JP4839182B2 - Multi-carrier MIMO system and communication method thereof - Google Patents

Description

  The present invention relates to a radio communication technique in a multiple input multiple output (MIMO) antenna system, and more particularly to a multicarrier MIMO communication system and a communication method thereof.

  Future wireless communication systems will need to provide high-speed data services such as video conferencing, video-on-demand, and opposed gaming. According to the ITU-RM1645 document, a high-speed wireless service (High Mobility) requires a speed of up to 100 Mbps, and a low-speed (Low Mobility) or fixed wireless (Fixed Wireless) service requires a speed of 1 Gbps.

  In wireless communication, the channel speed is equal to the product of the frequency band of the channel and the frequency utilization efficiency of the applied technology. In order to improve the speed, it is necessary to improve the frequency utilization efficiency of the frequency band or the technology applied. However, since the frequency resources are finite, it is impossible to increase the communication speed by increasing the frequency band without limitation, and the best method is to improve the frequency utilization efficiency of the applied technology. .

  Usually, frequency utilization efficiency is improved mainly by two methods. One is a method for improving frequency utilization efficiency at the link level by physical layer technology such as advanced coding technology and signal processing technology. Another method is to perform resource allocation flexibly under the control of higher layers, thereby improving system-class frequency utilization efficiency. Methods based on multiple input multiple output (MIMO) technology and channel user scheduling (Channel-Aware User Scheduling) are two types of methods for realizing the above goal. Random beamforming is a method for improving the performance of a user scheduling system, which can more effectively combine these two different protocol layer methods, thereby realizing optimization of system performance. However, modern communication systems are all based on a cellular configuration, and the basic communication mode is a mode in which one base station (Mobile station, MS) in a cellular simultaneously serves multiple users. It is related to multiple access which is an access problem. Conventional access methods include FDMA, TDMA, and CDMA, all of which are based on circuit switching. That is, one fixed frequency band (FDMA), time slot (TDMA), or spreading code (CDMA) is assigned to each user.

  Taking GSM as an example, a base station performs communication by assigning 8 time slots of one frame to 8 users by a fixed time slot assignment method in a 200K channel. The merit of this method is that it is possible to guarantee the time delay characteristic of the communication service, which is suitable for a service sensitive to time delay such as voice communication. The disadvantage is that fixed resource allocation does not take into account radio channel conditions during user communication. Radio channels vary greatly and if a channel is in deep fading, assigning a channel to a user will result in a loss of system performance.

Future communication systems are mainly data services, and the demand for time delay is not so strict. For this reason, a packet access multi-access method can also be used. When adopting packet switching, the base station needs to assign channels to different users in real time, which is called user scheduling. Currently, the two most basic user scheduling methods are applied to wireless communication systems. One is round robin scheduling, that is, channels are allocated to all users in a round robin manner. This method has the effect of guaranteeing the characteristics of time delay and fairness among users, as in circuit switching, but does not improve performance. Another user scheduling technique is Channel-aware Scheduling, where user channel attenuation

(In a single antenna system, which is a complex scalar) dynamically assigns the right to use the current channel to the maximum carrier-to-interference ratio (simply

Assigned to a user who has In this way, the performance of the system can be greatly improved. The performance gain obtained by the maximum carrier-to-interference ratio scheduling is called multi-user diversity.

  However, since channel-sensitive scheduling determines common channel allocation based on channel conditions, it is highly dependent on channel conditions. In this way, the performance of the system can be significantly reduced in special channel situations.

  (A) and (b) of FIG. 1 are diagrams showing a system configuration in which a base station (transmission side) has one transmission antenna and two users (reception side). In this system, channel sensing scheduling determines common channel assignments based on channel conditions.

  FIG. 2A shows the channel gain situation when the channel situation is good. (b) shows the state of the channel gain when the channel has a line of sight (LOS). (c) shows the channel gain situation when the system is in slow fading situation.

In FIG. 2, curve 1 shows a channel gain curve that changes with the passage of time of user 1, and curve 2 shows a channel gain curve that changes with the passage of time of user 2. The dotted line shows the average channel gain curve as the current system changes over time. As can be seen from (a), at different times, the system determines the allocation of the common channel based on the channel gain of user 1 and user 2, i.e., the user 1 in the time period of 0-t _1, t ₁ - For example, it is assigned to user 2 in the time zone t ₂ , and “1” and “2” are displayed on the time axis, respectively. Finally, the channel gain of the system is an envelope on curves 1 and 2, and the average is obtained to obtain a system average channel gain curve indicated by a dotted line.

  As can be seen by comparing (a) and (b), when the line of sight is present in the channel, the line of sight reduces the variation of the channel coefficient, so the system average channel gain that can be realized is lowered. Further, as can be seen from (b) and (c) (the time period shown in parentheses), the transmission time delay is larger when the fading of the system is moderate.

  To solve this problem, P. Viswanath, D. N. C. Tse, and R. Laroia have proposed a solution. (See “Opportunistic beamforming using dumb antennas”, IEEE Trans. Infor. Theory, Vol. 48, No. 6, pp. 1277-1294. June. 2002, hereinafter referred to as “Reference 1”).

In the above method, the base station

If one antenna is attached and each user has one receiving antenna, the user's channel is one vector.

It is. Before sending the data signal

Dimensional random complex vector

And the above data signal

Transmit from a book antenna. At this time, the channel gain detected by each user is the equivalent channel gain combining the actual channel and the transmission vector.

It is. Each user feeds back the detected equivalent channel gain to the base station, and further assigns a channel to the user having the maximum equivalent channel gain in the base station.

For example, in (a) and (b) of FIG. 1, the user with the maximum equivalent channel gain is just in the main lobe of the transmit beam formed by the transmit vector h _k . In this case, by changing the random complex vector W, it is possible to change the statistical characteristics (for example, correlation characteristics, time characteristics, etc.) of the equivalent channel gain, and to satisfy the user scheduling requirements.

