JP3206146B2 - Fading simulator device - Google Patents

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 caused by fading in a baseband.

[0002]

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

[0003] As a communication system in a mobile communication system, a frequency division multiplexing (FDMA) communication system and a time multiplexing (TDMA) communication system have been used. On the other hand, recently, a code division multiplexing communication system using spread spectrum may significantly improve the spectrum utilization rate [1]: KSGilhousen, IMJacobs, R. Pad
ovani, A. Viterbi, LAWeaver, Jr. and CEWheatley I
II, "On the Capacity ofa Cellular CDMA System", IEEE
Trans.VT, Vol.VT-40, pp.303-312, 1991, have been actively studied for its practical use.

[0004] Generally, the performance of a transmission / reception apparatus in a wireless section depends on a part for processing a complex baseband signal (hereinafter, referred to as a "part").
The performance of a complex baseband signal processing unit) and the performance of a part that processes signals in a radio frequency band (hereinafter, referred to as a radio frequency band signal processing unit) can be considered separately.
Roughly, the former complex baseband signal processing unit corresponds to processing until a complex modulated signal is generated in a transmitter, and processing after synchronous or quasi-synchronous detection of a received signal in a receiver. The latter radio frequency band signal processing unit performs a process of orthogonally modulating a carrier with a complex modulation signal at a transmitter, a process of power amplification and transmission to space, and a process of synchronizing or quasi-synchronous detection of a received signal at a receiver. Corresponding to the processing of. These performances are often evaluated independently of each other.
In particular, with the recent development of digital signal processing technology, the processing content of the complex baseband signal processing unit tends to be sophisticated, and many functions are being performed in the complex baseband band. There is a strong demand for independently evaluating the performance of the signal processing unit.

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

[0006] Non-frequency selective fading, ie, multipath fading without frequency selectivity, can be modeled as synergistic noise (complex) for 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 complex amplitude of fading between a transceiver that processes a complex baseband signal. Usually, the performance of the radio frequency band signal processing unit in the receiver is often evaluated by converting it into equivalent complex white noise (AWGN) power generated here. This means that an equivalent AWGN can be simulated by generating an equivalent AWGN in the equivalent complex baseband transmission system and performing complex addition on the received signal.

[0007] Advantages of evaluating the performance of the radio section signal transmission system in equivalence complex baseband transmission system as described above is as follows. First, characteristic deterioration due to imperfections in the hardware configuration when a transceiver is configured and fine adjustment of analog circuit components mainly occurs in a radio frequency band signal processing unit. Therefore, it is appropriate to evaluate the operation principle of the wireless section signal transmission system in a complex baseband signal band which is not affected by such a deterioration factor. Secondly, the characteristic degradation occurring in such a radio frequency band can be simulated in the equivalent baseband region by appropriately modeling the cause of the degradation, so that the characteristic degradation appearing as a result of a plurality of causes can be reduced. It is possible to isolate each factor and examine its effect. In addition, compensation for them,
This can be easily achieved in an equivalent baseband region.

[0008]

As described above, the performance of a radio section signal transmission system can be easily evaluated by an equivalent complex baseband transmission system, and the above-mentioned great advantages can be obtained. Actually, characteristic evaluation by computer simulation is often performed in an equivalent complex baseband band.

However, fading simulators operating in a radio frequency band have been widely used in the past in real time. Therefore, in the performance evaluation method of the wireless section signal transmission system that has been conventionally adopted, the complex baseband signal is frequency-converted to the radio frequency band by actually using the transceiver, and then connected to this fading simulator to measure the characteristics. The way to do it. For this reason, there are drawbacks in that it is difficult to distinguish the cause of the characteristic deterioration and to optimize the signal processing in the equivalent complex baseband band. Therefore, it is desired to realize a fading simulator that can operate in an equivalent complex baseband band.

It is an object of the present invention to provide a fading simulator apparatus which operates in an equivalent complex baseband and can thereby evaluate the performance of a radio section signal transmission system in an equivalent complex baseband.

[0011]

According to the present invention, fading occurs when a received signal of a mobile station moving in a direction inclined at a predetermined angle with respect to a plurality of signals having no propagation delay time difference undergoes a Doppler shift. A fading simulator device that simulates the input complex signal corresponding to the received ray and outputs the input complex data; a sampler that receives the incoming ray with respect to the traveling direction of the mobile station; Phase and amplitude, a fading complex amplitude generator that generates complex amplitude data determined based on the Doppler frequency determined from the moving speed of the mobile station, and complex multiplying the complex amplitude data and input complex data There is provided a fading simulator apparatus comprising: a complex multiplication means for obtaining a fading simulator output.

