Performance Evaluation of LTE and Wi-Fi Coexistence in Unlicensed Bands
02 Jun 2013-pp 1-6
TL;DR: A simulator-based system- level analysis in order to assess the network performance in an office scenario shows that LTE system performance is slightly affected by coexistence whereas Wi-Fi is significantly impacted by LTE transmissions.
Abstract: The deployment of modern mobile systems has faced severe challenges due to the current spectrum scarcity. The situation has been further worsened by the development of different wireless technologies and standards that can be used in the same frequency band. Furthermore, the usage of smaller cells (e.g. pico, femto and wireless LAN), coexistence among heterogeneous networks (including amongst different wireless technologies such as LTE and Wi-Fi deployed in the same frequency band) has been a big field of research in the academy and industry. In this paper, we provide a performance evaluation of coexistence between LTE and Wi-Fi systems and show some of the challenges faced by the different technologies. We focus on a simulator-based system- level analysis in order to assess the network performance in an office scenario. Simulation results show that LTE system performance is slightly affected by coexistence whereas Wi-Fi is significantly impacted by LTE transmissions. In coexistence, the Wi-Fi channel is most often blocked by LTE interference, making the Wi-Fi nodes to stay on the LISTEN mode more than 96% of the time. This reflects directly on the Wi-Fi user throughput, that decreases from 70% to ≈100% depending on the scenario. Finally, some of the main issues that limit the LTE/Wi-Fi coexistence and some pointers on the mutual interference management of both the systems are provided.
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01 Feb 2017
TL;DR: The CA of licensed and unlicensed spectrum when QoS of user cannot be met with licensed spectrum is explored by deploying dual mode small cell base station (SBS) and considering minimum requirement of unlicensed WiFi access points (WAP).
Abstract: Wireless communication industry is facing storm of exponential mobile traffic increase due to richer contents sharing over the network through smart devices. A innocent resolution for envisaging this contravention is to employ more licensed spectrum. But this is a scare resource and sufficient additional spectrum will be unavailable in the upcoming days. So, both academia and industry are engaging different new technologies to deal with this traffic cyclone in cellular networks. Long Term Evaluation-Advanced (LTE-A) is such a recent technology that serves heavy mobile traffic. But with insufficient licensed spectrum, LTE-A also cannot meet the quality of service (QoS) requirements of all it's users. So, by augmenting the benefits of LTE-A into unlicensed spectrum known as LTE-U with the help of carrier aggregation (CA) technique, we can boost the performance of 4G/5G cellular network. The process will degrade the performance of other technologies which are already using same unlicensed band. Moreover, if multiple cellular network operators (CNOs) use the same unlicensed band then they will diminish the benefits of each others. In this paper, we explore the CA of licensed and unlicensed spectrum when QoS of user cannot be met with licensed spectrum by deploying dual mode small cell base station (SBS) and considering minimum requirement of unlicensed WiFi access points (WAP). Here, we formulate the resource allocation as an optimization problem which wants to maximize the sum-rate of LTE-U system. Then we solve this problem with the help of Nash bargaining game (NBG) between LTE-U and WAP by cooperative approach. Simulation results show the effectiveness and efficiency of the proposed approach considering QoS requirement of LTE-U users and coexistence issue with WAPs.
10 citations
Cites background or methods from "Performance Evaluation of LTE and W..."
...Currently, there are three proposed operation mode for LTEU network: supplemental downlink (SDL), time division LTE (TD-LTE) with CA and standalone LTE-U [4]....
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...SBSs work in SDL mode with CSAT and CA technology....
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TL;DR: The Q-learning (QL) framework is introduced into LTE licensed assisted access (LAA) scheme in the paper and the proposed chaotic QL LAA scheme outperforms the other LAA schemes in terms of throughput, collision probability, fairness and delay.
