Satellite-based precipitation estimation using watershed segmentation and growing hierarchical self-organizing map

This paper outlines the development of a multi-satellite precipitation estimation methodology that draws on techniques from machine learning and morphology to produce high-resolution, short-duration rainfall estimates in an automated fashion. First, cloud systems are identified from geostationary infrared imagery using morphology based watershed segmentation algorithm. Second, a novel pattern recognition technique, growing hierarchical self-organizing map (GHSOM), is used to classify clouds into a number of clusters with hierarchical architecture. Finally, each cloud cluster is associated with co-registered passive microwave rainfall observations through a cumulative histogram matching approach. The network was initially trained using remotely sensed geostationary infrared satellite imagery and hourly ground-radar data in lieu of a dense constellation of polar-orbiting spacecraft such as the proposed global precipitation measurement (GPM) mission. Ground-radar and gauge rainfall measurements were used to evaluate this technique for both warm (June 2004) and cold seasons (December 2004-February 2005) at various temporal (daily and monthly) and spatial (0.04 and 0.25) scales. Significant improvements of estimation accuracy are found classifying the clouds into hierarchical sub-layers rather than a single layer. Furthermore, 2-year (2003-2004) satellite rainfall estimates generated by the current algorithm were compared with gauge-corrected Stage IV radar rainfall at various time scales over continental United States. This study demonstrates the usefulness of the watershed segmentation and the GHSOM in satellite-based rainfall estimations

A simple adaptive MAC scheduling scheme for bluetooth scatternet

A simple adaptive MAC scheduling algorithm, called Gateway Oriented Scatternet Scheduling (GOSS), is proposed for data exchange in a Bluetooth scatternet. Unlike the existing scheme MDRP (Maximum Distance Rendezvous Point) that has a global superframe schedule shared by all gateways, the schedule used by each gateway is individually determined. Equal partition of the superframe schedule at a gateway to each connected piconet can thus be guaranteed, which enables a more robust performance than MDRP. In addition, GOSS allows a variable sized superframe at each gateway. To maximize its performance, the frame size can be dynamically adjusted according to the scatternet topology and traffic load in every predefined adaptation interval. Simulation results show that even a static GOSS prevails over MDRP. If the adaptation technique is used, further performance enhancement can be found.published_or_final_versio

Autonomous proximity awareness of bluetooth devices

This paper focuses on designing autonomous device discovery algorithms for Bluetooth networks. We first extend the conventional asymmetric Bluetooth link model to three point-to-point symmetric link models. Their performances are compared analytically. To achieve proximity awareness among a group of Bluetooth devices, three control information exchanging methods are also proposed. Combining with the three link models, this gives 9 possible variants of autonomous device discovery algorithm. A comprehensive comparative study based on these 9 variants is then carried out using Bluehoc simulator. © 2005 IEEE.published_or_final_versio

Scheduling algorithms for input-queued switches with virtual output queueing

A set of packet scheduling algorithms are proposed for improving the performance of Iterative Longest Port First (iLPF) algorithm in [1] for Virtual Output Queueing Switch. In our proposed algorithms, scheduling priority is given according to different criteria that include input port occupancy, output port occupancy and critical port in VOQ. One of our proposed algorithm, called Longest Input Port First with Throughput Maximization (LIPF with TM), gives significant performance improvement in mean packet delay and throughput when compared with iLPF. We found that for a 16 × 16 switch with input load p = 0.85, the mean packet delay is 7.08 slots for iLPF and 3.21 slots for LIPF with TM. This represents a 55% cut in mean packet delay.published_or_final_versio

Low-delay perfect reconstruction two-channel FIR/IIR filter banks and wavelet bases with SOPOT coefficients

