IEEE Communications Magazine, vol. 47, no. 6, pp. 122-131, 2009.
WiMAX-EVDO interworking
using mobile IP
Peretz Feder, Ramana Isukapalli, and Semyon Mizikovsky,
Alcatel-Lucent
1
Outline
• Introduction
• Network Architecture
– WiMAX Network
– EV-DO Network
• Network Architecture for Interworking
• Call Flows
– Handoffs Using CMIP in WiMAX
– Handoffs Using PMIP in WiMAX
• Conclusions
2
Introduction
• WiMAX
– a fourth-generation wireless-access technology,
– has made significant progress both in the standard forums and with
wireless network carriers.
– it is important to interwork with existing third-generation access
networks before it is uniquely and ubiquitously deployed.
• This article addresses the full-mobility approach and presents
a solution using mobile IP (MIP)
– a dual-mode device with two (WiMAX and EVDO) separate radios
– ideally suited for service providers who use a phased approach when
evolving from third-generation to fourth-generation networks.
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Network Architecture – WiMAX
• Based on the IEEE 802.16e air interface
– orthogonal frequency-division multiple access (OFDMA)
• The Network Working Group (NWG) of the WiMAX
Forum specifies the end-to-end system architecture,
detailed protocols, and procedures beyond the airinterface standards
[1] WiMAX Forum, “Network Architecture Stage 2: Architecture Tenets, Reference Model and
Reference Points.”
[2] WiMAX Forum. “Network Architecture Stage 3: Detailed Protocols and Procedures.”
[7] IEEE Std 802.16e-2005, “IEEE Standard for Local and Metropolitan Area Networks Part 16:
Air Interface for Fixed and Mobile Broadband Wireless Access Systems,” Dec. 2005.
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connectivity-services network (CSN)
access-services network (ASN)
a global mobility anchor
Security anchoring,
network-access-server
(NAS) functionality,
traffic accounting, and
a mobility proxy client
can potentially connect
over the R6 interface
to any ASN-GW
ASN-GW relocation
release 1.0 v. 3
intra-ASN-GW,
inter-ASN-GW,
and anchored-CSN
mobility
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Network Architecture – EVDO
a global mobility anchor
accepts MIP registration
Base station controller and
packet control function (BSC/PCF):
Control and management for one
or more BTSs and relays packets
to the appropriate packet dataserving node (PDSN)
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• Evolution-Data Optimized (EVDO)
– requires a point-to-point protocol (PPP) layer between the MS and the
packet data-serving node (PDSN)
– MS always performs MIP registration following a PPP negotiation
• makes the link set-up time on EVDO a little longer than in WiMAX
• unicast access terminal identifier (UATI) session.
– The lifetime of a UATI session can be longer than a PPP/MIP session,
• but a PPP session can exist only if the MS already has a UATI session.
– the air-interface session set up (including negotiation of session parameters and
protocols) takes a few seconds
• To reduce the hand-off time, pre-establishing an air-interface
session and leaving it idle (without a PPP/MIP session) while the
MS is active in a WiMAX network is desirable.
• But consumes more battery power
[3] 3GPP2 A-S0008-A, “Interoperability Specification (IOS) for High Rate Packet 1 Data (HRPD)
Radio Access Network Interfaces with 2 Session Control in the Access Network.”
[4] 3GPP2 X.S0011-D, “CDMA 2000 Wireless IP Network Standard.”
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Network Architecture for Interworking
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• Inter-technology handoffs
– break before make
– make before break
– make-before-break-with-simultaneous-bindings
• accounts for the best service continuity with a minimum packet loss
during handoffs
• additional algorithms (e.g., duplicate packets coming along the two links)
required
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Network Architecture for Interworking
- Interworking models
• tightly coupled model
– The ASN-GW of WiMAX connect to the IP core network through PDSN
– the EVDO core network treats the WiMAX network as an extension of
an access network.
