For multiple-input multiple-output （MIMO） orthogonal frequency division multiplexing （OFDM） systems, a joint timing synchronization and frequency offset acquisition algorithm based on fractional Fourier transform ...For multiple-input multiple-output （MIMO） orthogonal frequency division multiplexing （OFDM） systems, a joint timing synchronization and frequency offset acquisition algorithm based on fractional Fourier transform （FRFT） is proposed. The linear frequency modulation signals superimposed on the data signals are used as the training signals. By performing FRFT on the received signals and searching the peak value of the FRFT results, the receiver can realize timing synchronization and frequency offset acquisition simultaneously. Compared with the existing methods, the proposed algorithm can provide better timing synchronization performance and larger frequency offset acquisition range even under multi-path channels with low signal to noise ratio. Theoretical analysis and simulation results prove this point.展开更多
Time synchronization is one of the important aspects in wireless sensor networks. Time synchronization assures that all the sensor nodes in wireless sensor network have the same clock time. There are various applicati...Time synchronization is one of the important aspects in wireless sensor networks. Time synchronization assures that all the sensor nodes in wireless sensor network have the same clock time. There are various applications such as seismic study, military applications, pollution monitoring where sensor nodes require synchronized time. Time synchronization is mandatory for many wireless sensor networks protocols such as MAC protocols and also important for TDMA scheduling for proper duty cycle coordination. Time synchronization is a stimulating problem in wireless sensor networks because each node has its own local clock which keeps on varying due to variation in the oscillator frequency. The oscillator frequency is time varying due to ambient conditions which leads to re-synchronization of nodes time and again. This re-synchronization process is energy consuming whereas energy is constraints in WSN. This paper proposes a novel cluster based time synchronization technique for wireless sensor networks in which cluster head rotation is based on minimum clock offset. Simulation results based on energy analysis of the proposed model demonstrate that proposed novel cluster based time synchronization technique reduces the energy consumption and also the synchronization error compared with other existing protocols.展开更多
In this paper, we consider the frequency offset estimation for Orthogonal Frequency-Division Multiple Access (OF-DMA) uplink (UL) transmissions. We first analyze the negative effect of Multi-Access-Interference (MAI) ...In this paper, we consider the frequency offset estimation for Orthogonal Frequency-Division Multiple Access (OF-DMA) uplink (UL) transmissions. We first analyze the negative effect of Multi-Access-Interference (MAI) on OFDMA UL, and then propose two interference reduction/elimination methods, i.e., the Reduced-Rank-Projector (RRP) and Shift-Sampling-Projector (SSP) methods, to eliminate/reduce the heavy MAI due to the frequency offsets. Finally, we propose a new training sequence group named the Round-Robin Training Sequence Group (RRTSG), which has a high interference mitigation capabilities for OFDMA UL transmission. The Cramer-Rao Lower Bound (CRLB) for an unbiased frequency offset estimator in a Multiple Access (MA) system is also derived. Numerical results show that the proposed methods are suitable to eliminate/mitigate the effect of the frequency offset on OFDMA UL transmission.展开更多
In this work we find a lower bound on the energy required for synchronizing moving sensor nodes in a Wireless Sensor Network (WSN) affected by large-scale fading, based on clock estimation techniques. The energy requi...In this work we find a lower bound on the energy required for synchronizing moving sensor nodes in a Wireless Sensor Network (WSN) affected by large-scale fading, based on clock estimation techniques. The energy required for synchronizing a WSN within a desired estimation error level is specified by both the transmit power and the required number of messages. In this paper we extend our previous work introducing nodes’ movement and the average message delay in the total energy, including a comprehensive analysis on how the distance between nodes impacts on the energy and synchronization quality trade-off under large-scale fading effects.展开更多
In this work, the existing trade-off between time synchronization quality and energy is studied for both large-scale and small-scale fading wireless channels. We analyze the clock offset estimation problem using one-w...In this work, the existing trade-off between time synchronization quality and energy is studied for both large-scale and small-scale fading wireless channels. We analyze the clock offset estimation problem using one-way, two-way and N-way message exchange mechanisms affected by Gaussian and exponentially distributed impairments. Our main contribution is a general relationship between the total energy required for synchronizing a wireless sensor network and the clock offset estimation error by means of the transmit power, number of transmitted messages and average message delay, deriving the energy optimal lower bound as a function of the time synchronization quality and the number of hops in a multi-hop network.展开更多
One of the important aspects in wireless sensor networks is time synchronization. Many applications such as military activity monitoring, environmental monitoring and forest fire monitoring require highly accurate tim...One of the important aspects in wireless sensor networks is time synchronization. Many applications such as military activity monitoring, environmental monitoring and forest fire monitoring require highly accurate time synchronization. Time synchronization assures that all the sensor nodes in wireless sensor network have the same clock time. It is not only essential for aforementioned applications but it is mandatory for TDMA scheduling and proper duty cycle coordination. Time synchronization is a challenging problem due to energy constraints. Most of the existing synchronization protocols use fixed nodes for synchronization, but in the proposed synchronization, algorithm mobile nodes are used to synchronize the stationary nodes in the sensing field. In this paper, we propose a new time synchronization algorithm, named controlled mobility time synchronization (CMTS) with the objective to achieve the higher accuracy while synchronizing the nodes. The proposed approach is used in this paper to synchronize the nodes externally by using the mobile nodes. Simulation results exhibit that proposed controlled mobility time synchronization increases the synchronization precision and reduces the energy consumption as well as synchronization error by reducing the collisions and retransmissions.展开更多
基金supported by the National Natural Science Foundation of China(60672047).
