Two typical MCDD (multi-carrier demultiplexer/demodulator) architectures, M-MCD (multistage multicarrier demultiplexer) and PPF (polyphase FFT) suitable for multimedia service via the on-board processing (OBP) satellite, are analytically modeled and their error performances are numerically evaluated in the presence of five degrading factors including: narrow-band AWGN, carrier frequency offset, phase error, ISI and quantization error. Cumulative effects of these factors on the BERs of the two different MCDD structures are also assessed and compared for possible tradeoff under MF-TDMA (Multi-Frequency Time Division Multiplex Access) scheme using QPSK modulation. Results show that both architectures are commonly vulnerable to most degrading factors. However, combined effect of phase error with AWGN is more critical to M-MCD than PPF. In addition, PPF method proves to be more sensitive to quantization error than M-MCD. When all five degrading factors are considered, MCDD using PPF method exhibits better BER performance than that of M-MCD, especially when carrier phase error is significant.

Performance Analysis of MF-TDMA Multi-Carrier Demultiplexer/Demodulators (MCDDs) in the Presence of Critical Degrading Factors

Derivations of the chirp Fourier transforms that can be easily implemented with surface acoustic wave (SAW) devices are described. Two configurations-the multiply-convolve-multiply (MCM) and convolve-multiply-convolve (CMC)-are treated. The derivations show that one gives the Fourier transform precisely and the other is an approximation, although a good one under most circumstances. Numerical results for the CMC are given. The results show that windowing is an effective means of reducing the sidelobe level of the output transform, but it is at the expense of widening the main lobe. >

Performance analysis of a SAW-based group demultiplexer for on-board processing communications satellites

A description is presented of the chirp Fourier transforms which can be implemented with surface acoustic wave (SAW) devices. Two configurations, the multiply convolve multiply (MCM) and convolve multiply convolve (CMC), are treated. The derivations show that one gives the Fourier transform precisely, the other is an approximation, although a good one under most circumstances. Numerical results for the CMC are given. The results show that windowing is an effective means of reducing the sidelobe level of the output transform but at the expense of widening the main lobe. >

Performance analysis of a SAW based group demodulator for on-board processing communications satellites

In order to develop one of key technologies for personal satellite communications, a regenerative transponder has been developed for the Communications and Broadcasting Engineering Test Satellite (COMETS), allowing MM-wave and Ka-band mobile communications This regenerative MODEM receives eight-channel SCPC continuous or packet signals at a rate of 24 or 48 kb/s, transmits one TDM signal with BPSK modulation, and supports special functions such as storing calls in a buffer memory This technology allows an earth terminal with a 10-cm antenna and a 1-W power amplifier to transmit a 24 kb/s signal via COMETS in Ka-band

Regenerative transponder of COMETS for advanced mobile communications experiments

Performance of two MCD (multi-carrier demultiplexer/demodulator) architectures (M-MCDD and PPF) for the on-board processing (OBP) satellite are analytically modeled and numerically evaluated in the presence of five critical degrading factors: narrow-band AWGN, carrier frequency offset/phase offset, ISI and quantization error Cumulative effects of these factors on two different MCD structures are also assessed for comparison and tradeoff assuming MF-TDMA signal using QPSK Results show that both MCDs are commonly vulnerable to most degrading factors When all five degrading factors are considered, PPF method exhibits better BER performance than M-MCDD, especially when carrier phase offset is significant

On the performance of MF-TDMA multi-carrier demultiplexer/demodulators (MCDs) under five critical degrading factors

The authors describe a Monte Carlo simulation of QPSK (quadrature phase shift keying) and offset QPSK group modems which take into account the effect of the nonlinearity of each ground terminal HPA. The effect of uplink fading due to rain, as encountered in satellite links operated in the Ka and Ku bands, is included. Results show that a normalized channel spacing with respect to a symbol rate of 2.5 or greater is required to reduce the effect of adjacent channel interference. At this spacing the performance of the model will still incur a E/sub b//N/sub 0/ (energy per bit/noise density) degradation of about 1.0 dB. In addition, design criteria for major components such as digital subfilter, rate conversion filter, carrier recovery circuits, and quantization are given. >

M. Umehira

Papers

Performance estimation and design of group demodulator for satellite FDMA/TDM transmission