Wimax

WiMAXKrishna Mevawala(07BEC047) Institute Of Technology, Nirma University Ahmedabad, India. [email protected] [email protected] Abstract- WiMAX is the most important and immerging technology. The air interface of WiMAX technology is based on the IEEE 802.16 standards. This paper gives the information about the Wimax technology In this paper first you would be informed about the basic information about wimax and then overview about the architecture of Wimax networking. This chapter is intended to provide a high-level overview of the current mobile WiMAX technology with an emphasis on the Physical layer and Medium Access Control (MAC) layer features. Keywords- Introduction, Structure, Key physical features, OFDMA, TDD, Key Mac features, Evolution path, Key Requirements of IEEE 802.16m, Conclusion. multimedia chats and mobile entertainment. In addition, the WiMAX connection can be used to deliver content to multimedia gadgets such as the iPod. Overview of State-of-the-art WiMAX Technology:1. Structure:- Introduction:WiMAX stands for Worldwide Interoperability for Microwave Access. WiMAX technology enables ubiquitous delivery of wireless broadband service for fixed and/or mobile users, and became a reality in 2006 when Korea Telecom started the deployment of a 2.3 GHz version of mobile WiMAX service called WiBRO in the Seoul metropolitan area to offer high performance for data and video. In a recent market forecast published in April 2008, WiMAX Forum Subscriber and User Forecast Study, the WiMAX Forum projects a rather aggressive forecast of more than 133 million WiMAX users globally by 2012 (WiMAX Forum, 2008c). The WiMAX Forum also claims that there are more than 250 trials and deployments worldwide. The air interface of WiMAX technology is based on the IEEE 802.16 standards. In particular, the current Mobile WiMAX technology is mainly based on the IEEE 802.16e amendment (IEEE, 2006a), approved by the IEEE in December 2005, which specifies the Orthogonal Frequency Division Multiple Access (OFDMA) air interface and provides support for mobility. Figure 1.1 Mobile WiMAX Release 1.0 products and certification. Selection of features:The selection of features to be implemented in WiMAX systems and devices is presented in the mobile WiMAX System Profile Release 1.0 (WiMAX Forum, 2007) which was developed in early 2006 and is currently maintained by theWiMAX Forum. The flexible bandwidth allocation and multiple built-in types of Quality-of- Service (QoS) support in the WiMAX network allow the provision of high-speed Internet access, Voice Over IP (VoIP) and video calls, As stated earlier, mobile WiMAX products and certification follow the IEEE 802.16 air interface specifications. The network specifications of mobile WiMAX products, however, are being developed internally by the WiMAX Forum, which include the end to-end networking specifications and network interoperability specifications. The NetworkWorking Group (NWG) within the WiMAX Forum is responsible for these network specifications, some of which involve Access Service Network (ASN) control and data plane protocols, ASN profiles, Connectivity Services Network (CSN) mobility support, Authentication, Authorization and Accounting (AAA) interworking with other technologies, and various services such as Location Based Service (LBS), Multicast and Broadcast Service (MCBCS) etc. In this chapter, however, we will focus on the overview of mobile WiMAX technology from the air interface perspective. Figure 1.1 presents the aforementioned composition of the current mobile WiMAX technology, commonly referred to as Release 1.0 profile. Its air interface MAC Features:Connection-based Data Transmission with Classification and QoS:TheWiMAX technology provides an environment for connection-oriented services. Bandwidth requests may be transmitted using a contention based mechanism or they can be piggybacked with the data messages. TDD is in many ways better positioned for mobile Internet services than FDD.specifications consist of four related IEEE 802. 1. 2. for example. Frequency Reuse One and Flexible Frequency Reuse:From the operators’ perspective. mobile WiMAX was the first commercially available cellular technology that actually realized the benefits of MIMO techniques promised by academia for years. Scheduled Transmissions:Bandwidth allocation mechanism is based on real time bandwidth requests transmitted by the terminals. For each service. It also enables real-time application of flexible frequency reuse where frequency reuse one applied to terminals close to the cell center whereas a fraction of frequency is used for terminals at the cell edge. resulting in up to 37 Mbps for downlink and 10 Mbps for uplink sector throughput using just 10 MHz TDD channel bandwidth. the minimum reserved rate and maximum sustained rate. 3. the WiMAX Forum Technical Working Group (TWG) published the first version of mobile WiMAX System Profile Release 1 in early 2006 (WiMAX Forum. both operators and end-users enjoy up to twice the data rates of Single-Input Single-Output (SISO) rate. With TDD products. conventional FDD with the same downlink