komedi filmi izle

Archive for the ‘Telecom and Networking’ Category

« Older Entries
Newer Entries »

Ethernet networks for telecom operators

Monday, March 21st, 2011

Hardware developers familiar with the history of Ethernet in the enterprise may find themselves overwhelmed by the service diversity and complexity which must be addressed in applications for the local exchange carrier, long-haul or inter-exchange provider, and wireless operator. Analyze service complexity in a common Ethernet infrastructure article tasks Ethernet is called upon to perform in telecommunications operator environment seem almost unbelievably complex.

Network aggregation points must handle constantly changing mixes of voice, video, and data, requiring a steady packet-transport service along with circuit emulation and fault-tolerant protection switching. These diverse services would need to be supported regardless of the transport protocol, or regardless of whether carriers had switched to an all-packet infrastructure. The reason that those different services needs to be supported is that they are widely used (many telecommunications system rely on them) and they are core business for the operators (where the money comes in).

Read also Metro Ethernet article from Wikipedia and Explaining Where Ethernet Fits Into the Mobile Operator’s Network Evolution Plans slide set.

Posted in Telecom and Networking | No Comments »

Last IPv4 Addresses Allocated

Friday, February 4th, 2011

Today is a historic milestone for the Internet: the allocation of the last remaining IPv4 Internet addresses from a central pool. The ICANN pool of available unallocated addresses for IPv4 is completely depleted.

The allocation of the final IPv4 addresses is analogous to the last crates of a product leaving a manufacturing warehouse and going to the regional stores or distributions centers, where they can still be distributed to the public. Once they are gone, the supply is exhausted. It’s only a matter of time before the Internet Service Providers (ISPs) must start denying requests for IPv4 address space.

This is not the IPocalypse. The Internet technical community has been planning for IPv4 depletion for some time. IPv6, a new Internet Protocol with a massive amount of address space, is already taking over as IPv4 runs out. For most users, all it means is that your computer’s IP address today might look like 192.0.2.10 (an example IPv4 address), but soon it may resemble 2001:0DB8::/feed:b766 (an example IPv6 address).

The next big event for IPv6 deployment is World IPv6 Day on 8 June, 2011. The goal of this Test Flight Day is to motivate organizations across the industry – Internet service providers, hardware makers, operating system vendors and web companies – to prepare their services for IPv6 to ensure a successful transition as IPv4 addresses run out. Want to find out your IPv6 readiness? Use this test.

Posted in Computers, Telecom and Networking | 4 Comments »

1G, 2G, 3G, 4G, and everything between

Sunday, January 23rd, 2011

Just what is “4G,” anyway? It’s one higher than 3G, sure, but does that necessarily mean it’s better? 2G, 3G, 4G, and everything in between: an Engadget wireless primer tries to answer those and some other questions on mobile communications technologies.

Here is my “short” summary of the different generations:

1G: Analogue cellphone technologies introduces in early 1980s: AMPS in the US, TACS and NMT in Europe
2G: The early nineties saw the rise of the first digital cellular networks: GSM in Europe, D-AMPS “TDMA” and IS-95 CDMA in the US
2.5G: You know you’re in trouble when you need a decimal place! GPRS packet data introduced to GSM system in 1997.
2.75G: EDGE was conceived as an easy way for operators of GSM networks to squeeze some extra juice out of their 2.5G networks
2.9G: Same EDGE that some call with name 2.75G. Now you know how in trouble you are with a decimal place!
3G: ITU IMT-2000 standard, CDMA2000 offered CDMA networks an “always-on” data in US (1xEV-DO protocol provided 3G speeds), UMTS (WCDMA) rose to the top as the 3G choice for GSM operators
3.5G: High Speed Packet Access (HSPA) extends and improves the performance of existing WCDMA protocols, designed provide mobile broadband access of several Mbit/s to laptop computers and smartphones.
3.75G: HSPA+ provides theoretical HSPA data rates up to 84 Megabits per second (Mbit/s) on the downlink and 22 Mbit/s on the uplink through the use of a multiple-antenna technique known as MIMO
4G: WiMAX and LTE almost meet the original ITU 4G criteria and are often marketed as “4G”, former tops out at around 40Mbps and the latter around 100Mbps theoretical
5G: 5G (5th generation mobile networks or 5th generation wireless systems) is a name used in some research papers and projects to denote the next major phase of mobile telecommunications standards beyond the 4G standards (expected to start being used around 2020), expected to offer peak download and upload speeds of more than the 1 Gbps

