FRESH (frequency-shift) filtering prior to Viterbi demodulation in GSM basestations and/or handsets can theoretically completely suppress 1 cochannel interferer with one antenna, 3 interferers with a diversity antenna pair, and 2M-1 interferers with M antennas. It also can partially suppress larger numbers of interfering signals. Network-level simulations reported in this paper clearly demonstrate that FRESH filtering prior to demodulation in GSM basestations and/or handsets provides a cost-effective means of substantially improving system performance regardless of the antenna subsystem used, In all cases considered, single antenna, pair of diversity antennas, fully adaptive array of four antennas per 120degrees sector, and switched-beam array of four 30degrees antennas per 120degrees sector, FRESH filtering substantially reduces BER and FER (thereby improving quality) and/or reduces required SNR (thereby increasing range) and/or enables reduced frequency reuse factor (thereby increasing capacity).
