Rendering multicast service with sufficient reception quality to wireless terminals
Abstract
This record has no abstract on file.
Term
Term ended
Expired 12 May 2020, 6.4 years ago.
- Priority and filed
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- Today
28 claims: 16 independent, 12 dependent
- 1サービスエリア内の無線端末に対して情報配信装置から無線区間を介してマルチキャスト情報を配信するようにしたマルチキャストサービス提供方法において、 情報配信装置は、同一のマルチキャスト情報を異なる複数の送信条件に従って配信し、 無線端末は、いずれかの送信条件にて配信されるマルチキャスト情報を受信し、 上記情報配信装置は、所定のネットワークから提供される情報をバッファに保持し、そのバッファに保持されたマルチキャスト情報を異なる複数の伝送速度にて送信するに際し、各伝送速度に対応した読み出し速度にて上記バッファから読み出されるマルチキャスト情報毎にチャネルを割当てる ようにしたマルチキャストサービス提供方法。
- 2請求項1記載のマルチキャストサービス提供方法において、 上記送信条件は、マルチキャスト情報の伝送速度を表すパラメータを含むマルチキャストサービス提供方法。
- 3請求項2記載のマルチキャストサービス提供方法において、 情報配信装置と無線端末が符号分割多元接続方式にて通信を行い、 上記伝送速度を表すパラメータは、マルチキャスト情報の送信に使用される拡散符号の数となるマルチキャストサービス提供方法。
- 4請求項2記載のマルチキャストサービス提供方法において、 情報配信装置と無線端末が時分割多元接続方式にて通信を行い、 上記伝送速度を表すパラメータは、マルチキャスト情報の送信に使用されるタイムスロットの数となるマルチキャストサービス提供方法。
- 5請求項2記載のマルチキャストサービス提供方法において、 上記伝送速度を表すパラメータは、マルチキャスト情報を変調する際の変調多値数となるマルチキャストサービス提供方法。
- 6請求項2記載のマルチキャストサービス提供方法において、 上記伝送速度を表すパラメータは、マルチキャスト情報の送信ビットレートとなるマルチキャストサービス提供方法。
- 7請求項1記載のマルチキャストサービス提供方法において、 情報配信装置と無線端末が符号分割多元接続方式にて通信を行い、 上記送信条件は、マルチキャスト情報の拡散処理を行う際の拡散の処理利得を含むマルチキャストサービス提供方法。
- 8請求項1記載のマルチキャストサービス提供方法において、 上記送信条件は、マルチキャスト情報の送信に割当てるタイムスロットの位置を含むマルチキャストサービス提供方法。
- 9請求項1乃至8いずれか記載のマルチキャストサービス提供方法において、 無線端末は、自端末での受信品質を測定し、その測定結果を情報配信装置に通知し、 情報配信装置は、無線端末からの受信品質の測定結果に基づいてマルチキャスト情報の送信条件を決定し、その決定された送信条件に従ってマルチキャスト情報を配信するようにしたマルチキャストサービス提供方法。
- 10請求項9記載のマルチキャストサービス提供方法において、 情報配信装置は、上記決定された送信条件を上記受信品質の測定結果の通知元となる無線端末に通知し、 無線端末は、その通知された送信条件に基づいて情報配信装置から配信されるマルチキャスト情報を受信するようにしたマルチキャストサービス提供方法。
- 11請求項1乃至9いずれか記載のマルチキャストサービス提供方法において、 情報配信装置は、同一のマルチキャスト情報を異なる複数の送信条件にて配信すると共に、その異なる複数の送信条件を無線端末に通知し、 無線端末は、受信品質の測定を行い、その測定結果に基づいて通知された複数の送信条件から選択される送信条件に基づいて情報配信装置から配信されるマルチキャスト情報を受信するようにしたマルチキャストサービス提供方法。
- 12請求項1乃至11いずれか記載のマルチキャストサービス提供方法において、 情報配信装置が同一のマルチキャスト情報を異なる複数の伝送速度にて送信するに際し、 伝送速度に応じて配信すべきマルチキャスト情報の情報量を、伝送速度が遅くなるほど少なくなるように調整するようにしたマルチキャストサービス提供方法。
- 13請求項12記載のマルチキャストサービス提供方法において、 伝送速度に応じて配信すべきマルチキャスト情報を圧縮する圧縮率を調整することにより、配信すべきマルチキャスト情報の情報量を調整するようにしたマルチキャストサービス提供方法。
- 14請求項 1 記載のマルチキャストサービス提供方法において、 情報配信装置は、各伝送速度の差に応じて生ずる配信されるマルチキャスト情報の読み出し遅延量に基づいて各伝送速度を調整するようにしたマルチキャストサービス提供方法。
- 15サービスエリア内の無線端末に対して無線区間を介してマルチキャスト情報を配信する情報配信装置において、 配信すべきマルチキャスト情報を格納するマルチキャスト情報格納手段と、 該マルチキャスト情報格納手段に格納されたマルチキャスト情報を異なる複数の送信条件に従って配信する情報配信制御手段と、 上記マルチキャリア情報格納手段に格納されたマルチキャスト情報を異なる複数の伝送速度にて送信するに際し、各伝送速度に対応した読み出し速度にてマルチキャリア情報をマルチキャリア情報格納手段から読み出す情報読み出し手段と、 各読み出し速度にて読み出されるマルチキャリア情報毎にチャネルを割当てる送信制御手段と、 を有する情報配信装置。
- 16請求項 15 記載の情報配信装置において、 上記送信条件は、マルチキャスト情報の伝送速度を表すパラメータを含む情報配信装置。
- 17請求項 16 記載の情報配信装置において、 無線端末と符号分割多元接続方式にて通信を行い、 上記伝送速度を表すパラメータは、マルチキャスト情報の送信に使用される拡散符号の種類となる情報配信装置。
- 18請求項 16 記載の情報配信装置において、 無線端末と時分割多元接続方式にて通信を行い、 上記伝送速度を表すパラメータは、マルチキャスト情報の送信に使用されるタイムスロットの数となる情報配信装置。
- 19請求項 16 記載の情報配信装置において、 上記伝送速度を表すパラメータは、マルチキャスト情報を変調する際の変調多値数となる情報配信装置。
- 20請求項 16 記載の情報配信装置において、 上記伝送速度を表すパラメータは、マルチキャスト情報の送信ビットレートとなる情報配信装置。
- 21請求項 15 載の情報配信装置において、 無線端末と符号分割多元接続方式にて通信を行い、 上記送信条件は、マルチキャスト情報の拡散処理を行う際の拡散の処理利得を含む情報配信装置。
- 22請求項 15 記載の情報配信装置において、 上記送信条件は、マルチキャスト情報の送信に割当てるタイムスロットの位置を含む情報配信装置。
- 23請求項 15乃至22のいずれか1項に 記載の情報配信装置において、 無線端末から通知される受信品質の測定結果に基づいてマルチキャスト情報の送信条件を決定する送信条件決定手段を有し、 上記情報配信制御部は、該送信条件決定手段にて決定された送信条件に従ってマルチキャスト情報を配信するようにした情報配信装置。
- 24請求項 23 記載の情報配信装置において、 上記決定された送信条件を上記受信品質の測定結果の通知元となる無線端末に通知する送信条件通知制御手段を有し、 無線端末がその通知された送信条件に基づいて情報配信装置から配信されるマルチキャスト情報を受信できるようにした情報配信装置。
- 25請求項 15乃至22のいずれか1項に 記載の情報配信装置において、 上記マルチキャスト情報格納手段に格納されたマルチキャスト情報を異なる複数の送信条件にて配信するに際し、その異なる複数の送信条件を無線端末に通知する送信条件通知手段を有し、 無線端末が、受信品質の測定を行い、その測定結果に基づいて通知された複数の送信条件から選択される送信条件に基づいて情報配信装置から配信されるマルチキャスト情報を受信できるようにした情報配信装置。
- 26請求項 15乃至25のいずれか1項に 記載の情報配信装置において、 上記マルチキャスト情報格納手段に格納されたマルチキャスト情報を異なる複数の伝送速度にて送信するに際し、伝送速度に応じて配信すべきマルチキャスト情報の情報量を、伝送速度が遅くなるほど少なくなるように調整するよう情報量調整手段を有する情報配信装置。
- 27請求項 26 記載の情報配信装置において、 上記情報量調整手段は、配信すべきマルチキャスト情報が当該情報配信装置に提供される際の情報レートとそのマルチキャスト情報を配信する際の伝送速度に応じて配信すべきマルチキャスト情報の圧縮率を決定する圧縮率決定手段と、 該圧縮率決定手段にて決定された圧縮率にて配信すべきマルチキャスト情報を圧縮することにより情報量を調整する情報圧縮手段とを有する情報配信装置。
