On the Static Resolution of Digitally Corrected Analog-to-Digital and Digital-to-Analog Converters With Low-Precision Components

This semi-tutorial paper considers the effect of component mismatch on the static accuracy of analog-to-digital converters (ADCs) and digital-to-analog converters (DACs) with digital correction. First, it is noted that the effective static resolution of flash ADCs is not much reduced by component mismatch: with proper digital correction, the loss due to mismatch is only about 1.3 bit, virtually independently of the mismatch level unless the mismatch is very small. Second, it is noted that current steering DACs may actually benefit from component mismatch. Moreover, with proper digital correction, current steering DACs can achieve an effective static resolution of m bits with as few as m+2 near-unit low-precision current sources     

A high performance CNFET-based operational transconductance amplifier and its applications

High performance electronic systems face several challenges in driving innovative integrated circuits when the internal transistors are scaled down below 45 nm. Carbon nanotube field effect transistors (CNFETs) are considered as excellent candidates for building energy-efficient electronic systems in the near future, due to their unique characteristics such as ballistic transport, scalability, and better channel electrostatics. In this paper, a new high performance operational transconductance amplifier (OTA) based on 32 nm CNFET devices is presented. The proposed OTA maintains a highly linear wide continuous tuning range and a wide frequency response range, enabled by splitting the linear voltage-to-current conversion and tuning two different blocks. As an application, a universal second-order transconductance-capacitor (G _m  ? C) filter realized using the OTA is introduced. Simulation results show that the CNFET-based OTA offers very a low current consumption of 2.35 μA from a ± 0.9 V power supply, achieves a bandwidth of 9.5 MHz, and has an input dynamic range of ± 0.2 V.     

Design of 0.5 V voltage-combiner based OTA with 60 dB gain 250 kHz UGB in CMOS

A gain enhancement technique for a pseudo differential OTA based on voltage combiner, suitable for sub-1 V supply is presented in this letter. The proposed technique uses a G _m boosted voltage combiner. Unlike the typical voltage combiner which has an approximated gain of \(2\,\frac{{\text{V}}}{{\text{V}}}\), this voltage combiner can produce gain more than \(5\,\frac{{\text{V}}}{{\text{V}}}\). So it help us achieve nearly 60 dB DC gain with 250 kHz UGB for the pseudo differential OTA at a capacitive load of 10 pF. Power dissipation is very low i.e. 716 nW at supply of 0.5 V. So as to facilitate maximum swing at 0.5 V supply and lower the power consumption, MOS transistors are biased in weak/moderate inversion. The OTA is designed in standard 45 nm CMOS process. Phase margin of is more than \(55^{\circ }\) for a typical load of 10 pF. The input referred noise is \(150\,\upmu {\text{V}}{/}\sqrt{{\text{Hz}}}\) at 10 Hz and slew rate \(0.02\,{\text{V}}{/}\upmu{\text{s}}\) for 10 pF load.     

An Optically Pumped Far-Infrared Folded Mirror-Less Cavity

A compact and efficient mirror-less cavity is presented for an optically pumped 192-μm far-infrared laser. With a gold-coated mirror and 30°-inclined anti-reflection coated Ge plate serving as highly reflective mirrors, a folded mirror-less CH₃F cavity is achieved. Maximum energy of 0.72 mJ is obtained with the pump energy of 600 mJ, which gives an energy increment of 75% in comparison with the previous 1.85-m mirror-less system. The beam divergence angle of the FIR radiation from this folded mirror-less cavity is measured to be 14.2 mrad.     

A Convex Programming for Range Assignment to Optimize Lifetime in Network-Coding-Based-Wireless-Sensor Networks

Wireless sensor networks (WSNs) are known to be highly energy-constrained and  consequently lifetime is a critical metric in their design and implementation. Range assignment by adjusting the transmission powers of nodes create a energy-efficient topology for such networks while preserving other network issues, however, it may effect on the performance of other techniques such as network coding. This paper addresses the problem of lifetime optimization for WSNs where the network employs both range assignment and network-coding-based multicast. We formulate the problem and then reformulated it as convex optimization that offer a numerous theoretical or conceptual advantages. The proposed programming leads to efficient or distributed algorithms for solving the problem. Simulation results show that the proposed optimized mechanism decreases end-to-end delay and improve lifetime as compared by other conventional ones.     

Millimeter-Wave Beam Multiplexing Method Using Subarray Type Hybrid Beamforming of Interleaved Configuration with Inter-subarray Coding

A millimeter-wave beam multiplexing method using a subarray type interleaved configuration hybrid beamforming with inter-subarray coding is proposed. By multiplexing of adequate directional beams, the proposed method can reduce inter-beam interference and create multiple beams of a theoretical maximum gain that an array antenna can generate. As results of performance comparison in subarray type beamforming with the feasibility, it is shown that channel capacity of the interleaved configuration with inter-subarray coding is larger than that of the localized configuration. Particularly, in user dense environments, the interleaved configuration is effective. Therefore, we think that the interleaved configuration is suitable for millimeter-wave beam multiplexing.     

