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Author: Eric Neal VanLandingham Publisher: ISBN: Category : Modulation (Electronics) Languages : en Pages : 118
Book Description
In this report an alternative approach to Direct Sequence Spread Spectrum acquisition and tracking will be explained and implemented. The system designed uses the impulse response of the channel to acquire and track the time difference between the locally generated pseudonoise code and received signal's pseudonoise code. The results of both simulation and over the air tests confirm the validity of this alternative approach. Several limitations and constraints that are innate in the technique and design used were also identified. Additional research and modifications that would improve the performance of this system are suggested.
Author: Eric Neal VanLandingham Publisher: ISBN: Category : Modulation (Electronics) Languages : en Pages : 118
Book Description
In this report an alternative approach to Direct Sequence Spread Spectrum acquisition and tracking will be explained and implemented. The system designed uses the impulse response of the channel to acquire and track the time difference between the locally generated pseudonoise code and received signal's pseudonoise code. The results of both simulation and over the air tests confirm the validity of this alternative approach. Several limitations and constraints that are innate in the technique and design used were also identified. Additional research and modifications that would improve the performance of this system are suggested.
Author: Meera Srinivasan Publisher: ISBN: Category : Languages : en Pages : 214
Book Description
Parallel search schemes are presented for the acquisition of spreading sequences in chip-asynchronous direct-sequence spread-spectrum communication systems. In a parallel acquisition scheme, an estimate of the delay of a direct-sequence signal is made directly from a number of correlations of the received signal against different shifted versions of the spreading signal. Parallel schemes acquire the signal very quickly, but are more computationally intensive than serial schemes. In this thesis, we investigate several parallel strategies for the acquisition for general binary spreading sequences and develop suboptimal acquisition schemes that are easier to implement than the previously proposed optimal schemes. The techniques presented are attractive in that they approximate the optimal parallel schemes in terms of probability of successful acquisition, but are much easier to implement than the optimal schemes. The single-user phase-coherent situation is considered first. In this case, both carrier frequency and phase are known. We first discuss the optimal and maximum likelihood estimators for general binary spreading sequences and then present two new suboptimal schemes. One of these schemes is a small signal approximation of the optimal scheme, and it performs very well over a large range of signal-to-noise ratio. The other scheme is a hybrid of the optimal and maximum likelihood schemes, and is extremely simple. The hybrid scheme can be analyzed precisely in terms of its probability of unsuccessful acquisition. It is shown that this hybrid scheme has error probability decreasing exponentially with increasing SNR, and that this scheme is practically the simplest possible parallel scheme that has this property. Our result also proves an earlier conjecture that the optimal parallel estimator has error probability that decreases exponentially with increasing SNR. The same approach is used to devise simple acquisition schemes for the single-user noncoherent situation. A locally optimal estimator for low SNR is presented, along with two different noncoherent analogues of the coherent hybrid scheme. One of the noncoherent hybrid schemes is analyzed, and it is shown that this scheme also has exponentially decreasing error probability. This also proves that the error probability of the optimal noncoherent estimator decreases exponentially with increasing SNR. The problem of acquiring several direct-sequence signals in the absence of data modulation is also considered. The chip-synchronous situation is considered first and decorrelating methods are used to develop two near-far resistant strategies. One of these schemes estimates the signal delays in multiple stages, with each delay estimate depending on previous delay estimates, while the other scheme estimates the delays simultaneously and independently of each other. Schemes for the chip-asynchronous case are then developed by combining the coherent hybrid scheme for the single-user situation with the multistage decorrelating method. Monte Carlo simulation is used to obtain the error probabilities for the various schemes.
Author: Eric Neal VanLandingham
Author: Eric Neal VanLandingham
Author: Alem, Ahmad Waddah Kayyaly
Author: Gregory Paul Rogers
Author: John C. Fakatselis
Author: Eric William Siess
Author: Marvin K. Simon
Author: Essam A. Sourour
Author: Frederick J. Block
Author: Eric Conway MacCalla
Author: Meera Srinivasan