Ring voltage-controlled-oscillators (VCOs) are increasingly being used to design ΔΣ ADCs. They have the merits of simple, highly digital and low-voltage tolerant, making them attractive alternatives for the classic scaling-unfriendly operational-amplifier-based methodology. This paper aims to provide a summary on the advancement of VCO-based ΔΣ ADCs. The scope of this paper includes the basics and motivations behind the VCO-based ADCs, followed by a survey covering a wide range of architectures and circuit techniques in both continuous-time (CT) and discrete-time (DT) implementation, and will discuss the key insights behind the contributions and drawbacks of these architectures.

We use network coding based on coded cooperation for the Two-Way Relay channel, where two nodes communicate with each other assisted by a third, relay node. We consider the time-division two-way relay channel without power control, which means the two users and the relay use the same transmission power. Using the proposed network coding approach, channel codes are used at both users and network coding is used at the relay. It is shown via simulation that the proposed scheme provides substantial coding gain in fading channels.