155.52 Mb/s data transmission on category 5 cable plant

EMI/EMC is a dominant problem encountered in high bit-rate transmission over unshielded twisted pair cable (UTP). This leads to a novel set of design tradeoffs between transceiver complexity (near term cost) and cable plant complexity (long term cost) for 155 Mb/s transmission on twisted pair cable which depends on the choice of line code. To understand the tradeoffs, the factors affecting RF emissions and susceptibility were examined in both installed cable plant and trellis configured cable plant models, which included both category 5 cable and interconnection hardware. In addition, the BER sensitivity to injected noise and pseudo-random data sequence length was measured for experimental 155 Mb/s links with 100 meters of category 5 cable using NRZ, MLT3, BPR1 and BPR4 line codes. A model for common-mode conversion in multi-pair UTP cables is presented. Radiated emissions occur in broad bands at 43, 53, 60, 70, and 80 MHz and show a positive correlation with the transmit signal spectrum. Termination of all propagating modes produced consistently lower radiated emissions than other standard cable termination procedures. For a given transmit level at 155 Mb/s, MLT3 has the lowest emissions between 30-50 MHz while BPR1 has the lowest emissions above 60 MHz. The emissions with MLT3 and BPR1 were 8-13 dB (10 dB typical) and 4-20 dB (13 dB typical) below NRZ levels, respectively. When the measured receiver penalty associated with three levels is included, MLT3, BPR1 and BPR4 still offer 5-15 dB better performance over NRZ at 155 Mb/s, although implementation complexity is greater as well.<
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