 Apparatus and method for cryopreparing corneal tissue for surgical procedures |
| What is claimed is: 1. A method for cryopreparing corneal tissue for use in surgical procedures ... |
|
| Dynamic shading compensation for IR tracking system |
| OF THE INVENTION A conventional IR tracking system is commonly known as a FLIR system. This type ... |
|
| Method and apparatus for scrambling a television signal |
| The present invention relates to a television signal scrambling method and apparatus which employ a ... |
|
| Laser spot projector |
| It is therefore an object of the present invention to provide a laser spot projector capable of ... |
|
| Pulsatile drug delivery device using stimuli sensitive hydrogel |
| It is an object of the present invention to provide a delivery system which enables the effective ... |
|
| Method for making late programmable read-only memory devices |
| It is, therefore, an object of this invention to provide a method of programming a ROM late in its ... |
|
| Method of fabricating trench cell capacitors on a semocondcutor substrate |
| It is hence a primary object of this invention to present a method of fabricating a trench cell ... |
|
| Mouth held switch assembly |
| This invention is concerned with a mouth held electrical switch assembly and more particularly with ... |
|
| Blood lancet |
| I claim: 1. A relatively flat blood lancet, having a handle portion and a tip portion having sharp ... |
|
|
Spread spectrum CDMA interference canceler system and method
| Details |
Inventors: Schilling, Donald L.; Kowalski, John; Moshavi, Shimon;
Assignee: InterDigital Communication Corporation (Wilmington, DE)
Primary Examiner: Kizou; Hassan
Assistant Examiner: Rao; Seema S.
Attorney, Agent or Firm: David Newman & Associates, P.C.
A spread-spectrum code division multiple access interference canceler system and method for reducing interference in a spread-spectrum CDMA receiver having N chip-code channels, with each of the N channels identified by a distinct chip-code signal. The interference canceler system comprises a plurality of interference cancelers, each having chip-code generators, delay devices, correlators, spread-spectrum-processing circuits, and subtracting means. Using a plurality of chip-code signals, the correlators despread the spread-spectrum CDMA signal as a plurality of despread signals, respectively. The spread-spectrum-processing circuits use a timed version of the plurality of chip-code signals, generated by the delay devices, for spread-spectrum processing the plurality of despread signals, respectively, with a timed chip-code-signal corresponding to a respective despread signal. For recovering a channel, subtracting means subtracts the spread-spectrum-processed-despread signals other than the signal of the desired channel of the spread-spectrum CDMA signal. The system may further comprise a CDMA/DS detector for receiving a spread-spectrum signal, a plurality of interference cancelers connected in series for generating a plurality of estimates of the spread-spectrum signal, combining means for combining the estimates as averaged estimates, and decision means for receiving the averaged estimates. |
|
DETAILED DESCRIPTION A general object of the invention is to reduce noise resulting from N-1 interfering signals in a direct sequence, spread-spectrum code division multiple access receiver.
The present invention, as embodied and broadly described herein, provides a spread-spectrum code division multiple access (CDMA) interference canceler for reducing interference in a spread-spectrum CDMA receiver having N channels.
Each of the N channels is spread-spectrum processed by a distinct chip-code signal.
The chip-code signal, preferably, is derived from a distinct pseudo-noise (PN) sequence, which may be generated from a distinct chip codeword.
The interference canceler partially cancels N-1 interfering CDMA channels, and provides a signal-to-noise ratio (SNR) improvement of approximately N/PG, where PG is the processing gain.
Processing gain is the ratio of the chip rate divided by the bit rate.
By canceling or reducing interference, the SNR primarily may be due to thermal noise, and residual, interference-produced noise.
Thus, the SNR may increase, lowering the BER, which reduces the demand for a FEC encoder/decoder.
The interference canceler, for a particular channel, includes a plurality of despreading means, a plurality of spread-spectrum-processing means, subtracting means, and channel-despreading means.
Using a plurality of chip-code signals, the plurality of despreading means despreads the spread-spectrum CDMA signals as a plurality of despread signals, respectively.
The plurality of spread-spectrum-processing means uses a timed version of the plurality of chip-code signals, for spread-spectrum processing the plurality of despread signals, respectively, with a chip-code signal corresponding to a respective despread signal.
The timed version of a chip-code signal may be generated by delaying the chip-code signal from a chip-code-signal generator.
Alternatively, a matched filter may detect a particular PN sequence in the spread-spectrum CDMA signal.
A chip-code-signal generator may use the detected signal from the matched filter to trigger a timed version of the chip-code signal
|
|
Television 
