Coexistence of DSRC and Wi-Fi in the ITS Band

Background

V2X concept

The 5.9 GHz band (5.85 - 5.925 GHz) has been allocated for Intelligent Transportation Systems (ITS) applications in the US. The under-utilization of this band has lead to interests in sharing the spectrum with unlicensed technologies such as Wi-Fi. Under this spectrum sharing scenario, DSRC devices will be the primary users of the spectrum, while Wi-Fi users will be allowed to use the spectrum opportunistically. In this project, we look at the impact of Wi-Fi on DSRC and vice-versa.

In this project, we study the problem of coexistence between DSRC and Wi-Fi systems in the 5.9 GHz ITS band. We study this coexistence scenario from the perspective of both, DSRC and Wi-Fi, systems.

External Resources

Introductory Papers

  • Dedicated Short-Range Communications (DSRC) Standards in the United States
    [IEEE Xplore | Open Access]
  • Design of 5.9 GHz DSRC-based Vehicular Safety Communication
    [IEEE Xplore]
  • Coexistence of unlicensed devices with DSRC systems in the 5.9 GHz ITS band
    [IEEE Xplore]

Our Contributions

  • Using Monte Carlo and System-level simulations, we evaluate the impact of Wi-Fi users on the system-wide performance of DSRC.
  • We observe that by changing certain contention parameters of Wi-Fi transmitters (e.g. Inter-frame space), the impact of Wi-Fi users on the DSRC performance can be alleviated.
  • We verify this claim using test-bed experiments and propose a real-time channelization algorithm that can be used at Wi-Fi devices in order to maximize Wi-Fi performance under the spectrum sharing scenario.

Publications

  • As the 2.4 GHz spectrum band has become significantly congested, there is growing interest from the Wi-Fi proponents, cellular operators, and other stakeholders to use the spectrum in the 5 GHz bands. The 5 GHz bands have emerged as the most coveted bands for launching new wireless applications and services, because of their relatively favorable propagation characteristics and the relative abundance of spectrum therein. To meet the exploding demand for more unlicensed spectrum, regulators across the world such as the United States (US) Federal Communications Commission (FCC) and the European Electronic Communications Committee (ECC) have recently started considerations for opening up additional spectrum in the 5 GHz bands for use by unlicensed devices. Moreover, to boost cellular network capacity, wireless service providers are considering the deployment of unlicensed Long Term Evaluation (LTE) in the 5 GHz bands. This and other emerging wireless technologies and applications have resulted in likely deployment scenarios where multiple licensed and unlicensed networks operate in overlapping spectrum. This paper provides a comprehensive overview of the various coexistence scenarios in the 5 GHz bands. In this paper, we discuss coexistence issues between a number of important wireless technologies—viz., LTE and Wi-Fi, radar and Wi-Fi, Dedicated Short Range Communication (DSRC) and Wi-Fi, and coexistence among various 802.11 protocols operating in the 5 GHz bands. Additionally, we identify and provide brief discussions on an impending coexistence issue – one between Cellular V2X and DSRC/Wi-Fi. We summarize relevant standardization initiatives, explain existing coexistence solutions, and discuss open research problems.


    [Download | IEEE Xplore]

  • The 5.9 GHz band is being actively explored for possible spectrum sharing opportunities between Dedicated Short Range Communications (DSRC) and IEEE 802.11ac networks in order to address the increasing demand for bandwidth-intensive Wi-Fi applications. In this paper, we study the implications of this spectrum sharing to the performance of Wi-Fi systems. Through experiments performed on our testbed, we first investigate band sharing options available for Wi-Fi devices. Using experimental results, we show the need for using conservative Wi-Fi transmission parameters to enable harmonious coexistence between DSRC and Wi-Fi. Moreover, we show that under the current 802.11ac standard, certain channelization options, particularly the high bandwidth ones, cannot be used by Wi-Fi devices without causing interference to the DSRC nodes. Under these constraints, we propose a Real-time Channelization Algorithm (RCA) for Wi-Fi Access Points (APs) operating in the shared spectrum. Evaluation of the proposed algorithm using a prototype implementation on commodity hardware as well as via simulations show that informed channelization decisions can significantly increase Wi-Fi throughput compared to static channelization schemes.


    [Download | IEEE Xplore | Slides]

  • To adequately support high-throughput applications in next-generation WLANs, more spectrum will be needed to accommodate wider channels. To address this issue, spectrum regulators and stakeholders from the wireless industry and the intelligent transportation system communities are exploring possible band sharing approaches in the 5.9 GHz band. Such approaches include techniques that enable the harmonious coexistence of Dedicated Short Range Communications (DSRC) networks and IEEE 802.11ac networks. In this paper, we provide in-depth discussions on how the coexistence of DSRC and 802.11ac impacts the performance of DSRC applications, with a particular focus on vehicular safety applications. We propose an analytical model that provides valuable insights on DSRC network performance and its vulnerability to interference induced by other DSRC nodes as well as 802.11ac nodes. Using the analytical results derived from the model and extensive simulation results, we also propose a methodology for adjusting 802.11ac parameters that enables a DSRC network to meet the performance requirements of safety applications. Using simulations, we also analyze the throughput of the coexisting 802.11ac network.


    [Download | IEEE Xplore | Slides]

Videos