Dynamic capacity allocation CDMA spread spectrum communications

I claim:

1. A method for dynamically allocating power and capacity of a spread spectrum system having at least one spread-spectrum-base station, with said spread spectrum system overlaying, at least in part, in frequency and in a same geographical area as a radio-relay system, said radio-relay system having at least one relay station within the geographical area, said radio-relay system having a signal with a radio-relay bandwidth, comprising the steps of:

coupling, with a diplexer, the signal received at said relay station to said radio-relay system;

measuring, at said radio-relay system, with a first receiver having a bandpass filter and with the first bandwidth overlapping the radio-relay bandwidth, a first power level within the radio-relay bandwidth of said radio-relay system;

measuring, at said radio-relay system, with a second receiver having a bandpass filter with the second bandwidth not overlapping the radio-relay bandwidth, a second power level outside the radio-relay bandwidth of said radio-relay system;

comparing the first power level to a predetermined threshold;

generating a ratio signal from the first power level and the second power level;

regulating, when the first power level exceeds the predetermined threshold, a power level transmitted from the at least one spread-spectrum-base station located within the geographical region in response to the ratio signal; and

regulating, when the first power level exceeds the predetermined threshold, a number of user units accessing the at least one spread-spectrum-base station.

2. The method as set forth in claim 1 wherein:

the step of measuring the first power level includes the step of detecting the first power level within the radio-relay bandwidth; and

the step of measuring the second power level includes the step of detecting the second power level outside the radio-relay bandwidth.

3. The method as set forth in claim 1 wherein the step of regulating the power level transmitted from the at least one spread-spectrum-base station includes the step of adjusting the power level transmitted from the at least one spread-spectrum-base station.

4. The method as set forth in claim 1 wherein the step of regulating a number of user units includes the step of sending a message signal to a plurality of spread-spectrum users, for indicating when the at least one spread-spectrum-base station is in a power-down mode.

5. The method as set forth in claim 2, further comprising the steps of:

multiplexing the detected first power level and the detected second power level; and

digitizing, using an analog-to-digital converter, the detected first power level and the detected second power level.

6. The method as set forth in claim 2, further comprising the steps of:

digitizing, using a first analog-to-digital converter, the detected first power level; and

digitizing, using a second analog-to-digital converter, the detected second power level.

7. A method for dynamically allocating power and capacity of a spread spectrum system having at least one spread-spectrum-base station, with said spread-spectrum system overlaying, at least in part, in frequency and in a same geographical area as a radio-relay system, said radio-relay system having a signal with a radio-relay bandwidth, comprising the steps of:

measuring a first power level within the radio-relay bandwidth of said radio-relay system;

measuring a second power level outside the bandwidth of said radio-relay system;

comparing the first power level to a predetermined threshold;

generating a ratio signal from the first power level and the second power level; and

regulating, when the first power level exceeds the predetermined threshold, a power level transmitted from the at least one spread-spectrum-base station in response to the ratio signal.

8. The method as set forth in claim 7 wherein:

the step of measuring the first power level includes the step of detecting the first power level within the radio-relay bandwidth; and

the step of measuring the second power level includes the step of detecting the second power level outside the radio-relay bandwidth.

9. The method as set forth in claim 7 wherein the step of regulating the power level transmitted from the at least one spread-spectrum-base station includes the step of adjusting the power level transmitted from the at least one spread-spectrum-base station.

10. The method as set forth in claim 8, further comprising the steps of:

multiplexing the detected first power level and the detected second power level; and

digitizing, using an analog-to-digital converter, the detected first power level and the detected second power level.

11. The method as set forth in claim 8, further comprising the steps of:

digitizing, using a first analog-to-digital converter, the detected first power level; and

digitizing, using a second analog-to-digital converter, the detected second power level.

12. A method for dynamically allocating power and capacity of a spread spectrum system having at least one spread-spectrum-base station, with said spread-spectrum system overlaying, at least in part, in frequency and in a same geographical area as a radio-relay system, said radio-relay system having a signal with a radio-relay bandwidth, comprising the steps of:

measuring a first power level within the radio-relay bandwidth of said radio-relay system;

measuring a second power level outside the bandwidth of said radio-relay system;

comparing the first power level to a predetermined threshold;

generating a ratio signal from the first power level and the second power level; and

regulating, when the first power level exceeds the predetermined threshold, a number of user units accessing the at least one spread-spectrum-base station.

