KR20140100258A - Resource allocation method for spectrum reuse in relay-assisted cellular networks - Google Patents

Abstract

Disclosed is a resource allocation method for spectrum reuse in a relay station (RS) based cellular network, which can increase spectral efficiency with minimized signal overhead. The resource allocation method for spectrum reuse in a RS-based cellular network comprises: a step in which an RS allocates a resource to a mobile station independently according to a subchannel allocation rule; a step in which the RS reports resource allocation information to a base station after allocating the resource to the mobile station from the RS; and a step in which the base station executes resource allocation for the RS and the mobile station in reference to the resource allocation information of the RS. Relay stations share a resource using a fractional frequency reuse method to avoid intra-cell and inter-cell interference between the relay stations, and the relay stations are grouped according to intra-cell interference and inter-cell interference between the relay stations to share a wireless resource.

Description

[Technical Field] The present invention relates to a resource allocation method for spectrum reuse in a repeater-based cellular system,

The present invention relates to resource allocation for spectrum reuse in repeater-based cellular systems, and more particularly, to resource allocation for spectrum reuse in a relay station (RS) based cellular system that increases bandwidth efficiency with minimal signal overhead. ≪ / RTI >

To meet the explosive growth of mobile communication services, next generation cellular systems must provide higher data rates than existing cellular systems. Relaying is emerging as one of the key technologies for next-generation cellular systems because of its relatively low deployment cost, service coverage, system capacity, and user data throughput at cell boundaries (cell-edge user throughput). In a relay station-based cellular system, a mobile station (MS) can receive data directly from a base station (BS) or indirectly via a relay station (RS). The relay station receives the data from the base station and delivers it to the mobile station, which is located at a cell boundary or deep in a shadowed area where no satisfactory service is obtained from the serving base station. The two-hop transmission method through the relay station can improve the throughput of user data at the cell boundary, but may reduce the overall data throughput. Therefore, an effective resource allocation method capable of maximizing bandwidth efficiency in a relay station-based cellular system should be designed.

A variety of resource allocation methods for a downlink in a relay station-based cellular system have been proposed. The resource allocation method proposed in References [1] to [5] is a method in which a base station assigns resources to all the links of the entire cell (i.e., link between base station and mobile station, link between base station and relay station, link between relay station and mobile station) Based resource allocation method. The centralized resource allocation method can maximize bandwidth efficiency.

References [6] and [7] introduce a distributed resource allocation method. This distributed resource allocation method is a method in which a relay station and a base station perform resource allocation for a subordinate user. Pan adopted an iterative waterfilling method for subcarrier allocation and power allocation. In Ref. [7], each relay station participates in resource allocation as a player in a non-cooperative RA game.

In [8], reuse of intracell between relay stations is introduced. In reference documents [9] and [10], resources used in the relay station To be reused by the base station.

In addition, Reference [11] suggests a resource allocation method in which a resource block is allocated to a user based on intra cell interference as well as intercell interference.

In addition, Reference [12] formulated a non-cooperative game in which all relay stations and base stations in the network perform power allocation as players.

Meanwhile, in order to solve the inter-cell interference problem between base stations, a technique that has been proposed in the past is fractional frequency reuse (FFR). Generally, the partial frequency reuse method has been considered to avoid inter-cell interference in a cellular network in which no relay station exists, as disclosed in reference [13]. The frequency band is divided into several subbands, and neighboring cells are assigned different subbands.

[One]. IEEE Std 802.16j-2009, "Part 16: Air introns for broadband wireless access systems - Amendent 1: Multiple relay specifications," June 2009. [2]. A. Ghosh, R. Ratasuk, B. Mondal, N. Mangalvedhe, and T. Thomas, "LTE-Advanced: Next-generation wireless broadband technology" IEEE Wireless Commun., Vol. 17, no. 3, pp. 10-22, June 2010. [3]. Y. Kim and M. L. Sichitiu, "Optimal max-min fair resource allocation in multihop relay-enhanced WiMAX networks" IEEE Trans. Veh. Commun., Vol. 60, no. 8, pp. 3907-3918, Oct. 2011. [4]. Z. Yang, Q. Zhang, and Z. Niu, "Throughput improvement by joint relay selection and link scheduling in relay-assisted cellular networks" IEEE Trans. Veh. Commun., Vol. 61, no. 6, pp. 2824-2835, July 2012. [5]. M. Salem, A. Adinoyi, M. Rahman, H. Yanikomeroglue, D. Falconer, and Y.-D. Kim, "Fairness-aware radio resource management in downlink OFDMA cellular relay networks" IEEE Trans. Wireless Commun., Vol. 9, no. 5, pp. 1628-1639, May 2010. [6]. Y. Pan, A. Nix, and M. Beach, "Distributed resource allocation for OFDMA-based relay networks" IEEE Trans. Veh. Commun., Vol. 60, no. 3, pp. 919-931, Mar. 2011. [7]. J. Han and W. S. Jeon "Game-theoretic approach to distributed scheduling for relay-assisted OFDMA systems," Proc. IEEE VTC 2011 Spring, Budapest, Hungary, May 2011. [8]. D. Su, X. Wen, B. Wang, W. Zheng, "Subcarrier allocation and dynamic frequency reuse in OFDMA relay networks, " in Proc. ICCET 2010, Chengdu, China, Apr. 2010. [9]. L. Zhang, H.C. Yang, and M. O. Hasna, "Analysis of Cell Spectral Efficiency of Infrastructure Relay-Enhanced Cellular System," in Proc. WCSP 2011, Nanjing, China, Nov. 2011. [10]. O. Oyman, "Opportunistic scheduling and spectrum reuse in relay-based cellular networks," IEEE Trans. Wireless. Commun., Vol. 9, no. 3, pp. 1074-1085, Mar. 2010. [11]. L. Liang, G. Feng, and Y. Zhang, "Resource allocation with interference coordination for relay-assisted cellular orthogonal frequency division multiple access systems," IET Commun., Vol. 6, no. 3, pp. 300-310, Mar. 2012. [12]. R. Yin, Z. Zhang, G. Yu, Y. Zhang, and Y. Xu, "Power allocation for relay-assisted TDD cellular system with dynamic frequency reuse," IEEE Trans. Wireless. Commun., Vol. 11, no. 7, pp. 2424-2435, July 2012. [13]. G. Boudreau, J. Panicker, N. Guo, R. Chang, N. Wang, and S. Vrzic, "Interference coordination and cancellation for 4G networks," IEEE Commun. Mag., Vol. 47, no. 4, pp. 74-81, Apr. 2009. [14] M. Liang, F. Liu, Z. Chen, Y. F. Wang, and D. C. Yang, "A novel frequency reuse scheme for OFDMA based relay enhanced cellular networks," Proc. IEEE VTC 2009 Spring, Barcelona, Spain, Apr. 2009.

