Your Guide to Wireless

by Reads (33,275)

Every few years we witness a “new wave” in computing, and with it a rash of unfamiliar terms and phrases. For a brief period thereafter there’s confusion, as users struggle to grasp the concepts and makes heads or tails of the new vernacular.

Take for example wireless. Lately we’ve become overrun with a plethora of new acronyms, such as PANs and MANs; a world of new concepts, such as 2.5G and 3G; and even odd new words like Bluetooth and WiFi. In this article, Your Guide to Wireless, we’re going to help you make understand the basics of wireless. We’ll start slowly, explaining some of the basic concepts and terms you may have heard about, and by the end we’ll have tied it all together with several real-world wireless uses for your PDA.

Let’s get started.

Introduction to wireless

Wireless communication is nothing new. Spoken word, smoke signals and lighthouses are all forms of wireless communications that have been around for years–and let’s not forget about radio and television. But nowadays we tend to think of wireless communications as some amazing new realm opened up by the recent wave of handheld digital devices, including PDAs and cellphones. Well, it isn’t.

Still, it only makes sense that now that these new devices are creeping more and more into our daily lives, we should learn more about wireless–what it is and how it works. But before we do let’s make sure we understand something about the basic physics of wireless technology. Don’t worry, we won’t delve too deeply (although you’re certainly welcome to do so on your own), rather we’ll cover a few basic concepts that will help when we talk about choosing and using wireless products with your PDA.

Ready? Here’s our first term: electromagnetic radiation. Uh oh, he started with a big one already. Don’t worry, as I said I’ll try to make it simple. Electromagnetic radiation are the waves of electric and magnetic force in space. They’re produced by varying the frequency and wavelength of an electric charge.

We’ll explain those two terms in just a minute, but first let’s consider at an analogy. Think about how you speak. In essence, speaking involves varying the tone, pitch, speed and volume of the sound waves coming from, or radiating from, your throat and out of your mouth (and nose, for some of us). Now, sound waves are actually mechanical rather than electromagnetic, but I think you get the point. It’s these electromagnetic waves that are the root of all wireless communications.

So now let’s explain frequency and wavelength. Frequency is the number of times a wave happens in a second. It is usually expressed in hertz. Wavelength is just what it sounds like, the distance of the wave from one crest to another. It’s sort of like the ripples on a lake when a boat passes. They can be few and long, such as when a row boat passes. Or they can be fast, frequent and choppy, like what happens when a motorboat speeds by. Why do you need to know about these things and what practical use is this to you? Well, you’ll see when we talk about personal area networks, or PANs. The devices in your personal wireless space must co-exist and “play well” together, and frequency is a big part of that equation. Like two surfers trying to ride the same wave, devices must have a way to determine which one can “shoot the frequency tube” and which one must wait for the next big Kahuna.

Electromagnetic radiation covers a wide range, or spectrum, of frequencies and wavelengths. This spectrum has been classified by physicists and engineers into radio waves, infrared, visible light, ultraviolet, X-rays, and Gamma rays. You’ve probably heard of most of these things. Let’s quickly explore the first three classifications: visible light, infrared, and the one we’re most interested in, radio waves. Visible light is the range of electromagnetic radiation that our eyes are able to translate into nerve impulses that our brains can use through a process called sight. How this all works is still very much a wonderful mystery, but it enables us to distinquish objects, distances and textures. Smoke signals, hand signals, flags, and lighthouses all use the visible light range of electromagnetic radiation to communicate wirelessly. Infrared is the form of radiation that occupys the frequency band just below that of visible light, except we can’t see it. You know those infrared binoculars used by the military? They work because they’re also high-powered flashlights that use infrared to enable our troops to see in the dark. Like visible light, infrared requires an unobstructed line of sight since it cannot pass through solid objects. Your current PDA likely has an infrared port that uses this form of electromagnetic radiation as its method of wireless communications, through something commonly referred to as beaming. Radio waves are just below infrared in the frequency spectrum. It’s this range, often called radio frequency, or RF, that we’ll be discussing over the next few days, as it’s this range that encompasses AM and FM radio, TV, GPS and cell phones. Radio waves have the advantage that they can pass through many physical objects and do not always require an unobstructed line of sight. Devices like the popular RIM Blackberry, the Palm VII and i705, and Nokia cellphones all use this form of electromagnetic radiation as their method of wireless communications.

