Method, equipment and system for bit allocationTechnical Field
The present invention relates to the field of mobile communications, and in particular, to a method, device, and system for bit allocation.
Background
In order to improve the cell average throughput and the cell edge throughput, technologies such as cooperative communication, distributed antenna system, inter-cell cooperation, network MIMO (multiple-input multiple-output) and the like are proposed in succession, and the essence of these technologies is to convert interference into useful signals through JP (Joint Processing). LTE-Advanced (Long Term Evolution-Advanced, Advanced Long Term Evolution) introduces the concept of distributed MIMO and proposes a coordinated multipoint transmission/reception technique. CoMP (Coordinated Multi-point Transmission) is a key technology of LTE-a, and can improve the capacity of downlink. The CoMP technology can fully utilize the advantage of independence of distributed multi-antenna channels, or obtain higher spatial multiplexing gain, or improve transmission diversity gain, thereby effectively improving the throughput and reliability of links. The "multipoint" in CoMP is equivalent to each distributed antenna that transmits or receives cooperatively. CoMP techniques are mainly classified into the following two categories: (1) JP: data transmitted to a specific UE comes from a plurality of BSs (Base stations) in a transmission set at the same time to improve the quality of received signals and cancel interference of other users; (2) CS/CB (coordinated scheduling and/or Beamforming): data sent to a specific UE (User Equipment) only comes from a serving cell BS where the UE is located, but corresponding scheduling, transmission weights, and the like require dynamic information interaction and coordination among cells to reduce mutual interference between different transmissions of multiple cells as much as possible.
The cell edge and the cell average throughput can be greatly improved through cooperation among all BSs in a transmission set, but a BS end needs to transmit channel information of all BSs in the transmission set, for an FDD (Frequency Division Duplex) system, the channel information can be obtained only through feedback of a UE (User Equipment) end, and the feedback information amount is in direct proportion to the number of BSs in the transmission set. Compared with the conventional system, the channel information feedback amount of the CoMP system is increased by a multiple, and the overhead of an uplink control link is increased. Although increasing the amount of uplink feedback can further improve the performance of the system, the capacity of the uplink is a serious challenge. Therefore, when the capacity of the uplink is limited, the uplink needs to be allocated reasonably to improve the uplink feedback efficiency. However, in the prior art, no reasonable bit allocation scheme for the uplink exists.
Disclosure of Invention
The embodiment of the invention provides a method, equipment and a system for bit allocation, which are used for performing bit allocation on feedback information of UE (user equipment) and improving the feedback efficiency.
The bit allocation method provided by the embodiment of the invention comprises the following steps:
the UE determines the bit number which is distributed to each base station BS in the cooperation area and used for quantizing the feedback information;
and the UE sends the bit number for quantizing the feedback information to a serving BS.
The user equipment provided by the embodiment of the invention comprises:
a bit allocation determining unit, configured to determine a number of bits allocated to each base station BS in the cooperation area for quantizing the feedback information;
a bit allocation feedback unit for transmitting the bit number for quantizing the feedback information to the serving BS.
The communication system provided by the embodiment of the invention comprises:
the user equipment UE is used for determining the bit number which is distributed to each base station BS in the cooperation area and is used for quantizing the feedback information; and transmitting the bit number for quantizing the feedback information to a serving BS.
A serving BS for receiving the number of bits for quantizing the feedback information.
Another bit allocation method provided in the embodiment of the present invention includes:
the serving BS determines the bit number which is allocated to each base station BS in the cooperation area and used for quantizing the feedback information;
and the serving BS sends the bit number for quantizing the feedback information to the UE and the cooperative BS in the cooperative area.
The base station device provided by the embodiment of the invention comprises:
a bit allocation determining unit, configured to determine a number of bits allocated to each base station BS in the cooperation area for quantizing the feedback information;
and a bit allocation sending unit, configured to send the number of bits used for quantizing the feedback information to the UE and the cooperative BS in the cooperation area.
The communication system provided by the embodiment of the invention comprises:
the service BS is used for determining the bit number which is distributed to each base station BS in the cooperation area and is used for quantizing the feedback information; sending the bit number for quantizing the feedback information to the UE and a cooperative BS in a cooperative area;
the UE is used for receiving the bit number used for quantizing the feedback information and sent by the serving BS;
and the cooperative BS is used for receiving the bit number used for quantizing the feedback information and sent by the serving BS.
According to the technical scheme, the UE or the service BS determines the bit number which is allocated to each base station BS in the cooperation area and used for quantizing the feedback information, and sends the bit number used for quantizing the feedback information to the service BS.
Drawings
Fig. 1 is a schematic diagram of a CoMP scenario in the prior art;
fig. 2 is a schematic UE-side flow chart of a method for bit allocation according to an embodiment of the present invention;
fig. 3 is a system flow diagram illustrating a method for bit allocation according to an embodiment of the present invention;
fig. 4 is a schematic diagram of a BS-side flow of another bit allocation method according to an embodiment of the present invention;
fig. 5 is a system flow diagram illustrating another method for bit allocation according to an embodiment of the present invention;
fig. 6 is a schematic diagram of feedback information reporting according to an embodiment of the present invention;
fig. 7 is a schematic structural diagram of a bit allocation apparatus according to an embodiment of the present invention;
fig. 8 is a schematic structural diagram of a bit allocation apparatus according to an embodiment of the present invention;
fig. 9 is a schematic structural diagram of another apparatus for bit allocation according to an embodiment of the present invention;
fig. 10 is a schematic structural diagram of another apparatus for bit allocation according to an embodiment of the present invention;
fig. 11 is a schematic structural diagram of another apparatus for bit allocation according to an embodiment of the present invention;
fig. 12 is a schematic structural diagram of a bit allocation system according to an embodiment of the present invention;
fig. 13 is a schematic structural diagram of a bit allocation system according to an embodiment of the present invention;
fig. 14 is a schematic structural diagram of a bit allocation system according to an embodiment of the present invention.
