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Unformatted text preview: EE 359: Wireless Communications - Fall 2004 SECOND EXAM This exam is open book and notes, and calculators and your reader are needed. Graded exams and solutions will be available within the next week. Good luck! Problem 1 (35 points): MIMO Channels and Diversity/Multiplexing Tradeoffs. This problem illustrates diversity/multiplexing tradeoffs in a MIMO system with adaptive modulation. Consider a 2x2 MIMO system with channel gain matrix H that has the following SVD decomposition: H = " . 3 . 5 . 7 . 2 # = "- . 5946- . 8041- . 8041 . 5946 # " . 8713 . 3328 # "- . 8507 . 5757- . 5757- . 8507 # . Assume H is known at both the transmitter and receiver, and that there is a total transmit power of P = 10 mW across the two transmit antennas, AWGN with power N = 10- 9 W/Hz at each receive antenna, and bandwidth B = 100 KHz. (a) Find the capacity of this channel. (b) Assuming transmit precoding and receiver shaping is used to transform this channel into two parallel independent channels with a total power constraint P . Find the maximum data rate that can be transmitted over this parallel set assuming MQAM modulation on each channel with optimal power adaptation across the channels subject to power constraint P . Assume a target BER of 10- 3 on each channel, the BER is bounded by . 2 e- 1 . 5 / ( M- 1) , and the constellation size of the MQAM is unrestricted. (c) Suppose now that the antennas at the transmitter and receiver are all used for diversity with optimal weighting at the transmitter and receiver to maximize the SNR of the combiner output....
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