Advances in Wlans

Tutorial on radio communications: From the basics to future developments Part 3: Advances in wireless LANs

Oliver Hoffmann Dortmund University of Technology, Germany [email protected]

MobiLight 2010, 12 May 2010, Barcelona Outline

• Motivation: What is a WLAN?

• Advances of WLANs

• Conclusion and future prospects

MobiLight 2010, 12 May 2010, Barcelona 2 What is a WLAN?

Typical definitions are ambiguous, lots of exceptions:

WLAN WPAN outdoor: few 100 meters outdoor: ~10 m Coverage range indoor: few rooms/house indoor: one room Data rates very high ultra-high

Transmit power moderate low

Power consumption moderate, not critical low, critical

Costs moderate low

Usage portable mobile infrastructure mode ad-hoc connection Topology with access to wired network between devices Network size can be large small

Connection duration long short

MobiLight 2010, 12 May 2010, Barcelona 3 What is a WLAN?

Possible definition I: Very high data rates over medium/long ranges

Coverage WAN LTE-A MAN IEEE 802.16m

LAN IEEE 802.11ac IEEE Bluetooth 802.15.4 v2 PAN 60 GHz (ZigBee) WiMedia IEEE BAN IEEE 802.15.6 802.15.7 Giga-IR THz 10 kb/s 100 kb/s 1 Mb/s 10 Mb/s 100 Mb/s 1 Gb/s 10 Gb/s PHY data rate

MobiLight 2010, 12 May 2010, Barcelona 4 What is a WLAN?

Possible definition I: Very high data rates over medium/long ranges Possible definition II: IEEE 802.11 = WLAN, IEEE 802.15 = WPAN

Coverage WAN LTE-A IEEE 802.11 MAN has no IEEE 802.16m competitor in LAN the WLAN IEEE 802.11ac area IEEE Bluetooth 802.15.4 v2 PAN 60 GHz (ZigBee) WiMedia IEEE BAN IEEE 802.15.6 802.15.7 Giga-IR THz 10 kb/s 100 kb/s 1 Mb/s 10 Mb/s 100 Mb/s 1 Gb/s 10 Gb/s PHY data rate

MobiLight 2010, 12 May 2010, Barcelona 5 WLAN applications

Originally designed for data communication and networking, the applications of WLANs are becoming more and more diverse

Environments

Home

Enterprise

Small office

Outdoor

Campus, hospital

Car and large vehicles

Factory

MobiLight 2010, 12 May 2010, Barcelona 6 WLAN applications

Originally designed for data communication and networking, the applications of WLANs are becoming more and more diverse

Category IEEE 802.11ac/ad usage model

Desktop display & storage at home or enterprise; Wireless Display Projection from PC to TV; In room gaming; Streaming from a camcorder to a display; Broadcast TV field pick-up

MobiLight 2010, 12 May 2010, Barcelona 7 WLAN applications

Originally designed for data communication and networking, the applications of WLANs are becoming more and more diverse

Category IEEE 802.11ac/ad usage model

Desktop display & storage at home or enterprise; Wireless Display Projection from PC to TV; In room gaming; Streaming from a camcorder to a display; Broadcast TV field pick-up Distribution of HDTV and Video streaming throughout the home or large vehicles; other media content Networking in the office; Remote medical assistance Rapid sync-n-go file transfer; Picture-by-picture viewing; Rapid upload/download Airplane docking; Video content download to car; Police / surveillance car upload

MobiLight 2010, 12 May 2010, Barcelona 8 WLAN applications

Originally designed for data communication and networking, the applications of WLANs are becoming more and more diverse

Category IEEE 802.11ac/ad usage model

Backhaul Multi-media mesh backhaul; Point-to-point backhaul Source: Cisco

Video demos or telepresence in auditoriums/lecture halls; Outdoor campus Public safety mesh Manufacturing floor Manufacturing floor automation

