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Transcript of Techmahindra - Techmahindra 80216e 3gpp Systems Network Hand Over
8/6/2019 Techmahindra - Techmahindra 80216e 3gpp Systems Network Hand Over
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© Tech Mahindra Limited 2010
802.16e & 3GPP Systems
Network Handover
Interworking
Venkat Annadata
Tech Mahindra (R&D) Services Ltd.
Abstract:
Next Generation Mobile Networks are paving its way
towards the ubiquitous wireless access abilities which
provide the automatic handovers for any moving
devices in the heterogeneous networks combining
different access technologies.
In this technical paper, intend to present a possible
Mobile WIMAX ‐3GPP/2 Network Interworking
architecture based on the 3GPP/2 standards and
propose the seamless inter ‐system handover schemewhich enables the service continuity with low
handover latency and packet loss.
This technical approach of enabling handover feature
is purely based on the IEEE 802.16e Mobile WiMAX &
3GPP/2 Standards.
APRIL ‐2010
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Introduction
Today Mobile WiMAX (IEEE 802.16e) is one of
the wireless broadband standards capable of
providing the Quadruple play Technologies ‐
Data, Voice, Video & Mobility using a single
network. The introduction of the 802.16e
WiMAX flavor is creating new markets for
mobile broadband services. Abilities of the
802.16e standard to provide seamless mobility
to end users in their homes, offices, and during
transit, are spurring the demand for innovative
mobile services. Users can now take advantage
of complex IP‐based data‐intensive applications
while traveling at vehicular speeds. This is made
possible by IP‐specific optimizations of 802.16
and its built‐in support for high‐speed handoffs.
Mobile customers shall now be able to
download full‐length DVD‐quality movies
quickly or host multi‐party video‐conferencing
sessions from their WiMAX–enabled handheld
devices. Regardless of the deployment of this
IP‐based version of WiMAX, it is clear that
802.16e is providing a strong mobility platform
to help accelerate convergence.
In the current paper Handover Interworking
scenarios for Mobile WiMAX and 3GPP/2 are
presented with Network Interworking
Architecture along with the call flows from
WiMAX to 3GPP and vice –versa.
Roadmap for evolution of WiMAX‐IMS (3GPP2)
interworking architecture is also presented as
per the NWG WiMAX stage 2 specifications.
Handover Solution Architecture
Architecture Description
At the onset, let us understand the differences
between 3GPP‐WLAN interworking and 3GPP‐
WIMAX interworking. The WLAN in hot‐spot
areas forms the micro‐cells within the 3GPP
macro‐cells. The mobility between 3GPP and
WLAN can be referred to fully overlapping
handover. Accordingly, the required time for
switching from 3GPP to WLAN connection can
be tolerantly long. Moreover, when the mobile
is connected to WLAN, it can maintain
simultaneously the Packet Data Protocol (PDP)
context of 3GPP so that it can reconnect
immediately to 3GPP without need of PDP
context re‐activation.
On the contrary, from the below figure 1, the
mobility between 3GPP and WIMAX is referred
to partially overlapping handover since the
WIMAX coverage is in order of 3GPP coverage
area. Consequently, the handover should be
done quickly to maintain the connection
particularly when the speed of the mobile
terminal is high. In order to enable the mobility
between two access networks 3GPP and
WIMAX, we propose a solution under some
following conditions: minimum change of the
existing network infrastructure of these two
technologies and feasible solution for short
term.
By
using
IP
as
the
common
interconnection protocol, the mobile can
connect to multiple networks seamlessly
ignoring the heterogeneity of access
technologies. This is achieved by using Mobile IP
mechanism that hides the heterogeneities of
lower‐layer technologies. The proposed
architecture for 3GPP‐WIMAX interworking,
depicted above is based on interworking
architecture models of 3GPP standards.
Figure: 1
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The mobile subscriber (MS) is a mobile node
that can communicate with both 3GPP network
and WIMAX network. However, note that it can
connect to only one access network at a time.
