## 1 Introduction  
Mobile video delivery continues its growth in volume and will reach an estimated 78% of the total mobile data traffic by 2021, compared to 60% in 2016 [1]. In absolute values, during the same period (2016-2021), the total volume of mobile data traffic will experience seven-fold increase [1]. This increase is due to the combination of ever increasing resolutions of user handsets and proliferation of 4K/8K ultra high-definition (UHD) formats [2], fueled by evolution of innovative video services relying on multi-view and 360-degree video [3], enhanced broadcast [4] and peer-to-peer video services [5]. Evolution of mobile cellular infrastructure capable to cope with the surge of video traffic is necessity for meeting these predictions. Towards this end, 3 rd Generation Partnership Project (3 GPP) have just completed the first phase in defining a new fifth generation (5G) New Radio (NR) interface [6]. One of the resting pillars of 3 GPP 5G NR is the support for enhanced Mobile Broadband (eMBB) services that target providing users with sufficient data rates to accommodate new, high-rate mobile video services. The support for eMBB will be achieved by novel throughput-enhancement solutions implemented both in radio access network (RAN) [7], such as massive multiple-input multiple-output (MIMO) antenna technology or migration to wider millimeter-wave bands (mmWave), and in core network (CN) domain, by supporting network slicing via network function virtualization (NFV) and software-defined networking (SDN) technologies [8]. For mobile video multicast/broadcast services, mobile cellular networks provide support in the form of 3 GPP-defined enhanced Multimedia Broadcast/Multicast Service (eMBMS) [9]. However, majority of mobile video traffic represents over-the-top (OTT) video streaming such as progressive downloading (PD) and adaptive bitrate streaming (ABR) for which mobile cellular network protocolsremain largely oblivious [10]. In order to optimize mobile video delivery, a number of solutions have been proposed in recent research studies, including video-aware resource allocation [11] and proactive edge caching and processing [12; 13; 14]. In this review paper, we focus on random linear network coding (RLNC) as a scheme identified to create potentially high impact on flexible, efficient and reliable mobile video delivery. RLNC is a packet-level erasure protection mechanism that is simple, efficient and has a number of useful features including rateless property, i.e., capability to produce arbitrary many encoded packets from a given source block, and network coding property, i.e., capability to increase throughput in certain network scenarios by re-encoding packets in intermediate network nodes [15; 16; 17; 18]. We provide an overview of RLNC placed in the context of a packet-level data processing protocol sublayer that can be easily integrated at different layers of protocol stack within mobile video delivery environment. The RLNC sublayer can be further optimized and improved with respect to complexity and video quality using sparse and unequal error protection RLNC design [19; 20; 21; 22]. In parallel with the review of RLNC, we provide an in-depth overview of mobile video delivery, focusing on unicast and multicast/broadcast mobile video services over fourth generation (4G) Long-Term Evolution (LTE) network [9; 23; 24; 25]. We then move on to investigate how RLNC sublayer can be integrated as part of the 4G LTE mobile video delivery services, discussing various options for both video unicast and multicast/broadcast across different protocol layers. In the final part, we provide possible directions for optimizing mobile video delivery and integrating RLNC sublayer within upcoming 5G NR standard. We conclude this overview paper by explicitly identifying and discussing in detail novel 5G NR features that could provide support for RLNC-based video delivery in 5G, thus pointing out to the promising avenues for future research. The paper is organized as follows.