Songlin Sun

Overlay cognitive radio OFDM system for 4G cellular networks

In this study, we integrate overlay cognitive radio technology into 4G cellular networks for the sharing of TV spectrum. On one hand, OFDM is a promising technique for high-speed data transmission over multipath fading channels and has been considered to be the best candidate for 4G mobile networks. On another hand, the overlay cognitive radio model makes it possible to have two concurrent transmissions in a given interference region, where conventionally only one communication takes place at a given time. We investigate different service provision scenarios and propose both time domain and frequency domain overlay cognitive radio OFDM systems for next generation cellular networks. Numerical results show our proposed schemes can achieve satisfying performance in different use cases.

Integrating network function virtualization with SDR and SDN for 4G/5G networks

The rapidly diversified market demands have presented a huge challenge to the conventional mobile broadband network architecture. On one hand, the limited machine room space and insufficient power supply make it impossible to accommodate exponentially growing amount of network equipment of operators. On the other hand, net heterogeneity caused by different specifications of wireless access equipment causes costly trouble related to management and optimization. This article, correspondingly, proposes a holistic solution involving different technologies, i.e. network function virtualization (NFV), software defined radio (SDR), and software defined network (SDN). In particular, we investigate both existing standards and possible extensions for 4G/5G mobile networks, followed by a few open issues for future research.

Inter-cell handoff performance improvement in LTE-a multi-hop relay networks

Multi-hop relay technology is one of the most promising candidate technologies to overcome the coverage and capacity problem in LTE-Advanced networks. Currently 3GPP is considering the incorporation of multi-hop relays into Release 12 of LTE-A standards. However, many issues remain to be resolved due to the complexity of multi-hop relaying paradigm, specifically resource allocation and mobility management. In this work we focus on the relay selection problem, where a user may have in his range several relay nodes to choose. The conventional selection scheme is based on the channel condition between the relay and the user, such that the user will achieve a high level of throughput. Alternatively we propose in this paper a novel relay selection strategy taking handoff into account over LTE-A multi-hop relay networks. Our goal is to achieve significant performance improvement against legacy centralized resource allocation and handoff algorithms such as disjoint path relay selection. Simulation results show that our design has the advantage of reducing inter-cell handoff frequency and lowering handoff failure ratio.

Adaptive SON and Cognitive Smart LPN for 5G Heterogeneous Networks

To overcome the challenge of large data demanding in future 5G cellular networks, heterogeneous networks (HetNets) take advantage of low power nodes (LPNs) to enhance capacity and coverage. This paper aims at 5G HetNets and presents a novel scheme of adaptive self-organization network (SON) by integrating cognitive radio (CR) with inter-cell interference coordination (ICIC). Particularly, we combine the spectrum sensing function from CR and the radio resource layering function from ICIC. Our work addresses the issues of smart low-power node (SLPN) development, which associates appropriate sectorization with radio resource allocation during the self-organization process. We further develop a Hungarian algorithm based self-organization strategy to improve the SLPN adaptive optimization. Simulation results show that our proposed scheme can achieve considerable gain in terms of throughput and coverage, with extra rewards of high flexibility and low complexity in HetNet SON.

SDN Controlled mmWave Massive MIMO Hybrid Precoding for 5G Heterogeneous Mobile Systems

In 5G mobile network, millimeter wave (mmWave) and heterogeneous networks (Hetnets) are significant techniques to sustain coverage and spectral efficiency. In this paper, we utilize the hybrid precoding to overcome hardware constraints on the analog-only beamforming in mmWave systems. Particularly, we identify the complicated antenna coordination and vast spatial domain information as the outstanding challenges in mmWave Hetnets. In our work, we employ software defined network (SDN) to accomplish radio resource management (RRM) and achieve flexible spacial coordination in mmWave Hetnets. In our proposed scheme, SDN controller is responsible for collecting the user channel state information (CSI) and applying hybrid precoding based on the calculated null-space of victim users. Simulation results show that our design can effectively reduce the interference to victim users and support high quality of service.

