CN106550039A - A kind of cross-layer cooperation content buffering method and system based on SD RAN - Google Patents

Abstract

The invention discloses a kind of cross-layer cooperation content caching system based on SD RAN, belongs to wireless communication technology field.The small cell base station that the system is provided several non-overlapping copies in the macrocell base stations and its coverage of control covering and is seamlessly connected by one is constituted, macrocell base stations and small cell base station provide data, services function jointly, system by by popularity highest content caching in cellulor cache node, secondary popular content caching is in macrocellular cache node, user can be reduced and the overhead that identical content brings is transferred from remote content server repeatedly, The invention also achieves a kind of cross-layer cooperation content buffering method based on SD RAN；The present invention makes full use of the advantage of software defined network and cross-layer cooperation caching, and by the content storage space partition coefficient for optimizing macrocell base stations and small cell base station, the average content that can significantly reduce system obtains expense.

Description

A kind of cross-layer cooperation content buffering method and system based on SD-RAN

Technical field

The invention belongs to wireless communication technology field, more particularly, to one kind, based on SD-RAN, (software definition wirelessly connects Network) cross-layer cooperation content caching system.

Background technology

Caching is a kind of content memory technology, generally popularity higher content is stored near user in radio communication Cache node in (such as base station), call repeatedly, transmit the probability of identical content from remote content server to reduce, so as to have Effect reduces transport overhead, alleviates the transmission bottleneck of backhaul network, realizes green communications.

Cisco's visual web index pointed out in " Globle mobile data traffic forecast update ", Video service and content occupy leading status in moving communicating field relative to other classs of business.2015, with video it is Main content of multimedia contribute to about 69% mobile service load.To the year two thousand twenty, this ratio will rise to 79%.Research table It is bright,

That is the high content of small part popularity can repeatedly be downloaded by user, be watched.By taking Youtube as an example, popularity row The video file of name front 10% contribute to about 80% business load.Additionally, the popularity change of these video contents is delayed relatively Slowly, for example, the news comprising video clip is generally updated once per 2-3 hours, and the film newly reached the standard grade typically updates weekly one It is secondary.Therefore, from the point of view of the time dimension that wireless access network content caching and information are paid, these video contents obey relative quiescent Popularity distribution.In this context, in the way of caching technology is as a kind of " exchanging bandwidth for store ", it is obtained extensive Research.

At present, the research of caching technology predominantly stays in monolayer caching system, i.e., each small cell base station is in macrocellular base Same layer cooperation caching is carried out to content under coordinating for the control stood and the information to user's request is responded, but monolayer caching There is spatial cache solidification in system, overhead optimizes the defect such as unobvious.

The content of the invention

For the disadvantages described above or Improvement requirement of prior art, the invention provides a kind of cross-layer cooperation based on SD-RAN Content caching system, its object is to be provided with cache node in macrocell base stations and small cell base station respectively, by grand honeybee Nest base station and the content of the cellulor different popularities of storage, reach the purpose for improving buffer efficiency.In addition, the system is also The function of software defined network is taken full advantage of, according to the user for monitoring from local small cell base station, macrocell base stations and remote End content server obtains the expense of content, in real time the size of distribution cellulor and macrocell base stations spatial cache, further real The optimization of existing SD-RAN content obtaining expenses, thus solves the solidification of monolayer caching system spatial cache, and overhead optimization is not clear The defect such as aobvious.

For achieving the above object, the invention provides a kind of cross-layer cooperation content caching system based on SD-RAN, this is The cellulor united by several non-overlapping copies in the macrocellular and its coverage of realizing control covering and be seamlessly connected is constituted, Under the control of SD-RAN, the system can realize that numerical control is separated, and the system includes key-course and data Layer：

The data Layer includes two sublayers：

Small cell base station cache node sublayer, for storing one group of content of popularity highest, performs cache contents initial Change or update, reduce the overhead that user is brought from distal end request identical content repeatedly；

Macrocell base stations cache node sublayer, the one group content high for storing popularity time, performs cache contents initial Change or update, expand the content storage total amount of global network, lift global buffer efficiency；

The key-course includes two modules：Content delivery module, for judging whether user's request content has in caching Hold in data Layer and which sublayer in data Layer, and notify that concrete sublayer pays content；

Buffer update module, when user's request content not in data Layer spatial cache when start, for each to data Layer The cache contents of sublayer spatial cache are updated.