- 28請求項 15 記載の情報配信装置において、 各伝送速度の差に応じて生ずる配信されるマルチキャスト情報の読み出し遅延量を演算する遅延量演算手段と、 該遅延量演算手段にて得られた読み出し遅延量に基づいて各伝送速度を調整する伝送速度調整手段を有する情報配信装置。
Independent claims28
98 paragraphs, as filed
[0002] The present invention relates to a method for providing a multicast service, and more specifically, distributes multicast information from an information distribution device to a wireless terminal in a service area via a wireless section. Regarding the method of providing the multicast service.
[0003] The present invention also relates to an information distribution device and a wireless terminal used in such a multicast providing system.
BACKGROUND ART [0004] In recent years, applications related to the distribution of music and video information using the Internet have been attracting attention. On the other hand, using wireless as an access link has an advantage that an information distribution service can be easily provided to a user. Therefore, it is very important to be able to provide distribution services such as music and video information in a network where the access link includes a wireless section.
[0005] In a multicast service providing system that distributes multicast information such as music information and video information via such a wireless section, a plurality of wireless terminals are transmitted from a wireless base station (generally, an information distribution device). It is a general configuration that multicast information is transmitted to and those wireless terminals receive the multicast information at the same time. When the wireless base station and each wireless terminal are configured to perform 1: 1 communication, the same multicast information is independently transmitted to multiple wireless terminals wishing to provide services using different channels. This is because the wireless resources cannot be used effectively.
[0006] When the distribution service of the same multicast information to a plurality of radio base stations is realized by one transmission, on the premise that each radio terminal is placed in a different propagation situation in the radio section, each radio terminal The reception quality of multicast information is different. For example, as shown in FIG. 17, since the radio terminals H and J relatively close to the radio base station BS are placed in a relatively good propagation condition, the reception quality of the multicast information delivered from the radio base station BS is compared. It becomes good. Since the wireless terminals F, G, and I located farther from the wireless base station BS than the wireless terminals H and J are placed in a worse propagation condition than the wireless terminals H and J, the reception quality of the multicast information is the wireless terminal. It is lower than that of H and J. Furthermore, since the wireless terminals A, B, C, D, and E located around the service area Es, which are relatively far from the wireless base station BS, are placed in a worse propagation situation, the multicast information distributed from the wireless base station BS The reception quality of the is further deteriorated.
PROBLEM TO BE SOLVED: To realize a multicast service by 1: n wireless communication between an information distribution device (for example, a wireless base station) and each wireless terminal as described above. Each wireless terminal that receives the multicast service has different reception qualities. While the reception quality is different in this way, a situation may occur in which there are many reception errors and the specified reception quality is not satisfied. Therefore, the first object of the present invention is to provide a multicast service providing method in which each of a plurality of wireless terminals in various reception states in a service area can receive multicast information with good reception quality. is there.
