CN101783758B - Family coaxial network MAC layer data transmission method based on service differentiation - Google Patents

Abstract

The present invention relates to a kind of family coaxial network MAC layer data transmission method based on service differentiation, comprises the following steps: 1) set the priority for each service; 2) set the corresponding transmission in a single transmission period for each priority number of time slots; 3) higher priority corresponds to more number of time slots, and lower priority corresponds to less number of time slots; in the scheduling cycle, according to the priority of the business, different priority Each service is assigned a corresponding number of transmission time slots; 4) The data of each service is transmitted in the transmission period. The present invention organically combines the QoS requirements of services with MAC medium access control, and uses targeted application of service feature analysis and extraction technology, data transmission mode switching technology, shared channel allocation protocol and dynamic self-adaptive adjustment technology, directly from network The bottom layer guarantees the bandwidth resources required by services with high QoS requirements, and can keep bandwidth reasonably allocated and efficiently utilized in services with various QoS requirements.

Description

A MAC layer data transmission method of home coaxial network based on service differentiation

technical field

The present invention relates to the technical field of broadband network, in particular, the present invention relates to a MAC layer protocol and a data transmission method in a home network system that provides various audio and video media services and has various household devices and terminals.

Background technique

With the popularization of broadband networks and the digital development of household equipment, people's demand for communication services is no longer simple voice and one-way video, but faster, richer, and interactive broadband multimedia services. Subsequently, the demand for building a home network with broadband access, internal interconnection, and content sharing has become increasingly prominent. In particular, audio and video media applications such as IPTV and DVR (Digital Video Record) with high-definition quality are becoming more and more popular, which puts forward higher requirements for home network technology, such as: high bandwidth, low delay, low bit error, good service quality ( QoS) etc. For quite a long time, media such as audio and video, especially high-definition video, have been the main services in the home network.

At present, the home network has begun to take shape and is growing day by day in many countries in the world, and it has also become a development trend in China. Domestic households have widely laid coaxial cables for cable TV, and their wiring is laid around TVs, audio and video equipment, etc., suitable for audio and video media services. Therefore, the home network based on the wired coaxial medium as the backbone has the advantages of convenient networking and easy expansion. Since the wired coaxial network belongs to the shared media network, when the transmission rate of the physical channel is constant, the MAC layer protocol is a key factor affecting the effective transmission rate of the network and providing QoS service guarantee. In a shared media network, only one device can send data at a time. Therefore, it is necessary to design a reasonable MAC layer control mechanism to properly solve and allocate the use of shared channel resources by multiple users, in order to achieve efficient and reliable data transmission and QoS guarantee. The traditional MAC mechanism research is mostly based on the characteristics analysis of the physical channel and the goal of avoiding data transmission conflicts, but is not related to the characteristics of the carried services, and fails to fully consider the differences in data transmission characteristics of different services. Therefore, it is difficult Ensure the efficient integration and development of different types of businesses.

When multi-services are carried out at fixed frequency points of coaxial cables, time-division multiplexing is often used. The basic channel acquisition strategies include contention protocols (such as CSMA, carrier sense multiple acces) and conflict-free protocols (such as reservation protocols). The commonly used home network MAC protocol uses a competition protocol, which is characterized by short delay under light load (that is, only a small number of devices or services need to send data at the same time or time slot), but under heavy load (that is, at the same time Or in a time slot, there are many devices or services that need to send data), the overhead of channel arbitration becomes larger, resulting in a decrease in channel utilization. For example, traditional Ethernet adopts carrier sense multiple access (CSMA) media access method, its collision and exponential back-off mechanism lead to uncertain network delay and delay jitter, which makes the traditional home network carry audio and video , voice and other real-time media business new network applications, service quality declines. When the competition protocol is adopted, when multiple channels of high-definition audio and video are carried out simultaneously in the home, the probability of collision increases, and the channel arbitration overhead is too large, which will lead to a sharp deterioration of network performance, service quality and user experience. On the other hand, the conflict-free protocol has the characteristics of longer delay under light load of network data than the former, and higher channel utilization under heavy load. However, the conflict-free protocol needs to pre-allocate the use time slots of each device. As the number of devices increases, the time slot allocation increases, the time for one cycle increases, and the delay increases, which is not conducive to enhancing the scalability of the home network. Therefore, the two protocols have their own advantages and disadvantages in different network environments, and cannot meet the simultaneous development of multiple high-quality services in the home network and provide good scalability requirements.

