Le L c e t c u t re r e /WiMax Ma A MA C/ C PHY HY Te T c e h c n h i n cal l Ov O er e v r iew e Ilenia Tinnirello

Transcript

1 Lecture /WiMax A MAC/PHY Technical Overview

2 1. Introduction

3 Moore s Law for Mobile Internet 3 Screen Ultra Mobile PC Sub-Notebook 17 Screen Entertainment & Productivity Notebook Thin and Light Notebook NEAR FUTURE ~10X LOWER POWER ~10X MORE MOBILE Statements are vs. current devices Product descriptions, plans and comparisons provided are estimates only and subject to change without notice

4 Monthly ARPU Est. The Economic Challenge: $100 Device Cost $80 $60 $40 $20 $0 90% Attach Rate Goal + WiMAX Tomorrow WiFi Today 3G Today <10% Attach Rate $20 $40 $60 $80 $100 $120 PC Card Cost Est. Source: Intel, Instat, Q year goal for the mobile Internet worldwide: $30 - $30 Can be achieved only by volume economics

5 Mobile Broadband Wireless Access (MBWA)

6 Think of Internet There are three possible ways to access internet. Broadband access Uses DSL or cable modem at home and T1 or T3 line at office WIFI Uses WIFI routers at home and hotspots on the road Dial Up Connection A new one: WiMax!! Target scenario: Wireless ADSL

7 How WiMax works?

8 Modes of Operation Non-Line of sight Uses a lower frequency range. Line of sight Uses a higher frequency range.

9 WIMAX CHIPS WiMAX Mini-PCI Reference Design Intel s first WIMAX chip

10 WiMax/IEEE Technical name: IEEE Requirements: Range- 50 km from base station Speed- 70 Megabits per second Frequency bands- 2 to 11 and 10 to 66(licensed and unlicensed bands respectively) Defines both MAC and PHY layer and allows multiple PHY layer specifications

11 IEEE Architecture IEEE Protocol Architecture has 4 layers: Convergence, MAC, Transmission and physical, which can be mapped to two OSI lowest layers: physical and data link.

12 IEEE Topologies P2MP Mesh BS connected to Public Networks BS serves Subscriber Stations (SS) Provides SS with first mile access to Public Networks Optional architecture for WiMAX

13 P2MP Topology

14 Mesh Topology

15 Benefits of WiMax Speed Faster than broadband service Wireless Not having to lay cables reduces cost Easier to extend to suburban and rural areas Broad Coverage Much wider coverage than WiFi hotspots

16 Benefits to Service Providers Allow service providers to deliver high throughput broadband based services like VoIP, high-speed Internet and Video Facilitate equipment compatibility Reduce the capital expenditures required for network expansion Provide improved performance and extended range

17 Benefits to Customers Range of technology and service level choices from both fixed and wireless broadband operators DSL-like services at DSL prices but with portability Rapidly declining fixed broadband prices No more DSL installation fees from incumbent

18 WiMax vs. WiFi: Scalability Wide (20MHz) frequency channels MAC designed to support 10 s of users a Channel bandwidths can be chosen by operator (e.g. for sectorization) 1.5 MHz to 20 MHz width channels. MAC designed for scalability. independent of channel bandwidth MAC designed to support thousands of users.

19 WiMax vs. WiFi: Performance Channel Bandwidth Maximum Data Rate Maximum bps/hz MHz 54 Mbps 2.7 bps/hz a MHz 100 Mbps 5.0 bps/hz

20 WiMax vs. WiFi: Quality of Service Contention-based MAC (CSMA/CA) => no guaranteed QoS a Grant-request MAC Standard cannot currently guarantee latency for Voice, Video Standard does not allow for differentiated levels of service on a per-user basis e (proposed) QoS is prioritization only Designed to support Voice and Video from ground up Supports differentiated service levels: e.g. T1 for business customers; best effort for residential. Centrally-enforced QoS

21 WiMax vs. WiFi: Range Optimized for ~100 meters a Optimized for up to 50 Km No near-far compensation Designed to handle many users spread out over kilometers Designed to handle indoor multipath delay spread of 0.8µ seconds Optimization centers around PHY and MAC layer for 100m range Designed to tolerate greater multi-path delay spread (signal reflections) up to 10.0µ seconds PHY and MAC designed with multimile range in mind

22 WiMax vs. 3G Using an assortment of proprietary and standards-based technologies, such as OFDM and W-CDMA,WiMax has a clear advantage over 3G The advantages include Higher Throughput Low Cost Lower Latency

