Sidelink Transmissions and Proximity Services in LTE-A and Beyond
Sidelink in LTE-A denotes a transmission direction from a user equipment (UE) to another UE(s), in contrast to downlink from an eNB to a UE and uplink from a UE to an eNB. In sidelink transmissions, if a UE has data to be transmitted to another UE(s), a UE can directly transmit data to the destination UE without signal relay via an eNB. Consequently, sidelink transmissions can only take place among two or more UEs within the signal coverage of each other, and such a framework is also known as proximity services (ProSe) or direct transmissions.
Since 2012, the First Responder Network Authority (FirstNet) of the United States (US) Department of Commerce (DoC) is tasked with creating a nationwide network to provide wireless services for public safety agencies across the United States. However, as the costs to develop and to maintain a mobile network particularly for public safety are...