@article{bottomley_cairns_2019, title={Approximate Maximum Likelihood Radio Emitter Geolocation With Time-Varying Doppler}, volume={55}, ISSN={0018-9251 1557-9603 2371-9877}, url={http://dx.doi.org/10.1109/taes.2018.2874150}, DOI={10.1109/taes.2018.2874150}, abstractNote={Direct geolocation of radio emitters has traditionally been formulated using short measurement intervals over which delay and Doppler frequency shift are approximated as constant. In this paper, we consider maximum likelihood position estimation using long measurement intervals for which the Doppler is time varying. A series of assumptions and approximations are used to develop an efficient solution involving coherent combining of traditional, complex ambiguity function processing outputs. Simulation results are used to demonstrate potential gains.}, number={1}, journal={IEEE Transactions on Aerospace and Electronic Systems}, publisher={Institute of Electrical and Electronics Engineers (IEEE)}, author={Bottomley, Gregory E. and Cairns, Douglas A.}, year={2019}, month={Feb}, pages={429–443} }
 @article{bottomley_zangi_2017, title={Direct Geolocation of Spread-Spectrum Emitters}, ISSN={1070-9908 1558-2361}, url={http://dx.doi.org/10.1109/lsp.2017.2699324}, DOI={10.1109/lsp.2017.2699324}, abstractNote={Position estimation (geolocation) of a direct-sequence, spread-spectrum radio emitter is particularly challenging because of low signal-to-noise ratio at the radio sensors. In this letter, we develop a maximum-likelihood approach to geolocation that utilizes knowledge of the spreading sequence. Simulation results are used to show that spreading sequence knowledge can provide significant gains in position accuracy.}, journal={IEEE Signal Processing Letters}, publisher={Institute of Electrical and Electronics Engineers (IEEE)}, author={Bottomley, Gregory and Zangi, Kambiz}, year={2017}, pages={1–1} }
 @article{bottomley_cairns_2015, title={Mitigating radio emitter clock offset in detection and geolocation}, volume={51}, ISSN={0018-9251}, url={http://dx.doi.org/10.1109/taes.2015.140285}, DOI={10.1109/taes.2015.140285}, abstractNote={When matched filtering is used for detection and geolocation (position estimation) of radio emitters, large emitter clock offset can cause a mismatch between the actual and synthesized (replica) waveforms in both carrier frequency and expansion/compression of the complex, baseband envelope. In this correspondence, the impact of this mismatch on performance is quantified, and an approach for addressing mismatch is presented. Specifically, the receivers employ multiple replicas that are time expanded/compressed as well as frequency shifted.}, number={2}, journal={IEEE Transactions on Aerospace and Electronic Systems}, publisher={Institute of Electrical and Electronics Engineers (IEEE)}, author={Bottomley, Gregory E. and Cairns, Douglas A.}, year={2015}, month={Apr}, pages={1583–1590} }
 @misc{bottomley_2011, title={Channel Equalization for Wireless Communications}, ISBN={9780470874271 9781118105283}, url={http://dx.doi.org/10.1002/9781118105283}, DOI={10.1002/9781118105283}, publisher={Wiley}, author={Bottomley, Gregory E.}, year={2011}, month={Jun} }
 @article{bottomley_wang_2010, title={A Novel Multistage Group Detection Technique and Applications}, volume={9}, ISSN={1536-1276}, url={http://dx.doi.org/10.1109/twc.2010.061710.091460}, DOI={10.1109/twc.2010.061710.091460}, abstractNote={In this letter, a multistage group detection (MSGD) approach to nonlinear equalization is proposed. At each stage, symbols are divided into groups, and maximum-likelihood detection (MLD) within the group is performed. The MLD process identifies a number of promising group values. It is constrained to only consider candidate symbol values identified in the previous stage. Groups are formed by combining groups from the previous stage. For example, symbols are detected one at a time, then two at a time, then four at a time, and so on. The last stage is a form of constrained maximum-likelihood sequence detection (MLSD). The overall demodulation process can be viewed as approximate MLSD, and results show that near-MLSD performance is possible with reasonable complexity. While the High Speed Downlink Packet Access (HSDPA) cellular system is used as an example, the approach can be applied other situations, including the Long Term Evolution (LTE) uplink and MIMO.}, number={8}, journal={IEEE Transactions on Wireless Communications}, publisher={Institute of Electrical and Electronics Engineers (IEEE)}, author={Bottomley, Gregory E. and Wang, Y.-P. Eric}, year={2010}, month={Aug}, pages={2438–2443} }
 @article{bottomley_wang_2010, title={Subblock Equalization and Code Averaging for DS-CDMA Receivers}, volume={59}, ISSN={0018-9545}, url={http://dx.doi.org/10.1109/tvt.2010.2050349}, DOI={10.1109/tvt.2010.2050349}, abstractNote={As third-generation (3G) cellular communication systems evolve to higher data rates, channel equalization becomes an important tool in maintaining receiver performance in dispersive channels. Because these systems employ direct-sequence code-division multiple-access (DS-CDMA), they pose unique challenges in equalizer design. In this paper, linear equalization (LE) and decision feedback equalization (DFE) designs are developed based on subblock equalization, in which a limited form of maximum-likelihood (ML) joint detection is used to detect symbols within a subblock. A pseudo-ML formulation is used, treating interference from symbols outside the subblock of interest as noise. This formulation leads to a feedforward filter (FFF) whose coefficients depend on the spreading codes of the symbols. These spreading codes change every symbol period, due to long-code scrambling, requiring constant recomputation of the FFF coefficients. To reduce complexity, code averaging is used, resulting in a code-independent periodically varying transversal filter. Another design is obtained by constraining the transversal filter to be time invariant. Simulation results for the high-speed packet-access uplink show that code averaging introduces a small loss in subblock equalization performance and that interesting gains over conventional LE can be obtained.}, number={7}, journal={IEEE Transactions on Vehicular Technology}, publisher={Institute of Electrical and Electronics Engineers (IEEE)}, author={Bottomley, Gregory E. and Wang, Y.-P. Eric}, year={2010}, month={Sep}, pages={3321–3331} }
 @article{fulghum_cairns_cozzo_wang_bottomley_2009, title={Adaptive generalized rake reception in DS-CDMA systems - [transactions papers]}, volume={8}, ISSN={1536-1276 1558-2248}, url={http://dx.doi.org/10.1109/twc.2009.060330}, DOI={10.1109/twc.2009.060330}, abstractNote={Direct-sequence code-division multiple-access (DSCDMA) cellular systems, such as wideband CDMA (WCDMA), are limited in performance by interference. Linear equalization, such as generalized Rake (G-Rake) receivers and transversal chip equalizers, can theoretically provide significant gains in performance by suppressing interference. In this paper, an adaptive G-Rake receiver is developed, employing practical algorithms for finger placement and weight computation. Finger placement is determined by selecting delays from a candidate set using a "maximal-weight" criterion. Weight computation includes estimation of an impairment covariance matrix using a parametric approach. While described in the context of the downlink, these algorithms can be used in the uplink as well. Both single-antenna and dual-antenna receivers are considered. Link and system performance are evaluated for the downlink, showing significant gains in high-rate coverage.}, number={7}, journal={IEEE Transactions on Wireless Communications}, publisher={Institute of Electrical and Electronics Engineers (IEEE)}, author={Fulghum, Tracy L. and Cairns, Douglas A. and Cozzo, Carmela and Wang, Y.-P. Eric and Bottomley, Gregory E.}, year={2009}, month={Jul}, pages={3464–3474} }
 @inproceedings{cairns_bottomley_fulghum_2009, title={Robust and Efficient Parametric Linear Equalization}, url={http://dx.doi.org/10.1109/vetecs.2009.5073837}, DOI={10.1109/vetecs.2009.5073837}, abstractNote={As 3G DS-CDMA cellular systems evolve to higher data rates, linear equalization is being used to address inter-symbol interference introduced by dispersive channels. When parametric designs are employed, elements of an impairment or data covariance matrix must be computed as part of equalizer weight calculation. The conventional approach is to express these elements in terms of path delays and path coefficients. This approach requires a significant amount of computation, and performance is sensitive to errors in the path delay estimates. In this paper, an alternative approach is developed, based on directly estimating net channel coefficients corresponding to an extended set of delays that includes the tap or finger delays of the equalizer. This avoids the need for path delay estimates, improving robustness. Also, the elements of the impairment or data covariance can be expressed in terms of efficiently computed convolutions of these net channel coefficients, even though these elements correspond to correlations of cyclostationary interference. Complexity estimates are used to show computational savings, and performance simulations are used to show gains in robustness.}, booktitle={VTC Spring 2009 - IEEE 69th Vehicular Technology Conference}, publisher={IEEE}, author={Cairns, Douglas and Bottomley, Gregory E. and Fulghum, Tracy}, year={2009}, month={Apr}, pages={1–5} }
 @misc{bottomley_2008, title={Block Equalization and Generalized MLSE Arbitration for the HSPA WCDMA Uplink}, url={http://dx.doi.org/10.1109/vetecf.2008.177}, DOI={10.1109/vetecf.2008.177}, abstractNote={High speed packet access (HSPA), the latest evolution of the wideband code division multiple access (WCDMA) standard, provides higher uplink data rates using higher-order modulation (16-QAM) and multicode transmission. Equalization is needed when the channel is dispersive. Despite gains from linear equalization, there is room for further improvement. In this paper, we consider two enhancements: block equalization with joint detection and a generalization of arbitration. Block equalization with joint detection, originally developed for non-spread systems, involves jointly detecting symbols from multiple symbol periods and using a feedback filter to remove interference from past symbol periods. Here we extend this idea to parallel symbol streams, add feedforward filtering, and introduce the notion of block linear equalization. Arbitration, also originally developed for nonspread systems, involves bidirectional decision feedback equalization and selection. Here we generalize the arbitration concept to other forms of equalization and improve the selection process using constrained maximum-likelihood sequence estimation (MLSE). These enhancements are then evaluated via simulation for the HSPA uplink, demonstrating their efficacy.}, journal={2008 IEEE 68th Vehicular Technology Conference}, publisher={IEEE}, author={Bottomley, Gregory E.}, year={2008}, month={Sep}, pages={1–5} }