MobiLight 2010, 12 May 2010, Barcelona 9 QoS requirements

With the extended field of WLAN applications, the QoS requirements are becoming more diverse and more challenging quasi error-free transmission, low latency, support of a large data rate range

Application Offered load (Mb/s) Max. PLR Max. delay (ms)

Internet streaming AV 0.1 – 4 10-4 200

HDTV 19.2 – 24 10-7 200

Blu-ray 50 10-7 20

Interactive Gaming >100 10-2 10

Lightly compressed video (H.264) 200 10-7 20

Uncompressed video 3000 10-8 10 (1080p, 24 bit/px, 60 frames/s)

 IEEE 802.11 needs continuous advancement

MobiLight 2010, 12 May 2010, Barcelona 10 Outline

• Motivation: What is a WLAN?

• Advances of WLANs – Overview – High throughput WLAN @ 2.4 and 5 GHz (IEEE 802.11n) – Vehicular WLAN @ 5.9 GHz (IEEE 802.11p) – Very high throughput WLAN @ 5 GHz (IEEE 802.11ac) – Very high throughput WLAN @ 60 GHz (IEEE 802.11ad) – Further amendments

• Conclusion and future prospects

MobiLight 2010, 12 May 2010, Barcelona 11 IEEE 802.11 standard and amendments

IEEE 802.11-2007 Base standard including all amendments until 2007 IEEE 802.11a-1999 OFDM PHY @ 5 GHz IEEE 802.11b-2001 DSSS PHY enhancement: 5.5 and 11 Mbit/s IEEE 802.11c-1998 Wireless bridging (now part of IEEE 802.1D-2004) IEEE 802.11d-2001 Global harmonization IEEE 802.11e-2005 MAC enhancements for QoS IEEE 802.11F-2003 Interworking of APs in the distribution system (withdrawn) IEEE 802.11g-2003 Extended rate PHY @ 2.4 GHz (OFDM, DSSS/CCK, PBCC, DSSS-OFDM) IEEE 802.11h-2003 Spectrum and transmit power management @ 5 GHz in Europe IEEE 802.11i-2004 MAC security enhancements IEEE 802.11j-2004 Half rate OFDM PHY @ 4.9 GHz–5 GHz (Japan) IEEE 802.11k-2008 Radio resource measurement IEEE 802.11n-2009 Enhancements for higher throughput IEEE 802.11r-2008 Fast roaming IEEE 802.11w-2009 Protected management frames IEEE 802.11y-2009 3.65 – 3.7 GHz operation in the USA

MobiLight 2010, 12 May 2010, Barcelona 12 IEEE 802.11 task groups

Planned Task group Topic release IEEE 802.11mb 802.11 accumulated maintenance changes Jun. 2011

IEEE 802.11p Wireless access for the vehicular environment (WAVE) Jun. 2010

IEEE 802.11s Mesh networking Jan. 2011

IEEE 802.11u Interworking with external networks Sep. 2010

IEEE 802.11v Wireless network management Sep. 2010

IEEE 802.11z Extensions to direct link setup Sep. 2010

IEEE 802.11aa Robust streaming of audio video transport streams Oct. 2011

IEEE 802.11ac Very high throughput <6 GHz Dec. 2012

IEEE 802.11ad Very high throughput at 60 GHz Dec. 2012

IEEE 802.11ae QoS management, prioritization of management frames Jun. 2012

IEEE 802.11af WLAN in the TV white space Jun. 2011

MobiLight 2010, 12 May 2010, Barcelona 13 Outline

• Motivation: What is a WLAN?

