On Wed, Apr 25, 2012 at 9:36 AM, Vignesh Rajendran <[email protected]> wrote: > On Thu, Apr 19, 2012 at 3:24 PM, Amirtharaja Alankaram < > [email protected]> wrote: > >> >> HI Friends >> I am one among the member of this group right now i am doing my >> ME in MIIT chennai,,if anyone could help me for knowing the basics of real >> time embedded system in open source or any pdf files about this topic or >> any wireless networks configuration in linux environment please help me >> regarding this...im eagerly waiting for your reply
In LUG we are very familiar with people eagerly waiting to do student projects, completing office deadlines and doing small projects. But the real joy of intellectual labor is when we solve real life problems in real life settings for businesses where networking problems will solve his business issues , give him peace of mind and also get you some cash in the bargain. There are very few such questions concerning work that is challenging, real life and long term. Anyway I will now proceed to answer your questions: You ask two things: 1) Real time embedded systems 2) Wireless configuration in Linux I only know little bit about wireless and Linux. Real time embedded systems are basically divided into two: 1) hard real time 2) soft real time Hard real time embedded systems are mission critical and used in surgical equipment, life saving equipment, rocket launching and plane cockpits. Soft real time embedded systems are used in routers, switches and networking equipment where a delay in performing a programming task will not endanger a life. There are two types of CPU scheduling broadly speaking. Pre emptive multi tasking and non pre emptive multitasking. In pre emptive multi tasking, the running process is forcibly jettisoned to replace with a new process to ensure fair allocation of resources to waiting processes in the Q. In non pre emptive multi tasking a long running process can starve others since it may be a rogue. In other words non pre emtive multi tasking is democracy in which rules are lenient. How does this relate to real time embedded systems? In embedded systems , say hard real time, you have pre emptive multitasking. Then there is priority queuing in which the mission critical processes like disk I/O, network interrupt processing when you receive packets are run at a higher importance than say some music playing or handling user interface. A real time OS also has other characteristics like low CPU, memory, secondary storage, no swap, usually no MMU(which means not multi processing based), and it will have power saving needs which are usually built into wireless antenna management software. Now let us talk about wireless. A wireless transceiver works based on certain characteristics: 1) What is the arbitration protocol for transmitting? Bus arbitration similar to CSMA/CD on ethernet or inside a computer , how the control bus interfaces the peripherals like memory, CPU, keyboard and so on 2) What is the encoding in wireless to transfer data? Say, CDMA(spread spectrum), QPSK and so on 3) The topology of the network, bus, star, mesh and so on Okay now the various wireless protocols in vogue are: 1) WiFi 802.11a to i 2) Bluetooth 3) WiMAX 4) IrDA 5) USB wireless for keyboard and mouse interfacing 6) Others like Zigbee probably are built on top of the above Bluetooth is low speed wireless and WiFi is the fastest. Usually wireless is unreliable and fixed wireless between satellite and earth station and between two line of sight microwave towers are the best. All other wireless technologies suffer from throughput issues. -Girish _______________________________________________ ILUGC Mailing List: http://www.ae.iitm.ac.in/mailman/listinfo/ilugc
