Quanxin Zhao

Energy-Efficient Offloading for Mobile Edge Computing in 5G Heterogeneous Networks

Mobile edge computing (MEC) is a promising paradigm to provide cloud-computing capabilities in close proximity to mobile devices in fifth-generation (5G) networks. In this paper, we study energy-efficient computation offloading (EECO) mechanisms for MEC in 5G heterogeneous networks. We formulate an optimization problem to minimize the energy consumption of the offloading system, where the energy cost of both task computing and file transmission are taken into consideration. Incorporating the multi-access characteristics of the 5G heterogeneous network, we then design an EECO scheme, which jointly optimizes offloading and radio resource allocation to obtain the minimal energy consumption under the latency constraints. Numerical results demonstrate energy efficiency improvement of our proposed EECO scheme.

QoS-aware energy-efficient multicast for multi-view video in indoor small cell networks

Multi-view video (MVV) consists of multiple video streams captured simultaneously by multiple closely spaced cameras and enables users to freely change their viewpoints by playing different video streams. Those close deployed cameras will capture overlapping frames (OFs) and then transmit OFs in multiple video streams. With the viewpoint change from one stream to another, redundant OFs in the latter stream can be useless for a user. Moreover, the redundant transmission will increase with the number of users and result in severe bandwidth waste for both base stations and users. In order to reduce the redundant transmission of OFs and increase energy efficiency (EE), a new architecture Overlapping Reduced Multi-view Video Transmission (ORMVVT), which is based on User dependent Multi-view video Streaming for Multi-users (UMSM), is proposed for downlink transmission of MVV in small cell networks (SCNs). Then, a novel resource allocation model is introduced to help users achieve different data rates according to their Quality of Service (QoS) requirements. Contrarily, for the simplicity of implementation, existing schemes can only support a single reception data rate for all users in a multicast group. Further, we formulate an optimization problem to maximize the EE with the QoS constraint of services. Finally, a suboptimal QoS-aware Energy-efficient Multicast Resource Allocation scheme (QEMRA) is proposed to reduce the computational complexity. Numerical results show that the proposed low-complexity QEMRA scheme is able to get a close-to-optimal performance under general fading distributions.

Multimedia Traffic Placement under 5G radio access techniques in indoor environments

It is a challenge to support multimedia services with high Quality of Service (QoS) requirements for upcoming 5G radio access techniques that has the characteristics of Heterogeneous network Architecture, Heterogeneous Terminals and Heterogeneous Spectrum (H3ATS). Multi-view Video (MVV) consisting of multiple video streams captured by close spaced cameras is increasingly popular, permitting changeable viewpoints by playing different streams. As those close spaced cameras will capture overlapping frames (OFs) and transmit OFs in multiple streams, when switching video streams from one to another, it is redundant to transmit and receive OFs in the latter stream for base stations and users, respectively. Moreover, since the data rate requirement of a MVV with multiple streams is much higher than that of the traditional video with single-stream, base stations will consume tremendous bandwidth if the number of playing MVVs increases. To eliminate OFs and offload traffic from base stations, we propose a new MVV stream architecture called Overlapping Reduced Multi-view Video Transmission (ORMVVT) and a new network architecture named Multicast Multi-Traffic Source (MMTS) for multicast small cell networks (MSCNs). Then, an optimization problem is formulated to minimize the data rate of small cells under QoS constraint. An Offloading Based Traffic Placement (OBTP) scheme is introduced to solve the optimization problem. Simulation results show that the proposed low-complexity OBTP is able to get a higher performance than the traditional schemes in terms of bandwidth saving.

A Markovian analytical framework for public‐safety video sharing by device‐to‐device communications

Monitoring video of city surveillance camera plays an important role in public security and disaster relief, which is often used by first responder teams, such as firefighters and police officers. The first responders in emergency situations require consistent connection with one another and request the remote real‐time monitoring video for effective cooperation and coordination. However, the capacity and privacy of public wireless networks fail to satisfy the requirements in many emergency scenarios, which often leads to exceptionally high traffic loads and insecurity. Device‐to‐device (D2D) communications have been deemed a key solution for this problem, as responders can use D2D links for traffic offloading and secure communications. To investigate the D2D‐based solution for public safety video sharing, this paper focuses on the Focus Geographical Area (FGA) video consisting of multiple camera streams requiring higher bandwidth consumption than that of the traditional single‐camera stream, which attracts a large number of contents delivery requests in emergency situations. This paper develops a new Traffic Burden Switching Markovian (TBSM) model to evaluate the performance of transmitting real‐time FGA video in wireless networks with D2D communications. First, a novel D2D area model is introduced to characterize link‐switching in wireless D2D communication networks. Based on the proposed D2D area model, the state and transition matrix of TBSM model are then derived by jointly considering user mobility, link‐switching, and FGA video view‐switching. Thereafter, some key performance metrics including system offloading ratio, D2D link‐switching ratio, and view‐switching ratio are derived on the basis of coverage probability and ergodic rate. The performance results show the significant varying performance among D2D areas with different geographical locations in D2D enabled wireless networks, which is referred to as multi‐D2D‐area diversity. The excellent match between simulation and model results validates the accuracy of the TBSM model, which can be used to provide guidelines for the deployment and optimization of future wireless video networks with D2D communications.