文摘For multiple-input multiple-output （MIMO） orthogonal frequency division multiplexing （OFDM） systems, a joint timing synchronization and frequency offset acquisition algorithm based on fractional Fourier transform （FRFT） is proposed. The linear frequency modulation signals superimposed on the data signals are used as the training signals. By performing FRFT on the received signals and searching the peak value of the FRFT results, the receiver can realize timing synchronization and frequency offset acquisition simultaneously. Compared with the existing methods, the proposed algorithm can provide better timing synchronization performance and larger frequency offset acquisition range even under multi-path channels with low signal to noise ratio. Theoretical analysis and simulation results prove this point.
文摘Time synchronization is one of the important aspects in wireless sensor networks. Time synchronization assures that all the sensor nodes in wireless sensor network have the same clock time. There are various applications such as seismic study, military applications, pollution monitoring where sensor nodes require synchronized time. Time synchronization is mandatory for many wireless sensor networks protocols such as MAC protocols and also important for TDMA scheduling for proper duty cycle coordination. Time synchronization is a stimulating problem in wireless sensor networks because each node has its own local clock which keeps on varying due to variation in the oscillator frequency. The oscillator frequency is time varying due to ambient conditions which leads to re-synchronization of nodes time and again. This re-synchronization process is energy consuming whereas energy is constraints in WSN. This paper proposes a novel cluster based time synchronization technique for wireless sensor networks in which cluster head rotation is based on minimum clock offset. Simulation results based on energy analysis of the proposed model demonstrate that proposed novel cluster based time synchronization technique reduces the energy consumption and also the synchronization error compared with other existing protocols.
文摘In this paper, we consider the frequency offset estimation for Orthogonal Frequency-Division Multiple Access (OF-DMA) uplink (UL) transmissions. We first analyze the negative effect of Multi-Access-Interference (MAI) on OFDMA UL, and then propose two interference reduction/elimination methods, i.e., the Reduced-Rank-Projector (RRP) and Shift-Sampling-Projector (SSP) methods, to eliminate/reduce the heavy MAI due to the frequency offsets. Finally, we propose a new training sequence group named the Round-Robin Training Sequence Group (RRTSG), which has a high interference mitigation capabilities for OFDMA UL transmission. The Cramer-Rao Lower Bound (CRLB) for an unbiased frequency offset estimator in a Multiple Access (MA) system is also derived. Numerical results show that the proposed methods are suitable to eliminate/mitigate the effect of the frequency offset on OFDMA UL transmission.
文摘In this work we find a lower bound on the energy required for synchronizing moving sensor nodes in a Wireless Sensor Network (WSN) affected by large-scale fading, based on clock estimation techniques. The energy required for synchronizing a WSN within a desired estimation error level is specified by both the transmit power and the required number of messages. In this paper we extend our previous work introducing nodes’ movement and the average message delay in the total energy, including a comprehensive analysis on how the distance between nodes impacts on the energy and synchronization quality trade-off under large-scale fading effects.
文摘In this work, the existing trade-off between time synchronization quality and energy is studied for both large-scale and small-scale fading wireless channels. We analyze the clock offset estimation problem using one-way, two-way and N-way message exchange mechanisms affected by Gaussian and exponentially distributed impairments. Our main contribution is a general relationship between the total energy required for synchronizing a wireless sensor network and the clock offset estimation error by means of the transmit power, number of transmitted messages and average message delay, deriving the energy optimal lower bound as a function of the time synchronization quality and the number of hops in a multi-hop network.
文摘One of the important aspects in wireless sensor networks is time synchronization. Many applications such as military activity monitoring, environmental monitoring and forest fire monitoring require highly accurate time synchronization. Time synchronization assures that all the sensor nodes in wireless sensor network have the same clock time. It is not only essential for aforementioned applications but it is mandatory for TDMA scheduling and proper duty cycle coordination. Time synchronization is a challenging problem due to energy constraints. Most of the existing synchronization protocols use fixed nodes for synchronization, but in the proposed synchronization, algorithm mobile nodes are used to synchronize the stationary nodes in the sensing field. In this paper, we propose a new time synchronization algorithm, named controlled mobility time synchronization (CMTS) with the objective to achieve the higher accuracy while synchronizing the nodes. The proposed approach is used in this paper to synchronize the nodes externally by using the mobile nodes. Simulation results exhibit that proposed controlled mobility time synchronization increases the synchronization precision and reduces the energy consumption as well as synchronization error by reducing the collisions and retransmissions.