We know there’s a wave and it’s carrying your communications in the form of electromagetic radiation. But how does the wave start and end, and how do we capture it and understand it? Well, for that you need a transmitter and a receiver. A transmitter is a component that creates the wave and can even vary the wave’s frequency and amplitude. A receiver is a component that accepts the wave and decodes the modulated signal. Your everyday one-way pager or those Global Positioning Systems used by boaters, for example, have a receiver, but do not require a transmitter. Two-way pagers, such as the popular RIM Blackberry, send and receive, so they require both a transmitter and a receiver, or a one-piece component that does both, something called a transceiver. Transmitters, receivers and transceivers also have other components such as antennas, oscillators, transducers, amplifiers, modulators and demodulators, but we won’t get into those details. This isn’t a course in electronics, after all.

Finally, let’s cover the basics of how wireless devices–that is, devices that contain transmitters, receivers or transceivers–are connected. There are two basic approaches: point-to-point and networked. Point-to-point, or ad hoc mode, enables two devices to communicate directly with one another by interfacing over the air. When you beam your contact information from your handheld computer to someone else’s using infrared, for example, it is considered point-to-point. Networked, or infrastructure mode, uses bridges (in the form of base stations of access points) to connect wireless devices to physical networks. When you connect to the Internet using a PDA with a 802.11b wireless card (more about 802.11b later) it is considered networked mode. Understanding the difference between point-to-point and networked will help you understand the uses for the different types of networks and wireless products that we’ll cover in this article.

So wireless is really nothing new. In fact, we’ve been using it for nearly a century now. PDAs and other handheld digital devices are just another extension of the growing wireless world and we hope this series of articles will help you understand it all just a bit better.

Personal Area Networks: Connecting Your Gadgets

Electronic devices have begun to overtake our lives. We’ve got cell phones, PDAs, computers and printers, to name just a few. They’re certainly all useful in their own right, but wouldn’t it be nice if they could all “talk” to one another in their own little digital language? For example, imagine if your PDA could tell your cell phone to connect to the Internet and fetch some data, or if your computer could say to your printer, “Hey, would you do me a favor and print this out?” Of course, it would all have to be wireless, since you wouldn’t want to be tripping over all those pesky cords. Well, that dream is quickly becoming a reality. Personal area networks, or PANs, and their wireless cousins, wireless personal area networks, or WPANs, are beginning to pop up all around us thanks in part to a technology with a funny name, Bluetooth.

Bluetooth, or 802.15 for those techies who love numbers, is a communications standard named after Harald Blatand, a tenth-century Danish king who united the Nordic countries. Similar to Blatand’s accomplishments, Bluetooth aims to do the same for your personal electronic devices by uniting them to work together to serve you. Wirelessly, of course.

Until Bluetooth came along there were basically only two options for connecting your devices: hook them together with physical cables or let them wink at one another using infrared light. The shortcoming with cables is obvious. Infrared, on the other hand, isn’t such a bad solution, and it’s wireless. In fact, millions of devices–from cellphones to printers to PDAs–use it to exchange information. It’s small, lightweight, inexpensive and consumes very little power.

But infrared has two shortcomings. First, it requires something called “line of sight”, so if you want to communicate between your cell phone and your PDA you would have to have them within a few feet and aimed precisely at each another. Secondly, infrared cannot pass through objects, so not only do they have to be directed at one another, nothing can be between them either, like a wall for instance.

Bluetooth, on the other hand, uses radio waves rather than light, so it doesn’t have those issues. And like infrared, it meets the three major criteria for portable devices: small, inexpensive (under $10 to incorporate in a device) and low power (1.5-2 mA in idle mode, 50-100 mA in transmit mode, and 50-80 mA in receive mode). And it also does the job. Bluetooth has a raw data rate of 1Mbps, although in practice it can only pump through up to 723 Kbps of your data, with the remaining bandwidth taken up by error correction and control data. Still, that’s plenty good enough for handhelds, which struggle to achieve 100 Kbps data rates, and faster than infrared.

