Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs) Submission Title: [ Multi-band OFDM Phy - PowerPoint PPT Presentation

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Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs) Submission Title: [ Multi-band OFDM Phy

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  1. Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs) Submission Title: [Multi-band OFDM Physical Layer Proposal] Date Submitted: [17 September, 2003] Source: [Presenter:Anuj Batra] Company [Texas Instruments] [see page 2,3 for the complete list of company names and authors] Address [12500 TI Blvd, MS 8649, Dallas, TX 75243] Voice:[214-480-4220], FAX: [972-761-6966], E-Mail:[batra@ti.com] Re: [This submission is in response to the IEEE P802.15 Alternate PHY Call for Proposal (doc. 02/372r8) that was issued on January 17, 2003.] Abstract: [This document describes the Multi-band OFDM proposal for IEEE 802.15 TG3a.] Purpose: [For discussion by IEEE 802.15 TG3a.] 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. A. Batra, Texas Instruments et al.

  2. This contribution is a technical merger between*: Texas Instrument [03/141]: Batra \ and femto Devices [03/101]: Cheah FOCUS Enhancements [03/103]: Boehlke General Atomics [03/105]: Ellis Institute for Infocomm Research [03/107]: Chin Intel [03/109]: Brabenac Mitsubishi Electric [03/111]: Molisch Panasonic [03/121]: Mo Philips [03/125]: Kerry Samsung Advanced Institute of Technology [03/135]: Kwon Samsung Electronics [03/133]: Park SONY [03/137]: Fujita Staccato Communications [03/099]: Aiello STMicroelectronics [03/139]: Roberts Time Domain [03/143]: Kelly University of Minnesota [03/147]: Tewfik Wisair [03/151]: Shor * For a complete list of authors, please see page 3. A. Batra, Texas Instruments et al.

  3. Authors femto Devices: J. Cheah FOCUS Enhancements: K. Boehlke General Atomics:J. Ellis, N. Askar, S. Lin, D. Furuno, D. Peters, G. Rogerson, M. Walker Institute for Infocomm Research: F. Chin, Madhukumar, X. Peng, Sivanand Intel:J. Foerster, V. Somayazulu, S. Roy, E. Green, K. Tinsley, C. Brabenac, D. Leeper, M. Ho Mitsubishi Electric:A. F. Molisch, Y.-P. Nakache, P. Orlik, J. Zhang Panasonic: S. Mo Philips: C. Razzell, D. Birru, B. Redman-White, S. Kerry Samsung Advanced Institute of Technology:D. H. Kwon, Y. S. Kim Samsung Electronics: M. Park SONY: E. Fujita, K. Watanabe, K. Tanaka, M. Suzuki, S. Saito, J. Iwasaki, B. Huang Staccato Communications:R. Aiello, T. Larsson, D. Meacham, L. Mucke, N. Kumar STMicroelectronics: D. Hélal, P. Rouzet, R. Cattenoz, C. Cattaneo, L. Rouault, N. Rinaldi,, L. Blazevic, C. Devaucelle, L. Smaïni, S. Chaillou Texas Instruments: A. Batra, J. Balakrishnan, A. Dabak, R. Gharpurey, J. Lin, P. Fontaine, J.-M. Ho, S. Lee, M. Frechette, S. March, H. Yamaguchi Time Domain: J. Kelly, M. Pendergrass University of Minnesota: A.H. Tewfik, E. Saberinia Wisair:G. Shor, Y. Knobel, D. Yaish, S. Goldenberg, A. Krause, E. Wineberger, R. Zack, B. Blumer, Z. Rubin, D. Meshulam, A. Freund A. Batra, Texas Instruments et al.

  4. In addition, the following individuals/companies support this proposal: Fujitsu Microelectronics America, Inc: A. Agrawal Hewlett Packard: M. Fidler Infineon: Y. Rashi NEC Electronics: T. Saito SVC Wireless: A. Yang TDK: P. Carson TRDA: M. Tanahashi UWB Wireless: R. Caiming Qui Wisme: N. Y. Lee Microsoft: A. Hassan Jaalaa: A. Anandakumar Tzero: O. Unsal A. Batra, Texas Instruments et al.

