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7.rrm overview

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  • WCDMA system is said to be interference limited. All cells and users are transmitting on the same frequency and information from individual users is retrieved by coding. The level of interference governs the likelihood of recovering the wanted signal. Minimising the levels of unwanted interference in both the forward and reverse links impacts link quality, cell capacity and cell coverage areas. Nokias RRM is responsible for using the air interface resources optimally and hence maximising cell capacity, cell coverage and ultimately the user link quality for each service.
  • Two areas in the functional split Cell based functions apply to all the current or even potential connections to a single cell, say of a 3 sector site.
    Connection based functions apply to every UE currently connected to the cell
  • Forward link load can be estimated based on throughput. From the equation, the loading is the sum of the bitrates of all currenty active connections divided by the specified maximum throughput for the cell.
    In the equation Rj is the bitrate of the connection j and N is the total number of connections. Rmax is the maximum thoughput for the cell. Note that in the summation, the bitrates of all the common channels need to be included also.
    In the reverse link, the load of the cell can be estimated based on the sum of the load factors of the users connected to the cell. In the equation, ā€˜iā€™ is the own cell to other cell interference ratio, loadj is the load of user j and N is the number of users.
  • Forward link load could be estimated by taking the total currently allocated transmit power at the base station PtxTotal and dividing by the maximum transmit power capability of the cell Ptxmax
    Ie nDL = PtxTotal/Ptxmax
    In the reverse link, the uplink load factor can be estimated byNul= (Iown+Iother)/PrxTotal.
    The uplink noise rise can be expressed by the equation NR =Prxtotal/PrxNoise hence PrxNoise/PrxTotal= 1/NR
    Hence nUL = 1-Prxnoise/Prxtotal = 1-1/NR
  • Lower area: RT RABS can be admitted as long as they do not inrease Ptx beyond Ptx_target
    Middle area RT RABS not admitted. NRT RABs can be admitted
    Higher area: Nothing admitted RT(NC) or NRT if Ptx_Target_BS is exceeded. NRT bit-rates are reduced until Ptx_Total reaches Ptx_targetb
  • If the IE Establishment Cause of the RRC: RRC Connection Request has any of the values "Emergency call", "Registration", "Detach", "Originating High Priority Signalling", "Terminating High Priority Signalling", "Inter-RAT cell reselection", or "Inter-RAT cell change order", then the RRC connection request is not rejected either for received wide band power or transmitted power reasons.
    When the IE Establishment Cause has any of the values "Originating Conversational Call", "Terminating Conversational Call", "Originating Streaming Call", "Terminating Streaming Call", "Originating Interactive Call", "Originating Background Call", "Terminating Interactive Call", "Terminating Background Call", "Originating Subscribed traffic Call", "Originating Low Priority Signalling", "Terminating Low Priority Signalling", "Call reestablishment", or "Terminating - cause unknown", the RRC connection request is admitted if non-controllable load is below target threshold
  • Allocates: UL scrambling and spreading
    DL spreading (but not scrambling as this is fixed per cell by RNP)
  • Like a lorry with a capacity to carry 1000kg (SF1), it can have 2 * 500 kg packages (SF2), 4 * 250 kg packages(SF3), etc.
    Draw picture with square that can be divided into sub-squares. Re-arranging the used squares can help to gain capacity.
