CN105516109B - A kind of transmission dispatching method ensureing wireless multi-hop network transmission of video service quality - Google Patents

Abstract

The invention discloses a transmission scheduling method for ensuring the service quality of real-time video transmission in a wireless multi-hop network. By dividing the video file according to the transmission and processing capabilities of the multi-hop links in the network, and sending them to the target node from multiple paths in sequence, the ratio of each code stream can be transcoded on each link and arrive in order receiving node. By eliminating the mutual waiting of each code stream on each link to avoid the problem of out-of-order and reordering of data packets at the receiving end in traditional multi-path transmission, effectively reducing the startup delay and buffer requirements of the receiving end, and enabling real-time playback .

Description

A transmission scheduling method to ensure the quality of service of wireless multi-hop network video transmission

technical field

The invention belongs to the technical field of wireless networks, and relates to a data transmission scheduling method, in particular to a transmission scheduling method capable of ensuring the service quality of real-time video transmission of multiple wireless networks.

Background technique

With the development of video coding and wireless multi-hop networks, real-time video communication under wireless multi-hop networks has become a development trend. However, due to the heterogeneity between networks and devices, the bandwidth and display capabilities of wireless terminals vary. Therefore, the high-quality code stream on some terminals cannot meet the requirements of other terminal equipment without transcoding. In the video communication in the wireless multi-hop network, the receiver hopes to play the received video uninterrupted and smooth in real time, which puts forward high requirements on the quality of service of the network. Because multi-path transmission has better flexibility than single-path transmission, it can effectively avoid congestion and increase the overall utilization of the network. Therefore, multi-path transmission has been widely studied for real-time multimedia services in multi-hop networks.

At the sending node, the video stream is encoded into N streams by the encoder. When N>1, it is called multi-stream encoding. The N code streams are assigned by the traffic distribution system to the m paths discovered by the multi-path routing protocol for network transmission. For traditional multi-path transmission, the sending node simply divides the video stream into blocks, and uses strategies such as polling to send these data blocks sequentially from multiple paths. Due to the different delays of multiple paths, the data packets do not arrive at the receiving node in a sequential manner. After the receiving node receives the packet, it cannot play it immediately. It needs to wait for the packet on the path with the longest delay to arrive and first reorder all the out-of-order packets, and then play them sequentially. This method has high requirements on the processing ability and buffering ability of the receiving node, and needs to reorder the data packets in real time, and at the same time needs to wait for a long time, which is not ideal for users. Therefore, there should be a real-time multi-path video transmission method in the wireless multi-hop network, which can transmit video transmission through multi-path between different network terminals. When the code stream reaches the receiving node, it does not need to be buffered and sorted by reordering. playback directly.

Contents of the invention

The purpose of the present invention is to overcome the problems existing in the existing wireless multi-hop network video transmission technology, and propose a transmission scheduling method to ensure the service quality of real-time video transmission in the wireless multi-hop network. By dividing the video files according to the transmission and processing capabilities of the multi-hop links in the network, and sending them from multiple paths to the target node in sequence, the ratio of each code stream can be transcoded on each link and arrive in order receiving node. By eliminating the mutual waiting of each code stream on each link, the problem of out-of-order and reordering of data packets at the receiving end in traditional multi-path transmission is avoided, which effectively reduces the start-up delay and buffer requirements of the receiving end, and enables real-time playback .

The technical scheme that adopts in order to solve the above-mentioned technical problem is as follows:

In order to achieve the above tasks, the present invention adopts the following technical solutions:

A transmission scheduling method that guarantees the service quality of real-time video transmission in a wireless multi-hop network. In a wireless multi-hop network, there are multiple communication links between a video sending node and a receiving node. The transcoding processing capability of the relay node on multiple communication links, the communication capability of the link between the sending node and the relay node, and the communication capability of the link between the relay node and the receiving node are allocated, and the allocated The video files are sent to the target node from the multiple communication links in sequence.

