On the Performance of Dense Wireless Networks: No Linear Scaling in Practice.
Song-Nam Hong, Giuseppe Caire · 2014
We consider the hierarchical cooperation architecture of Ozgur, Leveque and Tse, which is supposed to yield almost linear scaling of the capacity of a dense wireless network with the number of users n. Exploiting recent results on the optimality of “treating interference as noise” in Gaussian interference channels, we are able to optimize the achievable average per-link rate and not just its scaling law. Our optimized hierarchical cooperation architecture significantly outperforms the originally proposed scheme, which is yet good enough to achieve the claimed scaling law. On the negative side, we show that even for very large n, the rate scaling is far from linear, and the optimal number of stages t is between 2 and 3, instead of t→∞ as required for almost linear scaling. Combining our results and the fact that, beyond a certain user density, the network capacity is fundamentally limited by Maxwell laws, as shown by Franceschetti, Migliore and Minero, we argue that there is indeed no intermediate regime of linear scaling for dense networks in practice. On the positive side, we show that our optimized hierarchical cooperation scheme outperforms the classical multi-hop routing for a moderately large network size, having a larger and larger gain as network size increases. Thus, hierarchical cooperation with proper optimization is a very promising technique for ad-hoc wireless networks although it does not achieve linear rate scaling for practical network sizes.