Detailed Description
The embodiment of the invention provides a method, equipment and a system for bit allocation, which are used for performing bit allocation on feedback information of UE (user equipment) and improving feedback efficiency.
An application scenario corresponding to the present invention is shown in fig. 1, where N BSs in a cooperation area serve K UEs at the same time, and a BS side is equipped with multiple antennas; a BS transmitting a PDCCH (Physical Downlink Control Channel) to the UE is a serving BS of the UE, and other cells directly or indirectly participating in cooperative transmission are called cooperative BSs. In general, the gains of the serving BS and the cooperative BS to the UE side are different.
CDI (Channel Direction Information) and PMI (Precoding matrix index) are parameters for feeding back Channel Information of each BS, and are respectively applied to different scenes, and PI (Phase Information) is a parameter for feeding back Phase Information; the feedback of the parameters is convenient for the BS to adjust the sending signals in time, and the CoMP performance is improved. The system needs to feed back both CDI/PMI and PI, and the introduction of channel information feedback and PI feedback of a plurality of BSs greatly increases the feedback quantity of the UE.
Considering that channel gains and time delays from different BSs to the same UE are different and the CDI/PMI and PI of the same BS have different influence on the gain of the UE, the invention provides a method for dividing a bit allocation process into two steps of Inter-BS bit allocation (Inter-BA) in a cooperation area and CDI/PMI and PI bit allocation (Intra-BA) in the BS. The Inter-BA is bit distribution among different channels and is used for determining the total bit number which can be used when the UE feeds back the channels of each BS; the Intra-BA is a bit allocation between different pieces of information to determine the number of bits that can be used by each parameter when the UE feeds back the channel of each BS, for example, the allocation between the CDI and the PI. Inter-BA is realized at the BS side, and Intra-BA can be realized at the UE side and can also be realized at the service BS side.
Referring to fig. 2, on the premise that Intra-BA is implemented at the UE side, the method for bit allocation provided in the embodiment of the present invention includes:
s201, UE determines the bit number which is distributed to each base station BS in a cooperation area and used for quantizing feedback information;
s202, the UE sends the bit number used for quantizing the feedback information to the BS.
Preferably, the bit number for quantizing the feedback information includes: the number of bits used for quantizing the channel direction information CDI or the precoding matrix PMI, and the number of bits used for quantizing the phase information PI. That is, the Intra-BA needs to be performed, and is performed by the UE.
Preferably, the determining, by the UE, the number of bits allocated to each base station BS in the cooperation area for quantizing the feedback information includes: and the UE determines the bit number for quantizing the CDI or PMI and the bit number for quantizing the PI according to the total bit number which is distributed to each BS in the cooperation area and used for quantizing the feedback information.
Preferably, the total number of bits used by each BS for quantizing the feedback information is indicated to the UE by the serving BS in advance.
The UE determines the total bit number used for quantizing the feedback information according to the requirement of performing Intra-BA, the total bit number used for quantizing the feedback information is indicated after the serving BS performs Inter-BA, and the UE side stores the Inter-BA result indicated by the BS at the latest time, namely the total bit number used for quantizing the feedback information.
Preferably, the serving BS indicates to the UE the total number of bits used for quantizing the feedback information, including: the service BS determines the total bit number currently used by each BS for quantizing the feedback information; and if the total bit number currently used by each BS for quantizing the feedback information is changed compared with the previously stored total bit number currently used by each BS for quantizing the feedback information, the serving BS indicates the total bit number currently used by each BS for quantizing the feedback information to the UE. In order to save channel resources, the present embodiment defines that the serving BS sends the Inter-BA result to the UE only when the total number of bits changes.
Preferably, the serving BS determining the total number of bits currently used by each BS for quantizing the feedback information includes: the service BS determines large-scale fading from each BS to the UE according to the RSRP (Reference Signal Received Power) of each BS in the cooperation area reported by the UE; the service BS determines the time correlation coefficient of the channel of each BS according to the channel feedback time delay between each BS and the UE; and the serving BS determines the total bit number currently used for quantizing the feedback information according to the large-scale fading from each BS to the UE and the time correlation coefficient of the channel of each BS. Preferably, the calculation formula is as follows:
formula (1)
Where N is the total number of BSs in the transmission set, NtRepresents the number of transmission antennas per BS; b istotRepresenting the total number of feedback bits per UE, BiIs the number of bits allocated to the ith BS by the Inter-BA, i.e., the total number of bits used by BS i for CDI/PMI and PI, αiRepresenting the large scale fading from the ith BS to the UE, obtained from the RSRP reported by the UE side ηiRepresenting the time-related coefficient of the channel, f (α)i,ηi) To influence factor, αiAnd ηiIn direct proportion, i.e. αiAnd ηiThe larger the number of bits allocated.
