KR20220167917A - Wireless signal transmission method combining CNOMA-OAM for improving channel capacity - Google Patents

Abstract

According to an embodiment of the present invention, a wireless signal transmission method combining the CNOMA-OAM, which is able to transmit a signal between a CCU located near a base station and a CEU located far from the base station by using cooperative NOMA communication within a single cell, comprises: a step in which the base station simultaneously transmits a NOMA signal, in which a CCU signal to be sent to the CCU and a CEU signal to be sent to the CEU are overlapped, to the CCU and the CEU by using the same frequency band during a first time slot; a step in which the base station additionally transmits the CCU signal for the first time slot by using an OAM mode; and a step in which the CCU receives the CCU signal by decoding the overlapped NOMA signal during a second time slot and relay-transmits the decoded CEO signal to the CEU. Therefore, reliability can be improved.

Description

Wireless signal transmission method combining CNOMA-OAM for improving channel capacity

The present invention relates to a radio signal transmission method, and more particularly, to a CNOMA-OAM combined radio signal transmission method for channel capacity improvement.

Since next-generation wireless communication is expected to process data traffic by 1000 times, channel capacity becomes an important criterion, and thus efforts to improve channel capacity are required.

Non-Orthogonal Multiple Access (hereinafter referred to as NOMA) in the power domain, which has recently been spotlighted, provides a higher capacity gain than other existing multiple access methods.

When NOMA is used in the power domain, different information signals can be overlapped and transmitted simultaneously to several user symbols.

Based on the shortest distance to the base station (Base Station, BS, Source), CCU (Cell Center User) corresponds to the case where the relative distance is short, and CEU (Cell Edge User, Cell Edge User) corresponds to the case where the relative distance is long Received signals for remote users) are classified according to power allocation levels.

Recently, a method for improving channel capacity or for smooth wireless communication by combining various methods while utilizing existing NOMA has been researched.

Among them, Cooperative NOMA (CNOMA) is a cooperative non-orthogonal multiple access, which not only transmits signals from a base station to a plurality of UEs (which collectively refer to User Equipment, CCU, and CEU), but also cooperatively relays signals between UEs. In particular, by using the CCU as a relay for CEU, reliability of received data and coverage area can be improved even for a CEU having a weak channel.

As another method, the CCU decodes a signal by itself through Successive Interference Cancellation (SIC), and also decodes the symbols of the CEU and relays them to the CEU to improve reliability.

In addition, there are several studies on CNOMA to improve channel capacity, previous studies using user pairing, combination of Orthogonal Multiple Access (OMA) and NOMA, integration of Generalized Space Shift Keying (GSSK) with NOMA, and use of coordinated multipoint Methods such as (CoMP) and NOMA have been proposed.

On the other hand, there is tremendous potential for improving the sum capacity (SC) of CNOMA by utilizing Orbital Angular Momentum (OAM) signals. OAM uses a new degree of freedom known as OAM mode for signal transmission.

Therefore, in order to improve the total channel capacity of CNOMA, it is necessary to study a method of transmitting signals by combining OAM with CNOMA.

L. Dai, B. Wang, Y. Yuan, S. Han, C. I and Z. Wang, "Non-orthogonal multiple access for 5G: solutions, challenges, opportunities, and future research trends," in IEEE Communications Magazine, vol. 53, no. 9, p. 74-81, September 2015. J. W. Kim, S. Y. Shin and V. C. M. Leung, "Performance Enhancement of Downlink NOMA by Combination With GSSK," in IEEE Wireless Communications Letters, vol. 7, no. 5, p. 860-863, Oct. 2018. Y. Tian, A. R. Nix and M. Beach, "On the Performance of Opportunistic NOMA in Downlink CoMP Networks," in IEEE Communications Letters, vol. 20, no. 5, p. 998-1001, May 2016. K. Janghel and S. Prakriya, "Performance of Adaptive OMA/Cooperative-NOMA Scheme With User Selection," in IEEE Communications Letters, vol. 22, no. 10, p. 2092-2095, Oct. 2018. R. Jiao, L. Dai, J. Zhang, R. MacKenzie and M. Hao, "On the Performance of NOMA-Based Cooperative Relaying Systems Over Rician Fading Channels," in IEEE Transactions on Vehicular Technology, vol. 66, no. 12, p. 11409-11413, Dec. 2017.

