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Data-aided synchronization algorithm dispensing with searching procedures for UWB communications

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Science china(Information Sciences) 2012年第4期55卷 778-788页

作者： REN ZhiYuan 1,JIANG Ting1,ZHONG Yi 2 & ZHAO ChengLin 1 1 Key laboratory of Universal wireless Communications,Ministry of Education of china wireless network laboratory,beijing university of posts and telecommunications,beijing 100876,china 2 School of Information Engineering,North china university of Technology,beijing 100041,china Key laboratory of Universal wireless Communications Ministry of Education of China wireless network laboratory Beijing University of Posts and Telecommunications Beijing China School of Information Engineering North China University of Technology Beijing China

Rapid and accurate synchronization constitutes a major challenge in deploying Ultra-Wideband impulse radio (UWB-IR) for indoor wireless *** paper develops a data-aided (DA) synchro-nization algorithm dispensing with searching procedures for UWB-IR *** adopting a stream of alternating orthogonal pulses,frame-level synchronization can be achieved without channel ***-out utilizing any searching procedure,the timing offset estimator is obtained in a closed *** exhaustive search can be avoided,both computational complexity and synchronization time are *** and comparisons are provided to illustrate the advantages of our design over the alternatives.

关键词： Ultra-Wideband impulse radio synchronization dispensing with searching procedures searching space data-aided estimation

Hopping control channel MAC protocol for opportunistic spectrum access networks

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The Journal of china Universities of posts and telecommunications 2010年第6期17卷 65-71页

作者： FU Jing-tuan,JI Hong,MAO Xu Key laboratory of Universal wireless Communications,Ministry of Education,beijing university of posts and telecommunications,beijing 100876,china Key laboratory of Universal wireless Communications Ministry of Education Beijing University of Posts and Telecommunications Beijing 100876 China

Opportunistic spectrum access （OSA） is considered as a promising approach to mitigate spectrum scarcity by allowing unlicensed users to exploit spectrum opportunities in licensed frequency bands. Derived from the existing channel-hopping multiple access （CHMA） protocol,we introduce a hopping control channel medium access control （MAC） protocol in the context of OSA networks. In our proposed protocol,all nodes in the network follow a common channel-hopping sequence; every frequency channel can be used as control channel and data channel. Considering primary users＇ occupancy of the channel,we use a primary user （PU） detection model to calculate the channel availability for unlicensed users＇ access. Then,a discrete Markov chain analytical model is applied to describe the channel states and deduce the system throughput. Through simulation,we present numerical results to demonstrate the throughput performance of our protocol and thus validate our work.

关键词： channel hopping MAC protocol OSA Markov chain

Bandwidth allocation and admission control scheme based on Nash bargaining solution for WiMAX systems

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The Journal of china Universities of posts and telecommunications 2010年第2期17卷 53-58页

作者： CAI Dao-jin ,JI Hong,LI Xi Key laboratory of Universal wireless Communications,Ministry of Education,beijing university of posts and telecommunications,beijing 100876,china Key laboratory of Universal wireless Communications Ministry of Education Beijing University of Posts and Telecommunications Beijing 100876 China

Development of fair and efficient bandwidth allocation and admission control schemes is one of the key issues in the design of IEEE 802.16 broadband wireless access systems in time division multiple access （TDMA） mode. In this article, the problem of bandwidth allocation and admission control is formulated as a Nash bargaining model. The nash bargaining solution （NBS） derived from the cooperative game is adopted to maximize the spectrum utilization. Analysis and simulation results show that there is a unique Pareto optimal bandwidth allocation solution by using NBS among various flows. Furthermore, maximum utility of the system can also be maintained by using the admission control policy with different number of connections and variable channel qualities. The total throughput of the proposed scheme is close to the maximal one, while significantly improving fairness compared to the existing solutions.

