Jeffrey C. Dill

Wavelet packet modulation: a generalized method for orthogonally multiplexed communications

Building on recently introduced multidimensional signalling techniques, a multirate wavelet based modulation format is presented which can utilize existing channels designed for conventional QAM. Customizable wavelet packet basis functions are employed as novel pulse shapes upon which independent QAM data at lower rates are placed. The advantages include dimensionality in both time and frequency for flexible channel exploitation and an efficient all digital filter bank implementation.<<ETX>>

Lossless to Lossy Dual-Tree BEZW Compression for Hyperspectral Images

This paper proposes a lossless to lossy compression scheme for hyperspectral images based on dual-tree Binary Embedded Zerotree Wavelet (BEZW) algorithm. The algorithm adapts Karhunen-Loève Transform and Discrete Wavelet Transform to achieve 3-D integer reversible hybrid transform and decorrelate spectral and spatial data. Since statistics of the hyperspectral image are not symmetrical, the asymmetrical dual-tree structure is introduced. The 3-D BEZW algorithm compresses hyperspectral images by implementing progressive bitplane coding. The lossless and lossy compression performance is compared with other state-of-the-art predictive coding and transform-based coding algorithms on Airborne Visible/Infrared Imaging Spectrometer images. Results show that the 3-D-BEZW lossless compression performance is comparable with the best predictive algorithms, while its computational cost is comparable with those of transform-based algorithms.

The square root raised cosine wavelet and its relation to the Meyer functions

A special case of the Meyer scaling function is shown to coincide with the square root raised cosine (SRRC) communication pulse, provided the fractional excess bandwidth is bounded above by one third. This pulse is widely used in digital transmission systems including the North American TDMA cellular standard. Having made this connection, we proceed to derive the time-domain SRRC wavelet in closed form. Although the SRRC wavelet with nonzero excess bandwidth reduces to the ideal sinc wavelet, allowing for a valid nonzero excess bandwidth produces a wavelet of practical interest particularly for communication applications.

An anti-jamming algorithm using wavelet packet modulated spread spectrum

In this paper, a novel wavelet packet modulated direct sequence spread spectrum system is introduced, and an anti-jamming algorithm is also developed to suppress narrow band jamming signals. According to the time series theory, Fishers test can detect the hidden sinusoids in an AWGN environment, which give us a clue to detect the jamming signal. We generalize this algorithm so that we can detect the hidden wavelet packet components in an AWGN environment. The normalized energy distribution of the wavelet packet transformed signal is derived, a threshold is determined and the jamming signal is excised. Jamming signals with different strength and different bandwidth are investigated. Based on the simulation results, the generalized Fishers test can effectively suppress interference in wide ranges.

Fountain codes with message passing and maximum likelihood decoding over erasure channels

We investigate the performance of fountain codes on erasure channels with message passing and maximum likelihood decoding algorithms. Fountain codes under message passing decoding are efficient but, for short data length, the decoding overhead may not be optimal. We focus on reducing overhead without losing the codes efficiency and universality, and propose a hybrid message passing and fast maximum likelihood decoding algorithm for LT codes. We also design Raptor codes with one stage pre-codes which are remarkable LDPC codes in the IEEE 802.16e standard. Simulation results show that small dimension fountain codes can save impressive decoding overhead with the maximum likelihood algorithm and the hybrid scheme.

Simplex symbol assignment in circular trellis-coded modulation

This paper presents a method for the assignment of simplex signals in a circular trellis-coded modulation (CTCM) scheme. A background is given on both CTCM and simplex signaling. The CTCM trellis is then shown to have various properties that allow symbol assignment to be carried out in a systematic manner.

Hyperspectral images lossless compression using the 3D binary EZW algorithm

This paper presents a transform based lossless compression for hyperspectral images which is inspired by Shapiro (1993)’s EZW algorithm. The proposed compression method uses a hybrid transform which includes an integer Karhunrn-Loeve transform (KLT) and integer discrete wavelet transform (DWT). The integer KLT is employed to eliminate the presence of correlations among the bands of the hyperspectral image. The integer 2D discrete wavelet transform (DWT) is applied to eliminate the correlations in the spatial dimensions and produce wavelet coefficients. These coefficients are then coded by a proposed binary EZW algorithm. The binary EZW eliminates the subordinate pass of conventional EZW by coding residual values, and produces binary sequences. The binary EZW algorithm combines the merits of well-known EZW and SPIHT algorithms, and it is computationally simpler for lossless compression. The proposed method was applied to AVIRIS images and compared to other state-of-the-art image compression techniques. The results show that the proposed lossless image compression is more efficient and it also has higher compression ratio than other algorithms.

Digital transceiver implementation for wavelet packet modulation

Current transceiver designs for wavelet-based communication systems are typically reliant on analog waveform synthesis, however, digital processing is an important part of the eventual success of these techniques. In this paper, a transceiver implementation is introduced for the recently introduced wavelet packet modulation scheme which moves the analog processing as far as possible toward the antenna. The transceiver is based on the discrete wavelet packet transform which incorporates level and node parameters for generalized computation of wavelet packets. In this transform no particular structure is imposed on the filter bank save dyadic branching, and a maximum level which is specified a priori and dependent mainly on speed and/or cost considerations. The transmitter/receiver structure takes a binary sequence as input and, based on the desired time- frequency partitioning, processes the signal through demultiplexing, synthesis, analysis, multiplexing and data determination completely in the digital domain - with exception of conversion in and out of the analog domain for transmission.

Exploiting the synergies of circular simplex turbo block coding and wavelet packet modulation

This paper describes an experimental implementation of an interference avoidance waveform, suitable for mobile or fixed wireless channels, and comprised of orthogonal signaling using wavelet packets in cohesive combination with a multidimensional channel error coding technique. The patent pending adaptive waveform, known as circular simplex turbo block coded wavelet packet modulation (CSTBC-WPM), possesses an unrivaled time-frequency localization and agility capability for avoiding joint narrowband/impulsive interference patterns. Excision of residual interference at the receiver is facilitated by isolation to a sparse number of time-frequency cells and removal using energy thresholding. Moreover, the time dilation of symbols in the WPM subbands is useful in mitigating the adverse effects of multipath-induced, frequency-selective fading. For an even more potent countermeasure to nonGaussian interference sources and channel propagation anomalies, the patent pending CSTBC forward error correction component is distinctly mapped onto the orthogonally multiplexed WPM symbols and interleaved to exploit the subband frequency diversity. The shorter block sizes of CSTBC provide a bit error rate performance competitive with turbo product codings large code blocks, approaching the Shannon limit but with considerably lower latency (up to 20-fold improvement).

A minislot access protocol for CDMA packet radio networks with positive acknowledgement

The author presents and analyzes a minislotted channel-access protocol for code-division multiple-access (CDMA) packet radio networks that provides a number of distinct advantages. First, the protocol accomplishes active acknowledgement with very high reliability, while consuming only a small fraction of overhead channel bandwidth for the positive acknowledgement transmissions. Second, the minislot architecture reduces the vulnerability of the network to intelligent jammers, who may attempt to attack the acquisition preamble selectively. This is accomplished with only a modest reduction in overall network capacity. Finally, the minislot architecture provides a mechanism by which variable-length data packets may be accommodated without significant increase in design complexity, thereby improving the efficiency of the network. This protocol is analyzed by means of a discrete-time Markov chain model, and throughput performance is derived for a wide range of potential minislot sizes. A fundamental limit on the throughput of perfect CDMA networks is derived for both slotted and unslotted channels and is a consequence of the burstiness of traffic and the random pairing of transmitters and receivers.<<ETX>>