Download Document

IEEE Wireless Communications, Oct. 2008
Handover Management in Integrated
WLAN and Mobile WiMAX Networks
Allen Borges Pontes, Diego Dos Passos Silva, JosÉ Jailton, Jr.
Otavio Rodrigues
and Kelvin Lopes Dias
Federal University of Para
1
Outline
• Introduction
• WLAN and WMAN: Basic Integration Issues
• Mobility Management and Integration Solutions for
Heterogeneous All-IP Wireless Networks
• WMAN and WLAN Integration Scenarios
• Handover between WiMAX and WiFi Using the MIH
Framework
• Conclusion and Future Directions
2
Introduction
• fourth-generation (4G) networks
– allow mobile users to be always best connected (ABC) through a
number of underlying wireless technologies and networks
– efficient schemes are needed to provide seamless
intertechnology/vertical handovers
• WLAN and WMAN
– WiFi and WiMAX
• IEEE 802.21: Media Independent Handover (MIH)
– providing to the upper layers (L3 and higher) uniform information
about layer two (L2) triggers in order to help the handover decision
• 802 and non-802-based networks
3
WLAN and WMAN:
Basic Integration Issues
• Application and Cost
– WiFi: companies, hotspots; free or low-cost
– WiMAX: last mile access, backhaul connection
– Interference issues; pricing models
• Architecture and Operation Modes
– WiFi: infrastructure and ad hoc; mesh in 802.11s
– WiMAX: PMP and mesh; relay in 802.16j
– Integrating different metrics adopted in the MACs; routing
• Coverage and Data Rates
– WiFi: 2  11(b)  54(a/g)  600(n)  1000(VHT) Mb/s
– WiMAX: 75 Mb/s, radius{ 50km [LOS], 2-5km [NLOS] }
 100 Mb/s in 802.16m for high-mobility (250km/h) users
– Significant differences in the coverage area
4
WLAN and WMAN:
Basic Integration Issues (cont.)
• QoS Support
– WiFi: 802.11e HCF<EDCA, HCCA>; four access
categories; congestion windows
– WiMAX: connection-oriented; 5 service flows (BE for web
and email);
– QoS mapping;
– static translation scheme
• does not take into account current network load and therefore
– does not benefit from adaptation mechanisms in order to increase
operator revenue or alleviate congestion.
• the mapping is network-specific (e.g., WiFi-WiMAX or WiMAXUMTS),and thus neither flexible to new QoS-aware sessions nor
scalable
5
Mobility Management and Integration Solutions
for Heterogeneous All-IP Wireless Networks
• IETF Solutions: Upper Layer Protocols
• Solutions from 3G Standardization Group
– Voice Call Continuity (VCC) / IMS
– System Architecture Evolution (SAE) / LTE
• The IEEE 802.21 Standard (MIH)
• Comparison of Solutions for Integration and Handover
Management
6
IETF Solutions: Upper Layer Protocols
• Mobile IP
– Mobile IPv4
– Mobile IPv6
• allowing the CN to send packets directly to theMN
– Fast Handover Mobile IPv6
• Mobile Stream Control Message Protocol (mSCTP)
• Session Initiation Protocol (SIP)
7
Solutions from 3G Standardization Group
• IP multimedia subsystem (IMS)
– an architectural framework for delivering IP multimedia to
mobile users
– originally defined in 3GPP release 5 and builds on
Internet protocols
• IETF SIP is reused as much as possible
• adopting a network of servers (call session control functions
[CSCFs]) in order to control the multimedia sessions
– 3GPP2 standardized its own architecture, the multimedia
domain (MMD)
• Actually based on the IMS architecture.
8
VCC / IMS
• Voice Call Continuity (VCC)
– a mobility management scheme based on IMS in Releases 6 and 7
– for service continuity
– integrates UMTS and unlicensed spectrum technologies (e.g., WiFi)
into a seamless network
– to transfer voice sessions between the circuit-switched domain (e.g.,
GSM) and the packet-switched domain (e.g., WiFi and IMS/UMTS)
– does not define a set of universal link layer triggers in order to
efficiently explore the connectivity opportunities and enhance vertical
handover.
