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Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs) Submission Title: [SCBT based 60GHz PHY Proposal] Date Submitted: [18 July, 2007] Source: [D. Birru(1), R. Chen(1), C.-T. Chou(1), S.-S. Eom(2), B. Gaffney(5) , J.-K. Kim(3), Y.-S. Kim(3), K.-P. Kim(3), Y.-C. Ko(2), J. Laskar(4), W.-Y. Lee(3), M. Mc Laughlin(5) , S. Pinel(4), A. Seyedi(1), H. Zhai(1)] Company [(1) Philips, (2) Korea University, (3) ETRI, (4) GEDC, (5) Decawave] Address [(1) 345 Scarborough Rd. Briarcliff Manor, NY 10510 USA, (2) School of Electrical Engineering, Korea University, Anam-dong, Seungbuk-gu, Seoul 136-713, Korea, (3) 161 Yuseong-gu, Gajeong-dong, Daejeon, 305-700, Korea, (4) 85, 5th street, GEDC, TSRB, Atlanta, GA 30308, USA, (5) 25 Meadowfield, Sandyford, Dublin 18, Ireland] Voice:, FAX: , E-Mail:[ Please see slide 2 ] Re: [In response to TG3c Call for Proposals (IEEE P802.15-07-0586-02-003c)] Abstract: [This document contains the SCBT based 60GHz PHY proposal for TG3c] Purpose: [To describe the details of the SCBT based 60GHz PHY proposal] Notice: This document has been prepared to assist the IEEE P802.15. It is offered as a basis for discussion and is not binding on the contributing individual(s) or organization(s). The material in this document is subject to change in form and content after further study. The contributor(s) reserve(s) the right to add, amend or withdraw material contained herein. Release: The contributor acknowledges and accepts that this contribution becomes the property of IEEE and may be made publicly available by P802.15.
Introduction • Full PHY proposal • Fulfils TG3c’s requirements, use cases and usage models • Bit Rate (PHY SAP rate) 450Mbps-7Gbps • Supports flexible implementation strategies
Foreword • The contents of this document are a merged proposal • We consider this a first step towards further mergers • We will continue our discussions with COMPA for a potential merge. • We actively pursue and invite other merges with the rest of the group
Key Features • Single Carrier Block Transmission (SCBT) with Adaptive CP • Trellis Coded Modulation with Symbol Interleaving • Reduced PAPR • TX Antenna Switch Diversity • Preambles, midambles and pilots for robust performance • Unequal error protection (Block and Convolutional/TCM codes) • Adaptive Modulation (Link adaptation) • Wide band channels (Channel Bonding)
Self Evaluation • Satisfies all Technical Requirements • System Requirements (IEEE P802.15-07-0583-01-003c) • Selection Criteria: (IEEE P802.15-05-0493-27-003c) • Regulatory requirements • Supports all usage models and use cases • Usage Model Document (IEEE P802.15-06-0055-22-003c)
Applications 720p 1080i 1080p Monitor STB DVD-Player etc. Display Video Streaming Wireless Bridge HDD Gigabit Ethernet PMP Digital Camera PC Printer WPAN File Download
Channelization We have adopted COMPA’s original channelization due to simplicity of implementation
Channelization • Provides three non-overlapping data channels in each regulatory domain • Frequency alignment in different regulatory domains • Enables simple frequency synthesizer design • Large bandwidth allows high rate and further scalability
Pulse shaping • Raised Cosine (RC) pulse (Excess BW: 25%) • Data Channel • Bandwidth: W = 2080 MHz • Symbol rate: fsym = 1664 MHz • Allows simple implementation • Addresses tough OOB regulatory rules
Channel bonding • Where regulations permit, two or three adjacent data channels may be bonded
Channel bonding • All three channels can be bonded to provide widest possible channel • Channels 2 & 3 can be bonded to provide Worldwide Common Frequency Band • Same data rates can be achieved with lower constellation size • Higher rates can be achieved
Packet format • Payload carries S segments. • Each segment may or may not have different rate or length. • Each segment may or may not have FCS . • Each segment may or may not be followed by a midamble • A number of consecutive segments may be fragments of one large packet received from MAC • A field in the header will determine if training exist (after header) that can be used for fine beam training
Packet format • Allows for unequal error protection of Video (MSB or LSB), Audio, Encryption keys, CEC, etc. • Allows for dynamic placement of Midamble • Allows for “ACKed” or “best effort” payload • Allows for fragmentation of large packets (improved error rate) • Allows for fine beam tuning
Packet format: Simple packets • Simple packets can be generated simply by choosing the number of segments to be equal to one • This setting is used for common mode and beacons