关键词： NBS game theory bandwidth allocation admission control IEEE 802.16

Search recommendation model based on user search behavior and gradual forgetting collaborative filtering strategy

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The Journal of china Universities of posts and telecommunications 2010年第3期17卷 110-117页

作者： LIU Chuan-chang State Key laboratory of networking and Switching Technology, beijing university of posts and telecommunications, beijing 100876, china State Key laboratory of networking and Switching Technology Beijing University of Posts and Telecommunications Beijing 100876 China

The existing search engines are lack of the consideration of personalization and display the same search results for different users despite their differences in interesting and purpose. By analyzing user＇s dynamic search behavior, the paper introduces a new method of using a keyword query graph to express user＇s dynamic search behavior, and uses Bayesian network to construct the prior probability of keyword selection and the migration probability between keywords for each user. To reflect the dynamic changes of the user＇s preference, the paper introduces non-lineal gradual forgetting collaborative filtering strategy into the personalized search recommendation model. By calculating the similarity between each two users, the model can do the recommendation based on neighbors and be used to construct the personalized search engine.

关键词： search recommendation model search behavior expression keyword query graph gradual forgetting collaborative filtering

On-demand coding-aware routing in wireless Mesh networks

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The Journal of china Universities of posts and telecommunications 2010年第5期17卷 80-86,92页

作者： SUN Jian-zhen,LIU Yuan-an,HU He-fei,YUAN Dong-ming wireless Communications and EMC laboratory,beijing university of posts and telecommunications,beijing 100876,china wireless Communications and EMC laboratory Beijing University of Posts and Telecommunications Beijing 100876 China

network coding,which exploits the broadcast nature of wireless medium,is an effective way to improve network performance in wireless multi-hop networks,but the first practical wireless network coding system COPE cannot actively detect a route with more coding opportunities and limit the coding structure within two-hop *** on-demand coding-aware routing scheme （OCAR） for wireless Mesh networks is proposed to overcome the limitations specified above by actively detecting a route with more coding opportunities along the entire route rather than within two-hop *** more coding opportunities tends to route multiple flows ‘close to each other’ while avoiding interference requires routing multiple flows ‘away from each other’.OCAR achieves a tradeoff by adopting RC AIA as routing metric in route discovery,which is not only coding-aware but also considers both inter and intra flow *** results show that,compared with Ad-hoc on-demand distance vecfor routing （AODV） and AODV＋COPE,OCAR can find more coding opportunities,thus effectively increase network throughput,reduce end to end delay and alleviate network congestion.

关键词： Mesh networks network coding coding-aware routing protocol

A novel adaptive spectrum forming filter:Application in cognitive ultra-wideband

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Science china(Information Sciences) 2010年第12期53卷 2584-2599页

作者： LI Bin ,ZHOU Zheng & ZOU WeiXia Key Lab of Universal wireless Communications,MOE.wireless network Lab,beijing university of posts and telecommunications,beijing 100876,china Key Lab of Universal wireless Communications MOE. Wireless Network Lab Beijing University of Posts and Telecommunications Beijing China

Ultra wideband impulse radio(UWB-IR) has important applications in high data rate communications,high precision positioning and penetrating target *** with cognitive radio(CR),UWB can also greatly alleviate the current spectrum ***,the existing UWB waveforms are faced with two *** spectrum utilization of UWB signal is rather low,which reduces the communication ***,it appears difficult for UWB-IR to avoid spectrum collision with other incumbent *** UWB will inevitably interfere other legal wireless *** by these considerations,we model the UWB waveform design into an interpolation *** on radial basis function neural network,a novel UWB pulse is presented in this *** UWB pulse is then realized though reasonable simplification on the already proposed theoretical *** designed UWB pulses can adaptively track the external spectral environment where UWB devices work and reconfigure its emission spectrum according to the state of primer users without any modification on *** frequency utilization is maximized when there is no active primary *** adequate spectrum avoidance has also been achieved without much spectrum utilization degradation within the non-primary *** and analysis show that our UWB-IR pulse is much superior to the other existing UWB signals in the frequency utilization,spectrum avoidance and in the transmission performance.

