Background
Although the development of science and technology is changing day by day, the ground mobile communication system is becoming perfect; however, the terrestrial mobile communication system is limited by geographical conditions and conditions such as unbalanced global economic development, and the like, and has some worry about the problem of realizing global coverage; for example, the terrain of China is complex, and mountainous areas and hilly areas are more, so that the network construction work of the ground communication systems in the areas is difficult to complete; the ocean occupying the most part of the earth area is also the difficulty of ground mobile communication coverage; in recent years, natural disasters frequently occur, and network equipment of a ground mobile communication system is extremely easy to be paralyzed under the influence of the natural disasters, so that the subsequent disaster-resistant rescue activities are influenced; the precision requirement of the military field on communication is higher and higher, the communication safety in the information war is more and more important, and the ground mobile communication system equipment is extremely easy to be damaged by enemies and cannot meet the requirements of the military; especially, in the development of aerospace industry, the ground communication network cannot extend the coverage area to deep space. In this case, the satellite mobile communication system has been regarded by scientists of various countries and has become a research hotspot in the field of mobile communication.
The satellite communication system is a new wireless communication system which uses artificial earth satellites distributed in different orbits to replace a ground base station as a relay station and realizes communication between two or more earth stations by means of forwarding, amplifying or on-board processing radio waves, and the adopted radio wave frequency is a microwave frequency band, namely the frequency is 300MHz-300GHz, and the wavelength is about 1mm-1 m.
In recent years, satellite communication systems have increasingly been combined with modern mobile communication technology and aerospace technology, but have also revealed problems: for GEO satellite communication systems that employ the multi-beam technology, GEO satellites have a larger coverage in GEO systems, and satellite systems increasingly employ the satellite multi-beam technology in order to improve spectrum efficiency. But due to the height of the track, high time delay is brought; in addition, with the access of the user, the increase of the co-channel interference noise affects the size of the signal-to-interference-and-noise ratio, and further affects the transmission delay of the system. Therefore, a reasonable access control strategy needs to be formulated according to the service type of the user, the load conditions of different beams, the channel quality and the like to ensure the time delay requirement of the user. Meanwhile, the GEO satellite has high cost and scarce satellite resources such as bandwidth and power, and how to reasonably utilize the satellite resources is also one of the factors to be considered by the access control strategy.
The GEO satellite system provides a synchronous service for the world, can enlarge the ground communication area, provides an access service for global users, and is an important component in a communication system. However, due to the limited on-satellite processing power and on-satellite resources such as bandwidth and power, in some scenarios, the satellite system may not be able to meet the access requirements of a large number of users, which may increase the Call Blocking Probability (CBP) and thus may not guarantee the QoS (Quality of service) of the users. Secondly, the distance between the GEO satellite and the user is long, and the path loss and the transmission delay generated during communication cannot be ignored.
In summary, how to reduce the influence of path loss and transmission delay and maximize the throughput and resource utilization rate of the satellite system to ensure the service quality of the user becomes a main problem in the design of the access policy.
Disclosure of Invention
The invention maximizes the utilization rate of system resources on the premise of ensuring the access requirement of the user and provides higher service quality for the user; a multi-beam GEO system access control strategy based on maximized throughput is provided.
The method comprises the following specific steps:
step one, aiming at a call request queue of M new users, sequentially receiving call requests by a GEO satellite system under the current fixed frequency reuse factor, and searching channels meeting the requirement C according to the number of channels required by the current userio≤CiaThe beam of (a);
Ciathe number of available channels for a beam; cioThe number of channels required when the call request of the current new user is initiated;
the initial value of the call request of the current user is 1; satisfies C in GEO satellite systemio≤CiaThe total number of the wave beams is N;
step two, aiming at N wave beams meeting the conditions, respectively calculating the signal-to-noise ratio (SINR) of each wave beam for receiving the current user;
SINR when receiving a call request of a current user for an ith beamiThe calculation is as follows:
Siis the signal power when the current user accesses the ith beam; i isiIs the power of the interfering signal in the ith beam, NiRepresenting the noise power of the ith beam.
