Ravinder D. Koilpillai

Low complexity equalizers for US Digital Cellular System

Three low-complexity equalizer algorithms which meet all the US digital cellular (USDC) system performance specifications (IS-54) with a margin are presented. For the proposed equalizers, the BER performance results, under IS-54 stipulated multipath and fading conditions, including the effect of AWGN and cochannel interference, are provided. The effect of sample timing estimation, frequency offsets corrections, and practical IF filter distortion are included in the simulations. The results show that mobile radio equalizers, of fairly low complexity (<4 MIPS), that meet all the USDC performance specifications can be realized.<<ETX>>

Performance of a spectrally efficient modem for land-mobile radio

The spectral efficiency in land mobile radio (LMR) systems is limited by stringent adjacent-channel interference protection ratio (ACIPR) specifications of at least 60 dB. High spectral efficiency can be achieved using digital modulation techniques. Linear modulation schemes exhibit high spectral efficiencies but require linear power amplifiers. Power amplifiers typically used in LMR are nonlinear which degrade the ACIPR for conventional linear modulation schemes. The paper presents simulated performance results of a trellis-coded linear modulation scheme that is designed to be less sensitive to the nonlinearity exhibited by the power amplifier. Simulation results indicate that an ACIPR of 60 dB can be achieved. An E/sub b//N/sub 0/ of 14 dB is required to achieve a bit error rate of 3% with 3 users per 25 kHz channel, with an average data rate of 9.6 kbits/second/user.<<ETX>>