The integration of cognitive radio and Ultra wideband (UWB) networks has attracted lots of research interests. Cognitive UWB networks not only provide very high data rates but also guarantee the uninterrupted communic...The integration of cognitive radio and Ultra wideband (UWB) networks has attracted lots of research interests. Cognitive UWB networks not only provide very high data rates but also guarantee the uninterrupted communication of primary system operated in the same frequency band. In this work, the problem of the capacity analyses of cognitive UWB networks is investigated. Different from the conventional cognitive spectrum sharing model which can only utilize the idle spectrum hole, the cognitive UWB system can operate adaptively based on spectrum sensing results. Taking into account several factors such as the transmission power constraint of UWB, the interference constraint of the receivers in primary systems, the secondary UWB network capacity problem is modeled as a convex optimization problem over the transmission power. The optimal power allocation strategy and algorithm are derived based on this optimization problem. Two cases (Perfect Spectrum Sensing and Imperfect Spectrum Sensing) are studied in the paper. Numerical simulation results show that the proposed adaptive power allocationscheme improves the ergodic and outage capacity under both transmission power and interference constraints compared with constant transmission power scheme.展开更多
In this paper, the perfect dyadic binary sequence pair with one-value dyadic correlation functions is presented. That is, the perfect dyadic binary sequence pair is a perfect discrete signal, for its dyadic relative f...In this paper, the perfect dyadic binary sequence pair with one-value dyadic correlation functions is presented. That is, the perfect dyadic binary sequence pair is a perfect discrete signal, for its dyadic relative function is δ-function. The transformation features and some existing admissibility conditions of perfect dyadic binary sequence pair are discussed, and the properties for this kind of code in Walsh transformation spectrum and weight spectrum are also analyzed. From above, It is found that the perfect dyadic binary sequence pair can easily differentiate from its dyadic shifting. So these good signals can used in engineering as synchronization code, multi-user code and so on.展开更多
A rate adaptive multi-band ultra-wideband (UWB) system based on the quadrature fractal modulation (QFM) scheme was proposed.Exploring the use of homogeneous signals as modulating waveforms in UWB system,the signal wit...A rate adaptive multi-band ultra-wideband (UWB) system based on the quadrature fractal modulation (QFM) scheme was proposed.Exploring the use of homogeneous signals as modulating waveforms in UWB system,the signal within each 528MHz sub-band was divided into 8 different frequency bandwidths using wavelets transform and these data sequences to be transmitted were embedded into homogeneous waveforms.It is found that the use of homogeneous signals in such UWB system is quite feasible,leadings to a novel multi-rate diversity strategy.Within each 528MHz sub-band,the UWB-QFM system can provide much higher data rates than that of the UWB orthogonal frequency division multiplexing (OFDM) system.Simulation results also show that the bit error rate (BER) performance of the UWB-QFM system achieves a greatly improvement over existing UWB-OFDM system.Due to the fractal properties of the homogeneous signals,these data sequences to be transmitted can be recovered using arbitrarily short receiver signal.展开更多
Relay is considered as one of the candidate key technologies of LTE-advanced for it brings broader cell coverage and higher system capacity. Distributed Space-Time Coding （DSTC） not only exploits the spatial diversi...Relay is considered as one of the candidate key technologies of LTE-advanced for it brings broader cell coverage and higher system capacity. Distributed Space-Time Coding （DSTC） not only exploits the spatial diversity from the relay structure, but also brings some coding gains. According to the performances of existing DSTC schemes, the Demodulate-and-Forward （DMF） scheme is the best candidate for DSTC in LTE-Advanced system. Moreover, a threshold-based selective relaying scheme for DSTC is proposed to solve the error propagation of DMF. This scheme can achieve excellent performance gains at the cost of little system complexity.展开更多
This paper proposes a novel energy efficient unequal clustering algorithm for large scale wireless sensor network （WSN） which aims to balance the node power consumption and prolong the network lifetime as long as po...This paper proposes a novel energy efficient unequal clustering algorithm for large scale wireless sensor network （WSN） which aims to balance the node power consumption and prolong the network lifetime as long as possible. Our approach focuses on energy efficient unequal clustering scheme and inter-cluster routing protocol. On the one hand, considering each node＇s local information such as energy level, distance to base station and local density, we use fuzzy logic system to determine one node＇s chance of becoming cluster head and hand, adaptive max-min ant colony optimization is used to estimate the corresponding competence radius. On the other construct energy-aware inter-cluster routing between cluster heads and base station （BS）, which balances the energy consumption of cluster heads and alleviates the hot spots problem that occurs in multi-hop WSN routing protocol to a large extent. The confirmation experiment results have indicated the proposed clustering algorithm has more superior performance than other methods such as low energy adaptive clustering hierarchy （LEACH） and energy efficient unequal clustering （EEUC）.展开更多
基金supported by following projects:NSFC (No. 60432040, 60972079)Beijing Natural Science Foundation (No. 4052021)+1 种基金The Research Fund for the Doctoral Program of Higher Education(No.20060013008, 200700130293)UWB-ITRC Inha University, Korea,and iCHIP Project financed by Italian Ministry of Foreign Affairs,And it is partly supported by Project iCHIP financed by Italian Ministry of Foreign Affairs
文摘The integration of cognitive radio and Ultra wideband (UWB) networks has attracted lots of research interests. Cognitive UWB networks not only provide very high data rates but also guarantee the uninterrupted communication of primary system operated in the same frequency band. In this work, the problem of the capacity analyses of cognitive UWB networks is investigated. Different from the conventional cognitive spectrum sharing model which can only utilize the idle spectrum hole, the cognitive UWB system can operate adaptively based on spectrum sensing results. Taking into account several factors such as the transmission power constraint of UWB, the interference constraint of the receivers in primary systems, the secondary UWB network capacity problem is modeled as a convex optimization problem over the transmission power. The optimal power allocation strategy and algorithm are derived based on this optimization problem. Two cases (Perfect Spectrum Sensing and Imperfect Spectrum Sensing) are studied in the paper. Numerical simulation results show that the proposed adaptive power allocationscheme improves the ergodic and outage capacity under both transmission power and interference constraints compared with constant transmission power scheme.