System performance is somewhat random vector probability distribution density function

Related to. The method is applied in the case of a flat fading channel in a narrowband system. However, the current system is normally a wideband system and has strong frequency-selective fading. Therefore, even if the above method is adopted directly, a beam in a certain direction cannot be formed. At the same time, the signal band can be distributed to a plurality of subcarriers by the multicarrier modulation technique, and each subcarrier goes through one flat fading channel. Thereby, formation of a random beam can be realized for each subcarrier. Users compete for each subcarrier by measuring the equivalent channel gain of each subcarrier.

FIG. 3 shows signal processing on the transmission side in such a case. As can be seen from this figure, the data of each subcarrier

Randomly generated vector

To form frequency domain signals that are input to different antennas. The frequency domain signals from different antennas further form time domain signals via IFFT. After attaching a cyclic prefix to the time domain signal, the signal is transmitted through a corresponding antenna. As shown in Figure 3, for this system,

Pieces

Need to generate a random vector of dimensions, and

Need to do IFFT times. This causes the following problems.

  1. Random numbers are generally generated by a pseudo-random method. What is needed here is a random sequence having temporal correlation characteristics. In order to generate such a large number of random numbers, a corresponding number of pseudo-random generators are required, which increases hardware resources or increases the difficulty of the algorithm.

2. The performance of this system is to some extent a random vector probability distribution density function

Related to. In principle, this function has a certain optimization space, but it is difficult to optimize a function with a large number of variables mathematically.

3. This method requires IFFT as many times as the number of transmit antennas, so the difficulty of the algorithm is

And relatively expensive.

  Therefore, it is necessary to provide a communication system and a communication method for solving the above disadvantages.

  An object of the present invention is to provide a multi-carrier MIMO communication system.

  Another object of the present invention is to provide a communication method applied to the multi-carrier MIMO communication system.

  According to the first aspect of the present invention, in a multi-carrier MIMO communication system, a transmitting side that transmits a data frame having at least a channel estimation signal and user data, a data frame transmitted by the transmitting side, and a corresponding feedback signal And at least one receiver for generating and restoring user data. The transmitting side transmits a data frame and receives a feedback signal from the receiving side, a transmission antenna installed on the duplexer group, a multicarrier MIMO scheduler that generates scheduling information based on the feedback signal, A multi-carrier MIMO data processor that selects a user that needs scheduling based on the scheduling information and uses the selected user's data as a corresponding multi-carrier transmission signal. The reception side receives a data frame from the transmission side, generates a user feedback data based on the data frame and a duplexer group that transmits user feedback information and a transmission antenna installed on the duplexer group. A multi-carrier received signal processor for recovering data and a feedback information processor for converting user feedback information into a feedback signal.

  According to the second embodiment of the present invention, there is provided a communication method for a multi-carrier MIMO communication system, wherein a feedback signal is generated on the receiving side based on a channel fading situation between a transmitting antenna on a transmitting side and a receiving antenna on a receiving side. (A) feeding back the feedback signal to the transmitting side; receiving the feedback signal at the transmitting side; generating schedule information based on the feedback signal; and scheduling at the transmitting side. When a corresponding multi-carrier transmission signal is generated from the user data scheduled based on the information and this multi-carrier transmission signal is transmitted by the corresponding transmission antenna (c), on the receiving side, based on the received transmission beam And (d) restoring user data.

  Compared with the prior art, the channel capacity provided by the multi-carrier MIMO communication system and the communication method of the present invention is larger than the channel capacity provided by the conventional multi-carrier MIMO communication method. In addition, the multi-carrier MIMO communication method of the present invention uses a new multi-carrier beam former and random vector generator, so that the conventional multi-carrier MIMO communication system generates many random numbers with many pseudo-random generators. It is possible to reduce the complexity of the algorithm by simultaneously optimizing the association probability density function of random vectors.

  Next, the present invention will be described with reference to the drawings.

  FIG. 4 is a block diagram of the multi-carrier MIMO communication system of the present invention. Among them, the MIMO communication system includes one transmitting side 10 (base station) and a plurality of receiving sides 20 (users). FIG. 5 is a flowchart of user scheduling of the MIMO communication system shown in FIG. FIG. 6 is a diagram showing a frame structure adopted by the multi-carrier MIMO communication system of the present invention.

As shown in FIGS. 4 to 6, the transmitting side 10 includes a multi-carrier MIMO data processor 110, a multi-carrier MIMO scheduler 120, a duplexer group 130,

And a transmitting antenna. Each receiving side 20 includes a multi-carrier received signal processor 210, a feedback information processor 220, a duplexer group 230,

And a receiving antenna. Here, the number of receiving antennas on each receiving side 20 may be different. The frame structure includes a channel estimation time slot, a channel feedback time slot, and a data transmission time slot, and other time slots can be set according to system requirements. Therefore, it will be omitted.

Scheduling information acquisition process As can be seen from FIG. 6, before transmitting the user data signal, the transmitting side 10 first passes through the duplexer group 130.

A channel estimation signal is transmitted to the receiving side 20 by transmitting a beam from one transmitting antenna.

If the transmission signal of the transmitting side 10 is

Dimensional complex vector

So, each receiver 20 received

Dimensional complex vector

And between the sending side 10 and the receiving side 20,

Suppose that there is a dimensional channel fading matrix.

here,

Indicates channel transmission characteristics between the i-th transmitting antenna on the transmitting side 10 and the j-th antenna on the receiving side 20 (k indicates the k-th user).

Thus, the transfer function of the system can be expressed as:

here,

Is

It is a dimensional complex vector and represents white noise on the receiving side 20.

  In this way, each receiving side 20 can grasp a reliable channel fading situation. In fact, this channel fading situation combines the actual channel fading situation and the random complex vector on the transmitting side. Based on the channel fading situation, each receiving side 20 obtains user feedback information by processing it through the multicarrier received signal processor 210 and transmits it to the feedback information processor 220.

  The feedback information processor 220 processes the received user information and converts it into a feedback signal (RF signal) suitable for the MIMO communication system. This feedback signal is fed back to the transmitting side 10 via the feedback channel via the antenna on the receiving side 20.

