WO2008057014A1

WO2008057014A1 - Delay control using transmission diversity

Info

Publication number: WO2008057014A1
Application number: PCT/SE2006/001271
Authority: WO
Inventors: Dan Anders Lindqvist
Original assignee: Telefonaktiebolaget LM Ericsson AB
Current assignee: Telefonaktiebolaget LM Ericsson AB
Priority date: 2006-11-08
Filing date: 2006-11-08
Publication date: 2008-05-15
Anticipated expiration: 2009-05-08

Abstract

A transceiver device (110), a device (210) for receiving and transmitting electromagnetic signals in a wireless communication network, a method for minimising the delay between signals sent on at least one first and second transmission path in a wireless communication system and a wireless telecommunication infrastructure (100) are described, where the transceiver device (110) for a wireless communication system (100) comprises at least one first transmission path (212) and at least one second transmission path (214), where at least one of the transmission paths further comprises a transmission delay adjusting element (114), where each of the at least one first and second transmission paths (212, 214) further comprising a transmitter (116, 118) for sending a signal to an antenna system, characterised in that the transceiver device (110) is further arranged to receive an error signal indicative of the delay in arrival time between the signals sent on the at least one first and second transmission paths and where the delay adjusting element is adapted to adjust the time delay for a signal on the at least one first transmission path based on the error signal received.

Description

Delay control using transmission diversity

TECHNICAL FIELD

The present invention is related to wireless communication systems using transmission diversity.

BACKGROUND OF THE INVENTION

As wireless communication networks evolve to ever increasing data rates in order to meet user demands new technologies are developed to support this increase. One such technology for enhancing data rates and improving the signal-to-noise ratio for the received signals is transmission diversity.

Transmission diversity basically entails sending the same signal over two or more antennas (usually two), where the antennas are spaced apart from each other. Diversity may be achieved in the frequency-, angle-, time- and space domains or in two or more domains simultaneously. For example, transmission diversity in the time domain may be achieved by sending a signal from a first antenna and thereafter sending the same signal from a second antenna with a predefined time delay. As another example, transmission diversity in the space domain is achieved by spacing apart the antennas from which the same signal is to be transmitted a certain length which may correspond to a fraction of the wavelength of the signal to be transmitted.

In wireless communication systems, such as third generation wireless communication systems, of which the UMTS (Universal Mobile Telecommunication Service) is one example, both space and time transmission diversity methods are used.

However, in order to achieve efficiency, a minimum transmission delay in the time domain between the signals sent from the at least two antennas is required.

Usually, the required minimum delay is determined by calibration or calculation of the delay through the entire transmit chain, i.e. from the Radio Base Station (RBS) all the way to the antenna system. Such a system is schematically illustrated in Fig. 1. Time calibration for the signal may be carried out using several methods, such as by means of separate calibration equipment or calibration systems incorporated into the RBS. Experience has shown that in order to achieve maximum performance in terms of maximum achievable data-rate and signal-to-noise ratio the delay in each transmit chain may be calibrated for a minimum time difference of 30-60 ns. In other words, if the time delay for the first transmission chain is t1 , then the time delay for the second transmission chain may by way of example be t2 = t1+/- 30-60 ns. It should be pointed out that the above delay values are example values and may differ from one application field to another. However, in each such application field there is an optimum time difference for which there is a signal gain achieved and outside of which the signal is attenuated instead.

Presently built-in delay calibration systems are used, where the delay for the transmission chain is calculated manually. Manual input of the delay for the entire antenna system may however be prone to typing errors and wrongly stated values. Especially in cases with co- located base station equipment, where external filters, such as Diplex filters used for separation of 3G from 2G signals are used on feeding lines to the antennas, the above types of errors are likely to occur. One example of such a system according to known technology is schematically presented in Fig. 2. The correct determination of the delay in co-located systems becomes even more complicated when only one such diplex filter is located on one feeder branch of the antenna system, while the other branch carries either 2G or 3G signals.

One other aspect of the delay determination for an antenna system is that such delays may vary over time due to temperature variation in components along the transmission line. Also the ageing of the signal generating component in the transmitter may alter the initial delay in one or both branches may affect the delay balance. The characteristics of the above diplex filter may also be altered due to ageing. Yet another aspect is that replacing one or several components in the antenna system or in the signal generation parts will need recalibration of the system and thus measurements which originally were correct, may be misleading.