Further, when the video file is transmitted, the specific distribution and sending method of the video file is as follows:

The sending node divides the video file according to the following three system parameters, and sends it to the target node from multiple communication links in order, so that the ratio of each code stream can be transcoded on each communication link, and the sequence reaches the reception node:

①The video transcoding speed of each relay node relative to the standard processor; ②The transmission speed of each link between the sending node and the relay node relative to the standard link, the link between each relay node and the receiving node The transmission speed of the channel relative to the standard link; and: ③The compression ratio after video transcoding.

Further, when video files are transmitted, the proportion of video files allocated on multiple communication links between the sending node and the receiving node is:

The sending node divides the video file into m code streams, remember that α _i is the percentage of the video file assigned to the i-th path by the sending node, then:

During video file transmission, the optimal code stream transmission timing is:

Order in the above formula:

Available:

α _i =g _i α _i-1 (4)

It can be obtained from the above formula:

According to formula (1) (5) can get:

Then the proportion of video files that the sending node should send to the first link can be obtained as:

According to formula (4), the proportions of video files on other links can be obtained as follows:

In formulas (1) to (8), y _i is the transcoding speed of the relay node n _i relative to the standard processor, z _i is the speed of the link between the sending node and the relay node relative to the standard link transmission speed, z' _i is the transmission speed of the link between the relay node and the receiving node relative to the standard link, is the compression ratio after transcoding, T _tc is the time for the entire video file transcoding process to be completed on the standard processor, T _cm is the time for transmitting all input data of this video file on the standard link; K is the video file transmission time The number of relay nodes in the process.

Compared with the prior art, the present invention has the following technical characteristics:

The present invention divides the video file according to the transmission capability of the multi-hop link in the network and the transcoding processing capability of the relay node, and sends it from multiple paths to the target node in order, so that the ratio of each code stream can be just in each After transcoding on the link, they arrive at the receiving node in sequence. By eliminating the mutual waiting of each code stream on each link, the problem of out-of-order and reordering of data packets at the receiving end in traditional multi-path transmission is avoided, which effectively reduces the start-up delay and buffer requirements of the receiving end, and enables real-time playback .

Description of drawings

Fig. 1 is the real-time video service multi-path transmission architecture of the present invention;

Fig. 2 is wireless multi-hop network topological structure of the present invention;

Fig. 3 is a sequence diagram of multi-code stream transmission in the present invention;

FIG. 4 is a performance diagram of video transmission delay in the present invention.

Detailed ways

According to the above technical solution, as shown in Figures 1 to 4, the present invention proposes a transmission scheduling method that can guarantee the service quality of real-time video transmission on multiple wireless networks. Reach the receiving node, and consider the actual processing capacity of the link to maximize the application efficiency of the link.

Basic scheme of the present invention is:

A transmission scheduling method that guarantees the service quality of real-time video transmission in a wireless multi-hop network. In a wireless multi-hop network, there are multiple communication links between a video sending node and a receiving node. The transcoding processing capability of the relay node on multiple communication links, the communication capability of the link between the sending node and the relay node, and the communication capability of the link between the relay node and the receiving node are allocated, and the allocated The video files are sent to the target node from the multiple communication links in sequence.

When the present invention transmits video files between the sending node and the receiving node, the main considerations are the transcoding processing capabilities of all relay nodes between the sending node and the receiving node, and the link between the sending node and the relay node. Communication capability and the link communication capability between the relay node and the receiving node. According to these conditions, the file transmission is allocated reasonably, so that each link can be allocated a code stream that meets the current link load capacity, so that Maximize the transmission efficiency of each segment of the link. In addition, by adopting this transmission method, the time when each divided code stream arrives at the receiving node can be considered at the same time, which not only enables the transmission task to be completed in the shortest time, but also does not need to be reordered when the code stream arrives at the receiving node. Buffering and sequencing for direct playback.