However, the conventional techniques disclosed in the above-mentioned reference documents [1] to [5] have a disadvantage in that not only the computational complexity is high but also a huge amount of signal overhead is required. The reason for this is that the base station is involved in the allocation of the entire resources, and channel information of the entire link must be fed back to the base station. In practical implementations, even though resource allocation is optimized, excessive signal overhead limits bandwidth efficiency.

In addition, although the prior art disclosed in references [6] and [7] can reduce the computation complexity and signal overhead through the distributed resource allocation method, it avoids the interference problem between the relay station and the relay station, between the base station and the relay station There is a disadvantage in that information exchange is required. By allowing multiple transmitters (i. E., Base stations and relay stations) having sufficiently low mutual interference within the cell to simultaneously use the same resources, the radio resources can be utilized more efficiently.

In addition, the prior art disclosed in [8] to [10] has a disadvantage in that the interference caused by the simultaneous transmission (intra-cell interference) is considered in resource allocation so that space reuse can be performed. For example, when two relay stations are adjacent to each other and transmit on the same subchannel, the receiving mobile stations may receive intra-cell interference from undesired transmitting apparatuses. Because relay stations are typically located near cell boundaries to improve user data throughput at cell boundaries, relay stations may be adjacent to one another but may belong to different cells, which causes significant interference with each other (inter-cell interference between relay stations) .

SUMMARY OF THE INVENTION Accordingly, the present invention has been made in view of the above problems, and it is an object of the present invention to provide a method and apparatus for spectrum reuse in a relay station (RS) based cellular network that increases bandwidth efficiency with minimum signal overhead The purpose is to provide an allocation method.

Another object of the present invention is to provide a resource allocation method for spectrum reuse in a relay station-based cellular system in which a partial frequency reuse (FFR) technique is applied and interference between relay stations is reduced in an RS-based cellular system using orthogonal resource subsets I have to.

Yet another object of the present invention is to provide a relay station-based relay station in which a relay station performs resource allocation to lower users and a base station processes only one-hop users and relay stations to reduce signal overhead of channel information And to provide a resource allocation method for spectrum reuse in a cellular system.

Yet another object of the present invention is to provide a resource allocation method for spectrum reuse in a relay station-based cellular system in which relay stations perform resource allocation independently while reusing as much resources as possible by applying a subchannel allocation rule of a relay station have.

It is still another object of the present invention to provide a resource allocation method for spectrum reuse in a relay station-based cellular system in which a base station utilizes the same resources as relay stations to maximize space reuse.

According to another aspect of the present invention, there is provided a method for allocating resources for spectrum reuse in a relay station-based cellular system, the method comprising: (a) allocating resources independently to a mobile station in accordance with a subchannel allocation rule in a relay station;

(b) reporting the mobile station resource allocation information to the base station after allocating resources to the mobile station in the relay station;

(c) performing resource allocation for the relay station and the mobile station by referring to the resource allocation information of the relay station in the base station.

According to the present invention, the relay station can reuse the subchannels without mutual action according to the subchannel allocation rule, thereby allocating resources independently to the mobile station, thereby maximizing the spectral efficiency with the minimum signal overhead have.

In addition, according to the present invention, intracell interference and intercell interference between relay stations can be minimized by applying a partial frequency reuse (FFR) method.

In addition, according to the present invention, bandwidth efficiency can be improved by allocating as few subchannels as possible in two hop transmission at the time of resource allocation and allocating more subchannels without intrachannel interference at one hop transmission.

1 is a flowchart illustrating a resource allocation method for spectrum reuse in a repeater-based cellular system according to the present invention;
2 is a model diagram of a relay station based cellular system in the present invention.
3 is a diagram illustrating a resource allocation process according to the resource allocation method proposed by the present invention and a signal processing diagram between the BS and the RS.
4 is a diagram illustrating an example of a distance between a mobile station, a base station, and an RS in the present invention;

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the following description, well-known functions or constructions are not described in detail since they would obscure the invention in unnecessary detail.

1 is a flowchart illustrating a resource allocation method for spectrum reuse in a repeater-based cellular system according to the present invention.

As shown in FIG. 1, a resource allocation method for spectrum reuse in a repeater-based cellular system includes: (a) allocating resources to a mobile station (MS) independently from a relay station (RS) S40); (b) reporting mobile station resource allocation information to a base station (BS) after allocating resources to the mobile station (MS) in the relay station (RS) (S50); (c) performing resource allocation for the relay station (RS) and the mobile station (MS) by referring to the resource allocation information of the relay station (RS) in the base station (BS).

