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Techmahindra 80216e 3gpp_systems_networkhandover
May 27, 2011
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Techmahindra 80216e 3gpp_systems_networkhandover
1. APRIL ‐2010 Abstract: Next Generation Mobile Networks are paving its way towards the ubiquitous wireless access abilities which provide the automatic handovers for any moving802.16e & 3GPP Systems devices in the heterogeneous networks combining different access technologies. Network Handover In this technical paper, intend to present a possible Mobile WIMAX‐3GPP/2 Network Interworking Interworking architecture based on the 3GPP/2 standards and propose the seamless inter‐system handover scheme which enables the service continuity with low handover latency and packet loss. Venkat Annadata Tech Mahindra (R&D) Services Ltd. This technical approach of enabling handover feature is purely based on the IEEE 802.16e Mobile WiMAX & 3GPP/2 Standards. © Tech Mahindra Limited 2010
Introduction Architecture Description Today Mobile WiMAX (IEEE 802.16e) is one of At the onset, let us understand the differences the wireless broadband standards capable of between 3GPP‐WLAN interworking and 3GPP‐providing the Quadruple play Technologies ‐ WIMAX interworking. The WLAN in hot‐spot Data, Voice, Video & Mobility using a single areas forms the micro‐cells within the 3GPP network. The introduction of the 802.16e macro‐cells. The mobility between 3GPP and WiMAX flavor is creating new markets for WLAN can be referred to fully overlapping mobile broadband services. Abilities of the handover. Accordingly, the required time for 802.16e standard to provide seamless mobility switching from 3GPP to WLAN connection can to end users in their homes, offices, and during be tolerantly long. Moreover, when the mobile transit, are spurring the demand for innovative is connected to WLAN, it can maintain mobile services. Users can now take advantage simultaneously the Packet Data Protocol (PDP) of complex IP‐based data‐intensive applications context of 3GPP so that it can reconnect while traveling at vehicular speeds. This is made immediately to 3GPP without need of PDP possible by IP‐specific optimizations of 802.16 context re‐activation. and its built‐in support for high‐speed handoffs. Mobile customers shall now be able to On the contrary, from the below figure 1, the download full‐length DVD‐quality movies mobility between 3GPP and WIMAX is referred quickly or host multi‐party video‐conferencing to partially overlapping handover since the sessions from their WiMAX–enabled handheld WIMAX coverage is in order of 3GPP coverage devices. Regardless of the deployment of this area. Consequently, the handover should be IP‐based version of WiMAX, it is clear that done quickly to maintain the connection 802.16e is providing a strong mobility platform particularly when the speed of the mobile to help accelerate convergence. terminal is high. In order to enable the mobility between two access networks 3GPP and In the current paper Handover Interworking WIMAX, we propose a solution under some scenarios for Mobile WiMAX and 3GPP/2 are following conditions: minimum change of the presented with Network Interworking existing network infrastructure of these two Architecture along with the call flows from technologies and feasible solution for short WiMAX to 3GPP and vice –versa. term. By using IP as the common interconnection protocol, the mobile can Roadmap for evolution of WiMAX‐IMS (3GPP2) connect to multiple networks seamlessly interworking architecture is also presented as ignoring the heterogeneity of access per the NWG WiMAX stage 2 specifications. technologies. This is achieved by using Mobile IP mechanism that hides the heterogeneities of lower‐layer technologies. The proposed architecture for 3GPP‐WIMAX interworking, Handover Solution Architecture depicted above is based on interworking architecture models of 3GPP standards. Figure: 1 1 © Tech Mahindra Limited 2010
the mobile switches the connection to the 3GPP The mobile subscriber (MS) is a mobile node network, it will initiate the PDP context that can communicate with both 3GPP network activation procedure. No IP address is allocated and WIMAX network. However, note that it can to the MS at the PDP context activation. The connect to only one access network at a time. remote address provided by HA or an external Therefore, the handover between 3GPP‐WIMAX entity in PDN will be kept unchanged and will be must be the hard handover. The WIMAX Access informed to the GGSN via PDP context Network (AN) provides the WIMAX access activation. The remote IP address is a global services for the MS. The mobility inside WIMAX home address that is used to address to the network is managed by the WIMAX Home Agent external network and the correspondent node. (HA) located between the ASN gateway and the It may be a static address or a dynamic address WAG. The WIMAX HA is not necessarily included acquired from the HA or another external entity in 3GPP core network to keep its independence when the mobile first time connects to the from 3GPP system. The Foreign Agents (FA) network, discovers and registers with the HA. located in ASN Gateway is considered as the The PDG/GGSN is then responsible for relaying local FAs in the interworking architecture. The MS’s remote allocated IP address to the MS. 