Multi-Carrier and Spread Spectrum Systems: From OFDM and MC ...

References 12510 010 −1SS-MC-MA, HT 150 km/hSS-MC-MA, BU 3 km/hOFDMA, HT 150 km/hOFDMA, BU 3 kmh10 −2BER10 −310 −410 −5 8 9 10 11 12 13 14 15 16 17 18 19 20 21E b /N 0 in dBFigure 3-14 BER versus SNR for SS-MC-MA and OFDMA with one-dimensional pilot symbolaided channel estimation in the uplink: R = 2/3; QPSK; fully loaded systemthat MC-CDMA outperforms OFDMA. The SNR gain with MC-CDMA compared toOFDMA strongly depends on the propagation scenario and code rate.Figure 3-14 shows the BER versus the SNR per bit of an SS-MC-MA system andan OFDMA system in the uplink. The number of sub-carriers is 256. Both systemsapply one-dimensional channel estimation which requires an overhead on pilot symbols of22.6 %. The channel code rate is 2/3. The SS-MC-MA system applies maximum likelihooddetection. The performance of SS-MC-MA can be further improved by applying softinterference cancellation in the receiver. The SS-MC-MA system outperforms OFDMAin the uplink, but it requires more complex receivers. The SS-MC-MA system and theOFDMA system would improve in performance by about 1 dB in the downlink due tothe reduced overhead with two-dimensional channel estimation.References[1] Bennett C. L. and Ross G. F., “Time-domain electromagnetics and its applications,” Proceedings IEEE,vol. 66, pp. 299–318, March 1978.[2] Chen Q., Sousa E. S., and Pasupathy S., “Multi-carrier CDMA with adaptive frequency hopping formobile radio systems,” IEEE Journal on Selected Areas in Communications, vol. 14, pp. 1852–1858,Dec. 1996.[3] ETSI DVB-RCT (TS 301 958), “Interaction channel for digital terrestrial television (RCT) incorporatingmultiple access OFDM,” Sophia Antipolis, France, March 2001.[4] ETSI HIPERMAN (TS 102 177), “High performance metropolitan area network, Part 1: physical layer,”Sophia Antipolis, France, 2004.