Showing papers by "Ying Wang published in 2013"

Separate Horizontal amp; Vertical Codebook Based 3D MIMO Beamforming Scheme in LTE-A Networks

Abstract: Traditional two-dimensional (2D) multi-input multioutput (MIMO) beamforming technologies can only adjust the beamformers in the horizontal dimension according to horizontal channel information. However, due to the three-dimensional (3D) character of the real channel, 2D MIMO beamforming technologies can not achieve the optimal system throughput. In this paper, a 3D MIMO beamforming scheme is proposed, which takes into account vertical beamforming. In the proposed scheme, we first design a codebook for Vertical dimension based on 3D MIMO channel model; then a 3D MIMO beamforming scheme is proposed combining the proposed Vertical beamforming codebook and legacy horizontal dimension beamforming codebook. Through simulation, we evaluate the proposed 3D MIMO beamforming scheme and compare it with former 2D beamforming technology. Owing to the additional spatial degrees of freedom in Vertical dimension, our 3D MIMO beamforming scheme can effectively improve the overall system performance.

Joint power and rate allocation for spectrum sharing cognitive radio multicast networks under service outage constraint

Abstract: This letter considers a downlink spectrum sharing cognitive radio (CR) multicast network coexisting with a primary network. The problem of joint power and rate allocation to maximize the average sum rate is studied. In this regard, a joint power and rate allocation scheme is proposed, where the allocated rate can be higher than the lowest rate of all the secondary users (SUs) within the same group, which is different from the conventional multicast transmission scheme. To guarantee the quality of service (QoS) of the SU, the service outage probability defined as the probability that the maximum achievable rate of the SU is lower than the rate of the group, is constrained to be under a certain threshold, which is termed as the service outage constraint. The numerical results show that the proposed scheme provides significant improvement over the conventional scheme in terms of average sum rate.

Sensing-Throughput Tradeoff in Cluster-Based Cooperative Cognitive Radio Networks with A TDMA Reporting Frame Structure

Abstract: This paper proposes clustering schemes to solve the sensing throughput tradeoff problem in cooperative cognitive radio networks (CCRNs). The throughput of CCRNs extremely depends on the spectrum sensing performance and data transmission time. In CCRNs, the more secondary users (SUs) for cooperation, the better performance of spectrum sensing. However, the overhead consumption increases as the quantity of cooperative SUs becomes huge, which will lead to less time for data transmission. In this paper, we propose a frame structure that takes the sensing results reporting time into consideration. In order to reduce the reporting time consumption, a centralized cluster-based cooperative cognitive radio system model is created based on the frame structure. The sensing-throughput tradeoff problem under both the perfect reporting channel and imperfect reporting channel scenarios are formulated. The proposed clustering schemes reduce the reporting time consumption and ensure the maximum transmission time of each SU. Numerical results show that the proposed clustering schemes achieve satisfying performance.

RNTP-based resource block allocation in LTE downlink indoor scenarios

Abstract: In long term evolution (LTE) downlink indoor scenarios, we study an inter-cell interference coordination (ICIC) by interacting the relative narrow-band transmit power (RNTP) indicators among evolved NodeBs (eNBs). Assuming the data symbols of each user is only known by one eNB, a novel RNTP-based resource block (RB) allocation scheme is presented and carried out in two steps: 1) Each eNB partitions RBs for celledge and cell-center users, and then transmits such information to other eNBs within RNTP bit maps; 2) Based on the received RNTP bit maps, a novel scheduling algorithm is proposed to allocate RBs for cell-edge and cell-center users in each eNB. Simulation results show that the proposed RNTP-based RB allocation scheme improves the cell-edge users' performance, and yields up a certain overall cell throughput enhancement.

