Why does my phone have poor Wi-Fi reception? WiFi does not work well on Android and the Internet is slow

The problem is in the house - Wi-Fi reception is poor, the Internet barely loads. You can only access the Internet from your phone via Wi-Fi while sitting next to the router. How we understand you! Is it possible somehow without delving into technical details at the blonde level to solve the problem with the signal? Not always, but there is a chance. Here are some simple tips on how to try to improve the Wi-Fi signal from the router in your apartment, so that even in the toilet you can hang out with your phone longer.

Place the router in the center of the apartment

If the layout of the apartment allows you to place the router in its center, do it. The signal from the wi-fi router will be more evenly distributed throughout the apartment, penetrating into the farthest rooms and corners.

Raise the router as high as possible

Do not place the router on the floor; the higher the router is from the floor, the better. A router on the floor helps your neighbors receive a signal more than it does your phone or laptop. If it is possible, throw the router on a cabinet, no one will touch it there and at the same time the signal will spread better.

Move the router away from equipment

Equipment that is too close to the router degrades the signal, creating interference. There is no place for a router near a microwave. Move the router away from the TV, stereo system, or desktop computer. The quality of the Wi-Fi signal is also affected by a large number of wires near the router. This is another argument why a router on the floor is not the best solution.

Twist the antenna

If you are in the same room with the router, then the position of the antenna will have almost no effect on the signal, but if you go to other rooms, the kitchen or toilet, then it makes sense to rotate the antennas. If the router has an external antenna, twist it as best you can, check the signal. If the router has two or three antennas at once, place one antenna vertically, the other at a large angle, and turn the third even steeper. Experimentally find the best antenna position.

Use hint apps

Now you can turn your smartphone into a whole measuring device. For the same android there is free application Wi-Fi Analyzer, which allows you to show you all Wi-Fi networks nearby and their signal strength, including the signal from your router. Moving with a phone in your hands and running application On it you can see on a graph where the signal in the apartment is best. Or put the phone in a place where you usually access the Internet wirelessly and move the router.

Did it help at least a little? Has the Internet signal in your apartment become a little better? Share the link to this Ivstar page with others.

Unlike a wired network, a Wi-Fi connection requires additional authentication, since the connection to the network within the range of the signal emitted by the router is publicly available. Here, electronics are responsible for the Internet connection and there are no reasons why the phone cannot see wifi at home, there can be many: from ISP problems to router malfunctions. However, this problem is extremely common, and we will look at the most “popular” reasons that the phone does not connect to home wifi in this article.

Why the phone does not connect to wifi: establishing the correct “diagnosis”

So, if your phone does not receive Wi-Fi from the router, you should check:

• 1. Is the router frozen?.

Indeed, some of the reasons that the phone does not see Wi-Fi can be safely called mystical. After all, this is what all unexplained phenomena are called? In fact, all routers without exception periodically refuse to perform the tasks assigned to them, and even the manufacturers of this equipment cannot answer why this happens.

So, if your phone stops receiving wifi after fruitful work with a wireless connection, first of all you need to reboot the router. To do this, just turn off the device using the ON/OFF button on the device body (or unplug the power plug from the POWER socket), wait 30 seconds and reconnect the router to the power supply.

Thus, if the phone does not see the wifi router because it freezes, the problem will be resolved.

• 2. Correct phone authentication in the wireless network

If an authentication error occurs and the phone does not connect to WiFi, you first need to restart your mobile device.

• 3. Is the number of devices on the home network exceeded?

To find out why your phone doesn't see wifi at home, and see how many devices are allowed to use your wifi.

You may have turned on your laptop, tablet, phones, etc. and your router only supports 16 wireless connections to your home network.

Or, you bet too much, and the student from the next door decided to show his friends that he is a cool hacker. The young burglar picked up the password and gave it to his friends.

Unauthorized connections can be “banned” through the router’s web interface, after which be sure to change the password for accessing WiFi to a complex and unique one.

After changing the key, do not forget to delete all connections on your mobile communicators, and connect to the network with a new password.

• 4. Is the SSID repeated?

This is rare, but it happens. Some people either set a standard network identifier or simplify the unique name to a simple one, for example “dlink”, “tplink”, etc. If someone nearby also did not strain their imagination, then the next time they connect to their home wifi network an authentication error will occur.

Turn off your router and see if its name is in the list of available WiFi networks on your phone? If a network with the same name already exists, then change the SSID to a unique one, save the settings and reboot the router.

Please turn off the power

“All you bloggers need to do is turn off your base stations,” he said, getting more and more irritated. Steve Jobs(Steve Jobs) to the crowd at the iPhone 4 launch in June 2010. “If you want to see samples, turn off your laptops, turn off all Wi-Fi access points and put them on the floor.”

In a crowd of 5,000 people, barely 500 had working Wi-Fi devices. It was a real wireless apocalypse, and even a group of the best specialists from Silicon Valley could not do anything about it.

If this example of the urgent need for 802.11 seems inapplicable to your everyday life, think back to September 2009, when the THG team first highlighted the technology from Ruckus Wireless in their review "Beamforming technology: new WiFi capabilities". In that article, we introduced readers to the concept of beamforming and reviewed several comparative test results in a fairly large office environment. At that time, the review turned out to be very instructive, but, as it turned out, there was still a lot left to tell readers about.

