Mightylakers, a pretty detailed defense of HDR. Whereas you claim no knowledge of MCDN you have much in-depth knowledge of HDR. This is a curious combination. Nonetheless, all you need consider in order to compare is the following:
For the data transmission intervals of interest, none of the 3G, HDR, or MCDN systems actually overlaps usage of the spectrum. That is, as you know, the HDR system doesn't use CDMA when transmitting the data signal, so only one user within the entire cellular footprint can use the spectral bandwidth in question. Similarly, although the MCOM system uses FHMA for channel access, with complicated collision avoidance/resolution methods, the end result is that only one user within the MICROCELLULAR footprints of a small set of microcells, is using the spectral bandwidth in question.
So, all other things being equal (and that assumes efficient allocation of spectrum), the comparison between the two systems turns entirely upon the factor of the relative size of the footprint. The microcellular architecture of Metricom's system allows for complete scalability, with minimal expense, allowing for maintenance of the average quoted throughput rates as the number of users accessing the system at one time grows (i.e., as the number of subscribers grows).
IF any cellular carrier were to deploy a microcellular architecture equivalent to Metricom's, then for a given spectral bandwidth, the systems would provide equivalent access.
I think you can readily see, however, given the great disparity between the density of cells for current cellular architectures (avg. radius 1-1.5 miles) versus the current Metricom MCDN deployment (avg. number of microcells per sq. mile from 5-6 for moderate density of users, to 50-60 for high-density citiy locations such as Manhattan), there is no way that current cellular architectures, no matter whether they deploy HDR or some 3G variant, could provide levels of user throughput offered by the current Metricom rollout. Again, we must assume similar spectral bandwidth. FYI, the MCOM system uses 26 MHz of bandwidth for the mobile user to microcell radio link (902-928 MHz ISM band).
It's simply a matter of efficient frequency reuse in a spatial sense. |