ηiIs the correlation coefficient between the actual channel corresponding to the quantized channel and the channel corresponding to the quantized channel time obtained by the BS end, i.e. the assumed time T1The channel between the BS and the UE received by the UE is H1Quantized at the UE end toIs fed back to the BS, and the BS receivesAt a time T2The channel at this time is H2Then H is1And H2The correlation coefficient between is the time correlation coefficient, and for the channel type without considering the feedback channel delay, η in formula (1)i＝ηl1. The bit allocation result can be made more accurate by considering the feedback channel delay.
Preferably, the serving BS determining the total number of bits currently used by each BS for quantizing the feedback information includes: and the service BS determines the total bit number currently used for quantizing the feedback information by each BS according to the number of the BSs in the cooperation area.
Preferably, the serving BS indicates to the UE the total number of bits currently used by each BS for quantizing the feedback information, including: the service BS determines BAI (Bit Allocation Index, BAI) according to the total Bit number currently used for quantizing the feedback information of each BS and a Bit number Allocation storage table; the serving BS indicates the BAI to the UE; wherein, the bit number allocation storage table is determined by the service BS and the UE in advance through negotiation, and the BAI represents the sequence number of each item in the bit number allocation storage table. The serving BS indicates the BAI to the UE and also indicates the BAI to a cooperative BS; the transmission performance of the control information can be optimized by pre-storing bit number allocation storage tables at the UE side and the BS side and using the BAI to represent the sequence number of each item in the storage tables.
Preferably, the determining, by the UE, the number of bits used for quantizing the CDI or PMI and the number of bits used for quantizing the PI according to the total number of bits used for quantizing the feedback information allocated to each BS in the cooperation area includes: and the UE determines the bit number for quantizing the CDI or PMI and the bit number for quantizing the PI according to the useful signal power, the interference signal power and the total bit number of each BS for quantizing the feedback information. Preferably, the calculation formula is as follows:
formula (2)
And the sum is the integer i ═ 1,2, …, N
Wherein,represents the number of bits used to quantize the CDI/PMI of the ith BS,indicating the number of bits used to quantize the PI of the ith BS. T is1Representing the power of the useful signal, T2Representing the interfering signal power.
Preferably, the UE sending the number of bits used for quantizing the feedback information to the BS includes: the UE determines the current PIF (Phase Information Format) according to the bit number for quantizing the PI; and the UE sends the bit number for quantizing the feedback information to the BS through the current PIF. The Intra-BA allocation is indicated by PIF, which uses a fixed bit size to represent the number of bits allocated to the PI. For example, when 2 bits are used for PIF, there are four cases of 0 to 3 for PIF, each indicating that the number of bits allocated to PI is 0 to 3. Since the serving BS side knows the result of Inter-BA, the number of bits used for CDI/PMI quantization can be estimated by PIF.
Preferably, the UE sends the bit number for quantizing the feedback information to the BS through the current PIF, including: and if the current PIF is changed compared with the previously stored PIF, the UE sends the bit number for quantizing the feedback information to the BS through the current PIF. Here, the UE employs aperiodic feedback, and feeds back the serving BS only when Intra-BA changes. Of course, the UE may also use periodic feedback to feed back the currently stored PIF information to the serving BS at periodic time.
Preferably, the method further comprises: the UE quantizes the CDI corresponding to each BS according to the bit number for quantizing the CDI; and the UE quantizes the PI corresponding to each BS according to the bit number for quantizing the PI; the UE sends the quantized CDI and PI to a service BS; the service BS receives the quantized CDI and the quantized PI and forwards the received CDI and PI to a cooperative BS in a cooperative area; or, the UE quantizes the PMI corresponding to each BS according to the bit number used for quantizing the PMI; and the UE quantizes the PI corresponding to each BS according to the bit number for quantizing the PI; the UE sends the quantized PMI and the PI to a service BS; and the serving BS receives the quantized PMI and the quantized PI and forwards the received PMI and PI to the cooperative BS in the cooperative area.
And the UE quantifies the CDI/PMI and the PI according to the last Intra-BA result. Preferably, the UE performs vector quantization on the CDI/PMI of each BS and scalar quantization on the PI.
Preferably, the UE side quantizes the CDI by using the minimum chordal distance criterion, and the BS and the UE end need a plurality of codebooks of different sizes. Suppose that the CDI information of the ith BS isThe number of quantization bits is(derived from the Intra-BA guidelines):
formula (3)
Wherein, CiCodebook of size of BS i；cijRepresents the jth codeword in the codebook;show to makeThe sequence number of the codeword with the H maximum in the codebook.
The BS only needs to select the first code bookAnd each code word is the quantized CDI.
The PMI quantization may employ the same criteria.
Preferably, the PI is quantized uniformly, and no codebook is needed at both the BS and the UE. Suppose the ith BS has the bit number for PI as(derived from Intra-BA criteria), the feedback index of the quantized PI at the UE side is:
formula (4)
Wherein, thetaiRepresents PI [. C]Indicating rounding.
The criterion of the BS end for recovering the PI through the feedback index is as the formula (5):
formula (5)
Wherein,and represents PI.
