  In this paper, we consider the wireless broadcasting scenario with a source
node sending some common information to a group of closely located users, where
each link is subject to certain packet erasures. To ensure reliable information
reception by all users, the conventional approach generally requires repeated
transmission by the source until all the users are able to decode the
information, which is inefficient in many practical scenarios. In this paper,
by exploiting the close proximity among the users, we propose a novel two-phase
wireless broadcasting protocol with user cooperations based on an efficient
batched network code, known as batched sparse (BATS) code. In the first phase,
the information packets are encoded into batches with BATS encoder and
sequentially broadcasted by the source node until certain terminating criterion
is met. In the second phase, the users cooperate with each other by exchanging
the network-coded information via peer-to-peer (P2P) communications based on
their respective received packets. A fully distributed and light-weight
scheduling algorithm is proposed to improve the efficiency of the P2P
communication in the second phase. The performance of the proposed two-phase
protocol is analyzed and the channel rank distribution at the instance of
decoding is derived, based on which the optimal BATS code is designed.
Simulation results demonstrate that the proposed protocol significantly
outperforms the existing schemes. Lastly, the performance of the proposed
scheme is further verified via testbed experiments.
