Showing posts with label Connectivity Technology. Show all posts
Showing posts with label Connectivity Technology. Show all posts

Jul 18, 2011

Boost Weak Cell Service at Home: Your Options

Boost Weak Cell Service at Home: Your Options

Even the best wireless networks often can't deliver a consistent signal inside your house. Femtocells and repeaters will usually help, but they'll cost you.

The problem is familiar to many cell phone users: When you're indoors, even within your carrier's coverage area, the network's signal sometimes simply isn't strong enough to support voice calls or data services. With so many consumers ditching their landlines for cell phones, poor reception at home is no longer acceptable. Fortunately, a slew of products now address the problem, though they don't come cheap.

Ssignal-boosting products generally fall into one of two categories: femtocells or signal repeaters. Both types of equipment can deliver strong signals within buildings, but they work in fundamentally different ways.

Femtocells act as miniature cell phone towers that connect to a home network router and use your wired broadband connection to move voice calls and data services to and from your carrier's network. Femtocells don't rely on the carrier's towers at all, but because they use technology that can direct data and calls back to the carrier networks over the Internet, most of them are sold by the carriers themselves.

Repeaters and boosters, on the other hand, amplify and rebroadcast cell tower signals. Since they don't require carrier support, they tend to be manufactured and sold by third parties such as Wi-Ex (under the brand name ZBoost) and Wilson Electronics.
Understanding Femtocells

While repeaters have been around for several years, femtocells are relative newcomers to the mobile scene. Of the four major U.S. carriers, two--Sprint and Verizon--have been selling femtocells (under the brand names Airave and Network Extender, respectively) for the past few years; AT&T introduced its 3G MicroCell femtocell last year.

The first Sprint and Verizon Wireless femtocells supported only voice calls, but current models support high-speed data as well as voice. Sprint charges $130 for its Airave access point (with a two-year service plan); there's no additional charge for using Airave to enhance coverage with an existing plan, but Sprint does offer a $25-a-month unlimited calling plan for Airave calls--which might appeal to anyone who is considering dropping landline voice service. Current Airave access points support EvDO Rev. A 3G data speeds and up to six simultaneous calls.

Verizon Wireless charges $250 for its Network Extender, which also supports 3G data, and the carrier imposes no monthly service fee. AT&T sells the MicroCell for $150, also with no mandatory service fee; it also offer an optional $20-a-month unlimited calling plan, plus price breaks for customers who sign up for the company's DSL service.

The Beauty of the Femtocell
AT&T's 3G MicroCell, made by Cisco.


Femtocells appeal to consumers and carriers on several levels. Consumers like them because they provide immediate five-bar coverage across an area of up to 2500 square feet, regardless of how far you are from a cell phone tower. A strong signal typically means better voice quality, fewer dropped calls, and faster data speeds. Good signals also improve a phone's battery life, since its radios don't have to work as hard.


Femtocells are low-power wireless access points that operate within a licensed spectrum to connect standard mobile devices to a mobile operator’s network via residential DSL or cable broadband connections.


Another benefit: You can configure the femtocell to recognize and prioritize the phones you authorize, so neighbors can't mooch off your service at your expense. Interestingly, Verizon Wireless's FAQ for its Network Extender says that, though you can prioritize up to 50 Verizon Wireless numbers, the device will remain available to all Verizon Wireless subscribers within range when priority numbers aren't using it.

This brings us to a big reason why wireless providers like femtocells: They offload some of the expense that the carriers might otherwise incur in order to expand network capacity and/or coverage. Femtocells also help retain customers in locations where carriers can't significantly improve reception on their own (such as basements, suburbs that don't want new cell towers, locales with difficult topography such as steep hills and valleys, and skyscrapers with thick walls). In fact, forum posts indicate that Sprint has occasionally given customers Airave units to keep them from switching to another carrier.


Femtocell Weaknesses

Price aside, femtocells have some limitations. For one thing, you can use a femtocell only at the address where it is registered. To enforce that restriction, the FCC stipulates that all femtocells must be equipped with GPS receivers, and that they either must be placed close enough to a window to receive GPS signals directly or must be connected to a GPS antenna that can pick up the signals.

David Nowicki, marketing vice president for femtocell vendor Airvana and for the Femto Forum trade association, says that the FCC imposed the location restriction to enable carriers to track the femtocell's position and disable its operation in areas where the carrier doesn't own the frequencies that the femtocell supports and where, consequently, using the femtocell might interfere with another carrier's network. Even so, forum posts suggest that femtocells sometimes hurt neighbors' regular network reception when deployed in close proximity.

Then again, it’s not necessarily a bad thing that femtocells are aware of their location. That, coupled with the device's ability to recognize when an authorized phone is nearby, could enable carriers to offer customers additional services that go beyond improving reception, including 911 services.

Network handoff issues are another concern. You can start a call on femtocell service and then hand it off to the regular network as you leave the femtocell's coverage area (assuming that the nearest cell tower is close enough). But calls initiated on the regular network can't be handed off to a femtocell.

