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

Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs) Submission Title: TG4a (UWB)2-MAC proposal for UWB-LDR wireless networks Date Submitted: November 15, 2005 Source: G.M. Maggio (ST) & L. De Nardis, M.-G. di Benedetto (U. di Roma)

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

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  1. Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs) Submission Title: TG4a (UWB)2-MAC proposal for UWB-LDR wireless networks Date Submitted: November 15, 2005 Source: G.M. Maggio (ST) & L. De Nardis, M.-G. di Benedetto (U. di Roma) Contact: Gian Mario Maggio (STMicroelectronics) Voice: +41-22-929-6917, E-Mail: gian-mario.maggio@st.com Abstract: TG4a (UWB)2-MAC proposal for LDR location-aware UWB networks Purpose: To provide detailed information on (UWB)2-MAC proposal for Low-Data Rate location-aware UWB wireless networks 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. G.M. Maggio, L. De Nardis & M.-G. Di Benedetto

  2. (UWB)2-MAC Protocol for Low Data-Rate Location-Aware UWB Wireless Networks Gian Mario Maggio (ST) & Luca De Nardis, (U. di Roma) Maria-Gabriella Di Benedetto (U. di Roma) G.M. Maggio, L. De Nardis & M.-G. Di Benedetto

  3. UWB-LDR Specific MAC Design • Ultra Wideband based on Impulse Radio and Time Hopping is characterized by: • Low probability of pulse collision • Accurate ranging • Medium Access Control can therefore: • Exploit resilience to Multi-Access Interference (MAI) in Low Data-Rate (LDR) applications • Define procedures for bi-directional distance estimation (UWB)2: Uncoordinated, Wireless, Baseborn medium access for UWB G.M. Maggio, L. De Nardis & M.-G. Di Benedetto

  4. MAC Design Choices Key Assumptions Synchronization is achieved on a packet-by-packet basis Simple synchronization hardware (no precise clock requirements) Low Data-Rate and “rare” packets (peak rate 1 Mb/s, average rate  20 Kb/s) No Carrier Sensing: Pure Aloha (with TH coding) TH-CDMA: Common signaling code available to all devices + Dedicated data code unique for each transmitter Need for broadcast packets Time-Hopping Impulse Radio with ~GHz BW G.M. Maggio, L. De Nardis & M.-G. Di Benedetto

  5. (UWB)2–MAC Key Features • (UWB)2 is a hybrid multi-channel MAC protocol • Each channel is identified with a Time Hopping code • CONTROL packets are transmitted on a Common channel, i.e. using a Common TH-code known to all terminals • DATA packets are transmitted on dedicated channels identified by Transmitter-unique TH codes, • The agreement on the code to be used for a DATA packet is the result of a handshake performed on the Common code G.M. Maggio, L. De Nardis & M.-G. Di Benedetto

  6. Impact of (UWB)2-MAC • No Carrier Sensing required • Aloha approach can be applied for terminals adopting one TH-code (spread-Aloha), or no TH-coding at all  When switching between different TH codes is available, the code dimension is used in the protocol • Ranging capability at the PHY is required PHY MAC • TH-CDMA (vs. TDMA) • Support for ranging primitives G.M. Maggio, L. De Nardis & M.-G. Di Benedetto

  7. Backward Compatibility Issues:802.15.4 vs (UWB)2-MAC • Data rates of 250 kb/s, 40 kb/s and 20 kb/s • Star or Peer-to-Peer operation • Support for low latency devices • CSMA-CA channel access • Fully handshaked protocol for transfer reliability  Possible in (UWB)2  Possible in (UWB)2, as long as a slotted time axis is adopted (guaranteed slots can be defined, as in 802.15.4)  Possible in (UWB)2, with different channel access strategy; all topologies defined in 802.15.4 can be adopted without modifications •  Replaced by Aloha in (UWB)2: • Pure Aloha in Peer-to-Peer operations • Pure/Slotted Aloha in Star operations (slotted time axis provided by the PNC)  Same as for (UWB)2 (optional ACK is already in the protocol, as in 802.15.4) G.M. Maggio, L. De Nardis & M.-G. Di Benedetto

  8. Tx LE Rx TH-Flag Sync Trailer Rx Node ID Tx Node ID TH-Code CRC LE PDU Tx LC Rx CRC Tx Node ID Rx Node ID Sync Trailer LC PDU (UWB)2-MAC: Transmission Procedure (1/2) • Step 1: Tx node sends a Link Establishment (LE) PDU (Protocol Data Unit) to Rx using the Common TH code. The LE PDU contains: • IDs of TX and RX • Tx TH-Code • Sync. trailer + CRC field Step 2: Rx node replies with a Link Confirmation (LC) PDU and switches to the Tx TH-Code G.M. Maggio, L. De Nardis & M.-G. Di Benedetto

