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Device-to-Device Communications Technologies
Published in Yufeng Wang, Athanasios V. Vasilakos, Qun Jin, Hongbo Zhu, Device-to-Device based Proximity Service, 2017
Yufeng Wang, Athanasios V. Vasilakos, Qun Jin, Hongbo Zhu
In a typical Wi-Fi network, clients discover and associate to wireless local area networks (WLANs), which are created and announced by APs. In this way, a device unambiguously behaves either as an access point (AP) or as a client, each of these roles involving a different set of functionality. A major novelty of Wi-Fi Direct is that these roles are specified as dynamic, and hence a Wi-Fi Direct device has to implement both the role of a client and the role of an AP (sometimes referred to as SoftAP). These roles are therefore logical roles that could even be executed simultaneously by the same device, for instance, by using different frequencies (if the device has multiple physical radios) or by time-sharing the channel through virtualization techniques. In order to establish a communication, then, peer-to-peer (P2P) devices have to agree on the role that each device will assume. Wi-Fi Direct devices, formally known as P2P devices, communicate by establishing P2P groups, which are functionally equivalent to traditional Wi-Fi infrastructure networks. The device implementing AP-like functionality in the P2P group is referred to as the P2P group owner (P2P GO), and devices acting as clients are known as P2P clients. Given that these roles are not static, when two P2P devices discover each other, they negotiate their roles (P2P client and P2P GO) to establish a P2P group. Once the P2P group is established, other P2P clients can join the group as in a traditional Wi-Fi network. Legacy clients can also communicate with the P2P GO, as long as they are not 802.11b only devices, and support the required security mechanisms (discussed in subsection 1.2.3.1.2). In this way, legacy devices do not formally belong to the P2P group and do not support the enhanced functionalities defined in Wi-Fi Direct, but they simply see the P2P GO as a traditional AP [9].
A distribute and self-tuning wireless environment monitoring system for buildings based on the Wi-Fi Direct technology
Published in Science and Technology for the Built Environment, 2018
Wi-Fi technology has gotten a tremendous market success around the infrastructure mode of operation defined in the IEEE 802.11 standard and recently the Wi-Fi Alliance (WFA) has developed the Wi-Fi Direct (Wi-Fi ad hoc mode) technology which is a more extended and improved utilizing structure based on ad hoc (Wi-Fi Alliance 2009). In a Wi-Fi Direct network, each node has built up a SoftAP (an access point [AP] virtualized by software) and station (STA) inside, which enables the nodes to communicate with each other directly. The features of Wi-Fi Direct are discussed in detail and concretely in the technical specification. Wi-Fi Direct technology is more outstanding than other similar technologies in that it is easy-to-use, possessing high transmission speed, and able to immediately benefit from the technologies of the Ethernet. An energy efficient working strategy for access point (AP) based on Wi-Fi Direct has been studied by Camps-Mur et al. (2011) and the evaluation and application prospect of Wi-Fi Direct has been provided theoretically by Camps-Mur et al. (2013) and experimentally by Le and Ogawa (2014).