Adaptive power control and mobile station for use in a cellular communications network

ES 2 329 048 T3

DESCRIPTION

Mobile station for use in a cellular communication network.

This invention relates to a mobile station for use in a cellular communication network using spread spectrum modulation where a base station transmits spread spectrum signals that are received by the mobile station and the mobile station includes a transmitter and an associated antenna. to transmit spread spectrum signals to the base station, the mobile station including an adaptive power control.

A spread spectrum signal is typically generated by modulating an information data signal with a chip code signal. The information data signal can come from a data device such as a computer, or an analog device that outputs an analog signal that has been digitized to an information data signal, such as voice or video. The chip code signal is generated by a chip code where the time duration, TC, of ​​each chip is substantially less than a data bit or data symbol.

Spread spectrum provides a means for communication where a spread spectrum signal occupies a bandwidth in excess of the minimum bandwidth necessary to send the same information. Band extension is performed using a chip code that is independent of an information data signal. Chip code synchronized reception in a receiver is used for de-spreading of the spread spectrum signal and subsequent data recovery from the spread spectrum signal.

Spread spectrum modulation offers many advantages as a communications system for an office or urban environment. These advantages include reducing intentional and unintentional interference, combating multipath problems, and providing multiple access to a communication system shared by multiple users. Commercially, these applications include, but are not limited to, local area networks for computers and private communications networks for the telephone, as well as other data applications.

A cellular communication network that uses spread spectrum modulation to communicate between a base station and a plurality of users requires control of the power level of a particular mobile user station. Within a particular cell, a mobile station near the base station of the cell may be required to transmit at a lower power level than when the mobile station is near an outer perimeter of the cell. This is done to ensure a constant power level at the base station, received from each mobile station. A representative power level control system adapted to address the power control requirements within a particular cell is that discussed in a scientific paper by RF. Ormondroyd entitled, "Power Control for Spread-Spectrum Systems" pages 109-115 of the Proceedings of the Equipment and Systems Communications Conference, held April 20-22, 1982 in Birmingham, UK The Ormondroyd system is a closed-loop system that requires feedback, that is, the power level of a mobile unit transmission is measured at the base station and, sensitive to this measurement, the base station directs an increase or decrease in the transmitting power of the mobile unit. To implement such a system in an interference environment, a frequency hopping can be employed, as taught in an article by Munday and Pinches, entitled "Jaguar-V Frequency-Hopping Radio System", IEE Proceedings, Vol. 129, Part F , No. 3 (June 1982).

EP-A-0 392 079 discloses a radio transceiver that includes a control section to adjust a transmit output level higher or lower than a prescribed output level with a tolerance margin, in response to a signal from a circuit level conversion.

In a first geographic region, such as an urban environment, the architecture of the cells within the first geographic region may have small cells that are close to each other, requiring a low power level from each mobile user. In a second geographic region, such as a rural setting, the cellular architecture within the region may have large cells that expand, requiring a relatively high power level from each mobile user. A mobile user moving from a first geographic region to the second geographic region must adjust the power level of his transmitter to meet the requirements of a particular geographic region. Otherwise, if the mobile user travels from a sparsely populated region with few and expanded cells using the relatively higher power level with their spread spectrum transmitter, to a densely populated region with many cells without reducing the power level of their spread spectrum transmitter, your spread spectrum transmitter may cause undesirable interference within the cell in which it is located and / or cells adjacent to it.

An object of the invention is to provide an apparatus and method for automatically and adaptively controlling the power level of a plurality of mobile stations so that the power level received at the base station of each cell is the same for each mobile station.

Another object of the invention is to provide a spread spectrum apparatus and method that allows to operate a spread spectrum transmitter in different geographic regions, where each geographic region has a plurality of cells, and cells within a geographic region may have cells of different transmit power sizes and requirements.

These objects are found in accordance with the present invention, as generally incorporated and described herein, by a mobile station for use in a cellular communication network using spread spectrum modulation comprising the features of Aspect 1.

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Preferred embodiments of the invention are provided in the sub-aspects.

Preferably, each acquisition circuit includes a chip code generator, a band pass filter, and a product device coupled to said chip code generator and said band pass filter.

A first acquisition circuit is coupled to said detector, and a second, different acquisition circuit is coupled to said decoder.

According to another embodiment, said detector and said decoder are coupled to the same acquisition circuit.

Preferably, said decoder includes a data scrambler and said variable gain device includes a variable gain attenuator and / or a variable gain amplifier.

Additional objects and advantages of the invention are set forth in part in the description that follows, and in part are obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention can also be realized and achieved by means of the mediations and combinations particularly indicated in the annexed aspects.

