A JOINT MAXIMUM LIKELIHOOD SYNCHRONIZATION AND DEMODULATION ALGORITHM FOR THE STANAG 4285 MODEM

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Authors
  1. Kozminchuk, B.
  2. Huang, X.
Corporate Authors
Defence Research Establishment Ottawa, Ottawa ONT (CAN)
Abstract
An algorithm providing from and symbol-timing synchronization of a STANAG 4285 signal in the presence of frequency and phase offsets of the carrier has been developed. Some simplifications of the synchronization and demodulation problem have been made so that this algorithm could be characterized independently of several other variables. First, it is assumed that the signal's nominal symbol rate, frame structure, and pusle shape are known. Second, the sampling rate at the receiver is assumed to be an integer multiple of the symbol rate. Third, an ideal channel is assumed in the sense that multipath effects have not been considered. This implies that channel equalization is not required at the receiver. These more complicated issues will be dealt with in other reports. The algorithm is made up of two main parts. The first part consists of a maximum likelihood ratio test which is used as a means to indicate whether or not frame synchronization has occurred. This maximum likelihood ratio test is combined with a polynomial-based interpolation procedure to estimate the optimum symbol-timing so that the signal-to-noise ratio at the output of the receiver's matched filter is maximized. The second part of the algorithm is a maximum likelihood estimation of the carrier and phase offsets after frame and symbol synchronization have been achieved. Once the carrier and phase offsets have been estimated, message decoding cna then be carried out.
Keywords
Bling synchronization;Digital communication
Report Number
DREO-TN-96-005 — Technical Note
Date of publication
01 Oct 1996
Number of Pages
41
DSTKIM No
97-00615
CANDIS No
500746
Format(s):
Hardcopy;Document Image stored on Optical Disk

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