A Bandwidth Efficient Turbo Coding Scheme for VDSL Systems

The current forward error correction (FEC) scheme for very high bit-rate digital subscriber line (VDSL) systems in the ANSI standard employs a 16-state four-dimensional (4D) Wei code as the inner code and the Reed-Solomon (RS) code as the outer code. The major drawback of this scheme is that further improvement cannot be achieved without a substantial increase in the complexity and power penalty. Also, a VDSL system employing the 4D Wei-RS scheme operates far below the channel capacity. In 1993, powerful turbo codes were introduced whose performance closely approaches the Shannon limit. In this paper, we propose a bandwidth and power efficient turbo coding scheme for VDSL modems in order to obtain high data rates, extended loop reach and increased transmission robustness. We also propose a pipelined decoding scheme to reduce the latency at the receiver end. The objective of the proposed scheme is to provide a higher coding gain than that given by the 4D Wei-RS scheme, resulting in an improved performance of the VDSL modems in terms of bit rate, loop length and transmitting power. The scheme is investigated for various values of transmitting power, signaling frequencies and numbers of crosstalkers for a targeted bit error rate of 10⁻⁵ and is implemented in a system with a quadrature amplitude modulation in which a mixed set partitioning mapping is employed to reduce the decoding complexity. The effects of code complexity, interleaver length, the number of decoding iterations and the level of modulation on the performance of VDSL modems are explored. Simulation results are presented and compared to those of the 4D Wei-RS scheme. The results show that the choice of turbo codes not only provides a significant coding gain over the standard FEC scheme but also efficiently maximizes the loop length and bit rate at a very low transmitting power in the presence of dominant far-end crosstalk and intersymbol interference. In order to compare the hardware complexity, we synthesize the proposed and 4D Wei-RS schemes using SYNOPSYS with the target technology of Xilinx 4020e-3. The Xilinx field programmable gate array statistics of the proposed scheme is compared with that of the 4D Wei-RS scheme.     

Correlation matching method for the weak stationarity test of LRD traffic

The stationarity test of long-range dependent (LRD) traffic remains a challenge problem in the field of traffic engineering. Due to the importance of traffic theory in the Internet, to find a solution to that problem is greatly desired. This paper presents a method of the weak stationarity test of a single history LRD traffic series of finite length. How to apply this method to testing the stationarity of real traffic is demonstrated. The results in this paper suggest that there may be no general conclusion that traffic is either stationary or non-stationary since the stationarity of traffic is observation-scale dependent. Some of the investigated real-traffic traces that are stationary in an observation scale may be non-stationary in a larger observation scale.     

Efficient Output Mode Converter for 30 GHz Gyroklystron at IAP

An output mode converter for Ka-band multi-MW gyroklystron in the Institute of Applied Physics (IAP) operating in the TE₅₃ mode is suggested. Two variants of the converter, aimed for different applications, are presented: the TE₅₃ to TE₀₁ mode converter with power output along the device axis and the TE₅₃ mode to Gaussian wavebeam quasi-optical converter with a visor. The suggested designs include the built-in electron beam collector. The converters were designed using a new synthesis algorithm, which implies iterative improvement of the waveguide wall shape in order to achieve high efficiency. The calculation results were proven by HFSS simulation and low-power tests of one version of the converter.     

An Efficient and Robust Orthogonal Structure for Linear Discrete-Time Systems

An orthogonal structure is derived for system implementation. The expression of roundoff noise propagation gain for this structure is obtained. The proposed structure is an improved version of that reported in the paper by G. Li, M. Gevers, and Y.X. Sun (Performance analysis of a new structure for digital filter implementation, IEEE Trans. Circuits Syst. I 47:474–482, 2000), but is more efficient and robust against the quantization errors. For comparison, an alternative expression of roundoff noise gain for the normalized lattice structure is derived, based on which it is shown that the roundoff noise gain of an Nth order all-pass system, when implemented using the normalized lattice structure, is 4N and that an Nth order system implemented with the structure proposed in the paper by P.P. Vaidyanathan, S.K. Mitra, and Y. Neuvo (A new approach to the realization of low sensitivity IIR digital filters, IEEE Trans. Acoust. Speech Signal Process. ASSP-34(2):350–361, 1986), yields a roundoff noise gain of N+1, smaller than that of the classical optimal roundoff noise state-space realizations. Design examples are presented to illustrate the behavior of the proposed structure and to compare it with a class of existing orthogonal structures and the classical optimal roundoff noise realizations. It is shown that the proposed structure outperforms the others in terms of minimization of roundoff noise as well as implementation efficiency.     

