Method for transmitting downlink control signal

The present invention relates to a multi-carrier mobile communication system, and in particular, a downlink control signal structure for efficiently transmitting a downlink control signal required for uplink / downlink data transmission, and a downlink control signal thereof. It is related to the transmission method of.

In a multi-carrier mobile communication system, a base station transmits a downlink data packet to a user device (hereinafter, referred to as "UE") belonging to one or a large number of cells. On the other hand, a large number of UEs can exist in a cell, and each UE cannot know when and in what format a data packet is transmitted to itself. Therefore, when a base station transmits a downlink data packet to a specific UE, the data transmission includes the ID of the UE that receives the data packet, the time-frequency region in which the data packet is transmitted, the coding rate / modulation method, and the like. Necessary information such as format and HARQ related information shall be transmitted through the downlink at each downlink data packet transmission.

On the other hand, in order to enable data packet transmission over the UE uplink, the base station has the ID of the UE that is permitted to transmit the data packet, and the uplink time-frequency region in which the UE can transmit the data packet. , Data transmission format including coding rate / modulation method, and necessary information such as HARQ related information must be transmitted through the downlink at each uplink data packet transmission.

Further, in the case of uplink data packet transmission, the base station must transmit the reception success / absence (ACK / NAK) information for each data packet transmitted by the UE to the corresponding UE by downlink, and the uplink of each UE is performed. Power control information must be transmitted downlink to each UE to maintain the link transmit and receive power at an appropriate level.

Hereinafter, for convenience of explanation, as described above, all information transmitted through the physical hierarchy in the downlink for data transmission / reception between the base station and the UE is referred to as "downlink control information". A signal that transmits such information is called a "downlink control signal".

More specifically, the downlink control information can be divided as follows.

1. Scheduling information for uplink / downlink data (1) Category A information: UE ID for sending / receiving data packets, frequency-time domain allocation information for transmitting data packets, etc. (2) Category B information: Data transmission format such as code rate / modulation method, HARQ related information, etc. 2. Information unrelated to downlink data (1) ACK / NAK information, power control information, etc. In order to operate the system efficiently, it is necessary to effectively multiplex the downlink control signal that transmits the above control information with the data packet and other downlink signals in the downlink time-frequency resource. ..

Hereinafter, a general downlink signal transmission method will be described.

The downlink data packet transmission method can be roughly divided into two methods, a localized allocation method and a distributed allocation method. The regional allocation method is a method in which data for one UE is transmitted in a relatively limited frequency band through a continuous subcarrier, and the base station scheduler is a downlink radio channel reported by each UE in the cell. The cell transmission efficiency can be improved by selecting a band having a good radio channel frequency response for each UE based on the frequency response of the above and transmitting data. For reference, even in the regional allocation method, in some cases, the base station scheduler can transmit data to one UE through continuous subcarriers in a discontinuous band on two or more frequencies. ..

On the other hand, the distributed allocation method is a method in which data for one UE is intentionally scattered and transmitted over a relatively wide frequency band within the system band, and the base station scheduler estimates the downlink radio channel frequency response to the UE. It can be used when it is difficult to apply the frequency response to downlink data packet scheduling, and by transmitting one data packet through a wide frequency band, frequency diversity gain is obtained and the reception performance of the data packet is obtained. Can be improved.

The downlink signal transmission method described below supports all regional allocation methods and distributed allocation methods for downlink data packet transmission, and data packets transmitted by different methods are multiplexed within one transmission time. Suppose that it may happen.

Hereinafter, for convenience of explanation, the basic time-frequency domain unit for data packet transmission is referred to as a resource block (RB), and one RB has a large number of subcarrier regions over a large number of OFDM symbols. Is assumed to contain.

FIG. 1 is a diagram showing a structure in which a downlink signal is transmitted by a regional allocation method.

As shown in FIG. 1, for example, suppose there are 288 subcarriers used for downlink data transmission in the system band, and one RB contains 12 subcarriers over 6 OFDM symbols. There will be 24 RBs for every 6 OFDM symbols in the downlink. At this time, generally, when the RB for regional allocation is LVRB (localized virtual RB), the LVRB is composed of 12 continuous subcarriers as shown in FIG. 1, and is shown in FIG. As shown in the example of assigning LVRB to the first UE (UE1), regional allocation can be realized by transmitting data to one UE through continuous LVRB.

In addition, as shown in the example in which LVRB is assigned to UE (UE2) No. 2 in Fig. 1, data is transmitted to one UE through each LVRB that is separated from each other in the frequency domain, resulting in the effect of distributed allocation. And the frequency diversity gain can be obtained.

2A and 2B are diagrams showing a structure in which a downlink signal is transmitted by a distributed allocation method.

Unlike the case of Fig. 1, when the RB for distributed allocation is DVRB (distributed virtual RB), the DVRB is divided into frequency domain or time-frequency domain as shown in Fig. 2A or Fig. 2B. It is composed of carrier waves. In this case, as shown in the examples of FIGS. 2A and 2B, even if the data of one RB or a small number of RBs is transmitted to one UE, the DVRB is used to cover a wide band through a discontinuous subcarrier. By being scattered and transmitted, distributed allocation can be realized.

As described above, among the downlink signal transmission methods, the method for data packet transmission is clearly defined as a regional allocation method, a distributed allocation method, and a transmission method through a combination thereof. There is no clear specification for a method of efficiently transmitting the downlink control signal as described above together with such a downlink data packet by using regional allocation and / or distributed allocation, etc., and the downlink is down. Discussions on efficient transmission methods are required after considering each characteristic of link control signals, such as control signals that include scheduling information for downlink data transmission and control signals that include scheduling information for uplink data transmission. There is.

