Low-Complexity UWB Modulation for Low-Data-Rate WPAN

1. Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs) Submission Title: [802.15.4 Discussion Report July 03] Date Submitted: July, 2003 Source: [Liang Li, Yafei Tian, Chenyang Yang] Company: [Helicomm Inc] Address: [1947 Camino Vida Roble] Voice: [760-918-0856], FAX: [760-918-0338], E-Mail: [liang.li@helicomm.com] Re: [] Abstract:[Opening report for July 2003 San Francisco meeting] Purpose: [] 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 these viewgraphs becomes the property of IEEE and may be made publicly available by P802.15. Liang Li, Helicomm Inc.

2. Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs) Helicomm Proposal A Low-complexity UWB modulation and Demodulation Method for Low Data-Rate WPAN Liang Li, Yafei Tian, Chenyang Yang Helicomm Inc Liang Li, Helicomm Inc.

3. Purpose • Low cost, low complexity, low power, low rate UWB system. • Complete energy capture, symbol rate sampling, easy timing. • No down converter, no RAKE, no EQU, no PLL, no coding. Liang Li, Helicomm Inc.

4. Overview • The possible benefits as using the UWB in low rate system. • A proposed low complexity UWB modulation and demodulation method for low-data-rate WPAN. • Performance results. Liang Li, Helicomm Inc.

5. Possible Benefits • Multipath energy fading is less than 6dB, thus link margin will be small and transmit power will be reduced 10~30dB. • UWB signal use 3.1~10.6GHz band, thus the crowed 2.4G band is avoided and less interference will be received. • UWB pulse duration is very short, so it can be used to do precious location, and this ability is very useful when doing route selection in network organizing. • Compare with the high-rate UWB system, the low-rate system can cover longer distance. Liang Li, Helicomm Inc.

6. A Proposed low complexity UWB Modulation and Demodulation Method for Low-data rate WPAN Liang Li, Helicomm Inc.

7. Transmitter Structure • The Data Rate is supposed to be 1Mbps. • The 1st part is a differential encoder, the delay is 1 bit which equals to 1us when data rate is 1Mbps. • The 2nd part is a pulse generator, which generate UWB pulse and change its polarity corresponding to the bit value after differential encoder. • The 3rd part is a power amplifier. • The 4th part is a band pass filter. Liang Li, Helicomm Inc.

8. Pulse Shape • The occupied bandwidth of the pulse is not very wide and the center frequency of it is below 3.1GHz, so that carrier is required to modulate it to comply with FCC’s spectrum mask. • Pulse width is 3ns, -3dB bandwidth is 410MHz, -10dB bandwidth is 700MHz. Liang Li, Helicomm Inc.

9. Receiver Structure (1) The traditional Rake Receiver • The correlator before the ADC is a pulse shape matched filter. • The part after ADC and before the decision device is a traditional Rake combiner. The information bits will be recovered after the differential decoder. • In general case, when the maximal 8 path is selected, the performance of the selective Rake receiver is approximate to that of all Rake receiver. Liang Li, Helicomm Inc.

10. Receiver Structure (2) Analog differential demodulation(ADD) receiver: • The received signal is passed by a band pass filter, a low noise amplifier and an analog delay correlator(multiplier and integrator), where the delay is 1us. • The transmitted bits will be recovered after sampling and decision. • The sampling and decision device can be implemented with an 1 bit ADC, the sampling rate is very low, that is just the data rate. Liang Li, Helicomm Inc.

11. System Parameters & Link Margin Information data rate Rb = 1 Mb/s Power spectrum density Sf= -41.3dBm/MHz Tx signal –3dB bandwidth B= 410MHz Average Tx power Pt=Sf*B= -15.2 dBm Tx antenna gain Gf= 0 dBi Rx antenna gain Gr= 0 dBi Center frequency fc= 3.6 GHz Path loss at 1 meter L1=20log10(4Pifc/C)) = 43.6 dB Rx power at 1m Pr=Pt+Gt+Gr-L1= -58.8 dBm Noise power per bit N=-174+10log10(Rb)= -114 dBm Rx Noise Figure Referred to the Antenna Terminal Nf= 7 dB Total noise power per bit Pn=N+Nf= -107 dBm Eb/No at 1 meter is Pr-Pn = 48.2 dB Eb/No at d meter is 48.2 –20log10(d)dB Liang Li, Helicomm Inc.

12. Performance Liang Li, Helicomm Inc.

13. Performance Liang Li, Helicomm Inc.

14. Conclusion With the proposed modulation and transmitter structure, following benefits can be obtained with the referenced receivers: • The performance of ADD receiver is comparable to the performance of the 2tap SRake receiver, which can achieve 1% PER at 25m distance, and this performance will definitely meet the requirement of WPAN. • There will be 5dB deterioration of ADD receiver with respect to the all Rake receiver. However, much lower sampling rate is required in ADD receiver, no accurate timing and no channel estimation is required to completely capture the channel energy. Thus the preamble can be designed rather short. • No frequency acquisition and tracking is required. • The coding/decoding modular can be inserted if longer distance is required to be covered. The distance will be doubled if the coding gain is 6dB. Liang Li, Helicomm Inc.