The main system bottleneck in high-speed communications equipment is data transmission from chip to chip and over backplanes. Stratix™ GX devices help designers address this bottleneck by supporting 3.125-Gbps channels and integrating advanced functionality into the device's logic array. The devices are ideal for a variety of applications, including bridging applications, switch fabrics, traffic management functions, wireless, and high-definition television (HDTV) broadcast applications. The use of SerialLite with Stratix GX devices provides a low-risk path for serial I/O applications. Figure 1 shows Stratix GX devices in a generic communications system.
As shown in Figure 2, devices that have different standard interfaces may not be able to communicate with each other. Protocols A and B could be backplane or chip-to-chip protocols.
To allow the two devices to communicate, the designer must create a bridging solution. Flexibility is a key feature when designing bridging subsystems because:
- Protocols may be proprietary, not standardized, or may not be chosen yet.
- Protocols may not be final. For example, cutting-edge systems often use protocols that are under development and not yet formalized.
- The designer may need to implement additional logic between the bridged interfaces.
Designers who want multi-gigabit data rates but still need the ability to adapt to changes and differentiate their product, need a flexible device that supports fast data rates.
The flexibility of programmable logic devices (PLDs) allows customization and eliminates the risk normally associated with ASICs. The versatile Stratix GX gigabit transceiver block and source-synchronous channels support a variety of industry-standard and proprietary interfaces. This support, combined with the high-performance logic array, makes Stratix GX devices an ideal solution for bridging applications. Stratix GX devices allow designers to make changes to go beyond a protocol or logic array specification at any time during the system design phase without a significant impact in product delivery.
As shown in Figure 3, Stratix GX devices allow high-speed communication between various devices. For example, Stratix GX devices can bridge SPI-4.2 to XAUI, SPI-4.2 to a SONET/SDH scrambled backplane, or Network Packet Switching Interface (NPSI) to a custom backplane.
For more information on using Stratix GX devices in bridging applications, go to the Stratix GX Bridging Applications page.
A switch fabric is a connection element that redirects data from one line card port to another line card port in a system. The devices that perform the switch fabric function are often located on a separate card (often known as a switch fabric card) and typically connect to the line cards via high-speed channels.
When designing switch fabric sub-systems, designers require an integrated solution that supports a large number of transceiver channels to which they can add innovative functions. Stratix GX devices, with up to twenty 3.125 Gbps channels, an enhanced logic array, and TriMatrix™ memory, are a prime solution for these requirements. With these features, designers can use Stratix GX devices to create a flexible switch fabric solution with significant time-to-market advantages.
For more information on using Stratix GX devices in switch fabric subsystems, go to the Stratix GX Switch Fabric Applications web page.
Traffic Management Functions
Before data flows over the backplane to the switch fabric, the traffic is prioritized and controlled to support service level agreements. Service level agreements define how traffic should be shaped based on the properties of the packets. Designers can implement various scheduling algorithms for shaping traffic flows. One common method is weighted fair queuing (WFQ), which is shown in Figure 4. The WFQ algorithm operates based on the service level agreement set for each traffic flow. In Figure 4, the types of traffic flows are divided by priority and the very high priority queue receives heavy weighting and thus, the most bandwidth.
The WFQ algorithm requires many computations as the complexity of the service level agreement increases and as more intelligence is added to the algorithm. A WFQ system requires a high-bandwidth data path, and the algorithm requires a customizable, fast processing unit.
Historically, designers have used programmable logic to implement custom data path functions. Together, the high-performance Stratix GX logic array and the Altera® Nios® embedded processor can effectively implement WFQ systems.
Other functions that occur before the application sends data over the backplane include queue management, packet buffering, statistical metering, and control functions. Stratix GX devices, with a powerful logic array and TriMatrix memory, are a valuable solution for these functions.
To support new requirements, mobile communication systems must evolve to third-generation (3G) standards. 3G will provide a higher data rate of up to 2 Mbps, while making more efficient use of bandwidth. Diversity techniques, which have been incorporated in most of the 3G standard's specifications, are one of the key methods used at the edge of a network for increasing bandwidth. To lower the cost of the transceiver, and make 3G a more readily accepted technology at an earlier date, Digital IF and digital predistortion linearizer (DPL) techniques are utilized
For more information on using Stratix GX devices in base stations, go to the Stratix GX Base-station Transceiver Card page.
The core network of a 3G wireless system uses equipment similar to typical wired network routers. Wireless core network equipment—such as the gateway GPRS support node (GGSN), serving GPRS support node (SGSN), and packet data serving node (PDSN)—has some of the same processing functions found in the routers used in wired networks. These functions include address lookup, classification, QoS, traffic management, and switch fabrics. Other critical functions used in wireless network equipment include voice transcoding and echo cancellation. In addition to providing critical backplane, switch fabric, and traffic management capabilities, Stratix GX devices have DSP blocks that the designer can use to implement voice transcoding and echo cancellation functions.
HDTV Broadcast Applications
A typical, professional HDTV system requires real-time switching between multiple high-definition camera feeds and the subsequent recording and/or broadcasting of the event. To accomplish this, HDTV broadcast equipment must support uncompressed, high-definition serial digital data rates of up to 1.485 Gbps. Stratix GX devices are suitable for applications using the SMPTE 292M HDTV standard. Additionally, designers can use the Stratix GX DSP blocks for various video-processing algorithms.
For more information on using Stratix GX devices in HDTV broadcast systems, go to the Stratix GX HDTV Video Production Applications page
Current drivers in the storage market include: different storage and networking technologies, advances in storage and infrastructure bandwidth, and information growth. However, converging the two main types of storage networking-storage area network (SAN) and network-attached storage (NAS)-is a challenging task for storage infrastructure vendors. Additionally, users want a virtualized storage repository where they can view and manage all storage assets regardless of technology implementation (NAS or SAN), physical location, and various vendor brands.
These demands push designers of storage switches to create more flexible and highly integrated systems. Stratix GX devices provide up to 20 transceiver channels, enabling designers to use a flexible and integrated solution on the line side and on the backplane with traffic management.
For more information on using Stratix GX devices in storage switches, visit the Stratix GX Storage Applications page.