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IEEE 802.21 MEDIA INDEPENDENT HANDOVER
DCN: 21-06-0687-01-0000
Title: Implementing Quality of Service based handovers using the IEEE
802.21 framework
Date Submitted: July, 19th, 2006
Presented at IEEE 802.21 session #15 in San Diego, California
Authors or Source(s):
Nada Golmie, Ulises Olvera-Hernandez, Richard Rouil, Reijo Salminen,
Steve Woon
Abstract: This document discusses an example implementation of a Quality of
Service (QoS) based handover using the IEEE 802.21 framework. A mapping
between the application QOS requirements and the link and network
measurements available is presented. This mapping is useful to set
appropriate link trigger thresholds and exchange QOS metrics using the MIH.
Changes to the current P802-21-D01-00 draft are also highlighted.
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IEEE 802.21 presentation release statements
This document has been prepared to assist the IEEE 802.21
Working Group. It is offered as a basis for discussion and is not
binding on the contributing individual(s) or organization(s). The
material in this document is subject to change in form and
content after further study. The contributor(s) reserve(s) the right
to add, amend or withdraw material contained herein.
This is a contribution by the National Institute of Standards and
Technology and is not subject to copyright in the US. The
contributors do not have the authority to override the NIST policy
in favor of the IEEE 802.21 policy.
The contributor is familiar with IEEE patent policy, as outlined in
Section 6.3 of the IEEE-SA Standards Board Operations Manual
<http://standards.ieee.org/guides/opman/sect6.html#6.3> and in
Understanding Patent Issues During IEEE Standards
Development http://standards.ieee.org/board/pat/guide.html>
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Outline
1. What is a QOS-based handover?
•
Motivation and Objectives
2. Designing an example QOS-based Decision
Engine (QDE)
•
•
•
•
QDE architecture
Mapping of application QOS requirements & network
measurements
Use of 802.21 framework
Example scenario and simulation results
3. Changes to P802-21-D01-00
4. MIH support in obtaining end-to-end
information
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What is a QOS-based handover?
• A QOS-based handover is a decision to
perform a handover based on current (now) and
expected (future) network conditions and how
well they meet the application QOS
requirements.
• Current network conditions are measured using
network performance parameters from various
layers such as signal strength (layer 1), packet
loss (layer 2), throughput (layer 2+), delay
(layer 2+), retransmissions (layer 2+), etc.
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Application QOS Requirements
A definition for applications QOS requirements according to the
ITU-T Y.1540 is as follows:
• Packet Transfer Delay (PTD): maximum end-to-end
tolerated delay ( in seconds)
•
Packet Delay Variation (PTV), i.e. jitter: maximum packet
jitter (in seconds)
•
Packet Loss Ratio (PLR): maximum tolerated packet loss
•
Throughput: required data rate of successful packets (in
bits/s).
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QOS-based Handovers:
Building blocks
Given the application QOS requirements, there are three additional
building blocks in implementing a QOS-based handover:
1.
The QOS-based Decision Engine (QDE):
•
is an MIH user (outside the scope of the IEEE 802.21).
•
Considers application QoS requirements and network performance
measurements provided by the MIH
•
Performs appropriate actions when MIH triggers are received
2.
The Media Independent Handover (MIH) function
•
is used to exchange information between various network entities and
the QDE, including technology and protocol types, network
measurements
•
Sets and relays link triggers
3.
Measurements characterizing the network performance conditions:
•
Instantaneous measurements for current conditions
•
Cached measurements from past observations and previous connections
•
Default estimates.
•
Measurements can be obtained via the MIH using the Information
service or other network nodes.
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An example QDE architecture
The QDE can be located as a remote entity, as part of the MN, or the AP/BS.
For our specific example, we have placed it at the MN as illustrated below.
Application
QoS
Info
Decision
Engine (DE)
Measurements Query
or
or
configure
L2 trigger
MIH
Trigger
Set
Set
Trigger
trigger
trigger
Outside the scope of 802.21
Technology dependent
Technology independent
Query
or
configure
Measurements
or
L2 trigger
MIH
Set
trigger
Trigger
L22
L2
Mobile Node
Access Point
L21
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Query
or
configure
Measurements
or
L2 trigger
Mapping of QOS (application) requirements
onto (network) performance measurements
• The network is logically divided into segments:
• Core network: cloud providing connectivity between the access point/
point of attachment and the corresponding node.
• One or more access network(s) for the connection between end (mobile)
nodes and the access point/point of attachment.
