Background technology
Following wireless cellular network will support the integrated multimedia of different service quality (QoS, Quality of Service) demand to use.Provide QoS to distinguish a kind of good solution that is considered to for the growing multimedia demand of wireless terminal user.In the HSDPA system, a high speed descending sharing channel is shared by a plurality of users of same sub-district, has the difference of traffic performance between a plurality of users, and unique user also may transmit several business datums that have different QoS to require simultaneously.Such as, user can carry out FTP (File Transfer Protocol) download in browsing video Streaming Media etc.Therefore, the scheduler among the Node B will be simultaneously dispatched the different terminal use (UE) of the different QoS grades of service and shared HSDPA down link.Do not have to improve resource utilization as wide as possible under the congested prerequisite, under the heavier congested prerequisite of load, to satisfy user's as much as possible QoS demand.
Below the HSDPA technology is simply introduced.
HSDPA changes to adapt to subscriber channel by the data volume that adaptive scheduling sent apace, thereby improves user's average downlink transmission data rate.Dispatching algorithm is being controlled shared resource allocation, and each sending time slots has determined to have determined the performance of whole system to a great extent for the user provides the service quality of business and the quantity of service-user.Should be during scheduling mainly based on channel condition, data volume and professional situations such as priority level to be sent such as consideration simultaneously, and give full play to adaptive coding and modulating (AMC, Adaptive Modulation and Coding) and mix the ability of automatic repeat requests (HARQ, Hybrid AutomaticRepeat Request).In the HSDPA system, in order to make system's short term variations of adaptive channel better, dispatching algorithm is positioned among the MAC-hs rather than radio network controller (RNC, Radio Network Controller) of Node B.Below present main dispatching algorithm is introduced.
Repeating query (RR, Round-Robin) algorithm.This algorithm calls each user circularly, and from the scheduling probability, all same probability of each user takies Service Source (time slot, power etc.).During each the scheduling, do not consider the situation that the user was serviced in the past, be memoryless property mode.The repeating query algorithm is the most fair algorithm, and promptly each user probability of obtaining serving equates.But the resource utilization of algorithm is not high, can obtain service because work as the situation of certain user's channel condition very severe yet, and therefore, the throughput ratio of system is lower.
Max carrier to interference (C/I, Carrier-To-Interference Ratio) algorithm.Maximum C/I algorithm is only selected the user of max carrier to interference C/I when selecting transmission user, promptly allow the best CU resource transmission data of channel condition, after this subscriber channel variation, selects the best user of other channels again.The base station is always the best user's service of this transmission time channel condition.The throughput that maximum C/I algorithm obtains is the limiting value of throughput, but in mobile communication system, the residing position of user difference, the signal strength signal intensity that it received is different, maximum C/I algorithm must have been looked after user near from the base station, that channel is good, other users far away from the base station then can't obtain service, and the service coverage of base station is very little.This dispatching algorithm is least fair.
Direct ratio justice (PF, Proportional-Fair Scheduler) algorithm.This algorithm is to transmit for a long time on the roughly fair basis of data throughout keeping the user, considers simultaneously to utilize the short-term channel situation of change to increase efficiency of transmission.Be that system obtains a kind of compromise of maximum throughput rate and fairness.With respect to the round-robin scheduling algorithm, the max carrier to interference algorithm can obtain bigger cell throughout.But adopt the system of max carrier to interference algorithm, the user of service concentrates on the zone very near apart from Node B, and cell coverage area dwindles.And the direct ratio fair algorithm sends data in moment to the user with best channel condition, can reach the highest user data rate and maximum data throughout in each moment like this, but also consider fairness simultaneously to each user, based on channel condition, long process is taken into account all users' throughput in a short time.Also consider data volume to be sent such as user, sent situations such as professional type, priority.
In these dispatching algorithms, repeating query algorithm fairness is best, but throughput of system is lower; Maximum C/I algorithm has best throughput of system performance, but fairness is relatively poor.Therefore people seek some compromise algorithms between these two kinds of algorithms, on the basis that guarantees fairness, seek the maximization of throughput, so occurred such as direct ratio fair algorithm, the maximum C/I algorithm of rate-constrained, feedback controlled dispatching algorithm etc.
