JP5690480B2 - Base station, user terminal, and method for realizing single cell enhanced MBMS - Google Patents

Description

  The present invention relates to an EMBMS (Enhanced Multimedia Broadcast / Multicast Service, enhanced multimedia broadcast / multicast service) of a 3G LTE (Long Term Evolution) system, and more particularly, to a base station, a user terminal, and a method of realizing a single cell enhanced MBMS.

  Multicast and broadcast are techniques for transmitting data from one data source to multiple destinations. The World Standardization Organization 3GPP has proposed MBMS (Multimedia Broadcast / Multicast Service, multimedia broadcast / multicast service) in mobile networks. Supporting point-to-multipoint services that transmit data from one data source to multiple users enables sharing of network resources and improvement of utilization of network resources, and in particular, improvement of utilization of air interface resources. .

  The 3G LTE system is an evolution project in which the 3GPP organization establishes a 3G system, and is generally considered to be 3.9G. In 3G LTE system, MBMS is called Enhanced MBMS (EMBMS). In EMBMS, two types of transmission methods, multi-cell transmission and single-cell transmission, are defined.

  Single cell transmission supports link feedback and HARQ (Hybrid Automatic Repeat Request) retransmissions. For example, in a specific cell such as a cell covered by a home base station, a reliable MBMS service can be provided by single cell transmission.

  In MBMS defined by 3GPP, since there is no retransmission mechanism in the link layer, the radio link error is directly transmitted to the application layer, and the quality of the MBMS service is greatly reduced. To compensate for this problem, MBMS defines Raptor FEC (Forward Error Correction) in the application layer, which is used to provide forward error correction for a certain application layer. .

  Raptor is a special case of fountain code and belongs to a rateless coding plan. The fountain code is a code in which an arbitrary number of encoded packets are generated from K original packets, and the user terminal receives and decodes an arbitrary M encoded packets of the original packets. All packets can be recovered with high probability. In general, since M is slightly larger than K, a certain decoding cost S is introduced and defined as S = M / K-1.

  The fountain code is applied to the 3GPP MBMS standard in 2004 and is used as a forward error correction protection method in the application layer because it is very applicable to wireless broadcasting due to its own nature. In a recent LTE standard meeting, a mechanism different from that of the conventional MBMS has been proposed by each manufacturer for EMBMS, but there was no objection to the adoption of raptor FEC in the application layer.

  As an application layer coding scheme, Raptor FEC is expected to continue to be adopted in the EMBMS standard.

  However, in the process of realizing the present invention, the inventor of the present invention has found that radio resources are wasted by simultaneously using Raptor and HARQ in the case of EMBMS single cell transmission. Details are analyzed as follows.

  As shown in FIG. 1, it is assumed that the transmission scheduled file is divided into K source symbols in the application layer, and N encoded symbols are generated through a Raptor encoder. The N encoded symbols are transmitted to a MAC (Medium Access Control) layer and transmitted to a MAC layer of a user terminal via a wireless link.

  On the other hand, on the transmitting side, the HARQ retransmission mechanism is adopted to overcome unreliable radio links. If the error caused in the radio link by HARQ is completely overcome, the user terminal can receive the N encoded symbols and transmits the N symbols to the application layer. A Raptor decoder then performs decoding based on the N encoded symbols.

  In the actual case, depending on the nature of the Raptor coding, only M (M only needs to be slightly larger than K) signals are required to decode K source symbols. However, since there is no alternation between the application layer raptor FEC and the MAC layer HARQ, in general, the number N of encoded symbols generated by the application layer raptor FEC is the decoding of K source symbols. Is much larger than the number M of encoded symbols required for. However, since only M encoded symbols are required for Raptor decoding, (N−M) encoded symbols are extra for Raptor decoding. Therefore, energy and radio resources consumed by the MAC layer for transmission of the (N−M) extra symbols are also wasted.

  An object of the present invention is to provide a base station, a user terminal, and a method for realizing a single cell enhanced MBMS, and to improve a radio resource utilization rate when the enhanced MBMS simultaneously uses raptor and HARQ in single cell transmission.

  In order to achieve the above object, an embodiment of the present invention provides a method for realizing single cell enhanced MBMS that retransmits using Raptor coding and hybrid automatic repeat request HARQ.

  The method establishes a connection with a broadcast / multicast service center, obtains the number of source symbols and the number of encoded symbols, and satisfies the service demand based on the target decoding failure probability, the number of source symbols and the number of encoded symbols. To obtain a current packet loss rate during enhanced MBMS data transmission, and when the current packet loss rate is less than or equal to the target packet loss rate, control processing is performed and the average number of HARQ retransmissions is retransmitted. Reduce.

