1. Jui-Hung Yeh, Jyh-Cheng Chen, and Prathima Agrawal Presented By Yinan Li Oct. 20, 2009

2. Agenda Introduction Related Work Design Principles Proposed FINCH Performance Analysis Numerical Results Conclusions

3. Introduction WiMAX (IEEE 802.16) WiMAX (IEEE 802.16) A promising standard for next-generation broadband wireless access networks Mobility support for users moving at vehicular speed Components Access Service Network (ASN) providing radio access to WiMAX subscribers (mobile stations or MSs) Consisting of one or more ASN Gateways (ASN GWs) and Base Stations (BSs) Connectivity Service Network (CSN) providing IP connectivity services ASNs are connected by CSN

4. Generic Mobile WiMAX Network Architecture

5. Introduction Mobility Management Mobility Management Inter-domain (inter-CSN) Mobile IP (MIP) is suitable inter-CSN mobility management It is not suitable for intra-CSN mobility management, due to Large HO latency and signaling cost; large end-to-end delay Intra-domain (intra-CSN) Localizing location handoff and update operations to reduce the signaling cost Tunneling-based MIP, HMIP, IDMP Host-specific-routing-based Cellular IP and HAWAII

6. Fast Intra-Network and Cross-layer Handover (FINCH) Proposed for intra-CSN (intra-domain) mobility management Achieving fast handover (HO), especially for real-time services Cooperating with Mobile IP Localizing location update to reduce the handover latency and signaling cost in Mobile IP Cross-layer design: considering HO in both link and network layers (L2 and L3) FINCH is a generic protocol for other IEEE 802-series standards

7. Related Work (1/5) Inter-domain Mobility Management Protocols Inter-domain Mobility Management Protocols Mobile IP (MIP) Mobility support in the IP layer MIPv4 and MIPv6 (with route optimization) Session Initiation Protocol (SIP) Mobility support in the application layer Host Identity Protocol (HIP) A new protocol layer, HIP, lies in between the network and transport layers The roles of locator and identifier of IP addresses is decoupled IP address is only used for packet routing, a Host Identifier (HI), which is a public key, is used to represent the host identity Rendezvour Server (RVS) maps HIs of MSs to their IP addresses

8. Related Work (2/5) Intra-domain Mobility Management Protocols Intra-domain Mobility Management Protocols Tunneling-based Tunneling-based protocols generally employ a hierarchical mobility architecture (e.g., a tree structure) or require a gateway to tunnel packets to and from MSs HMIP, Intra-domain Mobility Management Protocol (IDMP), and Dynamic Mobile Anchor Point (DMAP) Host-specific-routing-based Host-specific-routing-based protocols generally adopt new routing protocols to support intra-domain mobility management Location information of MSs is maintained by access routers (AP) in a distributed location cache and is updated by regular packet routing Cellular IP and HAWAII

9. Related Work (3/5) Fast Handover (Fast HO; RFC 4988 & RFC 4068) Fast Handover (Fast HO; RFC 4988 & RFC 4068) Another technique for reducing HO latency and packet loss rate Fast HOs for MIPv4 and MIPv6 (F-MIPv4 and F-MIPv6) The basic idea is that an MS can determine whether it is moving to a new access router (NAR) before the HO happens The previous access router (PAR) of the MS forwards packets destined to the MS to its NAR, which buffers the packets for the MS Two modes of operations Predictive: PAR forwards packets to NAR, which starts buffering packets before L2 HO; Packets buffered by the NAR can be forwarded to the MS immediately after L2 HO. Reactive: The tunnel between the PAR and NAR for packet forwarding is established after L2 HO. PAR forwards packets to NAR after L2 HO, which then forwards packets to the MS.

