Sensing the spectrum in a reliable and efficient manner is crucial to cognitive radio. To combat the channel fading suffered by the single radio, cooperative spectrum sensing is employed, to associate the detection of...Sensing the spectrum in a reliable and efficient manner is crucial to cognitive radio. To combat the channel fading suffered by the single radio, cooperative spectrum sensing is employed, to associate the detection of multiple radios. In this article, the optimization problem of detection efficiency under the constraint of detection probability is investigated, and an algorithm to evaluate the required radio number and sensing time for maximal detection efficiency is presented. To show the effect of cooperation on the detection efficiency, the proposed algorithm is applied to cooperative sensing using the spectral correlation detector under the Rayleigh flat fading channel.展开更多
To restrain the interference of co-channel users using space-time block coding （STBC）, the proposed Gaussian-forcing soft decision multi-user detection （GFSDMUD） algorithm is applied in fiat-fading channels by usi...To restrain the interference of co-channel users using space-time block coding （STBC）, the proposed Gaussian-forcing soft decision multi-user detection （GFSDMUD） algorithm is applied in fiat-fading channels by using the relation among the users＇ signals, which can enhance the capacity by introducing co-channel users. During iterations, extrinsic information is calculated and exchanged between a soft multi-user detector and a bank of turbo decoders to achieve refined estimates of the users＇ signals. The simulations show that the proposed iterative receiver techniques provide significant performance improvement around 2 dB over conventional noniterative methods. Furthermore, iterative multi-user space-time processing techniques offer substantial performance gains around 8 dB by adding the number of receiver antennas from 4 to 6, and the system performance can be enhanced by using this strategy in multi-user STBC systems, which is very important for enlarging the system capacity.展开更多
expenditures and operational expenditures （OPEX） （CAPEX） for operator, the coverage and capacity optimization （CCO） is one of the key use cases in long term evolution （LTE） self-organization network （SON）. I...expenditures and operational expenditures （OPEX） （CAPEX） for operator, the coverage and capacity optimization （CCO） is one of the key use cases in long term evolution （LTE） self-organization network （SON）. In LTE system, some factors （e.g. load, traffic type, user distribution, uplink power setting, inter-cell interference, etc.） limit the coverage and capacity performance. From the view of single cell, it always pursuits maximize performance of coverage and capacity by optimizing the uplink power setting and intra-cell resource allocation, but it may result in decreasing the performance of its neighbor cells. Therefore, the benefit of every cell conflicts each other. In order to tradeoff the benefit of every cell and maximize the performance of the whole network, this paper proposes a multi-cell uplink power allocation scheme based on non-cooperative games. The scheme aims to make the performance of coverage and capacity balanced by the negotiation of the uplink power parameters among multi-cells. So the performance of every cell can reach the Nash equilibrium, making it feasible to reduce the inter-cell interference by setting an appropriate uplink power parameter. Finally, the simulation result shows the proposed algorithm can effectively enhance the performance of coverage and capacity in LTE network.展开更多
In this paper a new automatic frequency control （AFC） scheme was proposed, which could be used for the receiver of low earth orbit （LEO） satellite communication system in continuous transmitting scenario. By emplo...In this paper a new automatic frequency control （AFC） scheme was proposed, which could be used for the receiver of low earth orbit （LEO） satellite communication system in continuous transmitting scenario. By employing the time varying characteristic of particle filter technique, the new scheme combined the preamble based estimating step and data based estimating step to provide initial probability density recursively. Theoretical analysis proved that the proposed AFC scheme could provide better performance than the two-step scheme. The same conclusion was achieved by computer simulations with the criteria of root-mean square （RMS） frequency estimating performance and bit error rate performance.展开更多
