  The problem of designing efficient feedback-based scheduling policies for
chunked codes (CC) over packet networks with delay and loss is considered. For
networks with feedback, two scheduling policies, referred to as random push
(RP) and local-rarest-first (LRF), already exist. We propose a new scheduling
policy, referred to as minimum-distance-first (MDF), based on the expected
number of innovative successful packet transmissions at each node of the
network prior to the "next" transmission time, given the feedback information
from the downstream node(s) about the received packets. Unlike the existing
policies, the MDF policy incorporates loss and delay models of the link in the
selection process of the chunk to be transmitted. Our simulations show that MDF
significantly reduces the expected time required for all the chunks (or
equivalently, all the message packets) to be decodable compared to the existing
scheduling policies for line networks with feedback. The improvements are
particularly profound (up to about 46% for the tested cases) for smaller chunks
and larger networks which are of more practical interest. The improvement in
the performance of the proposed scheduling policy comes at the cost of more
computations, and a slight increase in the amount of feedback. We also propose
a low-complexity version of MDF with a rather small loss in the performance,
referred to as minimumcurrent-metric-first (MCMF). The MCMF policy is based on
the expected number of innovative packet transmissions prior to the "current"
transmission time, as opposed to the next transmission time, used in MDF. Our
simulations (over line networks) demonstrate that MCMF is always superior to RP
and LRF policies, and the superiority becomes more pronounced for smaller
chunks and larger networks.