In the above method, when K is the number of source symbols, N is the number of encoded symbols, x is the number of encoded symbols received, and P _f is the target decoding failure probability, the target packet loss rate p is calculated by the following formula: The

上記制御処理は、具体的に、エンハンスド基地局がＨＡＲＱの現在最大再送回数を減らし、上記現在最大再送回数が減らされて１以上となる。

Specifically, in the control process, the enhanced base station decreases the current maximum number of retransmissions of HARQ, and the current maximum number of retransmissions is decreased to 1 or more.

  When the current packet loss rate is larger than the target packet loss rate, the enhanced base station increases the current maximum number of retransmissions of HARQ, and the current maximum number of retransmissions is increased to 3 or less.

  The control process blocks an operation of feeding back an NACK to the enhanced base station when the user terminal detects a data reception error.

  When the current packet loss rate is larger than the target packet loss rate, NACK is fed back to the enhanced base station when the user terminal detects a data reception error.

  In order to achieve the above object, an embodiment of the present invention provides a method for realizing single cell enhanced MBMS that retransmits using Raptor coding and hybrid automatic repeat request HARQ.

  The method establishes a connection with a broadcast / multicast service center, obtains the number of source symbols and the number of encoded symbols, and satisfies the service demand based on the target decoding failure probability, the number of source symbols and the number of encoded symbols. The target packet loss rate is calculated, the current packet loss rate is obtained during enhanced MBMS data transmission, the first feedback probability is calculated based on the target packet loss rate and the current packet loss rate, and the user terminal receives the data When an error is detected, NACK is fed back to the enhanced base station with a second feedback probability that is equal to or higher than the first feedback probability and smaller than 1.

In the above method, K is the number of source symbols, N is the number of encoded symbols, x is the number of encoded symbols received, P _f is the target decoding failure probability, and the target packet loss rate p is calculated by the following formula.

P _target is the target packet loss rate, P _current is the current packet loss rate, and the first feedback probability P _opt is calculated by the following formula.

上記目的を実現するために、本発明の実施例では、Ｒａｐｔｏｒ符号化とハイブリッド自動再送要求ＨＡＲＱを利用して再送するシングルセルエンハンスドＭＢＭＳに用いる基地局を提供している。

In order to achieve the above object, an embodiment of the present invention provides a base station used for single-cell enhanced MBMS that retransmits using Raptor coding and hybrid automatic repeat request HARQ.

  The base station receives a first reception module for receiving the number of source symbols and the number of encoded symbols from a broadcast / multicast service center, a target decoding failure probability, and a service based on the number of source symbols and the number of encoded symbols. A target packet loss rate calculation module for calculating a target packet loss rate that satisfies the demand of the current packet, a current packet loss rate calculation module for obtaining a current packet loss rate during enhanced MBMS data transmission, and the current packet loss rate If the current packet loss rate is equal to or lower than the target packet loss rate, a control process is performed to reduce the average number of HARQ retransmissions. And an adjustment module.

In the base station, if K is the number of source symbols, N is the number of encoded symbols, x is the number of encoded symbols received, and P _f is the target decoding failure probability, the target packet loss rate calculating module The rate p is calculated by the following formula.

上記基地局の上記調節モジュールにおいて、上記現在パケットロス率が上記目標パケットロス率以下となる場合には、ＨＡＲＱの現在最大再送回数を減らし、上記現在最大再送回数が減らされて１以上となり、上記現在パケットロス率が上記目標パケットロス率よりも大きい場合には、ＨＡＲＱの現在最大再送回数を増やし、上記現在最大再送回数が３以下となるための第１の調節ユニットを含む。

In the adjustment module of the base station, when the current packet loss rate is less than or equal to the target packet loss rate, the current maximum number of retransmissions of HARQ is reduced, and the current maximum number of retransmissions is reduced to 1 or more, When the current packet loss rate is larger than the target packet loss rate, a first adjustment unit for increasing the current maximum number of retransmissions of HARQ and reducing the current maximum number of retransmissions to 3 or less is included.

  In order to achieve the above object, an embodiment of the present invention provides a user terminal used for single-cell enhanced MBMS that retransmits using Raptor coding and hybrid automatic repeat request HARQ.

  The user terminal determines a service demand based on a receiving module for receiving the number of source symbols and the number of encoded symbols from a broadcast / multicast service center, a target decoding failure probability, and the number of source symbols and the number of encoded symbols. A target packet loss rate calculation module for calculating a target packet loss rate to be satisfied; a current packet loss rate calculation module for acquiring a current packet loss rate during enhanced MBMS data transmission; and the current packet loss rate is the target A comparison module for comparing whether or not the packet loss rate is greater than, and when the current packet loss rate is larger than the target packet loss rate and a data reception error is detected, NACK is fed back to the base station, Current packet loss rate is the target packet loss rate Ri is large, and if not the detection of the data reception errors, and a first feedback module, for maintaining silence.

In the user terminal, K is the number of source symbols, N is the number of encoded symbols, x is the number of encoded symbols received, P _f is the target decoding failure probability, and the target packet loss rate calculating module The rate p is calculated by the following formula.

