Energy efficiency(EE)of downlink distributed antenna system(DAS)with multiple receive antennas is investigated over composite Rayleigh fading channel that takes the path loss and lognormal shadow fading into account.O...Energy efficiency(EE)of downlink distributed antenna system(DAS)with multiple receive antennas is investigated over composite Rayleigh fading channel that takes the path loss and lognormal shadow fading into account.Our aim is to maximize EE which is defined as the ratio of the transmission rate to the total consumed power under the constraints of the maximum transmit power of each remote antenna.According to the definition of EE,the optimized objective function is formulated with the help of Lagrangian method.By using the Karush-KuhnTucker(KKT)conditions and numerical calculation,considering both the static and dynamic circuit power consumptions,an adaptive energy efficient power allocation(PA)scheme is derived.This scheme is different from the conventional iterative PA schemes based on EE maximization since it can provide closed-form expression of PA coefficients.Moreover,it can obtain the EE performance close to the conventional iterative scheme and exhaustive search method while reducing the computation complexity greatly.Simulation results verify the effectiveness of the proposed scheme.展开更多
The problem of channel estimation for multiple an- tenna orthogonal frequency division multiplexing (OFDM) systems subject to unknown carrier frequency offset (CFO) is addressed. Multiple signal classification (M...The problem of channel estimation for multiple an- tenna orthogonal frequency division multiplexing (OFDM) systems subject to unknown carrier frequency offset (CFO) is addressed. Multiple signal classification (MUSIC)-Iike algorithm, which generally has been used for direction estimation or frequency estimation, is used for channel estimation in multiple antenna OFDM systems. A reduced dimensional (RD)-MUSIC based algorithm for channel estimation is proposed in multiple antenna OFDM systems with unknown CFO. The Cramer-Rao bound (CRB) of channel estimation in multiple antenna OFDM systems with unknown CFO is derived. The proposed algorithm has a superior performance of channel estimation compared with the Capon method and the least squares method.展开更多
Space-time coding is an important technique that can improve transmission performance at fading environments in mobile communication systems. In this paper, we propose a novel diversity scheme using spread spacetime b...Space-time coding is an important technique that can improve transmission performance at fading environments in mobile communication systems. In this paper, we propose a novel diversity scheme using spread spacetime block coding (SSTBC) in multiple antenna systems. At the transmitter, the primitive data are serial to parallel converted to multiple data streams, and each stream is rotated in constellation. Then Walsh codes are used to spread each symbol to all antenna space in a space-time block. The signals received from all receiver antennas are combined with the maximum ratio combining (MRC), equalized with linear equalizer to eliminate the inter-code interference and finally demodulated to recover to transmit data by using the one-symbol maximum likelihood detector. The proposed scheme does not sacrifice the spectrum efficiency meanwhile maintains the transceiver with low complexity. Owing to the transmission symbols of different transmit antennas passing through all the spatial subchannels between transceiver antenna pairs, the system obtains the partial additional space diversity gain of all spatial paths. It is also shown that the diversity gain is better than the previous space-time block coding (STBC) schemes with full transmission rate.展开更多
The complexity of the indoor environment brings great challenges to predict the electromagnetic radiation field of multiple antenna systems. Based on the Finite Difference Time Domain (FDTD) algorithm, using the mobil...The complexity of the indoor environment brings great challenges to predict the electromagnetic radiation field of multiple antenna systems. Based on the Finite Difference Time Domain (FDTD) algorithm, using the mobile phone shielding device as the multiple antenna systems example, the mobile phone shielding device's indoor electromagnetic radiation field is researched by measurment method and simulation method. The effectivity of prediction method is verified by comparing the prediciton results with the measurment results. About 80% of the error can be controlled less than dB. The quantitative research has certain guiding significance to the prediction of the multiple antenna systems radio wave propagation.展开更多
Worldwide Interoperability for Microwave Access (WiMAX) technology has rapidly developed in recent years. It is becoming one of the hotspots among broadband wireless access technologies. A WiMAX system can provide ban...Worldwide Interoperability for Microwave Access (WiMAX) technology has rapidly developed in recent years. It is becoming one of the hotspots among broadband wireless access technologies. A WiMAX system can provide bandwidth efficiency higher than 2 bps/Hz. In order to improve coverage and reliability of the WiMAX system,the IEEE 802.16 standard supports multiple antenna techniques such as Alamouti Space-Time Coding (STC),Adaptive Antenna System (AAS) and Multiple Input Multiple Output (MIMO). The applications of the multiple antenna techniques improve system capacity and bandwidth efficiency significantly,and enhance the competence of the WiMAX technology greatly.展开更多
