INTRODUCTIONBACKGROUND PROJECT DEVELOPMENT ON WIMAX WASSTART IN 1998.WHY WIMAX????? Wi-Fi signals can not cover more than ahundred meters. Both LOS and NLOS support. Higher data rate than former technologies. Fewer base stations.
CONT…. WIMAX refers to interoperable implementationsof the IEEE 802.16 family of wireless-networksstandards ratified by the WiMAX Forum. There were some earlier version of Wimax thatwere used for testing purposes:802.16a ,802.16b ,802.16c . The current versions are 802.16d(FIXED) and802.16e(MOBILE).
CURRENT DEPLOYMENT INPAKISTAN: Pakistan is the first country with world’s largest nationwideinstalled WiMAX network Providers: Wi-Tribe, Wateen (3.5GHz), Mobilink Infinity,Qubee. WiMAX could potentially be deployed in a variety of spectrumbands: 2.3GHz, 2.5GHz, 3.5GHz, and 5.8GHz Operates in both licensed and un-licensed bands
WIMAX NETWORKCHARACTERISTICS There are two scenarios for a wireless deployment: point-to-point and point-to multipoint.Point to Point (P2P): Point to point is used where there are twopoints of interest: one sender and onereceiver. As the architecture calls for a highly focusedbeam between two points range andthroughput of point-to pointradios will be higher than that ofpoint-to-multipoint products.
CONT...Point-to-Multipoint (PMP): One base station can serve hundreds of dissimilarsubscribers in terms of bandwidth and services offered.
LINE OF SIGHT (LOS) OR NON-LINE OF SIGHT (NLOS): WiMAX functions best in line of sight situations. Buildingsbetween the base station and the subscriber diminish therange and throughput, but in an urban environment, thesignal will still be strong enough to deliver adequate service.
WiMAX ability to deliver services non-line-of-sight, the WiMAX service provider can reachmany customers in high-rise office buildings toachieve a low cost per subscriber because somany subscribers can be reached from one basestation.
CPE OR MS CPE and MS are end-user products whichintegrates with user devices Like laptops, mobile phones. it also includes USBmodem, PCMCIA cards Can be fixed or mobile
BASE STATION It provides connectivity tothe consumer equipments Base station consist ofwireless electronic tower Coverage area theoreticallyup to 50km but practically 10 km Additional functions are: handoff triggering, QoS policyenforcement, DHCP etc BS can be point-to point or point-to-multipoint BS are LOS as well as NLOS
ENTITIES OF THE WIMAXNETWORK ASN: Access Serving Network Logical representation of the functions of a NAP, e.g. 802.16 interface network entry and handover Radio Resource Management & Admission ctrl. L2 Session/mobility management QoS and Policy Enforcement Foreign Agent (FA) Forwarding to selected CSN
ASN-GW Access service network-Gate Way acts as a layer 2traffic aggregation points within an ASN. management, network optimization, and forwardingof all subscriber traffic, routing to the selected CSN ,AAA client functionality.
CSN Connectivity service network provides: AAA servers that support authentication forthe devices Operations tools IP & traffic management QoS & Policy Pre paid billing Billing control support for roaming betweendifferent NSPs
AUTHENTICATION,AUTHORIZATION ANDACCOUNTING AAA refers to Authentication, Authorization andAccounting. The AAA server provides the following services toWiMAX: Authentication Services These include MS, user, or combined MS and userauthentication. Authorization Services These include the delivery of information to configure thesession for access, mobility, QoS and other applications. Accounting Services These include the delivery of information for the purpose ofbilling (both prepaid and post paid billing) and informationthat can be used to audit session activity by both the homeNSP and visited NSP.
INTERNETWORKING WITH 3GPPScope:WiMAX-3GPP Interworkingrefers to the integration of aWiMAX Access Network to anexisting 3GPP core network.3GPPCardWiMAXCardUELoosely-CoupledInternetworking3GPP AccessNetworkRNCGCSNSGSN3GPP CoreNetworkWAGPDGBilling ServerHome AAAInternetHome AgentWiMAX NetworkService ProviderLocal AAAWiMAX Base StationsWiMAX ASN
QOS CLASSES Five QOS services are supported in WIMAX: UGS (Unsolicited Grant Service) RT-VR (Real-Time -Variable Rate Service) NRT-VR (Non-Real Time -Variable Rate service) BE (Best Efforts) ERT-VR (Extended Real-Time Variable Rate)
UNSOLICITED GRANT SERVICE(UGS) support real-time data streams consisting offixed-size data packets issued at periodicintervals Such as T1/E1 and Voice over IP without silencesuppressionVoIP
REAL-TIME POLLING SERVICE(RTPS) support real-time data streams consisting ofvariable-sized data packets that are issued atperiodic intervals Such as moving pictures experts group (MPEG)video.