 @article{bottomley_wilhelmsson_2008, title={Recovering Signal Energy From the Cyclic Prefix in OFDM}, volume={57}, ISSN={0018-9545 1939-9359}, url={http://dx.doi.org/10.1109/tvt.2007.914057}, DOI={10.1109/tvt.2007.914057}, abstractNote={In orthogonal frequency-division multiplexing (OFDM) systems, a cyclic prefix (CP) is often added at the transmitter and discarded at the receiver. When the length of the CP exceeds the delay spread of the channel, a portion of the CP can be used to recover additional signal energy. In the past, Nyquist windowing techniques have been proposed to recover signal energy, thereby improving performance. In this paper, linear maximum-likelihood (ML) and minimum-mean-square-error (MMSE) approaches are developed, which further improve performance, particularly when the signal-to-noise ratio (SNR) is low. Simpler two-valued windowing (TVW) solutions are also provided, which generally employ one or two non-Nyquist windows.}, number={5}, journal={IEEE Transactions on Vehicular Technology}, publisher={Institute of Electrical and Electronics Engineers (IEEE)}, author={Bottomley, G.E. and Wilhelmsson, L.R.}, year={2008}, month={Sep}, pages={3205–3211} }
 @misc{wang_bottomley_khayrallah_2007, title={Transmit Diversity and Receiver Performance in a WCDMA System}, url={http://dx.doi.org/10.1109/glocom.2007.800}, DOI={10.1109/glocom.2007.800}, abstractNote={In this paper, we study the performance of transmit diversity schemes in a wideband code-division multiple-access (WCDMA) system. We consider a space-time transmit diversity (STTD) scheme using the Alamouti code and a simple switch transmit diversity (STD) scheme in which the transmitter selects instantaneously the best antenna for transmission. Receiver impairment is generally modeled as a colored, complex Gaussian process, which gives rise to temporal and spatial correlations. First, we extend the G-Rake formulation to process a STTD signal, accounting for the space-time code structure as well as the temporal and spatial correlations of the impairments. The performance of STTD and STD for a WCDMA system is then evaluated. We show that STTD improves the coverage of low-to-medium rate services significantly for users at cell edge compared to the scheme without transmit diversity. Such improvements are observed even when the channels already have diversity through multipath and multiple receive antennas. Thus, STTD is well suited for broadcast when feedback from mobiles is not available. For high-data-rate availability, however, using one feedback bit to allow the STD scheme to transmit only on the better antenna achieves significantly better performance compared to STTD. This is because sending the desired signal through one radio channel makes it easier for linear equalizers to restore orthogonality. For mobiles dominated by self-interference due to loss of orthogonality, better equalization results in much improved data rates.}, journal={IEEE GLOBECOM 2007-2007 IEEE Global Telecommunications Conference}, publisher={IEEE}, author={Wang, Y.-P. and Bottomley, Gregory E. and Khayrallah, Ali S.}, year={2007}, month={Nov}, pages={4205–4209} }
 @article{wang_bottomley_2006, title={DS-CDMA downlink system capacity enhancement through interference suppression}, volume={5}, ISSN={1536-1276}, url={http://dx.doi.org/10.1109/twc.2006.1673088}, DOI={10.1109/twc.2006.1673088}, abstractNote={In the downlink of direct-sequence code-division multiple-access (DS-CDMA) cellular systems, system capacity is limited by multiuser interference. This interference can be suppressed at the receiver by interference whitening approaches such as chip equalization and generalized RAKE (G-RAKE) reception. In this paper, we show how these advanced receivers can increase system capacity. First, the G-RAKE receiver formulation is extended to include soft handoff and other-cell interference. Then, voice capacity is evaluated, including the effects of fast fading, interference correlation, power control, orthogonality properties of own-cell signals, and soft handoff. Numerical results for the wideband CDMA system show that when the channel is dispersive, advanced receivers improve capacity by 30-34%}, number={7}, journal={IEEE Transactions on Wireless Communications}, publisher={Institute of Electrical and Electronics Engineers (IEEE)}, author={Wang, Y.-P.E. and Bottomley, G.E.}, year={2006}, month={Jul}, pages={1767–1774} }
 @misc{fulghum_cairns_bottomley_cozzo_2006, title={Low Complexity Parameter Estimation for the Multi-antenna Generalized Rake Receiver}, volume={4}, url={http://dx.doi.org/10.1109/vetecs.2006.1683172}, DOI={10.1109/vetecs.2006.1683172}, abstractNote={We develop a parametric receiver for packet data systems based on the generalized Rake (G-Rake) formulation. The focus here is on multi-antenna receivers to exploit both the spatial and temporal dimensions in suppressing interference. We extend previous G-Rake formulations to multi-antenna reception and propose an adaptive, parametric form to handle the (potentially) rapid interference variation in packet data systems. This parametric form estimates an impairment covariance matrix using a model, and calculates the model parameters based solely on short-term received data. The parameter calculation involves least-squares fitting of a short-term estimated impairment covariance matrix to the model. Simulation of a two-antenna G-Rake receiver shows that significant gains in performance are possible in both the uplink and downlink}, journal={2006 IEEE 63rd Vehicular Technology Conference}, publisher={IEEE}, author={Fulghum, T. and Cairns, D. and Bottomley, G.E. and Cozzo, C.}, year={2006}, month={Sep}, pages={1874–1878} }
 @article{bottomley_cozzo_2006, title={Rake Reception With Channel Estimation Error}, volume={55}, ISSN={0018-9545}, url={http://dx.doi.org/10.1109/tvt.2006.883794}, DOI={10.1109/tvt.2006.883794}, abstractNote={Several digital cellular systems employ coherent RAKE reception, wherein channel estimates are used to combine despread values. In this paper, a maximum likelihood (ML) approach to RAKE combining that accounts for channel estimation error, including error correlation across despread values, is examined. Fading and noise correlation are also considered. The performance of the ML approach is compared to traditional RAKE combining as well as approximate ML-based approaches. Results show that when the channel estimation error and noise are of the same order, ML-based approaches can provide gains on the order of 1 dB over traditional RAKE reception}, number={6}, journal={IEEE Transactions on Vehicular Technology}, publisher={Institute of Electrical and Electronics Engineers (IEEE)}, author={Bottomley, Gregory E. and Cozzo, Carmela}, year={2006}, month={Nov}, pages={1923–1926} }
 @misc{khayrallah_bottomley_2006, title={Rake finger allocation in the DS-CDMA uplink}, volume={1}, url={http://dx.doi.org/10.1109/vetecf.2005.1557484}, DOI={10.1109/vetecf.2005.1557484}, abstractNote={In a cellular direct-sequence code-division multiple- access (DS-CDMA) base station, each user signal is recovered using a dedicated set of Rake receiver fingers that collect energy together. In this paper, we explore allocating users different numbers of fingers from a pool of fingers. An approach for finger allocation is developed based on channel probing, in which the instantaneous fading of each path is monitored. Performance is studied for a single-cell Wideband CDMA (WCDMA) system with power control, showing how finger allocation impacts per- formance in terms of coverage (range), capacity, and complexity. Results show that pooling is most beneficial when users have different delay spreads or different data rates. Also, channel probing is shown to have a significant impact on performance. I. INTRODUCTION}, journal={VTC-2005-Fall. 2005 IEEE 62nd Vehicular Technology Conference, 2005.}, publisher={IEEE}, author={Khayrallah, A.S. and Bottomley, G.E.}, year={2006}, month={Jan}, pages={122–126} }
 @misc{bottomley_wilhelmsson_2006, title={Recycling the Cyclic Prefix in an OFDM System}, url={http://dx.doi.org/10.1109/vtcf.2006.372}, DOI={10.1109/vtcf.2006.372}, abstractNote={In orthogonal frequency division multiplexing (OFDM) systems, a cyclic prefix (CP) is often used. With traditional reception, the CP is discarded. However, if the length of the CP exceeds the delay spread of the channel, a portion of the CP can be used to improve performance. In the past, Nyquist windowing techniques have been used to recover signal energy from the CP while maintaining orthogonality between symbols. In this paper, a maximum-likelihood (ML) approach is developed, which improves performance further, particularly when the signal-to-noise ratio (SNR) is low. An approximate ML solution is also given which employs a non-Nyquist window.}, journal={IEEE Vehicular Technology Conference}, publisher={IEEE}, author={Bottomley, Gregory and Wilhelmsson, Leif}, year={2006}, month={Sep}, pages={1–5} }
 @misc{wang_khayrallah_bottomley_2006, title={WLC04-3: Dual Branch Receivers for Enhanced Voice and Data Communications in WCDMA}, ISSN={1930-529X}, url={http://dx.doi.org/10.1109/glocom.2006.635}, DOI={10.1109/glocom.2006.635}, abstractNote={The system benefits of using an advanced dual-branch diversity receiver at the mobile terminal are studied in a Wideband Code-Division Multiple-Access (WCDMA) cellular system. The receiver considered is an extension of the generalized Rake (G-Rake) receiver which provides a form of array processing. In addition to exploiting the temporal correlation in receiver impairments and the orthogonality between spreading codes, spatial correlation is also accounted for in the formulation of finger combining weights. We show that this dual-branch G-Rake receiver, even with a pessimistic antenna configuration, has a potential to increase the system capacity, relative to the conventional single-branch Rake receiver, by 94% for voice communications. For data communications, high-data-rate availability can be significantly improved. This allows a HSDPA user at the cell border to enjoy a data rate close to 4 Mbps in dispersive channels. For end-user performance of TCP/IP applications, users with a dual-branch G- Rake receiver experience significantly higher packet bit rates and shorter download times.}, journal={IEEE Globecom 2006}, publisher={IEEE}, author={Wang, Y. P. Eric and Khayrallah, Ali S. and Bottomley, Gregory E.}, year={2006}, month={Nov}, pages={1–5} }
