KR101209291B1 - Method for Improvement Performance Using Relay Uplink of 3GPP LTE System based Hybrid OFDMA/SC-FDMA, and Mobile Communication Terminal therefor - Google Patents

Abstract

The present invention relates to a method for improving performance using an uplink relay in a hybrid OFDMA / SC-FDMA based 3GPP LTE system, and a mobile communication terminal for the same. The present invention relates to selecting a relay for transmitting data from a cell boundary to a communication network, and time. In order to increase throughput, one of SC-FDMA and OFDMA is selected as a data transmission technique for each slot.

Description

Method for Improvement Performance Using Relay Uplink of 3GPP LTE System based Hybrid OFDMA / SC-FDMA, and Mobile Communication Terminal in 3GPP LTA based 3GPP LTE system therefor}

The present invention relates to a method for improving performance using an uplink relay in a hybrid OFDMA / SC-FDMA based 3GPP LTE system and a mobile communication terminal for the same. More specifically, the relay is selected for data transmission in a cell boundary region. Hybrid OFDMA to expand cell coverage and increase transmission efficiency in 3GPP LTE system by applying either Orthogonal Frequency Division Multiple Access (OFDMA) or Single Carrier Frequency. Division Multiple Access (SC-FDMA) as a data transmission technology The present invention relates to a performance improvement method using an uplink relay in a 3GPP LTE system based on / SC-FDMA, and a mobile communication terminal for the same.

In 3GPP LTE system, uplink uses Single Carrier Frequency Division Multiple Access (SC-FDMA).

1 is a diagram illustrating a general SC-FDMA block diagram.

In this scheme of transmitting data using one carrier, as shown in A and B of FIG. 1, a Discrete Fourier Transform (DFT) and an Inverse Discrete Fourier Transform (IDFT) are added to the transmitting and receiving terminals, respectively, than OFDMA. . SC-FDMA has a lower Peak-to-Average Power Ratio (PAPR) than Orthogonal Frequency Division Multiple Access (OFDMA) due to the use of one carrier. Low PAPR increases power efficiency, which is an important factor in the terminal.

However, when the signal is severely distorted by the channel in the frequency domain, SC-FDMA uses the frequency domain equalizer at the receiving end and then spreads and degrades the effects of the severely distorted portion through the IDFT.

In addition, as the modulation level is increased, the efficiency of PAPR, which is an advantage of SC-FDMA, is reduced. In 3GPP LTE-Advanced, Hybrid OFDMA / SC-FDMA has been proposed as a technique to properly compensate for such PAPR efficiency and performance difference between OFDMA and SC-FDMA.

2 is a diagram for explaining SC-FDMA and Hybrid OFDMA / SC-FDMA.

2 (a) shows a case of using only SC-FDMA, and (b) shows an example of using Hybrid OFDMA / SC-FDMA.

Hybrid OFDMA / SC-FDMA is a technology that uses OFDMA when the mobile communication terminal is located in the cell center region close to the base station, and SC-FDMA with good PAPR performance when located in the cell boundary region. SC-FDMA is slightly lower in performance than OFDMA as described above, but is applied because power efficiency is an important factor in mobile communication terminals.

However, when SC-FDMA is used in the cell center region, the loss due to the difference in performance from OFDMA is greater than the gain obtained by using low PAPR.

For this reason, SC-FDMA is used in the cell boundary area where power efficiency is important in Hybrid OFDMA / SC-FDMA, but OFDMA is used in the cell center area where power efficiency is more stable. will be.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and the relay is selected to transmit data from the cell boundary area to the communication network, and transmission is performed by selecting one of SC-FDMA and OFDMA as a data transmission technique for each time slot. There is a technical problem to provide a method for improving performance using an uplink relay in a hybrid OFDMA / SC-FDMA based 3GPP LTE system to increase throughput and a mobile communication terminal for the same.

The present invention also aims to increase cell coverage.

In order to achieve the above object, a system for improving performance using an uplink relay according to the present invention selects a relay terminal for transmitting data to a mobile communication system as it moves to a cell boundary region, and transmits data according to a predetermined criterion. A mobile communication terminal for transmitting data to the relay terminal using the selected transmission technology after selecting a transmission technology for transmitting the data; And

And a relay terminal for detecting data transmitted from the mobile communication terminal, selecting a transmission technology for transmitting data according to a predetermined criterion, and then transmitting the data to the mobile communication system using the selected transmission technology.