[0008] Further, a second object of the present invention is to provide an information distribution device provided for such a multicast service providing method.
[0009] Further, a third object of the present invention relates to a wireless terminal applied to such a multicast providing method.
Means for Solving the Problems [0010] In order to solve the first problem, the present invention is used.<u style="single">According to one aspect</u>In a multicast service providing method in which multicast information is distributed from an information distribution device to a wireless terminal in a service area via a wireless section, the information distribution device distributes the same multicast information according to a plurality of transmission conditions. The wireless terminal is configured to be able to receive the multicast information delivered under any of the transmission conditions.
[0011] In such a multicast service providing method, the information distribution device distributes the same multicast information according to a plurality of different transmission conditions, so that each wireless terminal located in the service area of the information distribution device is the own terminal. It is possible to receive multicast information delivered under transmission conditions that give better reception quality according to the reception status (propagation environment).
[0012] The above transmission condition is a condition necessary for transmitting multicast information to a wireless terminal, and affects the reception quality of the wireless terminal.
[0013] This transmission condition is<u style="single">According to one aspect of the invention</u>It can include parameters that represent the transmission rate of multicast information.
[0014] With such a multicast service providing method, a wireless terminal in a receiving state whose sufficient quality cannot be ensured by high-speed transmission can receive multicast information delivered at a lower speed.
[0015] When the information distribution device and the wireless terminal communicate by the code division multiple access method, the parameter representing the transmission speed is<u style="single">According to one aspect of the invention</u>It can be the type of spreading code used to transmit multicast information.
[0016] When the information distribution device and the wireless terminal communicate with each other by the time division multiple access method, the parameter representing the transmission speed is set.<u style="single">According to one aspect of the invention</u>It can be the number of time slots used to send multicast information.
Further, the parameter representing the transmission speed is<u style="single">According to one aspect of the invention</u>It can be a modulation multi-value number when modulating multicast information.
Further, the parameter representing the transmission speed is further set.<u style="single">According to one aspect of the invention</u>It can be the transmission bit rate of multicast information.
[0019] When the information distribution device and the wireless terminal communicate by the code division multiple access method, the above transmission conditions are set.<u style="single">According to one aspect of the invention</u>It can include the processing gain of spreading when performing the spreading processing of multicast information.
[0020] From the viewpoint of avoiding the same channel interference and receiving multicast information with better reception quality, the present invention presents the present invention.<u style="single">According to one aspect of the invention</u>In the multicast service providing method, the transmission condition is configured to include the position of the time slot assigned to the transmission of the multicast information.
[0021] In such a multicast service providing method, the level of the same channel interference may differ depending on the position of the time slot, so that the wireless terminal has the lowest level of the same channel interference according to the reception state of its own terminal. Multicast information can be received in the time slot.
[0022] From the viewpoint that the information distribution device can distribute multicast information under transmission conditions suitable for the reception quality of each wireless terminal, the present invention relates to the present invention.<u style="single">According to one aspect of the invention</u>In each of the above multicast service providing methods, the wireless terminal measures the reception quality at its own terminal and notifies the information distribution device of the measurement result, and the information distribution device is based on the measurement result of the reception quality from the wireless terminal. It is possible to determine the transmission conditions of the multicast information and configure the multicast information to be distributed according to the determined transmission conditions.
[0023] From the viewpoint that the wireless terminal can relatively easily receive the multicast information distributed under the transmission conditions suitable for the reception state of the own terminal, the present invention has been made.<u style="single">According to one aspect of the invention</u>In the multicast service providing method, the information distribution device notifies the wireless terminal that is the notification source of the measurement result of the reception quality of the determined transmission condition, and the wireless terminal provides information based on the notified transmission condition. It can be configured to receive the multicast information distributed from the distribution device.
[0024] From the viewpoint that each wireless terminal can voluntarily receive multicast information with better reception quality.<u style="single">According to one aspect of the invention</u>In each of the above multicast service providing methods, the information distribution device distributes the same multicast information under a plurality of different transmission conditions, and notifies the wireless terminal of the different plurality of transmission conditions, and the wireless terminal measures the reception quality. Is performed, and the multicast information distributed from the information distribution device is received based on the transmission condition selected from the plurality of transmission conditions notified based on the measurement result. Multicast service provision method.
[0025] When delivering the same multicast information at different transmission speeds, the delivery time at each transmission speed can be made substantially the same.<u style="single">According to one aspect of the invention</u>In each of the above multicast service providing methods, when the information distribution device transmits the same multicast information at a plurality of different transmission speeds, the amount of information of the multicast information to be distributed according to the transmission speed decreases as the transmission speed becomes slower. It can be configured to adjust as such.
[0026] Further, the above-mentioned method for providing a multicast service is described.<u style="single">According to one aspect of the invention</u>By adjusting the compression rate for compressing the multicast information to be delivered according to the transmission speed, the amount of information of the multicast information to be delivered can be adjusted.
[0027] From the viewpoint of enabling distribution of multicast information stored in a single buffer at different transmission speeds,<u style="single">According to one aspect of the invention</u>In each of the above multicast service providing methods, the information distribution device holds information provided from a predetermined network in a buffer, and when transmitting the multicast information held in the buffer at a plurality of different transmission speeds, each transmission speed. It can be configured to allocate a channel for each multicast information read from the buffer at a read speed corresponding to.
[0028] When delivering multicast information stored in a single buffer at different transmission speeds, from the viewpoint of eliminating problems due to delivery delays according to the transmission speed difference.<u style="single">According to one aspect of the invention</u>In the above-mentioned multicast service providing method, the information distribution device can be configured to adjust each transmission speed based on the read delay amount of the distributed multicast information generated according to the difference in each transmission speed.