IEEE International Conference on Acoustics, Speech and Signal Processing, Istanbul, Turkey, 5-9 June 2000In this paper, a new family of two-channel low-delay filter banks and wavelet bases using the PR structure in [3] with SOPOT coefficients are proposed. In particular, the functions alpha(z) and beta(z) in the structure are chosen as nonlinear-phase FIR and IIR filters, and the design of such multiplier-less filter banks is performed using the genetic algorithm. The proposed design method is very simple to use, and is sufficiently general to construct low-delay filter banks with flexible lengths, delays, and regularity. Several design examples are given to demonstrate the usefulness of the proposed method.published_or_final_versio

A Novel MAC Scheduling Algorithm for Bluetooth System

Data exchange within a Bluetooth piconet is masterdriven. The channel/slot utilization thus depends on the efficiency of the scheduling algorithm adopted by the master. In this paper, a novel MAC layer scheduling algorithm, called Floating Threshold (FT), is proposed. Unlike existing approaches, FT allows the master to estimate the backlog queue status at each slave accurately based only on a single feedback bit and a floating threshold. The master can then derive an optimized packet transmission schedule. Using simulations, we show that FT outperforms existing algorithms in terms of channel utilization, packet delay and packet dropping probability.published_or_final_versio

Low-delay perfect reconstruction two-channel FIR/IIR filter banks and wavelet bases with SOPOT coefficients

IEEE International Conference on Acoustics, Speech and Signal Processing, Istanbul, Turkey, 5-9 June 2000In this paper, a new family of two-channel low-delay filter banks and wavelet bases using the PR structure in [3] with SOPOT coefficients are proposed. In particular, the functions alpha(z) and beta(z) in the structure are chosen as nonlinear-phase FIR and IIR filters, and the design of such multiplier-less filter banks is performed using the genetic algorithm. The proposed design method is very simple to use, and is sufficiently general to construct low-delay filter banks with flexible lengths, delays, and regularity. Several design examples are given to demonstrate the usefulness of the proposed method.published_or_final_versio

Multiplier-less low-delay FIR and IIR wavelet filter bank with SOPOT coefficients

In this paper, a new family of multiplier-less two-channel lowdelay wavelet filter banks using the PR structure in [3] and the SOPOT(sum-of-powers-of-two) representation is proposed. In particular, the functions α (z) and β (z) in the structure are chosen as nonlinear-phase FIR and IIR filters, and the design of such multiplier-less filter banks is performed using the genetic algorithm. The proposed design method is very simple to use, and is sufficiently general to construct low-delay wavelet bases with flexible length, delay, and number of zero at π (or 0) in their analysis filters. Several design examples are given to demonstrate the usefulness of the proposed method.postprin

Multiplierless perfect reconstruction modulated filter banks with sum-of-powers-of-two coefficients

This paper proposes an efficient class of perfect reconstruction (PR) modulated filter banks (MFB) using sum-of-powers-of-two (SOPOT) coefficients. This is based on a modified factorization of the DCT-IV matrix and the lossless latrice structure of the prototype filter, which allows the coefficients to be represented in SOPOT form without affecting the PR condition. A genetic algorithm (GA) is then used to search for these SOPOT coefficients. Design examples show that SOPOT MFB with a good frequency characteristic can be designed with very low implementation complexity. The usefulness of the approach is demonstrated with a 16-channel design example.published_or_final_versio

Perfect reconstruction modulated filter banks with sum of powers-of-two coefficients

IEEE International Symposium on Circuits and Systems, Geneva, Switzerland, 28-31 May 2000In this paper, a new family of multiplier-less modulated filter banks, called the SOPOT MFB, is presented. The coefficients of the proposed filter banks consist of sum of powers-of-two coefficients (SOPOT), which require only simple shifts and additions for implementation. The modulation matrix and the prototype filter are derived from a fast DCT-IV algorithm of Wang and the lattice structure in [1]. The design of the SOPOT MFB is performed using the genetic algorithm(GA). An 16-channel SOPOT MFB with 34 dB stopband attenuation is given as an example, and its average number of terms per SOPOT coefficient is only 2.6.published_or_final_versio