By Tammy Parker

In demanding, high-density markets like Israel, Japan and Korea, vocoder technology faces the problem of maintaining high voice quality without sacrificing capacity. Could the 8K Enhanced Variable Rate Vocoder offer the solution? Tammy Parker

Advances in cdmaOne are coming thick and fast, with one in particular setting the pace: an enhancement in vocoder technology that promises improved capacity and better voice quality for networks worldwide. The eight kilobit Enhanced Variable Rate Vocoder (EVRC) is already making an impact in Korea, Japan and Israel; now the U. S. is ready to join in as handset manufacturers, network vendors and carriers collaborate on deployment logistics.

The earliest cdmaOne vocoder was the 8K Qualcomm Code-Excited Linear Predictive (QCELP) coder, first deployed in cellular networks. Some early users of those networks in the United States were less than thrilled with the voice quality afforded, however. Calls generally had good clarity, but they did not provide true renditions of a cellular caller's voice to the party on the other end of the call. While the 8K QCELP coder nonetheless scored some limited victories in the United States, it experienced phenomenal success across the Pacific in Korea. There, millions of subscribers showed that the technology was seemingly well suited to the intonations and other attributes of Asian languages.

Next step
The next step in the evolution of cdmaOne vocoder technology was 13K QCELP, which used a higher data rate to provide vastly improved voice quality, albeit at a cost to network capacity. U.S. PCS carriers deployed their networks using 13K technology, as did PCS carriers in Korea. Yet the sheer success of these networks prompted a quest for vocoders that would maintain 13K's high voice quality while providing at least double the capacity.

The solution is 8K EVRC. Fortunately for existing carriers, cdmaOne can support multiple vocoders within a single network, enabling a smooth transition as this new coder technology comes along.

"The bottom line is 13 kilobit still has exceptional voice quality, but EVRC buys back the carriers some more flexibility," notes Jeffrey Belk, vice president of marketing for Qualcomm's Subscriber Products Division.

Adds Neal Campbell, director of product management at Motorola's CDMA Products Division within the Network Solutions Sector: "In lab testing and MOS (mean opinion score) testing that we've performed here at Motorola, EVRC offered in all cases comparable voice quality (with 13K) and in some cases, depending on the deployment scenario, better voice quality."

Further, tests have shown that in many applications EVRC can offer improved voice quality over 13K, thanks to the fact that EVRC is designed for complete background noise suppression. "The background noise algorithms on the 8K EVRC vocoder do much, much better in MOS testing than the 13 kilobit," Campbell says. He adds that 8K EVRC also provides improved in-building penetration thanks to increased RF gains.

Such praise is begetting a new crop of EVRC-compatible handsets. Phillip Redman, project manager with Boston-based consultancy the Yankee Group, notes: "There still isn't a ton of major manufacturers offering it, but there's going to be a lot more."

Operator demand
Early cdmaOne market entrants like Qualcomm, Sony and Samsung will be among the first to provide EVRC-compatible handsets this year in the United States, he says, but smaller players will eventually jump on the bandwagon to satisfy operator demand. Redman notes many cdmaOne carriers are requesting EVRC compatibility because they envision needing more capacity in high-traffic areas. And as data applications place more strain on network capacity, all carriers will need to do whatever they can to squeeze in more calls.

The availability of EVRC-friendly handsets "will depend on the semiconductor guys," Redman adds. Qualcomm's Belk agrees, noting that there are two major ways a phone vendor can add 8K EVRC capability: "They can put the codec on a DSP (digital signal processor) or they can integrate it into a chipset."

Chip vendors have been actively marketing EVRC solutions for the past 18 months. For instance, in November 1997 Lucent Technologies announced that it had become the first integrated circuits manufacturer to ship an EVRC-equipped DSP to the Korean market. At that time, Samsung Electronics, Hyundai Electronics Industries, and LG Information & Communications began manufacturing EVRC-compatible phones using Lucent's DSP1627 chip and EVRC software. LGIC and Hyundai also used Lucent's EVRC chip in their CDMA wireless base stations.