The object of the invention is to overcome at least some of the issues with known technology described above. SUMMARY OF THE INVENTION

This object is achieved by a transceiver device for a wireless communication system comprising at least one first transmission path and at least one second transmission path, at least one of the transmission paths further comprising a transmission delay adjusting element, each of the at least one first and second transmission paths further comprising a transmitter for sending a signal to an antenna system, where the transceiver device is characterised in that it is further arranged to receive an error signal indicative of the time delay between the signals sent on the at least one first and second transmission paths and where the delay adjusting element is adapted to adjust the time delay for the signal on the at least one first transmission path based on the error signal received.

The advantage of the automatic and adaptive nature of the adjustment of transmission delay leads to a more accurate and effective calculation of the transmission delay for the signal transmitted and also to a more robust system.

In one embodiment of the present invention the transceiver device may further comprise a signal generator for generating a test signal in both of the at least one first and second transmission paths. Although not absolutely necessary, using a test signal would have the advantage to be able to select a signal which is easily generated and where the transmission delay between the test signals is easily determined. Such a test signal may for instance be a sine wave or some other suitable signal.

However, instead of using a signal generator for determining the time delay for the signals on the at least one first and second transmission line, one may use the data signal itself.

In yet one other embodiment of the present invention, the transceiver device may comprise coupling elements for coupling the test signal into both of the at least one first and second transmission paths. These coupling elements may, for example be switches for directing the test signal into both of the at least one first and second transmission paths

Even though not absolutely necessary, the coupling elements may be operated synchronously to direct the signal into the at least one first and second transmission path. This may be done at system start-up or some other appropriate time. In one other embodiment of the present invention, the signal generator may also be provided as external to the transceiver device described above.

According to another embodiment of the present invention, the transceiver device may comprise a feedback loop for receiving the delay signal.

According to another aspect of the present invention, a device for receiving and transmitting electromagnetic signals in a wireless communication network is provided, where the device further comprises at least two transceivers for sending and receiving electromagnetic signals, the device being further arranged to receive signals on at least one first and second transmission path, characterised in that the device for receiving and transmitting electromagnetic signals further comprises a time difference meter for measuring a delay time being the arrival difference between the signals received on the at least one first and second transmission path.

In one embodiment of the device for receiving and transmitting electromagnetic signals the device may further comprise a signal amplifier for amplifying the signals received on the at least one first and second transmission path.

In one other embodiment, the signal amplifier may comprise the time difference meter. However, the difference meter may equally be located externally in relation to the signal amplifier.

The signal amplifier described above may also comprise an interface for sending an error signal indicative of the measured delay between the signals received on the at least one first and second transmission paths to a control device. One possibility is to use an O&M- type (Operation & Maintenance) interface. However the error signal may also be sent directly sent to a control device without using the O&M-interface.

According to another embodiment of the present invention, the signal amplifier may comprise a device for capturing a portion of the signals received on the at least one first and second transmission paths and for directing this portion to the time difference meter. An advantage of the device for capturing a portion of the signals is that the time delay measurement for the two signals received may be performed on actual data signals with no disturbance to data traffic. The signal amplifier may further comprise at least one filter for filtering out signals received on the at least one first and second transmission paths not used in the time difference meter. One example where it would be advantageous to use such a filter is in so called co-located systems, such as for example a combination of a GSM- and a 3G- system. In this fashion, if one is interested in achieving optimum diversity for 3G-signals, the filters filter out disturbances from GSM signals corrupting time delay measurements for the two signals received.

According to yet another embodiment of the device for receiving and transmitting electromagnetic signals according to the present invention the time difference meter may comprise an arrangement for receiving a portion of the signals received on the at least one first and second transmission paths. One example of such a time difference meter may be a hybrid combiner for combining a received portion of the transmitted signals and for generating a relative error signal indicative of the delay between the received portions of the signals. Using a hybrid combiner has the advantage of easily being able to determine magnitude of the phase delay between the two signals received when the signals are treated in the analog domain. Thus, in the case when both received signals are in phase, the hybrid combiner may output a "zero" level signal on one of its outputs.

If one is interested both in the sign of the phase delay (+/- delay thus) and to be able to deal with signals in the digital domain, one may use a pulse shape and a phase detector, where the pulse shaper may alter the shape of the received signal portions and the phase detector would detect the relative phase of the thus shaped signal portions. Here, the phase detector may be digital or analogue.