  After receiving the feedback signal, the transmitting side 10 antenna transmits it to the multi-carrier MIMO scheduler 120. The multi-carrier MIMO scheduler 120 generates scheduling information based on this signal, and uses the generated scheduling information to control the operation of the multi-carrier MIMO data processor 110, thereby making the MIMO communication system have the maximum system capacity. Reach the scheduling state. That is, user scheduling optimized based on scheduling information is performed.

  The method of acquiring the channel fading status is performed by using a channel estimation signal (that is, a pilot signal), inserting the channel estimation signal into a data frame, and the receiving side 20 uses the channel estimation signal based on the channel estimation signal. Channel fading status between the receiver 20 and the receiving side 20, and after processing the channel fading status by the multicarrier received signal processor 210, user feedback information is acquired.

  However, in the present invention, the channel fading situation can also be obtained using the channel blind estimation method. That is, there is no need to set a channel estimation time slot in the data frame, and the receiving side 20 receives the data transmitted by the transmitting side 10 and simultaneously acquires the channel fading status by channel blind estimation, and then receives the multicarrier received signal processor. After processing the channel fading situation at 210, user feedback information is obtained. At this time, waste of spectrum resources due to insertion of a channel estimation signal can be avoided.

  FIG. 7 is a diagram showing the configuration of the transmission side 10 of the MIMO communication system of the present invention. FIG. 8 is a specific configuration diagram of one type of multicarrier beam former 114 shown in FIG. FIG. 9 is a diagram illustrating a configuration of a transmission RF link group on the transmission side 10. FIG. 10 is a diagram showing the duplexer group 130 on the transmission side 10 of the present invention. FIG. 11 is a diagram showing the configuration of the receiving side 20 of the MIMO communication system of the present invention. 7 and 11 illustrate performing MIMO communication using a hierarchical space-time signal processing method. Similarly, the signal processing can be executed by employing other signal processing methods and apparatuses disclosed in the prior art such as a space-time coding method.

User data transmission / reception and scheduling process
Sender 10
In FIG. 7, the transmitting side 10 includes a multi-carrier MIMO data processor 110, a multi-carrier MIMO scheduler 120, a duplexer group 130,

Including a transmitting antenna.

  The multicarrier MIMO scheduler 120 includes a reception RF link group 123, a MIMO reception signal processor 122, and a scheduler 121. Here, the reception RF link group 123 includes a number of reception RF links corresponding to transmission antennas for converting the received feedback signal into a corresponding code stream. The MIMO received signal processor 122 performs space-time signal processing on the converted code stream to obtain corresponding scheduling information. This scheduling information includes a user who intends to perform scheduling, a code stream supported by each user, and a predetermined transmission beam of a predetermined subcarrier that transmits each code stream. The scheduler 121 controls signal processing of the multicarrier MIMO data processor 110 using the scheduling information.

  The multi-carrier MIMO data processor 110 includes a user selector 111, a plurality of parallel shunts 112, a carrier beam allocator 113, a plurality of parallel multi-carrier beam formers 114, an adder group 118, and a cyclic A prefix unit group 115, a transmission RF link group 116, and a random vector generator 117 are included.

  Among them, under the control of scheduling information (based on “users that require scheduling” in the scheduling information), the user selector 111 selects the users that require scheduling, where the quantity is displayed as nS and the corresponding users Output data.

  Under the control of scheduling information, nS shunts 112 are selected to perform shunting processing on the scheduled user data of nS users. That is, based on the “code stream supported by each user” in the scheduling information, user data of nS users to be scheduled is divided into L code streams and output. Of these, L is the total number of code streams obtained by dividing the data of each user to be scheduled.

Then, the carrier beam allocator 113 processes the L code streams output from the shunt 112 as L different layers, and the scheduling information indicates “a predetermined transmission beam of a predetermined subcarrier transmitting each code stream”. The L code streams transmitted are each assigned to a given transmit beam of a given subcarrier, i.e., L code streams are assigned to the frequency domain and the spatial domain channel, and a plurality of frequency domain signals are assigned. Form. Here, the number of subcarriers in the multicarrier MIMO communication system is

And the number of transmit antennas

Then, the output at this time is

Frequency domain signals, i.e., in each subcarrier

Support for multiple transmit beams.

Of the frequency domain signals, only L frequency domain signals have user data.

continue,

Frequency domain signals

Multiple multi-carrier beamformers 114, and in principle, on the same subcarrier

Each frequency domain signal

Input to one corresponding multicarrier beamformer 114 of the multicarrier beamformers 114, i.e.

Belong to the same spatial domain channel in multiple frequency domain signals

The frequency domain signals are input to one corresponding multi-carrier beamformer 114. As a result, each subcarrier beamformer 114 is

Frequency domain signals corresponding to the subcarrier beamformers are received, and each frequency domain signal corresponds to one subcarrier.

  The random vector generator 117 generates a random vector and inputs the generated random vector to the corresponding multicarrier beamformer 114.

Each multicarrier beamformer 114 is input based on a random vector generated by a random vector generator 117.

Perform beam forming processing for each frequency domain signal,

Against the antenna of the book

Form time domain transmission signals, i.e. each time domain signal is

Corresponds to one transmission antenna among the two transmission antennas. That is, each time domain transmission signal is all

Corresponds to one independent spatial domain channel of subcarriers. All

The multi-carrier beamformer 114 is

A number of transmission signals are formed.

In the adder group 118 having one adder, one corresponding adder corresponds to the same transmission antenna.

Time domain transmission signals are stacked to form a total transmission signal, so that time domain transmission signals corresponding to the same transmission antenna from different multicarrier beamformers are in one independent spatial domain-frequency domain channel Will correspond. Thereafter, each adder inputs the formed transmission signal to the cyclic prefix group 115.

Each adder corresponds to one transmit antenna

Output transmission signals.

The cyclic prefix device group 115

Each cyclic prefix is associated with one transmit antenna. Each cyclic prefix unit inserts a cyclic prefix into a transmission signal corresponding to the same transmission antenna from multicarrier beam former 114, and generates a transmission signal in which the corresponding cyclic prefix is inserted.