Abstract: To meet the ever-increasing demand for mobile data traffic, mobile operators are seeking to utilize unlicensed spectrum as a supplement to the licensed spectrum. The harmonious and spectrum-efficient coexistence scheme between LTE and incumbent users on the unlicensed spectrum is thus mandatory. Currently, advanced intelligent technologies are being expected to play the crucial role in the future communication system. We thus introduce the Q-learning (QL) framework into LTE licensed assisted access (LAA) scheme in the paper, thereby forming a QL based LAA scheme. We first redefine the fairness in the sharing of unlicensed spectrum and then divide the state space into six states based on the predefined throughput and fairness thresholds, followed by the definition of the action set and reward function. In the proposed scheme, based on the convergent Q table, where each element is used to evaluate the pros and cons of taking an action, the agent can repeatedly interact with the environment until it reaches the terminal state, i.e. selects the optimal action (i.e. contention window size). Additionally, the chaotic motion with ergodicity, regularity and randomness is first introduced into the action-decision strategy to accelerate the training velocity with the balance consideration of exploration and exploitation. The simulation results prove that the proposed $\epsilon$ -chaotic greedy selection strategy has faster convergence velocity compared with other methods such as $\epsilon$ -greedy, pure greedy, Bolzmann and random selection strategy, and that the proposed chaotic QL LAA scheme outperforms the other LAA schemes such as the 3GPP, linear, fixed LAA and Listen Before Talk (LBT) adaptive schemes in terms of throughput, collision probability, fairness and delay.
10 citations
Cites background from "Performance Evaluation of LTE and W..."
...Some researchers claim that the fair coexistence is feasible based on their experiment resultswhereas the other researchers suggest their concern of the impact of LAAon theWiFi networks [7], [8]....
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01 Jan 2018
TL;DR: A user-level throughput study of Wi-Fi in the presence of LTE-U using a testbed and observes a clear unfairness in throughput distribution among Wi-fi users, and highlights a need for incorporating additional functionalities in either LTE- U orWi-Fi to overcome the present challenges.
Abstract: The deployment of LTE in unlicensed spectrum is a plausible solution to meet explosive traffic demand from mobile users. However, fair coexistence with the existing unlicensed technologies, mainly Wi-Fi, needs to be ensured before any such deployment. Duty cycled LTE (LTE-U) is a simple and an easily adaptable scheme which helps in fair coexistence with the Wi-Fi. Nonetheless, the immense deployment of Wi-Fi necessitates a user-oriented study to find the effects of LTE-U operation, primarily in scenarios where the LTE-U eNB remains hidden from Wi-Fi Access Point. To comprehend these effects, we perform a user-level throughput study of Wi-Fi in the presence of LTE-U using a testbed and observe a clear unfairness in throughput distribution among Wi-Fi users. Furthermore, we also notice inability among the disadvantaged users to receive the periodic Wi-Fi beacon frames successfully. The reasons and the subsequent consequences, of throughput unfairness and beacon losses, are carefully elaborated. Also, to validate the beacon loss results, we present a beacon loss analysis which provides a mathematical expression to find the beacon loss percentage. Finally, we examine the results and highlight a need for incorporating additional functionalities in either LTE-U or Wi-Fi to overcome the present challenges.
10 citations
Cites methods from "Performance Evaluation of LTE and W..."
...This was shown in [14] using a system-level simulator....
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01 May 2017
TL;DR: This work considers load based equipment (LBE) based MAC protocol where stochastic geometry is used to model and analyze the coexistence of three LTE-LAA networks with persistent downlink transmissions, and shows the impact of channel access priorities used by different operators on their network performance.
Abstract: The growing demand on data to enhance the user experience has motivated research toward increasing the efficiency of spectrum utilization by extending cellular technology such as LTE toward unlicensed bands. In order to study the effect of channel access priorities on coexistence of several LAA networks, we consider load based equipment (LBE) based MAC protocol where we use stochastic geometry to model and analyze the coexistence of three LTE-LAA networks with persistent downlink transmissions. Mainly, we focus on single unlicensed frequency band transmissions. The locations of LAA eNodeBs (eNBs) for the three operators are modeled as three independent homogeneous Poisson point processes. Furthermore, we derive analytical closed form expressions for a set of performance metrics which are the medium access probability (MAP), signal-to-interference-plus-noise ratio (SINR) coverage probability, and rate coverage probability. Our analysis shows the impact of channel access priorities used by different operators on their network performance.
10 citations
07 Dec 2015
TL;DR: This work proposes a preliminary design for a semi-distributed LTE-Unlicensed scheme where the LTE Base Station uses WiFi-like carrier sense, back-off, and Quality of Service facility techniques, and presents a study on LAA-WiFi-coexistence through ns3 simulations.
