Quality of service


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Quality of Service (QoS) is an important concept in any network which ultimately leads to network efficiency and customer satisfaction. In this PPT, we deal mainly with the Quality of Service aspects relating to Femto Access Point (FAP) of UMTS technology. PPT mainly deals with the Guaranteed Bit Rate (GBR) implementations.

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Quality of service

  1. 1. Krishna Adapa V MUMTS System Architecture
  2. 2.  UMTS QoS architecture and Evolution Service and User Prioritization Strategies QoS Management in RNS/FAP  Release 99 Channels  HSDPA Channels  HSUPA Channels QoS Management in Core Network Elements QoS Management in Backhaul Network
  3. 3.  Scope: Quality of Service (QoS) is a network wide topic and its actual scope in-terms of depth and width are tremendous. This presentation is primarily meant to focus on the Home Node B (HNB) NW element related functionality pertaining to Guaranteed Bit Rate (GBR) implementations. Other aspects are just touched to provide relevant overview of the topic under consideration. Some aspects are purposefully simplified when compared to the functionality of macro network element (NodeB/RNC) Acknowledgements: Simulations, Algorithms and other concepts referred in this presentation are obtained from listed references. They are, by no means, original contributions from the author.
  4. 4. 3GPP Architecture Evolution
  5. 5.  Voice over IP (VOIP):  Mouth to ear delays (200 to 300 msec)  Packet RTT (150 to 200msec)  Bit Rate (16 to 64 kbps) depending on CoDeCs Web browsing:  High data rate (200 to 400kbps)  Short packet RTT (<200msec) Streaming:  Bit rate 64kbps to 128kbps  Stable bit rates and small bit rate variations
  6. 6. UMTSTE MT RAN CN CN TE EDGE Gateway NODE End-to-End Service TE/MT Local UMTS Bearer Service External Bearer Bearer Service Service Radio Access Bearer Service CN Bearer Service Radio Bearer RAN Access Backbone Service Bearer Service Bearer Service Physical Radio Physical Bearer Service Bearer Service
  7. 7. TE MT RAN CN EDGE Gateway Ext. Netw. Adm./Cap. Adm./Cap. Adm./Cap. Subscr. Adm./Cap. Transl. Control Control Control Control Control Transl. Local Ext.Service ServiceControl UMTS BS UMTS BS UMTS BS Control Manager Manager Manager RAB Manager Local BS Radio BS Radio BS RA BS RA BS CN BS CN BS Ext. BS Manager Manager Manager Manager Manager Manager Manager Manager RAN RAN RA NS RA NS BB NS BB NS ph. BS M ph. BS M Manager Manager Manager Manager protocol interface service primitive interface
  8. 8. TE MT RAN CN EDGE Gateway Ext. Netw. Class if. Class if. Cond. Cond. Cond. Mapper Mapper Mapper Local BS Resource Resource Resource Resource Resource Resource External BS Manager Manager Manager Manager Manager Manager RAN phys. BS RAN Access network service BB network service data flow with indication of direction
  9. 9.  Traffic Class Maximum Bit Rate Guaranteed Bit Rate Delivery Order Maximum SDU Size SDU Format Information SDU Error Ratio Residual Bit Error Ratio Delivery of Erroneous SDUs Transfer Delay Traffic Handling Priority Allocation/Retention Priority Source Statistics Descriptor
  10. 10.  QoS Parameter Request by the UE at PDP Ctx Activation to SGSN. SGSN Admission Control. QoS parameter negotiation between SGSN – GGSN in Create PDP context request/response. GGSN Admission Control. QoS parameter negotiation between SGSN – FAP through RAB Assignment Request/Response Radio Interface Protocol parameters derivation by FAP Admission Control (RLC modes, SIR/BLER targets, Transport channels selection, TFCS selection/definition, Scheduling Priority Indicator derivation, GBR configuration etc) and Radio Bearer configuration Negotiated QoS profile to UE in PDP Context Accept (if accepted)
  11. 11.  In R5: Allows Proxy Call Session Control Function (P-CSCF) (Policy Decision Function - PDF) to provide dynamically the IMS application characteristics to GGSN through Go interface GGSN acts as an enforcement point (PEP) and thus enables dynamic QoS control by performing gating on the user data flows In R6: The PDF is logically separated from Application Function (ex, P-CSCF) through Gq interface, allows dynamic QoS support for non IMS domains Also allows other than SIP and SDP application session protocols to be used Allows the possibility to multiplex several service applications/multimedia components on to the same PDP context. The PDF remains single and same QoS is applied to all components. NOTE: This is just for information: Clearly 3GPP R5/R6 is a significant architectural shift from the existing base architecture. So, proposal is we will not implement this.
