W. (mg dung nhu vey la jr tuong cho cac mpg cam bien khOng day S6 luqng clit lieu
4.3.2.Flooding vii cdc ban th
Flooding la mOt ky thuat chung thu6ng dUng trong phat tan thong tin vi tim dul:mg trong mong c6 day va khong day ad hoc. Chien thuat djnh tuyen don elm vi khong doi NM cau hinh mong ton kern vi thuat Wan tim duling pink top. Flooding dUng phuong phip reactive (phin Ung loi), khi mgi node nhon duqc mOt g6i dieu khien hay dff lieu ne se eri den tat cit cac node xung quanh no. Sau khi truyen, mOt gel di theo tit ca cac &tong c6 the duqc. Neu Ichong bj mitt ket n6i, goi se den dich. Han nffa, khi cau hinh mong thay d6i, vier truyen &Si se theo niteng tuyen mai. Hinh 4 3 minh
hqa nhOng quy uac flooding trong mong. Flooding don gian nhit c6 the lam cac goi bj
sao chop loi mOt cach khong giai hon khi di qua cac node mong.
Ifinh 4.3. Flooding cdc &Si du lieu trong mong thong tin
ngan ch#n met &Si dr di yang yang khong )(tic djnh trong mong, met truZmg duqc goi la hop count duac them vao g6i. Ban diu, hop count ducyc d#t gia tri xip xi duang Idnh mong. Khi gii di qua mpg, hop count bi giam di 1 sau mid buoc (mOt buac duqc tinh la met lin truyen ta node nay sang node Ida). Khi hop count ve 0, gal
a bi htly di. MOt cach tuang tu dirge dung la them vao twang time-to-live, truang nay
ghi lai thei gian ma goi duqc phep tin tai trong mpg. Khi het thbi gian nay, gai lchang duqc truyen di ilea. Flooding c6 the duqc cli den bin each 'tic Win gii dft
lieu duy nhAt, m& node mong se b6 di cac gai di nt*
M#c du don gian trong quy lust hoot ding va phi, hap vii ceu hinh mong ci chi phi thip nhung flooding gip nhieu bat lqi khi alp ding vao mong WSNs. Nhuqc diem
dau tien dm flooding 11 gsp phial yin de traffic implosion (bung no hay khep kin cac
gii dit lieu tai met node). Nhu tren hinh 4 4, hien ttrong kh8ng mong mu& xay ra khi ban sao cult cling met gel dit lieu cling gin den met node.
Hinh 4.4. Bung nd hen hiqng do flooding
Nhuqc diem thin hai la van de ching lin (overlap). Minh 4.5, overlap )(ay ra khi hai node cling gal gii den cling met node. Nhuqc diem thin ba la nhuqc diem nguy hiem nhit cua flooding 11 resource blindness (sir mu quang tai nguyen). Quy luSt don gian ciia flooding kh8ng xem xet den hon chi ye ngu6n ning lucmg cua cac node. Nang lucing cda node ci the suy giam nhanh chang, elm ding ke thoi gian sing cult mpg.
Hinh 4.5. Kin de cluing lin do flooding
De giai quyet nhuqc diem neu tren, mOt huong m6i g9i la gossiping. Tucmg tv flooding, gossiping dung quy lu#t don gitin va kh8ng dei hoi ciu hinh mong dit tien hay thu#t toan djnh tuyAn phirc top. Ithac v6i flooding, gel der lieu duqc phat quang ba den tit a cac node, gossiping chi yeu ciu me•i node girl g6i vita nh#n duqc den mOt node duqc lira chon ngau nhien khac. Qua trinh cu the tiep din den khi goi den thrqc dich hay hop count bj giOi hen. Gossiping tranh duqc yin de bung n6 ltru luqng mong bang each gioi hon s6 goi ma mgi node ph den cac node Ian c#n no. Tuy nhien, d8 trg &Si tai dich den c6 the rat Ion, d#c biet trong mpg c6 kich thuOc len do bin chit, chi c6 mOt lien ket duqc to thanh tai mOt thoi diem.