Abstract ：

Advanced light sources in the blue-green band are crucial for underwater wireless optical communication (UWOC) systems. Vertical-external-cavity surface-emitting lasers (VECSELs) can produce high output power and good beam quality, making them suitable for UWOC. This paper presents a 108 m distance UWOC based on a 100 mW 490 nm blue VECSEL and an acousto-optic modulator (AOM). The high-quality beam, which is near diffraction-limited, undergoes relatively small optical attenuation when using a conventional avalanche photodiode (APD) as the detector and employing 64-pulse position modulation (PPM). At the time-slot frequency of 50 MHz, the bit error rate (BER) of the UWOC was 2.7 x 10-5. This is the first reported AOM-based UWOC system with a transmission distance over 100 m. The estimated maximum transmission distance may be improved to about 180 m by fully utilizing the detection accuracy of the APD according to the measured attenuation coefficient of the blue VECSEL used. This type of UWOC system, composed of a high-beam-quality light source and a conventional detector, make it more closely suited to practical applications.

Keyword ：

vertical-external-cavity surface-emitting laser PPM AOM underwater wireless optical communication

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Abstract ：

Non-orthogonal multiple access (NOMA) is regarded as a promising technology in achieving high capacity and massive connectivity. In this paper, the reliable transmission scheme of downlink NOMA systems is investigated. In particular, we divide the disc covered by the base station into several annular areas, where the receivers are randomly located following a uniform distribution. In this way, NOMA pairing is performed by randomly selecting receivers from two different areas. Firstly, we derive the closed-form expressions of bit error rate (BER) with quadrature phase-shift keying (QPSK) modulation, where the channel is modeled as small-scale Rayleigh fading and large-scale path loss. To achieve reliable communications, then, the BER performance of the receiver with the worst channel gain in each area is studied. Finally, an optimal power allocation algorithm is proposed, which obtains the minimum transmission power and optimal power allocation factor with a given BER constraint of all receivers. Extensive simulations demonstrate the accuracy of obtained BER expressions and the effectiveness of the proposed algorithm. These results provide valuable insight into realizing on reliable transmission of NOMA with randomly deployed receivers.

Keyword ：

NOMA reliable communications power allocation BER

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Abstract ：

This paper presents improved underwater wireless optical communication (UWOC) based on a 490 nm passively mode-locked vertical-external-cavity surface-emitting laser (VECSEL) with the repetition rate of 1.46 GHz and the pulse width of 2.25 ps. After conducting a comprehensive evaluation of the performance characteristics of quasi-cyclic low-density parity-check (QC-LDPC) coding and pulse-position modulation (PPM) in relation to biterror-rate (BER) and communication capacity across different signal-to-noise ratios (SNRs), a passively modelocked VECSEL based UWOC system is designed and experimentally performed. The UWOC system employs the QC-LDPC encoding technique and PPM modulation scheme that are most suitable for the system. Compared with the case without QC-LDPC, the minimum received optical power with coding is improved by 3.5 dBm, and the SNR with coding is improved by 0.4 dB under condition of 256-PPM and forward error correction (FEC) threshold of 3.8x10- 3. Meanwhile, compared with the UWOC system using a continuous-wave (CW) VECSEL as the light source, the attenuation coefficient of the UWOC system based on the mode-locked VECSEL is decreased by 0.04 m-1, and the BER of the mode-locked VECSEL based UWOC system is decreased by 0.3 dB.

Keyword ：

QC-LDPC PPM Underwater wireless optical communications Vertical-external-cavity surface-emitting laser Mode-locked

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Abstract ：

Quantum communication protocols should take the effect of noise into account in a real environment. To analyze the security of the quantum B92 protocol presented by Bennett in collective-rotation noise channel, an excellent model of noise analysis is proposed. In the security analysis, the eavesdropping can be detected with the increment of the qubits error rate (ber). When the level of noise less than 0.50, it will cause a larger bit error rate if the eavesdropper Eve wants to obtain the same amount of information. In our analysis, Eve can maximally get about 50% of the key from the communication when the noise level approximates to 0.5. We also presented a new idea in analyzing the protocol security in collective-rotation noise channel with the idea of the Markov process.

Keyword ：

The quantum B92 protocol Security analysis Collective rotation noise Qubit error rate Information entropy

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Abstract ：

The impact of the variations of threshold voltage (V-th) and hold voltage (V-hold) of threshold switching (TS) selector in 1S1R crossbar array is investigated. Based on ON/OFF state I-V curves measurements from a large number of Ag-filament TS selectors, V-th and V-hold are extracted and their variations distribution expressions are obtained, which are then employed to evaluate the impact on read process and write process in 32 x 32 1S1R crossbar array under different bias schemes. The results indicate that V-th and V-hold variations of TS selector can lead to degradation of 1S1R array performance parameters, such as minimum read/write voltage, bit error rate (BER), and power consumption. For the read process, a small V-hold variation not only results in the minimum read voltage increasing but it also leads to serious degradation of BER. As the standard deviation of V-hold and V-th increases, the BER and the power consumption of 151R crossbar array under 1/2 bias, 1/3 bias, and floating scheme degrade, and the case under 1/2 bias tends to be more serious compared with other two schemes. For the write process, the minimum write voltage also increases with the variation of V-hold from small to large value. A slight increase of V-th standard deviation not only decreases write power efficiency markedly but also increases write power consumption. These results have reference significance to understand the voltage variation impacts and design of selector properly.

