In telecom network Transmission backhaul is the main Backbone of the network.
Whatever technology we may use 2G, 3G, LTE or even 5G the main support provided by transmission network only and desired data speed can only be obtained if we have sufficient available bandwidth in transmission links.
These transmission links may be:
- Microwave
- Fibre
- VSAT
- Or any other medium.
In telecom network first three types of transmission medium is mainly used.
VSAT is only used in cases where the target location is very remote and Line of Sight (LOS) is not cleared anyhow.
Additionally installation as well as maintenance cost of VSAT is very high. And available bandwidth is low. So expected bandwidth are usually 512 Kbps or somewhat nearby.
So main transmission medium till 3G network was only Microwave though fibre was preferred for redundancy, path protection and main backhaul connectivity.
When 4G came, fibre become a part and parcel of the network as to get desired data speed of 4G. We need huge bandwidth to support 4G speed.
In 4G it is a combination of Fibre as well as Microwave connectivity.
When 5G will come up as a normal service fibre will play the main role of connectivity.
Transmission Bandwidth Requirement:
Per site bandwidth requirement based on technology wise and spectrum wise are as below:
TDD & MM coexistence site:
For a site where TDD and MM (Massive MIMO) both are present then bandwidth of MM is considered as the bandwidth of the site.
TDD bandwidth for that particular site is not added to the MM bandwidth.
More than 1 sector MM site:
For more than 1 sector MM (Massive MIMO) site, total bandwidth of the site is considered as:
Site BW= MM Bandwidth of 1 sector * 1.5
We can take the below examples:
Let’s take 20 MHz bandwidth scenario for both MM and TDD
Site with 1 MM sector + 2 TDD sectors:
Site bandwidth will be 200 Mbps.
Site with 2 MM sectors+ 1 TDD sector:
Site bandwidth will be 300 Mbps.
i.e 200 Mbps of 1 sector of the MM * 1.5 times.
Site with 3 MM sectors:
Site bandwidth will be 300 Mbps.
i.e 200 Mbps of 1 sector of the MM * 1.5 times
Massive MIMO sites required very high backhaul requirement.
So these sites are ideally planned in fibre pop locations only.
Here we should not be confused with bandwidth of Radio frequency planning and transmission bandwidth.
Here we are discussing only about transmission/backhaul bandwidth. About Radio Frequency bandwidth we discussed in “Voice and Data Capacity Calculation of 2G, 3G and LTE Network”.
Now we can understand that based on backhaul available bandwidth we can expect data speed on our mobile. Speed is also depends on Technology i.e. 3G, 4G or 5G and their modulation scheme.
If congestion occurs in transmission network, data speed gets reduced.
These congestion are mainly happens in case of data linked sites i.e. 3G or 4G sites.
So it is very much required to check and do optimization of the transmission links.
If utilization of a transmission link goes beyond 70% then we should plan to optimize or upgrade the links.
There are mainly 3 different methods we can apply to upgrade or optimize a link.
- Bandwidth up-gradation
- Link re-routing
- Link equipment up-gradation.
Bandwidth up-gradation:
For IP nodes we can upgrade the available bandwidth of the microwave links.
Suppose a link is working on available bandwidth of 183 Mbps then we can upgrade it to 214 or 240 Mbps and check if the link utilization is going down or not.
If some links are working below 183 Mbps, then we can upgrade those links to 183 Mbps.
Only problem in upgradation of bandwidth is that with new bandwidth if we run link budget in some cases it may shows loss of availability of the link.
If this problem occurs then we should not prefer bandwidth upgradation.
This problem occurs because, with bandwidth increase we have to also increase power.
If power is already in maximum, then this may give a low receive level at the receiver end.
Advantageofbandwidth upgradation is that no additional cost involved and less time consuming. If link budget in planning tool works perfect then we can immediately implement the same in the system.
Link re-route Engineering:
We take an example of the above figure as a part of our network.
In the above figure “A” to “F” are Base stations (BTS). Serving route of F is in the direction from Fiber pop up to BTS location “F”. The physical route of serving E1 is “Fibre PoP-A-B-F”.
Link “A-B”is congested and bandwidth upgradation can’t be done. This link is carried traffic of nodeB (3G)/enodeB(4G) “B” as well as nodeB(3G)/enodeB(4G) “F”.
Remaining all other links are not highly utilized.
So if we reroute path of “F” then congestion level may goes down in the link between “A-B”.
Here we can make a new route in the direction “Fibre PoP-C-D-B-F”.
This is a very simple case we are considering here for ease of understanding.
Main issue in such type of activity is that once we route “F” through new route “Fibre PoP-C-D-B-F” there may be chances that any link of this route may get congested.
So, for that, before making a new route we have to check each link of the new route whether they are able to handle new traffic of “F” or not.
If not then there is no meaning of doing of all these rerouting activities and plan for some other alternatives.
Link equipment up-gradation
Third option is link equipment up gradation.
We can replace the MW hop with XPIC (Cross Polarization) hop.
This will double the capacity of the link.
If the congested link is already a XPIC hop then we may plan for some new fibre PoP.
XPIC upgradation and Fibre PoP plan both have cost involvement.
So this is the last option we choose if all other possibilities failed.
Summary:
Once we have noticed any link utilization greater than 70% we plan for any of the three methods that we discussed above.
Transmission Link should have enough available bandwidth in 3G, 4G and 5G network to get desired data speed.
Thanks for reading this blog.
Your feedback, comments, suggestions or like are highly appreciated.
Pranabjyoti Hazarika
BE | MBA | PMP | IoT-Certified