[0029] In order to solve the above second problem,<u style="single">According to one aspect of the invention</u>, In an information distribution device that distributes multicast information to wireless terminals in a service area via a wireless section, a multicast information storage means for storing multicast information to be distributed and a multicast information stored in the multicast information storage means. Is configured to have an information distribution control means that distributes the data according to a plurality of different transmission conditions that affect the reception quality at the receiving terminal.
[0030] In order to solve the above-mentioned third problem,<u style="single">According to one aspect of the invention</u>In a wireless terminal that receives a multicast information distribution service from an information distribution device via a wireless section, the reception quality measuring means for measuring the reception quality of the signal from the information distribution device and the multicast information in which the information distribution device is the same are transmitted to the wireless terminal. Information for receiving multicast information from an information distribution device based on transmission conditions determined based on reception quality obtained by the reception quality measuring means when delivering according to a plurality of different transmission conditions that affect the reception quality of It is configured to have a reception control means.
BEST MODE FOR CARRYING OUT THE INVENTION [0031] Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0032] The multicast service providing system according to the embodiment of the present invention is configured as shown in FIG. 1, for example.
[0033] In FIG. 1, the radio zone of the radio base station 20 serving as the information distribution device is the service area Es. The wireless base station 20 acquires information to be distributed via a network NW (for example, an IP network), and provides a distribution service of the acquired multicast information to each wireless terminal 10 in the service area Es. The radio base station 20 is configured as shown in FIG. 2, for example.
[0034] In FIG. 2, the radio base station 20 includes a transmitter / receiver 21, a multicast information storage unit 22, a network control unit 23, and an information distribution control unit 24. The transmitter / receiver 21 wirelessly communicates with each wireless terminal 10 in the service area Es. The network control unit 23 communicates with a server, which is an information provider, via a predetermined network (IP network, etc.), and acquires multicast information to be distributed. The multicast information storage unit 22 stores the multicast information to be distributed received by the network control unit 23 via a predetermined network (buffering). The information distribution control unit 24 executes control for distributing the multicast information sequentially stored in the multicast information storage unit 22 from the transmitter / receiver 21 to each wireless terminal 10 in the service area Es.
[0035] Each wireless terminal is basically configured as shown in FIG.
[0036] In FIG. 3, each wireless terminal 10 has a transmitter / receiver 11, an output unit 12, and a control unit 13. The transmitter / receiver 11 transmits / receives information to / from the transmitter / receiver 21 in the radio base station 20. The output unit 12 outputs multicast information (music, video, etc.) from the wireless base station 20 received by the transmitter / receiver 11 in a format (audio, video) according to the type of the information. The control unit 13 controls the transmitter / receiver 11 and the output unit 12, and measures the reception quality (reception level, interference level, noise level, error rate, etc.) of the downlink signal received by the transmitter / receiver 11.
[0037] In the multicast service providing system as described above, in each wireless terminal 10 located in the service area Es of the wireless base station 20, the reception level of the free downlink channel received by the control unit 13 by the transmitter / receiver 11 and the like. Is measured as reception quality. Then, each wireless terminal 10 notifies the wireless base station 20 of the measurement result. The notification of the measurement result of the reception quality can be performed, for example, by adding the measurement result to the request signal transmitted to the radio base station 20 in order to receive the distribution service of the desired multicast group (multicast information channel). .. When each wireless terminal 10 performs communication with the wireless base station 20 (coexistence with the unicast) other than the reception of the multicast information, the above reception quality is used by using the control channel attached to the channel for transmitting the unicast information. The wireless base station 20 may be notified of the measurement result of.
[0038] When the wireless base station 20 receives the request signal of the multicast group from the wireless terminal 10, it transmits the transmission condition of the multicast information corresponding to the multicast group to the wireless terminal 10. The transmission conditions of this multicast information are the conditions necessary for transmitting the multicast information to the wireless terminal 10, the wireless channel, the transmission speed, the number of modulation multi-values, the transmission time slot, the processing gain PG of the spread, the spread code and the spread code thereof. The number and the like can be included, and it becomes the information necessary for the wireless terminal 10 to receive the multicast information from the wireless base station 20. These conditions may affect the reception quality when the multicast information is received by the wireless terminal 10. The radio base station 20 can transmit the transmission condition of the multicast information when transmitting the response signal to the radio terminal 10 after receiving the request signal from the radio terminal 10.
[0039] The information distribution control unit 24 of the wireless base station 20 determines at least one of the information rate of the multicast information acquired from the network and the measurement result of the reception quality received from the wireless terminal 10 that is the request source of the multicast information. Determine how to send the multicast information related to the request in consideration.
[0040] For example, in the case of a code division multiple access (CDMA) system, the transmission band after spreading changes by changing the spreading processing gain PG. In general, the transmission quality can be improved by increasing the processing gain PG for transmission. FIG. 4 shows how the processing gain PG is controlled according to the required transmission speed, and the multicast information to wireless terminals having different propagation environments is multiplexed and transmitted on different transmission lines.
[0041] It is assumed that the information rate of a certain multicast information is I and the bandwidth after spreading is B. Since the wireless terminals A to E shown in Fig. 4 have a poor propagation environment such as weak reception radio waves, it is assumed that the required quality is not satisfied unless transmission is performed at low speed (fb). On the other hand, since the wireless terminals H to L shown in FIG. 4 are in a good propagation environment, it is assumed that the required quality is satisfied even if they are transmitted at high speed (fa). In such a case, if the same multicast information is transmitted at low speed and high speed at the same time, as shown in Fig. 5, the information transmitted at high speed (fa) will be transmitted for a short time, and the information transmitted at low speed (fb) will be transmitted for a long time. It takes.
