CN102932308A - Scheduling method and scheduling system under mixed business scenes in orthogonal frequency division multiplexing (OFDM) relay system - Google Patents

Abstract

The invention discloses a resource scheduling system and a method based on user quality experience under mixed business scenes in an OFDM relay system, and relates to the OFDM relay system. According to the method and the system, a uniform user satisfaction model is built for users to reflect the current satisfaction degree of the users according to requirements of real time polling service (rtPS) for average delay and requirements of non real time polling service (nrtPS) for average speed. Sub-channels are allocated to the user with the largest satisfaction increasing range on the sub-channels to improve the whole user satisfaction of the system. By using the method, the problem of waste of resources caused by the fact that the mobile communication system only considers form the system perspective and ignores user experience at present can be solved, and the resource scheduling algorithm base on quality of experience (QoE) can be achieved.

Description

Method and system for scheduling mixed service scene in OFDM relay system

Technical Field

The invention relates to the technical field of mobile communication, in particular to a technical scheme for scheduling resources of an OFDM relay system and realizing the maximization of the integral satisfaction degree of system users.

Background

In the next generation wireless communication system, the goal is to achieve high-speed data transmission and seamless global coverage. In the case of scarce and expensive spectrum resources, this goal can only be achieved by increasing the spectrum utilization by frequency reuse. Orthogonal Frequency Division Multiple Access (OFDMA) is the focus of attention for its better resistance to multipath effects. In addition to better reducing frequency selective fading caused by multipath effect, the frequency band is divided into a plurality of sub-carriers in the OFDM network, and the sub-carriers are mutually independent, so that the wireless resource allocation mode is more flexible, and the utilization rate of the system frequency spectrum is improved. In order to achieve seamless coverage in a conventional network, the number of Base Stations (BSs) must be increased, which causes an increase in costs. The Relay (Relay) network can reduce the network cost, expand the network coverage and have better flexibility. Fig. 1 is a schematic diagram of a topology of an OFDMA relay system. In fig. 1: the BS is a cell base station, the RS is a relay, the UE is a user, and buffer areas are respectively set for the user on the BS and the RS to store user data.

The wireless resource scheduling algorithm plays a crucial role in improving the performance of a wireless network, and particularly in an OFDM relay system, a plurality of subcarriers and two-hop links make a resource scheduling mode more flexible. The reasonable resource scheduling algorithm can improve the system capacity to a great extent and ensure the user fairness.

At present, the scheduling algorithm for the OFDM relay system is mostly performed based on channel state information, queue length, or user QoS. These resource scheduling algorithms are based on the system perspective, and aim to maximize the system performance, without considering the subjective experience quality of the user, and cannot perform reasonable wireless resource allocation according to the urgency of the user's needs. In this case, the concept of qoe (quality of experience) is introduced. QoE may be understood as a service evaluation method based on user experience or perception. It is influenced by service, user and environment, and directly reflects the satisfaction degree of user to the obtained resource or service by approximate quantification method. That is, the satisfaction degree of the user is not only objectively influenced by the amount of the resources allocated by the system, but also influenced by the subjective consciousness of the person, for example, when the user obtains enough resources and the satisfaction degree is higher, the resources are continuously allocated to the user, the increase of the satisfaction degree of the user is smaller and smaller, and if the traditional resource scheduling algorithm is adopted, the unfairness of resource allocation is caused.

The theory of QoE is still immature at present, and different researchers try to quantitatively evaluate QoE from different angles, so that many different quantitative methods and evaluation methods emerge. Meanwhile, different users have different requirements on services, for example, real-time services have higher requirements on delay and relatively lower requirements on average rate, while non-real-time services or BE services have lower requirements on delay and relatively higher requirements on average rate. The same resources are allocated to different kinds of users, and the satisfaction improvement of the users is not the same. This also presents a significant challenge for scheduling allocation of radio resources in a mixed traffic scenario.

