Proportional Fairness-Based Resource Allocation for LTE-U Coexisting With Wi-Fi
TL;DR: A cross-layer proportional fairness (PF)-based framework to jointly optimize the protocol parameters of the medium access control layer and physical layer of an LTE-U network to achieve throughput-oriented PF between the two heterogeneous networks is proposed.
Abstract: To further boost the performance of LTE to meet the ever-increasing mobile traffic demand in a cost-effective way, applying LTE in unlicensed spectrum, known as LTE-U technology, is considered as a promising complementary solution for achieving the ultra-capacity foreseen in 5G and beyond. In the unlicensed spectrum, LTE-U will share the channel with other unlicensed networks, e.g., Wi-Fi. However, the centralized control architecture of LTE networks is inherently different from the distributed channel access of Wi-Fi network, which poses great challenges to achieve fair coexistence of the two networks. To this end, in this paper, we propose a cross-layer proportional fairness (PF)-based framework to jointly optimize the protocol parameters of the medium access control layer and physical layer of an LTE-U network. Specifically, to achieve throughput-oriented PF between the two heterogeneous networks, the cross-layer optimization framework can be decoupled into a device number weighted time occupation ratio-oriented PF optimization problem and a channel-power allocation-based instantaneous transmission rate-oriented PF optimization problem. Given that LTE-U base stations adopt a listen-before-talk-based channel access scheme, the interactions between the LTE-U and the Wi-Fi networks are modeled by two interactive Markov chains. The effectiveness and the superior performance of the proposed cross-layer PF-based optimization framework are demonstrated and verified by simulations.
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TL;DR: In this article, the design challenges, opportunities, and solutions for New Radio-based access to Unlicensed spectrum (NR-U) by taking into account the beam-based transmissions and the worldwide regulatory requirements are discussed.
Abstract: This paper elaborates on the design challenges, opportunities, and solutions for New Radio-based access to Unlicensed spectrum (NR-U) by taking into account the beam-based transmissions and the worldwide regulatory requirements. NR-U intends to expand the applicability of 5th generation New Radio access technology to support operation in unlicensed bands by adhering to Listen-Before-Talk (LBT) requirements for accessing the channel. LBT was already adopted by different variants of 4th generation Long Term Evolution (LTE) in unlicensed spectrum, i.e., Licensed-Assisted Access and MulteFire, to guarantee fair coexistence among different radio access technologies. In the case of beam-based transmissions, the NR-U coexistence framework is significantly different as compared to LTE in unlicensed spectrum due to the use of directional antennas, which enhance the spatial reuse but also complicate the interference management. In particular, beam-based transmissions are needed in the unlicensed spectrum at millimeter-wave (mmWave) bands, which is an attractive candidate for NR-U due to its large amount of allocated spectrum. As a consequence, some major design principles need to be revisited to address coexistence for beam-based NR-U. In this paper, different problems and the potential solutions related to channel access procedures, frame structure, initial access procedures, re-transmission procedures, and scheduling schemes are discussed. A simulation evaluation of different LBT-based channel access procedures for NR-U/Wi-Fi indoor mmWave coexistence scenarios is also provided.
102 citations
TL;DR: Stochastic geometry is used to develop a framework for a multi-radio access technologies (multi-RAT) heterogeneous network, which consists of an LTE-U tier and a Wi-Fi tier, and optimization of the retention probability of LTE- U nodes is optimized to maximize the minimum weighted spatial throughput ofWi-Fi and LTE-u networks.
Abstract: Shortage of available licensed spectrum is a major barrier to the development of 5G networks. The deployment of long term evolution (LTE) in unlicensed spectrum (LTE-U) is a promising solution to overcome such a barrier. However, the interaction between LTE-U and Wi-Fi in unlicensed spectrum has not been well understood. In this paper, we use stochastic geometry to develop a framework for a multi-radio access technologies (multi-RAT) heterogeneous network, which consists of an LTE-U tier and a Wi-Fi tier. To reduce the intra- and inter-RAT interference, LTE-U employs an ALOHA-like random access scheme and Wi-Fi performs carrier sensing and energy detection before transmission. We derive the coverage probability and spatial throughput of Wi-Fi and LTE-U networks, and perform the asymptotic analysis when the density of Wi-Fi and LTE-U nodes approach infinity. Based on our analysis, we investigate the effect of network parameters on the coverage probability and spatial throughput of these networks. Furthermore, in order to achieve weighted max-min fairness, we optimize the retention probability of LTE-U nodes to maximize the minimum weighted spatial throughput of Wi-Fi and LTE-U networks.