 @misc{bottomley_cozzo_2005, title={Coherent rake reception using noisy channel estimates}, volume={3}, url={http://dx.doi.org/10.1109/vetecf.2004.1400346}, DOI={10.1109/vetecf.2004.1400346}, abstractNote={With traditional Rake reception, channel estimates are used to combine despread values. In this paper, a maximum-likelihood approach is used to reformulate the Rake combining weights, accounting for the channel estimation error. Specifically, Ling's formulation is extended to include fading, noise, and channel estimation error correlation between fingers. The resulting combining weights are similar to the generalized Rake receiver, except that the known channel response is replaced by a minimum mean-square error (MMSE) estimate, and the noise covariance matrix is augmented by a term related to channel estimation. The performance of this and other combining approaches are compared, showing how performance depends on the available energy for channel estimation and the Rake finger placement strategy.}, journal={IEEE 60th Vehicular Technology Conference, 2004. VTC2004-Fall. 2004}, publisher={IEEE}, author={Bottomley, G.E. and Cozzo, C.}, year={2005}, month={Apr}, pages={1801–1805} }
 @misc{cozzo_bottomley_2005, title={DS-CDMA SIR estimation with bias removal}, volume={1}, url={http://dx.doi.org/10.1109/wcnc.2005.1424506}, DOI={10.1109/wcnc.2005.1424506}, abstractNote={In direct-sequence code-division multiple-access (DS-CDMA) systems, signal quality estimation is an important receiver function used for power control and rate adaptation. Signal quality is usually measured in terms of a signal-to-interference ratio (SIR). Typically, a short term signal power estimate and a long term interference power estimate are used. As a result, estimation error is mostly due to the short term signal power estimate. In this paper, we consider both subtractive and multiplicative forms of bias removal for SIR estimation, and show that multiplicative bias removal provides lower root-mean-square (rms) error. These bias removal forms are developed for a traditional SIR estimation approach that has been extended to account for interference correlation across Rake fingers due to receive filtering or dispersion. The extension provides an SIR estimation approach suitable for use in conjunction with generalized Rake reception, which also accounts for interference correlation.}, journal={IEEE Wireless Communications and Networking Conference, 2005}, publisher={IEEE}, author={Cozzo, C. and Bottomley, G.E.}, year={2005}, month={Apr}, pages={239–243} }
 @inproceedings{cairns,_bottomley_wang_2005, title={Low complexity parameter estimation for the generalized rake receiver}, url={http://dx.doi.org/10.1109/dspws.2004.1437940}, DOI={10.1109/dspws.2004.1437940}, abstractNote={RAKE reception is commonly used in the downlink of direct-sequence code-division multiple-access (DS-CDMA) cellular systems. However, RAKE receivers suffer performance losses in frequency selective channels due to inter-symbol interference (ISI) and multiple access interference (MAT). Recently, the generalized RAKE (G-RAKE) receiver has emerged as a low complexity technique for downlink interference suppression. We propose simple approaches herein to place fingers and estimate key parameters of the G-RAKE receiver. Simulations show that a G-RAKE receiver utilizing this approach provides significant performance improvement over a conventional RAKE receiver.}, booktitle={3rd IEEE Signal Processing Education Workshop. 2004 IEEE 11th Digital Signal Processing Workshop, 2004.}, publisher={IEEE}, author={Cairns,, D. A. and Bottomley, G. E. and Wang, Y.-P. E.}, year={2005}, month={Jun}, pages={191–195} }
 @misc{wang_cheng_grant_bottomley_2005, title={MLSE and MAP detectors for high-data-rate DS-CDMA reception in dispersive channels}, volume={2}, url={http://dx.doi.org/10.1109/vetecf.2004.1400164}, DOI={10.1109/vetecf.2004.1400164}, abstractNote={A maximum likelihood sequence estimation (MLSE) and a maximum a posteriori (MAP) detector for DS-CDMA are proposed. The proposed receivers are attractive when the desired signal is in multi-code reception scenarios and when propagation channels are dispersive. Multipath results in loss of orthogonality among own-cell signals in the downlink and among same-user signals in the uplink. In these cases, receiver performance is limited by self-interference from the desired signal itself and interference from all other signals. The generalized RAKE (C-RAKE) receiver can be used to suppress both forms of interference, treating them as colored noise. To improve receiver performance further, we use an MLSE or a MAP detector to alleviate self-interference. The MAP detector can be used with the outer code decoder to form a turbo equalizer to further improve the receiver performance. Our numerical results show that gains larger than 2 dB over G-RAKE can be achieved by the proposed receivers for a WCDMA radio-access bearer of 4.6 Mbps using a 64-state sequence detector.}, journal={IEEE 60th Vehicular Technology Conference, 2004. VTC2004-Fall. 2004}, publisher={IEEE}, author={Wang, Y.-P.E. and Cheng, Jung-Fu and Grant, S.J. and Bottomley, G.E.}, year={2005}, month={Apr}, pages={963–967} }
 @misc{bottomley_2005, title={The effects of cross-correlated noise and multi-channel signal on ORing loss}, volume={12}, url={http://dx.doi.org/10.1109/icassp.1987.1169849}, DOI={10.1109/icassp.1987.1169849}, abstractNote={To reduce the amount of information presented to a human observer, ORing has been used to combine frequency-time plots from several acoustic channels. ORing introduces a loss which is measured as a rise in the minimum detectable signal-to-noise ratio. Equations for ORing loss are derived for a general signal processing system with arbitrary signal and noise distributions. Results are provided for the case of Gaussian noise and Gaussian signal. Simulation is used to verify the analytical results, and to provide insight into how cross-correlated noise and signal present on multiple channels reduce ORing loss. Results suggest: 1) if signal is present on only one channel, noise correlation reduces ORing loss, but not as much as currently estimated, and 2) if noise is independent from channel to channel, signal on more than one channel also reduces ORing loss. However, the two effects are not independent. Consequently, they must be considered together when estimating ORing loss.}, journal={ICASSP '87. IEEE International Conference on Acoustics, Speech, and Signal Processing}, publisher={Institute of Electrical and Electronics Engineers}, author={Bottomley, G.}, year={2005}, month={Mar}, pages={1103–1106} }
 @article{hafeez_molnar_arslan_bottomley_ramesh_2004, title={Adaptive Joint Detection of Cochannel Signals for TDMA Handsets}, volume={52}, ISSN={0090-6778}, url={http://dx.doi.org/10.1109/tcomm.2004.836443}, DOI={10.1109/tcomm.2004.836443}, abstractNote={In mobile communication systems, downlink (forward link) system capacity is limited by the ability of mobile receivers to recover the desired signal in the presence of cochannel interference (CCI). Joint detection of the desired and cochannel signals is a useful approach to improving receiver performance, thus increasing system capacity. In this paper, we show that a practical single-antenna joint-detection receiver can provide significant gains in system capacity for the time-division multiple-access (TDMA) standard Telecommunications Industry Association/Electronic Industry Association/Interim Standard-136 (TIA/EIA/IS-136 or IS-136). For a sectorized system, joint detection provides a capacity gain of 47% in a typical urban environment. When used in conjunction with transmit beamforming, the synergy between the two approaches leads to a capacity gain of over 200%. In determining these gains, practical aspects of the IS-136 system are considered, namely, unsynchronized networks, limited receiver complexity, and adaptability. A semiblind acquisition process, which uses the training sequence of the desired user only, is employed, because the desired and interfering base stations are not synchronized. The receiver complexity is controlled by processing only one sample per symbol period, even though it is shown that multiple samples per symbol period should ideally be used. Finally, because receiver performance may be limited by its own intersymbol interference instead of CCI, an adaptive joint-detection process is used which selects between joint demodulation and single-user equalization for each slot.}, number={10}, journal={IEEE Transactions on Communications}, publisher={Institute of Electrical and Electronics Engineers (IEEE)}, author={Hafeez, A. and Molnar, K.J. and Arslan, H. and Bottomley, G.E. and Ramesh, R.}, year={2004}, month={Oct}, pages={1722–1732} }
 @article{bottomley_2004, title={Editorial}, volume={53}, ISSN={0018-9545}, url={http://dx.doi.org/10.1109/tvt.2003.822646}, DOI={10.1109/tvt.2003.822646}, number={1}, journal={IEEE Transactions on Vehicular Technology}, publisher={Institute of Electrical and Electronics Engineers (IEEE)}, author={Bottomley, G.E.}, year={2004}, month={Jan}, pages={1–1} }
