A framework is proposed for segmenting image textures by using Gabor filters to detect boundaries between adjacent textured regions. By performing a multi-channel filtering of the input image with a small set of adaptively selected Gabor filters, tuned to underlying textures, feature images are obtained. To reduce the variance of the filter output for better texture boundary detection, a Gaussian post-filter is applied to the Gabor filter response over each channel. Significant local variations in each channel response are detected using a gradient operator, and combined through channel grouping to produce the texture gradient. A subsequent post-processing produces expected texture boundaries. The effectiveness of the proposed technique is demonstrated through experiments on synthetic and natural textures.

In the wireless asynchronous transfer mode (ATM) networks, a custom data link control (DLC) layer protocol with stronger error correction ability is needed for mitigating the affect of radio channel errors. This paper applies punctured turbo code schemes to the protection of the header and various payloads in wireless ATM cell, which are realized by the combination of programmable interleaving and puncturing. Their performance is analyzed for Rayleigh fading channel, which shows more significant reduction in cell loss rate (CLR) than the previous systems. Our proposal also provides good balance designs for CLR and the payload bit error rate (BER), and offers potential for future evolutionary improvement of the wireless ATM coding scheme.

This paper presents the outline of the systolic array recursive least-squares (RLS) processor prototyped primarily with the aim of broadband mobile communication applications. To execute the RLS algorithm effectively, this processor uses an orthogonal triangularization technique known in matrix algebra as QR decomposition for parallel pipelined processing. The processor board comprises 19 application-specific integrated circuit chips, each with approximately one million gates. Thirty-two bit fixed-point signal processing takes place in the processor, with which one cycle of internal cell signal processing requires approximately 500 nsec, and boundary cell signal processing requires approximately 80 nsec. The processor board can estimate up to 10 parameters. It takes approximately 35 µs to estimate 10 parameters using 41 known symbols. To evaluate signal processing performance of the prototyped systolic array processor board, processing time required to estimate a certain number of parameters using the prototyped board was comapred with using a digital signal processing (DSP) board. The DSP board performed a standard form of the RLS algorithm. Additionally, we conducted minimum mean-squared error adaptive array in-lab experiments using a complex baseband fading/array response simulator. In terms of parameter estimation accuracy, the processor is found to produce virtually the same results as a conventional software engine using floating-point operations.

We will present the theoretical analysis of and experimental measurements on the transmission characteristics of multi-channel long period fiber gratings in terms of the physical parameters like the separation distance, grating length and number of gratings. These parameters can be used to control the spectral channel spacing, number of channels, loss peak depth, and channel bandwidth of multi-channel long period fiber gratings.

We will present the theoretical analysis of and experimental measurements on the transmission characteristics of multi-channel long period fiber gratings in terms of the physical parameters like the separation distance, grating length and number of gratings. These parameters can be used to control the spectral channel spacing, number of channels, loss peak depth, and channel bandwidth of multi-channel long period fiber gratings.

We propose a new structure of decision feedback adaptive equalizer (DFE) suitable for use in mobile radio systems. The proposed structure named Commutating Decision Feedback Equalizer (CDFE) has two DFEs that operate in a commutating fashion; the two DFEs commutate between training and equalization. Such a commutating operation effectively lengthens the equalizer tracking period over time variant channels. Thus, the CDFE has a superior performance over the conventional DFE in fading channels. Simulation results are presented in the paper.

We have developed a new planar lightwave circuit (PLC) platform eliminating Si terraces for hybrid integrated optical modules. This PLC platform has the advantage of a lower fabrication cost than the conventional PLC platform with an Si terrace, because it does not require fabrication processes such as Si terrace forming and mechanical polishing. Using our new PLC platform structure, we fabricated a transceiver for optical access networks and an 8-channel multi-channel photoreceiver for wavelength division multiplexing (WDM) interconnection systems.

We have developed a new planar lightwave circuit (PLC) platform eliminating Si terraces for hybrid integrated optical modules. This PLC platform has the advantage of a lower fabrication cost than the conventional PLC platform with an Si terrace, because it does not require fabrication processes such as Si terrace forming and mechanical polishing. Using our new PLC platform structure, we fabricated a transceiver for optical access networks and an 8-channel multi-channel photoreceiver for wavelength division multiplexing (WDM) interconnection systems.

This paper describes the design, implementation and testing of wideband code division multiple access (CDMA) base station demodulator for the international mobile telecommunication-2000 (IMT-2000) system test plant based on cdma2000 radio transmission technology (RTT). The performance of the implemented base station demodulator is measured and compared with the theoretical performance bound. The system test plant equipped with this demodulator provides wireless services, such as high quality speech (9.6 kbps), real-time video (384 kbps) and internet protocol (IP) based data services (144 kbps) in a mobile radio environment.

To achieve a sound field reproduction system, it is important to design multichannel inverse filters which cancel the effects of room transfer functions. The design method in the frequency domain based on the least-norm solution (LNS) requires less memory and less calculation than the design method in the time domain. However, the LNS method cannot guarantee the causality or stability of the filters. In this paper, a design method of a time-domain inverse filter using iterative processing in the frequency domain for multichannel sound field reproduction is proposed, and the result of numerical analysis is described. The proposed method can decrease the squared error of every control point by 3-12 dB. Furthermore, the sound reproduced by this method attains over 13 dB improvement in the segmental signal-noise ratio (SNR) compared with that designed by the LNS method for real environment impulse responses.

We evaluate the performance of indoor infrared wireless systems using on-off keying code division multiple access (OOK-CDMA) with decision-feedback equalizer (DFE) on diffuse channels. To estimate the impulse response, we use the training sequence that alternates '1' and '0. ' We show that the OOK-CDMA with DFE and the training sequence can achieve better performance than the OOK-CDMA without DFE. We also show that the OOK-CDMA with DFE and the training sequence can achieve almost the same performance as the OOK-CDMA with DFE and the known impulse response.

