CN104283820A - Method for determining signal to noise ratio (SNR) of communication system - Google Patents

Abstract

A method for determining signal to noise ratio (SNR) of a communication system comprises the steps that the best pilot frequency point is determined according to the position of an RE where a PDSCH is located; the SNR of the best pilot frequency point is calculated, and the SNR of the RE is equal to the SNR of the best pilot frequency point. By means of the method, the calculation frequency of the SNR is reduced, calculation complexity is obviously lowered, and hardware resources are saved.

Description

The method of signal to noise ratio is determined in a kind of communication system

Technical field

The application relates to communication technical field, more specifically, relates to a kind of method determining signal to noise ratio in communication system.

Background technology

LTE system downlink reception end, after estimating channel parameter and noise variance result, need do equilibrium treatment to each control channel and Traffic Channel respectively.Balanced output is the estimation and the sub-carrier signal-noise ratio that send signal.

For space multiplexing system, for single sub-carrier, corresponding reception data and channel estimation results are respectively Y and H, then the estimated value using ZF (ZF) or minimum mean-squared error algorithm algorithm (MMSE) to carry out the equilibrium of signal and detection to obtain transmitting its formula is:

$\hat{X}=H^{+}Y$

Wherein, $H^{+}=\left\{\begin{array}{cc}{(H\′H)}^{-1}H\′& \mathrm{ZF}\\ {(H\′H+{\mathrm{\σ}}_n^{2}I)}^{-1}H\′& \mathrm{MMSE}\end{array}\right.$

for Noise Variance Estimation result, H' is the associate matrix of H, and I is unit matrix.

Signal to noise ratio snr computing formula on subcarrier is:

$\mathrm{SNR}=\left[\begin{array}{cc}\frac{1}{{\mathrm{\σ}}_n^2*\mathrm{diag}\left({(H\′*H)}^{-1}\right)}& \mathrm{ZF}\\ \frac{1}{{\mathrm{\σ}}_n^2*\mathrm{diag}\left({(H\′*H+{\mathrm{\σ}}_n^{2}I)}^{-1}\right)}-1& \mathrm{MMSE}\end{array}\right]$

For MMSE algorithm, the Output rusults of above-mentioned equilibrium and SNR, in its computational process, all comprise calculating, and this calculating is part the most complicated in whole formula, therefore with the calculating tool durability of SNR.

Due to with in the computational process of SNR, there is durability, therefore calculate all simultaneously.And in current project, in hardware implementing process, can adopt and call balanced accelerator and realize MMSE equilibrium treatment.But this balanced accelerator, only possesses calculating function, without the output of SNR.Therefore also extra computation SNR is needed.If conventionally subcarrier calculates SNR one by one, then complexity is higher, and hardware implementing faces the inadequate problem of resource.

Summary of the invention

The embodiment of the present invention proposes a kind of method determining signal to noise ratio in communication system, decreases the calculation times of SNR, obviously reduces computation complexity, save hardware resource.

The technical scheme of the embodiment of the present invention is as follows:

Determine a method for signal to noise ratio in communication system, described method comprises:

Optimal pilot point is determined in position according to Physical Downlink Shared Channel PDSCH place resource lattice RE;

Calculate the signal to noise ratio snr of optimal pilot point, the SNR of described RE equals the SNR of optimal pilot point.

The described position according to PDSCH place RE determines that optimal pilot point comprises:

Described RE is positioned at first or the 5th on orthogonal frequency division multiplex OFDM symbol, and described RE is positioned at the upper half of Resource Block RB, be then positioned at RB upper half and be optimal pilot point with the pilot point of described RE in identical OFDM symbol.

The described position according to PDSCH place RE determines that optimal pilot point comprises:

Described RE is positioned at first or the 5th in OFDM symbol, and described RE is positioned at the bottom half of RB, being then arranged in RB bottom half with the pilot point of described RE in identical OFDM symbol is optimal pilot point.

The described position according to PDSCH place RE determines that optimal pilot point comprises:

Described RE is positioned at second or the 3rd in OFDM symbol, and described RE is positioned at the upper half of RB, then the pilot point be positioned in the first OFDM symbol of RB upper half is optimal pilot point.

The described position according to PDSCH place RE determines that optimal pilot point comprises:

Described RE is positioned at second or the 3rd in OFDM symbol, and described RE is positioned at the bottom half of RB, then the pilot point be positioned in the first OFDM symbol of RB bottom half is optimal pilot point.