At present, there are still some mixed MAC protocols, which combine the characteristics of the two basic protocols to improve some performances of the network. For example: a hybrid protocol based on request-based reserved access and competitive access is used to solve the bandwidth problem of business bursts with large data volumes. The mixed MAC protocol of CSMA/CD and token control switches to the token control mode under high load and switches to CSMA/CD mode under low load, and reduces the network load by selecting the protocol switching threshold and detecting the network load. response time. These hybrid MAC protocols are not fully integrated with the characteristics of the business. They provide the same service for different services. In the case of limited network bandwidth, the QoS of various services decreases as a whole. Among them, services with high QoS requirements (such as real-time Business) user experience will be greatly affected. Home Plug over Coax adopts HomePlugAV, a home network standard developed by HPA (Home Plug Powerline Alliance, Home Plug Powerline Alliance). The MAC layer of this standard supports both contention-free TDMA and contention-based CSMA/CA two multiple access methods: TDMA is connection-oriented and provides strict QoS guarantees to ensure bandwidth reservation, high reliability and strict delay and jitter control; CSMA/CA is connectionless and provides services with QoS guarantees based on service priorities. However, when the number of HomePlug device nodes in the network increases, the probability of collision will increase, and the data transmission rate will also be greatly reduced, so it is suitable for home networking occasions with fewer node devices. The MAC protocol of HomePNA 3.0 also combines contention and non-conflict methods. Among them, it uses CSMA/CD to implement an asynchronous MAC protocol, provides priority-based media access control, and uses signaling protocols to solve media conflicts; and uses CSMA The /CA technology implements the synchronous MAC protocol, under the control of the host, avoids conflicts by pre-planning the timing of all media accesses. Similarly, when the number of device nodes in the network increases, the delay caused by collisions also increases greatly.

In view of this, the present invention provides an efficient hybrid MAC mechanism based on service differentiation, based on home network service subdivision, and according to different data transmission characteristics of the service, the service is divided into QoS priority levels; at the MAC layer, according to the service QoS priority Level, using a limited competition protocol based on service differentiation and prediction mechanism, to ensure the optimized and efficient transmission of various service data, and provide sufficient QoS guarantee from the bottom layer of the network; at the same time, it adopts a dynamic self-adaptive adjustment strategy to provide equipment expansion for the home network good support.

The benefit of using the present invention is that it provides different levels of QoS underlying guarantees for different data transmission characteristics of services, thereby ensuring optimized and efficient transmission of various service data under the condition of constant bandwidth, thereby improving the quality of high-definition audio and video programs, etc. It provides a good user experience and provides good support for the device expansion of the home network.

Contents of the invention

The purpose of the present invention is to provide a home network hybrid MAC mechanism based on service differentiation. Based on the business subdivision of the home network, this mechanism divides the QoS priority levels for different services according to the different data transmission characteristics of the services; at the MAC layer, according to the service QoS priority levels, a limited competition protocol based on the service differentiation and prediction mechanism is adopted to ensure that each The optimized and efficient transmission of various business data provides sufficient QoS guarantee from the bottom layer of the network; at the same time, the dynamic self-adaptive adjustment strategy is adopted to provide good support for the expansion of home network equipment.

In order to achieve the above object, the present invention provides a kind of family coaxial network MAC layer data transmission method based on business differentiation, comprises the following steps:

1) Set priorities for each business;

2) Set the number of corresponding transmission time slots in a single transmission period for each priority; a higher priority corresponds to a larger number of time slots, and a lower priority corresponds to a smaller number of time slots;

3) In the scheduling period, according to the priority of the business, allocate the corresponding number of transmission time slots for each business of different priority;

4) The data of each service is transmitted in the transmission period.

Among them, for different service data with the same priority, a competition mechanism is used to compete for corresponding transmission time slots.

