KR20160106994A - System for streaming layered video in the wireless LAN and method thereof - Google Patents

Abstract

A hierarchical video streaming system in a wireless LAN according to an embodiment of the present invention is a hierarchical video streaming system in a wireless LAN for transmitting video packets, the system comprising: a bandwidth measurement module for measuring an available bandwidth; And a packet transmission module for layering video data into a hierarchical structure including one base layer and one or more enhancement layers and allocating video packets layered according to the available bandwidth to a plurality of AC (Access category) . ≪ / RTI >

Description

Technical Field [0001] The present invention relates to a hierarchical video streaming system and a method thereof in a wireless LAN,

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hierarchical video streaming system and method in a wireless LAN, and more particularly, to a technique for streaming video hierarchically without degrading video quality in a wireless LAN environment.

When providing a high-quality H.264 / AVC video stream in a broadcast service in an IP-based wired and wireless network environment, the available bandwidth of the receiving terminal decreases due to network congestion and jitter, Thereby making it impossible to guarantee a seamless video streaming service.

In order to solve this problem, in the prior art, a video stream is re-encoded using a bit-rate transcoding according to the dynamically changing loss rate of the network bandwidth, or a scalable video (SVC) coding technique, a video stream is layered and coded according to the performance of the receiving terminal in advance to selectively receive the video stream in accordance with the available bandwidth of the receiving terminal.

However, the method using the transcoder has difficulty in adaptively converting and transmitting high-quality video packets in real time to the available bandwidth reduced due to the change of the transmission environment of the network. This is because it is difficult to guarantee QoS of a video packet due to a coding delay and an image deterioration phenomenon occurring in a process of re-encoding a high-quality video packet to an available bandwidth. In addition, when the available bandwidth of a plurality of receiving terminals watching the same broadcasting program changes independently, it is difficult to convert high-quality video packets into a transcoder in real time according to the available bandwidth allowed by each receiving terminal, .

In the method using the SVC technology, it is difficult to process high-quality video packets in real time by coding video packets in accordance with the available bandwidth of the receiving terminal in advance. In addition, there is a problem in that there is a lot of overhead for determining a layered stream according to the performance of a receiving terminal.

Patent Publication No. KR 2005-0065979

An embodiment of the present invention provides a hierarchical video streaming system and a method thereof in a wireless LAN that can guarantee QoS (Quality of Service) by hierarchically streaming video packets using a wireless LAN access point in a wireless LAN environment I want to.

A hierarchical video streaming system in a wireless LAN according to an embodiment of the present invention is a hierarchical video streaming system in a wireless LAN for transmitting video packets, the system comprising: a bandwidth measurement module for measuring an available bandwidth; And a packet transmission module for layering video data into a hierarchical structure including one base layer and one or more enhancement layers and allocating video packets layered according to the available bandwidth to a plurality of AC (Access category) . ≪ / RTI >

In addition, the packet transmission module may allocate a video packet of the base layer to a first AC, allocate a video packet of the first enhancement layer to a second AC, when the one or more enhancement layers are the first to third enhancement layers, AC, allocating the video packets of the second enhancement layer to the third AC, and allocating the video packets of the third enhancement layer to the third AC.

In addition, the first AC that has allocated the video packet of the base layer may transmit in the first priority order.

In addition, the packet transmission module may define the allocation of the plurality of ACs using a ToS (Type of Service) field value of the video packet.

The bandwidth measurement module may calculate a current available bandwidth and transmit the current available bandwidth to the packet transmission module. The packet transmission module may determine a change in the current available bandwidth, The AC can be reallocated according to the rate of change of the current available bandwidth.

In addition, the packet transmission module reallocates the AC according to whether the number of the base layer and the enhancement layer is reducible when the current available bandwidth decreases, and when the current available bandwidth increases, And reassign the AC depending on whether the number of enhancement layers is increasing.

In accordance with another aspect of the present invention, there is provided a hierarchical video streaming method in a wireless local area network (WLAN), the method comprising: receiving a video streaming request from a receiving terminal, Layering video packets; Allocating an access category (AC) for each layered video packet; And the streaming server transmitting the video packet including the AC allocation information to the receiver to perform video streaming.

In addition, layering the video packets may layer the video packets into one base layer and one or more enhancement layers.