This idea came to us a few months ago, when one of our employees installed a nettop for his children, using it to connect to his point Cisco access Small Business-Class 802.11n Dual Band Wireless USB Adapter (2.4 GHz and 5.0 GHz) Linksys with 802.11n support. The performance of this wireless device was terrible. Our employee couldn't even watch streaming video from the YouTube site. We believe that the problem was the nettop's poor ability to process information and display data graphically. One day he tried to replace the device with wireless bridge 7811, described in our article "Wireless 802.11n routers: test of twelve models", taking it from previously used equipment. And I immediately felt the difference, since streaming video could now be watched at a fairly good level. As if there was a switch to wired connection Ethernet.

What happened? Our employee was not in the audience with 500 bloggers who were blocking his connection. He used what was generally considered the best small business equipment from Cisco/Linksys, which he had personally tested and knew had better performance than most competing products. brands. We felt that switching to the Ruckus wireless bridge was not enough. There are too many questions left unanswered. Why did one product perform better than another? And why did the original article indicate that performance is affected not only by too close a similarity between the client and the access point, but also by the shape of the AP (access point) itself?

Unanswered Questions

Six months ago, Ruckus attempted to develop a test case to help us understand unanswered questions by analyzing the impact of airborne electromagnetic interference on the performance of Wi-Fi equipment, but before the tests could begin, the company stopped the experiment. Ruckus installed high-frequency noise generators and standard client machines, but the test results measured one minute were replaced by completely different values ​​two minutes later. Even averaging five measurements at a given location would be meaningless. That's why you never see actual interference research published in the press. Managing the environment and variables becomes so difficult that testing becomes completely impossible. Vendors can talk all they want about all the performance numbers they've obtained from testing optimal configurations in high-frequency soundproof chambers, but all those statistics are meaningless in the real world.

To be honest, we've never seen anyone explain and explore these issues, so we decided to take the initiative by shedding light on the nature of Wi-Fi device performance and revealing their hidden secrets. The review will be quite large. We have a lot to tell you, so we're going to split the article into two parts. Today we will get acquainted with the theoretical aspects (how Wi-Fi equipment works at the data level and hardware level). Then we'll continue to put theory into practice - actually testing in the most extreme wireless environments we've ever encountered; this includes 60 laptops and nine tablets, all tested on the same access point. Whose technology will survive and whose technology will be far behind the competition? By the time we finish our research, you will not only have the answer to this question, but you will also understand why we got the results we did and how the technology behind those results works.

Network congestion versus line seizure

We typically use the word "congestion" to describe situations where wireless traffic is overloaded, but when it comes to... important issues about networks, congestion doesn't really mean anything. It is better to use the term "capture". Packets of information must compete with each other to be sent or received at the appropriate moment when there is a free gap in the transmission of traffic. Remember that Wi-Fi is a half-duplex technology, and therefore at any given moment only one device can transmit data on the channel: either the AP or one of its clients. The more equipment there is on a wireless LAN, the more important line capture management becomes, since there are many clients vying for the airwaves.

With wireless communications networks poised to continue to grow rapidly, who gets ready to transmit data and when is of utmost importance. And here there is only one rule: whoever exchanges information in silence wins. If no one is trying to transmit data at the same moment as you, then you will be able to interact with the necessary devices unhindered. But if two or more clients try to do the same thing at the same time, a problem will arise. It's like talking to your friend using a walkie-talkie. When you speak, your friend has to wait and listen. If you both try to speak at the same time, neither of you will hear the other. To communicate effectively, both you and your friend must control air access and line acquisition. That's why you say something like "welcome" when you finish speaking. You are sending a signal that the airwaves are free and someone else can speak.

If you've ever gone on the road with a walkie-talkie, you might have noticed that it only has a few available channels - and there are also a lot of people around who have also come up with the idea of ​​walking with a walkie-talkie in their hands. This is especially true of the time when there were no cheap cell phones- it seemed that everyone we met had a walkie-talkie. You might not have talked to your friend, but there were other people next to you with walkie-talkies, which, as it later turned out, were using the same channel. Every time you were about to get a word in, someone was already occupying your channel, making you wait... and wait... and wait.

This type of interference is called "co-channel" interference, in which those creating the interference impede communication on your channel. To solve the problem, you can try to switch to another channel, but unless something better is available, you will be stuck with very, very slow data rates. You will only have to transmit data when all the chattering idiots around you stop talking for a moment. You may need to say nothing at all, such as "Gee! There's that inter-channel interference again!"

Sources of interference

What's complicated about this internal channel interference problem is the fact that the Wi-Fi traffic flow is never uniform. We're dealing with high-frequency (RF) interference that randomly interferes with packets' paths, hitting anywhere, anytime, and lasting for varying amounts of time. Interference can come from a number of different sources, from cosmic rays to competing wireless networks. For example, microwave ovens and cordless phones are well-known offenders in the 2.4 GHz band.

To illustrate, imagine playing Hot Wheels cars with a friend, and each car you push across the floor towards your friend represents a data packet. Interference is your little brother playing marbles with a friend in front of your transport column. The ball may not hit your car at any given point in time, but it is obvious that it will be hit one way or another. When a collision occurs, you will have to stop playing, pick up the damaged car and take it to the starting line, trying to start it again. And, like all tomboys, your little brother doesn't always just play with marbles. Sometimes he'll throw a beach ball or a stuffed dog your way.

An effective Wi-Fi network is primarily about managing the wireless or radio frequency spectrum - helping the user get in and out of the wireless highway as quickly as possible. How do you make your Hot Wheels cars go faster and aim them more accurately? How do you keep more and more cars scurrying around, not paying attention to your little brother's pathetic attempts to ruin your mood? This is the secret of wireless equipment suppliers.