Cyclic prefixes

Corresponding to each transmit antenna

Output transmission signals.

The transmission RF link group 116 is output from the cyclic prefix group 115.

Received transmission signals, and

Each of the transmission signals is converted into a corresponding RF signal, and the RF signal corresponding to each transmission signal is converted on the duplexer group 130.

Transmit through the transmitting antenna of the book.

  Specifically, the multi-carrier beam shaping process in the multi-carrier MIMO communication system will be described in detail below with reference to FIG.

As shown in FIG. 8, each multicarrier beamformer 114 includes one IFFT modulator 1141, a multiplier 1142, and a time delay 1143.

Including a series combination of paths.

The IFFT modulator 1141 corresponds to the corresponding one from the multicarrier beam assigner 113.

Receiving frequency domain signals, forming a serial time domain signal by IFFT modulation, and consisting of a multiplier 1142 and a time delay 1143 in parallel with the serial time domain signal

Input to each series combination of paths. Of which

The subcarriers corresponding to the frequency domain signals are different from each other.

At the same time, the random vector generator 117 calculates the generated random vector.

Each multicarrier beamformer 114 is input to a corresponding multicarrier beamformer 114. The random vector is a vector

And the vector

Of which

Represents the weight and time delay of the serial time domain signal of the jth path output from the IFFT modulator 1141 of the i-th multicarrier beamformer 114, respectively.

It is.

The serial combination of each path consisting of the multiplier 1142 and the time delay 1143 is the vector output from the random vector generator 117.

To weight the input serial time domain signal and

Thus, a time delay process is performed on the serial time domain signal to form one transmission signal. The weighting process and the time delay process

Is equal to

Thus, each multi-carrier beamformer 114 is

In order to form a transmission signal

The multi-carrier beamformer 114 is

A number of transmission signals are formed. Where each multi-carrier beamformer 114 formed

Each transmitted signal

Corresponds to one of the two transmit antennas.

Multi-carrier beamformers 114 output

Among the transmission signals, the transmission signals corresponding to the same transmission antenna are stacked by the corresponding adders in the adder group 118 to form the corresponding transmission signals, and then the corresponding transmission signals in the cyclic prefix unit group 115. The cyclic prefix is input to the cyclic prefix unit, the cyclic prefix unit inserts the cyclic prefix into the input transmission signal, and the transmission signal with the cyclic prefix inserted is transmitted to the transmission RF link group 116. In cyclic prefix group 115

All the cyclic prefixes

A transmission signal with a number of cyclic prefixes inserted is output.

FIG. 9 further describes a specific configuration of the transmission RF link group 116. This transmit RF link group 116 is

Each of the transmit RF links includes a modulator 1161, an up-converter 1162, and a power amplifier 1163 connected in series, which may be a high power linear amplifier. . Of which

Transmission RF links are output from the cyclic prefix group 115, respectively.

The transmission signals are converted into corresponding RF signals.

FIG. 10 is a diagram showing the duplexer group 130 on the transmission side 10 of the present invention. Of these, the duplexer group 130

Includes parallel duplexers. Each duplexer is connected to one corresponding transmit antenna and is connected to the transmit RF link group 116 and the receive RF link group 123.

Receiver 20
For simplicity of explanation, only one receiver 20 is shown here.

In FIG. 11, the receiving side 20 includes a multi-carrier received signal processor 210, a feedback information processor 220, a duplexer group 230,

Including a book antenna.

  Among these, the multicarrier received signal processor 210 includes a received RF link group 211 and a MIMO received signal processor 212. The feedback information processor 220 includes a MIMO transmit signal processor 221 and a transmit RF link group 222.

The received RF link group 211 restores the received RF signal to a corresponding code stream, and the number of receiving antennas for transmitting to the MIMO received signal processor 212

With the same parallel receive RF link (not shown).

  The MIMO received signal processor 212 restores the code stream to the first user data and outputs it.

  Next, the scheduling process of the present invention will be described based on different scheduling methods. For the receiving side 20, in the scheduling of the present invention, each receiving side 20 having a plurality of antennas may be considered as the receiving side 20 having the same number of antennas. Therefore, the case where each receiving side 20 has one antenna will be described as an example, but the present invention can be applied to the case where each receiving side 20 has a plurality of antennas.

(First scheduling method)
Each receiving side 20 obtains user feedback information by processing the received signal via the multicarrier received signal processor 210 based on the channel fading situation, and transmits it to the feedback information processor 220. Among them, the user feedback information is the combination of the best transmission beams for the receiving side in each subcarrier.

And the signal-to-interference ratio corresponding to each transmit beam of this best transmit beam combination

including.

here,

Indicates the random complex vector on the sending side (in formula (3))

Fall under)

Indicates a channel fading matrix between the transmitting side 10 and the receiving side 20.

  The feedback information processor 220 processes the received user feedback information and converts it into a feedback signal suitable for the MIMO communication system. This feedback signal is fed back to the transmitting side 10 through the feedback channel via the antenna on the receiving side 20.

When the scheduler 121 on the transmission side 10 receives the feedback signal, it performs system scheduling. Each receiver 20 has the best transmit beam combination on each subcarrier

And the signal to interference ratio corresponding to each transmit beam of the best transmit beam combination

So the scheduling process is mainly
A step (1) for freeing a scheduling user list SU and an assigned transmission beam list SB;
For each subcarrier,
All signal-to-interference ratios that have been fed back

The maximum signal-to-interference ratio

I) selecting and filling in the scheduling user list SU and filling in the corresponding transmit beam in the assigned transmit beam list SB;
All signal-to-interference ratios that have been fed back

The maximum signal-to-interference ratio among unscheduled users

Step ii) to select and fill in the scheduling user list SU and fill the corresponding transmit beam in the assigned transmit beam list SB, and
Repeat step i) and step ii) until user scheduling is complete Step iii) Repeat step (2), and finally assign the scheduling user list SU finally generated for all subcarriers Based on the transmitted transmission beam list SB, the multi-carrier MIMO data processor 110 is controlled to divide the scheduled user data stream into independent code streams, assign them to predetermined transmission beams of predetermined subcarriers, and transmit antennas. The step (3) of making it send out from is included.

