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VISHNU

VISHNU VASANT PAVAN ABHILASH. Contents. Introduction What is WiMAX? IEEE 802.16 Extensions

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VISHNU

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  1. VISHNU VASANT PAVAN ABHILASH

  2. Contents Introduction What is WiMAX? IEEE 802.16 Extensions Architecture Functionality WiMAX Protocol Scenario Features Security Issues Benefits WiFi vs WiMAX WiMAX Applications Future of WiMAX Conclusion References

  3. Introduction Broadband access - In your home, you have either a DSL or cable modem At the office, your company may be using a T1 or T3 line. WiFi access - In your home, you may have set up a WiFi router that lets you surf the Web while you lounge with your laptop on the road, you can find WiFi hot spots in restaurants, hotels, coffee shops and libraries. Dial-up access - If you are still using dial-up, chances are that either broadband access is not available, or you think that broadband access is too expensive

  4. Contd.. The main problems with broadband access are that it is pretty expensive and it doesn't reach all areas. The main problem with WiFi access is that hot spots are very small, so coverage is sparse. There is a need for a system which provides high speed of Broadband and is wireless instead of wired. WiMAX(Worldwide Interoperability Microwave Access) provides these features .Its also known as IEEE 802.16

  5. What is WiMAX? WiMAX (Worldwide Interoperability for microwave access) A technology based on an evolving standard for point-to-multi point wireless networking The commercialization of IEEE 802.16 standard Solution for Wireless Metropolitan Area Network BWA (Broadband Wireless Access) Solution Comply with European BWA standard European Telecommunications Standards Institutes's High-performance radio metropolitan area network (HiperMAN)

  6. Wireless MAN (Metropolitan Area Network)

  7. Contd.. Coverage range up to 50km and speeds up to 70Mbps(shared among users).

  8. Operation of WiMAX WiMAX consists of two parts A WiMAX tower, similar in concept to a cell-phone tower - A single WiMAX tower can provide coverage to a very large area -- as big as 3,000 square miles A WiMAX Receiver The receiver and antenna could be a small box or PCMCIA card, or they could be built into a laptop the way WiFi access is today

  9. Service Types Non-Line-Of-Sight A Service where a small antenna on your computer connects to the tower. In this mode, WiMAX uses a lower frequency range -- 2 GHz to 11 GHz (similar to WiFi) Line-Of-Sight A Service where a fixed dish antenna points straight at the WiMAX tower from a rooftop or pole. Line-of-sight transmissions use higher frequencies, with ranges reaching a possible 66 GHz

  10. IEEE 802.16 IEEE 802.16 was completed on Oct, 2004 Range - 30-mile (50-km) radius from base station Speed - 70 megabits per second Line-of-sight not needed between user and base station Frequency bands - 2 to 11 GHz and 10 to 66 GHz (licensed and unlicensed bands) Defines both the MAC and PHY layers and allows multiple PHY-layer specifications

  11. IEEE Extensions 802.16a use the licensed and license-exempt frequencies from 2 to 11Ghz Support Mesh-Network 802.16b Increase spectrum to 5 and 6GHz Provide QoS (for real-time voice and video service) 802.16c Represents a 10 to 66GHz system profile 802.16d Improvement and fixes for 802.16a 802.16e Addresses on Mobile Enable high-speed signal handoffs necessary for communications with users moving at vehicular speeds

  12. Architecture P2MP(Point to Multi point) Wireless MAN BS connected to Public Networks BS serves Subscriber Stations(SS) Provides SS with first mile access to Public Networks Mesh Architecture Optional architecture for WiMAX

  13. P2MP Architecture

  14. WiMAX Mesh Architecture

  15. WiMAX FUNCTIONALITY

  16. WiMAX Protocol Covers MAC layer and PHY layer PHY layer Transmission Convergence sublayer MAC layer

  17. Reference Model

  18. PHY Layer In the design of the PHY specification for 10–66 GHz, line-of-sight propagation was deemed a practical necessity. Because of the point-to-multipoint architecture, the BS basically transmits a TDM signal, with individual subscriber stations allocated time slots serially. The PHY specification defined for 10–66 GHz uses burst single-carrier modulation with adaptive burst profiling in  which transmission parameters, including the modulation and coding schemes, may be adjusted individually to each subscriber station (SS) on a frame-by-frame basis. Both TDD and burst FDD variants are defined. Channel bandwidths of 20 or 25 MHz (typical U.S. allocation) or 28 MHz (typical European allocation) are specified, along with Nyquist square-root raised-cosine pulse shaping with a roll off factor of 0.25.

  19. Contd.. Adaptive Burst Profiles On DL, multiple SS's can associate the same DL burst On UL, SS transmits in an given time slot with a specific burst Allows use of directional antennas Improves range Allows use of two different duplexing schemes: Frequency Division Duplexing (FDD) Time Division Duplexing (TDD) Support for both full and half duplex stations

  20. Adaptive PHY

  21. FDD (Frequency Division Duplexing) In case of FDD both uplink and downlink channels are on separate frequencies The capability of downlink to be transmitted in bursts simultaneously supports two different modulation types Full Duplex SS's( which can transmit and receive simultaneously) Half Duplex SS's( which cannot)

  22. FDD Frame bursting

  23. TDD (Time Division Duplexing) In case of TDD both uplink and downlink transmissions share the same frequency but are separated on time A TDD frame has a fixed duration and also consists of one uplink and one downlink frame TDD framing is Adaptive

  24. Time Division Duplexing

  25. Data Rates • Data rates determined by exact modulation and encoding schemes • TDD and FDD supported in 802.16 to accommodate burst profiling • 802.16a adds OFDM and OFDMA to support NLOS multipath propagation

