Shambhu J Upadhyaya 1 Shambhu Upadhyaya Computer Science & Eng. University at Buffalo Buffalo, New York WIMAX & IEEE BROADBAND WIRELESS ACCESS

Part I  LAN, WAN, MAN  TCP/IP Protocol architecture, OSI Model  Spread spectrum concept – FHSS, DSSS  Coding and error control  Generations of cellular networks (1G, 2G, 3G, 4G)  Cordless systems  WiMax & IEEE Broadband wireless access standards  Mobile IP Shambhu Upadhyaya 2

Reading Exercise  Cordless systems  Time division duplex (TDD)  TDMA/TDD  Mobile IP  Wireless Application Protocol Shambhu Upadhyaya 3

Orthogonal Frequency Division Multiplexing (OFDM)  Uses multiple carrier signals at different frequencies  All subchannels are dedicated to a single data source  OFDM is the foundation for WiMax  OFDMA is foundational for 4G systems and replaces spread spectrum used in 3G  Also expanded rates Shambhu Upadhyaya 4

OFDM Illustration  Data stream - R bps  Available bandwidth - Nf b centered at f 0  Split data stream into N streams using S/P converter  Substream data rate - R/N transmitted on a separate subcarrier with a spacing between subcarriers of f b  Uses QPSK modulation Shambhu Upadhyaya 5

Illustration of Orthogonality  OFDM uses advanced DSP to distribute data over multiple carriers  Orthogonality – precise relationship among the subcarriers  Minimal interference between adjacent carriers (peaks are distinct)  For transmission, subcarriers further modulated to a higher frequency band Shambhu Upadhyaya 6

Orthogonality  Given a OFDM subcarrier bit time of T  f b must be a multiple of 1/T  Example: IEEE n wireless LAN  20 MHz total bandwidth  Only 15 MHz can be used  48 subcarriers  f b = MHz  Signal is translated to 2.4 GHz or 5 GHz bands Shambhu Upadhyaya 7

Benefits of OFDM  Benefits of CDMA carry over  Better immunity to fading as only a small portion of the energy for any one link is typically lost due to a fade  Fast power control to keep the noise floor as low as possible  Additional advantages  Highly resistant to fading and inter-symbol interference  Modulation is applied at a much lower rate on each of the many sub-carriers  Sophisticated error correction  Scales rates easier than CDMA  Allows more advanced antenna technologies, like MIMO  Breaks information into pieces and assigns each one to a specific set of sub-carriers Shambhu Upadhyaya 8

Standards Development  Use wireless links with microwave or millimeter wave radios  Use licensed spectrum  Are metropolitan in scale  Provide public network service to fee- paying customers  Use point-to-multipoint architecture with stationary rooftop or tower-mounted antennas Shambhu Upadhyaya 9

Standards Development  Provide efficient transport of heterogeneous traffic supporting quality of service (QoS)  Use wireless links with microwave or millimeter wave radios  Are capable of broadband transmissions (>2 Mbps)  The WiMAX (Worldwide Interoperability for Microwave Access) Forum  Industry consortium  Formed to promote the standards and to develop interoperability specifications Shambhu Upadhyaya 10

IEEE Protocol Architecture Shambhu Upadhyaya 11

Protocol Architecture  Physical and transmission layer functions:  Encoding/decoding of signals  Preamble generation/removal  Bit transmission/reception  Medium access control layer functions:  On transmission, assemble data into a frame with address and error detection fields  On reception, disassemble frame, and perform address recognition and error detection  Govern access to the wireless transmission medium Shambhu Upadhyaya 12

Protocol Architecture  Convergence layer functions:  Encapsulate PDU framing of upper layers into native MAC/PHY frames  Map upper layer’s addresses into addresses  Translate upper layer QoS parameters into native MAC format  Adapt time dependencies of upper layer traffic into equivalent MAC service Shambhu Upadhyaya 13

Protocol Structure in Context Shambhu Upadhyaya 14

IEEE Services  Digital audio/video multicast  Digital telephony  ATM  Internet protocol  Bridged LAN  Back-haul  Frame relay Shambhu Upadhyaya 15