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 Handover Procedure gateway through which the data from/to WIMAX AN is routed to provide MS with 3GPP To reduce the interruption time during the services. The functions of WAG include handover, we have specified a forward enforcing routing of packets through PDG, handover procedure. That is to say, before performing accounting Information and filtering leaving the serving network, the mobile out packets. The main functions of PDG are to prepares a new attachment in the target route the packets received from/sent to the network. In order to reduce the packet loss PDN to/from the MS and to perform the FA during handover, the old FA notifies the HA the functions. MS’s movement so that the HA can buffer the The mobility within the 3GPP network is packets and forward them to the MS as soon as managed by its own mobility mechanism and the HA receives the MIP update from the MS. the FA functions implemented in the GGSN. In order to enable the vertical handover between these two technologies, the HA is placed in the Handover Call Flows PDN and manages FAs of both WIMAX and 3GPP networks. Scenario 1: Handover from WIMAX Access Network to 3GPP Network IP Address Management From the Figure:2 below, before the handover is In WIMAX network, each time the mobile initiated, the mobile is connected to the 3GPP changes its ASN gateway; it will obtain a new services through WIMAX access network. When local IP address through the DHCP server. The the MS enters to an overlapped zone, the MS ASN GW can learn this new local IP address and can measure signal quality from the 3GPP also ask to the DHCP server the WIMAX HA’s neighboring cells. If the triggering conditions for address since it plays the role of the DHCP relay vertical handovers are satisfied, the handover agent in the DHCP discovery process. The ASN decision is then taken. The target 3GPP‐UTRAN GW then informs the serving BS the MS’s new will be notified the imminent handover from the local IP address and sends the Mobile IP (MIP) WIMAX network via the HO request message registration to the WIMAX HA. A generic IP‐in‐IP routed through the core network. The MS will tunnel such as Generic Routing Encapsulation perform the GPRS attach procedure with the (GRE) may be used to transport the IP packets 3GPP‐UTRAN. Mobility management contexts between the WIMAX HA and the FA. Each time are established at the MS and SGSN. The MIP registration between the HA and new GGSN/FA 2 © Tech Mahindra Limited 2010
can be updated after the PDP context is frequency, should be included in advertisement activated between GGSN and MS. The details of messages. handover procedure from a WIMAX cell to a 3GPP cell is depicted in below call flow: 3. After the measurement step, the mobile shall send the measurement report to the WIMAX BS. The report must contain the signal quality Figure: 2 level of each candidate 3GPP cell. 1. The WIMAX BS sends periodically the topology advertisement message to inform the 4. The WIMAX BS initiates the handover MS of neighboring WIMAX BSs and NodeBs. procedure by notifying the potential target Alternatively, the MS can scan different 3GPP via handover (HO) request message. The channels to discover the neighboring topology. PDG will perform a DNS request to know the However, it is not a good solution and it will be addresses of GGSNs which serve the current our future work. Throughout our study here, we MS’s Access Point Name (APN). The PDG then assume that there exists a total cooperation selects one GGSN in the result list of GGSNs between the 3GPP and WIMAX networks from the DNS request phase and sends the HO operators. Thus, the 3GPP NodeB can transmit request to this selected one. If the PDG does to the MS the WIMAX neighboring cell not receive any response from the GGSN for a information and vice versa. certain time, it will select another GGSN in the found list and resend the HO request message. 2. Based on the topology advertisement, the MS performs synchronization and measurement 5. The GGSN then sends the HO request procedure. The event‐triggered inter‐system message to the SGSNs who serve the indicated measurement may be based on the degradation nodeBs. In order to be able to retrieve the of current signal quality or on the necessity of address of SGSN that serves a specific nodeB, switching between access technologies to we assume that the DNS server or the Home support higher QoS requirements or low cost. Location Register (HLR) stores this routing Since the WIMAX operates in TDD mode, during information. the downlink frame duration, only some OFDM symbols are addressed to the mobile. 6. The target RAN establishes bearer resources, Accordingly, the remaining time can be used to including radio resources, for the MS. This step measure neighboring cell signals. Note that, to aims to check if the candidate 3GPP NodeBs can facilitate the measurement on 3GPP cell, the accept the MS handover with the required QoS. information such as scrambling code, carrier 3 © Tech Mahindra Limited 2010