A resource allocation method for spectrum reuse in a repeater-based cellular system according to the present invention will now be described in detail with reference to FIGS. 1 to 4. FIG.

로 표기된다. 본 발명에서 기지국(BS)으로부터 직접 서비스를 받는 이동국(MS)을 직접 이동국(direct MS)이라 칭하며, 데이터가 중계국(RS)에 의하여 중계되는 이동국(MS)을 간접 이동국(indirect MS)라고 칭한다.A Relay-assisted Cellular Network to which the present invention is applied relates to a downlink of a relay station-based cellular network in which the entire cell operates in the same frequency band having a bandwidth of W. A frequency band is divided into M subchannels with the same bandwidth, and time is divided into frames having a fixed length. In the relay operation, the downlink frame is divided into two slots. The relay station RS receives data from a base station (BS) in a first slot and delivers the data to a corresponding lower mobile station (MS) in a second slot. The ratio of the s-th slot length to the downlink frame length is

Respectively. In the present invention, a mobile station (MS) receiving a service directly from a base station (BS) is referred to as a direct mobile station (MS) and a mobile station (MS) whose data is relayed by a relay station (RS) is referred to as an indirect mobile station (MS).

The relay stations of each cell are located at a distance of D _RS from the home cell base stations BS1, BS2, and BS3, as shown in FIG. It is assumed that the mobile stations located closer to the D _RS receive service directly by the base stations (BS1, BS2, BS3). This is because there is no advantage of relaying except when the mobile station is located deep in the shadow area. On the other hand, when the mobile station is more than D _RS from the home cell base station, the mobile station selects the best transmission device among the base station and the relay station through an appropriate relay selection method.

는 중계국 k를 의미한다. 수신장치는 이동국(MS) 또는 중계국(제1슬롯인 경우만)을 나타낸다. 중계국(RS)은 간접 이동국으로 중계되는 데이터를 제1슬롯에서 기지국(BS)으로부터 수신한다.

가 전송장치k에 의하여 서비스를 받는 이동국의 수라 할 때, 수신장치들은 제1슬롯에서

으로 인덱스되며, 제2슬롯에서

로 인덱스된다.

는 제s번 째 슬롯에서 송신장치k와 수신장치 사이의 링크 수라고 할 때,

대하여

및

를 만족한다.K and j denote the indexes of the transmitting apparatus and the receiving apparatus, respectively. Transmission device 0 represents a base station,

Means relay station k. The receiving apparatus indicates a mobile station (MS) or a relay station (only in the case of the first slot). The relay station (RS) receives the data relayed to the indirect mobile station from the base station (BS) in the first slot.

Lt; RTI ID = 0.0 > k < / RTI > is the number of mobile stations served by transmission apparatus k,

, And in the second slot

.

Is the number of links between the transmitting apparatus k and the receiving apparatus in the s-th slot,

about

And

.

가 중계국 그룹 i에 허락된 서브채널 집합이라고 하면, 이웃하는 중계국들은 서로 다른 중계국그룹을 할당받아서 중계국 사이의 간섭문제를 피할 수 있다. 부분 주파수 재사용(FFR) 방법이 이웃하는 중계국들에 적용되며, 중계국 각각은 서로 다른 셀에 속한다. 도 2는 중계국(V=3인 경우)들 사이의 부분 주파수 재사용 기반 자원 공유 방법의 예를 보여주는 도면이다. 도 2에서 각 셀 내의 중계국은 인트라셀 간섭에 따라서 그룹핑한 다음 중계국 그룹은 중계국 사이의 인터셀 간섭에 따라서 인덱스되어 있다. 예를 들어, 동일한 셀 내에서 서로 밀접하게 위치한 RS1-1, RS1-2 및 RS 1-6은 서로 다른 중계국 그룹(RS group)

및

을 할당받는다. 서로 다른 셀에 속하는 이웃하는 중계국 RS1-1, RS2-5 및 RS3-3은 다른 서브채널 집합을 사용하여 중계국 사이의 간섭을 피한다. 설명의 편의를 위하여,

,

이라 하고,

는

보다 크지 않은 가장 큰 정수라고 한다. 부분 주파수 할당(FFR) 기반 자원 공유 정책을 통하여, 중계국들은 서로 독립적으로 자원할당을 수행할 수 있다. 왜냐하면, 중계국 사이의 상호 간섭이 무시 될 수 있기 때문이다. (S10 ~ S20)In the present invention, multiple relay stations can simultaneously transmit data on the same subchannel in the second slot. However, simultaneous transmission of relay stations may cause intra-cell and inter-cell interference between relay stations. In order to overcome such an interference problem while achieving minimum signal overhead, the present invention adopts the concept of partial frequency reuse (FFR) as shown in FIG. 2 to share resources among relay stations. The entire subchannel of the second slot is divided into a set of V subchannels. Relay stations in a cell are divided into the same number of RS groups, and each relay station group can use a different set of sub-channels.

