1、 STD-ITU-R RECMN M.584-2-ENGL 1997 - 4855232 0533324 ATO 1 RECOMMENDATION ITU-R M.584-2 CODES AND FORMATS FOR RADIO PAGING (Question ITU-R 1218) (1982-1986-1997) Summary This Recommendation describes codes and formats which may be used to provide radio paging. The ITU Radiocommunication Assembly, co
2、nsidering this Recommendation which describes codes and formats presently used by some of a) administrations; b) Recommendation ITU-R M.539; c) that the studies necessary to define the requirements for new radio-paging systems are ongoing; d) that some administrations need to implement, or intend to
3、 implement, radio paging systems offering higher transmission speeds, to increase data throughput and subscriber handling capability; e) that, among other things, standard code(s) and format(s) are necessary to permit radio f) that the codes and formats described in the annexes are presently used fo
4、r radio paging, recommends that future work should allow for possible future changes in these codes and formats; that studies should continue in order to meet the evolving requirements for paging systems. paging; 1 2 M:COMPUIT-RVOL-97M-P 1 -S IBL-26EV2.DOC (52126) 20.07.98 24.07.98 COPYRIGHT Interna
5、tional Telecommunications Union/ITU RadiocommunicationsLicensed by Information Handling Services2 ANNEX I Radio-paging code No. 1 1 Code and format This code is sometimes referred to as POCSAG. A transmission consists of a preamble followed by batches of complete codewords, each batch commencing wit
6、h a synchronization codeword (SC). The format of the signals is illustrated in Fig. 1. Transmission may cease at the end of a batch when there are no further calls. FIGURE 1 - Sig?dfmit A: preamble. Duration at least 576 bits = the duration 1 batch + 1 codeword B: first batch C: second and subsequen
7、t batches D: one frame = 2 codewords SC: synchronization codeword Dobc Nore - 1 batch = synchronization codeword + 8 frames = 17 codewords. 1.1 Preamble Each transmission starts with a preamble to aid the pagers to attain bit synchronization and thus help in acquiring word and batch synchronization.
8、 The preamble is a pattern of reversals, 101010 . repeated for a period of at least 576 bits, Le. the duration of a batch plus a codeword. 1.2 Batch structure Codewords are structured in batches which comprise a synchronization codeword followed by 8 frames, each containing 2 codewords. The frames a
9、re numbered O to 7 and the pager population is divided into 8 groups. Thus each pager is allocated to one of the 8 frames according to the 3 least significant bits (LSB) of its 21 bit identity (see 9 1.3.2), i.e. O00 = frame O, 11 1 = frame 7, and only examines address codewords in that frame. There
10、fore each pagers address codewords must be transmitted only in the allocated frame. M:COMPUIT-RVOL-97-P1 -S lBL-26EV2.DOC COPYRIGHT International Telecommunications Union/ITU RadiocommunicationsLicensed by Information Handling Services3 1 2 -19 20-21 22-31 I: I J K J ig L, ii i M ) PP Message codewo
11、rds for any receiver may be transmitted in any frame but follow, directly, the associated address codeword. A message may consist of any number of codewords transmitted consecutively and may embrace one or more batches but the synchronization codeword must not be displaced by message codewords. Mess
12、age termination is indicated by the next address codeword or idle codeword. There is at least one address or idle codeword between the end of one message and the address codeword belonging to the next message. In any batch, wherever there is no meaningful codeword to be transmitted, an idle codeword
13、 is transmitted. The last codeword in any transmission should be an idle codeword. 1.3 Types of codewords Codewords contain 32 bits which are transmitted with the most significant bit first. The structure of a codeword is illustrated in Fig. 2. 32 L L E: bit number F: address codeword G: message cod
14、eword H: flag bit I: address bits (2-19) J: function bits K: check bits L: even parity bit M: message bits (2-21) w2& 1.3.1 Synchronization Codeword The synchronization codeword is shown in Table 1 : TABLE 1 M:COMPUIT-RVOL-97M-P1 -S lBL-26EV2.DOC (52126) 20.07.98 24.07.98 COPYRIGHT International Tel
15、ecommunications Union/ITU RadiocommunicationsLicensed by Information Handling ServicesSTD-ITU-R RECMN M.584-2-ENGL I777 i855212 U533327 50T 4 1.3.2 Address Codewords The structure of an address codeword is illustrated in Fig. 2. Bit 1 (the flag bit) of an address codeword is always a zero. This dist
16、inguishes it from a message codeword. Bits 2-19 are address bits corresponding to the 18 most significant bits of a 21 bit identity assigned to the pager. For information regarding the least significant bits see 0 1.2. Bits 20 and 21 are the two function bits which are used to select the required ad
17、dress from the four assigned to the pager. Hence the total number of addresses is 223 (over 8 million). Bits 22 to 3 1 are the parity check bits (see 5 1.4) and the final bit (bit 32) is chosen to give even parity. 1.3.3 Message Codewords The structure of a message codeword is shown in Fig. 2. A mes
