KR100931376B1 - The network-adaptive method for controlling data stream transmission and the system thereof - Google Patents

Abstract

PURPOSE: A control method and a control system for transmitting a network adaptive data stream are provided to offer an improved QoS by previously eliminating the data of a lower priority in an application layer. CONSTITUTION: The control method for transmitting a network adaptive data stream includes the steps of: calculating total packet loss rate in a determined period; identifying a priority and type of a created transmission-predetermined data by parsing the transmission-predetermined data; calculating a packet elimination rate from the transmission-predetermined data of a lower priority by using the total packet loss rate; filtering the transmission-predetermined data by removing a part of the transmission-predetermined data according to the packet elimination rate; and mapping the filtered transmission-predetermined data in each access category according to their priority.

Description

A network adaptive data stream transmission control method and system

The present invention relates to a network adaptive data stream transmission control method and system, and more particularly, to provide an improved QoS and system by removing in advance the low-priority data determined to be less likely to be transmitted based on the packet loss rate in the application layer The present invention relates to a network adaptive data stream transmission control method and system that enables efficient management of resources.

Wireless network environment provides extended mobility and convenience that wired network environment cannot provide, but packet loss and packet retransmission occur more frequently due to unstable channel condition than wired network environment. As a result, there is a problem in that the quality of a service having a time constraint such as video streaming is degraded.

For efficient multimedia transmission in such wireless networks, IEEE 802.11e, which recently enhanced the Qos function, has been standardized. Conventional wireless network environments that transmit video streams are essentially systems based on best-in-class services, and are not suitable for guaranteeing quality of time-constrained services such as video streaming. IEEE 802.11e is to improve this problem.

In addition, recently standardized H.264 video coding scheme has improved compression performance compared to conventional coding schemes, and more efficiently copes with errors that may occur during transmission over a network, such as data partitioning, PSC, FMO, etc. It has many of the same error recovery techniques.

However, according to the conventional video streaming transmission method, the loss rate of the transport packet varies according to the network condition due to the limitation of the bandwidth, and congestion of the network is attempted for transmission of all data without considering the current network condition. Problem, causing a decrease in overall communication efficiency and inability to cope with changes in wireless network state.

In addition, there is a problem in that system resources are wasted and queue overflow occurs due to an attempt to transmit packets that are likely to fail to be transmitted by not adaptively adjusting and adjusting the amount of packets to be transmitted.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and a network adaptive data stream transmission control method and system according to the present invention has an object of providing an efficient multimedia data stream transmission control method in a wireless network environment. It is done.

In addition, it aims to predict network state information using packet loss rate for network adaptive transmission control and adjust the quality of the multimedia data stream to be transmitted by using data partitioning function in the application layer.

In addition, the object of the present invention is to provide improved QoS and efficiently manage system resources by removing in advance the low-priority data that is determined to be less likely to be transmitted based on packet loss rate in the application layer.

The network adaptive data stream transmission control method of the present invention for achieving the above object comprises the steps of calculating the total packet loss rate for every transmitted packet at predetermined intervals, and parsing the generated transmission schedule data to transmit the scheduled data. Checking the priority and data type of the data, filtering the transmission data using the total packet loss rate, mapping the filtered transmission data to each access category according to the priority; And transmitting the filtered transmission schedule data mapped to the access category through a medium occupancy method.

Also in the above-described configuration,

The total packet loss rate may be calculated using packet loss rates measured for each access category.

Also in the above-described configuration,

The total packet loss rate may be calculated by Equation 1 below.

[Equation 1]

Here, P is the total packet loss rate, TxFrame [AC] is the number of packets transmitted for each AC, and RxFrame [AC] is the number of packets that are recognized as being successfully received among the packets transmitted for each AC.

Also in the above-described configuration,

The type of data to be transmitted includes control data, I frames, P frames, and B frames, and the mapping may include mapping the control data and the I frame to an access category 3, mapping the P frame to an access category 2, and The B frame may be mapped to the access category 1.

Also in the above-described configuration,

Data to be transmitted is encapsulated in NALU units according to the H.264 standard, where NALU includes a 1-byte header, which includes a 5-bit type field, a 2-bit priority field, and a 1-bit header. It may be characterized by consisting of the Forbidden (Forbidden) field.

