KR100837324B1 - Improving the performance of a receiver in interfering conditions - Google Patents

Abstract

The invention relates to an apparatus (22) comprising a communication system transceiver (40) for exchanging signals in a first frequency band and a receiver (30) for receiving signals in a second frequency band. In order to improve the performance of the receiver, it is proposed that the apparatus comprises a processing section 34 for detecting the presence of signals and interference signals in the second frequency band. The processing section also determines a timing pattern for interfering signals based on the timing information indicative of the timing for transmission used by the transceiver 40. Next, in order to reduce performance degradation due to interference signals coming from the transmitter 21 using timing for transmission, such as the transceiver 40, the processing portion may have intervals defined by the determined timing pattern. Resulting in manipulation of the signals arriving at the receiver 30. The present invention relates to a corresponding method equivalently.

Description

Improving the performance of a receiver in interfering conditions}

The present invention relates to an apparatus comprising a communication system transceiver for exchanging signals over an air interface in a first frequency band in a communication system and a receiver for receiving signals over the air interface in a second frequency band. The present invention relates to a method for improving the performance of such a receiver.

Devices that make up a communications system transceiver are state of the art, such as Global System for Mobile communication (GSM), US Time Division Multiple Access or IS-136 (US-TDMA), Code Division (CDMA) of a device over some communications network. It is known from the state-of-the-art technology that enables multiple access, or wideband CDMA (WCDMA) communication. Moreover, a receiver operating in a frequency band other than such a communication system may be, for example, a satellite positioning system such as a Global Positioning System (GPS) receiver of a GPS system or a Digital Video Broadcast-Terrestrial (DVB-T) receiver of a DVB-T system. It may be a receiver. Communication system transceivers operating in the first frequency band and receivers operating in the second frequency band may also be implemented together in a single device, such as a mobile phone, a personal computer, or a laptop.

However, during the time interval when wideband noise reaches the receiver in the second frequency band, the performance of the receiver may be degraded, because this wideband noise may cause a signal-to-noise ratio of the received signals. , SNR) can be significantly reduced.

Broadband noise may be generated, in particular, by a communication system transceiver integrated into the same device, such as a receiver, or by a communication system transceiver external to such a device.

For example, in a GPS system, many GPS satellites orbiting the earth transmit signals that are received and evaluated by GPS receivers. All GPS satellites use the same two carrier frequencies L1 and L2 of 1575.42 MHz and 1227.60 MHz. The modulation of these carrier frequencies L1 and L2 is described in FIG. 1. After a phase shift of 90 degrees, the sinusoidal L1 carrier signal is Bi-Phase Shift Key (BPSK) modulated by each satellite with a different Coarse Acquisition (C / A) code known at the receivers. Thus, different channels are obtained for transmission by other satellites. The C / A code, which spreads the spectrum over the 1.023 MHz bandwidth, is a pseudorandom noise sequence that repeats every 1023 chips, with an epoch of 1ms. The term chips is used to distinguish bits of data and bits of a modulation code. In parallel, the L1 carrier signal is BPSK modulated after being attenuated by 3 dB with a P-code (Precision Code), and the L2 carrier signal is BPSK modulated with the same P-code before being attenuated by 6 dB. Prior to transmission, two differently modulated portions of the L1 carrier signal are added again. The L2 carrier signal currently carries only P-codes. P-codes are much longer than C / A codes. Its chip rate is 10.23 MHz, which repeats every seven days. In addition, the P-code is currently encoded, and for that reason is sometimes referred to as a P (Y) -code. Decryption Keys for using P (Y) -code are categorized and civil users cannot access them. Thus, only L1 carrier C / A code is available in civilian GPS receivers.

Before the C / A-code and P (Y) -code are modulated onto the L1 signal and the L2 signal, the navigation data bits are modulated using a modulo-2 addition at a bit rate of 50 bits / second. Is added to the C / A-code and P (Y) -codes. The navigation information making up the data sequence can be evaluated, for example, to determine the location of each receiver. The L1 signal received at the receiver is further modulated due to the Doppler effect and possibly higher order dynamic stresses.

The reception bandwidth of a GPS receiver receiving modulated satellite signals is related to the reception code. For example, if the GPS is based on an L1 carrier C / A code, the signal needs a frequency band of 1575.42 MHz +/- 5 MHz. If a P-code capable receiver is used, the reception band of the GPS receiver will be wider, resulting in 1575.42 MHz +/- 24 MHz. The actual GPS reception bandwidth used is also related to the practical implementation, so the previously mentioned bandwidths are provided for demonstration purposes. The mentioned GPS bandwidth will therefore only be used in the following method by way of example.

The GPS standard is currently being modernized. One of the main components of modernization is in two new navigation signals that will be available for private use in addition to the existing private service broadcasts of the L1-C / A code at 1575.42 MHz.

The first of these new signals would be a C / A code located at 1227.60 MHz, ie modulated onto the L2 carrier frequency, and would be universally available in non-safety critical applications. The new civilian signal in L2, referred to as "L2CS", is generally characterized by a valid ranging code of 1.023 Mcps (second chips) with a time division multiplex of two half rate codes. Will lose. With the P (Y) -code, the L2CS signal will be BPSK modulated onto the L2 carrier. Beginning with the initial GPS block IIF satellite, scheduled for launch in 2003, these C / A codes will be available.

