Distributed video coding (DVC) technology has been considered to be capable of reducing the processing complexity of the encoder immensely, while majority of the computational overheads are taken over by the decoder. In the common DVC framework, the pictures are decoded using the Wyner-Ziv encoded bit stream received from the encoder and the side information estimated using previously decoded information. As a result, accuracy of the side information estimation is very critical in improving the coding efficiency. In this paper we propose a novel side information refinement technique for DVC using multiple side information streams and sequential motion compensation with luminance and chrominance information involving iterative fusion of parallel information streams. In the bit plane wise coding architecture, previously decoded higher order bit planes are incrementally used to perform the motion estimation jointly in luminance and chrominance spaces to estimate multiple redundant bit streams for iterative fusion to produce more improved side information for subsequent bit planes. Simulation results show significant objective quality gain can be achieved at the same bit rate by utilizing the proposed refinement algorithms.

We propose a dimension reduction algorithm for the receiver of the downlink of direct-sequence code-division multiple access (DS-CDMA) systems in which both the transmitters and the receivers employ antenna arrays of multiple elements. To estimate the high order channel parameters, we develop a layered architecture using dimension-reduced parameter estimation algorithms to estimate the frequency-selective multipath channels. In the proposed architecture, to exploit the space-time geometric characteristics of multipath channels, spatial beamformers and constrained (or unconstrained) temporal filters are adopted for clustered-multipath grouping and path isolation. In conjunction with the multiple access interference (MAI) suppression techniques, the proposed architecture jointly estimates the direction of arrivals, propagation delays, and fading amplitudes of the downlink fading multipaths. With the outputs of the proposed architecture, the signals of interest can then be naturally detected by using path-wise maximum ratio combining. Compared to the traditional techniques, such as the Joint-Angle-and-Delay-Estimation (JADE) algorithm for DOA-delay joint estimation and the space-time minimum mean square error (ST-MMSE) algorithm for signal detection, computer simulations show that the proposed algorithm substantially mitigate the computational complexity at the expense of only slight performance degradation.

Ball Grid Array packages in which I/O pins are arranged in a grid array pattern realize a number of connections between chips and a printed circuit board, but it takes much time in manual routing. We propose a fast routing method for 2-layer Ball Grid Array packages that iteratively modifies via assignment. In experiments, in most cases, via assignment and global routing on both of layers in which all nets are realized and the violation of wire congestion on layer 1 is small are speedily obtained.

This paper analyzes frequency tracking characteristics of a complex-coefficient adaptive infinite impulse response (IIR) notch filter with a simplified gradient-based algorithm. The input signal to the complex notch filter is a complex linear chirp embedded in a complex zero-mean white Gaussian noise. The analysis starts with derivation of a first-order real-coefficient difference equation with respect to steady-state instantaneous frequency tracking error. Closed-form expression for frequency tracking mean square error (MSE) is then derived from the difference equation. Lastly, closed-form expressions for optimum notch bandwidth coefficient and step size constant that minimize the frequency tracking MSE are derived. Computer simulations are presented to validate the analysis.

We describe the applicability of photonic crystal fiber (PCF) with an enlarged effective area Aeff to a distributed Raman amplification (DRA) transmission. We investigate the DRA transmission performance numerically over a large Aeff PCF taking account of the signal-to-noise ratio (SNR) improvement RSNR in the S, C, and L bands. We show that an RSNR of 3 dB can be expected by utilizing DRA with a maximum pump power of 500 mW when the Aeff of the PCF is 230 µm2.

In an embedded system where a single application or a class of applications is repeatedly executed on a processor, its cache configuration can be customized such that an optimal one is achieved. We can have an optimal cache configuration which minimizes overall memory access time by varying the three cache parameters: the number of sets, a line size, and an associativity. In this paper, we first propose two cache simulation algorithms: CRCB1 and CRCB2, based on Cache Inclusion Property. They realize exact cache simulation but decrease the number of cache hit/miss judgments dramatically. We further propose three more cache design space exploration algorithms: CRMF1, CRMF2, and CRMF3, based on our experimental observations. They can find an almost optimal cache configuration from the viewpoint of access time. By using our approach, the number of cache hit/miss judgments required for optimizing cache configurations is reduced to 1/10-1/50 compared to conventional approaches. As a result, our proposed approach totally runs an average of 3.2 times faster and a maximum of 5.3 times faster compared to the fastest approach proposed so far. Our proposed cache simulation approach achieves the world fastest cache design space exploration when optimizing total memory access time.