  In the scheduling step (2), for each subcarrier, when a certain receiving side 20 (user) has already joined the scheduling user list SU and selects another transmission beam in the best transmission beam combination, Since the receiving side 20 has only one antenna, it cannot be scheduled again. At this time, scheduling for the subcarrier ends.

  At the same time, in the scheduling step (2), for each subcarrier, if a transmission beam corresponding to the user has already been added to the allocated transmission beam list SB, the user is not scheduled again. At this time, scheduling for the subcarrier ends.

  If each receiving side 20 has multiple antennas, assuming that each antenna is one receiving side (user), the scheduling situation when each receiving side has multiple antennas is that each receiving side has only one antenna Close to the scheduling situation.

(Second scheduling method)
The multi-carrier MIMO communication system of the present invention considers interference between transmission beams on each subcarrier, and the number of users to be scheduled is fixed

If so, the user feedback information is obtained by processing the received signal by the multicarrier received signal processor 210 on the receiving side 20 based on the channel fading situation, and is transmitted to the feedback information processor 220. Among them, the user feedback information is the best transmission beam combination for the receiving side 20 in each subcarrier.

And the best transmit beam combination

Signal-to-interference ratio for each transmit beam

And a combination of transmission beams with minimum interference to the receiving side

Including. Where the best transmit beam combination for each subcarrier

(M-1) transmit beam combinations with the least number of transmit beams and minimum interference on the receiver side

May be selected based on the actual channel condition. In principle, the same transmit beam cannot be included in the two combinations at the same time.

Where S is the number of subcarriers

We show the set of all possibilities to select the (M-1) different minimum beams of interference from the beams.

  The feedback information processor 220 processes the received user feedback information and converts it into a feedback signal suitable for the MIMO communication system. This feedback signal is fed back to the transmitting side 10 via the feedback channel by the antenna on the receiving side 20.

When the scheduler 121 on the transmission side 10 receives the feedback signal, it performs system scheduling. At this time, each receiving side 20 has the best transmission beam combination in each subcarrier.

And the best transmit beam combination

Signal-to-interference ratio for each transmit beam

And (M-1) transmission beam combinations with minimum interference to the receiving side

The scheduling process is mainly
A step (1) for freeing a scheduling user list SU and an assigned transmission beam list SB;
For each subcarrier,
All signal-to-interference ratios that have been fed back

The maximum signal-to-interference ratio

I) selecting and filling in the scheduling user list SU and filling in the corresponding transmit beam in the assigned transmit beam list SB;
Corresponding combinations for users in the scheduling user list

The corresponding minimum transmission beam of interference is selected, and the corresponding maximum signal-to-interference ratio user is selected based on the minimum transmission beam of interference, and the user is entered in the scheduling user list. And step ii) of entering the transmit beam corresponding to the user in the assigned transmit beam list;
Step (2) repeating step iii), repeating steps i) and ii) until user scheduling on the subcarrier is finished, and finally scheduling generated for all subcarriers Based on the user list SU and the assigned transmission beam list SB, the multi-carrier MIMO data processor 110 is controlled to divide the scheduled user data stream into independent code streams, and a predetermined transmission beam of a predetermined subcarrier. And transmitting from the transmitting antenna (3).

(Third scheduling method)
In the multicarrier MIMO communication system of the present invention, when the interference between transmission beams and the influence of this interference on the system capacity are taken into consideration, the reception signals are received by the multicarrier reception signal processor 210 on the reception side 20 based on the channel fading situation. By processing, user feedback information is obtained and transmitted to the feedback information processor 220. Among them, this user feedback information includes the best transmission beam combination for the receiving side 20 in each subcarrier.

And the best transmit beam combination

At each transmit beam and the corresponding equivalent channel gain

And a transmission beam combination that minimizes interference with the receiving side

And the combination

Where each transmit beam is the best transmit beam performance loss ratio for the receiver

And are included.

  The feedback information processor 220 processes the received user feedback information and converts it into a feedback signal (RF signal) suitable for the MIMO communication system. This feedback signal is fed back from the antenna on the reception side 20 to the transmission side 10 via a feedback channel.

When the scheduler 121 on the transmission side 10 receives the feedback signal, it performs system scheduling. At this time, each receiving side 20 has the best transmission beam combination on each subcarrier.

And the combination

At each transmit beam equivalent channel gain

And a transmission beam combination with minimum interference to the receiving side

And the combination

Each transmit beam at the best transmit beam performance loss ratio for the receiver

The scheduling process is mainly
Step (1) of making the scheduling user list SU and the allocated transmission beam list SB empty,
For each subcarrier,
All equivalent channel gains that have been fed back

The maximum equivalent channel gain

I) selecting and filling in the scheduling user list SU and filling in the corresponding transmit beam in the assigned transmit beam list SB;
For users in the scheduling user list, their corresponding combinations

Selecting a transmission beam with a minimum corresponding interference from ii, then selecting a user with a maximum signal-to-interference ratio corresponding to the transmission beam with the minimum interference; and ii)
Performance loss ratio that has been fed back

To determine whether the user's subscription has increased system capacity, and if the user's subscription has increased system capacity, enter the user in the scheduling user list SU and send corresponding to the user If the beam is entered in the assigned transmit beam list SB, and the user's subscription reduces system capacity, the user does not enter the scheduling user list, and the scheduling is completed, step iii), and the user has subscribed Then, repeat step i) and iii) until step iv) is repeated until scheduling on the subcarrier is completed.Step (2) repeats, and finally, scheduling user list SU generated for all subcarriers finally. And the MIMO data processor 110 based on the assigned transmit beam list SB and the user Divided into code stream independent data streams, allocated in a predetermined transmission beam of a given sub-carrier, comprising the step (3) to be transmitted from the transmitting antenna.

