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Proceedings ArticleDOI

Heterogeneous networks in LTE-Advanced

Stefan Brueck1
01 Nov 2011-pp 171-175
TL;DR: The need for an alternative deployment model and topology using heterogeneous networks and advanced techniques, which are needed to manage and control interference and deliver the full benefits of such networks are described.
Abstract: 3GPP Long-term Evolution (LTE) allows operators to use new and wider spectrum and complements 3G networks with higher data rates, lower latency and a flat, IP-based architecture. To further improve the broadband user experience in an ubiquitous and cost-effective manner, 3GPP has been working on various aspects of LTE-Advanced. Since radio link performance is quickly approaching theoretical limits with 3G enhancements and LTE, the next performance leap will come from an evolved network topology. This paper discusses the need for an alternative deployment model and topology using heterogeneous networks. The concept of LTE-Advanced based heterogeneous networks is about improving spectral efficiency per unit area. Using a mix of macro, pico, femto and relay cells, heterogeneous networks enable flexible and low-cost deployments and provide a uniform broadband experience. To enhance the performance of these networks, advanced techniques are described, which are needed to manage and control interference and deliver the full benefits of such networks. These techniques include cell range expansion, adaptive inter cell interference coordination and interference cancellation receivers.
Citations
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Journal ArticleDOI
TL;DR: A holistic survey of existing literature on the control-data separation architecture (CDSA) for cellular radio access networks is presented, and limitations of the conventional architecture in futuristic deployment scenarios are pointed out.
Abstract: Conventional cellular systems are designed to ensure ubiquitous coverage with an always present wireless channel irrespective of the spatial and temporal demand of service. This approach raises several problems due to the tight coupling between network and data access points, as well as the paradigm shift towards data-oriented services, heterogeneous deployments and network densification. A logical separation between control and data planes is seen as a promising solution that could overcome these issues, by providing data services under the umbrella of a coverage layer. This article presents a holistic survey of existing literature on the control-data separation architecture (CDSA) for cellular radio access networks. As a starting point, we discuss the fundamentals, concepts, and general structure of the CDSA. Then, we point out limitations of the conventional architecture in futuristic deployment scenarios. In addition, we present and critically discuss the work that has been done to investigate potential benefits of the CDSA, as well as its technical challenges and enabling technologies. Finally, an overview of standardisation proposals related to this research vision is provided.

139 citations


Cites background from "Heterogeneous networks in LTE-Advan..."

  • ...Although transferring the data channel only will incur less overhead and delay as compared with the traditional HO procedures, new signalling mechanisms are required to enable such lightweight HOs [110]....

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  • ...On the other hand, the signalling radio bearers and few DRBs are established at the MCs which manage all the DRBs even though the latter are established at the SC layer....

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  • ...Thus mobility robustness is considered as the main benefit of dual connectivity with control-data separation [110]....

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  • ...As the cell size decreases, mobility management becomes complex because the HOs will happen frequently even for low mobility users....

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  • ...In Cloud-HetNet, all cells (i.e., MCs and SCs) are connected to a Cloud-RAN in a star topology and they act as radio resource heads....

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Journal ArticleDOI
TL;DR: The resource-allocation problems of mobile terminals (MTs) are investigated in a heterogeneous wireless network, where both a visible light communication system and an RF femtocell system are deployed in a room, and a suboptimal decentralized method is proposed for solving it.
Abstract: The resource-allocation (RA) problems of mobile terminals (MTs) are investigated in a heterogeneous wireless network, where both a visible light communication system and an RF femtocell system are deployed in a room. We consider diverse quality-of-service requirements in terms of the data rate, fairness, and statistical delay requirements. Inspired by the concept of effective capacity, we formulate our optimization problems applying $\alpha$ -proportional fairness while satisfying specific statistical delay constraints. Two types of MTs, namely, multihoming MTs and multimode MTs, are considered, where multihoming MTs have the capability of aggregating resources from different networks, whereas the multimode MTs always select a single network for their connection. Our optimization procedure solves the RA probability problem for multihoming MTs with the aid of a decentralized algorithm. By contrast, our optimization problem involves both network selection and RA probability optimization for multimode MTs, which may be regarded as a mixed-integer nonlinear problem. Since this problem is computationally intractable, a suboptimal decentralized method is proposed for solving it. Simulation results are also presented for clarifying the performance of the proposed algorithm. It is shown that the multimode MTs are capable of achieving similar performance to that of the multihoming MTs when the statistical delay requirements are loose. However, as expected, the multihoming MTs attain a better performance when we tighten the delay requirements.