Step three, calculating the transmission time delay when the current user respectively accesses each wave beam by using N signal-to-noise ratios SINR, selecting the wave beam with the transmission time delay smaller than the system time delay threshold tau, entering the step four, and if not, rejecting the access of a new user;
transmission delay D of the user accessing ith wave beam
i:
BiDenotes a bandwidth of an ith beam, C denotes an amount of data to be transmitted by a user;
sequentially accessing the current user to N' wave beams meeting the conditions, and respectively calculating the total throughput of the GEO satellite system under each wave beam;
when the user accesses the ith wave beam, the total throughput T of the GEO satellite systemi;
Step five, selecting the maximum value of the N' total throughputs of the GEO satellite system, and accessing the current user to the beam corresponding to the maximum value;
step six, sequentially selecting the next call request, repeating the steps from the first step to the fifth step until all the M call requests are accessed into the corresponding beams, and calculating the sum of the total throughput of the GEO satellite system at the moment;
step seven, selecting the next fixed frequency multiplexing factor, repeating the steps from the first step to the sixth step, and calculating the sum of the total throughput of the GEO satellite system of the call request queue under the fixed frequency multiplexing factor;
and step eight, selecting the maximum value in the sum of the total throughputs until all the fixed frequency reuse factors are used up, taking the corresponding frequency reuse factor as the optimal frequency reuse factor, and taking the beam corresponding to each call request as the final access mode.
The invention has the advantages that:
1) the multi-beam GEO system access control method based on the maximized throughput maximizes the system throughput under the condition of meeting the transmission delay threshold by considering the path loss, the user arrival frequency and the frequency multiplexing factor.
2) The frequency reuse factor greatly influences the system performance in some scenes and is an important parameter. Compared with the traditional scheme, the strategy provided by the invention has better performance in the aspect of optimizing the resource utilization rate and has remarkable effect in the aspect of maximizing the system throughput.
DETAILED DESCRIPTION OF EMBODIMENT (S) OF INVENTION
The following describes in detail a specific embodiment of the present invention with reference to the drawings.
The invention provides a Multi-beam GEO System access Control strategy (A CallAdmission Control Scheme Based on maximum knowledge through for the Multi-beam GEO Satellite Communication System) Based on maximum Throughput; firstly, modeling analysis is carried out on a GEO communication system, as shown in figure 1, the GEO communication system is a multi-beam GEO satellite which can provide services for mobile phones, airplanes, vehicle-mounted phones and the like; the channel condition of each beam is not the same due to uneven distribution of user terminals and randomness generated by new calls. The main problem in the access control strategy of multi-beam GEO systems is therefore the selection of beams: assuming that there are multiple beams for 1 GEO satellite system, when there is a new call request, the system will decide whether to allow the new call request to be accessed, if it is allowed to allocate the appropriate beam; and the channel conditions of the beams must meet the requirements of the new call request while maximizing throughput of the GEO satellite system.
The multi-beam makes frequency reuse possible, and in the multi-beam GEO satellite system of the present embodiment, considering the frequency reuse technique, as shown in fig. 2, F1 to F7 represent 7 beams different in frequency, and their frequency reuse factors are 3, 4, and 7, respectively. Overall, the higher the frequency reuse factor, the higher the spectrum utilization; however, co-channel interference between adjacent beams can increase substantially, especially at the beam edges, resulting in a decrease in the signal-to-noise ratio of the access user. When the same frequency interference is reduced, the satellite system can achieve higher total throughput; therefore, an optimal system frequency reuse factor is selected, and the key point is to maximize the system throughput.
When there is C in the GEO satellite
tA channel, a frequency reuse factor of
The channel of each beam is therefore
The multi-beam GEO system access control strategy based on the maximized throughput is as follows:
1) calculating and updating the resource allocation condition of the GEO satellite system in real time;
2) when a new user initiates a call request, firstly checking the resource state and determining whether to allow call access;
3) if the current idle resources are enough, calculating the transmission time delay of each wave beam;
firstly, calculating the transmission delay of the model root wave beam, wherein the access of a new user can bring changes to the network and the channel condition, thereby changing the transmission delay; then, the transmission delay of the co-frequency beam is calculated, and due to different channel interferences, the signal-to-noise ratio of the co-frequency beam may be influenced by the access of a new user, which also changes the transmission delay.
