KR20080053008A - Transmission method and transmitter for supporting broadcast transmission, multicast transmission and unicast transmission - Google Patents

Abstract

A transmission method and a transmitter for supporting broadcast transmission, multicast transmission, and unicast transmission are provided to minimize interference applied to a user which does not receive a unicast signal and a multicast signal, thereby improving transmission efficiency. A transmitter(200) comprises a multiplexing processor(210), a data processor(230-1~4), a power controller(240-1~4), and a beam forming unit(250-1~4). The transmitter has four transmission antennas(290-1~4). A first transmission antenna transmits a broadcast signal(XBC). A second transmission antenna transmits a multicast signal(XMC). A third transmission antenna transmits a first unicast signal(X1). A fourth transmission antenna transmits a second unicast signal(X2). The multiplexing processor processes inputted broadcast data, multicast data, unicast data #1, and unicast data #2 and outputs a broadcast stream(SBC), a multicast stream(SMC), a first unicast stream(S1), and a second unicast stream. The data processor codes and modulates streams(SBC,SMC,S1,S2) according to determined coding and modulating methods. The power controller allocates transmission power to a coded and modulated symbol. The beam forming unit processes a beam forming vector for an input signal to generate a transmission signal.

Description

Transmission method and transmitter for supporting broadcast transmission, multicast transmission and unicast transmission}

1 illustrates a wireless communication system.

2 shows one cell containing multiple multi-users.

3 is a block diagram illustrating a transmitter having multiple transmit antennas.

4 is a block diagram illustrating an example of a data processor.

5 is a flowchart illustrating a transmission method according to an embodiment of the present invention.

6 is a block diagram illustrating a transmission method.

7 is a flowchart illustrating a method of obtaining an optimum data rate.

8 is a block diagram showing a transmission method according to another embodiment of the present invention.

9 is a block diagram illustrating a receiver for receiving a broadcast signal.

10 is a block diagram illustrating a receiver for receiving a broadcast signal and a multicast signal simultaneously.

11 is a block diagram illustrating a receiver that simultaneously receives a broadcast signal and a unicast signal.

12 is a block diagram illustrating a receiver that simultaneously receives a broadcast signal, a multicast signal, and a unicast signal.

13 is a graph showing a transmission rate according to a merge ratio.

14 is a graph illustrating an example of weighted sum rates according to merging ratios.

15 is a graph illustrating another example of a weighted rate sum based on a merge ratio.

Figure 16 is a graph comparing the transmission rate according to the prior art and the present invention.

** Explanation of symbols in main part of drawing **

210: multiplexing handler

230-1 ~ 4: Data Processor

240-1 ~ 4: Power control unit

250-1 to 4: beam forming part

The present invention relates to wireless communications, and more particularly, to a transmission method and a transmitter for efficiently supporting broadcast transmission, multicast transmission, and unicast transmission.

Next generation mobile and wireless communication systems require a system for transmitting high capacity data at high speed. In order to meet these demands, multiple input multiple output (MIMO) technology, which transmits and receives using a plurality of antennas, has been introduced. MIMO technology, which uses multiple antennas for the transmitter and the receiver, can be expected to dramatically improve the frequency efficiency and the network link capacity, and has recently attracted attention as a major technology of the mobile communication system requiring high-speed data transmission.

A transmitter with multiple antennas can transmit multiple transmit signals simultaneously via broadcast, multicast and / or unicast transmissions. Broadcast transmissions are sent to all users in a particular area (eg, cells and / or sectors), multicast transmissions are sent to specific groups of users, and unicast transmissions are sent to specific users.

A user in an area served by a base station may only be interested in signals that are needed for them. For example, other multicast or unicast signals may act as interference to the broadcast signal.

In general, broadcast, multicast and / or unicast transmissions are at a constant rate. However, the capacity of each broadcast, multicast and / or unicast transmission channel may be larger than the transmission rate. For example, if a transmission rate required for broadcast transmission is 10 bit / s, the capacity of the channel may be 20 bit / s. This wastes extra capacity, resulting in lower efficiency over the entire rate.