Cognitive radio based adaptive SON for LTE-A heterogeneous networks

This paper presents a novel scheme of adaptive self-organization network (SON) by integrating cognitive radio (CR) with inter-cell interference coordination (ICIC) for LTE-A heterogeneous networks (HetNets). Particularly, we take advantage of the spectrum sensing function from CR and the radio resource layering function from ICIC. Our work addresses the issues of smart low-power node (SLPN) development, which associates appropriate sectorization with radio resource allocation during the self-organization process. We further develop a Hungary algorithm based self-organization strategy to improve the SLPN adaptive optimization. Simulation results show that our proposed scheme can achieve considerable gain in terms of throughput and coverage, with extra rewards of high flexibility and low complexity in HetNet SON.

C-SURF: Colored Speeded Up Robust Features

SURF has been proven to be one of the state-of-the art feature detector and descriptor, and mainly treats colorful images as gray images. However, color provides valuable information in the object description and recognition tasks. This paper addresses this problem and adds the color information into the scale-and rotation-invariant interest point detector and descriptor, coined C-SURF (Colored Speeded Up Robust Features). The built C-SURF is more robust than the conventional SURF with respect to rotation variations. Moreover, we use 112 dimensions to describe not only the distribution of Harr-wavelet responses but also the color information within the interest point neighborhood. The evaluation results support the potential of the proposed approach.

Artificial frequency selective channel for covert cyclic delay diversity orthogonal frequency division multiplexing transmission

Multiple-input multiple-output orthogonal frequency division multiplexing has become an attractive air-interface solution for the next generation wireless networks because of its high spectrum efficiency. This paper addresses the security concern and proposes to achieve covert orthogonal frequency division multiplexing transmission using cyclic delay diversity featured multiple-input multiple-output technology. Particularly, our physical layer security scheme takes the advantage of cyclic delay diversity formed periodical frequency selective channel and utilizes uneven comb pilots to confuse unauthorized receivers and benefit authorized receivers. We conduct simulation study to evaluate the impact of different cyclic delay, antenna number, and interpolation algorithms on our scheme. Numerical results show that our scheme can provide authorized users with significant advantage over eavesdroppers without complicated upper-layer encryption and decryption. Moreover, the scheme has flexible choice of parameters and thus can be easily deployed in a variety of wireless networks with different requirements. Copyright

Covert OFDM transmission using CDD based frequency selective channel

Orthogonal Frequency Division Multiplexing (OFDM) has become an increasingly common technique in communication systems and raised tremendous security concerns recently. This paper proposes to achieve covert OFDM transmission with cyclic delay diversity (CDD) featured multiple input multiple output (MIMO) technology. Particularly, our physical layer security scheme takes the advantage of CDD formed frequency selective channel and addresses uneven comb pilots to confuse unauthorized receivers and benefit authorized receivers. Numerical results justify that, with our design, the CDD paradigm can efficiently safeguard OFDM system, and the performance can be further optimized by fine tuning channel estimation for authorized users.

Traffic aware power allocation and frequency reuse for green LTE-A heterogeneous networks

The next generation cellular networks target significant capacity improvements and require dense frequency reuse of the scarce radio spectrum, resulting in a danger of severe interference. Fractional frequency reuse (FFR) techniques have been proposed for macro-cell networks to mitigate interference. However, these static schemes are not adaptive to meet the traffic demand changes from mobile users, and thus inefficient with respect to power consumption in many scenarios. This paper starts with the basic soft fractional frequency reuse (SFFR) framework and proposes a traffic demand orientated green power control scheme that can make power allocation by considering different traffic demands. Afterwards, this green concept is extended to heterogeneous network (HetNet) for the power control strategies in low-power nodes (LPNs). Numerical results show that our proposed schemes can achieve considerable improvement in terms of throughput and power consumption, as well as extra rewards of high flexibility and low complexity.