Patent Application
20140313994
The present application claims priority to Chinese Patent Application No. 201110257228.5, filed with the State Intellectual Property Office of China on Sep. 1, 2011 and entitled “Method and device for transmitting downlink control information”, which is hereby incorporated by reference in its entirety,
The present invention relates to the field of wireless communication and particularly to a method and a device for transmitting downlink control information.
Physical Downlink Control Channel (PDCCH) is used for transmission of scheduling indicator, resource allocation indicator, transmission mode indicator and other L1/L2 control information in Long Term Evolution (LTE). in the earlier releases (Releases 8/9/10 or Rel 8/9/10) of LTE, PDCCH is multiplexed with Physical Downlink Shared Channel (PDSCH) through Time Division Multiplexing (TDM) so that PDCCH occupies first 1-4 Orthogonal Frequency Division Multiplexing (OFDM) symbol(s) of each downlink sub-frame. The particular number of occupied symbols depends upon the amount of control information carried over PDCCH, bandwidth of the system and type of the sub-frame.
In LTE Rel8/9/10, PDCCH is transmitted based upon a Cell-Specific Reference Signal (CRS). When the number of CRS ports is 1, PDCCH is transmitted via a single port, port 0; when the number of CRS ports is 2, PDCCH is transmitted through Space-Frequency Block Coding (SFBC); and when the number of CRS ports is 4, PDCCH is transmitted through the combination of Space-Frequency Block Coding (SFBC) and Frequency Switched Transmit Diversity (FSTD).
Along with further evolvement of transmission technology and expansion of network deployment, there is a new requirement by the LTE system for transmission of downlink control information, and the original PDCCH mechanism also has conic to suffer from numerous problems as follows.
With an increasing number of users, a plurality of User Equipments (UEs) need to be scheduled concurrently, particularly in Multi-User Multiple Input Multiple Output (MU-MIMO) and Coordinated Multi-Point Transmission/Reception (CoMP). In the course of scheduling Rel-10 or higher-release UE, Downlink Control Information (DCI) format 2C or downlink control information format at a higher overhead is largely used.
Considering of controlling CRS overhead, a system subsequent to the Rel-10 is largely configured with a Multimedia Broadcast Single Frequency Network (MBSFN) sub-frame in which there are at most two symbols that can be used for transmission of PDCCHs, thus making the capacity of PDCCHs further insufficient.
In Carrier Aggregation (CA), cross-carrier scheduling may be performed by scheduling transmission of a plurality of Component Carriers (CCs) over a PDCCH of one CC, thus making control resources further insufficient.
With PDCCH and PDSCH multiplexed through TDM, it may be difficult to obviate inter-cell PDCCH interference by allocating resources.
In a Heterogeneous Network (HetNet) scenario, Home eNodeB (HeNB) and other nodes are usually deployed without reasonable network design, and interference between PDCCHs may become more serious.
Along with expansion of LTE network deployment, the coverage of the LTE system will be extended gradually from the urban area to the suburb and the exurb and even to the countryside, so the edge coverage capability of the control channel needs to be taken into account; and in the CoMP, the UE tends to be located at the boundary of a cell, and a better edge coverage capability of the control channel is also desired.
For the UE at the edge of a cell, PDCCHs tend to be aggregated at a her level, thus the capacity of PDCCHs will be more limited.
Only 4 antenna ports at most can be supported in LTE Rel-8/9, and at most 8 antenna ports can be supported in LTE Rel-10 specification. Along with expansion of LTE network deployment, the number of antennas at the system side will also be upgraded gradually from single-antenna configuration mode to 2, 4 or 8-antenna configuration mode. With an increasing number of antennas, a more flexible multi-antenna transmission method can be used with PDSCH, and PDCCH can only be transmitted based upon a single port or transmit diversity of 1/2/4 CRS port. Considering of controlling CRS overhead, it is very likely for the Rel-10 and later releases to configure only two CRS ports. In this case, transmission performance of the PDCCH may be further insufficient.
With an increasing number of antennas, a CRS needs to be mapped to a real antenna port through antenna virtualization. In order to ensure a sector direction to be covered effectively by sector shaping as a result of weighted integration of a plurality of array elements, some constraint needs to be put on the design of the array elements and the selection of a weighting vector. In this case, the sector shaping as a result of virtualization may have an adverse influence on the coverage at the edge.