上記目的を実現するために、本発明の実施例では、Ｒａｐｔｏｒ符号化とハイブリッド自動再送要求ＨＡＲＱを利用して再送するシングルセルエンハンスドＭＢＭＳに用いるユーザ端末を提供している。

In order to achieve the above object, an embodiment of the present invention provides a user terminal used for single-cell enhanced MBMS that retransmits using Raptor coding and hybrid automatic repeat request HARQ.

  The user terminal determines a service demand based on a receiving module for receiving the number of source symbols and the number of encoded symbols from a broadcast / multicast service center, a target decoding failure probability, and the number of source symbols and the number of encoded symbols. A target packet loss rate calculation module for calculating a target packet loss rate to be satisfied, a current packet loss rate calculation module for obtaining a current packet loss rate during enhanced MBMS data transmission, and the target packet loss rate and the current packet A first feedback probability calculation module for calculating a first feedback probability satisfying the demand for the service based on the loss rate; and when a data reception error is detected, the first feedback probability is equal to or higher than the first feedback probability. And a second field smaller than 1 And a second feedback module, for feeding back a NACK to the enhanced base station in Dobakku probability.

In the user terminal, if K is the number of source symbols, N is the number of encoded symbols, x is the number of encoded symbols received, and P _f is the target decoding failure probability, the target packet loss rate calculation module The rate p is calculated by the following formula.

上記ユーザ端末では、Ｐ_{ｔａｒｇｅｔ}が上記目標パケットロス率、Ｐ_{ｃｕｒｒｅｎｔ}が上記現在パケットロス率とし、上記第１のフィードバック確率計算モジュールが上記第１のフィードバック確率Ｐ_ｏｐｔを、下記公式で計算する。

In the user terminal, P _target is the target packet loss rate, P _current is the current packet loss rate, and the first feedback probability calculation module calculates the first feedback probability P _{opt according} to the following formula.

上記目的を実現するために、本発明の実施例では、Ｒａｐｔｏｒ符号化とハイブリッド自動再送要求ＨＡＲＱを利用して再送するシングルセルエンハンスドＭＢＭＳの実現方法を提供している。

In order to achieve the above object, an embodiment of the present invention provides a method for realizing single cell enhanced MBMS that retransmits using Raptor coding and hybrid automatic repeat request HARQ.

  Before decoding is completed, when the user terminal detects a data reception error, NACK is fed back to the enhanced base station.

  After the decoding is completed, the user terminal blocks an operation of feeding back NACK to the enhanced base station when detecting a data reception error.

  According to the embodiment of the present invention, the following excellent effects can be obtained.

  In the embodiment of the present invention, when the service demand is satisfied, NACK is fed back with a certain probability when there is an error in data reception of the mobile terminal. In the prior art, NACK is fed back every time there is an error in data reception, whereas under the same network situation, the number of NACKs fed back is relatively small. Since HARQ retransmission is triggered by NACK, the average number of HARQ retransmissions is necessarily reduced, that is, the resource utilization rate is improved. In another implementation, when the base station satisfies the service demand, the average HARQ retransmission number of the E-Node B is reduced by automatically reducing the maximum number of HARQ retransmissions. The utilization rate will be improved.

  Therefore, the embodiment of the present invention reduces the average number of HARQ retransmissions as much as possible when the service demand is satisfied, thereby improving the utilization rate of radio resources.

A conventional EMBMS shows a data stream in the case of retransmitting using Raptor and HARQ. 1 shows a flow of a method according to a first embodiment of the present invention. It is a structural diagram of the user terminal of the first embodiment of the present invention. The flow of the method of the 2nd example of the present invention is shown. FIG. 6 is a structural diagram of a base station according to a second embodiment of the present invention. The flow of the method of the 3rd example of the present invention is shown. It is a structural diagram of the user terminal of the fourth embodiment of the present invention.

  In the base station, user terminal, and single cell enhanced MBMS implementation method of the embodiment of the present invention, when the service demand is satisfied, the number of retransmissions of E-Node B is reduced as much as possible to improve the utilization rate of radio resources. I am letting.

  Before describing the embodiment of the present invention in detail, first, parameters related to the embodiment of the present invention will be described in detail.

K: number of source symbols N: number of encoded symbols x: number of received encoded symbols p: packet loss rate P _f : Raptor decoding failure probability Retrans_Num: average number of HARQ retransmissions, which is 3 or less X <K Since the user terminal has not acquired enough information for decoding, the decoding failure rate is 1, that is, it always fails. When X ≧ K, P _f is smaller than 2- ^(X−K) , which is the upper limit.

Based on the above, the decoding failure probability P _f of the user terminal is expressed by the following equation.

上記公式から分かるように、Ｐ_ｆはパラメータｐとＮに関係する。

As can be seen from the above formula, P _f is related to the parameters p and N.