  Therefore, this third scheduling method can adaptively schedule users and can fully utilize channel conditions and provide maximum channel capacity.

In order to clearly show the superiority of the scheduling system and the scheduling method of the present invention, referring to FIGS. 12 to 14, performance comparison of different scheduling methods in an actual channel is shown. Of these, the number of subcarriers

The number of code streams is L = 3, and the transmission power is P = 10.

In FIG. 12, the abscissa is the Ricean factor.

And the ordinate indicates the channel capacity obtained. If the number of antennas on the transmitting side is 2 and the number of users is 32, the Ricean factor

As the channel capacity increases, the channel capacity gradually decreases. Compared with the method disclosed in Reference 1 and the conventional random Gaussian weighting method, the communication method of the present invention has a smaller amount of decrease in channel capacity and is relatively flat. .

In FIG. 13, the abscissa indicates the number of users and the ordinate indicates the obtained channel capacity. Ricean factor

10 and the number of antennas on the transmission side is 2, compared with the method disclosed in Reference 1 and the conventional random Gaussian weighting method, the communication method of the present invention has a larger channel capacity as the number of users increases. Increase amount can be acquired.

  In FIG. 14, the abscissa indicates the number of transmitting antennas on the transmitting side, and the ordinate indicates the obtained channel capacity. When the number of users is 256, compared with the method disclosed in Reference 1 and the conventional random Gaussian weighting method, the communication method of the present invention can acquire a larger channel capacity increase amount as the number of transmission antennas increases. .

  As can be seen from the above comparison, the channel capacity provided by the multicarrier communication system and communication method of the present invention is larger than the channel capacity provided by the method disclosed in Reference 1 and the conventional random Gaussian weighting method.

  As described above, the multi-carrier MIMO communication system and the communication method of the present invention can perform user scheduling according to the channel status at that time, different feedback signals, improve system control intelligence and communication stability, Always maintained maximum system capacity. In addition to obtaining the maximum system capacity, the multi-carrier MIMO communication system of the present invention employs a new algorithm, so the conventional multi-carrier MIMO communication system generates many random numbers using many pseudo-random generators. In addition to solving the disadvantages, the associated probability density function of random vectors can be optimized, and the difficulty of the algorithm can be reduced.

(a) And (b) is a figure which shows the system configuration | structure at the time of having one transmission antenna in a base station and having two users. (a) shows the channel gain when the channel condition is good, (b) shows the channel gain when the channel has line of sight (Line Of Sight, LOS), and (c) shows that the system The channel gain when in the fading state is shown. It is a figure which shows the apparatus which implement | achieves shaping | molding of a multicarrier random beam in the conventional MIMO communication system. 1 is a block diagram of a multi-carrier MIMO communication system based on shaping a random transmit beam of the present invention. FIG. 5 is a flowchart of user scheduling of the multicarrier MIMO communication system shown in FIG. 4. It is a figure which shows the structure of the flame | frame employ | adopted by the multicarrier MIMO communication system of this invention. Furthermore, it is a figure which shows the structure of the transmission side 10 of the MIMO communication system of this invention. FIG. 8 is a specific structural diagram of the multicarrier beam former 114 shown in FIG. 7. 3 is a diagram illustrating a configuration of a transmission RF link group on a transmission side 10. FIG. It is a figure which shows the duplexer group 130 of the transmission side 10 of this invention. Furthermore, it is a figure which shows the structure of the receiving side 20 of the MIMO communication system of this invention. It is a performance comparison figure of the different scheduling methods in an actual channel condition. It is a performance comparison figure of the different scheduling methods in an actual channel condition. It is a performance comparison figure of the different scheduling methods in an actual channel condition.

Explanation of symbols

  10 ... Transmitting side, 20 ... Receiving side, 110 ... Multicarrier MIMO data processor, 120 ... Multicarrier MIMO scheduler, 130 ... Duplexer group, 210 ... Multicarrier received signal processor, 220 ... Feedback information processor, 230 ... Duplexer group 111 ... User selector, 112 ... Shunt, 113 ... Carrier beam allocator, 114 ... Multicarrier beamformer, 116 ... Transmit RF link group, 117 ... Random vector generator, 118 ... Adder group, 121 ... Scheduler, 122 ... MIMO received signal processor, 123 ... received RF link group, 211 ... received RF link group, 212 ... MIMO received signal processor, 221 ... MIMO transmitted signal processor, 222 ... transmitted RF link group, 1141 ... IFFT modulator, 1142 ... Multiplier, 1143 ... time delay, 115 ... cyclic prefix unit glue , 1161 ... modulator, 1162 ... upconverter, 1163 ... power amplifier,

Claims (11)

A transmitting side (10) for transmitting a data frame having at least a channel estimation signal and user data; and a data frame transmitted by the transmitting side (10) is received, a corresponding feedback signal is generated, and at least user data is restored A multi-carrier MIMO communication system including one receiving side (20),

The sender (10)
A duplexer group (130) for transmitting a data frame and receiving a feedback signal from the reception side (20), and a transmission antenna installed thereon;
A multi-carrier MIMO scheduler (120) that generates scheduling information based on the feedback signal;
A multi-carrier MIMO data processor (110) that selects a user who needs scheduling based on scheduling information and generates a corresponding multi-carrier transmission signal from the selected user's data;
And generating scheduling information based on the feedback signal, performing user scheduling using the scheduling information,

The scheduling information includes a user to be scheduled, a code stream supported by each user, a predetermined transmission beam of a predetermined subcarrier that transmits each code stream , and

The receiving side (20)
A duplexer group (230) for receiving a data frame from the transmission side (10) and transmitting user feedback information, and a transmission antenna installed thereon;
A multi-carrier received signal processor (210) that generates feedback data based on the data frame and recovers user data;
A feedback information processor (220) for converting user feedback information into a feedback signal;

The multi-carrier MIMO scheduler (120)
A received RF link group (123) for converting the received feedback signal into a corresponding code stream;
A MIMO reception signal processor (122) that performs space-time signal processing on the converted code stream to obtain corresponding scheduling information;
A scheduler (121) for controlling signal processing of the multicarrier MIMO data processor (110) based on the scheduling information;
Including

