KR101989005B1 - Apparatus and method for saving power consumption in broadband wireless communication system - Google Patents

Abstract

A method of operating a device in accordance with various embodiments includes the steps of determining whether a traffic amount based on a predetermined period is greater than or equal to a threshold value and if the amount of traffic is greater than or equal to the threshold value, Transmitting a second signal using a part of the plurality of resources through a part of the plurality of antennas when the amount of traffic is less than the threshold; And controlling a transmission power of the second signal to be greater than a transmission power of the first signal.

Description

[0001] APPARATUS AND METHOD FOR SAVING POWER CONSUMPTION IN BROADBAND WIRELESS COMMUNICATION SYSTEM [0002]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a broadband wireless communication system, and more particularly, to an apparatus and method for reducing power consumption in a broadband wireless communication system.

In the fourth generation (4G) communication system, which is a next generation communication system, active research is being conducted to provide users with various QoS (Quality of Service) services at a transmission rate of about 100 Mbps. The IEEE 802.16 communication system includes an Orthogonal Frequency Division Multiplexing (OFDM) / Orthogonal Frequency Division Multiplexing (OFDMA) system in a physical channel in order to support a broadband transmission network, and a typical communication system thereof is an Institute of Electrical and Electronics Engineers (Orthogonal Frequency Division Multiple Access) scheme.

In a communication system based on OFDM / OFDMA (Orthogonal Frequency Division Multiple Access), a multiple input multiple output (MIMO) scheme using multiple transmit antennas may be applied to improve the reliability of a system or to support a higher data rate . In order to improve the reliability of the system, a space-time coding (STC) technique can be used, thereby increasing the spatial diversity gain. In order to improve the transmission rate, a spatial multiplexing (SM) technique can be used. According to the above-described two schemes, the transmitting end transmits a plurality of different streams through different transmitting antennas all at the same time.

1 shows an example of a transmission frame for each antenna according to the MIMO scheme in a broadband wireless communication system. FIG. 1 shows a transmission frame structure when two transmission antennas are used. The downlink subframe is divided into a preamble region 110 of one symbol length, a MAP region 120 for transmitting burst allocation information, and a data burst allocation region 130 . Signals transmitted through the antennas in the preamble region 110 and the map region 120 are subjected to an antenna CDD (Cyclic Delay Diversity) technique. The CDD scheme is a technique for giving a cyclic delay different for each antenna when transmitting a single stream through a plurality of transmission antennas, and a diversity gain is obtained. The signals transmitted through the data burst region 130 include different data streams in the case of the antenna # 0 and in the case of the antenna # 1. Also, although not shown, when four transmission antennas are used, transmission frames as shown in FIG. 1 are used for each pair of antennas. That is, four transmission frames are transmitted through each antenna, and a CCD technique can be applied to each antenna pair.

Since the MIMO scheme is an alternative for increasing the data rate, it is very effective when the traffic volume is large. However, if the traffic volume is small, the MIMO scheme by multi-antenna transmission may be inefficient. This is because transmitting a signal through a plurality of transmission antennas in a situation where transmission of a high data rate is not necessary may cause unnecessary power consumption. That is, even if a signal is transmitted using only one transmission antenna, a required data rate can be achieved. However, if a plurality of transmission antennas are used, power consumption due to overlapping preambles, . At this time, as the number of used transmit antennas increases, the power consumption increases. Therefore, when the MIMO scheme is used, an alternative scheme for preventing unnecessary power consumption due to a decrease in traffic volume should be proposed.

Accordingly, it is an object of the present invention to provide an apparatus and method for preventing unnecessary power consumption caused by a decrease in a traffic volume when a MIMO scheme is used in a broadband wireless communication system.

It is another object of the present invention to provide an apparatus and method for turning on / off a power amplifier according to a traffic amount in a broadband wireless communication system.

It is still another object of the present invention to provide an apparatus and method for maintaining coverage using some transmission antennas in a broadband wireless communication system.