• Conclusion and future prospects

MobiLight 2010, 12 May 2010, Barcelona 14 Overview on IEEE 802.11n

PHY MAC

Transmission technique OFDM Data plane Control plane Man. plane

Frequency bands 2.4 and 5 GHz Frame Enhanced aggregation Block Ack Channel bandwidth M: 20 MHz (52) (data subcarrier) O: 40 MHz (108) RIFS burst TxBF control

M: 4 µs OFDM symbol duration Fast link O: 3.6 µs (short GI) adaptation

Modulation M: BPSK up to 64-QAM Reverse direction 20/40 MHz M: BCC grant BSS FEC O: LDPC Channel Protection switching Code rates M: 1/2, 2/3, 3/4, 5/6

M: 1, 2 (APs), direct mapping Phased coexistence operation MIMO: Spatial Streams O: 3, 4, TxBF, STBC Power save multi-poll M: 6.5 – 65 (APs: 130) Mb/s PHY Data rates O: 6 – 600 Mb/s

Spectral efficiency 0.3 – 15 bit/s/Hz Mandatory Optional

MobiLight 2010, 12 May 2010, Barcelona 15 IEEE 802.11n transmitter block diagram

Constellation Insert GI Analog Interleaver IDFT Mapper and window and RF

Constellation Insert GI Analog Interleaver CSD IDFT

FEC encoder FEC mapper and window and RF STBC

Scrambler Constellation Insert GI Analog Stream parser Stream Encoder parser Encoder Interleaver CSD IDFT Mapper mapping Spatial and window and RF

FEC encoder FEC Constellation Insert GI Analog Interleaver CSD IDFT Mapper and window and RF

MobiLight 2010, 12 May 2010, Barcelona 16 IEEE 802.11n MIMO techniques

Space-time Spatial expansion block coding

Spatial division multiplexing (direct mapping)

Receiver diversity Transmit beamforming

MobiLight 2010, 12 May 2010, Barcelona 17 IEEE 802.11n MIMO techniques

2.4 GHz band, 20 MHz, 64-QAM, R=5/6 MMSE equalizer, considers PHY impairments, synchronization, channel estimation, phase tracking

Channel model B (residential), NLOS, Channel model D (typical office), NLOS, two spatial streams (MCS 15) SDM with two spatial streams (MCS 15), all others with one spatial stream (MCS 7)

6.7 dB 9.8 dB

STBC vs. RX diversity (MRC): 3.2 dB offset => 3 dB transmit TxBF with singular vector decomposition, channel state power penalty, 0.2 dB impairment susceptibility information determined from noisy channel estimate

MobiLight 2010, 12 May 2010, Barcelona 18 IEEE 802.11n frame aggregation

A-MSDU A-MPDU MSDU or A-MSDU

Bytes: 6 6 2 0-2304 0-3 Bytes: 4 (MPDU Delimiter) max. 4095 0-3 Destination Source Length MSDU Padding Address Address MPDU Delimiter Reserved CRC MPDU Padding Length Signature

A-MSDU subframe 1 A-MSDU subframe 2 … A-MSDU subframe n A-MPDU subframe 1 A-MPDU subframe 2 … A-MPDU subframe n

max. A-MSDU length: 3839 or 7935 Byte max. A-MPDU length: 65535 Byte

PHY MAC PHY A-MSDU FCS Tail+Pad A-MPDU Tail+Pad Header Header Header

MPDU PSDU

A-MSDU A-MPDU

Max. length (Byte) 3839 or 7935 8191 or 16383 or 32767 or 65535

Max. number of subframes no limitation 64 Receiver the same for all subframes

Traffic identifier(s) the same for all subframes can be different

Subframe recovery not possible possible

Implementation HW, buffering of MSDUs possible SW, delay of channel access possible, more complex

MobiLight 2010, 12 May 2010, Barcelona 19 MAC throughput with IEEE 802.11n frame aggregation

One video transmission in the 2.4 GHz band, PER = 10%, max. 7 retransmissions, 64-QAM, R=5/6, short GI, EQM, SDM

without frame aggregation with frame aggregation

O. Hoffmann, „Efficient Configurations for Wireless Home Area Networks Based on IEEE 802.11n,“ ITG Symposium on Electronic Media "Systems, Technologies, Applications", TU Dortmund, March 2009 O. Hoffmann, R. Kays, „Efficiency of Frame Aggregation in Wireless Multimedia Networks based on IEEE 802.11n,“ accepted for publication at the 14th IEEE International Symposium on Consumer Electronics (ISCE2010), Braunschweig, June 2010

