A recent (Dec2012) wireless demonstration Parameter Value Data - PowerPoint PPT Presentation

G IGABIT A CCESS IN W IRELESS A. Chockalingam Department of ECE, IISc Second Annual NKN Workshop Bangalore 18 October 2013 A. Chockalingam ( Department of ECE, IISc ) Gigabit Access in Wireless 18 October 2013 1 / 53

Outline 1 G IGABIT W IRELESS - S TATE - OF - THE - ART 2 MIMO - A N ACE PHY FEATURE IN G IGABIT WIRELESS 3 S PATIAL MODULATION - A NOTHER ACE PHY FEATURE A. Chockalingam ( Department of ECE, IISc ) Gigabit Access in Wireless 18 October 2013 2 / 53

Gigabit Wireless - State-of-the-art A recent (Dec’2012) wireless demonstration Parameter Value Data rate 10 Gbps Bandwidth 400 MHz Spectral efficiency 25 bps/Hz Carrier frequency 11 GHz Environment Urban Mobility 9 km/hr Technology 8 × 16 MIMO 64-QAM (a) (b) A. Chockalingam ( Department of ECE, IISc ) Gigabit Access in Wireless 18 October 2013 3 / 53

Gigabit Wireless - State-of-the-art Another recent (May’2013) wireless demonstration Parameter Value Data rate 1.056 Gbps Bandwidth ? Spectral efficiency ? Carrier frequency 28 GHz Distance 2 km Technology * Adaptive antenna array * 64 antenna elements A. Chockalingam ( Department of ECE, IISc ) Gigabit Access in Wireless 18 October 2013 4 / 53

Gigabit Wireless - State-of-the-art Gartner’s hype cycle Source: Internet A. Chockalingam ( Department of ECE, IISc ) Gigabit Access in Wireless 18 October 2013 5 / 53

Gigabit Wireless - State-of-the-art Moore’s law drives wireless data rates Source: SPAWC’2010 plenary talk slides of Dr. Gerhard Fettweis A. Chockalingam ( Department of ECE, IISc ) Gigabit Access in Wireless 18 October 2013 6 / 53

Gigabit Wireless - State-of-the-art Moore’s law drives wireless data rates Source: SPAWC’2010 plenary talk slides of Dr. Gerhard Fettweis A. Chockalingam ( Department of ECE, IISc ) Gigabit Access in Wireless 18 October 2013 7 / 53

Gigabit Wireless - State-of-the-art Moore’s law drives wireless data rates Source: SPAWC’2010 plenary talk slides of Dr. Gerhard Fettweis A. Chockalingam ( Department of ECE, IISc ) Gigabit Access in Wireless 18 October 2013 8 / 53

Gigabit Wireless - State-of-the-art Moore’s law drives wireless data rates Source: SPAWC’2010 plenary talk slides of Dr. Gerhard Fettweis A. Chockalingam ( Department of ECE, IISc ) Gigabit Access in Wireless 18 October 2013 9 / 53

Gigabit Wireless - State-of-the-art Increasing wireless data rates New spectrum (bps) increase BW ( e.g., 60 GHz band, mm wavelength, 7 GHz BW ) +: unlicensed (free) -: propagation characteristics, devices, short range, cost Increase QAM size (bps/Hz) MIMO (bps/Hz) +: Theory has predicted unlimited capacity -: Practicality, complexity, cost (bps/Hz/km 2 ) Dense deployments Femtocells +: 1000x speed up (claimed) -: interference management, backhaul, cost A. Chockalingam ( Department of ECE, IISc ) Gigabit Access in Wireless 18 October 2013 10 / 53