A specific way to consider the above-mentioned transcoding capabilities of relay nodes and link communication capabilities between nodes is:

When video files are transferred, the specific allocation and sending methods of video files are as follows:

The sending node divides the video file according to the following three system parameters, and sends it to the target node from multiple communication links in order, so that the ratio of each code stream can be transcoded on each communication link, and the sequence reaches the reception node:

①The video transcoding speed of each relay node relative to the standard processor; ②The transmission speed of each link between the sending node and the relay node relative to the standard link, the link between each relay node and the receiving node The transmission speed of the channel relative to the standard link; and: ③The compression ratio after video transcoding.

As shown in FIG. 2 , it is a topological structure diagram of the wireless multi-hop network involved in the present invention. In this scheme, there are m paths from the source node n _s to the destination node n _d in the network. There are a total of m+2 nodes in the network, where n _s represents the sending node, n _d represents the receiving node, and the relay nodes are respectively represented as n _i , i=1,...,m. The communication link between the sending node and the relay node is denoted as l _s,i , i=1,....,m respectively, and the communication link between the relay node and the receiving node is respectively denoted as l _i,d , i=1, ....m to represent.

The sending node divides the video file into m code streams, and sends these code streams to the receiving node from m paths. Definition α _i is the percentage of video files assigned to the i-th path by the sending node. It can be seen from the definition that:

Obtain the transcoding speed y _i of node n _i relative to the standard processor; the transmission speed z _i of the link l _i relative to the standard link; the compression ratio after transcoding Definition T _tc is the time for the entire transcoding service to be completed on the standard processor, and T _cm is the time for transmitting all input data of this video file on the standard link, so α _i y _i T _tc is the time for the relay node n _i to transfer α _i z _i T _cm is the time when the node sending node n _s sends the corresponding code stream to the relay node n _i through the l _s,i link, α _i z' _i T _cm is the The time when the following node n _i sends the corresponding transcoded code stream to the receiving node n _d through the link l _i,d .

The above-mentioned standard processor and standard link refer to any processor and link, and may be any processor and link in the network. That is to say, a communication link is usually taken, and its communication delay is used as a reference standard, and the standard link is defined as a link with z _i =1; a processor is taken, and its processing speed is used as a reference standard, and the standard processor is defined as y _i =1 processor.

In order to see the transmission timing of each code stream more intuitively, please refer to Figure 3. It can be seen from the figure that the optimal code stream transmission timing is:

Order in the above formula:

Available:

α _i =g _i α _i-1 (4)

It can be obtained from the above formula:

According to formula (1) (5) can get:

Then the proportion of video files that the sending node should send to the first link can be obtained as:

According to formula (4), the proportions of video files on other links can be obtained as follows:

The start-up delay of the receiving node is the time when the video stream is sent on the first path, which is:

In the above formula, g _i and g _j are the same parameter, but the subscripts are different; z _i is the l _{s, i} link (that is, the link between the sending node and the relay node) relative to the standard link is the transmission speed of the link, z' _i is the transmission speed of the l _i,d link (that is, the link between the relay node and the receiving node) relative to the standard link, and K is the relay in the entire video transmission system number of nodes.

In the wireless multi-hop network, according to the transcoding processing capability and link transmission capability of the relay node in the network, the internal link that can sequentially transmit the segmented video to the receiving node according to the sequence of multi-path links can be obtained by the above steps. The proportion of video transmission tasks that should be allocated on the link and the shortest overall service transmission time, so that the proportion of each stream can be transcoded on each link and then arrive at the receiving node in sequence. By removing the mutual waiting of each code stream on each link, it avoids the problem of data packet disorder and reordering at the receiving end in traditional multi-path transmission, effectively reduces the startup delay and buffer requirements of the receiving end, and can perform real-time playback.

Specific cases and analysis:

The correctness and effectiveness of the proposed method are verified by the built experimental platform, and the results are analyzed.

