CN105049099B - The multi-antenna adaptive dispatching method of LTE multiaerial systems - Google Patents

Abstract

The invention discloses a multi-antenna self-adaptive scheduling method for an LTE multi-antenna system. The receiving end feeds back the signal-to-noise ratio of each channel to the sending end, and the sending end calculates the equivalent information quality in three antenna modes according to the signal-to-noise ratio. information, and then calculate the channel capacity of the three antenna modes, and then calculate the decision coefficient, if the judgment coefficient is greater than or equal to the preset threshold, then use the single antenna mode; otherwise, further determine whether the channel capacity of the transmit diversity mode is greater than or equal to the spatial multiplexing mode The channel capacity of , if yes, adopt transmit diversity mode, otherwise adopt spatial multiplexing mode. The invention self-adaptively sets the antenna mode of the sending end through the channel signal-to-noise ratio, so that the antenna mode can automatically adapt to the current channel environment, thereby improving the system throughput rate.

Description

Multi-antenna adaptive scheduling method for LTE multi-antenna system

technical field

The invention belongs to the technical field of LTE communication, and more specifically, relates to a multi-antenna self-adaptive scheduling method of an LTE multi-antenna system.

Background technique

In order to meet the challenges of broadband access technology and to meet the needs of new services, the international standardization organization 3GPP (3rd Generation Partnership Project) launched the Long Term Evolution (Long Term Evolution) of the Universal Mobile Telecommunications System (UMTS) at the end of 2004. , LTE) project. The purpose of this project is to develop a mobile communication system with high data rate, high channel capacity, low delay and low cost. The LTE system adopts the core technology of Orthogonal Frequency Division Multiplexing (OFDM) and Multiple Input Multiple Output (MIMO), and also uses Adaptive Modulation and Coding (Adaptive Modulation and Coding, AMC) technology to further improve the performance of the system.

MIMO technology is to use multiple antennas at both the transmitting and receiving ends of wireless transmission. Compared with traditional single-antenna transmission, multiple antennas at the transmitting end and multiple antennas at the receiving end can form multiple parallel spatial sub-channels, and these Sub-channels can transmit information in parallel and independently, so that on the one hand, the data transmission rate can be greatly improved to meet the requirements of high speed and large capacity; on the other hand, the anti-fading and anti-noise capabilities of the system can be well improved. Therefore, MIMO technology is also considered to be an important way to realize high-speed data transmission and improve transmission quality in future mobile communication and personal communication systems.

The AMC technology is to dynamically select an appropriate modulation and coding scheme (Modulation and Coding Scheme, MCS) according to changes in channel conditions. This technique has been widely used in existing wireless communication systems. The basic idea is to use the receiver to feed back the measured channel state information at the transmitter, and obtain parameters such as modulation and coding mode MCS, data rate, and transmission power through certain processing, and then use these parameters to transmit data, so that in different Under certain channel conditions, the system performance can be optimized.

The basic principle of adaptive modulation and coding is to dynamically adjust the coding and modulation mode of the transmission channel at the receiving end, so that the wireless channel Maximize resource utilization. However, simply using adaptive modulation and coding cannot really maximize system gain and system performance, and multi-antenna scheduling is also required for cooperation. Figure 1 is a block diagram of the adaptive modulation and coding AMC model. As shown in FIG. 1 , in addition to using adaptive modulation and coding, multi-antenna scheduling can also be used to control the antenna mode of the transmitting end.

Contents of the invention

The purpose of the present invention is to overcome the deficiencies of the prior art and provide a multi-antenna adaptive scheduling method for an LTE multi-antenna system, so that the antenna mode can automatically adapt to the current channel environment and improve the system throughput.