Further, according to the present invention, fading for simulating fading caused by receiving a Doppler shift of a received element wave of a mobile station moving in a direction inclined by a predetermined angle with respect to a plurality of element waves having no propagation delay time difference. A simulator device, which samples an input complex signal corresponding to the received element wave and outputs input complex data, a plurality of variable delay means having a variable delay time for delaying the input complex data, A fading complex amplitude generator that generates complex amplitude data determined based on the arrival angle and initial phase and amplitude of the received beam with respect to the traveling direction of the mobile station, and a Doppler frequency obtained from the moving speed of the mobile station; , A complex multiplier for complexly multiplying the complex amplitude data and input complex data to obtain a fading simulator output A plurality of non-frequency-selective fading simulators each constituted by: and a plurality of complex addition means for obtaining a frequency-selective fading simulator output by complex-adding the outputs of the plurality of non-frequency-selective fading simulators. A fading simulator device is provided.

[0013]

[Effect] 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). In the fading simulator device according to the present invention, for example, fading equivalent complex amplitude data based on this model is generated in real time. According to the above, fading occurs when N beams having no propagation delay time difference (different in initial phase) arrive at the mobile station, and these incoming beams 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 having undergone these Doppler shifts and sequentially complex multiplying the complex amplitude data by the input complex data.

[0014]

Embodiments of the present invention will be described below. Consider the i-th arriving wave among the N arriving waves that have undergone Doppler shift due to the movement of the mobile station as described above. The complex amplitude z _i of this ray can be written as:

Z _i = E _i exp {j (2πf _D cos β _i + θ _i )} where β _i is the ray (reception element) with respect to the traveling direction of the mobile station.
Arrival angle of the wave), theta _i is the initial phase, E _i is the amplitude, and f _D is a maximum Doppler frequency, f _D is the wavelength lambda, transfer
Assuming that the moving speed of the mobile station is v, f _D = λ / v.

Accordingly, the in-phase component (COS component) of the complex amplitude z _i with respect to time t is E _i cos (2πf _D tcos β _i + θ).
_i ) and the orthogonal component (SIN component) is E _i sin (2πf _D tcos
β _i + θ _i ). This variation is cos (2πf
A complex amplitude table in which numerical data of _D tcosβ _i + θ _i ) and sin (2πf _D tcosβ _i + θ _i ), that is, complex amplitude data are prepared in advance, and complex amplitude data is converted from these complex amplitude tables at a speed of 2πf _D tcosβ _i while reading in of, it can be created by multiplying the result E _i. As a method of realizing the complex amplitude table, only one table of SIN or COS is provided, and by reading data separated by an address difference corresponding to a phase difference of π / 2, the table becomes one type. You can also.

The initial address of the read from the complex amplitude table, ie reading start position is set at a position corresponding to the initial position phase theta _i. The read address is incremented at a speed corresponding to 2πf _D cos β _i , but it goes without saying that both components are periodic functions and are repeated at MOD (2π).

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

FIG. 1 is a block diagram showing a configuration of a fading simulator according to an embodiment of the present invention based on the above-described principle. In this embodiment, a description will be given assuming that all incoming rays to the mobile station have the same amplitude. This corresponds to the case where all the aforementioned _Ei are 1.

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

The fading complex amplitude generator 4 includes fading complex amplitude generators 4a and 4b for I-channel component (COS component) and Q-channel (SIN component) component.
Consists of The I-channel component fading complex amplitude generator 4a includes a complex amplitude table 411 storing one cycle of complex amplitude data of the I-channel component, and a read address generation circuit 412 for generating a read address of the complex amplitude table. The Q channel component fading complex amplitude generator 4b includes a complex amplitude table 421 storing complex amplitude data for one cycle of the Q channel component, and a read address generation circuit 422 for generating a read address of the complex amplitude table 421.

The complex amplitude tables 411 and 421 are
An I-channel component table 4111 of N rays each
411N and Q channel component tables 4211-4
21N, and the read address generation circuits 412 and 422 store the tables 4111 to 411N and 4211
To 421N read address generation units 4121 to 412N and 4221 to 422N.

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.
Similarly to N, a common address update timing clock 9 is input. Read address generators 4121 to 412N
And the read addresses output from 4221 to 422N are incremented from the set initial addresses 4131 to 413N in synchronization with the address update timing clock 9. In this case, the read address output as described above repeats 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 an I-channel component adder 5a and a Q-channel component adder 5b, respectively. Some fading complex amplitude I channel component 6a
And Q channel component 6 b are provided to one input of complex multiplier 7. The other input of the complex multiplier 7 is supplied with sampled I-channel data 3a and Q-channel data 3b.

The complex multiplier 7 performs complex multiplication of both inputs, and outputs (8a) = (3a) as an I-channel component output.
× (6a) − (3b) × (6b), (8b) = (3a) × (6b) + (3b) × (6)
Output a). Outputs 8a and 8b of this complex multiplier 7
Is the non-frequency selective equivalent baseband fading simulator output 8.