An apparatus according to various embodiments includes a control block configured to determine whether a traffic amount based on a predetermined period is greater than or equal to a threshold value, And transmit a second signal using a plurality of resources via a portion of the plurality of antennas if the amount of traffic is less than the threshold, And a boosting block configured to control a transmission power of the second signal to have a value greater than a transmission power of the first signal.

A method of operating a device in accordance with various embodiments includes the steps of determining whether a traffic amount based on a predetermined period is greater than or equal to a threshold value and if the amount of traffic is greater than or equal to the threshold value, Transmitting a second signal using a part of the plurality of resources through a part of the plurality of antennas when the amount of traffic is less than the threshold; And controlling a transmission power of the second signal to be greater than a transmission power of the first signal.

The power consumption and cost can be effectively reduced by turning on / off the operation of some power amplifiers considering the traffic volume in the transmitting terminal using a plurality of transmitting antennas.

1 is a diagram illustrating an example of a transmission frame for each antenna according to a MIMO scheme in a broadband wireless communication system,
2 is a diagram illustrating a transmission frame according to a MIMO + mode in a broadband wireless communication system according to an embodiment of the present invention;
3 is a diagram illustrating a transmission frame according to a SIMO + mode in a broadband wireless communication system according to an embodiment of the present invention;
4 is a block diagram of a transmitting end in a broadband wireless communication system according to an embodiment of the present invention.
5 is a diagram illustrating an operation procedure of a transmitter in a broadband wireless communication system according to an embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings. In the following description of the present invention, a detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention rather unclear.

Hereinafter, a technique for preventing unnecessary power consumption caused by a decrease in traffic volume when using the MIMO technique in a broadband wireless communication system will be described. Hereinafter, the present invention will be described by taking an example of a wireless communication system of Orthogonal Frequency Division Multiplexing (OFDM) / Orthogonal Frequency Division Multiple Access (OFDMA) , And can be similarly applied to other types of wireless communication systems.

The system according to an embodiment of the present invention determines an amount of traffic in real time and performs an operation for reducing power consumption according to a traffic amount. If it is determined that the traffic is above a certain level, the system transmits data according to the MIMO scheme. On the other hand, if it is determined that the amount of traffic is less than a predetermined level, the system turns off Power Amplifier modules connected to some antennas and changes the scheduling method to a packet allocation mode.

For effective power consumption reduction, the present invention defines a MIMO + mode and a SIMO + mode in addition to the conventional conventional MIMO mode as shown in FIG. In the MIMO + mode, a signal is transmitted using a plurality of transmit antennas, and only a part of resources are used on a frequency axis of a downlink subframe. The SIMO + mode transmits a signal to one transmit antenna, It is a method to use only some resources. For example, the transmission frame according to the MIMO + mode is as shown in FIG. 2, and the transmission frame according to the SIMO + mode is as shown in FIG.

FIG. 2 illustrates a transmission frame according to a MIMO + mode in a broadband wireless communication system according to an embodiment of the present invention. The MIMO + mode is used for a transmitter using four transmit antennas to perform communication using only two transmit antennas. In order for the signal to reach the coverage boundary, the transmitting end must use a transmission power higher than a certain level, and the transmission power is distributed to each antenna. Therefore, if only two of the four transmit antennas are used, a coverage hole may occur. Therefore, the transmitting terminal transmits signals using only some of the resources on the frequency axis. For example, some of the resources may be half of all subcarriers. Thus, the transmitting terminal can boost transmission power allocated to the two antennas. Thus, coverage can be maintained when four transmission antennas are used with only two transmission antennas. 2, a signal transmitted through each transmission antenna includes a preamble 210, a map 220, and a data burst 230 according to the MIMO + mode. In this case, since the preamble 210 needs to transmit all the predefined sequences, it is transmitted over the entire band. However, in the case of the MAP 220 and the data burst 230, only a part of all subcarriers are used, 3dB boosting is applied.

