WO2003036997A1

WO2003036997A1 - Estimate method for sinr of cellular mobile communication and the apparatus of the same

Info

Publication number: WO2003036997A1
Application number: PCT/CN2001/001503
Authority: WO
Inventors: Dongdong Shen
Original assignee: Linkair Communications,Inc.
Priority date: 2001-10-25
Filing date: 2001-10-25
Publication date: 2003-05-01
Also published as: CN1493162A; CN1221147C

Abstract

The present invention discloses an estimate method for SINR of cellular mobile communication and the apparatus of which realize that. The first sub-frame of traffic channel frame structure is used to transmit pilot symbol. The other sub-frames are used to transport traffic signal, the sub-frame of which transmit pilot symbol adopt on-off structure. The channel estimation of traffic channel is preformed by the on-off pilot structure at the receive terminal; using the method the value of SINR can be estimated accurately in conduction of multi-cell interface is exist and arbitrary channel fade. It is easily to realize and can be used for fast transmission power control in communication system.

Description

SINR estimation method for cellular mobile communication and implementation device thereof

Technical field:

The present invention relates to a cellular mobile communication system, and in particular, to a SINR estimation method for measuring a non-constant envelope modulation signal in a cellular mobile communication system and a device for implementing the method. Background technique:

In a cellular mobile communication system, in order to perform accurate and fast power control, it is often necessary to obtain a more accurate signal to interference & noise ratio (SINR or SNR) statistical value; and based on SINR The estimated power control algorithm is also the most efficient. For a cellular mobile communication system: The so-called interference includes multiple access interference (Mul t iple Access Interference, referred to as MAI) and cell interference (Adjacent Cel l Interference, referred to as ACI). To accurately obtain the parameters of multiple signals, multi-user detection is necessary, which greatly increases the complexity of the system and cannot be applied to fast power control algorithms. There are quite a few SINR estimation methods that can generate a constant envelope modulation signal. For example, a SINR measurement method proposed in WCDMA is to calculate the SINR measurement value by calculating the variance of the received signal ("Physical Layer Standard for WCDMA, 3GPP TS25. 211 "); However, for non-constant envelope modulation signals, there is currently no corresponding SINR estimation method. Summary of the invention:

In order to overcome the above-mentioned shortcomings and defects in the prior art, the main object of the present invention is to provide a SINR estimation method for cellular mobile communications, which performs SINR estimation for non-constant envelope modulation signals, and can be used in conditions where multi-cell interference exists In addition, and under arbitrary channel fading conditions, the SINR value is accurately estimated.

Another object of the present invention is to provide a device for implementing SINR estimation in cellular mobile communications, which does not require complicated calculation when performing SINR estimation on non-constant envelope modulation signals, It is simple and can be applied to fast power control in communication systems.

The object of the present invention is achieved by the following technical solutions:

A SINR estimation method for cellular mobile communication, in which the first subframe of a traffic channel frame structure is used to send pilot symbols, the remaining subframes are used to send service signals, and the subframes used to send pilot symbols are switched. The pilot structure of the channel is used at the receiving end to complete the channel estimation of the service channel through the switched pilot structure.

The above-mentioned switched pilot structure is: In two consecutive time slots in a subframe, one time slot is used to transmit fixed pilot symbols, and the other time slot does not transmit any signals. The pilot channel Closed.

The receiving end completes the channel estimation of the service channel through the switched pilot structure and includes at least the following steps:

Step 1: The receiving end sequentially extracts pilot symbols in adjacent slots in the subframe, obtains a pilot signal strength, and calculates an average value of the pilot symbol energy in the subframe;

Step 2: Calculate the average energy value of the interference noise in the subframe;

Step 3: Calculate the SINR estimated value of the pilot symbols in the subframe, that is, the SINR statistical value of the pilot channel;

Step 4: According to the position of the current traffic channel multilevel signal in the constellation diagram, the SINR estimation of the traffic channel is obtained from the correspondence between the pilot symbols and the traffic symbols, and the SINR statistics of the pilot channel in step 3. value.

