JP2012195973A - Repeating device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a repeating device capable of dynamically changing an interleave period according to the quality of a transmission path via which real time data is to be transmitted.SOLUTION: The repeating device comprises: a reception part which receives, as real-time data, video stream data including plural reference pictures and plural non-reference pictures; a monitoring part which periodically detects the quality of a transmission path which should transmit the real-time data toward a destination; a determination part which determines the length of an interleave period according to the quality of the transmission path; an interleaving part which when interleaving the real-time data with the determined interleave period, performs interleaving of the reference pictures and that of the non-reference pictures within the determined interleave period; and a transmission part which transmits the interleaved real-time data to the transmission path.

Description

  The present invention relates to a dynamic interleaving cycle changing method in a relay device for real-time data transferred through a wireless network (mobile communication network).

As a typical wireless network system, there is a network system (wireless LAN system) using a wireless LAN (IEEE 802.11) as shown in FIG. 1 and a cellular network system (3GPP) as shown in FIG.

For example, as shown in FIG. 1, a wireless LAN system includes a media server, a wireless network gateway connected to the media server via a link (network), and an access point (AP) accommodated in the wireless network gateway. A terminal (PC (Personal Computer), PDA (Personal Digital Assistant), etc.) is connected to the AP via a wireless link (wireless transmission path). A wireless section of the data transmission path is configured between the AP and the terminal.

For example, as shown in FIG. 2, a cellular network system (mobile phone network system) includes a server, a gateway (GW: router) connected to the server via a link, and a GW via an IP network such as the Internet. A switch (xGSN) to be connected, a base station controller (Radio Network Controller: RNC) connected to the switch via a link, and a base station (Node B or Node B) connected to the base station controller via a link BS). A mobile terminal (User Equipment or mobile node) is connected to the base station apparatus via a wireless link (wireless transmission path). A radio section of the data transmission path is configured between the mobile terminal and the base station apparatus.

As an effective technique for reducing transmission errors in received data for wireless communication (wireless communication), interleave for transmitted data, FEC (Forward)
There is error correction using Error Collection. These are employed, for example, in cellular network systems.

FIG. 3 is a diagram showing a general protocol stack when IEEE802.11 is applied to a wireless network. As one of video compression standards applied to a real-time streaming service applicable to a wireless network system, H.264 / AVC. H. In H.264 / AVC, in order to implement a streaming service, RTP / RTCP (Realtime Transfer Protocol / RTP Control Protocol) is used as a lower layer protocol.
The real-time data (RTP packet) transferred according to the RTP / RTCP can be interleaved in consideration of the wireless environment (see Non-Patent Document 1, especially Chapters 12.6 and 13).

  As a result, the transmission protocol positioned above RTP / RTCP can provide robust data transmission even if the lower layer link is a wireless link.

  Streaming data is used for services that require immediate reproduction, such as live broadcast, live broadcast, and video teleconference. Alternatively, in services such as on-demand video program delivery, streaming data may be allowed to be temporarily buffered. For example, with respect to the reproduction timing on the timeline (time axis) in data reproduction, reproduction is started after a certain amount of data buffering is performed. In a service such as television program distribution, it is not required that all data transmitted from the media server reach the receiving side when reproducing data.

JP 2005-536097 A JP 2002-198946 A JP-A-6-181567 JP 2000-156646 A

RFC3984 RTP Payload Format for H.264 VIDEO

  However, the radio environment is drastically changed compared to a fixed line. For this reason, the period at which interleaving is performed (interleaving period) is not always a period suitable for the wireless environment. For this reason, the case where the transmission error reduction effect by interleaving is not fully exhibited may occur.

  For streaming data (real-time data), which is a real-time service, there are very few rescue opportunities by resending when a transmission error occurs compared to a non-real-time service. For this reason, the concealment technique (error correction technique) when a transmission error relating to a real-time service occurs is more important than the non-real-time service.

  Here, wireless transmission is, for example, a method for maintaining the quality of the transmission path constant when the situation changes from an error-free environment to an error-prone environment, that is, an error-correctable radio. In order to achieve transmission path quality, in addition to transmission power control, increase the number of redundant codes that make up the error correction code and / or change the modulation method (for example, change the modulation method from QPSK to BPSK) The transmission band may be reduced when viewed from the viewpoint.

  Such a situation where the transmission bandwidth decreases is not convenient for real-time data. That is, the reduction of the transmission band due to the transmission quality deterioration includes a possibility that the arrival time of the data to be transmitted in a certain time interval is significantly delayed. In addition, before the band adjustment in the wireless section, there is a possibility that continuous data discard at the destination occurs due to the deteriorated transmission path quality.

  The situation where the arrival time delay or the continuous data discard occurs as described above is also caused by hard handover. FIG. 4 is an explanatory diagram of data discard and retention during hard handover.

  That is, if the bandwidth that can be used at the handover destination is narrower than the bandwidth that was used at the handover source, temporary data loss occurs during the handover. That is, when switching the route of data for a certain area to another area, data in the middle of switching may be lost. When such data loss occurs, reproduction is not performed on the destination side until the missing data is replenished by retransmission, and there is a possibility that data retention (long buffering time) occurs. In other words, it can have a significant impact on the playback of real-time data at a particular time.

