JPH06140950A - Fading simulator - Google Patents

Abstract

PURPOSE:To provide the fading simulator operated at an equivalent complex base band. CONSTITUTION:The fading simulator is provided with complex amplitude tables 411, 421 storing complex amplitude data of at least one period from element waves subject to Doppler shift caused by movement of a mobile station in a space to which plural element waves without any propagation delay time difference, read initial address and read address generating circuits 412, 421 whose read speed is variable to read complex amplitude data from the complex amplitude tables 411, 421 and a complex multiplier 7 applying complex multiplication between complex amplitude data 6a, 6b read from the complex amplitude tables 411, 421 and input complex data 3a, 3b sampled from input complex signals 1a, 1b with a sampler 2 to obtain fading simulator outputs 8a, 8b.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fading simulator for simulating amplitude and phase fluctuations due to fading in a baseband.

[0002]

2. Description of the Related Art Recently, social needs for mobile communication have been rapidly increasing. Regarding a system providing mobile communication, various improvements and new system configuration methods have been proposed with the aim of accommodating more subscribers. Along with this, the complexity of the signal transmission method and its operating method in the wireless section is gradually increasing. This indicates that the spectrum utilization rate of the mobile communication system largely depends on the signal transmission performance in the wireless section.

Frequency division multiplex (FDMA) and time multiplex (TDMA) communication systems have been used as communication systems in mobile communication systems. On the other hand, there is a possibility that the code division multiplex communication system using spread spectrum can significantly improve the spectrum utilization rate recently (1): KSGilhousen, IMJacobs, R.Pad.
ovani, A.Viterbi, LAWeaver, Jr.and CEWheatley I
II, "On the Capacity of a Cellular CDMA System", IEEE
Since it was presented by Trans.VT, Vol.VT-40, pp.303-312, 1991, studies for its practical use have become active.

By the way, in general, the performance of a transmitter / receiver in a radio section is determined by a portion for processing a complex baseband signal (hereinafter, referred to as
The performance of a complex baseband signal processing section) and the performance of a section that processes a signal in the radio frequency band (hereinafter referred to as a radio frequency band signal processing section) can be considered separately.
Roughly speaking, the former complex baseband signal processing unit corresponds to the process until the transmitter produces a complex modulated signal, and the receiver corresponds to the process after synchronous or quasi-synchronous detection of the received signal. The latter radio frequency band signal processing unit performs processing until the transmitter orthogonally modulates a carrier with a complex modulation signal, then amplifies the power and transmits to space, and the receiver performs synchronous or quasi-synchronous detection of the received signal. Corresponding to the processing of. These performances are often evaluated independently of each other.
In particular, due to recent advances in digital signal processing technology, the processing contents of the complex baseband signal processing section tend to be sophisticated, and many functions are being performed in the complex baseband band. There is a strong demand to independently evaluate the performance of the signal processing unit.

A characteristic of mobile communication is that a transmission signal from a transmitter is affected by multipath fading in its propagation process. Therefore, when evaluating the performance of the wireless section signal transmission system, how much the characteristic under fading is improved is an important evaluation criterion.

Non-frequency selective fading, ie multipath fading without frequency selectivity, can be modeled as synergistic noise (complex number) on the complex amplitude of the transmitted signal. This indicates that the transmission characteristics can be evaluated only by the complex baseband signal processing unit described above. That is, an equivalent complex baseband transmission system can be configured by installing a fading simulator having a function of multiplying a signal by a fading complex amplitude between transmitters and receivers that process a complex baseband signal. Usually, the performance of the radio frequency band signal processing unit in the receiver is often evaluated by converting it to the equivalent complex white noise (AWGN) power generated here. This means that it can be simulated by generating an equivalent AWGN in the equivalent complex baseband transmission system and performing a complex addition to the received signal.

The merits of evaluating the performance of the wireless section signal transmission system with the equivalent complex baseband transmission system as described above are as follows. Firstly, the characteristic deterioration due to the incompleteness of the hardware configuration of the transceiver and the delicate adjustment of the analog circuit parts mainly occurs in the radio frequency band signal processing unit. Therefore, it is appropriate to evaluate the operating principle itself of the wireless section signal transmission system in a complex baseband signal band that is not affected by such deterioration factors. Secondly, the characteristic deterioration occurring in such a radio frequency band can be simulated in the equivalent baseband region by appropriately modeling the cause of deterioration, so that the characteristic deterioration that appears as a result of multiple causes can be eliminated. It is possible to separate each factor and examine its effect. Furthermore, compensation for them can be easily performed in the equivalent baseband region.

