Presentation is loading. Please wait.

Presentation is loading. Please wait.

Doc.: IEEE 802.15-05-273r0 Submission May 2005 C. Razzell et alSlide 1 Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs)

Similar presentations


Presentation on theme: "Doc.: IEEE 802.15-05-273r0 Submission May 2005 C. Razzell et alSlide 1 Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs)"— Presentation transcript:

1 doc.: IEEE r0 Submission May 2005 C. Razzell et alSlide 1 Project: IEEE P Working Group for Wireless Personal Area Networks (WPANs) Submission Title: [MB-OFDM Proposal Update] Date Submitted: [ 11 May, 2005] Source: [C. Razzell] Company [Philips] Address [1151 McKay Drive, San Jose, CA 95131] Voice:[ ], FAX: [ ], Re: [TG3a Down selection Process] Abstract:[Contains technical details of Merged Proposal #1] Purpose:[Provides motivation and justification for the MB-OFDM proposal under consideration] 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 r0 Submission May 2005 C. Razzell et alSlide 2 MB-OFDM Proposal Summary C. Razzell

3 doc.: IEEE r0 Submission May 2005 C. Razzell et alSlide 3 Contents: Spectrum mask requirements Why OFDM is preferred Time-frequency codes for additional spreading MB-OFDM PHY details and performance Summary of benefits compared with direct sequence approach Conclusions

4 doc.: IEEE r0 Submission May 2005 C. Razzell et alSlide 4 Spectrum Mask Requirements (USA) Max. Total Tx power = log( ) + 30 = – 2.5dBm For 10m 4GHz need approx. –10dBm

5 doc.: IEEE r0 Submission May 2005 C. Razzell et alSlide 5 Ultra wideband signals using OFDM Orthogonal Frequency Division Multiplexing –Can efficiently multiplex many sub-carriers to occupy ~500MHz of spectrum –OFDM intrinsically deals with multipath issues by keeping the symbol rate low (e.g., 3.2MHz) –Technology similar to a But only supports QPSK, not 16-QAM nor 64-QAM –Uses less ADC precision and lower arithmetic precision than a/g signal processing

6 doc.: IEEE r0 Submission May 2005 C. Razzell et alSlide 6 Why OFDM is preferred(1) OFDM is spectrally efficient: –IFFT/FFT operation ensures that sub-carriers do not interfere with one other. –Since the sub-carriers do not interfere, the sub-carrier can be brought closer together  High spectral efficiency. OFDM has an inherent robustness against narrowband interference: –Narrowband interference will affect at most a couple of tones.  Do not have to drop the entire band because of narrowband interference.  Erase information from the affected tones, since they are known to be unreliable. Use FEC to recover the lost information.

7 doc.: IEEE r0 Submission May 2005 C. Razzell et alSlide 7 Why OFDM is preferred(2) OFDM has excellent robustness in multi-path environments. 1.Zero prefix preserves orthogonality between sub-carriers --- linear convolution with the c.i.r. is made to look like circular convolution

8 doc.: IEEE r0 Submission May 2005 C. Razzell et alSlide 8 Why OFDM is preferred(3) OFDM has excellent robustness in multi-path environments: 2.Allows receiver to capture multi-path energy more efficiently.

9 doc.: IEEE r0 Submission May 2005 C. Razzell et alSlide 9 Why OFDM is preferred(4) Ability to comply with worldwide regulations: –Channels and tones can be turned on/off dynamically to comply with changing regulations. –Can arbitrarily shape spectrum in software with a resolution of ~4 MHz.

10 doc.: IEEE r0 Submission May 2005 C. Razzell et alSlide 10 Time-frequency codes for additional spreading The FCC requires that UWB systems transmit with a bandwidth of >500MHz at all times Direct generation of OFDM signals of ~500MHz bandwidth is feasible with current CMOS technology However, 500MHz bandwidth alone is not optimum –Tx power is limited to –14.3dBm under FCC rules –Limited frequency diversity –Desire a method to multiply the occupied bandwidth without impacting signal processing requirement…

11 doc.: IEEE r0 Submission May 2005 C. Razzell et alSlide 11 Example OFDM UWB Tx chain 128 pt IFFT in 312.5ns MHz 128 pt IFFT, 100 QPSK data tones, 12 pilots 528 MHz

12 doc.: IEEE r0 Submission May 2005 C. Razzell et alSlide 12 MB-OFDM uses sequenced multiband approach to enhance OFDM Total wideband power is log 10 (3) + 10log 10 (122) + 10log 10 (4.125) = -9.5dBm Occupied bandwidth (and power) multiplied by a factor 3 with almost no signal processing overhead!

