The S[ *-S0 absorption spectrum of jet-cooled azulene has been observed by two-color population-labeling spectroscopy. The depopulation of the S0 00 level induced by the S, <-S0 transition with laser light iq was monitored by observing the depletion of the fluorescence from the S2 state excited by another laser light iq or by observing the depletion of the ion current resulting from the one-photon resonant two-photon ionization of the S0 00 level molecule with iq. The magnitude of the homogeneous broadening of the 0°band in the St *-S0 transition was found to be 4-5.5 cm-1, from which the rate of the internal conversion in the S, state was estimated to be 1 X 1012 s_l. On the basis of the vibrational frequencies in the S] state, it is suggested that a great difference in the potentials of low-frequency modes between S0 and Si is responsible for the large internal conversion rate.
This paper addresses a multiple-symbol differential detection scheme for 16 DAPSK. At the outset, conventional differential detection of 16 DAPSK is scrutinized analytically. As a result, it is seen that the energy penalty of differential amplitude detection compared with ideal coherent detection is larger than that of phase detection. Then, to improve the overall performance of 16 DAPSK, an MLSE algorithm is proposed for a large C/N as well as a suboptimum algorithm. Both allow multiple-symbol differential amplitude and phase detection. Their performances also are evaluated through computer simulation.
Aiming at actual evaluation of IMT-Advanced system performance using field tests, this paper presents a developed IMT-Advanced testbed system with transmission bandwidth of 100 MHz. IMT-Advanced supports the "new capability of systems beyond IMT-2000" as indicated by the ITU-R van diagram [1] and requires a peak data rate of 1 Gbps with low mobility. In consideration of the enhanced IMT-2000 systems undergoing standardization, orthogonal frequency division multiple access (OFDMA) with multi-input multi-output (MIMO) are also promising technologies in the IMT-Advanced system. In addition, in order to meet the requirements for IMT-Advanced, the system seems to have about 100 MHz bandwidth with the aid of MIMO transmission. The developed system is based on the above prediction regarding the IMT-Advanced era, which is a more reliable prediction compared with previous studies, and the goals of this development are to provide a more realistic transmission performance, judgment criteria for operators introducing new air interfaces, and to explore new applications. In addition, the testbed enables us to conduct feasibility studies of rotational OFDM (R-OFDM) and the twin turbo decoder, which is our previous work [2][3]. This paper performs pre-experiments before field tests, and verifies that the testbed transmits signals with 100 MHz bandwidth and the coverage providing a throughput of more than 100 Mbps without MIMO will reaches about 650 m.
Channel occupancy is key information to realize efficient operation of the wireless system. Channel occupancy can be defined as the time occupancy ratio in the case of Wireless LAN (WLAN). We propose a novel passive method to estimate the time occupancy ratio of WLAN. The proposed method produces greater improvement in estimation accuracy compared with that of conventional methods. In this paper, we introduce the definition of the time occupancy ratio as the utilization index of a WLAN radio resource. Then, details of the proposal are introduced. Finally, the excellent evaluation results executed on an experimental system are introduced even when many loss packets exist.
This paper presents an experimental evaluation of open-loop precoding MIMO (Multiple Input Multiple Output) using a testbed targeted at IMT-Advanced systems. Open-loop MIMO is realized by applying Rotational OFDM (R-OFDM), that is previously proposed by authors, to MIMO transmission. MIMO R-OFDM is more robust with respect to correlated channels than conventional open-loop MIMO-OFDM, because it optimizes the distances between the constellation points using simple phase rotation. The angle of phase rotation depends on the modulation orders and coding rate, hence the receiver does not need to feed the CSI (Channel State Information) back to the transmitter. In this paper, MIMO R-OFDM is implemented in a testbed targeted at IMT-Advanced systems, it is then evaluated experimentally and by computer simulations. The results of the evaluation reveal that MIMO R-OFDM is effective in correlated channels, and the gain in terms of the CIR (Carrier to Interference Ratio) with respect to conventional MIMO OFDM to achieve PER (Packet Error Rate) = 0.01 is about 1.5 dB when MIMO R-OFDM is used in correlated channels.
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