Feng Chongxi

Modified efficiency importance sampling and its application in the simulation of MQAM systems

Modified efficiency importance sampling (MEIS), an importance sampling technique which can be used to yield a significant saving of run time for the assessment of bit error rate (BER) in digital communication systems using computer simulation, is described. The concept of equivalent noise source is introduced to avoid the effect of system memory on the efficiency of importance sampling, and a nonGaussian probability density function (p.d.f.) is selected as the biased equivalent noise to further improve run time. MEIS has been used successfully in the simulation of M-ary quadrature amplitude modulation (MQAM) systems. The MEIS is shown to be effective in the simulation of systems with large memory length, and in mildly nonlinear systems. The experimental results show that MEIS is a great improvement over Monte Carlo (MC) methods and that is even more efficient than the efficient importance sampling (EIS) technique.<<ETX>>

Performance analysis of multicast replication mechanism in shared-memory switch with speedup

A multicast replication algorithm is proposed for shared memory switches. It uses a dedicated FIFO to multicast by replicating cells at receiver and the FIFO is operating with shared memory in parallel. Speedup is used to promote loss and delay performance. A new queueing analytical model is developed based on a sub-timeslot approach. The system performance in terms of cell loss and delay is analyzed and verified by simulation.

Design of interpolation filter for all digital receiver—On the interpolation problem of full response modulation signals

All digital implementation of receiver is a main topic on digital communication recently. The design of interpolation filter is one of the important problems for all digital implementation of receiver. In this paper, for full response linear modulation signal, a interpolation criterion is proposed. An interpolation formula is presented on bandwidth-limited transmission signal. For example, using the raised cosine roll off function as the system pulse response, the feasibility and effectiveness on the interpolation formula are certified by theoretical and numerical analysis. The computer simulation result on 16-QAM signal is given.

Performance comparison of cell-based and Packet-Based Switching schemes for shared memory switches

Shared Memory (SM) switches are widely used for its high throughput, low delay and efficient use of memory. This paper compares the performance of two prominent switching schemes of SM packet switches: Cell-Based Switching (CBS) and Packet-Based Switching (PBS). Theoretical analysis is carried out to draw qualitative conclusion on the memory requirement, throughput and packet delay of the two schemes. Furthermore, simulations are carried out to get quantitative results of the performance comparison under various system load, traffic patterns, and memory sizes. Simulation results show that PBS has the advantage of shorter time delay while CBS has lower memory requirement and outperforms in throughput when the memory size is limited. The comparison can be used for tradeoff between performance and complexity in switch design.Shared Memory (SM) switches are widely used for its high throughput, low delay and efficient use of memory. This paper compares the performance of two prominent switching schemes of SM packet switches: Cell-Based Switching (CBS) and Packet-Based Switching (PBS). Theoretical analysis is carried out to draw qualitative conclusion on the memory requirement, throughput and packet delay of the two schemes. Furthermore, simulations are carried out to get quantitative results of the performance comparison under various system load, traffic patterns, and memory sizes. Simulation results show that PBS has the advantage of shorter time delay while CBS has lower memory requirement and outperforms in throughput when the memory size is limited. The comparison can be used for tradeoff between performance and complexity in switch design.

Design of multi-service SDH networks: Formulation and heuristics

Multi-service SDH networks support both packet- and circuit-switched traffic. Optimal design of such a network means to guarantee the circuit connections and configure a logical packet-switched topology with lowest congestion. This letter first formulates the problem as a mixed integer linear programming, which achieves optimal solution but has high computation. Then a heuristic algorithm is proposed to yield near-optimal solution efficiently. Performance of the algorithm is verified by an example.

Semantic expression in management information exchange

This paper presents semantic expression of management information and an information exchange model. They are particularly suitable for management integration in a multi-vendor environment and adaptation to new technologies and services in network management.

A simple and efficient algorithm for block matching motion estimation in video coding

Computational complexity and accuracy of motion vector are two key factors of block matching motion estimation in video coding. This paper proposes a simple and efficient algorithm named edge pixels classification (EPC) algorithm. According to the fact that human eyes are highly sensitive to the motion of the edge, the EPC algorithm makes full use of the pixels in the edge. After edge detection, the pixels in the edge are classified into two categories: matching pixels and mismatching pixels. The best matching block within a search area is the one with the highest number of matching pixels. Compared with some well-known algorithms which use mean absolute difference (MAD) matching criteria, the EPC algorithm can provide much higher performance with much lower computational complexity.

Some new results on Z transform

In signal analysis and processing, the Z transform plays the same-important role in the discrete signal system as that of the Laplace transform in a continuous signal system. The limitation of the application of the Z transform is analysed. A new concept of the wide sense Z (WSZ) transform for a bandlimited signal is proposed, some new results is obtained, and the transform theory is expanded. In practical applications, some problems which are difficult to solve with the traditional Z transform can be solved easily by the proposed theory.

Design of the elastic buffer size for SDH equipments

In the SDH frame structure, a large amount of non-information bits and the pointer adjustment mechanism make the design of the buffer size more complicated compared with that of the PDH. The paper analyzes the buffer operation in the pointer processor, and gives the proper buffer size for different phase detection methods. The paper also analyzes the main elements that influence the buffer size of the desynchronizer (demultiplexer). These analyses are useful for the design of the buffer size in SDH equipment.

A real-time 8000 bps ACELP coder with low complexity and high quality

A kind of real time speech coder with low complexity and high quality at a bit rate of 8.0 kbps is presented. The encoding algorithm is based on algebraic code excited linear prediction (ACELP). Efficient pitch and codebook search strategies along with efficient quantization procedures, have been developed to achieve high quality encoded speech with a complexity implementable on current low price fixed point DSP chips such as the TMS320C25. Through subjective tests we have verified that the proposed algorithm is comparable to the CVSD coder at 32 kbps.