Difference between Wi-Fi traffic and interference

We'll get to this a little later, but first understand that the 802.11 standard does a lot of things that allow packet control to be controlled. Let's return to car metaphors. When you drive on the road in a car, you are faced with speed limits and other obstacles that affect how your car behaves under certain characteristics. But if your great-grandmother was in your shoes, wearing her thick glasses, listening to Lawrence Welk, and trudging down an eight-lane interstate at 35 mph, other drivers would soon lose patience and start honking at her. Traffic on the road will slow down. But everyone will continue to drive, even at this reduced speed.

This is similar to what happens when Wi-Fi traffic your neighbor gets into your wireless network. Because all traffic follows the 802.11 standard, all packets are governed by the same rules. Unwanted traffic that comes your way slows down the overall movement of packets, but it doesn't have the same impact as, say, radiation from a microwave oven, which doesn't follow the rules and just zips through the various Wi-Fi traffic lanes (channels) like a group. suicide pedestrians.

Obviously, the relative impact of RF noise in Wi-Fi devices at the 2.4 and 5.0 GHz frequency ranges is worse than that of competitor WLAN (wireless LAN) traffic, but one of the goals of improving performance is achieved to the benefit of both networks. As we will see later, there are many ways to achieve this. For now, just remember that all these pieces of traffic competing with each other and interference eventually become background noise. A packetized data stream that starts out quite powerfully at -30 dB eventually fades to -100 dB or less over some distance. These levels are too low to be clear to the access point, but they can still disrupt traffic, just like that old lady with the thick glasses.

In war and on the air, all means are good

Let's talk about how access points (including routers) manage traffic rules. Think of a typical two-lane freeway on-ramp. On each lane there are cars lined up and on each of them there is a traffic light. Let's say each thread has a green light for five seconds.

The wireless network has changed this idea slightly through a process called air fairing. The access point estimates the number of existing client devices and sets equal time intervals of stable communication for each device, as if a camera monitoring the entrance to a highway could estimate the number of cars caught in a traffic jam and use this information to decide How long should the green light stay on? As long as the light remains green, cars can continue to use the highway entrance. When the light turns red, traffic in that lane will stop, and then the green light will turn on for the next lane.

Let's assume there are three lanes on this backbone, one for each standard: 802.11b, 11g and 11n. It is obvious that information packets are transmitted with at different speeds; it's as if one lane was for fast sports cars and the other for slow, heavy-duty trailers. Over a certain period of time, you will receive more “fast” packets in your traffic than slow ones.

Without the principle of air fairness, traffic is reduced to the lowest common denominator. All vehicles line up on one lane, and if a fast car (11n) ends up in a traffic jam behind a car with average speeds (11b), the entire chain reduces the speed to the speed of this “average” car. This is why, if you analyze traffic quite often using consumer routers and access points, you will come to the conclusion that performance can drop dramatically if you connect an old 11b device to an 11n network; This is why many access points have an “11n only” mode. This approach, of course, causes the access point to ignore more slow device. Unfortunately, most consumer Wi-Fi products do not yet support over-the-air fairness. This feature is becoming so popular in business circles that we hope it will soon reach ordinary users.

When with good packages bad things happen

Enough about cars. Let's look at data packets and interference from a different angle. As mentioned earlier, interference can burst into the air at any time and last for any amount of time. When noise gets into the data packet, the latter becomes corrupted and must be sent again, which leads to a delay and an increase in the overall sending time.

When we say we want better performance, it most likely means that we want our data packets to be delivered from the access point to the client (or vice versa) much faster. To make this happen, access points tend to use one or all three tactics: reducing the physical layer (PHY) data rate, reducing the transmit power (Tx), and changing the radio channel.

PHY is like a speed limit sign (we're trying to move away from the car examples, honestly!). This is the theoretical data rate at which traffic is believed to begin to change. When your wireless client says you are connected at 54 Mbps, you are not actually transmitting data packets at that speed. This is just the level of the approved speed at which the access point and hardware are still communicating. We will understand what is happening with the packages and with the real production standards after we see this coordination.

Physical Layer (PHY) Data Rate

When noise intrudes into the wireless traffic, causing packets to be sent repeatedly, the access point may drop to a speed lower than its physical speed. It's like talking in slow motion to someone who doesn't speak your language fluently, and in the wired world, it works great. Our package was previously transmitted at a speed of 150 Mbit/s. Physical speed dropped to 25 Mbit/s. Faced with the appearance of random noise, we wondered what happens to the likelihood that our data packet will encounter another stream of noise? It's growing, right? The longer a data packet is in the air, the more likely it is to encounter interference. And therefore, yes, the technique of reducing physical speeds, which worked so well in wired networks,is now becoming the responsibility of wireless networks. To make matters worse, low physical speeds make communication Wi-Fi channels(where two channels at 2.4 or 5.0 GHz are used in tandem to increase throughput) is much more complex because there is a risk to channels on different frequencies work at different speeds.

It is incredible and sad that the practice of using the method of reducing physical speeds is increasing. Almost every vendor uses this method despite the fact that it is counterproductive in terms of performance.

What are you saying?

