WO2016101386A1 - 通信方法、设备及系统 - Google Patents

通信方法、设备及系统 Download PDF

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Publication number
WO2016101386A1
WO2016101386A1 PCT/CN2015/071975 CN2015071975W WO2016101386A1 WO 2016101386 A1 WO2016101386 A1 WO 2016101386A1 CN 2015071975 W CN2015071975 W CN 2015071975W WO 2016101386 A1 WO2016101386 A1 WO 2016101386A1
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Prior art keywords
rru
terminal
rsrp
frequency
bbu
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PCT/CN2015/071975
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English (en)
French (fr)
Inventor
徐明涛
胥恒
阙程晟
黄晖
顾春颖
王新宇
Original Assignee
华为技术有限公司
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Application filed by 华为技术有限公司 filed Critical 华为技术有限公司
Priority to EP15871465.9A priority Critical patent/EP3232625B1/en
Priority to CA2972341A priority patent/CA2972341C/en
Priority to JP2017534666A priority patent/JP6537204B2/ja
Publication of WO2016101386A1 publication Critical patent/WO2016101386A1/zh

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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L25/00—Baseband systems
    • H04L25/02—Details ; arrangements for supplying electrical power along data transmission lines
    • H04L25/0202—Channel estimation
    • H04L25/0222—Estimation of channel variability, e.g. coherence bandwidth, coherence time, fading frequency
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L25/00—Baseband systems
    • H04L25/02—Details ; arrangements for supplying electrical power along data transmission lines
    • H04L25/0202—Channel estimation
    • H04L25/0204—Channel estimation of multiple channels
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L25/00—Baseband systems
    • H04L25/02—Details ; arrangements for supplying electrical power along data transmission lines
    • H04L25/03—Shaping networks in transmitter or receiver, e.g. adaptive shaping networks
    • H04L25/03006—Arrangements for removing intersymbol interference
    • H04L25/03343—Arrangements at the transmitter end

Definitions

  • the present invention relates to the field of communications, and more particularly to a communication method, apparatus, and system for adjusting a frequency offset in a system that implements networking using a combined cell.
  • the downlink signal transmitted by the base station is affected by the Doppler effect, which causes the signal to have a certain Doppler frequency offset when it reaches the terminal (the full name of the frequency can be frequency deviation), and the degree of the frequency offset can be It is called Doppler frequency offset value (Chinese abbreviation can be Doppler frequency offset value or frequency offset value, English full name can be frequency offset), this Doppler frequency offset will affect the performance of the terminal demodulation downlink signal .
  • the terminal may estimate the frequency offset value of a downlink signal of the base station, and actively adjust its own crystal oscillator to keep its own frequency consistent with the frequency of the downlink signal with the frequency offset, thereby preventing the terminal from demodulating the downlink signal. Performance is reduced.
  • the terminal may determine a frequency offset value of the downlink signal according to a phase difference between channel estimation values of the two pilot symbols of the downlink signal and a time interval between the two pilot symbols, and adjust the self according to the Crystal oscillator.
  • the base station includes a baseband unit (BBU) and a plurality of remote radio units (RRUs).
  • BBU baseband unit
  • RRUs remote radio units
  • Each RRU corresponds to one physical cell
  • a logical cell composed of multiple physical cells corresponds to one BBU, and all physical cells in one logical cell perform downlink joint transmission and uplink joint reception, thereby implementing a group of merged cells.
  • the mobile terminal A 1 may be in an overlapping coverage area of two RRUs.
  • the angles between the downlink signals of the RRU 0 and the RRU 1 and the moving direction of the terminal A 1 are ⁇ 1 and ⁇ 2 , respectively.
  • the difference between the actual frequency offset values of the downlink signals transmitted by RRU 0 and RRU 1 respectively when arriving at terminal A 1 is very large. Since the RRU 0 and the RRU 1 adopt the downlink joint transmission mode, that is, the content of the downlink signal is the same, the signal received by the terminal A 1 can only be the mixed signal of the downlink signals of the RRU 0 and the RRU 1 . If the terminal A 1 estimates the frequency offset value of the downlink signal by using the prior art in the scenario of FIG. 1 , the estimated frequency offset value must be very different from the two actual frequency offset values, thereby reducing the terminal demodulation downlink. Signal performance.
  • the performance of the mobile terminal demodulating the downlink signal may be low.
  • the embodiments of the present invention provide a communication method, device, and system, which can solve the problem that the performance of the mobile terminal demodulating the downlink signal may be low in the existing communication system using the combined cell.
  • a first aspect of the present invention provides a communication device, including: a baseband unit BBU and two radio remote units RRU 0 and RRU 1 , wherein the BBU is used to control a first logical cell, and the first logical cell includes RRU 0 physical cell coverage and coverage of the physical cell RRU 1; RRU 0 and the physical cell coverage RRU 1 in a first physical cell coverage areas overlap; wherein the RRU 1 and the RRU 0 for: frequency f 0 respectively Transmitting a first downlink signal, and then transmitting a second downlink signal by using a first frequency and a second frequency, respectively; the first frequency is a difference between f 0 and a first correction amount f d_dl_0 , and the second frequency is f 0 And a sum of the second correction amount fd_dl_1 ; wherein at least one of the fd_dl_0 and the fd_dl_1 is not 0.
  • Another aspect of the present invention provides a communication system comprising: the above communication device.
  • a second aspect of the present invention provides a communication method, including: a base station transmitting a first downlink signal by using a frequency f 0 , and then transmitting a second downlink signal by using a first frequency and a second frequency, respectively;
  • the frequency is a difference between f 0 and a first correction amount f d — d — d , the second frequency being a sum of f 0 and a second correction amount f d — d — 1 ; wherein at least one of the f d — d — d and the f d — d — d are not 0
  • the base station includes: a baseband unit BBU, two radio remote units RRU 0 and RRU 1 ; the BBU is used to control a first logical cell, where the first logical cell includes a physical cell and an RRU covered by the RRU 0 1 Covered physical cell; the physical cell covered by RRU 0 and the physical cell covered by RRU 1 overlap
  • f d_dl_0 and f d_dl_1 respectively satisfy certain conditions, so as to ensure the demodulation performance of the terminal is more obvious.
  • the above conditions may include:
  • a third aspect of the present invention provides a communication device, including: a baseband unit BBU, two radio remote units RRU 0 and RRU 1 , wherein the BBU is used to control a first logical cell, and the first logical cell includes a physical cell covered by RRU 0 and a physical cell covered by RRU 1 ; a physical cell covered by RRU 0 and a physical cell covered by RRU 1 overlap in a first area; said RRU 0 and RRU 1 are used to receive a mobile from RRU 1 to RRU 0
  • the value of R is 1; or, when the BBU works in the FDD system, R is a ratio of a downlink carrier frequency to an uplink carrier frequency in the FDD system.
  • the BBU may be further used to determine an RSRP of an uplink signal received by the RRU 0 and the RRU 1 . And determine a(i) according to the following formula;
  • RSRP_i RSRP 0 (i)+RSRP 1 (i);
  • the RSRP 0 (i) represents the reference signal received power RSRP of the uplink signal received by the RRU 0 from the terminal A i
  • the RSRP 1 (i) represents the RSRP of the uplink signal received by the RRU 1 from the terminal A i .
  • the first region distance RRU 0 and RRU 1 are both d, wherein
  • Q% indicates the tolerance for the difference between the frequency offset values of different terminals.
  • the value range of q is [ 0 , 100 ], and the range of D min is [L 0 , L 1 ], where L 0 represents RRU 0
  • L 0 represents RRU 0
  • L 1 represents the vertical distance between the RRU 1 and the mobile line of the terminal A i .
  • the BBU is further configured to: before determining the f d_dl , determining that the n terminals are in Within the first area.
  • the BBU is specifically configured to: when the first condition and the second condition are met, determine The n terminals are in the first area; the first condition includes: the Doppler frequency offset estimation value of each of the n terminals is positive or negative; The second condition includes: the absolute value of the difference between the Doppler frequency offset estimates of each of the n terminals is less than or equal to
  • the BBU is further configured to: if the n terminals are in the The first region determines the f d_dl according to the period T.
  • the BBU is further configured to: determine the T, where the value range of the T is [m*t, D s /v], where t represents a period during which the terminal A i reports the measurement quantity, where The measurement quantity is a measurement result of the RSRP of the terminal A i for the downlink signal from the RRU 0 ; m is greater than 0; D s represents the distance between the RRU 0 and the RRU 1 ; and v represents the moving speed of the terminal A i .
  • the RRU 0 and The RRU 1 is configured to separately send the downlink signal according to the frequency adjusted according to the f d_dl, where the RRU 0 is used to send the downlink signal by using the first frequency, where the first frequency is the difference between the f 0 and the first correction amount f d — dl_0
  • the RRU 1 is configured to send a downlink signal by using a second frequency, where the second frequency is a sum of f 0 and a second error correction amount f d — dl_1 , wherein at least one of the f d_dl_0 and the f d_dl_1 is not 0.
  • the f d_dl_0 and the f d_dl_1 respectively satisfy the following conditions:
  • the communication method, device and system provided by the foregoing solution can be applied to a communication system using a combined cell network mode In the system, it is beneficial to avoid reducing the performance of the mobile terminal demodulating the downlink signal.
  • 1 is a schematic diagram of a scenario in which a terminal estimates a frequency offset value of a downlink signal from a base station;
  • terminal A 1 estimates frequency offset values of downlink signals from two RRUs
  • FIG. 3 is a schematic diagram of a high-speed rail communication system using a networking mode of a merged cell
  • FIG. 4 is a schematic diagram of another high-speed rail communication system using a networking mode of a merged cell
  • FIG. 5 is a schematic diagram of another high-speed rail communication system using a networking mode of a merged cell
  • FIG. 6 is a schematic structural diagram of a communication device according to an embodiment of the present invention.
  • FIG. 7 is a schematic flowchart diagram of a communication method according to an embodiment of the present invention.
  • FIG. 8 is a schematic plan view showing the relative positions of the terminal and the RRU 0 and the RRU 1 in an embodiment of the present invention.
  • Embodiments of the present invention are applicable to a variety of communication systems, for example, Long Term Evolution (Long Term Evolution, LTE) systems, and other communication systems with downlink common pilots.
  • the embodiments of the present invention have obvious effects on ensuring demodulation performance and communication system performance of the terminal when applied to certain scenarios, including but not limited to: in a communication system using a combined cell networking mode, the terminal Move (especially fast moving) scenes. For example, the scenes shown in FIGS. 3, 4, and 5.
  • the poles 0 to the poles n are n poles along the high-speed railway, and there is a certain distance between each two poles, which is formed by each of the two poles.
  • the line is parallel to the (track) line on which it is listed, and the distance between the above parallel lines is represented by D min .
  • Each RRU corresponds to one physical cell, and a logical cell composed of multiple physical cells corresponds to one BBU, and all physical cells in one logical cell perform downlink joint transmission and uplink joint reception, thereby implementing a networking mode of the merged cell.
  • the physical cell n can be regarded as a first partial coverage area and a second partial coverage area that are symmetric about the pole n.
  • the first partial coverage area of the physical cell n overlaps with the partial coverage area of one physical cell
  • the second partial coverage area of the physical cell n overlaps with the partial coverage area of another physical cell.
  • the physical cell 1 overlaps with the physical cell 0 on the right side of the pole 0 in the left portion of the pole 1 and the physical cell 1 is in the right portion of the pole 1 and the physical community. 2 overlaps on the left side of the pole 2.