According to yet another aspect of the present invention the object of the invention is solved by a method for minimising the delay between signals sent on at least one first and second transmission path in a wireless communication system, where the method comprises the steps of:

a) sending a signal on the at least one first and second transmission paths; b) delaying further transmission of the signal on at least one of the transmission paths c) receiving the signals sent on the at least one first and second transmission paths, the method being characterised by the further steps of: d) receiving an error signal indicative of the difference in arrival time for the signals sent on the first and second transmission paths e) adjusting the transmission delay for the signal on at least one of the transmission paths based on the error signal.

Of course, the signal referred to in step a) of the method according to the present invention may be either a data signal or a test signal.

According to one embodiment of the method according to the present invention the above method steps may further comprise the steps of a1) generating the test signal a2) synchronously coupling the test signal into the at least one first and second transmission paths c1) determining the difference in arrival time between the test signals received on the at least one first and second transmission paths.

As already mentioned earlier, using a test signal would give a wider choice of signals suitable for delaying and for measuring the delay in arrival time, such as for example sine signals and other suitable signals. By inputting the signal synchronously into the at least one first and second transmission line would also give a much better control of the instant when the signal is launched.

According to one other embodiment of the method according to the present invention the method may be further characterised in that the step of adjusting the transmission delay in at least one of the at least one first and second transmission paths is performed so as to minimise the error signal indicative of the difference in arrival times for the signals sent on the first and second transmission paths to a predefined value range.

The transmission delay according to experience may for example be located in the range of 10-90 ns, more preferably in the range of 20-80 ns and even more preferably in the range of 30-60 ns. It has been shown in certain fields of application that transmission delays in these ranges in certain application fields give a signal gain at a diversity receiver, while outside this range the signal gain achieved through transmission diversity decreases and even turns into signal loss. According to a third aspect of the present invention, the object of the invention is achieved by a telecommunication infrastructure comprising a transceiver for communication in a communication system comprising at least one first transmission path and at least one second transmission path, one of the transmission paths further comprising a delay adjusting element, each of the at least one first and second transmission paths further comprising a transmitter for sending a signal to an antenna system, the antenna system further comprising at least two antennas for sending and receiving of electromagnetic signals, the antenna system being further arranged to receive signals on the at least one first and second transmission paths, where the antenna system further comprises a time difference meter for measuring the delay in arrival time between the signals received on the at least one first and second transmission path and in that the wireless transceiver device is further arranged to receive an error signal from the device for receiving and transmitting electromagnetic signals, the error signal being indicative of the delay in arrival time between the signals sent on the at least one first and second transmission paths and where the delay adjusting element is adapted to adjust the delay for a signal on one or both of the at least one first and second transmission paths based on the error signal received.

SHORT DESCRIPTION OF THE DRAWINGS

Fig. 1 shows a schematical view of a Radio Base Station system and an antenna system according to known technology.

Fig. 2 shows another schematical view of a Radio Base Station and antenna system according to known technology.

Fig. 3 gives a schematical view of a Radio Base Station and antenna system according to the present invention.

Fig. 4 illustrates a principal diagram of a Dual Tower Mounted Amplifier (DTMA) according to one embodiment of the present invention.

Fig. 5 illustrates an embodiment of a Time Difference Meter according to the present invention. Fig. 6 illustrates another embodiment of a Time Difference Meter according to the present invention,

Fig. 7 illustrates a flow chart of a method according to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention will be more readily understood from the following description and references to relevant figures. It should be mentioned here that that reference numbers for the same components will retain their reference numbers in all drawings where the component is to be found.

Fig. 1 shows schematically a view of a part of a wireless communication network 100 according to known technology consisting of a Radio Base Station (RBS) 110 and an antenna system 210. In this presentation of the RBS₁ the receiving part of the RBS is not taken into consideration. It may also be worth mentioning that Fig. 1 only illustrates one transmission sector of the RBS 110, whereas the RBS in effect comprises many such transmission sectors. The RBS in Fig. 1 comprises baseband processing circuitry 112 for transforming an RF signal down to baseband, two transmitters 116 and 118 transmitting the same signal on two different transmission lines, where the first transmitter 116 receives a signal from the baseband processing circuitry 112 which is time adjusted

(+ or -) by the circuit 114 in relation to the signal received by the second transmitter 118.

