In this paper,a new idea based on pseudolite signal acquisition method aiming to mitigate the near-far effect problemin the satellite positioning is proposed.After analyzing the signal capture principle based on coher...In this paper,a new idea based on pseudolite signal acquisition method aiming to mitigate the near-far effect problemin the satellite positioning is proposed.After analyzing the signal capture principle based on coherent integration and non-coherentaccumulation,the cross-correlation interference of strong and weak signals is eliminated by means of normalization of reconstructedstrong signal and judgement of the characteristics of the peak value,which can avoid the near-far effect of the pseudolitesignal.It can also estimate all the strong signals without any additional hardware.By building an indoor pseudolite positioningsystem,the capture performance becomes better based on improved acquisition algorithm compared with that based on thenon-coherent accumulation after coherent integration algorithm.The near-far effect is restrained effectively and the probabilityof weak signal detection is increased by25%.展开更多
Radio resources must be wisely managed, in wireless communication systems, when implementing different multiple access techniques. This perspective is pivotal since the variations in propagation channel are very fast ...Radio resources must be wisely managed, in wireless communication systems, when implementing different multiple access techniques. This perspective is pivotal since the variations in propagation channel are very fast and the system is highly complex due to random and unpredictable movement of mobile users continuously. The complexity in the cellular system periodically contributes to different interference levels, high or low, resulting in the degradation of the system capacity. Transmitter power control is an efficient technique to mitigate the effect of interference under fading conditions, combat the Near-Far problem and conserve the battery life. Several remedial measures—like space diversity, frequency diversity, route diversity, increase in antenna height, antenna tilting, etc.—have been tried by many operators to overcome the debilitating effect of multipath fading in fixed line-of-sight microwave and mobile communication links. Among these remedial measures, diversity techniques have been extensively studied in terms of improvement factor, whereas the concept of antenna tilting is relatively less explored compared with other remedial measures. In this study, the effect of antenna tilting on fixed and mobile communication links is investigated to find out the optimum tilting angles in terms of design parameters, as well as on quality of service (QoS). The paper established that a deviation of more than 1.5o in antenna elevation angle would impact on QoS requirements and seriously affect the quality of signal to be received by the mobile systems.展开更多
The main shortcomings of direct sequence spread spectrum multiple ac-cess(DS-SSMA)communication systems are the near-far effect and multiaccess in-terferences,which impair the stability,capacity and application areas ...The main shortcomings of direct sequence spread spectrum multiple ac-cess(DS-SSMA)communication systems are the near-far effect and multiaccess in-terferences,which impair the stability,capacity and application areas of the commu-nication systems.In this paper,a new kind of multiuser detector——decorrelatingdetector with decision feedback is proposed.In linear channels,this detector can e-liminate the multiaccess interferences with low complexity.Computer simulationsverify the theoretical analysis in this paper.展开更多
The paper presents a modified least squares despread respread multitarget constant modulus algorithm (LS-DRMTCMA). The cost function of the original algorithm was modified by the minimum bit error rate (MBER) criterio...The paper presents a modified least squares despread respread multitarget constant modulus algorithm (LS-DRMTCMA). The cost function of the original algorithm was modified by the minimum bit error rate (MBER) criterion. The novel algorithm tries to optimize weight vectors by directly minimizing bit error rate (BER) of code division multiple access (CDMA) mobile communication system. In order to achieve adaptive update of weight vectors, a stochastic gradient adaptive algorithm was developed by a kernel density estimator of possibility density function based on samples. Simulation results showed that the modified algorithm remarkably improves the BER performance, capacity and near-far effect resistance of a given CDMA communication system.展开更多
基金Gansu Province Basic Research Innovation Group Plan(No.1606RJIA327)Natural Science Foundation of Gansu Provinc(No.1606RJYA225)+1 种基金Lanzhou Jiaotong University Youth Fund(No.2014031)Longyuan Youth Innovative Support Program(No.2016-43)
文摘In this paper,a new idea based on pseudolite signal acquisition method aiming to mitigate the near-far effect problemin the satellite positioning is proposed.After analyzing the signal capture principle based on coherent integration and non-coherentaccumulation,the cross-correlation interference of strong and weak signals is eliminated by means of normalization of reconstructedstrong signal and judgement of the characteristics of the peak value,which can avoid the near-far effect of the pseudolitesignal.It can also estimate all the strong signals without any additional hardware.By building an indoor pseudolite positioningsystem,the capture performance becomes better based on improved acquisition algorithm compared with that based on thenon-coherent accumulation after coherent integration algorithm.The near-far effect is restrained effectively and the probabilityof weak signal detection is increased by25%.
文摘Radio resources must be wisely managed, in wireless communication systems, when implementing different multiple access techniques. This perspective is pivotal since the variations in propagation channel are very fast and the system is highly complex due to random and unpredictable movement of mobile users continuously. The complexity in the cellular system periodically contributes to different interference levels, high or low, resulting in the degradation of the system capacity. Transmitter power control is an efficient technique to mitigate the effect of interference under fading conditions, combat the Near-Far problem and conserve the battery life. Several remedial measures—like space diversity, frequency diversity, route diversity, increase in antenna height, antenna tilting, etc.—have been tried by many operators to overcome the debilitating effect of multipath fading in fixed line-of-sight microwave and mobile communication links. Among these remedial measures, diversity techniques have been extensively studied in terms of improvement factor, whereas the concept of antenna tilting is relatively less explored compared with other remedial measures. In this study, the effect of antenna tilting on fixed and mobile communication links is investigated to find out the optimum tilting angles in terms of design parameters, as well as on quality of service (QoS). The paper established that a deviation of more than 1.5o in antenna elevation angle would impact on QoS requirements and seriously affect the quality of signal to be received by the mobile systems.
文摘The main shortcomings of direct sequence spread spectrum multiple ac-cess(DS-SSMA)communication systems are the near-far effect and multiaccess in-terferences,which impair the stability,capacity and application areas of the commu-nication systems.In this paper,a new kind of multiuser detector——decorrelatingdetector with decision feedback is proposed.In linear channels,this detector can e-liminate the multiaccess interferences with low complexity.Computer simulationsverify the theoretical analysis in this paper.
文摘The paper presents a modified least squares despread respread multitarget constant modulus algorithm (LS-DRMTCMA). The cost function of the original algorithm was modified by the minimum bit error rate (MBER) criterion. The novel algorithm tries to optimize weight vectors by directly minimizing bit error rate (BER) of code division multiple access (CDMA) mobile communication system. In order to achieve adaptive update of weight vectors, a stochastic gradient adaptive algorithm was developed by a kernel density estimator of possibility density function based on samples. Simulation results showed that the modified algorithm remarkably improves the BER performance, capacity and near-far effect resistance of a given CDMA communication system.
