2 nd Exam Announcements. EE359 Lecture 20 Outline. Synchronization. Review of Last Lecture. Main Points. RAKE Receiver

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1 EE359 Lecture 20 Outline Announcement Project due Friday at 5 pm (extend to Sunday 5pm). HW due Friday at 5. τβπ eval at end of cla (0 bonu poit), then pizza Mut be turned in no later than at exam. 2 nd Exam next Wedneday, 2/4, 9:30-:30, McCoull5 Review of Lat Lecture+Synch+RAKE Coure Summary EE359 Megatheme Wirele Network Hot Reearch Topic 2 nd Exam Announcement 2nd Exam next Wed., 2/4, 9:30-:30, MCCULL5, Local SCPD tudent take in cla, other contact Joice. Open book/note Cover Chapter 9,0,2,3 (and related prior tuff) Similar format to firt exam Practice final poted (0 bonu point) Exam review eion Sunday 6-7 room TBD Extra OH My OH: today 2:30-:30, Th 2-, next M 6-7 & by appt. Riteh: Sun 7-8, T 2-4. Review of Lat Lecture Synchronization Direct Sequence Spread Spectrum S(f) S(f)*S c (f) ISI rejection by code autocorrelation Maximal linear code Good propertie Long veru hort code I(f) Info. Signal Receiver Input Depread Signal S(f) S(f)*S c (f)[αδ(t)+β(t-τ)] S(f) αs(f) I(f)*S c (f) βρs (f) Info. Signal Receiver Input Depread Signal - N -T c T c Interference Rejection ISI Rejection NT c Adjut delay of c (t-τ) to hit peak value of autocorrelation. Typically ynchronize to LOS component Complicated by noie, interference, and MP Synchronization offet of t lead to ignal attenuation by ρ c ( t) RAKE Receiver Main Point Multibranch receiver Branche ynchronized to different MP component y(t) x c (t) x c (t-it c ) Demod Demod Diverity Combiner d^ k Synchronization alo depend on autocorrelation propertie of preading code. RAKE receiver combine energy of all MP Ue ame diverity combining technique a before x Demod c (t-nt c ) Thee component can be coherently combined Ue SC, MRC, or EGC

2 Wirele Viion Ubiquitou Communication Among People and Device Wirele Internet acce Nth generation Cellular Wirele Ad Hoc Network Senor Network Wirele Entertainment Smart Home/Space Automated Highway All thi and more Hard Delay Contraint Hard Energy Contraint Coure Summary Signal Propagation and Channel Model Modulation and Performance Metric Impact of Channel on Performance Fundamental Capacity Limit Flat Fading Mitigation Diverity Coding and Interleaving Adaptive Modulation ISI Mitigation Equalization Multicarrier Modulation Spread Spectrum Signal Propagation Statitical Multipath Model Path Lo Shadowing Multipath P r /P t d=vt d Random # of multipath component, each with varying amplitude, phae, doppler, and delay Narrowband channel Signal amplitude varie randomly (complex Gauian). 2 nd order tatitic (Beel function), Fade duration, etc. Wideband channel Characterized by channel cattering function (B c,b d ) Modulation Conideration Want high rate, high pectral efficiency, high power efficiency, robut to channel, cheap. Linear Modulation (MPAM,MPSK,MQAM) Information encoded in amplitude/phae More pectrally efficient than nonlinear Eaier to adapt. Iue: differential encoding, pule haping, bit mapping. Nonlinear modulation (FSK) Information encoded in frequency More robut to channel and amplifier nonlinearitie Linear Modulation in AWGN ML detection induce deciion region Example: 8PSK P depend on # of nearet neighbor Minimum ditance d min (depend on γ ) Approximate expreion P α Q M ( β γ ) M d min

3 Linear Modulation in Fading In fading γ and therefore P random Metric: outage, average P, combined outage and average. T Outage T P P(target) P P = P ( γ ) p( γ ) dγ Moment Generating Function Approach Simplifie average P calculation Ue alternate Q function repreentation P reduce to MGF of γ ditribution Cloed form or imple numerical calculation for general fading ditribution Fading greatly increae average P. Doppler Effect High doppler caue channel phae to decorrelate between ymbol Lead to an irreducible error floor for differential modulation Increaing power doe not reduce error Error floor depend on B d T Delay pread exceeding a ymbol time caue ISI (elf interference). 0 ISI Effect ISI lead to irreducible error floor Increaing ignal power increae ISI power ISI require that T >>T m (R <<B c ) Tm Capacity of Flat Fading Channel Four cae Nothing known Fading tatitic known Fade value known at receiver Fade value known at receiver and tranmitter Optimal Adaptation Vary rate and power relative to channel Optimal power adaptation i water-filling Exceed AWGN channel capacity at low SNR Suboptimal technique come cloe to capacity Variable-Rate Variable-Power MQAM Uncoded Data Bit Delay γ(t) log 2 M(γ) Bit Point Selector One of the M(γ) Point BSPK 4-QAM 6-QAM M(γ)-QAM Modulator Power: S(γ) γ(t) Goal: Optimize S(γ) and M(γ) to maximize EM(γ) To Channel

