WiMAX Models
WiMAX is a worldwide certification addressing interoperability across IEEE 802.16 standards-based products . The IEEE 802.16 standard with specific revisions addresses two usage models:
• Fixed
• Portable
Fixed :
The IEEE 802.16-2004 standard (which revises and replaces IEEE 802.16a and 802.16REVd versions) is designed for fixed-access usage models. This standard may be referred to as “fixed wireless” because it uses a mounted antenna at the subscriber’s site. The antenna is mounted to a roof or mast, similar to a satellite television dish. IEEE 802.16-2004 also addresses indoor installations, in which case it may not be as robust as in outdoor installations .
The 802.16-2004 standard is a wireless solution for fixed broadband Internet access that provides an interoperable, carrier-class solution for the last mile. The Intel WiMAX solution for fixed access operates in the licensed 2.5-GHz, 3.5-GHz and license-exempt 5.8-GHz bands. This technology provides a wireless alternative to the cable modem, digital subscriber lines of any type (xDSL), transmit/exchange (Tx/Ex) circuits and optical carrier level (OC-x) circuits.
Portable:
The IEEE 802.16e standard is an amendment to the 802.16- 2004 base specification and targets the mobile market by adding portability and the ability for mobile clients with IEEE 802.16e adapters to connect directly to the WiMAX network to the standard. The 802.16e standard is expected to be ratified in early 2005 .
The 802.16e standard uses Orthogonal Frequency Division Multiple Access (OFDMA), which is similar to OFDM in that it divides the carriers into multiple sub carriers. OFDMA, however, goes a step further by then grouping multiple sub carriers into sub-channels . A single client or subscriber station might transmit using all of the sub-channels within the carrier space, or multiple clients might transmit with each using a portion of the total number of sub-channels simultaneously
The WiMAX Scenario
Here's what would happen if you got WiMAX
Channel acquisition, Initial Ranging and Negotiation of SS station capabilities
1. Subscriber station, SS, scans for the pre-set frequency Base station.
2. Base Station, BS, responds to the Subscriber station and synchronizes with it.
3. If SS station does not find any BS station it would increase the transmitting frequency power so that it would get a response from a BS station.
4. Now that the link has been established, Initial Ranging (IR) parameters are set and UL-MAP-Mobile Application part up link. SS station broadcasts with a MAC using minimum radio frequency transmission.
5. BS station now transmits power, timing adjustments and connection identification (CID).
6. SS station responds with physical layer capabilities ( modulation and coding schemes)
7. BS station authorizes SS station and service begins.
SS station Authorization and Registration
1. SS station sends an authorization and authentication request using X.509 digital certificate.
2. BS station responds with authorization reply which consists of the authorization key encrypted with the SS stations’ public key and intervals refreshing for keys.
3. With validation SS registers with the network.
4. SS station sends an IP address request on the DHCP (Dynamic Host Configuration Protocol) server.
5. BS station and SS station maintain the current date and time using the time of the day protocol. The SS station receives( downloads) operational parameters using TFTP (Trivial File Transfer Protocol) over UDP (User Datagram Protocol)
WiMAX Strengths
WiMAX strategies are different but they are based on following WiMAX strengths
• Superior Performance: Due to OFDMA multiplexing which gives WiMAX in providing better performance in delivering IP data services as compared to 3G technologies.
• Flexibility: It allows internet service providers to carry multiple kinds of technologies which comprised of fixed and mobile access, over the same WiMAX network and to function their networks in multiple spectrum bands.
• Advanced IP-based architecture: Which includes IMS (IP Multimedia Subsystem)deliver to carry rapid, low cost, turning up of new applications and of interworking with 3G and other technologies.
Economic Advantage of WIMAX
Wireless technologies provide a cost effective solution for service providers .these technologies do not need private or public property to give services to the customer, there are buildings where fiber optic cannot be reached because one cannot dugout through another property and running the cable but with the help of WiMAX and other affiliated technologies it is possible to merely beam the data flow to that building, this solution is for SOHO(small office/home office) market where fiber optic and other higher bandwidth services are not available . WiMAX provides more a feasible business case with broader profit regions because of low cost and flexibility. The installation of WiMAX will notably improve the economics of network equipment. Major companies like Intel, Motorola, Fujitsu, Siemens and Alcatel are already dedicated to develop suchequipment on the basis of these standards. WiMAX chipset in laptops and other mobile
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