7. The NodeB which supports the MS handover 11. The MS performs the GPRS attachment will send a HO support message to the ASN GW procedure to 3GPP‐3GPP‐3GPP‐UTRAN which contains the handover decision function. network. The GPRS attachment procedure 8. Upon receiving HO support messages, the consists of accessing to SGSN, authenticating ASN GW selects the best target 3GPP cell and with the AAA server and updating the location. then returns the HO command to the MS. This message must include the recommended target 12. After performing successfully the GPRS NodeB and all the required information for attachment, the MS starts the PDP context setting up a new connection. The above activation through which the MS informs its exchange may require a large amount of remote IP address (its global home address) to information and add more latency to handover, the GGSN. it is therefore Preferable to use a pre‐ configuration mechanism. It means that only a 13. After the connection is established between reference number corresponding to a a new GGSN/FA and MS, the GGSN/FA will predefined set of 3GPP‐3GPP‐3GPP‐UTRAN perform the MIP registration with the HA parameters is inserted in the handover including the MS’s remote IP address and its command. The MS should download the care of address (address of GGSN/FA). The data predefined radio configurations before. During will then be transmitted to MS via the new this temporary connection, the MS can NodeB and the handover procedure is reconfigure the connection into a suitable one. completed. 9. Right after that the ASN GW sends the Scenario 2: Handover from 3GPP to WIMAX handover confirmation which includes the Access Network target NodeB identifier to the PDG/FA. The allocated resources in the WIMAX network will Before the handover is initiated, the MS is in the be then released. 3GPP network. When the MS moves to an overlapped zone, it can measure the signal 10. Upon reception the handover confirmation quality from the neighboring WIMAX BSs. When message, PDG/FA will send a MIP update the network decides to handover to WIMAX, message to HA to notify the MS’s movement. the MS will set up the connection with WIMAX The HA then stops sending the packets to the AN, perform the authentication and MIP MS via this PDG/FA and buffers the inbound registration update, etc. The handover scheme packets until it receives the MIP update from from a 3GPP cell to a WIMAX cell is depicted in the target 3GPP network. below figure 3: Figure: 3 4 © Tech Mahindra Limited 2010
1. The 3GPP‐3GPP‐UTRAN is responsible for from the 3GPP network and starts the detecting the handover need and initiating the connection setup to the target WIMAX BS. inter‐system measurement process by sending the measurement control message to the MS. 8. Upon receiving the handover confirmation, This message contains the neighboring WIMAX GGSN/FA sends a MIP update message to the cell information, the compressed mode pattern, HA to notify the MS’s movement. The HA then etc. stops sending the packets to the MS via this GGSN/FA and buffers the inbound packets until 2. While the MS has an on‐going it receives the MIP update from the target communication in FDD mode, in order to WIMAX network. perform the measurement on the neighboring WIMAX cells, it must enter in the compressed 9. Based on the information included in the HO mode. Note that the measurement on WIMAX request message, the WIMAX BS can provide a cell is performed on the preamble of each non‐contention based initial‐ranging WIMAX frame. opportunity to the MS by placing a Fast Ranging Information Element in the UL MAP. This 3. After the measurement period, the MS sends information will facilitate the RAN connection the measurement report to the network. The setup of the MS. If not, the MS must perform report must contain the parameters indicating the normal ranging procedure which takes more the signal quality level of the neighboring time. WIMAX BSs. 10. The MS initiates the connection setup by 4. The RNC initiates the handover procedure by exchanging Ranging Request (RNGREQ)/ notifying the potential target WIMAX BSs where Ranging Response (RNG‐RSP) with the target the mobile may handover. The HO request WIMAX BS. message including the MS’s APN, the candidate BS identifiers, the required QoS of MS’s current 11. In the WIMAX AN, the MS will perform applications, etc. will be sent to the GGSN. The DHCP request to obtain new local IP address. In GGSN performs the DNS request to learn the this scenario, we describe an address allocation addresses of the PDGs which serve the MS’s procedure based on IPv4 mechanism. If IPv6 is current APN. The GGSN selects one PDG in the used, the local address can be allocated by result list and sends it the HO request message. Stateless Address Autoconfiguration mechanism If the GGSN does not receive any response from without the presence of the DHCP server. the PDG after a certain time, it will send the HO Through this procedure, the ASN GW will also request to another PDG in the list. The HO learn the WIMAX HA address which serves for request message will then be transmitted to the MIP registration in the following step. potential WIMAX BSs based on the routing information at the PDG. This step aims to check 12. The MS will perform the MIP registration to if the target WIMAX BS can accept the MS associate the MS’s local address with its care of handover with the required QoS. address. 5. The WIMAX BSs which support the MS 13. The MS performs DNS resolution for PDG handover will return a HO support to the RNC. address. MS uses APN to indicate the network service it wants to access. The DNS request will 6. The RNC will select the best target WIMAX BS be relayed to ASN GW which in turn relays the among the supporting BSs and then sends the request to the DNS server. The MS will select HO command to the MS. This message includes one suitable PDG among the list of PDGs given all the required information for setting up the in DNS response. Note that the selected PDG connection to the selected target WIMAX BS. here may be different from the PDG selected by GGSN during HO request/support step. 7. Right after that the RNC sends the HO confirmation. The mobile is then disconnected 5 © Tech Mahindra Limited 2010