In order to achieve the above-mentioned purpose of the invention, the multi-antenna adaptive scheduling method of the LTE multi-antenna system of the present invention comprises the following steps:

S1: The receiving end feeds back the signal-to-noise ratio of each channel to the sending end Wherein, i represents the serial number of the channel, and the value range is i=1, 2,..., T, and T is the number of feedback channels;

S2: According to the signal-to-noise ratio at the receiving end Calculate the equivalent information quality information SINR _SISO , SINR _TD and SINR _SM under the three antenna modes respectively, where the subscript SISO indicates the single antenna mode, the subscript TD indicates the transmit diversity mode, and the subscript SM indicates the spatial multiplexing mode; the calculation formula They are:

Among them, M represents the number of antennas at the transmitting end, and N represents the number of antennas at the receiving end;

S3: Calculate the channel capacities C _SISO , C _TD and C _SM of the three antenna modes respectively, and the calculation formula is:

C _SISO = log ₂ (1+SINR _SISO )

C _TD =log ₂ (1+SINR _TD )

C _SM ＝M×log ₂ (1+SINR _SM )

S4: Calculate the decision coefficient α, the calculation formula is:

S5: If α≥α _th , adopt single-antenna mode; if not, further judge whether C _TD ≥C _SM , if yes, adopt transmit diversity mode, otherwise adopt spatial multiplexing mode.

In the multi-antenna adaptive scheduling method of the LTE multi-antenna system of the present invention, the receiving end feeds back the signal-to-noise ratio of each channel to the sending end, and the sending end calculates the equivalent information quality information under the three antenna modes respectively according to the signal-to-noise ratio, and then calculates Get the channel capacity of the three antenna modes, and then calculate the decision coefficient, if the judgment coefficient is greater than or equal to the preset threshold, then use the single antenna mode; otherwise, further determine whether the channel capacity of the transmit diversity mode is greater than or equal to the channel capacity of the spatial multiplexing mode, If yes, adopt transmit diversity mode, otherwise adopt spatial multiplexing mode. The invention self-adaptively sets the antenna mode of the sending end through the channel signal-to-noise ratio, so that the antenna mode can automatically adapt to the current channel environment, thereby improving the system throughput rate.

Description of drawings

Fig. 1 is a block diagram of an adaptive modulation coding AMC model;

Fig. 2 is the flowchart of the multi-antenna adaptive scheduling method of the LTE multi-antenna system of the present invention;

Fig. 3 is a system throughput curve diagram under different decision coefficient thresholds;

Fig. 4 is a graph of the throughput of the PedB channel in different antenna modes when the number of antennas is 2×2;

Fig. 5 is a graph of the throughput of the PedB channel in different antenna modes when the number of antennas is 4×4;

Fig. 6 is a graph of the throughput of the VehA channel in different antenna modes when the number of antennas is 2×2;

Fig. 7 is a graph of the throughput of the VehA channel in different antenna modes when the number of antennas is 4×4;

Fig. 8 is a graph of the throughput of the HI channel in different antenna modes when the number of antennas is 2×2;

Fig. 9 is a graph showing the throughput of the HI channel in different antenna modes when the number of antennas is 4×4.

Detailed ways

Specific embodiments of the present invention will be described below in conjunction with the accompanying drawings, so that those skilled in the art can better understand the present invention. It should be noted that in the following description, when detailed descriptions of known functions and designs may dilute the main content of the present invention, these descriptions will be omitted here.

Example

FIG. 2 is a flowchart of a multi-antenna adaptive scheduling method for an LTE multi-antenna system according to the present invention. As shown in each Figure 2, the multi-antenna adaptive scheduling method of the LTE multi-antenna system of the present invention includes the following steps:

S201: Receiver feedback channel signal-to-noise ratio:

The receiver feeds back the signal-to-noise ratio of each channel to the transmitter Wherein, i represents the serial number of the channel, and the range of values is i=1, 2, ..., T, and T is the number of feedback channels, that is, the number of receiving channels at the receiving end.

