GB2335570A

GB2335570A - Traffic distribution measurement in a mobile radio network

Info

Publication number: GB2335570A
Application number: GB9806012A
Authority: GB
Inventors: Helmut Muehlbauer
Original assignee: Siemens AG
Current assignee: Siemens AG
Priority date: 1998-03-21
Filing date: 1998-03-21
Publication date: 1999-09-22
Also published as: GB9806012D0; WO1999049683A1

Abstract

Monitoring apparatus 3 for determining the distribution of call traffic between mobiles and base stations of a mobile radio network comprises a receiver 5 connected to processor 16. Signals 6 from the uplink or downlink transmissions between the mobile and base station are detected by the receiver and sampled. The distance between the mobile and the receiver is determined by monitoring the propagation delay of signals arriving at the receiver. This information is combined with the sampled data to determine traffic distribution. The monitoring apparatus may be used in accordance with a TDMA system such as GSM or a CDMA system. The data may be used to determine the allocation of channels to base stations.

Description

2335570 1

Description of invention:

Measurement apparatus and method of measuring a distribution 5 of traffic in a mobile radio network The present invention relates to mobile radio telecommunications networks and methods for operating mobile radio telecommunications networks. More particularly, the present invention relates to measurement apparatus which operate to determine an amount and distribution of traffic supported by a mobile radio telephone network. Furthermore the present invention relates to methods of measuring traffic distribution in a mobile radio telephone network.

The term traffic as used herein with reference to mobile radio telecommunications networks refers to a number of calls established with mobile units to the effect of communicating data via the mobile radio telephone network. The term call as is used in the telecommunications art refers to a connection between a transmitting apparatus and a receiving apparatus between which data is communicated. The data may be representative of speech or any other information. As is known to those skilled in the art the traffic in a telecommunications system may be measured in units of Erlangs per km2.

Mobile radio telephone networks serve to provide mobile units with a means for communicating data via radio signals whilst the mobile units move within a radio coverage area provided by the mobile radio network. To this end, mobile radio systems are provided, inter alia, with a plurality of interconnected base stations which form the mobile radio network. Associated with each base-station is a geographical area within which a mobile unit can effect communication of data via radio signals with the base station, in preference to another base station. This geographical area is known as a 2 cell, and together the cells provided by the base stations of the mobile radio network provide a combined radio coverage area to the effect that mobiles may roam within the coverage area whilst enjoying substantially uninterrupted communications.

Mobile radio telephone systems are arranged to provide a plurality of communications channels through which communication with mobiles may be contemporaneously supported. In a system such as the known system the global system for mobiles (GSM), a radio frequency spectrum allocated to the mobile radio svstem is divided into a number of parts in which carrier frequency signals conveying data are transmitted. Furthermore, the GSM system is provided with means to divide the communication of data on each of the radio frequency carrier signals into a number of time slots. By arranging for mobile units to be allocated one of the plurality of time slots within a pre-determined repetitive frame of time slots, a plurality of mobiles may be supported on each of the carrier frequency radio signals provided by the mobile radio system.

An operator of a mobile radio telephone system must take considerable care in planning and deploying base stations of a mobile radio network so that a demand for communications channels at certain points within the mobile radio network satisfied. To this end, the operator of a mobile radio network may increase a number of carrier frequency radio signals allocated to particular base stations within the network, so that these base stations are provided with a greater capacity, to meet the demand for communications channels in an area served by the base stations. Furthermore, the operator of the mobile radio network may increase a number of base stations within a particular area in which a very high traffic demand is expected.

3 Although mobile radio networks are known to measure an amount of traffic served by a particular base station, estimation of traffic within a particular coverage area provided by a mobile radio network is not known. Measuring a traffic distribution within a coverage area of a mobile radio network, represents a technical problem which is addressed by the present invention.

According to the present invention there is provided a measurement apparatus for use in determining a distribution of radio communications traffic within a radio coverage area provided by a mobile radio network, said measurement apparatus comprising a receiver which operates to sample radio signals communicated between mobile units and base stations on communications channels provided by said mobile radio network, and a data processor coupled to said radio receiver which operates to determine distances from which said radio signals were transmitted by said mobile units or said base stations, wherein said data processor further operates to estimate said traffic distribution from said distances in combination with a number of said communications channels on which said radio signals are communicated.

