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NSN teams up with MediaTek to improve VAMOS GSM spectral efficiency

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Nokia Siemens Networks is collaborating with MediaTek to help operators to reduce the spectral capacity required on GSM networks when refarming spectrum to LTE and WCDMA.

Specifically, the two companies are implementing Orthogonal Sub-Channel (OSC) support for Voice services over Adaptive Multi-user channels on One Slot (VAMOS) handsets.

OSC is a technical method of doubling voice channel capacity that NSN claims to have invented in 2011, and is already in commercial use by over 500 million users. 

Previously, OSC enabled four handsets carrying out two simultaneous calls on legacy Single Antenna Interference Cancellation (SAIC) handsets to be served at the same time within a radio time slot.

With MediaTek’s help, now 3GPP VAMOS handsets can be supported as well, enabling a five percent average capacity increase.

This is achieved by adopting a quaternary modulation scheme in the downlink and spatially orthogonal sub channels in the uplink (also known as a multi-user MIMO), tied to adaptive multi-rate (AMR).

NSN estimates that there are about one billion mobile handsets supporting AMR and SAIC on the market right now.

Since the radio techniques work for existing and new handsets, a simple software upgrade in the GSM radio networks can instantly offer numerous benefits to operators.

Besides capex and opex savings, the use of OSC also reduces cell site energy consumption by 20 to 50 percent and provides better coverage, which means not as much cell site hardware is required, reducing the number of cell sites for the same population area.

Another key benefit to increasing voice capacity on available spectrum is that capacity can then be freed up for data traffic.

This would enable an operator to be allocated to a downlink dual carrier without compromising voice quality of capacity in a four TRX per cell configuration, for example.

“Enhanced VAMOS chipsets have been available since December 2012, which was fully in line with Nokia Siemens Networks’ expectations,” said Jeffrey Ju, general manager of the Smartphone Business Unit at MediaTek. “VAMOS functionality has now become a baseline feature of MediaTek powered handsets.”

“Collaboration with MediaTek to implement OSC enhancements for VAMOS-capable devices puts us in a position to offer even better GSM spectral efficiency to our customers,” said Kimmo Virkki, head of GSM product management at Nokia Siemens Networks. “We will continue innovating in this area.”