<p> The present invention is for solving the above-mentioned problems, and an object of the present invention is a method for efficiently using the above-mentioned regional allocation method and distributed allocation method in transmitting a downlink control signal. Is to provide.</p>

<p> A method in which a base station transmits a downlink control signal including scheduling information for uplink / downlink data transmission according to an embodiment of the present invention for achieving the above-described object is the downlink data to a predetermined UE. When there is transmission, the regional allocation method is used for the downlink control signal transmission including the scheduling information for the uplink data transmission of the UE, and the distributed allocation method is used for the other downlink control signal transmission. It is characterized by doing.</p><p> In this case, the distributed allocation method is used for one or more OFDM symbols from the first available OFDM symbol, and the downlink control signal is multiplexed using the regional allocation method from the one or more OFDM symbols onward. It can be converted and transmitted. Further, the downlink control signal assigned by the distributed allocation method is determined to match the size of the resource block (RB) used for the uplink / downlink data transmission or an integral multiple of the size. It is distributed and assigned in groups of a predetermined number of continuous subcarriers.</p><p> Further, the downlink control signal transmitted using the regional allocation method is transmitted through a part of a resource block in which downlink data is transmitted to the UE, and is used in the distributed allocation method. The number of the above symbols and the number of symbols used in the regional allocation method are transmitted to all UEs in the cell through the downlink common channel.</p><p> Further, when the downlink control signal transmitted using the distributed allocation method is scheduling information for downlink data transmission to a predetermined UE, the downlink control signal is scheduled for uplink data transmission to the UE. The information can include an indicator indicating whether the downlink data for the UE is transmitted within the resource area to which the downlink data is transmitted, and the scheduling information for the uplink / downlink data transmission included in the downlink control signal. Indicates a group of resource blocks used for the scheduled uplink / downlink data transmission.</p><p> On the other hand, among the subcarriers in one or more OFDM symbols set to enable the downlink control signal transmission, the downlink data may be transmitted to the subcarrier to which the downlink control signal is not transmitted. The base station can broadcast the amount of time / frequency resources at which the downlink control signal is transmitted to the one or more symbols set to enable transmission of the downlink control signal. .. At this time, the base station and all UEs in the cell receiving service by the base station have a transmission pattern of the downlink control signal determined in advance by the amount of time / frequency resources in which the downlink control signal is transmitted. You may also know the information. As a result, the UE becomes aware of the downlink signal region in which the downlink control signal should be received and the downlink signal region in which the downlink data should be received.</p><p> Here, the transmission pattern of the uplink control signal, which is predetermined by the amount of time / frequency resources in which the downlink control signal is transmitted, is determined by the amount of time / frequency resources in which the downlink control signal is transmitted. The downlink control signal can be transmitted in the order of the first available OFDM symbol to the next OFDM symbol, and the base station can use the amount of time / frequency resources in which the downlink control signal is transmitted and the down. It is possible to broadcast the sum of the amount of time / frequency resources in which nothing is transmitted within the OFDM symbol in which the link control signal is transmitted.</p><p> Further, the base station may broadcast the amount information of the time / frequency resource at which the downlink data is transmitted to the one or more OFDM symbols set so as to enable the downlink control signal transmission. it can.</p><p> On the other hand, the number of data packets that can be transmitted by uplink within one transmission time interval (TTI) and the number of downlink data packets can be combined with the uplink data packets and downlink data packets that can be transmitted within one TTI. The number of scheduling information for the uplink data transmission, the number of scheduling information for the downlink data transmission, and these, which can be limited to be smaller than the maximum number of each, or can be transmitted within one transmission time interval (TTI). The total number of data can be limited to be smaller than the maximum number of scheduling information that can be transmitted within the TTI, and transmission is performed using either the distributed allocation method or the regional allocation method for each UE. The information about whether the downlink control signal should be received is predetermined in a time longer than one TTI, and the base station needs the information for each UE when it is needed for each UE. Each can be notified in advance through RRC signaling.</p><p> In addition, each UE is transmitted by the regional allocation method only in a predetermined resource area where the downlink radio channel quality is reported to be good through the downlink radio channel quality information reported to the base station by itself. The downlink control signal is searched for, or the base station uses the regional allocation method to inform all UEs in the cell of information on the resource area in which the downlink control signal is transmitted by a bitmap method. .. Further, for each UE, the downlink control signal transmission format, that is, the coding rate, the modulation method, the number of subcarriers used, and the like are specified in advance for a longer time than one TTI, and the base station. Can notify the downlink control signal transmission format for each UE in advance through RRC signaling or the like when necessary.</p>

<p> According to the downlink control signal transmission method according to the embodiment of the present invention, the transmission efficiency of the regional allocation method and the diversity gain of the distributed allocation method are taken into consideration in consideration of the advantages and disadvantages of the regional allocation method and the distributed allocation method. Can be acquired.</p><p> Further, in the downlink control signal transmission structure for transmitting using the regional allocation method and the distributed allocation method described above, the transmission signal by the general distributed resource allocation method is arranged at the front end of one transmission time interval (TTI). By arranging the transmission signal by the regional allocation method at the rear end of the corresponding TTI, it is possible to flexibly deal with the amount of the control signal. Further, the reception efficiency can be increased by including an indicator for the control information included in the regional allocation method in the portion of the distributed resource allocation method.</p>

