This paper compares the performance of passive RF emitter geolocation algorithms based on the Hough Transform and the particle filter. Three Hough Transform variants are considered: (a) the generalized Hough Transform, (b) the Randomized Hough Transform and (c) the Hybrid Hough Transform. In each case, the emitter is assumed to provide a signal from which angle of arrival measurements and time difference of arrival measurements can be made by pairs of mobile receiving platforms, such as fixed-wing UAVs or fast jets, as well as rotorcraft. Typical emitters include cellphones and other types of communication equipment. The paper demonstrates that the Hough Transform and the particle filter provide similar performance in terms of robustness of the RMS positional error and the computational time.

The paper will consider the viability of exploiting the spatial diversity that exists in doubly-spread, underwater acoustic communications channels to provide enhanced capacity using an OFDM-MIMO system. The proposed method offers two forms of diversity. First, coded orthogonal frequency-division multiplexing (COFDM) provides frequency diversity by exploiting the frequency selectivity inherent in channels that suffer from multipath propagation. Second, multiple transducers are used to exploit the spatial diversity that exists in underwater acoustic channels, also due to multipath propagation. This allows the multi-transducer communication system to be viewed as a multi-input, multi-output (MIMO) system to provided potential capacity gain.

This paper describes a novel source localization algorithm based on the Hough transform that allows different types of sensor data, such as angle of arrival and time difference of arrival data to be fused together by means of a transformation into a consistent parameterized space. A particular advantage of this method is that terrain data can also be fused with the various types of sensor data to aid accurate source localization

This paper presents a new method of cancelling wideband interference from digital acoustic communication signals used in underwater communication systems. The interference is from other co-channel acoustic systems, such as navigation systems, that have a bandwidth comparable to the acoustic communication signal. The effectiveness of the new successive interference cancellation algorithm is largely due to a blind interference estimator that uses a multi-objective evolutionary algorithm

The paper considers the viability of exploiting the spatial diversity that exists in shallow water, doubly-spread, underwater acoustic communications channels to use space-time methods. Using a simple 2D geometric ray model of an underwater acoustic channel, it is shown that sufficient spatial diversity exists for the underwater channel to be treated as a MIMO channel supporting space-time processing. Two different types of space-time communications system are examined: a space-time block code and a layered space-time system. Depending on the separation of the transducers, it is shown that the bit error probability performance of the two systems for the simple 2D acoustic channel can be close to that provided by an ideal Rayleigh channel in which each path suffers independent and uncorrelated fading.

This paper presents an improved system for high data rate digital acoustic communication over a shallow underwater channel that is doubly spread. The method uses cancellation of interfering multipath signals rather than delay equalisation. In this improved system, an Evolutionary Algorithm is used to obtain an accurate estimate of the Doppler spread. This novel implementation of a Doppler estimator significantly improves the accuracy of the channel estimator thus enabling more effective interference cancellation. BER performance results of the improved system in a typical underwater scenario are presented.

Space-time techniques for multiple-input multiple-output (MIMO) systems potentially provide vast increases in capacity. In order to achieve the quoted capacity gains the MIMO channel impulse response (CIR) must be known or estimated. Thus far, existing MIMO channel estimation techniques have been limited to the narrowband case or cater specifically for coded space-time systems. In this paper, we present a novel training-based MIMO channel estimation scheme for an uncoded layered space-time system that operates in the wideband frequency-selective fading environment. The method uses a pilot matrix consisting of pilot symbols derived from the Paley-Hadamard matrix in order to jointly estimate the individual CIR of the MIMO channel. The orthogonal property of the pilot matrix is utilized to resolve both intersymbol interference and intercarrier interference of the multiple transmit and received signals. The Paley Toeplitz structure is also exploited in order to minimise the length of the pilot sequence for a given length of CIR and thus maximise the effective data throughput. Results are presented which demonstrate the accuracy of the proposed channel estimation scheme and its performance in a layered space-time system.

An adaptive wavelet packet orthogonal modulation scheme using an adaptive 'best tree' search algorithm is presented and its performance is compared with that of a conventional coded orthogonal frequency division multiplexed system over a frequency selective fading channel. The capacity of the OFDM system is compromised by the need for a cyclic prefix to counter ISI Conversely, a communication system based on wavelet packets allows the signal energy to be intelligently localised both in time and frequency without the need of a cyclic prefix. Using the known time and frequency selective fading characteristics of the channel, an adaptive algorithm is used to find the best basis tree using the Karush-Kuhn-Tucker condition that optimises the capacity subject to the constraint of the available power for the fading channel by maximising the symbol energy in the received signal in both frequency and time. The performance of the new system without a cyclic prefix is superior to that of the OFDM system with a cyclic prefix in frequency selective fading and it can achieve a higher data rate.

