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On the Impact of LTE-U on Wi-Fi Performance

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Abstract

With the exponential growth in mobile data traffic taking place currently and projected into the future, mobile operators need cost effective ways to manage the load of their networks. Traditionally, this has been achieved by offloading mobile traffic onto Wi-Fi networks due to their low cost and increasingly ubiquitous deployment. Recently, LTE operating in the unlicensed spectrum has drawn significant interests from mobile operators due to the availability of the unlicensed spectrum. Using this technology, the unlicensed spectrum is directly utilized by LTE without the need to offload traffic to an alternative radio access technology such as Wi-Fi. However, the deployment of LTE networks in the unlicensed band poses significant challenges to the performance of current and future Wi-Fi networks. We discuss the LTE and Wi-Fi coexistence challenges and present analysis on performance degradation of the Wi-Fi networks at the presence of LTE.

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Notes

  1. Since July 2014, 3GPP has been using License Assisted Access (LAA) as the official 3GPP term, and ETSI amended “Listen before talk” into LAA. By the time this paper was accepted, both FDD and TDD modes were introduced in TR36.889. Meanwhile, the LTE-U forum, formed by Verizon and a few other vendors in 2014, released an LTE supplemental downlink (SDL) coexistence specification, where an adaptive duty cycle based coexistence scheme was introduced, and the term “LTE-U” was used instead of “LAA” in the specification. Hence, there are now technical and business related differences between LTE-U and LAA. Various vendors and operators have developed positions in support of one or the other. However, since this paper focuses on duty cycle based LTE on unlicensed spectrum, we still use the short and conventional term LTE-U for convenience.

  2. Although point coordination function is also defined in Wi-Fi, it is not widely implemented, and therefore not discussed in this paper.

  3. Only standard slot configuration is considered, i.e., normal cyclic prefix with seven symbols per slot. No MIMO configuration is considered.

  4. Note that, even if the LTE-U quiet period is long enough that the Wi-Fi user can access the channel, its transmission may be interfered by LTE-U users, seriously degrading its throughput. This is however outside the scope of this paper.

  5. Since Wi-Fi to Wi-Fi interference below \(-82\,{\hbox {dbm}}\), LTE interference and noise can also cause transmission failure, the Wi-Fi access probability we obtain in this paper is an upper bound.

  6. Note it is generally not true that \(p_{s}=1-p_{c}\).

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Authors and Affiliations

  1. Cable Television Laboratories, 858 Coal Creek Circle, Louisville, CO, 80027, USA

    Alireza Babaei, Jennifer Andreoli-Fang & Belal Hamzeh

  2. ECEE Department, University of Colorado Boulder, 425 UCB, Boulder, Colorado, 80309, USA

    Yimin Pang

Authors
  1. Alireza Babaei
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  2. Jennifer Andreoli-Fang
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  3. Yimin Pang
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  4. Belal Hamzeh
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Correspondence to Alireza Babaei.

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Babaei, A., Andreoli-Fang, J., Pang, Y. et al. On the Impact of LTE-U on Wi-Fi Performance. Int J Wireless Inf Networks 22, 336–344 (2015). https://doi.org/10.1007/s10776-015-0288-6

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  • DOI: https://doi.org/10.1007/s10776-015-0288-6

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