John Proakis - Academia.edu (original) (raw)

Papers by John Proakis

MTS/IEEE Oceans 2001. An Ocean Odyssey. Conference Proceedings (IEEE Cat. No.01CH37295)

We investigate the application of iterative equalization and decoding techniques to the shallow w... more We investigate the application of iterative equalization and decoding techniques to the shallow water acoustic channel. The first receiver is a joint decision feedback equalizer (DFE) and turbo decoder. The second receiver is a turbo equalizer, which jointly estimates the channel, performs MAP equalization, and decodes received symbols. Although the MAP equalizer is optimum for a known channel, channel estimation

2000 IEEE International Conference on Communications. ICC 2000. Global Convergence Through Communications. Conference Record

The public reporting burden for this collection of information is estimated to average 1 hour per... more The public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggesstions for reducing this burden, to Washington Headquarters Services, Directorate for Information Operations and Reports,

2006 IEEE 17th International Symposium on Personal, Indoor and Mobile Radio Communications, 2006

We consider the performance of an FMT system with perchannel equalization over frequency-selectiv... more We consider the performance of an FMT system with perchannel equalization over frequency-selective time-varying fading channels. Due to the distortion caused by frequency and time selectivity of the fading channel, both ICI and ISI exist in an FMT system and cause performance degradation. By using a per-channel equalizer at the FMT receiver with sufficiently large number of equalizer taps, the ISI can be mitigated significantly, but the ICI still exists. In this paper, the effects of the interference caused by the time-frequency dispersive channel is quantified by analyzing the average system carrier to interference (C/I) ratio of the FMT system under different fading conditions. A closed-form expression for the C/I ratio and its upper bound are provided for the FMT system, which lead to a better understanding of the trade-off between spectral efficiency and system performance degradation. Moreover, comparisons between FMT and OFDM systems under the same channel conditions and spectral efficiency are also provided. Numerical and simulation results of the system C/I ratio further confirm and support the obtained analytical results.

Oceans '04 MTS/IEEE Techno-Ocean '04 (IEEE Cat. No.04CH37600)

ICASSP '84. IEEE International Conference on Acoustics, Speech, and Signal Processing

This paper investigates the numerical accuracy and the numerical stability of adaptive estimation... more This paper investigates the numerical accuracy and the numerical stability of adaptive estimation algorithms. A feedback system model is provided to investigate the numerical stability of the algorithms. Simulation results on the comparison of numerical accuracy of LS adaptive algorithms are given. Two new methods are given that improve the numerical accuracy of the adaptive algorithms when a short word

Proceedings of MILCOM '93 - IEEE Military Communications Conference

Estimation of a fading channel with high accuracy is a key factor for successful signal detection... more Estimation of a fading channel with high accuracy is a key factor for successful signal detection in many mobile, indoor and personal radio communication systems. The optimal windowed recursive least squares (OW-RLS) algorithm developed previously (1993) results in a significant improvement over an exponential windowed recursive least squares algorithm when it is applied to tracking a fading channel. The improvement is confirmed by simulation on a single path fading channel. However, no improvement in performance has been obtained in the simulation of multipath frequency selective channels. This paper shows that the undesirable result is caused by an additional error which is introduced by an incomplete decoupling of cross-correlation terms. The authors design a feedback decoupling method which can cancel the bias almost completely. Simulations show that the theoretical improvement of an OW-RLS algorithm on a fading multipath channel can be completely recovered. With this modification, an enhanced OW-RLS algorithm is described

1970 IEEE Symposium on Adaptive Processes (9th) Decision and Control, 1970

... filters are designed to combat the two major obstacles in high speed digital signaling over s... more ... filters are designed to combat the two major obstacles in high speed digital signaling over such channels, namely, the presence of intersymbol interference due to the non-ideal frequency response of the channel and the slow ... For example, consider the detection of the symbol Io. ...

IEEE Vehicular Technology Conference, 2006

In this paper, we analyze the effect of interference diversity on the capacity of a cellular syst... more In this paper, we analyze the effect of interference diversity on the capacity of a cellular system that employs frequency hopping, power control and bit-interleaved coded modulation. Interference is created when the hopping patterns of adjacent cells intersect with the patterns of the cell of interest, with a probability that depends on the occupancy of each cell. However, due to frequency hopping and power control, the power of the interference varies randomly across the received symbols creating what is usually named in the literature as interference diversity. We explicitly take into account this randomness and, under a channel model that accounts for fading and path loss, analyze the performance of two receivers; a receiver that tracks the variations of the interference power across the received symbols and a receiver that remains oblivious to these variations. Our results demonstrate under what circumstances the additional complexity of tracking the interference power variations is justified.

MILCOM 2006, 2006

In this paper we consider the problem of equalizing constant envelope orthogonal frequency divisi... more In this paper we consider the problem of equalizing constant envelope orthogonal frequency division multiplexing (CE-OFDM) signals that have been corrupted by frequency-selective multipath fading channels. A cyclic prefix guard interval is used to avoid interblock interference (IBI), and to make possible frequency-domain equalization (FDE) using the discrete Fourier transform. It is shown that CE-OFDM exploits the multipath diversity of the channel due to frequency spreading of the data symbols. CE-OFDM compares favorably with conventional OFDM when the impact of nonlinear power amplification and power backoff is taken into account.