Single-chip solution
More recently, in June 1998 Qualcomm's ASIC division announced production quantities of its MSM2310 Mobile Station Modem, billed as the first-ever integrated single-chip, tri-mode vocoder solution supporting EVRC.

Infrastructure vendors are taking varied but similar tacks for integrating 8K EVRC compatibility into existing networks, be they 8K or 13K. For instance, Lucent is offering a software upgrade to the existing speech coder platform. Similarly, Motorola requires a software change and an upgrade to the network vocoder cards at the base station controller to enable the network to serve all three (8K, 13K and 8K EVRC) handsets. The current hardware/software supports 13K and the original 8K vocoder.

EVRC has received early play in Korea, where 800 MHz cellular providers SK Telecom and Shinsegi initially adopted the early 8K QCELP vocoder because it was all that was available. The three 1.7 GHz PCS providers, KT Freetel, Hansol and LG Telecom, arrived later and were able to implement 13K vocoders. The tremendous difference in sound quality between those PCS and cellular networks emerged as part of a public debate over the past couple of years, with the PCS carriers successfully marketing their superior voice quality. That experience led Korea's cellular providers to examine EVRC.

"Cellular carriers such as SKT and Shinsegi have been pushing manufacturers, both of handsets and networks, very hard for EVRC since the introduction of PCS," says Youn Kwan Kim, executive director for LG Telecom.

SK Telecom, which counted more than five million subscribers at the end of 1998, acknowledges that it adopted 8K EVRC "in order to increase customer satisfaction." According to a statement from the company, SK claims to have completed nationwide deployment of EVRC in November 1997 and released EVRC handsets the following January.

It's worth noting that 8K EVRC also can be used to increase an 8K network's capacity if better voice quality is not the immediate goal. Campbell notes that one of the advantages of the variable rate codec is that it's possible to target different frame erasure rates (FER). He explains that using a lower average FER while matching regular 8K voice quality affords higher capacity through EVRC. "You have equal voice quality, but you actually have higher capacity with the EVRC 8K system," he says.

Korea's PCS operators are now looking at EVRC in order to improve capacity over their existing 13K systems. "Concerning the EVRC, we do not have a firm deployment plan yet," says Kim. "However, as we approach 2.5 million subscribers we see EVRC, along with 1x RTT, as a valuable alternative for increasing network capacity."

While U.S. cdmaOne-based PCS carriers are not yet experiencing widespread capacity constraints on their networks, they are eyeing EVRC as a way to prepare for future growth. Some of the operators, even though they do have quite a bit of spectrum, are finding that the infrastructure costs to add second, third and fourth carriers can be prohibitive.

"The option to employ EVRC is one of those cost-effective steps that an operator can take to increase capacity without necessarily needing additional hardware for the existing BTS (base station transceiver subsystem), which typically if you look at an operator's cost structure is a large percentage of their capital investment for their CDMA system," says Campbell.

Capacity gains
"We think EVRC is the way to go," says Jonathan Marshall, spokesman for cellular carrier AirTouch Communications. "It has better voice quality than 13K, which in turn was better than the old 8K." EVRC "obviously is more spectrum-efficient," he says, adding AirTouch's tests have shown capacity gains of 70 percent over 13K. However, he observes, "You only get 70 percent more capacity if everyone switches over."

In fact, EVRC's capacity gains may be even more impressive. According to Campbell, Motorola's lab testing and actual field testing of working EVRC systems has generally shown a doubling of system capacity over 13K networks.

Marshall adds that AirTouch wants to ensure "the network remains compatible with the older 13-kilobit phones, but eventually we'll economize on capacity by migrating people over to EVRC." He notes that the carrier has already begun carrying a Motorola Star-TAC model that is EVRC-compliant, adding: "Some of the phones that we're beginning to sell are compatible, but the network isn't ready yet. We're still testing."

Similarly, Sprint PCS intends to offer EVRC phones later this year, according to company spokesman Tom Murphy. "We have actually looked at some in our labs from various manufacturers," he says.