Conception approach of access control in heterogeneous information systems using UML

The development of the information systems should answer more and more to the problems of federated data sources and the problems with the heterogeneous distributed information systems. The assurance of data access security realized in the cooperative information systems with loose connection among local data sources is hard to achieve mainly for two reasons: the local data sources are heterogeneous (i.e. data, models, access security models, semantics, etc.) and the local autonomy of systems does not allow to create a global integrated security schema. The paper proposes to use one common set of access control concepts to support the access control management in security of heterogeneous information systems. The UML (Unified Modeling Language) concepts can be used to define and implement the most popular access control models, such as DAC, MAC or RBAC. Next, the concepts derived from different models can be joined to use one common approach comprehensible for each administrator of each cooperative information system in the federation.     

Efficient algorithms for constructing broadcast disks programs in asymmetric communication environments

A well-known technique for broadcast program construction is the Broadcast Disks technique. However, in the Broadcast Disks approach there are some important disadvantages. For example some parts of the broadcast program remain empty during the construction procedure and the disk relative frequencies have to be selected very carefully. This paper gives a new approach of the broadcast program construction in a Broadcast Disk System, presenting three new algorithms, which face successfully these problems. According to this approach, the broadcast program is constructed with the minimum possible length, while retaining the selected disk relative frequencies and keeps the average delays on retrieving data-items low. The constructed broadcast programs have no empty parts, and retain their desired properties in any numbered combination of disk relative frequencies. We implemented all methods in a simulator application and experimental results show that our approach is more efficient than Broadcast Disks in all cases.     

Proportional Plus Integral Control for Set-Point Regulation of a Class of Nonlinear RLC Circuits

In this paper we identify graph-theoretic conditions which allow us to write a nonlinear RLC circuit as port-Hamiltonian with constant input matrices. We show that under additional monotonicity conditions on the network’s components, the circuit enjoys the property of relative passivity, an extended notion of classical passivity. The property of relative passivity is then used to build simple, yet robust and globally stable, proportional plus integral controllers. This work was partially supported by CONACyT, México.     

An Efficient Frame Aggregation and Block-ACK Scheme for 60 GHz Short-Range Point-to-Point Transmission

The exploitation of the 60 GHz band is a very promising approach to fulfill the rapidly increasing data rate requirement of wireless indoor communication. One important 60 GHz application is the short-range point-to-point data transmission with Ultra-High-Rate (UHR, up to 10 Gbps) (Krone et al. in International Journal of Microwave and Wireless Technologies, 2011, 189–200). The design of such high data rate systems is very challenging. Except for Analog-Front-End (AFE) and physical layer (PHY) designs, the Medium Access Control (MAC) layer design is also crucial for the achievable system throughput. Among the MAC functionalities, the acknowledgment (ACK) mechanism is a very important component affecting the transmission efficiency and reliability. In this paper, a Hybrid Dynamic Frame Aggregation and Block-Acknowledgment (HD-FABA) scheme is proposed, which enables large-scale frame aggregation and can achieve significant ACK overhead reduction compared to the existing schemes. A theoretical model is developed for throughput analysis, which is verified by packet-level simulation. Both theoretical- and simulation results show that the HD-FABA scheme allows a number of MAC parameters to be optimized according to the PHY conditions (e.g. BER), leading to much higher throughput than with the state-of-the-art scheme.     

Compact Efficient Feed-Horn at 30–38 GHz for a Multi-beam Radio Telescope

The requirements for a feed suitable for a radio telescope multi-beam focal plane array are considered. A smooth-walled spline-profile horn covering the 30–38 GHz frequency band to be used in a multi-beam receiving array of a radio telescope has been optimized, manufactured and tested. The achieved cross-section aperture size of the horn allows us to provide a neighboring beam spacing equal or less than 2HPBW for the RATAN-600 radio telescope. The measured sidelobe levels of the radiation pattern is less than −30dB/−24dB/−26dB in H/E/45⁰-planes, cross-polarization levels better than −20 dB, an input return loss better than −18 dB and the −3dB/−10dB-beamwidths are of the order of 40o/ 80o over the frequency band. Mutual-coupling of adjacent horns is less than −38 dB.     

