This paper presents a new type of wireless networking applications in data centers using steered-beam mmWave links. By taking advantage of clean LOS channels on top of server racks, robust wireless packet-switching network can be built. The transmission latency can be reduced by flexibly bridging adjacent rows of racks wirelessly without using long cables and multiple switches. Eliminating cables and switches also reduces equipment costs as well as server installation and reconfiguration costs. Security can be physically enhanced with controlled directivity and negligible wall penetration. The aggregate data transmission BW per given volume is expected to scale as the fourth power of carrier frequency. The paper also deals with the architecture of such network configurations and a preliminary demonstration system.

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The temperature dependence of the diagonal conductivity, a"(T),at integer and fractional quantum Hall effect (FQHE) minima was measured in a sample at various densities. We find o "", the 1/T~O extrapolated value of o. ""(T)from Arrhenius plots, is different for different densities. While a reasonable (1/q) scaling of e"'"at the filling factors v=p/q is observed at lower densities, the scaling is not seen in the highest density data. We explain this loss of scaling by a breakdown of the assumption for a simple activated formula caused by a crossover between the extended state width, I, and T for the measurement. For kT )I, the scaling of the 1/T intercept is recovered by plotting o ""(T) X T vs 1/T and fitting to cr""(T)=(cr"*"'/T)exp( -hE/kT). We attribute the (1/q)' scaling in 0"'"and 0. ""'observed at each density to a (1/q)' scaling in the T =0 conductivity. This supports the assertion of Clark et al. that the charge e of the quasiparticle excitation from the FQHE ground state at v=p/q can be determined from o ""( T) and the charge is e * = e/q.

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