An L-band 4-bit RL/RC-switched active phase shifter using differential switches is developed. It employs RL/RC circuits in the design of series feedback loops of the quadrature differential amplifier and achieves 90, 45, and 22.5of phase shift by switching on and off the RL/RC circuits alternatively. On the other hand, a 180phase shift is achieved with the use of a phase difference between the differential outputs. By cascading all four bits, an insertion gain of 16 to 23 dB, a phase error of less than 8.5, and an RMS phase error of 4.6have been achieved at 1 GHz.

To achieve an automated implementation for the application-specific heterogeneous multiprocessor systems-on-chip (MPSoC), partitioning and mapping the sequential programs onto multiple parallel processors is one of the most difficult challenges. However, the existing traditional parallelizing techniques cannot solve the MPSoC-related problems effectively, so designers are still required to manually extract the concurrency potentials in the program. To solve this bottleneck, an automated application partition technique is needed. However, completely automatic parallelism is ineffective, so it is promising to explore concurrency for certain practical special structures. To settle those issues, this paper proposes a template-based algorithm to automatically partition a special load-compute-store (LCS) loop structure. Since specific-instruction customization for the application specific instruction-set processors (ASIPs) has interactions with task partitioning, the proposed algorithm integrates the dynamic pipelining and ASIP techniques using an iterative improvement strategy: first, an initial pipelining scheme is generated to obtain the maximum parallelism; second, under the primary partition results specific instructions are customized respectively for each subprogram; third, the program is repartitioned via pipelining under the specific instruction configurations. The proposed method has been implemented in the context of a commercial extensible multiprocessor design flow, using the Xtensa-based XTMP platform from Tensilica Inc. Based on a case study of Fast Fourier Transform (FFT), the experimental results indicate that the partitioned programs by the proposed method demonstrate an average speedup of 10 compared to the original sequential programs which have not been partitioned and run on the uniprocessor system.

In this paper, a method of the signal subspace interpolation to constructing a continuous fingerprint database for radio localization is proposed. When using the fingerprint technique, enhancing the accuracy of location estimation requires very fine spatial resolution of the database, which entails much time in collecting the data to build up the database. Interpolated signal subspace is presented to achieve a fine spatial resolution of the fingerprint database. The angle of arrival (AOA) and the measured signal subspace at known locations are needed to obtain the interpolated signal subspaces. The effectiveness of this method is verified by an outdoor experiment and the estimated location using this method was compared with those using the geometrically calculated fingerprint and the measured signal subspace fingerprint techniques.

Modular multiplication is the most dominant arithmetic operation in elliptic curve cryptography (ECC), that is a type of public-key cryptography. Montgomery multiplier is commonly used to compute the modular multiplications and requires scalability because the bit length of operands varies depending on its security level. In addition, ECC is performed in GF(P) or GF(2n), and unified architecture for multipliers in GF(P) and GF(2n) is required. However, in previous works, changing frequency is necessary to deal with delay-time difference between GF(P) and GF(2n) multipliers because the critical path of the GF(P) multiplier is longer. This paper proposes unified dual-radix architecture for scalable Montgomery multiplications in GF(P) and GF(2n). This proposed architecture unifies four parallel radix-216 multipliers in GF(P) and a radix-264 multiplier in GF(2n) into a single unit. Applying lower radix to GF(P) multiplier shortens its critical path and makes it possible to compute the operands in the two fields using the same multiplier at the same frequency so that clock dividers to deal with the delay-time difference are not required. Moreover, parallel architecture in GF(P) reduces the clock cycles increased by dual-radix approach. Consequently, the proposed architecture achieves to compute a GF(P) 256-bit Montgomery multiplication in 0.28 µs. The implementation result shows that the area of the proposal is almost the same as that of previous works: 39 kgates.

This paper presents a new signaling architecture for radio-access control in wireless communications systems. Called THREP (for THREe-phase link set-up Process), it enables systems with low-cost configurations to provide tetherless access and wide-ranging mobility by using autonomous radio-link controls for fast cell searching and distributed call management. A signaling architecture generally consists of a radio-access part and a service-entity-access part. In THREP, the latter part is divided into two steps: preparing a communication channel, and sustaining it. Access control in THREP is thus composed of three separated parts, or protocol phases. The specifications of each phase are determined independently according to system requirements. In the proposed architecture, the first phase uses autonomous radio-link control because we want to construct low-power indoor wireless communications systems. Evaluation of channel usage efficiency and hand-over loss probability in the personal handy-phone system (PHS) shows that THREP makes the radio-access sub-system operations in a practical application model highly efficient, and the results of a field experiment show that THREP provides sufficient protection against severe fast CNR degradation in practical indoor propagation environments.

We have developed a novel downlink packet scheduling scheme for a multiuser OFDMA system in which a subchannel can be time-multiplexed among multiple users. This scheme which is called Matrixed-based Proportional Fairness can provide a high system throughput while ensuring fairness. The scheme is based on a Proportional Fairness (PF) utility function and can be applied to any of the PF-based schedulers. Our scheduler explores multichannel multiuser diversity by using a two-dimensional matrix combining user selection, subchannel assignment, and time slot allocation. Furthermore, unlike other PF-based schemes, our scheme considers finitely backlogged queues during the time slot allocation. By doing so, it can exploit multichannel multiuser diversity to utilize bandwidth efficiently and with throughput fairness. Additionally, fairness in the time domain is enhanced by limiting the number of allocated time slots. Intensive simulations considering finitely backlogged queues and user mobility prove the scheme's effectiveness.