关键词： UWB-IR cognitive radio pulse design RBF network spectrum efficiency spectrum avoidance

Cross layer scheduling for real-time traffic in multiuser MIMO-OFDMA systems

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The Journal of china Universities of posts and telecommunications 2009年第3期16卷 24-29页

作者： SUN Qiao-yun,TIAN Hui,DONG Kun,ZHANG Ping Key laboratory of Universal wireless Communications,Ministry of Education,beijing university of posts and telecommunications,beijing 100876,china Key laboratory of Universal wireless Communications Ministry of Education Beijing University of Posts and Telecommunications Beijing 100876 China

A novel cross layer scheduling algorithm is proposed for real-time （RT） traffic in multiuser downlink multiple-input multiple-output orthogonal frequency division multiple access （MIMO-OFDMA） wireless systems. The algorithm dynamically allocates resources in space, time and frequency domain based on channel state information （CSI）, users＇ quality of service （QoS） requirements and queue state information （QSI）. To provide higher data rate and spectrum efficiency, adaptive modulation and coding （AMC） is employed. The proposed algorithm can improve cell throughput and increase the number of users that can be supported while guaranteeing users＇ QoS requirements and fairness among all users. Simulation results indicate that the proposed algorithm can achieve superior performance.

关键词： MIMO-OFDMA cross layer QoS AMC

Emergency access mechanism in IEEE 802.15.4 for wireless body area sensor networks

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The Journal of china Universities of posts and telecommunications 2009年第6期16卷 24-31页

作者： GUO Yan-yan,KANG Gui-xia,CAO Yu,ZHANG Ping Key laboratory of Universal wireless Communications,Ministry of Education,beijing university of posts and telecommunications,beijing 100876,china Key laboratory of Universal wireless Communications Ministry of Education Beijing University of Posts and Telecommunications Beijing 100876 China

IEEE 802.15.4 protocol has attracted much attention in research and industrial communities as candidate technology for wireless body area sensor networks（WBASNs）.IEEE 802.15.4 supports the exclusive use of a wireless channel through guaranteed time slot（GTS）.However,on one hand,bandwidth underutilization rate may be lower because of the variance between the guaranteed bandwidth and the arrival *** the other hand,the waiting time for transmitting emergency notification is getting longer when the GTSs assigned to the nodes increase in *** solve these problems,in this article,a new scheme is proposed to reduce transmission delay for the alarm notification in emergent *** results are presented to validate the efficiency of the proposed scheme by comparing it with the medium access control（MAC） protocol of IEEE 802.15.4.

关键词： WBASN GTS IEEE 802.15.4 emergency mechanism

Performance evaluation of channel inversion precoding for downlink multi-user MIMO system

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The Journal of china Universities of posts and telecommunications 2009年第5期16卷 20-24页

作者： CHEN Zhi-yong , WANG Wen-bo, PENG Mu-gen, LI Ren wireless Signal Processing and network laboratory, Key laboratory of Universal wireless Communication, Ministry of Education, beijing university of posts and telecommunications, beijing 100876, china wireless Signal Processing and network laboratory Key Laboratory of Universal Wireless Communication Ministry of Education Beijing University of Posts and Telecommunications Beijing 100876 China

In downlink multi-user multi-input multi-output （MU-MIMO） system, not every user （user equipment （UE）） can calculate accurately signal to interference and noise ratio （SINR） without prior knowledge of the other users＇ precoding vector. To solve this problem, this article proposes a channel inversion precoding scheme by using the lower bound of S1NR and zero-forcing （ZF） algorithm. However, the SINR mismatch between lower bound SINR and actual SINR causes the inaccurateness of adaptive modulation and coding （AMC）. As a result, it causes degradation in performance. Simulation results show that channel inversion precoding provides lower throughput than that of single user multi-input multi-output （SU-MIMO） at high signal-to-noise ratio （SNR）（〉14 dB）, due to the SINR mismatch, although the sum-rate of channel inversion precoding is higher than that of SU-MIMO at full SNR regime.

关键词： MU-MIMO channel inversion precoding CQI feedback AMC lower bound S1NR zero-forcing