A kind of network resource allocation method under the non-homogeneous topological structure heterogeneous network of two-layer
Technical field
The present invention relates to moving communicating field, especially the network resource allocation method under the non-homogeneous topological structure heterogeneous network of a kind of two-layer, the method is in the non-homogeneous topological structure heterogeneous network Access Layer of two-layer, the total throughout of system, the power of completion system and resource distribution is maximized when ensureing user fairness.
Background technology
Nowadays Mobile Communication Development is rapid, and the extensive use of the universal and various real-time media business of mobile intelligent terminal, in broadband wireless network, the traffic increases with exponential rate, and the demand hence for more high coverage rate, faster data rate services is also higher.Owing to frequency spectrum resource is limited, it is improve the availability of frequency spectrum in an efficient way, LTE-Advanced proposes the base station that some are smaller, the general power ratio in this base station is relatively low, and it is arranged in the user density relatively larger hot spot region distance for furthering between user and base station, thus improving user throughput.This in macrocellular network the network architecture of superposition low power nodes be referred to as heterogeneous network (HeterogneousNetworks, HetNets).The application of low power base station brings new opportunity, equally also brings a new difficult problem.The deployment of low power base station can cause minizone overlapping region to increase, owing in order to maximize availability of frequency spectrum employing identical networking mode, region overlaps the interference aggravation meaning minizone.In order to tackle the interference of minizone, interference coordination (enhancedInter-CellInterferenceCoordination between enhancement type district, eICIC) it is a kind of interference coordination technique introduced in LTE-A, distributed by the resource in time domain, coordinate user's interconnection technique, can be diverted on small station by certain customers to improve resource distribution, and improve the channel condition of small station user, thus improving the overall performance of system.Time-domain resource distribution and Macro base station are at some ABS (AlmostBlankSubframe) subframe low power communication, and therefore lower powered base station can use the ABS subframe communication that interference is less, has reached the purpose of interference coordination.
Therefore, at LTE-A as under the main research background of next generation mobile communication system, how coordinates interference power and resource distribution improve overall system throughput, have significantly high researching value and meaning.
Summary of the invention
Goal of the invention: for solving above-mentioned technical problem, the present invention proposes the network resource allocation method under the non-homogeneous topological structure heterogeneous network of a kind of two-layer, total user rate that the method can improve system and the fairness that ensure that between user.
Technical scheme: for realizing above-mentioned technique effect, the technical solution used in the present invention is:
A kind of network resource allocation method under the non-homogeneous topological structure heterogeneous network of two-layer, including:
Step 1: to ensure premised on user rate fairness, set up the total speed maximization problems model of system user, target problem is converted to and is split as three subproblems, respectively P1: user connects and frequency spectrum resource distribution, P2: time-domain resource is distributed, and P3:Macro base station is arranged in the transmit power of ABS time slot;
Step 2: successively three subproblems being solved, solution procedure includes:
(1) power at ABS time slot of the Macro base station in non-homogeneous for two-layer topological structure heterogeneous network and ABS ratio are initialized as constant parameter;And obtain under the power and the initialized situation of ABS ratio of ABS time slot, the connection status of user and the distribution of base station frequency domain resource in the non-homogeneous topological structure heterogeneous network of two-layer;
(2) after user connects and base station frequency domain resource distribution condition is determined, ABS ratio arrangement optimum in current network is solved;
(3) when ABS ratio is determined, all Macro base stations transmitting power at ABS time slot is calculated;
(4) circulation performs step (1) to (3), and arranges end condition according to user's request, stops circulation when meeting end condition.
Concrete, the solution procedure of subproblem P1 is included by described step (1):
The Macro base station in non-homogeneous for the two-layer topological structure heterogeneous network power at ABS time slot and ABS ratio are initialized as 0 by 2-1;
Each Macro base station in non-homogeneous for two-layer topological structure heterogeneous network and Pico base station are equivalent to two independent virtual base stations by 2-2 respectively;Definition BABSAnd BnABSRepresent the base station of ABS timeslot scheduling and the base station of non-ABS timeslot scheduling respectively;Define the ratio of total user's number in the user's number and the non-homogeneous topological structure heterogeneous network of two-layer that ABS ratio is the base station connecting ABS timeslot scheduling;The frequency domain resource that in two-layer non-homogeneous topological structure heterogeneous network, each user obtains is allocated as follows:
Wherein, yubRepresent the user u normalization bandwidth obtained when connecting base station b, KbRepresent the total user's number under the b of base station, b ∈ B under current connection strategynABS, BABSRepresenting the base station of non-ABS and ABS timeslot scheduling, β represents ABS ratio;
2-3 set user u connect base station b time obtain transfer rate as:
Rub=yubBlog(1+SINRub)(2)
Wherein, B represents the total bandwidth of the non-homogeneous topological structure heterogeneous network system of two-layer, SINRubRepresent signal to noise ratio during user u connection base station b.