For years you’ve probably seen people argue that WiMax or LTE technically is not true fourth generation (”4G”) wireless because it didn’t meet certain criteria. Although LTE is often marketed as 4G, first-release LTE does not fully comply with the IMT Advanced 4G requirements. Since the International Telecommunications Union had never set a standard for what 4G was, it was a little hard to make any qualification. LTE, WiMax Now Officially Not Technically ‘4G’ article tells that ITU has officially come out with a statement declaring that only WiMax 2 (802.16m, or WirelessMAN-Advance 2) and LTE-Advanced can technically be declared “4G”: “Harmonization among these proposals has resulted in two technologies, “LTE-Advanced1″ and “WirelessMAN-Advanced2″ being accorded the official designation of IMT-Advanced, qualifying them as true 4G technologies.”

Everything LTE is a brand new microsite from Test & Measurement World dedicated to the long-term-evolution (LTE) wireless technology market. It features insightful blogs industry news, videos, whitepapers, case studies, etc. Interesting looking site.

Posted in Mobile, Telecom and Networking | No Comments »

Communicating LED lamps

Friday, January 7th, 2011

LEDs are used for a long time for all kinds of data communications applications ranging from wireless IR remote controls and IrDA to wired fiber optics communication. There has been many years ago also ideas on optical wireless LANs based on infrared, but they faded quickly. But now when LED lights are becoming very popular this idea could see a second coming.

Ceiling lights in Minn. send coded Internet data article tells about LED lights that will transmit data to specially equipped computers on desks below by flickering faster than the eye can see. The first few light fixtures built by LVX System will be installed in six municipal buildings in the central Minnesota. The LVX system puts clusters of its light-emitting diodes in a standard-sized light fixture. The LEDs transmit coded messages A light on the modem talks back to the fixture overhead, where there is sensor to receive the return signal and transmit the data over the Internet. It works in almost exactly the same way that fiber optic systems do, except the sender and receiver aren’t connected by a cable. Communicating lights are set up using just ordinary power connections. The first generation of the LVX system will transmit data at speeds of about 3 megabits per second. If you are interested check video from Get ElectricTV.

vermeil_IEC_LED_Symbol

There is another application that also combines wireless communications and LED lights. Finnish article Wlan ohjaa yksittäisiä led-loisteputkia (read English translation) tells about LED light tubes can be controlled by a WLAN connection, even individually. Finnish company Valtavalo has licensed Netled control technology from Yashima Dengyo Co., Ltd. and sells their products. Netled technology is designed to provide means to monitor in electricity consumption in real time and control the various LED light tube groups.

Posted in Entertainment Technology, LEDs, Telecom and Networking | 14 Comments »

GSM is insecure

Monday, January 3rd, 2011

Whatever assurances have been given about the security of GSM cellphone calls, forget about them now. Breaking GSM With a $15 Phone … Plus Smarts article tells that a pair of researchers demonstrated a start-to-finish means of eavesdropping on encrypted GSM cellphone calls and text messages, using only four sub-$15 telephones as network “sniffers,” a laptop computer and a variety of open source software. To create a network sniffer, the researchers replaced the firmware of a simple Motorola GSM phone with their own alternative, which allowed them to retain the raw data received from the cell network, and examine more of the cellphone network space than a single phone ordinarily monitors. Upgrading the USB connection allowed this information to be sent in real time to a computer.

While such capabilities have long been available to law enforcement with the resources to buy a powerful network-sniffing device, the pieced-together hack takes advantage of security flaws and shortcuts in the GSM network operators’ technology and operations to put the power within the reach of almost any motivated tech-savvy programmer.

GMS is all a 20-year-old infrastructure, with lots of private data and not a lot of security. Several of the individual pieces of this GSM hack have been displayed before. For example the ability to decrypt GSM’s 64-bit A5/1 encryption was demonstrated last year.

tonyk_phone

“GSM is insecure, the more so as more is known about GSM,” said Security Research Labs researcher Karsten Nohl on the article. “It’s pretty much like computers on the net in the 1990s, when people didn’t understand security well.”

