  This paper deals with throughput scaling laws for random ad-hoc wireless
networks in a rich scattering environment. We develop schemes to optimize the
ratio, $\rho(n)$ of achievable network sum capacity to the sum of the
point-to-point capacities of source-destinations pairs operating in isolation.
For fixed SNR networks, i.e., where the worst case SNR over the
source-destination pairs is fixed independent of $n$, we show that
collaborative strategies yield a scaling law of $\rho(n) = {\cal
O}(\frac{1}{n^{1/3}})$ in contrast to multi-hop strategies which yield a
scaling law of $\rho(n) = {\cal O}(\frac{1}{\sqrt{n}})$. While, networks where
worst case SNR goes to zero, do not preclude the possibility of collaboration,
multi-hop strategies achieve optimal throughput. The plausible reason is that
the gains due to collaboration cannot offset the effect of vanishing receive
SNR. This suggests that for fixed SNR networks, a network designer should look
for network protocols that exploit collaboration. The fact that most current
networks operate in a fixed SNR interference limited environment provides
further motivation for considering this regime.
