CN103581959B

CN103581959B - It is a kind of to improve the method, apparatus and system of cell downlink covering

Info

Publication number: CN103581959B
Application number: CN201210264099.7A
Authority: CN
Inventors: 刘劲楠
Original assignee: Huawei Technologies Co Ltd
Current assignee: Huawei Technologies Co Ltd
Priority date: 2012-07-27
Filing date: 2012-07-27
Publication date: 2017-07-28
Anticipated expiration: 2032-07-27
Also published as: CN103581959A; WO2014015684A1

Abstract

The embodiment of the present invention provides a kind of method, apparatus and system of improvement cell downlink covering, is related to the communications field, to solve the problem of cell downlink covering is not enough, this method includes：Base station determines the limited UE of descending covering, obtains the descending circuit loss value from the base station to the UE, and be worth to covering compensating parameter according to the descending path loss；The base station performs covering compensation process according to the covering compensating parameter, and pass through the combination of physical layer signaling or high-level signaling or the physical layer signaling and the high-level signaling, the covering compensating parameter is sent to the UE, so that the UE is demodulated according to the covering compensating parameter to the data of reception.The embodiment of the present invention is used to improve cell downlink covering.

Description

Method, equipment and system for improving cell downlink coverage

Technical Field

The present invention relates to the field of communications, and in particular, to a method, device, and system for improving downlink coverage of a cell.

Background

Modern wireless communication systems increasingly emphasize spectral efficiency and support for large data throughput, such as the third Generation Partnership Project (3 GPP) research, Long Term Evolution (LTE) system designed, and Worldwide Interoperability for Microwave Access (WiMAX) system researched by the Institute of Electrical and Electronics Engineers (IEEE), and the maximum data rate can reach 100 Mbps.

However, since the type of traffic being transmitted determines the size of the transmitted information data and the delay requirement for transmission, these systems may have insufficient coverage for a particular delay or a particular rate of users when emphasizing large data throughput transmissions for different types of traffic being transmitted.

Disclosure of Invention

Embodiments of the present invention provide a method, a device, and a system for improving downlink coverage of a cell, so as to solve the problem of insufficient downlink coverage of the cell.

In a first aspect, a method for improving downlink coverage of a cell is provided, including:

a base station determines a terminal UE with limited downlink coverage;

the base station acquires a downlink path loss value from the base station to the UE, and obtains a coverage compensation parameter according to the downlink path loss value;

and the base station executes a coverage compensation process according to the coverage compensation parameter and sends the coverage compensation parameter to the UE through physical layer signaling or high layer signaling or the combination of the physical layer signaling and the high layer signaling, so that the UE demodulates the received data according to the coverage compensation parameter.

In a first possible implementation manner of the first aspect, the physical layer signaling includes a downlink control information DCI signaling;

the high layer signaling comprises Radio Resource Control (RRC) signaling;

the combining of physical layer signaling with higher layer signaling comprises using a combination of DCI signaling and RRC signaling.

With reference to the first aspect or the first possible implementation manner of the first aspect, in a second possible implementation manner, the determining, by the base station, the UE with limited downlink coverage specifically includes:

and the base station receives the error response NACK fed back by the UE and determines that the downlink coverage of the UE is limited when the modulation and coding scheme MCS allocated to the UE is determined to be the lowest level.

With reference to the first aspect to the second possible implementation manner of the first aspect, in a third possible implementation manner, the acquiring, by the base station, a downlink path loss value from the base station to the UE specifically includes:

the base station receives a Channel Quality Indicator (CQI) value fed back by the UE, and according to the CQI value, the base station: p_L＝P_S-P_rCalculating the downlink path loss value; wherein, P_LFor said downlink path loss value, P_SFor the transmission power value, P, of the base station on the downlink traffic channel_rSNR + N, where P_rThe receiving power value of the UE on a downlink traffic channel is obtained, the SNR is the signal-to-noise ratio corresponding to the CQI value, and N is the noise power of each carrier; or,

the base station receives a reference signal power value measured and reported by UE, and according to the power value of the reference signal, the base station passes through a formula: p_L＝P_S-P_RSRPCalculating the downlink path loss value; wherein, P_LFor said downlink path loss value, P_STransmitting the power value, P, of the downlink reference signal for a base station_RSRPThe reference signal power value received for the UE; or,

and the base station receives the downlink path loss value reported after the UE is measured.

With reference to the first aspect to the third possible implementation manner of the first aspect, in a fourth possible implementation manner, the obtaining a coverage compensation parameter according to the downlink path loss value specifically includes:

by the formula: n is a radical of_S＝R_S+P_L-P_S+ delta, calculating a coverage compensation factor, and obtaining a coverage compensation parameter according to the coverage compensation factor; wherein N is_SFor the coverage compensation factor, P_LFor said downlink path loss value, P_SFor the transmission power value, R, of the base station on the lower traffic channel_SAnd delta is a preset value and is a non-negative real number, wherein the MCS used by the UE on the service channel is the receiving sensitivity of the lowest level.

With reference to the fourth possible implementation manner of the first aspect, in a fifth possible implementation manner, the method further includes: and when the coverage compensation factor is determined to be negative, returning to the step of re-executing the UE with the determined downlink coverage limitation.

With reference to the fourth possible implementation manner or the fifth possible implementation manner of the first aspect, in a sixth possible implementation manner, the obtaining a coverage compensation parameter according to the coverage compensation factor includes: adjusting the maximum retransmission times of a hybrid automatic repeat request (HARQ) according to the coverage compensation factor;

the executing the coverage compensation process according to the coverage compensation parameter includes:

and updating the original HARQ maximum retransmission times by using the adjusted HARQ maximum retransmission times.

With reference to the fourth possible implementation manner or the fifth possible implementation manner of the first aspect, in a seventh possible implementation manner, the obtaining a coverage compensation parameter according to the coverage compensation factor includes: by the formula:calculating a repetition factor, wherein N_PIs the repetition factor, N_SA compensation factor for the coverage;

make N for each pre-encoded information bit_PMultiple repetition(ii) a Or,

make N to the whole coded data bit_PRepeating the steps; or,

make N for all modulated symbols_PAnd (4) doubling.

With reference to the fourth possible implementation manner or the fifth possible implementation manner of the first aspect, in an eighth possible implementation manner, the obtaining a coverage compensation parameter according to the coverage compensation factor includes: by the formula:calculating a spreading factor, wherein N_PFor said spreading factor, N_SA compensation factor for the coverage;

n-spreading the modulated symbols with a spreading sequence_PDirect sequence spread spectrum of multiples.

