Efficient coupled PHY and MAC use of physical Bursts in WiMAX/IEEE 802.16e networks

We address several issues related to the efficient use of Bursts in WiMAX/IEEE 802.16e systems. We look on the relation between the PHY layer budding blocks (FEC blocks) and the allocation of MAC level frames (PDUs) over these FEC blocks. In particular, we show how to transmit a given amount of MAC level data bits over a given Burst in order to maximize the number of successfully transmitted data bits in the Burst. We also compute, given an amount of data bits to transmit, what is the Burst size that maximizes each of the following three performance criterion: the number of successfully transmitted data bits in the Burst, the maximum ratio between the number of successfully transmitted data bits to the Burst size, and the number of successfully transmitted data bits per PHY slot. For the first problem the paper shows how to optimally divide the Burst into PDUs and shows that sometimes it is more efficient to use less reliable Modulation/Coding schemes. For the second problem the paper shows that using the PHY slots efficiently is the best criterion to consider.     

Efficient coupled PHY and MAC use of physical bursts by ARQ-enabled connections in WiMAX/IEEE 802.16e networks

In this paper we address an aspect of the mutual influence between the PHY layer budding blocks (FEC Blocks) and the MAC level allocations in the Uplink and Downlink of IEEE 802.16e/WiMAX networks. In these networks it is possible to transmit MAC level frames, denoted MAC PDUs, such that a PDU contains an integral number of fixed size Data Blocks. PDUs are transmitted over PHY Bursts, which are divided into FEC Blocks. We suggest several algorithms to compute the best way to define PDUs in a Burst in order to maximize several performance criteria. We also give guidelines on how to choose the best Modulation/Coding Scheme (MCS) to use in the Burst, given the SNR of the channel and the performance criteria.     

Coupled PHY,MAC and repetition scheduling in IEEE 802.16 WiMAX systems

We address some issues related to the mutual influence between the PHY layer budding blocks (FEC blocks ), the MAC level allocations, and repetition, in IEEE 802.16e/WiMAX systems, in order to increase the overall combined efficiency. We suggest three methods to use repetition: two are based on the increased transmission success probability due to the transmission and decoding of several copies of the same data, and one is based on signal adding and the decoding of one copy with a larger SNR. The last method turned out to be the most efficient one. We show quantitatively that repetition is efficient mainly in low SNRs where otherwise transmissions are not possible, and in particular in negative SNRs. However, there are cases where using repetition is more efficient than using a stronger Modulation/Coding scheme without repetition. Finally, we also show that repetition shall be used with several Modulation/Coding schemes, and not just with QPSK-1/2 as the IEEE 802.16e/WiMAX standard mandates.     

PHY modulation/rate control for fountain codes in 802.11a/g WLANs

In this paper we consider the joint performance of fountain codes and 802.11a/g PHY modulation/coding. We consider optimality both in terms of maximizing goodput and minimizing energy, and results are presented for both theoretical and experimental channel models. In contrast to studies in cellular networks, we find that in 802.11a/g WLANs the cross-layer approach of a higher-layer fountain coding with a PHY layer modulation and FEC coding can yield very limited gains, and the PHY modulation/rate that optimizes the uncoded multicast performance is also close to that for fountain-coded multicast traffic over a wide-range of network conditions. This is potentially an important observation as it indicates that in 802.11a/g WLANs cross-layer design for multicast rate control would bring few benefits and PHY layer rate control can be carried out without regard to the use of fountain coding at higher layers.     

Implement of FEC in the Optical Transport Network

Forward error correction (FEC) is a method by which extra information is included along with the original signal to provide redundancy for correcting bit errors. According to Reed Solomon code regularity, a certain amount of bit errors can be corrected. The appropriate capability of correcting burst bits in error may be more flexible implement of FEC in the optical transport network. The suitable choice can effectively reduce cost of the optical transport network.     

State preparation based on Grover’s algorithm in the presence of global information about the state

In a previous paper, we described an efficient algorithm to prepare an arbitrary state of a quantum register with arbitrarily high fidelity. Here we present an alternative algorithm that uses a small number of quantum oracles encoding the most significant bits of the absolute value of the complex amplitudes and, similarly, a small number of oracles encoding the most significant bits of the phases. The alternative algorithm is considerably simpler than the one described previously, on the assumption that a sufficient amount of knowledge about the distribution of the absolute values of the complex amplitudes is available.     

Implement of FEC in the Optical Transport Network

Forward error correction (FEC) is a method by which extra information is included along with the original signal to provide redundancy for correcting bit errors. According to Reed Solomon code regularity, a certain amount of bit errors can be corrected. The appropriate capability of correcting burst bits in error may be more flexible implement of FEC in the optical transport network. The suitable choice can effectively reduce cost of the optical transport network.     