The second of the new signals will use the third carrier frequency L5 located at 1176.45 MHz. The L5 carrier frequency will be modulated with C / A codes, more specifically with a CL code of 767,250 chips and a CM code of 10,230 chips. The L5 signal will provide a 10.23 Mcps ranging code and it is expected that improved cross correlation properties will be realized. The L5 signal will be message based. The L5 signal will include an I (phase) channel carrying a 10-symbol Newman / Hoffman encoding and a Q (quadrature phase) channel carrying a 20-symbol Newman / Hoffman encoding. I and Q channels will be modulated onto the L5 carrier orthogonally. The L5 signal corresponds to a globally protected frequency band for aviation radionavigation, and will therefore be protected for life-safe applications. In addition, it will not cause any interference to existing systems. Thus, without modifying existing systems, the addition of additional L5 signals will make GPS a more robust radio navigation service for many aviation applications as well as all land-based users such as sea, rail, surface, shipping, and the like. The new L5 signal will be available for GPS block IIF satellites scheduled for 2005.

At the current GPS satellite supply rate, all three civilian signals, L1-C / A, L2-C / A and L5, will be available for initial operational capability by 2010, and will be fully operational by 2013. Will be available for you.

If no action is taken, the measurements show that the SNR of the GPS signal received by the GPS receiver is reduced by approximately 2 dB if the GSM transceiver implemented in the same device uses a single slot TX (transmit) mode for transmission. It is shown that the GSM transceiver implemented inside is degraded by about 3dB when using the dual slot TX mode for transmission.

In particular, communication systems operating in the 1900 band, such as GSM1900, commonly referred to as Personal Communication System (PCS), and communication systems operating in the 1800 band, such as GSM1800, commonly referred to as Digital Communication System (DCS), support GPS. When a C / A code is used, broadband noise will occur in this GPS L1 band of 1575.42 MHz +/- 5 MHz. When new L2 and L5 frequency GPS signals are used, lower frequency GSM signals, namely GSM900 and GSM800, will cause broadband noise problems such as GSM1800 in the L1 GPS signal.

However, in order to be able to correctly acquire and track signals based on their C / A code, and thus to use their content, the GPS receiver needs a sufficient SNR of the received satellite signals. For the performance of a GPS receiver, it is better to receive signals with particularly low SNR, rather than not receiving a signal at all during short time intervals.

Typically in spread spectrum systems, AGC (Automatic Gain Control) tunes the received information signal level for A / D (Analog / Digital) conversion based on the noise level. In typical operating situations, the noise comes from background noise with a constant power level. The problem arises when the noise level rises sharply and when the AGC adjusts the input signal to some appropriate level for A / D conversion. Fast changing high noise levels can cause saturation in the A / D converters, and signal amplification is clipped. If the signal is clipped at the time of conversion, some information signal is lost and therefore receiver performance is degraded.

In addition, when multiple communication system transceivers are transmitting in the same area at the same time, external interferences may completely block GPS receiver operation.

2 illustrates a communication system having a base station 10 of a communication network, a mobile station MS1 11 including a GSM transceiver, and a second base station MS2 12 including a GSM transceiver in addition to a GPS receiver. . The first and second mobile stations 11, 12 may exchange signals with the base station in uplink and downlink transmissions. During the uplink transmission of either of the two mobile stations 11, 12, wideband noise is generated in the GPS frequency band, which can interfere with the performance of the GPS receiver of the second mobile station 12. In order to inform the increase in noise at the GPS receiver of the second mobile station 12 during the GSM transmission by the first mobile station 11, the first mobile station 11 must be adjacent to the second mobile station 12. This is due to the fact that as the distance between transmitter and receiver increases, propagation loss, i.e., attenuation on the air interface, increases.

Problems such as in the GPS case may arise, for example, when a Galileo receiver is used instead of a GPS receiver. Galileo is a European satellite positioning system, with commercial launch scheduled for 2008. Galileo contains 30 satellites, which are distributed in three circular orbits to cover the entire surface of the earth. Satellites are further supported by broadband networks of ground stations. Galileo uses the RHCP (Right Hand Circular Polarization) in the frequency ranges 1164-1215 MHz using E5a and E5b, 1215-1300 MHz using carrier signal E6, and 1559-1592 MHz using carrier signals E2-L1-E1. It is planned to provide ten navigation signals. Similar to GPS, carrier frequencies E5a, E5b, E6 and E2-L1-E1 will be modulated by each satellite with multiple PRN codes and data spreading the spectrum. Thus, GSM transmitters will equally generate wideband interferences in the frequency band used by Galileo.

Clearly, in the case of other types of communication system transceivers and / or other types of receivers, the performance of the receiver due to transmission by the communication system transceiver may be equally degraded in similar situations.

In US Pat. No. 6,107,960, a method for reducing cross-interference in a combined satellite positioning system receiver and communication system transceiver device is proposed. When the communication transceiver transmits data over the communication link, control signals are sent from the communication system transceiver to the satellite positioning system receiver. The control signal causes the satellite positioning system signals from the satellites to be blocked from the receiving circuits of the satellite positioning system receiver or to be ignored by the processing circuits of the satellite positioning system receiver. For GSM transceivers using single slot TX mode, the resulting degradation is always 0.6dB = (10 * log10 (1/8)).

However, if the interfering signals are generated by a communication system transmitter integrated into a device such as a satellite positioning system receiver, this method can only improve the performance of the satellite positioning system receiver.

Similar degradation can occur in a DVB-T receiver system, such as in a satellite positioning receiver system.