Preferably, the UE side feeds back the CDI/PMI and PI in the original manner, and may adopt aperiodic feedback or periodic feedback.
The above steps are performed for a single user serving the BS, and the same procedure is used for other users.
Obviously, the information that the UE may feed back in this embodiment includes PIF, CDI/PMI and PI; and the UE side feeds back PIF, and the UE side feeds back CDI/PMI and PI which are respectively and independently reported. At a certain time, for example, when the feedback mode of the PIF and the feedback modes of the CDI/PMI and PI both adopt aperiodic feedback, the information fed back by the UE side may include the PIF, the CDI/PMI and the PI, may only have the PIF or only have the CDI/PMI and PI, or may not have feedback information.
Referring to fig. 3, a flow diagram for performing Intra-BA correspondence for the UE is shown. After the service BS carries out Inter-BA, the UE executes Intra-BA and feeds back the CDI/PMI and PI according to a preset period of the system. The period of the Intra-BA is preset as shown in FIG. 3 for cyclic calculation, so that the PIF can be adjusted in time; the Intra-BA can be performed only once in a scene with a more stable channel environment, and the Intra-BA is performed after the next time the service BS sends the Inter-BA result.
Referring to fig. 4, on the premise that the Intra-BA is implemented at the BS side or a scenario without the Intra-BA, the method for bit allocation provided in the embodiment of the present invention includes:
s401, the service BS determines the bit number which is distributed to each base station BS in the cooperation area and used for quantizing the feedback information;
s402, the serving BS sends the bit number for quantizing the feedback information to the UE and the cooperative BS in the cooperation area.
Preferably, the bit number for quantizing the feedback information includes: the number of bits used for quantizing the channel direction information CDI or the precoding matrix PMI, and the number of bits used for quantizing the phase information PI. That is, the Intra-BA needs to be performed, and is performed by the serving BS.
Preferably, S401 includes: and the service BS determines the bit number for quantizing the CDI or PMI and the bit number for quantizing the PI according to the total bit number which is distributed to each BS in the cooperation area and used for quantizing the feedback information.
Preferably, the total number of bits used by each BS for quantizing the feedback information is predetermined by the serving BS. The serving BS predetermines the procedures of the BS, which are the procedures of Inter-BA.
Preferably, the determining, by the serving BS, the total number of bits for quantizing the feedback information includes: the service BS determines large-scale fading from each BS to the UE according to Reference Signal Received Power (RSRP) of each BS in a cooperation area reported by the UE; the service BS determines the time correlation coefficient of the channel of each BS according to the channel feedback time delay between each BS and the UE; and the service BS determines the total bit number currently used by each BS for quantizing the feedback information according to the large-scale fading from each BS to the UE and the time correlation coefficient of the channel of each BS. Preferably, withThe UE performs Inter-BA in the same way, and calculates the total bit number currently used for quantizing the feedback information by using a formula (1), wherein ηiIs a parameter related to the delay of the feedback channel, η in equation (1) for the type of channel that does not take into account the delay of the feedback channeli＝ηl＝1。
Preferably, the determining, by the serving BS, the total number of bits for quantizing the feedback information includes: and the service BS determines the total bit number currently used by each BS for quantizing the feedback information according to the number of the BSs in the cooperation area.
Preferably, after determining the total number of bits currently used by each BS for quantizing the feedback information, the method further includes: and if the total bit number currently used by each BS for quantizing the feedback information is changed compared with the previously stored total bit number for quantizing the feedback information, the serving BS sends the total bit number currently used by each BS for quantizing the feedback information to the UE and the cooperative BSs in the cooperative area.
Preferably, the serving BS sends the total number of bits currently used by each BS for quantizing the feedback information to the UE and the cooperative BSs in the cooperation area, including: the service BS determines a bit allocation indication BAI according to the total bit number currently used by each BS for quantizing the feedback information and a bit allocation storage table; the serving BS indicates the BAI to the UE; the bit number allocation storage table is determined by negotiation in advance of the serving BS, the UE and the cooperative BS, and the BAI represents a sequence number of each item in the bit number allocation storage table. The transmission performance of the control information can be optimized by pre-storing bit number allocation storage tables at the UE side and the BS side and using the BAI to represent the sequence number of each item in the storage tables.
Preferably, the determining, by the serving BS, the number of bits used for quantizing the CDI or PMI and the number of bits used for quantizing the PI according to the total number of bits used for quantizing the feedback information allocated to each BS in the cooperation area includes: and the service BS determines the bit number for quantizing the CDI or PMI and the bit number for quantizing the PI according to the useful signal power, the interference signal power and the total bit number of each BS for quantizing the feedback information. Preferably, the number of bits for quantizing the CDI or PMI and the number of bits for quantizing the PI are calculated using the calculation formula (2) as in the Intra-BA method performed by the UE.
Preferably, the serving BS sending the bit number for quantizing the feedback information to the UE and the cooperative BS in the cooperation area includes: the service BS determines the current phase information format PIF according to the bit number used for quantizing the PI; and the serving BS sends the bit number for quantizing the feedback information to the UE and the cooperative BS in the cooperation area through the current PIF. Since the UE side knows the result of Inter-BA, the PIF can estimate the bit number used for CDI/PMI quantization.
