WCDMA Key Technologies :WCDMA Key Technologies ZTE University TD&W&PCS BSS Course Team


Course Objectives :Course Objectives At the end of this course, you will be able to: Master key technologies of WCDMA Master characteristic of WCDMA system capacity


Content :Power Control Handover Rake receiver Call Admission Control & traffic control Capacity of WCDMA system Content


Why Power Control? :Why Power Control? All CDMA users occupy the same frequency at the same time! Frequency and time are not used as discriminators. CDMA operates by using CODES to discriminate between users. CDMA interference comes mainly from nearby users Each user is a small voice in a roaring crowd -- but with a uniquely recoverable code. Transmit power on all users must be tightly controlled so their signals reach the base station at the same signal level and at the absolute minimum power level necessary to ensure acceptable service quality. Power Control


Near-Far Effect :Overpowered by strong signals Block the whole cell Near-Far Effect Power Control


Power control :Power control Nearby terminals have higher probability of success Power control tech reduce the interference among each UEs and increase system capacity Power Control


Power Control :Power Control Overcome Near-Far effect and fading compensation Reducing multi-address interference, ensuing network capacity Prolonging the working time of cell DL power control Cell transmitting power Transmitting power control bit UE signal Power control order UL power control Power Control


Three methods of power control :Three methods of power control Open loop: measure received signal level and adjust transmitting power Inner-loop (closed loop): Frequency:1500HZ Measured SIR> Target SIR, lower transmitting power Measured SIR< Target SIR, increase transmitting power Outer-loop (closed loop): Measure BLER, adjust target SIR Power Control


Power control :Power control UE RNC Node B Open loop power control（no feedback） Closed loop power control（feedback） UE Node B Outer-loop Inner-loop Power Control


Open loop power control :Open loop power control If received signal is stronger,then UE can speak softer Node B Node B 1 2 1 2 problem： Unbalanced for UL/DL signal, not accurate, only used in initial stage Open loop If received signal is weaker,then UE can speak louder Power Control


Closed loop power control :Closed loop power control Inner-loop power control is fast Inner-loop ：according to SIR estimation,Node-B control UE transmission power.conducted every 0.66ms (1500Hz ) Outer-loop： according to BLER measurement estimation RNC control and adjust SIR target Node B ... ”Power down” Power up command ”Power ...” SIR estimation SIR estimation SIR target ”Power up” TPC:1500Hz BLER tar SIR tar Power down command Power Control


Closed loop power control :Closed loop power control Inner Loop Power control UL/DL (fast) UE or Node-B will use: Signaling channel, TPC, Continuously @ rate 1500 times/s, To relatively changes (up or down) the power to reach the SIR target. Outer loop Power control (Slow) If the BLER measured is below/above the target, UE/RNC increase/reduce SIR target. Use the new target for the Inner loop PC. Power Control


The Effect of Power Control :The Effect of Power Control The purpose of DL power control: Saving power resource of NodeB, reducing interference to other NodeB. The purpose of UL power control: Overcoming Near-Far effect, save power of UE WCDMA system capacity depend on power control Power Control


Content :Power Control Handover Rake receiver Call Admission Control & traffic control Capacity of WCDMA system Content


Handover :Handover Handover refers to the process in which when a UE moves from one Node B to another during calling. Purpose: Keep service continuity. In the WCDMA system, handover is divided into soft handover and hard handover. Handover


Type of handover :Type of handover Intra-RNC, inter-Node B Inter-RNC Soft handover： Same Node B, Inter- sector Softer handover： Intra-frequency handover Inter-frequency handover Inter-system (3G&2G) Inter-mode (FDD&TDD) Hard handover： WCDMA system support multi handover technology Handover


Hand-over :Hand-over Hard Handover Soft Handover Handover


Soft/Softer Hand-over :Soft/Softer Hand-over Handover


Soft/Softer Handover :Soft/Softer Handover The soft/softer handover allows to swap from one cell to another without call interruption or without deleting all old radio links (by opposition to hard HO). It also allows the UE to be connected to more than one cell simultaneously and take benefit from macro-diversity. Handover


Hard Handover :Hard Handover The hard handover procedure is used in case of service quality degradation or for traffic distribution management. During the hard handover procedure, all the old radio links with the UE are abandoned before new ones are established. Hard handover may occur in the following main cases : When the UE is handed over another UTRAN carrier, or another technology mode. When soft handover is not permitted (if O&M constraint) Handover


