Wireless Networks Part I

Transcription

1 ICT Technical Update Module Wireless Networks Part I Prof. Dr Harsha Sirisena Electrical and Computer Engineering University of Canterbury Outline Course Objective and Additional References Motivation Some History Future Wireless Network Technology Design Challenges Current Wireless Systems Emerging Wireless Systems Spectrum Regulations and Wireless Standards IEEE Family WLAN Wireless Routing Protocols Post Graduate Certificate in Professional Development Slide 2 Course Objectives After studying this course, you are expected to Demonstrate understanding of the fundamental problems, tradeoffs, and design issues that arise in wireless networking, as well as identify and critically evaluate wireless network technologies and solution approaches Understand the details of several particular protocols, as example implementations of fundamental principles, and digest descriptions of specific protocols, extracting the salient concepts Engage in original work and research in the area of wireless networks Post Graduate Certificate in Professional Development Slide 3 Post Graduate Certificate in Professional Development 1

2 Additional References Wireless communications : principles and practice,2nd Edition Theodore S. Rappaport. Computer networks 3rd Edition Andrew S. Tanenbaum. Data and computer communications, 7th Edition William Stallings. Post Graduate Certificate in Professional Development Slide 4 Motivation- Why wireless networks? No cost for installing wires or rewiring - Communications can reach where wiring is infeasible or costly, e.g., rural areas, mountains, old buildings, battlefield. - Auto-magical instantaneous communications without setup physical connection, e.g., WLAN - Communication satellites, global coverage, e.g., Iridium system Roaming allows flexibility to keep contacted Anywhere and Any time Post Graduate Certificate in Professional Development Slide 5 Motivation (cont.) Rapidly growing market trigger the public need for mobility and uninterrupted communications Consumers are used to the flexibility and will demand instantaneous, uninterrupted, fast access regardless where and when. Consumers and businesses are willing to pay for it Increasing dependence on telecommunication services for business and personal reasons Post Graduate Certificate in Professional Development Slide 6 Post Graduate Certificate in Professional Development 2

3 Some Wireless History Ancient Systems: Smoke Signals, Carrier Pigeons, The Birth of Radio - Radio invented in the 1880s by Guglielmo Marconi Sophisticated military radio systems were developed during and after the WW NTT/Japan deploys first cellular communication system Advanced Mobile Phone System (AMPS) deployed in U.S. in 900 MHz Band: supports 666 duplex channels Group Special Mobile defines European digital cellular standard, GSM US Digital Cellular phone system introduced IS-95 code-division multiple-access (CDMA) spread- spectrum digital cellular system deployed in U.S GSM system deployed in US, relabeled Global System for mobile communications FCC auctions off frequencies in Personal Communications System (PCS) band at 1.8 GHz for mobile telephony Number of cellular telephone users in U.S. > 50M Third generation cellular system standards Bluetooth standards.. Post Graduate Certificate in Professional Development Slide 7 Generations of Wireless Networking 1G: deployed in the 1980s was based on analog FM technologies. 2G: introduced on market in 1991 with applied digital technologies such as, TDMA,GSM, cdmaone. 2G offered short messages and low-rate data services for customers. 2.5G : introduced ability to use packet switched (vs. circuit switched) radio connections. For GSM system, this is called General Packet Radio Service (GPRS). GPRS offers users the opportunity to be always online, while only being charged for data transferred. 3G: achieves a maximum bit rate of 2 Mbps and offers packet-switched multimedia services (data, video, etc.) as well as voice services. GSM/TDMA operators can evolve towards EDGE or WCDMA with higher and variable bit rates and improved spectrum efficiency. cdmaone operators can evolve to cdma2000 4G: Expected to build upon 3G and evolved 3G systems. A current discussion is a 4G of wireless networks envisaged available in about a decade Post Graduate Certificate in Professional Development Slide 8 Future Trends and Technologies Multi-input and Multi-output i.e., multi-antenna systems (MIMO) Ultra Wideband (UWB) Software-Defined Radio (SDR) Ad hoc and Sensor Networks Fixed (or semi-fixed) Broadband 4G Cellular (discussed already) New generations of wireless networking (terrestrial wireless i.e., cellular or satellite) will result in higher rate integrated multimedia communications The complexity of the management of network resources (e.g. bandwidth, power, capacity) will be significant with increasing generation or evolution. Post Graduate Certificate in Professional Development Slide 9 Post Graduate Certificate in Professional Development 3

