Co-Existence of LTE-U and Wi-Fi with Direct Communication

One of the most prominent cellular technologies, Long Term Evolution (LTE), is currently operating on some 800MHz, 2GHz, and 3.5GHz licensed bands. Wi-Fi is currently operating on 2.5GHz and 5GHz unlicensed bands. The declaration stating that 5GHz bands are unlicensed enables LTE to operate on 5GHz bands. It is challenging, however, for different wireless technologies to co-exist. The two standards, LTE-U and LTE-LAA, for LTE to coexist with Wi-Fi on the 5GHz band have evolved. The LTE-U standard is based on the duty cycle, while LTE-LAA is based on listen-before-talk (LBT). In existing LTE-U systems, the LTE base station (eNB) estimates the fair portion of Wi-Fi usage based on channel state information. The usage estimation from channel state information is not as accurate enough as well as the fair portion. In this paper, we study the fair coexistence between LTE-U and Wi-Fi in the scenario where an LTE eNB can exchange information with Wi-Fi access points (AP). The communication can be done in both wired and wireless mediums. The wired medium is ethernet point-to-point communication, and the wireless communication is done using the reserved bits in Wi-Fi packets. Both ways are applicable to the operator, who has both LTE and Wi-Fi coverage. Therefore, the Wi-Fi AP can collect information about other APs and send it to its LTE eNB. The LTE eNB can adjust its parameters according to the received information to achieve fairness.