KR101054047B1 - Method and operation method for peer of P2P broadcasting system to receive data - Google Patents

Abstract

The present invention relates to a method and a method of operating a peer of a P2P broadcasting system for receiving data, comprising: accessing a predetermined channel group; Receiving the predetermined channel data of high capacity; And receiving adjacent channel data of low capacity.

P2P, Peer, IPTV, Broadcast

Description

Method and operation of peer to receive data of P2P broadcasting system {DATA RECEIVING AND OPERATING METHOD OF PEER OF P2P BROADCASTING SYSTEM}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for suppressing the occurrence of delay time during channel switching in a P2P broadcasting system, and more particularly, to a method of receiving data by a peer and a method of operating a peer.

As IPTV service with real-time broadcasting service is provided, users want to receive higher quality service. One of the important elements of the quality of experience (QOE) that users experience in IPTV is the delay time that occurs when changing channels. In over-the-air broadcasting, all channel signals are provided to the TV receiver at the same time regardless of the user watching the channel, so there is no delay when the user changes the channel. However, in the case of IPTV, the network bandwidth is limited or all channel data cannot be simultaneously transmitted to a specific node for economical use of the bandwidth. Therefore, when the channel is changed, the newly changed channel data is received from the server or peer of the same group and displayed on the screen. As a result, the delay time is generated and the occurrence of the channel change delay time lowers the QOE.

1 is a diagram illustrating a configuration of a multi-chain IPTV system.

Peers watching the same channel in one Digital Subscriber Line Access Multiplexer (DSLAM) are composed of L levels, and each level is divided into S spans. The level peer head peer has information about all peers belonging to level l and head peers of level l + 1, and the level information is obtained when a new peer joins level l or the peer belonging to level l leaves. It updates to know the number of peers belonging to each span of the current level. In addition, all levels of the head peer periodically provide their information to the ISP tracker, and when a new peer wants to join, the ISP tracker refers to the information received from the head peer to locate the new peer. This structure has the advantage that since most peers except the head peer are connected in a chain structure, data transmission between the peers is simple and the reorganization of the entire structure is simple in an environment in which peers are frequently joined and withdrawn.

On the multi-chain structure, [Ji-Hun Kim, Young-Han Kim, "Design of Peer-to-Peer-based IPTV System Using Multi-Chain Structure," Journal of the Institute of Electronics and Information Engineers, Vol. 45, No. 12, pp. 72-82, 2008 12 Month].

The multi-chain structure is only one of the structures of various IPTV systems, and the following description is not limited to the multi-chain structure.

2 is a diagram illustrating a process in which a peer leaves an existing channel group CH1 and joins a new channel group CH2 by changing a channel of a user in a conventional IPTV system.

Tsrch indicates the time it takes for the tracker to send a registration message to the channel 2 (CH2) group and the tracker finds a valid peer and sends an address, and Trv connects to the peer of the channel 2 (CH2) group. It shows the time it takes to receive the image data.

When watching channel 1 (CH1) and a channel change occurs at '201' time, the peer sends a registration message to the tracker to the channel 2 (CH2) group, and the channel 2 (CH2) at '202' time after Tsrch time. The address of a valid (accessible) peer of the group is passed. The peer then connects to the group of channel 2 (CH2). After that, it takes a time of Trv to receive data of channel 2 (CH2), and the peer outputs the screen of channel 2 (CH2) from time '203'. The peer may leave the channel 1 (CH1) group and join the channel 2 (CH2) group at the same time.

The image is not displayed on the screen during the combined delay time between Tsrch and Trv, which causes the user to feel the QOE deterioration.

Many studies have been conducted to reduce the channel change delay time. Most of the researches to reduce the channel change delay time in the IPTV system have been conducted on the multicast IPTV system environment. In order to reduce the delay of channel change, the proposed method is to provide popular channel data in advance on the assumption that it is highly likely to change to a popular channel by analyzing viewer ratings. By providing the data in a high speed unicast method first, the buffering time is shortened and aired on the screen, and then the data is sent by the original multicast method and the delay is reduced by switching from the temporarily sent unicast data. Secondary multicast tree) is used to transmit low-capacity channel data with low resolution regardless of user's viewing, and to reduce delay time by receiving changed channel data from sub-multicast quickly when the user changes channels. This has been proposed.