Providing a measurement apparatus with a receiver which operates to sample radio signals communicated between mobile units and base stations of the mobile radio network, and a data processor which operates to determine a distance of the mobile units or base stations from the measurement apparatus from the samples of the radio signals, the measurement apparatus may determine a distribution of traffic within a coverage area provided by the mobile radio network. The traffic distribution may be calculated from the measured distances in combination with a proportion of available communications channels provided by the network which are used for communicating the radio signals, or alternatively a number of calls effected at a certain distance from the measurement apparatus.

4 The measurement apparatus may further include a data store in which predetermined reference distances representative of distances travelled by radio signals are stored, wherein said 5 data processor operates to compare said distances with said pre-determined reference distances in combination with said number of communications channels on which said radio signals are communicated, whereby a distribution of mobile units communicating radio signals in relation to said-pre- determined reference distances is determined.

Advantageously the radio receiver may further include a directional antenna from which radio signals received from coherent beam associated with an antenna of the radio receiver serves to provide information appertaining to an anale of arrival of the radio signals at the receiver. The data processor may further operate to determine a traffic distribution profile from the distance of the mobiles making calls on the mobile radio system in combination with a relative angular displacement of those mobiles with respect to the measurement apparatus.

The radio receiver may further operate to determine a power of the received signal samples. The data processor may operate to determine a distance of the mobiles from the measurement apparatus in accordance with a path-loss determined from the power of the received signal samples in comparison with a pre-determined power with which the signals were transmitted.

The radio receiver may furthermore be provided with means for determining a time of arrival of said radio signals in comparison to a start of a time slot in which said radio signals are transmitted, and in dependence upon a re'Liative delay between said start of said time slot and said radio signals, said data processor may operate to determine a relative distance of said mobiles from said measurement apparatus.

The present invention provides a particular advantage in that by providing a distribution of traffic within a cell area, an operator of a mobile radio network is provided with information from which effective planning of network improvements and enhancements may be made. This may include a redistribution of communications channels between base stations and the installation of further base stations in areas of particularly high traffic distribution. Furthermore, with knowledge of a traffic distribution within a cell, an operator may target a marketing campaign to the effect that low areas of traffic distribution are increased. In particular the present invention provides a high resolution of traffic density determined in accordance with a degree of accuracy with which the distance of the transmitting mobiles may be determined from the measurement apparatus.

The measurement apparatus may be used in macro-, micro or pico-cells. In particular the measurement apparatus may be used in determining a location of micro- and pico-cells within a mobile radio network in which radio coverage is effected with macro-cells.

The radio receiver may sample radio signals transmitted on either the uplink or the down-link.

According to a first aspect of the present invention there is provided a mobile radio network comprising a plurality of base stations and a plurality of mobile units which operate to communicate data via the base stations, and at least one measurement apparatus as herein before described which operates to determine a traffic distribution of said mobile units operating within said mobile radio network and in dependence upon said traffic distribution said mobile radio network operates to allocate communications channels to said 6 base stations, whereby radio communications traffic is supported by said mobile radio network.

According to a second aspect of the present invention there is provided a method of estimating a distribution of radio communications traffic supported by a mobile radio telephone network, said method comprising the steps of; - sampling radio signals communicated between mobile units and base stations on communications channels provided by said mobile radio network; - determining distances from which said radio signals were transmitted by said mobile units or said base stations; and - estimating said traffic distribution from said distances in combination with a number of radio communications channels on which said radio signals are communicated.

According to a third aspect of the present invention there is provided a method of deploying base stations within a mobile radio network, using a measurement apparatus as herein before described in any preceding claim, comprising the steps of; - using said measurement apparatus to determine a traffic distribution at a plurality of positions for each of a plurality of operating frequencies used by surrounding base stations of the mobile radio network; - determining a target location of a base station from said traffic distribution and said plurality of positions, at which location a level of interference generated from the surrounding base stations is at a substantially tolerable level; - deploying said base station at said target location, and - allocating to said deployed base station at least one of said plurality of frequencies for which traffic determined from said traffic distribution is a substantially low level.

