ee359 lecture 19 outline n.
Download
Skip this Video
Download Presentation
EE359 – Lecture 19 Outline

Loading in 2 Seconds...

play fullscreen
1 / 11

EE359 – Lecture 19 Outline - PowerPoint PPT Presentation


  • 106 Views
  • Uploaded on

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

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about 'EE359 – Lecture 19 Outline' - wayne


Download Now An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
ee359 lecture 19 outline
EE359 – Lecture 19Outline
  • 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
  • Synchronization
  • RAKE Receivers
  • Multiuser Spread Spectrum
final exam announcements
Final Exam Announcements
    • Final Friday, 12/13, 12:15-3:15
    • Covers Chapters 9, 10, 12, 13.1-13.2 (+ earlier chps)
  • Similar format to MT, but longer: open book, notes.
  • Practice finals posted next week(10 bonus points)
    • Turn in to Pat or Mainakfor solns, by exam for bonus pts
    • Course summary Dec 6 12:30-2:05 here (pizza@noon)
    • Final review (Mainak) : Mon 12/9, 6 pm to 7 pm?
    • OHs next 3 weeks:
      • Me: next MTW by appt, 12/2 9-10am, 12/6 2-3pm, 12/9 by appt, 12/12 6:30-7:30pm (pls confirm), 12/13 9-10am, Skype
      • Mainak: Please respond to Piazza poll (see last slide)
review of last lecture fft implementation of ofdm

cos(2pfct)

cos(2pfct)

LPF

A/D

D/A

Serial

To

Parallel

Converter

x

x

+

Review of Last LectureFFT Implementation of OFDM

X0

x0

n(t)

TX

R bps

Add cyclic

prefix and

Parallel

To Serial

Convert

  • Design Issues
    • PAPR, frequency offset, fading, complexity
    • MIMO-OFDM
    • Pulse shaping

v

QAM

Modulator

IFFT

h(t)

+

Pulse

shaping

XN-1

xN-1

m=sTm/Tsamp

RX

Y0

y0

Remove

cyclic

prefix and

Serial to

Parallel

Convert

R bps

QAM

Modulator

Parallel

To Serial

Convert

FFT

yN-1

YN-1

Yi=HiXi+ni

review of last lecture intro to spread spectrum

Tc

Review of Last Lecture:Intro. to Spread Spectrum
  • 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(f)

s(t)

sc(t)

Sc(f)

S(f)*Sc(f)

1/Tb

1/Tc

Tb=KTc

isi and interference rejection

S(f)

I(f)

S(f)

S(f)*Sc(f)

I(f)*Sc(f)

Despread Signal

Receiver Input

Info. Signal

ISI and Interference Rejection
  • Narrowband Interference Rejection (1/K)
  • Multipath Rejection (Autocorrelation r(t))

aS(f)

S(f)*Sc(f)[ad(t)+b(t-t)]

S(f)

brS’(f)

Despread Signal

Receiver Input

Info. Signal

maximal linear codes

1

-Tc

Tc

-1

N

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

1

-Tc

Tc

-1

2n-1

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)

r(Dt)

Dt

rake receiver

x

x

x

RAKE Receiver
  • Multibranch receiver
    • Branches synchronized to different MP components
  • These components can be coherently combined
    • Use SC, MRC, or EGC

Demod

sc(t)

y(t)

^

dk

Diversity

Combiner

Demod

sc(t-iTc)

Demod

sc(t-NTc)

multiuser dsss
Multiuser DSSS
  • Each user assigned a unique spreading code; transmit simultaneously over same bandwidth
  • Interference between users mitigated by code cross correlation
  • In downlink, signal and interference have same received power
  • In uplink, “close” users drown out “far” users (a1>>a2: near-far problem)

a

a1

a2

a

main points
Main Points
  • Spread spectrum increases signal bandwidth above that required for information transmission
    • Benefits include ISI and interference rejection, multiuser technique
  • 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
proposed days times for mainak s ohs final review and discussion
Proposed days/times for Mainak’s OHs, final review, and discussion

Please respond to

Piazza poll on this

proposal

12/2 (8:30 am to 10:30 am): Discussion session for Homework 8 + Office hour (to replace Tuesday DH and Wednesday OH)

12/6 (11 am to 12 noon): OH (instead of Thursday OH)

12/9 (6 pm to 7 pm): Final review session

12/10 (7 pm to 8 pm): Extra

12/11 (7 pm to 8 pm): OH

12/12 (7 pm to 8 pm): OH