Also in the above-described configuration,

The priority information of the transmission schedule data may be reflected in the service type field of the IP packet, and the service type field information of the IP packet may be used to map the transmission schedule data to the access category.

In addition, in the above-described configuration, the filtering step

Calculating a removal rate of the transmission data to be mapped to the access category 1 (AC1) by applying a total packet loss rate to the transmission data to be mapped to the access category 1 (AC1), and when the calculated removal rate exceeds 100% And only calculating a removal rate of transmission data to be mapped to access category 2 (AC2), and removing a portion of transmission data according to the calculated removal rates for each transmission priority data. It may be characterized by.

Also in the above-described configuration,

The removal rate of transmission schedule data to be mapped to the access category 1 (AC1) and the removal rate of transmission schedule data to be mapped to the access category 2 (AC2) may be calculated by Equations 2 and 3, respectively. Can be.

[Equation 2]

[Equation 3]

Here, Drop_P _AC1 is the packet drop rate of AC1, Drop_P _AC2 is the packet drop rate of AC2, P is the total packet loss rate, TxFrame [AC] is the number of packets transmitted for each AC, and TxFrame [AC1] is the number of packets transmitted by AC1.

In addition, the network-adaptive multimedia data streaming system according to the characteristic aspect of the present invention encodes the multimedia data and encapsulates the encoded multimedia data according to data type and priority to classify the encapsulated multimedia data by priority. A filtering unit for filtering the classified multimedia data using a coding unit, a total packet loss rate calculated based on the packet loss rate for each access category, and a mapping unit for mapping the filtered multimedia data to an mapped access category. And a media access control unit for providing differentiated media access opportunities to at least two access categories to transmit the mapped multimedia data through a physical layer unit.

Also in the above-described configuration,

The medium access controller periodically calculates the total packet loss rate using the packet information successfully received at the receiving end among the transmission packet information for each access category and the packet for each access category and transmits the total packet loss rate information to the filtering unit. It can be characterized.

Also in the above-described configuration,

The filtering unit calculates a removal rate of the encapsulated data to be mapped to the access category 1 (AC1) by applying the total packet loss rate to the encapsulated data to be mapped to the access category 1 (AC1), and the calculated removal rate exceeds 100%. In the case of calculating the removal rate of the encapsulated data to be mapped to the access category 2 (AC2),

The filtering may be characterized by removing a portion of the encapsulated data for each priority according to the calculated removal rates.

Also in the above-described configuration,

The mapping unit may be configured to map the encapsulated multimedia data to access categories by parsing the service type field of the IP packet set according to the priority of the encapsulated multimedia data.

According to the present invention, it is possible to periodically determine the packet loss rate in a wireless network environment and to efficiently control the multimedia data stream transmission adaptively to the network condition.

In addition, for network adaptive transmission control, the packet loss rate is used to predict network state information, and accordingly, the application layer can adjust the quality of the multimedia data stream to be transmitted by using a data partitioning function.

In addition, by removing the low-priority data that is considered unlikely to be transmitted based on the packet loss rate from the application layer in advance, it is possible to prevent system resource waste and queue overflow, improve QoS, and efficiently manage system resources. And there is an advantage that can provide a smoother and improved streaming service.

DETAILED DESCRIPTION Hereinafter, specific aspects of the present invention will be described in detail with reference to the accompanying drawings and preferred embodiments so that those skilled in the art can easily understand and reproduce the present invention.

1 is a flowchart illustrating a process of encoding and encapsulating a multimedia data stream according to an H.264 scheme according to an embodiment of the present invention.

As shown in FIG. 1, H.264 conceptually consists of two layers, a video coding layer (VCL) and a network abstraction layer (NAL). VCL is a layer associated with video compression technology that compresses (encodes) video signals, while NAL is responsible for encapsulating the data coded through the VCL over various networks.

