Radio Resource Management Overview.pptx 3G

3G Basic

1. Radio Resource Management Overview Sit Dolor Amet

2. RRM Tasks RRM must be able to: Predict the impact on interference (power) of the admitting a new user for UL & DL Perform appropriate actions (e.g. new call admissions, bitrate increase/decrease etc.) in accordance with prevailing load conditions 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 Load Target Overload Margin Power Time Estimated capacity for NRT traffic Measured load caused by non-controllable load (RT) RT services must have higher quality assurance than NRT

3. RRM is made up of a number of closely interdependent functions (i.e. algorithms) These functions can be divided into; Cell Based Load Control (LC) Admission Control (AC) Packet Scheduling (PS) Resource Manager (RM) Connection Based Handover Control (HC) Power Control (PC) RRM Functional Split PC HC Connection based functions LC AC Cell based functions PS RM

4. Power Control PC WCDMA systems are interference limited; therefore, it is beneficial to reduce transmission power as far as possible (without violate the required quality). Thus, the target of PC is to achieve the min. SIR that is required to offer sufficient quality of the connection. PC works on a per-connection basis. Power Control Power Control Load Control RNC BTS MS Power Control Handover Control Admission Control Load Control Packet Scheduler

5. Load Control functions The load control function within RRM can be divided: Preventative load control (e.g. congestion) Overload control (e.g. dropping of calls in worst case) Preventative actions are performed before the cell is overloaded (threshold y) Overload actions are performed after cell is overloaded (threshold x) RNP parameters define the thresholds for the RRM functionalities The thresholds define a stable functionality within a cell & with surrounding cells Overload threshold x Load Target threshold y Power Time Estimated capacity for NRT traffic. Measured load caused by non-controllable load (RT) Preventative Load Control Overload Control

6. Load Control LC LC performs the function of load control in association with Admission Control AC & Packet Scheduling PS Updates load status using measurements & estimations provided by AC & PS Continuously feeds cell load information to PS & AC: Interference levels BTS power levels Non-controllable load LC AC PS NRT load Load change info Load status Load differentiation: Total load = Controllable load + Semi-controllable load + Non-controllable load

7. Admission Control AC Checks that admitting a new user will not sacrifice planned coverage or quality of existing connections Determines whether RABs or RRC connections can be admitted Handles RT RABs by estimating the increase in non-controllable load In the decision UL interference & DL power measurements by BTS are used Since RAS06 the UL throughput is considered for AC, too UL & DL admission conditions must both be fulfilled to admit a new call or modified existing call Provides RLC parameters to PS for NRT users, e.g. Bearer class Transport Formats AC sets quality and power parameters for the radio link, e.g.: UL/DL BLER, Eb /No targets, SIR target Initial DL transmission power AC takes place in the RNC Admission Decision Grant Reject

8. PS allocation times need to be fast to accommodate changing conditions & accurate (up-to-date load info) Capacity requests sent via traffic volume measurement reports (governed by RNP parameters) PS comprises two parts: UE specific & Cell specific HSDPA & HSUPA resources are scheduled by the Node B power time non-controllable load controllable load Total Load Target threshold Overload threshold Packet Scheduler in RNC schedules radio resources for both UL & DL R99 NRT RABs Scheduling period defined by RNP parameters PS relies on up-to-date information from AC & LC Capacity allocated on a needs basis using ‘best effort’ approach Packet Scheduler PS Non Controllable Load : RT (R99) Controllable Load : HSDPA

9. Handover Control HC Intra-Frequency Handovers Softer/Soft Handover UE simultaneously connected to multiple cells from same/different Node Bs Mobile Evaluated Handover MEHO Hard Handover when Inter-RNC SHO is not possible ( Iur not supported or Iur congestion) in case of HSDPA Inter-Frequency Handover can be Intra-BS, Intra-RNC or Inter-RNC Network Evaluated Handover NEHO Inter-RAT Handover Handovers between WCDMA and GSM, LTE or WLAN Network Evaluated Handover NEHO WCDMA F1 WCDMA F1 WCDMA F1 WCDMA F2 WCDMA F2 WCDMA F1 HC is responsible for: Managing the mobility aspects of an RRC connection as UE move around network Maintaining connection quality by ensuring UE is always served by best cell saving capacity GSM GSM WCDMA MEHO : UE prepares the HO decision, final decision is RNC (because RNC knows overall load of system and other info regarding HO NEHO : RNC decide the HO

10. Resource Manager RM Responsible for managing the logical radio resources of the RNC in co-operation with AC and PS On request for resources, from either AC(RT) or PS(NRT), RM allocates: DL Channelization Code UL Scrambling Code cares about code tree management (to maintain orthogonality); Initial code selection – codes concentrated to same branch Code de-fragmentation – dynamic reallocation of codes as users enter/leave system DL spreading code allocation for HSDPA users can be dynamic from RAS06 on Code Type Uplink Downlink Scrambling codes Channelization codes User separation Cell separation Data & control channels from same UE Users within one cell

11. HSDPA - general principle Fast scheduling is done directly in Node-B based on feedback information from UE and knowledge of current traffic state. Hard Handover only UE2 Channel quality (CQI, Ack / Nack , TPC) Channel quality (CQI, Ack / Nack , TPC) Data Data Users may be time and/or code multiplexed New WBTS functions : Fast HARQ retransmissions Fast Adaptive Modulation & Coding Fast Packet data scheduling (short TTI) UE1

12. HSUPA / Comparing HSUPA to R99 and HSDPA HSUPA is 3GPP Rel6 “Enhanced FDD Uplink” main characteristics: Fast WBTS Packet Scheduling Fast L1 HARQ algorithms Fast Link Adaptation 2ms or 10ms TTI periods Soft Handover SF down to SF = 2 Peak Rates up to 5.76 Mbps Feature Rel99 DCH Rel5 HSDPA Rel6 HSUPA Var. spreading factor Y N Y Fast power control Y N Y Adaptive modulation N Y N WBTS based scheduling N Y Y Fast L1 HARQ N Y Y Soft Handover Y N Y TTI length [ms] 80,40,20,10 2 10,2 E-DCH