Disclosure of Invention

Aiming at the technical problems in the prior art, the invention aims to establish a uniform user satisfaction model under a mixed service scene in an OFDM relay system and allocate wireless resources according to the user satisfaction, thereby improving the overall efficiency of the system.

The technical scheme adopted by the invention for solving the technical problems is as follows: buffer areas are set in a Base Station (BS) and a Relay (RS) to store user data, a BS end is provided with a channel state information collection module and a queue state information collection module to collect channel state information of each link in a two-hop link and queue state information of the buffer areas of the BS and the RS end, and the satisfaction degree of a user is estimated. The sub-channels are allocated according to user satisfaction.

The user communicates with the base station through the relay, and the relay sets a buffer area to store the data sent by the base station and forwards the data in the next sub-time slot. And the base station collects the channel state information between the links and the queue state information of the buffer area, estimates the user satisfaction degree and then performs resource allocation according to the user satisfaction degree. The specific scheduling method comprises the following steps:

the channel state information extraction unit and the queue state information extraction unit respectively extract the time delay required by the QoS of the userRate of change ofAnd maximum delay that a real-time user can tolerate

Calculating the average time delay of the current time slot of the user

And average rate

；

According to different requirements of real-time service and non-real-time service on time delay and average rate, a user satisfaction degree estimation unit carries out normalization processing on the average time delay or average rate of a user to establish a user satisfaction degree equation:

${\mathrm{MOS}}_m\left(t\right)={\log }_2({\∂}_m\·a\·\frac{D_{\max }^m-\stackrel{\‾}{D_m\left(t\right)}}{D_{\mathrm{req}}^m}+(1-{\∂}_m)\·a\·\frac{\stackrel{\‾}{R_m\left(t\right)}}{R_{\mathrm{req}}^m})$ ；

taking the maximum user satisfaction as an optimization target, and taking the lower limit of the queue length of the user buffer area and the upper limit of the user satisfaction as limiting conditions, establishing an objective function:

determining the current satisfaction degree of a user;

a feedback information receiving unit receives channel state information and RS end queue length information in a two-hop link in a feedback channel;

and the scheduling and distributing unit distributes each sub-channel according to the current satisfaction of the user and the channel state information to schedule the user resources of the relay link.

And carrying out resource scheduling according to the length of the data queues of the base station and the relay terminal.

A feedback information receiving unit acquires channel state information in the first hop and RS end queue state information from a feedback channel, and initializes to acquire a subchannel set of X; selecting a subchannel n with the best channel condition from the available subchannels; selecting a user m with the maximum difference between the queue length of the BS end and the queue length of the RS end; distributing a subchannel n to a user m, updating data queue information of a BS end and an RS end of the user, and updating a subchannel set to X' = X \ n; until the set of sub-channels is empty.

Each sub-channel is allocated to the user with the maximum satisfaction degree on the sub-channel so as to improve the satisfaction degree of the system user.

Acquiring channel state information in the second hop from the feedback channel, wherein the initial subchannel set is X, and the user set is U; selecting one subchannel n from available subchannels, and allocating the subchannel to a user; for real-time service users, calculating the average time delay of the users, and according to a formula:

computing subchannel n assignmentThe user satisfaction degree after the user increases, the user average rate is calculated for the non-real-time service user, and according to a formula:

calculating the user satisfaction increase amplitude after the sub-channel n is distributed to the user, wherein the MOS_m(t) is the current satisfaction of the user,

user satisfaction after subchannel n is assigned to the user; selecting a user m with the maximum delta MOS (t), distributing a subchannel n to the user m, and updating queue state information and average rate of the user m; until the set of sub-channels is empty.

