MBSFN : Multicast/Broadcast – Single Frequency Network.
Focus to e-UTRAN
Types of Logical and Transport channels available
Main Functions : Coding , Phy. Layer hybrid ARQ processing, modulation, multi antenna processing, mapping of signals to corresponding time-freq. resources
-. 1 resource grid per antenna.
Multi path intensity profile
-. Cross Correlation of AWGN is an impulse response. What is the meaning of this?-. Spaced freq. Correlation function is generated by cross correlating two carriers which are separated by Delta(f)-. Disadv. Of single carrier transmission??
-. Symbol periods are now longer compared to single carrier. but bits are txd parallel in order to achieve the desired data rate. -. As Ts is high ISI can completely be removed from the system.-. Depending on the channel condition each subcarrier can be modulated using different modulation schemes (QPSK, 16QAM, 64 QAM etc..)
-. Each OFDM symbol is a liner combination of instantaneous signals on each of the subcarriers in the channel.
Time Spreading (Freq. SelectiveFading) When an impulse is transmitted , how Power Delay Profiledoes the average power received by Mobilevary as a function of time delay ζ ? Freq. Selective Fading : Ts < ζ0 Non Freq. Selective Fading : Ts > ζ0
Power Delay Profile Spaced Freq. Correlation function FTInside Coherence BW channel passes all freq. components withequal gain and linear phase Freq. Selective Fading : W > f0 Non Freq. Selective Fading : W < f0
Symbol rate not increased in order to achieve high data rates. Instead of that Available BW breaks in to many narrower subcarriers and modulate generated symbols to these subcarriers. These subcarriers then combine linearly and transmit (OFDM symbol).
: Single Carrier Transmission1 0 1 1 : OFDM Transmission 0 1 t
Cyclic Prefix added to the beginning of the OFDM symbol in order to eliminate ISI ICI – Inter Carrier Interference has already been removed by selecting subcarriers with Ts > ζ0