Yongyu Chang’s research while affiliated with Beijing University of Posts and Telecommunications and other places

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Publications (114)


Distributed Resource Allocation with Inter-Cell Interference Coordination in OFDMA Uplink
  • Conference Paper

September 2012

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20 Reads

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1 Citation

Vehicular Technology Conference, 1988, IEEE 38th

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Yongyu Chang

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Guangde Wang

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Dacheng Yang

In this paper, we propose a distributed resource allocation mechanism with inter-cell interference (ICI) coordination for practical orthogonal frequency division multiple access (OFDMA) uplink. The designed scheme combines soft frequency reuse (SFR) and interference limited power control of neighboring cells. It avoids severe interference to neighboring cells through adjusting the interference limited power constraints according to the load variations across cells. The computational complexity is greatly lowered by decomposing a multi-cell optimization problem into distributed single-cell sub-problems. The simulation results demonstrate that the proposed scheme not only guarantees the cell-edge UEs' quality of service (QoS) but also improves the overall system performance significantly. Moreover, this scheme can adapt to the load variations in a certain cell or across cells.


An Efficient Inter-Cell Interference Coordination Scheme in Heterogeneous Cellular Networks

September 2012

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13 Reads

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6 Citations

Vehicular Technology Conference, 1988, IEEE 38th

As a mainstream technology in the 4G TDD (Time Division Duplex) systems, TD-LTE (Long Term Evolution) introduces heterogeneous network topology, utilizing a diverse set of base stations, to improve spectral efficiency per unit area. In heterogeneous network deployment comprised of macrocell and picocell, inter-cell interference coordination (ICIC) is very important to significantly improve the system and cell-edge throughput. Moreover, variety of complex situation of inter-cell interference (ICI) occurs in heterogeneous TDD LTE cellular networks due to different downlink/uplink (DL/UL) sub-frame configurations of macrocell and picocell. Therefore, this paper proposes an efficient ICIC scheme consisting of four sub-schemes according to relevant interference scenarios based on different sub-frame configurations. The scheme first analyzes interference level and finds out strong interference for each scenario. The basic idea of ICIC is that only primary interfering sources of each scenario avoid using the same frequency resource occupied by interfered victim, and other interfering sources can reuse frequency resource. Numerical results show that our proposed ICIC scheme can not only improve performance of whole region including macrocell area and picocell area, but also significantly achieve higher throughput for cell edge users.


Outage Probability of Joint Relay Selection and Power Allocation for Two-Way Relay Networks over Rayleigh Fading Channels

May 2012

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21 Reads

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6 Citations

This paper investigates the outage probability of joint relay selection and power allocation for two- way relay networks over Rayleigh Fading channels. Firstly, a tight lower bound of outage probability with equal power allocation is derived. Furthermore, a joint relay selection and optimum power allocation scheme is proposed, which minimizes the outage probability, then, a lower bound of outage probability is also obtained. Based-on the closed-form outage probabilities, we obtain a relay selection strategy, which requires only a single integer parameter to be broadcasted to all relays. The analysis is verified by using Monte-Carlo simulations.


Efficient Low Complexity Turbo Equalization with Soft Interference Cancellation in MIMO System

May 2012

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11 Reads

An efficient frequency domain soft interference cancellation (FD-SIC) scheme is proposed for turbo frequency domain equalization (FDE) in multiple-input multiple-output (MIMO) system. It is designed that at the receiver the inter-antenna interference (IAI) is cancelled by prior information in terms of data expectation. It can improve the input signal to interference and noise ratio (SINR) for the equalizer. Then block (data of one transmit antenna) wise frequency domain minimum mean square error (MMSE) equalization is implemented. Later a low complexity algorithm on the basis of single frequency tone (SFT) is deduced. Symbol Log-likelihood ratio (LLR) is calculated from the output of equalizer. Simulation results show that the proposed scheme has better link performance than traditional algorithms.


Distributed Resource Allocation in Two-Hierarchy Networks

April 2012

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14 Reads

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8 Citations

Etri Journal

In this paper, a new distributed resource allocation algorithm is proposed to alleviate the cross-tier interference for orthogonal frequency division multiplexing access macrocell and femtocell overlay. Specifically, the resource allocation problem is modeled as a non-cooperative game. Based on game theory, we propose an iterative algorithm between subchannel and power allocation called distributed resource allocation which requires no coordination among the two-hierarchy networks. Finally, a macrocell link quality protection process is proposed to guarantee the macrocell UE's quality of service to avoid severe cross-tier interference from femtocells. Simulation results show that the proposed algorithm can achieve remarkable performance gains as compared to the pure waterfilling algorithm.