The invention also provides a resource scheduling system under the mixed service scene in the OFDM relay system, which comprises: the system comprises a feedback information receiving unit, a channel state information extracting unit, a queue state information extracting unit, a user satisfaction estimating unit and a resource scheduling unit, wherein the channel state information extracting unit and the queue state information extracting unit respectively extract the time delay required by the QoS of a user

Rate of change of

And maximum delay that a real-time user can tolerate

Calculating the average time delay of the current time slot of the userAnd average rate(ii) a The user satisfaction estimating unit carries out normalization processing on the average time delay or the average speed of the user to establish a user satisfaction equation:

(ii) a Establishing an objective function by taking the maximum user satisfaction as an optimization target and taking the lower limit of the queue length of the user buffer area and the upper limit of the user satisfaction as limiting conditions, and determining the current user satisfaction; a feedback information receiving unit receives channel state information and RS end queue length information in a two-hop link in a feedback channel; and the resource scheduling unit allocates each sub-channel according to the current satisfaction of the user and the channel state information to schedule the relay link user resources.

The invention establishes a unified user satisfaction model for different types of users in a mixed service scene, and adopts a resource scheduling method which is based on the user satisfaction and aims at maximizing the overall satisfaction of the system users, thereby realizing reasonable distribution of wireless resources.

Drawings

FIG. 1 is a schematic diagram of a topology of a cellular mobile communication system of a relay station

FIG. 2 is a schematic diagram of a scheduling mechanism system according to an embodiment of the present invention

FIG. 3 is a flowchart of scheduling resources of a first hop of a relay link according to an embodiment of the present invention

FIG. 4 is a flowchart of scheduling resources of a second hop of a relay link according to an embodiment of the present invention

Detailed Description

In order to make the technical solution advantages of the present invention more apparent, the following detailed description of the embodiments of the present invention is made with reference to the accompanying drawings.

Fig. 1 is an application scenario of the present invention, and as shown in fig. 1, the system includes a Base Station (BS), a Relay (RS), and a User Equipment (UE), and it is assumed that all UEs can only communicate with the BS through the RS due to distance and cannot directly communicate with the BS. The BS end and the RS end are both provided with buffer intervals to store user data. The system adopts OFDM access mode, divides the bandwidth into a plurality of independent orthogonal sub-channels on the frequency domain, and divides a time slot into two sub-time slots on the time domain for data transmission on the BS-RS link and the RS-UE link respectively.

Fig. 2 is a schematic diagram of a BS-side information collection module and a scheduling module. The method comprises the following steps: feedback information receiving section 201, temporary data storage section 202, channel state information extraction section 203, queue state information extraction section 204, user satisfaction estimation section 205, and resource scheduling section 206.

The feedback information receiving unit is responsible for receiving information fed back in a feedback channel, wherein the information comprises channel state information in a two-hop link and RS end queue length information.

The temporary data storage unit is used for accessing temporary data, such as user average rate, average queue length of the BS end and the RS end, and the like.

The channel state information extraction unit and the queue state information extraction unit respectively extract channel state information and queue state information. The method comprises the following steps: time delay of user QoS requirementRate of change of

And maximum delay that a real-time user can tolerateObtaining the average time delay of the current time slot of the user

And average rate

，

Can be deduced by Little theorem in queuing theory,

can be obtained by setting a time window.

The user satisfaction estimating unit is responsible for estimating the current satisfaction of the user, and the specific method is to calculate the user satisfaction according to the channel state information, the queue state information, the temporary data and the QoS requirements of different types of users.

The scheduling and allocating unit is responsible for allocating each sub-channel according to the current satisfaction degree of the user and the channel state information.

The user communicates with the base station through the relay, and the relay sets a buffer area to store the data sent by the base station and forwards the data in the next sub-time slot. And the base station collects the channel state information between the links and the queue state information of the buffer area, estimates the user satisfaction degree and then performs resource allocation according to the user satisfaction degree.