4 Design Challenges Wireless channels are a difficult and capacity-limited broadcast communications medium Traffic patterns, user locations, and network conditions are constantly changing Applications are heterogeneous with hard constraints that must be met by the network Energy and delay constraints change design principles across all layers of the protocol stack Post Graduate Certificate in Professional Development Slide 10 Multimedia Requirements Delay Packet Loss BER Data Rate Traffic Voice Data Video <100ms - <100ms <1% 0 <1% Kbps Mbps 1-20 Mbps Continuous Bursty Continuous One-size-fits-all protocols and design do not work well Post Graduate Certificate in Professional Development Slide 11 Current Wireless Systems Cellular Systems and its evolution -GSM - GPRS -UMTS Satellite System Bluetooth Post Graduate Certificate in Professional Development Slide 12 Post Graduate Certificate in Professional Development 4

5 Wide Area Cellular Services The Cellular Principle Relies on the concept of concurrency - delivered through channel reuse i.e. reusing channels in different cells Total coverage area is divided into cells - only a subset of channels available in each cell All channels partitioned into sets - sets assigned to cells Rule: assign the same set to two cells that are sufficient geographically distant so that interference is small Purpose: increased capacity! Post Graduate Certificate in Professional Development Slide 14 Advantages of Cellular Networks More capacity due to spectral reuse Lower transmission power due to smaller transmitter/receiver distances More robust system as Base Station problem only effects the immediate cell More predictable propagation environment due to shorter distances Post Graduate Certificate in Professional Development Slide 15 Post Graduate Certificate in Professional Development 5

6 SD Disadvantages of Cellular Networks Need for more infrastructure Need for fixed network to connect Base Stations Some residual interference from co-channel cells Handover procedure required Post Graduate Certificate in Professional Development Slide 16 Architecture of a GSM Network Mobile Station Base Station Subsystem Network Subsystem Other Networks SIM ME BTS BSC MSC/ VLR GMSC PSTN PLMN + EIR HLR AUC Internet Note: Interfaces have been omitted for clarity purposes. Post Graduate Certificate in Professional Development Slide 17 Mobile Station (MS) Mobile Equipment -Fixed - Portable - International Mobile Equipment Identity (IMEI) number Subscriber Identity Module (SIM) - Personal Identification Number (PIN) - International Mobile Subscriber Identity (IMSI) number - Enables access to subscribed services - Smart card Post Graduate Certificate in Professional Development Slide 18 Post Graduate Certificate in Professional Development 6

7 Base Transceiver Station - BTS Usually referred to as the Base Station Provides the interface to the network for the MS Handles all communications with the MS Less intelligent than analogue equivalent - cheaper than analogue systems - bypass analogue in less wealthy countries intelligence now deployed on MS - for example, when to perform a handover Transmitting power determines cell size Post Graduate Certificate in Professional Development Slide 19 Base Station Controller - BSC Controls Base Stations - up to several hundred depending on manufacturer Manages radio channels - allocation and release Coordinates Handover Physical location may vary Abis interface - between BSC and BTS Post Graduate Certificate in Professional Development Slide 20 Mobile Switching Centre (MSC) Performs all switching/exchange functions Handles - Registration - Authentication - location updating A GSM network must have at least one MSC May connect to other networks, e.g., PSTN - Gateway MSC (GMSC) Post Graduate Certificate in Professional Development Slide 21 Post Graduate Certificate in Professional Development 7