76 citations
Cites background from "Proportional Fairness-Based Resourc..."
...[17] analyzed the throughput of Wi-Fi and LTE-U....
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TL;DR: A flexible coexistence framework is proposed using the listen-before-talk mechanism, based on which the QoS metrics of LAA-LTE and WiFi systems are quantified and an efficient algorithm called successive user removal is proposed.
Abstract: The licensed-assisted access-based long term evolution (LAA-LTE) is a promising solution to provide enhanced LTE services by sharing unlicensed bands with WiFi systems. However, the intense contention with the incumbent WiFi system makes it challenging for the LAA-LTE system to support guaranteed quality-of-service (QoS) for the users. This paper is interested in the QoS-aware LAA-LTE/WiFi coexistence system. We first propose a flexible coexistence framework using the listen-before-talk mechanism, based on which the QoS metrics of LAA-LTE and WiFi systems are quantified. Then, a joint user association and resource allocation problem is formulated, which aims to maximize the number of QoS-preferred users supported by LAA-LTE, while protecting the WiFi users. The considered optimization problem is equivalently decomposed into two subproblems, the sum-power minimization problem and the user association problem. For the first subproblem, the deep-cut ellipsoid method is adopted to optimize the LAA-LTE transmission time, subcarrier assignment, and power allocation. For the latter one, an efficient algorithm called successive user removal is proposed. The simulation results have demonstrated the effectiveness of the proposed scheme, based on which the tradeoff among different QoS metrics in the coexistence system is observed.
69 citations
Cites methods from "Proportional Fairness-Based Resourc..."
...In [21], a crosslayer optimization method is proposed to maximize the overall...
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TL;DR: A methodology to determine the proper clear channel assessment energy detection (CCA-ED) threshold for LTE-U is proposed and experimental results show that SDL mechanism guarantees relatively friendly and harmonious coexistence between LAA and WiFi only in the sparse scenario, while basic Cell ON/OFF mechanism is more effective to ensure coexist between L AA and WiFi than the SDL.
Abstract: To alleviate the problem of scarce spectrum resources and meet the ever-increasing of mobile broadband data traffic demands, Licensed Assisted Access (LAA)-Long Term Evolution (LTE), operating in the unlicensed spectrum, is a promising solution. Considering that the unlicensed spectrum is shared by a few incumbent systems, such as IEEE 802.11 (i.e., WiFi), one main target is to guarantee the friendly and harmonious coexistence of LTE with other wireless systems in the unlicensed spectrum. Both listen-before-talk (LBT) and duty cycle methods are regarded as effective ways to solve the coexistence problem in academia and industry so far. Although there are a large number of theoretical researches on LTE in unlicensed spectrum (LTE-U), field trail results are still lacking. In this paper, an experimental testing platform is deployed to model the realistic environment. This paper focuses on three aspects. First, a typical indoor field trial scenario in 5.8 GHz unlicensed bands is deployed, and the performance of LTE-U and WiFi, including coverage and capacity, is evaluated. Specifically, a methodology to determine the proper clear channel assessment energy detection (CCA-ED) threshold for LTE-U is proposed to implement the friendly coexistence between LTE-U and WiFi systems. Second, supplementary downlink (SDL) and Cell ON/OFF mechanisms are investigated to verify the fair coexistence between LAA and WiFi in the unlicensed spectrum. Third, the Enhanced Cell ON/OFF scheme, which introduces Clear to Send (CTS)-to-Self (CTS2S) message, is discussed and evaluated. Based on the built testbed, we obtain threefold conclusions. First of all, introducing LTE into unlicensed spectrums can greatly improve the spectrum efficiency and optimize wireless resources. Furthermore, test results and analyses show that a proper CCA-ED threshold is necessary for coexisting friendly and fairly among different systems, and experiments are also provided to validate the feasibility of the suggested method in various scenarios. Second, experimental results show that SDL mechanism guarantees relatively friendly and harmonious coexistence between LAA and WiFi only in the sparse scenario, while basic Cell ON/OFF mechanism is more effective to ensure coexistence between LAA and WiFi than the SDL. Finally, with the introduction of CTS2S message, the Enhanced Cell ON/OFF scheme is able to achieve more peaceful coexistence between LTE and WiFi users employed in the same bands compared with the Basic Cell ON/OFF scheme.