An object of the present invention is to provide a radio signal transmission method combining CNOMA-OAM that can improve channel capacity, transmit CCU signals without interference by OAM mode, and improve reception reliability of CEU signals by cooperative NOMA communication. is to provide

A radio signal transmission method combining CNOMA-OAM according to an embodiment of the present invention is a signal transmission method using cooperative NOMA communication within a single cell between a CCU located in a short distance from a base station and a CEU located in a long distance, wherein the base station comprises: simultaneous transmission of a NOMA signal in which a CCU signal to be transmitted to the CCU and a CEU signal to be transmitted to the CEU are superimposed to the CCU and the CEU using the same frequency band during a first time slot; additionally transmitting, by the base station, a CCU signal during a first time slot using an OAM mode; The CCU decodes the overlapped NOMA signal during a second time slot to receive a CCU signal to be received by the CCU, and relays and transmits the decoded CEU signal to the CEU.

In the above, when using the OAM mode, it is characterized in that a Rician fading channel is considered due to a short-range assumption between the CCU and the base station.

In the above, the OAM beam used in the OAM mode is a Fresnel-zone-plate lens antenna in the base station to reduce attenuation caused by divergence in a high-intensity region during signal transmission and not to affect the helical phase profile of the OAM beam. It is characterized in that the CCU signal of the OAM mode is transmitted using

및 CEU신호

의 달성 가능한 용량

은 각각 하기 수학식 1 및 수학식 2와 같이 획득되는 것을 특징으로 한다.In the above, considering the normalized time and total transmit power (T = 1 and P = 1, respectively), the CCU signal

and CEU signal

achievable capacity of

Is characterized in that it is obtained as in Equation 1 and Equation 2, respectively.

[Equation 1]

[Equation 2]

는 전송신호에 대한 신호대잡음비(SNR)이고, AWGN (additive white Gaussian noise) 잡음 분산은 모든 수신 신호에 대해

이며, P는 총 전송 전력이고,

,

및

는 각각 CCU, OAM을 위한 CCU 및 CEU에 할당된 전력이며,

,

및

는 각각 CCU신호, CEU신호 및 CCU의 CEU로의 중계신호에 대한 Rician 페이딩 채널 계수이다.) (here,

is the signal-to-noise ratio (SNR) for the transmitted signal, and the additive white Gaussian noise (AWGN) noise variance is for all received signals

, P is the total transmit power,

,

and

is the power allocated to CCU and CEU for CCU and OAM, respectively;

,

and

is the Rician fading channel coefficient for the CCU signal, the CEU signal, and the relaying signal from the CCU to the CEU, respectively.)

의 용량

은 하기 수학식 3과 같이 획득 되는 것을 특징으로 한다.In the above, the CCU signal by the OAM beam

capacity of

is characterized in that it is obtained as in Equation 3 below.

[Equation 3]

는 전송신호에 대한 신호대잡음비(SNR)이고, AWGN (additive white Gaussian noise) 잡음 분산은 모든 수신 신호에 대해

이며, P는 총 전송 전력이고,

,

및

는 각각 CCU, OAM을 위한 CCU 및 CEU에 할당된 전력이다.) (here,

is the signal-to-noise ratio (SNR) for the transmitted signal, and the additive white Gaussian noise (AWGN) noise variance is for all received signals

, P is the total transmit power,

,

and

is the power allocated to CCU and CEU for CCU and OAM, respectively.)

