KR20120082742A - Method and apparatus for optimizing the persistent scheduling in two-hop relay networks - Google Patents

Abstract

PURPOSE: A method and apparatus for persistent scheduling in a two-hop relay network are provide to efficiently build a wireless telecommunication system by providing a protocol optimization method providing an optimal average resource usage. CONSTITUTION: A MCS(Modulation and Coding Scheme) level and the permissible maximum number of re-transmission are respectively selected as a predetermined value. An overall ARU(Average Resource Usage) of the protocol is calculated based on the selected MCS level and permissible maximum number of re-transmission. A packet error rate of the protocol is calculated based on the selected MCS level and permissible maximum number of re-transmission. The calculated ARU is optimized from the combination of the MCS level and the permissible maximum number of re-transmission.

Description

Method and Apparatus for Efficient Sustained Resource Allocation in Two-hop Relays {Method and Apparatus for Optimizing the Persistent Scheduling in Two-hop Relay Networks}

The present invention relates to an efficient persistent scheduling method and apparatus for a wireless communication network, and more particularly, to a scheduling protocol and a scheduling protocol applicable to a two-hop relay network based on a WiMAX system. The present invention relates to a method and apparatus for optimizing average resource usage (ARU) by selecting a modulation and coding scheme level and a maximum number of retransmissions as optimal values.

Recent wireless communication systems, such as IEEE 802.16e / m WiMAX or 3GPP LTE, have adopted Orthogonal Frequency Division Multiple Access (OFDMA) as the basic transmission method at the physical layer to achieve high spectral efficiency. Has been applied. In general, such a system is known to be very efficient for bulk data transmission, but in a system such as Voice over IP (VoIP) which requires a small packet transmission, it is not very efficient due to the burden of a large control signal. For example, in the case of IEEE 802.16e WiMAX system for VoIP service, the overhead of such a control signal has been known to occupy a relatively large portion.

As a method for reducing such overhead, a persistent resource scheduling scheme has been proposed, for example, in IEEE 802.16e / m WiMAX and 3GPP LTE systems. Sustainable resource allocation scheme refers to a method of allocating a resource of a fixed size and a fixed modulation and coding scheme (MCS) level at the time a burst is started. It has been proposed in the art that such a sustainable resource allocation scheme is efficient for VoIP services.

Because the sustained resource allocation scheme does not change the MCS level, packet decoding errors may occur due to channel changes. Therefore, a hybrid auto repeat request (HARQ) technique may be applied to reduce the packet error rate (PER). Accordingly, in the sustainable resource allocation scheme, it is required to select an efficient MCS level at the beginning of communication, and accommodate as many users as possible by reducing resources allocated per user within a range that satisfies a predetermined quality of service (QoS). You should be able to.

In this regard, Cho et., Published in September 2009 at the International Symposium on Personal, Indoor and Mobile Radio Communications (PIMRC) in Tokyo, Japan. In al. "MCS selection algorithms for a persistent allocation scheme to accommodate VoIP services in IEEE 802.16e OFDMA system", minimizing the resource usage of the sustainable resource allocation scheme using the HARQ scheme on a single link, that is, a single hop. A method of selecting an MCS level can be proposed.

Meanwhile, in recent years, multi-hop relay techniques have been studied to increase the range of cells and increase throughput in a wireless communication system. However, there is no research on how to apply the sustained resource allocation scheme to the multi-hop relay network in services that handle real-time traffic such as VoIP service. Therefore, there is a need for technology development.

In order to solve the above problems, an object of the present invention is to provide a sustainable resource allocation protocol applicable to a relay-based wireless communication system.

Another object of the present invention is to provide a method and apparatus for optimizing a sustainable resource allocation protocol applicable to a relay-based wireless communication system.

The object of the present invention is not limited to the above-mentioned object, and other objects that are not mentioned will be clearly understood by those skilled in the art from the following description.

According to an embodiment of the present invention for achieving the above object, in a method of optimizing the Persistent Scheduling protocol in a two-hop relay network, a) modulation and Selecting a maximum allowable retransmission number between a modulation and coding scheme (MCS) level and a source-relay as a predetermined value, and b) totaling the protocol based on the selected MCS level and the maximum allowable retransmission number. Calculating an average resource usage (ARU), c) calculating a packet error rate of the protocol based on the selected MCS level and the maximum allowed retransmission number, and d) calculating the packet error rate MCS that optimizes the calculated average resource usage, among a combination of MCS levels and values of maximum allowed retransmissions that do not exceed a first threshold A method for optimizing a sustainable resource allocation protocol for selecting a level and a value of a maximum allowable retransmission number is provided.