With reference to the fourth possible implementation manner to the eighth possible implementation manner of the first aspect, in a ninth possible implementation manner, after the UE demodulates the received data according to the coverage compensation parameter, the method further includes:

if the base station receives the correct response ACK fed back by the UE, the base station recalculates the coverage compensation factor, obtains the coverage compensation parameter again according to the recalculated coverage compensation factor, and executes the coverage compensation process according to the coverage compensation parameter obtained again;

and if the base station receives the NACK fed back by the UE, adjusting the coverage compensation factor by adjusting the preset value.

With reference to the first aspect to the ninth possible implementation manner of the first aspect, in a tenth possible implementation manner, the coverage compensation parameter includes: HARQ maximum retransmission times, or repetition factor, or spreading factor, and parameters necessary to generate a spreading sequence.

In a second aspect, a base station is provided, including:

the processing unit is used for determining UE with limited downlink coverage, acquiring a downlink path loss value from the base station to the UE, obtaining a coverage compensation parameter according to the downlink path loss value, and executing a coverage compensation process according to the coverage compensation parameter;

a sending unit, configured to send the coverage compensation parameter to the UE through a physical layer signaling or a high layer signaling or a combination of the physical layer signaling and the high layer signaling, so that the UE demodulates received data according to the coverage compensation parameter.

In a first possible implementation manner of the second aspect, the physical layer signaling includes downlink control information, DCI, signaling;

the high layer signaling comprises Radio Resource Control (RRC) signaling;

With reference to the second aspect or the first possible implementation manner of the second aspect, in a second possible implementation manner, the method further includes:

a receiving unit, configured to receive an error response NACK fed back by the UE after the UE demodulates the data sent by the base station;

the processing unit is specifically configured to determine that the UE is restricted in downlink coverage when the receiving unit receives the NACK and the processing unit determines that the modulation and coding scheme MCs allocated to the UE is the lowest level.

With reference to the second aspect to the second possible implementation manner of the second aspect, in a third possible implementation manner, the receiving unit is specifically configured to receive a channel quality indication CQI value sent by the UE;

the processing unit is specifically configured to, after the receiving unit receives the CQI value, according to the CQI value, via a formula: p_L＝P_S-P_rCalculating the downlink path loss value; wherein, P_LFor said downlink path loss value, P_SFor the transmission power value, P, of the base station on the downlink traffic channel_rSNR + N, where P_rThe receiving power value of the UE on a downlink traffic channel is obtained, the SNR is the signal-to-noise ratio corresponding to the CQI value, and N is the noise power of each carrier; or,

the receiving unit is specifically configured to receive a reference signal power value reported by UE measurement;

the processing unit is specifically configured to, after the receiving unit receives the reference signal power value, according to a formula, according to the power value of the reference signal: p_L＝P_S-P_RSRPCalculating the downlink path loss value; wherein, P_LFor said downlink path loss value, P_STransmitting the power value, P, of the downlink reference signal for a base station_RSRPThe reference signal power value received for the UE; or,

the receiving unit is specifically configured to receive the downlink path loss value reported after the UE measures the downlink path loss value.

With reference to the second aspect to the third possible implementation manner of the second aspect, in a fourth possible implementation manner, the processing unit is specifically configured to: n is a radical of_S＝R_S+P_L-P_S+ delta, calculating a coverage compensation factor, and obtaining a coverage compensation parameter according to the coverage compensation factor; wherein N is_SFor the coverage compensation factor, P_LFor said downlink path loss value, P_SFor the transmission power value, R, of the base station on the lower traffic channel_SAnd delta is a preset value and is a non-negative real number, wherein the MCS used by the UE on the service channel is the receiving sensitivity of the lowest level.

With reference to the fourth possible implementation manner of the second aspect, in a fifth possible implementation manner, the processing unit is further configured to, when it is determined that the coverage compensation factor is a negative number, return to re-execute the UE with the determined downlink coverage limitation.

With reference to the fourth possible implementation manner or the fifth possible implementation manner of the second aspect, in a sixth possible implementation manner, the processing unit is specifically configured to adjust the maximum HARQ retransmission times according to the coverage compensation parameter, and update the original maximum HARQ retransmission times by using the adjusted maximum HARQ retransmission times.

With reference to the fourth possible implementation manner or the fifth possible implementation manner of the second aspect, in a seventh possible implementation manner, the processing unit is specifically configured to:calculating a repetition factor, wherein N_PIs the repetition factor, N_SA compensation factor for the coverage; the processing unit is specifically further configured to perform N on each information bit before encoding_PRepeating the steps; or, do N for the whole coded data bit_PRepeating the steps; or, do N for all modulated symbols_PAnd (4) doubling.

With reference to the fourth possible implementation manner or the fifth possible implementation manner of the second aspect, in an eighth possible implementation manner, the processing unit is specifically configured to:calculating a spreading factor, wherein N_PFor said spreading factor, N_SCompensating the factor for the coverage and N-spreading the modulated symbols by a spreading sequence_PDirect sequence spread spectrum of multiples.

With reference to the fourth possible implementation manner to the eighth possible implementation manner of the second aspect, in a ninth possible implementation manner, the receiving unit is further configured to receive an ACK or NACK fed back by the UE after the UE demodulates the received data according to the coverage compensation parameter;

the processing unit is further configured to, if the receiving unit receives the ACK fed back by the UE, recalculate the coverage compensation factor, obtain a coverage compensation parameter again according to the recalculated coverage compensation factor, and execute the coverage compensation process according to the obtained coverage compensation parameter; and if the receiving unit receives the NACK fed back by the UE, adjusting the coverage compensation factor by adjusting the preset value.

With reference to the second aspect to the ninth possible implementation manner of the second aspect, in a tenth possible implementation manner, the coverage compensation parameter includes: HARQ maximum retransmission times, or repetition factor, or spreading factor, and parameters necessary to generate a spreading sequence.

In a third aspect, a communication system is provided, including: a base station and a terminal, wherein,

the base station is the base station of the second aspect;

and the terminal is used for receiving the coverage compensation parameters sent by the base station, demodulating the received data according to the coverage compensation parameters, and feeding back ACK or NACK to the base station.

By adopting the scheme, the base station executes the coverage compensation process according to the obtained coverage compensation parameter and sends the coverage compensation parameter to the UE so that the UE demodulates the received data according to the coverage compensation parameter, thus the base station can enhance the coverage of the user with limited coverage and solve the problem of insufficient downlink coverage of the cell.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.

Fig. 1 is a schematic diagram of a method for improving downlink coverage of a cell according to an embodiment of the present invention;

fig. 2 is a flowchart illustrating another method for improving downlink coverage of a cell according to an embodiment of the present invention;

fig. 3 is a schematic structural diagram of a base station according to an embodiment of the present invention;

fig. 4 is a schematic structural diagram of another base station according to an embodiment of the present invention;

fig. 5 is a communication system according to an embodiment of the present invention.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

An embodiment of the present invention provides a method for improving downlink coverage of a cell, as shown in fig. 1, where an execution subject of the method is a base station, and the method includes:

s101, a base station determines a UE (User Equipment, i.e., a terminal) with limited downlink coverage.