The radio signal transmission method combining CNOMA-OAM of the present invention can improve SC through CNOMA-OAM communication. It shows that it provides a much higher SC than other methods of , and the provided analysis results are proven by simulation results, and it is possible to perform optimal transmission power for OAM beams, and future CNOMA-OAM-based simultaneous radio information and power transmission research can contribute to

In addition, signals can be received by the CCU without signal interference by additional transmission to the CCU in OAM mode, and in the case of CEU, even when the channel is weak due to relay transmission, signals can be safely transmitted through relaying of the CCU, increasing reliability. can improve

1 is a conceptual diagram of a CNOMA-OAM system model for radio signal transmission combining CNOMA-OAM according to an embodiment of the present invention.
2 is a diagram showing an example of a communication protocol using the CNOMA-OAM system of FIG. 1;
3 is a comparison example of the influence of the allocated power of the OAM beam on the SC of CNOMA-OAM communication.
4 is a diagram showing an example of capacity comparison of CCUs with respect to SNR.
5 is a diagram showing an example of capacity comparison of CEUs with respect to SNR.
6 is a diagram showing an SC comparison example of a method different from CNOMA-OAM.
7 is a flowchart of a radio signal transmission method combining CNOMA-OAM according to an embodiment of the present invention.

Hereinafter, specific embodiments of the present invention will be described in detail with reference to the drawings. However, the spirit of the present invention is not limited to the presented embodiments, and those skilled in the art who understand the spirit of the present invention may add, change, delete, etc. other elements within the scope of the same spirit, through other degenerative inventions or the present invention. Other embodiments included within the scope of the inventive idea can be easily proposed, but it will also be said to be included within the scope of the inventive concept. In addition, components having the same function within the scope of the same idea appearing in the drawings of each embodiment are described using the same reference numerals.

The OAM used in the present invention uses the phase change with respect to the azimuthal angle of the propagated electromagnetic wave, leading to the spiral phase structure of the wave, and the considered interaction between CNOMA and OAM will be named CNOMA-OAM in the present invention.

In the present invention, the existing CNOMA communication as communication combining OAM with CNOMA communication will be described as follows.

First of all, cooperative communication based on NOMA, which performs a communication connection between a source and a destination through the help of one or multiple relays, is a technology that expands the communication range and effectively copes with multi-path fading effects to increase system capacity. In an enemy communication system, a relay transmits a received information signal to a related destination by applying a forwarding protocol such as Amplify and Forward (AF) and Decode and Forward (DF).

In addition, relays are largely classified into half-duplex (HD) and full-duplex (FD) according to operation. The combination of cooperative communication and NOMA can further improve NOMA's system efficiency.

In addition, the cooperative NOMA transmission method is divided into two stages: a direct transmission stage (Non-cooperative NOMA) and a cooperative transmission stage.

In the direct transmission step, the base station overlaps and transmits messages for user A and user B. In the relay transmission step, user B performs SIC on the signal of user A to decode its own message, and then acts as a relay to transmit the decoded information to user A. Therefore, user A receives two identical messages through different channels.

As a result, cooperative communication based on NOMA can significantly improve reception reliability of user B having a weak channel condition.

A system model for CNOMA-OAM communication of the present invention for downlink (DL) communication according to an embodiment of the present invention is shown in FIG.

A system for CNOMA-OAM communication includes a base station (BS) and a cell center user (CCU) and a cell edge user (CEU) corresponding to a plurality of user terminals, and assumes a single cell.

The CCU is assumed to be much closer to the BS than the CEU, perfect channel state information (CSI) is assumed, and the CCU is assumed to have a higher channel gain compared to the CEU. In addition, in order to improve data reliability and coverage area, the CCU performs cooperative communication to be used as a relay that performs decode and forward (DF) for the CEU.

및

는 BS에서 CCU 및 CEU의 각각 정규화된 거리를 의미한다. BS-to-CCU (링크 1), BS-to-CEU (링크 2) 및 CCU-to-CEU(링크 4)의 독립적 인 Rician 페이딩 채널 계수는 각각

,

및

로 표시된다. shown in Figure 1

and

Means each normalized distance of CCU and CEU in BS. The independent Rician fading channel coefficients of BS-to-CCU (link 1), BS-to-CEU (link 2) and CCU-to-CEU (link 4) are respectively

,

and

is indicated by

,

및

는 각각 BS-CCU, BS-CEU 및 CCU-CEU 링크의 평균 전력이다. 여기서는

<

로 가정한다.

,

and

is the average power of the BS-CCU, BS-CEU and CCU-CEU links, respectively. here

<

Assume

으로 표시되며, 또한

은 고려된 OAM 모드를 나타낸다. Also, the OAM channel of BS-to-CCU (Link 3) is

, and also

denotes the considered OAM mode.