Therefore, the handover between 3GPP‐WIMAX
must be the hard handover. The WIMAX Access Network (AN) provides the WIMAX access
services for the MS. The mobility inside WIMAX
network is managed by the WIMAX Home Agent
(HA) located between the ASN gateway and the
WAG. The WIMAX HA is not necessarily included
in 3GPP core network to keep its independence
from 3GPP system. The Foreign Agents (FA)
located in ASN Gateway is considered as the
local FAs in the interworking architecture. The
WIMAX AN is connected to the 3GPP network
via WAG and to the 3GPP AAA server for the
WIMAX
authentication
process.
The
WAG
is
a
gateway through which the data from/to
WIMAX AN is routed to provide MS with 3GPP
services. The functions of WAG include
enforcing routing of packets through PDG,
performing accounting Information and filtering
out packets. The main functions of PDG are to
route the packets received from/sent to the
PDN to/from the MS and to perform the FA
functions.
The mobility within the 3GPP network is
managed by its own mobility mechanism and
the FA functions implemented in the GGSN. In
order to enable the vertical handover between
these two technologies, the HA is placed in the
PDN and manages FAs of both WIMAX and
3GPP networks.
IP Address Management
In WIMAX network, each time the mobile
changes its ASN gateway; it will obtain a new
local IP address through the DHCP server. The
ASN GW can learn this new local IP address and
also ask to the DHCP server the WIMAX HA’s
address since it plays the role of the DHCP relay
agent in the DHCP discovery process. The ASN
GW then informs the serving BS the MS’s new
local IP address and sends the Mobile IP (MIP)
registration to the WIMAX HA. A generic IP‐in‐IP
tunnel such as Generic Routing Encapsulation
(GRE) may be used to transport the IP packets
between the WIMAX HA and the FA. Each time
the mobile switches the connection to the 3GPP
network, it will initiate the PDP context
activation procedure. No IP address is allocated
to the MS at the PDP context activation. The
remote address provided by HA or an external
entity in PDN will be kept unchanged and will be
informed to the GGSN via PDP context activation. The remote IP address is a global
home address that is used to address to the
external network and the correspondent node.
It may be a static address or a dynamic address
acquired from the HA or another external entity
when the mobile first time connects to the
network, discovers and registers with the HA.
The PDG/GGSN is then responsible for relaying
MS’s remote allocated IP address to the MS.
Handover Procedure
To reduce the interruption time during the
handover, we have specified a forward
handover procedure. That is to say, before
leaving the serving network, the mobile
prepares a new attachment in the target
network. In order to reduce the packet loss
during handover, the old FA notifies the HA the
MS’s movement so that the HA can buffer the
packets and forward them to the MS as soon as
the HA receives the MIP update from the MS.
Handover Call Flows
Scenario 1: Handover from WIMAX Access
Network to 3GPP Network
From the Figure:2 below, before the handover is
initiated, the mobile is connected to the 3GPP
services through WIMAX access network. When
the MS enters to an overlapped zone, the MS
can measure signal quality from the 3GPP
neighboring cells. If the triggering conditions for
vertical handovers are satisfied, the handover
decision is then taken. The target 3GPP‐UTRAN
will be notified the imminent handover from the
WIMAX network via the HO request message
routed through the core network. The MS will
perform the GPRS attach procedure with the
3GPP‐UTRAN. Mobility management contexts
are established at the MS and SGSN. The MIP
registration between the HA and new GGSN/FA
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can be updated after the PDP context is
activated between GGSN and MS. The details of
handover procedure from a WIMAX cell to a
3GPP cell is depicted in below call flow:
1. The WIMAX BS sends periodically the
topology advertisement message to inform the
MS of neighboring WIMAX BSs and NodeBs.
Alternatively, the MS can scan different
channels to discover the neighboring topology.
However, it is not a good solution and it will be
our future work. Throughout our study here, we
assume that there exists a total cooperation
between the 3GPP and WIMAX networks
operators. Thus, the 3GPP NodeB can transmit
to the MS the WIMAX neighboring cell
information and vice versa.
2. Based on the topology advertisement, the MS
performs synchronization and measurement
procedure. The event‐triggered inter‐system
measurement may be based on the degradation
of
current
signal
quality
or
on
the
necessity
of
switching between access technologies to
support higher QoS requirements or low cost.