 In a communication system in which broadcast, multicast and / or unicast transmissions are performed simultaneously, a technique for reducing interference between users and increasing overall transmission efficiency is required.

An object of the present invention is to provide a transmission method and a transmitter for reducing interference due to broadcast, multicast and / or unicast transmission.

Another object of the present invention is to provide a transmission method and a transmitter for improving transmission efficiency.

According to the transmission method according to an aspect of the present invention, an uppercast stream is provided by merging lowercast data received by one terminal with highercast data received by a plurality of terminals. Modulation and coding are performed on the higher cast stream to transmit the higher cast signal.

According to a transmission method according to another aspect of the present invention, multicast data is merged with broadcast data to provide a broadcast stream. Unicast data is merged with the multicast data to provide a multicast stream. Modulation and coding are performed on the broadcast stream and the multicast stream to provide the broadcast signal and the multicast signal. The broadcast signal and the multicast signal are transmitted.

According to another aspect of the present invention, a transmitter includes a multi-antenna, a multiplexing processor for providing a higher-cast stream by merging lower-cast data received by one terminal with higher-cast data received by a plurality of terminals, and the upper-cast stream. It includes a data processor that performs modulation and coding.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. Like numbers refer to like elements throughout.

1 illustrates a wireless communication system.

Referring to FIG. 1, a wireless communication system 100 includes a number of base stations 110 distributed throughout the system. The base station 110 generally refers to a fixed station, and may be referred to in other terms such as node-B, base transceiver system (BTS), and access point. The user equipment 120 may be fixed or mobile, and may be called by other terms such as a mobile station (MS), a user terminal (UT), a subscriber station (SS), and a wireless device. Hereinafter, downlink means communication from the base station 110 to the terminal 120, and uplink means communication from the terminal 120 to the base station 110. An area in which one base station 110 provides a service is called a cell 150. One cell 150 may be divided into a plurality of sectors (not shown). Although seven cells 150 are shown here, the number and arrangement of the cells 150 may vary depending on the communication system 100.

2 shows one cell containing multiple multi-users.

Referring to FIG. 2, the base station 130 has multiple antennas and transmits multiplexed multiplexed transmission signals to the terminals 140a, 140b, 140c, and 140d. The terminals 140a, 140b, 140c, and 140d may have one or more antennas. The communication system may be a multiple input multiple output (MIMO) system or a multiple input single output (MISO) system. The MIMO system uses multiple transmit antennas and multiple receive antennas. The MISO system uses multiple transmit antennas and one receive antenna.

A base station 130 having multiple antennas can transmit multiple transmit signals simultaneously via broadcast, multicast and / or unicast transmissions. Broadcast transmissions are sent to all users in a particular area (eg, cells and / or sectors), multicast transmissions are sent to specific groups of users, and unicast transmissions are sent to specific users. All terminals 140a, 140b, 140c, 140d in the cell may receive broadcast signals. In addition, the terminals 140b and 140c belonging to a specific group may receive a multicast signal. Specific terminals 140c and 140d may receive unicast signals for themselves. If this is indicated from the viewpoint of the terminal, each terminal 140a, 140b, 140c, 140d may receive a signal necessary for itself. The first terminal 140a receives only a broadcast signal. The second terminal 140b receives a broadcast signal and a multicast signal. The third terminal 140c receives a broadcast signal, a multicast signal, and a unicast signal. The fourth terminal 140d receives the broadcast signal and the unicast signal.

The number of unicast signals supported by the base station 130 may be represented by min (Nt-Nc-Nm, Nr * K). Here, Nt is the number of transmit antennas, Nr is the number of receive antennas, Nc is the number of broadcast signals, Nm is the number of multicast signals, K is the number of terminals requesting unicast transmission. For example, in the 4 × 1 (Nt = 4, Nr = 1) system, if there is no broadcast transmission and multicast transmission, up to four unicast signals may be transmitted to four terminals, respectively. If one broadcast transmission and two multicast transmissions are required in a 4x1 system, one unicast signal may be transmitted to one terminal.

3 is a block diagram illustrating a transmitter having multiple transmit antennas.