Thus, in a mobile communication network in which various changes in the communication environment occur, for example, RFC3984
It may happen that the implemented interleaving period uniquely determined at 1 is not necessarily an appropriate period.

  An object of the present invention is to provide a relay apparatus that can dynamically change the interleaving cycle in accordance with the quality of a transmission path through which real-time data is transmitted.

One aspect of the present invention is a receiving unit that receives real-time data;
A monitoring unit that periodically detects the quality of the transmission path to be transmitted to the destination of the real-time data;
A determination unit for determining a length of an interleaving period according to the quality of the transmission path;
An interleaving unit that interleaves real-time data with the determined interleaving period;
And a transmission unit that transmits interleaved real-time data to the transmission path.

  In the relay apparatus, the determination unit may be configured to lengthen the interleaving cycle when the monitoring unit detects deterioration in quality of the transmission path.

  In the relay apparatus, the determination unit may be configured to shorten the interleaving cycle when the monitoring unit detects improvement in the quality of the transmission path.

  In the relay apparatus, the determination unit may be configured to determine a minimum unit of an interleaving cycle and determine an interleaving cycle by an integer multiple of the minimum unit.

  In the relay device, when the real-time data received by the receiving unit is interleaved with a predetermined interleaving cycle, the determining unit is configured to determine the length of the predetermined interleaving cycle as the minimum unit. can do.

  In the relay apparatus, whether or not interleaving is performed at the transmission source included in the capability exchange information transmitted / received between the real-time data transmission source and the destination via the relay apparatus, and interleaving at the time of performing interleaving An information collecting unit that acquires data indicating the period and gives the data to the determining unit can be further provided.

The relay device further includes an information collection unit that acquires a size of a buffer for storing the real-time data before decoding, which the destination of the real-time data has,
The determining unit may be configured to determine a maximum value of an interleaving period based on the size of the buffer.

In the relay device, the real-time data is video stream data including a reference picture and a non-reference picture,
The interleaving unit may be configured to individually execute interleaving for a reference picture and interleaving for a non-reference picture.

A second aspect of the present invention is a relay device that relays real-time data transmitted from a transmission device to a reception device.
Receive real-time data,
Monitoring the quality of the transmission path to send the real-time data to the destination,
Determining the length of the interleaving period according to the quality of the transmission path;
Interleave real-time data with the determined interleaving cycle,
A relay device real-time data transfer method including transmitting interleaved real-time data to the transmission path.

  ADVANTAGE OF THE INVENTION According to this invention, the relay apparatus which can change an interleaving period dynamically according to the quality of the transmission line in which real-time data is transmitted can be provided.

It is a figure which shows the example of a wireless LAN system. It is a figure which shows the example of a cellular network system. It is a figure which shows the general protocol stack at the time of applying IEEE802.11 to a wireless network. It is explanatory drawing of generation | occurrence | production of the data discard at the time of hard handover, and a stay. It is a figure which shows the example of a basic network structure in embodiment. It is explanatory drawing of the interleaving period dynamic change method, and shows the case where the same kind (reference pictures and non-reference pictures) are interleaved. It is explanatory drawing of the interleaving period dynamic change method, and shows the mode at the time of the change of an interleaving period. It is explanatory drawing of the relationship between the maximum interleaving period and the buffer before decoding. It is a figure which shows the definition of an interleaving period in the case of performing interleaving at the transmission side. It is a figure which shows the structural example of the wireless LAN system in an application example. It is a block diagram which shows the example of a fundamental structure of SW shown in FIG. It is a flowchart which shows the example of the interleave period determination process by the interleave period determination part. It is a flowchart which shows the example of the change process of an interleaving period. It is a figure which shows the data structure of a NAL unit header. It is explanatory drawing of the interleaving with respect to the video stream (For example, the video stream data encoded according to H.264 / AVC) containing an I picture and a B picture. It is a figure which shows a mode that the interleaving period was changed.

  Hereinafter, embodiments of the invention will be described. The configuration of the embodiment is an exemplification, and is not limited to the configuration of the embodiment.

[Background of the Invention]
As described above, when the data interleaving cycle on the transmission side does not match the wireless environment, the transmission band may be reduced. In such a situation, when, for example, RFC3984 is applied in wireless communication and encoding and transmission are performed in real time, the transmission side is incompatible with the interleaving cycle and the wireless environment based on feedback information and the like. It is conceivable to change the interleaving cycle at. However, the above method cannot be applied because there is a wide variety of feedback information during broadcast-type data transmission.

  When the data to be interleaved is already encoded data including interleave processing, the interleaving cycle determined at the time of encoding is fixed. For this reason, it is not possible to change the interleaving cycle according to the wireless environment (communication status) while ignoring such an interleaving cycle.

  The relay apparatus according to the embodiment absorbs errors due to fluctuations in transmission channel quality on the transmission side and suppresses degradation of reception quality on the data reception side when transmitting real-time data received from the transmission source toward the destination. For the purpose.

