JPH03220825A - Diversity receiver - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a diversity receiving device used in a digital mobile communication system, particularly a high-speed digital mobile communication system that is expected to be introduced in the future and in which the influence of propagation delay waves cannot be ignored. .

[Background Art] With the rapid progress of telecommunications technology in recent years, communication equipment has become smaller and more sophisticated, and mobile objects such as vehicles are now equipped with various communication devices. There is.

One of the most important things in mobile communications is
The second problem is how to receive high-quality radio waves.

That is, the position of a moving body changes from moment to moment, and the relative positional relationship with the other party of transmission and reception also changes constantly.

In particular, in urban areas, multi-path propagation occurs due to urban structures such as buildings around the mobile object, and the received signal undergoes fading, resulting in significant deterioration of signal quality.

Therefore, there is a Daihacity reception system as a system that constantly detects the condition of the received signal, which changes greatly as the vehicle moves, and performs optimal reception. This Daihacity reception system is a system in which a plurality of antennas are installed on a mobile object, and the one with the highest quality, that is, the one with the highest reception level, is selected from among the received signals from the plurality of antennas. In such a diversity reception system, a system using reception antennas with different directivity is particularly called angular diversity. and,
This angular diversity is suitable for mobile station reception where the direction of arrival of multiple waves is large.

According to the daihacity reception system represented by such angle guavacity, fading E= is eliminated,
Good reception can be achieved depending on the surrounding conditions,
It is possible to improve reception quality in mobile communications.

Regarding such a Daiha City reception system, for example, see ``Mobile Communication Fundamentals 112 Chapter 7 1'' edited by the Institute of Electronics and Communication Engineers.
Please refer to pages 63 to 164 or Japanese Patent Application No. 1-8889.

[Problem to be solved by the invention] However, as described above, the conventional technology that attempts to perform optimal reception by switching to the antenna with the highest reception level is not suitable for digital mobile communication systems, especially at high speeds where the influence of propagation delay waves cannot be ignored. In the case of digital mobile communication systems, even if the reception level is high, the transmission quality may deteriorate under multiple wave propagation conditions such as in urban areas, so it has not always been possible to achieve optimal reception.

The reason for this will be explained with reference to FIG. In the figure, it is assumed that in data transmission requiring a transmission time T of 1 bit length, a delayed wave B arrives with a delay of time τ relative to the preceding wave A. In such a case, a code amount interference portion (■, ■, ■, ■, ■) occurs where the leading wave A and the delayed wave B have different codes (■, ■, ■, ■, ■), and this code amount interference causes a code error during demodulation. Note that no code errors caused by delayed waves occur in the code amount non-interference portions (■, ■, ■, ■). As described above,
Code amount interference due to delay time τ occurs due to multiple wave propagation and occurs even when the reception level is high.

For this reason, in the conventional diversity receiving apparatus that monitors and switches the reception level, it has not been possible to prevent code errors due to code amount interference as described above. For example, in high-speed digital communication transmission, when the code amount interference portion, that is, the delay time τ becomes larger than the 1-bit length T, normal code demodulation can no longer be expected.

The present invention has been made to solve the problems of the prior art as described above, and its two objects are to provide a die-heavy city receiver with fewer code errors during demodulation in high-speed digital communications.

[Means for Solving the Problems] As shown in FIG. 1, the diversity receiving device according to the first aspect of the present invention has six directional antennas ATL to ATn installed in a predetermined direction. In a diversity receiving device that performs reception under optimal conditions by selecting one of these directional antennas ATI to ATn, the spread of multipath propagation delay time for each of the directional antennas ATL to ATn is calculated. A delay spread measuring means 10 for measuring, a comparing means 12 for comparing the spreads of each measured delay time, and a directional antenna with the minimum delay time spread based on the above comparison results are selected from ATI to ATn.
It is characterized in that it includes an ECU 14 that selects from among the following antenna selection means and controls the switching operation of a changeover switch 16 as an antenna selection means.