2-4 defined variable xubRepresent user's connectivity problem, work as xubRepresent when=1 that user u connects base station b, work as xubRepresent there is no access base station b when=0;Adopting distributed algorithm to solve user's connectivity problem, algorithm performs at user side and base station end respectively, including step:
1) K is calculatedb, and by KbIt is broadcast to all base stations in two-layer non-homogeneous topological structure heterogeneous network;
2) the transfer rate R returned according to userubAnd Kb, calculate xub:
Above step is repeated, as user link variable set { x at user side and base station endubNo longer change time stop iteration.
Concrete, the solution procedure of subproblem P2 is included by described step (2): after user connects and base station frequency domain resource distribution condition is determined, calculating ABS ratio β is:
Wherein, N represents total number of users of system, and namely ABS ratio represents the ratio of user's number and the total user's number of system connecting ABS base station.
Concrete, the solution procedure of subproblem P3 is included by described step (3): by solve all Macro base stations transmit power at ABS time slot be converted into the logarithm solving the transfer rate that user obtains under the non-homogeneous topological structure heterogeneous network of two-layer and:
Wherein, P represents that required Macro base station is vectorial in the transmit power of ABS time slot, 0 < Pb< PMRepresent the transmit power restriction of Macro base station b, RubIt is the equation about P, uses the gradient descent method in convex optimization that expression formula (4) is solved, obtain the optimum results of subproblem P3.
Concrete, the end condition in described step (4) is set to:
5-1 sets the longest iteration cycle number of times according to channel characteristics, the finishing iteration process when finding iterations more than the threshold value set;Or
5-2 by the front logarithm of user's transfer rate and with current logarithmic and subtract each other and obtain user's transfer rate logarithm and difference, according to user's transfer rate logarithm and difference, threshold interval [l is set1, l2], when user's transfer rate logarithm and difference fall into threshold interval [l1, l2] time, terminate iterative process;l1Represent threshold interval lower limit, l2Represent the threshold interval upper limit.
Beneficial effect: compared with prior art, the invention have the advantages that
1 present invention is based on the two-layer heterogeneous network model of non-uniform Distribution, and allows different Macro base stations to use different transmitting powers at ABS time slot, so can more adapt to base station distribution heterogeneous.
2 present invention adopt combined optimization power and the algorithm of resource distribution, eliminate Macro base station to a certain extent to the interference of user under Pico base station, improve overall system throughput and ensure that the fairness between user.
Accompanying drawing explanation
Fig. 1 is the principle flow chart of one embodiment of the present of invention;
Fig. 2 is the isomerism network structure schematic diagram in the embodiment of the present invention, and * represents eNB, × represent Pico base station, ● represent user.
Fig. 3 is the connection strategy of ZP-ABS connection strategy, LP-ABS connection strategy, no-eICIC connection strategy and present invention proposition user rate CDF figure under identical network layout;
Fig. 4 is base station edge customer speed and user's mean speed comparison diagram under different connection strategy.
Detailed description of the invention
In order to make those skilled in the art be more fully understood that the technical scheme that the present invention proposes, below in conjunction with embodiment, the technical scheme in the present invention is carried out clear, complete description, obviously, described embodiment is only a part of embodiment of the present invention, rather than whole embodiments.
Embodiment: the present embodiment is for the non-homogeneous heterogeneous network of two-layer, this two-layer isomerism network structure schematic diagram is as shown in Figure 2: have 21 Macro base stations in non-homogeneous heterogeneous network, represent by numbering 1 to 21 respectively, wherein being respectively arranged with 5 Pico base station random distributions in 7 Macro base stations, remaining 14 Macro base stations then do not comprise Pico base station.Each base station arranges 10 user's random distributions.Macro base station and Pico base station operation in 2GHz carrier wave and have 10MHz bandwidth, transmit power respectively 46dBm and the 30dBm of Macro base station and Pico base station.In the present embodiment, receive model and only consider that path loss and shadow fading are left out rapid fading.
Introducing Pico base station is the overlapped coverage in order to tap certain customers, present Macro base station and Pico base station for Macro base station, so management calculates the connectivity problem of user, is connect Macro base station or Pico base station.Again since it is desired that alleviate Macro base station to the interference of user under Pico base station, thus Macro base station within a period of time (ABS time slot) with low power communication, and different Macro base stations can adopt different power.Using the ABS ratio of how many ratios is also our one of work.Finally, due to Macro base station at the power of ABS time slot with low power communication, then how many power communication should be adopted then to need to calculate.
