Network Design - Chapter 10: Wireless Technology in Access Networks Continued - University of Pittsburgh

Nội dung text: Network Design - Chapter 10: Wireless Technology in Access Networks Continued - University of Pittsburgh

1. Wireless Technology in Access Networks David Tipper Associate Professor Department of Information Science and Telecommunications University of Pittsburgh Slides 10 Wireless in Access Networks • Increasing use of wireless technology in access networks – IEEE 802.11 technology for Wireless LANS – WiMAX for last mile – Free Space Optical for short line of sight high bandwidth connections – Proprietary solutions for wireless multi- hop mesh networks (based on 802.11 or WiMAX) – Variety of Speeds,Cost, Coverage Range, etc. 2 Telcom 2110 Spring 06
2. Future/Emerging Technology • Focus on increasing data rates, expanding coverage area of existing technology – IEEE 802.11n > 100 Mbps for 802.11 networks – New technology or application proposed • Multi-hop wireless mesh networks based on 802.11 – IEEE 802.11s (1-2 years?) or proprietary (now) • Wireless MAN and last mile – WiMAX, HyperMAN • Cognitive/Software Radios – handset/wireless card is programmable can be reconfigured to different radio technologies and different frequency bands – (e.g., cellular -> 802.11a -> WiMAX, etc.) 5 Telcom 2110 Spring 06 WiMAX Standard • Worldwide Interoperability for Wireless Microwave Access (WiMAX) – Focus is interoperable multi-vendor fixed/nomadic/mobile/ wireless access networks using microwaves – European Telecommunication Standards Institute (ETSI) • High performance radio metropolitan area network (HiperMAN) – IEEE 802.16 group (now main standardization body) – WiMAX forum industry alliance focusing on interoperability • WiMAX developed as a Metropolitan Area Network (MAN) protocol intended as a wireless alternative to DSL and T1 level services for last mile broadband access. – Point to Multipoint (PMP) protocol – Scope expanded to include mobility and higher data rates • Focus on both licensed and unlicensed spectrum deployment • TDD and FDD duplexing support with flexible channel sizes 6 Telcom 2110 Spring 06
3. WiMAX Architecture 7 Telcom 2110 Spring 06 WiMax Service Architectures WiMax services Point to Multi-Point •Non-LOS, Wi-Fi sort of service, where a small antenna on a computer/ roof top connects to the tower. Possible mobile service to computer/handset • LOS, where a fixed antenna points straight at the WiMax tower from a rooftop or pole. (LOS can provide higher data rates) Point to Point • Focused LOS antennas – high data rates with longer distances 30-40 miles 8 Telcom 2110 Spring 06
4. IEEE 802.16 WiMAX Standards • 802.16a-2003 – System for 2-11GHz range • 802.16-2004 (802.16d) – System for 2-66 GHz range • 802.16e – Mobility support • 802.16f – Multi-hop functionality • 802.16g – addresses efficient handover and further improves the QoS support • 802.16 a/d define three MAC layers – SCa – single carrier – OFDM – 256 carriers – OFDMA – 2048 carriers (multiple access by assigning a subset to a user) • Flexible channel size 9 Telcom 2110 Spring 06 Physical layer definitions SCa OFDM OFDMA Frequency 2-11 GHz 2-11 GHz 2-11 GHz Modulation BPSK, QPSK, QPSK, QPSK, 16QAM, 16QAM, 16QAM, 64QAM, 64QAM 64QAM 256QAM No. of N/A 256 2048 subcarriers Duplexing TDD, FDD TDD, FDD TDD, FDD Channel 1.75-20 MHz 1.75-20 MHz 1.75-20 MHz Bandwith 10 Telcom 2110 Spring 06
5. Techniques used in 802.16 • Orthogonal Frequency Division Multiplexing (OFDM) – to reduce multipath effects and provide higher speeds • Error correction techniques • Adaptive modulation – adjust the modulation depending on the quality of the radio link • Admission control – Ensures that new flows do not degrade the quality of established flows • Scheduling: – traffic scheduling to provide some QoS traffic classes • Flexible Channel size • TDD and FDD modes supported 11 Telcom 2110 Spring 06 802.11/802.16 Spectrum UNII International International US Japan ISM Licensed ISM Licensed Licensed Licensed 1 2 3 4 5 GHz 802.16a has both licensed and license-exempt options ISM: Industrial, Scientific & Medical Band – Unlicensed band (802.11a,b, g) UNII: Unlicensed National Information Infrastructure band – Unlicensed band Licensed band 2.5 GHz US and 3.5 GHz International 13 Telcom 2110 Spring 06
6. Licensed Vs. License-Exempt Licensed License-Exempt Better QoS Fast Rollout Better NLOS reception at Lower Costs lower frequencies Higher barriers for More worldwide options entrance • Both solutions are based on IEEE 802.16-2004 standard, which uses OFDM in the physical (PHY) layer. • For creating bi-directional channels for uplink and downlink both Frequency Division Duplexing and Time Division Duplexing are used 14 Telcom 2110 Spring 06 Time Division Duplexing (TDD) Description A duplexing technique primarily used in license-exempt systems, which uses a single channel for uplink and downlink. Advantages Enhanced flexibility, easier to pair with smart antenna technologies, asymmetrical. Disadvantage Cannot transmit and receive at the same time. s Usage “Bursty”, asymmetrical data applications, environments with varying traffic patterns, where RF efficiency is more important than cost. 15 Telcom 2110 Spring 06
