Jinhui Chen

Codebook Design for LTE-A Downlink System

Multiple-input multiple-output (MIMO) has been adopted by long term evolution (LTE) and its updated version LTE-Advanced (LTE-A) to increase the spectrum efficiency. However, the benefits of multi-user (MU) MIMO highly rely on the accurate channel knowledge at the transmitter. So proper codebook design is a key problem for LTE-A FDD downlink system. In this paper, a codebook design with phase adjustment in the precoder targeting wideband channel properties is proposed. The average cell spectrum efficiency and cell-edge user spectrum efficiency of the proposed scheme are evaluated through system level simulation and compared to the discrete Fourier transform (DFT) based feedback scheme. The results show that the proposed codebooks significantly improve feedback efficiency and system performance for co-polarized linear antenna array.

Load Balance Based Dynamic Inter-Cell Interference Coordination for Relay Enhanced Cellular Network

The relaying technologies have been considered in cellular networks (such as LTE-A and WiMAX) as one of the advanced techniques to extend the network coverage and enhance the cell edge performance. However, the relays will bring extra interference to macro cell and the popular solution is to allocate different bandwidth for relays and base stations. In this paper, we use proportional fairness mode to formulate this frequency resource allocation optimization problem and presented a new adaptive method (both centralized and distributed algorithm) with interference coordination based on dynamic traffic load for cell-edge relay deployment. This resource allocation scheme with both intra and inter cell interference coordination (ICIC) can greatly improve the spectrum efficiency compared with conventional static ICIC schemes, in which the cell- edge bandwidth is equally allocated among the neighboring base stations or relays. Based on our performance evaluation, the proposed method can flexibly adapt the case when the traffic load distribution is non-uniformed or mobility occurs frequently, which accordingly exploit the cellular capacity with the experience enhancement of the cell-edge users.

Enhanced Multiuser Eigenmode Transmission for Joint Frequency-Spatial Resource Allocation in OFDM-MIMO Downlink Systems

Orthogonal frequency-division multiplexing (OFDM) and multiple-input-multiple-output (MIMO) are two key technologies adopted in future wireless communication systems, such as LTE/LTE-A. There are many papers addressed the resource allocation problems for OFDM and MIMO systems independently. However few discussions targets on the joint frequency-spatial resource allocation problem, particularly on eigenmode scheduling level. In this paper, we try to propose novel resource allocation schemes on eigenmode selection level, with the joint consideration of precoding problem in spatial domain, eigenmode scheduling and power allocation cross spatial and frequency domains.

Codebook Design for Cross-Polarized Linear Antenna Array in LTE-A Downlink System

Multiple-input multiple output (MIMO) has been adopted by long term evolution (LTE) and its updated version LTE-Advanced (LTE-A) to increase system spectrum efficiency. However, the benefits of multi-user (MU) MIMO highly rely on an accurate channel knowledge at the transmitter. So proper codebook design is a key problem for LTE-A FDD downlink system. In this paper, the channel characteristic specific to cross-polarized linear antenna array is analyzed, then its codebook design based on amplitude and phase adjustment is proposed for LTE-A downlink system. The proposed codebooks are compared to the differential scheme [7] on the average cell spectral efficiency and cell-edge user spectral efficiency evaluated through system level simulations. Simulation results show that the proposed codebooks significantly improve channel feedback efficiency and system performance.

On Implementing Spatial-Correlation-Information Aided Feedback in Practical MIMO Systems

This work investigates implementing spatial-correlation-information aided feedback in practical multiple-input multiple-output (MIMO) systems. It is presented that the existing spatial-correlation-information aided feedback approach could be simplified in computational complexity with little performance loss. In comparison with Grassmannian codebooks, the feedback codebooks in the 3GPP LTE Release-8 specification is shown to be a near-optimal base codebook. An efficient quantization approach is proposed for quantizing transmit spatial covariances matrices for closely-spaced co-polarized uniform linear arrays (ULA). The good performance of the entire practical feedback solution is demonstrated via system-level simulation.

Ordered Precoder Designs for MIMO Interference Channels Based on Interference Alignment

Recent research shows that K user time-varying interference channel is capable of achieving K/2 degrees of freedom based on interference alignment (IA). In multiple-input-multiple-output (MIMO) interference channels, appropriate transmit precoder design plays a pivotal role in efficiently suppressing the co-channel interference. In this paper, we propose two heuristic ordered precoder design algorithms for MIMO interference channels based on global search and chordal distance, respectively. Simulation results are provided to demonstrate that the proposed ordered precoder designs are capable of significantly improving the system sum capacity.

Precoding with Known Transmit Coupling and Spatial Covariance Matrices

A closed-form precoding scheme using the knowledge of transmit coupling and spatial covariance matrices is proposed, which ensures that the achievable rate increases with the number of transmit antennas when the size of the transmit antenna array is fixed and the radiated power, but not the amplifier output power, is constrained. Eigenvalue-proportional power allocation is employed in this precoding scheme. Simulation shows that the performance of eigenvalue-proportional power allocation is close to that of covariance matrix based waterfilling power allocation. Energy efficiency of different schemes is evaluated and compared.