Jiqing Ni

MIMO Beamforming Designs With Partial CSI Under Energy Harvesting Constraints

In this letter, we investigate multiple-input multiple-output (MIMO) communications under energy harvesting (EH) constraints. In our considered EH system, there is one information transmitting (ITx) node, one traditional information receiving (IRx) node and multiple EH nodes. EH nodes can transform the received electromagnetic waves into energy to enlarge the network operation life. When the ITx node sends signals to the destination, it should also optimize the beamforming/precoder matrix to charge the EH nodes efficiently simultaneously. Additionally, the charged energy should be larger than a predefined threshold. Under the EH constraints, in our work both minimum mean-square-error (MMSE) and mutual information are taken as the performance metrics for the beamforming designs at the ITx node. In order to make the proposed algorithms suitable for practical implementation and have affordable overhead, our work focuses on the beamforming designs with partial CSI and this is the distinct contribution of our work. Finally, numerical results are given to show the performance advantages of the proposed algorithms.

Robust Coordinated Beamforming for Secure MISO Interference Channels with Bounded Ellipsoidal Uncertainties

This letter addresses the robust optimization problem of downlink coordinated beamforming over the multiple-input single-output (MISO) interference channel with confidential messages (IFC-CM) exploiting imperfect channel state information (CSI) at the transmitters. Our aim is to minimize the total transmitted power subject to the worst-case individual signal-to-interference-plus-noise-ratio (SINR) and equivocation rates. To model the imperfect CSI, bounded ellipsoidal uncertainties for channel vector and covariance are both considered. By deriving the equivalent forms for the SINR and secrecy constraints, the worst-case robust problem can be reformulated as a semi-definite programming (SDP) with the help of rank relaxation. Simulation results show the effectiveness of the proposed algorithm.

Performance analysis for range expansion in heterogeneous networks

In this paper, the uplink and downlink performance of a two-tier heterogeneous network (HetNet) with range expansion (RE) is analyzed. Different from previous works, base stations (BSs) are modeled as a spatial Poisson point process. This model can not only capture the irregularity of the BS deployment but also lead to closed form expressions. With the analytical results, the impacts of several key parameters on the coverage and throughput performance are investigated. Our results justifies the effectiveness of RE and Pico deployment. Based on our analyses, certain attention should be made on the RE design to balance the uplink and downlink performance. Our analyses are corroborated by simulations and can thus serve as a flexible and quick guidance for system design without complicated and time-consuming system-level platform construction and simulation.

Secrecy-Rate Balancing for Two-User MISO Interference Channels

This paper considers a two-user multiple-input single-output (MISO) interference channel with confidential messages (IFC-CM), where the beamforming vectors at the two transmitters are jointly optimized using the closed-form Pareto-optimal parameterization. We show that coordinated beamforming is secrecy-rate optimal which is achieved by agreeing on the parameters between the two transmitters. We first analyze the feasible set of the beamforming parameters that guarantees positiveness of the secrecy rates. We then derive a quadratic relationship that finds the Pareto-optimal parameters to achieve secrecy-rate balancing beamforming.

Ergodic secrecy rate of two-user MISO interference channels with statistical CSI

This paper considers a two-user multiple-input single-output (MISO) interference channel with confidential messages (IFC-CM), where the beamforming vectors at the two transmitters are jointly optimized using the closed-form Pareto-optimal parameterization. We prove that artificial noise cannot improve the secrecy rate performance, and coordinated beamforming is secrecy-rate optimal which is achieved by agreeing on the parameters between the two transmitters. We analyze the feasible set of the beamforming parameters that guarantees positiveness of the secrecy rates when the transmitters know only statistical CSI, and then analysis in the ergodic secrecy rate region is discussed. More importantly, we derive the closed form of the ergodic secrecy rates and illustrate the Pareto-optimal structure of the beamforming vectors.摘要本文考虑两用户多输入单输出的带有安全信息的干扰信道, 采用闭式帕累托最优参数法来联合优化发送端的波束成形向量。 其次, 证明加入人为噪声不能提高安全速率, 且对发送端参数的一致性调整可获得协作波束成形的最优安全速率。 当发送端已知信道的统计信息时, 通过分析波束成形参数的可行集来保证安全速率的正定性, 进而得到遍历安全速率域。 最后, 提出遍历安全速率的闭式解, 并阐明波束成形向量的帕累托最优解的结构。

