With so many different possibilities and options available to the operators for deployments it is necessary that the planning is done in such a way as to keep the interference to minimum and throughput to maximum. Let’s look at two simple deployment situations.

 

For simplicity let’s assume that the operator has won 20MHz of contiguous spectrum. We have 5 UE’s. UE#1, UE2 and UE#5 are basic Rel-8 LTE UE’s and UE#3 and UE#4 are LTE-A UE’s with support for Carrier Aggregation (CA) and enhanced Inter-Cell Interference Coordination (eICIC)

 

4-14-pic1-edit.png

 

Operator 1 decides to split the 20MHz spectrum into 15MHz for macrocell and 5MHz for small cell. In this case:

 

UE#1 and UE#2 get 5MHz of spectrum

 

UE#3 gets 15MHz + 5MHz using CA. Total 20MHz

 

UE#4 and UE#5 get 15MHz of spectrum.

 

The advantage of this scenario is a simple Hierarchical Cell Structure (HCS) deployment. There is no need to worry about the interference.

 

4-14-pic2-edit.png

 

Operator 2 decides to deploy macrocell and small cells in Heterogeneous Network (HetNet) deployment (co-channel). They have used the complete 20MHz channel for both the Macrocells and Small cells. Due to the interference experienced by the UE’s on small cells, the Macrocell is using ABS (Almost Blank Subframes). The advantage of using ABS is that it can be dynamically configured. Let’s consider a peak and non-peak scenario from macrocell point of view. In the peak scenario macrocell is having 10% ABS and in non-peak it is having 50% ABS. Let’s look at the user impact

 

Non-Peak scenario (50% ABS)


UE#1 – 20MHz (Since it’s in the center of the cell, we will assume no interference from Macrocell)

 

UE#2 and UE#3 – 20MHz (High interference in 50% of the time)

 

UE#4 and UE#5 – 20MHz (ABS for 50%)

 

In this situation, the throughput for UE#4 and UE#5 would be half or equivalent of 10MHz scenario. The throughput for UE#2 and UE#3 would equivalent to somewhere in between 10MHz and 20MHz scenario.

 

Peak scenario (10% ABS)


UE#1 – 20MHz (Since it’s in the center of the cell, we will assume no interference from Macrocell)

 

UE#2 and UE#3 – 20MHz (High interference in 90% of the time)

 

UE#4 and UE#5 – 20MHz (ABS for 10%)

 

In this situation, the throughput for UE#4 and UE#5 would be or equivalent of 18MHz scenario. The throughput for UE#2 and UE#3 would equivalent to somewhere in between 2MHz and 20MHz scenario.

 

Even though it may be advantageous to have the deployment as proposed by Operator 2, interference may cause more problems in the long term.

 

I am interested in hearing what option do you think will work best and why.