Furthermore, in the embodiment of the present invention, a preferred MAC layer data transmission method based on service differentiation is also provided. Based on the traditional MAC mechanism, the MAC layer data transmission method uses the service Feature analysis and extraction technology, data transmission mode switching technology, limited competition protocol based on business differentiation and prediction mechanism, and dynamic self-adaptive adjustment technology.

Among them, the business feature analysis and extraction technology is used to analyze the data characteristics and real-time QoS requirements of the business, and map the different QoS requirements of the business to different business priorities (the mapping of business priorities can be defined in the form of IEEE 802.1D. Of course, this is not the only mapping form of service priority, and those skilled in the art can also customize the mapping scheme of service priority according to needs), divide the transmission time of the channel into time slots, and allocate more time slots for high-priority data Time slots, so as to meet the real-time requirements of physical quantity data, multimedia QoS guarantee and file data transmission, and the implementation is simple, convenient and reliable. The division of business priority can be divided into network system commands, mandatory real-time data services with time limit requirements, flexible real-time data services with periodic requirements, and non-real-time data services without time limit requirements according to the type of real-time data requirements. There are 4 levels, which can also be divided according to other characteristic parameters.

The data transmission mode switching technology is used for data transmission with different real-time requirements, using a composite transmission mode for data transmission. The composite transmission mode refers to a transmission mode in which the normal transmission mode and the priority transmission mode are combined. In normal transmission mode, through the access control protocol, data with different priorities can be transmitted. When a station has high-priority data to be transmitted that exceeds the upper threshold of the buffer queue, it broadcasts a high-priority transmission request to the network, and carries information such as service priority. After the home gateway receives it, it decides whether to switch to the priority transmission mode according to the network conditions (the home gateway can make a decision based on whether it has already switched to the priority transmission mode and other factors), and if it agrees to switch, it will send a broadcast frame starting from the priority transmission mode . At this time, the data of this site and the data with higher priority in the network can be transmitted. After the data transmission is completed, return to the normal transmission mode. The priority transmission mode can solve the situation of high priority, high rate data burst and urgent need of home network bandwidth support. Therefore, adopting the composite transmission mode can ensure the transmission quality of the home network data flow and high bandwidth utilization. For high-speed, high-priority media business bursts, the composite transmission mode can ensure its smooth development and provide better service quality.

The limited contention protocol based on service differentiation and prediction mechanism is used to allocate channels when multiple devices apply for using channels. The limited contention protocol combines the respective advantages of the non-conflict protocol and the competition protocol. Through reasonable grouping of devices, the devices in the same group compete for channels, and different groups apply for channels sequentially in a non-conflict manner, so that its performance can be optimized at light loads. The delay under the condition is reduced, which is as close as possible to the contention protocol, and the arbitration overhead is reduced under heavy load, which is close to the collision-free protocol. The limited competition protocol based on service differentiation, according to the service priority of the application channel, between different priority services, apply for channels in a non-conflict manner; between the same priority services, use limited competition to compete for channels . The prediction mechanism refers to judging whether the device is using the channel in the current cycle according to the queue scheduling and buffering parameters encapsulated in the data frame of the business in the previous cycle, and grouping the devices that are expected to use the channel separately to reduce the possibility of conflicts within the group , so as to reasonably group devices in the network and improve channel utilization. Through the hybrid MAC mechanism of the conflict-free protocol combined with the limited contention protocol, the channel utilization rate under heavy load can be improved, and different priority services can be provided for each priority service under a certain bandwidth, giving priority to ensuring the high-quality development of high-priority services; In the case of light load, the delay of this mechanism is lower than that of the non-collision protocol; it supports the addition of home devices at any time and the expansion of the home network.