55 citations
Cites background from "Proportional Fairness-Based Resourc..."
...Different coexistence schemes can be classified into LBT based mechanisms [13], [14], [20]–[24] and duty cycle based approaches [25]–[28]....
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...parameters of the medium access control layer and physical layer of an LTE-U network is proposed in [20]....
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16 Apr 2018
TL;DR: LtFi, a system which enables to set-up a cross-technology communication between nodes of co-located LTE-U and WiFi networks, follows a two-step approach: using an innovative side channel on their air-interface LTE- U BSs are broadcasting connection and identification information to adjacent WiFi nodes, which is used in a subsequent step to create a bi-directional control channel over the wired backhaul.
Abstract: LTE in Unlicensed (LTE-U) constitutes a new source of interference in the 5 GHz ISM band with a potentially strong impact on WiFi performance. Cross-technology interference and radio resource management are the best ways to assure efficient coexistence but require proper signaling channels. We present LtFi, a system which enables to set-up a cross-technology communication between nodes of co-located LTE-U and WiFi networks. LtFi follows a two-step approach: using an innovative side channel on their air-interface LTE-U BSs are broadcasting connection and identification information to adjacent WiFi nodes, which is used in a subsequent step to create a bi-directional control channel over the wired backhaul. The simple LtFi is fully compliant with LTE-U and works with COTS WiFi hardware. The achievable data rate on the air-interface based broadcast side channel (up to 665 bps) is sufficient for this and multiple other purposes. Experimental evaluation of a fully operational prototype has demonstrated reliable data transmission even in crowded wireless environments for LTE-U receive power levels down to −92 dBm. Moreover, system-level simulations demonstrate accurate recognition of the complete set of interfering LTE-U BSs in a typical LTE-U multi-cell environment.
47 citations
Cites background from "Proportional Fairness-Based Resourc..."
...Finally, many solutions already envisioned in the literature [14], [15], [16], [17], [18] would directly benefit from our LtFi system....
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References
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TL;DR: In this paper, a simple but nevertheless extremely accurate, analytical model to compute the 802.11 DCF throughput, in the assumption of finite number of terminals and ideal channel conditions, is presented.
Abstract: The IEEE has standardized the 802.11 protocol for wireless local area networks. The primary medium access control (MAC) technique of 802.11 is called the distributed coordination function (DCF). The DCF is a carrier sense multiple access with collision avoidance (CSMA/CA) scheme with binary slotted exponential backoff. This paper provides a simple, but nevertheless extremely accurate, analytical model to compute the 802.11 DCF throughput, in the assumption of finite number of terminals and ideal channel conditions. The proposed analysis applies to both the packet transmission schemes employed by DCF, namely, the basic access and the RTS/CTS access mechanisms. In addition, it also applies to a combination of the two schemes, in which packets longer than a given threshold are transmitted according to the RTS/CTS mechanism. By means of the proposed model, we provide an extensive throughput performance evaluation of both access mechanisms of the 802.11 protocol.
8,072 citations
Posted Content•
TL;DR: A quantitative measure called Indiex of FRairness, applicable to any resource sharing or allocation problem, which is independent of the amount of the resource, and boundedness aids intuitive understanding of the fairness index.