In some ways, wireless network– it’s just a “big squabble”. Imagine you are at a dinner party. It's 6:00 pm and only a few people have arrived. They are thinking about something, talking quietly. You hear the whisper of voices and the hum of the air conditioner. Your colleague approaches you and you have no problem keeping up the conversation. The owner's four-year-old kids come up to you and start singing a song from Sesame Street. But even with these three sources of interference, you and your partner have no problems understanding each other, partly because your partner grew up in a large family and speaks loudly, as if through a megaphone.

IN in this example The sounds of other people talking and the air conditioner operating are "minimum noise levels". He is always present, always on this level. When we talk about how much interference is affecting your conversation, we don't take into account the noise floor. It's as if we put a tray on a kitchen scale and then press a button so that the weight value becomes zero. Tray on scales and background noise are constant, just like the background radio frequency noise that surrounds us. Every environment has its own noise floor.

However, the child and his admiration for Big Bird (a Sesame Street character) are a hindrance. Even though your partner is loud, you can still communicate effectively, but what happens when your polite friend approaches you and engages in a discussion? You find yourself the one who casts irritated glances at the baby’s dancing and asks your interlocutor “what?”

In contrast to the background RF noise floor, we set wireless phone with a measured noise value of -77 dB at the location of our client device. This is our singing four-year-old baby. If you have a reputable access point that only transmits a -70 dB signal, then this will be enough for the client to “hear” the data despite the interference, but not too much. The difference between the minimum noise level and the received (listened to) signal is only 7 dB. However, if we had an access point transmitting data at a louder sound level, say at -60 dB, then we would get a much more significant 17 dB difference between the interference and the received signal. When you can hear someone without any problems, the conversation will flow much more effectively than when you can barely hear what they are saying to you. Moreover, think about what happens when another four-year-old wants to sing something from Lady Gaga's repertoire. Two singing children will likely drown out your friendly friend, while your more talkative companion can still be heard clearly.

What are you saying? – I say "SINR"!

In the radio world, the range from the noise floor to the received signal is the signal-to-noise ratio (SNR). This is what you see printed on almost every access point, but it's not exactly what you care about. What you're really interested in is the range from the top noise level to the received signal, that is, the signal-to-noise ratio (SINR), that's what makes sense. It's not that you can always know in advance what the SINR signal will turn out to be, since you can't determine the level of interference in specified time and place until you measure them. But you can feel the average level of interference in a particular environment. Along with this, you will have better ideas about exactly what signal level the access point needs to maintain high level of functionality.

Knowing this, you may ask, "Why on earth would anyone want to reduce the transmit (Tx) signal strength despite interference?" Good question, since this is one of the three standard reactions to resending packets. The answer is that the drop in Tx signal strength compresses the AP's coverage area. If you have a noise source outside your coverage area, effectively eliminating that source from the AP's range of awareness frees the latter from having to try to deal with the problem. Provided the client is in a reduced coverage area, this can help significantly reduce co-channel interference and improve overall performance. However, if your client is also in the outer range of AP coverage (like Client 1 in our picture), then it simply falls out of view. Even in the best case scenario, a drop in transmit power will greatly reduce the coverage area, i.e. SINR value, and leave you with reduced data rates.

So many channels, but nothing to watch

As we have seen, the first two generally accepted approaches to dealing with interference reduce physical speed and reduce power. The third principle is the one covered in the walkie-talkie example: changing the wireless channel, which essentially changes the frequency at which the signal travels. This is the key idea behind spread spectrum, or frequency hopping, technology, which was discovered by Nikola Tesla in the 20th century and saw widespread military use during World War II. In an instant, the famous and beautiful actress Hedy Lamarr helped discover a frequency hopping technique that could disable radio-controlled torpedoes. When this approach is used over a larger frequency range than the one in which the signal is usually transmitted, then it is called spread spectrum.

Wi-Fi devices use spread spectrum technology primarily to increase bandwidth, reliability, and security. Anyone who has ever depended on the settings of their Wi-Fi devices knows that there are 11 channels in the 2.4 to 2.4835 GHz band. However, since the total bandwidth used for 2.4 GHz Wi-Fi extensions spectrum is 22 MHz, you get a partial overlap of these channels on top of each other. In fact, in, say, North America, you will only have three channels at your disposal - 1, 6 and 11 - that will not intersect. In Europe, you can use channels 1, 5, 9 and 13. If you use the 2.4 GHz 802.11n standard with 40 MHz channel width, then your choice is reduced to two: channels 3 and 11.

In the 5 GHz band things are a little better. Here we have 8 non-overlapping internal channels (36, 40, 44, 48, 52, 56, 60 and 64.) High-performance access points usually combine radio broadcasting in both the 2.4 GHz and 5.0 GHz bands, and it would be correct to assume , that there is less interference on the 5.0 GHz bandwidth. Just getting rid of 2.4 GHz Bluetooth interference can make a big difference. Unfortunately, the end result is inevitable: the 5.0 GHz spectrum is now becoming saturated with traffic, just as the 2.4 GHz spectrum was. With the 40 MHz channel width used in the 802.11n standard, the number of non-overlapping channels is sharply reduced to four (dynamic frequency selection (DFS), channels are eliminated due to military problems associated with conflicting radar signals), and users Already at times we are faced with situations where there is not one in the range sufficient open channel. It's as if we had more television channels that you could watch all day long and show nothing but commercials about personal hygiene. Few people want to watch this from morning to night.

Omnidirectional, but not omnipotent

Well, we've given you enough bad news for now. But there are more of them. It's time to talk about antennas.