3 shows a transmission frame according to the SIMO + mode in a broadband wireless communication system according to an embodiment of the present invention. The SIMO + mode is used for a transmitter using two transmission antennas to perform communication using only one transmission antenna. In order for the signal to reach the coverage boundary, the transmitting end must use a transmission power higher than a certain level, and the transmission power is distributed to each antenna. Therefore, when only one of the two transmit antennas is used, a coverage hole may occur. Therefore, the transmitting terminal transmits signals using only some of the resources on the frequency axis. For example, some of the resources may be half of all subcarriers. Thus, the transmitting terminal can boost transmission power allocated to one antenna. Thus, coverage can be maintained when two transmission antennas are used with only one transmission antenna. As shown in FIG. 3, in accordance with the SIMO + mode, a signal transmitted through each transmission antenna includes a preamble 310, a map 320, and a data burst 330. Since the preamble 310 needs to transmit all the predefined sequences, it is transmitted over the entire band. However, in the case of the MAP 320 and the data burst 330, only a part of all subcarriers are used, 3dB boosting is applied.

4 shows a block diagram of a transmitting end in a broadband wireless communication system according to an embodiment of the present invention.

4, the transmitter includes a DU (Digital Unit) 400, a RU (Radio Unit) 440, and a plurality of antennas 480. The DU 400 processes a digital signal and includes a control block 402, a DSP (Digital Signal Processor) block 404, and a modem block 406. The RU 440 processes a radio frequency (RF) signal, and includes a plurality of PA (Power Amplifier) modules 442 and a plurality of ON / OFF controllers 444.

The control block 402 controls the functions of the blocks in the DU 400. [ In particular, according to an embodiment of the present invention, the control block 402 receives information on resource usage from the DSP module 404, and determines a traffic volume using information on the resource usage. That is, the control block 402 receives SUI (Slot Utilization Information) from the DSP module 404. The SUI is generated for each frame and represents the ratio of the number of actually allocated slots to the total number of slots that can be allocated in the downlink subframe. Specifically, the control block 402 uses the SUI to determine long-term averaged slot utilizations. For example, the long period average slot usage rate can be determined as Equation (1).

In Equation (1), Su (n) denotes an n-th determined long period average slot usage rate,? Denotes a forgotten factor, and SUI (n) denotes an n-th SUI provided.

In accordance with the determination of the amount of traffic, the control block 402 controls ON / OFF of the power amplifier module and controls the mode change. That is, the control block 402 transmits a PCI (Power Control Indicator) to the on / off controller 444 to turn on / off the power amplifier module, and controls the DSP block 404 MSI (Mode Switch Indicator). That is, the control block 402 may be configured to operate in the MIMO mode if the long period average slot usage rate is greater than or equal to a threshold value, and to operate in the MIMO + mode or the SIMO + mode if the long period average slot usage rate is below a threshold value. And controls the on / off controller 444.

The DSP block 404 performs scheduling for the transmission packets. The DSP block 404 generates an SUI according to the scheduling result and provides the SUI to the control block 402. [ In addition, the DSP block 404 performs scheduling by reflecting the operation mode indicated by the control block 402. [ Here, the operation mode includes a MIMO mode, a MIMO + mode, and a SIMO + mode. That is, the DSP block 404 performs scheduling according to the operation mode indicated by the MSI provided from the control block 402. [ For example, in the MIMO + mode, the DSP block 404 distributes streams to a plurality of transmit antennas, and performs scheduling using only a part of resources on a frequency axis of a frame. On the other hand, in the SIMO + mode, the DSP block 404 allocates a stream to one transmission antenna, and performs scheduling using only a part of resources on the frequency axis of the frame.

The modem block 406 performs modulation and channel coding on data to be transmitted according to the scheduling result of the DSP block 404. [ The modem block 406 maps complex symbols to resources according to a scheduling result of the DSP block 404 and inserts an Inverse Fast Fourier Transform (IFFT) operation and a CP (Cyclic Prefix) Create a symbol. At this time, if the MIMO + mode or the SIMO + mode is applied, the modem block 406 applies 3dB boosting.

