Download presentation

Presentation is loading. Please wait.

Published byAustin Crewse Modified over 2 years ago

1
doc.: IEEE /141r1 Submission March 2003 Anuj Batra et al., Texas InstrumentsSlide 1 Project: IEEE P Working Group for Wireless Personal Area Networks (WPANs) Submission Title: [TI Physical Layer Proposal] Date Submitted: [03 March, 2003] Source: [Anuj Batra, Jaiganesh Balakrishnan, Anand Dabak, et al.] Company [Texas Instruments] Address [12500 TI Blvd, MS 8649, Dallas, TX 75243] Voice:[ ], FAX: [ ], Re: [This submission is in response to the IEEE P Alternate PHY Call for Proposal (doc. 02/372r8) that was issued on January 17, 2003.] Abstract:[This document describes the TI physical layer proposal for IEEE TG3a.] Purpose:[For discussion by IEEE TG3a.] Notice:This document has been prepared to assist the IEEE P 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 P

2
doc.: IEEE /141r1 Submission March 2003 Anuj Batra et al., Texas InstrumentsSlide 2 TI Physical Layer Proposal: Time-Frequency Interleaved OFDM Anuj Batra, Jaiganesh Balakrishnan, Anand Dabak Ranjit Gharpurey, Paul Fontaine, Jerry Lin Jin-Meng Ho, Simon Lee, Michel Frechette Steven March, Hirohisa Yamaguchi Texas Instruments TI Blvd, MS 8649 Dallas, TX March 3, 2003

3
doc.: IEEE /141r1 Submission March 2003 Anuj Batra et al., Texas InstrumentsSlide 3 Outline Examine the trade-offs in the design of a UWB system: Choice of operating bandwidth Spreading gain vs. Pulse repetition frequency (PRF) Overview of Time-Frequency Interleaved OFDM (TFI-OFDM) Performance results for the TFI-OFDM system Selected responses to the selection criteria Advantages of the TFI-OFDM system Summary

4
doc.: IEEE /141r1 Submission March 2003 Anuj Batra et al., Texas InstrumentsSlide 4 Trade-offs in Designing a UWB system: - Choice of Operating Bandwidth - Spreading Gain vs. PRF

5
doc.: IEEE /141r1 Submission March 2003 Anuj Batra et al., Texas InstrumentsSlide 5 What Operating BW to Use? Goals to keep in mind when selecting the operating BW: Early time to market: want to enable UWB technology ASAP. CMOS friendly solutions: want solutions that can be integrated. Low cost: enable adoption of technology in portable CE devices. U-NII interference robustness: a is the incumbent device. World-wide compliance: one solution that is flexible enough to work worldwide. Antenna/filter design: want to be able to use off-the-shelf components. We now examine the various trade-offs in choosing the operating BW. We want to select the operating BW in such a way as to achieve all of these goals.

6
doc.: IEEE /141r1 Submission March 2003 Anuj Batra et al., Texas InstrumentsSlide 6 Small Gains by Increasing BW (1) Assume that the TX signal occupies the BW from f L to f U. Assume that f L is fixed at 3.1 GHz. Vary upper frequency f U between 4.8 GHz and 10.6 GHz. Assume that the transmit spectrum is flat over entire BW. TX power = dBm + 10log 10 ( f U – f L ). a has specified a free-space propagation model: f g is the Geometric mean of lower/upper frequencies (10-dB points) d is the UWB transmitter-receiver separation distance (assume d = 10 m) c is the speed of light Look at Received Power = TX Power Path Loss, as a function of upper frequency.

7
doc.: IEEE /141r1 Submission March 2003 Anuj Batra et al., Texas InstrumentsSlide 7 Small Gains From Increasing BW (2) Increasing the upper frequency to 7.0 GHz (10.5 GHz) gives at most a 2.0 dB (3.0 dB) advantage in total received power. On the other hand, increasing the upper frequency, results in an increased noise figure: For f u = 7.0 GHz, by at least 1.0 dB. For f u = 10.5 GHz, by at least 2.0 dB. Result: using frequencies larger than 4.8 GHz increases the overall link margin by at most 1.0 dB with the current RF technology, but at the cost of higher complexity and higher power consumption. Conclusion: only incremental gains in the link budget can be realized by using frequencies above 4.8 GHz.

