Design of a performance enhanced traceback algorithm for theViterbi decoder

The authors propose an efficient traceback scheme for the parallel hardware implementation of the Viterbi algorithm. Compared to the conventional Viterbi algorithm, where output is selected arbitrarily when multiple survivor paths exist, the proposed algorithm decides decoding output by analysing the survivor paths of consecutive tracebacks. Experimental results show that the proposed algorithm exhibits improved error-correction capability compared to the existing algorithms     

Scalable parallel computers for real-time signal processing

We assess the state-of-the-art technology in massively parallel processors (MPPs) and their variations in different architectural platforms. Architectural and programming issues are identified in using MPPs for time-critical applications such as adaptive radar signal processing. We review the enabling technologies. These include high-performance CPU chips and system interconnects, distributed memory architectures, and various latency hiding mechanisms. We characterize the concept of scalability in three areas: resources, applications, and technology. Scalable performance attributes are analytically defined. Then we compare MPPs with symmetric multiprocessors (SMPs) and clusters of workstations (COWs). The purpose is to reveal their capabilities, limits, and effectiveness in signal processing. We evaluate the IBM SP2 at MHPCC, the Intel Paragon at SDSC, the Gray T3D at Gray Eagan Center, and the Gray T3E and ASCI TeraFLOP system proposed by Intel. On the software and programming side, we evaluate existing parallel programming environments, including the models, languages, compilers, software tools, and operating systems. Some guidelines for program parallelization are provided. We examine data-parallel, shared-variable, message-passing, and implicit programming models. Communication functions and their performance overhead are discussed. Available software tools and communication libraries are also introduced     

Publicly verifiable authenticated encryption

Ma and Chen [2003] have proposed an authenticated encryption scheme with public verifiability. The scheme claims that the TTP can publicly verify the sender's signature without running a zero knowledge proof protocol. The problem in verification which causes the TTP to reject a valid signature with non-negligible probability is pointed out.     

A graphic approach to performance analysis of multistage linear interference canceller in long-code CDMA systems

The signal-to-interference-plus-noise-ratio performance of the multistage linear parallel and successive interference cancellers (LPIC and LSIC) in a long-code code-division multiple-access system is analyzed using a graphical approach. The decision statistic is modeled as a Gaussian random variable, whose mean and variance can be expressed as functions of moments of R for the LPIC and L for the LSIC, respectively, where R is the correlation matrix of signature sequences and L is the strict lower triangular part of R. Since the complexity of calculating these moments increases rapidly with the growth of the stage index, a graphical representation of moments is developed to facilitate the computation. Propositions are presented to relate the moment calculation problem to several well-known problems in graph theory, i.e., the coloring, the graph decomposition, the biconnected component finding, and the Euler tour problems. It is shown that the derived analytic results match well with simulation results.     

Fast Firmware Implementation of RSA-Like Security Protocol for Mobile Devices

In modern mobile communications, personal privacy and security are of top concern to mobile phone subscribers. Yet, owing to the limit of their processing capability, mainstream mobile manufacturers are still unable to apply advanced security protocol to mobile devices. It should be noted that many security protocols are based on RSA algorithm. To implement RSA algorithm and thus apply many advanced security protocols to mobile networks, this paper proposes an efficient and practical method based on the Texas Instruments TMS320C55x family. When the proposed method is employed, it takes only 7.9 milliseconds to perform a 1024-bit RSA encryption operation at the clock frequency of 200 MHz. Our decryption operation is at least 3.5 times faster than the time taken to perform the same operation without employing the proposed method. In addition, the proposed method can stop any power-analysis attack on RSA-based security protocols, thereby enhancing the security of mobile environments.     