23 WiMax vs. 3G WiMax spectrum is more economical than 3G. The price paid per Hz is as much as 1000 times lower than for 3G spectrum The low cost is a clear driver for service providers to enter the field of wireless services with WiMax

24 Bandwidth Allocation

25 WiMax in Europe Spain: Iberbanda has integrated a pre-wimax technology to its broadband network Norway: Allocations of about 150 licences for the frequency range GHz Switzerland: Licences assigned for WLL in the range GHz enabled for WiMax too UK: Telabria has started a public network based on WiMax Italy: assigned at beginning in the range GHz

26 WiMax in Italy: National Licenses ARIADSL S.p.A A.F.T. BLOCCO A

27 WiMax in Italy: National Licenses BLOCCO B E-VIA GRUPPO RETELIT TELECOM ITALIA S.p.A. TOURIST FERRY-BOAT/ TEMIX/MEDIANET COMUNICAZIONI

28 BLOCCO C WiMax in Italy: Regional Licenses A.F.T. BRENNERCOM MGM Productions/Profit Group Ribes/Hal Service/Lan Service/ Informatica System/Tex97/B.B.Bell Assomax Infracom City Carrier ARIADSL

29 Active Offers (from October 2008) ARIA Family 2 Mbit/s VELOCITÀ DI CONNESSIONE 2MBIT/S (UP/DOWN) 100 KBIT/s DI BANDA GARANTITA CANONE MENSILE 23,94 ARIA Family 4 Mbit/s VELOCITÀ DI CONNESSIONE 2MBIT/S (UP/DOWN) 180 KBIT/s DI BANDA GARANTITA CANONE MENSILE 34,94 ARIA Entry 2 Mbit/s VELOCITÀ DI CONNESSIONE 2MBIT/S (UP/DOWN) 230 KBIT/s DI BANDA GARANTITA CANONE MENSILE 40,00 ARIA Office 4 Mbit/s VELOCITÀ DI CONNESSIONE 2MBIT/S (UP/DOWN) 340 KBIT/s DI BANDA GARANTITA CANONE MENSILE 70,00 ARIA Enterprise 4 Mbit/s VELOCITÀ DI CONNESSIONE 2MBIT/S (UP/DOWN) 480 KBIT/s DI BANDA GARANTITA CANONE MENSILE 120,00

30 Active Offers MAX 20 Velocità di 7Mega al secondo in download e 1 Mega al secondo in upload, senza limiti di tempo nè di traffico. MAX 30 Velocità di 7Mega al secondo in download e 1 Mega al secondo in upload, senza limiti di tempo nè di traffico + VOCE MAX 45 Velocità di 7Mega al secondo in download e 1 Mega al secondo in upload, senza limiti di tempo nè di traffico + VOCE + 3 ore/mese verso i cellulari Canone di attivazione 50 se in addebito diretto o 100 se con bollettino postale Modem radio Gratuito Navigazione gratuita negli hot spot

31 2. Network Architecture

32 Point-to-Multipoint Wireless MAN: not a LAN Base Station (BS) connessa alle reti pubbliche Ogni BS serve un certo numero di Subscriber Stations (SSs) Ogni SS tipicamente copre un edificio Rappresenta la connettivita radio a larga banda per l ultimo miglio Confronto con le Wireless LAN: Servizio multimediali e a qualita di servizio Molti piu utenti Data rate molto piu alti Distanze maggiori

33 Wireless MAN Adaptive PHY (burst-by-burst adaptivity not shown)

34 Network Architecture Divisione fornitore di rete da fornitore di servizi!!

35 Network Topology MAC Address

36 Point-to-Multi Point (PMP)

37 MESH Mode

38 3. Protocolli

39 BWA Working group

40 Wireless Interoperability for Microwave Access (WiMAX) Il WiMAX Forum promuove la tecnologia IEEE per l accesso wireless in ambiente metropolitano (Wireless Metropolitan Area Network, WMAN) certificha l interoperabilità tra i dispositivi basati sulla tecnologia IEEE

41 Protocolli

42 MAC Sub-Layers

43 MAC Sub-Layers (2)

44 MAC Sub-Layers (3)

45 Frequency Bandwidths GHz con licenza fenomeno attenuativo dovuto a strutture, pioggia, ecc. Line-Of-Sight (LOS) 2-11 GHz con licenza Non-Line-Of-Sight (NLOS) fenomeno multi-path 2-11 GHz senza licenza Non-Line-Of-Sight (NLOS) fenomeno multi-path interferenza dovuta ad altri utenti

46 Physical Layer (PHY) Modulazione Single-Carrier Modulazione Multi-Carrier Orthogonal Frequency Division Multiplexing (OFDM)