The plurality of PA modules 442 amplifies a transmission signal and transmits the amplified signal through the plurality of transmission antennas 480. The number of PA modules 442 is equal to the number of transmit antennas 480 and corresponds to each of the plurality of transmit antennas 480. The plurality of on / off controllers 444 turn on / off the operation of each of the plurality of PA blocks 442 under the control of the control block 402. That is, each of the ON / OFF controllers 444 turns on / off the operation of the corresponding PA block 442 according to the PCI value provided from the control block 402.

5 illustrates an operation procedure of a transmitter in a broadband wireless communication system according to an embodiment of the present invention.

Referring to FIG. 5, in step 501, the transmitter determines whether resource allocation for a downlink subframe is completed. At this time, the range of resources used for resource allocation is determined according to the current operation mode. That is, in the case of operating in the MIMO mode, only the resources on the entire frequency axis, that is, all the subcarriers are allocated, and in the case of operating in the MIMO + mode or the SIMO + mode, only some resources are allocated on the frequency axis. For example, some resources on the frequency axis may be half of all subcarriers.

When the resource allocation for the downlink subframe is completed, the transmitter proceeds to step 503 and calculates the resource usage of the frame. That is, the transmitting terminal calculates the ratio of the number of actually allocated slots to the total number of slots that can be allocated. Here, the total number of slots that can be allocated is determined according to the current operation mode. The resource usage of the frame may be expressed by a specific parameter to be transmitted to the block that determines the amount of traffic in the transmitter, and the specific parameter may be referred to as SUI.

In step 505, the transmitting end calculates a long period resource usage rate using the resource usage amount of the frame. The long cycle resource utilization rate is an average of the resource usage of the frame calculated for each frame. For example, the long period resource utilization rate can be determined as Equation (1).

After calculating the long period resource usage rate, the receiving terminal proceeds to step 507 and determines whether the long period resource usage rate is equal to or greater than a threshold value. That is, the receiving terminal determines whether the amount of traffic is large or small using the long period resource usage rate. The comparison result of the long period resource usage rate and the threshold value may be expressed as a specific parameter to be transmitted to the block responsible for scheduling in the transmitter, and the specific parameter may be referred to as MSI.

If the long period resource usage rate is greater than or equal to the threshold value, the transmitter proceeds to step 509 and operates in the MIMO mode in the next frame. That is, the transmitter uses all the transmit antennas and performs downlink communication according to the MIMO scheme.

On the other hand, if the long period resource usage rate is greater than or equal to the threshold, the transmitter proceeds to step 511 and operates in the MIMO + mode or the SIMO + mode in the next frame. That is, the transmitting terminal uses only some of the transmission antennas of all transmission antennas and performs downlink communication. At this time, the transmitter uses only a part of resources on the frequency axis and applies 3dB boosting to the transmission signal. However, the transmitting terminal transmits the preamble through all bands, and does not apply 3dB boosting. For example, in the MIMO + mode, the transmitter configures a transmission frame as shown in FIG. 2. In the SIMO + mode, the transmitter configures a transmission frame as shown in FIG. In other words, in the next frame, the transmitting end performs scheduling using only some resources on the frequency axis in some transmission antennas and downlink subframes, applies boosting to signals transmitted through the partial resources, And turns off the operation of at least one power amplifier corresponding to at least one of the transmission antennas.

While the present invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not limited to the disclosed embodiments, but is capable of various modifications within the scope of the invention. Therefore, the scope of the present invention should not be limited by the illustrated embodiments, but should be determined by the scope of the appended claims and equivalents thereof.

