Mr. Winn, maybe you can work with this information that corrects some numbers that I gave on Globalstar capacity yesterday. I perhaps gave the numbers too quickly, but I am now correcting them just as quickly I hope. Here is the reply.
"Each Globalstar LEO has 2800 voice circuits, which multiplied by 48 LEOs gives you a raw capacity number of 134,000, as you call them, 'simultaneous' calls. 134,000 voice circuits can be operated simultaneously. That information is in the public domaign. However, this number is a 'raw number', and probably not good guidance as to the overall capacity as to how many users at any one time can be 'on' the Globalstar system. (1) You need to know if one beam covers only a city. If it does, capacity numbers are already skewed. (2) You need to know frequency re-use capacity on each beam [Globalstar uses a mix of FDMA and channelized CDMA. Being a pure "bent-pipe" system, its 16 spot beams form a Beam Forming Network. Each antenna on the LEO amplifies the uplink signal. Each beam has 13 channels (sub bands). Each of the channels has 128 codes for spread spectrum.] (3) You need to know switching capacity of each gateway, where the gateway is, how many LEOs see the customer at any given time. (4) 'Path diversity' gives Globalstar a capacity to have two-three LEOs see one customer at any given moment, and here you need to know if one LEO, two LEOs, are going to route his call to the gateway to see how many customers in that footprint the system will process through for a call. In other words, 2800 calls 'in the abstract' can be handled by a LEO's footprint-- but this number is actually uninformative given the nature of path diversity and frequency re-use protocols. (5) How many voice circuits are operated at any given interval (any given 'atomic time interval') is also a calculation to consider.
These are just a few of the variables to consider, but I think these are the major ones.
So, your number of 66,000 'simultaneous' calls is somewhat understated as to the total number of individuals who at any one time can be using the Globalstar system worldwide. This is the best guidance I can give you, and I am thinking that models of user base activity that Wall Street cites would be only a small guide to what Globalstar actual capacity going forward looks like. I say that, of course, as a matter of conjecture. I cannot give you any firm number on overall capacity for Globalstar at any given moment in time, but I think these considerations above give you an idea of how difficult it is to give any real number. As the system functions out the capacity issue will become clearer." |
