SK164596A3 - Repeater for relay station - Google Patents

Abstract

The intermediate amplifier uses a regulated wideband HF amplifier (4) with an amplification factor controlled by a regulation path (6) between the signal path (1) and the control input (5) of the amplifier. The regulation path contains a power measuring circuit (7) for measuring the signal power, a mean value stage (8) and a time delay stage (9), for delaying the regulating signal fed to the amplifier control input.

Description

RELAY STATION

Technical field

The present invention relates to an intermediate amplifier for a relay station for the universal deployment of a transmitted burst of stacked, periodic TDMA signals and possibly permanent carrier signals in radiotelephony networks, in particular for transmitting broadcast signals between mobile stations in shielded vehicles and a base station, with by a controllable, in particular a high-frequency amplifier on the signal path, the amplification of which is regulated along a control path departing from the signal path.

BACKGROUND OF THE INVENTION

To operate mobile stations in shaded areas, such as tunnels, underground railways, shielded vehicles, etc., relay stations (Repeater) are deployed that receive frequency channels transmitted in the open area and transmit them to the shaded areas and vice versa. On the one hand, systems with multiple narrowband inter-amplifiers are used that carry a certain number of preset frequency channels, and on the other hand, other systems with broadband amplifiers that carry all available channels. The systems of the first type are particularly suitable for stationary relay stations, in which the frequencies of the surrounding base stations are known, so that only their channels or channels must be transmitted to the screened space. only assigned response channels from the shielded area shall be transmitted to the open area. In one variant of the first system, narrowband amplifiers are set to the desired channels based on channel sampling, which is correspondingly expensive.

Connecting mobile shaded space, e.g. A rail carriage with metallized windows, at an affordable cost, can only be realized by systems of the second kind, since the channel environment of the mobile space is unknown and constantly changing.

There is a problem that in certain radiotelephony network systems, e.g. GSM network (global system for mobile communication), several calls are transmitted on one channel in a sequence of assigned time gaps, which contain one transmitted group of pulses. The resulting signal is referred to as a TDMA signal (time division multiple access signal). Since the transmit power of the different mobile stations is generally different and in addition not all time gaps are always occupied, the TDMA signal has a strongly fluctuating power over time. To avoid over-regulation of the inter-amplifier in the relay station, the inter-amplifier should be sized to a correspondingly wide band of dynamics, i. extremely high output power, which in practice is not viable or is provided with an automatic gain amplifier control that evaluates the signal power on the signal path (e.g. US 5,095,528, EP 114,066, GB 2,257,874).

The gain control must have sufficient bandwidth to be able to quickly monitor the variation in the power of the TDMA signal, so that the front of the transmitted pulse group is eliminated. However, the high bandwidth of the control path (e.g.,> 200 kHz) has the side effect that low-frequency mixing of the signals of the simultaneously transmitting mobile stations directly affects the gain control. For example, if two mobile stations whose carrier frequencies are 100 kHz apart are simultaneously transmitting, the inter-amplifier signal will be modulated with 100 kHz jitter along the control path.

If only TDMA system mobile stations are operated in the shaded space, it is very rare due to the time distribution of the transmitted group of pulses of individual mobile stations that two mobile stations simultaneously transmit with closely adjacent frequencies. However, if mobile stations with a permanent carrier signal are operated in the space, this is the case e.g. in ETACS (D-network), the probability of occurrence of this effect is significantly higher.

SUMMARY OF THE INVENTION The present invention aims to provide an intermediate amplifier for a relay station which enables cost-effective transmission of both TDMA signals and the persistent carrier signals occurring in the radiotelephone network at an economically acceptable cost.

SUMMARY OF THE INVENTION

This object is achieved by an inter-amplifier of the kind mentioned in the introduction, in which the control path comprises, in sequence, a power measuring device for determining the signal path signal power, an averaging means for generating a time signal mean value and storing the mean value over time a pulse group or an integer part of the last, as well as a delay member for a control signal whose delay time corresponds to the period of the TDMA signal or its integer multiple reduced by said time.