Thus the first signal on its way from the base processing circuitry 112, the transmission line, the delay adjustment circuit 114, the first transmitter 116 and the first feeder 212 will arrive at the first antenna 213 after a time ti depicted as reference number 216 in Fig. 1. At the same time, the same signal traveling from the base processing circuitry 112, the transmission line, the second transmitter 118 and the second feeder 214 will arrive at the second antenna 215 after a time t₂ depicted as reference number 218 in Fig. 1.

Usually, in co-located antenna systems, i.e. in systems where both GSM and UMTS signals are sent over the same antenna, external filters are used to separate the two types of signals by filtering out wideband noise and spurious signals from the frequency band of the other signal. In such a scenario, calculated delay times for the entire delay chain described above are no longer accurate. The two signals with different arrival times t-i 216 and X₂ 218 sent out from the first and second antennas 213, 215 in order to achieve transmission diversity and thus improved signal-to-noise ratio at the receiver are thereafter sent to the mobile station or UE 350.

Fig. 2 illustrates a co-located antenna system according to known technology. The antenna system 210 in Fig. 2 is equipped with diplex filters 222, 224 and Tower Mounted Amplifiers (TMAs) 242, 244. A connection to the other system, which, for example, may be a GSM system, is indicated by the lines 226 and 228. Otherwise, the RBS 110 is identical with the one depicted in Fig. 1.

However, using the diplex filters on the feeder introduces additional delay to the signal which is to be fed to the respective antenna. Therefore, the delay on the feeder lines to the antennas has to be dealt separately. Hence, the total delay chain for a signal to be transmitted may be divided into an internal delay 120 caused by delays in the RBS and an external delay 220 caused by the feeder lines 212, 214 and the two diplex filters 222 and 224. Manual collection of delay values for the total delay of the delay chain will in this case be prone to errors, since the many components in the propagation path of the signal make it difficult to obtain exact values for the delay of the transmitted signal It also quite common that only one of the feeder lines 212, 214 comprises a diplex filter 222, 224, which makes the determination of the total delay between the two feeder lines 212, 214 even more difficult.

Fig. 3 describes a part of a wireless communication system according to one embodiment of the present invention. In order to be able to control the delay of the signal sent through the delay chain, a test pattern generator 115 generates a signal, which, for example may be a sine-shaped signal, and sends the signal into both transmission lines 122, 124, whereafter the signal is sent through the transmission line 122 with a delay adjustment circuit 114 and towards the first transmitter 116, whereas the same signal pattern is sent on the other transmission line 124 towards the second transmitter 118. Naturally, the test pattern generator 115 may produce any other test signal which is easy to generate.

The function of the delay adjustment circuit 114 is to delay the further transmission of the signal in order to achieve two identical but somewhat time-delayed signals in the two transmission lines. Examples of delay adjustment circuits are PLL (Phase-Locked-Loop) and DLLs (Delay Locked Loop) circuits (not shown), but the delay may equally be achieved by more simple circuits, such as two inverters in series (not shown) where the delay is regulated by the variation of the control voltage to the inverters or in some other suitable way. The delay circuit can also be also be implemented directly in the baseband processing parts 112 by adjusting the phase in one of the digital modulators.

The switches 113 and 117 shown in Fig. 3 are used to direct the signal produced by the test pattern generator 115 to the first and second transmission lines 122 and 124, respectively. Normally, when the test pattern generator 115 is switched on, both switches 113, 177 will be turned on in order to direct the test signal to the first and second transmission lines 122 and 124. However, the switches may also be turned on at any desired moment in time. Especially when using solid-state switches the turning on or off of the switches is easy to perform in a way known in the art. They may be operated synchronously or asynchronously, as preferred. In case they are turned on asynchronously it would however be advantageous if the time difference between turning on one switch and the other were well defined.

The antenna system 210 according to the first embodiment of the present invention comprises a Dual Tower Mounted Amplifier (DTMA) 230 for amplifying the received antenna signal to be transmitted where the DTMA 230 also comprises a Time Difference Meter 290 for measuring the time difference between the test signal pattern launched on both feeder lines 212 and 214 as close as possible to the first and second antennas 213 and 215.

