WiMAX Evolution Path
The WiMAX Forum developed specifications of the network infrastructure which complement the 802.16e specifications of the air interface (see WiMAX Forum (2008b). Provides an overview of mobile WiMAX roadmaps for standards and products. The first release labeled as Release 1.0 is described earlier in this chapter. The other two, Releases 1.5 and 2.0, are short-term and long-term migration, respectively, and their brief summaries are provided in this section. The corresponding IEEE baseline standards for Releases 1.5 and 2.0 are IEEE 802.16 REV2 (IEEE, 2008) and IEEE 802.16m (IEEE, 2006b), respectively. Owing to the dependency on the ongoing IEEE standards, REV2 and 16m, the schedules of Releases 1.5 and 2.0 are projections by the authors and may change. Each new generation of the technology needs changes in the profile and/or the standard itself.
Wimax Release 1.5
The WiMAX Forum is currently working on the short-term migration of the profile called Release 1.5. Generally it is focused on optimization introducing optimized FDD/HFDD operations and features that can be added to Release 1.0WiMAX devices through a software upgrade. This generation includes additional selection of 802.16 elements available through the ongoing IEEE 802.16 REV2 standard to address the following.
Optimization of FDD/HFDD operations is based on splitting the 802.16 frame into partitions to be used by two distinct groups of mobiles having separated the control channels such as downlink and uplink MAPs, fast feedback channels and HARQ ACK channels. Such a solution allows for the reuse of the design of Release 1.0 (TDD) chipsets while not compromising on the system performance in order to address FDD markets around the world.
Enhanced MAC Performance (Particularly Improved VoIP Capacity)
Release 1.0 is highly optimized to data communication such as TCP/IP. The nature of the data
traffic implies ‘bursty’ transmission demand. To properly serve such a demand, Release 1.0 technology uses the mechanism of downlink and uplink MAPs which are control messages transmitted each frame, that is, every 5 ms.While this is perfect for bursty traffic, support for streaming (VoIP, video) data needs further optimization. The idea for optimization is to use persistent resource allocation so that a singleMAP message provides information on periodic resources assignment matching the needs of a specific stream.
Extended and Enhanced Networking Features
Most of the extensions are related to MBSs. The Release 1.5 extension provides for more flexible allocation of MBS zones which is suitable also for small (micro and pico) cells. Another attractive part of Release 1.5 is the set of features supporting LBSs.
Support forWiMAX and WiFi: Bluetooth Coexistence in the Same Mobile
Special attention is paid to provide more efficient support to WiMAX terminals having additional wireless Local Area Network (LAN) and/or Personal Area Network (PAN) interfaces. As the timing of WiFi or Bluetooth interfaces does not match the timing of the WiMAX interface, special arrangements are needed to, for example, prevent the Bluetooth transmitter from interfering with the WiMAX receiver and vice versa.
Wimax Release 2.0
As was mentioned earlier, the long-term migration from Release 1.0 is known as Release 2.0 and the corresponding specification is being developed in the IEEE 802.16m project (IEEE, 2006b). Unlike Release 1.5, which focused on FDD/HFDD and software-based additions to Release 1.0, the goal of Release 2.0 is to meet International Mobile Telecommnications (IMT)-Advanced requirements for next-generation mobile networks which will be done by providingmajor improvements in all areas. The requirements for 16m can be found in (IEEE, 2007) and Table 1.1 summaries some of the key requirements of 16m.
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