technique

This paper proposes an optical access system that enables voice communication services to continue when a power failure occurs. In particular, we propose applying a digital signal processing technique namely blind speech separation (BSS) to an optical multiple access system for demultiplexing randomly mixture signals received from an upstream user. We present a brief overview and the target of proposed system and describe the key technique, namely the BSS procedure. We then report system feasibility studies for the first step of a numerical simulation (assuming two wavelengths and three users) and experimental tests (assuming two wavelengths and two users) using actual sample voice signals. We confirmed that separation was realized by using a subjective assessment that consisted of listening to obtained signals.