基金Supported by the National Natural Science Foundation of China (No.60372097)Beijing Municipal Natural Science Foundation (No.4052021)University IT Re-search Center Project (INHA UWB-ITRC), Korea.
文摘In this paper, the perfect dyadic binary sequence pair with one-value dyadic correlation functions is presented. That is, the perfect dyadic binary sequence pair is a perfect discrete signal, for its dyadic relative function is δ-function. The transformation features and some existing admissibility conditions of perfect dyadic binary sequence pair are discussed, and the properties for this kind of code in Walsh transformation spectrum and weight spectrum are also analyzed. From above, It is found that the perfect dyadic binary sequence pair can easily differentiate from its dyadic shifting. So these good signals can used in engineering as synchronization code, multi-user code and so on.
基金National Natural Science Fund of China(60372097), Beijing Municipal Natural Science Fund(4052021),University IT Research Center Project(INHA UWB-ITRC)Korea, KDDI R&D Labs Co-Project, Japan.
文摘A rate adaptive multi-band ultra-wideband (UWB) system based on the quadrature fractal modulation (QFM) scheme was proposed.Exploring the use of homogeneous signals as modulating waveforms in UWB system,the signal within each 528MHz sub-band was divided into 8 different frequency bandwidths using wavelets transform and these data sequences to be transmitted were embedded into homogeneous waveforms.It is found that the use of homogeneous signals in such UWB system is quite feasible,leadings to a novel multi-rate diversity strategy.Within each 528MHz sub-band,the UWB-QFM system can provide much higher data rates than that of the UWB orthogonal frequency division multiplexing (OFDM) system.Simulation results also show that the bit error rate (BER) performance of the UWB-QFM system achieves a greatly improvement over existing UWB-OFDM system.Due to the fractal properties of the homogeneous signals,these data sequences to be transmitted can be recovered using arbitrarily short receiver signal.
基金supported by the National Basic Research Program of China ("973" Program) under Grant No.2007CB310602
文摘Relay is considered as one of the candidate key technologies of LTE-advanced for it brings broader cell coverage and higher system capacity. Distributed Space-Time Coding （DSTC） not only exploits the spatial diversity from the relay structure, but also brings some coding gains. According to the performances of existing DSTC schemes, the Demodulate-and-Forward （DMF） scheme is the best candidate for DSTC in LTE-Advanced system. Moreover, a threshold-based selective relaying scheme for DSTC is proposed to solve the error propagation of DMF. This scheme can achieve excellent performance gains at the cost of little system complexity.
基金supported by National Science and Technology Major Project of the Ministry of Science and Technology of China (2009ZX03006-006, 2009ZX03006-009)the National Natural Science Foundation of China (60902046, 60972079)
文摘This paper proposes a novel energy efficient unequal clustering algorithm for large scale wireless sensor network （WSN） which aims to balance the node power consumption and prolong the network lifetime as long as possible. Our approach focuses on energy efficient unequal clustering scheme and inter-cluster routing protocol. On the one hand, considering each node＇s local information such as energy level, distance to base station and local density, we use fuzzy logic system to determine one node＇s chance of becoming cluster head and hand, adaptive max-min ant colony optimization is used to estimate the corresponding competence radius. On the other construct energy-aware inter-cluster routing between cluster heads and base station （BS）, which balances the energy consumption of cluster heads and alleviates the hot spots problem that occurs in multi-hop WSN routing protocol to a large extent. The confirmation experiment results have indicated the proposed clustering algorithm has more superior performance than other methods such as low energy adaptive clustering hierarchy （LEACH） and energy efficient unequal clustering （EEUC）.