  • Transcript

    • 1. Radio Resource Manager Overview Company Confidential 1 © Nokia Siemens Networks Radio Resource Manager / June2007
    • 2. Contents • RRM Introduction • Power Control • Load Control • Admission Control • Packet Scheduler • Resource Manager Company Confidential 2 © Nokia Siemens Networks Radio Resource Manager / June2007
    • 3. RRM Introduction Company Confidential 3 © Nokia Siemens Networks Radio Resource Manager / June2007
    • 4. Radio R esource Management Radio Resource Management (RRM) is responsible for optimal utilisation of the air interface resources Target for RRM is to ensure the RAN offers: • The planned coverage for each targeted service • High capacity i.e. low blocking (new calls, handovers) • The required Quality of Service (QoS) • Optimize the use of available capacity (priorities) By continuously monitoring/adjusting how the available resources are used in accordance with user requests Link Quality Cell Capacity Company Confidential 4 © Nokia Siemens Networks Radio Resource Manager / June2007 RRM Cell Coverage
    • 5. Radio Resource Management tasks RRM must be able to: • Predict the impact on interference (power) of admitting a new user for UL & DL • Provide different quality of service for real time (RT) and non-real time (NRT) users • Take appropriate corrective action when the different cell load thresholds are exceeded in order to maintain cell stability (i.e. load control) Overload Margin Load Target Power • Perform appropriate actions (e.g. new call admissions, bitrate increase/decrease etc.) in accordance with prevailing load conditions Overload Time Estimated capacity for NRT trafficload caused Measured by non-controllable load (RT) RT services must have higher quality assurance than NRT Company Confidential 5 © Nokia Siemens Networks Radio Resource Manager / June2007
    • 6. RRM Module • Power Control • Load Control • Admission Control • Packet Scheduling • Handover Control • Resource Manager Company Confidential 6 © Nokia Siemens Networks Radio Resource Manager / June2007
    • 7. RRM Functional Split • RRM is made up of a number of closely interdependent functions (i.e. algorithms) • These functions can be divided into; • Cell Based LC • Load control (LC) RM • Admission control (AC) • Packet scheduling (PS) • Resource manager (RM) • Connection Based • Handover control (HC) PS AC Cell based functions PC HC • Power control (PC) Connection based functions Company Confidential 7 © Nokia Siemens Networks Radio Resource Manager / June2007
    • 8. Load Control Company Confidential 8 © Nokia Siemens Networks Radio Resource Manager / June2007
    • 9. Radio Resource Indication BTS Measurements … RRI Period Company Confidential 9 © Nokia Siemens Networks Radio Resource Manager / June2007
    • 10. Load Estimation Methods • Actual prevailing load in the cell depends on multiple factors • Number of active connections • Properties of the connections • Bit rate • Eb/No requirement • BLER requirement • Propagation channel conditions (speed, multipath profile etc.) • SHO condition • Activity • Different methods can be applied to measure/estimate prevailing load conditions, e.g. • Throughput Based Load Estimation • Power Based Load Estimation Company Confidential 10 © Nokia Siemens Networks Radio Resource Manager / June2007
    • 11. Throughput Based Load Estimation • The downlink load of the cell can be estimated by using the sum of the downlink allocated bit rates as follows N ηDL = ∑R j j= 1 Rmax Max. allowed throughtput of the cell • The uplink load of the cell can be estimated by using the sum of the load factors of the users connected to this cell. N ηUL = (1 + i ) ⋅ ∑load j j =1 • Definition of Rmax and loadj requires estimates of Eb/No, little i, activity, SHO overhead etc. Company Confidential 11 © Nokia Siemens Networks Radio Resource Manager / June2007
    • 12. Power Based Load Estimation • The downlink load of the cell can be estimated by dividing the total downlink transmission power, Ptx_total by the maximum Node B transmission power Ptx_BTS,max. η DL = Ptx _ total Ptx _ BTS ,max • The uplink load can be estimated with P rx_noise, the background and receiver noise and Prx_total, the total received power, according to this formula: rx _ noise UL rx _ total η = 1− P P 1 = 1− NR Company Confidential © Nokia Siemens Networks Radio • Measures the loadResource Manager / June2007conditions in actual 12