• The performance of each segment is characterized by the following metrics:
• Maximum packet delay (Dx) in seconds
• Maximum packet jitter (Jx) in seconds
• Maximum loss (Lx)
• Maximum throughput (Thx) in bits/s
Where ‘x’ is replaced by ‘c’ for Core network and by ‘a’ for Access
network.
• The link layer between the AP/BS and the MN provides additional
measurements from layer 1 and 2. They are noted Dm, Jm, Lm, and Thm.
• Errors are not produced at layer 3 (e.g. IP). This means loss at layer 3 is
equal to loss at layer 2.
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An example of a QoS Parameter
Mapping Chart
802.21
802.11
Max Bitrate
Guaranteed (Min)
Bitrate
Minimum Data Rate
Peak Rate
Peak Data Rate
802.16
3GPP
Maximum Sustained
Traffic Rate
Maximum
Bitrate
Minimum Reserved
Traffic Rate
Guaranteed
Bitrate
Peak_Rate
Packet Loss Rate
Before Retransm.
Max_IP_Packet_
Loss_Rate
Packet Error Rate
Packet Error Rate
Max Packet Size
Maximum MSDU
Size
Delay
Delay Bound
Jitter
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3GPP2
Maximum Latency
Tolerated Jitter
SDU Error Ratio
Maximum SDU
Size
Packet_Size
Transfer Delay
Max_Latency
Delay_Var_Sensi
tive
Computing target network performance
and setting link parameter thresholds
Application
Transport
QoS: PTD, PTV, PLR, TH
UDP, TCP, …
Access Network
Network
Core Network
Network measurements:
Dc, Jc, Lc, Thc
Link Layer
Network measurements:
Da, Ja, La, Tha
Link measurements:
Dm, Jm, Lm, Thm
1- compute
target
network
performance
2- map target
network
performance
to link
parameter
thresholds
Given the application QoS requirements and assuming default values for the
network core, let’s compute:
1. target values for the access network performance
2. Link parameter thresholds
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Computing target network performance
Using the application’s QoS, transport layer for the application,
and the core network performance, we can derive the access
network performance as follows:
Dm  Da  PTD  D c
J m  J a  PTV  J c
PTL1/( R 1)  Ltc
Lm  La 
1  Ltc
Thm  Tha  TH
where R is the number of retries provided by the transport layer
due to error or loss. For UDP, R=0 and for TCP, R=3.
Depending on the application direction, target values will be
assigned to either the sender or receiver measurements (if layer
2 provides separate measurements).
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QDE algorithm for link selection
When the MN first connects to a network or performs a handover,
it needs to choose a network interface to support its application
and their QOS requirements. This is known as the link selection
phase and the procedure is described as follows:
if no L2 connection
Establish L2 connection for preferred interface
end
for each interface
Obtain estimated end-to-end core network QoS measures (e.g. from IS)
Obtain estimated L2 metrics from AP
Mark interface which satisfy application QoS
end
Connect on best interface
Set L2 trigger thresholds
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Example scenario using QDE
CN
IS
802.16 BS
802.11 AP
MN
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Edge network
Internet
Scenario description
• A MN appears in the WLAN area and starts a voice
conversation with the CN
• The QDE decides that WLAN offers the best connection and
sets the link parameter thresholds accordingly (throughput in
the downlink measured at the MN is used to trigger a QOSbased handover)
• The WLAN network conditions deteriorate due to congestion
(increase in the offered load).
• QDE receives a trigger (via MIH) from the lower layer and
performs a link selection. A handover is performed towards the
IEEE 802.16 interface in order to support the application’s QOS
requirements.
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Simulation parameters
• A voice conversation is modeled with two one-way CBR connections (traffic
flowing in opposite directions). Each connection sends 160 bytes every 0.02
s, equating to 64 kbit/s (88 kbit/s including L2 overhead).
• MNs with two-way voice conversations are added to the WLAN network
every second.
• The data rate for IEEE 802.11 is set to 11 Mbit/s.
• The data rate for IEEE 802.16 is set to 12 Mbit/s.
• Buffer size is set to 50 frames.
• Links in the core network have a data rate of 100 Mbit/s.
• The delay through the core network is 80 ms one-way when using either the
IEEE 802.11 or IEEE 802.16 access network.
• A trigger threshold for the downlink throughput is set to 85 Kbit/s.