In this way, the frequency of the TDMA signal is utilized. Power measurement by generating the mean value of the transmitted pulse group cleared of interfering components is used as a starting value for setting the next transmitted pulse group of the same mobile station. When the next transmitted pulse group is set, the control may be instantaneous, i. ideally fast. Control is performed by pulse groups if the mean value is generated over the entire pulse group transmitted and applied to the next transmitted pulse group shifted by the delay time or even in the proportions of the integer parts of the transmitted pulse group.

A further significant benefit of the invention is that the output signal of the power measuring device is supplied to a signal front detector which synchronizes the start of the average of the averaging to the rising face of the output signal of the power measuring device. In this way, the accuracy of the regulation can be further increased.

It is particularly preferred that the averaging adds discrete sampled values, and upon detecting the ascending signal front, the signal head detector replaces the previous sampled value for the averaging with the current sampled value and synchronizes the start of the mean value generation with the previous sampled value. As a result, the growing pulse group from its signal front is evaluated by a higher power to the previous transmitted pulse group, so that the gain control of the inter-amplifier adjusts it suppressively (i.e., at the first deployment of the transmitted pulse group after delay).

A further preferred embodiment of the invention is that the output signal of the power measuring device is provided to a logic control unit that continuously monitors a particular mobile station associated with the transmitted pulse group and, from omitting the pulse group, provides a control signal for the preset number of consecutive pulse groups. corresponding to the last assigned pulse group. This is justified by the fact that the newer TDMA standards during speech breaks omit the transmitted pulse groups and only at larger intervals require the transmission of a pulse group equipped with special standby information.

This is particularly advantageous if, according to a further feature of the invention, the output signal of the power measuring device is supplied to a logic control unit which detects TDMA signal statistics from the measured power signal, e.g. the periodicity and the number of transmitted pulse groups per period, and adapts to this the mean and intermediate storage time and / or the delay time of the delay member. In this way, the inter-amplifier can cooperate with any radiotelephone network of different TDMA signal standards.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be explained in more detail on the basis of the exemplary embodiments shown in the drawings. In the drawings, FIG. 1 is a block diagram of a first embodiment of an intermediate amplifier according to the invention, FIG. 2 shows a block diagram of a second embodiment, FIG. 3 shows a time course of the power of an example TDMA signal and FIG. 4 shows the TDMA signal pulse group of FIG. 3 in an enlarged view.

DETAILED DESCRIPTION OF THE INVENTION

In FIG. 1 shows a simple embodiment of an intermediate amplifier according to the invention. The inter-amplifier has a signal path 7 between input 2 and output 3, in which the signal path is a high-frequency amplifier 4.

The amplification of the high-frequency amplifier 4 is regulated by a control signal via a control input 5, which is included in the control path 6. The control path 6 is connected to the signal path 7 by its input and in the example shown in FIG. 1 to a point in front of the high-frequency amplifier 4. On the control path, a power measuring device 7, a specifically illustrated averaging 8, lies in sequence.

Delay member 9.

The description of the principle of operation of the control path 6 is based on FIG. 3, which shows the transmission power time pattern P of the six TDMA system mobile stations, which cyclically transmit on six time slots 0, 1, 2, 3, 4 and 7 of the TDMA system with eight time slots (solid line). Each mobile station periodically transmits a transmitted pulse group 10 of duration T _B , the period being T _P. the transmitted pulse groups 10 together form the TDMA signal 1T The values given in the example for the real TDMA signal are T _P = 60/13 ms (~ 4.6 ms) and T _B = 7500/13 ps («577 ps).

Additionally, FIG. 3 shows the waveforms of two other mobile stations (dashed lines) that transmit with the continuous carrier signal 12. (not shown) the overlay signal of the pulse group 10 and the continuous carrier signal 12 is measured by the power measuring device 7 and output. In practice, a plurality of TDMA signals 11 comprised of the transmitted pulse group 10 may overlap on different channels together with the continuous carrier signal 12 of the different frequency channels.