Further, as shown in FIG. 5, the Daihacity receiving device according to the second aspect of the present invention includes a base station map memory 20 in which base station position information is stored, and own vehicle position detection means for detecting own vehicle position information. 22, an urban infrastructure data memory 24 in which urban structure data is stored, and a recognition means 26 that recognizes the own vehicle position and base station position within the urban structure data, and has the own vehicle and base station as the focus. an ellipse estimation means 28 for assuming a Sui circular zone model within the urban structure data; a structure search means 30 for searching for the same structure based on the urban structure data; and a propagation path defining means 32 for defining a propagation path for each structure within the directional plane for each of the directional antennas ATL to ATn. , calculation means 34 for calculating the propagation time and received signal strength in each propagation path defined for each of the directional antennas ATL-ATn, and each of the directional antennas ATL-ATn.
~A delay spread calculating means 38 for calculating the delay spread of the propagation time based on one hour of propagation of each propagation path calculated for ATn, a comparing means 40 for comparing the spread of the calculated delay time, and the above-mentioned Based on the comparison results, select the directional antenna with the smallest delay time spread from ATL-ATn, and select the switch switch as antenna selection means.
It is characterized by including an ECU 14 that controls the switching operation of No. 6.

[Function] The diversity receiving device according to the first aspect of the present invention has a high-speed configuration, can select a directional antenna with the smallest delay spread, and can achieve high quality with less code amount interference. You can get a good reception signal.

Further, the diversity receiving device according to the second aspect of the present invention has the above-described configuration, and can obtain a delay profile through simulation, and can select a directional antenna with a minimum delay spread. .

[Embodiment 1] A diversity receiving apparatus according to an embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram of an embodiment showing the first invention, in which n directional antennas ATL-ATn are provided as antennas for receiving signals (however, n directional antennas ATL-ATn are provided).
n is an integer). The directional antennas ATL to ATn are arranged so as to be oriented in a direction necessary to achieve angular diversity reception, such as in front and behind a vehicle as a moving object.

FIG. 2 is an antenna directivity characteristic diagram in the case of n-4.

FEI-FEn is a receiving section provided corresponding to the directional antennas ATL to ATn, which demodulates the received waves and outputs demodulated data DAI to DAn, respectively.

10 is a delay spread measuring means for each demodulated data DA1-D.
The spread of multipath propagation delay time (described later) is measured for each of the directional antennas ATL to ATn based on An. Reference numeral 12 denotes a comparison means that compares the spread of each measured delay time. 14 is an ECU as a processing device, which selects the directional antenna with the minimum spread of delay time from ATL-AT, n based on the above comparison results, issues a switching signal, and operates a changeover switch as an antenna selection means. 16 switching operations are controlled. 18 is a communication control unit which outputs any one of the demodulated data DAl=DAn input via the changeover switch 16 to a terminal device (not shown) at a predetermined timing, thereby controlling communication with the base station. Performs various communication controls such as control and zone switching control.

In the above configuration, each of the directional antennas ATI to ATn receives radio waves that are rarely visible within direct line of sight from the base station, and that radio waves that have been reflected and diffracted by buildings, etc., and have passed through various routes arrive at the same time. are doing.

This is called multipath propagation, and if we take low-speed digital transmission as an example, the spread of multipath propagation delay time is greater than the signal pulse width or the spread of multipath propagation delay time. Since it is sufficiently long, the effect of delay (demodulation code error) can be ignored. However, in high-speed digital transmission, as explained in FIG. 9, delayed waves cause code amount interference and increase the code error rate.

Therefore, in this embodiment, the spread of multipath propagation delay time is measured by the delay spread measuring means 10, and the optimum receiving antenna is selected based on this value. The spread of multipath propagation delay time can be obtained by measuring a delay profile showing multipath propagation characteristics as shown in FIG. A delay profile is basically obtained by transmitting a narrow pulse and observing the response (echo). That is, in the figure, the horizontal axis shows the delay time τ of the propagation wave that arrived via multiple paths, and the vertical axis shows the delay time τ
the respective received signal strength at, in the figure the relative power hx
(τ) is shown.

Here, τ is the delay time based on the assumed human-sensible delay time 10 of the direct wave. That is, in this embodiment, for example, delay profiles as shown in FIGS. 3 and 4 are measured for two antennas, and when the delay spread is determined by statistical processing, the antenna with the smaller propagation delay time spread is used for reception. selected as the antenna. Such antenna selection is determined by comparing the delay spreads of all provided directional antennas AT1=ATn. This reduces the amount of code interference and enables demodulation without code errors.