4 Optimal Adaptive Scheme Practical Contraint Power Water-Filling γ 0 S( γ ) γ γk γ K = γ 0 K = S 0 ele Spectral Efficiency R = p d B log γ ( γ ) γ. 2 γ γ K K γ k γ γ γ 0 γk Contellation retriction Contant power retriction Contellation update. Etimation error. Etimation delay. Equal Shannon capacity with an effective power lo of K. Diverity Send bit over independent fading path Combine path to mitigate fading effect. Independent fading path Space, time, frequency, polarization diverity. Combining technique Selection combining (SC) Equal gain combining (EGC) Maximal ratio combining (MRC) Diverity Performance Maximal Ratio Combining (MRC) Optimal technique (maximize output SNR) Combiner SNR i the um of the branch SNR. Ditribution of SNR hard to obtain. Can ue MGF approach for implified analyi. Exhibit 0-40 db gain in Rayleigh fading. Selection Combining (SC) Combiner SNR i the maximum of the branch SNR. Diminihing return with # of antenna. CDF eay to obtain, pdf found by differentiating. Can get up to about 20 db of gain. Multiple Input Multiple Output (MIMO)Sytem MIMO ytem have multiple (M) tranmit and receiver antenna With perfect channel etimate at TX and RX, decompoe to M indep. channel M-fold capacity increae over SISO ytem Demodulation complexity reduction Multicarrier Modulation Divide bit tream into N ubtream Modulate ubtream with bandwidth B/N Separate ubcarrier B/N<B c flat fading (no ISI) FDM ha ubtream completely eparated OFDM overlap ubtream More pectrally efficient Subtream eparated in receiver Efficient FFT Implementation

5 Fading Acro Subcarrier Compenation technique Frequency equalization (noie enhancement) Precoding Coding acro ubcarrier Adaptive loading (power and rate) Practical Iue for OFDM Peak-to-average power ration Sytem imperfection Direct Sequence Spread Spectrum Bit equence modulated by chip equence T c (t) c (t) T b =KT c S c (f) Spread bandwidth by large factor (K) Depread by multiplying by c (t) again ( c (t)=) Mitigate ISI and narrowband interference ISI mitigation a function of code autocorrelation Mut ynchronize to incoming ignal S(f) S(f)*S c (f) /T b /T c 2 RAKE Receiver Megatheme of EE359 Multiple branche ynchronize to each multipath component: N h( t) = α δ ( t τ ) i= i N receiver preading code, the ith one ynchronized to delay τ i. Thee component can be coherently combined. Same diverity combining technique a dicued earlier. i The wirele viion poe great technical challenge The wirele channel greatly impede performance Low fundamental capacity. Channel i randomly time-varying. ISI mut be compenated for. Hard to provide performance guarantee (needed for multimedia). We can compenate for flat fading uing diverity or adapting. MIMO channel promie a great capacity increae. A plethora of ISI compenation technique exit Variou tradeoff in performance, complexity, and implementation. What we didn t cover Multiple Acce (BW Sharing) Multiple Acce Spectral Reue Cellular Sytem Deign Ad-Hoc Network Deign Networking Iue Dedicated channel aignment Frequency Diviion Time Diviion Code Diviion Hybrid Scheme Code Space Frequency Code Space Frequency Code Space Frequency Time Time Time 7C Cimini-9/97

