One-way paging to NPCS: Strategies for migration Carriers can minimize the risk of narrowband personal communications services (NPCS) deployment by using wireless messaging transfer protocol to share another network or by using ReFlex protocol to add a re
Several American paging companies spent a total of more than $1 billion for radio frequency (RF) licenses in the 1994 FCC spectrum auctions. Those large, public companies now are pursuing the burgeoning narrowband personal communications services (NPCS) market aggressively.
As the next evolutionary step in paging, NPCS promises to deliver many advanced wireless messaging services such as wireless E-mail, two-way messaging and voice messaging. Building a NPCS network to market such services will require a substantial investment. So how does a small- or medium-size carrier with limited human and capital resources enter the NPCS market?
Many carriers are reviewing business plans for the next round of narrowband auctions, the MTA/BTAs (major trading areas/basic trading areas), which are commencing in late 1996. Carriers are challenged by the need to pursue new NPCS revenue opportunities while they protect their one-way paging business. Carriers are advised to position themselves for NPCS by carefully choosing technologies and services that allow the most economical migration from one-way paging to NPCS. The central question is whether new one-way paging infrastructure purchased today will allow migration to NPCS. With proper system planning, the existing transmitters, control systems, distribution and switches can be used for NPCS as well as for one-way paging.
Protocol and service selection Paging carriers face many choices regarding which particular NPCS voice and data services to offer and the specific technology to operate them. These choices are driven by the market and by the cost and complexity of the necessary infrastructure. Among the protocol options and services available, Motorola’s ReFlex 25 offers the easiest migration path.
Voice Marketed as a wireless answering machine, PageNet’s VoiceNow is a voice application that uses the InFlexion paging protocol. The RF system design for InFlexion is cellular as opposed to the traditional simulcast design used with Flex and ReFlex protocols. Because InFlexion requires a completely new RF infrastructure, migration from Flex to InFlexion is impractical.
Instead, to take advantage of the opportunity to sell voice paging service, smaller carriers easily can resell a large carrier’s voice service by connecting with the larger carrier’s RF network. This connection can be made with the Glenayre-licensed networking standard, the wireless messaging transfer protocol (WMtp). Developed for NPCS and one-way paging, WMtp is based on TCP/IP (transmission control protocol/Internet protocol), and it supports the transfer of NPCS (including InFlexion voice) messages between paging switches. Any link media that supports TCP/IP, such as frame relay or integrated services digital network (ISDN), can be used. WMtp surpasses the current one-way protocol, TNPP (Telocator network paging protocol), by increasing capacity, simplifying network management and improving congestion control.
Data Many carriers prefer a data application to voice because it appeals to the market they serve. NPCS protocols that support data include ReFlex 25, ReFlex 50, pACT and InFlexion. With the exception of ReFlex 25, these encoding formats have relatively complex modulation schemes to support higher data rates on the forward channel. Because ReFlex 25 can operate with conventional FM transmitters, it is best suited for easy migration from one-way Flex paging.
One-way alphanumeric paging is hitting its stride in the North American marketplace. Some of the impressive services now available include wireless E-mail, World Wide Web (Internet connectivity) and information services (e.g., stock reports, sports scores and weather reports). With Flex alpha pagers now available, carriers that are upgrading their systems to Flex to add capacity will find ReFlex 25’s features to be an excellent extension of one-way alpha paging.
From a cost perspective, ReFlex 25 offers frequency reuse that greatly increases system capacity. New services that will be possible include guaranteed delivery and short responses. In addition, the response channel can add interesting enhancements to the one-way services (wireless E-mail and information services) mentioned above. For example, mobile customers could subscribe to local weather or traffic reports while they are on the road.
ReFlex 25 can be described as a Flex forward channel coupled with a response channel. Two-way capability is created by adding a receiver network to the Flex system. As with Flex, ReFlex 25 is a synchronous protocol that uses 6,400bps, 4-level FSK (frequency-shift keying) modulation, and it has a single carrier in a 25kHz channel. Figure 1 on page 20 shows a Reflex 25 system. The paging switch, distribution system and transmitter infrastructure are the same as that of a Flex system. The only components that differ are the RF switch and the receivers.
Example America’s largest private carrier, Westlink Paging of San Diego, has selected its migration solution in implementing NPCS and Flex technology. Westlink is a partner in Benbow PCS Ventures (June Walsh, president and majority owner), which holds licenses to a common NPCS channel in the West and Central regions.
Driven by the demand for capacity and the advent of Flex alpha pagers, Westlink decided to upgrade its transmitter network to be compatible with Flex. Westlink purchased a Flex system that also can serve as the forward channel of a ReFlex 25 system. Westlink chose conventional FM transmitters with satellite distribution, as well as a high-speed control system capable of supporting both Flex and ReFlex. Able to switch among POCSAG, Flex and ReFlex traffic, the Glenayre-supplied transmitters will serve as the forward channel for Westlink’s ReFlex 25 beta test and market trial in San Diego.
Rex Snyder, Westlink’s vice president of technology, described Benbow’s approach: “Although we have over 450,000 subscribers, we have chosen to minimize the risks of early NPCS deployment. We prefer to keep close to the technology and understand the benefits, market applications and costs thoroughly to deploy efficiently at the appropriate time. We are testing ReFlex 25, and we will be poised to implement quickly as devices become available. At the same time, we are evaluating the potential of other advanced NPCS protocols and planning long-term migration paths. We are excited by the opportunity to provide high-value services to more customers.”
Linear technology vs. FM Linear transmitters are necessary to support several NPCS encoding formats such as InFlexion and ReFlex 50. The linear transmitters now offered by paging infrastructure suppliers also are capable of supporting one-way protocols such as Flex and POCSAG. This leads to the question, Why not purchase linear transmitters to satisfy present one-way requirements? At first, linear technology seems to offer easy migration from one-way to more advanced protocols. However, carriers must carefully analyze their requirements and determine whether this new technology is a wise investment. Linear technology is more expensive than traditional FM transmitters. Carriers should invest in linear transmitters only if they plan to employ a protocol with a complex modulation scheme (such as InFlexion) or if they run multiple FSK carriers in a 50kHz channel.
Infrastructure checklist The following list summarizes some important questions to consider when selecting a two-way system or purchasing new one-way infrastructure.
## Transmitter * Will the transmitter control system support Flex and ReFlex? * Will the transmitter support Flex and ReFlex frequency deviation? * Can the transmitter’s exciter switch efficiently between one-way and NPCS frequencies? * Can the control system be upgraded to support linear transmitters?
## Switch * Will the switch support the NPCS networking protocol WMtp? * Can you resell other carriers’ voice service? * Will the switch support data applications? * What upgrades are required for your billing system?
Entering the NPCS marketplace may at first seem like a costly venture. The paging industry’s great expectations for NPCS are evidenced by the great investment that has been made so far. Smaller carriers, though, can greatly reduce their investment by choosing technologies and services that leverage existing paging infrastructure. By employing such a strategy, carriers can be competitive and take advantage of the new opportunities of NPCS.
