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LTE Advanced

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  1. 1. LTE-Advanced October 2011 Bong Youl (Brian) Cho, 조 봉 열 brian.cho@nsn.com
  2. 2. TTA LTE/MIMO Standards/Technology Training 2 © Nokia Siemens Networks Contents • Beyond R8 LTE Standardization • LTE-Advanced Technologies • SON • Long Term HSPA Evolution (LTHE)
  3. 3. TTA LTE/MIMO Standards/Technology Training 3 © Nokia Siemens Networks Beyond R8 LTE Standardization
  4. 4. TTA LTE/MIMO Standards/Technology Training 4 © Nokia Siemens Networks Release of 3GPP specifications 1999 2000 2001 2002 2003 2004 2005 Release 99 Release 4 Release 5 Release 6 1.28Mcps TDD HSDPA, IMS W-CDMA HSUPA, MBMS, IMS+ 2006 2007 2008 2009 Release 7 HSPA+ (MIMO, HOM etc.) Release 8 2010 2011 LTE, SAE ITU-R M.1457 IMT-2000 Recommendations Release 9 LTE-AdvancedRelease 10 GSM/GPRS/EDGE enhancements Small LTE/SAE enhancements
  5. 5. TTA LTE/MIMO Standards/Technology Training 5 © Nokia Siemens Networks Definition • What is IMT-Advanced? – A family of radio access technologies fulfilling IMT-Advanced requirements – Relates to 4G as IMT-2000 relates to 3G – IMT spectrum will be available to both IMT-2000 and IMT-Advanced • What is LTE-Advanced? – Formal name: Advanced E-UTRA /Advanced E-UTRAN – Evolution from 3GPP LTE specifications, not a revolution  Comparable potential of 3GPP LTE with target requirements of IMT-advanced  Fast and efficient correspondence against the timeline of WP5D’s specification and commercialization for IMT-advanced  Cost-efficient support for backward and forward compatibility between LTE and LTE-A  Natural evolution of LTE (LTE release 10 & beyond)
  6. 6. TTA LTE/MIMO Standards/Technology Training 6 © Nokia Siemens Networks System Performance IMT-Advanced requirements and time plan Rel. 8 LTE LTE-Advanced targets Time General Requirements for LTE-Adv • LTE-Advanced is an evolution of LTE • LTE-Advanced shall meet or exceed IMT-Advanced requirements within the ITU-R time plan • Extended LTE-Advanced targets are adopted • LTE-Advanced will be deployed as an evolution of LTE R8 and on new bands. • LTE-Advanced shall be backwards compatible with LTE R8 in the sense that – an LTE Release 8 terminal can work in an LTE-Advanced NW – an LTE-Advanced terminal can work in an LTE Release 8 NW
  7. 7. TTA LTE/MIMO Standards/Technology Training 7 © Nokia Siemens Networks • Comparison b/w IMT-Advanced and LTE-Advanced System Performance Requirements
  8. 8. TTA LTE/MIMO Standards/Technology Training 8 © Nokia Siemens Networks System Performance Requirements • Average Spectral Efficiency (SE) and Edge Spectral Efficiency for LTE Case-1  40~60% improvement of average spectrum efficiency over LTE Rel-8
  9. 9. TTA LTE/MIMO Standards/Technology Training 9 © Nokia Siemens Networks Release 9 • Enhanced Home NodeB / eNodeB • Support for IMS Emergency Calls over LTE • LCS for LTE and EPS • MBMS support in EPS • Enhanced Dual-Layer transmission for LTE • SON • Deleted - Support of WiMAX - LTE Mobility • Deleted - Support of WiMAX - UMTS Mobility
  10. 10. TTA LTE/MIMO Standards/Technology Training 10 © Nokia Siemens Networks Release 10 • Network Improvements for Machine-Type Communications • Carrier Aggregation for LTE • Enhanced Downlink Multiple Antenna Transmission for LTE • Uplink Multiple Antenna Transmission for LTE • Relays for LTE • Enhanced Inter-Cell Interference Control (ICIC) for non- Carrier Aggregation (CA) based deployments of heterogeneous networks for LTE • LTE Self Optimizing Networks (SON) enhancements • Further enhancements to MBMS for LTE • Minimization of Drive Tests for E-UTRAN and UTRAN • HNB and HeNB Mobility Enhancements
  11. 11. TTA LTE/MIMO Standards/Technology Training 11 © Nokia Siemens Networks Release 11 • Network-Based Positioning Support in LTE • Study on System Enhancements for Energy Efficiency • Study on Coordinated Multi-Point operation for LTE