The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate preferred embodiments of the invention, and with the description serve to explain the principles of the invention.

Fig. 1 shows an adaptive power control receiver and transmitter according to the present invention;

Fig. 2 shows an adaptive power control receiver and transmitter according to the present invention;

Fig. 3 shows the relative effect of a plurality of spread spectrum communication users in a cell environment with and without adaptive power control; Y

Fig. 4 is a flow chart of the method of the present invention.

Reference will now be made in detail to the present preferred embodiments of the invention, examples being illustrated in the accompanying drawings, where like reference numerals indicate similar elements throughout the different views.

The present invention assumes that a plurality of mobile stations operate in a cellular communication network using spread spectrum modulation. The cellular communication network has a plurality of geographic regions, with a plurality of cells within a geographic region. The size of cells in a first geographic region may differ from the size of cells in a second geographic region. In a first geographic region such as an urban setting, a cell architecture within the region may have small cells that are close to each other. In a second geographic region such as a rural setting, a cell architecture within the region may have large cells that are expanded.

A mobile station while in the first geographic region may be required to transmit a lower power level than there is while in the second geographic region. This requirement may be due to a decreased range of the mobile station from the base station. Within a particular cell, a mobile station near the cell's base station may be required to transmit at a lower power level than when the mobile station is near an outer perimeter of the cell. This is done to ensure a constant power level at the base station, received from each mobile station.

In the present invention, a base station within a particular cell transmits a generic spread spectrum signal and an APC data signal. The APC data signal can be transmitted with or separated from the generic spread spectrum signal. For example, a spread spectrum signal using a first chip keyword can be considered a first channel having the generic spread spectrum signal, and a spread spectrum signal using a second chip keyword can be considered a channel. secondary. The APC data signal can be transmitted on the same channel, ie the first channel, as the generic spread spectrum signal, or on a secondary channel that is different from the generic spread spectrum signal.

In the exemplary arrangement shown in Fig. 1, an apparatus for adaptive power control of a spread spectrum transmitter is provided. Each mobile station comprises acquisition means, detector means, decoder means, difference means, transmission means, an antenna, and variable gain means. The apparatus, for example, may have the acquisition means incorporated as a first product device 101, a first chip code generator 102, and a band pass filter 103. The detector means may be incorporated as an envelope detector 104 Other types of detectors can be used with the present invention, such as quadratic detectors or coherent detectors, as is well known in the art. The decoder means can be incorporated as a decoder 105. The difference means can be incorporated as a differential amplifier 106, the transmitter means as a transmitter 112 and the variable gain means as

ES 2 329 048 T3 variable gain device 111. Variable gain device 111 can be a variable gain amplifier, variable gain attenuator or any device that performs the same function as variable gain device 111 and described herein.

The first product device 101 is coupled to the first chip code generator 102 and the band pass filter 103. The cladding detector 104 is coupled between the band pass filter 103 and the differential amplifier 106. The decoder 105 is coupled between band pass filter 103 and differential amplifier 106. Decoder 105 may alternatively be coupled to the output of coating detector 104. Variable gain device 111 is coupled to differential amplifier 106 and between transmitter 112 and antenna.

The decoder 105, as illustratively shown in Fig. 2, can be alternatively coupled between a second band pass filter 203 and a differential amplifier 106. In this particular embodiment, the second band pass filter 203 is coupled to a second product device 201. The second product device 201 is connected to a second chip code generator 202. The embodiment of Fig. 2 it could be used where the APC data signal is transmitted on the second channel simultaneously while the generic spread spectrum signal is transmitted on the first channel. The second channel uses a spread spectrum signal with a second chip keyword, and the second chip code generator 203 generates a second chip code signal using the second chip keyword.

Product device 101, Figures 1 or 2, using a first chip code signal from the first chip code generator 102 acquires the generic spread spectrum signal transmitted from the base station. The first chip code signal has the same chip keyword as the generic spread spectrum signal. The coating detector 104 detects a received power level from the generic spread spectrum signal. The received power level can be measured at the detector.

Decoder 105 decodes the APC data signal from the generic spread spectrum signal as a threshold. More particularly, the data that sets or adjusts the threshold for the differential amplifier 106 is sent with the APC data signal.

Differential amplifier 106 generates a comparison signal by comparing the received power level of the generic spread spectrum signal to the threshold. Differential amplifier 106 may employ differential amplifier or other circuitry to perform the comparison function.

