The rapidly growing demand of wireless network services has led the mobile network operators (MNOs) to consider the possibility of exploring unlicensed spectrum to offload the data traffic from the licensed bands. Most recently, 3GPP and other industry alliances are considering extending LTE into the unlicensed spectrum to offload part of the LTE data traffic. Compared to data offload using Wi-Fi, this approach has the advantage of seamless integration into the existing LTE evolved packet core (EPC) architecture.
Wi-Fi and LTE-Unlicensed (LTE-U) technologies have drawn some fire in the telecommunications industry for their ability to coexist without negative ramification. We decided to take a closer look to find out just exactly how WiFi performs in the presence of duty cycle based LTE-U transmission on the same channel.
A simple static air-time sharing between unlicensed LTE and Wi-Fi is generally not sufficient to ensure fair coexistence between these systems. On the other hand, other mechanisms such as listen-before-talk that have been incorporated in the 3GPP version of unlicensed LTE are well studied and enhance coexistence performance. Alternatively, adaptive air-time sharing, where the duty cycle of LTE transmission dynamically changes considering Wi-Fi traffic, improves the coexistence performance.– Alireza Babaei, Senior Technical Staff
It gets even more specific than that. One LTE-U cell and one Wi-Fi basic service set (BSS) coexist by allowing LTE-U devices to transmit their signals only in predetermined duty cycles. Wi-Fi stations, on the other hand, simply contend the shared channel using the distributed coordination function (DCF) protocol. And it does this without cooperation with the LTE-U system or prior knowledge about the duty cycle period or duty cycle of LTE-U transmission.
In the paper, we set out to draw some conclusions about how these two technologies coexist. Depending on the interference to noise ratio (INR) being above or below − 62 dbm, we classify the LTE-U interference as strong or weak and establish mathematical models accordingly. The average throughput and average service time of Wi-Fi are both formulated as functions of Wi-Fi and LTE-U system parameters using probability theory. Lastly, we use the Monte Carlo analysis to demonstrate the fairness of Wi-Fi and LTE-U air time sharing.
We conclude that some other schemes (e.g., similar to the listen-before-talk mechanism used in 802.11 networks) need to be developed for LTE-U networks in order to overcome the observed unfairness.
Co-existence of different technologies using the same frequencies is important in implementing a healthy ecosystem in spectrum sharing. This paper shows Ofinno’s commitment to quality and detailed technical analysis on complex technological issues facing the industry.- Esmael Dinan, CEO
Take a closer look at our analysis and conclusions…
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