Optionally, after the UE demodulates the data sent by the base station, the base station receives a NACK (error response) fed back by the UE, and determines that the UE downlink coverage is limited when determining that an MCS (Modulation and Coding Scheme) allocated to the UE is a lowest level. The UE with limited downlink coverage is the UE with the lowest MCS level.

Specifically, the lower the MCS level is, the lower the corresponding spectral efficiency is, and the lower the operating SINR (Signal to interference plus Noise Ratio) is, the longer the downlink transmission distance that the base station can support is, therefore, when the base station determines that the MCS allocated to the UE is the lowest level, that is, the downlink transmission distance that the base station can support has reached the farthest distance, and if the base station still receives the NACK fed back by the UE at this time, that is, the farthest distance does not guarantee that the UE performs correct demodulation, it is determined that the downlink coverage of the UE is limited.

For example, in the LTE system, the MCS is defined as shown in the following table:

MCS level	Modulation system	Code rate × 1024	Spectral efficiency
				0	-	-	-
1	QPSK	78	0.1523
				2	QPSK	120	0.2344
3	QPSK	193	0.3770
				4	QPSK	308	0.6016
5	QPSK	449	0.8770
				6	QPSK	602	1.1758

7	16QAM	378	1.4766
				8	16QAM	490	1.9141
9	16QAM	616	2.4063
				10	64QAM	466	2.7305
11	64QAM	567	3.3223
				12	64QAM	666	3.9023
13	64QAM	772	4.5234
				14	64QAM	873	5.1152
15	64QAM	948	5.5547

In the table, MCS levels of 15, i.e., MCS1 to MCS15(MCS0 is not defined in the LTE system), MCS1 is the lowest level, and MCS15 is the highest level, are defined. The method comprises the steps that a base station receives a CQI (Channel quality Indicator) value reported by UE (user equipment), allocates the level of MCS (modulation and coding scheme) to the UE according to the CQI value reported by the UE and a measurement result of an uplink Channel, and determines that the downlink coverage of the UE is limited if the MCS level allocated to the UE by the base station is MCS1 and receives that the response feedback of the UE to a downlink transmission data HARQ (hybrid automatic Repeat-reQuest) is NACK, wherein the CQI value indicates the level of the MCS reported by the UE. Here, the description is given only by way of an example of the LTE system, and is not particularly limited.

S102, the base station obtains a downlink path loss value from the base station to the UE, and obtains a coverage compensation parameter according to the downlink path loss value.

The downlink path loss value can be obtained in any one of the following three ways:

the first method is as follows: the base station receives the CQI fed back by the UE, and according to the CQI value, the base station passes a formula: p_L＝P_S-P_rAnd calculating the downlink path loss value.

Wherein, P_LFor the downlink path loss value, P_SFor the transmission power value, P, of the base station on the downlink traffic channel_rSNR + N, where P_rAnd for the receiving power value of the UE on the lower traffic channel, SNR (Signal-to-Noise Ratio) is a Signal-to-Noise Ratio corresponding to the CQI value, and N is Noise power of each carrier.

For example, in the LTE system, if the MCS level indicated by the CQI reported by the UE is MCS4, and when the block error rate is determined to be 10 percent, the SNR corresponding to the MCS is-2.2 dB, and N is the noise power on each 15khz carrier, then N is-174 +101g (15 × 10 g)³) -132.24, then: p_rSNR + N-2.2-132.24-134.44 dBm, if P_SAt 40dBm, the following equation yields: downlink path loss value P_L＝P_S-P_r＝40-(-134.44)＝174.44dB。

The second method comprises the following steps: the base station receives a reference signal power value measured and reported by the UE, and according to the power value of the reference signal, the base station passes through a formula: p_L＝P_S-P_RSRPAnd calculating the downlink path loss value.

Wherein, P_LFor the downlink path loss value, P_STransmitting the power value, P, of the downlink reference signal for the base station_RSRPThe reference signal power value received for the UE.

For example, in the LTE system, if the UE measures P on CRS (Cell-specific Reference Signal)_RSRPAt-100 dBm, the transmission power value P of the base station on the CRS_SWas 40 dBm. The UE will send P of CRS in the mobility measurement report_RSRPAnd reporting to the base station through an uplink message. The base station can calculate the downlink path loss value P according to the following formula_L：

P_L＝P_S-P_RSRP＝40-(-100)＝140dB。

The third method comprises the following steps: and the base station receives the downlink path loss value reported after the UE measures.

That is, the calculation in the second embodiment may be performed on the UE side, and the downlink loss value P may be calculated on the UE side_L＝P_S-P_RSRPAfter 140dB at 40- (-100), the UE will calculate the P_LThe value is sent to the base station via an uplink message.

It should be noted that, in the first method, it is assumed that the UE is only interfered by AWGN (Additive White gaussian noise) and is not interfered by other co-frequency signals, so that the calculation result is an ideal state value, and an error is large in a multi-cell co-frequency interference scenario, and therefore, in practical applications, it is preferable to adopt the second method or the third method to obtain the downlink loss value.

In addition, after obtaining the downlink path loss value, the base station uses the formula according to the downlink path loss value: n is a radical of_S＝R_S+P_L-P_SAnd + delta, calculating the coverage compensation factor and obtaining a coverage compensation parameter according to the coverage compensation factor.

Wherein N is_SFor this coverage compensation factor, the unit is dB, P_LFor the downlink path loss value, P_SFor the transmission power value, R, of the base station on the lower traffic channel_SFor the receiving sensitivity of the UE with the lowest MCS level on the traffic channel, Δ is a preset value and is a non-negative real number.

For example, in LTE system, if R_SIs-100 dBm, P_LIs 160dB, P_SAt 40dBm, according to the above equation: n is a radical of_S＝R_S+P_L-P_S+ Δ, may yield N_S10+ Δ, that is, N_SNot less than 10dB, but in order to improve the use efficiency of the transmission channel, a preset value delta is introduced, which can be set according to practical application or experience value, and the function of the preset value delta is to compensate the coverage compensation factor N needing compensation under the condition of a wireless channel_SIn practical use, a certain protection pre-set is provided, and the preset value delta is not limited in the invention, so that the base station can adjust the preset value delta to ensure sufficient downlink coverage and improve the use efficiency of a transmission channel.

Further, if the base station determines that the obtained coverage compensation factor is negative, the step of re-executing the UE with limited downlink coverage is returned, and if the re-determined UE is still the UE, it indicates that the UE cannot perform correct demodulation under the condition of sufficient power, and it is determined that the UE is abnormal.