  As can be seen from the description in the background art section, radio resources are wasted when enhanced MBMS retransmits simultaneously using Raptor and HARQ in single cell transmission. In order to reduce the waste of resources, it is necessary to reduce the transmission of useless packets on the premise that the demand for enhanced MBMS is satisfied.

  When enhanced MBMS retransmits simultaneously using Raptor and HARQ in single-cell transmission, it can be understood that the following two aspects are started to reduce the transmission of useless packets.

1) reducing the number of coded symbols and / or 2) reducing the average number of HARQ retransmissions.

  In a specific embodiment of the present invention, it is possible to sufficiently use radio resources by reducing the average number of HARQ retransmissions.

<First embodiment>
In the first embodiment of the present invention, the average number of HARQ retransmissions is reduced by the user terminal controlling the number of NACK packets. Satisfying the demand for services refers to the decoding failure rate.

  The probability of Raptor decoding failure is mainly affected by the error packet rate and the number of encoded symbols. If the error packet rate is high, the decoding failure probability increases. If the number of encoded symbols is small, the decoding failure probability increases.

In a specific embodiment of the present invention, the current packet loss rate P _current corresponds to the target decoding failure probability so that the probability of Raptor decoding failure can satisfy the demand in order to maintain the number of the encoded symbols constant. What is necessary is just to make it smaller than target packet loss rate _Ptarget (link layer packet loss rate).

  As can be seen from the HARQ operation process, since the NACK packet is transmitted from the user terminal, the transmission side starts HARQ retransmission. If the number of NACK packets transmitted from the user terminal is reduced, the average number of HARQ retransmissions can always be reduced.

Therefore, in the first embodiment of the present invention, when the user terminal detects a packet error, NACK is not immediately fed back, but when the current packet loss rate P _current is higher than the target packet loss rate P _target. NACK is fed back. When the current packet loss rate P _current is equal to or less than the target packet loss rate P _target , NACK is not fed back even if there is an error in the packet.

  As shown in FIG. 2, in the method according to the first embodiment of the present invention, enhanced MBMS retransmits simultaneously using Raptor and HARQ in single cell transmission.

  In step 21, the user terminal establishes a connection with a BM-SC (Broadcast Multicast Service Center), and acquires the number K of source symbols and the number N of encoded symbols.

In step 22, the user terminal calculates a _target packet loss rate P _target using the following formula based on the target decoding failure probabilities P _f , K, and N.

In step 23, at the time of EMBMS data transmission, the user terminal acquires the _current packet loss rate P _current based on the current packet reception status.

In step 24, it is determined whether or not the current packet loss rate P _current is larger than the target packet loss rate P _target . If the current packet loss rate P _current is larger than the target packet loss rate P _{target, the} process proceeds to step 25. If the current packet loss rate P _current is not larger than the target packet loss rate P _target , the process goes to step 23. Return (ie, block the operation of feeding back NACK to the enhanced base station when a data reception error is detected).

  In step 25, when a data reception error is detected, NACK is fed back to E-Node B, and the process returns to step 23.

In the first embodiment of the present invention, when the current packet loss rate P _current is larger than the target packet loss rate P _target , the current channel condition is bad, and the current decoding failure probability is made equal to or less than the target decoding failure probability P _f . This means that the user terminal needs to feed back NACK when there is an error in data reception. On the other hand, when the current packet loss rate P _current is smaller than the target packet loss rate P _target , the decoding failure probability decreases if the error packet rate is small. In such a case, the current decoding failure probability is equal to or less than the target decoding failure probability P _f. Therefore, it is possible to satisfy the demand for service, and even if there is an error in the received service data, there is no need to feed back NACK.

  According to the above processing, since the user terminal does not feed back NACK for all received data with errors, the number of NACKs received on the transmitting side is reduced. Since HARQ retransmission is triggered by NACK, the average number of HARQ retransmissions is necessarily reduced, that is, the resource utilization rate is improved.

ＥＭＢＭＳデータ伝送時に、現在のパケット受信状況に基づいて現在パケットロス率Ｐ_{ｃｕｒｒｅｎｔ}を取得する現在パケットロス率計算モジュールと、上記現在パケットロス率Ｐ_{ｃｕｒｒｅｎｔ}が上記目標パケットロス率Ｐ_{ｔａｒｇｅｔ}よりも大きいか否かを比較する比較モジュールと、現在パケットロス率が目標パケットロス率よりも大きく、且つデータ受信エラーを検出した場合には、Ｅ‐Ｎｏｄｅ ＢにＮＡＣＫをフィードバックし、現在パケットロス率が目標パケットロス率よりも大きく、且つデータ受信エラーを検出したことではない場合には、サイレンスを維持する第１のフィードバックモジュールとを有する。 As shown in FIG. 3, the user terminal according to the first embodiment of the present invention includes a receiving module that receives the number K of source symbols and the number N of encoded symbols from the BM-SC through a connection with the BM-SC. A target packet loss rate calculation module for calculating a target packet loss rate P _target according to the following formula based on the target decoding failure probability P _f , K, N:

A current packet loss rate calculation module for acquiring a _current packet loss rate P _current based on the current packet reception status during EMBMS data transmission, and whether the current packet loss rate P _current is greater than the target packet loss rate P _target When the current packet loss rate is larger than the target packet loss rate and a data reception error is detected, NACK is fed back to the E-Node B, and the current packet loss rate is set to the target packet loss rate. A first feedback module for maintaining silence if greater than the rate and not detecting a data reception error.