  5. Overview of OFDM • OFDM was invented more than 40 years ago. • OFDM has been adopted for several technologies: • Asymmetric Digital Subscriber Line (ADSL) services. • IEEE 802.11a/g. • IEEE 802.16a. • Digital Audio Broadcast (DAB). • Digital Terrestrial Television Broadcast: DVD in Europe, ISDB in Japan • OFDM is also being considered for 4G, IEEE 802.11n, IEEE 802.16, and IEEE 802.20. A. Batra, Texas Instruments et al.

  6. Strengths of OFDM • OFDM is spectrally efficient. • IFFT/FFT operation ensures that sub-carriers do not interfere with each other. • OFDM has an inherent robustness against narrowband interference. • Narrowband interference will affect at most a couple of tones. • Information from the affected tones can be erased and recovered via the forward error correction (FEC) codes. • OFDM has excellent robustness in multi-path environments. • Cyclic prefix preserves orthogonality between sub-carriers. • Cyclic prefix allows the receiver to capture multi-path energy more efficiently. A. Batra, Texas Instruments et al.

  7. Details of the Multi-band OFDM System *More details about the Multi-band OFDM system can be found in the latest version of 03/268. A. Batra, Texas Instruments et al.

  8. Overview of Multi-band OFDM • Basic idea: divide spectrum into several 528 MHz bands. • Information is transmitted using OFDM modulation on each band. • OFDM carriers are efficiently generated using an 128-point IFFT/FFT. • Internal precision is reduced by limiting the constellation size to QPSK. • Information bits are interleaved across all bands to exploit frequency diversity and provide robustness against multi-path and interference. • 60.6 ns prefix provides robustness against multi-path even in the worst channel environments. • 9.5 ns guard interval provides sufficient time for switching between bands. A. Batra, Texas Instruments et al.

  9. Multi-band OFDM: TX Architecture • Block diagram of an example TX architecture: • Architecture is similar to that of a conventional and proven OFDM system. Can leverage existing OFDM solutions for the development of the Multi-band OFDM physical layer. A. Batra, Texas Instruments et al.

  10. Multi-band OFDM System Parameters • System parameters for mandatory and optional data rates: * Mandatory information data rate, ** Optional information data rate A. Batra, Texas Instruments et al.

  11. Frequency-Domain and Time-Domain Spreading • Frequency-domain spreading: • Spreading is achieved by choosing conjugate symmetric inputs for the input to the IFFT. • Exploits frequency diversity and helps reduce the transmitter complexity/power consumption. • Time-domain spreading: • Spreading is achieved in the time-domain by repeating the same information in an OFDM symbol on two different sub-bands. • Exploits frequency diversity as well as enhances SOP performance. A. Batra, Texas Instruments et al.

  12. Simplified TX Analog Section • For rates up to 80 Mb/s, the input to the IFFT is forced to be conjugate symmetric (for spreading gains  2). • Output of the IFFT is REAL. • The analog section of TX can be simplified when the input is real: • Need to only implement the “I” portion of DAC and mixer. • Only requires half the analog die size of a complete “I/Q” transmitter. • For rates > 80 Mb/s, need to implement full “I/Q” transmitter. A. Batra, Texas Instruments et al.

  13. More Details on the OFDM Parameters • 128 total tones: • 100 data tones used to transmit information (constellation: QPSK) • 12 pilots tones used for carrier and phase tracking • 10 guard tones (used to be known as dummy tones) • 6 NULL tones • Exact use of guard tones is left to implementer – adds a level of flexibility in the standard. • Advantages of using guard tones: • Can relax the analog transmit and receive filters. • Helps to relax filter specifications for adjacent channel rejection. • Can be used to help reduce peak-to-average power ratio (PARP). • Could be used to transmit proprietary information (data/signaling). • If data is mapped onto the guard tones, then this scheme is analogous to the concept of Excess Bandwidth as used in Single-carrier Systems. • Received signal in guard tones can be combined appropriately with the remaining information data tones to improve performance. A. Batra, Texas Instruments et al.

  14. Zero-padded Prefix (1) • Ripple in the transmitted spectrum can be eliminated by using a zero-padded prefix. • Using a zero-padded (ZP) prefix instead of a cyclic prefix is a well-known and well-analyzed technique. • Almost no ripple in PSD. A. Batra, Texas Instruments et al.