FIG. 6 illustrates the relationship between the spread bandwidth B represented on the frequency axis, the high-speed (fa) information band, and the low-speed (fb) information band. As shown in FIG. 6, the high-speed (fa) information band is wider than the low-speed information band.
[0043] When transmitting high-speed information and low-speed information, if the bandwidth after spreading is B, the information at both speeds is spread over the bandwidth B and transmitted. Let PGa be the processing gain for spreading high-speed (fa) information, and PGb be the processing gain for spreading low-speed (fb) information. The relationship between the speed of this information, the processing gain, and the bandwidth B after spreading is as follows.
[0044] For high-speed transmission: fa × PGa = B For low-speed transmission: fb × PGb = B In this example, the diffusion processing gain is determined according to the transmission speed based on the above relational expression, and the transmission environment. Therefore, the same multicast information is transmitted to wireless terminals having different reception qualities using different processing gains, for example, as shown in FIG. As a result, the wireless terminal capable of receiving at high speed can receive the multicast information in a short time. On the other hand, wireless terminals that try to receive services in an unfavorable propagation environment, such as in a place with weak radio waves, receive multicast information with increased processing gain and improved transmission quality at low speed, and the time to receive it is long. However, you will be able to receive the service.
[0045] Here, the case where the reception quality of the wireless terminal trying to receive the same multicast service is two types has been described, but there are more types of reception quality, and three or more information speeds and processing are performed. It is also possible to transmit multicast information multiple times with gain.
[0046] The radio base station BS (hereinafter, BS is used instead of 20 for the reference code of the radio base station) multicasts the processing gain of the spread determined as described above to the radio terminal requesting the multicast service. Notify as a condition for transmitting information. Then, the wireless terminal receives the multicast information distributed from the wireless base station BS with the notified diffusion processing gain.
[0047] The parameter that determines the transmission speed of the multicast information delivered to the wireless terminal that requests the multicast information can be determined as the transmission condition of the multicast information based on the measurement result of the reception quality from the wireless terminal. it can.
[0048] In a CDMA system, the transmission speed can generally be made variable by controlling the number of spreading codes. From this, the same multicast information can be delivered at different transmission speeds by changing the number of spread codes used in different time slots on the premise of a multiple access method having a plurality of time slots.
FIG. 8 shows how the same multicast information is transmitted by changing the number of spreading codes. Assuming that the information rate when acquiring certain multicast information from the network NW is I, the multicast information is transmitted at the transmission speed corresponding to this information rate I by transmitting in a certain time slot using three spread codes. Suppose it can be transmitted. In the example shown in FIG. 8, since the reception quality of the wireless terminals H to L, which are relatively close to the wireless base station BS, is relatively good, three diffusion codes 1, 2, and 3 are used for the wireless terminals H to L. Even if multicast information is transmitted at a relatively high speed (corresponding to information rate I), the service quality (reception quality) of the wireless terminals H to L is maintained at a predetermined level or higher. Therefore, for the wireless terminals H to L, the three diffusion codes 1, 2, and 3 are determined as the transmission conditions of the multicast information based on their reception quality.
[0050] On the other hand, since the reception quality of the wireless terminals A to E relatively far from the wireless base station BS is relatively poor, the multicast information is used for the wireless terminals A to E by using three spreading codes as described above. Is transmitted, the service quality (reception quality) above a predetermined level cannot be obtained by the wireless terminals A to E. In such a situation, for example, for wireless terminals A to E having relatively poor reception quality, the wireless terminals A to E can transmit multicarrier information at a relatively low speed by using two spreading codes. It is possible to maintain the service quality of the above at a predetermined level or higher. Therefore, for the wireless terminals A to E, the two spreading codes 1 and 2 are determined as the transmission conditions of the multicast information based on their reception quality.
[0051] In such a case, as shown in FIG. 9, the radio base station BS spreads the multicast information using the three spreading codes 1, 2, and 3 and the spreading using the two spreading codes 1, 2. The same multicast information is included in different time slots t (k) and t (k ́) for multiple transmission. Then, the wireless base station BS notifies the wireless terminals H to L of the time slots t (k) and the three diffusion codes 1, 2, and 3 as transmission conditions for the multicast information, and notifies the wireless terminals A to E. On the other hand, the time slot t (k ́) and the two spread codes 1 and 2 are notified as the transmission conditions of the multicast information.
As a result, the wireless terminals H to L receive the downlink time slot t (k) from the wireless base station BS, and decode the received signal using the three diffusion codes 1, 2, and 3. .. Further, the wireless terminals A to E receive the time slot t (k ́) of the downlink signal from the wireless base station BS, and decode the received signal using the two spreading codes 1 and 2. As a result, all of the wireless terminals A to L can receive the same multicast information distribution service while maintaining the service quality of a predetermined level or higher.
[0053] In the above example, the diffusion code (number) corresponding to one of the two types of transmission speeds is determined based on the reception quality of each wireless terminal, but any of the more types of transmission speeds. It is also possible to determine the diffusion code (number) corresponding to. In this case, the information distribution control unit 24 of the radio base station BS has, for example, as shown in FIG. 10, a table that defines the relationship between the reception quality and the number of diffusion codes used. In FIG. 10, at reception quality level 5 (highest quality), transmission at a transmission speed of T5 (highest speed) is possible using five types of spreading codes. At reception quality level 4, transmission at a transmission speed of T4 (<T5) is possible using four types of spreading codes. At reception quality level 3, transmission at a transmission speed of T3 (<T4) is possible using three types of spreading codes. At reception quality level 2, transmission at a transmission speed of T2 (<T3) is possible using two types of spreading codes. In addition, at reception quality level 1 (lowest quality), transmission at a transmission speed of T1 (<T2) is possible using one type of spreading code. The information distribution control unit 24 determines the type (number) of diffusion codes corresponding to the level of reception quality reported from the wireless terminal by referring to the table as described above.