An image encryption scheme based on three-dimensional Brownian motion and chaotic system

At present, many chaos-based image encryption algorithms have proved to be unsafe, few encryption schemes permute the plain images as three-dimensional(3D) bit matrices, and thus bits cannot move to any position, the movement range of bits are limited, and based on them, in this paper we present a novel image encryption algorithm based on 3D Brownian motion and chaotic systems. The architecture of confusion and diffusion is adopted. Firstly, the plain image is converted into a 3D bit matrix and split into sub blocks. Secondly, block confusion based on 3D Brownian motion(BCB3DBM)is proposed to permute the position of the bits within the sub blocks, and the direction of particle movement is generated by logistic-tent system(LTS). Furthermore, block confusion based on position sequence group(BCBPSG) is introduced, a four-order memristive chaotic system is utilized to give random chaotic sequences, and the chaotic sequences are sorted and a position sequence group is chosen based on the plain image, then the sub blocks are confused. The proposed confusion strategy can change the positions of the bits and modify their weights, and effectively improve the statistical performance of the algorithm. Finally, a pixel level confusion is employed to enhance the encryption effect. The initial values and parameters of chaotic systems are produced by the SHA 256 hash function of the plain image. Simulation results and security analyses illustrate that our algorithm has excellent encryption performance in terms of security and speed.     

Memristor-based vector neural network architecture

Vector neural network(VNN) is one of the most important methods to process interval data.However,the VNN,which contains a great number of multiply-accumulate(MAC) operations,often adopts pure numerical calculation method,and thus is difficult to be miniaturized for the embedded applications.In this paper,we propose a memristor based vector-type backpropagation(MVTBP) architecture which utilizes memristive arrays to accelerate the MAC operations of interval data.Owing to the unique brain-like synaptic characteristics of memristive devices,e.g.,small size,low power consumption,and high integration density,the proposed architecture can be implemented with low area and power consumption cost and easily applied to embedded systems.The simulation results indicate that the proposed architecture has better identification performance and noise tolerance.When the device precision is 6 bits and the error deviation level(EDL) is 20%,the proposed architecture can achieve an identification rate,which is about 92% higher than that for interval-value testing sample and 81% higher than that for scalar-value testing sample.     

Online AL-FEC policy problem on mobile unicast services

Forward error correction (FEC) is a method for error control of data transmission adopted in several mobile multicast standards. FEC is a feedback free error recovery method where the sender introduces redundant data in advance with the source data enabling the recipient to recover from different arbitrary packet losses. Recently, the adoption of FEC error control method has been boosted by the introduction of powerful Application Layer FEC (AL-FEC) codes, e.g. RaptorQ codes. Furthermore, several works have emerged aiming to address the shortcomings of AL-FEC protection application utilizing deterministic or randomized online algorithms to enhance the efficiency of AL-FEC error control method. In this work, since the investigation of AL-FEC application as primary or auxiliary error protection method over mobile multicast environments is a well investigated field but the opportunity of utilizing the AL-FEC over mobile unicast services as the only method for error control replacing common feedback based methods that are now considered to be obsolete, we provide an analysis on the feasibility of AL-FEC protection over unicast delivery utilizing online algorithms in conjunction with AL-FEC codes with exceptional recovery performance.     

The combination of aggregation,ARQ, QoS guarantee and mapping of Application flows in Very High Throughput 802.11ac networks

We investigate the performance of the IEEE 802.11ac MAC layer Aggregation schemes in light of QoS guarantee with the use of an ARQ protocol, and in very high PHY rates. The investigation is done in different models of mapping Application flows into Traffic Streams and Access Categories. We show that when the IEEE 802.11ac ARQ protocol is used with relatively high bit error rates, it is not effective to use the full aggregation capability. Second, we show that there is not one best model of mapping Application flows into Traffic Streams and Access Categories. In particular, using two Access Categories is sometimes less efficient than using one.     

Oscillator strengths and lifetimes calculated by the Dirac-Fock method for the levels of ions of the cesium isoelectronic sequence

A new method of data transmission in DWDM systems along existing long-distance fiber-optic communication lines is proposed. The existing method, e.g., uses 32 wavelengths in the NRZ code with an average power of 16 conventional units (16 units and 16 zeros on the average) and transmission of 32 bits/cycle. In the new method, one of 124 wavelengths with a duration of one cycle each (at any time instant, no more than 16 obligatory different wavelengths) and capacity of 4 bits with an average power of 15 conventional units and rate of 64 bits/cycle is transmitted at every instant of a 1/16 cycle. The cross modulation and double Rayleigh scattering are significantly decreased owing to uniform distribution of power over time at different wavelengths. The time redundancy (forward error correction (FEC)) is about 7% and allows one to achieve a coding enhancement of about 6 dB by detecting and removing deletions and errors simultaneously.     