[0008]

As described above, the performance of the wireless section signal transmission system can be easily evaluated by the equivalent complex baseband transmission system, and the great merit described above can be obtained. In fact, the characteristic evaluation by computer simulation is often performed in the equivalent complex baseband.

However, as a fading simulator operating in real time, one operating in a radio frequency band has been widely used. Therefore, in the performance evaluation method of the wireless section signal transmission system that has been adopted conventionally, after the frequency of the complex baseband signal is converted to the wireless frequency band by actually using the transceiver, the characteristic is measured by connecting to this fading simulator. How to do it. For this reason, there is a drawback that it is difficult to isolate the characteristic deterioration factor and to optimize the signal processing in the equivalent complex baseband. Therefore, it is desired to realize a fading simulator that can operate in the equivalent complex baseband band.

It is an object of the present invention to provide a fading simulator device which operates in the equivalent complex baseband band and thereby enables performance evaluation of a radio section signal transmission system to be performed in the equivalent complex baseband band.

[0011]

According to the present invention, at least one cycle of an elementary wave that has been Doppler-shifted by a mobile station moving in a space where a plurality of elementary waves having no propagation delay time difference arrive. Storage means for storing the complex amplitude data, reading means for reading the complex amplitude data from the storage means, the reading start position and the reading speed being variable, and the complex amplitude read by the reading means from the storage means. A non-frequency selective fading simulator device is provided by including complex multiplication means for complexly multiplying data and input complex data to obtain a fading simulator output.

Further, according to the present invention, the mobile station moves in a space in which a plurality of delay means for delaying the input complex data and having a variable delay time and a plurality of elementary waves having no difference in propagation delay time arrive. Storage means for storing complex amplitude data for at least one cycle of the elementary wave subjected to Doppler shift by: and read means for reading the complex amplitude data from the storage means, the read start position and the reading speed being variable, A plurality of non-complexers each configured by complex multiplication means for complex-multiplying the complex amplitude data read by the reading means from the storage means and the input complex data delayed by the delay means to obtain a fading simulator output. Complex output of the frequency selective fading simulator and the output of these multiple non-frequency selective fading simulators. Frequency selective fading simulator apparatus is provided by calculation to comprise a plurality of complex addition means for obtaining a frequency selective fading simulator output.

[0013]

[Function] The equivalent complex amplitude of non-frequency selective fading is described in Ref. (2): WCJakes, Jr., "Microwave Mobile Comm.
unications ", John Wiley & Sons, pp. 67-76 (1974). The fading simulator apparatus according to the present invention generates fading equivalent complex amplitude data based on this model in real time. According to the above, fading occurs when N elementary waves having no propagation delay time difference (different initial phases) arrive at the mobile station, and these arriving elementary waves undergo Doppler shift due to movement of the mobile station. Fading can be simulated in the equivalent baseband band by generating complex amplitude data of the composite wave of the elementary waves subjected to these Doppler shifts, and sequentially complex-multiplying this with the input complex data.

[0014]

EXAMPLES Examples of the present invention will be described below. Consider the i-th incoming wave among the N incoming waves that have undergone the Doppler shift due to the movement of the mobile station as described above. The complex amplitude z _i of this elementary wave can be written as the following equation.

Z _i = E _i exp {j (2πf _D cos β _i + θ _i )} where β _i is the arrival angle of the ray with respect to the traveling direction of the mobile station, θ _i is the initial phase, E _i is the amplitude, and f _D is the maximum Doppler frequency, and f _D is given by f _D = λ / v where λ is the wavelength and v is the traveling speed.

Therefore, the in-phase component (COS component) of the complex amplitude z _i with respect to the time t is E _i cos (2πf _D tcosβ _i + θ
_i ), the orthogonal component (SIN component) is E _i sin (2πf _D tcos
β _i + θ _i ). This fluctuation is cos (2πf
_{D tcosβ i} + _{θ i)} and providing a numerical data, that complex amplitude table stored in advance the complex amplitude data _{sin (2πf D tcosβ i + θ} i), fast from these complex amplitude table complex amplitude data 2πf _D tcosβ _i Then, it can be created by multiplying the result by E _i while reading. As a method of realizing the complex amplitude table, only one of the SIN and COS tables is provided and the data separated by the address difference corresponding to the phase difference of π / 2 is read to make one table. You can also do it.