= 1이 고려될 수 있다. OAM은 LOS(Line-of-Sight) 조건에서 더 나은 성능을 제공하고, 채널 조건이 더 좋은 사용자에게 있어 OAM은 도 1에서 CCU에서만 전송되도록 고려되는 이유이다. A low number of OAM modes to reduce attenuation, i.e.

= 1 can be considered. OAM provides better performance in line-of-sight (LOS) conditions, and this is why OAM is considered to be transmitted only in the CCU in FIG. 1 for users with better channel conditions.

,

및

는 각각 CCU, OAM을 위한 CCU 및 CEU에 할당된 전력이며, 여기서,

>

+

및

=

=

이다. P는 총 전송 전력으로 표시된다.

,

and

Is the power allocated to CCU and CEU for CCU and OAM, respectively, where

>

+

and

=

=

to be. P is denoted as the total transmitted power.

An example of a communication protocol for transmission of a download link (DL) in the present invention for the CNOMA-OAM combined communication scheme is shown in FIG. 2 .

과

는 T/2 시간의 첫 번째 타임 슬롯(First Time Slot)에서 CNOMA에 의해 각각 CCU와 CEU로 전송된다.Here, T corresponds to the total duration of time slots for all DL transmissions, and according to the communication protocol of the present invention,

class

is transmitted to the CCU and CEU respectively by CNOMA in the first time slot of time T/2.

은 간섭없이 OAM 모드에 의해 CCU로 동시에 전송된다. T/2 시간 동안의 두 번째 시간 슬롯(Second Time Slot)에서 CCU(DF)는

를 CEU에 중계하여 신뢰성을 향상시킬 수 있다.Also slot at the same time

are simultaneously transmitted to the CCU by OAM mode without interference. In the second time slot for T/2 time, the CCU (DF)

can be relayed to the CEU to improve reliability.

1. Direct Transmission

과

의 중첩을 CCU와 CEU로 전송한다.According to the CNOMA communication concept, in the first time slot, the BS has two different data signal symbols as shown in Equation 1 below

class

The superposition of is transmitted to the CCU and CEU.

는 i 번째 데이터 기호를 나타낸다. CCU는 SIC를 사용하여 상기 수학식 1로부터

을 산출한다. CCU에서 수신 신호

및

에 대한 신호대간섭및잡음비(SINR, signal-to-interference plus noise ratio)은 각각 하기 수학식 2와 수학식 3과 같이 얻을 수 있다.here

represents the i-th data symbol. From Equation 1 above, the CCU uses SIC.

yields Receive signal from CCU

and

The signal-to-interference plus noise ratio (SINR) for can be obtained as shown in Equations 2 and 3, respectively.

는 전송신호에 대한 신호대잡음비(SNR)이고, AWGN (additive white Gaussian noise) 잡음 분산은 모든 수신 신호에 대해

이다.here

is the signal-to-noise ratio (SNR) for the transmitted signal, and the additive white Gaussian noise (AWGN) noise variance is for all received signals

to be.

는 CEU에 의해 디코딩될 수 있으며, CEU에서 신호

에 대해 수신된 SINR은 하기 수학식 4와 같이 산출될 수 있다.Also

can be decoded by the CEU, and a signal in the CEU

The received SINR for can be calculated as shown in Equation 4 below.

은

와 함께 OAM (

= 1)을 사용하여 동시에 CCU로 직접 전송된다. CCU와 BS 사이의 근거리 가정으로 인해 Rician 페이딩 채널이 고려된다. NOMA 링크는 OAM 모드의 차이로 인해 OAM 링크를 방해하지 않으며, CCU에서 신호

에 대해 수신된 SINR은 하기 수학식 5와 같이 표현할 수 있다.Also

silver

with OAM (

= 1) and transmitted directly to the CCU at the same time. A Rician fading channel is considered due to the assumption of a short distance between the CCU and the BS. The NOMA link does not interfere with the OAM link due to the difference in OAM mode, and the signal from the CCU

The received SINR for can be expressed as in Equation 5 below.

는 내림차순으로 표시된 OAM 채널의 특이값이다.here

is the singular value of the OAM channels expressed in descending order.