In order to facilitate the calculation, the ideal SNR calculation formula is used in this embodiment, that is, the channel estimation error at the receiving end and the influence of channel time variation are not considered, and the calculation formula is:

Wherein, _PSRS is the receiving power of the pilot measurement signal (Sound Reference Signal, SRS) of the cell where the node is located; is the channel power spectrum of the jth subcarrier, Q is the number of transmission subcarriers, which is determined by the system bandwidth B; β is the channel fading coefficient, and different channels have different values; N ₀ is the power spectral density of the channel noise; S _I represents The interference power, that is, the sum of the received power of all user pilot signals in the adjacent cell, is expressed as in Refers to the pilot power value in the kth adjacent cell, and the value range of k is k=1, 2, ..., K, K refers to the number of pilot signals in the adjacent cell. When only a single user in one cell is considered, the value of the interference power S _I can be ignored.

S202: Calculate equivalent channel quality information:

According to the signal-to-noise ratio at the receiver Calculate the equivalent channel quality information SINR _SISO , SINR _TD and SINR _SM under the three antenna modes respectively, and the calculation formulas are respectively:

Among them, M represents the number of antennas at the transmitting end, and N represents the number of antennas at the receiving end; the subscript SISO represents the single-antenna mode, the subscript TD represents the transmit diversity mode, and the subscript SM represents the spatial multiplexing mode.

S203: Calculate channel capacity:

According to Shannon's theorem, the channel capacities C _SISO , C _TD and C _SM of the three antenna modes are respectively:

C _SISO = log ₂ (1+SINR _SISO ) (5)

C _TD ＝log ₂ (1+SINR _TD ) (6)

C _SM ＝M×log ₂ (1+SINR _SM ) (7)

S204: Calculate the decision coefficient α:

It can be seen from formulas (5), (6), and (7) that when M=N=1, the three antenna modes have the same equivalent channel quality information and channel capacity, then SINR _SISO = SINR _TD = SINR _SM , C _SISO =C _TD =C _SM ; when M,N>1, the equivalent channel quality information and channel capacity of the multiplexing mode SM and the diversity mode TD are larger than those of the single antenna mode SISO. Based on the above analysis, the present invention introduces the decision coefficient α, whose expression is:

Obviously, the value range of the decision coefficient α is 0<α≤1. The decision coefficient α can be used to measure the relative size of the channel capacity under the three antenna modes.

S205: Judging whether α≥α _th , α _th represents a preset decision threshold, which is set according to the actual situation. After experimental statistics, the general value range of α _th is 0.85≤α _th <1. If yes, go to step S206, otherwise go to step S207.

S206: Set the antenna mode as a single antenna mode. This is because when α≥α _th , it means that the channel capacity values that can be achieved under the three antenna modes are very close, which means that the single-antenna mode can obtain similar system performance to the multi-antenna mode, but because the single-antenna mode is more convenient And it is easy to implement, so through the compromise of performance and complexity, it is more suitable to choose the antenna mode transmission with single input and single output.

S207: Determine whether C _TD ≥ C _SM , if yes, it means that compared with the spatial multiplexing mode, adopting the transmit diversity mode will obtain better system performance, so it is more appropriate to select the transmit diversity mode, go to step S208, otherwise adopt the spatial multiplexing mode The multiplexing mode will obtain better system performance, go to step S209.

When antenna α<α _th , it shows that the use of multiple antennas can obtain better channel capacity, then it is necessary to further select from two modes of transmit diversity TD and spatial multiplexing SM, and the present invention directly performs according to the size of the channel capacity choose.

S208: Set the antenna mode as the transmit diversity mode.

S209: Set the antenna mode as the spatial multiplexing mode.

In practical applications, the scheduling result of the antenna mode can be expressed in the form of codes to facilitate the identification of multi-antenna modules. For example, the corresponding code of the single-input single-output SISO mode is set to 0, the corresponding code of the transmit diversity TD mode is 1, and spatial multiplexing The corresponding code of SM mode is 2.

In order to illustrate the technical effects of the present invention, a specific example is used to simulate and verify the present invention. The antenna modes used in this simulation mainly include single-antenna SISO mode, transmit diversity TD mode (2×2, 4×4) and spatial multiplexing SM mode (2×2, 4×4).