[0054] In the above table, each transmission speed has the following relationship.
[0055] T2 = 2 × T1 T3 = 3 × T1 T4 = 4 × T1 T5 = 5 × T1 For example, in a time division multiple access (TDMA) system, the transmission speed is generally controlled by controlling the number of time slots. It can be made variable and the position of the time slot used can be changed to avoid same channel interference. In this example, the same multicast information is duplicated and transmitted at the same time on the premise of TDMA, which determines the number of time slots according to the multicast information rate. FIG. 11 shows how the position of the time slot is changed to transmit the same multicast information. It is assumed that the information rate of a multicast is I, and the information of rate I can be transmitted by transmitting using three time slots. It is assumed that the wireless terminals H to L shown in FIG. 11 satisfy the service quality by the transmission of the tori of this assumption. That is, the radio base station BS transmits multicast information using the time slot group t (k) composed of the three time slots shown in FIG. 12, and each wireless terminal H to L receives the time slot to improve the service quality. I am satisfied.
Since the wireless terminals A to E shown in FIG. 11 cannot correctly receive the information transmitted in the time slot group t (k) due to the same channel interference, it is assumed that the service quality cannot be satisfied if the information is transmitted under the above assumption. In such a case, as shown in FIG. 12, the radio terminals A to E transmit the same multicast information at the same time as the time slot t (k) using the time slot group t (k ́) by the radio base station BS. As a result, all the wireless terminals A to L that receive the same multicast service can receive the service that satisfies the service quality.
In this example, the time slot group t (k ́) has two available time slots. By reducing the number of time slots used in this way from three to two, the transmission speed is also reduced.
[0058] Further, the transmission speed can be made variable by controlling the modulation method (modulation multi-value number) regardless of the multiple access method. Therefore, the same multicast information can be distributed at different transmission speeds by transmitting the same multicast information modulated by different modulation methods (multi-value modulation) in different time slots.
FIG. 13 shows how the same multicast information is transmitted by changing the number of modulation multi-values. Assuming that the information rate when acquiring certain multicast information from the network NW is I, the multicast information is modulated by the 16QAM modulation method and transmitted, so that the multicast is transmitted at the transmission rate corresponding to this information rate I. Suppose information can be transmitted. In the example shown in FIG. 13, since the reception quality of the wireless terminals H to L, which are relatively close to the wireless base station BS, is relatively good, the wireless terminals H to L are modulated by the 16QAM modulation method and relatively. Even if the multicast information is transmitted at high speed (corresponding to the information rate I), the service quality of the wireless terminals H to L is maintained at a predetermined level or higher. Therefore, for the wireless terminals H to L, the 16QAM modulation method is determined as the transmission condition of the multicast information based on their reception quality.
[0060] On the other hand, since the reception quality of the wireless terminals A to E relatively far from the wireless base station BS is relatively poor, the multicast information is transmitted to the wireless terminals A to E by the 16QAM modulation method as described above. When modulated and transmitted, it is not possible to obtain a service quality of a predetermined level or higher on the wireless terminals A to E. In such a situation, for example, the wireless terminals A to E having relatively poor reception quality are modulated by the BPSK modulation method and the multicarrier information is transmitted at a relatively low speed, so that the wireless terminals A to E are transmitted. It is possible to maintain the service quality at E above a predetermined level. Therefore, for the wireless terminals A to E, the BPSK modulation method is determined as the transmission condition of the multicast information based on their reception quality.
In such a case, as shown in FIG. 14, the radio base station BS obtains the multicarrier information modulated by the 16QAM modulation method and the same multicarrier information modulated by the BPSK modulation method, respectively. Send in different time slots t (k), t (k ́). Then, the wireless base station BS notifies the wireless terminals H to L of the modulation method of the time slot t (k) and 16QAM as the transmission condition of the multicarrier information, and notifies the wireless terminals A to E of the modulation method. Notify the modulation method of time slot t (k ́) and BPSK as a transmission condition of multicarrier information.
As a result, the wireless terminals H to L receive the downlink signal time slot t (k) from the wireless base station BS, and demodulate the received signal by a demodulation method corresponding to 16QAM. Further, the wireless terminals A to E receive the time slot t (k ́) of the downlink signal from the wireless base station BS, and demodulate the received signal by a demodulation method corresponding to BPSK. As a result, all of the wireless terminals A to L can receive the same multicast information distribution service while maintaining the service quality of a predetermined level or higher.
[0063] In the above example, the modulation method (multi-valued modulation) corresponding to one of the two types of transmission speeds is determined based on the reception quality of each wireless terminal, but any of the more types of transmission speeds. It is also possible to determine the modulation method (multi-value modulation) corresponding to. In this case, the information distribution control unit 24 of the radio base station BS has, for example, as shown in FIG. 15, a table that defines the relationship between the reception quality and the modulation method (multi-value modulation). In FIG. 15, at reception quality level 5 (highest quality), transmission at a transmission speed of T5 (highest speed) is possible with the 256QAM modulation method having the largest number of modulation multi-values. At reception quality level 4, transmission at a transmission speed of T4 (<T5) is possible with a modulation method of 64QAM. At reception quality level 3, transmission at a transmission speed of T3 (<T4) is possible with a 16QAM modulation method. At reception quality level 2, transmission at a transmission speed of T2 (<T3) is possible using the QPSK modulation method. Further, at reception level 1, transmission at a transmission speed of T1 (<T2) is possible by the BPSK modulation method. The information distribution control unit 24 determines a modulation method (multi-value modulation) corresponding to the level of reception quality reported from the wireless terminal by referring to the table as described above.
[0064] In the above table, each transmission speed has the following relationship.
