Zhiyong Bu

A coordinated mechanism for multimode user equipment accessing wireless sensor network

User Equipment UE as a basic device in cellular networks may contain different types of sensor module for specified usage, called multimode UE. With the natural mobility characteristics, this new type of UE is similar to an enhanced type of mobile sensor, with more energy and more flexibility. Since Wireless Sensor Network WSN can be deployed easily as no major infrastructure and human control are needed, the integration of cellular network and wireless sensor network becomes attractive by combining the sensing part and the connection part in a flexible way, which expands both scalability and service applications for the networks. In this paper, we propose a coordinated accessing mechanism when UE interacts with WSN network. Through the analysis of the accessing problem, we can optimise the contention period for accessing in order to enhance the heterogeneous network performance. The simulation result shows the proposed accessing mechanism outperforms the conventional method in an integrated network.

A grouped and proportional-fair subcarrier allocation scheme for multiuser OFDM systems

In this paper, we propose a new and rather simple grouped-subcarrier allocation algorithms with proportional fairness among users in downlink OFDM transmission. The proposed algorithm tries to minimize the required transmit power while satisfying the rate requirement and BER constraint of each user. Subcarrier and power allocation are performed in two steps. We are mainly focusing on the subcarrier allocation step. First subcarriers are grouped to reduce the computational complexity of the allocation algorithm. Then we employ proportional constraints in terms of rate ratios to assure each user to achieve the target data rate in advance. Simulation results show that this low complexity resource allocation scheme achieves better performance than the fixed frequency division approach and shows comparable performance compared to previously derived suboptimal resource distribution schemes. It is also shown that with rate constraints the capacity is distributed more fairly and rationally among users

An Efficient Peak-to-Average Power Ratio Reduction Algorithm for WiMAX System

In order to decrease implementation complexity, a method which can effectively reduce the peak-to-average power ratio (PAPR) of the WiMAX system is proposed. We firstly oversample the WiMAX system, then normalize, finally clip and filter the signals. Improvements on PAPR reduction, out-of-band radiation and bit error rate performances are discussed in this paper. Simulation results show that the proposed method can effectively reduce the PAPR of WiMAX system

An Adaptive Uplink Resource Allocation Scheme for LTE in Smart Grid

Data transmission is crucial for smart grid. Long Term Evolution (LTE) is considered to be a promising solution for smart grid communication because it uses a variety of new technologies to improve communication efficiency. Resource Blocks (RBs) allocation is applied to provide different levels of Quality-of-Service (QoS) in LTE. In this paper, we propose an Adaptive Wireless Resource Allocation (AWRA) scheme for the uplink of LTE-based cellular systems, which takes into account the user’s priority and fairness. According to QoS requirements, users are assigned three different priorities, so that AWRA performs flexible and efficient RBs allocation based on users’ priorities, thus satisfying a specific QoS requirement. Given Packet Loss Rate (PLR), a mathematical optimization framework is formulated for maximizing the total capacity. The proposed scheme allocates the RBs to the predefined user types with considering Signal Noise Ratio (SNR). An adaptive-scheduling scheme based on the delay time of the queues and the length of the queues is further introduced. Simulation results show that the proposed algorithm has better throughout and fairness than the conventional algorithms, it considerably reduce the data drop rate and satisfies the users’ QoS requirements of smart grid. 

A novel mechanism for surveillance transmission in smart grid

Herein, we propose a novel resilient forwarding mechanism to address the contradictory problem between transmission performance and power saving problems. Through automatic backup and transmission line switch, self-healing and autonomous troubleshooting can be achieved for online monitoring in transmission grid. Autonomous surveillance transmission network can be achieved through transmission line indicators. Even though several parts of the transmission network are breakdown, resilient forwarding mechanism may still provide robust pre-alarming and data transmission services. We also evaluate the performance of our approach by reducing the transmission latency to improve network performance. We further analysis the transmission latency gain with resilient forwarding mechanism through simulations. It is shown that our mechanism outperforms the conventional scheme.

Proportional-Fair Bit and Power Adaptation in Multiuser OFDM Systems

In this paper, we investigate efficient and linear bit and power allocation algorithms with proportional fairness among users in downlink OFDM transmission. The objective is to minimize the total transmit power while satisfying the rate requirement and BER constraint of each user. To relieve heavy computational burden, bit loading and power allocation is performed after subcarrier allocation. Proportional constraints are employed in terms of rate ratios to assure each user to achieve the target data rate. Comparison through computer simulation indicates that our approach results in an efficient assignment of transmit power in terms of the energy required of transmitting each bit of information. It is also shown that with proportional constraints the capacity is distributed more fairly and rationally among users

Delay Spread Statistics in a Two-Path Distributed Antenna System with Gamma-Lognormal Fading Channels

This letter analyzes the statistical properties of the root-mean-square (RMS) delay spread in a two-path distributed antenna system, where the received signal power from each path is subject to composite gamma fading and lognormal shadowing. The channel power delay profile considered consists of two delta functions with correlated power levels. We present analytical expressions for the probability density function of the RMS delay spread, as well as the cumulative distribution function, mean value and standard deviation. These analyses are validated through comparison with Monte-Carlo simulation results.

Beacon routing algorithm in wireless sensor networks with mobile gateway

In this article, we first propose a reverse sector mechanism and an optimization division mechanism, which can provide enormous energy conservation benefits. Based on these mechanisms, an efficient sensory data collection mechanism over a cellular-WSN integrated network, named beacon routing algorithm, is proposed to spontaneously renew the local WSN topology according to the position of the UE relative to the location of the beacon cluster under an optimized network division pre-set. Different from the previous studies, beacon routing algorithm achieves the adaptive topology renewal without additional re-clustering overhead. Through performance evaluation, we can implement WSN by making a trade-off between network scale and sector division. Moreover, optimal energy efficiency can be obtained in each divided sub-network; therefore, the WSN lifetime can be increased significantly and the data collection efficiency will be enhanced. Simulation results are presented to show the performance of the proposed algorithm.

Interference cancellation based receive scheme to combat ICI for OFDM systems

In his paper, we analyses and proposes a new receiver structure to mitigate the effect of interchannel interference (ICI) on the reception of OFDM signals. The system operates in a frequency selective Rayleigh fading channel. Interchannel interference is caused by the time variations in channel gain within OFDM symbol and leads to an error floor, which is a function of Doppler frequency. In this study, it was found that by performing parallel interference cancellation at the receiver, we were able to significantly reduce the error floor.

Data caching policies for device to device within cellular networks

Together with an explosive growth of the mobile devices with various applications and great demand for bandwidth, Device-to-Device (D2D) communication has been introduced to be a potential technology for mobile services mainly due to its particular advantages to offload cellular traffic effectively via content sharing. A device can directly retrieve its desired message from one of its neighboring devices if the message is available in the vicinity of the device. The main challenge becomes how to select messages to cache in order to maximize traffic offloading and improve system performance via D2D communication. In this paper, we describe the caching problem as a maximum weighted matching problem and put forward a caching strategy in which the weights of various contents are defined to determine the order of caching messages leveraging Kuhn-Munkres (KM) algorithm. Based on theoretical and experimental analysis, we identify the reliability and feasibility of the above mechanism.