Keyword ：

RRAM threshold switching selector variation crossbar array

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Abstract ：

The bit error in quantum communication is mainly caused by eavesdropping and noise. However, most quantum communication protocols only take eavesdropping into consideration and ignore the result of noise, making the inaccuracy situations in detecting the eavesdropper. To analyze the security of the quantum E91 protocol presented by Ekert in collective-rotation noise channel, an excellent model of noise analysis is proposed. The increment of the qubits error rate (ber) is used to detect eavesdropping. In our analysis, eavesdropper (Eve) can maximally get about 50% of the key from the communication when the noise level approximates to 0.5. The results show that in the collective-rotation noise environment, E91 protocol is secure and the raw key is available just as we have knew and proved. We also presented a new idea in analyzing the protocol security in noise channel.

Keyword ：

qubit error rate security analysis The quantum E91 protocol collective-rotation noise quantum key distribution

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Abstract ：

In the past three decades, major technologies and economic developments have been made on the telecommunication sector. HF communication has now become the main feature of the telecommunication industry. An advantage of the use of HF communication is that high frequency system is inexpensive and allows long range communication with minimal equipment requirements and easy to implement in the isolated areas as well Frequencies ranging from 1.6 MHz to 30 MHz is called High Frequency spectrum. One of the important developments in the HF communication is Automatic Link Establishment. ALE method is widely used by the military and other organizations. In this paper we have tried to describe the implementation of ALE military standard (188-141A). This standard defines a 2G HF ALE standard. We design a communication system that allows reliable data communication over HF radio by using the Matlab environment. Our work is divided into two parts. In first part at the transmitter level, we perform the encoder to encode the data bits for error correction and detection by using the golay code. After the encoder, interleave the encoded data bits and perform the 8 array FSK modulation to transmit the data. In the second part at the receiver, we demodulated the data and then deinterleave it. After the deinterleaving we perform the decoder by using the golay decoder. At the end there is a performance analysis that comprises SNR and BER plots.

Keyword ：

carrier sense multiple access(CSMA) continuous phase frequency shift keying(CPFSK) forward error correction(FEC) frequency shift keying(FSK) north atlantic treaty organization(NATO)

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In this paper, a scheme for optical modulation format conversion from one 20 Gbps quadrature phase-shift keying (QPSK) signal to one 20 Gbps binary phase-shift keying (BPSK) signal with information integrity is proposed and verified by simulation. The theory of degenerate phase-sensitive amplifier (PSA) employed as a phase de-multiplexer is derived in detail and used to decompose the in- (I) and quadrature- (Q) phase components of QPSK. Then the I and Q components are parallel-to-series converted into one BPSK. The constellations show that the phase noise of the original signal is effectively restrained by the conversion system through use of the PSA. The error vector magnitude and bit-error rate (BER) of the QPSK, converted BPSK, and a back-to-back BPSK are measured and compared with each other. We find that the BER performance of the converted BPSK is better than QPSK and maintains the original information integrity with different input signal quality. Some potential issues are also discussed as to practical implementation of the scheme. This modulation-format-conversion scheme has potential applications in improving the signal BER performance and flexible transmitters and receivers in software-defined networks. (C) 2017 Optical Society of America

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A modified Mach-Zehnder interferometric phase sensitive amplifier (MMZI-PSA) configuration is proposed and simulated, which combined the four-wave mixing phase-sensitive amplifier (FWM-PSA) with the fiber interference phase-sensitive amplifier (FI-PSA). This modified scheme for an all-optical communication system can not only eliminate phase noise, but also reduce additional amplitude noise, reducing intrinsic amplitude noise and suppressing phase-to-amplitude noise conversion tremendously. Compared with the traditional FWM-PSA configuration, the proposed configuration can obtain higher gain, as well as reduce bit-error rate (BER) and error vector magnitude (EVM). The simulation results suggest that MMZI-PSA can effectively regenerate QPSK signals and obtain 6.9-dB gain. Furthermore, it can reduce BER to 3.98 x 10(-6) and reduce EVM to 22%, which improves system noise tolerance. (C) 2017 Society of Photo-Optical Instrumentation Engineers

Keyword ：

four wave mixing phase regeneration amplitude regeneration phase sensitive amplifier

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Abstract ：

首先对主流轻量级应用层通信协议进行研究,结合各类协议的优缺点,以及健康监测大数据平台的应用环境,探索了一种在客户端服务器模式下的应用层通信协议.它遵循应用层协议设计要求,采用应用层协议广泛使用的ASN.1语言进行协议描述.在调研用户群体、设备端和健康监测大数据平台三者之间关系以及健康监测大数据环境独有特点的情况下,设计了用于设备端与健康监测大数据平台进行协议交互的各种操作请求,在编解码方面选择了相对于XM L有更好效率的BER编解码方法,使得网络带宽利用率更加充分.

Keyword ：

异构性 大数据 健康监测 通信协议

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