CN101355583B - Method for searching buffer based on loose location dependence in wireless self-networking - Google Patents
Method for searching buffer based on loose location dependence in wireless self-networking Download PDFInfo
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- CN101355583B CN101355583B CN2008101960417A CN200810196041A CN101355583B CN 101355583 B CN101355583 B CN 101355583B CN 2008101960417 A CN2008101960417 A CN 2008101960417A CN 200810196041 A CN200810196041 A CN 200810196041A CN 101355583 B CN101355583 B CN 101355583B
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Abstract
The invention discloses a method for searching a buffer memory based on loose position dependence in a wireless ad-hoc network. The searching process under the mode of loose position dependence comprises the following steps of: 1) generating a request; 2) searching a local buffer memory, and executing step 3) if no result; 3) sending a searching request to a neighbored user who executes the local searching of step 2) and returns a result to the user who submits the request and selects an optimal result, and executing step 4) if no result; and 4) submitting a searching request to a server to return the optimal result. The user can add overhead which can be afforded by the user according to particular conditions when the user submits the searching request, and determines whether buffer data is available or not through comparing effective areas of the buffer data and corresponding restriction values. The method not only improves the hit rate of the buffer memory, but also reduces the energy consumption during the process of communication transmission.
Description
Technical field
The present invention relates to the data cached management of dependence information service in position in the wireless self-networking, specially refer to definition and describing method for data cached space effective zone.
Technical background
Position dependent information service (Location Dependent Information Services is called for short LDISs) is current moving and next type of general environment important use.Different with information service in the past, rely on the request that the user proposes in the information service in the position and in global scope, possibly have a plurality of alternative results, and actually which to be only the user needed, be that the geographical location information when being initiated by request determines.Along with wireless and popularization general fit calculation, a large amount of position dependent information services like traffic inquiry and automobile navigation etc., has demonstrated great application prospect.Different with wire communication, this category information service facing many-sided problem under wireless environment, and caching technology has very positive effect to promoting this type of systematic function.
In the position relies on information service, except Data Update, data cachedly also can become invalid data, promptly so-called " cache invalidation that the position relies on " owing to user's position change.In order to solve the cache invalidation problem that the position relies on, can in data cached, preserve the effective coverage of these data usually, the user just can judge whether this is data cached effective based on the effective coverage in this locality like this.Need extra storage and transport overhead yet preserve the effective coverage, therefore how to define effectively and represent that the effective coverage becomes important research contents in the cache invalidation research that the position relies on.
Existing research only is confined to strict position dependence for the definition of effective coverage; The effective coverage that is each data object is disjoint; Appoint and give a query requests; This object a suitable data object arranged and only has, if not in local cache, then must obtain from server in arbitrary zone.And in a large amount of practical applications, user's request need not returned optimal results, as long as object within user's acceptable scope, can return to the user as suitable result.The benefit of introducing this loose restriction relation be more to fit user's actual request provides more alternative result simultaneously, can obviously improve the hit rate of buffer memory.Existing work can not define the restriction relation of this " loose ", so we need define new describing method.
Summary of the invention
The objective of the invention is to rely on the position dependence of information service, proposed a kind of definition and described the new method that loose location dependence concerns to position in the wireless self-networking.
Based on the method for searching buffer of loose location dependence, it is characterized in that in a kind of wireless self-networking of the present invention with space constraint (r), internal object collection (P
In) and peripheral object set (P
Out) a data object q described
0Loose effective coverage, and the search procedure under the loose location dependence pattern comprises following 4 steps:
1) generates request Q (X, (xc, yc), Δ d);
2) if local cache search is no result execution in step 3 then);
3) send searching request to neighbours user, each neighbours user's execution in step 2) local search, the result is returned the generation requesting users, select optimum result by this user, if no result execution in step 4 then);
4) submit searching request to server, return optimal result by server.
