  Source delay, the time a packet experiences in its source node, serves as a
fundamental quantity for delay performance analysis in networks. However, the
source delay performance in highly dynamic mobile ad hoc networks (MANETs) is
still largely unknown by now. This paper studies the source delay in MANETs
based on a general packet dispatching scheme with dispatch limit $f$ (PD-$f$
for short), where a same packet will be dispatched out up to $f$ times by its
source node such that packet dispatching process can be flexibly controlled
through a proper setting of $f$. We first apply the Quasi-Birth-and-Death (QBD)
theory to develop a theoretical framework to capture the complex packet
dispatching process in PD-$f$ MANETs. With the help of the theoretical
framework, we then derive the cumulative distribution function as well as mean
and variance of the source delay in such networks. Finally, extensive
simulation and theoretical results are provided to validate our source delay
analysis and illustrate how source delay in MANETs are related to network
parameters.