  15. Zero-Padded Prefix (2) • A Zero-Padded Multi-band OFDM has the same multi-path robustness as a system that uses a cyclic prefix (60.6 ns of protection). • The receiver architecture for a zero-padded multi-band OFDM system requires ONLY a minor modification (less than < 200 gates). • Added flexibility to implementer: multi-path robustness can be dynamically controlled at the receiver, from 1.9 ns up to 60.6 ns. A. Batra, Texas Instruments et al.

  16. Band Plan (1) • Group the 528 MHz bands into 4 distinct groups. • Group A: Intended for 1st generation devices (3.1 – 4.9 GHz). • Group B: Reserved for future use (4.9 – 6.0 GHz). • Group C: Intended for devices with improved SOP performance (6.0 – 8.1 GHz). • Group D: Reserved for future use (8.1 – 10.6 GHz). A. Batra, Texas Instruments et al.

  17. Band Plan (2) • The relationship between the center frequency fc and the band number nb is: A. Batra, Texas Instruments et al.

  18. Multi-mode Multi-band OFDM Devices (1) • Having multiple groups of bands enables multiple modes of operations for multi-band OFDM devices. • Different modes for multi-band OFDM devices are: • Future expansion into groups B and D will enable an increase in the number of modes. A. Batra, Texas Instruments et al.

  19. Multi-mode Multi-band OFDM Devices (2) • Frequency of operation for a Mode 1 device: • Frequency of operation for a Mode 2 device: A. Batra, Texas Instruments et al.

  20. Frequency Synthesis (1) • Example: frequency synthesis for Mode 1 (3-band) device: • A single PLL can also be used to generate the center frequencies for a Mode 2 (7-band) device. A. Batra, Texas Instruments et al.

  21. Frequency Synthesis (2) • Circuit-level simulation of frequency synthesis: • Nominal switching time = ~2 ns. • Need to use a slightly larger switching time to allow for process and temperature variations. A. Batra, Texas Instruments et al.

  22. Multi-band OFDM: PLCP Frame Format • PLCP frame format: • Rates supported: 55, 80, 110, 160, 200, 320, 480 Mb/s. • Support for 55, 110, and 200 Mb/s is mandatory. • Mode 1 (3-band): • Preamble + Header = 11.875 ms. • Burst preamble + Header = 7.1875 ms. • Mode 2 (7-band): • Preamble + Header + Band Extension = 15.625 ms. • Burst preamble + Header + Band Extension = 10.9375 ms. • Header is sent at an information data rate of 55 Mb/s using Mode 1. • Maximum frame payload supported is 4095 bytes. A. Batra, Texas Instruments et al.

  23. More Details on the PHY Header • PHY Header: • Band Extension (3 bit field): • Indicates the mode of transmission for the payload (Mode 1 or Mode 2). • Rate (4 bit field): • Indicates the rate of transmission for the payload. • Rate field also specifies the coding rate, puncturing pattern, and spreading technique. • Length (12 bit field): • Indicates the number of bytes in the payload (excludes the FEC). • Scrambler (2 bit field): • Conveys information about the scrambler state. A. Batra, Texas Instruments et al.

  24. Multiple Access • Multiple piconet performance is governed by the bandwidth expansion factor. • Bandwidth expansion can be achieved using any of the following techniques or combination of techniques: • Spreading, Time-frequency interleaving, Coding • Ex: Multi-band OFDM obtains its BW expansion by using all 3 techniques. • Time Frequency Codes: A. Batra, Texas Instruments et al.

  25. PLCP Preamble (1) • Multi-band OFDM preamble is composed of 3 sections: • Packet sync sequence: used for packet detection. • Frame sync sequence: used for boundary detection. • Channel estimation sequence: used for channel estimation. • Packet and frame sync sequences are constructed from the same hierarchical sequence. • Correlators for hierarchical sequences can be implemented efficiently: • Low gate count. • Extremely low power consumption. • Preamble sequences are designed to be extremely robust. A. Batra, Texas Instruments et al.

  26. PLCP Preamble (2) • In the multiple overlapping piconet case, it is desirable to use different hierarchical preambles for each of the piconets. • Basic idea: define 4 hierarchical preambles, with low cross-correlation values. • Preambles are generated by spreading a length 16 sequence by a length 8 sequence. A. Batra, Texas Instruments et al.

  27. Link Budget and Receiver Sensitivity • Assumption: Mode 1 DEV (3-band), AWGN, and 0 dBi gain at TX/RX antennas. A. Batra, Texas Instruments et al.