6 MAC Iue Fundamental capacity limit Practical deign Performance for voice, data, & multimedia Flexibility to adapt rate, power, code, etc. RANDOM ACCESS TECHNIQUES Random Acce Dedicated channel wateful for data ue tatitical multiplexing Technique Aloha Carrier ening Colliion detection or avoidance Reervation protocol PRMA Retranmiion ued for corrupted data Poor throughput and delay characteritic 7C Cimini-9/ Wirele LAN 802.b Standard for 2.4GHz ISM band (80 MHz) DSSS,.6 Mbp, 500 ft range Star or peer-to-peer architecture 802.a Standard for 5GHz NII band (300 MHz) OFDM with time diviion Mbp (adapt. modulation/coding), variable range Aloha acce, Peer-to-peer architecture 802.g Same a 802.a but in the 2.4 GHz ISM band 802.n, 802.e Standard being developed to include MIMO or QoS WiMax Emerging tandard for long-range wirele LANS. Utilize multiple antenna to get high data rate 40 Mbp fixed, 5 Mbp mobile Projected range of everal kilometer Fixed tandard finalized and being certified Could be a competitor to cellular Intel heavily inveted. Ad-Hoc Network Deign Iue Ad-hoc network provide a flexible network infratructure for many emerging application. The capacity of uch network i generally unknown. Peer-to-peer communication. No backbone infratructure. Routing can be multihop. Topology i dynamic. Fully connected with different link SINR Tranmiion, acce, and routing trategie for ad-hoc network are generally ad-hoc. Crolayer deign critical and very challenging. Energy contraint impoe intereting deign tradeoff for communication and networking.

7 Cellular Sytem Deign Deign Iue BASE STATION Frequencie, timelot, or code reued at patially-eparate location Efficient ytem deign i interference-limited Bae tation perform centralized control function Call etup, handoff, routing, adaptive cheme, etc. Reue ditance Cell ize Channel aignment trategy Interference management Power adaptation Smart antenna Multiuer detection Dynamic reource allocation 8C Cimini-7/98 3G Cellular Deign: Voice and Data Emerging Sytem 3G cellular ue CDMA (cdma2000 or WCDMA).25-5 MHz bandwidth Small difference between cdma2000 and WCDMA, but they are incompatible. Data rate on order of 2.4 Mbp (projected up to 8). Variable modulation and coding (convolutional and turbo) Starting to get traction in US/Europe/Aia Evolution of GSM (time-diviion): GPRS: timelot aggregation (40.8 Kbp) EDGE: GPRS with adaptive modulation and coding (384 Kbp) Evolution of IS-95 (CDMA) IS-95b (CDMA): Aggregate Walh function (5 Kbp) Ultrawideband 4G in wirele LAN and cellular Senor network Ditributed control network Ultrawideband Radio (UWB) UWB i an impule radio: end pule of ten of picoecond(0-2 ) to nanoecond (0-9 ) Duty cycle of only a fraction of a percent A carrier i not necearily needed Ue a lot of bandwidth (GHz) Low probability of detection Excellent ranging capability Multipath highly reolvable: good and bad Can ue OFDM to get around multipath problem. Why i UWB Intereting? Unique Location and Poitioning propertie cm accuracy poible Low Power CMOS tranmitter 00 time lower than Bluetooth for ame range/data rate Very high data rate poible 500 Mbp at ~0 feet under current regulation 7.5 Ghz of free pectrum in the U.S. FCC recently legalized UWB for commercial ue Spectrum allocation overlay exiting uer, but it allowed power level i very low to minimize interference Moore Law Radio Data rate cale with the horter pule width made poible with ever fater CMOS circuit

8 4G Cellular/WLAN Senor Network Energy i the driving contraint Nobody know what thi will be Major quetion Merging of cellular and WiFi? OFDM or CDMA? Single hop or multihop (meh network)? QoS? What are the killer app? Node powered by nonrechargeable batterie Data flow to centralized location. Low per-node rate but up to 00,000 node. Data highly correlated in time and pace. Node can cooperate in tranmiion, reception, compreion, and ignal proceing. Energy-Contrained Node Each node can only end a finite number of bit. Tranmit energy minimized by maximizing bit time Circuit energy conumption increae with bit time Introduce a delay veru energy tradeoff for each bit Short-range network mut conider tranmit, circuit, and proceing energy. Sophiticated technique not necearily energy-efficient. Sleep mode ave energy but complicate networking. Change everything about the network deign: Bit allocation mut be optimized acro all protocol. Delay v. throughput v. node/network lifetime tradeoff. Optimization of node cooperation. IEEE / ZigBee Radio Low-Rate WPAN Data rate of 20, 40, 250 kbp Star cluter or peer-to-peer operation Support for low latency device CSMA-CA channel acce Very low power conumption Frequency of operation in ISM band Focu i primarily on radio and acce technique Ditributed Control over Wirele Link Automated Vehicle -Car - UAV - Inect flyer Joint Deign Challenge There i no methodology to incorporate random delay or packet loe into control ytem deign. The bet rate/delay tradeoff for a communication ytem in ditributed control cannot be determined. Current autonomou vehicle platoon controller are not tring table with any communication delay Packet lo and/or delay impact controller performance. Controller deign hould be robut to network fault. Joint application and communication network deign. Can we make ditributed control robut to the network? Ye, by a radical redeign of the controller and the network.

9 The End Thank!!! Have a great winter break