Source: http://www.google.com/patents/US6594248?dq=7,181,690
Timestamp: 2015-04-26 06:43:49
Document Index: 778539582

Matched Legal Cases: ['art.\n6', 'art.\n7', 'art.\n14', 'art.\n16', 'art 102', 'art 102', 'art 102', 'art 102']

Patent US6594248 - Data transmission method and a radio system - Google PatentsSearch Images Maps Play YouTube News Gmail Drive More »Sign inAdvanced Patent SearchPatentsThe invention relates to a data transmission method used in a CDMA-type radio system. A base station and terminal equipments exchange data at least in a packet switched mode, and a terminal equipment transmits to the base station on a random access channel a random access signal comprising at least a...http://www.google.com/patents/US6594248?utm_source=gb-gplus-sharePatent US6594248 - Data transmission method and a radio systemAdvanced Patent SearchPublication numberUS6594248 B1Publication typeGrantApplication numberUS 09/407,568Publication dateJul 15, 2003Filing dateSep 28, 1999Priority dateFeb 12, 1998Fee statusPaidAlso published asCN1256812A, EP0974203A1, US6625138, US20020114297, WO1999041845A1Publication number09407568, 407568, US 6594248 B1, US 6594248B1, US-B1-6594248, US6594248 B1, US6594248B1InventorsJuha K�rn�, Antti Toskala, Pekka Soininen, Kari Kallioj�rvi, Ari Hottinen, Risto WichmanOriginal AssigneeNokia CorporationExport CitationBiBTeX, EndNote, RefManPatent Citations (17), Non-Patent Citations (1), Referenced by (22), Classifications (17), Legal Events (4) External Links: USPTO, USPTO Assignment, EspacenetData transmission method and a radio system
US 6594248 B1Abstract
What is claimed is: 1. A data transmission method used in a CDMA-type radio system comprising at least one base station and a plurality of terminal equipments that exchange data at least in a packet switched mode, a terminal equipment transmitting to the base station on a random access channel a random access signal comprising at least a preamble and a data part multiplied by a spreading code, wherein
a predetermined set of spreading codes and signature sequences are stored at the terminal equipment or the terminal equipment generates such a predetermined set of spreading codes and signature sequences, and each signature sequence determines one spreading code; the terminal equipment selects one signature sequence by a random process from the set of signature sequences and adds the selected signature sequence to the preamble of the random access signal; the terminal equipment uses the spreading code corresponding to the selected signature sequence in the data part of the random access signal; interference cancellation is performed at the base station according to the signature sequence of the preamble of the received random access signal, such that at least the interference caused by the received data part is eliminated from at least one other received signal in order to increase data transmission capacity and to improve detection, and wherein when the base station performs interference cancellation on the random access signals, it indicates on the broadcast control channel a total interference level of the received signals that is higher than the real interference level so that the terminal equipment would increase the power of the random access signal it transmits according to the interference cancellation capacity of the base station. 2. A method according to claim 1, wherein in addition to the spreading code of the data part, the signature sequence indicates to the base station the telecommunication rate or spreading ratio of the data part that may be different for different signature sequences.
3. A method according to claim 1, wherein when the base station comprises rake branches, the rake receiver branches are tuned specifically to each terminal equipment by means of a signature sequence.
4. A method according to claim 1, wherein the preamble and the data part are transmitted substantially simultaneously.
5. A method according to claim 1, wherein the signature sequence is added to the preamble of the random access signal, such that the signature sequence is a symbol-level bit sequence that indicates to the base station the spreading code of the data part.
6. A method according to claim 1, wherein the signature sequence is added to the preamble of the random access signal, such that the signature sequence is a spreading code by which the preamble is multiplied and which indicates to the base station the spreading code of the data part.
7. A method according to claim 1, wherein the set of signature sequences only comprises one signature sequence, and the preamble comprises known reference symbols.
8. A method according to claim 1, wherein when a dedicated channel is a transmission channel that is more efficient than the random access channel and that utilizes a spreading code according to the signature signal, and when transmission is switched from the random access channel to the dedicated channel, interference cancellation is also performed at the base station on the signal of the dedicated channel in addition to the random access signal.
9. A method according to claim 1, wherein the preamble is used at the base station for synchronization of data transmission and for establishing a channel estimate.
10. A method according to claim 1, wherein the spreading-coded signals transmitted by the terminal equipments form a combined signal received by the base station, and interference is eliminated at the base station by forming a reference signal by means of a channel estimate and at least the data part of the detected packet switched signal, and by subtracting the reference signal from the received combined signal.
11. A method according to claim 10, wherein the base station stores the combined signal it has received, and at least the reference signal corresponding to the greatest packet switched interference signal is subtracted from the combined signal.