For given q
0And r, the building method of loose effective coverage is: make Poly
iThe q that expression is divided with Voronoi figure
i(i=1 ..., the limit collection of effective coverage N) is at first q
iBy arriving q
0Distance sort from small to large, take out nearest object q
k, do curve f (M (x, y)): | q
0M|-||q
kIf M|=r is this curve and Poly
kIntersection point be less than 2, then get next object and repeat aforesaid operations, if this curve and Poly
k2 intersection point P are arranged
1And P
2(the q of this moment
kBe a peripheral object), get an intersection point P
2, then must have another object q
K ', P
2Also at Poly
K 'A limit on, do new curve f ' (M (x, y)): | q
0M|-|q
K 'M|=r obtains another intersection point P
3, go down to obtain new intersection point P successively
4, P
5..., P
mOwing to cross some P
1, P
2..., P
mZone with the hyperbolic line segment is surrounded is sealed, i.e. P
M+1=P
1, q so far
0The limit collection structure of loose effective coverage accomplish, also found out all peripheral objects simultaneously, the internal object collection just can be confirmed in the position that next can contrast each data object, promptly is positioned at other alternative data objects of this loose effective coverage.
Above-mentioned steps 2) process is: the search local cache, find out alternative result set Ai}, i.e. its loose effective coverage coverage rate user's current location, for each Ak ∈ Ai}, if its space constraint value rk≤Δ d, then Ak is suitable Search Results of Q; Otherwise, find out that (coordinate is nearest alternative objects qx (the ∈ P of M (xc, yc)) from Q
In), make e=|qkM|-|qxM|, if e>=Δ d, then Ak also be suitable result of Q, returns the suitable result with minimum e, as if no result execution in step 3 then
According to the present invention; User's its overhead that can bear of affix (comparing the expense that need pay more with optimal result) as the case may be when proposing searching request is through comparing data cached effective coverage and corresponding binding occurrence decides this data cached whether available.This method had both improved the hit rate of buffer memory, had also reduced the energy expense in the communication transmission process simultaneously.
Description of drawings
Fig. 1 is the effective coverage sketch map under the loose location dependence pattern;
Fig. 2 is the search procedure sketch map under the loose location dependence pattern.
Embodiment
Wireless self-networking is made up of base station and one group of mobile terminal device (being the user), and one group of portable terminal is interconnected to form a self-organizing network.Each portable terminal all has the function of data route, can be other device forwards data.The base station is a fixing accessing points, can be regarded as a data server, and the data of all requests of portable terminal can be got from the base station.The part portable terminal is positioned at the communication range of base station, they can with the base station direct communication.If a portable terminal is positioned at outside the communication range of base station, it can pass through the multi-hop communication mode, utilizes other-end to transmit, thereby can have access to the data of base station.There are a plurality of alternative data objects (its physical location is fixed) in a searching request for portable terminal proposes in global scope, when the user proposed searching request, service routine can be confirmed suitable data object according to user's current location.
Based on the loose request of loose location dependence pattern, for example " look near the hotel the family, the there from the distance of current position compared with no more than 100 meters of the distance in a nearest tame hotel ", its user can bear overhead (Δ d) for walking 100 meters more.Fig. 1 is the effective coverage sketch map under the loose location dependence pattern, wherein data object q
2For from the nearest alternative objects of user M, q
1The distance that leaves the user is than q
2Δ d rice far away.Can object of proof q
1Be that the loose effective coverage of binding occurrence is the closed area that is surrounded by one group of hyperbolic line segment with Δ d.
We are with space constraint (r), internal object collection (P
In) and peripheral object set (P
Out) a data object q described
0Loose effective coverage.Wherein the border of loose effective coverage is by r and P
OutConfirm P
InBe used to calculate q
0And the difference between the actual optimum result of request.
For given q
0Can find a unique description with r, concrete grammar is following: make Poly
iThe q that expression is divided with Voronoi figure
i(i=1 ..., the limit collection of effective coverage N), at first we are q
iBy arriving q
0Distance sort from small to large, take out nearest object q
k, do curve f (M (x, y)): | q
0M|-|q
kIf M|=r is this curve and Poly
kIntersection point be less than 2, then get next object and repeat aforesaid operations.If this curve and Poly
k2 intersection point P are arranged
1And P
2(the q of this moment
kBe a peripheral object), get an intersection point P
2, then must have another object q
k, P
2Also at Poly
K 'A limit on.Do new curve f ' (M (x, y)): | q
0M|-|q
K 'M|=r obtains another intersection point P
3, go down to obtain new intersection point P successively
4, P
5..., P
mOwing to cross some P
1, P
2..., P
mZone with the hyperbolic line segment is surrounded is sealed, i.e. P
M+1=P
1So far q
0The limit collection structure of loose effective coverage accomplish, also found out all peripheral objects simultaneously.Internal object collection (being positioned at other alternative data objects of this loose effective coverage) just can be confirmed in the position that next can contrast each data object.