  • the train travels from right to left into the overlapping area of physical cell 0 and physical cell 1.
  • the moving direction of the terminal A 1 may be described as being away from the RRU 1 and close to the RRU 0 , or the terminal A 1 moving from the RRU 1 to the RRU 0 .
  • the terminal A1 can receive the downlink signals from the RRU 0 and the RRU 1 at the same time.
  • Figure 4 is different from Figure 3 in that the number of RRUs on each pole is different, that is, two RRUs are placed on each pole in Figure 4, and one RRU is placed on each pole in Figure 3.
  • the physical cell area covered by each RRU is different. For example, RRU 0 (1) and RRU 0 (2) in FIG. 4 each cover half of the physical cell 0 covered by RRU 0 shown in FIG. 3.
  • Figure 5 is compared with Figure 3, the difference is that the poles in Figure 5 are staggered on both sides of the track line, that is, the two adjacent RRUs are on both sides of the moving line of the terminal A1; the pole arrangement in Figure 3 On the same side of the track line, that is, two adjacent RRUs are on the same side of the moving line of the terminal A1.
  • two RRUs may also be disposed on each pole, and each RRU covers half of the physical cell 0 covered by the RRU 0 as shown in FIG.
  • the terminal A 1 on the train is in the overlapping area of the physical cell 0 corresponding to the RRU 0 and the physical cell 1 corresponding to the RRU 1 .
  • other terminals A 2 to A n exist on the train, that is, There are a total of n terminals. If different terminals are used to represent different terminals, the value of i ranges from 1 to n, and the i-th terminal can be represented as A i . That is, the RRU 0 and the RRU 1 can receive the uplink signals sent by the n terminals, such as a demodulation reference signal (DMRS), so the BBU can perform the present invention according to all or part of the foregoing uplink signals.
  • DMRS demodulation reference signal
  • an embodiment of the present invention provides a communication device 60, which may be a base station.
  • the communication device 60 includes: a BBU 601 and two RRUs, RRU 0 (2) and RRU 1 (1), respectively, wherein the BBU 601 is used to control a first logical cell, where the first logical cell includes RRU 0 (2)
  • the covered physical cell and the physical cell covered by the RRU 1 (1); the physical cell covered by the RRU 0 (2) and the physical cell covered by the RRU 1 (1) partially overlap in the first region.
  • both RRU 0 (2) and RRU 1 (1) can be used to transmit the downlink signal with the frequency f 0 , and if the frequency f 0 changes, the RRU 0 (2) and the RRU 1 (1) can also be used to transmit the downlink signal with the changed frequency respectively.
  • the RRU 0 (2) and the RRU 1 (1) are configured to: send the first downlink signal by using the frequency f 0 respectively, and then send the second downlink signal by using the first frequency and the second frequency, respectively; a difference frequency f 0 and f d_dl_0 first correction amount of the second frequency is f 0 and the second correcting quantity fd _dl_1 sum.
  • f 0 is the center frequency of RRU 0 (2) and RRU 1 (1), and at least one of f d_dl_0 and f d_dl_1 is not 0.
  • f d_dl_0 and f d_dl_1 satisfy the following conditions (1) to (3):
  • condition (3) may include various cases, as shown in Table 1.
  • the RRU 0 (2) and the RRU 1 (1) are used to: send the first downlink signal by using the frequency f 0 , and then send the second downlink signal by using the first frequency and the second frequency respectively;
  • the first frequency is the sum of f 0 and the first correction amount f d — dl — 0
  • the second frequency is the sum of f 0 and the second correction amount fd — dl_1 .
  • f 0 is the center frequency of RRU 0 (2) and RRU 1 (1)
  • at least one of f d_dl_0 and f d_dl_1 is not 0.
  • f d_dl_0 and f d_dl_1 satisfy the following conditions (4) to (6):
  • f d_dl and f d_dl_1 are both non-positive, and f d_dl_0 is non-negative; or both f d_dl and f d_dl_1 are non-negative, and f d_dl_0 is non-positive.
  • f d_dl in the embodiment of the present invention is generally not 0. Therefore, Table 1 and Table 2 above are all exemplified by the case where f d_dl is a positive number and a negative number.
  • the downlink signals sent by the RRU 0 (2) and the RRU 1 (1) after adjusting the frequency are gradually added to the overlapping coverage areas of the RRU 0 (2) and the RRU 1 (1).
  • a terminal close to the RRU 0 (2) and gradually away from the RRU 1 (1) the frequency offset value when the downlink signal arrives at the terminal has a reduced impact on the demodulation performance of the terminal, that is, the demodulation downlink signal of the terminal is improved. Performance.
  • the frequency offset value of the downlink signal may reach the same when the terminal signal arrives at the terminal, and at this time, the terminal demodulates. The performance guarantee of the downlink signal is obvious.
  • the communication device 60 is not limited to including only two RRUs. As shown in FIG. 6, the communication device 60 may further include RRU 0 (1), RRU 1 (2), RRU 2 (1), RRU 2 (2), etc., and the physical cells covered by these RRUs may be as shown in FIG. Show.
  • the communication device 60 will be described in detail below.
  • the RRU 0 (2) and the RRU 1 (1) may also determine the parameter f d_dl according to the change of the frequency f 0 before transmitting the downlink signal with the changed frequency.
  • the communication device 60 determines f d_dl using the uplink signals transmitted by the n terminals, wherein the n terminals are in the first region, and the moving direction is the RRU 1 (1) to the RRU 0 (2)
  • the i-th terminal uses the terminal A i to indicate that i is any value between 1 and n, and the RRU 0 (2) and the RRU 1 (1) respectively receive the uplink signals transmitted from the n terminals, and the BBU 601 is based on
  • the uplink signal determines a process variable f d (i) for the terminal A i and determines f d_dl according to the following formula (6.1).
  • f d_dl when the BBU 601 determines f d_dl by using the formula (6.1), it is necessary to have available f d (i) and a(i).
  • f d (i) may be referred to as a Doppler frequency offset estimation value or a pre-correction amount of the terminal A i
  • a(i) may be referred to as a weight.
  • the following example illustrates how the BBU 601 determines f d (i) and a(i) before determining f d_dl .
  • ⁇ f 0 (i) represents the frequency offset value of the uplink signal received by the RRU 0 (2) from the terminal A i
  • ⁇ f 1 (i) represents the frequency offset value of the uplink signal received by the RRU 1 (1) from the terminal A i .
  • the variable R is greater than zero.
  • the BBU 601 determines the value of R according to the system of the communication system in which it operates (that is, the communication system in which the communication device 60 is located). For example, if the BBU 601 is operating in a TDD system, the BBU 601 can determine R as one. As another example, if the BBU 601 is operating in an FDD system, the BBU 601 can determine R as the ratio of the downlink carrier frequency to the uplink carrier frequency in the FDD system.
  • the estimated value may be regarded as Doppler shift value of the terminal a i a i of the terminal for the process variable f d (i), referred to as multi- Pule frequency offset estimate.
  • RSRP_i RSRP 0 (i)+RSRP 1 (i);
  • RSRP_sum ⁇ RSRP_i.
  • RSRP 0 (i) represents the reference signal received power of the uplink signal received by the RRU 0 (2) from the terminal A i (RSRP, RSRP 1 (i) indicates that the RRU 1 (1) is from the terminal A i RSRP of the received uplink signal.
  • the above RSRP unit can be milliwatts.
  • the BBU 601 has various methods for determining f d (i) and a (i), and is not limited to the above formula.
  • the BBU 601 simulates the frequency at which the RRU 0 (2) and RRU 1 (1) transmit downlink signals, respectively, with all possible frequency adjustment values Yi as parameters, if RRU 0 (2) and RRU 1 (1) respectively
  • the downlink signal transmitted by the frequency adjusted by Y i has the same frequency offset value X when the i-th terminal (A i ) is reached (for example, the frequency offset value X is 0), then Yi may be referred to as the terminal.
  • the pre-correction amount of A i that is, is suitable for adjusting f d (i) of the downlink signal according to the above formula (6.1).
  • the pre-correction amount can be interpreted as: before the frequency adjustment is performed by using Y i , the simulation is performed for the possible adjustment process, thereby selecting the appropriate process variable.
  • the simulation here can be implemented by actions such as simulation and/or mathematical calculation of the communication process.
  • the communication device 60 determines f d_dl_0 and f d_dl_1 with f d_dl as a parameter, and then adjusts the frequency f 0 according to f d_dl_0 and f d_dl_1 , which may be referred to as frequency adjustment with f d_dl as a parameter.
  • the frequency adjustment made by the communication device 60 with the parameter f d_dl is the adjustment of the downlink signal that is actually applied to the plurality of terminals, and the frequency adjustment made by using f d (i) as the parameter is virtually applied to the transmission. Adjustment of the downlink signal of a single terminal.
  • the adjustment of the frequency in the embodiment of the present invention includes correcting the amount corresponding to the frequency offset on the basis of the original frequency. Therefore, the actual adjustment value in this embodiment may also be referred to as a correction amount, and a virtual adjustment value (ie, The process variable f d (i)) can also be referred to as a pre-correction amount.
  • the first region distance RRU 0 (2) and RRU 1 (1) are both d, that is, when the terminal moves in a region where both the distance RRU 0 (2) and the RRU 1 (1) are d,
  • the embodiment of the invention has obvious guarantee effect on the performance of the terminal demodulating the downlink signal.
  • the frequency offset values of the terminals in the first area may be the same. Therefore, the downlink signals sent by the RRU 0 (2) and the RRU 1 (1) using the adjusted frequency are within the first area.
  • the frequency offset value at each terminal is improved. That is to say, the terminal in the first area is more obviously benefiting from the method of transmitting the downlink signal by the RRU using the adjusted frequency in the embodiment of the present invention, compared to the terminal in the first area. Therefore, for the terminal in the first area, the BBU 601 performs more efficiently and achieves better results when performing the method provided by the embodiment of the present invention.
  • the BBU 601 may also determine that the n terminals are in the first area before determining f d_dl_0 and f d_dl_1 (even before determining the f d_dl ), thereby facilitating the BBU 601 decision. Whether RRU 0 (2) and RRU 1 (1) are used to transmit the downlink signal with the adjusted frequency. If the n terminals are not in the first area, the BBU 601 may decide that the RRU 0 (2) and the RRU 1 (1) continue to transmit the downlink signal by using the frequency f 0. In this case, the BBU 601 does not need to determine the f d_dl_0. And f d_dl_1 (not even determining f d_dl ).
  • Embodiments of the present invention do not limit which parameters the BBU 601 determines based on which parameters are within the first region.
  • the BBU 601 determines the specific area that the terminal enters by measuring the uplink signals sent by the n terminals.
  • the BBU 601 can be configured to: when the first condition and the second condition are satisfied, determine that the n terminals are in the first area.
  • the first condition includes: the pre-correction amount of each of the n terminals is positive or negative.
  • the second condition includes: an absolute value of a difference of pre-correction amounts of each of the n terminals is less than or equal to
  • q% represents the tolerance for the difference between the frequency offset values of different terminals, and the value range of q is [0, 100]. It can be understood that the difference between the frequency offset values of different terminals is less than or equal to q%, and the frequency offset value is considered to be the same. That is, the difference between the frequency offset values of different terminals is within the difference tolerance (q%), and the difference can be ignored.