Another mobile communication terminal of the present invention includes a relay application determination unit that determines whether to use a relay to transmit data to the mobile communication system as the mobile communication terminal moves to the cell boundary area;

A relay selecting unit configured to select a mobile communication terminal having the highest transmission / reception performance value among other mobile communication terminals located around the mobile communication terminal as a relay terminal;

A transmission technology selection unit for determining to apply either SC-FDMA (Single Carrier Frequency Division Multiple Access) or OFDMA (Orthogonal Frequency Division Multiple Access) according to a preset criterion;

And a data transmitter for transmitting data to the relay terminal using the transmission technique selected by the transmission technique selection unit.

The preset reference is a signal-to-noise ratio (SNR), and the transmission technology selector selects OFDMA when the signal-to-noise ratio is greater than or equal to the reference value, and selects SC-FDMA when the signal-to-noise ratio is less than or equal to the reference value.

Preferably, the relay selecting unit selects one or a plurality of relay terminals.

Another relay terminal of the present invention includes a data receiving unit for receiving data transmitted from a mobile communication terminal located in a cell boundary area;

A transmission technology selection unit for selecting one of a single carrier frequency division multiple access (SC-FDMA) or an orthogonal frequency division multiple access (OFDMA) to transmit data to a mobile communication system according to a predetermined criterion; And

And a data transmitter for transmitting data to the mobile communication system using the transmission technology selected by the transmission technology selection unit.

The preset reference is a signal-to-noise ratio (SNR),

The transmission technology selection unit preferably selects OFDMA when the signal-to-noise ratio is greater than or equal to the reference value, and selects SC-FDMA when the signal-to-noise ratio is less than or equal to the reference value.

In another hybrid OFDMA / SC-FDMA based 3GPP LTE system of the present invention, a method for improving performance using an uplink relay includes: a) searching for a mobile communication terminal except for itself as the mobile communication terminal moves to a cell boundary; ;

b) selecting a mobile communication terminal (relay terminal) to be used as a relay by the mobile communication terminal;

c) transmitting, by the mobile terminal, data to the relay terminal by selecting either SC-FDMA or OFDM according to a preset criterion; And

and d) selecting, by the relay terminal, any one of SC-FDMA and OFDM according to a preset criterion and transmitting data received from the mobile communication terminal to the base station.

In step c),

The mobile terminal selects OFDMA when the signal-to-noise ratio is above the reference value, and selects SC-FDMA when the signal-to-noise ratio is below the reference value.

In step d),

Preferably, the relay terminal selects OFDMA when the signal-to-noise ratio is greater than or equal to the reference value, and selects SC-FDMA when the signal-to-noise ratio is less than or equal to the reference value.

As described above, in the hybrid OFDMA / SC-FDMA based 3GPP LTE system of the present invention, a method for improving performance using an uplink relay and a mobile communication terminal for selecting the relay to transmit data to a communication network in a cell boundary region, As one of SC-FDMA and OFDMA is selected as a data transmission technique for each time slot, an effect of increasing throughput may be expected.

In addition, the present invention can be expected to increase the cell coverage as the mobile communication terminal transmits data to the communication network using a relay terminal.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

Another powerful technology proposed for 3GPP LTE-Advanced is multi-hop relay technology. Among the various forms proposed, the present invention assumes a structure as shown in FIG. 3.

3 is a view for explaining the structure of a multi-hop relay according to the present invention, and shows the structure of the mobile communication terminals UE1 and 10 and the mobile communication terminals P1 and 20 (hereinafter, referred to as relay terminals) selected as relays.

First, the mobile communication terminal 10 located in the cell boundary region searches for other mobile communication terminals except itself that can be used as a relay.

The mobile communication terminal 10 transmits the data to the relay terminal 20, and the relay terminal 20 transmits the received data back to the base station 30 to transmit the data of the mobile communication terminal 10 located in the cell boundary region. Increase the transmission rate This, in turn, extends cell coverage.

In the following description, it will be assumed that the mobile communication terminal is capable of transmitting and receiving both SC-FDMA and OFDMA. In addition, it is assumed that the relay protocol is a relay protocol disclosed in FIG. 4.