The dynamic self-adaptive adjustment technology handles the request of site joining, ranging, and exiting the network by controlling the frame cycle, and the online detection mechanism of the site, dynamically adjusts the QoS priority level of the service and the number of transmission time slots allocated in a single transmission cycle, and quickly Reasonably establish grouping and dynamic management for sites, and dynamically adjust the order of service delivery. The home gateway sends detection messages to sites that have been silent for a long time to detect whether the device is online, so as to dynamically update the site list and delete devices that are powered off or abnormal. Since services such as high-definition audio and video have strong continuity, based on the bandwidth occupied by the service in the previous transmission cycle, a more accurate prediction of the bandwidth required for the next transmission cycle can be made. Therefore, the site where the business is located encapsulates queue scheduling and buffering parameters, bandwidth, and delay requirements in the transmitted data frame. According to this parameter, the home gateway predicts the time slots required by the service in the next transmission cycle and allocates the corresponding number of time slots. If a site has services with multiple priorities, piggybacking technology is used. When the highest priority service of the site uses the channel, all its services are sent sequentially in order of priority from high to low, thereby reducing the number of sites using the channel The number of switching times can reasonably improve the efficiency of use.

Comprehensively utilizing the above technologies, the hybrid MAC mechanism of the home network based on service differentiation provided by the present invention is specifically as follows: in the home network, after the service is initiated, the home gateway uses the service characteristic analysis and extraction technology to analyze the data characteristics and real-time performance of the service. QoS Requirements, divide the business into business priorities. According to the service priority results, the home network adopts dynamic self-adaptive adjustment technology to establish a site list corresponding to each service priority, and quickly and reasonably establish groups and dynamically manage the sites that initiate the service. And with the completion and withdrawal of existing services and the addition of new services, the site list can be dynamically adjusted by controlling the frame cycle to process site joining, ranging, and network exit requests; and through user-defined, network monitoring, etc., Adjust the QoS priority level of the service, quickly and reasonably establish grouping and dynamic management for the site. According to the priority level of each business and the queue scheduling and buffering conditions of the business encapsulated in the data frame, different timeslot numbers are allocated to each priority business, so that the QoS of the high-priority business is guaranteed first, so as to meet the real-time physical quantity data sexual demands. For real-time and non-real-time data, the home gateway uses the data transmission mode switching technology and adopts the MAC data transmission mode with priority distinction. In the normal transmission mode, through the limited contention protocol based on service differentiation and prediction mechanism, when multiple devices apply for the use of the channel, the channel is allocated according to the service priority of the applied channel. Between services of different priorities, a conflict-free method is used to apply for channels sequentially; between services of the same priority, channels are competed for in a limited competition based on a prediction mechanism. At this time, data with different priorities have the opportunity to be transmitted. When a site has a large amount of data with a high priority to transmit, it broadcasts a high-priority transmission request to the network. At this time, the network's intervention in the home gateway is transformed into a priority transmission mode. The data of this site and the network are prioritized. Higher level data can be transmitted. When the priority data transmission is completed, return to the normal transmission mode.

Compared with the currently existing home network MAC mechanism, the home network hybrid MAC mechanism based on service differentiation in the present invention organically combines the service's demand for QoS with MAC medium access control, and through targeted application of service feature analysis and extraction technology, Data transmission mode switching technology, shared channel allocation protocol and dynamic self-adaptive adjustment technology directly guarantee the bandwidth resources required by high-QoS services from the bottom layer of the network. Compared with the traditional MAC mechanism of resource reservation, it is more flexible and can Keep the bandwidth reasonably allocated and efficiently utilized in various QoS-demanding services; at the same time, make full use of the interactivity of the home network, users can interact with the home gateway through scene settings, custom settings, and input devices such as remote controls , designate the service that needs to be prioritized, so as to improve the user experience of carrying out various services in the home network.

Description of drawings

Fig. 1 is a schematic diagram of a typical application scenario of the scheme of the present invention;

Figure 2 is an example diagram of the transmission process of eight priority levels; the model is composed of the competition cycle, the transmission cycle and the idle cycle generated when all stations are at rest.

specific implementation plan

The home network hybrid MAC mechanism based on service differentiation provided by the present invention organically combines service requirements for QoS with MAC medium access control, classifies them according to service characteristics of the home network, and can guarantee QoS requirements from the bottom layer of the network Bandwidth resources required by high-volume services are more flexible and controllable than traditional resource reservation mechanisms, and can be adjusted adaptively to keep bandwidth reasonably allocated and efficiently utilized in various QoS-demanding services. At the same time, making full use of the interactivity of the home network, users can interact with the home gateway through scene settings, custom settings, and input devices such as remote controls, and specify services that need priority, thereby improving the user experience of various services in the home network. This method can be applied to develop various services such as high-definition audio and video in a home network, and the specific application and implementation of this method will be introduced below in combination with the development process of services.

