Feedback delay and its impact on adaptive modulation and coding in VHF narrowband mobile ad-hoc networks

Mobile ad-hoc networks (MANETs) enable operation without fixed infrastructure, making them attractive for disaster search and rescue (SAR) and tactical applications. Reliability is an issue in such applications and increasing MANET communication reliability is critical for the acceptance of these systems. In this paper we investigate the impact of feedback delay on adaptive modulation and coding (AMC) in VHF narrowband MANETs. We analyse communication reliability and quality of service (QoS) under realistic conditions and study user net throughput and packet delivery ratio (PDR) for various AMC feedback delays using Monte Carlo computer simulation. We show that feedback delays of multiple frame durations are tolerable even for higher velocities (300 km/h) without significant reliability issues, on the other hand for high delays the system trades throughput for reliability.