Multi-Cell Downlink Joint Transmission with 3D Beamforming

Abstract: This paper proposes a scheme combining multi-cell downlink joint transmission(JT) with 3- Dimensional(3D) beamforming. The proposed scheme is based on the following two observations: 1) The performance of multi-cell joint transmission is highly dependent on the received signal strength from the coordinated cells, 2) Interference may become more severe at the cell boundary due to the extremely flat beams serving the cell edge users with 3D beamforming. In the proposed scheme, users at the cell boundary are served with JT and 3D beamforming simultaneously, and those at the cell center are served with 3D beamforming. Simulation results based on LTE-Advanced systems show that significant gains can be achieved by the scheme, with about 14% gain on cell average spectral efficiency and about 58% gain on edge user spectral efficiency compared to traditional single cell transmission with 2-Dimensional(2D) beamforming.

Bias-based self-organized cell selections for outdoor open-access picocell networks

Abstract: Cellular structures are to be enhanced by heterogeneous deployments. One type of such deployments is to add outdoor pico evolved NodeBs (PeNBs), formulating a hierarchical cell structure with macro eNBs (MeNBs). The cell selection in such system is facing challenges, including problems of coverage and cross interference. One method is called cell range expansion (RE), typically in which a common fixed bias value is added to the users' receiving signal power from PeNBs to adjust their coverage. However, it might not be appropriate to use the same bias for all the PeNBs. This paper focus on the specific bias design. By defining the interfered region, it proposes a mechanism to obtain the average interference suffered by each PeNB. The interference is from MeNBs with sector antennas and other randomly located PeNBs. In the discussion, it is further pointed out that its implementation follows a self-organized manner, with sustainable signalling overhead. Simulation results show that the proposed method achieves much better cell edge performances than those with fixed bias values.

Codebook precoding-based paired user selecting method and codebook precoding-based paired user selecting device

Abstract: The invention discloses a codebook precoding-based paired user selecting method and a codebook precoding-based paired user selecting device in the technical field of network communication. The method comprises the following steps of: firstly, receiving channel state information transmitted by a user terminal, and scheduling a first user according to the channel state information; secondly, selecting the matched precoding matrix index set of the first user according to the precoding matrix index and the rank indication of the first user; searching the precoding matrix index of the prospected paired user according to the matched precoding matrix index set of the first user; selecting a secondary user matched with the first user according to the precoding matrix index; and transmitting data to the first secondary user and the secondary user. According to the invention, on the premise that any feedback overhead is not added to the user terminal, the influence of the interference to a matching result can be reduced, the computation complexity of a base station end can be reduced, the more effective and exact user pairing can be realized, and the downstream data transmission performance of an MU-MIMO (multi-user multiple-input multiple-output) system can be further improved.

Cluster-based Cooperative Spectrum Sensing in two-layer hierarchical Cognitive Radio Networks

Abstract: The paper investigates cluster-based Cooperative Spectrum Sensing (CSS) issues in two-layer hierarchical Cognitive Radio Networks (CRNs). Most previous studies focus on hard decision fusion under the assumption of perfect reporting channels. However, wireless channels are not error-free in reality. Therefore, we propose a novel cluster-based CSS scheme with imperfect reporting channels between SUs and cluster heads (CHs) to optimize cluster strategy. A weighted reporting channel method is adopted in our analysis. To further reduce the complexity, 1st order Taylor series expansion approximation scheme is proposed. Numerical results show that the proposed scheme achieves a satisfying performance.

MU-MIMO user pairing algorithm to achieve overhead-throughput tradeoff in LTE-A systems

Abstract: This paper investigates user pairing algorithm in multiple-user multi-input multi-output (MU-MIMO) systems Considering that users report Precoding Matrix Index (PMI) and Rank Indicator (RI) to indicate precoding matrix, multiple orthogonal PMI&RI clusters are designed to reduce the MU-channel state indicator (MU-CSI) feedback overhead On the basis of such predefined orthogonal clusters, a novel user pairing algorithm is proposed to make the tradeoff between cell throughput and MU-CSI feedback overhead To further simplify computational complexity, we propose a suboptimal algorithm Unlike previous researches, the transmission data streams of paired users are adaptively adjusted according to the channel condition Simulation results show that the cell throughput gain achieved by our proposed algorithms is close to that achieved by other user pairing algorithms, with less feedback overhead in Long Term Evolution-Advanced (LTE-A) systems