JPH11243361A - Wireless communication system multiple access method selection method - Google Patents

Abstract

(57) [Problem] To provide a selection method for easily selecting a multiple access method without evaluating communication quality such as an error rate and the number of retransmissions. SOLUTION: A radio wave propagation model is created from measured radio wave propagation characteristics, and a required transmission bandwidth for each of the multiple access schemes to be selected is calculated. Using a radio wave propagation model for each of the multiple access methods of choice, a received signal instantaneous level indicating an arbitrary cumulative probability of 20% or more and an arbitrary cumulative probability of 10% or less in instantaneous reception level fluctuation characteristics with respect to a required transmission bandwidth. Calculate the instantaneous reception level fluctuation width defined by the difference between the signal instantaneous levels. The multiple access method is selected based on the instantaneous reception level fluctuation width.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the selection of a multiple access system in studying a wireless communication system. As a main multiple access system of a wireless communication system, a time division multiple access system (TDM) with a narrow
A) and code division multiple access (CDM) with a wide occupied bandwidth
A), etc., and which of the multiple access systems to select greatly depends on the design of the entire system.

[0002]

2. Description of the Related Art A conventional wireless communication system multiple access method selection method based on communication quality selects a multiple access method according to the following procedure.

(1) A delay profile characteristic of a frequency band used for communication is measured at a place where a wireless communication system is to be developed. (2) Analyze the power delay profile characteristics measured in (1) and create a radio wave propagation model. (3) Using the radio wave propagation model created in (2), conducted a computer simulation or transmission experiment using a radio wave propagation path simulating device for each of the multiple access methods of choice,
The communication quality is evaluated from transmission characteristics such as an average bit error rate with respect to an average carrier to noise power ratio. (4) The communication quality of each option of the multiple access method evaluated in (3) is compared, and the multiple access method is selected.

FIG. 1 shows a flowchart of this procedure.

[0005]

The conventional wireless communication system multiple access method selection method can be obtained by computer simulation using a radio wave propagation model or transmission experiment using a radio wave propagation path simulating apparatus for each of the multiple access system options. The communication quality was evaluated from the transmission characteristics such as the average bit error rate to the average carrier to noise power ratio. But,
This computer simulation was time consuming. In addition, transmission experiments using a radio propagation path simulator require as many multiple access systems as there are options for the multiple access method, and sufficient specifications for the radio propagation path simulator are required to realize an effective radio propagation model. Things requested. As described above, in order to obtain the evaluation amount of the communication quality, which is the selection criterion, from the transmission characteristics, there is a great problem in terms of time or equipment.

An object of the present invention is to provide a radio communication system multiple access method selection method which does not evaluate the communication quality such as the error rate and the number of retransmissions accompanied by time or equipment problems.

[0007]

SUMMARY OF THE INVENTION In order to solve the problems of the conventional wireless communication system multiple access method selection method, the wireless communication system multiple access method selection method of the present invention has the following procedures as the most main features.

(1) A radio wave propagation characteristic in a frequency band used for communication at a place where a wireless communication system is to be developed is measured. (2) Create a radio wave propagation model from the radio wave propagation characteristics. (3) Calculate the required transmission bandwidth for each of the alternative multiple access schemes. (4) A received signal instantaneous level indicating an arbitrary cumulative probability equal to or higher than a first reference value in an instantaneous reception level fluctuation characteristic with respect to a required transmission bandwidth using a radio wave propagation model for each of the multiple access methods of choice, and a second reference value An instantaneous reception level fluctuation range defined by a difference between received signal instantaneous levels indicating the following arbitrary cumulative probabilities is calculated.

The first reference value is, for example, 20%, and the second reference value is, for example, 10%.

The difference from the prior art is that the evaluation quantity of the communication quality, which is the selection criterion, is obtained from radio wave propagation characteristics whose time and equipment problems are smaller than transmission characteristics.

In the procedure for solving the above-mentioned problem, each procedure works as follows. In the procedure (1), a radio wave propagation characteristic in a frequency band used for communication in a place where a wireless communication system is to be developed is obtained. Procedure (2)
Creates a radio wave propagation model from the radio wave propagation characteristics obtained in step (1). The procedure (3) obtains a required transmission bandwidth for each of the multiple access methods of choice. The procedure (4) uses the radio wave propagation model created in the procedure (2), and the procedure (3)
And the instantaneous reception level fluctuation width with respect to the required transmission bandwidth obtained in (1). Therefore, it is possible to use the instantaneous level fluctuation width of the received signal, which is a physical quantity from the radio wave propagation characteristic having a small time and facility problem, as a selection criterion of the multiple access method,
It is possible to select a wireless communication system multiple access method without evaluating communication quality accompanied by a problem with time or equipment, which is the object of the present invention.