In addition, according to another embodiment of the present invention for achieving the above object, in the method for optimizing the sustained resource allocation protocol in a two-hop relay network, the device, the device is to provide information related to the current channel state Prior to the input channel state information input unit, the optimization parameter combination calculation unit for setting the combination of the parameters to be optimized, the average resource usage required to transmit data in the two-hop relay network and the average resource usage required for MAP overhead An average resource usage calculation unit calculating based on a combination of input channel state information and optimization parameters, a packet error rate calculating unit determining whether a packet error rate exceeds a first threshold value, and an average resource usage required for transmitting the data And an average ruler for the MAP overhead And an optimization parameter selecting section for selecting a combination of the optimization parameters for which the total average resource usage, which is the sum of the usages, can be optimized, wherein the optimization parameters include the MCS level at the source and repeater links, the MCS level at the repeater and destination links, and the source; Provided is a protocol optimization apparatus including a maximum allowable number of retransmissions between repeaters.

Specific details according to still another embodiment of the present invention are included in the following description and drawings.

As mentioned above, the present invention provides a sustainable resource allocation protocol applicable to, for example, a two-hop relay network.

In addition, according to the present invention, there is provided a protocol optimization technique that can provide the optimal average resource usage while satisfying the predetermined QoS requirements in the above resource allocation protocol, an efficient wireless communication system, for example, a wireless communication system for VoIP services There is an effect that can be built.

1 is a diagram illustrating a sustainable resource allocation protocol in a two-hop relay network system according to an embodiment of the present invention;
2 is a diagram illustrating a sustainable resource allocation protocol in a two-hop relay network system according to another embodiment of the present invention;
3 is a flowchart of a method for selecting a maximum number of retransmissions between an MCS level and a source-repeater in a two-hop relay network to optimize system resource efficiency according to an embodiment of the present invention;
FIG. 4 is a schematic diagram of an apparatus for selecting a maximum number of retransmissions between an MCS level and a source-relay to optimize system resource efficiency in a two-hop relay network according to an embodiment of the present invention.

Advantages and features of the present invention and methods for achieving them will be apparent with reference to the embodiments described below in detail with the accompanying drawings. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention. It is provided to fully inform the scope of the invention, and the invention is defined only by the scope of the claims. Like reference numerals refer to like elements throughout. In addition, when it is determined that the detailed description of the related well-known configuration or function may obscure the subject matter of the present invention, the detailed description thereof will be omitted.

The present invention provides a method and apparatus for selecting a modulation and coding scheme in a wireless communication network. In the present specification, a two-hop relay network scheduling scheme is proposed based on a Voice over IP (VoIP) system according to the IEEE 802.16e standard, and thus embodiments of the present invention are described, but the wireless communication method provided by the present invention and It is obvious that the device can be applied not only to a wireless communication system according to the IEEE 802.16e standard, but also to other similar communication systems. In addition, in the present specification, embodiments of the present invention are described based on an operation of controlling an MCS level for a base station (BS) and one mobile station (MS), but a wireless communication method and apparatus provided by the present invention are numerous. Of course, it can be applied to each of the mobile terminal (MS) of.

In this specification, a terminal includes a mobile station (MS), a mobile terminal (MT), a subscriber station (SS), a portable subscriber station (PSS), a user equipment , An access terminal (UE), an access terminal (AT), and the like, and may include all or some functions of a terminal, a mobile terminal, a subscriber station, a mobile subscriber station, a user equipment,

In this specification, a base station (BS) includes an access point (AP), a radio access station (RAS), a node B, an evolved NodeB (eNodeB) A base station (BTS), a mobile multihop relay (MMR) -BS, or the like, and may perform all or a part of functions of an access point, a radio access station, a Node B, an eNodeB, a base transceiver station, .

In VoIP services, talk bursts typically last hundreds of milliseconds or more. During the talk burst duration, packets are generated periodically and the packet size is almost constant. The transmitter does not need to request resource allocation for each packet since the time at which each packet is transmitted can be estimated at the transmitter and the receiver. Also, if the MCS level is fixed, the overhead of indicating the MCS level for each packet can be reduced. Under this principle, the Sustainable Resource Allocation Protocol determines the MCS level, the resource allocation interval and the amount of each resource at the start of the talk burst. Since the packet decoding error may occur due to channel fluctuations or thermal noise after initiation, the HARQ technique is used to achieve diversity gain. Since decoding errors occur aperiodically, signaling overhead for resource allocation, i.e., MAP overhead, is required at each retransmission.

