UWB_Lecture11_v2 - Ultrawideband systems: Fundamentals and...

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1 1 Ultrawideband systems: Fundamentals and Standardization Lecture 11 Min-Kuan Chang National Chung Hsing University 教育部通訊教改計畫 教育部通訊教改計畫 2 Outline • IEEE 802.15 3a –DS-UWB – MB-OFDM
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2 3 Introduction • History of UWB 4 Introduction • UWB research started in 2002, when 3.1 – 10.6 GHz band approved by FCC • Based on IEEE 802.15 task group 3a (started 2003) • Today there are two competing proposals – OFDM-UWB and DS-UWB – Need 75% of all votes
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3 5 • 2003.07 US$ 20~30 US$ 10~20 Cost Single Band Multiband Technology Xtreme Spectrum Motorola Intel TI Main players DS-CDMA MB-OFDM Introduction 6
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4 7 DS-UWB 8 DS-UWB PHY Overview • Utilizes 3.1 – 10.6 GHz UWB band • DSSS is adopted – Modulation scheme: BPSK and 4-BOK – Various rate is achieved by using variable-length spreading • Sequence length: 1 to 24 • 28/55/110/220/500/660/1000/1320 Mbps • Convolutional code with code rate ½ and ¾
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5 9 DS-UWB PHY Overview • DS-UWB supports two independent bands of operation. – lower band occupies the spectrum • 3.1 GHz ~ 4.85 GHz (below U-NII) • Support piconet channel: 1~4 • Supporting piconet channel: 5~6 is optional – upper band occupies the spectrum 6.2 GHz ~ 9.7 GHz (above U-NII) • Supporting piconet channel: 7~12 is optional – Baseband data pulses 10 DS-UWB Operating Bands Each piconet operates in one of two bands Low band High band Different personalities : propagation & bandwidth Both have ~ 50% fractional bandwidth Each band supports up to 6 different piconets 34567891 01 1 Low Band 0 1 1 High Band GHz GHz
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6 11 DS-UWB PHY Overview • Preamble –6 PAC s – 3 Lengths • Short preamble –5 μ S – Suitable for high-rate and short-range transmission • Normal preamble – 15 μ S – Default preamble choice • Long preamble – 50 μ S – Used for a poor SNR condition – Intended for extended range application 12 DS-UWB PHY Frame MAC Header Frame Body & FCS ↓↓ PHY Header MAC Header Frame Body & FCS PHY Header MAC Header HCS Frame Body & FCS Preamble PHY Header MAC Header HCS Frame Body & FCS SB 24 c/s Preamble PHY Header MAC Header HCS Frame Body & FCS SB & TS First to air Last to air 24 chips/symbol 1,2,3,6,12 or 24 chips/symbol
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7 13 Scrambler • Used for MAC header and frame body • Preamble and PHY header not used • Pseudo random binary sequence (PRBS) g(D )= 1+D 14 +D 15 , D is a single bit delay x n = x n-14 x n-15 s n = b n x n + D D D D D + 14 Scrambler • To initialize the LFSR, 15-bit seed value is used • The seed values is chosen so that the initial scramble states are 8192 states away from each other • The seed identifier is used to inform the receiver about the seed value – contained in the PHY header
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8 15 Scrambler Seed Selection 0111 1000 0000 111 1,1 0111 1111 0000 000 1,0 0111 0000 1111 111 0,1 1111 1111 1111 111 0,0 Seed Value Seed Identifier 16 Forward Error Correction Mandatory for Tx: Rate ½&¾ Optional for Rx: Rate ½ & ¾ Rate ½ or ¾ Constraint length K=4, Generating polynomial (15,17) Convolutional Mandatory for Tx: Rate
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This note was uploaded on 09/27/2010 for the course UWB 164 taught by Professor Minkuan during the Fall '01 term at National Cheng Kung University.

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UWB_Lecture11_v2 - Ultrawideband systems: Fundamentals and...

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