An apparatus for implementing a SINR estimation method for cellular mobile communication, which at least includes:

The first device is configured to measure the SINR estimated value of the pilot signal according to the switched pilot structure. The second device is configured to receive the output of the first device and calculate the SINR estimated value of the service channel based on the pilot signal SI estimated value.

The first device includes at least: a demodulation device, a serial parallel device, an adder, a first calculation device, a squarer, a divider, a second calculation device, and a logarithmic calculation module;

The demodulation device demodulates the pilot received signal and outputs it to the serial-parallel device. The output of the serial-parallel device is divided into two paths: The first path is connected to an adder. The adder extracts the pilot signal strength and outputs it to a first computing device for accumulation and average. The first computing device outputs the average to a squarer, and the pilot signal is calculated in the squarer. Energy value, and then output the energy value to the divider;

The second channel is connected to a second calculation device, which calculates an average value of the power statistics of noise and interference, and outputs the average value to the divider;

Finally, the divider outputs its operation result to a logarithmic calculation module, and the logarithmic calculation module converts it into the pilot S INR estimation value.

The second device includes at least: a service symbol receiver demodulation device, a calculation module, a logarithmic calculation module, a calculation device, and an adder;

The service symbol receiver demodulation device demodulates a service received signal and outputs the demodulated signal to a calculation module. The calculation module determines a ratio factor between the constellation of the demodulated symbol and the pilot symbol and outputs the factor to the pair. A number calculation module, a logarithm calculation module accumulates all the ratio factors in a frame, and outputs it to a calculation device to calculate an average value. The average value is sent to the adder together with the calculated pilot SINR estimate value, and the adder calculates the service. SINR estimate of the symbol.

The present invention is described in further detail below with reference to the drawings and specific embodiments. Brief description of the drawings:

Figure 1 is a basic block diagram of a cellular mobile communication system.

FIG. 1 is a schematic diagram of a frame structure according to an embodiment of the present invention.

FIG. 3 is a schematic structural diagram of a switched pilot subframe structure according to the present invention.

FIG. 4 is a 16QAM constellation diagram used in a preferred embodiment of the present invention.

FIG. 5 is a principle block diagram of the SINR estimation device of the present invention.

Figure 6 is a graphical display of the rectangular 16QAM constellation Q function.

FIG. 7 is a statistical graph of normalized variance of the present invention. detailed description:

Referring to FIG. 1, it is a block diagram of an implementation of a cellular mobile communication system in the prior art. Under the environment of a mobile communication system, when a signal sent from a transmitter of a communication system is sent to a receiver of the communication system through a multipath fading channel, it will be subject to multiple access interference MAI and neighboring cell interference ACI. At the same time, background noise is also inevitable of. The impulse response of a multipath fading channel can be quantitatively described by the following formula (1):

h {t) = _j a _k e ^ 5 {t-T _k ) (1) where a _k , e _k , T _k are the fading factors, phase offsets, and delay spreads of each channel, respectively; L is Channel multipath weight.

When the system sends pilot symbols, the signal of the receiver front end at sampling time 1 in FIG. 1 is: rrS _pI + I ₁ + n _J ; where S _pl and I _n are the received signal sampling value and pilot at time 1. The signal sampling value, the interference sampling value, and the background noise sampling value. When sending a service signal, the signal expression at sampling time 1 is:

Among them, the definition of r I is the same as that of the pilot, and ₇ represents the sampled value of the service signal at time 1.

In the present invention, only pilot symbols are used for SINR estimation, and the SINR estimation value of the service channel is obtained indirectly. In a preferred embodiment of the present invention, the length of the sub-frame is set to 20ms. Since the length of one sub-frame is about 20ms, it can be generally considered that the fading characteristics of the channel in the length of one sub-frame are almost constant, that is, The parameters of the channel remain unchanged during this time. Therefore, this short-term invariance can be used to extract the actual pilot symbol strength and make statistics on noise and interference.

Referring to FIG. 2, it is a frame structure of a traffic channel of a communication system designed according to the method of the present invention. In each frame, there are several subframes, where the first subframe is used to send pilot symbols, and the other subframes are used to send service signals. The length of the subframe used for transmitting pilot symbols is 2L, where L is the number of non-zero pilot symbols, and the specific value is determined by the structure of the pilot frame, that is, a pilot whose SINR estimation period T _SINR is 2L times Symbolic time.

