“The wireless capacity has doubled every 30 months over the last 104 years¹. This translates into an approximately million-fold capacity increase since 1957. Analyzing these gains shows a 25x improvement from wider spectrum, a 5x improvement by dividing the spectrum into smaller slices, a 5x improvement by designing better modulation schemes, and a whopping 1600x gain through reduced cell sizes and transmit distance. The enormous gains reaped as a result of smaller cell sizes arise from efficient spatial reuse of spectrum, or alternatively, a higher area spectral efficiency measured in bits per second per hertz per unit area”^2.

Take away:  The vast majority of historical gains achieved in data capacity have been accomplished by reducing or confining the coverage size and/or transmit distance. This is driven by physics—there is a limit to how many bits/Hz can be squeezed out of a single wireless stream (Shannon’s Law). The best way to increase capacity is to increase the density of access points. This combined with the the fact that 70% of all cell phone sessions begin and end in a building³ (increasing to 80% by 2016), with demonstrations showing greatest capacity gains for indoor cellular deployments that are overlaid within conventional macro cells, supports the strategic use of in-building DAS and heterogeneous networks to meet exponentially increasing data demands.

[1] M. S. Alouini and A. J. Goldsmith, “Area Spectral Efficiency of Cellular Mobile Radio Systems,” IEEE Trans. Vehic. Tech., vol. 48, no. 4, July 1999, pp. 1047–66.

[2] X. Tao, X. Xu, and Qimei Cui, “An Overview of Cooperative Communications”, IEEE Communications, June 2012, pp. 65-71.

[3] “LTE Amplify and Forward Relaying for Indoor Coverage Extension”, Thomas Wirth, Lars Thiele, Thomas Haustein, Oliver Braz and Jörg Stefanik, Vehicular Technology Conference Fall (VTC 2010-Fall), 2010 IEEE 72nd, Sept. 2010