In this review paper we showcase recent activities on silicon photonics science and technology research in Hong Kong regarding two important topical areas--microresonator devices and optical nonlinearities. Our work on silicon microresonator filters, switches and modulators have shown promise for the nascent development of on-chip optoelectronic signal processing systems, while our studies on optical nonlinearities have contributed to basic understanding of silicon-based optically-pumped light sources and helium-implanted detectors. Here, we review our various passive and electro-optic active microresonator devices including (i) cascaded microring resonator cross-connect filters, (ii) NRZ-to-PRZ data format converters using a microring resonator notch filter, (iii) GHz-speed carrier-injection-based microring resonator modulators and 0.5-GHz-speed carrier-injection-based microdisk resonator modulators, and (iv) electrically reconfigurable microring resonator add-drop filters and electro-optic logic switches using interferometric resonance control. On the nonlinear waveguide front, we review the main nonlinear optical effects in silicon, and show that even at fairly modest average powers two-photon absorption and the accompanied free-carrier linear absorption could lead to optical limiting and a dramatic reduction in the effective lengths of nonlinear devices.

Combination of mutually complementary features is necessary to cope with various changes in pattern classification between normal and pathological voices. This paper proposes a method to improve pathological/normal voice classification performance by combining heterogeneous features. Different combinations of auditory-based and higher-order features are investigated. Their performances are measured by Gaussian mixture models (GMMs), linear discriminant analysis (LDA), and a classification and regression tree (CART) method. The proposed classification method by using the CART analysis is shown to be an effective method for pathological voice detection, with a 92.7% classification performance rate. This is a noticeable improvement of 54.32% compared to the MFCC-based GMM algorithm in terms of error reduction.

A rate control scheme is described for zero-forcing beamforming (ZFBF) multiuser multiple-input and multiple-output (MU-MIMO) systems with a QR-decomposition maximum likelihood detector (MLD) at the receiver. For selected users, a modulation-and-coding set is selected for each substream by estimating the per-substream post-MLD signal-to-interference-plus-noise ratio. Iterative modified QR-decomposition MLD is employed at the receiver to achieve the throughput expected from the transmitter. The simulation results demonstrated that the proposed rate-control scheme achieved the target packet error rate while increasing the throughout for ZFBF-MU-MIMO systems as the number of user candidates increases.

This study has demonstrated that the clock tree construction in an SoC should be expanded to consider the intrinsic delay and skew of each IP's clock sink. A novel algorithm, called GDME, is proposed to combine grey relational clustering and DME approach for solving the problem of clock tree construction. Grey relational analysis can cluster the best pair of clock sinks and that guide a tapping point search for a DME algorithm for constructing a clock tree with zero skew and minimal delay. Experimentally, the proposed algorithm always obtains an RC- or RLC-based clock tree with zero skew and minimal delay for all the test cases and benchmarks. Experimental results demonstrate that the GDME improves up to 3.74% for total average in terms of total wire length compared with other DME algorithms. Furthermore, our results for the zero-skew RLC-based clock trees compared with Hspice are 0.017% and 0.2% lower for absolute average in terms of skew and delay, respectively.

A novel Uniform Discrete Multitone (DMT) transceiver is proposed, utilizing a wavelet packet based filter bank transmultiplexer in conjunction with a DMT transceiver. The proposed transceiver decomposes the channel spectrum into subbands of equal bandwidth. The objective is to minimize the bit error rate (BER), which is increased by channel-noise amplification. This noise amplification is due to the Zero-Forcing equalization (ZFE) technique. Quantization of the channel-noise amplification is presented, based on post-equalization signal-to-noise ratio (SNR) and probability of error in all subbands of the Uniform DMT system. A modified power loading algorithm is applied to allocate variable power according to subband gains. A BER performance comparison of the Uniform DMT with variable and uniform power-loading and with a conventional DMT system in a Digital Subscriber Line (DSL) channel is presented.

The Project Authorization Request (PAR) for the IEEE P1900.4 Working Group (WG), under the IEEE Standards Coordinating Committee 41 (SCC41) was approved in December 2006, leading to this WG being officially launched in February 2007 [1]. The scope of this standard is to devise a functional architecture comprising building blocks to enable coordinated network-device distributed decision making, with the goal of aiding the optimization of radio resource usage, including spectrum access control, in heterogeneous wireless access networks. This paper introduces the activities and work under progress in IEEE P1900.4, including its scope and purpose in Sects. 1 and 2, the reference usage scenarios where the standard would be applicable in Sect. 4, and its current system architecture in Sect. 5.

A novel low insertion-loss and wideband microstrip bandpass filter has been designed and tested. The basic configuration of this novel dual-mode filter is a square ring resonator with direct-connected orthogonal feed lines, and dual-perturbation elements are introduced within the resonator at symmetrical location. The effects of the size of the perturbation element are studied. A new filter having wider bandwidth and transmission zeros are presented. The proposed filter responses are in good agreement with the simulations and experiments.