And finally, critics complain about having to pay for a service that essentially deliver what the wireless network is supposed to have provided all along. "It's a fair point," Nowicki concedes. But carrier spokespeople say that no carrier can provide coverage in all locations of its service area. Verizon Wireless spokesperson Thomas Pica describes the Network Extender as a "niche product," given that the vast majority of Verizon customers don't need one because of the carrier's robust network.

What about the broadband ISP that now gets to carry the wireless carrier's traffic? Nowicki says that the bandwidth consumption of mobile devices is tiny compared to that of most home and office networks. For that reason, femtocells don't impose a significant burden on the ISP, which in some cases is run by the same company as the mobile carrier anyway.
T-Mobile’s Approach

T-Mobile has taken a different approach to improving weak cell signals. Phones that support Wi-Fi Calling use UMA (Unified Mobile Access) technology to route calls over Wi-Fi hotspots. T-Mobile notes that this helps with calls made through any hotspot that its phones can access, and not just at a single location (which is the case with femtocells). However, T-Mobile's Android phones can't hand off calls made using Wi-Fi hotspots to T-Mobile's cellular network; other phones that support Wi-Fi Calling can. T-Mobile has no announced plans to introduce femtocells, but a spokesperson says that the carrier continues to review customer equipment options for improving coverage.


Repeaters and Boosters

Repeaters (also called "boosters")--the other class of products designed to improve poor cell reception--depend on at least a weak cell tower signal to amplify and rebroadcast. They work with specific frequencies, independent of carrier; some support more than one frequency. On the frequencies they support, repeaters improve both voice calls and data speeds.




Many repeaters have multiple parts, starting with an antenna that you place as close as possible to the strongest cell tower signal--typically, near a window or even outdoors. The antenna transmits signals over a cable connected to an amplifier, which boosts the signal and retransmits it indoors. In some cases, the amplifier and indoor antenna are integrated; in others, the amplifier hooks up to a separate, centrally located indoor antenna in the home or office. The area of coverage depends on the strength of the amplifier and of the signal being amplified.

Unlike femtocells, repeaters can't be configured to recognize specific phones. Consequently, the amplified signals benefit any mobile device within range that operates on the supported frequencies--though obviously the owner's devices are more likely to benefit than a neighbor's devices located farther away from the indoor antenna. It's up to you (with the help of your reseller) to ensure that your repeater kit amplifies the frequency or frequencies that your carrier uses in your area. You can get help in choosing the right repeater kit from specialty retailers such as wpsantennas.com or RepeaterStore.
Repeaters Don’t Come Cheap

Repeater kits can be more expensive than femtocells. Pricing depends on how large an area you want to cover. Wi-Ex's ZBoost line includes SoHo products that range in price from $169 to $399, and you can spend up to $600 for kits that cover areas larger than 2500 feet--the maximum handled by femtocells. On the other hand, Wi-Ex marketing vice president Sharon Cupett notes, there are no monthly fees for repeaters--and of course, no broadband service is involved.

Though repeaters rebroadcast over carrier-owned frequencies, they are legal if they don't interfere with cell tower signals (which is why repeater signals have limited strength). One way to avoid problems is to look for FCC-certified repeaters; some are still awaiting approval, however. Check with the reseller.
Repeater vs. Femtocell

Should you get a repeater or a femtocell? Generally, femtocells are a good match for cell phone customers with broadband service who don't want to pay $300 or more for equivalent repeater coverage and who want to avoid many of the antenna-positioning hassles that repeaters entail. You do need a GPS signal, but those are available pretty much everywhere. Cell tower sites with signals that repeaters can work with are probably less common. But if your carrier doesn't offer a femtocell, a repeater may be the only way to improve your indoor coverage.


Aug 16, 2010

Review : D-Link DIR-685 Xtreme N Storage Router

D-Link DIR-685 Xtreme N Storage Router
Price: Rs 13,000


Summary

Wireless routers are generally seen as boring devices that only serve to provide signal coverage for Internet access throughout the house. But the latest "storage router" from D-Link is quite a big exception, and an exciting one at that. Those who live in geek-land will be glad to see that the DIR-685 offers plenty of opportunities for tweaking and making full-use of the router long after its initial setup.




Pros:

* Two USB ports for storage/print server
* Internal SATA 2.5-inch drive bay
* Wired Gigabit ports
* Wireless-N (802.11n)
* Built-in color LCD screen as photo frame and status info

Cons:

* Can get noisy with HDD installed
* Expensive, yet only 1 year warranty


The built-in 3.2-inch LCD screen in front is about as large as many mobile phone screens today.


Full Review

The D-Link DIR-685 Xtreme N Storage Router is quite the multi-functional device. It is only as small as other wireless routers, but it packs in a lot more than just Wi-Fi and wired Ethernet ports. In addition to the basic functionality of a networking device, you can also use it as a networked storage device (NAS or file server), print server (by sharing it out via USB), streaming media server, digital photo frame, RSS reader and as a digital weather-man.