  28. Link Budget and Receiver Sensitivity • Assumption: Mode 2 DEV (7-band), AWGN, and 0 dBi gain at TX/RX antennas. A. Batra, Texas Instruments et al.

  29. System Performance (Mode 1: 3-band) • The distance at which the Multi-band OFDM system can achieve a PER of 8% for a 90% link success probability is tabulated below: * Includes losses due to front-end filtering, clipping at the DAC, ADC degradation, multi-path degradation, channel estimation, carrier tracking, packet acquisition, etc. A. Batra, Texas Instruments et al.

  30. System Performance (Mode 2: 7-band) • The distance at which the Multi-band OFDM system can achieve a PER of 8% for a 90% link success probability is tabulated below: * Includes losses due to front-end filtering, clipping at the DAC, ADC degradation, multi-path degradation, channel estimation, carrier tracking, packet acquisition, etc. A. Batra, Texas Instruments et al.

  31. Simultaneously Operating Piconets (1) • Assumptions: • Mode 1 DEV (3-band) operating at a data rate of 110 Mbps. • Simultaneously operating piconet performance as a function of the multipath channel environments: • Results incorporate SIR and erasure estimation at the receiver. * Acquisition limited. ** Numbers based on July results. Currently running simulations to obtain updated numbers. A. Batra, Texas Instruments et al.

  32. Simultaneously Operating Piconets (2) • Assumptions: • Mode 2 DEV (7-band) operating at a data rate of 110 Mbps. • Simultaneously operating piconet performance as a function of the multipath channel environments: • Results incorporate SIR estimation at the receiver. * Acquisition limited. ** Numbers based on July results. Currently running simulations to obtain updated numbers. A. Batra, Texas Instruments et al.

  33. Simultaneously Operating Piconets (3) • Assumptions: • Mode 2 DEV (7-band) operating at a data rate of 200 Mbps. • Simultaneously operating piconet performance as a function of the multipath channel environments: • Results incorporate SIR estimation at the receiver. * Acquisition limited. ** Numbers based on July results. Currently running simulations to obtain updated numbers. A. Batra, Texas Instruments et al.

  34. Signal Robustness/Coexistence • Assumption: Received signal is 6 dB above sensitivity. • Value listed below are the required distance or power level needed to obtain a PER  8% for a 1024 byte packet at 110 Mb/s and a Mode 1 DEV (3-band). • Coexistence with 802.11a/b and Bluetooth is straightforward because these bands can be completely avoided. A. Batra, Texas Instruments et al.

  35. PHY-SAP Throughput • Assumptions: • MPDU (MAC frame body + FCS) length is 1024 bytes. • SIFS = 10 ms. • MIFS = 2 ms. • Assumptions: • MPDU (MAC frame body + FCS) length is 4024 bytes. A. Batra, Texas Instruments et al.

  36. Complexity (1) • Unit manufacturing cost (selected information): • Process: CMOS 90 nm technology node in 2005. • CMOS 90 nm production will be available from all major SC foundries by early 2004. • Die size for Mode 1 (3-band) device: • Die size for Mode 2 (7-band) device: * Component area. * Component area. A. Batra, Texas Instruments et al.

  37. Complexity (2) • Active CMOS power consumption for Mode 1 (3-band) and Mode 2 (7-band) devices: A. Batra, Texas Instruments et al.

  38. Complexity (3) • Manufacturability: • Leveraging standard CMOS technology results in a straightforward development effort. • OFDM solutions are mature and have been demonstrated in ADSL and 802.11a/g solutions. • Scalability with process: • Digital section complexity/power scales with improvements in technology nodes (Moore’s Law). • Analog section complexity/power scales slowly with technology node. • Time to market: 1H 2005. • Size: Solutions for PC card, compact flash, memory stick, SD memory in 2005. A. Batra, Texas Instruments et al.

  39. Scalability of Multi-band OFDM • Data rate scaling: • Data rates from 55 Mb/s to 480 Mb/s has been defined in the current proposal. • Frequency scaling: • Mode 1 (3-bands) and optional Mode 2 (7-band) devices. • Guaranteed interoperability between different mode devices. • Power scaling: • Implementers could always trade-off power consumption for range and information data rate. • Complexity scaling: • Digital section will scale with future CMOS process improvements. • Implementers could always trade-off complexity for performance. A. Batra, Texas Instruments et al.