A novel adaptive power control and beam-forming joint optimization algorithm is proposed in cognitive radio （CR） underlay networks, where cognitive network share spectrum with primary network which spectrum is licen...A novel adaptive power control and beam-forming joint optimization algorithm is proposed in cognitive radio （CR） underlay networks, where cognitive network share spectrum with primary network which spectrum is licensed. In this paper, both primary base station （PBS） and cognitive base station （CBS） are all equipped with multi antennas, while each primary user （PU） and cognitive user （CU） has only one antenna. Different from traditional algorithms, an adaptive weight factor generating solution is supplied to different access users （both PUs and CUs） in this paper, and the different priority of users is also considered, because PUs have higher priority, the weight factor of PUs is fixed as constant and signal-to-interference and noise ratio （SINR） threshold is unchanged, while for CUs, it is set adaptively and SINR threshold is also changed accordingly. Using this algorithm, the transmit power is decreased, which relax the strict requirements for power amplifier in communication systems. And moreover, owing to PUS has fixed SINR threshold, the calculated SINR at receiver is nearly unchanged, but for CUs, the S1NR is changing with the adaptive weight factor. Under the assurance of quality of service （QoS） of PUs, the solution in this paper can enable CRs access to the CR network according to adaptive SINR threshold, therefore which supplies higher spectrum utilization efficiency.展开更多
Multi-cell processing （MCP） is capable of providing significant performance gain, but this improvement is accompanied by dramatic signaling overhead between cooperative base stations. Therefore, balancing the perfor...Multi-cell processing （MCP） is capable of providing significant performance gain, but this improvement is accompanied by dramatic signaling overhead between cooperative base stations. Therefore, balancing the performance gain and overhead growth is crucial for a practical multi-base cooperation scheme. In this paper, we propose a decentralized algorithm to jointly optimize the power allocation and beamforming vector with the goal of maximizing the system performance under the constraint of limited overhead signal and backhaul link capacity. In particular, combined with calculating the transmission beamforming vector according to the local channel state information, an adaptive power allocation is presented based on the result of sum capacity estimation. Furthermore, by utilizing the concept of cell clustering, the proposed framework can be implemented in a practical cellular system without major modification of network architecture. Simulation results demonstrate that the proposed scheme improves the system performance in terms of the sum capacity and cell-edge capacity.展开更多
This paper analyzed the structure of Orthogonal Frequency Division Multiplex （OFDM） system and presented a new Carrier Frequency Offset （CFO） tracking algorithm, which depends on comparability between the decision...This paper analyzed the structure of Orthogonal Frequency Division Multiplex （OFDM） system and presented a new Carrier Frequency Offset （CFO） tracking algorithm, which depends on comparability between the decision data and the original data to correct carrier frequency offset. Therefore it is robust during the normal communization process since the Bit Error Rate （BER） of the decision data is low. We can utilize pilot data in time domain for channel estimation to track CFO without reducing system efficient and to enhance the tracking scope largely. Simulation results denote the presented algorithm can track the frequency offset and control it under ± 1% using only 1 frame if the original frequency offset is within ±8% .展开更多
A novel scheme to joint phase noise （PHN） correcting and channel noise variance estimating for orthogonal frequency division multiplexing （OFDM） signal was proposed, The new scheme was based on the variational Bay...A novel scheme to joint phase noise （PHN） correcting and channel noise variance estimating for orthogonal frequency division multiplexing （OFDM） signal was proposed, The new scheme was based on the variational Bayes （VB） method and discrete cosine transform （DCT） approximation. Compared with the least squares （LS） based scheme, the proposed scheme could overcome the over-fitting phenomenon and thus lead to an improved performance. Computer simulations showed that the proposed VB based scheme outperforms the existing LS based scheme展开更多
This paper analyzes and simulates the performance of irregular low-density parity check(LDPC)codes on Rician fading channels.The authors also modified the brief propagation decoding algorithm,proved the symmetry and s...This paper analyzes and simulates the performance of irregular low-density parity check(LDPC)codes on Rician fading channels.The authors also modified the brief propagation decoding algorithm,proved the symmetry and showed the stability conditions of the channels,and calculated the Shannon limits on Rician channels in this paper.By using Visual C++programming to simulate the performance,the result indicates that when code length N=3,072 and code rate R=1/3,the difference with the Shannon limit is about 2 dB.Therefore,the performance of LDPC is also very effective on all kinds of channels,including the Rician kind.展开更多
文摘Sensing the spectrum in a reliable and efficient manner is crucial to cognitive radio. To combat the channel fading suffered by the single radio, cooperative spectrum sensing is employed, to associate the detection of multiple radios. In this article, the optimization problem of detection efficiency under the constraint of detection probability is investigated, and an algorithm to evaluate the required radio number and sensing time for maximal detection efficiency is presented. To show the effect of cooperation on the detection efficiency, the proposed algorithm is applied to cooperative sensing using the spectral correlation detector under the Rayleigh flat fading channel.
