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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 fixed-rate mod- ulation with outage can come fairly close to channel capacity. This is significant since the fixed-rate 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