Based on the above, the present invention proposes a sustainable resource allocation protocol applicable to a two-hop relay network system, and further proposes a technique for optimizing such a protocol.

Hereinafter, with reference to the accompanying drawings will be described embodiments of the present invention;

1 is a diagram illustrating a sustainable resource allocation protocol in a two-hop relay network system according to an embodiment of the present invention.

The protocol shown in FIG. 1 is based on a link between a base station (BS) and a repeater (RS) and a link between a repeater (RS) and a terminal (MS), that is, a source-relay link (SR link) and a repeater-destination (RD link). Each applies a Persistent Scheduling protocol. In the present specification, such a protocol is referred to as a PS-PS protocol, but the content thereof is not limited or limited by such a name, and the content of the protocol should be understood as described below.

A protocol for VoIP service in a repeater-based WiMAX system shown in FIG. 1 will be described. As a protocol that can be applied to a downlink model in which a packet is transmitted from a base station (BS) to a terminal (MS), first, P _BS (m, j) and P _RS (m, j) in FIG. 1 are respectively a base station (BS). In the RS, the resource region for the j th transmission of the m th packet is indicated. ACK _BS (m) and ACK _RS (m) indicate an ACK signal for the m th packet transmitted from the base station BS and the relay RS, respectively. NACK _BS (m) and NACK _RS (m) indicate a NACK signal for the m th packet transmitted from the base station BS and the relay RS, respectively. M _BS (m, j) and M _RS (m, j) indicate MAP overhead for the j th transmission of the m th packet transmitted from the base station BS and the relay RS, respectively. In addition, one frame is illustrated to be composed of a downlink (DL) subframe and an uplink (UL) subframe.

The operation of the PS-PS protocol will now be described by looking at the case where the transmission succeeds and fails. In the following description, Pck (m) means the m-th packet generated by the repeater (BS). First, resources for Pck (m) are reserved at P _BS (m, 1) and P _RS (m, 1) without signaling overhead. That is, since each resource uses a sustainable resource allocation scheme, signaling overhead is not required for the first transmission. Pck (1), ie, the first packet is illustrated as being transmitted in the i-th frame of the base station BS and decoded in the repeater RS. In this case, Pck (1) is transmitted from the repeater RS to the terminal MS in the i + 1th frame. Since two frames are required when a packet is transmitted without error, for example, if one frame takes 5 msec, a delay due to packet transmission is 10 msec. In general, since VoIP packets are generated every 20 msec, it is common to allocate resources every 4 frames. Therefore, Pck (2) is transmitted in the i + 4th frame as shown in FIG. If the Pck 2 is not successfully decoded in the RS as shown in FIG. 1, the NACK _BS 2, i.e., the NACK signal for the second packet is transmitted in the i + 5th frame. At this time, in the i + 7 th frame, Pck (2) is retransmitted to M _BS (2,2), that is, P _BS (2,2) together with MAP overhead information for the second transmission of the second packet. The _BS informs the BS of the new MAP overhead for receiving the second packet as the P _BS (2,1), which was expected to be used according to the sustainable resource allocation scheme, is not used. Because you have to give. Through this process, in the i + 8th frame, the relay RS receives the Pck (2) and loads it with the M _RS (2,1) on the P _RS (2,1) to transmit to the terminal MS. . Thereafter, the terminal MS successfully decodes Pck (2) in the i + 11 th frame. In this process, eight frames are used to transmit Pck (2), so the delay is less than 40 msec.

As described in conjunction with the exemplary scenario above, in the two-hop relay network, the sustained resource allocation is applied to both the source-relay link and the relay-destination link, and the packet is transmitted through the MAP overhead according to the case of receiving and failing the packet. A protocol for retransmitting has been proposed.

2 is a diagram illustrating a sustainable resource allocation protocol in a two-hop relay network system according to another embodiment of the present invention.

The protocol shown in FIG. 2 applies a sustainable resource allocation protocol to a link between a base station (BS) and a repeater (RS), that is, a source-relay link (SR link), and a link between the repeater (RS) and a terminal (MS). That is, the dynamic resource allocation protocol is applied to the RD link. In the present specification, such a protocol is referred to as a PS-DS protocol, but the content thereof is not limited or limited by such a name, and the content of the protocol should be understood as described below.

Looking at the difference from the protocol shown in Figure 1, the resources of Pck (m) are pre-assigned to P _BS (m, 1) for the source-relay link (where the sustainable resource allocation protocol is applied). It is not reserved for repeater-destination links (where dynamic resource allocation protocols apply). Thus, MAP overhead is required for each transmission of the repeater-destination link. As shown in the example of FIG. 1, when the second packet fails to transmit, the relay-destination link does not generate any wasted resources since there is no reserved resource. Such a protocol can reduce the resources that can be wasted in the relay-destination link if retransmission occurs frequently on the source-relay link, that is, in the case of frequent transmission failures.