This glossy black colored Wireless-N router with internal antenna looks stylish whether it is wall-mounted or stood on its stand. It is a high-end product and does not skimp on the feature-set, with 5 Ethernet ports, 2 USB ports, a SATA 2.5-inch HDD internal drive bay, built-in LCD screen and touch-buttons to control the LCD. Since you can see a detailed list of features on the "Specifications" tab of this review and the product's homepage"http://www.dlink.com/products/?pid=DIR-685&print=1", we shall get into our observations and the real-world user experience right away.

Significant Features
Not only were the 4 LAN ports of the Gigabit type, but the WAN port (network uplink for internet or cascading network) was a Gigabit one too, thus being faster than the usual 100Mbps ports. The power cable had a switch in the middle, which you could use to switch on/off the router and that was a nice touch. Setting up the router was a cinch with its easy interface and help tips. All of the usual security standards and routing settings were present. The WPS (Wi-Fi Protected Standard) functionality was straight-forward with a touch button to be pressed for quick connection, and the small LCD screen provided status updates and hand-holding all the way. Considering that it has 3 possible storage options, storage settings were well provided for, with user access control, streaming media server support, and BitTorrent download manager. You can have it e-mail activity logs to an administrative mail address of your choice, you need to provide details of the outgoing mail server of course.

For home users whose external IP address would keep changing, hosting a publicly accessible Internet server is made possible via support for Dynamic DNS updating services. In addition to the widely used DynDNS, it also supports D-Link's own DDNS service – note that this second option is not currently supported by other router brands or even by D-Link’s own lower-end ones – so stick to DynDNS if you are likely to change routers frequently. A “website filter” is offered, using which you can implement parental control – up to 25 sites can be listed on the filter, which you can then either whitelist (only allow these) or blacklist (only block these) as per your requirement. The “guest zone” and its controls of schedule, allowed clients and routing/isolation is mention-worthy. There is a “Schedule” configuration option, which is used to manage rules for "Internet Setup", "Wireless Setup", "Network Filter", "Guest Zone", "Firewall Settings" and "Website Filter".

Web UI
Logging in through the Web UI (web browser-based user interface) to administer the D-Link DIR-685 Xtreme N router threw up interesting features. You can have CAPTCHA enabled even for Web UI login, which it terms as "graphical authentication", this could theoretically stave off brute-force bot/malware logins. A "System Check" option allows for checking to graphically view which wired Ethernet ports are physically connected, which helps while trouble-shooting connection problems. As usual, the settings could be exported/imported from a saved file, and the firmware was upgradable. A version 2.0 of the firmware was available with improvements for the router, so we promptly upgraded to the newer firmware downloaded off D-Link’s support section.

The Web UI is the one that allows for configuring settings/security, and we found this to be well organized. It uses a system of 4-way navigation. Main configuration sections are at a top navigation bar, sub-sections when you enter each of these show up on a left-hand pane, and the actual settings/options being configured show in the middle pane. The fourth pane is on the right-hand side, and calls itself "Helpful Hints". Unfortunately these "hints" are not as in-depth as expected and there is no context-sensitive help on a per-setting basis. The "hints" only offer the most basic information, of the sort that the user already knows (a person who’d pour Rs. 13k into this kind of a router rarely is a novice). Mercifully, the "Save Settings" button which you have to click after making changes in any section is quite responsive and quick in functionality (unlike some routers that take almost a minute each time you save settings to get back to a usable state, which can quickly get exasperating).

LCD and touch-buttons
The touch-based buttons on the front of the device were workable but unresponsive at times. So while there is a lot you can do directly with the router and its buttons, you’d try to avoid using the buttons after the novelty has faded off. The Framechannel service is the one that delivers internet content (weather forecast, RSS feed, photo sites) directly onto the router’s screen. The 3.2-inch LCD screen is about as large as many mobile phone screens today, and while watching photos on it is not optimal, the fact that it can be done at all is pretty good. Photos can be viewed from any of the connected storage devices, and you can configure the brightness/idle time of the screen. During idle time in-between uses, the screen displays a clock with time and date for the specified idle time, and then blanks out when it enters standby mode.

Performance
During tests, the D-Link DIR-685 WiFi router did not match the levels we saw with the Asus RT-N16, but still performed quite well. The range was good enough to cover a large home across three floors (router was in the intermediate floor) and yet have some range left to cover the lawn. The area (range) it did cover could see good speeds, never going below 65% signal strength (three bars out of five). What we have in the performance tab is the consistent performance averaged over a period of time. The speeds seen are all from real world testing, and include walls and floors (of a multi-storey building) placed in-between the wireless router and client. On flat open ground/surface with no objects to interfere in between and no walls, just a green field – we saw a maximum range of 27m for the wireless signal when no other devices were interfering.