One issue with Bluetooth is that it uses the 2.4GHz frequency band, which is also employed by a variety of consumer products, including microwave ovens and some indoor wireless telephones. Also, current 802.11b wireless local area networks, or WLANs (we’ll cover local area networks soon), use the 2.4 GHz band, which can result in somewhat of a conflict. Some preventive measures are in place to help avoid interference between Bluetooth and 802.11b (far too technical to cover in this article), but it’s likely that eventually wireless LANs will move to a higher frequency and make the issue a thing of the past. In fact, the 802.11a wireless LAN standard operates in the relatively unused 5GHz frequency band.

Eventually Bluetooth will be incorporated into hundreds of products. In fact, Cahners In-Stat predicts there will be 780 million Bluetooth-enabled devices sold in 2005. We’re beginning to see the first wave of these products, including cellphones such as the T68 from Ericsson and the Timeport 270c from Motorola and printers such as the Deskjet 995c from Hewlett-Packard. There’s even the iPAQ 5450 Pocket PC from Hewlett Packard and Tungsten T from Palm that have Bluetooth built-in. You can also add Bluetooth to an existing printer or laptop using adapters from AnyCom. AnyCom also has USB and serial Bluetooth adapters, and Bluetooth access points for connecting wirelessly to local and wide area networks. I’ve been using a Bluetooth-enabled cellphone, PDA and laptop for nearly six months now and have found them relatively simple to set up and use, although it requires compatible software on both sides of the Bluetooth connection to be entirely useful.

A handheld with Bluetooth built-in, or enabled through the use of a Bluetooth SD or CompactFlash card, lets you “discover” and “bond” with other Bluetooth devices in your immediate surroundings, including laptop and desktop computers, printers, cellphones, and access points.

Personal area networks, or PANs, encompass the gadgets you’ll find in your immediate surroundings, from your cellphone and PDA to your computer and printer. Now’s a good time to start looking at your wireless devices and developing a plan for your own personal area network, and be sure to give Bluetooth a major role in it.

Local Area Networks: Gateway to the Internet

Now let’s extend your wireless reach to include what’s long been an important part of most corporate computing infrastructures and is fast finding a significant role in homes as well, the local area network, or LAN. So, if a wireless personal area network is called a WPAN, then what’s a wireless local area network called? A WLAN, of course. But while a WPAN uses an IEEE standard called 802.15, or Bluetooth, a WLAN relies on another IEEE standard called 802.11b, or Wi-Fi.

So, what’s with all these numbers? Well, more than twenty years ago, back when LANs were just getting started, the Institute for Electrical and Electronic Engineers (IEEE) created a committee to develop standards for these developing networks. Since it was formed in February 1980, or 80/2, it was named the IEEE 802 Standards Committee. (And you thought it was some big technical reason, right?)

As the committee appointed working groups, or WGs, within it to explore specific areas, such as Ethernet, token ring or fiber optics, it assigned sub-numbers to them. The Ethernet WG became 802.3, token ring became 802.5 and fiber optics became 802.8. Eventually wireless technology became a hot topic and so the Wireless LAN Working Group was formed. By then the committee had ten existing WGs, so the WLAN Working Group became 802.11. (Not long thereafter the Wireless PAN Working Group became 802.15.)

To complicate matters, the 802.11 Working Group eventually began working on many sub-issues and found it necessary to create Task Groups, or TGs, to handle these. Each task group was assigned an alphabetic suffix, so one TG was called 802.11a while another was called 802.11g. The Task Group that became the most well recognized was 802.11b, which released a standard for “a high data rate extension of the wireless local area network standard using Direct Sequence Spread Spectrum, or DSSS” in late 1999. (Now you can see why many people are pushing to use the more “user friendly” terms Bluetooth and Wi-Fi.) Practically speaking, 802.11b, or Wi-Fi, is a wireless LAN standard capable of transmitting data at up to 11 Mbps for a distance of up to 100 meters using the 2.4 GHz frequency. Yes, it’s quite a mouthful.

While Bluetooth is just now making its way into products, 802.11b is further along in the adoption process, and there are two reasons for that. One is that it’s an earlier standard, so it makes sense that it’s seen more widespread use. Second is that it’s easy to deploy. All is takes is a wireless access point that serves as the connecting point between your devices and your LAN. The access point contains an antenna, a transceiver and an Ethernet port that connects to your wired network. These are relatively simple to set up.