NON-REAL-TIME POLLING SERVICE(NRTPS) support delay-tolerant data streams consisting ofvariable-sized data packets for which a minimumdata rate is required such as FTP
BEST EFFORT (BE) support data streams for which no minimumservice level is required and therefore may behandled on a space-available basis.
EXTENDED REAL-TIMEVARIABLE RATE (ERT-VR)SERVICE support real-time applications with variabledata-rates, which require guaranteed data anddelay, for example VoIP with silence suppression.
MULTIPLEXING TECHNIQUESOFDM OFDM divides the bandwidth into multiplefrequency sub-carriers. In OFDM sub-carriers are orthogonal to eachother. OFDM also uses multiple sub-carriers but thesub-carriers are closely spaced to each otherwithout causing interference, removing guardbands between adjacent sub-carriers. For fixed devices Orthogonal sub carriers produce no signalpower in adjacent sub carriers
CONT.... As a reminder, IFFT (Inverse Fast FourierTransform) is used in a WiMAX transmitter tocreate an OFDM waveform from modulated datastreams, while FFT (Fast Fourier Transform) isused in a WiMAX receiver to demodulate thedata streams.
WHY IS OFDM SO POPULAR FORNEW BROADBAND SYSTEMS? Most broadband systems are subject to multipath transmission Conventional solution to multipath is an equalizer in the receiver With OFDM there is a simple way of dealing with multipathrelatively simple DSP algorithms. It uses cyclic prefix to avoid residual ISI If multipath delay is less than the cyclic prefix-no intersymbol or intercarrier interference-amplitude may increase or decrease
OFDMA: OFDMA employs multiple closely spaced sub-carriers,which are divided into groups of sub-carriers. For mobile services Point-to-point systems are OFDM, and do not supportOFDMA. Point-to-multipoint fixed and mobile systems useOFDMA.
CONT.... (OFDMA) is a multi-user version of the popular(OFDM) digital modulation scheme Assigns different subset of sub-carriers toindividual user Bandwidth options 1.25, 5, 10, or 20 MHz Entire bandwidth divided into 128, 512, 1024 or2048 subcarriers
SOFDMA: SOFDMA is used for mobile Wi-Max mode. It adjusts the size of FFT while fixing the sub-carrier frequency Smaller FFT size is given to lower bandwidthchannels, while larger FFT size to widerchannels Capacity of each individual sub-channel remainconstant By making the sub-carrier frequency spacingconstant, SOFDMA reduces system complexity ofsmaller channels and improves performance ofwider channels.
SUB-CHANNELIZATION Defines sub-channels that can be allocated tosubscriber stations (SSs) Depends on : Channel Conditions Data requirement Base Station (BS) can allocate : more transmit power to user devices (SSs) with lowerSNR like for indoor SSs. less power to user devices with higher SNR. Subchannelization in the uplink can save a userdevice transmit power because it can concentratepower only on certain sub-channel allocated to it.
Picture. Uplink Subchannelization in WiMAXIn OFDM, only one SS transmits in one time slot.In OFDMA, several SSs can transmit at the same time slot over several sub-channels.
MODULATION SCHEMES In Wimax the modulation schemes used are: Qpsk (Quadrature Phase Shift Keying) QAM-16, 64, & 256 QPSK uses four points on the constellationdiagram In QPSK the phase is changed in 4 ways forsending data bits. QPSK can encode two bits per symbol.
QAM is a technique in which the amplitude andphase varies simultaneously for sending higherdata rate QAM is a combination of ASK and PSK. In QAM-16, 4 bits are send on each single changewith the phase change of 22.5 degree In QAM-64, 6 bits are send on each single changewith the phase change of about 5.5 degree Same as for QAM-256 , 8 bits are send.
WI-MAX RADIOS A radio contains both a transmitter (sends) and a receiver(receives). WiMAX antennas, just like the antennas for carradio, cell phone, FM radio, or TV, are designedto optimize performance for a given application.
OMNI DIRECTIONAL ANTENNAS Omni directional antennas are used for point-to-multipointconfigurations. Omni directional antenna broadcasts 360 degree from the basestation. Omni directional antennas are good for situations where thereare a lot of subscribers located very close to the base station.
SECTOR ANTENNAS A sector antenna, by 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-degreeservice area rather than use an omni-directional antenna due tothe superior performance of sector antennas over an omni-directional antenna.
PANEL ANTENNAS Panel antennas are most often used for point-to-pointapplications Panel antennas are usually a flat panel of about one footsquare.
WIMAX VOIP Voice over Internet Protocol (VoIP) offers a wider range ofvoice services at reduced cost to subscribers and serviceproviders alike. The diagram below illustrates a typical solution where aWiMAX service provider can obtain wholesale VoIP services(no need for the WiMAX service provider to install and operatea VoIP soft switch) at about $5/number/month and resell toenterprise customers at $50.