[0012]

(Embodiment 1) Embodiments of the present invention will be described below with reference to the drawings.

FIG. 2 is a flowchart of a multiple access method selection method according to the present invention. In FIG. 2, reference numeral 10 denotes a power delay profile characteristic measuring procedure for measuring a power delay profile characteristic in a radio wave propagation environment in a communication range in a frequency band used for communication, and 15 denotes a frequency band used for communication based on the power delay profile characteristic. The radio wave propagation model generation procedures A and 20 for generating a radio wave propagation model for the radio wave propagation environment in the communication range are required transmission bandwidth calculation procedures A and 25 for calculating the required transmission bandwidth for each of the multiple access methods. The instantaneous reception level fluctuation characteristic calculation procedures A and 30 for calculating an instantaneous reception level fluctuation characteristic with respect to a required transmission bandwidth using a radio wave propagation model for each of the multiple access systems are 20% in the instantaneous reception level fluctuation characteristics for each of the alternative multiple access systems.
The instantaneous level of the received signal indicating the arbitrary cumulative probability as described above, and 1
The instantaneous reception level variation width calculation procedures A and 35 for calculating the instantaneous reception level variation width defined by the difference between the received signal instantaneous levels indicating an arbitrary cumulative probability of 0% or less are the instantaneous values determined for each of the multiple access methods of choice. This is a multiple access method selection procedure A in which a multiple access method is selected based on the reception level variation width.

FIG. 3 is a measurement system diagram for implementing the power delay profile characteristic measurement procedure 10. In FIG. 3, 10
Reference numeral 1 denotes a reference frequency generator that outputs a reference frequency signal having high stability necessary for measuring the power delay profile characteristic to a transmission side device, and 102 denotes a pseudo random noise signal (hereinafter, PN).
PN signal generator 103 for outputting a signal in a frequency band used for communication, 104 for performing BPSK modulation using the PN signal from the PN signal generator 102, and BPSK modulation for transmitting a wideband signal 105, a transmission antenna for emitting a transmission signal to a radio wave propagation path, 106, a reception antenna for receiving a reception signal, 107, a frequency converter for converting the frequency of the reception signal, 108, a communication used for the operation of the frequency converter 107. A local oscillator for outputting a signal in a frequency band; 109, a PN signal generator for outputting the same PN signal as the PN signal generator 102; 110, a PN signal from the PN signal generator 109;
A sliding correlator for measuring a power delay profile characteristic by taking a sliding correlation between a signal and a received signal. Reference frequency generator 111 outputs a reference frequency signal having the same high stability as reference frequency generator 101 to a receiving device. It is a vessel. The transmission speed of the PN signal generated by the PN signal generators 102 and 109 determines the delay time resolution in the power delay profile characteristic measurement. The delay time resolution is the reciprocal of the transmission speed. Therefore, the higher the transmission rate, the greater the delay time resolution, and the power delay profile characteristics can be measured with high accuracy. Further, the sequence length of the PN signal determines the maximum delay time in the power delay profile characteristic measurement in relation to the transmission speed. The maximum delay time is a value obtained by dividing the sequence length by the transmission speed. These two specifications are determined by the radio wave propagation environment. If the measurement location is a general urban area, the delay time resolution is required to be less than about 40 nsec, and the maximum delay time is required to be about 10 μsec or more. Transmitting antenna 10
1 and the receiving antenna 102 have the same directivity as those used in actual communication.

FIG. 4 shows an example of the average power delay profile and the radio wave propagation model obtained in the radio wave propagation model creation procedure A15. The average power delay profile is obtained by calculating the average value of the received power for each delay time from the power delay profile characteristics measured in the power delay profile characteristic measurement procedure 10. In this example, as shown in FIG.
An incoming wave with a maximum value of -70 dBm or more was extracted and a radio wave propagation model was created. Instantaneous reception level fluctuation characteristic calculation procedure A
In the calculation of the instantaneous reception level fluctuation characteristic at 25, the calculation is performed under the condition that the incoming wave undergoes Nakagami Rice fluctuation.