文摘To restrain the interference of co-channel users using space-time block coding （STBC）, the proposed Gaussian-forcing soft decision multi-user detection （GFSDMUD） algorithm is applied in fiat-fading channels by using the relation among the users＇ signals, which can enhance the capacity by introducing co-channel users. During iterations, extrinsic information is calculated and exchanged between a soft multi-user detector and a bank of turbo decoders to achieve refined estimates of the users＇ signals. The simulations show that the proposed iterative receiver techniques provide significant performance improvement around 2 dB over conventional noniterative methods. Furthermore, iterative multi-user space-time processing techniques offer substantial performance gains around 8 dB by adding the number of receiver antennas from 4 to 6, and the system performance can be enhanced by using this strategy in multi-user STBC systems, which is very important for enlarging the system capacity.
基金supported by the Key Project of Next Broadband Wireless Mobile Communication Network (2010ZX03003-001)the Key Science and Technology Achievement Transformation Project of Beijing Municipal Science & Technology Commission(Z101101054010004)
文摘expenditures and operational expenditures （OPEX） （CAPEX） for operator, the coverage and capacity optimization （CCO） is one of the key use cases in long term evolution （LTE） self-organization network （SON）. In LTE system, some factors （e.g. load, traffic type, user distribution, uplink power setting, inter-cell interference, etc.） limit the coverage and capacity performance. From the view of single cell, it always pursuits maximize performance of coverage and capacity by optimizing the uplink power setting and intra-cell resource allocation, but it may result in decreasing the performance of its neighbor cells. Therefore, the benefit of every cell conflicts each other. In order to tradeoff the benefit of every cell and maximize the performance of the whole network, this paper proposes a multi-cell uplink power allocation scheme based on non-cooperative games. The scheme aims to make the performance of coverage and capacity balanced by the negotiation of the uplink power parameters among multi-cells. So the performance of every cell can reach the Nash equilibrium, making it feasible to reduce the inter-cell interference by setting an appropriate uplink power parameter. Finally, the simulation result shows the proposed algorithm can effectively enhance the performance of coverage and capacity in LTE network.
基金supported by the National Basic Research Program of China (2009CB320401)the National Science and Technology Major Project of China (2012ZX03004005-002)+1 种基金the New Generation Broadband Wireless Mobile Communication Network of Major Special Projects (2010ZX03003-001)the Fundamental Research Funds for the Central Universities (2010PTB-03-04 G470220)
文摘In this paper a new automatic frequency control （AFC） scheme was proposed, which could be used for the receiver of low earth orbit （LEO） satellite communication system in continuous transmitting scenario. By employing the time varying characteristic of particle filter technique, the new scheme combined the preamble based estimating step and data based estimating step to provide initial probability density recursively. Theoretical analysis proved that the proposed AFC scheme could provide better performance than the two-step scheme. The same conclusion was achieved by computer simulations with the criteria of root-mean square （RMS） frequency estimating performance and bit error rate performance.