<figref num="1">It is a figure which showed the structure which transmits the downlink signal by the area allocation system.</figref><figref num="2A">It is a figure which showed the structure which transmits the downlink signal by the distributed allocation system.</figref><figref num="2B">It is a figure which showed the structure which transmits the downlink signal by the distributed allocation system.</figref><figref num="3A">It is a figure which showed the structure which transmits the downlink control signal to the 1st OFDM symbol which can be used by one Embodiment of this invention by the distributed allocation system.</figref><figref num="3B">It is a figure which showed the structure which transmits the downlink control signal to the 1st OFDM symbol which can be used by one Embodiment of this invention by the distributed allocation system.</figref><figref num="4">It is a figure which showed the structure which transmits the downlink control signal by the regional allocation system after the OFDM symbol by the distributed allocation system by one Embodiment of this invention.</figref><figref num="5">It is a figure which showed the structure which transmits the downlink data to the resource block which the control signal is not transmitted in the OFDM symbol for downlink control signal transmission by one Embodiment of this invention.</figref><figref num="6">4 is a diagram showing a comprehensive structure for transmitting a downlink control signal according to an embodiment of the present invention in relation to FIGS. 4 and 5.</figref><figref num="7">It is a figure which showed the magnitude change of the time-frequency resource required for scheduling signal transmission by different scheduling information transmission formats.</figref><figref num="8A">It is a figure which showed the example which each UE which received the designation of the scheduling information transmission format different from each other by one Embodiment of this invention searches a scheduling signal.</figref><figref num="8B">It is a figure which showed the example which each UE which received the designation of the scheduling information transmission format different from each other by one Embodiment of this invention searches a scheduling signal.</figref><figref num="9">It is a figure which showed the example which each UE which received the designation of each transmission type searches the scheduling signal when the scheduling information transmission styles which are different from each other have different priorities by one Embodiment of this invention.</figref>

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. The detailed description disclosed below, along with the accompanying drawings, is intended to illustrate exemplary embodiments of the invention and does not represent the only embodiment in which the invention is practiced. For example, in the following description, the scheduling signal will be mainly described as the downlink control signal, but this can be applied to other downlink control signals unless otherwise specified.

The following detailed description includes specific details to provide a complete understanding of the present invention. However, those skilled in the art will appreciate that the present invention can be practiced without such specific details. In some cases, in order to avoid obscuring the concept of the present invention, known structures and devices are omitted or shown in the form of block diagrams centered on the core functions of each structure and device. In addition, the same components throughout the present specification will be described using the same drawing reference numerals.

Hereinafter, a method of multiplexing the downlink control signal by appropriately using all of the regional allocation method and the distributed allocation method according to the embodiment of the present invention will be described.

Two methods, a regional allocation method and a distributed allocation method, are considered as methods for transmitting the downlink scheduling signal, which is a control signal including scheduling information for the downlink data, in the same context as in the case of the downlink data packet transmission described above. can do.

For example, when transmitting a data packet to a predetermined UE, if the downlink data packet is transmitted to a specific frequency band determined by the regional allocation method to have good downlink radio channel characteristics for that UE, the downlink data packet is transmitted within the same band. By transmitting a scheduling signal for such downlink data packet transmission to (that is, a part of the band in which the downlink data packet is transmitted), the reception performance of the scheduling signal can also be improved.

On the other hand, for UEs whose downlink radio channel characteristics are difficult to estimate or which are difficult to reflect in downlink data packet transmission, the scheduling signal is distributed over a wide band in the same way as when data packets are transmitted by the distributed allocation method. The frequency diversity gain can be obtained in the reception of the scheduling signal by transmitting the data. It is also necessary to transmit the scheduling signal corresponding to the downlink data packet transmission by the distributed allocation method regardless of the transmission method of the downlink data packet due to other system operation requirements.

On the contrary, a distributed allocation method is generally suitable as a method for transmitting a downlink scheduling signal including scheduling information for uplink data transmission. This is because it is difficult for the base station to estimate the downlink radio channel characteristics of a given UE if downlink data packet transmission is rare for a given UE and only uplink data packet transmission from that UE is frequent. Is. However, if a base station transmits a downlink data packet to that UE in a regional allocation manner at a time when a given UE should transmit the uplink data packet, the base station knows the downlink radio channel characteristics for that UE. Therefore, in this case, it is advantageous to transmit the downlink scheduling signal for the uplink data of the UE within the frequency band in which the downlink data packet is transmitted, because higher transmission efficiency can be obtained.

Therefore, in one embodiment of the present invention, in consideration of the above-mentioned advantages and disadvantages, all of the regional allocation method and the distributed allocation method in the downlink control signal transmission including the scheduling information for the uplink / downlink data packet transmission. If there is downlink data transmission to a specific UE, use the regional allocation method for downlink control signal transmission including scheduling information for the uplink data transmission of that UE, and use the distributed allocation method in other cases. We propose a method of multiplexing and transmitting downlink control signals using this method.

In one embodiment of the present invention in which a more specific downlink control signal transmission structure is considered, a scheduling signal is transmitted to each UE by downlink, and a basic time interval in which data packets can be transmitted is set by TTI (transmit time interval). When defined as, from the first OFDM symbol in one TTI, or from the second OFDM symbol if the first OFDM symbol is used for another purpose (hereinafter "from the first available symbol"). ) Use the distributed allocation method for downlink scheduling signal transmission in one or more OFDM symbol sections up to a predetermined OFDM symbol section, and use the regional allocation method if necessary from the subsequent OFDM symbols. We propose to transmit the link control signal.

In such an embodiment of the present invention, the downlink control signal transmission method is generally a distributed allocation method, and the regional allocation method is a line in a special case where downlink data is transmitted to the corresponding UE. However, by having the downlink control signal transmission structure for each OFDM symbol as described above, the downlink control signal can be multiplexed more flexibly. Further, as explained below, the presence / absence of control signals multiplexed by the regional allocation method is located in the first half of one TTI, and the indicator of the control signal multiplexed by the distributed allocation method is set. By using and expressing, the amount of control signals multiplexed by the distributed resource allocation method can be reduced.

3A and 3B are diagrams showing a structure in which a downlink control signal is transmitted in a distributed allocation manner to the first OFDM symbol available according to an embodiment of the present invention.

As described above, when a downlink control signal is transmitted by a distributed allocation method from the first OFDM symbol available according to one embodiment of the present invention to a predetermined symbol interval, the uplink or the corresponding TTI is transmitted within one TTI. A large number of scheduling signals are distributed and assigned and multiplexed with one or many OFDM symbols so that scheduling information for a large number of data packets transmitted on the downlink can be transmitted.

