Yang X.,University of Surrey |
Sun Z.,University of Surrey |
Miao Y.,University of Surrey |
Wang N.,University of Surrey |
And 3 more authors.
Proceedings - UKSim-AMSS 17th International Conference on Computer Modelling and Simulation, UKSim 2015 | Year: 2015
In recent years, Mobile Ad hoc Networks (MANETs) have been great interest all over the world for its advantage of high mobility and flexibility. It is also among the greatest challenges in wireless communications. As a special type of MANET, Vehicular Ad hoc Networks (VANETs) are considerably important in Next-Generation Networking (NGN). Unlike typical MANETs, VANETs are much more challenging due to high velocity, which makes classic MANET routing protocols cannot fit in such scenarios efficiently. This paper is intended to evaluate performance of two different routing protocols, namely DSDV and AODV, in various realistic scenarios. Thus, a DSDV optimization approach is therefore proposed to improve DSDV's performance in VANETs. © 2015 IEEE.
Tu X.,Beijing University of Posts and Telecommunications |
Li X.,Beijing University of Posts and Telecommunications |
Zhou J.,Sichuan University |
Chen S.,China Academy of Telecommunication Technology
Proceedings - 2014 IEEE International Conference on Cloud Engineering, IC2E 2014 | Year: 2014
Software-defined networking has emerged as a promising solution for supporting dynamic network functions and intelligent applications through decoupling control plane from forwarding plane. OpenFlow is the first standardized open management interface of SDN architecture. But it is unrealistic to simply swaping out conventional networks for new infrastructure. How to integrate OpenFlow with existing networks is still a serious challenge. We propose a tunnel splicing mechanism for heterogeneous network with MPLS and OpenFlow routers. Two key mechanisms were suggested: first, abstract the underlying network devices into uniformed nodes in order to shield the details of various equipments, second, strip the manipulation of flow table and lable switch table from controller and fulfill it in an independent module. This new paradigm has been developed on Linux system and tests have been carried out in experiment networks. The emulation results proved its feasibility and efficiency. © 2014 IEEE.
Shen Z.,China Academy of Telecommunication Technology |
Papasakellariou A.,Samsung |
Montojo J.,Qualcomm |
Gerstenberger D.,Ericsson AB |
Xu F.,China Academy of Telecommunication Technology
IEEE Communications Magazine | Year: 2012
To satisfy the ever increasing demand for higher throughput and data rates, wireless communication systems need to operate in wider bandwidths. 3GPP LTE-Advanced with carrier aggregation enables operators to maximally and optimally utilize their available spectrum resources for increased data rates and user experience while reducing their incurred OPEX and CAPEX. This article provides a tutorial overview of 3GPP LTE-Advanced with carrier aggregation as specified in Rel-10 including deployment scenarios of interest, main design features, PHY/MAC procedures, and potential enhancements for future standard releases. © 2012 IEEE.
Zhang W.,Wuhan University |
Tian M.,Wuhan University |
He H.,Wuhan University |
Shen Z.,China Academy of Telecommunication Technology
Hsi-An Chiao Tung Ta Hsueh/Journal of Xi'an Jiaotong University | Year: 2011
Since the downlink outage probability expressed with bound value is not precise enough in co-channel interference-limited tiered networks, the stochastic geometry theory is used to model network framework and closed-expressions of per-tier downlink outage probability are derived based on the framework. The received signal to interference ratio (SIR) is formulated as a function of macrocell signal power and femtocell aggregated interference power. Then the probability for received SIR less than a threshold is derived according to the probability distribution of macrocell signal power in the condition on the aggregated interference power. The downlink outage probability is obtained by applying the probability distribution of aggregated interference power to calculate the expectation of conditioned outage probability. Simulation results show that the downlink outage probability in macrocell reduces about 20% and 5%, respectively, when the femtocell transmit power decreases 3.16 mW (the number of femtocells is 100 on average) or the number of femtocells decreases 20 on average (the femtocell transmit power is 100 mW).
Dai X.,China Academy of Telecommunication Technology |
Zou R.,Central South University |
An J.,Beijing Institute of Technology |
Li X.,Beijing Institute of Technology |
And 2 more authors.
IEEE Transactions on Vehicular Technology | Year: 2012
A companding-based transformation method is introduced to quasi-maximum-likelihood (ML) detectors, such as the QR-decomposition-based M-algorithm (QRD-M) and list sphere decoding, for coded multiple-input-multiple- output (MIMO) systems in this paper. The key idea of the proposed companding technique is to compress (i.e., down-weight) the dubious observation of the accumulated branch metric by taking into account its statistical characteristics so that, after companding, the estimation error of the unreliable detected information bits due to insufficient candidate size and/or channel estimation error is significantly mitigated without disproportionate compromise of the reliable information bits. By employing the proposed companding method, the original leptokurtically distributed log-likelihood ratio of the detected information bits becomes more Gaussian distributed. As an illustrative example, the QRD-M detector is employed in this paper. Numerical results show that the QRD-M detector based on the proposed companding paradigm achieves significant performance gain over the conventional method and approaches the performance of the ML detector for a 16-ary quadrature-amplitude-modulated (16-QAM) 4 × 4 MIMO multiplexing system with lower-than-linear-detector computational complexity. © 2006 IEEE.