Is a set of subchannels allowed to the relay station group i, neighboring relay stations can be allocated different relay station groups to avoid interference problems between the relay stations. A partial frequency reuse (FFR) method is applied to neighboring relay stations, and each relay station belongs to a different cell. 2 is a diagram illustrating an example of a partial frequency reuse-based resource sharing method between a relay station (when V = 3). In Fig. 2, the relay stations within each cell are grouped according to the intra-cell interference, and the relay station group is indexed according to inter-cell interference between the relay stations. For example, RS1-1, RS1-2, and RS1-6, which are closely located within the same cell,

And

. Neighboring relay stations RS1-1, RS2-5, and RS3-3 belonging to different cells avoid interference between relay stations using different sub-channel sets. For convenience of explanation,

,

And,

The

It is said to be the largest integer not greater than. Through the partial resource allocation (FFR) based resource sharing policy, relay stations can independently perform resource allocation. This is because mutual interference between relay stations can be ignored. (S10 to S20)

To maximize space reuse, the base station (BS) may also utilize resources used by the relay station (RS). As shown in FIG. 2, the base stations RS1, RS2, and RS3 can use the entire subchannel in the second slot even though a part of the subchannel can be used by the relay station RS (s). However, base station transmissions can cause severe interference between indirect mobile stations. Therefore, if the subchannels are reused by the relay stations, the power transmission of the base station on the subchannel is limited to protect the transmission of the relay station.

On the other hand, the indirect mobile stations can receive additional interference as the transmission occurs at the same time. However, this problem can be overcome through the base station scheduling method. For example, the base station may assign a subchannel used by the relay station to a user at the center of the cell. This is because the users in the center of the cell receive less power interference from the relay station than users in other areas.

Since the resource allocation is performed based on the cell and the inter-cell interference between the relay stations is negligible through the partial frequency reuse-based bandwidth reuse policy, in the present invention, in consideration of interference from neighboring base stations, Only one cell (target cell) is concentrated.

Meanwhile, the signal-to-interference ratio (SIR) and the transmission capacity model should be considered for resource allocation.

를 이진 서브채널 할당 변수라고 하고,

를 만족한다고 가정한다. 상기의 변수가 1인 경우는 서브채널 m이 s번째 슬롯에서 송신기k 및 수신기 j사이의 링크에 할당됨을 의미한다. 반대의 경우는 서브채널 m이 상기 링크에 할당되지 않음을 의미한다.

는 s번째 슬롯에서 수신기 j에 할당된 서브채널 m상에서의 전송기 k의 전송 전력을 의미한다.

인 경우,

이다. 그리고 그 역의 관계도 성립한다.

Is called a binary subchannel allocation variable,

. If the above variable is 1, it means that subchannel m is allocated to the link between transmitter k and receiver j in the s-th slot. In the opposite case, the subchannel m is not assigned to the link.

Is the transmit power of transmitter k on subchannel m allocated to receiver j in the s < th > slot.

Quot;

to be. And the inverse relationship holds.

가 주어지고,

가 성립한다.

이고,

가 전송기k와 수신기 사이의 링크에 대하여 홈 셀 간섭자의 전송 파워 매트릭스 리스트를 의미하는 경우,

가 성립한다.

와

에 대한 파워 할당 정보가 제공되었다면, s번째 슬롯에서 서브채널 m상에서의 전송기k로부터 수신기j로의 신호대간섭비(SIR)는 아래의 식(1)로 표현될 수 있다.the transmit power of transmitter k on subchannel m in the s < th > slot,

Is given,

.

ego,

Quot; means a list of transmission power matrices of a home cell interferer for a link between transmitter k and receiver,

.

Wow

The signal to interference ratio (SIR) from transmitter k to receiver j on subchannel m in the s < th > slot can be expressed by the following equation (1).

는 s번째 슬롯에서 서브채널 m상에서의 전송기k와 수신기j사이의 채널 이득이고,

는 수신 인트라셀 간섭전력을 의미하고,

는 이웃하는 기지국들로부터의 수신 인터셀 간섭전력을 의미한다. 셀룰러 시스템은 잡음보다는 간섭에 의하여 제한되기 때문에 본 발명에서 사용한 시스템 모델에서는 잡음(thermal noise)은 무시한다. 제1슬롯에서 기지국은 단지 송신기로서 역할을 하며, 직교 서브채널을 수신기에 할당하므로(즉,

) 제1슬롯에서의 SIR은

로 간략화될 수 있다. 반면, 기지국과 중계국 사이에 자원이 재사용되는 경우, 제2슬롯에서 인트라셀 간섭이 존재한다(

).In the above equation (1)

Is the channel gain between transmitter k and receiver j on subchannel m in the s < th > slot,

Denotes the receiving intra-cell interference power,

Refers to the received inter-cell interference power from neighboring base stations. Since the cellular system is limited by interference rather than noise, the system model used in the present invention ignores the thermal noise. In the first slot, the base station serves only as a transmitter and assigns orthogonal subchannels to the receiver (i.e.,

) The SIR in the first slot is

. ≪ / RTI > On the other hand, if resources are reused between the base station and the relay station, intra-cell interference exists in the second slot (

).

의 SIR값을 가진 서브채널에 대하여 성취할 수 있는 전송용량은

로서 주어지며,

는 목표 비트 에러율이다. 본 발명에서 s번째 슬롯의 서브채널 m이 전송기k와 수신기j 사이의 링크에 할당되는 경우, 상기 서브채널에 대한 성취할 수 있는 전송용량은

로서 표현될 수 있다. 여기에서,

를 만족한다. 그 다음 상기 링크의 전송률은

이다.Assume that continuous-time M-ary quadrature amplitude modulation is applied.

The achievable transmission capacity for a subchannel with an SIR value of < RTI ID = 0.0 >

Lt; / RTI >

Is the target bit error rate. In the present invention, when the subchannel m of the s-th slot is allocated to the link between the transmitter k and the receiver j, the achievable transmission capacity for the subchannel is

. ≪ / RTI > From here,

. The transmission rate of the link is then

to be.

