Cellular Phone Technology

Analog Service is similar to FM radio in that modulating radio signals carry information such as voice or data. The receiver and transmitter must be tuned to the same frequency within a small band width for the receiver to rebuild the signal, amplify it, and send it to the speaker. There are limitations on the number of channels that can be used making this technology soon to be outlived. Effective February 2008, many wireless providers will be discontinuing support of this service.

Digital Service is a method similar to computers, in that it uses binary code of Os and 1s. Most new wireless phones and networks use digital technology. The analog signal in Digital is converted into binary code and transmitted as a series of on and off transmissions. There are three digital wireless technologies, CDMA, TDMA and GSM and I will explain these three as phones that work with one may not work on another.

TDMA (Time Division Multiple Access) was released in 1994; it uses the frequency bands available to the wireless network and divided them into time slots with each phone user having access to one time slot at regular intervals. In North America TDMA uses both 800 MHz and 1900 MHz bands. Most of the major wireless carriers use TDMA.

CDMA (Code Division Multiple Access) technology dates back to the 1940′s, when it was developed for military use because it was resistant to interference from enemy signals. Known as spread spectrum technology this technology was restricted to military use and top secret during World War 2. In the 1980′s the commercial use of this technology was realized after a 1976 publication of Spread Spectrum Systems by Robert Dixon was published.

Previous publications were classified military reports or narrow subtopics on academic papers. By 1993 CDMA was accepted as a standard and went into operation in 1996. CDMA also exists at both the 800 MHz and 1900 MHz band, and is used by the major carriers.

GSM (Global System for Mobile Communications) is based upon an improved version of TDMA technology. In 1982, a conference in Europe created a digital standard to allow users to roam from country to country in Europe. By 1987, the GSM standard was created based upon both analog and TDMA digital technologies. Using wider 200 kHz channels instead of the 30 kHz channels TDMA used along with other modifications they were able to speed up the bit rate with a more natural sounding voice-compression algorithm.

This also enabled GSM to provide such other data services as email, fax, internet browsing, and internet/LAN wireless access. The GSM standard was accepted in the United States in 1995 and is the only phone that can be used around the world. This technology will be the bases of future growth in the wireless phone industry as it offers the multifunction capabilities today’s users require.

CDMA Phones Employs Spread Spectrum Technology

CDMA stands for Code Division Multiple Access, a cellular technology that competes with GSM technology for dominance in the cellular world. Originally, it was developed by the Qualcomm and later on was enhanced by Ericsson. CDMA phones are characterised by high capacity small cell radius, employing spread-spectrum technology and a special coding scheme. In short, we can say that CDMA is a form of spread spectrum signaling.

For CDMA implementations there are many terms used. The original that was defined by the Qualcomm was known as IS-95. Later on, it was revised by the IS-2000 standard (CDMA 2000). All the major communication companies round the globe such as Nokia, Samsung, LG, Motorola Etc., utilize this cellular network of CDMA. The added advantage of CDMA phones is that it can be used as a USB Modem on Mac OS X.

Now a days there are different and exciting variations in CDMA phones. We now have cdma2000 and its variants like 1X EV, 1XEV-DO, and MC 3X. They refer to variants of usage of a 1.25 MHz channel. 3X uses a 5 MHz channel.

More and more added facilities and additions have been introduced such as:

Sprint has launched Mobile Movies on CDMA Phones

Live ABC TV News Programming over US Smart Phones

China Unicom has launched Dual Mode GSM CDMA Phones

Ericsson gets MTN South Africa 3G CDMA contract

QUALCOMM tests Assisted-GPS over CDMA

Lucent to support CDMA at 450 MHz

Nokia to Supply WCDMA 3G Network Expansion to MTC

CDMA 1xECDMA 1xEV-DO deployments grow

CDMA Phones include very accurate time signals (usually referenced to a GPS receiver in the cell base station), so cell phone CDMA-based clocks are an increasingly popular type of radio clock for use in computer networks. The main advantage of using CDMA cell phone signals for reference clock purposes is that they work better inside buildings, thus often eliminating the need to mount a GPS antenna outside a building.

