WiMAX WiMAX is one of the hottest broadband wireless technologies around today. WiMAX is based on IEEE 802.16 specification and it is expected to deliver high quality broadband services.

Topics WiMAX Protocol Fixed / Mobile WiMAX WiMAX vs Wi-Fi About WiMAX Physical layer MAC layer Fixed / Mobile WiMAX WiMAX vs Wi-Fi WiMAX applications

What is WiMAX Worldwide Interoperability for Microwave Access a "last mile" broadband wireless access (BWA) alternative to cable modem, Digital Subscriber Line (DSL) or T1/E1 service. Wireless Metropolitan Area Network (WMAN) Based on IEEE 802.16

IEEE 802.16 Standards 802.16.1-2001 (10-63 GHz, line-of-sight, up to 134Mbit/s) 802.16.2 (minimising interference between coexisting WMANs.) 802.16a-2003 (2-11 Ghz, Mesh, non-line-of-sight) 802.16b-2004 (5-6 Ghz) 802.16c (detailed system profiles) 802.16e-2005 (Mobile Wireless MAN) – called Mobile WiMAX 802.16m-2011, data rates of 100 Mbit/s mobile & 1 Gbit/s fixed (4G) 802.16-2012, 16p, 16n, current

Standard Family Primary Use Radio Tech Downlink (Mbit/s) Uplink (Mbit/s) Notes WiMAX 802.16 Mobile Internet MIMO-SOFDMA 128 (in 20MHz bandwidth) 56 (in 20MHz bandwidth) IEEE 802.16m expected to offer peak rates of at least 1 Gbit/s fixed speeds and 100Mbit/s to mobile users. LTE UMTS/GSM General 4G OFDMA/MIMO/SC-FDMA 100 (in 20MHz bandwidth) 50 (in 20 MHz bandwidth) LTE-Advanced expected to offer peak rates up to 1 Gbit/s fixed speeds and 100 Mb/s to mobile users.

Purpose of WiMAX Providing mobile broadband connectivity across cities and countries through a variety of devices. Providing a wireless alternative to cable and DSL for "last mile" broadband access. Providing data, telecommunications (VoIP) and IPTV services. Providing a source of Internet connectivity as part of a business continuity plan.

Fixed and Mobile WiMAX Fixed WiMAX is optimised for home/office networks Mobile WiMAX is optimised for mobiles

http://www.conniq.com/InternetAccess_WiMAX-02.htm

Fixed WiMAX Architecture

WiMAX as cellular alternative

WiMAX as a mobile voice and data network is potentially exponentially more efficient (profitable) than the legacy cellular infrastructure

WiMAX Architecture MIB – Management Information Base

802.16 protocol

802.16 protocol stack 802.16 covers data link and physical layer

802.16 MAC Sublayer Protocol Classes of service Constant bit rate service. Real-time variable bit rate service. Non-real-time variable bit rate service. Best-effort service.

Physical layer (PHY)

PHY cont. BPSK: 1 bit/baud QPSK: 2 bits/baud QAM-16: 4 bits/baud Example: a 25 MHz bandwidth, QPSK can deliver 50 Mbps, QAM-16 100 Mbps, QAM-64 150 Mbps Baud (Bd): measure of the symbol rate; the number of distinct symbolic changes (signalling event) made to the transmission medium per second in a digitally modulated signal 25 Bd means that 25 symbols are transmitted per second.

