The IEEE 802.16 standard is emerging as a Wireless Access technologies most promising in the world and MAN networks within the IEEE 802.x family of standards is a the most accepted has gained in the world because of the great advantages of addition to ease of use and maintenance. The IEEE 802.16 standard allows the implementation of broadband networks for wireless access over large areas, which are capable of providing any type of service because of its great capacity to carry information. These networks have gained great success in this market in recent years, making increasingly larger equipment suppliers such as Intel, Nokia, Samsung and Motorola which support this standard devices come to market that meet the standard specifications and in turn, many companies acquire the technology as a solution to your connection needs.
1 EVOLUTION OF IEEE 802.16 STANDARD
Since its inception in the 90's, the IEEE 802.16 standard has been the primary objective of providing different types of network services over a wireless high-bit transfer. To this end define interface specifications including MAC (Medium Access Control) and PHY (physical layer). Despite having these specifications from the outset to meet the objectives proposed, some failures have been mainly in the MAC layer, where the management in the delivery of information is performed without encrypting the data to facilitate proper operation of this Similarly, in a passive listening channel network could easily access the unencrypted information. Because of this situation have been different fixes that have led to several revisions and additions to the specifications for the MAC and PHY layers adding new functions to them over time. These corrections are presented in different versions of the standard: IEEE 802.16
2001: First version of the standard that gave the first specifications for the MAC and PHY layer, provides broadband wireless access, network configuration Point to Point ( P2P) or point-multipoint (PMP). Support for TDD (Time Division Multiplexing) and FDD (Multiplexing Frequency Division). Unlike 802.11, or Wi-Fi that uses CSMA / CD to transmit, 802.16 uses a totally different paradigm to perform this function controlled by the base stations (BS). Opera in the range of 10 to 66 GHz, as these high frequencies is only functional in environments LOS (Line of Sight). Uses QPSK, QAM-16 and QAM-64 with the ability to switch between different modulations depending on weather conditions including. Provides different levels of QoS (Quality of Service) parameters controlling the sum of time delays within the network (latency) and the variation of some data packets received due to latency (jitter). The core Standard safety lies in the privacy sublayer belonging to the MAC layer using this data encryption algorithms in their messages between base stations (BS) and subscriber station (SS) and making use of X.509 digital certificates .
IEEE 802.16c: 2002: Published in December 2002, standardized wireless technology in more detail, corrected some errors in the original version by defining a set of features and functions that are used in implementation. Increasing interoperability and consistency between equipment from different manufacturers and the widespread and increasing use of the standard in the future. Detailed profiles are added to systems operating in the band 10-66 GHz IEEE 802.16a
: 2003: Published in June 2003, introduces new features like support for the licensed bands from 2-11 GHz and thus have the ability to penetrate barriers because it low frequency and thus be viable for applications where NLOS (Non Line of Sight). New MAC and PHY specifications for better handling of multipath interference from also using a new antenna array which produces a better management of the power used by the system. New support multiplexing orthogonal frequency division (OFDM) to avoid interference with other network systems operating in the same range often 2 to 11 GHz improved security by requiring authentication of the issuer for some MAC messages. Specific QoS to optimize data services, voice and video as well as ARQ to improve the performance point to point. Support for mesh networks. She was appointed initially as HUMAN Wireless Metropolitan Area Network for High Speed \u200b\u200bis not graduate.
IEEE 802.16: 2004: Publication made in June 2004, is the fusion between IEEE 802.16: 2001 and IEEE 802.16c: 2002 integrating all the existing family of standards at the time under the same document. Gave support to licensed and unlicensed bands but the band of 10 - 66 GHz LOS environments requires in turn for frequencies below 11 GHz supports NLOS environments. The MAC layer supports PMP and mesh architecture. This version is the standard that is used for WiMAX certification.
IEEE 802.16e: 2005: transfer functions provides communication between cells while the user moves in the service area (handover) between Base Stations (BS), these entities provide functionality on the link admission control and management radio resources in the uplink and downlink, giving the possibility of having subscriber stations (ES) solutions, this IS are the entities that allow the reception of information in the client side and the transmission from East to BS.
IEEE 802.16f: 2005: Defines the MIB (Management Base for Information) for MAC and PHY layers. It also defines a procedure to create a standard Network Management for IEEE 802.16-based systems.
With these revisions and improvements made by the standard can determine some advantages or benefits that this type of network provides users:
Large Coverage: up to 50Km in LOS environments, for NLOS environments to 8KM
High capacity Bit-rates: Ideally the network is capable of transferring data at 70Mbps
support NLOS environments: In the indicated frequencies a network can be implemented under the standard without line of sight.
flexible channel size: This is a very important feature because you can set the width of the channels of communication optimizing their use and avoiding waste of network resources.
mesh networking support: This option allows the ES to routing between each other without going through the EB making this clear to her role.
Support for mobile users: An ES can access the network moving at vehicular speeds. This gives the possibility of ES service using mobile devices.
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