MAN- Metropolitan Area Network Resilient Packet Ring a : 5GHz 54Mbps b : 2.4GHz 11Mbps c : MAC Bridge 802.1D 80

Size: px

Start display at page:

Download "MAN- Metropolitan Area Network Resilient Packet Ring a : 5GHz 54Mbps b : 2.4GHz 11Mbps c : MAC Bridge 802.1D 80"

贡冀居
9 years ago
Views:

1 IEEE a 1 (WLAN) [1] 1963 IEEE Institute Of Electrical and Electronics Engineers LAN MAN-Metropolitan Area Network IEEE 802 IEEE 802 Working Group IEEE LAN MAN Token Bus Token Ring MAN- Metropolitan Area Network MAC Demand Priority Access Methods Cable TV network WPAN-Wireless Personal Area Network 1

2 MAN- Metropolitan Area Network Resilient Packet Ring a : 5GHz 54Mbps b : 2.4GHz 11Mbps c : MAC Bridge 802.1D d : e : WhiteCAP MAC QoS f : Access Point g : 2.4GHz 54Mbps h : a HiperLAN i : MAC a/b/g e MAC-Media Access Control ~ ~ MAC Header ~ 1Mbps, 2Mbps a/b/g 2

3 a/b High Speed Physical layer in The 5GHz Band High Speed Physical layer Extension in The 2.4GHz Band MAC a b a b IEEE a b GHz 5.5Mbps 11Mbps a 5GHz 6MBPs 54Mbps 8 2 IEEE a V.S. Hiperlan2 [4] Hiperlan a PHY 5GHz IEEE 802 ESTI ITU-R WLAN IEEE a NTT Lucent (OFDM) WLAN OFDM (multipath channel fading effect) IEEE a ESTI WLAN Hiperlan2 OFDM a Hiperlan2 PHY PHY MAC(Medium Access Control) 3

4 3 IEEE a 3-1 IEEE a U-NII (Unlicensed-National Information Infrastructure) 300MHz WLAN 5GHz 6GHz Lower and Middle U-NII Band Upper U-NII Band WLAN Hiperlan2 5~6GHz 455MHz a HiperLan a (Channel) 20MHz 2 5GHz FCC-UNII WLAN (Lower and Middle U-NII Band) 200MHz (Upper U-NII Band) 100MHz 5GHz WLAN 300MHz Lower and Middle U-NII Band U-NII (5150MHz) (5350MHz) 30MHz Upper U-NII Band 20MHz 4

5 2. IEEE a 3-2 OFDM a (multi-carrier modulation) OFDM OFDM 3 ( ) FFT IFFT FEC encoder Interleaver 5

6 3-2.1 OFDM [3] 3. OFDM OFDM main lob spacing 2-4 ICI OFDM IFFT 4. (a) (b) 6

7 3-2.2 (Guard Interval or Cyclic Prefix) OFDM IFFT FFT OFDM symbol (ISI) OFDM symbol (cyclic prefix ; CP) T g delay spread ISI CP 5 5. Guard Interval Windowing [2] OFDM QAM sinc OFDM (out-of-band) OFDM window main lob side lob Windowing ICI window side lob ICI a window function 7

8 T OFDM symbol transition time 6 6. CP window OFDM symbol Window function n OFDM sample a symbol 80 sample Scrambler Scrambler a Frame Data field ( ) scrambler scrambler (Generator Polynomial) 8

9 802.11a generator polynomial X 7 + X a scrambler Convolutional Encoder 7. Data scrambler (Forward Error Correction Code ; FEC) a convolutional code FEC convolution code generator polynomial g o = g 1 = code rate 1/2 Viterbi algorithm Convolutional Encoder 8 8. Convolutional Encoder ( k=7 ) 9

10 bit A B R = 1/ a R 1/2 2/3 3/4 code rate puncturing Puncturing convolutional encoder bits bits bits coding rate Puncturing convolution encoder Viterbi decoder code rate 2dB 2dB IEEE a puncturing pattern Puncturing Pattern (R = 3/4) 10

11 10. Puncturing Pattern (R = 2/3) Interleaver Convolutional encoder bits interleaving Interleaver Interleaver bits bits bits (independent) burst error IEEE a Interleaver (R 1/2 2/3 3/4) (BPSK QPSK 16~64QAM) OFDM (coded bits per OFDM symbol) interleaver coded bit coded bits mapping QAM less and more significant bit bit (reliability) 11

12 IEEE a 24Mbps Interleaver 24Mbps 2 OFDM coded bits 192 interleaving 192 bits 12x16 interleaving table Interleaving Table 12. Table 12

13 13. Interleaving Table 12x16 Table 12 Interleaving Table 13 24Mbps 48Mbps Interleaving Table 18x16 Table a a OFDM 64 IFFT (modulator) 64 (subcarrier) a 20MHz (subcarrier spacing) 20MHz 64 = 312.5KHz subcarrier spacing OFDM (symbol period) a OFDM (frequency offset) ICI(Intercarrier Interference) (frequency selective fading) 13

14 64 IFFT 64 subcarrier 64 subcarrier 6 5 (virtual carrier) (guard band) DC = pilot a BPSK QPSK 16-QAM 64-QAM convolutional encoder coding rate 6 ~ 54 Mbits/s a Mbits/s a 14

15 a 5 IEEE a Frame [2] OSI PHY PHY 0 1 PHY RF PHY MAC layer (Medium Access Control Layer) PHY MAC PHY MAC PHY MAC PHY IEEE a PHY (1). PMD system function PMD (physical medium dependent) system 15

16 OFDM (transceiver) (2). PHY convergence function physical layer convergence procedure (PLCP) IEEE PHY service data units (PSDU ; ) frame frame OFDM PMD system MAC PMD PLCP PLCP a 5-1 IEEE a frame format a (PSDU) PSDU MAC a frame format frame format 14 (1). PLCP Preamble (2). Signal Field (3). Data Field 16