    • 13. Radio interface load • The BTS measures the total received power (P rxTotal) and the total transmitted power (P txTotal) on cell basis • The BTS reports Prx To ta l and Ptx To ta l of each cell to the RNC by sending RADIO RESOURCE INDICATION message periodically (R IndicationP R eriod) • LC updates cell load status for each cell based on RADIO RESOURCE INDICATION • LC updates non-controllable UL (PrxNC) and DL (PtxNC) load in cell • AC and PS algorithms work on the current cell load status provided by LC • Denying call admission (AC) and throttling back NRT traffic (PS) are the overload actions • After scheduling PS provides LC with PrxNRT, PtxNRT & LNRT estimates • After admitting RT RAB, AC provides LC with NC load increase estimate Company Confidential 13 © Nokia Siemens Networks Radio Resource Manager / June2007
    • 14. UL power based load measurement PRxTotal = PRx_Own + PRx_Other + PNoise = PRx_NRT + PRx_RT + PRx_Other + PNoise = PRx_NRT + PRx_NC = PRx_Other / PRx_Own Company Confidential 14 © Nokia Siemens Networks Radio Resource Manager / June2007 PRx_Other PRx_Own
    • 15. DL power based load measurement PTxTotal = PTx_Own PTx_Common on Ch an ne ls = PTx_NRT + PTx_RT + PTx_Common Co m m = PTx_NRT + PTx_NC PTx_Own PRx_Own_DL PRx_Other_DL i DL Company Confidential 15 © Nokia Siemens Networks = PRx_Other_DL / PRx_Own_DL Radio Resource Manager / June2007
    • 16. total received power Prx Total [dBm] UL Preventive & Overload Thresholds Overloaded Area Marginal Load Area Feasible Load Area Range Prx Total [Prx noise ... inf] © Nokia Siemens Networks load factor η Range [0..1] Company Confidential 16 PrxTarget [dB] + PrxOffset [dB] Prx Target [dB] Radio Resource Manager / June2007
    • 17. Uplink preventive threshold Preventive threshold = PrxTarget Prx Target is relative to the system noise, it gives an upper threshold for the noise rise Target threshold defines the optimal operating point of the cell load, up to which PS & AC can operate normally If cell load exceeds these limits then AC & PREVENTIVE STATE function PS move to New RT RABs are blocked, and PS can't schedule more NRT bit rates in the cell PrxTarget range: 0...30 dB, step 0.1 dB default: 4 dB Company Confidential 17 © Nokia Siemens Networks Radio Resource Manager / June2007
    • 18. Uplink overload threshold Overload threshold = P rxTarget + P rxOffset • Overload Threshold defines the limit when the cell is considered to be overloaded • If load in the cell exceeds these limits then AC & PS move to OVERLOAD STATE function • New calls are blocked, and PS starts to decrease NRT bit rates in the cell P rxOffset range: default: 0...6 dB, step 0.1 dB 1 dB Company Confidential 18 © Nokia Siemens Networks Radio Resource Manager / June2007
    • 19. DL Preventive & Overload Thresholds total transmitted power Ptx Total [dBm] Cell Maximum Overloaded Area Marginal Load Area Ptx Target [dBm] + PtxOffset [dB] Ptx Target [dBm] Feasible Load Area Range Ptx Total [0… Ptx BS total] Company Confidential 19 © Nokia Siemens Networks Radio Resource Manager / June2007 load factor η
    • 20. Downlink Preventive threshold Preventive threshold = P txTarget • Target threshold defines the optimal operating point of the cell load, up to which PS & AC can operate normally • If cell load exceeds these limits then AC & PS move to PREVENTIVE STATE function • New RT RABs are blocked, and PS can't schedule more NRT bit rates in the cell P txTarget range: default: -10...50 dBm, step 0.1 dB 40 dBm • Default value depends on the cell max TX power: in case the cell max power is 43 dBm, the PtxTarget should be 40 dBm (3 dB below max) Company Confidential 20 © Nokia Siemens Networks Radio Resource Manager / June2007
    • 21. Downlink overload threshold Overload threshold = P txTarget + P txOffset • Overload Threshold defines the limit when the cell is considered to be overloaded • If load in the cell exceeds these limits then AC & PS move to OVERLOAD STATE function • New calls are blocked, and PS starts to decrease NRT bit rates in the cell P txOffset range: default: 0...6 dB, step 0.1 dB 1 dB Company Confidential 21 © Nokia Siemens Networks Radio Resource Manager / June2007
    • 22. Admission Control Company Confidential 22 © Nokia Siemens Networks Radio Resource Manager / June2007
    • 23. Admission Control Functional Overview • • Decides if new RAB request is admitted into RAN • AC decision procedure set according to whether; • • Request is for RRC connection and RT or NRT RAB Setup • RAB setup can be for call setup or handover Admission control for RAB setup is different for RT and NRT • For RT RAB admission requests AC; RNC Maximises capacity whilst maintaining stability LC RM PS AC Network based functions • estimates the non-controllable power (load) increase that would result from admitting the new RAB • checks if the new non-controllable load is below a certain threshold • Bearer is not admitted if the predicted load exceeds defined thresholds in UL or DL • AC is also responsible for determining quality requirements of the RB including; • setting RLC and TrCH parameters • BLER & Eb/No targets • initial SIR target (used in Outer Loop PC) & upper and lower limits for the uplink SIR target • AC determines the power allocation for the requesting UEs (initial, minimum and maximum Company Confidential transmission power) 23 © Nokia Siemens Networks Radio Resource Manager / June2007