and uplink channel bandwidth does not provide the optimum use of resources. thereby reducing heavy co-channel interference. Even though future WiMAX Releases will have FDD mode as well. First of all. Naturally it is in their best interest if a technology allows decent performance in the highly interference-limited conditions with frequency reuse one. Through extensive technical investigation analysis to build up the best competitive products. per connection. TDD is inherently better suited to more advanced antenna techniques such as Adaptive Antenna System (AAS) or Beamforming (BF) than FDD due to the channel reciprocity between the uplink and downlink. With its downlink and uplinkMIMO features. The simple transceiver structure of OFDMA also enables feasible implementation of advanced antenna techniques such as MIMO with reasonable complexity. low rate coding and power boosting and deboosting features.16 Broadband Wireless Access Standards. certain classification rules are specified to define the category of traffic associated with the connection. As a matter of fact. The latest published version to date (Release 10 rev. OFDMA demonstrates superior performance in non-line-of-sight (NLOS) multi-path channels with its relatively simple transceiver structures and allows efficient use of the available spectrum resources by time and frequency subchannelization. A special scheduling type (ertPS) is defined for the VoIP service with silence suppression and adaptive codecs. The Base Station executes resources Advanced Antenna Techniques:- . certain QoS parameters are defined. thus. Physical features:Scalable OFDMA:OFDMA is the multiple access technique for mobile WiMAX. OFDMA is the Orthogonal Frequency Division Multiplexing (OFDM) based multiple access scheme and has become the de-facto single choice for modern broadband wireless technologies adopted in other competing technologies such as 3GPP’s Long Term Evolution (LTE) and 3GPP2’s Ultra Mobile Broadband (UMB). operators are capable of adjusting downlink and uplink ratios based on their service needs in the networks. Mobile WiMAX technology was designed to meet this goal in a respectable way with its cell-specific subchannelization. In addition. securing greater frequency spectrum for their services is always costly. There are several types of scheduling such as real-time services that can be applied based on the application requirements.6. Internet traffic is asymmetric typically with the amount of downlink traffic exceeding the amount of uplink traffic. 2007). Not all of the optional features defined in these IEEE Standards are implemented in WiMAX products and tested for certifications. it could be Internet Protocol (IP) traffic destined for a specific IP address/port. Various advanced antenna techniques have been implemented in the mobile WiMAX Release 1 profile to enable higher cell and user throughputs and improved coverage.1) incorporated error fixes and minor corrections without touching the main features selected in the first revision. For example. TDD:The mobileWiMAX Release 1 Profile has only TDD as the duplexing mode even though the baseline IEEE Standards contain both TDD and Frequency Division Duplex (FDD). For each connection. allocation based on the requests and QoS parameters of the connection. REV2 and 16m. Information collected during scanning such as central frequencies of the neighbor base stations can then be used in actual handover. To resume traffic between the network and the mobile. Operating bandwidth Duplex . 2006b). the schedules of Releases 1. normally of exponentially increasing size. the mobile can apply a scanning process when the mobile is away from the serving base station to scan the wireless media for neighbor base stations. a paging procedure may be used by the network. TABLE I KEY REQUIREMENTS OF IEEE 802. are short-term and long-term migration. information about the central frequency and parameters of the neighbor base stations is periodically advertised by the serving base station.0 are IEEE 802. Security:The security sublayer provides Extensible Authentication Protocol (EAP)-based mutual authentication between the mobile and the network.0 are projections by the authors and may change.16M.16m (IEEE. Handover:Handover procedures include numerous means of optimization.0. the security sublayer employs an authenticated client/server key management protocol which allows the base station to distribute keying material to mobiles. PHS can be used for packets of virtually any format such as IPv4 or IPv6 over Ethernet.5 and 2. TDD Power Saving: Idle Mode:-If the mobile has no traffic for a long time it can switch to idle mode in which it is no longer registered at any particular base station. In sleep mode the mobile is away from the base station for certain time intervals. It is beneficial if a considerable part of the traffic has identical headers which are typical for IP or Ethernet destination addresses. MAC Overhead Reduction:WiMAX technology includes support of the general Purpose Header Suppression (PHS) and IP Header Compression (ROHC). respectively. The corresponding IEEE baseline