In TD-LTE-A systems, feedback information of uplink channel is of importance for eNodeB to perform downlink scheduling, beamforming, and adaptive Modulation and Coding Scheme (MCS). Channel quality indicator (CQI) is the most important parameter in all feedback information, and therefore, how to improve the accuracy of CQI feedback is a key issue for system configuration. In this paper, we propose a frequency domain CQI feedback algorithm, using channel capacity invariability criterion and channel reciprocity. Simulations show that periodic feedback with frequency domain CQI feedback algorithm can reduce system first retransmission ratio by about 4% and improve system throughput by about 7%, compared with normal periodic feedback Mode 1-1. In addition, compared with aperiodic feedback Mode 3-1, the proposed CQI feedback algorithm costs less signaling overhead, while keeping similar performance in terms of system first retransmission ratio.

In order to solve the problem of spectrum shortages, dynamic spectrum access based cognitive radio technology was proposed, and the technology of spectrum sensing is the foundation of cognitive radio. In this paper, a semi-definite programming based waveform design algorithm is proposed for spectrum sensing. Considering the energy concentration property of Chirp signal, the Chirp signal is adopted as the basic function, which makes the composite waveform perform like impulse function in fractional Fourier transform domain. Simulation results show that the NESP (Normalized Effective Signal Power) of the designed waveform using the proposed algorithm can be over 70%, and the designed waveform also retains good energy concentration property in fractional domain.

In TD-LTE-A system, the objective of conventional non-codebook beamforming algorithms is to maximize sum capacity to accommodate more users. However, fairness among users is not considered by these algorithms, and the performance of users with poor channel quality will always be bad. To relax the fairness requirement in resource allocation, this paper first introduces two parameters of user satisfaction into TD-LTE-A system for Guaranteed Bit Rate (GBR) and Non-GBR traffics, respectively. Then a user-satisfaction-based beamforming algorithm is proposed. This algorithm employs user satisfaction parameter to adjust the weights for weighted Signal-to-Leakage-plus-Noise Ratio (SLNR) algorithm. Finally, the weights of different traffics are also considered in the proposed beamforming algorithm so that average user satisfaction across different types of traffics can be modified according to the requirement of telecommunication operators. Simulation results show that the proposed algorithm can improve user satisfaction and user fairness, and average user satisfaction of GBR and Non-GBR traffics can be adjusted by changing of GBR priority parameter.

In TD-LTE-A system, the signal-to-leakage-and-noise ratio (SLNR) beamforming algorithm shows better performance in terms of sum capacity and average BER compared with other beamforming algorithms with moderate complexity. In order to further improve the performance of TD-LTE-A system, power-allocation scheme is analyzed based on the framework of SLNR beamforming and a user fairness-based adaptive power-allocation algorithm is proposed. Simulations show that the proposed algorithm can obtain the trade off between user fairness and system performance in TD-LTE-A downlink.

An adaptive MIMO detection algorithm for LTE-A system which is based on sphere detection is proposed in this paper. The proposed algorithm uses M-algorithm for reference to remove unreliable constellation candidates before search, and the number of constellation reservation is adaptively adjusted according to SNR. Simulations of LTE-A downlink show that the BER performance of the proposed detection algorithm is nearly the same as maximum likelihood (ML) detection algorithm. However, the complexity is reduced by about 30% compared with full constellation sphere detection.

By analyzing the indoor office LOS channel model defined by IEEE 802.15.4a standard and deducing the variance for intra-symbol interference (IASI), inter-symbol interference (ISI) and multiuser interference (MUI), performance analysis model for ultra-wideband (UWB) based wireless sensor networks (WSN) is proposed, and the bit error rate (BER) formulation is also obtained. The comparison of performance analysis model with and without intra-symbol interference shows that the intra-symbol interference cannot be neglected and such interference will significantly decrease the system performance. In order to verify the proposed performance analysis model and BER formulation, the semi-definite programming (SDP) algorithm is used to obtain the pulses complying with the spectrum requirement of China and IEEE 802.15.4a standard, and by using such pulses, simulations and theoretical analysis are compared, the comparison results show the validity of the proposed performance analysis model and BER formulation.

In order to satisfy the requirement for higher data rates, the UWB spatial multiplexing system that combines MB-OFDM UWB and V-BLAST scheme is presented in this paper. And then, various detection algorithms are studied and simulated in this system for the sake of a better performance. Simulation results show that MMSE-BLAST is an appropriate one among the conventional suboptimal algorithms, and the accuracy of the first detected layer determines the degree of error propagation. At last, a modified algorithm with the combination of ML and MMSE-BLAST is employed to reduce error propagation in the UWB channel with rich multipath.

By analyzing the indoor office LOS channel model defined by IEEE 802.15.4a standard and deducing the variance for intra-symbol interference (IASI), inter-symbol interference (ISI) and multiuser interference (MUI), performance analysis model for ultra-wideband (UWB) based wireless sensor networks (WSN) is proposed, and the bit error rate (BER) formulation is also obtained. The comparison of performance analysis model with and without intra-symbol interference shows that the intra-symbol interference cannot be neglected and such interference will significantly decrease the system performance. In order to verify the proposed performance analysis model and BER formulation, the semi-definite programming (SDP) algorithm is used to obtain the pulses complying with the spectrum requirement of China and IEEE 802.15.4a standard, and by using such pulses, simulations and theoretical analysis are compared, the comparison results show the validity of the proposed performance analysis model and BER formulation.

In order to increase the peak transmission data rate of Zigbee and expand its application scenario, IEEE 802.15.4a standard has been proposed in 2007, and ultra-wideband (UWB) technique has been selected as one of its physical layer standard. The performance of wireless sensor networks (WSN) will be affected by the pulse waveform transmitted in the channel, hence, in this paper, the Chinese regulation for UWB devices is firstly given, and then, a semi-definite programming based pulse shaping algorithm to comply with such regulation is proposed. Simulation results show that the proposed algorithm can comply with the given regulation with high power efficiency, which can increase the signal to noise ratio (SNR) in the receiver end.

In cognitive radio, spectrum sensing is used to find spectrum hole and identify the primary users. Cognitive users should continuously sense the spectrum and detect the presence of primary user as soon as possible. When cognitive user is far away from the primary user, the signal received from the primary user may be weak and difficult to be detected, causing the problem of low detection probability and long detection time. To solve such problems, this paper proposes a distributed cooperative spectrum sensing strategy based on the joint use of network coding and transform domain processing. Chirp signals with different parameters are used for cognitive users and conventional communication system is used for primary user. In the receiver end, fractional Fourier transform domain based signal processing method is used to separate cognitive users with different parameters and primary user. Network coding is used in different cognitive users to improve the spectrum efficiency of cognitive frequency bands. Theoretical analyses show that the proposed strategy can increase the detection probability, reduce detection time and improve the agility of the system at the same time.