Random Acces Channel Self-Tuning in LTE

Blanca GONZÁLEZ Francisco MICÓ

SUMMARY

•  Introduction •  Random access in LTE •  Self Optimizing Networks •  Case study: Self-tuning of random access •  Conclusion

page 1 Summary

Looking for synchronization

¢ Random access uses: •  Connected UE, not uplink-synchronized

–  Send new data or control information –  Hand-over process –  ACK/NACK message in the uplink –  Positioning purposes.

•  Transitions from Idle state to Connected •  Recovering from radio failure •  Exceptionally, to send a Scheduling Request if no

other uplink resource is allocated.

page 2 What is RA?

Contention resolution

page 3 How works RA?

¢ Random access procedure:

A wide range of parameters

¢ PRACH design

page 4 Inside PRACH

PRACH

Format

Sequence

Duration

Preamble

Banswidth

Length

Cyclic shift

CP

GT

Resource configuration

Load

Interferences

page 5

What is SON?

RACH Self-Tuning Introduction to SON

Source: Self-Organizing Networks (SON) in 3GPP Long Term Evolution. Sujuan Feng, Eiko Seidel Nomor Research GmbH, Munich, Germany 20th of May 2008

Rising expectations on QoS, coverage and capacity

Goals ·Reduce OPEX (Operational Expenditures) by automating funcionality currently performed manually ·Reduce CAPEX (Capital Expenditures) by optimized use of network elements

page 6

SON use cases ¢ Revenues of Mobile network depend (++) on its operational

efficiencyà reduce OPEX ¢ Self-Optimizationàselect and adjust proper algorithms and

system parameters to achieve optimal system capacity and service coverage

¢ 8 use cases: »  1. Automatic Neighbor Relation (ANR) »  2. Coverage and Capacity Optimization »  3. Energy Saving »  4. Interference Reduction »  5. Physical Cell ID Automatic Configuration »  6. Mobility Robust Optimization »  7. Mobility Load Balancing Optimization »  8. RACH (Random Access Channel) Optimization

Source: 3GPP TR36.902

RACH Self-Tuning Link between RACH and Self-Optimization

page 7

RACH Optimization

¢ Role of RACH •  Initial network access without user data

¢ Necessity for RACH optimization •  Performance of RACH influences the capacity of

whole mobile network ¢ Possible RACH optimization algorithm •  Phy resources •  Preambule allocation •  Persistence level •  Transmission power control

RACH Self-Tuning Role of RACH and optimization necessity

page 8

Key performance metrics

¢ Acces Probability (AP) ¢ Detection Miss Probability (DMP)

¢ Detection Miss Ratio (DMR) ¢ Contention Ratio (CR)

¢ Access Ratio (AR)

RACH Self-Tuning Metrics and Modeling of RA

page 9

Experiments

RACH Self-Tuning tuneables parametres, performance and interferences

¢ Effects of Varying PUSCH Load ¢ Effects of Varying Power Control Parameters ¢ Effects of Varying RACH Load and Configuration ¢  Interference on PUSCH by Random Access

Preambles

CONCLUSION

page 10 RACH Self-Tuning

¢ Performance: heavily affected by the choice of design parameters

¢ LTE possibilities ¢ Self Optimizing Networks : a hot research topic

nowadays ¢ Encouragement and potential

page 11

References [1] Towards Random Access Channel Self-Tuning in LTE. Mehdi Amirijoo, Pål Frenger, Fredrik Gunnarsson, Johan Moe, Kristina Zetterberg Wireless Access Networks, Ericsson Research, Ericsson AB, Sweden [2] Self-Configuration and Self-Optimization for LTE Networks. Honglin Hu and Jian Zhang, Chinese Academy of Sciences Xiaoying Zheng, Chinese Academy of Sciences and Southeast University Yang Yang, Chinese Academy of Sciences and University College London Ping Wu, Uppsala University [3] Challenges in mobile network operation: Towards Self-Optimizing Networks. Martin Döttling1, Ingo Viering2 1: Nokia Siemens Networks GmbH & Co. KG, Munich, Germany 2: Nomor Research GmbH, Munich, Germany [4] Random Access Channel (RACH) Parameters Optimization in WCDMA Systems. Juan Reig, Oscar López-Jiménez, Lorenzo Rubio and Narcis Cardona Departamento de Comunicaciones Universidad Politécnica de Valencia, España. [5] Self Organization Network. “NEC’s proposals for next-generation radio network management”. White paper. [6] LTE. The UMTS Long Term Evolution. From theory to practice. Sesia, Toufik & Baker. Ed: Wiley, second edition.

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