The initial position θ _i corresponds to the initial address for reading from the complex amplitude table, that is, the reading start position. The read address is incremented by 2πf _D cos β
_Although it is performed at a speed corresponding to _i , it goes without saying that both components are periodic functions and are repeated at MOD (2π).

Then, N complex amplitude tables described above are provided corresponding to N elementary waves arriving at the mobile station, and complex amplitude data is 2πf _D cos β _i from these complex amplitude tables.
After reading at a variable speed controlled to a speed corresponding to, the complex amplitude data is added for each in-phase component and each quadrature component to obtain fading equivalent complex amplitude data. An equivalent baseband fading transmission line, that is, an equivalent baseband fading simulator can be realized by performing a complex multiplication of the equivalent complex amplitude data and the input complex data (sampled from the input complex signal). The initial address for reading from the complex amplitude table corresponding to the initial phase of each elementary wave is variable, and is set randomly from the outside or at every reset.

FIG. 1 is a block diagram showing the configuration of a fading simulator apparatus according to an embodiment of the present invention based on the above-mentioned principle. In the present embodiment, it will be explained that all the incoming elementary waves to the mobile station have the same amplitude. This corresponds to the case where all of the above E _i are 1.

In FIG. 1, the input complex signal 1 comprises an I channel signal 1a and a Q channel signal 1b. Sampler 2
Is the input complex data composed of the I channel data 3a and the Q channel data 3b, which are sampled value series, sampled at the timing of the sampling clock from the clock generator 10 3 is output.

The fading complex amplitude generating section 4 includes fading complex amplitude generating sections 4a and 4b for the I channel component (COS component) and the Q channel component (SIN component).
Consists of. The fading complex amplitude generation unit 4a for the I channel component includes a complex amplitude table 411 that stores complex amplitude data for one period of the I channel component, and a read address generation circuit 412 that generates a read address of the complex amplitude table. The fading complex amplitude generation unit 4b for the Q channel component includes a complex amplitude table 421 that stores complex amplitude data for one cycle of the Q channel component, and a read address generation circuit 422 that generates a read address of the complex amplitude table 421.

The complex amplitude tables 411 and 421 are
I-channel component table 4111 of N elementary waves
~ 411N and Q channel component tables 4211-4
21N, and the read address generating circuits 412 and 422 are provided in the tables 4111 to 411N and 4211.
Read address generators 4121 to 412N and 4221 to 422N which generate read addresses of ˜421N.

Read address generators 4121 to 412N
And 4221 to 422N have initial addresses 4131 to 413 common to the I channel component and the Q channel component.
The same address update timing clock 9 as N is input. Read address generators 4121 to 412N
The read addresses output from the and 4221 to 422N are incremented in synchronization with the address update timing clock 9 from the set initial addresses 4131 to 413N. In this case, the read address output as described above is repeated at MOD (2π).

The complex-amplitude I-channel component 414 and Q-channel component 424 read from the complex-amplitude tables 411 and 412 are added by the I-channel component adder 5a and the Q-channel component adder 5b, respectively. A fading complex amplitude I channel component 6a
And the Q channel component 6b are provided to one input of the complex multiplier 7. The sampled I channel data 3a and Q channel data 3b are applied to the other input of the complex multiplier 7.

Complex multiplication of both inputs is performed in the complex multiplier 7, and (8a) = (3a) as the I channel component output.
× (6a) − (3b) × (6b), as a Q channel component output (8b) = (3a) × (6b) + (3b) × (6
a) is output. Outputs 8a and 8b of the complex multiplier 7
Is the non-frequency selective equivalent baseband fading simulator output 8.

The address update timing clock 9 is supplied from the clock generator 10, and its clock frequency is set by the external setting input 11. That is, the external setting input 11 makes variable the speed of reading data from the complex amplitude tables 411 and 421 by the read address generating circuits 412 and 421.

Therefore, according to the fading simulator device of this embodiment, the fading complex amplitude based on the model described in the above-mentioned reference (2) can be faithfully generated.

In the above description, all the incoming elementary waves have the same amplitude. However, when the wave intensity is different depending on the incoming direction, that is, when there is directivity, FIG.
Of the complex amplitudes read out from the complex amplitude tables 411 and 421 are used as the weighting adders.
The channel component 414 and the Q channel component 424 may be weighted and then added.