Since the WIMAX operates in TDD mode, during
the downlink frame duration, only some OFDM
symbols are addressed to the mobile.
Accordingly, the remaining time can be used to
measure neighboring cell signals. Note that, to
facilitate the measurement on 3GPP cell, the
information such as scrambling code, carrier
frequency, should be included in advertisement
messages.
3. After the measurement step, the mobile shall
send the measurement report to the WIMAX
BS. The report must contain the signal quality
level of each candidate 3GPP cell.
4. The WIMAX BS initiates the handover
procedure by notifying the potential target
3GPP via handover (HO) request message. The
PDG will perform a DNS request to know the
addresses of GGSNs which serve the current
MS’s Access Point Name (APN). The PDG then
selects one GGSN in the result list of GGSNs
from the DNS request phase and sends the HO
request to this selected one. If the PDG does
not receive any response from the GGSN for a
certain time, it will select another GGSN in the
found list and resend the HO request message.
5. The GGSN then sends the HO request
message to the SGSNs who serve the indicated
nodeBs. In order to be able to retrieve the
address of SGSN that serves a specific nodeB,
we assume that the DNS server or the Home
Location Register (HLR) stores this routing
information.
6. The target RAN establishes bearer resources,
including radio resources, for the MS. This step
aims to check if the candidate 3GPP NodeBs can
accept the MS handover with the required QoS.
Figure: 2
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7. The NodeB which supports the MS handover
will send a HO support message to the ASN GW
which contains the handover decision function.
8. Upon receiving HO support messages, the
ASN GW selects the best target 3GPP cell and
then returns the HO command to the MS. This
message must include the recommended target NodeB and all the required information for
setting up a new connection. The above
exchange may require a large amount of
information and add more latency to handover,
it is therefore Preferable to use a pre‐
configuration mechanism. It means that only a
reference number corresponding to a
predefined set of 3GPP‐3GPP‐3GPP‐UTRAN
parameters is inserted in the handover
command. The MS should download the
predefined radio configurations before. During
this
temporary
connection,
the
MS
can
reconfigure the connection into a suitable one.
9. Right after that the ASN GW sends the
handover confirmation which includes the
target NodeB identifier to the PDG/FA. The
allocated resources in the WIMAX network will
be then released.
10. Upon reception the handover confirmation
message, PDG/FA will send a MIP update
message to HA to notify the MS’s movement.
The HA then stops sending the packets to the
MS via this PDG/FA and buffers the inbound
packets until it receives the MIP update from
the target 3GPP network.
11. The MS performs the GPRS attachment
procedure to 3GPP‐3GPP‐3GPP‐UTRAN
network. The GPRS attachment procedure
consists of accessing to SGSN, authenticating
with the AAA server and updating the location.
12. After performing successfully the GPRS
attachment, the MS starts the PDP context
activation through which the MS informs its
remote IP address (its global home address) to
the GGSN.
13. After the connection is established between
a new GGSN/FA and MS, the GGSN/FA will
perform the MIP registration with the HA
including the MS’s remote IP address and its
care of address (address of GGSN/FA). The data
will then be transmitted to MS via the new
NodeB
and
the
handover
procedure
is
completed.
Scenario 2: Handover from 3GPP to WIMAX
Access Network
Before the handover is initiated, the MS is in the
3GPP network. When the MS moves to an
overlapped zone, it can measure the signal
quality from the neighboring WIMAX BSs. When
the network decides to handover to WIMAX,
the MS will set up the connection with WIMAX
AN, perform the authentication and MIP
registration update, etc. The handover scheme
from a 3GPP cell to a WIMAX cell is depicted in
below figure 3:
Figure: 3
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1. The 3GPP‐3GPP‐UTRAN is responsible for
detecting the handover need and initiating the
inter‐system measurement process by sending
the measurement control message to the MS.
This message contains the neighboring WIMAX
cell information, the compressed mode pattern,
etc.
2. While the MS has an on‐going
communication in FDD mode, in order to
perform the measurement on the neighboring
WIMAX cells, it must enter in the compressed
mode. Note that the measurement on WIMAX
cell is performed on the preamble of each
WIMAX frame.
