Performance Analysis of
Decentralized RAN (Radio
Access Network) Selection
Schemes
December 28th, 2004
Yang, Sookhyun
Contents
Introduction
Previous Works
RAN Selection Schemes
Evaluation Method
Performance Analysis
Conclusion
2/17
Background
Emerging various wireless access technologies
– 2G, 3G celluar, satellite, WiBro/WiMax (IEEE 802.16), Wi-Fi
(IEEE 802.11a/b/g), Bluetooth (IEEE 802.15)
WWAN: large coverage, high cost
WLAN: high speed, moderate cost
(HPi)
WPAN: small area,
low speed, low cost
In the Fourth-generation (4G) wireless network
– Multiple broadband wireless access
– Seamless mobility across heterogeneous networks
3/17
Motivation
RAN Discovery
WiMax
Bluetooth
Wi-Fi
Satellite
Celluar
– Discover available access
networks
– Scan a wide range of
frequencies
– Power management
RAN selection
– Determine the optimal access
network among available RANs
– Many selection parameters
User’s network preference
Communication charge
Available bandwidth
Power dissipation
4/17
Previous Works
Centralized approaches
–
–
–
–
A centralized server collects and monitors available RANs
A centralized server manages a mobile host’s position (GPS)
BAN (Basic Access Network)-based scheme
WISE (Wise Interface Selection)
Decentralized approaches
– A mobile host itself monitors available RANs
– PPM (Power and Performance Management)
– NAV (Network Allocation Vector)-based scheme
5/17
Decentralized Approaches
RAN discovery
– Periodically turns on NICs (Network Interface
Card)
– Static or Dynamic period
– All NIC or a CAN (Candidate Access Network)
RAN selection
–
–
–
–
–
QoS guarantee
Signal strength is increasing
Minimum power consumption
Select before a handoff occurs
Handoff occurs when QoS does not guarantee
6/17
How to discover available RANs
Static/Dynamic period
– Static period ∝ {network’s coverage}
– Dynamic period ∝
{network’s coverage}
{mobile host’s velocity}
– {mobile host’s velocity} ≈ {∆signal strength}
CAN (Candidate Access Network)
– Pre-select the optimal RAN among available RAN as a CAN
– Periodically check that a selected CAN guarantees QoS
7/17
How to select the optimal RAN
Available Access Network
QoS <= Available
bandwidth
If there is no QoSguaranteeing access network
YES
Signal strength is
increasing?
YES
Power consumption
is minimum?
Available bandwidth
is maximum?
Optimal Access Network
8/17
Objective
Evaluate the performance of the following
RAN selection schemes
–
–
–
–
–
Static period with a CAN
Dynamic period with a CAN
Static period without a CAN
Dynamic period without a CAN
Continuously active scheme
Performance Metrics
– Achieved bandwidth
– Number of handovers
– Power consumption per seconds
9/17
Evaluation Environments
AP
BS
BS
AP
BS
BS
NS2’s
mobility generator
AP
0Mbps 1.2Mbps 2.4Mbps
SignalSignal
is bad~!
is not Signal
good~! is Good~!
10/17
Configuration
Mobile node
– 100 nodes, maximum 11m/s (≒ 40km/h)
– Equipped with all types of network interfaces
Network characteristics
Type
Coverage Bandwidth
Power Consumption
Receive
Transmit
Idle
Off
ON
2.4
0.206
1.169
0.082
-
-
1
5
(0.13)
(0.264)
(0.2)
-
-
802.11a
0.4
54
0.035
0.022
1
-
-
802.11b
0.4
11
0.123
0.205
0.75
802.11g
0.4
54
0.026
0.037
0.75
(Km)
(Mbps)
CDMA1X
2.5
802.16
(J/Mbits)
(J/Mbits)
(W)
(W)
(W)
1.7(1ms) 2.3(0.3s)
-
11/17
Network Topologies
(a) Insufficient network resource
(b) Sufficient network resource
12/17
Performance Analysis (1/3)
Achieved bandwidth
3.0
3.0
2.5
2.5
2.0
2.0
Achieved
bandwidth
1.5
(Mbps)
Achieved
bandwidth
1.5
(Mbps)
1.0
1.0
0.5
0.5
0.0
0.1
0.2
0.4
0.8
1.6
Target bandwidth (Mbps)
(a) Insufficient network resource
3.2
0.0
0.1
0.2
0.4
0.8
1.6
3.2
Target bandwidth (Mbps)
(b) Sufficient network resource
13/17
Performance Analysis (2/3)
Number of handovers
50
50
45
45
40
40
35
35
30
Number
of
25
handoff
20
30
Number
of
25
handoff
20
15
15
10
10
5
5
0
0.1
0.2
0.4
0.8
1.6
Target bandwidth (Mbps)
(a) Insufficient network resource
3.2
0
0.1
0.2
0.4
QoS
degradation
0.8
1.6
3.2
Target bandwidth (Mbps)
(b) Sufficient network resource
14/17
Performance Analysis (3/3)
Power consumption per Sec
1.4
1.4
1.2
1.2
1.0
1.0
Power
0.8
consumption(W)
0.6
Power
0.8
consumption(W)
0.6
0.4
0.4
0.2
0.2
0.0
0.0
0.1
0.2
0.4
0.8
1.6
Target bandwidth (Mbps)
(a) Insufficient network resource
3.2
4.5 ~ 40% of
a continuously
active
0.1
0.2
0.4
0.8
1.6
3.2
Target bandwidth (Mbps)
(b) Sufficient network resource
15/17
Observations and Analysis
Four selection schemes show the same
achieved bandwidth
Dynamic or a CAN give large energy-saving
But, when bandwidth is sufficient
– Static/dynamic with a CAN trigger too many
handovers
But, when bandwidth is not sufficient
– Static with a CAN consumes more power than
Dynamic without a CAN
16/17
Conclusion
Evaluated decentralized approaches for RAN
selection
Implemented a simulator for wireless overlay
network environment
Dynamic with a CAN reduces large amount of
power consumption without degrading
achieved bandwidth
But, too many handovers occur when
bandwidth is sufficient
17/17
A CAN is NOT valid!
QoS guarantee check
Network Candidate
Adapter #1 ALL 0
Network Candidate
Adapter #2
ALL 0
Network Candidate
Adapter #3 ALL 0
time
QoS guarantee check
time
time
18/17
Network Topologies
(a) Insufficient network resource
CDMA1X
802.11g (4)
(10)
802.16
(10)
802.11b
(31)
65
802.11a
(10)
(b) Sufficient network resource
CDMA1X
(4)
802.11g
802.16
(26)
(20)
802.11b
(25)
96
802.11a
(21)
19/17