Supervisor Professor Riku Jäntti Instructor MSc Ari Kynäslahti 11.06.2009 Otaniemi

1. Macro diversity combining optimization in flat HSPA architectureMaster’s Thesis PresentationPetri Hakola Supervisor Professor Riku Jäntti Instructor MSc Ari Kynäslahti 11.06.2009 Otaniemi

2. Content Objective of this thesis UMTS Network Architecture In Rel06 and flat architecture 3GPP UMTS Rel06 Architecture 3GPP UMTS Rel07 Evolved Architecture - flat architecture SHO and flat architecture Proposed UL MDC Alternatives in 3GPP Improvement of UL Macro Diversity Combining in Serving NodeB MDC & Cell Interference control in eHSPA architecture Proposal of interference control and MDC in eHSPA architecture Service Differentiated Uplink Macro Diversity Combining in Flat Evolved HSPA Architecture Comparison of the proposals – implementation complexity Comparison of the proposals – Transport resource need Comparison of the proposals – Latency Comparison of the proposals – addition needs for current 3GPP specifications Conclusions and considerations

3. Objective of this thesis • Macro Diversity Combining Optimisation in High Speed Packet Access Flat Architecture • The objective of this thesis is to present a optimized uplink Macro Diversity Combining (MDC) solution in flat architecture that • minimize the needed transmission capacity on Iur link between serving and drift eNodeB in soft handover situation, and • has minimum effect in radio interface performance in inter eNodeB soft handovers. • The basis of this study are implementation alternatives presented in 3GPP.

4. UMTS Network Architecture In Rel06 and flat architecture • In the next two slides the evolution from Rel06 architecture towards flat architecture in Rel07 is shown • Flat architecture – (evolved HSPA) • In flat architecture the RNC functions are integrated in the NodeB, which we will call as evolved NodeB (eNodeB). • The flat architecture networks are designed for packet access only, with the possibility to relocate circuit switched services to the legacy 3G network under the coverage of RNC’s. • The packet user plane starting from eNodeB is terminated either in SGSN or in case of one direct tunnel approach in GGSN. • Flat architecture is designed with full mobility support • Intra eNodeB handovers (softer handover) • Inter eNodeB handovers (soft handover) • Handovers towards legacy 3G networks are standard serving RNC relocations (hard handover) • In a flat architecture the soft handover MDC is done in the eNodeB’s integrated RNC unit • thus generating a large need for Iur transmission capacity in case full MDC is utilized • Flat architecture system does not require any modifications in the air interface nor UE’s.

5. A’ Uu HLR MGW MSC Iu-CS Iub Gs Node B Iu-PS RNC Gr UE Iur SGSN Uu Gc Gn Iub Gi RNC GGSN Node B Iu Uu UE UTRAN Core 3GPP UMTS Rel06 Architecture

6. 3GPP UMTS Rel07 Evolved Architecture - flat architecture A’ Iu-CS Evolved HSPA Node B HLR MGW MSC Gs RNC Iu-PS Gr Iu-PS CP SGSN Iu-PS UP Gc Iur Gn Iu-PS CP Gi Iu-PS UP Evolved HSPA Node B GGSN

7. Soft Handovers and flat architecture • Flat evolved UTRAN architecture is able to support handovers like in Rel06 architecture, this is due to locating the UL Macro Diversity Combining in the eNodeB’s RNC functionality. • There are two options for implementing the inter eNodeB handover • Handover without Iur connectivity between adjacent eNodeB’s – no UL MDC possibility • Handover with Iur connectivity between adjacent eNodeB’s – UL MDC possible • In this thesis the main interest is in the scenario where Iur is in use, as in figure below Serving eNode B Iu-PS CP SGSN Iur Iu-PS UP Gn Iu-PS CP Drift eNode B Iu-PS UP GGSN

8. Proposed UL MDC Alternatives in 3GPP • The main motivation for optimizing the UL MDC in 3GPP is • minimize the Iur traffic between serving and drift eNodeB , specially user plane since it’s the largest contributor to overall traffic • Four proposal have been presented in 3GPP • Improvement of UL Macro Diversity Combining in Serving NodeB – (Huawei and China Mobile) • MDC & Cell Interference control in eHSPA architecture – (Vodafone Group, NSN) • Proposal of interference control and MDC in eHSPA architecture – (Huawei) • Service Differentiated Uplink Macro Diversity Combining in Flat Evolved HSPA Architecture – (China Mobile, ZTE, Huawei)