As can be apparent, the existing PDCCH can only be transmitted at a single CRS-based layer, thus the efficiency of transmission is limited; it is very likely for the Rel-10 and later releases to configure only two CRS ports, and in this case, PDCCH can only be transmitted through SFBC, thus the efficiency of transmission will be more limited; and the process of mapping a CRS port to a physical antenna through antenna virtualization may ha an adverse influence upon the coverage at the edge of the PDCCHs.
The invention provides a method and device for transmitting downlink control information so as to address the problem in the prior art with single-layer CRS port-based transmission.
The invention provides a method for transmitting downlink control information, which includes:
The invention further provides a method for transmitting downlink control information, which includes:
The invention provides a device for transmitting downlink control information, which includes:
The invention further provides a device for transmitting downlink control information, which includes:
With the method and device for transmitting downlink control information provided by the invention, there are the following advantageous effects: the use of DMRS port-based transmission and multi-layer mapping can greatly reduce occupied resources to thereby extend he capacity of PDCCHs, and DMRS transmission is a transmission method for a single UE, so even a user equipment at the edge can be well covered to thereby satisfy a demand for extending coverage; and a demand for at most 8 antennas can be supported.
A method and device for transmitting downlink. control information according to the invention will be described below in further details with reference to the drawings and the embodiments.
As illustrated in
Step 101, the downlink control information is processed to generate downlink control information codewords.
The process here is primarily to add some redundancy check info nation, perform channel encoding, etc.
Step 102, the downlink control information codewords are scrambled and modulated sequentially to generate a sequence of modulated symbols.
A fixed modulation scheme can be adopted, for example, Quadrature Phase Shift Keying (QPSK), or a modulation scheme can be determined as needed.
Step 103, the sequence of modulated symbols is mapped onto v data layers, where v is an integer more than or equal to 1.
Step 104, the modulated symbols on the v data layers are mapped to Demodulation Reference Signal (DMRS) antenna ports.
Step 105, the modulated symbols on the DMRS antenna ports are mapped onto physical antennas and sent to a User Equipment (UE), particularly to the UE over a PDCCH.
In the method for transmitting downlink control information according to the embodiment of the invention, the information is transmitted based upon the DMRS ports which support multi-layer transmission of data, so in the embodiment of the invention, the downlink control information to be transmitted can be transmitted to the UE through multi-layer transmission in the case of insufficient resources and through single-layer transmission in the case of sufficient resources or a low amount of data, thus enabling more flexible transmission. Multi-layer transmission can be performed in the ease of a high amount of data and insufficient resources to thereby occupy a lower amount of resources and consequently improve the capacity of PDCCHs; and moreover transmission via the DMRS ports is transmission for a single UE unlike CRS-based broadcast transmission, so even a user equipment the edge can be well covered to thereby satisfy a demand for extending coverage; and the DMRS ports can support transmission over at most 8 antennas to thereby satisfy a demand of an LTE system for multi-antenna transmission.
Preferably, in the embodiment of the invention, the particular DMRS antenna ports for use are determined by the number of DMRS antenna ports supported by the UE, and the number v of data layers for use in mapping is determined by a channel condition of the UE, where v is determined to be no more than the number of DMRS antenna ports supported by the UE.
Preferably, in the step 101, the downlink control information is processed as follows:
The foregoing process is known in the art and will not be detailed again here, and of course, the downlink control information codewords may alternatively be generated in other processes.
Preferably, in the step S102, the downlink control information codewords are scrambled as follows:
Of course, they may alternatively be scrambled in other ways.
Preferably, in the step 102, the scrambled downlink control information codewords are modulated as follows.
The modulation scheme is determined according to the channel condition of the UE, and the scrambled downlink control information codewords are modulated in the determined modulation scheme, and since the channel condition of the UE is taken into account in the modulation scheme, the transmission efficiency can be improved while ensuring the transmission reliability.
Particularly, the sequence of modulated symbols generated after modulation is a sequence of complex modulated symbols, and in the embodiment, the sequence of modulated symbols generated alter modulation is represented as d(0), . . . , d (Msymbol−1), where Msymbol is the total number of modulated symbols in the sequence of modulated symbols.
Preferably, in the step 103, the sequence of modulated symbols d(0), . . . , d (Msymbol−1) is mapped onto the v data layers as follows.