DVB-T was first adopted as a standard in 1997 and is now rapidly expanding in Europe, Australia, and Asia. DVB-T is a fixed receiver that provides 24 Mbit / s data transfer capability, while mobile receivers that use omnidirectional antennas provide approximately 12 Mbit / s data transfer capability. Some distinguishing technical features of DVB-T include the following: DVB-T provides a net bit rate in the range of approximately 4.98 to 31.67 Mbit / s per frequency channel, and a UHF range of 470 to 862 MHz. Operates with 8MHz channel seperation. In the VHF range of 174-216 MHz, the channel separation is 7 MHz. Single frequency networks can be used. DBV-T uses Coded Orthogonal Frequency Division Multiplex (COFDM) multi-carrier technology with 16QAM or 64QAM carrier modulation, Quadrature Amplitude Modulation (QAM). The number of sub-carriers can be between 1705 (2k) and 6817 (8k). Inward forward error correction coding (FEC) uses conventional coding with rates of 1/2, 2/3, 3/4, 5/6, or 7/8, while external The coding scheme uses Reed-Solomon 204, 188, t-8 coding. External bit-interleaving uses conventional interleaving with a depth of 0.6-3.5 ms. For the 8k mode, the period of the symbol portion is 896 kHz, for the 2k mode it is 224 kHz. The DVB-T symbol length actually seen is the guard time and symbol period, which can be 1/4, 1/8, 1/16, and 1/32.

DBV-T was developed for MPEG-2 transport stream delivery, but can also carry other types of data. For example, DVB-T may provide broadband mobile wireless data transmission for video, audio, data, and Internet Protocol (IP) data.

DVB-T is scalable, for example, with cell sizes ranging from 100 km to tens of hundreds of picocells. The capacity is very large. For example, 54 channels may be supported, each operating at 5-32 Mit / s. One time slot packet is 188 (204) bytes long. Because of the large number of sub-carriers, symbol time can be made very long. For example, for the 8k sub-carrier case, the symbol time is similar to 1 ms. A guard interval is inserted before each symbol.

Thus, as long as DVB-T is suitable for providing digital video streams, DVB-T can also be used to provide high speed data streams for other types of applications such as interactive services, Internet access, gaming and e-commerce services. have. As expected, for the interactive and other services to be provided, a return link or channel is required again from the user to any server or other controller. One example of such a system is MediaScreenJ by Nokia. Such a device provides an LCD display screen for displaying information received from the DVB-T downlink and includes a GSM function with a transmitter to provide a return link or channel.

With such constellations, in European channel assignments, the lower end of the GSM transmit band starts at 880 MHz, while the upper end of the received DVB-T frequency band starts at 862 MHz. Problem occurs. Thus, the energy transmitted from the GSM band may leak to the DVB-T receiver as broadband interference, causing errors in the processing of the received data.

It should be noted that while the previous representation is concentrated on specific DVB-T frequencies and GSM systems in Europe, the same problem may occur at other points where DVB-T is specified for use. For example, in the United States, digital television is referred to as Advanced Television Systems Committee (ATSC), and the FCC has now allocated frequency bands of 764-776 MHz and 794-806 MHz for digital television broadcasting. One US cellular transmission band already occupied was set from 824-849 MHz. As can be noted, the upper boundary of the DTV band of 806 MHz is separated by only 18 MHz from the lower band of the cellular transmission band of 824 MHz, as shown in the DVB-T / GSM embodiment mentioned above. Is the same separation.

When the DVB-T receiver and the GSM transmitter are combined in a single device, the GSM transmitter can inform the DVB-T receiver about its transmission, and the DVB-T receiver can only integrate the input signal when the GSM transmission is not active. Proposed. In a DVB-T system, the symbol length is long compared to the length of the GSM burst, so that multiple GSM bursts can occur during one DVB-T symbol time.

However, if the interference signals are generated by a GSM receiver integrated in the same device as the DVB-T receiver, this approach is only suitable for improving the performance of the DVB-T receiver.

It is an object of the present invention to improve the performance of a receiver.

In particular, it is an object of the present invention to reduce the performance degradation of a receiver integrated into a single device with a communication system transceiver due to interference signals generated by other transceivers of the same communication system.

On the other hand, an apparatus is proposed, the apparatus comprising a communication system transceiver for exchanging signals over an air interface in a first frequency band and a receiver for receiving signals over the air interface in a second frequency band. It is done. The proposed apparatus also includes a processing unit for detecting the presence of interfering signals in the second frequency band. The proposed apparatus further includes a processing unit for determining a timing pattern for the detected interference signals based on the timing information provided by the communication system transceiver. The timing information is indicative of a timing for transmission used by the communication system transceiver. Finally, the proposed apparatus provides for the time intervals defined by the determined timing pattern to reduce performance degradation due to interfering signals from the transmitter using timing for transmission, such as the communication system transceiver of the apparatus. And a processing unit for causing manipulation of signals arriving at the receiver.

On the other hand, a method for improving the performance of a receiver is proposed. The receiver is coupled in a single device with a communication system transceiver that exchanges signals over the air interface in the first frequency band, while the receiver receives signals over the air interface in the second frequency band. The proposed method includes detecting the presence of interfering signals in the second frequency band. The proposed method includes determining a timing pattern for detected interference signals based on timing information indicative of timing for transmission used by the communication system transceiver. Finally, the proposed method provides for the time intervals defined by the timing pattern to reduce performance degradation due to interference signals coming from the transmitter using timing for transmission, such as the communication system transceiver of the device. Manipulating the signals arriving at the receiver.

In most cases, the invention proceeds from the fact that external interference is connected to a base station, such as the communication system transceiver of the device itself, and is generated by a transmitter of the communication system transceiver that is somewhat adjacent to the communication system transceiver of the device itself. Thus, the interfering transmitter uses timing such as the communication system transceivers of the device, including timing advance for its transmission. For example, if time slots are used for transmission in a communication system, these time slots will be synchronized among all communication system transceivers connected to the same base station. Thus, the communication system transceiver of the apparatus can provide accurate timing information, and based on this timing information, a timing pattern can be determined for detected interference. The timing pattern can then be used for interference cancellation with accurate timing. Interference cancellation is performed by any suitable manipulation of the signals arriving at the receiver.

It should be noted that, unless there is an inversion, any reference to the receiver is for such a receiver operating in a frequency band other than the communication system.

It is an advantage of the present invention to allow to improve the performance of a receiver coupled to a single device with a communication system transceiver.