  26. Medium Access Control(MAC) WirelessMAN: Point-to-Multipoint and optional mesh topology Connection-Oriented Connection ID(CID),Service Flows(FS) MAC layer is further subdivided into three layers Convergence sub-layer (CS) Common part sub-layer (CPS) Privacy sub-layer

  27. MAC Addressing SS has 48-bit 802.3 MAC address BS has 48-bit base station ID Not a MAC address Connection ID (CID) 16 bit Used in MAC PDU Connection Oriented Service

  28. Frame Structure and PDU Each MAC packet consists of the three components, A MAC header, which contains frame control information. A variable length frame body, which contains information specific to the frame type. A frame check sequence(FCS), which contains an IEEE 32-bit cyclic redundancy code (CRC).

  29. MAC PDU

  30. MAC CS Sub Layer Interoperability requires convergence sub-layer to be service specific Separate CS layers for ATM & packet protocols CS Layer: Receives data from higher layers Classifies data as ATM cell or packet Forwards frames to CPS layer

  31. Contd.. Packet Convergence Sub-Layer Initial support for Ethernet, VLAN, IPv4, and IPv6 Payload header suppression Full QoS support ATM Convergence Sub-Layer Support for VP/VC switched connections Support for end-to-end signaling of dynamically created connections ATM header suppression Full QOS support

  32. MAC CPS Layer Performs typical MAC functions such as addressing Each SS assigned 48-bit MAC address Connection Identifiers used as primary address after initialization MAC policy determined by direction of transmission Uplink is DAMA-TDM Downlink is TDM Data encapsulated in a common format facilitating interoperability Fragment or pack frames as needed Changes transparent to receiver

  33. MAC PDU Types Data MAC PDUs HT = 0 Payloads are MAC SDUs/segments, i.e., data from upper layer (CS PDUs) Transmitted on data connections Management MAC PDUs HT =0 Payloads are MAC management messages or IP packets encapsulated in MAC CS PDUs Transmitted on management connections BW Req. MAC PDUs HT =1; and no payload, i.e., just a Header

  34. MAC PDU Transmission MAC PDU’s are transmitted on PHY bursts The PHY burst can contain multiple FEC blocks Concatenation Multiple MAC PDU's can be concatenated into a single transmission in either uplink or downlink direction Fragmentation Each MAC SDU can be divided into one or more MAC PDU's Packing Packs multiple MAC SDU's into a single MAC PDU

  35. MAC Privacy Sub Layer Provides secure communication Data encrypted with cipher clock chaining mode of DES Prevents theft of service SSs authenticated by BS using key management protocol

  36. Transmission Convergence Sublayer This layer performs the transformation of variable length MAC protocol data units (PDUs) into the fixed length FEC blocks (plus possibly a shortened block at the end) of each burst. The TC layer has a PDU sized to fit in the FEC block currently being filled. It starts with a pointer indicating where the next MAC PDU header starts within the FEC block. The TC PDU format allows resynchronization to the next MAC PDU in the event that the previous FEC block had irrecoverable errors.

  37. WiMAX Scenario • Consider a scenario where a wimax-enabled computer is 10 miles away from the wimax base station. • A special encryption code is given to computer to gain access to base station. • The base station would beam data from the Internet required for computer (at speeds potentially higher than today's cable modems)

  38. Contd.. The user would pay the provider monthly fee for using the service. The cost for this service could be much lower than current high-speed Internet-subscription fees because the provider never had to run cables. The WiMAX protocol is designed to accommodate several different methods of data transmission, one of which is Voice Over Internet Protocol (VoIP). If WiMAX-compatible computers become very common, the use of VoIP could increase dramatically. Almost anyone with a laptop could make VoIP calls.

  39. WiMAXFeatures Scalability Quality of service Range Coverage

  40. Scalability The 802.16 standard supports flexible radio frequency (RF) channel bandwidths. The standard supports hundreds or even thousands of users within one RF channel. As the number of subscribers grow the spectrum can be reallocated with process of sectoring.

  41. Quality Of Service Primary purpose of QoS feature is to define transmission ordering and scheduling on the air interface. These features often need to work in conjunction with mechanisms beyond the air interface in order to provide end to end QoS or to police the behaviour or SS. Standard defines several QoS related concepts. - Service flow Qos scheduling. - Dynamic service Establishment. -Two Phase Activation Model.

  42. Theory Of Operation All protocol mechanisms support Qos for both uplink and downlink traffic through the SS and BS. Requirements for QoS : - A configuration and registration function to pre configure SS based QoS service flows and traffic parameters. - A signalling function for dynamically establishing Qos enabled service flows and traffic parameters. - Utilization of MAC scheduling and QoS traffic parameters for uplink service flows. - Utilization of QoS traffic parameters for downlink service flows.

  43. Service flows A service flow is a MAC transport service that provides unidirectional transport of packets either to uplink packets transmitted by the SS or to downlink packets transmitted by the BS. A service flow is characterized by a set of QoS parameters such as latency,jitter and throughput assurances. In order to standardize operations between SS and BS these attributes include details of how the SS requests uplink bandwidth allocations and the expected behaviour of the BS uplink scheduler.

  44. Range Optimized for up to 50 Km. Designed to handle many users spread out over kilometres. Designed to tolerate greater multi-path delay spread (signal reflections) up to 10.0μ seconds. PHY and MAC designed with multi-mile range in mind.

  45. Coverage Standard supports mesh network topology. Optimized for outdoor NLOS performance. Standard supports advanced antenna techniques.

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