    • 24. Admission Control Functional Overview 0 RRC Connection Establishment NRT Admission Decision Process (PS) 6 RAB Establishment UL/ Load Change DL Report to LC 5 Nokia RNC NR P T S call R ASSIGNMENT AB R EQUEST AC RAB admitted Radio Access Bearer Service Request R CScall T 4 RAB request denied Admission Decision 3 Power Increase Estimates Company Confidential © Nokia Siemens Networks Quality Requirements of Radio Bearer 2 RB attributes (RNC); • target BLER • target Eb/No • initial SIRtarget Queue RAB 24 Core Network Radio Resource Manager / June2007 1 RAB attributes (HLR); • SDU error ratio • traffic class • max bit rate
    • 25. Load Based Admission Decision Process • To maintain stability, UL and DL loads at each cell must be maintained below defined thresholds. • Admission decision takes into account 3 main issues; P rx _ total • The measured power quantities (current load status of P tx _ total the cell) P UL = P rx _ total − Prx _ NRT • Average total wideband rx _ NC received power Ptx _ NC = P tx _ total • Average total DL transmit power − Ptx _ NRT • Non-controllable UL power • Non-controllable DL power • Non-controllable power increase estimation associated with new admissions Company Confidential 25 • Comparison Radio Resource Manager / June2007 against admission criteria thresholds © Nokia Siemens Networks
    • 26. UL Admission Procedure Summary BTS sends periodically the received UL power to the RNC RNC compares the measured received power levels against the set thresholds PrxTotal [dBm] Noise Rise NR [dB] If measured UL (PrxTotal) load exceeds overload thresholds (PrxTarget+PrxOffset) no RABs can be admitted and NRT bitrates are reduced until PrxTotal reaches again PrxTarget Over Load Marginal Load Feasible Load If measured UL (PrxTotal) load exceeds target thresholds (PrxTarget) The NRT RAB bitrate can not be increased and remains at the same level as after previous scheduling period 0 PrxTarget [dB]+ PrxOffset [dB] PrxTarget [dB] XX [dB] Load curve in UL Fractional load [0..1] 1 In feasible load area the admission decision is based on the power rise estimate of the new RT bearer Prx_nc + ∆Prx_nc ≥ Prx_target If the resulting power is still below PrxTraget the RAB is admitted Company Confidential 26 PrxNoise [dBm] OVER LOAD AREA MARGINAL LOAD AREA FEASIBLE LOAD AREA © Nokia Siemens Networks Radio Resource Manager / June2007 In case the RAB can not be admitted it is put into the queue
    • 27. DL Admission Procedure Summary BTS sends periodically the total transmitted DL power to the RNC RNC compares the measured transmitted power levels against the thresholds Over Load If measured DL (PTxTotal) transmitted power exceeds overload thresholds (PtxTarget+PtxOffset) no RABs can be admitted and NRT bitrates are reduced until PtxTotal reaches again PtxTarget PtxTotal [dBm] Cell maximum [dBm] PtxTarget [dBm]+ PtxOffset [dB] PtxTarget [dBm] Feasible Load Load curve in DL 0 1 Load [0...1] Ptx_total + ∆Ptx ≥ Ptx_target If the resulting power is still below PtxTraget the RAB is admitted Company Confidential 27 MARGINAL LOAD AREA FEASIBLE LOAD AREA If measured DL (PtxTotal) transmitted power exceeds target thresholds (PtxTarget) ,The NRT RAB bitrates can not be Marginal increased and they remain at the same level as after previous scheduling period Load In feasible load area the admission decision is based on the power rise estimate of the new RT bearer OVER LOAD AREA © Nokia Siemens Networks Radio Resource Manager / June2007 In case the RAB can not be admitted it is put into the queue
    • 28. Admission Control for R and NRT T RRC connection setup Emergency call RT NRT RRC connection request is not rejected either for received wide band power or transmitted power reasons RT over NRT and pre-emption procedure can be applied Admitted if non-controllable load is below target threshold RT over NRT pre-emption procedure can be applied Admitted if non-controllable load is below target threshold Company Confidential 28 © Nokia Siemens Networks Radio Resource Manager / June2007 RAB setup Admitted if non-controllable load added by estimated change is below target If non-controllable load added by estimated change is above target, RT RAB preemption procedure can be applied In case of congestion, RT over NRT procedure can be applied Admitted always at 0 bit rate, capacity requests scheduled by PS