From the perspective of home network service characteristics, information flow mainly includes: physical quantity data (such as: voltage, current, power, temperature, flow, switching value, etc.), multimedia data (such as audio, image, video, etc.), file data (such as: printed data, shared documents, etc.). These data can be divided into multiple levels according to the real-time requirements, for example:

(1) The first level: network system command data. This kind of data determines the initialization and operation status of the network, etc., and the real-time and correctness of the data must be guaranteed. For example, network system commands such as data priority allocation and management commands, bus reset commands, and network initialization commands.

(2) Second level: Mandatory real-time data with time limit requirements. This kind of data has a limited and definite transmission delay, and the correctness of the data must be guaranteed, otherwise the reliability of the equipment cannot be satisfied and even cause accidents. Examples include measurement and control data for the control subnet.

(3) The third level: flexible real-time data with periodic requirements. This type of data allows a finite, but non-deterministic transmission delay, and a small amount of data errors is not a problem, such as the transmission of audio and video data streams.

(4) The fourth level: non-real-time data with no time limit requirement. This type of data does not have strict transmission delay requirements, such as file data, printing files, etc.

The scheme of the present invention divides the transmission time of the channel into time slots, and allocates more time slots to high-priority data according to the bandwidth it occupies, thereby giving priority to ensuring the smooth development of services with high QoS requirements and low delay requirements.

A typical application scenario of the solution of the present invention is shown in Figure 1, in which, the three networks such as the Internet, the cable TV network, and the telecommunication network can all communicate through the home gateway, and various household devices in the home, such as PCs, TVs, digital set-top boxes, etc. The device is interconnected with the home gateway through wired and wireless methods. Combined with the existing home network networking technology, the information interconnection and intercommunication of various networks and home devices can be realized.

In combination with the above application scenarios, the specific process of the MAC mechanism applied by the method of the present invention is described as follows, as shown in Figure 2:

(1) When members of the family need to use home equipment, turn on the equipment. The device starts to listen to the channel, and when it hears the application joining and exiting periods, it sends out the application joining broadcast frame in the corresponding time slot; after receiving the request, the home gateway registers the device in the device management table and assigns it a network address , broadcast the control frame containing the network address and serial number to all devices, and notify the device to join the home network; The gateway achieves clock synchronization, and other devices need to remain silent to avoid conflicts.

(2) The user triggers to start a certain service (such as performing video on demand VOD, starting to upload/download data services, etc.); the device carrying the service analyzes the service parameters, maps the service QoS priority according to a certain strategy, and starts to listen to the channel. Send channel application bits in the QoS priority contention time slot;

(3) If in the contention time slot, only this service applies for the channel, the application is successful; if in the contention time slot, there are multiple services applying for the channel at the same time, a conflict will occur: the conflicting business is based on the station number, according to the fixed The strategy (such as: priority binary to counting protocol, the station with a small number to use the channel first; adaptive tree search protocol and other strategies) adjudicates the right to use the channel;

(4) After the contention time slot ends, the home gateway allocates the number of time slots occupied in this transmission cycle to each service. When the service is transmitted for the first time, the home gateway allocates the number of time slots according to its QoS priority; otherwise, it allocates according to the queue scheduling and buffering conditions encapsulated in the data frame, bandwidth and delay requirements of the service in the previous transmission cycle time slot. In the case of limited resources, the home gateway first meets the requirements of high-priority services with a certain strategy. The number of time slots is encapsulated in the transmission control frame and broadcast, and then enters the transmission cycle;

(5) When the transmission period arrives, the corresponding station carrying the service transmits the corresponding data in the order specified by the transmission control frame and within the corresponding occupied time slot number, and carries the bandwidth and delay required by the service in the data frame Requirements, site queue conditions and other parameters. If a site has services with multiple priorities, piggybacking technology is used. When the highest priority service of the site uses the channel, all its services are sent in order from high priority to low priority;

(6) After the transmission of all stations applying for the channel is completed, enter the next cycle. That is: the station application join and exit period, each priority application channel period and transmission period.