Channel change is a problem that requires a tradeoff between frequency band use and delay time. In other words, if all channel data are transmitted at the same time, such as over-the-air broadcasting, channel change delay does not occur, but the network load is increased by using a lot of frequency bands. On the contrary, the basic method of sending the changed channel signal when the user changes the channel while sending a single channel signal is efficient use of the frequency band, but the user experiences a large delay time, which results in lower satisfaction.

In particular, users often move channels continuously to find the channel they want to watch, and if the channel change occurs continuously, the current channel group is left and the new channel group is repeatedly performed. There is a problem that time occurs and the user's quality of experience QOE is lowered.

The present invention has been proposed to solve the above-mentioned problems of the prior art, and aims to increase the user's haptic quality QOE by reducing the time delay occurring when changing a channel.

The objects of the present invention are not limited to the above-mentioned objects, and other objects of the present invention, which are not mentioned above, can be understood by the following description, and will be more clearly understood by the embodiments of the present invention. It will also be readily apparent that the objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.

According to an aspect of the present invention, there is provided a data receiving method, comprising: accessing a predetermined channel group by a peer of a P2P broadcasting system; Receiving the predetermined channel data of high capacity; And receiving adjacent channel data of a low capacity.

The receiving of the predetermined channel data and the receiving of the adjacent channel data may be performed simultaneously. The peer may receive the address of the adjacent channel of the currently connected channel group periodically. have.

In addition, the operation method according to the present invention includes a method for operating a peer of a P2P broadcasting system, comprising: a first step of connecting to an N-channel group; A second step of receiving the broadcast data of the N channel at a high capacity, receiving the broadcast data of the N + 1 channel and the broadcast data of the N-1 channel at a low capacity, and displaying the broadcast data of the N-1 channel; And a third step of displaying broadcast data of the N + 1 channel or broadcast data of the N-1 channel received in the second step when changing a channel by a user input.

The operation method may include a fourth step of accessing an N + 1 channel group or an N-1 channel group; And a fifth step of receiving N + 2 channel broadcast data or N-2 channel broadcast data with low capacity from the channel group connected in the fourth step.

If there is no input for changing the channel of the user for a threshold time from the channel change time by the user input, broadcast data of N + 1 channel or broadcast data of N-1 channel from the channel group connected in the fourth step. A sixth step of receiving at a high capacity; And a seventh step of displaying the high capacity broadcast data received in the sixth step.

According to the present invention, data of a channel currently being watched is received at a high capacity, and data of an adjacent channel of a channel currently being watched is received at a low capacity, thereby immediately displaying broadcast data of a low capacity when a channel is changed. Therefore, when the channel is changed, it is possible to display the screen of the adjacent channel immediately, thereby reducing the delay time of the channel change and increasing the user experience quality QOE.

In addition, when the user's channel search is completed, it is possible to increase the perceived quality QOE that the user feels by determining and displaying the broadcast data of high capacity again.

Although receiving the broadcast data of the adjacent channel increases the total amount of data received by the peer, the broadcast data of the adjacent channel is received at a low capacity, so there is almost no increase in the total data amount.

Hereinafter, symbols used to explain the present invention are shown in Table 1 below.

P Peer N Start channel before changing channel N + 1, N-1 Immediately above the start channel, directly below the channel: The immediate channel immediately below the channel does not mean a channel with a higher or lower number, but a channel that is changed when the user issues a channel up / down command. For example, there are 6, 7, 9, and 11 TV channels in Korea. If N = 9, N + 1 = 11 and N-1 = 7. P (N + 1) P denotes a peer, and () denotes a channel that the peer is currently watching. θ Channel change delay time
= Tdelay-Tchange, Tdelay> Tchange
0, Tdelay <Tchange