Further, the popularity of the content is defined as：

If content library is arranged as { x by its frequency descending being requested by a user by M Composition of contents₁,…,x_m,…,x_M, Then the requested popularity of m-th content can be expressed as

Wherein, α is Zipf profile exponents；It characterizes the inclined degree of request model：α is bigger, and user's request is more concentrated The larger content of probability；α is less, and user's request is more disperseed.Present invention assumes that user is to content x in n-th cellulor_mRequest Probability beDue to each cellulor user distribution and user be identical to the request probability of same content, therefore deposit

Wherein, N is the sum of small cell base station under global network.

Further, the key-course also includes spatial cache distribute module, for distributing each sublayer spatial cache, specifically For：

Global total spatial cache is denoted as into S, it is assumed that storage size shared by each content is 1, therefore global buffer is empty Between can at most store S content.Memory allocation coefficient τ (0≤τ≤1) is defined, then macrocell base stations cache node The spatial cache S of layer_mWith the spatial cache S of each small cell base station cache node sublayer_sSize be

S_m=τ S

The scene that the present invention considers is, the request probability of the user distribution and user of each small cell base station to same content It is identical, therefore the storage content of each small cell base station cache node sublayer is identical.To realize that global average content is obtained Take away the optimization of pin, the system is by popularity highest S_sSmall cell base station cache node sublayer is arrived in individual content storage, by secondary stream Capable S_mIndividual content storage is to macrocell base stations cache node sublayer.By user's institute's request content in small cell base station cache node The hit rate of sublayer and macrocell base stations cache node sublayer is denoted as h respectively_l、h_m, by user in the miss rate of SD-RAN, that is, use Family obtains the probability of request content from remote content server, is denoted as h_r.Then have

h_r=1-h_l-h_m.

User is taken from local small cell base station cache node sublayer, macrocell base stations cache node sublayer and remote content Business device obtains the average overhead of single content and is denoted as c respectively_l、c_m、c_r, without loss of generality, have c_l＜ c_m＜ c_r.Therefore, system list The object function of individual content average acquiring expense Cost can be expressed as

Derivation is carried out to above-mentioned formula, is made derived function be zero, can be obtained

Due to 0≤τ≤1, therefore the spatial cache partition coefficient τ of optimum^*For

According to the optimum spatial cache partition coefficient τ for obtaining^*, the spatial cache S of macrocell base stations cache node sublayer_mWith The spatial cache S of each small cell base station cache node sublayer_sOptimal distributing scheme be

S_m=τ^*S

When spatial cache partition coefficient is optimum, it is minimum that system obtains single content expense.

Further, the content delivery module includes following submodule：

Request receiving submodule, for the content requests from small cell base station receive user；

Caching pays submodule, for inquiring about whether small cell base station cache node sublayer has cached request content, if slow The request content is deposited, has then been responded user's request and is notified small cell base station and carry out content delivery；Otherwise, macrocell base stations are inquired about Whether cache node sublayer has cached the request content, if having cached the request content, response user's request notifies macrocellular Base station simultaneously carries out content delivery；Otherwise, enable long-range delivery module；

It is long-range to pay submodule, submit to user content to ask to remote content server, notify that remote content server enters Row content delivery.

Further, when user's request content not in data Layer spatial cache when start the buffer update module, delay Deposit update module and specifically include following submodule：

First updates submodule, and small cell base station cache node sublayer spatial cache hollow content popularit is set to 0；Again Compare minimum content x of popularity in small cell base station cache node sublayer_aPopularity P_sminWith request content x₀Popularity P₀Between size, if P₀＞ P_smin, then by the popularity of macrocell base stations cache node sublayer minimum content x_bIn being substituted for Hold x_a, by content x of small cell base station cache node sublayer_aContent is substituted for for x₀；Second renewal submodule is enabled otherwise；

Second updates submodule, and macrocell base stations cache node sublayer spatial cache hollow content popularit is set to 0；Again Compare minimum content x of popularity in macrocell base stations cache node sublayer_bPopularity P_mminWith request content x₀Popularity P₀Between size, if P₀＞ P_mmin, then by content x of macrocell base stations cache node sublayer_bContent is substituted for for x₀；Otherwise not Process.