8
doc.: IEEE /141r1 Submission March 2003 Anuj Batra et al., Texas InstrumentsSlide 8 Optimal Operating Bandwidth Start with the frequency band from 3.1 to 4.8 GHz: Simplifies the front-end design: LNA and mixers (CMOS friendly). Can use higher precision, lower sampling rate ADCs. Capturing multi-path energy is easier. U-NII rejection is simplified. Quicker time to market! As the RF technology improves, start using the higher band as well. 3.1 GHz10.6 GHz4.8 GHz5.9 GHz Start with this band Use this band in the future as technology improves U-NII band: a

9
doc.: IEEE /141r1 Submission March 2003 Anuj Batra et al., Texas InstrumentsSlide 9 Spreading vs. PRF A full-band system obtains its processing gain by spreading (high PRF) the signal across the entire UWB bandwidth. A sub-band system obtains its processing gain by using a lower pulse repetition frequency (PRF) in each of the sub-bands. Spreading (High PRF) Low PRF UWB system parameters Higher A/D speed, accurate timing Higher transmit power, multiple receiver chains Coding Low PRF Spreading TFI-OFDM Lower rate ADC, low transmit power, single receive chain, relaxed timing Coding Full-band Sub-band

10
doc.: IEEE /141r1 Submission March 2003 Anuj Batra et al., Texas InstrumentsSlide 10 Proposed System: TFI-OFDM

11
doc.: IEEE /141r1 Submission March 2003 Anuj Batra et al., Texas InstrumentsSlide 11 Time-Frequency Interleaved OFDM Basic idea is to use OFDM over the entire BW: Start with frequencies from 3168 MHz to 5280 MHz. Total of 512 tones, where each tone has a bandwidth of MHz. Use different subsets of frequency tones from one OFDM symbol to the next. Equivalent to interleaving OFDM symbols across time and across frequency.

12
doc.: IEEE /141r1 Submission March 2003 Anuj Batra et al., Texas InstrumentsSlide 12 Simplified TFI-OFDM The implementation of TFI-OFDM can be simplified by introducing a small guard interval (9.5 ns) between the OFDM symbols. The simplified TFI-OFDM system can now be implemented using a single TX/RX chain, 128-point IFFT/FFT, and low rate DACs/ADCs.

13
doc.: IEEE /141r1 Submission March 2003 Anuj Batra et al., Texas InstrumentsSlide 13 Alternative Views of TFI-OFDM Full-band interpretation of TFI-OFDM: TFI-OFDM can be interpreted as a full-band OFDM system using a 512-point IFFT/FFT. Sub-band interpretation of TFI-OFDM: TFI-OFDM can also be interpreted as a sub-band OFDM system using a 128-point IFFT/FFT on each of the sub-channels. Because TFI-OFDM can be viewed as both a full-band and a sub- band approach, it inherits strengths from both types of systems. We choose to view TFI-OFDM in terms of the second approach, because it leads to a much lower complexity solution and can be realized in today’s CMOS technology.

14
doc.: IEEE /141r1 Submission March 2003 Anuj Batra et al., Texas InstrumentsSlide 14 Details of the TFI-OFDM System *More details about the TFI-OFDM system can be found in the latest version of 03/142.

15
doc.: IEEE /141r1 Submission March 2003 Anuj Batra et al., Texas InstrumentsSlide 15 TFI-OFDM: Example 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 TFI-OFDM physical layer. For a given superframe, the interleaving pattern is specified in the beacon by the PNC. The interleaving pattern is rotated across multiple superframes to mitigate multi-piconet interference.

16
doc.: IEEE /141r1 Submission March 2003 Anuj Batra et al., Texas InstrumentsSlide 16 TFI-OFDM System Parameters System parameters for rates specifically mentioned in selection criteria document: Info. Data Rate110 Mbps200 Mbps480 Mbps Modulation/ConstellationOFDM/QPSK FFT Size128 Coding Rate (K=7)R = 11/32R = 5/8R = 3/4 Spreading Rate221 Information Tones Data Tones100 Info. Length242.4 ns Cyclic Prefix60.6 ns Guard Interval9.5 ns Symbol Length312.5 ns Channel Bit Rate640 Mbps Frequency Band3168 – 4752 MHz Multi-path Tolerance60.6 ns

17
doc.: IEEE /141r1 Submission March 2003 Anuj Batra et al., Texas InstrumentsSlide 17 Simplified TX Analog Section For rates up to 200 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 > 200 Mb/s, need to implement full “I/Q” transmitter.