The peer of the present invention simultaneously receives the adjacent channels N + 1 and N-1 together with the channel N selected by the user. However, adjacent channels are received encoded with low volume data to reduce bandwidth usage. By receiving adjacent channels together (N + 1 and N-1 are adjacent channels of N), when the user changes the channel, the adjacent channel data received together is displayed on the screen to eliminate the delay time caused by the channel change. For example, when a user of a peer is watching the N channel, the broadcast data of the N channel is received at a high capacity and displayed on the screen, and the broadcast data of the N + 1 and N-1 channels are received at a low capacity. Then, by directly displaying the low-capacity broadcast data received when the channel is changed from N → N + 1 or N → N-1, the user does not feel the delay time due to the channel change. Peers of each channel group have high capacity broadcast data of their own channel and low capacity broadcast data of adjacent channels. For example, a peer of an N-channel group has high capacity N-channel broadcast data and a low capacity of N + 1 and N-1 channel broadcast data, and a peer of an N + 1 channel group has a high capacity of N + 1 channel broadcast data and a low capacity of N And N + 2 channel broadcast data.

In addition, the present invention uses a method for improving the process of finding a valid peer of the changed channel group when changing the channel. While the user is correcting in one channel group, the tracker periodically receives the address of a valid peer in the channel group watching the adjacent channel. To do this, the tracker creates and manages a table that properly allocates valid peers of adjacent channels to peers in each channel group. Since the joining and leaving of the peers occurs frequently, the tracker periodically updates the table and sends it to the peers. When a channel change occurs from N → N + 1 or N → N-1, P (N) may connect to P (N + 1) or P (N-1) using information previously received from the tracker. By doing so, it is possible to reduce the time it takes for the peer to join the N + 1 group and the N-1 group. If P (N + 1) or P (N-1) has already changed to another channel when connected to a valid P (N + 1) or P (N-1) belonging to the changing channel group, the existing method Ask the tracker for the address of a valid peer for the channel group to change.

The foregoing and other objects, features and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings, in which: There will be. In the implementation of the present invention, when it is determined that the detailed description of the known technology related to the present invention may unnecessarily obscure the gist of the present invention, the detailed description thereof will be omitted. Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

3 is a diagram illustrating a process of changing a channel from N to N + 1 by a peer of a P2P broadcasting system according to the present invention.

In the drawing, the pattern part represents a channel displayed on the screen, and the thicknesses of N-1, N, N + 1, and N + 2 represent the capacity of broadcast data to be received.

Before the time T1, the peer connects to the N-channel group, receives the N-channel broadcast data in high capacity, displays it on the screen, and receives the N + 1 channel and N-1 channel broadcast data in low capacity.

When an input to change the channel from N to N + 1 is applied by the user input at the time T1, the peer displays the low-capacity N + 1 channel broadcast data previously received on the screen. As a result, the user does not feel a delay due to channel conversion. After a predetermined time (Tdelay), the peer accesses the N + 1 channel group. Here, Tdelay means a delay Tdelay for the peer to access the N + 1 group. In the present invention, since the peer uses a method of receiving valid address information of the adjacent channels N + 1 and N-1 in advance, the delay time Tdelay can be reduced. After the peer accesses the N + 1 channel group, the peer receives broadcast data of the N + 2 channel with low capacity in preparation for the next channel change.

If the user no longer changes the channel at N + 1 and the state exceeds the critical time, the peer determines that the user does not change the channel anymore and from the peer of the already connected N + 1 channel group It receives high-capacity N + 1 channel broadcast data and displays high quality clear screen. Td in the figure indicates the time taken to receive high capacity N + 1 channel broadcast data from peers of the N + 1 channel group. The threshold time is the channel search threshold time, which is the time when the user does not change the channel and determines that the user's channel search is finished. Naturally, the threshold time may be changed according to the setting (for example, the threshold time may be set as 5 seconds 10 seconds, etc.).

It is possible to receive high-capacity N-channel broadcast data from the N-channel group even after the critical time, but since there is a high possibility that the user will no longer search for a channel from the time after the threshold time has passed, the N + 1 channel It is preferable to connect only to a group to receive all broadcast data (high capacity N + 1, low capacity N, low capacity N + 2).