8 SD Home Location Register (HLR) Administrative information for all subscribers IMSI number actual phone number permitted supplementary services current location i.e. which VLR subscriber is currently registered with parameters for authentication and ciphering One HLR per GSM PLMN Post Graduate Certificate in Professional Development Slide 22 Integrating GPRS Mobile Station Base Station Subsystem Network Subsystem Other Networks SIM ME BTS BSC MSC/ VLR GMSC PSTN EIR HLR AUC PLMN + SGSN GGSN Internet Post Graduate Certificate Note: in Interfaces Professional have Development been omitted for clarity purposes. Slide 23 GPRS MS Two Components - Mobile Terminal (MT) - SIM card Three Classes of terminal - Class A - simultaneous circuit switched (GSM) and packet switched (GPRS) traffic - Class B- supports both GSM and GPRS connections but not both at the same time. One call is suspended for the duration of the other - Class C - handless both GPRS or GSM but can only be connected to one at the same time. Post Graduate Certificate in Professional Development Slide 24 Post Graduate Certificate in Professional Development 8

9 GPRS NSS Two new nodes introduced for packet data Serving GPRS Support Node (SGSN) : handles all packet data for the appropriate geographic area - monitors GPRS users - handles security and access control - may be regarded as the packet switched equivalent of the circuit-switched MSC Gateway GPRS Support Node (GGSN) - internetworking functionality - routes incoming data to correct SGSN - translates between different protocols and formats Details of data services added to HLR Post Graduate Certificate in Professional Development Slide 25 GPRS Characteristic Data capacity increased considerably Depending on 14.4 kb/s per channel, kb/s 21.4 kb/s per channel, kb/s achieved BUT up to 8 users per channel! Minimum set-up time always-on connection Charging determined by actual data not time Post Graduate Certificate in Professional Development Slide 26 Integrating EDGE Minimum changes to the existing network New Modulation scheme - 8 phase shift keying (8PSK) - 3 bits of information per signal pulse - data rates increased by a factor of three Post Graduate Certificate in Professional Development Slide 27 Post Graduate Certificate in Professional Development 9

10 SD EDGE - NSS Minimum impact on the core network SGSN & GGSN practically independent of data rates Some minor software upgrades Post Graduate Certificate in Professional Development Slide 28 3G - UMTS Mobile Station Base Station Subsystem Network Subsystem Other Networks SIM ME BTS BSC MSC/ VLR GMSC PSTN EIR HLR AUC PLMN RNS USIM ME Node B RNC SGSN GGSN Internet + UTRAN Note: Interfaces have been omitted for clarity purposes. Post Graduate Certificate in Professional Development Slide 29 UMTS - MS User Equipment Mobile Equipment UMTS SIM (USIM) Air interface UMTS Terrestrial Radio Access (UTRA) -W-CDMA -TD-CDMA Post Graduate Certificate in Professional Development Slide 30 Post Graduate Certificate in Professional Development 10

11 UMTS BSS Radio Network Subsystem Two new network elements Node B equivalent of a BTS Radio Network Controller supports a number of Node Bs equivalent of a BSC Obviously, UMTS has major implications for the BSS Post Graduate Certificate in Professional Development Slide 31 CDMA BASIC CDMA (Code Division Multiple Access) splits calls into fragments and send them over different frequencies simultaneously The use of multiple frequencies gives CDMA effective protection against interference and lost calls CDMA supports true packet switching and does not use time slots, therefore is more bandwidth efficient than TDMA -- also a more direct path to 3G Post Graduate Certificate in Professional Development Slide 32 Why do carriers want to move to 3G? Faster speeds--able to handle more calls Efficiencies in data handling - Integration with the Internet technology More capable, multi-media handsets and devices Global interoperability and roaming Advanced services and more profitable revenue opportunities Post Graduate Certificate in Professional Development Slide 33 Post Graduate Certificate in Professional Development 11

