HSDPA/HSUPA Packet Scheduling JARNO NIEMELÄ

Advanced Topics in Radio Network Planning, TUT2 Outline  Principles of packet scheduling in WCDMA / HSDPA Rel’05  Performance analysis of HSDPA PS for NRT services [1]  Scheduling in E-DCH/HSUPA (NRT services) [2]

Advanced Topics in Radio Network Planning, TUT3 Packet scheduling in WCDMA/HSDPA Rel’05  NodeB controlled packet scheduling (fast). MULTIUSER DIVERSITY (Selection diversity) TIME SHARED ALLOCATION OF HS-DSCH

Advanced Topics in Radio Network Planning, TUT4 Sensitivity of throuhgput for channel quality

Advanced Topics in Radio Network Planning, TUT5 Task of packet scheduler  To schedule interactive and background services (NRT) for users.  To allocate radio resources efficienctly for a cell such that cell capacity will be maximized while fulfilling the QoS requirements according to certain policy.  To monitor allocation of NRT services and system loading.  To perform load control actions.

Advanced Topics in Radio Network Planning, TUT6 Input parameters for packet scheduler  Resource allocation  HS-PDSCH and HS-SCCH powers  HS-PDSCH codes  Number of HS-SCCHs  Downlink channel quality measurements  CQI reports  Power measurements on associated DPCH  HARQ acknowledgements  QoS parameters  QoS attributes  Scheduling priority indicator (SPI)  Guarantee bit rate  Miscellaneous  Amount of buffered data  Mobile capabilities

Advanced Topics in Radio Network Planning, TUT7 Fairness  Selection of scheduling approach is always a trade- off between the fairness and maximum cell throughput.  C/I scheduling maximizes the system capacity with the cost of lack of fairness.  Fair resources scheduling distributes equally the radio resources (codes, power and allocation time). Not completely fair.  Fair throughput tries to provide the same throughput for all users.

Advanced Topics in Radio Network Planning, TUT8 Packet scheduling algorithms  Slow scheduling methods (Blind)  Average C/I  Round robin  Fair throughput  Does not consider instantaneous radio conditions  Fast scheduling methods (Advanced/opportunistic)  Maximum C/I  Proportional fair  Fast fair throughput  Utilizes temporary changes of radio conditions Per TTI basis (2ms) ~100 ms scheduling period

Advanced Topics in Radio Network Planning, TUT9 Slow scheduling methods  Average C/I (Avg. C/I)  Priorities users with the highest average C/I (~100 ms period)  Fast fading averaged out  Round Robin (RR)  Cyclic order used without considering channel conditions  Blind method  Simple and allocates radio resources evenly between the users (=high fairness)  Fair Throughput (FTH)  No instantaneous channel information utilized  Priorities users with lowest average throughput

Advanced Topics in Radio Network Planning, TUT10 Fast scheduling methods (1/2)  Maximum C/I (Max. C/I)  Serves in every TTI (transmission time interval) the user with the best radio conditions with the largest supportable bit rate.  High cell throughput, low fairness.  Proportional fair (PF)  Serves the user with largest relative channel quality: where P i (t) denotes the user priority.  User’s with relatively good channel conditions are served. Available information of CQI and previous transmissions is utilized.

Advanced Topics in Radio Network Planning, TUT11 Fast scheduling methods (2/2)  Fast fair throughput (FFTH)  Aims at providing a fair throughput distribution among all the users in the cell, while still taking advantage of the fast fading variations where is the average supportable data rate of a user i andis a constant that indicates the maximum average supportable data from all j users.

Advanced Topics in Radio Network Planning, TUT12 Summary

Advanced Topics in Radio Network Planning, TUT13 Multi-user diversity  Fast allocation (2ms TTI) of radio resources  Users with good radio conditions served  Multi- user diversity (selection diversity)  Increases the system/ cell throughput  The gain naturally depends on the dynamics of fast fading (short term variations)

Advanced Topics in Radio Network Planning, TUT14 Throughput vs. E s /N 0

Advanced Topics in Radio Network Planning, TUT15 Gain of multi-user diversity Diversity order = number of scheduled users

Advanced Topics in Radio Network Planning, TUT16 Performance analysis of PS in HSDPA

Advanced Topics in Radio Network Planning, TUT17 User throughput distribution 2 Mbps load for slow and 3 Mbps load for fast scheduling algorithms Pedestrian A channel (3 km/h)

Advanced Topics in Radio Network Planning, TUT18 Average user throughput CELL EDGE CLOSE TO BS

Advanced Topics in Radio Network Planning, TUT19 Efficiency of resource utilization  Fast scheduling is able to use more efficiently higher MCSs.

