Generalized construction of binary bent sequences with optimal correlation property

We generalize the construction method of the family of binary bent sequences introduced by Olsen, Scholtz, and Welch (1982) to obtain a family of generalized binary bent sequences with optimal correlation and balance property by using the modified trace transform. Then, the conventional binary bent sequence becomes a special case of our construction method. Several families of the generalized binary bent sequences are constructed by using the bent functions on the intermediate field. Using some of the generalized binary bent sequences, new families of binary sequences with optimal correlation and balance property can be constructed by the lifting idea similar to No (1988) sequences, which are referred to as binary bent-lifted sequences.     

Variable structure observer of mismatched uncertain dynamical systems

To improve the steady state estimation error due to mismatched uncertainty, a variable structure observer for mismatched uncertain dynamical systems is proposed by using the generalised matrix inverse. Simulation results show that the estimation error is largely decreasing using the proposed observer.<>     

Electrical and optical properties of deep-red top-surface-emittinglasers

By studying thermal behavior of all-MBE surface-emitting lasers, barrier heights and optimum cavity design parameters are obtained. The barrier heights for holes between hetero-interfaces of Al_0.3Ga_0.7As-Al_0.65Ga_0.35As and AlAs-Al_0.65Ga_0.35As (Δx=-0.35) are measured to be 77 meV at zero bias for the deep-red top-surface-emitting laser. The barrier height decreases linearly with forward bias voltage, explaining the nonlinearity in current-voltage characteristics of the top-surface-emitting laser. The contribution of electrons to electrical resistance is estimated to be negligibly small compared to that of holes for the structure consisting of Δ_x =0.35. Minimum threshold current and maximum differential quantum efficiency observed around 200 K indicate slight mismatch between gain maximum and Fabry-Perot resonance for the deep-red top-surface-emitting laser     

Low operating currents of monolithically integrated 780 nm/650 nm-band self-sustained pulsating lasers with silicon nitride current blocking layers

The characteristics of monolithically integrated 780 nm/650 nm-band self-sustained pulsating (SSP) lasers with silicon nitride current blocking layers are reported. The record low operating current of 60 mA at 5 mW, 70/spl deg/C and a characteristic temperature of 90 K over 20 to 70/spl deg/C were obtained from the 650 nm-band SSP lasers. The attenuation factor of the visibility was observed to be as low as 0.3, which ensures SSP operations of the dual-mode lasers.     

DS-CDMA reverse link channel assignment based on interferencemeasurements

The authors propose a DS-CDMA reverse link channel assignment algorithm based on received interference. A new channel is assigned if the required power is less than the `current interference margin'. The proposed algorithm is adaptable to dynamically changing environments with the capability of assigning more channels than conventional channel assignment methods in nonhomogeneous traffic loads and path loss changes     

Scalable and efficient approach for secure group communication using proxy cryptography

Multicast is a scalable solution for group communications. In order to offer security for multicast applications, a group key has to be changed whenever a member joins or leaves the group. This incurs 1-affects-n problem, which is a constraint on scalability. Decentralized approaches solve the scalability problem by dividing a group into several subgroups that use independent group keys. These approaches, however, introduce new challenges: problem of trusting third party and inefficiency of data delivery. Proxy encryption is a good approach to solve the problem of trusting third party. In this paper, we propose a novel secure multicast scheme using the proxy cryptography. The proposed scheme provides not only scalability but also data transmission efficiency by dynamic subgrouping of group members while intermediate data-relaying third parties are not required to be trusted.     

Bulk Undoped GaAs–AlGaAs Substrate-Removed Electrooptic Modulators With 3.7-V-cm Drive Voltage at 1.55 $mu$ m

Substrate removed bulk GaAs-AlGaAs electrooptic modulators with 3.7-V-cm drive voltage at 1.55 mum were realized. The 1.94-mum-thick undoped GaAs-AlGaAs epilayer removed from its substrate behaves as an electrooptic dielectric layer and has electrodes placed directly on both sides. This allows a very strong modulating electric field overlapping very well with the optical mode. The propagation loss in the presence of electrodes is less than 2.9dB/cm. There is very good agreement between the measured and simulated values     

Construction of block orthogonal golay sequences and application to channel estimation of mimo-ofdm systems

In this paper, we construct a family of block orthogonal Golay sequences that have low peak-to-mean envelope power ratio (PMEPR) as well as block wise orthogonal properties. We then present an application of the sequences to channel estimation of multiple-input multiple-output orthogonal frequency division multiplexing (MIMO-OFDM) systems. We compare the performance of the proposed algorithm with that of a frequency division multiplexing (FDM) piloting algorithm, and investigate the effect of co-channel interference (CCI) on the channel estimation performance.     

An Interactive Design Environment for C-Based High-Level Synthesis of RTL Processors

Much effort in register transfer level (RTL) design has been devoted to developing "push-button" types of tools. However, given the highly complex nature, and lack of control on RTL design, push-button type synthesis is not accepted by many designers. Interactive design with assistance of algorithms and tools can be more effective if it provides control to the steps of synthesis. In this paper, we propose an interactive RTL design environment which enables designers to control the design steps and to integrate hardware components into a system. Our design environment is targeting a generic RTL processor architecture and supporting pipelining, multicycling, and chaining. Tasks in the RTL design process include clock definition, component allocation, scheduling, binding, and validation. In our interactive environment, the user can control the design process at every stage, observe the effects of design decisions, and manually override synthesis decisions at will. We present a set of experimental results that demonstrate the benefits of our approach. Our combination of automated tools and interactive control by the designer results in quickly generated RTL designs with better performance than fully-automatic results, comparable to fully manually optimized designs.