Transforming 3G radio Access Architecture

1. Transforming 3G radio Access Architecture Ionut BIBAC & Emmanuel DUJARDIN

2. Agenda • Main Triggers for New Access Architecture • Toward Flat Architecture: Issue and Limitation • The 3M of beyond 3G: Multi-Carrier, Multi-Antenna (MiMo) and Multi-Layer • One Word on SDR… • Conclusion

3. Main Triggers for Deploying New Access Architecture • Access to a larger (and variable) spectrum allocation • Higher spectrum efficiency which implies: • Reduction latency with a better QoS and user experience • Variable channel BW and harmonized FDD/TDD enables greater flexibility to exploit different band allocations. • Spectrum reframing where we can take advantage of the flexible channel BW and/or better potential use of TDD spectrum. • Optimized for flat architecture (should leave to lower cost network in the long term) • Not burdened by need to support legacy terminals and protocols leads to optimized spectrum efficiency and latency performance. • Higher capacity per site should lead to lower cost/bit at high traffic levels. • Capability to support new service and/or competition with other technologies that requires the lower latency of LTE to achieve good/equivalent customer satisfaction.

4. Towards Flat Architecture • flat architecture • fewer layers of network elements (collapsed architectures) • fewer central bottlenecks • more any to any connectivity • drivers / expected benefits (to be confirmed) • costs: lot of small not redundant units cheaper than few central high capacity, highly reliable network elements (including hosting costs) • performance: traffic go through fewer equipments, more direct routes => less latency, jitter, better throughput • Examples: • LTE/EPC • HSPA flat architecture / I-HSPA • Direct Tunnel • femtocells

5. 3G – LTE/EPC – HSPA Flat MSC PSTN 3G: HLR NB RNC SGSN GGSN Data LTE/EPC (3GPP R8): MME HLR Serving Gateway PDN Gateway eNB Data HSPA Flat Architecture (3GPP R8 option) / I-HSPA: RNC MSC PSTN HLR NB/RNC SGSN GGSN Data

6. Direct Tunnel - Femto MSC PSTN Direct Tunnel: (3GPP R7) HLR SGSN NB RNC GGSN Data Direct Tunnel + HSPA Flat: RNC MSC PSTN HLR SGSN Data NB/RNC GGSN Femto (not standard yet): MSC PSTN HLR HNB= ~NB/RNC FGW SGSN GGSN Data

7. Issue and Limitations of Flat Architecture • data only (except femto*): if voice on circuit, feasibility and performance to be checked (for example on I-HSPA): • About Femto: most issues are currently handled with a gateway/proxy that hides complexity from CN…but not really flat..though collapsed • signalling: all mobility is managed at CN level => either CN correctly designed to handle it (EPC?) or best fitted for slow moving users • Security: • any to any connectivity assumes IP transport network, could be 3rd party network or even public internet • collapsing RNC functions into NB involves that radio ciphering is done in NB • direct connection to CN equipments (except femto*) • impact on existing equipments (configuration and interface): more network nodes visible (except femto*) • interworking and interconnections to legacy architectures need to have a centralized point of interconnection

8. The 3M of beyond 3G: Multi-Carrier • 5 MHz Bandwidth • FFT • Sub-carriers • OFDM basic principles • Carrier (e.g. 5 MHz) is subdivided into many narrower band sub-carriers with lower rates • User receives many sub carriers together to achieve higher rates • Designed to achieve low distortion on each sub-carrier due to radio reflections and adjacent sub-carriers • Guard Intervals • … • Symbols • Frequency • … • Time

9. The 3M of beyond 3G: Multi-Antenna (Mimo) x1 y1 MIMO = Canal matriciel  x2 y2 xi : Signaux émis Yi : Signaux reçus N canaux de' transmission parallèles xN yN Problème du récepteur: Retrouver signaux émis X X = H-1 Y Possible si H est inversible • Eléments hij décorrélés Conditions les plus favorables: Milieu très réflectif Plutôt Indoor

10. The 3M of beyond 3G: Multi-Layer

11. One Word on SDR… • Software Defined Radio stands for a radio technology agnostic Hardware platform in which some or all Radio and Baseband functionalities are controlled by Software. • Early GSM specifications, about filters and frequency blocking, are challenging.Some demand for relaxation of the band. • Difficulty to precisely estimate today the necessary processing power for a later use, towards LTE for instance and ultimately any other new usage. • Coexistence of technologies in same modules is not easy to manage. • Vendors are tied with their current chipset choices. Moving to fully SW defined platform means initially full re-development of firmware. On the other hand they gain full flexibility on future development. • Roadmaps shows no OSS evolution with SDR introduction. For instance, changing the technology is done by deletion & recreation of cells, all of the earlier settings and optimisations are lost. SDR cannot (yet) be considered as a dynamic configuration enabler

12. Conclusion • Operator benefits of the new air interface • Access to larger (and variable) spectrum allocations • Higher spectrum efficiency: lower cost per bit • Reduced latency: better QoS ans user experience • Reasons for migration • Higher spectrum efficiencies can also be achieved by HSPA+ with lower migration cost (assuming 5 MHz spectrum allocation) • New spectrum allocations or re-farming may motivate migration (currently 20 MHz allocations seem very unlikely but 10 MHz may be possible) • E-UTRAN will be deployed together with evolved packet core (EPC) • Air Interface evolution will continue • IMT advanced seems far away for operators. • Concurrent systems are in starting blocks so 3GPP also has to respond.