Your connecting devices require an adapter, such as an 802.11b CompactFlash or PC Card. Again, these are painless to install and configure. All you’ve basically done is swapped an Ethernet cable between the devices with transceivers on both ends and a lot of air in the middle!

Although you can use a Palm Powered handheld or a Pocket PC with an 802.11b adapter to connect to a wireless LAN, 802.11b is actually much more suited to laptops than PDAs. For one thing, current handhelds cannot take advantage of the full 802.11b bandwidth, but laptops can. Wi-Fi’ed PDAs typically achieve less than 100 Kbps (which is easily achievable by Bluetooth), however, laptops with 802.11b cards can reach 3-5 Mbps. Also, 802.11b draws significantly more power–at least six times as much as Bluetooth–something you must be much more concerned about with a PDA than a laptop. We’d be remiss to say that 802.11b is the only wireless LAN option. Other standards, including HiperLAN and HomeRF SWAP, are available, but haven’t attained the same widespread acceptance as 802.11b. Also, the IEEE has created an alternative standard, 802.11a, which operates at up to 54 Mbps over the 5GHz frequency band. This speeds data along even faster than 802.11b and also eliminates the frequency conflict with 2.4GHz PAN standards, like Bluetooth, which by the way can also be use for wireless LAN access.

Lately people have begun to confuse Bluetooth and 802.11b, even going so far as to label them competitors. They’re not. In fact, they should co-exist comfortably in our growing wireless world. Bluetooth is recommended for wirelessly connecting the myriad of devices within your personal space, or PAN. This includes cellphones, PDAs, printers, computers and, yes, even access points that connect to the Internet. 802.11b, on the other hand, was designed solely for high-speed wireless access between computers and local area networks. But to achieve this higher data rate it requires more power. Therefore, 802.11b is much more suited for plugged-in laptops than battery-powered PDAs. Now you won’t be one of those confusing Bluetooth with 802.11b.

Wide Area Networks: The Wireless World

So far we’ve talked about creating your own wireless personal area network, or WPAN, and wireless local area networks, or WLANs. Now we’ll extend our wireless reach even furthur by exploring metropolitan area networks, or MANs, and wide area networks, or WANs.

Say you’ve got three buildings in your corporate campus and you want to have shared high-speed wireless access throughout the campus. However, your wireless transceiver can’t carry a signal that far. Now’s the time for a wireless Metropolitan Area Network, or WMAN. Wireless MANs extend the range of wireless transceivers, however, there’s a slight catch: WMANs require an unobstructed line of sight connection similar to infrared. Still, in many cases WMANs are preferred to running cables between buildings or leasing another T1 line from one of the major telecom companies.

One interesting aspect of MANs that we may see more of in the future is something called Wireless Local Loop, or WLL. WLL may be an eventual solution to the customer “last mile” situation by bringing the benefits of high-speed access to rural areas and small businesses without the delay or expense of running cables. Some even see it as a major competitor to Digital Subscriber Line, or DSL, in the future.

Wireless WANs are when you start getting into the use of the familiar cellular networks that support our cellular telephones, or cellphones. Cellular networks are simply arrangements of cells, or areas, that contain base stations that function in part as transceivers to pass signals along from their senders to their receivers. These networks work over different frequencies within the RF band and employ different protocols to efficiently and effectively pass signals.

OK, that was a mouthful, so let’s explain it simply using an analogy. Let’s say that you want to talk with someone who is standing close enough in proximity to you that they can hear you and you can hear them. The area that surrounds you, the one that your voice can be clearly heard in, is effectively a circle. But for this analogy, we’ll call it a cell. You begin speaking to the other person in English. If he doesn’t understand English, maybe he only speaks French or Spanish, then you really have no way to effectively communicate. But let’s say that you both do speak English, you now have to have a system for who speaks and who listens. If you both spoke at the same time then communication would be stilted.

In the above example, English is our frequency and the rules for who speaks and who listens is our protocol. Now, what if instead of next to you, the person is 100 meters away. It’s now impossible to hear one another’s voice. Let’s also say that he speaks French while you speak Spanish. Fortunately there’s a man halfway between the two of you who can hear and speak to both of you. Unfortunately, he only speaks English. Can you see where we’re going here? You must get a translator to translate your Spanish into English and talk to the “man-in-the-middle.” On the other end, the other gentleman must use a French-English translator for the same purpose.