Specifically, as shown in FIG. 3A, each scheduling signal such as the control signal 1 and the control signal 2 is distributed in units of subcarriers, or as shown in FIG. 3B, a large number of continuous signals in the frequency domain. It is distributed in groups formed by subcarriers. FIG. 3B shows that four continuous subcarriers in the frequency domain form a group.

In particular, when the downlink control signal is distributed in units of subcarrier groups as shown in FIG. 3B in the frequency region, the number of subcarriers in the group is the number of subcarriers assigned to one RB in which the data packet is transmitted. When the number is the same as the number (for example, 12 subcarriers in the case of LVRB of FIG. 1) or an integral multiple thereof, the scheduling signal is used for data packet transmission according to a preferred embodiment of the present invention described below. When occupying a part of the RB area, there is an advantage that the amount of decrease in the actual RB size can be uniformly adjusted.

FIG. 4 is a diagram showing a structure in which a downlink control signal is transmitted by a regional allocation method after the OFDM symbol by a distributed allocation method according to an embodiment of the present invention.

According to one embodiment of the present invention as described above, among the OFDM symbols in one TTI, the OFDM symbols transmitted after the OFDM symbol used for transmission by the distributed allocation method of the scheduling signal are regional of the scheduling signal. It is transmitted using the allocation method. In such an arbitrary TTI, the downlink control signal transmission by the regional allocation method to a specific UE (for example, UE1 in FIG. 4) is the downlink data packet transmission through the LVRB to the UE within the TTI. It can only be applied at certain times. At this time, as shown in FIG. 4, the scheduling signal is transmitted using a part of each LVRB in which the downlink data packet for the corresponding UE is transmitted.

On the other hand, the scheduling signal transmission by the distributed allocation method can be used for all the scheduling information transmission for the downlink data packet transmission using LVRB and DVRB, and the scheduling signal transmission by the regional allocation method is the downlink data using LVRB. Used only for scheduling information transmission for packet transmission.

Further, in one embodiment of the present invention as shown in FIG. 4, how many OFDM symbols are used for scheduling signal transmission by the distributed allocation method, and how many OFDM symbols are used for scheduling signal transmission by the regional allocation method. This can be announced on a TTI-by-TTI basis, periodically or as needed, through a downlink common channel that all UEs in the cell can receive.

According to the above-described embodiment of the present invention, basically, the scheduling information for the uplink data packet transmission is transmitted through the control signal by the distributed allocation transmission method. However, when transmitting a downlink data packet to an arbitrary UE within an arbitrary TTI and at the same time transmitting scheduling information for uplink data packet transmission to the same UE, that UE is transmitted through a control signal by a regional allocation transmission method. While transmitting the scheduling information for the downlink data packet transmitted to the UE, the scheduling information for the uplink data packet can be transmitted to the RB area for transmitting the data packet to the UE.

In the above scheduling signal transmission method, the information transmitted through the scheduling signal transmitted by the distributed allocation method includes at least category A scheduling information described in relation to the prior art for downlink data packet transmission. For uplink data packet transmission, all or part of Category B scheduling information may be included in addition to Category A information.

Further, the scheduling signal transmitted by the regional allocation method can include all or a part of the category B scheduling information in addition to the category A information.

On the other hand, in a preferred embodiment of the present invention, the scheduling information of the control signal transmitted by the distributed allocation method is either the scheduling information for downlink data packet transmission or the scheduling information for uplink data packet transmission. It can include an indicator that tells if it is.

Further, when the scheduling information of the scheduling signal transmitted by the distributed allocation method is the scheduling information for the downlink data packet transmission, the scheduling information for the uplink data transmission for the corresponding UE is the downlink data for the UE. It can contain an indicator that indicates whether the packet is transmitted within the RB area where it is transmitted. In this case, as can be seen through the downlink control signal structure according to the embodiment of the present invention as shown in FIG. 4, the OFDM symbol by the preceding distributed allocation method corresponds to the OFDM symbol section by the subsequent regional allocation method. By notifying the UE of the presence or absence of scheduling information for the uplink data packet transmission transmitted to the UE, the corresponding UE can easily search for the scheduling information. Further, through this, the amount of control signals transmitted by the distributed resource allocation method can be reduced.

Category A scheduling information transmitted to any UE, on the other hand, can be used to inform that UE of each RB used to transmit downlink data packets, or to allow that UE to transmit uplink data packets. It can contain packet information to inform each RB. That is, when there are N RBs in one TTI, each bit in the N-bit bitmap information is mapped to each RB existing in the TTI according to a predetermined rule, and each bit is It can represent information that tells if the RB in question is assigned to the data.

At this time, when there are many RBs in one TTI, a large number of bits are required to inform the availability of each RB through bitmap information, which can increase the overhead of scheduling information. .. Therefore, in one embodiment of the present invention, in this case, each RB in one TTI is grouped by a predetermined number, for example, M according to a predetermined rule, and scheduled instead of the scheduled RB. By notifying the RB group as bitmap information, the overhead of scheduling information can be reduced. Here, M is an integer of 2 or more, and one RB group can include RBs different from each other in the frequency domain and the time domain.

With the above method, the UE basically decodes the scheduling information for all downlink control signal positions that can be transmitted by the regional allocation or distributed allocation method in order to read the scheduling information transmitted to itself. If there is scheduling information including its own ID, it knows that the scheduling information is the scheduling information transmitted to itself, and receives downlink data packets or uplink data according to that information. Packets can be sent. In this case, since the amount of information that the UE should try to read increases, which can be a burden, it is preferable to limit the downlink control signal that the UE should try to read, which will be described later. To.

On the other hand, in one embodiment of the present invention, when the downlink control signal is not actually transmitted to the OFDM symbol set so that the downlink control signal can be transmitted, the downlink data is transmitted to the corresponding symbol. It is proposed and will be described below.

FIG. 5 is a diagram showing a structure in which downlink data is transmitted to a resource block in which a control signal is not transmitted within an OFDM symbol for downlink control signal transmission according to an embodiment of the present invention.