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Event flow diagram: Initial stage
MS
App
Decision
Engine
MIH
L2
802.11
802.11 AP
802.11 AR
L2
MIH
L2
802.16
802.16 BS
MIH
L2
Network Discovery Phase
Collect information
about neighboring
networks
MIH_Get_Information.request (Available networks)
MIH_Get_Information.request (Available networks)
MIH_Get_Information.request (Available networks)
MIH_Get_Information.response (802.11, 802.16)
MIH_Get_Information.response (802.11, 802.16)
MIH_Get_Information.response (802.11, 802.16)
Establish layer 2 connection
with preferred interface
Link_UP.indication
Link_UP.indication
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IS
MIH
Event flow diagram: Link selection
MS
App
Decision
Engine
MIH
L2
802.11
L2
802.16
802.11 AP
802.11 AR
L2
MIH
802.16 BS
MIH
L2
New application
sets QoS requirements
Link Selection
MIH_Get_status (802.11 link)
Link_Get_status.request
Link_Get_status.response
MIH_Get_status.response
MIH_Get_status (802.16 link)
MIH_Get_status (802.16 link)
Link_Get_status.request
Link_Get_status.response
MIH_Get_status.response
Map QoS to
L2 thresholds
MIH_configure_thresholds.request
Link_configure_thresholds.request
Link_configure_thresholds.confirm
Link_configure_thresholds.confirm
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IS
MIH
Event flow diagram: handover
MS
App
Decision
Engine
MIH
L2
802.11
L2
802.16
802.11 AP
802.11 AR
L2
MIH
Change in network condition
(InitAction threshold crossed)
Link_parameters_change.indication
MIN_Link_parameters_report.indication
Link Selection
Change in network condition
(ExecAction threshold crossed)
Link_parameters_change.indication
MIN_Link_parameters_report.indication
Continue handover
decision
MIH_Switch
Link_connect
MIH Handover Preparation and Execution
Link_UP.indication
Link_UP.indication
Link_disconnect
Link_Down.indication
Link_Down.indication
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Higher Layer Handover Completion
802.16 BS
MIH
L2
IS
MIH
Performance results: Throughput
Frame throughput between MN and WLAN AP
End-to-End throughput
2.6
downlink w/o QoS trigger
downlink w/ QoS trigger
offered load
100
90
downlink w/o QoS trigger
downlink w/ QoS trigger
uplink w/o QoS trigger
uplink w/ QoS trigger
2.4
80
Throughput crosses threshold
and handover
2.2
70
2
1.6
60
1.4
1.2
40
1
Throughput (kbit/s)
1.8
Offred load
Throughput (kbit/s)
80
60
50
Handover
40
30
0.8
20
0.6
20
0.4
10
0.2
0
5
10
15
20
Time (s)
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25
30
0
5
10
15
20
Time (s)
25
30
Performance results: Delay
Frame delay between MN and WLAN AP
120
End-to-End packet delay
2.6
w/o QoS trigger
w/ QoS trigger
offered load
1600
1400
2.2
100
2
80
1.6
1.4
60
1.2
1
40
Packet delay (ms)
1200
1.8
Offred load
Frame delay (ms)
w/o QoS trigger
w/ QoS trigger
2.4
1000
800
600
0.8
0.6
Handover
20
0.4
400
Handover
Over 802.11 link
200
Over 802.16 link
0.2
0
5
10
15
20
Time(s)
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25
30
0
5
10
15
20
Time (s)
25
30
Performance results: Jitter
Frame jitter between MN and WLAN AP
18
End-to-End packet jitter
2.6
w/o QoS trigger
w/ QoS trigger
offered load
16
800
w/o QoS trigger
w/ QoS trigger
2.4
700
2.2
14
2
10
1.4
8
1.2
1
Jitter (ms)
1.6
Offered load
1.8
12
Jitter (ms)
600
500
400
300
6
0.8
Over 802.16 link
200
4
Handover
0.6
Handover
2
0.4
100
Over 802.11 link
0.2
0
5
10
15
20
Time (s)
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25
30
0
5
10
15
20
Time (s)
25
30
How to support a QDE implementation
using IEEE 802.21 specifications?
•
The IEEE 802.21 specifications facilitate the exchange of
network parameters and measurements between various
network entities and thus support interoperability between
different vendor implementations.
•
There are two types of information:
1. Parameter exchanged between the MIH function and the
MIH users
2. Parameter exchanged between lower layers and the MIH
function
•
Both types of information may have a different set of
parameters.