은 하기 수학식 6과 같이 표현할 수 있다.OAM beams can diverge in the high-intensity region and cause attenuation, but using a Fresnel-zone-plate lens antenna in the BS can alleviate this problem without affecting the helical phase profile of the OAM beam. normalized channel matrix

Can be expressed as in Equation 6 below.

Here, m is the index of the receiving antenna, and M is the total number of receiving antennas.

을 전송하기 위해 하나의 OAM 빔이 고려되기 때문에, LOS 시스템을 위한 OAM 빔 사이에 심볼 간 간섭 또는 모드 간 간섭의 가능성이 없다.here by OAM.

Since one OAM beam is considered to transmit , there is no possibility of inter-symbol interference or inter-mode interference between OAM beams for the LOS system.

2. Relay Transmission

를 완벽하게 디코딩할 수 있다고 가정한다. CCU에서 중계하여

신호에 대해 CEU에서 수신된 SINR은 하기 수학식 7과 같이 표현할 수 있다.In Figure 1, in the second time slot, link 4 transmits at full transmit power. In addition, the CCU has signal symbols in the first time slot.

Assume that can be perfectly decoded. relayed by the CCU

The SINR received at the CEU for the signal can be expressed as Equation 7 below.

3. Sum Capacity

및

의 달성 가능한 용량은 각각 하기 수학식 8, 수학식 9와 같이 얻을 수 있다.Considering the normalized time and total transmitted power (T = 1 and P = 1, respectively),

and

The achievable capacity of can be obtained as shown in Equation 8 and Equation 9, respectively.

용량은 하기 수학식 10과 같이 획득할 수 있다.Also by the OAM beam

The capacity can be obtained as shown in Equation 10 below.

where K is the rank of the OAM channel matrix.

Therefore, the total capacity is calculated as in Equation 13 by adding Equations 11 and 12 below.

및

는 본 발명의 CNOMA-OAM 방식에 대한 CCU 및 CEU의 용량이다. CNOMA-OAM 방식은 종래의 CNOMA 및 OMA-OAM 방식 및 Rician 페이딩 채널과 비교되며, 구체적 비교는 후술하기로 한다.Here E [.] represents the expectation operator. On the other hand

and

is the capacity of CCU and CEU for the CNOMA-OAM scheme of the present invention. The CNOMA-OAM scheme is compared with conventional CNOMA and OMA-OAM schemes and Rician fading channels, and detailed comparisons will be described later.

4. Conventional OMA-OAM scheme

,

및

)에 대해 CCU 및 CEU에 할당된 다른 시간 슬롯과

에 대한 릴레이는 다음과 같이 표시된다. For OMA, Time Division Multiple Access (TDMA) is considered. In this case, the BS independently transmits information signals for the CCU and CEU in different time slots with a total transmit power of P. Other signal symbols, e.g.

,

and

) with the other time slots assigned to the CCU and CEU for

The relay for is shown as

,

,

및

. 또한 T = 1이 여기에서 고려되므로 전체 시간 슬롯은 OMA-OAM 방식의 각 시간 슬롯에 대해 동일하게 분할된다.

,

,

and

. Also, since T = 1 is considered here, the entire time slot is equally divided for each time slot in the OMA-OAM scheme.

=

=

=

=

가 고려되며, 달성 가능한

및

용량은 OMA-OAM 방식에 대해 하기 수학식 14 및 수학식 15와 같이 달성할 수 있다. So here

=

=

=

=

is considered, achievable

and

Capacity can be achieved as shown in Equations 14 and 15 below for the OMA-OAM scheme.

용량을 이용하여 CCU와 CEU의 OMA-OAM 방식에서의 합계 용량에 대해 하기 수학식 16 내지 수학식 20과 같이 획득할 수 있다.Also achievable by OAM beams

The total capacities of the CCU and CEU in the OMA-OAM scheme can be obtained using the capacities as shown in Equations 16 to 20 below.

Therefore, SC of the OMA-OAM method can be obtained by Equation 19 below using Equations 17 and 18 below.