The present invention eliminates or at least reduces the performance degradation of such a receiver resulting from cross-interference in the frequency band used by signals processed by the receiver, even when interference is caused by communication system transceivers outside the device. Allow it.

The present invention is suitable for handling interfering signals caused by any transceiver that uses timing for communication, such as the communication system transceiver of the device. Preferred embodiments of the invention will be apparent from the dependent claims.

The proposed invention also takes into account the interference caused by the transmission of the communication system transceiver of the device itself. Advantageously, however, interference caused by the transmission of the communication system transceiver of the device is considered individually. Since the apparatus knows the exact time intervals that the communication system transceiver is transmitting, the signals arriving at the receiver can be manipulated within this time interval to reduce performance degradation without having to determine the first timing pattern. In addition, the intensity of the interference without any measurement should be taken into account in the operation since the power level of the transmitted signals directly related to the resulting interference intensity is known to the device.

Manipulation of the signals arriving at the receiver in various ways is realized not only for external interference caused by transceivers external to the device comprising the receiver but also for internal interference caused by the transceiver within the device comprising the receiver. Can be.

In a first possible approach, the operation is carried out as set forth in the document US 6,107,960 cited above. In other words, the reception of signals is ignored when there is an interfering signal, ie blocked by a switch, or the received signals are ignored in the evaluation when there are interfering signals.

If the interfering signals are caused by the GSM transceiver, the degradation that can be obtained with this first approach is 0.6 dB for single slot TX mode and 1.2 dB for two slot TX mode.

In a second alternative approach, the frequency range over which the receiver can receive signals is detuned when there are interfering signals, ie detuning the antenna system used to receive the signals processed by the receiver. By detuning.

When the interfering signal is caused by the GSM transceiver, the degradation that can be obtained with this second approach is less than 0.6 dB for the single slot TX mode and less than 1.2 dB for the two slot TX mode.

However, in a third preferred approach, the signals received by the receiver are attenuated or attenuated with increased attenuation when there is an interfering signal. Advantageously, the attenuation can moreover be variable. More specifically, the applied attenuation is advantageously set high for high interference levels and low for low interference levels. This allows the receiver to adapt to each interference level.

If the interfering signal is caused by the GSM transceiver, the degradation that can be obtained with adaptive attenuation is 0 dB to 0.6 dB in single slot TX mode and 0 dB to 1.2 dB in two slot TX mode.

Thus, the third presented approach results in optimal performance.

Operation by signal attenuation has any suitable attenuating component, for example with an external gain attenuator in the receiver chain of the receiver, or with the integrated Automatic Gain Control (AGC) function in the receiver. Can be realized. For example, in a GPS receiver such AGC functionality is already built in and only needs to be extended. Thus, the implementation with variable attenuation is quite simple and requires no additional components at least in the case of a GPS receiver. The necessary processing can be implemented by software, which can be implemented in the existing digital signal processor (DSP) of the receiver.

The presence of interfering signals can in particular be recognized at the communication system transceiver or receiver. The processing portion that recognizes the presence of interfering signals thus forms part of the communication system transceiver or receiver.

The present invention can be used in any device including a communication system transceiver and an additional receiver, i.e., a mobile phone, a laptop.

The communication system transceiver may be, for example, but not exclusively, a GSM transceiver, a US-TDMA transceiver, a WCDMA-GSM transceiver, or a CDMA transceiver.

The receiver can be any type of receiver that can suffer from performance degradation due to interfering signals of the communication system. The receiver may be a receiver for receiving satellite signals, for example a GPS receiver or a Galileo receiver. The receiver may also be a DVB-T receiver, for example.

Other objects and features of the present invention will become apparent from the following detailed description considered in conjunction with the accompanying drawings.

1 describes the modulation of GPS carrier frequencies.

2 shows a communication system in which a GPS receiver of a mobile station receives interference signals from another mobile station.

3 is a block diagram of a mobile station designed in accordance with the present invention.

4 illustrates multislot operation in a communication system and the resulting noise level in a GPS receiver.

5 is a flow chart describing the interference cancellation portion implemented in the mobile station of FIG.

FIG. 6 describes the performance of interference cancellation implemented in the mobile station of FIG.

7 illustrates interference in a DVB-T receiver by a GSM system.

The communication system presented in FIG. 1 has already been described above.

3 is a schematic block diagram of a mobile station MS2 22 that supports mobile communication and GPS positioning over a GSM network, such as the second mobile station 12 of the communication system of FIG. However, the mobile station 22 of FIG. 3 is designed in accordance with the present invention, thereby providing improved interference cancellation.

Only selected components of the mobile station 22 are described.

In order to support GSP positioning, the mobile station 22 includes a GPS receiver 30. The GPS receiver 30 includes a low noise amplifier (LNA) 31, a mixer 32, a variable gain attenuator 33, and converters and a digital signal processor (DSP) connected in series with each other. It includes a processing block 34. Converters and DSP processing block 34 may additionally control access to variable gain attenuator 33. Local oscillator 35 is additionally connected to mixer 32. The mobile station 22 further comprises a GPS antenna 36 connected to the low noise amplifier (LNA) 31 of the GPS receiver 30. To support mobile communication, the mobile station 22 includes a GSM1800 transceiver 40 in which only a GSM transmitter chain is shown. The transmitter chain comprises converters connected in series with each other and a DSP processing block 41, a first variable power amplifier 42, a mixer 43, and a second variable power amplifier 44. The converters and the DSP processing block 41 further control access the variable power amplifiers 42 and 44. The local oscillator 45 is additionally connected to the mixer 43. The mobile station 22 further comprises a GSM antenna 46 connected to the second variable amplifier 44.

The converters and DSP processing block 41 of the GSM transceiver 40 are connected to the converters and DSP processing block 34 of the GPS receiver 30.