MobiLight 2010, 12 May 2010, Barcelona 20 Coverage range of IEEE 802.11n

2x2, SDM, 40 MHz, 2.4 GHz, channel model B (residential), Throughput vs. Range, 2X2X40, Channel B 1000 Byte MSDU size, 17 dBm transmit power, noise figure 10 dB 300

250 BPSK,R=1/2 QPSK,R=1/2 QPSK,R=3/4 16-QAM,R=1/2 200 16-QAM,R=3/4 64-QAM,R=2/3 64-QAM,R=3/4 64-QAM,R=5/6 150 BPSK,R=1/2,2X QPSK,R=1/2,2X QPSK,R=3/4,2X

Throughput(Mbps) 16-QAM,R=1/2,2X 100 16-QAM,R=3/4,2X 64-QAM,R=2/3,2X 64-QAM,R=3/4,2X 64-QAM,R=5/6,2X 50 FLA

0 0 10 20 30 40 50 60 70 80 90 100 Range (m) IEEE 802.11-04/0895r6

MobiLight 2010, 12 May 2010, Barcelona 21 Outline

• Motivation: What is a WLAN?

• Conclusion and future prospects

MobiLight 2010, 12 May 2010, Barcelona 22 IEEE 802.11p: Wireless access for the vehicular environment

• Origin: Dedicated short range communication (DSRC) to be used by intelligent transportation systems (ITS) • Diverse applications: Car-to-car, car-to-infrastructure; e.g. toll collection, safety • Regulation bodies allocated exclusive frequency band for DSRC – Europe: 5.855 – 5.925 GHz, 5/10/20 MHz spacing, 33 dBm max. EIRP • IEEE 802.11p defines PHY and MAC – PHY based on IEEE 802.11a, 10 MHz channel bandwidth, max. 27 Mb/s PHY rate, higher receiver performance requirements, stricter transmission masks, targeted coverage range up to 1 km – MAC: possibility to immediately communicate without establishing a BSS, modified channel access parameters (AIFSN values, TXOP limits) – Status: TG since Sep. 2004, current version D11.0 (March 2010), 2nd SA sponsor ballot recirculation closed on 8 April 2010, planned release in January 2011

• Higher layer protocols defined by IEEE 1609 IEEE 1609.3 UDP TCP – IEEE 1609.1: Architecture Networking services IP – IEEE 1609.11: Secure electronic payments LLC IEEE 1609.4 Multi-channel operation

IEEE 802.11p MAC

IEEE 1609.2 Security 1609.2 IEEE IEEE 802.11p PHY

MobiLight 2010, 12 May 2010, Barcelona 23 Outline

• Motivation: What is a WLAN?

• Conclusion and future prospects

MobiLight 2010, 12 May 2010, Barcelona 24 IEEE 802.11ac Very high throughput @ 5 GHz

Goals • Max. multi-station throughput > 1 Gb/s • Max. single link throughput > 500 Mb/s • Higher range of operation • Reduce power consumption (peak and average) • Increase spectrum efficiency • Improve user experience

Approach • Design by committee • Ad-hoc groups: PHY, MAC, MU-MIMO, Coexistence • Status: Composing first draft until Nov. 2010 • Planned Release: Dec. 2012

MobiLight 2010, 12 May 2010, Barcelona 25 IEEE 802.11ac enhancements under discussion

Multiple access techniques • Multi-user (MU)-MIMO as extended SDMA concept – Simultaneously transmit different spatial streams to different users – Complex implementation, requires precoding and user scheduling • Linear precoding (unitary, zero-forcing) • Non-linear precoding (dirty paper coding) – CSI required at transmitter – Users interfere – MU diversity can be exploited