7. Frequency Division Duplexing (FDD) Description A duplexing technique primarily used in licensed systems that uses a pair of spectrum channels, one for the uplink and another for the downlink. Advantages Proven technology for voice, designed for symmetrical traffic, does not require guard time. Disadvantage Cannot be deployed where spectrum is s unpaired, spectrum is usually licensed, higher cost associated with spectrum purchase. Usage Environments with predictable traffic patterns, where equipment costs are more important than RF efficiency. 16 Telcom 2110 Spring 06 Licensed Systems in U.S. • In U.S. have licensed spectrum 2.459 GHz – 2.69 GHz • License 22.5 MHz - 8 licenses per geographic area – operator can acquire multiple licenses • Outside U.S. 3.5 GHz band widely used have range of 7 – 56 MHz license depending on country • TDD and FDD options – For example , TDD used with 5 MHz channels in 2.5 GHz band – For example FDD pair of 3.5 MHz channels (one uplink, one downlink) in 3.5 GHz band 17 Telcom 2110 Spring 06
8. WiMAX • Security – Authentication and Registration • PKI with X.509 digital certificates – Access Control • (similar to WPA) • MAC/IP address filtering • VPN etc. – Privacy • DES with 128 bit key (triple DES) • Plans to move to AES • Mobility/spectrum/cost are crucial issues as well as actual data rates 18 Telcom 2110 Spring 06 WiMax Applications • According to WiMax Forum it supports 5 classes of applications: 1. Multi-player Interactive Gaming. 2. VOIP and Video Conference 3. Streaming Media 4. Web Browsing and Instant Messaging 5. Media Content Downloads „ Basically the Triple Play 19 Telcom 2110 Spring 06
9. Application Requirements 20 Telcom 2110 Spring 06 Market Models WiMAX Benefits Small Wireless ISPs Lower Network CapEx Hot Spot Providers Lower backhaul OpEx DSL fill-in. Cost effective coverage of low Wireline / ILECs density areas Nomadic/Mobile broadband data services Cellular Operators competitive with wireline Cable Providers Broadband data service to businesses Alternative last mile to compete with ILEC Large ISPs broadband services New Entrants (e.g. Utilities, Leverage existing assets to deliver broadband Railroads, Retailers) service Satellite Need alternative last mile for uplink 21 Telcom 2110 Spring 06
10. Characteristics: xDSL vs. WiMAX Characteristics XDSL WiMAX Media specific Dedicated media Shared media Typical max. coverage 5 km (ADSL) / 7 km (SHDSL) 12 ~ 15 km (LOS), 1~2 km (NLOS) Central end – DSLAM Central end – Base Station (BS) Architecture Subscriber – xDSL NT Subscriber – Subscriber Station (SS) PTP, PTMP and mesh topologies ADSL downstream – 8 Mb/s BS – 70 Mb/s (bandwidth 14 MHz), 100 Mb/s (bandwidth 20 MHz) Bit Rate (max.) ADSL upstream – 800 kb/s SS – No limit (up to BS capacity), practical mean value is 4 Mb/s Roaming No Yes ATM level QoS Native MAC QoS support. QoS Service differentiation levels Scalability Some limitation because of To some hundreds per cell, depending crosstalk, DSLAM capacity on the traffic, interference limited dependent Symmetry Asymmetrical and Asymmetrical and symmetrical symmetrical Power requirement – Mains Battery or mains subscriber side 22 Telcom 2110 Spring 06 Characteristics: 802.111 vs. WiMAX WLAN WiMAX Typical max. Inferior to 100 m 12 ~ 15 km (LOS), 1~2 km (NLOS) coverage For NLOS environments (2-11 GHz Optimisation For indoor short range spaces band). Supports advanced antenna techniques LAN application. The number Efficient support of hundreds of SSs with of users can vary between one a limited number of users per SS. Scalability to several tens, with a Flexible bandwidth channels ranging 1.5- subscriber per CPE 20 MHz. Maximum spectral efficiency Maximum spectral efficiency 5 b/s/Hz. Bit Rate 2,7 b/s/Hz. 100 Mb/s in 20 MHz. channels 54 Mb/s in 20 MHz channels. Native MAC QoS support. QoS Without QoS support Service differentiation levels 23 Telcom 2110 Spring 06
11. WiMax Network Design • Network Design Factors are similar to cellular network and WLAN design • Factors are – Coverage Planning • Adequate Received Signal Strength throughout geographic coverage area • RF Interference: – Capacity Requirements • Need to provide enough data capacity – may need additional radio channels or base stations – Infrastructure Placement: • Site physical structure that houses or supports the base station must be RF friendly and have power. • Must be able to connect to backhaul network 24 Telcom 2110 Spring 06 WiMAX design steps • Obtain site topology • Determine coverage goals • Determine user population, location and application requirements • Create network design and installation guidelines • Make field measurements to verify design • Adjust design as required • Complete installation 25 Telcom 2110 Spring 06