In addition, the base station obtains the coverage compensation parameter according to the coverage compensation factor includes the following three ways, which are not limited in the present invention:

the first method is as follows: the base station adjusts the maximum retransmission times of the HARQ (Hybrid Automatic repeat request) according to the coverage compensation parameter.

And the gain corresponding to the maximum HARQ retransmission number meets the coverage compensation parameter.

For example, in the LTE system, if the maximum number of HARQ retransmissions is 4, and the gain corresponding to the 4 HARQ retransmissions is 6dB, but the coverage compensation parameter corresponding to the coverage compensation requirement is 10dB, the maximum 4 retransmissions still cannot meet the requirement of the coverage extension, so the maximum number of HARQ retransmissions can be adjusted to be greater than 4, for example, 6 or 8, to meet the requirement of the coverage extension.

It should be noted that the gain corresponding to the HARQ maximum retransmission number is obtained by the base station by querying a table of correspondence between the level of the MCS allocated by the base station to the UE and the gain; or, the base station obtains, according to actual experience, for example, gains of different retransmission times corresponding to different MCS levels are obtained through link simulation, instrument test, and the like, so as to obtain the maximum HARQ retransmission times meeting the coverage extension requirement according to the gains.

The second method comprises the following steps: base station passing formulaA repetition factor is calculated.

Wherein N is_PIs a repetition factor, N_SIs a coverage compensation factor.

The third method comprises the following steps: the base station is represented by the formula:and calculating a spreading factor.

Wherein N is_PIs a spreading factor, N_SA coverage compensation parameter; the spreading sequence is a row or a column in any one of the sets of spreading sequences. E.g. N_PWhen 4, the set of spreading sequences may be the following matrix H of length 4:

the spreading sequence of length 4 may be any of the above matrices HA row or a column. The necessary parameter for generating the spreading sequence in this example is the spreading sequence length N_PAnd the number value of the row or column of the spreading sequence.

As another example, if the spreading sequence is a Zadoff-Chu sequence, the length is N_PThe generation formula for a certain spreading sequence is:

the necessary parameter for generating the spreading sequence in this example is the spreading sequence length N_PAnd a sequence number q.

S103, the base station executes a coverage compensation process according to the coverage compensation parameter, and sends the coverage compensation parameter to the UE through physical layer signaling or high layer signaling or the combination of the physical layer signaling and the high layer signaling, so that the UE demodulates the received data according to the coverage compensation parameter.

The specific coverage compensation process includes the following three ways, which are not limited by the present invention:

the first method is as follows: and the base station updates the original HARQ maximum retransmission times by using the adjusted HARQ maximum retransmission times.

Further, the sending, by the base station to the UE, the coverage compensation parameter may be: and the base station sends the HARQ maximum retransmission times to the UE so that the UE caches or combines the data with wrong demodulation before the HARQ retransmission times reach the HARQ maximum retransmission times.

For example: when the UE receives the data and performs demodulation and decoding of the physical layer, if the decoding result is wrong, it indicates that the UE cannot correctly demodulate the data through the current data, and the UE may cache the incorrectly demodulated decoded soft bit data. And when the UE receives the data sent to the UE by the base station for the second time, the UE combines the demodulated and decoded soft bit data demodulated for the first time and the second time. The manner of combining depends on the particular HARQ transmission scheme used. When the data which are completely the same are sent for the first time and the second time, the UE side can carry out combination by using a mode based on Chase combination; when the first time and the second time are sent different coding versions of the same data, the UE side carries out merging decoding by using an incremental redundancy mode. The manner of Chase combining and incremental redundancy combining decoding is well known in the art and will not be described further herein.

The second method comprises the following steps: the base station makes N for each information bit before coding_PAnd (4) doubling.

For example: if the information bits before encoding are b1, b2_PWhen the repetition is 4 times, the following repeated data bits will be obtained:

b1b1b1b1，b2b2b2b2，...，bMbMbMbM

or the base station makes N for the whole coded data bit_PAnd (4) doubling.

Doing N with the information bit_PThe manner of the multiple repetition is similar, except that here, instead of operating on information bits, N is done on coded data bits_PAnd (5) operating.

Or the base station makes N for the modulated symbols of all constellations_PAnd (4) doubling.

For example: the symbol after constellation modulation of data is represented as: d1, d 2.., dN, then N is performed_PThe operation was 4 times as follows:

d1d1d1d1，d2d2d2d2，...，dNdNdNdN

further, the sending, by the base station to the UE, the coverage compensation parameter may be: and the base station sends the repetition factor to the UE so that the UE can carry out corresponding de-repetition according to the repetition factor, and then data after de-repetition is obtained.

The third method comprises the following steps: the base station carries out N on the modulated symbols through the spread spectrum sequence_PDirect sequence spread spectrum of multiples.

For example: the symbol after constellation modulation of data is represented as: d1, d 2.. multidot.dn, a spreading sequence hs [ +1, -1, with a length of 4, is used]Carry out N_PThe operation was 4 times as follows:

d1、-d1、d1、-d1，d2、-d2、d2、-d2，...，dN、-dN、dN、-dN

the Modulation may be Modulation performed by a constellation diagram, such as QPSK (Quadrature Phase shift keying) Modulation, 16QAM (Quadrature Amplitude Modulation), 64QAM Modulation, 256QAM Modulation, and the like, but the present invention is not limited thereto.

It should be noted that, in the above-mentioned manner, to implement correct transmission of a data packet, multiple retransmissions are required, and the time for retransmitting an uplink and a downlink once is at least 8ms, the time delay caused by 4 retransmissions is 32ms, and the time delay caused by 8 retransmissions is 64ms, so that it is only applicable to user services with insensitive time delay, such as web browsing, file transmission, etc.; the second and third modes can achieve the purpose of correct transmission only by one transmission as long as appropriate coverage compensation is performed, so that the method is suitable for user services with insensitive time delay, and is also suitable for user services with sensitive time delay, such as Voice Over Internet Protocol (VOIP) services, games and the like.

Further, the sending, by the base station to the UE, the coverage compensation parameter may be: the base station sends the spreading factor and the parameter necessary for generating the spreading sequence to the UE, so that the UE performs corresponding despreading according to the spreading factor and the parameter necessary for generating the spreading sequence, and further obtains data after despreading.

In addition, the physical layer signaling includes DCI (Downlink Control information) signaling.

Optionally, the base station may send the coverage compensation parameter to the UE by multiplexing a specific information bit field in the existing DCI signaling; a new DCI domain can be added in the DCI signaling to send the coverage compensation parameter to the UE; the coverage compensation parameter may also be sent to the UE via a special physical layer channel, which may be multiplexing an existing physical layer channel or a newly added physical layer channel. The invention is not limited in this regard.

The high layer signaling includes RRC (Radio Resource Control) signaling.