The aim of the regulation of the high-frequency amplifier 4 is to reduce the dynamic range on the signal path in order to achieve optimal regulation of the high-frequency amplifier 4 over time, i.e. in the transmitted group of high power pulses, the gain of the high-frequency amplifier 4 is reduced and vice versa.

In order to ensure a rapid response to step changes in the power signal of FIG. 3, the control route 6 would have to have an appropriate bandwidth, e.g. over 200 kHz, otherwise the signal faces of the transmitted pulse group could be collided or overregulated.

Due to the narrow channel rasters of both TDMA radiotelephony networks and those with sustained carrier signals (eg 100 kHz, often up to 25 kHz), low-frequency (100 kHz resp.

kHz) mixed signals that would be released at broadband control path 6 and would modulate the amplifier signal. The effect of such a failure on the transmitted pulse groups 10 is shown in the example of FIG. 4. The transmitted group of pulses 10 is modulated by a pulsating signal 13 with a period t _s . (In practice, the amplitude of the interfering signal 13 in relation to the power of the transmitted pulse group W is significantly higher than shown).

In order to eliminate the influence of jamming 13 on the gain control, the averaging carries out the formation of a mean value for t _m . In the example shown in FIG. 4, this is done digitally, with the interval t _m divided into four sampling intervals t a _, and 14 values are sampled in each sampling interval 4, the averaging 8 adds the sampled values 14 in the interval t _m, and provides a mean value for that t _m . Then averaging 8 calculates the mean value for the next interval t _m. For the duration t _m of the mean value calculation, the mean value of the previous interval remains stored and is available at the averaging output 8.

Instead of creating a mean value in a digital way, the same function could be realized analogously. Mean formation could also be accomplished by a low-pass filter to which a sampling and holding member is attached to retain the mean determined for a given interval t _m for the next interval t _m .

Finally, the averaging output signal 8 is delayed in the delay member 9 by a time ΔΤ equal to the difference between the period T _{p of the} TDMA signal and the mean formation interval t _m , ie:

ΔΤ - Tp - dark

Thus, prior to the initiation of the transmitted pulse group 10 for the RF amplifier, an (estimated) control signal is provided, which was determined from the power of the previous, same mobile station associated with the transmitted pulse group 10 (FIG. 3).

The regulation may be the same method used in a TDMA-standards, in which one time slot used alternately by two different mobile stations (half rate channel), when the delay time is set to ΔΤ 2T _L - T _m. In general:

=T = nTp-t _m (n = 1..N)

For the correct function of the control it is necessary that the interval t _m is an integer multiple of the period T _{p of the} transmitted pulse group 10, ie

t _m = Tp / n (n = 1..N)

Without further possibility, the interval t _{m can} be equal to the duration of the transmitted pulse group Tb (n = 1), in which case the control is performed in parts of the duration of the transmitted pulse group. by pulse groups.

For the correct generation of the mean value, it is also necessary that the duration of the sampling interval t _a is an integer part of the interval t _m , ie:

t _a = t _m / n (n = 1..N)

Furthermore, it is: t _a <ts / 2

Thus, for each flicker 13, two sample values are available to produce a mean value.

In FIG. 2 shows an alternative embodiment of the invention, wherein the control path 6 is connected to the output 3 of the signal path 1. This creates a control loop that includes the components of the high-frequency amplifier 4 as well as the connected end amplifier 15 so that its tolerances, temperature drift and Come.

In the embodiment of FIG. 2, a signal front detector is additionally connected to the output of the power measurement device 7. The detector 16 detects the positions of signal rising front of signal 17 (FIG. 4) of the transmitted pulse V sync and determining the start of the interval of the mean t _m averaging 8 to this point. It is not necessary (and indeed impossible for two consecutive pulse groups of equal power) for the signal front detector to recognize the signal front of each transmitted pulse group 10, but this is sufficient when it happens here to perform additional averaging synchronization 8th

With the positions of the detector signal 16 may additionally perform a correction of the form of the mean averaging 8. The detected signal 17 rising front face of the detector signal 16 replaces the sample values 14 'of the previous sampling period t _{and the} sampled value 14 of the current sampling period t _{and the} start of a sync interval of the formation of the mean value t _m to a sampled value of 14 '. This prevents over-regulation of the high-frequency amplifier 4 at the beginning of the transmitted pulse group 10 '.

