The File - Oct 1, 2008 - (Page 12)

In Focus | Wireless Networking Mobile WiMAX enables IP convergence By R&D Services, MindTree Ltd In recent years, we have witnessed a drastic shift in the needs of mobile users. Video, voice services and content sharing that need high-bandwidth Internet access are some of the new demands in addition to user mobility. In such a scenario, mobile WiMAX is emerging as the preferred deployment for providing end-to-end converged IP services. Converged IP services are cheaper because of the widespread usage of the same in wireline communication networks. Moreover, the services can be enhanced rapidly, due to the availability of large number of IP-based application and services developers. IP networks also offer ease of manageability due to uniformity in setup, and have been known to provide efficient utilisation of resources by virtue of QoS-based routing and forwarding. Mobile WiMAX is the IEEE 802.16e standard that provides broadband services that significantly increase performance and expand coverage. The mobile WiMAX network is composed of the Access Service Network (ASN) and the Connectivity Service Network (CSN). Figure 1: WiMAX network architecture. Connectivity service The CSN provides IP connectivity. It broadly performs the following tasks: • Authenticating and authorising the users; • Accounting/Billing; • Identification to the mobile station for communication; • Inter-ASN mobility. Meanwhile, the ASN comprises two key elements: the base station (BS) and ASN gateway (ASN GW). ASNs broadly provide these major functionalities: 1. Radio connectivity to mobile stations (cell phones, laptops, PDAs)—Radio connectivity is provided by the BS. Once the base station receives the mobile user’s data, it has to send it to the CSN through the ASN GW. To ensure that appropriate QoS to the user is provided and also to protect the user data from getting jumbled, the data is sent using tunnels. A tunnel is established for each user. Tunnelling between the Base Station and the ASN GW is usually done using Generic Route Encapsulation (GRE) and the GRE key acts as a unique identifier of a connection stream. BS classifies the user data and performs the encapsulation. 2. Aggregating the traffic received from multiple BS and transmitting the same to CSN—this task is performed by the ASN GW. ASN GW functions as a traffic concentrator from BS to the CSN and as a distributor from CSN to multiple BS. Apart from that, ASN GW also has to handle mobility of a user from one BS to another without loss of connectivity. The three major features of ASN-GW include support for mobility, traffic management and security. Mobility management In a typical scenario, a mobile station (MS) can roam from one BS to another. To enable this handover, context information is exchanged from the incumbent BS to the new BS. ASN-GW acts as a nodal point, and either multi-casts the packets to both the BS or buffers the packet when the transition happens. Once the transition is completed, the buffered packets are sent to the new BS. The mobility can also happen when an MS moves from one BS of an ASN to another BS of a different ASN. The handover in this case is anchored by the CSN. There is a mobile IP home agent (HA) that resides in the CSN. Each ASN has a foreign agent (FA) hosted by ASN GW servicing one or more BS. The communication between FA and HA takes place through tunnels. When the MS transitions from one BS of an ASN to another BS of a different ASN, a new tunnel is created between the FA of the new ASN and the CSN, and the tunnel between the old FA and HA is terminated. For rapid handover, a tunnel can also be formed between the two FAs. GW. BS extracts user data from the radio network. It is encapsulated in the GRE packet with a unique key and sent to the ASN-GW. The encapsulation between the BS and the ASN GW is used to uniquely identify a flow based on the GRE key. ASN-GW uses the key to forward the packet to the respective CSN. The GRE key also becomes the basis for providing other functionalities discussed above. When the packet is to be sent from ASN GW to CSN, an IP-in-IP tunnel is requiredfor mobility management. Hence ASN GW would decapsulate the GRE header and encapsulate the packet an IP-in-IP tunnel. The WiMAX defines the following Reference Points (RPs) for standardised communication. The R1 interface between the MS and the ASN includes: • IEEE 802.16 standards specified physical layer and MAC layer; • Network layer protocols; • Procedures related to control and management plane interactions; • Bearer plane traffic termination at the ASN. Meanwhile, the R3 interface between the ASN and CSN includes: • AAA, policy enforcement and mobility management; • Tunnelling to transfer user data between the ASN and the CSN. continued on page 13 Security factor ASN-GW works with AAA server in CSN for authentication of MS. Optionally, IPsec can also be used in case the user data needs to be encrypted. IP differentiated service is the preferred methodology of providing per user traffic management. ASN GW performs the task of assigning appropriate diffserv code point (DSCP) values, the basis on which the nodes in CSN provide differentiated traffic services. User traffic flows from MS to the CSN through the BS and ASN- 12 EE Times-India | October 1-15, 2008 | www.eetindia.com http://www.eetindia.co.in/article/email_friend.php3?article_id=8800515679&type=TA&cat_id=1800000&back_url=%2Farticle%2Farticle_content.php3%3Fin_param%3D8800515679_1800000_TA_427b9233%26 http://www.eetindia.co.in/SEARCH/SUMMARY/technical-articles/WiMAX.HTM?ClickFromNewsletter_081001 http://www.eetindia.co.in/article/email_friend.php3?article_id=8800515679&type=TA&cat_id=1800000&back_url=%2Farticle%2Farticle_content.php3%3Fin_param%3D8800515679_1800000_TA_427b9233%26 http://www.eetindia.co.in/article/email_friend.php3?article_id=8800515679&type=TA&cat_id=1800000&back_url=%2Farticle%2Farticle_content.php3%3Fin_param%3D8800515679_1800000_TA_427b9233%26 http://www.eetindia.co.in/article/email_friend.php3?article_id=8800515679&type=TA&cat_id=1800000&back_url=%2Farticle%2Farticle_content.php3%3Fin_param%3D8800515679_1800000_TA_427b9233%26 http://www.eetindia.co.in/article/email_friend.php3?article_id=8800515679&type=TA&cat_id=1800000&back_url=%2Farticle%2Farticle_content.php3%3Fin_param%3D8800515679_1800000_TA_427b9233%26 http://www.eetindia.co.in/article/email_friend.php3?article_id=8800515679&type=TA&cat_id=1800000&back_url=%2Farticle%2Farticle_content.php3%3Fin_param%3D8800515679_1800000_TA_427b9233%26 http://www.eetindia.co.in/article/email_friend.php3?article_id=8800515679&type=TA&cat_id=1800000&back_url=%2Farticle%2Farticle_content.php3%3Fin_param%3D8800515679_1800000_TA_427b9233%26 http://www.eetindia.co.in/article/email_friend.php3?article_id=8800515679&type=TA&cat_id=1800000&back_url=%2Farticle%2Farticle_content.php3%3Fin_param%3D8800515679_1800000_TA_427b9233%26 http://www.eetindia.co.in/SEARCH/SUMMARY/technical-articles/cell phones.HTM?ClickFromNewsletter_081001 http://www.eetindia.co.in/SEARCH/SUMMARY/technical-articles/PDA.HTM?ClickFromNewsletter_081001 http://www.eetindia.com/STATIC/REDIRECT/Newsletter_081001_EETI02.htm?ClickFromNewsletter_081001

Table of Contents for the Digital Edition of The File - Oct 1, 2008

EETimes India - October 8, 2008
National Semiconductor
Tech Insights
Trends
Cadence
Texas Instruments
Fine-tuning RF Platform Shrinks Design Time
DigiKey
Mobile WiMAX Enables IP Convergence

The File - Oct 1, 2008