CDMA Spread Spectrum in Communications Systems

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1 Muhaad Ali Jinnah University, Islaabad Capus, akistan in Counications Systes ORIGIAL SIGAL BI Lecturer: Assoc. rof. Dr oor M Khan Departent of Electronic Engineering, Muhaad Ali Jinnah University, Islaabad Capus, Islaabad, AKISTA h: +9 (5) , Ext. 47 Fax: +9 (5) 8743 eail: noor@ieee.org, noorkhan@jinnah.edu.pk SECTRUM SREADIG AWG MAI SIGAL SECTRUM DESREADIG SIGAL AWG BI MAI Week -; Spring - 03

2 Muhaad Ali Jinnah University, Islaabad Capus, akistan Spread Modulation Spread spectru odulation (SSM) uses signals which have a transission bandwidth that is several orders of agnitude greater than the iniu required RF bandwidth. A pseudo-noise () sequence converts a narrowband signal to a wideband noise-like signal before transission. SSM provides robust ultiple access capability and iunity against ulti-path interference. Week -; Spring - 03

3 Muhaad Ali Jinnah University, Islaabad Capus, akistan SS Modulation Bandwidth Efficiency SS odulation is not very bandwidth efficient when used by a single user only. When any users can share the sae spread spectru bandwidth without interfering with one another, spread spectru systes becoe bandwidth efficient in a ultiple user environent in a ultiple cell environent. Week -; Spring

4 Muhaad Ali Jinnah University, Islaabad Capus, akistan Types of Spread Direct Sequence Spread (DSSS) The carrier is odulated by a digital code Digital code chip rate is uch larger then the inforation signal bit rate Frequency Hopping Spread (FHSS) The carrier frequency is shifted in increents in a rando pattern generated by code sequence The FHSS could be fast FHSS or slow FHSS Tie Hopping Spread (THSS) Transission tie is divided into fraes and fraes are divided in tie slots. Signal transission takes place in a rando tie slot controlled by a rando code (THSS has liited application, so far ) Week -; Spring

5 Muhaad Ali Jinnah University, Islaabad Capus, akistan Frequency Hopped Multiple Access(FHMA) In FHMA the carrier frequencies of the individual users are varied in a pseudorando fashion within a wideband channel. The instantaneous bandwidth of any one transission burst is uch saller than the total spread bandwidth. At any given point in tie, a frequency hopped signal only occupies a single, relatively narrow channel. M( ω ) F(t) ( ω ) Fp(t) ω ω B B a Week -; Spring

6 Muhaad Ali Jinnah University, Islaabad Capus, akistan FH Classification Fast frequency hopping syste If the rate of change of the carrier frequency is greater than the sybol rate. Slow frequency hopping If the channel changes at a rate less than or equal to the sybol rate.. A frequency hopped syste provides a certain level of security. An intercepting receiver not knowing the sequence of frequency slots ust chase rapidly the signal it wishes to intercept. Week -; Spring

7 Muhaad Ali Jinnah University, Islaabad Capus, akistan DS SS Syste Model (t) Transitter p(t) (t) Message a(t) Spreading Code a(t) Channel n(t) p(t) Spreaded Signal n(t) AWG oise d(t) Receiver r(t) r(t) Received Signal d(t) Despread Signal a(t) r(t) (t) a(t) n(t) d(t) r(t) a(t) Week -; Spring

8 Muhaad Ali Jinnah University, Islaabad Capus, akistan DS SS Modulation in Tie and Frequency - - Tie Frequency Week -; Spring

9 Muhaad Ali Jinnah University, Islaabad Capus, akistan Spreading Code, a(t) roperties M( ω ) F (t) ) a(t) a(t) ω ) B a B B A( ω ) F a(t) ω d(t) r(t) a(t) d(t) (t)a(t)a(t) n(t)a(t) d(t) (t) n a (t) B a Week -; Spring

10 Muhaad Ali Jinnah University, Islaabad Capus, akistan of SS Signal M( ω ) F (t) ω p(t) (t)a(t) B A( ω ) F a(t) ω ( ω ) M( ω ) A( since B a B ω ) ( ω ) F p(t) B a B B a ω Bp B a B G = B a Week -; Spring

11 Muhaad Ali Jinnah University, Islaabad Capus, akistan Spread Syste Before Spreading After Spreading After Despreading M( ω ) B ( ω ) M( ω ) B - signalpower B B a 0 kt ω ω ω SR a(t) σ 0B B G= B Spread a Gσ SRo σ Week -; Spring - 03

12 Muhaad Ali Jinnah University, Islaabad Capus, akistan Hiding Signal in oise ( ω ) AWG 0 kt D( ω ) Before despreading AWG B After despreading LI Low robability of Interception Week -; Spring - 03