10. Related Work (4/5) L2 HO PAR starts forwarding received packets to NAR before the HO NAR delivers buffered packets to the MS after the HO

11. Related Work (5/5) L2 HO Tunnel between PAR and NAR is established after the HO PAR forwards received packets to NAR after the tunnel is established NAR delivers packets to the MS after the HO

12. Design Principles Fast HO: Supporting fast HO for real-time services Cross-layer: Reducing not only HO delay, but also packet delivery overhead Scalability: Avoid using centralized management facilities, operation of the protocol should be distributed Paging Support: Paging is an effective solution that enables mobile nodes to reduce unnecessary location update Timely of deployment: Considering only IPv4 /Ethernet because IPv4 over Ethernet like link model is most likely to be deployed for current WiMAX networks Flexibility: the proposed FINCH should be a generic protocol for not only WiMAX, but also other types of IP networks

13. Mobility Management in WiMAX: Current Status MAC Layer Handover (L2 HO) MAC Layer Handover (L2 HO) When an MS moves from one BS to another BS, L2 HO is needed IEEE 802.16e standardizes the MAC layer (L2) HO only Network Layer Handover (L3 HO) Network Layer Handover (L3 HO) When an MS moves to a new BS in a different subnet, a new CoA (NCoA) is acquired and registered with its HA Packet delivery follows the standard MIP procedure MIP is chosen by the WiMAX Forum to deal with mobility management in the network layer (L3) The Home Agent (HA) of a MS is located in the CSN of the MS’s Home Network Service Provider (H-ISP); ASN GW supports the Foreign Agent (FA) functionality

14. Cross-Layer Design Motivation Motivation Simplifying the HO procedure Two HO procedures if L2 and L3 are considered separately Reducing the overhead and latency Reducing the number of ARP messages Approach Approach Integrated mobility management and packet routing within a domain (CSN) through the so-called Forwarding Table (FT) A special table lookup technique that works in both link and network layers Location updates in the link layer and network layer are coupled together Completely replaces ARP in Ethernet over IPv4

15. The Forwarding Table (FT) Used by both L2 and L3 devices Used by both L2 and L3 devices FT replaces routing tables in L3 devices and bridging tables in L2 devices FT Fields FT Fields MS MAC Address MS IP Address: HoA or permanent address Forwarding MAC address: specifying to which the IP packets destined to the MS should be forwarded to Wireless port: if the MS is maintained by a BS Time stamp The FT in BS1

16. Packet Forwarding - Algorithm

17. Packet Forwarding - Examples From the perspective of BS1 From the perspective of BS1 Packets destined to MS1 currently attached to BS1 Packets destined to MS1 currently attached to BS1 The packet can be directly transmitted to the MS using MS’s MAC address as specified in the 1 st column of BS1’s FT Packets destined to MS2 currently in CSN-2/ASN-2 Packets destined to MS2 currently in CSN-2/ASN-2 Encapsulated into a MAC frame and forwarded to ASN-1’s GW whose MAC address is specified in the 3 rd column of BS1’s FT The FT of ASN-1’s GW is looked at to find out the forwarding MAC address of the next node to which the packet should be forwarded ASN-1’s GW encapsulates the packet into a MAC frame and forwards the frame to the next node using the MAC address specified in the 3 rd column of its FT The process is repeated until the packet reaches the destination

18. Packet Forwarding (Cond.) The Usage of the FT The Usage of the FT The 1 st column of the FT is used as indices by L2 devices The 2 nd column of the FT is used as indices by L3 devices The 3 rd column is used to find out the forwarding MAC address NULL if the 1 st column is used as the destination MAC address, i.e., the destination MS is currently attached to the BS. ARP in IPv4 over Ethernet is replaced by simple lookup in the FT The 1 st and 2 nd columns form a mapping between IP and MAC addresses

19. Reducing ARP Messages Address Resolution Protocol (ARP) in WiMAX Address Resolution Protocol (ARP) in WiMAX Broad-and-reply nature wasting bandwidth and causing extra delay Executed frequently if an MS moves frequently To achieve fast HO, address resolution should be highly efficient The Solution of FINCH: FT replaces ARP The Solution of FINCH: FT replaces ARP Mapping between the IP address and MAC address of an MS is done by simple table lookup in the FT Whenever an IP packet comes in, the IP address field of the FT is searched to locate the entry for the target MS The IP packet is then encapsulated into a MAC frame using either the target MS’s MAC address as specified in the 1 st column or the Forwarding MAC Address as specified in the 3 rd column