14. The MS then establishes an end‐to‐end tunnel with the selected PDG using IKEv2 Solution benefits protocol. Through this process, the MS will inform the PDG about its local and remote IP address. Each time the mobile changes its ANS This network architecture approach offers network, it obtains a new local IP address and the following benefits: therefore a new tunnel should be correctly configured. Regarding inter‐WIMAX mobility, • Offers interworking handover the time required for setting up a new IPSec functionality between Mobile WiMAX & tunnel when changing of ASN may be too long 3GPP Networks. that the seamless mobility cannot be achieved. • Seamlessly integrates wireless To speed up this kind of IPSec tunnel relocation, technology specific functionality with IP we can use the MOBIKE mechanism proposed networking equipment by the IETF MOBIKE WG. • Allows for the use of a common IP 15. The PDG performs the MIP registration with network for multiple wireless access the HA as soon as it will be notified the MS’s technologies remote IP address. The data packets will be transmitted to MS via the WIMAX AN. The • Enables cost‐effective implementation handover procedure is completed. for deployments ranging from small to large scale Proposed WiMAX –IMS interworking • Enables the use of mobile devices and Network Reference Model optimizes handovers NOTE: Figure:4 below architecture diagram is • Scalable to 3GPP2 IMS Networks for evolving. It may contain old representations feature rich multimedia applications & that will be resolved at a later stage of quadruple play technologies. investigation. Also, this assumes that the CSN • Enables new types of transport functionality is provided by the 3G Network. networks such as metro Ethernet, and This includes IP address space allocation. wireless point‐to‐point for backhaul • Enables distribution of “application level” functionality such as content delivery networks Figure: 4 6 © Tech Mahindra Limited 2010
Conclusion & Future Work References 1. An Architecture for UMTS‐WIMAX Interworking ‐ Quoc‐Thinh In this paper, we have introduced a practical Nguyen‐Vuong, Lionel Fiat and Nazim Agoulmine 3GPP‐WIMAX interworking architecture based 2. IEEE P802.16e/D11, ”Part 16: Air Interface for fixed and mobile on 3GPP standards and proposed a handover broadband wirelessaccess system”, Sept. 2005. procedure which promises a low packet loss and 3. Salkintzis,A.K.; Fors, C.; Pazhyannur, R.; ”WLAN‐GPRS low interruption time during the switching of integration for nextgeneration mobile data networks”, IEEE the communication. The mobility between two Wireless Communication, Vol.9, pp. 112‐124, Oct. 2002. access networks is achieved by the MIP 4. Shiao‐Li Tsao; Chia‐Ching Lin; ”Design and evaluation of 3GPP‐mechanism at the network layer. The packet WLAN interworking strategies”, Proceedings. VTC 2002‐Fall, IEEE loss during handover is reduced since the old FA 56th Volume 2, pp.777 ‐781, Sept. 2002 notifies the HA the MS’s movement and 5. Hyun‐Ho Choi; Song, O.; Dong‐Ho Cho; ”A seamless handoff consequently scheme for 3GPPWLAN interworking”, Globecom, 2004, pp.1559 ‐ the HA buffers the data packets destined to the 1564, Vol.3. Dec. 2004 MS. The proposed interworking architecture 6. V. Varma, S. Ramesh, K.D. Wong, M. Barton, G. Hayward and J. does not require lot of changes on existing Friedhoffer. ”Mobility Management in Integrated 3GPP/WLAN network infrastructures which is a big Networks”, IEEE ICC, Anchorage, Alaska, USA, May 2003. advantage. The proposed handover scheme needs the exchange of messages between the 7. Muhammad Jaseemuddin. ”An Architecture for Integrating PGD and the GGSN which serve the same APN 3GPP and 802.11 WLAN Networks”, 8th IEEE ISCC,p.716, 2003. with the help of the DNS server. In case the MS 8. N. Vulic, S.H. Groot, I. Niemegeers, ”A comparison of connects to multiple APNs, the handover Interworking Architectures for WLAN Integration at 3GPP Radio Access Level”,ConWIN05, July 2005. preparation phase may be more complex, which will be our future work with some performance 9. G. Cunningham, P. Perry and L. Murphy, ”Soft, Vertical evaluation of our proposed mechanisms in a Handover of Streamed Multimedia in a 4G network”,5th International Conference on 3G mobile communications large scale network. Moreover, we aim to Technologies, London, UK, Oct. 2004. consider the tightly‐coupled interworking architecture approach for 3GPP‐WIMAX and 3GPP‐WLAN interworking which allows a seamless handover with less handover latency Glossary and less packet loss. The future interworking AAA Authentication, Authorization & Accounting architecture should be based on the E2E End to End architecture evolution proposed by 3GPP IMS IP Multimedia Subsystem standards. We therefore plan to consider the IP Internet Protocol roaming architecture as well as the mobility MGC Media Gateway Controller scheme in the context of multiple operator MGW Media Gateway environments. 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 7 © Tech Mahindra Limited 2010
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