Why uncapped wireless Internet always breaks

The MyBroadband South African ISP rankings for July 2020 recently showed that Rain has replaced Telkom as the lowest-ranked Internet service provider (ISP) in the country.

Subscribers using Rain’s uncapped LTE and 5G services continue to complain about unreliable network performance, saying that at certain times of day they struggle to use the Internet at all.

Uncapped wireless broadband services in South Africa have repeatedly run into this challenge.

When the service first launches and the network is empty, subscribers are extremely pleased with their purchase.

However, as more subscribers buy the service and climb onto the network, performance degrades. In the worst cases, the network becomes unusably slow.

The same thing happened to Telkom uncapped LTE in 2016, and before that to Sentech MyWireless in 2009.

Sentech MyWireless

Sentech launched its MyWireless broadband service in 2004, offering an uncapped alternative to the prescribed 3GB cap Telkom had on DSL.

MyWireless enjoyed a strong uptake, but poor service levels dogged the broadband provider.

This resulted in consumer backlash that damaged the reputation of the company and product, something which Sentech never recovered from.

Sentech MyWireless was discontinued on 30 November 2009.

Telkom uncapped LTE

Telkom offered its uncapped LTE service to customers who connected via a specific base station. After several trials, the company expanded the offer nationally in December 2015.

In September 2016, Telkom started throttling the connections of subscribers who consumed more than 185GB in a month to 4Mbps. When you exceeded 250GB of usage, connections were throttled to 256kbps.

Following a backlash on social media, Telkom revised its throttling policy and said that it would throttle subscribers in stages based on their monthly usage.

Bandwidth on wireless vs fibre

The reason uncapped wireless services will inevitably suffer from performance problems is simple: spectrum is limited, while demand for data constantly grows.

Spectrum is the raw capacity available to a network. In wireless networks, this is measured on megahertz (MHz) while on fibre networks it is measured in nanometers (nm).

It is possible to convert between MHz and nanometers using equations such as “frequency = speed of light ÷ wavelength”. Frequency is measured in hertz, the speed of light in meters per second, and the wavelength in meters.

The amount of raw capacity available in a strand of fibre cable is at least 100,000 times greater than in any one of South Africa’s wireless networks.

To illustrate this, we compared the amount of spectrum currently assigned to network operators ins South Africa and compared it to the amount of raw bandwidth available in commonly-used wavelengths of light in fibre.

The bands of light used in our calculations were taken from the website of the Fibre Optic Association (FOA).

The O-band runs from wavelengths of 1,260nm to 1,360nm, which translates to around 17.5 terahertz (17,500,000 MHz) of raw capacity.

Similarly, the dense wavelength division multiplexing bands (C-band and L-band) together have 11.4THz of bandwidth.

It should be noted that this is a conservative estimate of the amount of bandwidth available in fibre, as it only looks at certain bands of light.

The FOA states that a single-mode fibre has roughly 100THz of bandwidth in total.

The following table shows how the amount of raw network capacity on South Africa’s wireless networks compare to that of the fibre O-band.

Network Total capacity
Vodacom 81MHz
MTN 86MHz
Cell C 76MHz
Telkom 162MHz
Liquid Telecom 90MHz
Rain 191MHz
Fibre (O-band) 17,500,000MHz

Now read: These numbers show why Vodacom and MTN desperately need more spectrum

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Why uncapped wireless Internet always breaks