基金supported by the National Basic Research Program of China (2009CB320401)the Next Generation Broadband Wireless Mobile Communication Network of Major Special Projects(2010ZX03003-001,2012ZX03004-002)the National Natural Science Foundation of China (61171100)
文摘A novel adaptive power control and beam-forming joint optimization algorithm is proposed in cognitive radio （CR） underlay networks, where cognitive network share spectrum with primary network which spectrum is licensed. In this paper, both primary base station （PBS） and cognitive base station （CBS） are all equipped with multi antennas, while each primary user （PU） and cognitive user （CU） has only one antenna. Different from traditional algorithms, an adaptive weight factor generating solution is supplied to different access users （both PUs and CUs） in this paper, and the different priority of users is also considered, because PUs have higher priority, the weight factor of PUs is fixed as constant and signal-to-interference and noise ratio （SINR） threshold is unchanged, while for CUs, it is set adaptively and SINR threshold is also changed accordingly. Using this algorithm, the transmit power is decreased, which relax the strict requirements for power amplifier in communication systems. And moreover, owing to PUS has fixed SINR threshold, the calculated SINR at receiver is nearly unchanged, but for CUs, the S1NR is changing with the adaptive weight factor. Under the assurance of quality of service （QoS） of PUs, the solution in this paper can enable CRs access to the CR network according to adaptive SINR threshold, therefore which supplies higher spectrum utilization efficiency.
基金supported by the National Basic Research Program of China (2009CB320401)the National Natural Science Foundation of China (61171099)and the National Science and Technology Major Project of China (2012ZX03003-007)
文摘Multi-cell processing （MCP） is capable of providing significant performance gain, but this improvement is accompanied by dramatic signaling overhead between cooperative base stations. Therefore, balancing the performance gain and overhead growth is crucial for a practical multi-base cooperation scheme. In this paper, we propose a decentralized algorithm to jointly optimize the power allocation and beamforming vector with the goal of maximizing the system performance under the constraint of limited overhead signal and backhaul link capacity. In particular, combined with calculating the transmission beamforming vector according to the local channel state information, an adaptive power allocation is presented based on the result of sum capacity estimation. Furthermore, by utilizing the concept of cell clustering, the proposed framework can be implemented in a practical cellular system without major modification of network architecture. Simulation results demonstrate that the proposed scheme improves the system performance in terms of the sum capacity and cell-edge capacity.
基金This work is supported by National Natural Science Fundation of China(60372099) , and National "863" High Technology Projects of China(2001AA123016) .
文摘This paper analyzed the structure of Orthogonal Frequency Division Multiplex （OFDM） system and presented a new Carrier Frequency Offset （CFO） tracking algorithm, which depends on comparability between the decision data and the original data to correct carrier frequency offset. Therefore it is robust during the normal communization process since the Bit Error Rate （BER） of the decision data is low. We can utilize pilot data in time domain for channel estimation to track CFO without reducing system efficient and to enhance the tracking scope largely. Simulation results denote the presented algorithm can track the frequency offset and control it under ± 1% using only 1 frame if the original frequency offset is within ±8% .
基金supported by the National Basic Research Program of China (2009CB320401)the National Key Scientific and Technological Project of China (2012ZX03004005-002,2010ZX03003-001)the National Natural Science Foundation of China (61171099)
文摘A novel scheme to joint phase noise （PHN） correcting and channel noise variance estimating for orthogonal frequency division multiplexing （OFDM） signal was proposed, The new scheme was based on the variational Bayes （VB） method and discrete cosine transform （DCT） approximation. Compared with the least squares （LS） based scheme, the proposed scheme could overcome the over-fitting phenomenon and thus lead to an improved performance. Computer simulations showed that the proposed VB based scheme outperforms the existing LS based scheme
基金supported by the National Natural Science Foundation of China (No.60272052).
文摘This paper analyzes and simulates the performance of irregular low-density parity check(LDPC)codes on Rician fading channels.The authors also modified the brief propagation decoding algorithm,proved the symmetry and showed the stability conditions of the channels,and calculated the Shannon limits on Rician channels in this paper.By using Visual C++programming to simulate the performance,the result indicates that when code length N=3,072 and code rate R=1/3,the difference with the Shannon limit is about 2 dB.Therefore,the performance of LDPC is also very effective on all kinds of channels,including the Rician kind.