Wrapping up
Besides the minor negatives already mentioned above, there were some other things to report. Firstly, at its price-level it is strange that the DIR-685 is not a dual-band router, it operates only over 2.4 GHz spectrum and not 5 GHz unlike other routers that sell at half its price. This means you have to keep watching out for interference and speed/signal strength drops. Secondly, the provided 2-pin Indian plug does not have grounding, so be careful with the metal parts of the 2 USB ports at the back, it is possible to receive a slight shock. Thirdly, the internal hard drive bay was a good idea but needs better implementation. The bay only supports 2.5-inch laptop internal HDDs, so we inserted a 500GB drive. But there was a problem with removing it, since the eject mechanism (a deep-push button at the back) could only do so much, and we had to use other tools to pull the HDD out. When the HDD is plugged in and gets warm (which is normal with a 24x7 device like a router), the router’s internal fan becomes very audible in the midst of silence. The router supports power conservation and can “suspend” the internal hard disk, but this is still something to keep in mind. D-Link offers a warranty of one year with this product, as against some other brands with a warranty period of 3 years.

Bottom Line

All said and done, this router turns in a respectable performance as a router, and the extra features are great for enthusiasts. Being able to fit all of that functionality in there and making it compact enough to facilitate carrying an internal HDD is not something to sneer at. If converging so much into a single device is the template for wireless routers in the future, the DIR-685 sure is a pioneer even if some of its features still need polishing. At the moment though, the high price and lack of dual-band operation is a deterrent and stands between it and an even better rating.


Source : PCW

Apr 15, 2009

How To Master New Norton Internet Security 2009

How To Master New Norton Internet Security 2009

The 2009 edition of Norton Internet Security (NIS alias) is the fast, compact and economical resources. It is also full of new ideas and innovations. Discover the new Norton Internet Security 2009 and learn to master his new protections through 12 very useful steps.


Step 1: Maximum Speed, Minimum Occupation

Based on a complete makeover and more than 300 optimizations on the foundations of its protection, Norton Internet Security 2009 has a very low impact on the performance of the PC. Occupying only 10 MB on the hard drive and about 6 MB memory, it is undoubtedly a result of the lightest security market.

Norton Internet Security is so proud of this impact minimalist it does not hesitate to openly display its occupancy rate and provides the user with very interesting statistics.

From the home screen software, a small pad on the left shows the current CPU occupation of the system and part of Norton 2009 in it. By clicking on CPU usage, the software displays more comprehensive statistics, showing including memory and the history of Norton 2009 (what was called, when and if these actions have worked or not).

Quote:
Tip: The display of CPU usage can also specify the period of inactivity. Norton benefits from the time of not using the machine to trigger updates and scans. One can specify the length of time from which Norton will consider that the machine is really unused. By default, this period is 10 minutes. But it may be useful to extend to 20 or 30 minutes.

Step 2: Norton Insight

This is the main innovation of Norton 2009. Its technology "Insight" opens a new approach scan. We know, with over one million variants per year, the suites have to invent new concepts of protection. Norton Insight enables NIS / NAV 2009 to identify known files ( "malware" as "goodware") without having to compare to the millions of signatures. The result is an astonishing speed scanning, and a lesser impact on the system. This function is both used to speed up disk scans and to monitor the work in progress and draw your attention to any codes unknown and potentially dangerous.

* On the home screen, click on the link "Norton Insight"
* The program started when an analysis of tasks running on the machine
* The system queries the online community to learn more about the application that has not already classified as healthy.
* The program then displays a list of active tasks. Those are colorful Green certified healthy.
* The level of approval column indicates whether the file is certified healthy by "Norton" or certified healthy by the "community of users."
* When a file is not colored green, it is not known to the network Norton Insight. Therefore it will be systematically re-analyzed and monitored closely by the software.


Quote:
Tip: You must pay special attention to these tasks active non-colored green. They are potentially suspicious. Look at what the publisher, and above all, what is its star rating. This note is attributed by technology pro-active SONAR Norton studying the code and behavior of a file to define its dangerousness. A file that gets a score of 5 stars is a priori safe. However, a file that gets less than 3 stars is particularly suspect.

Protect Computers With New Norton Internet Security 2009

Step 3: Pulse Update

How to resist the avalanche of new threats when it was born more than a thousand per day? One of the tracks is regularly send signatures to users. Under Norton 2009, these updates are sent to users every 5 to 15 minutes (usually) by a mechanism called "Pulse Update". Most of the time, Norton 2009 awaits a time of inactivity to retrieve updates driven by servers.

* On the homepage in the computer section, note the presence of the link "Update definitions"
* It shows 2009 when Norton received its last update signatures
* Click for details


Quote:
Tip: If for any reason, your Norton has missed an impetus for updating, you can force the update of signatures by clicking on the link "Run Live Update" on the home screen.

Step 4: Analysis Network

The standard license Norton 2009 covers a three posts! So you can not only protect computers from the home with your CD Norton, but also from your PC monitor activity and the safety of other positions.

More surprising still, especially useful when using mobile and connecting to open WiFi points, Norton 2009 provides a "map" of the network on which you are connected and so graphically identify machines that are connected and to indicate their level of access to your machine.

