VoIP: Packetized Voice Over Everything

Another IEEE effort, the 802.11r standard, defines a protocol that facilitates the use of IP telephone over Wi-Fienabled phones. It will speed handoffs between access points in a wireless LAN. However, CDMA manufacturers and providers like Qualcomm, Verizon, and Sprint haven't yet bought into this technology.

Don't forget WiMAX, either. These broadband wireless networks are expected to spring up in many locales beginning next year. With many local WiMAX cell sites installed throughout the area, a WiMAX cell phone can roam around the vicinity communicating with standard VoIP technology. Without a doubt, we can expect at least one cell phone to incorporate all three modes.

PRODUCTS FOR VoIP
VoIP's heart lies in its software. This includes the voice compression/decompression, jitter buffering, and echo cancellation usually handled by digital signal processing. Some systems have standalone DSP chips, while others have built-in DSP on a chip. Still others run on an ARM or MIPS core with DSP instructions. The SIP or H.323 and other protocols run in stacks on an embedded controller like the ARM, MIPS, or Power PC.

For instance, Broadcom's BCM1101 and BCM1103 form the core of many enterprise IP phones. The BCM1103 features dual 16-bit ADCs and DACs (codecs). Its DSP core handles the voice compression and decompression with G.711, G.729a/b, G.723.1, G.726, and Broadcom's own BroadVoice16. It also has broadband voice coders such as G.722, G.722.1, and Broad-Voice32. A MIPS32 core runs the show and can handle the SIP, H.323, MGCP, and Megaco/H.248 protocol stacks. The chip features two 10/100/1000 Ethernet MACs, two 10/100 Ethernet transceivers, and a three-port 10/100/ 1000 Ethernet switch. Two RGMII ports are available with external Gigabit Ethernet transceivers.

Centillium makes chips for the customer-premise-equipment (CPE) and infrastructure ends of the VoIP path. The Entropia III CT-GCW4672 is a system-on-a-chip (SoC) processor for implementing voice and media gateways, wireless-infrastructure gateways, class 4 and 5 switchers, digital loop carriers, voice-enabled IP routers, and IP PBX systems. With multiple embedded DSPs and packet processors, its primary function is to bridge standard telephone TDM and VoIP wireless and wireline converged voice calls.

It has an amazing 1008 G.711 (PCM) VoIP or voice-over-ATM (VoATM) carrier-class voice channels with 128-ms echo cancellation. It can handle any of the ITU voice-compression standards as well as voice codecs used in CDMA, WCDMA, GSM, and UMTS cell phones. Interfaces include 16 standard TDM circuit pairs to a standard switched network and MII and GMII Ethernet physical-layer (PHY) ports, POS-PHY II, and Utopia for ATM network connection. A host processor interface handles PCI or Freescale buses. A 504-channel version called the 4002 is available, too.

LSI Logic offers a chip for implementing voice-over-Wi-Fi products. Its 7- by 7-mm LSI403US facilitates adding VoIP to cell phones, PDAs, and other handheld devices (Fig. 2). This extremely lowpower, 16-bit, fixed-point DSP is based on LSI Logic's well-known ZSP400 DSP core. The maximum 150-MHz clock rate produces 600 MIPS or millions of multiply and accumulates (MMACs). Its two high-speed serial/TDM ports are compatible with T1/E1 framers and H.100/H.110 bit-stream I/O. In addition, the DSP possesses an asynchronous, 8-bit, parallel host processor interface (HPI). It's ideal for low-cost and portable products where low power is essential.

Mindspeed Technologies focuses on the infrastructure side of the system. Its variety of chips and software takes care of almost all infrastructure options. The M82710 Comcerto 700 Series Carrier Convergence Processor offers multiple DSPs and ARM processors.

With the processor, telecom equipment manufacturers can create a product that transmits highly secure, carrier-class quality voice across wireless and wireline networks with integrated voice encryption, authentication, and denial-of-service protection. It contains 404 G.711 PCM channels and 168 channels of G.729a/b voice. Besides the TDM lines, interfaces include Ethernet, UTOPIA L2, and POS L2 for both Ethernet and ATM connections. A PCI bus connects to an external host processor where the signaling protocols are implemented.

Mindspeed's M82820 includes the host processor on chip so vendors can customize it using Linux. Also incorporated are 32 VoIP ports, encryption, and a PCI bus for connection to an external 802.11a/b/g chip for wireless operation.

Texas Instruments offers chips for virtually any application. The TNETV1050 combines TI's popular TMS320C55 x DSP with a MIPS32 RISC processor and Telogy software to take on all voice processing and signaling. On top of that, it handles H.323, SIP, and MGCP and all of the voice coding protocols. The popular VxWorks real-time operating system is embedded. An IPsec engine that features DES, 3DES, and AES encryption provides security. Then there's the TNETV1600 gateway chip, which includes connections for wireless for a Wi-Fi transceiver for IP wireless LAN phones.

Not to be left out are the SLIC manufacturers. The SLIC is the set of circuits usually installed at the telephone company's central office to support standard POTS telephones. This includes the BORSCHT functions of battery feed, overvoltage protection, ringing, line supervision, codec, hybrid, and test. SLIC chips are required inside the home ATAs and gateways to plug in any standard POTS phone. Chips used in VoIP ATAs and gateways include Legerity's VE880 series and Silicon Labs' Si3216.

Version 2.0 of Trinity Convergence's VeriCall Edge software implements full VoIP on a standard processor (e.g., ARM, MIPS, Freescale). No separate DSP is needed. It runs under embedded Linux and permits voice and video over IP (see "Video Over IP" at www.elecdesign.com, Drill Deeper 11114). Manufacturers will be able to make voice and full-feature video phones. VeriCall 4.0 targets infrastructure platforms (Fig. 3).