This PDF file contains the front matter associated with SPIE Proceedings Volume 8404, including the Title Page, Copyright information, Table of Contents, and the Conference Committee listing.

Wireless sensor networks (WSN) have become powerful tools for gathering and monitoring environmental data. These networking systems can be utilized for many different applications due to their autonomy, ability to withstand harsh conditions, and the reduced cost associated with their collection of data. These characteristics are beneficial across a wide range of applications including those specific to the military, environmental, industrial, and medical industries. Additionally, they become increasingly more relevant in remote sensing applications where size weight and power trade-offs are of particular importance. Conversely, these applications also demonstrate the Achilles heel of a large percentage of WSNs in that they run on limited power sources. Thus, energy efficiency is a major concern and therefore a significant amount of research has been dedicated to identifying methods of making WSNs as energy efficient as possible. The purpose of this paper is to detail a reactive wireless sensor network protocol that will minimize network overhead and energy consumption in an effort to provide longevity to the overall network. The underlying components of the Sensor-Triggered Efficient Routing protocol, STER, will be covered and the asynchronous handshaking method used to transmit data between the sending and receiving nodes will also be described. The power consumption performance results of STER will then be compared to those obtained from other protocols in the current literature. The data will show that implementation of the STER protocol should result in a wireless sensor network with an increased life span.

The goal of this paper is to reliably estimate a vector of unknown deterministic parameters associated with an underlying function at a fusion center of a wireless sensor network based on its noisy samples made at distributed local sensors. A set of noisy samples of a deterministic function characterized by a nite set of unknown param- eters to be estimated is observed by distributed sensors. The parameters to be estimated can be some attributes associated with the underlying function, such as its height, its center, its variances in dierent directions, or even the weights of its specic components over a predened basis set. Each local sensor processes its observation and sends its processed sample to a fusion center through parallel impaired communication channels. Two local processing schemes, namely analog and digital, are considered. In the analog local processing scheme, each sensor transmits an amplied version of its local analog noisy observation to the fusion center, acting like a relay in a wireless network. In the digital local processing scheme, each sensor quantizes its noisy observation before trans- mitting it to the fusion center. A at-fading channel model is considered between the local sensors and fusion center. The fusion center combines all of the received locally-processed observations and estimates the vector of unknown parameters of the underlying function. Two dierent well-known estimation techniques, namely maximum-likelihood (ML), for both analog and digital local processing schemes, and expectation maximization (EM), for digital local processing scheme, are considered at the fusion center. The performance of the proposed distributed parameter estimation system is investigated through simulation of practical scenarios for a sample underlying function.

This paper first describes the innovative topology and structure of a wireless ad hoc and sensor network in a so called line-in-the-underground formation and the feasibility of achieving a reliable wireless connection underground with regards to a borehole telemetry system. It further describes a routing algorithm/protocol implementation based on a modification of the ad hoc on-demand distance vector protocol to achieve a reliable underground communication scheme for the wireless ad hoc network deployed underground for sensor data acquisition in real time as applied in the borehole telemetry system. Simulations and experiments are conducted to investigate and verify the effectiveness of this routing technique and the performance results are shown.

Future military wireless communication in a battlefield will be mobile ad hoc in nature. The ability to geolocate and track both friendly forces and enemies is very important in military command and control operations. However, current mobile ad hoc networks (MANET) have no capabilities to geolocate radio emitters that belong to enemy mobile ad hoc networks. This paper presents a distributed geolocation algorithm using received signal strength differences to geolocate enemy radio emitters by leveraging friendly force MANET infrastructure, and proposes a communication protocol for radio emitter geolocation applications. An enemy's radio emitter signal is detected, and its signal strength is measured by the nodes in a friendly mobile ad hoc network. The identity of the enemy radio emitter is extracted from the decoded message header of the medium access control layer. By correlating and associating the enemy's radio emitter identity with its received signal strength, the enemy radio emitter is identified. The enemy's radio emitter identity and its received signal strength are distributed and shared among friendly mobile ad hoc nodes. Using received signal strength differences, a master friendly node can calculate the enemy's radio emitter geolocation, and build a recognized MANET picture (RMP). This MANET picture is then distributed to all friendly nodes for effective command and control operations. An advantage of this method is that mobile ad hoc nodes do not need special RF antennas to geolocate the enemy radio emitter as conventional electronic warfare techniques do. MATLAB-based simulations are presented to evaluate the accuracy and reliability of the proposed distributed geolocation algorithm under different MANET placements.