If the mobile communication terminal does not use a relay, OFDMA is applied in the cell center region, and the existing hybrid OFDMA / SC-FDMA scheme using SC-FDMA is applied in the cell boundary region.

Hereinafter, a case in which a mobile communication terminal that can be utilized as a relay around the mobile communication terminal 100 will be described as an example.

5 is a view showing the configuration of a mobile communication terminal according to the present invention.

As shown, the mobile communication terminal 100 includes a wireless communication unit 110, an input unit 120, an output unit 130, a memory 140, a relay application determining unit 150, a relay selecting unit 160, A transmission technology selection unit 170 and a data transmission unit 180.

A wireless communication unit 110 for performing communication with a mobile communication network, an input unit 120 for input control of the mobile communication terminal 100, and an output for providing audio or visual data necessary for using a voice call service or a data service. The unit 130 and the memory 140 for storing various data are general configurations of the mobile communication terminal, and thus detailed description thereof will be omitted.

The relay application determining unit 150 determines whether to use a relay to transmit data to the base station 300 as the mobile communication terminal 100 is located in the cell boundary region.

The relay selecting unit 160 selects as a relay terminal a mobile communication terminal having an excellent transmission / reception performance among other mobile communication terminals located around the mobile communication terminal 100.

Here, since the relay selecting unit 160 checks the signal transmitting / receiving performance between the other mobile communication terminal and the communication network, since it corresponds to a known technology, a detailed description thereof will be omitted.

The transmission technology selector 170 determines to apply either SC-FDMA or OFDMA when transmitting data to the relay terminal 200 according to a preset criterion.

Here, the preset reference is a signal-to-noise ratio, SNR is equal to or greater than the reference value, OFDMA is applied, and if SNR is equal to or less than the reference value, SC-FDMA is applied.

For example, the transmission technology selector 170 transmits data by applying SC-FDMA at a low SNR and transmits data by applying OFDMA at a high SNR.

Meanwhile, the preset reference may further include a distance in addition to the signal-to-noise ratio, and apply the signal-to-noise ratio and the distance, or both.

The data transmitter 180 transmits data to the relay terminal 200 using the transmission technique selected by the transmission technique selector 170.

6 is a diagram illustrating a configuration of a relay terminal according to the present invention.

As illustrated, the relay terminal 200 includes a wireless communication unit 210, a data receiver 220, a transmission technology selector 230, and a data transmitter 240 for performing communication through a communication network.

The data receiver 220 receives data transmitted through the communication network, including data transmitted from the mobile communication terminal 100.

The transmission technology selecting unit 230 determines whether to apply either SC-FDMA or OFDMA when transmitting data to the base station 300 according to a preset criterion.

Here, the preset reference is SNR, and when the SNR is equal to or greater than the reference value, OFDMA is applied and when the SNR is equal to or less than the reference value, SC-FDMA is applied.

That is, the transmission technology selector 230 transmits data by applying SC-FDMA at low SNR and transmits data by applying OFDMA at high SNR.

The data transmitter 240 transmits data to the base station 300 by using the transmission technique selected by the transmission technique selector 230.

FIG. 7 is a diagram for describing Hybrid OFDMA / SC-FDMA and a multi-hop relay according to the present invention, and various cases of the above-described technology will be described.

First, (a) of FIG. 7 illustrates a case in which a mobile communication terminal 200 located in a cell center area is used for relay selection when the mobile communication terminal 100 is located in a cell boundary area.

Since the distance between the mobile communication terminal 100 and the relay terminal 200 is far, in the first slot (phase 1), the mobile communication terminal 100 transmits data to the relay terminal 200 using SC-FDMA with high power efficiency. send.

In the second slot (phase 2), the relay terminal 200 transmits data transmitted from the mobile communication terminal 100 to the base station 300 using OFDMA. In this case, the power efficiency is lower than that of SC-FDMA, but because it is close to the base station 300, it is possible to increase the transmission efficiency (throughput) by using the high-performance OFDMA, and at the same time can increase the coverage by using a relay have.

FIG. 7B illustrates a case in which the mobile communication terminal 100 located in the cell boundary region selects and uses a relay terminal 200 closer to the base station 300.

