Topology-aided cross-layer fast handoff designs for IEEE 802.11/mobile IP environments

This study first reviews state-of-the-art fast handoff techniques for IEEE 802.11 or Mobile IP networks. Based on that review, topology-aided cross-layer fast handoff designs are proposed for Mobile IP over IEEE 802.1.1 networks. Time-sensitive applications, such as voice over IP (VoIP), cannot tolerate the long layer-2 plus layer-3 handoff delays that arise in IEEE 802.11/Mobile IP environments. Cross-layer designs are increasingly adopted to shorten the handoff latency time. Handoff-related layer-2 triggers may reduce the delay between layer-2 handoff completion and the associated layer-3 handoff activation. Cross-layer topology information, such as the association between 802.11 access points and Mobile IP mobility agents, together with layer-2 triggers, can be utilized by a mobile node to start layer-3 handoff-related activities, such as agent discovery, address configuration, and registration, in parallel with or prior to those of layer-2 handoff. Experimental results indicate that the whole handoff. delay can meet the delay requirement of VoIP applications when layer-3 handoff activities occur prior to layer-2 handoffs.     

Nitride-based flip-chip ITO LEDs

Nitride-based flip-chip indium-tin-oxide (ITO) light-emitting diodes (LEDs) were successfully fabricated. It was found that the forward voltage and the 20 mA output power of the flip-chip ITO LED were 3.32 V and 14.5 mW, respectively. Although the operation voltage of such a flip-chip ITO LED was slightly larger, it was found that its output power was much larger than those of conventional nonflip-chip LEDs. It was also found that flip-chip ITO LEDs were more reliable.     

Cost-Effective Joint Echo-NEXT Canceller Designs for 10GBase-T Ethernet Systems Based on a Shortened Impulse Response Filter (SIRF) Scheme

Echo canceller plays an important role in the full-duplex communication system. Conventional implementations of echo cancellers are often the adaptive transversal filter architectures due to the simplicity and robustness of stability and convergence. However, the conventional echo cancellers suffer from high cost problem especially when the response time of the echo is long. In this paper, a new cost-efficient architecture of echo cancellers, targeting on 10GBase-T Ethernet System, is presented. The proposed scheme inherits the concept of channel shortening which is widely employed in DSL systems. A shortened impulse response filter is implemented at the receiver to shorten the impulse response of the echo signal. Hence, the overall cost of echo cancellers can be reduced. We generalize the channel shortening architecture to a joint multi-channel shortening scheme. The joint multi-channel shortening architecture can be applied to multiple-input multiple-output wireline communication systems to further reduce both the cost of echo and near-end crosstalk (NEXT) cancellers. We apply the proposed scheme to 10GBase-T Ethernet system. The simulation results show that the proposed echo and NEXT cancellers can save up to 35% hardware cost compared to the conventional transversal implementations.

UPCF: a new point coordination function with QoS and power management for multimedia over wireless LANs

In this paper, we propose a new novel polling-based medium access control protocol, named UPCF (Unified Point Coordination Function), to provide power conservation and quality-of-service (QoS) guarantees for multimedia applications over wireless local area networks. Specifically, UPCF has the following attractive features. First, it supports multiple priority levels and guarantees that high-priority stations always join the polling list earlier than low-priority stations. Second, it provides fast reservation scheme such that associated stations with real-time traffic can get on the polling list in bounded time. Third, it employs dynamic channel time allocation scheme to support CBR/VBR transportation and provide per-flow probabilistic bandwidth assurance. Fourth, it employs the power management techniques to let mobile stations save as much energy as possible. Fifth, it adopts the mobile-assisted admission control technique such that the point coordinator can admit as many newly flows as possible while not violating QoS guarantees made to already-admitted flows. The performance of UPCF is evaluated through both analysis and simulations. Simulation results do confirm that, as compared with the PCF in IEEE 802.11, UPCF not only provides higher goodput and energy throughput, but also achieves lower power consumption and frame loss due to delay expiry. Last but not least, we expect that UPCF can pass the current Wi-Fi certification and may coexist with the upcoming IEEE 802.11e standard.     

CPW-fed circular slot antenna with slit back-patch for 2.4/5 GHz dual-band operation

A circular slot antenna fed by a coplanar waveguide (CPW) is proposed for dual-band operations. Dual frequency bands that cover the 2.4 GHz (2400-2484 MHz) and 5 GHz (5150-5825 MHz) bands were obtained by embedding a pair of slits in the circular back-patch that is printed on the backside of the substrate and concentric with the circular slot. This design resulted in broadside far-field patterns with low cross-polarisation levels in both frequency bands and a small antenna size of 40/spl times/40 mm with the ground plane regarded as part of the antenna structure.     

