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Unformatted text preview: EE455/ 591 EE455/ 591 Link Power Budget Link Power Budget Reading: Focus on these notes. Read section 7.7 Reading: Focus on these notes. Read section 7.7 Review: Viterbi Decoding and Example Review: Viterbi Decoding and Example Topics: Topics: 1. 1. Power Requirement for Modulation Power Requirement for Modulation 2. 2. Coding Gains using Error Correction Codes Coding Gains using Error Correction Codes 3. 3. Antenna Gains and Path Losses Antenna Gains and Path Losses 4. 4. Total Link Budget Total Link Budget Review: Viterbi Decoding I nput x: 1 1 Output y: 0 1 1 0 1 0 1 1 1 Received r: 0 1 0 1 0 1 1 Decoding: Observing r, what is the most likely x sent? Viterbi Algorithm (VA): Each state in time i has shortest path from s=00 at time i=0. Find the shorter among the two paths leading into the state The Main I dea of the Viterbi Algorithm • I nitialization (Start from state s=0 at i=0) Path starts from state s=0 with zero weight, if s 0 ∞ ≠ • Time iteration: (Merge the two paths into state s at time i) Update weight of two paths going into state s Choose path with smaller weight merging into s • Data decoding : (Backtrack from s=0, i=n to s=0, i=0) i=0 i=1 i=2 i=n-1 i=n s=0 W s =0 s=0 W s s=0 W s s=0 W s s=0 W s W p(s) w(y i ,y p(s)->s ) s 0 ≠ W s = ∞ W s’ The Main I dea of the Viterbi Algorithm • Start from state s=0 at i=0, end in s=0 at i=n Data length = n, including the flushing K-1 zeros • I nitialization (Path starts from state s=0) For all state s: Weight W s =0 if s=0, W s = if s 0 ∞ ≠ • Time iteration: For i=1 to n : (p(s) is the predecessor of s) For all state s: W s = min p(s) [W p(s) + w(y i ,y p(s)->s ) ] • Data decoding : Backtrack for sequence from s=0 at stage n i=0 i=1 i=2 i=n-1 i=n s=0 W s =0 s=0 W s s=0 W s s=0 W s s=0 W s W p(s) w(y i ,y p(s)->s ) s 0 ≠ W s = ∞ W s’ I nput x:...
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