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

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

Although the above description has been made on the assumption that all arriving rays have the same amplitude, when the waves have different intensities depending on the direction of arrival, that is, when there is directivity, FIG.
Of the complex amplitudes read from the complex amplitude tables 411 and 421 are used as the weighted adders 5a and 5b.
The channel component 414 and the Q channel component 424 may be added after weighting.

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 of incoming rays (N), respectively.
N is required.

FIG. 2 shows the I channel and Q of a plurality of incoming rays.
It has a table after combining each channel component,
FIG. 4 is a block diagram showing a fading simulator according to another embodiment of the present invention in which addresses are reciprocated to simplify the configuration of FIG. 1 according to another embodiment of the present invention. And different.

That is, in the present embodiment, each of N in FIG.
The complex amplitude tables 411 and 421 of the I channel component and the Q channel component are divided into K sets. FIG.
Shows the case where K = 2.

Then, for each of the K sets, a value (finite number) of the combined I-channel component and Q-channel component is stored as a table. In this case, the number of tables for the I channel component and the Q channel component is 2K. Tables 2011-201K and 2021-202K
Is an I-channel component table and Q channel component table of values after their synthesis, respectively L _1,
L ₂ ,..., L _K data are stored.

On the other hand, these tables 2011-201
Read address generators 4121 to 412K (I channel component) and 4221 to 422K (Q channel component) for generating read addresses of K and 2021 to 202K
Then, the set initial addresses 4131 to 413N (I
The reading is started from the same channel component and the Q channel component), and when the read address reaches the end point of the data in the table, the address is reciprocated by reversing the increment / decrement of the address.

By doing so, continuity of fading complex amplitude data can be ensured with a more simplified configuration. Also, L _1, L _2, ... by relatively prime values of L _K, it can be sufficiently long period of data generated.

According to the two embodiments described above, a field simulator apparatus simulating a non-frequency selective equivalent baseband fading transmission path can be realized. But,
To realize a higher-speed 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 of frequency selective fading can be realized by combining a plurality of non-frequency selective equivalent baseband fading transmission lines in the above-described embodiment. That is, M complex data are added to M data obtained by delaying input data by M predetermined time periods (determined from measured values of channel delay profiles) using M non-frequency selective equivalent baseband fading transmission paths. After complexly multiplying the amplitude data, the results are sequentially weighted and complexly added and output. The weight coefficient in the weighted addition is also determined from the measured value of the channel delay profile.

FIG. 3 is a block diagram showing a configuration example of an equivalent baseband frequency selective fading simulator configured based on such a concept. Here, signals corresponding to all propagation paths have the same average power. It 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
Samples the I-channel signal 1a and the Q-channel signal 1b of the input complex signal 1 at the timing of the sampling clock 9, and outputs complex input data 3 composed of the sampled I-channel data 3a and Q-channel data 3b.

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

The non-frequency-selective equivalent baseband fading simulator 14 comprises the complex amplitude generator 4, the adders 5a and 5b and the complex multiplier 7 shown in FIG.
Have M non-frequency-selective equivalent baseband fading simulators 141 to 14M, respectively. 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 an I-channel component adder 16a and a Q-channel component adder 16b, respectively. The I-channel component 17a and the Q-channel component 17b of the baseband fading simulator output 17 are obtained.

In the embodiment shown in FIG. 3, it has been described that the signals corresponding to all the propagation paths have the same average power. However, the delay profile is not uniform, and the signal power is different depending on the propagation path. Are different, 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 complex addition may be performed by weighting the output signals of 41 to 14M with variable weighting coefficients. As described above, by enabling the M delay times and the weighting factors in frequency selective fading to be changed, delay profiles of various channels can be easily simulated.

A quasi-synchronous detection circuit for quasi-synchronous detection of a radio frequency is arranged on the input side of the equivalent baseband fading simulator according to the present invention, and a frequency conversion circuit for frequency-converting the equivalent baseband signal to a radio frequency on the output side. It is obvious that the disposition of this allows the fading simulator to be operated as a fading simulator for a radio frequency band.

[0043]

As described above, according to the present invention, the transmission
Inclination at a predetermined angle with respect to multiple beams with no difference in transport delay time
Received by a mobile station moving in a different direction
Simulates fading
A fading simulator device that is a fading simulator device that operates in real time in an equivalent complex baseband can be easily configured. by this,
The performance of the wireless section signal transmission system can be evaluated by the equivalent complex baseband transmission system.

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

[Brief description of the drawings]

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

FIG. 2 is a block diagram showing a 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 apparatus according to still another embodiment of the present invention.