Preamble Design Considerations • Expected frequency offset high (10x UWB) • Preamble should be short-enough to allow unambiguous frequency offset estimation • Better if phase change in one preamble symbol is less than 90o • Longer preamble intervals to allow fine freq. estimation • Should be low PAPR • Should allow low-cost high-speed implementation • Overall preamble length should be as small as possible for better BW efficiency • Channel delay spread determines minimum length
+ + + - CP Burst detection, timing/freq, AGC, frame sync, etc Chan est., fine freq Preamble • Use Frank-Zadoff sequence for channel estimation • Possesses CAZAC properties • Length: 2x256 • Use hierarchical Frank-Zadoff for synchronization (burst detection, etc.) • Easy Implementation • Good cyclic correlation property • Composed of binary values for certain length • Initial proposed length 8*256 (16x16)
Sample Hierarchical Preamble and Receiver A = [ 1i -1 -1i 1 -1 1 -1 1 -1i -1 1i 1 1 1 1 1] B = [-1 1 1 1] C = [AxB(1) AxB(2) AxB(3) AxB(4)]
Hierarchical Sequence Correlation output • Negligible side-lobs
Preamble Properties-Summary • Frank-Zadoff • Cyclically orthogonal • N-PSK constellation • Low PAPR, very important for 60GHz • About 2dB PAPR after pulse shaping (5dB for BPSK) • Transmitted power can be boosted • Flat frequency response • length limited to N2 • Hierarchical Frank-Zadoff structure • Pseudo-orthogonal to their circular shifts • Receiver uses efficient hierarchical correlator using binary values (no expensive multiplier) • Good for burst detection, frequency error estimation, AGC setting • Hierarchical structure allows to do faster detection in LOS
Modulation Options • A multiple modulations are considered • SCBT (as proposed in this document) • Traditional SC (May merge with SCBT) • OFDM • All devices shall have a common mode and common channelization • We propose that the common mode shall be the SCBT data mode 0 (as described in following slides) with preamble and simple packet format above • Details of other optiona (OFDM, Traditional SC, etc) are not defined in this document
Single Carrier Block Transmission (SCBT) • Header and Payload are transmitted using SCBT (N=256) • A Cyclic Prefix (CP) of length NCP is appended to the beginning of the block • SCBT has low PAPR • SCBT does not require a strong code • SCBT does not require high resolution ADC in AWGN • SCBT enables frequency domain equalization with low complexity • No equalization necessary in AWGN
Adaptive CP length • CP length (NCP) is adaptively selected by the receiver • Start with a large default NCP • Receiver feedbacks the desired NCP using a field in the header of the return packet • Adaptive CP length enables the system to have high BW efficiency when little or no multipath exists • Zero CP length can be used if channel is AWGN or if receiver has a time-domain equalizer • Adaptive CP length enables the system to use reduced CP length with more robust data rate modes • Adaptive CP length gives freedom to receiver design: frequency domain or time domain equalization
Adaptive CP length • Case 1: Receiver does not observe significant multipath (circ polarized antennas, very narrow antennas, clean environment, etc) • First packet will be transmitted with a large default NCP • Receiver asks for NCP=0 in its feedback • Consecutive signal will be conventional single carrier • Case 2: Receiver has a time domain equalizer • First packet will be transmitted with a large default NCP • Receiver asks for NCP=0 in its feedback • Consecutive signal will be conventional single carrier
Adaptive CP length • Case 3: Receiver has a frequency domain equalizer, but does not have a CP length estimation mechanism • First packet will be transmitted with a large default NCP • Receiver asks for a predetermined NCP • Consecutive signal will be SCBT with the predetermined NCP • Case 4: Receiver has a frequency domain equalizer, with a CP length estimation mechanism • First packet will be transmitted with a large default NCP • Receiver asks for a desired NCP (based on the estimation algorithm) • Consecutive signal will be SCBT with the desired NCP
Pilot symbols • Residual frequency error (10-200KHz) and phase noise need to be tracked and compensated for • A pilot sequence is added at the beginning of each SCBT block. (NP = 4 to 16 samples) • These sequences may also be used for multipath channel tracking (short delay spread)
Encoding • Three different coding modes are used: • Convolutional Code / TCM • Four parallel convolutional Encoder/Decoders are used • Block code • Uncoded • Unequal Error Protection (UEP) is provided.