13. The method as set forth in claim 12 wherein:

the step of measuring the first power level includes the step of detecting the first power level within the radio-relay bandwidth; and

the step of measuring the second power level includes the step of detecting the second power level outside the radio-relay bandwidth.

14. The method as set forth in claim 12 wherein the step of regulating a number of user units includes the step of sending a message signal to a plurality of spread-spectrum users, for indicating when the at least one spread-spectrum-base station is in a power-down mode.

15. The method as set forth in claim 13, further comprising the steps of:

multiplexing the detected first power level and the detected second power level; and

digitizing, using an analog-to-digital converter, the detected first power level and the detected second power level.

16. The method as set forth in claim 12, further comprising the steps of:

digitizing, using a first analog-to-digital converter, the detected first power level; and

digitizing, using a second analog-to-digital converter, the detected second power level.

17. A system for dynamically allocating power and capacity of a spread spectrum system having at least one spread-spectrum-base station, with said spread spectrum system overlaying, at least in part, in frequency and in a same geographical area as a radio-relay system, said radio relay system having at least one relay station within the geographical area, said radio-relay system having a signal with a radio-relay bandwidth, comprising:

first means, located near a relay receiver of said radio-relay system, for measuring with a first receiver having a bandwidth approximately equal to the radio-relay bandwidth for transmitting the signal to said radio-relay system, a first power level within the radio-relay bandwidth of said radio-relay system;

second means, located near said relay receiver of said radio-relay system, for measuring with a second receiver having a bandwidth approximately equal the radio-relay bandwidth for transmitting the signal to said radio-relay system, a second power level outside the radio-relay bandwidth of said radio-relay system;

means, located at each relay station, for coupling the signal received at said relay station to at said first measuring means and to said second measuring means;

means for comparing the first power level to a predetermined threshold;

means for generating a ratio signal from the first power level and the second power level; and

first means for regulating, when the first power level exceeds the predetermined threshold, a power level transmitted from the at least one spread-spectrum-base station located within the geographical region in response to the ratio signal; and

second means for regulating, when the first power level exceeds the predetermined threshold, a number of user units accessing the at least one spread-spectrum-base station.

18. The system as set forth in claim 17 wherein said coupling means includes a diplexer for coupling the signal received at said relay station to said first measuring means and to said second measuring means.

19. The system as set forth in claim 18 wherein:

said first measuring means includes a first bandpass filter with a first bandwidth approximately equal to the radio-relay bandwidth and with the first bandwidth overlapping the radio-relay bandwidth; and

said second measuring means includes a second bandpass filter with a second bandwidth approximately equal to the radio-relay bandwidth and with the second bandwidth located near in frequency and not overlapping the radio-relay bandwidth.

20. The system as set forth in claim 19 wherein:

said first measuring means further includes a first detector, coupled to said first bandpass filter, for detecting the first power level within the radio-relay bandwidth; and

said second measuring means further includes a second detector, coupled to said second bandpass filter, for detecting the second power level outside the radio-relay bandwidth.

21. The system as set forth in claim 20, further comprising:

a multiplexer, coupled to the first detector and the second detector, for multiplexing the detected first power level and the detected second power level;

an analog-to-digital converter for digitizing the detected first power level and the detected second power level; and

wherein said comparing means and said generating means are embodied in a processor for comparing the first power level to the predetermined threshold and for generating the ratio signal from the first power level and the second power level.

22. The system as set forth in claim 21 wherein said first regulating means includes a variable gain device, responsive to the ratio signal, for adjusting a power level transmitted from the at least one spread-spectrum-base station.

23. The system as set forth in claim 21 wherein said second regulating means includes a controller, located at the at least one spread-spectrum-base station, the controller responsive to the ratio signal for sending a message signal to a plurality of spread-spectrum users communicating with the at least one spread-spectrum-base station, indicating when the at least one spread-spectrum-base station is in a power-down mode.

24. The system as set forth in claim 20 further comprising:

a first analog-to-digital converter for digitizing the first power level;

a second analog-to-digital converter for digitizing the second power level; and

wherein said comparing means and second generating means are embodied in a processor for comparing the first power level to the predetermined threshold and for generating the ratio signal from the first power level and the second power level.

