Multiple user CDMA basestation modem

Details Multiple user CDMA basestation modem Multiple user CDMA basestation modem

1998-08-11

2001-12-25

Chin, Wellington (Department: 2664)

Multiplex communications

Communication over free space

Having a plurality of contiguous regions served by...

C370S320000, C375S144000, C375S148000

Reexamination Certificate

active

06333926

ABSTRACT:

FIELD OF THE INVENTION
The invention relates to CDMA (code division multiple access) basestation modems.
BACKGROUND OF THE INVENTION
In CDMA (code division multiple access) systems, the modem is the heart of the BTS (basestation transceiver subsystem). The modem performs the base band CDMA signal processing that converts data received from the BSC (basestation controller) to the CDMA air interface format on the forward link (the transmitter), and it receives the reverse link CDMA air interface signals from the mobile and converts the information into a format that the BSC understands. There is modem in every CDMA BTS regardless of manufacture.
Typically, a single BTS is designed to support multiple users. Furthermore, the BTS may need to be designed to support more than one of the various different air interface standards currently available. Current modems each process a single user for a single standard. If multiple users or multiple standards are to be supported by a BTS, multiple modems are required, one for each user of a particular standard. Thus, BTS complexity scales directly in proportion to the number of users and standards supported. Typically, BTS modems are designed on a single chip. Recently, chips have been designed which simply replicate the functionality of a single modem to create multiple-modem chips. Replicating a single modem on a chip does not alter this direct proportionality factor, it only shrinks the size of the system packaging.
SUMMARY OF THE INVENTION
It is an object of the invention to obviate or mitigate one or more of the above identified disadvantages.
According to a first broad aspect, the invention provides a CDMA transmitter signal processing apparatus comprising: an encoder/interleaver bank having a plurality of encoder/interleavers each having an input and an output; a modulator bank comprising a plurality of modulators each having an input and an output; a modulator switch for connecting any encoder/interleaver output to any one or more modulator inputs; a plurality of summers each having a respective plurality of inputs and an output; and an output switch for connecting any modulator outputs to any summer input.
According to a second broad aspect, the invention provides a CDMA receiver apparatus comprising: a plurality of fingers each having an input and an output; a switch for switching each of a plurality of receive inputs to any one or more finger inputs; a plurality of summers each having a respective plurality of inputs and an output; a weighting and thresholding circuitry connected to the outputs of the fingers and having thresholded outputs connected to an output switch which connects any thresholded output to any summer input.
According to a third broad aspect, the invention provides a configurable modulator comprising: a first modulator path containing BPSK modulation functions and functions for a first half of a QPSK modulator; a second modulator path containing functions for a second half of a QPSK modulator; input routing circuitry switchable between a first state and a second state, which when in said first state routes entire received bit streams to the first modulator path thereby causing the configurable modulator to function in a BPSK mode, and when in said second state routes the received bit streams to said first path and to said second path thereby causing the configurable modulator to function in a QPSK mode.
According to a fourth broad aspect, the invention provides a configurable encoder/interleaver comprising: an add reserved bits block; an add CRC block; an add encoder tail block; a convolutional encoder block; a symbol repetition block; a symbol deletion block; a block interleaver block; a long code modulation block; wherein each block of the encoder/interleaver is individually configurable or bypassable.
According to a fifth broad aspect, the invention provides a configurable decoder/de-interleaver comprising: a long code demodulation block; a block de-interleaver block; a symbol integration block; a convolutional decoder block; a remove encoder tail block; a remove and check CRC block; and a remove reserved bits block, wherein each block of the decoder/de-interleaver is individually configurable or bypassable.
According to a sixth broad aspect, the invention provides a CDMA demodulator comprising: a plurality of functional blocks each configurable to function for at least two different standards; for each said standard, a respective plurality of functional blocks permanently configured to function for the standard; switching means for switching the demodulator between different standards by configuring each configurable block to that standard, by switching in each permanently configured block for that standard, and by switching out each permanently configured block for any other standard.
The multiple user CDMA BTS modem architecture provided by the invention does not increase in size in direct proportionality to the number of users and standards to be supported. It achieves this firstly by supporting multiple users across multiple standards on a single modem on a single chip and secondly by efficiently sharing the key modem resources across the users and across the standards. This enables an economy of scaling in which an ‘N’ user modem is less than ‘N’ times more complex that the single user modem. This economy of scaling translates into a reduced cost for the multiple user modem on a per user basis than the single user modem.


REFERENCES:
patent: 4641238 (1987-02-01), Kneib
patent: 5367563 (1994-11-01), Sainton
patent: 5577105 (1996-11-01), Baum et al.
patent: 5956642 (1999-09-01), Larsson et al.
Qualcomm CMA Cell Site Modem (CSM) Data Sheet.

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