Investigation of data transmission over an adaptive delta modulated voice channel by simulations using a spreadsheet program

摘要

This paper presents voice and data transmission simulations of the tactical telecommunication network. Recommendations and measurements show that adaptive delta modulation (ADM) is suitable only to low frequencies 0...2600 Hz if the sample frequency is 16 kHz. The measurements have demonstrated the present performance of analogue data transmission over ADM-channel. A large number of message transmission systems with frequency shift keying (FSK) modems are used on voice grade circuits. Also standard PSK modems are in critical use. These message or data transmissions are the basis for the proper operation of weapons and intelligence systems in the tactical networks. Thus it is important to investigate data transmission over tactical network. To find optimum waveforms for the ADM-channel and quantitative measures of the delta modulation parameters a special simulator was built using a worksheet program. We investigate (1) the effect of different ADM-parameters on quality of service (QOS) of the channel: step size, adaptation memory, and sample rate (2) the effect of some information waveforms on BER vs. S/N and thus (3) the selection of data modulation method to give best BER values for the available bandwidth of the ADM-channel. Thus we consider some combinations of amplitude, frequency, and phase modulation, symbol (modulation) rates, and bit rates. We develop optimum waveforms especially MFSK-coding by simulations using BER-values as QOS. We find that new non-standard waveforms have much better BER values in the ADM-channel than standard ITU-modems. Thus we could use seamless data transmissions through different analogue or digital telecommunication network with these new analogue waveforms.