Abstract: In order to accommodate the exponentially-growing data traffic, LTE operators are considering the extension of the LTE operation into the unlicensed bands. In a recent technical report for the third Generation Partnership Project, Licensed-Assisted Access (LAA) to the unlicensed spectrum has been introduced. The report and other works in the literature reveal coexistence challenges that are raised when the LTE system coexists with other technologies such as WiFi, with fairness being the primary challenge. In this work, we propose a preliminary design for a semi-distributed LTE-Unlicensed scheme where the LTE Base Station uses WiFi-like carrier sense, back-off, and Quality of Service facility techniques. We also present a study on LAA-WiFi-coexistence through ns3 simulations. We conclude from our simulations that our preliminary design can achieve fairness in a limited set of scenarios, and we highlight the requirements and challenges that need to be considered in future work for designing a fair scheme for a wider set of scenarios.
10 citations
References
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TL;DR: An overview of the techniques being considered for LTE Release 10 (aka LTEAdvanced) is discussed, which includes bandwidth extension via carrier aggregation to support deployment bandwidths up to 100 MHz, downlink spatial multiplexing including single-cell multi-user multiple-input multiple-output transmission and coordinated multi point transmission, and heterogeneous networks with emphasis on Type 1 and Type 2 relays.
Abstract: LTE Release 8 is one of the primary broadband technologies based on OFDM, which is currently being commercialized. LTE Release 8, which is mainly deployed in a macro/microcell layout, provides improved system capacity and coverage, high peak data rates, low latency, reduced operating costs, multi-antenna support, flexible bandwidth operation and seamless integration with existing systems. LTE-Advanced (also known as LTE Release 10) significantly enhances the existing LTE Release 8 and supports much higher peak rates, higher throughput and coverage, and lower latencies, resulting in a better user experience. Additionally, LTE Release 10 will support heterogeneous deployments where low-power nodes comprising picocells, femtocells, relays, remote radio heads, and so on are placed in a macrocell layout. The LTE-Advanced features enable one to meet or exceed IMT-Advanced requirements. It may also be noted that LTE Release 9 provides some minor enhancement to LTE Release 8 with respect to the air interface, and includes features like dual-layer beamforming and time-difference- of-arrival-based location techniques. In this article an overview of the techniques being considered for LTE Release 10 (aka LTEAdvanced) is discussed. This includes bandwidth extension via carrier aggregation to support deployment bandwidths up to 100 MHz, downlink spatial multiplexing including single-cell multi-user multiple-input multiple-output transmission and coordinated multi point transmission, uplink spatial multiplexing including extension to four-layer MIMO, and heterogeneous networks with emphasis on Type 1 and Type 2 relays. Finally, the performance of LTEAdvanced using IMT-A scenarios is presented and compared against IMT-A targets for full buffer and bursty traffic model.
1,044 citations
"Performance Evaluation of LTE and W..." refers background in this paper
...4GHz band has already been established [7], and the recent inclusion of features on LTE standard [12] are promoting its usage on pico and femto cells, it is possible that in the near future coexistence between LTE (-ADV) and Wi-Fi will become important....
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TL;DR: Concepts underlying the "property" and "commons" debate are presented, options for spectrum reform are clarified, and the trade-offs of spectrum sharing are described.
Abstract: Many complain about severe spectrum shortage. The shortage comes from outdated spectrum policies that allows for little sharing. Regulators have granted licenses that offer exclusive access to the spectrum. When these licensees are not transmitting, the spectrum sits idle. A new technology regarding spectrum shortage enables more spectrum sharing that unleashes innovative products and services, provided that we adopt the appropriate spectrum policies. Two camps are pushing for extreme reform, one for "property rights" and the other for "spectrum commons". This article presents concepts underlying the "property" and "commons" debate, clarifies options for spectrum reform, and describes the trade-offs of spectrum sharing
592 citations
"Performance Evaluation of LTE and W..." refers background in this paper
...One of the most promising techniques for dealing with the lack of available spectrum is the concept of spectrum sharing [1] ....
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22 Apr 2007
TL;DR: An adjusted Shannon capacity formula is introduced, where it is shown that the bandwidth efficiency can be calculated based on system parameters, while the SNR efficiency is extracted from detailed link level studies.