[Explanation of symbols]

Reference Signs List 1: input complex signal 2: sampler 3: input complex data 4: fading complex amplitude generator 4a: fading complex amplitude I-channel component generator 4b: fading complex amplitude Q-channel component generator 411: complex amplitude of I-channel component Table 421... Q channel complex amplitude table 4111 to 411N... N elementary wave I channel component tables 4211 to 421N... N elementary wave Q channel component tables 4121 to 412N... I channel component table read address generator 4221 .. 422N... Q-channel component table read address generator 4131 to 413N... Initial address 414... Complex amplitude I-channel component read from table 424... Complex amplitude Q-channel component read from table 5a. Adder 5b ... Adder for Q channel component 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 value 2021-202K ... Q-channel component table of combined value 4121-412K ... I-channel component table read address generator 4221-422K ... Q-channel component table read address generator 12 delay unit 1221 to 121M delay circuit with delay time setting 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 Adder for I-channel component 16b Adder for Q-channel component 17 ... Equivalent baseband frequency Selective fading simulator output

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-59-101938 (JP, A) JP-A-3-14327 (JP, A) JP-A-6-104855 (JP, A) JP-A-1- 254026 (JP, A) JP-A-1-274526 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H04B 17/00 H04B 1/10 H04B 7/26

Claims (7)

(57) [Claims] 1. A fading simulator apparatus for simulating fading caused by a received ray of a mobile station moving in a direction inclined at a predetermined angle with respect to a plurality of rays having no difference in propagation delay time due to receiving a Doppler shift. A sampler that samples an input complex signal corresponding to the received ray and outputs input complex data; an arrival angle, an initial phase and an amplitude of the received ray with respect to a traveling direction of the mobile station, and a movement of the mobile station. A fading complex amplitude generator that generates complex amplitude data determined based on the Doppler frequency obtained from the speed, and a complex multiplying unit that performs complex multiplication of the complex amplitude data and input complex data to obtain a fading simulator output. A fading simulator device comprising: 2. A fading simulator apparatus for simulating fading due to a received ray of a mobile station moving in a direction inclined at a predetermined angle with respect to a plurality of rays having no propagation delay time difference, receiving a Doppler shift. A sampler that samples an input complex signal corresponding to the received elementary wave and outputs input complex data; a plurality of variable delay units having a variable delay time for delaying the input complex data; and a traveling direction of the mobile station. A fading complex amplitude generator that generates complex amplitude data determined based on the arrival angle, initial phase, and amplitude of the received ray with respect to the Doppler frequency obtained from the moving speed of the mobile station, and the complex amplitude data And complex complex means for complexly multiplying the input complex data to obtain the fading simulator output. A plurality of non-frequency-selective fading simulators, and a plurality of complex adders for complex-adding the outputs of the plurality of non-frequency-selective fading simulators to obtain a frequency-selective fading simulator output. A fading simulator device characterized by the following. 3. A fading complex amplitude generating section, comprising: storage means for storing an in-phase component and a quadrature component of the complex amplitude data; and reading for reading the in-phase component and the quadrature component of the complex amplitude data from the storage means. 3. The fading simulator apparatus according to claim 1, further comprising: a reading unit having a variable start position and a variable reading speed. 4. The fading complex amplitude generating section generates the complex amplitude data respectively corresponding to a plurality of received element waves, and the complex multiplying means outputs a plurality of receiving elements from the fading complex amplitude generating section. 4. A complex multiplication of complex amplitude data generated corresponding to a wave and input complex data output corresponding to a plurality of received element waves from the sampler. 2. The fading simulator device according to claim 1. 5. The fading complex amplitude generating section: z _i = E _i exp {j (2πf _D cos β _i + θ _i )} for the i-th received beam, where β _i is the traveling direction of the mobile station. arrival angle of the received rays for, theta _i is the initial phase, E _i is the amplitude, f _D f _D the maximum Doppler frequency (wavelength lambda, the moving speed of the mobile station as v
The fading simulator apparatus according to any one of claims 1 to 4, wherein the fading simulator generates complex amplitude data represented by: Wherein said fading complex amplitude generating unit, to the i th received _{rays, z i = E i exp {} j (2πf D cosβ i + θ i)} where, beta _i is the traveling direction of the mobile station arrival angle of the received rays for, theta _i is the initial phase, E _i is the amplitude, f _D f _D the maximum Doppler frequency (wavelength lambda, the moving speed of the mobile station as v
= Λ / v), wherein the read means sets the read start position to a position corresponding to the initial phase θ _i , and sets the read speed to 6. The fading simulator according to claim 5, wherein the speed is set to a speed corresponding to 2πf _D cosβ _i . 7. The fading method according to claim 2, wherein said plurality of complex addition means weights the outputs of said plurality of non-frequency selective fading simulators with variable weighting coefficients and performs complex addition. Simulator device.