Nowadays, we can get the wireless devices easily, such as cell phone, PDA, etc. It can make the life convenient. The P2P network which has been constructed by the wireless devices does not need the central server. They can communicate by themselves. Not only have protected in the privacy, but also add the convenience. The reason is that the devices are portable, we can get the newest information. Some P2P software focuses on the sharing. They can share files with other peer. The file can separate into several modes. The software will share these nodes. Every peer shares his own node, and it will speed up the rate of sharing. There are some selfish peers in this environment, and they will not want to share their own node. Moreover, some of them share the incorrect file. The software will solve this kind of problem by some mechanism. And it set some incentive mechanism to make the sharing to go on. Because the wireless devices are portable, we can use these devices for exchanging immediate information. Sharing the files is similar to the exchanging. Both of the users trust each other. They can exchange automatically. So, our research has designed a reputation based mechanism for exchanging. The users can evaluate each other to exchanging the information automatically. By this mechanism, the user in our system will exchange continuously. We can reach our purpose which makes the user in our environment can exchange automatically.

As the global wireless network becoming mature, the growing number of mobile devices, and the personal need of keeping in touch with others daily, mobile communication is becoming a necessity of life. Using mobile devices, such as cell phones or PDAs, everyone could communicate with each other independently; and this communication environment is similar with P2P network. Utilizing the connection network of cell phones is becoming a brand new business channel. Since group-buying is part of our daily life, people live in the same area could buy products or services together based on mutual needs, and this could enhance the bargaining power of customers and lower the purchase price. This research proposes a group-buying system architecture under mobile environment, and discusses the problems that customers might encounter in every stage of the buying process. Mobile device users under the environment could exchange information with each other and this could help customers search group-buying information efficiently. Sensor Network combines with MP2P Network accelerates the spread of group-buying information in a marketplace, and helps the originator and other buyers to negotiate with the supplier. Based on the observation of the variation of the group-buying information distribution in the experiment, we summarize under what situation a better information distribution would take place in a specific marketplace.

The goodness of group buying is consumers can buy product with lower price, and seller can reduce the bargain cost by collecting orders. But it is hard to be realized in the mall. A recent survey shows most everyone has his own mobile device. In this research, we organize a mobile P2P network by exchanging between two mobile devices. We propose a system for consumers and sellers to exchange group buying information. In Mobile P2P Network environment, group buying initiator is hard to decide the best timing to end the group buying. Because buyers can easily participate or leave the group buying group, and initiator may not know the exactly how many buyers participate the group buying. So we simulate a virtual mall with the realistic data and try to find the suitable group buying model in this environment. Then we examine if participation externality effect, price drop effect and ending effect will appear in this model. Finally, we observe the trend of the number of buyers in group buying to suggest the group buying ending time. The research result indicates that participation externality effect and price drop effect still appear in the Mobile P2P Network environment. But ending effect is not obvious. Because the group buying information is distributed by participating buyers, the distribution will affect the trend of participation and participation externality effect. With suggestion of the system, initiator will not waste much time to wait few participations, and participators can reduce the time cost.