  That is, in view of the above situation, a technique is proposed that can dynamically change the interleaving cycle in accordance with the transmission path quality when handling a real-time service such as video stream transmission.

[Outline of Embodiment]
FIG. 5 is a diagram illustrating a basic network configuration example according to the embodiment. The network system shown in FIG. 5 generally includes at least one receiving device (# 0 to #n), a relay device (transmission device) connected to each receiving device via a link, and a link to the relay device. And a transmission device connected via the network. The data transmission path between the transmission device and each reception device includes a section A from the relay apparatus to the relay apparatus and a section B from the transmission apparatus to the relay apparatus.

  The method for dynamically changing the interleaving cycle described in the following embodiment is applied to, for example, the relay apparatus shown in FIG. If the network system shown in FIG. 5 is a wireless LAN system, the relay device corresponds to, for example, a wireless network gateway or an access point. If the relay apparatus of FIG. 5 is a cellular network system (mobile phone network) system, the relay apparatus corresponds to, for example, a base station controller (RNC: Radio Network Controller) and / or a base station apparatus (Node B).

The interleaving cycle dynamic change method is an environment in which the transmission path quality in section A varies greatly with time, and the transmittable band varies according to the transmission path quality (for example, section A is a wireless transmission path). In some cases). However, in FIG. 5, even when the section A is a wired transmission path or when there is almost no fluctuation in the transmission path quality of the section A, the application of the interleave period dynamic change method is hindered. Absent.

The main features of the interleaving cycle dynamic change method will be described with reference to FIG. 6 and 7 are explanatory diagrams of the interleaving cycle dynamic change method, and FIGS. 6 and 7 illustrate a case where interleaving of the same type (reference pictures, non-reference pictures) is performed. FIG.
Shows a state when the interleaving cycle is changed.

Here, for the sake of explanation, a video compression standard for real-time data that can be used in wireless communication (
For example, transmission of a video frame (picture) encoded according to H.264 / AVC, MPEG-4, MPEG-2) is taken as an example. 6 and 7, “R” indicates a reference picture (I picture), and “nR” indicates a non-reference picture (B picture, including a P picture depending on the standard).

Here, the reference picture is a picture (frame) that is independently encoded only within the screen irrespective of the preceding and following frames, and the non-reference picture is located in a predetermined picture (for example, before and after the target picture). This is a frame that is predictively encoded from (picture).

  FIG. 6 shows pictures # 0 to # 11 in a certain interleaving cycle. In the example shown in FIG. 6, twelve pictures are subject to interleaving in one interleaving cycle. Here, pictures # 0, # 3, # 6, and # 9 are reference pictures R, and the remaining pictures # 1, # 2, # 4, # 5, # 7, # 8, # 10, and # 11 are non-existing. Reference picture nR.

  The arrangement order of the pictures # 0 to # 11 is changed between pictures of the same type. That is, the interleaving process for the reference picture R and the interleaving process for the non-reference picture nR are executed within the interleaving cycle.

FIG. 7 shows a state in which the interleaving cycle is shortened and 6 pictures are changed to be interleaved in one interleaving cycle. In the example shown in FIG. 7, one interleave period shown in FIG. 6 is changed to two interleave periods # 0 and # 1. Pictures # 0 to # 5 are subject to interleaving in interleaving cycle # 0, and pictures # 6 to # 11 are subject to interleaving in interleaving cycle # 1. In each interface cycle # 0, # 1, interleaving processing is performed between the same type.

In the interleaving cycle dynamic changing method according to the embodiment, the interleaving cycle is shortened if the radio condition (the transmission path quality of the section A shown in FIG. 5) is good. On the other hand, when the radio situation (transmission path quality) deteriorates, the interleaving cycle is lengthened.

  Here, when the interleaving cycle is lengthened, it is desirable to set the interleaving cycle so as not to affect the reproduction of streaming. That is, the maximum interleaving cycle should be set to a value that takes into account the size of the buffer in which the streaming data before decoding is accumulated on the decoding side (receiving device). This is because an appropriate decoding process (deinterleaving) cannot be performed unless the buffer can store data of one interleave period. However, in the present application, a method for determining the maximum interleave period is not particularly mentioned.

  FIG. 8 is an explanatory diagram of the relationship between the maximum interleaving cycle and the buffer before decoding. The interleaving cycle of streaming data (real-time data) transmitted from the sender (sender) to the receiver (receiver) is the buffer before decoding. It is adjusted to be a value smaller than the buffer size.

If the interleaving cycle is lengthened, the delay becomes weaker. That is, the occurrence of a slight delay exceeds the buffering time in the pre-decoding buffer on the decoding side (receiving side). In general, real-time services such as streaming data generally have a high transmission priority in a network. For this reason, when the quality of the radio transmission path is poor, the interleaving effect (error reduction) is given priority as much as possible over the risk of delay. Thereafter, when the quality of the wireless transmission path is improved, the interleaving cycle is shortened. This is because there is no need to take the risk of unnecessary delays.

