In most cases, the enabling technologies for IP-based services are available today. What hasn't emerged yet, and what needs to catch up with the enabling technologies, are the management and control mechanisms that are essential to operating an efficient IP network of subscribers.
The bedrock of any management process is information. Without knowing what's going on, decisions can't be made and actions can't be taken. The task of gathering and reporting information on an operating IP network is complicated by the architecture inherent in the network. Unlike circuit-switched networks where intelligence resides in nicely defined categories of central office switches, a significant amount of the intelligence in an IP network is located at the far reaches of the network in customer premise equipment (CPE). Residential gateways, smart home phone systems, DSL and cable modems, set-top-boxes, wireless routers and access points, and other new types of CPE systems are emerging to serve the needs of residential and small or home business subscribers who want to tap into new IP-based services. For service providers keen on offering a compelling user experience, the situation demands gathering information at every level in the network, starting at the extreme edge in CPE systems and continuing through every intermediate level.
Because its digital signal processing (DSP) and other technologies have been integrated throughout IP networks, TI is uniquely positioned to play a key role in providing the kind of operational information service providers need to manage quality IP networks. TI's response to this need is the PIQUA™ real-time, multi-threaded system of quality management elements for IP networks. As such, PIQUA technology spans multiple layers of technology, devices and applications, knitting together a quality of service (QoS) management fabric. This management fabric addresses all of the discovery, configuration, monitoring and repair tasks in the diverse and widely dispersed elements of IP networks.
 Operational Imperatives
Retaining new subscribers will be a critical factor that will determine how quickly IP networks grow. Certainly new subscribers are attracted to the advanced services and compelling value proposition of IP services, but any subscriber who has experienced the public switched telephone network (PSTN) has a preconceived set of expectations. Accustomed as they are to the five-nine reliability of the PSTN, subscribers can become disenchanted quickly with new service offerings that fall short of expectations. A high level of churn in the subscriber base would not bode well for accelerated growth and expansion of IP services.
The first wave of VoIP service offerings has provided some valuable insight into the effects a quality management and control system can have on maintaining a compelling subscriber experience and, thereby, reducing churn. All too often, VoIP service providers lack the visibility into their networks that is needed to rapidly identify and solve possible service impairments before they are detected by subscribers. Instead, subscribers will experience unsatisfactory service and report their displeasure to the operator. Since the subscriber is reporting difficulties he is experiencing with at his instrument, the service provider's support personnel often resort to simply replacing a CPE instrument or gateway system as the most logical solution to the problem.
Unfortunately, this sort of fix is just a shot in the dark. Without the ability to isolate impairments, replacing CPE systems may or may not ensure subscriber satisfaction. Moreover, the whole process can be devastating to the service provider's cost structure. Not only is there the possibility that the subscriber's problem has not been solved, but the operator has incurred significant labor and capital costs by sending a technician to the site to replace equipment that may, in fact, be functioning properly.
PIQUA technology is able to gather performance and operational information from the silicon and software that's embedded in an IP networks at every level, including the many VoIP phones and residential gateways that currently have TI silicon and software already embedded in them. This gives operators the visibility they need to determine where faults could arise before they reach the point of affecting the subscriber's experience with the service. And when an impairment does reach a critical level, the source of the problem can be pinpointed so it can be quickly alleviated.
Isolating Impairments
Service impairments on IP networks come from a number of factors, but the most common are usually traced back to conditions involving echo in VoIP applications, dropped packets, line delays and jitter. With PIQUA technology, operators can establish acceptable operating parameters, monitor in real-time the performance of the network and diagnose the cause of impairments. Corrective actions can then be taken before the impairment sours a subscriber's experience.
Echo, since it is the most prominently cited cause of subscriber dissatisfaction with VoIP service, provides an interesting example of how line impairments can emanate from any number of sources. Echo can become particularly bothersome in networks that interface the legacy PSTN with packet-based IP networks. Echo cancellers have been deployed extensively throughout the PSTN to control the echo that is produced whenever a four-wire channel is interfaced to a two-wire connection. This most often occurs at the junction of interoffice trunks with local loops. At these so-called hybrid interfaces, signal energy is quickly reflected backward onto the four-wire network, causing echo.