One embodiment of the present invention will now be described, by way of example only, with reference to the accompanying drawings, wherein; 7 FIGURE 1 is a schematic block diagram of part of a mobile radio telephone network; FIGURE 2 is a schematic block diagram of a traffic distribution measurement apparatus; FIGURE 3 is is a schematic block diagram of the traffic distribution measurement apparatus shown in figure 2 operating within the mobile radio network shown in figure 1; FIGURE 4 FIGURE 5 is a representation of bursts of radio signals transmitted on a time- division multiple access carrier signal; and is a representation of a traffic measurement scenario associated with a deployed mobile radio telephone system.

An example of a mobile radio network is shown in Figure 1 which provides an illustrative representation of parts which make up a mobile radio network in accordance with the Global System for Mobiles (GSM). In Figure 1 seven base stations BS, are shown to be respectively connected to two base station controllers BSC, which are thereafter connected to an operation and maintenance centre OMC, and a mobile switching centre MSC. The MSC is thereafter connected to a public switch telephone network PSTN. The mobile switching centre MSC, operation and maintenance centre OMC, base station controllers BSC, and base stations BS together form the mobile radio network providing a means for data communication with a plurality of mobile units MU, which roam within a radio coverage area provided by the mobile radio network. Each mobile units MU is arranged to communicate data via radio signals with a base station. A radio coverage area provided by a base station forms a cell 1 the boundaries of 8 which are illustrated by the lines 2. As already explained, a cell is an area in which a mobile unit forms effective radio communications with the base station in preference to any other base station.

Although the illustrative representation of a mobile radio network shown in Figure 1 has regular cells, in practice a size and shape of cells will be determined by the physical environment in which the base stations BS are disposed.

Furthermore, in some applications a base station may form a cell within an enclosed area such as a shopping centre or airport terminal in which the cell will be very much smaller than a cell formed in an open area. Cells formed in an open area are known to those skilled in the art as macro-cells whereas cells formed in a substantial closed area are known as micro-cells. Furthermore, cells formed in rooms or groups of rooms within a building are know as pico-cells.

An operator of a mobile radio network derives incorite by provid.J.n(i radio communications channels to subscribers to the mobile radio system. In return for payment at a certain tariff the subscribers are provided with a facility for making calls from mobile radio telephones within a coverage area provided by the mobile radio network. The tariff determines the rate of charging calls per unit of time for which a radio communications channel is occupied. If subscribers are unable to make a call as a result of all the radio communications channels being occupied by other subscribers, the operator will lose revenue. Therefore, lt is highly desirable that the operator is provided with accurate information associated with a distribution of radio communications traffic within the coverage area provided by the radio communications network.

The distribution and movement of traffic within a radio coverage area is determined substantially by a natural congregation of mobile subscribers at points of attraction 9 such as shopping centres and airport terminals. However, the congregation of mobile subscribers within a mobile radio network is difficult to predict and may vary with time. Furthermore known methods of assessing traffic generated by mobile subscriber units are associated only with traffic supported by particular base stations.

A traffic measurement apparatus which operates to measure mobile radio telephone traffic within a particular radio coverage area, such as a cell, is shown in Figure 2. In Figure 2, the traffic measurement apparatus 3, is shown to comprise two antennas 4, 40, forming part of a receiver 5, which operates to detect radio signals 6. The radio signals are combined by a beam forming processor 42. The receiver 5, further comprises a band-pass filter 8 and a low-noise amplifier and splitter 10. The detected radio signals are fed to the splitter 10, via the band-pass filter 8. The splitter 10, operates under control of a data processor 16 to select signals transmitted on one of n different carrier frequency signals and to feed the selected signals to an amplifier and intermediate frequency filter 12. The amplifier and intermediate frequency filter 12, operates to amplify the signals received on the selected carrier frequency and to convert these signals to an intermediate frequency at which they can be sampled. The intermediate frequency signals are fed to a sampling measurement unit 14, which operates to measure a pre-determined set of parameters associated with the received radio frequency signals. These parameters are, for example, the power of the received signal in decibels, and may further include a measurement of time with respect to a temporal reference 15, at which the radio signals were received. The amplifier and intermediate frequency unit 12, and the sampling measurement unit 14, are controlled by the data processor 16, to which they are connected. Coupled to the data processor 16 is a data store 17, and a position indicator 19, which may operate in accordance with the Global Positioning System, to provide the data processor 16, with data appertaining to the position at which the measurement apparatus 3, sampled the radio signals. Also coupled to the data processor 16, of the measurement apparatus 3, is a personal computer 18.

