TDMA can operate as wideband or narrowband. In the wideband TDMA, the entire spectrum is used by each individual user. For the wideband TDMA, multiple access spectral efficiency is given as:
where:
τ = duration of a time slot that carries data
Tf = frame duration
Mt = number of time slots per frame
In Equation 6.4 it is assumed that the total available bandwidth is shared by all users. For the narrowband TDMA schemes, the total band is divided into a number of sub-bands, each using the TDMA technique. For the narrowband TDMA system, frequency domain efficiency is not unity as the individual user channel does not use the whole frequency band available to the system. The multiple access spectral efficiency of the narrowband TDMA system is given as:
where:
Bu = bandwidth of an individual user during his or her time slot
Nu = number of users sharing the same time slot in the system, but having access to different frequency sub-bands
ETDMA
means
Extended Time Division Multiple Access
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