6 Wireless networks Wireless PANs (Bluetooth – IEEE 802.15) very low rangewireless connection to printers etcWireless LANs (WiFi – IEEE )infrastructure as well as ad-hoc networks possiblehome/office networkingMultihop Ad hoc Networksuseful when infrastructure not available, impractical, or expensivemilitary applications, emergenciesWireless MANs (WiMAX )Similar to cellular networkstraditional base station infrastructure systemsSridhar IyerIIT Bombay
8 WiMAXGoal: Provide high-speed Internet access to home and business subscribers, without wires.Base stations (BS) and subscriber stations (SS)Centralized access control to prevents collisionsSupports applications with different QoS requirementsWiMAX is a subset of IEEE standardIIT BombaySridhar Iyer
9 IEEE standards(10-66 GHz, line-of-sight, up to 134Mbit/s)(minimizing interference between coexisting WMANs)802.16a (2-11 Ghz, Mesh, non-line-of-sight)802.16b (5-6 Ghz)802.16c (detailed system profiles)P802.16e (Mobile Wireless MAN)IIT BombaySridhar Iyer
11 WiMAX Forum In April of 2001, the WiMAX forum is set up. This forum participates inauthenticating the standardization and interoperability of the broadbandradio access products based on IEEE and ETSI HiperMAN. This forum is organized by many radio communication equipment suppliers, component suppliers, operators, which is a nonprofit organization. In November of 2004, the Network Working Group (NWG) is set up, which participates in setting downing the network standards for the IEEE d and IEEE e.
12 IEEE Working Group In 1999, the IEEE working group is set up, which studies thebroadband radio access technology standard. The aim of this group is IEEE Working Groupto establish a global broadband radio access standard. This group sets down the broadband access system standards,including the air interface standards and associated standards. At the beginning of 2003, this group issues the a standard that defines the 2 GHz to 11 GHz NLOS fixed access system. On October 1 of 2004, this group issues the d fixed access standard. In the end of 2005, this group issues the e standard. Now, the e Release3 has been issued.
13 Introduction to IEEE 802.16 Series SNTechnical Field802.1610-66 GHz, fixed broadband wireless access system airstandard802.16a2-11 GHz fixed broadband wireless access system airstandard802.16cSupplementary provisions about the compatibility of 10-66GHz fixed broadband wireless access system802.16d2-11 GHz fixed wireless access system air standard802.16e2-11 GHz fixed and mobile broadband wireless accesssystem air standard802.16fFixed broadband wireless access system air interface MIBrequirements802.16g Fixed and mobile broadband wireless access system airinterface management plane flow and service requirements802.16d and e are two mainstream Um interface standards.
18 Access Service Network (ASN) The ASN consists of BS and ASN-GW. The ASN can access to multiple connectivity service networks (CSNs) and provide radio access service to the CSN of different network service providers (NSPs). The ASN manages the air interface of IEEE and provides radio access to the WiMAX subscribers.
19 Orthogonal Frequency Division Multiplexing (OFDM) is a multiplexing technique that subdivides the bandwidth into multiple frequency sub-carriers. In an OFDM system, the input data stream is divided into several parallel sub-streams and each sub-stream is modulated and transmitted on a separate orthogonal sub-carrier. It enables a large number of sub-carriers (up to 2048).
20 Orthogonal Frequency Division Multiple Access (OFDMA) is a multiple-access/multiplexing scheme that provides multiplexing operation of data streams from multiple users onto the downlink sub-channels and uplink multiple accesses by means of uplink sub-channels.
21 TDD Frame StructureThe e supports TDD operation; however the initial release of Mobile WiMAX certification profiles will only include TDD. With ongoing releases, FDD profiles will be considered by the WiMAX Forum to address specific market opportunities where local spectrum regulatory requirements either prohibit TDD or are more suitable for FDD deployments. TDD is the preferred duplexing mode for the following reasons:TDD enables adjustment of the downlink/uplink ratio to efficiently support asymmetric downlink/ uplink traffic, while with FDD, downlink and uplink always have fixed and generally, equal DL and UL bandwidths.TDD assures channel reciprocity for better support of link adaptation, MIMO and other closed loop advanced antenna technologies.Unlike FDD, which requires a pair of channels, TDD only requires a single channel for both downlink and uplink providing greater flexibility for adaptation to varied global spectrum allocations.Transceiver designs for TDD implementations are less complex and therefore less expensive.
22 Advanced Features of WiMAX Technology Adaptive Modulation and Coding (AMC): Support for QPSK,16QAM & 64QAM are mandatory in the DL with Mobile WiMAX. Hybrid Automatic Repeat Request (HARQ): supported by Mobile WiMAX. HARQ is enabled using “Stop and Wait” protocol which provides fast response to packet errors and improves cell edge coverage. A dedicated ACK channel is provided in the uplink for HARQ ACK/NACK signaling.
23 MIMO: Smart antenna technologies typically involve complex vector or matrix operations on signals due to multiple antennas. OFDMA allows smart antenna operations to be performed. OFDMA is very well-suited to support smart antenna technologies. In fact, MIMO-OFDM/OFDMA has evolved as the corner-stone for next generation broadband communication systems.
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