Claims (16)

An apparatus in a wireless communication system,
A radio unit;
A control block; And
Includes a boosting block,
The control block includes:
Wherein the device is configured to determine whether a traffic amount associated with the device is greater than or equal to a threshold, as determined by the device based on a predetermined period,
For a first time interval for transmitting data in a subframe, a first transmission scheme using a plurality of antennas and a plurality of frequency resources when the amount of traffic is greater than or equal to the threshold, , ≪ / RTI >
Transmitting a second signal using the radio unit in accordance with a second transmission scheme that uses a portion of the plurality of antennas and a portion of the plurality of frequency resources during the first time interval when the amount of traffic is less than the threshold Lt; / RTI >
And to control the transmit power of the second signal using the boosting block to have a value greater than the transmit power of the first signal.
2. The apparatus of claim 1,
And determine the amount of traffic by determining an amount of allocated slots versus total available slots for the predetermined period or by calculating an average amount of time resources utilized during the predetermined period.
The method according to claim 1,
Wherein the portion of the plurality of antennas used in accordance with the second transmission scheme comprises at least two antennas.
The method according to claim 1,
Wherein the subframe further includes a second time interval for transmitting allocation information for the data,
The control block includes:
And to transmit allocation information for the data using the radio according to the first transmission scheme during the second time interval if the amount of traffic is greater than or equal to the threshold value,
And transmit the allocation information for the data using the radio according to the second transmission scheme for the second time period if the amount of traffic is less than the threshold.
2. The apparatus of claim 1,
And to use the boosting block to increase the transmit power of the second signal by 3 dB over the transmit power of the first signal.
2. The apparatus of claim 1,
And to increase the transmit power of the second signal for each of the plurality of antennas using the boosting block, based on the number of remaining antennas of the plurality of antennas except for a portion of the plurality of antennas Device.
2. The apparatus of claim 1,
And to select a portion of the plurality of antennas that transmit the second signal among the plurality of antennas based on channel quality for each of the plurality of antennas.
2. The apparatus of claim 1,
And to deactivate at least one power amplifier (PA) corresponding to at least one antenna among the plurality of antennas except a part of the plurality of antennas using the wireless unit.
A method of operating an apparatus in a wireless communication system,
Determining whether a traffic amount associated with the device is greater than or equal to a threshold, as determined by the device based on a predetermined period;
Transmitting a first signal according to a first transmission scheme using a plurality of antennas and a plurality of frequency resources during a first time interval for transmitting data in a subframe when the amount of traffic is greater than or equal to the threshold;
Transmitting a second signal according to a second transmission scheme using a part of the plurality of antennas and a part of the plurality of frequency resources for the first time interval when the amount of traffic is less than the threshold,
And controlling a transmission power of the second signal to be greater than a transmission power of the first signal.
The method of claim 9,
Determining the amount of traffic by determining an amount of allocated slots versus total available slots or calculating an average amount of time resources utilized during the predetermined period during the predetermined period.
The method of claim 9,
Wherein a portion of the plurality of antennas used in accordance with the second transmission scheme comprises at least two antennas.
The method of claim 9,
Wherein the subframe further includes a second time interval for transmitting allocation information for the data,
Transmitting allocation information for the data according to the first transmission scheme during the second time interval when the amount of traffic is greater than or equal to the threshold value;
And if the amount of traffic is less than the threshold, transmitting allocation information for the data according to the second transmission scheme during the second time interval.
The method as claimed in claim 9, wherein the step of controlling the transmission power of the second signal comprises:
And increasing the transmission power of the second signal by 3 dB from the transmission power of the first signal.
The method as claimed in claim 9, wherein the step of controlling the transmission power of the second signal comprises:
And increasing the transmission power of the second signal for each of the plurality of antennas based on the number of remaining antennas excluding a part of the plurality of antennas among the plurality of antennas.
The method of claim 9,
Selecting a portion of the plurality of antennas to transmit the second signal among the plurality of antennas based on channel quality for each of the plurality of antennas.
The method of claim 9,
Further comprising the step of deactivating at least one power amplifier (PA) corresponding to at least one antenna among the plurality of antennas except a part of the plurality of antennas.

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