CDMA Reaches New Heights
By Doug Dwyre
Global Mobile Personal Communications Systems will soon offer remote subscribers connection into terrestrial networks by relaying signals through one or more satellites. One of the companies planning to offer this service is Globalstar, whose President, Doug Dwyre, explains the companys approach to the market and the role played in its service by CDMA technology.
CDMAS: What point will the project have reached by the end of the year?
Doug Dwyre: On December 4 our launch window opens. Well be launching the first four satellites in December from Cape Canaveral and the next four in late February. Then we move to Kazakhstan where we start launching on heavy lifters on a Ukrainian and Russian launcher; that launches twelve at a time. By late 98 we will have enough satellites to start a preliminary operation because well have some overlapping coverage. Path diversity is a powerful feature that comes through CDMA and particularly through the proprietary technology developed by Qualcomm. This is what brought Loral and Qualcomm together almost seven years ago.
CDMAS: Did you have in mind a CDMA operation then?
Doug Dwyre: Yes, from the beginning. It was by far the most powerful technique for this fom of satellite communication.
CDMAS: What are the similarities and differences between your system and IS-95?
Doug Dwyre:Well the similarities are probably greater than the differences. Its using the same 1.25 MHz channelisation and so allows a lot of the infrastructure development of Qualcomm to be used in our gateways and a great deal of similarity between the user terminals. We are able then to make multi-mode user terminals that can operate in AMPS, in the IS-95 mode and in the Globalstar mode. The chief differences are due to the satellite motion so that you obviously have much wider Doppler Shifts and you have a variation in range which is greater in an absolute sense but in a relevant sense much less. You dont have nearly the power change of 64dB that you have for terrestrial ours is more like 20dB. There are some more forgiving aspects compared to IS-95 terrestrial. These are essentially just variants on the now proven recipe for IS-95.
CDMAS: So it had been planned to go ahead with this long before Qualcomm made its own decision to go ahead in the terrestrial market?
Doug Dwyre: What we were looking for at the time we first joined up with Qualcomm was their design and their technology contributions. By the time we signed the operating agreement the same time as we signed the founding service provider agreements, in 94 they had already made their commitment to go into the hardware business with Sony and they had already made an investment decision on what they call the commercial base station, the CBS.
CDMAS: Although youre offering a CDMA satellite technology, there will still be IS-95/Globalstar handsets on the ground.
Doug Dwyre: There will be multi-mode handsets. The two principal ones will be a dual-mode GSM/Globalstar that Ericsson and Telital are building and a tri-mode AMPS, IS-95 and Globalstar. D-AMPS and some of the others will come out soon after, depending on the market. But you can imagine with the proliferation of standards that already exists in the terrestrial world you could start permutations and have 20 or 30 different types of handset!
CDMAS: And what about the market for Globalstar-only phones?
Doug Dwyre: We see a large market in the extractive industries, people doing surveys, forestry, public service, fire-fighting, this kind of thing; theyll probably be Globalstar-only. Compared to setting up any other type of communications network it should be the cheapest and the easiest.
CDMAS: The paper you gave in Singapore was fairly generous to the other satellite companies. You argued that there was room for four systems or even five.
Doug Dwyre: First of all you have to look at the spectrum
availability. Then you have to look at whether the market is big enough
to support them, and finally you have to look at the capitalization.
There are only two that are fully capitalized: Iridium and Globalstar.
I dont doubt that ICO will be capitalized. Whether anybody else
will be is a big question which others in the investment community are
better qualified to answer than I am. As far as capacity goes, we believe
that each of us is going to be limited by the bandwidth thats
allocated and conditions are being placed upon it by interference criteria
I think theres going to be certainly going to be three systems
thatll run a service. Beyond that Im not sure how many more.
Doug Dwyre: We hope to continue operating in the presently allocated bands so that we do not orphan our current users. As for the next generation, should we get one of the adjacent bands the two GHz bands that are up for grabs both in the US and in the EU we would then probably have to have multi-band operation in a second and third generation Globalstar terminal to handle more than one band.
