An industry leader in integrated digital baseband solutions and at the forefront of the cellular/mobile WiMAX convergence, Comsys Mobile turned to Mentor’s Nucleus RTOS for a system that would enable the high performance, flexibility, and small footprint of its ComMAX™ CM1125 — the only single-chip, multimode mobile WiMAX/GSM-EDGE baseband processor on the market today.
“Nucleus came to us by way of one of our protocol stack partners — and we found it to be fast and flawless within that protocol.”
Ehud Reshef, Director of WiMAX Product Marketing, Comsys Mobile
When Comsys Mobile was established in 1998, the computing and telecommunications industries were moving in separate directions, growing and evolving as the markets and technology dictated. Back then, laptop computing was leading the PC/Internet space while cell phones were slowly growing in popularity and functionality.
As a company providing baseband IP solutions for integrated device manufacturers (IDMs) and original equipment manufacturers (OEMs), it wasn’t long before Comsys Mobile provided a variety of field-proven solutions for the 2G and 3G telecommunications industry, and by 2005, millions of handsets were enabled by Comsys Mobile’s cellular IP products.
Today, an entirely new set of challenges face the wireless industry. Foremost is the onset of 4G and new radio technology standards that provide optimal “anytime, anywhere” connectivity, a type of connectivity which requires much higher data rates for both current and emerging mobile broadband services. While 3G mobile network operators are already providing services using HSDPA and HSUPA technologies, it’s clear that current 3G networks do not have the required bandwidth. And only with emerging 4G technologies, first with mobile WiMAX, and later with Long Term Evolution (LTE), will these mobile services be able to achieve wide acceptance.
Early False Start For WiMAX
A few companies from the fixed broadband arena saw early opportunities in mobile WiMAX. But rather than offering a true multimode solution, these companies simply added a mobile WiMAX modem to an existing cellular handset. This ‘Velcro’ approach resulted in the substantial increase in Bill of Materials (BoM), board space, and power consumption – all critical factors in handset development – which lead to a shaky start for WiMAX. Equally significant, this half-baked approach did not provide the “always connected” user experience expected of next-generation mobile handsets.
Comsys Mobile Develops Single- Chip Multimode Solution
Against this backdrop, Comsys Mobile decided to leverage its cellular expertise and develop a multimode mobile WiMAX/Cellular communications processor that would enable the highly coveted “always connected” user experience.
In 2006, the company started developing the ComMAX line of full mobile WiMAX baseband processors and platforms. The ComMAX product line was designed to support mobile WiMAX and cellular platforms by meeting service requirements from emerging 4G standards, while providing mobile device manufacturers with a comprehensive low-power solution.
To achieve this, Comsys Mobile would have to transition from being an industry leader in IP baseband solutions to also becoming an industry leader in silicon-baseband solutions.
Ehud Reshef, director of WiMAX product marketing, recalls these early challenges quite well, “The biggest issue for us was using a new platform and a new processor – just how much could we leverage from our existing technologies?” When it was time to select an operating system, Comsys Mobile first considered the Nucleus® Real Time Operating System (RTOS) because it was the embedded OS of choice for many of the middleware components the company had used in the past. “Prior to this project we knew of Nucleus, but we had not used it as our designated OS,” added Reshef.
Nucleus Meets The Challenge
The Comsys Mobile team was curious to see how Nucleus would perform as the primary operating system across the entire design. The team knew that Nucleus would work well for GSM/EDGE processing, but the real challenge would come from the mobile WiMAX side where processing was far more complex. The goal was to retain as much of the core competencies as possible from the already developed GSM side, while leveraging the strengths of Nucleus for mobile WiMAX. In doing so, Comsys Mobile would be able to significantly reduce development costs.
Once Nucleus was moved over to WiMAX, the team was pleased with the results. “When we ported Nucleus, we were thoroughly impressed with real-time performance, small footprint size, as well as achievable data throughput and packet rates. Nucleus easily matched the more stringent data needed for WiMAX,” recalled Vladimir Podbrezsky, infrastructure team manager at Comsys Mobile.
Perhaps the most important aspect to the success of Nucleus running on WiMAX was how well the OS addressed latency issues.
A few of the specific performance requirements included: less than 20uSec context switching, less than 10uSec interrupt latency, and the capability to support more than 1,000 context switches per second. Podbrezsky recalls when the team first received the results on Nucleus, “We needed something well below a millisecond. There was plenty of complex processing going on – and Nucleus delivered beautifully.”