13 Muhaad Ali Jinnah University, Islaabad Capus, akistan Two Signals in oise r(t) (t)a (t) (t)a (t) n(t) d(t) r(t)a (t) d(t) (t)a (t)a (t) p(t)a (t) n(t)a (t) d(t) (t) p(t)a (t) n(t)a (t) Signal Interference oise We want to find output SR o to evaluate the erforance, i.e. the BER Week -; Spring

14 Muhaad Ali Jinnah University, Islaabad Capus, akistan Two SS Signals M ( ) M ( ) B ( ) ( ) B 0 k T M ~ ( ) Signal Interference B a AWG 0 k T B B Week -; Spring - 03 a B a 4

15 Muhaad Ali Jinnah University, Islaabad Capus, akistan Output Signal to oise Ratio Signal power - oise Effective Total power noise interference power SR power o σ G SR SR G σ G σ G Week -; Spring

16 Muhaad Ali Jinnah University, Islaabad Capus, akistan k Signals in oise r(t) (t)a (t) (t)a (t) k(t)a k(t) n(t) d(t) r(t)a (t) d(t) (t)a (t)a (t) p(t)a (t) pk(t)a (t) n(t)a (t) d(t) (t) p(t)a(t) pk(t)a (t) n(t)a(t) Signal Interference oise Again we want to find output SR o ; -> BER Week -; Spring

17 Muhaad Ali Jinnah University, Islaabad Capus, akistan K SS Signals M ( ω ) ω ( M ω ) ω M k ( ω ) ω B (ω) B (ω) k (ω) B 0 k T ω ~ M ( ω ) Signal Interference B a AWG 0 k T ω B B Week -; Spring - 03 a B a 7

18 Muhaad Ali Jinnah University, Islaabad Capus, akistan Output Signal to oise Ratio Signal power - oise power Effective interference power Total noise power σ (k -) G (k -) σ G SR o σ (k -) G SR (k -) SR G Week -; Spring

19 Muhaad Ali Jinnah University, Islaabad Capus, akistan High SR SR o σ (k -) G SR (k -) SR G SR o k k - G k - G SR o Week -; Spring

20 Muhaad Ali Jinnah University, Islaabad Capus, akistan CDMA Frequency Reuse Reuse Factor =/7 Reuse Factor = FDMA/TDMA B CDMA G C A G F B E C D B A G C F D A E F D E Week -; Spring

21 Muhaad Ali Jinnah University, Islaabad Capus, akistan Overview of Adaptive CDMA Multi-user Detection ORIGIAL SIGAL BI SECTRUM SREADIG AWG MAI SIGAL SIGAL BS SECTRUM DESREADIG AWG BI MAI Week -; Spring - 03

22 Muhaad Ali Jinnah University, Islaabad Capus, akistan Technical challenges Is the obile Internet possible in the sae for as the wire-line Internet? Does the existing CDMA-based 3G obile counication infrastructure support increased capacity deand of the future obile Internet? If not, how it can be fixed? Does Adaptive Multi-user Detection help to solve any of the entioned questions? Week -; Spring - 03

23 Muhaad Ali Jinnah University, Islaabad Capus, akistan Convergence of Applications Old but Still Existing Services: Radio, TV, Telephone, VCR, CD, G/G Cellular; Very LIMITED choice, Capacity Req: << Mbps/user Dedicated Hardware. Current Services: CD/DVD, WiFi, cable TV, Satellite hone, 3G Cellular, Wireless Broadband Internet Access, ersonal Video; Large but still LIMITED choice, Capacity Req: = Mbps/user Soewhat converged but still Dedicated Hardware. Future Services: Wireless Broadband, Gaes, I Library, ITV, ersonal Video, 4G Unliited choice Capacity Req: >> Mbps/user Internet software terinal, Software Defined Radio (SDR) Week -; Spring

24 Muhaad Ali Jinnah University, Islaabad Capus, akistan Wireless Cellular Mobile Syste MSC ST Week -; Spring

25 Muhaad Ali Jinnah University, Islaabad Capus, akistan Migration ath to 4G Mobile Co. Systes First Major Migration ath (Europe ) I Gen, 80 s, ETACS (C-450,MT-450..),(FDMA), Analog II Gen, 90 s, GSM, GRS, EDGE, (TDMA) Digital III Gen, 00 s, W-CDMA, (CDMA), All Digital Second Major Migration ath (USA) I Gen, 80 s, AMS, (FDMA), Analog II Gen, 90 s, IS-54 (TDMA), IS-95 (CDMA), Digital III Gen, 00 s, CDMA000 (CDMA), All Digital Universal 3G Migration ath (USA, Europe and Asia) IV Gen, 0 s, HSA+-A, EVDO-A, x-a (CDMA), All Digital IV Gen, 0 s, LTE-A, WiMAX-MA (OFDM), All Digital Week -; Spring

