(click here for Part I) In a previous article, I talked about how IMS, 3G and WiMAX fit together at a conceptual level. As promised, in this article, let’s delve a bit into what it means to interwork IMS and WiMAX. I wanted to get this article out by end this year, so that we have some ‘meat’ to this thread before I forget all about this in 2007. Note: as usual, click on images to make them larger What needs to be interworked ? At a macro level, we know that IMS is a session control layer, while the Wimax forum’s NWG efforts stop at IP-Connectivity. So when we think of interworking, we need to focus on Policy – how will one enforce that network policies such as QoS, admission control, etc. are enforced uniformly ? Security – how does one ensure that a subscriber is authenticated at the WiMAX and at the IMS layer, since they both provide different levels of services ? (for example, a UE may connect to a WiMAX network , but may not be allowed to place a call via IMS due to call barring) Charging – how will one ensure that voice/video/data related

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Disclaimer: I don’t know if and when there will be a part II, but I have a lot to say in this area, and I get the feeling that a single post will not be enough. So let me at least start the article naming in the right way. As I decide to author followups, I will link each post to the other. Updated Dec 20 2006: Link to part II There is a lot of confusion and misunderstanding in the market today on technologies that could potentially co-exist or replace one another. This article presents my view of how IMS, 3G and WiMax fit into the larger equation. I First, let us talk about these conceptual layers: (You would find most network architectures are based on derivations of these layered principles) Starting from bottom up: Access Layer: Simply put, the Access Stratum involves all the physical characteristics and the mechanisms needed to connect devices with each other. This may be WiMAX radio engineering (802.16, 802.16e etc.), WiFI engineering, UMTS RAN or other technologies. The job of the access stratum is to define and implement the required protocols to be able to physically connect multiple nodes of a network together.

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