Search procedure under the loose location dependence pattern can be divided into 4 steps (as shown in Figure 2).
1. generate request Q (X, (xc, yc), Δ d).
2. the search local cache is found out alternative result set { Ai}, i.e. its loose effective coverage covering user's current location.For each Ak ∈ Ai}, if its space constraint value rk≤Δ d, then Ak is suitable Search Results of Q; Otherwise, find out that (coordinate is nearest alternative objects qx (the ∈ P of M (xc, yc)) from Q
In), make e=|qkM|-|qxM|, if e>=Δ d, then Ak also is suitable result of Q.Return suitable result, if no result execution in step 3 then with minimum e.
3. send searching request to neighbours user, each neighbours user carries out local search (with step 2), and the result is returned the generation requesting users, selects to have the suitable result of minimum e by this user, if no result execution in step 4 then.
4. submit searching request to server, return optimal result by server.
Claims (1)
- In the wireless self-networking based on the method for searching buffer of loose location dependence, it is characterized in that with space constraint r, internal object collection P InWith peripheral object set P OutA data object q is described 0Loose effective coverage: for given q 0And r, make Poly iThe q that expression is divided with Voronoi figure iThe limit collection of effective coverage, i=1 wherein ..., N is at first q iBy arriving q 0Distance sort from small to large, take out apart from q 0Nearest object q k, do curve f (M (x, y)): | q 0M|-|q kIf M|=r is this curve and Poly kIntersection point be less than 2, then get next apart from q 0Nearest object q nRepeat aforesaid operations, promptly make curve f " (M (x, y)): | q 0M|-|q nIf M|=r is this curve and Poly n2 intersection point P are arranged 1And P 2, get an intersection point P 2, then must have another object q k', P 2Also at Poly k' a limit on, do new curve f ' (M (x, y)): | q 0M|-|q k' M|=r obtains another intersection point P 3, go down to obtain new intersection point P successively 4, P 5..., P mOwing to cross some P 1, P 2..., P mZone with the hyperbolic line segment is surrounded is sealed, i.e. P M+1=P 1, q so far 0The limit collection structure of loose effective coverage accomplish, also found out all peripheral objects simultaneously, the internal object collection just can be confirmed in the position that next contrasts each data object, promptly is positioned at other alternative data objects of this loose effective coverage; And comprise following 4 steps based on the method for searching buffer of loose location dependence:1) (wherein, X is the data object of being asked for X, (xc, yc), Δ d), and (xc is the coordinate that the user sends the position M of request Q yc), and Δ d is the overhead that the user can bear to generate request Q;2) the search local cache is found out the set of all data of loose effective coverage coverage rate user's current location, as alternative result set Ai}, and for each Ak ∈ Ai}, if its space constraint value rk≤Δ d, then Ak is suitable Search Results of Q; Otherwise, find out the nearest alternative objects qx of position M that sends request Q from the user, qx ∈ P In, make e=|AkM|-|qxM|, if e≤Δ d, then Ak also be suitable result of Q, returns the suitable result with minimum e, as if no result execution in step 3 then);3) send searching request to neighbours user, each neighbours user's execution in step 2), the result is returned the generation requesting users, select optimum result by this user, finish; If no result is execution in step 4 then);4) submit searching request to server, return optimal result by server.
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Citations (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
CN1278977A (en) * | 1997-09-04 | 2001-01-03 | 艾利森电话股份有限公司 | Method and arrangement for finding information |
CN1736061A (en) * | 2003-01-10 | 2006-02-15 | 皇家飞利浦电子股份有限公司 | Dynamic network formation for wireless adhoc networks |
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Publication number | Priority date | Publication date | Assignee | Title |
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CN1278977A (en) * | 1997-09-04 | 2001-01-03 | 艾利森电话股份有限公司 | Method and arrangement for finding information |
CN1736061A (en) * | 2003-01-10 | 2006-02-15 | 皇家飞利浦电子股份有限公司 | Dynamic network formation for wireless adhoc networks |
Non-Patent Citations (2)
Title |
---|
JP特开2006-237666A 2006.09.07 |
袁繁华等.移动自组网的一种启发式地理位置路由协议.《福建电脑》.2007,(第6期),87-88. * |
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