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Use of energy efficient construction materials is increasing all the time due to more and more tightened building regulations, which aim is to reduce overall energy consumption and thereon e.g. mitigate climate change. Energy efficient building materials and structures improve heat insulation but also change the propagation characteristics of radio signals between outdoor and indoors. This paper examines in details such propagation effects and increased levels of outdoor-indoor attenuation in modern apartment buildings, and their impact on mobile cellular networks. In particular, the aim is to compare external wall attenuations for the modern and older apartment buildings and to assess the impact of increased attenuations for the density and planning of cell sites of mobile cellular macro networks. We also demonstrate and evaluate the opportunities for increased indoor signal coverage by using a dedicated aperture installed in building materials.

Three methods suitable for on-site window and wall penetration loss measurements are presented and compared. The methods are (i) outdoor-to-indoor channel measurement, (ii) far-field penetration loss measurement, and (iii) near-field penetration loss measurement. It is shown that the different methods give similar penetration loss results. The measured window exhibits bandstop characteristics due to the internal reflections in the periodic structure of the triple-layer window. The brick wall has penetration loss that increases as a function of the frequency.

In this article, we study and analyze the impact of modern buildings, with increased building penetration losses (BPLs), on different cellular deployment strategies based on tra ditional outdoor (macro) and dedicated indoor (femto) solutions in a suburban environment. The analysis covers both indoor and outdoor use cases, and the performance of the deployment strategies is evaluated in terms of network coverage, spectral and energy efficiency. The obtained results indicate that the indoor performance of pure macrocellular network in terms of coverage, capacity and energy efficiency is highly degraded with increasing wall penetration losses of modern buildings. Hence, the best strategy to overcome this problem is by deploying indoor femtocells, whose indoor performance is shown to actually benefit from increased BPLs. However, the outdoor performance of pure femtocell deployment is shown to degrade due to increased BPLs. Stemming from this, a heterogeneous Macro-Femto co channel deployment solution is also analyzed and shown to deliver a balanced performance for both outdoor and indoor environments in terms of coverage, capacity and energy efficiency.These findings strongly motivate towards heterogeneous network deployments in the future, where indoor network elements play an increasingly important role.

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