The described position according to PDSCH place RE determines that optimal pilot point comprises:

Described RE is positioned in the 4th, the 6th or the 7th OFDM symbol, and described RE is positioned at the upper half of RB, then the pilot point be positioned in the 5th OFDM symbol of RB upper half is optimal pilot point.

The described position according to PDSCH place RE determines that optimal pilot point comprises:

Described RE is positioned in the 4th, the 6th or the 7th OFDM symbol, and described RE is positioned at the bottom half of RB, then the pilot point be positioned in the 5th OFDM symbol of RB bottom half is optimal pilot point.

As can be seen from technique scheme, determine optimal pilot point according to the position of PDSCH place RE in embodiments of the present invention; Calculate the SNR of optimal pilot point, the SNR of described RE equals the SNR of optimal pilot point.Adopt optimal pilot point to calculate the SNR of RE, decrease the calculation times of SNR, and reduce complexity, thus save hardware resource.

Accompanying drawing explanation

Fig. 1 is the method flow schematic diagram determining signal to noise ratio in communication system;

Fig. 2 is single port Resource Block schematic diagram;

Fig. 3 is dual-port Resource Block schematic diagram;

Fig. 4 is the single port Resource Block schematic diagram adopting technical solution of the present invention;

Fig. 5 is prior art and the contrast schematic diagram adopting technical solution of the present invention determination signal to noise ratio.

Embodiment

Express clearly clear for making the object, technical solutions and advantages of the present invention, below in conjunction with drawings and the specific embodiments, the present invention is further described in more detail.

In embodiments of the present invention, first determine the optimal pilot point of PDSCH place RE, the SNR of optimal pilot point replaces the SNR of PDSCH place RE thus, decreases the calculation times of SNR, and reduces complexity, thus save hardware resource.

Be the method flow schematic diagram determining signal to noise ratio in communication system see accompanying drawing 1, specifically comprise the following steps:

101, optimal pilot point is determined according to the position of PDSCH place RE.

In the schematic diagram of RB in the protocol, transverse axis represents time domain, and the longitudinal axis represents frequency domain, is single port RB schematic diagrames see accompanying drawing 2, and accompanying drawing 3 is dual-port RB schematic diagrames.A RB comprises two time slots, and a time slot comprises 7 OFDM symbol, i.e. l=0 ..., l=7.RE represents subcarrier.Prior art needs the SNR calculating each subcarrier machine RE.

No matter be single port, dual-port or four ports, in time domain, be knownly positioned at first and the 5th on OFDM in pilot point, second, third, the 4th, all there is no pilot point in the 6th and the 7th OFDM symbol.On frequency domain, every half RB(6 RE) there is a pilot point to exist.Namely the number of the upper half pilot point of RB is identical with the number of the bottom half pilot point of RB.

Because near pilot point, the SNR of RE and the SNR of pilot point is more or less the same, therefore can determine optimal pilot point with according to the position of PDSCH place RE, then the SNR of this RE equals the SNR of optimal pilot point.

According to following scheme selection SNR.

Mode one:

RE is positioned at first or the 5th in OFDM symbol, and this RE is positioned at the upper half of RB, be then positioned at RB upper half and be optimal pilot point with the pilot point of this RE in identical OFDM symbol.

Mode two

RE is positioned at first or the 5th in OFDM symbol, and this RE is positioned at the bottom half of RB, be then positioned at RB bottom half and be optimal pilot point with the pilot point of this RE in identical OFDM symbol.

Mode three

RE is positioned at second or the 3rd in OFDM symbol, and this RE is positioned at the upper half of RB, then the pilot point be positioned in the first OFDM symbol of RB upper half is optimal pilot point.

Mode four

RE is positioned at second or the 3rd in OFDM symbol, and this RE is positioned at the bottom half of RB, then the pilot point be positioned in the first OFDM symbol of RB bottom half is optimal pilot point.

Mode five

RE is positioned in the 4th, the 6th or the 7th OFDM symbol, and this RE is positioned at the upper half of RB, then the pilot point be positioned in the 5th OFDM symbol of RB upper half is optimal pilot point.

Mode six

RE is positioned in the 4th, the 6th or the 7th OFDM symbol, and this RE is positioned at the bottom half of RB, then the pilot point be positioned in the 5th OFDM symbol of RB bottom half is optimal pilot point.