Further, the key-course also includes monitoring modular, for the buffer status of each sublayer of Monitoring Data layer, respectively Individual base station and the expense of remote content server response contents.

On the other hand, for achieving the above object, the invention provides a kind of cross-layer cooperation content caching based on SD-RAN Method, it is characterised in that be respectively provided with a cache node sublayer in small cell base station and macrocell base stations, small cell base station is delayed Node sublayer is deposited for storing one group of content of popularity highest, macrocell base stations cache node sublayer is used to store popularity One group of high content, the method are specifically divided into following steps：

Content delivery step：Judge whether user's request content there are cache contents in cache node sublayer, and notify tool Body cache node sublayer pays content；If user's request content not in each cache node sublayer when, notify remote content service Device carries out content delivery；

Buffer update step：If user's request content not in each cache node sublayer when, compare user's request content and The popularity of each cache node sublayer cache contents, if each cache node sublayer cache contents popularity is popular less than request content Degree, then be updated to the cache contents in the spatial cache of each cache node sublayer.

Further, it is characterised in that the popularity of the content is defined as：

If content library is arranged as { x by its frequency descending being requested by a user by M Composition of contents₁,…,x_m,…,x_M, Then the requested popularity of m-th content can be expressed as

Wherein, α is Zipf profile exponents；It characterizes the inclined degree of request model：α is bigger, and user's request is more concentrated The larger content of probability；α is less, and user's request is more disperseed.；

In n-th small cell base station, user is to content x_mThe popularity of request isFor

Wherein, N is the sum of small cell base station under global network.

Further, it is characterised in that the small cell base station cache node sublayer and macrocell base stations cache node The spatial cache of layer distributes as follows：

The spatial cache of macrocell base stations cache node sublayer is designated as S_m, each small cell base station cache node sublayer it is slow Deposit space and be designated as S_s, optimal distributing scheme is：

S_m=τ^*S

Wherein, S is global total spatial cache；τ^*For optimum spatial cache partition coefficient

Wherein, c_lIt is that the average overhead for obtaining single content is cached from small cell base station；c_mIt is to obtain from macrocell base stations caching Take the average overhead of single content；c_rIt is the average overhead that single content is obtained from remote content server, when spatial cache point When distribution coefficient is optimum, the single content average acquiring expense of system is minimum.

Further, the content delivery step is specifically divided into following sub-step：

Request receives sub-step：From the content requests of small cell base station receive user；

Caching pays sub-step：Whether inquiry small cell base station cache node sublayer has cached request content, if caching The request content, then respond user's request and notify small cell base station and carry out content delivery；Otherwise, inquire about macrocell base stations caching Whether node sublayer has cached the request content, if having cached the request content, response user's request notifies macrocell base stations And carry out content delivery；Otherwise, long-range delivery steps are enabled；

It is long-range to pay sub-step：Submit to user content to ask to remote content server, notify that remote content server enters Row content delivery.

Further, when user's request content not in each cache node sublayer spatial cache when carry out buffer update, institute State buffer update step and be specifically divided into following sub-step：

First updates sub-step, and small cell base station cache node sublayer spatial cache hollow content popularit is set to 0；Again Compare minimum content x of popularity in small cell base station cache node sublayer_aPopularity P_sminWith request content x₀Popularity P₀Between size, if P₀＞ P_smin, then by the popularity of macrocell base stations cache node sublayer minimum content x_bIn being substituted for Hold x_a, by content x of small cell base station cache node sublayer_aContent is substituted for for x₀；Second renewal sub-step is enabled otherwise；

Second updates sub-step, and macrocell base stations cache node sublayer spatial cache hollow content popularit is set to 0；Again Compare minimum content x of popularity in macrocell base stations cache node sublayer_bPopularity P_mminWith request content x₀Popularity P₀Between size, if P₀＞ P_mmin, then by content x of macrocell base stations cache node sublayer_bContent is substituted for for x₀；Otherwise not Process.

