Upload
doanthuan
View
224
Download
2
Embed Size (px)
Citation preview
1
“Vertical Handoff in
Heterogeneous Wireless
Networks”
Enrique Stevens Navarro
March 10th, 2006
UBC-IEEE Workshop on Future Wireless Systems
2
Presentation Outline
� Heterogeneous Wireless Networks
� Always Best Connected
� Mobility Management
� Handoff Management
� Vertical Handoff
� WLAN/Cellular Interconnection
� Project research at the Communications Group
2
3
Heterogeneous Wireless Networks
� A mix of radio access technologies will co-exist.
4
Heterogeneous Wireless Networks
� Different Access Technologies (radio interfaces) and overlapping coverage.
� Different Network Architectures and Protocols for transport, routing and mobility management.
� Different Service Demands from mobile users (low-data-rate, high-data rate, voice, etc)
� Different Operators in the market.
3
5
Always Best Connected (ABC)
6
Always Best Connected (ABC) [1]
� The ABC concept allows a person connectivity to applications using the devices and access technologies that best suit his/her communication needs.
� The ABC scenario generates great complexity and a number of requirements.� Technical solutions.
� Business relationships.
� Subscriber handling.
[1] E. Gustafsson and A. Jonsson, “Always Best Connected,” IEEE Wireless Communications, February 2003.
4
7
� Different Wireless Networks are complementary to
each other, their integration will allow mobile users
to be connected using the best available access
network that fits their needs.
� To deal with this problem, Mobility Management
Techniques are required…
Mobility Management
Mobility Management
Handoff Management
Location Management
8
Mobility Management
� Location Management: It enables the system to track the locations of mobile terminals (MT).
� Handoff Management: It is the process by which an MT keeps its connection when it moves from one point of attachment (base station or access point) to another.
Handoff or handover
Vertical Handoff (VHO)
Horizontal Handoff (HHO)
5
9
Handoff Management Requirements
� Reduction of signaling and processing overhead.
� Minimize packet loss and delay (seamless HO).
� QoS guarantees during the process and transfer of
context.
� Use of any “triggers” or metrics available to decide
when and where (planned HO).
� Efficient use of network and MT resources.
� Enhanced scalability, reliability and robustness.
� Allow inter-technology handoff (VHO).
10
[2] M. Stem and R. Katz “Vertical handoffs in wireless overlay networks,” Mobile Networks and Applications, 1998.
Horizontal vs. Vertical Handoff [2]
Horizontal
Handoff
Vertical
Handoff
6
11
� Horizontal HO – mainly use received signal strength
(RSS) to decide the handoff…
� But Vertical HO?
� RSS?
� Offered bandwidth?
� Price?
� Power consumption?
� Speed?
� ….
Handoff
Metrics
Handoff Metrics
12
Vertical Handoff Process
Step 1: “System Discovery”
The MT must know which wireless networks are reachable.
Step 2: “Handoff Decision”
The MT then evaluates the reachable wireless networks to
make a decision.
Step 3: “Handoff Execution”
If the MT decides to perform a VHO, it executes the VHO
procedure required to be associated with the new
wireless network.
7
13
Step 1: System Discovery
� Periodic beacons from AP.
� Signal measurements.
� Database query.
� Handoff metrics gathering.
�Bandwidth, cost, delay, SNR, power, etc.
� Periodic / Adaptive network scanning.
� All interfaces always on.
14
Step 2: Handoff Decision
� Fuzzy Logic / Neural Networks.
� Multiple Attribute Decision Making.
� Decision based on utility / cost functions.
� User triggered.
� Decision based on proposed policies:� “Always use the cheapest network”.
� “Always use the interface with lower power consumption”.
� “Always use the WLAN”.
� “Always use the network with more bandwidth”.
� Decision + stability period. (Avoid ping-pong effect)
8
15
Step 3: Handoff Execution
� Network Layer:� Mobile IP v4 vs. Mobile IP v6.
� Transport Layer:� Stream Control Transmission Protocol (SCTP).� Transmission Control Protocol (TCP).
� Application Layer:� Session Initiation Protocol (SIP).� Application-based.
� Infrastructure-based approach
� End-to-end approach.
16
WLAN – Cellular Networks
� Important case of heterogeneous wireless
networks integration.
� Two architectures are proposed:
�Tightly-coupled inter-working.
�Loosely-coupled inter-working.
9
17
WLAN – Cellular Networks [3]
[3] M. Buddhikot, G. Chandranmenon, S. Han, Y. Lee, S. Miller and L. Salgarelli, “Integration of 802.11 and 3G Wireless Data Networks” in Proc. of IEEE Infocom’03.