18、sage codeword always starts with a 1 (the flag bit) and the whole message always follows directly after the address codeword. The framing rules of the code format do not apply to a message and message codewords continue until terminated by the transmission of the next address codeword or idle codewo
19、rd. Each message displaces at least one address codeword or idle codeword and the displaced address codewords are delayed and transmitted in the next available appropriate frame. Although message codewords may continue into the next batch, the normal batch structure is maintained, Le., the batch wil
20、l consist of 16 codewords, preceded by a synchronization codeword. At the conclusion of a message any waiting address codewords are transmitted, starting with the first appropriate to the first free frame or half frame. Message codewords have 20 message bits, viz bit 2 to bit 21 inclusive and these
21、are followed by the parity check bits obtained according to the procedure outlined in 0 1.4 below. 1.3.4 Idle Codeword In the absence of an address codeword or message codeword, an idle codeword is transmitted. The idle codeword is a valid address codeword, which must not be allocated to pagers and
22、has the following structure as shown in Table 2: TABLE 2 1.4 Each codeword has 21 information bits, which correspond to the coefficients of a polynomial having terms from x30 down to x10. This polynomial is divided, modulo-2, by the generating polynomial x10 + x9 + x8 + x6 + x5 + x3 + 1. The check b
23、its correspond to the coefficients of the Codeword Generation (31: 21 BCH + Parity) M:COMPUIT-RVOL-97-P1 -S iWL-26EV2.DOC COPYRIGHT International Telecommunications Union/ITU RadiocommunicationsLicensed by Information Handling ServicesSTD-ITU-R RECMN M.584-2-ENGL 2777 Li855212 0533328 Liqb II 5 term
24、s from x9 to xo in the remainder polynominal found at the completion of this division. The complete block, consisting of the information bits followed by the check bits, corresponds to the coefficients of a polynomial which is integrally divisible in modulo-2 fashion by the generating polynomial. To
25、 the 3 1 bits of the block is added one additional bit to provide an even bit parity check of the whole codeword. 2 Message formats Although in principle, any message format can be inserted into message codewords, the following formats are regarded as standard. Adherence to these standards will enab
26、le a greater measure of interworking to be possible. The formats are not mixed within any one message. 2.1 “Numeric-only” message format The “numeric-only” format is provided for the transmission of messages which may be represented solely in decimal numerals together with spaces, hyphens, opening a
27、nd closing brackets, an urgency symbol “U” and one other symbol. There are 4 bits per character in this format and its use will save air-time compared to the other format. The address which introduces a message (or segment of a message) using this format has its function bits set to OO. The characte
28、r-set used for the message is as shown in Table 3 which is based on Binary Coded Decimal (BCD). The bits of each character are transmitted in numerical order starting with bit No. 1. Characters are transmitted in the same order as they are to be read and are packed 5 per message codeword. Any unwant
29、ed part of the last codeword of the message is filled with space characters. TABLE 3 “Numeric-only” character set I 4-bit Combination Bit No.: 4 3 2 1 O000 0001 O010 0011 O100 O101 0110 o111 1000 1001 1010 1011 1100 1101 1110 1111 Displayed character O 1 2 3 4 5 6 7 8 9 Spare U (urgency indicator) S
30、pace Hyphen 1 c M:COMPUIT-RVOL-97-P1 -S 1WL-26EV2.DOC (52126) 20.07.98 24.07.98 COPYRIGHT International Telecommunications Union/ITU RadiocommunicationsLicensed by Information Handling Services STD*ITU-R RECMN M-584-2-ENGL 1777 D 4855232 0533327 382 D 6 2.2 This format can be used for the transmissi
31、on of messages requiring a greater range of characters than that provided within the “numeric-only” format but it may also be used to replace the latter when circumstances make this essential or desirable. There are 7 bits per character in this format. The pager address which introduces a message (o
32、r segment of a message) using this format has its function bits set to 11. The International Alphabet No. 5 (7 bits per character) is used in this format. As in the case of the “nmeric-only format, bit order starting with bit No. 1 of each character, and character reading order are preserved in tran
33、smission. The complete message is partitioned into contiguous 20 bit blocks for the purpose of filling consecutive message codewords. Thus a character may be split between one message codeword and the next. Any unwanted part of the last codeword of the message is filled with appropriate non-printing