– The MS implement an EVDO protocol stack on top of the WiMAX
– no practical standards
• the complexity of implementing this model must be evaluated carefully visà-vis the benefits
• loosely coupled mode
– each network follows its unique network entry procedures,
authentication methods, intra-technology mobility, paging, and so on
– the WiMAX and EVDO networks are connected to a common IP core
network,
• enabling common billing for both the networks and access technology
specific authentication
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• The data paths are separate for WiMAX and EVDO access
networks.
– useful when the same provider owns the same core network and can
serve disparate access networks
• an essential feature during transition from third-generation to fourthgeneration wireless networks.
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Network Architecture for Interworking
- Client MIP and PMIP models
• Client MIP (CMIP) model
– the MS integrates an additional MIP stack
• PMIP model
– the network (ASN-GW), on behalf of the MS, sends a MIP
registration request to the HA
• WiMAX networks support both CMIP and PMIP, whereas
EVDO supports only CMIP.
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Network Architecture for Interworking
- Functionality of Various Components
• HA
– enforces the use of the same Network Access Identifier (NAI) on
both the WiMAX and EVDO networks
– support simultaneous bindings for the WiMAX and EVDO
seamless handoff
• maintains both the old and the new bindings through both technologies
for a brief period of time
– supports session revocation and releases the resources
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• MS
– supports dual radio (two separate MAC and physical layers)
• possibly with simultaneous bindings during handoffs
– uses the same NAI in both WiMAX and EVDO
– uses CMIP procedures compliant with IS-835D [3, 4] in EVDO
networks and MIP procedures compliant with WiMAX [2]
– accessible with the same IP address (HoA) to any correspondent
node
– a connection manager (CM) function monitors the signal
strength in the other network for possible handoffs
• Trigger handoffs based on configuration parameters
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• AAA
– authenticates WiMAX terminals as specified in [1, 2] and EVDO
terminals as specified in [3, 4]
– stores the assigned HA address and the HoA corresponding to a
NAI
• returns the same HA address for an MS when there are subsequent
binding requests for the HA
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Network Architecture for Interworking
- Network Protocol Stack
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Network Architecture for Interworking
- QoS Issues
• EVDO supports a device-initiated QoS model,
– the QoS classifier is obtained mostly from the MS
• WiMAX initial release supports a network-initiated QoS
model
– QoS classification information must come from the network
• Handoffs
– WiMAX  EVDO
• the MS in an EVDO network can request the same assigned QoS.
– EVDO  WiMAX
• require further algorithms not presently developed.
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Call Flows
18
WiMAX
↓
EVDO
using CMIP
in WiMAX
19
WiMAX
↓
EVDO
using PMIP
in WiMAX
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Conclusions
• We discussed the need for interworking and presented an
interworking model between WiMAX and EVDO networks
using MIP protocols
– provide session continuity
• We discussed the loosely coupled network architecture with
separate data paths between WiMAX and EVDO networks.
• We presented detailed call flows for both CMIP and PMIP
implementations in WiMAX
– and discussed the various steps of the call flows.
• the interworking model presented here can be easily
extended to other access networks
– WiFi, the universal mobile telecommunications system (UMTS), longterm evolution (LTE), and so on.
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MIP - Registration
(“foreign agent care-of address” mode)
foreign agent register its
address (e.g. 140.234.1.1) to the
home agent of the mobile node
visited
network
home
network
Home Agent
mobile node
1
2
wide area
network
Foreign Agent
1) Agent Discovery:
mobile node contacts foreign agent
on entering visited network
2) Obtain care-of address (CoA):
The termination point of a tunnel toward a mobile node
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MIP - Communication
(“foreign agent care-of address” mode)
foreign agent receives
packets, detunnels and
forwards to the mobile node
home
network
home agent intercepts packets,
tunnels and forwards to the
foreign agent
mobile node
3
Home Agent
1
correspondent node
addresses packets using
the home address of the
mobile node
visited
network
wide area
network
2
Foreign Agent
4
correspondent node
mobile node replies
directly to the
correspondent node
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