4) Will DiCompared with a transmission delay threshold tau if DiIf the value is less than or equal to tau, the next step is carried out, otherwise, the calling request is rejected;
5) aggregate throughput of computing system
Selecting and distributing optimal wave beams to allow users to access;
6) and repeating the steps when a new user requests access.
The method comprises the following specific steps:
step one, aiming at a call request queue of M new users, a multi-beam GEO satellite system sequentially receives call requests under the current fixed frequency reuse factor, and searches channels meeting the requirement of C according to the number of channels required by the current userio≤CiaThe beam of (a);
Ciathe number of available channels for a beam; cioThe number of channels required when the call request of the current new user is initiated;
the set of call request queues is {1, 2.., M.,. M }; the initial value of the call request of the current user is 1;
satisfies C in multibeam GEO satellite system
io≤C
iaThe total number of the wave beams is N; channel in multi-beam GEO satellite system is C
tA frequency reuse factor of
The channel of each beam is therefore
Step two, aiming at N wave beams meeting the conditions, respectively calculating the signal-to-noise ratio (SINR) of each wave beam for receiving the current user;
SINR when receiving a call request of a current user for an ith beamiThe calculation is as follows:
Sithe signal power when the current user accesses the ith wave beam is related to the path loss; i isiIs the power of the interfering signal in the ith beam, NiRepresenting the noise power of the ith beam.
Step three, calculating the transmission time delay when the current user respectively accesses each wave beam by using N signal-to-noise ratios SINR, selecting the wave beam with the transmission time delay smaller than the system time delay threshold tau, entering the step four, and if not, rejecting the access of a new user;
average transmission time delay D of the user accessing ith wave beam
i:
BiDenotes a bandwidth of an ith beam, C denotes an amount of data to be transmitted by a user;
sequentially accessing the current user to N' wave beams meeting the conditions, and respectively calculating the total throughput of the GEO satellite system under each wave beam;
current user satisfies Cio≤CiaAnd DiAccessing to the ith wave beam after tau is less than or equal to calculate the total throughput T of the GEO satellite systemi;
Step five, selecting the maximum value of the N' total throughputs of the GEO satellite system, and accessing the current user to the beam corresponding to the maximum value;
as can be seen from the formula, the key to maximize the system throughput is the signal-to-noise ratio SINR, which is affected by co-channel beam interference; when more users access the network, more interference is brought; the interference increases and the SINR will decrease. Every time when a user initiates a request, the method calculates the resource allocation condition of the current satellite system and the SINR of each beam to select the optimal beam to access the user; the requirement of the transmission delay threshold value is also considered.
Step six, sequentially selecting the next call request, repeating the steps from the first step to the fifth step until all the M call requests are accessed into the corresponding beams, and calculating the sum of the total throughput of the GEO satellite system at the moment;
step seven, selecting the next fixed frequency multiplexing factor, repeating the steps from the first step to the sixth step, and calculating the sum of the total throughput of the GEO satellite system of the call request queue under the fixed frequency multiplexing factor;
and step eight, selecting the maximum value in the sum of the total throughputs until all the fixed frequency reuse factors are used up, taking the corresponding frequency reuse factor as the optimal frequency reuse factor, and taking the beam corresponding to each call request as the final access mode.
Under each fixed frequency reuse factor, the call request of each user is accessed to different qualified wave beams in the GEO satellite system, so that the GEO satellite system generates different throughputs, and the optimal access wave beam of each user is selected according to the maximum value of the throughputs;
when the call request queues of the M new users are respectively accessed to the optimal beams of the GEO satellite system under the fixed frequency reuse factor, the GEO satellite system generates the sum of the optimal total throughput.
For different frequency reuse factors, the call request queues of the M new users can cause the GEO satellite system to generate different optimal total throughput sums, and the maximal optimal total throughput sum is selected as a final access mode.