The test uses a sequence of video files to test the transmission performance of the method of the present invention. Use an MPEG-2 encoder to generate a code rate of 4Mbit/s, D1 format (720*576) and a frame rate of 25 frames/s. The Group of Pictures (GOP) structure is (15,3). The display resolution of the terminal equipment is CIF format (352*288). Code rate after transcoding: the code rate of the basic layer is 325.4Kbit/s, the code rate of the truncated FGS layer is 327.5Kbit/s, and the frame rate remains unchanged.

In the network environment where the number of relay nodes is 1 to 9 nodes respectively, the video transmission delay comparison is carried out for the method proposed in the patent of the present invention. Set the available bandwidth of the link to be evenly distributed between 1 and 10Mbps. Deploy a pair of source node and destination node on both sides of the relay node.

Figure 4 shows the time delay from when the sending node starts to send the video file to when the receiving node can play back the video file under the multi-path video transmission method. The results show that this method can reduce the video transmission delay, that is, the start-up delay of the receiver, which is beneficial to the transmission of multimedia services with high real-time requirements. Moreover, in a general wireless multi-hop network video transmission scheduling method, the receiving node needs to wait for the arrival of data on all paths before starting to play the video stream. In this case, the buffer size requirement is relatively high, and the start-up delay is relatively large, which is the delay of the longest path. The transmission scheduling method proposed by the present invention to ensure the quality of service of real-time video transmission in wireless multi-hop networks can ensure the continuous arrival of data in order, and does not need to reorder them at the receiving node. At this time, the buffer requirement is larger than that in general reduce.

Claims (3)

1. a kind of transmission dispatching method ensureing wireless multi-hop network transmission of video service quality, which is characterized in that wireless more It jumps in network, there are multiple communication links between video sending node and receiving node, in video file transfer, by video text Part according between the transcoding processing capacity of the relay node on this multiple communication links, sending node and relay node link it is logical The communication capacity of link is allocated between letter ability, relay node and receiving node, and by the video file after distribution according to Sequence is sent from the multiple communication links to destination node.

2. ensureing the transmission dispatching method of wireless multi-hop network transmission of video service quality, feature as described in claim 1 It is, in video file transfer, the specific distribution of video file and sending method are：

Sending node is split video file according to following three systematic parameters, sequentially to target from multiple communication links Node is sent so that the ratio of each code stream just can sequentially reach receiving node on each communication link after transcoding：

1. video code conversion speed of each relay node relative to standard processor；2. each sending node is to chain between relay node Transmission speed, each relay node biography to link receiving node between relative to standard link of the road relative to standard link Defeated speed；And：3. the compression ratio after video code conversion.

3. ensureing the transmission dispatching method of wireless multi-hop network transmission of video service quality, feature as claimed in claim 2 It is, in video file transfer, the video file ratio that is distributed on the multiple communication links between sending node and receiving node Example be：

Video file is divided into m code stream by sending node, remembers α_iIt is the video file hundred that sending node distributes to the i-th paths Divide ratio, then has：

In video file transfer, bit stream sequential is：

It is enabled in above formula：

It can obtain：

α_i=g_iα_i-1 (4)

As available from the above equation：

It can be obtained according to formula (1) (5):

The video file ratio that sending node should be sent to first link, which can then be obtained, is：

The video file ratio that other chain roads can be obtained according to formula (4) is respectively：

In formula (1) to (8), y_iFor relay node n_iRelative to the transcoding speed of standard processor, z_iFor sending node and relaying Transmission speed of the link relative to standard link between node, z'_iLink between relay node and receiving node is opposite In the transmission speed of standard link,For the compression ratio after transcoding, T_tcIt is entire video file transcoding process in standard processor The time of upper completion, T_cmIt is the time for fully entering data that this video file is transmitted on standard link；K is video file Relay node number in transmission process.