With the growth in mobile data traffic, there is increasing interest in fourth-generation (4G) cellular technologies, especially the Long Term Evolution (LTE) of the 3rd Generation Partnership Project (3GPP) – the successor to GSM/EDGE and UMTS/HSxPA technologies. LTE has gained a decided momentum advantage over WiMax and is expected to be the most important 4G technology. BDTI recently spoke with mimoOn, a company headquartered in Duisburg, Germany that licenses LTE software for both terminals and base stations. mimoOn was founded in 2006 by Thomas Kaiser, a researcher from University of Duisburg-Essen. mimoOn currently employs about 50 people, including wireless experts with backgrounds at companies such as BenQ, TTPCom, and Nokia. mimoOn’s focus is on developing software implementations of the physical layer (PHY) of LTE modems for DSP processors.
4G cellular standards (such as LTE) are much more complex than their 3G predecessors, due to the increasing algorithmic complexity required to squeeze more bandwidth out of the cellular spectrum, and to the challenges associated with providing seamless roaming with older 2.5G and 3G networks. This complexity has driven most 4G baseband chip vendors (both for handsets and base stations) to adopt highly programmable architectures incorporating a number of DSP processor cores along with relatively few hard-wired coprocessors. This is often referred to as a “software-defined radio” or “SDR” approach. The DSP cores typically utilize classical DSP architecture techniques including some combination of very long instruction word (VLIW) architectures, single instruction multiple data (SIMD) instructions, vector processing, and specialized instructions designed to improve efficiency on wireless algorithms. Licensable processor core vendors including CEVA, Tensilica, and Silicon Hive have developed DSP cores for these applications. Several cellular chipset manufacturers, such as ST Ericsson and Icera, have revealed details of their in-house architectures which make it clear that they are using an SDR approach.
mimoOn has developed a software implementation of the LTE PHY and has been updating it with each new release of the standard. This software PHY has been implemented using a cross-platform strategy that separates the driver components (which must be modified for each processor), from the core algorithms (which are not processor-specific). For processors that have a strong C compiler, mimoOn claims that it can port the reference code for evaluation purposes using a mostly automated process. To create a production version, mimoOn estimates that 10-40% of the code must be optimized for the target processor. Typical optimizations include customizing the software based on the number of cores, the memory architecture, and custom instructions that the compiler may not utilize without assistance.
mimoOn believes that implementing the LTE PHY (layer 1) requires more expertise than implementing the protocol stack (layers 2 and 3), since the protocol stack’s implementation is well specified by the standard. Therefore, mimoOn has focused on developing PHY software for all classes of devices – including handsets, femto and pico-cell base stations, and macro cell base stations. mimoOn has integrated its PHY solution with a protocol stack from another company, and can deliver the combined package to customers. mimoOn claims that it is the only independent supplier for LTE PHY software for terminals and base stations. mimoOn has publicly disclosed the availability of its PHY software for CEVA and Tensilica DSP cores, and for Texas Instrument DSPs. In addition to licensing its software, in many cases mimoOn provides porting and optimization services.
The growth in mobile data promises big opportunities for 4G cellular equipment and chip manufacturers. But these companies also face significant challenges, including stringent time-to-market and cost constraints. As a result, we expect to see strong interest in licensable software solutions for 4G equipment. Clearly, mimoOn agrees, and hopes to build its business on the 4G wave.