Showing papers by "Zheng Chang published in 2014"

Radio Resource Allocation for Collaborative OFDMA Relay Networks with Imperfect Channel State Information

Abstract: This paper addresses the resource allocation problem in collaborative relay-assisted OFDMA networks. Recent works on the subject usually ignored either the selection of relays, asymmetry of the source-to-relay and relay-to-destination links or the imperfections of channel state information. In this article we take into account all these together and our focus is two-fold. Firstly, we consider the problem of asymmetric radio resource allocation, where the objective is to maximize the system throughput of the source-to-destination link under various constraints. In particular, we consider optimization of the set of collaborative relays and link asymmetries together with subcarrier and power allocation. Using a dual approach, we solve each sub-problem in an asymptotically optimal and alternating manner. Secondly, we pay attention to the effects of imperfections in the channel-state information needed in resource allocation decisions. We derive theoretical expressions for the solutions and illustrate them through simulations. The results validate clearly the additional performance gains through an asymmetric cooperative scheme compared to the other recently proposed resource allocation schemes.

Energy efficient user grouping and scheduling for collaborative mobile cloud

Abstract: In order to fully exploit the high speed broadband multimedia services, prolonging the battery life of user equipment is critical, especially for the current smartphones. In this work, we investigate the problem of designing a content sharing collaborative mobile cloud (CMC) via user cooperation to reduce the energy consumption at terminal side. Given a group of users interested in downloading the same content from an operator, a grouping and scheduling based algorithm is proposed in order to select the proper data receiver in each scheduling time. The objective of the presented algorithm is to obtain energy efficiency as well as user fairness among the members of CMC. The proposed scheme can take both base station and terminal aspects into consideration and it is shown that the significant energy saving performance can be achieved without scarifying and drowning the battery of any terminal.

Energy efficient resource allocation for collaborative mobile cloud with hybrid receiver.

Abstract: In order to fully exploit the high speed broadband multimedia services, prolonging the battery life of user equipment (UE) is critical from user's perspective, especially for the smartphone users. A collaborative mobile cloud (CMC), which consists of several UEs offers one potential solution for reducing the energy consumption at the terminal side. In this paper, an OFDMA mobile cloud system with simultaneous wireless information and power transfer has been considered. The considered CMC is formed by a number of hybrid receivers which have both functionalities of harvesting energy and decoding information from the radio signal. In particular, we study the resource allocation and user scheduling algorithm for minimizing the energy cost of data transmission in the context of mobile cloud. With the objective to minimize the system energy consumption, in each scheduling time, one UE will be selected for receiving and relaying the data, and radio resource will be allocated to the dedicated UE by the proposed scheme. Simulation results demonstrate the proposed user scheduling and resource allocation algorithms can achieve the significant energy saving performance.

Collaborative Mobile Clusters: An Energy-Efficient Emerging Paradigm

Abstract: Future wireless communication systems are expected to offer several gigabits data rate. It can be anticipated that the advanced communication techniques can enhance the capability of mobile terminals to support high data traffic. However, aggressive technique induces high energy consumption for the circuits of terminals, which drain the batteries fast and consequently limit user experience in future wireless networks. In order to solve such a problem, a scheme called collaborative mobile cluster is foreseen as one of the potential solutions to reduce energy consumption per node in a network by exploiting collaboration within a cluster of nearby mobile terminals. This chapter provides a detailed analysis of the energy consumption of a terminal joining the cluster and also analyzes the conditions for energy savings opportunities.

Energy efficient power allocation for collaborative mobile clouds with information and power transfer

Abstract: Prolonging the battery life of mobile terminals (MTs) is critical for mobile users, especially for the smartphone users to enjoy the high data rate services offered by the future wireless networks. A collaborative mobile cloud (CMC), which consists of several MTs offers one potential solution for reducing the energy consumption at the terminal side in the downlink. In addition, as RF signal can carry both information and energy simultaneously, the induced simultaneous wireless information and power transfer (SWIPT) is also capable of prolonging the battery of MTs. In this paper, the power allocation algorithm for CMC with SWIPT is formulated as a non-convex optimization problem which takes into account the baseband circuit power consumption, RF transmit and receiver power, harvested energy and the minimum required data rate. Accordingly, by exploiting the properties of nonlinear fractional programming, the formulated non-convex optimization problem, of which objective function is in fractional form, is transformed into an equivalent optimization problem having an objective function in subtractive form and is able to be solved in dual domain. Simulation results demonstrate that the proposed user scheduling and resource allocation algorithms can achieve significant energy saving performance.

Multi-domain collaborative spectrum sensing and power control in presence of multiple primary users

Abstract: Spectrum sensing is one of the most important technique in the cognitive radio. The existing works so far primarily focus on single primary user detection. In this work, we consider cooperative spectrum sensing in cognitive radio networks (CRNs), when there are multiple primary users (PUs) existing. To address the problem of multiple PUs detection, we introduce a novel multi-domain spectrum sensing algorithm in the context for determining the status and number of PUs. After extracting the feature of detecting signal with tensor decomposition method, we propose a multi-domain spectrum sensing (MDS) framework to improve the opportunity detection performance in multiple primary users network. Moreover, based on the spectrum sensing results, we further propose a power control algorithm allowing SUs to transmit without generating harmful interference to primary user. The effectiveness of the proposed scheme is demonstrated through extensive simulation studies.