3. After the measurement period, the MS sends
the measurement report to the network. The
report
must
contain
the
parameters
indicating
the signal quality level of the neighboring
WIMAX BSs.
4. The RNC initiates the handover procedure by
notifying the potential target WIMAX BSs where
the mobile may handover. The HO request
message including the MS’s APN, the candidate
BS identifiers, the required QoS of MS’s current
applications, etc. will be sent to the GGSN. The
GGSN performs the DNS request to learn the
addresses of the PDGs which serve the MS’s
current APN. The GGSN selects one PDG in the
result list and sends it the HO request message.
If the GGSN does not receive any response from
the PDG after a certain time, it will send the HO
request to another PDG in the list. The HO
request message will then be transmitted to the
potential WIMAX BSs based on the routing
information at the PDG. This step aims to check
if the target WIMAX BS can accept the MS
handover with the required QoS.
5. The WIMAX BSs which support the MS
handover will return a HO support to the RNC.
6. The RNC will select the best target WIMAX BS
among the supporting BSs and then sends the
HO command to the MS. This message includes
all the required information for setting up the
connection to the selected target WIMAX BS.
7. Right after that the RNC sends the HO
confirmation. The mobile is then disconnected
from the 3GPP network and starts the
connection setup to the target WIMAX BS.
8. Upon receiving the handover confirmation,
GGSN/FA sends a MIP update message to the
HA to notify the MS’s movement. The HA then
stops sending the packets to the MS via this GGSN/FA and buffers the inbound packets until
it receives the MIP update from the target
WIMAX network.
9. Based on the information included in the HO
request message, the WIMAX BS can provide a
non‐contention based initial‐ranging
opportunity to the MS by placing a Fast Ranging
Information Element in the UL MAP. This
information will facilitate the RAN connection
setup of the MS. If not, the MS must perform
the
normal
ranging
procedure
which
takes
more
time.
10. The MS initiates the connection setup by
exchanging Ranging Request (RNGREQ)/
Ranging Response (RNG‐RSP) with the target
WIMAX BS.
11. In the WIMAX AN, the MS will perform
DHCP request to obtain new local IP address. In
this scenario, we describe an address allocation
procedure based on IPv4 mechanism. If IPv6 is
used, the local address can be allocated by
Stateless Address Autoconfiguration mechanism
without the presence of the DHCP server.
Through this procedure, the ASN GW will also
learn the WIMAX HA address which serves for
MIP registration in the following step.
12. The MS will perform the MIP registration to
associate the MS’s local address with its care of
address.
13. The MS performs DNS resolution for PDG
address. MS uses APN to indicate the network
service it wants to access. The DNS request will
be relayed to ASN GW which in turn relays the
request to the DNS server. The MS will select
one suitable PDG among the list of PDGs given
in DNS response. Note that the selected PDG
here may be different from the PDG selected
by GGSN during HO request/support step.
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14. The MS then establishes an end‐to‐end
tunnel with the selected PDG using IKEv2
protocol. Through this process, the MS will
inform the PDG about its local and remote IP
address. Each time the mobile changes its ANS
network, it obtains a new local IP address and
therefore a new tunnel should be correctly
configured. Regarding inter‐WIMAX mobility,
the time required for setting up a new IPSec
tunnel when changing of ASN may be too long
that the seamless mobility cannot be achieved.
To speed up this kind of IPSec tunnel relocation,
we can use the MOBIKE mechanism proposed
by the IETF MOBIKE WG.
15. The PDG performs the MIP registration with
the HA as soon as it will be notified the MS’s
remote IP address. The data packets will be
transmitted
to
MS
via
the
WIMAX
AN.
The
handover procedure is completed.
Proposed WiMAX –IMS interworking
Network Reference Model
NOTE: Figure:4 below architecture diagram is
evolving. It may contain old representations
that will be resolved at a later stage of
investigation. Also, this assumes that the CSN
functionality is provided by the 3G Network.
This includes IP address space allocation.
Solution benefits
This network architecture approach offers
the following benefits:
• Offers interworking handover
functionality between Mobile WiMAX &
3GPP Networks.
