LTE-advanced: next-generation wireless broadband technology [Invited Paper]
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.
Citations
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TL;DR: A survey of different tradeoff mechanisms proposed in the literature for EE tradeoffs based on each protocol layer and its affect in the network energy efficiency is provided.
Abstract: Energy efficient (EE) communication has earned tremendous interest in recent years due to ever increasing number of wireless devices operating in shrinking cells, while demanding high data rates with high Quality of Services (QoS) and Quality of Expectation (QoE). To support these objectives, energy is consumed in every protocol layer. Establishing and maintaining a successful wireless communication link to simultaneously achieve all these objectives becomes challenging since the energy consumption requirements of the user and network are different for different objectives. Thus, there is a need for tradeoff techniques to achieve energy efficiency in each protocol layer. In this paper, we provide a survey of different tradeoff mechanisms proposed in the literature. The EE tradeoffs have been classified based on each protocol layer and discussed its affect in the network energy efficiency. These other QoS parameters include spectral efficiency, deployment, delay, routing, scheduling, bandwidth and coding etc. This survey also discusses the various EE techniques to improve energy-efficiency in infrastructure mode. Finally, the work provides an discussion, where impact of EE tradeoffs have been presented based on different wireless architecture towards realizing a green wireless communication network.
183 citations
TL;DR: A device-to-device communication-based algorithm to enhance the QoE of users in software defined multi-tier LTE-A networks and numerical results are presented to illustrate the performance gains that can be achieved by applying the proposed algorithm to a typical 3GPP network scenario.
Abstract: 3GPP has been developing LTE-A standard to significantly enhance the performance of cellular networks by utilizing various radio access techniques to provide ubiquitous and seamless broadband access to a rich diversity of mobile connected devices, which usually demand high QoE in spite of of access location or time. Consequently, it imposes unprecedented stringent requirements on centralized network management at the operator side, which has to overcome formidable complexity in designing, managing, and configuring network architectures, protocols, and algorithms before being able to fully support all LTE-A techniques. It is noticed that the software defined wireless network concept appears to be a promising direction to address such complexity, by decoupling control logic from all network elements and then providing fine-grained control and measurement in LTE-A networks. Toward this end, we propose in this article a device-to-device communication-based algorithm to enhance the QoE of users in software defined multi-tier LTE-A networks. Besides discussing research issues that deserve further study, we also present numerical results to illustrate the performance gains that can be achieved by applying the proposed algorithm to a typical 3GPP network scenario.
177 citations
01 Jan 2011
TL;DR: In this article, a two-tier heterogeneous network with random deployment for femtocells and the absence of macro-femto backhaul coordination is considered, and interference cancellation via novel decoding techniques is proposed.
Abstract: To successfully deploy femtocells underlaying the macrocell as a heterogeneous network, which has been proven to greatly improve indoor coverage and system capacity, the cross-tier interference among the macrocell and femtocells as well as the intratier interference among femtocells must be mitigated. However, some unique features present a challenge in interference mitigation in a two-tier heterogeneous network such as random deployment for femtocells, nonexistence of macro-femto backhaul coordination, and mandates allowing no modifications of existing macrocells. Carefully examining the existing distributed information acquisition mechanisms, cognitive radio is the most promising solution for two-tier heterogeneous networks. We therefore study possible interference mitigation approaches, including orthogonal radio resource assignment in the time-frequency and antenna spatial domains, as well as interference cancellation via novel decoding techniques. According to the information acquired by cognitive radio technology, recent innovations such as game theory and the Gibbs sampler have been explored to mitigate both cross-tier and intratier interferences. Performance evaluations show that considerable performance improvement can be generally achieved, and thus demonstrate the potential of applying cognitive radio in mitigating interference.
170 citations
TL;DR: In this article, a double-layer mushroom structure is proposed to enhance the interelement isolation of a four-element antenna system, wherein four closely positioned substrate-integrated cavity-backed slot (SICBS) antenna elements are configured for multiple-input multiple-output (MIMO) applications.