The serving BS feedback PIF may employ either periodic feedback or periodic feedback. Preferably, when the aperiodic feedback is adopted, the serving BS sends the bit number for quantizing the feedback information to the UE and the cooperative BS in the cooperation area through the current PIF, including: and if the current PIF is changed compared with the previously stored PIF, the serving BS sends the bit number for quantizing the feedback information to the UE and the cooperative BS in the cooperation area through the current PIF.
Preferably, the method further comprises: the UE quantizes the CDI corresponding to each BS according to the bit number for quantizing the CDI; and the UE quantizes the PI corresponding to each BS according to the bit number for quantizing the PI; the UE sends the quantized CDI and PI to a service BS; the service BS receives the quantized CDI and the quantized PI and forwards the received CDI and PI to a cooperative BS in a cooperative area; or, the UE quantizes the PMI corresponding to each BS according to the bit number used for quantizing the PMI; and the UE quantizes the PI corresponding to each BS according to the bit number for quantizing the PI; the UE sends the quantized PMI and the PI to a service BS; and the serving BS receives the quantized PMI and the quantized PI and forwards the received PMI and PI to the cooperative BS in the cooperative area.
And the UE quantizes the CDI/PMI and the PI according to a preset period according to the last Intra-BA result notified by the service BS. The specific quantization scheme is the same as the scheme when the Intra-BA is performed by the UE, and the quantization formula is shown in formula (3) and formula (4).
Since the PIF is determined by the serving BS, the UE only needs to feed back the quantized CDI/PMI and PI, and does not need to feed back the PIF.
Preferably, the number of bits used for quantizing the feedback information is the number of bits used for quantizing the channel direction information CDI or the precoding matrix PMI. That is, the present embodiment may also process a scene that does not use PI, that is, only perform Inter-BA.
Preferably, the determining, by the serving BS, the number of bits allocated to each base station BS in the cooperation area for quantizing the feedback information includes: the service BS determines large-scale fading from each BS to the UE according to Reference Signal Received Power (RSRP) of each BS in a cooperation area reported by the UE; the service BS determines the time correlation coefficient of the channel of each BS according to the channel feedback time delay between each BS and the UE; and the serving BS determines the current bit number used for quantizing the CDI or PMI by each BS according to the large-scale fading from each BS to the UE and the time correlation coefficient of the channel of each BS. The specific calculation method is shown in formula (1).
Preferably, the serving BS sending the bit number for quantizing the feedback information to the UE and the cooperative BS in the cooperation area includes: if the current bit number used for quantizing the CDI of each BS is changed compared with the previously stored bit number used for quantizing the CDI, the serving BS sends the current bit number used for quantizing the CDI of each BS to the UE and the cooperative BS in the cooperative area; and if the bit number currently used for quantizing the PMI by each BS is changed compared with the previously stored bit number used for quantizing the PMI, the serving BS sends the bit number currently used for quantizing the PMI by each BS to the UE and the cooperative BS in the cooperation area.
Preferably, the sending, by the serving BS, the number of bits currently used for quantizing the CDI or PMI to the UE and the cooperative BS in the cooperation area includes: the service BS determines a bit allocation indication BAI according to the bit number currently used by each BS for quantizing the CDI or PMI and a bit allocation storage table; the serving BS indicates the BAI to the UE; the bit number allocation storage table is determined by negotiation in advance of the serving BS, the UE and the cooperative BS, and the BAI represents a sequence number of each item in the bit number allocation storage table.
And after receiving the BAI, the UE updates the quantization bit number of the CDI/PMI, and performs quantization and feedback of the CDI/PMI according to the updated quantization bit number of the CDI/PMI. Further, the UE quantizes the CDI corresponding to each BS according to the number of bits used for quantizing the CDI; the UE sends the quantized CDI to a serving BS; the service BS receives the quantized CDI and forwards the received CDI to a cooperative BS in a cooperative area; or, the UE quantizes the PMI corresponding to each BS according to the bit number used for quantizing the PMI; the UE sends the quantized PMI to a serving BS; and the serving BS receives the quantized PMI and forwards the received PMI to the cooperative BS in the cooperative area.
Referring to fig. 5, a flow chart for bit allocation on the BS side is shown. After the service BS carries out Inter-BA, carrying out Intra-BA according to the Inter-BA result, and feeding back the CDI/PMI and PI by the UE according to the last Intra-BA result and the preset period. The Intra-BA performs the cyclic calculation as shown in FIG. 3, the period is preset, and the PIF is convenient to adjust in time; in a scene with a more stable channel environment, the Intra-BA can be calculated only once, and the Intra-BA is carried out after the Inter-BA is carried out by the service BS next time.
Specific examples of the present invention are given below.
In a specific embodiment, a serving BS performs Inter-BA calculation.
Definition of Ri(i-1, 2, … N) is RSRP of each BS reported by the UE, α in formula (1)iCan be represented by RiTo indicate that is
αi＝RiFormula (6)
In this embodiment, the Gauss-Markov channel model is used to represent the correlation of the channels, thenηiIs about time delay DiOf the first class of zeroth order Betherl functions, i.e.
ηi＝J0(2πDifdT) formula (7)
Wherein f isdRepresenting the Doppler spread, T the duration of the symbol, and a delay variable DiThe sum of the processing delay and the feedback delay at the UE side is represented, and for the cooperative BS, the delay forwarded by the serving BS to the cooperative BS is also included. DiThe measurements can be obtained at the BS side or by UE side feedback.
