A Performance Comparison of LBE Based Coexistence Protocols for LAA and Wi-Fi

Long Term Evolution (LTE) deployment in the unlicensed spectrum is considered a promising solution to overcome spectrum shortage. To ensure fair coexistence among unlicensed users, two Load Based Equipment (LBE) access technologies are introduced in European Telecommunications Standards Institute (ETSI) standard. However, it is not clear whether the two LBE protocols can ensure fair channel access between unlicensed Licensed Assisted Access (LAA) and Wi-Fi users. To this end, renewal theory based analytical models are developed to study the performance of these two LBE random access protocols. Specifically, the throughput performance of Wi-Fi users and LAA users is first derived and compared. Our results show that both options may not achieve throughput fairness among Wi-Fi and LAA users if the key protocol parameters are not fine tuned. Generally option A favors Wi-Fi users, while option B favors LAA users. To improve the fairness performance, channel access parameters in both protocols should be adapted to network conditions in order to achieve the best coexisting performance in terms of both fairness and network throughput. The analysis provides important guidance for the implementation of Listen-before-Talk based access mechanisms in LAA. Extensive simulations using NS-3 are conducted to validate the accuracy of the models.