(Source: Motorola, author Joel Sandahl)

TIMELESS SIMULCAST CONTROL

INTRODUCTION
During the late 1980’s, the paging industry began experiencing significant growth in digital paging, as evidenced by the increased number of large regional and nationwide paging systems constructed. As subscriber growth continues at double-digit rates, systems become more heavily loaded, creating the demand for additional capacity.

As a result of this demand to increase capacity, several phenomena are occurring. First is the need to increase paging data rates to provide the channel capacity required. Second, satellite link distribution is becoming an increasing necessity due to the large geographical areas paging systems are covering. Finally, in many metropolitan areas, radio link frequencies are simply not available. Complex System’s C-NET technology was developed to provide the necessary simulcast control for this emerging market.

Originally conceived in mid-1990, the C-NET technology is the first digital simulcast control system that fully addresses the technical challenges of today’s high-speed digital paging, fully functional satellite distribution and link system multiplexing.

JITTER-FREE PAGING DATA • The world of high-speed paging data rates demands that paging data is properly timed and jitter-free. C-NET’s proprietary format provides for completed regeneration of all paging data prior to transmission, providing less than one microsecond of jitter.

FORWARD ERROR-CORRECTION • As paging data rates exceed 2400 bps, it is not sufficient to rely on the forward error-correction of the paging code itself, or simply encoding the key command-burst information. C-NET encodes all paging data, including code check bits, with forward error-correction. This ensures that link-induced bit errors are eliminated prior to data transmission.

LINK SYSTEM DIAGNOSTICS • Built into each C-NET product are extensive diagnostic capabilities, which provide such benefits as continuous signal-to-noise ratio measurement, bit error rate and receive levels. For the first time, paging system operators are able to continuously monitor the link distribution system(s) in real time.

AUTOMATICALLY REDUNDANT COMMON CONTROL EQUIPMENT • This assures that the system is able to continuously accept paging data from its data source(s), and to continuously provide paging data to the distribution network.

FULL SIMULCAST OPTIMIZATION AND DIAGNOSTIC CAPABILITY VIA SATELLITE DISTRIBUTION • As higher speed paging codes are developed, satellite-linked systems will dominate. C-NET offers precise automatic simulcast alignment, even over digital satellite link channels.

ECONOMIC ADVANTAGE
The many benefits of C-NET are not limited to technology. In today’s marketplace, it is essential to operate capital-intensive paging systems with an eye to minimizing operating costs. C-NET Platinum provides many features which, over the life of the paging system, greatly enhance the long-term benefit of ownership.

PAGER SIGNALLING UP TO 6,400 BPS • This assures that C-NET-based paging systems are engineered to resist obsolescence as higher speed paging formats are developed.

REMOTE SITE SOFTWARE UPDATES VIA THE C-NET LINK OR DIAL-UP CIRCUITS • This feature provides a new level in obsolescence protection by allowing hardware parameters to be reconfigured remotely.

NO AIRTIME REQUIRED FOR KEY CONTROL SIGNALLING • As C-NET’s digital key command is part of the continuous high-speed data stream, more airtime is available to generate subscriber revenue. This feature also enables base stations to key and transmit paging data at any point in a paging transmission. Momentary link system glitches or command-burst errors do not force the system down waiting for a pre-batch key command.

MINIMAL AIRTIME REQUIRED FOR SIMULCAST ALIGNMENT • Since generating pages is the lifeblood of any paging operation, C-NET’s proprietary maintenance cycles are performed during non-paging time. This feature increases revenue-generating minutes per hour.

Key to any operational plan is how to take full advantage of the capital assets already in place.

FLEXIBILITY IN SELECTING RF TRANSMISSION EQUIPMENT • Gives paging system operators the ability to select the equipment which best suits their requirements, and to choose to upgrade existing base stations with minimal expense.

MIXING DIFFERENT BASE STATIONS IN THE SAME SIMULCAST SYSTEM • Provides the means to utilize all base station assets more efficiently.

LINK SYSTEM MULTIPLEXING • Allows multiple digital paging systems to be combined over a single link distribution path. This feature eliminates the capital costs associated with duplicating link distribution hardware and also reduces recurring costs such as site leases and equipment maintenance.

