# Multi-Connectivity-Based Adaptive Fractional Packet Duplication in Cellular Networks
## 2 Related Work
In order to combat the connection failures and throughput degradation experienced by cell-edge users due to their mobility, a multi-connectivity idea for a cloud radio access network was developed in [20]. The authors in [21] examined the performance analysis of packet duplication in 5G with the goal of improving the dependability of wireless links. Two potential network designs were provided in [22] with simulation tools to test and compare their performance in order to deliver ultra-reliable services to mobile consumers by combining the LTE and mmWave radio-access technologies. The authors in [23] proposed partial packet duplication to satisfy traffic reliability requirements when dual connectivity is available to provide macro diversity. The idea is to only duplicate what needs to be completed; this utilizes potentially far fewer resources from the secondary access point. By analytically estimating the associated SNR gain, the authors of [24] demonstrated the significant transmit power decrease of multi-connectivity over single-connectivity. Ref. [25] provided analytical research of the improvement in outage probability with multi-connectivity as well as an analysis of the resource consumption cost. In addition, the performance study was compared to standard single-connection transmission. The purpose of [26] was to provide a detailed review of the fundamental trade-offs involved in URLLC as well as the concepts that were used to develop access protocols. Two survey papers provide overviews of multi-connectivity and cite multiple papers referring to the packet duplication; however, most are not close to our research work, which proposes a dynamic and adaptive fractional packet duplication scheme. They focus on the following different areas. Many of them discuss the Wi-Fi and LTE/5G multi-connectivity or any other multi-radio-access technology (MRAT) implementing multi-connectivity. However, these are mostly focused on the protocol portion of communication using finite sliding window network coding, redundant multipath TCP, latency control TCP, etc. Some also focus on the architectural enhancements. Other research work has used CoMP and coordinated MIMO analysis, link scheduling optimization, or even managing the set of coordinating cells on the inter and intra frequency multi-connectivity. Other works analyze the impacts of mobility and cyclic prefix configurations in multi-connectivity scenarios and discuss the optimized SNR utilization for multi-connectivity and/or stochastic geometry with the physical layer abstraction. Some authors propose network slicing and machine learning to implement multi-connectivity but often rely on full packet duplication over the second wireless link. The authors in [12] have very recent work on packet duplication in mobility scenarios. Furthermore, to the best of our knowledge, this is the only work that is close to our work since it involves utilizing packet duplication only when required. They compare received RSSI to a power threshold to determine how much packet duplication is utilized. If received power on one of the links is high, duplication is not used. On the other hand, we propose three different techniques--namely, SINR-difference-based, fade-threshold-based and distribution-based--to determine the amount of packet duplication. For using SINR difference, we argue that, to minimize the amount of duplication, we should only duplicate when it would be beneficial, i.e., when packets on either link could be the best. However, if one link is much stronger than another, duplication on the secondary link is not beneficial and wastes resources.