[0065] T2 = 2 × T1 T3 = 2 × T2 T4 = 2 × T3 T5 = 2 × T4 In the above example, controlling the modulation method (multicast modulation number) based on the reception quality at each wireless terminal. Alternatively, the bit rate of the multicast information may be controlled.
[0066] The radio base station BS sequentially stores the multicast information acquired from the network NW at the information rate I in the multicast information storage unit 22 (buffer), and stores the multicast information in the multicast information storage unit 22. As described above, transmission is performed sequentially under different transmission conditions (transmission speed, etc.). When the same multicast information is transmitted to a plurality of wireless terminals at different transmission speeds in this way, if the distribution times for each wireless terminal are made uniform, the multicast information transmitted at a low speed cannot be completely distributed. .. When trying to align the delivery time for each wireless terminal in this way, by compressing the multicast information to be delivered to each wireless terminal according to its transmission speed, the multi-carrier information transmitted at low speed can be delivered completely. It can be prevented that there is no such thing.
As described above, the information distribution control unit 24 has the transmission speed (number of spreading codes, number of time slots, number of modulation multi-values, bits) of multicast information to be distributed based on the reception quality from each wireless terminal. Determine the rate, etc.). At that time, the information distribution control unit 24 compresses the multi-carrier information according to the determined transmission speed. This compression rate CR is determined as follows based on the information rate I when acquiring the multicast information from the network NW and the transmission rate T determined as the transmittable rate as described above.
When the information rate I of the multicast information is equal to or less than the determined transmission speed T (I T) (in the case of high-speed transmission), the compression rate CR is determined to be 1. That is, the multicast information is not compressed. On the other hand, when the information rate I of the multicast information is larger than the determined transmission rate T (I> T) (in the case of low-speed transmission), the compression rate CR is determined according to CR = 1- (IT) / I. Then, the information distribution control unit 24 compresses the multicast information stored in the multicast information storage unit 22 at the determined compression rate CR according to a predetermined algorithm, and supplies the multicast information to the transmitter / receiver 21. The compressed multicast information is delivered from the transmitter / receiver 21 to the wireless terminal.
[0069] In this case, the radio base station BS notifies the wireless terminal of the information compression rate CR as a transmission condition of the multicast information. The control unit 13 of the wireless terminal that receives the multi-carrier information distribution service at a predetermined transmission speed decompresses the received multi-carrier information based on the notified compression rate CR according to an algorithm corresponding to the above-mentioned compression algorithm. , Get the original multi-carrier information.
[0070] When selecting the optimum compression rate from a plurality of preset compression rates, the calculation is performed at a compression rate equal to or higher than the compression rate calculated based on the information rate I and the transmission speed T of the multicarrier as described above. The compression rate closest to the compression rate may be selected from the plurality of compression rates set above.
[0071] When the multi-carrier information is provided from the information source (server) to the radio base station via the network, the multi-carrier information is simply a still image or information encoded so as to superimpose the still image. By deleting information at regular intervals to reduce the amount of information, multi-carrier information can be transmitted at low speed. In this case, the reduction rate of the amount of information is equivalent to the compression rate described above. Therefore, for example, when the reduction ratio must be set to 4/5, one image frame for every five image frames may be omitted and transmitted to the wireless terminal.
Further, when the multicast information acquired from the network NW at the rate I is transmitted to a plurality of wireless terminals at different transmission speeds, the transmission speed can be reduced unless the amount of information is adjusted as described above. The more, the timing of reading from the multi-carrier information storage unit 22 is delayed. Each transmission speed is adjusted so that this delay does not adversely affect the processing in the radio base station BS.
[0073] For example, as shown in FIG. 16, the multi-carrier information supplied from the network NW is temporarily stored in the multi-carrier information storage unit 22 (buffer). Then, since the accumulated multi-carrier information is transmitted at a plurality of transmission speeds, the read point differs depending on each transmission speed. For example, when the radio base station BS is transmitting multicarrier information at two transmission speeds T and T ́, the buffer has a pointer corresponding to each transmission speed. For example, when the transmission speed T is larger than the transmission speed T ́ (T> T ́), the multicarrier information read from the buffer according to the operation of the pointer 1 is transmitted at the transmission speed T ́ using a channel having a certain channel. , The multicarrier information read from the buffer according to the operation of the pointer 2 is transmitted at the transmission speed T using another channel.
Therefore, the information stored in the area before the pointer 1 can be cleared. If T and T ́ are the average transmission rates, then the average delay time is based on the average value D of the amount of information in the area between pointer 2 and pointer 1, and the average delay time = D / (TT ́). Required according to. The information distribution control unit 24 adjusts each transmission speed T, T ́ determined as described above within a range in which the average delay time calculated in this way does not affect the quality of the application of the radio base station BS.
[0075] In the above example, each wireless terminal measures the reception quality and notifies the wireless base station BS of the measurement result. Then, the radio base station BS determines the transmission condition of the multicarrier information based on the measurement result of the reception quality from each of the notified radio terminals, and the transmission condition (diffusion processing gain, number of diffusion codes, use). The time slot, modulation method (multi-value modulation), information compression rate, etc.) are notified to each wireless terminal, and the same multi-carrier is transmitted according to the determined transmission conditions. Each wireless terminal receives the multi-carrier information so as to meet the transmission condition of the notified multi-carrier information. As a result, each wireless terminal in various propagation environments can receive multi-carrier information while maintaining the highest level of quality possible.
[0076] In the above example, each wireless terminal measures the reception quality representing the propagation environment and notifies the wireless base station BS, but it is also possible to prevent such notification. For example, the radio base station BS transmits the same multi-carrier information under a plurality of different transmission conditions (transmission speed, time slot position, etc.), and the plurality of transmission conditions are set to each radio using, for example, a perch channel. Notify the terminal. Each wireless terminal selects a transmission condition that gives the highest level of service quality in the state of reception quality measured from among the plurality of notified transmission conditions, and conforms to the selected transmission condition. Receive multicast information.