The quality-of-service (QoS) metrics in a wireless sensor network (WSN) of multiple sensor types depend on the performance of the network protocol layers, motivating a comprehensive cross-layer design approach to optimize QoS. Advances in energy-harvesting techniques enable increases in WSN lifetime by prolonging operation of the wireless nodes. While the primary objective of energy harvesting is to prolong network lifetime, it may cause lower values of other QoS metrics during that lifetime. From the author's previous work, cross-layer protocol interactions are represented through a set of concatenated parameters and resource levels for a real-time WSN under energy harvesting (EH-WSN). The cross-layer parameters that determine QoS values in the EH-WSN are established in terms of solutions to stochastic dynamic programming conditions derived from multivariate point-process (MVPP) models of transient information flows. Simulation results evaluate the extent to which QoS values are degraded in an EH-WSN compared to a WSN of the same structure without energy harvesting.

In scenarios where channel state information is available to the receiver, making use of the information in detection significantly improves system performance. Such transmission scheme is called coherent detection. In this work, we propose a new family of space-time codes for coherent detection schemes in a wireless environment using multiple transmitter and receiver antennas. The decoding problem can be efficiently solved by parallel sphere decoder algorithm. A combination of Genetic algorithms and stochastic gradient descendent algorithms is established for the code optimization. Our simulation results indicate that such a wireless communication technique is suitable for sensing systems with reliable transmission of high volume of data.

In this paper we introduce Integer Quadratic Programming (MIQP) approach to optimally detect QPSK Code Spread OFDM (CS-OFDM) by formulating the problem as a combinatorial optimization problem. The Branch and Bound (BB) algorithm is utilized to solve this integer quadratic programming problem. Furthermore, we propose combined preprocessing steps that can be applied prior to BB so that the computational complexity of the optimum receiver is reduced. The first step in this combination is to detect as much as possible symbols using procedures presented in [9], which is basically based on the gradient of quadratic function. The second step detects the undetected symbols from the first step using MMSE estimator. The result of the latter step will be used to predict the initial upper bound of the BB algorithm. Simulation results show that the proposed preprocessing combination when applied prior to BB provides optimal performance with a significantly reduced computational complexity.

In Orthogonal Frequency Division Multiplexing (OFDM) systems, the technique used to estimate and track the time-varying multipath channel is critical to ensure reliable, high data rate communications. It is recognized that wireless channels often exhibit a sparse structure, especially for wideband and ultra-wideband systems. In order to exploit this sparse structure to reduce the number of pilot tones and increase the channel estimation quality, the application of compressed sensing to channel estimation is proposed. In this article, to make the compressed channel estimation more feasible for practical applications, it is investigated from a perspective of Bayesian learning. Under the Bayesian learning framework, the large-scale compressed sensing problem, as well as large time delay for the estimation of the doubly selective channel over multiple consecutive OFDM symbols, can be avoided. Simulation studies show a significant improvement in channel estimation MSE and less computing time compared to the conventional compressed channel estimation techniques.

In this paper, partial spread OFDM system has been presented and its performance has been studied when different detection techniques are employed, such as minimum mean square error (MMSE), grouped Maximum Likelihood (ML) and approximated integer quadratic programming (IQP) techniques . The performance study also includes applying two different spreading matrices, Hadamard and Vandermonde. Extensive computer simulation have been implemented and important results show that partial spread OFDM system improves the BER performance and the frequency diversity of OFDM compared to both non spread and full spread systems. The results from this paper also show that partial spreading technique combined with suboptimal detector could be a better solution for applications that require low receiver complexity and high information detectability.

Continuous Phase Modulation (CPM) waveforms offer some very appealing characteristics such as constant envelope and bandwidth efficiency. Orthogonal Frequency Division Multiplexing (OFDM) is a popular technique used for digital data transmission due to its low computational complexity and simple equalization process. One of its main drawbacks is the very large peak power to average power ratio (PAPR) which requires the use of very linear power amplifiers (PA) and a large power back-off into the PA. In recent years a variant of OFDM has been developed known as constant envelope OFDM. This paper will compare the bandwidth efficiency and performance of CPM and constant-envelope OFDM waveforms.

Accurate propagation models are required for predicting the propagation of electromagnetic waves within complex environments. This paper proposes the use of a new method to accurately compute the divergence and curl of electromagnetic fields. The computation of the derivatives of vector fields is normally approximated using numerical methods such as the Finite-Dierence Time-Domain Method (FDTD), the Finite Integration Technique and the Multi-Resolution Time-Domain Method. These methods are all limited in terms of their accuracy, resolution, computational efficiency and numerical stability. This paper introduces a new method for computing derivatives based on Two-Dimensional (2D) Digital Signal Processing (DSP) techniques. The method involves computing a numerical approximation of the derivative of a function by considering the frequency domain definition of the derivative and designing a 2Dfinite impulse response (FIR) filter that implements the differentiation. Appropriate windowing functions are used to ensure that the FIR response is as close to the ideal 2D differentiator response as possible. This paper provides an example where the curl of a vectorfield is determined using this method and accuracy within a few percent is achieved. The proposed innovative method can be extended to three dimensions and used to find numerical solutions of Maxwells Equations, thus allowing it to be applied to the design of accurate propagation models.