The measured delay is then sent via the feedback line 300 back to the RBS 110 and used to control the delay adjustment circuit 114 in the first branch of the RBS. Although the Time Difference Meter 290 may be located anywhere along the transmission lines 212 and 214, it would be advantageous if it is located as close to the antennas 213, 215 as possible. In this fashion essentially all delays in the signal propagation path from the RBS 110 to the antennas 213 and 215 will be accounted for.

Also the TDM 290 may be located outside the DTMA 230 as preferred.

Turning now to Fig. 4 a schematical view of a DTMA 230 is presented. Its main function in known technology is to act as an amplifier and filter for signals received from the antennas 213 and 215 which are to be sent over the air interface (not shown) and signals received at the antennas 213 and 215 received via the air interface. In this example, a test signal produced by the test pattern generator 115 in figure 3 will eventually arrive at the DTMA 230 via the first and second transmission lines 212 and 214, where one of the signals (in this case the signal on the first transmission line 212) will arrive time delayed in relation to the signal on the second transmission line 214.

Both signals pass through the duplex filters 240 and 241 (the delayed signal) and 243 and 242, where the uplink signals are separated from downlink signals, Next, the two filtered signals pass through the diplex filters 281 and 282 where the 3G signals are separated from 2G signals for the abovementioned reasons. Thus, in this example, after the uplink/downlink and 3G/2G filtering process essentially only the test signal is left. Using the couplers 271 and 272 a portion of both signals is extracted and directed to the TDM 250 in order to determine the delay in arrival time for the two signals. Basically, any means for coupling a portion of the filtered signals may be used, such as 3dB-couplers, circulators or the like. Equally possible is the use of switches, where the two signals are directed to the TDM 250 in their entirety. This may be used when a test signal is used to calculate the difference in arrival time for the two signals in the TDM 250. However, using couplers would provide for the use of the determination of arrival time delay for the two signals also in cases where a data signal is used instead of only a test signal.

Since the DTMA 230 is also used to amplify signals received via the air interface at the antennas 213 and 215, these signals are filtered by the duplex filters 240, 241 and 242,

243 and amplified by the amplifiers 231 and 232 before they are sent further to a radio base station, such as the RBS 110 illustrated in Fig. 1 for baseband processing. The receiving branch of the RBS 110 in Fig. 1 however is not shown.

This process may be implemented according to a method illustrated by the flow chart in Fig. 4

After the determination of the delay in arrival time in the TDM (Time Difference Meter) 250, the error signal is sent to an O&M (Operation & Maintenance) interface 260 which produces a control signal related to the error signal and forwards it via the feedback line 300 to the RBS 110. It may be mentioned here, that the feedback line may be a completely separate feedback line or a control link for exchange of control signals between the antenna system 210 and the RBS 110.

The TDM (Time Difference Meter) 250 may be realized in several different ways of which two examples are given in Fig. 5 and Fig. 6 Fig. 5 shows a schematic illustration of a TDM 250 realized as a hybrid combiner. After the extraction of a portion the received test signals on the transmission lines 212 and 214 by the couplers 271 and 272, the two signals, illustrated as sine-like signals, arrive at the input ports 251 and 252 of the hybrid combiner 255. The hybrid combiner 255 produces a sum signal at its output port 253 with essentially the double amplitude of the original signals at the input ports 251 and 252 if both signals are in phase. On its other output port 254, the hybrid combiner 255 produces a difference signal, i.e. an error signal, which, in the case that both signals on the input ports 251 and 252 are in phase is essentially zero. In the case the error signal is non-zero, i.e. there is some delay in arrival time for the two signals this error signal is forwarded via the output port 254 to the O&M-interface 260 illustrated in Fig. 4 earlier.

In the example in Fig. 5, the TDM 250 was realized exclusively by analog components.

Also, the TDM 250 in Fig. 5 will produce only signals with positive sign, i.e. one may obtain the information on the magnitude of the delay between the signals on the input ports 251 and 252.

Another example of a TDM 250 is given in Fig. 6

Here, the hybrid combiner 255 from Fig. 5 is replaced by a pulse shaper 258 followed by a phase detector 259. The error signal produced at the output 254 of the phase detector 259 will be a signed error signal. Thus in addition to determining the magnitude of the delay in arrival time for the signals at the input ports 251 and 252 of the pulse shaper, the sign of the delay may be obtained.

Also, the pulse shaper 258 may convert the sine signals received to digital signals and the phase detector 259 may also be either analog or digital, depending on the application desired.