Code division multiple access (CDMA) technique is used widely since it can flexibly support multi-rate multi-media services by changing the number of orthogonal spreading codes. In this paper, we present a new adaptive code assignment algorithm, which consists of three steps: reserved-space, improved-crowded-first-space, and multi-code combination to fully use the code space. Compared with the existing algorithms, the proposed algorithm can avoid the code blocking problem and lower its total blocking probability while keeping its computational complexity relatively low. Simulation results show that increasing the free space reduces the average total blocking probability while increasing the blocking probability of high rate users.

This paper proposes efficient single-carrier (SC) based multiplexing schemes for Layer 1 (L1)/Layer 2 (L2) control signals in SC-FDMA radio access using DFT-Spread OFDM in the Evolved UTRA uplink. L1/L2 control signals are necessary for key packet access techniques such as downlink scheduling, link adaptation, hybrid automatic repeat request (ARQ) with soft combining, and for uplink feedback control signals. We first propose a SC-based multiplexing scheme for L1/L2 control signals within a shared data channel for a set of user equipment (UE) that transmits both an uplink shared data channel and L1/L2 control signals within the same subframe. We also propose a multiplexing scheme for L1/L2 control signals without uplink data transmission that takes advantage of intra-subframe frequency hopping (FH) using multiple exclusively-assigned time-frequency resource blocks (RBs) to obtain a frequency diversity gain. Furthermore, we propose an orthogonal CDMA-based multiplexing scheme using cyclic shifts of a constant amplitude zero auto-correlation (CAZAC) sequence for L1/L2 control signals from different UEs within the same narrowband time-frequency RB. Computer simulation results show that the proposed SC-based multiplexing scheme for the L1/L2 control signals within the shared data channel achieves a higher user throughput than a multicarrier-based multiplexing scheme. The results also show that the proposed multiplexing scheme for the L1/L2 control signals that takes advantage of the intra-subframe FH for the UE without uplink data transmission achieves high quality reception through large frequency diversity gain. Furthermore, we show that the proposed cyclic-shift based orthogonal CDMA multiplexing is effective in the multiplexing of multiple L1/L2 control signals from different UEs within the same RB.

With the growth of the Internet, various types of services are rapidly expanding; such services include the World Wide Web (WWW), the File Transfer Protocol (FTP), and remote login. Consequently, managing authentication information, e.g., user ID/password pairs, keys, and certificates- is difficult for users, since the amount of required authentication information has been increased. To address this problem, researchers have developed a Single Sign-On (SSO) system that makes all the services available for a user via a one-time authentication: however, existing authentication systems cannot provide such SSO services for all kind of services on the Internet, even if the service provider deploys the SSO server. Further, existing systems also cannot provide the SSO service which does not make it conscious of a network domain to a user on secure network environment. Therefore, in this paper, we propose a new SSO system with a hardware token and a key management server to improve the safety, ubiquity, and adaptability of services. Further, we implement the proposed system and show its effectiveness through evaluation. Adding any functions for this system provides various conveniences to us. We also explore the ability to add functions to this system; for example, we add high trust connection functionality for a Web server and show its effectiveness.

Mobile positioning using Received Signal Strength (RSS) measurements is regarded as a low cost solution which is applicable in a wide range of wireless networks. In this paper, we propose a cooperative RSS-based positioning algorithm, that relies on the promising idea of mobile to mobile communications in the next generation of cellular networks. Simulations performed in this paper indicate that utilizing the additional RSS data of the short range communications between Mobile Stations (MS's), enhances the accuracy of the traditional RSS-based positioning algorithms.

