Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs)

1. Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs) Submission Title: [A proposal for the optional MAC protocol – the TDMA type multiplexed preamble] Date Submitted: November 11, 2005] Source: [Bin Zhen, Yihong Qi, Huan-Bang Li, Shinsuke Hara and Ryuji Kohno, Company: National Institute of Information and Communications Technology ] Contact: Bin Zhen Voice:+81 46 847 5445, E-Mail: zhen.bin@nict.go.jp] Abstract: [A CSMA scheme is proposed for 15.4a MAC protocol.] Purpose: [To propose the TDMA-type multiplexed preamble to support CSMA] 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.

2. A Proposal for the optional MAC protocol -- TDMA type multiplexed preamble Bin Zhen, Yihong Qi, Huan-Bang Li, Shinsuke Hara and Ryuji Kohno National Institute of Information and Communications Technology (NICT)

3. 0.2 preamble-only CS whole packet CS 0.15 pure aloha 0.1 normalized payload throughput 0.05 0 -1 0 1 10 10 10 offered load Background • We proposed a scheme which can ``carrier sense” the whole packet. • Main advantage:greatly improved throughput 1ms preamble, 0.25ms data(1Mbps, 32 bytes data)

4. Performance comparison based on analytical results 0.35 CS all frame (TDMA or CDMA type multiplexing) 0.3 0.25 0.2 normalized payload throughput 0.15 FSK 0.1 0.05 Pure ALOHA 0 -1 0 10 10 offered load 0.5ms preamble, 0.25ms data(1Mbps, 32 bytes data)

5. Current packet structure Preamble Header Payload Acquisition; channel sounding Control information

6. The proposed data packet in doc. 625r3 Preamble + (CDMA type multiplexing) Preamble Header Payload Preamble is multiplexed in the header and payload section as in a CDMA manner.

7. Main problem with the CDMA type multiplexing Power level Regular preamble Header and payload Power of the pulse in superimposed preamble is greatly reduced, about -10dB reduction compared with the regular pulse. Superimposed preamble 0.25, 1, 4ms 0.25ms

8. Two Main Concerns • Implementation complexity due to the small amplitude of pulses in the superimposed preambles. • Interference to non-coherent receivers

9. What is the solution? Regular preamble superimposed preamble CDMA Type Regular preamble … TDMA Type Header and payload

10. Then, no problem with • Implementation concerns on the irregular pulse amplitude • Interference to non-coherent receivers

11. How to do the transformation numerically? • CDMA type multiplexing: 10dB power reduction, Eb/N0=10dB and CS window of 25us • TDMA type multiplexing with constraint • Low extra consumption • Same power level of pulses in TDMA multiplexed preambles • CS window as small as possible due to the crystal offset concern 8us = 16 data symbols 1us = 1 preamble symbol … CS window =27us

12. A CS scheme Receiving a signal within certain time window Matched filter to the ternary code s1 BPF ``de-spreading” ``Energy detection” CCA • CS is to use the energy detector to determine whether the received signal contains a preamble structure. • The energy detector is to test whether the computed energy is over certain threshold or not.

13. Key points of the CS scheme • The preamble symbol(s) are inserted periodically. • After passing a multipath channel, the received preamble symbols still appear with the same periodicity. • regardless symbol synchronization, • regardless multipath distortion • The CS scheme exploits the ``regularity” of the received periodic preamble symbols.

14. Parameters and assumptions • Pulse: • Bandwidth 500MHz with duration 2ns, • Peak PRF= 494MHz; average PRF=16MHz • Preamble: • Ternary code with length 31, symbol duration=1us • Total length: 0.5ms, 1ms, 4ms • Data • Modulation: 2 PPM + BPSK, • Walsh code with length 8, symbol duration=0.5us • Data length: 256us

15. Ratio of extra energy consumed by the multiplexed preamble Observation: Extra energy consumption is low, less than 5% Power reduction = pulse energy of data / pulse energy of the superimposed preamble.

16. Successful CS probability with Eb/N0=10dB, false alarm around 5% and +40ppm crystal offset CS window=27us Observation: Successful CS probability is almost over 85~95% .

17. Conclusions The packet with TDMA type multiplexed preambles • No interference to data detection and SOP • Up to 4 times maximal payload throughput compared that of pure ALOHA • Low extra energy consumption of less than 5% • Effective CS performance, success probability 85~95% with CS window of 27us and crystal offset 40ppm. • No confliction with the non-coherent reception