This paper presents one of the emerging applications of the GSM technology. We present the design of a stand – alone embedded system that can monitor and control home appliances local using built-in I/0 peripherals. Remotely, the system allows the house owner to monitor and control his house appliances via his mobile phone set by sending commands in the form of SMS messages and receiving the appliances status as well. The system has two parts namely Hardware and software. The hardware architecture consists of a stand-alone embedded system that is based on 8 bit Microcontroller, an interface and a driver circuit to connect the devices to the Microcontroller, an LCD display, and a GSM modem. The GSM modem provides the communication media between the house owner and the system by means of SMS messages. The system software driver is developed using an interactive C programming language platform.
In this project, the home appliance is controlled with the help of a cell phone. The system uses SMS facility to give the commands and receive the status from the receiver. The mobile user sends a secret code with control data. In the receiver section, GSM modem receives the commands and sends the signal to the Microcontroller. The microcontroller verifies the secret code and performs the command function. The controller also triggers the relay circuit through the relay drivers. The Relay drivers in turn control the load. The status is sent back to the mobile user as well as sends to pc.
The automatic Timely device control system is implemented by using 32-bit embedded micro controller. The embedded micro controller used here is LPC2148 micro controller. Since, this micro controller has in-built peripherals it is called as embedded controller. The LPC2148 is a 32-bit RISC micro controller based on ARM7TDMI architecture.
The device is connect with the embedded micro controller acting as the CPU to decide the operation of the device and the GSM module to read the command from the remote mobile. The GSM module is always ready to read the message from the airborne signal. If it reads any message corresponding to it, it stores the message. GSM Modem provides full functional capability to Serial devices to send SMS and Data over GSM Network. The GSM Modem supports popular "AT" command set so that users can develop applications quickly. The product has SIM Card holder to which activated SIM card is inserted for normal use. By using “AT” commands the micro controller reads the message from the GSM module.
According to the message the micro controller is programmed to switch on or switch off the relays connected with the devices. Relay is an electromechanical device, which transforms an electrical signal into mechanical movement, through which we can control the devices. It is possible to switch ON/OFF any devices in the industry, from anywhere.
GSM has been the backbone of the phenomenal success in mobile telecom over the last decade. Now, at the dawn of the era of true broadband services, GSM continues to evolve to meet new demands. GSM is an open, non-proprietary system that is constantly evolving. One of its great strengths is the international roaming capability. This gives consumers seamless and same standardized same number contact ability in more than 212 countries. This has been a vital driver in growth, with around 300 million GSM subscribers currently in Europe and Asia. In the Americas, today's 7 million subscribers are set to grow rapidly, with market potential of 500 million in population, due to the introduction of GSM 800, which allows operators using the 800 MHz band to have access to GSM technology too. GSM satellite roaming has extended service access to areas where terrestrial coverage is not available. GSM differs from first generation wireless systems in that it uses digital technology and time division multiple access transmission methods. Voice is digitally encoded via a unique encoder, which emulates the characteristics of human speech. This method of transmission permits a very efficient data rate/information content ratio.
Cellular mobile communication is based on the concept of frequency reuse. That is, the limited spectrum allocated to the service is partitioned into, for example, N non-overlapping channel sets, which are then assigned in a regular repeated pattern to a hexagonal cell grid. The hexagon is just a convenient idealization that approximates the shape of a circle (the constant signal level contour from an Omni directional antenna placed at the center) but forms a grid with no gaps or overlaps. The choice of N is dependent on many tradeoffs involving the local propagation environment, traffic distribution, and costs. The propagation environment determines the interference received from neighboring co-channel cells, which in turn governs the reuse distance, that is, the distance allowed between co-channel cells (cells using the same set of frequency channels).
The cell size determination is usually based on the local traffic distribution and demand. The more the concentration of traffic demand in the area, the smaller the cell has to be sized in order to avail the frequency set to a smaller number of roaming subscribers and thus limit the call blocking probability within the cell. On the other hand, the smaller the cell is sized, the more equipment will be needed in the system as each cell requires the necessary transceiver and switching equipment, known as the base station subsystem (BSS), through which the mobile users access the network over radio links. The degree to which the allocated frequency spectrum is reused over the cellular service area, however, determines the spectrum efficiency in cellular systems. That means the smaller the cell size, and the smaller the number of cells in the reuse geometry, the higher will be the spectrum usage efficiency.
Since digital modulation systems can operate with a smaller signal to noise (i.e., signal to interference) ratio for the same service quality, they, in one respect, would allow smaller reuse distance and thus provide higher spectrum efficiency. This is one advantage the digital cellular provides over the older analogue cellular radio communication systems. It is worth mentioning that the digital systems have commonly used sectored cells with 120-degree or smaller directional antennas to further lower the effective reuse distance. This allows a smaller number of cells in the reuse pattern and makes a larger fraction of the total frequency spectrum available within each cell. Currently, research is being done on implementing other enhancements such as the use of dynamic channel assignment strategies for raising the spectrum efficiency in certain cases, such as high uneven traffic distribution over cell
we respect your privacy.