A decade ago, wireless systems transformed in two ways. One transformation was technical, analog to digital, yielding higher quality and efficiency. The other transformation came from the marketing, pricing and acceptance of wireless technology into the mass market, yielding a boom in the growth of wireless users. Just like the transformation a decade ago, 3G or UMTS is on the threshold of transforming the wireless landscape. 

It is no secret that the telecommunications market in 2002 has been a difficult one. Driven by a collapse in confidence in the general market, the telecommunications market has lost many investors. However, the drivers for growth and profitability in the wireless market have not changed. Wireless usage continues to grow on a global scale, stressing the current infrastructure. 3G systems developed by many vendors allow for enhanced services and efficiency gains of up to 10 times when compared with legacy GSM technology, according to Dresdner Klienwort Wasserstien (DKW) Research. 3G deployments have begun in Europe and Asia, and MM02 has announced its tariff for service targeting business users with data and voice services. DKW Research estimates the 3G market to reach $40 billion by 2005 with two-thirds of that coming from Europe and Asia. 

Wireless users will see a dramatic change in the utility of their wireless services. Voice will always be the primary use and volume revenue generator for 3G. The addition of efficient data transmission enables 3G phones to offer Internet connectivity, embedded video and digital imaging, VPN connectivity for business and SME users, digital music and text messaging services (which has seen amazing growth and profitability). MM02 estimates that these types of services will generate 100% to 200% more revenue per subscriber than current GSM subscribers. This increase in profitability and utility will drive the deployment and acceptance of 3G that began in 2002. 

3G transmission systems are built around one of two fundamental technologies: IP and ATM. The debate over the capabilities and advantages of these two technologies has been ongoing in the enterprise and public/global telephone networks for the past 15 years. It has now entered debate in the wireless area as well. Internet protocol has become the primary data networking standard for business and commercial networks. Asynchronous transfer mode has become the primary data and voice networking standard within the global telephone networks. In fact, almost every Internet connection for business and residential customers uses ATM to transport IP. Many engineers and scientists are working diligently to converge these two standards into a single standard that will transport voice and data efficiently at low cost within the business networks and the global telephone network.

For the time being, ATM will dominate the telephone networks and will most likely be the standard for 3G transmissions. Unlike GSM networks, 3G networks have different types of traffic that are constantly vying for priority. ATM will be used to efficiently transmit the different types of data efficiently as it has been done in fixed wireline networks. Voice traffic in the 3G networks will be transmitted over ATM using AAL2; IP data traffic will be transmitted over ATM using AAL5; and video will be transmitted over ATM using AAL1. This enables the best known and reliable standard to offer the type of services like Internet connectivity, voice and video using a wireless phone.

The deployment of 3G networks using ATM coincides with the growing deployment of broadband DSL services worldwide. Billions of Euros have been spent on the infrastructure in Europe and globally to offer high-speed Internet access to both businesses and residential consumers. While the boom in broadband continues, and faster, more profitable services like 10 Mb/s SHDSL IMA services are deployed, telecommunications companies are searching for ways to use the investment in their broadband Infrastructure to transport legacy services like E-1 and new services like 3G wireless. 

The good news for telecom companies is that the broadband infrastructure uses the same ATM standard that will be employed in the 3G wireless networks. This allows the same infrastructure equipment to be utilized to connect the 3G wireless base stations to the telecommunications network. Figure 1 illustrates how a 3G wireless base station, commonly referred to as a node B, can be connected to a DSLAM that is currently used to terminate DSL services. Using the broadband infrastructure to transport the ATM traffic from 3G networks rather than using traditional E-1 circuit-switched technology saves more than 2000 Euros in upfront capitol expenditures and up to 1000 Euros per month in recurring operating cost. In addition to the cost savings quality, reliability and less complex provisioning and management can be achieved. Until recently, this type of solution was not possible because the 3G equipment and the broadband equipment had different interface types, one using SHDSL and the other E1.

Figure 1: 3G UMTS backhaul using SHDSL

Figure 1 depicts how a SHDSL NTU might be configured to backhaul broadband traffic from a 3G base station, or node B. The NTU provides a standard E-1 based ATM UNI (I.432.3) interface to the node B controller, with quality-of-service (QOS) facilities through the application of the various ATM traffic classes, such as CBR, VBR and UBR. The copper facility can be single or multiple pair. Multiple pairs can be used to provide virtual bandwidth multiples of 2.3 Mb/s (with E-1 or STM-1 interfaces to the node B equipment) and/or can be exploited to increase the effective reach of the transmission loop beyond 3 kilometers. For instance, with two copper pairs, it is possible to take 2 Mb/s (E-1) out to 5.5 kilometers without the need for repeaters. The latter point is of paramount importance, from the point of view of operational simplicity and lower ongoing expenses.

Lastly, the use of multiple loop pairs can be exploited for achieving increased reliability, by applying physical diversity via different binder groups or even different wire centers.

The central office termination can be a standard, multi-purpose DSLAM or an ATM switch using SHDSL line cards. The transport infrastructure consists of an ATM network that is used for general-purpose metro/regional transport. The ATM network acts as a virtual aggregation, concentration and grooming point for all the wireless traffic that is being funneled from the node Bs to the mobile switching center (MSC). In comparison to a corresponding TDM network, the nature of an ATM network provides greater resiliency, adherence to QOS policies and the ability to function under failure conditions. To illustrate the above, assume a situation where the connection to the MSC is degraded through a facility or equipment failure and the resulting throughput to the MSC is less than the total offered traffic from the collector node Bs. The ATM node that is interfacing to the MSC would respond by prioritizing the incoming node B traffic based on QOS requirements as specified by the customers' service level agreements (SLAs). If we complicate the scenario by assuming there is a similar degradation at a node B site, then the affected node B would send only high-priority traffic. Therefore, the ATM network utilizes whatever remaining capacity is available in order to filter and organize transmissions so that the most important data gets through first. This is a very powerful feature, especially for mission-critical business applications, which may carry SLA guarantees and corresponding financial penalties for the service provider. An ATM network also achieves operational benefits that come from end-to-end provisioning utilizing the full capabilities of PNNI signaling, and the natural advantages that come from consolidating more access and transport infrastructure into a smaller, common set of technologies.

In the above application, it is important to note that there is heavy reuse of existing service provider equipment and structures: copper loop plant, ATM transport networks and DSLAM multiplexors. The above methodology realizes a highly functional backhaul capability with minimal incremental cost. In fact, early estimates using already available SHDSL NTUs indicate cost reductions of about 50% over E-1 backhaul alternatives in terms of both initial capital costs and ongoing operational expenses.

The evolution and deployment of 3G wireless networks has begun and will change the landscape of telecommunications and the services available to consumers. 3G will enable efficient voice, data and video transmission, allowing new services and utility for individuals. The cost-effective method, described above, of transporting 3G wireless information using the existing broadband infrastructure can save billions of Euros on a global scale. Additionally, location services can be enabled, allowing people in trouble to be located by emergency workers quickly, thus saving lives. 3G networks will enhance not only the services available to wireless users, but it will enhance their lives. Additionally, the profitability of new services and cost savings of new technologies will allow telecom companies to once again become profitable.

Jeremy Bennington is Manager of International Business Development & Product Line Management for Symmetricom's Broadband Access Division.

Visit Symmetricom online.