We propose a neurodynamical approach to a large-scale optimization problem in Cognitive Wireless Clouds, in which a huge number of mobile terminals with multiple different air interfaces autonomously utilize the most appropriate infrastructure wireless networks, by sensing available wireless networks, selecting the most appropriate one, and reconfiguring themselves with seamless handover to the target networks. To deal with such a cognitive radio network, game theory has been applied in order to analyze the stability of the dynamical systems consisting of the mobile terminals' distributed behaviors, but it is not a tool for globally optimizing the state of the network. As a natural optimization dynamical system model suitable for large-scale complex systems, we introduce the neural network dynamics which converges to an optimal state since its property is to continually decrease its energy function. In this paper, we apply such neurodynamics to the optimization problem of radio access technology selection. We compose a neural network that solves the problem, and we show that it is possible to improve total average throughput simply by using distributed and autonomous neuron updates on the terminal side.

In one-cell-frequency-reuse Orthogonal Frequency Division Multiple Access based Time Division Multiple Access (OF/TDMA) systems, communication is blocked by interference from adjacent cells. The most promising solution would be an adaptive modulation and coding scheme that is controlled by estimating the signal-to-interference ratio (SIR). However, there has so far been no way to accurately estimate the SIR using the spreading codes for OF/TDMA systems, because of the asynchronous fast Fourier transform (FFT). In this paper, we propose a novel SIR estimation method that uses a spread pulse-wave symbol and carrier interferometry. Moreover, to introduce multi- input multi-output systems, we modify the proposed method by allocating a different spreading code to each cell. Computer simulation confirmed that the SIR is estimated accurately even if the FFT is asynchronous. On cell boundaries, the average estimation errors that are a ratio between accurate and estimated propagation characteristics are less than 2 dB.

In OFDM systems, the pilot signal averaging channel estimation is generally used to identify the channel state information (CSI). In this case, large pilot symbols are required for obtaining an accurate CSI. As a result, the total transmission rate is degraded due to large number of pilot symbols transmission. To reduce this problem, in this paper, we propose time-frequency interferometry (TFI) for OFDM to achieve an accurate CSI.

The present paper introduces an integrated construction of binary sequences having a zero-correlation zone. The cross-correlation function and the side-lobe of the auto-correlation function of the proposed sequence set is zero for the phase shifts within the zero-correlation zone. The proposed method enables more flexible design of the binary zero-correlation zone sequence set with respect to its member size, length, and width of zero-correlation zone. Several previously reported sequence construction methods of binary zero-correlation zone sequence sets can be explained as special cases of the proposed method.

A new scheme for reducing optical beat interference noise in a reflective semiconductor optical amplifier based wavelength division multiplexed/subcarrier multiplexing -- passive optical network is proposed. This method uses an Fabry Perot laser locked by modulated lights from optical network units in a central office. As an experimental verification, it is reported that carrier to noise ratio is enhanced by 10 dB and power penalty is improved by 16 dB.

Most wireless networks consist of heterogeneous nodes with diverse characteristics. These heterogeneous nodes have various moving characteristics such as speed and pausing time. Since conventional wireless routing schemes are designed for networks with homogeneous mobility, it is difficult to accomplish communication without degrading its quality, e.g., packet reachability and delay, in networks with heterogeneous mobility. In this paper, we propose efficient extensions of a proactive routing protocol to achieve sufficient communication quality in networks with heterogeneous mobility. The proposed extensions consist of three features, i.e., differential topology update, unidirectional movement notification and link quality based route calculation. Complementary actions among these functions can improve communication quality with acceptable control overhead. Simulation results reveal that the proposed scheme can achieve higher packet reachability and lower delay with low control overhead compared with existing routing schemes.

In this paper, class DE inverter with second order constant K band-pass filter is proposed. In the proposed inverter, the band-pass filter is used instead of the resonant filter in class DE inverter presented at the previous papers. By using band-pass filter, two important results can be gotten. One is the sensitivity of the output voltage to the operating frequency is suppressed by using band-pass filter. The other is that zero voltage switching operation appears when the operating frequency is lower than the nominal frequency. Moreover, it keeps the advantage of class DE inverter with resonant filter, that is, high power conversion efficiency under high frequency operation because of class E switching. The laboratory experiments achieve 90.4% power conversion efficiency under 1.98 W output power and 1.0 MHz operation.

The present paper introduces a new construction of a class of binary periodic sequence set having a zero-correlation zone sequence set. The cross-correlation function and the side-lobe of the auto-correlation function of the proposed sequence set is zero for the phase shifts within the zero-correlation zone. The present paper shows that such a construction generates a binary zcz sequence set by using an arbitrary pair of an even-perfect sequence and an odd-perfect sequence. The proposed zcz sequence set reaches the theoretical upper bound of the member size of the sequence set.