In the above embodiment, the complex amplitude table 4
11 and 421 have the same number of tables 4111 to 411N and 4211 to 421 as the number (N) of incoming elementary waves, respectively.
N is needed.

FIG. 2 shows the I channels and Q of a plurality of incoming elementary waves.
It has a table after synthesizing each channel component,
FIG. 6 is a block diagram showing a fading simulator according to another embodiment of the present invention in which an address is reciprocally generated to simplify the structure of FIG. 1, and a fading complex amplitude generator 4 has a structure of the embodiment of FIG. 1. Different from

That is, in this embodiment, each N in FIG.
The complex amplitude tables 411 and 421 of the I and Q channel components are divided into K sets. Figure 2
The example of shows the case of K = 2.

Then, a value (a finite number) after combining the respective I channel components and Q channel components is held as a table for these K sets. By doing so, the number of tables for the I channel component and the Q channel component becomes 2K. Tables 2011-201K and 2021-202K
Are the I channel component table and the Q channel component table of these combined values, respectively L ₁ ,
L ₂ , ..., L _K data are stored.

On the other hand, these tables 2011 to 201
Read address generation units 4121 to 412K (I channel component) and 4221 to 422K (Q channel component) that generate read addresses of K and 2021 to 202K
Then, the set initial addresses 4131 to 413N (I
The read is started from the channel component and the Q channel component), and when the read address reaches the end point of the data in the table, the increment / decrement of the address is reversed to reciprocate the address.

By doing so, the continuity of the fading complex amplitude data can be secured with a more simplified structure. Further, by making the values of L ₁ , L ₂ , ... L _K relatively prime, the cycle of generated data can be made sufficiently long.

According to the two embodiments described above, a field simulator device simulating a non-frequency selective equivalent baseband fading transmission line can be realized. But,
When realizing a faster wireless section signal transmission system,
Channel coherence is lost in the transmission bandwidth.
In such channels, fading becomes frequency selective.

The equivalent baseband transmission line for frequency selective fading can be realized by combining a plurality of non-frequency selective equivalent baseband fading transmission lines in the above-mentioned embodiment. That is, M non-frequency selective equivalent baseband fading transmission lines are used, and input data is delayed by M predetermined times (determined from the measurement value of the delay profile of the channel). After performing complex multiplication on the amplitude data, the results are sequentially weighted and complex-added and output. The weighting coefficient in the weighted addition is also determined from the measured value of the channel delay profile.

FIG. 3 is a block diagram showing an example of the configuration of an equivalent baseband frequency selective fading simulator constructed on the basis of such an idea. Here, signals corresponding to all propagation paths have the same average power. Will be described as having.

In FIG. 3, the input complex signal 1 comprises an I channel signal 1a and a Q channel signal 1b. Sampler 2
Of the input complex signal 1 samples the I channel signal 1a and the Q channel signal 1b at the timing of the sampling clock 9 and outputs the complex input data 3 including the sampled I channel data 3a and Q channel data 3b.

Sampled I channel data 3a
The Q channel data 3b and the Q channel data 3b are input to the delay unit 12. The delay unit 12 is composed of M delay circuits 1221 to 121M whose delay times can be set.
21 to 121M are delay time setting inputs 1221 to 122M
The input I channel signal 3a and the Q channel signal 3b are delayed by the time set by
To the non-frequency selective equivalent baseband fading simulator unit 14.

The non-frequency selective equivalent baseband fading simulator section 14 includes the complex amplitude generating section 4, the adders 5a and 5b and the complex multiplier 7 in FIG. 1 or 2.
M non-frequency selective equivalent baseband fading simulators 141 to 14M respectively configured by The I channel component and the Q channel component of the output 15 of the non-frequency selective equivalent baseband fading simulators 141 to 14M are added in the I channel component adder 16a and the Q channel component adder 16b, respectively, to obtain the frequency selective equivalent. It becomes the I channel component 17a and the Q channel component 17b of the baseband fading simulator output 17.

In the embodiment of FIG. 3, the signals corresponding to all the propagation paths have been described as having the same average power, but the delay profile is not uniform, and the signal power depends on the propagation paths. , The non-frequency selective equivalent baseband fading simulators 141 to 14
The output of M may be weighted and added. That is, the non-frequency selective equivalent baseband fading simulator 1
The output signals of 41 to 14M may be weighted with a variable weighting coefficient to perform complex addition. By making it possible to change the M delay times and the weighting coefficients in the frequency selective fading in this way, it is possible to easily simulate delay profiles of various channels.