MobiLight 2010, 12 May 2010, Barcelona 26 IEEE 802.11ac enhancements under discussion

 Achieves 11ac throughput goals without 80 MHz mode, moderate MAC efficiency, and more antennas only at powerful devices (e.g. APs)  Only DL MU-MIMO is considered

IEEE 802.11-09/0303r1

MobiLight 2010, 12 May 2010, Barcelona 27 IEEE 802.11ac enhancements under discussion

Multiple access techniques • OFDMA – Exclusively assign specific users a subset of data subcarriers – Comparable complexity of OFDMA on downlink as MU-MIMO on downlink – Better performance with CSI, but not required – No interference between users – MU diversity can be exploited when CSI is available

 Does not increase max. throughput, only improves efficiency with multiple lower rate and mixed clients

pilot subcarriers frequency data subcarriers of user #1, user #2, user #3, user #4, user #5

MobiLight 2010, 12 May 2010, Barcelona 28 IEEE 802.11ac enhancements under discussion

• Increase channel bandwidth to 80 MHz – Doubles PHY rate at negligible cost increase – Complex coexistence methods necessary in case of adjacent channels or significant receiver complexity in case of non-adjacent channels – Number of available bonded non-overlapping 80 MHz channels very limited (4 in EU) – New proposals for 160 MHz option (March 2010)

• Higher order modulation (256-QAM, EQM in single-user case) – Simple enhancement of the architecture – Lower robustness, higher TX and RX requirements  Benefit for short range, direct link applications

• More antennas, more spatial streams

– SU: NSS ≤ 8; MU: NSTS ≤ 4 per user, NSTS ≤ 8 summed over all users – Linear increase of PHY rate, some benefit in certain environments – Feasible only for large, powerful devices like APs

MobiLight 2010, 12 May 2010, Barcelona 29 Outline

• Motivation: What is a WLAN?

• Conclusion and future prospects

MobiLight 2010, 12 May 2010, Barcelona 30 60 GHz basics

Regulation in Europe • 8 GHz unlicensed spectrum • Max. EIRP: 40 dBm • Max. transmit power: 10 dBm

Typical channelization • Four channels of 2.16 GHz each • 12 narrow channels of 98 MHz each (IEEE 802.15.3c & WirelessHD) • Channel bonding (Ecma International)

MobiLight 2010, 12 May 2010, Barcelona 31 60 GHz characteristics

IEEE 802.15-10/0149r1 Challenges

• High pathloss – Higher free space attenuation – Higher attenuation by oxygen absorption, objects, and persons  Directional communication  Appropriate beamforming concepts  Device discovery  CSMA/CA is problematic

• Higher Doppler shift • Higher phase noise • Very high sampling rate required  Sophisticated circuit design

ETSI TR 102 555 V1.1.1

MobiLight 2010, 12 May 2010, Barcelona 32 60 GHz characteristics

Challenges Benefits

• High pathloss • Ultra-broad, unlicensed frequency band – Higher free space attenuation • Spatial reuse exploitable – Increase aggregated capacity – Higher attenuation by oxygen – Reduce interference absorption, objects, and persons • Reduced multipath propagation effects  Directional communication – Single carrier (SC) PHY attractive  Appropriate beamforming concepts alternative  Device discovery OFDM Channel

 CSMA/CA is problematic CP CP ZF IFFT H FFT insertion removal Equalizer • Higher Doppler shift SCBT • Higher phase noise Channel

CP CP MMSE H FFT IFFT • Very high sampling rate required insertion removal Equalizer  Sophisticated circuit design O. Hoffmann, R. Kays, R. Reinhold, “Coded Performance of OFDM and SC PHY of IEEE 802.15.3c for Different FEC Types,” IEEE Global Communications Conference (GLOBECOM 2009), Honolulu, Hawaii, November 2009

MobiLight 2010, 12 May 2010, Barcelona 33 60 GHz standardisation

Max. Forum Status TT PHY rate FEC MAC Remarks [Gb/s]