12. A radio system that is of the CDMA type and that comprises at least one base station and a plurality of terminal equipments which are arranged to exchange data at least in a packet switched mode, a terminal equipment being arranged to transmit to the base station on a random access channel a random access signal that comprises at least a preamble and a data part multiplied by a spreading code, wherein
the terminal equipment comprises signature sequence means and spreading code means that are arranged to provide a predetermined set of spreading codes and signature sequences, each signature sequence determining one spreading code; the terminal equipment is arranged to select one signature sequence by a random process from the set of signature sequences, and to add the selected signature sequence to the preamble of the random access signal; the terminal equipment is arranged to use the spreading code corresponding to the selected signature sequence in the data part of the random access signal; the base station is arranged to perform interference cancellation according to the signature sequence of the preamble of the received random access signal, such that the base station is arranged to eliminate at least the interference caused by the received data part from at least one other received signal in order to increase transmission capacity and to improve detection, wherein when the base station performs interference cancellation on the random access signals, the base station is arranged to indicate on the broadcast control channel a total interference level of the received signals that is higher than the real interference level so that the terminal equipment would increase the power of the random access signal it transmits according to the interference cancellation capacity of the base station. 13. A radio system according to claim 12, wherein the terminal equipment is arranged to add a signature sequence to the preamble of the random access signal, such that the signature sequence is a symbol-level bit sequence that indicates to the base station the spreading code of the data part.
14. A radio system according to claim 12, wherein signature sequence means are arranged to generate only one signature sequence, in which case the preamble comprises known reference symbols.
15. A radio system according to claim 12, wherein the terminal equipment is arranged to add a signature sequence to the preamble of the random access signal, such that the signature sequence is a spreading code by which the preamble is multiplied and which indicates to the base station the spreading code of the data part.
16. A radio system according to claim 12, wherein when a dedicated channel is a transmission channel that is more efficient than the random access channel and that utilizes a spreading code according to the signature sequence, and when the terminal equipment switches from the random access channel to the dedicated channel, the base station is arranged to also perform interference cancellation on the signal of the dedicated channel in addition to the random access signal.
17. A radio system according to claim 12, wherein the base station is arranged to use the preamble for synchronization of data transmission and for establishing a channel estimate.
18. A radio system according to claim 12, wherein the spreading-coded signals transmitted by the terminal equipments form together a combined signal received by the base station, and the base station is arranged to eliminate interference by forming a reference signal by means of the channel estimate and at least the data part of the detected packet switched signal, and by subtracting the reference signal from the received combined signal.
19. A radio system according to claim 18, wherein the base station is arranged to store the received combined signal, and the base station is arranged to eliminate from the combined signal at least the reference signal corresponding to the greatest packet switched interference signal.
20. A radio system according to claim 12, wherein addition to the spreading code of the data part, the signature sequence transmitted by the terminal equipment is arranged to indicate to the base station the telecommunication rate or spreading ratio of the data part that may be different for different signature sequences.
21. A radio system according to claim 12, wherein when the base station comprises rake branches, the base station is arranged to tune the rake receiver branches specifically to each terminal equipment by means of the signature sequence.
22. A radio system according to claim 12, wherein the terminal equipment is arranged to transmit the preamble and the data part substantially simultaneously.
This is a continuation of PCT/FI99/00107 filed Feb. 11, 1999.
FIG. 2b shows transmission of a random access burst,
FIG. 1b illustrates the possibility that the preamble 100 can be transmitted substantially simultaneously with the data part 102. Since the preamble 100 is typically shorter than the data part 102, the preamble 100 is repeated so many times that it will be as long as the data part 102. The preamble 100 is transmitted preferably on a Q channel of I/Q modulation, and the data part 102 is transmitted on an I channel.
FIG. 6 is a block diagram of a base station receiver. The receiver operates in the following manner. A received signal propagates from an antenna 600 first to radio-frequency means 602, where the signal frequency is converted in a known manner from a radio frequency into a baseband or an intermediate frequency. This signal is converted into a digital signal in an A/D converter 604. The digital signal is correlated in a known manner with the spreading code of the preamble of the random access signal in a matched filter 606, which forms an impulse response estimate for the radio channel. This impulse response estimate is filtered coherently in an adder 608, which sums up the samples of the output signal of the matched filter 606 one by one during the preamble. A desired number of symbols can be taken into account in the summing. Since each preamble comprises a signature sequence, the number of the adders needed for the summing equals the number of the signature sequences. The output of the matched filter is also correlated in the adder 608 with a symbol-level signature sequence. The adder that utilizes a signature sequence corresponding to the symbol-level signature sequence added to the preamble provides the greatest output signal. This output signal of the adder, which is also the averaged channel impulse response estimate, propagates to a peak detector 610. The peak detector 610 further controls a timing estimator 612 when the output signal of the adder 608 exceeds a predetermined threshold value. By means of peaks of the impulse response estimate, the timing estimator 612 tunes a rake combiner 616, which also comprises a detector, to the strongest multipath components of the signal in a known manner. The rake branches utilize the spreading code and the spreading factor indicated by the signature sequence. A delay line 614 delays a signal arriving at the rake combiner 616 by a delay caused by the means 606 to 612.
Correlation C(τ) is formed mathematically for example in the following manner for functions x(t) and y(t): C  ( t ) = ∫ a b  x  ( τ )  y  ( τ + t )    τ , wherein a and b represent the calculation interval for correlation. Correlation matrix C is calculated digitally as a cross product for variable matrices X and Y in the following manner: C  ( n ) = ∑ i = 1 N   x  ( i )  y  ( n + i ) , wherein C(n) corresponds to matrix C.
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