  Further, in interleaving, as described above, interleaving is performed between reference pictures R and non-reference pictures nR. This is for avoiding consecutive reference pictures due to interleaving. Thus, the reference picture and the non-reference picture are individually interleaved, so that the reference picture transmission interval can be maximized.

Note that the examples shown in FIGS. 6 and 7 are based on the assumption that the real-time data stream has already been interleaved according to RFC3984 or the like.

  When interleaving is performed on the stream transmission side (transmission apparatus in FIG. 5), the interleaving period applied in the interleaving period dynamic changing method in the embodiment is defined as follows.

  FIG. 9 shows the definition of the interleaving period when interleaving is performed on the transmission side. As shown in FIG. 9, when interleaving is performed on the transmission side, the minimum interleaving period A applied in the dynamic change method is defined with a length that matches the length of the transmission side interleaving period. Further, the maximum interleaving period B applied in the dynamic change method is defined as n times the minimum interleaving period A (n = 1, 2, 3,..., N). The interleaving cycle is changed in units of the minimum interleaving cycle A.

In addition, although not shown, for example, IDR (Instantaneous Decoding in H.264 / AVC)
Refresh pictures such as (Refresh) pictures are delayed in transmission due to interleaving,
Considering the possibility of resending remedies is reduced, it is not subject to interleaving. That is, since the IDR picture is a refresh picture and is the first picture in the image sequence, the number of pictures is very small compared to other pictures. The emphasis is therefore on the certainty of delivery rather than the dispersion of errors. In this way, the refresh picture can be transmitted without being affected by the implementation of interleaving in the relay device.

[Application example]
Hereinafter, application examples of the embodiment will be described. As an application example, assuming that the above-described interleave period dynamic change method is applied in a wireless network system, a case where a wireless LAN system is targeted as a wireless network system is shown.

<Example of network configuration>
FIG. 10 shows a configuration example of a wireless LAN system in the application example. In FIG. 10, a wireless LAN system has a plurality of access points (hereinafter referred to as “AP” as a plurality of wireless transceivers).
And a relay apparatus (relay station, switch (SW)) having a function as a controller for controlling each of the plurality of APs # 0 to #n.

  SW1 corresponds to, for example, the radio network gateway (RN-GW) shown in FIG. The SW 1 is connected to a media server (server) 3 as a transmitting station via a network (IP network such as the Internet) 2.

Each of the plurality of wireless terminals # 0 to #m as a plurality of receiving stations (receiving devices) performs wireless connection (wireless access) with a predetermined AP (for example, the nearest AP) and is distributed from the media server 3 in real time. Data provided by the system service (real-time data, for example, multimedia data, particularly video stream data) can be received via SW1 and an AP wirelessly connected to itself.

  For example, “MANE: Media Aware Network Element” described in RFC3984 is mounted on SW1. MANE is a network element such as a middle box or an application layer gateway that can parse a part of the RTP payload header or the RTP payload to cope with the contents of the media.

  The terminal-oriented data is transmitted from SW1 to the AP having the data destination terminal. For example, when SW1 receives data for terminal # 0, this data is transmitted to terminal # 0 via AP # 0. Here, the radio link quality information between AP # 0 and terminal # 0 is reported from AP # 0 to SW1. AP # 0 receives the transmission power control information of AP # 0 via the uplink radio link provided with terminal # 0, and such power control information is reported to SW1. . Alternatively, when retransmission control is performed with a terminal (for example, terminal # 0) under the control of AP # 0, AP # 0 can report retransmission information received from the terminal to SW1.

<Configuration example of SW (relay device)>
FIG. 11 is a block diagram illustrating a basic configuration example of SW1. SW1 includes a network side receiving unit 11 connected to a network (for example, the network 2 in FIG. 10), a transmission schedule unit 12 as an interleaving unit connected to the network side receiving unit 11 and the interleave period determining unit 16, and a transmission schedule. Is connected to the unit 12, is connected to one or more APs (for example, AP # 0 to #n in FIG. 10) and is connected to the reception unit 14, and is connected to the network (for example, the network 2 in FIG. 10). ) Connected to the network side transmission unit 15, a quality management unit 16 as a monitoring unit connected to the reception unit 14, an interleaving cycle determination unit 17 as a determination unit connected to the quality management unit 16, and the network side An information collecting unit 18 connected to the receiving unit 11, the receiving unit 14, and the interleave period determining unit 17 is provided.

The network side receiving unit 11 receives data for terminals from the network (network 2). The network-side receiving unit 11 analyzes the content of the received data and provides information related to the analysis result to the information collecting unit 18. The information related to the analysis result is, for example, capability exchange information performed between a transmitting station (for example, the media server 3 in FIG. 10) and a terminal (receiving station) of data (real-time data) provided by a real-time service. . The capability exchange information may include information regarding whether or not to perform interleaving and information indicating an interleaving cycle at the time of performing interleaving. The network side transmission unit 15 transmits the data from the reception unit 14 to the network side (network 2).