 @misc{cozzo_bottomley_khayrallah_2004, title={Rake receiver finger placement for realistic channels}, url={http://dx.doi.org/10.1109/wcnc.2004.1311564}, DOI={10.1109/wcnc.2004.1311564}, abstractNote={This paper deals with finder placement for Rake receivers, which is a key aspect in the design of receivers for spread-spectrum communications. Finger placement is typically performed using a path searcher, which estimates the power/delay profile (PDP) of the received signal to determine where signal energy is present. A commonly used finger placement approach is to place fingers at delays corresponding to the peaks of the PDP, with a restriction that fingers he no closer than some minimum spacing. Another approach is to place fingers on an equally-spaced grid of delays. For the typical urban (TU) channel model, we quantify performance of the two approaches in terms of acquired signal-to-noise ratio (SNR) and modem bit- error-rate (BER). We show that performance depends primarily on minimum finger spacing and number of fingers. The grid approach performs well when there are enough fingers to collect most of the signal energy. For a channel model in which path delays vary dynamically, we find that the grid approach provides robust performance.}, journal={2004 IEEE Wireless Communications and Networking Conference (IEEE Cat. No.04TH8733)}, publisher={IEEE}, author={Cozzo, C. and Bottomley, G.E. and Khayrallah, A.S.}, year={2004}, pages={316–321 Vol.1} }
 @misc{bottomley_alexander_2003, title={A theoretical basis for divergence of conventional recursive least squares filters}, url={http://dx.doi.org/10.1109/icassp.1989.266576}, DOI={10.1109/icassp.1989.266576}, abstractNote={The authors identify several specific sources of instability in the conventional recursive least squares (CRLS) algorithm. They explore why the algorithm is numerically unstable under fixed-point precision and examine how it can be stabilized. A form of the CRLS algorithm that maintains symmetry in the inverse autocorrelation matrix estimate is first presented, and divergence phenomena are discussed. Several sources of instability are identified as well as practical techniques for combating each instability source. Experimental results that demonstrate the usefulness of these techniques are presented. Initial simulation results indicate that by compensating for the source of numerical instability, it is possible to obtain numerical stability with negligible loss in performance.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">></ETX>}, journal={International Conference on Acoustics, Speech, and Signal Processing}, publisher={IEEE}, author={Bottomley, G.E. and Alexander, S.T.}, year={2003}, month={Jan}, pages={908–911} }
 @article{bottomley_2003, title={Cdma downlink interference suppression using i/q projection}, volume={2}, ISSN={1536-1276}, url={http://dx.doi.org/10.1109/twc.2003.817434}, DOI={10.1109/twc.2003.817434}, abstractNote={Interference suppression at the receiver can be used to improve performance and capacity in the downlink of direct-sequence code-division multiple-access systems. In this paper, an interference suppression technique is developed which uses partial knowledge of spreading sequences to cancel a group of interfering signals. Specifically, knowledge of a complex scrambling sequence is used to project the desired signal away from the interference in the in-phase/quadrature (I/Q) complex plane. A maximum likelihood receiver formulation is used, treating both the desired signal and interference as being conditionally noncircular. A zero-forcing equalization approach is used to preserve orthogonality between signals from the same base station. The development of the technique is based on the assumption that the group of signals corresponds to another base station that does not transmit the signal of interest. However, the technique is also applied to the path diversity scenario (dispersion, soft handoff, transmit delay diversity), in which the group of interfering signals includes a desired signal component. The approach, referred to as I/Q projection, provides significant gains when performance is interference limited.}, number={5}, journal={IEEE Transactions on Wireless Communications}, publisher={Institute of Electrical and Electronics Engineers (IEEE)}, author={Bottomley, G.E.}, year={2003}, month={Sep}, pages={890–900} }
 @misc{bottomley_arslan_2003, title={Channel Tracking in Wireless Communication Systems}, ISBN={9780471369721 9780471219286}, url={http://dx.doi.org/10.1002/0471219282.eot326}, DOI={10.1002/0471219282.eot326}, abstractNote={Abstract Channel estimation is an integral part of standard adaptive receiver designs used in digital wireless communication systems. In this article, commonly used approaches to channel tracking are reviewed, including both filtering and recursive approaches. These approaches are based on approximate models of how the channel response changes with time. Both reference‐assisted (pilot symbols, pilot channel) and data‐directed channel tracking are considered. Applications include second and third generation digital cellular communication systems, which employ time‐division multiple‐access (TDMA) or direct‐sequence code‐division multiple‐access (DS‐CDMA).}, journal={Wiley Encyclopedia of Telecommunications}, publisher={Wiley}, author={Bottomley, Gregory E. and Arslan, Hüseyin}, year={2003}, month={Apr} }
 @misc{hafeez_molnar_bottomley_2003, title={Co-channel interference cancellation for D-AMPS hand set}, volume={2}, url={http://dx.doi.org/10.1109/vetec.1999.780504}, DOI={10.1109/vetec.1999.780504}, abstractNote={Co-channel interference is a major impairment for IS-136 handsets. Joint estimation of cochannel signals can be used to minimize this effect, but traditional approaches require transmissions from different base-stations to be synchronized. In this paper, we consider a semi-blind approach for cancelling asynchronous interference using generalized per-survivor processing for channel acquisition and tracking. Signal delays and medium responses are jointly estimated for symbol-asynchronous co-channel signals assuming knowledge of the signal structure. Simulation results are presented that show C/I gains of 15 dB in the presence of one interferer.}, journal={1999 IEEE 49th Vehicular Technology Conference (Cat. No.99CH36363)}, publisher={IEEE}, author={Hafeez, A. and Molnar, K.J. and Bottomley, G.E.}, year={2003}, month={Jan}, pages={1026–1031} }
 @misc{arslan_bottomley_ramesh_brismark_2003, title={Coherent MAP detection of DQPSK signals in non-ISI channels}, url={http://dx.doi.org/10.1109/wcnc.1999.797818}, DOI={10.1109/wcnc.1999.797818}, abstractNote={Both IS-136 and PDC digital cellular systems employ forward error correction (FEC) encoding followed by a form of DQPSK modulation. To optimize FEC decoder performance at the receiver, soft information from the DQPSK demodulator is required. For frequency nonselective fading channels, which occur often in these systems, coherent demodulation optimizes performance. In this paper, we derive the maximum a posteriori (MAP) bit estimate for DQPSK modulation in non-ISI channels, assuming knowledge of the channel response. The MAP estimator forms a bit log-likelihood ratio, which provides the optimal "soft information" for MLSE or MAP convolutional decoding. Both single and multiantenna receivers are considered. MAP estimation requires exponentiation and logarithm operations, as well as knowledge of the noise covariance. To reduce complexity, two approximate forms are developed which avoid the exponentiation and logarithm operations. If the noise has the same power on each antenna and is uncorrelated between antennas, then knowledge of the noise covariance is also not needed. Performance of the optimal and approximate schemes is evaluated via simulation for single and multi-channel receivers under static and frequency non-selective Rayleigh fading conditions. The approximate approaches are shown to be within 0.5 dB of the optimal approach and to outperform existing approaches.}, journal={WCNC. 1999 IEEE Wireless Communications and Networking Conference (Cat. No.99TH8466)}, publisher={IEEE}, author={Arslan, H. and Bottomley, G.E. and Ramesh, R. and Brismark, G.}, year={2003}, month={Jan}, pages={216–220} }
 @misc{arslan_gupta_bottomley_chennakeshu_2003, title={Combined successive cancellation and joint demodulation for the suppression of adjacent channel interference}, url={http://dx.doi.org/10.1109/wcnc.1999.796846}, DOI={10.1109/wcnc.1999.796846}, abstractNote={The capacity and signal quality of wireless communication systems can be improved dramatically by enhancing the receiver performance in the presence of adjacent channel interference (ACI). The sequence error rate is minimized through joint demodulation of all signals, but with high implementation complexity. Complexity can be greatly reduced through the use of successive cancellation, in which signals are detected and subtracted in descending order of signal power. However, successive cancellation performs poorly when signals have similar power levels. In this paper, an improved successive cancellation receiver for adjacent channel signals is proposed. The conventional detector is replaced with a simple form of joint demodulation. As a result, the receiver combines the benefits of joint demodulation, which works well when signals have similar power levels, with the benefits of successive cancellation, which works well when signals have dissimilar power levels. Performance results for the Global System for Mobile (GSM) communication digital cellular system show an order of magnitude reduction in bit-error-rate when adjacent channel signals are closely spaced and have comparable power levels.}, journal={WCNC. 1999 IEEE Wireless Communications and Networking Conference (Cat. No.99TH8466)}, publisher={IEEE}, author={Arslan, H. and Gupta, S.C. and Bottomley, G.E. and Chennakeshu, S.}, year={2003}, month={Jan}, pages={1114–1118} }
 @misc{sourour_bottomley_ramesh_2003, title={Delay tracking for direct sequence spread spectrum systems in multipath fading channels}, volume={1}, url={http://dx.doi.org/10.1109/vetec.1999.778090}, DOI={10.1109/vetec.1999.778090}, abstractNote={This paper considers the problem of multipath delay tracking in direct sequence spread spectrum systems operating in multipath fading channels. Due to the pulse shaping of the PN code chips, tracking multipath delays is a challenging problem, for which we introduce three novel techniques. In the first technique, maximum likelihood estimation, we search all possible combinations of delays and select the set of delays that minimize a metric derived from the error between the received signal and an estimated signal based on these postulated delays. To reduce complexity, we introduce the ordered maximum likelihood technique, in which the above mentioned metric is minimized iteratively assuming that the channel has one path, then two paths, etc. At each iteration, the delay estimates derived from previous iterations are fixed. Therefore, in each iteration only one delay estimate is produced. Another technique presented in this paper is envelope tracking with subtraction. In this technique, we select peaks of the correlation function between the received direct sequence spread spectrum signal and the local replica. After selecting each peak, the contribution due to the corresponding channel path is subtracted from the correlation function.}, journal={1999 IEEE 49th Vehicular Technology Conference (Cat. No.99CH36363)}, publisher={IEEE}, author={Sourour, E. and Bottomley, G. and Ramesh, R.}, year={2003}, month={Jan}, pages={422–426} }
