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.
Citations
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10 Apr 2016
TL;DR: Performance evaluation indicates that near-optimal spectrum access can be achieved with guaranteed fairness between U-LTE and Wi-Fi, and a solution algorithm to solve the resulting fairness constrained mixed integer nonlinear optimization problem is proposed.
Abstract: To cope with the increasing scarcity of spectrum resources, researchers have been working to extend LTE/LTE-A cellular systems to unlicensed bands, leading to so-called unlicensed LTE (U-LTE). However, this extension is by no means straightforward, primarily because the radio resource management schemes used by LTE and by systems already deployed in unlicensed bands are incompatible. Specifically, it is well known that coexistence with scheduled systems like LTE degrades considerably the throughput of Wi-Fi networks that are based on carrier-sense medium access schemes. To address this challenge, we propose for the first time a cognitive coexistence scheme to enable spectrum sharing between U-LTE and Wi-Fi networks, referred to as CU-LTE. The proposed scheme is designed to jointly determine dynamic channel selection, carrier aggregation and fractional spectrum access for U-LTE networks, while guaranteeing fair spectrum access for Wi-Fi based on a newly designed cross-technology fairness criterion. We first derive a mathematical model of the spectrum sharing problem for the coexisting networks; we then design a solution algorithm to solve the resulting fairness constrained mixed integer nonlinear optimization problem. The algorithm, based on a combination of branch and bound and convex relaxation techniques, maximizes the network utility with guaranteed optimality precision that can be set arbitrarily to 1 at the expense of computational complexity. Performance evaluation indicates that near-optimal spectrum access can be achieved with guaranteed fairness between U-LTE and Wi-Fi. Issues regarding implementation of CU-LTE are also discussed.
123 citations
TL;DR: A fair listen-before-talk (F-LBT) algorithm for coexistence of LTE-U and WLAN in unlicensed bands is proposed that can improve the total system throughput while providing the fairness between LTE- U and W LAN.
Abstract: Recently, there has been an increasing interest in operating long-term evolution (LTE) in unlicensed bands (i.e., LTE-U). However, since LTE and wireless local area networks (WLANs) are designed to operate in different bands, they have no coexistence mechanism, which leads to significant performance degradation. In particular, since LTE does not sense channel vacancy prior to transmissions, the LTE interference severely affects the WLAN operation. To address this problem, we propose a fair listen-before-talk (F-LBT) algorithm for coexistence of LTE-U and WLAN in unlicensed bands. F-LBT jointly considers the total system throughput and the fairness between LTE-U and WLAN and then allocates an appropriate idle period for WLAN. Evaluation results demonstrate that F-LBT can improve the total system throughput while providing the fairness between LTE-U and WLAN.
116 citations
Cites background from "Performance Evaluation of LTE and W..."
...In particular, since LTE does not sense channel vacancy prior to transmissions, the interference due to LTE transmissions severely affects the WLAN performance [5]....
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09 Mar 2015
TL;DR: This paper proposes a Q-Learning based dynamic duty cycle selection technique for configuring LTE transmission gaps, so that a satisfactory throughput is maintained both for LTE and WiFi systems, and evaluates the coexistence performance of WiFi and LTE using the proposed technique.
Abstract: In order to coexist with the WiFi systems in the unlicensed spectrum, Long Term Evolution (LTE) networks can utilize periodically configured transmission gaps. In this paper, considering a time division duplex (TDD)-LTE system, we propose a Q-Learning based dynamic duty cycle selection technique for configuring LTE transmission gaps, so that a satisfactory throughput is maintained both for LTE and WiFi systems. By explicitly taking the impact of IEEE 802.11n beacon transmission mechanism into account, we evaluate the coexistence performance of WiFi and LTE using the proposed technique. Simulation results show that the proposed approach can enhance the overall capacity performance by 19% and WiFi capacity performance by 77%, hence enabling effective coexistence of LTE and WiFi systems in the unlicensed band.
110 citations
03 Dec 2015
TL;DR: Numerical results are presented showing significant gains in both Wi-Fi and LTE performance with the proposed inter-network coordination approach, as well as possible techniques for enabling improved co-existence.
Abstract: This paper investigates the co-existence of Wi-Fi and LTE networks in emerging unlicensed frequency bands which are intended to accommodate multiple radio access technologies. Wi-Fi and LTE are the two most prominent wireless access technologies being deployed today, motivating further study of the inter-system interference arising in such shared spectrum scenarios as well as possible techniques for enabling improved co-existence. An analytical model for evaluating the baseline performance of co-existing Wi-Fi and LTE networks is developed and used to obtain baseline performance measures. The results show that both Wi-Fi and LTE networks cause significant interference to each other and that the degradation is dependent on a number of factors such as power levels and physical topology. The model-based results are partially validated via experimental evaluations using USRP-based SDR platforms on the ORBIT testbed. Further, inter-network coordination with logically centralized radio resource management across Wi-Fi and LTE systems is proposed as a possible solution for improved co-existence. Numerical results are presented showing significant gains in both Wi-Fi and LTE performance with the proposed inter-network coordination approach.
107 citations
Cites background from "Performance Evaluation of LTE and W..."
...LTE is designed to operate solely in a spectrum, which when operating in unlicensed spectrum, is termed LTE-U....
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...To address this problem, we further presented an architecture for coordination between heterogeneous networks, with a specific focus on LTE-U and Wi-Fi, to cooperate and coexist in the same area....
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...Recently, Wi-Fi and LTE coexistence has been studied in the context of TV white space [23], in-device coexistence [24], and LTE-unlicensed (LTE-U) [25]–[27]....
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...Wi-Fi and LTE coexistence has been studied in the context of TV white space [26], in-device coexistence [27], and LTE unlicensed (LTE-U) [28]–[30]....
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...It is suggested in 3GPP, that LTE-U will be used as a supplemental downlink, whereas the uplink will use licensed spectrum....
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TL;DR: This paper provides a comprehensive overview of the various coexistence scenarios in the 5 GHz bands, and discusses coexistence issues between a number of important wireless technologies—viz.
Abstract: 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 Federal Communications Commission and the European Electronic Communications Committee 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.
103 citations
Cites background from "Performance Evaluation of LTE and W..."
...Findings from [28] and [29] highlight the need for developing suitable coexistence mechanisms between LTE and Wi-Fi in the unlicensed spectrum....
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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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