(7) When the priority level of the data to be transmitted by a certain station reaches the priority threshold, and the data volume of the data exceeds the upper limit threshold of the buffer queue to be transmitted, the station broadcasts a high-priority transmission request to the network, And carry information such as business priority. The priority threshold is a preset priority threshold for triggering the priority transmission mode, and the priority level of data exceeding or equal to the priority threshold is one of the prerequisites for triggering the priority transmission mode. After the home gateway receives the high-priority transmission request, it decides whether to switch to the priority transmission mode according to the network conditions (the home gateway can make a decision based on whether it has already switched to the priority transmission mode and other factors), and if it agrees to switch, it will send the priority Broadcast frame for start of transfer mode. At this time, the data of this application site and the data with the same or higher priority in the network can be transmitted. After the part of the data transmission is completed, the broadcast exits the priority mode request and returns to the normal transmission mode. The priority transmission mode can solve the situation of high priority, high rate data burst and urgent need of home network bandwidth support. Therefore, adopting the composite transmission mode can ensure the transmission quality of the home network data flow and high bandwidth utilization.

(8) When the device in the home network is shut down normally, listen to the channel before shutting down, and when the application join and exit cycle is detected, it will send out the broadcast frame for requesting exit in the corresponding time slot; after the home gateway receives the request, it will send the device Delete it from the device management table to release its assigned network address and number.

(9) If a device in the home network is shut down abnormally (such as a device suddenly powering off, misoperation, etc.) or malfunctions, an application exit broadcast frame cannot be sent. The home gateway sends a message to a device that has been silent for a long time through the site online detection mechanism to detect whether the device is connected normally. If no reply is received from the device after sending several times, the home gateway will consider that the device has exited the network, delete the device from the device management table, and release its assigned network address and number.

Claims (4)

1. A family coaxial network MAC layer data transmission method based on service differentiation, comprising the following steps: 1) Set priorities for each business; 2) Set the number of corresponding transmission time slots in a single transmission period for each priority; a higher priority corresponds to a larger number of time slots, and a lower priority corresponds to a smaller number of time slots; 3) In the scheduling period, according to the priority of the business, allocate the corresponding number of transmission time slots for each business of different priority; 4) transmit the data of each business in the transmission period, it is characterized in that, In the described step 4), the data transmission adopts a composite transmission mode combining normal transmission and priority transmission; under the normal transmission mode, through the access control protocol, data with different priorities have the opportunity to transmit; when a certain site has high When data with a priority level and exceeding the upper threshold of the buffer queue is to be transmitted, a high-priority transmission request is broadcast to the network, and the information carried in the high-priority transmission request includes service priority information; The status judges whether to switch to the priority transmission mode. If the switch is agreed, the broadcast frame of the priority transmission mode will be sent. At this time, the data of the site and the data with the same or higher priority in the network can be transmitted. When the data transmission is completed After that, return to normal transfer mode. 2. MAC layer data transmission method according to claim 1, is characterized in that, adopts the limited contention agreement based on business distinction and prediction mechanism to carry out channel allocation, for each business belonging to the same priority, adopt the mode of competition to obtain channel, Services with different priorities apply for channels sequentially in a conflict-free manner. 3. The MAC layer data transmission method according to claim 1, characterized in that, the priority order from high to low is: network system command, mandatory real-time data service with time limit requirement, flexible service with periodic requirement Real-time data services, non-real-time data services without time limit requirements. 4. MAC layer data transmission method according to claim 2, it is characterized in that, in described step 2), through control frame periodic processing station joins, ranging and the request of withdrawing from network, station online detection mechanism, dynamically adjusts business The QoS priority level and the number of allocated transmission time slots can quickly and reasonably establish grouping and dynamic management for the site, and dynamically adjust the service sending sequence.

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