RU2502193C1 - Method for dynamic backup of capacity of return channels in interactive access satellite communication network - Google Patents

Abstract

FIELD: radio engineering, communication.

SUBSTANCE: method involves measuring in each active satellite terminal the rate of packet data traffic from terminal equipment and the occupation of the input buffer of the satellite terminal in periods of time that are multiples of the super-frame duration; determining the optimum value of the quantile level for predicted values of the rate of packet data into the satellite terminal buffer one, two and three super-frames ahead; generating a request for dynamic backup of capacity taking into account QoS requirements based on the occupation of the input buffer and requests generated at previous super-frames, as well as packet traffic rate prediction data, carried out taking into account the quantile level characterising backup redundancy.

EFFECT: dynamic backup of return channel capacity resource, which enables to increase network efficiency in conditions without traffic overload due to minimal redundancy of capacity backup while meeting requirements for average delay and delay jitter for transmitted RBDC traffic packet data, to which VoIP and video conferencing traffic relates.

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Description

The invention relates to the field of radio communications, and in particular to methods for reserving bandwidth in multimedia satellite interactive access networks, providing high efficiency of using the bandwidth of reverse satellite channels and maintaining traffic quality requirements.

In interactive satellite communication networks deployed in accordance with the DVB-RCS (ETSI EN 301 790 v1.3.1, 2003) and IPoS (TIA-1008, 2003) standards, resource allocation of reverse channel network bandwidth for active satellite interactive terminals is performed using the BoD procedure (bandwidth on demand - providing a resource on demand).

The mechanisms for providing network bandwidth on demand recommended in the DVB-RCS standard are to allocate time slots to each active satellite terminal in the superframe structure in accordance with dynamic reservation requests received from them.

According to the literature methodology (see, for example, Karaliopou-los, M. Support of elastic TCP traffic over broadband GEO satellite networks. Center for Communication Systems Research School of Electronics and Physical Sciences University of Surrey, April 2004, as well as Celandroni , N. Comparison between distributed and centralized demand assignment TDMA satellite access schemes / Celandroni, N., Ferro, E., Potorti, F. // International Journal of Satellite Communication 14, 2 (Mar.-Apr. 1996), p. 95-111), the amount of SIT reserved at the kth clock interval of the bandwidth resource R _req (k) can be determined based on the number of packets (PDUs) in the buffer of the satellite terminal Q (k), the superframe period T _CK, and the previously generated requests reservation R _req (ki) according to the following formula:

обозначает минимальное целое число, включая нуль, которое больше х.Expression

denotes the minimum integer, including zero, which is greater than x.

In another model that implements the BoD mechanism (e.g., Golta, A. Simulating Dynamic Bandwidth Allocation on Satellite Links / Gotta, A., Potorti, F., Secchi R. // WNS2, 2006, October 10, 2006, Pisa, Italy) , the volume of the reservation request is calculated based on an estimate of the data arrival rate R _in (k) without taking into account previously generated requests:

An analysis of expressions (1) and (2) indicates that these expressions make it possible to formulate a reservation of the satellite network bandwidth for packet data that is not critical to the time delay that occurs due to the inertia of the resource allocation process and the propagation delay of the radio signal in the satellite channel. According to the DVB-RCS standard, this type of graphics includes VBDC (Volume-Based Dynamic Capacity) traffic. An example of this type of traffic is file exchange, fax transmission, e-mail, etc.

For traffic critical to the time delay, which is designated in the DVB-RCS standard as RBDC (Rate-Based Dynamic Capacity) traffic, for example, VoIP traffic or video conferencing, this method of generating bandwidth request is not suitable, which allows us to conclude that there is no adequate models for generating a request for bandwidth reservation, which ensures efficient distribution of the bandwidth network resource and takes into account the amount of traffic received, transmitted, and buffered in the satellite terminal, which allows adapting fall under the inertia of the resource allocation process, which is important when allocating a resource for a given type of traffic.

A known method for the dynamic allocation of resource bandwidth in interactive multimedia satellite communications networks, which is described in the patent (patent US 7346069 B2, H04L 12/28, "Apparatus and method for dynamic resource allocation in interactive satellite multimedia system", dated March 18, 2008).

According to the invention, in order to increase the computational efficiency of bandwidth allocation, the dynamic planning device (scheduler) of the central station (CA) estimates the volume of requests for resource allocation received from active SITs, forms paired frames in the super-frame structure, divides the total amount of requested bandwidth resource by the number of paired frames. Next, the CA distributes the shares of the requested bandwidth resource per pair within this pair sequentially for all active SITs and duplicates the resulting distribution in the remaining paired frames, thereby achieving a reduction in the computational time required to allocate the resource in a superframe.