The influence of cells groupings factor to the performance of the cells groupings time-shift pilot scheme is researched for the multiple cells large scale antennas systems(LSAS). The former researches have confirmed...The influence of cells groupings factor to the performance of the cells groupings time-shift pilot scheme is researched for the multiple cells large scale antennas systems(LSAS). The former researches have confirmed that the cells groupings time-shift pilots scheme is effective to reduce inter-cell interference, especially pilot contamination, which results from the pilot reuse in adjacent cells. However, they have not specified reasonable cells groupings factor, which plays a critical role in the general performance of the LSAS. Therefore, this problem is researched in details. The time for reverse-link data transmission will be compressed, when the groupings factor surpasses a certain range. Thus it is not always beneficial to increase the cells groupings factor without limitation. Furthermore,a reasonable cells groupings factor is deduced from the perspective of optimization to enhance the system performance. Simulations verify the proposed cell grouping factor.展开更多
This paper investigates the effects of the outdated channel state information(CSI)on the secrecy performance of an underlay spectrum sharing cognitive radio networks(CRNs),where the secondary user(SU)source node(Alice...This paper investigates the effects of the outdated channel state information(CSI)on the secrecy performance of an underlay spectrum sharing cognitive radio networks(CRNs),where the secondary user(SU)source node(Alice)aims to transmit the trusted messages to the full-duplex(FD)aided SU receiver(Bob)with the assistance of cooperative relay(Relay).Considering the impact of feedback delay,outdated CSI will aggravate the system performance.To tackle such challenge,the collaborative zero-forcing beamforming(ZFB)scheme of FD technique is further introduced to implement jamming so as to confuse the eavesdropping and improve the security performance of the system.Under such setup,the exact and asymptotic expressions of the secrecy outage probability(SOP)under the outdated CSI case are derived,respectively.The results reveal that i)the outdated CSI of the SU transmission channel will decrease the diversity gain from min(NANR,NRNB)to NRwith NA,NRand NBbeing the number of antennas of Alice,Relay and Bob,respectively,ii)the introduction of FD technique can improve coding gain and enhance system performance.展开更多
Mutual coupling reduction or isolation enhancement in antenna arrays is an important area of research as it severely affects the performance of an antenna.In this paper,a new type of compact and highly isolated Multip...Mutual coupling reduction or isolation enhancement in antenna arrays is an important area of research as it severely affects the performance of an antenna.In this paper,a new type of compact and highly isolated Multiple-Input-Multiple-Output(MIMO)antenna for ultra-wideband(UWB)applications is presented.The design consists of four radiators that are orthogonally positioned and confined to a compact 40×40×0.8 mm3 space.The final antenna design uses an inverted L shape partial ground to produce an acceptable reflection coefficient(S11<−10 dB)in an entire UWB band(3.1–10.6)giga hertz(GHz).Moreover,the inter-element isolation has also been enhanced to>20 db for majority of the UWB band.The antenna was fabricated and tested with the vector network analyzer(VNA)and in an anechoic chamber for scattering parameters and radiation patterns.Furthermore,different MIMO diversity performance metrics are also measured to validate the proposed model.The simulation results and the experimental results from the constructed model agree quite well.The proposed antenna is compared with similar designs in recently published literature for various performance metrics.Because of its low envelope correlation coefficient(ECC<0.1),high diversity gain(DG>9.99 dB),peak gain of 4.6 dB,reduced channel capacity loss(CCL<0.4 b/s/Hz),and average radiation efficiency of over 85%,the proposed MIMO antenna is ideally suited for practical UWB applications.展开更多
