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: [Preliminary Proposal for TG4a] Date Submitted: [13 July, 2004] Source: [Dani Raphaeli] Company [Inforange] E-Mail: ［danr@eng.tau.ac.il] Re: [] Abstract: [] Purpose: [Providing technical contributions to IEEE 802.15.4a. ] 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. Dani Raphaeli, InfoRange

2. Preliminary Proposal for TG4a Dani Raphaeli DanR@eng.tau.ac.il InfoRange Inc Dani Raphaeli, InfoRange

3. Overview • TG4a Requirements • Approaches needed to meet the requirements • PHY Proposal • Presentation of the Pulse interleaving method • Pulse structure to meet FCC requirements • Ranging using the Synchronous ACK • Frequency planning • MAC implications Dani Raphaeli, InfoRange

4. Technical Requirements • Low complexity and cost • Low power consumption • Precision location (highly desired – relative ranging) • Extended range • Robustness (against MP, against interference) • Mobility (many meanings) • Low bit rate for each individual link • High Aggregated rate at a collector node • Random, ad-hoc, topology • Work under current MAC YES!! We can we satisfy all the above concurrently! Dani Raphaeli, InfoRange

5. Symbol Interleaved Impulse Radio • Basic principle: Use pulse trains with constant large separation between them. Each pulse train represents one symbol. • Pulse train is used instead of single pulse to decrease peak to average, which serves to: • Simplify implementation • Meet FCC peak power constraint in the UWB band • Pulse train polarity corresponding to the 11 bit barker sequence 10110111000 ~100ns ~20s Dani Raphaeli, InfoRange

6. Symbol Interleaved Impulse Radio (cont) Many users can transmit concurrently without interference: (each color represents a different packet from a different user) ~20s Dani Raphaeli, InfoRange

7. Benefits • There is no Near-Far Problem • There is no need for a difficult and slow synchronization process (if each user would have a different sequence, how would receivers know which sequence to tune to?) • Easy implementation • Passes FCC rules • No sensitivity to Multipath (see figure below) if separation is more than the delay spread. Dani Raphaeli, InfoRange

8. Discussion of Modulation and Channel Access • Why use wideband modulation? • Higher time resolution for ranging. • Lower fading • Why use UWB? • Very wide bandwidth is available • Can this be used in non-UWB bands? yes • ~200MHz are available at 5GHz • ~80MHz are available at 2.4GHz worldwide • ~An unknown band might be available in the UHF in the future • Why do we need large gaps between pulse trains? • Separation between each two users > max delay spread of 200ns • 200ns  100 users = 20s • Possible to switch from transmit to receive for the response – see later • Why use multiuser detection instead of CSMA – see doc 15-04-0354-00-004a-comparing-csma-and-cdma-2-multiple-access-approaches-use-in-802-15-4a • Why use a barker sequence in the pulse train? • Spectrum is white, Autocorrelation is good Dani Raphaeli, InfoRange

9. Frequency Plan • Specifying solution that covers both 2.4GHz for international allowance and UWB for US indoor or outdoor handheld. • The 2.4 band will be different than the other only by pulse shape. • More details in 15-04-0356-00-004a-comparing-2-4ghz-and-uwb-band-use-in-802-15-4a.ppt Dani Raphaeli, InfoRange

10. Ranging Methods • Two popular methods for location finding using UWB • DTOA: receiving the signal in at least 3 nodes having common time base • Round Trip Delay: sending a signal, receiving it back and measuring the delay. From that the distance is calculated. • Why should we choose RTD for 4a? • No need for fixed expensive infrastructure. • No need to generate a very accurate time base. • The only one that can be used in Relative systems. • Each node makes its own measurement autonomously. • Easy to handle Multipath (take the earliest component). • Straightforward to implement. • Can handle distance measurement with a single node in case x,y,z coordinate is not necessary Dani Raphaeli, InfoRange

