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Internet Access Guide : WiMAX

For Fixed WiMAX, the 802.16-2004 is harmonized with similar work by the European standard body, i.e. ETSI HiperMAN. The 802.16-2004 supports LOS (line-of-sight) fixed wireless access (FWA) in 10 - 66 GHz licensed frequency bands using single carrier air interface. The two multi-carrier air interfaces of Fixed WiMAX (i.e. OFDM and OFDMA) support LOS and NLOS applications in licensed and license-exempt sub-11 GHz bands. The first Fixed WiMAX profiles use OFDM with 256 carriers as its PHY (physical layer) in the licensed 3.5 GHz band using a pair of 3.5 MHz or 7 MHz TDD/FDD channels and the unlicensed 5.8 GHz band using a 10 MHz TDD channel.

Meanwhile, Mobile WiMAX will operate in sub-6 GHz bands and support scalable channel bandwidths from 1.25 MHz to 20 MHz over SOFDMA (Scalable OFDMA) air interface. Release-1 Mobile WiMAX profiles cover 5, 7, 8.75, 10 MHz channel bandwidths for licensed spectrum in the 2.3 GHz, 2.5 GHz and 3.5 GHz bands. Even though with PHY and MAC not fully compatible with Mobile WiMAX specification, WiBro (Wireless Broadband) which is the Korean implementation of IEEE 802.16e, is included as one of Mobile WiMAX profiles. WiBro operates in the 2.3 GHz band over an 8.75 MHz TDD-channel. More details of Fixed and Mobile WiMAX system profiles can be found on this page.

WiMAX Point-To-Multipoint residential broadband Internet access
Picture: WiMAX Point-To-Multipoint (PMP) application

WiMAX MAC (media access control) sublayer supports point-to-multipoint (PMP) and optionally mesh topology. In PMP mode, traffic only occurs between Base Station (BS) and Subscriber Stations (SSs) while in mesh mode, traffic can occur directly between SSs. WiMAX supports traffic scheduling, dynamic bandwidth allocation and QoS (Quality of Service) per service flow, which guarantees every type of traffic will be handled with its associated bandwidth, latency, jitter, and priority requirements. Therefore, WiMAX can deliver toll quality VoIP while maintaining best effort traffic such as e-mail and web browsing at the same time.

Every WiMAX traffic is encrypted using DES (Data Encryption Standard) or AES (Advanced Encryption Standard) for securing its transmission over the air. The encryption keys are distributed from the BS to the SSs using PKM (Privacy Key Management) protocol to ensure that only authorized SSs can receive the keys. Every WiMAX user device is authenticated using a digital certificate or SIM (Subscriber Identity Module). This way, WiMAX keeps user traffic from eavesdropping and protects operator or service provider from becoming a victim of bandwidth theft by unauthorized users.

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