This letter presents a new concatenated code and a new criterion for the new concatenated code in fast Rayleigh fading channel. The new concatenated code consists of the cascade of a new space-time trellis code (STTC) as an inner code and a new convolutional code as an outer code. The new criterion maximizes the minimum free distance for the new convolutional code and both the minimum trace and the average trace of distance matrix for the new STTC. The new concatenated code improves the frame error rate (FER) performance significantly with low complexity. The new STTC and convolutional code are designed so as to satisfy the new criterion for 4-state 4 phase shift keying (PSK). The results of the suggested concatenated code are obtained using two transmit antennas, and shown to be significantly superior to the new and existing STTCs. As the number of receive antennas increases, the performance of the new concatenated code significantly improves, for instance, reaches FER = 10-3 at signal-to-noise ratio (SNR) = 5.2 dB for four receive antennas. Note that the proposed concatenated code also improves significant FER performance by using only one receive antenna for high SNR.

This paper presents a strictly time- and communication-optimal distributed sorting algorithm in a line network. A strictly time-optimal distributed sorting algorithm in a line network has already been designed. However, its communication complexity is not strictly optimal and it seems to be difficult to extend it to other problems, such as that related to multiple elements in a process, and also the dynamic sorting problem where the number of elements each process should have as its solution is not the same as that in the initial state. Therefore, the algorithm in this paper was designed by an alternative approach to make it strictly time- and communication-optimal. Moreover, an extension to the dynamic sorting problem is described.

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.

This paper presents new High Speed Downlink Shared Channel (HS-DSCH) code management schemes on High Speed Downlink Packet Access (HSDPA) for IP-based multimedia provisioning. The proposed management schemes simplify HS-DSCH code allocation while simultaneously increasing HS-DSCH code utilization. Applying the code management schemes, furthermore, we implement two scheduling algorithms for real-time packets to guarantee the quality-of-service (QoS) requirement. The Real-Time Code Allocation (RTCA) algorithm applies the functionalities of the radio management framework to decide the admission for a new real-time service. Once a new real-time session is established, RTCA allocates HS-DSCH codes to that session such that all real-time packets in the session are scheduled before their related deadlines. Based on the RTCA algorithm, the Real-Time Code Sharing (RTCS) algorithm implements the Early-Deadline-First (EDF) scheme for the schedulability analysis, increasing the schedulable probability for the real-time sessions and thus to improve the utilization of HS-DSCH codes. Experimental results show that RTCS outperforms RTCA in terms of packet drop rates, HS-DSCH code blocking rates and the number of code-domain reassignments.

In recent years, there has been a rapid and widespread proliferation of non-traditional embedded computing platforms such as digital camcorders, cellular phones, and portable medical devices. As applications become increasingly sophisticated and processing power increases, the application designer has to rely on the services provided by the real-time operating systems (RTOSs). These RTOSs must not only provide predictable services but must also be efficient and small in size. Kernel services should also be deterministic by specifying how long each service call will take to execute. Having this information allows the application designers to better plan their real-time application software so as not to miss the deadline of each task. In this paper, we propose a generalized deterministic scheduling algorithm that makes the task scheduling time constant irrespective of the number of tasks created in an application. The proposed algorithm eliminates the restriction on the maximum number of task priorities imposed on the existing ones, without additional memory overhead.

In this letter, we investigate serially concatenated space-time codes (SC-STs) applying iterative decoding topologies in wideband code division multiple access (WCDMA) communication systems. In the decoding algorithm, an iterative (turbo) process is used, where a priori probability (APP) is exchanged between the symbol-by-symbol space-time (ST) decoder and the bit-by-bit convolutional decoder. The experimental results show that in a Rayleigh fading channel environment the serially concatenated interleaved space-time coding systems show significant error correction capability, and based on the applied system configurations, the nonrecursive ST code outperforms the recursive ST code.

This paper proposes a new decision feedback decoding scheme for Alamouti-based space-time block coding (STBC) transmission over time-selective fading channels. In wireless channels, time-selective fading effects arise mainly due to Doppler shift and carrier frequency offset. Modelling the time-selective fading channels as the first-order Gauss-Markov processes, we use recursive algorithms such as Kalman filtering, LMS and RLS algorithms for channel tracking. The proposed scheme consists of the symbol decoding stage and channel tracking algorithms. Computer simulations confirm that the proposed scheme shows the better performance and robustness to time-selectivity.

An Ad Hoc network is a collection of wireless mobile nodes dynamically forming a temporary network without the use of any existing network infrastructure or centralized administration. The choice of medium access is difficult in Ad Hoc networks due to the time-varying network topology and the lack of centralized control. In this paper, we propose a novel multichannel schedule-based Medium Access Control (MAC) protocol for Ad Hoc networks named Multichannel Reservation Protocol for TDMA-based networks (MRPT). MRPT ensures collision free in successfully reserved data links, even when hidden terminals exist. The reservation of MRPT is based a control channel and in order to improve throughput we propose Four-Phase-Two-Division (FPTD) as a media access scheme of the control channel for broadcasting control or reservation messages. In FPTD, the collision can be solved rapidly with an efficient backoff algorithm which results in that system block is avoided in case of high traffic. In this paper, we also present the throughput performance of MRPT, which shows a high value and no system block even in case of high traffic load.