CDMA Phones have the facility of international roaming globally. With this facility, you can expect your phones to work everywhere with all services. Regional, National or International roaming have several elements that are required in order for CDMA roaming to be facilitated, such as CDMA roaming business elements, technical elements, service features, roaming service providers, inter-carrier implementation and roaming carrier maintenance.

What Is Mobile Satellite Internet Service?

Do you frequently need the internet while you are on the go and get tired of dealing with limited data availability from mobile carriers? Then mobile satellite internet services might be the solution for which you are looking. With this type of connection, you can get fast speed coverage no matter where you are, even if you are past the typical cellular-based or terrestrial-based network coverage area. There are a few key factors about the service that you need to know before you search for the best satellite internet provider.

Where Can You Connect to the Internet?

The benefit of this type of internet service is that you can connect no matter where you are. You can mount a satellite on a truck, RV, van, trailer, railroad car or any other type of vehicle. Then, you can access the web no matter where you roam, even if you head into areas that typical mobile connections do not cover. Depending on the equipment, you also do not have to worry about dealing with inclement weather messing up your satellite link. As long as you have clear access to the sky, you can access the web.

What Equipment Is Needed?

When you work with the best satellite internet provider, you do not have to worry about bringing your own equipment. They will determine the best options for your situation and service plan. Typically, you will need to have some type of satellite that attaches to your automobile, trailer or other vehicle. Then, you will also need to have some type of power, which might be the use of a generator or a turnkey or some other powering device. There might also be some type of modem or similar device that acts as a mobile hotspot so that your device can connect to the internet. The exact equipment requirements will depend on your needs and provider.

How Fast of a Connection Is Available?

Although satellite internet is not as fast as cable or DSL, it does have quite high speed capability. Depending on the provider, you can have high speeds that are faster than you thought possible in such remote areas. You can typically get between 10 and 20 MBPS x 5 MBPS speed, although with the best satellite internet provider you might get higher rates.

Who Benefits From This Service?

There are many people who rely on mobile satellite internet services. Reporters and media personnel who travel to cover stories will never know where they might need the internet. Those who travel around the country in an RV might wish to have this type of service so that they never have to worry about not having access to the internet. It also serves as a source of emergency communication for when you travel outside of mobile coverage. Law enforcement agencies might use it when they are patrolling certain areas without easy access to the web, and government and nonprofit agencies use it during disaster response. There are many other reasons that people might decide that they are in need of internet on the go.

There are many reasons why people might need to access the internet on the go. When this takes you to remote areas, choosing a mobile satellite provider keeps you in touch no matter where you are.

Wireless Video Camera Technology Explained

Video systems are becoming a part of our everyday lives. When video surveillance systems first hit the market in the mid 80′s, they immediately made a major impact on crime prevention and the way crimes are investigated. Early video systems required a hardwired connection between the camera and the recording system. Recent innovations in wireless video transmission are changing that requirement.

Wireless video systems are popping up all over the place to satisfy a range of consumer requirements. From wireless baby monitors to high-end high-definition wireless broadcast systems, wireless video systems are available in a wide range of prices, features and functions.

Most modern, consumer grade wireless video systems will fall into one of the following frequencies; 900 MHz, 2.4 GHZ or 5.8 GHz. Almost all of the affordable consumer grade wireless cameras on the market fall into the 2.4 GHz range.

Every wireless video system consists of a camera, a transmitter, a receiver, an antenna and a power supply. Transmission ranges can vary greatly depending on the frequency, the antenna and the rated power output.

With the exception of higher end, high power broadcast quality systems; most wireless video systems do not require a license from the Federal Communication Commission (FCC) to operate. No matter what frequency you plan on using, if you are installing a high powered installation, especially near a highway or an airport, you should secure the appropriate FCC license.

For the best results and the longest range, most wireless video transmission systems require a clear line of site between the transmitter and the receiver to operate consistently. Wireless video signals do not penetrate very well through glass, walls, concrete, trees, steel or other obstructions.

