CEVA DSP does LTE in software - Embedded.com

CEVA DSP does LTE in software

San Jose, CA – Core licensor CEVA today unveiled the CEVA-XC, a vectorized DSP for 3.5G/4G terminals, picocells, and femtocells. The CEVA-XC is capable of handing a complete LTE class 5 or WiMAX II transceiver in software. In addition, the CEVA-XC can simultaneously handle 3G, 3.5G, Wi-Fi, GPS and MobileTV air interfaces.

The CEVA-XC is based on the CEVA-X DSP, which is currently deployed in HSDPA and WiMAX chips. The CEVA-XC builds on the CEVA-X by adding up to four vector units, giving it performance of up to 200 billion operations per second—enough to handle aggressive multi-antenna schemes such as MIMO 4×4. The fully-configured CEVA-XC is also powerful enough to handle multiple LTE or WiMAX channels in base station applications.


Figure 1. The CEVA-XC features vector units have specialized features for wireless operations such as MIMO detection and channel estimation.

The CEVA-XC is also available in less-powerful configurations with either one or two vector units. The vector units themselves are configurable through optional instruction sets for floating-point, CORDIC, maximum likelihood detection, and transmit path acceleration. Even in its minimal configuration, the CEVA-XC is impressively powerful. For example, a CEVA-XC with only one vector unit and no optional instructions can handle a 100 MHz LTE downlink stream in 157 MHz. (This example assumes a challenging combination of 20 MHz bandwidth, QAM64 modulation, and MIMO 2×2.)


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Figure 2. The CEVA-XC is able to handle an LTE transceiver in software. Shown here is an LTE receive channel. Only the forward error correction (FEC) is implemented in hardware.

The flexibility of the CEVA-XC earns it high marks from analysts. “They're heading in a very promising direction,” said Jeff Bier, president of technology analysis firm BDTI. “They're really thinking about scalability.” Bier also pointed out that the core is fully C-programmable. “There is a history of compilers for vector machines going back to Cray computers,” he noted, which means that the CEVA-XC should be a good compiler target.

Of course, performance and flexibility are meaningless unless they can fit into a handset's power budget. CEVA says it has this angle covered. According to the company, a 65 nm CEVA-XC can handle a 50 Mbps LTE downlink in just 10 mW. CEVA expects most customers to use 45 nm or smaller processes, so their power numbers should be even lower. To help keep power down, the CEVA-XC includes a PowerWise-compatible power management unit. This unit shuts down inactive parts of the core, and it allows the core to operate over a range of frequencies and voltages. These low-power features make it practical for the CEVA-XC to run a full transceiver in software.

The move to a software solution represents a new direction not only for CEVA but also for the wireless industry as a whole. “As the industry moves closer to mass deployment of 4G technologies such as WiMAX and LTE, software-defined processors are emerging as the basis for the next generation of wireless chipsets,” said Will Strauss, founder and president, Forward Concepts. The motivation for software-defined radio (SDR) is obvious: phones have too many processors. A high-end handset might contain multiple cellular baseband CPUs, processors for Bluetooth, GPS, and mobile TV, a WiFi chip, and more. Add 4G on top of all this and things get really overcrowded. A better solution is to consolidate these many functions onto a single processor—exactly what the CEVA proposes.


Figure 3. SDR can greatly reduce power and area in a system that contains many radios.

SDR has other benefits. Instead of building separate LTE and WiMAX chips, for example, you could build a single chip that can be programmed for either standard. That same processor could handle any of the global mobile TV standards through a simple change of software—or you could cerate a low-cost version without mobile TV by simply leaving out that software.

CEVA is not the first company to identify the benefits of SDR, nor is it the first to offer an SDR solution for handsets. For example, Sandbridge Technologies already offers an SDR chip for 4G handsets. However, CEVA has a unique relationship with tier-one vendors that its competitors cannot match. Unlike startup Sandbridge, CEVA already has extensive design wins at tier-one vendors, and has been working with these vendors for many years. In fact, CEVA claims that it designed the CEVA-XC in collaboration with its tier-one customers. Thus, vendors are likely to be more open to CEVA's technology than to similar offering form small startups. This is particularly true for existing CEVA customers. “If you are going to be in LTE you have to backtrack and do 3G as well,” said Forward Concept's Strauss. “If you already have all the 3G software written for a CEVA-X, this makes life easy.”

CEVA also competes with industry heavyweights like Qualcomm and TI. CEVA also has a unique advantage here: Unlike Qualcomm and TI, CEVA does not make chips. Instead, CEVA licenses its cores to a number of manufacturers, including Infineon and Ericsson Mobile Platforms. Thus, handset manufacturers who choose a CEVA-based solution are not locked in to a single hardware provider as they would be with Qualcomm or TI. Given the large number of functions that could be consolidated onto the CEVA-XC platform, this is a major consideration. “You don't want to be a slave to Qualcomm,” said Forward Concept's Strauss.

The CEVA-XC is available for licensing to select customers. To learn more, see www.ceva-dsp.com/4G.

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