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.

In this letter, we address the performance evaluation of a space-time block coded (STBC) orthogonal frequency and code division multiplexing (OFCDM) system encountered with time-variant channels. For the performance evaluation, the average bit error rate (BER) impairment due to imperfect channel information is investigated taking into account the effect of time-varying channels. Derived results show that the loss of orthogonality due to the time variation of the channel incurs the channel estimation error, which causes performance degradation.

A cache replacement policy which takes the transcoding time into account in making replacement decisions, for the emerging transcoding proxy servers is proposed. Simulation results show the proposed policy outperforms the conventional LRU in both the cache hit rate and the average object transcoding time.

It is inevitable for driver assist and warning systems to consider the drivers' state of consciousness. Drowsiness is one of the important factors in estimating the drivers' state of consciousness. A Method to extract the driver's initial stage of drowsiness was developed by means of the eyelid's opening relevant to each various characteristic of objects with motion pictures processing in the actual driving environment. The result was that an increase of the long eyelid closure time was the key factor in estimating the initial stage of drivers' drowsiness while driving. And the state of drowsiness could be presumed by checking the frequencies of long eyelid closure time per unit period.

A new bipolar scan waveform is proposed to increase the light emission duty factor by achieving the fast address in AC plasma display panel (AC-PDP). The new bipolar scan waveform consists of two-step scan pulse, which can separate the address discharge mode into two different discharge modes: a space charge generation mode and a wall charge accumulation mode. By adopting the new bipolar scan waveform, the light emission duty factor is increased considerably under the single scan ADS driving scheme due to the reduction of address time per single subfield.

In this paper, using the exact expression for the pairwise error probability derived in terms of the message symbol distance between two message vectors rather than the codeword symbol distance between two transmitted codeword matrices, the exact closed form expressions for the symbol error probability of any linear orthogonal space-time block codes in slow Rayleigh fading channel are derived for QPSK, 16-QAM, 64-QAM, and 2 56-QAM.

We analytically investigate combinatorial effects of timer control and backoff algorithms on performance of bulk data transfer over two-state Markovian packet error channels. Numerical results for throughput, energy efficiency, and the probabilities of packet loss and loss of bulk data indicate that linear backoff algorithms outperform binary exponential ones as a whole when they are employed at the logical link sublayer with timer control.

Linking schemes have been proposed assuming the model where the time-stamp issuer need not be trusted. However, in that environment, a fake chain attack and forward or backward dating attacks are still a residual risk in Time-Stamping services (TSS). In this paper, we propose a new time-stamping scheme that focuses on these problems. In our scheme, we use pseudonyms to prevent the time-stamp issuer from dating the time that the specific entity requests. Our scheme doesn't rely on only one trustworthy entity, and uses mutual communication between each entity. Two types of entities, server and clients without any trustworthy entities are configured in our system. The server provides an anonymous communication channel, but doesn't provide TSS, and the clients are not only time-stamp requesters but also issuers. So, when a client requests a time-stamp from the system, it is issued by one of the other clients.

A new robust extended Kalman filter is proposed for the discrete-time nonlinear systems with norm-bounded parameter uncertainties. After linearization of the nonlinear systems, the uncertainties described by the energy bounded constraint can be converted into an indefinite quadratic cost function to be minimized. The solution to the minimization problem is given by the extended Kalman filter derived in a Krein space, which leads to a robust version of the extended Kalman filter. Since the resulting robust filter has the same structure as a standard extended Kalman filter, the proposed filter can be readily designed by simply including the uncertainty terms in its formulas. The results of simulations are presented to demonstrate that the proposed filter achieves the robustness against parameter variation and performs better than the standard extended Kalman filter.

This paper investigates the performance of an integrated voice/data wireless mobile network where a finite buffer is provided for voice calls since they can endure a tolerable time, or the reneging time, for service. Based on a given humanistic reneging time, we analyze the voice traffic blocking probability. The probability distribution of receiving service within the reneging time is obtained for each buffered voice call and based on this result, an appropriate amount of voice buffer is obtained. To alleviate the impact on data blocking probability caused by the voice buffer and to enhance the efficiency of data service, a dynamic multi-channel allocation scheme with channel de-allocation and guard channels is proposed for data traffic. Compared with the conventional method where the system adopts a single-channel allocation scheme without guard channel for data users, the proposed scheme shows significant improvement in data blocking probability, throughput and the mean service time. Furthermore, a system with an appropriate size of buffer for voice traffic can receive good improvement in voice blocking probability.

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.