In addition, other RF signals around the same frequency can cause interference or be interfered with by wireless video systems. In the 2.4 GHz range popular with most security applications, interference can be experienced between cordless phones, microwave ovens, local television broadcasts, computer monitors, power supplies or wireless LAN/WANs. Sometimes interference problems can be solved by re-locating the transmitters or receivers.

Since 90% of consumer grade wireless video systems fall into the 2.4 GHz category, we will discuss the features of both the 2.4 GHz analog and digital systems and the limitations and benefits of each.

The entire 2.4 GHZ bandwidth allocated for consumer use is from 2,412 MHz to 2,462 MHz. As per the FCC standards, there are 11 possible channels which are 22 MHz wide with a 5 MHz spacing interval between each.

In order to allow multiple cameras on the same system, residential, consumer grade 2.4 GHz analog video transmitters such as a wireless baby monitor or a front door camera require fixed frequency, non-overlapping channels to reduce interference.

These 2.4 GHz analog wireless cameras are some of the most popular video surveillance systems for consumers and end users, yet very few professional security providers will offer these wireless cameras.

At best, professional security installers consider the 2.4 GHz analog video systems as low-end residential solutions which are notoriously unreliable. The analog 2.4 GHz cameras are easily identified by their price tag which is usually in the $ 69.00 to $ 140.00 range per camera.

If you take away the benefit of their low cost, there are several inherent limitations to Analog 2.4 GHz video transmission including:

In the 2.4 GHz range, there are only 4 available non-overlapping channels. This limits these systems to a total of 4-cameras, each of which is tuned to a different pre-defined frequency. Each of these fixed frequencies is capable of transmitting about 11 mega-bits per second of data (Mbps).

Because the analog 2.4 GHz wireless video transmitters are on fixed frequencies, they are especially susceptible to interference from outside sources. A typical transmission range for an analog 2.4 GHz wireless video link is about 200 to 300 feet when installed outdoors with a clear line of site. The relative transmission distance is greatly reduced when installed indoors with some lower end analog systems typically providing about 10-30 feet.

Since these cameras are transmitted on a fixed, un-secured open frequency, the signal is easily intercepted and can be seen by anyone with a 2.4 GHz 4-channel receiver. A voyeur or a burglar could simply drive around a neighborhood with a receiver and see inside your home. If you have one of these systems installed, perhaps a burglar is watching you right now.

In 1997, the Institute of Electrical and Electronics Engineers (IEEE) created the first Wireless Local Area Network (WLAN) standard which was named 802.11. The original 802.11 utilized the 2.4 GHz frequency to allow reliable transmission of 2-Mbps of bandwidth. In 1999, the standard was upgraded to 802.11b which supports up to 11 Mega-Bits per Second (Mbps) which was comparable to traditional Ethernet connectivity speeds.

The 802.11 protocol works by sub-dividing the entire 2.4 GHz frequency into channels and switching between them during transmissions. As the signal is sent, it sends a packet of data at one frequency and then hops to the next channel and sends another packet and so on, until the entire data package is sent.

In 2003, WLAN products began supporting a new 2.4 GHz wireless standard called 802.11g which supports a bandwidth of 108 Mbps of data. The days of cost effective, reliable and secure wireless video transmission have finally arrived.

The added features and benefits of using internet protocol cameras and 802.11g for wireless video transmission in a security application are many.

The 802.11g protocol utilizes digital bi-directional signals which support the use of pan/tilt/zoom functions and presets found in many newer cameras. The digital signal used is duplex (bi-directional) as opposed to the simplex (one-way) binary signal used in analog type systems.

Because 802.11g utilizes the entire 2.4 GHz frequency spectrum, interference is greatly reduced and longer transmission ranges can be expected. If an area of the frequency is noisy then the transmitter/receivers will adapt the signal by sending smaller packets in the noisy affected area and larger packets in the non-effected areas of the frequency. A wireless IP video system will offer almost the same performance as a professional grade wired system with a reliable transmission range of 150-200 feet.