Referring to FIG. 3, the transmitter 200 includes a multiplexing processor 210, a data processor 230-1-4, a power controller 240-1-4, and a beam forming unit 250-1-4. It includes. In downlink, the transmitter 200 may be part of a base station, and the receiver may be part of a terminal. In uplink, the transmitter 200 may be part of a terminal, and the receiver may be part of a base station. The base station may include a plurality of receivers and a plurality of transmitters. The terminal may include a plurality of receivers and a plurality of transmitters.

The transmitter 200 may include at least two transmit antennas, and the number or type of broadcast signals, multicast signals, and / or unicast signals transmitted for each transmit antenna may be changed. For clarity below, the transmitter 200 has four transmit antennas 290-1-4, the first transmit antenna 290-1 transmits a broadcast signal x _BC , and a second transmit The antenna 290-2 transmits the multicast signal x _MC , the third transmit antenna 290-3 transmits the first unicast signal x ₁ , and the fourth transmit antenna 290-4 transmits the second unicast signal. It is assumed that the cast signal x ₂ is transmitted. The broadcast signal x _BC , the multicast signal x _MC , the first unicast signal x _1, and the second unicast signal x ₂ are transmission signals transmitted through the transmission antennas 290-1 to 4, and corresponding transmission antennas ( 290-1 to 4) may be transmitted at the same time.

The multiplexing processor 210 processes the input broadcast data, the multicast data, the unicast data # 1, and the unicast data # 2 according to a transmission method to be described later, and transmits the broadcast stream s _BC , the multicast stream s _MC , and the first. Outputs the _first unicast stream s ₁ and the second unicast stream s ₂ . The broadcast data is data for broadcast transmission, the multicast data is bit data for multicast transmission, unicast data # 1 is data for the first terminal, and unicast data # 2 is for the second terminal. Data.

The data processors 230-1 to 4 code and modulate the streams s _BC , s _MC , s ₁ , and s _{2 according} to a predetermined coding and modulation scheme.

4 is a block diagram illustrating an example of a data processor.

Referring to FIG. 4, the data processor 230-1 includes a channel encoder 232, a mapper 234, and an OFDM modulator 236.

The channel encoder 232 encodes the input stream s _{BC according} to a predetermined coding scheme to form coded data. The mapper 234 maps the encoded data into symbols representing positions on the signal constellation. If there is no limitation on the modulation scheme performed by the mapper 234, it may be m-Phase Shift Keying (m-PSK) or m-Quadrature Amplitude Modulation (m-QAM). For example, m-PSK may be BPSK, QPSK or 8-PSK. m-QAM may be 16-QAM, 64-QAM or 256-QAM. The OFDM modulator 236 modulates the constellation mapped symbols according to an orthogonal frequency division multiplexing (OFDM) scheme. The OFDM modulator 236 may perform an inverse fast Fourier transform (IFFT) and add a CP (cyclic prefix) to the symbol on which the IFFT is performed. Here, the data processor 230-1 is based on an OFDM multicarrier scheme, but the present invention is not limited thereto, and the present invention can be applied to a single carrier scheme as it is.

Referring back to FIG. 3, the power controllers 240-1 to 4 allocate transmission power to the coded and modulated symbols. P _BC is the power allocated for broadcast transmission, P _MC is the power allocated for multicast transmission, P is the power allocated for the first unicast transmission, P ₁ , P is the power allocated for the second unicast transmission, and ₂

The beam formers 250-1 ˜ 4 process the beamforming vector with respect to the input signal to generate a transmission signal. U _BC for beamforming vector for broadcast transmission, u _MC for beamforming vector for multicast transmission, u ₁ for beamforming vector for _first unicast transmission, and u for beamforming vector for second unicast transmission. ₂

Hereinafter, a method of multiplexing and transmitting broadcast data, multicast data, unicast data # 1, and unicast data # 2 according to a multiplexing method in the multiplexing processor 210 will be described.

5 is a flowchart illustrating a transmission method according to an embodiment of the present invention.

