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Network coding has been studied as a solution to mitigate traffic concentration at a bottleneck node in wireless multihop networks. When network coding is applied to a unicast flow, the decoding nodes overhear packet transmissions, receive all packets which are headed for not only themselves but also the other nodes, and store them. The reception of undesired packets is, however, unreliable, and this unreliability causes the decoding failure for network coding. In this case, the encoding node has to retransmit the packet somehow. In this paper, we discuss an ARQ scheme using a negative acknowledgement (NACK). By simple model simulation, our proposed scheme can improve overflow rate, compared with no network coding. Furthermore, a realistic protocol for our proposed scheme is developed, and its simulation results show that our proposed scheme is very effective to mitigate the degradation at the bottleneck node.