Further, the key-course also includes monitoring step, the buffer status of each sublayer of Monitoring Data layer, each base Stand and remote content server response contents expense.

In general, by the contemplated above technical scheme of the present invention compared with prior art, it is special with following technology Levy and beneficial effect：

(1) the cross-layer cooperation content caching system based on SD-RAN proposed by the present invention realizes macrocell base stations and chalcid fly The cooperation caching of nest base station, system by by secondary popular content caching in macrocellular cache node, it is to avoid from remote content Server transfers the expense that higher popularity content brings repeatedly,

(2) further, the present invention makes full use of the advantage of SD-RAN, obtains user from local cellulor base according to monitoring Stand, macrocell base stations and remote content server obtain the expense of content, divide cellulor and macrocellular cache node in real time Spatial cache size, optimizes spatial cache structure, improves the buffer efficiency of system, reduce further of the invention average interior Hold and obtain expense.Additionally, there is no excessive computation complexity in system design, it is easy to manipulate and implements.

Description of the drawings

Fig. 1 is present system structural representation；

Fig. 2 be present system in mono- timings of space partition coefficient τ, average content obtains expense with Link State factor gamma Between relation；

Data Layer cache contents distribution schematic diagrams of the Fig. 3 for present system；

Content request responses schematic flow sheets of the Fig. 4 for present system；

Initialization and update method of the Fig. 5 for the cache contents of present system.

Specific embodiment

In order that the objects, technical solutions and advantages of the present invention become more apparent, it is below in conjunction with accompanying drawing and emulation example, right The present invention is further elaborated.It should be appreciated that specific embodiment described herein is only to explain the present invention, and It is not used in the restriction present invention.As long as additionally, technical characteristic involved in invention described below each embodiment Do not constitute conflict each other can just be mutually combined.

As shown in figure 1, present system includes key-course and data Layer：

In order to avoid transferring repeatedly the high expense that higher popularity content brings, the data from remote content server Layer includes two sublayers：

Small cell base station cache node sublayer, for storing one group of content of popularity highest, performs cache contents initial Change or update, reduce the overhead that user is brought from distal end request identical content repeatedly；

Macrocell base stations cache node sublayer, the one group content high for storing popularity time, performs cache contents initial Change or update, expand the content storage total amount of global network, lift global buffer efficiency；

The key-course includes two modules：Content delivery module, for judging whether user's request content has in caching Hold in data Layer and which sublayer in data Layer, and notify that concrete sublayer pays content；

Buffer update module, when user's request content not in data Layer spatial cache when start, for each to data Layer The cache contents of sublayer spatial cache are updated.The popularity of the content is defined as：

If content library is arranged as { x by its frequency descending being requested by a user by M Composition of contents₁,…,x_m,…,x_M, Then the requested popularity of m-th content can be expressed as

Wherein, α is Zipf profile exponents；

In n-th small cell base station, user is to content x_mThe popularity of request isFor

Wherein, N is the sum of small cell base station under global network.

The key-course also includes spatial cache distribute module, for distributing each sublayer spatial cache, specially：

The spatial cache of macrocell base stations cache node sublayer is designated as S_m, each small cell base station cache node sublayer it is slow Deposit space and be designated as S_s, optimal distributing scheme is：

S_m=τ^*S

Wherein, S is global total spatial cache；τ^*For optimum spatial cache partition coefficient

Wherein, c_lIt is the average overhead that single content is obtained from small cell base station cache node；c_mIt is slow from macrocell base stations Deposit the average overhead that node obtains single content；c_rIt is the average overhead that single content is obtained from remote content server, when slow Deposit space partition coefficient for it is optimum when, the single content average acquiring expense of system is minimum.

Emulation embodiment：

Simulation parameter arranges as follows：General act content is 5000, and the total spatial cache of system is 2000, Zipf profile exponent α For 0.7, cellulor sum is 2.Above the present invention is it has been mentioned that c_l、c_m、c_rRepresent user from cellulor (local), grand honeybee respectively Nest and distal end obtain content obtaining expense, and assume c_l＜ c_m＜ c_r.For the ease of research, the present invention makes c_l=1, c_r=10, c_m =γ c_r, wherein 0.1 ＜ γ ＜ 1.

