Joint Network Coding for interfering wireless multicast networks

Interference in wireless networks is one of the key-capacity limiting factor. The multicast capacity of an ad-hoc wireless network decreases with an increasing number of transmitting and/or receiving nodes within a fixed area. Digital Network Coding (DNC) has been shown to improve the multicast capacity of non-interfering wireless network. However recently proposed Physical-layer Network Coding (PNC) and Analog Network Coding (ANC) has shown that it is possible to decode an unknown packet from the collision of two packet, when one of the colliding packet is known a priori. Taking advantage of such collision decoding scheme, in this paper we propose a Joint Network Coding based Cooperative Retransmission (JNC-CR) scheme, where we show that ANC along with DNC can offer a much higher retransmission gain than that attainable through either ANC, DNC or Automatic Repeat reQuest (ARQ) based retransmission. This scheme can be applied for two wireless multicast groups interfering with each other. Because of the broadcast nature of the wireless transmission, receivers of different multicast group can opportunistically listen and cache packets from the interfering transmitter. These cached packets, along with the packets the receiver receives from its transmitter can then be used for decoding the JNC packet. We validate the higher retransmission gain performance of JNC with an optimal DNC scheme, using simulation.