By RiAnd Di(i ═ 1,2, … N), the serving BS obtains α from formula (6) and formula (7)iAnd ηi(i ═ 1,2, … N). Under Gauss-Markov channel model, influence factorThen equation (1) translates to:
formula (8)
The serving BS side obtains the number of bits B allocated to each BSi。
It can be easily seen that if the influence factor f (α) between the user and each BS isi,ηi) Equal in size (e.g., the user is centered on three BSs), then the second term to the right of the medium sign in equation (8) is zero, and the Inter-BA equivalence is equal bit allocation, i.e., the user is located in the center of three BSs。
In the second embodiment, the serving BS performs Intra-BA calculation.
Assuming that the transmission power of each BS is P, the useful signal power T1Such asFormula (9):
formula (9)
Interference signal power T2As shown in equation (10):
formula (10)
α in formula (9) and formula (10) based on the first embodimentiAnd ηi(i ═ 1,2, … N) can still be obtained by equation (6) and equation (7). This example provides an embodiment of an exhaustive search solving equation (2), for each（Is an integer, respectively) Combining, calculating separatelyFor those obtained under each bit combinationComparing to select the largestThe corresponding bit combination is the result of Intra-BA. Since each one isThe Intra-BA results for BS i are B in commoniSo that the UE needs to calculateBiNext, the process is carried out. On the basis of Inter-BA, BiThe determination reduces the searching times and accelerates the calculation speed of the UE end.
For the channel types without considering the feedback channel delay, only η in formula (9) and formula (10) is neededi＝ηm＝ηn＝1。
The specific embodiment of the UE performing Intra-BA calculation is similar and will not be described herein again.
In the third embodiment, the UE quantizes the CDI and the PI.
The codebook used for quantizing the CDI may adopt a Grassmannian codebook, and for codebooks not given corresponding sizes, a codebook of a required size may be constructed in an existing Grassmannian codebook by maximizing a minimum chord distance principle. In practical application, different codebooks have different performances in different scenes, and the required codebooks can be selected according to different scenes.
According to the most recently determined Intra-BA result, the UE selects a corresponding codebook for the CDI/PMI quantization of each BS i, and the size of the codebook is. In the criterion for selecting the codeword, formula (3) is represented in the codebook, selected such thatThe largest code word and the serial number of the code word in the codebookAnd feeding back to the serving BS. Thus, the BS locates the corresponding codebook according to the predetermined Intra-BA result, and then feeds back the result according to the stepThe corresponding codeword in the codebook is found.
Even quantization is adopted for PI, and no codebook is needed at both BS and UE ends. Suppose the ith BS has the bit number for PI as(derived from Intra-BA criteria), the feedback index of the quantized PI at the UE side is:
formula (11)
Wherein, thetaiRepresents PI [. C]Indicating rounding.
The criterion of the BS end for recovering the PI through the feedback index is as follows:
formula (12)
Wherein,and represents PI.
The fourth specific embodiment is a feedback mode when the UE performs Intra-BA.
Performing Intra-BA by the UE, wherein the UE needs to feed back PIF to the service BS; meanwhile, the UE feeds back the quantized CDI and PI to the serving BS according to a preset period. Although the feedback of the two is independent, the case that the PIF and the PI are fed back simultaneously may occur.
Referring to fig. 6, the serving BS indicates the total number of bits of CDI and PI as B for a certain period of time. In the figure, (a) is a schematic diagram of non-periodic feedback of the PIF, and (b) is a schematic diagram of periodic feedback of the PIF; after PIF feedback, the UE side changes the bit number used for quantizing PI and CDI according to the feedback PIF.
Referring to fig. 7, a user equipment UE provided in the present invention includes:
a bit allocation determining unit 71, configured to determine the number of bits allocated to each base station BS in the cooperation area for quantizing the feedback information;
a bit allocation feedback unit 72 for transmitting the number of bits for quantizing the feedback information to the serving BS.
Preferably, the bit number for quantizing the feedback information includes: the number of bits used for quantizing the channel direction information CDI or the precoding matrix PMI, and the number of bits used for quantizing the phase information PI.
Preferably, the bit allocation determining unit 71 is specifically configured to: determining the bit number for quantizing the CDI or PMI and the bit number for quantizing the PI according to the total bit number for quantizing the feedback information distributed to each BS in the cooperation area; wherein the total number of bits of the respective BSs for quantizing the feedback information is previously indicated by the serving BS.
Referring to fig. 8, preferably, the bit allocation feedback unit 72 includes:
a PIF determining unit 81, configured to determine a current PIF according to the number of bits used for quantizing the PI;
a PIF transmitting unit 82, configured to transmit the number of bits used for quantizing the feedback information to the BS through the current PIF.
Preferably, the PIF sending unit 82 is specifically configured to: and if the current PIF is changed compared with the PIF stored before, the bit number used for quantizing the feedback information is sent to the BS through the current PIF.
Referring to fig. 9, a base station apparatus provided in the present invention includes:
a bit allocation determining unit 91 for determining the number of bits for quantizing the feedback information allocated to each base station BS in the cooperation area;
a bit allocation sending unit 92, configured to send the number of bits used for quantizing the feedback information to the UE and the cooperative BS in the cooperation area.