이 송신기k와 수신기j 사이 링크에 대한 최소한의 데이터 전송속도 요건을 나타낸다. 상기 직접 이동국이 임의의 슬롯에서 기지국에 의하여 서비스를 받을 수 있기 때문에,

이 성립한다.Meanwhile, the resource allocation method proposed in the present invention has to fulfill the minimum data rate requirement of the mobile station, and the minimum data rate requirement of the mobile station reflects QoS (quality of service) of the cellular users.

Represents the minimum data rate requirement for the link between transmitter k and receiver j. Since the direct mobile station can be serviced by the base station in any slot,

.

이 성립된다. 수학식 (3)에서,

은 중계국그룹(RS group)의 색인을 나타내며, 이 중계국그룹에 중계국 k(RS k)가 속해 있다. 두 번째, 상기 기지국은 제1슬롯 동안 충분한 양의 데이터를 중계국에 전송하여, 중계국들이 제2슬롯에서 그들의 하위 이동국에 데이터를 전달하도록 하여야 한다. 그러므로,

성립한다.On the other hand, in order to satisfy the minimum data rate requirement of the indirect mobile station, two constraints are considered when designing the resource allocation method. First, since the indirect mobile station only receives data from the relay station in the second slot,

. In the equation (3)

Represents an index of a relay station group (RS group), and relay station k (RS k ) belongs to this relay station group. Secondly, the base station must transmit a sufficient amount of data to the relay station during the first slot so that the relay stations transmit data to their lower mobile stations in the second slot. therefore,

Respectively.

와

로 각각 한정된다고 가정한다. 즉,

The total transmission power of the base station and the relay station is

Wow

Respectively. In other words,

이 만족한다.Wow

Is satisfied.

(

및

)라는 제약조건을 만족하여야 한다. 반면, 중계국 k (RS k)의 자원 할당 시 모든

에 대하여

이 만족한다.A transmitter (base station or relay station) can not supply data to one or more receivers on a subchannel. This is to avoid interference between the transmitter and the receiver. The next base station resource allocation method

(

And

). On the other hand, at the time of allocation of the relay station k (RS k )

about

Is satisfied.

Based on this system model, the resource allocation method for spectrum reuse will be described below.

The resource allocation method for spectrum reuse proposed in the present invention is designed to satisfy the minimum data rate requirement of a user while maximizing bandwidth efficiency. In addition, signal overhead is one of the important considerations when designing the proposed method. This is because, in practical implementations, the signal overhead has a profoundly adverse effect on bandwidth efficiency. To reduce the reporting overhead of channel information, the relay station or base station considers a distributed resource allocation method that is only responsible for its downstream users. Through the FFR-based resource sharing method between relay stations, each relay station does not need to consider interference from other relay stations in resource allocation. Accordingly, the RSs independently perform resource allocation according to the proposed resource allocation method.

On the other hand, since the base station and the relay stations can transmit data on the same subchannel of the second slot at the same time, intra-cell interference between the base station and the relay station must be considered in resource allocation. However, it is difficult to control when the BS and the RS simultaneously perform resource allocation. This is because the relay station resource allocation affects the base station resource allocation and conversely the base station resource allocation affects the relay station resource allocation. The present invention proposes a sequential resource allocation method in which a relay station directly performs resource allocation to a mobile station, and then the relay station and the mobile station allocate resources to the relay station while referring to the resource allocation of the relay station. The relay station data transmission scheduled prior to the base station resource allocation is protected by limiting the transmission power of the base station on the reused subchannel.

FIG. 3 shows a resource allocation process according to the proposed resource allocation method and a signal process between a BS and an RS.

(RS-RA) and base station resource allocation (BS-RA) are described in detail in the following description of a method for handling an intra-cell interference problem between a base station and an RS according to a resource allocation method for the proposed spectrum reuse Explain.

First, a method for processing intra-cell interference between a base station and an RS is as follows.

로서 주어질 때, 수신 간섭 파워는

로서 표시되며,

는 경로손실 지수이며,

는 로그노말 쉐도잉 이득과 지수 함수적으로 분포된 단위 평균 페이딩(unit-mean fading) 이득의 곱을 나타낸다. 복합 로그노말-지수함수 랜덤 변수(composite lognormal-exponential random variable)

는

의 자연로그의 평균과 표준편차를 각각 나타내는 파라미터

와

와 함께 로그노말 랜덤 변수로 모델링된다. 그 다음,

와

는 기지국과 간접 이동국 사이의 링크에 대한 로그노말 쉐도잉 이득(단위 dB)의 평균(

)과 표준 편차(

)를 이용하여 계산되며,

와

(

)로서 표현된다.As described above, the transmission power of the base station should be limited within a certain level to protect relay station transmission. Consider the worst case where the indirect mobile station experiences the highest intra cell from its home cell base station to determine the base station transmit power limit on the reused subchannel. It is assumed that the mobile station (indirect MS) is located at a distance D _RS from the base station by a distance equal to the distance between the base station (BS) and the associated service relay station (RS), as shown in FIG. The present invention models received interference power from a home cell base station in an indirect mobile station in consideration of path loss, lognormal shadowing, and Rayleigh fading. Then, the transmission power of the base station on the reused sub-channel is

Lt; / RTI >< RTI ID = 0.0 >

Lt; / RTI >

Is the path loss index,

Represents the product of the log normal shadowing gain and the exponentially distributed unit-mean fading gain. Composite lognormal-exponential random variable

The

A parameter representing the mean and standard deviation of the natural log of

Wow

And are modeled as log normal random variables. next,

Wow

Is the average of the log normal shadowing gain (in dB) for the link between the base station and the indirect mobile station

) And standard deviation (

), ≪ / RTI >

Wow

(

).