Since the distance between the mobile communication terminal 100 and the relay terminal 200 is close in the first slot (phase 1), the mobile communication terminal 100 transmits data to the relay terminal 200 by using OFDMA having better performance. The relay terminal 200 far from the base station 300 in the second slot (phase 2) uses SC-FDMA. In this case, as in (a), OFDMA and SC-FDMA are appropriately used according to SNR (or distance) to increase throughput and coverage.

7C illustrates a case where the distance between the base station 300, the relay terminal 200, and the mobile communication terminal 100 is close to each other.

Because of their close proximity to each other, they are less power efficient, but they can use all the better OFDMAs.

In the case of (b) and (c) described above, unlike the hybrid OFDMA / SC-FDMA, the transmission scheme is selected according to the position of the relay.

On the other hand, even if the mobile communication terminal 100 is located in the cell boundary region, the OFDMA can be used if the relay is located near.

FIG. 7D illustrates a case in which a relay is introduced into a conventional system using only SC-FDMA. As shown, coverage increases most when using only relays and SC-FDMA.

8 is a view for explaining a data transmission method using a plurality of relays according to the present invention, a case where a plurality of mobile communication terminals to be used as a relay is selected. This method is also applicable to the methods proposed in FIG.

The number of mobile communication terminals selected as relays in FIG. 8 is three, P1, P2, and P3.

First, the mobile communication terminal 100 selects the mobile communication terminals P1, P2, P3 in an environment of excellent transmission and reception performance among the mobile communication terminals located around the relay terminal.

In this case, the mobile communication terminal 100 transmits data to all of the plurality of relay terminals P1, P2, P3 and 200 in the first slot (phase 1), and relay terminal 200 in the second slot (phase 2). ) Transmits the data received from the mobile communication terminal 100 to the base station 300. In this case, the diversity gain can be expected through the cooperation of the mobile communication terminal 100 and the relay terminal 200.

9 is a flowchart illustrating a data transmission method using a relay according to the present invention.

First, as the mobile communication terminal 100 is located in the cell boundary region, it determines the use of the relay (S101).

Subsequently, the mobile communication terminal 100 searches for a plurality of mobile communication terminals 200 located in the vicinity (S103).

The mobile communication terminal 100 selects a mobile communication terminal in an environment having excellent transmission / reception performance among the searched plurality of mobile communication terminals 200 as a relay terminal (S105).

Here, the mobile communication terminal 100 can select one or more relay terminals. If a plurality of relay terminals are selected, diversity effects can also be expected.

In step S105, since the technology for confirming the signal transmission and reception performance between the other mobile communication terminal and the communication network corresponds to a known technique, a detailed description thereof will be omitted.

The mobile communication terminal 100 determines to apply either SC-FDMA or OFDMA when transmitting data to the relay terminal 200 according to a preset criterion (S107).

Here, the preset reference is SNR, and when the SNR is equal to or greater than the reference value, OFDMA is applied and when the SNR is equal to or less than the reference value, SC-FDMA is applied.

That is, the mobile communication terminal 100 transmits data by applying SC-FDMA at low SNR and transmits data by applying OFDMA at high SNR.

Meanwhile, the preset reference may further include a distance in addition to the signal-to-noise ratio, and apply the signal-to-noise ratio and the distance, or both.

The mobile communication terminal 100 transmits data to the relay terminal 200 using the transmission technique selected in step S107 (S109).

The relay terminal 200 detects data received from the mobile communication terminal 100 (S111), and selects a transmission technology for transmitting data to the base station 300 according to a preset criterion (S113).

Thereafter, the relay terminal 200 transmits data to the base station 300 using the transmission technique selected in step S113 (S115).

Thus, those skilled in the art will appreciate that the present invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. It is therefore to be understood that the embodiments described above are to be considered in all respects only as illustrative and not restrictive. The scope of the present invention is shown by the following claims rather than the detailed description, and all changes or modifications derived from the meaning and scope of the claims and their equivalents should be construed as being included in the scope of the present invention. do.

As described above, in the Hybrid OFDMA / SC-FDMA-based 3GPP LTE system of the present invention, a method for improving performance using an uplink relay and a mobile communication terminal selecting the relay to transmit data to a communication network in a cell boundary region, As one of SC-FDMA and OFDMA is selected as a data transmission technique for each time slot, it is suitable for a high need for increasing throughput and cell coverage.