The 5th generation mobile communications aims at connecting everything and future Internet of Things(IoT)will get everything smartly connected.To realize it,there exist many challenges.One key challenge is the battery...The 5th generation mobile communications aims at connecting everything and future Internet of Things(IoT)will get everything smartly connected.To realize it,there exist many challenges.One key challenge is the battery problem for small devices,such as sensors or tags.Batteryless backscatter,also referred to as or battery-free backscatter,is a new potential technology to address this problem.One early and typical type of batteryless backscatter is ambient backscatter.Generally,batteryless backscatter utilizes environmental wireless signals to enable battery-free devices to communicate with each other.These devices first harvest energy from ambient wireless signals and then backscatter these signals so as to transmit their own information.This paper reviews the current studies about batteryless backscatter,including various backscatter schemes and theoretical works,and then introduces open problems for future research.展开更多
This paper investigates the transmission scheme of the orthogonal time frequency space(OTFS)system with multiple antennas.Previous works have studied the multi-antenna transmitter diversity scheme with the ideal pulse...This paper investigates the transmission scheme of the orthogonal time frequency space(OTFS)system with multiple antennas.Previous works have studied the multi-antenna transmitter diversity scheme with the ideal pulse shaping in OTFS systems assuming the wireless channels of two consecutive frames duration are invariant.However,the ideal pulse shaping can not be realized in practice and the channel varies rapidly in two consecutive frames in the high-speed mobility scenarios.To this end,we redesign the multi-antenna transmitter diversity scheme to ensure its practicability in the rectangular-pulsebased OTFS systems.At first,the information symbols of each antenna are divided into two half frames along the Doppler domain.Then,the guard symbols are carefully arranged to eliminate the interference between two half frames,and to ensure the equivalent channels of two half frames being identical.By considering the positions of the guard symbols,the transmission codeword is designed and a low complexity linear detection is proposed.Finally,simulation results validate that the bit error rate performance of the proposed scheme has the superiority over the existing works.展开更多
Spectrum sensing with multiple antennas for cognitive radio systems in microcell environments is affected by the spatial correlation among multiple antennas.To reduce the adverse effects of the spatial correlation on ...Spectrum sensing with multiple antennas for cognitive radio systems in microcell environments is affected by the spatial correlation among multiple antennas.To reduce the adverse effects of the spatial correlation on the spectrum sensing performance,we employ multiple dual polarization antennas at the sensing node of secondary users.The analysis of the spatial correlation is derived using the propagation characteristics of the electromagnetic wave based on the scattering patch model in a multipath microcell environment.The superiority of spectrum sensing with multiple dual polarized antennas over multiple mono-polarized antennas is shown by analyzing the false alarm and detection probabilities with the correlation among the antennas in a microcell environment.展开更多
Recent research challenges in the wireless communication include the usage of diversity and efficient coding to improve data transmission quality and spectral efficiency. Space diversity uses multiple transmitting and...Recent research challenges in the wireless communication include the usage of diversity and efficient coding to improve data transmission quality and spectral efficiency. Space diversity uses multiple transmitting and/or receiving antennas to create independent fading channels without penalty in bandwidth efficiency. Space-time block coding is an encoding scheme for communication over Rayleigh fading channels using multiple transmitting antennas. Space-time block codes from complex orthogonal designs exist only for two transmitting antennas. This paper generalizes a new complex orthogonal space-time block code for four transmitting antennas, whose decoding complexity is very low. Simulations show that the generalized complex orthogonal space-time block code has low bit error rate, full rate and possibly large diversity.展开更多
A new quasi-orthogonal space-time block code (QO-STBC) based on ABBA code with lower decoding complexity and higher bit error statistics (BER) performance was proposed by U. Park recently, which can obtain full tr...A new quasi-orthogonal space-time block code (QO-STBC) based on ABBA code with lower decoding complexity and higher bit error statistics (BER) performance was proposed by U. Park recently, which can obtain full transmission rate and full diversity. In this article, the authors proposed an improved U. Park scheme based on rotational ABBA code. For eliminating the interference terms resulting from neighboring signals during signal detection, two different matrixes are used. And independent decoding can be realized when maximum-likelihood decoding at the receiver is used. Simulation results demonstrate that the BER performance is improved dramatically without increasing the decoding complexity compared with U. Park scheme.展开更多