FIG. 3 further shows a mobile station MS1 21 corresponding to the first mobile station 11 of FIG. 2, which is responsible for applying external interference to the GPS receiver 30 of the mobile station 22 during transmission. Can be generated. It is assumed that the additional mobile station 21 is connected to a base station of a communication network such as the mobile station 22 and is located within a distance of 10 meters from the mobile station 22.

The radio frequency signal received via the GPS antenna 36 is processed by the GSP receiver 30. More specifically, the radio frequency signal is amplified by the LNA 31, mixed by the mixer 32 with the signal provided by the local oscillator 35 for down-conversion to the baseband, and a variable gain attenuator. It is attenuated with the gain currently set by 33 and processed in a conventional manner in the converters and DSP processing block 34. The processes in the converters and DSP processing block 34 may, for example, determine and track the C / A code in the signal, decode the navigation information contained in the tracked signal, and determine the current location of the mobile station 22. Positioning calculations.

The signals to be transmitted by the GSM transceiver 40 to the base station in the scope of mobile communication are processed by the GSM transmitter chain to be transmitted in a conventional manner. The signal is provided to the first variable power amplifier 42 by converters and DSP processing block 41, which amplifies the signal with the currently set amplification factor. To up-convert to a radio frequency signal having a carrier frequency in the range 1710-1785 Mz, the amplified signal is mixed with the signal provided by the local oscillator 45 by the mixer 43. The radio frequency signal is further amplified by the second variable power amplifier 44 with the currently set amplification factor. The amplification factors are set by the AGC at the request of the base station of the communication network to which the mobile station 22 is connected. The signal output by the second variable power amplifier 44 is transmitted through the GSM antenna 46, causing wideband noise in the GPS band of 1575.42 MHz +/- 5 MHz. This broadband noise is added to any satellite signal that reaches the GPS antenna 36.

In a similar manner, the other mobile station 21 generates and transmits radio frequency signals for mobile communication, thereby causing wideband noise in the GPS band of 1575.42 MHz +/- 5 MHz, which is the GPS of the mobile station 22. Equally added to any satellite signal arriving at antenna 36.

The performance of the GPS receiver 30 of the mobile station 22 may be degraded by the wideband noise generated by the other transceiver 21 or the GSM transceiver 40 of the mobile station 22.

The possible evolution of wideband noise reaching the GPS receiver 30 over time is described in FIG. 4.

4 illustrates an exemplary use of time slots by mobile stations MS1 21 and MS2 22 for transmission and reception. All mobile stations use multislot class 10, i. E. Mobile stations can use three receive timeslots and two transmit timeslots in eight consecutive timeslots. The two mobile stations 21, 22 use different radio frequency channels in the GSM frequency band.

The first row presents the numbering of the time slots in the sequence of nine time slots, slot 1 through slot 8 and slot 9. As shown in the second row, mobile station 21 uses timeslots 2 and 3 for transmission. As shown in the third row, mobile station 21 uses timeslots 5, 6, and 7 for reception. As shown in the fourth row, mobile station 22 uses timeslots 4 and 5 for transmission. As shown in the fifth row, the mobile station 22 uses timeslots 7, 8 and 1 for reception.

Below the sequences of timeslots, the figure illustrates the noise level in the GPS frequency band reaching the GPS antenna 36 of the mobile station 22 over time. As shown, there is only a thermal noise level during the first timeslot, because neither of the mobile stations 21, 22 transmits signals, and therefore none of the mobile stations 21, 22. This is because it does not generate wideband noise in the GPS frequency band. During the second and third timeslots, the noise level increases due to the interference generated by the mobile station 21. The noise level of the GPS receiver 30 depends on the GSM transmit power from the mobile station 21 requested by the base station and antenna isolation from the GPS receiver 30 to the mobile station 21. During the fourth and fifth timeslots, the noise level increases further due to the interference generated by the mobile station 22. The noise level at the GPS receiver 30 now depends on the GSM transmitter power from the mobile station 22 requested by the base station. The interference generated by the mobile station 22 itself may be seen at a higher level than external interferences. After the fifth timeslot, the noise level decreases back to the thermal noise level because none of the mobile stations 21, 22 are transmitting anymore.

Noise levels during the second to fifth timeslots reduce the SNR of the received satellite signals. If the SNR falls below the detection threshold, the reduction of the SNR can degrade the performance of the GPS receiver 30.

To prevent such performance degradation, each attenuation gain applied by the variable gain attenuator 33 of the GPS receiver 30 for received radio frequency signals is continuously adjusted. This adjustment is performed separately for internal and external interferences.

Each time the GSM transceiver 40 of the mobile station 22 transmits signals, the converters and DSP processing block 41 of the GSM transceiver 40 vary according to the power level requested by the base station to which the mobile station 22 is currently connected. Set the amplification factors used by the power amplifiers 42, 44. Moreover, the transducers and the DSP block 41 provide the transducers of the GPS receiver 30 and the DSP processing block 34 with information about the power level used, respectively. If GPS reception is switched on, the transducers of the GPS receiver 30 and the DSP processing block 34 adjust the gain of the variable gain attenuator 33 based on the received information. The attenuation actually applied in dBs can thereby be related to its interference level and known antenna isolation input by it.

More specifically, the higher the gain of the variable gain attenuator 32 is set, the higher the power level used by the GSM transceiver 40 for transmitting signals. Thereby, in the case of a low noise level, stronger satellite signals with sufficiently high SNR despite the noise reaching the GPS receiver 30 can still be evaluated, because at point A of the GPS receiver 30 This is because the power level of the attenuated composite signal is still high enough for the evaluation. At the same time, weaker satellite signals arriving at the GPS receiver 30 with an SNR that is too low to detect due to noise will not be evaluated, because the attenuated composite signal at point A of the GPS receiver 30 will not be evaluated. Because it will have a power level too low.

