An Experimental Evaluation of Coexistence Challenges of Wi-Fi and LTE in the unlicensed band Vasilis Maglogiannis [1], Jerome A. Arokkiam [2], Adnan Shahid [1], Dries Naudts [1], Ingrid Moerman[1] [1] – IDLab, imec - Ghent University, Ghent, Belgium [2] – CONNECT Centre, Trinity College Dublin, Ireland
Motivation The fundamental differences in the PHY/MAC design and operation methodology The coexistence performance of LTE & Wi-Fi vary significantly in different deployment scenarios Throughput of Wi-Fi usually decreases when sharing with any type of unlicensed LTE The performance of either LTE-LAA or Wi-Fi should not be affected by each other while deployed in 5 GHz spectrum together What are some of the deployment challenges associated with the coexistence of LTE and Wi-Fi? Y. Huang, Y. Chen, Y. T. Hou, W. Lou, and J. H. Reed, “Recent Advances of LTE/WiFi Coexistence in Unlicensed Spectrum,” IEEE Network, vol. 32, no. 2, pp. 107–113, March 2018 B. Chen, J. Chen, Y. Gao, and J. Zhang, “Coexistence of LTE-LAA and Wi-Fi on 5 GHz With Corresponding Deployment Scenarios: A Survey,” IEEE Communications Surveys Tutorials, vol. 19, no. 1, pp.7–32,Q1’17 “LTE in unlicensed spectrum: Harmonious coexistence with WiFi,” San Jose, CA, USA, 2012. [Online]. https://www.qualcomm.com/media/documents/files/lteunlicensed-coexistence-whitepaper.pdf Z. Zhou, S. Mumtaz, K. M. S. Huq, A. Al-Dulaimi, K. Chandra, and J. Rodriquez, “Cloud Miracles: Heterogeneous Cloud RAN for Fair Coexistence of LTE-U and Wi-Fi in Ultra Dense 5G Networks,” IEEE Communications Magazine, vol. 56, no. 6, pp. 64–71, June 2018.
Signal Combiner/Splitter unit Network Setup TX RX TR/RX TX/RX Signal Combiner/Splitter unit LTE Base Station (srsLTE , FDD) 802.11g Wi-Fi AP Zotac nodes, Qualcomm Atheros AR928X chip Spectrogram LTE Client Wi-Fi Client Guide: Coax cables
Network Setup COTS LTE and Wi-Fi hardware equipment has been used in a fully controlled environment. Targeting a clean and controlled environment without any interference from other co-located networks, both the LTE and the Wi-Fi equipment were interconnected with each other using COAX cables through combiner and splitter units. The experiments were performed at the LTE and Wi-Fi infrastructure of the iLab testbed of IMEC. For LTE, the B210 USRP boards are connected to Gigabyte BRIX Compact PCs that are used as host nodes, on which the LTE software srsLTE runs. srsLTE is a highly modular LTE software framework developed by SRS and includes complete SDR LTE applications for the eNB, the UE and the Evolved Packet Core (EPC) side. The srsLTE framework is LTE Release 8 compliant with selected features of Release 9. Frequency Division Duplex (FDD) mode has been selected, similar to what is being used in LTE LAA. The Wi-Fi network consists of Zotac nodes configured in infrastructure mode. One node operates as Access Point (AP) and it can have multiple associated stations. All the Wi-Fi nodes use a Qualcomm Atheros AR928X wireless network adapter together with the ath9k driver [39]. The Wi-Fi has been configured to use the 802.11g mode. This mode has been selected as it does not support frame aggregation and MIMO and it provides relatively low data rate compared to the newest Wi-Fi standards (e.g. 802.11n/ac). The proposed model can be used for identification of a wide range of Wi-Fi standards.
Experiment 1 of 2 Impact of Tx power and Bandwidth LTE Throughput when having 20MHz Wi-Fi Wi-Fi Throughput when having LTE Control Signals High Power LTE Low Power LTE High Power Wi-Fi Low Power Wi-Fi Wi-Fi causes signification interference to LTE when having a similar or higher Wi-Fi Tx power than LTE High Power LTE Signalling causes interference to Wi-Fi Low Power LTE Signalling is a hidden terminal for Wi-Fi
Experiment 1 of 2 Impact of Tx power and Bandwidth Wi-Fi Throughput when having LTE Data 20Mhz LTE 1,53 7,61 DIS-Associate 7,5 10MHz LTE 0.3 6,04 6,29 5MHz LTE 0,37 1,62 1,45 High LTE Low LTE High Wi-Fi Low Wi-Fi High Power Wi-Fi Low Power Wi-Fi Low Power LTE Data Tx causes significant interference to Wi-Fi High Power LTE Data Tx causes Wi-Fi de-association
Experiment 1 of 2 Impact of Tx power and Bandwidth 20MHz Wi-Fi Throughput when having 5MHz LTE at different positions of the Wi-Fi Spectrum 2437 MHz 2447 MHz 2427 MHz Wi-Fi 5 MHz LTE 2432 LTE Control Signal LTE Data 2437 MHz 2447 MHz 2427 MHz Wi-Fi 5 MHz LTE 2444.5 5MHz middle 5MHz edge 5MHz LTE Tx causes Wi-Fi throughput degradation in different ways depending on the relative position of LTE Tx within the Wi-Fi spectrum
Experiment 2 of 2 Adjacent Channel Interference 2437 MHz 2447 MHz 2417 MHz 2407 MHz 2427 MHz Wi-Fi LTE LTE Transmission creates a lot of adjacent-channel interference to Wi-Fi
Conclusions When a 20MHz Wi-Fi transmission coexists with a 20, 10 and 5MHz LTE transmission, individually, Wi-Fi causes signification interference to LTE when having a similar or higher Wi-Fi Tx power than LTE High Power LTE Signalling causes interference to Wi-Fi while Low Power LTE Signalling acts as a hidden terminal for Wi-Fi Low Power LTE Data transmission causes significant interference to Wi-Fi while High Power LTE Data transmission causes Wi-Fi de-association When a 20MHz Wi-Fi transmission coexists with a 5MHz LTE transmission depending on the relative position of LTE Tx within the Wi-Fi spectrum, 5MHz LTE Tx causes Wi-Fi throughput degradation in several different ways During adjacent-channel transmission of LTE and Wi-Fi LTE transmission creates a lot of adjacent-channel interference to Wi-Fi, while Wi-Fi does not create interference towards LTE
Questions Thank you it’s time for Vasils Maglogiannis (vasilis.maglogiannis@ugent.be) Jerome A. Arokkiam (jerom2005raj@yahoo.com / j.arokkiam@osram.com) Adnan Shahid (adnan.shahid@ugent.be) Dries Naudts (dries.naudts@ugent.be) Ingrid Moerman (ingrid.moerman@ugent.be)
Spectrogram Results
Fully overlapping LTE (20MHz) and Wi-Fi (20MHz)
Fully overlapping LTE (10MHz) and Wi-Fi (20MHz)
Fully overlapping LTE (5MHz) and Wi-Fi (20MHz) – Edge overlap
Fully overlapping LTE (5MHz) and Wi-Fi (20MHz) – Middle overlap
Adjacent Channel LTE (20MHz) and Wi-Fi (20MHz)