Now, a method implementing the present invention will be described with reference to the flow chart in Fig. 7.

At step 400, the test pattern generator 115 is started and a test signal, such as a sine signal or some other easily produced test signal is generated. In the next step, 410, the switches 113 and 117 are turned on synchronously in order to direct the generated test signal to the first and second transmission lines 122 and 124. At step 420 the further transmission of the test signal on the transmission line 122 is delayed in the delay adjustment circuit 114 before it is sent further to the transmitter 116, while the same test signal on the transmission line 124 is sent to the transmitter 118 without delay.

At step 430, both signals are further transmitted on the transmission lines 212 and 214 to the antenna system 210.

Next, at step 440, a portion of the signals sent on transmission lines 212 and 214 is extracted in the DTMA (Dual Tower Mounted Amplifier) 230 and directed towards the TDM (Time Difference Meter) 250.

At step 450, the delay in arrival time of the two signals is determined in the TDM 250 and an error signal is produced indicative of the delay.

At the next step, 460, the error signal is sent to an O&M-interface 260 which sends the signal via the feedback line 300 to the RBS 110.

Thereafter, at step 470, the error signal received via the feedback line 300 is used to adjust the delay for the test signal in the first transmission line 113 in order to minimize the delay in arrival time detected by the TDM 250.

At step 480 it is checked whether the delay in arrival time for the test signals received on the first and second transmission lines 212 and 214 and measured in the TDM 250 has been minimized to the required value interval. If the delay has been minimized, it is checked at step 490 whether it was the last branch of the RBS 110 where the delay in arrival time for the two test signals received on the transmission lines 212 and 214 has been minimized. In case it was not the last branch, the delay adjustment process jumps at step 5000 to the next branch of the RBS 110 where the whole procedure is repeated from step 400 again. If it was the last branch of the RBS 110 the delay adjustment process is terminated at 510.

Finally, it may be remarked that the embodiments of the present invention are described for illustrative purposes only and should not be construed as limitations of the present invention. A person skilled in the art will realize with the help of the description and the accompanying drawings that many other embodiment and modifications of the present invention within the scope of the accompanying claims are possible.

Claims

1. A transceiver device (110) for a wireless communication system (100) comprising at least one first transmission path (212) and at least one second transmission path (214) , at least one of said transmission paths further comprising a transmission delay adjusting element (114), each of the at least one first and second transmission paths (212, 214) further comprising a transmitter (116, 118) for sending a signal to an antenna system,

characterised in that

the transceiver device (110) is further arranged to receive an error signal indicative of the delay in arrival time between the signals sent on the at least one first and second transmission paths (212, 214) and where the delay adjusting element is adapted to adjust the time delay for a signal on the at least one first transmission path based on the error signal received.

2. A transceiver device according to claim 1 ,

characterised in that

the transceiver device further comprises a signal generator (115) for generating a test signal in both of the at least one first and second transmission paths (113, 117).

3. A transceiver device according to claim 1

characterised in that ■

the transceiver device is connected to a signal generator (115) for generating a test signal in both of the at least one first and second transmission paths (112,

124), the signal generator being external to the transceiver device (110).

4. A transceiver device according to claims 2 or 3,

characterised in that said transceiver device comprises coupling elements (113, 117) for coupling said test signal into both of the at least one first and second transmission paths.

5. A transceiver device according to claim 4,

characterised in that

said coupling elements comprise switches for directing said test signal into both of the at least one first and second transmission paths.

6. A transceiver device according to claims 4 or 5,

characterised in that

said coupling elements are operated synchronously.

7. A transceiver device according to one of the preceding claims 4-6,

characterised in that

said coupling elements (113, 117) are arranged to couple said test signal at startup of the transceiver device (110).

8. A transceiver device according to one of the preceding claims 1-6

characterised in that

said transceiver device comprises a feedback loop for receiving said delay signal.

9. A device (210) for receiving and transmitting electromagnetic signals in a wireless communication network comprising at least two transceivers (213, 215) for sending and receiving electromagnetic signals, said device being further arranged to receive signals on at least one first and second transmission path (212, 214) characterised in that

said device (210) for receiving and transmitting electromagnetic signals further comprises a time difference meter (250) for determining a delay being the difference in arrival time between said signals received on said at least one first and second transmission path.

10. A device according to claim 9,

characterised in that

said at least two transceivers comprise antennas.

