  Network coding is a novel solution that significantly improve the throughput
and energy consumed of wireless networks by mixing traffic flows through
algebraic operations. In conventional network coding scheme, a packet has to
wait for packets from other sources to be coded before transmitting. The
wait-and-code scheme will naturally result in packet loss rate in a finite
buffer. We will propose Enhanced Network Coding (ENC), an extension to ONC in
continuous time domain.
  In ENC, the relay transmits both coded and uncoded packets to reduce delay.
In exchange, more energy is consumed in transmitting uncoded packets. ENC is a
practical algorithm to achieve minimal average delay and zero packet-loss rate
under given energy constraint. The system model for ENC on a general renewal
process queuing is presented. In particular, we will show that there exists a
fundamental trade-off between average delay and energy. We will also present
the analytic result of lower bound for this trade-off curve, which can be
achieved by ENC.