Basic concepts :Basic concepts Active Set: The set of cells connected with UE; User information is transmitted from these cells. Monitor Set: The set of cells not within the active set but being monitored by a UE according to the adjacent node list allocated by UTRAN. Detect Set: The set of cells in neither the active set nor the monitor set. Handover


Soft handover process :Soft handover process Measurement The RNC sends a measurement control message to UE. UE should perform measurement as required and report the measurement result. Generally, the measured quantity is the common pilot’s Ec/No. Decision The RNC stores data of different cells according to the measurement results. The RNC makes preliminary decision according to the event decision method. e.g. When the event is reported and the target cell is acceptable, send an active set update command to add/delete the cell into/from the active set. Execution The RNC sends an active set update command to UE and UE starts handover. Handover


Soft handover event :Soft handover event Handover


Example of soft handover :Example of soft handover


Content :Power Control Handover Rake receiver Call Admission Control & traffic control Capacity of WCDMA system Content


RAKE Receiving :RAKE Receiving d1 d2 t t t d3 transmitting Receiving Rake combination noise Rake receiver


Multi-finger receiver :Multi-finger receiver A ? receiver A A transmitter coding decoding A Direct signal Reflect signal Dispersive time 1 chip length Multi-finger receiver can supply multi-finger diversity,improve signal gain coding Rake receiver


RAKE Receiving :RAKE Receiving RAKE overcome multi-finger interference，improve receive capability receiver Single receiving Single receiving Single receiving searcher calculate combining t t s(t) s(t) signal Rake receiver


Multi-finger receiver :Multi-finger receiver Maximal ratio combining(MRC) at each time delay phase shifting by adding Finger 1 Finger 2 Finger 3 Rake receiver


Content :Power Control Handover Rake receiver Call Admission Control & traffic control Capacity of WCDMA system Content


Call Admission Control :Call Admission Control When user initiates a call, RRM decides weather access or deny this call according to the resource situation. When accessing, network allocate resource (such as OVSF, Scramble code) Call Admission Control & traffic control


Traffic control :Traffic control When traffic surpass system threshold, traffic control begin. To accept as many as possible services while keep the stability of the system. Call Admission Control & traffic control


Example for load control :Example for load control Breath effect of cell With the increase of activated terminals, interference increase the increase of high speed service,the increase of interference The shrink of cell coverage area Coverage blind spot occurs Drop of call will happen at the edge of cell Coverage and capacity are relative Call Admission Control & traffic control


Content :Power Control Handover Rake receiver Call Admission Control & traffic control Capacity of WCDMA system Content


Soft Capacity :System capacity and QoS can be interconverted Different service has different capacity Soft Capacity Capacity of WCDMA system


Capacity of WCDMA System :Capacity of WCDMA System = = = Under the circumstance of single services: Capacity of WCDMA system


Capacity of WCDMA System :Capacity of WCDMA System Under the circumstance of mixture of services： X Y Z + + Capacity of WCDMA system


Coverage and Capacity :Coverage and Capacity WCDMA performance is determined by such factors as： Number of users Transmission rate Mobile rate Wireless environment indoors Outdoors The sizes of cell depend on such factors as: Local radio conditions (local interference) Traffic in neighbouring cells (distanced interference) Cell Radius decrease according to the Increase of user number Capacity of WCDMA system


Coverage/capacity vs Data Rate :Coverage/capacity vs Data Rate Higher rate needs higher power High data rate transmission is only available nearby the station >12.2 kbps >64 kbps >384 kbps >144 kbps Coverage decrease Subscriber num increase Capacity of WCDMA system


Coverage and Capacity :DL transmission diversity (Tx Div) high power amplifier(TEU 50 W) UL tower mounted amplifier (TMA) 4RxDiv MUD OTSR DL/UL: Add carrier six sectors Smart antenna Add basestation “last choice” Coverage and Capacity In order to overcome cell breath caused by increased traffic and different requirement for capacity and coverage in different environment ,such solution supplied: Capacity of WCDMA system


Exercise :Exercise what is the near-far effect what is the purpose of Power Control . Power control is diveided into ( ) ( ) ( ) pls describe WCDMA Hand Over Technology category. soft handover events include( ) ( ) ( ) ( )( ) ( ) What is the cell breath effect.