Sentech's plans for its valuable spectrum

Sentech has an allotment of spectrum in a band which is considered prime radio frequency real-estate for wireless broadband technologies such as Long Term Evolution (LTE) and WiMAX.

LTE is widely considered to be the natural upgrade path for 3G technologies such as HSPA and HSPA+, although it is not backwards compatible with 3G.

Many industry players also consider LTE to be the evolution of technologies outside the 3G family such as WiMAX and CDMA, which is the technology used by Neotel for its consumer broadband and telephony offering.

Use it, or lose it

However, other than stating its plans to roll out a new national wireless broadband network (NWBN), Sentech hasn’t made use of its 50 MHz in the 2.6 GHz band it is licensed to use.

ICASA, the South African telecommunications regulator, has been criticised for not rescinding Sentech’s spectrum under its “use-it-ot-lose-it” policy to make it available for industry to roll-out evolved mobile broadband networks.

2.6 GHz spectrum assignments in South Africa

Never gonna give you up

Setumo Mohapi, CEO of Sentech, said that the state-owned signal distributor won’t be relinquishing any of its spectrum in the 2.6 GHz band.

Mohapi said that Sentech is committed to using all of it for the roll out of its NWBN.

Getting technical

However, Sentech’s bandwidth allocation in 2.6GHz occupies a spot required for the most popular configuration of LTE, known as Frequency Division Duplex (FDD). The 2.6GHz band is 190MHz wide, of which Sentech already occupies 50MHz and Wireless Business Solutions (WBS) has 15MHz.

General manager of Engineering and Technology at ICASA, Dumisa Ngwenya, explained in July 2010 that FDD systems need a space of 120 MHz between the upstream and downstream parts of the FDD frequency pair.

With this constraint in mind, the optimal configuration of the 2.6 GHz band for FDD technologies is what the International Telecommunications Union calls “Option 1.”

ITU-T 2.6 GHz band assignment options

Option 1 allocates 140 MHz of spectrum (70 MHz paired at the beginning and end of the band) to FDD and 50 MHz to Time Division Duplex (TDD) technologies.

In-band migration

This means that if Sentech does not agree to migrate their spectrum it would leave mobile network operators interested in offering FDD LTE services in the 2.6 GHz band without the ability to do so.

Mohapi affirmed that Sentech is open to migrating their 50MHz inside the 2.6GHz band and are considering options such as splitting their 50MHz up into FDD and TDD portions. This will allow for the band to be harmonised to the ITU’s “Option 1,” Mohapi said.

Potential assignments in 2.6GHz after in-band migration

According to Mohapi, in-band migration of its allotment is pending the finalisation of the “mandate issue” of providing emergency and police services with bandwidth for voice-based applications like TETRA (Terrestrial Trunked Radio).

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Sentech's plans for its valuable spectrum