| 1. |
- Carvalho, E. de, et al.
(författare)
-
EU FP7 INFSO-ICT-317669 METIS, D3.1 Positioning of multi-node/multi-antenna technologies
- 2013
-
Rapport (övrigt vetenskapligt/konstnärligt)abstract
- This document describes the research activity in multi-node/multi-antenna technologies within METIS and positions it with respect to the state-of-the-art in the academic literature and in the standardization bodies. Based on the state-of-the-art and as well as on the METIS objectives,we set the research objectives and we group the different activities (or technology components) into research clusters with similar research objectives. The technologycomponents and the research objectives have been set to achieve an ambidextrous purpose. On one side we aim at providing the METIS system with those technological components that are a natural but non-trivial evolution of 4G. On the other side, we aim at seeking for disruptivetechnologies that could radically change 5G with respect to 4G. Moreover, we mapped the different technology components to METIS’ other activities and to the overall goals of theproject.
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| 2. |
- Chen, Xin, 1980, et al.
(författare)
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Optimal and Efficient Power Allocation for OFDM Non-Coherent Cooperative Transmission
- 2012
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Ingår i: IEEE Wireless Communications and Networking Conference, WCNC. - 1525-3511. - 9781467304375 ; , s. 1584-1589
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Konferensbidrag (refereegranskat)abstract
- In this paper, we study the subchannel (SC) power allocation for orthogonal frequency division multiplexing (OFDM) multiple access points (APs) systems with non-coherent cooperative transmission. The objective is to maximize the total capacity under per-AP power constraints. It can be proved that the optimal solution can be obtained by the combination of an optimal SC partition search and the power allocation across SCs for each feasible partition. Existing work exhaustively searched the optimal SC partition and used Lagrange dual method to compute the power allocation across SCs. Since the entire complexity increases exponentially with the number of SCs, the existing method is unsuitable for practical implementation. In this paper, we propose a novel optimal power allocation algorithm for non-coherent cooperative transmission with a much lower complexity. Firstly, a concept of “cut-off SC” is proposed for searching the optimal SC partition. Then, an efficient optimal power allocation algorithm across SCs is proposed for any given cut-off SC. Simulation results demonstrate that the proposed algorithm is optimal with a polynomial complexity, and ends within an acceptable number of iterations.
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| 3. |
- D’Amico, Valeria, et al.
(författare)
-
EU FP7 INFSO-ICT-247223 ARTIST4G, D1.4 Interference Avoidance Techniques and System Design
- 2012
-
Rapport (övrigt vetenskapligt/konstnärligt)abstract
- In this document we provide performance assessments of the most promising techniques that were studied within Work Package 1 (WP1) of the ARTIST4G project related to interference avoidance. The results are based on evolved techniques that were identified and classified in deliverable D1.1 and investigated in deliverable D1.2 and D1.3, as well as novel alternative techniques that are introduced and assessed in this document.Based on the insights from these performance results we provide a synthetic perspective over the most promising solutions for interference avoidance. We argue that these solutions can reach a satisfactory trade-off in terms of performance benefits vs complexity of implementation. Some of these techniques are also identified as complementary techniques towards an integrated interference avoidance concept.
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| 4. |
- Fang, Chao, 1991, et al.
(författare)
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Coordinated Hybrid Precoding for Energy-Efficient Millimeter Wave Systems
- 2018
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Ingår i: IEEE Workshop on Signal Processing Advances in Wireless Communications, SPAWC. ; 2018-June
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Konferensbidrag (refereegranskat)abstract
- Hybrid precoding/combining architectures, which use fewer radio frequency (RF) chains than the number of antennas, have the potential to reduce energy consumption and provide high data rate for millimeter wave systems with large antenna arrays. In this paper, by allowing joint transmissions from multiple base stations (BSs), we jointly optimize over the hybrid precoders and the BSs sleep/active modes such that the total power consumption is minimized with per-user quality-of-service constraints. We present a decoupled hybrid beamforming scheme where the analog precoders are designed based on the equal gain transmission method and the digital precoders are found by solving a convex semidefinite problem. We define realistic models for the hardware power consumption and the channel’s blocking probabilities to compare the performance of our scheme with the fully-digital precoding scheme and to assess the value of BS cooperation. The simulation results show that our proposed method results in almost the same RF transmit power as the fully-digital precoding scheme while saving considerable hardware power due to the reduced number of RF chains and digital-to-analog converters. Moreover, the network densification is shown to further reduce the total power consumption through the optimal cooperative BS active/sleep mode selection.