In order for the GPS receiver 30 to attenuate the received signals in any case at the right time, the information about the power level used is sent to the GSM transceiver 40 with the correct or extra timing information at each transmission time. Provided by

Signal attenuation received by the GPS receiver due to external interferences will be described below with reference to the flowchart of FIG. 5.

When GPS reception is switched on, interference presence analysis is performed in the transducers of the GPS receiver 30 and the DSP processing block 34.

For interference presence analysis, the converters and DSP processing block 34 first determine which timeslot has the maximum SNR in the received GPS signals, and as the reference signal level, which power level of the corresponding signal is used. do. When the power level of the signal arriving at the converters and DSP processing block 34 exceeds this reference signal level, it is assumed that there is external interference in the corresponding timeslots. Elevated noise levels due to transmission by the GSM transceiver 40 of the mobile station 22 are not detected because the received signal is attenuated by the variable gain attenuator 33 during this transmission as described above. Because.

When the presence of interference is detected, the next timing pattern is selected by the converters and the DSP processing block 34 based on the correct timing information received from the converters and the DSP processing block 41 of the GSM transceiver 40. do. Accurate timing, including timing advance, can be considered in interference cancellation because all interfering mobile stations 21 can be connected to the same base station. In addition, the timing advance can be assumed to be the same because the interfering mobile station 21 must be adjacent to the device 22.

For example, in GSM, the received signal and the transmitted signal timings are related to each other. The transmit and receive start timings are linked so that the RX and TX slots have the same start time without the TX timing advantage. If the exact receive slot start time is known, the possible transmission times are also known because of the known shift in the possible start time.

Thus, as shown in FIG. 5, if GSM transceiver 40 is active, either GSM reception or GSM reception and transmission are active. If only GSM reception is active, the converters and DSP processing block 41 determine the transmission timing based on the timing of the received slots, and inform the converters and DSP processing block 34 of the determined transmission timing. In addition, the level of the received signals is known to the transducers and the DSP processing block 34. If GSM reception and transmission is active, converters and DSP processing block 41 determines transmission timing based on either timing of received slots or transmission slot timing, and converters and DSP processing block 34. Inform the determined transmission timing. In addition, the transmit power and the received signal level are known to the converters and the DSP processing block 34.

In converters and DSP processing blocks 34, the detected interference times are compared with possible slot assignments. Because of the correct timing information received, the converters and DSP processing block 34 know the exact location of the time slots, and predicted interference may occur during the timeslots. Thus, the timing pattern corresponds to a sequence of specific timeslots, during which time the interference is predicted with the correct time of timeslots as used in the GSM system. In addition, the interference level is determined based on the received GPS signals, the indicated level of the received GSM signals, and the transmit power of the GSM transceiver 40.

When an optimal matching timing pattern is found, the current interference strength is processed to determine the corresponding gain value. The gain is more specifically determined by repeating the SNR of the received GPS signal, which is reduced with increasing interference levels. Similarly, in the case of internal interference, the higher the gain of the variable gain attenuator 33 is selected, the lower the SNR of the received signal. Based on the timing pattern and the determined gain, the GPS receiver 30 is operated. That is, the gain of the variable gain attenuator 33 is accurately set by the converters and the DSP processing block 34 to a value determined for the exact time of the timeslots identified by the timing pattern. In the middle, the gain is set to zero or a value selected to cancel internal interference. Until GPS reception is switched off again, the gain is always adjusted by the transducers and the DSP processing block 34 in a loop to correspond to the current interference strength.

The process according to the invention can be performed by software implemented in the existing DSP of the converters and DSP processing block 34, for example. The processing may be integrated into existing GPS AGC functionality within this block 34 or outside this block 34. The gain determined in accordance with the invention as described above is combined with a gain selected based on other criteria. The processing according to the invention can also be performed by dedicated components outside of the GPS receiver chain. Moreover, some of the processing steps may also be considered by the GSM transceiver 40, ie the converters and the DSP processing block 41. In particular, recognition of current interference and determination of timing patterns can be performed by the GSM transceiver 40. Only the selected timing pattern can be provided to the GPS receiver to adjust the gain according to each interference intensity at the correct timing.

In summary, the exact timing of the noise can be provided by the GSM transceiver 40, since only certain transmission times are allowed in the GSM system, and information about the exact timing received from the GSM transceiver 40 can be obtained. In consideration the DSP of the GPS receiver 30 is used to optimize the determination of the onset time of the noise.

The attenuation results according to the invention are shown in FIGS. 6a and 6b.

Both figures describe signal levels in dBm of a GPS signal received by GPS receiver 30 over time. The variation in signal level corresponds to the variation in the interference intensity shown in FIG. 4. In addition, a reception threshold for a GPS signal in dBm is shown. Only when the signal level of the received GPS signal is above this threshold can the signal be detected. In FIG. 6A, the signals are always above the threshold, so GPS information can always be detected regardless of interferences. In FIG. 6B, the signal level more particularly lies below the threshold during timeslots 4 and 5, during which high internal interference exists. During these timeslots, the signal cannot be detected.

Moreover, both figures show the power level of noise in the GPS signal received at point A of the GPS receiver 30 of FIG. 3 over time when the attenuation according to the invention is applied by the variable gain attenuator 33. It explains.

Accurately timing attenuation reduces the noise level up to the thermal noise level. At the same time, attenuation reduces the power level of the GPS signal. If the power level of the signal is high enough, only the GSP signal arriving at the converters and the DSP processing block 34 can be evaluated. Because of the attenuation with an adjustable gain, whenever the signal level of the signal falls below the detection threshold, the power level of the signal reaching the converters and the DSP processing block 34 will not be high enough for evaluation. Thus, in the case of FIG. 6A, no GPS information is lost. In the case of FIG. 6B, the GPS signal cannot be evaluated during two timeslots where the signal cannot be detected because of the low GPS signal level. Thus, the GPS signal cannot be detected in as few cases as possible.

