1. 1 OFDM based Applications DAB-OFDM  Digital Audio Broadcasting DVD-OFDM  Digital Video Broadcasting ADSL-OFDM  Asynchronous Digital Subscriber Line Wireless Local Area Network IEEE-802.11a, IEEE-802.11g ETSI BRAN (Hyperlan/2) Wireless MAN 802.16 Working Group of IEEE 802.16 -- 2 to 11 GHz

2. 2 OFDM Systems SystemTransform Size Number Carriers Channel Spacing kHz Bandwidth MHz Sample Rate MHz Symbol Duration  sec Data Rate Mbits/s HyperLAN/26452 4 312.516.25203.2 0.8 6-54 802.11a6452 4 312.516.56203.2 0.8 6-54 DVB-T2048 1024 1712 842 4.4647.6439.1742240.68-14.92 DAB2048 8192 15361.001.5362.04824/48/96 msec 3.072 ADSL256 (down) 64 (up) 36-127 7-28 4.31251.104 231.90.64-8.192

3. 3 DAB Standardized in 1995 by ETSI Improved sound quality & high spectral efficiency Single frequency by all transmitters – if t p < t g  no ISI, ICI – diversity achieved Sampling at 48 KHz, frame 24 ms, SOF – null symbol Differentially encoded QPSK - ref, symbol tx. Rate ¼ conv. Code CL = 7  8/9 by puncturing Maximum data rate = 1536 x 2 x 8/(9 x 1.246 ms ) = 2.4 Mbps

4. 4 DAB transmission modes Mode IMode IIMode IIIMode IV No. of subcarriers 1,536384192768 Subcarrier spacing 1 KHz4 KHz8 KHz2 KHz Symbol time1.246 ms 311.5  s155.8  s623  s Guard time 246  s61.5  s30.8  s123  s Carrier frequency < 375 MHz< 1.5 GHz< 3 GHz< 1.5 GHz Transmitter separation < 96 Km< 24 Km< 12 Km< 48 Km

5. 5 DVB - T Standardized in 1997 2K mode Size of IFFT, 1705 subcarriers 8K mode Size of IFFT, 6817 subcarriers, FFT interval 896  s, guard time – 28 to 224  s

6. 6 Block diagram of DVB-T Scrambler RS outer code Outer interleave Conv. inner code Inner interleave QAM mapping Pilot insertion Guard time insertion DAC RF Tx. Input data Group of 188 bytes (204,188,t=8) Byte-wise Depth-12 Rate ½, 7 (2/3, ¾, 5/6, 7/8) QPSK 16-QAM 64-QAM 768 pilots/ 192 pilots, Position change every 4 OFDM symbols 28 to 224  s

7. 7

8. 8 Digital Subscriber Line (DSL) -Broadband Access Customer Premises downstream upstream Voice Switch Central Office DSLAM DSL modem LPF Telephone Network Interne t DSLAM - Digital Subscriber Line Access Multiplexer LPF – Low Pass Filter

9. 9 Splitter ADSL modem Phone Telephone line Voice + ADSL Voice (only) ADSL (only) Splitter ADSL modem Phone Telephone line Voice + ADSL Voice (+ ADSL leakage) ADSL (only) ADSL Filter

10. 10 Selected DSL Standards Courtesy of Shawn McCaslin (Cicada Semiconductor, Austin, TX)

11. 11 Multicarrier Modulation Divide channel into narrowband subchannels No inter-symbol interference (ISI) in subchannels if constant gain within every subchannel and if ideal sampling Discrete multitone modulation Based on fast Fourier transform (FFT) Standardized for ADSL Proposed for VDSL subchannel frequency magnitude carrier DTFT -1 pulse sinc  k cc  c channel Subchannels are 4.3 kHz wide in ADSL and DMT VDSL

12. 12 Discrete Multitone (DMT) ADSL – Asymmetric DSL (G.DMT Standard) Maximum data rates supported (ideal case) Echo cancelled: 14.94 Mbps downstream, 1.56 Mbps upstream Frequency division multiplexing: 13.38 Mbps downstream, 1.56 Mbps up VDSL – Very High Rate DSL (Proposed Standard) Also has symmetric mode: 13, 9, or 6 Mbps Single carrier and DMT DMT VDSL Higher speed G.DMT ADSL Frequency division multiplex 2 m subcarriers m  [8, 12]

13. 13 Create Multiple Channel FDM POTS Upstream Downstream Echo Cancellation Frequency 1 Mhz

14. 14 ADSL Transceiver P/S QAM demod decoder invert channel = frequency domain equalizer S/P quadrature amplitude modulation (QAM) encoder mirror data and N -IFFT add cyclic prefix P/S D/A + transmit filter N -FFT and remove mirrored data S/P remove cyclic prefix TRANSMITTER RECEIVER N/2 subchannelsN real samples N/2 subchannels time domain equalizer (FIR filter) receive filter + A/D channel Bits 00110 conventional ADSL equalizer structure

15. 15 Wireless LAN IEEE 802.11  IEEE Hyperlan/2  ETSI MMAC (Multimedia Mobile Access Communication)  MPT Phy & MAC standardized Phy at 900 MHz, 2.5 GHz & 5 GHz

16. 16 OFDM Transceiver Coding Binary Input Data Interleaving QAM mapping Pilot Insertion S - P IFFT FFT Decoding De-Interleaving QAM demapping Channel Correction P - S Binary Output Data S - P P - S Add Cyclic extension & Windowing DACRF Tx Remove Cyclic extension Timing & Freq. Sync. ADCRF Rx

17. 17 Typical PHY Configuration Small differences exist in PHY for the three WLANs Carrier frequency 5 GHz 52 subcarriers (4 pilots)  64 point FT/IFFT FFT period 3.2 µs Guard time 800 ns OFDM Symbol time 4 µs Modulations  BPSK, QPSK, 16-QAM, 64-QAM Coding rates 1/2,3/4,2/3 Bit rates 6,9,12,18,24,36,48,54 Mbps Subcarrier spacing 312.5 KHz Channel spacing 20 MHz 3-dB bandwidth 16.56 MHz Tolerable delay spread about 250 ns at 24 Mbps

18. 18 Medium Access Control IEEE 802.11 CSMA / CA Hyperlan/2 Centralized & scheduled MAC MMAC Supports both MACs

19. 19 Wireless LAN IEEE 802.11a/b/g/h/j/n b:1999~2.4 GHz ISM a:2002 – 2003~5.0 GHz ISM g:2002 – 2003~2.4 GHz ISM h:2003 – 2004~5.0 GHz ISM j:2004~5.0 GHz ISM n:2006

20. 20 Modulation & Filter type b  DBPSK / DQPSK ( 11Mbps ) Gaussian filter or vendor specific a/g/h/j  upto 64 QAM on 52 OFDM subcarriers, rectangular filter or vendor specific (54 Mbps ) n  upto 64 QAM on 108 OFDM subcarriers, rectangular filter or vendor specific ( > 100 Mbps ), MIMO

21. 21 WMAN – IEEE 802.16 IEEE802.16e - WiMAX Carrier Fixed Access : < 11 GHz Mobile Access : 2 to 6 GHz MAC : TDMA Modulation Fixed Access : OFDM with BPSK, QPSK, 16-QAM, 64-QAM Mobile Access : OFDMA with BPSK, QPSK, 16-QAM, 64- QAM Channel spacing Fixed Access : 1.25 to 20 MHz Mobile Access : 1.25, 5, 10, 20 MHz Single user data rate  upto 75 Mbps