One transmission unit encapsulated through the NAL is a NALU (NAL Unit) and includes a 1-byte header. 2 bits in the header is an NRI (Nal_Ref_Idc) field indicating the type of data included in the corresponding NALU, that is, the priority of the data. The type of NALU data is made by data partitioning, which is one of the error resilience techniques of H.264. In data partitioning, all symbols of MB (Marco Block) are bitstreams forming one slice. Coded and encapsulated in NALU. There are several types of partitions in H.264. Partition A contains header information such as MB type or quantization parameter and has the highest priority because it contains information necessary for decoding other partitions. Partition B, also called intra-partition, contains intra CBP (Intra Coded Block Pattern) or coefficients. Partition A is required to use this data, and likewise contains the information needed to use partition C below. Partition C, also called inter-partition, contains Inter CBP or coefficients and has a lower priority than Partitions A and B.

FIG. 2 is a flowchart illustrating a mapping and transmission process of encapsulated data according to priorities according to the IEEE 802.11e EDCA scheme according to an embodiment of the present invention.

IEEE standardizes IEEE 802.11e as an improved channel access mechanism to support differentiation by service type. Hybrid Coordination Function (HCF), a channel access mechanism of IEEE 802.11e, is similar to the existing wireless LAN standard. ).

As shown in FIG. 2, EDCA defines a plurality of access categories to support differentiated QoS in a differentiated channel approach based on priority, and each access category (AC) is previously defined. Arbitration IFS (ACFS), which replaces defined channel contention parameters and Distributed Inter Frame Space (DIFS), and minimum and maximum content window (CW) parameters differentiated by access category (CWmin [AC], CWmax [, respectively). AC]).

There are four access categories from AC3 to AC0, and the structure of the WSTA (Wirelee Station) having parameters for determining the priority among the access categories is shown. When a plurality of access categories existing in one WSTA attempt to access a channel at the same time, a virtual collision handler prevents this, thereby giving one access category an opportunity to access a wireless channel.

3 illustrates a wireless media approach of IEEE 802.11e EDCA.

As shown in FIG. 3, since AIFS [AC] is set differently for each access category according to the priority, AC3 to which the traffic having the highest priority is queued is set to the shortest AIFS and has the lowest priority. AC0 to which best-effort traffic is queued is set to the longest AIFS. If the wireless medium (physical layer unit) is idle (IDLE) during AIFS for each set of access categories, each access category attempts to transmit data by occupying the wireless medium. Put off.

As a result, the data included in the higher priority access category is more likely to be able to transmit data faster by occupying the wireless medium first than the relatively low priority access category. Similarly, each access category has different CWmin [AC] and CWmax [AC] values according to the priority, so that high priority data can reduce the waiting time until the next medium access even if a collision occurs during the wireless medium access process. As a result, data can be preferentially transmitted by occupying the wireless medium relatively quickly.

However, since it attempts to transmit all data regardless of the current network state, that is, its transmission capacity, it cannot adapt to changes in the wireless network state and, if the network condition is poor, packets for data that are significantly less likely to be transmitted. There is still a problem that consumes system resources and causes transmission queue overflow in the process of mapping, mapping by access category, and queuing for access category.

4 is a flowchart illustrating a network adaptive multimedia data transmission model according to an embodiment of the present invention.

As shown in FIG. 4, the multimedia data stream encoded and encapsulated by the H.264 scheme is mapped for each access category according to the priority of data present in the header of the NALU. That is, basic information such as parameter set concepts (PSC), which is the most important information for decoding each frame of a data stream, is assigned to AC3 having the highest media access priority, partition A to AC2, and partitions B and C to the least important. Is mapped to AC1.

Data compressed and encapsulated by the H.264 method may be classified into an I frame corresponding to a key frame and a P frame and a B-predicted frame interpolated between the key frames. have. I-frames needed to accurately decode other frames with control information are mapped to AC3 with the highest priority, while P-frames and B-frames with relatively lower priority are mapped to AC2 and AC1, respectively. As described above, the data queued to each AC according to the priority of the multimedia data is provided with differentiated media access opportunities by AIFS [AC], CWmin [AC], and CWmax [AC], which are QoS parameters for each AC. This allows important data components, ie high AC, to occupy the wireless medium more quickly, enabling faster and safer transmission of high priority data.

Meanwhile, the channel state of the variable wireless network is predicted based on the total packet loss rate calculated based on the packet loss rate for each AC.