•
By definition, the MIHF interacts with several technology
dependent entities such as link layer implementations and
measurements, handover decision engines, etc.
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Information exchanged between
MIHF and MIH users
For interoperable parameter exchange between different MIHF implementations and an
MIH user:
• A standard set of parameters are defined at the MIH based on the application QOS
requirements
• Parameter values can be modified and read by the MIHF and MIH users.
MIH
User
Standard set of parameters
exchanged between MIHFs
and MIH users.
MIHF1
L21
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L22
MIHF2
L21
L22
Support in 802.21 draft: MIH Primitives
To support the configuration of link parameter threshold and
monitoring, we use the following primitives:
• MIH_Configure_Thresholds (request/confirm): to configure
threshold and update intervals.
• MIH_Link_Parameters_Report (indication): events sent to
upper layers indicated new parameter values.
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MIH_Configure_Threshold (1)
Modify section 7.4.8 as follows:
7.4.8 MIH_Configure_Threshold.request
7.4.8.1 Function
This primitive is generated by an upper layer to configure thresholds for
MIH_Link_Parameter_Report.indication.
7.4.8.2 Semantics of primitives
The primitive parameters are as follow:
MIH_Configure_Threshold.request (
LinkIdentifier
LinkParameterList
)
For parameter description, see next slide
7.4.8.3 When generated
This primitive is generated by an upper layer entity that wishes to be notified of lower layers changes.
7.4.8.4 Effect on receipt
The MIH entity receiving this command will generate a series of link commands in order to monitor the status of
the target lower layers and inform upper layers of the changes.
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MIH_Configure_Threshold (2)
Name
Type
Valid range
Description
LinkIdentifier
TBD
N/A
ID of the link for which the parameters
changed.
LinkParameterList
List
N/A
A list of the following set of
parameters:
LinkParameterType
InitiateActionThreshold
RollbackActionThreshold
ExecuteActionThreshold
UpdateFrequency
LinkParameterType
INTEGER
0-255
Parameter type as define in following
table.
InitiateActionThreshold
Threshold values dependent on
parameter type.
N/A
Threshold value which may cause
Upper layers to start “setup” type
activities in response to actual
parameter values crossing this
thresholds.
RollbackActionThreshold
Threshold values dependent on
parameter type.
N/A
Threshold value which may cause
Upper layers to cancel or rollback the
above setup type operation if the actual
parameter values retreat to this
threshold.
ExecuteActionThreshold
Threshold values dependent on
parameter type.
N/A
Threshold value which may cause
Upper layers to execute taking
appropriate action if the actual
parameter values cross this threshold.
UpdateFrequency
INTEGER
0-65535
Interval time (in ms) at which the MIH
must generate an
MIH_Link_Parameters_Report to
provide updated values to Upper
layers.
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MIH_Configure_Threshold (3)
The following table lists the generic parameters to be used for communicating between MIHF and
MIH Users
Value
Name
Value size
(octets)
Valid range
Description
0
Throughput
2
0-(264-1)
Link throughput in Mbps
1
Delay
1
0-65535
Frame delay in ms
2
Jitter
1
0-65535
Frame jitter in ms
3
Frame loss rate
1
0-100
Percentage of the number of frame lost over the number
of frames successfully received.
4
Frame error rate
1
0-100
Percentage of the number of frame received with error
over the number of frames successfully received.
6~255
Reserved
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MIH_Configure_Threshold (4)
Modify section 7.4.8 as follows:
7.4.8 MIH_Configure_Threshold.response
7.4.8.1 Function
This primitive is generated by MIH function in response to MIH_Configure_Threshold.request primitive. It
specifies the status of the configuration operation.
7.4.8.2 Semantics of primitives
The primitive parameters are as follow:
MIH_Configure_Threshold.confirm (
LinkIdentifier
LinkParameterStatusList
)
For parameter description, see next slide
7.4.8.3 When generated
This primitive is generated in response to MIH_Configure_Threshold.request primitive
7.4.8.4 Effect on receipt
The Upper layers receiving the confirmation can prepare to receive notification of MIH_Link_Parameters_Report
for successful configuration.
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MIH_Configure_Threshold (5)
Name
Type
Valid range
Description
LinkIdentifier
TBD
N/A
ID of the link for which the parameters
changed.
LinkParameterStatusList
List
N/A
A list of following set of parameters:
LinkParameterType
OldValue
NewValue
LinkParameterType
INTEGER
0-255
Parameter type as define in table of
MIH_Configure_Thresholds.