18
doc.: IEEE /141r1 Submission March 2003 Anuj Batra et al., Texas InstrumentsSlide 18 OFDM Parameters Transmit information using a set of contiguous orthogonal carriers that occupies a bandwidth greater than 500 MHz at all times, according to the FCC requirement: Carriers are efficiently generated using a 128-point IFFT. Use 100 tones for data (QPSK modulation). Use 12 tones for standard pilots. Use 10 tones for user-defined pilots (used to meet 500 MHz BW requirement). Remaining 6 orthogonal tones are NULL (zero). Sub-carrier frequency spacing = MHz. Cyclic prefix length = 32 samples (60.6 ns). Guard interval length = 5 samples (9.5) – time used for switching. Total OFDM symbol length = 165 samples (312.5 ns).

19
doc.: IEEE /141r1 Submission March 2003 Anuj Batra et al., Texas InstrumentsSlide 19 Convolutional Encoder and Bit Interleaver Assume a mother convolutional code of R = 1/3, K = 7. Having a single mother code simplifies the implementation. Generator polynomial: g 0 = [133 8 ], g 1 = [145 8 ], g 2 = [175 8 ]. Higher rate codes are achieved by puncturing the mother code. Bit interleaving is performed across bits within an OFDM symbol and across at most three OFDM symbols. Exploits frequency diversity and randomizes any interference.

20
doc.: IEEE /141r1 Submission March 2003 Anuj Batra et al., Texas InstrumentsSlide 20 Channelization The relationship between f c and channel number n ch is Initially, only the first 3 channels will be defined. More channels can be added as RF technology improves. CHNL_ID ( n ch )Center Frequency ( f c ) MHz MHz MHz

21
doc.: IEEE /141r1 Submission March 2003 Anuj Batra et al., Texas InstrumentsSlide 21 TFI-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. Preamble length = 9.38 s. Burst preamble length = 4.69 s. For the sake of robustness, the PLCP header, MAC header, HCS, and tail bits are always sent at the information data rate of 55 Mb/s. PLCP header + MAC header + HCS + tail bits = 2.19 s. Maximum frame payload supported is 4095 bytes.

22
doc.: IEEE /141r1 Submission March 2003 Anuj Batra et al., Texas InstrumentsSlide 22 Link Budget and Receiver Sensitivity Assumption: AWGN and 0 dBi gain at TX and RX antennas. ParameterValue Information Data Rate110 Mb/s200 Mb/s480 Mb/s Average TX Power-10.3 dBm Total Path Loss64.2 dB 10 meters) 56.2 dB 4 meters) 50.2 dB 2 meters) Average RX Power-74.5 dBm-66.5 dBm-60.5 dBm Noise Power Per Bit-93.6 dBm-91.0 dBm-87.2 dBm RX Noise Figure6.6 dB Total Noise Power-87.0 dBm-84.4 dBm-80.6 dBm Required Eb/N04.0 dB4.7 dB4.9 dB Implementation Loss3.0 dB Link Margin5.5 dB10.2 dB12.2 dB RX Sensitivity Level-80.0 dBm-76.7 dBm-72.7 dB

23
doc.: IEEE /141r1 Submission March 2003 Anuj Batra et al., Texas InstrumentsSlide 23 System Performance (1) PER as a function of distance and information data rate in an AWGN and CM2 environment *. * Results obtained using old channel model. All results incorporate shadowing.

24
doc.: IEEE /141r1 Submission March 2003 Anuj Batra et al., Texas InstrumentsSlide 24 System Performance (2) PER as a function of distance and information data rate in an CM3 and CM4 environment *. * Results obtained using old channel model. All results incorporate shadowing.