Though the fairness that above-mentioned miscellaneous service dispatching method has adopted corresponding scheduling rule and considered resource allocation at business features, because above-mentioned dispatching algorithm all is based on scheduling of resource to different UEs, do not consider professional such as guaranteeing QoS characteristic demands such as bit rate, time delay.Rich based on data service, the data service of UE can have different QoS characteristic demands, therefore in order to guarantee the QoS demand of different business, must carry out resource control to the class of service of multiple QoS demand.In addition, in case system loading is heavier, the user can occurs in the system and can not get scheduling, the situation that QoS is not being met.Under this situation, dispatching algorithm also should be experienced angle from the user except considering fairness and QoS demand, considers that sacrificial section user's speed satisfies user's as much as possible QoS demand.
Summary of the invention
In view of this, main purpose of the present invention is to provide a kind of business scheduling method and device, with the QoS of further raising service dispatching.
For achieving the above object, technical scheme of the present invention is achieved in that
A kind of business scheduling method comprises:
Transmission time delay parameters C according to service queue
Td, service queue dispatching priority indication parameter C
SPIAnd scheduling of user terminals relevant parameter C
UEIn at least one determine to treat the priority of dispatching services formation, be followed successively by the described dispatching services queue assignment physical resource for the treatment of by described priority order from high to low, carry out queue scheduling.
Wherein, described C
TdDetermine that mode is: determine propagation delay time Td according to the UE under the service queue, Td>0 o'clock, C
TdGet positively related value, Td<=0 o'clock, C with Td
TdValue is 0; Described C
SPIValue is the grade point of service queue priority; Described C
UEDetermine by user's channel condition, the basic weighted value and the assurance bit rate of service queue priority.
Wherein, described C
TdGet positively related value, be specially with Td:
Get a Td and a constant sum as C
TdValue or get Td and a constant long-pending as C
TdValue.
Wherein, determine propagation delay time Td, be specially according to UE under the service queue:
Td
i=T
i-Tm
i, wherein, T
iBe to be scheduled and stand-by period of long data piece of stand-by period Tm among the service queue i
iBe the control delay parameter of service queue i, Tm
i=Max (0, δ-Tad
Max), δ is the mac-hs delay requirement of service queue i, Tad
Max=α * T
Harq* N
Max, T
HarqBe that the automatic repeat requests HARQ process of mixed once retransmits required shortest time, N
MaxBe the maximum transmission times of this formation, the corrected parameter of α for setting.
Wherein, C
UEDetermine by following mode:
Wherein, pf
Kj(t) be the weighted value of the described service queue that obtains according to the direct ratio fair algorithm; PriorityQueueWeight[j] be the basic weights of the service queue of j for priority; γ
IkBe K user UE
kThe basic weights of middle formation i are adjusted the factor, γ
Ik=R
g/ R
r, R
gFor guaranteeing bit rate, R
rBe actual transfer rate.
Wherein, determine that the described related parameter of priority for the treatment of the dispatching services formation is two when above, for described parameter is provided with weight coefficient.
Wherein, described weight coefficient is set to fixed value.
Wherein, described weight coefficient dynamically arranges according to the priority of described parameter.
Wherein, described weight coefficient dynamically arranges according to the priority of described parameter, is specially:
The weight coefficient of the parameters C 1 that priority is minimum is made as constant m, and the weight coefficient A2 of the parameters C 2 that priority is time high is made as max, and (C1 * m), the weight coefficient A3 of the parameters C 3 that priority is the highest are made as MAX (max (C1 * m), max (A2 * C2)).
A kind of service dispatching device comprises:
The priority parameters computing unit is used for the transmission time delay parameters C according to service queue
Td, service queue dispatching priority indication parameter C
SPIAnd scheduling of user terminals relevant parameter C
UEIn at least one determine to treat the priority of dispatching services formation; And
Physical source distributing and scheduling unit are used for being followed successively by the described dispatching services queue assignment physical resource for the treatment of by described priority order from high to low, carry out queue scheduling.
Wherein, described priority parameters computing unit comprises C
TdComputing module, C
SPIComputing module and C
UEIn the computing module at least one, wherein, described C
TdComputing module is determined propagation delay time Td according to the UE under the service queue, Td>0 o'clock, C
TdGet positively related value, Td<=0 o'clock, C with Td
TdValue is 0; Described C
SPIComputing module is determined according to the grade point of service queue priority; Described C
UEComputing module is determined by user's channel condition, the basic weighted value and the assurance bit rate of service queue priority.
