Massive MIMO Systems with Hardware-Constrained Base Stations

Massive multiple-input multiple-output (MIMO) systems are cellular networks where the base stations (BSs) are equipped with unconventionally many antennas. Such large antenna arrays offer huge spatial degrees-of-freedom for transmission optimization; in particular, great signal gains, resilience to imperfect channel knowledge, and small inter-user interference are all achievable without extensive inter-cell coordination. The key to cost-efficient deployment of large arrays is the use of hardware-constrained base stations with low-cost antenna elements, as compared to today's expensive and power-hungry BSs. Low-cost transceivers are prone to hardware imperfections, but it has been conjectured that the excessive degrees-of-freedom of massive MIMO would bring robustness to such imperfections. We herein prove this claim for an uplink channel with multiplicative phase-drift, additive distortion noise, and noise amplification. Specifically, we derive a closed-form scaling law that shows how fast the imperfections increase with the number of antennas.

Dignity and the Challenge to Liberty :Reading Andras Sajo's Constitutional Sentiments

This paper considers debates about the anti-liberal tendencies of the concept of “human dignity”, in particular those conceptions that are “expressivist”. My aim is to examine how far conceptions of dignity are expressivist, and if so what problems the concept of dignity understood in this way poses for liberty. I consider concerns about dignity’s potential illiberality, in particular the potential illiberality of respect-based conceptions of dignity, in the context of Professor András Sajó’s recent writing, illustrating the discussion with examples drawn from recent judicial decisions of the European Court of Human Rights regarding freedom of speech.