The Finite-Difference Time-Domain (FDTD) technique is presented in this paper as an estimation method for radio propagation prediction in large and complex wireless local area network (WLAN) environments. Its validity is shown by comparing measurements and Ray-trace method with FDTD data. The 2 GHz (802.11b/g) and 5 GHz (802.11a) frequency bands are used in both the calculations and experiments. The electric field (E-field) strength distribution has been illustrated in the form of histograms and cumulative ratio graphs. By using the FDTD method to vary the number of human bodies in the environment, the effects on E-field distribution due to human body absorption are also observed for 5 GHz WLAN design.

In modern VLSI physical design, huge integration scale necessitates hierarchical design and IP reuse to cope with design complexity. Besides, interconnect delay becomes dominant to overall circuit performance. These critical factors require some modules to be placed along designated boundaries to effectively facilitate hierarchical design and interconnection optimization related problems. In this paper, boundary constraints of general floorplan are solved smoothly based on the novel representation Single-Sequence (SS). Necessary and sufficient conditions of rooms along specified boundaries of a floorplan are proposed and proved. By assigning constrained modules to proper boundary rooms, our proposed algorithm always guarantees a feasible SS code with appropriate boundary constraints in each perturbation. Time complexity of the proposed algorithm is O(n). Experimental results on MCNC benchmarks show effectiveness and efficiency of the proposed method.

We investigate numerically the applicability of photonic crystal fiber (PCF) with a uniform air hole structure as a wide-band transmission medium. We show that accumulated dispersion over the PCF can be reduced effectively by optimizing the index profile of dispersion compensating fiber (DCF). We also show that a bandwidth of more than 300 nm will be available for 40 Gbit/s NRZ transmission by using the PCF as a transmission medium instead of conventional 1.3 µm zero-dispersion single-mode fiber (SMF).

This paper describes a reading miscue detection system based on the conventional Large Vocabulary Continuous Speech Recognition (LVCSR) framework [1]. In order to incorporate the knowledge of reference (what the reader ought to read) and some error patterns into the decoding process, two methods are proposed: Dynamic Multiple Pronunciation Incorporation (DMPI) and Dynamic Interpolation of Language Model (DILM). DMPI dynamically adds some pronunciation variations into the search space to predict reading substitutions and insertions. To resolve the conflict between the coverage of error predications and the perplexity of the search space, only the pronunciation variants related to the reference are added. DILM dynamically interpolates the general language model based on the analysis of the reference and so keeps the active paths of decoding relatively near the reference. It makes the recognition more accurate, which further improves the detection performance. At the final stage of detection, an improved dynamic program (DP) is used to align the confusion network (CN) from speech recognition and the reference to generate the detecting result. The experimental results show that the proposed two methods can decrease the Equal Error Rate (EER) by 14% relatively, from 46.4% to 39.8%.

A coordinate plane representation of the resource requirements of digital modulation methods is presented, and an overall resource efficiency measure is proposed. This measure can be used for the comparison of digital modulation methods and the evaluation of an emerging modulation technique. Several typical digital modulation methods are compared based on this measure to show its validity.

In this paper, we propose a modified scheme of MSODB and PMS, called Predictive User Mobility Behavior (PUMB) to improve performance of resource reservation and call admission control for cellular networks. This algorithm is proposed in which bandwidth is allocated more efficiently to neighboring cells by key mobility parameters in order to provide QoS guarantees for transferring traffic. The probability is used to form a cluster of cells and the shadow cluster, where a mobile unit is likely to visit. When a mobile unit may change the direction and migrate to the cell that does not belong to its shadow cluster, we can support it by making efficient use of predicted nonconforming call. Concomitantly, to ensure continuity of on-going calls with better utilization of resources, bandwidth is borrowed from predicted nonconforming calls and existing adaptive calls without affecting the minimum QoS guarantees. The performance of the PUMB is demonstrated by simulation results in terms of new call blocking probability, handoff call dropping probability, bandwidth utilization, call successful probability, and overhead message transmission when arrival rate and speed of mobile units are varied. Our results show that PUMB provides the better performances comparing with those of MSODB and PMS under different traffic conditions.

