| 1. |
- Cao, CongZhe, et al.
(författare)
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An extended packetization-aware mapping algorithm for scalable video coding in finite-length fountain codes
- 2013
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Ingår i: Science China Information Sciences. - : Springer Science and Business Media LLC. - 1674-733X .- 1869-1919. ; 56:4, s. 042311-
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Tidskriftsartikel (refereegranskat)abstract
- We propose an extended packetization-aware mapping algorithm based on fountain codes to enhance video stream performance which is vulnerable to packet losses. By properly utilizing the proposed algorithm in finite-length cases, the edges connecting to a source symbol are scattered over multiple encoding packets so that the decoding probabilities are increased. Furthermore, an improved degree distribution is designed to obtain better decoding probabilities. Numerical results, it is confirmed that the proposed algorithm in finite-length cases can augment decoding probabilities and the improved degree distribution can increase peak signal-to-noise ratio (PSNR) of scalable video coding (SVC) in a hostile communication environment.
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| 2. |
- Chai, R., et al.
(författare)
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Utility-based bandwidth allocation algorithm for heterogeneous wireless networks
- 2013
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Ingår i: Science in China, Series F: Information Sciences. - : Springer Science and Business Media LLC. - 1009-2757 .- 1862-2836. ; 56:2, s. 95-107
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Tidskriftsartikel (refereegranskat)abstract
- In next generation wireless network (NGWN), mobile users are capable of connecting to the core network through various heterogeneous wireless access networks, such as cellular network, wireless metropolitan area network (WMAN), wireless local area network (WLAN), and ad hoc network. NGWN is expected to provide high-bandwidth connectivity with guaranteed quality-of-service to mobile users in a seamless manner; however, this desired function demands seamless coordination of the heterogeneous radio access network (RAN) technologies. In recent years, some researches have been conducted to design radio resource management (RRM) architectures and algorithms for NGWN; however, few studies stress the problem of joint network performance optimization, which is an essential goal for a cooperative service providing scenario. Furthermore, while some authors consider the competition among the service providers, the QoS requirements of users and the resource competition within access networks are not fully considered. In this paper, we present an interworking integrated network architecture, which is responsible for monitoring the status information of different radio access technologies (RATs) and executing the resource allocation algorithm. Within this architecture, the problem of joint bandwidth allocation for heterogeneous integrated networks is formulated based on utility function theory and bankruptcy game theory. The proposed bandwidth allocation scheme comprises two successive stages, i.e., service bandwidth allocation and user bandwidth allocation. At the service bandwidth allocation stage, the optimal amount of bandwidth for different types of services in each network is allocated based on the criterion of joint utility maximization. At the user bandwidth allocation stage, the service bandwidth in each network is optimally allocated among users in the network according to bankruptcy game theory. Numerical results demonstrate the efficiency of the proposed algorithm.
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| 3. |
- ChengWen, Xing, et al.
(författare)
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Statistically robust resource allocation for distributed multi-carrier cooperative networks
- 2013
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Ingår i: Science China Information Sciences. - : Springer. - 1674-733X .- 1869-1919. ; 56:2, s. 109-121
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, we investigate joint subcarrier and power allocation scheme for distributed multi-carrier cooperative networks with imperfect channel state information. Using practical channel estimation algorithms, the statistic model of the channel estimation error is first derived. Then based on the channel error model, the resource allocation scheme aims at maximizing the sum rate of the overall network. Specifically, both subcarrier allocation and power allocation are taken into account. In the subcarrier allocation, a realistic problem of the power leakage between neighboring subcarriers is also addressed. Furthermore, based on Lagrange dual-decomposition algorithm, a practical power allocation algorithm is proposed. Finally, the simulation results demonstrate the performance advantages of the proposed robust design.
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| 4. |
- DengSheng, Lin, et al.
