Hot topic: physical-layer network coding

ABSTRACT

A main distinguishing feature of a wireless network compared with a wired network is its broadcast nature, in which the signal transmitted by a node may reach several other nodes, and a node may receive signals from several other nodes simultaneously. Rather than a blessing, this feature is treated more as an interference-inducing nuisance in most wireless networks today (e.g., IEEE 802.11). The goal of this paper is to show how the concept of network coding can be applied at the physical layer to turn the broadcast property into a capacity-boosting advantage in wireless ad hoc networks. Specifically, we propose a physical-layer network coding (PNC) scheme to coordinate transmissions among nodes. In contrast to "straightforward" network coding which performs coding arithmetic on digital bit streams after they have been received, PNC makes use of the additive nature of simultaneously arriving electromagnetic (EM) waves for equivalent coding operation. PNC can yield higher capacity than straight-forward network coding when applied to wireless networks. We believe this is a first paper that ventures into EM-wave-based network coding at the physical layer and demonstrates its potential for boosting network capacity. PNC opens up a whole new research area because of its implications and new design requirements for the physical, MAC, and network layers of ad hoc wireless stations. The resolution of the many outstanding but interesting issues in PNC may lead to a revolutionary new paradigm for wireless ad hoc networking.

REFERENCES

• 1: Jinyang Li , Charles Blake , Douglas S.J. De Couto , Hu Imm Lee , Robert Morris, Capacity of Ad Hoc wireless networks, Proceedings of the 7th annual international conference on Mobile computing and networking, p.61-69, July 2001, Rome, Italy [doi>10.1145/381677.381684]
• 2: P. C. Ng, and S. C. Liew, "Offered Load Control in IEEE 802.11 Multi-hop Ad-hoc Networks," The 1st IEEE International Conference on Mobile Ad-hoc and Sensor System, Nov. 2004, Florida, USA.
• 3: T. Ojanpera, and R. Prasad, "An Over View of Air Interface Multiple Access For IMT 2000/UMTS," IEEE Communication Magazine, pp. 82--91, Sep. 1998.
• 4: S.-Y. R. Li, R.W. Yeung and N.Cai, "Linear Network Coding," IEEE Trans. Inform. Theory, vol. 49, no.2, pp. 1204--1216, Feb. 2003.
• 5: R.Ahlswede, N.Cai, S.-Y. R. Li, and R.W. Yeung, "Network information flow," IEEE Trans. on Information theory, vol. 46, no. 4, pp. 1204--1216, Jul 2000.
• 6: J. N. Laneman, D. N. Tse, G. W. Wornell, "Cooperative diversity in Wireless Networks: Efficient Protocols and Outage Behavior," IEEE Trans on Information theory, vol. 50, pp. 3062--3080, Dec.2004.
• 7: T.M. Cover and A.A. El Gamal, "Capacity theorems for the relay channel," IEEE Trans on Information theory, pp. 572--584, Sept.1979.
• 8: Y. Wu, P. A. Chou, and S. Y. Kung, "Information Exchange in Wireless Networks with Network Coding and Physical Layer Broadcast," Technical Report MSR-TR-2004-78, Microsoft Research, Redmond WA, Aug. 2004.
• 9: Christina Fragouli , Jean-Yves Le Boudec , Jörg Widmer, Network coding: an instant primer, ACM SIGCOMM Computer Communication Review, v.36 n.1, January 2006 [doi>10.1145/1111322.1111337]
• 10: J. R. Proakis, Digital Communication. New York: McGraw Hill, 1989.
• 11: Kamal Jain , Jitendra Padhye , Venkata N. Padmanabhan , Lili Qiu, Impact of interference on multi-hop wireless network performance, Proceedings of the 9th annual international conference on Mobile computing and networking, September 14-19, 2003, San Diego, CA, USA [doi>10.1145/938985.938993]
• 12: S. Zhang, S. Liew and P. Lam, "Physical Layer Network Coding (PNC)", http://personal.ie.cuhk.edu.hk/~slzhang5/, Technical Report, July. 2006.
• 13: M. Morelli, "Timing and frequency sunchronization for the uplink of an OFDMA system," IEEE Trans. Commun., vol. 52, no. 2, pp. 296--306, Feb. 2004.
• 14: Jeremy Elson , Lewis Girod , Deborah Estrin, Fine-grained network time synchronization using reference broadcasts, Proceedings of the 5th symposium on Operating systems design and implementation

  Due to copyright restrictions we are not able to make the PDFs for this conference available for downloading

  , December 09-11, 2002, Boston, Massachusetts [doi>10.1145/1060289.1060304]
• 15: Y. Tu and G. J.Pottie, "Coherent Cooperative Transmission from Multiple Adjacent Antennas to a Distant Stationary Antenna through AWGN Channels," VTC'02, pp. 130--134, 2002.
• 16: R Mudumbai, G Barriac, U Madhow , "On the feasibility of distributed beamforming in wireless networks", IEEE Trans. on Wireless Commun (under review).

INDEX TERMS

Primary Classification:
  C. Computer Systems Organization
  C.2 COMPUTER-COMMUNICATION NETWORKS
      C.2.1 Network Architecture and Design
          Subjects: Wireless communication

General Terms:
Algorithms, Design, Performance, Theory

Keywords:
ad hoc netrworks, cooperative transmission, multiple-access networks, network coding, relay networks, wireless networks