  • the value range of D min is [L 0 , L 1 ], where L 0 represents the vertical distance of the RRU 0 (2) from the mobile line of the terminal A i , and L 1 represents the RRU 1 (1) and the terminal.
  • both q and D min described above may be preset values.
  • the experience value is configured in the BBU 601.
  • the above q and D min may also be specific values determined by the BBU 601 according to other calculation processes.
  • the BBU 601 is further configured to: determine the f d_dl according to the period T. For example, after determining that the n terminals are in the first area, the BBU 601 determines the f d_dl according to the period T.
  • the value range of T is [m*t, D s /v]; t represents a period during which the terminal A i reports the measurement amount, and the measurement quantity is that the terminal A i is from the RRU 0 (2) or the RRU 1 (1)
  • the BBU 601 may determine the f d_dl multiple times according to the period T, thereby implementing multiple adjustments of the RRU 0 (2) and the RRU 1 (1) to send downlink signals. Frequency of. Specifically, the f d_dl determined by the BBU 601 may be different in each period T.
  • the BBU 601 determines f d_dl_0 and f d_dl_1 according to Z 1 and makes RRU 0 (2) RRU 1 (1) adjusts the frequency of transmitting the downlink signal on the basis of f 0 , and then, in T2 , the BBU 601 determines a new f d_dl_0 and a new f d_dl_1 according to Z 2 , and makes RRU 0 (2) and RRU 1 ( 1) Re-adjust the frequency of transmitting the downlink signal on the basis of f 0 , thereby enhancing the effect of ensuring the demodulation performance of the terminal.
  • BBU 601 when determining the BBU 601 may be f d_dl f d (i) as a parameter, and f d_dl_0 and can also be determined after determining the f d_dl_1 f d_dl according to the f d_dl, therefore, be regarded as BBU 601 determines that the periods of f d (i), f d_dl , f d_dl_0 , and f d_dl_1 are the same.
  • the frequency offset values of the downlink signals transmitted by the RRU 0 (2) and the RRU 1 (1) adjusted by using f d (i) respectively reach the terminal A i are X 0 .
  • X 1 when applying the embodiment of the present invention, the frequency offset values of the downlink signals transmitted by the RRU 0 (2) and the RRU 1 (1) after adjusting by f d (i) respectively reach the terminal A i are respectively X 0 ' and X 1 ', the difference between X 0 ' and X 1 ' must be smaller than the difference between X 0 and X 1 , that is, the embodiment of the present invention can reduce the frequency offset value of the downlink signal to the terminal solution. Adjust the adverse effects of performance.
  • the downlink signal transmitted has the same frequency offset value X when reaching the terminal A i .
  • X is 0, when RRU 0 (2) and RRU 1 (1) transmit the downlink signal with the adjusted frequency, the downlink signal received by the terminal Ai can be regarded as having no frequency offset, and the terminal A i does not need Adjusting the crystal oscillator can also maintain the performance of the demodulated downlink signal.
  • the RRU 0 (2) and the RRU 1 (1) adjusted by using f d (i) respectively have the same frequency offset value X when reaching the terminal A i , and X is not 0, the RRU 0 (2) and RRU 1 (1)
  • the downlink signal received by the terminal A i may have a frequency offset, and the terminal A i may determine the received downlink signal according to the prior art.
  • FIG. 7 another embodiment of the present invention provides a communication method.
  • the following describes the scenario that can be included in the communication method by taking the scenario shown in FIG. 3 as an example.
  • the communication method is also applicable to the scenarios of Figures 4 and 5, and may be performed by the communication device 60 (e.g., base station) described above, i.e., the communication method and the details provided by the above embodiments may be cross-referenced.
  • the BBU 601 can be used to perform the actions of the BBU in the following steps, and RRU 0 (2) and RRU 1 (1) are respectively used to perform the actions of RRU 0 and RRU 1 in the following steps.
  • the BBU determines a frequency offset value of the uplink signal received by the RRU 0 and the RRU 1 from each terminal.
  • the BBU is used to control the first logical cell, where the first logical cell includes a physical cell covered by the RRU 0 and a physical cell covered by the RRU 1 ; the physical cell covered by the RRU 0 and the physical cell covered by the RRU 1 are in the first area.
  • each of the above terminals refers to a plurality of terminals moving from the RRU 1 to the RRU 0 in the overlapping area.
  • the RRU 0 and the RRU 1 respectively receive an uplink signal from the ith terminal (A i ), and the BBU may perform measurement on the received uplink signal, thereby determining an uplink signal received by the RRU 0 from the terminal A i .
  • the frequency offset value ⁇ f 0 (i) and the frequency offset value ⁇ f 1 (i) of the uplink signal received by the RRU 1 from the terminal A i are provided.
  • the BBU determines a pre-correction amount (or a Doppler frequency offset estimation value) for each terminal.
  • RRU 0 and RRU 1 respectively adjust the frequency of the downlink signal sent by the first variable according to the first variable, there is a certain value Y i of the first variable, so that RRU 0 and RRU 1 respectively use the frequency after the adjustment to send the downlink.
  • the signal has the same frequency offset value when it arrives at the terminal A i , and this value Y i of the first variable is the pre-correction amount for the terminal A i and can be represented by f d (i).
  • the BBU determines the pre-correction amount f d (i) of the terminal A i by using the frequency offset value of the uplink signal received by the RRU 0 and the RRU 1 from the terminal A i as a parameter. For example, the BBU determines the value of the variable R according to the type of system in which the BBU is located, and then determines f d (i) using the above formula (6.2).
  • RRU frequency 0 from F 0 to adjust the difference f 0 is f d (i) of, for frequency RRU 1 is adjusted by f 1 is f f d (i) the sum of 1 and, then, RRU 0
  • the downlink signal transmitted by the RRU 1 after adjusting the frequency is the same as the frequency offset value when reaching the terminal A i .
  • f 0 and f 1 are the center frequencies at which RRU 0 and RRU 1 operate, respectively. It can be understood that f 0 is the same as f 1 .
  • the uplink signal arrives at the terminal A i .
  • the frequency offset value is 0.
  • the above formula (6.2) is an example of a method for the BBU to determine the amount of pre-correction for each terminal, but the present invention is not limited thereto, and the BBU may adopt other methods, such as the modification of the above formula (6.2). Determining which value of the first variable is such that the downlink signals transmitted by the RRU 0 and the RRU 1 respectively after the adjusted frequency have the same frequency offset value (not limited to 0) when reaching the terminal A i , thereby This value of the first variable is taken as the amount of pre-correction for the terminal A i .
  • BBU determines the distance L 0 between each terminal and each terminal and the distance between the RRU 0 1 RRU L 1 if greater than d. If yes, execute S740.
  • This step is an optional step. That is, the BBU may also perform step S740 after step S720 without performing step S730.
  • q% and D min are pre-configured in the BBU.
  • the tolerance for the difference between the frequency offset values of different terminals is q%
  • the straight line formed by RRU 0 (2) and RRU 1 (1) is parallel to the moving line of the terminal A i
  • the distance between the two lines is D Min .
  • d can be expressed by the above formula (6.4).
  • the timing of the preset q is not limited, as long as the base station (such as the above BBU) has a valid q when executing S730. It can be understood that the smaller the value of q is, the larger d is. That is to say, the smaller the tolerance for the difference between the frequency offset values, the smaller the probability that the BBU performs S740, but the better the effect achieved by performing the method provided by the embodiment, that is, ensuring that more terminals are better. Demodulation of downlink signal performance.
  • the distance between two adjacent RRUs is relatively large, for example, 1 km. Therefore, the vertical height of the RRU on the pole can be ignored, that is, the RRU and the pole where the RRU is located are regarded as At the same point, and the distance L 0 between the terminal and the RRU 0 can be regarded as the distance between the terminal and the perpendicular line of the RRU 0 and the moving direction of the terminal.
  • the distance between RRU 0 and RRU 1 is D s
  • the distance between the line formed by RRU 0 and RRU 1 and the line moved by the terminal is D min .
  • the frequency offset values of the terminals in the region of D s -2*d can be regarded as the same. Therefore, the RRU 0 and the RRU 1 can adjust the transmission downlink signal by using the parameters with universality. The frequency so that the downlink signals transmitted by different RRUs (ie, RRU 0 and RRU 1 ) have the same frequency offset value when they arrive at the same terminal.
  • the BBU may not know L 0 and L 1 , and may not know d, the BBU may determine each according to whether the pre-correction amount of each terminal satisfies the condition (1) and the condition (2). a distance L 0 between the terminal and the terminals and the distance between the RRU 0 i 1 RRU L 1 if the average is greater than d.
  • Condition (1) The pre-correction amount of each terminal is positive or negative.
  • Condition (2) the absolute value of the difference between the pre-correction amounts of each two terminals is less than or equal to
  • the above conditions (1) and (2) respectively comprise two options, when any of each BBU determining an option condition is satisfied, the equivalent of: determining a distance L 0 between each terminal and the RRU 0 a i and the distance between terminal 1 RRU L 1 is greater than d.
  • the BBU may determine whether the foregoing condition (1) and condition (2) are satisfied by using a plurality of calculation processes with the pre-correction amount of each terminal as a parameter.
  • condition (2) as an example: the BBU can calculate the absolute value of the difference between the pre-correction amounts of each two terminals, and compare it with
  • the BBU determines the first correction amount fd_dl_0 and the second correction amount fd_dl_1 according to the pre-correction amount of each terminal.
  • the BBU may be first pre-determined correction amount f d_dl according to each terminal, and then determine f d_dl_0 f d_dl_1 The f d_dl.
  • a(i) is a weight, and different values of a(i) may result in different values of f d_dl .
  • f d_dl is the same as the pre- distortion amount of terminal Ai.
  • Equation (7.2) that is, a(i) constitutes an equivalence sequence, and f d_dl is a linear average of the pre-correction amounts of n terminals.
  • the parameters RSRP 0 (i) and RSRP 1 (i) may be determined by the BBU before executing S740.
  • S710 further includes: the BBU determines an RSRP of the uplink signal received by the RRU 0 and the RRU 1 from each terminal.
  • the BBU and f d_dl_0 f d_dl_1 may be selected to satisfy the above conditions (1) to (3) or alternatively any one f d_dl_0 conditions and determined according to f d_dl_1 f d_dl may be selected to satisfy the above condition (4) Any of f d_dl_0 and f d_dl_1 to (6) or its alternative conditions.
  • RRU 0, and RRU 1 respectively transmit downlink signals according to frequencies adjusted according to f d_dl_0 and f d_dl_1 .
  • the frequency at which the RRU 0 transmits the downlink signal may be: f 0 -f d_dl_0
  • the frequency at which the RRU 1 transmits the downlink signal is :f 1 +f d_dl_1 .
  • the frequency at which the RRU 0 transmits the downlink signal may be: f 0 +f d_dl_0 , and the frequency at which the RRU 1 transmits the downlink signal. Is: f 1 +f d_dl_1 .
  • some processes of the BBU or the RRU in this embodiment may be such that the frequencies at which the RRU 0 and the RRU 1 transmit the downlink signals are respectively adjusted according to f d_dl_0 and f d_dl_1 .
  • the following examples are given.
  • This method of maintaining the phase difference between two adjacent samples enables the frequency at which the RRU 0 transmits the downlink signal according to f d_dl_0 .
  • the BBU uses the coefficient related to f d_dl_1 when convolving the downlink signal in the frequency domain, and can also adjust the frequency of transmitting the downlink signal by the RRU 1 according to f d_dl_1 .