The disadvantage of the analogue method is that the introduced procedures provide for the reduction of computational complexity in the allocation of bandwidth resources, rather than achieving high efficiency of its use. Quality of Service (QoS) requirements for various types of traffic are not taken into account.

Another method for allocating bandwidth resource in satellite interactive access networks, taking into account the time delay and jitter requirements for multimedia graphics, is proposed in the invention (patent US 7385943 B2, Н04В 7/212, "Method of allocating communication resources in an MF-TDMA telecommunication system ", dated 10.06.2008).

According to the invention, all multimedia traffic declared for transmission in reverse channels, depending on the transmission quality requirements, is divided into information flows (service classes) that are sensitive to time delay (real-time traffic: speech, video conferencing), and information flows that are not critical time delay (interactive data traffic: file transfer, Internet access, e-mail, etc.). The analogue method involves reserving on a fixed basis time slots from one superframe to another to transmit a real-time graph in order to reduce the time delay and jigger. For interactive data traffic on each period of the superframe, the time slots remaining in the superframe after serving real-time graph requests are assigned. The main attention in the analogue method under consideration is paid to the technical implementation of the algorithm for assigning time slots sequentially by service class (justification of performance, processor clock frequency, bus capacity), which reduces the time spent on the procedure for generating the time-frequency transmission plan (VTR).

The disadvantage of the analogue method is that the proposed method, aimed at increasing computational efficiency in the allocation of bandwidth resources, does not take into account dynamic (statistical) traffic characteristics (packet arrival rate in buffers and their volume), the degree of provision of differentiated requirements to the quality of packet data service and does not provide for the achievement of high resource utilization.

In the invention (patent US 2007/0104101 A1, H04L 12/26, "Dynamic resource allocation based on quality-of-service", 05/10/2007), a method for dynamically allocating a resource in interactive satellite communication networks is described.

According to the invention, all dynamic reservation requests arriving at the CA from satellite terminals are classified by service class on the basis of the requested speed, the amount of data transferred, and the level of QoS service quality requirements. The dynamic scheduling device of the CA, in accordance with the class of requests, sequentially distributes the time-frequency resource available in the current superframe. Bandwidth resource allocation is performed by time-frequency blocks of a fixed volume [ΔF · Δτ], where ΔF is the frequency band corresponding to the minimum symbol rate, Δτ is the duration of the time slot.

The disadvantage of the analogue method is the low network bandwidth due to the low computational efficiency of actually exhaustive time-frequency resource allocation procedures performed sequentially from requests of the highest class of service to less priority and the need for re-redistribution with limited resources.

The closest in technical essence and the functions performed to the claimed solution is a method for dynamically allocating a resource of bandwidth of reverse channels in an interactive access satellite multimedia network described in the invention (patent RU 2410838 C1, H04J 4/00, "Method for dynamically allocating a resource of bandwidth of reverse channels in the multimedia network of satellite communications of interactive access ", published in the bulletin No. 3 of 01/27/2011).

According to the invention, satellite interactive terminals generate requests for dynamic reservation of time slots for the duration of the next superframe, send the generated requests to the central station of the network. The central station recalculates the capacity requested by the terminal in the number of time slots that are allocated to the terminals for the duration of the next superframe.

However, the prototype method has a drawback: it does not disclose a method for generating a dynamic bandwidth reservation request, which is due to its focus on achieving a high bandwidth utilization rate only under traffic congestion.

The objective of the invention is to develop a method for dynamically reserving the bandwidth resource of reverse channels in an interactive access satellite communication network, which allows to increase the efficiency of using the frequency and energy resource of a transponder allocated to an interactive access satellite communication network in the absence of schedule overload due to minimally excessive bandwidth reservation with providing requirements for average delay and delay jitter for transmission The specified packet data is the RBDC schedule, which includes VoIP and video conferencing traffic.

This problem is solved in that in a method for dynamically reserving a resource of bandwidth of reverse channels in an interactive access satellite communication network, satellite interactive terminals generate requests for dynamically reserving time slots for the duration of a next superframe, send generated requests to the central station of the network, which recalculates the volume requested by the terminal bandwidth in the number of time slots allocated to terminals for a duration o erednogo superframe. According to the invention, in each active satellite terminal, the packet data traffic rate received from the terminal equipment and the satellite buffer input buffer occupancy in time periods that are multiples of the superframe duration are measured, the optimum quantile level value for the predicted packet data arrival rate in the satellite terminal buffer is determined by one , two and three superframes forward, form a request for dynamic bandwidth reservation taking into account QoS requirements based on the completeness of the input buffer and the queries generated on previous superframes, as well as the data of the forecast of the arrival rate of the packet schedule, taking into account the level of the quantile characterizing the redundancy of the reservation.