A robust and distributed design for coordinated downlink beamforming for secure MISO interference channels

In this paper, we address the optimization problems of downlink coordinated beamforming over the K-user multiple-input single-output interference channel with confidential messages. Our design objective is to minimise the total transmit power subject to the constraints of individual signal-to-interference plus noise ratio and equivocation rates. For the case with perfect channel state information CSI, by deriving the equivalent forms for the signal-to-interference plus noise ratio and the secrecy constraints, the optimization problem is reformulated as a second-order cone programme problem. Then, an optimal distributed algorithm using the partial Lagrangian duality is discussed. In addition we extend the analysis to the imperfect CSI scenario with bounded ellipsoidal errors, the centralised algorithm has been proposed by solving a semi-definite programme with the help of rank relaxation, whereas the distributed robust algorithm is devised by using ADMM. Finally, the simulation results have shown that with perfect CSI, the centralised and distributed algorithms have nearly the same performance, but in the case of imperfect CSI, the centralised algorithm shows a slightly better performance. Copyright

Secrecy Balancing over Two-User MISO Interference Channels with Rician Fading

This paper considers a 2-user multiple-input single-output (MISO) interference channel with confidential messages (IFC-CM), in which the Rician channel model is assumed. The coordinated beamforming vectors at the two transmitters have the similar parameterizations as those for perfect CSI, which could be optimized jointly and achieved by agreeing on the real parameters between the two users. Our main contribution is that a quadratic relationship between the two real-valued parameters can be derived for the Rician channel to reach the ergodic secrecy rate balancing point. Simulation results present the secrecy performance over the 2-user MISO IFC-CM scenario.

Robust Filter-and-forward Beamforming Design for Two-way Multi-antenna Relaying Networks

In this paper, we investigate a robust filter-and-forward (FF) beamforming design for two-waymulti-antenna relaying networks, where multiple relays assist two terminals to exchange information. With Gaussian distributed channel errors, the proposed robust beamforming design aims at maximizing the signal-to-interference-plus-noise-ratio (SINR) under individual transmit power constraints at each relay. Exploiting the elegant convex optimization mathematical tools, the optimization problem can be efficiently solved. Finally, simulation results demonstrate that the proposed robust beamformer reduces the sensitivity of the two-way multi-antenna relay networks to channel estimation errors, and outperforms the algorithm with estimated channels only. Moreover, the length of robust beamformer also influences the system performance.

On the performance of two-way relaying with dirty paper coding

Recently two-way relaying has become a promising protocol. The design of the processing matrix of the two-way relay channel is of significant importance since it could dramatically influence the system performance. In this paper, we propose a nonlinear design of the relay processing matrix with dirty paper coding (DPC). And compared with the traditional linear schemes, it could amplify the useful signal and mitigate the impact of interference and noise. Moreover, the multi-user scenario, which is more common in the practice, is also taken into consideration. And based on different receive criterions DPC-ZF algorithm and DPC-MMSE algorithm are proposed. Simulation results show that both DPC-ZF and DPC-MMSE have a higher throughput and lower bit error ratio (BER) performance compared with the traditional AF algorithm and zero-forcing (ZF) algorithm.

Terminal-based Dynamic Clustering Algorithm in Multi-Cell Cellular System

A terminal-based dynamic clustering algorithm is proposed in a multi-cell scenario, where the user could select the cooperative BSs from the predetermined static base stations (BSs) set based on dynamic channel condition. First, the user transmission rate is derived based on linear precoding and per-cell feedback scheme. Then, the dynamic clustering algorithm can be implemented based on two criteria: (a) the transmission rate should meet the user requirement for quality of service (QoS); (b) the rate increment exceeds the predetermined constant threshold. By adopting random vector quantization (RVQ), the optimized number of cooperative BSs and the corresponding channel conditions are presented respectively. Numerical results are given and show that the performance of the proposed method can improve the system resources utilization effectively.