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Journal ArticleDOI

Potentials and Challenges of C-RAN Supporting Multi-RATs Toward 5G Mobile Networks

01 Oct 2014-IEEE Access (IEEE)-Vol. 2, pp 1187-1195
TL;DR: An overview of the cloud radio access network (C-RAN), which is a key enabler for future mobile networks in order to meet the explosive capacity demand of mobile traffic, and reduce the capital and operating expenditure burden faced by operators, is presented.
Abstract: This paper presents an overview of the cloud radio access network (C-RAN), which is a key enabler for future mobile networks in order to meet the explosive capacity demand of mobile traffic, and reduce the capital and operating expenditure burden faced by operators. We start by reviewing the requirements of future mobile networks, called 5G, followed by a discussion on emerging network concepts for 5G network architecture. Then, an overview of C-RAN and related works are presented. As a significant scenario of a 5G system, the ultra dense network deployment based on C-RAN is discussed with focuses on flexible backhauling, automated network organization, and advanced mobility management. Another import feature of a 5G system is the long-term coexistence of multiple radio access technologies (multi-RATs). Therefore, we present some directions and preliminary thoughts for future C-RAN-supporting Multi-RATs, including joint resource allocation, mobility management, as well as traffic steering and service mapping.
Citations
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Journal ArticleDOI
TL;DR: In this article, the authors survey the state-of-the-art in NFV and identify promising research directions in this area, and also overview key NFV projects, standardization efforts, early implementations, use cases, and commercial products.
Abstract: Network function virtualization (NFV) has drawn significant attention from both industry and academia as an important shift in telecommunication service provisioning. By decoupling network functions (NFs) from the physical devices on which they run, NFV has the potential to lead to significant reductions in operating expenses (OPEX) and capital expenses (CAPEX) and facilitate the deployment of new services with increased agility and faster time-to-value. The NFV paradigm is still in its infancy and there is a large spectrum of opportunities for the research community to develop new architectures, systems and applications, and to evaluate alternatives and trade-offs in developing technologies for its successful deployment. In this paper, after discussing NFV and its relationship with complementary fields of software defined networking (SDN) and cloud computing, we survey the state-of-the-art in NFV, and identify promising research directions in this area. We also overview key NFV projects, standardization efforts, early implementations, use cases, and commercial products.

1,634 citations

Journal ArticleDOI
TL;DR: In this article, the authors investigate and discuss serious limitations of the fourth generation (4G) cellular networks and corresponding new features of 5G networks, and present a comparative study of the proposed architectures that can be categorized on the basis of energy-efficiency, network hierarchy, and network types.

363 citations

Journal ArticleDOI
TL;DR: This paper provides a comprehensive overview on the extensive on-going research efforts and categorize them based on the fundamental green tradeoffs and focuses on research progresses of 4G and 5G communications, such as orthogonal frequency division multiplexing and non-orthogonal aggregation, multiple input multiple output, and heterogeneous networks.
Abstract: With years of tremendous traffic and energy consumption growth, green radio has been valued not only for theoretical research interests but also for the operational expenditure reduction and the sustainable development of wireless communications. Fundamental green tradeoffs, served as an important framework for analysis, include four basic relationships: 1) spectrum efficiency versus energy efficiency; 2) deployment efficiency versus energy efficiency; 3) delay versus power; and 4) bandwidth versus power. In this paper, we first provide a comprehensive overview on the extensive on-going research efforts and categorize them based on the fundamental green tradeoffs. We will then focus on research progresses of 4G and 5G communications, such as orthogonal frequency division multiplexing and non-orthogonal aggregation, multiple input multiple output, and heterogeneous networks. We will also discuss potential challenges and impacts of fundamental green tradeoffs, to shed some light on the energy efficient research and design for future wireless networks.

298 citations


Cites background or methods from "Potentials and Challenges of C-RAN ..."

  • ...An economic and energy efficient approach is to distribute the computational tasks over the heterogeneous UDN nodes with different computational capabilities [180]....

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  • ...In [179], the detailed delay requirement and potential issues for front-haul processing in LTE advanced HetNet have been analyzed and a joint design of baseband unit processing and front-haul transmission for a UDN has been proposed in [180]....

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Posted Content
TL;DR: In this article, the authors investigate and discuss serious limitations of the fourth generation (4G) cellular networks and corresponding new features of 5G networks, and present a comparative study of the proposed architectures that can be categorized on the basis of energy-efficiency, network hierarchy, and network types.
Abstract: The rapidly increasing number of mobile devices, voluminous data, and higher data rate are pushing to rethink the current generation of the cellular mobile communication The next or fifth generation (5G) cellular networks are expected to meet high-end requirements The 5G networks are broadly characterized by three unique features: ubiquitous connectivity, extremely low latency, and very high-speed data transfer The 5G networks would provide novel architectures and technologies beyond state-of-the-art architectures and technologies In this paper, our intent is to find an answer to the question: "what will be done by 5G and how?" We investigate and discuss serious limitations of the fourth generation (4G) cellular networks and corresponding new features of 5G networks We identify challenges in 5G networks, new technologies for 5G networks, and present a comparative study of the proposed architectures that can be categorized on the basis of energy-efficiency, network hierarchy, and network types Interestingly, the implementation issues, eg, interference, QoS, handoff, security-privacy, channel access, and load balancing, hugely effect the realization of 5G networks Furthermore, our illustrations highlight the feasibility of these models through an evaluation of existing real-experiments and testbeds