Notice of Violation of IEEE Publication Principles "Resilient adaptive wavelet packet modulation scheme for use in time and frequency selective channels using a best tree search algorithm," Kaewmannee", P.; Ormondroyd, R.F.; Walters, C.R.; Proceedings of the IEEE Military Communications Conference 2004 (MILCOM 2004), vol. 3, 31 Oct.-3 Nov. 2004, pp. 1566 - 1571, DOI 10.1109/MILCOM.2004.1495172 After careful and considered review of the content and authorship of the above paper by a duly constituted expert committee, the principal author of this paper has been found to be in violation of IEEE?s Publication Principles. This paper contains significant portions of original text from the paper cited below. The original text was copied without attribution (including appropriate references to the original author(s) and/or paper title) and without permission. Due to the nature of this violation, reasonable effort should be made to remove all past references to this paper, and future references should be made to the following article: "Optimal wavelet packet modulation under finite complexity constraint," Daly, D.; Heneghan, C.; Fagan, A.; Vetterli, M.; Proceedings of IEEE International Conference on Acoustics, Speech, and Signal Processing 2002 (ICASSP ?02), vol. 3, 13-17 May 2002, pp. :III-2789 - III-2792, DOI 10.1109/ICASSP.2002.1005265 An adaptive wavelet packet orthogonal modulation scheme using an adaptive 'best tree' search algorithm is presented and its performance is compared with that of a conventional coded orthogonal frequency division multiplexed system over a frequency selective fading channel. The capacity of the OFDM system is compromised by the need for a cyclic prefix to counter ISI. Conversely, a communication system based on wavelet packets allows the signal energy to be intelligently localised both in time and frequency without the need of a cyclic prefix. Using the known time and frequency selective fadin- g characteristics of the channel, an adaptive algorithm is used to find the best basis tree using the Karush-Kuhn-Tucker condition that optimises the capacity subject to the constraint of the available power for the fading channel by maximising the symbol energy in the received signal in both frequency and time. The performance of the new system without a cyclic prefix is superior to that of the OFDM system with a cyclic prefix in frequency selective fading and it can achieve a higher data rate.

This paper presents a new method of phase estimation that is based on Evolutionary Algorithms. Unlike traditional phase estimators, this method does not require detailed a priori knowledge of the signal. The estimator operates by generating a model of the signal and optimising the model parameters including phase, to provide the best match in the frequency domain. The results show that the estimation process is capable of providing a good phase estimate of the signal, even in significant noise and for a wide range of waveforms.

A novel fractionally-spaced MIMO channel estimation scheme is presented for the layered space-time system that operates in a time-varying, frequency selective, fading channel. The new method estimates delay-spreads of several symbols, where the spacing of the echo arrivals is within fractions of a symbol period. The new method uses Pilot symbols to estimate the channel characteristics. These are generated from a Paley-Hadamard pilot symbol matrix whose orthogonal and Toeplitz-like structure is able to resolve interference as well as minimise the length of the pilot sequence. Results of the performance of the fractionally-spaced MIMO channel estimator in a layered space-time system are presented for different channel scenarios.

The paper addresses the problem of tracking a cellphone handset in a multipath environment using two or more base stations equipped with smart antenna arrays in conjunction with an extended Kalman filter. The Kalman filter is very sensitive to both the measurement variances and trajectories of the target handset. However, by suitably tuning the Kalman filter, the error in the position estimate of the handset can be significantly reduced. A new method is proposed to provide improved tracking of cellphone handsets in a typical urban multipath environment. In this new method, an estimate of the measurement errors in the angle of arrival measurement due to multipath is obtained from an antenna array at each base-station using a modified MUSIC algorithm and this is used to tune the extended Kalman filter. The proposed technique can be used to improve the tracking performance for non-linear trajectories.

This paper presents a novel method for estimating the Doppler velocity using complex broadband waveforms such as non-linearly chirped waveforms in SONAR systems. For such waveforms, even when the Doppler velocity is constant, the Doppler shift on these waveforms varies across the bandwidth, resulting in a frequency spread, and traditional Doppler velocity estimators based on estimating a single frequency shift do not perform well. The new method uses Evolutionary Algorithms to relate the spread in the spectrum of most complex wide bandwidth signals to the Doppler velocity that caused it. Furthermore, if the signal return is affected by multiple targets, each with Different velocities, the method will resolve each Doppler velocity. The use of this method as a novel means of mitigating range-Doppler coupling is also presented.