In other words, what you’re creating is a wireless network.

All three of you–you, the “man in the middle,” and your French-speaking friend 100 meters away–are all in different “cells” of this network. The “man-in-the-middle” is the “carrier” and the two translators are “transceivers.” Finally, English is the “frequency” and the rules you’ve all employed to get the messages back and forth are the “protocol.”

Now, let’s take it one step further. Say there’s not only you, but four other people next to you who want to communicate with other people at a distance and need the services of the translator and the man-in-the-middle. The translator says that he can only accomodate four words at a time from each of you, that’s his bandwidth. To satisfy all five of you he must use a scheme to provide multiple access to his services. He can give each of you an alternating slice of time in a round-robin style, or he can assign each of you a number, or code, and send that along as part of the translation.

In our analogy, the first alternative is called Time Division Multiple Access, or TDMA, and the second alternative is called Code Division Multiple Access, or CDMA. (Can you see which one would be able to service more people, more quickly? That’s correct, CDMA.)

Finally, every now and then your translator, the “man-in-the-middle” and the translator at the other end has a problem translating, or doesn’t quite hear what the other person has said. These transmission errors can only be corrected by repeating the words.

So, in this brief analogy you’ve gotten a taste for the issues that come into play with wireless WAN communications. And all of these factors contribute to the speed and accuracy of any network.

The Wireless Generation Gap

Let’s start with the “wireless Generation Gap,” which encompasses the three generations of mobile networks.

First Generation, or 1G, networks were the first mobile networks created to handle voice communications. Analog rather than digital, they’re not designed for passing data, therefore they’re quickly nearing obsolescence.

Second Generation, or 2G, networks are the digital networks we commonly use today. They’re optimized for voice communications but can also pass data at speeds up to 10 Kbps.

Third Generation, or 3G, networks are the future. They’re fully digital networks designed for both voice and data. In fact, they can pass data at speeds up to 1 Mbps.

What’s the big difference between 2G and 3G? Well, 2G used something called circuit-switching for passing data, while 3G used packet-switching. We won’t get into all of the details of circuit versus packet but it’s safe to say that packet data is faster and makes more effective use of the network’s bandwidth.

There are a few well-known packet data networks in existance, however, these are relatively low-speed, up to 20 Kbps. For example, there Cellular Digital Packet Data (CDPD), Mobitex (used by RIM Blackberry and Palm i705), ReFlex and DataTAC. It’s expected that these will eventually give way to 2.5G and 3G networks. Then there is something called 2.5G, which is currently being deployed by a number of cellular carriers. Think of 2.5G as a stepping-stone to 3G, a transitional digital technology that uses a combination of circuit and packet data with speeds up to 100 Kbps.

Real World Implementations

Now that we covered what RF communications are and what roles frequency (800, 900, 1500, 1800 and 1900 MHz), multiple access (TDMA, CDMA), and circuit-switched and packet-switched play, let’s look at some real-world implementations. The most popular digital mobile phone standard in the world is Global System for Mobile Communications, or GSM. It uses the TDMA standard operating at 900 MHz, 1,800 MHz, and 1,900 MHz, depending on the country. It’s a 2G technology (limited to 14.4 Kbps for data) with a natural path to the 2.5G technologies of GPRS and EDGE and the 3G technology UMTS (not expected for several years), which uses CDMA. In North America, cdmaOne (often simply referred to as CDMA) is the most popular. It uses the CDMA standard operating at 900 and 1,800 MHz. It’s a 2G technology with a natural path to the 2.5G technology 1xRTT (data rates up to 150 Kbps) and the 3G technology cdma2000 (up to 2 Mbps). There’s also satellite communications, however, for the sake of brevity we’ve chosen to skip this technology.

Communications networks are constantly evolving. We’ve progressed from strictly voice networks to networks that also include sending and receiving data. So-called 2.5G networks, while enabling wireless access of email and limited Web browsing, have recently arrived. But it’s the third generation, or 3G, networks, which employ new standards such as UMTS and cdma2000, that will become the magic doorways to true wireless multimedia and high-speed Web access. Unfortunately we’re still several years away from the manifestation of that dream.

Security and Applications

It been said that it’s easier to predict how something will be ten years from now than two years from now. With that in mind, we’re going to attempt to do both. But before we do, let’s cover a few final areas of wireless computing: security, applications and everyone’s favorite, devices.

