WiFi Technology

What is Wi-Fi? WiFi is a wireless technology brand owned by the Wi-Fi Alliance intended to improve the operating of wireless products. Common applications for Wi-Fi include Internet and VoIP phone access, gaming, and network connectivity for consumer electronics such as mobile phones, laptops, game consoles, MP3 players and PDA's. Wi-Fi also allows connectivity which enables devices to connect directly with each other. This connectivity mode is useful in consumer electronics and gaming applications. It's faster and has a greater range than Bluetooth, and is ideal for home or office connectivity. In the near future, wireless networking may become so widespread that you can access the Internet just about anywhere at any time, without using wires. The easy access of emails for business orientated individuals is also a bonus, as urgent messages can be downloaded on the go once the email settings are configured on to the WiFi enabled handset.

The mobile phones market has received a lot of attention lately as several operators across the world have launched various types of handsets which allow users to connect to the Internet via Wi-Fi, the iPhone being the ultimate example.

Mobile VoIP

A new study from a London-based research firm claims that mobile voice-over-IP will become a mainstream form of communication by the end of 2012, based on rapid growth of voice-over-3G wireless users. Disruptive Analysis said its research shows mobile VoIP will eclipse fixed-mobile convergence services that use dual-mode handsets with voice-over-WiFi capabilities.

VoIP has become popular largely because of the cost advantages to consumers over traditional telepone networks. VoIP calls can be placed across the Internet. Most Internet connections are charged using a flat fee structure. Using the Internet connection for both data traffic and voice calls can allow consumers to get rid of one monthly payment. In addition, VoIP plans do not charge a per-minute fee for long distance. For International calling, the monetary savings to the consumer from switching to VoIP technology can be enormous.

Today, Skype, TruPhone and a company called Fring already offer VoIP over 3G smartphones and 3G-enabled laptops allowing users to communicate with other VoIP users via the Internet. This service is expected to provide customers with a cheaper alternative to connecting calls via GSM in the near future.

HSDPA

High-Speed Downlink Packet Access (HSDPA) is a 3G (third generation) mobile telephony communications protocol in the High-Speed Packet Access (HSPA) family, which allows networks based on Universal Mobile Telecommunications System (UMTS) to have higher data transfer speeds and capacity. Current HSDPA deployments support down-link speeds of 1.8, 3.6, 7.2 and 14.4 Mbit/s. Further speed increases are planned for the near future

The Latest Mobile Phone Technology

The latest mobile phone handsets provide a wide range of services and technology that allows the user to be as interactive as possible with the global community. These new mobile technologies offer the user accessibility to the worldwide web via WiFi connectivity, download and transfer large amounts of data via high speed connectivity and find a location via satellite with mobile Global Positioning Systems (GPS) devices.

Todays mobile phones have now evolved to incorporate all types of online activity, here is a little breakdown of some of the latest technology to grasp the mobile market.

Neelesh SiNgh

Difference between time sharing and multitasking

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1.Time-sharing refers to sharing a computing resource among many users by multitasking.Because early mainframes and minicomputers were extremely expensive it was rarely possible to allow a single user exclusive access to the machine for interactive use. But because computers in interactive use often spend much of their time idly waiting for user input it was suggested that multiple users could share a machine by using one user's idle time to service other users. Similarly small slices of time spent waiting for disk tape or network input could be granted to other users.The concept was first described publicly in early 1957 by Bob Bemer as part of an article in Automatic Control Magazine. The first project to implement a time-sharing system was initiated by John McCarthy in late 1957 on a modified IBM 704 and later an additionally modified IBM 7090 computer. Although he left to work on Project MAC and other projects one of the results of the project known as the Compatible Time Sharing System or CTSS was demonstrated in November 1961. CTSS has a good claim to be the first time-sharing system and remained in use until 1973. The first commercially successful time-sharing system was the Dartmouth Time-Sharing System (DTSS) which was first implemented at Dartmouth College in 1964 and subsequently formed the basis of General Electric's computer bureau services. DTSS influenced the design of other early timesharing systems developed by Hewlett Packard Control Data Corporation UNIVAC and others (in addition to introducing the BASIC programming language).Other historical timesharing systems some of them still in widespread use include: IBM CMS (part of VM/CMS) IBM TSS/360 (never finished; see OS/360) IBM Time Sharing Option (TSO) KRONOS (and later NOS) on the CDC 6000 series Michigan Terminal System Multics MUSIC/SP WYLBUR RSTS/E UNIX

Time-division multiplexing

Time-division multiplexing (TDM) is a type of digital or (rarely) analog multiplexing in which two or more signals or bit streams are transferred apparently simultaneously as sub-channels in one communication channel, but are physically taking turns on the channel. The time domain is divided into several recurrenttimeslots of fixed length, one for each sub-channel. A sample byte or data block of sub-channel 1 is transmitted during timeslot 1, sub-channel 2 during timeslot 2, etc. One TDM frame consists of one timeslot per sub-channel plus a synchronization channel and sometimes error correction channel before the synchronization. After the last sub-channel, error correction, and synchronization, the cycle starts all over again with a new frame, starting with the second sample, byte or data block from sub-channel 1, etc.

External Bus

The external bus is also referred to as the expansion bus. There are six major types of external bus’s found on the common motherboard. Only a few of these are actually found on the home PC such as ISA, PCI, AGP, USB and IDE. These slots are easily recognized on the board. They are usually covered with pins on the inside channel. Some of these pins are made of tin or gold. The pins themselves actually mount into the internal bus. Some pins provide power to you component or connect to the data, address bus’s. Here is a description of some common buses

ISA (Industry Standard Architecture), This bus is the low speed work horse of the system. You will commonly find a Sound Card hooked up this type BUS.

