WIN Alternative

The IN has become an international standard for increasing the capability and interoperability of wireline telephone systems. Wireless carriers have evolved their own form of IN based on IS-41 interoperability standards. But the model has been slow to live up to its promise in the market. The expectations for additional revenues via rapidly deployable, low-cost features and services have not been a reality.

Many factors have limited the implementation of IN-based services. Switch manufacturers have been reluctant to embrace IN because it opens the doors to their closed, proprietary markets. Carriers do not understand how to market or support enhanced services successfully. There are limitations of a centralized IN approach.

As a result, enhanced service penetration in wireless networks is less than 2% and accounts for less than 10% of total minutes of use. Meanwhile, carriers are watching revenue per user erode on a monthly basis as competition continues to drop the charge per minute and to increase churn rates.

To identify and roll out features and services to counter these trends, wireless operators are creating the WIN standard, which attempts to integrate the components of the wireline IN into wireless networks. The WIN 1.0 ballot is complete, and WIN 2.0 will reach ballot sometime next year. The basics of the proposals are a set of service definitions based on a centralized network philosophy, targeted at the HLR, that uses IS-41 as the basic signaling interface into the rest of the wireless network. WIN 1.0 defines calling name delivery, incoming call screening and voice-activated dialing as the service offerings. WIN 2.0 will add debit billing as the major enhancement, but because most carriers will roll out these same services, there will be minimal brand differentiation. The desire to bond customers to your brand is still a long way off if you have to wait for WIN.

Another Option But there are alternatives to WIN solutions available today. One alternative is based on the concept of an interworking function that leverages the existing wireless IS-41 network and the trigger mechanisms in IS-41 Revision C. This approach offers a low initial cost and a highly scaleable alternative. Unlike a centralized architecture, this distributed design allows you to customize services for individual users and user groups, and it is transparent across multiple wireless network nodes.

The IS-41-based virtual network solution uses a pseudo HLR (PHLR) and the interworking function (IWF) to provide a simple, cost-effective and scale-able solution. The PHLR and IWF provide an interworking function between the wireless IS-41 network and the fixed-network nodes such as the service node (SN), IP Class 5 switch and PBX. (See Figure 1.) At the same time, they provide the capability to migrate more intelligence to the edges of the network, which makes it easier to decouple the functions from the switching core.

The PHLR acts to the wireless network like the HLR of an MSC. In reality it supports only a subset of the IS-41 HLR definition in order to provide the interworking functions with the IWF. The IWF is a circuit-switched intelligent node that acts like a combination of the IN service switching point and SN. It can provide enhanced services on its own or act as a wireline interface to existing enhanced service components.

The PHLR-IWF provides many mappings of IWF to PHLR to allow for a single PHLR to host multiple enhanced services on separate IWF modules or on a single multi-tenanted IWF module.

For the PHLR-IWF to operate, carriers migrate end users from their current HLR to the PHLR. The PHLR becomes responsible for granting the permissions and feature sets that the wireless system will provide to those users. The serving MSC still provides the wireless service, so when a user registers (by turning on his phone or moving within range of a cell site), the serving system will generate a registration request to the PHLR. After validation, the PHLR will indicate that originating triggers should be put into effect for the user. Originating triggers are an IS-41C capability that indicates that any call origination by the user should be verified, and in most cases modified, by the PHLR before the call is set up. This allows you to offer diverse services and produce them locally. Yet, you can offer them on a nationwide basis independent of other wireless systems because the operation is basically transparent to the rest of the network. This allows carriers to offer services such as localized 800 number capabilities.

The distributed client-server architecture of this approach also will allow you to offer services such as wireless office solutions based on IN and PHLR implementations. A distributed solution relies on the integration with the enterprise to make the operation as seamless as possible. You do not have to plan and program a virtual network to emulate the enterprise, and most of the day-to-day programming is up to the enterprise. In the PHLR example, the carrier provides a block of MIN/ESN combinations to the enterprise in a similar manner that direct inward dialing numbers are assigned. The IT department manages the individual numbers. You manage the MIN/ESN combination on the PHLR, and the enterprise manages the user services on the IWF.

Call control is integrated with the PBX through the operation of the IWF. The IWF emulates a node in the PBX network if a trunking interface is used, or an intelligent umbilical if a computer-telephony integration link is used. Calls to a mobile user will be delivered to the IWF as a node in the network. The PHLR will locate the mobile to complete the call. The extension number or name of the originator is displayed as it would appear on a desk phone display. If the call setup fails, or is not answered, the call is deflected back into the PBX voice mail. During the setup phase, the PBX can regain control of the call if interception is required. The IWF also includes the capability to integrate the voice-mail notification, and the IWF call control allows for feature enhancements such as call transfer and follow-me services.

Advantages of PHLR-IWF The PHLR-IWF was not envisioned as a replacement for IN. More than likely, it will co-exist with IN, allowing you to decide whether a service is more appropriate as a centralized or distributed solution. But there are specific advantages of PHLR-IWF.

The WIN reference model reflects a centralized, HLR/SCP-based architecture. The initial query goes to the HLR followed by an interaction between the HLR and an IN SCP before the response is sent from the HLR to the serving VLR. This hides most of the interworking behind the HLR.

It is difficult to overlay a fixed-network design on a network with a highly mobile population. Therefore, the IN service platforms may have to be replicated wherever a user goes. This makes deployment complex and costly.

The centralized network approach is particularly challenging for small PCS or regional carriers that rely on roaming agreements for nationwide coverage. Using an IN-based solution can be a costly and complex networking issue for these carriers.

Centralized IN HLR/SCP combinations can range from $1 million to $6 million. Such a platform cannot provide a return on investment for a single feature or service. Implementation to date has shown these solutions are effective only when a suite of appropriate applications is available.

In contrast, the PHLR-IWF is designed to be highly scaleable and distributed, which means low up-front costs, around $100,000, and the ability to grow. Distributed solutions provide high levels of availability per dollar because the failure points are geographically remote and replicated.

Managing a centralized IN-based system requires the carrier be closely involved. For example, with wireless office solutions, you would have to perform all of the additions, moves and changes for the enterprise, but with the PHLR-IWF, the enterprise has the option to administer its own changes on the IWF. Currently, operations, administration and maintenance functions are major headaches for carriers that have deployed IN solutions. There will be a partial remedy to alleviate this problem with web-based management front ends to the IN platforms. This will allow the customer to manage features, but it results in low capability for each customer.

Today's Option Despite the challenges of WIN, the PHLR alternative is available today. Using the basic IS-41C capability, you can network almost any existing enhanced service. The IN standardization process is excruciatingly slow, so innovative service offerings could take several years to roll out if they need to go through the standards mill.

PHLR is not reliant on a wide area network footprint. IN implies that the operator has a wide- range network to enable features and services to be rolled out. The PHLR-IWF would allow an operator with a single MSC to offer a unique service and then provide access to it on a nationwide basis.

One of the key factors that this approach takes advantage of is the disappearance of distance-sensitive pricing in the backbone networks. Bandwidth in backbone networks is doubling every 18 months, which means the cost of backhauling a call to a PHLR-IWF point of presence is no longer an obstacle to the carrier compared to the economic benefit of being able to bond a customer and provide a value-added service.