Here, regarding the delay profile, various statistics can be obtained from the delay profile through arithmetic processing. Hereinafter, (i) Average ExcessD
elay, (ii) Delay 5pread
, (iii) : ] Taking the heerence bandwidth as an example,
The calculation processing method for delay profiles will be explained.

(i) Average Excess Delay An arbitrary impulse response peak (i.e., t-th emitted power) on the delay profile is hX (τ), and the power value at the delay time τ at that time is lh.

(τ) I2. The power of the average delay profile at the time of 2, that is, the average power PXA(τ) is determined by: where M is the number of impulse response peaks in the delay profile to be averaged.

Moreover, ExM is determined by: Total power EXM−' 1oPXA (τ)dτ [2] in this average power PxA(τ). Here, tl is a delay time corresponding to the measurement end time of one average delay profile.

Further, the weighted average DxM of the average power PXA(τ) at this time is obtained as follows.

This weighted average Dx, i>< Average Exce
ss Delay. That is, Average
EXCeSS oe+ay is the expected value of the delay time of a multipath arriving in the interval in which the delay profile was measured. The shorter this measurement interval is, the better so that it can respond to changes in surrounding buildings, but it is usually
The distance is set to about 0 to 20 m. (Left below) (if) Delay 5pread The average power PxA(τ) of the average delay profile is... [Determined by 4.

This standard deviation SxA is Delay 5pread. That is, Delay 5pread S XA indicates the degree of delay spread of multipaths arriving in the measurement section.

(iii) Coherence Bandwidth The coherence bandwidth of the average delay profile is determined as the Fourier transform p (f) of the average power PXA(τ). That is, P (“) −f , oPxA(τ) exp(−j
2πfτ)dτ... [5] Usually, the coherence bandwidth p (f) has a correlation value of 0.
This is the value of f when it becomes 5. coherence bandwidth p
(f) is when information is transmitted on a certain propagation path,
One shift is a guideline for determining the maximum transmission speed.

As mentioned above, each directional antenna ATL to ATn
Define a delay profile for
y or Delay 5pread and switch the directional antenna. This is the best configuration to bring out the performance of the Angle Daihanty. However, obtaining the delay profile in real time is expected to be extremely difficult in terms of processing speed. Therefore, a configuration for predicting a delay profile without relying on actual measurements is shown in FIG. 5, and will be described below.

FIG. A5 is a block configuration diagram showing an embodiment of the second invention, and the same components as those in FIG.

In the figure, reference numeral 20 denotes a base station map memory in which base station position information such as base station position and transmission strength is stored. Reference numeral 22 denotes, for example, a navigation device serving as vehicle position detection means, which displays vehicle position information and reveals the location of the vehicle currently running.

An urban structure data memory 24 stores urban structure data such as building structures and road widths within the city.

26 is a recognition means that recognizes the own vehicle position and base station position within the above urban structure data. 28 is a clear circle selection means, and as shown in FIG. 6, a Sui circle zone model (indicated by a broken line in the figure) with the own vehicle R and base station Q as focal points is assumed in the above urban ditch road data. . Reference numeral 30 denotes a structure search means that searches for structures U that are located on an ellipse within each directional plane shown in FIG. is searched based on the urban structure data. 32 is a propagation path defining means that defines a propagation path U formed through the searched structure U shown in FIG. 6 for each directional antenna ATI to ATn having a directional plane where the structure is present. . 34 is a calculation means which calculates the propagation time τ and received signal strength h in each propagation path U defined for each directional antenna ATL-ATn.
Calculate x(τ). That is, the propagation path U corresponds to the peak of the received signal strength hx (τ) shown in FIG. In addition, in FIG. 6, u1 to 3 are used as propagation paths.
is exemplified. Note that structures U1. on the same ellipse.
Since the propagation paths ul, u, formed through U2 have the same path length, the propagation times and received signal strengths are the same.

36 is a selection means that selects a propagation path U having a received signal strength hX (τ) of a predetermined value or more for each of the directional antennas ATI to ATn. Reference numeral 38 denotes a delay spread calculating means, which calculates the Average Excel based on the propagation time τ for each propagation path U selected for each directional antenna ATL=ATn.
Calculate ss Delay or Delay 5pread. 40 is a comparison means, and the calculated AVerageE
xcess De+ay or Delay 5pread
Compare. Based on the above comparison results, the ECU 14
AVerageExcess Delay or Dela
y 5pread is the minimum directional antenna ATL-A
Tn is selected, and a switching signal is generated to control the switching operation of the selector switch 16 as antenna selection means.