25. The system as set forth in claim 24 wherein said first regulating means includes a variable gain device, responsive to the ratio signal, for adjusting a power level transmitted from the at least one spread-spectrum-base station.

26. The system as set forth in claim 24 wherein said second regulating means includes a controller, located at the at least one spread-spectrum-base station, the controller responsive to the ratio signal for sending a message signal to a plurality of spread-spectrum users communicating with the at least one spread-spectrum-base station, indicating when the at least one spread-spectrum-base station is in a power-down mode.

27. The system as set forth in claim 18 wherein said first regulating means includes a variable gain device, responsive to the ratio signal, for adjusting a power level transmitted from the at least one spread-spectrum-base station.

28. The system as set forth in claim 18 wherein said second regulating means includes a controller, located at the at least one spread-spectrum-base station, the controller responsive to the ratio signal for sending a message signal to a plurality of spread-spectrum users communicating with the at least one spread-spectrum-base station, indicating when the at least one spread-spectrum-base station is in a power-down mode.

29. A system for dynamically allocating power and capacity of a spread spectrum system having at least one spread-spectrum-base station, with said spread spectrum system overlaying, at least in part, in frequency and in a same geographical area as a radio-relay system, said radio-relay system having a signal with a radio-relay bandwidth, comprising:

first means for measuring a first power level within the radio-relay bandwidth of said radio-relay system;

second means for measuring a second power level outside the radio-relay bandwidth of said radio-relay system;

means for comparing the first power level to a predetermined threshold;

means for generating a ratio signal from the first power level and the second power level; and

means for regulating, when the first power level exceeds the predetermined threshold, a power level transmitted from the at least one spread-spectrum-base station in response to the ratio signal.

30. A system for dynamically allocating power and capacity of a spread spectrum system having at least one spread-spectrum-base station, with said spread spectrum system overlaying, at least in part, in frequency and in a same geographical area as a radio-relay system, said radio-relay system having a signal with a radio-relay bandwidth, comprising:

first means for measuring a first power level within the radio-relay bandwidth of said radio-relay system;

second means for measuring a second power level outside the radio-relay bandwidth of said radio-relay system;

means for comparing the first power level to a predetermined threshold;

means for generating a ratio signal from the first power level and the second power level; and

means for regulating, when the first power level exceeds the predetermined threshold, a number of user units accessing the at least one spread-spectrum-base station.

Description Submit all comments and votes

BACKGROUND OF THE INVENTION

This invention relates to spread spectrum communications, and more particularly to dynamically allocating power and capacity of spread spectrum communications so as to prevent interference to a radio-relay system, such as a microwave relay system, or to a cellular communications system, such as the system conforming to the AMPS or IS54 standards. This disclosure refers to either system as a radio relay system.

DESCRIPTION OF THE RELEVANT ART

Radio-relay systems, such as the fixed service, microwave systems or cellular telephone systems, employing digital transmission systems and/or analog transmission systems, have requirements for interference. In digital transmission systems, some aspects of system interference require a slightly different treatment than traditionally applied to analog systems. In particular, the effect of interference on a victim digital receiver is primarily one of threshold degradation. Threshold degradation of a digital receiver is defined, for the purpose of interference calculations, as the received carrier level that produces a bit error rate (BER) of 10.sup.-6. Threshold degradation for analog systems typically is defined in terms of received signal-to-noise ratio.

Digital systems have the following characteristics:

a) Digital receiver thresholds vary because of differences in bit rate, modulation technique and noise figure.

b) "Normal" received carrier level has little meaning in digital systems because the received carrier level is determined by the fade margin requirements of each hop.

c) Noise degradation criteria are inappropriate because noise and interference lead to bit errors which generally do not result in random noise in voice channels. One might hear an infrequent "click" at the 10.sup.-6 BER.

A parameter, called the threshold-to-interference (T/I) ratio, is defined for digital systems. Threshold-to-interference ratio is defined as the ratio of desired signal to undesired signal that degrades performance from 10.sup.-6 to 10.sup.-5 BER.

The advantage of the T/I ratio is that the difference in thresholds due to bit rate, modulation technique, and noise figure are all taken into account and the absolute level of allowable interference can be easily determined by subtracting the T/I ratio from the threshold of a particular receiver.

