So, it should be tried to avoid PCI modulo3 conflicts wherever possible. Such an interference will reduce the overall RS SINR and demodulation capability resulting in throughput degradation. Introducing PDCCH optimization also helps in such cases as it can add to the PDSCH capacity relieving congestion to an extent.Īs described in my PCI planning article, if the adjacent cells with overlapping coverages have same PCI modulo 3, then there is a probability of RS interference between them. If TA is pretty high and CQI is below 8 (value depends on the frequency layer) then it might be a better idea to physically optimize the area or cell. In case, the traffic is not high but utilization is still high, it is a good idea to see the TA and CQI for the cell. This is usually caused due to low signal quality as the users with bad SINR will take a lot RBs at a lower modulation. Sometimes, the actual traffic volume is not that high but the utilization of the cell is still very high. This can be done using Load Balancing features or by tuning the cell reselection or mobility parameters. So, if the load increases above a threshold, it is better to add another carrier or if another carrier already exists, then it will be better to offload the congested carrier and shift the load to the uncongested carrier. For neighbouring cell, such a power is considered interference. As the load increases, the power per Resource Element increases which will result in higher aggregate power in the area increasing the RSSI. Higher the load, higher the interference to the neighbouring cells. Second factor is the load in the area or cluster. This is a big topic so I am just touching it here and will cover this in more details in the future articles. So, that improves the credibility of PDSCH and can result in better throughput results. This happens because previously with 0,-3 configuration, the RS were taking the extra available power but now with the 0,0 configuration, the extra power is used by the other channels instead of RS. Moreover, the PDCCH/PDSCH symbols in which Reference Signals are present will have a slightly higher power for 2 and 4 antenna port systems. However, in case of small inter-site distance, Pb and Pa values of 0 might provide a more optimized solution as in this case, the RS power will not be boosted compared to the PDSCH symbols. If the inter-site distance is large then this configuration can be helpful as a 3dB Reference Signal boost will improve coverage as LTE coverage is controlled with RSRP and RSRP is the direct outcome of RS power. When the inter-site distance is low, then high reference signal power can result in higher interference. If the Pa is -3 and Pb is 1, then that means that the Reference Signals will be having 3 dB higher power than the PDSCH symbols. There are two parameters in LTE Pa and Pb which define the power of the Reference Signals against the other symbols e.g. Pa & Pb: Another thing that can be done in case of smaller inter-site distance is to use a more balanced RS power (Reference Signal).So, it is a good idea to keep this in mind in the design or expansion phase. If the network uses the same RET port for LTE and other RATs (3G or 2G) then any change on LTE tilt will impact the other RAT and it takes away the flexibility. That provides flexibility for optimization. Electrical Tilt Ports: It is better to use antennas which assign a different RET port (electrical tilt) to LTE.So, there is not much to do at this level other than downtilts to improve SINR and reduce overshooting. The distance is something that is usually fixed as LTE sites mostly use the previously deployed network. If sites are too close to each other, they will have a higher tendency to interfere with each other and will require aggressive down-tilts to limit overshooting. Let’s check some of the factors that impact SINR So, the first thing to verify is the average SINR of the network. If the SINR of a network is bad, then that puts a limit on the throughput gain that it can achieve. The most basic and common factor that controls the spectral efficiency and throughput is the SINR (Signal to Noise and Interference Ratio).