We mentioned the signal strength, but not the direction of the signal. As you probably know, most antennas do not have a specific direction of action. Like a set of speakers that blast loud sounds in all directions simultaneously (with attached microphones that pick up sounds evenly from all 360 degrees), omnidirectional microphones give you great coverage. It doesn't matter where the client is located. As long as it is within coverage range, the omnidirectional antenna will be able to detect and communicate with it. The disadvantage is that the same omnidirectional antenna also intercepts any other source of noise and interference in a given range. Omnidirectional systems pick up everything—good sound, bad sound, terrible sound—and there's little you can do about it.

Imagine that you are standing in a crowd and trying to talk to someone who is a few meters away from you. Because of the noise around you, you can hardly hear anything. So what will you do? Well, of course, put your palm to your ear. You will try to better focus on sound coming from one direction, while simultaneously blocking sounds coming from other directions, that is, those that are “blocked” by your palm. An even better sound insulator is a stethoscope. This device attempts to block out all environmental sounds by using ear muffs that are inserted into the ears and only allow sounds coming from the chest to pass through.

In the radio world, the equivalent of a stethoscope is a technology called beamforming.

And again about beamforming technology

The goal of beamforming technology is to create a zone with increased wave energy in a certain location. A classic example of this phenomenon: drops of water falling into a swimming pool. If there were two faucets above it, and you opened each faucet at precisely the right moment so that they periodically released time-synchronized drops of water, concentric ring waves radiating from each epicenter (where the drops hit) would create a partial overlapping patterns. You see such a model in the illustration above. Where a wave finds itself at the highest point of intersection with another wave, you get the additional effect that the energy from both waves combines and leads to the formation of an even larger crest in the waveform. Due to the regularity of the droplets, such amplified ridges are clearly visible in certain directions, they constitute a kind of "beam" of amplified energy.

In this example, the waves diverge in all directions. They uniformly tend outward from the point of origin until they reach some opposing object. Wi-Fi signals emitted from an omnidirectional antenna behave in the same way, releasing waves of radio frequency energy that, when combined with waves from another antenna, can form beams of increased signal strength. When you have two waves in phase, the result can be a beam with almost double the signal strength of the original wave.

Used in all directions

As you can see from the previous photo of the interference level, beam formation from omnidirectional antennas occurs in numerous, often opposite, directions. By varying the timing of the signals at each antenna, the shape of the beamforming pattern can be controlled. This is a good thing because it allows you to focus energy in fewer directions. If your access point "knew" that its client was at the three o'clock position, would it be reasonable to send a beam at the 9 or 11 o'clock position? Well, yes... if the presence of this "lost" ray is inevitable.

In fact, if you are dealing with omnidirectional antennas, then such a loss is truly inevitable. Technically speaking, what you see in the top row is the result of a phased array antenna (PAA) - a group of antennas in which the relative phases of the corresponding signals feeding the antennas differ in such a way that the effective radiation pattern of the array is amplified in the desired direction and is suppressed in several undesirable directions. This is similar to squeezing the middle part of a balloon that is not fully inflated. As the compression increases, we will get a part of the ball that protrudes excessively in one direction, but we will also encounter a corresponding overshoot in the other direction. You can see this in the figure above, where the top row shows the different beamforming patterns produced by two dipole omnidirectional antennas.

Making changes during beamforming

Obviously you want the generated beam coverage to include the client device. When forming a beam with a phased array antenna, as illustrated in the figures above, in top lines(this time three dipole antennas are taken), the access point analyzes the signals coming from the client and uses algorithms to change the radiation pattern, thus changing the direction of the beam to better target the client. These algorithms are calculated in the access point controller, which is why you can sometimes see another name for this process - “chip-based beamforming”. This technology is also commonly known as directional signaling by Cisco and other companies, and remains an optional, less widely used component of the 802.11n specification.

Phased antenna array Hardware-controlled is the method used by most manufacturers, who now widely advertise support for beamforming technology in their products. Ruckus does not use this method. In this regard, we were wrong in our previous article. On page six, our writer stated that "Ruckus uses 'on-antenna' beamforming, a technology developed and patented by Ruckus...[which] uses an antenna array." But this is not the case. Beamforming with a phased array antenna requires the use of a large number of antennas. Ruckus' approach is different from this method.

With Ruckus technology, the beam can be directed to each antenna, independently of other antennas. This is achieved by deliberately placing metal objects in the vicinity of each antenna in the antenna array to independently influence the radiation pattern. We'll come back to this issue in a bit more depth shortly, but you can see a few different types of beamforming models using the Ruckus approach in the second row of the pictures above. Looking at both approaches simultaneously, it is impossible to determine which of them will give the highest practical performance. The three-antenna phased array produces a more focused beam than the Ruckus relative coverage units. Intuitively, we can assume that the more focused the beam, the better the performance, if all other factors are equal. It will be interesting to find out if this is the case during our tests.

I can not hear you!

Remember the effect of putting your palm to your ear? Eliminating interference from the unwanted side can improve reception quality, even though the client has not changed the signal emission pattern. According to Ruckus, simply ignoring signals from opposite direction can bring the client up to 17 dB extra due to the exclusion of interference.

At the same time, improving the strength of the transmitted signal can add an additional 10 dB. Considering the previous explanation about the influence of signal strength on throughput, you'll understand why signal conditioning can be so important and why it's a shame that most manufacturers in the wireless market haven't taken the aforementioned technologies into account until now.