Optionally, the base station may send the coverage compensation parameter to the UE in a direct manner or an indirect manner, where the direct manner is to directly send the value of the coverage compensation parameter to the UE, and the indirect manner is to send the quantized value to the UE.

For example, if the overlay compensation parameter is (2)¹、2²、2³、2⁴) In a direct manner, the (2) bit is replaced by 4 bits¹、2²、2³、2⁴) Any one of them is sent to UE, and the indirect method is (2)¹、2²、2³、2⁴) The 2 bits are used for coding quantization to be (2, 4, 8, 16), the corresponding 2 bits are (00, 01, 10, 11) respectively, and any one of (00, 01, 10, 11) is sent to the UE, because the indirect method only needs 2 bits to send the coverage compensation parameter to the UE, and the direct method may occupy more bits, the indirect method can significantly reduce signaling overhead, and the indirect method is especially suitable for sending the coverage compensation parameter by using a physical layer channel.

The above combination of physical layer signaling and higher layer signaling includes using a combination of DCI signaling and RRC signaling.

For example, the system may select one of the spreading methods for repetition or spreading at the same time, and only a few bits are used to indicate the repetition or spreading factor (N) through DCI signaling_P) A few bits are then used to indicate which type of RRC signaling is selected. As in the above example, DCI signaling of 2 bits may be used to indicate N_PWhich value of (2, 4, 8, 16) and then use 2 bits to indicate which RRC signaling is used. Such as:

the parameters necessary for generating the spreading sequences include generation parameters of the set of spreading sequences and the spreading sequences used are rows or columns in the set of generated spreading sequences.

Further, after the UE demodulates the received data according to the coverage compensation parameter, if the base station receives an ACK fed back by the UE, the base station recalculates the coverage compensation factor, and obtains a coverage compensation parameter again according to the recalculated coverage compensation factor, and performs the coverage compensation process according to the obtained coverage compensation parameter, so that the lower the MCS level is, the lower the channel utilization efficiency is, and thus the obtained coverage compensation parameter can ensure sufficient downlink coverage, and at the same time, improve the MCS level, thereby improving the utilization efficiency of the transmission channel.

If the base station receives the NACK fed back by the UE, the coverage compensation factor is adjusted by adjusting the preset value, so that the UE can correctly demodulate the received data.

The HARQ maximum retransmission number, the repetition factor, the spreading factor, and the parameters necessary for generating the spreading sequence are the coverage compensation parameters.

By adopting the scheme, the base station can enhance the coverage of the users with limited coverage through the coverage compensation parameters, thereby solving the problem of insufficient downlink coverage of the cell.

Preferably, an embodiment of the present invention provides a method for improving downlink coverage of a cell, as shown in fig. 2, the method includes:

s201, the base station determines UE with limited downlink users.

Optionally, after the UE demodulates the data sent by the base station, the base station receives NACK fed back by the UE, and determines that the UE downlink coverage is limited when determining that the MCS allocated to the UE is the lowest level. The UE with limited downlink coverage is the UE with the lowest MCS level.

Specifically, the lower the MCS level is, the lower the corresponding spectral efficiency is, the lower the operating SINR is, the longer the downlink transmission distance that the base station can support is, therefore, when the base station determines that the MCS allocated to the UE is the lowest level, that is, it indicates that the downlink transmission distance that the base station can support has reached the farthest distance, and if the base station still receives the NACK fed back by the UE at this time, that is, it indicates that the farthest distance cannot ensure that the UE performs correct demodulation, it determines that the downlink coverage of the UE is limited.

S202, the base station acquires a downlink path loss value from the base station to the UE.

Wherein, P_LFor the downlink path loss value, P_SFor the transmission power value, P, of the base station on the downlink traffic channel_rSNR + N, where P_rAnd the SNR is the signal-to-noise ratio corresponding to the CQI value, and N is the noise power of each carrier.

The second method comprises the following steps: the base station receives the reference signal power measured and reported by the UEAnd according to the power value of the reference signal, the power value is calculated by the formula: p_L＝P_S-P_RSRPAnd calculating the downlink path loss value.

Wherein, P_LFor the downlink path loss value, P_STransmitting the power value, P, of the downlink reference signal for the base station_RSRPThe reference signal power value received for the UE

P_L＝P_S-P_RSRP＝40-(-100)＝140dB。

That is, the calculation in the second method may be performed at the UE side, and the downlink loss value P may be calculated at the UE side_L＝P_S-P_RSRPAfter 140dB at 40- (-100), the UE will calculate the P_LThe value is sent to the base station via an uplink message.

It should be noted that, in the first method, it is assumed that the UE is only interfered by AWGN, not interfered by other co-frequency signals, and not interfered by other co-frequency signals, so that the calculation result is an ideal state value, and an error is large in a multi-cell co-frequency interference scenario, and therefore, in practical applications, it is preferable to acquire the downlink path loss value by using the second method or the third method.

S203, the base station according to the downlink path loss value through a formula: n is a radical of_S＝R_S+P_L-P_S+ Δ, the coverage compensation factor is calculated.

Wherein N is_SFor this coverage compensation factor, the unit is dB, P_LIs the downlink path lossValue, P_SFor the transmission power value, R, of the base station on the lower traffic channel_SFor the receiving sensitivity of the UE with the lowest MCS level on the traffic channel, Δ is a preset value and is a non-negative real number.

For example, in LTE system, if R_SIs-100 dBm, P_LIs 160dB, P_SAt 40dBm, according to the above equation: n is a radical of_S＝R_S+P_L-P_S+ Δ, may yield N_S10+ Δ, that is, N_SNot less than 10dB, but in order to improve the use efficiency of the transmission channel, a preset value delta is introduced, which can be set according to practical application or experience value, and the effect of the preset value delta is to give a coverage factor N needing compensation under the condition of a wireless channel_SIn practical use, a certain protection pre-set is provided, and the preset value delta is not limited in the invention, so that the base station can adjust the preset value delta to ensure sufficient downlink coverage and improve the use efficiency of a transmission channel.

S204, the base station judges whether the coverage compensation factor is non-negative.

If yes, go to step S205 to step S208.

If the determination result is no, the process returns to step S201.

And S205, the base station obtains a coverage compensation parameter according to the coverage compensation factor.

This step may include the following three ways:

the first method is as follows: and the base station adjusts the maximum retransmission times of the HARQ according to the coverage compensation parameter.

Wherein N is_PIs a repetition factor, N_SIs a coverage compensation factor.

Wherein N is_PIs a spreading factor, N_SA coverage compensation parameter; the spreading sequence is a row or a column in any one of the sets of spreading sequences.