System-level analysis and evaluation of SF-DC transmit mode in HSPA+ system

April 2012

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12 Reads

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6 Citations

Cooperated multi-point technique in HSPA+ system has not been paid attention until the Single Frequency Dual Cell (SF-DC) mode, where one user equipment (UE) may be served by dual NodeBs simultaneously in the single carrier frequency network, is proposed recently. In the previous research, the system-level performance with SF-DC operation had not been studied comprehensively. The main contribution of this paper is to exploit SF-DC transmit mode in the perspective of the system level and evaluate the system-level performance of SF-DC in HSPA+ system with different simulation scenes. The impact of SF-DC on legacy UEs and the load balancing capability of SF-DC in asymmetric loading case are investigated properly in different channel conditions. System-level simulation results show that SF-DC transmit mode performs better compared with single point transmission and the influence of SF-DC mode on legacy UEs is negligible. It also reflects that SF-DC has the ability to balance load in asymmetric loading case.


A simple hybrid coordination scheme with semi-distributed mode in multi-cell network

April 2012

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11 Reads

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1 Citation

The problem of distributed coordination in multi-cell wireless network has been concerned in the research community recently due to its ability to enhance intended signal and mitigate interference in the system. In the previous research, the design of beamforming weights at transmitter has been addressed from the perspective of egoism and altruism concepts considering the tradeoff between egoistic and altruistic solutions. The main contribution of this paper is to extend the existing strategy and exploit a much simpler hybrid coordination scheme with semi-distributed mode in multi-cell wireless network using the analytic hierarchy process. The significant advantage of our approach is to provide transmitter with a method which is easier to achieve compared with the existing pattern in a semi-distributed way. The performance of proposed scheme is finally illustrated through the numerical simulation results.


Vertical handoff scheme concerning mobility in the two-hierarchy network

December 2011

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22 Reads

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2 Citations

In a two-hierarchy cellular network — comprised of a central macrocell underlaid with shorter range femtocell, seamless vertical handoff (VHO) is a challenging issue to be approached. With regard to VHO performance requirement in heterogeneous networks, there is a critical demand to develop schemes of the connection managements with synthetically considering additional factors, such as, monetary cost, offered services, user velocity, network conditions, and user preferences besides received signal strength (RSS). To achieve this, a new VHO decision method consisting of the handoff candidates picking and a well-defined objective function optimization is proposed in this paper. When the handoff candidates are picked, the practical constraints will be considered in the new scheme, including femtocell access manner, RSS, and UE velocity. The objective function combines multiple factors that the network operator concerns and thus owns good expansibility and portability. By applying this scheme, the optimal overall performance can be achieved in the integrated system of macrocell and femtocell access networks. Results based on the detailed performance evaluation demonstrate promoted efficacy of the proposed scheme compared to the traditional ones.


Performance of Selection Combining Amplify-and-Forward Relaying with Adaptive Modulation over Nakagami-m Fading Channels

September 2011

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7 Reads

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2 Citations

Vehicular Technology Conference, 1988, IEEE 38th

This paper investigates the performance of selection combining (SC) amplify-and-forward (AF) relaying with adaptive modulation to maximize the spectral efficiency. We derive the closed-form expressions of the average spectral efficiency and the outage probability of the proposed scheme over independent and non-identical Nakagami-m fading channels. The analysis results are verified by using Monte Carlo simulations. Our results indicate that the proposed scheme not only has simplified receiver architecture, but also can offer similarly high spectral efficiency as the MSE-AM scheme proposed in [1], when the relay link is stronger enough than the direct link.


Extension of 4-Tx Precoding Codebook to 8-Tx Downlink Closed-Loop MIMO

September 2011

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27 Reads

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2 Citations

The codebook based precoding is an effective form of limited feedback closed-loop multiple input multiple output (MIMO) scheme. An efficient methodology to build low complexity and high performance codebook is crucial for the closed-loop MIMO precoding algorithm. In this paper, we present a simplified codebook design scheme for 8-Tx MIMO based on the 4-Tx codebook in LTE Rel-8 and Kronecker product. In additional to low complexity and good backward compatibility properties, the codebook design based on this method can inherit most of the desired properties of Rel-8 codebook.


Citations (53)


... A different line of research has considered enhancing Channel Estimation Capacity from SRS information, e.g., by using deep learning tools, hence inherently improving the utilization of SRS sequences [36]. Also, multi-user grouping has been proposed as a strategy to minimize SRS resource requirements, by bringing together users based on channel state information [37], or channel correlation [38]. ...