Calculating the total packet loss rate P of the wireless channel based on the packet loss rate for each AC may be calculated by Equation 1 below.

[Equation 1]

Here, TxFrame [AC] refers to the number of packets transmitted for each AC, and RxFrame [AC] refers to the number of packets recognized to have been successfully received among the packets transmitted for each AC. The RxFrame [AC] can receive and grasp statistical information periodically transmitted from a client.

If channel conditions are good, data on all ACs can be sent to the client, but if channel conditions are bad, all data cannot be sent and AC0 has a relatively low priority due to AC-specific priority for media access. The transmission probability of data mapped to AC1 becomes low.

Based on the total packet loss rate calculated by Equation 1, the probability of data that can be successfully transmitted in the channel state of the current wireless network can be estimated.

The total packet loss rate is periodically reported to the application layer in order to remove the data that has low priority as much as the amount of data predicted to be low in the current channel state. In consideration of the characteristics of NALUs having different priorities, the total packet loss rate delivered through the cross-layer is first applied to the low priority NALUs, and the data removal rate is calculated first. In this way, the packet drop rate is calculated by applying the total packet loss rate to the data to be transmitted to AC1, the lowest priority AC except AC0.

The packet drop rate of data to be transmitted to AC1 may be obtained by Equation 2 below.

[Equation 2]

Here, TxFrame [AC1] means the number of packets transmitted by AC1, and TxFrame [AC] means the number of packets transmitted by each AC. If the packet drop rate (Drop_P _AC1 ) of the data to be transmitted to AC1 obtained in this way exceeds 100%, the packet drop rate of data to be sent to AC1 becomes 100% and if the value is less than 100%, the value itself obtained is the data to be transmitted to AC1. Packet drop rate.

Meanwhile, the packet drop rate of the data to be transmitted to AC2 is calculated only when the packet drop rate of the data to be transmitted to AC1 exceeds 100%, which can be obtained by Equation 3 below.

[Equation 3]

Since the data to be transmitted to the AC3 having the highest priority includes the basic data for decoding the multimedia data stream, it is preferable to perform the transmission attempt for the entire packet without packet dropping.

For example, suppose that AC1 to AC3 transmit 10 packets each during a predetermined period, and 5 packets each successfully received. The total packet loss rate is 1- (5 + 5 + 5) / ( 10 + 10 + 10) = 50%, and the packet drop rate of the data to be transmitted to AC1 is 50 * 30/10 = 150% according to equation (2). In addition, the packet drop rate of the data to be transmitted to AC2 is 150-100 = 50% by Equation 3.

When total packet loss rate information is periodically transmitted through the cross layer scheme, the NALU removal rate for each AC is first calculated. Next, the NAL parses the encapsulated NALU packet, applies the pre-calculated NALU removal rate for each data type to be transmitted to each AC, performs filtering, and requests mapping and transmission to a lower layer.

FIG. 5 illustrates a process of identifying priorities and mapping ACs for NALUs.

As shown in FIG. 5, the streaming server according to the network adaptive data stream transmission model knows the priority and data type of data included in the NALU through parsing the H.264 stream parser. For proper mapping in the lower layer according to the priority of the data, the priority of the actual NALU may be set to the type of service (ToS) field of the IP packet by calling the socket function. Parses the ToS field of the IP packet and queues the packet to the appropriate AC based on priority based on the ToS field information.

While various embodiments of the present invention have been described above with reference to the accompanying drawings, the above embodiments are not intended to limit the scope of the present invention and are not limited to the above-described embodiments, but are within the scope of the technical spirit of the present invention. It can be carried out in a variety of variations.

1 is a flowchart illustrating a process of encoding and encapsulating a multimedia data stream according to an H.264 scheme according to an embodiment of the present invention.

2 is a flowchart illustrating a process of mapping and transmitting encapsulated data according to priorities according to the IEEE 802.11e EDCA scheme according to an embodiment of the present invention.

3 illustrates a wireless media approach of IEEE 802.11e EDCA.

4 is a flowchart illustrating a network adaptive multimedia data transmission model according to an embodiment of the present invention.

FIG. 5 illustrates a process of identifying priorities and mapping ACs for NALUs.