 @misc{sourour_bottomley_2003, title={Effect of frequency offset on DS-SS acquisition in slowly fading channels}, url={http://dx.doi.org/10.1109/wcnc.1999.796707}, DOI={10.1109/wcnc.1999.796707}, abstractNote={In practical direct sequence spread spectrum (DS-SS) receivers a frequency offset between the received carrier frequency and the receiver oscillator often exists. This offset is corrected after the DS-SS signal is acquired. This paper considers the effect of frequency offset on the acquisition performance of DS-SS systems in frequency non-selective fading channels. A rapid acquisition system employing sliding correlation (matched filter) is utilized. To combat the effect of frequency offset, the total length of the sliding correlator is divided into shorter sections. We derive analytical expression for the probability of detection when the fading process is constant across all the sections. This is the case in most practical channels. The squared magnitude of the correlation results of each section are added (which we denote as non-coherent combining). The effect of frequency offset on the the probability of detection, probability of false alarm and the mean acquisition time are analyzed, allowing the trade-off between coherent and non-coherent correlation to me optimized.}, journal={WCNC. 1999 IEEE Wireless Communications and Networking Conference (Cat. No.99TH8466)}, publisher={IEEE}, author={Sourour, E. and Bottomley, G.E.}, year={2003}, month={Jan}, pages={569–573} }
 @misc{grant_molnar_bottomley_2003, title={Generalized RAKE receivers for MIMO systems}, url={http://dx.doi.org/10.1109/vetecf.2003.1285052}, DOI={10.1109/vetecf.2003.1285052}, abstractNote={Recently, a variety of multiple-input multiple-output (MIMO) antenna techniques have been proposed for inclusion in the WCDMA standard. We develop two novel, multi-antenna receiver structures for MIMO operating in frequency-selective fading environments that offer a significant reduction in complexity compared to other MIMO equalizer structures. Both receivers are extensions of the generalized RAKE receiver (GRAKE) for single antenna systems; which receiver to use depends on the degree of dispersion in the channel. However, the two receivers together provide an attractive adaptive solution whereby the receivers are switched as the degree of dispersion changes. Moreover, it is shown that the combined solution is able to achieve performance close to the matched filter bound in a wide variety of frequency-selective fading environments.}, journal={2003 IEEE 58th Vehicular Technology Conference. VTC 2003-Fall (IEEE Cat. No.03CH37484)}, publisher={IEEE}, author={Grant, S.J. and Molnar, K.J. and Bottomley, G.E.}, year={2003}, pages={424–428 Vol.1} }
 @misc{fulghum_bottomley_2003, title={Matched filter bounds for low spreading factor DS-CDMA with random spreading sequences}, url={http://dx.doi.org/10.1109/vetecf.2003.1285151}, DOI={10.1109/vetecf.2003.1285151}, abstractNote={We evaluate the matched filter bound (MFB) for QPSK symbols with random QPSK spreading sequences at low spreading factors in discrete-multipath, Rayleigh fading channels. We recognize the importance of the effect of the autocorrelation of the symbol waveform (spreading sequence) in the form of inter-path interference (IPI) on the performance of the matched filter receiver. With the decision statistic as a quadratic form of complex Gaussian variables dependent on the aperiodic code autocorrelation, we perform eigenvalue and characteristic function analysis to arrive at a probability of bit error or bit error rate (BER). For a 3GPP Case 3 dispersive channel and a spreading factor of SF=4, we note a spread of the MFBs of the individual codes of 1.4 dB in E/sub b//N/sub 0/ at BER=1%. Examining the MFB averaged over codes, we note a 0.5 dB difference at BER=1% between this and the MFB with no consideration of IPI. For a 3GPP typical urban channel, we note a spread of 1.1 dB at BER=1%, and for average MFB, there is a 0.4 dB difference from the MFB with no consideration of IPI. Thus we see that, at low spreading factors, the inclusion of the autocorrelation of the random spreading sequence, or the IPI, is an important consideration in obtaining accurate results for the MFB. The paper further extends the analysis to multiple receiver branches, and evaluates the MFB for other dispersive channels and additional spreading factors.}, journal={2003 IEEE 58th Vehicular Technology Conference. VTC 2003-Fall (IEEE Cat. No.03CH37484)}, publisher={IEEE}, author={Fulghum, T.L. and Bottomley, G.E.}, year={2003}, pages={902–906 Vol.2} }
 @misc{bottomley_ottosson_wang_2002, title={A generalized RAKE receiver for DS-CDMA systems}, volume={2}, url={http://dx.doi.org/10.1109/vetecs.2000.851263}, DOI={10.1109/vetecs.2000.851263}, abstractNote={In this paper, a generalized RAKE receiver for interference suppression and multipath mitigation is proposed. The receiver exploits the fact that time dispersion significantly distorts the interference spectrum from each base station in the downlink of a CDMA system. Compared to the conventional RAKE receiver, this generalized RAKE receiver may have more fingers and has different combining weights. The weights are derived from a maximum likelihood formulation, modeling the intracell interference as colored Gaussian noise. For a wideband CDMA (W-CDMA) system and a realistic mobile radio channel, capacity gains on the order of 100% are shown.}, journal={VTC2000-Spring. 2000 IEEE 51st Vehicular Technology Conference Proceedings (Cat. No.00CH37026)}, publisher={IEEE}, author={Bottomley, G.E. and Ottosson, T. and Wang, Y.-P.E.}, year={2002}, month={Nov}, pages={941–945} }
 @misc{molnar_bottomley_ramesh_2002, title={A novel fractionally-spaced MLSE receiver and channel tracking with side information}, volume={3}, url={http://dx.doi.org/10.1109/vetec.1998.686158}, DOI={10.1109/vetec.1998.686158}, abstractNote={The performance of adaptive MLSE receivers depends upon channel estimation accuracy and the metric being optimized. In this paper, channel estimation is improved by estimating the transmission medium response, using pulse shaping side information. An optimal fractionally-spaced MLSE metric is formulated in terms of the pulse shape autocorrelation and the transmission medium response. Performance gains are quantified for the IS-136 (D-AMPS) digital cellular system.}, journal={VTC '98. 48th IEEE Vehicular Technology Conference. Pathway to Global Wireless Revolution (Cat. No.98CH36151)}, publisher={IEEE}, author={Molnar, K.J. and Bottomley, G.E. and Ramesh, R.}, year={2002}, month={Nov}, pages={2251–2255} }
 @misc{bottomley_jamal_2002, title={Adaptive arrays and MLSE equalization}, volume={1}, url={http://dx.doi.org/10.1109/vetec.1995.504827}, DOI={10.1109/vetec.1995.504827}, abstractNote={In digital cellular communication systems, receivers are designed to combat the problems of fading, time dispersion, and interference. Separately, these problems can be solved using antenna diversity, equalization, and adaptive array processing, respectively. Joint solutions have been proposed which combine adaptive array processing with either linear equalization (LE) or decision feedback equalization (DFE). However, LE is sensitive to spectral nulls and DFE has the problem of decision error feedback. In this paper, an algorithm is proposed which combines adaptive array processing with MLSE equalization to mitigate fading, time dispersion, and interference. The optimal metric for the MLSE structure is derived. The receiver reduces to well known forms for special cases. D-AMPS simulation results illustrate the potential performance of the proposed algorithm, including the case when the fading on the different antennas is correlated.}, journal={1995 IEEE 45th Vehicular Technology Conference. Countdown to the Wireless Twenty-First Century}, publisher={IEEE}, author={Bottomley, G.E. and Jamal, K.}, year={2002}, month={Nov}, pages={50–54} }
 @misc{guey_khayrallah_bottomley_2002, title={Adjacent channel interference rejection for land mobile radio systems}, volume={3}, url={http://dx.doi.org/10.1109/vetec.1998.686049}, DOI={10.1109/vetec.1998.686049}, abstractNote={Adjacent channel interference (ACI) rejection for the uplink of a narrowband land mobile radio system in flat Rayleigh fading channel is considered. Receive antenna diversity with interference rejection combining (IRC) that accounts for the spatial correlation of the interfering signal is shown to achieve significant gains over traditional maximal ratio combining (MRC). The approach is then extended to exploit the temporal correlation of the ACI through fractionally-spaced processing. These approaches provide 10-30 dB ACI suppression gain, depending on the vehicle speed and noise level.}, journal={VTC '98. 48th IEEE Vehicular Technology Conference. Pathway to Global Wireless Revolution (Cat. No.98CH36151)}, publisher={IEEE}, author={Guey, Jiann-Ching and Khayrallah, A. and Bottomley, G.E.}, year={2002}, month={Nov}, pages={1715–1719} }
 @misc{arslan_gupta_bottomley_cheunakeshu_2002, title={Adjacent channel interference suppression in FDMA/TDMA mobile radio systems using joint demodulation}, volume={2}, url={http://dx.doi.org/10.1109/icc.1998.685105}, DOI={10.1109/icc.1998.685105}, abstractNote={The capacity and signal duality of wireless communications systems can be improved by enhancing receiver performance in the presence of adjacent channel interference (ACI). In this paper, an MLSE receiver for joint demodulation of adjacent channel signals is developed. This receiver provides significant improvement in performance over a wide range of carrier to interference ratios. A practical approach is taken, in which conventional down-conversion of each signal is performed followed by joint demodulation at baseband. To provide coherent reception, a novel form of joint channel estimation is used, exploiting knowledge of the transmit and receive filter responses. Receiver performance is evaluated via simulation for the GSM digital cellular system.}, journal={ICC '98. 1998 IEEE International Conference on Communications. Conference Record. Affiliated with SUPERCOMM'98 (Cat. No.98CH36220)}, publisher={IEEE}, author={Arslan, H. and Gupta, S.C. and Bottomley, G.E. and Cheunakeshu, S.}, year={2002}, month={Nov}, pages={723–727} }