Referring to FIG. 5, the required rate R ^req and the optimum rate R ^opt are determined for each antenna (S210). In the following description, 'req' represents a required data rate and 'opt' indicates an optimal data rate among the superscripts of the data rate R. In the subscripts of the rate R, 'BC' indicates broadcast transmission, 'MC' indicates multicast transmission, and '1', '2', 'k' and the like indicate unicast transmission. The optimal rate Ropt is a rate optimized according to the current channel, and a method of obtaining the same is described below with reference to FIG. 6. The required rate R ^req is determined based on the required rate between the base station and each terminal. The request rate R ^req may be determined by a quality of service (QoS) or a minimum request rate. The required rate R ₁ ^req , R ₂ ^req, etc. for unicast transmission is determined by the rate determined between each terminal. The required transmission rate R _MC ^req for multicast transmission is determined as the minimum transmission rate among the transmission rates of the terminals belonging to the group so that all terminals in the corresponding group can decode the signal. For example, if two terminals belong to a group for multicast transmission, and the required transmission rates are R ₁ ^req and R ₂ ^req , then R _MC ^req = min (R ₁ ^req , R ₂ ^req ). The required transmission rate R _BC ^req for broadcast transmission is determined as the minimum transmission rate among all transmission rates so that all terminals in a corresponding region can decode the signal. The transmission rate R _k ^req required between the base station and each terminal may be determined in various ways. In one embodiment, the required transmission rate R _k ^req may be determined by the base station in consideration of resource allocation or channel conditions. In another embodiment, the required transmission rate R _k ^req may be determined by the base station based on the channel state received from each terminal. In another embodiment, the requested rate R _k ^req may be directly returned to the base station by each terminal.

Subsequently, it is determined whether the required rate R _BC ^req for broadcast transmission is smaller than the optimum rate R _BC ^opt (S220). If the required rate R _BC ^req is greater than the optimal rate R _BC ^opt , a broadcast stream is formed using broadcast data (S235). If the required transmission rate R _BC ^req is smaller than the optimal transmission rate R _BC ^opt , some or all of the multicast data is merged with the broadcast data to form a broadcast stream (S230). If the required rate R _BC ^req is less than the optimal rate R _BC ^opt , the broadcast stream may have free space left even with the broadcast data. The free space may be an extra time in the case of a time division multiplexing (TDM) scheme or an extra subcarrier in the case of a scheme using multiple subcarriers. The transmission efficiency can be improved by carrying more multicast data in the free space. In addition, since a multicast signal can be decoded only by a terminal of a specific group, the multicast signal acts as an interference to a terminal not belonging to the group. However, the broadcast signal is capable of sequential interference cancellation (SIC) for all terminals. Therefore, if some or all of the multicast data is sent to the broadcast signal, interference may be reduced.

Although a case in which one multicast data exists is described herein, a plurality of multicast data may exist. In this case, there may be a problem in which multicast data is selected and loaded in the broadcast stream. Among the multicast data, multicast data having the highest transmission rate may be selected. The broadcast signal is a signal that can be decoded by all users, and the higher the data rate, the more data can be loaded into the broadcast signal.

Next, it is determined whether the required transmission rate R _MC ^req for multicast transmission is smaller than the optimal transmission rate R _MC ^opt (S240). If the required transmission rate R _MC ^req is greater than the optimal transmission rate R _MC ^opt , a multicast stream is formed using the multicast data (S255). If the required transmission rate R _MC ^req is smaller than the optimal transmission rate R _MC ^opt , a part or all of the unicast data is merged into the multi data to form a multicast stream (S250). If the required transmission rate R _MC ^req is smaller than the optimal transmission rate R _MC ^opt , the multicast stream may have free space left even with unicast data. Transmission efficiency can be improved by carrying more unicast data in the free space. In addition, since only a specific terminal can be decoded, the unicast signal acts as an interference to other terminals. However, since the multicast signal can be decoded by all terminals belonging to a specific group, if a specific terminal receiving the unicast signal belongs to the group, another terminal in the group can SIC the multicast signal. Therefore, if some or all of the unicast data is loaded on the multicast signal, interference may be reduced.

If there is a large number of unicast data, it may be a question of which unicast data is selected and loaded on the multicast stream. Among the unicast data, it belongs to a group of multicast signals, and the unicast data having the highest transmission rate is required. Can be selected.