Spatial association

One of the major improvements to the 802.11n specification is the addition of spatial aggregation. This includes the use of the so-called natural splitting of one primary radio signal into sub-signals that reach the recipient at different times. If you draw the access point at one end of the gym and the client at the other, the direct path of the radio signal to the center of the gym will take slightly less time than the signal reflected from the side wall. There are usually many possible ways the passage of signals (spatial streams) between wireless devices, and each path may contain a stream with different data. The receiver receives these subsignals and recombines them. This process is sometimes called channel diversity. Spatial multiplexing (SM) works very well in enclosed spaces, but terribly in less confined environments such as an open field, since there are no objects for signals to bounce off of to create a sub-stream. When this can be done, SM serves to increase the channel bandwidth and improve the signal-to-noise ratio.

To get a clear sense of the difference between streaming aggregation and beamforming, imagine two buckets - one filled with water (data) and the other sitting empty. We need to transfer data from one bucket to another. Beam shaping involves one hose connecting both buckets and we increase the water pressure to transfer the liquid faster. With flow pooling (SM), we already have two (or more) hoses moving water at normal pressure. With a single radio chain, that is, transmitting a radio signal from one device to one or more antennas, SM typically performs better than beamforming. With two or more radio circuits, most often the opposite happens.

Is it possible to use both methods?

We're not too fond of the picture above, but it can help you understand why you can't combine stream aggregation and beamforming using a three-antenna design (which is the latter option we currently have in many access points). Essentially, if two antennas are busy beamforming the first stream, a third antenna remains to launch the second stream. You might think that with two incoming streams, SM shouldn't have any problems. However, directed flow is likely to have much higher speed data transfer is so large that the receiving client cannot effectively synchronize the two threads. The only way to get both streams close enough to data rates to synchronize is to reduce the power of the beamforming signal... which kind of defeats the whole point of beamforming in the first place. You get two streams with “standard pressure”, as in our previous illustration.

What if you had four antennas? Yes, it might work. Two will deal with signal generation, and the other two will deal with streaming integration. Naturally, adding another antenna increases the cost of the entire set. In the world of enterprise access points, buyers may readily accept a price increase, but what about someone who also needs four antennas at once? Only recently we received three antennas for working with laptops - there were fierce disputes about this. And then there’s a fourth one? More importantly, what will happen to energy consumption? In the absence of answers and/or enthusiasm in this market, manufacturers have simply shelved the idea of ​​developing quad-antenna designs.

Antennas and radio modules

Previously we used the term "radio circuit", but in many cases it does not provide a sufficiently deep and precise definition. There is a relevant representation of the relationship between radio circuits and spatial flows that is important to remember when evaluating wireless mechanisms.

Take a look at the expression 1x1:1. Yes, we can already hear “experts” pronouncing it: “one multiplied by one and divided by one.” Is not it? Can't be found the best way records than with a colon?

The 1x1 part refers to the number of circuits involved in transmitting (Tx) and receiving (Rx) data. A:1 is related to the number of spatial streams used. Thus, the industry standard 802.11g access point can be denoted by the expression 1x1:1.

300 Mbps speed quoted in most modern products 802.11n, depends on two spatial streams. These products are designated 3x3:2. You have probably not yet encountered designs in which the transfer speed is 450 Mbps. This is already 3x3:3, but despite the theoretical speed of 450 Mbps, such products have very little, if any, advantage over 3x3:2 products. Why? We repeat again: you cannot combine beamforming and spatial aggregation across three radios very effectively. Instead, you have to work with three streams at a standard signal level, which, as we have already seen, limits the range and causes packets to be resent. This is why 450Mbps routers have a hard time finding their way into remote niches in the mass market. Under ideal conditions, 3x3:3 products will be much better, but we live in an imperfect world. Instead, we have a world filled with competition and disruption.

SRC vs MRC: can you hear me now?

Obviously, listening is the key to effective communication, and a lot depends on how you listen to the speaker. As in the example in our illustration, if someone is speaking at one end of the field, and three people are listening to him at the other end, the strange thing is that the listeners, for some unknown reason, will not hear the same thing. In wireless networks, you can ask, "Okay, which of you listeners heard what the transmitter said best?" And choose the one who seems to have heard more than others. This is called simple ratio combining (SRC), and it is closely related to the idea of ​​switching between antennas, in which whichever antenna has the best signal is used.

A more efficient and widely used multi-antenna approach is maximum ratio combining (MRC). In very general terms, this involves three receivers "joining forces" and comparing the information sent, and then coming to a consensus on "what was said." With the MRC approach, the customer enjoys better coverage in wireless devices and an improved quality of service. Also, the client is less sensitive to the exact location of the antennas.

Of course, you probably have a question: if three antennas are better than two, then...

Why not use a million antennas?

Well, yes, why not use a hundred thousand billion antennas?

Aesthetics aside, the real reason manufacturers don't make porcupine APs like this is because they can't do anything about the law of diminishing returns. Test data shows that the jump from two to three antennas is no longer as significant as from one to two. Again, we come back to the issue of cost and (by at least, client side) energy consumption. The consumer market has settled on three omnidirectional antennas. In the business world you can find more, but usually not much.

Ruckus is one of the rare exceptions in this case because it uses directional antennas. In the round access points, which you have already seen in the pictures in this review, the disk-shaped platform houses 19 directional antennas. If you combine the coverage areas of all 19 antennas, you get coverage of a full 360 degrees. Nineteen omnidirectional antennas would be excessive, but 19 directional antennas (or so, depending on the AP design) can provide performance gains that would not be expected from simply increasing the number of antennas, but still consume less power because obviously only a few of them are in use at any given time.