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| 5. |
- Fang, Chao, 1991, et al.
(författare)
-
Hybrid Precoding in Cooperative Millimeter Wave Networks
- 2021
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Ingår i: IEEE Transactions on Wireless Communications. - 1558-2248 .- 1536-1276. ; 20:8, s. 5373-5388
-
Tidskriftsartikel (refereegranskat)abstract
- In this paper, we study the performance of cooperative millimeter wave (mmWave) networks with hybrid precoding architectures. Considering joint transmissions and BS silence strategy, we propose hybrid precoding algorithms which minimize the sum power consumption of the base stations (BSs), for both fully-and partially-connected hybrid precoding (FHP and PHP, respectively) schemes, for single-carrier and orthogonal frequency-division multiplexing systems. We reformulate the analog precoding part as an equal-gain transmission problem, which only depends on the channel information, and the digital precoding part as a relaxed convex semidefinite program subject to per-user quality-of-service constraints that gives the optimal sum power consumption in terms of the BS silence strategy. In order to reduce the complexity of the hybrid precoding algorithm with optimal BS silence strategy, we propose a sub-optimal hybrid precoding algorithm that iteratively put BSs with small power into the silent mode. The simulation results show that, depending on the parameter settings, the power consumption of the PHP may be dominated by the RF transmit power and it may result in a larger power consumption than the FHP. For the cases with 2 BSs and 4 users, implementation of the FHP and the PHP in cooperative networks reduces the required RF transmit power, compared to the case in a non-cooperative network, by 71% and 56%, respectively.
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| 6. |
- Fantini, R, et al.
(författare)
-
EU FP7 INFSO-ICT-317669 METIS, D3.2 First performance results for multi-node/multi-antenna transmission technologies
- 2014
-
Rapport (övrigt vetenskapligt/konstnärligt)abstract
- This deliverable describes the current results of the multi-node/multi-antenna technologies investigated within METIS and analyses the interactions within and outside Work Package 3. Furthermore, it identifies the most promising technologies based on the current state of obtained results. This document provides a brief overview of the results in its first part. The second part, namely the Appendix, further details the results, describes the simulation alignment efforts conducted in the Work Package and the interaction of the Test Cases. The results described here show that the investigations conducted in Work Package 3 are maturing resulting in valuable innovative solutions for future 5G systems.
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| 7. |
- Hong, Y., et al.
(författare)
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Cross-tier Handover Analyses in Small Cell Networks: A Stochastic Geometry Approach
- 2015
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Ingår i: IEEE International Conference on Communications. - 1550-3607. - 9781467364324 ; 2015-September, s. 3429-3434
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Konferensbidrag (refereegranskat)abstract
- In this paper, we make theoretical analysis on cross-tier handover in Small Cell Networks (SCNs). The cross-tier handover is defined as the handover occurred from a macro cell tier to a small cell tier, or vice versa. Based on stochastic geometry, we first propose a linear approximation approach to study the coverage of small cells. Using the proposed method, we then derive analytical expressions for cross-tier handover rate and sojourn time inside a small cell, which are the key parameters in mobility performance evaluation of an SCN. According to the analysis, we show that the small cell coverage area can be well represented by a biased circle, and the expected value of small cell size is inversely proportional to the square root of the BS density in the macro cell tier. Another important observation is that the handover rate and sojourn time change linearly with the reciprocal of small cell radius. These analytical results could provide fundamental supports for improving mobility management in SCNs.
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| 8. |
- Huang, Binru, et al.
