On the feasibility to overlay a narrowband IoT signal in IEEE 802.11

We study the case where a narrowband (NB) signal, intended possibly for an Internet of Things (IoT) application, is concurrently transmitted with a legacy wideband (WB) Wi-Fi signal by means of overlay - meaning that the two signals are not orthogonal to each other. Concurrent operation is particularly seen as a means to achieve high spectral efficiency in the future IoT society. Although, under certain conditions, concurrent transmission may be possible without any modifications to the legacy Wi-Fi transceiver, we show that minimal adjustments to the Wi-Fi receiver can in fact lead to significant gains for the concurrent WB transmissions. Furthermore, if also the WB transmitter is aware of the scheduled overlay, small modifications to it can help improve the performance of the NB transmissions. Both these aspects are studied here in detail under various assumptions for the WB and NB transceivers.