Then, a unicast stream is formed using each unicast data (S260). The formed broadcast stream, multicast stream, and unicast stream are modulated and coded, respectively (S270). The modulated and coded stream is converted into a transmission signal by appropriate power limitation and beamforming and transmitted (S280).

As described above, unicast data can be loaded on a multicast signal to reduce interference, and multicast data can be loaded on a broadcast signal to reduce interference, resulting in two levels of interference attenuation. .

6 is a block diagram illustrating a transmission method.

Referring to FIG. 6, when the required transmission rate R _BC ^req for broadcast transmission is smaller than the optimal transmission rate R _BC ^opt , some or all of the multicast data is merged with the broadcast data to form the broadcast stream s _BC . The broadcast stream s _BC is modulated and coded and then converted into a broadcast signal x _BC and transmitted.

When the required transmission rate R _MC ^req for the multicast transmission is smaller than the optimal transmission rate R _MC ^opt , the multicast stream s _MC is formed by merging some or all of the unicast data into the multicast data. The multicast stream s _MC is modulated and coded and then converted into a multicast signal x _MC and transmitted.

Unicast data is modulated and coded and then converted into unicast signals x ₁ and x ₂ and transmitted.

7 is a flowchart illustrating a method of obtaining an optimum data rate.

Referring to FIG. 7, initial weights μ _BC , μ _MC , μ ₁ , μ ₂ are determined (S410). The weight is a value for optimizing the transmission rate according to proportional fairness. La weights μ _BC for the broadcast transmission rate R _BC and LA multicast weights for the transmission rate R _MC μ _MC, and the first unicast rate R la weights μ ₁ for the _first and the second unicast transmission rate R _The weight for _{2 is} called μ ₂ .

The transmission rate is calculated using the powers P _BC , P _MC , P ₁ , P ₂ and beamforming vectors u _BC , u _MC , u ₁ , u ₂ for each transmission antenna (S420). The transmission rate R _k for the kth transmission antenna may be expressed by Equation 1 below.

Here, SINR _k is a signal to interference and noise ratio for the k th transmit antenna.

When k = 0, that is, when a broadcast signal is transmitted through the first transmission antenna, SINR ₀ may be obtained as in Equation 2 below.

Here, hi is a channel vector to the i-th terminal.

When k = 1, that is, when transmitting a multicast signal through the second transmission antenna, SINR ₁ can be obtained as shown in Equation 3 below.

Here, A represents a group for receiving a multicast signal.

SINR _i for the i-th unicast signal can be obtained as shown in Equation 4 below.

Here, K is the number of terminals through which the unicast signal is transmitted.

The SINR is obtained assuming that ZF (zero-forcing) beamforming is performed on a unicast signal. When calculating the SINR, it can be said that there is no interference with other unicast signals by ZF in the case of a unicast signal. Since broadcast signals are SICs, only multicast signals can act as interference. Since the multicast signal is in the form of all interference from the unicast signal, there is no interference by the broadcast signal. The broadcast signal interferes with both the unicast signal and the multicast signal. The transmission rate of the broadcast signal is determined to the minimum value of the SINR of all the terminals so that all terminals can decode the broadcast signal. The SINR of the multicast signal is determined to be the minimum value of the SINR of the UEs in the group so that all UEs in the group can decode it. Accordingly, the transmission rate of the multicast signal is determined.

It is determined whether the optimization criteria are satisfied based on the obtained transmission rate and the weight (S430). Here, a transmission rate that satisfies an optimization criterion as shown in Equation 5 is obtained.

If the optimization criterion is satisfied, the obtained transmission rate becomes the optimal transmission rate. If the optimization criteria are not satisfied, the weight is updated (S440). In addition to weights, you can also change the power or beamforming vector. The data rate is calculated again using the updated weight to determine whether to optimize again.

A proportional-fair scheduling scheme is used to update the weights. The proportional fair scheduling scheme used to obtain fairness and multi-user diversity at the same time is compared with the average throughput of each user and the transmission rate according to the current channel, and is reflected as a weight. This method aims to guarantee the longest yield for the terminal with a good radio channel condition, and allocates the transmission rate proportionally according to the number of paths of each traffic. Assign. The proportional-fair scheduling scheme may be represented by Equation 6 below.