Preferably, the bit number for quantizing the feedback information includes: the number of bits used for quantizing the channel direction information CDI or the precoding matrix PMI, and the number of bits used for quantizing the phase information PI.
Preferably, the bit allocation determining unit 91 is specifically configured to: and determining the bit number for quantizing the CDI or PMI and the bit number for quantizing the PI according to the total bit number allocated to each BS in the cooperation area for quantizing the feedback information.
Referring to fig. 10, preferably, the apparatus further comprises: a total bit number determination unit 90 for determining in advance the total bit number of the BSs for quantizing the feedback information.
Referring to fig. 11, preferably, the total bit number determining unit 90 includes:
a parameter determining unit 1101, configured to determine large-scale fading from each BS to the UE according to reference signal received power RSRP of each BS in a cooperation area reported by the UE; the service BS determines the time correlation coefficient of the channel of each BS according to the channel feedback time delay between each BS and the UE;
a total bit number calculating unit 1102, configured to determine, according to the large-scale fading from each BS to the UE and the time correlation coefficient of the channel of each BS, a total bit number currently used by each BS for quantizing the feedback information.
Preferably, the total bit number determining unit 90 includes: and the total bit number average calculating unit determines the total bit number currently used by each BS for quantizing the feedback information according to the number of the BSs in the cooperation area.
Preferably, the total bit number determining unit 90 further includes: and a total bit number sending unit, configured to send the total bit number currently used for quantizing the feedback information to the UE and the cooperative BS in the cooperation area if the total bit number currently used for quantizing the feedback information changes compared with a previously stored total bit number used for quantizing the feedback information.
Preferably, when the total bit number sending unit is configured to send the total bit number currently used for quantizing the feedback information to the UE and the cooperative BS in the cooperation area, the total bit number sending unit is specifically configured to: determining a bit allocation indication BAI according to the total bit number currently used for quantizing the feedback information and a bit allocation storage table; indicating the BAI to a UE; the bit number allocation storage table is determined by negotiating with the UE and other BSs in the cooperation area in advance, and the BAI represents the sequence number of each item in the bit number allocation storage table.
Similar to fig. 8, preferably, the bit allocation transmitting unit includes:
a PIF determining unit, configured to determine a current PIF according to the bit number for quantizing the PI;
and the PIF sending unit is used for sending the bit number used for quantizing the feedback information to the UE and the cooperative BS in the cooperation area through the current PIF.
Preferably, the PIF sending unit is specifically configured to: and if the current PIF is changed compared with the PIF stored before, the bit number for quantizing the feedback information is sent to the UE and the cooperative BS in the cooperative area through the current PIF.
Preferably, the number of bits used for quantizing the feedback information is the number of bits used for quantizing the channel direction information CDI or the precoding matrix PMI.
Similar to fig. 11, preferably, the bit allocation determining unit includes:
the parameter determining unit is used for determining large-scale fading from each BS to the UE according to Reference Signal Received Power (RSRP) of each BS in a cooperation area reported by the UE; the service BS determines the time correlation coefficient of the channel of each BS according to the channel feedback time delay between each BS and the UE;
and the total bit number calculation unit is used for determining the current bit number used for quantizing the CDI or PMI by each BS according to the large-scale fading from each BS to the UE and the time correlation coefficient of the channel of each BS.
Preferably, the bit allocation sending unit 92 is specifically configured to: if the bit number of each BS currently used for quantizing the CDI is changed compared with the previously stored bit number used for quantizing the CDI, the bit number of each BS currently used for quantizing the CDI is sent to the UE and the cooperative BSs in the cooperative area; and if the bit number currently used for quantizing the PMI by each BS is changed compared with the previously stored bit number used for quantizing the PMI, sending the bit number currently used for quantizing the PMI by each BS to the UE and the cooperative BS in the cooperative area.
Preferably, the bit allocation sending unit 92 is configured to, when sending the current bit number for quantizing the CDI or PMI to the UE and the cooperative BS in the cooperation area, specifically: determining a bit allocation indication BAI according to the bit number currently used by each BS for quantizing the CDI or PMI and a bit number allocation storage table; the BAI is indicated to the UE; the bit number allocation storage table is determined by negotiating with the UE and other BSs in the cooperation area in advance, and the BAI represents the sequence number of each item in the bit number allocation storage table.
Referring to fig. 12, a communication system provided by the present invention includes:
the user equipment UE1201 is used for determining the bit number which is allocated to each base station BS in the cooperation area and used for quantizing the feedback information; and transmitting the bit number for quantizing the feedback information to a serving BS.
A serving BS1202 configured to receive the number of bits for quantizing feedback information.
Preferably, the serving BS1202 is further configured to: determining the total bit number currently used by each BS for quantizing the feedback information; if the total bit number currently used by each BS for quantizing feedback information changes compared with the previously stored total bit number used for quantizing feedback information, the total bit number currently used by each BS for quantizing feedback information is indicated to the UE 1201.
Preferably, when the serving BS1202 is configured to determine the total number of bits currently used by each BS for quantizing the feedback information, it is specifically configured to: determining large-scale fading from each BS to the UE according to Reference Signal Received Power (RSRP) of each BS in a cooperation area reported by the UE; and, the serving BS1202 determines the time correlation coefficient of the channel of each BS according to the channel feedback delay between each BS and the UE; and determining the total bit number currently used for quantizing the feedback information according to the large-scale fading from each BS to the UE1201 and the time correlation coefficient of the channel of each BS.
