Performance Analysis of License Assisted Access LTE with Asymmetric Hidden Terminals

Abstract

License Assisted Access (LAA) LTE (LAA-LTE) is a new type of LTE that aggregates the licensed LTE bands with the unlicensed bands via carrier aggregation. To operate in unlicensed bands, LAA-LTE adopts the listen-before-talk policy and designs its channel access mechanism similar to WLAN's DCF. This paper considers an LAA-LTE eNB coexisting with asymmetric hidden Wi-Fi APs where the eNB can detect the APs while the APs cannot, which is caused by the asymmetric CCA thresholds. The behavior of such a network is modeled by a joint Markov chain (MC), using which steady-state probabilities, throughput, and channel access delay are derived analytically. An extensive evaluation confirms that the proposed analysis correctly models the dynamics of LAA-WLAN coexistence, and identifies important design guidelines for fair coexistence as follows. First, LAA-LTE should enable channel access priority class 4 to exploit its large contention window (CW). Second, LAA-LTE should re-design its CW doubling policy to restore the balance between LAA-LTE and WLAN in throughput and channel access delay. Third, to protect Wi-Fi, the maximum CW stage should be used more times by increasing the retry count.