13 doc.: IEEE r0 Submission May 2005 C. Razzell et alSlide 13 Time Frequency Codes for Multiple Access Typical methods for achieving multiple access: Spreading (CDMA), Coding In MB-OFDM, an additional method is used: Time-Frequency (TF) Codes: Time-Frequency Codes: –Spread information over all three bands in a given period of time. –Designed such that (on average) only 1/3 of the symbols would collide (FEC code can compensate for the collisions). Performance is governed by SIR = (P sig /P int ) (W/R). –In realistic multi-path conditions: “BW expansion = (W/R) is all that matters”. –Systems with same BW expansion have similar multiple piconet capability. Channel NumberPreamble PatternMode 1 DEV: 3-band Length 6 TFC

14 doc.: IEEE r0 Submission May 2005 C. Razzell et alSlide 14 Overview of Multi-band OFDM Key Idea #1: –Divide the spectrum into bands that are 528 MHz wide. Advantages: –Transmitter and receiver process smaller bandwidth signals (528 MHz).

15 doc.: IEEE r0 Submission May 2005 C. Razzell et alSlide 15 Overview of Multi-band OFDM Key Idea #2: –Interleave OFDM symbols across all bands. Advantages: –Exploits frequency diversity. –Provide robustness against multi-path / interference. –Same transmit power as if the entire band is used.

16 doc.: IEEE r0 Submission May 2005 C. Razzell et alSlide 16 Overview of Multi-band OFDM Key Idea #3: –Insert a zero-padded prefix before IFFT output: Advantages: –Prefix provides robustness against multi-path even in the worst case channel environments.

17 doc.: IEEE r0 Submission May 2005 C. Razzell et alSlide 17 Overview of Multi-band OFDM Key Idea #4: –Insert a Guard Interval between OFDM Symbols: Advantages: –Guard interval allows TX/RX sufficient time to switch between channels.

18 doc.: IEEE r0 Submission May 2005 C. Razzell et alSlide 18 System Parameters Info. Data Rate110 Mbps200 Mbps480 Mbps Modulation/ConstellationOFDM, QPSK FFT Size128 Coding Rate (K=7)R = 11/32R = 5/8R = 3/4 Frequency-domain SpreadingNo Time-domain SpreadingYes No Data Tones100 Zero-padded Prefix60.6 ns Guard Interval9.5 ns Symbol Length312.5 ns Channel Bit Rate640 Mbps Multi-path Tolerance60.6 ns

19 doc.: IEEE r0 Submission May 2005 C. Razzell et alSlide 19 PLCP Frame Format PLCP frame format: Rates : 55, 80, 110, 160, 200, 320, 400, 480 Mb/s. –Support for 55, 110, and 200 Mb/s is mandatory. Preamble + Header = ms.

20 doc.: IEEE r0 Submission May 2005 C. Razzell et alSlide 20 Link Budget and Receiver Sensitivity Assumption: BG#1, AWGN, and 0 dBi gain at TX/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 CMOS 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 Loss2.5 dB 3.0 dB Link Margin6.0 dB10.7 dB12.2 dB RX Sensitivity Level-80.5 dBm-77.2 dBm-72.7 dB

21 doc.: IEEE r0 Submission May 2005 C. Razzell et alSlide 21 System Performance: Band Group #1 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. Range * AWGN LOS: 0 – 4 m NLOS: 0 – 4 m NLOS: 4 – 10 m RMS Delay Spread 25 ns 110 Mbps20.5 m11.4 m10.7 m11.5 m10.9 m 200 Mbps14.1 m6.9 m6.3 m6.8 m4.7 m 480 Mbps8.9 m2.9 m2.6 mN/A

22 doc.: IEEE r0 Submission May 2005 C. Razzell et alSlide 22 Signal Robustness/Coexistence Assumption: Received signal is 6 dB above sensitivity. Values 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 BG #1. Coexistence with b and Bluetooth is relatively straightforward because they are out-of-band. Multi-band OFDM is also coexistence friendly with both GSM and WCDMA. –MB-OFDM has the ability to tightly control OOB emissions. InterfererValue IEEE 2.4 GHz d int  0.2 meter IEEE 5.3 GHz d int  0.2 meter Modulated interferer SIR  –9.0 dB Tone interferer SIR  –7.9 dB