E.g. N_PWhen 4, the set of spreading sequences may be the following matrix H of length 4:

the spreading sequence of length 4 may be any row or column in the above matrix H. The necessary parameter for generating the spreading sequence in this example is the spreading sequence length N_PAnd the number value of the row or column of the spreading sequence.

As another example, if the spreading sequence is a Zadoff-Chu sequence, it is longIs N_PThe generation formula for a certain spreading sequence is:

And S206, the base station executes a coverage compensation process according to the coverage compensation parameters.

b1b1b1b1，b2b2b2b2，...，bMbMbMbM

or the base station makes N for the whole coded data bit_PAnd (4) doubling.

d1d1d1d1，d2d2d2d2，...，dNdNdNdN

For example: the symbol after constellation modulation of data is represented as: d1, d 2.., dN, then use a spreading sequence hs [ +1, -1, with a length of 4]Carry out N_PThe operation was 4 times as follows:

d1、-d1、d1、-d1，d2、-d2、d2、-d2，...，dN、-dN、dN、-dN

the modulation may be modulation performed by a constellation diagram, such as QPSK modulation, 16QAM modulation, 64QAM modulation, 256QAM modulation, etc., but the present invention is not limited thereto.

It should be noted that, in the above-mentioned manner, to implement correct transmission of a data packet, multiple retransmissions are required, and the time for retransmitting an uplink and a downlink once is at least 8ms, the time delay caused by 4 retransmissions is 32ms, and the time delay caused by 8 retransmissions is 64ms, so that it is only applicable to user services with insensitive time delay, such as web browsing, file transmission, etc.; the second and third modes can achieve the purpose of correct transmission only by one transmission as long as appropriate coverage compensation is performed, so that the method is not only suitable for user services with insensitive time delay, but also suitable for user services with sensitive time delay, such as VOIP services, games and the like.

S207, the base station sends the coverage compensation parameter to the UE through physical layer signaling or high layer signaling or the combination of the physical layer signaling and the high layer signaling.

Corresponding to step S206, the base station sending the coverage compensation parameter to the UE includes the following three ways:

in the first method, the base station sends the HARQ maximum retransmission times to the UE, so that the UE buffers or combines the data with the demodulation error before the HARQ retransmission times reach the HARQ maximum retransmission times.

For example: when the UE receives the data and performs demodulation and decoding of the physical layer, if the decoding result is wrong, it indicates that the UE cannot correctly demodulate the data through the current data, and the UE may cache the incorrectly demodulated decoded soft bit data. And when the UE receives the data sent to the UE by the base station for the second time, the UE combines the demodulated and decoded soft bit data demodulated for the first time and the second time. The manner of combining depends on the particular HARQ transmission method used. When the data which are completely the same are sent for the first time and the second time, the UE side can carry out combination by using a mode based on Chase combination; when the first time and the second time are sent different coding versions of the same data, the UE side carries out merging decoding by using an incremental redundancy mode. The manner of Chase combining and incremental redundancy combining decoding is well known in the art and will not be described further herein.

And in the second mode, the base station sends the repetition factor to the UE so that the UE can perform corresponding de-repetition according to the repetition factor to further obtain data after de-repetition.

And thirdly, the base station sends the spreading factor and the parameter necessary for generating the spreading sequence to the UE, so that the UE performs corresponding despreading according to the spreading factor and the parameter necessary for generating the spreading sequence, and further obtains the data after despreading.

Wherein the physical layer signaling includes DCI signaling.

Specifically, the base station may transmit the coverage compensation parameter to the UE by multiplexing a specific information bit field in the existing DCI signaling; a new DCI domain can be added in the DCI signaling to send the coverage compensation parameter to the UE; the coverage compensation parameter may also be sent to the UE via a special physical layer channel, which may be multiplexing an existing physical layer channel or a newly added physical layer channel. The invention is not limited in this regard.

The higher layer signaling includes RRC signaling.

Specifically, the base station may send the coverage compensation parameter to the UE in a direct manner or an indirect manner, where the direct manner is to directly send the value of the coverage compensation parameter to the UE, and the indirect manner is to send the quantized value to the UE.

For example, if the overlay compensation parameter is (2)¹、2²、2³、2⁴) In a direct manner, the (2) bit is replaced by 4 bits¹、2²、2³、2⁴) Any one of them is sent to UE, and the indirect method is (2)¹、2²、2³、2⁴) The 2 bits are used for coding quantization to be (2, 4, 8, 16), the corresponding 2 bits are (00, 01, 10, 11) respectively, and any one of (00, 01, 10, 11) is sent to the UE, because the indirect method only needs 2 bits to send the coverage compensation parameter to the UE, and the direct method may occupy more bits, the indirect method can significantly reduce signaling overhead, and the indirect method is especially suitable for sending the coverage compensation parameter by using a physical layer channel. .

And S208, the UE demodulates the received data according to the coverage compensation parameter.

Further, after the UE demodulates the received data according to the coverage compensation parameter, if the base station receives the ACK fed back by the UE, the step S202 is returned to calculate the coverage compensation factor again, and obtains the coverage compensation parameter again according to the coverage compensation factor calculated again, and performs the coverage compensation process according to the coverage compensation parameter obtained again.

The HARQ maximum retransmission number, the repetition factor, the spreading factor, and parameters necessary for generating the spreading sequence are the coverage compensation parameters.

It should be noted that, for simplicity of description, the above-mentioned method embodiments are all described as a series of action combinations, but those skilled in the art should understand that the present invention is not limited by the described action sequence. Further, those skilled in the art should also appreciate that the embodiments described in the specification are preferred embodiments and that the acts and modules referred to are not necessarily required by the invention.

An embodiment of the present invention provides a base station 300, as shown in fig. 3, including:

a processing unit 301, configured to determine a UE with limited downlink coverage, obtain a downlink path loss value from the base station to the UE, obtain a coverage compensation parameter according to the downlink path loss value, and execute a coverage compensation process according to the coverage compensation parameter;

a sending unit 302, configured to send the coverage compensation parameter to the UE through a physical layer signaling or a higher layer signaling or a combination of the physical layer signaling and the higher layer signaling, so that the UE demodulates the received data according to the coverage compensation parameter.

Wherein the physical layer signaling comprises DCI signaling.

The higher layer signaling includes RRC signaling.

The combining of physical layer signaling with higher layer signaling includes using a combination of DCI signaling and RRC signaling.

Further, as shown in fig. 4, the base station further includes: a receiving unit 303, configured to receive NACK fed back by the UE after the UE demodulates the data sent by the base station;

the processing unit 301 is specifically configured to determine that the UE is downlink coverage limited when the processing unit 301 determines that the MCS allocated to the UE is the lowest level after the receiving unit 303 receives the NACK.

