Title :
Dual rate mobile data system
Author :
Hansson, Ulf ; Sjöberg, Sten
Author_Institution :
Eritel, Gothenburg, Sweden
Abstract :
A mobile data system that uses two significantly different data rates on the air interface is described. In a cellular system it is the conditions prevailing for a mobile terminal at the cell border that is setting the limit for a reasonable data rate. However, there are conditions in the cell, e.g. a stationary terminal close to the base station, where it is possible to use a higher data rate. A system is described that is designed for 12.5 kHz LMR channels. The system uses a binary digital FM of GMSK-type as the default transmission mode, but it switches to multilevel CPM when radio conditions are found to be good by the terminal. Considerations on the choice of the number of levels, and on the performance and complexity of the multilevel signalling, are given. Criteria for deciding when conditions are good enough for a rate increase are also suggested
Keywords :
cellular radio; data communication systems; frequency modulation; minimum shift keying; phase modulation; 12.5 kHz; GMSK; LMR channels; air interface; base station; binary digital FM; cell border; cellular system; data rates; default transmission mode; dual rate mobile data system; land mobile radio; mobile terminal; multilevel CPM; multilevel signalling; performance; radio conditions; stationary terminal; Application software; Base stations; Bit rate; Data systems; Digital signal processing; Frequency modulation; Land mobile radio; Modems; RF signals; Switches;
Conference_Titel :
Personal, Indoor and Mobile Radio Communications, 1992. Proceedings, PIMRC '92., Third IEEE International Symposium on
Conference_Location :
Boston, MA
Print_ISBN :
0-7803-0841-7
DOI :
10.1109/PIMRC.1992.279876
