Gang Feng

Distributed Energy-Efficient Power Control for Macro–Femto Networks

Driven by dramatic increase in the number of users and data usage, the rapidly increasing energy consumption in mobile cellular networks has become an urgent concern to address recently. Macro-femto network has been considered as one of the most promising infrastructure for the upcoming next generation cellular networks, where the energy efficiency issue has not been well investigated as most existing related work is focused on spectrum sharing and interference avoidance. In this paper, we study transmit power control for macro-femto networks, aiming at maximizing energy efficiency while meeting the requirement of received signal-to-interference-plus-noise ratio (SINR). We design an energy-efficient power control (EEPC) scheme for closed access femtocell networks. In EEPC scheme, the macro base station (BS) and femto access points (FAPs) periodically exchange information on the gradient of allocated power and the total system power. The BS or a FAP adjusts the transmit power of allocated resource blocks (RBs) based on the information it receives. We conduct extensive simulation experiments to validate the effectiveness of EEPC scheme and numerical results show that EEPC can effectively improve the system energy efficiency while satisfying the minimum SINR requirements of the macrocell users and the femtocell users well.

Enhancing software-defined RAN with collaborative caching and scalable video coding

The ever increasing video demands from mobile users have posed great challenges to cellular networks. To address this issue, video caching in radio access networks (RANs) has been recognized as one of the enabling technologies in future 5G mobile networks, which brings contents near the end-users, reducing the transmission cost of duplicate contents, meanwhile increasing the Quality-of-Experience (QoE) of users. Inspired by the emerging software-defined networking technology, recent proposals have employed centralized collaborative caching among cells to further increase the caching capacity of the RAN. In this paper, we explore a new dimension in video caching in software-defined RANs to expand its capacity. We enable the controller with the capability to adaptively select the bitrates of videos received by users, in order to maximize the number and quality of video requests that can be served, meanwhile minimizing the transmission cost. To achieve this, we further incorporate Scalable Video Coding (SVC), which enables caching and serving sliced video layers that can serve different bitrates. We formulate the problem of joint video caching and scheduling as a reward maximization (cost minimization) problem. Based on the formulation, we further propose a 2-stage rounding-based algorithm to address the problem efficiently. Simulation results show that using SVC with collaborative caching greatly improves the cache capacity and the QoE of users.

Cellular Offloading in Heterogeneous Mobile Networks With D2D Communication Assistance

The next-generation mobile communication system [fifth-generation (5G)] needs to address the challenges stemming from the performance requirements in diverse technical scenarios, such as seamless wide-area coverage, high-capacity hot-spots, and low-power massive connections. It is widely recognized that traditional single-tier cellular network architecture is not adequate to meet these requirements, and thus, the heterogeneous cellular network (HetNet) has been identified as a promising network architecture for 5G. In HetNets, traffic offloading can be exploited to effectively improve network capacity by utilizing complementary network communication techniques. In this paper, we propose a device-to-device (D2D) communication assisted mobile traffic offloading (DATO) scheme, with focus on massive connections for machine type communications (MTC). DATO determines access mode for user equipments (UEs) to offload UEs from macro base stations (MBSs) to small base stations via D2D communications to improve the overall network capacity and mitigate the traffic congestion at MBSs. We formulate the DATO problem as a 0–1 linear programing and prove it to be NP-hard. We resort to dynamic programing to provide the optimal solution, as well as the theoretical performance upper bound of DATO. We develop an efficient algorithm to solve the DATO problem while preserving the optimality by making use of the location relationship of BSs and UEs. We apply our proposed DATO scheme to a series of typical network scenarios to validate its effectiveness. Numerical results reveal that DATO significantly outperforms traditional UE access mode in terms of network capacity and UE energy consumption, which are important to massive MTC.

Cooperative Sleep-mode and performance modeling for heterogeneous mobile network

Configuration of eNB Sleep-mode is a promising strategy in improving network energy efficiency of next generation mobile networks. The main idea of sleep-mode mechanism is to reduce the energy consumption of cells during the periods when they are not necessary due to low traffic. In this paper, we propose a cooperative sleep-mode strategy for heterogeneous mobile networks where several small cells supply the overlapping coverage, and provide a mathematical model for analyzing the performance of the strategy. Specifically, we develop a cooperative sleep-mode mechanism, which is implemented by an Adaptive sleep-mode mechanism (ASM) algorithm. We then use E/M/1 and E/M/n queuing model to analyze the energy efficiency of our proposed algorithm. Our model takes into account the traffic density and system transmission capacity. We also conduct intensive simulation experiments based on the model with realistic broadband channel propagation conditions, to verify advantages of the cooperative sleep mode for improving network energy efficiency and demonstrate the effectiveness of our analytical model.

Energy-efficient relay deployment in next generation cellular networks

Relay enhanced cellular system is a promising infrastructure redesign to enhance the performance of next generation mobile networks. The use of intermediate nodes to relay information from source to destination is efficient in eliminating black spots, extending coverage region, prolonging battery lifetime of users. Recently, energy efficiency of mobile networks has drawn research attentions. Relay deployment from the perspective of energy efficiency is an interesting issue which has not been deeply addressed. In this paper, we investigate energy-efficient relay deployment by determining the optimal number and location of relays in next generation cellular networks. We establish a mathematic model for analyzing energy efficiency measured by `Joule per bit in relay aided cellular networks, where the pathloss status related to the cell traffic busy level is considered. We conduct intensive simulation experiments based on the model with realistic broadband channel propagation conditions. Our findings suggest that introducing appropriate number of relay nodes with proper locations into the cellular system can improve system energy efficiency without compromising system throughput.