If the channel change of the peer is made as described above, when the channel change is made from N → N + 1, the delay time due to the channel change is excluded, except that the picture quality of the N + 1 channel is displayed in low quality for Tcritical + Td time. Will not feel.

In general, the user wants to reduce the delay caused by the channel change and display high quality image quality. However, when checking the contents of a channel while searching for a channel, it is not a problem even if the image quality is not clear. This means that viewers can choose to decide whether to continue watching this channel or move on to the next channel, even if the screen is not clear, because the delay is long when the channel is changed. Want. The present invention fulfills this need of the user. Of course, if it is determined that the user's channel search is over (if there is no channel change during critical), the corresponding channel is displayed in high quality, so that the user can enjoy a high quality screen.

In FIG. 3, the process of changing the channel from N → N + 1 has been described. The process of changing the channel from N → N-1 may be performed in the same manner.

FIG. 4 is a diagram illustrating a process of changing a channel from N to N + 1 → N + 2 by a peer of a P2P broadcasting system according to the present invention.

Before the time T1, the peer connects to the N-channel group, receives the N-channel broadcast data in high capacity, displays it on the screen, and receives the N + 1 channel and N-1 channel broadcast data in low capacity.

When an input to change the channel from N to N + 1 is applied by the user input at the time T1, the peer displays the low-capacity N + 1 channel broadcast data previously received on the screen. As a result, the user does not feel a delay due to channel conversion. After a certain time, the peer accesses the N + 1 channel group. After the peer accesses the N + 1 channel group, it receives the N + 2 channel broadcast data with low capacity from the peer of the N + 1 channel group in preparation for the next channel change.

When the user changes the channel from N + 1 to N + 2 at time T2, the peer displays the previously received low capacity N + 2 channel broadcast data on the screen. In the case of Tchange> Tdelay, since the channel is changed while the low capacity N + 2 channel broadcast data is already received, the low capacity N + 2 channel broadcast data is displayed on the screen without time delay. In the case of Tchange <Tdelay, after a delay of Tdelay-Tchange is delayed, N + 2 channel broadcast data of low capacity is displayed on the screen. After a predetermined time (Tdelay) from the T2 time, the peer connects to the N + 2 channel group and receives the low capacity N + 3 channel broadcast data from the N + 2 channel group in preparation for the next channel change.

After the T2 time, if the user does not change any more channels for more than the critical time, the peer determines that the user does not change the channel anymore, and a high capacity from the peer of the N + 2 channel group that is already connected Receives N + 2 channel broadcast data and displays high quality clear screen. Td represents the time taken to receive a high capacity N + 2 broadcast data from a peer of an N + 2 channel group.

It is also possible to receive high-capacity N-channel broadcast data and low-capacity N-1, N + 1 broadcast data from the N-channel group even after the threshold time has elapsed. Since there is a high possibility of not searching, it is preferable that a peer connects only to an N + 2 channel group to receive all broadcast data (high capacity N + 2, low capacity N + 1, low capacity N + 3).

In FIG. 4, the process of changing the channel from N → N + 1 → N + 2 has been described. The process of changing the channel from N → N-1 → N-2 may also be performed in the same manner.

5 is a diagram illustrating a process of changing a channel from N to N + 1 → N + 2 → N + 3 by a peer of a P2P broadcasting system according to the present invention.

The process of changing the channel from N → N + 1 → N + 2 is as described with reference to FIG. 4. If the user changes the channel to N + 2 at T2 time, and the user changes the channel to N + 3 at T3 time before the critical time, the peer displays the previously received low-capacity N + 3 channel broadcast data on the screen. Display.

When the channel change occurs three times continuously as described above, the connection with the N-channel group that was connected before T1 time is disconnected. Until T3 hours, the user could change the channel from N + 2 → N + 1, so the connection was maintained with the peer of the N channel group that was transmitting the N + 1 channel data, but if the channel was changed to N + 3 channel, The +1 channel is no longer an adjacent channel and thus disconnects from the N channel group. If the connection with the previous channel group is maintained, the user needs to connect with too many peers at the same time if the user keeps changing channels such as N + 3 → N + 4 → ... → N + M. Therefore, it is preferable to connect only with a peer for receiving channel data adjacent to a peer of a channel outputted on the current screen which was previously connected. That is, when the channel change by the user input is repeatedly repeated more than a preset number of times, the peer releases the connection with some of the previously connected channel groups. In the above example, when the user changes the channel up three times in succession, the user is disconnected from some of the previous channel groups. However, the number of times may be changed according to the setting. Depending on the condition of disconnecting the connection with the previous channel group may vary depending on the configuration.