Gigabit Wireless - State-of-the-art Evolution to Gigabit WiFi (and beyond) IEEE Band BW Data rates PHY features Spectral Eff. Standard per channel (bps/Hz) 802.11b 2.4 GHz 5 MHz 11,5.5,2,1 Mbps DS-SS, CCK 0.5, 2 802.11g 2.4 GHz 20 MHz 1 - 54 Mbps OFDM 2.5 802.11a 5 GHz 20 MHz 54,48,36,24,18 OFDM 12,9,6 Mbps 64 subcarriers 2.5 MIMO-OFDM 802.11n 5/2.4 GHz 20/40 MHz 600 Mbps 4 × 4 MIMO 15 128 subcarriers 802.11ac 5 GHz 80/160 MHz 1 Gbps MU-MIMO 6.25 802.11ad 60 GHz 7 GHz up to 7 Gbps Beamforming < 2 HEW ? ? ? ? ↑ HEW: High Efficiency WiFi Bands other than 2 GHz and 5 GHz 802.11af (White-Fi) : TV white spaces, sub-1GHz ( cognitive radio, geographic sensing ) 802.11ah: non-TV white spaces, sub-1GHz ( Internet of Things (IoT), Machine to Machine (M2M) ) 802.11aj: 60 GHz (5 GHz BW) – China-centric Emerging use cases (under discussion) – relevant for India A. Chockalingam ( Department of ECE, IISc ) Gigabit Access in Wireless 18 October 2013 11 / 53

Gigabit Wireless - State-of-the-art IEEE 802.11 MAC Two protocols PCF: Point coordination function (polling) DCF: Distributed coordination function (random access) DCF CSMA/CA RTS/CTS handshake before transmission of data packet Avoids hidden node problem ACK for data packet Backoff mechanism to resolve collisions backoff parameters: CWmin, CWmax Minimum silence periods between transmissions DIFS: DCF Inter-Frame Spacing SIFS: Short Inter-Frame Spacing Shorter minimum waiting implies higher priority (ACK, CTS) A. Chockalingam ( Department of ECE, IISc ) Gigabit Access in Wireless 18 October 2013 12 / 53

Gigabit Wireless - State-of-the-art IEEE 802.11 MAC - CSMA/CA Source: http://secowinet.epfl.ch/slides A. Chockalingam ( Department of ECE, IISc ) Gigabit Access in Wireless 18 October 2013 13 / 53

Gigabit Wireless - State-of-the-art IEEE 802.11 MAC (DCF) Throughput IEEE 802.11b Max. raw data rate: 11 Mbps Useful throughput is much less due to CSMA/CA overhead Application using TCP: 5.9 Mbps Application using UDP: 7.1 Mbps CSMA/CA overhead Min. overhead for sending one data packet = Tx time of (1 RTS + 1 CTS + 1 ACK + 3 SIFS + 1 DIFS + 4 preambles) In addition, loss due to collision and retransmissions A. Chockalingam ( Department of ECE, IISc ) Gigabit Access in Wireless 18 October 2013 14 / 53

Gigabit Wireless - State-of-the-art DCF MAC (In)efficiency in Gigabit WiFi Suppose RTS = CTS = ACK = Preamble = 20 bytes SIFS = 16 µ sec, DIFS = 34 µ sec, Data packet = 2500 bytes Assume ideal conditions No channel errors, no collision (i.e., point-to-point Tx) Case a) say, Rate = 54 Mbps. Useful throughput? Ans: 42.3 Mbps (about 78% of 54 Mbps) Case b) say, Rate = 1 Gbps. Useful throughput? Ans: 194 Mbps (only 19.4% of 1 Gbps) MAC (in)efficiency is a concern in Gigabit WiFi A. Chockalingam ( Department of ECE, IISc ) Gigabit Access in Wireless 18 October 2013 15 / 53

Gigabit Wireless - State-of-the-art Back to Gartner’s hype cycle Hype cycle for Communication and Networking, 2011 Source: Internet A. Chockalingam ( Department of ECE, IISc ) Gigabit Access in Wireless 18 October 2013 16 / 53