Rapid growth in mobile computing and other wireless multimedia services isinspiring many research and development activities on high-speed wireless communication systems.Main challenges in this area include the develo...Rapid growth in mobile computing and other wireless multimedia services isinspiring many research and development activities on high-speed wireless communication systems.Main challenges in this area include the development of efficient coding and modulation signalprocessing techniques for improving the quality and spectral efficiency of wireless systems. Therecently emerged space-time coding and signal processing techniques for wireless communicationsystems employing multiple transmit and receive antennas offer a powerful paradigm for meeting thesechallenges. This paper provides an overview on the recent development in space-time coding andsignal processing techniques for multiple-input multiple-output (MIMO) communication systems. Wefirst review the information theoretic results on the capacities of wireless systems employingmultiple transmit and receive antennas. We then describe two representative categories of space-timesystems, namely, the BLAST system and the space-time block coding system, both of which have beenproposed for next-generation high-speed wireless system. Signal processing techniques for channelestimation and decoding in space-time systems are also discussed. Finally, some other coding andsignal processing techniques for wireless systems employing multiple transmit and receive antennasthat are currently under intensive research are also briefly touched upon.展开更多
This article studies the closed-form expressions of outage performance for opportunistic relay under aggregate power constraint in decode-and-forward (DF) relay networks over Rayleigh fading channels, assuming that ...This article studies the closed-form expressions of outage performance for opportunistic relay under aggregate power constraint in decode-and-forward (DF) relay networks over Rayleigh fading channels, assuming that multiple antennas are available at the relay node. According to whether instantaneous signal-to-noise ratio (SNR) or average SNR can be utilized for relay selection, two opportunistic relay schemes, opportunistic multi-antenna relay selection (OMRS) and average best relay selection (ABRS) are proposed. The performances of both two schemes are evaluated by means of theoretical analysis and simulation, it is observed that OMRS is outage-optimal among multi-antenna relay selection schemes and closely approaches the beamforming (BF) scheme known as theoretical outage-optimal. Compared with previous single-antenna opportunistic relaying (OR) scheme, OMRS brings remarkable performance improvement, which is obtained from maximum ratio combining (MRC) and beamforming techniques. It is also shown that the performance of ABRS in asymmetric channels is close to OMRS in the low and median SNR range.展开更多
基金supported by the National Natural Science Foundation of China(Nos.61571225,61571224)the Fundamental Research Funds for the Central Universities+2 种基金the Research Founding of Graduate Innovation Center in NUAA (No.kfjj20160409)the Qing Lan Project of Jiangsu,Shenzhen Strategic Emerging Industry Development Funds(No.JSGG20150331160845693)the Six Talent Peaks Project in Jiangsu Province(No.DZXX-007)
文摘Energy efficiency(EE)of downlink distributed antenna system(DAS)with multiple receive antennas is investigated over composite Rayleigh fading channel that takes the path loss and lognormal shadow fading into account.Our aim is to maximize EE which is defined as the ratio of the transmission rate to the total consumed power under the constraints of the maximum transmit power of each remote antenna.According to the definition of EE,the optimized objective function is formulated with the help of Lagrangian method.By using the Karush-KuhnTucker(KKT)conditions and numerical calculation,considering both the static and dynamic circuit power consumptions,an adaptive energy efficient power allocation(PA)scheme is derived.This scheme is different from the conventional iterative PA schemes based on EE maximization since it can provide closed-form expression of PA coefficients.Moreover,it can obtain the EE performance close to the conventional iterative scheme and exhaustive search method while reducing the computation complexity greatly.Simulation results verify the effectiveness of the proposed scheme.
基金supported by the National Natural Science Foundation of China(6137116961301108+1 种基金61071164)the Fundamental Research Funds for the Central Universities(NS2013024)
文摘The problem of channel estimation for multiple an- tenna orthogonal frequency division multiplexing (OFDM) systems subject to unknown carrier frequency offset (CFO) is addressed. Multiple signal classification (MUSIC)-Iike algorithm, which generally has been used for direction estimation or frequency estimation, is used for channel estimation in multiple antenna OFDM systems. A reduced dimensional (RD)-MUSIC based algorithm for channel estimation is proposed in multiple antenna OFDM systems with unknown CFO. The Cramer-Rao bound (CRB) of channel estimation in multiple antenna OFDM systems with unknown CFO is derived. The proposed algorithm has a superior performance of channel estimation compared with the Capon method and the least squares method.