FIG. 5 shows an example of the multiple access system selection on the received signal instantaneous level cumulative probability distribution. In this example, a time division multiple access method (TDMA method) and a code division multiple access method (CDMA method) are selected as options of the multiple access method. The required transmission bandwidth of the TDMA system is determined by the transmission speed per channel, the modulation system, and the number of multiplexes in time division. On the other hand, the required transmission bandwidth of the CDMA system is determined by the spread code transmission rate and the spread modulation system. In this example, the required transmission bandwidth of the TDMA system is 300 kHz.
z, the required transmission bandwidth of the CDMA system is set to 30 MHz. The required transmission bandwidth is calculated by the required transmission bandwidth calculation procedure A20.
And set it as a parameter in the instantaneous reception level fluctuation characteristic calculation procedure A25. An example of this calculation result is shown in FIG.
Is the received signal instantaneous level cumulative probability distribution. From the received signal instantaneous level cumulative probability distribution, a received signal instantaneous level change width defined by a difference between two received signal instantaneous levels indicating a sufficiently large cumulative probability is obtained in an instantaneous received level change width calculation procedure A30. In this example, the cumulative probability 50% value and 1%
The difference between the received signal instantaneous levels of the values is defined as the received signal instantaneous level fluctuation width. In this example, the received signal instantaneous level fluctuation width in the TDMA system is 15.5 dB, and the received signal instantaneous level fluctuation width in the CDMA system is 3.4 dB. Finally, in the multiple access method selection procedure A35, the transmission characteristic evaluation amount is obtained from the received signal instantaneous level fluctuation width for each multiple access method, and the multiple access method is selected by comparing the evaluation amounts. In this example, the transmission characteristic evaluation amount for each multiple access system was obtained as follows.

(1) In the TDMA system, the waveform distortion of the received signal due to the propagation delay of the radio wave is quantitatively indicated by the decrease in the instantaneous level fluctuation width of the received signal. That is, the transmission characteristics are better as the received signal instantaneous level fluctuation width is larger. Therefore, the transmission characteristic evaluation amount is the difference between the received signal instantaneous level fluctuation width between the required transmission bandwidth and the transmission bandwidth of 100 kHz. (2) In the CDMA system, when the radio wave propagation delay is large and each arriving wave fluctuates independently, the effect of the path diversity by the RAKE receiver increases. The received signal instantaneous level fluctuation width quantitatively indicates the effect of the path diversity. In other words, the smaller the instantaneous level fluctuation of the received signal, the better the transmission characteristics. Therefore, the received signal instantaneous level fluctuation width itself in the required transmission bandwidth is used as the transmission characteristic evaluation amount.

From the method of obtaining the transmission characteristic evaluation amount, the TDM
The transmission characteristic evaluation amount of the A method is 2.0 dB (the received signal instantaneous level fluctuation width at a transmission bandwidth of 100 kHz is 17.5 dB), CDMA
The transmission characteristic evaluation amount of the method is 3.4 dB. In this example, the TDMA method is selected because the smaller the transmission characteristic evaluation amount is, the better the transmission characteristic is.

(Embodiment 2) An embodiment of the present invention will be described below with reference to the drawings.

FIG. 6 is a flowchart of a multiple access method selection method according to the present invention. In FIG. 6, reference numeral 40 denotes a radio wave propagation characteristic measuring procedure for measuring a power delay profile characteristic and a frequency correlation characteristic in a radio wave propagation environment in a communication range in a frequency band used for communication, and 45 denotes a power delay profile characteristic used for communication. A radio wave propagation model creation procedure B, 50 for creating a plurality of radio wave propagation models having different numbers of arriving waves and delay times of arriving waves in a radio wave propagation environment in a communication range in a frequency band includes a frequency correlation for each of the plurality of radio wave propagation models. A frequency correlation characteristic calculation procedure for calculating characteristics, 55 is a required transmission bandwidth calculation procedure B for calculating a required transmission bandwidth for each of the alternative multiple access schemes, and 60 is a plurality of radio wave propagation models for each of the alternative multiple access schemes. Select a radio propagation model from which the calculated frequency correlation characteristics within the required transmission bandwidth can be approximated and evaluated from the measured frequency correlation characteristics. Propagation model selection procedure, 65 the instantaneous receive level variation characteristics calculation procedure B for calculating the instantaneous receive level variation characteristics relative to the required transmission bandwidth use propagation model for each multiple access scheme options,
Reference numeral 70 denotes an instantaneous reception level fluctuation width calculation for calculating an instantaneous reception level fluctuation width defined by a difference between two instantaneous reception levels indicating a cumulative probability that has a sufficiently large difference in the instantaneous reception level fluctuation characteristics for each of the multiple access system choices. Procedures B and 75 are multiple access method selection procedures B for selecting a multiple access method based on the instantaneous reception level fluctuation width obtained for each of the multiple access method options.