11. A device according to claim 9

characterised in that

said device further comprises a signal amplifier (230) for amplifying said signals received on said at least one first and second transmission path.

12. A device according to claim 11

characterised in that

said signal amplifier comprises said time difference meter.

13. A device according to claims 11 or 12

characterised in that

said signal amplifier further comprises an interface (260) for sending an error signal indicative of said delay determined between said signals received on the at least one first and second transmission paths to a control device.

14. A device according to claim 13

characterised in that

said interface for sending said error signal is an O&M (Operation & Maintenance) interface.

15. A device according one of the preceding claims 11 to 14

characterised in that

said signal amplifier comprises at least one device (271 , 272) for capturing a portion of said signals received on said at least one first and second transmission paths and for directing said portion to said time difference meter.

16. A device according to one of the preceding claims 11 to 15

characterised in that

said signal amplifier further comprises a filter (240, 241 , 242, 243) for filtering out signals received on said at least one first and second transmission paths not used in said time difference meter.

17. A device according to one of the preceding claims 9 to 16

characterised in that

said time difference meter comprises an arrangement for receiving a portion of said signals received on said at least one first and second transmission paths.

18. A device according to one of the preceding claims 9 to 16

characterised in that

said time difference meter further comprises a hybrid combiner (255) for combining said received portion of said signals and for generating said error signal indicative of the delay between the received portions of said signals.

19. A device according to one claim 18

characterised in that

said hybrid combiner is arranged to output a "zero" level signal on one of its outputs when both of the received portions of said signals are in phase.

20. A device according to one of the preceding claims 9 to 17

characterised in that

said time difference meter further comprises a pulse shaper (258) for altering the shape of the received signal portions and a phase detector (259) for detecting the relative phase of the thus pulse shaped signal portions.

21. A device according to claim 20

characterised in that

said phase detector is an analogue or digital phase detector.

22. A device according to one of the claims 9-21

characterized in that

said time difference meter is located outside of said device (210).

23. A method for minimising the delay between signals sent on at least one first and second transmission path in a wireless communication system comprising:

a) sending a signal on the at least one first and second transmission paths; b) delaying further transmission of said signal on at least one of said transmission paths c) receiving said signals sent on said at least one first and second transmission paths

characterised by

d) receiving a signal indicative of the difference in arrival time for the signals sent on the first and second transmission paths

e) adjusting the transmission delay for said signal on at least one of said transmission paths based on the signal indicative of the difference in arrival times for the signals sent on the first and second transmission paths.

24. A method according to claim 22

characterised by that

said signal sent in step a) is a data signal.

25. A method according to claim 22

characterised by that

said signal sent in step a) is a test signal.

26. A method according to claim 24

characterised by the further steps of:

a1) generating said test signal a2) synchronously coupling said test signal into the at least one first and second transmission paths c1) determining the difference in arrival time between said test signals received on said at least one first and second transmission paths.

27. A method according to one of the preceding claims 22 to 25

characterised in that said step of adjusting the transmission delay in at least one of said at least one first and second transmission paths is performed so as to minimise said signal indicative of the difference in arrival times for the signals sent on the first and second transmission paths to a predefined value range.

28. A method according to claim 26

wherein the value range for delay between the signals in the at least one first and second transmission paths is located in the range of 10-90 ns, more preferably in the range of 20-80 ns and even more preferably in the range of 30-60 ns.

29. A wireless telecommunication infrastructure comprising a wireless transceiver (110) for communication in a wireless communication system comprising at least one first transmission path and at least one second transmission path (122, 124), one of said transmission paths further comprising a delay adjusting element (114), each of the at least one first and second transmission paths further comprising a transmitter (116, 118) for sending a signal to an antenna system (210), said antenna system further comprising at least two antennas (213, 215) for sending and receiving of electromagnetic signals, said antenna system (210) being further arranged to receive signals on the at least one first and second transmission paths

characterised in that

said antenna system further comprises a time difference meter (250) for measuring the delay in arrival time between said signals received on said at least one first and second transmission path and in that said wireless transceiver device (110) is further arranged to receive an error signal from said antenna system (210), said error signal being indicative of the delay in arrival time between the signals sent on the at least one first and second transmission paths (212, 214) and where said delay adjusting element (114) is adapted to adjust the transmission delay for a signal on one error signal received.