Fig. 3 is a graph of system throughput under different decision coefficient thresholds. As shown in Fig. 3, the throughputs of three channels: PedB, VehA and HI are demonstrated. It can be seen that the throughput of the adaptive system is different under different values of the single-antenna and multi-antenna decision threshold _αth . When the value of _αth is between 0.9 and 0.95, the throughput of the system can reach the maximum. Therefore, in this embodiment, the decision threshold value α _th =0.9 is selected, that is, when the decision coefficient α≥0.9, the SISO mode is selected; when α<0.9, the TD or SM mode is selected. The simulation comparison diagram of the system throughput under different antenna modes is given below.

Fig. 4 is a graph showing the throughput of the PedB channel in different antenna modes when the number of antennas is 2×2. Fig. 5 is a graph showing the throughput of the PedB channel in different antenna modes when the number of antennas is 4×4. As shown in Figure 4 and Figure 5, when the channel conditions are average and the SNR is relatively low, the throughput values that the system can achieve in the three modes of SISO, transmit diversity TD, and spatial multiplexing SM are very limited, and the values are also low. very close. Compared with it, the present invention has obvious advantages, and the system can obtain higher throughput in the multi-antenna self-adaptive scheduling mode. Under the same channel environment, as the signal-to-noise ratio (SNR) increases, the throughput in various antenna modes increases, and the multi-antenna adaptive scheduling mode of the present invention still has advantages. When the channel condition is relatively good, no matter the number of antennas is 2×2 or 4×4, SISO mode, TD mode, and SM mode are very close to the throughput value that the present invention can obtain, and it can be observed that when the signal-to-noise ratio SNR reaches 5dB Afterwards, the present invention basically selects the spatial multiplexing SM mode as the multi-antenna transmission mode.

Fig. 6 is a graph of the throughput of the VehA channel in different antenna modes when the number of antennas is 2×2. Fig. 7 is a graph of the throughput of the VehA channel in different antenna modes when the number of antennas is 4×4. Fig. 8 is a graph showing the throughput of the HI channel in different antenna modes when the number of antennas is 2×2. Fig. 9 is a graph showing the throughput of the HI channel in different antenna modes when the number of antennas is 4×4. As shown in Fig. 6 to Fig. 9, although compared with PedB channel, VehA channel and HI channel are worse, and the throughput value of each mode has decreased, but on the whole, compared with fixed single-multiple Compared with antenna modes, the system still has more outstanding performance in the multi-antenna adaptive scheduling mode of the present invention.

From the above simulation verification results, it can be seen that no matter in which simulation environment and channel conditions, compared with the other three fixed antenna modes, the multi-antenna adaptive scheduling mode of the present invention has good throughput performance , and all show stable performance advantages. Therefore, it can be proved that the multi-antenna adaptive scheduling method proposed by the present invention can significantly improve the performance of the LTE communication system.

Although the illustrative specific embodiments of the present invention have been described above, so that those skilled in the art can understand the present invention, it should be clear that the present invention is not limited to the scope of the specific embodiments. For those of ordinary skill in the art, As long as various changes are within the spirit and scope of the present invention defined and determined by the appended claims, these changes are obvious, and all inventions and creations using the concept of the present invention are included in the protection list.

Claims (3)