IEEE Services  Voice transport  Data transport  Bridged LAN Shambhu Upadhyaya 16

IEEE Frame Format Shambhu Upadhyaya 17

IEEE Frame Format  Header - protocol control information  Downlink header – used by the base station  Uplink header – used by the subscriber to convey bandwidth management needs to base station  Bandwidth request header – used by subscriber to request additional bandwidth  Payload – either higher-level data or a MAC control message  CRC – error-detecting code Shambhu Upadhyaya 18

MAC Management Messages  Uplink and downlink channel descriptor  Uplink and downlink access definition  Ranging request and response  Registration request, response and acknowledge  Privacy key management request and response  Dynamic service addition request, response and acknowledge Shambhu Upadhyaya 19

MAC Management Messages  Dynamic service change request, response, and acknowledge  Dynamic service deletion request and response  Multicast polling assignment request and response  Downlink data grant type request  ARQ acknowledgment Shambhu Upadhyaya 20

Physical Layer – Upstream Transmission  Uses a DAMA-TDMA technique  Error correction uses Reed-Solomon code  Modulation scheme based on QPSK Shambhu Upadhyaya 21

Physical Layer – Downstream Transmission  Continuous downstream mode  For continuous transmission stream (audio, video)  Simple TDM scheme is used for channel access  Duplexing technique is frequency division duplex (FDD)  Burst downstream mode  Targets burst transmission stream (IP-based traffic)  DAMA-TDMA scheme is used for channel access  Duplexing techniques are FDD with adaptive modulation, frequency shift division duplexing (FSDD), time division duplexing (TDD) Shambhu Upadhyaya 22

Review of Mobile IP and WAP  Two standards for application level support for wireless networking  Popular at the time of palm-top devices and PDA  Current trend is to phase out these technologies in favor of all-IP telco  It is expected that all-IP (next generation network) will become standard by 2018 Shambhu Upadhyaya 23

Mobile IP Uses  Enable computers to maintain Internet connectivity while moving from one Internet attachment point to another  Mobile – user's point of attachment changes dynamically and all connections are automatically maintained despite the change  Nomadic - user's Internet connection is terminated each time the user moves and a new connection is initiated when the user dials back in  New, temporary IP address is assigned Shambhu Upadhyaya 24

Operation of Mobile IP  Mobil node is assigned to a particular network – home network  IP address on home network is static – home address  Mobile node can move to another network – foreign network  Mobile node registers with network node on foreign network – foreign agent  Mobile node gives care-of address to agent on home network – home agent Shambhu Upadhyaya 25

Mobile IP Scenario Shambhu Upadhyaya 26

Capabilities of Mobile IP  Discovery – mobile node uses discovery procedure to identify prospective home and foreign agents  Registration – mobile node uses an authenticated registration procedure to inform home agent of its care-of address  Tunneling – used to forward IP datagrams from a home address to a care-of address Shambhu Upadhyaya 27

Wireless Application Protocol (WAP)  Open standard providing mobile users of wireless terminals access to telephony and information services  Wireless terminals include wireless phones, pagers and personal digital assistants (PDAs)  Designed to work with all wireless network technologies such as GSM, CDMA, and TDMA  Based on existing Internet standards such as IP, XML, HTML, and HTTP  Includes security facilities Shambhu Upadhyaya 28

How WAP Works WAP - Internet and advanced telephony services  WAP bridges mobile world, Internet and corporate intranets  WAP defines WAE (wireless application environment)  Micro browser  Scripting facilities   World Wide Web (WWW)–to -mobile-handset messaging  Mobile-to-telefax access, etc. Shambhu Upadhyaya 29

WAP Protocol Stack Shambhu Upadhyaya 30

WAP Programming Model Shambhu Upadhyaya 31

References  Corey Beard & William Stallings, Wireless Communication Networks & Systems, Pearson, 2016 (Chapters 15, 16) Shambhu Upadhyaya 32