20. Handover and Location Update Packet forwarding relies on the correctness of the FT Packet forwarding relies on the correctness of the FT FT should be properly updated each time when an MS moves HO Procedure HO Procedure When an MS handovers to a new BS, it sends the new BS a MAC frame to update its entry in the new BS’s FT; the new BS then forwards the MAC to all adjacent nodes All nodes that received the MAC frame also forward the MAC frame to their adjacent nodes in the same domain All nodes that received the MAC frame including the old BS, the new BS, and other nodes update their FTs accordingly to the following algorithms If a node has already received the MAC frame, it will not rebroadcast it As the frame propagates, new routes through the network can be established to reach the MS

21. Location Update Algorithm

22. Location Update Algorithm (cond.)

23. Crossover Node Forwarding direction

24. P-FINCH: Paging Extension for FINCH (1/3) Motivation Motivation Enhancing the energy efficiency and minimizing the signaling overhead of location update An optional component in FINCH Paging Group (PG) Paging Group (PG) Each BS in a WiMAX system is assigned to a PG, which is similar to a cluster The assignment can be based on geographical or load-balancing considerations Each PG has a unique PG Identifier (PGI) In each PG, there is a Paging Controller (PC) An idle MS performs location update only when it moves to another PG, otherwise, the MS keeps silent

25. P-FINCH: Paging Extension for FINCH (2/3) Paging Procedure Paging Procedure Entering Idle Mode When an MS intends to enter Idle Mode, it sends the current serving BS a Deregistration message to initiate the Idle Mode The serving BS sends an IM-Entry_MS_State_Change request to the PC of the PG to which the BS belongs, which then registers the MS to a paging list and sends out a location update message on behalf of the MS Future packets destined to the MS will be forwarded to and buffered by the PC Handover while in Idle Mode When the MS handovers to a new PG while it is still in Idle Mode, it must send a location update message to the PC of the new The PC of the new PG will send out a location update message on behalf of the MS After the location update, packets sent to the MS will be forwarded to and buffered by the new PC

26. P-FINCH: Paging Extension for FINCH (3/3) Paging Procedure Paging Procedure When the PC wants to awake the MS and deliver buffered packets to the MS, it sends a paging request to all the BSs within the PG Upon receiving the request, the MS sends a location update message to the PC Upon receiving the location update, the PC removes the entry for the MS in the paging list and starts delivering buffered packets to the MS Energy Conservation Energy Conservation Because location update is required only when an MS handovers to a new PG, the paging extension significantly reduces the energy consumption of the MS

28. Performance Analysis: Handover Latency (1/3) HO Latency: HO Latency: the time interval during which an MS cannot receive and transmit packets due to the HO procedure The time interval between the time the MS loses the L2 connection and the time it can receive or transmit packets through the new BS HO Latency consists of HO Latency consists of Link layer switching latency, which reflects the 802.16e L2 HO latency IP connectivity latency, which includes the duration of IP layer movement detection, IP address acquisition, and configuration Location update latency, which includes the latency for binding update and the latency for forwarding packets to the MS’s new IP address through the new BS

29. Handover Latency (2/3) Address resolution delay One way delay for packet transmission between HA and the MS One way delay for packet transmission between NAR and the MS One-way delay for packet transmission between the crossover node(CR) and the MS Computation delay of the host- specific-routing-based micro- mobility management protocols IP connectivity latency is eliminated in F-MIP-Pre because the new CoA can be configured before L2 HO

30. Handover Latency (3/3) One-way delay for packet transmission between the crossover node and the MS Computation delay of the tunneling-based micro-mobility management protocols One way delay for packet transmission between PAR and NAR Latency for IP layer movement detection; this is needed because the tunnel between PAR and NAR is established after L2 HO

31. Performance Analysis: Packet Loss (1/2) In FINCH, packets are lost when the location update messages are still propagating to the crossover node In MIP, packets are lost before an MS registers its new CoA with its HA In F-MIP predictive mode, packets are lost if the coordination of fast HO signaling is not correct or packets are failed to be buffered in NAR.