Preferably, when the serving BS1202 is configured to determine the total number of bits currently used by each BS for quantizing the feedback information, it is specifically configured to: and determining the total bit number currently used for quantizing the feedback information according to the number of the BSs in the cooperation area.
Preferably, when the serving BS1202 is configured to indicate the total number of bits currently used by each BS for quantizing the feedback information to the UE1201, the serving BS is specifically configured to: the serving BS1202 determines a bit allocation indication BAI according to the total bit number currently used by each BS for quantizing feedback information and a bit allocation storage table; the serving BS1202 indicates the BAI to the UE; wherein, the bit number allocation storage table is determined by the serving BS1202 in advance by negotiation with the UE1201, and the BAI represents a sequence number of each entry in the bit number allocation storage table.
Preferably, the UE1201 is further configured to quantize the CDI corresponding to each BS according to the number of bits used for quantizing the CDI; and quantizing the PI corresponding to each BS according to the number of bits used to quantize the PI; sending the quantized CDI and PI to the serving BS 1202; or, the UE1201 is further configured to quantize the PMIs corresponding to each BS according to the number of bits used for quantizing the PMIs; and quantizing the PI corresponding to each BS according to the number of bits used to quantize the PI; the quantized PMI and PI are sent to the serving BS 1202.
Referring to fig. 13, preferably, the system further includes a cooperative BS 1203; the serving BS1202 is further configured to receive the quantized PMI and receive the quantized PI, and forward the received PMI and PI to the cooperative BS1203 in the cooperative area; alternatively, the serving BS1202 is further configured to receive the quantized CDI and receive the quantized PI, and forward the received CDI and PI to the cooperative BS1203 within the cooperation area.
Referring to fig. 14, a communication system provided by the present invention includes:
a serving BS1401 for determining the number of bits for quantizing feedback information allocated to each base station BS in the cooperation area; sending the bit number for quantizing the feedback information to the UE and a cooperative BS in a cooperative area;
a UE1402 configured to receive the bit number for quantizing feedback information sent by the serving BS 1401;
a cooperative BS1403 for receiving the number of bits for quantizing feedback information transmitted by the serving BS 1401.
Preferably, the bit number for quantizing the feedback information includes: the number of bits used for quantizing the channel direction information CDI or the precoding matrix PMI, and the number of bits used for quantizing the phase information PI.
Preferably, the UE1402 is further configured to quantize the CDI corresponding to each BS according to the number of bits used for quantizing the CDI; and quantizing the PI corresponding to each BS according to the number of bits used to quantize the PI; the quantized CDI and PI are sent to the serving BS 1401; the serving BS1401 is further configured to receive a quantized CDI and a quantized PI, and forward the received CDI and PI to a cooperative BS1403 in a cooperative area; or, the UE1402 is further configured to quantize the PMIs corresponding to the BSs according to the number of bits used for quantizing the PMIs; and quantizing the PI corresponding to each BS according to the number of bits used to quantize the PI; the quantized PMI and PI are sent to a serving BS 1401; the serving BS is further configured to receive the quantized PMI and receive the quantized PI, and forward the received PMI and PI to the cooperative BS1403 in the cooperative area.
Preferably, the number of bits used for quantizing the feedback information is the number of bits used for quantizing the channel direction information CDI or the precoding matrix PMI.
Preferably, the UE1402 is further configured to quantize the CDI corresponding to each BS according to the number of bits used for quantizing the CDI; transmitting the quantized CDI to the serving BS 1401; the serving BS1401 is further configured to receive the quantized CDI and forward the received CDI to the cooperative BS1403 in the cooperative area; or, the UE1402 is further configured to quantize the PMIs corresponding to the BSs according to the number of bits used for quantizing the PMIs; transmitting the quantized PMI to the serving BS 1401; the serving BS1401 is further configured to receive the quantized PMI and forward the received PMI to the cooperative BS1403 within the cooperative area.
The invention provides a new bit allocation mechanism in a CoMP technology. Generally, bit allocation between different channels and bit allocation between different information are considered separately, and the two are not used in a system jointly, and how to obtain the bit allocation result is not mentioned, and the high frequency bit allocation will increase extra overhead. The invention jointly considers the bit allocation among different BSs and among different information (CDI/PMI and PI) in the same BS, reasonably utilizes feedback bits under the condition of unchanged feedback overhead, and further improves the performance of the system compared with the mode of separately considering the bit allocation among different channels or the mode of bit allocation among different information; and the use scenarios are more extensive.
As will be appreciated by one skilled in the art, embodiments of the present invention may be provided as a method, system, or computer program product. Accordingly, the present invention may take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects. Furthermore, the present invention may take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, optical storage, and the like) having computer-usable program code embodied therein.
The present invention is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each flow and/or block of the flow diagrams and/or block diagrams, and combinations of flows and/or blocks in the flow diagrams and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instruction means which implement the function specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
It will be apparent to those skilled in the art that various changes and modifications may be made in the present invention without departing from the spirit and scope of the invention. Thus, if such modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include such modifications and variations.