If the user does not change the channel (watching N + 3 channels for more than the critical time) after T3 hours or more, the peer determines that the user's channel search is over, and the high capacity from the N + 3 channel group Receives N + 3 channel broadcast data and displays a high definition clear screen. In addition, as described above, after the critical time, it is preferable that the peer accesses only the N + 3 channel group to receive all data (high capacity N + 3, low capacity N + 2, low capacity N + 4).

In FIG. 5, a process of changing a channel from N → N + 1 → N + 2 → N + 3 has been described, but a process of changing a channel from N → N-1 → N-2 → N-3 may be performed in the same manner. Can be.

6 is a diagram illustrating a pseudo code representing a channel change method according to the present invention. 6 is a pseudo code representation of the above-described method, and a separate description thereof will be omitted.

Hereinafter, the delay time according to the channel change when the channel change is made in the same manner as the present invention. When the user changes from the current channel to the next channel, assuming that there are enough valid peers in the DSLAM to change the channel group, and if the user continuously changes the channel, whether to change to the next channel after viewing the screen of the changed channel Suppose you decide to continue watching this channel. And it is assumed that the head-end server can encode low-capacity video data consisting of only I-frames for all channels.

When the user changes to the N + 1 channel while watching the N channel (the first channel change), the delay time due to the channel change does not occur as shown in FIG. 7. If the N + 1 channel is watched for more than a critical time, the low capacity N + 2 and N channel broadcast data are received from the P (N + 1) together with the high capacity N + 1 channel broadcast data. If you look at the N + 1 channel and change it to N + 2 channel before the critical time (second channel change), there may be no delay or partial delay depending on the time you change the channel. It may be. That is, in FIG. 4, if Tchange is greater than Tdelay, no delay occurs due to channel change, but if Tchange is less than Tdelay, a partial delay θ occurs.

In FIG. 7, the black area is a delay time due to channel change, and the screen is not output during this time. Assuming that the user makes the second channel change after the first channel change as an exponential distribution, the probability density function of time t is expressed by Equation 1 below.

Since t = Tdelay-θ, the probability density function of the channel change delay time is shown in Equation 2 below.

Therefore, the expected value of delay time that occurs when changing the channel is expressed by Equation 3 below.

In Equation 3, λ means the inverse of the average value of the channel request time Tchange.

FIG. 8 is a chart showing an expected value of a channel change delay time according to a Tdelay value after a first channel change.

As shown in FIG. 8, as the Tdelay value increases, the E (θ) value also increases. In other words, the longer the delay time for receiving new channel data, the longer the average delay time for the user to change the channel. In addition, as the value of λ increases, the value of E (θ) also increases, which means that a large value of λ means that the average value of the time Tchange when a user changes a channel is small. Therefore, the quicker the user changes the channel, the longer the channel change delay time.

Equation 3 is to calculate the expected value of the channel change delay time assuming that the user changes the second channel. Therefore, if the user knows the probability of changing the channel after the reference time (t = 0), the expected value of the total delay time that occurs during the user's channel search can be obtained. The probability that the user changes the channel after the reference time can be obtained by the renewal process [D.E. Smith, "IP TV Bandwidth Demand: Multicast and channel surfing". IEEE INFOCOM'07, pp 2546-2550, Alaska, USA, May 2007]. That is, the user tosses a coin at the reference time to turn the channel when the front comes out and maintain the current channel when the back comes out. Toss a coin and toss it again in case of face up. If the front comes out again, change to the next channel. After changing the channel, keep tossing coins and searching for channels until the back side comes out. If the user throws a coin before the channel search threshold time (Tcritical) and the probability of the front face is Pt, the expected value of the total delay time caused by the channel change is expressed by Equation 4 below.