  The information collecting unit 18 provides the data provided from the network side receiving unit 11 and the data provided from the receiving unit 14 to the interleave period determining unit 16. The data from the receiving unit 14 can include at least the capability exchange information as described above.

  The transmission schedule unit 12 interleaves the data received from the network side reception unit 11 according to the information provided from the interleaving cycle determination unit, and transfers the data to the transmission unit 13. The transmission schedule unit 12 includes a data buffer for interleaving processing or the like, and the data received from the network side reception unit 11 is temporarily stored in the data buffer.

  The interleaving cycle is changed in units of interleaving cycles. That is, for a schedule that has already been completed, even if it is decided to change the interleaving cycle, the interleaving cycle for which use of the schedule has been decided is not canceled.

  In other words, if interleaving in a certain interleaving cycle has already been scheduled when the change of the interleaving cycle is determined, the transmission scheduling unit 12 cancels the interleaving cycle applied in the schedule (cancellation). Without interleaving the data stored in the data buffer in the certain interleaving cycle. After that, when the schedule is completed, the transmission schedule unit 12 changes the interleaving cycle according to the information provided from the interleaving cycle determination unit 17 at the next schedule.

  The interleaving cycle determination unit 17 determines an interleaving cycle based on the information provided from the quality management unit 16 and the information collection unit 18. The interleaving cycle is determined in units of the minimum interleaving cycle. That is, the interleaving period is determined to be an integral multiple of the minimum interleaving period.

For example, the interleaving cycle determination unit 17 can receive information on the maximum interleaving cycle from the quality management unit 16. The information on the maximum interleaving period is, for example, the size of the pre-decoding buffer that the terminal has. When the pre-decoding buffer size is provided, the interleaving cycle determining unit 17 determines the maximum interleaving cycle within a range not exceeding the pre-decoding buffer size (buffering time), and the minimum interleaving cycle is m of the maximum interleaving cycle. It is defined to be a double (m is a positive integer).

Further, for example, when information (including an interleaving cycle) indicating that interleaving between the real-time data transmitting station (media server 3) and the terminal is performed is provided from the information collecting unit 18, it is performed in SW1. As the minimum unit of the interleaving cycle (minimum interleaving cycle), the same value as the interleaving cycle implemented between the transmitting station and the terminal is determined. The maximum interleaving period at this time is defined as n times the minimum interleaving period (n is a positive integer). At this time, when the pre-decoding buffer size of the terminal is known, the maximum interleaving cycle is determined in a range not exceeding the maximum interleaving cycle determined based on the buffer size (buffering time). Regardless of whether or not interleaving is performed between the transmitting station and the terminal, the interleaving cycle is changed in units of the minimum interleaving cycle.

The definition of the interleaving cycle is summarized as follows.
Maximum interleaving cycle = minimum interleaving cycle l × m
Interleaving cycle = Minimum interleaving cycle l × n (n ≦ m)

The interface cycle determination unit 17 receives information (radio link quality information) from the quality management unit 16 as to whether the radio link quality (radio transmission path quality) between the AP and the terminal is in a tendency of deterioration or improvement. Can receive. When the radio link quality information indicates the deterioration direction, the interleaving cycle determining unit 17 determines an interleaving cycle longer than the currently used interleaving cycle (lengthens the interleaving cycle). On the other hand, when the radio link quality information indicates an improvement direction, the interleaving cycle determination unit 17 determines an interleaving cycle shorter than the currently used interleaving cycle (shortens the interleaving cycle). However, the interleaving cycle determination unit 17 determines the interleaving cycle in a range from the minimum interleaving cycle to the maximum interleaving cycle.

The quality manager 16 periodically determines the radio link quality based on information from the receiver 14 (
And the determined radio link quality information is provided to the interleave period determining unit 17. The quality management unit 16 receives ACK / NACK information (information indicating success / failure of physical layer data reception) and / or power increase / decrease information (in the inner loop) from the terminal confirmed by the reception unit 14 from the reception unit 14. Received transmission power increase / decrease instruction information associated with fluctuations in the target SIR (signal to interference ratio) can be received (increase = quality degradation decrease = quality improvement). The quality management unit 16 can generate radio link quality information using at least one of ACK / NACK information and power increase / decrease information.

The receiving unit 14 receives data transmitted from the terminal via the corresponding AP, and transfers the received data to the network side transmitting unit 15. In addition, the reception unit 14 provides the quality management unit 16 with information on the radio link quality in the received data, for example, ACK / NACK information from the terminal and power increase / decrease information. The transmission unit 13 follows the order of the data transferred from the transmission schedule unit 12 in accordance with the terminal (
Data is transmitted to the corresponding AP).

  SW1 is a device composed of a plurality of hardware such as a processor (control device) such as a CPU, a memory (storage device), an input / output interface (I / O), and a communication interface, as shown in FIG. Each block is a function realized by executing at least one of the hardware described above or a software (program) by a processor.