Claims (12)

In the multimedia data stream transmission control method, Calculating a total packet loss rate for the entire transmitted packet at predetermined intervals; Parsing the generated transmission schedule data and checking the priority and data type of the transmission schedule data; Calculating a packet removal rate for each priority from the low priority transmission data using the total packet loss rate, and filtering the scheduled transmission data by removing a portion of the transmission scheduled data according to the packet removal rate; Mapping the filtered transmission schedule data to respective access categories according to priority; And And transmitting the filtered transmission schedule data mapped to the access category through a medium occupancy method. The method of claim 1, The total packet loss rate is calculated using the packet loss rate measured for each access category, network adaptive data stream transmission control method. The method of claim 2, The total packet loss rate is calculated by Equation 1 below, where P is the total packet loss rate, TxFrame [AC] is the number of packets transmitted for each AC, and RxFrame [AC] is the packet transmitted for each AC. Network adaptive data stream transmission control method characterized in that the number of packets that are successfully received. [Equation 1]

The method of claim 1, The type of data to be transmitted includes control data, I frames, P frames, and B frames, The mapping may include mapping the control data and the I frame to the access category 3, the P frame to the access category 2, and the B frame to the access category 1. Way. The method of claim 4, wherein The data to be transmitted is encapsulated in NALU units according to the H.264 standard, wherein the NALU includes a header of 1 byte, and the header includes a 5-bit type field, a 2-bit priority field, and 1 A network adaptive data stream transmission control method comprising a forbidden field of bits. The method of claim 5, The priority information of the transmission schedule data is reflected in the service type field of the IP packet, and the service type field information of the IP packet is used to map the transmission schedule data to the access category. Transmission control method. The method of claim 1, wherein the filtering step, Calculating a removal rate of transmission data to be mapped to the access category 1 (AC1) by applying the total packet loss rate to transmission data to be mapped to the access category 1 (AC1); Calculating a removal rate of transmission data to be mapped to the access category 2 (AC2) only when the calculated removal rate exceeds 100%; And And removing a part of transmission data according to the calculated removal rates for each transmission priority data according to each priority. The method of claim 7, wherein The removal rate of the transmission schedule data to be mapped to the access category 1 (AC1) and the removal rate of the transmission schedule data to be mapped to the access category 2 (AC2) are calculated by Equations 2 and 3, respectively, 2 and 3, Drop_P _AC1 is the packet drop rate of AC1, Drop_P _AC2 is the packet drop rate of AC2, P is the total packet loss rate, TxFrame [AC] is the number of packets transmitted for each AC, and TxFrame [AC1] is transmitted from AC1. Network adaptive data stream transmission control method characterized in that the number of packets. [Equation 2]

[Equation 3]

A data coding unit for encoding multimedia data and encapsulating the encoded multimedia data according to data type and priority to classify the encapsulated multimedia data by priority; A filtering unit for calculating a packet removal rate for each priority from the multimedia data having a lower priority using a total packet loss rate, and filtering multimedia data by removing a portion of the classified multimedia data according to the packet removal rate; A mapping unit which maps the filtered multimedia data into a mapped access category; And  And a media access control unit for providing at least two access categories with differentiated media access opportunities to transmit the mapped multimedia data through a physical layer unit. The method of claim 9, The medium access controller periodically calculates the total packet loss rate using the packet information successfully received at the receiving end of the transport packet information for each access category and the transport packet for each access category, and calculates the total packet loss rate information. Network adaptive multimedia data streaming system, characterized in that the transmission to the filtering unit. The method of claim 10, The filtering unit calculates a removal rate of the encapsulated data to be mapped to the access category 1 (AC1) by applying the total packet loss rate to the encapsulated data to be mapped to the access category 1 (AC1), and the calculated removal rate is 100%. If exceeded, the removal rate of the encapsulated data to be mapped to the access category 2 (AC2) is calculated, And said filtering removes a portion of said encapsulated data for each priority in accordance with said calculated removal rates. The method of claim 11, And the mapping unit parses the service type field of the IP packet set according to the priority of the encapsulated multimedia data and maps the encapsulated multimedia data to the access categories.

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