에 의하여 표시되는 임의의 임계값 이상인 확률로 정의된다. 간섭 확률은

로서 주어지며,

는 다음 수식(7)로 표현된다.The interference probability is a function of the interference power of the indirect mobile station

Lt; RTI ID = 0.0 > a < / RTI > The interference probability is

Lt; / RTI >

Is expressed by the following equation (7).

는 Q 함수이다. 기지국과 간접 이동국 사이의 심각한 간섭을 피하기 위하여, 기지국의 전송 파워는 한정되어

를 만족하여야 한다. 수식(7)로부터,

에 의하여 표현되는 재사용 서브채널 상에 최대 기지국 전송 파워는

로서 얻어진다. 상기 기지국은 최대 기지국 전송파워

를 방송하며, 중계국들은 그들의 자원할당 동안 홈 셀 기지국이 최대 기지국 전송파워

에서 데이터를 전송한다고 가정한다.In equation (7)

Is a Q function. In order to avoid significant interference between the base station and the indirect mobile station, the transmission power of the base station is limited

. From equation (7)

The maximum base station transmit power on the reused subchannel represented by < RTI ID = 0.0 >

. The base station transmits maximum base station transmit power

And the relay stations broadcast the maximum base station transmit power < RTI ID = 0.0 >

As shown in FIG.

Next, how inter-cell interference from relay stations is considered when allocating base station resources will be described. Direct mobile stations suffer intra-cell interference from relay stations. In this case their assigned subchannels are used by the relay station. This intra-cell interference can be easily predicted. This is because the relay station first performs resource allocation and reports power allocation information to the base station. However, collecting power information for all reused subchannels from the relay station requires a significant amount of uplink signal overhead.

으로 표시된다. 그 다음, 상기 기지국은 그것의 자원 할당에 대하여

를 가진 SIR의 하부 경계를 추정한다.

가 중계국 k(RS k)의 전송 파워 매트릭스인 경우

가 정의된다. 이 경우, 각 요소는 다음 수식으로 설정된다.Therefore, according to the proposed resource allocation method, each RS transmits only the maximum transmission power among the used subchannels, and the maximum transmission power corresponds to the relay station k (RS k )

. Then, the base station notices about its resource allocation

Lt; RTI ID = 0.0 > SIR. ≪ / RTI >

Is a transmission power matrix of the relay station k (RS k )

Is defined. In this case, each element is set to the following formula.

가 성립하기 때문에, 제2슬롯에서 하부경계 SIR 추정치를

로서 얻을 수 있다.

Lt; RTI ID = 0.0 > SIR < / RTI > estimate in the second slot

.

The purpose of the proposed resource allocation method is to maximize bandwidth efficiency. In the present invention, a method is proposed to allocate as few subchannels as possible for a two-hop transmission so that a subchannel with no intra-cell interference from a relay station is allocated to one-hop transmission, thereby achieving the purpose of resource allocation. In order to reduce the total number of subchannels used by the relay station in the cell, each relay station must provide service to its lower mobile station using as few subchannels as possible that satisfy the minimum data rate requirement of the mobile station. Also, since the relay stations in the same relay station group do not interfere with each other, the relay stations should use as many sub-channels as possible. However, since each relay station independently performs resource allocation, the subchannel allocated by each relay station is different from the subchannel of other relay stations. Therefore, according to the proposed base station resource allocation method, the relay stations propose a subchannel allocation rule to reuse the subchannels without exchanging signals therebetween (S30). That is, a subchannel with a low index is allocated first. According to the subchannel allocation rules, subchannel reuse can be induced even though each relay station performs resource allocation independently.

및 슬롯 번호 2를 생략하여

및

대신

및

로 표현하였다. 지정된 중계국이 중계국 그룹 i에 속한다는 가정하에,

에 있는 서브채널만이 중계국 RS에 대하여 허락됨을 고려할 때,

로서 주어지는 서브채널 색인

을 사용한다.Each relay station performs resource allocation only for the corresponding lower mobile station (S40), and resource allocation is performed only for the second slot (s = 2). Then, when describing the proposed base station-resource allocation,

And slot number 2 are omitted

And

instead

And

Respectively. Assuming that the designated relay station belongs to relay station group i,

And only the subchannels in the relay station RS are permitted to the relay station RS,

The subchannel index given as

Lt; / RTI >

를 개입시킨다.

이고

라고 하자. 지정된 중계국이 중계국 그룹i에 속하는 경우, 중계국 자원할당(RS-RA) 문제는 다음 식(8)로 정의될 수 있다.A relay station resource allocation method has been formulated to minimize the index of the assigned subchannel while satisfying the minimum data rate requirement of the user. In order to express the purpose of the relay station resource allocation problem, a variable greater than or equal to any index of the assigned subchannel

Lt; / RTI >

ego

Let's say. If the designated relay station belongs to relay station group i, the RS resource allocation (RS-RA) problem can be defined by the following equation (8).

가 0과 1사이의 실수 값을 갖도록 한다. 그 다음,

인 마지막 제약조건이 제거된다. 다음, 참조문헌 C.Y. Wong, R.S. Cheng, K. B. Lataief, and R. D. Murch, "Multiuser OFDM with adaptive subcarrier, bit and power allocation," IEEE J. Sel. Areas Commun., vol. 17, no. 10, pp. 1747-1758, Oct. 1999.에서처럼 컨벡스 최적화 문제에 대하여 새로운 변수

를 개입시킨다.