Since the number of downlink and uplink data packets scheduled within one TTI can vary from TTI to TTI, the number of scheduling signals transmitted on the downlink can vary from TTI to TTI. However, for example, when a specific number of downlink OFDM symbols are always reserved for scheduling signal transmission and used exclusively, in TTI where a small number of scheduling signals are transmitted, the scheduling signals are actually scheduled within the reserved OFDM symbols. Will waste time-frequency resources outside the frequency domain in which it is transmitted.

Therefore, in one embodiment of the invention as described above, even within one or more OFDM symbols configured to allow scheduled signal transmission, it is down to the time-frequency region where the scheduled signal is not actually transmitted. A method for transmitting link packet data is proposed, and in this case, the downlink transmission signal structure is as shown in FIG.

In Figure 5, one TTI consists of 6 OFDM symbols, the first of which is configured to be used for UE1 to UE3 downlink control signal transmission in a distributed allocation scheme, but within that OFDM symbol. However, an example is shown in which all areas other than the area where the scheduling signal by the distributed allocation method is actually transmitted are allocated to the downlink data packet transmission for UE1.

At this time, the size of the frequency-time resource allocated to data transmission through substantially one downlink RB varies from TTI to TTI depending on whether a part of the RB is used for scheduling signal transmission by the distributed allocation method. obtain. That is, as can be seen through the example of FIG. 5, UE1 is a scheduling signal in which a part of the downlink RB allocated for the data packet transmitted to itself is transmitted to other UEs (UE2 and UE3). Without knowing the fact that it is used by, it is not possible to know exactly what area in the scheduled RB the data transmitted to itself will be transmitted, so that the data packet can be received accurately. It disappears.

Therefore, in one embodiment of the invention, any region within each OFDM symbol configured for each UE in the cell to be used for scheduling signal transmission within any TTI is actually used for scheduling signal transmission. In order to know, we propose a method in which the base station informs each UE in the cell of the number of scheduling signals transmitted in each TTI (or if necessary).

In this case, a rule can be predetermined so that the region in which the scheduling signal is transmitted is determined by the number of scheduling signals actually transmitted in each TTI. Therefore, for all UEs in the cell, not only the scheduling signal transmitted to itself but also the scheduling signal transmitted to other UEs is transmitted to other UEs through the number of scheduling signals notified by the base station. You will know what region to use, and thereby what region the time-frequency region actually used for data transmission in each downlink RB is.

More specifically, in one embodiment of the present invention, as the number of scheduled signals to be transmitted increases, each OFDM symbol set to be used for scheduling signal transmission is set to be sequentially used. I suggest that. That is, for example, if the first OFDM symbol in the TTI is set to be used for scheduling signal transmission, as the number of scheduling signals increases, the scheduling signal with the first OFDM symbol according to a predetermined rule. Time available for transmission-means the method of starting to use the next OFDM symbol after using all the frequency resources. An example of sequentially assigning OFDM symbols for control signal transmission in this way is shown in FIG. 6 described below, and the specific structure thereof will be described later.

At this time, since the number of scheduling signals actually transmitted can change for each TTI, the scheduling signal transmitted for each TTI through a physical channel separate from the scheduling signal so that all UEs in the cell can receive it. It is preferable that the number is broadcast.

On the other hand, the scheduling signal needs to be transmitted with a large power in order to guarantee the reception performance in the UE far away from the base station, and at this time, the subcarrier is the scheduling signal in each OFDM symbol in which the scheduling signal is transmitted. Even if it cannot transmit, there may be a subcarrier that cannot transmit anything because the scheduling signal consumes most of the maximum transmission power of the base station.

In this case, in one embodiment of the invention, not only in the area (or number of scheduling signals) used by the base station for scheduling signal transmission as described above, but also within each OFDM symbol in which the downlink control signal is transmitted. By broadcasting information that includes the entire subcarrier region (or the number of scheduling signals corresponding to that region) that does not transmit anything, each UE is used for data transmission within the OFDM symbol in which the scheduling signal is transmitted. You can know the part.

In another method according to an embodiment of the present invention in which the same effect can be obtained, as described above, what is the area where the base station transmits information to the area where the scheduling signal is transmitted or where the scheduling signal is transmitted? Instead of broadcasting information for areas that are not transmitted, the area information actually used for data transmission at that TTI can be broadcast directly within each OFDM symbol in which the scheduling signal is transmitted.

Therefore, the scheduling signal area (number) information in the following description means the area information in which the scheduling signal is transmitted, the area information in which nothing is transmitted, or the area information used for data transmission.

On the other hand, as described above, instead of the base station broadcasting the scheduling signal area information to each UE in the cell, the scheduling signal area information is included in the downlink data packet scheduling signal for each UE that transmits data in the downlink. It is also possible to transmit. That is, what you really need to know at a given TTI how long-frequency domain the scheduling signal uses and how long-frequency domain the data is transmitted is in the downlink. Since each UE receives data, the same purpose can be achieved by including the scheduling signal domain information in the information transmitted by the downlink scheduling signal for each UE. In this way, the scheduling signal area information is channel-coded together with other scheduling information, so that there is an advantage that a coding gain can be further obtained. However, the same information can be transmitted to many UEs by one TTI. Since each is transmitted, the resulting performance gain may vary depending on the number of scheduling signals transmitted to one TTI, the channel coding method of the scheduling signals, and the like. When transmitting the scheduling signal area information together with the scheduling information, it is particularly preferable to include the scheduling signal area information in the above-mentioned category A information.

Also, in one embodiment of the invention, the maximum number of downlink data packets that can be scheduled within a single TTI to reduce the UE scheduling signal reception load and efficiently use the downlink time-frequency resources. And the maximum number of uplink data packets can be limited to be smaller than the maximum number that can actually be transmitted.

In another method according to an embodiment of the present invention for obtaining the same result, it is possible to limit the number of scheduling information for downlink data packets and scheduling information for uplink data packets that can be transmitted within one TTI. it can.