Wherein, described C
TdGet positively related value, be specially with Td:
Get a Td and a constant sum as C
TdValue or get Td and a constant long-pending as C
TdValue.
Wherein, described C
TdComputing module is determined propagation delay time Td according to UE under the service queue, is specially:
Td
i=T
i-Tm
i, wherein, T
iBe to be scheduled and stand-by period of long data piece of stand-by period Tm among the service queue i
iBe the control delay parameter of service queue i, Tm
i=Max (0, δ-Tad
Max), δ is the mac-hs delay requirement of service queue i, Tad
Max=α * T
Harq* N
Max, T
HarqBe that the automatic repeat requests HARQ process of mixed once retransmits required shortest time, N
MaxBe the maximum transmission times of this formation, the corrected parameter of α for setting.
Wherein, described C
UEComputing module calculates C
UEMode be:
Wherein, pf
Kj(t) be the weighted value of the described service queue that obtains according to the direct ratio fair algorithm; PriorityQueueWeight[j] be the basic weights of the service queue of j for priority; γ
IkBe K user UE
kThe basic weights of middle formation i are adjusted the factor, γ
Ik=R
g/ R
r, R
gFor guaranteeing bit rate, R
rBe actual transfer rate.
Wherein, determine that the described related parameter calculating module of priority for the treatment of the dispatching services formation is two and comprises that also weight coefficient is provided with the unit when above, be used to described parameter that weight coefficient is set.
Wherein, described weight coefficient is provided with the unit weight coefficient and is set to fixed value.
Wherein, the unit is set is that described parameter dynamically arranges weight coefficient according to the priority of described parameter to described weight coefficient.
Wherein, described weight coefficient dynamically arranges according to the priority of described parameter, is specially:
The weight coefficient of the parameters C 1 that priority is minimum is made as constant m, and the weight coefficient A2 of the parameters C 2 that priority is time high is made as max, and (C1 * m), the weight coefficient A3 of the parameters C 3 that priority is the highest are made as MAX (max (C1 * m), max (A2 * C2)).
The present invention is directed to and treat dispatching services, take into full account the traffic performance relevant, utilize professional characteristic to determine its dispatching priority with QoS; The priority of service queue of the present invention and the transmission time delay parameters C of service queue
Td, service queue dispatching priority indication parameter C
SPIIn at least one is relevant, the determined service queue priority of the present invention has fully guaranteed professional QoS, has improved the performance of service dispatching.
Embodiment
Below in conjunction with accompanying drawing technical scheme of the present invention is elaborated.
Fig. 1 is the flow chart of the business scheduling method of the embodiment of the invention, and as shown in Figure 1, the business scheduling method of the embodiment of the invention may further comprise the steps:
Step 101: according to the transmission time delay parameters C of service queue
Td, service queue dispatching priority indication parameter C
SPIAnd scheduling of user terminals relevant parameter C
UEIn at least one determine to treat the priority of dispatching services formation.
The dispatching method of the embodiment of the invention promptly is channel condition, the delay character of service queue, the assurance bit rate (GBR that takes all factors into consideration terminal, Guaranteed Bit Rate), priority level of service queue etc., under the prerequisite that satisfies user QoS demand, improve the data throughout of sub-district as far as possible.Based on the dual consideration of user terminal and service queue, dispatching method of the present invention can embody user's demand for services better, and user experience is better, and provides high as far as possible transfer of data according to channel condition for the user.Below introducing the present invention is how to determine service queue priority.
Represent to determine the parameter of service queue priority, to calculate the relevant parameter C of this service queue with CQ for arbitrary service queue
Td, C
SPIAnd C
UE, then the CQ of service queue presses following formula and determines:
Wherein, i represents the numbering of service queue.