 @misc{wang_bottomley_2002, title={CDMA downlink system capacity enhancement through generalized RAKE reception}, volume={2}, url={http://dx.doi.org/10.1109/vtc.2001.956961}, DOI={10.1109/vtc.2001.956961}, abstractNote={The benefit of generalized RAKE reception to downlink system capacity is studied. System capacity is evaluated for certain cell and user outage probabilities. Fast fading, noise correlation, power control, and soft handoff are all included in our study. The site selection diversity transmission (SSDT) approach to power allocation between soft handoff links is shown to be optimal in the sense that it minimizes total transmit power to a given user. Numerical results show that G-RAKE receivers can improve system capacity by as much as 30-45% in a highly dispersive channel.}, journal={IEEE 54th Vehicular Technology Conference. VTC Fall 2001. Proceedings (Cat. No.01CH37211)}, publisher={IEEE}, author={Wang, Y.-P.E. and Bottomley, G.E.}, year={2002}, month={Nov}, pages={1177–1181} }
 @misc{hafeez_molnar_bottomley_ramesh_2002, title={Capacity and quality enhancement for ANSI-136 downlink using interference cancellation and beamforming}, volume={5}, url={http://dx.doi.org/10.1109/vetecf.2000.883297}, DOI={10.1109/vetecf.2000.883297}, abstractNote={In this paper, we investigate the capacity and quality gains for the downlink of an ANSI-136 system when handsets equipped with co-channel interference cancellation are deployed together with base stations employing array antennas. We find that the two capacity-enhancing techniques complement each other very well. Cell sectorization and beamforming increase interferer strength disparity which is exploited by an interference cancelling receiver Compared to a 7/21 re-use system with conventional receivers, the capacity can be almost tripled by means of four fixed beams per sector and two-user joint detection receivers for a slowly-varying flat fading environment.}, journal={Vehicular Technology Conference Fall 2000. IEEE VTS Fall VTC2000. 52nd Vehicular Technology Conference (Cat. No.00CH37152)}, publisher={IEEE}, author={Hafeez, A. and Molnar, K.J. and Bottomley, G.E. and Ramesh, R.}, year={2002}, month={Nov}, pages={2414–2421} }
 @misc{molnar_bottomley_2002, title={D-AMPS performance in PCS bands with array processing}, volume={3}, url={http://dx.doi.org/10.1109/vetec.1996.504007}, DOI={10.1109/vetec.1996.504007}, abstractNote={Cellular systems that are upbanded from 800 MHz to 1900 MHz for PCS deployment will have to contend with additional path loss (6-7 dB), and faster fading, in addition to time dispersion and co-channel interference. On the downlink, additional power can be used to compensate for the path loss. On the uplink, increasing the power output from the hand portable is not possible from regulatory and battery life considerations. Faster fading further complicates adaptive equalization as well as adaptive interference mitigation techniques. For the digital-AMPS (D-AMPS or IS-136) standard, these impairments can be overcome through a combination of array processing and adaptive equalization using MLSE techniques.}, journal={Proceedings of Vehicular Technology Conference - VTC}, publisher={IEEE}, author={Molnar, K.J. and Bottomley, G.E.}, year={2002}, month={Dec}, pages={1496–1500} }
 @misc{hagerman_ostman_molnar_bottomley_2002, title={Field test performance results for D-AMPS in PCS bands with array processing}, volume={3}, url={http://dx.doi.org/10.1109/vetec.1997.605824}, DOI={10.1109/vetec.1997.605824}, abstractNote={For the digital-AMPS (D-AMPS or IS-136) standard, performance gains for diversity and interference cancellation are quantified for a prototype system that implements a combination of array processing and adaptive equalization using MLSE techniques. For the site location, field tests show a 3.5 dB C/N improvement at 1% bit error-rate for a four-branch space and polarization diversity receiver relative to a receiver with two space diversity antennas. A 5 dB C/I improvement is observed for an interference cancellation receiver with two antennas and one interferer present, and 9 dB gain in C/I is measured for a combined space-polarization diversity antenna configuration. Furthermore, measurement results confirm that interference cancellation performance is not dependent upon the angular separation between the desired and interfering mobiles.}, journal={1997 IEEE 47th Vehicular Technology Conference. Technology in Motion}, publisher={IEEE}, author={Hagerman, B. and Ostman, T. and Molnar, K.J. and Bottomley, G.E.}, year={2002}, month={Nov}, pages={1582–1586} }
 @misc{wang_bottomley_2002, title={Generalized RAKE reception for cancelling interference from multiple base stations}, volume={5}, url={http://dx.doi.org/10.1109/vetecf.2000.883276}, DOI={10.1109/vetecf.2000.883276}, abstractNote={A generalized RAKE (G-RAKE) receiver structure is developed to suppress both own-cell and other-cell interference in the downlink of a CDMA system. Interference suppression is achieved by accounting for the interference coloration introduced by the dispersive channel. Compared to the conventional RARE receiver, this G-RAKE receiver may have more fingers and has different finger delays and combining weights. The performance in soft handoff is addressed, and the coding used in the IS-95 and IS-2000 systems is used to study the frame-error-rate (FER) performance. It is shown that with coding, the performance is more limited by other-cell interference than own-cell interference. By using the proposed G-RAKE receiver to suppress own-cell and other-cell interference, a gain of 1-2 dB can be achieved.}, journal={Vehicular Technology Conference Fall 2000. IEEE VTS Fall VTC2000. 52nd Vehicular Technology Conference (Cat. No.00CH37152)}, publisher={IEEE}, author={Wang, Y.-P.E. and Bottomley, G.E.}, year={2002}, month={Nov}, pages={2333–2339} }
 @misc{khayrallah_ramesh_bottomley_koilpillai_2002, title={Improved channel estimation with side information}, volume={2}, url={http://dx.doi.org/10.1109/vetec.1997.600490}, DOI={10.1109/vetec.1997.600490}, abstractNote={In this paper, we describe a technique to incorporate side information into the channel estimation operation at the receiver in a GSM-based system. The technique has a complexity comparable to that of the standard method. Simulations indicate that in terms of coded bit error rate (BER), our technique produces gains of about 0.8 dB in a static channel, and 1 dB in non-dispersive Rayleigh and Rician fading channels. Similar gains are achieved for uncoded BER and probability of detected error. Such gains are desirable in a cellular system. They are considerable in a satellite system, where link margin is at a high premium.}, journal={1997 IEEE 47th Vehicular Technology Conference. Technology in Motion}, publisher={IEEE}, author={Khayrallah, A.S. and Ramesh, R. and Bottomley, G.E. and Koilpillai, D.}, year={2002}, month={Nov}, pages={1049–1053} }
 @misc{bottomley_2002, title={Improved successive cancellation of DS-CDMA signals using signal orthogonalization}, volume={1}, url={http://dx.doi.org/10.1109/icupc.1996.557794}, DOI={10.1109/icupc.1996.557794}, abstractNote={In DS-CDMA communication systems, multiple access interference can be mitigated with multi-user receiver techniques. One such technique, successive cancellation, is limited in performance because cancelled signals are not entirely removed. An improvement to successive cancellation is proposed which employs orthogonalized signature sequences. This allows all cancelled signal energy to be removed. Alternatively, orthogonalized signature sequences can be used in the detection process, eliminating the need for the cancellation process. Simulation results demonstrate the improved performance of the proposed approach. Extensions of the approach for asynchronous signals, time-dispersed signals, and other forms of DS-CDMA are also discussed.}, journal={Proceedings of ICUPC - 5th International Conference on Universal Personal Communications}, publisher={IEEE}, author={Bottomley, G.E.}, year={2002}, month={Dec}, pages={141–144} }
 @misc{bottomley_molnar_2002, title={Interference cancellation for improved channel estimation in array processing MLSE receivers}, volume={1}, url={http://dx.doi.org/10.1109/vetec.1997.596335}, DOI={10.1109/vetec.1997.596335}, abstractNote={Array processing techniques provide significant gains in performance for digital cellular communications systems. While array processing has the potential of mitigating severe co-channel interference, performance is limited by the need to estimate the channel of the desired signal. In this paper, practical approaches for improving channel estimation in the presence of interference are proposed. Simulation of these approaches for the IS-136 TDMA cellular system demonstrate that improved channel estimation can provide gains in C/I as high as 8 dB at 1% BER.}, journal={1997 IEEE 47th Vehicular Technology Conference. Technology in Motion}, publisher={IEEE}, author={Bottomley, G.E. and Molnar, K.J.}, year={2002}, month={Nov}, pages={140–144} }
 @misc{bottomley_2002, title={Optimizing the RAKE receiver for the CDMA downlink}, url={http://dx.doi.org/10.1109/vetec.1993.508798}, DOI={10.1109/vetec.1993.508798}, abstractNote={The optimal filter solution for the code division multiple access (CDMA) downlink is derived. A practical suboptimal filter that recovers part of the loss introduced by the RAKE receiver is presented. A significant performance advantage is obtained when the proportion of total interference that comes from the same base station as the signal is large. There is a design tradeoff between the complexity of the practical filter and its performance. As the complexity increases, the performance approaches that of the optimal filter.}, journal={IEEE 43rd Vehicular Technology Conference}, publisher={IEEE}, author={Bottomley, G.E.}, year={2002}, month={Dec}, pages={742–745} }