(författare)
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A Utility-Based Joint Resource Allocation Approach for Multi-Service in CoMP Networks
- 2013
-
Ingår i: Wireless Personal Communications. - : Springer Science and Business Media LLC. - 1572-834X .- 0929-6212. ; 72:3, s. 1633-1648
-
Tidskriftsartikel (refereegranskat)abstract
- Coordinated multi-point (CoMP) joint transmission is considered as a key technique to mitigate inter-cell interference and improve the cell-edge performance in 3GPP LTE-Advanced. In this paper, a utility-based joint resource allocation approach is proposed to support CoMP joint transmission in an orthogonal frequency division multiple access (OFDMA) systems. Two different utility functions are considered with diverse quality of service (QoS) provisioning. The objective is to maximize the sum utility of a clustered CoMP network, considering mixed real-time voice over IP (VoIP) and best-effort (BE) traffic patterns. A centralized joint resource allocation algorithm is proposed by decoupling the optimization problem into per-subchannel subproblems. Furthermore, a greedy user selection based low-complexity algorithm is proposed for practical implementation. For the sake of performance comparison, the proportional-fair based joint scheduling, as well as two non-coordinated scheduling schemes are also evaluated. Via system-level simulation we show that the proposed algorithms not only substantially improve the cell-edge spectrum efficiency of BE users, but also significantly decrease the packet drop ratio and call outage ratio of VoIP users.
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| 9. |
- Huang, Binru, et al.
(författare)
-
A Utility-Based Scheduling Approach for Multiple Services in Coordinated Multi-Point Networks
- 2011
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Ingår i: 2011 the 14th International Symposium on Wireless Personal Multimedia Communications: Communications, Networking and Applications for the Internet of Things, WPMC'11. - 9782908849264 ; , s. 1-5
-
Konferensbidrag (refereegranskat)abstract
- Coordinated Multi-Point (CoMP) joint transmission is considered as a key technique to mitigate inter-cell interference (ICI) and improve the cell-edge performance in 3GPP LTE-Advanced. In this paper, a utility-based coordinated transmit scheduling method is proposed to support joint transmission in CoMP systems. The objective is to improve the cell-edge performance in downlink packet-based CoMP networks with mixed real-time voice over IP (VoIP) and best-effort (BE) traffic patterns. Via simulation results we show that compared to the traditional scheduling schemes with neither CoMP joint transmission nor diverse quality of service (QoS) provisioning, the proposed algorithm in this paper improves the cell-edge efficiency of BE users by greater than 45%, while better satisfying the QoS requirements for VoIP users with significant decrease in call outage by greater than 98%.
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| 10. |
- Huang, Binru, et al.
(författare)
-
Joint Scheduling for Multi-Service in Coordinated Multi-Point OFDMA Networks
- 2012
-
Ingår i: IEEE Vehicular Technology Conference. - 1550-2252. - 9781467309905 ; , s. Art. no. 6240135-
-
Konferensbidrag (refereegranskat)abstract
- In this paper, the issues upon user scheduling in the downlink packet transmission for multiple services are addressed for coordinated multi-point (CoMP) OFDMA networks. We consider mixed traffic with voice over IP (VOIP) and best effort (BE) services. In order to improve cell-edge performance and guarantee diverse quality of service (QoS), a utility-based joint scheduling algorithm is proposed, which consists of two steps: ant colony optimization (ACO) based joint user selection and greedy subchannel assignment. We compare the proposed algorithm with the greedy user selection (GUC) based scheme. Via simulation results, we show that 95% of BE users are satsified with average cell-edge data rate greater than 200kbps by using either of the two algorithms. Whereas, our proposed algorithm ensures that more than 95% of VoIP users are satisfied with packet drop ratio less than 2%, compared to 78% by the GUC based algorithm.
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| 11. |
- Kolomvakis, Nikolaos, 1985, et al.