및

는 OMA-OAM 체계에 대한 CCU 및 CEU의 용량이다.Here E [.] represents the expectation operator. Also

and

is the capacity of CCU and CEU for the OMA-OAM scheme.

5. Capacity analysis

In this capacity analysis, the total capacity of the CNOMA-OAM of the present invention through independent Rician fading channels will be described in detail.

을 지정하고,

의 CDF는 하기 수학식 20과 같다.first

specify,

The CDF of is shown in Equation 20 below.

이다.here

to be.

의 CDF는 하기 수학식 21과 같이 구할 수 있다.Also, subscript x denotes a BS-CEU link, y denotes a BS-CCU link, and w denotes a CCU-CEU link. Likewise

The CDF of can be obtained as shown in Equation 21 below.

Here, the parameter is defined by Equation 16.

의 정확한 표현은 수학식 22와 같이 구할 수 있다.thus

The exact expression of can be obtained as in Equation 22.

Here, D(ρ) is equal to Equation 23.

는 D (ρ)로 유도될 수 있으며, 마찬가지로

의 정확한 표현은 하기 수학식 24와 같다.Also

can be derived as D(ρ), and likewise

The exact expression of is as shown in Equation 24 below.

의 정확한 표현은 하기의 수학식 25와 같이 얻을 수 있다. In addition, the OAM channel is performed in LOS communication to the CCU, and the CCU has a better channel condition than the CEU. Therefore, by OAM

The exact expression of can be obtained as in Equation 25 below.

Using Equations 22, 24, and 25, the total capacity can be obtained as shown in Equation 28 by adding Equations 26 and 27 below.

및

는 본 발명의 CNOMA-OAM 방식에 대한 CCU 및 CEU의 정확한 용량을 의미한다.Here E [.] represents the expectation operator. Also

and

Means the exact capacities of CCU and CEU for the CNOMA-OAM method of the present invention.

6. Analysis of arithmetic results

=

= 5 및

= 2로 간주된다. 또한 모든 시뮬레이션 결과 분석에 대해

= 0.5 및

= 1이 고려된다.

= 9 <

=

= 36은 시뮬레이션을 위해 고려된다. 또한 여기에서는 시뮬레이션 목적으로 P = 1로 가정한다.The Rician fading parameter is

=

= 5 and

= 2 is considered. Also for analysis of all simulation results

= 0.5 and

= 1 is considered.

= 9 <

=

= 36 is considered for simulation. Also here we assume P = 1 for simulation purposes.

비교에 대해 ρ = 15 및

= 0.6이 고려된다. 도 3에서 볼 수 있듯이

= 0.2는 본 발명의 CNOMA-OAM 방식에 최적의 SC를 제공한다. 따라서 용량 대 SNR 비교를 위해

= 0.2,

= 0.2 및

= 0.6이 고려된다.The influence of the allocated power of the OAM beam on the SC of the CNOMA-OAM communication of the present invention is analyzed in FIG. 3 . SC versus the scheme of the present invention

ρ = 15 for comparison and

= 0.6 is considered. As can be seen in Figure 3

= 0.2 gives the optimal SC for our CNOMA-OAM scheme. So for capacity versus SNR comparison

= 0.2;

= 0.2 and

= 0.6 is considered.

The capacity comparison of CCU and CEU for SNR is shown in FIGS. 4 and 5 for another existing scheme of the present invention.

In addition, SC comparison of CNOMA-OAM and other methods is shown in FIG. 6. The CNOMA-OAM method provides a higher SC than the existing CNOMA and OMA-OAM shown in FIG. 6 .

을 동시에 전송하기 위해 추가 OAM 채널을 활용함으로써 달성될 수 있다. On the other hand, SC is the capacity addition of CCU and CEU. Therefore, in the case of the method of the present invention, the capacity improvement of the CCU is from the BS to the CCU in the first time slot shown in FIG.

It can be achieved by utilizing an additional OAM channel to transmit simultaneously.

However, OMA-OAM offers slightly higher capacity in the CCU than CNOMA-OAM due to maximum power transfer. The achieved capacity of CEU is the same for CNOMA-OAM and conventional CNOMA shown in Figure 5. CNOMA-OAM also provides much higher capacity than OMA-OAM shown in FIG. 5 . As a result, SC is further improved in the CNOMA-OAM scheme by effectively utilizing CNOMA and OAM concepts. The analysis results of the CNOMA-OAM method of the present invention are also verified by Monte-Carlo simulation results.

