2nd International ICST Conference on Cognitive Radio Oriented Wireless Networks and Communications

Research Article

Scaling Laws of Cognitive Networks

  • @INPROCEEDINGS{10.1109/CROWNCOM.2007.4549764,
        author={Mai Vu and Natasha Devroye and Masoud Sharif and Vahid Tarokh},
        title={Scaling Laws of Cognitive Networks},
        proceedings={2nd International ICST Conference on Cognitive Radio Oriented Wireless Networks and Communications},
        keywords={Ad hoc networks  Cognitive radio  Electronic mail  FCC  Frequency measurement  Licenses  Multiple access interference  Radio transmitters  Spread spectrum communication  TV},
  • Mai Vu
    Natasha Devroye
    Masoud Sharif
    Vahid Tarokh
    Year: 2008
    Scaling Laws of Cognitive Networks
    DOI: 10.1109/CROWNCOM.2007.4549764
Mai Vu1,*, Natasha Devroye1,*, Masoud Sharif2,*, Vahid Tarokh1,*
  • 1: Harvard University
  • 2: Boston University
*Contact email: maivu@seas.harvard.edu, ndevroye@seas.harvard.edu, sharif@bu.edu, vahid@seas.harvard.edu


Opportunistic secondary spectrum usage has the potential to dramatically increase spectral efficiency and rates of a network of secondary cognitive users. In this work we consider a cognitive network: n pairs of cognitive transmitter and receiver wish to communicate simultaneously in the presence of a single primary transmitter-receiver link. We assume each cognitive transmitter-receiver pair communicates in a realistic single-hop fashion, as cognitive links are likely to be highly localized in space. We first show that under an outage constraint on the primary link’s capacity, provided that the density of the cognitive users is constant, the sum-rate of the n cognitive links scales linearly with n as n ! 1. This scaling is in contrast to the sum-rate scaling of pn seen in multi-hop ad-hoc networks. We then explore the optimal radius of the primary exclusive region: the region in which no secondary cognitive users may transmit, such that the outage constraint on the primary user is satisfied. We obtain bounds that help the design of this primary exclusive region, outside of which cognitive radios may freely transmit.