    • 29. Packet Scheduler Company Confidential 29 © Nokia Siemens Networks Radio Resource Manager / June2007
    • 30. W Packet Scheduling ? hy • It is characteristic for RT traffic that it’s load cannot be controlled in efficient way. Load caused by RT traffic, interference from other cell users and noise together is called non-controllable load. • The available capacity, which is not used by non-controllable load, can be used for NRT radio bearers on best effort basis. To fill the whole load budget and achieve the maximum capacity, the allocation of nonGBR traffic needs to be fast. • The Packet scheduler is a general feature, which takes care of scheduling radio resources for NRT radio bearers for both uplink and downlink directions; Packet scheduling happens periodically and is implemented for both dedicated (DCH) and common control transport channels (RACH/FACH). • Scheduled capacity depends on the UE capabilities, Node B capabilities, current load of the cell as well as the availability of the physical radio resources. Company Confidential 30 © Nokia Siemens Networks Radio Resource Manager / June2007
    • 31. Packet Scheduling Principles • Packet Scheduler switches between common channels (FACH/RACH = low capacity) and dedicated channels (DCH = higher bit rates) • Packet Scheduler allocates to RABs temporarily dedicated channels with a set of maximum bit rates • For instance within an allocation for 384kbit/s, the instantaneous bit rate can be {0, 8, 16, 32, 64, 128, 384} kbit/s • Packet Scheduler allocates DCH based on Capacity R equests • A Ca p a c ity Re q ue s t (Nokia term) is triggered based on traffic volume measurement info: the sender (UE or RNC) has data in buffer and no sufficient dedicated channel • Packet Scheduler releases DCH upon inactivity • Packet Scheduler re-schedules continuously DCH to serve all requests equally, and take into account changes in non-controllable load Company Confidential 31 © Nokia Siemens Networks Radio Resource Manager / June2007
    • 32. Packet Scheduling overload Power /Load PtxTargetBTS PrxTargetBTS PtxOffset PrxOffset PtxTarget PrxTarget PtxTotal (variable) PrxTotal PtxNrt PrxNrt PtxRt De s ire d Prx /Ptx Va lue PrxRt s controllable load i.e. non RT Traffic non-controllable load i.e. RT Traffic Company Confidential 32 © Nokia Siemens Networks Radio Resource Manager / June2007 time
    • 33. Packet Scheduler as part of RRM • The packet scheduler (PS) co-operates with other radio resource management functions like handover control (HC), load control (LC), admission control (AC) and the resource manager (RM) • HC provides active set information • LC provides periodical load information to PS on a cell basis • PS informs AC and LC of the load caused by non-real time radio bearers • AC informs PS when new non-real time radio bearers are admitted, reconfigured or released • RM allocates the RNC internal resources, downlink spreading codes and takes care of allocating radio links using the base station application protocol (NBAP) Company Confidential 33 © Nokia Siemens Networks Radio Resource Manager / June2007
    • 34. Packet Scheduler functions • Packet Scheduler consists of multiple different functions which can be categorised based on the scope of the function • UE-specific part • Functions working based on single radio link/bearer status, measurements and conditions • Cell-specific part • Functions working based on cell level measurements and conditions Company Confidential 34 © Nokia Siemens Networks Radio Resource Manager / June2007
    • 35. Packet Scheduler actions during call – Loaded cell Overload Load Margin Normal load Allocated bit rate PS 2 PS 4 PS 5 Max. bit rate PS 3 PS1 Initial bit rate A C Minimum bit rate Actual throughput FLXU Company PBS Confidential 35 © Nokia Siemens Networks EOLC Radio Resource Manager / June2007 FLXU
    • 36. R State Machine RC Frequent cell updates Cell Update, UL Tx UL Tx UTRA RRC Connected Mode UE in DRX mode discontinous reception Dedicated resources allocated (DCH) URA_PCH CELL_DCH CELL_PCH CELL_FACH Tx and Rx mode Cell re-selection © Nokia Siemens Networks discontinous receiption Common resources allocated (RACH-FACH) Traffic volume RACH load Idle Mode Company Confidential 36 UE in DRX mode Tx and Rx mode Inactivity Timer Overload Cell selection UL/DL activation timer Radio Resource Manager / June2007
    • 37. Power Control Company Confidential 37 © Nokia Siemens Networks Radio Resource Manager / June2007
