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Broadband Wireless Technology: Current Status & Future Directions

Broadband Wireless Technology: Current Status & Future Directions. DEMO’98 Oct. 15, 1998 Berlin, Germany D. Raychaudhuri NEC USA, C&C Research Laboratories Princeton, NJ 08540. ray@ccrl.nj.nec.com. Introduction. Introduction: Broadband Wireless Vision.

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Broadband Wireless Technology: Current Status & Future Directions

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  1. Broadband Wireless Technology:Current Status & Future Directions DEMO’98 Oct. 15, 1998 Berlin, Germany D. Raychaudhuri NEC USA, C&C Research Laboratories Princeton, NJ 08540. ray@ccrl.nj.nec.com

  2. Introduction

  3. Introduction: Broadband Wireless Vision • Broadband wireless networks a key enabling technology for mobile multimedia services of the future……. (while also facilitating rapid/flexible deployment of high-speed access to fixed computing devices in the near-term) Growing Proportion of User Terminals --> 50% +? Future Telecom Network Mobile Comm Devices Broadband Wireless Access Network Mobile PDA/PIA Future Internet Semi-mobile Laptop, etc. Fixed PC/WS

  4. Introduction: Broadband Wireless Services Future wireless network should provide a range of generic transport services for various current & future applications Application Degree of Mobility Desired Bit-Rate Transport Modes Telephony high, med or low 9.6 Kbps-64 Kbps CBR Videophone/ camera uplink med or low 384 Kbps - 6 Mbps CBR or VBR ~ 1 Mbps peak E-mail packet/UBR med or low Mobile Internet Access low ~ 5-10 Mbps peak packet/UBR or VBR Fixed Internet Access static ~ 10-25 Mbps peak packet/UBR or VBR Video-on- demand CBR or VBR ~ 10-25 Mbps peak static

  5. Introduction: Broadband Wireless Application Regime 10 Mbps+ services Fixed - Moderate Mobility Packet Data + Voice/Video Application Regime for Broadband Wireless Microwave broadband 100 Mbps 10 Mbps Broadband PCS High-Speed WLAN Service Bit-Rate UMTS/ IMT-2000 Wireless LAN 1 Mbps LEOS, etc. 100 Kbps PCS Cellular 10 Kbps Mobility

  6. Introduction: Broadband Wireless Requirements • The above vision for ubiquitous broadband wireless implies the following high-level requirements for systems to be developed: • high-speed access capabilities • service integration & QoS • scalable (in terms of users, traffic, coverage area, etc.) • spectrally efficient • protocol compatibility (with future telecom network and Internet) • support for user mobility • mass-market cost/performance • …. • Important to consider all the above factors when evaluating candidate system architectures and component technologies...

  7. Network/Protocol Architecture

  8. Network Architecture: Integrated vs. Overlay Overlay Mobile Network (e.g. GSM) + broadband services More suitable for scalable/ubiquitous services... • Basic architectural options for broadband wireless systems: Multiple radio air interfaces “plugged in” to mobility-enhanced core network Radio Air Interface B Radio Air Interface A Radio Air Interface B Radio Air Interface A Core Network + Mobility Fixed Network Integrated Broadband + Mobile Network + separate radio access components Overlay Mobile Network + Broadband Services + separate core network

  9. Network Architecture: Seamless Wired+Wireless System Typical architecture of integrated (broadband + mobile) network: Switch/Router Multiservices Broadband Network Mobility Support Switch/Router to Internet & PSTN Gateways Media Servers Home/Office Gateway cellular, PCS air interface Radio Port ........... Microcellular Mobile Network broadband air interface MM PDA PC, STB, etc. Wireless Local Access ...........