  12. 12. Subscription Profile AF Repository (SPR) Rx Sp Policy and Charging Rules Function (PCRF) Online Charging System (OCS) CAMEL Service Data Flow SCP Based Gx Credit Control PCEF Gy GW Gz Offline Charging System (OFCS)NOTE: This is just for information: Clearly 3GPP R5/R6 is a significant architectural shift from the existing base architecture. So, proposal is we will not implement this.
  13. 13.  Diverse applications and diverse QoS requirements For the purpose of QoS management, applications can be categorized (3GPP R99 categorization) in to:  Conversational  Streaming  Interactive  Background For the simplicity, we would propose maintaining four distinctive QoS profiles at the Core Network each correspond to one Traffic Class. These profiles shall be configurable (be careful when changing since we would only change to a value that we are sure we could sustain in our network) and are picked by SGSN depending on the Traffic Class received
  14. 14.  In many a network, operator would like to prioritize a certain group of users depending on their subscription/user profiles. For ex, users could be categorized in to: Gold Users: Gold users are users by the virtue of their subscription gets highest privilege in the network Silver Users: Silver users are next to Gold users in terms of their treatment (data of course!) Bronze Users: Bronze users receive the lowest attention. Their QoE depends on the presense/absence of other higher priority users in the network at any given moment
  15. 15.  Priority assignment/differential treatment that a user’s data flow gets in the network depends on:  The application characteristics and/or  User prioritizations and/or  Other operator policies For ex, we could imagine:  Case1: An operator policy which is user category centric  Case2: An operatory policy which is application centric
  16. 16. • I would propose to make this mapping configurable to leave the flexibility to the customer to accommodate their changing requirements • For ex, one could assign SPI15 to SPI4 to MC0 to MC11 A Management Class (MC) is a way that we would like to treat a user’s data in the network
  17. 17. NOTE: Study is pending on the need for the requirement of PDP context modification procedure and/or Secondary PDP context support depending on different scenarios (explained in later slides). For ex,1) An application is launched when no PDP context exist. This might lead to a primary PDP context activation with a proper Traffic Class included2) An application is launched when a primary PDP context is already active (for ex, through a former web browsing session). This might lead to a PDP context modification to activate/re-negotiate a QoS profile which is the best of both applications. Another possibility could be that it leads to a Secondary PDP context activation depending on whether the UE supports secondary PDP context
  18. 18.  In summary, there are practical difficulties in selecting one of them:  MS do not request any QoS  Many MS support single PDP context  The Application API being open, potential misuse of RT PDP contexts One possibility is to implement non-standard defined service differentiation in GGSN for ex, by looking inside the IP flow through Layer4/7 lookup Once the user service is identified, then the QoS is upgraded/downgraded through PDP context modification. When several IP flows are existing for the same PDP context, the one with the need of maximum QoS can be provisioned
  19. 19.  Parameters relevant for the QoS treatment in the Core Network for traffic differentiation are:• Bandwidth Management and CPU utilization management are two aspects that can be considered for QoS management in CNE nodes• We could consider some BW is allocated for each TC and the AC will monitor this for the RT/NRT user admission• Similarly for CPU thresholds can be defined for the AC purposes for RT/NRT users• These Topics are FFS
  20. 20.  There are three area of QoS treatment in CNE: Functions/procedures that implement QoS inside the CNE nodes, for ex, as described earlier:  BW management  CPU management QoS management at CNE edge interfaces for the Traffic Management  Interface towards external networks (DiffServe edge functionality towards external IP network)  Interface towards Iu, Gn (DiffServ edge functionality towards radio and backbone network)
  21. 21.  SGSN and GGSN will mark the DSCP in the transport IP header according the the traffic handling priorities previously defined QoS aware (DiffServe supported functionality) routers in the IP network would examine this DSCP filed and treat according to the priorities defined An example of DiffServ marking table is include in Appendix – C NOTE: We many not need to implement this functionality of DSCP marking towards Iu since it would be either a VLAN or LAN between SGSN and FAP in our network (this is FFS)
  22. 22.  The traffic conditioning in GGSN is used to monitor the ingress traffic characteristics (data rate) against the negotiated QoS parameters (Maximum Bit Rate - MBR/Guaranteed Bit Rate - GBR) One typical example algorithm that could be used (proposed as normative reference algorithm in 3GPP) is a Token Bucket Algorithm: The input to the bucket is the incoming bursty data flow and the out put is the conditioned data flow at the negotiated rate.