1 is a diagram showing a general SC-FDMA block diagram,

2 is a diagram for explaining SC-FDMA and Hybrid OFDMA / SC-FDMA;

3 is a view for explaining a multi-hop relay structure according to the present invention;

4 is a diagram showing a relay protocol according to the present invention;

5 is a view showing the configuration of a mobile communication terminal according to the present invention;

6 is a view showing the configuration of a relay terminal according to the present invention;

7 is a diagram for explaining a hybrid OFDMA / SC-FDMA and a multi-hop relay according to the present invention;

8 is a view for explaining a data transmission method using a plurality of relays according to the present invention;

9 is a flowchart illustrating a data transmission method using a relay according to the present invention.

<Explanation of symbols for the main parts of the drawings>

100: mobile communication terminal 110, 210: wireless communication unit

120: input unit 130: output unit

140: memory 150: relay application determination unit

160: relay selector 170: transmission technology selector

180: data transmission unit 200: relay terminal

220: data receiving unit 230: transmission technology selection unit

240: data transmission unit

Claims (8)

As it moves to the cell boundary area, it selects a relay terminal for transmitting data to the mobile communication system, selects a transmission technique for transmitting data according to a predetermined criterion, and then sends the data to the relay terminal using the selected transmission technique. A mobile terminal for transmitting; And A relay terminal for detecting data transmitted from the mobile communication terminal, selecting a transmission technology for transmitting data according to a predetermined criterion, and then transmitting the data to the mobile communication system using the selected transmission technology; Performance enhancement system using an uplink relay comprising a. A relay application determining unit determining whether to use a relay to transmit data to the mobile communication system as the mobile communication terminal moves to a cell boundary area; A relay selecting unit configured to select a mobile communication terminal having the highest transmission / reception performance value among other mobile communication terminals located around the mobile communication terminal as a relay terminal; A transmission technology selection unit for determining to apply either SC-FDMA (Single Carrier Frequency Division Multiple Access) or OFDMA (Orthogonal Frequency Division Multiple Access) according to a preset criterion; A data transmitter for transmitting data to a relay terminal using a transmission technique selected by the transmission technique selection unit; Mobile communication terminal comprising a. 3. The method of claim 2, The preset reference is a signal-to-noise ratio (SNR), The transmission technology selection unit, And selecting OFDMA when the signal-to-noise ratio is greater than or equal to the reference value, and selecting SC-FDMA when the signal-to-noise ratio is less than or equal to the reference value. The method of claim 3, The relay selection unit, A mobile communication terminal, characterized in that for selecting one or a plurality of relay terminals. A data receiver configured to receive data transmitted from a mobile communication terminal located at a cell boundary area; A transmission technology selection unit for selecting one of a single carrier frequency division multiple access (SC-FDMA) or an orthogonal frequency division multiple access (OFDMA) to transmit data to a mobile communication system according to a predetermined criterion; And A data transmitter for transmitting data to a mobile communication system using a transmission technique selected by the transmission technique selection unit; Relay terminal comprising a. The method of claim 5, The preset reference is a signal-to-noise ratio (SNR), The transmission technology selection unit, And selecting the OFDMA when the signal-to-noise ratio is greater than or equal to the reference value, and selecting the SC-FDMA when the signal-to-noise ratio is less than or equal to the reference value. a) searching for a mobile communication terminal excluding itself as the mobile communication terminal moves to a cell boundary area; b) selecting a mobile communication terminal (relay terminal) to be used as a relay by the mobile communication terminal; c) transmitting, by the mobile terminal, data to the relay terminal by selecting either SC-FDMA or OFDM according to a preset criterion; And d) selecting, by the relay terminal, either SC-FDMA or OFDM according to a preset criterion and transmitting data received from the mobile communication terminal to the base station; Performance improvement method using an uplink relay in a 3GPP LTE system based on Hybrid OFDMA / SC-FDMA including a. The method of claim 7, wherein In step c), The mobile terminal selects OFDMA when the signal-to-noise ratio is above the reference value, and selects SC-FDMA when the signal-to-noise ratio is below the reference value. In step d), When the relay terminal selects OFDMA when the signal-to-noise ratio is greater than or equal to the reference value, and selects SC-FDMA when the signal-to-noise ratio is less than or equal to the reference value, a method of improving performance using an uplink relay in a hybrid OFDMA / SC-FDMA-based 3GPP LTE system .

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