In this paper, an interference cancellation (IC) scheme for a multirate VPG DS/CDMA system is evaluated in a multipath fading mobile channel and is designed to accommodate the multimedia sources of varying data-rate requirements. In the this scheme, the strongest user with high-rate transmission will benefit from the multiple access interference (MAI) reduction of the weaker users, which yields more clean estimates in the next cancellation stage. From the numerical results, the proposed scheme outperforms the conventional SIC scheme under the condition of the approximately identical decoding delay at the cost of the hardware burden.

This paper presents a transmit diversity scheme that allocates space-time block codes (STBC) to beamspace and spreading codes for two-dimensional spreading orthogonal frequency-division multiplexing code-division multiplexing (OFDM-CDM) downlink transmission. In this scheme, the STBC output symbols are beam-steered using a pair of neighboring beams selected via closed-loop beam selection. The beam-steered symbols in two adjacent time slots are spread by two distinct spreading codes and multiplexed in the same spreading segment. User signals transmitted from different pairs of beams, but that share the same beam, interfere with each other when decoding STBC. Spreading codes are thus allocated to users according to beam pairs used. This is to suppress the interference in time-direction despreading that precedes decoding of STBC. Simulation results demonstrated that the proposed scheme provides beam gains or beam diversity gains or both and that it alleviates inter-code interference by spatially separating user signals by using transmit beam. The proposed scheme also provides high tolerance to large Doppler spread.

SMIL is a markup language which enables us to describe multimedia contents. This paper proposes a design model of SMIL browser functionality for mobile phones whose resources are limited. We introduce SMIL Component, which is based on attachable software architecture to a pre-installed generic web browser and an event-based SMIL scheduler, which is a part of SMIL Component, to provide the multimedia presentation scheduling functionality. These lead to reducing the memory amount that SMIL Component consumes and brings high portabilty of SMIL Component for various web browsers. We implement SMIL Component and evaluate RAM sizes and presentation delays. As a result, we conclude that SMIL Component is practical for MMS presentations on a mobile phone.

A computationally efficient time delay and Doppler estimation algorithm is proposed for active sonar with a Linear Frequency Modulated (LFM) signal. To reduce the computational burden of the conventional estimation algorithm, an algebraic equation is used which represents the relationship between the time delay and the Doppler in the cross-ambiguity function (CAF) of the LFM signal. The algebraic equation is derived based on the Fast Maximum Likelihood (FML) algorithm. The use of this algebraic relation enables the time delay and Doppler to be estimated with two 1-D searches instead of the conventional 2-D search.

This paper discusses far-end crosstalk (FEXT) cancellation methods for multicarrier transmission system. A system arrangement and its tap update method are proposed when FEXT cancelers and a frequency-domain equalizer (FEQ) are jointly adapted to combat channel intersymbol interference, FEXT, and other additive noise. We present mathematical formulation of minimum mean-square error (MSE) and the optimum tap coefficients for the FEXT cancelers and the FEQ when FEXT cancellation techniques are introduced for multiuser discrete multitone (DMT) based very high-speed digital subscriber line (VDSL) transmission. It is shown that FEXT cancellation enhances the achievable bit rate in FEXT-limited systems. Computer simulation and analytical results show that the performance of jointly adapted FEXT cancelers and an FEQ is better than that of separately adapted FEXT cancelers and an FEQ.

We implement an efficient Secure Socket Layer (SSL) accelerator, which is embedded in the kernel level and utilizes kernel threads as the same number of CPUs. In comparison with the conventional Apache with/without our SSL accelerator, the SSL accelerator significantly improves the web-server performance by up to 200%.

In mobile OFDM systems, sub-carriers orthogonality will be broken due to Doppler shift, and this results in inter-carrier interference (ICI). Many methods have been proposed to compensate for this, however, these methods won't be suitable for fast fading caused by high mobile speed. In this letter, we propose a novel sampling theorem based pilot symbol-aided technique which can not only estimate the channel fading envelope (CFE) accurately under high relative Doppler frequency (RDF) but also achieve lower BER than conventional methods. The validity of the proposed method is demonstrated by computer simulations.