(författare)
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Massive MIMO with IQ Imbalance: Performance analysis and compensation
- 2015
-
Ingår i: IEEE International Conference on Communications. - 1550-3607. - 9781467364324 ; 2015-September, s. 1703-1709
-
Konferensbidrag (refereegranskat)abstract
- In this paper, we consider the uplink of a single-cell massive multiple-input multiple-output (MIMO) system with inphase and quadrature-phase imbalance (IQI). This scenario is of particular importance in massive MIMO systems, where the deployment of lower-cost, lower-quality components is desirable to make massive MIMO a viable technology. Particularly, we investigate the effect of IQI on the performance of massive MIMO employing maximum-ratio combining (MRC) receivers. In order to study how IQI affects channel estimation, we derive a new channel estimator for the IQI-impaired model and show that IQI can substantially downgrade the performance of MRC receivers. Moreover, a low-complexity IQI compensation scheme, suitable for massive MIMO, is proposed which is based on the IQI coefficients' estimation and it is independent of the channel gain. The performance of the proposed compensation scheme is analytically evaluated by deriving a tractable approximation of the ergodic achievable rate and providing the asymptotic power scaling laws assuming transmission over Rayleigh fading channels with log-normal large-scale fading. Finally, we show that massive MIMO effectively suppresses the residual IQI effects, as long as, the compensation scheme is applied.
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| 12. |
- Lakshmana, Tilak Rajesh, 1980, et al.
(författare)
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On the Potential of Broadcast CSI for Opportunistic Coordinated Multi-Point Transmission
- 2012
-
Ingår i: IEEE International Symposium on Personal, Indoor and Mobile Radio Communications, PIMRC. - 9781467325691 ; , s. 1262-1267
-
Konferensbidrag (refereegranskat)abstract
- Coordinated Multi-Point transmission is a promising technique to improve the performance of the users at the cell-edge. To achieve this, in case of a centralized approach, users need to unicast the quantized channel state information (CSI), typically to the anchor base station (BS), and then each BS forwards this information to a central coordination node for precoding and scheduling. In the case of a decentralized approach, users broadcast the quantized CSI such that the coordinating BSs could simultaneously receive the CSI. The advantage of a decentralized approach is that it does not require a central coordination node, thereby not imposing stringent latency constraints on the backhaul. The CSI transmission over the erroneous feedback channel in the uplink gives rise to precoding loss and scheduling loss. In the decentralized framework, the feedback errors could result in BSs receiving a different version of the CSI. In this work, we propose a decentralized opportunistic scheduling approach, which only requires a minimal sharing of scheduling information between BSs. The results show that the sum rate achieved with the proposed method is comparable to that of the centralized approach even when there is a high bit error probability introduced by the feedback channel. We also show that when the bit error probabilities in the feedback channel are less than 10^{-4}, the decentralized approach achieves the sum rate of the centralized approach.
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| 13. |
- Lakshmana, Tilak Rajesh, 1980, et al.
(författare)
-
Partial joint processing for frequency selective channels
- 2010
-
Ingår i: IEEE Vehicular Technology Conference. - 1550-2252. - 9781424435746
-
Konferensbidrag (refereegranskat)abstract
- In this paper, we consider a static cluster of base stations where joint processing is allowed in the downlink. The partial joint processing scheme is a user-centric approach where subclusters or active sets of base stations are dynamically defined for each user in the cluster. In frequency selective channels, the definition of the subclusters or active set thresholding of base stations can be frequency adaptive (per resource block) or non-adaptive (averaged over all the resource blocks). Frequency adaptive thresholding improves the average sum-rate of the cluster, but at the cost of an increased user data interbase information exchange with respect to the non-adaptive frequency thresholding case. On the other hand, the channel state information available at the transmitter side to design the beamforming matrix is very limited and rank deficiency problems arise for low values of active set thresholding and users located close to the base station. To solve this problem, an algorithm is proposed that defines a cooperation area over the cluster where the partial joint processing scheme can be performed, frequency adaptive or non-adaptive, for a given active set threshold value.
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| 14. |
- Lakshmana, Tilak Rajesh, 1980, et al.
