Today's post was inspired by a friend's troubles after buying an expensive phone in the USA. The phone was on sale on Amazon at around [$500+](https://www.ebay.com/itm/Meizu-Pro-7-Plus-Dual-Sim-Silver-5-7-6GB-64GB-Dual12MP-Android-Phone-By-FedEx/332536487379?hash=item4d6cb81dd3:g:3eAAAOSww-BabuAu), shipping inclusive.

After six days the phone arrived, almost everything worked great till it was time to hook up with the internet. He only got 3G reception. But the phone was listed as a 4G phone! Yes, the cellphone was a 4G LTE enabled device. He made one little mistake; he did not check the band of the particular 4G LTE network he wanted to use! He is pissed off for this oversight and is now making a deal with the seller for a return that will cost him about $40 or more in courier cost.

![](https://steemitimages.com/DQmdqBNddRZvZSZLaMCignZKGJPdPjLxPk5ZBkwXoe5XVLx/image.png)

<br>


#### What is a frequency band?
<br>

In telecommunication, a band or frequency band is a range or group of frequencies with sometimes an upper or lower limit.

The cellular phone has antennas and amplifiers that are frequency specific, so if you are looking for a new phone, you must ensure that its antenna has support from the frequency of the carrier (cellular phone provider) in the locality that you want to make use of the cell phone.


Let's discuss a little on the different 4G LTE frequency bands and their various spectrum and channels.


The LTE frequency bands allocated across the world are numerous. Even in the same country, the carriers operate on different frequency bands.

To make it easier for identification, each frequency band has a number designated to it which covers the frequency range or group that the particular number represents.


<br>

#### Transmission Techniques
<br>

To have a better understanding of the two duplex system that is employed in the LTE 4G system, it will be nice to understand the following transmission technique.

1. **Simplex**: This is a simple one-directional method of transmission. One device transmits, the other receives. The communication here is one way, and the channel (frequency) is one. A great example of the traditional radio communication and non-interactive television

2. **Half Duplex**: One party can transmit and receive but not **simultaneously** or at the same time. This is a two-way transmission method using one frequency (channel). A great example is the two-way walkie-talkie transceiver (push to talk); at any particular time only one user can transmit or receive but never both at the same time.

3. **Full Duplex**: Here, both communicating party can simultaneously transmit and receive at the same time. The communication is two-way, and two frequencies are employed. A good example is a telephone. Both parties can talk at the same time as well as hear what the other is saying.






In 4G LTE technology, there are two types of LTE standards which depend on the method of duplex configuration scheme or mode.

To share this limited scarce spectrum resource, the following full duplex communication system is applied.

<br>
#### The 4G LTE TDD Spetrum
<br>

This is the **Time Division Duplexing (TDD)** which involves the use of one frequency for both transmitting and receiving. Looking at the above technology, it would appear that the TDD is using a full duplex system on a half-duplex channel.

<br>
#### The 4G LTE FDD Spetrum
<br>

The **Frequency Division Duplexing (FDD)** is the communication system whereby two frequencies are used for simultaneous transmitting (uplink frequency between the device and tower) and receiving (downlink frequency between the communication tower and device) of signals. 

The two frequencies are allowed a sufficient separation, i.e. the uplink and downlink frequency spectrum have a gap to avoid the impairment or class of the two frequencies. The spacing of these two frequencies is called the **band gap** which is shown for different bands in the table below.

This band gap must be sufficient to reduce the incidence of received signal getting "blocked" or impaired.

The 4G networks are designed to support both the *unpaired spectrum* for time division duplexing (TDD) and the *paired spectrum* of the Frequency Division Duplex (FDD) .
<br>
<center>**LTE FDD**</center>
<br>

Band|Uplink| Downlink|Width of Band| Duplex Spacing| Band Gap
-|:---|:---:|--|--|--
-|(MHz)| (MHz)|(MHz)| (MHz)| (MHz)
|||||
1|1920 - 1980|2110 - 2170|60|190|130
2|1850-1910| 1930-1990|60|80|20
3|1710-1785|1805 -1880| 75|95|20
4|1710-1755|2110 - 2155|45|400|355
5|824-849| 869-894|25|45|20
6|830-840| 875-885| 10|35|25
7|2500 - 2570|2620 - 2690|70|120|50
8|880 - 915| 925-960|35|45|10
9|1749.9 - 1784.9| 1844.9 - 1879.9| 35|95|60
10|1710 - 1770    |2110 - 2170|60|400|340
11|1427.9 - 1452.9    |1475.9 - 1500.9|20|48|28
12|698 - 716|728 - 746|    18|30|12
13|777 - 787|746 - 756|    10|-31|41
14|788 - 798    |758 - 768|10|-30|40
15|1900 - 1920|2600 - 2620|20|700|680
16|2010 - 2025|2585 - 2600|15|575|560
17|704 - 716|734 - 746|12|30|18
18|815 - 830|860 - 875|15    |45|30
19|830 - 845|875 - 890|15|45    |30
20|832 - 862|791 - 821|30|-41|71
21|1447.9 - 1462.9    |1495.5 - 1510.9|15|48|33
22|3410 - 3500|3510 - 3600|90|100|10
23|2000 - 2020|2180 - 2200|20|180|160
24|1625.5 - 1660.5    |1525 - 1559|34|-101.5|135.5
25|1850 - 1915|1930 - 1995|65|80|15
26|814 - 849|859 - 894|30 / 40|-|10
27|807 - 824|852 - 869|17|45|28
28|703 - 748|758 - 803|    45    |55|10
29|n/a|717 - 728|11|-|-
30|2305 - 2315|    2350 - 2360|10|45|35
31|452.5 - 457.5|462.5 - 467.5|5    |10    |5
32|DL CA Only|1452 - 1496|    44    |N/A|N/A


DL CA is the band used for DownLink Carrier Aggregation.

