Energy efficiency of radio link protocols in 3GPP systems

The paper deals with data transfer techniques at the link layer, which have been specified in 3GPP to preserve information integrity over the wireless link. We consider the acknowledged transfer mode, which implements a selective ARQ protocol. We enhance the 3GPP specification with a control mechanism of the transmitter activity that allows the system to save radio resources as well as energy in the case of bad channel conditions. In this way, we can obtain a significant energy saving at the expense of the provided QoS. By developing a Markovian model of the ARQ scheme, we study the protocol behavior as channel characteristics change and we find a trade-off between traffic QoS and energy efficiency.