<Interleave cycle decision flow>
FIG. 12 is a flowchart showing an example of interleaving cycle determination processing by the interleaving cycle determination unit 17. In FIG. 12, when a connection for transmitting data (real-time data (eg, video stream data)) between the data transmission station (eg, media server 3) and the terminal is registered in SW1 (step S01), the RTP session As information on the start procedure, the capability exchange information of the transmitting station and the terminal is transmitted and received between the transmitting station and the terminal.

At this time, information indicating the presence / absence of interleaving performed from the transmitting station as capability exchange information, and information indicating the interleaving cycle at the time of interleaving are received by the network side receiving unit 11 and provided to the information collecting unit 18; This is provided to the interleaving cycle determination unit 17 (step S02).

  The interleaving cycle determining unit 17 determines whether or not interleaving between the transmitting station and the terminal is performed based on information indicating whether or not interleaving is performed, acquired from the information collecting unit 18 (step S03). At this time, when interleaving is performed (S03; Y), the interleaving cycle determination unit 17 advances the processing to step S04. When interleaving is not performed (S03; N), the interleaving cycle determination unit 17 advances the processing to step S05.

  In step S04, the interleaving cycle determining unit 17 sets the interleaving cycle between the transmission station and the terminal acquired from the information collecting unit 18 to the minimum cycle (minimum interleaving cycle) of the interleaving cycle implemented in SW1, and step S06. Proceed to the process.

  In step S05, the interleaving cycle determination unit 17 determines the minimum interleaving cycle, and advances the process to step S06.

  In step S06, the interleaving cycle determining unit 17 determines the maximum interleaving cycle. The maximum interleaving period is determined by n times or m times the minimum interleaving period (where n ≦ m). At this time, if the information from the information collecting unit 18 includes the buffer size before decoding of the terminal, the maximum interleaving cycle is determined in consideration of this buffer size.

  When step S06 ends, the maximum and minimum interleaving cycle determination processing ends. In step S06, the initial value of the interleaving cycle is determined. As an initial value, for example, a minimum interleaving period is applied. However, an interleave period of an arbitrary length can be applied as an initial value.

<Example of determining radio link quality>
The quality management unit 16 determines the radio link quality periodically (every predetermined quality monitoring period). The quality management unit 16 can determine the radio link quality based on the monitoring result of the ACK / NACK information received within a predetermined measurement period (time interval) within the quality monitoring period, for example. For example, the quality management unit 16 calculates transmission quality (radio link quality) in the measurement period from ACK / NACK information in the measurement period (for example, 1 second). For example, the number of NACKs (ACK) during the measurement period can be calculated as the radio link quality.

  The quality management unit 16 compares the calculated radio link quality with the radio link quality calculated for the previous measurement period, and determines whether the radio link quality has improved, deteriorated, or not changed. For example, when the number of NACKs during the measurement period indicates the radio link quality, if the current NACK number exceeds the previous NACK number, it is determined as “quality degradation”. When the current NACK number is lower than the previous NACK number, it is determined as “quality improvement”, and when the current NACK number and the previous NACK number are the same, it is determined as “no change”.

  Such a determination result (any one of “quality degradation”, “quality improvement”, and “no change”) is provided to the interleave period determination unit 17 as radio link quality information.

Further, when the power increase / decrease information is used for determining the radio link quality, the following processing is performed. For example, one number of power increase instructions and power decrease instructions during a predetermined measurement period (
For example, the number of power increase instructions) is calculated. Subsequently, the number of current power increase instructions and the number of power increase instructions in the previous measurement period are compared. If this time exceeds the previous time, it is determined as “quality degradation”. On the other hand, if the current time is lower than the previous time, it is determined as “quality improvement”. If this time and the previous time are the same, it is determined that there is no change.

Both the quality judgment based on the number of ACK / NACK and the quality judgment based on the power increase / decrease information are executed, and the logical product (AND) or logical sum (OR) of the respective judgment results is shown as the final quality judgment result It may be provided to the interleave period determining unit 17 as radio link quality information.

<Interleaving cycle change flow>
FIG. 13 is a flowchart illustrating an example of interleaving cycle changing processing. The quality management unit 16 provides the radio link quality information for each quality monitoring cycle to the interleaving cycle determination unit 17. When the quality monitoring period expires (S101), the interleaving cycle determination unit 17 refers to the radio link quality information provided from the quality management unit 16 and determines whether or not the radio link quality information indicates quality degradation (S102). ).

  At this time, if the radio link quality information indicates quality degradation (S102, Y), the process proceeds to step S103. If the radio link quality information does not indicate quality degradation (S102, N), the process proceeds to step S105.

  When the process proceeds to step S103, the interleave period determining unit 17 determines whether or not the current interleave period is already the maximum interleave period (maximum period).

  At this time, if the current interleaving cycle is not the maximum cycle (S103, N), the interleaving cycle determining unit 17 changes the interleaving cycle (S104). That is, the interleaving cycle determination unit 17 changes the current interleaving cycle to an interleaving cycle obtained by adding one minimum interleaving cycle, and notifies the transmission scheduling unit 12 of the changed interleaving cycle. Thereafter, the process returns to step S101.