Where Tc is the window length used to calculate the average rate, m is the time slot, and k is the antenna index. When R _k is the current transmission rate of the k th antenna, T _k may be referred to as the average transmission rate of the k th antenna.

The weight may be determined as follows through the average data rate T _k obtained by Equation 6.

In the above description, a two-stage transmission method from unicast to multicast and multicast to unicast has been described. However, the present invention may be modified in various ways.

8 is a block diagram showing a transmission method according to another embodiment of the present invention.

Referring to FIG. 8, when the required transmission rate R _upper ^req for higher cast transmission is smaller than the optimal transmission rate R _upper ^opt , some or all of the lower cast data is merged with upper cast data to form an _upper cast stream s _upper . The upper cast stream s _upper is transformed and transmitted to the _upper cast signal x _upper through modulation and coding. Subcast data is modulated and coded and then converted into subcast signals x ₁ and x ₂ and transmitted.

The higher cast signal refers to a signal transmitted to a plurality of terminals including a specific terminal receiving the lower cast signal. More terminals receive the higher cast signal than terminals receive the lower cast signal. For example, when the lower cast signal is a unicast signal for a specific terminal, the higher cast signal may be a broadcast signal or a multicast signal for a group to which the specific terminal belongs. As another example, when the lower cast signal is a multicast signal, the upper cast signal may be a broadcast signal.

Hereinafter, the operation of the receiver will be described. The receiver uses the SIC to eliminate the interference. The detection of the signal transmitted from the antenna with the largest SINR is started and a transmission signal is generated from the detected signal. Noise is removed by removing the generated transmitted signal from the entire received signal. By repeating this process, the transmission signal generated in each step is removed to increase the SINR of the received signal, thereby eliminating interference from the received signal.

9 is a block diagram illustrating a receiver for receiving a broadcast signal.

9, the receiver 500 includes a data processor 501 and a BC extractor 502. The receiver 500 includes one receive antenna 509, but there may be more than one receive antenna 509.

를 추출한다.In response to the data processors 230-1 to 4 of the transmitter 200 of the data processor 501, a signal received from the receiving antenna 509 is demodulated and channel decoded to provide a received signal y. BC extractor broadcasts signal from received signal y

Extract

10 is a block diagram illustrating a receiver for receiving a broadcast signal and a multicast signal simultaneously.

를 추출한다. 가산기(513)는 수신신호 y에서 브로드캐스트 신호 를 빼고, MC 추출기(514)는 가산기(513)의 출력에서 멀티캐스트 신호

를 추출한다. 사용자가 수신된 브로드캐스트 신호

를 필요로 하지 않는 경우에는 SIC로 멀티캐스트 신호

의 SINR을 높이는 데 이용되고, 필요로 하는 경우는 멀티캐스트 신호

의 전송률을 높이는데 사용된다.Referring to FIG. 10, the BC extractor 512 receives a broadcast signal from the received signal y provided by the data processor 511.

Extract The adder 513 broadcasts the broadcast signal at the received signal y. MC extractor 514 adds the multicast signal at the output of adder 513.

Extract Broadcast signal received by the user

Multicast signal to SIC if not needed

Used to increase the SINR of the multicast signal, if required

Used to increase the baud rate.

11 is a block diagram illustrating a receiver that simultaneously receives a broadcast signal and a unicast signal.

를 추출한다. 가산기(523)는 수신신호 y에서 브로드캐스트 신호

를 빼고, 데이터 추출기(524)는 가산기(523)의 출력에서 유니캐스트 신호

를 추출한다. 사용자가 수신된 브로드캐스트 신호

를 필요로 하지 않는 경우에는 SIC로 유니캐스트 신호

의 SINR을 높이는 데 이용되고, 필요로 하는 경우는 유니캐스트 신호

의 전송률을 높이는데 사용된다.Referring to FIG. 11, the BC extractor 522 broadcasts a broadcast signal from the received signal y provided by the data processor 521.