The system of the invention comprises real-time users and non-real-time users, which have different requirements on QoS, real-time service has higher requirement on time delay, and non-real-time users have higher requirement on average rate. However, from the perspective of the user, the real-time service and the non-real-time service have the same characteristics, that is, after the resource obtained by the user reaches a certain degree, the resource is continuously allocated to the user, and the increase of the user satisfaction degree is gradually reduced. Based on this characteristic, a unified user satisfaction model is established. The user satisfaction estimating unit carries out normalization processing on the average time delay or the average speed of the user to establish a unified satisfaction equation:

${\mathrm{MOS}}_m\left(t\right)={\log }_2({\∂}_m\·a\·\frac{D_{\max }^m-\stackrel{\‾}{D_m\left(t\right)}}{D_{\mathrm{req}}^m}+(1-{\∂}_m)\·a\·\frac{\stackrel{\‾}{R_m\left(t\right)}}{R_{\mathrm{req}}^m})$

wherein, MOS_m(t) represents the satisfaction of user m at time t, the "mean estimate score" (MOS) is between 1 and 4.5 according to the widely used subjective assessment criteria, and the MOS is serialized. a is constant, and the value of a ensures MOS_m(t) is a value of [1,4.5 ]]Any value in the closed interval.

On behalf of the type of the user,

indicating that the user is a real-time user,

indicating that the user is a non-real-time user.

The method comprises the following steps of establishing an objective function to estimate the current satisfaction of a user by taking the maximum system user satisfaction as an optimization target and taking the lower limit of the queue length of a user buffer area and the upper limit of the user satisfaction as limiting conditions:

wherein

， I(t)_mThe method can reflect the resources obtained by the user m, and the corresponding real-time service and non-real-time service are respectively related to the user average delay and the user average rate in the multi-service environment.

A minimum rate or delay representing the QoS requirements of the user,

representing user type when the user is a real-time service

When the user is a non-real-time user. a is a constant, which can ensure that the value of the user satisfaction is in a certain range. When I (t)_mGreater than or equal toThe user is in a satisfied state, otherwise, the user is not satisfied.

Representing the rate that user m achieved on the second hop of the relay link at time t,

indicating queue length, MOS, of user m in relay buffer at time t_m(T) represents the satisfaction of user m at time T, T₀M is the number of users and is the length of the time slot. The limiting condition can ensure that when the RS end user queue has no data or the user satisfaction reaches the maximum, the user is not allocated with excessive resources any more, so as to avoid allocating excessive resources.

Since the objective function is a non-convex mixed integer optimization problem, it is difficult to directly find the optimal solution, and a scheduling algorithm based on the satisfaction degree increase amplitude can be adopted in this embodiment. Other methods known to those skilled in the art may also be used to solve.

The feedback information receiving unit receives information fed back in a feedback channel, wherein the information comprises channel state information in a two-hop link and RS end queue length information.

And the scheduling and distributing unit distributes each sub-channel according to the current satisfaction of the user and the channel state information to schedule the user resources of the relay link.

In order to ensure the balance of the data in the buffer area of the base station end and the data in the buffer area of the relay end, the resource scheduling is carried out according to the length of the data queue of the base station and the relay end, and the specific implementation method is as follows:

fig. 3 is a flowchart illustrating a scheduling process of a first-hop user resource of a relay link in the present embodiment, where the scheduling process includes the following steps:

step 301: a feedback information receiving unit acquires channel state information in the first hop and RS end queue state information from a feedback channel, and initializes to acquire a subchannel set of X;

step 302: selecting a subchannel n with the best channel condition from the available subchannels;

step 303: selecting the user m with the largest difference between the queue length of the BS end and the queue length of the RS end, wherein the method for acquiring the user m can be according to a formula:

and (4) determining. Wherein,

and

respectively representing the data queue lengths of a BS end and an RS end, wherein q is a constant, and M is the number of system users.

Step 304: and distributing the subchannel n to a user m, updating the data queue information of a BS end and an RS end of the user, and updating the subchannel set to X' = X \ n.

Step 305: and judging whether the subchannel set is empty, if not, continuing to execute the step 304 to allocate the subchannels until the subchannel set is empty.