As shown in Fig. 2 when the spatial cache of two sublayers is not reaching to optimum allocation coefficient, for the distribution of arbitrary space is Number τ, average content obtain expense and increase with the increase of Link State factor gamma.For arbitrary Link State factor gamma, Corresponding space partition coefficient τ is different for minimum average B configuration content obtaining expense.Therefore, the content caching system based on SD-RAN System is particularly important, and system can be average so as to realize by real-time link state, the space partition coefficient for dynamically optimizing Content obtaining minimizing overhead.From figure 2 it may also be seen that the algorithm of the present invention is under arbitrary Link State, can try to achieve Optimum space partition coefficient τ^*, so as to the average content for substantially reducing obtains expense.

After distributing each sublayer spatial cache, expense is obtained in order to reduce average content, it is of the invention by popularity highest x₁ ～x_mContent be stored in the spatial cache of each small cell base station cache node sublayer, by popularity time high x_m+1～x_m+nIn individual Appearance is stored in the spatial cache of macrocell base stations cache node sublayer, wherein, n=S_m=τ^*S；Such as Fig. 3 institutes Show, cached by above-mentioned cross-layer, system cache structure can be optimized, buffer efficiency is improved, so as to reduce average content acquisition Expense.

As shown in figure 4, the content delivery module includes following submodule：

Request receiving submodule, for the content requests from small cell base station receive user；

Caching pays submodule, for inquiring about whether small cell base station cache node sublayer has cached request content, if slow The request content is deposited, has then been responded user's request and is notified small cell base station and carry out content delivery；Otherwise, macrocell base stations are inquired about Whether cache node sublayer has cached the request content, if having cached the request content, response user's request notifies macrocellular Base station simultaneously carries out content delivery；Otherwise, enable long-range payment submodule；

It is long-range to pay submodule, submit to user content to ask to remote content server, notify that remote content server enters Row content delivery.

As shown in figure 5, when user's request content not in data Layer spatial cache when start the buffer update module, delay Deposit update module and specifically include following submodule：

First updates submodule, and small cell base station cache node sublayer spatial cache hollow content popularit is set to 0；Again Compare minimum content x of popularity in small cell base station cache node sublayer_aPopularity P_sminWith request content x₀Popularity P₀Between size, if P₀＞ P_smin, then by the popularity of macrocell base stations cache node sublayer minimum content x_bIn being substituted for Hold x_a, by content x of small cell base station cache node sublayer_aContent is substituted for for x₀；Second renewal submodule is enabled otherwise；

Second updates submodule, and macrocell base stations cache node sublayer spatial cache hollow content popularit is set to 0；Again Compare minimum content x of popularity in macrocell base stations cache node sublayer_bPopularity P_mminWith request content x₀Popularity P₀Between size, if P₀＞ P_mmin, then by content x of macrocell base stations cache node sublayer_bContent is substituted for for x₀；Otherwise not Process.

Presently preferred embodiments of the present invention is the foregoing is only, not to limit the present invention, all essences in the present invention Any modification, equivalent and improvement made within god and principle etc., should be included within the scope of the present invention.

Claims (10)

1. a kind of cross-layer cooperation content caching system, it is characterised in that the system is included for key-course and data Layer：

The data Layer includes two sublayers：Small cell base station cache node sublayer, for storing in one group of popularity highest Hold；Macrocell base stations cache node sublayer, the one group content high for storing popularity time；

The key-course includes two modules：Content delivery module, for judging whether user's request content is stored in data Layer And in which sublayer of data Layer, and notify that concrete sublayer pays content；Buffer update module, when user's request content does not exist Start when in data Layer spatial cache, for being updated to the cache contents of each sublayer spatial cache of data Layer.