The multi-carrier MIMO data processor (110) is
A user selector (111) for selecting users to be scheduled based on scheduling information;
A plurality of parallel shunts (112) for shunting user data of users to be scheduled and outputting a plurality of code streams;
A carrier beam allocator (113) for allocating a code stream output from the shunt to a corresponding beam of a corresponding subcarrier designated by the scheduling information based on the scheduling information, and forming a plurality of frequency domain signals;
A random vector generator (117) for generating and outputting a random vector;
A plurality of parallel multi-carrier beams each forming a time domain signal corresponding to one transmission antenna based on the frequency domain signal from the carrier beam allocator (113) and the random vector from the random vector generator (117) A former (114);
An adder group (118) comprising a plurality of adders, each adder stacking time domain signals corresponding to the same transmission antenna to form one transmission signal;
A cyclic prefix group (115) including a plurality of cyclic prefix units, each cyclic prefix unit respectively inserting a cyclic prefix into the corresponding transmission signal output from the adder;
A transmission RF link group (116) for receiving a plurality of transmission signals output from the cyclic prefix group (115) and converting the plurality of transmission signals into corresponding RF signals, respectively. A featured multi-carrier MIMO communication system.
The feedback signal includes a best transmit beam combination for each receiver (20) on each subcarrier and a signal to interference ratio corresponding to each transmit beam in the best transmit beam combination. The multicarrier MIMO communication system according to 1.
The multi-carrier MIMO communication system according to claim 2, wherein the feedback signal further includes a transmission beam combination with the smallest interference to each receiving side (20) in each subcarrier.
The feedback signal includes the best transmit beam combination for each receiver on each subcarrier, the equivalent channel gain of each transmit beam with the combination, the transmit beam combination with the least interference to the receiver , and the receive side. The multi-carrier MIMO communication system according to claim 1, further comprising: a performance loss ratio of a best transmission beam to the receiving side of each transmission beam in a combination of transmission beams having the least interference .
The transmission RF link group (116) includes a plurality of parallel transmission RF links that respectively convert a plurality of transmission signals output from the cyclic prefix unit (115) into corresponding RF signals, and each transmission RF link includes The multi-carrier MIMO communication system according to claim 1 , comprising one modulator (1161) connected in series, one up-converter (1162), and one power amplifier (1163). .
The multi-carrier received signal processor (210)
A received RF link group (211) that performs demodulation and frequency conversion processing on the received RF signal and obtains a corresponding code stream;
A MIMO reception signal processor (212) for generating corresponding user feedback information based on the code stream and restoring and outputting user data;
The feedback information processor (220)
A MIMO transmit signal processor (221) for converting user feedback information into a feedback signal;
The multi-carrier MIMO communication system according to claim 5 , further comprising: a transmission RF link group (222) for converting the feedback signal into a corresponding RF signal.
The multicarrier MIMO communication system according to claim 6 , wherein the vectors generated by the random vector generator are a weight vector and a time delay vector.
Each multi-carrier beamformer (114) includes one IFFT modulator (1141) and a plurality of serial combinations of a multiplier (1142) and a time delay (1143), and the IFFT modulator (1141) IFFT modulation is performed on the frequency domain signal from the carrier beam assigner (113) to form a serial time domain signal, and the serial time domain signal is simultaneously input to the plurality of serial combinations;
In each series combination of the multiplier (1142) and the time delay (1143), the multiplier (1142) and the time delay (1143) are based on the weight vector and the time delay vector from the random vector generator (117). The multi-carrier MIMO communication system according to claim 7 , wherein weighting processing and time delay processing are sequentially performed on the serial time domain signal to generate a time domain signal corresponding to one transmission antenna.
A multi-carrier MIMO communication method for performing random beam forming ,
On the receiving side, generating a feedback signal based on the channel fading situation between the transmitting antenna on the transmitting side and the receiving antenna on the receiving side, and feeding back the feedback signal to the transmitting side (a);
Receiving (b) the feedback signal on the transmission side and generating scheduling information based on the feedback signal;
On the transmitting side, a step of forming a corresponding multicarrier transmission signal from user data scheduled based on the scheduling information, and further transmitting the multicarrier transmission signal by a corresponding transmission antenna;
Step (d) of restoring user data on the receiving side based on the received transmission beam;
Including
Step (c)
Selecting a user to be scheduled based on scheduling information i);
Ii) dividing user data of users scheduled based on scheduling information into corresponding code streams;
Each code stream is allocated to a predetermined transmission beam of a predetermined subcarrier based on the scheduling information, and IFFT modulation is performed on each code stream for all subcarriers allocated to the same spatial domain channel. Step iii) of outputting parallel multipath serial time domain signals respectively corresponding to the transmitting antennas by
The serial time domain signal of each path is sequentially weighted and time-delayed to form a corresponding transmission signal, and the transmission signals corresponding to the same transmission antenna are stacked, and the multicarrier transmission signal obtained by stacking is transmitted to the multicarrier transmission signal. Insert a click prefix and transmit through the corresponding transmit antenna iv) and
Including

The scheduling information includes a user to be scheduled, a code stream supported by each user, and a predetermined transmission beam of a predetermined subcarrier that transmits each code stream,

The feedback signal includes, on each subcarrier, the best transmit beam combination for each receiver and a signal to interference ratio corresponding to each transmit beam in the best transmit beam combination;

