ee359 – lecture 19 outline
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EE359 – Lecture 19 Outline. Announcements Final Exam Announcements HW 8 (last HW) due Friday 5pm (no late HWs) 10 bonus points for course evaluations online Projects due Dec. 6 Direct Sequence Spread Spectrum ISI and Inteference Rejection Spreading Codes and Maximal Linear Codes - PowerPoint PPT PresentationTRANSCRIPT
EE359 – Lecture 19 Outline
AnnouncementsFinal Exam AnnouncementsHW 8 (last HW) due Thursday 5pm (no late
HWs)10 bonus points for course evaluations onlineProjects due Dec. 6 at 5pm
ISI/Inteference Rejection:Time-domain Analysis
Spreading Codes and Maximal Linear Codes
SynchronizationRAKE Receivers
Final Exam Announcements
Final 12/8/14 8:30am-11:30am in Thornton 102
Covers Chapters 9, 10, 12, 13.1-13.2 (+ 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: 2:30-4pmTuesday 12/2: 10-11:30amSaturday 12/6: 2:30-4pm
TAs: Tues 12/2 : 4-6 pm, OHs+ disc,
Milind, 380-380YWed 12/3: 5-7 pm, OHs, Milind, Pack
109 Thursday 12/4: 1.30-2.30 pm,
Mainak, Pack 340Saturday 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 ISIAlso used as a multiple access
techniqueTwo types: Frequency Hopping
and DSSSFH: Hops info. signals over a wide
bandwidthDSSS: modulates info signal by chip
sequence
s(t) sc(t)
Tb=KTc Tc
S(f)Sc(f)
1/Tb 1/Tc
S(f)*Sc(f)
Review Cont’dISI and Interference
RejectionNarrowband Interference
Rejection (1/K)
Multipath Rejection (Autocorrelation ( ))r t
S(f) S(f)I(f)S(f)*Sc(f)
Info. Signal Receiver Input Despread Signal
I(f)*Sc(f)
S(f) aS(f)S(f)*Sc(f)[ad(t)+b(t-t)]
Info. Signal Receiver Input Despread Signal
brS’(f)
Today: We will derive the time-domain analysis for ISI and NB interference rejection
Maximal Linear Codes
Autocorrelation determines ISI rejectionIdeally equals delta function
Maximal Linear CodesNo DC componentLarge period (2n-1)TcLinear autocorrelationRecorrelates every periodShort code for acquisition, longer for
transmissionIn SS receiver, autocorrelation taken
over TbPoor cross correlation (bad for MAC)
1
-1 N Tc -Tc
Synchronization
Adjusts delay of sc(t-t) to hit peak value of autocorrelation.Typically synchronize to LOS
component
Complicated by noise, interference, and MP
Synchronization offset of Dt leads to signal attenuation by r(Dt)
1
-12n-1 Tc -Tc
Dt(r Dt)
RAKE Receiver Multibranch receiver
Branches synchronized to different MP components
These components can be coherently combinedUse SC, MRC, or EGC
x
x
sc(t)
sc(t-iTc)
xsc(t-NTc)
Demod
Demod
Demod
y(t)
DiversityCombiner
dk^
Main Points
DSSS rejects ISI by code autocorrelationMaximal linear codes have good
autocorrelation properties but poor cross correlation
Synchronization depends on autocorrelation properties of spreading code.
RAKE receivers combine energy of all MPUse same diversity combining techniques as
before