32. Packet Loss (2/2) In F-MIP reactive mode, packets are lost in PAR before the tunnel between PAR and NAR is established and packets can be forwarded to the MS In CIP and HAWAII, packets are lost when the location update messages are still propagating to the crossover node In HMIP, packets are lost when the location update messages are still propagating to the crossover node (GFA)

33. Network Topology ASN-GWs are abstracted as leaf nodes An MS is assumed to move i steps (ASNs) from the kth node (ASN) Each domain (CSN) is modeled as a complete binary tree with K leaf nodes (ASNs)

34. Performance Analysis: Location Update Cost (1/7) Parameters Parameters : Call to Mobility Ratio (CMR) : the average cost of location update to an MS’s HA in MIP : the cost of setting up a single link when the intra-domain mobility management protocol sets up the path in the intra- domain : the cost of address resolution : the cost of a unicast signaling message between the PC and the BS. The cost is used for location update from the BS to the PC and paging request from the PC to the BS : the cost of setting up the direct connection between the NAR and PAR in F-MIP

35. Location Update Cost (2/7) The probability that an MS moves i steps between two consecutive packet arrivals F-MIP reduces the HO latency by forwarding packets from PAR to NAR. However, there is an additional signaling cost to setup the direct connection between PAR and NAR

36. Location Update Cost (3/7) Based on the given network topology, the number of hops for a location update message when an MS moves from the first cell to the nth cell within the complete binary tree. Deriving this quantity is equivalent to finding the height of the crossover node or the lowest common ancestor problem.

37. Location Update Cost (4/7) The cell residence time is assumed to be a random variable with a general density function fm(t) with the Laplace transform g; lambda is the packet arrival rate Because an MS can move across several domains, let i = jK + q, where j is the number of domains crossed

38. Location Update Cost (5/7) The signaling cost of location registration with the HA The signaling cost of intra- domain location update

39. Location Update Cost (6/7) In HAWAII, an MS only needs to register with the Domain Root Router (DRR) by using the same message of MIP registration The cost of address resolution (ARP) is considered

40. Location Update Cost (7/7) Assuming that each PG is rooted at the PC and has P (P=2^n) nodes. The location update cost consists of the normal location update cost originated by the PC and the unicast location update cost from BS to the PC

41. Performance Analysis: Overall Cost (1/3) Overall cost = location update cost + packet delivery cost Overall cost = location update cost + packet delivery cost Parameters Parameters M: the packet delivery cost of MIP F: the packet forwarding/routing cost in a single CSN T: the additional re-encapsulation and decapsulation cost of MIP, F-MIP, and HMIP B: the cost for buffering packets at NAR in F-MIP Additional forwarding cost, encapsulation cost, and buffering cost

42. Overall Cost (2/3) HA first tunnels packets to the serving CSN, which then forwards them to the MS hop by hop

43. Overall Cost (3/3) HMIP incurs additional encapsulation/decapsulation costs (T) When packets arrive (M) 1)the PC must page all P cells in the PG to locate an MS (PV) 2)Upon receiving the paging request, the MS sends the PC a location update message, which traverse (log(P) hops (Slog(P)) 3)Packets will be forwarded to the MS by the PC (F)

44. Energy Consumption (1/2) Mainly determined by the location update signaling Mainly determined by the location update signaling FINCH vs. P-FINCH FINCH vs. P-FINCH Parameters Parameters Each uplink transmission consumes u units of energy In active mode, each MS also consumes r units of energy per time unit while the receiver is on An MS in idle mode consumes b units of energy per time unit

45. Energy Consumption (2/2)

46. Numerical Results: Parameters

47. Numerical Results: Handover Latency

48. Numerical Results: Packet Loss

49. Numerical Results: Location Update Cost

50. Numerical Results: Location Update Cost (Cond.)

51. Numerical Results: Overall Cost

52. Numerical Results: Energy Conservation

53. Conclusion Mobile WiMAX designed to support MSs moving at vehicular speed MIP is designed for inter-domain mobility management, but not suitable for intra-domain mobility management Cannot support fast HO for MSs moving frequently Exaggerated for real-time services FINCH is proposed to support fast intra-domain mobility management Complementary to MIP Cross-layer design that reduces both location update and overall costs P-FINCH: Paging Extension for FINCH Reduces the signaling overhead and energy consumption

54. Questions? Questions?