Thanks to the new set of essential features in the method, it is possible to increase the efficiency of using a dedicated satellite communications network of interactive access of a bandwidth resource by reducing redundancy in a dynamic reservation request generated in the satellite terminal.

The analysis of the prior art made it possible to establish that analogues that are characterized by a combination of features that are identical to all the features of the claimed technical solution are absent, which indicates the compliance of the claimed method with the condition of patentability "novelty".

Search results for known solutions in this and related fields of technology in order to identify features that match the distinctive features of the prototype of the claimed method showed that they do not follow explicitly from the prior art. The prior art also did not reveal the fame of the distinctive essential features that determine the same technical result, which is aimed at solving the problem, therefore, the claimed invention meets the patentability condition "inventive step".

The possibility of implementing the inventive method on modern computing processors, for example using programmable logic integrated circuits (FPGAs), allows us to claim its "industrial applicability".

The claimed method is illustrated by drawings, which show:

figure 1 - structure of a multimedia satellite communications network that implements time-division multiple access (MF-TDMA) in reverse channels;

figure 2 - time-frequency structure of a superframe;

figure 3 - mechanism for providing resource bandwidth on demand (BoD) in interactive satellite communications networks;

figure 4 is a block diagram of the algorithm for generating a request for dynamic reservation of bandwidth for the duration of the super-frame;

5 is a composition of the equipment of a satellite interactive terminal.

6 - the results of experimental verification of the effectiveness of the developed method.

The possibility of implementing the claimed method is illustrated as follows.

Figure 1 presents a multimedia satellite communications network of interactive access, where: 11 is the central station of the network (CA, HUB), 12 is a communications repeater located on board the spacecraft in geostationary orbit, 13 are satellite interactive terminals.

In the direct satellite channel 14 from the DS 11 through the communication repeater 12, data streams for all satellite interactive terminals of the network 13 (SIT 1, SIT 2, ..., SIT N) are transmitted in a single multiplexed high-speed digital stream on one carrier 14 in the fixed lock mode (mode TDM / PAMA). In the reverse channels 15 from the SIT to the DS, time division multiple access (MF-TDMA) is implemented, in which the SITs can transmit data on one of the carrier frequencies currently available to the terminal at the allocated positions of the time slots. The number of carrier frequencies is determined by the technical capabilities of the terminals, and corresponds to the number of demodulators in the composition of the CA equipment.

The public time-frequency resource of the return channels of a satellite network is divided into superframes 20, each of which in turn is divided into frames 21 (FIG. 2).

Each frame 21 occupies a set of frequency bands Δf _s1 , Δf _s2 , Δf _s3 , corresponding to the symbolic transmission rate, and is limited in time by a fixed duration divided by time slots 22. The number of time slots in a superframe at the positions of which data is transmitted with information bit rate determines Potential network bandwidth resource. For example, in the structure shown in FIG. 2, superframe 20 consists of 8 frames 21, each of which has 15 time slots 22. The information rate for a duration of one time slot is 32 kbit / s. In this case, the network bandwidth resource is 8 · 15 · 32 = 3840 kbit / s.

To gain access to the bandwidth resource of the next super-frame, the SIT goes through the registration procedure, which includes the steps of initializing the terminal, synchronizing on the carrier frequency, cyclic and clock synchronization, after which it can send dynamic reservation requests to the central station and receive it allocated for packet traffic bandwidth resource in the form of the required number of time slots.

After processing the requests, the CA distributes and assigns to each SIT the necessary number of graphical time slots according to the principle of fixed reservation for the duration of a superframe. Time-frequency assignment information is dynamically updated from superframe to superframe based on new estimates of request volumes.

Data on the allocation of a radio resource CA for the operation of satellite interactive terminals (frequency band, carrier number, time intervals for slot transmission) is transmitted in the form of additional service information tables: superframe composition, frame composition, structure of time slots, correction messages, terminal information messages, time information packet transfer plan by the terminal.

Within the frame of the CIT, any traffic time slots can be allocated. For example, in FIG. 2, the arrows show the sequence of allocation of time slots for one terminal, first slot 1 in the frequency band Δf _s1 , then slot 12 in the frequency band Δf _s3 , and slot 9 in the frequency band Δf _s2 . Such a distribution of time slots can be duplicated in all frames of a given superframe or have a different distribution.