This paper presents comparisons between common and dedicated reference signals (RSs) for channel estimation in MIMO multiplexing using codebook-based precoding for orthogonal frequency division multiplexing (OFDM) radio access in the Evolved UTRA downlink with frequency division duplexing (FDD). We clarify the best RS structure for precoding-based MIMO multiplexing based on comparisons of the structures in terms of the achievable throughput taking into account the overhead of the common and dedicated RSs and the precoding matrix indication (PMI) signal. Based on extensive simulations on the throughput in 2-by-2 and 4-by-4 MIMO multiplexing with precoding, we clarify that channel estimation based on common RSs multiplied with the precoding matrix indicated by the PMI signal achieves higher throughput compared to that using dedicated RSs irrespective of the number of spatial multiplexing streams when the number of available precoding matrices, i.e., the codebook size, is less than approximately 16 and 32 for 2-by-2 and 4-by-4 MIMO multiplexing, respectively.

An interference cancellation (ICAN) scheme for mobile communication radio repeaters is presented. When a radio repeater has a gain that is larger than the isolation between its transmit and receive antennas, it oscillates due to feedback interference signals. To prevent feedback oscillation of a radio repeater, we first formulate a feedback oscillation model of the radio repeater and then derive an ICAN model from that model. From the derived ICAN model, we show that the stability and the signal quality of the repeater depend on the repeater's gain and delay, the propagation delay on feedback paths, feedback channel characteristics, and the capability of the feedback channel estimation algorithm. It is also shown that the stability condition of the repeater does not guarantee the quality of the repeater's output signal. To guarantee repeater's stability and signal quality, an ICAN scheme based on an iterative algorithm is subsequently proposed. The simulation results confirm the relationship between the stability and signal quality of the repeater and the impact of the aforementioned factors. Using the proposed ICAN scheme, a mean error vector magnitude (quality indicator) of about 6.3% for the repeater's output signal was achieved.

The 3GPP Long Term Evolution Advanced (LTE-A) system, as compared to the LTE system, is anticipated to include several new features and enhancements, such as the usage of channel bandwidth beyond 20 MHz (up 100 MHz), higher order multiple input multiple output (MIMO) for both downlink and uplink transmissions, larger capacity especially for cell edge user equipment, and voice over IP (VoIP) users, and wider coverage and etc. This paper presents some key enabling technologies including flexible uplink access schemes, advanced uplink MIMO receiver designs, cell search, adaptive hybrid ARQ, and multi-resolution MIMO precoding, for the LTE-A system.

This paper presents the best transmit diversity schemes for three types of common/shared control signals from the viewpoint of the block error rate (BLER) performance in the Evolved UTRA downlink employing OFDM radio access. This paper also presents the coverage performance of the common/shared control signals using transmit diversity with respect to the outage probability that satisfies the required BLER performance, which is a major factor determining the cell configuration. Simulation results clarify that Space-Frequency Block Code (SFBC) and the combination of SFBC and Frequency Switched Transmit Diversity (FSTD) are the best transmit diversity schemes among the open-loop type transmit diversity candidates for two-antenna and four-antenna transmission cases, respectively. Furthermore, we show through system-level simulations that SFBC is very effective in reducing the outage probability at the required BLER for the physical broadcast channel (PBCH), for the common control signal with resource block (RB)-level assignment such as the dynamic broadcast channel (D-BCH) and paging channel (PCH), and in increasing the number of accommodated L1/L2 control signals over one transmission time interval duration, using mini-control channel element (CCE)-level assignment.

In this paper, we study and propose an inter-cell co-channel interference (CCI) mitigation method for pilot signals using cyclic shift Zadoff-Chu (CS-ZC) sequences for SC-FDMA-based uplink without tight scheduler coordination among cells. Firstly, we investigate the issue of severe detection performance degradation created by the lack of orthogonality among the pilot signals without alignment of the allocated frequency resource positions among cells when using the conventional CS-ZC sequences generation scheme. Secondly, we identify the primary factor causing the issue. Thirdly, we propose a frequency-dependent CS-ZC sequence generation scheme by allocating the same spectrum elements of the ZC sequence to the overlapped subcarriers among cells to mitigate the inter-cell CCI of the pilot signals without alignment of the frequency resource positions among cells. Finally, we confirm the validity of the proposal using uplink data BLER evaluation under a multipath fading condition by computer simulation compared to the conventional method, and show that the proposal achieves around 0.9 dB and 0.6 dB better performance at 10% BLER than the conventional method for 1 RB and 2 RBs frequency offsets in 3 RBs transmission bandwidth, respectively.