Abstract: Fairness is an important performance criterion in all resource allocation schemes, including those in distributed computer systems However, it is often specified only qualitatively The quantitative measures proposed in the literature are either too specific to a particular application, or suffer from some undesirable characteristics In this paper, we have introduced a quantitative measure called Indiex of FRairness The index is applicable to any resource sharing or allocation problem It is independent of the amount of the resource The fairness index always lies between 0 and 1 This boundedness aids intuitive understanding of the fairness index For example, a distribution algorithm with a fairness of 010 means that it is unfair to 90% of the users Also, the discrimination index can be defined as 1 - fairness index
4,476 citations
01 Jan 1997
TL;DR: This paper addresses the issues of charging, rate control and routing for a communication network carrying elastic traffic, such as an ATM network offering an available bit rate service, from which max-min fairness of rates emerges as a limiting special case.
Abstract: This paper addresses the issues of charging, rate control and routing for a communication network carrying elastic traffic, such as an ATM network offering an available bit rate service. A model is described from which max-min fairness of rates emerges as a limiting special case; more generally, the charges users are prepared to pay influence their allocated rates. In the preferred version of the model, a user chooses the charge per unit time that the user will pay; thereafter the user's rate is determined by the network according to a proportional fairness criterion applied to the rate per unit charge. A system optimum is achieved when users' choices of charges and the network's choice of allocated rates are in equilibrium.
3,067 citations
"Proportional Fairness-Based Resourc..." refers background in this paper
...Taking both efficiency and fairness in the heterogeneous network into account [17], the utility of any device in the unlicensed band is defined as the logarithm function about its throughput in (5) to achieve a proportional fairness-based resource allocation...
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TL;DR: A potential cellular architecture that separates indoor and outdoor scenarios is proposed, and various promising technologies for 5G wireless communication systems, such as massive MIMO, energy-efficient communications, cognitive radio networks, and visible light communications are discussed.
Abstract: The fourth generation wireless communication systems have been deployed or are soon to be deployed in many countries. However, with an explosion of wireless mobile devices and services, there are still some challenges that cannot be accommodated even by 4G, such as the spectrum crisis and high energy consumption. Wireless system designers have been facing the continuously increasing demand for high data rates and mobility required by new wireless applications and therefore have started research on fifth generation wireless systems that are expected to be deployed beyond 2020. In this article, we propose a potential cellular architecture that separates indoor and outdoor scenarios, and discuss various promising technologies for 5G wireless communication systems, such as massive MIMO, energy-efficient communications, cognitive radio networks, and visible light communications. Future challenges facing these potential technologies are also discussed.
2,048 citations
TL;DR: The results show that using adaptive modulation even without any power control provides a significant throughput advantage over using signal-to-interference-plus-noise ratio (SINR) balancing power control and combining adaptive modulation and a suitable power control scheme leads to a significantly higher throughput as compared to no power control or using SINR-balancing power control.
Abstract: Adaptive modulation techniques have the potential to substantially increase the spectrum efficiency and to provide different levels of service to users, both of which are considered important for third-generation cellular systems. In this work, we propose a general framework to quantify the potential gains of such techniques. Specifically, we study the throughput performance gain that may be achieved by combining adaptive modulation and power control. Our results show that: (1) using adaptive modulation even without any power control provides a significant throughput advantage over using signal-to-interference-plus-noise ratio (SINR) balancing power control and (2) combining adaptive modulation and a suitable power control scheme leads to a significantly higher throughput as compared to no power control or using SINR-balancing power control. The first observation is especially important from an implementation point of view. Adjusting the modulation level without changing the transmission power requires far fewer measurements and feedback as compared to the SINR-balancing power control or the optimal power control. Hence, it is significantly easier to implement. Although presented in the context of adaptive modulation, the results also apply to other variable rate transmission techniques, e.g., rate adaptive coding schemes, coded modulation schemes, etc. This work provides valuable insight into the performance of variable rate transmission techniques in multi-user environments.
692 citations
"Proportional Fairness-Based Resourc..." refers background in this paper
...Besides, β is a constant specified in [16] related to a targeted bit-error rate (BER) by...
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