Applying Ad-Hoc Relaying to Improve Capacity, Energy Efficiency, and Immission in Infrastructure-Based WLANs

  • Martin Kubisch
  • Seble Mengesha
  • Daniel Hollos
  • Holger Karl
  • Adam Wolisz
Conference paper
Part of the Informatik aktuell book series (INFORMAT)


In classical infrastructure-based wireless systems such as access point-equipped wireless LANs, all mobile terminals communicate directly with the access point. In order to improve the capacity or energy efficiency of such systems, the use of mobile terminals as intermediate relays has been proposed. The rationale is that intermediate relays reduce the communication distance and hence the emitted power. Therefore, relaying could also reduce electromagnetic immission. To assess these potential benefits, we study the effectiveness of various relaying algorithms in a uniform, HiperLAN/2-based system model that has been amended by relaying functionality. These algorithms jointly select intermediate relay terminals and assign transmission power as well as modulation to mobile terminals. The energy efficiency of a point-to-point communication is indeed improved by relaying, however, this effect only marginally transfers to scenarios taking into account several terminals. Nevertheless, it is still possible to extend the lifetime of a network by taking into account available battery capacities.

For a discussion of capacity improvements, two different modes of conceiving system fairness are identified. For both system modes, we present relaying algorithms. Moreover, adding an additional frequency to a cell is beneficial: Using two frequencies can almost double the cell capacity, and for one fairness mode, even relaying with one frequency can improve capacity by up to 30%.

In addition, all these algorithms reduce the immitted power averaged over the area of a cell. All algorithms show improvements, an additional algorithm specialized to reduce immission power can cut the average power almost in half.

Key words

Relaying capacity energy efficiency immission WLAN HiperLAN/2 


Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.


  1. [1]
    M. Bronzei, W. Rave, P. Herhold, and G. Fettweis. Interference Reduction in Single Hop Relay Networks. In Proc. of 11th Virginia Tech Symposium on Wireless Personal Communications (to appear), Blacksburg, VA, June 2001.Google Scholar
  2. [2]
    B. Burns and J.-P. Ebert. Power Consumption, Throughput and Packet Error Measurements of an IEEE 802.11 WLAN Interface. Technical Report TKN-01-007, Telecommunication Networks Group, Technische Universität Berlin, August 2001.Google Scholar
  3. [3]
    T. A. ElBatt, S. V. Krishnamurthy, D. Connors, and S. Dao. Power Management for Throughput Enhancement in Wireless Ad-Hoc Networks. In ICC 2000, New Orleans, LA, June 2000. IEEE.Google Scholar
  4. [4]
    L. M. Feeney and M. Nilsson. Investigating the Energy Consumption of a Wireless Network Interface in an Ad Hoc Networking Environment. In INFOCOM, Anchorage, AK, US, April 2001. IEEE.Google Scholar
  5. [5]
    M. Gastpar and M. Vetterli. On the Capacity of Wireless Networks: The Relay Case. In Proc. INFOCOM, New York, NY, June 2002.Google Scholar
  6. [6]
    J. Gomez, A. T. Campbell, M. Naghshineh, and C. Bisdikian. Conserving Transmission Power in Wireless Ad Hoc Networks. In 9th International Conference on Network Protocols, Riverside, California, November 2001. IEEE.Google Scholar
  7. [7]
    M. Grossglauser and D. Tse. Mobility Increases the Capacity of Wireless Adhoc Networks. In Proc. Infocom, 2001.Google Scholar
  8. [8]
    P. Gupta and P. R. Kumar. The Capacity of Wireless Networks. IEEE Trans. on Information Theory, November 1998." Key=".
  9. [9]
    D. Hollos and H. Karl. A HiperLAN/2 simulation model in OMNeT++. In Proc. 2nd Intl. OMNeT++ Workshop, pages 61–70, Berlin, Germany, January 2002.Google Scholar
  10. [10]
    D. Hollos and H. Karl. A protocol extension to HiperLAN/2 to support single-relay networks. In Proc. of 1st German Workshop on Ad-Hoc Networks, pages 91-108, Ulm, Germany, March 2002.
  11. [11]
    H. Karl and S. Mengesha. Analyzing Capacity Improvements in Wireless Networks by Relaying. In Proc. IEEE Intl. Conf Wireless LANs and Home Networks, pages 339–348, Singapore, December 2001.Google Scholar
  12. [12]
    J. Khun-Jush, G. Malmgren, P. Schramm, and J. Torsner. HIPERLAN type 2 for broadband wireless communication. Ericsson Review, 2:108-119, 2000. Google Scholar
  13. [13]
    J. Peetz. HiperLAN/2 Multihop Ad Hoc Communication by Multiple-Frequency Forwarding. In Proc. of Vehicular Technology Conference (VTC) Spring 2001, Rhodes, Greece, May 2001.Google Scholar
  14. [14]
    Y. Xu, J. Heidemann, and D. Estrin. Geography-Informed Energy Conservation for Ad Hoc Routing. In Seventh Annual ACM/IEEE International Conference on Mobile Computing and Networking. ACM, July 2001.Google Scholar

Copyright information

© Springer-Verlag Berlin Heidelberg 2003

Authors and Affiliations

  • Martin Kubisch
    • 1
  • Seble Mengesha
    • 1
  • Daniel Hollos
    • 1
  • Holger Karl
    • 1
  • Adam Wolisz
    • 1
  1. 1.Fachgebiet TelekommunikationsnetzeTechnische Universität BerlinBerlin

Personalised recommendations