基金This project was supported by the National Science Foundation of China (60496314)
文摘Space-time coding is an important technique that can improve transmission performance at fading environments in mobile communication systems. In this paper, we propose a novel diversity scheme using spread spacetime block coding (SSTBC) in multiple antenna systems. At the transmitter, the primitive data are serial to parallel converted to multiple data streams, and each stream is rotated in constellation. Then Walsh codes are used to spread each symbol to all antenna space in a space-time block. The signals received from all receiver antennas are combined with the maximum ratio combining (MRC), equalized with linear equalizer to eliminate the inter-code interference and finally demodulated to recover to transmit data by using the one-symbol maximum likelihood detector. The proposed scheme does not sacrifice the spectrum efficiency meanwhile maintains the transceiver with low complexity. Owing to the transmission symbols of different transmit antennas passing through all the spatial subchannels between transceiver antenna pairs, the system obtains the partial additional space diversity gain of all spatial paths. It is also shown that the diversity gain is better than the previous space-time block coding (STBC) schemes with full transmission rate.
基金Supported by the State Environmental Protection Commonweal Industry Research Special of China (No.200909106)
文摘The complexity of the indoor environment brings great challenges to predict the electromagnetic radiation field of multiple antenna systems. Based on the Finite Difference Time Domain (FDTD) algorithm, using the mobile phone shielding device as the multiple antenna systems example, the mobile phone shielding device's indoor electromagnetic radiation field is researched by measurment method and simulation method. The effectivity of prediction method is verified by comparing the prediciton results with the measurment results. About 80% of the error can be controlled less than dB. The quantitative research has certain guiding significance to the prediction of the multiple antenna systems radio wave propagation.
文摘Worldwide Interoperability for Microwave Access (WiMAX) technology has rapidly developed in recent years. It is becoming one of the hotspots among broadband wireless access technologies. A WiMAX system can provide bandwidth efficiency higher than 2 bps/Hz. In order to improve coverage and reliability of the WiMAX system,the IEEE 802.16 standard supports multiple antenna techniques such as Alamouti Space-Time Coding (STC),Adaptive Antenna System (AAS) and Multiple Input Multiple Output (MIMO). The applications of the multiple antenna techniques improve system capacity and bandwidth efficiency significantly,and enhance the competence of the WiMAX technology greatly.
基金supported by the National Natural Science Foundation of China(6110602261574013)
文摘The influence of cells groupings factor to the performance of the cells groupings time-shift pilot scheme is researched for the multiple cells large scale antennas systems(LSAS). The former researches have confirmed that the cells groupings time-shift pilots scheme is effective to reduce inter-cell interference, especially pilot contamination, which results from the pilot reuse in adjacent cells. However, they have not specified reasonable cells groupings factor, which plays a critical role in the general performance of the LSAS. Therefore, this problem is researched in details. The time for reverse-link data transmission will be compressed, when the groupings factor surpasses a certain range. Thus it is not always beneficial to increase the cells groupings factor without limitation. Furthermore,a reasonable cells groupings factor is deduced from the perspective of optimization to enhance the system performance. Simulations verify the proposed cell grouping factor.