47 Orthogonal Frequency Division Multiplexing (OFDM)

48 Physical Layer Details PHY basato sul frame Accesso multiplo Time Division Multiple Access (TDMA) Duplexing Frequency Division Duplexing (FDD) Time Division Duplexing (TDD)

49 Duplexing Time-Division Duplex (TDD) DL & UL time-share the same RF channel Dynamic asymmetry SS does not transmit/receive simultaneously (low cost) Frequency-Division Duplex (FDD) Downlink & Uplink on separate RF channels Static asymmetry Half-duplex SSs supported SS does not transmit/receive simultaneously (low cost)

50 Duplexing

51 Physical Layer Summary Designation Applicability MAC Duplexing WirelessMAN-SC GHz Licensed Basic TDD, FDD WirelessMAN-SC 2-11 GHz Licensed Basic, (ARQ), (STC), (AAS) TDD, FDD 2-11 GHz Licensed Basic, (ARQ), TDD, FDD (STC), (AAS) WirelessMAN-OFDM 2-11 GHz Licenseexempt Basic, (ARQ), (STC), (DFS), (MSH), (AAS) TDD 2-11 GHz Licensed Basic, (ARQ), (STC), (AAS) TDD, FDD WirelessMAN-OFDMA 2-11 GHz Licenseexempt Basic, (ARQ), (STC), (DFS), (MSH), (AAS) TDD

52 Definitions Service Data Unit (SDU) Data units exchanged between adjacent layers Protocol Data Unit (PDU) Data units exchanged between peer entities Connection and Connection ID a unidirectional mapping between MAC peers over the airlink (uniquely identified by a CID) Service Flow and Service Flow ID a unidirectional flow of MAC PDUs on a connection that provides a particular QoS (uniquely identified by a SFID)

53 Adaptive Burst Profiles Burst profile Modulation and FEC Dynamically assigned according to link conditions Burst by burst, per subscriber station Trade-off capacity vs. robustness in real time Roughly doubled capacity for the same cell area Burst profile for downlink broadcast channel is well-known and robust Other burst profiles can be configured on the fly SS capabilities recognized at registration

54 General Downlink Frame Structure Downlink Interval Usage Code (DIUC) indicates burst profile Per le stazioni half-duplex, in modalita FDD

55 Burst FDD Framing DOWNLINK UPLINK frame Broadcast Half Duplex Terminal #1 Full Duplex Capable User Half Duplex Terminal #2 Allows scheduling flexibility

56 General Uplink Frame Structure Uplink Interval Usage Code (UIUC) indicates burst profile

57 Frame Structure Summary

58 MAC Common Part Sub-Layer Management operations Access to the network Multi access Scheduling QoS support Power control

59 MAC Common Part Sub-Layer MAC Characteristics Connection oriented: service flows (SF) over virtual connections (CID: 16 bit) SS have standard bit MAC, only used as equipment id Channel access controlled by BS through UL-MAP, DL-MAP Services offered to higher layers Legacy time-division multiplex voice and data Internet protocol connectivity Support any application flow: data, voice, VoD, video streaming Continuous and bursty traffic support Reservation/Polling scheme for resource allocation Scheduling non standardized: provide a way for vendors to differentiate their equipments

60 Management Connections Upon entering the network, the SS is assigned three management connections in each direction Basic connection: transfer of short time-critical control messages Primary management connection: longer delay-tolerant messages (used of authentication and connection setup) Secondary management connection: transfer of other management protocols messages such as DHCP, TFTP, SNMP SS Basic Primary Secondary

61 Data Connections SSs are allocated transport unidirectional connections for the contracted services Typically assigned in pairs Additional connections for other purposes Contention-based initial access Broadcast or multicast transmissions SS CID1 CID2 CID3

62 MAC PDU

63 MAC Management Messages

64 Generic MAC Header

65 MAC Sub-Header Esistono 5 tipi Mesh Fragmentation Packing Fast Feedback Allocation Grant Management

66 Sub-Header

67 Fragmentation

68 Fragmentation sub-header

69 Packing

70 Packing sub-header

71 Difference between concatenation and packing

72 Network Entry Process

73 Network Entry Process 1. syncronization 3. registration 2. ranging to find the RTD

74 Initial Ranging

75 Capability Negotiation

76 Service Flow Ad ogni flusso di dati dello stesso tipo e associato un Service Flow Ogni service flow e caratterizzato da un set di parametri diqos throughput ritardo jitter probabilità di perdere un pacchetto Ogni service flow appartiene ad una classe di servizio a seconda dei parametri di QoS specificati