The first term in Equation 4 is 0 because the delay time due to the first channel change is zero. The expected value of the total channel change delay time according to the probability Pt of the user to change the channel by Equation 4 is shown in a chart as shown in FIG. 9. As shown in FIG. 9, the higher the probability that a user changes a channel, the larger the total channel change delay time, and the higher the probability value, the greater the degree.

The present invention described above is capable of various substitutions and modifications within the scope of the present invention to those skilled in the art without departing from the spirit of the present invention by the above-described embodiments and accompanying drawings It is not limited.

In particular, it is natural that various modifications can be made to set a range of adjacent channels for receiving low-capacity broadcast data and to maintain a connection with a range of channel groups.

1 is a diagram illustrating the configuration of a multi-chain IPTV system.

2 is a diagram illustrating a process in which a peer leaves an existing channel group CH1 and joins a new channel group CH2 by changing a channel of a user in a conventional IPTV system.

3 is a diagram illustrating a process of changing a channel from N to N + 1 by a peer of a P2P broadcasting system according to the present invention;

4 is a diagram illustrating a process of changing a channel from N to N + 1 → N + 2 by a peer of a P2P broadcasting system according to the present invention;

5 is a diagram illustrating a process of changing a channel from N to N + 1 → N + 2 → N + 3 by a peer of a P2P broadcasting system according to the present invention;

6 is a view showing a pseudo code representing a channel change method according to the present invention.

7 is a diagram illustrating a case where a delay occurs when a channel is changed.

8 is a graph showing a channel change delay time.

9 is a graph showing the total channel change delay time due to channel search.

Claims (8)

delete delete delete In the way that the peer of the P2P broadcasting system operates, A first step of receiving broadcast data of N channel with high capacity, receiving broadcast data of N + 1 channel and broadcast data of N-1 channel with low capacity, and displaying the broadcast data of N channel; A second step of displaying broadcast data of the N + 1 channel or broadcast data of the N-1 channel received in the first step when changing a channel by a user input; A third step of receiving and displaying broadcast data of the N + 1 channel or broadcast data of the N-1 channel with a high capacity when there is no channel change of the user for a threshold time from the channel change time by the user input; Operation method comprising a. delete In the way that the peer of the P2P broadcasting system operates, A first step of connecting to an N-channel group; Receiving the broadcast data of the N channel with a high capacity, receiving broadcast data of the N + 1 channel and broadcast data of the N-1 channel with a low capacity, and displaying the broadcast data of the N channel; A third step of displaying broadcast data of the N + 1 channel or broadcast data of the N-1 channel received in the second step when changing a channel by a user input; A fourth step of accessing the N + 1 channel group or the N-1 channel group; And A fifth step of receiving N + 2 channel broadcast data or N-2 channel broadcast data at a low capacity from the channel group connected in the fourth step; If there is no input related to the channel change of the user for a threshold time from the channel change time by the user input, A sixth step of receiving N + 1 channel broadcast data or N-1 channel broadcast data with a high capacity from the channel group connected in the fourth step; And A seventh step of displaying the high capacity broadcast data received in the sixth step; Operation method characterized in that it further comprises. In the way that the peer of the P2P broadcasting system operates, A first step of connecting to an N-channel group; Receiving the broadcast data of the N channel with a high capacity, receiving broadcast data of the N + 1 channel and broadcast data of the N-1 channel with a low capacity, and displaying the broadcast data of the N channel; A third step of displaying broadcast data of the N + 1 channel or broadcast data of the N-1 channel received in the second step when changing a channel by a user input; A fourth step of accessing the N + 1 channel group or the N-1 channel group; And A fifth step of receiving N + 2 channel broadcast data or N-2 channel broadcast data at a low capacity from the channel group connected in the fourth step; When the channel change by the user's input is repeatedly repeated more than a preset number of times, The peer releases a connection with some of the previously connected channel groups. The method of claim 6, The peer, And periodically receiving an address of an adjacent channel of a channel group to which the channel is currently connected.

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