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Impact of mobile packet core signaling delays to overall radio system performance

Impact of mobile packet core signaling delays to overall radio system performance. Henri Poikonen 7.9.2011. Contents. Introduction Motivation for the subject Methods used in the thesis Results Conclusion. Introduction.

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Impact of mobile packet core signaling delays to overall radio system performance

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  1. Impact of mobile packet core signaling delays to overall radio system performance Henri Poikonen 7.9.2011

  2. Contents • Introduction • Motivation for the subject • Methods used in the thesis • Results • Conclusion

  3. Introduction • Impact of packet core network signaling delays to radio system performance in HSPA and LTE was studied • Focused on effect of handover signaling • Impact to cell capacity and single user throughput was studied

  4. Motivation • Handover essential for enabling mobility • Handover performance depends on the delays of the network elements • Mobile data traffic grows significantly every year • The impact of packet core network delay to radio system performance not studied

  5. Background information • HSPA (High Speed Packet Access) is an extension to WCDMA • Improves performance • Reduced latency and higher peak data rates • I-HSPA is an NSN product where RNC functionalities are located in the base station • LTE (Long Term Evolution) is a successor for the UMTS. • Often referred to as 4G • Peak data rates up to 100 Mbps

  6. Methods • Impact to cellcapacityanalyzedbased on the networkimplementationand procedures • Simulationsused to study the impact to single userthroughput • Implemented with Matlab • Simulations for macro- and microcellscenarios • Packetcorenetworkinvolvementanalyzed • Based on meassurementsfrom live networks

  7. Packet Core involvement • Packet Core network is involved only in the execution phase • Only part of the handovers involve packet core network • Depends on the network technology • HSDPA: ~10-20% of handovers • I-HSPA: ~60-70% of handovers • Depends also on the antenna configuration • LTE: No data available for LTE • Estimated to be close to zero

  8. Impact to cell performance • HSPA: • The transmit power divided equally among users • Only the modulation and coding scheme change every TTI • Delays in handovers affect only that particular user  No impact to the cell performance

  9. Impact to cell performance • LTE • LTE has no power control in downlink • Similar to HSPA, the modulation and coding scheme changed every TTI • Delays in handover affect only the particular user No impact to cell performance

  10. Impact to single user • HSDPA throughputdepends on: • Power and multi-coderesourcesallocated to HSDPA • Number of HSDPA user in the cell • Interference and pathlossbetween UE and NodeB • Throughputdegrades as usermovesawayfrom the sourceNodeB • Similarsituation in LTE Delays in corenetworksignalinglower the throughput

  11. Simulations • The simulation was implemented in Matlab • Two scenarios were identified: • Macro cell • Micro cell • Both scenarios contain 7 base stations • 100% load is assumed for each base station • Throughput estimated based on Geometry Factor (G-factor) • Path loss and Shadow fading estimated • Throughput degradation calculated with 5 different delay values

  12. SRNS Relocation • ’UE involved’ SRNS Relocation used in the Inter-RNC hard handovers in UMTS CN delay Total delay CN delay

  13. S1 based Handover • Only handover in LTE that involves packet Core network signaling CN delay Total delay CN delay

  14. Macro cell scenario • UE velocity: 50 km/h • Central cell acting as the serving cell • UE moves away from the serving base station • 360 different directions used (circle with 1 degree separation) • Calculated 100 times for each direction

  15. Micro cell scenario • Manhattan street grid building layout with 7 base stations. • Travelledroute of the UE marked with a redarrow • Degradationcalculated 10000 times • UE velocity: 6 km/h

  16. Results (Macro) • HSDPA • Throughput degradation less than 5 %: • 95th percentile: • Delay: < 30 ms • Average: • Delay: < 120 ms

  17. Results (Macro) • LTE • Throughput degradation less than 5 %: • 95th percentile: • Delay: < 50 ms • Average: • Delay: < ~150 ms

  18. Results (Micro) • HSDPA • Throughput degradation less than 5%: • 95th percentile: • Delay: < 25 ms • Average: • Delay: < 40 ms

  19. Results (Micro) • LTE • Throughput degradation less than 5 %: • 95th percentile: • Delay: < 35 ms • Average: • Delay: < 70 ms

  20. Summary • In HSPA and LTE, the delays have only effect on the single user throughput • LTE is more resistant to packet CN delays than HSPA • Micro cells more critical than macro cells • The effect of the delays diminishes when new features for HSPA become more common • In LTE, the number of handovers including packet CN is estimated to be close to zero

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