A quasi-coherent detection circuit for quasi-coherent detection of a radio frequency is arranged on the input side of the equivalent baseband fading simulator apparatus according to the present invention, and a frequency conversion circuit for frequency conversion of the equivalent baseband signal to the radio frequency is provided on the output side. It is obvious that the fading simulator device can be operated as a fading simulator device in the radio frequency band by arranging.

[0043]

As described above, according to the present invention, it is possible to easily configure a fading simulator device that operates in real time in the equivalent complex baseband band.
This makes it possible to evaluate the performance of the wireless section signal transmission system with the equivalent complex baseband transmission system.

Further, the fading simulator apparatus according to the present invention has an advantage that delay profiles of various channels can be easily simulated because M delay times and weighting coefficients in frequency selective fading can be easily changed.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of a fading simulator device according to an embodiment of the present invention.

FIG. 2 is a block diagram showing the configuration of a fading simulator device according to another embodiment of the present invention.

FIG. 3 is a block diagram showing a configuration of an equivalent baseband frequency selective fading simulator device according to still another embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Input complex signal 2 ... Sampler 3 ... Input complex data 4 ... Fading complex amplitude generation part 4a ... Fading complex amplitude I channel component generation part 4b ... Fading complex amplitude Q channel component generation part 411 ... I channel component complex amplitude Table 421 ... Q channel complex amplitude table 4111 to 411N ... N channel I channel component table 4211 to 421N ... N channel Q channel component table 4121 to 412N ... I channel component table read address generator 4221 ... 422N ... Read-out address generator of Q channel component table 4131-413N ... Initial address 414 ... Complex amplitude I channel component read from table 424 ... Complex amplitude Q channel component read from table 5a ... For I channel component Adder 5b ... Q channel component adder 6a ... Fading complex amplitude I channel component 6b ... Fading complex amplitude Q channel component 7 ... Complex multiplier 8 ... Non-frequency selective equivalent baseband fading simulator output 9 ... Address update timing clock 10 ... Clock generator 11 ... Clock frequency external setting input 2011-201K ... I-channel component table of combined values 2021-202K ... Q-channel component table of combined values 4121-412K ... Read-out address generation unit 4221-422K of I-channel component table ... Q channel component table read address generation unit 12 ... Delay unit 1221 to 121M ... Delay time configurable delay circuit 1221 to 122M ... Delay time setting input 13 ... Delay circuit output 14 ... Non-frequency selective equivalent baseband phase Non-frequency selective equivalent baseband fading simulator 15 ... Non-frequency selective equivalent baseband fading simulator output 16a ... I channel component adder 16b ... Q channel component adder 17 ... Equivalent baseband frequency Selective fading simulator output

Claims (3)

[Claims] 1. Storage means for storing complex amplitude data for at least one cycle of the elementary waves that have been Doppler-shifted by a mobile station moving in a space in which a plurality of elementary waves having no propagation delay time difference arrive. Reading means for reading the complex amplitude data from the storage means, the reading start position and the reading speed being variable, and complex multiplication of the complex amplitude data read by the reading means from the storage means and the input complex data. And a complex multiplication means for obtaining a fading simulator output by the fading simulator. 2. A plurality of delay means for delaying input complex data and a variable delay time, and a mobile station moving in a space in which a plurality of elementary waves having no propagation delay time difference arrive to receive a Doppler shift. Storage means for storing complex amplitude data for at least one cycle of the elementary wave, read-out means for reading the complex amplitude data from the storage means, the read-out position and reading speed being variable, and the storage means for storing the complex amplitude data. A plurality of non-frequency selective fading simulators each configured by complex multiplication of the complex amplitude data read by the reading means and the input complex data delayed by the delay means to obtain a fading simulator output. And frequency selection by complex adding the outputs of these multiple non-frequency selective fading simulators. Fading simulator apparatus characterized by comprising a plurality of complex addition means for obtaining a fading simulator output. 3. The fading according to claim 2, wherein the plurality of complex adding means perform complex addition by weighting outputs of the plurality of non-frequency selective fading simulators with variable weighting coefficients. Simulator device.