Next, a technique for optimizing the Persistent Scheduling Parameter while satisfying predetermined QoS requirements in the above-described protocol will be described. The parameters to be optimized in the present invention are k _SR and k _RD which represent the MCS level of the source-relay link and the relay-destination link and N _SR which means the maximum number of allowable retransmissions in the source-relay link.

In a wireless communication system, the modulation and coding scheme should be selected to an appropriate value depending on the state of the channel. For example, in the case of VoIP service, the number of slots required for one VoIP packet increases at a low MCS level, and in the case of a high MCS level, the number of slots required for one VoIP packet becomes small. . The modulation and code rate according to the MCS level and the number of slots required accordingly may be determined as shown in the following table.

That is, it should be possible to select an MCS level that can exhibit optimal performance according to a given channel situation among the various MCS levels, that is, the average resource usage (ARU) can be most optimized. In other words, there is a need to derive an optimization method for determining a parameter of a protocol so as to minimize the number of slots required to send a packet in consideration of the retransmission probability of the data and the MAP overhead according to the channel state. Determining the parameters of a protocol based on such a criterion is meaningful in that the most efficient protocol can be selected not only in terms of increasing system throughput but also in terms of system resources.

Based on the above, the parameter optimization method for each of the sustainable resource allocation protocols of the two-hop relay network will be described. First, we examine the case of the PS-PS protocol that uses the sustained resource allocation scheme in both the source-relay link and the repeater-destination link. Consider the case of the PS-DS protocol using the technique.

PS - PS  protocol

로 표시되는데 여기서

는 데이터 전송을 위한 ARU를 의미하고

는 MAP 오버헤드를 위한 ARU를 의미한다. 즉, 특정의 MCS 레벨 및 특정의 최대 재전송 횟수를 가지는 경우 전체 ARU가 최소화되는 값을 판단한다.

는 다음과 같은 세 가지 경우의 값의 합으로 결정할 수 있는데, 1) 성공적으로 데이터가 디코딩 되는 경우, 2) 소스-중계기 링크가 실패하는 경우, 3) 소스-중계기 링크가 성공하나 중계기-목적지 링크가 실패하는 경우가 그들이다. 재전송 확률까지 고려하여 각각의 ARU는 다음의 수식으로 표현될 수 있다.Overall average resource usage (ARU) is

Where

Means ARU for data transmission

Means ARU for MAP overhead. That is, when the specific MCS level and the specific maximum retransmission number have been determined, a value for minimizing the entire ARU is determined.

Can be determined by the sum of the following three cases: 1) if the data is successfully decoded, 2) if the source-relay link fails, and 3) the source-relay link is successful but the relay-destination link If they fail. In consideration of the retransmission probability, each ARU may be represented by the following equation.

는 A라는 사건이 발생하는 경우에 필요한 ARU를 의미하고,

및

는 각각 소스-중계기 링크, 중계기-목적지 링크의 역 SNR (inverse SNR) 값을 의미하며, N _SR 및 N _SD는 각각 소스와 중계기 사이의 최대 허용 재전송 횟수 및 소스와 목적지 사이의 최대 허용 재전송 횟수를 의미하고, k _SR 및 k _RD는 각각 소스-중계기 링크의 MCS 레벨 및 중계기-목적지 링크의 MCS 레벨을 의미하며, B(k)는 k번째 MCS 레벨이 사용되는 경우에 필요한 자원을 의미하고,

은 i 번째 패킷이 k _SR-MCS 레벨을 가지고 소스-릴레이 링크에서 전송이 실패하는 경우의 확률을 의미한다. 이와 유사한 표기법이

,

등에도 적용되며 당업자에게 그 의미가 쉽게 이해될 수 있을 것이다.here

Means the ARU required in the event of an incident A,

And

Are the inverse SNR values of the source-relay link and the repeater-destination link, respectively. N _SR and N _SD indicate the maximum allowable retransmissions between the source and repeater and the maximum allowable retransmissions between the source and destination, respectively. K _SR and k _RD mean MCS level of the source-relay link and MCS level of the repeater-destination link, respectively, B (k) means resources required when the k-th MCS level is used,

Denotes the probability that the i th packet has a k _SR -MCS level and transmission fails on the source-relay link. Similar notation

,

And the like will be readily understood by those skilled in the art.

The following equations may be used to summarize the above Equations 1 to 3.