• Seamlessly integrates wireless
technology specific functionality with IP
networking equipment
• Allows for the use of a common IP
network for multiple wireless access
technologies
• Enables cost‐effective implementation
for deployments ranging from small to
large scale
• Enables the use of mobile devices and
optimizes handovers
• Scalable to 3GPP2 IMS Networks for
feature rich multimedia applications &
quadruple play technologies.
• Enables new types of transport
networks such as metro Ethernet, and
wireless point‐to‐point for backhaul
• Enables distribution of “application
level” functionality such as content
delivery networks
Figure: 4
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Conclusion & Future Work
In this paper, we have introduced a practical
3GPP‐WIMAX interworking architecture based
on 3GPP standards and proposed a handover
procedure which promises a low packet loss and
low interruption time during the switching of
the communication. The mobility between two
access networks is achieved by the MIP
mechanism at the network layer. The packet
loss during handover is reduced since the old FA
notifies the HA the MS’s movement and
consequently
the HA buffers the data packets destined to the
MS. The proposed interworking architecture
does not require lot of changes on existing
network infrastructures which is a big
advantage. The proposed handover scheme
needs the exchange of messages between the
PGD and the GGSN which serve the same APN
with the help of the DNS server. In case the MS
connects to multiple APNs, the handover
preparation phase may be more complex, which
will be our future work with some performance
evaluation of our proposed mechanisms in a
large scale network. Moreover, we aim to
consider the tightly‐coupled interworking
architecture approach for 3GPP‐WIMAX and
3GPP‐WLAN interworking which allows a
seamless handover with less handover latency
and less packet loss. The future interworking
architecture should be based on the
architecture evolution proposed by 3GPP
standards. We therefore plan to consider the
roaming architecture as well as the mobility
scheme in the context of multiple operator
environments.
References
1. An Architecture for UMTS‐WIMAX Interworking ‐ Quoc‐Thinh
Nguyen‐Vuong, Lionel Fiat and Nazim Agoulmine
2. IEEE P802.16e/D11, ”Part 16: Air Interface for fixed and mobile
broadband wirelessaccess system”, Sept. 2005.
3. Salkintzis,A.K.; Fors, C.; Pazhyannur, R.; ”WLAN‐GPRS
integration for nextgeneration mobile data networks”, IEEE
Wireless Communication, Vol.9, pp. 112‐124, Oct. 2002.
4. Shiao‐Li Tsao; Chia‐Ching Lin; ”Design and evaluation of 3GPP‐
WLAN interworking strategies”, Proceedings. VTC 2002‐Fall, IEEE
56th Volume 2, pp.777 ‐781, Sept. 2002
5. Hyun‐Ho Choi; Song, O.; Dong‐Ho Cho; ”A seamless handoff
scheme for 3GPPWLAN interworking”, Globecom, 2004, pp.1559 ‐
1564, Vol.3. Dec. 2004
6. V. Varma, S. Ramesh, K.D. Wong, M. Barton, G. Hayward and J.
Friedhoffer. ”Mobility Management in Integrated 3GPP/WLAN
Networks”, IEEE ICC, Anchorage, Alaska, USA, May 2003.
7. Muhammad Jaseemuddin. ”An Architecture for Integrating
3GPP and 802.11 WLAN Networks”, 8th IEEE ISCC,p.716, 2003.
8. N. Vulic, S.H. Groot, I. Niemegeers, ”A comparison of
Interworking Architectures for WLAN Integration at 3GPP Radio
Access Level”,ConWIN05, July 2005.
9. G. Cunningham, P. Perry and L. Murphy, ”Soft, Vertical
Handover of Streamed Multimedia in a 4G network”,5th
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Glossary
AAA Authentication, Authorization & Accounting
E2E End to End
IMS IP Multimedia Subsystem
IP Internet Protocol
MGC Media Gateway Controller
MGW Media Gateway
P‐CSCF Proxy‐Call Session Control Function
PDF Policy Decision Function
POC Proof Of Concept
QoS Quality of Service
RADIUS Remote Access for Dial‐In User Services
SBC Session Border Controller
TM Tech Mahindra
VoIP Voice over IP
VSA Vendor Specific Attributes
WISP Wireless Internet Service Provide