Separately from this, it is possible to limit the total number of scheduling information for uplink data packets and scheduling information for downlink data packets that can be transmitted within one TTI. Such a maximum value is transmitted from the base station to the UE through RRC signaling in the upper layer.

In particular, in a method in which the scheduling signal by the distributed allocation method and the scheduling signal by the regional allocation method proposed in one embodiment of the present invention are used together, the method of notifying each UE of the number of the scheduling signals and the number of scheduling signals can be determined. The limiting method may be applied only to scheduling signals by the distributed allocation method.

In this method, when the base station broadcasts the number of scheduling signals by the distributed allocation method for each TTI, each UE has a predetermined time-frequency domain so that the scheduling signals by the distributed allocation method are transmitted according to the number. If there is scheduling information including its own ID, it will follow the scheduling information.

However, since the scheduling signal by the regional allocation method is transmitted in the time-frequency domain in each RB in which the downlink data packet is transmitted, the UE is basically a possible regional allocation method in all RBs. Scheduling by the signal transmission area should be attempted to receive. Moreover, if the UE should try to receive all the scheduling signals by the distributed allocation method and the regional allocation method, the burden becomes larger. In order to reduce the burden of receiving such a scheduling signal of the UE, it is proposed to apply the following method in one embodiment of the present invention.

The first method determines whether each UE should receive the scheduling signal by the distributed allocation method or the scheduling signal by the regional allocation method, and the base station informs each UE of this information. It is a method.

Whether it is advantageous to transmit the scheduling signal to a predetermined UE by the distributed allocation method or the regional allocation method changes relatively frequently, such as the movement speed and service characteristics of the UE. This information does not need to be transmitted frequently, as it depends on factors that do not. Therefore, this information is transmitted from the base station to each UE through higher layer signaling without using a separate physical layer signal. At this time, any UE attempts to receive only the scheduling signal transmitted by the method specified by itself among the distributed allocation method and the regional allocation method.

The second method is that the UE has the best channel quality, especially for each scheduling signal transmitted by the regional allocation method, by referring to the downlink radio channel quality information that the UE reported to the base station. A method that attempts to receive scheduling signals by the regional allocation method only for one reported RB (or RB group) or a specific number of RB (or RB group) regions in the order in which channel quality is reported to be good. is there.

Generally, each UE in the cell will report downlink radio channel quality information to the base station periodically or as needed to aid in the base station's downlink data packet scheduling. Therefore, when a base station transmits a downlink data packet to a given UE in a cell, it refers to the downlink radio channel quality reported by that UE and the best channel quality RB (or RB group), Alternatively, it operates in a method that always uses one RB (or RB group) out of a specific number of RBs (or RB groups) selected in order of channel quality, and depends on the regional allocation method within the RB (or RB group) area. When the scheduling signal is transmitted, the UE can receive the scheduling signal by the regional allocation method transmitted to itself by the method described above.

At this time, the downlink radio channel quality report information that each UE should refer to is limited to the most recently reported information, a specific number of recently reported information, or the information reported within a specific time from the present. In each case, the base station should properly define the RB (or RB group) to be used for downlink radio data packet transmission. In addition, the base station assigns each UE a range of radio channel quality information that the UE should refer to or how many RBs (or RB groups) for one radio quality information by a regional allocation method through higher-level signaling. It can transmit what should be considered for scheduling signal reception.

The third method is a method in which the base station informs all UEs in the cell for each TTI by the bitmap method of the RB (or RB group) to which the scheduling signal by the regional allocation method is transmitted.

That is, if there are N RBs (or RB groups) in one TTI on the downlink, each bit of the N-bit bitmap information is mapped to each RB (or RB group), and each bit corresponds. Can represent information that informs the RB (or RB group) of whether or not a scheduling signal by the regional allocation method is transmitted. Therefore, by reading this bitmap information for each TTI, the UE does not have to try to receive the scheduling signal by the regional allocation method for all RBs (or RB groups), but actually by the regional allocation method. It is possible to attempt to receive the scheduling signal by the regional allocation method only for the RB (or RB group) to which the scheduling signal is transmitted.

In a more specific embodiment of the present invention, this bitmap information is encoded together with the number information of the scheduling signals by the above-mentioned distributed allocation method and broadcast for each TTI.

In the fourth method, the downlink scheduling signal for the data transmitted on the downlink is transmitted only by the distributed allocation method, and the downlink scheduling signal for the data transmitted on the uplink has no data transmitted on the downlink. Sometimes it is transmitted by the distributed allocation method, and when there is data transmitted by the downlink, it is transmitted by the regional allocation method within the RB (or RB group) where the data is transmitted.

One or more of the above four methods can be applied to the system at the same time, and the burden on the UE scheduling signal reception can be reduced.

FIG. 6 is a diagram showing a comprehensive structure for transmitting a downlink control signal according to the above-described embodiment of the present invention in relation to FIGS. 4 and 5.

In FIG. 6, one TTI is composed of 6 OFDM symbols, and a downlink pilot signal is transmitted to some subcarriers of the 1st OFDM symbol and the 5th OFDM symbol. In addition, in the first OFDM symbol, the number of scheduling signals by the distributed allocation method transmitted to the TTI, or in addition to this, the bitmap information for the scheduling signals by the regional allocation method is distributed in units of subcarriers. Will be broadcast.

The distributed allocation scheduling signal is distributed and transmitted from the first OFDM symbol at the subcarrier level, and in the example of FIG. 6, up to a part of the second OFDM symbol is used for the distributed allocation scheduling signal transmission. ing. Further, in the example of FIG. 6, the downlink data packet scheduling signal for UE1 is transmitted by the regional allocation method through a part of the RB in which the downlink data packet is transmitted to UE1.

On the other hand, in one embodiment of the present invention, a method for supporting the variability of the scheduling information transmission format is proposed, which will be described below.

