Energy efficiency and enhanced backbone capacity is obtained by exploiting the geometric orientation of cooperative nodes in wireless sensor network. The cooperative communication in wireless sensor networks (WSN) giv...Energy efficiency and enhanced backbone capacity is obtained by exploiting the geometric orientation of cooperative nodes in wireless sensor network. The cooperative communication in wireless sensor networks (WSN) gives us leverage to get the inherent advantages of its random node’s locations and the direction of the data flow. Depending on the channel conditions and the transmission distance, the number of cooperative nodes is selected, that participate in an energy efficient transmission/reception. Simulation results show that increasing the cooperative receive diversity, decreases the energy consumption per bit in cooperative communications. It has also been shown that the network backbone capacity can be increased by controlled displacement of antennas at base station at the expense of energy per bit.展开更多
Aimed at that only one form of channel statistic information is utilized in traditional robust precoder schemes: either the channel mean or the transmit antenna correlation in multiple-input multiple-output (MIMO) wir...Aimed at that only one form of channel statistic information is utilized in traditional robust precoder schemes: either the channel mean or the transmit antenna correlation in multiple-input multiple-output (MIMO) wireless system, this paper proposes robust precoder designs which exploit both of statistic information to minimize the equalization mean-square error (MSE) with power constraint. Two different power constraints are studied. Besides the usual sum power constraint over all antennas, the per-antenna power constraint is imposed at transmitter in this paper. Since each antenna has its own amplifier, individual power constraint on each antenna is more realistic. Especially in MIMO-OFDM systems, the Peak-to-Average Ratio (PAR) is one of main practical problems. Simulations show that the proposed schemes have better performance than traditional normalized zero forcing schemes for imperfectly known correlated channel. Moreover, per-antenna power constraint can efficiently decrease the demand of dynamic range of power amplifier on each transmit antenna, especially in MIMO-OFDM systems.展开更多
Time Division-Synchronous Code Division Multiple Access(TD-SCDMA),a home-grown standard for the third generation mobile communications,is already mature and ready for commercial deployment.The enhancement and evolutio...Time Division-Synchronous Code Division Multiple Access(TD-SCDMA),a home-grown standard for the third generation mobile communications,is already mature and ready for commercial deployment.The enhancement and evolution of the TD-SCDMA system is a hot topic recently.Many strategies for TD-SCDMA enhancements and evolutions have been proposed,but there are no integrated solutions that can jointly consider the development both in the short term and in the long term.This paper discusses four evolution phases,which are proposed according to the key technologies.Phase 1 is about the current TD-SCDMA system.Phase 2 is the short term evolution of TD-SCDMA,i.e.,the period of HSxPA,including the evolution of High Speed Downlink Packet Access(HSDPA),High Speed Uplink Packet Access(HSUPA)and High Speed Packet Access plus(HSPA+).Phase 3 is the Long Term Evolution(LTE).Phase 4 is the Beyond 3G(B3G)/Fourth Generation(4G)mobile communication Time Division Duplex(TDD)system,which is based on TD-SCDMA.Key characters for every evolution phase are discussed,as well as the advanced technologies adopted in the evolution process such as Multiple Input Multiple Output(MIMO)and Orthogonal Frequency Division Multiplexing(OFDM).展开更多
The process of changing the channel associated with the current connection while a call is in progress is under consideration. The estimation of dropping rate in handover process of a one dimensional traffic system is...The process of changing the channel associated with the current connection while a call is in progress is under consideration. The estimation of dropping rate in handover process of a one dimensional traffic system is discussed. To reduce the sample size of simulation, dropping calls at base station is considered as rare event and simulated with importance sampling - one of rare event simulation approaches. The simulation results suggest the sample size can be tremendously reduced by using importance sampling.展开更多
A hybrid system of cellular mode and device-to-device （D2D） mode is considered in this paper, where the cellular resource is reused by the D2D transmission. With the objective of capacity maximization, the power opt...A hybrid system of cellular mode and device-to-device （D2D） mode is considered in this paper, where the cellular resource is reused by the D2D transmission. With the objective of capacity maximization, the power optimization of D2D sub-system is considered, taking into account quality of service （QoS） requirement. The power optimization problem is divided into two stages： The first stage is the admission control scheme design based on the QoS requirement of D2D users, and the second is power allocation to maximize aggregate throughput of admissible D2D users. For the D2D admission control problem, a heuristic sorting-based algorithm is proposed to index the admissible D2D links, where gain to Interference ratio （GIR） sorting criterion is used. Applying an approximate form of Shannon capacity, the power allocation problem can be solved by convex optimization and geometric programming tools efficiently. Based on the theoretical analysis, a practical algorithm is proposed. The precision can reach a trade-off between complexity and performance. Numerical simulation results confirm that combining with GIR sorting method, the proposed scheme can significantly improve the D2D system＇s capacity and fairness.展开更多