USER SELECTABLE LINK SPEEDS • Allow system operators to select link speeds which are best suited for their systems’ requirements. Link speeds of 4,800, 9,600, or 19,200 bps are software-programmable, depending on the type of link distribution system(s).

EXPERIENCE - INNOVATION - FINANCIAL STRENGTH
Complex Systems’ Research and development team is staffed with the most experienced and dedicated simulcast control experts in the industry. Complex’s team has designed simulcast control products for more than 10 years, giving them experience, knowledge and insight into overcoming the technical obstacles inherent in high-speed simulcast control development. This collective experience includes practical design work as well as experience in operating paging systems. Developing innovative digital simulcast control technology and products is the single focus behind Complex Systems’ research and development effort. An impressive list of "industry firsts" clearly depicts this innovative determination.

C-NET FIRSTS:

• first to provide link system multiplexing;
• first to signal in excess of 1200 baud;
• first to provide mid-batch start-up;
• first one-way linked, pure digital simulcast system;
• first to provide hardware reconfiguration via the link system;
• first to provide forward error-correction of paging data;
• first to operate with the new FM cubed digital satellite;
• first to operate via a 19.2 kbps digital synchronous satellite channel;
• first to provide fully synchronized dial backup capability;
• first to provide continuous link system performance monitoring;
• first to signal Motorola’s FLEX paging protocol;
• first to provide software updating via the link system.

The C-NET technology and Platinum hardware platform were developed to provide paging systems throughout the world with a simulcast control system which addresses the needs of today and tomorrow.

Part of that significant challenge was to properly identify and address the technical parameters required for high-speed digital paging. In addition, the increased evolution of satellite technology as a distribution medium and the ever-decreasing number of available radio link frequencies create the market niche for C-NET.

The C-NET Platinum control point equipment is by far the most functionally superior digital simulcast control system available to paging system operators.

Complex Systems’ C-NET Platinum control point equipment provides for the overall control of the C-NET network. The control point equipment is comprised of Channel Interface Units (CIU), Network Control Units (NCU), Network Control Switches (NCX), and a Network Control Chassis (NCC). The CIUs, NCUs, and NCXs are housed inside the Network Control Chassis.

Depending on individual requirements, the C-NET Platinum control point equipment can be configured for multiplexed or non-multiplexed operation. The multiplexed configuration provides for the multiplexing of multiple digital paging systems over a single link system. Complete redundancy is available for both multiplexed and non-multiplexed configurations. A non-redundant configuration would simply have the redundant CIU and NCU removed.

Collectively, the control point equipment is responsible for the overall control of a C-NET Platinum digital simulcast paging system. The interface to a paging terminal (channel) is made via the CIU. The CIU is responsible for accepting paging data from the source (and analyzing the data to determine the baud rate, i.e. GOLAY, 1200 POCSAG, etc.). The CIU then stores the paging data in its internal buffer. The CIU is also responsible for all channel related activities such as generating C-NET’s proprietary maintenance cycle requests, and processing and distributing all synchronization adjustments.

C-NET Platinum is the most technologically advanced digital simulcast controller available to paging operators.

LINK SYSTEM MULTIPLEXING • C-NET Platinum allows paging system operators to distribute multiple digital paging channels via a single link distribution system.

REMOTE SITE SOFTWARE DOWNLOADS • System operators are able to download new software to remote transmitter sites via the C-NET link system or dial-up circuits.

REMOTE SITE HARDWARE RECONFIGURATION • System operators are able to remotely reconfigure C-NET Platinum hardware via the C-NET link system or dial-up circuits.

FORWARD ERROR-CORRECTION OF PAGING DATA • The C-NET Platinum control equipment encodes the entire C-NET data stream, including paging data, for forward error-correction.

VARYING LINK SPEEDS • Each C-NET system user may select the link speed which best suits the paging system’s requirements. Analog link systems may operate at 4,800 or 9,600 bps, while digital link systems may operate at 4,800, 9,600, or 19,200 bps.

AUTOMATIC REDUNDANCY • Each C-NET Platinum control point may be configured for virtually complete redundant operation. The CIUs and NCUs can be arranged in redundant sets; the NCC contains a dual power bus and the C-LAN data network contains dual paths.

