Digital Cellular Systems


Chapter 4

[1]  Introduction
[2]  Global Systems for Mobile Communications (GSM)
[3]  Code Division Multiple Access

Introduction

In the last chapter we dealt with Analog Cellular systems, for reasons including better quality, greater flexibility and more efficient use of the medium, Analog systems have been surpassed by Digital systems. In table 1 below some digital cellular systems are mentioned along with there most important characteristics, from this list we are going to discuss :

"Global Systems for Mobile Communications - GSM" which has become the standard for Digital Cellular in Europe, and
"Code Division Multiple Access - CDMA" which is emerging as the de-facto wireless multiple access scheme.

	TDMA (IS-54/-136)	CDMA (IS-95)	GSM	DCS-1800	PDC
Transmit Band (MHz)	824 - 849	824 - 849	880 - 915	1710 - 1785	940 - 956 1477 - 1501 824 - 849
Receive Band (MHz)	869 - 894	869 - 894	925 - 960	1805 - 1880	810 -826 1429 - 1453 869 - 894
Multiple Access Method	TDMA/FDM	CDMA/FDM	TDMA/FDM	TDMA/FDM	TDMA/FDM
Duplex Method	FDD	FDD	FDD	FDD	FDD
Channel Spacing (KHz)	30	1250	200	200	25
Users per Channel	3	798	8	8	3
Number of Channels	832	20	124	374	1600
Channel Bit Rate(kbits/s)	48.6	1228.8	270.8	270.8	42
Modulation	¶/4 DQPSK	QPSK/OQPSK	GMSK	GMSK	¶/4 DQPSK
Voice coding	VSELP	QCELP	RPE-LTP	RPE-LPT	VSELP

Table 1: Digital Cellular Technologies

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Copyright � 1997 Derek Mc Donnell.
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Last updated 07-Apr-1998.