Wireless networks contain an inherent distributed spatial diversity that can be exploited by relays.Relay networks can take advantage of the broadcast-oriented nature of wireless transmission,but require more radio re...Wireless networks contain an inherent distributed spatial diversity that can be exploited by relays.Relay networks can take advantage of the broadcast-oriented nature of wireless transmission,but require more radio resource to transmit data for their multi-hop traits.Fortunately,incremental relaying technique,which can choose direct or multi-hop transmission adaptively,can efficiently utilize resource.In this article,the incremental transmission with amplify-and-forward(AF)relays is focused on.A practical hybrid-automatic retransmission request(HARQ)protocol is designed,and the related optimal relay selection strategy is proposed.To analyze the cooperative diversity of system with the proposed protocol,the capacity lower bound is deduced.Simulation and analytical results indicate that by adopting the optimal relay selection strategy,the system with the proposed HARQ protocol can achieve an order of cooperative diversity that equals the aggregated number of the relay and source nodes.展开更多
Hybrid automatic repeat request（HARQ） is a well-known technique for improving system throughput and link performance of wireless communication systems,including cooperative communication systems.The amplify-and-forw...Hybrid automatic repeat request（HARQ） is a well-known technique for improving system throughput and link performance of wireless communication systems,including cooperative communication systems.The amplify-and-forward（AF） relaying method is one of the most attractive cooperative diversity schemes because of its low complexity.In this article,the end-to-end performance in terms of block error rate（BLER） and normalized throughput of AF relaying with HARQ transmission under the Rayleigh fading channel is analyzed.Numerical results validate the proposed analysis and demonstrate the gain of HARQ schemes in AF relaying systems.This analytical method can be extended to the systems with other HARQ protocols and other cooperative relaying schemes.展开更多
In this article a bridge between the expected complexity and performance of sphere decoding （SD） is built. The expected complexity of SD for infinite lattices is then investigated, which naturally is the upper-bound...In this article a bridge between the expected complexity and performance of sphere decoding （SD） is built. The expected complexity of SD for infinite lattices is then investigated, which naturally is the upper-bound of those for all the finite lattices if given by the same channel matrix and signal noise ratio （SNR）. Such expected complexity is an important characterization of SD in multi-antenna systems, because no matter what modulation scheme is used in practice （generally it has finite constellation size） this upper-bound holds. Above bridge also leads to a new method of determining the radius for SD. The numerical results show both the real value and upper-bound of average searched number of candidates in SD for 16-QAM modulated system using the proposed sphere radius determining method. Most important of all new understandings of expected complexity of SD are given based on above mentioned theoretic analysis and numerical results.展开更多
文摘Energy efficiency and enhanced backbone capacity is obtained by exploiting the geometric orientation of cooperative nodes in wireless sensor network. The cooperative communication in wireless sensor networks (WSN) gives us leverage to get the inherent advantages of its random node’s locations and the direction of the data flow. Depending on the channel conditions and the transmission distance, the number of cooperative nodes is selected, that participate in an energy efficient transmission/reception. Simulation results show that increasing the cooperative receive diversity, decreases the energy consumption per bit in cooperative communications. It has also been shown that the network backbone capacity can be increased by controlled displacement of antennas at base station at the expense of energy per bit.
基金Sponsored by the National Natural Science Foundation of China(Grant No.60572120)
文摘Aimed at that only one form of channel statistic information is utilized in traditional robust precoder schemes: either the channel mean or the transmit antenna correlation in multiple-input multiple-output (MIMO) wireless system, this paper proposes robust precoder designs which exploit both of statistic information to minimize the equalization mean-square error (MSE) with power constraint. Two different power constraints are studied. Besides the usual sum power constraint over all antennas, the per-antenna power constraint is imposed at transmitter in this paper. Since each antenna has its own amplifier, individual power constraint on each antenna is more realistic. Especially in MIMO-OFDM systems, the Peak-to-Average Ratio (PAR) is one of main practical problems. Simulations show that the proposed schemes have better performance than traditional normalized zero forcing schemes for imperfectly known correlated channel. Moreover, per-antenna power constraint can efficiently decrease the demand of dynamic range of power amplifier on each transmit antenna, especially in MIMO-OFDM systems.
基金the 863 Program of China under grant 2006AA01Z257the National Natural Science Foundation of China under grants 60602058 and 60572120.