Quote:
Tip: To force a maximum security:

* On the home screen, click View home network
* Click OK
* In "Details of the network," click Edit.
* Click Edit
* Select Restricted and click OK


All machines are as having limited access to your PC. But you can change this setting general for one or more devices on the network by selecting it and clicking Edit.

Step 5: Fashion Players

There are times when we prefer that the virus is carried as discreet as possible, and in particular it does not interfere with what we do, or slow down the machine at the least appropriate time. This is especially true when you play a game or watch that movie. Norton 2009 automatically detects when the "full screen" is used, and then passes automatically "silent".

* Click on Settings in the Computer
* Open the Settings Divers
* Locate the subsection Settings Silent
* Make sure the switch "Detection full screen" is set to Enabled


Quote:
Tip: You can switch Norton 2009 silent during a given period, even if not using applications in full screen. If you make an important task that does no notification, interruption or slowdown, proceed as follows:

* In the Home screen, click Using the UC
* Locate the switch "silent mode" and pass the position ON
* Select a time
* During the specified time, Norton remain silent and disable this mode once the deadline expired.

Scan And Protect With New Norton Internet Security 2009

Step 6: Programming Scans

Under normal circumstances, it is totally unnecessary to seek a scan disk or to schedule a scan disk in Norton 2009. The software actually uses the idle time of the system to automatically achieve a full scan. It is advisable therefore to ensure that the full scan is done on a weekly basis.

To do this:

* In the Computer section, click Settings
* Deploy the "Computer settings"
* In sub-section Analysis of the Computer, choose from the menu Weekly "Analysis period of inactivity."


If you prefer to return to a more conventional analysis that is made in a day and date, follow these steps:

* In the Computer section, click Settings
* Deploy the "Computer settings"
* Manage In the analysis, click Setup +
* Click on Planning, then click Yes
* Can specify the information programming task analysis.


Quote:
Tip: To run a full scan manually return to the home screen, click Analyze Now and then click on "Make a complete system scan."

Step 7: Consultation of historical

2009 Norton works pretty much silent. By default, it allows the user when action is required, or if something serious happened. Its firewall, in particular, is very intrusive with an excellent knowledge of the most popular.

But advanced users retain control and a complete view of what happens via the advanced settings and particularly via the historical powerful events.

* In the home screen, click History.
* Use the Pop-up View menu to specify the items you wish to consult
* Click on the column headers to sort the history as you want
* If you're looking for a particular event, do not hesitate to use the search box


Quote:
Tip: Remember to go regularly in the background, select the display mode "Complete History" then click on the column level of risk to display first events at risk "high". Study these events to check that your machine is not the target of repeated attacks and machinery and identify sites that pose the most danger.

For each one, select the event and click More Info to get a very detailed description of the risk ...

Step 8: Setting advanced protections

The more advanced users will find Norton in 2009 many settings to adjust the level of protection as their continued their use of the Internet and the risks they face.

To access these multiple settings, just click on Settings in the computer.

Quote:
Tip: To increase the security of the suite, be sure to:

* Enable Auto Protect -> Loading Anticipated "
* Enable the "Automatic Analysis Microsoft Office"
* Position "Protection Advanced Heuristic" Aggressive mode (it may increase the rate of false positive, so this option is intended only for advanced users).

Control Intrusions Using Norton Internet Security 2009
Step 9: Autoblock Intrusion

Norton Internet Security 2009 provides a mechanism for intrusion detection that includes when someone tries to attack your machine. The software then automatically configures the firewall so that any communication is impossible with this machine attacking during a period defined as you wish.

Quote:
Tip: You can check the list of machines that are banned by going to Settings, and then deploying the "Internet Settings" and selecting Set + at Autoblocker intrusion. The bottom of the list window shows you the machines currently prohibited communication.

Step 10: Advanced Control Program

If the firewall Norton Internet Security 2009 is minimally invasive and disruptive for a genuine two-way firewall is mainly because it only takes decisions by blocking and opening depending on what he hears applications and their use of the Internet.

However, users can have a very specific codes and programs to communicate through the firewall and adjust the behavior of firewall against them. In addition, this list has the advantage of being a comprehensive inventory executables communicating your system, and nothing as such, it deserves to be consulted regularly to ensure that spyware is lagging behind not recognized :

* Click Settings
* Deploy the Internet settings
* Locate the subsection Firewall intelligent
* Click the option Set Program Control
* Study the list of programs that have requested Internet access
* Put on the Block pop-up menu of the applications you want to prohibit access to the Internet.


Quote:
Tip: Expert users can finely control the flow of communication of each application by selecting the menu Pop-Up Personalize option. The settings are very numerous and go beyond this step by step. But the online help of Norton IS 2009 is very well done and effectively help you in creating custom application rules.

Control Firewall And Select A Theme In Norton Internet Security 2009

Step 11: Control of intelligent firewall

The two-way firewall Norton Internet Security 2009 also offers classic settings to control communications not at the level of software but at the same protocols and TCP / UDP ports.