In this letter, we propose a novel approach using wireless sensor networks (WSNs) to enhance the safety and efficiency of four-way stop-sign-controlled (FWSC) intersections. The proposed algorithm provides right of way (RoW) and crash avoidance information by means of an intelligent WSN system. The system is composed of magnetic sensors, embedded in the center of a lane, with relay nodes and a base station placed on the side of the road. The experimental results show that the vehicle detection accuracy is over 99% and the sensor node battery life expectancy is over 3 years for traffic of 5,800 vehicles per day. For the traffic application we consider, a strong effect is observed as the projected conflict rate was reduced by 72% compared to an FWSC intersection operated with only driver perception.

Equipping wireless routers with multiple radios further improves the capacity by transmitting over multiple radios simultaneously using orthogonal channels. Efficient channel assignment schemes can greatly alleviate the interference effect of nearby transmissions. One of the distinctive features in wireless multi-hop networks is the lack of any central controller, in which each node makes its own decisions. Therefore, fully cooperative behaviors, such as cooperation for increasing link capacity, alleviating interferences for one another, might not be directly applied. In this paper, we aim to present some applications to show how such a framework can be invoked to design efficient channel assignment algorithms in a non-cooperative, topology-blind environment as well as in environments where the competing players share perfect information about channel usage and topology environment and so on. Simulation results are presented to illustrate the effectiveness of the algorithms.

A new analog mismatch model in circuit level has been developed. MOS transistor's small signal parameters are modeled in term of their matching character for both strong- and weak-inversion operations. Mismatch analysis on basic CMOS amplifiers are conducted with proposed model and Monte Carlo SPICE simulations. We successfully derived simple analytical formula on performance mismatch for analog CMOS circuits, which is verified to be accurate in using actual analog circuit design, within an average error of less than 10%.

In this paper, we propose a distance-based howling canceller with high speech quality. We have developed a distance-based howling canceller that uses only distance information by noticing the property that howling occurs according to the distance between a loudspeaker and a microphone. This method estimates the distance by transmitting a pilot signal from the loudspeaker to the microphone. Multiple frequency candidates for each howling are computed from the estimated distance and eliminated by cascading notch filters that have nulls at them. However degradation of speech quality occurs at the howling canceller output. The first cause is a shot noise occurrence at the beginning and end of the pilot signal transmission due to the discontinuous change of the amplitude. We thus develop a new pilot signal that is robust against ambient noises. We can then reduce the shot noise effect by taking the amplitude small. The second one is a speech degradation caused from overlapped stopbands of the notch filters. We thus derive a condition on the bandwidths so that stopbands do not overlap, and propose an adaptive bandwidth scheme which changes the bandwidth according to the distance.

Three-dimensional integrated circuits (3-D ICs), i.e., stacked dies, can alleviate the interconnect problem coming with the decreasing feature size and increasing integration density, and promise a solution to heterogenous integration. The vertical connection, which is generally implemented by the through-the-silicon via, is a key technology for 3-D ICs. In this paper, given 3-D circuit placement or floorplan results with white space reserved between blocks for inter-layer interconnections, we proposed methods for assigning inter-layer signal via locations. Introducing a grid structure on the chip, the inter-layer via assignment of two-layer chips can be optimally solved by a convex-cost max-flow formulation with signal via congestion optimized. As for 3-D ICs with three or more layers, the inter-layer signal via assignment is modeled as an integral min-cost multi-commodity flow problem, which is solved by a heuristic method based on the lagrangian relaxation. Relaxing the capacity constraints in the grids, we transfer the min-cost multi-commodity flow problem to a sequence of lagrangian sub-problems, which are solved by finding a sequence of shortest paths. The complexity of solving a lagrangian sub-problem is O(nntng2), where nnt is the number of nets and ng is the number of grids on one chip layer. The experimental results demonstrated the effectiveness of the method.