25
doc.: IEEE /141r1 Submission March 2003 Anuj Batra et al., Texas InstrumentsSlide 25 System Performance (3) The distance at which the TFI-OFDM system can achieve a PER of 8 % for a 90% link success probability is tabulated below ** : * Includes losses due to front-end filtering, ADC degradation, multi-path degradation, channel estimation, carrier tracking, packet acquisition, etc. Range * AWGNCM1CM2CM3CM4 110 Mbps19.1 mN/A9.8 m9.7 m8.8 m 200 Mbps13.5mN/A6.3 m5.8 m5 m 480 Mbps8.7 m2 m N/A ** Results obtained using old channel model. All results incorporate shadowing.

26
doc.: IEEE /141r1 Submission March 2003 Anuj Batra et al., Texas InstrumentsSlide 26 Simultaneously Operating Piconets Assumptions: Received signal is 6 dB above sensitivity d ref = 9.55 meters Single co-channel interferer separation distance as a function of the reference and interfering multipath channel environments. Test Link/InterfererCM1CM2CM3CM4 CM112.6 m13.0 m12.3 m12.4 m CM313.0 m12.3 m12.2 m12.5 m CM413.8 m12.7 m12.2 m12.7 m All results incorporate shadowing.

27
doc.: IEEE /141r1 Submission March 2003 Anuj Batra et al., Texas InstrumentsSlide 27 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. Coexistence with a/b and Bluetooth is relatively straightforward because these bands are completely avoided. InterfererValue IEEE 2.4 GHz d int = 0.3 meter IEEE 5.3 GHz d int = 0.3 meter Modulated interfererSIR -3.8 dB Tone interfererSIR -4.8 dB

28
doc.: IEEE /141r1 Submission March 2003 Anuj Batra et al., Texas InstrumentsSlide 28 PHY-SAP Throughput Assumptions: MPDU (MAC frame body + FCS) length is 1024 bytes. SIFS = 10 s. MIFS = 2 s. Assumptions: MPDU (MAC frame body + FCS) length is 4024 bytes. Number of Mb/s Mb/s130.4 Mb/s211.4 Mb/s Mb/s155.6 Mb/s286.4 Mb/s Number of Mb/s Mb/s175.9 Mb/s362.4 Mb/s Mb/s186.3 Mb/s409.2 Mb/s

29
doc.: IEEE /141r1 Submission March 2003 Anuj Batra et al., Texas InstrumentsSlide 29 Complexity Unit manufacturing cost (selected information): Process: CMOS 90 nm technology node in Analog section: die size of 2.7 mm 2. Digital section: 295K gates, die size of 1.5 mm 2. Power consumption: Manufacturability: Leveraging standard CMOS technology results in a straightforward development effort. OFDM solutions are mature and have been demonstrated in a/g solutions, which are currently shipping. Time to market: the earliest a complete CMOS PHY solution would be ready for integration is Size: Solutions for PC card, compact flash, memory stick, SD memory in RateTXRXDeep Sleep 110 Mb/s93 mW142 mW15 W 200 Mb/s93 mW156 mW15 W

30
doc.: IEEE /141r1 Submission March 2003 Anuj Batra et al., Texas InstrumentsSlide 30 FFT/IFFT Complexity Calculate the number of complex multipliers and complex adders needed per clock cycle for a 128 point FFT/IFFT. Actual gate count will be dependent upon the process and the architecture. 15 complex 99 MHz to a 3-tap 495 MHz OFDM combines the multi-path energy efficiently with reduced complexity! 128-point FFT/IFFT is realizable in current CMOS technology. Additional reference: Pok et al. “Chip Design for Monobit Receiver”, IEEE Transactions of Microwave Theory and Techniques, vol. 45, no. 12, December ClockComplex Multipliers / clock cycleComplex Adders / clock cycle 66 MHz MHz MHz MHz823

31
doc.: IEEE /141r1 Submission March 2003 Anuj Batra et al., Texas InstrumentsSlide 31 MAC Enhancements Add a time-frequency interleaving information element (TFI IE) to the beacon: TFI IE contains parameters for synchronizing DEVs using TFI-OFDM PHY. IE payload contains Interleaving Sequence (IS) and Rotation Sequence (RS) parameters. IS field specifies the current pattern for interleaving over the channels. RS field specifies the current rotation pattern for the interleaving sequences. PNC updates the IS parameter in the beacon for each superframe according to the RS parameter. DEVs that miss the beacon can determine the IS based on the definition of the RS in the last beacon received. PNC may change the RS parameter by applying the piconet parameter change procedure specified in the IEEE draft standard. Reuse “New Channel Index” as “New Channel Index/RS Number”.