Where P ^suc (n, k, λ, m) represents the probability that decoding will succeed when the nth transmission has a given lambda and m at the kth MCS level, i.e., the inverse SNR value and the diversity parameter value of the link. P ^err (n, k, λ, m) represents the probability that transmission will fail when they have the same variable. That is, the probability of success of the nth transmission may be expressed as a combination of probability values of transmission failure.

Substituting Equation 4 into Equations 1 to 3 and adding up Equations 1 to 3, the value of the ARU required for data transmission of the PS-PS protocol may be calculated as follows.

In Equation 5 above, the first term is the ARU for data transmission at the source-relay link, the second term is the ARU for data transmission at the repeater-destination link, and the third term is not utilized at the relay-destination link. Represents a resource. Where N ^mean means the average number of total (re) transmissions, the subscripts indicated by subscripts indicate source-relay link, and RD means repeater-destination link.

는 위의 수학식 5에서 B(k _SR) 및 B(k _RD)을 1로 대체하고, 세 번째 항, 즉, 실제 전송에서 사용되지 않은 자원을 제외함으로써 다음과 같이 얻어질 수 있다.Average number of total (re) transmissions per packet in PS-PS protocol

Can be obtained as follows by substituting B ( k _SR ) and B ( k _RD ) with 1 in Equation 5 and excluding the third term, that is, resources not used in the actual transmission.

의 확률로 발생한다. 따라서

은 다음의 수학식과 같이 계산할 수 있다.Next, the ARU required for the MAP overhead required to transmit a packet in the PS-PS protocol is calculated as follows. MAP overhead is not required for the first transmission of the source-relay link, nor is it necessary for the first transmission of the repeater-destination link if the first transmission of the source-relay link is successfully decoded. The former case always occurs every packet, while the latter case is the probability that the first transmission of the source-relay link will be decoded successfully, i.e.

Occurs with a probability of therefore

May be calculated as in the following equation.

Where M is the size of one MAP overhead and the remaining variables are as described above.

, 즉, PS-PS 프로토콜에서 전체 평균 ARU를 구할 수 있다.By adding up the result of equation (5) and equation (7)

In other words, the overall average ARU can be found in the PS-PS protocol.

On the other hand, the packet error rate (PER) in the PS-PS protocol can be expressed as follows.

Considering the values calculated in this way, when given λ _SR , m _SR , λ _RD , m _RD , that is, given a predetermined SNR value and diversity order, an MCS capable of optimizing the protocol The level and the maximum number of retransmissions can be obtained by obtaining a value satisfying the following optimization condition.

을 만족하는 범위 내에서, PS-PS 프로토콜의 전체 평균 자원 사용량인

이 최소화될 수 있을 소스-중계기의 MCS 레벨 k _SR, 중계기-목적지의 MCS 레벨 k _RD, 소스-중계기의 최대 재전송 허용 횟수 값 N _SR 을 찾는 것이다. 본 발명의 이러한 기법에서 또 한 번 주목해야 할 것은 소스-중계기 간의 최대 재전송 허용 횟수 값인 N _SR을 조절하여 최적화를 달성한다는 점이다. N _SR은 통상 소스-목적지 간의 최대 재전송 횟수인 N _SD보다 1 작은 값, 즉, N _SD-1으로 설정되는 것이 종래기술의 설정이었다. 이와 같은 종래의 설정은 통신이 두절되지 않는 것을 최대한으로 보장해준다는 관점에서는 유리할지 모르나 시스템 자원의 효율 측면에서는 바람직하지 못했다. 본 발명의 일 실시예에 따르면, N _SR의 값을 시스템 효율 측면을 고려하여 조정하면서도 소정의 PER을 만족시킴으로써, 시스템 자원 효율과 통신의 품질을 모두 충족시킬 수 있는 프로토콜을 설정하는 것이 가능하다. Looking back at the equation above, the PER constraint that the service must satisfy,

Within the range of satisfying the overall average resource usage of the PS-PS protocol,

MCS level k _SR of the source-repeater, MCS level k _RD of the repeater-destination, and the maximum number of retransmission allowance values N _SR of the source-repeater can be minimized. It should be noted again that this technique of the present invention achieves optimization by adjusting the N _SR , the maximum retransmission allowance value between the source and the repeater. In the prior art, the N _SR is generally set to a value smaller than N _SD , that is, the maximum number of retransmissions between source and destination, that is, N _SD -1. Such a conventional configuration may be advantageous in terms of maximally guaranteeing that communication is not interrupted, but is undesirable in terms of efficiency of system resources. According to an embodiment of the present invention, by adjusting the value of the N _SR in consideration of the system efficiency, while satisfying the predetermined PER, it is possible to set a protocol capable of satisfying both system resource efficiency and communication quality.

