Jose, if you are referring to me I'm not saying that theoretically it is correct to use as much bandwidth as possible. This is a conclusion you have drawn on your own.
Using a 100 kHz bandwith to communicate information at a rate of 1 bit/s could by sure approach any channel capacity, but the spectral efficiency of such a communication channel would be quite questionable. Let this option to NASA deep space communications. What we need are modes which are both power AND bandwidth efficient. I think that the term "spread spectrum" here is misleading. What's the difference between a communication system which uses a FEC code with a very low rate, say R=0.01 (one information bit per one hundreds symbols), and a communication system which hops or spreads the modulating signal on an equivalent bandwidth? In my opinion: NONE. Both systems are using a bandwidth which is one hundreds time the bandwidth which would be used by an uncoded system. The problem is not whether a system is spread spectrum or not. The problem is how much it is bandwidth efficient. Everyone knows that an ortoghonal signalling system approaches the (AWGN) channel capacity. The legitimate question is if the whole 20 m band should be used to achieve such a result to communicate information at 3 bit/s. For what I know ROS has a really poor bandwidth efficience nor it copes with MUI (multiuser interference) issues. I do not doubt that it can achieve an exciting performance under the power efficiency point of view, but that's not all. We are called to develop systems which are efficient also in respect to bandwidth. The spread spectrum story is just a bad motivation used against true concerns. 73s Nico, IV3NWV --- In [email protected], "Jose A. Amador" <ama...@...> wrote: > > > I agree with Nino, theoretically it is correct to use as much bandwidth > as possible, 3 kHz in the ROS case, but due to the small spreading, the > ROS signal does not have a "negligble level" compared to others on the > channel, so it is a halfbreed, it has spread spectrum characteristics, > but does not quite behave like the "pure" definition. > > ROS still had problems in version 1.6.3 and it is easy to notice that it > works in a free channel, but does not stand burst errors (in fact, > errors long as a packet or pactor frame length) and its ability to copy > crumbles. That does not happen, at least so noticeably, with JT65 or Olivia. > > 73, > > Jose, CO2JA > > ----