Measurement of the T/I ratio for a digital system is accomplished by fading the receiver to the point where a 10.sup.-6 BER is present on the system. Interference is then injected until a BER of 10.sup.-5 is present on the system. The ratio of the relative level of the desired received signal and the interference is then measured and this ratio of relative levels is the T/I ratio.

Sample plots of the required T/I ratio for a typical receiver are shown in FIGS. 1 and 2. FIG. 1 shows the T/I ratio for digital interference and FIG. 2 shows the T/I ratio for FM interference for cochannel and adjacent channel cases. The receiver threshold and T/I ratio for a particular type of digital equipment would normally be supplied by the equipment manufacturer. The T/I ratios referred to in these figures are for a single exposure. Multiple exposures can be calculated through relative power addition. T/I can be converted to the more familiar carrier-to-interference (C/I) ratio if the T/I ratio and fade margin are known:

C/I=T/I+Fade Margin (dB).

For an analog microwave system, the T/I ratio is determined by "fading" the receiver until the output signal-to-noise ratio (SNR) is 30 dB. Interference is then injected until a SNR of 29 dB is present on the system. In either the digital or the analog case, the T/I ratio occurs when the interference is approximately 6 dB below the internal noise level of the receiver.

OBJECTS OF THE INVENTION

A general object of the invention is to allow spread spectrum communications to use the same frequencies and to overlay the same geographical region as a radio-relay system.

Another object of the invention is a system for spread spectrum communications which can be used concurrently with a radio-relay system without interfering with the radio-relay system.

An additional object of the invention is a system for spread spectrum communications which approaches the maximum capacity possible, without interfering with the radio-relay system.

A further object of the invention is a system for spread spectrum communications which allocates overall power level and capacity in response to a dynamically changing communications environment.

SUMMARY OF THE INVENTION

The present invention provides a system and method for dynamically allocating capacity and power of spread spectrum communications overlaying, geographically and in frequency, a radio-relay system. The capacity and power of each cell for spread spectrum communications are allocated so as to prevent interference to the radio-relay system. The radio-relay system has at least one relay station within the geographical area, and the radio-relay system transmits at least one signal with a radio-relay bandwidth. Each relay station has at least one radio-relay transmitter and at least one radio-relay receiver. The radio-relay bandwidth is defined herein as the transmission bandwidth of the signal of the radio-relay system.

The dynamic capacity allocation is performed with a monitoring system placed at a representative sample of, or all, radio-relay receiver sites. The monitoring system is connected, preferably using a dedicated telephone line, to an appropriate spread-spectrum-base station(s). If the monitoring system detects an excess of interference, then the monitoring station immediately notifies the spread-spectrum-base station. In response to this notification, the spread-spectrum-base station does not accept and/or reduces the number of spread-spectrum users allowed to access the spread-spectrum-base station(s). Alternately, the monitoring station can continuously, or at regular intervals e.g. one millisecond, notify the base station(s) regarding the radio-relay receiver's status, and thereby employ prediction techniques to estimate the future status of the radio-relay receiver. In this manner, the capacity of the spread-spectrum-base station(s) is dynamically controlled by the tolerable signal-to-noise ratio or bit error rate of the radio-relay system. By using these techniques, users of the radio-relay system do not experience interference independent of the received, faded signal level of the radio-relay system. Also, users of the spread spectrum communications system are not envisaged as being cut off, since the predictive techniques permit a smooth load shedding.

Accordingly, the present invention, as embodied and broadly described herein, provides a system as well as a method for measuring, using a first radio receiver, a first power level within the radio-relay bandwidth of the radio-relay system. The receiver of the radio-relay system is defined herein as the relay receiver. The first receiver is located near the relay receiver of the radio-relay system, and has a first bandpass filter, respectively, with the first bandpass filter having a first bandwidth, which, by way of example, may be 100 kHz, 1 MHz, or 10 MHz.

The system and method also measure, using a second receiver, a second power level outside the radio-relay bandwidth of the radio-relay system. The second receiver is located near the relay receiver of the radio-relay system, and has a bandpass filter with a second bandwidth, which, by way of example, may be 100 kHz, 1 MHz, or 10 MHz.

The first power level is compared to a predetermined threshold, and, in addition, a ratio signal is generated from the first power level and the second power level. The ratio signal typically represents a ratio of the first power level to the second power level, and indicates the received input C/I ratio. Using the ratio signal and the first power level, a power level transmitted from each spread-spectrum-base station located within the geographical region is regulated and the capacity of the spread spectrum communications is dynamically allocated.