  10. Network Architecture: Protocol Selection • Once the integrated network approach is selected, basic issue is that of selecting a multimedia-capable core network protocol to use as foundation: • ATM • IP • both ATM and IP in some suitable combination? • future open programmable/active network? • Selection is complicated by the existence of different protocols for telecom networks and Internet (though gradual convergence is now a definite possibility…)

  11. Network Architecture: Wireless ATM System • Wireless ATM is a candidate architecture which assumes that the multimedia services infrastructure is ATM-based: • Support for service integration & QoS • Connection-oriented framework suitable for dynamic handoff • ATM cells reasonable unit for radio link retransmission Radio Microcell 1 ATM ACCESS POINT WATM TERMINAL WATM cells ATM cells ATM HOST/SERVER ATM SWITCH + Mobility Ext Standard UNI (+M): ATM or IP/ATM WATM Radio Air Interface Mobile ATM “M” UNI/NNI Standard UNI: ATM or IP/ATM Radio Microcell 2

  12. Network Architecture: Wireless IP System • Wireless IP an alternative approach based on the notion that today’s Internet protocols will evolve to provide most multimedia services: • Provides a robust packet-switched solution for radio access • Connectionless protocols offer lower complexity implementation • Enhancements needed for QoS support and dynamic mobility Radio Microcell 1 IP ACCESS POINT IP TERMINAL IP Pkts w/ DLC segments IP packets IP HOST/SERVER IP ROUTER + Mobility Ext Standard IP/RSVP “+M” Radio Air Interface IP/RSVP + “M” Standard IP Radio Microcell 2

  13. RSVP + Mob Ext Application Data TCP/UDP/RTP IP Network Layer (incl.. Mob IP) Radio link control .. Flow # 1 n Wireless Control Data Link Control (or “LLC”) Medium Access Control Multiplexed user data Radio Transport Convergence Layer Radio PHY Radio Physical Medium Dependent Layer Radio Signal Network Architecture: “+M” Protocol Stacks Optional Signaling, etc. + mobility ext Application Data Control Plane User Plane ATM Adaptation Layers ATM Network Layer Radio link control Control Flow SIG VC n VC# 1 2 .. Wireless Control Data Link Control (or “LLC”) Radio Access Layers Medium Access Control Multiplexed user data Radio Transport Convergence Layer Radio PHY Radio Physical Medium Dependent Layer Radio Signal Wireless ATM Protocol Stack Wireless IP Protocol Stack

  14. Network Architecture: Technology Components Major technology components of a broadband wireless system are thus identified as: Radio/PHY Medium Access & Data Link Control Core Network Mobile Network Extensions Radio Link Broadband + Mobile Access Network

  15. Major Technology Components

  16. Technology Components: Radio/PHY Spectrum • Total spectrum needed for broadband wireless services a function of: • Microcell size/radio link power • User density • User traffic characteristics • Modulation/MAC/DCA efficiency • Required spectrum estimates for mobile broadband services range from 100-500 Mhz depending upon assumptions • US FCC allocation of 300 Mhz in 5 Ghz U-NII band • ETSI allocation of 500 Mhz (total) in 5 Ghz Hiperlan band • Future MMAC allocation in Japan, etc.

  17. Technology Components: Radio/PHY Spectrum • Key policy issue for broadband wireless spectrum: standards (e.g. ETSI BRAN) vs. technology neutral (US U-NII) • Arguments for and against a radio standards include: • Universal compatibility of radio equipment • Potentially lower equipment costs due to volume • Cannot accommodate rapid technology evolution (higher speed, etc.) • Difficult to optimize radios for various scenarios (home, LAN, public..) • Overall, U-NII approach seems preferable for relatively immature high-speed radio technologies, especially since they can be designed to “plug-in” into standard network infrastructures...

  18. Packet service Channel: #1 ..... #2 WATM service A #3 .... #4 WATM service B #5 .... #6 Periodic announcements incl..: Service type (WATM,..), User #, Channel #, service params, Priority, Cost/Price Bids, etc. #N Technology Components: Radio/PHY Spectrum • Spectrum etiquette procedure a key issue for U-NII scenario • “CSCC” approach proposed as possible solution... • Coordination channel using simple standard protocol at edge of band • Semantics of higher layer coordination protocol TBD... • Support arbitrary spectrum policies based on user priority, cost bids, etc. • Also serves as a “program guide” to U-NII equipment entering area Common Spectrum Coord Channel (CSCC)

  19. A wins contention ( B records & reports transaction!) Service Type User ID Price Bid $.05/hr Technology Components: Radio/PHY Spectrum Example of CSCC etiquette used for “dynamic pricing” based spectrum allocation: A fn B fn B contends for fn A raises bid on fn channel channel fn fn A B A CSCC Price Bid $.09/hr Price Bid $.07/hr …e-cash exchange ?