Wherein, C
TdDelay requirement according to service queue is determined, described delay requirement is relevant with the grade of service of user's selection, the priority of service etc., each business user-selected or customization is corresponding with a priority level, and the service queue of each priority level all has corresponding delay requirement, can determine propagation delay time Td according to UE under the service queue, be specially:
Td
i=T
i-Tm
i, wherein, T
iBe to be scheduled and stand-by period of long data piece of stand-by period Tm among the service queue i
iBe the control delay parameter of service queue i, Tm
i=Max (0, δ-Tad
Max), δ is the mac-hs delay requirement of service queue i, Tad
Max=α * T
Harq* N
Max, T
HarqBe that a HARQ process retransmits required shortest time, N
MaxBe the maximum transmission times of this formation, the corrected parameter of α for setting, the α value is big more, and the priority of corresponding service formation is high more, and the α value can rule of thumb be provided with, and for the service queue of each priority, all correspondence is provided with the α value.For the service queue that does not have delay requirement, can its Td value be set to constant, for example-1, be set to cause this service queue always can not be scheduled after the negative value, can unconfinedly not wait in order to guarantee this service queue, can be set to a bigger value by δ, to reduce the stand-by period of service queue.In a word, for the service queue that does not have delay requirement, can be set its stand-by period according to service feature.The present invention just is being based on the Td value of service queue and is determining C
Td, when Td>0, illustrate that service queue is overtime, need scheduling as early as possible, this moment C
TdGet positively related value, and when Td<=0, service queue is described as yet not to the time of being scheduled with Td, at this moment, C
TdValue is 0.Here, C
TdValue and Td positive correlation, for example: C
Td=Td+b, wherein, b is a positive constant, for example value is 1,2 or 5; Perhaps, C
Td=Td * b.Certainly, if C
TdThe evolution value or the square root of getting Td also can.
C
SPIValue is the grade point of service queue priority.For example for general service, its C
SPIBe set to 0, set gradually according to priority order from low to high for the business that special priority is arranged be 1,2 ..., 15.Above-mentioned C
SPIValue just the priority level value with business is identical, also can get and react corresponding other values, high more its corresponding value of priority is big more.
C
UEBy the basic weighted value of user's channel condition, service queue priority and guarantee that bit rate etc. determines:
Wherein, pf
Kj(t) for the weighted value of the service queue that obtains according to the direct ratio fair algorithm, it will be appreciated by those skilled in the art that the direct ratio fair algorithm is a known technology, repeat no more here.PriorityQueueWeight[j] be the basic weights of the service queue of j for priority, these basic weights are by default.γ
IkBe K user UE
kThe basic weights of middle formation i are adjusted the factor, γ
Ik=R
g/ R
r, R
gFor guaranteeing bit rate, R
rBe actual transfer rate.
When there is the phenomenon of being transferred sky in buffer memory service queue in dispatching cycle, just with γ
IkValue is set to initial value.γ
IkAdjusting range at γ
i MinAnd γ
Ik Max For example M gets 100,150 or 200.
The CQ value that calculates is big more, and the priority of corresponding service queue is high more.
Need to prove, determine that parameter that the CQ of service queue relates to reaches two when above, promptly at C
Td, C
SPIAnd C
UEIn relate to two or all the time, be preferably each parameter setting weight coefficient, to determine CQ more accurately, at this moment,
Weight coefficient A
Td, A
SPI, A
UECan be set to fixed value, promptly according to C
Td, C
SPIAnd C
UEPriority orders, for each parameter is provided with fixing weight coefficient, relate to which parameter when calculating CQ, promptly select its corresponding weight coefficient for use.
Weight coefficient A
Td, A
SPI, A
UEAlso can be according to each parameters C
Td, C
SPIAnd C
UEPriority dynamically arrange, promptly according to its significance level to CQ.The weight coefficient of the parameters C 1 that priority is minimum is made as constant m, and the weight coefficient A2 of the parameters C 2 that priority is time high is made as max, and (C1 * m), the weight coefficient A3 of the parameters C 3 that priority is the highest are made as MAX (max (C1 * m), max (A2 * C2)).
Generally speaking, C
UE, C
Td, C
SPIThe proportion shared to the CQ value increases successively.As establish A
UE=1, A
Td=max (A
UE* C
UE)=max (C
UE), maximum is got in max () expression, promptly gets A
UE* C
UEIn maximum.A
SPI=MAX(max(C
UE),max(A
Td×C
Td))。
Step 102: be followed successively by the described dispatching services queue assignment physical resource for the treatment of by described priority order from high to low, carry out queue scheduling.Be about to current system resource and distribute, carry out resource allocation for the high formation of priority earlier, finish the scheduling of service queue successively by the priority of service queue.