A localized algorithm for bi-connectivity of connected mobile robots

Teams of multiple mobile robots may communicate with each-other using a wireless ad-hoc network. Fault-tolerance in communication can be achieved by making the communication network bi-connected. We present the first localized protocol for constructing a fault-tolerant bi-connected robotic network topology from a connected network, in such a way that the total movement of robots is minimized. The proposed distributed algorithm uses p-hop neighbor information to identify critical head robots that can direct two neighbors to move toward each other and bi-connect their neighborhood. Simulation results show that the total distance of movement of robots decreases significantly (e.g. about 2.5 times for networks with density 10) with our localized algorithm when compared to the existing globalized one. Proposed localized algorithm does not guarantee bi-connectivity, may partition the network, and may even stop at connected but not bi-connected stage. However, our algorithm achieved 100% success on all networks with average degrees ≥10, and over 70% success on sparse networks with average degrees ≥5.     

A 60 GHz receiver front-end with PLL based phase controlled LO generation for phased-arrays

This paper presents a front-end architecture for fully integrated 60 GHz phased array receivers. It employs LO-path beamforming using a phase controlled phase-locked loop (PC-PLL). To demonstrate the architecture a circuit is implemented featuring a two stage low noise amplifier, two cascaded active mixers, and a PC-PLL. The receiver downconverts the 60 GHz signal in two steps, using LO signals from the 20 GHz QVCO of the PLL. A differential 2nd-order harmonic is coupled from the sources of the current commutating pairs of the QVCO, feeding the LO-port of the first mixer and downconverting the 60 GHz RF signal to a 20 GHz intermediate frequency. Quadrature 20 GHz LO signals are then used in the second mixer to down-convert the IF signal to baseband. The PLL is locked to a relatively high reference frequency, 1.25 GHz, which reduces the size of the PLL loop filter and enables a compact layout. The measurements show an input return loss better than ?10 dB between 57.5 and 60.8 GHz, a 15 dB voltage gain, and a 9 dB noise figure. Two-tone measurements show ?12.5 dBm IIP3, 29 dBm IIP2, and ?24 dBm ICP1. The PC-PLL phase noise is ?105 dBc/Hz at 1 MHz offset from a 20 GHz carrier, and the phase of the received 60 GHz signal is digitally controllable with a resolution of 3.2°, covering the full 360° range with a phase error smaller than 1°. The chip consumes 80 mA from a 1.2 V supply, and measures 1,400 μm × 660 μm (900 μm × 500 μm excluding pads) including LNAs, mixers, and PC-PLL in a 90 nm RF CMOS process.     

Synthesized Parameters of MIG for 200 kW, 42 GHz Gyrotron

In this paper, a synthesized design of the magnetron injection gun (MIG) for a 200 kW, 42 GHz gyrotron is presented. The synthesis steps involve the selection of the type of the MIG, the development of the design criteria, the selection of initial design parameters and the development of a program for the estimation of the synthesized parameters for the MIG design. The presented approach estimates the cathode, the beam and the anode parameters, enabling one to build a synthesis model of a complete MIG system.     

Distributed and localized construction of routing structure for sensor data gathering

Several routing structures have been proposed for data gathering in a wireless sensor network. They are considered to be near-optimal with respect to energy efficiency or delivery delay, but they overlook the construction cost of a routing tree which may make trouble in implementation. Our primary goal in this work is to construct a routing tree with negligible cost, which performs as well as those near-optimal schemes. First, we propose a distributed and localized framework for tree construction called Local Parent Designation (LPD), where the node status information is exchanged locally and decision based on the local information leads us to construct a routing tree. Secondly, we extend LPD to so called LPD-Local Fix (LPD-LF) to reduce further the construction cost with less local information exchange. Simulation results validate that our goal is achieved.     

Design of 100 μW Wireless Sensor Nodes for Biomedical Monitoring

Wireless sensor nodes span a wide range of applications. This paper focuses on the biomedical area, more specifically on healthcare monitoring applications. Power dissipation is the dominant design constraint in this domain. This paper shows the different steps to develop a digital signal processing architecture for a single channel electrocardiogram application, which is used as an application example. The target power consumption is 100 μW as that is the power energy scavengers can deliver. We follow a bottleneck-driven approach: first the algorithm is tuned to the target processor, then coarse grained clock-gating is applied, next the static as well as the dynamic dissipation of the digital processor is reduced by tuning the core to the target domain. The impact of each step is quantified. A solution of 11 μW is possible for both radio and DSP running the electrocardiogram algorithm.

Cryptanalysis of block-wise stream ciphers suitable for the protection of multimedia and ubiquitous systems

In this paper we introduce a general framework of related-key attack on block-wise stream ciphers which are suitable for the protection of multimedia and ubiquitous systems. As a case study, we show how our cryptanalytic framework is applied to a block-wise stream cipher TWOPRIME: we construct various related-key differentials of TWOPRIME and use them to show that recovering related keys of TWOPRIME can be performed with a data complexity of 2¹⁴ known plaintext blocks and a time complexity of 2³² 8-bit table lookups. We expect that our general framework for a related-key attack would be useful tool for analyzing many of block-wise stream ciphers.     

