South African networks see the worst 4G signal strength but fastest 4G download speeds at night

Opensignal analyzed how energy usage changes on South African networks throughout the day. We observe that South African operators use less spectrum and carrier bands at night, while the 4G signal strength is also the weakest at night. For the purpose of the analysis, we focus on 4G metrics, as only MTN and Vodacom have launched commercial mobile 5G services in South Africa.

We looked at the average amount of mobile spectrum that our users see when connecting to 4G services across four national operators in South Africa over the period of 180 days between November 1, 2022 and April 29, 2023. We observe much lower bandwidths used at night, between midnight and 6 am, than at other times of the day. At night, our users on Cell C, MTN, and Vodacom’s networks see 18.7%, 14.9%, and 13% less spectrum bandwidth connected to their devices than in the mornings, between 6 a.m. and 12 p.m. Meanwhile, our Telkom users see no statistically significant difference in the amount of bandwidth used for 4G connectivity throughout the whole day.

Operators often set networks to offer users less mobile spectrum at night, as there are lower levels of network traffic and so not as much spectrum is needed to offer a good experience. By switching off spectrum bands, operators can save network energy costs. However, our users on MTN and Vodacom’s networks observe the fastest average 4G speeds between midnight and 6 a.m. MTN and Vodacom’s speeds gradually slow over the day, dropping to the lowest levels in the evenings, between 6 p.m. and midnight. Cell C and Telkom users also experience the lowest average 4G download speeds in the evenings — noteworthily, our Cell C users observe no statistically significant differences in average 4G download speeds between night, morning and afternoon.

To further explore the impact of energy management on the quality of mobile network experience, Opensignal looked at the average values of 4G Reference Signal Received Power (4G RSRP) — which reflects 4G signal strength — and 4G Reference Signal Received Quality (4G RSRQ), which is the measure of the 4G signal quality and is affected by network congestion.

Our users observe the worst signal strength across all South African operators, at night ranging from -100.3 dBm for Telkom to -104 dBm for Cell C. Evenings are the time of the day with the second lowest 4G RSRP scores for all South African operators and our users observe the strongest signal in the mornings and afternoons. 

However, if operators dedicate less spectrum and users see lower signal strength at night to save energy consumption, then why do we see the highest 4G download speeds at night for three of them — MTN, Telkom, and Vodacom — and lower speeds over the day? Looking at 4G RSRQ can give us some answers, as the metric includes the ratio of the carrier power to the interference power, so it is possible to indirectly determine the degree of congestion on the radio network.

All South African operators have the best values of 4G RSRQ at night, indicating the lowest level of radio network congestion. During the day, 4G signal quality deteriorates which indicates increased interference potentially caused by higher data traffic. 

Mobile operators commonly use Carrier Aggregation to increase spectrum bandwidth and boost network capacity. This technology allows a smartphone to connect to multiple spectrum frequency bands (carriers) at once, but more carriers enabled means more power consumed. To manage the cost efficiency of Carrier Aggregation, operators in South Africa tend to use fewer carriers at night — with more than 50% of readings on Cell C and Telkom seeing just one carrier used at night. The percentage of readings using two or fewer carriers generally drops over the day compared to the night, in favor of South African operators using three or more carriers during busier hours.

Opensignal looked at time with no signal across nine provinces of South Africa, throughout the day. The time of day, when users spend the most time with no signal, varies slightly across provinces. Smartphone users in the Eastern Cape and Northern Cape provinces spend the most time with no signal in the mornings, while those in KwaZulu-Natal — in the afternoon. The afternoon is the time when our users in Limpopo struggle the least with connecting to mobile services. However, some provinces like Gauteng or Western Cape don’t observe substantial differences in time with no signal throughout the day. These provinces also have the lowest time with no signal throughout the day, while Limpopo and Northern Cape see significantly more time with no signal.

Mobile operators struggle with load shedding in South Africa

Load shedding has been a major issue in South Africa, as frequent rolling blackouts scheduled by the government for different times in various areas affect everyday life in the country — and can partly explain differences in time in no signal between different regions at different times of the day. Mobile operators use backup batteries to keep their sites operating in the case of planned blackouts. But while they invest in costly power backup options to retain the resilience of their networks, mobile sites are frequently plagued with battery thefts, which forces the operators to install additional elaborate safeguarding measures. 

Operators like MTN or Vodacom have pledged to invest in improving their network resilience and countering the effects of load shedding, e.g. with the deployment of additional emergency generators or bringing in additional engineers from abroad. MTN estimated that load shedding cost its South African operations around R695 million ($35.7 million) in 2022, which was around 3.4% of its EBIDTA. Additional financing that South African operators have to commit to counter load shedding hampers their ability to invest in other areas of their operations, e.g. more accelerated deployments of 5G infrastructure in the country.