12 Some Urgent 3G Drivers Need to increase wireless data revenues and ARPU as voice prices decline Staggering investment already made in preparing for 3G upgrades Pressure by device makers and governments - 3G License clock ticking in Europe Dramatic success stories: - Korea, Japan markets are embracing 3G Fear of falling even further behind - Competition from WiFi as the high-speed alternative Post Graduate Certificate in Professional Development Slide 34 3G Systems Overview 3G Migration SOURCE: CDMA Development Group (CDG) Post Graduate Certificate in Professional Development Slide 35 Future mobility will be provided with higher data rates and Ubiquitous access - This implies the need for seamless wide area and office coverage - Future remote access techniques will mirror existing to protect current investments Higher data rates and better coverage will be realized using disparate types of Wireless Technologies - Mobility across disparate networks is a significant change to the paradigm of current mobile networks. - Mobility is attributed to L2 and L1 abstraction through use of IP (Mobile IP). Mobility Overview Data Rates and Ranges of Wireless Technologies SOURCE: ITU Post Graduate Certificate in Professional Development Slide 36 Post Graduate Certificate in Professional Development 12

13 Standards Evolution to 3G Worldwide Japan Europe/Parts of Asia Americas/Parts of Asia 1st Gen TACS NMT/TACS/Other AMPS 2nd Gen PDC GSM TDMA CDMA 3rd Gen W-CDMA/UMTS cdma2000 EDGE cdma2000 Instead of solving the 2G network differences via 3G, we will continue to have W-CDMA and cdma2000 as separate networks. Both will be optional implementation modes in one 3G standard specification. Basic 3G phones will support one or the other. Global phones will be able to roam from one to the other. Post Graduate Certificate in Professional Development Slide 37 Application Platforms for Cellular Networks WAP: discredited in first outing, but still alive and well as a backend mobile server standard SMS: proven worldwide but just emerging in US; limited to plain text messaging MMS: standard behind the exchange of pictures from camera phones; also for many audio and graphic formats imode: proven in Japan; export still in doubt J2ME (Java for mobile): large developer following and handset deployment; confused business models BREW: CDMA app platform: big in a few areas; clearer business and distribution model Post Graduate Certificate in Professional Development Slide 38 Examples: Evolution of messaging Rich Call Browsing Messaging Versatility of Content and User Benefits SMS Text Picture Messaging Text & Graphics Multimedia Message Service Digital image input Mobile Multimedia New content types Time Post Graduate Certificate in Professional Development Slide 39 Post Graduate Certificate in Professional Development 13

14 SMS SMS=Short Message Service=Current Worldwide Killer Application A basic text messaging service for sending messages up to 160 characters to mobile phones Runs on separate channel from voice traffic-much cheaper for operators to carry text messages (started out as free service in many countries) Overwhelming user uptake in Europe and A/P --billions of messages sent each month; very profitable for carriers Post Graduate Certificate in Professional Development Slide 40 Emerging Systems Ad hoc wireless networks Ultra Wideband Network Post Graduate Certificate in Professional Development Slide 41 Ad hoc Networks Post Graduate Certificate in Professional Development 14

15 Introduction and Basic Concepts Post Graduate Certificate in Professional Development Slide 43 Ad Hoc Network Definition In Latin, "ad hoc" literally means " for this purpose only " An ad-hoc network is a wireless LAN, in which some devices are part of the network only for the duration of a communication session or while in some close proximity to the rest of the network. A "mobile ad hoc network " (MANET) is an autonomous system of mobile routers (and associated hosts) connected by wireless links forming an arbitrary graph. Routers are free to move randomly and organize themselves arbitrarily; network topology may change rapidly and unpredictably. May operate in a stand-alone fashion, or may be connected to the Internet. An ad hoc network can be regarded as a "spontaneous network " : a network that automatically "emerges " when nodes gather together. Post Graduate Certificate in Professional Development Slide 44 Ad Hoc Networks Advantages Ease of deployment Speed of deployment Decreased dependence on infrastructure Post Graduate Certificate in Professional Development Slide 45 Post Graduate Certificate in Professional Development 15