Physical Communication, 2008

Public Reporting burden for this collection of information is estimated to average 1 hour per res... more Public Reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comment regarding this burden estimates or any other aspect of this collection of information, including suggestions for reducing this burden, to Washington Headquarters Services, Directorate for information Operations and Reports,

The Journal of the Acoustical Society of America, 1999

Sound is the best form of energy for broadcasting communication signals in the ocean. However, th... more Sound is the best form of energy for broadcasting communication signals in the ocean. However, the physical channel is impaired by nonwhite noise, frequency-selective absorption, a refractive medium, a sloping seafloor, a dynamic sea-surface, and scattering at the boundaries. Temporal variability of these influences and motion of the link terminals introduce fluctuations in the received signal and noise fields. These oceanographic and geometric factors produce measurable effects on underwater acoustic communication systems. The relevant direct measures of these channel effects include multipath spreading, Doppler shifts and spreading, coherence time, and noise statistics. Measuring and understanding these effects support optimization of both modulation and demodulation parameters. Such channel adaptation strategies enhance quality of service for the communication link. Theory, simulation, and ocean experiment illustrate link improvements. [Work funded by ONR 32, the SSC-SD Independe...

International Journal of Wireless Information Networks, 1994

One of the main problems in time-division multiple-access (TDMA) digital mobile communications is... more One of the main problems in time-division multiple-access (TDMA) digital mobile communications is the poor performance of the receiver for fast-fading channels. We propose to use a novel joint data and channel estimation (JDCE) technique to improve performance, The basic idea of this method originates from the so-called generalized likelihood ratio (GLR) test of classical detection theory. The technique was combined with the well-known Viterbi algorithm and applied to blind equalization by Seshadri [1]. In this paper, we introduce this technique to TDMA mobile communications. We find that the problems of delayed channel updating and divergence caused by error decision feedback in conventional maximum likelihood sequence estimation with decision delay (MLSE/DD) can be completely solved. An improvement of 4.5 dB can be obtained compared with the MLSE/DD method when it is applied to the Northern American Digital Cellular (NADC) system. The specified IS-54 requirement of 19 dB signal-to-noise ratio (SNR) at a bit error rate (BER) of 3% and a vehicle speed of 100 km/h can be met with a remarkable margin of 8 dB. When the intersymb01 interference (ISI) of a channel is not severe, the required computation is moderate. For example, in the NADC system, the computational burden of the JDCE method is twice that of the MLSE/DD method if the least-mean-squares (LMS) algorithm is used for channel tracking.

IEEE Wireless Communications, 2006

The benefits of using multiple antennas in wireless communications have been known for some time.... more The benefits of using multiple antennas in wireless communications have been known for some time. However, there are many open issues regarding how this increased capacity at the physical layer can be exploited to provide improved networking performance by the use of new protocol design techniques.

IEEE Transactions on Wireless Communications, 2007

Frequency hopping (FH) combined with coding is a popular technique in wireless communication appl... more Frequency hopping (FH) combined with coding is a popular technique in wireless communication applications. Motivated by the commercial system outlined in [1], this paper investigates the performance of a coherent FH Multiple Access (FH-MA) cellular system, where hopping patterns are constructed from Latin squares. Some of the patterns carry pilot symbols, which the users track to estimate the channel on the data patterns and perform coherent detection. The Latin squares construction enables us to analytically evaluate the bit error probability (BEP) over each data pattern, when convolutional codes are employed for error protection. The focus of our work is to precisely determine the effect that frequency and interference diversity, ensuing from FH, have on the coded performance. Regarding frequency diversity, it is shown that the performance can vary widely for different Latin squares. Moreover, under pilot-assisted channel estimation, a performance tradeoff is observed, as an increasing frequency selectivity results in more diversity, but also more inaccurate channel state information. With respect to interference diversity, we analyze the performance when the interference power variations are perfectly known or ignored by the receiver. Our results confirm that interference tracking is important in harnessing the error correcting power of convolutional coding.

IEEE Transactions on Vehicular Technology, 1991

IEEE Transactions on Communications, 1990

An extension is presented of the work of V.M. Eyubogin (see ibid., vol.36, p.401-9, Apr. 1988) on... more An extension is presented of the work of V.M. Eyubogin (see ibid., vol.36, p.401-9, Apr. 1988) on decision-feedback equalization (DFE) applied to coded systems with interleaving. The authors study the adaptive implementation of the DFE using recursive-least-squares algorithms (RLS). System performance on time-dispersive channels with nulls as well as on channels with relatively small intersymbol interference is investigated. A reference

IEEE Transactions on Communications, 2008

IEEE Transactions on Communications, 2009

IEEE Transactions on Communications, 2001

A formula that computes the maximum number of users supported per base station in a cellular radi... more A formula that computes the maximum number of users supported per base station in a cellular radio network is generalized to consider the frequency reuse number and arbitrary processing gains. The generalization quantifies a cost associated with in-cell interference by accounting for the lack of interference from the desired user on the total interference and by considering the impact of the frequency reuse number on the out-of-cell interference. This interference cost results in an increase in the received Eb/Io relative to FDMA which should be weighted against a reduction in the Eb/Io requirement resulting from using CDMA.