Gigabit Wireless - State-of-the-art Back to Gartner’s hype cycle Hype cycle for Communication and Networking, 2013 Source: Internet A. Chockalingam ( Department of ECE, IISc ) Gigabit Access in Wireless 18 October 2013 17 / 53

MIMO - An ace PHY feature in Gigabit wireless MIMO – an ace PHY feature Why MIMO? n t : # of transmit antennas, n r : # receive antennas # Antennas Error Probability ( P e ) Capacity ( C ) , bps/Hz SISO P e ∝ SNR − 1 n t = n r = 1 C = log ( SNR ) SIMO P e ∝ SNR − n r n t = 1 , n r > 1 C = log ( SNR ) MIMO P e ∝ SNR − n t n r n t > 1 , n r > 1 C = min ( n t , n r ) log ( SNR ) MIMO technology scores high on Spectral efficiency Power efficiency Link reliability A. Chockalingam ( Department of ECE, IISc ) Gigabit Access in Wireless 18 October 2013 18 / 53

MIMO - An ace PHY feature in Gigabit wireless Increasing spectral efficiency: QAM vs MIMO (c) SISO/SIMO with 64-QAM (d) MIMO with n t = 6 and BPSK Spectral efficiency in both systems: 6 bps/Hz A. Chockalingam ( Department of ECE, IISc ) Gigabit Access in Wireless 18 October 2013 19 / 53

MIMO - An ace PHY feature in Gigabit wireless Increasing spectral efficiency: QAM vs MIMO 0 10 SISO, nt=1, nr=1, 64-QAM SIMO, nt=1, nr=6, 64-QAM MIMO, nt=6, nr=6, BPSK 6 bps/Hz -1 10 Bit Error Rate -2 10 -3 10 -4 10 0 5 10 15 20 25 30 35 40 45 50 Average recieved SNR (dB) A. Chockalingam ( Department of ECE, IISc ) Gigabit Access in Wireless 18 October 2013 20 / 53

MIMO - An ace PHY feature in Gigabit wireless Large MIMO systems Larger the number of antennas, better will be the spectral efficiency power efficiency reliability Large MIMO systems MIMO systems where communication terminals use tens to hundreds of antennas Achieve very high spectral efficiencies in the range of tens to hundreds of bps/Hz A. Chockalingam ( Department of ECE, IISc ) Gigabit Access in Wireless 18 October 2013 21 / 53

MIMO - An ace PHY feature in Gigabit wireless Technological challenges Placement of large no. of antenna elements Feasible in moderately sized communication terminals Use high carrier frequencies (small carrier wavelengths); e.g., 5 GHz, 60 GHz Compact antenna arrays RF technologies Multiple IF/RF transmit and receive chains Spatial modulation Allows use of less number of Tx RF chains than the number of Tx antennas Large MIMO signal processing Signal detection, channel estimation, decoding, precoding Channel hardening in large random matrices help A. Chockalingam ( Department of ECE, IISc ) Gigabit Access in Wireless 18 October 2013 22 / 53

MIMO - An ace PHY feature in Gigabit wireless Channel hardening in large random matrices Magnitude plots of H H H for different sizes of random matrix H 8 x 8 15 10 5 0 -5 -10 8 6 4 8 6 2 4 2 0 0 (e) 8 × 8 A. Chockalingam ( Department of ECE, IISc ) Gigabit Access in Wireless 18 October 2013 23 / 53

MIMO - An ace PHY feature in Gigabit wireless Channel hardening in large random matrices Magnitude plots of H H H for different sizes of random matrix H 8 x 8 32 x 32 15 60 10 40 5 20 0 0 -20 -5 -40 -10 40 8 30 6 4 8 20 40 6 30 10 2 4 20 2 10 0 0 0 0 (i) 8 × 8 (j) 32 × 32 A. Chockalingam ( Department of ECE, IISc ) Gigabit Access in Wireless 18 October 2013 23 / 53