  • RRU 0 reduces f d_dl_0 based on frequency f 0
  • RRU 1 increases f d_dl_1 based on frequency f 1
  • RRU 0 and RRU 1 can also adjust the frequency of transmitting downlink signals by RRU 0 and RRU 1 according to f d_dl_0 and f d_dl_1 , respectively.
  • each terminal receives the downlink signal sent by RRU 0 and RRU 1 in S750.
  • the terminal A i can adjust to the crystal oscillator by a certain degree. Avoid the degradation of terminal demodulation performance.
  • the frequency offset value of the downlink signal sent by the RRU 0 and the RRU 1 respectively after the adjustment of the terminal A i is 0, it can be regarded as the downlink of the RRU 0 and the RRU 1 received by the terminal A i .
  • the terminal A i does not need to adjust its own crystal oscillator, and can maintain the good performance of demodulating the downlink signal. If the frequency offset values of the downlink signals sent by the RRU 0 and the RRU 1 respectively after the adjusted frequency are the same when the terminal A i is reached, but not 0, the downlink signals of the RRU 0 and the RRU 1 received by the terminal A i may be There is a frequency offset, so the terminal A i can determine the frequency offset value of the received downlink signal according to the prior art, and adjust its own crystal oscillator accordingly, thereby maintaining good performance of demodulating the downlink signal.
  • a scenario in which the n terminals are in the overlapping coverage area of the RRU 0 and the RRU 1 controlled by the BBU is taken as an example.
  • the terminal moves along the track's line and leaves the overlapping coverage areas of RRU 0 and RRU 1 at a certain time and enters the overlapping coverage areas of other RRUs controlled by the BBU. Therefore, when the BBU in the base station learns that the terminal enters the overlapping coverage area of some RRUs, the method provided in this embodiment may be performed again.
  • the BBU can determine the specific area that the terminal enters by measuring the uplink signal sent by the terminal, and details are not described herein again.
  • the method provided in the foregoing embodiment may also be periodically performed by a base station.
  • the smaller the period T the more frequently the base station performs the above method, that is, the smaller value T makes it possible for the base station to determine the accurate frequency offset value in a more timely manner, thereby better guaranteeing fast-moving terminal demodulation.
  • Downlink signal performance the larger the period, the larger the time interval when the base station performs the above method, that is, the larger value T makes the base station satisfy the performance of the demodulated downlink signal of the terminal moving at the general speed, and is also beneficial for reducing the base station.
  • Internal processing complexity reduces the power consumption of the base station.
  • the period T used by the base station to perform the foregoing method is pre-configured, or is calculated immediately when the foregoing manner needs to be performed.
  • the base station may use different calculation methods to determine different periods, and in the case where the application scenario tends to be stable, the experience value of a certain T is regarded as a pre- The configured T, that is, the base station continues to use the T, does not perform the calculation of T for a certain period of time.
  • the pre-configured T may also be stored in a certain storage area of the base station before the base station is shipped or powered on.
  • the base station may start performing the foregoing method when the power is turned on, or may start to perform the foregoing method when the RRU 0 and the RRU 1 respectively receive the uplink signal from the terminal A i .
  • T may be equal to t or greater than t. That is, the T pre-configured by the base station is any value greater than or equal to t, or the base station calculates the value of T by using t as a parameter, so that T satisfies greater than or equal to t.
  • period T used by the base station to periodically perform the above method can be applied to different steps, for example, the base station performs S720 and/or S740 according to T.
  • Another embodiment of the present invention also provides a communication system including the communication device 60 provided by the above embodiment, and may further include a plurality of terminals in communication with the communication device 60.
  • the communication method, device, and system provided in the foregoing embodiments are applicable to a communication system in a networking manner using a combined cell, which is advantageous for improving performance of a mobile terminal to demodulate a downlink signal.
  • the functions involved in the communication method, the communication device, and the system provided by the embodiments of the present invention can be stored in a computer readable if they are implemented in the form of software functional units and sold or used as independent products.
  • the storage medium may be embodied in the form of a software product, which is stored in a storage medium, including
  • the instructions are used to cause a computer device (which may be a personal computer, server, or network device, etc.) to perform all or part of the steps of the methods described in various embodiments of the present invention.
