Serial Code Acquisition Research Articles

Code acquisition schemes using antenna arrays for DS-SS systems and their performance in spatially correlated fading channels

We propose parallel and serial code-acquisition schemes using antenna arrays for initial acquisition of direct-sequence spread-spectrum signals, which can lower substantially the range of detectable signal-to-noise ratio (SNR) as compared to the corresponding conventional schemes with a single antenna. The proposed schemes use the sum of all the single-antenna decision samples from antenna arrays, corresponding to an identical subsequence of a given pseudonoise code as a decision variable in order to enhance SNR of the resulting signal. We analyze the mean acquisition time performance under an additive white Gaussian noise channel and spatially correlated time-varying flat Rayleigh fading channels by deriving the expressions for the probabilities of detection, missing, and false alarm. We consider two extreme cases of spatial fading correlation among antenna arrays, the case of uncorrelated diversity antennas and the case of perfectly correlated antennas. From numerical results, we see that the acquisition performance of the proposed schemes using antenna arrays becomes improved continually as the number of antennas increases and the performance improvement depends on the degree of spatial fading correlation.

Modeling of code acquisition process in CDMA networks-asynchronous systems

In this paper, we discuss modeling of the serial code acquisition process in a code division multiple access (CDMA) network. Due to multiple access interference (MAI), the process is characterized by a different probability of signal detection P/sub D/ and probability of a false alarm P/sub FA/ in each cell of the code delay uncertainty region. We derive exact expressions for average code acquisition time and its variance. In addition to this, we also present several useful approximations, which enable easy engineering use of these results for practical applications in future Universal Mobile Telecommunications System (UMTS) solutions. Numerical results based on this analysis are used for decision threshold optimization in code acquisition process for asynchronous CDMA networks.

Modeling of code acquisition process in CDMA networks-quasi-synchronous systems

We present a model of serial code acquisition process in code-division multiple-access networks. The difference between this model and the existing work is in using the assumption that in each cell of delay uncertainty region the probability of false alarm, is different. This is caused by the fact that in each cell cross correlations between the local code and the codes used by the other users in the network are different. A closed-form expression for the average acquisition time is derived and discussed.