Cooperative content distribution for 5G systems based on distributed cloud service network

Future mobile communications face enormous challenges as traditional voice services are replaced with increasing mobile multimedia services. To address the vast data traffic volume and the requirement of user Quality of Experience (QoE) in the next generation mobile networks, it is imperative to develop efficient content distribution technique, aiming at significantly reducing redundant data transmissions and improving content delivery performance. On the other hand, cloud computing as a new content-centric paradigm is exploited to fulfil the multimedia requirements by provisioning data and computing resources on demand. In this paper, we propose a cooperative caching framework which implements State based Content Distribution (SCD) algorithm for future mobile networks. In our proposed framework, cloud service providers deploy a plurality of cloudlets in the network forming a Distributed Cloud Service Networks (DCSN). We formulate a content distribution optimization model, and data contents are distributed in local cloudlets according to the optimal solution to minimize redundant content transmissions. We use simulation experiments to validate the effectiveness of our proposed framework. Numerical results show that the proposed framework can significantly improve content cache hit rate, reduce content delivery latency and outbound traffic volume in comparison with known existing caching strategies.

D2D Communication Assisted Traffic Offloading for Massive Connections in HetNets

The next generation mobile communication system (5G) needs to address the challenges stemming from the performance requirements in diverse technical scenarios, such as low power massive connections for machine type communications (MTC). Heterogeneous Network (HetNet) has been identified as a promising network architecture for 5G. In HetNets, traffic offloading can be exploited to effectively improve network capacity by utilizing complementary network communication techniques. In this paper, we propose a new Device-to-Device (D2D) communication assisted mobile traffic offloading (DATO) scheme, with focus on massive connectivity. In DATO, some user equipments (UEs) can be offloaded from macro base stations (MBSs) to small base stations (SBSs) via D2D communications, so as to improve overall network capacity. We formulate the DATO problem as a 0-1 Linear Programming and use dynamic programming to provide the optimal solution for determining the access mode of UEs. Numerical results reveal that DATO significantly outperforms traditional UE access schemes in terms of number of admitted UEs and UE energy consumption, etc.

Intrusion detection system for RPL from routing choice intrusion

RPL is specifically designed for Low power and Lossy Networks (LLNs). With the expansion of LLNs applications, security of RPL becomes one of the major concerns. This paper mainly addresses the security aspect of RPL. We first analyze the vulnerability of RPL self-organising properties, and identify a new RPL internal intrusion, named routing choice (RC) intrusion. We specially analyze the harm of a type RC intrusion in RPL using ETX metric, which further validates the effectiveness of our work. Second, we design IDSs for RPL to defense intrusions. Our design discusses detection methodologies, system architectures, detection data and intrusion respose with some promotions. To satisfy the energy efficiency requirements, we propose three type Monitor Nodes (MNs) devices for different RPL applications. To explicitly show the design of IDSs, we apply our IDS to defense the type of RC intrusion in RPL using ETX metric on Contiki OS, and the results verify the effectiveness of our IDSs. Finally, we theoretically analyzed the applicability of IDSs for RPL.

A Comparison Study of Coupled and Decoupled Uplink-Downlink Access in Heterogeneous Cellular Networks

The rapid evolution of cellular networks has brought great changes to mobile network architecture. One trend is the dense deployment of base stations (BSs) in heterogeneous cellular network (HetNets) architecture. On the other hand, the booming mobile Internet applications introduce increasingly significant imbalance in regard to Signal to Interference and Noise Ratio (SINR) statistics and traffic load between uplink (UL) and downlink (DL) in HetNets. These evolutions inspire us to exploit decoupling of UL and DL in HetNets for improving system performance. In this paper, we conduct a comparison study for the system performance of the decoupled UL/DL access (DUDA) mode and traditional coupled UL/DL access (CUDA) mode based on stochastic geometry theory. Compared to existing related work, we establish an analytical model for CUDA mode as a comparison reference and consider a more realistic system model, where we employ dynamic transmit power control in UL transmission by applying fractional power control (FPC) to model a location-dependent per-mobile power state. Numerical results reveal that DUDA mode significantly outperforms CUDA mode in terms of system rate, spectral efficiency (SE) and energy efficiency (EE) in HetNets. In addition, results also show that DUDA mode can improve load balance and fairness. Simulation results further validate the accuracy of our analytical model.

Layered Space Shift Keying Modulation Over MIMO Channels

Space shift keying (SSK) modulation is an emerging transmission technique for multiple-input multiple-output (MIMO) wireless channels, which exploits the spatial domain to convey information. In this paper, we present a layered space shift keying (LSSK) modulation scheme to fully exploit the spatial domain to transmit information bits, where a layered architecture is developed to achieve spatial multiplexing transmission in an SSK system. Specifically, LSSK leverages the rotated signals predetermined at the transceiver to identify different layers and improve the bit-error-rate (BER) performance. The layered signals are directly generated by the proposed LSSK modulation method with a low computational overhead. Furthermore, we propose a layered-and-joint (LJ) near-optimal detection algorithm based on the layered architecture of LSSK to reduce the detection complexity. In LJ detection, layered detection is performed to find a set of detection candidates for each layer, and then, joint detection is performed with these candidates. We show that the performance of LJ detection is quite close to that of optimal maximum-likelihood detection with significantly reduced detection complexity for high-spectrum-efficiency scenarios. Results demonstrate that the proposed LSSK scheme substantially improves the spectrum efficiency of an SSK system and outperforms other existing MIMO schemes.