    • 38. Power Control types Open Loop Power Control (Initial Access) MS (Fast) Closed Loop Power Control BS DL Outer Loop Power Control BLER target Company Confidential 38 © Nokia Siemens Networks Radio Resource Manager / June2007 UL Outer Loop Power Control RN C
    • 39. Open Loop Power Control • Purpose: To set the initial transmitted power of PRACH & DPCCH in the UL. • UE determines the uplink preamble power of PRACH • UE PRACH First Preamble Power = Path loss calculations Transmission power of CPICH (Broadcast on BCH, SIB 5)) Downlink RSCP measurement from active cell on CPICH (Measured by UE) + Additional Power required Total received wideband interference power at WCDMA BTS (Broadcast on BCH, SIB 7) + Required received C/I at the WCDMA BTS (Broadcast on BCH, SIB 5) • Open loop PC is a part of the random access procedure for PRACH channel Example: PtxCPICH=33dBm (Parameter per Node-B) DL RSCP = -80dBm (Measured by UE) UL_IF = –100 dBm UL_Required_C/ = -25 dB (Parameter per Node-B) I UE PRACH First Preamble Power = 33 dBm – (-80 dBm) + (-100 dBm) + (-25 dB) = -12 dBm Company Confidential 39 © Nokia Siemens Networks Radio Resource Manager / June2007
    • 40. Random Access Procedure DL AICH access slots RX at UE One access slot Acq. Ind. t p-a Pp-m P U L PRACH access slots TX at UE 0 Preamble t p-p Company Confidential 41 © Nokia Siemens Networks Radio Resource Manager / June2007 Message part Preamble tp-m
    • 41. Random Access Procedure (1/ 3) • UE transmits the first preamble with the power determined by UL open loop PC • If the UE does not detect any acquisition indicator in AICH, it increases the preamble Tx power by a specified offset Po • If the UE detects the positive indicator in AICH, it transmits the random access message, 3 or 4 access slots after the UL access slot of the last transmitted preamble • The Tx power of the control part of random access message should be Pp-m higher than the last transmitted preamble power • The required power offset values for random access procedure owerOffsetL astP ream bleP ACH essage in PRACH(Pp-m) R m • P owerR pS am tepP ACH R pream (Power Ramp Step)(Po) ble • P Company Confidential 42 © Nokia Siemens Networks Radio Resource Manager / June2007
    • 42. Random Access Procedure (2/ 3) • The power ramp-up process will continue until 1) A positive AI is received from the network 2) A negative AI is received from the network 3) R ACH _pream ble_retrans value is exhausted 4) UE reaches UE owerM R txP axP ACHvalue • When the R ACH _pream ble_retrans value is exhausted, PRACH preamble power will be reset to the initial value of the cycle and a new power ramp-up cycle initiated. The preamble power ramp-up cycle will be repeated R ACH _tx_M times. At this stage the UE will send ax a RACH failure message to the network. • The maximum allowed UE transmit power for the PRACH procedure is defined by UE owerM R txP axP ACH Layer 1 of the UE controls the UE transmit power during the . PRACH procedure using the ‘commanded transmit power’. If the commanded transmit power exceeds the maximum allowed transmit power then the UE transmits the maximum allowed transmit power. • If the commanded transmit power exceeds the maximum allowed transmit power by 6 dB then layer 1 of the UE is able to inform higher layers and exit the PRACH procedure. If the step size is 1 dB then this corresponds to transmitting 6 preambles at maximum power. Company Confidential 43 © Nokia Siemens Networks Radio Resource Manager / June2007
    • 43. Random Access Procedure (3/ 3) Downlink /BS UEtx Po we rM x PRA a CH …. Uplink /UE Preamble 1 Preamble n PRA CH_ p re a m b le _ re tra ns : The maximum number of preambles allowed in one preamble ramping cycle RA CH_ tx _ M x : # of preamble a power ramping cycles that can be done before RACH transmission failure is reported, Company Confidential 44 © Nokia Siemens Networks Radio Resource Manager / June2007 …. Message part
    • 44. Random Access Procedure Parameters owerOffsetL astP ream bleP ACH essage in PRACH(Pp-m) R m • P • The power offset between the last transmitted preamble and the control part of the PRACH message (added to the preamble power to receive the power of the message control part) • range: -5 ... 10 dB, step 1 dB default: 2 dB • The power offset between last preamble and and message part should ensure decoding the RACH message at BS with high probability. Still, it should be mimised to reduce UL interference owerR pS am tepP ACH R pream (Power Ramp Step)(Po) ble • P • The power ramp step on PRACH preamble when no acquisition indicator (AI) is detected by the UE • range: 1 ... 8 dB, step 1 dB default: 2 dB • If the "power ramp step" is too low then the RACH preamble ramping takes a too long time. If it is too high, then it may cause high noise rise at BS Company Confidential 45 © Nokia Siemens Networks Radio Resource Manager / June2007