11. Packet Structure Response Period (optional) Preamble DATA (MAC fields) Unmodulated PPM Unmodulated Dani Raphaeli, InfoRange

12. The Response Period DATA Response Period ACK DATA ACK Preamble The ACK is transmitted during the response period of the original Packet Dani Raphaeli, InfoRange

13. The Synchronous ACK • The ACK is transmitted during the response period of the original packet thereby allowing synchronization of the response to measure the channel round trip delay. • The Response Period duration is minimally equal to the ACK preamble duration, and at maximum lasts for the entire ACK • The response (the ACK) is transmitted at a fixed (known) delay relative to the RP pulses. The Node receiving the ACK can measure the RTD and calculate the distance accordingly. • The symbols of the RP are used for synchronizing the response • This allows the use of low accuracy clocks, which serves to: • REDUCE THE COST • MINIMIZE SYSTEM COMPLEXITY (MAC/higher layer not involved in generating accurate time base) • Since the ACKs are transmitted at a fixed delay, ACK collisions are avoided as long as the original packets were not colliding Dani Raphaeli, InfoRange

14. Benefits of Synchronous ACK • For each ACK received, the PHY transfers to the MAC the distance to that node. • No intervention of higher layer needed for ranging. • No special packets are needed for ranging. • Low accuracy clocks can be used. • No collision of the ACKs. • Very low system complexity and cost. Dani Raphaeli, InfoRange

15. Discussion of Modulation and Bit Rate • Why use PPM? • Very simple to implement • Non-coherent receiver: No need for generating phase reference and no need for stable clocks • Why isn’t the preamble modulated? • To shorten synchronization time • Very simple to implement • What is the bit rate? • The symbol rate is 50kbps. We should allow some rate reduction for ECC (TBD), so rate will be around 40kbps. • Extension to higher rates can be achieved by using M-ary PPM and/or by transmitting few packets simultaneously (higher data rate will always be trading off the sensitivity). Dani Raphaeli, InfoRange

16. FFD RFD Types of Devices PAN coordinator • The 802.15.4 defines two types of devices*: • The low complexity RFD (Reduced Function Device) which can be only a leaf on the network. • The full complexity FFD (Full Function Device). • A typical topology composed of many RFDs as the sensors or tags and few FFDs as coordinators and data concentrators. • *see 15-04-0218-00-004a-ieee802-15-4-mac-overview.ppt Dani Raphaeli, InfoRange

17. Types of Devices (cont) • We propose asymmetric PHY: FFD with higher functionality and higher cost and RFD with lower functionality and cost • The ultra low cost RFD (Reduced Function Device) is not required to be able to receive multiple packets. It will be capable of: • Responding to FFD requests. • Sending packets to a FFD • Requesting for a pending packet • The FFD (Full Function Device) is expected to be able to receive simultaneous multiple packets concurrently. It will be capable of: • Receiving many packets at the same time and responding each of them with ACK. • Calculating the distance to each node it received ACK from • Responding to RFD data requests Dani Raphaeli, InfoRange

18. Effects of the new PHY on the MAC and the system performance • Ranging information is just another parameter transferred from the PHY to the MAC • No intervention of higher layer needed for ranging. • No CCA is assumed necessary* • Almost eliminates the hidden node problem • Very little change in the MAC • No limitation on mobility, ranging is performed per packet with no prior information or coordination • *Though CCA per slot can improve performance Dani Raphaeli, InfoRange

19. Did we meet Technical Requirements? • Low complexity and cost small single CMOS 0.13u, inexpensive oscillators • Low power consumption low speed signalling, low power hardware for IR UWB • Precision location yesrelative rangingyes • Extended range low bit rate, efficient MP resolution • Robustness (against MP, against interference) yes • Mobility (many meanings) yes • Low bit rate for each individual link yes • High Aggregated rate at a collector node yes • Random, ad-hoc, topology yes • Work under current MAC yes Dani Raphaeli, InfoRange

20. Thank You! Dani Raphaeli, InfoRange