C S SAP ) LOP con hOMU Ogc M
331 Type (3) BR /ASS (II)
3.3.4. Co' the yeu cau va cap phit bang thong Yen cau
Yen cau
Co the you au bang thong dugc tram SS sir dung de thong bao cho tram BS can cap phat bang thong. ThOng bao yeu cau bang thong c6 thE 11 tieu de yeu cau bang thong hoac thong bao PiggyBack.
Cac you au bang thong chia lam Mn kieu:
Implicit request: Trong third t6, kieu you au nay la nheng thoa thuan tAi thoi diem thiett lap ket n6i.
Chuang 3: Kiln Ink :wing truy cpp WiMAX
Bandwidth Request message: Co hai kieu thong bao incremental hoc aggregate. Khi tram BS nhAn &roc mot th8ng bao yeu eau bang thong kieu incremental, se cap phat bei sung mot Wong bang th6ng theo you cau cho lc& noi. Ngtrqc tai, khi tram BS nhAn duqc mot th8ng bao you cau bang thong kieu aggregate, se cap phat mot Itrong bang thong thay the cho luong bang thong hien tai. Truing Type trong tieu de yeu cau bAng thong chi thj kieu thong bao yeu au bang thong la incremetal hay aggregate.
PiggyBacked request (cho the djch vp khac UGS): Duqc china trong tieu d'i con Grant Management, khong co twang Type, do do mAc dinh kieu incremental.
Poll-Me bit (chi cho djch vti UGS): Duqc tram BS sir ding de tham do bAng th6ng cho cac djch v4 khric UGS.
CAp phat
Lop MAC chuan IEEE 802.16 cung cap hai kieu cap phat bang thong cho tram SS, &roc phan biet a hinh thirc cap phat bang thong cho m6i kat nal hay cap phat bAng th6ng cho m6i tram SS. Ca hai kieu cap phat deu you cau bang thong ten cac ket nai, cho phep cac tram BS dieu chinh cac you cau QoS cho phu hop khi tien hanh cap phat bang th6ng.
Hai kieu cap phat bang thong duqc dinh nghia:
Cap phat ten mei kit nai GPC (Grant per Connnection): Bang thong duqc BS cap phat rieng cho m8i kat nal, va SS sir ding bang thong duqc cap phat chi cho kat nai do. Thich hop trong twang hop so Wong cac ket noi hart the tren m61 tram SS.
Cap phat ten m8i tram thue bao GPSS (Grant per SubScrible): BAng thong duqc BS cap phat town b0 tucmg 1mg vii you cau coa SS. SS chju trach nhiem phan phei Itrong bAng th8ng duqc cap phat cho cac ket nai, duy tri mac QoS trOn cac ket noi
va th6a thuAn cac mire dich vv. Thich hop trong truing hop co nhiEu ket n8i tren
m8i tram SS.
Trong thvc te, mat so"' yeu to inh huang den qua trinh cap phat bang thong nhu: Tram BS khong nhAn duqc thong bao you cau bling thong hay tram SS kh6ng nh(in duqc bAng thong dugc cap do 16i 16p vet ly, hoac tram BS khong cung cap dit ltrong bAng thong theo yeu cau...
Chuang 3: Kiln Ink mgng truy cap WiMAX
Do do, trong ca hai kieu cAp phat, lap MAC chuAn IEEE 802.16 sir dung ca the ti sera 161 (self-correcting) thay cho ca the gin acknowledge. Ca the self-correcting it ton bang th6ng va dO tre nho han ca the acknowledge.
Si yeti ca the ti sea 161, cac yeu t6 gay anh Inning den qua trinh cAp phat bang th8ng se duqc giai guy& ding mOt lac. Sau mOt khoang thin gian timeout thich hqp, tram SS se giri Banwidth Request den tram BS. Th6ng thuemg loai thong bao yeu eau IA incremental nghia la tram SS yeu cAu b6 sung bang thong cho mOt ket n6i. Tuy nhien del hic thong bao you cAu bang thong la aggregate nghia IA tram SS you
cAu bang thong cho town be) cac ket nai ma no quan
Polling
Ca the polling &roc thoc hien tai BS, la qua trinh tham do de cAp phat bang th8ng cho SS giri Banwidth Request. CO the cAp phat cho tong SS rieng biet hay cho men nhem cac SS. CO hai kieu polling:
Unicast: tham do mot SS rieng biet. Neu nhu mot tram SS khong can cap phat bang thong, no giri lai request co dO dai 0 byte.
Multicast va Broadcast: tham do mOt [Mom hay toan b0 cac tram do khong dti bang th6ng de tham do timg tram SS rieng le.