In an alternative to the presented approach, it is possible to approximate the timing for cancellation from the measurement results. The accuracy of the time at which the rise in the noise level is detected is related in this case to the ratio of noise measurements. In GSM transmissions, the transmission timeslot has only a period of 0.577 ms. Thus, the noise level generated by the GSM transmission cannot be accurately detected, for example with a measurement rate of every 1 ms. As a result, interference cancellation may not work properly, that is, interference cancellation starts too late and ends too late. This means that sometimes noise constantly interrupts the operation of the GPS receiver, and sometimes a good signal cannot be evaluated. Thus, GPS performance is also unstable. In the case of an external GSM transceiver using single slot TX mode, the resulting degradation exceeds 0.6 dB due to incorrect timing. In order to obtain accurate timing of interference cancellation with this method, the repetition rate of the noise measurement must be 10 times higher than the rate of transmission timeslots in the communication system. The high repetition rate of these measurements will significantly increase current consumption. Moreover, such a high repetition rate of measurements will take up a lot of processing time and thus degrade the performance of the satellite positioning system.

With the proposed mobile station, the timing of GSM bursts can be known very accurately at about several milliseconds, without requiring high rate measurements. When GSM noise attenuation is performed with this exact timing, the current GPS AGC can also be maintained and the GPS degradation is minimal compared to the absence of interferences.

When the correct timing is known, in the worst case a theoretical degradation of 1.2 dB can occur with two slot GSM transmissions. This worst case is given when external interference always causes too much noise in the GPS frequency band during each of the two timeslots, so that when the SNR of the received GPS signal is always below the detection threshold during these timeslots. If the interference level is low enough, the performance degradation approaches 0 dB.

A similar implementation as presented above for a device comprising a GSM transceiver and a GPS receiver can be used for a device that includes a DVB-T receiver instead of a GPS receiver.

7 is a time scale representation of problems with a DVB-T receiver with GSM bursts.

In the upper half of FIG. 7, the occurrence of two GSM transmission bursts 71 is shown over time. Each burst 71 has a period of 577 ms. With one slot TX mode, bursts 71 of a particular GSM transceiver occur once per GSM frame. The GSM frame contains eight timeslots and thus has a period of 8 * 577 ms = 4616 ms.

In the lower half of FIG. 7, DVB-T received symbols 72 are shown over time. Each symbol 72 has a period of 896 kHz.

The wideband noise generated by the GSM burst 71 overlaps with the DVB-T receive bits 72 and slips through the bit stream from one burst 71 to the next burst. The hatched box 73 shows which portion of each DVB-T receive bit 72 has been damaged by the GSM transmission. For the second butts 71, an overlay time of 76 ms is represented.

When a DVB-T receiver is used instead of a GPS receiver in the mobile station of Fig. 3, the DVB-T receiver detects noise similar to interference with a periodic pattern. The GSM transceiver reports the possible transmission times to the DVB-T receiver, and the received signals are only detected by the DVB-T receiver while there is no external interference. The times at which received signals can be detected can be seen from the timing pattern determined as described above with reference to FIG. 5.

If the DVB-T receiver knows the exact time when bursts 71 of the GSM transmission would impair its reception, then the DVB-T receiver may ignore that portion of the received bit 72 respectively. Nevertheless, it can obtain the correct information from the remaining intact bit 72 because the bit detection is performed by integrating the input signal shape and then comparing the integration result with a threshold. . Thus, as long as the SNR ratio is high enough, bit detection will work even when the entire bit cannot be integrated. If the degraded bits 72 are completely ignored, then the probability of correctly receiving zero bits is 50.8% and the probability of correctly receiving all second bits is 49.2%. It is not possible to correctly receive all the bits.

It should be noted that the described embodiments provide only one of the various possible embodiments of the present invention.

Claims (34)

