Uplink Grant-Free Pattern Division Multiple Access (GF-PDMA) for 5G Radio Access

Massive machine type communication(m MTC) is one of the key application scenarios for the fifth generation mobile communication(5 G). Grant-free(GF) transmission can reduce the high signaling overhead in m MTC. Non-orthogonal multiple access(NMA) can support more users for m MTC than orthogonal frequency division multiple access(OFDMA). Applying GF transmission in NMA system becomes an active topic recently. The in-depth study on applying GF transmission in pattern division multiple access(PDMA), a competitive candidate scheme of NMA, is investigated in this paper. The definition, latency and allocation of resource and transmission mechanism for GF-PDMA are discussed in detail. The link-level and system-level evaluations are provided to verify the analysis. The analysis and simulation results demonstrate that the proposed GF-PDMA has lower latency than grant based PDMA(GB-PDMA), possesses strong scalability to confront collision and provides almost 2.15 times gain over GF-OFDMA in terms of supporting the number of active users in the system.

A Frame Breaking Based Hybrid Algorithm for UHF RFIDAnti-Collision

Multi-tag collision imposes a vital detrimental effect on reading performanceof an RFID system. In order to ameliorate such collision problem and to improve thereading performance, this paper proposes an efficient tag identification algorithm termedas the Enhanced Adaptive Tree Slotted Aloha (EATSA). The key novelty of EATSA is toidentify the tags using grouping strategy. Specifically, the whole tag set is divided intogroups by a frame of size F. In cases multiple tags fall into a group, the tags of the groupare recognized by the improved binary splitting (IBS) method whereas the rest tags arewaiting in the pipeline. In addition, an early observation mechanism is introduced toupdate the frame size to an optimum value fitting the number of tags. Theoretical analysisand simulation results show that the system throughput of our proposed algorithm canreach as much as 0.46, outperforming the prior Aloha-based protocols.

Tunable Supercontinuum Generated in a Yb^3＋-Doped Microstructure Fiber Pumped by Ti：Sapphire Femtosecond Laser

We experimentally demonstrate that a tunable supercontinuum（SC） can be generated in a Yb3＋-doped microstructure fiber by the concept of wavelength conversion with a Ti：sapphire femtosecond（fs） laser as the pump.Experimental results show that an emission light around 1040 nm in an anomalous dispersion region is first generated and amplified by fs pulses in the normal dispersion region. Then, SC spectra from 1100 to 1380 nm and 630 to 840 nm can be achieved by combined effects of higher-order soliton fission and Raman soliton self-frequency shift in the anomalous dispersion region and self-phase modulation, dispersive wave, and four-wave mixing in the normal dispersion region. It is also demonstrated that the 20 nm change of pump results in a 280 nm broadband shift of soliton and the further red-shift of soliton is limited by OH-absorption at 1380 nm.

Direct Digital Frequency Control Based on the Phase Step Change Characteristic between Signals

We present a new digital phase lock technology to achieve the frequency control and transformation through high precision multi-cycle group synchronization between signals without the frequency transformation circuit. In the case of digital sampling, the passing zero point of the phase of the controlled signal has the phase step characteristic, the phase step of the passing zero point is monotonic continuous with high resolution in the phase lock process, and using the border effect of digital fuzzy area, the gate can synchronize with the two signals, the quantization error is reduced. This technique is quite different from the existing methods of frequency transformation and frequency synthesis, the phase change characteristic between the periodic signals with different nominal is used. The phase change has the periodic phenomenon, and it has the high resolution step value. With the application of the physical law, the noise is reduced because of simplifying frequency transformation circuits, and the phase is locked with high precision. The regular phase change between frequency signals is only used for frequency measurement, and the change has evident randomness, but this randomness is greatly reduced in frequency control, and the certainty of the process result is clear. The experiment shows that the short term frequency stability can reach 10-12/s orders of magnitude.

A simplified dispersion-compensation microstructure fiber with seven cores

In order to compensate the dispersion accumulated in a single mode fiber(SMF)for higher communication capacity,a simplified dispersion-compensation microstructure fiber(DC-MSF)with seven cores is proposed in this paper.The fiber’s cladding is made of pure silica without air holes,and its outer cores are composed of six germanium up-doped cylinders,which has the advantage of simple structure.The finite element method(FEM)and beam propagation method(BPM)are used to study the properties of the fiber,and the relationship between the structural parameters of the fiber and the dispersion,as well as the phase matching wavelength,is obtained.By optimizing the structural parameters of the fiber,the dispersion of the fiber can reach-5291.47 ps·nm^(-1)·km^(-1) at 1550 nm,and the coupling loss to the conventional single-mode fiber is only 0.137 d B.Compared with the conventional dispersion-compensation fiber,the fiber has lots of advantages,such as single mode transmission,easy to fabricate and low coupling loss with traditional SMF,etc.

Preparation and laser properties of Yb^3＋-doped microstructure fiber based on hydrolysis-melting technique

The Yb^(3+)-doped silica glass was prepared by the Si Cl_4 hydrolysis doping and powder melting technology based on high frequency plasma. The absorption and emission characteristics of the Yb^(3+)-doped silica glass are studied at room temperature. The integrated absorption cross section,stimulated emission cross section and fluorescence lifetime are calculated to be 8.56×10~4 pm^3,1.39 pm^2 and 0.56 ms,respectively. The Yb^(3+)-doped microstructure fiber(MSF) was also fabricated by using the Yb^(3+)-doped silica glass as fiber core. What's more,the laser properties of the Yb^(3+)-doped MSF are studied.

Target detection algorithm in side-scan sonar image based on pixel importance value measurement

Side-scan sonar detection application always combines with unstable results.A two-stage novel pixel importance value measurement algorithm is proposed to stabilize the detection ability and false alarm probability simultaneously.In first stage of the algorithm,a new feature defined as pixel importance value(PIV)is proposed in terms of distances between the target pixel and each other pixels.PIV measurement of current pixel is defined as the weighted sum of all remaining segmented pixels.The weighted part refers to Gaussian kernel,which means closer pixels gets higher weight.Thus,targets with higher PIV can be located.In the second stage,we use convolutional neural network as classifier to eliminate the dot-like false targets.Our experiment data is obtained by autonomous underwater vehicle,where we demonstrate superior performance of our algorithm over the state-of-the-art sonar detection algorithms in terms of 90.39% recall rate and 2.39% false alarm probability.