To access the advanced settings of the firewall, follow these steps:

* Click Settings
* Deploy the Internet settings
* Locate the subsection Firewall intelligent
* Click the Configure advanced settings
* For the experts, it is possible to disable the automatic control programs and then activate the control of events advanced.


Quote:
Tip: It is advisable to regularly reset the firewall to its default settings to avoid indefinitely retain settings obsolete. Takes place in resetting this way:

* Click Settings
* Deploy the Internet settings
* Locate the subsection Firewall intelligent
* Click the Configure advanced settings
* Click Reset


Step 12: A New Look

It can adapt to its liking the look of the user interface:

* Click Settings
* Deploy the Settings Divers
* Locate the sub-section Changing the background
* Select a theme in the pop-up menu ...


Quote:
Tip: To cancel all settings made manually and find a Norton Internet Security 2009 configured as the first day, do the following:

* Click Settings
* At the bottom of the window on the left, click Defaults then click Apply.


Source : techarena

Mar 4, 2009

Digital Video Broadcasting (DVB)

Digital Video Broadcasting (DVB)

Digital Video Broadcasting (DVB) is a suite of internationally accepted open standards for digital television. DVB standards are maintained by the DVB Project, an international industry consortium with more than 270 members, and they are published by a Joint Technical Committee (JTC) of European Telecommunications Standards Institute (ETSI), European Committee for Electrotechnical Standardization (CENELEC) and European Broadcasting Union (EBU). The interaction of the DVB sub-standards is described in the DVB Cookbook. Many aspects of DVB are patented, including elements of the MPEG video coding and audio coding.

Transmission

DVB systems distribute data using a variety of approaches, including by satellite (DVB-S, DVB-S2 and DVB-SH; also DVB-SMATV for distribution via SMATV); cable (DVB-C); terrestrial television (DVB-T, DVB-T2) and digital terrestrial television for handhelds (DVB-H,DVB-SH); and via microwave using DTT (DVB-MT), the MMDS (DVB-MC), and/or MVDS standards (DVB-MS).

These standards define the physical layer and data link layer of the distribution system. Devices interact with the physical layer via a synchronous parallel interface (SPI), synchronous serial interface (SSI), or asynchronous serial interface (ASI). All data is transmitted in MPEG-2 transport streams with some additional constraints (DVB-MPEG). A standard for temporally-compressed distribution to mobile devices (DVB-H) was published in November 2004.

These distribution systems differ mainly in the modulation schemes used and error correcting codes used, due to the different technical constraints. DVB-S (SHF) uses QPSK, 8PSK or 16-QAM. DVB-S2 uses QPSK, 8PSK, 16APSK or 32APSK, at the broadcasters decision. QPSK and 8PSK are the only versions regularly used. DVB-C (VHF/UHF) uses QAM: 16-QAM, 32-QAM, 64-QAM, 128-QAM or 256-QAM. Lastly, DVB-T (VHF/UHF) uses 16-QAM or 64-QAM (or QPSK) in combination with COFDM and can support hierarchical modulation.

The DVB-T2 standard is expected to be published at the end of June 2008 and is expected to be approved and submitted to ETSI during 2008.

The DVB-T2 standard will give more-robust TV reception and increase the possible bit-rate by over 30% for single transmitters (as in the UK) and is expected to increase the max bit-rate by over 50% in large single-frequency networks (as in Germany, Sweden).

Encryption and metadata

The conditional access system (DVB-CA) defines a Common Scrambling Algorithm (DVB-CSA) and a physical Common Interface (DVB-CI) for accessing scrambled content. DVB-CA providers develop their wholly proprietary conditional access systems with reference to these specifications. Multiple simultaneous CA systems can be assigned to a scrambled DVB program stream providing operational and commercial flexibility for the service provider.

DVB is also developing a Content Protection and Copy Management system for protecting content after it has been received (DVB-CPCM), which is intended to allow flexible use of recorded content on a home network or beyond, while preventing unconstrained sharing on the Internet. DVB-CPCM has been the source of much controversy in the popular press and it's said that CPCM is the DVB's answer to the failed American Broadcast Flag.

DVB transports include metadata called Service Information (DVB-SI, ETSI EN 300 468, ETSI TR 101 211) that links the various elementary streams into coherent programs and provides human-readable descriptions for electronic program guides as well as for automatic searching and filtering.

Recently, DVB has adopted a profile of the metadata defined by the TV-Anytime Forum (DVB-TVA, ETSI TS 102323). This is an XML Schema based technology and the DVB profile is tailored for enhanced Personal Digital Recorders. DVB lately also started an activity to develop a service for IPTV (DVB-IPI, ETSI TR 102033, ETSI TS 102034, ETSI TS 102814) which also includes metadata definitions for a broadband content guide (DVB-BCG, ETSI TS 102 539).

Feb 23, 2009

Applications and Layered architecture

Applications and Layered architecture

Communication network must support wide range of services. Normally people use networks to communicate, send e-mails, transfer of files and so on. Industry people use communication network for transfer of funds, update information about the product and so on. Hence, to provide support for current service and future services, a complete plan is required. This necessitates developing a complete flexibility in network architecture.

communications functions are grouped into the following tasks
• The transport across a network of data from a process in one machine to the process at another machine.
• The routing and forwarding of packets across multiple hops in a network
• The transfer of a frame of data from one physical interface to another.