基金supported by the National Natural Science Foundation of China(No.62201606 and No.62071486)the Project of Science and Technology Planning of Guizhou Province(No.[2020]-030)+3 种基金the Project of Science and Technology Fund of Guizhou Provincial Health Commission(gzwkj2022524)the Project of Youth Science and Technology Talent Growth Guizhou Provincial Department of Education(No.KY[2021]230)the Key Research Base Project of Humanities and Social Sciences of Education Department of Guizhou Provincethe Project of Science and Technology Planning of Zunyi City(No.2022-381 and No.2022-384)。
文摘This paper investigates the effects of the outdated channel state information(CSI)on the secrecy performance of an underlay spectrum sharing cognitive radio networks(CRNs),where the secondary user(SU)source node(Alice)aims to transmit the trusted messages to the full-duplex(FD)aided SU receiver(Bob)with the assistance of cooperative relay(Relay).Considering the impact of feedback delay,outdated CSI will aggravate the system performance.To tackle such challenge,the collaborative zero-forcing beamforming(ZFB)scheme of FD technique is further introduced to implement jamming so as to confuse the eavesdropping and improve the security performance of the system.Under such setup,the exact and asymptotic expressions of the secrecy outage probability(SOP)under the outdated CSI case are derived,respectively.The results reveal that i)the outdated CSI of the SU transmission channel will decrease the diversity gain from min(NANR,NRNB)to NRwith NA,NRand NBbeing the number of antennas of Alice,Relay and Bob,respectively,ii)the introduction of FD technique can improve coding gain and enhance system performance.
基金Deanship of ScientificResearch,King Abdulaziz University for providing financial vide grant number (KEP-MSc-41-135-1443).
文摘Mutual coupling reduction or isolation enhancement in antenna arrays is an important area of research as it severely affects the performance of an antenna.In this paper,a new type of compact and highly isolated Multiple-Input-Multiple-Output(MIMO)antenna for ultra-wideband(UWB)applications is presented.The design consists of four radiators that are orthogonally positioned and confined to a compact 40×40×0.8 mm3 space.The final antenna design uses an inverted L shape partial ground to produce an acceptable reflection coefficient(S11<−10 dB)in an entire UWB band(3.1–10.6)giga hertz(GHz).Moreover,the inter-element isolation has also been enhanced to>20 db for majority of the UWB band.The antenna was fabricated and tested with the vector network analyzer(VNA)and in an anechoic chamber for scattering parameters and radiation patterns.Furthermore,different MIMO diversity performance metrics are also measured to validate the proposed model.The simulation results and the experimental results from the constructed model agree quite well.The proposed antenna is compared with similar designs in recently published literature for various performance metrics.Because of its low envelope correlation coefficient(ECC<0.1),high diversity gain(DG>9.99 dB),peak gain of 4.6 dB,reduced channel capacity loss(CCL<0.4 b/s/Hz),and average radiation efficiency of over 85%,the proposed MIMO antenna is ideally suited for practical UWB applications.
基金This paper is funded by Scientific Research Program of Beijing Municipal Commission of Education No.KM201910853003.
文摘The 5th generation mobile communications aims at connecting everything and future Internet of Things(IoT)will get everything smartly connected.To realize it,there exist many challenges.One key challenge is the battery problem for small devices,such as sensors or tags.Batteryless backscatter,also referred to as or battery-free backscatter,is a new potential technology to address this problem.One early and typical type of batteryless backscatter is ambient backscatter.Generally,batteryless backscatter utilizes environmental wireless signals to enable battery-free devices to communicate with each other.These devices first harvest energy from ambient wireless signals and then backscatter these signals so as to transmit their own information.This paper reviews the current studies about batteryless backscatter,including various backscatter schemes and theoretical works,and then introduces open problems for future research.
基金supported in part by the Fundamental Research Funds for the Central Universities under Grants 2020JBM081 and 2020JBZD005in part by the National Key R&D Program of China under Grant 2020YFB1806903in part by the National Natural Science Foundation under Grant U1834210。
文摘This paper investigates the transmission scheme of the orthogonal time frequency space(OTFS)system with multiple antennas.Previous works have studied the multi-antenna transmitter diversity scheme with the ideal pulse shaping in OTFS systems assuming the wireless channels of two consecutive frames duration are invariant.However,the ideal pulse shaping can not be realized in practice and the channel varies rapidly in two consecutive frames in the high-speed mobility scenarios.To this end,we redesign the multi-antenna transmitter diversity scheme to ensure its practicability in the rectangular-pulsebased OTFS systems.At first,the information symbols of each antenna are divided into two half frames along the Doppler domain.Then,the guard symbols are carefully arranged to eliminate the interference between two half frames,and to ensure the equivalent channels of two half frames being identical.By considering the positions of the guard symbols,the transmission codeword is designed and a low complexity linear detection is proposed.Finally,simulation results validate that the bit error rate performance of the proposed scheme has the superiority over the existing works.