Nitrogen implanted polysilicon resistor for high-voltage CMOStechnology application

A nitrogen-implanted polysilicon thin film resistor has been proposed to improve the electrical characteristics of resistors in high-voltage CMOS technologies. The SIMS profile shows the proposed nitrogen-implanted polysilicon resistor can raise 100 times of the concentration of nitrogen. Thereby, the temperature coefficient of resistance (TCR), voltage coefficient of resistance (VCR), and mismatch are improved 20.4%, 35.9%, and 23.5% in average, respectively. The improvements are attributed to the suppression of both hydrogen intrusion by the presence of high-nitrogen concentration in polysilicon     

Amplification of Cerenkov Luminescence Using Semiconducting Polymers for Cancer Theranostics

The therapeutic efficacy of photodynamic therapy is limited by the ability of light to penetrate tissues. Due to this limitation, Cerenkov luminescence (CL) from radionuclides has recently been proposed as an alternative light source in a strategy referred to as Cerenkov radiation-induced therapy (CRIT). Semiconducting polymer nanoparticles (SPNs) have ideal optical properties, such as large absorption cross-sections and broad absorbance, which can be utilized to harness the relatively weak CL produced by radionuclides. SPNs can be doped with photosensitizers and have ≈100% energy transfer efficiency by multiple energy transfer mechanisms. Herein, an optimized photosensitizer-doped SPN is investigated as a nanosystem to harness and amplify CL for cancer theranostics. It is found that semiconducting polymers significantly amplify CL energy transfer efficiency. Bimodal positron emission tomography (PET) and optical imaging studies show high tumor uptake and retention of the optimized SPNs when administered intravenously or intratumorally. Lastly, it is found that photosensitizer-doped SPNs have excellent potential as a cancer theranostics nanosystem in an in vivo tumor therapy study. This study shows that SPNs are ideally suited to harness and amplify CL for cancer theranostics, which may provide a significant advancement for CRIT that are unabated by tissue penetration limits.     

Fabrication and Characterization of Benzocyclobutene Optical Waveguides by UV Pulsed-Laser Illumination

Buried-type benzocyclobutene (BCB) optical waveguides fabricated by UV pulsed-laser illumination are proposed and comprehensively characterized in this paper. The fabrication process is greatly simplified as compared to conventional dry-etched ridge-type BCB waveguides. The measured propagation loss at 1548 nm is as low as 0.6 dB/cm due to the buried waveguide structure. And the produced refractive index change is dependent upon the number of laser shots such that single-mode waveguides with different mode sizes can be tailored for efficient coupling. Furthermore, rigorous analyses of surface damage threshold, rms roughness, and chemical characteristics under different illumination conditions are presented to illustrate the design considerations and the chemical mechanism of the UV-induced BCB waveguides     

Effect of hydrogen annealing on hot-carrier instability of X-Ray irradiated CMOS devices

In the very large scale integration (VLSI) technology, the need for high density and high performance integrated circuit (IC) chip demands advanced processing techniques that often result in the generation of high energy particles and photons. Frequently, the radiation damage are introduced by these energetic particles and photons during device processing. The radiation damage created by x-ray irradiation, which can often occur during metal sputtering process, has been shown to potentially enhance hot-carrier instability if the neutral traps which act as electron or hole traps in the silicon dioxide is not annealed out. In this paper, we investigate the effects of annealing using different hydrogen contents and temperatures on the device characteristics and hot carrier instability of 0.5 μm CMOS devices after 1500 mJ/cm² synchrotron x-ray irradiation. Three different annealing conditions were employed; 400° C H₂, 450° C H₂, and 400° C H₂ + N₂. It is found that for all three different hydrogen anneals the normal characteristics of irradiated CMOS devices can be effectively recovered. The hot-carrier instability of bothp- andn-channel MOSFETs are significantly enhanced after x-ray irradiation due to the creation of neutral traps and positively charged oxide traps. After high H₂ (100%) concentration anneals at 450° C, the hot-carrier instability in irradiatedn-channel devices is greatly reduced and comparable to the non-irradiated devices. Although the hot-carrier instability inp-channel devices is also significantly reduced after annealing, the threshold voltage shifts are still enhanced as compared to the devices without exposure to x-ray irradiation during maximum gate current stress. For those non-irradiated, but hydrogen-annealedp-channel devices, the hot-carrier instability was observed to be worse than the non-irradiated device without hydrogen annealing.     

Two schemes for detecting CMOS analog faults

A design-for-testability scheme for detecting CMOS analog faults was reported by Favalli et al. (see ibid., vol.25, no.5, p.1239-46, 1990). The authors propose two alternative designs, one for small circuits and another for large circuits, which require significantly less area overhead (about 1/4 to 1/3) than that of Favalli's design. With the proposed modification in the first design, the untestable problem, which occurred in Favalli's design, can be alleviated. Furthermore, the proposed schemes are also fit to be implemented in VLSI circuits