standards for Releases 1. The other two. scanning can be performed without service interruption.5 and 2. Item Carrier frequency Requirement Licensed band under 6 GHz 5-20 MHz Full-duplex FDD. and their brief summaries are provided in this section. Basic security mechanisms are strengthened by adding digital certificate-based Subscriber Station (SS) device authentication to the key management protocol. Releases 1. Each new generation of the technology needs changes in the profile and/or the standard itself. Owing to the dependency on the ongoing IEEE standards.2 Roadmap of mobileWiMAX standards and products. Power Saving: Sleep Mode:Sleep mode is the primary procedure for power saving. During these intervals the mobile remains registered at the base station but can power down certain circuits to reduce power consumption. Halfduplex FDD.2 provides an overview of mobile WiMAX roadmaps for standards and products. It protects against unauthorized access to the transferred data by applying strong encryption of data blocks transferred over the air. The PHS mechanism replaces the repeated part of the header with a short context identifier.16 REV2 (IEEE. To keep the encryption keys fresh. 2008) and IEEE 802. WiMAX Evolution Path:Figure 1.5 and 2.Figure 1. respectively. The first release labeled as Release 1. thus reducing the overhead associated with headers. In some deployment scenarios. For this purpose. In particular.0 is described earlier in this chapter. to reduce time expenses for the mobile to find the central frequency and acquire parameters of the neighbor base station. Wi-Fi uses unlicensed spectrum to provide access to a local network. . special arrangements are needed to.0 5.5 is the set of features supporting LBSs. 802.Antenna Technique Data latency State transition latency Handover interruption time MBS Spectral efficiency Position accuracy Packet data rate Downlink ≥ (2Tx. 2Rx) Downlink < 10 ms.11 supports also direct ad hoc or peer to peer networking between end user devices without an access point while 802. WiMAX: WiMAX is a long range system. WiFi vs. in most cases the Internet.11 (which includes Wi-Fi) and 802. where an end user communicates to users or servers on another Local Area Network (LAN) using its access point or base station. which is connectionless and contention based. The Release 1. for example. As the timing of WiFi or Bluetooth interfaces does not match the timing of the WiMAX interface. greatly reducing their throughput. Wi-Fi is more popular in end user devices. 300 m (95% of cdf) `Table-II Uses:    Providing portable mobile broadband connectivity across cities and countries through a variety of devices. This can cause subscriber stations distant from the AP to be repeatedly interrupted by closer stations.5 km> 2 bps/Hz Network-based: 100 m (67% of cdf).0 2. Each connection is based on specific scheduling algorithms.   Support forWiMAX and WiFi: Coexistence in the Same Mobile:- Bluetooth Special attention is paid to provide more efficient support to WiMAX terminals having additional wireless Local Area Network (LAN) and/or Personal Area Network (PAN) interfaces. Another attractive part of Release 1.    Type Baseline Target TABLE III Packet Data Rate Link MIMO Downlink Uplink Downlink Uplink 2*2 1*2 4*4 2*4 Data Rate(bps/Hz) 8. Uplink < 10 ms max 100 ms Intra-frequency handover latency <30 ms Inter-frequency handover latency <100 m Inter-base station distance 0.all subscriber stations that wish to pass data through a wireless access point (AP) are competing for the AP's attention on a random interrupt basis. Wi-Fi uses contention access .5 extension provides for more flexible allocation of MBS zones which is suitable also for small (micro and pico) cells.16 (which includes WiMAX) define Peerto-Peer (P2P) and ad hoc networks. Both 802. 2Rx) Uplink ≥ (1Tx. Providing data. telecommunications (VoIP) and IPTV services (triple play).6   Extended and Enhanced Networking Features:Most of the extensions are related to MBSs. prevent the Bluetooth transmitter from interfering with the WiMAX receiver and vice versa. Providing a wireless alternative to cable and DSL for "last mile" broadband access. covering many kilometres.16 end user devices must be in range of the base station. that uses licensed or unlicensed spectrum to deliver connection to a network. WiMAX and Wi-Fi have quite different quality of service (QoS) mechanisms: WiMAX uses a QoS mechanism based on connections between the base station and the user device.8 15. Wi-Fi runs on the Media Access Control's CSMA/CA protocol. Providing a source of Internet connectivity as part of a business continuity plan. whereas WiMAX runs a connection-oriented MAC. However.5 km> 4 bps/Hz Inter-base station distance 1. www. Data communication and networking by Forozone 3.REFERENCES: 1. 5. 4. 2ND EDITION. 6. October. 2. JOHN W ILEY & SONS.0 Approved Specification.wirelessman. IEEE (2007) IEEE 802. 2008. http://www. System Requirements.org/tgm/docs/802 16m-07_002r4.pdf.16m. SPECTRUM SYSTEMS: FROM OFDM AND MC-CDMA TO LTE AND WIMAX.com .techonline. WiMAX Forum (2007) WiMAX Forum Mobile System Profile Release 1.