26 Inforation Bit Rate, Mb/s Muhaad Ali Jinnah University, Islaabad Capus, akistan Wired Terinal Mobile etwork Capacity 00 0 WLA & WiMAX MBS 60GHz This is where we want to be for 4G.0 0. Cordless 3G Cellular G Cellular and CS Office Building Stationary Walking Vehicle Indoors Outdoors MOBILITY Week -; Spring

27 Muhaad Ali Jinnah University, Islaabad Capus, akistan Week -; Spring

28 Muhaad Ali Jinnah University, Islaabad Capus, akistan Counication Channel Capacity Counication Channel Resources are: T - Tie B - Bandwidth - Signal to oise Ratio σ S I I = T B S T B S Week -; Spring - 03 σ log Aount of inforation (nuber of bits) transitted/received, with arbitrarily sall probability of error (Shannon 948) C σ B log 8

29 Muhaad Ali Jinnah University, Islaabad Capus, akistan Multiple Access S T S T S T FDMA AMS B TDMA GSM B CDMA IS-95 B S I T B Week -; Spring

30 Muhaad Ali Jinnah University, Islaabad Capus, akistan CDMA a Case of DMA Multi-user channel with with bit rates R satisfiesr R log C. y x x andsingleusercapacity C log ; R log n R R log log Week -; Spring

31 Muhaad Ali Jinnah University, Islaabad Capus, akistan 3 Week -; Spring - 03 Users Multi-user Channel log R R log C log (ab) log log b a log b a b b a log used identities

32 Muhaad Ali Jinnah University, Islaabad Capus, akistan Users Multi-user Channel The sae applies for channel y x x... x n With power liitation And data rates R R R log log log... Week -; Spring - 03 ; - - ; C R R R.... 3

33 Muhaad Ali Jinnah University, Islaabad Capus, akistan 33 Week -; Spring - 03 Users Multi-user Channel ; log log log C R R R C log C log C log C n x x x y n x y log C

34 Muhaad Ali Jinnah University, Islaabad Capus, akistan Multi-user Channel The previous result requires involveent of powerful coding techniques and interference cancellation In reality channel coding is part of every current digital obile counication standards Interference cancellation/suppression is still a hot research topic In order to ipleent power division ultiple access (DMA) concept in current practice we rely on the spread spectru technique such as code division ultiple access (CDMA) Week -; Spring

35 Muhaad Ali Jinnah University, Islaabad Capus, akistan Why CDMA? Advantages of CDMA (IS-95, CDMA000, WCDMA) Digital Syste (extensive use of digital algoriths) Voice activity factor (flexible use of channel resources) Frequency reuse factor (All cells on the sae frequency) Fading resistant (wideband syste, RAKE diversity) Liitations of CDMA (IS-95, CDMA000, WCDMA) ear-far effect ecessity of strict user power control Week -; Spring

36 Muhaad Ali Jinnah University, Islaabad Capus, akistan CDMA Syste Model x Transitter y=sx+n y Receiver ^ x s s x Transitter S y Receiver ^ x s + s x K Transitter K s K AWG y Receiver K s K ^ x K Week -; Spring

37 Muhaad Ali Jinnah University, Islaabad Capus, akistan Multi-user Receivers Classification Multi-user Detectors Adaptive Multi-user Detectors Optiality criterion Source of Sufficient Statistics Type of detector Short ae Ref. Source of Sufficient Statistics Type of detecto r Short ae Ref. ML; BER MF Single user liiter ML; ZF MF Decorelator R - MMSE MF Sybol MMSE (R+ I) - MF MF- DEC MF- MMSE ZF; MMSE MF DFE MF- CDEC ML MF ML MF- ML ursley77 ursley8 Schneider80 Lupas89 Xie90 Madhow94 Duel-Hallen A-MMSE Single user liiter A-MMSE DFE MMSE- DFE DFE MMSE Rapajiic 9-94 Miller95 MMSE- CDFE Verdu86 A-MMSE ML MMSE- ML Abdulrahan9-94 ; Woodward000 ; Rapajiic 94 Rapajiic 99 Borah00 Week -; Spring

CDMA Spread Spectrum in Communications Systems

CDMA Spread Spectrum in Communications Systems in Communications Systems ORIGINAL SIGNAL NBI Lecturer: Assoc. rof. Dr Noor M Khan Department of Electronic Engineering, Muhammad Ali Jinnah University, Islamabad Campus, Islamabad, AKISTAN h: +9 (5) -878787,