A scalable gather point based data delivery scheme in mobile social networks

Mobile social networks (MSNs) are a special kind of delay tolerant networks that can apply social knowledge of user clustering to improve the performance of data delivery scheme in MSNs. However, the existing user clustering schemes ignore the fact that prediction accuracy will decrease with the increase of the network scale, which restricts the scalability of existing data delivery schemes and results in the degradation of the network data delivery ratio and delay. This paper proposes a two-layer data delivery model to increase the scalability for large-scale MSNs. Besides, a Two-Layer QoS-aware data Delivery (TLD) scheme is proposed with much lower computational complexity than that of the existing algorithms. The obtained simulation results indicate that the proposed TLD scheme outperforms the existing mobility-based MSN schemes in terms of both delivery ratio and delay.

Energy-efficient resource allocation strategy in ultra dense small-cell networks: A Stackelberg game approach

This paper focuses on resource allocation in heterogeneous Ultra Dense small-cell Networks (UDNs), in which massive overlaid small cells are under the coverage of a macro cell. In UDN, both co-tier and cross-tier interference need to be taken into account. When increasing the deployment density of Small-cell Base Stations (SBSs) and the unreasonable energy usage, it results in serious interference and degrades the users satisfaction, which encourages us to agree on maximizing the total system Energy Efficiency (EE). This problem is non-convex and cannot be solved within polynomial time. Therefore, an efficient hierarchical Resource Allocation (RA) algorithm with reduced computational complexity is proposed to decompose the EE optimization problem into two sub-optimization problems: Sub-Channel Allocation (SCA) process and Power Allocation (PA) process. To solve these two processes, thereafter, we employ a uniform pricing scheme to reduce the feedback overhead and build the PA problem into a two-stage Stackelberg game, where the Macro-cell Base Station (MBS) acts as a follower and SBSs are leaders. The obtained simulation results show that the proposed hierarchical RA algorithm and the two-stage game can achieve a higher EE and a lower computation complexity.

Traffic-aware resource allocation for full duplex wireless networks

With simultaneous transmission on both uplink and downlink within the same band, full duplex (FD) wireless communication is an emerging technique for next generation networks to significantly improve network throughput and spectrum efficiency. The symmetric capacity in the FD wireless network come from the same throughput obtained in both uplink and downlink with the same bandwidth. However, it will waste lots of radio resources for transmitting asymmetric traffic in the FD wireless network with the symmetric capacity. Moreover, residual self-interference (SI) from imperfect self interference cancelling in the FD wireless network can significantly decrease the uplink throughput. To tackle the above challenges, we propose a full duplex multi-subcarrier aggregation transmission (FD-MST) analytical model for residual SI enabled FD wireless systems. Based on the FD-MST model, we formulate a resource allocation problem in the FD wireless network with asymmetric traffic. To solve the original NP-hard problem, we propose a two-stage suboptimal scheme. Simulation results show that there is at least a 77.3% increase in the network throughput under the proposed scheme compared to those of the existing schemes.

Service-Oriented Wireless Multimedia Multicasting with Partial Frequency Reuse

Service-Oriented Architecture (SOA) is employed in a wide range of applications because it promises to expose computation-intensive tasks as services and combine them with new applications to accelerate their applications development process. For service-oriented multimedia applications, the performance of multicasting transmission services under multimedia traffic must be evaluated. Multiview Video (MVV) is a promising and emerging type of multimedia traffic that consists of multiple video streams, allows stream switching, and requires strict Quality-of-Service (QoS). In this study, we investigated multicast transmission of MVV in wireless cellular networks with Partial Frequency Reuse (PFR) and focused on two challenging problems: (1) multicast group formation and (2) subchannel and power allocation. Initially, we propose a novel Content-based Partial frequency reuse Diversity Grouping (CPDG) scheme to allocate users to multicast groups on the basis of Partial frequency reuse Diversity (PD) in wireless networks with PFR. After group formation, an optimization problem for subchannel and power allocation is formulated to minimize network power consumption under QoS constraint. Thereafter, the optimization problem is divided into two subproblems and solved using simplex method and Karush-Kuhn-Tucker (KKT) condition. Finally, to solve the optimization problem, a suboptimal scheme referred to as Partial frequency reuse Diversity Based Energy-efficient Multicasting (PDEM) is proposed by dynamically allocating wireless resources under QoS constraint. The simulation results show that the proposed PDEM scheme can achieve close-to-optimal performance. Moreover, mathematical analysis of the effect of PD on network performance can provide guidelines for optimization of multimedia traffic in multicasting-enabled wireless cellular networks with PFR.

QoS-aware energy-efficient multicast for multi-view video with Fractional Frequency Reuse

It is very challenging to support multimedia services with the strict requirements of Quality-of-Service (QoS) in bandwidth limited wireless cellular networks, especially for cell edge users who often suffer from co-channel interference. Multi-view Video (MVV) is an increasingly popular multimedia service, which consists of multiple video streams captured by close spaced cameras and permits changeable viewpoints by playing different streams. To eliminate Overlapping Frames (OFs) of MVV and guarantee the required QoS, this paper develops a new stream architecture called Overlapping Reduced Multi-view video Transmission (ORMT) and proposes a novel multicast Fractional Frequency Reuse (FFR) network model. An optimization problem is then formulated to maximize the Energy Efficiency (EE) of the network under QoS constraint. This problem can be relaxed to a suboptimal one, which is proved to be convex. A low-complexity scheme solving the optimization problem is then proposed to allocate frequency resources based on the QoS requirements for both cell edge users and cell center users. The simulation results demonstrate that the proposed ORMT architecture can save the bandwidth up to 50%. Meanwhile, there is only 4% gap between the performance of the proposed scheme and that of the optimal solution.