Coverage, Infill, Capacity, In-building Solution, Small Cell, Femto Cell and Repeater
Today we are going to discuss about different types of Cell site in telecom field.
These cell sites can be used in 2G, 3G, 4G or 5G technologies.
There are seven types of cell site or solution we can have to provide network coverage and capacity.
They are:
- Coverage site.
- Infill Site.
- Capacity Site.
- Samll Cell.
- Femto Cell.
- In-Building Solution (IBS)
- Repeater.
Out of all these, we know most of the things about coverage, Infill and capacity sites and repeater.
But Small cell, Femto cell are some new concept those are coming along with 4G and 5G technology.
1.Coverage / New Site
A location where Operator-A does not have any coverage and planning to expand its coverage in that particular location then this type of site/sites are called Coverage site.
In that particular area customers will get Operator-A network for the 1st time.
The coverage distance of a capacity site is as much as possible so that it can cover maximum distance.
Basic Planning Part of Coverage Site:
1800 MHz Band:
Usually coverage sites are planned based on frequency band.
If we are using 1800MHz band then in ideal condition 1800MHz site can give coverage up to 2.5Km.
So we prefer a site which is not coming within 2 to 2.5 Km rang of an existing site.
This concept is not always applicable especially in case of Dense Urban, Urban, and Semi-Urban area.
Because in such kind of area due to high rise and congested buildings indoor coverage issue is always seen.
So in such type of area we may plan coverage sites for the first time within 1 Km or even 500m or may be less based on clutter density and terrain conditions.
900 MHz Band:
In case of 900 MHz the coverage range of a site may goes up to 4 Km.
So in that case we should not prefer a new site below 3.5 Km from an existing site.
Highway:
On highway sites the distance between the sites are kept at a greater distance than normal sites, as at highway sites we generally use comparatively high gain antenna than normal sites.
High gain antenna gives a long distance coverage e.g. like 4 Km gap for 1800 MHz band.
2.Infill Site:
In a location, suppose a in a town name X, Operator-A already has coverage either with one site or may be 2, 3 or more sites (for bigger town).
But inside the town or location there are some places where there is some coverage gap or black holes of coverage and the existing sites are unable to provide proper coverage in those particular locations.
In such cases we plan new site specially to remove coverage gap inside a town or a location.
These sites are called Infill site.
Infill sites are planned to cover a distance up to 500-700m or may be up to 1Km based on coverage gap and the location where we want to provide network coverage.
Coverage distance of infill sites is totally based on the area where we want to mitigate the coverage gap.
For a dense city with hilly terrain we may plan a new infill site even at a distance of 100m from exiting tower. But for a same kind of dense city with plain terrain we may prefer a new site beyond 300-500m from existing site.
In case of Infill site, site optimization is done properly so that we should not face the problem of interference of nearby site as well as coverage overlapping.
3.Capacity Site:
Suppose in a location there are 3, 4 sites or any no of sites and provide good coverage in the whole town.
There is no coverage gap in any place. But sites are over loaded. All or may be one,two sites or may be 2, 3 sectors of the town are highly congested and we can’t add any more capacity to that site.
In such scenario we plan some new sites to off load the congested cells.
This type of site is called Capacity Site.
Basic Planning Part of Capacity Site:
2G:
Earlier when we have only 2G technology and if traffic for a particular site increasing day by day and equipped capacity of that sites is more than 160% utilized then we planned for TRX addition.
If TRX addition reached to a level of exhaustion based on the BTS capacity then we plan for a new site nearby to offload 1 or 2 sectors of that site.
TRX handling capacity is depends on the type of BTS we are using.
Suppose if we use a Nokia ULTRA BTS (which is obsolete now a days) then it can handle only 12 TRX (4/4/4). If we want to increase TRX capacity at a ULTRA BTS site then we need to install 1 more BTS box to support additional TRXs.
If we use Nokia BTS like Flexi Edge then additional hardware not required, only software upgradation required.
But whatever the upgradation capacity (TRX capacity) of a BTS, it also depends on the available bandwidth of 2G.
3G & 4G:
4G VoLTE (voice over LTE) is totally based on packet switched concept i.e. only data. No circuit switching.
In case of 3G, though voice traffic is handled by circuit switching, still as 3G is going to become obsolete very soon operator are not much concern about increasing 3G capacity at site.
Gradually 3G layers will be converted to 4G layer on the same frequency band.
Equipment for 3G and 4G will be almost same except we have to replace the 3G baseband (a card inside the BTS) with a new 4G baseband.
No need to replace antenna and Radio unit. But sometimes based on the 4G compatibility of Radio unit (RRU) we may need to replace the existing 3G RRU with new 4G RRU.
But this is not applicable for all cases.
How to convert a 3G layer to a 4G layer in same frequency band of 3G we will discussed in my upcoming blog in details.
Alternate Options of Capacity Site:
Now a days we avoid to implement or integrate capacity sites.