1. a multi-antenna adaptive scheduling method of LTE multi-antenna system, is characterized in that, comprises the following steps: S1: The receiving end feeds back the signal-to-noise ratio of each channel to the sending end Wherein, i represents the serial number of the channel, and the value range is i=1, 2,..., T, and T is the number of feedback channels; S2: According to the signal-to-noise ratio at the receiving end Calculate the equivalent information quality information SINR _SISO , SINR _TD and SINR _SM under the three antenna modes respectively, and the calculation formulas are: <mrow><msub><mi>SINR</mi><mrow><mi>S</mi><mi>I</mi><mi>S</mi><mi>O</mi></mrow></msub><mo>=</mo><mfrac><mn>1</mn><mi>T</mi></mfrac><munderover><mo>&amp;Sigma;</mo><mrow><mi>i</mi><mo>=</mo><mn>1</mn></mrow><mi>T</mi></munderover><msubsup><mi>SINR</mi><mi>R</mi><mi>i</mi></msubsup></mrow> <mrow><msub><mi>SINR</mi><mrow><mi>T</mi><mi>D</mi></mrow></msub><mo>=</mo><mfrac><mi>M</mi><mi>T</mi></mfrac><munderover><mo>&amp;Sigma;</mo><mrow><mi>i</mi><mo>=</mo><mn>1</mn></mrow><mi>T</mi></munderover><msubsup><mi>SINR</mi><mi>R</mi><mi>i</mi></msubsup></mrow> <mrow><msub><mi>SINR</mi><mrow><mi>S</mi><mi>M</mi></mrow></msub><mo>=</mo><msup><mn>2</mn><mrow><mfrac><mn>1</mn><mi>T</mi></mfrac><munderover><mo>&amp;Sigma;</mo><mrow><mi>i</mi><mo>=</mo><mn>1</mn></mrow><mi>T</mi></munderover><msub><mi>log</mi><mn>2</mn></msub><msup><mrow><mo>(</mo><mn>1</mn><mo>+</mo><msubsup><mi>SINR</mi><mi>R</mi><mi>i</mi></msubsup><mo>)</mo></mrow><mi>N</mi></msup></mrow></msup><mo>-</mo><mn>1</mn></mrow> Among them, M represents the number of antennas at the transmitting end, and N represents the number of antennas at the receiving end; S3: Calculate the channel capacities C _SISO , C _TD and C _SM of the three antenna modes respectively, and the calculation formula is: C _SISO = log ₂ (1+SINR _SISO ) C _TD =log ₂ (1+SINR _TD ) C _SM ＝M×log ₂ (1+SINR _SM ) S4: Calculate the decision coefficient α, the calculation formula is: <mrow><mi>&amp;alpha;</mi><mo>=</mo><mfrac><msub><mi>C</mi><mrow><mi>S</mi><mi>I</mi><mi>S</mi><mi>O</mi></mrow></msub><mrow><mi>m</mi><mi>a</mi><mi>x</mi><mrow><mo>(</mo><msub><mi>C</mi><mrow><mi>T</mi><mi>D</mi></mrow></msub><mo>,</mo><msub><mi>C</mi><mrow><mi>S</mi><mi>M</mi></mrow></msub><mo>)</mo></mrow></mrow></mfrac></mrow> S5: If α≥α _th , adopt single-antenna mode; if not, further judge whether C _TD ≥C _SM , if yes, adopt transmit diversity mode, otherwise adopt spatial multiplexing mode. 2. The multi-antenna adaptive scheduling method according to claim 1, wherein the signal-to-noise ratio in step S1 The calculation formula is: <mrow><msubsup><mi>SINR</mi><mi>R</mi><mi>i</mi></msubsup><mo>=</mo><mfrac><mrow><mi>&amp;beta;</mi><mo>&amp;CenterDot;</mo><msub><mi>P</mi><mrow><mi>S</mi><mi>R</mi><mi>S</mi></mrow></msub><mo>&amp;CenterDot;</mo><munderover><mo>&amp;Sigma;</mo><mrow><mi>j</mi><mo>=</mo><mn>1</mn></mrow><mi>Q</mi></munderover><msubsup><mi>p</mi><mi>c</mi><mi>j</mi></msubsup></mrow><mrow><msub><mi>S</mi><mi>I</mi></msub><mo>+</mo><msub><mi>N</mi><mn>0</mn></msub><mi>B</mi></mrow></mfrac></mrow> Wherein, _PSRS is the receiving power of the pilot measurement signal (Sound Reference Signal, SRS) of the cell where the node is located; is the channel power spectrum of the jth subcarrier, Q is the number of transmission subcarriers, B is the system bandwidth, β is the channel fading coefficient, N ₀ is the power spectral density of the channel noise, S _I is the interference power. 3 . The multi-antenna adaptive scheduling method according to claim 1 , wherein the value range of the decision threshold α _th in step S5 is 0.85≦α _th <1. 4 .