In addition, when the one or more enhancement layers are referred to as first to third enhancement layers, a video packet of the base layer is allocated to a first AC, a video packet of the first enhancement layer is allocated to a second AC, 2 enhancement layer video packets to the third AC and the video packets of the third enhancement layer to the third AC.

In addition, the step of allocating the AC for each layered video packet may define the allocation of the plurality of ACs using the ToS (Type of Service) field value of the video packet.

The method may further include, after the step of performing the video streaming, determining whether a loss of a video packet is lost in the receiving terminal and delivering the loss state information of the video packet to the streaming server when loss of the video packet occurs .

Measuring a change in a current available bandwidth of the streaming server when packet loss occurs during the video streaming; And reallocating the AC according to the change of the available bandwidth.

The reallocating AC according to the change of the available bandwidth may reallocate the AC according to whether the number of the base layer and the enhancement layer is reducible when the current available bandwidth is decreased.

In addition, in the step of reallocating the AC according to the change of the available bandwidth, the AC can be reallocated depending on whether the number of the base layer and the enhancement layer can increase when the current available bandwidth increases.

The present technology can enhance the quality of service (QoS) of video streaming by performing hierarchical video streaming using a wireless LAN access point without an additional module.

1 is a block diagram of a hierarchical video streaming system in a wireless LAN according to an embodiment of the present invention.
FIG. 2 is a table showing the AC allocation according to the ToS field value of the WLAN access point according to the embodiment of the present invention.
3 is a diagram for explaining a ToS-based AC allocation method in a wireless LAN access point according to an embodiment of the present invention.
4 is a flowchart illustrating a hierarchical video streaming method in a wireless LAN according to an embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings, in order to facilitate a person skilled in the art to easily carry out the technical idea of the present invention.

The present invention assumes an environment in which a receiving terminal receives a video streaming service in an IEEE 802.11e based wireless LAN network. The hierarchical video streaming in the wireless LAN of the present invention also utilizes a layer of video packets and an AC allocation of 802.11e.

Hereinafter, embodiments of the present invention will be described in detail with reference to FIGS. 1 to 4. FIG.

 1 is a block diagram of a hierarchical video streaming system in a wireless LAN according to an embodiment of the present invention.

A hierarchical video streaming system in a wireless LAN according to an exemplary embodiment of the present invention includes a receiving terminal 100, a wireless LAN access point 200, and a streaming server 300.

The receiving terminal 100 receives the video packet from the streaming server 300 through the wireless LAN access point 200. [ At this time, the receiving terminal 100 may include a station (laptop, PDA, smart phone, etc.) equipped with a wireless LAN device capable of interfacing with a wireless network.

To this end, the receiving terminal 100 includes a packet receiving module 110 and a bandwidth measuring module 120. The packet receiving module 110 receives the video packet transmitted from the streaming server 300 and determines whether the packet is damaged. When the packet is damaged, the packet receiving module 110 notifies the streaming server 300 of the packet loss occurrence status. The bandwidth measurement module 120 calculates the available bandwidth. At this time, packet corruption occurs when the available bandwidth is insufficient.

The WLAN access point 200 connects a receiving terminal 100 and an Internet network in a wireless LAN environment and serves as a bridge between wireless and wired networks. Wireless LAN is a network that can transmit and receive data between stations within a certain distance without wiring on the floor as in a general LAN, and the stations are free to move within the wireless LAN.

The WLAN access point 200 provides an AC (Access category) based differentiating service to provide a high level of QoS and supports a total of four ACs. That is, the WLAN access point 200 has four transmission queues associated with each AC, and the transmission amount of each queue is different according to the characteristics of the traffic (refer to FIG. 3). For example, a base layer having a high priority among audio or video packets is allocated to a high priority AC, and an enhancement layer such as a background data packet is classified as an AC having a low priority.

The WLAN access point 200 stores an AC allocation table for each type of service (ToS). 2, assuming that the ToS field value of the received video packet is 0 to 63, a field value from 0 to 15 is allocated to AC_BK, and a field up to 16-31 Value is assigned to AC_BE, field values from 32-47 are assigned to AC_VI, and field values from 48-63 are assigned to AC_VO. The ToS field value of the packet includes priority information of the packet. 2, the higher the ToS field value is, the higher the priority is, but the present invention is not limited to this, and the priority order according to the ToS field value can be variously set. The AC allocation information for each ToS field value is stored in advance in the wireless LAN access point 200 in the form of a table as shown in FIG.

