Munehiro Matsui

69.1-Tb/s (432 × 171-Gb/s) C- and extended L-band transmission over 240 km Using PDM-16-QAM modulation and digital coherent detection

We demonstrate the record total capacity of 69.1 Tb/s with a spectral efficiency of 6.4 b/s/Hz by employing 21.4-Gbaud 16-QAM modulation, blind digital coherent detection, and 10.8-THz ultra-wideband amplification in the C- and extended L-bands.

Ultra-High Capacity WDM Transmission Using Spectrally-Efficient PDM 16-QAM Modulation and C- and Extended L-Band Wideband Optical Amplification

This paper describes ultrahigh capacity transmission based on spectrally-efficient multi-level modulation and wideband optical amplification techniques. 21.4-Gbaud polarization-division multiplexed (PDM) 16-ary quadrature amplitude modulation (QAM) signals are generated by utilizing an optical synthesis technique, wavelength-multiplexed with 25-GHz spacing by optical pre-filtering, and received by an intradyne coherent receiver based on digital signal processing (DSP) with pilotless algorithms. These techniques realize a spectral efficiency (SE) of 6.4 b/s/Hz. Furthermore, a hybrid amplification technique that combines distributed Raman and dual-band erbium-doped amplifiers (EDFAs) realizes 10.8-THz signal bandwidth in C- and extended L-bands. By using these techniques, we successfully demonstrate 69.1 Tb/s transmission over 240 km of low loss pure silica core fibers.

100 × 120-Gb/s PDM 64-QAM transmission over 160 km using linewidth-tolerant pilotless digital coherent detection

We demonstrate 11.2-Tb/s transmission of 12.5-GHz spaced 120-Gb/s PDM 64-QAM signals over 160 km by using a digital coherent receiver with pilotless demodulation algorithms. The spectral efficiency of 9.0 b/s/Hz is the highest reported for 100-Gb/s/ch-class transmission.

A Novel Cooperative Sensing Technique for Cognitive Radio

Cognitive radio, which utilizes frequency effectively, needs a highly reliable sensing technique. Cooperative sensing techniques have been studied to meet this need. However, conventional techniques have a high false alarm rates. To solve this problem, we propose an innovative cooperative sensing technique in which the power levels at several radio stations are multiplied by different weights and added. Whether or not radio waves are present is determined based on this added power level. We used computer simulations to evaluate the proposed technique and demonstrated that it can perform at the required misdetection rate but has a lower false alarm rate than conventional techniques. We also propose an improved technique that takes account of correlated shadowing and is more effective in correlated shadowing environments.

Non-data-aided wide-range frequency offset estimator for QAM optical coherent receivers

We propose and experimentally demonstrate a novel blind frequency offset estimator for coherent quadrature amplitude modulation (QAM) receivers. Its frequency offset estimation range is more than three times the conventional estimation range.

Intermodal group velocity dispersion of few-mode fiber

The intermodal dispersion of few-mode fiber limits the propagation distance of mode division multiplexing (MDM). We numerically investigate the propagation constant and group velocity of few-mode fibers. The refractive index profile of few-mode fibers should be designed to achieve long and dense MDM transmissions with digital coherent receivers.

Wide-range and fast-tracking frequency offset estimator for optical coherent receivers

A blind spectrum-based frequency offset estimator with fast tracking time is presented. A receiver using the proposed estimator to eliminate the frequency ambiguity of the mth power algorithm can achieve precise estimation over a wide frequency range.

Network controlled frequency channel and bandwidth allocation scheme for IEEE 802.11a/n/ac wireless LANs: RATOP

The first giga-bit class wireless local area network (wireless LAN) below 6 GHz frequency (the IEEE 802.11ac standard) is attracting attention due to its capability of handling much more of the rapidly growing data traffic. The increased density of wireless LAN access points (APs), however, has induced inter-cell interference that severely degrades system performance. This problem seems to be getting worse with the increase of 802.11n- and 802.11ac-based APs, which establish basic service sets (BSSs) with wider channel bandwidths. In order to mitigate this problem, we propose an efficient radio resource allocation scheme called RATOP that can be applied to a managed wireless LAN system with a central coordinator. On the basis of channel monitoring results, capability, and data traffic information obtained from APs, the central coordinator computes the quasioptimal frequency channel and channel bandwidth of each AP in such a way that the given utility function is maximized. Numerous simulations with UDP traffic flows on the coexistence scenarios of 802.11a/n/ac show that the RATOP works well and reduces the number of overlapping BSSs by 65%-89%. As a result, the RATOP improves the minimum throughput and fairness among throughput of APs even when there exist foreign APs of other network domains that cannot be controlled by the coordinator.

Performance Evaluation of Reconfigurable Processor for SDR Mobile Terminals and SDR Base Station using Autonomous Adaptive Control Technology

It is expected that software defined radio (SDR) technology that can access multiple wireless communication systems will be applied to mobile terminals and base stations as a beyond 3G wireless system. An SDR wideband mobile terminal must be capable of high-speed data processing and low power consumption. To evaluate the performance of reconfigurable processors for SDR wideband mobile terminals, we developed software that runs on a reconfigurable processor for the IEEE 802.11a wireless LAN baseband part, and evaluated the performance of the reconfigurable processor. Moreover, we describe the system design of the new SDR base station, which uses autonomous adaptive control technology. We evaluated the characteristic performance through computer simulations, and confirmed its efficiency

Gain/phase imbalance compensation for multi-band quadrature receivers

This paper presents a compensation technique for the gain/phase imbalance of quadrature demodulators for direct conversion receivers. The power measurements for the imbalance estimation can be done in less than ten symbol periods of the test signals. This means that the compensation method does not need many iterative cycles using the least mean square method or discrete Fourier transform that previous methods need. Experimental results show that the differences between the estimated and actual values are small: the gain imbalance was 0.3 dB, and the phase imbalance was 1.1/spl deg/.