As the rapid development of network technology, Internet has become an integral part of our lives. Withthe popularity of smart mobile devices, surfing the Internet anytime, anywhere has become a kind of necessityfor the modern life. How to combine the coming mobile communication technologies with other existenttechnologies to support modern networking services in mobile networks is one of the major issues.The 4G LTE-A (Long Term Evolution - Advanced) standard developed by 3GPP organization is the maintrend of the future wireless mobile communication industry. The 4G LTE-A standard adopts small cell as wellas unlicensed spectrum (5.8GHz LTE-U) to offload heavy traffic from licensed band to unlicensed band. Suchmajor technology is known as Licensed Assisted Access (LAA) technology. On the other hand, thedevelopment of IEEE 802.11 standard has been matured everywhere. All IEEE 802.11 products use CSMA/CA(Carrier Sense Multiple Access with Collision Avoidance) with request-to-send/clear-to-send (RTS/CTS)protocol to solve contention and hidden-node problems. Therefore, the LTE-U shall have the new mechanismto coexist with pervasive IEEE 802.11 products. Therefore, how to avoid the effects of operating LAA onunlicensed band, where there are IEEE 802.11 products, is the research objective of this project.The Listen-Before-Talk (LBT) procedure is the main procedure for LAA to accomplish fair and friendlycoexistence with other operators or technologies operating over unlicensed spectrum. However, lacking theLayer 2 RTS/CTS protocol with the other existing systems, it is uneasy to solve the hidden-node problem(HNP). Intuitively, the drawback of hidden-node problem may be the advantage of expose-node problem wherethe transmitters which are not hidden to each other can simultaneously transmit if the receivers are hiddennodes to each other. In order to fully understand the essential problem of coexistence issue between LAA andWiFi systems, we have done the thorough analyses on hidden-node and exposed-node probabilities by meansof mathematical approach. Analytical results surprisingly reveal that the exposed-node probability is as highas 39.33%, which means the current coexistence solution may waste about 40% system bandwidth. Therefore,this project aims to propose the compliance solution(s) for LBT mechanism in order to optimize the overallsystem performance. Besides, owing to the derived equations for estimating the probabilities of differentscenarios are too sophisticated to calculate, this project will also find out an approximate method to quicklyestimate the results.
|Effective start/end date||1/08/17 → 31/10/18|
In 2015, UN member states agreed to 17 global Sustainable Development Goals (SDGs) to end poverty, protect the planet and ensure prosperity for all. This project contributes towards the following SDG(s):