回旋速调管调制腔模拟分析

 多腔回旋速调管中的调制腔采用内外腔同轴结构,对回旋电子注角向群聚起着关键作用。用场匹配理论及HFSS软件对调制腔冷腔特性进行了研究,对多种输入结构、耦合缝尺寸和方位、腔体长度、半径进行了模拟。分析表明,耦合狭缝中心线与输入波导轴线成45°,耦合缝长度达到0.72时,内外腔储能比值达到41.65;耦合缝尺寸对腔体Q值影响较大,但并非呈简单线性关系,并且Q值对缝长的变化比缝宽的变化要敏感得多;而狭缝尺寸变化对谐振频率的影响不大;计算了内外腔储能,得到了模式转换效率高、内外腔储能比高、性能优良的调制腔。     

Unveiling the secrets of gamma ray bursts

Gamma Ray Bursts are unpredictable and brief flashes of gamma rays that occur about once a day in random locations in the sky. Since gamma rays do not penetrate the Earth's atmosphere, they are detected by satellites, which automatically trigger ground-based telescopes for follow-up observations at longer wavelengths. In this introduction to Gamma Ray Bursts we review how building a multi-wavelength picture of these events has revealed that they are the most energetic explosions since the Big Bang and are connected with stellar deaths in other galaxies. However, in spite of exceptional observational and theoretical progress in the last 15 years, recent observations raise many questions which challenge our understanding of these elusive phenomena. Gamma Ray Bursts therefore remain one of the hottest topics in modern astrophysics.     

Performance analysis of OTDM system in the presence of FEC using symmetric Mach-Zehnder switch

Optical time division multiplexing is an emerging and promising alternative for future high-speed photonic networks because of its ability to accommodate higher bit rate and flexible bandwidth. SMZ have been found to be the most suitable switching element than all the available de-multiplexing switches because of compact size, thermal stability, and low-power operation. In this paper, we simulate four channel OTDM systems (all-channel multiplexer and de-multiplexer) with a Mach-Zehnder modulator and an SMZ de-multiplexer to investigate the impact of FEC on the OTDM system. It is observed that the presence of FEC in OTDM transmission can greatly improve the system performance.     

Hiding Quantum Data

Recent work has shown how to use the laws of quantum mechanics to keep classical and quantum bits secret in a number of different circumstances. Among the examples are private quantum channels, quantum secret sharing and quantum data hiding. In this paper we show that a method for keeping two classical bits hidden in any such scenario can be used to construct a method for keeping one quantum bit hidden, and vice–versa. In the realm of quantum data hiding, this allows us to construct bipartite and multipartite hiding schemes for qubits from the previously known constructions for hiding bits.     

Analysis of scalability for AODV routing protocol in wireless sensor networks

This paper presents preliminary work to address scalability concern over AODV protocol in wireless sensor network. Firstly, we discussed the scalability design issues with related work in context of wireless sensor networks (WSN). Following, we designed and illustrated wireless sensor network model. Finally, significance of scalability on the behaviour of application, MAC, transport and physical layer performance is described.     

全钒液流电池充放电测试系统设计

针对以太网技术在高速图像传输中常见的带宽利用率低,传输协议受限的问题,设计了一种基于可编程逻辑器件FPGA实现千兆以太网传输系统的方案,分析了基于IEEE802.3标准的以太网帧格式和循环冗余校验(CRC),实现了MAC数据包的封装和PHY芯片88E1111的配置,完成了千兆网络系统的设计和高速数据的传输。结果表明,该方案具有成本低,传输速率快且传输协议不受限制的优势,并最终成功应用于某水下高速图像传输系统中。     

Information Bottleneck Signal Processing and Learning to Maximize Relevant Information for Communication Receivers

Digital communication receivers extract information about the transmitted data from the received signal in subsequent processing steps, such as synchronization, demodulation and channel decoding. Technically, the receiver-side signal processing for conducting these tasks is complex and hence causes bottleneck situations in terms of power, delay and chip area. Typically, many bits per sample are required to represent and process the received signal in the digital receiver hardware accurately. In addition, demanding arithmetical operations are required in the signal processing algorithms. A popular recent trend is designing entire receiver chains or some of their crucial building blocks from an information theoretical perspective. Signal processing blocks with very simple mathematical operations can be designed to directly maximize the relevant information that flows through them. At the same time, a strong quantization reduces the number of bits processed in the receiver to further lower the complexity. The described system design approach follows the principle of the information bottleneck method. Different authors proposed various ideas to design and implement mutual information-maximizing signal processing units. The first important aim of this article is to explain the fundamental similarities between the information bottleneck method and the functionalities of communication receivers. Based on that, we present and investigate new results on an entire receiver chain that is designed following the information bottleneck design principle. Afterwards, we give an overview of different techniques following the information bottleneck design paradigm from the literature, mainly dealing with channel decoding applications. We analyze the similarities of the different approaches for information bottleneck signal processing. This comparison leads to a general view on information bottleneck signal processing which goes back to the learning of parameters of trainable functions that maximize the relevant mutual information under compression.