Extract The adder 523 broadcasts the broadcast signal at the received signal y.

Subtracts the data extractor 524 from the output of the adder 523.

Extract Broadcast signal received by the user

If you do not need a unicast signal to the SIC

Is used to increase the SINR of the unicast signal, if necessary

Used to increase the baud rate.

12 is a block diagram illustrating a receiver that simultaneously receives a broadcast signal, a multicast signal, and a unicast signal.

를 추출한다. 제1 가산기(533)는 수신신호 y에서 브로드캐스트 신호

를 빼고, MC 추출기(534)는 제1 가산기(533)의 출력에서 멀티캐스트 신호

를 추출한다. 제2 가산기(535)는 제1 가산기(533)의 출력에서 멀티캐스트 신호

를 빼고, 데이터 추출기(536)는 제2 가산기(535)의 출력에서 유니캐스트 신호

를 추출한다. Referring to FIG. 12, the BC extractor 532 receives a broadcast signal from the received signal y provided by the data processor 531.

Extract The first adder 533 is a broadcast signal at the received signal y.

The MC extractor 534 subtracts the multicast signal at the output of the first adder 533.

Extract The second adder 535 is a multicast signal at the output of the first adder 533.

Subtracting the data extractor 536 from the output of the second adder 535.

Extract

The simulation results will now be described. Simulation is performed for the first stage transmission scheme shown in FIG. The upper cast is broadcast, the lower cast is unicast, and one broadcast signal and two unicast signals are considered. The required data rates for broadcast are called R _BC ^req , and the required data rates for unicast are called R ₁ ^req and R ₂ ^req , respectively. The data rates after data merging are referred to as R _BC ^m , R ₁ ^m , and R ₂ ^m , respectively. Data merging is done only for unicast data, and the ratio of broadcast data to unicast data is called b: (1-b). If b = 1, no merging is done. If b <1, merging is done. Since no merge is performed on unicast data, R ₁ ^m = R ₁ ^req and R ₂ ^m = R ₂ ^req .

13 is a graph showing a transmission rate according to the merge ratio b.

Referring to FIG. 13, the weight ratio and the data rate are calculated using Equation 8 by changing the merge ratio b according to a given channel.

In Equation 8, the weights μ _BC , μ ₁ , μ _2, and the transmission rates R _BC ^m , R ₁ ^m , and R ₂ ^m have different values satisfying the left and right sides unless the merge ratio b is 1. 'Is displayed.

According to Equation 8, μ _BC <μ ₁ must be satisfied. To simply prove this, assume that R ₂ ^m is fixed. In this case, for all points (R _BC ^m ', R ₁ ^m ') on the boundary of the two-dimensional region, the boundary image of the two-dimensional region is larger than max (μ _BC 'R _BC ^m ' + μ ₁ 'R ₁ ^m '). For all points (R _BC ^m , R ₁ ^m ) at max ({μ ₁ (1-b) + μ _BC b} R _BC ^m + μ ₁ R ₁ ^m ), the question is whether it can be larger. When the merge ratio b is slightly smaller than 1 (i.e. b = 1-ε), according to Equation 8 max ({μ ₁ (1-b) + μ _BC b} R _BC ^m + μ ₁ R ₁ ^m ) > max (μ _BC 'R _BC ^m ' + μ ₁ 'R ₁ ^m ') Given the inequality at the given rate, if you move the left side to the right side, {μ ₁ (1-b) + μ _BC b} R _BC ^m + μ ₁ R ₁ ^m -μ _BC 'R _BC ^m' -μ ₁ 'R ₁ ^m '> 0. Substituting b = 1-ε, μ ₁ (R ₁ ^m -R ₁ ^m ') + μ _BC (R _BC ^m -R _BC ^m ') + ε (μ ₁ -μ _BC ) R _BC ^m > 0 do. The difference between (R ₁ ^m -R ₁ ^m ') and (R _BC ^m -R _BC ^m ') is so small that the value can be seen as almost zero, so that inequality is established with μ _BC <μ ₁ .

14 is a graph illustrating an example of weighted sum rates according to merging ratios.