IEEE Released in SC 5.28 RS/LDPC Central, Focus on point-to-point, 802.15.3c Sep. 2009 OFDM 3.807 RS & CC 802.15.3 WirelessHD PHY integrated

Released in SC 6.35/25.402 decentral, Networking of ECMA-387 RS & CC Oct. 2008 OFDM 4.234 WiMedia heterogeneous device types

TG, CFP, Wide influence of WiGig, use IEEE OFDM Enhances Release ~7 LDPC market penetration and maintain 802.11ad SC 802.11 MAC > Dec. 2012 user experience of 802.11

>10m with beamforming, also for Released v1.0 OFDM Enhances WiGig 7 LDPC low power devices, fast session in Dec. 2009 SC 802.11 MAC transfer between 2.4/5/60 GHz

Proprietary, focus on A/V Released v1.0 WirelessHD OFDM 3.807 RS & CC Central streaming without HDMI cabling, in Oct. 2007 DRM concept

MobiLight 2010, 12 May 2010, Barcelona 34 IEEE 802.11ad Standardization

• TG since Dec. 2008 • Issued call for proposals (75% approval required) – Presentation of complete proposals or new techniques at March and May meetings 2010 – Wide influence of WiGig Alliance (Intel, Broadcom, Marvell, Atheros, NXP, STM, Samsung, Toshiba, Microsoft, Nokia, TI, Dell, Panasonic, NEC…) • Will present complete proposal based on WiGig spec. v1.0 at May meeting 2010, very likely to become initial draft, maybe some slight modifications • High number of voters present – March 2010: 7 new techniques presented, 9 strawpolls, all failed approval – May 2010: 3 complete proposals, 27 new techniques • Initial draft planned for Sep. 2010 • Release planned for Dec. 2012

MobiLight 2010, 12 May 2010, Barcelona 35 IEEE 802.11ad enhancements: WiGig PHY

• Unified and interoperable PHY – Common preamble, common MCS, common coding, common packet structure • SC PHY (mandatory) • OFDM PHY (optional) – Low power, low complexity transceivers  High performance on – Optional low power SC PHY with RS coding frequency selective channels

Chip rate 1.76 GHz Sample rate 2.64 GHz

Chips per block (data, guard) 512 (448, 64) FFT size (data, pilot) 512 (336, 16)

Chip time 57 ns Subcarrier spacing 5.15625 MHz

Modulation BPSK up to 16-QAM Guard interval 128 samples, 48.4 ns

PHY rates 385– 4620 Mb/s Symbol duration 242 ns

Modulation QPSK up to 64-QAM

• Control PHY (mandatory) PHY rates 693 – 6756.75 Mb/s – based on SC PHY • LDPC coding – Four codes of common codeword length of 672 bits, Code rates: 1/2, 5/8, 3/4, 13/16 – Cyclic shifted identity construction

MobiLight 2010, 12 May 2010, Barcelona 36 IEEE 802.11ad enhancements: WiGig MAC

• Personal basic service set (PBSS) – Enhance IBSS mode to accommodate directionality – Introduce network coordination by PBSS central point • Channel access supporting directionality and spatial frequency reuse Beacon interval

BT A-BFT AT CBP 1 SP 1 SP 2 CBP 2

time

Data transmission time

BT: Beacon Time CBP: Contention-based period A-BFT: Association beamforming training (EDCA tuned for directional access) AT: Announcement time SP: Service period • Flexible beamforming scheme – Tunable to simple, low power devices but also to complex devices – Two phases: sector level sweep and beam refinement protocol – Supports beam tracking

MobiLight 2010, 12 May 2010, Barcelona 37 IEEE 802.11ad enhancements: WiGig MAC

• Enhanced security – GCMP: Galois/Counter mode (128-bit AES) • Coexistence mechanisms – Same channelization as other 60 GHz systems – Energy detection, interference mitigation, transmit power control, dynamic frequency selection • Fast session transfer – Enable transition of communicating stations to another supported band (2.4, 5 or 60 GHz)

band B1, channel C1, band B1, channel C1, MAC addr. M1 MAC addr. M3 Transparant FST band C2, channel B2, band C2, channel B2, STA 1 MAC addr. M1 MAC addr. M3 STA 2 Non-transparant FST band B3, channel C3, band B3, channel C3, MAC addr. M2 MAC addr. M4

MobiLight 2010, 12 May 2010, Barcelona 38 Outline

• Motivation: What is a WLAN?