34、 characters such as “End of Message”, “end of Text”, Null, etc. All characters, except Null, are complete. Alpha-numeric or general data format 2.3 Loss of synchronization If a receiver losses synchronization, or if it commences receiving after the preamble has been completed, it is desirable that i
35、t can achieve synchronization on receipt of a number of valid batches. 2.4 A decimal representation of pager identity might also be useful. If so, it is suggested that it should be the decimal equivalent of the 21 bit identity. Decimal representation of pager identities 2.5 Message reception, displa
36、y and alerting 2.5.1 End of message It is desirable that the pager ceases decoding a message when either an idle or address codeword is received or when two successive information codewords are indecipherable, even if they immediately follow a message indication pager address. 2.5.2 Minimum message
37、storage capacity Some form of storage will be necessary for pagers which do not provide a printed output. It is suggested that the minimum storage capacity in pagers designed for the “numerical-only ” format should be 20 characters and for the “alphanumeric” format, 40 characters. M :COMPUIT-RVOL-97
38、M-P 1 - S 1 B L-26EV2. DOC COPYRIGHT International Telecommunications Union/ITU RadiocommunicationsLicensed by Information Handling Services STDmITU-R RECMN M-584-2-ENGL 1777 = 4855232 0533330 UT4 7 ANNEX 2 FLEX-TD Annex 2 describes the code and format FLEX-TD. In Japan, the air-interface technical
39、standard for radio paging was established by ARIB (Association of Radio Industries and Businesses, formerly RCR) in 1995. FLEX-TD is a paging code that uses the FLEX protocol as a foundation for the air interface. It is capable of applying Time Diversity (TD) to pages. FLEX-TD and the FLEX protocols
40、 are described and incorporated in RCR STD 43 (Reference 1). 1 Code and Format 1.1 Basic structure M:COMPUIT-RVOL-97-PI -S iWL-26EV2.DOC (52126) 20.07.98 24.07.98 COPYRIGHT International Telecommunications Union/ITU RadiocommunicationsLicensed by Information Handling Services8 Frame 127 FIGURE 3 BAS
41、IC STRUCTURE 128 frames cycle = 4 minutes O Frame0 Frame 1 Frame2 Frame 3 Frame4 BI 1 Sync 1 Block O I Block 1 I Block 2 I Block 3 & 3-1 AF VF MF IB L Sync = 115 ms SYNC BI 2 level FM 144 bits at 1600 bDs AF VF MF IB BI AF VF MF IB Interleaved blocks = 160 = 8 x 32 bits 1600 bps 2 level = 16 x 32 bi
42、ts 1600 bps 2 or 4 level SYNC FRAME STRUCTURE (no repeat case) Frame structure for blocks O thru BI AF VF MF IB BI AF VF MF - iB FRAME STRUCTURE (repeat case) BI AF VF MF IB 2 transmissions: SYNC BI AF VF MF IB BI AF VF MF 3 transmissions: Sub frame 2 (on 2nd transmission) . != Sub frame 1 (on 1st t
43、ransmission) L 4 transmissions: - -1 -!- Sub frame 2 (on 2nd transmission) Sub frame 1 (on 1st transmission) 0584-03 M:COMPUIT-RVOL-97-Pl -S lBL-26EV2.DOC COPYRIGHT International Telecommunications Union/ITU RadiocommunicationsLicensed by Information Handling Services STD-ITU-R RECMN M.584-2-ENGL 37
44、77 W 4855232 0533332 777 D 9 The Frame structures are indicated in Figure 3. An hour is divided into 15 Cycles numbered sequentially from O to 14. Each Cycle consists of 128 Frames (4 minutes), each numbered sequentially from O to 127. Each Frame is 1.875 sec long, and consists of a sync signal (1 1
45、5 ms.) and 1 1 interleaved blocks (1 60 ms each). The Sync 1 portion and Frame Information Word (FI) of each Frame is transmitted at 1 600 bith. The Sync 1 portion provides a means for obtaining Frame timing and an indication of speed and modulation for the remainder of the Frame. The FI portion con
46、sists of Cycle number, Frame number, multiple transmission indicator, and roaming channel indicator. The Sync 2 portion of each Frame is designated to provide synchronization at the block transmission speed. In the case of multiple transmission Time Diversity, blocks O to 10 are divided into two sub
47、-Frames for two transmissions, three sub-Frames for three transmissions, four sub-Frames for four transmissions. Each sub-Frame consists of Block Information Field (BI), Address Field (AF), Vector Field (VF), Message Field (MF), and Idle Blocks (IB). The repeat transmission interval for a page is sp
48、ecified using a value called the System Collapse Cycle (12128 Frames). A page is repeated in the appropriate sub-Frame of a future Frame as determined by the System Collapse Cycle. A pager can perform TD (Time Diversity) processing of the repeated transmission signals. Block Information Field (BI) i
49、s usually one code word (a code word consists of BCH (3 1,21) plus even parity), but may be up to four code words. Address Field (AF), Vector Field (VF) and Message Field (MF) contain individual addresses, paging types, and messages. An Idle Block (B) does not contain information, just a 1 600 bit/s alternating pattern of symbols modulated at 4.8 kHz and -4.8 kHz. 1.2 Sync Structure The sync consists of a Sync 1, a Frame Information, and a Sync 2 part. During the Sync 1 part, information regarding bit synchronization and how t