Fig. 4 is a flowchart of scheduling resources of a second hop user in a relay link according to the present embodiment. According to the optimization target, a suboptimal scheduling algorithm is adopted to allocate each sub-channel to the user with the maximum satisfaction degree on the sub-channel so as to improve the satisfaction degree of the system user, and the specific implementation method is as follows:

step 401: acquiring channel state information in the second hop from the feedback channel, wherein the initial subchannel set is X, and the user set is U;

step 402: selecting one subchannel n from available subchannels;

step 403: for each user in the set of users, according to

Determine its user type, e.g.Step 404 is executed for the real-time service user, otherwise, step 405 is executed;

step 404: calculating the average user time delay (which can be calculated according to Little theorem) after the sub-channel n is distributed to the user, and calculating the satisfaction degree of the corresponding user

. According to the formula:

and calculating the user satisfaction increase amplitude after the subchannel n is allocated to the user. Wherein the MOS is_m(t) is the current satisfaction of the user;

step 405: calculating the average user rate after the subchannel n is distributed to the user, and calculating the satisfaction degree of the corresponding user. According to the formula:

and calculating the user satisfaction increase amplitude after the subchannel n is allocated to the user. Wherein the MOS is_m(t) is the current satisfaction of the user;

step 406, selecting the largest user m of the Δ mos (t), allocating the subchannel n to the user m, and updating queue state information and average rate of the user m;

step 407: and judging whether the satisfaction degree of the user m is 4.5 or the RS end queue is empty. If yes, executing step 408, otherwise executing 409;

step 408: updating the user set to enable U' = U \ m;

step 409: and judging whether the sub-channel set is empty, if not, continuing to allocate the sub-channels according to the method, and if not, ending.

The above description is only a preferred embodiment of the present invention, and is not intended to limit the scope of the present invention.

Claims (9)

1. A resource scheduling method under a mixed service scene in an OFDM relay system is characterized by comprising the following steps: the channel state information extraction unit and the queue state information extraction unit respectively extract the time delay required by the QoS of the user

Rate of change of

And maximum time that a real-time user can tolerateDelay time

Calculating the average time delay of the current time slot of the user

And average rate

(ii) a The user satisfaction estimating unit carries out normalization processing on the average time delay or the average speed of the user to establish a user satisfaction equation:

(ii) a Establishing an objective function by taking the maximum user satisfaction as an optimization target and taking the lower limit of the queue length of the user buffer area and the upper limit of the user satisfaction as limiting conditions, and determining the current user satisfaction; a feedback information receiving unit receives channel state information and RS end queue length information in a two-hop link in a feedback channel; the dispatching distribution unit distributes each sub-channel according to the current satisfaction degree of the user and the channel state information to dispatch the user resource of the relay link, wherein, the MOS_m(t) represents the satisfaction of user m at time t, a is a constant,

representing user type when the user is a real-time service

When the user is a non-real-time user

。

2. The method according to claim 1, wherein the established objective function is:

wherein I (t)_mIndicating the resources that are acquired by the user m,a minimum rate or delay representing the QoS requirements of the user,

representing the rate that user m achieved on the second hop of the relay link at time t,

indicating queue length of user m in relay buffer at time T, mosm (T) indicating satisfaction of user m at time T, T₀Is the slot length.

3. The method for scheduling resources in a mixed service scenario according to claim 1, wherein the scheduling of the relay link user resources specifically comprises: and performing resource scheduling according to the length of the data queue of the base station and the relay terminal, and allocating each subchannel to the user with the maximum satisfaction degree improvement on the subchannel.

4. The method for scheduling resources in a mixed service scenario according to claim 3, wherein the resource scheduling is performed according to the length of the data queue of the base station and the relay terminal, and specifically includes: a feedback information receiving unit acquires channel state information in the first hop and RS end queue state information from a feedback channel, and initializes to acquire a subchannel set of X; selecting a subchannel n with the best channel condition from the available subchannels; selecting a user m with the maximum difference between the queue length of the BS end and the queue length of the RS end; distributing a subchannel n to a user m, updating data queue information of a BS end and an RS end of the user, and updating a subchannel set to X' = X \ n; until the set of sub-channels is empty.

