CSM2000TM CELL SITE MODEM CDMA TECHNOLOGIES CSM2000 TM CELL SITE MODEM QUALCOMM H T T P : / / W W W. C D M AT E C H . C O M ENABLING THE FUTURE OF COMMUNICATIONS TM Receive Samples CSM2000 Transmit Chain Inputs Channel Element 0 Tx Channel Element 1 Channel Element 6 Tx Tx Channel Element 7 Tx Transmit Chain Outputs Microprocessor Interface CSM2000 Transmit Chain Diagram Overview Channel Element Functions The CSM2000TM device, developed by QUALCOMM Incorporated, is a CDMA digital baseband modem which replaces QUALCOMM's previous generation of Cell Site ModemTM (CSMTM) devices, the CSM1.0TM and CSM1.5TM devices. The previous CSM devices supported only one Forward Link and one Reverse Link channel per device. The CSM2000 device has been enhanced to support eight Forward Link channels and eight Reverse Link channels. Searcher The searcher selects an antenna set for a search and programs the position and size of the search window. Then, the searcher initiates the search and finds the largest multipath peaks within the search parameter set. Normally, the searcher operates continuously; while the results from a search are read, the next search is already underway. For acquisition searches, the searcher results can be used to detect the presence of a mobile attempting to access the CDMA network. For demodulator multipath searches, fingers may be assigned to the reported paths to improve the demodulator performance of the rake receiver. The CSM2000 device provides QUALCOMM's CDMA licensees with an IS-95A compliant system capable of supporting both 9.6 kbps and 14.4 kbps channels. The CSM2000 device is made up of eight integrated Channel Elements. Each Channel Element is accessed as if it were a single CSM1.0 or CSM1.5 device. This allows the CSM2000 device to be controlled by software written for the CSM1.0 or CSM1.5 devices with only minor changes. Performance The high integration of the CSM2000 device allows a substantial savings in power consumption. The CSM2000 device provides more than 75% power savings when replacing eight CSM1.0 devices and more than 50% power savings when replacing eight CSM1.5 devices. Improvements in the demodulator of the CSM2000 device provide up to 1.2 dB of improvement over the CSM1.0 and CSM1.5 devices. This reduces the output power required from the mobile unit, resulting in improved Reverse Link system capacity and increased battery life in the mobile unit. Q U A L C O M M , I N C O R P O R AT E D CDMA TECHNOLOGIES Four Fingers The four fingers make up a front-end interface to the demodulator. The fingers provide timing, Walsh chip accumulation and Walsh chip storage for the demodulation process. The fingers may be programmed to accept data from the same or different antenna sources. Demodulation Processor The demodulation processor performs Fast Hadamard Transforms for the searcher and the four fingers. It also performs optimal soft combining of data from the fingers and performs power calculations, including lock detection and power control decisions. 5775 MOREHOUSE DRIVE SAN DIEGO, CA 92121 h t t p : / / w w w. c d m a t e c h . c o m / a b o u t _ u s / c o n t a c t . j s p CSM2000 TM CELL SITE MODEM QUALCOMM CDMA TECHNOLOGIES H T T P : / / W W W. C D M AT E C H . C O M ENABLING THE FUTURE OF COMMUNICATIONS TM 2 Searcher Demodulation Processor RXI RXQ Deinterleaver & Viterbi Decoder The interleaver is used to provide time diversity in transmitted symbols, thereby providing protection from relatively long transmission fades and burst errors. The effects of the interleaver are reversed in the mobile unit deinterleaver. RX Data Packets Four Fingers P/N Sequence Generator TX Data Packets Encoder & Interleaver Modulator Transmit Summer TXI, TXQ Modulator The modulator contains three individually programmable sections that generate Forward Link information streams from the interleaver output. The symbols from the interleaver are scrambled with the long code PN sequence and punctured with power control bits, if appropriate. The punctured symbols are covered with the proper Walsh code and spread with the I and Q PN sequences. The resulting chips are then bandlimited with FIR filters and multiplied by a programmable gain factor. Each of the three transmit sectors can be driven by a particular section of the modulator, the sum of all three sections or zero. Cascade I,Q Inputs CSM2000 Channel Element Functional Block Diagram Deinterleaver & Viterbi Decoder The deinterleaver is used to reverse the interleaving performed by the mobile unit. Interleaving provides protection against burst errors and fades. The Viterbi decoder, using the Viterbi algorithm, optimally decodes the convolutional coding from the mobile unit. Quality bits and Cyclic Redundancy Check (CRC) bits are used to verify the quality of the decoded data. PN Sequence Generators There are several Pseudorandom Noise (PN) generators within the CSM device. The PN sequences generated are the I channel, Q channel and long code sequences for both Forward and Reverse Link processing. Encoder & Interleaver The encoder takes Forward Link data frames, convolutionally encodes them, and performs symbol repetition for bit rates less than full rate. The encoder also automatically generates CRCs for the frames that require them. Transmit Summer The transmit summer of each Channel Element combines its outputs with the outputs of the previous Channel Element and passes the result to the next Channel Element. Channel Element 0 receives its inputs from the CSM2000 device pins, and Channel Element 7 sends its result to the CSM2000 device pins. This allows the transmit chains of several CSM2000 devices to be tied together. Each Channel Element in the chain can be programmed to do any one of these three things: * Pass the samples on its cascade inputs straight through to its outputs * Ignore the samples on its cascade inputs and only output the samples it generated * Sum the samples it generates with the samples on its cascade inputs The transmit summer adds a parity bit to the output samples and can also do parity checks on the cascade input samples. If the samples fail the parity check, the transmit summer can automatically ignore those samples. Copyright (c) 2004 QUALCOMM Incorporated. All rights reserved. QUALCOMM is a registered trademark, and CSM2000, Cell Site Modem, CSM, CSM1.0, and CSM1.5 are trademarks of QUALCOMM Incorporated. All other trademarks and service marks are the property of their respective owners. Data subject to change without notice. Printed in USA 2/2004 CSM2000-SS X7 Q U A L C O M M , I N C O R P O R AT E D CDMA TECHNOLOGIES 5775 MOREHOUSE DRIVE SAN DIEGO, CA 92121 h t t p : / / w w w. c d m a t e c h . c o m / a b o u t _ u s / c o n t a c t . j s p