  23. 23. OK OK Non-compliantTBC L1<TBC L2<TBC L3>TBCb b-L1+r* T b-L1 TimeNotation Used in the Above Algorithm: b – Bucket Size TBC – Token Bucket Counter (available tokens) L1, L2, L3 – Received Packet Lengths R – Conditioned Rate/Output rate
  24. 24. Release 99 Channels
  25. 25.  Transport Channel Selection Power Control (Not treated in length in this presentation)  Open Loop Power Control  Fast Power Control (Inner Loop)  Slow Power Control (Outer Loop) Admission Control (R99, HSDPA, HSUPA) Load Control Packet Scheduling (R99, HSDPA, HSUPA) Handover Control (Not dealt in this presentation)
  26. 26.  The type of transport channel selected is influenced by for ex, the QoS attributes and system performance. As an example, the delay sensitive applications involving conversational traffic class can be carried over DCH One idea would be to make the mapping table operator configurable
  27. 27.  NGBR traffic is always admitted except in the case of system overload, defined by:• GBR traffic is admitted when in addition to above condition:• Where: – PtxTotal: Current total transmitted power: Available from FAP common measurements – PtxTarget: Target transmit power: Known at FAP – PtxNC: Non Controlled power of GBR users: To be calculated (TBD) – DelP: Estimated power for the new GB users (see next Slide)
  28. 28.  The downlink power needed for the new GBR user can be calculated by the open-loop method as follows:• Where:• R: Required Guaranteed Bit Error Rate (GBR): Known at FAP• (Eb/No)dl: Downlink needed to achieve a level of error performance (BLER). Derived from the service, coverage and capacity planning: To be Derived (TBD)• CPICH_Tx_power: Total transmitted CPICH power: Known at FAP• (Ec/No)cpich: CPICH received Chip energy to Noise power. Available from UE measurement report• PtxTotal: Total transmitted power in the cell: Known at FAP• Alpha: Orthogonality factor: Configurable/Tunable parameter at FAP
  29. 29.  An NRT bearer is admitted if:• An RT bearer is admitted when above condition is fulfilled and if:• PrxTotal: Received Total Wideband Power (RTWP): Available from PICO L1 measurements• PrxTarget: Target Received Total Wideband Power (RTWPtarget): Known at FAP• DelI: Increase of wide band power caused by RT user: Unknown (To be Estimated)• PrxNC: Non-controlled power received (GBR users + Other cell users) – Need to see if this is Reference Total Wideband Power (when reported by PICO L1)
  30. 30.  The increase in the received wide band power due to admitting a GBR user can be calculated using:  Derivative method:• Integral method:• The fractional load increase is calculated by (refer next slide):
  31. 31.  Calculate the CDMA uplink load which is the sum of the loads of each user• Or by using (a simplified equation when the power of user Pk << IownNOTE: Above load equations are derived from general CDMA Eb/No notion:
  32. 32. • In some exceptional cases (exceptional when system is designed properly), the system can be overload. The overload condition is defined by: When such overloaded occurs, Load Control is used to bring the system back under control. Different strategies exist:  Reduce the NGBR bit rates  Drop low priority connections  Reduce GBR bit rates  Drop GBR connections (for ex, based on SPI)
  33. 33.  Assign Radio Resource Priority (RRP) for each bearer during Admission Control Dynamically manage the RRP according to the served bit rate Determine the TFC set according to the QoS parameters received (for ex, maximum and minimum bit rates) for GBR and NGBR bearers For a GBR bearer, the resource requests are always treated (provided the Ptarget criteria is met) The Pngbr is derived as the power available for NGBR bit rate scheduling
  34. 34.  Different scheduling algorithms possible: Ex, Fair Throughput Sharing, Fair Resource Sharing In FT, the Pngbr is equally allocated to users according to their priorities and request arrival times. In FR, the Pngbr is allocated keeping in view of the signal quality experience by users (for ex, users nearer to BS/experiencing good conditions get better share) . This is achieved by TFC resizing.