The embodiment of FIG. 2 further comprises a device which utilizes the property of certain standards of radiotelephony networks, wherein the transmitted pulse group 10 speech pauses are suppressed and only the standby information (DTX, discontinuos transmit) is transmitted with the pulse groups at larger intervals (0.5 s). If the transmitted pulse group is omitted, one TDMA-period delay would set the gain to the max. to the default idle value; a later deployment of the transmitted pulse group of this time gap could lead to over-regulation of the high-frequency amplifier.

To avoid this, a power control unit 7 is connected to a logic control unit 18 which, in the event of a missed pulse group of a particular mobile station being missed, uses the last detected control signal during a preset, at least DTX overlapping time interval. For this purpose, a buffer 19 is provided for the control signal and the logic control unit 20 switches between the memory content and the control signal by means of a switch 20. Alternatively, the intermediate memory 19 and the switch 20 may be wired elsewhere in the block diagram of FIG. 2, for example between the averaging 8 and the delay member 9.

Logic control unit 18 can additionally be programmed to, on the basis of the statistical evaluation of the measured signal power calculated period T _p, the number of transmitted groups of pulses per cycle, duration of the transmission pulse and T b below. and sets the duration of the formation of the mean and medziukladania _TM respectively. delay ΔΤ.

It is clear that the peripheral realization of the present intermediate amplifier can be realized for all species known to those skilled in the art. In particular, a programmable digital signal processor can be used in which the functions of these components are implemented in a known manner as program modules in order to realize the power measuring device 7, the averaging 8, the delay member 9, the signal front detector 16, the logic control unit 18 of the memory 19 and the switch 20. .

Claims (5)

PATENT CLAIMS 1. An inter-amplifier for a relay station for the universal deployment of a pulsating group consisting of intermittent, periodic TDMA signals and, where appropriate, permanent carrier signals in radiotelephone networks, in particular for transmitting broadcast signals between mobile stations in shielded vehicles and a base. a signal path, the gain of which is regulated along a control path departing from the signal path, characterized in that the control path (6) comprises successively a power measuring device (7) for determining the power of the signal path signal (1); formation of the mean power of the signal and medziukladanie mean value over a period (T b, T _m) of transmission of the pulse (10) and an integer portion of the last, and the retarding member (9) for the control signal, the delay (ΔΤ) corresponds to the period (T _p) TDMA-sig nal (11) or an integer multiple thereof, reduced by said time (T _B , tm). Inter-amplifier according to claim 1, characterized in that the output signal of the power measuring device (7) is applied to a signal front detector (16) which synchronizes the start of the averaging (8) to the rising signal front (17). power measuring equipment (7). The inter-amplifier according to claim 1 or 2, characterized in that the averaging device (8) sums the time-discrete sampled values (14) and the signal front detector (16) after detecting the rising signal front (17) of the previous sampled value (14 '). (8) replaces this with the sampled value (14) and synchronizes the start of the mean value interval to the previous sampled value (14 '). Inter-amplifier according to claims 1 to 3, characterized in that the output signal of the power measuring device (7) is supplied to a logic control unit (18) which continuously monitors a particular mobile unit associated with the transmitted pulse groups (10) and omits one group. applying a control signal corresponding to the last assigned transmitted pulse group (10) to a high frequency amplifier (4) for a preset number of the last assigned pulse group (10). Inter-amplifier according to Claims 1 to 4, characterized in that the output signal of the power measuring device (7) is applied to a logic control unit (18), which detects TDMA signal statistics from the power measurement signal, e.g. the period (T _p ) and the number of pulse groups transmitted per period, and the mean and intermediate storage time (T _B1 t _m ) and / or adjusts the delay time (ΔΤ) of the delay member (9).