The sequence of modulated symbols is mapped onto the v data layers in a preset first mapping scheme so that numbers of modulated symbols at each data layer are equal.
As described above, after the number v of data. layers is determined, the number of modulated symbols at each data layer can be determined by the number of modulated symbols in the sequence of modulated symbols, and the sequence of modulated symbols can be mapped to the plurality of data layers in the preset first mapping scheme, and in this embodiment, the modulated symbols mapped onto the plurality of data layers are represented as x(j)=[x(0)(j), . . . , x(0−1)(j)]T, wherein j=0, . . . , Msymbollayer−1, and Msymbollayer represents the total number of modulated symbols at each data layer.
Preferably, in the embodiment, the sequence of modulated symbols is mapped onto the v data. layers in the following mapping scheme:
wherein x(l)(j) is a modulated symbol at the l-th data layer, l=0, . . . v−1, j=0, . . . , Msymbollayer −1, Msymbollayer represents the total number of modulated symbols at each data layer, d(k) is the sequence of modulated symbols, k=0, . . . , Msymbol−1. Msymbol is the total number of modulated symbols in the sequence of modulated symbols, and Msymbollayer=Msymbol/v.
Preferably, in the step 104, the modulated symbols on the v data layers are mapped onto the WARS antenna ports as follows:
The modulated symbols on the v data layers are mapped onto the DMRS antenna ports in a preset second mapping scheme according to the number v of data layers and the number of DMRS antenna. ports.
As described above, the number v of data layers is no more than the number of DMRS antenna ports, so all the data can be mapped to the DRMS antenna ports under a particular mapping rule which can be determined as needed.
Preferably, the number v of data layers is equal to the number of DMRS antenna ports, and the modulated symbols on the v data layers are mapped to the DMRS antenna ports by the way that the data layers correspond to the DMRS antenna ports in a one-to-one manner.
For the DMRS antenna ports, the value of the number of the DMRS antenna ports pDMRS ranges as pDMRS ε[1, . . . , 8], and the value of a port number p ranges as p ε [7, . . . , 14], and in the embodiment of the invention, the modulated symbols as a result of mapping to the DMRS antenna ports are represented as y(j)=[ . . . y(p)(j) . . . ]T, where y(p)(j) represents data on a DMRS antenna port p.
If the data layers correspond to the DMRS antenna ports in a one-to-one manner as described above, then the following mapping scheme can be adopted:
thus, the resulted y(j) is a pDMRS×Msymbollayer-dimensioned matrix.
Preferably, in the step 105, the modulated symbols on the DRMS antenna ports are mapped onto the physical antennas as follows:
The modulated symbols on the DRMS antenna ports are mapped onto the physical ante as in the following mapping scheme:
{tilde over (y)}(j)=W·y(j),
W is an Ant×pDMRS-dimensioned complex matrix, where Ant is the number of physical antennas, thus resulting in Ant×Msymbollayer-dimensioned data, where a number Msymbollayer of modulated symbols are transmitted on each physical antenna.
In the embodiment of the invention, the data mapped onto the physical antennas is represented as {tilde over (y)}(j)=[ . . . {tilde over (y)}(Ant)(j) . . . ]T, wherein {tilde over (y)}(Ant)(j) represents data on an antenna Ant.
Ant may or may not be equal to pDMRS, and particular Ant for use is determined by the configuration of an eNB. In the embodiment of the invention, for DMRS port-based mapping, unlike antenna virtualization used in the prior art, the network side device, an evolved NodeB (eNB), can select from pre-coding codebooks a pre-coding matrix matching the channel condition of the UE according to the channel condition of the UE, and the eNB can determine the channel condition of the UE as follows.
1) The UE searches a set of pre-coding codebooks for a pre-coding matrix matching its own channel condition according to the channel condition and feeds it back to the eNB, that is, the eNB determines W for use based upon feedback information of the UE.
2) The UE feeds an uplink signal back to the eNB over an uplink channel, and the eNB determines the channel condition of the UE according to the uplink signal reported by the UE and searches a set of pre-coding codebooks for a pre-coding matrix matching the channel condition, that is, the eNB determines W for use based upon channel reciprocity.