  20. Technology Components: Radio/PHY Modem • Typical broadband wireless modem defined as 10 Mbps+, operating in 100-250m microcells (both indoor & outdoor) • Modem technologies currently in use include: • BPSK/QPSK/GSMK with equalizer or FH spreading • OFDM with 32-64 carriers • 16-QAM with trellis coding & equalization • No clear technical “winner” - choice depends upon various cost/performance factors and usage scenario…. • Although OFDM has initially been selected for ETSI/BRAN, it is unlikely to be the only modem technology used for broadband wireless systems worldwide… • In an era of exponentially increasing BW, need to start thinking about a 100 Mbps+ modem 2-3 years from now..!

  21. Technology Components: Medium Access Control • Two kinds of MAC protocols have been considered so far: • Packet-oriented protocols based on CSMA • Integrated packet/flow oriented protocols based on dynamic TDMA • CSMA-type protocols OK for basic IP services without flow/QoS support • Dynamic TDMA protocol class demonstrated to be viable for integrated QoS-based services, both ATM and IP/RSVP • As with modulation, a single MAC standard is not mandatory as long as interfaces are consistent with core network protocols

  22. TDMA Frame (~1-2 ms) TDM Downlink D-TDMA Uplink Modem preamble S-ALOHA control User B Burst from User A To Base Station User C Burst from Base Station -> Mobiles Cell Sequence No. # Data Cells Type RSN VPI GFC AP Identifier # Control Pkts VPI VCI TDMA Frame No. Mobile ID Mobile ID # Dn Control Slots VCI CLP PTI # Slots Req/Start.. VCI # Up contention slots .. ..Slot HEC # Dn data cells RT Reserved Resvd/# Slots Alloc Superframe size Standard ATM Payload (48 bytes) CRC-16 CRC-16 Reserved (8 Bytes) BW Req/Alloc Pkt Uplink Subframe Header CRC-16 CRC-16 Frame Header WATM Cell Technology Components: TDMA/TDD MAC Example • Typical dynamic TDMA/TDD protocol used for WATM provides both packet and QoS/stream services. Same MAC layer readily extends to RSVP/IP...

  23. Technology Components: Data Link Control • DLC (also called LLC) for correcting radio link errors critical for high-bandwidth wireless services • DLC is effective in microcellular channels because: • FEC alone cannot compensate for rapid multipath variations • radio link propagation delay is short (<<1ms) • error conditions on channel become uncorrelated after several ms • ATM cell size a reasonable basis for DLC (after addition of seq. #); IP packets will require segmentation though not necessarily at 48 bytes. • Special considerations needed for stream/QoS services….

  24. Technology Components: Data Link Control • DLC mechanism such as SREJ/ARQ used for packet data selective retx initial data tx 5 4 3 2 1 3 Transmit DLC buffers Receive DLC buffers 5 4 3 2 1 5 4 2 1 3 MAC Interface MAC Interface VC x VC x AAL5 packet for UBR/ABR ACK (1,2,4,5) ACK(3) • Additional real-time constraint for media flows (i.e. data released with or without errors after specified  secs)

  25. Technology Components: Data Link Control • DLC can significantly improve end-to-end ATM performance • Experiments (on NEC’s WATMnet system) show ~2-3 times improvement in TCP/AAL5/UBR throughput... • For CBR/VBR, 2-3 orders of magnitude improvement in CLR obtained with ~10 ms buffer delay

  26. Technology Components: Mobile Network/Protocols • As discussed, broadband mobile networks will require integrated mobility support as a “first-class” service • no distinction between mobile & fixed users (unified address space) • terminal movement supported by core routing/switching protocols • Above objectives recognized by groups working on core network protocols: • mobile IP as standard service within IPv6 (..completed) • mobile ATM as optional extensions to UNI/NNI (..complete in ‘99) • Further work needed on • IP/ATM integration with mobility • mobility extensions for new IP features such as mcast, QoS