CDMAS: So the first wave would mainly be voice and a few added services?
Doug Dwyre: We see voice as the predominant service. We do have data rates up to 9.6 which is not very impressive but itll handle a fax and itll handle your messaging services. Mostly itll be just a mobile office. It wont be traveling around with mainframes.
CDMAS: And does research into the CDMA side continue?
Doug Dwyre: Yes, but because of the nature of our partnership, thats predominantly Qualcomm. The marriage was between a space factory and a communications factory. Recognizing that, unlike Motorola, which was the obvious competition at the time, neither one of us were household names in mobile communications, weve concentrated on drawing our strategic partners from the service providers with operating experience. Most appealing to us were those that had international operations France Telecom, Vodafone, AirTouch. Whats happened is that, through their current operations in terrestrial mobile, we have 106 territories and theyre assigned, with commercial arrangements made. And in a number of other areas we have operating licenses from the national authorities.
What weve built upon is the capabilities of our strategic partners and some of the founding partners along with Loral and Qualcomm. Many times there is an equipment and service joint venture like France Telecom and Alcatel where Alcatel are responsible for the communications payload on the satellites and also for the radio frequency transmitters and the gateways; this type of duality is one that we were looking for. What we put the highest premium on was not the investment dollars so much as operating experience and the local influence, the understanding that they had. That then leads to these arrangements in 106 nations which are, we think, informed arrangements. Thats the most important thing to us; we dont think theres much risk on the technological side of things given that in the past you may vary 1dB against 1.5dB depending on the type of usage, which we cant be sure of. When weve got 10dB power control, if everybody were at the high end of it youd obviously have much less capacity. But were not counting on perverse operators.
CDMAS: The basic architecture is quite simple. Was that deliberate policy from the start?
Doug Dwyre: We said: "We dont want our switchboard up in orbit. We dont need to replicate and compete with the existing international backhaul circuits. We want to use whats already there rather than reinvent it and reinvest in it." So we dont have onboard processing in the satellite and we dont have inter-satellite links. Of course, the price of that is that we have more gateways. It turns out that this is a tremendous advantage politically as most of the national authorities want to have their own gateway.
CDMAS: And as you said, the CDMA choice was a given from the outset.
Doug Dwyre: Yes, due to the capacity and the path diversity advantages that help to avoid blockage and fading.
CDMAS: And also in space you dont have to worry about obstacles...
Doug Dwyre: Well, you do because the service provider or the subscriber may be blocked and the frequencies we have are very close to the 1900 frequencies being used for PCS, so there is much more blockage at those higher frequencies than people had at 800 and 900 MHz.
CDMAS: And that will be overcome...
Doug Dwyre: Through path diversity. Or you can try to do it through sheer force. Thats what Iridium says they have 16dB margin. Itd be a lot better to have three satellites up there at different aspects so that at least one of them would be clear or combine the signals from these. You also have unfortunate effects like the picket fence effect. Say youre driving down the road in the French countryside with all those poplars standing there. If youve just had a rainstorm, the attenuation of a wet tree is rather high.
CDMAS: And the orbit?
Doug Dwyre: The orbit is a Walker orbit. A British scientist named Walker came up with the best coverage back in the late 40s when people were talking about satellites but Sputnik hadnt even gone up yet. This gives the best coverage if you dont want polar coverage. Well we didnt find much need for polar coverage so we put our inclination at 52 degrees; this gives us coverage up to about 70 degrees north and south latitude, and thats all we want.
CDMAS: Marketing and publicity will be next presumably?
Doug Dwyre: Yes, except we just want people to become aware that this will be offered. We have a coordinated marketing and advertising activity with our service providers where they have the interest of making a feature of their existing service. So we have co-branding kind of an "Intel inside" type of branding that says that, to the degree that Globalstar gives a certain cachet to AirTouchs advertising, they will be combined. But they will use their own distribution channels and their techniques that theyre comfortable with they dont want something that runs cross-grain with their current approach to the markets.
CDMAS: Cooperation and delegation?
Doug Dwyre: Yes. Delegation in the sense that they do best what they do best and we do what we do