Influence of single frequency network transmission on the physical layer of a multi carrier modulation system

摘要

The application requirements and existing experience in the PLC market show that it is necessary to cover large areas or long distances. In these kinds of PLC networks repeaters are necessary. A single frequency network, however, allows a very simple repeater concept, e.g.: all participants who have correctly received a packet from the master retransmit this packet at the same time, i.e. in the next time slot, which is reserved for the repetition, on the same medium and the same frequency. iAd has already presented a paper on this item at the ISPLC 2002(G. Bumiller, 2002) . The new paper now analyses the influence of transmission in a single frequency network on the physical layer of a multi carrier system. Several transmitters at various locations transmit identical information on the same medium and the same frequencies at the same time. The receivers see the superposition of the signals. In the first paper we showed, that it is possible to understand this superposition in the same way as multi path propagation and the bandwidth of the system has to be broad enough to overcome the notches of the transfer function on certain frequencies. Yet, in some cases it is not possible to meet this requirement. Furthermore, there are additional effects on the physical layer if phase and frequency of transmitters differ. These effects depend on each other and will be analysed. Due to these effects, the frequencies of the notches in the transfer function change over time. The paper discusses possibilities to use these effects for systems with smaller bandwidth. Here, the repetitions allow other concepts than used by broadcast systems.