Optimisation of relay placement in wireless butterfly networks

As a typical model of multicast network, wireless butterfly networks (WBNs) have been studied for modelling the scenario when two source nodes wish to convey data to two destination nodes via an intermediary node namely relay node. In the context of wireless communications, when receiving two data packets from the two source nodes, the relay node can employ either physical-layer network coding or analogue network coding on the combined packet prior to forwarding to the two destination nodes. Evaluating the energy efficiency of these combination approaches, energy-delay trade-off (EDT) is worth to be investigated and the relay placement should be taken into account in the practical network design. This chapter will first investigate the EDT of network coding in the WBNs. Based on the derived EDT, algorithms that optimize the relay position will be developed to either minimize the transmission delay or minimize the energy consumption subject to constraints on power allocation and location of nodes. Furthermore, considering an extended model of the WBN, the relay placement will be studied for a general wireless multicast network with multiple source, relay and destination nodes

On the energy efficiency of HARQ-IR protocols for wireless network-coded butterfly networks

In this paper, we investigate the energy-delay tradeoff (EDT) of data transmissions in wireless butterfly networks consisting of two source nodes, a relay node and two destination nodes. Two network coding (NC) techniques, namely physical-layer NC (PLNC) and analog NC (ANC), are exploited to reduce the number of transmissions at the relay by half. Additionally, hybrid automatic repeat request with incremental redundancy (HARQ-IR) is applied to assure the reliability of data transmissions in wireless network-coded butterfly networks (WNCBNs). By deriving the EDT of both PLNC and ANC schemes in WNCBNs, we evaluate not only their energy efficiency, but also the effectiveness of the relay positions in WNCBNs. It is found that the PLNC scheme is more energy efficient than both the ANC and direct transmission (DT) schemes when the relay is located either at the centre or close to the destinations. In addition, it is shown that both the PLNC and ANC schemes are shown to be less energy efficient than the DT scheme when the relay is located near the sources

On the energy efficiency of HARQ-IR protocols for wireless network-coded butterfly networks

In this paper, we investigate the energy-delay tradeoff (EDT) of data transmissions in wireless butterfly networks consisting of two source nodes, a relay node and two destination nodes. Two network coding (NC) techniques, namely physical-layer NC (PLNC) and analog NC (ANC), are exploited to reduce the number of transmissions at the relay by half. Additionally, hybrid automatic repeat request with incremental redundancy (HARQ-IR) is applied to assure the reliability of data transmissions in wireless network-coded butterfly networks (WNCBNs). By deriving the EDT of both PLNC and ANC schemes in WNCBNs, we evaluate not only their energy efficiency, but also the effectiveness of the relay positions in WNCBNs. It is found that the PLNC scheme is more energy efficient than both the ANC and direct transmission (DT) schemes when the relay is located either at the centre or close to the destinations. In addition, it is shown that both the PLNC and ANC schemes are shown to be less energy efficient than the DT scheme when the relay is located near the sources