  Voice control in the smart home is commonplace, enabling the convenient
control of smart home Internet of Things hubs, gateways and devices, along with
information seeking dialogues. Cloud-based voice assistants are used to
facilitate the interaction, yet privacy concerns surround the cloud analysis of
data. To what extent can voice control be performed using purely local
computation, to ensure user data remains private? In this paper we present a
taxonomy of the voice control technologies present in commercial smart home
systems. We first review literature on the topic, and summarise relevant work
categorising IoT devices and voice control in the home. The taxonomic
classification of these entities is then presented, and we analyse our
findings. Following on, we turn to academic efforts in implementing and
evaluating voice-controlled smart home set-ups, and we then discuss open-source
libraries and devices that are applicable to the design of a privacy-preserving
voice assistant for smart homes and the IoT. Towards the end, we consider
additional technologies and methods that could support a cloud-free voice
assistant, and conclude the work.