    • 45. Random Access Procedure Parameters • R ACH _pream ble_retrans • The parameter describes the number of PRACH preamble retransmissions in a preamble power ramping-up cycle • range: -1 ... 64, step 1 default: 8 • Note: As the 3GPP requires almost certain detection of PRACH preamble at -19.5dB. The default of 8 retransmissions with 2dB power step, starting from -25dB should be sufficient • R ACH _tx_M ax • Maximum number of RACH preamble cycles defines how many times the PRACH pre-amble power ramping-up procedure can be repeated before UE MAC reports a failure on RACH transmission to higher layers • range: 1,2...32 default: 8 Company Confidential 46 © Nokia Siemens Networks Radio Resource Manager / June2007
    • 46. Outer Loop Power Control Company Confidential 47 © Nokia Siemens Networks Radio Resource Manager / June2007
    • 47. Outer Loop Power Control BS RNC 4 Outer L oop P ower Control • Outer PC loop is performed to adjust the TARGET SIR in BS/UE, according to the needs of individual radio link: • • • • • UE speed Changes in the propagation conditions Available multipath diversity UE power control dynamics (close to peak power) SHO branches (Macro Diversity Combining) • SIR is constantly adjusted in order to maintain a constant QUALITY, usually defined as a certain target BLER Company Confidential 48 © Nokia Siemens Networks Radio Resource Manager / June2007
    • 48. Uplink Outer Loop Power Control Entities RNC • In the RNC the functionality of the UL outer loop PC is divided into two parts: UL Outer Loop PC ⇒ UL outer loop PC Controller, one for each RRC connection UL Outer Loop PC Controller UL Outer Loop PC Entity #1 BTS 1 UL Fast Closed Loop PC ⇒ UL outer loop PC Entities, one for each transport channel UL Outer Loop PC Entity #N BTS 2 UL Fast Closed Loop PC Company Confidential 49 © Nokia Siemens Networks Radio Resource Manager / June2007
    • 49. Uplink Outer Loop Power Control Controller RNC • An UL Outer Loop PC Controller controls all UL OLPC Entities under the same RRC connection. UL Outer Loop PC • The UL OLPC Controller sets the parameters for each UL OL PC Entities at the RAB Setup/Modification. UL Outer Loop PC Controller UL Outer Loop PC Entity #1 BTS 1 UL Fast Closed Loop PC • The UL OLPC Controller also combines SIR Target changes from the UL OLPC Entities and sends the result to the UL OLPC Entity, which is selected to transmit it to the WCDMA BTS. UL Outer Loop PC Entity #N • There is one UL outer loop PC Entity for each transport channel in the RNC. • This UL OLPC Entity calculates the required change in SIR Target according to UL quality BTS 2 estimates (CRC). UL Fast Closed Loop PC Company Confidential 50 © Nokia Siemens Networks Radio Resource Manager / June2007 • One of UL OLPC Entities under the same radio link is selected to transmit the New SIR Target to the WCDMA BTS.
    • 50. Uplink Outer Loop Power Control Algorithm Admission Control 2. PC Parameters at RAB setup Overload info Load Control (not used in RAN1) UL Outer Loop PC Controller 1. RAB Setup: Initial SIR Target 2. - PC Parameters - Initial SIR target 3. Setting of the UL Outer Loop PC Entities 8. Collection of the SIR target changes and calculation of new SIR Target 4. Parameters 7. SIR Target modification command 9. New SIR Target UL Outer Loop PC Entity #n 4. - PC parameters - Activity reporting period - Entity selected to transmit new SIR target 6. Calculation of SIR Target change 10. Transmission of new SIR Target value to MDC 5. Quality info: BER, BLER 10. New SIR Target MDC 10. L1 FP: SIR Target 5. L1 FP: UL quality info BTS Company Confidential 51 © Nokia Siemens Networks 1. SIR Target 1. Radio Resource Manager / June2007 UL fast closed loop PC
    • 51. Downlink Outer Loop Power Control • This function is implemented in the UE in order to set the SIR target on each CCTrCH used for the DL closed loop PC. • This SIR value is adjusted according to an autonomous function of the UE in order to achieve the same measured quality as the quality target set by the RNC. • In order to control the downlink outer loop PC quality target in UE, Admission Control (AC) determines the value of the DL BLER target for each DCH mapped on a DPCH. • After Admission Control functionality has determined the DL BLER target for each transport channel, the RNC sends these values to the UE. Company Confidential 53 © Nokia Siemens Networks Radio Resource Manager / June2007
    • 52. Close Loop Power Control Company Confidential 54 © Nokia Siemens Networks Radio Resource Manager / June2007
