Detection method and device

Details Detection method and device Detection method and device

2002-01-04

2004-11-02

Phan, Man (Department: 2665)

Multiplex communications

Communication over free space

Having a plurality of contiguous regions served by...

C370S342000, C370S441000, C370S208000, C375S146000, C375S130000

Reexamination Certificate

active

06813258

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to a detection method in which a CDMA-coded data signal is transmitted in the form of a data stream of spread data bursts between a transmitter and a receiver, hierarchical CDMA codes being used for the transmission, as well as a corresponding detection device.
BACKGROUND INFORMATION
Although applicable in principle to any data transmissions, the present invention and the idea upon which it is based are explained with reference to a cellular CDMA detection system (CDMA=code division multiple access).
In particular, using code multiple access (CDMA code division multiple access), a plurality of data streams can be transmitted simultaneously via a shared frequency band. In this context, the data-stream symbols to be transmitted are converted by so-called spreading codes into signal pieces having the length of the spreading codes. The signal pieces of the data symbols of one instant are summed up, and the summed pieces are sent according to their chronological sequence, as is known from
Nachrichtenübertragung
[Information Transmission] by K. D. Kammeyer, 2nd edition, Information Technology Series, Teubner, Stuttgart, 1996.
The data symbols of the data streams can be recovered from the received signal pieces by despreading using the spreading codes. When transmitting the signals over a plurality of paths (as, for example, in the case of mobile radio communications), it is advantageous to carry out the despreading separately for all paths, and to sum up the despread signals of all paths weighted (with the coefficients of the channel pulse response). A CDMA receiver functioning in this manner is called a rake receiver.
The multi-path transmission causes mutual interferences of the transmitted signals at the receiver. In contrast to the rake receiver, these interferences can be eliminated, for example, by joint detection (JD=joint detection) in the receiver, as is known from “
Zero Forcing and Minimum Mean
-
Square
-
Error Equalization for Multiuser Detection in Code
-
Division Multiple Access Channels
” by A. Klein, G. K. Kaleh and P. W. Baier, IEEE Trans. Vehic. Tech., Vol. 45 (1996), 276-287.
CDMA codes having a large spreading factor can be constructed from two codes having a smaller spreading factor by Kronecker multiplication. A quantity of CDMA codes thus constructed is called hierarchical. The OVSF codes (OVSF=Orthogonal Variable Spreading Factor) used in the UMTS (UMTS=Universal Mobile Telephone System) are hierarchically constructed codes (see Concept Group Alpha: “EVALUATION DOCUMENT (DRAFT 1.0), Part 1”, ETSI Tdoc SMG2 270/97).
It is furthermore known that initially the received CDMA signals having a smaller than necessary spreading factor are detected, and are subsequently despread with the codes used for constructing the hierarchical code.
Large spreading factors permit the use of a great number of codes. The detection of a great number of codes is very costly.
SUMMARY OF THE INVENTION
An idea underlying the present invention is that the codes are detected stepwise. First, codes having a small spreading factor are detected. The results thus obtained are then used in detecting codes having a larger spreading factor. Consequently, only a part of the total code tree has to be detected, since only the despread signals of existing codes are passed on to the next step. The existence is expediently determined by the fact that the power (performance) of the codes exceeds a specific threshold.
The detection method and device of the present invention offer the special advantage that they permit detection of hierarchical codes with lower expenditure.
According to one preferred further development, in the first step, the master (parent) code c
(1,1)
having the spreading factor 1 is detected.
In another preferred embodiment, only a part of the total code tree is detected.
According to a further preferred refinement, OVSF codes are detected.
In another preferred development, the respective preceding step is taken into account in the manner that the powers of the CDMA signals already despread are determined, and only the already despread CDMA signals which exceed a predefined power threshold are passed on to the next step.


REFERENCES:
patent: 5533047 (1996-07-01), Mourot et al.
patent: 5544156 (1996-08-01), Teder et al.
patent: 5566206 (1996-10-01), Butler et al.
patent: 5910964 (1999-06-01), Sugita
patent: 5940433 (1999-08-01), Sawahashi et al.
patent: 6091757 (2000-07-01), Cudak et al.
patent: 6108369 (2000-08-01), Ovesjo et al.
patent: 6163524 (2000-12-01), Magnusson et al.
patent: 6167037 (2000-12-01), Higuchi et al.
patent: 6222875 (2001-04-01), Dahlman et al.
patent: 6233231 (2001-05-01), Felix et al.
patent: 6240099 (2001-05-01), Lim et al.
patent: 6301293 (2001-10-01), Huang et al.
patent: 6381229 (2002-04-01), Narvinger et al.
patent: 6393047 (2002-05-01), Popovic
patent: 6400755 (2002-06-01), Harris et al.
patent: 6424618 (2002-07-01), Uesugi et al.
patent: 6477158 (2002-11-01), Take
patent: 6526065 (2003-02-01), Cheng
patent: 6532250 (2003-03-01), Palenius et al.
patent: 6560194 (2003-05-01), Gourgue et al.
patent: WO 99 03225 (1999-01-01), None
patent: WO 01 24395 (2001-04-01), None
Hasanudin, H. et al., “Reducing Switch Delay by Reconstruction of Tree Structured Orthogonal Codes in CDMA Mobile Switching System”, Workshop Notes, IEEE International Workshop on Intelligent Signal Processing and Communication System, Dec. 8, 1999, pp. 585-588.

Affiliated with

Also associated with

Rating

Detection method and device does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Detection method and device, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Detection method and device will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-3362886