Question: In a GSM Public Land Mobile Network (PLMN), what characterizes a non-transparent lower layer capability when using an Automatic Repeat Request (ARQ) technique on the radio path?
Option 1: Constant throughput, constant transit delay, and improved error rate
Option 2: Variable throughput, variable transit delay, and constant error rate
Option 3: Improved error rate with constant throughput and variable transit delay
Option 4: Improved error rate with variable transit delay and variable (potentially increased with compression) throughput
Explanation: A non-transparent lower layer capability, as defined in the context of GSM PLMN, utilizes an ARQ technique to enhance reliability. This leads to an improved error rate. However, the use of ARQ can introduce variability in transit delay due to potential retransmissions. Additionally, throughput can be variable and may be increased through optional data compression on the DTE/DCE interface, aligning with the characteristics described for non-transparent capabilities.