The Radio Paging (RP) feature is intended to permit multiplexing of the pag- ing signals (type 1A groups, 4A groups, 7A groups, and 13A groups—used only for the enhanced paging mode) into the (RDS) data stream containing any of the other RDS features. This technique permits the provision of Radio Paging using existing VHF/FM broadcasts as a transport facility, thereby avoiding the
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need for a dedicated network of transmitters and at the same time making use of the relatively large service areas of FM transmitters.
RDS Radio Paging has the great advantage that an existing VHF/FM broadcast network can be used to carry this service. This is especially true in developing countries, where it is difficult to implement a special radio transmit- ter network to only carry a paging service, as would be required for a POCSAG paging system. From an economics point of view, this is usually the most cost- effective solution for implementing a Radio Paging service, and for a broad- caster or transmission operator, there is also the opportunity to earn revenue from using RDS to provide such a service. The capacity of an RDS Radio Pag- ing service is approximately 40,000 subscribers per broadcast network of trans- mitters. The capacity is strongly influenced by the mix of paging services that is provided to users. If the paging service carries only a bleep tone to alert the subscriber, the capacity will be higher; but if long alphanumeric messages are carried, then the capacity will, of course, be much lower since these require more paging data groups to carry the information.
Some of the countries already making extensive use of the RDS Radio Paging technique are France [1], Germany, Sweden, Bulgaria, Hungary, Slove- nia, Croatia, the Czech and Slovak Republics, Ireland, Spain, Dubai, India, China, Indonesia, Russia, Ukraine, Tanzania, South Africa, Mexico, and the United States.
The full specification for the implementation of RDS Radio Paging is given in Annex M of the new RDS/RBDS specifications [2,3].
In comparison to former RDS/RBDS standards, significant enhance- ments were included, as follows:
1. A set of variable-length message types for numeric and function mes- sages has been added to the RDS paging definition, enabling more flexible and efficient use of the transmission.
2. The new definition includes message types for both national and international paging. Previously, only fixed-length messages were defined for numeric paging.
3. A repetition flag has been added. This enables more intelligent proc- essing of the received messages when messages are repeated to improve the reception reliability.
4. A paging call counter has been added. This is a running number for each individual message sent to a subscriber. This number permits the user to be alerted when a message could not be received.
5. The type 13A group concept was introduced for the enhanced paging mode.
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6. A global addressing scheme was added for country, operator, and operator’s service area management purposes, which permits several operators (15 operators per country; that is, operator codes (OPC), with 63 different service areas per country, which are paging area codes (PAC) to provide Radio Paging services for the same service area without any conflict among them). These codes are carried in type 1A groups, variants 0 and 2.
7. Roaming (international links) for international paging is also possible.
8. A paging network can now be defined without any connection to the PI code, as was previously the case. Only the country code compo- nent of the PI code is being used.
9. It is possible to design and manage a paging network completely unrelated to the radio programmes that the transmissions carry.
10. A new battery-saving mode has been defined that improves signifi- cantly (10 to 15 times) the power consumption of paging receivers (i.e., the pager is only fully powered during 0.3 seconds out of a two- minute cycle). This is achieved thanks to type 13A groups being placed at the beginning of the six-second interval, already defined in the basic paging mode. Battery life can be as high as up to 2,000 hours.
11. The address range of receivers was enhanced from one million to ten million subscriber address codes.
The enhancements described permit an easy upgrade of existing networks.
Radio Paging is intended to provide a broadcast paging service making use of the type 7A group for transporting the paging messages (see Figure 8.1), associated with the use of type 1A, 4A, and 13A groups (enhanced paging mode only). Subscribers to a paging service will require a special pocket paging receiver in which the subscriber address code is stored. Five types of call mes- sages are possible:
1. A simple call (bleep tone) without additional message;
2. A 10- or 15-digit (international), or 18-digit numeric message;
3. An alphanumeric message of 80 characters, maximum;
4. Variable-length message;
5. Functions message.
Basic and Enhanced Radio Paging 171
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PI code PTY Paging Paging
Paging A/B
Paging segment address code
A/B T3 T2 T1 T0 Checkword
+ offset A
Checkword + offset B
Checkword + offset C
Checkword + offset D B0TP
0 1 1 1 0
Figure 8.1 Type 7A groups convey the messages for Radio Paging, but other group types (1A, 4A, 13A) are also required for control and battery- saving functionality. (Source: EBU.)
In Figure 8.1, block 1 comprises the PI code found as the first block of every RDS group type. Blocks 3 and 4 are used to carry the paging message information. In block 2, the last five bits are used to control the paging infor- mation. Bit A/B is used as a flag that changes its value between different paging calls, thus indicating the start of a new or repeated call. Bits T3–T0are used as a four-bit paging segment address code and to indicate the type of an additional message that follows.