Additional objects and advantages of the invention are set forth in part in the description which 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 also may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

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

FIG. 1 shows a typical threshold-to-interference characteristic for digital interference;

FIG. 2 shows a typical threshold-to-interference characteristic for analog FM interference;

FIG. 3 illustrates a system for spread spectrum communications overlaying geographically a radio-relay system;

FIG. 4 is a block diagram of the dynamic capacity allocated spread spectrum communications;

FIG. 5 is a block diagram of an alternate embodiment of the dynamic capacity allocated spread spectrum communications;

FIG. 6 is a block diagram of a first embodiment of spread-spectrum-base station transmitters;

FIG. 7 is a block diagram of a second embodiment of spread-spectrum-base station transmitters;

FIG. 8 is a block diagram of a spread spectrum processor for a spread-spectrum-unit receiver;

FIG. 9 is a block diagram of a first embodiment of a spread-spectrum-unit transmitter;

FIG. 10 is a block diagram of a second embodiment of a spread-spectrum-unit transmitter;

FIG. 11 is a block diagram of a spread-spectrum-unit receiver;

FIG. 12 is a first embodiment of a spread-spectrum-unit transmitter;

FIG. 13 is a second embodiment of a spread-spectrum-unit transmitter;

FIG. 14 shows the spectrum of a spread spectrum signal with an AM signal of equal power at its carrier frequency;

FIG. 15 shows a spread spectrum data signal when the spread spectrum signal power is equal to an AM signal power;

FIG. 16 shows an audio signal when the spread spectrum signal power is equal to the AM signal power;

FIG. 17 shows a possible pseudo-random sequence generator;

FIG. 18 shows possible position settings of switches of FIG. 17 to form PN sequences; and

FIG. 19 illustrates a geographic architecture for spread spectrum communications according to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Reference is now made in detail to the present preferred embodiments of the invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals indicate like elements throughout the several views.

As illustratively shown in FIG. 3, a spread spectrum geographic architecture is shown, with a multiplicity of microcells each having a spread-spectrum-base station for communicating with a plurality of spread-spectrum users. The spread spectrum communications of the present invention is located within a same geographical region as occupied by at least one radio-relay system, such as a fixed service, microwave system or cellular communications system. Each radio-relay system communicates over a channel, defined herein as a radio-relay channel, which has a radio-relay bandwidth. In presently deployed fixed service microwave systems, the radio-relay bandwidth is 10 MHz or less.

The radio-relay system may be a fixed-service, microwave system, a cellular telephone system, or any other system having pre-assigned channels of radio spectrum. The radio-relay system may employ analog modulation techniques such as amplitude modulation (AM), frequency modulation (FM), or digital modulation techniques such as amplitude-shift-keying (ASK), frequency-shift-keying (FSK), or phase-shift-keying (PSK) modulation. Time division multiple access (TDMA) or frequency division multiple access (FDMA) may also be employed.

In the 1.85-1.99 GHz region, the spectrum is used by a plurality of narrowband users, i.e. narrow in bandwidth relative to the spread spectrum bandwidth, with each microwave user using one of a plurality of radio-relay-microwave channels. A first radio-relay microwave system using a first radio-relay microwave channel is separated in frequency by a guard band from a second radio-relay microwave channel. The first radio-relay microwave system usually is also separated geographically or spatially from the second radio-relay microwave system.

The spread spectrum communications may use code division multiple access (CDMA) with direct sequence (DS) spread spectrum modulation, and includes at least one spread-spectrum-base station and at least one spread-spectrum unit located within the same geographical region as occupied by the radio-relay system such as the fixed service microwave system. The spread spectrum communications also could employ either frequency hopping spread spectrum, narrowband CDMA, or broadband CDMA. The spread spectrum CDMA communications system can be used for communicating data between a plurality of spread-spectrum users. The data may be, but are not limited to, computer data, facsimile data or digitized voice.

A spread-spectrum-base station, which typically is not collocated geographically with a fixed service microwave station, communicates data between a plurality of spread-spectrum users. A first spread-spectrum user uses a first spread-spectrum unit, and a second spread-spectrum user uses a second spread-spectrum unit, etc.