The Fabrication and Characterization of Single‐Component Polymeric White‐Light‐Emitting Diodes

By using Ni⁰‐mediated polymerization, we have systematically synthesized a series of fluorene‐based copolymers composed of blue‐, green‐, and red‐light‐emitting comonomers with a view to producing polymers with white‐light emission. 2,7‐Dibromo‐9,9‐dihexylfluorene, {4‐(2‐[2,5‐dibromo‐4‐{2‐(4‐diphenylamino‐phenyl)‐vinyl}‐phenyl]‐vinyl)‐phenyl}‐diphenylamine (DTPA), and 2‐{2‐(2‐[4‐{bis(4‐bromo‐phenyl)amino}‐phenyl]‐vinyl)‐6‐tert‐butyl‐pyran‐4‐ylidene}‐malononitrile (TPDCM) were used as the blue‐, green‐, and red‐light‐emitting comonomers, respectively. It was found that the emission spectra of the resulting copolymers could easily be tuned by varying their DTPA and TPDCM content. Thus with the appropriate red/green/blue (RGB) unit ratio, we were able to obtain white‐light emission from these copolymers. A white‐light‐emitting diode using the polyfluorene copolymer containing 3 % green‐emitting DTPA and 2 % red‐emitting TPDCM (PG3R2) with a structure of indium tin oxide/poly(3,4‐ethylenedioxythiophene):poly(styrene sulfonic acid)/PG3R2/Ca/Al was found to exhibit a maximum brightness of 820 cd m^–2 at 11 V with Commission Internationale de L'Eclairage (CIE) coordinates of (0.33,0.35), which are close to the standard CIE coordinates for white‐light emission (0.33,0.33).     

ZnS/CuInS2/Mo/钠钙玻璃衬底上射频溅射ZnO∶Al薄膜的SEM研究

结合ZnO薄膜在Cu-III-VI2基薄膜太阳电池上的应用，采用射频磁控溅射技术以陶瓷ZnO∶Al2O3为靶材在ZnS/CuInS2/Mo/钠钙玻璃衬底上于固定沉积条件下低温（200℃）制备了铝掺杂氧化锌（ZnO∶Al）薄膜. 运用扫描电子显微镜研究了底层材料特别是ZnS和CuInS2的生长参数对沉积的ZnO∶Al薄膜的表面形貌的影响. 实验发现，衬底材料中硫含量的增加（无论来自ZnS还是来自CuInS2) ，都会引起沉积ZnO∶Al薄膜结晶质量的提高，而金属含量的增大将有利于薄膜均匀性的改进.     

2/spl times/4 optical add-drop module with no difference in propagation length

We developed a micromachined X-type 2/spl times/4 optical add-drop module (OADM) featuring no difference in propagation length. Four pairs of lensed fibers are aligned in "X" position, and four micromirrors are located between the pairs of optical fibers. The OADM was fabricated utilizing a silicon-on-insulator process. Electrostatic comb actuators can be driven up to 90 /spl mu/m to change the light path within 1 ms. The insertion loss and the on-off ratio were less than 3 and 70 dB, respectively. The loss uniformity in every channel was 1.5 dB.     

Research activities on next-generation mobile communications and services in Korea

In this article we present a perspective on next-generation mobile communications and services. As a preliminary research work on next-generation mobile communications, we exploit what next-generation mobile services will be (S. Ryu et al., May 2003). We define next-generation mobile services as a hierarchy of services consisting of three different service levels: the service areas, the service functionalities, and the service technologies. We derive these service levels by means of scenario-based analysis. Next we propose conceptual reference network architecture, focusing on the realization of the service technologies. We divide the network into four different parts: a user equipments and access part, a network service provisioning layer part, a network control layer part, and non-mobile network operator service pan, according to characteristics of information and service flows within a network. In this reference network architecture, service elements such as servers, processors, and gateways are placed in each network part to support the derived next-generation mobile services. Finally, we give a brief introduction of research and development activities for next-generation mobile communication systems and services in Korea.     

Dielectric reliability of stacked Al2O3–HfO2 MIS capacitors with cylinder type for improving DRAM data retention characteristics

Dielectric reliability in Al₂O₃(2–3.1nm)–HfO₂(3nm) stack capacitor with Metal–Insulator–Si(MIS) structure is investigated in this paper. We propose an optimized capacitor process through the Time–Dependent Dielectric Breakdown (TDDB) data under various process conditions. Furthermore, due to asymmetric current at both negative and positive voltage stress polarities, we show different lifetime extrapolation by a fluence–driven model. As a result, the maximum allowed operating voltage is projected to be 1.7V (failure rate 10ppm during 10year @ 85°C) for Data “0” retention lifetime.