(författare)
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Packet combining based on cross-packet coding
- 2013
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Ingår i: Science China Information Sciences. - : Springer Science and Business Media LLC. - 1674-733X .- 1869-1919. ; 56:2, s. 022302-
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Tidskriftsartikel (refereegranskat)abstract
- We propose a packet combining scheme of using cross-packet coding. With the coding scheme, one redundant packet can be used to ensure the error-correction of multiple source packets. Thus, the proposed scheme can increase the code rate. Moreover, the proposed coding scheme has also advantages of decoding complexity, reducing undetectable errors (by the proposed low-complexity decoder) and flexibility (applicable to channels with and without feedback). Theoretical analysis under the proposed low-complexity decoding algorithm is given to maximize the code rate by optimizing the number of source packets. Finally, we give numerical results to demonstrate the advantages of the proposed scheme in terms of code rates compared to the traditional packet combining without coding or ARQ (automatic repeat-request) techniques.
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| 5. |
- Ding, Liang-Hui, et al.
(författare)
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Lifetime maximization routing with network coding in wireless multihop networks
- 2013
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Ingår i: SCIENCE CHINA-INFORMATION SCIENCES. - : Springer Science and Business Media LLC. - 1674-733X .- 1869-1919. ; 56:2, s. 1-15
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, we consider the lifetime maximization routing with network coding in wireless multihop networks. We first show that lifetime maximization with network coding is different from pure routing, throughput maximization with network coding and energy minimization with network coding. Then we formulate lifetime maximization problems in three different cases of (i) no network coding, (ii) two-way network coding, and (iii) overhearing network coding. To solve these problems, we use flow augmenting routing (FA) for the first case, and then extend the FA with network coding (FANC) by using energy minimized one-hop network coding. After that, we investigate the influence of parameters of FANC, evaluate the performance of FANC with two-way and overhearing network coding schemes and compare it with that without network coding under two different power control models, namely, protocol and physical ones. The results show that the lifetime can be improved significantly by using network coding, and the performance gain of network coding decreases with the increase of flow asymmetry and the power control ability.
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| 6. |
- Gong, Jie, et al.
(författare)
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On precoding for overlapped clustering in a measured urban macrocellular environment
- 2013
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Ingår i: Science in China, Series F: Information Sciences. - : Springer Science and Business Media LLC. - 1009-2757. ; 56:2, s. 38-022301
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, we study the performance of precoding schemes for cooperative transmission of multiple coherent base stations (BSs) that allow for overlapped clustering in a measured urban macrocellular environment at 2.66 GHz, in order to verify previous findings obtained by using simulated channel data. The evaluated precoding schemes include zero-forcing (ZF), layered virtual signal-to-interference-plus-noise ratio (SINR) maximization (LVSM) and clustered virtual SINR maximization (CVSM). The results show that the sum rate of the CVSM scheme outperforms the other precoding schemes. In addition, the ZF achieves higher rates than the LVSM, except when the channel condition is poor. When greedy proportional user scheduling is considered, the CVSM scheme and the ZF scheme offer similar performance, whereas the LVSM scheme gives little gain over a non-cooperative transmission scheme used as the baseline.
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| 7. |
- Hockerdal, Erik, et al.
(författare)
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Real-time performance of DAE and ODE based estimators evaluated on a diesel engine
- 2018
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Ingår i: Science China Information Sciences. - : SCIENCE PRESS. - 1674-733X .- 1869-1919. ; 61:7
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Tidskriftsartikel (refereegranskat)abstract
- Computation and sampling time requirements for real-time implementation of observers is studied. A common procedure for state estimation and observer design is to have a system model in continuous time that is converted to sampled time with Euler forward method and then the observer is designed and implemented in sampled time in the real time system. When considering state estimation in real time control systems for production there are often limited computational resources. This becomes especially apparent when designing observers for stiff systems since the discretized implementation requires small step lengths to ensure stability. One way to reduce the computational burden, is to reduce the model stiffness by approximating the fast dynamics with instantaneous relations, transforming an ordinary differential equations (ODE) model into a differential algebraic equation (DAE) model. Performance and sampling frequency limitations for extended Kalman filter (EKF)s based on both the original ODE model and the reduced DAE model are here analyzed and compared for an industrial system. Furthermore, the effect of using backward Euler instead of forward Euler when discretizing the continuous time model is also analyzed. The ideas are evaluated using measurement data from a diesel engine. The engine is equipped with throttle, exhaust gas recirculation (EGR), and variable geometry turbines (VGT) and the stiff model dynamics arise as a consequence of the throttle between two control volumes in the air intake system. The process of simplifying and modifying the stiff ODE model to a DAE model is also discussed. The analysis of the computational effort shows that even though the ODE, for each time-update, is less computationally demanding than the resulting DAE, an EKF based on the DAE model achieves better estimation performance than one based on the ODE with less computational effort. The main gain with the DAE based EKF is that it allows increased step lengths without degrading the estimation performance compared to the ODE based EKF.