In addition, the ToS field consists of a total of 8 bits of the IP packet header, and 1 bit is not currently used but a total of 7 bits are used. Three of the six bits are the PRECEDENCE field and four bits are used for data processing.

3, when the WLAN access point 200 receives a video packet from the streaming server 300, the wireless LAN access point 200 allocates AC to the receiving terminal 100 according to the ToS field value. At this time, AC can be called a queue. For example, if the value of the ToS field of the video packet is "33 ", the WLAN access point 200 allocates the video packet to AC_VI and transmits it to the receiving terminal 100. [

The streaming server 300 layers the video packets and determines layered video packets for each AC, and layer-layered video packets are layered by AC through the WLAN access point 200 and transmitted.

To this end, the streaming server 300 includes a packet transmission module 310 and a bandwidth measurement module 320.

The packet transmission module 310 layer the video packets, select the number of transport layers of the layered video packets according to the current available bandwidth, and allocate AC according to the number of selected transport layers. At this time, the video packet is composed of a bit stream of a base layer and a bit stream of an enhancement layer, and the video packet is composed of one base layer and one or more enhancement layers. At this time, the frames in each layer may be divided into two or more slices for parallel processing, and each slice may include a plurality of consecutive macroblocks. In addition, the packet transmission module 310 allocates the base layer to the high priority AC and the enhancement layer to the low priority AC, and transmits the AC to the wireless LAN access point 200.

The bandwidth measurement module 320 calculates the current available bandwidth and transmits the calculated available bandwidth to the packet transmission module 310.

Hereinafter, a hierarchical video streaming method in a wireless LAN according to an embodiment of the present invention will be described with reference to FIG.

First, it is assumed that the WLAN access point 200 stores a table in which an AC is allocated for each ToS field value of a packet (S101). For example, as shown in FIG. 2, four queues AC_VO, AC_VI, AC_BE, and AC_BK are stored for each ToS field value.

When the receiving terminal 100 requests the streaming server 300 for video streaming using the wireless LAN access point 200 in step S102, the streaming server 300 layers the video packets in step S103. For example, video packets can be layered into one base layer and three enhancement layers, allowing the base layer to be preferentially transmitted.

The streaming server 300 allocates an AC for each layer of the video packet according to the bandwidth (S103). For example, the base layer is allocated to AC_VO among four queues, and the first enhancement layer is allocated to AC_VI, the second enhancement layer is allocated to AC_BE, and the third enhancement layer is allocated to AC_BK. That is, a value between 48 and 63 is stored in the ToS field of the video packet including the base layer, a value between 32 and 47 is stored in the ToS field of the video packet including the first enhancement layer, A value between 16 and 31 is stored in the ToS field of the video packet and a value between 0 and 15 is stored in the ToS field of the video packet including the third enhancement layer.

Thereafter, the streaming server 300 performs streaming for each video packet layered to the receiving terminal 100 through the wireless LAN access point 200 (S105). That is, if the value of the ToS field for each packet is set according to the AC allocation in step S103 and then transmitted, the WLAN access point 200 checks the ToS field value of the received packet, To the receiving terminal (100).

Then, the packet receiving module 110 of the receiving terminal 100 determines whether a loss of a packet occurs while receiving the packet (S106).

When packet loss occurs, the receiving terminal 100 notifies the streaming server 300 that packet loss has occurred (S107). The streaming server 300 again calculates the available bandwidth (S108). At this time, the bandwidth is calculated using a conventional method, so a detailed description thereof will be omitted.

Then, the streaming server 300 determines whether the bandwidth is increased or decreased (S109). When the bandwidth decreases, the streaming server 300 determines whether the number of transport layers can be reduced, and reallocates the AC (S110). In this case, the number of transport layers refers to the number of the base layer, the enhancement layer, and the like. For example, when two enhancement layers are allocated to the AC_VI, the streaming server 300 adjusts to allocate only one enhancement layer to the AC_VI if the bandwidth decreases.

On the other hand, if the bandwidth increases, the streaming server 300 confirms whether the number of transport layers can be increased, and reallocates the AC (S111). For example, when one enhancement layer is allocated to the AC_VI, the streaming server 300 adjusts the two enhancement layers to be allocated to the AC_VI when the bandwidth decreases.

Thereafter, the streaming server 300 continues video streaming with the reallocated AC (S112).