Currently the main concern is with data rather than voice traffic. As we have now 3G and 4G both technologies over and above 2G.
In Case of 4G we don’t prefer a capacity site to offload one or 2 sectors of an existing 4G site.
In 4G we have so many alternate options.
If payload of a site increases we can take any of the below mentioned steps.
Option 1- Bandwidth Expansion:
Considering existing 4G site is operating at 1800MHz band FDD and in 5MHz.
Then we can upgrade it to
- 10 MHz band
- 15 MHz band
- 20 MHz band
And even beyond 20MHz also provided the operator has a continuous frequency band of 20MHz or beyond.
For that we need to take only software licenses. No need to do any changes in hardware part.
Option 2- TDD Site:
Going for a TDD (Time Division Duplexing) site at the same location.
If we have 2500 MHz or 2300 MHz TDD frequency band then we add equipment of the respective band at the same sites.
Equipment will include Antenna, Radio and baseband unit.
Addition of TDD layer will increase the data handling capacity of that site.
Even in TDD also we have options to increase our bandwidth of sites, suppose from 10MHz to 20 MHz, based on availability of frequency band of the Operator.
Putting a new technology like TDD on existing FDD site or bandwidth expansion is cheaper compared to installation of a new site.
Option 3- Small Cell:
And the last option for increasing the capacity of a 4G or 5G site is Small Cell.
So now a days capacity site planning is not preferred until and unless all above mentioned attempts fail to handle the carried traffic/payload of the site.
4.In-Building Solution (IBS)
In Building Solution (IBS) is to provide coverage inside a building and in each floor.
Here there is a MACO BTS like any other normal site. We can use 1 or 2 sectors as Outdoor site as normal site and 1 sector can be used only for Indoor coverage purpose.
That sector will serve lots of small indoor antennas in each floor.
In some cases we don’t use any outdoor sector to provide coverage outside the building.
This type of site is installed in big hotels or large complex.
In all above discussed cases, we use MACRO BTSs.
Now we come to discussion of all new kind of BTSs or solutions based on different requirement.
The new cell concept that now we are going to discuss is about Samll Cell, Femto Cell and Repeater are some solutions for the coverage and capacity requirements for the hotspot locations, enterprise accounts and high values subscribers.
5.Small Cell:
There are broadly three types of solutions namely
- Outdoor Small Cell
- Residential Small Cell.
- Enterprise Small Cell.
Here we are discussing only about types of small cell. We will discuss in details about small cell in a separate blog.
Outdoor Small Cells:
To meet coverage and capacity requirements at Hot spot or small area coverage requirement, outdoor small cell is solution for such requirement. It is IP65 and consumes low power.
The unit can be mounted on walls, poles or masts. This is all in one (AiO) solution need AC power supply and backhaul connectivity to integrate.
In 5G only small cell concept is used. Its coverage distance is 50 to 100m. So lot of cell site will be required if we plan to provide 5G in a particular area.
Camouflage Outdoor Small Cell
Below is the example of a camouflaged outdoor small cell.
It was installed in a restaurant with garden outside. In that garden this small cell was camouflaged like a coconut tree.
Residential Small Cells:
Residential indoor small cells solution is for hot spots as the complementary coverage and capacity solution. It can be used in Small Office Home Office (SOHO), SME (Small and Medium Enterprise), government offices, stations, entertainment places, hotels and airports etc.
It is a small and light all-in-one system which integrated baseband and radio modules. It can be flexibly installed in many places such as on the desk, on the wall or under the ceiling. It
Aims to provide ultra-high-speed data services especially for hot spots or poor/no coverage area as a supplemental of macro base station. This is also all in one (AiO) solution need AC/DC power supply and backhaul connectivity to integrate.
This type of small cell we usually plan to give better coverage and capacity at the Stores owned by the Operator itself.
Enterprise Small Cells:
To full fill unprecedented amount of mobile broadband capacity inside buildings enterprise small cell is the solution. This is the solution to multiflorous commercial building.
It involves floor wise planning and deployment of radios with hub devise and baseband. Enterprise small cells can be used at retail stores, branch offices, corporate headquarters and university campuses etc.
6.Femto Cells:
Femto solution is similar to small cell indoor solution, suitable for residential, enterprise deployments. It provides backhaul flexibility from traditional Optical or Ethernet to any IP public or private backhaul and make this solution easy to deploy.
Apart from backhaul Hetnet gateway also required which is for security and IPsec tunnelling purpose.
7.Digital Repeaters:
Digital repeaters amplify weak signal and provide coverage in deep indoor or poor signal areas, these devices can be used to provide coverage in indoor residential building or small commercial buildings or specific floor of multistory building.
Digital repeaters do not actively involve radio devices to generate signals, these repeaters are also knows as signal boosters. Outdoor repeaters are also available in high power range.
These devices boosts specific band signal and assigned sub bands. These are coverage solution and do not contribute in capacity.
Pranabjyoti Hazarika
BE | MBA | PMP|IoT-Certified