Jiancun Fan

MCS Selection for Throughput Improvement in Downlink LTE Systems

In this paper, we investigate resource block (RB) assignment and modulation-and-coding scheme (MCS) selection to maximize downlink throughput of long-term evolution (LTE) systems, where all RBs assigned to the same user in any given transmission time interval (TTI) must use the same MCS. We develop several effective MCS selection schemes by using the effective packet-level SINR based on exponential effective SINR mapping (EESM), arithmetic mean, geometric mean, and harmonic mean. From both analysis and simulation results, we show that the system throughput of all the proposed schemes are better than that of the scheme in [7]. Furthermore, the MCS selection scheme using harmonic mean based effective packet-level SINR almost reaches the optimal performance and significantly outperforms the other proposed schemes.

Joint User Pairing and Resource Allocation for LTE Uplink Transmission

In this paper, we investigate joint user pairing and resource allocation under the practical constraints in single-carrier frequency-division multiple access (SC-FDMA) LTE uplink systems. We first introduce a joint optimal algorithm based on branch-and-bound search as a benchmark. To reduce complexity, we divide the joint optimization problem into two subproblems: user pairing and resource allocation. For both these subproblems, we develop several low-complexity algorithms by exploiting the properties of the application of the optimization problem itself. It is shown by the simulation results that the proposed algorithms have better throughput and fairness than the conventional algorithms in and in for LTE uplink no matter whether power control is perfect or not.

Adaptive Block-Level Resource Allocation in OFDMA Networks

In this paper, we investigate adaptive resource allocation in downlink transmission of orthogonal frequency division multiple access (OFDMA) networks. A block-level resource allocation scheme is developed to maximize the overall throughput of the networks by appropriately allocating resource blocks (RBs) and power to different users. We focus on application in long term evolution (LTE) systems where all RBs allocated to the same user must use the same modulation and coding scheme (MCS). Unfortunately, the complexity of solving such an optimization problem is prohibitively high in general. In order to reduce the complexity, we divide the original joint optimization problem into two subproblems. We first allocate appropriate RBs to users with the best channel condition and then perform power allocation. Then, a more effective MCS is selected in our scheme, which not only ensures the block-error rate (BLER) of the RB with the worst channel condition but also makes full use of the RBs with better channel conditions. Simulation results show that the proposed resource allocation scheme can improve the overall throughput of the network by 20% compared with the existing scheme when the number of users is 4 and the signal-to-interference-plus-noise ratio (SINR) is 10 dB.

Multi-Cell Coordinated Scheduling and MIMO in LTE

This paper provides an overview of multi-cell coordinated scheduling and multiple-input multiple-output (MIMO) techniques in LTE. We first discuss single-user MIMO (SU-MIMO) and multi-user MIMO (MU-MIMO) for LTE and identify potential techniques for further improving the performance of LTE, such as enhanced channel state information feedback and adaptive switching between SU-MIMO and MU-MIMO. Then, we address inter-cell interference mitigation techniques for downlink and uplink, respectively. Finally, potential research challenges and topics in the area are discussed.

Faster-Than-Nyquist Signaling: An Overview

Faster-than-Nyquist (FTN) signaling can improve the bandwidth utilization. In this paper, we will provide a comprehensive survey on the topic. The history and the applications of FTN signaling are first introduced. Then, the basic principles and the system framework of FTN signaling are presented. Next, more details on transmitter and receiver optimization are discussed. Finally, the current research challenges on FTN signaling are identified and conclusions are provided.

Multiuser MIMO Scheduling for LTE-A Downlink Cellular Networks

In this paper, we investigate multiuser MIMO scheduling in LTE downlink cellular networks. We formulate the downlink LTE-A MIMO scheduling as a weighted sum rate maximization problem by allocating the RBs to users or user pairs subject to some constraints in LTE-A. We develop a low-complexity MU-MIMO scheduling and resource allocation algorithm and propose an adaptive switching approach between SU-MIMO and MU-MIMO to improve network performance. System-level simulation results demonstrate significantly performance improvement of the proposed MU-MIMO scheduling algorithm and the adaptive switching algorithm.

Performance Analysis of MU-MIMO in Downlink Cellular Networks

In this article, we investigate achievable sum-rates of a multiuser multiple-input multiple-output (MU-MIMO) network with maximal ratio transmission (MRT) and zero-forcing (ZF) precoders for downlink cellular scenarios. We use Gamma distribution to derive tight lower and upper bounds of the achievable sum-rates. From the analytical results, the sum-rates of the MRT and ZF precoders are increased with the number of the transmit antennas and transmit power, and there exists an optimal number of served users for the highest achievable sum-rates when using the ZF precoder.

Analysis of spectral and energy efficiency in ultra-dense network

To meet the challenge of the ever-growing traffic volume in current wireless communications, ultra-dense network (UDN) deployment with high system capacity has attracted wide attention in recent years. However, existing researches on UDN mainly focus on system throughput while ignore energy efficiency (EE). Therefore, we will analyze the UDN performance including not only system throughput but also EE in this paper. We first theoretically analyze the performance of UDN in terms of cell average spectral efficiency, area throughput, and network energy efficiency using the tools from stochastic geometry. Then, we demonstrate the effects of the frequency reuse factor on these performance metrics, and conclude that when taking the overall performance into consideration, the network performance can not be optimal simultaneously under the same parameters. Some tradeoffs need to be considered to achieve a better network performance. Finally, we validate the analysis through simulations.

Joint User Pairing and Resource Allocation for Uplink SC-FDMA Systems

In this paper, we investigate joint user pairing and resource allocation under the practical constraints in singlecarrier frequency-division multiple access (SC-FDMA) LTE uplink systems. We first introduce a joint optimal algorithm based on branch-and-bound search as a benchmark. To reduce complexity, we divide the joint optimization problem into two subproblems: user pairing and resource allocation. For these subproblems, we develop several suboptimal but low-complexity algorithms. The simulation results show that the proposed algorithms outperform the conventional one.

Low complexity transmit antenna selection for spatial multiplexing systems

In spatial multiplexing systems, transmit antenna selection is a very promising technique for reducing implementation cost and computational complexity. In this paper, we propose two novel effective near-optimal antenna selection algorithms based on channel capacity maximization. We use an effective iterative process to reduce computational complexity and retain near-optimal performance. Compared with the conventional algorithm, our algorithms have lower computational complexity and achieve almost the same capacity and bit error ratio (BER) performance as the optimal selection algorithm regardless the channel is correlated or not. Finally, computer simulations are presented to validate and demonstrate the performance of our algorithms.