In the embodiment of the invention, downlink control information is transmitted over a PDCCH in a single-codeword multi-layer scheme, and DMRS port-based transmission can support multi-layer transmission of data, thus enabling more flexible transmission and higher transmission efficiency; and in DMRS port-based transmission, mapping of the DMRS ports to the physical antennas can be optimized by a channel condition of each UE without the presence of an edge coverage loss due to sector shaping.
As illustrated in
Step 201, a signal transmitted from the network side is received over physical antennas and the signal is mapped onto Demodulation Reference Signal (DMRS) antenna ports to obtain modulated symbols.
Step 202, the modulated symbols on the DMRS antenna ports are napped to v data layers, where v is an integer more than 1.
Step 203, the modulated symbols on the v data layers are mapped to a sequence of modulated symbols.
Step 204, the sequence of modulated symbols is demodulated and descrambled sequentially to obtain downlink control information codewords.
Step 205, the downlink control information codewords are processed to obtain the downlink control information.
A particular process thereof is an inverse process of the foregoing transmission process of the downlink control information and will not be detailed again here.
Based upon the same inventive idea, embodiments of the invention further provide devices for transmitting downlink control information, and since these devices address the problem under a similar principle to the methods of transmitting downlink control information, reference can be made to the implementations of the methods for implementations of these devices, and a repeated description thereof will be omitted here.
As illustrated in
A scrambling and modulating unit 302 configured to scramble and modulate the downlink control information codewords sequentially to generate a sequence of modulated symbols;
A first mapping unit 303 configured to map the sequence of modulated symbols onto v data layers, where v is an integer more than or equal to 1;
A second mapping unit 304 configured to map the modulated symbols on the v data layers to Demodulation Reference Signal (DMRS) antenna ports; and
A third mapping unit 305 configured to map the modulated symbols on the DMRS antenna ports onto physical antennas and to send to a User Equipment (UE).
Preferably, the device for transmitting downlink control information is an evolved NodeB (eNB).
As illustrated in
Preferably the device for transmitting downlink control information in the embodiment of the invention is a User Equipment (UE).
Those skilled in the art shall appreciate that the embodiments of the invention can be embodied as a method, a system or a computer program product. Therefore the invention can be embodied in the form of an all-hardware embodiment, an all-software embodiment or an embodiment of software and hardware in combination. Furthermore the invention can be embodied in the form of a computer program product embodied in one or more computer useable storage mediums (including but not limited to a disk memory, a CD-ROM, an optical memory, etc.) in which computer useable program codes are processed.
The invention has been described in a flow chart and/or a block diagram of the method, the device (system) and the computer program product according to the embodiments of the invention. It shall be appreciated that respective flows and/or blocks in the flow chart and/or the block diagram and combinations of the flows and/or the blocks in the flow chart and/or the block diagram can be embodied in computer program instructions. These computer program instructions can be loaded onto a general-purpose computer, a specific-purpose computer, an embedded processor or a processor of other programmable data processing device to produce a machine so that the instructions executed on the computer or the processor of the other programmable data processing device create means for performing the functions specified in the flow(s) of the flow chart and/or the block(s) of the block diagram.
These computer program instructions can also be stored into a computer readable memory capable of directing the computer or the other programmable data processing device to operate in a specific manner so that the instructions stored in the computer readable memory create an article of manufacture including instruction means which perform the functions specified in the flow(s) of the flow chart and/or the block(s) of the block diagram.
These computer program instructions can also be loaded onto the computer or the other programmable data processing device so that a series of operational steps are performed on the computer or the other programmable data processing device to create a computer implemented process so that the instructions executed on the computer or the other programmable data processing device provide steps for performing the functions specified in the flow(s) of the flow chart and/or the block(s) of the block diagram.
Although the preferred embodiments of the invention have been described, those skilled in the art benefiting from the underlying inventive concept can make additional modifications and variations to these embodiments. Therefore the appended claims are intended to be construed as encompassing the preferred embodiments and all the modifications and variations coming into the scope of the invention.
Evidently, those skilled in the art can make various modifications and variations to the invention without departing from the scope of the invention. Thus the invention is also intended to encompass these modifications and variations thereto so long as the modifications and variations come into the scope of the claims appended to the invention and their equivalents.
| Number | Date | Country | Kind |
|---|---|---|---|
| 201110257228.5 | Sep 2011 | CN | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/CN2012/080443 | 8/22/2012 | WO | 00 | 7/3/2014 |