Working hard
Marshall says AirTouch expects to begin network deployment of EVRC in late 1999. "We are working hard with vendors and other carriers through the CDG (CDMA Development Group) to ensure that everyone standardizes on the right software and so on to make sure that roaming is easy and that we're all interoperable," he says.

Motorola's NSS has targeted one of those roaming challenges to which Marshall alludes. In early January 1999, the company announced its Service Option Negotiation (SON) solution to let customers on 8K EVRC networks take their digital features with them when they roam throughout Motorola NSS-based networks.

SON, an industry standard protocol, sets up the commands by which a base station communicates with handsets. According to Motorola, a lack of SON causes roamers' EVRC digital calls to be converted to analog systems or dropped entirely when the EVRC handsets cannot negotiate calling rules with a non-EVRC network.

Motorola's Campbell explains that "if you're in an 8K EVRC system and you're going to roam into a 13K system, the network has to do some type of rate negotiation in order to uprate the phone so it can interoperate on a 13K system."
Operators with cdmaOne equipment supplied by Motorola NSS, or by a combination of Motorola and other vendors, can implement the software upgrade at their centralized base station controller (CBSC) to provide their EVRC customers with seamless digital coverage throughout all of their markets.

"We are enthusiastic about our interoperability solutions, such as Service Option Negotiation, and hope other infrastructure vendors will take a similar approach," comments John Cipolla, vice president and general manager of Motorola NSS' CDMA Systems Division.

Vendors also are expected to help the migration to EVRC through software products that help operators optimize their networks to suit the capacity and coverage differences that come with EVRC. For instance, Motorola has introduced new algorithms in its software to accommodate legacy and EVRC networks. "When the mobile asks for EVRC, there would be different traffic channel gains and different parameters that would be looked at vs. a 13K user. So the mobile would be picking up specific parameters within the software in the infrastructure just for 8K EVRC and just for 13K," says Anil Barot, Motorola NSS product manager. "Thus, the operator does not have to go out and resize their footprint or do extensive optimization." The goal, he adds, is to make the migration to EVRC "painless."

While EVRC upgrades are big news for legacy networks, Israeli wireless operator Pele-Phone Communications and Japanese operator DDI have already set the stage for the future by launching their cdmaOne networks with EVRC rather than migrating to it. "If you look at both the Japan marketplace and the Israel marketplace, the subscriber density indicates that if they had deployed 13-kilobit vocoders in those markets, the operators wouldn't have been able to keep up with the capacity demands," Campbell observes.

Pele-Phone commercially launched its cdmaOne network in January 1999. At the time, Yigal Bar-Yossef, the operator's CEO, noted that Israel's cellular phone users "are quite demanding in today's world of wireless telecommunications due to their unusually heavy use of the technology."

Public transportation
Meanwhile, 8K EVRC-with its background-noise suppression capability-is proving especially well suited to Japan, where wireless customers frequently use their phones on trains and other modes of public transportation. DDI launched its cdmaOne network in July 1998, garnering some 400,000 subscribers by the end of the year. Its partner, Nippon Idou Tsushin (IDO), is slated to provide cdmaOne coverage to the Tokyo and Chubu regions beginning in April 1999.

Despite EVRC's proven successes, it may be a while before the technology becomes ubiquitous worldwide. For one, handset availability could be a gating factor to widespread EVRC deployment, although early signs indicate that enough phones will be ready when the networks are. In addition, companies such as U.S. operators that have mixed-vendor networks will need to ensure that all of their vendors are ready to provide compatible EVRC equipment.

In the meantime, some interim solutions are expected to hit the marketplace. In early 1999, Qualcomm's Global SmartRate solution is slated for commercial availability. This software feature offers multiple vocoding rates between 8K and 13K, allowing a network administrator to hike overall system capacity temporarily.

Global SmartRate is designed as a solution to boost capacity during high-traffic periods such as large public gatherings and conventions. Unlike EVRC, Global Smart Rate does not require any new infrastructure or handset equipment.

Nonetheless, it's clear that operator interest in capacity and voice quality issues is pulling EVRC into the global marketplace, making 8K EVRC well positioned to win kudos as a long-term vocoder solution.