MAXIMUM FLEXIBILITY

The C-NET Platinum control point equipment provides system users with maximum flexibility.

MODULARITY • The three main units comprising the C-NET Platinum control point equipment are designed to easily slide into the NCC housing. Each card can be placed into various slots within the NCC.

EXPANDABILITY • As additional paging channels are required, system operators can simply add more NCC chassis and tie individual chassis together via the C-LAN redundant connection.

MULTIPLE LINK DISTRIBUTION CHOICES • C-NET Platinum allows users to select the link distribution system best suited to their paging system’s requirements. System operators can select conventional analog distribution media, such as radio link or wireline, or digital synchronous methods, such as satellite. C-NET Platinum also provides the ability to mix and match various analog and digital link distribution media.

STATUS AND ALARM REPORTING • Each CIU and NCU contains an extensive set of internal alarms. These alarms may be programmed to "dump" to a local PC or to dial out to a different location.

The NCU is solely responsible for constructing the C-NET data stream. The NCU will scan the buffer of any on-line CIU for paging data. If sufficient data is present, the NCU will transfer the paging data via Complex’s Local Area Network (C-LAN). Upon transferring the paging data, the NCU will add network control and timing information to the paging data, and will encode all of the information, including the paging data, for forward error-correction. The resulting information becomes the C-NET data stream. The NCU passes the C-NET data stream to the link distribution system.

The NCX provides several basic operations. First and foremost, the NCX provides the electrical connection between a paging terminal (channel) and the CIU, and the electrical connection between the NCU and the link distribution system, In addition, the NCX operates as the switching mechanism between pairs of CIUs and NCUs. The NCX will monitor pairs of CIUs or NCUs, selecting one to be on-line. In the event of a malfunction, the NCX will automatically switch to the off-line unit.

The NCC provides a home for each of the units described above. The 19-inch wide, 10.5-inch high card cage has four sets of card slots which can house sets of CIU/NCX/CIUs or NCU/NCX/NCUs. The NCC contains a dual power bus (+10 to +30V DC), which allows primary and secondary power sources to be used. The NCC also contains a dual C-LAN bus to provide a redundant communication path between CIUs and NCUs.

As additional paging channels are required, system operators can simply add more NCC chassis and tie individual chassis together via the C-LAN connection.

Great flexibility allows C-NET operators to use virtually any simulcast paging transmitter, and to tailor the design of simulcast systems to their requirements.

The C-NET Platinum Network Interface Unit (NIU) was designed to provide the most sophisticated digital simulcast transmitter controller in the world. The C-NET Platinum NIU’s superior design provides obsolescence protection to paging system operators as it is ready to incorporate new, high-speed paging codes as they are made available. The NIU does not require the purchase of complicated and expensive equipment in order to interface to it. A standard IBM compatible laptop PC with Procomm Plus allows the most novice user to begin immediate communication with the NIU.

The NIU can be configured with three different I/O boards, which provide specific interface connections to various paging transmitters. This great flexibility allows C-NET operators to use virtually any simulcast paging transmitter, and to tailor the design of simulcast systems to their requirements.

The NIU’s primary function is to interface a paging transmitter to the C-NET network. The NIU can accept the C-NET data stream via numerous distribution paths, such as radio link, wireline, microwave and satellite.

The NIU decodes the paging network data for instructions and data addressed to it. NIUs are user configurable to respond to a system/zone address (for multiplexing) or individual device address. When relevant information is found in the data stream, the NIU responds accordingly.

When used with a paging monitor receiver, the NIU also performs the monitoring of C-NET’s proprietary "over-the-air" maintenance cycles.

AUTOMATIC SYNCHRONIZATION • C-NET is a synchronous digital format, not link-path dependent, such as existing control system technology. Groups of simulcast transmitters are synchronized initially when the system is turned on, and periodically rechecked during C-NET’s proprietary maintenance cycles. The accuracy of C-NET’s synchronization measurements is �2 microseconds. Adjustments to individual NIUs can be made in 1 microsecond steps.

SYNCHRONIZATION UTILIZING REMOTE MONITOR RECEIVERS • C-NET maintenance cycles are performed in the forward direction, meaning that individual NIUs are monitored and measured at specific monitoring sites. This allows C-NET-based systems to use dial-up circuits back from monitoring sites instead of costly leased lines. Monitor NIUs are interfaced to various paging channel receivers equipped with a receiver interface board provided by Complex Systems.