"Where's Wally?"* and Wi-Fi

We've already seen that the access point can adjust the phases of signals to obtain the maximum signal strength at a given point, but how does the AP know where exactly that point (i.e. the client) is located? An omnidirectional access point detecting a client device with a -40 dB signal looks the same at the 4 o'clock position as it does at the 10 o'clock position. In the case of multipath diversity, where you have different signals coming from different directions, the AP has no way of telling you whether the client is transmitting a high-power signal from far away or a low-power signal from a short distance away. If the client is moving, the access point cannot determine which way to turn to detect it. The effect is very similar to the situation when you cannot determine where the siren is coming from if you are standing between several high-rise buildings. The sound seems too strong for you to pinpoint the direction from which it is coming.

This is one of the inherent dangers of beamforming technology. Optimizing the beam from an access point to a given client device requires knowing exactly where the latter is located, mathematically if not spatially. The AP receives many signals and must, over time, track down one or two of them that it needs. With so many similar types of signals and external distractions (in radio parlance), the result for the access point may be to search for a single character on an ad advertising "Where's Wally?" How quickly an AP can determine the location of its stupid client will largely determine how the client itself attempts to communicate its location to the AP, if at all.

*Note: "Where's Wally/Waldo?" (“Where”s Wally/Waldo?” is an attention game for computers and mobile phones. The player’s task is to find Wally hidden in the crowd.)

Implicit and Explicit

Returning to the idea of ​​how hearing can deceive you, we typically isolate sounds that are directly related to the difference in time between when the sound reaches one ear and when it reaches the other. This is why we get confused when we hear sound reflected from a building, because we cannot determine how long it takes for the wave to reach each ear. Our brain perceives the phase difference of the source signals as abnormal.

If the access point has multiple antennas, it uses them as ears, then evaluates the phase difference of the signals to fix in the direction of the client. This is called implicit beamforming. The signal is generated in the direction that is implicitly derived from the detected phase of the signal. However, the AP can become stymied by "weird" bouncing signals, just like the brain. This confusion can be supplemented by the difference in the directions of the ascending and descending lines.

With explicit beamforming, the customer communicates exactly what they need, as if placing an order for an intricate cup of espresso. The client sends requests related to transmission phases and energy, as well as other factors relevant to the current situation in its environment. The results are much more accurate and efficient than implicit beamforming. So what's the catch? No product supports explicit beamforming, at least not any current client devices. Both the implicit and explicit method must be built into the Wi-Fi chipset. Fortunately, samples supporting an explicit beamforming method should be available soon.

Polarization

In addition to all the questions about wireless communication that we have encountered, we can add polarization to the list. Polarization means a lot more than some suspect, and we were able to see with our own eyes all the effects on iPad 2, so to speak, first hand. But first, a little theory...

You may know that light travels in waves and all waves have a directional orientation. This is why polarized sunglasses work so well. Light reflected from the road or snow into your eyes is polarized in a horizontal direction, parallel to the ground. The coating with polarizing filters in glasses is oriented in the vertical direction. Think of the wave as a big, long piece of cardboard that you're trying to push through the blinds. If you hold the cardboard horizontally and the curtains vertically, the cardboard will not fit through the cracks. If the blinds are horizontal, for example, lifting, then it costs nothing for the cardboard to easily overcome the obstacle. Sunglasses are designed to block glare, which is mostly horizontal.

But let's get back to Wi-Fi. When a signal is sent from an antenna, it carries the polarization orientation of that same antenna. And therefore, if the access point is on the table, and the antenna emitting the signal points directly upward, the emitted wave will have a vertical direction. Therefore, the receiving antenna, if it wants to have the best possible sensitivity, must also have a vertical directionality. The opposite statement is also true - the receiving AP must have an antenna (antennas) that are adjusted in polarization to the sending client. The farther the antennas are from the polarization adjustment, the worse the signal reception. Good news is that most routers and access points are equipped with movable antennas that allow users to find the best position to receive the signal from the client, just like using an antenna with "horns" for TVs. The bad news is that because so few people understand the principles of polarization in Wi-Fi devices, it's unlikely that anyone is performing this polarization optimization.

Looking at the illustration above, remembering everything we told you about, you will see that the access point emits both horizontal (above) and vertical signal waves to the client iPad 2. Which direction will give us the best reception quality and performance? This depends on how many antennas are connected to the client and what their directivity is.

With poor reflection

And now about our experience obtained with polarization iPad 2. We were near where the camera was when this photo was taken. It shows the Aruba access point we connected to hanging from the ceiling in the background. Our employee held the tablet by the corners with both hands. We simply observed the quality of signal reception; At first the position was vertical, and then the tablet was rotated to a horizontal position. At first the signal was good and did not disappear for a long time. When turning iPad 2 in the vertical position the connection is broken. Our employee tried not to change the position of his hands, grip and location of the tablet in space. But the signal disappeared... that's all. We wouldn't believe it if we hadn't seen it with our own eyes.

After reading the previous page, you can guess the nature of what happened to our device. As it turned out, while the first iPad had two Wi-Fi antennas, y iPad 2 only one is used, located along the bottom edge of the case. Obviously, in horizontal mode, the tablet's antenna was in the same plane as the access point's antennas, which, as you can see, are in a vertical position. In horizontal, the client and AP antennas were in different planes.