5. The method of claim 3, wherein the step of allocating each sub-channel to the user with the highest satisfaction improvement on the sub-channel comprises: acquiring channel state information in the second hop from the feedback channel, wherein the initial subchannel set is X, and the user set is U; selecting one subchannel n from available subchannels, and allocating the subchannel to a user; for real-time service users, calculating the average time delay of the users, for non-real-time service users, calculating the average speed of the users, and according to a formula:calculating the user satisfaction increase amplitude after the sub-channel n is distributed to the user, wherein the MOS_m(t) is the current satisfaction of the user,

user satisfaction after subchannel n is assigned to the user; selecting a user m with the maximum delta MOS (t), distributing a subchannel n to the user m, and updating queue state information and average rate of the user m; until the set of sub-channels is empty.

6. A resource scheduling system under mixed service scene in OFDM relay system is characterized in that the system includes: the system comprises a feedback information receiving unit, a channel state information extracting unit, a queue state information extracting unit, a user satisfaction estimating unit and a resource scheduling unit, wherein the channel state information extracting unit and the queue state information extracting unit respectively extract the time delay required by the QoS of a user

Rate of change of

And maximum delay that a real-time user can tolerateCalculatingAverage time delay of current time slot of userAnd average rate

(ii) a The user satisfaction estimating unit carries out normalization processing on the average time delay or the average speed of the user to establish a user satisfaction equation:

${\mathrm{MOS}}_m\left(t\right)={\log }_2({\∂}_m\·a\·\frac{D_{\max }^m-\stackrel{\‾}{D_m\left(t\right)}}{D_{\mathrm{req}}^m}+(1-{\∂}_m)\·a\·\frac{\stackrel{\‾}{R_m\left(t\right)}}{R_{\mathrm{req}}^m})$ (ii) a Establishing an objective function by taking the maximum user satisfaction as an optimization target and taking the lower limit of the queue length of the user buffer area and the upper limit of the user satisfaction as limiting conditions, and determining the current user satisfaction; a feedback information receiving unit receives channel state information and RS end queue length information in a two-hop link in a feedback channel; the resource scheduling unit allocates each sub-channel according to the current satisfaction of the user and the channel state information to schedule the user resource of the relay link, wherein the MOS_m(t) represents the satisfaction of user m at time t, a is a constant,

representing user type when the user is a real-time service

When the user is a non-real-time user

。

7. The system of claim 6, wherein the established objective function is:

wherein I (t)_mIndicating the resources that are acquired by the user m,

minimum rate or delay to indicate user QoS requirementWhen the temperature of the water is higher than the set temperature,

representing the rate that user m achieved on the second hop of the relay link at time t,

indicating queue length, MOS, of user m in relay buffer at time t_m(T) represents the satisfaction of user m at time T, T₀Is the slot length.

8. The system according to claim 6, wherein said scheduling the user resources of the relay link specifically comprises the feedback information receiving unit acquiring channel state information in the first hop and RS-side queue state information from the feedback channel, and initializing to obtain a subchannel set as X; selecting a subchannel n with the best channel condition from the available subchannels; selecting a user m with the maximum difference between the queue length of the BS end and the queue length of the RS end; distributing a subchannel n to a user m, updating data queue information of a BS end and an RS end of the user, and updating a subchannel set to X' = X \ n; until the set of sub-channels is empty.

9. The system according to claim 6, wherein said scheduling the user resources of the relay link specifically comprises obtaining channel state information in the second hop from the feedback channel, initializing a set of subchannels to X, and a set of users to U; selecting one subchannel n from available subchannels, and allocating the subchannel to a user; for real-time service users, calculating the average time delay of the users, for non-real-time service users, calculating the average speed of the users, and according to a formula:

calculating the user satisfaction increase amplitude after the sub-channel n is distributed to the user, wherein the MOS_m(t) is the current satisfaction of the user,

user satisfaction after subchannel n is assigned to the user; selecting a user m with the maximum delta MOS (t), distributing a subchannel n to the user m, and updating queue state information and average rate of the user m; until the set of sub-channels is empty.

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