Encoding: Block Code • A high rate block code (probably punctured) is used • Reed-Solomon (RS) code: RS(255,239)
Encoding: CC/TCM • Four parallel convolutional Encoder/Decoders are used • Requirements on decoding speed is reduced by a factor of four
Encoding: CC/TCM • Data bits are encoded using: • Convolutional Code (CC) for BPSK and QPSK • Pragmatic Trellis Coded Modulation (TCM) for NS8QAM and 16QAM • For all cases a punctured rate 1/2 code with K=5 (16 state) and generator polynomials (238,358) is used. • Code is punctured to rates 2/3, 3/4, 5/6 and 7/8 using puncturing patterns as given in [Haccoun’89] • The inner code may not be used for the high rate/simple modes • CC provides very good performance with low complexity • Small K allows low cost parallelization • TCM provides better performance and reduced decoding speed requirements
Encoding: TCM • For TCM, coded and uncoded data bits are then mapped to symbols. • Examples:
Constellation Mapping • Bits are mapped to BPSK, QPSK, NS8QAM and 16QAM constellations:
PAPR Reduction • To reduce the PAPR, every other BPSK and NS8QAM constellation are rotated by 90 degrees NS8QAM BPSK
Additional Modulation and Coding • The modulation and coding as described in the document 15-07-0683-06-003c are added as optional modes • Star-8QAM • Systematic convolutional code • Reed-Solomon code RS(63,55) • Further details will be provided in future updates.
Encoding: Symbol Interleaving • The symbol stream from each mapper is interleaved using a Double Helical Scan (DHS) Interleaver (8x8)
Symbol Repetition • To obtain a lower rate more robust data rate mode, each data symbol is repeated Q times • This mode of transmission is used for the Header • It can also be used for other sensitive data (e.g. encryption keys) • 10log10(Q) gain in Eb/N0 (or better) is obtained
Data rate modes * “Base Data Rate” does not consider CP and pilot symbols
Data rate modes (continued) * “Base Data Rate” does not consider CP and pilot symbols
Data rate modes: Adaptive Modulation • Adaptive Modulation (Link adaptation) • PHY mode used will be chosen for each packet (or for each segment of each packet). • Choice of PHY mode may be based on • Link quality (Distance, multipath, etc) • Data type (Video, Audio, Data, etc)
Data rate modes: Compressed Mode • Compressed Mode*: • Different PHY modes (e.g. constellations) may be used to achieve “compressed mode”. * “Compressed” mode refers to the shortening of the video packet length by choosing a higher rate transmission mode (e.g. QPSK as opposed to BPSK). It does not suggest that the video data is compressed. Mini Slot/ One Video Line Normal Mode Compressed Mode
Data rate modes: UEP • Unequal Error Protection: • Important control packets (e.g. Beacons, ACKs, etc) will always be sent using the most robust mode (Mode 0, with default CP) • Video data may be sent using high rate/simple modes (e.g 2B,2U,5B,5U,8B,8U,10B, or 11) • Unequal error protection may be applied to MSBs and LSBs of video data, i.e. different modes used for MSB and LSBs. • UEP may be applied on a packet by packet basis or be applied to different segments of one packet
Ant 1 . . . TX Receiver RF chain Ant L Comparator < Threshold> Switching control Feedback Antenna switching indicator TX Antenna Switch Diversity • Transmit antenna switch diversity is used to achieve diversity gain from shadowing or blockage.