To reduce their design complexity, most networks are organized as a series of layers or levels, each one built upon its predecessor. The number of layers, the name of the each layer, the contents of each layer and the function of each layer differ from network to network.

Interaction between the layers must be defined precisely. Interaction is done with definition of the service provided by each layer and to the layer above. Interface between layers through which a service is requested and through which results are conveyed. New services that build on existing services can be introduced even at the later stage. The layered approach accommodates incremental changes readily.


We know , in all networks, the purpose of each layer is to offer certain services to the higher layers. The entities comprising the corresponding layers on different machines are called peer processes. Between each pair of adjacent layers there is an interface. The interface defines which primitive operations and services the lower layer offers to the upper one. The set of layers and protocols is called the network architecture.

A protocol is a set of rules that governs how two or more communicating devices are to interact. HTTP protocol enables retrieval of web pages and TCP protocol enables the reliable transfer of streams of information between computers.

HTTP

Let us consider a client/server architecture, a server process in a computer waits for incoming requests by listening to a port. Port is an address that identifies which process is to receive a message that is delivered to a given machine. The server provide response to the requests. The server process always runs a process in the background called daemon. httpd refers to server daemon for HTTP. The documents are prepared using Hyper Text Markup Language (HTML) which consists of text, graphics and other media are interconnected by links that appear within the documents. The www is accessed through a browser program that displays the documents and allows the user to access other documents by clicking one of these links. Each link provides the browser with a uniform resource Locator (URL) that specifies the name of the machine where the document is located and the name of the file that contains the requested document. The HTTP ( Hyper Text Transfer Protocol ) specifies rules by which the client and server interacts so as to retrieve a document.


In HTTP, we use two-way connection that transfer a stream of bytes in correct sequential order and without errors. The TCP protocol provides this type of communication service between two processes in two machines connected to a network. Each HTTP inserts its messages into a buffer and TCP transmits the contents of the buffer to the other TCP in blocks of information called segments. Each segment contains port number information in addition to the HTTP message information. The following figure shows how communication is carried between HTTP client and HTTP server.



Signals and systems

Signals and systems

Information is the one transmitted via communication. It may be very simple message like “yes” or “no”. It can be huge and complex message, such as he files containing the book or a television broadcast of a movie. It doesn’t matter if the “information” doesn’t contain anything a critic might agree was “information”.

A signal transmits that information. Signals may take many forms, such as optical, acoustic, electronic or radio-frequency. Signals may be converted from one form into another and still contain the same information. When we make a long-distance telephone call, the sound waves from our mouth are converted to an electrical signal at the telephone, that electrical signal is converted to optical form at the telephone switching office, back to electrical form at the local switching office on the other end and back to sound waves at the other person’s telephone.

A system is the equipment that performs a task, like transmitting signals. We often speak of telephone system as if it is the whole network of telephone equipment from our phone to the high-capacity fiber-optics cables that carry long-distance calls. However, parts of the telephone system also may be called systems, such as a switching systems that directs phone calls. We can assume a system which is a collection of stuffs designed to work together.


Basic components of data communication system

A data communication system is made up of five components.

i) Message

ii) Sender

iii) Receiver

iv) Medium

v) Protocol


Message - the message is the information to be communicated

Sender – The sender is the device that sends the data message. It can be computer, workstation, telephone etc.,

Receiver – The receiver is the device that receives the message. It can be a computer , workstations, telephone, fax machine

Medium – The transmitting medium is the physical path by which a message travels from sender to receiver . It can consists of twisted pair wire, coaxial cable, fiber optic cable or radio waves.

Protocol – A protocol is a set of rules that govern data communication. It represents an agreement between the communicating devices. Without a protocol two devices may be connected but not communicating , just as a person speaking German cannot be understood by a person who speaks only Russian.

COMMUNICATION FUNDAMENTALS

COMMUNICATION FUNDAMENTALS


Communication concepts

Communication is the process of transmitting information. It’s a big, vague, fuzzy word and broadly applied. The “Communications Department “ at a university may include speech teachers, public relations specialists, writers and broadcasters, who have nothing to do with hardware. By that definition , a writer is in the communication business.

Evolution of communications

We the human beings are communicating from early days that is by drawing the pictures on cave walls. It can be how to attack the animal or how to the save the life from the threats or it may be a route to go to another cave.

The earlier long-distance communications was by signal fires that relayed simple information. The signal used to represent “yes” or “no” – the question being asked had to be known beforehand. It’s only a single bit information, not a detailed message.

A written letter or a human messenger could carry more information. The first systems we might call telecommunications were series of hilltop towers, built by French engineer Claude Chappe in the 1790s. The towers had to be in sight of each other, with an operator in each one. The operator relayed a message by moving arms on top of the tower. The operator of the next tower looked through a telescope to watch the arms move, reading the message, recording it, then moving the arms of his tower to relay it to the next tower. Chappe invented a code that used arm position to indicate letters or certain common words. His system was called an optical telegraph.

