Introduction to UMB TM Air Interface Upper Layers

1. Introduction to UMBTM Air Interface Upper Layers Source: TSG-C WG 2 Abstract: This contribution presents an introduction to UMB upper layers. Ultra Mobile Broadband™ and (UMB™) are trade and service marks owned by the CDMA Development Group (CDG).

2. Design goals • Efficiently support OFDMA MAC/Phy • Fully support centralized as well as distributed access networks • Streamline inter-access network interfaces • Continue to support fast layer 2 handoff • Seamless handoff across air interface revision boundaries • Apply lessons learnt from EV-DO

3. UMB efficiently supports centralized access network • AT maintains separate protocol stack for each AN in the Active Set • Each protocol stack is called a “Route” • Extension of EV-DO Route A/B concept • Each BSC is a separate AN No coordination of RoHC/EAP/RLP/Connection state between BSCs

4. UMB efficiently supports distributed access network • AT maintains separate protocol stack for each AN in the Active Set • Each cell is a separate AN No coordination of RoHC/EAP/RLP/Connection state between eBSs

5. UMB simplifies the inter-AN interface by requiring the AT to support multiple Routes • Each eBS in the Active Set uses a separate data Route • No need to transfer RLP and header compression state between eBSs • Traffic flowing between an eBS and the AT can be tunneled through the serving eBS • Support fast and seamless re-pointing between cells • Each eBS in the Active Set could use a separate Personality • Seamless handoff across air interface revision boundaries • Signaling messages of protocols between an eBS and the AT can be tunneled through the serving eBS • The eBS which acts as a tunnel need not interpret the tunneled messages • No protocol conversion between eBSs • No eBS has to maintain Connection state of other eBSs in the Active Set • No need to synchronize Connection state across eBSs • UMB reverse link allows manycast • AT can send a packet once over the air and address it to multiple ANs Simple inter-eBS interface leads to standardized, inter-operable implementations

6. Anchor Route • One of the protocols stacks is designated the Anchor Route • Anchor Route is retained when the AT goes idle • Other Routes are torn down • Anchor Route determines idle state behavior • UATI points to the AN that hosts the Anchor Route • Upon connection set up, AT tunnels priority data the Anchor Route through the serving Route • Data can flow before serving Route fetches the session • Useful for applications with stringent call set-up latency requirements

7. Requirements on inter-AN interface • Inter-AN interface must support • Tunneling of layer 2 packets • Tunneling of layer 3 packets • Session transfer • Other functions such as paging, neighbor discovery etc. • Inter-AN interface need not support • One AN in control of connection state at another AN • Interpretation/translation of tunneled packets by serving AN • Transfer of RoHC/Connection/RLP state

8. UMB layering reduces the number of protocols in the data path • Application Layer: Signaling Application, IP, RoHC, EAP, inter-technology tunneling etc. • Radio Link Layer: RLP and associated protocols • MAC Layer: Packet Consolidation Protocol and control of Physical Layer channels • Physical Layer: defines characteristics of air interface channels • Security Functions: protocols for ciphering, message integrity, and key exchange • Route Control Plane: controls the creation and maintenance of air interface protocol stacks, one for each eBS • Session Control Plane: provides session negotiation • Connection Control Plane: controls the Connection between the AT and an eBS

9. Data Path Packets may be transmitted over the air or tunneled through the serving Route

10. UMB performs ciphering in RLP • Ciphering is located in RLP • Ciphering is applied to RLP fragments before addition of RLP header • Advantages of ciphering in RLP • Ciphered packets are tunneled through serving eBS • Source eBS and AT tunnel ciphered packets through serving eBS • Serving eBS cannot interpret the packets • Low latency for push-to-X applications • AT sends priority data to the anchor eBS without requiring serving eBS to fetch the session • Lower AT implementation complexity compared to ciphering above RLP • Ciphering can be performed in the access terminal modem without having to re-assemble upper layer packet • Possible software-based ciphering implementation at the AN • Encryption mask can be pre-computed in software • No header overhead • Cryptosync derived from RLP sequence number Ciphering entity must be aware of RLP sequence numbers

11. UMB support for header compression • UMB allows header compressor to be located either in the eBS or a node deeper inside the network • AT maintains separate header compression instance for each AN (BSC or eBS) • RoHC state need not be transferred upon layer 2 handoff

12. UMB facilitates seamless handoff across air interface revision boundaries • Each eBS in the Active Set has its own protocol stack at the AT • Each eBS in the Active Set has a copy of the negotiated Personalities • Each eBS and the AT decide what Personality to use for their protocol stack • Different eBSs may choose the same or different Personality as InUse • AT capability determines how many different Personalities can be InUse at the same time Different eBS in the Active Set may have different capabilities

13. Summary • UMB efficiently supports centralized and distributed access networks • UMB AT maintains a separate protocol stack (Route) for each AN (eBS) • Serving Route can send packets over the air • Non-serving Route can tunnel packet through the serving Route • Serving Route simply tunnels packets without interpreting them • UMB does not require RoHC/Connection/RLP state to be transferred between ANs (eBSs) • UMB simplifies the inter-AN interface