Question: From a User Equipment (UE) perspective, how does a Relay Node behave within the Radio Access Network (RAN), and what dual functionality does it exhibit in terms of physical layer entities?
Option 1: A Relay Node behaves like a UE and has only one physical layer entity for communicating with both UEs and the donor eNB.
Option 2: A Relay Node behaves like an eNB, incorporating at least two physical layer entities: one for UE communication (like an eNB) and another for donor eNB communication (emulating UE functionality).
Option 3: A Relay Node acts as a standalone device with a single physical layer entity that dynamically switches between eNB and UE functionalities based on the communication need.
Option 4: A Relay Node is seen as a network extension without any defined behavior like an eNB or UE, having variable physical layer entities based on configuration.
Explanation: This correct answer reflects the nuanced behavior of a Relay Node in the RAN. From a UE's perspective, interacting with a Relay Node is akin to interacting with an eNB. However, the Relay Node itself communicates with a donor eNB using a separate physical layer entity that mimics UE functionality. This dual role highlights the complexity and flexibility of Relay Nodes in enhancing network coverage and capacity, especially in areas where direct eNB-UE connectivity is challenging.