By the determined priority of CQ cost function of step 101, and when dispatching, when traffic load is not heavy, under the prerequisite that guarantees all kinds of QoS of survice, utilized the efficient of resource substantially by this priority.And under the heavier prerequisite of load, system can not satisfy all users' QoS, and the present invention adopts sacrificial section user's speed to satisfy other users' QoS demand.By adjusting the γ in the dispatching algorithm
IkMax threshold γ
Ik MaxCan realize this purpose.
If have at least more than one the assurance bit rate of service queue in time t1 not reach requirement, and have
Can reduce the γ of certain customers so
Ik MaxThereby, reduce its scheduling ratio, satisfy other users' rate requirement.Reduce γ
Ik MaxThe user can be the relatively poor user of channel condition, can be that actual speed rate and expected rate differ bigger user.If after channel condition improves or number of users reduces, need to adopt the readjustment strategy, raise above-mentioned user's γ
Ik MaxThe condition that raises is the γ when all formations
IkAll less than γ
Max* s (s<=1) and duration surpass the t2 time, and promptly all GBR users satisfy assurance bit rate and certain time.In order to prevent that table tennis from switching γ
Ik MaxThe downward modulation process as quickly as possible, and the rise process wants slow, i.e. γ
Ik MaxThe downward modulation grade is less, and the rise grade is more.Above-mentioned t1 and t2 are set point, set according to the system requirements of reality to get final product.
Fig. 2 is the composition structural representation of the service dispatching device of the embodiment of the invention, as shown in Figure 2, the service dispatching device of the embodiment of the invention comprises priority parameters computing unit 20 and physical source distributing and scheduling unit 21, wherein, priority parameters computing unit 20 is used for the transmission time delay parameters C according to service queue
Td, service queue dispatching priority indication parameter C
SPIAnd scheduling of user terminals relevant parameter C
UEIn at least one determine to treat the priority of dispatching services formation.Represent to determine the parameter of service queue priority, all to calculate the relevant parameter C of this service queue with CQ for arbitrary service queue
Td, C
SPIAnd C
UE, then the CQ of service queue presses following formula and determines:
Wherein, i represents the numbering of service queue.Priority parameters computing unit 20 promptly is the CQ value that calculates service queue.Physical source distributing and scheduling unit 21 are used for being followed successively by the described dispatching services queue assignment physical resource for the treatment of by described priority order from high to low, carry out queue scheduling.
Wherein, priority parameters computing unit 20 comprises C
TdComputing module 201, C
SPIComputing module 202 and C
UEIn the computing module 203 at least one, wherein, C
TdComputing module 201 is determined propagation delay time Td, Td according to the UE under the service queue
i=T
i-Tm
i, wherein, T
iBe to be scheduled and stand-by period of long data piece of stand-by period Tm among the service queue i
iBe the control delay parameter of service queue i, Tm
i=Max (0, δ-Tad
Max), δ is the mac-hs delay requirement of service queue i, Tad
Max=α * T
Harq* N
Max, T
HarqBe that a HARQ process retransmits required shortest time, N
MaxBe the maximum transmission times of this formation, the corrected parameter of α for setting, the α value is big more, and the priority of corresponding service formation is high more, and the α value can rule of thumb be provided with, and for the service queue of each priority, all correspondence is provided with the α value.For the service queue that does not have delay requirement, can its Td value be set to constant, for example-1, be set to cause this service queue always can not be scheduled after the negative value, can unconfinedly not wait in order to guarantee this service queue, can be set to a bigger value by δ, to reduce the stand-by period of service queue.In a word, for the service queue that does not have delay requirement, can be set its stand-by period according to service feature.The present invention just is being based on the Td value of service queue and is determining C
Td, when Td>0, illustrate that service queue is overtime, need scheduling as early as possible, this moment C
TdGet positively related value, and when Td<=0, service queue is described as yet not to the time of being scheduled with Td, at this moment, C
TdValue is 0.Here, C
TdValue and Td positive correlation, for example: C
Td=Td+b, wherein, b is a positive constant, for example value is 1,2 or 5; Perhaps, C
Td=Td * b.Certainly, if C
TdThe evolution value or the square root of getting Td also can.C
SPIComputing module 202 is determined according to the grade point of service queue priority; C
SPIComputing module 202 is determined C
SPIMode be: C
SPIValue be the grade point of service queue priority.For example for general service, its C
SPIBe set to 0, set gradually according to priority order from low to high for the business that special priority is arranged be 1,2 ..., 15.Above-mentioned C
SPIValue just the priority level value with business is identical, also can get and react corresponding other values, high more its corresponding value of priority is big more.C
UEComputing module 203 is determined by user's channel condition, the basic weighted value and the assurance bit rate of service queue priority.C
UEComputing module 203 calculates C
UEMode be:
Wherein, pf
Kj(t) be the weighted value of the described service queue that obtains according to the direct ratio fair algorithm; PriorityQueueWeight[j] be the basic weights of the service queue of j for priority; γ
IkBe K user UE
kThe basic weights of middle formation i are adjusted the factor, γ
Ik=R
g/ R
r, R
gFor guaranteeing bit rate, R
rBe actual transfer rate.