Echo cancellers in the PSTN network are designed to reduce these relatively fast signal reflections. Unfortunately, packet-based IP networks have longer delays than the PSTN, leading to signal reflections that exceed the echo tail length limits of the PSTN's echo cancellers. VoIP CPE systems like media gateways or VoIP phone systems must be equipped with embedded echo cancellers that detect and cancel the echo, introduced by the additional delay of the packet network.
Dropped packets, line delays and jitter on VoIP networks can trigger subscriber complaints similar to those that are caused by echo. A subscriber may say that his voice line is noisy or that he can hear clicks on the line. The source of these conditions could come from jitter, line delay or dropped packets.
PIQUA technology is able to sort through all of the possible causes of line impairments, including echo, dropped packets, delays, jitter and others. In real-time, PIQUA technology then determines the root cause or causes of the problems wherever they are located. One of the critical capabilities of PIQUA technology is its ability to compile pertinent data from all levels in an IP network and report back to a centralized point where the information is aggregated and analyzed. Without comprehensive information on the workings of the entire network, any attempt to determine the source of an impairments would never be complete.
Beyond Voice
Aside from voice service, consumers have pre-conceived notions derived from the PSTN concerning fax and modem operations, as well as voice-mail, conference calling and virtual-attendant systems. All of these types of services rely on touch-tones or Dual Tone Multi-Frequency (DTMF) signaling. Huge amounts of legacy equipment in addition to cellular phones rely on DTMF signaling and this will not change for many years to come.
All layers of IP equipment, including VoIP phones, residential gateways, media gateways and others, must detect DTMF tones and recreate them digitally, encapsulating the signals in multiple digital communications packets. Today's high-quality VoIP phones and other equipment can exceed the ITU Q.24 tone detection standards, but problems relating to DTMF signaling are still quite common. Some impairments may stem from poor user equipment such as cordless handsets that simply do not transmit tones properly, while other sources of difficulties may be traced back to the digital encoding techniques that have been implemented or to the fact that DTMF tones can arrive at the receiver in different packets. Differing global standards for generating tones can also exacerbate the problem.
Fortunately for service providers, there are certain metrics that can be embedded in IP-based equipment, including user instruments and home gateways, that can be collected and analyzed by PIQUA technology to avoid impairments or to troubleshoot problems when they come up. Until such time as the entire network becomes IP-based, which may require several decades, operators will have to develop methods for coping with heterogeneous network equipment.
Quality of IP
IP networks certainly hold great promise for service providers. On the revenue-generating side, the advanced and media-rich services they are capable of carrying are sure to be a powerful attraction for new subscribers for many years to come. And on the operational side, IP networks have the potential for operational efficiencies that can form the basis for a number of successful business models. But potential is one thing and bottom line success is sometimes quite another. At this point in the deployment of IP networks it is apparent that tools for quality management, like PIQUA technology, are needed to ensure that this great potential comes to full fruition for service providers.
About
the Author
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Debbie Greenstreet oversees worldwide Voice over Packet strategic marketing for TI's DSP Systems (DSPS) organization and works closely with Service Providers to ensure TI develops solutions tailored to the wide variety of IP applications and services being planned and deployed globally. Prior to this role, she served as a product management director for TI's Voice over Packet group, where she was responsible for product definition and direction of all customer premises equipment (CPE) voice products including Voice over Cable, Voice over DSL and small-to-medium enterprise gateway solutions.
Greenstreet has more than 20 years of experience in the networking and telecommunications field, in hardware and software design, as well as program and product management at companies such as Hyundai Network Systems and Raytheon. Greenstreet received a bachelor's degree in electrical engineering from the University of Virginia and performed graduate work in computer engineering at George Mason University.
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About Texas
Instruments
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Texas
Instruments Incorporated provides innovative DSP and analog
technologies to meet our customers' real world signal processing
requirements. In addition to Semiconductor, the company's businesses
include Sensors & Controls, and Educational & Productivity
Solutions. TI is headquartered in Dallas, Texas, and has manufacturing,
design or sales operations in more than 25 countries.
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