The implementation of Network Coding (NC) in IEEE 802.11-based wireless networks presents the important challenge of providing additional transmission priority for the relay nodes responsible for coding. These nodes are able to convey more information in each transmission than those that forward single packets, by combining several received packets in a single coded packet. To transmit data, the nodes execute the IEEE 802.11 Medium Access Control (MAC) protocol, called the Distributed Coordination Function (DCF). Thus, they compete for the access to the wireless channel and get equal transmission opportunities under high congestion. As a result, congested relay nodes will severely limit the performance of the network. In this paper, we investigate a backwards-compatible mechanism, called Reverse Direction DCF (RD-DCF), that allows relay nodes to transmit data upon successful reception of data. We analyze the performance limits of the proposed protocol with and without NC in terms of throughput and energy efficiency. The performance evaluation considers different traffic loads, packet lengths, and data rates. The results of this work show that the proposed RD-DCF+NC protocol can improve throughput and energy efficiency up to 335% when compared to legacy DCF.
BBR is a promising new congestion control algorithm (CCA) that has been shown to result in significantly lower latency compared to conventional loss-based CCAs. However, in cellular networks, where there is a high variability in the available rate, BBR does not perform as well as expected. In such scenarios, BBR tends to overestimate the available capacity and create queues that cause longer packet delays. In this work, we propose Receiver-driven BBR (RBBR), a modified version of BBR that uses rate estimates made at the receiver side rather than at the sender side. We employ a Kalman filter to make a more accurate estimate of the available bandwidth, and we implement the algorithm in QUIC. An evaluation of the proposed CCA is done through extensive 4G trace-based emulations, real 4G network tests and mmWave trace-based emulations representing a 5G scenario. The results show that RBBR is able to achieve an RTT reduction of up to 80% with a worst-case throughput loss of about 30%. The results also show that in real 4G networks, RBBR flows experience a more predictable and consistent RTT than what BBR flows do.
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