를 이용하여, 제1 및 제2 제약조건은

및

로 각각 재형성된다. 그 다음, 참조문헌 S. Boyd and L. Vandenberghe, Convex Optimization, Cambridge Univrsity Press, 2004.에 개시된 라그란지안 듀얼 방법(Lagrangian dual method)을 이용한다Equation (8) is a mixed-integer optimization problem. Also, although the objective in Equation (8) is a convex function, the first and second constraint conditions do not have a convex property. Therefore, it is difficult to obtain an optimal solution. To make Equation (8) easier to handle, the binary subchannel assignment variable

Has a real value between 0 and 1. next,

The last constraint is removed. Next, reference CY Wong, RS Cheng, KB Lataief, and RD Murch, "Multiuser OFDM with adaptive subcarrier, bit and power allocation," IEEE J. Sel. Areas Commun., Vol. 17, no. 10, pp. 1747-1758, Oct. As in 1999., a new variable for the convex optimization problem

Lt; / RTI >

, The first and second constraints < RTI ID = 0.0 >

And

Respectively. Then, the Lagrangian dual method disclosed in S. Boyd and L. Vandenberghe, Convex Optimization, Cambridge Univrsity Press, 2004. is used

인 경우, 재 공식화된 문제의 라그란지안 함수는

, Then the Lagrangian function of the re-formulated problem is

및

은 라그란지안 승수이며,

및

가 성립한다.Lt; / RTI > In the above equation (9)

And

Is the Lagrangian multiplier,

And

.

는 수학식(10)으로 표현된다.Raglan Gian Dual Function

Is expressed by equation (10).

은 x에 대한 아핀 함수(affine function)이며,

의 기울기를 갖는다. 듀얼함수가

인 경우를 제외하고 음의 무한대(negative infinity)를 갖는다. 반면, 최적

에 대한 필요조건은

에 대하여

를 미분함으로써 얻어질 수 있다. 특히,

인 경우, 최적

은

을 만족하여야 한다. 즉, 수학식(11)을 만족해야 한다.Lagrangian function

Is an affine function for x,

. Dual function

(Negative infinity) except when On the other hand,

The requirements for

about

. ≪ / RTI > Especially,

, The optimum

silver

. In other words, the equation (11) must be satisfied.

및

이 된다.In the equation (11)

And

.

라고 하면, 듀얼 함수(10)은 다음 수식(12)로서 재작성된다.

, The dual function 10 is rewritten as the following equation (12).

In the equation (12)

관계가 성립된다. 듀얼함수(12)에서 제1항목은

의 선형 함수이며, 수학식(13)에서 도시된 바와 같이

의 기울기를 갖는다. 상기 듀얼함수의 나머지 항목은

와 무관하다. 따라서, 수학식[13]에서 도시된 바와 같이,

를 만족하는 도달 가능한 공간(feasible space) 내에 최적의 a를 획득할 수 있다.

The relationship is established. In the dual function (12), the first item

, And as shown in equation (13)

. The remaining items of the dual function

. Thus, as shown in equation [13]

The optimum a in the feasible space satisfying the condition a can be obtained.

라면,

일 때,

는 최소의 값을 갖는다. 그렇지 않은 경우,

인 경우,

는 최소의 값을 갖는다.

Ramen,

when,

Has a minimum value. Otherwise,

Quot;

Has a minimum value.

라고 하자.

이기 때문에, 주어진 m에 대한

의 최소값은 이동국에 대하여

인 경우 얻어질 수 있다.

인 경우

이고,

가 된다. 수학식(11)로부터,

인 경우,

이 성립하고, 그렇지 않은 경우,

가 성립되기 때문에, P의 해를 얻을 수 있다.

Let's say.

So, for a given m

The minimum value of < RTI ID = 0.0 >

Can be obtained.

If

ego,

. From equation (11)

Quot;

And if not,

, The solution of P can be obtained.

The algorithm is expressed as follows.

및

; n을 0으로 설정)STEP1) Perform initialization (

And

; n is set to 0)

STEP2) Repeat the following steps until the Lagrangian multipliers converge.

및

에 대하여 해

및

를 계산하라; 및a. Given in Equations (11) and (12)

And

About

And

Calculate; And

b. Update the Lagrangian multipliers as follows;

은 n번째 순환의 포지티브 스텝 사이즈를 의미한다.From here,

Means the positive step size of the n-th cycle.

The dual problem of the primary problem (8) is defined as (14).

는 성분별 부등호(component-wise inequality)를 의미한다. 서브그래디언트(Subgradient) 방법[2]을 이용함으로써, 알고리즘 1에서 도시된 바와 같이 최적의 라그란지안 승수

및

를 발견할 수 있다. 각 순환 과정에서, 갱신 과정 후에

는 초 평면상에 투영되어

을 갖는다. 알고리즘 1에서,

는 그래디언트 대신

로 갱신된다. 왜냐하면,

를 포함하는 항이 투영과정(projection)을 하는 동안 소거될 것이다. 따라서, 라그란지안(Lagrangian)해는

와 상관없이 얻어진다.

의 최적의 값은 수학식의 제약조건(

에 대한

)에 따라서 얻어질 수 있다.In Equation (14)

Means component-wise inequality. By using the subgradient method [2], as shown in algorithm 1, the optimal Lagrangian multiplier

And

Can be found. In each cycle, after the update process

Lt; RTI ID = 0.0 >

Respectively. In algorithm 1,

Instead of a gradient

. because,

Will be erased during the projection. Therefore, the Lagrangian

.

The optimal value of < RTI ID = 0.0 >

For

). ≪ / RTI >

과

에 대한 최적의 값

이 0이나 1의 값을 갖기 때문이다.Since the re-formed equation (8) is a convex problem and the condition of the slater is maintained, a strong duality is obtained. In addition, the solution of the re-formed equation (8) has the same solution as the circular equation (8). because,

and

The optimal value for

Has a value of 0 or 1.

