On the Impact of Mode Selection on Effective Capacity of Device-to-Device Communication

Consider a device-to-device (D2D) link which utilizes the mode selection to decide between the direct mode and cellular mode. This letter investigates the impact of mode selection on effective capacity (EC)-the maximum sustainable constant arrival rate at a transmitter's queue under statistical quality-of-service constraints-of a D2D link for both overlay and underlay scenarios. Due to lack of channel state information, the transmit device sends data at a fixed rate and fixed power; this fact combined with mode selection makes the D2D channel a Markov service process. Thus, the EC is obtained by calculating the entries of the transition probability matrix corresponding to the Markov D2D channel. Numerical results show that the EC decays exponentially (and the gain of overlay D2D over underlay D2D diminishes) with the increase in estimation error of the pathloss measurements utilized by the mode selection.