The objective of this paper is to evaluate the impacts of impulsive class-A noise, co-channel interference due to other piconet, Rician fading on the packet error rate (PER), and throughput performance in the Bluetooth scatternet. Simulation results illustrate the significant difference in performance between synchronous and asynchronous Bluetooth systems. The paper also provides the insights on how to design Bluetooth scatternet for minimal PER and maximum throughput performance.

This paper describes a novel mobile video monitoring system. The receiver is a PDA (Personal Digital Assistant) with a PHS (Personal Handy Phone system) card. The sender is a PC-based video encoding system, which is connected to an ISDN line by ISDN-TA. Functions such as camera selection, remote camera control and high-resolution snap shot are implemented. In this paper, details of the system are explained and a practicability assessment is performed. An experiment was conducted to measure the upward and downward transmission delay. From the results, the system performs consistently to a theoretical behavior. Furthermore, the performance of this system is quite practical for mobile video monitoring.

In this letter, an analysis of bit error probability of 4-state soft decision Viterbi decoding is presented. The bit error probability of recursive systematic convolutional code is also derived.

In this paper, we propose a new resource management scheme for multiple video stream transmission in a wireless environment. The proposed scheme adaptively determines transmission parameters such as the number of assigned time slots, modulation format, and forward error correction (FEC) code rate according to the required bit rate and error sensitivity of the video stream as well as the channel state. The computer simulation results show that the proposed scheme drastically improves the image quality degradation due to channel errors.

In conventional Web Geographic Information System (GIS), there are serious drawbacks of high waiting time and low accessibility because the subsequent query has to wait until all the spatial data has been completely transmitted. In addressing these problems, this paper proposes a progressive transmission method which can reduce waiting time and increase accessibility. The proposed method has the following steps. First, significant vertices of geographic objects are selected into based on an algorithm, Priority_Order_Estimation (POE). Second, the selected vertices are inserted the data structure, Priority_Order_Queue (POQ). This allows a client to view, to request and occasionally to reject spatial data, rather than waiting for the whole map to arrive. Third, the transmission steps are processed progressively, where significant vertices of POQ are sent from server to client one by one. In the final step, if necessary, the entire spatial data set of SENDOBJSP, which is a transmission structure, is transmitted so that the original map is accurately displayed. The performance of the system proposed here has been evaluated according to the factors such as system response time and client storage space. For the comparisons, the total transmission method, layer transmission method and the proposed four-step transmission method were used. Compared with the conventional Web-based GIS, the system response time is twenty-two percent shorter and client storage space is reduced by about twenty-one percent. As a result, performance improvement, fast response time and less client storage usage, is achieved. Therefore, the proposed method can make a significant contribution in support of Web-based Vector GIS applications such as Environmental Management, Map On Demand Service and Assessment and Planning System.

Emerging requirement for higher rate data services and better spectrum efficiency is the main driving force identified for the third generation mobile radio systems. Moreover, it needs the capability of providing predictable qualities of service (QoS) for different applications. To maintain different QoS requirements, mechanisms such as call admission control (CAC) and load control, etc. are needed to achieve the required services. In this paper, we propose a CAC algorithm based on channel assignment in a multi-chip rate direct-sequence CDMA (MCR-DS-CDMA) cellular system supporting multi-rate services. Five multi-MBC (mapping of information bit rates to chip rates) channel assignment schemes and corresponding channel selection rules are proposed herein. Computer simulation, where multimedia applications are considered, is used to evaluate the system performance (e.g., blocking probability and system capacity) with different channel assignment schemes. Numerical results demonstrate that scheme 5 (i.e., Minimum-influence scheme) performs better because it provides the highest system capacity and least blocking probability.

In this paper, a contention-based reservation MAC protocol is proposed for non-real-time burst traffic class in wireless ATM networks. The proposed protocol is characterized by the contention-based transmission of the reservation request and contention-free transmission of burst traffic. The design objective of the proposed protocol is to reduce contention delay during the contention phase of a connection. In order to reduce collision of reservation requests, the base station calculates the transmission probability based on the estimated load of reservation requests and the number of random access minislots, and broadcasts it over the frame header period of downlink channel. Wireless terminal, which has traffic burst, selects a random access minislot and transmits its reservation request with a received transmission probability. Based on the successfully received reservation, the scheduler allocates the uplink data slots to wireless terminal. Simulation results show that the proposed protocol can provide higher channel utilization, and furthermore, maintains constant delay performance in a heavy traffic environment.

