Abstract: A receiver and a method are applied in a wireless communication system for detecting interference with a coexisting radar system. A signal received from an antenna is fed through an analog part and a subsequent digital part of said receiver. The receiver has an element with a-priori known attenuation values for a predefined set of frequencies, a first branch-off element for deriving a first detection signal from the signal before the element and a second branch-off element for deriving a second detection signal from the signal after the element. The receiver processes the first and the second detection signal such that a difference between the first and second detection signal is comparable with a threshold value, where the threshold value depends on the a-priori known attenuation values of the element. Depending on the comparison result, a frequency is identified as interfering or not a co-existing radar system.

Abstract: The invention relates to a method and a device for controlling frequency selection within a wireless communication system in response to radar-like interference signals. The method comprises continuously or quasi-continuously monitoring and assessing a plurality of frequencies with respect to a radar-like interference signal and allocating a quality parameter to each assessed frequency, the quality parameter indicating the probability that the frequency is occupied. The method further comprises selecting one or more frequencies in dependence on the allocated quality parameters and subsequent frequency monitoring.

Abstract: The invention relates to a method of multiplexing data words in a multicarrier transmit diversity system. The method comprises the step of generating a plurality of data blocks, each data block comprising data words and each data word containing data symbols derived from a data signal, the step of determining for one or more data blocks in dependence on at least one transmission constraint if the data words of said one or more data blocks are to be multiplexed in the time domain or in the frequency domain and the step of multiplexing the data words of the data blocks in accordance with the determination result.

Abstract: Interference Measurements in a Wireless Communications SystemA method and a transmitting unit for performing an interference measurement in a multiple access wireless communications system utilizing a carrier sensing technique is described. In accordance with the carrier sensing technique, it is monitored during a sensing period (Tmin) if a carrier is idle. A continuous or quasi-continuous interference measurement is performed on the carrier during a measurement period (TM) which is typically longer than the sensing period (Tmin). While performing the interference measurement, pulses are transmitted on the carrier such that an interval between the end of a pulse and the beginning of the next pulse is typically shorter than the sensing period (Tmin). The interference measurements preferably relate to detection of interference from radar signals or radar like signals.

Abstract: In a packet transmission system, especially wireless transmission system, where data is transmitted in packets at different error protection levels and where the error protection level of one packet (=the succeeding packet) may differ from the error protection level of a preceding packet without providing code termination between the said preceding and the said succeeding packet the performance may degrade in case a different error protection level is used by the preceding packet and the succeeding packet. The invention proposes in these cases to insert a supplementary packet between the preceding and the succeeding packet whereby the error protection level of the supplementary packet is higher than the lowest error protection level that is used either by the preceding or the succeeding packet.

Abstract: A method and a stage for estimating channel coefficients in a multi carrier system operating in accordance with a block-code based transmit diversity scheme, in which a data content of a code matrix is multiplexed in a frequency domain are described. The method comprises determining a phase ramp in the frequency domain or an equivalent thereof in the time domain, the phase ramp or the equivalent thereof being comprised within a receive signal after timing synchronization, processing the receive signal to remove the phase ramp or the equivalent thereof and estimating the channel coefficients on the basis of the processed receive signal.

Abstract: In order to correct frequency deviations of signals in a multicarrier system, such as a OFDM-system, the present invention provides a frequency tracker and a method to operate the same. The frequency tracker is based on a decision directed digital phase locked loop exhibiting a predictive character. On the basis of an estimated phase offset for a received signal (signal component, signal symbol) a predicted phase offset is calculated and applied to the signal (signal component, signal symbol). Further, received signals (signal components, signal symbols) are sampled and for each sample a sample phase offset to be corrected is calculated in dependence to the related estimated phase offset to incorporate the predictive character.

Abstract: A method and a receiver for determining the quality of a wireless communications link are described. The link quality is determined on the basis of an encoded signal that is transmitted via the communications link and that includes at least two signal portions experiencing different states of one or more transmission channels. The method comprises the steps of providing individual channel quality values for the different channels and determining a quality measure indicative of the link quality by averaging the individual channel quality values in the exponential domain.

Abstract: A method and a circuit (44) for estimating channel coefficients in a multi carrier transmit diversity system operating in accordance with a block-coding scheme is described. The method comprises determining from a receive signal (Y) for each channel estimated channel coefficients (?) comprising interference components from adjacent channels artificially introduced during the estimation, deriving estimates for interference components and determining interference-compensated estimates (?F+IC) for the channel coefficients on the basis of the estimates for the interference components.

Abstract: A radio receiver system (30) comprises a radio receiver (41), a receiver sample clock (60), which is used for sampling a modulated base-band signal; and a timing correction unit (100). The timing correction unit (100) performs, in the frequency domain, a timing drift compensation between a transmitter sample clock (66) and the receiver sample clock (60). In one example context of implementation, the plural modulated radio frequency carriers have been modulated using Orthogonal Frequency Division Multiplexing (OFDM).