Status
BOOLEAN
True/false
Status of operation:
True: success
False: failure
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MIH_Link_Parameters_Report (1)
Add new section as follows:
7.4.8 MIH_Link_Parameters_Report.indication
7.4.8.1 Function
This primitive is generated by the MIH Function to inform Upper layers that parameters have crossed thresholds
or that the timer for periodic update has expired.
7.4.8.2 Semantics of primitives
The primitive parameters are as follow:
MIH_Link_Parameters_Report.indication (
LinkIdentifier
LinkParameterReportList
)
For parameter description, see next slide
7.4.8.3 When generated
This primitive is generated when the MIH Function detected that some link parameters have crossed thresholds or
that it is time to send a periodic update.
7.4.8.4 Effect on receipt
Upper layers entities inspect the new values and may take actions such as preparing for handover.
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MIH_Link_Parameters_Report (2)
Name
Type
Valid range
Description
LinkIdentifier
TBD
N/A
ID of the link for which the parameters
changed.
LinkParameterReportList
List
N/A
A list of following set of parameters:
LinkParameterType
OldValue
NewValue
LinkParameterType
INTEGER
0-255
Parameter type as define in table of
MIH_Configure_Thresholds.
OldValue
Threshold values dependent on
parameter type.
N/A
Old parameter value.
NewValue
Threshold values dependent on
parameter type.
N/A
New parameter value.
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Information exchanged between
the lower layers and MIHF
•
MAC layers of different technologies provide different measurements.
•
Vendors also provide implementation specific measurements for the same technology.
 Defining unified list of parameters may be difficult
Proposal:
•
Leave the parameter exchanged between the lower layers and the MIHF out of the scope of the
802.21 standard.
•
Assume that an MIH implementation will include mechanisms for
• Extracting and setting parameters for layers implemented by specific vendors.
• Mapping from vendor layer parameters to standard MIH parameters, and vice versa.
MIH
User
MIH
L2 to MIH parameter map
Vendor specific layer parameters
exchanged between layer 2 and MIH.
L21
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L22
The case for obtaining end-to-end
network performance measurements
In order to provide users with the so-called seamless connectivity, end-to-end network
performance measurements may be critical.
Network performance measurements are constantly changing:
• For wireless nodes, movement and physical environment are are changing
quickly.
• For wired nodes, congestion, change in routing also affect performance.
 Need for an MIH User to query status of network/End-to-End information.
Illustrative example:
Using the same scenario described in slides 12 and 13, let’s look at what happens
when the performance of the local cell does not change but the core network is
subject to changes in delay and bandwidth. The changes to the core network are as
follows:
time = 0 s, delay = 80 ms and capacity = 100 Mbit/s
time = 15 s, delay = 125 ms and capacity = 100 Mbit/s
time = 20 s, delay = 165 ms and capacity = 100 Mbit/s
time = 22 s, delay = 165 ms and capacity = 300 kbit/s
time = 25 s, delay = 80 ms and capacity = 300 kbit/s
time = 27 s, delay = 80 ms and capacity = 100 Mbit/s
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Performance results: delay
End-to-End packet delay
400
3
350
2.5
300
Packet delay (ms)
Frame delay (ms)
Frame delay between MN and WLAN AP
3.5
2
1.5
250
200
1
150
0.5
100
0
50
5
10
15
20
Time (s)
25
30
5
10
15
20
Time (s)
Layer 2 measurements do not detect change in the end-to-end delay
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25
30
Performance results: jitter
Frame jitter between MN and WLAN AP
End-to-End packet jitter
2.5
90
80
2
70
1.5
Jitter (ms)
Jitter (ms)
60
50
40
1
30
20
0.5
10
0
0
5
10
15
20
Time (s)
25
30
5
10
15
20
Time (s)
 Layer 2 measurements do not detect change in end-to-end jitter
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25
30
How to obtain end-to-end network
performance measurements?
An MIH User such as a QOS Decision Engine requests the MIHF
for network performance measurements. This is done using the
MIH_Get_Information primitives.
We propose to use the extended schema to add an IE containing
the network performances as defined in ITU-T Y.1541.
The local MIHF receiving the request can do the following:
• If the MIHF implementation collects network measurements
from the network layer, it may be able to reply directly to the
MIH User.
• Otherwise, the request is forwarded to an IS. The MIHFs on
the network are responsible for updating the information
contained in the IS.
• If no information is available, the MIH user may consider
default values.
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