<Second embodiment>
In the first embodiment of the present invention, the average number of HARQ retransmissions is reduced by the user terminal controlling the number of NACK packets. Satisfying the demand for services refers to the decoding failure rate.

  On the other hand, in the second embodiment of the present invention, the E-Node B mainly reduces the number of retransmissions by reducing the number of retransmissions dynamically. Satisfying the demand for services refers to the decoding failure rate.

  The probability of Raptor decoding failure is mainly affected by the error packet rate and the number of encoded symbols. If the error packet rate is high, the decoding failure probability increases. If the number of encoded symbols is small, the decoding failure probability increases.

In a specific embodiment of the present invention, the current packet loss rate P _current corresponds to the target decoding failure probability so that the probability of Raptor decoding failure can satisfy the demand in order to maintain the number of the encoded symbols constant. What is necessary is _{just to make} it smaller than the target packet loss rate _Ptarget .

  In the second embodiment of the present invention, the user terminal normally feeds back the NACK, but the E-Node B does not retransmit based on the NACK fed back from the user terminal.

  In 3GPP TS 36.321 E-UTRA: MAC protocol specification, the maximum number of HARQ retransmissions is set to 3. However, as can be seen from the above, when the number of encoded symbols of the Raptor is large, retransmitting HARQ three times wastes a lot of resources, so the maximum number of HARQ retransmissions must be reduced.

ＥＭＢＭＳデータ伝送時に、Ｅ‐Ｎｏｄｅ Ｂは、ユーザ端末がデータ受信エラーのときに送信したＮＡＣＫを受信するステップ４３と、Ｅ‐Ｎｏｄｅ Ｂが、受信したＮＡＣＫに基づいて現在パケットロス率Ｐ_{ｃｕｒｒｅｎｔ}を取得するステップ４４と、現在パケットロス率Ｐ_{ｃｕｒｒｅｎｔ}が上記目標パケットロス率Ｐ_{ｔａｒｇｅｔ}よりも大きいか否かを判断し、現在パケットロス率Ｐ_{ｃｕｒｒｅｎｔ}が上記目標パケットロス率Ｐ_{ｔａｒｇｅｔ}よりも大きいと判断した場合、ステップ４６へ進むが、現在パケットロス率Ｐ_{ｃｕｒｒｅｎｔ}が上記目標パケットロス率Ｐ_{ｔａｒｇｅｔ}よりも大きいと判断しない場合ステップ４７に戻るステップ４５と、Ｅ‐Ｎｏｄｅ ＢがＨＡＲＱの現在最大再送回数を増やしてステップ４３に戻るステップ４６と、Ｅ‐Ｎｏｄｅ ＢがＨＡＲＱの現在最大再送回数を減らしてステップ４３に戻るステップ４７とを含む。 As shown in FIG. 4, according to the second embodiment of the present invention, when the enhanced MBMS retransmits simultaneously using Raptor and HARQ in single cell transmission, the E-Node B is connected to the BM-SC. Step 41 for obtaining the number K of source symbols and the number N for encoded symbols, and the step for the E-Node B to calculate the _target packet loss rate P _target using the following formula based on the target decoding failure probabilities P _f , K, N 42,

During EMBMS data transmission, the E-Node B receives the NACK transmitted when the user terminal has a data reception error, and the E-Node B obtains the current packet loss rate P _current based on the received NACK. step 44, if the current packet loss rate _{P current} is determined whether greater than the target packet loss rate _{P target,} the current packet loss rate _{P current} has a value greater than the target packet loss rate _{P target} If the current packet loss rate P _current is not determined to be larger than the target packet loss rate P _target , step 45 returns to step 47, and the E-Node B increases the current maximum number of retransmissions of HARQ. Step to return to step 43 46 and step 47 in which the E-Node B reduces the current maximum number of retransmissions of HARQ and returns to step 43.

  The current maximum number of retransmissions of HARQ after adjustment is 1 or more and 3 or less.

