## 2 Literature Review  
### OTT Services  
Recent statistics show that OTT consumers are moving away from traditional television (TV)-based content viewing. In the US market, the proportion of those who have subscribed to a streaming video service at least once (68%) has already surpassed the ratio of paid TV subscribers (65%). Furthermore, the average number of streaming subscriptions has increased by 33% since the beginning of the COVID-19 outbreak [16]. As of December 2020, US consumers spent an average of USD 47 per month, a significant increase from the USD 38 reported in April of the same year [17]. An increasing number of companies are entering the OTT market, intensifying competition. In the second quarter of 2020, Netflix had the highest streaming proportion in the US market, accounting for 34%. This was followed by the traditional OTT powerhouses of YouTube, Hulu, and Amazon Prime, with 20, 11, and 8%, respectively. Disney Plus then launched, quickly garnering 4% [18] after acquiring the 21 st Century Fox library [19]. Because existing OTT companies already dominate the market to some extent, TV broadcasting companies, telecommunication carriers, and cable operators are now releasing their own apps or investing in other platforms. After acquiring Warner Media, AT&T launched an OTT service leveraging their new HBO content [20]. The rapidly changing market is looming as both a threat and an opportunity for OTT operators. Notably, it is expected that many subscriptions will not be renewed after COVID-19 restrictions are lifted. Thus, OTT operators must find ways to retain customers. For this, the Boston Consulting Group has advised OTT operators to analyze user patterns and to classify them into groups for customized strategies [6]. Pricing plans comprise an important customer lure. The biggest reason that customers cancel subscriptions is the expense, and this accounts for 36% of all cancellations [16]. Telecommunication carriers, cable operators, and Internet-protocol TV (IPTV) operators are struggling under the competitive OTT environment [21; 22]. For example, the IPTV market overlaps and encroaches many OTT services. Bundled service strategies are sometimes required to prevent IPTV subscriptions from being canceled for OTT viewing [23]. In South Korea, KT, the operator with the highest IPTV market share, is partnering with Netflix to create synergies. Netflix is using this opportunity to enter the South Korean market. Additionally, KT will receive network fees by providing Internet bandwidth to Netflix. Furthermore, an increase in the number of KT customers is expected when Netflix is provided as a bundled service [24]. Mobile network providers are also required to make infrastructure investments to maintain the quality of live streaming. With the spread of 5G, an increasing number of users are enjoying OTT services wirelessly. However, failure to provide a stable QoS will result in customer churn. In fact, about 30% of consumers are willing to for pay premium prices if the mobile networks, especially 5G, can deliver better video quality and reduce buffering [25]. As more consumers use real-time services, network operators face difficulties because of infrastructure investments [10; 26]. Network operators must build a sound service-quality degradation strategy that minimizes network resource consumption, while also satisfying consumer demand and QoS. As such, it is crucial for all providers to establish appropriate pricing schemes for the OTT environment. Various studies have been conducted on pricing systems related to content providers, network operators, and service users based on net neutrality. These include a study based on QoS [9], a study based on the quality of experience [27], a study using shadow prices [28], and a study based on CDNs [29] or software defined networks [30] (see Section 2.1 of our previous study [13] for a brief description of these constructs).