PHY cont. TDD (time-division duplex) - use same bandwidth for uplink and downlink - controlled by timing FDD (frequency-division duplex) - use different frequency for uplink and downlink OFDM (orthogonal frequency-division multiplexing) - enhancement of frequency division multiplexing (FDM) - maximise use of bandwidth Also Adaptive Antenna Support (AAS) and MIMO

TDD and FDD

Figure 16.5: Frame structure at the physical layer (TDD) In each time slot, a frame is in the air. The base station fills the data to send to substation in the downstream subframe; the substations fill the data to send to the base station in the upstream subframe. how bidirectional communication can be achieved in WiMAX using a frame in following figure 1. (Let us assume that WiMAX uses only TDM)? Let us assume that WiMAX uses only TDM. In each time slot, a frame is in the air. The base station fills the data to send to substation in the downstream subframe; the substations fill the data to send to the base station in the upstream subframe. Let us give a very simplified example to make the point clear. Assume that the time slot is one minute and the communication is instantaneous. This means in each minute there is a frame in the air. ① During the first half of each minute, the base station is sending data to the substations and the substations are receiving data from the base station (downstream communication). ② During the second half of each minute, the substations are sending data to the base station and the base station is receiving data from the substations (upstream communication). 16.#

OFDM OFDM uses bandwidth which is not available for use in FDM FDM

WiMAX Antennas

Omni directional antenna Omni directional antennas are used for point-to-multipoint configurations. its energy is greatly diffused in broad-casting 360 degrees This limits its range and ultimately signal strength good for situations where there are a lot of subscribers located very close to the base station

Sector antennas focusing the beam in a more focused area offers greater range and throughput with less energy Many operators will use sector antennas to cover a 360-degree service area rather than use an omni directional antenna

Panel antennas a flat panel of about one foot square often used for point-to-point applications

Frequency Plan By reusing frequencies at different base stations, a WiMAX operator can avoid interference from their own network

WiMAX vs Wi-Fi

WiMAX vs Wi-Fi cont. WiMAX is designed to cover large area (multiple homes/buildings), while Wi-Fi is to cover small area (a home/building)

Comparison of WiMAX, WiFi and 3G technology

WiMAX applications Broadband Internet Multimedia IP multimedia subsystem (IMS) Cellular Alternative A clear alternative to connect areas without pre-existing physical cable or telephone networks or just areas without BB access

Broadband Internet Fixed WiMAX is substitute for T1 Mobile WiMAX has larger coverage than WiFi

WiMax in UK Freedom4′s WiMAX Licence Sold For £12.5m. June 29, 2010. UK Broadband, a subsidiary of PCCW (owned by Hong Kong Telecom)  Freedom4 (formerly Pipex Wireless) had the necessary spectrum to launch these wireless networks in the UK, but only Freedom4 opted to do so with a WiMax network in Milton Keynes and Stratford Upon Avon. These WiMax networks were up and running in real world situations years before LTE arrived on the scene.

http://www.europa-network.com/wimax/

Why did LTE beat WiMax UK Broadband’s chief executive, Nicholas James http://www.ukbroadband.com/ Most WiMax backers, including Clearwire in the United States (which has already built WiMax networks in many US cities), have signalled their intent to move across to LTE. It was never cost effective for WiMax networks to compete effectively against fixed-line broadband networks. What happened was that LTE came along early enough so that all operators adopted it,” said James. “No one adopted 16m because there were no economies of scale. Indeed, all WiMax operators have signalled they will move to LTE. WiMax is dead as a mobile technology but it is not dead as a fixed technology. UK Broadband brought Freedom4′s spectrum, because it is adjacent to UKB’s spectrum. “We now have 124MHz of LTE”

Sprint will KILL OFF WiMax in 2015 Third-ranked US mobile network Sprint appears to be poised to kill off its implementation of its less-regarded 4G technology, WiMax. The spectrum it frees up will all move to LTE. http://www.theregister.co.uk/2014/10/06/sprint_wimax_to_close_in_2015/

Number of WiMAX subscriber worldwide from 2010 to 2014 (in millions) http://www.statista.com/statistics/277656/number-of-wimax-subscriber-worldwide-since-2010/

Reference Tannenbaum “Computer Networks” Stallings “wireless communications & Networks” Frank Ohrtman: “Wimax overview”: http://www.wimax.com/education/wimax/wimax_overview “The 802.16 WirelessMAN™ MAC: It’s Done, but What Is It?” (2001-11-12)