    • 53. Closed Loop Power Control MS (Fast) Closed Loop Power Control BS DL Outer Loop Power Control BLER target Company Confidential 55 © Nokia Siemens Networks Radio Resource Manager / June2007 UL Outer Loop Power Control RN C
    • 54. UL Closed loop power control MS • UL fast closed loop PC shall be active as soon as the frame synchronization has been established in the dedicated physical channels. • PC delay approx. one slot Measure received SIR on UL DPCCH Pilot Compare measured SIR with SIR target value received from UL outer loop PC PC step 1dB • UL DPCCH PC frequency 1500 Hz • BS Measured SIR < SIR target --> TPC bit = '1' Measured SIR => SIR target --> TPC bit = '0' Send TPC bit on DL DPCCH MS sets the power on UL DPCCH and UL DPDCH on following way: TPC = '1' --> increase power by 1 dB TPC = '0' --> decrease power by 1 dB Changed power on UL DPCCH Company Confidential 56 © Nokia Siemens Networks Radio Resource Manager / June2007
    • 55. DL Fast Loop PC: UTRAN behaviour WCDMA BTS MS DL DPCCH + DPDCHs Measure received SIR on DL DPCCH • Upon receiving the TPC commands BS adjusts its downlink DPCCH/DPDCH power accordingly. • UTRAN shall estimate the transmitted TPC command TPCest to be 0 or 1, and shall update the power every slot. Compare measured SIR with SIR target value received from DL outer loop PC Measured SIR < SIR target --> TPC command is "1" Measured SIR => SIR target --> TPC command is "0" • After estimating the k:th TPC command, UTRAN shall adjust BS sets the power on DL DPCCH and the current downlink power DL DPDCH following way: TPC command = "1" --> increase power by 1 dB TPC command = "0" --> decrease power by 1 dB P(k-1) [dB] to a new power P(k) [dB] according to the following formula: Send TPC command on UL DPCCH Changed power on DL DPCCH + DPDCHs P(k) = P(k - 1) + PTPC(k) DownlinkInnerLoopPCStepSize Company Confidential 57 © Nokia Siemens Networks Radio Resource Manager / June2007 where PTPC(k) is the k:th power adjustment due to the
    • 56. Resource Manager Company Confidential 58 © Nokia Siemens Networks Radio Resource Manager / June2007
    • 57. Resource Manager • The main function of RM is to allocate logical radio resources of BS according to the channel request by the RRC layer for each radio connection • The RM is located in the RNC and it works in close cooperation with AC and PS • The actual input for resource allocation comes from AC/PS and RM informs the PS about the resource situation • The RM is able to switch codes and code types for different reasons such as soft handover and defragmentation of code tree • Manages the BS logical resources • BS reports the available logical HW resources • Requests for other resources such as ATM • Transport resource manager • RNC HW manager (L1/L2) • Maintains the code tree • Allocates the DL spreading (=channelization) codes, UL scrambling code, UL Company Confidential spreading (=channelisation) code type 59 © Nokia Siemens Networks Radio Resource Manager / June2007 • Prevents fragmentation, may cause extra HO's
    • 58. Spreading Code Allocation • Code Allocation Algorithm chooses the correct spreading code depending on the TFC type C 2 (0)=(1,1,1,1) C1 (0)=(1,1) C 2 (1)=(1,1,-1,-1) C 0 (0)=(1) C 2 (2)=(1,-1,1,-1) C1 (1)=(1,-1) C 2 (3)=(1,-1,-1,1) Code Order 0 (SF 1) Code Order 1 (SF 2) Code Order 2 (SF 4) C 3 (0)=(…) C 3 (1)=(…) C 3 (2)=(…) C 3 (3)=(…) C 3 (4)=(…) C 3 (5)=(…) C 3 (6)=(…) C 3 (7)=(…) Code Order 3 (SF 8) The codes are layered from 0 to 11 according to the Spreading Factor (SF) • Cm(n) : The code order, m, and the code number, n, designates each and every code in the layered orthogonal code sequences • In DL code order 2 to 8 (SF 4 to 512) are available (Nokia RAN does not support SF = 512) • In ULConfidential Company code order 2 to 7 (SF 4 to 256) are available 60 © Nokia Siemens Networks Radio Resource Manager / June2007
    • 59. Spreading Code Allocation • A code is always allocated from the optimum location in the code tree. It makes the allocated code and the codes in the branches below and above the allocated code unavailable • Code tree will fragment quickly if releases is not re-arranged • Re-arrangements in the code tree is done by reallocating the codes in better locations • The above code tree has 4 codes of equal order. The best locations are in the same branch and very close to one another. The badly located codes are released and optimally reallocated allowing the use of upper layer codes • Codes are only reallocated when there is a benefit at two code tree layers above the code being reallocated Company Confidential 61 © Nokia Siemens Networks Radio Resource Manager / June2007

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