The common packet channel (CPCH) adopted by 3GPP is used to carry small and medium sized packets, such as SMS (short message service) and web data. We analyze the system performance of the non-real time channel monitoring scheme when the periodic broadcast method is deployed. If user equipment (UE) can continuously monitor the CPCH status, the performance of the channel monitoring scheme is satisfactory. However, in practice, a CPCH status broadcast period exists and, therefore, an UE can request a CPCH channel based on incorrect CPCH status information. This incorrect CPCH status information results in performance degradation in the channel monitoring scheme. We analyze this performance degradation and show the relationship between system performance and the status broadcast period.

To satisfy huge service demand and multi-traffic requirements with limited bandwidth, this paper proposes two different procedures of multi-channel multiple access schemes with the slotted ALOHA operation for both data and voice traffic and presents an exact analysis to numerically evaluate the performance of the systems. In scheme I, there is no limitation on access between data transmissions and voice transmissions, i.e., all channels can be accessed by all transmissions. In scheme II, a channel reservation policy is applied, where a number of channels are used exclusively for voice packets while the remaining channels are used for both data packets and voice packets. We call the system using scheme I "Non-reservation system" and call the system using scheme II "Reservation system. " Performance characteristics we obtained include loss probability for voice traffic, average packet delay for data traffic and channel utilization for both traffic. The performance of the schemes and the effects of the design parameters are numerically evaluated and compared to a wide-bandwidth conventional single-channel slotted ALOHA system with single data traffic. The analysis presented in this paper will be not only useful for the performance evaluation and the optimum design of multi-channel multi-traffic systems in wireless environments, but also applicable to evaluate other performance measures in priority networks, cellular mobile radio networks or multi-hop wireless networks.

This paper describes an 8b 52 MHz CMOS subranging analog-to-digital converter (ADC) for digital subscriber loop applications. The proposed ADC based on an improved time-interleaved architecture removes the holding time which is typically observed in the conventional double-channel subranging ADC's to increase the throughput rate by 50%. The ADC employs the interpolation technique in the back-end subranging ADC's for residue signal processing to minimize the active die area and the power consumption. A layout technique is adopted to reduce the plasma-induced comparator offsets and the die area of the ADC. The fabricated and measured prototype ADC in a 0.8 µm CMOS process shows nonlinearities less than 0.4 LSB and the signal-to-noise-and-distortion ratio of 43 dB for a 1 MHz input at a 52 MHz sampling rate with 230 mW.

In this paper, we propose an efficient channel estimation technique for orthogonal frequency-division multiplexing (OFDM) systems with transmitter diversity. The proposed technique estimates uniquely all channel frequency responses needed in space-time coded OFDM systems using "comb-type" training symbols. The computational complexity of the proposed technique is reduced dramatically, compared with the previous minimum mean-squared error (MMSE) technique, due to the processing made all in the frequency-domain. Also, several other techniques for mitigating random noise effect and tracking channel variation are discussed to further improve the performance of the proposed approach. The performances of the proposed approach are demonstrated by computer simulation for mobile wireless channels.

In this letter, we propose an efficient channel allocation scheme to provide multicast traffic in multitier cellular systems. Our proposed scheme allocates microcell/macrocell channels based on the 'microcell-group size' and probability. Also, we analyze the performance of the scheme in view of the call blocking probability in case of considering overflow traffic or not. Numerical results show that our proposed scheme exhibits a better performance than conventional schemes.

The performance of a twisted-pair channel under ADSL environment is assumed to be dominated by far end crosstalk (FEXT) and additive white Gaussian noise (AWGN). In this paper, we study the channel capacity of the copper twisted pair and the optimum input power spectral density distribution at this channel capacity in the presence of ADSL environment. The channel capacity under different loop length and different input power will also be given. The simulation results show that the distribution of the optimum input power spectral density in the presence of AWGN and FEXT is not uniform. This is different from the situation where AWGN is the only interference, where the input power distribution is approximately uniform.

This paper presents a Mix-net that has the following properties; (1) it efficiently handles long plaintexts that exceed the modulus size of the underlying public-key encryption scheme as well as very short ones (length-flexibility), (2) input ciphertext length is not impacted by the number of mix-servers (length-invariance), and (3) its security in terms of anonymity can be proven in a formal way (probable security). If desired, one can add robustness so that it outputs correct results in the presence of corrupt users and servers. The security is proven in such a sense that breaking the anonymity of our Mix-net is equivalent to breaking the indistinguishability assumption of the underlying symmetric encryption scheme or the Decision Diffie-Hellman assumption.

This letter presents a channel estimation and a DC-offset estimation technique in a short-ranged Bluetooth system. Each of the Bluetooth devices in the connection state knows the access codes used in the ad-hoc networks, which is utilized as a reference signal for the parameter estimation. The proposed estimators can be implemented without degradation of frame and spectral efficiency thanks to using the access code specified for the Bluetooth system.

In this article, we shall propose an efficient anonymous channel protocol for wireless communications. The most important feature of our proposed protocol has the property of untraceability. In our scheme, the mobile stations (MSs) and the home network (HN) must authenticate each other. Moreover, the HN is untraceable in such a way that supports location anonymity and MSs identity anonymity for MSs roaming, dynamic channel assignment and broadcasting. Compare our protocol with Juang et al.'s protocol, our mobile agent communication cost is 3m which is more efficient than the Juang et al.'s protocol 5m. At the same time, our mobile agent computation cost is 2Th which is also more efficient than the Juang et al.'s protocol 1Tpublic+1Th. We can avoid employing public key cryptography in the anonymous channel ticket authentication phase since to keep the computation cost down.