As described above, the present invention utilizes AC of IEEE 802.11e in hierarchical video streaming operation, and prevents a video quality degradation due to packet loss. That is, the wireless LAN access point 200 allocates the layered video packets on a predetermined AC basis by using AC information for each ToS field value already stored in the wireless LAN access point 200.

At this time, since a video packet containing information of the base layer is allocated to the AC having a high priority, a loss occurs first from the packet of the enhancement layer. The receiving terminal 100 notifies the streaming server 300 that a packet loss has occurred, and the streaming server 300 calculates a bandwidth available at present. Then, it selects a layer of video to be transmitted in accordance with the new bandwidth and reassigns to which AC each layer is assigned.

Therefore, the present invention utilizes the To-S-specific AC information already stored in the existing WLAN access point 200 and does not add a separate function or physical equipment to the WLAN access point 200, Do not.

However, in the present invention, a layered video packet is hierarchically layered and transmitted by each AC, so that the video packets are classified into VoIP, Web casting, video telephony, Video conferencing, and streaming services.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, It should be regarded as belonging to the claims.

Claims (15)

A hierarchical video streaming system in a wireless LAN for transmitting video packets,
A bandwidth measurement module for measuring available bandwidth; And
A packet transmission module for layering video data into a hierarchical structure including one base layer and one or more enhancement layers, and assigning video packets layered according to the available bandwidth to a plurality of access categories (AC);
A streaming server
Wherein the hierarchical video streaming system comprises: The method according to claim 1,
Wherein the packet transmission module comprises:
If the one or more enhancement layers are referred to as first to third enhancement layers,
Assigning a video packet of the base layer to a first AC, assigning a video packet of the first enhancement layer to a second AC, assigning a video packet of the second enhancement layer to a third AC, And assigning a video packet to a third AC. The method of claim 2,
Wherein a first AC assigned a video packet of the base layer is transmitted in a first priority order. The method according to claim 1,
Wherein the packet transmission module comprises:
Wherein the allocation of the plurality of ACs is defined using a ToS (Type of Service) field value of the video packet. The method according to claim 1,
Wherein the bandwidth measurement module comprises:
When receiving the packet loss state information from the receiving terminal, calculates the current available bandwidth and delivers the current available bandwidth to the packet transmission module. The method of claim 5,
Wherein the packet transmission module determines a change in the current available bandwidth and reallocates the AC according to a rate of change of the current available bandwidth. The method of claim 6,
Wherein the packet transmission module comprises:
If the current available bandwidth decreases,
Allocating the AC according to whether the number of the base layer and the enhancement layer is reducible,
If the current available bandwidth increases,
And reallocates the AC according to whether the number of the base layer and the number of enhancement layers can be increased. A method for performing hierarchical video streaming between a streaming server and a receiving terminal,
Layering a video packet in the streaming server when the video streaming is requested from the receiving terminal;
Allocating an access category (AC) for each layered video packet;
Wherein the streaming server transmits a video packet including the AC allocation information to the receiver and performs video streaming
The method comprising the steps of: The method of claim 8,
Wherein layering the video packet comprises:
Wherein the video packets are layered into one base layer and one or more enhancement layers. The method of claim 9,
If the one or more enhancement layers are referred to as first to third enhancement layers,
Assigning a video packet of the base layer to a first AC, assigning a video packet of the first enhancement layer to a second AC, assigning a video packet of the second enhancement layer to a third AC, And assigning a video packet to a third AC. The method of claim 8,
Wherein the step of allocating an AC for each layered video packet comprises:
Wherein the allocation of the plurality of ACs is defined using a ToS (Type of Service) field value of the video packet. The method of claim 8,
After performing the video streaming,
Determining whether a loss of a video packet is lost or not by the receiving terminal and delivering the loss state information of the video packet to the streaming server when loss of the video packet occurs;
The method of claim 1, further comprising: The method of claim 12,
Measuring a change in a current available bandwidth of the streaming server when packet loss occurs during the video streaming; And
And reallocating the AC according to the change in the available bandwidth
The method of claim 1, further comprising: 14. The method of claim 13,
The step of reallocating the AC according to the change of the available bandwidth comprises:
If the current available bandwidth decreases,
And reassigning the AC according to whether the number of the base layer and the number of the enhancement layers is reducible. 14. The method of claim 13,
The step of reallocating the AC according to the change of the available bandwidth comprises:
If the current available bandwidth is increased, reallocating the AC according to whether the number of the base layer and the enhancement layer can be increased.

Images