 @misc{bottomley_sourour_ramesh_chennakeshu_2002, title={Optimizing the performance of limited complexity RAKE receivers}, volume={2}, url={http://dx.doi.org/10.1109/vetec.1998.686384}, DOI={10.1109/vetec.1998.686384}, abstractNote={Channel estimation is critical to coherent RAKE receiver performance. We investigate maximum likelihood (ML) channel estimation with side information, using knowledge of the transmit and receive filter responses. Such an approach accounts for the interaction between multipath components. For delay estimation, the ML approach optimizes the RAKE finger placement, even when there are an insufficient number of RAKE fingers. For channel coefficient estimation, the ML approach optimizes combining, regardless of the delay estimation approach used. Suboptimal approaches are also developed, which reduce the complexity at a slight cost in performance.}, journal={VTC '98. 48th IEEE Vehicular Technology Conference. Pathway to Global Wireless Revolution (Cat. No.98CH36151)}, publisher={IEEE}, author={Bottomley, G.E. and Sourour, E. and Ramesh, R. and Chennakeshu, S.}, year={2002}, month={Nov}, pages={968–972} }
 @misc{bottomley_haartsen_2002, title={Realizing intermediate reuse factors for capacity evaluation}, url={http://dx.doi.org/10.1109/vetec.1994.345335}, DOI={10.1109/vetec.1994.345335}, abstractNote={The goal of many cellular system studies is the capacity evaluation and comparison of planned cellular systems. The capacity definition includes multiple quality requirements which must be met, such as a blocking probability for new calls and an outage probability for connected calls. The reuse factor and Erlang loading of each cell are adjusted so that all quality criteria are met. However, some quality criteria are exceeded. This makes capacity comparisons difficult, since systems may be compared with different qualities. One of the problems is that the site reuse factor can only take on a restricted number of values, e.g. 1,3,4,7. This paper proposes a practical method for obtaining intermediate reuse values, so that multiple quality criteria can be more closely met. This is achieved by partitioning the total channel set into two subsets, each subset being allocated with a different reuse factor. Such an approach is physically realizable and straightforward to use in capacity evaluation simulations. Also, the approach can be extended to provide a continuum of reuse values. As an example, this method is applied to evaluate the capacity benefit of receive antenna diversity for the American Digital Cellular (ADC) standard.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">></ETX>}, journal={Proceedings of IEEE Vehicular Technology Conference (VTC)}, publisher={IEEE}, author={Bottomley, G.E. and Haartsen, J.C.}, year={2002}, month={Dec}, pages={1450–1454} }
 @misc{arslan_gupta_bottomley_chennakeshu_2002, title={Successive cancellation of adjacent channel signals in FDMA/TDMA digital mobile radio systems}, volume={3}, url={http://dx.doi.org/10.1109/vetec.1998.686050}, DOI={10.1109/vetec.1998.686050}, abstractNote={Capacity and signal quality can be improved in mobile radio systems by designing digital receivers with interference mitigation capability. In this paper, coherent MLSE receivers based on successive cancellation of adjacent channel interference in FDMA/TDMA mobile radio systems are developed. The proposed technique requires estimation of impulse response of the desired and adjacent channels, these are obtained via a novel approach employing pulse shaping information and band extrapolation. The receiver is simulated for the GSM digital cellular system under Rayleigh and Rician fading. The results show substantial improvements in bit error rate in interference limited environments.}, journal={VTC '98. 48th IEEE Vehicular Technology Conference. Pathway to Global Wireless Revolution (Cat. No.98CH36151)}, publisher={IEEE}, author={Arslan, H. and Gupta, S.C. and Bottomley, G.E. and Chennakeshu, S.}, year={2002}, month={Nov}, pages={1720–1724} }
 @article{arslan_bottomley_2001, title={Channel estimation in narrowband wireless communication systems}, volume={1}, ISSN={1530-8669 1530-8677}, url={http://dx.doi.org/10.1002/wcm.14}, DOI={10.1002/wcm.14}, abstractNote={Abstract Channel estimation is an integral part of standard adaptive receiver designs used in narrowband, digital wireless communication systems. In this tutorial paper, commonly used approaches to channel estimation are reviewed. Both time‐invariant and time‐varying channels are considered. For time‐varying channels, both pilot symbol interpolation and data‐directed channel tracking are considered. Applications include the Global System for Mobile communications, the Enhanced Data rates for Global Evolution system, and another Time‐Division Multiple‐Access system known as Telecommunications Industry Association/Electronics Industry Association/Interim Standard—136 (TIA/EIA/IS‐136 or IS‐136). Copyright © 2001 John Wiley & Sons, Ltd.}, number={2}, journal={Wireless Communications and Mobile Computing}, publisher={Wiley}, author={Arslan, Hüseyin and Bottomley, Gregory E.}, year={2001}, month={Mar}, pages={201–219} }
 @article{bottomley_ottosson_wang_2000, title={A generalized RAKE receiver for interference suppression}, volume={18}, ISSN={0733-8716}, url={http://dx.doi.org/10.1109/49.864017}, DOI={10.1109/49.864017}, abstractNote={Currently, a global third-generation cellular system based on code-division multiple-access (CDMA) is being developed with a wider bandwidth than existing second-generation systems. The wider bandwidth provides increased multipath resolution in a time-dispersive channel, leading to higher frequency-selectivity. A generalized RAKE receiver for interference suppression and multipath mitigation is proposed. The receiver exploits the fact that time dispersion significantly distorts the interference spectrum from each base station in the downlink of a wideband CDMA system. Compared to the conventional RAKE receiver, this generalized RAKE receiver may have more fingers and different combining weights. The weights are derived from a maximum likelihood formulation, modeling the intracell interference as colored Gaussian noise. This low-complexity detector is especially useful for systems with orthogonal downlink spreading codes, as orthogonality between own cell signals cannot be maintained in a frequency-selective channel. The performance of the proposed receiver is quantified via analysis and simulation for different dispersive channels, including Rayleigh fading channels. Gains on the order of 1-3.5 dB are achieved, depending on the dispersiveness of the channel, with only a modest increase in the number of fingers. For a wideband CDMA (WCDMA) system and a realistic mobile radio channel, this translates to capacity gains of the order of 100%.}, number={8}, journal={IEEE Journal on Selected Areas in Communications}, publisher={Institute of Electrical and Electronics Engineers (IEEE)}, author={Bottomley, G.E. and Ottosson, T. and Wang, Y.-P.E.}, year={2000}, month={Aug}, pages={1536–1545} }
 @article{bottomley_arslan_ramesh_brismark_2000, title={Coherent MAP detection of DQPSK bits}, volume={4}, ISSN={1089-7798}, url={http://dx.doi.org/10.1109/4234.892200}, DOI={10.1109/4234.892200}, abstractNote={Both IS-136 and PDC digital cellular systems employ forward error correction (FEC) encoding followed by a form of DQPSK modulation. In this letter, we derive the maximum a posteriori (MAP) bit detector for DQPSK modulation in non-ISI channels for a coherent receiver with one or more antennas. The MAP detector forms a bit log-likelihood ratio, which provides the optimal "soft information" for MLSE or MAP convolutional decoding. MAP detection requires exponentiation and logarithm operations, as well as knowledge of the noise covariance. To avoid these operations, two approximate forms are developed, which do not require the noise covariance value under certain assumptions. Both approximate approaches, when used with soft FEC decoding, are within 0.5 dB of the optimal approach.}, number={11}, journal={IEEE Communications Letters}, publisher={Institute of Electrical and Electronics Engineers (IEEE)}, author={Bottomley, G.E. and Arslan, H. and Ramesh, R. and Brismark, G.}, year={2000}, month={Nov}, pages={354–356} }
 @article{bottomley_2000, title={Editorial}, volume={49}, ISSN={0018-9545 1939-9359}, url={http://dx.doi.org/10.1109/tvt.2000.901860}, DOI={10.1109/tvt.2000.901860}, number={6}, journal={IEEE Transactions on Vehicular Technology}, publisher={Institute of Electrical and Electronics Engineers (IEEE)}, author={Bottomley, G.E.}, year={2000}, month={Nov}, pages={2042–2042} }
 @article{arslan_gupta_bottomley_chennakeshu_2000, title={New approaches to adjacent channel interference suppression in FDMA/TDMA mobile radio systems}, volume={49}, ISSN={0018-9545}, url={http://dx.doi.org/10.1109/25.875219}, DOI={10.1109/25.875219}, abstractNote={The capacity and signal quality of wireless communication systems can be improved by enhancing receiver performance in the presence of adjacent channel interference (ACI), In this paper, maximum-likelihood sequence estimation (MLSE) receivers based on joint demodulation and successive cancellation of adjacent channel signals are developed. The proposed receivers provide significant improvement in performance over a wide range of carrier-to-interference ratios. To provide coherent reception, novel channel estimation techniques are used, exploiting knowledge of the transmit and receive filter responses. Performance is evaluated and compared via simulation for the Global System for Mobile communications (GSM) digital cellular system.}, number={4}, journal={IEEE Transactions on Vehicular Technology}, publisher={Institute of Electrical and Electronics Engineers (IEEE)}, author={Arslan, H. and Gupta, S.C. and Bottomley, G.E. and Chennakeshu, S.}, year={2000}, month={Jul}, pages={1126–1139} }