In the exemplary arrangement, illustrated in FIG. 4, the spread spectrum communications of the present invention for dynamically allocating power and capacity of the spread spectrum communications includes first measuring means, second measuring means, comparing means, generating means, regulating means, and informing means. The first measuring means measures a first power level within the radio-relay bandwidth of the radio-relay system. The second measuring means measures a second power level outside the radio-relay bandwidth of the radio-relay system, the comparing means compares the first power level to a predetermined threshold. The generating means generates a ratio signal from the first power level and the second power level. The regulating means regulates a power level transmitted from at least one spread-spectrum-base station in response to the ratio signal when the first power level exceeds the predetermined threshold, with the predetermined threshold being the absolute level of allowable interference of the spread spectrum communications. The spread spectrum communications also includes means for informing mobile spread spectrum units whether:

(1) additional users can be added to a cell;

(2) whether each user must be powered down and by how much; and

(3) which users must be powered off, if necessary.

The first measuring means may be embodied as a first receiver having a first bandpass filter 45 and a first detector 47. The first bandpass filter 45 has a first bandwidth, and the first bandwidth overlaps the radio-relay bandwidth. The first receiver measures a first power level within the radio-relay bandwidth of the radio-relay system, i.e. the first power level is an in-band voltage, which is proportional to the received, desired microwave signal level. The first bandwidth, by way of example, may be 100 kHz, 1 MHz, or 10 MHz.

The second measuring means may be embodied as a second receiver having a second bandpass filter 46 and a second detector 48. The second bandpass filter 47 has a second bandwidth. The second bandwidth is located near in frequency and not overlapping the radio-relay bandwidth. The second bandwidth, by way of example, may be 100 kHz, 1 MHz, or 10 MHz. The second receiver measures a second power level outside the radio-relay bandwidth of the radio-relay system, i.e. the second power level is an out-of-band voltage, which is proportional to the spread spectrum interference level.

The present invention further includes coupling means as well as an antenna 41 and amplifier 42 located at the relay station, coupled, through power splitter 44, to the first bandpass filter 45 and to the second bandpass filter 46, for receiving the signal at a relay station, as shown in FIG. 4. The coupling means may be embodied as a diplexer 43 for coupling the signal received at the relay station by the antenna 41 to bandpass filters 45, 46 respectively.

Alternatively, the coupling means may be a collocated antenna located near antenna 41, or any other device for coupling or receiving the signal received by the radio-relay system.

The present invention may include a multiplexer 49 coupled to first bandpass filter 45 and to second bandpass filter 46 for multiplexing the detected first power level and the detected second power level. In a preferred embodiment, the multiplexer 49 is coupled to first and second bandpass filters 45, 46 through first and second detectors 47, 48, respectively.

An analog-to-digital converter 50 may be employed for digitizing the detected first power level and the detected second power level. A preferred embodiment, as shown in FIG. 4, has the analog-to-digital converter 50 coupled to multiplexer 49.

Another embodiment is shown in FIG. 5, with a first analog-to-digital converter 55 and second analog-to-digital converter 56 for digitizing, respectively, the detected first and second power levels from first detector 47 and second detector 48, respectively.

The comparing means and the generating means may be embodied in a processor 51 for comparing the first power level to the predetermined threshold and for generating the ratio signal from the first power level and the second power level. In a preferred embodiment, the ratio signal represents the ratio of the first power level to the second power level, i.e. the ratio signal represents the ratio of the in-band voltage divided by the out-of-band voltage, i.e. the input signal-to-interference (C/I) ratio. The ratio signal is transmitted, preferably over a dedicated line, to the spread-spectrum-base station(s).

Additionally, as shown in FIGS. 6 and 7, each spread-spectrum-base station 80, 82, 84 includes regulating means, respectively, located at each spread-spectrum-base station for regulating a power level transmitted from a corresponding spread-spectrum-base station located within the geographical region. In a preferred embodiment, as illustrated in FIG. 6, the regulating means of each spread-spectrum-base station, 80, 82, 84, respectively, is embodied as variable gain devices 60, 62, 64, respectively, which respond to the ratio signal from the processor 51 by adjusting a power level transmitted from the spread-spectrum-base station 60, 62, 64, respectively.

In another embodiment of the present invention, the regulating means of each spread-spectrum-base station 80, 82, 84 is embodied as a controller 70, 72, 74, respective