FIG. 7 is a measurement system diagram for realizing the radio wave propagation characteristic measurement procedure 40. In FIG. 7, reference numeral 201 denotes a reference frequency generator that outputs a reference frequency signal having a high degree of stability necessary for measuring the power delay profile characteristic to a transmitting device, and 202 outputs a pseudo random noise signal (hereinafter, a PN signal). PN signal generator, 203 is a local oscillator for outputting a signal in a frequency band used for communication, 204 is PN signal generator 2
BPSK modulator that performs BPSK modulation with the PN signal from 02 and transmits a wideband signal, 205 is a transmission antenna that emits a transmission signal to a radio wave propagation path, 206 is a reception antenna that receives a reception signal, and 207 is power distribution of a reception signal. 209, a frequency converter that converts the frequency of the received signal, 210, a local oscillator that outputs a signal in a communication frequency band used for the operation of the frequency converter 209 , 211 are PN signal generators that output the same PN signal as the PN signal generator 202, 2
12 is a sliding correlator for measuring a power delay profile characteristic by taking a sliding correlation between the PN signal from the PN signal generator 211 and the received signal, and 213 is a reference frequency signal having the same stability as the reference frequency generator 201 and having the same high stability. Is a reference frequency generator that outputs to the receiving device. The parts other than those related to the measurement of the frequency correlation characteristic are the same as those in the first embodiment, and therefore the description in this embodiment is omitted. The transmission speed and sequence length of the PN signal generated by the PN signal generator 202 have a relationship with the setting of the frequency resolution of the FFT analyzer 208 in the measurement of the frequency correlation characteristic. Because
The value obtained by dividing the transmission rate by the sequence length is the spectrum interval of the transmission signal. If the frequency resolution is set narrower than this spectrum interval, accurate frequency correlation characteristics cannot be measured. For example, the transmission speed and sequence length of the PN signal are each 30 Mbit / s.
And 1023, the frequency resolution limit is about 29.3 kHz
z.

FIG. 8 shows an example of the average power delay profile and a plurality of radio wave propagation models obtained in the radio wave propagation model creation procedure B45. The average power delay profile is the same as in FIG. In this example, the reception level is -60d in this average power delay profile as shown in FIG.
Bm and extract the incoming wave that takes the maximum value of -70dBm or more,
Two radio wave propagation models were created. In the calculation in the frequency correlation characteristic calculation procedure 50 and the instantaneous reception level fluctuation characteristic calculation procedure B65, the calculation is performed under the condition that the incoming wave undergoes Nakagami Rice fluctuation.

The calculation of the required transmission bandwidth in the required transmission bandwidth calculation procedure B55 for each multiple access system is the same as the required transmission bandwidth calculation procedure A of the first embodiment, and a description thereof will be omitted. However, the fact that the choice of the multiple access method in the first embodiment is selected between the TDMA method and the CDMA method, and that the required transmission bandwidth of the TDMA method is 300 kHz and the required transmission bandwidth of the CDMA method is 30 MHz is the present embodiment. It should be mentioned again here that the same applies to No. 2.

FIG. 9 shows an example of the measured value of the frequency correlation characteristic measured in the radio wave propagation characteristic measurement procedure 40 and the frequency correlation characteristic calculated in the frequency correlation characteristic calculation procedure 50 for each radio wave propagation model. In this example, the required transmission bandwidth of the CDMA system is 30 MHz in the radio wave propagation model 2 than in the radio wave propagation model 1.
In the range of the above, the characteristic close to the frequency correlation characteristic of the measured value is shown, so that the radio wave propagation model 2 is selected in the radio wave propagation model selection procedure 60.

The procedure after the radio wave propagation model selection procedure is the same as that in the first embodiment, and the description is omitted.

[0026]

As described above, the method of selecting a multiple access system of the present invention does not involve a computer simulation having a time problem and a transmission experiment using a radio wave path simulator having a facility problem. Since the communication quality can be evaluated, there is an effect that the entire system can be quickly designed.

