AQAM under high time delay spread conditions

An analysis process is described for adaptive quadrature amplitude modulation(AQAM)of constant-power constant-symbol-rate over frequency-selective Rayleigh fading channels with inter symbol interference(ISI)and Gaussian noise.The delay spread resistance of the AQAM scheme is put forward by studying its average throughput and average bit-error-rate(BER),both of which can be expressed as functions of two variables,the ratio of root mean square(RMS)delay spread to symbol period and the ratio of average symbol energy to noise.Average throughput reacts regularly to the latter,whereas it does not react to the former.The AQAM scheme is highly superior in the delay spread resistance in comparison with the fixed modulation modes.Gains of the AQAM scheme over the fixed modes become more significant as the delay spread becomes severer or the average throughput decreases.

Analysis for MIMO correlated frequency-selective channel in the presence of interference

The space time spreading, superimposed training sequences, and space-time coding are used to present a multiple input and multiple output （MIMO） systems model, and a closed-form of average error probability upper bound expression for MIMO correlated frequency-selective channel in the presence of interference （co-channel interference and jamming signals） is derived. Moreover, the correlation at both ends of the wireless link that can be incorporated equivalently into correlation at the transmit end is also derived, which is significant to analyze space-time link algorithm of MIMO systems.

Optimal design of basic pulse waveforms for THSS UWB radio systems

Ultrawide bandwidth (UWB) radio, a very promising technique carrying information in very short basic pulses, has properties that make it a viable candidate for short-range wireless communications. In this paper, several short-pulse waveforms based on Gaussian genetic monocycle as well as Gaussian pulse waveform, as candidates of basic UWB pulse waveforms, are firstly proposed and investigated. Their spectrum characteristics, bit transmission rate (BTR), and bit error rate (BER) performance in AWGN channel using time hopping spread spectrum (THSS) and pulse position modulation (PPM) are simulated and evaluated. The numerical results are compared and show that the basic pulse waveforms determine the spectrum characteristics of UWB signals and have much effect on the performance of UWB radio system. The performance of UWB radio system achieved by the proposed basic pulse waveforms is much better than that of UWB radio system realized by other used basic pulse waveforms under the uniform conditions. Also, the polarity of these short basic pulses does not affect the performance of UWB radio system.

Characterization of 3-inch photomultiplier tubes for the JUNO central detector

Background Jiangmen Underground Neutrino Observation(JUNO)is one of the largest experimental facilities for neutrino detecting.As its main structure,the central detector contains 20 kiloton liquid scintillator filled in an acrylic shell,and there are 18,00020-inch photomultiplier tubes(PMTs)and 25,0003-inch PMTs covering the shell.Purpose As an independent photon detection system,3-inch PMTs have been required to have excellent resolution for the single photoelectron detection,high quantum efficiency,small transit time spread and low dark noise rate.Methods Two kinds of 3-inch PMTs from HZC Photonics and Hamamatsu have been investigated as candidates.A dedicated test system for 3-inch PMTs has been designed,and various characterization parameters have been studied.Conclusion The preliminary results show these PMTs can meet the requirements of JUNO.