101 citations


Cites background from "Heterogeneous networks in LTE-Advan..."

  • ...A heterogeneous cellular system may consist of regular macro-cell base stations (BS) that typically transmit at a high power level and overlaid pico-cells, femtocells as well as relays, which transmit at substantially lower power levels [4]....

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Journal ArticleDOI
TL;DR: In this paper, a two-level reinforcement learning (RL) approach is proposed for joint interference management and cell association in a multi-agent system, where macro-and picocells learn their optimal cell range expansion bias and transmit power allocation for multi-flow transmissions.
Abstract: In this paper, we focus on inter-cell interference coordination (ICIC) techniques in heterogeneous network (HetNet) deployments, whereby macro- and picocells autonomously optimize their downlink transmissions with loose coordination. We model this strategic coexistence as a multi-agent system, aiming at joint interference management and cell association. Using tools from Reinforcement Learning (RL), agents (i.e., macro- and picocells) sense their environment and self-adapt based on local information to maximize their network performance. Specifically, we explore both time- and frequency domain ICIC scenarios and propose a two-level RL formulation. Here, picocells learn their optimal cell range expansion (CRE) bias and transmit power allocation, as well as appropriate frequency bands for multi-flow transmissions, in which a user equipment (UE) can be simultaneously served by two or more base stations (BSs) from macro- and pico-layers. To substantiate our theoretical findings, Long-Term Evolution Advanced (LTE-A) based system-level simulations are carried out in which our proposed approaches are compared with a number of baseline approaches, such as resource partitioning (RP), static CRE, and single-flow Carrier Aggregation (CA). Our proposed solutions yield substantial gains up to 125% compared to static ICIC approaches in terms of average UE throughput in the time domain. In the frequency domain, our proposed solutions yield gains up to 240% in terms of cell-edge UE throughput.

69 citations

Journal ArticleDOI
TL;DR: This paper focuses on inter-cell interference coordination techniques in heterogeneous network (HetNet) deployments, whereby macro- and picocells autonomously optimize their downlink transmissions with loose coordination, and proposes a two-level RL formulation of ICIC scenarios.
Abstract: In this article, we focus on inter-cell interference coordination (ICIC) techniques in heterogeneous network (Het-Net) deployments, whereby macro- and picocells autonomously optimize their downlink transmissions, with loose coordination. We model this strategic coexistence as a multi-agent system, aiming at joint interference management and cell association. Using tools from Reinforcement Learning (RL), agents (i.e., macro- and picocells) sense their environment, and self-adapt based on local information so as to maximize their network performance. Specifically, we explore both time- and frequency domain ICIC scenarios, and propose a two-level RL formulation. Here, picocells learn their optimal cell range expansion (CRE) bias and transmit power allocation, as well as appropriate frequency bands for multi-flow transmissions, in which a user equipment (UE) can be simultaneously served by two or more base stations (BSs) from macro- and pico-layers. To substantiate our theoretical findings, Long Term Evolution Advanced (LTEA) based system level simulations are carried out in which our proposed approaches are compared with a number of baseline approaches, such as resource partitioning (RP), static CRE, and single-flow Carrier Aggregation (CA). Our proposed solutions yield substantial gains up to 125% compared to static ICIC approaches in terms of average UE throughput in the timedomain. In the frequency-domain our proposed solutions yield gains up to 240% in terms of cell-edge UE throughput.