How can you secure the air? Well, you can’t. But you can do a few things to your device and to your transmissions to make it less vulnerable to theft.

First of all, mobile devices such as cellphones and PDAs are easy to lose, so it’s important to secure the device itself. This can be done with passwords but even passwords can be bypassed, cracked, or even “shoulder surfed” in a public place, such as an airport. And if you cache your passwords on your device to make it easier to access your applications or corporate network then you’ve provide a loaded gun to someone looking to steal information. And it’s also possible to eavesdrop on communications over wireless networks since the airways are open access to all.

You can also use encryption software to encrypt the data on your device. Another option is smart cards, which are hardware tokens that contain PINs, passwords and private keys. GSM cellphones use a form of smart card called a SIM, or Subscriber Information Module. It identifies you to the network; without the SIM card your cellphone does not work.

Bluetooth, 802.11b and mobile standards such as TDMA and CDMA have security layers built-in, but most security experts say that they’re all “crackable.” This will certainly be an important topic as we move to a more ubiquitous, wireless world.

Wireless applications will eventually be what it’s all about. Many current applications will also run on wireless networks but they may not be optimized to do it effectively and securely. Therefore, other forms of wireless applications have become popular, including Wireless Access Protocol, or WAP, applications; Terminal services applications; Short Message Service, or SMS, applications; i-mode applications; Web-based, or HTML, applications; and proprietary solutions.

Picking a device

Most men, and women too, love their gadgets. Our cellphones and PDAs have become personal extentions of our own beings. But with so many devices out there, and many more in the works, how do you choose the right device?

Well, that’s easily the most frequent question I’m asked and I must admit that it’s not always as easy as it seems. What if you purchase a cellphone only to find out that it doesn’t work in some areas of the country that you frequent? Or what if you buy a hot, new 802.11b-enabled PDA only to discover that your company has decided to use Bluetooth access points to jump on its network? Or what if the type of PDA you have cannot synchronize with your company’s servers?

No, device selection is not a simple task.

We’ve talked a bit about PANs, LANs and WANs, and we’ve briefly addressed security and application concerns. All of these are factors you must take into account when choosing a mobile wireless device. Unfortunately many people start by picking a device first, rather than by exploring their entire wireless world–from PAN to LAN to WAN–and developing a strategy. For example, what are your requirements? Do you want to access email wirelessly? Do you need to send quick messages to co-workers or will you be using voice communications? From there you might look at some limiting factors, such as what type of email system your company uses and is it open to mobile access? Are you going to carry the device in your pocket or in a briefcase? What areas of the country, or the world, will you be using the device in?

Once you understand all of your requirements and limiting factors you are ready to find the device that meets your needs. It’s then that you might find several devices that will do the job for you and you can use your personal discretion (such as do you like to enter data with a stylus or a keyboard–to pick the one you prefer most.

So, start with your needs, explore your limiting factors, and then look for devices that fit that mold.

Wireless handheld computers and cellphones should be selected based on your own personal requirements and needs, as well as the limiting factors imposed by your company, your current technology and the area of the country or world you live in. Don’t be tempted to pick up that “cool, new gadget” before determining whether it is truly the best device for you.

The near term may not be quite as bright as the long term due in part to a sagging economy and a slowdown in the overall adoption of new technologies as companies corral their spending. Still, during the next two years we’re sure to see a steady build-up of 2.5 and 3G networks, albeit a bit slower than originally expected, and a move toward convergent devices. However, the limiting factor won’t be technology, but the ability of companies to transition their applications and systems to take advantage of these new wireless technologies.

During the past ten years we’ve transitioned from one pound, inch thick, monochrome PDAs with 640KB of memory to units half that size and weight, with remarkable color screens and 100 times the memory. With a bit of extrapolation it’s safe to say that in another ten years we’ll have improved displays, possibly 640×480 with crisp transreflective color, battery life around 10 hours, and 2GB of RAM, all in a package around 2-3 ounces in weight and less than 1/4 inch thick.

And then there’s wireless.

We’ll certainly have ubiquitous, built-in wireless by then, most likely Bluetooth for connecting to local devices and peripherals, and a 3G transceiver for connecting directly to the wireless Internet.

Yes, despite a slow start, it should be an exciting wireless future.



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