ECE 4371, Fall, 2013 Introduction to Telecommunication Engineering/Telecommunication LaboratoryDistributionSlide 3OutlinePure AlohaCSMA: Carrier Sense Multiple AccessMACA – Medium Access with Collision AvoidanceHidden Terminal ProblemExposed Terminal ProblemSolution for Hidden Terminal ProblemSolution for Exposed Terminal ProblemCSMA/CA Collision AvoidanceMulticell InterferenceDog Barking (Party) EffectRate ControlSource CodingPractical Voice CoderDCT Image compressionComparison of DF and DCTQuantization and CodingJPEG : Lena survived after 12:1 compressionMotion Compensation ApproachMotion estimation for different framesA typical group of pictures in display orderA Simplified MPEG encoderScalability of Image/Video EncoderRate Control for Network/MACClassificationAdaptive Channel CodingAdaptive (Coded) ModulationAdaptive Processing GainJoint Source Channel CodingTradeoffJoint Power Control and Rate AdaptationFading ParametersDiversity TechniquesDiversity MotivationDiversity ExampleECE 4371, Fall, 2013Introduction to Telecommunication Engineering/Telecommunication Laboratory Zhu HanDepartment of Electrical and Computer EngineeringClass 23Dec. 9nd, 2013DistributionDistributionHome workFirst exam Second exam20 22 24 26 28 30 32 3400.511.522.5360 65 70 75 80 85 90 95 10000.511.522.5340 50 60 70 80 90 10000.511.522.53DistributionDistributionFirst projectSecond project4 5 6 7 8 9 10 11 12 13 1400.20.40.60.811.21.41.61.827 7.5 8 8.5 9 9.5 1000.511.522.533.544.55OutlineOutlineReviewRate ControlDiversityPure AlohaPure AlohaBM1M2M3Ignoring the propagation delay between mobilesand base station:The time difference between the timea mobile send the first bit of packet and thetime the base station receives the last bit ofthe packet is given by 2T. T = C/P T: packet time. C: channel data rate (bps) P: packet length (bits)During this 2T period of time, the packet may collidewith someone else packet. DataAck/NackAlgorithm:A mobile station transmits immediately whenever is has data. It then waits for ACK or NACK. If ACK is not received, it waits a random amount of time and retransmits.ECE6331CSMA: Carrier SenCSMA: Carrier Sensse Multiple Accesse Multiple AccessAloha does not listen to the carrier before transmission. CSMA listen to the carrier before transmission and transmits if channel is idle.Detection delay and propagation delay are two important parameters for CSMA –Detection delay: time required to sense the carrier and decide if it is idle or busy–Propagation delay: distance/speed_of_ligth. The time required for bit to travel from transmitter to the receiver.MACA – Medium Access with Collision AvoidanceMACA – Medium Access with Collision AvoidanceCSMA protocols sense the carrier, but sensing the carrier does not always releases true information about the status of the wireless channel–There are two problems that are unique to wireless channels (different than wireline channels), that makes CSMA useless in some cases. These problems are:Hidden terminal problemExposed terminal problem.Hidden Terminal ProblemHidden Terminal ProblemB CA• A is transmitting to B. • C is sensing the carrier and detects that it is idle (It can not hear A’s transmission). • C also transmits and collision occurs at B. • A is hidden from C. A’s cellC’s cellHiddenterminalExposed Terminal ProblemExposed Terminal ProblemB CAB’s cellC’s cellD• B is transmitting to A. C is hearing this transmission. • C now wants to transmit to D. It senses the existence of carrier signal and defers transmission to D. • However, C can actually start transmitting to D while B is transmitting to A, • Since A is out of range of C and C’s signals can not be heard at A.• C is exposed to B’s transmission.ExposedterminalSolution for Hidden Terminal ProblemSolution for Hidden Terminal ProblemB CAA’s cellC’s cellCTS(n)Data(n)CTS(n)XRTS(n)RTS(n)C defers transmission for duration of n bytes of data transmission. Node Ais no longer hidden from C effectively. X defers transmission until expected CTS reception time by RTS sender. Waiting time of node X is much smaller than waiting time of node C. A is transmitting to B.Solution for Exposed Terminal ProblemSolution for Exposed Terminal ProblemB CAB’s cellC’s cellDB is transmitting to ARTS(n)CTS(n)Data(m)RTS(n)RTS(m)CTS(m)Data(n)• C defers transmission upon hearing B’s RTS until B could get CTS from A.• After that C can start transmission to D. For that it first sends an RTS.• C is not longer exposed to the data transmission of B.CSMA/CA Collision AvoidanceCSMA/CA Collision AvoidanceRTSCTSDATAACKAccess PointMobileRTS/CTS is used to reserve channel forthe duration of the packet transmission. This prevents hidden and exposed terminalproblemsACK is required to understand if the packet is correctly received (without any collisions ) at the receiver. Ethernet does not require ACK to be sent, since the transmitter can detect the collision on the channel (cable) without requiring an explicit feedback from the receiver. A wireless transmitter can not detect collision, because:1) Transmit power is much larger than the received power: received signal is regarded as noise (not collision). 2) There could be a hidden terminalMulticell InterferenceMulticell InterferenceSNRDog Barking (Party) EffectDog Barking (Party) EffectTarget SNRRate ControlRate ControlSource Rate Control–Voice–VideoNetwork/MAC Layer–Queuing theory and buffer controlRate control for Phy Layer–Adaptive channel coding–Adaptive modulation–AMC (adaptive modulation and coding)–Adaptive processing gain for CDMAJoint Source Channel CodingJoint Power Control and Rate ControlSource CodingSource CodingVoice source encoder quantizer distortion can be written as:Embedded encodersource encoder distortion-rate functionPractical Voice CoderPractical Voice CoderDCT Image compressionDCT Image compressionWhat linear combination of 8x8 basis signals produces an 8x8 block in the image?Comparison of DF and DCTComparison of DF and DCTQuantization and CodingQuantization and CodingZonal Coding: Coefficients outside the zone mask are zeroed. •The coefficients outside the zone may contain significant energy•Local variations are not reconstructed properlyJPEG : Lena survived after 12:1 compressionJPEG : Lena survived after 12:1 compressionMotion Compensation ApproachMotion