Spectrum scarcity hampers mobile network experience in Sri Lanka

In our new analysis, Opensignal has observed that our smartphone users in Sri Lanka connected to 4G networks using a limited amount of mobile spectrum — ranging from 3 MHz to 20 MHz. This, linked to the scarcity of spectrum assigned to mobile operators in Sri Lanka, impacted the average 4G download speeds our users experienced. Also, we found out that some operators like Dialog or Airtel have been refarming the 2100 MHz band used for 3G to dedicate more spectrum assets to 4G connectivity.

We looked at the average 4G download speeds, broken down per bandwidth and band used. Our Sri Lankan users experienced the fastest 4G download speeds on Airtel, Dialog and Mobitel’s networks when using a bandwidth of 20 MHz on the 1800 MHz and 2600 MHz bands — as we observed a statistical tie between them.

Average 4G download speeds grew almost in a linear manner for Dialog and Mobitel in the 1800 MHz band, when operators used different bandwidths within the same speed. The average 4G download speed — 18 Mbps — on the 1800 MHz band using 20 MHz was 46.3% faster than what our Dialog users saw on the same band, but with only 15 MHz bandwidth used — 12.3 Mbps. Also, it was nearly three times faster than what they experienced with just 5 MHz — 6.1 Mbps.

We saw a similar thing on Mobitel’s network — our users on this network enjoyed their fastest average 4G download speeds — 18.6 Mbps — when connected to the 1800 MHz band, with the support of 20 MHz of bandwidth. This was 48.8% faster than in the case of 15 MHz (12.5 Mbps) and almost 2.5 faster than when only 5 MHz bandwidth was used (7.5 Mbps). 

On the other hand, our Hutch users did not experience average 4G download speeds above the 10 Mbps mark on any combination of band and bandwidth used. Aside from using 20 MHz bandwidth in the 2600 MHz band, Airtel used only 5 MHz blocks in the 850 MHz and 2100 MHz bands, which also resulted in average 4G download speeds below 10 Mbps.

Overall, our users on Dialog saw the fastest average download speeds of 11 Mbps, ahead of Mobiltel's score of 8.7 Mbps, Airtel’s score of 7.3 Mbps and Hutch’s score of 4.9 Mbps.

The lower overall 4G download speeds achieved by Airtel and Hutch could be explained by the relatively small amount of bandwidth dedicated to 4G connectivity. In the case of Hutch, almost half of the readings showed the use of 5 MHz only as well, in the 900 MHz band. Deploying 4G networks in the lower, sub-1 GHz bands may provide better coverage, but this comes at the cost of limited capacity. Noteworthy, Hutch was the only operator on which network we didn’t observe bandwidths higher than 15 MHz, with 86.2% of all readings seeing either 5 or 10 MHz bandwidths. This resulted in Hutch’s overall 4G speeds lagging behind its competitors, with a score of 4.9 Mbps.

In 72.1% of measurements, we observed the bandwidth of 5 MHz used by our Airtel users, both on the 850 MHz and 2100 MHz bands. By contrast, our users saw the bandwidth of 20 MHz in the 2600 MHz band used in nearly 28% of our measurements — the most out of all operators in Sri Lanka, which drove the overall 4G download speeds to a score of 7.3 Mbps.

Meanwhile, our users saw bigger bandwidths used on higher frequency bands on Mobitel and Dialog’s network. 15 MHz of spectrum bandwidth or higher supported more than 55% of 4G connections on Mobitel’s network. As for Dialog, 81.4% of measurements showed the use of 15-20 MHz. While Dialog acquired 40 MHz in the 2600 Mhz band (3GPP 41) earlier this year, the use of this band accounted for only 4.3% of all our readings for Dialog for which we had spectrum bandwidth information. The overwhelming majority of readings came from using the 1800 MHz band, just like in the case of Mobitel.

None of our users in Sri Lanka connected to bandwidths higher than 20 MHz. This means very limited use of Carrier Aggregation — we observed our users experience Carrier Aggregation, but never exceeding the bandwidth of 20 MHz in total. We saw the benefits of Carrier Aggregation and substantial bandwidths of 4G spectrum used to support 5G connectivity in Germany, Italy, the UK or South Korea. These are examples of countries where operators hold significantly more spectrum than in Sri Lanka, so it is feasible for them to support mobile connectivity with higher bandwidth. However, the case of India shows that the additional spectrum assigned to mobile operators like Airtel or Jio has boosted capacity on their existing networks and our users saw improvements in their mobile network experience.

To deal with spectrum scarcity and dedicate more assets to 4G connectivity, some Sri Lankan mobile operators have repurposed some of their existing spectrum assets that were previously used for 3G services. We looked at the use of spectrum blocks in the 2100 MHz between April and September 2021, as seen by our users. Our data shows that Airtel and Dialog re-farmed 5 MHz of their 2100 MHz holding from 3G to 4G services. We observed Airtel phase out one of its 5 MHz blocks entirely after July 2021 — around the time when the mobile operator launched its 4G network. At the same time, we saw no clear 4G re-farming trends for Hutch or Mobitel on their 2100 MHz blocks.

More mobile spectrum is crucial for improving mobile network quality in Sri Lanka

Mobile operators in Sri Lanka struggle with spectrum scarcity — and this affects the overall mobile network experience of users. The 700 MHz band (3GPP 28) has not been assigned to mobile use yet and mobile operators have also faced legal issues around the non-utilization of the mobile spectrum and signal interference from neighboring countries. The low amount of available mobile spectrum becomes an even greater challenge as the demand for mobile data soars, especially in the times of the COVID-19 pandemic. As our Quantifying the Impact of 5G and COVID-19 on Mobile Data Consumption report shows, average mobile data consumption in Sri Lanka increased by almost 2.5 times over the course of two years — from 3.9 GB per month in Q1 2019 to 9.7 GB in Q1 2021

However, spectrum availability may improve next year, as the Telecommunications Regulatory Commission of Sri Lanka (TRCSL) is intending to hold a spectrum auction, which will include 5G-capable spectrum — although the regulator is yet to share any further details. TRCSL expects 5G roll-outs to happen in the country in 2022 and 2023. But for that to happen, mobile operators need more spectrum allocated to mobile services as they won’t be able to build a strong 4G and 5G experience and meet the growing appetite for mobile internet from Sri Lankan users unless they can increase the capacity of their networks.