In the above configuration, digitally modulated electromagnetic waves are transmitted from the base station Q and received by the own vehicle R as a mobile object via multiple wave propagation paths (multipaths). Electromagnetic waves are transmitted by the na directional antennas ATI to ATr+, and the delay profile is measured differently for each antenna.

The electromagnetic waves are demodulated by each receiving section FEI-FEn, and demodulated data DAl-DAn are obtained. These demodulated data D
Data that is least affected by multipath among At-DAn is estimated according to the processing procedure shown in FIG. 7, and the directional antenna receiving this data is selected from among ATL-ATn.

FIG. 7 is a flowchart showing the process-L order in FIG.

First, in step 101, the base station map memory 20 is searched based on the device registration signal α (signal indicating whether the own vehicle Q or which base station R is within the transmission 13 area) configured by the communication control unit 18. Base station location information Q (x
l, yl) are obtained. Next, beacons, GPS, dead reckoning l
Vehicle position information R (xO.

yO) is obtained. Finally, from the urban structure data memory 24, regarding the base station location information Q (xl, yl) and own vehicle location information R (xO, yO), urban ditch road data ( xj, yj). That is, the recognition means 26 uses the above urban structure data (x
The vehicle position R (xO, yO) and the base station position Q (x l, y l) within the base station position Q (x l, y l) within the range j, y j) are recognized.

Next, for the directional antennas ATL to ATn, the antenna numbers whose delay profiles are to be measured are set to -1 (step 102). However, k-1 to n.

Then, the range covered by the processing after step 102 is determined by the eighth step.
As shown in the figure, the direction is limited to BTk within the directional plane of antenna ATk (step 103). Note that the range of the directional plane is 2
It is within π/n radians.

Next, in step 10, the amount of increase in the long sleeve between the ellipses drawn by the ellipse imagining means 28 is set by Imi.
4), base station position Q (xiyl) and own vehicle position R
IRQ
+11 to define an ellipse in the directional plane BTk (step 105). Note that the increase amount l of the long sleeves of the ellipse may be set to an arbitrary value depending on estimation accuracy and processing speed.

Subsequently, in the structure search means 30, BTk in the orientation plane
Step 106) to judge whether the structure U exists on the ellipse of Position Qx ('xi, yl) and own vehicle position R
In step 107), it is determined whether or not both can be seen from )
is calculated (steps 108 and 109).

Note that the propagation delay time τ is It is determined by However, C is the speed of light.

In addition, the received No. 13 strength hx (τ) is hx (τ)
It is determined by - (transmission power) - (propagation loss). In Uni, the propagation loss is the distance of propagation between base station Q - structure U - eye vehicle (structure
It is determined by the correlation between the long axis of the ellipse in which the object U exists) and the transmission frequency, and the reflection coefficient at the structure U.

That is, the propagation loss increases as the distance increases in proportion to the square of the transmission frequency. Incidentally, received signals for which the received signal strength hx (τ) is not calculated to be greater than or equal to a predetermined value are excluded from this process.

Now, after calculating the propagation delay time τ and the received signal strength hx (τ) by the above processing, the elliptical long sleeve I
It is determined whether RQ +II is, for example, 5000 m or more x. That is, it is determined whether the ellipse has been assumed within the 5000 m transmission area (step 110). If YES, the propagation delay time τ in the direct wave from the base station Qx to the own vehicle R, that is, the arrival time in FIG. to and the received signal strength hx (τ) (
Step 111).

Next, the calculation means 38 converts the propagation delay time τ and received fa signal strength hX (τ) in each propagation path U obtained by the calculation means 34 into the propagation delay time τ(τ) in the direct wave.
Obtain the delay profile by plotting it on a graph against the average
Delay or Delay 5preaa is calculated (step 112). Here = n, that is, for directional antenna ATL-ATn, all Avera
ge Excess Delay or Delay 5p
Step 11: Determine whether read has been calculated.
3) If YES, the comparison means 40 calculates the delay spread θl to θ. After comparing (step 114), the ECU
14, based on the above comparison results, Average
Excess Delay or Delay 5pre
The directional antenna with the minimum ad is selected from ATI-ATn, and a switching signal is output (step 115).

