A rapid adaptive PN code acquisition with antenna diversity for DS-CDMA communication

A robust auto‐adaptive approach for serial acquisition of generalized multi‐carrier spread spectrum in multipath fading mobile channels

“…where X k ð Þ is the k th OS. As the data samples of Equation 11in a non-homogeneous environment may contain an interfering signals group with an unknown location dividing the data into two parts, it is necessary to find the rank order index k of the ordered sample X k ð Þ that indicates the separator between the smallest and largest samples within Equation (11). Hence, the ordered sample X k + 1 ð Þ indicates the first sample of the interfering signals group.…”

“…Hence, the ordered sample X k + 1 ð Þ indicates the first sample of the interfering signals group. In order to find the rank order index k, we assume that the OSs of Equation (11) are independent elements of the reference set X i , i = 1;M f g , where the subset X i 1 , i 1 = 1;k f gcontains the first k elements of the thermal noise only from X i f g, each with power level β N , while the subset X i 2 , i 2 = k + 1;M f gcontains the last M − k elements of the interfering signals from X i f g , each with power level β I . We also assume that the OSs of both subsets are independent and identically distributed (i.i.d.)…”

“…For this reason, a large number of different adaptive threshold mechanisms known in the Radar systems have been applied to the code acquisition problems, where these mechanisms are based on constant false alarm rate (CFAR) algorithms that are used to determine the threshold value according to the actual environmental conditions. [7][8][9][10][11][12][13] As the arithmetic averaging CFAR detector and its modifications [8][9][10] suffer a serious detection performance degradation when the reference window used to estimate the background noise level is infected by interfering signals, 11 a variety of alternatives have been proposed to develop CFAR detectors applied to the PN code acquisition to overcome these drawbacks. These alternatives include the fixed point(s) censoring CFAR detectors, where the largest ranked cells are censored, and only the remaining ranked cells are used to estimate the background noise level.…”

“…These alternatives include the fixed point(s) censoring CFAR detectors, where the largest ranked cells are censored, and only the remaining ranked cells are used to estimate the background noise level. 2,[11][12][13] The fixed censoring point CFAR detectors are effective against the appearance of interfering signals in the reference window, as long as they are disposed of properly. This implies that to censor the unwanted ranked cells, which may not be available in many applications, some prior information about the background environment is needed.…”

“…Therefore, it is difficult to get the right phase to adjust the synchronization even if the channel quality is improved. For this reason, a large number of different adaptive threshold mechanisms known in the Radar systems have been applied to the code acquisition problems, where these mechanisms are based on constant false alarm rate (CFAR) algorithms that are used to determine the threshold value according to the actual environmental conditions 7‐13 …”