Dai X.,China Academy of Telecommunication Technology |
Sun S.,China Academy of Telecommunication Technology |
Wang Y.,China Academy of Telecommunication Technology
Wireless Personal Communications | Year: 2012
This paper proposes a rotation and scaling based transformation method to simplify the (quasi-)maximum-likelihood (ML) detectors (such as QRD-M, sphere decoding (SD), etc.) for the square quadrature amplitude modulation (S-QAM) modulated multiple-input and multiple-output (MIMO) systems with no performance degradation. The key idea of the simplification is to utilize the symmetric shape of the S-QAM constellation so that after rotation and scaling, real multiplication and addition with certain constellation points in symbol replica generation simply transform into bit shifting or even vanish. As an illustrative example, the QRD-M detector is employed in this work. By using the proposed method, the number of real multiplications of the symbol replica generation required for the QRD-M detector is reduced by 50% and 25% for 4-QAM and 16-QAM, respectively. The numbers of real addition reduction is twice the amount of multiplication. The underlying principle of the proposed rotation and scaling transformation can be straightforwardly extended to amplitude and phase-shift keying (APSK) modulated MIMO systems employing the QRD-M, SD, list sequential sphere decoder (LISS), list sphere decoding (LSD), and the full ML detectors. © Springer Science+Business Media, LLC. 2011.
China Academy Of Telecommunication Technology | Date: 2013-03-04
Disclosed are a response information transmission method, system and device. A base station can configure at least two PUCCH transmission carriers for user equipment, accordingly, the user equipment can select at least one PUCCH transmission carrier from the at least two PUCCH transmission carriers which are configured by the base station to transmit response information fed back on a corresponding subframe, and accordingly, the base station can receive the response information which is fed back by the user equipment on at least one PUCCH transmission carrier. The technical solution increases the number of PUCCH transmission carriers, so that compared with the manner of only configuring one PUCCH transmission carrier in the prior art, the reconfiguration operations caused by the movement of user equipment can be reduced, thereby reducing the condition that UE cannot normally communicate in the process of reconfiguration, and reducing the signaling overhead caused by the reconfiguration operation.
China Academy Of Telecommunication Technology | Date: 2010-01-14
The present invention discloses a method for configuring a Physical Downlink Control Channel (PDCCH), a base station and a UE, wherein the base station configures a component carrier or component carriers for monitoring the PDCCH for the UE and notifies the UE about information on the configured component carrier or component carriers so that the UE monitors the PDCCH only over the configured component carrier or component carriers. Stated otherwise, in this way, the UE will operate only over a necessary component carrier or component carriers without monitoring respective component carriers in an LTE-A system to thereby reduce the number of concurrently monitored component carriers, and in the case of nonconsecutive component carriers, also reduce the number of consequently enabled receivers and consequently the amount of consumed power of the UE for monitoring the PDCCH.
China Academy Of Telecommunication Technology | Date: 2012-09-25
Disclosed is a method for transmitting channel state information, for realizing the transmission of channel information which supports CoMP transmission. The method includes: a terminal receiving from a base station control signaling which indicates to the terminal to perform channel information feedback, the control signaling including indication information about a plurality of CSI-RS resources for performing aggregation feedback; the terminal obtaining the plurality of CSI-RS resources based on the indication information to perform channel estimation and constructing a channel matrix according to a PDSCH transmission solution over a preset CSI reference resource, the correlation between the signal over the plurality of CSI-RS resources and the signal of a UERS port and the constructed channel matrix and transmitting the CSI to the base station. Also disclosed is a device for implementing the method.
China Academy Of Telecommunication Technology | Date: 2013-01-09
Disclosed are a method and device for determining user equipment (UE) positioning information during a minimum drive test (MDT) process to ensure that during the MDT realization process, the acquisition of the UE position information is not limited by the positioning capabilities of a network positioning server or the UE, that is, a network side can determine the UE position information required by the MDT without the positioning support function of the positioning server and the UE. The method of the present invention for determining the user equipment (UE) positioning information during a minimum drive test (MDT) process comprises: selecting a UE in a connected state, and determining an MDT measurement result corresponding to the UE (S101); determining the UE positioning information, and adding the UE positioning information to the MDT measurement result corresponding to the UE (S102).