In the case of the PS-PS protocol, the SNR of the source-relay may be relatively good, especially when the optimization performance is good, because the HARQ scheme will not work frequently in the source-relay link, and thus, between source-relay It indicates that the maximum number of retransmissions can be set to a low value, unlike conventional studies. According to an embodiment of the present invention, a parameter that shows optimization may be differently selected according to channel conditions, thereby showing excellent performance in terms of system resource utilization.

PS - DS  protocol

는 다음과 같이 계산될 수 있다.Next, the optimization method in the PS-DS protocol will be described. In the case of the PS-DS protocol, unlike in the case of the PS-PS protocol, since there are no pre-allocated resources in the relay-destination link, no resources can be wasted due to resource reservation and decoding failure. Therefore, by removing the third term of Equation 5 above, the PS-DS protocol

Can be calculated as follows.

The meaning of each term is as described above in Equation 5.

는 PS-PS 프로토콜에서 계산한 수학식 6과 같다. Next, the average value of the total number of retransmissions per packet in the PS-DS protocol,

Equation 6 is calculated by the PS-PS protocol.

은 다음과 같이 계산할 수 있다.Next, when calculating the ARU of the MAP overhead in the PS-DS protocol, the MAP overhead is required for each transmission except for the first transmission of the source-relay link for the PS-DS protocol. Therefore, the PS-DS protocol

Can be calculated as

을 구할 수 있다. PS-DS 프로토콜에서의 PER 제한요건은 앞서 살펴 본 수학식 8과 동일하다.By adding the values obtained in Equation 10 and Equation 11, the total ARU value in the PS-DS protocol, that is,

Can be obtained. The PER constraint in the PS-DS protocol is the same as Equation 8 discussed above.

Considering the values calculated in this way, when given λ _SR , m _SR , λ _RD , m _RD , that is, given a predetermined SNR value and diversity order, an MCS capable of optimizing the protocol The level and the maximum number of retransmissions can be obtained by obtaining a value satisfying the following optimization condition.

In the PS-DS protocol optimization method according to an embodiment of the present invention, the maximum number of allowable (re) transmissions of the source-relay link is also adjusted, so that system resource efficiency and communication performance are the same as in the case of the PS-PS protocol described above. Can satisfy all of them.

In the case of the PS-DS protocol, like the PS-PS protocol described above, the maximum number of retransmissions may be selected according to an embodiment of the present invention so as to optimize the efficiency of system resources, unlike the conventional research.

As described above, the optimization parameter selection method of the present invention may select a combination of parameters showing the best performance (the lowest average resource usage) among the combination of various parameters, and of course, when the predetermined threshold is satisfied. Of course, a combination of parameters to be selected may be selected. It should be noted that various modifications in this regard may be made depending on the state of each channel and the specifications of the wireless communication system.

3 is a flowchart illustrating a method of selecting a maximum number of retransmissions between an MCS level and a source-relay in an two-hop relay network to optimize system resource efficiency according to an embodiment of the present invention.

As shown in FIG. 3, the method 300 receives information relating to a current channel state in step 310. The information that can be input in one embodiment of the present invention includes, but is not limited to, the above-mentioned SNR value, diversity order, packet error rate constraints, and the like.

Next, in step 320, a combination of parameters to be optimized is set. In one embodiment of the present invention, there is, but is not limited to, the MCS level of each hop and the maximum allowable number of retransmissions between the source and the repeater.

Next, in step 330, the average resource usage required for transmitting data in the two-hop relay network is calculated based on a combination of channel state information and optimization parameters previously input, and in step 340, the average required for MAP overhead. Calculate resource usage. The detailed information necessary for such calculation is as described above, and the detailed description thereof will be omitted.

Next, in step 350, it is calculated whether the packet error rate satisfies a predetermined value, for example, the minimum value that is set to be satisfied in order to perform the VoIP service.

Next, the average resource usage (the number of slots required for data transmission and the number of slots required for MAP overhead) calculated based on the parameters currently input in step 360 is stored. This is to compare the result values for various parameter combinations in the step of selecting a value representing the optimum efficiency, as described below.

Next, in step 370, it is determined whether the average resource usage is calculated for all combinations of optimization parameters, and if not, the process returns to step 320 and repeats the above-described steps. Alternatively, the above-described steps may be repeated only a predetermined number of times without being calculated for all combinations, and by limiting the value of a specific parameter to a certain range, for example, by limiting the MCS level to a value of 3 or more, It may be repeated to calculate the average resource usage.