(författare)
-
Scheduling for Backhaul Load Reduction in CoMP
- 2013
-
Ingår i: IEEE Wireless Communications and Networking Conference, WCNC. - 1525-3511. - 9781467359399 ; , s. 227-232
-
Konferensbidrag (refereegranskat)abstract
- Coordinated multi-point (CoMP) transmission has received a lot of attention, as a way to improve the system throughput in an interference limited cellular system. For joint processing in CoMP, the user equipments (UEs) need to feed back the channel state information (CSI), typically to their serving base stations (BSs). The BS forwards the CSI to a central coordination node (CCN) for precoding. These precoding weights need to be forwarded from the CCN to the corresponding BSs to serve the UEs. In this work, a feedback load reduction technique is employed via partial joint processing to alleviate the CSI feedback overhead. Similarly, to achieve backhaul load reduction due to the precoding weights, scheduling approaches are proposed. The state of the art block diagonalization solution is compared with our proposed constrained and unconstrained scheduling. Our main contribution is the method of choosing the best subset of the BSs and UEs at the CCN that yields the best sum rate under the constraint of efficient backhaul use. In particular, with constrained scheduling, the choice of a smaller subset proportionally reduces the backhaul load. Simulation results based on a frequency selective WINNER II channel model, show that our proposed constrained scheduling outperforms the block diagonalization approach in terms of the average sum rate per backhaul use.
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| 15. |
- Li, Jingya, 1986, et al.
(författare)
-
A novel frequency reuse scheme for coordinated multi-point transmission.
- 2010
-
Ingår i: IEEE Vehicular Technology Conference Spring, Taipei, Taiwan, May 2010. - 1550-2252. - 9781424425198 ; , s. 1-5
-
Konferensbidrag (refereegranskat)abstract
- Coordinated Multi-Point (CoMP) transmission is considered in 3GPP LTE-Advanced as a key technique to improve the cell-edge performance. In order to support joint resource allocation among coordinate cells in CoMP systems, efficient frequency reuse schemes need to be designed. However, most of the existing frequency reuse schemes are not suitable for CoMP transmission due to not considering multi-cell joint transmission scenario in their frequency reuse rule. To solve this problem, a cooperative frequency reuse (CFR) scheme is proposed in this paper, which divides the cell-edge area of each cell into two types of zones, and defines a frequency reuse rule to support CoMP transmission for users in these zones. Compared with the conventional soft frequency reuse (SFR) scheme, simulation results demonstrate that the CFR scheme reduces the blocking probability by more than 50%, and improves the cell-edge throughput by 30~40%, with 5~9% additional cell-average throughput.
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| 16. |
- Li, Jingya, 1986, et al.
(författare)
-
Downlink Radio Resource Allocation for Coordinated Cellular OFDMA Networks
- 2010
-
Ingår i: IEICE Transactions on Communications. - 1745-1345. ; E93B:12, s. 3480-3488
-
Tidskriftsartikel (refereegranskat)abstract
- Base station coordination is considered as a promising technique to mitigate inter-cell interference and improve the cell-edge performance in cellular orthogonal frequency division multiple-access (OFDMA) networks. The problem to design an efficient radio resource allocation scheme for coordinated cellular OFDMA networks incorporating base station coordination has been only partially investigated. In this contribution, a novel radio resource allocation algorithm with universal frequency reuse is proposed to support base station coordinated transmission. Firstly, with the assumption of global coordination between all base station sectors in the network, a coordinated subchannel assignment algorithm is proposed. Then, by dividing the entire network into a number of disjoint coordinated clusters of base station sectors, a reduced-feedback algorithm for subchannel assignment is proposed for practical use. The utility function based on the user average throughput is used to balance the efficiency and fairness of wireless resource allocation. System level simulation results demonstrate that the reduced-feedback subchannel assignment algorithm significantly improves the cell-edge average throughput and the fairness index of users in the network, with acceptable degradation of cell-average performance.
