Method of reducing interference, and radio system

Abstract

The invention relates to a method of reducing interference in a radio system comprising at least one base station and a subscriber terminal. The data to be transmitted is converted into symbols (40) in a transmitter and each symbol (40) is multiplied by a connection-specific spreading code composed of chips (41). The data to be transmitted on connections in a synchronizing phase is multiplied by a spreading code whose duration in time differs from the spreading code in the other connections.

Description

technical field

[0001] The present invention relates to a method for reducing interference in a wireless system and a wireless system. Background technique

[0002] In CDMA (Code Division Multiple Access), a user's narrowband signal is multiplied by a spreading code and spread over a much wider frequency band. Multiple users transmit on the same frequency band simultaneously. On each connection between the base station and the user terminal, a different spreading code is used, and the signals of the users are differentiated in the receiver based on the spreading code of each user. Appropriate spreading codes are chosen such that their correlation with each other is as small as possible. Ideally, the signal multiplied by another spreading code would not correlate, would not revert to narrowband, and would appear as noise.

[0003] However, in conventional CDMA, the cross-correlation between different spreading codes is generally too high, because the time lengths and usual...

Examples

Embodiment Construction

[0021] The invention can be applied to any wireless system using spreading codes, such as a CDMA system.

[0022] figure 1 A typical CDMA wireless system is shown. The radio system comprises a plurality of cells, each cell generally comprising a base station 1 and 2, and a plurality of user terminals 3 to 5, preferably mobile telephones. Both the base stations 1 and 2 and the user terminals 3 and 5 comprise at least one transceiver, via which a connection 6 between the user terminals 3 to 5 and the base stations 1 and 2 is established and maintained. The subscriber terminals 3 to 5 are preferably mobile telephones, and during the connection 6 they and the base stations 1 and 2 transmit spread spectrum coded signals to each other.

[0023] figure 2 A block diagram of a typical transceiver is shown. The transceiver comprises antenna 20 , radio frequency means 21 , transmitter multiplier 23 , encoding means 22 , demodulator 24 , modulator 25 , control means 26 and receiver m...

technical field

[0001] The present invention relates to a method for reducing interference in a wireless system and a wireless system. Background technique

[0002] In CDMA (Code Division Multiple Access), a user's narrowband signal is multiplied by a spreading code and spread over a much wider frequency band. Multiple users transmit on the same frequency band simultaneously. On each connection between the base station and the user terminal, a different spreading code is used, and the signals of the users are differentiated in the receiver based on the spreading code of each user. Appropriate spreading codes are chosen such that their correlation with each other is as small as possible. Ideally, the signal multiplied by another spreading code would not correlate, would not revert to narrowband, and would appear as noise.

[0003] However, in conventional CDMA, the cross-correlation between different spreading codes is generally too high, because the time lengths and usual...

Examples

Embodiment Construction

[0021] The invention can be applied to any wireless system using spreading codes, such as a CDMA system.

[0022] figure 1 A typical CDMA wireless system is shown. The radio system comprises a plurality of cells, each cell generally comprising a base station 1 and 2, and a plurality of user terminals 3 to 5, preferably mobile telephones. Both the base stations 1 and 2 and the user terminals 3 and 5 comprise at least one transceiver, via which a connection 6 between the user terminals 3 to 5 and the base stations 1 and 2 is established and maintained. The subscriber terminals 3 to 5 are preferably mobile telephones, and during the connection 6 they and the base stations 1 and 2 transmit spread spectrum coded signals to each other.

[0023] figure 2 A block diagram of a typical transceiver is shown. The transceiver comprises antenna 20 , radio frequency means 21 , transmitter multiplier 23 , encoding means 22 , demodulator 24 , modulator 25 , control means 26 and receiver m...

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