Hi! > I kicked the can down the road with Matt Ettus and Tom Rondeau. We have > spent two weeks on this total and others are welcome to contribute. We > need to have the argument: How do we specify the constellations? How do > we map carrier usage (which are pilots, clocks, etc.)?
To open a discussion on that topic, here is my first proposition: We create a generic OFDM mapper block. It should treat every occupied carrier as a proper channel. I think of something like: gr_make_io_signature (nchannels, nchannels, sizeof(unsigned char)) The input streams are unpacked bytes, containing 1 to 8 bits. In front of the mapper, connect several packed_to_unpacked blocks and some stream_to_streams. A parameter to the mapper block is a channel list that assigns a modulation type to every subchannel. The mapper's task is, in this model, to map chunks to symbols independently for each subchannel. Additionally, it periodically outputs known symbols that help synchronisation in the receiver(s). Maybe a new packed_to_unpacked block can be created that fulfills two tasks; to unpack and to split the input. I think of a block taking a packed byte stream as input and outputting several unpacked byte streams with different pack-sizes per output stream. In the receiver, we do the inverse thing. Information exchange transmitter <-> receiver could be done through a network (for a testing platform). By this, we can benefit of the OFDM's main advantage - to use the optimal modulation to every subchannel. In the background, there can be a control application that evaluates SNRs, receives them from the clients (for first try: through network) and assigns modulation etc. We can also insert pilot channels - simply connect a "pilot block" to a subchannel input. This may help on synchronization and channel estimation. And it allows a new use case: 1 to N transmission, with one transmitter and several receivers. This system will allow to evaluate new algorithms for subcarrier assignment, channel estimation, synchronization etc. Greetings, Dominik _______________________________________________ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
