Modular Software Key to Communications Systems

By Justin Mills and Peter Carlston

Hardware comprises only a small part of the overall cost of developing communications equipment such as Radio Network Controllers (RNC). Software development, testing, qualification, support, and maintenance can comprise over 90 percent of the total cost of an RNC during the life of the product. For service providers to remain competitive, software development and support costs must be reduced, and standards-based modular software is the key.

The software costs of communications systems costs are influenced by many things beyond the salaries and productivity of the engineers. One important factor relates to the cost and feature set of the operating system, together with the maturity of development and optimization tools. Without a comprehensive operating system and mature tools, software development becomes both more difficult and more error-prone. Both add considerably to development and maintenance costs. Widespread deployment also means that royalty payments for the software can be significant, as well.

Another major cost factor has to do with the architecture of the software itself. Modular software architectures are somewhat more difficult to design and implement, but are less expensive to test, enhance, and support over the long run. Hardware that changes underneath monolithic software, for example, often requires corresponding changes in low-level drivers, then platform management drivers, then element management middleware, and so on, right up to the management GUI itself. Modular designs, on the other hand, permit adding new functionality to a layer with the only changes to adjacent layers being the new code needed to feed or consume that functionality.

Standards and Modularity Are the Keys

Adding standards-based interfaces between software layers is the final key to enhanced flexibility and reduced costs. Without standard interfaces, manufacturers are locked into having to develop every part of the software themselves - even those areas that have little strategic value. Standards-based interfaces, on the other hand, allow specialized independent software vendors to quickly and cheaply supply modules that equipment manufacturers see as “necessary evils” rather than strategic.

Modular software with standard interfaces solves a number of issues for carriers as well. For one thing, standard interfaces, especially between platform management functionality, allow them freedom to quickly integrate and deploy new services into their managed networks as marketplace conditions change. Recognizing these benefits, a number of industry groups are working to address the need for standards-based modular software. As a foundation for standards-based software, the PCI Industrial Computer Manufacturer’s Group (PICMG) has developed the Advanced Telecommunications Computer Architecture (ATCA), a standardized hardware platform for communications systems networks.


Figure 1 - Standard interfaces between software layers simplify software integration as well as making the software modular for ease of development.

Figure 1 shows how standards-based modular software architecture can be applied to an RNC using an ATCA platform. Starting from the bottom, notice that Intelligent Platform Management Interface (IPMI) elements are designed into the ATCA hardware itself. IPMI is a set of industry initiative specifications governing message and system interfaces to platform management hardware as well as inter- and intra-chassis management busses. The details of these manageability elements are abstracted from upper layers by the IPMI standard interface, so that ATCA 3.0 shelf management modules can discover and manage all the hardware resources in the chassis or rack. Operating System (OS) platform drivers also use IPMI to access hardware and firmware management functionality.

The Service Availability Forum (SAF) Hardware Platform Interface (HPI) is the next standard interface. It hides the details of platform management from the management middleware and network stacks - and vice versa. Above that, the SAF’s Application Interface Specification (AIS) provides the standard interface between the management middleware, the network stacks, the Operations, Administration, and Management (OA&M) software, and the high-level RNC application itself.

One additional standard interface remains-that between the User Plane stacks (also termed “Data Plane” stacks) and the signaling plane stacks. The Network Processor Forum (NPF) has defined a standard interface between user and signaling planes for IP switches, and is now defining a standard interface for wireless communications equipment such as RNCs. NPF APIs and the SAF AIS will allow modular signaling plane stack implementations to be integrated with a minimum of work.

This could prove very beneficial for manufacturers. Signaling is a very specialized and complex area, with constantly evolving specifications. But carriers evaluate equipment manufacturers primarily on the strength of their user plane and reliability, not on their signaling stacks. So a standard interface between user and signaling planes will help make it possible to outsource this area in order to concentrate their resources on other areas.

Linux OS a Vital Component

Linux is becoming an important, modular component of next-generation RNCs. The Open Source* Development Laboratory (OSDL) is developing “carrier-grade” enhancements to Linux that meet the requirements of both carriers and equipment manufacturers. Support for POSIX standards, for example, has enabled manufacturers to more easily port proprietary UNIX code to Linux. Soft real-time support (with response times around 10 milliseconds or less) is proving to be a good fit for signaling and control plane applications. Linux distributors such as MontaVista (Sunnyvale, CA), Red Hat (Raleigh, NC), and SuSE (San Francisco, CA) either bundle carrier-grade features into their standard distributions or release special carrier-grade editions of Linux, based on the OSDL enhancements.

An operating system must also have solid development tool support to be cost-effective. Fortunately, a rich set of Intel and third-party Linux development and optimization tools exists for Intel applications processors. Some key tools available from Intel and others include C++ compilers for Linux that are optimized for Intel® processors and performance analyzers that allow developers to capture the application flow and the time spent in each function so they can focus their optimization efforts.

Such tools, coupled with standard interfaces, help ensure the efficient development of software with top performance. Further, the modular nature that results ensures that maintenance and upgrades can be performed reliably and efficiently. With so much of a communication system’s total cost tied up in software, the standards are a key to producing competitive systems.

References:

Peter Carlston is the wireless platform architect and a staff technical marketing engineer in Intel’s Embedded Intel Architecture Division. He is the technical lead on the Intel proof-of-concept RNC project, which has used Intel and third-party “building block” hardware and software products to create a working RNC.

Justin Mills is a business development manager in Intel’s Embedded Intel Architecture Division. Justin holds a bachelors degree in Electrical/Computer engineering from the University of Washington and a Masters in Business Administration from the W.P. Carey Executive MBA program at Arizona State University (expected 2005).

This article is an excerpt of a whitepaper titled: Intel® Architecture Processors for 3G Control: Design Considerations for an ATCA Radio Network Controller “Control Plane” Design, which can be read in full at www.intel.com/design/intarch/PAPERS/300991.htm