  12. 12. TTA LTE/MIMO Standards/Technology Training 12 © Nokia Siemens Networks LTE-Advanced Technologies
  13. 13. TTA LTE/MIMO Standards/Technology Training 13 © Nokia Siemens Networks LTE-Advanced The advanced toolbox for making more out of LTE GSM LTE CDMA/EVDO HSPA+ LTE LTE HSPA+ LTE Subscribers reached Band- width HSPA+ GSM LTE TD-LTE More users More intensive usage At more locations Intial LTE rollout • LTE on initial bands • Macro topology Straight-forward evolution • Additional bands (paired, unpaired) • Refarming Advanced evolution • Macro + small cell topology • Aggregated bands • Advanced antenna schemes LTE-Advanced + More bandwidth Higher data rates Enhanced coverage Enhance macro network performance Enable efficient use of small cells
  14. 14. TTA LTE/MIMO Standards/Technology Training 14 © Nokia Siemens Networks The LTE-Advanced toolbox for delivering more data efficiently to wide areas and hotspots Enable efficient use of small cells Enhance macro network performance Relaying Heterogeneous Networks 100 MHz Carrier Aggregation Carrier1 Carrier2 Carrier3 … Carrier5 up to 100 MHz MIMO 8x 4x Coordinated Multipoint Peak data rate and throughput scaling with aggregated bandwidth Peak data rate scaling with antenna paths for urban grid and small cells MIMO Capacity and cell edge performance enhancements by active interference cancelation Enables focused capacity enancement with small cells by interference coordination Enables focused coverage extensions with small cells by self- backhaul
  15. 15. TTA LTE/MIMO Standards/Technology Training 16 © Nokia Siemens Networks HetNet • Consist of deployments where low power nodes are placed throughout a macro- cell layout • The interference characteristics in a heterogeneous deployment can be significantly different than in a homogeneous deployment • Mainly, two different heterogeneous scenarios are under consideration – Macro-Femto (CSG: Closed Subscriber Group) case – Macro-Pico case
  16. 16. TTA LTE/MIMO Standards/Technology Training 17 © Nokia Siemens Networks TDM eICIC Principle - combined macro+pico+HeNB case Almost blank, or MBSFN sub-frame Sub-frame with normal transmission Macro-layer Pico-layer HeNB-layer Macro-eNBs and Pico-eNBs can schedule also users that are close to non-allowed CSG HeNB(s), but not pico-UEs with larger RE. Pico-nodes can schedule UEs with larger RE, if not interfered from non- allowed CSG HeNB(s) Pico-UEs with larger RE, close to CSG HeNB(s) are schedulable
  17. 17. TTA LTE/MIMO Standards/Technology Training 18 © Nokia Siemens Networks Coordination between two cell layers
  18. 18. TTA LTE/MIMO Standards/Technology Training 19 © Nokia Siemens Networks Relay • Relay – as a tool to improve e.g. the coverage of high data rates, group mobility, temporary network deployment, the cell-edge throughput and/or to provide coverage in new areas • Rel-10 relay deployment scenario – Stationary relay – Single hop relay – No Inter relay handover
  19. 19. TTA LTE/MIMO Standards/Technology Training 20 © Nokia Siemens Networks Relay Types • Type 1 Relay – It control cells, each of which appears to a UE as a separate cell distinct from donor cell  Has unique physical-layer cell identity (defined in Rel.8)  Shall transmit its own synchronization, reference symbols, .. – The same RRM mechanisms as normal eNB – No difference in accessing cells controlled by a relay and cells controlled by a “normal” eNB from a UE perspective – Shall appear as a Rel.8 eNB to Rel.8 UE • Type 2 Relay – It does not have a separate Physical Cell ID – It is transparent to Rel-8 UEs;  A Rel-8 UE should not be aware of the presence of a type 2 relay node – At least part of the RRM is controlled by the eNB to which the donor cell belongs – It can transmit PDSCH – At least, it does not transmit CRS and PDCCH – L2 relay, smart repeaters, decode-and-forward relays – Not included in Rel.10
  20. 20. TTA LTE/MIMO Standards/Technology Training 21 © Nokia Siemens Networks Type 1 vs. Type 2 Coverage extension perspective Throughput enhancement perspective