Samuel Morse’s electrical telegraph eventually replaced Chappe’s optical one. It also required operators, but they used keys that completed an electrical circuit, sending bursts of currents through a wire. The Morse code was a series of dots an dashes ( short and long pulses) that represented letters.

The electrical telegraph spread across the continents and in 1866 across the Atlantic. Its wires formed a network running between major cities. Telegraphers received signals and either sent them for local delivery or relayed them to more distant stations. We can think of each dot and dash of the telegraph as a bit of information.

Later Alexander Graham Bell developed telephone. He borrowed some principles from the telegraph , but instead of transmitting dots and dashes, it sent a continuously changing electrical current that represented a speaker’s voice. The telephone network was bigger and more complex than the telegraph network.

After that radio waves are used to carry signals through air. Radio first carried telegraph signals. Wires worked fine on land, but only radio could send telegrams to ships at sea and relay urgent messages such as request for help. It was radio rescue calls that sent ships to help the survivors of the sinking of the Titanic. Radio communications started for ships and airplanes in the world war II.

Radio communication started at low frequencies, but gradually moved to higher ad higher frequencies as electronics improved. The higher the frequency the more information the signal can carry. Pictures need more transmission capacity than sound alone, so television are broadcast at higher frequencies than audio radio.

By the 1970s , satellites were beaming radio signals around the globe. The telephone system had become global and known popularly “telecommunication network” . We could make phone calls to anywhere in the world.

After that fiber optics arrived. Fiber provides high bandwidth. It carries high capacity information at faster rate. Now it is a integral part of telecommunication network.

COMMUNICATION NETWORK

COMMUNICATION NETWORK

A communication network, consists of a set of equipment and facilities that provide a service, the transfer of information between users located at various geographical points. For example telephone networks provides telephone service, computer networks, television broadcast networks, cellular networks and Internet.

Communication network and transportation networks have become essential infrastructure in every society.

The capacity to transfer high volume of data for a long distance almost immediately are the features of network-based services. For example Internet provides e-mail, information search and retrieval, various forms of electronic service.

EVOLUTION OF NETWORK ARCHITECTURE AND SERVICES

A communication service which is used of transfer of information. Different services differ in the details of how and in what form information is transferred.

Let us consider three example networks
i) Telegraph networks
ii) Telephone networks
iii) Computer networks

TELEGRAPH NETWORKS AND MESSAGE SWITCHING


In the year 1987 Samuel B. Morse demonstrated a practical telegraph that provided the basis for telegram service, the transmission of text message over long distance. Here the text was encoded into sequence of dots and dashes. Each dot and dash which is used to be represented by short and long pulses of electrical current over a copper wire. By relying on two signals, telegraphy made use of digital transmission system. In Morse code the pause between letter was 3 dots and for word is 5 dots.

In store-and-forward process, the message is completely received and stored at an intermediate point and then forward to the next node depending on the availability of link. The process of selecting an appropriate link is known as routing. If the information is message, then it is known as message switching. In simpler terms, message switching is a switching method that sends data from point-to-point with each intermediate node storing the data , waiting for a free transmission channel and forwarding the data to the next point until the destination is reached.

In the beginning communication channel used to carry information sent by one person. Naturally transmission rate (in bits/second) was less. To increase the transmission rate multiplexing was developed. Multiplexing is a technique used to place multiple signals on a single communication channel. Multiplexing partitions a channel into many separate channels, each capable of transmitting its own independent signal, thereby enabling many different transmission over a single medium.

One approach of multiplexing involves modulation. Binary symbols can be transmitted by sending a sinusoidal signal of a given frequency for a given period of time. Multiple sequence of binary symbols could be transmitted simultaneously by using multiple pairs of frequencies for the different telegraphy signals. This concept is used in Modems.

We know characters can be represented by ASCII ( American Standard Code for Information Interchange) , is a 7 bit code. The equipments can communicate with ASCII code.

The telegraph service involves the transmission of text messages between geographically far places. To provide the service , the architecture of the telegraph network contains the following key elements or functions.

i) Digital transmission takes in the network that is information is represented either 0 or 1. It can make use of ASCII code also. The transmission medium can be copper wire and radio.
ii) To identify the messages exactly, messages are covered by beginning and ending by sequence of characters. This is known as framing.
iii) There should be destination address that is to whom it want to deliver. Routing procedure determines the path that a message follows across a network of telegraph stations interconnected by digital lines



TELEPHONE NETWORKS AND CIRCUIT SWITCHING

In 1876 Alexander Graham Bell developed a device that can transmit voice signals. The device that is known as Telephone. The telephone network provides a two-way, real-time transmission of voice signals across a network.

Telephone service became popular due to its voice service and expert operator with knowledge of Morse code is not required like in the case of telegraph. Here voice signals are converted into equivalent electrical signal and passed through cable.

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