Software defined radio (SDR) hardware platform is in high demand for ultra-wideband digital EW receiver to carry out different mission requirements. Due to the limitations of current Analog-to-Digital conversion (ADC) techniques, the ideal receiver structure of SDR, with digital RF frequency conversion, cannot be achieved. In this article, a new channelization technique called ADC polyphase fast Fourier transformation (ADC PFFT) filter bank channelization is demonstrated. The key concept is to separate the speed at which the two functional units of an ADC - the sample and hold and the quantizer - operate. The sample and hold unit operates at the sampling frequency f_s and the quantizer (the speed limiting factor in ADCs) can operate at a much slower rate, f_s/M, where M is the decimation factor for digital filter bank. By integrated this ADC PFFT technique in ultra-wideband digital channelized EW receivers, directly digital RF down conversion can be achieved. With the ADC PFFT channelization for RF down conversion and polyphase FFT channelization for IF down conversion, 2-18 GHz frequency coverage can be accomplished in such ultra-wideband digital channelized EW receivers without the requirement of EW receivers being time-shared among outputs from many subbands due to bandwidth limitation in digital IF channelized EW receivers. Because the frequency down conversion from RF to BB are all processed digitally, issues such as image rejection and I/Q imbalance due to analog mixing will be eliminated in the ultrawideband digital channelized EW receivers.

For radio communication systems, powerful error correction codes are necessary to operate in noisy and fading channel conditions. Iterative forward error correction schemes like Turbo codes can achieve near Shannon capacity performance on memory-less channels and also perform well on correlated fading channels. The key to the excellent decoding performance of the Turbo coding systems is the BCJR algorithm in conjunction with the iterative processing of soft information. A very popular modulation technique is Differential Phase Shift Key (DPSK) which is not only a simple non-coherent modulation and demodulation technique; it is also a recursive rate one code. Combining DPSK with a single convolutional code structure as an iterative inner outer forward error correction system can provide excellent Turbo like performance. Bit Interleaved Coded Modulation with Iterative Demodulation (BICM-ID), another powerful iterative technique achieves near Turbo code performance with significantly less mips. We will also introduce and compare with the latter systems yet another novel iterative scheme that utilizes coherent demodulation in conjunction with convolutional codes. This new system can easily be extended to higher order modulations such as 16 and 64 Quadrature Amplitude Modulation (QAM) while only requiring modest amounts of processing power. Monte Carlo simulation results will be shown for the Additive White Gaussian Noise (AWGN) channels.

Probability of bit-error P_er performance of asynchronous direct-sequence code-division multiple-access (DS-CDMA) wireless communication systems employing the generalized detector (GD) constructed based on the generalized approach to signal processing in noise is analyzed. The effects of pulse shaping, quadriphase or direct sequence quadriphase shift keying (DS-QPSK) spreading, aperiodic spreading sequences are considered in DS-CDMA based on GD and compared with the coherent Neyman-Pearson receiver. An exact P_er expression and several approximations: one using the characterristic function method, a simplified expression for the improved Gaussian approximation (IGA) and the simplified improved Gaussian approximation are derived. Under conditions typically satisfied in practice and even with a small number of interferers, the standard Gaussian approximation (SGA) for the multiple-access interference component of the GD statistic and P_er performance is shown to be accurate. Moreover, the IGA is shown to reduce to the SGA for pulses with zero excess bandwidth. Second, the GD P_er performance of quadriphase DS-CDMA is shown to be superior to that of bi-phase DS-CDMA. Numerical examples by Monte Carlo simulation are presented to illustrate the GD P_er performance for square-root raised-cosine pulses and spreading factors of moderate to large values. Also, a superiority of GD employment in CDMA systems over the Neyman-Pearson receiver is demonstrated

The joint optimization of source beamformer and distributed relay coefficients is considered for a cooperative network that uses the output mean-square error (MSE) as the performance metric. Two methods are proposed for solving this nonconvex optimization problem. The first approach iteratively optimizes the source beamformer and relay coefficients, whereas the second method optimizes the relay coefficients keeping the source beamformer as the maximum-ratio-transmitter (MRT). Both approaches are reformulated as relaxed semidefinite programming problems. The optimality of MRT is proven analytically under some conditions. The superiority of the proposed methods is verified using numerical examples.

Constant Envelope, Continuous Phase Modulation (CPM) is highly desirable for low-power, battery-operated systems as well as for small-profile vehicular and aircraft systems where large amplifiers won't fit. In the past, CPM was noted for increased demodulator complexity (over simple PSK or FSK receivers) but with modern computational power it is possible to continue to improve the power efficiency of CPM modulation at the receiver. In the specific case of multipath, there are several known methods (Rake Receiver is one example) to resolve and correct for inter-symbol interference and phase distortion. This paper develops a standard CPM demodulation and compares the optimal coherent performance with a partially coherent receiver. Several methods are developed to compensate and correct for ISI due to various types of multipath and the power efficiency is compared to the original, coherent demodulation.