23 doc.: IEEE r0 Submission May 2005 C. Razzell et alSlide 23 Zero IF Transceiver block diagram

24 doc.: IEEE r0 Submission May 2005 C. Razzell et alSlide 24 Brief Comparison with DS-UWB technology (1) Both technologies occupy similar bandwidth below 5GHz (~1.5GHz) –Tx power & link distance performance are therefore similar MB-OFDM is a multiband technology –Allows cost-effective all-CMOS implementation –Improves feasibility of on-chip filtering for truly monolithic solutions Reduces cost of total solution –System is robust to loss of one of the sub-bands Due to a strong interferer Due to application of a dynamic frequency selection algorithm DS-UWB is a single-band technology

25 doc.: IEEE r0 Submission May 2005 C. Razzell et alSlide 25 Multi-Band OFDM is an OFDM technology –Allows fine-grained adaptation of frequency spectrum shape for future regulatory compliance –Channel impulse response equalization comes essentially for free and is standard between implementations Multiple levels of diversity are applied –Convolutional FEC –Time-domain spreading –Frequency domain spreading Multiple companies have now shown silicon feasibility Brief Comparison with DS-UWB technology (2) All these combine to reduce impact of fading of individual sub-carriers

26 doc.: IEEE r0 Submission May 2005 C. Razzell et alSlide 26 Conclusions The industry has overwhelmingly opted to support MB-OFDM as the first major wireless PAN PHY –Inherent robustness to multi-path in all expected environments. –Excellent robustness to U-NII and other generic narrowband interference. Ability to comply with worldwide regulations: –Channels and tones can be turned on/off dynamically to comply with changing regulations. –Can arbitrarily shape spectrum because the tones resolution is ~4 MHz.

27 doc.: IEEE r0 Submission May 2005 C. Razzell et alSlide 27 Conclusions Enhanced coexistence with current and future services: –Channels and tones can be turned on/off dynamically to coexist with other devices. Scalability: –More channels can be added as RF technology improves and as capacity requirements increase. –Multi-band OFDM is digital heavy. Digital section complexity and power scales with improvements in technology node (Moore’s Law). MB-OFDM meets all the TG3a PAR requirements and offers the best trade-off between the various system parameters. We would welcome your support of this proposal!

28 doc.: IEEE r0 Submission May 2005 C. Razzell et alSlide 28 Backup

29 doc.: IEEE r0 Submission May 2005 C. Razzell et alSlide 29 Die size for PHY core: Active CMOS power consumption for PHY core: Complexity (numbers supplied by TI) ProcessComplete Analog* Complete Digital 90 nm3.0 mm mm nm3.3 mm mm 2 * Component area. ProcessTX 55 Mb/s TX 110, 200 Mb/s RX 55 Mb/s RX 110 Mb/s RX 200 Mb/s 90 nm85 mW128 mW147 mW155 mW169 mW 130 nm104 mW156 mW192 mW205 mW227 mW

30 doc.: IEEE r0 Submission May 2005 C. Razzell et alSlide 30 Frequency Synthesis 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.

31 doc.: IEEE r0 Submission May 2005 C. Razzell et alSlide 31 Zero-padded Prefix In a conventional OFDM system, a cyclic prefix is added to provide multi- path protection. Cyclic prefix introduces structure into the TX waveform  structure in the signal produces ripples in the PSD. In an average PSD-limited system, any ripples in the TX waveform will results in back-off at the TX (reduction in range). Ripple in the transmitted spectrum can be eliminated by using a zero-padded prefix. A Zero-Padded Prefix provides the same multi-path robustness as a cyclic prefix (60.6 ns of protection).

32 doc.: IEEE r0 Submission May 2005 C. Razzell et alSlide 32 Proposed OFCOM (United Kingdom) Emissions Mask for UWB

33 doc.: IEEE r0 Submission May 2005 C. Razzell et alSlide 33 Capacity vs. distance for UWB vs. WLAN This area is ripe for exploitation (Assumes 20MHz WLAN, 1GHz UWB bandwidth)


Download ppt "Doc.: IEEE 802.15-05-273r0 Submission May 2005 C. Razzell et alSlide 1 Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs)"

Similar presentations


Ads by Google