WAYNE, N.J. Skyworks will start licensing its selectable mode vocoder (SMV) technology to developers of CDMA handsets and infrastructure equipment, a move that the company said will allow designers to increase voice capacity and quality in their networks.
While the wireless industry focuses on the evolution to a data centric world, carriers are also equally concerned with improving the quality and capacity of voice calls on their network. To help out, the 3GPP2 committee and Telecommunications Industry Association (TIA), have adopted SMV as an evolution path from the current enhanced variable rate codec (EVRC) used in today's CDMA designs.,
SMV is a multi-mode codec that allows designers to choose the optimal voice quality or capacity for their network. For example, in mode 0, the SMV codec delivers higher quality voice at the same capacity levels provided by EVRC, said Gary McDermott, director of business development for SMV at Skyworks. In situations where more capacity is needed, carriers can opt for mode 2 of the SMV spec, which McDermott said provides similar call quality to EVRC vocoder but enables support for more voice channels.
Overall, the 3GPP2 and TIA specifications define five modes for the SMV codec: mode 0, mode 1, mode 2, mode 3, and HRMax (see Figure 1 below). Depending on the speech pattern, successive bits of speech can be digitized at one of four different baseband bit rates: 9.6, 4.8, 2.4, and 1.2 kbit/s. The codec is also designed so that carriers can move between modes. "Operators can change modes on the fly," McDermott said.
The move to SMV, however, could be a costly one. To support SMV, McDermott said that operators and equipment vendors will have to change out transcoder cards in their base station controllers (BSCs). Changes will also have to happen in the baseband portion of CDMA mobile phone designs, McDermott added.
Licensing could also be challenging for system and chipset designers that are looking to keep costs to a minimum. McDermott said that the quality improvements provided by SMV are outweighing the concerns over licensing. "SMV offers a clear advantage," McDermott said. "There is definitely interest with chipset companies."
Qualcomm CDMA Technologies is one major chipset company that is throwing support behind SMV. According to McDermott, Qualcomm has added support for the SMV vocoder in its MSM6100 series of baseband processors.
Even though chipset vendor interest is there and a licensing model is in place, McDermott said it was difficult to determine when SMV would be deployed in live CDMA networks. Depending on the carrier, he said that SMV could be in the field by the end of 2005.
Editor's Note: For a detailed look at the SMV vocoder and a comparison of its performance against EVRC, click here..
Figure 1: SMV operating modes and average bit rate (ABR) for conversational voice.