Not only was Nucleus delivering the latency WiMAX required, but it was also running two very complex, asynchronous protocol software stack modules.
Other Design Considerations
The new ComMAX design incorporated two different processors: An ARM1156 acting as the system controller, running the mobile WiMAX MAC and the cellular protocol stack software; and a CEVA DSP to handle specific portions of the PHY processing. Both processors operate at about 200MHz with a total footprint of over 4.5M gates. In order to handle the processing capabilities of these two software stack modules and address the overall requirements of the ComMAX design, Nucleus had to deliver on a number of key fronts.
First, this type of design required hard real-time performance. As a deterministic, real-time operating system, Nucleus was well equipped to handle very fast operation.
A small footprint was also extremely important to the ComMAX design.“We were extremely pleased with Nucleus because it was lean, compact, and highly efficient to use,” added Podbrezsky. This realization is no surprise to many Nucleus users as the OS has one of the smallest footprints of any embedded OS on the market today – delivering a host of real-time capabilities with no discernible loss in performance.
Regarding performance, low latency rates were a primary concern for the team. Not only did Nucleus handle latency issues, but it also had the capability to support multiple, unrelated, complex protocol software (Mobile WiMAX in parallel with GSM/EDGE). It was imperative that the OS offer small overhead while delivering fast task switch times.
Another reason Comsys selected Nucleus was the availability of an extensive set of middleware components that could easily be added to the OS. The company found it helpful that Mentor support was available for numerous peripheral devices and protocols – and actually provided Comsys with a complete application middleware.
It was especially easy to port the Nucleus OS to the new ARM 1156 processor. This was due primarily to the high modularity of the Nucleus RTOS design and its architecture – where only a few OS components are CPU independent.
Finally, because of its licensing model, Nucleus offered a competitive total solution cost. Comsys Mobile found the licensing model highly attractive in keeping the per-device cost down. “We particularly liked the straight-forwardness of the cost structure,” said Reshef, “The Nucleus licensing model is perfectly suited for mass market devices such as ours.”
Added Support from Mentor
An interesting side note to this story is when development first began, Nucleus did not support the MCU core Comsys Mobile had planned to use – the ARM1156. In the early stages, the Comsys team ported Nucleus OS to the specific ARM core on their own with the assistance of Mentor support. So from the start, Mentor support was active in the development process.
In addition to providing a rather custom CPU port, Mentor ESD support also helped with internal porting efforts throughout the entire development of the ComMAX design. Mentor support created a reference hardware development board for the porting process and porting support.
(The completed reference board continues to assist Comsys Mobile today when the company approaches potential new customers.)
Looking Back – And To The Future
Because of the innovation behind the ComMAX multimode design, there were a few areas Comsys Mobile needed to address quickly with no margin for error. Successfully porting Nucleus allowed the company to leverage as much of the core functionality as possible. And because of the successful porting, Comsys was able to build the infrastructure quickly, which required no design revisions later. The short period of time it took the Comsys team to implement Nucleus allowed extra time for the team to concentrate on the uniqueness of the ComMAX design. The bottom line: The quickness of Nucleus – in porting over and in performance – helped the company keep its per-unit costs down.
Comsys Mobile has won numerous industry awards for its innovative 4G solution, while the ComMAX product line has already announced some early design wins. The company recently announced that is has supplied its first batch of ComMAX 1100 chips to Taiwanese handset manufacturer, dmedia, to enable early development of its G6 WiMAX-enabled Personal Navigation Device (PND).
The future looks promising for Comsys Mobile. The company continues to address the future needs of its customers by supporting multiple communication protocols as demand and the market require.
“We find the Nucleus RTOS to be an extremely stable OS. At the same time, it’s very flexible. It has great flexibility to build.”
Vladimir Podbrezsky, Infrastructure Team Manager, Comsys Mobile
About Comsys Mobile
Comsys Communication and Signal Processing Ltd is a fabless semiconductor vendor specializing in integrated digital baseband solutions for mobile devices.
The ComMAX™ product line of baseband processors provides manufacturers with comprehensive multimode solutions optimized to meet low power and small footprint requirements, with architecture spanning 2G to 4G standards such as GSM/EDGE, mobile WiMAX, and 3GPP-LTE.
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