Synchronization of MIMO OFDM systems by perfect complete generalized complementary orthogonal loosely synchronous code groups

This article proposes a time/frequency synchronization algorithm in the multiple input multiple output （MIMO） systems, in which the perfect complete generalized complementary orthogonal loosely synchronous code groups are used as the synchronization sequence. The synchronization algorithm is divided into four stages： 1） synchronization in time domain by signal autocorrelation; 2） synchronization in frequency domain by fast Fourier transform （FFT）; 3） multipath dissociation using coherent detection and fine time synchronization; 4） fine frequency offset estimation by phase rotation. As per the perfect complete generalized complementary orthogonal loosely synchronous code groups, the cross-correlation and out-of-phase auto-correlation for any relative shift between any two codes is always zero. This ideal property makes the time/frequency synchronization algorithm simple and efficient. The simulation results show that even in the multipath fast fading channel with low signal noise ratio （SNR）, the MIMO system can get synchronized both in the time domain and frequency domain with high stability and reliability.

Microwave Oscillator Phase Noise Requirement for TD-SCDMA Wireless Communication Systems

In time division synchronous code division multiple access （TD-SCDMA） wireless communication systems, QPSK or 8PSK has been employed to support high data rate services and high efficiency in available bandwidth. The performance of such systems is affected by the phase noise of the microwave local oscillator. The phase noise model of synthesizer and the RF transceiver model for the phase noise effect are proposed for applications of TD-SCDMA systems. The relationship between the power spectral density （PSD） and root mean square （RMS） phase error is given. Then, the error vector magnitude （EVM） performance is analytically evaluated by using the single side band （SSB） phase noise. Theoretical results show agreement with those obtained by measurement data and therefore can be used to derive the TD-SCDMA system performance.

A LARGE CLASS OF BINARY ZCZ SEQUENCE FAMILIES CONSTRUCTED BY PERIOD DOUBLING

In an Approximately Synchronized Code Division Multiple Access (AS-CDMA) commu-nication system,a family with large number of Zero Correlation Zone (ZCZ) sequences is desired,which can satisfy the rapid increase of users. This paper presents a method to generate a (2L ,2M ,Zc' z )-ZCZsequence family from an original (L ,M ,Z cz)-ZCZsequence family,where Z c' z =Zcz if Z czis even and Z c' z = Zcz 1if Z czis odd. This method can also recursively act on a ZCZ sequence family to construct a series of ZCZ sequence families with large sequence number and zero correlation zone length identical to or one less than that of original ZCZ sequences.

Web Voice Browser Based on an ISLPC Text-to-Speech Algorithm

A kind of Web voice browser based on improved synchronous linear predictive coding （ISLPC） and Text-toSpeech （TTS） algorithm and Internet application was proposed. The paper analyzes the features of TTS system with ISLPC speech synthesis and discusses the design and implementation of ISLPC TTS-based Web voice browser. The browser integrates Web technology, Chinese information processing, artificial intelligence and the key technology of Chinese ISLPC speech synthesis. It＇s a visual and audible web browser that can improve information precision for network users. The evaluation results show that ISLPC-based TTS model has a better performance than other browsers in voice quality and capability of identifying Chinese characters.

Constructions of optimal difference systems of sets

Difference systems of sets (DSSs) are combinatorial configurations which were introduced in 1971 by Levenstein for the construction of codes for synchronization. In this paper, we present two kinds of constructions of difference systems of sets by using disjoint difference families and a special type of difference sets, respectively. As a consequence, new infinite classes of optimal DSSs are obtained.

Diference Systems of Sets Based on Cosets Partitions

Difference systems of sets （DSS） are combinatorial configurations that arise in connection with code synchronization. This paper proposes a new method to construct DSSs, which uses known DSSs to partition some of the cosets of Zv relative to subgroup of order k, where v = km is a composite number. As applications, we obtain some new optimal DSSs.

Stimulus discrimination via responses of retinal ganglion cells and dopamine-dependent modulation

Neighboring retinal ganglion cells（RGCs）fire with a high degree of correlation.It has been increasingly realized that visual perception of the environment relies on neuronal population activity to encode and transmit the information contained in stimuli.Understanding how neuronal population activity contributes to visual information processing is essential for understanding the mechanisms of visual coding.Here we simultaneously recorded spike discharges from groups of RGCs in bullfrog retina in response to visual patterns（checkerboard,horizontal grating,and full-field illumination）using a multi-electrode array system.To determine the role of synchronous activity mediated by gap junctions,we measured the correct classification rates of single cells＇firing patterns as well as the synchronization patterns of multiple neurons.We found that,under normal conditions,RGC population activity exhibited distinct response features with exposure to different stimulus patterns and had a higher rate of correct stimulus discrimination than the activity of single cells.Dopamine（1μmol/L）application did not significantly change the performance of single neuron activity,but enhanced the synchronization of the RGC population activity and decreased the rate of correct stimulus pattern discrimination.These findings suggest that the synchronous activity of RGCs plays an important role in the information coding of different types of visual patterns,and a dopamine-induced increase in synchronous activity weakens the population performance in pattern discrimination,indicating the potential role of the dopaminergic pathway in modulating the population coding process.