Abstract: The invention discloses a method for use in a wireless communications system with a plurality of broadcasting nodes, comprising the step of enabling one node in the system to function as a central node in said system and letting said node enable measurements on at least one frequency in a frequency band used by the system. Said measurements are carried out to detect if said at least one frequency is being utilized by a transmitter foreign to the system. Preferably, the measurement is enabled by means of the node transmitting a message to other nodes in the system, said message being a message pre-defined within the system as a message prohibiting all nodes from transmitting during a certain interval, said message being transmitted after the system has been detected by the node to be silent during a predefined interval between frame transmissions from the nodes in the system.

Abstract: The invention relates to a method and a device for controlling frequency selection within a wireless communication system in response to radar-like interference signals. The method comprises continuously or quasi-continuously monitoring and assessing a plurality of frequencies with respect to a radar-like interference signal and allocating a quality parameter to each assessed frequency, the quality parameter indicating the probability that the frequency is occupied. The method further comprises selecting one or more frequencies in dependence on the allocated quality parameters and subsequent frequency monitoring.

Abstract: Interference Measurements in a Wireless Communications System A method and a transmitting unit for performing an interference measurement in a multiple access wireless communications system utilizing a carrier sensing technique is described. In accordance with the carrier sensing technique, it is monitored during a sensing period (Tmin) if a carrier is idle. A continuous or quasi-continuous interference measurement is performed on the carrier during a measurement period (TM) which is typically longer than the sensing period (Tmin). While performing the interference measurement, pulses are transmitted on the carrier such that an interval between the end of a pulse and the beginning of the next pulse is typically shorter than the sensing period (Tmin). The interference measurements preferably relate to detection of interference from radar signals or radar like signals.

Abstract: The invention discloses a method for use in a wireless communications system with a plurality of broadcasting nodes, comprising the step of enabling one node in the system to function as a central node in said system and letting said node enable measurements on at least one frequency in a frequency band used by the system. Said measurements are carried out to detect if said at least one frequency is being utilized by a transmitter foreign to the system. Preferably, the measurement is enabled by means of the node transmitting a message to other nodes in the system, said message being a message pre-defined within the system as a message prohibiting all nodes from transmitting during a certain interval, said message being transmitted after the system has been detected by the node to be silent during a predefined interval between frame transmissions from the nodes in the system.

Abstract: A method and a receiver for determining the quality of a wireless communications link are described. The link quality is determined on the basis of an encoded signal that is transmitted via the communications link and that includes at least two signal portions experiencing different states of one or more transmission channels. The method comprises the steps of providing individual channel quality values for the different channels and determining a quality measure indicative of the link quality by averaging the individual channel quality values in the exponential domain.

Abstract: A method and a stage (60) for estimating channel coefficients in a multi carrier system operating in accordance with a block-code based transmit diversity scheme, in which a data content of a code matrix is multiplexed in a frequency domain are described. The method comprises determining a phase ramp (&phgr;est) in the frequency domain or an equivalent (&Dgr;t) thereof in the time domain, the phase ramp (&phgr;est) or the equivalent (&Dgr;t) thereof being comprised within a receive signal (Y) after timing synchronization, processing the receive signal (Y&Dgr;t) to remove the phase ramp (&phgr;est) or the equivalent (&Dgr;t) thereof and estimating the channel coefficients on the basis of the processed receive signal.

Abstract: A method and a circuit (44) for estimating channel coefficients in a multi carrier transmit diversity system operating in accordance with a block-coding scheme is described. The method comprises determining from a receive signal (Y) for each channel estimated channel coefficients (ĥ) comprising interference components from adjacent channels artificially introduced during the estimation, deriving estimates for interference components and determining interference-compensated estimates (ĤF+IC) for the channel coefficients on the basis of the estimates for the interference components.

Abstract: In order to correct frequency deviations of signals in a multicarrier system, such as a OFDM-system, the present invention provides a frequency tracker and a method to operate the same. The frequency tracker is based on a decision directed digital phase locked loop exhibiting a predictive character. On the basis of an estimated phase offset for a received signal (signal component, signal symbol) a predicted phase offset is calculated and applied to the signal (signal component, signal symbol). Further, received signals (signal components, signal symbols) are sampled and for each sample a sample phase offset to be corrected is calculated in dependence to the related estimated phase offset to incorporate the predictive character.

Abstract: In a packet transmission system, especially wireless transmission system, where data is transmitted in packets at different error protection levels and where the error protection level of one packet (=the succeeding packet) may differ from the error protection level of a preceding packet without providing code termination between the said preceding and the said succeeding packet the performance may degrade in case a different error protection level is used by the preceding packet and the succeeding packet. The invention proposes in these cases to insert a supplementary packet between the preceding and the succeeding packet whereby the error protection level of the supplementary packet is higher than the lowest error protection level that is used either by the preceding or the succeeding packet.

Abstract: A radio receiver system (30) comprises a radio receiver (41), a receiver sample clock (60), which is used for sampling a modulated base-band signal; and a timing correction unit (100). The timing correction unit (100) performs, in the frequency domain, a timing drift compensation between a transmitter sample clock (66) and the receiver sample clock (60). In one example context of implementation, the plural modulated radio frequency carriers have been modulated using Orthogonal Frequency Division Multiplexing (OFDM).