FIG. 7 is a diagram showing changes in the magnitude of time-frequency resources required for scheduling signal transmission by different scheduling information transmission formats.

The downlink / uplink scheduling information for each UE transmitted on the downlink for each TTI is transmitted in the form of a scheduling signal through appropriate coding and modulation. For convenience of explanation, the coding rate and the modulation method applied to the scheduling information are referred to as "scheduling information transmission format" or "scheduling signal transmission format".

At this time, the radio channel status of each UE in the cell is different from each other, and can vary greatly depending on the distance of the UE from the base station and the presence or absence of obstacles. Therefore, it is inefficient to apply the same transmission format for scheduling information transmission to all UEs in the cell, and it is preferable to apply different transmission formats depending on the radio channel environment of each UE. When the transmission format applied to the scheduling information changes, the amount of time-frequency resources required to actually transmit the corresponding scheduling signal may change. Figure 7 shows the amount of time-frequency resources required by these different scheduling information transmission formats.

On the other hand, when the transmission format applied to the scheduling information transmitted by the base station to a predetermined UE is arbitrarily selected for each TTI, the UE receives the scheduling signal for all possible transmission formats for each TTI. You should try. Hereinafter, this will be described in more detail with an example of a 3GPP LTE system.

In a 3GPP LTE system, a large number of CCEs (control channel elements) are transmitted through the first n OFDM symbols of each subframe. Here, the CCE can be considered as a unit of control information transmission, and one CCE is arranged continuously or distributed in the time-frequency domain. Each CCE is composed of a specific number of REs (Resource Elements), and the PDCCH transmitted to any UE in any subframe is mapped to one or more CCEs and transmitted. At this time, the coding rate for the PDCCH is determined by how many CCEs the PDCCH is transmitted through. That is, for example, if the code rate when a specific amount of PDCCH is transmitted through one CCE is 3/4, the code rate when the same amount of information PDCCH is transmitted through two CCEs. Is 3/8, the code rate when PDCCH with the same amount of information is transmitted through 4 CCEs is 3/16, and the code rate when PDCCH with the same amount of information is transmitted through 8 CCEs is 3. Can be adjusted to be / 32.

Each CCE that should confirm the existence of PDCCH transmitted to itself is assigned to the UE in advance. For example, suppose that PDCCHs that transmit predetermined information are transmitted at code rates of 3/4, 3/8, 3/16, and 3/32 through 1, 2, 4, and 8 CCEs. , If a given terminal is assigned to check from CCE 1 to CCE 16, the terminal has a PDCCH of 3/4, 3 / for 16 CCEs per subframe. Assuming that transmission is performed at a code rate of 8, 3/16, or 3/32, decoding should be performed for each CCE, so a maximum of 16 + 8 + 4 + 2 = 30 decryptions should be performed. You must do this and check for the existence of the PDCCH transmitted to you. This is based on the assumption that the mapping of PDCCH to CCE consists of a tree structure only through adjacent CCEs, and the more free the PDCCH mapping, the greater the number of decryptions the UE should do.

In order to reduce the reception operation load of such UE, specifically, as in the case of 3GPP LTE system, the UE reduces the number of decodings required for PDCCH reception, and reduces problems such as UE battery consumption. In order to achieve this, in one embodiment of the present invention, a method of designating a scheduling information transmission format applied to scheduling signal transmission is proposed for each UE. At this time, as the scheduling information transmission format applied to the scheduling signal transmission for each UE, only a specific format can be specifically specified, but the range of the coding rate or the CCE group in which each UE tries to receive PDCCH It is also possible to use a method of specifying the size and the like.

In particular, in one embodiment of the present invention, a method is proposed in which the maximum coding rate of the scheduling information transmission formats is specified for each UE, or the smallest CCE group size is specified.

When notifying the maximum code rate or the minimum CCE size for each UE in this way, even if a specific UE is assigned to check from the 1st CCE to the 16th CCE in the above example, it is applicable. When a UE informs that the maximum code rate at which it tries to receive PDCCH is 3/8, or that the minimum CCE group size is 2 CCEs, the corresponding UE is 1 CCE. Since it is not necessary to decode (that is, when the code rate is 3/4), it is only necessary to perform decoding up to 8 + 4 + 2 = 14 times.

In this way, when the method of specifying the maximum code rate or the minimum CCE group size for each UE is used, it has the following advantages as compared with the method of notifying the minimum code rate or the maximum CCE group size. be able to.

For example, in the case of a UE in which the maximum coding rate is specified to be 3/8 as in the above example, the subsequent channel situation deteriorates and the scheduling information is encoded with a low code rate such as 3/16. Even if it is transmitted, it is possible to detect the corresponding scheduling information. However, in the case of a UE with a minimum code rate of 3/8, if the subsequent channel situation deteriorates and the scheduling information is encoded and transmitted at a low code rate such as 3/16, it will be transmitted. , It becomes difficult to detect the corresponding scheduling information. That is, the method of specifying the maximum code rate or the minimum CCE group size applied to the scheduling information transmission as in the present embodiment is compared with the method of specifying the minimum code rate or the maximum CCE group size. Therefore, it is possible to more efficiently deal with the application of a low code rate due to the channel deterioration later.

For the same purposes as the embodiments described above, in another embodiment of the invention, the maximum code rate (or the smallest CCE group size) and minimum code for each UE at the base station to attempt to receive PDCCH. It is suggested to inform the conversion rate (or the largest CCE group size).

That is, even if one UE is assigned to check from CCE 1 to CCE 16 as in the example above, in addition to this, the maximum code rate at which that UE attempts to receive PDCCH is If you tell us that it is 3/8 (or the smallest CCE group size is 2 CCEs) and the minimum code rate is 3/16 (or the largest CCE group size is 4 CCEs), the UE will , Decoding assuming 1 CCE (when the code rate is 3/4) and decoding assuming 8 CCEs (when the code rate is 3/32) are not required, so the maximum Only 8 + 4 = 12 decryptions need to be done.