2. a kind of cross-layer cooperation content caching system according to claim 1, it is characterised in that the popularity of the content It is defined as：

If content library is arranged as { x by its frequency descending being requested by a user by M Composition of contents₁,…,x_m,…,x_M, then m The requested popularity of individual content can be expressed as

$P_m=\frac{\frac{1}{m^{\mathrm{\α}}}}{\underset{m=1}{\overset{M}{\Σ}}\frac{1}{m^{\mathrm{\α}}}},$

Wherein, α is Zipf profile exponents；

In n-th small cell base station, user is to content x_mThe popularity of request isFor

$P_m^{\left(n\right)}=\frac{1}{N}{P}_m,$

Wherein, N is the sum of small cell base station under global network.

3. a kind of cross-layer cooperation content caching system according to claim 1, it is characterised in that the key-course also includes Spatial cache distribute module, for distributing each sublayer spatial cache, specially：

The spatial cache of macrocell base stations cache node sublayer is designated as S_m, the caching sky of each small cell base station cache node sublayer Between be designated as S_s, optimal distributing scheme is：

S_m=τ^*S

$S_s=\frac{(1-{\mathrm{\τ}}^{*})S}{N},$

Wherein, S is global total spatial cache；τ^*For optimum spatial cache partition coefficient

${\mathrm{\τ}}^{*}=max\left\{0,\frac{{\[(N-1)(c_r-c_m)\]}^{\frac{1}{\mathrm{\α}}}-{(c_m-c_l)}^{\frac{1}{\mathrm{\α}}}}{{\[(N-1)(c_r-c_m)\]}^{\frac{1}{\mathrm{\α}}}+(N-1){(c_m-c_l)}^{\frac{1}{\mathrm{\α}}}}\right\},$

Wherein, c_lIt is the average overhead that single content is obtained from small cell base station cache node；c_mIt is to save from macrocell base stations caching Point obtains the average overhead of single content；c_rIt is the average overhead that single content is obtained from remote content server, when caching sky Between partition coefficient for it is optimum when, the single content average acquiring expense of system is minimum.

4. a kind of cross-layer cooperation content caching system according to claim 1,2 or 3, it is characterised in that the content is handed over Paying module includes following submodule：

Request receiving submodule, for the content requests from small cell base station receive user；

Caching pays submodule, for inquiring about whether small cell base station cache node sublayer has cached request content, if caching The request content, then respond user's request and notify small cell base station and carry out content delivery；Otherwise, inquire about macrocell base stations caching Whether node sublayer has cached the request content, if having cached the request content, response user's request notifies macrocell base stations And carry out content delivery；Otherwise, enable long-range payment submodule；

It is long-range to pay submodule, submit to user content to ask to remote content server, notify that remote content server is carried out interior Hold and pay.

5. a kind of cross-layer cooperation content caching system according to claim 1,2 or 3, it is characterised in that work as user's request Content not in data Layer spatial cache when start the buffer update module, buffer update module specifically includes following submodule Block：

First updates submodule, and small cell base station cache node sublayer spatial cache hollow content popularit is set to 0；Compare again Minimum content x of popularity in small cell base station cache node sublayer_aPopularity P_sminWith request content x₀Popularity P₀It Between size, if P₀＞ P_smin, then by the popularity of macrocell base stations cache node sublayer minimum content x_bIt is substituted for content x_a, by content x of small cell base station cache node sublayer_aContent is substituted for for x₀；Second renewal submodule is enabled otherwise；

Second updates submodule, and macrocell base stations cache node sublayer spatial cache hollow content popularit is set to 0；Compare again Minimum content x of popularity in macrocell base stations cache node sublayer_bPopularity P_mminWith request content x₀Popularity P₀It Between size, if P₀＞ P_mmin, then by content x of macrocell base stations cache node sublayer_bContent is substituted for for x₀；Otherwise do not do Process.

6. a kind of cross-layer cooperation content buffering method, it is characterised in that be respectively provided with small cell base station and macrocell base stations Individual cache node sublayer, small cell base station cache node sublayer are used to store one group of content of popularity highest, macrocell base stations Cache node sublayer is used to store one group of high content of popularity time, and the method is specifically divided into following steps：

Content delivery step：Judge whether user's request content there are cache contents in cache node sublayer, and notify concrete slow Deposit node sublayer and pay content；If user's request content not in each cache node sublayer when, notify remote content server enter Row content delivery；

Buffer update step：If user's request content is not stored in each cache node sublayer, compare user's request content With the popularity of each cache node sublayer cache contents, if each cache node sublayer cache contents popularity be less than request content stream Row degree, then be updated to the cache contents in the spatial cache of each cache node sublayer.