This letter proposes a method which can embed index data such as memos into JPEG images. The method embeds digital watermarks using the quantitative relation between quantized DCT coefficients in JPEG images. In the method, we can embed extra data to represent index data and can extract the index data without parameters used in embedding process. Furthermore, the method is tolerant of JPEG recompression and prevents the degradation of image quality by rewriting index data.

To obtain a high throughput for transmission control protocol (TCP) connections over the wireless links, we previously proposed a novel transmission power control method for code division multiple access (CDMA) packet communication systems. By using this transmission power control method, we developed a transmission power control method and a packet multiplexing method to transmit constant bit rate (CBR) and TCP packets over CDMA wireless systems. Our methods can guarantee the quality of service (QoS) for CBR connections and utilize bandwidth effectively without modifying the TCP protocol or using slot assignments. Evaluation of our methods by computer simulation showed that the proposed methods provide a near-maximum throughput and guarantee the packet loss ratio of CBR connections regardless of the number of connections.

The pre-Rake system is known as a technique in TDD DS/CDMA system to reduce the mobile complexity and achieve the same BER performance like Rake receiver. The pre-Rake system itself is not optimum, since the channel impulse responses of uplink and downlink are slightly different in TDD system, so the signal- to-noise ratio (SNR) can be maximized with a matched filter based Rake receiver, which has not been considered in the conventional pre-Rake system. Furthermore pre-Rake system is sensitive to the Doppler frequency. Even though the pre-Rake system has the ability to suppress other user interference, it is not efficient to maximize the received signal in high Doppler frequency. However, Rake combiner is utilized for the detection method in our proposed system. So the maximized signal can keep the orthogonality better than the pre-Rake system and our proposed system can compensate the Doppler frequency effect. From these reasons, our system achieves better BER performance than that of the pre-Rake system with increasing the number of users in high Doppler frequency.

In this paper, a method is proposed to construct an n-out-of-n visual secret sharing scheme for gray-scale images, for short an (n,n)-VSS-GS scheme, which is optimal in the sense of contrast and pixel expansion, i.e., resolution. It is shown that any (n,n)-VSS-GS scheme can be constructed based on the so-called polynomial representation of basis matrices treated in [15],[16]. Furthermore, it is proved that such construction can attain the optimal (n,n)-VSS-GS scheme.

Test compression/decompression is an efficient method for reducing the test application cost. In this paper we propose a test generation method for obtaining test-patterns suitable to test compression by statistical coding. In general, an ATPG generates a test-pattern that includes don't-care values. In our method, such don't-care values are specified based on an estimation of the final probability of 0/1 occurrence in the resultant test set. Experimental results show that our method can generate test patterns that are able to be highly compressed by statistical coding, in small computational time.

This paper proposes a channel monitor-based unequal error protection scheme using a dynamic OFDM subcarrier assignment technique for broadband video transmission systems in frequency selective fading environments. In the proposed system, to achieve stable regeneration of the received video, subcarriers with relatively high channel gain are assigned to the high priority data (HPD) in the MPEG data. To further guarantee a required transmission quality of the HPD, the proposed system also employs subcarrier transmission power control with delay profile information (DPI) feedback-type channel estimation technique. Computer simulation confirms that the proposed technique is effective in preventing quality degradation with about 20 dB lower transmission power than the conventional systems in frequency selective fading environments.

In this paper, we propose and evaluate a new channel assignment scheme for a micro-cellular network integrating data and conversational services. The channel assignment scheme combines handover processing depending on terminal speed with a preemptive scheme. High-speed terminals take over the channels of data terminals upon entering a full cell, while the data terminals are put in a queue until new resources are available. Simulating several variations of the scheme, allowing both fast moving data and voice terminals to preempt data terminals yielded the best result. Suspension time for fast moving data terminals was reduced dramatically, reducing the disadvantage caused by a high number of handovers. The cost was a small increase in blocking probability for new terminals.

