Frequency reuse underwater: capacity of an acoustic cellular network

ABSTRACT

Spatial frequency reuse is considered for large area coverage in bandwidth-limited underwater acoustic networks. The acoustic propagation laws -- namely, the dependence of the path loss on both the distance and the frequency -- lead to a set of constraints that the frequency reuse number N and the cell radius R must satisfy in order to constitute a valid solution for the network topology. For a required signal-to-interference ratio SIR₀, and per-user bandwidth W₀, the region of admissible solutions (R,N) depends on the desired user density ρ and the available bandwidth B. User capacity is defined as the maximal density ρ_max that can be supported within a given bandwidth, and it is derived analytically. Numerical results illustrate the fact that capacity-achieving architectures are characterized by N that grows with ρ_max. In a practical system, the bandwidth may be traded off for a smaller reuse number. The capacity is also shown to increase as the operational bandwidth is moved to higher frequencies. Although higher frequencies demand greater transmission power to span the same distance, they also imply a reduction in the cell size, which in turn provides an overall reduction in the transmission power. While complex relationships are involved in system optimization, the analysis presented offers a relatively simple tool for the design of autonomous underwater systems based on cellular network architectures.

REFERENCES

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INDEX TERMS

Primary Classification:
  A. General Literature
  A.1 INTRODUCTORY AND SURVEY

Additional Classification:
  H. Information Systems
  H.1 MODELS AND PRINCIPLES
      H.1.1 Systems and Information Theory

General Terms:
Theory

Keywords:
cellular systems, power allocation, spatial frequency reuse, underwater acoustic networks, user capacity