295 citations

Journal ArticleDOI
TL;DR: This paper studies the deployment of D2D communications as an underlay to long-term evolution-advanced (LTE-A) networks based on novel architectures such as cloud radio access network (C-RAN).
Abstract: Device-to-device (D2D) communication is a key enabler to facilitate the realization of the Internet of Things (IoT). In this paper, we study the deployment of D2D communications as an underlay to long-term evolution-advanced (LTE-A) networks based on novel architectures such as cloud radio access network (C-RAN). The challenge is that both energy efficiency (EE) and quality of service (QoS) are severely degraded by the strong intracell and intercell interference due to dense deployment and spectrum reuse. To tackle this problem, we propose an energy-efficient resource allocation algorithm through joint channel selection and power allocation design. The proposed algorithm has a hybrid structure that exploits the hybrid architecture of C-RAN: distributed remote radio heads (RRHs) and centralized baseband unit (BBU) pool. The distributed resource allocation problem is modeled as a noncooperative game, and each player optimizes its EE individually with the aid of distributed RRHs. We transform the nonconvex optimization problem into a convex one by applying constraint relaxation and nonlinear fractional programming. We propose a centralized interference mitigation algorithm to improve the QoS performance. The centralized algorithm consists of an interference cancellation technique and a transmission power constraint optimization technique, both of which are carried out in the centralized BBU pool. The achievable performance of the proposed algorithm is analyzed through simulations, and the implementation issues and complexity analysis are discussed in detail.

243 citations


Cites background from "Potentials and Challenges of C-RAN ..."

  • ...…Communications Underlaying Cloud-RAN-Based LTE-A Networks Zhenyu Zhou, Member, IEEE, Mianxiong Dong, Member, IEEE, Kaoru Ota, Member, IEEE, Guojun Wang, Member, IEEE, and Laurence T. Yang, Member, IEEE Abstract—Device-to-device (D2D) communication is a key enabler to facilitate the realization…...

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  • ...The game G can be described as the triplet G = [{S}, {A}, {U}], wherein S = {S1,S2, . . . ,SM} is the set of active UEs participating in the game, A = {A1,A2, . . . ,AM} is the set of possible actions (strategies) that UEs can take, and U = {U1,U2, . . . ,UM} is the set of UEs’ utilities....

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  • ...Energy-Efficient Resource Allocation for D2D Communications Underlaying Cloud-RAN-Based LTE-A Networks Zhenyu Zhou, Member, IEEE, Mianxiong Dong, Member, IEEE, Kaoru Ota, Member, IEEE, Guojun Wang, Member, IEEE, and Laurence T. Yang, Member, IEEE Abstract—Device-to-device (D2D) communication is a key enabler to facilitate the realization of the Internet of Things (IoT)....

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References
More filters
Journal ArticleDOI
05 Feb 2014
TL;DR: Measurements and capacity studies are surveyed to assess mmW technology with a focus on small cell deployments in urban environments and it is shown that mmW systems can offer more than an order of magnitude increase in capacity over current state-of-the-art 4G cellular networks at current cell densities.
Abstract: Millimeter-wave (mmW) frequencies between 30 and 300 GHz are a new frontier for cellular communication that offers the promise of orders of magnitude greater bandwidths combined with further gains via beamforming and spatial multiplexing from multielement antenna arrays. This paper surveys measurements and capacity studies to assess this technology with a focus on small cell deployments in urban environments. The conclusions are extremely encouraging; measurements in New York City at 28 and 73 GHz demonstrate that, even in an urban canyon environment, significant non-line-of-sight (NLOS) outdoor, street-level coverage is possible up to approximately 200 m from a potential low-power microcell or picocell base station. In addition, based on statistical channel models from these measurements, it is shown that mmW systems can offer more than an order of magnitude increase in capacity over current state-of-the-art 4G cellular networks at current cell densities. Cellular systems, however, will need to be significantly redesigned to fully achieve these gains. Specifically, the requirement of highly directional and adaptive transmissions, directional isolation between links, and significant possibilities of outage have strong implications on multiple access, channel structure, synchronization, and receiver design. To address these challenges, the paper discusses how various technologies including adaptive beamforming, multihop relaying, heterogeneous network architectures, and carrier aggregation can be leveraged in the mmW context.

2,452 citations


"Potentials and Challenges of C-RAN ..." refers background in this paper

  • ...addressed again due to the advances in circuit technologies, with which wide bandwidth (up to several GHz) can be provided, enabling multi-Gbps data rate [31]....