Position residing for RE, just can adopt the pilot point in this region to calculate the schematic diagram of SNR.In accompanying drawing 4, the SNR belonging to same region RE equals to belong to the SNR of the pilot point in this region.

102, calculate the SNR of optimal pilot point, the SNR of RE equals the SNR of optimal pilot point.

The SNR of optimal pilot point is conventionally calculated according to the channel estimating of optimal pilot point and noise variance.In figure 4, the SNR belonging to the RE in a region with optimal pilot point together equals the SNR of optimal pilot point.

Adopt the SNR of optimal pilot point to obtain the method for the SNR of PDSCH place RE, the complexity of calculating can be reduced.Need the SNR calculating each RE one by one in the prior art, and have employed technical scheme of the present invention, when single port, complexity is reduced to during dual-port, have two RE can not carry PDSCH data due in the OFDM symbol that exists in pilot point, then complexity is reduced to

But SNR adopts the approximate calculation of optimal pilot point, inevitably brings error, produces certain influence to decode results.Under postponing greatly space division multiplexing pattern, adopt 2 × 2 antennas, MCS class 5, SCME channel, during speed 120km/h, the method conventionally calculating SNR by subcarrier and the SNR adopting technical scheme of the present invention to be calculated RE by optimal pilot point, the BLER performance difference of PDSCH is see accompanying drawing 5.From simulation result, even if at high speeds, the performance difference of the BLER of PDSCH is also maximum at about 1dB, and hydraulic performance decline can accept.

The above, be only preferred embodiment of the present invention, be not intended to limit protection scope of the present invention.Within the spirit and principles in the present invention all, any amendment done, equivalent replacement, improvement etc., all should be included within protection scope of the present invention.

Claims (7)

1. determine a method for signal to noise ratio in communication system, it is characterized in that, described method comprises: optimal pilot point is determined in the position according to Physical Downlink Shared Channel PDSCH place resource lattice RE; Calculate the signal to noise ratio snr of optimal pilot point, the SNR of described RE equals the SNR of optimal pilot point.

2. determine the method for signal to noise ratio according to claim 1 in communication system, it is characterized in that, the described position according to PDSCH place RE determines that optimal pilot point comprises:

Described RE is positioned at first or the 5th on orthogonal frequency division multiplex OFDM symbol, and described RE is positioned at the upper half of Resource Block RB, be then positioned at RB upper half and be optimal pilot point with the pilot point of described RE in identical OFDM symbol.

3. determine the method for signal to noise ratio according to claim 1 in communication system, it is characterized in that, the described position according to PDSCH place RE determines that optimal pilot point comprises:

Described RE is positioned at first or the 5th in OFDM symbol, and described RE is positioned at the bottom half of RB, being then arranged in RB bottom half with the pilot point of described RE in identical OFDM symbol is optimal pilot point.

4. determine the method for signal to noise ratio according to claim 1 in communication system, it is characterized in that, the described position according to PDSCH place RE determines that optimal pilot point comprises:

Described RE is positioned at second or the 3rd in OFDM symbol, and described RE is positioned at the upper half of RB, then the pilot point be positioned in the first OFDM symbol of RB upper half is optimal pilot point.

5. determine the method for signal to noise ratio according to claim 1 in communication system, it is characterized in that, the described position according to PDSCH place RE determines that optimal pilot point comprises:

Described RE is positioned at second or the 3rd in OFDM symbol, and described RE is positioned at the bottom half of RB, then the pilot point be positioned in the first OFDM symbol of RB bottom half is optimal pilot point.

6. determine the method for signal to noise ratio according to claim 1 in communication system, it is characterized in that, the described position according to PDSCH place RE determines that optimal pilot point comprises:

Described RE is positioned in the 4th, the 6th or the 7th OFDM symbol, and described RE is positioned at the upper half of RB, then the pilot point be positioned in the 5th OFDM symbol of RB upper half is optimal pilot point.

7. determine the method for signal to noise ratio according to claim 1 in communication system, it is characterized in that, the described position according to PDSCH place RE determines that optimal pilot point comprises:

Described RE is positioned in the 4th, the 6th or the 7th OFDM symbol, and described RE is positioned at the bottom half of RB, then the pilot point be positioned in the 5th OFDM symbol of RB bottom half is optimal pilot point.