Impact of hidden node problem in association and data transmission for LAA Wi-Fi coexistence

Abstract

Small-cell LTE and Wi-Fi networks has been globally deployed in the unlicensed 5 GHz bands, leading to the need for new coexistence regulations between two very different access technologies. To address coexistence challenges, 3GPP standardized LTE Licensed Assisted Access (LAA) in 5 GHz bands through the incorporation of similar sensing and back-off features. The success of LAA’s fair and efficient coexistence with Wi-Fi can be considered a benchmark for collaborative cellular operation in unlicensed bands. In this paper, we discuss the hidden node scenario when T-Mobile LAA coexists with the Wi-Fi APs that we deployed at the Illinois Institute of Technology (IIT) university campus. In this setup, we observed problems on the Wi-Fi client association and inefficient data transmission when it tries to connect to its corresponding Wi-Fi APs. As LAA is unaware of the Wi-Fi AP’s transmission (low transmission power received at LAA BS), LAA BS continuously transmits with maximum transmission opportunity time, thus highly impacting Wi-Fi performance. Further, the hidden node problem is modeled analytically capturing the root cause of inefficiency.