18
WLAN – Cellular Networks Integration
Some interoperability open issues:
� When to switch?, VHO policies:
�WLAN to Cellular ≠ Cellular to WLAN
� Seamless handoff (level of integration).
�Packet loss and VHO latency.
� Load balancing between networks.
� QoS guarantees and transfer of context.
� Security and Authentication.
� Billing and revenue sharing.
� Implementation.
10
19
WLAN – Cellular Networks Integration
Standardization efforts:
� Both 3GPP and 3GPP2 are working in the inter-
working with WLAN as an extension of their radio
access networks.
� IEEE 802.21 Media Independent Handover Group is
working toward the seamless handoffs between:
� IEEE 802.XX family.
� IEEE 802.XX and 3G Cellular
� Between 802.11 ESSs.
20
Current Research:
� Comparison of different decision algorithms
proposed for vertical handoff.
� Four algorithms:
� SAW (Simple Additive Weighting) [4]
� TOPSIS (Technique for Order Preference by Similarity to Ideal Solution) [4]
� MEW (Multiplicative Exponent Weighting) [5]
� GRA (Grey Relational Analysis) [6]
[4] W. Zhang, “Handover Decision Using Fuzzy MADM in Heterogeneous Networks” in IEEE WCNC’04, March 2004.
[5] K. Yoon and C. Hwang, Multiple Attribute Decision Making: An introduction, Sage Publications, 1995.
[6] Q. Song and A. Jamalipour, “A Network Selection Mechanism for Next Generation Networks” in IEEE ICC’05, May 2005.
11
21
Decision Matrix
MNMM
N
N
xxx
xxx
xxx
...
:...::
...
...
21
22221
11211
Networks to Select
- WLAN
- CDMA2000
- GSM/GPRS
M – Number of networks.
N – Number of parameters
Parameters to Consider
- Bandwidth
- Delay
- Jitter
- Bit Error Rate (BER)
22
Decision Methods
∑=
∈=
N
j
ijjMi
SAW rwA1
*maxarg
� SAW
∏∈
= jw
ijMi
MEW xA maxarg*
� MEW � GRA
iMi
GRAA ,0
* maxarg Γ=∈
** maxarg iMi
TOP cA∈
=
� TOPSIS
12
23
Performance Comparison
� A set of importance weights are calculated
according to the QoS requirements of the four traffic
classes: conversational, streaming, interactive and
background.
� Simulation: the connection lifetime of the mobile
follows an exponential distribution and each network
evolves according to a Markov chain. Every time
that the status of a network changes the mobile
terminal must decide which network to use.
24
1 2 3 4 5 6 7 8 9 1060
62
64
(a) Conversational
Avg. bandw
idth
(K
bps)
Avg. connection time (mins)
1 2 3 4 5 6 7 8 9 105600
5800
6000
6200(b) Streaming
Avg. bandw
idth
(K
bps)
Avg. connection time (mins)
1 2 3 4 5 6 7 8 9 104500
5000
5500
6000(c) Interactive
Avg. bandw
idth
(K
bps)
Avg. connection time (mins)
1 2 3 4 5 6 7 8 9 104500
5000
5500
6000(b) Background
Avg. bandw
idth
(K
bps)
Avg. connection time (mins)
SAW MEW TOPSIS GRA
� Average Bandwidth (Kbps)
13
25
1 2 3 4 5 6 7 8 9 1010
12
14
16(a) Conversational
Avg
. d
ela
y (
ms)
Avg. connection time (mins)
1 2 3 4 5 6 7 8 9 1058
60
62
64(b) Streaming
Avg
. d
ela
y (
ms)
Avg. connection time (mins)
1 2 3 4 5 6 7 8 9 1060
70
80(c) Interactive
Avg
. d
ela
y (
ms)
Avg. connection time (mins)
1 2 3 4 5 6 7 8 9 1060
70
80(b) Background
Avg
. d
ela
y (
ms)
Avg. connection time (mins)
SAW MEW TOPSIS GRA
� Average Delay (ms)
26
Students working in the project:
Pricing StrategiesPhDJun Wang
Vertical HandoffPhDJie Zhang
Vertical HandoffPhDEnrique Stevens
Navarro
AreaProgramName
14
27
Summary:
� Heterogeneous Wireless Networks
� Mobility Management
� Handoff Management and Vertical Handoff
� WLAN/Cellular Inter-working
� Research
28
Contact Information:
Enrique Stevens Navarro
Office: Kaiser 4090
Email: [email protected]
Thank
You!