Recognition of Digital Modulations

Abstract

In modern communication systems, digital modulation techniques rather than analogue ones are frequently used. So, the new trend is the digital modulation recognisers. Most of the digital modulation recognisers discussed in Chapter 1 utilise the pattern recognition approach such as [4], and [14]. So, they require long signal duration and the processing time may be very long; and this leads to the use of these algorithms in off-line analysis. Furthermore, some of these recognisers such as [4] require excessive computer storage to ensure correct modulation recognition. Indeed, most of them are assigned to a subset of modulation types of interest. Also, the practical implementation for some of these recognisers such as [14], [21], and [22] is excessively complex. However, the work on some of these recognisers attempts to identify digital modulations with number of levels > 4. On the other hand, the number of samples used in the algorithms presented in this thesis to decide about the modulation type is 2048 (equivalent to 1.707 msec.) and this is likely to be suitable for on-line analysis.