16 Applications of Ad Hoc Networks Post Graduate Certificate in Professional Development Slide 46 Characteristics and Requirements Autonomous and spontaneous nature of nodes Distributed Algorithms to support security, reliability and consistency of exchanged and stored information Time-varying network topology (no pre-existing infrastructure or central administration) Scalable routing and mobility management techniques to face network dynamics Fluctuating link capacity and network resources Enhanced functionalities to improve link layer performance, QoS network support and end-to-end efficiency Low-power devices Energy conserving techniques at all layers Post Graduate Certificate in Professional Development Slide 47 Challenges Broadcast nature of the wireless medium - Limited wireless transmission range - Hidden terminal problem - Exposed terminal problem - Capture problem - Intruding terminal problem Packet losses due to transmission errors Mobility-induced route changes Mobility-induced packet losses Battery constraints Potentially frequent network partitions Ease of snooping on wireless transmissions Post Graduate Certificate in Professional Development Slide 48 Post Graduate Certificate in Professional Development 16

17 Multi Hopping Data routes may traverse multiple links to reach a destination It increases overall network capacity since the spatial domain could be reused for concurrent but physically separate sessions It conserves transmit energy resources reduces interference. Post Graduate Certificate in Professional Development Slide 49 Ultra Wideband Networks What is Ultra Wideband Short pulse waveforms Carrier-free, baseband, impulse A few cycles of an RF carrier Very large fractional bandwidths Bandwidth inversely proportional to pulse duration Typically > 20% (FCC 2002 definition) Low duty cycles resulting in low average energy densities Typically produced by impulse- or step-excited antennas, filters, etc. Not all UWB is non-interfering (Regulatory issues) Spectrally filtered Spectrally unfiltered Post Graduate Certificate in Professional Development Slide 51 Post Graduate Certificate in Professional Development 17

18 UWB Bandwidth FCC report and order Part 15 (Feb,2002) pave the way for commercialization of UWB Post Graduate Certificate in Professional Development Slide 52 Unique UWB Properties Advantages: 1.Low-power operation : transceiver circuitry power requirements are low, under noise roof 2.Low cost: the complexity of the analogy front-end is drastically reduced due to its intrinsic baseband transmission,. 3.Low probability of detection& jamming: low energy per frequency band and the use of precisely timed patterns 4.Ability to penetrate walls in indoor environment: the lower frequencies used 5 Higher immunity to multi-path fading effects: increased signal diversity (frequency diversity) 6.Availability of precise location information: precise nanosecond pulses for transmission Disadvantage: 1.Long channel acquisition time in the order of milliseconds, compared to microseconds in narrow band system 2.Regulatory considerations over such a wide bandwidth will limit the radiated power( mobile service distance) Post Graduate Certificate in Professional Development Slide 53 Major UWB Application Areas Communications LPD (Low Probability of Detection) Wireless Audio, Data & Video Distribution RF Tagging & Identification Radar Collision/Obstacle Avoidance Precision Altimetry Intrusion Detection ( see through wall ) Ground Penetrating Radar Precision Geolocation Asset Tracking Personnel localization Post Graduate Certificate in Professional Development Slide 54 Post Graduate Certificate in Professional Development 18

19 Spectrum Regulation Spectral Allocation in US controlled by FCC (commercial) or OSM (defense) FCC auctions spectral blocks for set applications. Some spectrum set aside for universal use Worldwide spectrum controlled by ITU-R Regulation can stunt innovation, cause economic disasters, and delay system rollout Post Graduate Certificate in Professional Development Slide 55 Standards Interacting systems require standardization Companies want their systems adopted as standard - Alternatively try for de-facto standards Standards determined by TIA/CTIA in US - IEEE standards often adopted Worldwide standards determined by ITU-T - In Europe, ETSI is equivalent of IEEE Post Graduate Certificate in Professional Development Slide 56 Conclusion The wireless vision encompasses many exciting systems and applications Technical challenges transcend across all layers of the system design Wireless systems today have limited performance and interoperability Standards and spectral allocation heavily impact the evolution of wireless technology Post Graduate Certificate in Professional Development Slide 57 Post Graduate Certificate in Professional Development 19