  • the foregoing storage medium includes: a U disk, a mobile hard disk, a read-only memory (ROM), a random access memory (RAM), a magnetic disk, or an optical disk, and the like. .

Abstract

本发明实施例提供了一种通信方法、设备和系统。其中，该通信设备包括：基带单元BBU和两个射频拉远单元RRU0和RRU1，其中，所述BBU用于控制第一逻辑小区，所述第一逻辑小区包括RRU0覆盖的物理小区和RRU1覆盖的物理小区；RRU0覆盖的物理小区和RRU1覆盖的物理小区在第一区域部分重叠；所述RRU0和RRU1用于：分别采用频率f0发送第一下行信号，然后，分别采用第一频率和第二频率发送第二下行信号；其中，所述第一频率为f0与第一纠偏量fd_dl_0之差，所述第二频率为f0与第二纠偏量fd_dl_1之和；其中，所述fd_dl_0和所述fd_dl_1中的至少一个不为0。上述通信设备可应用于采用合并小区的组网方式的通信系统中，有利于提高移动的终端解调下行信号的性能。

Description

通信方法、设备及系统
本申请要求于2014年12月27日提交中国专利局、申请号为201410841019.9、发明名称为“通信方法、设备及系统”的中国专利申请的优先权，其全部内容通过引用结合在本申请中。
技术领域
本发明涉及通信领域，并且更具体地，涉及在采用合并小区实现组网的系统中调整频率偏移的通信方法、设备及系统。
发明背景
在终端与基站之间的通信过程中，如果该终端处于快速移动中，则该终端和该基站之间的通信会受到影响。
一方面，基站发射的下行信号会受到多普勒效应的影响，从而导致该信号在到达终端时存在一定的多普勒频率偏移(英文全称可以是frequency deviation)，该频率偏移的程度可以称为多普勒频率偏移值(中文简称可以是多普勒频偏值或频偏值，英文全称可以是frequency offset)，这种多普勒频率偏移会影响终端解调下行信号的性能。
现有技术中，终端可以估计基站的一个下行信号的频偏值，并主动调整自身晶振，以使自身的频率与存在频率偏移的下行信号的频率保持一致，从而避免终端解调下行信号的性能降低。
如图1所示，终端对基站的下行信号的频偏值进行估计的场景中，fd-max为该下行信号的最大频偏值，fc为该基站发射该下行信号的频率，θ为该终端的移动方向与该基站相对于终端的方向之间的夹角，V为该终端的移动速度，实线箭头表示该基站向该终端发射信号的方向，虚线箭头表示该终端的移动方向。则，该终端可以根据该下行信号的两个导频符号的信道估计值之间的相位差和这两个导频符号之间的时间间隔确定该下行信号的频偏值，并据此调整自身晶振。
另一方面，快速移动的终端可能频繁进行小区切换而导致系统性能下降。因此，存在快速移动的终端的通信系统，例如高速铁路沿线的通信系统，可以采用合并小区的组网方式，减少终端的切换次数。假设包括基站和终端的通信系统中，基站包括一个基带单元(Baseband Unit，BBU)与多个射频拉远单元(Remote Radio Unit，RRU)。每个RRU对应于一个物理小区，由多个物理小区构成的逻辑小区对应于一个BBU，在一个逻辑小区内的所有物理小区进行下行联合发送和上行联合接收，从而实现合并小区的组 网方式。
现有技术中，移动中的终端A1可能处于两个RRU的重叠覆盖区域内。如图2所示，终端A1对基站的下行信号的频偏值进行估计的场景中，RRU0和RRU1的下行信号与终端A1的移动方向的夹角分别为θ1和θ2，RRU0和RRU1分别发送的下行信号在到达终端A1时的实际频偏值的差异非常大。由于RRU0和RRU1采用下行联合发送的方式，即下行信号的内容相同，所以终端A1接收到的信号只能是RRU0和RRU1的下行信号混合后的信号。如果终端A1采用如图1场景的现有技术去估计下行信号的频偏值，则该估计的频偏值必然与两个实际频偏值的差异都非常大，从而降低了终端解调下行信号的性能。
可见，现有技术中，采用合并小区的组网方式的通信系统中，移动的终端解调下行信号的性能可能较低。
发明内容
本发明实施例提供了一种通信方法、设备及系统，可以解决现有的采用合并小区的组网方式的通信系统中，移动的终端解调下行信号的性能可能较低的问题。
本发明的第一方面提供一种通信设备，包括：基带单元BBU和两个射频拉远单元RRU0和RRU1，其中，所述BBU用于控制第一逻辑小区，所述第一逻辑小区包括RRU0覆盖的物理小区和RRU1覆盖的物理小区；RRU0覆盖的物理小区和RRU1覆盖的物理小区在第一区域重叠；其中，所述RRU0和RRU1用于：分别采用频率f0发送第一下行信号，然后，分别采用第一频率和第二频率发送第二下行信号；所述第一频率为f0与第一纠偏量fd_dl_0之差，所述第二频率为f0与第二纠偏量fd_dl_1之和；其中，所述fd_dl_0和所述fd_dl_1中的至少一个不为0。
本发明的另一方面提供一种通信系统，包括：上述通信设备。
本发明的第二方面提供一种通信方法，包括：基站分别采用频率f0发送第一下行信号，然后，分别采用第一频率和第二频率发送第二下行信号；其中，所述第一频率为f0与第一纠偏量fd_dl_0之差，所述第二频率为f0与第二纠偏量fd_dl_1之和；其中，所述fd_dl_0和所述fd_dl_1中的至少一个不为0；其中，所述基站包括：基带单元BBU，两个射频拉远单元RRU0和RRU1；所述BBU用于控制第一逻辑小区，所述第一逻辑小区包括RRU0覆盖的物理小区和RRU1覆盖的物理小区；RRU0覆盖的物理小区和RRU1覆盖的物理小区在第一区域重叠。
可选的，在上述通信设备、系统和方法中，fd_dl_0和fd_dl_1分别满足一定条件，以对 终端解调性能的保证更明显。上述条件可以包括：|fd_dl_0|<|2*fd_dl|；|fd_dl_1|<|2*fd_dl|；其中，参数fd_dl、所述fd_dl_0和所述fd_dl_1均为非正数，或者，所述fd_dl、所述fd_dl_0和所述fd_dl_1均为非负数。例如，所述fd_dl_0和所述fd_dl_1均与所述fd_dl相等，且不为0。
本发明的第三方面提供一种通信设备，包括：基带单元BBU，两个射频拉远单元RRU0和RRU1，其中，所述BBU用于控制第一逻辑小区，所述第一逻辑小区包括RRU0覆盖的物理小区和RRU1覆盖的物理小区；RRU0覆盖的物理小区和RRU1覆盖的物理小区在第一区域重叠；所述RRU0和RRU1用于接收从RRU1向RRU0移动的n个终端发送的上行信号，其中，所述n个终端处于所述第一区域内，第i个终端用终端Ai表示，i为1至n之间的任一值；所述BBU用于确定参数fd_dl；所述RRU0和RRU1还用于分别采用根据fd_dl进行调整后的频率发送下行信号；其中，用fd(i)表示根据所述上行信号确定的终端Ai的多普勒频偏估计值；
Figure PCTCN2015071975-appb-000001
Figure PCTCN2015071975-appb-000002
且0≤a(i)≤1。
本发明的第三方面的第一种实现方式中，所述BBU可以具体用于采用如下公式确定fd(i)：fd(i)＝R*(Δf0(i)-Δf1(i))/2；其中，Δf0(i)表示RRU0从终端Ai接收的上行信号的频偏值，Δf1(i)表示RRU1从终端Ai接收的上行信号的频偏值；R为大于0的变量。可选的，所述BBU工作于TDD系统时，R的取值为1；或者，所述BBU工作于FDD系统时，R为所述FDD系统中的下行载波频率与上行载波频率的比例。
结合本发明的第三方面及其第一种实现方式，在本发明的第三方面的第二种实施方式中，所述BBU还可以用于确定RRU0和RRU1接收的上行信号的RSRP，并按照如下公式确定a(i)；
RSRP_i＝RSRP0(i)+RSRP1(i)；
RSRP_sum＝∑RSRP_i；
a(i)＝RSRP_i/RSRP_sum；
其中，RSRP0(i)表示RRU0从终端Ai接收到的上行信号的参考信号接收功率RSRP，RSRP1(i)表示RRU1从终端Ai接收到的上行信号的RSRP。
结合本发明的第三方面及其上述各种实现方式，在本发明的第三方面的第三种实施方式中，所述第一区域距离RRU0和RRU1均为d，其中，
Figure PCTCN2015071975-appb-000003
q％表示针对不同终端的频偏值之间的差异的容忍度，q的取值范围为[0,100]，Dmin的取值范围为[L0,L1]，其中，L0表示RRU0与所述终端Ai的移动线路的垂直距离，L1表示RRU1与所述终端Ai的移动线路的垂直距离。
结合本发明的第三方面及其上述各种实现方式，在本发明的第三方面的第四种实施方式中，所述BBU还用于：在确定fd_dl之前，确定所述n个终端处于所述第一区域内。
结合本发明的第三方面及其上述各种实现方式，在本发明的第三方面的第五种实施方式中，所述BBU具体用于：在第一条件和第二条件被满足时，确定所述n个终端处于所述第一区域内；所述第一条件包括：所述n个终端中的每个终端的多普勒频偏估计值均为正数或均为负数；所述第二条件包括：所述n个终端中的每两个终端的多普勒频偏估计值之差的绝对值均小于或等于|q％*fd-max|，其中，fd-max为RRU0或RRU1的下行信号的最大频偏值。
结合本发明的第三方面的第四种和第五种的实现方式，在本发明的第三方面的第六种实施方式中，所述BBU还用于：如果所述n个终端处于所述第一区域，按照周期T确定所述fd_dl。可选的，所述BBU还用于：确定所述T，所述T的取值范围为[m*t,Ds/v]；其中，t表示终端Ai上报测量量的周期，其中，所述测量量为所述终端Ai针对来自RRU0的下行信号的RSRP的测量结果；m大于0；Ds表示RRU0与RRU1之间的距离；v表示终端Ai的移动速度。
结合本发明的第三方面及其上述各种实现方式，在本发明的第三方面的第七种实施方式中，所述RRU0和RRU1的中心频率为f0时，所述RRU0和RRU1用于分别采用根据fd_dl进行调整后的频率发送下行信号包括：所述RRU0用于采用第一频率发送下行信号，所述第一频率为f0与第一纠偏量fd_dl_0之差；所述RRU1用于采用第二频率发送下行信号，所述第二频率为f0与第二纠偏量fd_dl_1之和；其中，所述fd_dl_0和所述fd_dl_1中的至少一个不为0。
可选的，所述fd_dl_0和所述fd_dl_1分别满足如下条件：
|fd_dl_0|<|2*fd_dl|；|fd_dl_1|<|2*fd_dl|；其中，参数fd_dl、所述fd_dl_0和所述fd_dl_1均为非正数，或者，所述fd_dl、所述fd_dl_0和所述fd_dl_1均为非负数。例如，所述fd_dl_0和所述fd_dl_1均与所述fd_dl相等，且不为0。
上述方案提供的通信方法、设备和系统可应用于采用合并小区的组网方式的通信系 统中，有利于避免降低移动的终端解调下行信号的性能。
附图简要说明
图1是终端对来自基站的一个下行信号的频偏值进行估计的场景示意图；
图2是终端A1对来自两个RRU的下行信号的频偏值进行估计的场景示意图；
图3是采用合并小区的组网方式的高铁沿线通信系统示意图；
图4是采用合并小区的组网方式的另一种高铁沿线通信系统示意图；
图5是采用合并小区的组网方式的另一种高铁沿线通信系统示意图；
图6是本发明的一个实施例提供的通信设备的结构示意图；
图7是本发明的一个实施例提供的通信方法的流程示意图；
图8是本发明的一个实施例中终端与RRU0、RRU1的相对位置平面示意图。
实施本发明的方式
下面将结合本发明实施例中的附图，对本发明实施例中的技术方案进行详细描述，显然，所描述的实施例是本发明的一部分实施例，而不是全部实施例。基于本发明中的实施例，本领域普通技术人员在没有做出创造性劳动的前提下所获得的所有其他实施例，都应属于本发明保护的范围。
本发明的实施例适用于多种通信系统，例如，长期演进(英文全称和简称可以分别是Long Term Evolution，LTE)系统，以及其他存在下行公共导频的通信系统。此外，本发明的实施例在应用于某些场景时，保证终端的解调性能和通信系统性能的效果明显，这些场景包括但不限于：在采用合并小区的组网方式的通信系统中，终端移动(特别是快速移动)的场景。例如，如图3、图4、图5所示的场景。