[0077] As described above, in order to configure the system so that each wireless terminal does not notify the wireless base station BS of the measurement result of the reception quality representing the propagation environment, it is optimal for each wireless terminal based on the measurement result. A function to select transmission conditions is required.
[0078] In each of the above examples, each function of the information distribution control unit 24 (see FIG. 2) in the radio base station is an information distribution control means, a transmission condition determination means, a transmission condition notification control means, an information amount adjustment means, and a delay amount. Corresponds to each of the calculation means and the transmission speed adjusting means. Further, each function of the control unit 13 (see FIG. 3) of each wireless terminal corresponds to the reception quality measuring means, the information reception control means, and the reception quality notification control means.
[Effects of the Invention] [0079] As described above,<u style="single">According to one aspect of the invention</u>Since the information distribution device distributes the same multicast information according to a plurality of different transmission conditions, each wireless terminal in the service area of the information distribution device is better depending on the reception state (propagation environment) of its own terminal. It is possible to receive multicast information delivered under transmission conditions that provide reception quality. Therefore, it is possible to realize a multicast service providing method in which each of a plurality of wireless terminals in various reception states in the service area can receive multicast information with good reception quality.
【0080】<u style="single">According to one aspect of the invention</u>It is possible to provide an information distribution device applied to such a multicast service providing method.
[0081] Furthermore,<u style="single">According to one aspect of the invention</u>, A radio end applicable to such a multicast delivery method can be provided.
BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram showing a multicast service providing system according to an embodiment of the present invention.
FIG. 2 is a block diagram showing a configuration example of a radio base station in the system shown in FIG.
FIG. 3 is a block diagram showing a configuration example of each wireless terminal in the system shown in FIG.
FIG. 4 is a diagram showing a state in which multicast information is distributed by changing the diffusion processing gain PG according to the state of reception quality at each wireless terminal.
FIG. 5 is a diagram showing a relationship between the information speed of multicast information and its delivery time.
FIG. 6 is a diagram showing a relationship between a frequency band corresponding to the information speed of multicast information and a bandwidth after spreading of multicast information.
FIG. 7 is a diagram showing a state in which multicast information in processing gain PGs of different spreads is assigned to different time slots.
FIG. 8 is a diagram showing a state in which multicast information is distributed by changing the number of spreading codes according to the state of reception quality at each wireless terminal.
FIG. 9 is a diagram showing a state in which multicast information spread with different spreading codes is assigned to different time slots.
FIG. 10 is a diagram showing the relationship between the reception quality level, the transmission speed, and the type (number) of diffusion codes used.
FIG. 11 is a diagram showing a state in which multicast information is distributed by changing the position of a time slot according to the state of reception quality at each wireless terminal.
FIG. 12 is a diagram showing a state in which multicast information is distributed by changing the time slot position.
FIG. 13 is a diagram showing a state in which multicast information is distributed by changing a modulation method according to a state of reception quality in each wireless terminal.
FIG. 14 is a diagram showing a state in which multicast information is assigned to different time slots after being modulated by different modulation methods.
FIG. 15 is a diagram showing a relationship between a reception quality level, a transmission speed, and a modulation method (multi-value modulation) used.
FIG. 16 is a diagram showing a state of a buffer pointer when the same multicast information is transmitted at different transmission speeds.
FIG. 17 is a diagram showing a state of reception quality of a plurality of wireless terminals located in a service area of a wireless base station.
[Description of code] 10 Wireless terminal 11 Transmitter / receiver 12 Output unit 13 Control unit 20 Wireless base station 21 Transmitter / receiver 22 Multicast information storage unit 23 Network control unit 24 Information distribution control unit
Every citation, both ways
| Document | Relation | Office |
|---|---|---|
| JP11331070A | Cites | Japan |
| JP05160776A | Cites | Japan |
| JP11501175A | Cites | Japan |
17 members in 8 offices
Priority claims2
| Document | Office | Kind | Date |
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| 2000140845 | Japan | A | |
| JP20000140845 | – | – | – |
Members17
| Document | Office | Kind | |
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| CA2345823A1 | Canada | A1 | |
| EP1154660A2 | European Patent Office (EPO) | A2 | |
| AU4381001A | Australia | A | |
| JP2001320324A | Japan | A | |
| KR20010104229A | Republic of Korea | A | |
| CN1324151A | China | A | |
| US2002003798A1 | United States of America | A1 | |
| EP1154660A3 | European Patent Office (EPO) | A3 | |
| KR100404519B1 | Republic of Korea | B1 | |
| AU769231B2 | Australia | B2 | |
| CN1136677C | China | C | |
| EP1154660B1 | European Patent Office (EPO) | B1 | |
| CA2345823C | Canada | C | |
| DE60108296D1 | Germany | D1 | |
| US6895216B2 | United States of America | B2 | |
| JP3662473B2This record | Japan | B2 | |
| DE60108296T2 | Germany | T2 |
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Numbers
- Publication
- 3662473
- Publication, DOCDB
- 3662473
- Publication, EPODOC
- JP3662473B
- Application
- 140845
- Application, DOCDB
- 2000140845
- Application, EPODOC
- JP20000140845
Titles2
- Japanese
- マルチキャストサービス提供方法及び情報配信装置
- English
- Multicast service provision method and information distribution device
Classification
- CPC, 5
- H04L1/0003
- H04W4/06
- H04L2001/0093
- Y02D30/50
- H04B7/26
- IPC, 14
- H04L27 18
- H04B7 26
- H04J3 00
- H04J13 00
- H04L1 00
- H04L27 26
- H04W4 06
- H04W16 02
- H04W28 06
- H04W28 18
- H04W28 22
- H04W72 04
- H04W74 08
- H04W84 12