The traffic distribution measurement apparatus shown in Figure 2 operates to determine a location and density of radio communications traffic within a cell of a mobile radio network. The operation of the traffic distribution measurement apparatus will now be described with reference to Figure 3 where parts also appearing in Figures 1 and 2 bear identical numerical designations.

In Figure 3, the measurement apparatus 3 is shown to be disposed within a cell served by a base station BS. Within the cell a mobile unit 20, is communicating via the base station BS. In this example embodiment the mobile unit 20, is transmitting with a power PMS. A radio signal with which the mobile unit MU is communicating with the base station BS is 0 illustrated by the line 22. However, the radio signal associated with the line 22 is also received via the artenna 4, of the measurement apparatus 3, as illustrated by line 23. The measurement apparatus 3, operates to detect the radio signal 22, and to generate samples of the radio signal by operation of the sampling unit 14, in combination with the data processor 16. The operation of sampling the radio signal 23, by the measurement apparatus 3 is illustrated in Figure 4.

Figure 4 provides an illustration of bursts of radio signals 24, transmitted in time slots TS, on one of the n carrier frequency signals allocated to the base station 22. This example illustration corresponds to a time division multiple access system, in which a radio frequency carrier signal is divided into a plurality of time slots. The x-axis of Figure 4 is representative of received power in decibels (dB) wit-h the y-axis representing time. The measurement apparatus 3 11 operates to sample the radio signals at sampling instances 26, and for each sampling instance 26 the sampling measurement unit 14 within the measurement apparatus 3 operates to generate a sample of the power and time of arrival of the bursts of radio signals 24. As will be appreciated by those skilled in the art, the rate at which the detected radio signals are sampled will determine a resolution with which a profile of the envelope of the radio signals with respect to time may be determined. " As such, if the sampling rate is high enough, the samples of the radio signals will detect a spread of the radio signals at the start and end of the bursts. The spread is caused by transmit and receive filtering in combination with multi-path delay spread resulting from the radio communications channel.

The spread may therefore cause signal energy to be detected at a time when no signal has been transmitted. In order to account for this spreading to the effect that a burst of radio signals is not erroneously detected, the data processor 16, may be arranged to compare successive radio signal samples, whereby the presence or absence of a burst of radio signals is determined by a difference in the amplitude of the signal samples.

Determination of the distribution and concentration of mobile units using the traffic distribution measurement apparatus will now be described. The received signal strength SV(t) can be used to determine a path loss Lpath, associated with a reduction in the strength of the radio signal in accordance with distance travelled. This is expressed by equation 1.

Lpath = PMS - SV(t) (1) The power path loss Lpath, provides a measure of the distance travelled by radio signals which is hereafter designated as Dradio, which is the radio distance. The radio distance therefore provides a relative measure of the distance of the 12 mobile unit or the base station BS, which is generating the radio signals detected by the measurement apparatus.

Returning to the measurement apparatus shown in Figure 2, the data store 17, is provided with pre-stored information appertaining to a set of distances associated with the propagation of the radio signals (radio distance Dradio) received by the measurement apparatus. The set of radio distances is determined for the plurality of n operating carrier frequencies, Dradio,n. Each of the bands is associated with a range of radio distances of the detected radio signal samples, which are greater than a lower threshold Lthres,n. Hence the data processor 16, operates to compare the determined radio distance Dradio, of the detected radio signal samples with the distance bands, and determines the radio distance band into which the detected radio signals fall. In this way, the data processor 16, generates a traffic distribution profile associated with a measure of the relative activity of mobile units and base stations within n communications channels provided by the mobile radio network. This is illustrated by equation 2 which generates a measure of the burst usage BU(ch) per which is the number of bursts transmitted in an associated time slot corresponding to a channel provided by the mobile radio network:

BU(f, Lthres, Tmon) o1Nactive/Nsample (2) In equation (2) the burst usage is calculated for SV(t) 5: Lthres, where a time for which the particular channel is monitored is Tmon, during which the number of active bursts of radio signals in the channel were Nactive, for a total number of Nsample samples, which were taken of the channel. Also in equation (2) oil is a correction factor associated with the sampling rate of the burst.

