applicat ion brief DSP-based Puma-4 Architecture Embedded Multimedia Terminal Adapter Applications

applicat ion brief 
DSP-based Puma-4 Architecture 
Embedded Multimedia Terminal 
Adapter Applications

applicat ion brief DSP-based Puma-4 Architecture Embedded Multimedia Terminal Adapter Applications

DSP-based Puma-4 Architecture for EMTA Applications As cable-based, voice-over-IP (VoIP) rollouts continue, it has become clear that deploying voice-over-cable (VoC) modem services are the next major revenue source for Multiple System Operators (MSOs). One of the keys to a profitable rollout of VoC is robustly integrating all of the functions a customer needs today ...onto an embedded multimedia terminal adapter (EMTA). An EMTA combines delivery of high-speed data with VoIP services by connecting legacy telephones and terminal equipment (like a fax machine) to a MSO’s advanced IP communications network. The minimum range of telephony services include basic phone functions such as call waiting, three- way calling, voice mail, and fax support. In addition, MSOs must provide enhanced functionality to differentiate their products. Since the EMTA is the MSO’s revenue gateway, any limitations of the device could limit profit. Therefore, an EMTA that provides only marginal voice quality or has difficulty interoperating with other telephony devices will not have long-term market viability. Understanding the Basics of an EMTA Today’s standard EMTA provides 2+2 voice service (two lines of telephone service with call waiting/conferencing capabilities on each line) with 32ms line echo cancellation. How- ever, the phone network carries more than just voice traffic, such as fax and data modem traffic, and EMTAs must support these “legacy” services as well. All this effort merely achieves parity with incumbent voice service providers. The challenge for designers is providing enhanced features beyond the minimum functional requirements in order to differentiate their products while managing cost. It is important to remember that in addition to potential cost savings, EMTAs need to provide more than the minimum set of telephony services to provide differentiation over the PSTN service offerings. An improved user experience will provide additional motivation for customers to switch off the PSTN and switch on VoIP. 1a Voice Compression (e.g., GSM AMR, SMV) Media Gateway Cell Phone BTS Voice Compression (Cable codecs) Media Gateway EMTA Telephone PSTN 1b Voice Compression (e.g., GSM AMR, SMV) Telephone Voice Compression (e.g., GSM AMR, SMV) Tandem Free Option – Voice Compression (e.g., GSM AMR, SMV) is end-to-end Figure 1: Tandem Free Operation. A cellular-to-EMTA call undergoes a minimum of two transitions (a) when voice encoded at the EMTA using a cable voice codec is converted to a cellular codec like GSM. By employing tandem free operation (b) where a Puma-4 based EMTA uses the native codec of the device it is conTnected with, the EMTA avoids multiple compression and decompression stages, andem end-to-end Free Option is SMV) – Voice AMR, Compression and maintains maximum call quality. GSM g. (e. Voice and the Puma-4 based EMTA In the telephony world, each time a voice packet is translated from one codec format to a second format (a process called trans- coding), voice quality is degraded. A call between a cell phone and EMTA undergoes at minimum two transitions (see Figure 1a) when packets are converted from/to GSM and to/from G.729. Compression is lousy, and the more transitions there are— especially Read the full applicat ion brief DSP-based Puma-4 Architecture Embedded Multimedia Terminal Adapter Applications.

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