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Unformatted text preview: EE 359  Wireless Communications  Winter 2008 Midterm 1. Wireless Channels [30 Points] Consider a wideband channel characterized by the autocorrelation function A c ( τ, Δ t ) = sinc( W Δ t ) 1 ¯ T m e τ ¯ Tm , τ ≥ where W = 50 Hz and ¯ T m = 20 microseconds. (a) [4 points] Does the channel correspond to an indoor or an outdoor channel? Why? (b) [4 points] Is the fading distribution for this channel closer to Rayleigh or to Rician? (c) [6 points] For 8PSK modulation at a data rate of 50 Kbps sent over the channel, what is the appropriate performance metric for this system and why? What about for a sensor network with BPSK modulation and a data rate of 5 bps? (d) [6 points] For BPSK modulation at a data rate of 500 Kbps sent over the channel, what is the irreducible error floor due to ISI? How about a Doppler floor? (e) [10 points] Suppose you have a different channel from the wideband channel given above. This channel has shadowing plus Rayleigh fading. The distribution of the shadowing at the receiver is uniformly distributed between 0 and 2 ¯ ¯ γ (in linear units). What should ¯ ¯ γ be such that the outage probability for DPSK modulation with an average error probabability of 10 3 is 10%. 2. How to be a billionaire: a day in the life of a startup [40 points] This problem illustrates tradeoffs in different types of fixed rate modulation, and that fixedrate mod ulation with outage can come fairly close to channel capacity. This is significant since the fixedrate modulation is easy to implement and requires no coding, which are both desirable from an implemen...
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This note was uploaded on 08/05/2008 for the course EE 359 taught by Professor Goldsmith during the Spring '08 term at Stanford.
 Spring '08
 Goldsmith

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