The IEEE 802.16e standard specifies the sleep mode and the idle mode of a mobile station (MS) for power saving. In this paper, to reduce the energy consumption of the MS, we employ the sleep mode while the MS is on-session, and the idle mode while it is off-session. Under the assumption that the time duration from the end of a session to the arrival of a new downlink session request follows an exponential distribution of the mean and that arrivals of messages during an on-session follow a Poisson process with rate λ, we analyze the awake mode period and the sleep mode period by using the busy period analysis of the M/G/1 queue, and then we derive the total mean length of an on-session which consists of a geometric number of awake mode periods and sleep mode periods. Since the sum of an on-session and an off-session constitutes a cycle, we can express the average power consumption in terms of the mean lengths of an awake mode period, a sleep mode period and an idle mode period. The average power consumption indicates how much the MS can save energy by employing the sleep mode and the idle mode. We also derive the Laplace Stieltjes transform (and the mean) of the queueing delay of messages to examine a tradeoff between the power consumption and the delay of messages. Analytical results, which are shown to be well-matched by simulations, address that our employment of the sleep mode and the idle mode provides a considerable reduction in the energy consumption of the MS.

This paper presents a content-based retrieval algorithm for motion capture data, which is required to re-use a large-scale database that has many variations in the same category of motions. The most challenging problem is that logically similar motions may not be numerically similar due to the motion variations in a category. Our algorithm can effectively retrieve logically similar motions to a query, where a distance metric between our novel short-term features is defined properly as a fundamental component in our system. We extract the features based on short-term analysis of joint velocities after dividing an entire motion capture sequence into many small overlapped clips. In each clip, we select not only the magnitude but also the dynamic pattern of the joint velocities as our features, which can discard the motion variations while keeping the significant motion information in a category. Simultaneously, the amount of data is reduced, alleviating the computational cost. Using the extracted features, we define a novel distance metric between two motion clips. By dynamic time warping, a motion dissimilarity measure is calculated between two motion capture sequences. Then, given a query, we rank all the motions in our dataset according to their motion dissimilarity measures. Our experiments, which are performed on a test dataset consisting of more than 190 motions, demonstrate that our algorithm greatly improves the performance compared to two conventional methods according to a popular evaluation measure P(NR).

The paper introduces both high-speed transmission and quality of system to offer the Internet services on a HFC (Hybrid Fiber Coaxial) network. This utilizes modulating the phase and the amplitude to the signal of the IPMS (Internet Protocol Multicasting Service). An IP-cable transmitter, IP-cable modem, and IP-cable management servers that support 30-Mbps IPMS on the HFC were developed. The system provides a 21 Mbps HDTV transporting stream on a cable TV network. It can sustain a clear screen for a long time.

For integrated WLAN/cellular networks, we propose an energy-efficient vertical handover mechanism that both improves the energy efficiency of the mobile nodes and reduces the WLAN frame overhead.

This paper describes an interactive experimental environment for autonomous soccer robots, which is a soccer field augmented by utilizing camera input and projector output. This environment, in a sense, plays an intermediate role between simulated environments and real environments. We can simulate some parts of real environments, e.g., real objects such as robots or a ball, and reflect simulated data into the real environments, e.g., to visualize the positions on the field, so as to create a situation that allows easy debugging of robot programs. The significant point compared with analogous work is that virtual objects are touchable in this system owing to projectors. We also show the portable version of our system that does not require ceiling cameras. As an application in the augmented environment, we address the learning of goalie strategies on real quadruped robots in penalty kicks. We make our robots utilize virtual balls in order to perform only quadruped locomotion in real environments, which is quite difficult to simulate accurately. Our robots autonomously learn and acquire more beneficial strategies without human intervention in our augmented environment than those in a fully simulated environment.

Wireless LAN access is now being offered by small personal terminals in addition to laptops. Since these terminals have very limited battery capacity, wireless LAN interfaces that offer some form of power saving are essential. IEEE802.11. specifies PSM (Power save management); it reduces power consumption by suspending some communications functions. However, since Multicasting and Broadcasting are invariably received by all terminals regardless of PSM, the terminals unnecessarily consume electric power, even if the terminal is not multicast subscriber. This paper clarifies this problem, and proposes a scheme for reducing power consumption. The results of an experiment confirm its excellent performance.

PCA-SIFT is an extension to SIFT which aims to reduce SIFT's high dimensionality (128 dimensions) by applying PCA to the gradient image patches. However PCA is not a discriminative representation for recognition due to its global feature nature and unsupervised algorithm. In addition, linear methods such as PCA and ICA can fail in the case of non-linearity. In this paper, we propose a new discriminative method called Supervised Kernel ICA (SKICA) that uses a non-linear kernel approach combined with Supervised ICA-based local image descriptors. Our approach blends the advantages of supervised learning with nonlinear properties of kernels. Using five different test data sets we show that the SKICA descriptors produce better object recognition performance than other related approaches with the same dimensionality. The SKICA-based representation has local sensitivity, non-linear independence and high class separability providing an effective method for local image descriptors.

Recently, frequency-domain equalization (FDE) has been attracting much attention as a way to improve single-carrier (SC) signal transmission in a frequency-selective wireless channel. Since the SC signal spectrum is spread over the entire signal bandwidth, FDE can take advantage of channel frequency-selectivity and achieve the frequency diversity gain. SC with FDE is a promising wireless signal transmission technique. In this article, we review the pioneering research done on SC with FDE. The principles of simple one-tap FDE, channel estimation, and residual inter-symbol interference (ISI) cancellation are presented. Multi-input/multi-output (MIMO) is an important technique to improve the transmission performance. Some of the studies on MIMO/SC with FDE are introduced.