9. Improvement of UL Macro Diversity Combining in Serving NodeB • In the first proposal, “Improvement of UL Macro Diversity Combining in Serving NodeB”, the idea for serving eNodeB is to ask packets from drift eNodeB’s in case serving eNodeB detects incorrect CRC’s in received data frames. In this solution data packets would load the Iur only when asked by serving eNodeB. • The CRC check as the trigger will only work for UL DCH channels but not for E-DCH (HSUPA). • The reason being, that the HARQ functionality in eNodeB should ensure that MDC entity shall receive only correct CRC’s in E-DCH (HSUPA) FP frames. • The delay seen by the application can grow vastly due to the proposed mechanism.

10. MDC & Cell Interference control in eHSPA architecture • The second proposal, “MDC & Cell Interference control in eHSPA architecture”, proposes four different options for selecting the Iur traffic • normal MDC • No MDC (No Iur) • only control plane over Iur (no user plane) • selective user plane and control per UE • From these four we take a closer look at the only control plane over Iur (no user plane) option. • This option has the advantage of having a partly improved interference control, based on initial SIR available for the radio links under the drift eNodeB. The reason being that the serving eNodeB can not get HARQ nor BER/BLER info over Iur Frame Protocol, but the initial SIR target can be utilized together with uplink closed loop power control. • Very low Iur load and no extra delay in user plane data like in the previous proposal. • When the user plane over Iur is not setup a problem pops up in HSUPA usage. In case the serving eNodeB did not receive a packet but the drift eNodeB did and signals this to the UE, the UE will continue sending the next packet in its buffers and since Iur user plane is not in use the packet not received by serving eNodeB will be completely lost. • Solution could be that the drift eNodeB always signals to the UEs that packets were not received correctly, by sending NACK.

11. Proposal of interference control and MDC in eHSPA architecture • The third proposal, “Proposal of interference control and MDC in eHSPA architecture”, is a combination from the first two proposals. Here the selected operation mode selected by serving eNodeB • ‘CRC check’ (as Improvement of UL Macro Diversity Combining in Serving NodeB) • ‘only control plane over Iur’ (as MDC & Cell Interference control in eHSPA architecture) would be based on the channel quality in the UE’s measurement report. • When the channel quality in the Measurement Report of a drift eNodeB is good enough before triggering serving cell change • ‘CRC check’ may be needed for better performance, • When the channel quality in the Measurement Report of a drift eNodeB is bad enough before triggering serving cell change • ‘only control plane over Iur’ can be utilized.

12. Service Differentiated Uplink Macro Diversity Combining in Flat Evolved HSPA Architecture • The fourth proposal, “Service Differentiated Uplink Macro Diversity Combining in Flat Evolved HSPA Architecture”, tries to solve the delay problems caused in the first proposal where the serving eNodeB needs to ask packets from the drift eNodeB. The serving eNodeB can select a suitable MDC scheme from • normal MDC • selective MDC (as Improvement of UL Macro Diversity Combining in Serving NodeB ‘crc check’) • no MDC (no Iur) • Considering the service characteristics low data rates and delay sensitive services • normal MDC scheme could be used • Considering the transport resources, if transport resources are stringent • the selective MDC (‘crc check’) or even the no MDC option could be used

13. Comparison of the proposals – implementation complexity

14. Comparison of the proposals – transport resource need between serving and drift eNodeB

15. Comparison of the proposals – Latency

16. Comparison of the proposals – addition needs for current 3GPP specifications

17. Conclusion • The best proposal, for keeping the transmission increase relatively low for MDC and also considering the ease if implementation on top of the current 3GPP specifications was found to be the second proposal MDC & Cell Interference control in eHSPA architecture – only control plane over Iur. • Low Iur utilization • In this solution only control plane would be established over Iur links between eNodeB’s in SHO situation, thus limiting the required transmission capacity on Iur links between eNobeB’s for control plane only. • Partly improved interference control • A partly improved interference control, based on initial SIR, is available for the radio links under the drift eNodeB. • No extra latency • Minimal additions needed to current 3GPP specifications • In addition to the proposal, the drift eNodeB should NACK all the received data packets, to avoid the situation where the serving eNodeB did not receive the packet correctly and UE moves to transmit next packets in its buffers.