Jinfeng Tian

Frequency-Shift Filtering for OFDM Systems and Its Performance Analysis

Orthogonal frequency division multiplexing (OFDM) technique has been widely used in high data rate wireless applications, but it suffers performance degradation at low signal-to-noise (SNR) regions due to the impairments caused by noise-induced channel estimation errors. In this article, we propose to use frequency-shift (FRESH) filtering technique to exploit temporal and spectral correlation of the OFDM signals for noise reduction purpose. A closed form time-varying minimum mean squared error (MMSE) expression has been derived to analyze the performance of FRESH filtering under additive white Gaussian noise (AWGN) and Rayleigh fading channels. The MMSE analysis carried out here can be a reference for the design of practical OFDM systems. In addition, theoretical SNR is analyzed in this article to show the performance gain achieved by FRESH filtering. The numerical results verify that the maximum SNR improvements offered by FRESH filtering are over 0.6 dB and 1.6 dB under AWGN and Rayleigh fading channels, respectively.

Terrestrial broadcast technologies for next generation broadcast wireless systems

The next generation broadcast wireless (NGB-W) system is aimed to provide high-speed, ubiquitous, and secure tri-play services to massive users. In this paper, a new terrestrial broadcast solution for the NGB-W system is proposed. The system and the key techniques of the proposed solution are introduced. The performance of the proposed solution is evaluated by simulations. It is shown that the performance of the proposed solution is better than that of the second generation terrestrial broadcast systems of Digital Video Broadcasting (DVB).

Methods of time slicing and mapping for next generation broadcasting-wireless

In order to realize flexible time slicing in the Next Generation Broadcasting-Wireless (NGB-W) system, new time slicing scheme and the associated mapping scheme are proposed. The performance of the proposed time slicing scheme is evaluated by extensive simulations. Simulation results show that the performance of broadcasting systems with the proposed time slicing scheme is much better than that of broadcasting systems without time slicing in mobile environment, especially in low Doppler scenario.

Cyclostationarity-Based Decision Reporting Scheme for Cooperative Spectrum Sensing

Cooperative spectrum sensing has emerged as a promising solution to the hidden terminal problem in cognitive radio networks (CRNs). It could significantly promote the sensing capability of CRNs by exploiting space diversity gains in a fading environment. However, owing to the decision reporting overhead, there exists a tradeoff between the system throughput and performance of cooperative spectrum sensing. In this paper, we propose a cyclostationarity-based decision reporting scheme for cooperative spectrum sensing in CRNs with cyclic delay diversity orthogonal frequency division multiplexing (CDD-OFDM). Decision information would be embedded into the CDD-OFDM signals in terms of cyclostationary signatures and shared among cognitive radio (CR) users along with data transmissions. As a result, satisfied system throughput could be achieved without additional spectral or temporal resources consumption when the number of cooperative users increases. Numerical results are presented to show the system throughput enhancement.

Cyclostationarity-Based Frequency Synchronization for OFDM Systems Over Doubly-Selective Fading Channels

Orthogonal frequency division multiplexing (OFDM) systems are highly sensitive to carrier frequency offset (CFO), especially in doubly-selective fading environment. Cyclostationarity-based blind synchronization methods are appealing in high-data-rate applications and low signal-to-noise regions. However, the cyclostationarity has not been exploited for frequency synchronization of OFDM systems under doubly-selective fading channels. In this paper, we derive the close-form second order cyclic statistics of the received OFDM signal in presence of CFO, by modeling the doubly-selective fading channel with basis expansion model. Both transmitter-induced cyclostationarity and doubly-selective channel information are contained in the derived cyclic moments, and they are efficiently utilized for CFO estimation. Simulation results demonstrate that the proposed estimator provides significant improvements on frequency synchronization performance.

Sensing of OFDM signals with cyclic delay diversity over doubly-selective fading channels

Orthogonal frequency division multiplexing signals with cyclic delay diversity (CDD) exhibit distinguishable cyclostationarity that can be used to design cyclostationary signatures for cognitive radio networks. However, such cyclostationary signatures are

An efficient channel estimation scheme of non-orthogonal multiple access system in 5G wireless networks

This paper presents an efficient channel estimation scheme of the non-orthogonal multiple access system which named CDMA-FMT in 5G wireless networks. The proposed channel estimation scheme is theoretically analyzed based on the equivalent sub-band channel model. Moreover, the simulation results show that, by using the proposed channel estimation scheme, the BLER performance of the CDMA-FMT system outperforms the traditional CDMA system.

Banker's algorithm based resource allocation in next generation broadcasting wireless systems

This paper studies the resource allocation issue of multiple broadcast signals over multiple carrier frequencies in the next generation broadcasting wireless (NGB-W) system, each of which has specific transmission requirements on time resources and number of carrier frequencies. Based on the modified bankers algorithm, we propose a resource allocation approach of all broadcast signals in the NGB-W system, under the limitation of minimum frame length. Safety judgment is introduced to gain an effective allocation result. If the safe condition is not satisfied, an adjustment strategy need be employed to get a more appropriate allocation result. The effectiveness of the proposed scheme is demonstrated in simulation results.

Reduction of physical layer signaling overhead in DVB-NGH systems

The Digital Video Broadcasting Next Generation Handheld (DVB-NGH) standard has adopted many advanced technologies, including overhead reduction schemes, to maximize the system capacity. However, some of the overhead reduction schemes of Layer-1 (L1) signaling result in increased initial capture time delays. In order to get a more flexible trade-off between overhead reduction and initial capture time delay, a full-truncated L1 signaling scheme is proposed in DVB-NGH systems. Simulation results demonstrate the effectiveness of the proposed scheme.

Vertex coloring based logical channel mapping for frequency hopping transmission in next generation broadcasting wireless systems

Frequency hopping transmission of logical channel offers significant gains in capacity and coverage, while requires its mapped physical frames on different carrier frequencies separated at least in a tuning time interval when considering the receiver with a single tuner. This limitation on the mapped physical frames is similar to the graph coloring problem. Thus we innovatively model the problem in this paper as a vertex coloring problem. A new coloring method is proposed by integrating the strategies of vertex selection, color selection, and color map adjustment into the classical backtracking algorithm. Simulation results indicate that the proposed method provides substantial advantages over the traditional backtracking method.