  21. 21. TTA LTE/MIMO Standards/Technology Training 22 © Nokia Siemens Networks  CoMP transmission schemes in downlink • Joint processing (JP)  Joint transmission (JT): Downlink physical shared channel (PDSCH) is transmitted from multiple cells with precoding using DM-RS among coordinated cells  Dynamic cell selection: PDSCH is transmitted from one cell, which is dynamically selected • Coordinated scheduling/beamforming (CS/CB) PDSCH is transmitted only from one cell site, and scheduling/beamforming is coordinated among cells  CSI feedback (FB) • Explicit CSI FB (direct channel FB) is investigated to conduct precise precoding, as well as implicit CSI FB (precoding matrix index FB) based on Rel. 8 LTE  Tradeoff between gain and FB signaling overhead Coherent combining or dynamic cell selection Coordinated scheduling/beamformingJoint transmission/dynamic cell selection CoMP Transmission in Downlink
  22. 22. TTA LTE/MIMO Standards/Technology Training 23 © Nokia Siemens Networks CoMP Operations – JP, CS/CB
  23. 23. TTA LTE/MIMO Standards/Technology Training 24 © Nokia Siemens Networks  CoMP reception scheme in uplink • Physical uplink shared channel (PUSCH) is received at multiple cells • Scheduling is coordinated among the cells  Improve especially cell-edge user throughput • Note that CoMP reception in uplink is implementation matter and does not require any change to radio interface Receiver signal processing at central eNB (e.g., MRC, MMSEC) Multipoint reception CoMP Reception in Uplink
  24. 24. TTA LTE/MIMO Standards/Technology Training 25 © Nokia Siemens Networks Multi-cell Joint Operations • Normal cellular unicast communications • Inter-cell interference! • Soft handover • Reduced inter-cell interference but with SE loss • MBSFN • No inter-cell interference w/o SE loss, but only for multicast communcations • COMP – JP • Reduced inter-cell interference w/o SE loss, but requires significant X2 bandwidth a b b a a b a a a a b
  25. 25. TTA LTE/MIMO Standards/Technology Training 26 © Nokia Siemens Networks DL MIMO Trend
  26. 26. TTA LTE/MIMO Standards/Technology Training 27 © Nokia Siemens Networks ? • In CL-SU-MIMO, SVD-MIMO is the optimum SVD MIMO as a closed-loop MIMO
  27. 27. TTA LTE/MIMO Standards/Technology Training 28 © Nokia Siemens Networks x~ x V VH U UH y minn 1 1 ~w min ~ nw  Pre-processing Post-processing Channel ),0(~,, 0 r rt n nn NΝCC Iwyx wHxy   y~ With number of transmitting antenna=nt and receiving antenna=nr, MIMO Channel Decomposition
  28. 28. TTA LTE/MIMO Standards/Technology Training 29 © Nokia Siemens Networks wUxD wxVUDVU wxUDVU wHxU yUy H HH HH H H      ~ )~( )( )( ~ wxDy ~~~  Channel Diagonalization
  29. 29. TTA LTE/MIMO Standards/Technology Training 30 © Nokia Siemens Networks • Benefits of Spatial Diversity – Array gain – Diversity gain and decreased error rate – Increased data rate – Increased coverage or reduced transmit power • Receive Diversity – Selection combining, Equal gain combining, and Maximal radio combining (MRC) • Transmit Diversity – Open-loop transmit diversity: e.g., Alamouti coding – Closed-loop transmit diversity: e.g., Linear precoding y = G(HFx + n) where x is the transmited symbol vector, y is the received symbol vector with M x 1, G is the post-coder matrix with M x Nr, H is the channel matrix with Nr x Nt, F is the precoder matrix with Nt x M For the diversity precoding, M = 1, and the SNR maximizing precoder F and postcoder G are the right- and left- singular vectors of H corresponding to its singular value, max. Spatial Diversity