의 정보는 사용된 서브채널의 수(

), 할당된 서브채널상의 최대 전소파워(

) 및 최소의 데이터 속도 요건(

)을 를 포함한다. 여기에서,

와

은 중계국

에 대한 자원할당 결과

및

이다.After performing the resource allocation, each relay station reports a resource allocation result to its home cell base station (S50). Reported relay station

Lt; RTI ID = 0.0 > number of sub-channels < / RTI &

), The maximum power to power on the assigned subchannel (

) And minimum data rate requirements (

). From here,

Wow

The relay station

Resource allocation results for

And

to be.

로 제한되어 중계국 전송을 보호한다는 것이다.The base station (BS) directly allocates resources to the mobile station and the relay station (S60 to S80). The relay station must receive data from the base station in the first slot to transmit data to the indirect mobile station in the second slot. Subchannels in both slots can then be used by the indirect mobile station. Here, subchannels in only the first slot are allocated to the relay station. Considering spatial reuse, the base station utilizes the subchannel mode in the second slot, as in the first slot, regardless of the slot used by the relay station. The only constraint is that if the subchannel is used by the relay station, the transmit power on the subchannel is

To protect relay station transmissions.

는 제2 슬롯에서 하나 이상의 중계국이 사용하는 서브채널 집합을 의미한다. 즉,

이 성립된다. 그 다음, 기지국 자원할당 문제는 수학식 (15)로서 정의된다.A problem of allocating base station resources for the purpose of satisfying the minimum data rate requirement of the mobile station and the relay station directly while maximizing the total data throughput for the direct base station has been formulated. The minimum data rate requirement of the relay station is collected via feedback from the relay station over the previous frame.

Denotes a set of subchannels used by one or more relay stations in the second slot. In other words,

. Then, the base station resource allocation problem is defined as Equation (15).

에 대하여

를 만족하는 수학식(15)의 마지막 제약 조건으로부터 기지국이 재사용된 서브 채널을 셀 중앙의 유저에게 할당하여 전체적인 데이터 처리율을 극대화시킬 수 있음을 기대할 수 있다. 왜냐하면, 다른 유저보다 높은 채널 이득을 갖는 셀 중앙 유저는 제한된 전송 파워에도 불구하고 높은 데이터 전송률을 획득할 수 있으며, 다른 유저들은 약한 신호 파워뿐만 아니라 높은 인트라셀 간섭에 의하여 만족스러운 데이터 전송률을 획득하지 못하기 때문이다.The base station uses the lower boundary SIR estimate when calculating the transmission capacity that can be acquired in the second slot. all

about

It can be expected that the overall data throughput can be maximized by allocating the re-used subchannel to the user at the center of the cell from the final constraint of Equation (15) that satisfies Equation (15). This is because a cell center user having a higher channel gain than other users can acquire a high data rate despite limited transmission power and other users can obtain a satisfactory data rate by not only weak signal power but also high intra- I can not.

를 실제 변수에 적용하고, 2. 컨케이브 문제(concave problem)에 대하여 새로운 변수

를 적용하며, 3. 라그란지안 듀얼 방법을 적용)을 이용하여 최적의 해답을 구할 수 있다. Since Equation (15) related to base station resource allocation (BS-RA) relates to a mixed-integer non-convex optimization problem similar to a relay station resource allocation problem, (1. Binary subchannel allocation variable

To a real variable, and 2. to a concave problem

And applying the 3. Raglanian dual method) can be used to obtain an optimal solution.

It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined in the appended claims and their equivalents. Of course, such modifications are within the scope of the claims.

BS ... Base station
RS ... Relay station
MS ... Mobile station

Claims (7)

A resource allocation method for spectrum reuse in a relay station-based cellular system relaying data between a mobile station (MS) and a base station (BS)
(a) allocating resources to a mobile station independently in accordance with a subchannel allocation rule at a relay station;
(b) reporting the mobile station resource allocation information to the base station after allocating resources to the mobile station in the relay station;
(c) performing a resource allocation for the relay station and the mobile station by referring to the resource allocation information of the relay station in the base station, and allocating resources for spectrum reuse in the relay station-based cellular system.
The relay station according to claim 1, wherein the relay stations are arranged in a plurality of cells and share resources between the relay stations by using a partial frequency reuse scheme to avoid intracell interference and intercell interference between relay stations. A method of resource allocation for spectrum reuse in a cellular system.
The relay station according to claim 1, wherein the relay stations are grouped according to intracell interference, grouped relay station groups are indexed according to inter-cell interference between relay stations, and relay stations having the same index use the same partial frequency resource. A method for resource allocation for spectrum reuse in a cellular system.
The method of claim 1, wherein the relay station in step (b) reports mobile station resource allocation information for maximum transmission power among the used subchannels to the base station in the relay station based cellular system.
The base station of claim 1, wherein the base station in step (c) determines the reuse status of the subchannels by referring to the resource allocation information of the relay station, and restricts power transmission to protect transmission of the relay station. A method of resource allocation for spectrum reuse in a system.
The method of claim 1, wherein the base station in step (c) calculates maximum base station transmission power for transmission protection of the relay station in the reused subchannel using the position information of the relay station and the boundary interference amount to the indirect mobile station by the base station transmission, Wherein the transmission power is limited within the calculated maximum transmission power value in the reused subchannel according to the resource allocation information of the relay station.
The method of claim 1, wherein the subchannel allocation rules share radio resources using a partial frequency reuse scheme between neighboring relay stations causing mutual interference, and relay stations in the same group (a group of relay stations having little mutual interference) A subchannel with a low index is reallocated to reuse the subchannels. A method for allocating resources for spectrum reuse in a relay station-based cellular system.

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