Owing to maximizing system user total speed when needing to ensure user rate fairness, so object module is configured to the logarithm cumulative sum of all user rates.Problem to be solved for object module is split as three subproblems solve successively:
First, initialize other parameter, solve the user under present case and connect and frequency resource allocation;Second, after user connects and frequency resource allocation situation is determined, solve currently most ABS ratio arrangement;Finally, each Macro base station transmitting power at ABS time slot is solved.Owing to object function is convex function relative to above variable, circulation three above step eventually converges on an optimum power and resource allocation strategy.
It is illustrated in figure 1 the principle flow chart of embodiment, comprises the following steps:
Step 1: at ABS time slot power, all Macro base stations are initialized as 0, namely represents that Macro does not communicate at ABS time slot.ABS ratio is also initialized as 0 and namely represents and do not adopt interference coordination.
Step 2: user connects and frequency spectrum resource allocation strategy is as follows:
Because there are ABS slotted communication and a non-ABS slotted communication two states in each base station, and each user can only connect a base station, and user or only at ABS time slot or non-ABS slotted communication.So herein each Macro base station and Pico base station being equivalent to two virtual base stations, wherein BABS(BnABS) represent ABS (non-ABS) base station communicated respectively.So the frequency domain resource that user obtains is as follows:
Wherein, yubRepresent the user u normalization bandwidth obtained when connecting base station b, KbRepresent the total user's number under the b of base station, b ∈ B under current connection strategynABS, BABSRepresenting the base station of non-ABS and ABS timeslot scheduling, β represents ABS ratio.Owing to Macro base station becoming two base stations with Pico base station equivalence, and user can only individually at ABS time slot or non-ABS slotted communication.It is R that user u obtains speed when connecting base station bubAs follows:
Rub=yubBlog(1+SINRub)(2)
Wherein, B represents the total bandwidth of base station.SINRubRepresent signal to noise ratio during user u connection base station b, note connecting BABSWhat adopt is the Macro base station transmit power at ABS time slot.
Use variable xubRepresent user's connectivity problem, i.e. xub=1 expression user u connection base station b, and xub=0 expression does not have access base station b.Adopting distributed algorithm to solve user's connectivity problem, algorithm performs at user side and base station end respectively, and all users perform the following step:
1) according to formula (2), transfer rate R when connecting each base station is calculated for all usersub。
All base stations perform the following step:
2) K is calculatedb, and value is broadcast to all base stations.
3) the transfer rate R returned according to userubAnd Kb, calculate x further according to following equationub:
Above step is repeated at user side and base station end, until user link variable set { xubNo longer change stopping iteration.
Step 3: calculating ABS ratio is:
Wherein, N represents total number of users of system, and namely ABS ratio represents the ratio of user's number and the total user's number of system connecting ABS base station.
Step 4: be equivalent to the optimization problem asking expression formula (4) by solving all Macro base stations transmit power at ABS time slot,
Wherein, P represents required vector power, 0 < Pb< PMRepresent the transmit power restriction of Macro base station, RubIt is the equation about P, uses the gradient descent method in convex optimization that expression formula (4) is solved.
Step 5: arrange end condition, repeats step 2 to step 4, until reaching end condition.Namely we need for required power and resource allocation proposal.
Described end condition includes:
1, can according to channel characteristics set the longest iteration cycle number of times, when find the cycle more than set threshold value time finishing iteration process;Or
2, finishing iteration process when network user's logarithm speed and when tending towards stability, the logarithm of the speed namely obtained for user under non-homogeneous topological structure heterogeneous network and arrange constant interval, when the logarithm of user rate with fall into this interval, finishing iteration process.Such as: by a front logarithm of user's transfer rate and with current logarithmic and subtract each other and obtain user's transfer rate logarithm and difference, according to user's transfer rate logarithm and difference, threshold interval [l is set1, l2], when user's transfer rate logarithm and difference fall into threshold interval [l1, l2] time, terminate iterative process;l1Represent threshold interval lower limit, l2Represent the threshold interval upper limit.
Fig. 3 is the connection strategy of ZP-ABS connection strategy, LP-ABS connection strategy, no-eICIC connection strategy and the present embodiment proposition user rate CDF figure under identical network layout;Fig. 4 is base station edge customer speed and user's mean speed comparison diagram under different connection strategy.As seen from the figure, the present invention eliminates Macro base station to a certain extent to the interference of user under Pico base station, improves overall system throughput and ensure that the fairness between user.
The above is only the preferred embodiment of the present invention; it is noted that, for those skilled in the art; under the premise without departing from the principles of the invention, it is also possible to make some improvements and modifications, these improvements and modifications also should be regarded as protection scope of the present invention.