EE359 – Lecture 19 Outline Announcements Final Exam Announcements HW 8 (last HW) due Thursday 5pm (no late HWs) 10 bonus points for course evaluations online Projects due Dec. 6 at 5pm ISI/Inteference Rejection: Time-domain Analysis Spreading Codes and Maximal Linear Codes Synchronization RAKE Receivers

Final Exam Announcements Final 12/8/14 8:30am-11:30am in Thornton 102 Covers Chapters 9, 10, 12, (+ earlier chps) Similar format to MT, but longer: open book, notes. If you need a book or calculator, let us know by 12/3/14 Practice finals posted (10 bonus points) Turn in for solns, by exam for bonus pts Course summary and bonus lecture on advanced topics today, 4pm, here (pizza/cake/beer) Final review, Sat Dec. 6, 4-5pm, followed by TA OHs, place TDB (check course calendar).

OHs this week Mine Monday 12/1: 2:30-4pm Tuesday 12/2: 10-11:30am Saturday 12/6: 2:30-4pm TAs: Tues 12/2 : 4-6 pm, OHs+ disc, Milind, Y Wed 12/3: 5-7 pm, OHs, Milind, Pack 109 Thursday 12/4: pm, Mainak, Pack 340 Saturday 12/6: 4-6pm, Final Rev. + OH, Mainak, location TBD (check course calendar) Sunday 12/7: 2-3 pm, Milind, Pack 340

Review of Last Lecture: Design in OFDM, SS Intro Design in OFDM: PAPR, time/freq offset, fading across subcarriers, MIMO-OFDM Modulation that increases signal BW to combat narrowband interference and ISI Also used as a multiple access technique Two types: Frequency Hopping and DSSS FH: Hops info. signals over a wide bandwidth DSSS: modulates info signal by chip sequence s(t) s c (t) T b =KT c Tc Tc S(f) S c (f) 1/ T b 1/ T c S(f) * S c (f)

Review Cont’d ISI and Interference Rejection Narrowband Interference Rejection (1/K) Multipath Rejection (Autocorrelation  S(f) I(f) S(f) * S c (f) Info. Signal Receiver Input Despread Signal I(f) * S c (f) S(f)  S(f) S(f) * S c (f)[  (t)+  (t-  )] Info. Signal Receiver Input Despread Signal  S ’ (f) Today: We will derive the time-domain analysis for ISI and NB interference rejection

Maximal Linear Codes Autocorrelation determines ISI rejection Ideally equals delta function Maximal Linear Codes No DC component Large period (2 n -1)T c Linear autocorrelation Recorrelates every period Short code for acquisition, longer for transmission In SS receiver, autocorrelation taken over T b Poor cross correlation (bad for MAC) 1 N T c -T c

Synchronization Adjusts delay of s c (t-  ) to hit peak value of autocorrelation. Typically synchronize to LOS component Complicated by noise, interference, and MP Synchronization offset of  t leads to signal attenuation by  (  t) 1 2 n -1 T c -T c tt  t)

RAKE Receiver Multibranch receiver Branches synchronized to different MP components These components can be coherently combined Use SC, MRC, or EGC x x s c (t) s c (t-iT c ) x s c (t-NT c ) Demod y(t) Diversity Combiner dkdk ^

Main Points DSSS rejects ISI by code autocorrelation Maximal linear codes have good autocorrelation properties but poor cross correlation Synchronization depends on autocorrelation properties of spreading code. RAKE receivers combine energy of all MP Use same diversity combining techniques as before