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| 8. |
- Hou, Xueying, et al.
(författare)
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On channel quantization for multi-cell cooperative systems with limited feedback
- 2013
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Ingår i: Science in China, Series F: Information Sciences. - : Springer Science and Business Media LLC. - 1009-2757. ; 56:2, s. 168-022308
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Tidskriftsartikel (refereegranskat)abstract
- Coherent multi-cell cooperative transmission, also referred to as coordinated multi-point transmission (CoMP), is a promising strategy to provide high spectral efficiency for universal frequency reuse cellular systems. To report the required channel information to the transmitter in frequency division duplexing systems, limited feedback techniques are often applied. Considering that the average channel gains from multiple base stations (BSs) to one mobile station are different and the number of cooperative BSs may be dynamic, it is neither flexible nor compatible to employ a large codebook to directly quantize the CoMP channel. In this paper, we employ per-cell codebooks for quantizing local and cross channels. We first propose a codeword selection criterion, aiming at maximizing an estimated data rate for each user. The proposed criterion can be applied for an arbitrary number of receive antennas at each user and also for an arbitrary number of data streams transmitted to each user. Considering that the resulting optimal per-cell codeword selection for CoMP channel is of high complexity, we propose a serial codeword selection method that has low complexity but yields comparable performance to that of the optimal codeword selection. We evaluate the proposed codeword selection criterion and method using measured CoMP channels from an urban environment as well as simulations. The results demonstrate significant performance gain as compared to an existing low-complexity method.
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| 9. |
- Jia, D., et al.
(författare)
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Enhanced frameless slotted ALOHA protocol with Markov chains analysis
- 2018
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Ingår i: Science China Information Sciences. - : Science in China Press. - 1674-733X .- 1869-1919. ; 61:10
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, we propose a novel approach to enhance the performance of frameless slotted ALOHA (SA) protocol. We employ signature codes to help the receiver identify the packets contained in collisions, and use successive interference cancellation (SIC) for packet recovery. We model the proposed scheme as a two-state Markov model represented by a uni-partite graph. We evaluate the throughput, expected delay and average memory size of the proposed scheme, and optimize the proposed scheme to maximize the throughput. We show that the theoretical analysis matches well with simulation results. The throughput and expected delay of the proposed protocol outperform the conventional slotted ALOHA protocol significantly.
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| 10. |
- Jie, Xu, et al.
(författare)
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Energy efficient downlink MIMO transmission with linear precoding
- 2013
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Ingår i: Science China Information Sciences. - : Springer Science and Business Media LLC. - 1674-733X .- 1869-1919. ; 56:2, s. 022309-
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Tidskriftsartikel (refereegranskat)abstract
- Energy efficiency (EE) is becoming increasingly important for wireless cellular networks. This paper addresses EE optimization problems in downlink multiuser MIMO systems with linear precoding. Referring to different active transmit/receive antenna sets and transmission schemes as different modes, we propose a joint bandwidth/power optimization and mode switching scheme to maximize EE. With a specific mode, we prove that the optimal bandwidth and transmit power is either full transmit power or full bandwidth. After deriving the optimal bandwidth and transmit power, we further propose mode switching to select the mode with optimal EE. Since the optimal mode switching, i.e. exhaustive search, is too complex to implement, an alternative heuristic method is developed to decrease the complexity through reducing the search size and avoiding the EE calculation during each search. Through simulations, we demonstrate that the proposed methods can significantly improve EE and the performance is similar to the optimal exhaustive search.
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