For the same purposes as the embodiments described above, in yet another embodiment of the invention, each UE at a base station has the maximum code rate (or the smallest CCE group size) at which the UE attempts to receive PDCCH. We propose a method to inform which code rate (or group size larger than the smallest CCE group size) should be attempted to receive PDCCH. That is, even if one UE is assigned to check from CCE 1 to CCE 16 as in the example above, in addition to this, the maximum of 3/8 that UE attempts to receive PDCCH. When informed to confirm the code rate (minimum CCE group size is 2 CCEs) and the 2-step code rate (or 2-step CCE group) with a code rate of 3/8 or higher, that Since the UE does not need to perform decoding assuming one CCE (when the code rate is 3/4) and decoding assuming eight CCEs (when the code rate is 3/32). , Only need to decrypt up to 8 + 4 = 12 times.

By using the above method, the number of decoding attempts for receiving the PDCCH of the UE can be reduced, and problems such as battery consumption of the UE can be reduced.

In each of the above embodiments, the scheduling information transmission format for each UE does not need to change frequently, so that this information can be communicated to each UE by the base station through higher layer signaling on the physical hierarchy, and each UE can: It is possible to try to receive the scheduling signal by assuming only the transmission format specified by itself. At this time, the UE searches for the scheduling signal in the unit of the time-frequency resource size specified for the scheduling information transmission format specified by itself for the downlink time-frequency domain in which the scheduling signal is transmitted. Will be.

In one more specific embodiment of the invention, the time-frequency resource magnitude used to transmit scheduling information in different transmission formats, and the smallest time-frequency used to transmit scheduling information. By setting it to an integral multiple of the resource size, the UE scheduling signal reception operation can be made easier.

At this time, the smallest time-frequency resource magnitude used to transmit the scheduling information can be the CCE as described above. That is, in the present embodiment, it is proposed to set the time-frequency resource size used for transmitting scheduling information of different transmission formats in CCE units. As mentioned above, the CCE may be a continuous region in the time-frequency domain or, unlike this, a distributed form in the time-frequency domain.

8A and 8B are diagrams showing an example in which each UE that has been designated with different scheduling information transmission formats according to an embodiment of the present invention searches for a scheduling signal.

Specifically, FIGS. 8A and 8B show the above-described method when the scheduling signal is transmitted to an arbitrary OFDM symbol through an adjacent subcarrier on the frequency axis and when the scheduling signal is distributed and transmitted in units of subcarriers. This is an example in which two UEs that have been specified with different scheduling information transmission formats search for a scheduling signal.

In the example shown in FIG. 8A, UE1 and UE2 each assume the scheduling information transmission format specified to them, that is, in the case of UE1, the unit frequency domain indicated by 1 in FIG. 8A, and in the case of UE2. Assume the unit frequency domain shown by 2 in Figure 8A, which attempts to receive the scheduling signal for the possible time-frequency domain. At this time, in the example of FIG. 8A, UE1 can read the scheduling signal transmitted to itself in the fourth search and end the scheduling signal search.

Further, according to one embodiment of the present invention, in the method in which the base station broadcasts the number of scheduled signals by the distributed allocation method actually transmitted for each TTI, the distributed allocation method is used instead of the number of scheduling signals by the distributed allocation method. The smallest time-frequency resource size used to transmit the scheduling signal by the unit size, and how many unit-sized time-frequency resources are used to transmit the scheduling signal by the distributed allocation method. By notifying, the above-mentioned operation can be supported.

As a result, in still another method according to the embodiment of the present invention, the number of scheduling signals by the distributed allocation method actually transmitted for each TTI is divided and notified according to the scheduling signals having different transmission formats. The burden of receiving the scheduling signal of the UE can be reduced. At this time, it is preferable to specify different priorities for each transmission type of scheduling information in advance before allocating the time-frequency domain for scheduling signal transmission.

FIG. 9 is a diagram showing an example in which each UE designated for each transmission format searches for a scheduling signal when different scheduling information transmission formats have different priorities depending on one embodiment of the present invention. ..

Specifically, when there are two transmission formats, transmission format 1 and 2, and the scheduling signal according to transmission format 1 has priority in time-frequency region allocation over the scheduling signal according to transmission format 2, transmission format 1 An example is shown in which three scheduling signals according to are transmitted and two scheduling signals according to transmission format 2 are transmitted.

When the scheduling signal is transmitted according to the same rule as the example shown in FIG. 9, if the UE knows this rule in advance and the base station informs how many scheduling signals are transmitted for each transmission type, Each UE knows in what time-frequency region a scheduling signal of the same transmission format as the transmission format specified by itself is transmitted, and can attempt to receive the scheduling signal only in that region.

Detailed descriptions of preferred embodiments of the invention disclosed as described above have been provided so that those skilled in the art can embody and practice the invention. Although the above description has been made with reference to a preferred embodiment of the present invention, a skilled person skilled in the art will be able to use the present invention as long as it does not deviate from the ideas and areas of the present invention described in the claims. You will understand that it can be modified and changed in various ways. Therefore, the present invention is not limited to each of the embodiments described above, but provides the broadest scope consistent with the principles and novel features disclosed herein.

According to the downlink control signal transmission method according to the embodiment of the present invention as described above, the transmission efficiency and distributed allocation of the regional allocation method are taken into consideration in consideration of the advantages and disadvantages of the regional allocation method and the distributed allocation method. All the diversity gains of the method can be obtained.

Further, in the downlink control signal transmission structure for transmitting using the regional allocation method and the distributed allocation method described above, the transmission signal by the general distributed resource allocation method is arranged at the front end of one transmission time interval (TTI). By arranging the transmission signal by the regional allocation method at the rear end of the corresponding TTI, it is possible to flexibly deal with the amount of the control signal. Further, the reception efficiency can be increased by including an indicator for the control information included in the regional allocation method in the portion of the distributed resource allocation method.