If the camera is to be located further than 200 feet, directional antennas are available which can increase the distance to 600 or more feet. If a greater distance than 600 feet is required, point to point, long range directional type systems can increase the distance to several miles.

In addition to standard 64/128-bit WEP Security, 802.11g protocol allows data packets to be encrypted using a 40-bit RCA key. When considered in conjunction with the inherent security built into DSSS spread spectrum technology, the data signals are at least as secure as data traveling over a wired network.

The 802.11g protocol can support a much larger number of wireless cameras by using a medium access control or MAC layer called CSMA/CA or Carrier Sense Multiple Access/Collision Avoidance. The collision avoidance in 802.11g supports the use of CTS/RTS signals (clear to send/ready to send) which tell each camera on the system when it is O.K. to begin transmitting or receiving data thereby avoiding interference.

Any hardwired IP Camera that is installed on your intranet or internet that is using the same CODEC (Coding & Decoding) algorithm can be integrated into the same software viewing and recording system.

An IP addressable camera system can be viewed or recorded from a properly equipped computer from any location in the world. This can allow you the freedom to move anywhere on the planet while still keeping track of your assets. In addition, if you ever decide to move your head end recording equipment to a different location, you simply pick it up and move it. No wires to re-route.

One thing to remember when deploying a multi-camera wireless IP based video system is that processing multiple streaming video signals places a substantial work load on a computers CPU.

Hard Wired systems have video capture cards which are installed in the PC/DVR. These cards take up to half of the work load off the computers CPU. Because wireless IP video systems do not have the help of these capture boards, the computers CPU must handle 100% of the processing workload.

What this means is that as you add cameras to a wireless system the total frame rate or the total images per second which can be viewed and recorded will decline due to the increased workload.

Some people shy away from IP and network security solutions because they appear to be complicated and difficult to set up. The fact is the initial set up does require some expertise and knowledge but the operation and day to day use of the systems are no different than using any other PC based security camera system. The required computer skills are minimal. If a person can check email, use a word processing program or load and play any type of game on a PC they most likely possess the skills needed to use and manage a PC based system.

Find A Quality Laptop Repair In San Diego Service Provider By Best Deal Computers

Search for a laptop repair service? What things do you remember before taking your laptop to Notebook Repair Center? In this article, you will find the details that help you pick the best mobile computer repair company in the area and get quality
laptop repair in san diego service without facing much trouble or stress.

There could be cases once you drop your notebook or spill over it coffee accidentally then you will definitely seek for a help of some good services center to fix the damage caused to your laptop. You need to find the quality service center in quick time to avoid any serious damage to your current laptop. In this article, the questions like how good the services center will be and what will it expense and how much significantly I have to travel to get my notebook fixed also arise in mind while you are trying to find a quality laptop repair in San Diego service provider. Not only this, another important question of what will happen to our data stored inside notebook also puts you in stress.

Here is a help getting provided to you with all the below mentioned suggestions you may follow regarding reaching a quality notebook repair service without facing much trouble or stress, since
Where to Go for Repair?

The particular computer service san diego service center of the respected company is the best choice initially for your notebook repair needs. Because the service center is run by the well-known brands and their committed staffs perform their responsibility in the best manner. Though their fees are the bit more than others yet what they charge are for high-quality repair, replacement and improve services. Otherwise, if you still want to get your laptop repaired at some reasonably priced repair facilities, you can search on the internet for such service facilities.

How much time is the Repair going to take?

The amount of time is dependent upon the nature of the damage caused for the laptop. The brand of the notebook is also an aspect that delays or accelerates the repair process as if the brand of the laptop is less famous because particular region or perhaps country then it will take the time to arrange its broken parts from other locations that are clearly a moment consuming process.

What’ll happen to Data Stored Inside?

It also depends upon the nature of the damage as if it is hardware related like display or else then to become alarmed regarding worry as data will be safe on the laptop and will be back as it is after the laptop will be repaired but if the damage is drive or disk related then there could be a data loss problem. But still making use of software, lost data can be recovered and saved as being a backup for the safety from such instances in future, if any.