Determining consistent global checkpoints of a distributed computation has applications in the areas such as rollback recovery, distributed debugging, output commit and others. Netzer and Xu introduced the notion of zigzag paths and presented necessary and sufficient conditions for a set of checkpoints to be part of a consistent global checkpoint. This result also reveals that determining the existence of zigzag paths between checkpoints is crucial for determining consistent global checkpoints. Recent research also reveals that determining zigzag paths on-line is not possible. In this paper, we present an off-line method for determining the existence of zigzag paths between checkpoints.

This paper examines the Inter Carrier Interference (ICI) due to Doppler spread in OFDM mobile reception and proposes the use of Beam-Space Adaptive Array Antennas for moving receivers. In the proposed system, firstly we separate the multi-path signals into multi-beams according to their incident directions, then correct the frequency shift of each beam signal, considering the beam direction, and finally combine the corrected signals based on Maximal Ratio Combining (MRC). Further this paper clarifies the excellent performance of the proposed system in suppressing the influence of Doppler spread by carrying out computer simulation. Particularly, it was certified that it is possible to suppress the influence of the Doppler spread efficiently for all the receiving directions by using eight-element beam-space array antenna with element spacing of (3/8)λ, and referring three past symbol data when calculating the weight vector of MRC.

This paper proposes a test generation method using several partly compacted test plan tables for RTL data paths. Combinational modules in data paths are tested using several partly compacted test plan tables. Each partly compacted test plan table is generated from each grouped test plan set and is used to test combinational modules corresponding to the grouped test plans. The values of control signals in a partly compacted test plan table are supplied by a test controller. This paper also proposes the architecture of a test controller which can be synthesized in a reasonable amount of time, and proposes a test plan grouping method to shorten test length for data paths under a test controller area constraint. Experimental results for benchmarks show that the test lengths are shortened by 4 to 36% with -9 to 8% additional test controller area compared with the test generation method using test plans.

In the paper we evaluate program susceptibility to hardware faults using fault injector. The performed experiments cover many applications with different features. The effectiveness of software techniques improving system dependability is analyzed. Practical aspects of embedding these techniques in real programs are discussed. They have significant impact on the final fault robustness.

In this paper, we propose a fault-tolerance mechanism for microprocessors, which detects transient faults and recovers from them. The investigation of fault-tolerance techniques for microprocessors is driven by two issues: One regards deep submicron fabrication technologies. Future semiconductor technologies could become more susceptible to alpha particles and other cosmic radiation. The other is the increasing popularity of mobile platforms. Cellular telephones are currently used for applications which are critical to our financial security, such as mobile banking, mobile trading, and making airline ticket reservations. Such applications demand that computer systems work correctly. In light of this, we propose a mechanism which is based on an instruction reissue technique for incorrect data speculation recovery and utilizes time redundancy, and evaluate our proposal using a timing simulator.

Asynchronous controllers effectively control high concurrence of datapath operations for high speed. Signal Transition Graphs (STGs) can effectively represent these concurrent events. However, highly concurrent STGs cause the state explosion problem in asynchronous synthesis tools. Many small but highly concurrent STGs cannot be synthesized to obtain control circuits. Moreover, STGs also lead to some control-time overhead of the four-phase handshake protocol. In this paper, we propose a method for deriving the serial control nodes from Control Data Flow Graphs (CDFGs) such that the concurrence of datapath operations is still preserved. The STGs derived from the serialized control nodes are serial STGs which are simpler for synthesis than the concurrent STGs. We also propose an implementation using these serialized controllers to generate local clocks at any necessary times. The implementation results in very small control-time overhead. The experimental results show that the number of synthesis states is proportional to the number of control signals, and the circuits with satisfiable small control-time overhead are obtained.

Since the characteristic to current information systems is the dynamic and concurrent change of their configurations and scales with non-stop provision of their services, the system management should inevitably rely on autonomic computing. Since fault tolerance is the one of important system management issues, it should also be incorporated in autonomic computing environment. This paper argues what should be taken into consideration and what approach could be available to realize the fault tolerance in such environments.