32
doc.: IEEE /141r1 Submission March 2003 Anuj Batra et al., Texas InstrumentsSlide 32 MAC Controlled Rules for Interleaving Piconet #1: Ex: RS_2 = {IS_2, IS_3, IS_1, IS_3, IS_2, IS_1, Repeat} Ex: IS_1 = {Chan_2, Chan_1, Chan_3, Chan_1, Chan_2, Chan_3, Repeat} Piconet #2: Ex: RS_2 = {IS_1, IS_3, IS_2, IS_1, IS_2, IS_3, Repeat}

33
doc.: IEEE /141r1 Submission March 2003 Anuj Batra et al., Texas InstrumentsSlide 33 TFI-OFDM Advantages (1) Suitable for CMOS implementation. Only one transmit and one receive chain at all times, even in the presence of multi-path. 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!

34
doc.: IEEE /141r1 Submission March 2003 Anuj Batra et al., Texas InstrumentsSlide 34 TFI-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: Channels and tones can be dynamically turned on/off to comply with changing regulations. Coexistence with current and future systems: Channels and tones can be dynamically turned on/off for enhanced coexistence with the other devices. Scalability: More channels can be added as the RF technology improves. Digital section complexity/power scales with improvements in technology nodes (Moore’s Law).

35
doc.: IEEE /141r1 Submission March 2003 Anuj Batra et al., Texas InstrumentsSlide 35 Summary The proposed system is specifically designed to be a low power, low complexity CMOS solution. Expected range for 110 Mb/s: 19.1 meters in AWGN, and nearly 10 meters in multipath environments. Expected power consumption for 110 Mb/s: 93 mW (TX), 142 mW (RX), 15 W (deep sleep) TFI-OFDM is coexistence friendly and complies with world-wide regulations. PHY solution are expected to be ready for integration in TFI-OFDM offers the best trade-off between the various system parameters.

36
doc.: IEEE /141r1 Submission March 2003 Anuj Batra et al., Texas InstrumentsSlide 36 Backup slides

37
doc.: IEEE /141r1 Submission March 2003 Anuj Batra et al., Texas InstrumentsSlide 37 TFI-OFDM: Example 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 TFI-OFDM physical layer.

38
doc.: IEEE /141r1 Submission March 2003 Anuj Batra et al., Texas InstrumentsSlide 38 Signal Acquisition Preamble was designed to be robust and work at 3 dB below sensitivity for 55 Mbps. The start of a valid OFDM transmission at a receiver sensitivity level -83 dBm shall cause CCA to indicate busy with a prob. > 90% in 4.69 s. Channel Environment Probability of miss detect P 110 Mb/s Probability of false alarm P f Acquisition Time AWGN< 2 < 4.69 s CM1< 2 < 4.69 s CM2< 2 < 4.69 s CM3< 2 < 4.69 s CM4< 2 < 4.69 s

39
doc.: IEEE /141r1 Submission March 2003 Anuj Batra et al., Texas InstrumentsSlide 39 Is Cyclic Prefix (CP) Sufficient? For a data rate of 110 Mb/s, studied effect of CP length on performance. Curves were averaged over 100 realizations of CM3. For a CP length of 60 ns, the average loss in collected multi- path energy is approx. 0.1 dB. Inter-carrier interference (ICI) due to multi-path outside the CP is approximately 24 dB below the signal.

40
doc.: IEEE /141r1 Submission March 2003 Anuj Batra et al., Texas InstrumentsSlide 40 Peak-to-Average Ratio (PAR) for TFI-OFDM Average TX Power = –9.5 dBm (this value includes pilot tones) PAR of 9 dB results in: Impact of clipping at TX DAC is negligible. Results in a performance loss of less than 0.1 dB in AWGN. Results in a performance loss of less than 0.1 dB in all multipath environments. Peak TX power 0 dBm. Implication: TX can be built completely in CMOS.

Similar presentations

© 2017 SlidePlayer.com Inc.

All rights reserved.

Ads by Google