  35. 35. High Speed Downlink Packet Access (HSDPA) Channels
  36. 36.  Scheduling Priority Indicator (SPI): Indicates the relative priority of each priority queue. Range from 0 to 15 (15 being the highest priority) Discard Timer (DT): Time to Live for a received MAC-hs SDU. The timer is started when the SDU is received at the queue. Range from 20msec to 7500msec MAC-hs GBR: Guaranteed no of bits that the Mac-hs needs to deliver under normal conditions.
  37. 37.  Non-HSDPA Power: Power of all codes not used for HS-DSCH and HS-SCCH transmission including common channels, simply termed as non-HSDPA power HS-DSCH Provided Bit Rate: Number of MAC-d PDU bits which are successfully transmitted over last measurement period divided by the measurement period. This is defined per SPI HS-DSCH Required Power: This is the power required for all users to meet their GBR criteria, reported per SPI. Non-GBR users are not included
  38. 38.  Unused power from DCH users is used for HSDPA scheduling In order to make sure that users admitted will meet their GBR criteria, it is important to dimension the DCH power and HSDPA power according to the capacity/coverage plans
  39. 39.  After transport channel selection, MAC-hs scheduler parameters defined above are assigned (SPI, GBR (same as the one received) and DT) as per policies defined. These policies could be, for ex, configurable at FAP/CNE, through a table. The following is such an example template (Note: MAC-hs GBR for Interactive/Background are optional)NOTE: The above is just an example: In reality there shall have to be a correspondence between the MCs defined earlier and the table above as detailed earleir
  40. 40.  A new HSDPA GBR user (or a user being considered for the incoming handover) is admitted provided the following is satisfied:• Phsdpa: Total configured HSDPA power: Known at FAP• Pnew: Estimated power required to satisfy the new GBR user• Pspi(x): Estimated power required to satisfy already admitted GBR users whose priority k greater than or equal to the priority of the new user (priority based AC): Obtained through PICO L1/L2 measurements• Pscch: HS-SCCH estimated power: Known at FAP with some in-accuracy• P0: Power Offset used to compensate estimation errors for Pnew, Pspi and Pscch: Configurable/Tunable Parameter
  41. 41.  The HS-DSCH SINR can be calculated from the following expression:• SF16: Spreading Gain factor corresponding to Spreading Factor 16• Ptx,dsch: HSDPA transmit power: Known at FAP• Ptx,pilot: CPICH transmit power: Known at FAP• Ppilot: CPICH Ec/Io: Obtained through UE measurement report• Alpha: Orthogonality factor: Configurable/Tunable Parameter• Pxtx,tot: Total Transmit Power: Known at FAP
  42. 42.  Calculate the maximum bit rate possible with the derived SINR figure (possibly through a table stored at FAP obtained through simulation studies - refer Annex for example)  Power needed to serve the GBR for the new user is then calculated as:• Ptx,dsch: HSDPA transmit power to achieve the throughput f(p): Known at FAP• GBRnew: Guaranteed Bit Rate of the new GBR user: Known at FAP• f(p): Derived throughput for the derived SINR: A priori knowledge from simulation study
  43. 43.  For an incoming handover, the same priority based admission control algorithm apply. Ie, The handover user with SPI x will have priority admission over all users with SPI <= x Usually in a macro scenario, the Admission Controls can implement special algorithms during intra-RNC handover procedure to see if the target cell can accommodate the GBR user. In the scenario of FAP no such special algorithms are possible since the view is limited to single cell