The monitor NIU reports transmitter misalignment back to the on-line CIU conventional dial-up circuits. Normally, a separate monitor NIU and monitor receiver are required for each paging channel in the C-NET network. A single dial-up circuit, however, can serve multiple monitor NIUs at a site.

Monitor NIUs are required at link transmitter sites to provide control of link transmitter keying, and also provide status and monitoring information for the RF link path. The monitor NIU also provides alarm monitoring for the link transmitter and diagnostic information about the link path.

AUTOMATIC MONITORING • The C-NET Platinum NIU is a complete alarm reporting and diagnostic tool. Each NIU maintains an alarm structure with 32 alarms, four of which are user-programmable analog or digital and are normally used for forward and reflected power, PA fault and exciter fault.

AUTOMATIC ALARM REPORTING • Alarms can be reported automatically or can be asked for by the system operator. These alarms are normally reported during the C-NET proprietary maintenance cycles, but can also be reported via dial-up telephone circuits. Each NIU may be programmed to send alarms to a PC. The NIU maintains an event log of the last 128 events which includes alarm information.

SYSTEM DIAGNOSTICS • As a diagnostic tool, the NIU provides a real time reading of signal-to-noise ratio, receive levels and bit error rate. This information provides instantaneous or historical data regarding the link system. Each NIU also provides time and date stamped information about any loss of the C-NET signal, the duration of that loss, any data frames which may have been missed, and a peak bit error rate since the last time the event log was reset.

INFORMATION MANAGEMENT • Each C-NET Platinum NIU contains an event log which maintains the most recent 128 events. Each event is date and time stamped to provide a detailed record of the occurrence.

All alarm and status information can be printed to a PC or local printer to provide written records of status reports.

Using Procomm Plus as an interface tool allows system operators to tailor scripts to provide information which is specific and relevant to their system requirements.

SIMPLE USER INTERFACE • System operators may communicate with the NIU locally through its front panel DB9 console connection using an IBM compatible PC and Procomm Plus, or remotely via a dial-up connection.

COMPLEX LOCAL AREA NETWORK (C-LAN) • The NIU uses C-LAN to poll other C-NET equipment for alarm information, if any, for "over-the-air" reporting during maintenance cycles; provide remote access, control and reconfiguration via the internal 2400 baud DIAL-MODEM to other C-NET equipment; access link backup facilities via the DIAL-MODEM; and accommodate future features and options.

MULTIPLE TRANSMITTER SELECTION • The NIU has three different I/O boards to interface to a wide variety of paging transmitters. This allows paging system operators to more efficiently utilize all base station assets.

SIGNAL REGENERATION PRIOR TO TRANSMISSION • The NIU completely regenerates all digital signaling at the transmission site, assuring properly timed, jitter-free data transmissions. This feature is critical to the success of high-speed digital paging.

REMOTE SITE SOFTWARE UPDATES • C-NET also provides the capability to completely and simultaneously reprogram all NIUs on a network via the link system. Specific sites can also be taken off the air and reprogrammed individually. The on-line CIU accepts the new code file and passes it to the on-line NCU for encoding into the C-NET data stream, complete with forward error-correction. This powerful feature provides for convenient, rapid software updating and assures that all sites operate with the same version of software. Future features can be implemented in a matter of minutes without site visits.

HARDWARE RECONFIGURATION • C-NET Platinum’s state-of-the-art design provides for the ability to remotely or locally reconfigure pieces of C-NET hardware. This feature will assure C-NET Platinum users that future enhancements and features can be incorporated into existing products, making them virtually obsolescence proof.

ADVANCED LINK SYSTEM DIAGNOSTICS • The NIU was the first simulcast transmitter controller to provide real time link system diagnostics. Each NIU can provide signal-to-noise ratio, bit error rate and receive level readings, while the system is operating.

MINIMIZES AIRTIME FOR KEY CONTROL SIGNALING • As C-NET’s digital key command is part of the continuous data stream, more airtime is available to generate subscriber revenue. This unique feature means that momentary link system impairments or command-burst errors do not force the site down, waiting for a pre-batch key command.