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| 17. |
- Li, Jingya, 1986
(författare)
-
Downlink Resource Allocation in Cooperative Wireless Networks
- 2015
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Wireless cooperative networks, which is based on exploiting coordination among multiple access nodes, has been considered as a promising approach to improve the spectral efficiency, reduce the energy consumption, and extend the network coverage of future wireless communication systems. In practice, the actual benefit of multi-node cooperation is affected by a variety of factors, including the quality of channel state information (CSI), the constraints on the feedback and backhaul links, hardware impairments, resource allocation and data processing schemes. This thesis investigates the design of resource allocation algorithms and the performance of different coordinated transmission schemes for downlink wireless cooperative systems under practical constraints.First, we consider multi-node cooperation in homogeneous cooperative networks. In [Paper A], a power allocation scheme is proposed for a worst case scenario, where the carrier phases between base stations (BSs) are un-synchronized so that joint transmission must be performed without precoding. We show that in this scenario, joint transmission happens with higher probability when the maximum transmit power is high, or the users are in the overlapped cell-edge area. In practice, the network is divided into clusters of coordinated BSs, and the cooperation gain is limited by the inter-cluster interference. In [Paper B] different fractional frequency reuse schemes are proposed to coordinate inter-cluster interference. Simulation results show that the proposed schemes can efficiently reduce the inter-cluster interference and provide considerable performance improvement in terms of both the cell-edge and cell-average user data rate. [Paper C] compares different coordinated transmission schemes, considering the effects of the feedback and backhaul latency. Compared to zero-forcing coherent joint transmission, we show that non-coherent joint transmission and coordinated scheduling are more robust to channel uncertainly.The second part of the thesis focuses on heterogeneous cooperative networks. In [Paper D], we analyze the performance of amplify-and-forward two-way relaying with in-phase and quadrature-phase imbalance (IQI) at the relay node. Different design guidelines and power allocation schemes are proposed to improve the system reliability under a total transmit power constraint. [Paper E] investigates adaptive power allocation for hybrid automatic repeat request based relay networks. Our results demonstrate that depending on the relay positions and the total power budget, the system should switch between the single-node transmission mode and the joint transmission mode, in order to minimize the outage probability. Finally, [Paper F] studies the joint design of precoding and load balancing for energy-efficient small cell networks with imperfect CSI. An optimal BS association condition is parameterized, which reveals how it is impacted by different system parameters. Our results also show that putting BSs into sleep mode by proper load balancing is an important solution for energy savings in heterogeneous networks.
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| 18. |
- Li, Jingya, 1986, et al.
(författare)
-
Energy Efficiency Analysis of Rank-1 Ricean Fading MIMO Channel
- 2014
-
Ingår i: IEEE Workshop on Signal Processing Advances in Wireless Communications, SPAWC. - 9781479949038 ; 2014-October:October, s. 349-353
-
Konferensbidrag (refereegranskat)abstract
- This paper studies the energy efficiency (EE) of a point-to-point rank-1 Ricean fading multiple-input-multiple-output (MIMO) channel. In particular, a tight lower bound and an asymptotic approximation for the EE of the considered MIMO system are presented, under the assumption that the channel is unknown at the transmitter and perfectly known at the receiver. Moreover, the effects of different system parameters, namely, transmit power, spectral efficiency (SE), and number of transmit and receive antennas, on the EE are analytically investigated. An important observation is that, in the high signal-to-noise ratio regime and with the other system parameters fixed, the optimal transmit power that maximizes the EE increases as the Ricean-K factor increases. On the contrary, the optimal SE and the optimal number of transmit antennas decrease as K increases.
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| 19. |
- Li, Jingya, 1986, et al.