A communication system transceiver for exchanging signals over an air interface in a first frequency band; A receiver for receiving signals via an air interface in a second frequency band; A processing unit configured to detect the presence of interference signals in the second frequency band; A processing unit configured to determine a timing pattern for detected interference signals based on the timing information provided by the communication system transceiver, the timing information indicating a timing for transmission used by the communication system transceiver; And Manipulation of signals arriving at the receiver during time intervals defined by a determined timing pattern to reduce performance degradation due to interfering signals from a transmitter using timing for transmission, such as the communication system transceiver of the device. Apparatus comprising a; processing unit configured to effect. The processor of claim 1, wherein the processing unit is configured to recognize the presence of interference signals in the second frequency band. And form part of the communication system transceiver. The processor of claim 1, wherein the processing unit is configured to recognize the presence of interference signals in the second frequency band. Forming part of the receiver. 4. A receiver as claimed in any preceding claim wherein the receiver is An attenuation element; wherein the processing portion is configured to cause manipulation of the signals arriving at the receiver, the attenuation element being applied by the attenuation element based on the timing pattern to attenuate the signals received by the receiver. By means of which the operation is effected. 5. The processing unit of claim 4, wherein the processing unit is configured to cause manipulation of signals arriving at the receiver. And the higher the intensity of the detected interference signals, the higher the attenuation is set. 4. The processing unit according to any one of claims 1 to 3, wherein the processing unit is configured to cause manipulation of signals arriving at the receiver. And cause the manipulation by causing blocking of reception of signals based on the timing pattern. 4. The processing unit according to any one of claims 1 to 3, wherein the processing unit is configured to cause manipulation of signals arriving at the receiver. And cause the operation by disregarding the signals in evaluating the signals based on the timing pattern. 4. The processing unit according to any one of claims 1 to 3, wherein the processing unit is configured to cause manipulation of signals arriving at the receiver. And detuning the second frequency range, thereby effecting the manipulation. The device according to claim 1, wherein the device is A signal arriving at the receiver at time intervals at which the communication system transceiver of the device transmits signals with at least some power level, so as to reduce performance degradation due to interference signals coming from the communication system transceiver of the device. And a processing unit configured to effect manipulation of the device. 4. A receiver as claimed in any preceding claim wherein the receiver is And a satellite positioning system receiver. 4. A receiver as claimed in any preceding claim wherein the receiver is Device characterized in that the DVB-T (Digital Video Broadcast-Terrestrial) receiver. A method for improving the performance of a receiver coupled to a single device with a communication system transceiver for exchanging signals over an air interface in a first frequency band, and receiving signals over the air interface in a second frequency band. silver Detecting the presence of interfering signals in the second frequency band; Determining a timing pattern for detected interference signals based on timing information indicative of timing for transmission used by the communication system transceiver; And In order to reduce performance degradation due to interference signals coming from the transmitter using timing for transmission, such as the communication system transceiver of the apparatus, signals arriving at the receiver during the time intervals defined by the timing pattern. Operating; method comprising the. The method of claim 12, wherein the method is A signal arriving at the receiver during time intervals in which the communication system transceiver of the device transmits signals with at least some power level, in order to reduce performance degradation due to interference signals coming from the communication system transceiver of the device. Manipulating them. The method of claim 12 or 13, wherein the signals arriving at the receiver are And by applying attenuation to the signals received by the receiver. The method of claim 14, The higher the intensity of the detected interference signals, the greater the attenuation applied to the signals arriving at the receiver. 13. The apparatus of claim 12, wherein the signals arriving at the receiver are Operating by blocking reception by the receiver. 13. The apparatus of claim 12, wherein the signals arriving at the receiver are Manipulated by being ignored in evaluating signals at the receiver. 13. The apparatus of claim 12, wherein the signals arriving at the receiver are Operating by detuning a second frequency range. A processing section configured to detect the presence of interfering signals in a second frequency band, wherein the second frequency band is used by a receiver to receive signals over the air interface while the first frequency band exchanges signals over the air interface. A processing unit, used by the communication system transceiver; A processing unit configured to determine a timing pattern for the detected interference signals based on timing information provided by the communication system transceiver, wherein the timing information indicates timing for transmissions employed by the communication system transceiver. part; And Of the signals arriving at the receiver during the time intervals defined by the determined timing pattern to reduce functional degradation due to interference signals originating from the transmitter employing a unified timing for transmission with the communication system transceiver of the apparatus. And a processing unit configured to effect an operation. The method of claim 19, And wherein said processing portion configured to detect the presence of interfering signals in said second frequency band forms part of said communications system transceiver. The method of claim 19, And said processing portion configured to detect the presence of interfering signals in said second frequency band forms part of said receiver. The method according to any one of claims 19 to 21, The processing unit configured to cause manipulation of the signals arriving at the receiver causes the manipulation by changing the attenuation applied by the attenuation element of the receiver based on the timing pattern for the attenuation signals received by the receiver. And the device is configured to. The method of claim 22, And said processing unit configured to cause manipulation of signals arriving at said receiver is configured to set said attenuation higher as the intensity of detected interference signals is higher. The method according to any one of claims 19 to 21, And said processing portion configured to cause manipulation of the signals arriving at the receiver is configured to cause the manipulation by causing blocking of reception of the signals based on the timing pattern. The method according to any one of claims 19 to 21, And said processing portion configured to cause manipulation of the signals arriving at the receiver, causing the manipulation by disregarding the signals in evaluating the signals based on the timing pattern. 22. The processing unit as claimed in any of claims 19 to 21, wherein the processing unit configured to effect manipulation of the signals arriving at the receiver is configured to effect the manipulation by detuning a second frequency range. Device characterized in that. 22. The device of any of claims 19-21, wherein the device is A signal arriving at the receiver at time intervals at which the communication system transceiver of the device transmits signals with at least some power level, so as to reduce performance degradation due to interference signals coming from the communication system transceiver of the device. And a processing unit configured to effect manipulation of the device. A computer program code coupled to a single device with a communication system transceiver for exchanging signals over a wireless interface in a first frequency band, and storing computer program code for improving the performance of a receiver receiving signals over the wireless interface in a second frequency band. In a computer-readable recording medium, The computer program code, Determining a timing pattern for interfering signals detected in the second frequency band based on timing information indicating timing for transmission used by the communication system transceiver; And In order to reduce performance degradation due to interference signals coming from the transmitter using timing for transmission, such as the communication system transceiver of the apparatus, signals arriving at the receiver during the time intervals defined by the timing pattern. And a step of manipulating the computer-readable recording medium. The computer program code of claim 28, wherein the computer program code comprises: A signal arriving at the receiver during time intervals in which the communication system transceiver of the device transmits signals with at least some power level, in order to reduce performance degradation due to interference signals coming from the communication system transceiver of the device. Manipulating the data; computer-readable recording medium further comprises. The method of claim 28 or 29, Signals arriving at the receiver And attenuate the signals received by the receiver. The method of claim 30, And the greater the intensity of the detected interference signals, the greater the attenuation applied to the signals arriving at the receiver. 29. The system of claim 28, wherein the signals arriving at the receiver are Computer-readable recording medium operated by blocking reception by the receiver. 29. The system of claim 28, wherein the signals arriving at the receiver are Computer-readable recording medium which is manipulated by being ignored in evaluating signals at the receiver. 29. The system of claim 28, wherein the signals arriving at the receiver are A computer-readable recording medium operable by detuning a second frequency range.

Images