The DVB-RCS-recommended mechanisms for providing a network bandwidth resource on demand include allocating time slots to each satellite network terminal 13 (Fig. 1) in the superframe structure (Fig. 2) in accordance with the dynamic reservation requests R _req received from them (Fig. .3).

In the satellite interactive terminal (Fig. 3), at the k-th moment in time, a dynamic reservation request for bandwidth resource 31 is generated, which is transmitted to the central station. Having processed the received request, the central station allocates to the SIT the necessary number of time slots, which in the form of a time-frequency plan 32 will be sent to the SIT at the time (k + 1). Having received the FWM, the satellite terminal will be able to transmit the packet data located in its buffer at time (k + 2) at the temporary positions of the allocated time slots. Thus, when using the BoD mechanism, a delay in data transmission occurs, which is equal to at least the duration of two superframes.

Based on the features of the functioning of interactive satellite communication networks, which consist of a time delay in allocating a resource to an incoming request due to the propagation of a radio signal in the satellite interval and the stochastic nature of the change in the intensity of packet arrival in the terminal buffer, the dynamic reservation request is generated taking into account the redundancy necessary for meeting QoS requirements when transmitting a packet schedule sensitive to time delay, for example p, compressed speech (after processing by the VAD detector) or video conferencing.

In accordance with the developed method for dynamic reservation of bandwidth (Fig. 4), for the duration of the next k-th superframe, the number of active satellite interactive terminals in network I, the rate of packet data R _i in the buffer of the i-th satellite terminal, is estimated (step 41), the number of bits of information Q _i located on a given clock interval in the buffer.

At step 43, in each terminal, a prediction is made of the rate of arrival of packet data into the terminal buffer by one, two and three super-frames. To ensure QoS requirements, depending on the type of transmitted packet schedule, forecasting is performed taking into account the quantile of the distribution of the predicted speed α, which characterizes the redundancy of the reservation and takes values from 0.5 to 1.

For all satellite terminals, the determination of the volume of the resource allocation request in the terminal is made on the basis of the buffer buffer of the terminal and estimation of the packet data arrival rate (step 44) in accordance with expression (3):

where Q (kT _CK ) is the size of the queue at the kth clock interval;

- статистические оценки прогноза скорости поступления пакетных данных в буфер терминала;

- statistical estimates of the forecast rate of arrival of packet data in the terminal buffer;

T _CK is the superframe period;

α is the quantile of the distribution of the predicted speed values characterizing the redundancy of the reservation, α = [0.5-1];

τ _RTD is the delay in the circular propagation of a radio signal equal to twice the duration of a superframe;

l is the set of natural numbers 1, 2, 3, etc.

The first term of expression (3) characterizes the amount of bandwidth allocated for packet data not served by previous requests at the time of receiving the time-frequency plan. The mathematical sign of the maximum in front of the square brackets means a choice of two values, recorded with a comma, larger. The second component takes into account the forecast of changes in the speed of packet data by k + 1 clock interval.

At step 45, a dynamic bandwidth reservation request is generated, which is performed by all active network terminals (steps 46, 47), after which they are sent to the central station of the network, which allocates for each request the required number of time slots 22 in the superframe 20 structure.

The problem of finding the optimal quantile value belongs to the class of nonlinear optimization problems. A rigorous solution to such optimization problems is associated with finding stochastic functional dependencies that characterize the dynamics of changes in particular indicators of network service quality and resource efficiency. One of the ways to solve this class of problems is the Lagrange multiplier method (Bertsekas, D. Conditional optimization and the Lagrange multiplier methods. Transl. From English. - M.: Radio and communications, 1987. - 400 pp .: ill.).

The prediction of the packet arrival rate to the satellite terminal (Fig. 5) is carried out in the dynamic reservation unit 518.

The satellite interactive terminal consists of two main devices: an indoor unit 51 (IDU-In Door Unit), which is installed inside a heated room and an outdoor unit 52 (ODU-Out Door Unit), which is installed in an open area that provides direct visibility between the antenna of the satellite terminal 524 and the antenna of the communication repeater located on board the spacecraft 12.

Subscriber traffic is generated by the terminal equipment: video conferencing equipment (VKS) 511, telephone VoIP device 512, fax machine 513 and computer 514 performing file exchange. From the VKS equipment, packet traffic is sent directly to the multiplexer 516. Packet data from the remaining devices (512-514) is transmitted to the multiplexer after converting the signal joints to a single form in the interface converter 515. After combining the digital streams of various sources in the multiplexer 516 into a single group stream, data received through the input interface port buffer satellite modem 517. in satellite modem estimated buffer occupancy Q _i and the data packet arrival rate R _i, which yavlyayuts the initial data for the formation of dynamic reservation request bandwidth 31 performed in dynamic redundancy block 518 in accordance with the expression (3).