  30. 30. TTA LTE/MIMO Standards/Technology Training 31 © Nokia Siemens Networks • DOA (Direction-Of-Arrival)-based Beamforming – Physically directed – Incoming signals to a receiver may consist of desired energy and interference energy. – From the acquired DOAs, a beamformer extracts a weighting vector for the antenna elements and uses it to transmit or receive the desired signal of a specific user while suppressing the undesired interference signals. – Often called null-steering beamformer – Viable only in LOS environments or in environments with limited local scattering around the transmitter • Eigen Beamforming – Mathematically directed – Eigen beamforming exploits CSI of each antenna element to find array weights that satisfy a desired criterion, such as SNR maximization or MSE minimization. – Eigen beamforming is conceptually nearly identical to the linear diversity precoding, the only difference being that the eigen beamforming takes interfering signals into account. – More viable in realistic wireless broadband environments, which are expected to have significant local scattering Beamforming
  31. 31. TTA LTE/MIMO Standards/Technology Training 32 © Nokia Siemens Networks 3GPP Release 8 LTE DL transmission modes Two approaches to multi-antenna transmission MCS CQI PMI Rank CQI MCS PMI Rank PDSCH Channel estimation based on common reference signal (CRS) MIMO Beamforming PDSCH Channel estimation based on dedicated reference signal (DRS) CRS DRS SRS Closed loop, codebook precoding (#4) Open loop, non-codebook precoding (#7)
  32. 32. TTA LTE/MIMO Standards/Technology Training 33 © Nokia Siemens Networks 3GPP Release 9 LTE DL transmission modes Enhanced beamforming: dual-layer beamforming (#8) With cross polar antennas in mind CMCC have been eager to extend Rel8 Beamforming to support two streams. Spatial multiplexing supported - Up to 2 layers per user (SU-MIMO) - Up to 4 layer in total (MU-MIMO) CRS based PMI and rank reporting supported for beamforming - Similar feedback schemes as for Rel-8 SU- MIMO (tx-mode 4) - TxD CQI also supported - One CRS per polarization via sector beam virtualization (as in Rel-9) CQI PMI Rank MCS Rank PDSCH Channel estimation based on DRS DRS SRS
  33. 33. TTA LTE/MIMO Standards/Technology Training 34 © Nokia Siemens Networks • Diversity – Same data on all the pipes  Increased coverage and link quality – But, the all pipes can be combined to make a kind-of beamforming • MIMO – Different data streams on different pipes (mode 4)  Increased spectral efficiency (increased overall throughput)  Power is split among the data streams • Beamforming – Data stream on only the strongest pipe (mode 7)  Use all the power on the strongest pipe (i.e., the most efficient pipe)  Increased coverage and signal SNR – Not any more focusing on the strongest pipe in transmission mode 8 in R9 Multi-Antenna Technology Summary
  34. 34. TTA LTE/MIMO Standards/Technology Training 35 © Nokia Siemens Networks  Extension up to 8-stream transmission • Rel. 8 LTE supports up to 4-stream transmission, LTE-Advanced supports up to 8-stream transmission  Satisfy the requirement for peak spectrum efficiency, i.e., 30 bps/Hz  Specify additional reference signals (RS) • Two RSs are specified in addition to Rel. 8 common RS (CRS) - Channel state information RS (CSI-RS) - UE-specific demodulation RS (DM-RS)  UE-specific DM-RS, which is precoded, makes it possible to apply non-codebook-based precoding  UE-specific DM-RS will enable application of enhanced multi-user beamforming such as zero forcing (ZF) for, e.g., 4-by-2 MIMO Max. 8 streams Enhanced MU-MIMO Higher-order MIMO up to 8 streams CSI feedback Enhanced Multi-antenna Techniques in DL
  35. 35. TTA LTE/MIMO Standards/Technology Training 36 © Nokia Siemens Networks  Introduction of single user (SU)-MIMO up to 4-stream transmission • Whereas Rel. 8 LTE does not support SU-MIMO, LTE-Advanced supports up to 4-stream transmission  Satisfy the requirement for peak spectrum efficiency, i.e., 15 bps/Hz  Signal detection scheme with affinity to DFT-Spread OFDM for SU-MIMO • Turbo serial interference canceller (SIC) is assumed to be used for eNB receivers to achieve higher throughput performance for DFT-Spread OFDM  Improve user throughput, while maintaining single-carrier based signal transmission Max. 4 streams SU-MIMO up to 4 streams Enhanced Multi-antenna Techniques in UL