文摘Time Division-Synchronous Code Division Multiple Access(TD-SCDMA),a home-grown standard for the third generation mobile communications,is already mature and ready for commercial deployment.The enhancement and evolution of the TD-SCDMA system is a hot topic recently.Many strategies for TD-SCDMA enhancements and evolutions have been proposed,but there are no integrated solutions that can jointly consider the development both in the short term and in the long term.This paper discusses four evolution phases,which are proposed according to the key technologies.Phase 1 is about the current TD-SCDMA system.Phase 2 is the short term evolution of TD-SCDMA,i.e.,the period of HSxPA,including the evolution of High Speed Downlink Packet Access(HSDPA),High Speed Uplink Packet Access(HSUPA)and High Speed Packet Access plus(HSPA+).Phase 3 is the Long Term Evolution(LTE).Phase 4 is the Beyond 3G(B3G)/Fourth Generation(4G)mobile communication Time Division Duplex(TDD)system,which is based on TD-SCDMA.Key characters for every evolution phase are discussed,as well as the advanced technologies adopted in the evolution process such as Multiple Input Multiple Output(MIMO)and Orthogonal Frequency Division Multiplexing(OFDM).
文摘The process of changing the channel associated with the current connection while a call is in progress is under consideration. The estimation of dropping rate in handover process of a one dimensional traffic system is discussed. To reduce the sample size of simulation, dropping calls at base station is considered as rare event and simulated with importance sampling - one of rare event simulation approaches. The simulation results suggest the sample size can be tremendously reduced by using importance sampling.
基金sponsored by Renesas, the National Natural Science Foundation of China (60572120, 60602058)the National Basic Research Program of China (2009CB320400)+1 种基金the Joint Funds of NSFC-Guangdong (U1035001)the Chinese Major Science and Technology Projects (2009ZX03007-004)
文摘A hybrid system of cellular mode and device-to-device （D2D） mode is considered in this paper, where the cellular resource is reused by the D2D transmission. With the objective of capacity maximization, the power optimization of D2D sub-system is considered, taking into account quality of service （QoS） requirement. The power optimization problem is divided into two stages： The first stage is the admission control scheme design based on the QoS requirement of D2D users, and the second is power allocation to maximize aggregate throughput of admissible D2D users. For the D2D admission control problem, a heuristic sorting-based algorithm is proposed to index the admissible D2D links, where gain to Interference ratio （GIR） sorting criterion is used. Applying an approximate form of Shannon capacity, the power allocation problem can be solved by convex optimization and geometric programming tools efficiently. Based on the theoretical analysis, a practical algorithm is proposed. The precision can reach a trade-off between complexity and performance. Numerical simulation results confirm that combining with GIR sorting method, the proposed scheme can significantly improve the D2D system＇s capacity and fairness.
基金supported by China Mobile Corporation Company(CMCC),the National Natural Science Foundation of China(60802082)the National Key Technology R&D Program of China(2008BAH30B11)the Research Fund for the Doctoral Program of Higher Education(200800131023)
文摘Wireless networks contain an inherent distributed spatial diversity that can be exploited by relays.Relay networks can take advantage of the broadcast-oriented nature of wireless transmission,but require more radio resource to transmit data for their multi-hop traits.Fortunately,incremental relaying technique,which can choose direct or multi-hop transmission adaptively,can efficiently utilize resource.In this article,the incremental transmission with amplify-and-forward(AF)relays is focused on.A practical hybrid-automatic retransmission request(HARQ)protocol is designed,and the related optimal relay selection strategy is proposed.To analyze the cooperative diversity of system with the proposed protocol,the capacity lower bound is deduced.Simulation and analytical results indicate that by adopting the optimal relay selection strategy,the system with the proposed HARQ protocol can achieve an order of cooperative diversity that equals the aggregated number of the relay and source nodes.
基金supported by the National Natural Science Foundation of China (60802082)
文摘Hybrid automatic repeat request（HARQ） is a well-known technique for improving system throughput and link performance of wireless communication systems,including cooperative communication systems.The amplify-and-forward（AF） relaying method is one of the most attractive cooperative diversity schemes because of its low complexity.In this article,the end-to-end performance in terms of block error rate（BLER） and normalized throughput of AF relaying with HARQ transmission under the Rayleigh fading channel is analyzed.Numerical results validate the proposed analysis and demonstrate the gain of HARQ schemes in AF relaying systems.This analytical method can be extended to the systems with other HARQ protocols and other cooperative relaying schemes.
基金supported by the National Natural Science Foundation of China (60572120, 60602058)the Hi-Tech Research and Development Program of China (2006AA01Z257)the National Basic Research Program of China (2007CB310602)
文摘In this article a bridge between the expected complexity and performance of sphere decoding （SD） is built. The expected complexity of SD for infinite lattices is then investigated, which naturally is the upper-bound of those for all the finite lattices if given by the same channel matrix and signal noise ratio （SNR）. Such expected complexity is an important characterization of SD in multi-antenna systems, because no matter what modulation scheme is used in practice （generally it has finite constellation size） this upper-bound holds. Above bridge also leads to a new method of determining the radius for SD. The numerical results show both the real value and upper-bound of average searched number of candidates in SD for 16-QAM modulated system using the proposed sphere radius determining method. Most important of all new understandings of expected complexity of SD are given based on above mentioned theoretic analysis and numerical results.