17 a frame format PLCP preamble Signal field PLCP header PLCP header MAC PMD PLCP header LENGTH (12 bits) RATE (4 bits) Reserved bit (1 bit) Parity bit (1 bit) Tail bit (6 bits) SERVICE (16 bits) SERVICE PLCP header Signal field OFDM symbol SERVICE bits Signal field SERVICE DATA field 14 Data field SERVICE (16 bits) Tail (6 bits) Pad bits PSDU ( ) 5-2 Preamble OFDM a (frequency offset) (oscillator) mobile (Doppler Effect) OFDM 17

18 ICI a OFDM a training sequence training sequence preamble Training sequence a training sequence short sequence 10 symbol 10 symbol burst mode frame synchronization (coarse synchronization) long sequence 2 symbol long sequence (channel estimation) (fine synchronization) a frame 10 short 2 long sequence a training sequence frame short sequence (frequency estimation) long sequence symbol 1/T short sequence 18

19 f 1 2 T ns = ± = ± = ± short short 625 KHz long sequence f 1 2 T us = ± = ± = ± long long KHz a subcarrier spacing 312.5KHz short sequence 2 subcarrier spacing long sequence 0.5 subcarrier spacing Short preamble Short training sequence 10 symbol a 64 IFFT 64 QAM mapping 64 subcarrier a 11 virtual carrier (guard band) 53 subcarrier short sequence 53 subcarrier IFFT S -26,26 S -26,26 13/6 OFDM (average power) (normalize) IFFT 19

20 r SHORT (t) = w TSHORT (t) N ST k = N / 2 ST S k / 2 exp( j2πk F t) W(t) window function IFFT 4 symbol 16 IFFT CP IFFT 5 short sequence symbol short sequence IFFT 10 short symbol IFFT 3.2 sec CP 1/4 IFFT Long preamble Long training sequence short sequence Long sequence 2 long symbol 1.6 sec guard interval (GI2) short sequence S -26,26 long sequence L -26,26 IFFT r LONG (t) = w TLONG (t) N ST k= N / 2 ST L k / 2 exp( j2πk F (t T G12 )) long sequence 2 IFFT CP 1/4 IFFT long sequence CP 20

21 IFFT OFDM symbol 1/4 1.6 sec CP 2 long symbol long sequence IEEE a Standard Annex G a IFFT OFDM IFFT subcarrier QAM mapping a subcarrier QAM mapping a IFFT subcarrier QAM mapping a IFFT Null 0+0j QAM symbol subcarrier 0 DC a subcarrier a (guard band) 64 subcarrier 6 5 guard band (channel) DC subcarrier 52 subcarrier 52 21

22 4 pilot (channel estimation) 48 subcarrier a subcarrier π 6 virtual carrier 5 virtual carrier a DC π DC a standard To avoid difficulties in D/A and A/D converter offsets and carrier feed through in the RF system, the subcarrier falling at DC (0 th subcarrier) is not used. short long sequence IFFT a IFFT 5-3 Signal field signal field signal field MAC PMD PLCP header PLCP header signal field LENGTH RATE Reserved bit Parity bit Tail bit SERVICE bit 18 22

23 18. Signal field bit Data rate (RATE) a Mbits/sec MAC PHY RATE PHY RATE 4 bits 3-1 RATE 3-1. RATE field 23

24 5-3.2 PLCP length field (LENGTH) a a frame PSDU PLCP length field (LENGTH) 12 bits PSDU PHY MAC LENGTH PSDU Parity (P), Reserved (R), Signal tail (SIGNAL TAIL) signal field 24 bits Bit 4 ( 5 bit) reserved bit default 0 Parity (P) Bit 17 ( 18 bit) 16 bits even parity check bit SIGNAL TAIL bits bits 0 convolutional encoder (states) SIGNAL field signal field MAC PHY 24 bits bits a signal field BPSK convolutional encoder code rate 1/2 Signal field convolutional encoding interleaving BPSK mapping pilot insertion OFDM modulation 19 signal field (Signal field OFDM symbol 24 bits) 24

25 24 Singal field bits Convolutional Encoding (R=1/2) 48 bits Interlevaing 48 bits BPSK Mapping 48 symbol Pilot Insertion (4 pilot) 52 symbol OFDM Modulation (64 points) Add CP (16 points) Windowing 19. Signal Field 5-4 Data field Data field PLCP header service field (SERVICE) PSDU TAIL bits PAD bits 25

26 5-4.1 Service field (SERVICE) IEEE SERVICE field 16 bits 20 Bits descrambler 9 bits default 20. SERVICE field bit PPDU tail bit field (TAIL) TAIL 6 bits 6 bits 0 convolutional encoder 6 ( register ) 0 convolutional decoder Pad bits (PAD) Data field bit OFDM symbol PSDU TAIL bits bit PAD bits PAD bits a standard Annex G 26

27 References [1] ; [2] Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specification, IEEE standard, supplement to standard 802 part 11: wireless LAN, New York, NY, [3] Duan Matiae, OFDM as a possible modulation technique for multimedia applications in the range of mm waves [4] Anibal Luis Intini, Orthogonal Frequency Division Multiplexing for Wireless Networks 27

WLAN 2

WLAN 2 1 WLAN 2 IEEE 802.11 HomeRF GSM/ GPRS CDMA 3 ( ) (Infrared) (Laser) (Microwave) (DSSS) (FHSS) (HomeRF) (Bluetooth) 4 ( ) IrDA (Direct-Beam IR, DB/ IR) (Diffuse IR, DF/ IR) (Ominidirectional IR, Omini/