Transmitter 112 transmits a spread spectrum signal from the transmitter. The variable gain device 111, using the comparison signal, adjusts a transmitter power level of the transmitter's transmit spread spectrum signal. Variable gain device 111 can be realized with a variable gain amplifier, variable gain attenuator, or equivalent device that can adjust the power level of the spread spectrum signal from the transmitter.

In operation, a base station in a cell can transmit the generic spread spectrum signal on a continuous basis or on a periodic repetitive basis. Mobile stations within the cell receive the generic spread spectrum signal. The received generic spread spectrum signal is acquired and de-spread with the first chip code signal from the first chip code generator 102 and first product device 101. The de-spread generic spread spectrum signal is filtered through bandpass filter 103. The mobile station detects the de-spread generic spread spectrum signal using the cladding detector 104, and measures the received power level of the spectrum signal. generic expanded.

The APC data signal can be transmitted on the same channel as the generic spread spectrum signal using the same chip codeword as the generic spread spectrum signal. In this case, the APC data signal is transmitted at a different time interval than when the generic spread spectrum signal is transmitted. This format allows the mobile station to acquire synchronization with the first chip code, using the generic spread spectrum signal.

As an alternative, the APC data signal can be transmitted on a different scrambled channel using a second chip codeword. In this case, the second spread spectrum signal having the APC data signal would be acquired by the second chip code generator 202 and second product device 201. In either case, the APC data signal is decoded using the decoder 105. Additionally, the APC data signal can be a simultaneous time division or frequency division simultaneously with the generic spread spectrum signal.

Decoder 105 decodes the APC data signal to the threshold value for use by differential amplifier 106. For example, if there were eight levels for which to set the threshold level, then at a minimum, a word of three would have to be used. bits with the APC data signal to transmit the threshold to the mobile station. The threshold is used to adjust and / or set the threshold of the differential amplifier 106. Consequently, the power level received from cladding detector 104 is compared to the threshold from differential amplifier 106.

If the received power level is greater than the threshold, then the variable gain device 111 would decrease or reduce the spread spectrum power level of the transmitter. If the received power level is lower than the

ES 2 329 048 T3 threshold in differential amplifier 106, then variable gain device 111 increases the spread spectrum power of the transmitter.

The APC circuit 110 of Figures 1 and 2 can be built into a digital signal processor chip. An analog-to-digital converter located at the output of the band pass filter 103 converts the received signal into a data signal. The envelope detector 104, decoder 105, and differential amplifier 106 can be implemented as part of the digital signal processing functions on the digital signal processor (DSP) chip. Analog to digital transformers can be included in the DSP chip.

Fig. 3 shows the advantage of using an adaptive power control apparatus with a mobile station in a private communication network. The number of mobile adaptive power control stations, N (APC), against the number of mobile stations that can be used in a similar region, N, is set relative to an internal radius, R₁, and an outer radius R_or. When the internal radius tends to zero, using spread spectrum as a code division multiplex, the number of users with adaptive power control that can operate within a cell is approximately ten times the number of users without adaptive power control that they can work inside the cell.

The present invention also includes a method for automatic power control of a spread spectrum transmitter for a mobile station operating in a cellular communication network using spread spectrum modulation.

Referring to FIG. 4, a base station transmits 701 a generic spread spectrum signal and an APC information data signal. Each mobile base station executes the phases of acquisition 702 of the generic spread spectrum signal transmitted from the base station, and of detection 703 of a received power level of the generic spread spectrum signal. The phases also include decoding 704 of the APC data signal as a threshold, from the generic spread spectrum signal, or from a signal separate from the generic spread spectrum signal. A threshold is set 705 from the APC data signal. The method further includes comparing 706 the received power level with the threshold, and adjusting 707 a transmit power level of a transmit spread spectrum signal in response to the comparison.

It will be apparent to those skilled in the art that various modifications of the method and apparatus can be made to adaptively control a power level of a spread spectrum signal in a cell environment of the present invention without departing from the scope of the invention, and the present invention is intended to cover modifications and variations of the method and apparatus for adaptively controlling a power level of a spread spectrum signal in a cell environment provided they fall within the scope of the appended claims.

References cited in description

This list of references cited by the applicant has been compiled exclusively for the information of the reader. It is not part of the European patent document. It has been made with the greatest diligence; However, the EPO does not assume any responsibility for eventual errors or omissions.

Patent documents cited in the description • EP 0392079 A [0006]

Non-patent bibliography cited in description • RF Ormondroyd Power Control for Spread-Spectrum Systems the Proceedings of the Conference on Communications Equipment and Systems, 1982, 109-115 [0005] • Munday Pinches Jaguar-V Frequency-Hopping Radio System IEE Proceedings , 1982, vol. 129, no. 3. [0005]