In the second embodiment of the present invention, when the current packet loss rate P _current is larger than the target packet loss rate P _target , the current channel condition is bad, and the current decoding failure probability is made equal to or less than the target decoding failure probability P _f . In order to satisfy the demand for service, it is necessary to increase the maximum number of HARQ retransmissions. However, the number of retransmissions cannot be increased without limit and can only be 3 or less. However, when the current packet loss rate P _current is smaller than the target packet loss rate P _target , the decoding failure probability becomes small if the error packet rate is small. In such a case, the current decoding failure probability is smaller than the target decoding failure probability P _f . Since it is small, it satisfies the demand for service, that is, since an extra encoded symbol is transmitted to the user terminal, the maximum number of HARQ retransmissions can be reduced.

  According to the above processing, since the maximum HARQ retransmission count is not always the maximum value 3, when the channel condition is very good, there is a possibility that the maximum HARQ retransmission count is 1 or 2. Thus, the average number of HARQ retransmissions is reduced, that is, the resource utilization rate is improved.

ＥＭＢＭＳデータ伝送時に、ユーザ端末がデータ受信エラーのときに送信したＮＡＣＫを受信する第２の受信モジュールと、受信したＮＡＣＫに基づいて現在パケットロス率Ｐ_{ｃｕｒｒｅｎｔ}を取得する現在パケットロス率計算モジュールと、上記現在パケットロス率Ｐ_{ｃｕｒｒｅｎｔ}が上記目標パケットロス率Ｐ_{ｔａｒｇｅｔ}よりも大きいか否かを比較する比較モジュールと、現在パケットロス率が目標パケットロス率よりも大きい場合、ＨＡＲＱの現在最大再送回数を増やし、現在パケットロス率が目標パケットロス率よりも大きくない場合、ＨＡＲＱの現在最大再送回数を減らす調節モジュールとを有する。 As shown in FIG. 5, the E-Node B of the second embodiment of the present invention receives the number K of source symbols and the number N of encoded symbols from the BM-SC through the connection with the BM-SC. 1, a target packet loss rate calculation module that calculates a target packet loss rate P _target according to the following formula based on the target decoding failure probability P _f , K, N:

A second reception module that receives a NACK transmitted when a data reception error occurs by the user terminal during EMBMS data transmission; a current packet loss rate calculation module that acquires a _current packet loss rate P _current based on the received NACK; A comparison module that compares whether or not the current packet loss rate P _current is larger than the target packet loss rate P _target, and if the current packet loss rate is larger than the target packet loss rate, increases the current maximum number of retransmissions of HARQ. And an adjustment module that reduces the current maximum number of retransmissions of HARQ when the current packet loss rate is not larger than the target packet loss rate.

<Third embodiment>
The method according to the embodiment of the present invention ensures that the service demand is satisfied by controlling the feedback of NACK with a certain probability when the user terminal detects a data reception error.

ＥＭＢＭＳデータ伝送時に、ユーザ端末は、現在パケット受信状況に基づいて現在パケットロス率Ｐ_{ｃｕｒｒｅｎｔ}を取得するステップ６３と、目標パケットロス率Ｐ_{ｔａｒｇｅｔ}と現在パケットロス率Ｐ_{ｃｕｒｒｅｎｔ}に基づいて、サービスの需要を満足するＮＡＣＫ送信確率を計算するステップ６４と、ユーザ端末がデータ受信エラーを検出したときに、上記ＮＡＣＫ送信確率でＮＡＣＫを送信するステップ６５とを含む。 As shown in FIG. 6, when the enhanced MBMS simultaneously uses Raptor and HARQ in single cell transmission, the method according to the third embodiment of the present invention determines the number of source symbols from the connection with the BM-SC. Step 61 for obtaining K and the number N of encoded symbols; Step 62 for calculating the _target packet loss rate P _target by the following formula based on the target decoding failure probability P _f , K, N;

At the time of EMBMS data transmission, the user terminal obtains the service demand based on the target packet loss rate P _target and the current packet loss rate P _current in step 63 for obtaining the _current packet loss rate P _current based on the current packet reception status. Step 64 for calculating a satisfactory NACK transmission probability and Step 65 for transmitting a NACK with the NACK transmission probability when the user terminal detects a data reception error.

In a specific embodiment of the present invention, the NACK transmission probability P _opt is calculated according to the following formula.

Ｐ_{ｔａｒｇｅｔ}と現在パケットロス率Ｐ_{ｃｕｒｒｅｎｔ}を取得した後、上記方程式がＰ_ｏｐｔの一元二次方程式であるため、Ｐ_ｏｐｔを得ることができる。

P _target and after the current to get the packet loss rate _{P current,} since the equation is one yuan quadratic equation of _{P opt,} can be obtained _{P opt.}

