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Design and Implementation of a Practical FLEX Paging Decoder

Grayson Wireless 11

letter (a, b, c, d). For 1600 bps FLEX, only phase a is transmitted. For 3200 bps FLEX, phase a

and phase c are transmitted and 6400 bps FLEX transmits all four phases. Each block contains

eight codewords for each phase and are multiplexed together so that the time to transmit the

block is 160 ms. For 6400 bps, each block would contain 8 codewords for phase a, 8 codewords

for phase b, 8 codewords for phase c, and 8 codewords for phase d.

The FLEX coding format is shown in Figure 2-7. The 11 blocks are shown with the order in

which information is placed. In the first codeword of the first block is the Block Information

Word which is an overhead codeword needed to identify the remaining codewords. The 2

codewords will be the address field, vector field, message data field, and idle codewords

field. The number of codewords used in each field is based on the information transmitted. The

address field identifies one or more pagers. The vector field identifies each pager’s message type

and where the message content is located in the message field.

Block

Information

Codeword

88 Codewords in 11 Blocks

Address

Field

Vector

Field

Message

Data Field

Idle

Codewords

Figure 2-7

FLEX coding format

The number of codewords required for the FLEX coding format for tone, 10 digit numeric, and

40 Character Alphanumeric page compared with POCSAG are shown in Table 2-1. The number

of codewords does not include the overhead codes associate with each paging standard. For each

1600 bps FLEX coding format, there is one overhead codeword per 88 codewords which is the

block information codeword. For POCSAG, there is one overhead codeword per 17 codewords

which is the synchronization word. The percent of the coding format designated for overhead

information is reduced from 5.88% for POSCAG to 1.14% for FLEX.

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Motorola Pro FLX Manuel d'utilisateur Page 19