GE MDS is a world leader in wireless data networking solutions with applications in the SCADA, telemetry, telecommunications, and on-line transaction processing markets. A CDPD network allows a cellular carrier to offer the idle time of a cellular voice network for low throughput, real-time transactional data services applications. To date this technology has only garnered limited utilization. However, where it is being used, integrating an MDS TransIt data networking solution enhances the performance of the CDPD network for the end customer.

MDS TransIt enhancement

A TransIt Wireless Data Network is a last mile solution for delivering data to fixed locations, with long coverage range and low deployment cost. This multi-frequency radio platform is available in licensed and unlicensed bands that operate in a point to multipoint configuration at speeds up to 19,200 bps. TransIt features a multi-protocol stack that is compatible with most applications needs.

The metropolitan area scenario

CDPD services have been deployed successfully in some metropolitan areas. When the cellular infrastructure for voice is already in place, but the system is not fully utilized, the idle cellular capacity can be offered for data services.

In a CDPD network, data transmission receives lower priority than voice due to the real time nature of voice channels. To transmit data, CDPD uses only idle time on a radio channel, interleaving voice calls with data packets. When voice utilization peaks there is a double negative effect: data traffic ties up resources that could be sold as voice services at a much more lucrative price, or data users trying to establish a connection cannot use the service. TransIt provides an excellent complement to an existing CDPD network. The carrier can selectively reassign fixed location data services to a TransIt network and free up resources for the voice market.

This allows the carrier to increase the quality of service offered to both data and voice customers. The voice services have more allotted channels, and the data services don't suffer from access delays during peak periods.

A TransIt cell has up to 30 miles coverage, enabling the carrier to initiate deployment with minimum investment, and scale it up as the market evolves. A couple of cells can support initial deployment in most scenarios

The sub-metropolitan area challenge

CDPD implementation requires capital investment for the additional software and equipment to support the digital data services. In some markets the demand for data services does not have the sufficient density to pay for the infrastructure deployment required by CDPD, or it results in very long payback periods.

In these smaller markets an MDS TransIt Network is the perfect entry-level system. A single TransIt cell covers up to 30 miles and supports 50 or more customer sites. This can be done on license free spread spectrum or in licensed bands. In the licensed bands, TransIt can use each individual frequency of a channel (one channel is made of a frequency pair, one for transmit and one for receive) to transmit and receive further optimizing the utilization of radio resources.

This scenario allows the carrier to offer data services for fixed applications with the lowest possible risk and with a minimal initial investment. Once the market has developed and the demand for data services grows, it may make sense to deploy CDPD for additional users and/or mobile services. The investment in this scenario is a sure bet since real customers will already exist for the service.

Fig. 1. TransIt incremental infrastructure cost is closely coupled with actual demand, reducing initial investment and overall risk.

Additional Features

MDS Security features make a TransIt network even more attractive to financial users. A wireless digital network such as TransIt is many times more secure than a regular landline based network. (See the white paper on "Security in a TransIt network.")

Wireless networks link to the rest of the world in three basic ways: over private connections, over the Internet, and over the PSTN (public switched telephone network). Private connections are the preferred approach for customers using X.25 over leased lines. Large CDPD customers, in contrast, use IP over frame relay PVCs (permanent virtual circuits) to connect to the carrier. TransIt provides both types of interfaces X.25 and Frame Relay directly at the master station resulting in a seamless integration that does not require additional conversion boxes.

Summary

TransIt Wireless Data Network can help jump-start the fixed location data services market while minimizing investment risk for the service provider. It can also enhance the operation of existing CDPD networks by increasing the quality of service for both the voice and the data services markets. Tiered quality and price levels are among the new options that can be offered, as well as seamless protocol integration for a broad range of data applications. The sum of a dedicated licensed band, a shared spread spectrum and a shared cellular service alternatives make up a broad portfolio that will better match the customer needs at a more cost-effective implementation.

Adding it all up, the MDS TransIt is the perfect complement for your CDPD based fixed location data services offering, whether you are thinking of doing an initial deployment, have the need to expand into additional markets, or simply want to offer a better experience to your current customers.

This application note is also available in PDF format.