  40. Comparison of OFDM Technologies • Qualitative comparison between Multi-band OFDM and IEEE 802.11a OFDM: 1. Assumes a 256-point FFT for IEEE 802.11a device. 2. Assumes a 128-point FFT for IEEE 802.11a device. 3. Even though the Multi-band OFDM ADC runs faster than the IEEE 802.11a ADC, the bit precision requirements are significantly smaller, therefore the Multi-OFDM ADC will consume much less power. A. Batra, Texas Instruments et al.

  41. Multi-band OFDMAdvantages (1) • Suitable for CMOS implementation (all components). • Antenna and pre-select filter are easier to design (can possibly use off-the-shelf components). • Early time to market! • Low cost, low power, and CMOS integrated solution leads to: • Early market adoption! A. Batra, Texas Instruments et al.

  42. Multi-band OFDMAdvantages (2) • Inherent robustness in all the expected multipath environments. • Excellent robustness to ISM, U-NII, and other generic narrowband interference. • Ability to comply with world-wide regulations: • Bands and tones can be dynamically turned on/off to comply with changing regulations. • Coexistence with current and future systems: • Bands and tones can be dynamically turned on/off for enhanced coexistence with the other devices. • Scalability with process: • Digital section complexity/power scales with improvements in technology nodes (Moore’s Law). • Analog section complexity/power scales slowly with technology node. A. Batra, Texas Instruments et al.

  43. Summary • The proposed system is specifically designed to be a low power, low complexity all CMOS solution. • Expected range for 110 Mb/s (90% link success probability): 20.5 meters in AWGN, and approximately 11 meters for a Mode 1 device and greater than 9 meters for a Mode 2 device in realistic multi-path environments. • Expected power consumption for 110 Mb/s using 130 nm CMOS process: • Mode 1 DEV: 117 mW (TX), 205 mW (RX), 18 mW (deep sleep). • Mode 2 DEV: 186 mW (TX), 271 mW (RX), 18 mW (deep sleep). • Multi-band OFDM is coexistence friendly and complies with world-wide regulations. • Multi-band OFDM offers multi-mode devices (scalability). • Multi-band OFDM offers the best trade-off between the various system parameters. A. Batra, Texas Instruments et al.

  44. Backup slides A. Batra, Texas Instruments et al.

  45. Self-evaluation Matrix (1) A. Batra, Texas Instruments et al.

  46. Self-evaluation Matrix (2) A. Batra, Texas Instruments et al.

  47. Convolutional Encoder • Assume a mother convolutional code of R = 1/3, K = 7. Having a single mother code simplifies the implementation. • Generator polynomial: g0 = [1338], g1 = [1458], g2 = [1758]. • Higher rate codes are achieved by puncturing the mother code. Puncturing patterns are specified in latest revision of 03/268. A. Batra, Texas Instruments et al.

  48. Bit Interleaver: Mode 1 (3-band) • Bit interleaving is performed across the bits within an OFDM symbol and across at most three OFDM symbols. • Exploits frequency diversity. • Randomizes any interference  interference looks nearly white. • Latency is less than 1 ms. • Bit interleaving is performed in three stages: • First, 3NCBPS coded bits are grouped together. • Second, the coded bits are interleaved using a NCBPS3 block symbolinterleaver. • Third, the output bits from 2nd stage are interleaved using a (NCBPS/10)10 block tone interleaver. • The end results is that the 3NCBPS coded bits are interleaved across 3 symbols and within each symbol. • If there are less than 3NCBPS coded bits, which can happen at the end of the header or near the end of a packet, then the second stage of the interleaving process is skipped. A. Batra, Texas Instruments et al.

  49. Bit Interleaver: Mode 1 (3-band) • Ex: Second stage (symbol interleaver) for a data rate of 110 Mbps • Ex: Third stage (tone interleaver) for a data rate of 110 Mbps A. Batra, Texas Instruments et al.

  50. Multi-band OFDM: RX Architecture • Block diagram of an example RX architecture: • Architecture is similar to that of a conventional and proven OFDM system. Can leverage existing OFDM solutions for the development of the Multi-band OFDM physical layer. A. Batra, Texas Instruments et al.