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

## TL;DR

This paper analyzes how mode selection affects the effective capacity of D2D communication links, revealing that estimation errors significantly reduce capacity and diminish the benefits of overlay over underlay modes.

## Contribution

It models the D2D channel as a Markov process considering fixed transmission parameters and evaluates the impact of pathloss estimation errors on effective capacity.

## Key findings

- Effective capacity decays exponentially with estimation errors.
- Overlay D2D gains diminish as estimation errors increase.
- Mode selection impacts capacity under statistical QoS constraints.

## Abstract

Consider a device to device (D2D) link which utilizes the mode selection to decide between the direct mode and cellular mode. This paper investigates the impact of mode selection on effective capacity (EC) (the maximum sustainable constant arrival rate at a transmitters 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.