NPCS technology development advances one-way paging Although driven by narrowband PCS two-way paging, the interswitch wireless messaging transfer protocol (WMtp) advances one-way paging systems to support E-mail gateways and World Wide Web access.
As the next evolutionary step in paging, narrowband personal communications services (NPCS) are attracting a great deal of research and development. NPCS represents the future of the paging industry and its players, and much of the current effort is directed at the voice and data trials that are taking place in selected cities.
In the NPCS technology race, paging carriers and vendors are spending enormous amounts of effort and money on developing next-generation services that will beam us into the wireless future. The NPCS family of advanced voice and data services will provide new conveniences, efficiencies and two-way messaging capabilities.
Conventional one-way paging is part of NPCS, and it will continue to grow at a healthy rate as new NPCS services are launched. In 1995, the number of one-way paging subscribers in the United States grew by 25% to 34 million, and the number is projected to reach nearly 52 million by 2000.* Companies are developing NPCS hardware and applications with this growth in mind. Here is how emerging NPCS technology will advance the performance and functionality of one-way paging.
Networking standards The current networking standard, Telocator Network Paging Protocol (TNPP), has served the paging industry well for many years. Its limitations, though, are becoming more evident with continued industry growth and the performance demands of NPCS. The latest generation of wireless messaging services require rates of several megabits per second; TNPP can support data rates of only 9,600bps or 19,200bps. The congestion control provided by TNPP also is inadequate; callers may be blocked unnecessarily, or pages may be lost when the network becomes congested during peak hours. In addition, TNPP represents the old style of “send-and-then-wait,” which reduces efficiency. A paging terminal must wait for an acknowledgment that can take 0.25 seconds, which is wasted time that could be spent sending more packets.
The only physical connection choices with TNPP are leased-line or dial-up; the protocol does not operate over such media as X.25, frame relay or ATM (asynchronous transfer mode), except perhaps by the inefficient use of a PAD (packet assembler/disassembler). Because TNPP is not used in the data communications industry, the paging industry cannot easily interconnect with certain communications data technologies (e.g., public packet networks or frame relay networks). This lack of connectivity also makes it impossible for service providers to benefit from less-expensive, off-the-shelf hardware and software.
A newly developed inter-switch protocol, WMtp (wireless messaging transfer protocol), promises to resolve several deficiencies of the old standard while supporting all the aspects of two-way paging. WMtp is based on TCP/IP (transmission control protocol/Internet protocol) switching that is used by many computer networks, including the Internet. With WMtp, service providers are effectively upgrading their internal networks to the same technology level as the Internet.
WMtp provides the fast data rates necessary for voice and data transmissions; 10Mbps and 100Mbps Ethernet (more than 100 times the capacity of today’s TNPP-based networks). Greater capacity allows more pages per second and the transmission of longer messages. In addition, WMtp’s universal support of TCP/IP means that any physical media can be used, including fractional T1, frame relay, X.25 and others. The support of TCP/IP also allows the use of the off-the-shelf routers, network analyzers and network management systems.
Remote encoders are becoming more common because of the use of satellites for connecting paging terminals to base stations. WMtp offers effective congestion control, which is especially needed where remote encoders are used. A remote encoder can detect that a paging channel is becoming overloaded, and it can relay this information back to the input paging terminals so that the flow can be regulated by limiting the number of messages entering the network. For increased efficiency, WMtp goes beyond “send-and-then-wait” by taking advantage of TCP/IP’s ability to send many packets while waiting for acknowledgments to earlier packets. Designed as an industry standard by Glenayre, WMtp is easily retrofitted to existing paging terminals by means of a software upgrade and the addition of an Ethernet card. Since its introduction, WMtp has been licensed by Motorola, Ex Machina, Real Time Strategies and TekNow for use in NPCS infrastructure products.
Throughput The need to accommodate higher data rates and digitized voice for NPCS is driving infrastructure vendors to increase throughput by using the latest technology. Some examples include: faster CPUs. faster random-access memory (RAM) and more of it, including cache RAM and local central processing unit (CPU) memory. faster and larger disk drivers and faster busses such as SCSI II (small computer system interface). intelligent communications cards, with processors and RAM equaling that of the host CPU.
Several vendors are working to make these performance improvements available for one-way paging systems by the end of the year. We believe our company, though, to be the only vendor that has designed these performance enhancements to be available as upgrades to existing paging terminals.
Voice storage and networking The analog voice pagers of the past were quite inefficient. NPCS technology has made voice paging viable once again. Whereas an analog voice channel may be capable of supporting about 1,500 subscribers, an NPCS system uses cellular frequency reuse, voice compression and high-speed modulation to put tens of thousands of subscribers on one frequency.
How does this apply to one-way paging? Paging terminals today often are used to store voice messages. Subscribers then are notified by a page that a message was received. The subscriber calls to listen to the message.
For service providers, the new technology can reduce the cost of operating a voice messaging network. The hardware and software that are used in NPCS for digital voice paging could be used in one-way paging to compress the stored voice mail messages, thereby offering more efficient storage.
As an example, voice messages often are stored using 24kbps or 32kbps ADPCM (analog-to-digital pulse-code modulation). High-speed digital signaling processors (DSPs) can use new compression techniques to compress voice down to 8kbps and less. Before NPCS technology, it was impractical or impossible to send voice messages between paging terminals. The new voice compression algorithms and higher-speed networking now make it feasible. Callers can make local calls to a local paging terminal, yet the voice message is kept with the subscriber database record in another terminal. This saves the caller from having to make a long-distance call. Voice networking also makes it possible to build paging terminals without subscriber databases. Carriers can place terminals and subscriber databases where they please, based on the organization of their technical support group and on financial models.
In the drive to make NPCS succeed, carriers and vendors are researching new applications that can use two-way paging technology, including E-mail gateways and World Wide Web access. Anyone with an existing E-mail account will be able to send E-mail to a pager and receive responses without any additional software or hardware. Although driven by NPCS, these new applications are perfectly suited to one-way paging. Those who are developing this new technology have carefully considered one-way from the start. NPCS technology is bringing one-way paging and the world of mobile communications to a new level of performance and functionality for service providers and end-users. All of the publicity, effort and money being spent on NPCS does not harm the future of one-way paging. Riding on the latest technology can only ensure its continued growth.