• Conclusion and future prospects

MobiLight 2010, 12 May 2010, Barcelona 39 Further amendments

IEEE 802.11s (TG since May 2004) • Need for extended range, need for mobile infrastructure, need for flexible, fail-safe networks  Mesh networking for configuring and using an IEEE 802.11 wireless distribution system • Auto-configuring paths (at MAC layer!) between stations over self-configuring multi-hop topologies using radio-aware metrics; automatic topology learning • Allow for alternative path selection metrics and/or protocols (reactive/proactive) • Status: Current version D5.0 (Apr. 2010), WG letter ballot (421 comments), planned release in Jan. 2011

IEEE 802.11v (TG since Dec. 2004) • No solution from IEEE 802.11 to manage and configure stations, only insufficient and complex other solutions (e.g. SNMP)  PHY/MAC extensions to enable wireless network management • Centralized and distributed operation, coherent upper layer interface • Create appropriate AP management information base • Status: Current version D10.0 (Mar. 2010), 2nd SA sponsor ballot recirculation closed on 14 Apr 2010, planned release in Sep. 2010

MobiLight 2010, 12 May 2010, Barcelona 40 Further amendments

IEEE 802.11u (TG since Aug. 2004) • No or proprietary interworking with external networks like cellular systems, e.g. for charging in an IEEE 802.11 hotspot infrastructure  PHY/MAC enhancements to support interworking with external networks • Enhanced protocol exchanges over the air, primitives for interaction with upper layers • Status: Current version D9.0 (Apr. 2010), 1st SA sponsor ballot recirculation closed on 23 Apr. 2010, planned release in Sep. 2010

IEEE 802.11z (TG since Aug. 2007) • Inefficient communication between two stations via the AP => direct link setup (DLS) in 11e • Upgrade necessary, WMM without DLS => Lack of DLS capable APs  Extensions to DLS to operate with non-DLS capable APs and support power save mode in active DLS session (only between exactly two stations) • Tunneled DLS: Specific Ethertype encapsulation to tunnel DLS frames through an AP • Power saving: Periodic wake-up schedule or unscheduled automatic power save delivery • Status: Current version D8.0 (Apr. 2010), 2nd SA sponsor ballot recirculation closed on 4 May 2010, planned release in Sep. 2010 (competitor: Wi-Fi Direct with soft-AP)

MobiLight 2010, 12 May 2010, Barcelona 41 Further amendments

IEEE 802.11aa (TG since Mar. 2008) • QoE of video streaming with IEEE 802.11 is not always satisfactory  MAC enhancements for robust video streaming • Graceful degradation (tag packets as drop eligible without deep packet inspection) • Increased robustness in OBSS without centralized management entity • Intra-AC prioritization by modifying EDCA parameter set (e.g. two alternative ACs) • Improved link reliability and low jitter characteristics for multi-/broadcast video streams • Status: Compose D1.0 for May meeting, planned release in Oct. 2011

IEEE 802.11ae (TG since Dec. 2009) • A lot of amendments defined crucial management frames, some require instantaneous reaction  Mechanisms for prioritization of management frames using existing mechanisms of medium access for improved support of QoS  Examples: Radio resource measurement, wireless network management, channel feedback frames of 11n/ac/ad, emergency services, location tracking, mesh path selection • Status: Call for technical presentations, initial draft in Nov. 2010, release in Sep. 2012