ＥＭＢＭＳデータ伝送時に、現在パケット受信状況に基づいて現在パケットロス率Ｐ_{ｃｕｒｒｅｎｔ}を取得する現在パケットロス率計算モジュールと、目標パケットロス率Ｐ_{ｔａｒｇｅｔ}とパケットロス率Ｐ_{ｃｕｒｒｅｎｔ}に基づいて、サービスの需要を満足するＮＡＣＫ送信確率を計算するＮＡＣＫ送信確率計算モジュールと、データ受信エラーを検出したときに、上記ＮＡＣＫ送信確率でＮＡＣＫを送信する第２のフィードバックモジュールとを有する。 As shown in FIG. 7, the user terminal according to the third embodiment of the present invention includes a receiving module that acquires the number K of source symbols and the number N of encoded symbols from the BM-SC through connection with the BM-SC. A target packet loss rate calculation module for calculating a target packet loss rate P _target according to the following formula based on the target decoding failure probability P _f , K, N:

Current packet loss rate calculation module that obtains the _current packet loss rate P _current based on the current packet reception status at the time of EMBMS data transmission, and satisfies the service demand based on the target packet loss rate P _target and the packet loss rate P _current A NACK transmission probability calculation module that calculates a NACK transmission probability to be transmitted, and a second feedback module that transmits a NACK with the NACK transmission probability when a data reception error is detected.

  In the third embodiment of the present invention, when there is an error in data reception of the terminal, NACK is not transmitted every time, but NACK is fed back with a certain probability. If NACK is fed back with this probability, the current service demand can be satisfied.

  Since NACK is fed back with a certain probability, according to the third embodiment of the present invention, feedback is performed under the same network condition, compared to feeding back NACK every time there is a data reception error in the prior art. The number of NACKs to be performed is relatively small. Since HARQ retransmission is triggered by NACK, the average number of HARQ retransmissions is necessarily reduced, that is, the resource utilization rate is improved.

  In the above description, the NACK is directly fed back with the optimum probability, but the feedback probability may be greater than the optimum probability and 1 or less. At this time, the average number of HARQ retransmissions is larger than the average number of HARQ retransmissions when NACK is fed back with an optimal probability. However, since the probability of feeding back NACK is smaller than 1 compared to the prior art, some There are NACKs that are not fed back. Since HARQ retransmission is triggered by NACK, the average number of HARQ retransmissions is necessarily reduced, that is, the resource utilization rate is improved.

<Fourth embodiment>
In order for the receiving side to perform Raptor decoding continuously, in the fourth embodiment of the present invention, processing is performed in two stages.

  Before decoding is completed, it indicates that the decoding request has not yet been satisfied with the received symbol because decoding has not yet been successful. At this time, when the user terminal detects a data reception error, NACK is fed back to the network side so that more correct symbols can be received and decoded.

  After decoding is completed, it indicates that the symbol has been sufficiently received because decoding was successful. At this time, even if the user terminal detects a data reception error, the user terminal does not feed back NACK to the network side. That is, NACK feedback is stopped after decoding is completed. In this case, the service is not affected.

  According to the above method, since the NACK is not fed back in one stage with respect to the entire transmission process, the fourth embodiment of the present invention is the same as when the NACK is fed back every time there is a data reception error in the prior art. The number of NACKs to be fed back is relatively small under the network conditions. Since HARQ retransmission is triggered by NACK, the average number of HARQ retransmissions is necessarily reduced, that is, the resource utilization rate is improved.

  Hereinafter, effects of the embodiment of the present invention will be described using simulation results.

The simulation parameters are shown in Table 1 below.

Table 2 below shows the average number of retransmissions in SNR and N in which the methods of the three embodiments are different under the above simulation conditions.

  The above is only a preferred implementation mode of the present invention. For general engineers in the field, some modifications and modifications are possible on the premise that the principle of the present invention is not deviated. However, it will be understood that these modifications and modifications are also within the protection scope of the present invention.

Claims (15)

A method for realizing single cell enhanced MBMS that retransmits using Raptor coding and hybrid automatic repeat request HARQ,
Establish a connection with the broadcast / multicast service center, obtain the number of source symbols and the number of encoded symbols,
Based on the target decoding failure probability, the number of source symbols and the number of encoded symbols, a target packet loss rate that satisfies the service demand is calculated,
When transmitting enhanced MBMS data, obtain the current packet loss rate,
Wherein if the current packet loss rate equal to or less than the target packet loss rate, have row control processing so as to reduce the average number of retransmissions of HARQ retransmissions,
Specifically, the control process is characterized in that the enhanced base station reduces the current maximum number of retransmissions of HARQ, and the current maximum number of retransmissions is reduced to 1 or more . When K is the number of source symbols, N is the number of encoded symbols, x is the number of encoded symbols received, and P _f is the target decoding failure probability, the target packet loss rate p is calculated by the following formula: The method according to claim 1.