  36. 36. TTA LTE/MIMO Standards/Technology Training 37 © Nokia Siemens Networks Carrier aggregation More dynamic spectrum usage for better user experience 1 Gbps and beyond • Will be specified in 3GPP Rel.11 or later • Most operators have significantly less spectrum for LTE • Even HD streaming services demand less than 20Mbps Resource allocation gain • Ultrafast resource allocation by scheduler instead of handover • Users dynamically get the best resources of aggregated carrier • Higher average data rates Peak data rate addition • enables competitive peak data rates on non- contiguous spectrum • Mitigates the challenge of fragmented spectrum Example: spectrum assets peak data rate on Cat.4 device With CA150 Mbps 75 Mbps 225 Mbps 20MHz in 2.6GHz band 10MHz in 800MHz band Relevant scenarios in near future (3GPP Rel.10) 20MHz 300Mbps 20MHz 300Mbps 20MHz 300Mbps 1.5Gbps 20MHz 300Mbps 20MHz 300Mbps
  37. 37. TTA LTE/MIMO Standards/Technology Training 38 © Nokia Siemens Networks  Wider bandwidth transmission using carrier aggregation • Entire system bandwidth up to, e.g., 100 MHz, comprises multiple basic frequency blocks called component carriers (CCs)  Satisfy requirements for peak data rate • Each CC is backward compatible with Rel. 8 LTE  Maintain backward compatibility with Rel. 8 LTE • Carrier aggregation supports both contiguous and non-contiguous spectrums, and asymmetric bandwidth for FDD  Achieve flexible spectrum usage Frequency System bandwidth, e.g., 100 MHz CC, e.g., 20 MHz UE capabilities • 100-MHz case • 40-MHz case • 20-MHz case (Rel. 8 LTE) Carrier Aggregation
  38. 38. TTA LTE/MIMO Standards/Technology Training 39 © Nokia Siemens Networks Carrier and Spectrum Aggregation Two types of aggregation • Contiguous carrier aggregation in a same frequency band – Maybe difficult to find out frequency bands where maximum of 200MHz (FDD) can be allocated in contiguous manner • Non-contiguous carrier aggregation in different frequency band – Possibility for wider total bandwidth without correspondingly wider contiguous spectrum – Feasibility, complexity and cost analysis should be done in RAN4 WG
  39. 39. TTA LTE/MIMO Standards/Technology Training 40 © Nokia Siemens Networks SON
  40. 40. TTA LTE/MIMO Standards/Technology Training 41 © Nokia Siemens Networks • 기지국 수의 증가  설치 및 운용 비용 증가 • Performance optimization  빈번한 re-configuration 필요 Why SON?
  41. 41. TTA LTE/MIMO Standards/Technology Training 42 © Nokia Siemens Networks How many parameters it takes to have one base station configured? 500
  42. 42. TTA LTE/MIMO Standards/Technology Training 43 © Nokia Siemens Networks How many parameters it takes to run a 3G network? Over 64,000,000
  43. 43. TTA LTE/MIMO Standards/Technology Training 44 © Nokia Siemens Networks Nokia Siemens Networks’ SON Suite is built on our detailed understanding of how networks operate Nokia Siemens Networks SON Suite LTE SON 2G/3G SON Open northbound interfaces SON Other vendor network Mobile Core Self configuration Automated Neighbor Relations Plug and Play Self optimization Interference optimization Load balancing Power saving Mobility robustness Minimization of Drive Tests Self healing Cell outage detection & compensation Self healing / alarm management
  44. 44. TTA LTE/MIMO Standards/Technology Training 45 © Nokia Siemens Networks PCI management 23 14 1 66 412 500 234 322 98 • “collision-free”: the Phy_ID is unique in the area that the cell covers, no two cells overlap with identical Physical Cell IDs  neighbors need to be known • “confusion-free”: a cell shall not have neighboring cells with identical Phy_ID  neighbors of the neighbors Automatic assignment of PCI parameter values ID A ID A ID A ID AID B
  45. 45. TTA LTE/MIMO Standards/Technology Training 46 © Nokia Siemens Networks PRACH management Automatic assignment of PRACH settings • Auto-configuration of parameter settings for • PRACH cyclic shift • PRACH configuration index • PRACH frequency offset • PRACH Root sequence • Considers dependencies and consistencies • Based on network configuration data / UE behavior / cell load / operator policy