7 is a flowchart of a radio signal transmission method combining CNOMA-OAM according to an embodiment of the present invention.

Basically, in the radio signal transmission method combining the CNOMA-OAM of the present invention for CNOMA-OAM communication, a base station (BS) and a plurality of user terminals, including CCU (Cell Center User) and CEU (Cell Edge User), , assuming a single cell.

The CCU is assumed to be much closer to the BS than the CEU, perfect channel state information (CSI) is assumed, and the CCU is assumed to have a higher channel gain compared to the CEU. In addition, in order to improve data reliability and coverage area, the CCU performs cooperative communication to be used as a relay that performs decode and forward (DF) for the CEU.

First, the base station simultaneously transmits a NOMA signal in which a CCU signal to be sent to the CCU and a CEU signal to be sent to the CEU are overlapped to the CCU and the CEU using the same frequency band during a first time slot (S100).

The base station additionally transmits the CCU signal during the first time slot using the OAM mode (S102).

Thereafter, the CCU decodes the received superimposed NOMA signal during the second time slot to receive a CCU signal to be received by the CCU, and relays and transmits the decoded CEU signal to the CEU (S104 and S106).

By this communication method, signals can be received from the CCU without signal interference by additional transmission to the CCU in the OAM mode. can improve reliability.

In addition, as a result, it is shown that CNOMA-OAM provides much higher SC than other conventional methods through the Rician fading channel, and it is possible to perform optimal transmission power for OAM beams, and in the future, CNOMA-OAM-based simultaneous radio information and It can contribute to research on power transmission.

Claims (5)

In a signal transmission method using cooperative NOMA communication within a single cell between a CCU located in a short distance from a base station and a CEU located in a long distance,
simultaneously transmitting, by a base station, a NOMA signal in which a CCU signal to be transmitted to the CCU and a CEU signal to be transmitted to the CEU are overlapped, to the CCU and the CEU by using the same frequency band during a first time slot;
additionally transmitting, by the base station, a CCU signal during a first time slot using an OAM mode;
The CCU decoding the overlapped NOMA signal during a second time slot to receive a CCU signal to be received by the CCU and relaying and transmitting the decoded CEU signal to the CEU.
Wireless signal transmission method combining CNOMA-OAM comprising a. According to claim 1,
When using the OAM mode, a radio signal transmission method combining CNOMA-OAM, characterized in that a Rician fading channel is considered due to a short-range assumption between the CCU and the base station. According to claim 2,
The OAM beam used in the OAM mode uses a Fresnel-zone-plate lens antenna in the base station to reduce attenuation caused by divergence in a high-intensity region during signal transmission and not to affect the helical phase profile of the OAM beam. A radio signal transmission method combining CNOMA-OAM, characterized in that for transmitting a CCU signal in OAM mode. According to claim 1,
Considering the normalized time and total transmitted power (T = 1 and P = 1, respectively),
CCU signal

and CEU signal

achievable capacity of

A radio signal transmission method combining CNOMA-OAM, characterized in that is obtained as in Equation 1 and Equation 2, respectively.
[Equation 1]

[Equation 2]

(here,

is the signal-to-noise ratio (SNR) for the transmitted signal, and the additive white Gaussian noise (AWGN) noise variance is for all received signals

, P is the total transmit power,

,

and

is the power allocated to CCU and CEU for CCU and OAM, respectively;

,

and

is the Rician fading channel coefficient for the CCU signal, the CEU signal, and the relaying signal from the CCU to the CEU, respectively.) According to claim 3,
CCU signal by the OAM beam

capacity of

A radio signal transmission method combining CNOMA-OAM, characterized in that is obtained as shown in Equation 3 below.
[Equation 3]

(here,

is the signal-to-noise ratio (SNR) for the transmitted signal, and the additive white Gaussian noise (AWGN) noise variance is for all received signals

, P is the total transmit power,

,

and

is the power allocated to CCU and CEU for CCU and OAM, respectively.)

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