Recent advances in space-time signal processing have enabled the realization of multiple-input multiple-output (MIMO) communication systems. It is highly probable that MIMO architectures will be important contenders for the next generation mobile communication systems (3G/4G). We investigate a receiver comprising two main processing blocks: a MIMO processor providing the spatial diversity and a UMTS processor. These are combined to produce a space-time UMTS (ST-UMTS) receiver system. Two ST-UMTS uplink receiver architectures are proposed. In the first configuration, the MIMO processor precedes the UMTS processor. In the second configuration, the MIMO processor operates after the UMTS processor. We compare their BER performance through the use of computer simulations. The BER performance curves show a small performance difference between the two architectures. Analysis into other aspects, such as capacity and MAI handling capability, is needed to compare the performance of the two architectures. However, both architectures present a solution to enhancing the data throughput of existing UMTS systems.

This paper describes a new parametric method of spectral analysis of complex signals which may contain multiple, overlapping, non-linear and linear chirps. The method parameterizes the time variation of the chirp frequencies and also provides an estimate of the phase and relative amplitudes of each chirp. The method exploits time windowing of the received signal and uses an Evolutionary Algorithm to optimize the estimated parameters. The new method works well in high levels of noise corresponding to SNRs of -7dB.

The paper describes a new method for the simultaneous detection and parametric estimation of multiple chirped waveforms using a method based on evolutionary algorithms. Unlike traditional time-frequency analyzers, which provide a distribution of the signal spectrum over a period of time, but do not inherently provide chirp parameters, this new method detects and provides as an output the start and stop frequencies of each chirp, its starting phase and amplitude. The new method is capable of detecting and characterizing multiple chirps which may be overlapping (in time and frequency) and in the presence of significant noise.

A novel semi-blind estimation scheme is proposed for an uncoded space-time system that uses a multi-element array pilot integration (MEA-PI) algorithm with Hadamard orthogonal structure combined with an auto-tracking algorithm. Central to the new method is a real-time channel estimator that introduces a very low pilot symbol overhead during the training process. The method is also capable of tracking the time variation of the channel using both the training vectors and a decision feedback algorithm during data acquisition process. As a result, a robust method of estimating the channel coefficients is possible, enabling the method to be used in real-time for a time-varying channel with a relatively short coherence time. The bit-error probability performance of this semi-blind method is investigated for different system configurations using non-linear MMSE decoding. It is found that the new method shows very little degradation in performance compared with the case where perfect channel estimates are assumed.

This paper describes a new system architecture for high data rate digital acoustic communication over a shallow underwater channel that is subject to severe Doppler and time delay spread. The method uses high-resolution channel characterization in the time and frequency domains to resolve the main multipath components. This is followed by successive interference cancellation using the Doppler and time delay information for each of the multipaths independently. Directional antennas are not required to spatially filter the multipath components and the simulation results presented are for an omnidirectional receiver. The method works at SNRs as low as 5dB.

WCDMA/TDD systems deal efficiently with asymmetric traffic because the number of uplink and downlink slots in the TDD frame can be dynamically adjusted to match the traffic asymmetry in a cell. In a multi-cellular environment however, the traffic asymmetry between TDD cells may be significantly different and the application of slot allocation strategies on a per cell basis can result in high levels of inter-cell interference during 'crossed-slots'. In this paper we propose an adaptive dynamic slot allocation strategy (DSA) that resolves crossed-slot interference in multi-cell environments by dividing the coverage area of each cell into a number of distinct service zones. This is coupled with a co-ordination algorithm that ensures that system resources are allocated to users according to the level of mutual interference between the service zones. System capacity calculations validate our DSA strategy and demonstrate that it outperforms both conventional 'same slot' allocation schemes and other previously proposed DSA schemes in heterogeneous traffic environments.

A new space-time W-CDMA architecture is proposed to improve the capacity and bit error probability performance of the 3G system. The proposed ST-UMTS system operates on the uplink, and it exploits the current technology in space-time systems, receiver diversity and spread spectrum CDMA. Using computer simulation, the performance of the new system is shown in terms of its bit error probability performance for a Rayleigh fading channel for different space-time configurations. In this paper, two space-time detection algorithms are compared for the single user case: linear zero-forcing (ZF) and non-linear minimum mean squares error (MMSE).