We will discuss these properties and more in the next chapter.
The Gaussian premodulation filter response is given below
(1.1)
with the following defined variable
(1.2)
Recall T is the bit time (3.69 sec 1/270.833 kbps), and B is the 3-dB bandwidth of the filter h(t).
This is usually defined together with the bit-time interval and given as BT 0.3.
'
2ln (2)
2p # BT
h(t)
expQt2
2'2T2R ' # T # !2p
The supported user data rates for full-rate mode are 13 and 12.2 kbps, and 5.6 kbps for the half
rate. We provide some GSM system design parameters in Table 1.2. Asimplified GSM architecture is
given in Fig. 1.8. Handheld devices called Mobile Stations (MS) communicate with Base Station
Transceiver Station (BTS). The BTS performs the modulation/demodulation (modem) functionality, provides
synchronization signals (time and frequency), frequency hopping, and performs measurements.
6 CHAPTER ONE
TABLE 1.2 An Overview of Some GSM System Parameters
System parameters Values
Channel BW 200 kHz
Modulation scheme GMSK
Channel bit rate 270.833 kbps
LPF Gaussian BT 0.3
Forward error correction Convolutional coding
Raw data rate 13 kbps
Voice frame length 4.615 msec
Interleaving depth 40 msec
Users/Channel 8
Spectral efficiency 1.
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