Next, in step 380, the combination of optimization parameters representing the optimal average resource usage is selected by comparing the values of the average resource usage calculated above.

In this specification, only one embodiment of the present invention has been described, and the above-described steps are not necessarily to be performed in a certain order, and the order may be changed or omitted in a range that does not depart from the spirit of the present invention. It is obvious to those skilled in the art.

FIG. 4 is a schematic diagram of an apparatus for selecting a maximum number of retransmissions between an MCS level and a source-relay to optimize system resource efficiency in a two-hop relay network according to an embodiment of the present invention.

As shown in FIG. 4, the apparatus 400 includes a channel state information input unit 410, an optimization parameter combination calculator 420, an average resource usage calculator 430, a packet error calculator 440, and an average resource usage. The storage unit 450 and the optimization parameter combination selection unit 460 may be included.

The channel state information input unit 410 receives information related to the current channel state. The information that can be input in one embodiment of the present invention includes, but is not limited to, the above-mentioned SNR value, diversity order, packet error rate constraints, and the like.

The optimization parameter combination calculator 420 sets a combination of parameters to be optimized. In one embodiment of the present invention, there is, but is not limited to, the MCS level of each hop and the maximum allowable number of retransmissions between the source and the repeater.

The average resource usage calculation unit 430 calculates the average resource usage required for data transmission in the two-hop relay network and the average resource usage required for MAP overhead based on a combination of previously input channel state information and optimization parameters.

The packet error rate calculator 440 calculates whether the packet error rate satisfies a predetermined threshold, for example, a minimum value that must be satisfied in order to perform a VoIP service.

The average resource usage storage unit 450 stores the average resource usage (the number of slots required for data transmission and the number of slots required for MAP overhead) calculated based on the currently input parameters.

The optimization parameter combination selecting unit 460 selects a combination of optimization parameters representing the optimal average resource usage by comparing the values of the previously calculated and stored average resource usage.

In this specification, only an embodiment of the present invention has been described, and each of the above-described elements is not necessarily regarded as a single independent element, and may be divided into several elements or several elements within the scope of the present invention. It will be apparent to those skilled in the art that the four components can be integrated into one component.

Embodiments of the present invention may be implemented in the form of program instructions that can be executed by various computer means and recorded in a computer-readable medium. The computer readable medium may include program instructions, data files, data structures, etc. alone or in combination. The media may be those specially designed and constructed for the purposes of the present invention, or they may be of the kind well-known and available to those having skill in the computer software arts. Examples of computer-readable recording media include magnetic media such as hard disks, floppy disks, and magnetic tape, optical media such as CD-ROMs, DVDs, and magnetic-optical media such as floppy disks. magneto-optical media and hardware devices specifically configured to store and execute program instructions, such as ROM, RAM, flash memory, and the like. The medium may be a transmission medium such as an optical or metal line, a wave guide, or the like, including a carrier wave for transmitting a signal designating a program command, a data structure, or the like. Examples of program instructions include not only machine code generated by a compiler, but also high-level language code that can be executed by a computer using an interpreter or the like.

Although the embodiments of the present invention have been described above with reference to the accompanying drawings, those skilled in the art to which the present invention pertains may be embodied in other specific forms without changing the technical spirit or essential features of the present invention. I can understand that. Therefore, the embodiments described above are illustrative in all respects and should not be understood as limiting.

Claims (12)

In the method of optimizing the Persistent Scheduling protocol in a two-hop relay network,
a) selecting a maximum allowable number of retransmissions between a modulation and coding scheme (MCS) level and a source-relay to a predetermined value, respectively;
b) calculating an overall average resource usage (ARU) of the protocol based on the selected MCS level and the maximum allowed retransmission number;
c) calculating a packet error rate of the protocol based on the selected MCS level and the maximum allowed retransmission number;
d) selecting a value of the MCS level and the maximum allowable retransmission number that optimizes the calculated average resource usage, from a combination of the values of the MCS level and the maximum allowed retransmission, such that the calculated packet error rate does not exceed a first threshold;
Sustainable resource allocation protocol optimization method.
The method of claim 1,
The MCS level comprises an MCS level between a source-repeater and an MCS level between a repeater-destination,
The total average resource usage includes the average resource usage required for data transmission and the average resource usage required for MAP overhead,
The protocol applies a sustainable resource allocation protocol for each link between the source and the repeater and the link between the repeater and the destination.
Sustainable resource allocation protocol optimization method.
The method of claim 2,
Repeating steps a) to c) for a combination of possible values of the MCS level and the maximum allowable retransmission number to calculate an overall average resource usage and packet error rate for each combination,
Selecting, from the combination of the possible values of the MCS level and the maximum allowable retransmission number, a combination of the MCS level and the maximum allowable retransmission number that indicate a minimum overall average resource usage;
Sustainable resource allocation protocol optimization method. The method of claim 3, wherein
Average resource usage required for the data transmission is calculated by the following formula,