Abstract: A double-layer mushroom structure is proposed to enhance the interelement isolation of a four-element antenna system, wherein four closely positioned substrate-integrated cavity-backed slot (SICBS) antenna elements are configured for multiple-input multiple-output (MIMO) applications. A wall with a double-layer mushroom structure is positioned in between the four antenna elements. An antenna prototype with a ground plane size of ${\mathbf{0}}.{\mathbf{96}}\;{{\mathbf{\lambda }}_{\mathbf{0}}} \times 0.96\;{{\mathbf{\lambda }}_{\mathbf{0}}}$ ( ${{\mathbf{\lambda }}_{\mathbf{0}}}$ is the free space-wavelength at 2.4 GHz) demonstrates an enhanced interelement isolation of 16 dB for parallel-directed antenna element pairs, while the isolation of the orthogonally directed antenna element pairs remains unchanged over the operating bandwidth ( $\vert {{\mathbf{S}}_{{\mathbf{11}}}}\vert ) of 2.396 –2.45 GHz. With the enhanced isolation larger than 42 dB between each antenna element pair, the envelope correlation coefficient (ECC) is lower than 0.02 across the operating bandwidth. The simulated and measured results validate the good MIMO diversity performance of the proposed antenna system.
167 citations
Additional excerpts
...W ITH further requirements of larger channel capacity in wireless communication systems, multiple-input multiple-output (MIMO) technology has been integrated into the fourth-generation long-term evolution (4G LTE) standard to overcome the shadowing and fading phenomena in multipath environments [1]....
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TL;DR: Although this paper focuses on 3GPP LTE/LTE-A mobile networks in the downlink, a similar framework can be applied for any typical multi-cellular environment based on OFDMA technology.
Abstract: The widely accepted OFDMA air interface technology has recently been adopted in most mobile standards by the wireless industry. However, similar to other frequency-time multiplexed systems, their performance is limited by inter-cell interference. To address this performance degradation, interference mitigation can be employed to maximize the potential capacity of such interference-limited systems. This paper surveys key issues in mitigating interference and gives an overview of the recent developments of a promising mitigation technique, namely, interference avoidance through inter-cell interference coordination (ICIC). By using optimization theory, an ICIC problem is formulated in a multi-cell OFDMA-based system and some research directions in simplifying the problem and associated challenges are given. Furthermore, we present the main trends of interference avoidance techniques that can be incorporated in the main ICIC formulation. Although this paper focuses on 3GPP LTE/LTE-A mobile networks in the downlink, a similar framework can be applied for any typical multi-cellular environment based on OFDMA technology. Some promising future directions are identified and, finally, the state-of-the-art interference avoidance techniques are compared under LTE-system parameters.
166 citations
Cites background from "LTE-advanced: next-generation wirel..."
...The latter scenario can be aggregated either in a single band or over multiple bands [119]....
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References
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01 Sep 2006
TL;DR: A preliminary look at the air interface for Evolved UTRA (E-UTRA) and associated key technologies required to reach its design objectives are provided.
Abstract: With the emergence of packet-based wireless broadband systems such as 802.16e, it is evident that a comprehensive evolution of the universal mobile telecommunications system specifications is required to remain competitive. As a result, work has begun on long term evolution (LTE) of the UMTS terrestrial radio access and radio access network aimed for commercial deployment in 2010. Goals for the evolved system include support for improved system capacity and coverage, high peak data rates, low latency, reduced operating costs, multi-antenna support, flexible bandwidth operations and seamless integration with existing systems. To reach these goals, a new design for the air interface is envisioned. This paper provides a preliminary look at the air interface for Evolved UTRA (E-UTRA) and associated key technologies required to reach its design objectives. Initial E-UTRA system performance results show a 2 to 3x improvement over a reference Rel-6 UMTS system configuration [1, 2] for both uplink and downlink.
30 citations
24 Oct 2008
TL;DR: The proposed channel estimation technique is shown to have significant gains in performance compared to other well known channel estimation techniques such as the maximum-likelihood (ML) and the inverse fast Fourier transform (IFFT) channel estimation methods.
Abstract: The performance of the uplink physical channel of the 3GPP LTE system is considered in this paper. Assuming a single user spatial division multiple access transmission scheme, where users' signals are transmitted over different subcarriers, a low complexity channel estimation technique is proposed for the physical uplink shared channel (PUSCH). The proposed channel estimation technique is shown to have significant gains in performance compared to other well known channel estimation techniques such as the maximum-likelihood (ML) and the inverse fast Fourier transform (IFFT) channel estimation methods [5]. Simulation results for different channel models and modulation and coding schemes (MCS) using incremental redundancy (IR) based hybrid automatic repeat request (HARQ) operation are also shown. Finally, a robust detection scheme is proposed for the physical uplink control channel (PUCCH) and simulation results are summarized.
10 citations
"LTE-advanced: next-generation wirel..." refers methods in this paper
...The DFT precoding operation is performed to reduce the cubic metric (CM) of the signal, leading to higher maximum transmit power [2]....
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