如图3所示的存在移动的终端的场景，抱杆0至抱杆n为在高速铁路沿线的n个抱杆，每两个抱杆之间存在一定的间距，每两个抱杆形成的直线与列出所在的(轨道)线路为平行线，上述平行线之间的距离用Dmin表示。在每个抱杆上设置一个RRU。每个RRU对应于一个物理小区，由多个物理小区构成的逻辑小区对应于一个BBU，在一个逻辑小区内的所有物理小区进行下行联合发送和上行联合接收，从而实现合并小区的组网方式。假设抱杆的编号和该抱杆上的RRU的编号相同，即抱杆n上设置RRUn，该RRUn的覆盖区域为物理小区n。则，物理小区n可以视为以抱杆n为中心对称的第一部分覆盖区域和第二部分覆盖区域。其中，物理小区n的第一部分覆盖区域与一个物理小区的部分覆盖区域重叠，物理小区n的第二部分覆盖区域与另一个物理小区的部分覆 盖区域重叠。例如，以高速铁路沿线的方向来看，物理小区1在抱杆1的左侧部分与物理小区0在抱杆0的右侧部分重叠，物理小区1在抱杆1的右侧部分与物理小区2在抱杆2的左侧部分重叠。列车从右向左行驶至物理小区0和物理小区1的重叠区域内。则，终端A1的移动方向可以描述为：远离RRU1且靠近RRU0，或者，终端A1从RRU1向RRU0移动。其中，终端A1能够同时接收来自RRU0和RRU1的下行信号。
图4与图3相比，差异在于：每个抱杆上的RRU数量不同，即图4中的每个抱杆上设置2个RRU，而图3中的每个抱杆上设置1个RRU；每个RRU覆盖的物理小区面积不同，例如，图4中RRU0(1)和RRU0(2)各覆盖图3所示的RRU0所覆盖的物理小区0的一半。
图5与图3相比，差别在于：图5中的抱杆交错部署于轨道线路的两侧，即相邻的两个RRU在终端A1的移动线路的两侧；图3中的抱杆部署于轨道线路的同一侧，即相邻的两个RRU在终端A1的移动线路的同一侧。在图5中，每个抱杆上也可以设置2个RRU，每个RRU覆盖如图3所示的RRU0所覆盖的物理小区0的一半。
可以理解的，上述图3、图4和图5所示的场景中，列车上可能存在多个终端。
在本发明实施例中，除了假设列车上的终端A1在RRU0对应的物理小区0和RRU1对应的物理小区1的重叠区域内，还假设列车上存在其他终端A2至An，即：共有n个终端，如果用不同的i的取值表示不同的终端，则i的取值范围为1至n，其中，第i个终端可以表示为Ai。也就是说，RRU0和RRU1可以接收到上述n个终端发送的上行信号，例如解调参考信号(demodulation reference signal，DMRS)，因此BBU可以根据上述上行信号中的全部或者部分执行本发明的实施例。
如图6所示，本发明的一个实施例提供一种通信设备60，该通信设备60可以为基站。该通信设备60包括：BBU 601和两个RRU，分别为RRU0(2)和RRU1(1)，其中，该BBU 601用于控制第一逻辑小区，该第一逻辑小区包括RRU0(2)覆盖的物理小区和RRU1(1)覆盖的物理小区；RRU0(2)覆盖的物理小区和RRU1(1)覆盖的物理小区在第一区域部分重叠。
可选的，在该通信设备60中，RRU0(2)和RRU1(1)均可以用于采用频率f0发送下行信号，且如果该频率f0发生变化，RRU0(2)和RRU1(1)还可以用于分别采用变化后的频率发送下行信号。
例如，RRU0(2)和RRU1(1)用于：分别采用频率f0发送第一下行信号，然后，分别采用第一频率和第二频率发送第二下行信号；其中，所述第一频率为f0与第一纠偏量 fd_dl_0之差，所述第二频率为f0与第二纠偏量fd_dl_1之和。其中，f0为RRU0(2)和RRU1(1)的中心频率，fd_dl_0和fd_dl_1中的至少一个不为0。
可选的，fd_dl_0和fd_dl_1满足如下条件(1)至(3)：
(1)fd_dl_0和fd_dl的关系，即|fd_dl_0|<2*|fd_dl|；
(2)fd_dl_1和fd_dl的关系，即|fd_dl_1|<2*|fd_dl|；
(3)参数fd_dl、fd_dl_0和fd_dl_1均为非正数或者均为非负数。
需要说明的是，条件(3)可以包括多种情况，如表1所示。例如，一种满足上述条件(1)至(3)的情况为：fd_dl_0＝fd_dl_1＝fd_dl≠0。
表1
fd_dl fd_dl_0 fd_dl_1
正数 正数 正数
正数 0 正数
正数 正数 0
负数 负数 负数
负数 0 负数
负数 负数 0
又如，RRU0(2)和RRU1(1)用于：分别采用频率f0发送第一下行信号，然后，分别采用第一频率和第二频率发送第二下行信号；其中，所述第一频率为f0与第一纠偏量fd_dl_0之和，所述第二频率为f0与第二纠偏量fd_dl_1之和。其中，f0为RRU0(2)和RRU1(1)的中心频率，fd_dl_0和fd_dl_1中的至少一个不为0。
可选的，fd_dl_0和fd_dl_1满足如下条件(4)至(6)：
(4)fd_dl_0和fd_dl的关系，即|fd_dl_0|<2*|fd_dl|；
(5)fd_dl_1和fd_dl的关系，即|fd_dl_1|<2*|fd_dl|；
(6)参数fd_dl和fd_dl_1均为非正数，且fd_dl_0为非负数；或者，fd_dl和fd_dl_1均为非负数，且fd_dl_0为非正数。
需要说明的是，条件(6)可以包括多种情况，如表2所示。例如，在一种满足上述条件(4)至(6)的情况为：fd_dl_0＝-fd_dl≠0，fd_dl_1＝fd_dl。
表2
fd_dl fd_dl_0 fd_dl_1
正数 负数 正数
正数 0 正数
正数 负数 0
负数 正数 负数
负数 0 负数
负数 正数 0
本发明实施例中的fd_dl通常不为0，因此，上述表1和表2均以fd_dl为正数和负数的情况进行举例说明。
需要说明的是，上述条件和举例还有多种其他变型，均可适用于本发明实施例，此处不再赘述。
本发明实施例提供的通信设备60中，假设RRU0(2)和RRU1(1)在调整频率之后发送的下行信号给在RRU0(2)和RRU1(1)的重叠覆盖区域内逐渐靠近RRU0(2)、且逐渐远离RRU1(1)的某终端，则上述下行信号到达该终端时的频偏值对终端解调性能的影响有所降低，即提高该终端解调下行信号的性能。特别的，在上述满足条件(1)至(3)和条件(4)至(6)的两个举例中，上述下行信号到达该终端时的频偏值可能相同，此时，该终端解调下行信号的性能的保障效果明显。
需要说明的是，该通信设备60并不限于仅包括两个RRU。如图6所示，该通信设备60还可以包括RRU0(1)、RRU1(2)、RRU2(1)、RRU2(2)等，这些RRU所覆盖的物理小区可以如图4所示。
以图4所示的场景为例，以下对该通信设备60做详细介绍。
可选的，如果频率f0发生变化，RRU0(2)和RRU1(1)还可以在采用变化后的频率发送下行信号之前，先确定频率f0发生变化所依据的参数fd_dl。例如，通信设备60使用n个终端发送的上行信号确定fd_dl，其中，该n个终端处于所述第一区域内，且移动方向为所述RRU1(1)向所述RRU0(2)，第i个终端用终端Ai表示，i为1至n之间的任一值，则RRU0(2)和RRU1(1)分别接收从这n个终端发送的上行信号，BBU 601根据所述上行信号确定针对终端Ai的过程变量fd(i)，并按照如下公式(6.1)确定fd_dl。
Figure PCTCN2015071975-appb-000004
    公式(6.1)
Figure PCTCN2015071975-appb-000005
且0≤a(i)≤1。
可以理解的，在本发明实施例中，BBU 601在采用公式(6.1)确定fd_dl时，需要存在可用的fd(i)和a(i)。其中，fd(i)可称为终端Ai的多普勒频偏估计值或预纠偏量，a(i)可称为权值。以下举例说明BBU 601在确定fd_dl之前，如何先确定fd(i)和a(i)。
如下公式(6.2)为BBU 601确定fd(i)的一个举例。
fd(i)＝R*(Δf0(i)-Δf1(i))/2    公式(6.2)
其中，Δf0(i)表示RRU0(2)从终端Ai接收的上行信号的频偏值，Δf1(i)表示RRU1(1)从终端Ai接收的上行信号的频偏值。
在上述公式(6.2)中，变量R大于0。可选的，BBU 601根据自身工作的通信系统(也即该通信设备60所处的通信系统)的制式确定R的取值。例如，如果BBU 601工作于TDD系统，则BBU 601可以将R确定为1。又如，如果BBU 601工作于FDD系统，则BBU 601可以将R确定为该FDD系统中的下行载波频率与上行载波频率的比例。
需要说明的是，如果根据上述公式(6.2)确定的fd(i)与fd-max之间的差异是可容忍的，其中，fd-max是RRU0(2)或RRU1(1)发送给终端Ai的下行信号的最大频偏值，则可以将针对终端Ai的过程变量fd(i)视为该终端Ai的多普勒频偏值的估计值，简称为多普勒频偏估计值。
如下公式(6.3)为BBU 601确定a(i)的一个举例。
a(i)＝RSRP_i/RSRP_sum；    公式(6.3)
RSRP_i＝RSRP0(i)+RSRP1(i)；
RSRP_sum＝∑RSRP_i。
其中，RSRP0(i)表示RRU0(2)从终端Ai接收到的上行信号的参考信号接收功率(reference signal received power，RSRP，RSRP1(i)表示RRU1(1)从终端Ai接收到的上行信号的RSRP。上述RSRP的单位可以为毫瓦。
需要说明的是，BBU 601确定fd(i)和a(i)的方法有多种，而不仅限于上述公式。
例如，BBU 601以所有可能的频率调整值Yi为参数，对分别调整RRU0(2)和RRU1(1)发送下行信号的频率进行模拟，如果RRU0(2)和RRU1(1)分别采用Yi进行调整之后的频率发送的下行信号在到达第i个终端(Ai)时具有相同的频偏值X(例如，频偏值X均 为0)，则Yi可称为针对该终端Ai的预纠偏量，也即适用于根据上述公式(6.1)调整下行信号的fd(i)。其中，预纠偏量可以解读为：在采用Yi对频率进行调整之前，针对可能的调整过程进行模拟，从而选择出的合适的过程变量。可选的，这里的模拟可以通过通信过程的仿真和/或数学计算等动作来实现。
可选的，通信设备60以fd_dl为参数确定fd_dl_0和fd_dl_1，然后根据fd_dl_0和fd_dl_1调整频率f0，该过程可称为以fd_dl为参数所作的频率调整。
可以理解的，通信设备60以fd_dl为参数所作的频率调整是真正作用于发送给多个终端的下行信号的调整，以fd(i)为参数所作的频率调整则是虚拟作用于发送给单个终端的下行信号的调整。由于本发明实施例中对频率的调整包括在原有频率基础上纠正与频率偏移相对应的量，因此，本实施例中的实际的调整值亦可称为纠偏量，虚拟的调整值(即过程变量fd(i))亦可称为预纠偏量。
需要说明的是，上述第一区域距离RRU0(2)和RRU1(1)均为d，也即终端在距离RRU0(2)和RRU1(1)均为d的区域内移动时，本发明实施例对于终端解调下行信号的性能的保障效果明显。具体的，该第一区域内的各终端的频偏值可视为相同，因此，RRU0(2)和RRU1(1)采用调整后的频率发送的下行信号在到达上述第一区域内的每个终端时的频偏值都有所改善。也就是说，相比于在上述第一区域之外的终端来说，上述第一区域内的终端更明显的受益于本发明实施例中由RRU采用调整后的频率发送下行信号的方法。因此，对于该第一区域内的终端来说，BBU 601执行本发明实施例提供的方法时的效率更高、达到的效果更好。
因此，可选的，BBU 601还可以在确定fd_dl_0和fd_dl_1之前(甚至是在确定所述fd_dl之前)，确定所述n个终端处于所述第一区域内，从而有利于BBU 601决定是否使得RRU0(2)和RRU1(1)采用调整后的频率发送下行信号。如果所述n个终端不在所述第一区域内，则BBU 601可以决定RRU0(2)和RRU1(1)继续采用频率f0发送下行信号，这种情况下，BBU 601无需确定fd_dl_0和fd_dl_1(甚至无需确定fd_dl)。
本发明的实施例并不限定BBU 601基于何种参数来确定所述n个终端处于上述第一区域内。例如，BBU 601通过测量n个终端发送的上行信号来确定终端进入的具体区域。又如，BBU 601可以用于：在第一条件和第二条件被满足时，确定所述n个终端处于所述第一区域内。其中，该第一条件包括：所述n个终端中的每个终端的预纠偏量均为正数或均为负数。该第二条件包括：所述n个终端中的每两个终端的预纠偏量之差的绝对值均小于或等于|q％*fd-max|，其中，fd-max为RRU0(2)或RRU1(1)的下行信号的最大频 偏值。
需要说明的是，上述d可以采用如下公式(6.4)表示。
Figure PCTCN2015071975-appb-000006
    公式(6.4)
其中，q％表示针对不同终端的频偏值之间的差异的容忍度，q的取值范围为[0,100]。可以理解的，不同终端的频偏值之差小于或等于q％的情况视为频偏值相同。也即，不同终端的频偏值之间的差异处于差异容忍度(q％)之内，则可以忽略该差异。