Referring to FIG. 3, the switched pilot structure of the present invention transmits fixed pilot symbols in time slots on odd bits, the energy of the pilot symbols is known, and no signal is transmitted in time slots on even bits, Guide The frequency channel is closed. Therefore, at the receiver side, the average strength of the pilot symbols can be extracted through the two adjacent time slots, that is, the detection symbols of the odd bits are subtracted from the null symbols of the even bits. Another advantage of this processing is that the noise and interference are zero-mean processed to make the estimation of signal strength more accurate.

In one SINR estimation period, a total of L pilot symbols can be extracted. In order to eliminate or reduce the influence of noise and interference on the signal strength estimation as much as possible, the L pilot symbols need to be averaged. Since the pilot signal is closed, the received signal at the receiver contains only noise and interference, so this part of the idle state can be used to estimate the strength of noise and interference. In this way, the following formula (2) can be used to obtain the average pilot SINR value in an SI R SINR estimation period.

SINR _pilo! =

Referring to FIG. 4, according to the strength of each signal in the constellation, the signals can be divided into three different levels, that is, in the 16QAM modulation constellation diagram in a preferred embodiment of the present invention, figure 0, figure X, and figure Δ is an energy symbol representing three different levels, and the ratio of the intensity of the signal at each level to the intensity of the pilot symbol is also fixed. Therefore, according to the modulated service symbol and the known pilot

To estimate the SINR estimate for each service symbol.

For the service symbol SINR value S / R _frI . Performing the averaging processing, the following formula (3) can be used to obtain the value of a service channel SINR estimation period:

Σ201 _0§ 77 ,.

SINR _{→ C} = SINR _pilol ^ (3) where N is the length of the service symbol.

Referring to FIG. 5, it is a device for estimating SINR of the method of the present invention. At the receiving end, the demodulation device 501 demodulates the received pilot signal, and then outputs the demodulated device to a series of parallelization device 502. After the serial conversion and parallel device 502 further processes the signal, its output is used to extract the signal strength of the pilot symbols in adjacent time slots through a subtractor 503, and the signal strength is accumulated and averaged in a computing device 504, and the squarer The average pilot signal strength is calculated in 505, and the value is then input to the divider 506. At the same time, the output signal from the above-mentioned serial-parallel device 502 is also input to the computing device 507, and the computing device 507 estimates the noise And the intensity of the interference, and calculate the average value. After that, the output of the calculation device 507 is also sent to the divider 506. The divider 506 and the logarithmic calculation module 508 connected in series perform the two signals entering the divider. Calculate to get the estimated value of the calculated pilot SINR. The service received signal is demodulated in the service symbol receiver demodulation device 513 and output to the calculation module 512. The calculation module 512 determines the power level between the pilot signal and the demodulated service signal according to the energy level of the service demodulation symbol constellation diagram. The ratio factor is then calculated in the logarithmic calculation module 511 and output by the logarithmic calculation module 511 to the calculation device 510 for accumulation and averaging. The result is input to the addition together with the pilot SINR estimation value output by the calculator 508. In the router 509, the SIM estimated value of the service symbol is finally obtained.

Referring to FIG. 6, it is a rectangular 16QAM constellation diagram. The constellation is divided into three levels according to strength. The SINR estimation accuracy of the service symbol largely depends on the error probability performance of the service symbol. The symbol error probability versus SINR will be analyzed in detail. Impact of estimation accuracy.

The following formula can be calculated from the constellation diagram:

J ² l _D

e ⁽ t ^{) + 2e (} t ^{) + e (} t) (7)

_{Wherein, e (l → 2),} P e (l →), P e (2 → 3), P e (2 → l), e (3 → l), P e (3 → 2), respectively, the level of 1 is mistaken for level 2, level 1 is mistaken for level 3, level 2 is mistaken for level 3, level 2 is mistaken for level 1, level 3 is mistaken for level 1, level 3 is mistaken for level 2 probability, D is the probability of 16QAM constellation most significant, and ^ is thousands interference noise power spectral density, Q (X) is a function Q. _{^{βω = _ ^ (- '2}} /, ≥0 Thus, the estimated traffic symbol level consistent with the error bound for the ratio &:

Where is the prior probability of the three levels of signals.