Abstract: In this paper we propose a modification to Shannon capacity bound in order to facilitate accurate benchmarking of UTRAN long term evolution (LTE). The method is generally applicable to wireless communication systems, while we have used LTE air-interface technology as a case study. We introduce an adjusted Shannon capacity formula, where we take into account the system bandwidth efficiency and the SNR efficiency of LTE. Separating these issues, allows for simplified parameter extraction. We show that the bandwidth efficiency can be calculated based on system parameters, while the SNR efficiency is extracted from detailed link level studies including advanced features of MIMO and frequency domain packet scheduling (FDPS). We then use the adjusted Shannon capacity formula combined with G-factor distributions for macro and micro cell scenarios to predict LTE cell spectral efficiency (SE). Such LTE SE predictions are compared to LTE cell SE results generated by system level simulations. The results show an excellent match of less that 5-10% deviation.
580 citations
"Performance Evaluation of LTE and W..." refers methods in this paper
...For physical layer (PHY) abstraction, Shannon-fitting [14] is employed to predict the PHY performance at the system-level....
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09 Jun 2013
TL;DR: This paper considers two of the most prominent wireless technologies available today, namely Long Term Evolution (LTE), and WiFi, and addresses some problems that arise from their coexistence in the same band, and proposes a simple coexistence scheme that reuses the concept of almost blank subframes in LTE.
Abstract: The recent development of regulatory policies that permit the use of TV bands spectrum on a secondary basis has motivated discussion about coexistence of primary (e.g. TV broadcasts) and secondary users (e.g. WiFi users in TV spectrum). However, much less attention has been given to coexistence of different secondary wireless technologies in the TV white spaces. Lack of coordination between secondary networks may create severe interference situations, resulting in less efficient usage of the spectrum. In this paper, we consider two of the most prominent wireless technologies available today, namely Long Term Evolution (LTE), and WiFi, and address some problems that arise from their coexistence in the same band. We perform exhaustive system simulations and observe that WiFi is hampered much more significantly than LTE in coexistence scenarios. A simple coexistence scheme that reuses the concept of almost blank subframes in LTE is proposed, and it is observed that it can improve the WiFi throughput per user up to 50 times in the studied scenarios.
324 citations
"Performance Evaluation of LTE and W..." refers background in this paper
...This kind of approach has started to be investigated in [16], where LTE/Wi-Fi coexistence is enabled by LTE blank subframe allocation....
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27 Aug 2007
TL;DR: A channel hopping design is prototype using PRISM NICs, and it is found that it can sustain throughput at levels of RF interference well above that needed to disrupt unmodified links, and at a reasonable cost in terms of switching overheads.
Abstract: We study the impact on 802.11 networks of RF interference from devices such as Zigbee and cordless phones that increasingly crowd the 2.4GHz ISM band, and from devices such as wireless camera jammers and non-compliant 802.11 devices that seek to disrupt 802.11 operation. Our experiments show that commodity 802.11 equipment is surprisingly vulnerable to certain patterns of weak or narrow-band interference. This enables us to disrupt a link with an interfering signal whose power is 1000 times weaker than the victim's 802.11 signals, or to shut down a multiple AP, multiple channel managed network at a location with a single radio interferer. We identify several factors that lead to these vulnerabilities, ranging from MAC layer driver implementation strategies to PHY layer radio frequency implementation strategies. Our results further show that these factors are not overcome by simply changing 802.11 operational parameters (such as CCA threshold, rate and packet size) with the exception of frequency shifts. This leads us to explore rapid channel hopping as a strategy to withstand RF interference. We prototype a channel hopping design using PRISM NICs, and find that it can sustain throughput at levels of RF interference well above that needed to disrupt unmodified links, and at a reasonable cost in terms of switching overheads.
300 citations
"Performance Evaluation of LTE and W..." refers background in this paper
...However, it is observed that the coexistence of heterogeneous systems in the same frequency bands causes a meaningful degradation on the system performance (e.g., Wi-Fi and Bluetooth [3], Wi-Fi and ZigBee [4], Wi-Fi and WiMAX [5])....
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..., Wi-Fi and Bluetooth [3], Wi-Fi and ZigBee [4], Wi-Fi and WiMAX [5])....
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