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What are the signal bars on your smartphone really there for?

Posted by on May 17, 2015

Signal bars on cell phone

Since we provide signal boosters to boost signal, we rely on a common terminology of "signal bars" to refer to "signal strength" of cell phones. However, most of us erroneously assume that signal bars on phones are standardized and display accurate signal reception at any given point in place and time. We’re always checking and comparing bars on our smartphones and attribute differences at a specific time and place to the respective service providers service quality. Is that what they really represent?

An assumption that the signal bars on any particular phone shows the actual strength of the signal we’re receiving is inherently flawed. It turns out that they do actually indicate signal strength, but there’s no defined standard unit for a bar on a phone: the manufacturer can come up with whatever algorithm they choose. Obviously they’re trying to satisfy the consumer by providing meaningful information; however the details of that information are up to the manufacturer. The handset reports what they experience back to the network, then the network endeavours to make an intelligent decision as to the technology, channel, band, and so on, the handset will be using for its next communication. So, the bar strength is not always based on the strength of the signal.

Let’s say you’re in a crowded stadium: you could be pushed onto a different wireless band just because your phone can support that capability. And even if you and the person next to you are connected to the same tower, there’s still no guarantee that you’ll both have the same number of bars on your screen.

Perhaps you’re surprised to hear that there are no set standards for bar measurements on a phone. Remember that manufacturers of handsets use different radios in their smartphones, and all these radios differ a little. So it’s up to the manufacturer to determine how their cell phone will report back to the base station, and how many bars will show for a specific signal level.

So, the question is: Do more bars mean a better signal? The answer is: Yes, almost always. Of course there are always going to be cases where there are capacity or interference issues and you might have plenty of signal bars, but that doesn’t necessarily mean that you have a reliable service. But generally, yes, these things work the way they’re designed to, and when you have more bars you should have better service.

Not All Phones Are Alike

We know that different manufacturers use different algorithms in order to calculate the bars displaying on a phone’s screen. It all begins with what’s known as the pilot channel.

The Waveform is the signal that comes from an operator: maybe it’s UMTS or LTE, and the waveform can be characterized by a constant pilot channel that’s always transmitted. Depending on how many people are using the network the traffic loading goes up and down. But it’s not simple, particularly signal strength, and the manufacturer will sometimes include another parameter beyond that channel.

If you place an iPhone next to an Android phone and purposefully reduce the signal-to-noise ratio while maintaining a constant signal level, you’ll see the bars decrease. This shows that there’s a more complicated algorithm when the number of bars are being determined. Perhaps it means that the iPhone takes into account how loaded the network is; perhaps it’s checking if there’s any interference which might decrease the signal-to-noise ratio. It does seem that it’s looking for other factors (beside signal strength) that might impair the call quality.

How Fast Do The Bars Change?

Because phones are complex devices, internal algorithms determine which functions will take priority at any given time. Some phones don’t seem to update the bars on the screen very often at all. It can be difficult to use a phone as a measuring tool because you might go 15 minutes without any update on the number of bars, so what you’re seeing and what’s reality might be two separate things. It really does depend on what kind of phone you have.

Some users are confused because their handset bars don’t update very often. If you were to install a booster device and you’re in an area with a lot of network congestion, an iPhone could show two or three bars due to the lower signal-to-noise ratio, whereas the Android next door might show five bars. Walking away from the booster you’d see the Android’s signal level drop and the number of bars slowly decreasing, but in that case of heavy loading the iPhone it might show less bars even though you’re right next to the booster: as you move away it will stay pretty constant because it’s favouring the network loading issue.

Algorithms are made up of many parameters.

How Are They Measured?

They’re measured in decibel-milliwatts – dBm. A good signal’s measurement will differ slightly depending on the technology used. For UMTS the level is about -106 dBm received signal code power (RSCP): for the LTE a reasonable level is -120 dBm reference signal received power (RSRP). It’s actually possible to measure your own phone’s signal strength yourself by gaining access to the field test mode: you may not be aware that most handsets have a hidden menu that provides radio information. The unlocking code for this function varies from phone to phone. Try putting *3001#12345#* into the dialer of your iPhone and you’ll have access to its field test menu. Or, search online for ‘field test mode’, find the model of your phone, and you’ll have the code for your specific device.

If You Have No Bars, How Do You Make Emergency Calls?

If you’re in the United States and you make an emergency call, your phone will use any channel available, with any operator. It doesn’t matter at all who your operator is or who your service contract is with. You may even be low on battery where normally your phone wouldn’t let you make the call, but an emergency call can be made at all times. In fact, this is a legal requirement in the United States and certain other countries, but this doesn’t relate to the bar system: the legality is that you must be able to make a phone call so your position can be determined, regardless of the number of bars.

Is There Any Other Way to Boost The Signal?

We know that the  cell phone signal boosters we carry are a fantastic way to boost reception indoors inside homes and buildings as well as inside cars and trucks. However, did you know that after the FCC introduced new regulations, the older signal booster technology has been restricted. The FCC’s reasoning is that some of the older amplifying technology was creating problems for operators; operators who pay a lot of money for their license. Injecting noise into a radio channel is effectively decreasing the channel’s capacity for other users, so it’s not good for either the consumer or the operators.


A Femtocell can boost your signal strength using your home internet connection.

Wi-Fi Calling:

Wi-Fi calling is a great backup for poor indoor service, and this is becoming quite popular. Apple’s iOS 8.3 update supports Wi-Fi Calling with EE and Sprint: T-Mobile also supports it, with Verizon and AT&T expected to follow suit shortly. 

Cellular Signal Booster (Cell Phone Signal Booster)

And finally, the Cell Phone Signal Booster detects the cell signal outside the home or office building: It brings the signal inside and amplifies it, then re-broadcasts the amplified signal to your interior area for use by your phone and other devices. This results in a strong, more reliable reception inside buildings. Please see our how boosters work page for a more detailed explanation.

Have a fabulous day!

Questions? Call us for a FREE product recommendation or try our automated Cell Phone Signal Booster Selector Tool. Need a cell phone booster installer? We offer installation services by a certified installing team that installs boosters nationwide across USA and Canada. Submit location details for cell phone signal booster system design & installation quote to have your amplifier kit installed by professionals.

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