– adds extra complexity through a call control continuity function
(CCCF)
– to provide seamless mobility all interfaces must be continuously
active to execute the network discovery procedure
9
SAE / LTE
• System Architecture Evolution (SAE)
– to provide a means for efficient vertical handover among
heterogeneous technologies
– focuses on the core network (CN) of a mobile network,
• changes in the radio access network (PHY and MAC layers) are handled
in the LTE project
• 100 Mb/s downlink and 50 Mb/s uplink
– IETF mobility protocols are under consideration
• network-based localized mobility management (NetLMM) for local
mobility and
• Mobile IP for global mobility
– but has also accepted the current GPRS Tunneling Protocol (GTP)
• Improvements in VCC/IMS are in the new 3GPP release
• It was not foreseen that handover would be seamless
– Expected in release 8 and beyond, but it still lacks standardized
triggers for helping with the network discovery and selection
procedures
10
The IEEE 802.21 Standard (MIH)
• Intended to facilitate handover and interoperability between
IEEE 802 and non-IEEE 802 technologies
• provide transparent service continuity across heterogeneous
networks
• a signaling framework and triggers that make available
information from lower layers (MAC and PHY) to the higher
layers
• unifying the various L2-specific technology information used
by the handover decision algorithms
– the signal strength
• offers commands to higher layers through an independent
technology service access point (SAP)
• the handover decision can be based on diverse factors such
as
– QoS, security support, economic cost, and users’ personal
preferences.
11
• MIEventS
– reporting both local
and remote events
– link characteristics,
link quality, and link
status
•
•
•
•
MIH_Link_Up
MIH_Link_Going_Down
MIH_Link_Down
MIH_Link_Detected
12
• MICommandS
– control, manage,
and send actions to
lower layers
– can be issued by
both local and
remote MIH users
13
• MIInformationS
– static information
• names and service
providers of the MN’s
current network
neighborhood
– dynamic information
• MAC addresses,
channel information,
and upper layer
service information
– through a set of socalled information
elements (IES)
– Format:
XML or ASN.1
14
The IEEE 802.21 Standard (MIH) (cont.)
• point of attachment (PoA).
• point of service (PoS),
– a network-side MIHF instance that exchanges MIH messages with an MNbased MIHF.
• Both PoA and PoS can be collocated.
• To integrate MIH functionality
– IEEE 802.11u, IEEE 802.16g
– IETF is working within MIPv6 Performance, Signaling and Handoff
Optimization (MIPSHOP) to address an L3 transport mechanism for the
reliable delivery of MIH messages
• QoS: a uniform framework consisting of MIH parameters in which the
technology-specific parameters are mapped.
– class of service (CoS) maximum packet transfer delay corresponds to
• IEEE 802.11’s transmit delay histogram,
• IEEE 802.16’s maximum latency, and
• UMTS’ maximum transfer delay.
– only provides the exchange of messages to carry out the QoS mapping, not
the mapping intelligence
15
16
WMAN and WLAN Integration Scenarios
17
Handover between WiMAX and WiFi
Using the MIH Framework
• MN3
18
802.11_LINK_DETECTED event
MN
Monetary cost,
security,
available bandwidth
CAC
MN
19
To confirm that the handover
will be executed.
Activate
WiFi
Resource reservation is
done.
Start redirecting
20
21
Conclusion and Future Directions
• No winner wireless technology suitable for all applications. The
integration of heterogeneous networks seems to be a good approach
– in order to offer the 4G always best connected vision.
• WLAN + WMAN
– Benefits WiMAX operators through a low-cost service deployment provided
by WiFi hotpots
• Some futuristic scenarios are discribbed.
• Two scenarios for WLAN MIH WiMAX
•
•
•
•
•
•
•
MIH support for multihop heterogeneous networks
QoS mapping
resource allocation mechanisms
Security support
Preventing DoS
Corrupted or compromised mesh points / relay stations
Mobility and connection/routing management
22