Optionally, the receiving unit 303 is specifically configured to receive a CQI value sent by the UE;

the processing unit 301 is specifically configured to, after the receiving unit 303 receives the CQI value, according to the CQI value, by using a formula: p_L＝P_S-P_rCalculating the downlink path loss value; wherein, P_LFor the downlink path loss value, P_SFor the value of the downlink transmission power of the base station, P_rSNR + N, where P_rThe receiving power value of the UE on a downlink traffic channel is represented, SNR is the signal-to-noise ratio corresponding to the CQI value, and N is the noise of each carrier waveThe acoustic power.

Optionally, the receiving unit 303 is specifically configured to receive a reference signal power value measured and reported by the UE;

the processing unit 301 is specifically configured to, after the receiving unit 303 receives the power value of the reference signal, according to the power value of the reference signal, through a formula: p_L＝P_S-P_RSRPAnd calculating the downlink path loss value.

Wherein, P_LFor the downlink path loss value, P_STransmitting the power value, P, of the downlink reference signal for the base station_RSRPThe reference signal power value is received for the UE.

P_L＝P_S-P_RSRP＝40-(-100)＝140dB。

Optionally, the receiving unit 303 is specifically configured to receive the downlink path loss value reported after the UE measures the downlink path loss value.

That is, the calculation in the second embodiment may be performed on the UE side, and the downlink loss value P may be calculated on the UE side_L＝P_S-P_RSRP＝40-(-100)＝140dAfter B, the UE will calculate the obtained P_LThe value is sent to the base station via an uplink message.

Further, the processing unit 301 is specifically configured to obtain, by the formula: n is a radical of_S＝R_S+P_L-P_S+ delta, calculating a coverage compensation factor and obtaining a coverage compensation parameter according to the coverage compensation factor; wherein N is_SFor this coverage compensation factor, the unit is dB, P_LFor the downlink path loss value, P_SFor the transmission power value, R, of the base station on the lower traffic channel_SFor the receiving sensitivity of the UE with the lowest MCS level on the traffic channel, Δ is a preset value and is a non-negative real number.

Further, the processing unit 301 is further configured to, when the coverage compensation factor is determined to be negative, return to the step of re-executing the UE that determines that the downlink coverage is limited.

Optionally, the processing unit 301 is specifically configured to adjust a maximum retransmission time of a hybrid automatic repeat request HARQ according to the coverage compensation parameter, and update the original HARQ maximum retransmission time by using the adjusted HARQ maximum retransmission time.

The sending unit sending the coverage compensation parameter to the UE specifically includes: and sending the HARQ maximum retransmission times to the UE so that the UE caches or combines the data with wrong demodulation before the HARQ retransmission times reach the HARQ maximum retransmission times.

For example, when the UE receives data and performs demodulation and decoding of the physical layer, if the decoding result is wrong, it indicates that the UE cannot correctly demodulate the data through the current data, and the UE may buffer the incorrectly demodulated decoded soft bit data. And when the UE receives the data sent to the UE by the base station for the second time, the UE combines the demodulated and decoded soft bit data demodulated for the first time and the second time. The manner of combining depends on the particular HARQ transmission scheme used. When the data which are completely the same are sent for the first time and the second time, the UE side can carry out combination by using a mode based on Chase combination; when the first time and the second time are sent different coding versions of the same data, the UE side carries out merging decoding by using an incremental redundancy mode. The manner of Chase combining and incremental redundancy combining decoding is well known in the art and will not be described further herein.

Optionally, the processing unit 301 is specifically configured to obtain, by the formula:calculating a repetition factor, wherein N_PIs the repetition factor, N_SThe factor is compensated for the coverage.

The processing unit 301 is further configured to do N for each pre-encoded information bit_PAnd (4) doubling.

b1b1b1b1，b2b2b2b2，...，bMbMbMbM

or, do N for the whole coded data bit_PAnd (4) doubling.

Doing N with the information bit_PThe way of the multiple repetition is similar, except that here, instead of operating on information bits, N is done on coded bits_PAnd (5) operating.

Or, do N for all modulated symbols_PAnd (4) doubling.

For example: the symbol after constellation modulation of data is represented as: d1, d 2.., dN, then N is performed_PThe operation was as follows, with 4 times weight:

d1d1d1d1，d2d2d2d2，...，dNdNdNdN

the sending unit sending the coverage compensation parameter to the UE specifically includes: the sending unit sends the repetition factor to the UE so that the UE can perform corresponding de-repetition according to the repetition factor.

Optionally, the processing unit 301 is specifically configured to obtain, by the formula:calculating a spreading factor, wherein N_PIs the spreading factor, N_SCompensating the factor for the covering and N-spreading the modulated symbols by a spreading sequence_PDirect sequence spread spectrum of the multiple; the spreading sequence is a row or a column in any one of the sets of spreading sequences.

d1、-d1、d1、-d1，d2、-d2、d2、-d2，...，dN、-dN、dN、-dN

The sending unit sending the coverage compensation parameter to the UE specifically includes: and sending the parameter information of the spreading factor and the spreading sequence to the UE so that the UE performs corresponding despreading according to the parameter information of the spreading factor and the spreading sequence.

In addition, the receiving unit 303 is further configured to receive an ACK or NACK fed back by the UE after the UE demodulates the received data according to the coverage compensation parameter;

the processing unit 301 is further configured to, if the receiving unit 303 receives the ACK fed back by the UE, recalculate the coverage compensation factor, obtain the coverage compensation parameter again according to the recalculated coverage compensation factor, and execute the coverage compensation process according to the obtained coverage compensation parameter; if the receiving unit 303 receives the NACK fed back by the UE, the coverage compensation factor is adjusted by adjusting the predetermined value.

By adopting the base station, the base station can enhance the coverage of the users with limited coverage through the coverage compensation parameters, thereby solving the problem of insufficient downlink coverage of the cell.

It can be clearly understood by those skilled in the art that, for convenience and brevity of description, the specific working process of the base station described above may refer to the corresponding process in the foregoing method embodiment, and is not described herein again.

An embodiment of the present invention provides a communication system, as shown in fig. 5, the communication system includes: the above embodiments describe the base station 300 and the UE500,

the UE is configured to receive the coverage compensation parameter sent by the base station 300, demodulate received data according to the coverage compensation parameter, and feed back ACK or NACK to the base station 300.

The base station is applied to the method for improving the downlink coverage of the cell, and each unit in the base station also corresponds to each step in the method.

It should be noted that the communication System may be a GSM (Global System for mobile communications), CDMA (Code Division Multiple Access) System, TDMA (Time Division Multiple Access) System, WCDMA (Wideband Code Division Multiple Access) System, FDMA (Frequency Division Multiple Access) System, OFDMA (Orthogonal Frequency-Division Multiple Access) System, FDMA (single carrier-Frequency Division Multiple Access) System, FDMA (General packet radio Service) System, LTE (Long Term Evolution) System, and other such communication systems.

