Suili Feng

A threshold companding scheme for reducing peak-to-average power ratio of OFDM signals

A companding technique based on threshold is proposed to reduce the PAPR of OFDM signals. In this technique, only the signals, whose amplitudes are higher than the threshold, are compressed in the transmitter. Using a simple judgment process, the expanding operation is executed to the compressed signals in the receiver. Compared with other scheme, the threshold companding scheme effectively improves the performance of PAPR by introducing a simple threshold judgment process.

A Subcarrier Allocation Algorithm for Efficiently Reducing Power in Multiuser OFDM Systems

Resource allocation in multiuser OFDM systems is a complex nonlinear optimization problem. In order to avoid direct solution, based on the analytical results of the problem of minimizing the total transmit power, a two-step subcarrier allocation algorithm is presented. The algorithm reduces the total transmit power by reducing the achievable minimum transmit power value required by each user. Subcarriers are allocated in the algorithm according to the data rate required by users and the channel characteristics. The required number of subcarriers allocated to users does not need to be known in advance. The allocation process consists of two steps: basic subcarrier allocation and residual subcarrier allocation. Numerical results demonstrate that the proposed algorithm can reduce the total transmit power effectively.

Performance of a queuing model With Pareto input traffic for wireless network nodes

In the past few years, packet traffic from various sources - Ethernet, ISDN, CCSN and VBR video - has been shown to exhibit self-similarity and related properties of long range correlation. Recent research has shown that self-similar nature of traffic still exists in the traffic of wireless networks. Since Pareto process generates self-similar arrivals, we analyzed the queue behavior with Pareto interarrival and exponential service time distribution via phase-type (PH) distributions fitting technique and matrix geometric solution approach. Average queue length and loss probability were derived and verified via extensive simulations and the results can provide a practical insight into the buffer dimensioning and admission control as well as QoS providing for wireless network.

A Spectrum Effective Adaptive Modulation and Coding Scheme for OFDM System

With variable code, variable power and variable rate, link adaptation has been shown to have significant benefits for high-speed wireless data transmission. In this paper, an adaptive modulation and coding (AMC) scheme applied to variable bit rate services is proposed for orthogonal frequency division multiplexing (OFDM) system. The objective is to maximize the spectral efficiency by adaptively selecting the code and allocating rate and power over the frequency band under the packet error rate constraint. Following analysis on rate-compatible punctured convolutional codes and linking adaptive techniques in OFDM, a sub-optimal AMC scheme with uniform power allocation is investigated. We realize the rate allocation by setting the instantaneous bit error rate to the average bit error rate which varies over different coding schemes. Simulation results indicate that the proposed scheme exhibits 4~8dB signal-noise-ratio gain relative to non-adaptive scheme. Compared to optimal scheme, the proposed scheme shows negligible loss at high SNR scenarios while the implementation complexity can be reduced significantly.

A Novel Error-resilient Video Codec Framework Based on Scene-Context Reference Picture

The transmission of video over wireless networks always confronts the risk of packet-losses and bit-errors, which result in the rapid propagation of errors in both time and space and the quick of degradation of the reconstructed video quality. In order to stop the error propagation, the traditional method is intra-frame refresh. This paper proposes a novel error-resilient video codec framework utilizing the predictive picture refresh based on scene-context reference picture. When the unreliable mobile IP network requires high intra-frame-refresh rates (In our experiment, we define that an I-frame is sent once every 20 sequence frames at a frame rate of 30 fps), compared with the traditional method, our method can achieve over 10% saving effect in frame bits while maintaining the similar quality incorporated in the H.264/AVC Joint Model 9.0

Three-Phase Scheduling Algorithm for IP Networks

Some scheduling algorithms have been developed to support QoS requirement for various applications in the IP networks. In this paper, we developed three-phase (TP) scheduling algorithm to get adjustable tradeoff between QoS requirement and fairness. TP can also improve the utilization of the scheduler. We analyzed the essence of TP and computed the average packets delay compared with the other algorithms. And the simulation has shown that TP can get a good fairness with little influence on delay requirement for high priority traffic

An approximate bandwidth evaluation algorithm with application to virtual path bandwidth allocation

In the solution procedure of virtual-path bandwidth allocation problem, the current searching algorithms include the process of bandwidth calculation through CBP and traffic load. This is an inverse process of calculating the CBP through traffic load and bandwidth. Because there is no strict expression of calculating CBP, the process of calculating bandwidth through CBP and traffic load adopts the iteration algorithm in common. It limits the computing speed by a long way. Therefore, a fast bandwidth algorithm is proposed and applied to the problem of bandwidth allocation, which aims at minimizing the worst call blocking probabilities in the network. This algorithm is proved to be accurate and fast. Finally, we provide the comparison curves for the exact optimal CBPs in the case of using OPBM and DCLPBM with the approximate fast bandwidth evaluation algorithm.