Acquisition of pseudonoise sequences in direct-sequence spread-spectrum systems
Chawla, Kapil K.
This item is only available for download by members of the University of Illinois community. Students, faculty, and staff at the U of I may log in with your NetID and password to view the item. If you are trying to access an Illinois-restricted dissertation or thesis, you can request a copy through your library's Inter-Library Loan office or purchase a copy directly from ProQuest.
Permalink
https://hdl.handle.net/2142/20574
Description
Title
Acquisition of pseudonoise sequences in direct-sequence spread-spectrum systems
Author(s)
Chawla, Kapil K.
Issue Date
1991
Doctoral Committee Chair(s)
Sarwate, Dilip V.
Department of Study
Electrical and Computer Engineering
Discipline
Electrical Engineering
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Engineering, Electronics and Electrical
Language
eng
Abstract
Various schemes for the acquisition of a pseudonoise (PN) sequence in a baseband direct sequence spread-spectrum (DS/SS) system are investigated. First, we consider acquisition schemes for receivers with chip synchronization, that is, the chips of the transmitter and receiver PN sequence generator are synchronized, and only the starting point (or phase of the PN sequence) is unknown. Acquisition schemes for such receivers can be divided into active acquisition schemes, in which the receiver uses the observations to directly deduce the phase of the received sequence, and serial search schemes, in which the receiver guesses the possible phases in some predetermined order and uses the observations only to check if a particular guess is correct.
Several active acquisition schemes are analyzed, and tight bounds on the probability of error of parallel search schemes are obtained. A method to reduce the complexity of a parallel search is outlined. We also consider parallel schemes with hard limited (binary) observations and show that, as might be expected, the probability of error for such schemes is very high compared with that for parallel schemes with soft decisions.
Different approximations for a PN sequence are considered in order to analyze the worst-case and the average-case performance of serial search schemes. A worst-case sequence is obtained that may be used to derive the worst-case performance of a certain class of serial search schemes. The average performance of serial search schemes is studied using sequential probability ratio tests (SPRTs), which are designed and analyzed using a zero sequence model and a random sequence model of a PN sequence. Simulation of the two tests on an actual PN sequence shows that the random sequence is an excellent approximation for a PN sequence and may be used to predict the performance of each of the SPRTs when applied to a PN sequence. In addition, significant performance degradation results if the test is based on a zero sequence model rather than on a random sequence model.
Finally, parallel acquisition schemes for receivers without chip synchronization are considered. Four schemes for such receivers are obtained, and approximations to the probability of error of two of the schemes are derived. The exact error probabilities of each of the schemes are obtained via Monte Carlo simulations. The results show that the approximations to the error probabilities are reasonably close to the values obtained by simulation.
Use this login method if you
don't
have an
@illinois.edu
email address.
(Oops, I do have one)
IDEALS migrated to a new platform on June 23, 2022. If you created
your account prior to this date, you will have to reset your password
using the forgot-password link below.