  On the other hand, when the current interleaving cycle is the maximum cycle (S103, Y), the interleaving cycle determining unit 17 returns the process to step S101 without changing the current interleaving cycle.

  When the process proceeds to step S105, the interleave period determining unit 17 determines whether or not the radio link quality information indicates quality improvement. At this time, if the radio link quality information indicates quality improvement (S105, Y), the process proceeds to step S106. If the radio link quality information does not indicate quality improvement (S105, N (no change)), the interleave period determining unit 17 returns the process to step S101 without changing the interleave period.

  When the process proceeds to step S106, the interleave period determination unit 17 determines whether or not the current interleave period is already the minimum interleave period (minimum period).

  At this time, if the current interleaving cycle is not the minimum cycle (N in S106), the interleaving cycle determining unit 17 shortens the current interleaving cycle. That is, the current interleaving cycle is changed to a length shorter by one minimum cycle, and the changed interleaving cycle is notified to the transmission schedule unit 12. Thereafter, the process returns to step S101.

  In contrast, if the current interleaving cycle is the minimum cycle (S106, Y), the interleaving cycle determining unit 17 returns the process to step S101 without changing the current interleaving cycle.

  The interleaving cycle determined by SW1 is notified from the transmission unit 13 to the terminal for deinterleaving processing on the receiving side. Thus, in SW1 (relay device), the interleaving cycle is dynamically changed according to the transmission path quality.

<Collecting information>
Next, various information collected by SW1 will be described. For example, H.M. In H.264, a NAL (Network Abstraction Layer) unit is stored in an RTP packet and transmitted.
A header is given to the NAL unit, and from this header information, it is possible to detect what kind of data the RTP packet carries. Information indicating the type of reference picture / non-reference picture can be obtained from the header information.

  FIG. 14 is a diagram illustrating the data structure of the NAL unit header. The AL unit header has a storage field of NRI bits, and by referring to the value of this NRI bit, it is possible to determine whether the data to be transported is data related to a reference picture or data related to a non-reference picture. Such determination is performed, for example, when the transmission schedule unit 12 performs interleaving.

Further, whether or not interleaving is performed at the transmission station regarding the stream data transferred from the transmission station (media server 3) to the terminal is as follows:
If the moving image compression standard of the stream data is H.264 / AVC, for example, it can be confirmed by the SW1 acquiring capability exchange information by SDP (Session Description Protocol).

  For example, when the value of the parameter “sprop-interleaving-depth” included in the capability exchange information is 0 or more, it indicates that interleaving is performed. Also, it is possible to know whether or not to perform interleaving from the parameter “packetization mode” based on SDP.

  Whether or not to perform interleaving can be determined from the type (type) of usable NAL units. That is, if the “Single NAL Unit Packet” type cannot be used and a type such as “STAP-B” type or “MTAP” type is used, it can be determined that interleaving is performed. The type of NAL can be identified from the value of the “Type” field of the NAL unit header shown in FIG.

The parameter “deint-buf-cap” from the terminal based on SDP indicates the capacity of a buffer (pre-decoding buffer) that stores data before decoding received by the terminal. Based on the buffer capacity indicated by this parameter, the maximum interleaving period can be determined.

<Interleaving method>
Next, the interleaving performed by the transmission schedule unit 12 will be described. FIG. 15 is an explanatory diagram of the interleaving process performed by the transmission schedule unit 12, and FIG. 16 is an explanatory diagram of the interleaving process to which an interleaving period shorter than the interleaving period shown in FIG. 15 is applied.

  In the example shown in FIGS. 15 and 16, it is assumed that a video frame is transmitted from the transmitting station (media server 3) to the terminal. 15 and 16, “I” indicates an I picture (Intra-Picture: reference picture (also referred to as I frame)), and “B” indicates a B picture (Bi-directional Predictiv-Picture: non-reference picture (B frame). Also called))).

  Here, the I picture is a picture (frame) that is independently encoded only within the screen regardless of the previous and subsequent frames on the time axis, and the B picture is both a past frame and a future frame. This is a picture (frame) that is predictively encoded from the direction.

In the example shown in FIG. 15, interleaving for 12 frames is performed by the transmission schedule unit 12 in one interleaving cycle. However, interleaving for I pictures and interleaving for B pictures are performed separately in order to avoid consecutive I pictures due to interleaving.

The example shown in FIG. 16 shows a state in which the interleave period change is determined by the interleave period determining unit 17 and the interleave period in the transmission schedule unit 12 is changed. In the example shown in FIG. 16, the radio link quality is improved. Shows how the interleaving cycle is shortened. In each interleaving cycle # 0 and # 1 shown in FIG. 16, interleaving is performed in the same manner as in FIG. 15 (interleaving for the same type of picture).

[Effect of the embodiment]
According to the embodiment, the interleaving cycle of real-time data (for example, video stream data) transmitted from the transmission station (media server 3) is dynamically changed according to the transmission path quality (radio link quality).

  As a result, when the radio link (wireless transmission path) deteriorates, the interleaving cycle is lengthened to disperse the data over a long interval, thereby reducing the transmission path error on the receiving side (data destination). it can.