Posted in Mobile, Telecom and Networking | 1 Comment »

Energy Efficient Ethernet

Sunday, December 19th, 2010

Ethernet link speeds of 100 megabits per second or even 1 Gbit/s per second are typical in today’s LANs. When everything is wired to Ethernet LAN very many LAN connections are needed and they consume some power. And the faster the Ethernet connection is, typically more power it consumes.

RJ45M8P1

IEEE Spectrum Energy-Efficient Ethernet article tells that Ethernet connections waste lots of watts and it need not necessarily need be so. On average, people use their Ethernet links at full throttle less than 5 percent of the time. But the circuitry on the network-interface controller, the chip that connects your computer to the network, is always running at full speed, thus wasting power.

One seemingly simple solution is to adapt the Ethernet link’s speed to match a device’s needs. This concept is called Adaptive Link Rate. The problem in this concept is that switching between Ethernet speeds is time-consuming. When you change link rate today, you have to drop the link and reestablish it, which takes up to 2seconds.

Another concept is called low-power idle, it proposes transferring data on an Ethernet link at the highest possible rate and then putting the network controller chip into a sleep-like state. The trouble is that turning on a dormant network card quickly is a challenge, but it is easier than switching between rates.

Wikipedia Energy Efficient Ethernet article tells that Energy Efficient Ethernet, also known as IEEE 802.3az, is a set of enhancements to the twisted-pair and backplane Ethernet networking standards that allow for less power consumption during periods of low link use. The goal is to reduce power use by 50% or more, while remaining fully compatible with existing equipment. The power reduction is accomplished in a few ways:

  • For 100 Mbit/s and gigabit speed links, Ethernet chips that don’t have data to send would put the physical layer of the system into sleep mode. Gigabit interface card might be able to reduce its power by up to 1.5 W.
  • For 10 Gbit/s links, speeds are stepped down to slower speeds saving 10 – 20 W per link (twisted pair Gbit/s links consume typically 15W or so power)
  • A new lower voltage mode was added to 10Base-T (lower voltage used when full voltage is not needed for example on shorter links)

There were some companies introduced technology to reduce the power required for Ethernet before the standard was set. The best known of them was D-Link’s and Broadcom’s Green Ethernet, which is a superset of the draft 802.3az. Green Ethernet was first employed on home switches and smart switches. D-Link claims that a power savings of up to 45 – 80 percent can be made using its Green Ethernet switches, but I think in real life applications the savings will be somewhat less than those promises.

Broadcom delivers energy-efficient Ethernet silicon article about Broadcom’s portfolio of available silicon supporting the newly ratified IEEE 802.3az-2010 Energy Efficient Ethernet (EEE) standard and proprietary AutoGrEEEn technology. Broadcom Infrastructure & Networking Group, said in a press release, “Energy efficiency is of crucial importance to our customers and to the networking industry as a whole.”

The power savings for an individual consumer level device are likely to be modest compared to the cost of device or the embodied energy, so turning off existing devices when they are idle is likely to be a more immediate savings. If Energy Efficient Ethernet is widely incorporated into new systems, it could reduce networking power requirements as systems are replaced. Green Ethernet Technology is pushing into networking hardware market.

eee

Posted in Computers, Data Center and Cloud, Telecom and Networking | No Comments »

System level transient voltage protection

Wednesday, November 24th, 2010

The challenge of protecting today’s systems from transient threats is more complex than ever before. As semiconductor manufacturers introduce new wireline transmission devices built on smaller CMOS geometries, more circuit protection challenges are emerging. CommsDesign article System level transient voltage protection–Five in-depth answers to ESD questions gives answers to important questions that can ensure that a system is adequately safeguarded against these damaging electrical transient threats. This article explores five frequently asked questions regarding the basics of ESD and transient voltage suppression for board level circuit protection on dataline communication circuits.

Currently, most electronic equipment manufacturers recognize the tradeoffs, understand the value of time to market, and opt for using good low-clamping off-chip protection to safeguard their systems from electrical overstress. Several different ESD immunity standards are used in the electronics industry, each one describing appropriate immunity levels for the intended ESD environment. IEC61000-4-2 describes and models the ESD threat level encountered at the system environment with fully packaged ICs operating in a complete electronic system.