SDN-based wireless user management system

The degradation of end-to-end quality of service (QoS) on mobile users is becoming a common issue for IEEE 802.11 infrastructure-based networks in crowded areas. This research tackles the issue by employing an SDN framework on an integrated wireless/wired environment. Thereby, we present the development and implementation of a system that performs user management by analyzing the network load from the OpenFlow statistics, as well as the wireless information collected from the associated users. In order to analyse the behaviour of the proposed user migration algorithm, we evaluate the system under scenarios with different traffic load and user session duration. From the experiments, we observed that in several cases wireless users get a considerable QoS improvement at the application layer (up to 30% improvement in throughput and up to 20% in delay in our simulations) once the system is activated. Based on the results, we present an analysis on how and when user migration in multi-access point IEEE 802.11 networks can be most effective.     

EPEC: an efficient privacy-preserving energy consumption scheme for smart grid communications

In this paper, we propose an efficient privacy-preserving energy consumption scheme with updating certificates, called EPEC, for secure smart grid communications. Specifically, the proposed EPEC scheme consists of four phases: gateways initialization, party registration, privacy-preserving energy consumption, and updating certificates. Based on the bilinear pairing, the identity-based encryption, and the strategy of updating certificates, EPEC can achieve data privacy, gateway privacy, and is robust to data replay attack, availability attack, modification attack, man-in-the-middle attack, and Sybil attack. Through extensive performance evaluations, we demonstrate the effectiveness of EPEC in terms of transmission delay performance at the HAN gateway and average delivery ratio, by implementing three types of curves including, the Barreto–Naehrig curve with modulus 256 bits, the Kachisa–Schaefer–Scott curve with modulus 512 bits, and the Barreto–Lynn–Scott curve with modulus 640 bits.     

The JDTDOA algorithm applied to signal recovery: a performance analysis

This article suggests a novel method to retrieve a narrowband signal sent in a multipath environment with a delay spread considering ISI between symbols. The proposed method does not require any preamble nor known signal. Using the joint direction and time delay of arrivals estimation algorithm developed in prior work, the directions and time delays of arrival in the multipath channel are jointly estimated and associated while keeping a low computational cost. In this process, a MVDR beamformed copy of each arriving signal is created. The quality of these “pseudo copies” is evaluated and compared to the original direct and reflected signals in this work. Another beamforming method, the Moore–Penrose pseudoinverse, with better retrieval of the direct and reflected signals is also proposed. Using a simple delay-and-sum operation on the previously beamformed copies, it is possible to substantially improve the the system’s performance in terms of bit error rate. An approach using oversampling on the array antenna is introduced to improve performance. Numerical simulations are discussed to support theory.     

Bounded Tamper Resilience: How to Go Beyond the Algebraic Barrier

Related key attacks (RKAs) are powerful cryptanalytic attacks where an adversary can change the secret key and observe the effect of such changes at the output. The state of the art in RKA security protects against an a-priori unbounded number of certain algebraic induced key relations, e.g., affine functions or polynomials of bounded degree. In this work, we show that it is possible to go beyond the algebraic barrier and achieve security against arbitrary key relations, by restricting the number of tampering queries the adversary is allowed to ask for. The latter restriction is necessary in case of arbitrary key relations, as otherwise a generic attack of Gennaro et al. (TCC 2004) shows how to recover the key of almost any cryptographic primitive. We describe our contributions in more detail below. (1) We show that standard ID and signature schemes constructed from a large class of \(\Sigma \)-protocols (including the Okamoto scheme, for instance) are secure even if the adversary can arbitrarily tamper with the prover’s state a bounded number of times and obtain some bounded amount of leakage. Interestingly, for the Okamoto scheme we can allow also independent tampering with the public parameters. (2) We show a bounded tamper and leakage resilient CCA-secure public key cryptosystem based on the DDH assumption. We first define a weaker CCA-like security notion that we can instantiate based on DDH, and then we give a general compiler that yields CCA security with tamper and leakage resilience. This requires a public tamper-proof common reference string. (3) Finally, we explain how to boost bounded tampering and leakage resilience [as in (1) and (2) above] to continuous tampering and leakage resilience, in the so-called floppy model where each user has a personal hardware token (containing leak- and tamper-free information) which can be used to refresh the secret key. We believe that bounded tampering is a meaningful and interesting alternative to avoid known impossibility results and can provide important insights into the security of existing standard cryptographic schemes.