72 CLTD system level block diagram.
2 This architecture is called multiple-input-single-output (MISO).
implies equal amplitude weighting across both antennas; however, the second weight is a complex
number and can have phase variations. Let us first present the solution and next we will derive it. The
solution is given as
and (5.152)
Assume the received signal is
(5.153)
After applying the transmit weights presented above the received signal is equal to the following:
(5.154)
(5.155)
(5.156)
Here the flat fading, channel responses are and ; they were calculated in the
channel estimation algorithm in the receiver.
The BTS antenna weights are chosen to maximize the UE??™s received signal power, P. Assuming
an L path channel model we have the following equation that needs to be maximized.
(5.157)
where
; ; (5.158)
Let us first consider a frequency flat fading channel as the UE would then need to calculate w1 and
w2 such that the following power is maximized (L 1).
(5.159)
(5.160)
After some simple manipulations we come to the final equation shown below for the power of the UE
received signal.
(5.161)
This is maximized when . Since w2 is quantized, the UE can either use the above solution
or exhaustively try all the possible options for w2 into the power equation and then choose the one that
maximizes the received signal power.
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