In this paper, a high performance 3232-bit multiplier for a DSP core is proposed. The multiplier is composed of a block of Booth Encoder, a block of data compression, and a block of a 64-bit adder. In the block of Booth encoder, a conditional sign decision Booth encoder that reduces the gate delay and power consumption is proposed. In the block of data compression, 4-2 and 9-2 data compressors based on a novel compound logic are used for the efficient compressing of extra sign bit. In the block of 64-bit adder, an adaptive MUX-based conditional select adder with a separated carry generation block is proposed. The proposed 3232-bit multiplier is designed by a full-custom method and there are about 28,000 transistors in an active area of 900 µm 500 µm with 0.25 µm CMOS technology. From the experimental results, the multiplication time of the multiplier is about 3.2 ns at 2.5 V power supply, and it consumes about 50 mW at 100 MHz.

Since the deployment of base stations (BS's) is far from optimum in 3-dimensional (3-D) space, i.e., the vertical baseline is relatively shorter than the planar baseline, the geometric degradation of precision of the altitude estimate is larger than that of the planar location. This paper considers the problem of 3-D range location and attempt to improve the altitude estimate. We first use a volume formula of tetrahedron to transform the range measurements to the volume measurements, then a novel pseudo-linear solution is proposed based on a linear relationship between the rectangular and the volume coordinates. Theory analysis and numerical examples are included to show the improved accuracy of the altitude estimate of mobile location. Finally, an improved estimate of 3-D mobile location is given by solving a set of augmented linear equations.

A quasi-synchronous (QS) Multi-Carrier time division duplex DS-CDMA is studied for reverse link on multipath indoor environment. Quasi-synchronous DS-CDMA drastically reduces the effect of multiple access interference with several interesting features of time division duplex (TDD) mode for mobile communications. In this paper, we use the time division duplex transmission mode and each user appropriately adjusts its transmission time, through feed back control from the base station, so its signal can arrive at the base station synchronously with the other mobile stations. This paper evaluates the performance of a quasi-synchronous multi-carrier TDD DS-CDMA for reverse link on multipath indoor environment. The performance results are shown with different quasi-synchronous accuracy and power control error values. Orthogonal codes are used for spreading the signals in QS transmission. On the other hand, random codes are used for an asynchronous transmission. From the results, when the performance of asynchronous system is assumed to be a reference, we can see that the constraint of quasi-synchronous accuracy equals 2.3 chips of multi-carrier system at spreading factor 32.

This paper investigates the behavior of one-dimensional discrete-time binary cellular neural networks with both the A- and B-templates and gives the necessary and sufficient conditions for the above network to be stable for unspecified fixed boundaries.

A simple system configuration was used to generate transform-limited optical pulses at 160 Gbit/s in the sub-picosecond range (625 fs). Pulse compression was achieved by broadening the spectrum using supercontinuum generation followed by a linear frequency chirping compensation.

Vector quantization (VQ) is an attractive image compression technique. VQ utilizes the high correlation between neighboring pixels in a block, but disregards the high correlation between the adjacent blocks. Unlike VQ, side-match VQ (SMVQ) exploits codeword information of two encoded adjacent blocks, the upper and left blocks, to encode the current input vector. However, SMVQ is a fixed bit rate compression technique and doesn't make full use of the edge characteristics to predict the input vector. Classified side-match vector quantization (CSMVQ) is an effective image compression technique with low bit rate and relatively high reconstruction quality. It exploits a block classifier to decide which class the input vector belongs to using the variances of neighboring blocks' codewords. As an alternative, this paper proposes three algorithms using gradient values of neighboring blocks' codewords to predict the input block. The first one employs a basic gradient-based classifier that is similar to CSMVQ. To achieve lower bit rates, the second one exploits a refined two-level classifier structure. To reduce the encoding time further, the last one employs a more efficient classifier, in which adaptive class codebooks are defined within a gradient-ordered master codebook according to various prediction results. Experimental results prove the effectiveness of the proposed algorithms.