  27. Technology Components: Mobility Support in IP • Mobile IP provides protocol extensions for rerouting data to a mobile user, but does not support dynamic handoff • Functions include: packet forwarding, route re-optimization Mobile IP provides mapping from A->current IP addr Packet with IP addr=A IP Addr A (permanent) Mob IP Router Home Agent Route of Packets before move IP Network Terminal Movement Mobile IP Access Network Fwd path for in-transit packets Location update initiates rerouting after radio handoff Route of Packets after move Temporary IP addr: B Foreign Agent Additional RSVP+M extensions under consideration for QoS & handoff

  28. Technology Components: Mobility Support in ATM • “M” UNI/NNI protocol extensions provide integrated & efficient support for mobility within ATM access network • Functions include: location mgmt, handoff control, mobile QoS/routing Location Mgmt provides mapping of A-> AL1, AL2 Connect (ATM Addr A) User Addr A (permanent) Crossover switch HO (BS1->BS2) Connection Before Handoff Initial Location AL1 ATM Network Terminal Movement Mobile ATM Access Network BS1 Handoff supports Dynamic rerouting Of active connections BS2 Rerouted Connection After handoff User Addr A Next Location AL2

  29. Technology Components: Mobile ATM Protocols • Location management can be integrated into existing ATM connection procedures.... (external servers can also be used) • simple extensions to current CONNECT, RELEASE IE’s, etc. • no need for a-priori partitioning of mobile & static address space ATM Host (4) (3) setup release (foreign_addr, (foreign_addr) home_addr) (2) setup (home_addr) (1) update Current Home Foreign switch switch move

  30. Technology Components: Mobile ATM Protocols • Handoff can be implemented via modest extensions to existing ATM UNI/NNI signaling... • new signaling messages/IE’s for handoff initiation, COS select, etc. • provides high-performance, scalable solution (compared with external MSC, BSC, etc.) Crossover tear down ATM Switch (COS) subpath Host add subpath COS select (1) handoff handoff confirm request move

  31. System Issues

  32. System Issues: Legacy Radio Service Integration • Network part of broadband wireless system can be used as a generic infrastructure for various current & future radio access technologies --> platform for IMT2000/UMTS migration • Generic +M protocols supported by network routers/switches • Interworking function at AP converts to/from radio protocol AP IP/WLAN TERMINAL Wdata pkts SWITCH/ROUTER + Mobility Ext Wireless data air interface Generic “+M” Protocol To Internet or Cellular/PCS Network Gateways Cellular/PCS Air Interface

  33. System Issues: Legacy Radio Service Integration • For mobile ATM infrastructure, a “proxy M-UNI” can be used at the AP for interworking with a non-WATM radio protocol... • GSM (or other cellular access protocol) converted to M-UNI at AP • Mobile ATM provides handoff and location mgmt to GSM user M UNI GSM GSM GSM GSM radio link GSM radio link Proxy M UNI M NNI GSM M NNI GSM/ATM gateway GSM radio air interface Terminal Movement HLR/VLR Mobile ATM Access Network Proxy migration M NNI GSM Network GSM GSM GSM radio link GSM radio link Proxy M UNI Handoff & loc mgmt within mobile ATM cloud provided By “M” UNI/NNI

  34. System Issues: Mobile (IP+ATM) solutions(1) IP-over-mATM • ATM connection appears as a link-layer “tunnel” to IP • Mobile ATM transparently supports terminal migration (mobile IP not needed for local mobility) IP M UNI IP radio link IP M NNI IP M UNI IP/ATM gateway Terminal Movement Mobile ATM Access Network IP/mATM link rerouted by mobile ATM Internet M NNI IP M UNI IP radio link

  35. System Issues: Mobile (IP+ATM) solutions - (2) IP Switching-over-WATM • (Mobile) IP protocol run directly on ATM/WATM hardware • Each WATM component operates as L3 IP router with addl. cut-through switching capability (e.g. Ipsofacto) • Support for IP multicasting & QoS IP Including Mobile IP Ipso- facto IP Ipso- facto Ipso- facto IP IP WATM radio Ipso- facto IP ATM PHY WATM radio Ipsofacto gateway Terminal Movement Ipsofacto/WATM Access Network IP/Ipsofacto/ WATM link Rerouted by Mobile IP Internet IP IP Ipso- facto Ipso- facto IP Ipso- facto WATM radio ATM PHY WATM radio