66 citations


Cites background from "Heterogeneous networks in LTE-Advan..."

  • ...As a result, the macrocell will be overloaded whereas picocells will be under-utilized [6]–[8]....

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Posted Content
TL;DR: It is argued that the widely perceived health risks that are attributed to 5G are not supported by scientific evidence from communications engineering, and how the solutions to minimize the health risks are already mature and ready to be implemented.
Abstract: The deployment of 5G wireless communication services requires the installation of 5G next-generation Node-B Base Stations (gNBs) over the territory and the wide adoption of 5G User Equipment (UE). In this context, the population is concerned about the potential health risks associated with the Radio Frequency (RF) emissions from 5G equipment, with several communities actively working toward stopping the 5G deployment. To face these concerns, in this work, we analyze the health risks associated with 5G exposure by adopting a new and comprehensive viewpoint, based on the communications engineering perspective. By exploiting our background, we debunk the alleged health effects of 5G exposure and critically review the latest works that are often referenced to support the health concerns from 5G. We then precisely examine the up-to-date metrics, regulations, and assessment of compliance procedures for 5G exposure, by evaluating the latest guidelines from IEEE, ICNIRP, ITU, IEC, and FCC, as well as the national regulations in more than 220 countries. We also thoroughly analyze the main health risks that are frequently associated with specific 5G features (e.g., MIMO, beamforming, cell densification, adoption of millimeter waves, and connection of millions of devices). Finally, we examine the risk mitigation techniques based on communications engineering that can be implemented to reduce the exposure from 5G gNB and UE. Overall, we argue that the widely perceived health risks that are attributed to 5G are not supported by scientific evidence from communications engineering. In addition, we explain how the solutions to minimize the health risks from 5G are already mature and ready to be implemented. Finally, future works, e.g., aimed at evaluating long-term impacts of 5G exposure, as well as innovative solutions to further reduce the RF emissions, are suggested.

42 citations

References
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Proceedings ArticleDOI
05 Jun 2011
TL;DR: System simulations results for an FTP traffic model indicate that, for a pico cell deployment with density of 4 picos per macro cell, 40% or more performance gain can be achieved when techniques enabling cell range expansion are deployed.
Abstract: This paper discusses the need and enabling mechanisms for a heterogeneous deployment model in LTE networks, where lower power nodes are deployed in a macro network. Cell range expansion, enabled through cell biasing and adaptive resource partitioning, is seen as an effective method to balance the load among the nodes in the network and to improve overall trunking efficiency. Interference cancellation receiver plays a crucial role to ensure acquisition of weak cells and reliability of control and data reception in the presence of legacy signal. System simulations results for an FTP traffic model indicate that, for a pico cell deployment with density of 4 picos per macro cell, 40% or more performance gain can be achieved when techniques enabling cell range expansion are deployed.

68 citations


"Heterogeneous networks in LTE-Advan..." refers background in this paper

  • ...Figure 6: X2 backhaul based inter for macro/pic tion is included in 3GPP LTE erference Coordination, eICIC) for time domain resource in [5] for pico cells and [6] for PP LTE the granularity of the es is one subframe, i....

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Proceedings ArticleDOI
01 Nov 2011
TL;DR: This work presents a general CoMP technique based on coordinated beam selection and applies this technique in a heterogeneous wireless network where a hexagonal layout of macro base stations is overlaid with clusters of femto cells with closed subscriber group functionality.
Abstract: Coordinated Multipoint (CoMP) techniques and heterogeneous wireless networks are two enablers to achieve improvements in data rate both for average as well as cell-edge users. We present a general CoMP technique based on coordinated beam selection and apply this technique in a heterogeneous wireless network where a hexagonal layout of macro base stations is overlaid with clusters of femto cells with closed subscriber group functionality. Without coordination, this scenario can be extremely challenging to mobile users that are located in the vicinity of the femto cells but are not allowed to connect to them. We show that the proposed CoMP technique leads to significant improvements for these users.

18 citations