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METHOD OF LENGTHY MESSAGE TRANSMISSION COMPATIBLE WITH PRESENT POCSAG SYSTEM

IP.com Disclosure Number: IPCOM000006337D
Original Publication Date: 1991-Dec-01
Included in the Prior Art Database: 2001-Dec-26
Document File: 4 page(s) / 154K

Publishing Venue

Motorola

Related People

E. Callaway: AUTHOR [+2]

Abstract

The POCSAG paging format uses a block code for error correction. Block codes, however, do not perform well in RF Iiis characterized by Rayleigh fading. While the (31,21) BCH code used in POCSAG is double error correcting, and is therefore good for correcting random errors, it is insufficient for channels characterized by burst noise,.where the errors tend to be grouped together. For the transmission of large messages, such as computer files, fax, or other large amounts of data, a more robust burst-error-protected encoding scheme is needed. Such a system must be compatible with existing subscriber equipment and not require rework of existing pages in the field. hi addition, it must be able to accept messages of arbitrary length. The encoding method outlined below meets these requirements using interleaving by batches; as a bonus it conserves pager battery life.

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MOTOROLA INC. Technical Developments Volume 14 December 1991

METHOD OF LENGTHY MESSAGE TRANSMISSION

COMPATIBLE WITH PRESENT POCSAG SYSTEM

by E. Callaway and Ft. Erhart

   The POCSAG paging format uses a block code for error correction. Block codes, however, do not perform well in RF Iiis characterized by Rayleigh fading. While the (31,21) BCH code used in POCSAG is double error correcting, and is therefore good for correcting random errors, it is insufficient for channels characterized by burst noise,.where the errors tend to be grouped together. For the transmission of large messages, such as computer files, fax, or other large amounts of data, a more robust burst-error-protected encoding scheme is needed. Such a system must be compatible with existing subscriber equipment and not require rework of existing pages in the field. hi addition, it must be able to accept messages of arbitrary length. The encoding method outlined below meets these requirements using interleaving by batches; as a bonus it conserves pager battery life.

Embodiment #l: -,n+.,d _ ) v&l wm2 ; Ww.D3 DATpi.. km=s IPAWYI ohm IP/.RsmI Lamw IPkwY 1 I

A pager using the proposed format, receiving a long message, would operate as follows:

1. Pager receives its address in word 1; stays on for the next word to determine. if a message was sent.

2. Pager receives word 2, which is a system con- trol word not presently used, signifying that the following word(s) will be interleaved.

3. ARer de-interleaving, the pager decodes word 3, which is constructed in the following manner:

re-paged and the message continued.

4. The interleaved message would then be sent. The decoder would de-interleave the required num- ber of batches, decode them, and then return to standard POCSAG operation.

This process is shown in flow chart #l.

Embodiment #2:

Batch 1

2 m&ME

3 FRAME....
aw.ma,m,rxass,mrm,-,~, I

Batch 2

FPAME

1 FRAME

FR&J.El FPAME 2 FPdME3 FR*hf 1...

Wm~-l-I~I~/~l 1

Without loss of generality, assume that a pager in frame 2 is to receive a long message.

1. Starting with a new batch, the paging central sends the control word in each frame excepf 2. This informs all pagers in these frames that a long message is to be sent, and that the next word will be the length ofthis message.

2. In each frame except 2, the next word will be a data word encoding the length in batches) of the interleaved message. This will allow all pagers in these frames to power-down for the length of this long message, extending their battery life.

3. In frame 2, the systems sends the address of the paged receiver as the first word, and the codeword as the second word. In this way, the correct pager is addressed, and is informed that the message will be the long, interleaved type, instead of a standard alpha-numeric, for example.

4. The next batches will be interleave& the first word of the first batch will be the length of the...