Here, SR used as a subscript in each term means a link between a source and a repeater, RD means a link between a repeater and a destination, and SD means a link between a source and a destination.
k is the kth MCS level, N is the maximum allowable number of retransmissions, B (k) is the average resource required at the kth MCS level, and N ^mean (N, k) is the average number of retransmissions of the packet at the kth MCS level. , P ^suc (i, k) is the probability that the i-th transmitted packet will be transmitted successfully when it has the k-th MCS level,
The average resource usage required for the MAP overhead is calculated by the following equation,

here

Is the average number of retransmissions per packet in the protocol of the two-hop relay network, M is the amount of resources allocated per MAP overhead,
The packet error rate is calculated by the following equation,

Here, P ^err (i, k) denotes the probability that transmission will fail when the i th transmitted packet has the k th MCS level.
Sustainable resource allocation protocol optimization method.
The method of claim 4, wherein
The average number of retransmissions per packet in the protocol of the two-hop relay network is calculated by the following equation,

Sustainable resource allocation protocol optimization method.
The method of claim 1,
The MCS level comprises an MCS level between a source-repeater and an MCS level between a repeater-destination,
The total average resource usage includes the average resource usage required for data transmission and the average resource usage required for MAP overhead,
The protocol applies a sustainable resource allocation protocol to a link between a source and a repeater, and dynamic resource scheduling (Dynamic Scheduling) is applied to a link between a repeater and a destination.
Sustainable resource allocation protocol optimization method.
The method according to claim 6,
Repeating steps a) to c) for a combination of possible values of the MCS level and the maximum allowable retransmission number to calculate an overall average resource usage and packet error rate for each combination,
Selecting, from the combination of the possible values of the MCS level and the maximum allowable retransmission number, a combination of the MCS level and the maximum allowable retransmission number that indicate a minimum overall average resource usage;
Sustainable resource allocation protocol optimization method.
The method of claim 7, wherein
Average resource usage required for the data transmission is calculated by the following formula,

Here, SR used as a subscript in each term means a link between a source and a repeater, RD means a link between a repeater and a destination, and SD means a link between a source and a destination.
k is the kth MCS level, N is the maximum allowable number of retransmissions, B (k) is the average resource required at the kth MCS level, and N ^mean (N, k) is the average number of retransmissions of the packet at the kth MCS level. , P ^suc (i, k) is the probability that the i-th transmitted packet is successfully transmitted when the k-th MCS level,
The average resource usage required for the MAP overhead is calculated by the following equation,

here

Is the average number of retransmissions per packet in the protocol of the two-hop relay network, M is the amount of resources allocated per MAP overhead,
The packet error rate is calculated by the following equation

Here, P ^err (i, k) denotes the probability that transmission will fail when the i th transmitted packet has the k th MCS level.
Sustainable resource allocation protocol optimization method.
The method of claim 8,
The average number of retransmissions per packet in the protocol of the two-hop relay network is calculated by the following equation,

Sustainable resource allocation protocol optimization method.
A computer-readable recording medium having recorded thereon a program for executing the method of any one of claims 1 to 9.
An apparatus in a method for optimizing a Persistent Scheduling protocol in a two-hop relay network, the apparatus comprising:
The apparatus may include a channel state information input unit configured to receive information related to a current channel state.
An optimization parameter combination calculation unit for setting a combination of parameters to be optimized;
An average resource usage calculation unit configured to calculate an average resource usage required for data transmission in the two-hop relay network and an average resource usage required for MAP overhead based on a combination of previously input channel state information and optimization parameters;
A packet error rate calculation unit for determining whether the packet error rate exceeds the first threshold value;
An optimization parameter selection unit configured to select a combination of the optimization parameters for which the overall average resource usage, which is the sum of the average resource usage required for transmitting the data and the average resource usage required for the MAP overhead, may be optimized;
The optimization parameter includes an MCS level at the source and repeater link, an MCS level at the repeater and destination link and a maximum allowable number of retransmissions between the source and repeater.
Protocol optimizer.
12. The device of claim 11, wherein the device is
Further comprising an average resource usage storage for storing the calculated total average resource usage
Protocol optimizer.

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