Referring to Figure 14, the _{μ BC = 1, μ 1 =} 4, μ 2 = 2 is merged to the reduction ratio b is larger weight stylized sum rate, as the case may be. The larger the merge ratio b, the smaller the unicast data is merged with the broadcast data, so the weighted rate sum is reduced.

15 is a graph illustrating another example of a weighted rate sum based on a merge ratio.

Referring to FIG. 15, in the case of μ _BC = 4, μ ₁ = 6, and μ ₂ = 2, the weighted rate sum decreases as the merge ratio b increases.

Figure 16 is a graph comparing the transmission rate according to the prior art and the present invention. When the transmission rates R _BC , R ₁ , R ₂ satisfy a certain ratio, the prior art and the attainable transmission rates according to the present invention are compared. While the results of FIGS. 14 and 15 are obtained by adding a bit rate at a given weight, a sum rate that can be achieved when a ratio of a bit rate is given is obtained. The prior art is described in TM Cover, "Broadcast Channels", IEEE Trans. Info. Theory, Vol. IT-18, No. 1, Jan. See 1972. According to Cober, signals for different users are overlapped and transmitted to share power.

Increasing the value of the merge ratio b from 0 to 1 results in one three-dimensional rate region as shown in FIG. 14 for each merge ratio b. Increasing the merge ratio b from 0 to 0.1 intervals yields a total of 10 three-dimensional data rate regions. The ten areas are combined to obtain a one-step rate region. The rate attainable when the rate is maintained at a certain rate is equivalent to finding the point where the rate region meets a straight line with a particular slope on FIG.

Referring to Fig. 16, the transmission rate B according to the present invention is higher than the transmission rate A according to the prior art. Therefore, the transmission efficiency is higher.

The invention can be implemented in hardware, software or a combination thereof. In hardware implementation, an application specific integrated circuit (ASIC), a digital signal processing (DSP), a programmable logic device (PLD), a field programmable gate array (FPGA), a processor, a controller, and a microprocessor are designed to perform the above functions. , Other electronic units, or a combination thereof. In the software implementation, the module may be implemented as a module that performs the above-described function. The software may be stored in a memory unit and executed by a processor. The memory unit or processor may employ various means well known to those skilled in the art.

Although the present invention has been described above with reference to the embodiments, it will be apparent to those skilled in the art that the present invention may be modified and changed in various ways without departing from the spirit and scope of the present invention. I can understand. Therefore, the present invention is not limited to the above-described embodiment, and the present invention will include all embodiments within the scope of the following claims.

As described above, according to the present invention, when simultaneously supporting broadcast, multicast, and unicast in a multi-user environment, the interference between the unicast signal and the multicast signal to the user who does not receive the signal is minimized, and consequently transmitted. The efficiency can be improved.

Claims (10)

Providing an uppercast stream by merging lowercast data received by one terminal with highercast data received by a plurality of terminals; Performing modulation and coding on the higher cast stream to provide a higher cast signal; And Transmitting the higher cast signal. The method of claim 1, The providing of the higher-cast stream may include merging the higher-cast data with the higher-cast data when the requested transmission rate of the higher-cast data is smaller than the required transmission rate of the higher-cast data. The method of claim 2, And the request rate is obtained from feedback information. The method of claim 2, The optimal transmission rate is obtained from a weighted sum rate. The method of claim 1, And the higher cast data is multicast data and the lower cast data is unicast data. The method of claim 1, And the higher cast data is broadcast data and the lower cast data is unicast data. The method of claim 1, And the higher cast data is broadcast data and the lower cast data is multicast data. Merging the multicast data with the broadcast data to provide a broadcast stream; Merging unicast data into the multicast data to provide a multicast stream; Performing modulation and coding on the broadcast stream and the multicast stream to provide the broadcast signal and the multicast signal; And Transmitting the broadcast signal and the multicast signal. The method of claim 8, The broadcast signal and the multicast signal are transmitted at the same time. Multiple antennas; A multiplexing processor for merging lowercast data received by one terminal to highercast data received by a plurality of terminals to provide an uppercast stream; And And a data processor to perform modulation and coding on the higher cast stream.

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