MobiLight 2010, 12 May 2010, Barcelona 42 Further amendments IEEE 802.11af

PHY and MAC modifications for channel access and coexistence in the TV white space (TV broadcasting frequencies in the VHF/UHF bands) • Very attractive frequency bands due to smaller pathloss, but: – Higher delay spread, smaller coherent bandwidth, primary users  Subcarrier spacing may be higher than coherent bandwidth  Guard interval may not suffice to mitigate ISI  Preamble may not be long enough for channel estimation • International inhomogeneity: – Different TV channel bandwidths (6/7/8 MHz) – Different number and allocation of available TV channels (max. 47 – 910 MHz)

 OFDM with fixed subcarrier spacing and different FFT sizes (64/128/256 or more)  Different guard interval durations (up to 12.8 µs)  5/10/20/40/80 MHz operation, find suitable channelization  Coexistence mechanisms like scanning and quiet periods

• Status: TG since Dec. 2009, compose D1.0 for May meeting, release in June 2011

MobiLight 2010, 12 May 2010, Barcelona 43 Outline

• Motivation: What is a WLAN?

• Conclusion and future prospects

MobiLight 2010, 12 May 2010, Barcelona 44 Conclusion

• WLANs provide an installation-free, flexible, low cost solution for a vast amount of applications • IEEE 802.11 is THE standard family for WLANs • High market penetration for years to come • IEEE 802.11 provides a very powerful toolbox  Efficient exploitation is the key, but beyond the scope of the standard

• IEEE standardization process is crucial but takes too long – Standard too late for the market, provokes proprietary solutions • 75 % approval requirement leads to inclusion of many optional “features” – Causes thousands of comments and years of comment resolution  Limit down selection  50% approval for initial draft  75 % approval for WG and SA ballots

MobiLight 2010, 12 May 2010, Barcelona 45 Future prospects

• For reasons of efficiency, implementation effort and energy consumption, the use of one single technology for all transmission tasks is not expedient  Map transmission tasks to technology hierarchy, which results from the trade-off between data rate and coverage range/robustness

MobiLight 2010, 12 May 2010, Barcelona 46 Future prospects

Vision Some research work • Determine the optimum toolbox configurations

Sat receiver • Overcome limited interaction between vertical and horizontal layers WLAN 2 • Scalable hardware implementation of network nodes • Technology improvement, e.g. robust control network • Convergence of WLAN and fiber (RoF) • Green communication

Home Local Gateway WLAN 1 Server

Control/Sensor Network WPAN

MobiLight 2010, 12 May 2010, Barcelona 47 Recommended background reading

• Eldad Perahia, Robert Stacey, “Next Generation Wireless LANs: Throughput, Robustness, and Reliability in 802.11n,” Cambridge University Press, 28 August 2008

• Benny Bing, “Emerging Technologies in Wireless LANs: Theory, Design, and Deployment,” Cambridge University Press, 5 November 2007

• Yang Xiao, Yi Pan, “Emerging Wireless LANs, Wireless PANs, and Wireless MANs: IEEE 802.11, IEEE 802.15, 802.16 Wireless Standard Family,“ John Wiley & Sons, 29 April 2009

• Bernhard H. Walke, Stefan Mangold, Lars Berlemann, “IEEE 802 Wireless Systems: Protocols, Multi-Hop Mesh/Relaying, Performance and Spectrum Coexistence,” John Wiley & Sons, 17 November 2006

• Matthew S. Gast, “802.11 Wireless Networks: The Definitive Guide,” O'Reilly Media, 6 May 2005

• Andreas Molisch, “Wireless Communications,” John Wiley & Sons, 23 September 2005

MobiLight 2010, 12 May 2010, Barcelona 48 Many thanks for your attention!

Tutorial on radio communications: From the basics to future developments Part 3: Advances in wireless LANs

Oliver Hoffmann Dortmund University of Technology [email protected]

MobiLight 2010, 12 May 2010, Barcelona