77 Service Flow Management Ciascun service flow ha un identificativo (SFID) di 32 bit associato ad un Connection Identifier (CID) di 16 bit I service flow possono essere configurati a priori o dinamicamente possono essere creati, modificati ed eliminati a tale scopo sono definiti dei messaggi di MAC management

78 Service Classes Unsolicited Grant Service (UGS) e.g. VoIP Real-time Polling Service (rtps) e.g. MPEG Non-Real-time Polling Service (nrtps) e.g. FTP Best effort

79 Unsolicited Grant Service (UGS) Allocazione statica di banda per la trasmissione uplink della SS Disegnato per supportare Service Flow realtime che generano pacchetti di dimensione costante su una base periodica (p.e. Voice over IP, VoIP) Non serve sollecitare ulteriori allocazioni Questo meccanismo consente di eliminare overhead ed i ritardi introdotti dal meccanismo di richiesta di banda garantire una banda costante che soddisfa i requisiti real-time dell applicazione

80 Real-time Polling Service rtps Allocazione statica di banda minima + possibilita di chiedere altra banda in piggybacking Disegnato per supportare traffico real-time che genera pacchetti di lunghezza variabile su una base periodica (p. e. MPEG video) Questo meccanismo consente soddisfare i requisisti real-time la SS richiede la banda di cui ha bisogno

81 Non real-time Polling Service nrtps Allocazioni periodiche di banda per trasmettere richieste di banda + ulteriori richieste di banda a contesa Disegnato per supportare traffico non real-time che genera burst di dimensione variabile su una base periodica (p.e. FTP) Le richieste di banda possono essere inviate ad intervalli regolari, senza bisogno di contendere Questo meccanismo introduce maggiore overhead dovuto alle richieste la banda è quella necessaria e questo incrementa l efficienza

82 Best Effort (BE) Allocazioni di banda solo dopo messaggi di richiesta inviati a contesa L obiettivo è fornire ad un traffico best effort un servizio più efficiente possibile

83 Multi Access Mechanisms Tre modalita di base banda garantita Voice over IP (VoIP) Polling Video streaming Contesa Web browsing Applicate, per ogni flusso di servizio, in base ai requisiti del servizio richiesto dalla SS banda ritardo

84 Requests and Grants La SS può richiedere banda in uplink adottando diversi meccansmi un messaggio di PiggyBack per richieste incrementali un messaggio di richiesta (BR) dopo polling o a contesa Le richieste sono espresse in byte poiché l allocazione temporale può variare in base alla modulazione e codifica adottata (adattamento al link) Le richieste da parte delle SS si riferiscono ad una connessione I grant generati dalla BS possono essere per connessione o per SS La SS ri-distribuisce il grant tra le sue connessioni

85 QoS Architecture

86 Contention-based BRs La scelta dello slot in cui trasmettere il Bandwidth Request (BR) avviene adottando un meccanismo di backoff esponenziale binario troncato la base della finestra di backoff è 2 la dimensione iniziale viene decisa dalla BS La SS estrae un numero casuale all interno della finestra di backoff la trasmissione della richiesta viene ritardata di un numero di slot pari al numero estratto Il Bandwidth Request (BR) viene trasmesso in un intervallo a contesa quindi si può verificare una collisione

87 Backoff Process

88 Contention Resolution

89 Polling-based BRs La BS alloca nel UL-MAP una banda che la SS può utilizzare per trasmettere Bandwidth Requests può essere per connessione o per SS Se la banda non è sufficiente per attivare un unicast polling verso tutte le SS inattive allora è possibile adottare un multicast polling anche in questo caso il polling non è un messaggio esplicito ma una banda allocata nel messaggio UL-MAP SS con delle connessioni UGS attive devono porre ad 1 il bit poll-me nel grant management sub-header per richiedere banda per il polling

90 OFDM/OFDMA PHY

91 OFDM PHY Parameters

92 Coding and Modulation

93 Downlink Sub Frame (FDD)

94 Downlink Sub Frame (TDD)

95 Uplink Sub Frame (TDD+FDD)

96 OFDMA Organization

97 Frame Structure (TDD+FDD)

98 Data Region

99 Example

100 Frame Structure

101 References IEEE (802.16REVd) IEEE (802.16e) Intel s Whitepapers, 2004 ( 08issue03/) IEEE Standard : A Technical Overview of the WirelessMAN Air Interface for Broadband Wireless Access, C. Eklund et al., IEEE Communication Magazine, June 2002 Broadband Wireless Access with /WiMax: Current Performance Benchmarks and Future Potential, A. Ghosh et al., IEEE Communication Magazine, Feb 2005 Fundamentals of WiMax, J. Andrews et al., Prentice Hall