  44. 44.  Same principles as mentioned earlier for R99 load control apply for HSDPA or for a mixed load (DCH + HSDPA)  Drop NGBR connections (note that the NGBR throughput is autonomously managed by scheduler with programmed SPI, so nothing much to be done there)  Reduce GBR configuration for ex based on SPI configuration  Possibly drop less priority GBR connections  Overload control action could start either from DCH or from HSDPA (which one to be given importance could be configured through an operator defined parameter)
  45. 45. High Speed Uplink Packet Access (HSUPA) Channels
  46. 46.  The power utilization in the uplink when E-DCH is configured is shown below:
  47. 47.  The Admission Control for HSUPA is based on similar principles are R99 uplink admission (FFS) The Guaranteed Bit Rate (GBR) of HSUPA users is achieved using the non-scheduled grants FAP programs PICO L1/L2 and UE with certain grants (non-scheduled grants). UE uses there grants to send uplink transmission whenever it has data. PICO L1/L2 uses this value to reserve the uplink resources for the GBR users Delay and Error performances parameters derivation, related to HSUPA, from the QoS attributes are FFS
  48. 48.  In conventional networks, the GPRS CN is based on the IP transport network. Different solutions can be used for the service differentiation  Differentiated service handling  Multi Protocol Label Switching (MPLS)  L2/L1 related methodologies like VLAN feature of ethernet Similar methods cold be used on IuB when the backhaul is based on the IP transport. If ATM is used, ATM specific methods like VBR, CBR can be used for differentiated traffic handling
  49. 49.  Quality of Service (QoS) Concept and Architecture – 3GPP 23.107 QoS and QoE Management in UMTS Cellular Systems - David Soldani, Man Li, Renaud Cuny. John Wiley & Sons, LTD QoS Management in UMTS Terrestrial Radio Access FDD Networks, D.Soldani, Dissertation for PhD in Technology, Helsinki University of Technology, October 2005 Policy and Charging Control Architecture – 3GPP 23.203 Quality Based HSDPA Access Algorithms – Claus I. Pedersen, IEEE VTC 2005
  50. 50.  Channel Profile: Pedestrian A UE Speed: 3 km/h Target BLER: 10% User positions simulated with Geometric (G) factor defined as own cell power to interference cell power received at UE Used MCS schemes are depicted in the table below
  51. 51.  HSDPA Throughput for a single code
  52. 52. Traffic class Conversational class Streaming class Interactive class Background classMaximum bitrate (kbps) <= 256 000 (2) (7) <= 256 000 (2) (7) <= 256 000 (2) (7) <= 256 000 (2) (7)Delivery order Yes/No Yes/No Yes/No Yes/NoMaximum SDU size (octets) <=1 500 or 1 502 (4) <=1 500 or 1 502 (4) <=1 500 or 1 502 (4) <=1 500 or 1 502 (4)SDU format information (1) (5) (5)Delivery of erroneous SDUs Yes/No/- Yes/No/- Yes/No/- Yes/No/-Residual BER 5*10-2, 10-2, 5*10-3, 10-3, 5*10-2, 10-2, 5*10-3, 10-3, 10- 4*10-3, 10-5, 6*10-8 (6) 4*10-3, 10-5, 6*10-8 (6) 10-4, 10-5, 10-6 4, 10-5, 10-6SDU error ratio 10-2, 7*10-3, 10-3, 10-4, 10-5 10-1, 10-2, 7*10-3, 10-3, 10-4, 10-3, 10-4, 10-6 10-3, 10-4, 10-6 10-5Transfer delay (ms) 80 – maximum value 250 – maximum valueGuaranteed bit rate (kbps) <= 256 000 (2) (7) <= 256 000 (2) (7)Traffic handling priority 1,2,3Allocation/Retention priority (1)- Priority Level 1,2, ..., 15 1,2, ..., 15 1,2, ..., 15 1,2, ..., 15- Pre-emption Capability Yes/No Yes/No Yes/No Yes/No- Pre-emption Vulnerability Yes/No Yes/No Yes/No Yes/NoSource statistic descriptor Speech/unknown Speech/unknownSignalling Indication Yes/No