Band 15 and 16 are no longer in use.



On the other side of the band allocation is the time division duplex where there is the same frequency for both uplink and downlink. The only separation between the two is time.

Below is a table listing the different band and its LTE band number


<br>
<center>**LTE TDD**</center>
<br>
Band No|Allocation(MHz)| Bandwidth(MHz)|
--|:---|:---:|
33|1900 - 1920|    20|
34|2010 - 2025    |15|
35|1850 - 1910|60|
36|1930 - 1990|60|
37|1910 - 1930|20|
38|2570 - 2620|50|
39|1880 - 1920|40|
40|2300 - 2400|100|
41|2496 - 2690|194|
42|3400 - 3600|200|
43|3600 - 3800|200|
44|703 - 803|100|
45|1447 - 1467|20|
46|5150 - 5925|775|
47|5855 - 5925|70|


<br>

Below are the 4G frequency bands of the primary telecommunication operators in Nigeria


##### 4G LTE Frequencies in Nigeria
<br>

[MTN](https://mtnonline.com/4G/faq)|
--|
Band 7(2600MHz)|
**[Glo](http://www.gloworld.com/ng/glo-4g-lte-faqs/)**|
Band 28 (700MHz)|
**[Airtel](http://www.africa.airtel.com/wps/wcm/connect/AfricaRevamp/Nigeria/Home/About/Airtel_and_CSR/The-Airtel-Network)**|
Band 3 (1800MHz)|
**[9Mobile](http://9mobile.com.ng/4g/)**|
Band 3 (1800MHz)|
**[NTel](http://www.ntel.com.ng/device-compatibility/)**|
Band 3 (1800MHz) and 8 (900MHz)|
**[Swift](http://www.swiftng.com/Home/about)**|
Band 40 (2300MHz)|
**[Spectranet](https://spectranet.com.ng/)**|
Band 40 (2300MHz)|
[Smile](https://smile.com.ng/)|
Band 20 (800MHz)|

<br>

The problem was the [phone](https://www.ebay.com/itm/Meizu-Pro-7-Plus-Dual-Sim-Silver-5-7-6GB-64GB-Dual12MP-Android-Phone-By-FedEx/332536487379?hash=item4d6cb81dd3:g:3eAAAOSww-BabuAu) my friend bought supports 4G LTE signals but not *all* the bands. It supports LTE band 1(2100MHz), 3(1800MHz), 7(2600MHz), 38(2600MHz), 39(1900MHz), 40(2300MHz), and 41(2500MHz). Unfortunately,  he wanted to use it on **[Glo](http://www.gloworld.com/ng/glo-4g-lte-faqs/)**'s 4G LTE network which unfortunately was Band 28(700MHz) as you could see above.

It is essential you check the compatibility of a phone to a carrier before making a purchase. The phone's full specification and network compatibility can also be viewed on the manufacturer's site or this website [here](https://www.gsmarena.com/).




This 700MHz spectrum overlaps the former digital TV signal known as the UHF (300MHz to 3GHz). It was licenced to be used for mobile telephony in 2014. 

Even though most cell phones do not support Band 28 700 MHz frequency, why do some carrier like Glo opt for it?

The 700Mhz band has a high penetrating power which is why if you are using a Glo 4G network you will get good coverage in elevators, inside building and other indoor location because of its low frequency.


<div class="pull-right">https://steemitimages.com/DQmSBW5MHxqUnsoQ3YXVaqsFhnmof1yqdvEx1bu7sC4YT2E/telecommunications-1693038_640.jpg</div>

The received power or amount of transmitted power an antenna gets decreases proportionally to the inverse of frequency. In other words, low-frequency signals like say 700 MHz will propagate better than a 2100 MHz signal under the same condition.



This outcome will mean less number of BTS antennas deployed, more wider coverage area by one antenna.





<sup>**References**</sup>

* <sup>[ITU,Spectrum Management for 4G-LTE](https://www.itu.int/en/ITU-D/Regional-Presence/AsiaPacific/SiteAssets/Pages/Events/2016/Oct-CandI2016/CAICT2016/Session%206-2%20Frequency%20Management%20for%204G-LTE-%E6%96%B9%E7%AE%AD-final.pdf)</sup>
* <sup>[LTE Spectrum Bands and Allocations](http://www.radio-electronics.com/info/cellulartelecomms/lte-long-term-evolution/lte-frequency-spectrum.php)</sup>
* <sup>[700 MHz LTE Band](https://www.slideshare.net/TMFEditorial/20100526)</sup>
* <sup>[700 MHz- Why is it so valuable](http://searchmobilecomputing.techtarget.com/tip/700-MHz-Why-is-it-so-valuable)</sup>

<hr>

<sup>**Image References**</sup>

* <sup>[Wikipedia][4G Sign by Wadzifox](https://commons.wikimedia.org/wiki/File:4G_Orange.jpg)</sup>
* <sup>[Pixabay][Cell Phone Tower](https://pixabay.com/en/telecommunications-cellular-network-1693038/)</sup>


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