There are many devices on the market for transient voltage protection with different specifications. It’s unfortunate, but transceiver IC datasheets (the devices that need to be protected) generally do not provide transient voltage immunity ratings. A good layout is very critical for transient protection performance. Even a very good protection circuit may not overcome a poor layout.

Posted in Electronics Design, Telecom and Networking | 1 Comment »

EU and cookies

Monday, November 22nd, 2010

EU Chews on Web Cookies article tells on Europe’s effort to regulate online “cookies”. The effort to regulate online “cookies” is crumbling, exposing how tough it is to curb the practice of tracking Internet users’ movements on the Web. EU officials see themselves as leaders on consumer-safety issues.

European Union last year passed a law requiring companies to obtain consent from Web users when tracking files such as cookies are placed on users’ computers. Now, Internet companies, advertisers, lawmakers, privacy advocates and EU member nations can’t agree on the law’s meaning. We’re now in a sort of no man’s land.

While the current EU telecom law states that cookies are allowed if Internet users are notified of them and have an opt-out option, in practice, the law has been interpreted more loosely. Internet-ad companies, Web portals and browser maker are watching closely. European regulators in Brussels promise guidance by early next year. The saga began more than two years ago, but somehow I see that this will not stop any time soon…..

kristarella_Cookie

Posted in Telecom and Networking, WWW dev | 2 Comments »

Mobile TV has failed

Thursday, October 7th, 2010

Very much hyped Mobile TV seems to be doomed. Mobile TV bubble has been busted. Consumer uptake had never met expectations for the mobile TV service. There has been very much worldwide Mobile TV subscriber uptake than projected by many. Separate mobile TV broadcasting networks seems to be doomed to demise in most markets.

DVB-H is nowadays practically useless. The most recent launches of broadcast Mobile TV in Europe show disappointing subscriber uptake so far: Switzerland, the Netherlands and Austria all report only a few thousand subscribers. Some companies operating the DVB-H networks want to kill them already, at least Digita in Finland.

Competing FLOtv that used MediaFLO technology used in USA has also failed. Qualcomm has stopped selling devices that support FLOtv. In October 2010, Qualcomm announced it was suspending new sales of the service to consumers. Consumer uptake had never met expectations for the mobile TV service the company invested hundreds of millions of dollar to create.

Nowadays there are both free and paid option or streaming or downloading video via the mobile Web and applications. There does not seem to be consumer need for the mobile TV vision the companies working on the field had few years ago in USA and in Europe.

Posted in Audio and Video, Mobile, Telecom and Networking | 6 Comments »

Apple and other USB charger secrets

Wednesday, August 18th, 2010

Everybody seems to be saying that you can’t charge Apple devices with normal USB power supplies. You need a special power supply from Apple or approved by Apple. I saw this kind of discussion at slashdot some time ago.

Usually, device makers need to sign a confidentially agreement with Apple if they want to say their charger ‘works with iPhone / iPod,’ and they’re not allowed to talk about how the insides work. I hate when manufacturers do crap like this to keep peripherals locked into a more profitable licensing agreement. Apples tendency toward total control is one of the things i don’t like about them. And many other manufacturers are just as bad. I wish companies would back off and be more open and/or use standard micro USB chargers.

The mysteries of Apple device charging article includes a 7-minute video we explore the mysteries of Apple device charging. The secret of Apple chargers is simple: just few resistors. If you don’t put these secret resistors on the data lines too, you get the dreaded Charging is not supported with this accessory. Those resistors like a way to signal to the iPhone that it can go ahead and “fast charge” by pulling 1A, or “slow charge” by pulling 0.5A. The iPhone needs to do a power negotiation to determine if the port is capable of providing 1000ma of power, because the upper-limit of a standard USB port is 500 mA. They just didn’t tell anyone about how to do that. I get why the resistors were initially added but I’m not understanding why it needs to be a trade secret.

usb4res

There is nothing to stop them just drawing the 500mA if the right sort of charger is not detected. Refusing to charge at all unless the licensed parts are present is pure market control, nothing else. Here is the resistor configuration for 500 mA charging:

usb4res500mA

Resistance is Futile. The The mysteries of Apple device charging article demonstrates how anyone can make their own chargers that work with iPhone 4, 3Gs, etc. The pictures on this blog posting are from that article.