The burst usage corresponds to the ratio of active bursts present within the communications channel in comparison to 13 C is the number of bursts which could have been communicated in the communications channel within the monitoring period Tmon Hence the burst usage is representative of a physical evaluation of the use of the air interface of the mobile radio system. From this factor, the traffic generated within the monitoring period Tmon and for the radio distance Dradio is calculated according in equation (3):

Y (f r Lthres, ni T mon) CL2BU(f, Lthres, Tmon) (3) Correspondingly, equation (3) can be expressed as equation (4):

Y(f, Lthres,n/ Tmon) O2ctlNactive/Nsample (4) in order to allow for factors associated with discontinuous transmission, frequency hopping and burst and carrier types, a scaling factor (X2 is incorporated. The scaling factor is determined in accordance with statistical considerations.

An illustration of a traffic measurement profile generated by the measurement apparatus 3 is shown in Figure 5. In Figure 5, the measurement apparatus 3 is shown to be disposed within a city comprising buildings 28 and streets 30. A traffic measurement profile provided by the measurement apparatus 3 is shown to be comprised of three example bands 32, 34, 36, each of which corresponds to a certain radio distance Dradio, determined by the measurement apparatus 3 in accordance with the sampled signal strength of the radio signals 24. As is shown in Figure 5, a result of a change in propagation characteristics associated with different materials, is that a radio distance for signals passing through the buildings 28 is less than that associated with open air. Correspondingly the distance bands 34, 36, adopt a shape which reflects the propagation characteristics of the area which is surveyed. The traffic measurement profile generated by the measurement apparatus 3 may be graphically displayed by the personal 14 computer 18 forming part of the measurement apparatus 3. Furthermore, other calculations may be effected by the personal computer 18 to provide an efficient presentation of the measured traffic information. These calculations may be effected after the measurements have been taken within the cell of the mobile radio network, provided the position at which the radio signals were sampled is contemporaneously determined. To this end, the position indicator 19, is provided which generates data representative of'a position of the measurement apparatus, which is fed to the data processor As will be appreciated by those skilled in the art, in order to determine the radio distance as herein before described, the measurement apparatus 3 requires knowledge of the power PMS of the transmitted radio signals. For up-link transmissions, which is from mobile units to the base station, the power of the radio signals is determined by the mobile units. In the GSM mobile radio system for example, the up-link power is determined by a power control process to the effect that signals arriving from mobiles in different parts of the cell arrive at the base station with approximately equal power. As such it may be necessary in this application to disable the power control process in order for the radio distance measurements to be effected. Thus the mobiles in this case would be arranged to transmit with the same power, which would therefore be known by the measurement apparatus. Alternatively, for mobiles communicating close to the base station, the power level of the transmit signal will be substantially at the lowest level and therefore constant for all mobiles within this area. In this case the radio distance measurements may be effected since the transmitted power will be known for mobiles transmitting close to the base station. Alternatively for micro-cell and pico-cell applications, power control may not be used in which case the power of the transmitted signals will be known by the measurement apparatus.

is As an alternative to measuring the radio distance by determining the path loss as described above, the measurement apparatus may be provided with a means for measuring the propagation delay of the radio signals communicated within a time slot. This may be effected for example by measuring a time taken for radio signals to be transmitted from a mobile unit or a base station to the measurement apparatus. To this end, the measurement apparatus is provided with a temporal reference 15, which may be a clock. The clock may be synchronised to the start of a time slot in which the radio signals are to be transmitted. Therefore a comparison of the time of arrival of a burst of radio signals with the start of the time slot, provides an indication of the propagation delay. In systems such as GSM, the mobile radio system operates to advance transmission of the radio signals in accordance with a determined propagation delay. Therefore, with such systems the measurement apparatus would be arranged to account for such timing advance in measuring the propagation delay. As will be appreciated in this case, the measurement apparatus 3, must be arranged to monitor the base station so as to acquire the timing of the transmission of bursts from the mobiles to the base station.

