Since standard statistical estimation methods are built on the models that treat numerical data as continuous variables, they can be inappropriate and misleading when quantization process is involved in estimation. In this paper, we propose novel distributed estimation algorithms based on the Maximum Likelihood (ML) method. Motivated by the observation that each quantized measurement corresponds to a region with which the parameter to be estimated is associated, we develop algorithms that estimates the likelihood of each of the regions rather than that of the parameter itself. Our simulation results show that the proposed algorithms achieve good performance as compared with traditional ML estimators.
Java Card technology is already a standard for smart cards and (U) SIM cards using an IC chip. Java Card technology has a problem related to slow execution speed of a program. It is also supports the transaction mechanism based on Flash memory to guarantee the integrity of data and a complete transaction during the execution of applets or downloading of applets. It is caused by too many Flash memory writing operations. In this paper, we have proposed a method to reduce the number of writing that new transaction mechanism in RAM memory.
A dual-band bow-tie antenna for wireless local area network (WLAN) is designed at both the 2.4 and 5GHz (IEEE 802.11b/g and 802.11a) WLAN bands. The design procedure involves obtaining a full resonance frequency in the 2.4GHz band and then using Parasitic Elements to achieve a secondary resonance at the 5GHz band. The proposed antenna can provide two separate impedance bandwidths of 800MHz (about 30% centered at 2.4GHz) and 1100MHz (about 20% centered at 5.5GHz), making it easily cover the required bandwidths for WLAN operation in the 2.4GHz band (about 3.4% bandwidth required) and 5.2/5.8GHz bands (about 13% bandwidth required). The antenna structure has a compact dimension of 45mm × 35mm when printed on a substrate of dielectric with a thickness of 1.58mm and a relative permittivity of 2.2. The simulated radiation patterns are nearly omni-directional. The uniplanar nature, simple feeding technique and compact structure make it easy for modular design.
In this paper, we present a novel variable step size subband affine projection (VSS-SAP) algorithm which dynamically selects subband filters in order to reduce the computational complexity and improve the convergence performance. It is called as dynamic selection variable step size subband affine projection algorithm (DS-VSS-SAP). The optimum selection of subband filters is derived by the largest decrease between the successive mean square deviations (MSDs) at every iteration. Simulation results show that the proposed algorithm has a lower misadjustment compared with the existing SAP algorithms. In addition, it retains a lower overall computational complexity.
A technique for developing highly miniaturized printed circuit antenna is proposed, which uses a meander line and Defected Ground Structure (DGS). This antenna's VSWR meets the requirements for the IEEE 802.11a (5.15-5.35GHz and 5.47-5.725GHz) American standard and HIPPER LAN/2 (5.15-5.35GHz and 5.725-5.825GHz) European standard. By changing certain antenna parameters its operational frequency can be controlled precisely. The prototype antenna exhibits an impedance bandwidth of 13% for which the return-loss is better than 10dB. The measured and simulated results confirm the antenna's viability for practical applications.
A wideband balun consisting of a transmission line transformer (TLT) and matching and phase conversion circuits is proposed and fabricated. A TLT using three 37.5-Ω coaxial cables converts the impedance from 50 to 25Ω, and a matching circuit using four resistors from a singly terminated filter improves the matching and isolation characteristics over a four-octave range. A phase conversion circuit is implemented by cross-connecting two coaxial cables. The fabricated balun provides matching (S11, S22) and isolation (S23) characteristics of about -15dB, an output magnitude difference within 0.3dB, and an output phase difference within 180°±1.4° from 62 to 960MHz.
In this article, a compact branch-line hybrid coupler (BLC) which can suppress upper order harmonics of the conventional BLC is proposed. By adding a radial stub in the center of each branch, a compact BLC which can suppress the upper order harmonics are achieved. The proposed BLC is designed and simulated at 0.93GHz. The proposed structure is 27% of the conventional BLC, while maintaining the characteristics of the conventional BLC at the center frequency. There are two transmission zeroes at 3.6 and 5.6GHz. The third upto seventh harmonic are suppressed at least 20dB.
A UHF-band RF tunable filter is developed for TV white space CMOS transmitter applications. It is based on the combined Sallen-Key and LC notch structure. The inherent transmission zero of the Sallen-Key core is carefully chosen to suppress the 7th-harmonic component of the transmitter output, and the LC notch filter is set to suppress the 9th-harmonic component. The filter is built in 0.18-µm CMOS process and consumes 6.2-mA from a 1.8-V supply. The filter's cutoff frequency is tuned from 100-MHz to 500-MHz in five steps. It is successfully adopted in a TV white space CMOS transmitter integrated circuit.
Virtualization technology can reduce the total cost of ownership by sharing resources with respect to the resource demand of each guest. Therefore, an efficient resource sharing mechanism is important for a virtual machine monitor (VMM). We introduce a hardware assisted dynamic memory balancing mechanism that balances memory among guests. Our proposed scheme estimates memory demand for each guest and periodically re-balances memory allocation based on this estimation. In order to estimate working set size (WSS), we use least recently used (LRU) histogram as a prediction model. Construction of LRU histogram is performed in a guest transparent way by using hardware memory management unit (MMU) virtualization support. Our experiments show that the proposed scheme accurately estimates the WSS with low overhead. They also show that it substantially improves performance over static memory allocation.
This letter proposes a differential common drain Colpitts VCO circuit suitable for low phase noise oscillation at the sub-1V supply voltage. Oscillation with low phase noise at the sub-1V supply voltage is facilitated by employing inductors as the current sources of the proposed circuit. One of the two feedback capacitors in the half circuit of the proposed VCO circuit is replaced by a MOS varactor in order to further increase negative resistance. Post-layout simulation results using a 0.18µm RF CMOS technology show that the phase noise performances of the proposed circuit at the sub-1V supply voltages are much better than those of the well-known cross-coupled VCO at the same supply voltages.
A modified covariance Frobenius norm (MCFN)-based spectrum sensing algorithm is proposed for cognitive radio systems with correlated multiple antennas. With some transformation, the MCFN detector can be regarded as a weighting version of the covariance Frobenius norm (CFN) detector. Consequently, the MCFN sensing algorithm is capable of achieving an improvement in detection performance.
In this letter, an efficient MIMO detection scheme combined with a QRD-M and a complex LR-aided detection scheme is proposed. For the first T stages, the QRD-M detection is executed, and then the complex LR-aided detection is executed for the last Nt-T stages. Simulation results show that the proposed scheme provides the comparable detection performance to the QRD-M. Also, the proposed scheme can significantly reduce the computational complexity compared with the QRD-M because the computations for the QRD-M is limited by the parameter T. The value of T is determined by the required system performance.