 @article{bottomley_molnar_1999, title={Adaptive channel estimation for multichannel MLSE receivers}, volume={3}, ISSN={1089-7798}, url={http://dx.doi.org/10.1109/4234.749356}, DOI={10.1109/4234.749356}, abstractNote={The performance of multichannel coherent maximum-likelihood sequence estimation (MLSE) reception in the presence of co-channel interference is limited by the channel estimation accuracy. An adaptive channel estimation approach is developed which improves the performance through interference cancellation. Significant performance gains (up to 8 dB) are demonstrated for the Digital Advanced Mobile Phone Service (D-AMPS) (IS-136) digital cellular system.}, number={2}, journal={IEEE Communications Letters}, publisher={Institute of Electrical and Electronics Engineers (IEEE)}, author={Bottomley, G.E. and Molnar, K.J.}, year={1999}, month={Feb}, pages={40–42} }
 @misc{sourour_bottomley_ramesh_1999, title={Direct sequence spread spectrum acquisition with sample accumulation in fading channels}, url={http://dx.doi.org/10.1109/vetecf.1999.797328}, DOI={10.1109/vetecf.1999.797328}, abstractNote={In this paper we consider direct sequence spread spectrum acquisition systems with a search mode employing a sliding correlator, followed by a verification mode employing parallel integrate-and-dump correlators. In this paper we focus on a technique to improve the performance of the search mode. Received PN code periods are correlated with a local section of the PN code. Delays corresponding to high correlation results are verified in the verification mode. If the verification process is not successful a new received PN code period is correlated. In conventional techniques, the correlation results from previous code periods are erased. In this paper we propose a method where these correlation results are retained and a moving average of correlation results is performed. A considerable improvement in the performance of the acquisition system is achieved.}, journal={Gateway to 21st Century Communications Village. VTC 1999-Fall. IEEE VTS 50th Vehicular Technology Conference (Cat. No.99CH36324)}, publisher={IEEE}, author={Sourour, E. and Bottomley, G.E. and Ramesh, R.}, year={1999}, pages={2198–2202 vol.4} }
 @article{bottomley_molnar_chennakeshu_1999, title={Interference cancellation with an array processing MLSE receiver}, volume={48}, ISSN={0018-9545}, url={http://dx.doi.org/10.1109/25.790506}, DOI={10.1109/25.790506}, abstractNote={the capacity and transmission quality in cellular systems can be improved by using receivers that mitigate cochannel interference and multipath propagation. In this paper, a class of multichannel maximum likelihood sequence estimation (MLSE) receivers is developed for this purpose. Interference mitigation is accomplished via adaptive antenna arrays, while multipath propagation is combated via MLSE. Practical considerations are included, such as fixed front-end filtering, sampling, and estimation of parameters from received samples. Maximal ratio combining, conventional array processing and metric combining (MC) are shown to be special cases of the proposed receivers. Performance is evaluated for /spl pi//4-shift DQPSK, using the parameters and transmission format of the time-division multiple-access (TDMA)-based IS-136 (D-AMPS) digital cellular standard. Semi-analytical performance predictions are developed which confirm simulation trends. The results show that these receivers can operate at significantly lower carrier-to-interferer (C/I) levels than conventional MC receivers.}, number={5}, journal={IEEE Transactions on Vehicular Technology}, publisher={Institute of Electrical and Electronics Engineers (IEEE)}, author={Bottomley, G.E. and Molnar, K.J. and Chennakeshu, S.}, year={1999}, pages={1321–1331} }
 @article{molnar_bottomley_1998, title={Adaptive array processing MLSE receivers for TDMA digital cellular/PCS communications}, volume={16}, ISSN={0733-8716}, url={http://dx.doi.org/10.1109/49.730444}, DOI={10.1109/49.730444}, abstractNote={Array processing is a promising approach for improving quality, coverage, and capacity in digital cellular communication systems. By combining array processing with maximum likelihood sequence estimation (MLSE), intersymbol interference (ISI) introduced by multipath propagation can be mitigated as well. Novel symbol-spaced and fractionally spaced adaptive array processing MLSE receivers are developed for both diversity and phased array antenna configurations. The practical issues of synchronization and channel estimation are addressed. A novel approach to automatic frequency error correction (AFC) is proposed and is shown to be critical when cancelling cochannel interference. Performance is evaluated for the reverse link of the IS-136 TDMA-based digital cellular system. Substantial improvements are obtained over conventional antenna configurations for receiver sensitivity (2.5-4 dB) and over traditional antenna combining when cochannel interference is present (0.5-25 dB).}, number={8}, journal={IEEE Journal on Selected Areas in Communications}, publisher={Institute of Electrical and Electronics Engineers (IEEE)}, author={Molnar, K.J. and Bottomley, G.E.}, year={1998}, pages={1340–1351} }
 @article{bottomley_chennakeshu_1998, title={Unification of MLSE receivers and extension to time-varying channels}, volume={46}, ISSN={0090-6778}, url={http://dx.doi.org/10.1109/26.664302}, DOI={10.1109/26.664302}, abstractNote={Forney (1972) and Ungerboeck (1974) have each developed maximum-likelihood sequence estimation (MLSE) receivers for intersymbol interference (ISI) channels. The Forney receiver uses a whitened matched filter, followed by a sequence estimation algorithm using the Euclidean distance metric. The Ungerboeck receiver uses a matched filter, followed by a sequence estimation algorithm using a modified metric. A unified development of both receivers is given, in which each receiver is derived from the other. By deriving the Ungerboeck receiver from the Forney receiver, we show that the whitening operation is cancelled in the Euclidean distance metric, leaving the modified metric. In addition, the Ungerboeck receiver is extended to the case of a time-varying known channel. When the channel is unknown, decision-directed channel estimation is assumed, which requires channel prediction to account for the decision delay. It is shown that the Ungerboeck receiver requires additional channel prediction, degrading performance due to prediction uncertainty. To solve this problem, two alternative receiver forms are developed which do not require additional prediction, though the computational complexity is increased. Performance and complexity of the receiver forms are compared for the IS-136 digital cellular time-division multiple-access (TDMA) standard.}, number={4}, journal={IEEE Transactions on Communications}, publisher={Institute of Electrical and Electronics Engineers (IEEE)}, author={Bottomley, G.E. and Chennakeshu, S.}, year={1998}, month={Apr}, pages={464–472} }
 @misc{bottomley_chennakeshu_1996, title={Adaptive MLSE equalization forms for wireless communications}, ISBN={9781461375098 9781461554912}, url={http://dx.doi.org/10.1007/978-1-4615-5491-2_18}, DOI={10.1007/978-1-4615-5491-2_18}, journal={Wireless Personal Communications}, publisher={Springer US}, author={Bottomley, Gregory E. and Chennakeshu, Sandeep}, year={1996}, pages={183–194} }
 @article{dent_bottomley_croft_1993, title={Jakes fading model revisited}, volume={29}, ISSN={0013-5194 1350-911X}, url={http://dx.doi.org/10.1049/el:19930777}, DOI={10.1049/el:19930777}, abstractNote={With the popular Jakes fading model, it is difficult to create multiple uncorrelated fading waveforms. In the Letter, modifications to the model are proposed which solve this problem.}, number={13}, journal={Electronics Letters}, publisher={Institution of Engineering and Technology (IET)}, author={Dent, P. and Bottomley, G.E. and Croft, T.}, year={1993}, month={Jun}, pages={1162–1163} }
 @article{bottomley_1993, title={Signature sequence selection in a CDMA system with orthogonal coding}, volume={42}, ISSN={0018-9545}, url={http://dx.doi.org/10.1109/25.192388}, DOI={10.1109/25.192388}, abstractNote={In code-division multiple-access (CDMA) systems, recent attention has focused on the use of orthogonal coding to provide spreading. Each signal is coded with the same orthogonal or biorthogonal code, followed by a modulo-2 addition of a unique signature sequence. The set of signature sequences used determines how much signals interfere with each other at a receiver, thus determining the performance of the system. An analysis is presented to determine the properties of an optimal set of signature sequences for such a system. Using a Kerdock code, a set of signature sequences is presented which optimizes performance in a direct sequence CDMA system with (a) synchronous transmission, (b) no multipath time dispersion, and (c) orthogonal or biorthogonal Walsh-Hadamard coding as a means of spreading the information signal. For a length-N-binary code (where N is an even power of two), the set contains N/2 signature sequences. Approaches are discussed for the cases when N is an odd power of two and when more sequences are needed.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">></ETX>}, number={1}, journal={IEEE Transactions on Vehicular Technology}, publisher={Institute of Electrical and Electronics Engineers (IEEE)}, author={Bottomley, G.E.}, year={1993}, pages={62–68} }
 @article{bottomley_alexander_1991, title={A novel approach for stabilizing recursive least squares filters}, volume={39}, ISSN={1053-587X}, url={http://dx.doi.org/10.1109/78.91147}, DOI={10.1109/78.91147}, abstractNote={A novel approach for stabilizing recursive least squares (RLS) filters is presented. The approach relies on a detailed fixed point analysis, which provides two important benefits. The analysis reveals a bias in the error propagation mechanism, providing an analytical basis for instability problems. The analysis then indicates which specific roundoff errors are causing instability. These roundoff errors are then biased in such a way that the overall filter is biased towards stable performance. Experimental results indicate that stability can be achieved with negligible loss in least squares performance.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">></ETX>}, number={8}, journal={IEEE Transactions on Signal Processing}, publisher={Institute of Electrical and Electronics Engineers (IEEE)}, author={Bottomley, G.E. and Alexander, S.T.}, year={1991}, pages={1770–1779} }
 @inproceedings{bottomley_beex_bostian_1985, title={Predicting rain fades}, booktitle={1985 International Geoscience and Remote Sensing Symposium (IGARSS '85)}, author={Bottomley, G.E. and Beex, L. and Bostian, C.W.}, year={1985} }