PCI (Peripheral Component Interconnect), Supports 32-64 bit bus and is the reigning standard of external buses. The PCI is fast and is slowly making the ISA fade away. Go with a PCI BusCard when possible.

AGP (Accelerated Graphics Port), This Bus provides from 2 to 4 times the speed of the PCI and is used for video expansion only. If you have this slot on your motherboard make sure and use it for you video card. This is great way to go and takes a lot of stress off the CPU, thus gaining in performance all the way around.

USB (Universal Serial Bus), This is something that is fairly new and allows you to hook up to 127 devices. This is probably going to wipe out PS/2 ports and more. The USB is allows you to hot swap devices or plug and unplug devices while system is running. This is a great feature and is incorporated on most new motherboards.

IDE (Intelligent Drive Electronics), This bus is used mostly for disk drives and connects up to two devices on one connection. More than likely you’re hard drive and CD-ROM are connected through this type bus.

There are a few more bus types that are not very common and some are not even in uses in modern computers. The buses above are the most common and found in modern motherboards.

-So what are the slots mad up off? We already know that there are little pins made out of gold and tin, but what else? Check out the Slot's Makeup

Overview of motherbord

A motherboard, like a backplane, provides the electrical connections by which the other components of the system communicate, but unlike a backplane, it also connects the central processing unit and hosts other subsystems and devices.




A typical desktop computer has its microprocessor, main memory, and other essential components connected to the motherboard. Other components such as external storage, controllers for video display and sound, and peripheral devices may be attached to the motherboard as plug-in cards or via cables, although in modern computers it is increasingly common to integrate some of these peripherals into the motherboard itself.



An important component of a motherboard is the microprocessor's supporting chipset, which provides the supporting interfaces between the CPU and the various buses and external components. This chipset determines, to an extent, the features and capabilities of the motherboard.



Modern motherboards include, at a minimum:



sockets (or slots) in which one or more microprocessors may be installed[3]

slots into which the system's main memory is to be installed (typically in the form of DIMM modules containing DRAM chips)

a chipset which forms an interface between the CPU's front-side bus, main memory, and peripheral buses

non-volatile memory chips (usually Flash ROM in modern motherboards) containing the system's firmware or BIOS

a clock generator which produces the system clock signal to synchronize the various components

slots for expansion cards (these interface to the system via the buses supported by the chipset)

power connectors, which receive electrical power from the computer power supply and distribute it to the CPU, chipset, main memory, and expansion cards.[4]



The Octek Jaguar V motherboard from 1993.[5] This board has 6 ISA slots but few onboard peripherals, as evidenced by the lack of external connectors.Additionally, nearly all motherboards include logic and connectors to support commonly used input devices, such as PS/2 connectors for a mouse and keyboard. Early personal computers such as the Apple II or IBM PC included only this minimal peripheral support on the motherboard. Occasionally video interface hardware was also integrated into the motherboard; for example, on the Apple II and rarely on IBM-compatible computers such as the IBM PC Jr. Additional peripherals such as disk controllers and serial ports were provided as expansion cards.



Given the high thermal design power of high-speed computer CPUs and components, modern motherboards nearly always include heat sinks and mounting points for fans to dissipate excess heat.

AM transmission

In order to better understand the way the radio transmitter works, block - diagram of a simple AM (amplitude modulated) signal transmitter is shown on Pic.2.2. The amplitude modulation is being performed in a stage called the modulator. Two signals are entering it: high frequency signal called the carrier (or the signal carrier), being created into the HF oscillator and amplified in the HF amplifier to the required signal level, and the low frequency (modulating) signal coming from the microphone or some other LF signal source (cassette player, record player, CD player etc.), being amplified in the LF amplifier. On modulator's output the amplitude modulated signal UAM is acquired. This signal is then amplified in the power amplifier, and then led to the emission antenna.

 

The shape and characteristics of the AM carrier, being taken from the HF amplifier into the modulator, are shown on Pic.2.3-a. As you can see, it is a HF voltage of constant amplitude US and frequency fS. On Pic.2.3-b the LF signal that appears at the input of the modulator at the moment t0 is shown. With this signal the modulation of the carrier's amplitude is being performed, therefore it is being called the modulating signal. The shape of the AM signal exiting the modulator is shown on Pic.2.3-c. From the point t0 this voltage has the same shape as that on Pic.2.3-a. From the moment t0 the amplitude of AM signal is being changed in accordance with the current value of the modulating signal, in such a way that the signal envelope (fictive line connecting the voltage peaks) has the same shape as the modulating signal.
Let's take a look at a practical example. Let the LF signal on Pic.2.3-b be, say, an electrical image of the tone being created by some musical instrument, and that the time gap between the points t0 and t2 is 1 ms. Suppose that carrier frequency is fS=1 MHz (approximately the frequency of radio Kladovo, exact value is 999 kHz). In that case, in period from t0 till t2 signals us on Pic.2.3-1 and uAM on 2.3-c should make a thousand oscillations and not just eighteen, as shown in the picture. Then It is clear that it isn't possible to draw a realistic picture, since all the lines would connect into a dark spot. The true picture of AM signal from this example is given on Pic.2.3-d. That is the picture that appears on screen of the oscilloscope, connected on the output of the modulator: light coloured lines representing the AM signal have interconnected, since they are thicker than the gap between them.
Block - diagram on Pic 2.2 is a simplified schematic of an AM transmitter. In reality there are some additional stages in professional transmitters that provide the necessary work stability, transmitter power supply, cooling for certain stages etc. For simple use, however, even simpler block diagrams exist, making the completion of an ordinary AM transmitter possible with just a few electronic components