A couple more things to remember: the lens effect in the photos above causes the access point to appear closer than it actually is. The client and AP had a line-of-sight distance of about 12m from each other, which is longer than the distances you'll see in our polarization tests in Part 2 of this review. Moreover, taking a couple of steps back, we were unable to reproduce these results. Our guess is that our employee was in a Wi-Fi dead zone... well, maybe half dead. In order to get a good signal again, our employee retreated a few more steps. But do not forget that the reflection of the signal can change the direction of the wave. The signal, which may have been perfectly aligned along the line of sight, after one or two reflections could “go” many degrees to the side, and this affects the quality of signal reception.

Mobile madness

After reading about our example with iPad 2, now try to think about signal polarization on other mobile devices. What about that smartphone - lying on the table, tilted to watch videos, pressed to your ear, etc.? Now imagine how much the signal from both your mobile phone and Wi-Fi will fluctuate with the slightest movement. We take the signals from these devices for granted, but in reality, wireless networks can be quite finicky and require all of our attention to function properly.

Speaking about signals from mobile devices, we note that there is little we can do in this case without having a phone with an external antenna (like, for example, car phones). In fact, any portable wireless device can only be tested for polarization diversity (multi-beam directivity of the antennas) and determine the gain in transmission speed, performance standards and/or battery life. An interesting picture emerges with laptops. Most models are equipped with an antenna(s) located in a frame around the perimeter of the LCD display. Have you ever thought that you can significantly improve signal reception by tilting the screen back or forward, or perhaps by rotating your laptop a few degrees?

Similarly, an access point that must serve many clients may provide best service, if one of its antennas is directed vertically and the other horizontally. Of course, the problem with this arrangement is that both antennas cannot interact and effectively generate a directional signal. Their polarizations do not coincide, and therefore, if the client receives one signal of very good quality, the other deteriorates due to the mismatch of planes.

If Rx antennas are only designed to search for waves in one direction, then this is a sure way to fail. This is why it is important to have more planes at the receiving end. If you have two receiving antennas, one vertical and the other horizontal, and two vertical Tx antennas, then you can only receive one stream at a fairly good level.

Putting all the puzzle pieces together

The material you have read on these pages is the necessary basis for understanding the results of our test analysis, which you will soon be able to read in the second part of the review. When an access point shows excellent results in a certain test or, conversely, fails to cope with a task, it is important to understand why. Now you know that for optimal 802.11n performance, AP/client interactions can benefit from beamforming, spatial aggregation, antenna diversity, optimal signal polarization, and others.

Some of these technologies may already be built into your access point. The table above shows a list of various technologies inherent in most modern 802.11n APs. The points in this table that we considered important for understanding the data from the second part of the review were given here in part 1.

Even if you don't read Part 2, we hope today's reading gives you a sense of how much mainstream 802.11n products can benefit from a few design improvements. The situation is especially dire at the consumer level. The manufacturers have given us a "pretty good" approach, although it is clear that there is still room for significant improvement. How significant? You will find out the answer to this question a little later...

Why do we value our laptop? For mobility, of course! What can hinder the mobility of a laptop at home? Certainly weak signal WIFI! Indeed, when moving a laptop from one room to another, we are faced with a weakening, or even complete loss of the wifi signal. This negatively affects Internet speed and work comfort.

Let's try to figure out the problem of a barely perceptible Wi-Fi signal in an apartment or house.

A weak or missing signal can be improved. How to do it!

Solving the problem of a weak wifi signal on a laptop

Here are a few basic rules that will help improve quality wifi connections at home:

When installing a Wi-Fi router, make sure that it is located approximately in the center of the network of future use. It should not be installed too close to the wall or on the floor, so that there is less chance of interference. If you install it near an outside wall, then part of the signal will go to nowhere.

If the signal is weak, then the problem may be in the router antenna; check it and, if necessary, replace it. Factory antennas are omnidirectional. They also do not have a power adjustment feature. But don't despair, you can buy an antenna that will boost your signal in the desired direction. And in this case, the router can be installed near an external wall. True, when choosing an antenna, you may need the help of a specialist.

A good solution is a repeater (signal repeater). It is enough to install it at the same distance from the computer and the router and the problem is solved. The advantage of the repeater is its convenience: no wires or complicated installation.

Routers are capable of broadcasting a signal on different channels, like a radio. Perhaps changing the channel will improve the signal. You can do this in the configuration settings of your Wi-Fi router.

Before firmly fixing the router in the place of your choice, try walking around the house with your laptop and checking the signal level in the intended places of work. Experiment with different locations for the router and choose the optimal location.

Reducing radio interference can help strengthen the signal. Almost every home now has a microwave oven, cordless telephone and other equipment that operates at the same frequency as the router. Even New Year's garland can create interference! At active use These devices may cause the router to lose ground. Reducing “noise” usually helps to achieve a stronger Wi-Fi signal. Such noise can be reduced by grounding emitting devices.

Perhaps the whole point is that your router is simply outdated and you need to improve its performance. In this case, flashing or updating drivers will help you. But you should note that it is best to use improvements from the manufacturer. And if the adapter with the Wi-Fi router is from the same manufacturer, then this will also have a positive effect on the degree of signal amplification.

Sometimes it happens that the router gives a good signal, but the laptop just cannot pick it up. Perhaps it's all about the laptop's wifi network adapter. Try updating your drivers.

Conclusion

Remember - signal amplification, a problem to be solved, the main thing is to set a goal! In this article, I gave several recommendations that will, although not completely solve, still reduce this problem to a minimum.