-
[show abstract]
[hide abstract]
ABSTRACT: In orthogonal frequency division multiplexing systems, significant inter-carrier interference (ICI) caused by doubly selective
channels make challenge for reliable reception. In this paper, channel estimation and ICI cancellation are considered jointly.
Relying on the basis expansion model (BEM) of time-varying channel, the linear system model of transceiver is established,
and the corresponding joint optimization of the transmitted data and BEM coefficients is formulated. Due to the separability
of the data and BEM coefficients, we use cyclic minimizing technique to perform channel estimation and equalization alternately.
This yields a linear minimum mean square-error (LMMSE) channel estimator and a block MMSE equalizer respectively. The block
MMSE equalizer has complexity O(N
3), where N is the number of data subcarriers. To reduce the complexity, instead of equalizing all the data simultaneously,
we consider estimating each data symbol successively. This idea results in the per subcarrier interference canceller with
lower complexity O(N
2). Finally, an iterative receiver consisting of the data-aided LMMSE channel estimator and the successive interference canceller
is developed. Simulation results show the scheme is effective over the channel with relatively large Doppler spread.
KeywordsOFDM-Basis expansion model-Channel estimation-Inter-carrier interference-Doppler spread
Wireless Personal Communications 04/2012; 55(2):289-303. · 0.46 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Cognitive radios are expected to improve the capacity of wireless mesh network dramatically. In this paper, we model the channel heterogeneity, which is a unique feature in cognitive radios, and present a cross-layer design framework which jointly considers the spectrum sharing, scheduling and routing with the objective of minimizing the system total activation time, i.e., maximizing the system capacity. An algorithm is proposed to generate all of the system concurrent transmission link-channel sets. Based on that, the optimization framework is simplified to a LP (linear programming) problem, so the global optimal solution could be easily found. Simulation results verify the significant benefit for the cross-layer spectrum sharing in cognitive mesh networks.
Communications Technology and Applications, 2009. ICCTA '09. IEEE International Conference on; 11/2009
-
[show abstract]
[hide abstract]
ABSTRACT: In this paper, we propose a dynamic approach for transmission holdoff time in IEEE 802.16 mesh mode with Coordinated Distributed Scheduling scheme (C-DSCH). This scheme allows different nodes to use different holdoff time values according to current node need of the control-plane bandwidth. Nodes that need to establish data scheduling use small XmtHoldoffExp, while others use large XmtHoldoffExp. Simulation results show that the proposed dynamic approach can reduce unnecessary transmission delays and improve network throughput.
Wireless Communications, Networking and Mobile Computing, 2009. WiCom '09. 5th International Conference on; 10/2009
-
[show abstract]
[hide abstract]
ABSTRACT: Cross-layer design is critical for efficient utilization of the scarce radio resources under time varying wireless channel. In this paper, a cross-layer design architecture named CLIME is proposed, which introduces the theory of modern software engineering to analyze the coupling in protocol stack brought by cross-layer designs. CLIME has the following distinct advantages. Firstly, DSA mechanism is used to build a loose coupling system by separating cross-layer interaction's implementation from its management. Secondly, the modularity of protocol stack is considered to simplify the implementation of cross-layer interaction, while keeping good system architecture. Thirdly, CLIME supports query based local and global crosslayer interaction, and proposes a simple way to manage the consistency of multiple cross-layer designs. And simulation is done on time expense of different cross-layer interactions in CLIME.
Wireless Communications, Networking and Mobile Computing, 2009. WiCom '09. 5th International Conference on; 10/2009
-
[show abstract]
[hide abstract]
ABSTRACT: Although OFDMA is a candidate physical layer protocol for 802.16, there are few solutions for the wireless resource-allocating problem in OFDMA mesh network. In this paper, we study the current resource allocation methods in OFDM and OFDMA network, and introduce the architecture of OFDMA mesh network. We build a mathematic system model for the OFDMA mesh network, and propose a sophisticated ACO-based algorithm for wireless resource allocation. With our algorithm, we get acceptable solution, while fulfilling power and QoS constraints. Since our algorithm is easy to adapt to more realistic problems, it turns out to be a feasible method. The simulation result showed our algorithm is able to find a suboptimal answer for resource allocation in OFDMA mesh network.
Wireless Communications, Networking and Mobile Computing, 2009. WiCom '09. 5th International Conference on; 10/2009
-
[show abstract]
[hide abstract]
ABSTRACT: With the widely applications of mobile communication networks, end-to-end secure voice has become a very important research issue and has attracted many people¿s interests. A simple and effective method for end-to-end secure communication is to encrypt speech signal at user ends. But the use of encryption techniques leads to a hard problem that encrypted speech data can not be directly transmitted on mobile voice channel. In this paper, we propose a scheme for encrypted speech transmitting on GSM voice channel. Not only does this scheme offer a good method for encrypted speech accessing mobile voice channel by using a proposed special modem called smodem based on linear predictive coding (LPC) technique, but also it can ensure the encrypted data transmitting through GSM networks with sufficient accuracy so that the received data can be decrypted correctly at the receiver. Moreover, the proposed scheme has advantages of no change to the existing clear voice communication procedure, short time of call establishment and propagation delay, good interoperability over heterogeneous networks, and favorableness to encryption information hidden. The results of experiment show that the proposed scheme is feasible.