  36. System Issues: Mobile (IP+ATM) Solutions -(3) IP-over-WATM radio • WATM AP can provide packet interface with IP routing • Link level MAC & QoS services provided by WATM radio • Conventional IP routed backbone network Including Mobile IP IP IP WATM radio IP IP WATM radio Terminal Movement WATM AP Rerouted by Mobile IP IP Internet IP IP WATM radio WATM radio

  37. System Issues: QoS Control Framework • QoS control in mobile networks more complex due to spatial movement of user terminals. Practical solution requires: • “Soft QoS” approach with adaptive application scaling • Renegotiation of UPC parameters, etc. (VBR+, RSVP,..) BS Controller User QoS (via Winsock, API, etc.) Set/Renegotiate QoS Satisfaction Profile Set/Reneg QoS S Switch Controller Mapping to WATM radio ATM BS Set/Reneg QoS BW User Data SERVER Mapping to ATM layer Scalable media Initial microcell WATM TERMINAL Terminal Movement QoS Renegotiation after handoff ATM SWITCH (w/ Mobility Ext) Server QoS (via Winsock, API, etc.) QoS Reneg after handoff Mapping to WATM radio User Data After handoff

  38. System Issues: Mobile Multimedia Software • Adaptive, QoS-aware application software based on distributed object technology…. “Heidi-II” GUI with QoS control, etc.

  39. Concluding Remarks

  40. Concluding Remarks: Technology Status • After about 5 years of R&D activity on broadband wireless technology, we have the following high-level results: • Technical feasibility of one system approach (WATM) validated, though commercial viability has yet to be proven (-> see today’s demos!) • Key technologies: 10 Mbps+ modems, MAC, mobATM or IP at early product development stage, maturing quite rapidly • Standardization efforts for WATM ongoing in ATM Forum and ETSI • Parallel efforts on high-speed IP initiated more recently for WLAN scenarios (802.11, ETSI). Further work needed on flow QoS & handoff support • Growing interest in IP or ATM based mobile network as basis for migration to IMT-2000/UMTS • Early commercial products expected to be released during 1999, at least on a trial basis (e.g. 10 Mbps+ 802.11, 25 Mbps WATM,..) • Initial applications likely to be in vertical mobile multimedia markets, gradually migrating to mass market semi-mobile broadband access...

  41. Concluding Remarks: NEC’s WATMnet System • NEC ATM switches (M5/7/16) with “M” UNI/NNI software • ATM base stations with plug-in radio modules • Compact 25 Mbps/5 Ghz U-NII band WATM NIC/modem • Laptop PC’s with UNI+M drivers and mobile MM middleware PCS/GSM/WLAN radio card PCS/GSM handset ATM Edge SW + mobility software (“M” NNI) WATM radio NIC (25 Mbps/5 Ghz) MM PDA, etc. (future) Dynamic TDMA MAC, data link contr + WATM drivers (“W” UNI), MM middleware ~10 Mbps ATM services ATM Base Station + mobility software (“M” UNI/NNI) NEC’s WATMnet™ System (… alpha trials 4Q’98)

  42. Concluding Remarks: Future Prospects • Broadband wireless/mobile access will inevitably grow in importance as portable computing and comm. devices proliferate…. • The move to broadband+mobile wireless services will be accompanied by a paradigm shift in mobile network architecture • integrated mobility services in next-generation access networks • high-speed radio links as “plug-ins” to core network • Premature to declare a single protocol (e.g. ATM or IP) as the sole basis for broadband mobility, since selection will depend upon the result of current telco/Internet convergence efforts • The likely result: IP and ATM, later migrating to open/active network protocols…..

  43. Concluding Remarks: Future Prospects • In any case, core technologies for broadband wireless are relatively protocol independent • high-speed radio modems • MAC/DLC with flow QoS support, etc. • mobile network protocols with QoS, handoff & loc mgmt • mobile multimedia terminals & related application software • Partial “Top 10” list for future work... • 100+ Mbps radio modem with 3+ bps/Hz and 250m+ range • Generic MAC/DLC for ATM, IP, etc. • Efficient IP/WATM mobile network solution • IMT-2000 platform implemented as generic mobile network • Mobile network based on active/programmable network principles • New/useful/interesting mobile terminals and applications... • The future for this technology area promises to be interesting and will eventually have a large impact on people’s lives...

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