If the current packet loss rate is greater than the target packet loss rate, claim 1, enhanced base station increases the current maximum number of retransmissions of HARQ, and said the current maximum number of retransmissions is increased 3 or less Or the method of 2 .   The method according to claim 1, wherein the control process specifically blocks an operation of feeding back an NACK to an enhanced base station when a user terminal detects a data reception error. The method according to claim 4 , wherein if the current packet loss rate is larger than the target packet loss rate, a NACK is fed back to the enhanced base station when a user terminal detects a data reception error. A method for realizing single cell enhanced MBMS that retransmits using Raptor coding and hybrid automatic repeat request HARQ,
Establish a connection with the broadcast / multicast service center, obtain the number of source symbols and the number of encoded symbols,
Based on the target decoding failure probability, the number of source symbols and the number of encoded symbols, a target packet loss rate that satisfies the service demand is calculated,
When transmitting enhanced MBMS data, obtain the current packet loss rate,
Calculating a first feedback probability based on the target packet loss rate and the current packet loss rate;
A method of feeding back an NACK to an enhanced base station with a second feedback probability that is equal to or higher than the first feedback probability and smaller than 1 when a user terminal detects a data reception error. When K is the number of source symbols, N is the number of encoded symbols, x is the number of encoded symbols received, and P _f is the target decoding failure probability, the target packet loss rate p is calculated by the following formula: The method according to claim 6 .

8. The method of claim 7 , wherein P _target is the target packet loss rate, P _current is the current packet loss rate, and the first feedback probability P _opt is calculated by the following formula.

A base station used for single-cell enhanced MBMS that retransmits using Raptor encoding and hybrid automatic repeat request HARQ,
A first receiving module for receiving the number of source symbols and the number of encoded symbols from a broadcast / multicast service center;
A target packet loss rate calculation module for calculating a target packet loss rate that satisfies a service demand based on a target decoding failure probability, the number of source symbols, and the number of encoded symbols;
A current packet loss rate calculation module for acquiring a current packet loss rate during enhanced MBMS data transmission;
A comparison module for comparing whether the current packet loss rate is greater than the target packet loss rate;
An adjustment module for performing control processing to reduce the average number of retransmissions of HARQ retransmissions when the current packet loss rate is equal to or less than the target packet loss rate ;
In the adjustment module,
If the current packet loss rate is less than or equal to the target packet loss rate, the current maximum number of retransmissions of HARQ is reduced, the current maximum number of retransmissions is reduced to 1 or more, and the current packet loss rate is set to the target packet loss rate. A base station comprising a first adjustment unit for increasing the current maximum number of retransmissions of HARQ and increasing the current maximum number of retransmissions to 3 or less if the rate is greater than the rate . When K is the number of source symbols, N is the number of encoded symbols, x is the number of encoded symbols received, and P _f is the target decoding failure probability, the target packet loss rate calculation module calculates the target packet loss rate p as follows: The base station according to claim 9 , wherein the base station is calculated by a formula.

A user terminal used for single-cell enhanced MBMS that retransmits using Raptor encoding and hybrid automatic repeat request HARQ,
A receiving module for receiving the number of source symbols and the number of encoded symbols from a broadcast / multicast service center;
A target packet loss rate calculation module for calculating a target packet loss rate that satisfies a service demand based on a target decoding failure probability, the number of source symbols, and the number of encoded symbols;
A current packet loss rate calculation module for acquiring a current packet loss rate during enhanced MBMS data transmission;
A comparison module for comparing whether the current packet loss rate is greater than the target packet loss rate;
If the current packet loss rate is greater than the target packet loss rate and a data reception error is detected, NACK is fed back to the base station. If the current packet loss rate is less than or equal to the target packet loss rate, data reception is performed. A user terminal comprising: a first feedback module for maintaining silence even when an error is detected. When K is the number of source symbols, N is the number of encoded symbols, x is the number of encoded symbols received, and P _f is the target decoding failure probability, the target packet loss rate calculation module calculates the target packet loss rate p as follows: the user terminal according to claim 1 1, wherein the calculating the official.

A user terminal used for single-cell enhanced MBMS that retransmits using Raptor encoding and hybrid automatic repeat request HARQ,
A receiving module for receiving the number of source symbols and the number of encoded symbols from a broadcast / multicast service center;
A target packet loss rate calculation module for calculating a target packet loss rate that satisfies a service demand based on a target decoding failure probability, the number of source symbols, and the number of encoded symbols;
A current packet loss rate calculation module for acquiring a current packet loss rate during enhanced MBMS data transmission;
A first feedback probability calculation module for calculating a first feedback probability satisfying a demand for service based on the target packet loss rate and the current packet loss rate;
A second feedback module for feeding back an NACK to the enhanced base station with a second feedback probability that is equal to or higher than the first feedback probability and smaller than 1 when a data reception error is detected. A user terminal characterized by. When K is the number of source symbols, N is the number of encoded symbols, x is the number of encoded symbols received, and P _f is the target decoding failure probability, the target packet loss rate calculation module calculates the target packet loss rate p as follows: the user terminal according to claim 1 3, characterized in that calculating the official.

The P _target is the target packet loss rate, the P _current is the current packet loss rate, and the first feedback probability calculation module calculates the first feedback probability P _{opt according} to the following formula: the user terminal according to 1 4.

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