After the central station 11 allocates time slots 22 to the satellite terminal 13, packet data from the input buffer of the satellite modem 517 is sent to the scrambling, noise-resistant coding devices and then to the modulator included in the modem. A modulator generates a radio signal at an intermediate frequency, for example 70 MHz, which, after amplification, is fed to the output of a satellite modem 517. A radio frequency signal is transmitted through a radio-frequency cable to the converter, which is part of the ODU 52, in which it is transferred to the range of the satellite terminal and amplified to rated power in the power amplifier 522, and using the antenna 524 is radiated in the direction of the communication repeater.

The radio signal from the central station 11 through the communication repeater 12, the antenna 524 enters the SIT receiving path, where it is amplified in the LNA 523 and converted to an intermediate frequency in the radio frequency converter 521. The amplified signal at the first intermediate frequency, via the radio frequency cable, enters the IDU 51 to the input of the satellite modem 517, where it is amplified and demodulated, followed by error correction in the noiseless decoder, descrambling. Further, the packet data in the form of a group stream is sent to the multiplexer 516, where it is divided into VKS data and VoIP, fax and file exchange data. The VKS data stream is transmitted to the VKS 511 receiver, the rest of the data is supplied to the corresponding terminal equipment through the interface converter 515.

The proposed method is based on a weighted distribution algorithm for the bandwidth of the time-frequency structure of a superframe between streams of different classes of active satellite terminal services and provides a significant reduction in the disadvantages of the prototype method by measuring the speed of packet data received from the terminal equipment and the saturation of the input buffer of the satellite terminal in time periods, multiples of the superframe duration, determining the optimal quantile level of the predicted values one, two, and three superframes forward of packet data arriving at the satellite terminal’s buffer, generating a dynamic bandwidth reservation request taking into account QoS requirements based on the input buffer full and requests generated on previous superframes, as well as predicting the packet arrival rate made with taking into account the quantile characterizing redundancy of redundancy.

An experimental verification of the developed method was performed on a computer in the Matlab R2011b application package (version 7.13.0.564) with the following initial data:

1) the number of sources of packet graphics (N _VoIP ) varies from 5 to 25;

2) the transmission rate of the packet schedule of one source varies from 5 to 15 kbit / s;

3) the formation of the dynamic reservation request is made for the quantile value of the distribution of the predicted speed equal to 0.5, 0.75 and 1.

The calculation results presented in Fig.6 (a solid line for the proposed method 601, a dashed line for reserving the bandwidth under the peak speed of the transmitted packet traffic 602) provide the basis for the conclusion that the claimed method for dynamically reserving the bandwidth resource of the reverse channels in a satellite communication network interactive access provides the best indicators of the coefficient of efficiency of bandwidth utilization in comparison with the prototype by reducing redundancy in the form emom request dynamic redundancy is achieved by predicting the arrival rate of the packet traffic in the satellite terminal buffer for one, two and three superframe and confirm the possibility of achievement of the task.

Thus, with such a combination of essential features, it is possible to increase the efficiency of using the bandwidth of the reverse channels of interactive satellite communication networks by reducing the redundancy in the generated dynamic reservation request, and as a result, increasing the efficiency of using the frequency-energy resource of the communication relay and can be implemented on modern computing processors, for example, using programmable logic integrated circuits (FPGAs). Commercial products on the market are distinguished by their performance, RAM capacity, number of valves, etc. The FPGAs of the Virtex FPGA series of Xilinx Inc (http://www.xilinx.com) satisfy the requirements to the fullest extent.

The indicated method can find its application in any wireless access systems transmitting multimedia information between subscriber terminals in conditions of limited frequency and energy resources.

Claims (1)

A method for dynamically reserving the resource of the bandwidth of the return channels in an interactive access satellite communication network, which consists in the fact that all satellite interactive terminals generate requests for dynamic reservation of time slots for the duration of the next superframe, send the generated requests to the central station of the network, which recalculates the amount of bandwidth requested by the terminal abilities in the number of time slots allocated to terminals for the duration of the essay a single superframe, characterized in that in each active satellite terminal, the packet data traffic received from the terminal equipment is measured and the input buffer of the satellite terminal is full in times multiple of the superframe duration, the optimal quantile level value for the predicted packet data arrival rate in the buffer is determined satellite terminal one, two and three superframes forward, form a request for dynamic reservation of bandwidth, taking into account the requirements Nij QoS based on the fullness of the input buffer and formed on superframes previous requests, as well as forecast data rate packet traffic proceeds made with the level of quantile characterizing backup redundancy.

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