A reconfigurable modem for increased network capacity and video, voice, and data transmission over GSM PCS
C. Brown, Kamilo Feher · IEEE Transactions on Circuits and Systems for Video Technology · 1996
A reconfigurable global mobile standard (GSM) compatible radio modem interface which doubles the number of simultaneous video and voice transmissions per channel is presented for personal communication systems (PCSs). The result is that an average video frame rate of up 14 frames per second (fps) can be supported within a single TDMA time slot, doubling the number of conventional GMSK multimedia transmissions per GSM channel. The design employs an in-circuit reconfigurable (ICR) cross-correlated Feher's (see Englewood Cliffs, NJ: Prentice-Hall, 1995). quadrature phase shift keyed (FQPSK) signal processing technique to support a data rate of 357.5 kb/s in a 200 kHz bandlimited GSM channel. This innovative new network modem is reconfigured in-circuit for high bit rate data transmission or voice operation that is compatible with existing GSM equipment. Spectrum efficiency /spl eta//sub f/ (b/s/Hz) is investigated in a nonlinear amplified (NLA) environment-providing a 6 to 9 dB advantage in power efficiency for increased battery life of hand-held terminals. Results show that RF power efficient nonlinear amplified spectrum efficiency is increased from 1.35 b/s/Hz to 1.85 b/s/Hz. Bit error rate (BER) performance is evaluated in a Gaussian and Rayleigh fading channel, and the merits of coherent demodulation in microcellular PCS are examined. Our results show that the GSM compatible configuration of a specific cross correlated FQPSK-KF implementation offers up to 2 dB improvement in E/sub b//N/sub 0/ over conventional GMSK BT/sub b/=0.3. The PCS network capacity /spl eta//sub T/ (Erlangs/Hz m/sup 2/) may be increased 37% over GMSK BT/sub b/=0.3.