Τετάρτη, 10 Ιουλίου 2013

WiMax Forum contribution to WiMax standardization

Wimax Forum is an industry-led, not-for-profit organization that certifies and promotes the compatibility and interoperability of broadband wireless products of IEEE 802.16. Its goal is to accelerate the adoption, deployment and expansion of WiMax technologies all over the world, while facilitating roaming agreements, sharing best practices within its members and certifying products [14].
WiMax forum has three main areas of standardization development:
·         air interface specifications ,which focus on the physical and the data link layer (layers 1 and 2 of the OSI reference model) and are based on IEEE 802.16
·         network specifications, which apply to higher layers and are not based on 802.16, but developed by WiMax Forum
·         roaming specifications, which deal with the roaming business framework with functions for wholesale rating etc
The relationship between IEEE 802.16 and the WiMax Forum with respect to the OSI reference model is shown in Figure 12 [7].
Figure 12: IEEE 802.16 and WiMax Forum standardization areas of the OSI reference model
The discussions in the WiMax Forum is carried out by industrial delegates. It releases the Wimax Forum’s Mobile WiMax System Profile, which does not describe precise specifications (unlike the IEEE WirelessMAN standard), but only lists functionalities and parameters that are to be used. This list enhances common functionalities and interoperability among WiMax products. The relationship between the WiMax standardization of these two entities is illustrated in Figure 13. A very representative example of the standardization differences of them lies in the physical layer, where IEEE 802.16 defines three options (Single Carrier, Orthogonal Frequency Division Multiplexing and Orthogonal Frequency Division Multiple Access), while the WiMax Forum refers only to OFDMA, as it provides suitable operation only for mobile users [1].
Due to the potential for very high growth and utilization, the WiMax Forum focuses its efforts on Multichannel Multipoint Distribution Service, the 3.5 GHz licensed bands and the unlicensed 5 GHz band.
Figure 13: WiMax Forum and IEEE 802.16 WiMax standardization
The 9 Working Groups of the WiMax Forum and their main functions are as follows:
·         the Network WG, that develops network architecture specification, network procedures and protocols. It includes the Network Interoperability Testing TG, which defines network-level interoperability testing specifications.
·         the Technical WG, which develops technical conformance specifications, system profiles and certification test suites for the air interface.
·         the Application WG, that benchmarks, characterizes and demonstrates best-practice solutions among different classes of applications.
·         the Service Provider WG, which develops the requirements on air-interface and network systems.
·         the Marketing WG, that promotes global adoption of the WiMax broadband wireless technology and informs about the progress and development of WiMax
·          the Certification WG, which manages the WiMax Forum certification program with the supervision of the test labs, the evaluation of the general tests themselves and especially the network-related interoperability tests.
·         the Regulatory WG, that is in charge of the spectrum policy and regulatory issues worldwide, promoting access to a spectrum “fit for purpose” .
·         the Global Roaming WG, which is responsible for the frameworks needed to achieve global roaming across the various WiMax networks with the respective roaming guidelines, interfaces and tests.
·         The Technical Steering Committee (or Technical Plenary), that is promoting better cross-working-group coordination and decision making on crucial issues.
The WiMax Forum issues profiles, releases and certificates, each of the three with a different role. The profiles are based on the IEEE 802.16 and ETSI HiperMAN standards [3]. Features that are optional in standards can be compulsory in a profile. At the beginning, the WiMax Forum was focusing on the spectrum of 10-66 GHz, but later on smaller frequencies were included. There are currently two system profiles: the fixed WiMax system profile for systems based on IEEE 802.16-2004, with 256 carriers in OFDM and the mobile WiMax profile for systems of IEEE 802.16e-2005 amendment. The certification profiles are derived by the system profile and depend on the spectrum used (eg 2.5 GHz or 3.5 GHz), the channel size (eg 1.25 MHz or 10 MHz etc) and the duplexing mode (frequency or time division duplex). These three parameters are dependent on the local regulatory rules. Complying to the same certification profiles ensures interoperability among products of different vendors [7].
Table 2: major WiMax releases and their features
WiMax Forum develops releases and waves within these releases, in order to implement new features .The equipment that meets the standards of a release has to be compatible with older releases. The release development process consists of six stages. The requirements of the first stage are created by the Service Provider WG, of the second to the fifth stage by the Technical WG, the Network WG and the Global Roaming WG concerning the air interface, network and roaming specifications. The major releases are 1, 1.5, 1.6 and 2, which are shown on Table 2 [3] .
WiMax Forum issues certificates for vendors, after they have submitted their products for testing at the six WiMax Forum designated certification labs around the world, which are in Spain, Taiwan, China, the USA, Malaysia and South Korea. The testing itself takes place in these labs without the WiMax Forum involving directly [7]. The certification process is described with the flow chart of Figure 14. After the equipment is submitted by the vendor, conformance and interoperability tests are conducted, before the certification can be issued. If any of the two tests fails, the process halts and the vendor is asked to make the necessary changes in order to comply with the requirements.
Figure 14: flow chart of the WiMax Forum certification

When the certification is finally issued, the product is added to the WiMax Forum Certified Product Registry [7].

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