Potential challenges of sharing 5 MHz Spectrum between nearby 3G and 4G Sites

RAN
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1

Hello All.

What potential issues could arise if two nearby sites operate with one using 3G and the other using 4G, while sharing the same 5MHz spectrum?

Will interference occur, and what is the safe distance for using both technologies simultaneously?

Potential challenges of sharing 5 MHz Spectrum between nearby 3G and 4G Sites
Potential challenges of sharing 5 MHz Spectrum between nearby 3G and 4G Sites1792×1024 265 KB

2

  1. Interference

    • Co-Channel Interference: Both 3G and 4G use similar transmission techniques, and overlapping signals can cause interference. This may degrade signal quality, result in dropped calls, and lead to data transmission errors.
    • Adjacent Channel Interference: Even when channels are not directly overlapping, adjacent channels can interfere with one another, particularly in areas with high signal strength.

  2. Reduced Network Capacity

    • Spectrum Efficiency: While 4G is more spectrum-efficient than 3G, sharing the same spectrum reduces overall network capacity, especially during peak usage periods.
    • Congestion: Increased interference leads to network congestion, causing slower data speeds, higher latency, and longer call setup times.
3

Thanks.

If all LTE sites/sectors operate on the same frequency and are differentiated by PCI/PSC, why would interference occur between 3G and 4G sites using the same ARFCN?

In my case, we have two sites accidentally configured with the same ARFCN, but there have been no noticeable performance issues in the reports, such as data volume, average throughput, or RTWP in 3G. Why might this be?

4

In our case, although 4G and 3G share the same frequency band (2100 MHz), we use different ARFCNs for 4G and 3G to mitigate the risk of interference.

5

Yes, that should be the plan.

However, my doubt is: would interference be observed if a 3G and 4G site are operating in close proximity, say around 1 km apart?

If interference occurs, what would be the reason behind it?

6

This is because the implementation of 4G advanced features there play the big role working smoothly under interference environment. Check if you have implemented them in the first case scenario. They are:

  1. Robust Modulation:
    • These techniques allow for reliable data transmission even in the presence of interference.
  2. Adaptive Modulation and Coding (AMC):
    • This enables the network to adjust modulation and coding rates based on channel conditions, further mitigating interference effects.
  3. Inter-Cell Interference Coordination (ICIC):
    • This technique allows base stations to coordinate their transmissions to reduce interference between cells.
  4. Beamforming:
    • Directing the signal towards the intended user can help to reduce interference to other users.
  5. OFDM Robustness to Interference:
    • OFDM is inherently resistant to interference due to its ability to divide the signal into multiple subcarriers.
  6. Adaptive Resource Allocation:
    • By allocating resources (subcarriers) dynamically, OFDM can efficiently utilize the spectrum and mitigate interference.