# Next-Generation Payment System for Device-to-Device Content and Processing Sharing
## 5 Conclusions  
In this study, we propose a framework for enabling content and process power sharing between mobile users in a next-generation cellular network. This framework also has the potential to be used:  
* Among users: to enable content and processing power sharing;
* Between users and the mobile operator: for purposes of charging based on specific content and/or application use;
* Between users and the content provider: for purposes of charging based on content access;
* In a system involving mobile users and multiple operators and/or providers, enabling data roaming and content sharing across domains;
* As a reference model for studies on reliability/availability of content in P2P-like systems where content is obtained through other users. Based on a simulation study of a single cell system in which users prioritize content quality (in terms of video quality in the specific scenario investigated), we have observed the following:  
* Content quality on the average is insensitive to the charge of downloading from the base station, and the average quality is greatly improved when the D2D mode is enabled;
* the charge of downloading from the base station affects the average cost of a unit piece of content, as there will always be a first time where content will be delivered from the content provider/cloud, which naturally is served through the base station;
* Even when the content from the base station is free of charge, a significant amount of content is downloaded from the users instead of the base station in order to achieve the best possible quality level;
* The ratio of the content downloaded from the base station can be kept to levels as low as 10% when the cost of downloading from the base station is no less than that of downloading from another user;
* Allowing transcoding has little effects on the average quality of the content, but it can decrease the average cost of the content. Figure 11: Ratios of the GOPs with respect to quality for different values of \(c_{b}\) when transcoding is disallowed. Purple and green lines show the best and (cumulative) mid-quality ratios when D2D mode is disallowed. The performance of the proposed scheme is investigated via a simulation of scenarios involving attraction points, such as shops in a mall, or restaurants, or social events. The concentration of users around these points is assumed to be higher, whereas free-roaming users are also allowed. In scenarios where users clustered together are interested in the same content such as videos from a sporting event or a disaster area, allowing users to exchange data directly alleviates a significant amount of load from the base station. The second use case of the proposed scheme would arise when traveling abroad. Rather than paying a considerable amount of roaming fees, the users who are part of this system can gain access to content provided by peer users existing in their vicinity using their TelCash balance and could even provide access to their content if there is demand, earning TelCash. In the usual operation of roaming systems, the roamer's data requests are directed to their origin country, and the response to their requests are routed through the same path, incurring long latency, which is very undesirable for multimedia content. The proposed method can improve latency performance in such scenarios. Another aspect to be addressed for such systems is the integration to the tax system of the governments. Since crypto-currency payment systems are still in the gray-zone of tax systems and the governments are trying to install regulations for such systems, the solution/requirements for the governments would easily be integrated to the system. Further studies can reach several directions. Discovery and advertisement for the services to be provided by the users could be defined more specifically. Devices within the D2D range should be discoverable and configurable easily.