Packet Scheduling Algorithm for Real-Time Services in Broadband WMAN

Packet scheduling algorithm is the key technology to guarantee Quality of Service (QoS) and balance the fairness between users in broadband Wireless Metropolitan Area Network (WMAN). Based on the research of Proportional Fairness (PF) algorithm and Modified Largest Weighted Delay First (M-LWDF) algorithm, a new packet scheduling algorithm for real-time services in broadband WMAN, called Enhanced M-LWDF (EM-LWDF), was proposed. The algorithm phases in new information to measure the load of service queues and updates the state parameters in real-time way, which remarkably improves system performance.Simulation results show that comparing with M-LWDF algorithm, the proposed algorithm is advantageous in performances of queuing delay and fairness while guaranteeing system throughput.

Realization of remote update technology for embedded equipment based on μC/OS-Ⅱ

Aiming at the inaccessible problem of remote embedded devices update and maintenance, this paper presents a method using general packet radio service （GPRS） to achieve update based on the embedded real-time operating system （RTOS） μC/OS-Ⅱ. It introduces architecture of the system first. And then it uses LPC1768 chip as the central processing unit, SIM900A module for data transmission, and SST25VF016B to store the data. To ensure accuracy of the data transmis- sion, cyclic redundancy code （CRC） is adopted. The software uses fixed bootstrap and mutable update program, and thus the embedded devices can still normally start in case of update failure. Finally, high stability and extensive adaptability of the system are verified by experimental data.

CHANNEL DE-ALLOCATION SCHEMES FOR GSM/GPRS NETWORKS

Several channel de-allocation schemes for GSM/GPRS(General Packet Radio Service) networks are proposed in this paper. For DRA (Dynamical Resource Allocation) with de-allocation mechanism, if a new voice call arrives and finds that all the channels are busy,then one of the GPRS packets which occupy more than one channel for data transmission may release a channel for the new voice call. This paper presents 5 de-allocation mechanisms, i.e.DA-RANDOM, DA-RICHEST, DA-POOREST, DA-OLDEST and DA-YOUNGEST, to select the GPRS packet for releasing the appropriate channel. Simulation results show that DAOLDEST achieves the best performance, especially in packets blocking probability, among all the de-allocation schemes. Although the performance of the proposed de-allocation schemes is not significantly different, they are all much better than that of the scheme without de-allocation.

Co-Simulation of an SRG Wind Turbine Control and GPRS/EGPRS Wireless Standards in Smart Grids

Wind energy can be considered a push-driver factor in the integration of renewable energy sources within the concept of smart grids.For its full deployment,it requires a modern telecommunication infrastructure for transmitting control signals around the distributed generation,in which,the wireless communication standards stand out for employing modern digital modulation and coding schemes for error correction,in order to guarantee the power plant operability.In some developing countries,such as Brazil,the high penetration of commercial mobile wireless standards GPRS and EGPRS(based on GSM technology)have captivated the interests of the energy sector,and they now seek to perform remote monitoring and control operations.In this context,this article presents a comparative performance analysis of a wireless control system for a wind SRG,when a GPRS or EGPRS data service is employed.The system performance is analyzed by co-simulations,including the wind generator dynamics and the wireless channel effects.The satisfactory results endorse the viability and robustness of the proposed system.

Remote positioning system based on GPS/GPRS

Considering the need of target positioning,a remote positioning system is designed based on global positioning system(GPS)and general packet radio service(GPRS);The data collection terminal is based on microcontroller unit(MCU)PIC24FV301.It uses GPRS network to create wireless link and transmits GPS source information which is collected by LEA-5H board to monitor center on the Internet.The monitor center obtains the target information through processing and analysis of the calculated data.Actual operation results indicate that the designed system has excellent performance and achieves the goal of the remote location.

Dynamic data packing towards the optimization of QoC and QoS in networked control systems

A class of networked control systems is investigated whose communication network is shared with other applications. The design objective for such a system setting is not only the optimization of the control performance but also the efficient utilization of the communication resources. We observe that at a large time scale the data packet delay in the communication network is roughly varying piecewise constant, which is typically true for data networks like the Internet. Based on this observation, a dynamic data packing scheme is proposed within the recently developed packet-based control framework for networked control systems. As expected this proposed approach achieves a fine balance between the control performance and the communication utilization: the similar control performance can be obtained at dramatically reduced cost of the communication resources. Simulations illustrate the effectiveness of the proposed approach.