7. a kind of cross-layer cooperation content buffering method according to claim 6, it is characterised in that the popularity of the content It is defined as：

If content library is arranged as { x by its frequency descending being requested by a user by M Composition of contents₁,…,x_m,…,x_M, then m The requested popularity of individual content can be expressed as

$P_m=\frac{\frac{1}{m^{\mathrm{\α}}}}{\underset{m=1}{\overset{M}{\Σ}}\frac{1}{m^{\mathrm{\α}}}},$

Wherein, α is Zipf profile exponents；

In n-th small cell base station, user is to content x_mThe popularity of request isFor

$P_m^{\left(n\right)}=\frac{1}{N}{P}_m,$

Wherein, N is the sum of small cell base station under global network.

8. a kind of cross-layer cooperation content buffering method according to claim 6, it is characterised in that the small cell base station is delayed The spatial cache for depositing node sublayer and macrocell base stations cache node sublayer distributes as follows：

The spatial cache of macrocell base stations cache node sublayer is designated as S_m, the caching sky of each small cell base station cache node sublayer Between be designated as S_s, optimal distributing scheme is：

S_m=τ^*S

$S_s=\frac{(1-{\mathrm{\τ}}^{*})S}{N},$

Wherein, S is global total spatial cache；τ^*For optimum spatial cache partition coefficient

${\mathrm{\τ}}^{*}=max\left\{0,\frac{{\[(N-1)(c_r-c_m)\]}^{\frac{1}{\mathrm{\α}}}-{(c_m-c_l)}^{\frac{1}{\mathrm{\α}}}}{{\[(N-1)(c_r-c_m)\]}^{\frac{1}{\mathrm{\α}}}+(N-1){(c_m-c_l)}^{\frac{1}{\mathrm{\α}}}}\right\},$

Wherein, c_lIt is the average overhead that single content is obtained from small cell base station cache node；c_mIt is to save from macrocell base stations caching Point obtains the average overhead of single content；c_rIt is the average overhead that single content is obtained from remote content server, when caching sky Between partition coefficient for it is optimum when, the single content average acquiring expense of system is minimum.

9. a kind of cross-layer cooperation content buffering method according to claim 6,7 or 8, it is characterised in that the content is handed over Pay step and be specifically divided into following sub-step：

Request receives sub-step：From the content requests of small cell base station receive user；

Caching pays sub-step：Whether inquiry small cell base station cache node sublayer has cached request content, please if having cached this Content is sought, is then responded user's request and is notified small cell base station and carry out content delivery；Otherwise, inquire about macrocell base stations cache node Whether sublayer has cached the request content, if having cached the request content, response user's request notifies that macrocell base stations are gone forward side by side Row content delivery；Otherwise, long-range delivery steps are enabled；

It is long-range to pay sub-step：Submit to user content to ask to remote content server, notify that remote content server is carried out interior Hold and pay.

10. a kind of cross-layer cooperation content buffering method according to claim 6,7 or 8, it is characterised in that work as user's request Content not in each cache node sublayer spatial cache when carry out buffer update, the buffer update step is specifically divided into following son Step：

First updates sub-step, and small cell base station cache node sublayer spatial cache hollow content popularit is set to 0；Compare again Minimum content x of popularity in small cell base station cache node sublayer_aPopularity P_sminWith request content x₀Popularity P₀It Between size, if P₀＞ P_smin, then by the popularity of macrocell base stations cache node sublayer minimum content x_bIt is substituted for content x_a, by content x of small cell base station cache node sublayer_aContent is substituted for for x₀；Second renewal sub-step is enabled otherwise；

Second updates sub-step, and macrocell base stations cache node sublayer spatial cache hollow content popularit is set to 0；Compare again Minimum content x of popularity in macrocell base stations cache node sublayer_bPopularity P_mminWith request content x₀Popularity P₀It Between size, if P₀＞ P_mmin, then by content x of macrocell base stations cache node sublayer_bContent is substituted for for x₀；Otherwise do not do Process.