WCDMA voice gets another look as HSPA+ takes off
Circuit-switched voice is starting to seem so passé, but it's going to be around for quite awhile. That's why companies such as InToTally and Qualcomm (NASDAQ:QCOM) are developing methods to make WCDMA voice more efficient so operators can wring out additional spectrum capacity to make room HSPA and HSPA+ data services.
Though they are taking different approaches, both companies are looking to limit the amount of power used by voice communications over WCDMA so there is more spectrum available for HSPA and HSPA+. "There is a huge amount of data coming and the voice is occupying most of the spectrum," said InToTally's CEO Alvaro Lopez-Medrano.
The mobile communications industry is migrating toward VoLTE and VoHSPA, "but it will take some time before those services have the quality and ubiquity of circuit-switched voice," said Rasmus Hellberg, Qualcomm's senior director of technical marketing.
Source: HSPA, EV-DP, TD-SCDMA and LTE subs
"4G is frequently promoted as the way to meet the huge demand for mobile capacity. But by 2016 only about 26 percent of subscribers will have moved to 4G networks and a hybrid solution with 3G will be essential to ensure adequate coverage for voice and data," said Sue Rudd, director of service provider analysis at Strategy Analytics.
While InToTally and Qualcomm agree on the need to improve WCDMA voice efficiency, they are tackling the issue from different angles. Further, while InToTally's proprietary approach is already available for licensing, Qualcomm is working to get its approach included in the planned Release 12 of specifications for 3GPP technologies.
Going after the outer loop
InToTally's solution is based upon solving outer loop power control issues found in CDMA and WCDMA. According to Lopez-Medrano, the OLPC sets the appropriate signal to interference ratio (SIR) target to maintain a given quality criterion, but traditional OLPS approaches based upon the Block Error Rate (BLER) are too slow to accommodate real-time power adaptation to different radio conditions, thus leading to voice communications inefficiencies.
For example, in a standard WCDMA voice call, the initial end-user device's power is set high at the beginning because the handset and base station are not yet aware of the radio conditions impacting the device. That high setting can causes unnecessary interference with other users, said Lopez-Medrano, and it takes a long time for the power loop to measure the call quality and instruct the device to power down. "We have developed a new technique that looks at a different metric that gathers and processes information much more quickly," Lopez-Medrano said.
InToTally's ToT-OLPC technology is aimed a providing faster convergence speed for the radio link between network antennas and mobile handsets, thus improving overall voice efficiency and capacity," said Lopez-Medrano. Field tests have shown a 20 percent capacity gain on average and 40 percent gain in highly saturated areas, said Lopez-Medrano, adding, "The room for improvement in the outer loop is huge."
Qualcomm, on the other hand is not tackling the outer loop to improve WCDMA voice efficiency but is going after the inner loop with a new approach it calls WCDMA+. Qualcomm's approach requires alteration of the standard for WCDMA, and the company has presented its approach to 3GPP for inclusion in Rel. 12.
Qualcomm's contention is that with a projected 2 billion HSPA/HSPA+ subscribers using WCDMA for voice services by 2015, HSPA/HSPA+ operators must plan to evolve their voice services to WCDMA+. "Employing WCDMA+ is a cost-effective strategy for boosting network efficiency as it enables HSPA/HSPA+ operators to make voice even more efficient thereby freeing-up resources for more data," said the company.
The concepts behind WCDMA+ are similar to what was done with CDMA 1X Advanced, which was created to make CDMA 1X voice calls four times more efficient. Qualcomm contends WCDMA+ will triple voice spectral efficiency, freeing up resources worth up to two-thirds of a 5 MHz carrier for HSPA+ data.
WCDMA+ entails two main components: an improved radio link and a new voice codec. "you need to update both the network and the device, so you get gains in both the uplink and the downlink," said Hellberg.
The improved radio link is achieved through reduced overhead, enabled through slower power control and removal of a dedicated downlink pilot. In addition, Qualcomm advocates using less energy to transmit a voice frame, which will lead to less interference and higher capacity.
When a WCDMA voice frame is sent, it is repeated 20 times and then decoded. Even if it is decoded at frame 16, the system continues to send all 20 frames. "So one of the tricks we are proposing is that when you have decoded the voice frame earlier, you can stop the transmission," in order in increase capacity and reduce interference with others," said Hellberg.
The codec that Qualcomm considers key to WCDMA+ is EVS WB2, which features a source controlled variable bit-rate mode.
Timing and availability
Qualcomm's WCDMA+ solution was unveiled just prior to CTIA's Wireless 2012 convention in May. "The objective is to make this very cost-effective for low-end, entry-level devices but also make it efficient for high-end devices. You really have to address the whole segmentation of devices in order to make this successful, said Hellberg.
Making the changes Qualcomm proposes for the WCDMA standard is an essential step toward enabling operators to open up more capacity for data services, said Hellberg. "This makes sense" because WCDMA voice "going to be around for a very long time, given the success of HSPA+," he added.
Days before CTIA Wireless 2012, InToTally announced that its TOT-OLPC software had won support from Vodafone Group. The operator signed on to have two of its infrastructure vendors upgrade WCDMA base stations in Italy, Spain and the United Kingdom with InToTally's software, and Vodafone intends to eventually roll out InToTally's technology in its markets worldwide. In addition, Vodafone Ventures, Vodafone's corporate venture capital arm, has made an equity investment in InToTally.
The base station upgrades will make efficiency improvements to the uplink only, however. Handset vendors will need to adopt IntoTally's software in order to improve downlink performance. Lopez-Medrano said InToTally's software will soon be included in handsets from one manufacturer that has partnered with Vodafone.
Lopez-Medrano sees room in the market for both InToTally and Qualcomm's approaches.
"Qualcomm needs to change the standard; we don't," he said. "But our solution is completely complementary to the Qualcomm solution. There is no incompatibility with the Qualcomm solution. The goal is the same but with different methods" being employed to achieve it.