When there is the phenomenon of being transferred sky in buffer memory service queue in dispatching cycle, just with γ
IkValue is set to initial value.γ
IkAdjusting range at γ
i MinAnd γ
Ik Max For example M gets 100,150 or 200.
As shown in Figure 2, determine that the described related parameter calculating module of priority for the treatment of the dispatching services formation is two when above, the service dispatching device of the embodiment of the invention also weight coefficient is provided with unit 22, is used to described parameter that weight coefficient is set.Weight coefficient is provided with unit 22 can be set to fixed value by weight coefficient.Also can be that described parameter dynamically arranges weight coefficient according to the priority of described parameter.Described weight coefficient dynamically arranges according to the priority of described parameter, be specially: the weight coefficient of the parameters C 1 that priority is minimum is made as constant m, the weight coefficient A2 of the parameters C 2 that priority is time high is made as max (C1 * m), the weight coefficient A3 of the parameters C 3 that priority is the highest is made as MAX (max (C1 * m), max (A2 * C2)).Generally speaking, C
UE, C
Td, C
SPIThe proportion shared to the CQ value increases successively.As establish A
UE=1, A then
Td=max (A
UE* C
UE)=max (C
UE), maximum is got in max () expression, promptly gets A
UE* C
UEIn maximum.A
SPI=MAX(max(C
UE),max(A
Td×C
Td))。
Physical source distributing and the scheduling unit 21 according to priority result of calculation of parameter calculation unit 20 are determined the priority of service queue to be followed successively by the described dispatching services queue assignment physical resource for the treatment of by described priority order from high to low, carry out queue scheduling.Be about to current system resource and distribute, carry out resource allocation for the high formation of priority earlier, finish the scheduling of service queue successively by the priority of service queue.When traffic load is not heavy, under the prerequisite that guarantees all kinds of QoS of survice, utilized the efficient of resource substantially.And under the heavier prerequisite of load, system can not satisfy all users' QoS, and the present invention adopts sacrificial section user's speed to satisfy other users' QoS demand.By adjusting the γ in the dispatching algorithm
IkMax threshold γ
Ik MaxCan realize this purpose.
If have at least more than one the assurance bit rate of service queue in time t1 not reach requirement, and have
Can reduce the γ of certain customers so
Ik MaxThereby, reduce its scheduling ratio, satisfy other users' rate requirement.Reduce γ
Ik MaxThe user can be the relatively poor user of channel condition, can be that actual speed rate and expected rate differ bigger user.If after channel condition improves or number of users reduces, need to adopt the readjustment strategy, raise above-mentioned user's γ
Ik MaxThe condition that raises is the γ when all formations
IkAll less than γ
Max* s (s<=1) and duration surpass the t2 time, and promptly all GBR users satisfy assurance bit rate and certain time.In order to prevent that table tennis from switching γ
Ik MaxThe downward modulation process as quickly as possible, and the rise process wants slow, i.e. γ
Ik MaxThe downward modulation grade is less, and the rise grade is more.Above-mentioned t1 and t2 are set point, set according to the system requirements of reality to get final product.
It will be appreciated by those skilled in the art that device shown in Figure 2 is a corresponding intrument of realizing method shown in Figure 1, the function of each unit and module can be understood with reference to the associated description among Fig. 1.Each unit and module shown in Figure 2 can realize function corresponding by corresponding software or corresponding hardware circuit.
The above is preferred embodiment of the present invention only, is not to be used to limit protection scope of the present invention.