Integration of different broadcast based protocol

Integration of different broadcast based protocol 

Integration of OR with NC 

The MORE protocol (Chachulski et al., 2007), integrates the OR with intra-session NC protocols. The results show that MORE improves performance of the network when compared to the EXOR protocol (Biswas et al., 2005) by leveraging the spatial reuse and it also removes the need for global coordination among the next hop forwarders. Nevertheless it requires complex associated hardware (Kim et al., 2013). Also the experiments have been conducted for only fixed data rate. In (Yan et al., 2010) the authors present the CORE protocol that integrates the OR and inter session NC. This protocol selects a group of forwarders which are close to the destination and the forwarding priority of these forwarder nodes are selected based on coding opportunities. It attempts to maximize the number of packets sent in each transmission. It is presented for fixed bit rate network, whereas multirate capability of the network is not considered. The authors compare its performance with EXOR and COPE and show that significant improvement in terms of network throughput and number of transmissions can be achieved.

In the INCOR protocol (Zhu et al., 2015), integration of the inter-session NC and OR protocols has been implemented. In particular, the authors proposed a new metric for integration of NC and OR protocol. The analysis presented in this paper employs probabilistic estimation of coding chances into the metric. The INCOR protocol was designed for basic data rate and when a multi-rate scheme is employed this analysis becomes erroneous. This is due to the fact that a link which is a strong link at the base rate, can be a weak/very weak link at the higher data rates. INCOR’s performance was compared with the inter-session NC and classic OR protocols, their results indicate that the integrated protocol out-performs either of them. Results have been presented in terms of the transmission count number, and they show that when the link quality is low, the OR protocol has better performance as compared to NC and when the link is strong, NC outperforms the OR protocol. But the integrated protocol outperforms both of the individual protocol as it capitalizes on both of their characteristics. This motivated us to integrate the third element on the network protocol stack, i.e., CP to provide spatial diversity to leverage the broadcast nature of the wireless channel further.

In (Koutsonikolas et al., 2008), the XCOR protocol was designed for single rate network. It integrates the inter-session NC with OR protocols. It is based on the ETX metric (De Couto et al., 2003). It is well known that the ETX metric does not takes into account the multi-rate capability of the network. In (Kim et al., 2012), (Aajami et al., 2012) integration of OR and NC was studied considering the multi-rate capability. The authors concluded that the integration of OR and NC outperforms, the multi-rate NC or the multi-rate OR when considered in isolation.

In (Abdallah, et al., 2015) the authors presented another integration of the intra-session NC with OR protocol. The main drawback of their work is that it is primarily focused on the network throughput alone because packets are transmitted in batches and acknowledgements are done for batches of packets. This is what separates this approach from our work where we encode packets locally and acknowledgements are done for each packet delivery.

In CCACK (cumulative coded acknowledgement) (Koutsonikolas et al., 2011) another integration of the intra-session NC and OR protocols was presented. As opposed to MORE, the authors overcome the challenge of acknowledging the upstream nodes about the reception of coded packets by estimating offline the link delivery probabilities which is based on the ETX metric. CCACK devises a novel mechanism to overcome the losses occurring due to offline estimation as the wireless channels are dynamic in nature. It introduces cumulative coded acknowledgement of the received packets at the forwarding nodes. The authors compared its performance with MORE to show the performance improvements in terms of the network throughput and the number of transmissions. It clearly shows the performance improvement, but it requires complex associated hardware. In MT_NCOR (Lan et.al., 2014) an integration of intra-session NC and OR protocols was implemented. Candidate forwarder set selection and coding/decoding of packets are similar to MORE protocol but the rate control mechanism employed at the source and the forwarding nodes differentiate the MT_NCOR protocol from the MORE protocol. It is designed for fixed data rate, which cannot harness the capacity of the wireless links to the full extent.

In (Qiang et al., 2013) an integration of the inter-session NC and OR protocols was presented resulting in the CoAOR protocol. The authors have presented a new metric for prioritizing the nodes where more coding opportunity arises. A node coding gain formula was presented, which takes into account the number of flows which can be coded together, expected number of those flows which can be decoded at the receiver nodes, and the total number of the neighbors who can decode the coded packets. The authors compared their results with the CORE protocol and showed that CoAOR protocol outperforms CORE protocol. But again their analysis is based on the ETX metrics which is estimated using the control packet from network layer sent at basic data rate and for multi-rate network this metric becomes erroneous.

Integration of NC with CP 

In (Manssour et al., 2009) performance of the network coding was evaluated in the presence of an opportunistic relay selection. Based on the results, the authors conjectured that the selection of the relay should take into consideration the coding opportunity which may arise in the relay node. Nevertheless no practical means was proposed for coding opportunity detection.

In (Wang et al., 2014) the NCAC-MAC protocol proposes another integration of the CP and inter-session NC protocols. It does answer an important question of how to cooperate when the direct transmission from the transmitter to the relay node fails. NCAC-MAC supports two forms of cooperation. Namely network coded cooperative retransmission (when there are coding opportunities at the relay node) and the pure cooperative retransmission (when there is no coding opportunity). The performance of the NCAC-MAC protocol is compared with the CSMA and Phoenix (Munari et al., 2009) protocols. NCAC-MAC was designed for single hop network, which is not suitable for WMN. The authors presented comparison of their protocol with CSMA and Phoenix in terms of network throughput, delay, delivery ratio and transmission energy consumption. It clearly shows that the integration of CP and NC is beneficial when the relay nodes are selected based on the coding opportunity.