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Under ideal conditions, the Globalstar satellite phone system had a very low drop rate which measured 2.6%. Under the same conditions, the Iridium system recorded a drop rate of 18.6%. The most dramatic difference of the two systems was the assessment of audio quality. It was noted that Globalstar audio quality was significantly superior to that of Iridium although audio quality of the call can be a subjective measure. A noticeable time log and the effects of degradation in the audio signal gave the Iridium calls a universally lower scoring in almost every instance. The receiver end had the most noticeable effect. The caller on the Iridium had a slurred voice which was known as the “Iridium drawl”. Iridium scored an average of 3.1 on a scale of 1 to 5 in ideal scenario. Iridium scores ranged from as low as 1 to as high as 4.
Compared to Iridium, conversations over the Globalstar telephone were rated superior. Some calls could even be described as approaching that of a good quality cellular phone call. Iridium never achieved cell phone quality in any of its ideal scenarios. This was defined by scoring 4.5 or better in a audio quality.
The second stage of the research was to undertake extensive testing of the handsets between the two satellite phones in significantly more challenging environments. The environments were urban and rural. This took the satellite phones to their limits in many ways. The testing was arranged so each satellite phone would be tested under conditions of increasingly severe degration. The urban testing measured the effect of the proverbial “urban canyon” and the rural testing brought in elements such as foliage and rugged landscapes.
The amount of call drops and unobtainable service was noted elevated when the physical interference with the signal was greater. The two systems performed as expected under these difficult situations.
Call completion rates were 77% for Iridium and 89% for Globalstar satellite phones, in the case of the urban environment. All in all, successful calls were made under situations with rather severe environments. |