Advanced Topics in Radio Network Planning, TUT20 Link utilization

Advanced Topics in Radio Network Planning, TUT21 Performance of Max C/I and PF under high load Provisioning of fairness in high load starts to be problem with Max C/I

Advanced Topics in Radio Network Planning, TUT22 Cell throughputs (1/2)  With minimum user throughput guarantees (< 64 kbps) PEDESTRIAN A (3 km/h) VEHICULAR A (3 km/h)

Advanced Topics in Radio Network Planning, TUT23 Cell throughputs (2/2) PEDESTRIAN A (3 km/h)

Advanced Topics in Radio Network Planning, TUT24 Summary table of cell throughputs with minimum user throughput 5 % OUTAGE LEVEL

Advanced Topics in Radio Network Planning, TUT25 Conclusions from PS methods for HSDPA  Selection of PS algorithm important for HSDPA capacity maximization and QoS provisioning.  Multi-user diversity gain for users 100 % in PedA and 50 % in VehA channels (over RR).  Max C/I maximizes the cell throughput (with degraded QoS provisioning)  Proportional fair scheduler seems to provide a trade-off between QoS and cell throughput (time dispersion of the channel still a great problem.

Advanced Topics in Radio Network Planning, TUT26 Fast packet scheduling for E-DCH/HSUPA

Advanced Topics in Radio Network Planning, TUT27 UL PS in REL’99  RNC –based packet scheduling  Upgrading based on capacity requests  Downgrading based on inactivity timer

Advanced Topics in Radio Network Planning, TUT28 PS approaches for Node B scheduling (1/2)  Blind data rate detection (BRD)  Instantaneous (TTI=10ms) data rate observed by Node B and compared to maximum allowed. This information is thereafter used for resource allocation according to UE´s actual needs.  PS algorithm based on resource utilization factor (RUF)

Advanced Topics in Radio Network Planning, TUT29 PS approaches for Node B scheduling (2/2)  Time Division Multiplexing (TDM)  Fast allocation (TTI=2ms) based on same approach as in HSDPA.  Easier to keep resource utilization closer to the planned one.  Exploitation of instantaneous channel conditions.  Requires uplink syncronization 1) Utilization of USTS (uplink synchronous transmittion scheme) [5] 2) Synchronization achieved through DL frames. Would require guard intervals together with using the information provided by RTT.  To support SHO, only one Node B is allowed to perform scheduling decisions.  Allocation strategies (RRFT, maximized transmit power efficincy (MTPE), PFT)

Advanced Topics in Radio Network Planning, TUT30 Performance analysis (macrocellular)

Advanced Topics in Radio Network Planning, TUT31 Performance analysis (macrocellular)

Advanced Topics in Radio Network Planning, TUT32 Performance analysis (microcellular)

Advanced Topics in Radio Network Planning, TUT33 Performance analysis (microcellular)

Advanced Topics in Radio Network Planning, TUT34 Performance analysis

Advanced Topics in Radio Network Planning, TUT35 Conclusions from PS for E-DCH/HSUPA  Node B PS based on BRD is able to provide % capacity gain over RNC based PS (TVM)  Intuitively, channel-dependent methods are able to provide better performance  Uplink synchronisation provides capacity gain of 20%.  Extra signalling load might reduce the capacity gains in some extent.

Advanced Topics in Radio Network Planning, TUT36 Main references 1. Pablo José Ameigeiras Gutiérrez, “Packet Scheduling and Quality of Service in HSDPA”, Ph. D. Thesis, Aalborg University, Denmark, October José Outes Carnero, “Uplink capacity enhancements in WCDMA,” Ph. D. Thesis, Aalborg University, Denmark, March H. Holma, A. Toskala (ed.), “WCDMA for UMTS,” 3rd ed., John Wiley & Sons, Ltd., 2004.

Advanced Topics in Radio Network Planning, TUT37 Accessory references 4. J. Laiho, A. Wacker, T. Novosad, “Radio Network Planning and Optimisation for UMTS,” John Wiley & Sons, Ltd., GPP, “Study report of Uplink Synchronous Transmission Scheme (USTS),” TR , Ver 5.00, Rel. 5., December 2001.