基金Project supported by the Brain Korea 21 Plus of Korea and the Ministry of Trade,Industry&Energy(MOTIE)IDEC Platform Center(IPC)for Smart Car of Korea
文摘Spectrum sensing with multiple antennas for cognitive radio systems in microcell environments is affected by the spatial correlation among multiple antennas.To reduce the adverse effects of the spatial correlation on the spectrum sensing performance,we employ multiple dual polarization antennas at the sensing node of secondary users.The analysis of the spatial correlation is derived using the propagation characteristics of the electromagnetic wave based on the scattering patch model in a multipath microcell environment.The superiority of spectrum sensing with multiple dual polarized antennas over multiple mono-polarized antennas is shown by analyzing the false alarm and detection probabilities with the correlation among the antennas in a microcell environment.
文摘Recent research challenges in the wireless communication include the usage of diversity and efficient coding to improve data transmission quality and spectral efficiency. Space diversity uses multiple transmitting and/or receiving antennas to create independent fading channels without penalty in bandwidth efficiency. Space-time block coding is an encoding scheme for communication over Rayleigh fading channels using multiple transmitting antennas. Space-time block codes from complex orthogonal designs exist only for two transmitting antennas. This paper generalizes a new complex orthogonal space-time block code for four transmitting antennas, whose decoding complexity is very low. Simulations show that the generalized complex orthogonal space-time block code has low bit error rate, full rate and possibly large diversity.
文摘A new quasi-orthogonal space-time block code (QO-STBC) based on ABBA code with lower decoding complexity and higher bit error statistics (BER) performance was proposed by U. Park recently, which can obtain full transmission rate and full diversity. In this article, the authors proposed an improved U. Park scheme based on rotational ABBA code. For eliminating the interference terms resulting from neighboring signals during signal detection, two different matrixes are used. And independent decoding can be realized when maximum-likelihood decoding at the receiver is used. Simulation results demonstrate that the BER performance is improved dramatically without increasing the decoding complexity compared with U. Park scheme.
文摘Rapid growth in mobile computing and other wireless multimedia services isinspiring many research and development activities on high-speed wireless communication systems.Main challenges in this area include the development of efficient coding and modulation signalprocessing techniques for improving the quality and spectral efficiency of wireless systems. Therecently emerged space-time coding and signal processing techniques for wireless communicationsystems employing multiple transmit and receive antennas offer a powerful paradigm for meeting thesechallenges. This paper provides an overview on the recent development in space-time coding andsignal processing techniques for multiple-input multiple-output (MIMO) communication systems. Wefirst review the information theoretic results on the capacities of wireless systems employingmultiple transmit and receive antennas. We then describe two representative categories of space-timesystems, namely, the BLAST system and the space-time block coding system, both of which have beenproposed for next-generation high-speed wireless system. Signal processing techniques for channelestimation and decoding in space-time systems are also discussed. Finally, some other coding andsignal processing techniques for wireless systems employing multiple transmit and receive antennasthat are currently under intensive research are also briefly touched upon.
基金supported by the Hi-Tech Research and Development Program of China (2009AA01Z247,2007AA01Z265)the National Natural Science Foundation of China (60972076)
文摘This article studies the closed-form expressions of outage performance for opportunistic relay under aggregate power constraint in decode-and-forward (DF) relay networks over Rayleigh fading channels, assuming that multiple antennas are available at the relay node. According to whether instantaneous signal-to-noise ratio (SNR) or average SNR can be utilized for relay selection, two opportunistic relay schemes, opportunistic multi-antenna relay selection (OMRS) and average best relay selection (ABRS) are proposed. The performances of both two schemes are evaluated by means of theoretical analysis and simulation, it is observed that OMRS is outage-optimal among multi-antenna relay selection schemes and closely approaches the beamforming (BF) scheme known as theoretical outage-optimal. Compared with previous single-antenna opportunistic relaying (OR) scheme, OMRS brings remarkable performance improvement, which is obtained from maximum ratio combining (MRC) and beamforming techniques. It is also shown that the performance of ABRS in asymmetric channels is close to OMRS in the low and median SNR range.