Reference:

Traffic-Driven Sounding Reference Signal Resource Allocation in (Beyond) 5G Networks
SRS Limited User Grouping Scheduling Algorithm for Downlink Massive MIMO Systems
  • Citing Conference Paper
  • April 2019

... The role of small cells was investigated in [20] for optimizing downlink heterogeneous cellular networks under LOS and NLOS transmissions. Beside using a convolutional neural network (CNN) in a 3-D massive MIMO channel model, LOS detection [21,22] treated the problem as a binary hypothesis test. Based on time-space-frequency channel correlation, the system in [22] aimed to improve the new radio capacity and spectral efficiency of the 5G network. ...

Channel Correlation Based Identification of LOS and NLOS in 3D Massive MIMO Systems
  • Citing Conference Paper
  • April 2019

... To tackle the local minima problem of K-means, [128] proposed a genetic algorithm based on K-means (GAK-means) to perform user grouping for obtaining the optimal UAV deployment. The aforementioned solutions consider only non-overlapping user grouping, which may lead to resource waste [130]. Neto et al. [129] exploited fuzzy C-means algorithm to construct overlapped user groups in mmWave systems, while [25] [132] investigated clustering techniques for dynamic user grouping. ...

Packet-Size Based Overlapping User Grouping in MU-MIMO Systems
  • Citing Conference Paper
  • April 2019

... There have been extensive studies that have appeared in the literature to present the potential gains of beamforming. Most of the reported work considers single cell scenarios [8,11,12]. Moreover, in the literature presenting larger-scale assessment, only physical layer metrics have been used to evaluate system performance [3,8,11,13]. ...

Multi-user Grouping Based Scheduling Algorithm in Massive MIMO Uplink Networks
  • Citing Conference Paper
  • December 2018

... The optimal number of the OPSs, that can be exploited, was fixed in [15], where half of the CI is dedicated for the channel training, while the other half is reserved for data transmission that is uplink/downlink data transmission. Standing on the spatial correlation of the channel vectors of the UEs, [16] analyzed the relationship between the users' signal-to-noise-plus-interference ratio (SINR) and the degree of correlation between the channel vectors; therefore, by properly separating the UEs of high correlation, it is possible to reach an enhanced SINR; however, perfect channel state information (CSI) is assumed, which is practically questionable. ...

SINR loss and user selection in massive MU‐MISO systems with ZFBF
  • Citing Article
  • April 2019

Etri Journal

... There are many excellent research works [3][4][5][6][7] and reviews [8][9][10] in the literature dealing with the channel estimation. In recent years, the research on channel estimation mainly focuses on the following aspects: channel estimation based on deep learning, 11,12 channel estimation based on iteration, [13][14][15] and channel estimation based on compressive sensing (CS). ...

Channel estimation for 3D MIMO system based on LOS/NLOS identification
  • Citing Article
  • Publisher preview available
  • April 2019

... To perform it in the best possible way, the Rxs within one group should not be correlated or should be correlated as little as possible. Thus, spatial correlation is an important aspect of environment analysis [2] [3]. The other aspect of the conference use case is the propagation environment. ...

CSI-RS Based Joint Grouping and Scheduling Scheme with Limited SRS Resources
  • Citing Conference Paper
  • September 2018

... In order to improve the positioning accuracy, NLoS error suppression is required after NLoS identification. Some algorithms can be used to discriminate between NLoS propagation and LoS propagation, such as residual analysis judgment method [142], statistical feature class identification method [143], machine learning methods [144][145][146][147][148][149], geometric relationship class [150], etc. Then, various NLoS error suppression algorithms, including weighted class, filter class, LoS reconfiguration, neural network algorithms, path tracing algorithm, optimization algorithm with constraints, etc., are employed to alleviate the adverse effects of NLoS propagation on positioning accuracy [151]. ...

CNN Based LOS/NLOS Identification in 3D Massive MIMO Systems
  • Citing Article
  • September 2018

IEEE Communications Letters

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Yongyu Chang

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Qi Zhang

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[...]

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Junyao Li

... To further reduce the complexity, a chordal distance method is proposed in [6] which performs selection in a way to maximize the channel matrix distance between the previously selected user and the new one. Its complexity order was regarded as the lowest one until maximum correlation value (MCV) method was not proposed in [7]. It utilizes correlation to measure the orthogonality degree between users and selects the one which has the highest value with already selected users. ...

Low complexity user selection method in 3D MU-MIMO systems
  • Citing Article
  • August 2018