Step (b)
Step (1) for freeing a scheduling user list and an assigned transmission beam list,
For each subcarrier,
Comparing all the signal-to-interference ratios that have been fed back, selecting the user with the highest signal-to-interference ratio and joining it to the scheduling user list, and joining the corresponding transmit beam to the assigned transmit beam list i) When,
Comparing all signal-to-interference ratios that have been fed back, selecting the user with the highest signal-to-interference ratio from among the unscheduled users, joining the scheduling user list, and assigning the corresponding transmit beam Step ii) to join the transmit beam list; and
Repeat steps i) and ii) until user scheduling on the subcarrier is completed.
Repeat step (2), and
Finally, based on the scheduling user list and allocated transmission beam list finally generated for all subcarriers, the step of performing system user scheduling (3)
Multicarrier MIMO communication method, which comprises a.
A multi-carrier MIMO communication method for performing random beam forming,
On the receiving side, generating a feedback signal based on the channel fading situation between the transmitting antenna on the transmitting side and the receiving antenna on the receiving side, and feeding back the feedback signal to the transmitting side (a);
Receiving (b) the feedback signal on the transmission side and generating scheduling information based on the feedback signal;
On the transmitting side, a step of forming a corresponding multicarrier transmission signal from user data scheduled based on the scheduling information, and further transmitting the multicarrier transmission signal by a corresponding transmission antenna;
Step (d) of restoring user data on the receiving side based on the received transmission beam;
Including
Step (c)
Selecting a user to be scheduled based on scheduling information i);
Ii) dividing user data of users scheduled based on scheduling information into corresponding code streams;
Each code stream is allocated to a predetermined transmission beam of a predetermined subcarrier based on the scheduling information, and IFFT modulation is performed on each code stream for all subcarriers allocated to the same spatial domain channel. Step iii) of outputting parallel multipath serial time domain signals respectively corresponding to the transmitting antennas by
The serial time domain signal of each path is sequentially weighted and time-delayed to form a corresponding transmission signal, and the transmission signals corresponding to the same transmission antenna are stacked, and the multicarrier transmission signal obtained by stacking is transmitted to the multicarrier transmission signal. Insert a click prefix and transmit through the corresponding transmit antenna iv) and
Including

The scheduling information includes a user to be scheduled, a code stream supported by each user, and a predetermined transmission beam of a predetermined subcarrier that transmits each code stream,

The feedback signal includes, on each subcarrier, the best transmit beam combination for each receiver, and a signal to interference ratio corresponding to each transmit beam in the best transmit beam combination, and each subcarrier. Including a combination of a plurality of transmission beams with the least interference for each receiving side ,

Step (b)
Step (1) for freeing a scheduling user list and an assigned transmission beam list,
For each subcarrier,
Compare all signal-to-interference ratios that have been fed back, select the user with the highest signal-to-interference ratio, fill in the scheduling user list, and fill the corresponding transmit beam in the assigned transmit beam list i) When,
For the users in the scheduling user list, select the corresponding transmission beam with the lowest interference from the corresponding combination, and then have the corresponding maximum signal to interference ratio based on the transmission beam with the lowest interference Step ii), selecting the user into the scheduling user list and simultaneously entering the corresponding transmit beam into the assigned transmit beam list;
Repeat steps i) and ii) until scheduling on the subcarrier is completed.
Repeat step (2), and
Finally, based on the scheduling user list and the allocated transmission beam list finally generated for all subcarriers, the step of performing system user scheduling (3)
A multi-carrier MIMO communication method comprising:
  A multi-carrier MIMO communication method for performing random beam forming,
  On the receiving side, generating a feedback signal based on the channel fading situation between the transmitting antenna on the transmitting side and the receiving antenna on the receiving side, and feeding back the feedback signal to the transmitting side (a);
  Receiving (b) the feedback signal on the transmission side and generating scheduling information based on the feedback signal;
  On the transmitting side, a step of forming a corresponding multicarrier transmission signal from user data scheduled based on the scheduling information, and further transmitting the multicarrier transmission signal by a corresponding transmission antenna;
  Step (d) of restoring user data on the receiving side based on the received transmission beam;
  Including
  Step (c)
  Selecting a user to be scheduled based on scheduling information i);
  Ii) dividing user data of users scheduled based on scheduling information into corresponding code streams;
  Each code stream is allocated to a predetermined transmission beam of a predetermined subcarrier based on the scheduling information, and IFFT modulation is performed on each code stream for all subcarriers allocated to the same spatial domain channel. Step iii) of outputting parallel multipath serial time domain signals respectively corresponding to the transmitting antennas by
  The serial time domain signal of each path is sequentially weighted and time-delayed to form a corresponding transmission signal, and the transmission signals corresponding to the same transmission antenna are stacked, and the multicarrier transmission signal obtained by stacking is transmitted to the multicarrier transmission signal. Insert a click prefix and transmit through the corresponding transmit antenna iv) and
Including

  The scheduling information includes a user to be scheduled, a code stream supported by each user, and a predetermined transmission beam of a predetermined subcarrier that transmits each code stream,

  The feedback signal includes, for each subcarrier, the combination, an equivalent channel gain corresponding to each transmit beam in the best transmit beam combination, and a transmit beam combination that minimizes interference to the receiving side; Each transmit beam in the best transmit beam combination for the receiver includes a ratio of performance loss to the best transmit beam for the receiver;

  Step (b)
  Step (1) for freeing a scheduling user list and an assigned transmission beam list,
  For each subcarrier,
  Comparing all the equivalent channel gains that have been fed back, selecting the user with the maximum equivalent channel gain and filling it in the scheduling user list and filling the corresponding transmission beam in the assigned transmission beam list i);
  For the users in the scheduling user list, select the transmission beam with the lowest interference from the corresponding combination, and then select the user with the maximum signal-to-interference ratio corresponding to the transmission beam with the lowest interference. Step ii)
  Based on the performance loss ratio that has been fed back, it is determined whether the user's subscription has increased system capacity, and if the user's subscription has increased system capacity, the user is entered in the scheduling user list and If the user fills the assigned transmit beam list in the assigned transmit beam list and the user's subscription reduces system capacity, the user does not fill the scheduling user list and completes scheduling on the subcarrier. Step iii), and
  Step iv) after repeating the steps i) and iii) in order after the user has joined and until user scheduling on the subcarrier is completed
Repeat step (2), and
  Performing user scheduling of the system based on the scheduling user list and allocated transmission beam list finally generated for all subcarriers (3)
A multi-carrier MIMO communication method comprising:

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