Computer Science and Computational Technology, 2008. ISCSCT '08. International Symposium on; 01/2009
-
IEEE Communications Letters. 01/2009; 13:826-828.
-
[show abstract]
[hide abstract]
ABSTRACT: Cross-layer interaction is an indispensable part of cross-layer design, which has been proved to greatly improve the performance of wireless networks. In this paper, a scheme for cross-layer interaction management (CLIM) is proposed. It has the following distinct advantages. Firstly, CLIM achieves efficiency by considering the modularity of protocol stack. Secondly, in CLIM, implementing cross-layer interaction is more flexible than before, because the way to access a layer¿s inner variable can be chosen freely, and will no longer be restricted to specific method like data sharing or signaling. Thirdly, CLIM maintains the good architecture of the wireless protocol stack by using DSA and message queue mechanism to manage the cross-layer interactions. CLIM can be amalgamated with 802.16 signalling system so as to make possible the use of multiple cross-layer designs in a 802.16 terminal.
Communication Systems, 2008. ICCS 2008. 11th IEEE Singapore International Conference on; 12/2008
-
[show abstract]
[hide abstract]
ABSTRACT: The LSP routing algorithm in MPLS becomes the core and hot topic of traffic engineering. This paper presents a new routing scheme that uses the current bandwidth availability and the traffic flow distribution to achieve traffic engineering in IP networks. It reduces the interference among competing flows by balancing the number and quantity of flows carried by a link to achieve efficient routing of MPLS bandwidth guaranteed LSPs. Simulation result shows the algorithm is better than other algorithms in reject ratio of the traffic requests, especially in computing time cost.
Wireless Communications, Networking and Mobile Computing, 2008. WiCOM '08. 4th International Conference on; 11/2008
-
[show abstract]
[hide abstract]
ABSTRACT: With variable code, variable power and variable rate, link adaptation has been shown to have significant benefits for high-speed wireless data transmission. In this paper, an adaptive modulation and coding (AMC) scheme applied to variable bit rate services is proposed for orthogonal frequency division multiplexing (OFDM) system. The objective is to maximize the spectral efficiency by adaptively selecting the code and allocating rate and power over the frequency band under the packet error rate constraint. Following analysis on rate-compatible punctured convolutional codes and linking adaptive techniques in OFDM, a sub-optimal AMC scheme with uniform power allocation is investigated. We realize the rate allocation by setting the instantaneous bit error rate to the average bit error rate which varies over different coding schemes. Simulation results indicate that the proposed scheme exhibits 4~8dB signal-noise-ratio gain relative to non-adaptive scheme. Compared to optimal scheme, the proposed scheme shows negligible loss at high SNR scenarios while the implementation complexity can be reduced significantly.
Innovative Computing Information and Control, 2008. ICICIC '08. 3rd International Conference on; 07/2008
-
[show abstract]
[hide abstract]
ABSTRACT: In this paper, a combined switched beam-forming and adaptive beam-forming algorithm is proposed for orthogonal frequency division multiplexing (OFDM) systems with antenna arrays in multi-path fading channels. Firstly, multiple beams are generated by using a set of known weight vectors to cover the direction of arrival (DOA) range from 0 to 360 degrees. Secondly, two adjacent beams, which contain the same delayed multi-path with the largest power, can be selected by calculating the correlation of each beam with a reference signal. Thirdly, the two selected beams are optimally combined by using adaptive beam- forming algorithms such as sample matrix inversion (SMI), etc. Computer simulation results show that the proposed algorithm has better performance than conventional MMSE based pre-FFT adaptive beam-forming algorithm in multi-path fading channels.
Wireless Communications, Networking and Mobile Computing, 2007. WiCom 2007. International Conference on; 10/2007
-
[show abstract]
[hide abstract]
ABSTRACT: This paper proposes a comb-type pilot inserted scheme and channel estimation technique for MIMO-OFDM systems. In the proposed scheme, the pilot tones sent by different transmit antennas can be superimposed on the same sub-carrier due to the pilot symbol orthogonality. This can save bandwidth and increase the system data rates. At the receiver, by separating the orthogonal pilot tones, the sampled frequency response could be obtained, and then used to track the whole channel frequency response in real time through interpolation. Due to the save of pilot sub-carriers and the real time tracking ability in the proposed algorithm, simulation results show effective performance in static and mobile situation.