  46. 46. TTA LTE/MIMO Standards/Technology Training 47 © Nokia Siemens Networks eNB-B IP@B 3GPP UE Based ANR 2. RRC measurement report (Phy_ID=3) 1. Measure the signal ( Phy_ID=3) 4. Read GID (“B10”) from BCCH 3. Report request to report GID for Phy_ID=3 5. Report GID=“B10” eNB-A IP@A 0. UE Measurement Configuration when UE enters RRC_CONNECTED Goal: retrieve Global Cell ID from new discovered neighbor cell Phy-ID: physical cell ID GID: Cell Global ID
  47. 47. TTA LTE/MIMO Standards/Technology Training 48 © Nokia Siemens Networks Minimization of drive tests (MDT) Detailed trace data collection allows detailed analysis MMES-GWNetAct Normal trace data + Periodic UE measurements + Timing Advance + UE RLF Report + UE logged data Trace Data collected also includes • Timing Advance information • Measurement information provided by periodic UE-measurements • UE Radio Link Failure Report (works only with Rel. 9 UEs) Usable for e.g. • Interference matrix (interference map) • Location analysis on radio link failures (RLF)  input for cell and coverage optimization
  48. 48. TTA LTE/MIMO Standards/Technology Training 49 © Nokia Siemens Networks SON - Mobility Robustness (MRO) Increased network performance by automatic adaptations • Optimizing the Intra-LTE (Intra-frequency) radio network HO-configuration for robustness of mobility procedures • MRO fine tunes based on long-running evaluation of KPIs / specific detections in eNBs / influenced by operator policies • Prevents too early HO, too late HO, and HO to wrong cell NetAct PM-history Height Measuremant dataMeasurement data MRO -SF MRO -SF Optimizer/Configurator CMPM PM Performance Measurements CM
  49. 49. TTA LTE/MIMO Standards/Technology Training 50 © Nokia Siemens Networks MRO Enhancement in Release 10 The use case is to enable detection and to provide tools for possible correction of following problems: • Connection failures in inter-RAT environment: o Priority 1: at HOs from LTE to UMTS/GSM o Priority 2: at HOs from UMTS/GSM to LTE • Obtaining UE measurements in case of unsuccessful re-establishment after connection failure • Ping-pongs in idle mode (inter-RAT and intra-LTE environment) • Ping-pongs in active mode (inter-RAT) • HO to wrong cell (in intra-LTE environment) that does not cause connection failure (e.g. short stay problem)
  50. 50. TTA LTE/MIMO Standards/Technology Training 51 © Nokia Siemens Networks Cell outage compensation (COC) Compensate the gap in network coverage - due non availability of cells / eNBs • Calculate modified radio network configuration for neighbor eNBs • Based on radio planning, data is available in NetAct • RET (Remote Electronic Tilt) changes Flexi Multiradio BTS SON entity Cell/sector outage compensationCell/sector outage
  51. 51. TTA LTE/MIMO Standards/Technology Training 52 © Nokia Siemens Networks Summary
  52. 52. TTA LTE/MIMO Standards/Technology Training 53 © Nokia Siemens Networks LTE-Advanced Improvements
  53. 53. TTA LTE/MIMO Standards/Technology Training 54 © Nokia Siemens Networks Long Term HSPA Evolution
  54. 54. TTA LTE/MIMO Standards/Technology Training 55 © Nokia Siemens Networks Long Term HSPA Evolution (beyond 3GPP Rel-10): Designed to offer 672 Mbps Present Future 3GPP Release 11+ Long Term HSPA Evolution New features Carrier Aggregation Multipoint Systems 8 x 5 MHz HSPA+LTE aggregation HSPA + LTE MIMO MIMO 2x4x HSPA/HSPA+ Long Term HSPA Evolution using similar technology as LTE- Advanced: • Carrier aggregation • MIMO • Multipoint Systems
  55. 55. TTA LTE/MIMO Standards/Technology Training 56 © Nokia Siemens Networks Thank you ! www.nokiasiemensnetworks.com Nokia Siemens Networks 20F, Meritz Tower, 825-2 Yeoksam-Dong, Kangnam-Gu Seoul 135-080, Korea Bong Youl (Brian) Cho RAN Solutions Manager, Ph. D. brian.cho@nsn.com Mobile 010-4309-4129

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