Design of Beam Tunnel for 42 GHz, 200 kW Gyrotron

A beam tunnel for a 42 GHz, 200 kW gyrotron for an Indian TOKAMAK system has been designed. The initial design of the beam tunnel has been carried out on the basis of the required electron beam parameters at the interaction cavity and the electron beam simulation of the magnetron injection gun. The design optimization of the beam tunnel has been done with the help of 3-D simulation software CST-Microwave Studio. In the simulation, the absorption, the reflection and the transmission of RF power by the beam tunnel have been analyzed. Three different lossy ceramics, Al₂O₃–SiC, AlN–SiC and BeO–SiC have been investigated during the simulation. The simulation results obtained with CST-Microwave Studio have been validated with another 3-D simulation software HFSS. The Q value of the beam tunnel for different ceramic material has also been analyzed to investigate the parasitic mode excitation in the beam tunnel.     

Flame-Retardant Host–Guest Films for Efficient Thermal Management of Cryogenic Devices

Phase change materials hold tremendous potential for thermal energy storage and temperature management due to their high latent heat and chemical stability. However, the manufacture of flame-retardant, form-stable phase change films working under a cryogenic environment remains difficult. Herein, an organic polydopamine-aramid nanofiber (PANF) aerogel film with a limiting oxygen index (LOI) of 32 is applied as a host to confine a unique phase change guest material (i.e., deep eutectic solvent, DES) to fabricate PANF-DES host–guest flame-retardant cryogenic phase change films. The PANF aerogel film is prepared through the in situ polymerization of dopamine within the aramid nanofiber hydrogel film, exhibiting a high specific surface area of 289 m² g⁻¹. The cryogenic phase change material is a ternary DES composed of ammonium chloride (NH₄Cl), ethylene glycol (Eg), and deionized water (H₂O). The as-prepared PANF-DES host–guest films with the phase transition temperature of −21 °C and melting enthalpy of 225 J g⁻¹ can withstand fire for 60 s without naked flame, and the peak of heat release rate (pkHRR) is only 26.0 MJ kg⁻¹. This study opens the way for developing ultra-low flammable phase change composite films, as well as shows great potential applications for thermal management in cryogenic devices.     

Design of a 30.5 GHz Transition for Gyro-TWT

A 30.5 GHz circular transition used to transmit TE₀₁ mode is proposed because of no suitable one available. Calculations and simulations indicate that it can transmit TE₀₁ mode with transmission efficiency over 0.99 (within a bandwidth of 3 GHz). At the same time, the good performance of it has been demonstrated in experiment. Furthermore, the transition has only a length of 80 mm much shorter than linear or the other nonlinear ones. Such short length is very helpful for construction of a compact microwave device.     

Fourth-Order Complex-Lag PWVD for Multicomponent Signals with Application in ISAR Imaging of Maneuvering Targets

The fourth-order complex-lag polynomial Wigner–Ville distribution (PWVD) is extended to generate a high resolution time–frequency distribution for multicomponent signals in this paper. For signals with polynomial phase up to order four, the interferences between different components are reduced by the convolution in the frequency domain of the complex-lag PWVD. The complex-lag PWVD can achieve optimal energy concentration, and it is used in the inverse synthetic aperture radar (ISAR) imaging of maneuvering targets, where high quality instantaneous ISAR images are obtained. Simulated results demonstrate the effectiveness of the method.     

Comparisons of various pulse shapes for DS-UWB signals over the UWB channel

In this paper, we first investigate the power spectral densities (PSD) of bipolar modulated Direct Sequence Ultra Wide Band (DS-UWB) signals using various pulse shapes under the FCC UWB emission mask. Considered pulse shapes are the first five derivatives of the Gauss pulse (p₁, p₂, p₃, p₄ and p₅), the first four orthogonal modified Hermite waveforms, and Daubechies wavelets (db-q). It is observed in the PSD results that p₄ and p₅ Gauss pulses, the Daubechies (db-q) for q>4 comply with the FCC UWB rule by selecting proper values for the pulse duration. Then, we derive the pulse shape dependent probability of error expression for bipolar DS-UWB signals over the standard UWB channel. The five pulse shapes (p₄, p₅, db-5, db-6 and db-7) complying with the FCC emission mask are numerically compared by using the derived probability of error expression over the CM1 model of the Standard UWB channel. Results reveal that the Daubechies have better performance than those of the two Gauss pulses.