Dmin的取值范围为[L0,L1]，其中，L0表示RRU0(2)与所述终端Ai的移动线路的垂直距离，L1表示RRU1(1)与所述终端Ai的移动线路的垂直距离。如果RRU0(2)和RRU1(1)所形成的直线可视为与终端Ai的移动线路平行(或基本平行)，则Dmin＝L0＝L1。
需要说明的是，上述q和Dmin均可以为预设值。例如，将经验值配置在BBU 601中。上述q和Dmin也可以是BBU 601根据其他计算过程确定的具体取值。
可选的，BBU 601还用于：按照周期T确定所述fd_dl。例如，BBU 601在确定上述n个终端处于该第一区域之后，按照周期T确定所述fd_dl。其中，T的取值范围为[m*t,Ds/v]；t表示终端Ai上报测量量的周期，所述测量量为所述终端Ai针对来自RRU0(2)或RRU1(1)的下行信号的RSRP的测量结果；m大于0；Ds表示RRU0(2)与RRU1(1)之间的距离；v表示终端Ai的移动速度。本发明实施例中，如果上述n个终端处于该第一区域，BBU 601可以按照周期T多次确定所述fd_dl，从而实现多次调整RRU0(2)与RRU1(1)发送下行信号的频率。具体的，每个周期T内，BBU 601确定的所述fd_dl可能不同。假设相邻的两个周期T1和T2内，BBU 601确定的fd_dl分别为Z1和Z2，则在T1内，BBU601根据Z1确定fd_dl_0和fd_dl_1，并使RRU0(2)与RRU1(1)在f0的基础上调整发送下行信号的频率，然后，在T2内，BBU601根据Z2确定新的fd_dl_0和新的fd_dl_1，并使RRU0(2)与RRU1(1)在f0的基础上重新调整发送下行信号的频率，从而增强保障终端解调性能的效果。
可以理解的，BBU 601确定所述fd_dl时可以将fd(i)作为参数，且在确定所述fd_dl后还可以根据所述fd_dl确定fd_dl_0和fd_dl_1，因此，可视为BBU 601确定fd(i)、fd_dl、fd_dl_0和fd_dl_1的周期相同。
如果未应用本发明实施例时，RRU0(2)和RRU1(1)分别采用fd(i)进行调整之后的频率发送的下行信号在到达终端Ai时的频偏值分别为X0和X1；应用本发明实施例时，RRU0(2)和RRU1(1)分别采用fd(i)进行调整之后的频率发送的下行信号在到达终端Ai时的频偏值 分别为X0’和X1’，则X0’与X1’之间的差距必然小于X0和X1之间的差距，也即本发明实施例可以降低下行信号的频偏值带给终端解调性能的不良影响。
特别的，本发明实施例中，如果RRU0(2)和RRU1(1)分别采用fd(i)进行调整之后的频率发送的下行信号在到达终端Ai时具有相同的频偏值X，且X为0，则RRU0(2)和RRU1(1)采用调整后的频率发送下行信号时，终端Ai接收到的下行信号可视为不存在频率偏移，该终端Ai不需要调整自身晶振，也能够保持较好的解调下行信号的性能。如果RRU0(2)和RRU1(1)分别采用fd(i)进行调整之后的频率发送的下行信号在到达终端Ai时具有相同的频偏值X，且X不为0，则RRU0(2)和RRU1(1)采用调整后的频率发送下行信号时，终端Ai接收到的下行信号可能存在频率偏移，该终端Ai可以按照现有技术确定接收到的下行信号的频偏值，并据此调整自身晶振，从而保持较好的解调下行信号的性能。
如图7所示，本发明的另一个实施例提供一种通信方法。如下以图3所示的场景为例，介绍该通信方法可以包括的步骤。可以理解的，该通信方法也适用于如图4和图5的场景，且可以由上述通信设备60(例如基站)执行，即该通信方法和上述实施例提供的细节可相互参照。例如，BBU 601可以用于执行如下步骤中BBU的动作，RRU0(2)和RRU1(1)分别用于执行如下步骤中RRU0和RRU1的动作。
S710、BBU确定RRU0和RRU1从各终端接收到的上行信号的频偏值。其中，该BBU用于控制第一逻辑小区，所述第一逻辑小区包括RRU0覆盖的物理小区和RRU1覆盖的物理小区；RRU0覆盖的物理小区和RRU1覆盖的物理小区在第一区域部分重叠，上述各终端指在上述重叠的区域内从RRU1向RRU0移动的多个终端。
本实施例中，RRU0和RRU1分别接收来自第i个终端(Ai)的上行信号，BBU可以针对上述接收到的上行信号进行测量，从而确定RRU0从终端Ai接收的上行信号的频偏值Δf0(i)和RRU1从终端Ai接收的上行信号的频偏值Δf1(i)。
S720、BBU确定针对各终端的预纠偏量(或称为多普勒频偏估计值)。
可选的，假设RRU0和RRU1按照第一变量分别调整自身发送下行信号的频率，则存在第一变量的某一取值Yi使得RRU0和RRU1分别采用调整之后的频率发送的下行信号在到达终端Ai时具有相同的频偏值，则该第一变量的这一取值Yi为针对该终端Ai的预纠偏量，可以用fd(i)表示。
本实施例中，BBU以RRU0和RRU1从终端Ai接收到的上行信号的频偏值为参数，来确定终端Ai的预纠偏量fd(i)。例如，BBU根据BBU所在的系统类型确定变量R的取 值，然后采用上述公式(6.2)确定fd(i)。
本实施例中，假设RRU0的频率由f0调整为f0与fd(i)之差，RRU1的频率由f1调整为f1与fd(i)之和，则，RRU0和RRU1在调整频率之后发送的下行信号在到达终端Ai时的频偏值相同。其中，f0和f1分别为RRU0和RRU1工作时的中心频率。可以理解的，f0与f1相同。
如果终端Ai与RRU0之间的距离和终端Ai与RRU1之间的距离相等，即终端Ai位于RRU0和RRU1之间的中点，则上述上行信号在到达终端Ai时的频偏值均为0。
需要说明的是，采用上述公式(6.2)是BBU确定针对各终端的预纠偏量的一种方法举例，但本发明并不限于此，BBU可以采用其他方法，例如上述公式(6.2)的变型，来确定第一变量的哪个取值可以使得RRU0和RRU1分别采用调整之后的频率发送的下行信号在到达终端Ai时具有相同的频偏值(并不限于均为0)，从而将该第一变量的这个取值作为针对该终端Ai的预纠偏量。
S730、BBU判断每个终端与RRU0之间的距离L0和每个终端与RRU1之间的距离L1是否均大于d。如果是，则执行S740。
本步骤为可选步骤。即，BBU也可以在步骤S720后执行步骤S740，而无需执行步骤S730。
本实施例中，假设BBU中预配置了q％和Dmin。其中，针对不同终端的频偏值之间的差异的容忍度为q％，RRU0(2)和RRU1(1)所形成的直线与终端Ai的移动线路平行，且两线距离为Dmin。则，d可以用上述公式(6.4)来表示。
需要说明的是，本实施例不限定预设q的时机，只要保证基站(如上述BBU)在执行S730时存在有效的q即可。可以理解的，q的取值越小，d越大。也就是说，针对频偏值之间的差异的容忍度越小，BBU执行S740的概率越小，但执行本实施例提供的方法所达到的效果越好，即保证更多的终端具有更好的解调下行信号的性能。
在实际部署时，相邻的两个RRU之间的距离较大，例如为1千米，因此，可以忽略RRU在抱杆上的垂直高度，即：将RRU与该RRU所在的抱杆视为同一点，并且，终端与RRU0的距离L0可视为该终端到RRU0与该终端移动方向的垂线之间的距离。如图7所示，RRU0与RRU1之间的距离为Ds，RRU0和RRU1形成的直线与终端移动的线路之间的距离为Dmin。则，如图7所示，在Ds-2*d的区域内的各终端的频偏值可视为相同，因此，RRU0和RRU1可以采用具有普适性的参数来调整发送下行信号的频率，从而实现不同RRU(即RRU0和RRU1)发送的下行信号在到达同一个终端时具有相同 的频偏值。
在本实施例的一种变型中，BBU可能未获知L0和L1，还可能未获知d，则BBU可以根据各终端的预纠偏量是否满足条件(1)和条件(2)来确定每个终端与RRU0之间的距离L0和终端Ai与RRU1之间的距离L1是否均大于d。
条件(1)：每个终端的预纠偏量均为正数或均为负数。
条件(2)：每两个终端的预纠偏量之差的绝对值均小于或等于|q％*fd-max|，其中，fd-max为RRU0或RRU1的下行信号的最大频偏值。可以理解的，一般来说，RRU0和RRU1的下行信号的最大频偏值相同。
上述条件(1)和条件(2)分别包括两个可选项，BBU确定每个条件中的任一个可选项被满足时，就相当于是：确定每个终端与RRU0之间的距离L0和终端Ai与RRU1之间的距离L1均大于d。
可选的，BBU可以用多种以每个终端的预纠偏量为参数的计算过程来确定上述条件(1)和条件(2)是否被满足。以条件(2)为例：BBU可以计算每两个终端的预纠偏量之差的绝对值，并将其与|q％*fd-max|进行比较；BBU也可以先在各终端的预纠偏量中选择出最大值和最小值，然后计算该最大值与最小值之差的绝对值，并将其与|q％*fd-max|进行比较。可以理解的，在后一种计算过程中，如果该最大值与最小值之差的绝对值小于或等于|q％*fd-max|，则说明每两个终端的预纠偏量之差的绝对值均小于或等于|q％*fd-max|，也即条件(2)被满足。
S740、BBU根据各终端的预纠偏量确定第一纠偏量fd_dl_0和第二纠偏量fd_dl_1。
其中，BBU可以先根据各终端的预纠偏量确定fd_dl，再根据fd_dl确定fd_dl_0和fd_dl_1。
以上述公式(6.1)为例，a(i)为权值，a(i)的不同取值可能导致fd_dl的不同取值。
例如，参见公式(7.1)，fd_dl与终端Ai的预纠偏量相同。
a(i)＝1,a(n)＝0；n！＝i,1≤i≤n    公式(7.1)
又如，参见公式(7.2)，即a(i)构成等值数列，fd_dl为n个终端的预纠偏量的线性平均值。
a(1)＝a(2)＝…＝a(n)＝1/n    公式(7.2)
如果本实施例采用上述公式(6.3)，则参数RSRP0(i)和RSRP1(i)可以是BBU在执行S740之前确定的。例如，S710还包括：BBU确定RRU0和RRU1从每个终端接收的上行信号的RSRP。
可选的，BBU根据fd_dl确定fd_dl_0和fd_dl_1时，可以选择满足上述条件(1)至(3) 或其替代条件的任一fd_dl_0和fd_dl_1，也可以选择满足上述条件(4)至(6)或其替代条件的任一fd_dl_0和fd_dl_1。
S750、RRU0和RRU1分别采用根据fd_dl_0和fd_dl_1进行调整后的频率发送下行信号。
例如，BBU根据上述条件(1)至(3)或其替代条件选择出fd_dl_0和fd_dl_1之后，RRU0发送下行信号的频率可以为：f0-fd_dl_0，RRU1发送下行信号的频率为：f1+fd_dl_1。
又如，BBU根据上述条件(4)至(6)或其替代条件选择出fd_dl_0和fd_dl_1之后，RRU0发送下行信号的频率可以为：f0+fd_dl_0，RRU1发送下行信号的频率为：f1+fd_dl_1。
可以理解的，本实施例中BBU或RRU的某些处理可以使得RRU0和RRU1发送下行信号的频率分别为根据fd_dl_0和fd_dl_1进行调整后的频率。以下举例说明。
例如,以RRU0为例，BBU在时域上的处理包括：将一个样点的相位上增加相位ψ，其中，ψ＝2*π*fd_dl_0*ΔT，ΔT表示相邻样点之间的时差。这种保持两个相邻样点之间的相位差的方法能够实现根据fd_dl_0调整RRU0发送下行信号的频率。
又如，以RRU1为例，BBU在频域上针对下行信号进行卷积时采用与fd_dl_1相关的系数，也可以实现根据fd_dl_1调整RRU1发送下行信号的频率。
又如，RRU0在频率f0基础上减少fd_dl_0，并且，RRU1在频率f1基础上增加fd_dl_1，也可实现分别根据fd_dl_0和fd_dl_1调整RRU0和RRU1发送下行信号的频率。
本实施例中，各终端接收RRU0和RRU1在S750中发送的下行信号。对终端Ai来说，即使RRU0和RRU1分别采用调整之后的频率发送的下行信号在到达终端Ai时的频偏值仍有差异，终端Ai通过调整自身晶振，也能够一定程度上避免终端解调性能的降低。进一步的，如果RRU0和RRU1分别采用调整之后的频率发送的下行信号在到达终端Ai时的频偏值均为0，则可视为终端Ai接收到的RRU0和RRU1的下行信号不存在频率偏移，因此终端Ai不需要调整自身晶振，也能够保持解调下行信号的良好性能。如果RRU0和RRU1分别采用调整之后的频率发送的下行信号在到达终端Ai时的频偏值相同，但是不为0，则终端Ai接收到的RRU0和RRU1的下行信号都可能存在一个频率偏移，因此终端Ai可以按照现有技术确定接收到的下行信号的频偏值，并据此调整自身晶振，从而保持解调下行信号的良好性能。