  In particular, when processing that causes data delay, such as transmission bandwidth reduction or handover, is performed due to degradation of wireless channel quality, the error rate of data reaching the receiving side is reduced in an interleaved manner. Data immediacy can be ensured as much as possible.

In other words, in an environment where real-time data arrival delay or loss may occur due to degradation of the quality of the transmission path of real-time data, the receiving side (
The effectiveness of real-time data reaching the (destination) can be increased with an interleaving effect,
It is possible to provide an appropriate real-time service.

  As a result, when a burst error or a temporary stagnation occurs, the situation where there is no data to be reproduced during the reproduction time of the real-time data on the receiving side can be alleviated by dispersing the data with a long interleaving cycle. As a result, even when the quality of the radio link varies, it leads to an effect of making the reproduction quality of the media uniform.

[Modification]
The configuration of SW1 shown in FIG. 11 can be modified so that an access point (AP) is provided instead of SW1 (wireless network gateway). The configuration of SW1 can be applied to a base station controller (RNC) or a base station device (Node B) in a cellular network system.

<Others>
(Supplementary note 1) A receiver that receives real-time data;
A monitoring unit that periodically detects the quality of the transmission path to be transmitted to the destination of the real-time data;
A determination unit for determining a length of an interleaving period according to the quality of the transmission path;
An interleaving unit that interleaves real-time data with the determined interleaving period;
A relay apparatus comprising: a transmission unit that transmits interleaved real-time data to the transmission path.

(Additional remark 2) When the said monitoring part detects the deterioration of the quality of the said transmission line, the said determination part,
The relay device according to attachment 1, wherein the interleaving cycle is lengthened.

(Additional remark 3) The said determination part is a relay apparatus of Additional remark 1 or 2 which shortens the said interleave period, when the said monitoring part detects the improvement of the quality of the said transmission line.

(Additional remark 4) The said determination part is a relay apparatus as described in any one of additional remarks 1-3 which determines the minimum unit of an interleave period, and determines an interleave period by the integral multiple of this minimum unit.

(Supplementary note 5) The supplementary note 4, wherein when the real-time data received by the reception unit is interleaved with a predetermined interleave period, the determination unit determines the length of the predetermined interleave period as the minimum unit. Relay device.

(Supplementary Note 6) Whether or not interleaving is performed at the transmission source included in the capability exchange information transmitted and received between the transmission source and the destination of the real-time data via the relay device, and an interleaving cycle at the time of performing interleaving The relay device according to appendix 5, further comprising: an information collection unit that acquires data indicating that and supplies the data to the determination unit.

(Additional remark 7) It further has the information collection part which acquires the size of the buffer for storing the real-time data before decoding which the destination of the real-time data has,
The relay device according to any one of appendices 1 to 6, wherein the determination unit determines a maximum value of an interleaving cycle based on a size of the buffer.

(Supplementary note 8) The real-time data is video stream data including a reference picture and a non-reference picture,
The relay apparatus according to any one of supplementary notes 1 to 7, wherein the interleaving unit separately executes interleaving for a reference picture and interleaving for a non-reference picture.

(Supplementary Note 9) In a real-time data transfer method for a relay device that relays real-time data transmitted from a transmission device to a reception device,
Receive real-time data,
Monitoring the quality of the transmission path to send the real-time data to the destination,
Determining the length of the interleaving period according to the quality of the transmission path;
Interleave real-time data with the determined interleaving cycle,
A relay device real-time data transfer method, comprising: transmitting interleaved real-time data to the transmission path.

1 ... Switch (SW, relay device)
2 ... Network 3 ... Media server (transmitting station, transmitting device)
DESCRIPTION OF SYMBOLS 11 ... Network side receiving part 12 ... Transmission schedule part 13 ... Transmitting part 14 ... Receiving part 15 ... Network side transmitting part 16 ... Quality management part 17 ... Interleaving cycle determination part 18 ... Information collection department

Claims (2)

A receiver that receives video stream data including a plurality of reference pictures and a plurality of non-reference pictures as real-time data;
A monitoring unit that periodically detects the quality of the transmission path to be transmitted to the destination of the real-time data;
A determination unit for determining a length of an interleaving period according to the quality of the transmission path;
An interleaving unit that executes interleaving of the plurality of reference pictures and interleaving of the plurality of non-reference pictures within the determined interleaving period when performing real-time data interleaving in the determined interleaving period;
A relay apparatus comprising: a transmission unit that transmits interleaved real-time data to the transmission path. In the relay device real-time data transfer method for relaying real-time data transmitted from the transmission device to the reception device,
As the real-time data, video stream data including a plurality of reference pictures and a plurality of non-reference pictures is received,
Monitoring the quality of the transmission path to send the real-time data to the destination,
Determining the length of the interleaving period according to the quality of the transmission path;
When interleaving the real-time data in the determined interleaving period, the interleaving of the plurality of reference pictures and the interleaving of the plurality of non-reference pictures are performed within the determined interleaving period;
A relay device real-time data transfer method, comprising: transmitting interleaved real-time data to the transmission path.

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