2. Multiuser Wonders 1 Multiuser in multicarrier systems for wireless and wireline. March 31, 2001 April 26 2001 September 9, 2001 Prof. Y. Bar-Ness Dept of EE New Jersey Inst. Tech. barness@yegal.njit.edu Prof. John M. Cioffi Dept of EE Stanford University cioffi@stanford.edu

3. Multiuser Wonders 2 Tutorial Outline/Schedule l 9:00-9:20Multiuser BasicsCioffi l 9:20-10:30Danish PhotosBar-Ness l 11:00-12:30 Academic SongsBar-Ness l 12:30-2:00 lunch l 2:00-3:30digital siestaCioffi l 4:00-5:10eliminate gasCioffi l 5:10-5:30SummaryBar-Ness

4. Multiuser Wonders 3 l Goal: Best PHY signals for user sharing of channel u Set spectra/signals, optimization via controller Multiuser Basics Base(DSLAM, MTXO ) User 1 User 2 User L... Controller

5. Multiuser Wonders 4 Digital Subscriber Lines (DSL) l Twisted-pairs share a “cable” u Radiate despite twisting u Crosstalk is severe – up to 50 wrapped together l Multiuser situation where base is DSLAM l Ethernet is another example (4 wires) PhoneCo=Base(DSLAM) user user Controller (net main center) NEXTFEXT

6. Multiuser Wonders 5 Wireless LAN l Wireless fundamentally shared u Crosstalk = co-channel interference l Base is control unit l 3G wireless, T/CDMA are other examples user user user user control base

7. Multiuser Wonders 6 Ethernet-like (VDSL) l Up to 4 coordinated tps, cat 3 (EFM), cat 5 (10,100, 1000 BT), cat7 (10GBT) l Vectored solution NEXTFEXT control Router PHY MUX Bridge/card control

8. Multiuser Wonders 7 Digital Audio Broadcasting l ETSI, 1995. l Replaces/augments analog FM radio l “broadcast” problem control base user user Zeke John

9. Multiuser Wonders 8 DAB coverage map Source: worldDAB.org

10. Multiuser Wonders 9 Digital Video Broadcasting l ETSI, 1997. l Defines terrestrial, cable and satellite digital television broadcasting. control base user user ZEKE

11. Multiuser Wonders 10 DVB adoption Source: DVB.org

12. Multiuser Wonders 11 Brief Mutlicarrier Modulation Review (single user) l DMT (wired) l OFDM l vectoring

13. Multiuser Wonders 12 Multitone: DMT Loading Basics (SINGLE USER) Frequency AttenTWISTED-PAIR Bits/chanFrequency Bits/chanFrequency Frequency Atten TWISTED-PAIR with TAP, AM/RF, and XTALK AM xtalk Bits/chanFrequency Frequency Bits/chan l Optimum – “waterfilling capacity” u Highest data rate, “capacity”, for single user

14. Multiuser Wonders 13 DMT Uses l ADSL (10 million lines) u 256 (4 kHz) carriers over 1.104 MHz u Rates to 10 Mbps down /1 Mbps up l EFM/VDSL u Up to 4096 (4 kHz) carriers over 17.6 MHz F Per line (up to 16384 carriers over 4 lines) u Rates to 100 Mbps symmetric l Advanced Ethernet (250 Mbps and up) u Many wider carriers

15. Multiuser Wonders 14 OFDM – no loading/coding Frequency Atten Wireless with fade and narrowband interference Other user Bits/chanFrequency code parity FrequencyBits/chan l Bit optimization per tone not permitted or possible l Use code instead to offset loss of some of tones l Suboptimal with respect to DMT, but used in wireless where channel cannot be easily identified at transmitter

16. Multiuser Wonders 15 OFDM Uses (wireless) l DAB to 2 Mbps u 192-1,536 carriers, 1kHz-8kHz wide each l Wireless LAN (802.11a) u 48 carriers, 312.5 kHz wide each u To 55 Mbps l Wireless Broadband/DSL (802.16) u Vectored OFDM – in process l DVB to 40 Mbps u 1,705/6,817 subcarriers, 1 to 8 kHz wide l 4G wireless portable seems destined to use OFDM

17. Multiuser Wonders 16 Multiuser Rate REGIONS l Plot of all possible rates of users l Any point in region is possible, but each with different spectra u Varies for each channel R short R long Spectral pair 1 Spectral pair 2

18. Multiuser Wonders 17 The “Down” problem l Base to Users u “Downstream” in DSL u “Downlink” in wireless l The “Broadcast Problem” in information theory u Solved recently l Base cordination level u Spectra: Spectra Balancing u Signals: Vectoring

19. Multiuser Wonders 18 The “Up” Problem l Users to Base u “upstream” in DSL u “uplink” in wireless l The “multiple access problem” in information theory u Solved about 10 years ago l Base coordination level u Spectral or none: multiuser detector (MUD) u Signal: vectoring

20. Multiuser Wonders 19 Tutorial Outline/Schedule l 9:00-9:20Multiuser BasicsCioffi l 9:20-10:30MC-CDMA/MUDBar-Ness l 11:00-12:30 Multirate wirelessBar-Ness l 12:30-2:00 lunch l 2:00-3:30wireline multiuserCioffi l 4:00-5:10DSL, Ethernet, VDMT Cioffi l 5:15-5:30SummaryBar-Ness