In this way, the ECU 14 performs Ave according to the above processing procedure.
rage Excess Delay or Delay
Find 5pread, Average Excess
A switching signal is sent to the changeover switch 12 in order to switch to the smallest directional antenna of Delay or Delay 5pread.

Thereafter, it is determined whether or not to continue this process (step 116); if YES, the process returns to step 101;
If so, the process ends.

On the other hand, if No in steps 106, 107, and 110, the count is increased by ■=-I+l, the oval long sleeve is set one size larger (step 117), and the process returns to step 105.

Also, if NO in step 113, +1 to k-
At step 118), the count is increased and the next antenna is set, and the process returns to step 103.

Note that the antenna selection operation according to the above processing procedure is performed when the own vehicle R
Based on the current position, direction of travel, speed, road, destination, etc., the vehicle R's movement position after a predetermined period of time is predicted, the delay spread θ for this movement position is simulated in advance, and an antenna is selected. It is also possible to switch immediately after moving.

[Effects of the Invention] As explained above, according to the dyno reception device according to the first invention, it is possible to select the directional antenna with the minimum delay spread, so there is less code amount interference in the received signal and High-quality reception characteristics with a low bit error rate can be obtained, which is particularly effective in high-speed digital communications.

Further, according to the diversity receiving device according to the second invention,
Since the delay profile can be estimated by simulation without the need to measure the delay profile in real time, it is possible to select the directional antenna with the minimum delay spread without actually measuring it.

[Brief explanation of drawings]

Figure 1 is a block configuration diagram showing an embodiment of the first invention. Figure 2 is an antenna directional characteristic diagram when four directional antennas are arranged. Figures 3 and 4 are multipath propagation characteristics. 5 is a block configuration diagram showing an embodiment of the second invention; FIG. 6 is a model diagram of a mobile communication propagation path using a clear circular zone with the own vehicle and a base station as focal points; Fig. 7 is a flowchart showing the processing procedure in Fig. 5, Fig. 8 is a model diagram showing the elliptical range in which the processing in Fig. 7 is performed, and Fig. 9 is a diagram for explaining code amount interference between leading waves and delayed waves. It is. ATL~ATn... Directional antenna 10...
Delay spread measuring means 12 ... Comparison means 14 ... ECU 16 ... Changeover switch (antenna selection means) 20
... Base station map memory 22 ... Own vehicle position detection means 24 ... Urban structure data memory 26 ... Recognition means 28 ... Ellipse estimation means 30 ... Structure search means 32 ... Propagation path Defining means 34 ... Calculating means 38 ... Comparison means 40 ... Comparing means U ... Structure U ... Propagation path

Claims (2)

[Claims] (1) In a diversity receiving device that has a plurality of directional antennas installed facing in a predetermined direction and performs reception under optimal conditions by selecting one of these directional antennas, a delay spread measurement means for measuring the spread of multipath propagation delay time for a multipath antenna, a comparison means for comparing the spread of each measured delay time, and a directivity with the minimum spread of delay time based on the above comparison results. A diversity receiving device comprising: antenna selection means for selecting an antenna. (2) In a diversity receiving device that has a plurality of directional antennas installed facing in a predetermined direction and performs reception under optimal conditions by selecting one of these directional antennas, the base station position A base station map memory in which information is stored; a vehicle position detecting means for detecting vehicle position information; an urban structure data memory in which urban structure data is stored; recognition means for recognizing the position of the base station, and ellipse estimation means for assuming an elliptical zone model with the own vehicle and the base station as focal points in the urban structure data; structure search means for searching for structures on an ellipse located within the line-of-sight from both the host vehicle and the base station based on the urban structure data; and a propagation path formed through the searched structures. Propagation path defining means for defining each directional antenna having a directional plane on which the structure exists; Calculating means for calculating the propagation time and received signal strength in each of the defined propagation paths for each of the directional antennas; a delay spread calculation means for calculating a propagation time delay spread based on the propagation time of each propagation path calculated for each directional antenna; a comparison means for comparing the calculated delay time spread; 1. Antenna selection means for selecting a directional antenna with a minimum delay time spread.