本发明实施例以n个终端处于BBU控制的RRU0和RRU1的重叠覆盖区域(例如图3、图4和图5中列车所在的位置)的场景为例进行说明。实际上，随着列车的行驶，终端沿轨道的线路移动，并在某个时刻离开RRU0和RRU1的重叠覆盖区域，并进入BBU控制的其他RRU的重叠覆盖区域。因此，基站中的BBU在获知终端进入某些RRU的 重叠覆盖区域时，可以再次执行本实施例提供的方法。可选的，BBU可以通过测量终端发送的上行信号来确定终端进入的具体区域，此处不再赘述。
可选的，上述实施例提供的方法还可以由基站周期性执行。一方面，周期T越小，基站就越频繁的执行上述方法，即：较小取值的T使得基站可能更为及时地确定准确的频偏值，从而更好的保障快速移动的终端解调下行信号的性能。另一方面，周期越大，基站执行上述方法时的时间间隔可能越大，即：较大取值的T使得基站满足一般速度移动的终端的解调下行信号的性能，还有利于降低基站的内部处理复杂度，减少基站的耗电量。
可选的，基站执行上述方法时采用的周期T是预配置的，或者是在需要执行上述方式时即时计算出来的。例如，在上述方法的应用场景存在较多不确定因素时，基站可以采用不同的计算方式确定不同的周期，并在上述应用场景趋于稳定的情况下，将某个T的经验值视为预配置的T，即基站持续使用该T，在一定时段内不再进行T的计算。当然，预配置的T也可能是在基站出厂或上电之前，已经保存于基站的某个存储区。可选的，基站可以在上电时开始执行上述方法，也可以在RRU0和RRU1分别接收到来自终端Ai的上行信号时开始执行上述方法。
以下针对T可能满足的条件或规律进行举例说明。
例一、假设终端上报RSRP测量量给基站的周期为t，则T可能等于t，也可能为大于t。即，基站预配置的T为大于或等于t的任一值，或者，基站以t为参数计算T的取值，使T满足大于或者等于t。上述计算可能采用多种公式，如下为一种简单的公式举例：T＝m*t，其中，m大于或等于1。
例二、该周期T还可能小于或等于相邻两个RRU(如RRU0和RRU1)之间的距离Ds与列车速度v的比值。即，T<Ds/v或者T＝Ds/v。
此外，上述例一和例二可以相结合。例如，m*t≦T≦Ds/v。假设t为5毫秒(ms)，Ds为1000米，v为300千米/小时，则T可取值为200ms。
可以理解的，基站周期性执行上述方法所采用的周期T可以应用于不同步骤，例如基站按照T执行S720和/或S740。
本发明的另一个实施例还提供一种通信系统，该系统包括上述实施例提供的通信设备60，还可以进一步包括多个与该通信设备60通信的终端。
上述实施例提供的通信方法、设备和系统可应用于采用合并小区的组网方式的通信系统中，有利于提高移动的终端解调下行信号的性能。
需要说明的是，本发明的实施例所提供的通信方法、通信设备和系统所涉及的功能如果以软件功能单元的形式实现并作为独立的产品销售或使用时，可以存储在一个计算机可读取存储介质中。基于这样的理解，本发明的技术方案本质上或者说对现有技术做出贡献的部分或者该技术方案的部分可以以软件产品的形式体现出来，该计算机软件产品存储在一个存储介质中，包括若干指令用以使得一台计算机设备(可以是个人计算机，服务器，或者网络设备等)执行本发明各个实施例所述方法的全部或部分步骤。而前述的存储介质包括：U盘、移动硬盘、只读存储器(ROM，Read-Only Memory)、随机存取存储器(RAM，Random Access Memory)、磁碟或者光盘等各种可以存储程序代码的介质。
以上所述，仅为本发明的具体实施方式，但本发明的保护范围并不局限于此，任何熟悉本技术领域的技术人员在本发明揭露的技术范围内，可轻易想到变化或替换，都应涵盖在本发明的保护范围之内。因此，本发明的保护范围应所述以权利要求的保护范围为准。

Claims (21)

  1. 一种通信设备，其特征在于，包括：基带单元BBU和两个射频拉远单元RRU0和RRU1，其中，所述BBU用于控制第一逻辑小区，所述第一逻辑小区包括RRU0覆盖的物理小区和RRU1覆盖的物理小区；RRU0覆盖的物理小区和RRU1覆盖的物理小区在第一区域重叠；
    所述RRU0和RRU1用于：分别采用频率f0发送第一下行信号，然后，分别采用第一频率和第二频率发送第二下行信号，所述第一频率为f0与第一纠偏量fd_dl_0之差，所述第二频率为f0与第二纠偏量fd_dl_1之和；其中，所述fd_dl_0和所述fd_dl_1中的至少一个不为0。
  2. 如权1所述的设备，其特征在于，所述fd_dl_0和所述fd_dl_1分别满足如下条件：
    |fd_dl_0|<|2*fd_dl|；
    |fd_dl_1|<|2*fd_dl|；
    其中，参数fd_dl、所述fd_dl_0和所述fd_dl_1均为非正数，或者，所述fd_dl、所述fd_dl_0和所述fd_dl_1均为非负数。
  3. 如权2所述的设备，其特征在于，
    所述BBU还用于：根据所述fd_dl确定满足所述条件的fd_dl_0和fd_dl_1。
  4. 如权3所述的设备，其特征在于，
    所述RRU0和RRU1还用于：在发送所述第二下行信号之前，分别接收从所述RRU1向所述RRU0移动的n个终端发送的上行信号，其中，所述n个终端处于所述第一区域内，第i个终端用终端Ai表示，i为1至n之间的任一值；
    所述BBU还用于：确定所述fd_dl；其中，
    Figure PCTCN2015071975-appb-100001
    Figure PCTCN2015071975-appb-100002
    且0≤a(i)≤1；
    fd(i)表示根据所述上行信号确定的终端Ai的多普勒频偏估计值。
  5. 如权4所述的设备，其特征在于，
    所述BBU还用于：采用如下公式确定所述fd(i)；
    fd(i)＝R*(Δf0(i)-Δf1(i))/2；
    其中，Δf0(i)表示RRU0从终端Ai接收的上行信号的频偏值，Δf1(i)表示RRU1从终 端Ai接收的上行信号的频偏值；R为大于0的变量。
  6. 如权5所述的设备，其特征在于，
    所述BBU工作于TDD系统时，R为1；或者，
    所述BBU工作于FDD系统时，R为所述FDD系统中的下行载波频率与上行载波频率的比例。
  7. 如权4至6任一项所述的设备，其特征在于，
    所述BBU还用于：确定RRU0和RRU1接收的上行信号的参考信号接收功率RSRP，并按照如下公式确定a(i)；
    RSRP_i＝RSRP0(i)+RSRP1(i)；
    RSRP_sum＝∑RSRP_i；
    a(i)＝RSRP_i/RSRP_sum；
    其中，RSRP0(i)表示RRU0从终端Ai接收到的上行信号的RSRP，RSRP1(i)表示RRU1从终端Ai接收到的上行信号的RSRP。
  8. 如权4至7任一项所述的设备，其特征在于，
    所述第一区域距离RRU0和RRU1均为d，其中，
    Figure PCTCN2015071975-appb-100003
    q％表示针对不同终端的频偏值之间的差异的容忍度，q的取值范围为[0,100]，Dmin的取值范围为[L0,L1]，其中，L0表示RRU0与所述终端Ai的移动线路的垂直距离，L1表示RRU1与所述终端Ai的移动线路的垂直距离。
  9. 如权4至8任一项所述的设备，其特征在于，
    所述BBU还用于：在第一条件和第二条件被满足时，确定所述n个终端处于所述第一区域内；
    所述第一条件包括：所述n个终端中的每个终端的多普勒频偏估计值均为正数或均为负数；
    所述第二条件包括：所述n个终端中的每两个终端的多普勒频偏估计值之差的绝对值均小于或等于|q％*fd-max|，其中，fd-max为RRU0或RRU1的下行信号的最大频偏值。
  10. 如权4至9任一项所述的设备，其特征在于，
    所述BBU还用于：按照周期T确定所述fd_dl，所述T的取值范围为[m*t,Ds/v]；其中，t表示终端Ai上报测量量的周期，其中，所述测量量为所述终端Ai针对来自RRU0 或RRU1的下行信号的RSRP的测量结果；m大于0；Ds表示RRU0与RRU1之间的距离；v表示终端Ai的移动速度。
  11. 一种通信系统，其特征在于，所述系统包括：如权1至10任一项所述的通信设备。
  12. 一种通信方法，其特征在于，所述方法包括：
    基站分别采用频率f0发送第一下行信号，然后，分别采用第一频率和第二频率发送第二下行信号；
    其中，所述第一频率为f0与第一纠偏量fd_dl_0之差，所述第二频率为f0与第二纠偏量fd_dl_1之和，所述fd_dl_0和所述fd_dl_1中的至少一个不为0；
    其中，所述基站包括：基带单元BBU，两个射频拉远单元RRU0和RRU1；所述BBU用于控制第一逻辑小区，所述第一逻辑小区包括RRU0覆盖的物理小区和RRU1覆盖的物理小区；RRU0覆盖的物理小区和RRU1覆盖的物理小区在第一区域重叠。
  13. 如权12所述的方法，其特征在于，所述fd_dl_0和所述fd_dl_1分别满足如下条件：
    |fd_dl_0|<|2*fd_dl|；
    |fd_dl_1|<|2*fd_dl|；
    其中，参数fd_dl、所述fd_dl_0和所述fd_dl_1均为非正数，或者，所述fd_dl、所述fd_dl_0和所述fd_dl_1均为非负数。
  14. 如权13所述的方法，其特征在于，所述方法还包括：
    所述基站根据所述fd_dl确定满足所述条件的fd_dl_0和fd_dl_1。
  15. 如权14所述的方法，其特征在于，所述基站在发送所述第二下行信号之前，所述方法还包括：
    所述基站分别接收从所述RRU1向所述RRU0移动的n个终端发送的上行信号，其中，所述n个终端处于所述第一区域内，第i个终端用终端Ai表示，i为1至n之间的任一值；
    所述基站确定所述fd_dl；其中，
    Figure PCTCN2015071975-appb-100004
    Figure PCTCN2015071975-appb-100005
    且0≤a(i)≤1；
    fd(i)表示根据所述上行信号确定的终端Ai的多普勒频偏估计值。
  16. 如权15所述的方法，其特征在于，
    所述基站采用如下公式确定fd(i)；
    fd(i)＝R*(Δf0(i)-Δf1(i))/2；
    其中，Δf0(i)表示RRU0从终端Ai接收的上行信号的频偏值，Δf1(i)表示RRU1从终端Ai接收的上行信号的频偏值；R为大于0的变量。
  17. 如权16所述的方法，其特征在于，
    所述基站工作于TDD系统时，R的取值为1；或者，
    所述基站工作于FDD系统时，R为所述FDD系统中的下行载波频率与上行载波频率的比例。
  18. 如权15至17任一项所述的方法，其特征在于，所述方法还包括：
    所述基站确定RRU0和RRU1接收的上行信号的参考信号接收功率RSRP，并按照如下公式确定a(i)；
    RSRP_i＝RSRP0(i)+RSRP1(i)；
    RSRP_sum＝∑RSRP_i；
    a(i)＝RSRP_i/RSRP_sum；
    其中，RSRP0(i)表示RRU0从终端Ai接收到的上行信号的RSRP，RSRP1(i)表示RRU1从终端Ai接收到的上行信号的RSRP。
  19. 如权15至18任一项所述的方法，其特征在于，
    所述第一区域距离RRU0和RRU1均为d，其中，
    Figure PCTCN2015071975-appb-100006
    q％表示针对不同终端的频偏值之间的差异的容忍度，q的取值范围为[0,100]，Dmin的取值范围为[L0,L1]，其中，L0表示RRU0与所述终端Ai的移动线路的垂直距离，L1表示RRU1与所述终端Ai的移动线路的垂直距离。
  20. 如权15至19任一项所述的方法，其特征在于，所述方法还包括：
    所述基站在第一条件和第二条件被满足时，确定所述n个终端处于所述第一区域内；
    所述第一条件包括：所述n个终端中的每个终端的多普勒频偏估计值均为正数或均为负数；
    所述第二条件包括：所述n个终端中的每两个终端的多普勒频偏估计值之差的绝对值均小于或等于|q％*fd-max|，其中，fd-max为RRU0或RRU1的下行信号的最大频偏值。
  21. 如权15至20任一项所述的方法，其特征在于，所述方法还包括：
    所述基站按照周期T确定所述fd_dl，所述T的取值范围为[m*t,Ds/v]；其中，t表示终端Ai上报测量量的周期，其中，所述测量量为所述终端Ai针对来自RRU0的下行信号的RSRP的测量结果；m大于0；Ds表示RRU0与RRU1之间的距离；v表示终端Ai的移动速度。
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