This paper presents a transmit diversity scheme that uses space-time block codes (STBC) in space-spreading code dimensions for time-direction spreading or two-dimensional spreading orthogonal frequency-division multiplexing code-division multiplexing (OFDM-CDM) downlink transmission. The STBC output symbols in two adjacent time slots are spread by two distinctive spreading codes and multiplexed in the same spreading segment. At a receiver, the received subcarrier signals are despread with the two spreading codes in the direction of time, space-time decoded, and then combined in the direction of frequency. Simulation results demonstrated that the proposed scheme provided high tolerance to Doppler spread and outperformed space-time transmit diversity (STTD) for high-mobility users.

The deployment of server replicas of a service across an asynchronous distributed system (e.g., Internet) is a real practical challenge. This target cannot be indeed achieved by classical software replication techniques (e.g., passive and active replication) as these techniques usually rely on group communication toolkits that require server replicas to run over a partially synchronous distributed system to solve the underlying agreement problem. This paper proposes a three-tier architecture for software replication that encapsulates the need of partial synchrony in a specific software component of a mid-tier to free replicas and clients from the need of underlying partial synchrony assumptions. Then we propose how to specialize the mid-tier in order to manage active replication of server replicas.

The traditional approach for establishing the correctness of group communication protocols is through rigorous arguments. While this is a valid approach, the likelihood of subtle errors in the design and implementation of such complex distributed protocols is not negligible. The use of formal verification methods has been widely advocated to instill confidence in the correctness of protocols. In this paper, we describe how we used the SPIN model checker to formally verify a group membership protocol that is part of an intrusion-tolerant group communication system. We describe how we successfully tackled the state-space explosion problem by determining the right abstraction level for formally specifying the protocol. The verification exercise not only formally showed that the protocol satisfies its correctness claims, but also provided information that will help us make the protocol more efficient without violating correctness.

The E-1-track switch torus array model and the "EAR" reconfiguration method are proposed for fault tolerance of mesh or torus-connected processor arrays, where the original idea of EAR is in EAM. The comparison among these and others is described in terms of the (run-time) array reliability, hardware overhead, and/or reconfiguration time. When a designer chooses one among fault tolerant methods, he should consider their features synthetically case by case, and we consider that the results given by this paper are useful for the choice.

We propose an efficient algorithm for making multi-layered neural networks (MLN) fault-tolerant to all multiple weight faults in a multi-dimensional interval by injecting intentionally two extreme multi-dimensional values in the interval into the weights of the selected multiple links in a learning phase. The degree of fault-tolerance to a multiple weight fault is measured by the number of essential multiple links. First, we analytically discuss how to choose effectively the multiple links to be injected, and present a learning algorithm for making MLNs fault tolerant to all multiple (i.e., simultaneous) faults in the interval defined by two multi-dimensional extreme points. Then it is proved that after the learning algorithm successfully finishes, MLNs become fault tolerant to all multiple faults in the interval. It is also shown that the time in a weight modification cycle depends little on multiplicity of faults k for small k. These are confirmed by simulation.

We propose a new dependable system called PREGMA (Platform for Reliable Environment based on a General-purpose Machine Architecture). PREGMA aims to meet two requirements -- fault tolerance and low cost -- for Internet services. It can provide fault tolerance, so we can avoid system failure and prevent data corruption, even if faults occur. That is, it masks the faults by running multiple replicated servers, each possessing its own data, in a loosely synchronized manner and delivering the majority vote as output to clients. Moreover, PREGMA is composed of COTS (Commercial Off-The-Shelf) components without modification, which makes it possible to offer the services at a low cost. We investigated two approaches for achieving redundancy of the Coordinator, which is the core of PREGMA: using the primary backup method and the active replication method. We evaluated the effectiveness of PREGMA in terms of throughput overhead, data integrity and recovery time. The results for a prototype show that PREGMA using the Coordinator with the primary backup method outperforms that with the active replication method and has throughput only 3% lower than a non-redundant system. The results also show that, in the event of failure, the recovery time is only less than one second and no data corruption occurs.