ENABLING “SOFT” TECHNOLOGIES ALPHABET SOUP Thirty seconds into a review of communication product specifications one encounters a babble of vee-dot (V.) versus MNP variations, and mysterious acronyms such as EC2, ETC, and TX-CEL. It is unwise to dismiss this sometimes unintelligible gibberish as an unimportant attempt to break/protect vendor proprietary interests. These alphabetic designators are often surrogates for key communication developments required for the success of wireless data. This chapter is a simplified look at some nonhardware technologies, protocols, and communication standards that drive both network and device development. The focus is on modulation techniques, error detection/correction, and data compression. . | The Wireless Data Haadbaak Fourth Edition. James F. DeRose Copyright 1999 John Wiley Sons Inc. ISBNs 0-471-31651-2 Hardback 0-471-22458-8 Electronic 15 ENABLING SOFT TECHNOLOGIES ALPHABET SOUP Thirty seconds into a review of communication product specifications one encounters a babble of vee-dot V. versus MNP variations and mysterious acronyms such as EC2 ETC and TX-CEL. It is unwise to dismiss this sometimes unintelligible gibberish as an unimportant attempt to break protect vendor proprietary interests. These alphabetic designators are often surrogates for key communication developments required for the success of wireless data. This chapter is a simplified look at some nonhardware technologies protocols and communication standards that drive both network and device development. The focus is on modulation techniques error detection correction and data compression. MODULATION Circuit Switched The modems initially used to transmit data via analog cellular channels were conventional dial-up wireline devices with CCITT-standardized V series modulation techniques. The most common are listed in Table 15-1. The user either could plug these modems into a cellular phone with adapter or use landlines via the usual wall phone jacks. A useful characteristic for cellular was under adverse conditions the 27 implementations dropped to half speed. They actually worked well but connected slowly and transmitted data oh-so-slowly. 247 248 ENABLING SOFT TECHNOLOGIES Table 15-1 Early wireline modulation techniques CCITT No. User bps HDX FDX Modulation Technique 300 Both Frequency shift 1 200 FDX Phase shift key PSK 2 400 FDX Quadrature amplitude 2 400 HDX Differential quadrature 4 800 HDX Differential 8-PSK Between 1976 and 1982 IBM s Gottfried Ungerboeck developed the theory and received the patent 1 on what is now known as trellis-coded modulation TCM . Briefly TCM introduces redundancy in the information bits to be .
