Since users will have their PC command time domain multiplexed under the same scrambling
code, downlink code usage can be dramatically reduced. On the uplink, supporting many E-DCH
users creates an increase in noise (noise rise). In order to combat this rise in interference the UEs can
either transmit with lower power or endorse some sort of DTX campaign (see Fig. 9.15). It is expected
that there are common scenarios when not all the users will be transmitting all the time. This implies
some users will transmit some of the time. In this case if we impose a restriction that the UE transmits
packets only when it has information to transmit, then uplink noise rise can be significantly
reduced [17]. When triggering the ???always on??? concept, the UE will be placed in the continuous
packet connected mode. What this means is that the UE will be capable to enter and exit this mode
depending on the particular service demand at that time instant.
3G AND BEYOND DISCUSSION 493
TABLE 9.3 Broadcasting System Comparison
System parameter MediaFLO DVB-H
FFT Size 4K 4K
Guard interval ratio 1/8 1/4, 1/8, 1/16, 1/32
Modulation QPSK, 16-QAM QPSK, 16-QAM, 64-QAM
Interactive capability Yes w/cellular system Yes w/cellular system
OFDM Yes Yes
Symbol duration 833.
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