Wireless Communications, Networking and Mobile Computing, 2007. WiCom 2007. International Conference on; 10/2007
-
Proceedings of the 8th ACIS International Conference on Software Engineering, Artificial Intelligence, Networking and Parallel/Distributed Computing, SNPD 2007, July 30 - August 1, 2007, Qingdao, China; 01/2007
-
[show abstract]
[hide abstract]
ABSTRACT: Resource allocation in multiuser OFDM systems is a complex nonlinear optimization problem. In order to avoid direct solution,
based on the analytical results of the problem of minimizing the total transmit power, a two-step subcarrier allocation algorithm
is presented. The algorithm reduces the total transmit power by reducing the achievable minimum transmit power value required
by each user. Subcarriers are allocated in the algorithm according to the data rate required by users and the channel characteristics.
The required number of subcarriers allocated to users does not need to be known in advance. The allocation process consists
of two steps: basic subcarrier allocation and residual subcarrier allocation. Numerical results demonstrate that the proposed
algorithm can reduce the total transmit power effectively.
Wireless Personal Communications 12/2006; 40(2):233-243. · 0.46 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: The classic detection algorithm of VBLAST, OSIC (ordered successive interference cancellation), is a good compromise between performance and complexity comparing to the optimum ML (maximum likelihood) algorithm. Due to the error propagation, the detection errors in the previous stages would degrade the accuracy of the forthcoming stages' detection and the overall performance of OSIC. We propose, in this paper, an POSIC (pairwise OSIC) algorithm aiming at reducing the errors in each detection stage and the numbers of the stages in the detection process to diminish the error propagation. Instead of detecting one substream in each stage, the POSIC algorithm using ML to jointly detect two strongest sub streams in each stage and then eliminate the contribution of the detected substreams from the received signals until all the transmitted substreams were detected
Wireless Communications, Networking and Mobile Computing, 2006. WiCOM 2006.International Conference on; 10/2006
-
[show abstract]
[hide abstract]
ABSTRACT: In modern wireless networks, call admission control (CAC) has received a lot of attention because of its central role for quality of service (QoS) provision. In this paper, a new admission control scheme using statistical priority queue (SQCAC) is proposed. Its objective is to get an optimal overall satisfaction for the customers in terms of an objective function defined in this paper. In SQCAC, handoff calls and new calls occupy the queue in basic station (BS) statistically. Handoff calls are given a higher probability to occupy the queue than new calls when the available bandwidth is used out. SQCAC can also provide a tradeoff between call block probability (CBP) and call dropping probability (CDP)
Wireless Communications, Networking and Mobile Computing, 2006. WiCOM 2006.International Conference on; 10/2006
-
[show abstract]
[hide abstract]
ABSTRACT: The transmission of video over wireless networks always confront the risk of packet-losses and bit-errors, which result in the rapid propagation of errors in both time and space and the quick degradation of the reconstructed video quality. In order to stop the error propagation, the traditional method is intra-frame refresh. This paper proposes a novel error-resilient method which names predictive picture refresh based on scene-context reference picture. When the unreliable wireless network requires high intra-frame-refresh rates, compared with the traditional method, our method can achieve apparent saving effect in frame bits while maintaining the similar quality
Wireless Communications, Networking and Mobile Computing, 2006. WiCOM 2006.International Conference on; 10/2006
-
[show abstract]
[hide abstract]
ABSTRACT: To combine the merits of symmetric key cryptosystem and public-key cryptosystem, the authors present a key distribution scheme based on both the Rabin public-key system and the Chinese remainder theorem (CRT) for conditional access system (CAS) in digital TV broadcast, in order to solve dynamic access control problems in user hierarchies. Due to the simplicity of key generation and derivation, the proposed scheme can greatly reduce the encrypting computation and transportation load in the meantime acquire high security. Dynamic access control problems, such as adding/deleting group, adding/deleting relationships and changing secret keys, are easily solved. The proposed scheme is also very suitable for the pay-per-view method
Advanced Communication Technology, 2006. ICACT 2006. The 8th International Conference; 03/2006
-
[show abstract]
[hide abstract]
ABSTRACT: This paper firstly reviews long range-dependence (LRD), self-similarity and scaling in network traffic traces. After remarking on several hierarchical MMPP models, we focus on a promising model. We search intrinsic orderliness and obtain approximate relations in the measured traffic trace by the AV estimator. Then, the paper gives a more accurate fitting approach for model parameters through interactive self-study method, which exploits two-level matches and shows its good efficiency. Finally some conclusions are given
Computational Intelligence for Modelling, Control and Automation, 2005 and International Conference on Intelligent Agents, Web Technologies and Internet Commerce, International Conference on; 12/2005
-
[show abstract]
[hide abstract]
ABSTRACT: A companding technique based on threshold is proposed to reduce the PAPR of OFDM signals. In this technique, only the signals, whose amplitudes are higher than the threshold, are compressed in the transmitter. Using a simple judgment process, the expanding operation is executed to the compressed signals in the receiver. Compared with other scheme, the threshold companding scheme effectively improves the performance of PAPR by introducing a simple threshold judgment process.
Wireless Communications, Networking and Mobile Computing, 2005. Proceedings. 2005 International Conference on; 10/2005