By adopting the communication system, the base station can enhance the coverage of the users with limited coverage through the coverage compensation parameters, thereby solving the problem of insufficient downlink coverage of the cell

Those of ordinary skill in the art will understand that: all or part of the steps for implementing the method embodiments may be implemented by hardware related to program instructions, and the program may be stored in a computer readable storage medium, and when executed, the program performs the steps including the method embodiments; and the aforementioned storage medium includes: various media that can store program codes, such as ROM, RAM, magnetic or optical disks.

The above description is only for the specific embodiments of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art can easily conceive of the changes or substitutions within the technical scope of the present invention, and all the changes or substitutions should be covered within the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the appended claims.

Claims

1. A method for improving downlink coverage of a cell, comprising:

a base station receives NACK fed back by UE, and determines that the UE is a terminal UE with limited downlink coverage when determining that MCS allocated to the UE is the lowest level;

the base station executes a coverage compensation process according to the coverage compensation parameter, and sends the coverage compensation parameter to the UE through a physical layer signaling or a high layer signaling or a combination of the physical layer signaling and the high layer signaling, so that the UE demodulates the received data according to the coverage compensation parameter;

the obtaining of the coverage compensation parameter according to the downlink path loss value specifically includes:

2. The method of claim 1, wherein the physical layer signaling comprises Downlink Control Information (DCI) signaling;

the high layer signaling comprises Radio Resource Control (RRC) signaling;

3. The method according to claim 1 or 2, wherein the determining, by the base station, the UE with limited downlink coverage specifically includes:

4. The method according to claim 1 or 2, wherein the obtaining, by the base station, the downlink path loss value from the base station to the UE specifically includes:

the base station receives a Channel Quality Indicator (CQI) value fed back by the UE, and according to the CQI value, the base station: p_L＝P_S-P_rComputing stationThe downlink path loss value; wherein, P_LFor said downlink path loss value, P_SFor the transmission power value, P, of the base station on the downlink traffic channel_rSNR + N, where P_rThe receiving power value of the UE on a downlink traffic channel is obtained, the SNR is the signal-to-noise ratio corresponding to the CQI value, and N is the noise power of each carrier; or,

5. The method of claim 4, further comprising: and when the coverage compensation factor is determined to be negative, returning to the step of re-executing the UE with the determined downlink coverage limitation.

6. The method of claim 1 or 5, wherein the deriving a coverage compensation parameter according to the coverage compensation factor comprises: adjusting the maximum retransmission times of a hybrid automatic repeat request (HARQ) according to the coverage compensation factor;

7. The method of claim 1 or 5, wherein the deriving a coverage compensation parameter according to the coverage compensation factor comprises: by the formula:calculating a repetition factor, wherein N_PIs the repetition factor, N_SA compensation factor for the coverage;

make N for each pre-encoded information bit_PRepeating the steps; or,

make N to the whole coded data bit_PRepeating the steps; or,

make N for all modulated symbols_PAnd (4) doubling.

8. The method of claim 1 or 5, wherein the deriving a coverage compensation parameter according to the coverage compensation factor comprises: by the formula:calculating a spreading factor, wherein N_PFor said spreading factor, N_SA compensation factor for the coverage;

9. The method of claim 5, wherein after the UE demodulates the received data according to the coverage compensation parameter, the method further comprises:

10. The method of any one of claims 1, 2 or 5, wherein the overlay compensation parameters comprise: HARQ maximum retransmission times, or repetition factor, or spreading factor, and parameters necessary to generate a spreading sequence.

11. A base station, comprising:

a processing unit, configured to receive NACK fed back by a UE, determine that the UE is a UE with limited downlink coverage when the MCS allocated to the UE is the lowest level, obtain a downlink path loss value from the base station to the UE, obtain a coverage compensation parameter according to the downlink path loss value, and perform a coverage compensation process according to the coverage compensation parameter;

a sending unit, configured to send the coverage compensation parameter to the UE through a physical layer signaling or a high layer signaling or a combination of the physical layer signaling and the high layer signaling, so that the UE demodulates received data according to the coverage compensation parameter;

the processing unit is specifically configured to: n is a radical of_S＝R_S+P_L-P_S+ delta, calculating a coverage compensation factor, and obtaining a coverage compensation parameter according to the coverage compensation factor; wherein N is_SFor the coverage compensation factor, P_LFor said downlink path loss value, P_SFor the transmission power value, R, of the base station on the lower traffic channel_SAnd delta is a preset value and is a non-negative real number, wherein the MCS used by the UE on the service channel is the receiving sensitivity of the lowest level.

12. The base station of claim 11, wherein the physical layer signaling comprises downlink control information, DCI, signaling;

the high layer signaling comprises Radio Resource Control (RRC) signaling;

13. The base station according to claim 11 or 12, further comprising:

a receiving unit, configured to receive NACK fed back by the UE;

the processing unit is specifically configured to determine that the UE is downlink coverage limited when the receiving unit receives the NACK and determines that the modulation and coding scheme MCS allocated to the UE is the lowest level.

14. The base station according to claim 11 or 12, wherein the receiving unit is specifically configured to receive a channel quality indication, CQI, value sent by the UE;

15. The base station of claim 11, wherein the processing unit is further configured to return to re-executing the step of determining the UE with limited downlink coverage when the coverage compensation factor is determined to be negative.

16. The base station according to claim 11 or 15, wherein the processing unit is specifically configured to adjust the HARQ maximum retransmission time according to the coverage compensation parameter, and update the original HARQ maximum retransmission time by using the adjusted HARQ maximum retransmission time.

17. The base station according to claim 11 or 15, wherein the processing unit is specifically configured to:calculating a repetition factor, wherein N_PIs the repetition factor, N_SA compensation factor for the coverage; the processing unit is specifically further configured to perform N on each information bit before encoding_PRepeating the steps; or, do N for the whole coded data bit_PRepeating the steps; or, do N for all modulated symbols_PAnd (4) doubling.

18. The base station according to claim 11 or 15, wherein the processing unit is specifically configured to:calculating a spreading factor, wherein N_PFor said spreading factor, N_SCompensating the factor for the coverage and N-spreading the modulated symbols by a spreading sequence_PDirect sequence spread spectrum of multiples.

19. The base station according to claim 11, 12 or 15, wherein the receiving unit is further configured to receive ACK or NACK fed back by the UE after the UE demodulates the received data according to the coverage compensation parameter;

20. The base station of claim 11, 12 or 15, wherein the coverage compensation parameters comprise: HARQ maximum retransmission times, or repetition factor, or spreading factor, and parameters necessary to generate a spreading sequence.

21. A communication system, comprising: a base station and a terminal, wherein,

the base station is the base station of any one of claims 11 to 20;