  9. Tx DATA Rx PDU N PAYLOAD CRC Tx Node ID Rx Node ID Sync Trailer Number PACKETS DATA PDU Tx ACK Rx DATA Packet Status Tx Node ID Rx Node ID Sync Trailer ACK PDU (UWB)2-MAC: Transmission Procedure (2/2) Step 3: Tx node sends the DATA PDU on the dedicated, transmitter-specific TH code communicated in the LE PDU Step 4: Rx node sends an ACK packet when required by the Tx node (not sent for PDUs transferring broadcast information) G.M. Maggio, L. De Nardis & M.-G. Di Benedetto

  10. Aloha vs. Slotted-Aloha • Both Pure Aloha/Slotted Aloha were analyzed • Slotted-Aloha could improve performance in centralized network topologies, where the coordinator can provide slot synchronization with low overhead • For NB systems, Slotted Aloha guarantees a higher (up to 2x) throughput w.r.t. Pure Aloha • What about UWB-LDR networks? G.M. Maggio, L. De Nardis & M.-G. Di Benedetto

  11. (UWB)2-MAC: Performance Analysis • Performance of (UWB)2 was analyzed as a function of: • # of users • User data rate, R • Transmission range • Channel model (LOS vs NLOS) • Assumptions: • Impulse Radio (IR) UWB terminals with TH-coding • Ghassemzadeh & Tarokh path loss model • Pulse Collision: MAI model specific for IR-UWB • No FEC was considered (all bits in a packet must be correct, for a packet to be correct)  ARQ (Automatic Repeat on reQuest) • Tx power is selected high enough to study the effect of MAI (impact of thermal noise is made negligible) G.M. Maggio, L. De Nardis & M.-G. Di Benedetto

  12. Simulation Settings G.M. Maggio, L. De Nardis & M.-G. Di Benedetto

  13. (UWB)2-MAC: Performance in AWGN (1/4) • Impact of # of terminals and transmission range on throughput: G.M. Maggio, L. De Nardis & M.-G. Di Benedetto

  14. (UWB)2-MAC: Performance in AWGN (2/4) • Impact of # of terminals and transmission range on delay: G.M. Maggio, L. De Nardis & M.-G. Di Benedetto

  15. (UWB)2-MAC: Performance in AWGN (3/4) • Impact of transmission range and user data-rate on throughput: 5 Users G.M. Maggio, L. De Nardis & M.-G. Di Benedetto

  16. (UWB)2-MAC: Performance in AWGN (4/4) • Impact transmission range and user data-rate on delay: 5 Users G.M. Maggio, L. De Nardis & M.-G. Di Benedetto

  17. (UWB)2-MAC: Performance in Multipath (1/2) • Throughput vs. channel models (CM1, CM2, CM5, CM6) @R=100kb/s: G.M. Maggio, L. De Nardis & M.-G. Di Benedetto

  18. (UWB)2-MAC: Performance in Multipath (2/2) • Delay vs. channel models (CM1, CM2, CM5, CM6) @R=100kb/s: G.M. Maggio, L. De Nardis & M.-G. Di Benedetto

  19. Conclusions • For UWB-LDR networks both Pure/Slotted Aloha lead to high throughputs (due to MAI resilience and low probability of packet collisions) • Gap increases with traffic (# of users) • Slotted Aloha leads in average to a higher delay (Δ~1ms) • Impact of traffic: Pure Aloha is more sensible  Decreased throughput, higher delay • With multipath: Slotted Aloha does not provide advantages in terms of throughput, but higher average delay • Effect of the channel: Indoor NLOS (CM2) with higher data rate exhibits poorer performances G.M. Maggio, L. De Nardis & M.-G. Di Benedetto

  20. References • M.-G. Di Benedetto, L. De Nardis, M. Junk, G. Giancola, "(UWB)2: Uncoordinated, Wireless, Baseborn, medium access control for UWB communication networks," Mobile Networks and Applications Special Issue on WLAN Optimization at the MAC and Network Levels (2005) • L. De Nardis and M.-G. Di Benedetto, “Joint communications, ranging, and positioning in low bit rate Ultra Wide Band networks,” IEEE INFOCOM 2005 Student Workshop, March 14 2005, Miami, Florida, USA • L. De Nardis, G. Giancola, M.-G. Di Benedetto, "Power-Aware Design of MAC and Routing for UWB Networks", in Proceedings of the IEEE Global Telecommunications Conference (Globecom), 2004, 19 November - 3 December 2004 • Di Benedetto, M. G., and Giancola, G. Understanding Ultra Wide Band Radio Fundamentals. Prentice Hall, 2004 • S. S. Ghassemzadeh and V. Tarokh, “UWB Path Loss Characterization In Residential Environments”, IEEE Radio Frequency Integrated Circuits Symposium, pp. 501-504, 2003 G.M. Maggio, L. De Nardis & M.-G. Di Benedetto

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