(författare)
-
I/Q Imbalance in AF Dual-Hop Relaying: Performance Analysis in Nakagami-m Fading
- 2014
-
Ingår i: IEEE Transactions on Communications. - 0090-6778 .- 1558-0857. ; 62:3, s. 836-847
-
Tidskriftsartikel (refereegranskat)abstract
- We analyze the performance of amplify-and-forward dual-hop relaying systems in the presence of in-phase and quadrature-phase imbalance (IQI) at the relay node. In particular, an exact analytical expression for and tight lower bounds on the outage probability are derived over independent, non-identically distributed Nakagami-m fading channels. Moreover, tractable upper and lower bounds on the ergodic capacity are presented at arbitrary signal to noise ratios (SNRs). Some special cases of practical interest (e.g., Rayleigh and Nakagami-0.5 fading) are also studied. An asymptotic analysis is performed in the high SNR regime, where we observe that IQI results in a ceiling effect on the signal-to-interference-plus-noise ratio (SINR), which depends only on the level of I/Q impairments, i.e., the joint image rejection ratio. Finally, the optimal I/Q amplitude and phase mismatch parameters are provided for maximizing the SINR ceiling, thus improving the system performance. An interesting observation is that, under a fixed total phase mismatch constraint, it is optimal to have the same level of transmitter (TX) and receiver (RX) phase mismatch at the relay node, while the optimal values for the TX and RX amplitude mismatch should be inversely proportional to each other.
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| 20. |
- Li, Jingya, 1986, et al.
(författare)
-
I/Q Imbalance in Two-Way AF Relaying
- 2014
-
Ingår i: IEEE Transactions on Communications. - 0090-6778 .- 1558-0857. ; 62:7, s. 2271-2285
-
Tidskriftsartikel (refereegranskat)abstract
- We analyze the performance of dual-hop, two-way amplify-and-forward relaying in the presence of in-phase and quadrature-phase imbalance (IQI) at the relay node. In particular, two power allocation schemes, namely, fixed power allocation and instantaneous power allocation, are proposed to improve the system reliability and robustness against IQI under a total transmit power constraint. For each proposed scheme, the outage probability is investigated over independent, non-identically distributed Nakagami-m fading channels, and exact closed-form expressions and bounds are derived. Our theoretical analysis indicates that without IQI compensation, IQI can create fundamental performance limits on two-way relaying. However, these limits can be avoided by performing IQI compensation at source nodes. Compared to the equal power allocation scheme, our numerical results show that the two proposed power allocation schemes can significantly improve the outage performance, thus reducing the IQI effects, especially when the total power budget is large.
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| 21. |
- Li, Jingya, 1986, et al.
(författare)
-
I/Q Imbalance in Two-Way AF Relaying: Performance Analysis and Detection Mode Switch
- 2014
-
Ingår i: Proceedings - IEEE Global Communications Conference, GLOBECOM. - 2334-0983 .- 2576-6813. - 9781479935116 ; , s. 4001-4007
-
Konferensbidrag (refereegranskat)abstract
- This paper studies the impact of in-phase and quadrature-phase imbalance (IQI) in two-way amplify-and-forward (AF) relaying systems. In particular, the effective signal-to-interference-plus-noise ratio (SINR) is derived for each source node, considering four different linear detection schemes, namely, uncompensated (Uncomp) scheme, maximal-ratio-combining (MRC), zero-forcing (ZF) and minimum mean-square error (MMSE) based schemes. For each proposed scheme, the outage probability (OP) is investigated over independent, non-identically distributed Nakagami-m fading channels, and exact closed-form expressions are derived for the first three schemes. Based on the closed-form OP expressions, an adaptive detection mode switching scheme is designed for minimizing the OP of both sources. An important observation is that, regardless of the channel conditions and transmit powers, the ZF-based scheme should always be selected if the target SINR is larger than 3 (4.77 dB), while the MRC-based scheme should be avoided if the target SINR is larger than 0.38 (-4.20 dB).
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| 22. |
- Li, Jingya, 1986, et al.
(författare)
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I/Q Imbalance in Two-Way AF Relaying: Power Allocation and Performance Analysis
- 2014
-
Ingår i: IEEE International Conference on Communications, ICC 2014, Sydney, Australia. - 9781479920037 ; , s. 5042-5048
-
Konferensbidrag (refereegranskat)abstract
- We investigate the performance of dual-hop two-way amplify-and-forward (AF) relaying in the presence of in-phase and quadrature-phase imbalance (IQI) at the relay node. In particular, the effective signal-to-interference-plus-noise ratio (SINR) at both sources is derived. These SINRs are used to design an instantaneous power allocation scheme, which maximizes the minimum SINR of the two sources under a total transmit power constraint. The solution to this optimization problem is analytically determined and used to analytically investigate the outage probability (OP) of the considered two-way AF relaying system. Both analytical and numerical results show that IQI can create fundamental performance limits on relaying systems, which cannot be avoided by simply improving the channel conditions.