For downlink transmissions, the measurement apparatus 3 serves to provide a measurement of traffic and transmitted signal power within a geographical area. This is particularly useful where this area is served by a plurality of base stations. As such, an amount of interference which will be generated by base stations having the same carrier frequencies may be determined with the measurement apparatus 3. This can be used in order to plan an appropriate location for supplementary base stations such as those used in micro-cells and pico-cells. The measurement apparatus may therefore be used to deploy a base station within an established mobile network, as illustrated by the follwing method:

16 First, the measurement apparatus 3 is used to determine a traffic distribution at a plurality of positions, and for each of a plurality of operating frequencies used by base stations of the mobile radio network. The position of the measurement apparatus 3, is determined by the positionindicator 19. The traffic distribution for radio signals transmitted on the down-link from the base stations, therefore provides an indication of an amount of interference generated on each of the operating frequencies, at each of the monitoring positions within the mobile radio network. From the traffic distribution a target location of a base station to be deployed is determined from the traffic distribution and the monitored positions. The target location is determined as a position at which a level of interference generated from the surrounding base stations is at a substantially tolerable level. The base station is then deployed at this location. Finally at least one of the operating frequencies, on which a level of detected traffic is at a substantially low level, is allocated to the deployed base station.

As a further enhancement, the measurement apparatus 3 may further include at least one further antenna 40 and a beam former processor 42. The plurality of antennas 40, in combination with the beam forming processor 42 may serve to provide a beam within which signals are combined coherently at the output of the beam forming processor 42. As such this may be controlled by the data processor 16, in order to provide a measurement of an angle of arrival of the received radio signals so that not only the distance of the communicating mobiles and base stations from a measurement apparatus is determined, but also the direction. Scanning of the area to be monitored may be effected in accordance with radar principles. This information may thereafter be fed to the personal computer 18 in order to provide an enhanced profile of traffic distribution within the cell. The profile 17 can show a concentration of traffic within part of a radio distance band.

As will be appreciated by those skilled in the art, various modifications may be made to the example embodiment as herein before described without departing from the scope of the present invention. In particular the measurement apparatus may be used with signals generated in accordance with a variety of multiple access schemes, such as time-division/code-division multiple access and wide-band code-division multiple access systems. Furthermore, other techniques for interpreting the distance and measured radio communications activity to the effect of generating an estimate of traffic distribution are envisaged.

18

Claims

CLAIMS:

1. A measurement apparatus (3) for use in determining a distribution of radio communications traffic within a radio coverage area provided by a mobile radio network, said measurement apparatus (3) comprising - a receiver (5) which operates to sample radio signals communicated between mobile units and base stations on communications channels provided by said mobile'radio 10 network, and - a data processor (16) coupled to said radio receiver (5) which operates to determine distances from which said radio signals were transmitted by said mobile units or said base stations, wherein said data processor further operates to estimate said traffic distribution from said distances in combination with said samples of said radio signals.

2. A measurement apparatus as claimed in claim 1, wherein said data processor (16) operates to estimate from said samples of said radio signals a number of said communications channels on which said radio signals are communicated, said traffic distribution being estimated from a combination of said distances and said number of communications channels on which radio signals are communicated.

3. A measurement apparatus as claimed in claim 1, wherein said data processor (16) operates to estimate from said samples of said radio signals a number of calls made with said mobile units via said communications channels, said traffic distribution being estimated from a combination of said distances and said number of calls.

4. A measurement apparatus as claimed and further including - a data store (17) in which pre-determined reference distances representative of distances travelled by radio signals are stored, wherein said data processor (16) operates in claims 1, 2, or 3, 19 to compare said distances with said pre-determined reference distances in combination with said number of communications channels on which said radio signals are communicated, whereby a distribution of mobile units communicating radio signals in relation to said pre-determined reference distances is determined.

5. A measurement apparatus as claimed in any preceding claim, wherein the radio receiver (5) further includes - means (4, 40, 42) for determining angles of arrival of the radio signals at the receiver, and consequent upon said angles of arrival of said radio signals in combination with said distances, said data processor (16) further operates to estimate said traffic distribution associated with parts of said radio coverage area.

6. A measurement apparatus as claimed in claim 5, wherein said means for determining the direction of arrival of said radio signals is a directional antenna (4, 40, 42) forming part of said receiver (5).

7. A measurement apparatus as claimed in any preceding Claim, wherein said radio receiver (5) further includes - means (14) to determine the power of the received signal samples, and said data processor (16) operates to determine said distances of the mobiles from the measurement apparatus in accordance with a pathloss determined from the power of the received signal samples in comparison with pre-determined reference powers representative of power with which said signals were transmitted.