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Journal ArticleDOI
TL;DR: It is estimated that the main driver of capacity growth is expected to come from network architecture advancements, with heterogeneous networks and convergence of information and communication technology being two of the key techniques.
Abstract: It has been projected that, in the next decade, a mobile traffic increase on the order of 1,000 times is expected compared to what we experience today. To meet that dramatic traffic growth, next-generation mobile networks are also expected to achieve a 1,000-fold capacity increase compared to the current generation of wireless network deployments. In this article, we discuss how such capacity growth could be achieved in a ten-year time frame. We discuss the techniques that we expect to have the highest opportunity for increasing the system capacity and estimate their gains based on analysis and simulation. We observe that the main driver of capacity growth is expected to come from network architecture advancements, with heterogeneous networks and convergence of information and communication technology being two of the key techniques. We also estimate that the air-interface evolution would focus not only on improving the link and system spectrum efficiency but also on facilitating the required network efficiency improvements. This article provides insights into the communication technology evolution and can be used as a guideline for technology development toward the fifth generation (5G).

556 citations


"Potentials and Challenges of C-RAN ..." refers methods in this paper

  • ...In previous work [41], WLAN/LTE interworking is taken as an example to estimate the gains by multi-RAT joint operation....

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Journal ArticleDOI
TL;DR: A holistic view on hyperdense HetSNets is presented, which include fundamental preference in future wireless systems, and technical challenges and recent technological breakthroughs made in such networks.
Abstract: The wireless industry has been experiencing an explosion of data traffic usage in recent years and is now facing an even bigger challenge, an astounding 1000-fold data traffic increase in a decade. The required traffic increase is in bits per second per square kilometer, which is equivalent to bits per second per Hertz per cell × Hertz × cell per square kilometer. The innovations through higher utilization of the spectrum (bits per second per Hertz per cell) and utilization of more bandwidth (Hertz) are quite limited: spectral efficiency of a point-to-point link is very close to the theoretical limits, and utilization of more bandwidth is a very costly solution in general. Hyper-dense deployment of heterogeneous and small cell networks (HetSNets) that increase cells per square kilometer by deploying more cells in a given area is a very promising technique as it would provide a huge capacity gain by bringing small base stations closer to mobile devices. This article presents a holistic view on hyperdense HetSNets, which include fundamental preference in future wireless systems, and technical challenges and recent technological breakthroughs made in such networks. Advancements in modeling and analysis tools for hyper-dense HetSNets are also introduced with some additional interference mitigation and higher spectrum utilization techniques. This article ends with a promising view on the hyper-dense HetSNets to meet the upcoming 1000× data challenge.

527 citations

Journal ArticleDOI
TL;DR: The design principles are provided and ongoing discussions on small cell enhancements in LTE Release 12 are introduced, and views from two active operators in this area are provided, CMCC and NTT DOCOMO.
Abstract: 3GPP LTE, or Long Term Evolution, the fourth generation wireless access technology, is being rolled out by many operators worldwide. Since LTE Release 10, network densification using small cells has been an important evolution direction in 3GPP to provide the necessary means to accommodate the anticipated huge traffic growth, especially for hotspot areas. Recently, LTE Release 12 has been started with more focus on small cell enhancements. This article provides the design principles and introduces the ongoing discussions on small cell enhancements in LTE Release 12, and provides views from two active operators in this area, CMCC and NTT DOCOMO.

498 citations

Proceedings ArticleDOI
10 Jun 2012
TL;DR: This work presents urban cellular and peer-to-peer RF wideband channel measurements using a broadband sliding correlator channel sounder and steerable antennas at carrier frequencies of 38 GHz and 60 GHz, and presents measurements showing the propagation time delay spread and path loss as a function of separation distance and antenna pointing angles for many types of real-world environments.
Abstract: As the cost of massively broadband® semiconductors continue to be driven down at millimeter wave (mm-wave) frequencies, there is great potential to use LMDS spectrum (in the 28–38 GHz bands) and the 60 GHz band for cellular/mobile and peer-to-peer wireless networks. This work presents urban cellular and peer-to-peer RF wideband channel measurements using a broadband sliding correlator channel sounder and steerable antennas at carrier frequencies of 38 GHz and 60 GHz, and presents measurements showing the propagation time delay spread and path loss as a function of separation distance and antenna pointing angles for many types of real-world environments. The data presented here show that at 38 GHz, unobstructed Line of Site (LOS) channels obey free space propagation path loss while non-LOS (NLOS) channels have large multipath delay spreads and can exploit many different pointing angles to provide propagation links. At 60 GHz, there is notably more path loss, smaller delay spreads, and fewer unique antenna angles for creating a link. For both 38 GHz and 60 GHz, we demonstrate empirical relationships between the RMS delay spread and antenna pointing angles, and observe that excess path loss (above free space) has an inverse relationship with transmitter-to-receiver separation distance.

409 citations


"Potentials and Challenges of C-RAN ..." refers background in this paper

  • ...from a potential low-power microcell or picocell base station with electrically steerable antennas, closing the gap between wireless and fiber backhaul [32]–[34]....

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