Triple-play telecommunications services—data, voice, and video—will add to the complexity of testing next-generation wireless system architectures. To handle this latency-sensitive traffic, emerging protocols and new hardware are needed that provide quality of service (QoS) via traffic management. Triple-play requirements are influencing network technologies like Universal Mobile Telecommunication System (UMTS), WiMAX, and digital-subscriber-line (DSL) broadband networks. These influences are driving architectural changes as well as testing requirements for triple-play services. Today's original equipment manufacturers (OEMs) need flexible architectures, which can be enabled by field-programmable-gate-array (FPGA)-based network-processing and traffic-management functions.

To understand the role of QoS, traffic management, and FPGA implementations, take a look at a current UMTS wireless network. UMTS is a third-generation (3G) wireless system that delivers high-bandwidth data and voice services to mobile users. This system evolved from the Global Systems for Mobile Communications (GSM). UMTS has a new air interface, which is based on Wideband Code Division Multiple Access (WCDMA). In addition, it has an intellectual-property (IP) core network that is based on General Packet Radio Service (GPRS). The voice and data transport are performed by the transport-layer nodes. In contrast, the call-control layer nodes generally perform the call-control function (Fig. 1).

The transport-layer node can be built on an asynchronous-transfer-mode (ATM) switch, an IP packet switch, or an Internet-protocol router. The node consists of an optional interface to call-control layer nodes, a host processor, adjacent-node interfaces, and switch fabric. Together, the adjacent-node interfaces and switch fabric form the voice and data path. Two parts of a transport-layer node are implemented in programmable logic: the call-control layer interface and the voice/data path (Fig. 2). The call-control layer interface is the interface logic to call-control layer nodes, such as HSS, CSCF, and MGCF. The voice and data path uses the Internet protocol to transport packet voice and data within the UMTS wireless network. The main functions of a packet-voice and data-path implementation include the following (Fig. 3):

• Physical-layer processing: The physical-layer function processes SONET/SDH or T/E/J frame headers and extracts point-to-point-protocol (PPP) packets on the receiver side. On the transmitter side, it places PPP packets into the frame payload and adds the frame header.
• Higher-layer processing: The higher-layer function performs parsing, framing, packet classification, and modification. Encryption and compression processors are usually supported. In addition, special processors are often used to accelerate the process. The queuing and traffic-manager function places packets on different priority queues and drops packets according to the traffic condition.
• Switching: The switch fabric performs switching and routing functions for voice and data. It also contains a queue manager.
• Control and management: The control and management function performs path control and collects data for management purposes.

Traffic-management functions must be created and tested for emerging Internet triple-play protocols and QoS capabilities. These functions will play a key role in providing the efficient deployment of triple-play equipment and verifying its proper operation. With such a wide range of factors driving the testing requirements, not all market requirements can be met with fixed application-specific standard products (ASSPs) and application-specific integrated circuits (ASICs). IPTV equipment must measure the device-undertest (DUT) response in terms of latency, throughput, missing packets, transaction rate, and mean opinion score (MOS). Furthermore, equipment must be able to assign different QoS parameters (physical/logical ports, priorities, classes, distribution, etc.) in order to test a DUT's ability to correctly implement QoS policies on its traffic.

An FPGA-based traffic manager reference design can provide QoS capabilities for triple play (Fig. 4). Programmable traffic-manager solutions can support high-speed throughput in a solution that can adapt to the changing market. The solution can be demonstrated in a hardware environment using a traffic-manager board. By using FPGA technology to enforce QoS, communications-equipment OEMs can quickly deliver customized test services to specific markets.

Test equipment for triple-play services must create or emulate many different types of Layer 4-7 traffic (HTTP, FTP, e-mail, video streams, audio streams, and VoIP). Each traffic pattern needs to be tested under different QoS characteristics to effectively evaluate a DUT's ability to correctly handle these different types. Measuring the performance for triple-play services means emulating and evaluating protocols in a step-by-step approach:

1. Create several baseline traffic types and measure the performance of a DUT when the traffic is run in isolation.
2. Combine all traffic types and re-assess the performance in terms of throughput, latency, and data loss.
3. Adjust QoS parameters on certain traffic flows and implement QoS policies on the DUT. It is then possible to measure the DUT's ability to properly prioritize certain streams within a tripleplay environment.