Hypothetical production

The error probability of a signal with level 1 is:

The error probability of a signal of level 1 is

The rating probability for a signal of level 3 is

This total sign error; ί both rate its consensus bound is-. (15)

The ratio of the level decision error probability to the symbol error probability is:

See Figure 6. For the Q (X) function, the larger the independent variable X, the smaller the function value Q (X), and the decreasing speed becomes faster and faster as the independent variable X increases. If X is large, then it holds, where "> 1

^-2 D

Therefore, formula (16) is dominant, from which we can know that λ <1. After the system performance is determined, it is assumed that the bit error probability BEI of the service channel is 10 " ³ , ^ BER, then for a small value of ⁷ , the error probability of the service symbol can be calculated by the following formula: ^{^ W '(l- Ρ) 4} -' · = 1- (1-P) 4 = P Accordingly, judgment error probability level less than 4P. This proves that this SINR estimation is an effective method under good performance guarantee.

Referring to FIG. 7, which shows the normalized variance of the SINR estimates of the pilot and service symbols obtained according to the present invention in a 120 km / h vehicle speed environment. It can be seen from FIG. 7 that the estimation accuracy of the pilot symbol is better than the estimation accuracy of the traffic symbol, which is consistent with the above-mentioned analysis of the probability error estimation of the traffic symbol. From the statistics point of view, the normalized variance ^{^10-3-10-2} of the order, such estimation accuracy is relatively high.

Claims

Claim

1. A SINR estimation method for cellular mobile communication, wherein a first subframe of a traffic channel frame structure is used to transmit pilot symbols, and the remaining subframes are used to transmit service signals, and is characterized by: used to transmit pilot symbols A switched pilot structure is used in the sub-frames, and the channel estimation of the service channel is completed at the receiving end through the switched pilot structure.

2. The SIM estimation method for cellular mobile communication according to claim 1, characterized in that: the switch-type pilot structure is: one of two consecutive time slots adjacent to each other in a subframe, and one time slot is used for transmitting fixed The pilot symbol in the other slot does not transmit any signal, and the pilot channel is in a closed state.

3. The SINR estimation method for cellular mobile communication according to claim 1, characterized in that the channel estimation of the service channel is completed at the receiving end through a switched pilot structure at least as follows:

4. A device for implementing an SINR estimation method for cellular mobile communication, which is characterized in that it includes at least:

The first device is used for measuring the SINR estimated value of the pilot signal with the pilot structure of the switching switch; the second device: it receives the output of the first device, and calculates the SINR estimated value of the traffic channel according to the SINR estimated value of the pilot signal.

5. An apparatus for implementing a SINR estimation method for cellular mobile communication according to claim 4, It is characterized in that: the first device includes at least: a demodulation device, a series-conversion juxtaposition, an adder, a first calculation device, a squarer, a divider, a second calculation device and a logarithmic calculation module;

The demodulation device demodulates the pilot received signal and outputs it to a serial-parallel device. The output of the serial-parallel device is divided into two paths:

The first path is connected to an adder. The adder extracts the pilot signal strength and outputs it to a first computing device for accumulation and average. The first computing device outputs the average to a squarer, and the pilot signal is calculated in the squarer. Energy value, and then output the energy value to the divider;

Finally, the divider outputs its operation result to a logarithmic calculation module, which is converted into a pilot SINR estimation value by the logarithmic calculation module.

6. The device for implementing the SINR estimation method for cellular mobile communication according to claim 4, characterized in that: the second device comprises at least: a service symbol receiver demodulation device, a calculation module, a logarithm calculation module, a calculation device and Adder

The service symbol receiver demodulation device demodulates a service received signal and outputs the demodulated signal to a calculation module. The calculation module determines a ratio factor between the constellation energy level of the demodulation symbol and the pilot symbol and outputs the factor. To the logarithmic calculation module, the logarithmic calculation module accumulates all the ratio factors in a frame and outputs it to the calculation device to calculate an average value. The average value is sent to the adder together with the calculated pilot SINR estimation value, and the adder Calculate the SINR estimate of the service symbol.