Flexibility, adaptation and distribution have been regarded as major challenges of modern interorganizational workflow. To address these issues, this paper proposes an interorganizational workflow execution framework based on process agents and ECA rules. In our framework, an interorganizational workflow is modeled as a multiagent system with a process agent for each organization. The whole execution is divided into two parts: the intra-execution, which means execution within a same organization, and the inter-execution, which represents interaction between organizations. For intra-execution, we use the method of transforming the graph-based local workflow into block-based workflow to design general ECA rules. ECA rules are used to control internal state transitions and process agents are used to control external state transitions of tasks in the local workflows. Inter-execution is realized by process agent interaction protocols. The proposed approach can provide flexible execution of interorganizational workflow with distributed organizational autonomy and adaptation. A case study of offshore software development is illustrated for the proposed approach.

In this paper, a compact ultra-wideband bandpass filter (UWB-BPF) using pseudo-interdigital stepped-impedance resonators (PIDT-SIRs) is designed and implemented on a commercial printed circuit board (PCB) of RT/Duroid 5880 substrate. The first two resonant modes of the SIR are coupled together and they are applied to create a wide passband. The proposed filter at center frequency f0 of 7.1 GHz has very good measured characteristics including the bandwidth of 3.68-10.46 GHz (3-dB fractional bandwidth of 95%), low insertion loss of -0.50.4 dB, sharp rejection due to two transmission zeros in the passband edge created by the inter-stage coupling. Experimental results of the fabricated filter show a good agreement with the predicted results.

Generalized Multi-protocol Label Switching (GMPLS) technologies are expected a key technology that creates high-performance Internet backbone networks. There were many GMPLS interoperability trials. However, most of them reported the successful results only. How to set up a trial network and how to test it was generally not discussed. In this paper, as a kind of tutorial, detailed GMPLS field trials in the National Institute of Information and Communications Technology (NICT) Kei-han-na Info-Communication Open Laboratory, Interoperability Working Group (WG) are reported. The interoperability WG is aiming at the leading edge GMPLS protocol based Inter-Carrier Interface that utilizes wide-bandwidth, cost-effective photonic technology to implement IP-centric managed networks. The interoperability WG is a consortium for researching the GMPLS protocol and advancing a de facto standard in this area. Its experimental results, new ideas, and protocols are submitted to standardization bodies such as the International Telecommunications Union-Telecommunication standardization sector (ITU-T), the Internet Engineering Task Force (IETF), and the Optical Internetworking Forum (OIF). This paper introduces the activities of the interoperability WG; they include a nationwide GMPLS field trial using the JGN II network with multi-vendor, multi-switching-capable equipment and a GMPLS multi routing area trial that used a multi-vendor lambda-switching-capable network.

The performance of TCP data transmission deteriorates significantly when a TCP connection traverses a heterogeneous network consisting of wired and wireless links. This is mainly because of packet losses caused by the high bit error rate of wireless links. We proposed receiver-based ACK splitting mechanism in [1]. It is a new mechanism to improve the performance of TCP over wired and wireless heterogeneous networks. Our mechanism employs a receiver-based approach, which does not need modifications to be made to the sender TCP or the base station. It uses the ACK-splitting method for increasing the congestion window size quickly in order to restrain the throughput degradation caused by packet losses due to the high bit error rate of wireless links. In this paper, we develop a mathematical analysis method to derive the throughput of a TCP connection, with/without our mechanism, which traverses wired and wireless heterogeneous networks. By using the analysis results, we evaluate the effectiveness of our mechanism in the network where both of packet losses due to network congestion and those caused by the high bit error rate of wireless links take place. Through An evaluation of the proposed method shows that it can give a good estimation of TCP throughput under the mixture networks of wired/wireless links. We also find that the larger the bandwidth of the wireless link is, the more effective our mechanism becomes, therefore, the mechanism's usability will increase in the future as wireless networks become faster.

Multicast delivery in heterogeneous wireless networks requires careful coordination, in order to take full advantage of the resources such an interworking network environment can offer. Effective coordination, however, may require interworking signaling from coordinating network entities to receivers of a multicast service. Scalable delivery of such signaling is of great importance, since a large number of receivers may be interested in a multicast service. This paper therefore investigates the use of a multicast signaling channel (MSCH) to carry such interworking signaling in a scalable manner. Applications of interworking signaling for multicast service delivery in heterogeneous wireless networks are presented, motivating the need for an MSCH. Then a comparative study is performed analysing potential benefits of employing an MSCH for signaling message delivery compared to conventional unicast signaling. The analysis reveals that the benefits of the MSCH depend mainly on the selection of an appropriate signaling network to carry the MSCH and also on efficient addressing of a subset of receivers within the MSCH. Based on the findings, guidelines for the selection of a suitable signaling network are provided. Furthermore a novel approach is proposed that allows efficient addressing of a subset of receivers within a multicast group. The approach minimizes the required signaling load on the MSCH by reducing the size of the required addressing information. This is achieved by an aggregation of receivers with common context information. To demonstrate the concept, a prototype of the MSCH has been developed and is presented in the paper.