Apple devices are not the only one USB charged devices that can have some problems with USB chargers. So here are some resources on USB charging in general.

USB As A Power Source article gives an introduction USB Power Form.

European Commission has reached a voluntary agreement with some of the biggest names in the electronics industry to introduce a common charger for cell phones that fits all models. Information on this USB charging connector is available at USB Approved Class Specification Documents document directory. Read also Battery Charging v1.1 Spec and Adopters Agreement document.

Dealextreme USB charger discussion posting says that USB standard has 4 lines (+5V, ground and +/- data lines). Most USB chargers let the data lines float. Technically, the USB standard says that a USB charger should set the two data lines to specific voltages (~ 2V) to indicate how much power it can provide (I have not verified that from standards yet). The recent iPhones will not charge if the data lines are set incorrectly (i.e. not according to the USB standard).

USB Charging Guide comment: I believe having the data pins connected to each other is in the latest USB specification for charging. I had to interconnect the D+ and D- pins inside my USB AC charger to get it working with my Zune. Perfectly according specs but frustrating enough.

Wikipedia USB article: The USB 1.x and 2.0 specifications provide a 5 V supply on a single wire from which connected USB devices may draw power. The specification provides for no more than 5.25 V and no less than 4.75 V (5 V±5%) between the positive and negative bus power lines. For USB 2.0 the voltage supplied by low-powered hub ports is 4.4 V to 5.25 V.

A unit load is defined as 100 mA in USB 2.0, and was raised to 150 mA in USB 3.0. A maximum of 5 unit loads (500 mA) can be drawn from a port in USB 2.0, which was raised to 6 (900 mA) in USB 3.0.
All devices default as low-power but the device’s software may request high-power as long as the power is available on the providing bus.

In Battery Charging Specification, new powering modes are added to the USB specification. A host or hub Charging Downstream Port can supply a maximum of 1.5 A when communicating at low-bandwidth or full-bandwidth, a maximum of 900 mA when communicating at high-bandwidth, and as much current as the connector will safely handle when no communication is taking place (USB 2.0 standard-A connectors are rated at 1500 mA by default).

A Dedicated Charging Port can supply a maximum of 1.8 A of current at 5.25 V. A portable device can draw up to 1.8 A from a Dedicated Charging Port. The Dedicated Charging Port shorts the D+ and D- pins with a resistance of at most 200Ω. The short disables data transfer, but allows devices to detect the Dedicated Charging Port and allows very simple, high current chargers to be manufactured. The increased current (faster, 9 W charging) will occur once both the host/hub and devices support the new charging specification.

Without negotiation, the powered USB device is unable to inquire if it is allowed to draw 100 mA, 500 mA, or 1 A. Some non-standard USB devices use the 5 V power supply without participating in a proper USB network which negotiates power draws with the host interface

In most cases, these items contain no digital circuitry, and thus are not Standard compliant USB devices at all. This can theoretically cause problems with some computers; prior to the Battery Charging Specification, the USB specification required that devices connect in a low-power mode (100 mA maximum) and state how much current they need, before switching, with the host’s permission, into high-power mode.

USB Charging Guide tells some more details on mini-USB plug: the mini-USB plug actually has 5 pins in it. This can be important as the extra pin (Pin 4) USB_ID is usually either connected to ground or left floating. Sometimes a pull up resistor needs to be added to from the USB_ID to Pin 1 (VDD) to select “Device Mode” rather than “Host Mode”. This resistor is in the device side plug as the USB_ID pin is not wired through to the PC side connector. The good news is that quite a few USB cables have this. So sometimes you can get round the not charging problem simply by trying out different leads and one may work rather than buying the manufacturers “special” cable. On some Creative players you can also solve this by pulling down both data lines (with 2×15k resistors) at the source to emulate what the host (PC) does when setting line speed. This is not so common.

So the current state of USB charging is a little bit of mess…

Posted in Electronics Design, Products, Telecom and Networking | 30 Comments »

« Older Entries
Newer Entries »
film izle - komedi filmi izle - film izle - film izle - film izle