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| 23. |
- Li, Jingya, 1986, et al.
(författare)
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Joint Precoding and Load Balancing Optimization for Energy-Efficient Heterogeneous Networks
- 2015
-
Ingår i: IEEE Transactions on Wireless Communications. - : Institute of Electrical and Electronics Engineers (IEEE). - 1558-2248 .- 1536-1276. ; 14:10, s. 5810-5822
-
Tidskriftsartikel (refereegranskat)abstract
- This paper considers a downlink heterogeneous network, where different types of multiantenna base stations (BSs) communicate with a number of single-antenna users. Multiple BSs can serve the users by spatial multiflow transmission techniques. Assuming imperfect channel state information at both BSs and users, the precoding, load balancing, and BS operation mode are jointly optimized for improving the network energy efficiency. We minimize the weighted total power consumption while satisfying quality-of-service constraints at the users. This problem is nonconvex, but we prove that for each BS mode combination, the considered problem has a hidden convexity structure. Thus, the optimal solution is obtained by an exhaustive search over all possible BS mode combinations. Furthermore, by iterative convex approximations of the nonconvex objective function, a heuristic algorithm is proposed to obtain a suboptimal solution of low complexity. We show that although multicell joint transmission is allowed, in most cases, it is optimal for each user to be served by a single BS. The optimal BS association condition is parameterized, which reveals how it is impacted by different system parameters. Simulation results indicate that putting a BS into sleep mode by proper load balancing is an important solution for energy savings.
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| 24. |
- Li, Jingya, 1986, et al.
(författare)
-
Joint Scheduling and Power Control in Coordinated Multi-Point Clusters
- 2011
-
Ingår i: IEEE Vehicular Technology Conference. - 1550-2252. - 9781424483273 ; , s. Art. no. 6092837-
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Konferensbidrag (refereegranskat)abstract
- In this paper, we address the problem of designing a joint scheduling and power control algorithm in a downlink coordinated multi-point (CoMP) cluster supporting CoMP joint transmission. The objective is to maximize the cell-edge throughput under per-point power constraints. By an analytical derivation, binary power control is proved to be the optimal solution for any given selected user group. Utilizing this analytical result, a centralized and a semi-distributed version of joint user selection and power control algorithms are proposed. Compared to algorithms without considering joint transmission and algorithms without considering power control, simulation results show that the proposed algorithms achieve a good trade-off between joint transmission and interference coordination, which helps to improve the cell-edge performance.
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| 25. |
- Li, Jingya, 1986, et al.
(författare)
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Multi-Beam Cooperative Frequency Reuse for Coordinated Multi-Point Systems
- 2010
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Ingår i: Journal of China Universities of Posts and Telecommunications. - 1005-8885. ; 17:6, s. 11-18
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Tidskriftsartikel (refereegranskat)abstract
- Coordinated Multi-Point (CoMP) transmission is considered in 3GPP LTE-Advanced as a key technique to mitigate inter-cell interference and improve the cell-edge performance. To apply CoMP joint transmission effectively, efficient frequency reuse schemes need to be designed to support resource management cooperation among coordinated cells. However, most of the existing frequency reuse schemes are not suitable for CoMP systems due to not considering multi-point cooperative transmission scenario in their frequency reuse rules. In addition, the restrictions of frequency resources in those schemes result in high blockingprobability. To solve the above two problems, a multi-beam cooperative frequency reuse (MBCFR) scheme is proposed in this paper, which reuses all the available frequency resources in each sector and supports multi-beam cooperative transmission for cell-edge users. Besides, the blocking probability is proved to be efficiently reduced. Then, a frequency-segment-sequence based MBCFR scheme is introduced to further reduce the inter-cell interference. System level simulations demonstrate that the proposedscheme results in higher cell-edge average throughput and cell-average throughput with lower blocking probability.
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