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in gsm we divide bandwidth in to time slots for better utilization of bandwidth.
it use cdma techniques as access mechanism . in cdma we allocate a unique code for every user separately and allocate bandwidth to user .
Another technical difference relates to the fact that GSM uses short time slots and hence each handset communicates in frequent short bursts. CDMA handsets on the other hand, communicate using much longer bursts.
GSM does not use spread spectrum codes and hence this form of precise time assistance is not intrinsically available in a GSM network. Therefore, in order to deliver precise time assistance (ie with uncertainties of 5 or 10 microseconds), GSM networks have to be augmented.
GSM technology has a limitation on its cell sizes of around 35km radius.
CDMA cell sizes, on the other hand, are only limited by transmission power and relevant standards (such as CDMA code phase search ranges). Hence they can be much larger. If the coarse location assistance is derived from the cell location then its uncertainty can be much larger in a CDMA system than in a GSM system.
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One difference between the two performance standards is that the handset must respond within 16 seconds in the CDMA case but has 20 seconds to respond in the GSM case.
However, in both cases the required sensitivity is -147dBm and the accuracy, although defined differently is similar at around 30m (horizontal).
the GSM standard allows for either precise time assistance or coarse time assistance. When only coarse time assistance is
provided the sensitivity test is conducted with one satellite at -142dBm. This is a recognition that there is a performance penalty for not providing precise time assistance.
the CDMA standard calls for the absolute codephase accuracy to be tested whereas the GSM standard calls for the location to be computed in accordance with a defined algorithm and for the accuracy of the result to be tested.
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