8. A measurement apparatus as claimed in any of Claims 1 to 6, wherein said radio receiver (5) is provided with - means for determining a time of arrival of said radio signals in comparison to a temporal reference (15), and in dependence upon a relative delay between transmission and said time of arrival of said radio signals with respect to said temporal reference, said data processor (16) operates to determine said distances of said mobiles from said measurement apparatus.

r, 9. A measurement apparatus as claimed in Claim 8, wherein said temporal reference is determined in relation to a start of a time slot in which said radio signals are communicated, said radio signals being communicated in accordance with a time division multiple access system, or code division multiple access system.

10. A measurement apparatus as claimed in any preceding claim, and further including a position indication means (19) coupled to said data processor (16) which operates to provide information corresponding to a position of said measurement device at which said radio signal were sampled.

11. A measurement apparatus as claimed in claim 10, wherein said position indication means is a position detector (16) operating in accordance with the Global Positioning System.

12. A measurement apparatus as claimed in any preceding claim, wherein said receiver (5) further includes means (10) for separating said radio signals in accordance with a frequency with which they are transmitted, said radio signals being sampled separately from each transmitted frequency.

13. A measurement apparatus as claimed in any preceding Claim, wherein said radio receiver (5) samples said radio signals communicated on either the up-link or the down-link.

14. A mobile radio network comprising a plurality of base stations and a plurality of mobile units which operate to communicate data via the base stations, and at least one measurement apparatus as claimed in any preceding claim, which operates to determine a distribution of radio communications traffic within said mobile radio network and 21 in dependence upon said traffic distribution said mobile radio network operates to allocate communications channels to said base stations, whereby said radio communications traffic is supported by said mobile radio network.

15. A method of estimating a distribution of radio communications traffic supported by a mobile radio telephone network, said method comprising the steps of; - sampling radio signals communicated between mobile units and base stations on communications channels provided by said mobile radio network; - determining distances from which said radio signals were transmitted by said mobile units or said base stations; and - estimating said traffic distribution from said distances in combination with a number of radio communications channels on which said radio signals are communicated.

16. A method of estimating a distribution of traffic as claimed in Claim 15, wherein said step of estimating said traffic distribution further includes the steps of; - comparing said distances with pre-determined reference distances representative of distances travelled by radio signals; and - determining from said distances a distribution of said mobile units communicating radio signals in relation to said pre-determined reference distances.

17. A method of estimating a distribution of traffic as claimed in any of claims 15 or 16, and further including the steps of; - determining a direction from which said radio signals arrive; and - estimating said traffic distribution within said radio coverage area from said distances and said direction of arrival of said radio signals, whereby said traffic distribution associated with parts of said radio coverage area is estimated.

22 18. A method of estimating a distribution of traffic as claimed in any of Claims 15 to 17, wherein the step of determining the distance from which said radio signals are transmitted comprises the steps of; determining a power with which said radio signals were transmitted; measuring the power of the received radio signals; and - determining a path-loss associated with said radio signals, which path-loss is indicative of a distance travelled by said radio signals.

19. A method of estimating a distribution of traffic as claimed in any of Claims 15 to 17, wherein the step of determining the distance from which said radio signals are transmitted comprises the steps of; - measuring a time of arrival of said radio signals in comparison to a temporal reference; - calculating a relative delay between a time of transmission and said time of arrival of said radio signals with respect to said temporal reference; and - determining said distance travelled by said radio signals in accordance with said relative delay indicative of a propagation delay of said radio signals.

20. A method of estimating a distribution of traffic as claimed in any of claims 15 to 18, and further including the step of; - determining a location within said cell at which said samples were taken; and determining said traffic distribution in accordance with the location at which said sampled were taken in combination with said distances.

21. A method of deploying base stations within a mobile radio network, using a measurement apparatus as claimed in any preceding claim, comprising the steps of; 23 - using said measurement apparatus to determine a traffic distribution at a plurality of positions for each of a plurality of operating frequencies used by surrounding base stations of the mobile radio network; - determining a target location of a base station from said traffic distribution and said plurality of positions, at which location a level interference generated from the surrounding base stations is at a substantially tolerable level; - deploying said base station at said target location, and - allocating to said deployed base station at least one of said plurality of frequencies for which traffic determined from said traffic distribution is a substantially low level.

22. A measurement apparatus as herein before described with reference to the accompanying drawings.