[Brief description of the drawings]

FIG. 1 is a flowchart of a conventional multiple access method selection method.

FIG. 2 is a flowchart of an embodiment of a multiple access method selection method according to the present invention.

FIG. 3 is a measurement system diagram of a power delay profile characteristic.

FIG. 4 is an example of an average power delay profile and a radio wave propagation model.

FIG. 5 is an example of a multiple access method selection.

FIG. 6 is a flowchart of another embodiment of the multiple access method selection method of the present invention.

FIG. 7 is a diagram of a radio wave propagation characteristic measurement system.

FIG. 8 is an example of an average power delay profile and a plurality of radio wave propagation models.

FIG. 9 is an example of measurement and calculation results of a frequency correlation characteristic.

[Explanation of symbols]

1 Received signal power delay profile characteristic measurement procedure 2 Radio wave propagation model creation procedure 3 Transmission simulation using computer simulation or radio wave propagation path simulator 4 Communication quality evaluation procedure 5 Multiple access method selection procedure based on communication quality 10 Power Delay profile characteristic measurement procedure 15 Radio propagation model creation procedure A 20 Required transmission bandwidth calculation procedure A 25 Instantaneous reception level fluctuation characteristic calculation procedure A 30 Instantaneous reception level fluctuation width calculation procedure A 35 Multiple access method selection procedure A 40 Radio propagation characteristic measurement Procedure 45 Radio propagation model creation procedure B 50 Frequency correlation characteristic calculation procedure 55 Required transmission bandwidth calculation procedure B 60 Radio propagation model selection procedure 65 Instantaneous reception level fluctuation characteristic calculation procedure B 70 Instantaneous reception level fluctuation width calculation procedure B 75 Multiple access method Selection procedure B

Claims (2)

[Claims] 1. A method for selecting a plurality of wireless base stations and a plurality of mobile stations connected to the wireless base stations via a wireless line, the method being used for communication in a wireless communication system multiple access method selection method. Measure the power delay profile characteristics in the radio wave propagation environment in the communication range in the frequency band to create a radio wave propagation model for the radio wave propagation environment in the communication range in the frequency band used for communication from the power delay profile characteristics, On the other hand, the required transmission bandwidth for each of the alternative multiple access schemes is calculated, and the instantaneous reception level fluctuation characteristics for the required transmission bandwidth are calculated using the radio wave propagation model for each of the alternative multiple access schemes. A received signal instantaneous level indicating an arbitrary cumulative probability equal to or greater than a first reference value in the instantaneous reception level variation characteristic for each time; Calculate the instantaneous reception level fluctuation range defined by the difference between the received signal instantaneous levels indicating the following arbitrary cumulative probabilities, and select the multiple access system using the instantaneous reception level fluctuation range obtained for each of the multiple access system options as a selection criterion. A method for selecting a multiple access method for a wireless communication system, comprising: 2. A method for selecting a wireless communication system according to a multiple access method for designing a wireless communication system comprising a plurality of wireless base stations and a plurality of mobile stations connected to the wireless base stations via wireless lines. Delay Profile Characteristics and Frequency Correlation Characteristics 1 in Radio Wave Propagation Environment in Communication Range in Changing Frequency Band 1
And a plurality of radio wave propagation models 1 having different numbers of arriving waves and delay times of arriving waves with respect to a radio wave propagation environment in a communication range in a frequency band used for communication are created from the power delay profile characteristics. Calculate the frequency correlation characteristic 2 for each of the radio wave propagation models 1, calculate the required transmission bandwidth for each of the alternative multiple access systems, and calculate the required transmission bandwidth from the radio wave propagation model 1 for each of the alternative multiple access systems. A radio wave propagation model 2 in which the frequency correlation characteristic 2 within the bandwidth can be evaluated as an approximation of the frequency correlation characteristic 1.
And calculating an instantaneous reception level fluctuation characteristic for the required transmission bandwidth using the radio wave propagation model 2 for each of the multiple access schemes of choice. Calculating an instantaneous reception level variation width defined by a difference between a received signal instantaneous level indicating an arbitrary cumulative probability equal to or higher than the reference value and a received signal instantaneous level indicating an arbitrary cumulative probability equal to or lower than the second reference value; A method for selecting a multiple access system, wherein the multiple access system is selected based on an instantaneous reception level fluctuation range obtained for each multiple access system.