He thong thong tin di dong

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  • 1. Luan van tot nghiep CHNG 1 CAC KY THUAT C S VA CAC BO PHAN CHNH TRONG HE THONG THONG TIN DI SO I. CAC BO PHAN CHNH TRONG HE THONG THONG TIN DI ONG SO 1. Gii thieu - Mang vien thong to ong la mot trong cac ng dung ky thuat vien thong co nhu cau ln nhat va phat trien nhanh nhat. - GSM (Global system for mobile communication he thong thong tin di ong toan cau) vi tieu chuan thong so toan Chau Au mi, se giai quyet s han che dung lng hien nay. Thc chat dung lng se tang 2 3 lan nh viec s dung tan so tot hn va ky thuat o nho, do vay so thue bao phuc vu se tang len. - Lu ong la hoan toan t ong, ban co the em may di ong cua mnh khi i du lch va s dung mot nc khac. He thong se t ong cap nhat thong tin ve v tr cua ban cho he thong tai nha ban. Ban cung co the goi i va nhan cuoc goi en ma ngi goi khong can biet v tr cua ban. Ngoai tnh lu ong quoc te, tieu chuan GSM con cung cap mot so tnh nang nh thong tin toc o cao, faxcimile va dch vu thong bao ngan. Cac may ien thoai di ong se ngay cang nho hn va tieu thu t cong suat hn cac the he trc chung. - Tieu chuan GSM c thiet ke e co the ket hp vi ISDN va tng thch vi moi trng di ong. Nh vay tnng tac gia hai tieu chuan nay am bao. - Nam 1982 GSM bat au phat trien khi cac nc Bac Au gi e ngh en CEPT e quy nh mot dch vu vien thong chung Chau Au 900MHz. - T nam 1982 en nam 1985 ngi ta ban luan ve viec xay dng mot he thong so hay tng t. Nam 1985 quyet nh he thong so. Bc tiep theo la chon la giai phap bang hep va bang rong. - Nam 1986 mot cuoc kiem tra ngoai hien trng a c to chc tai Paris cac hang khac nhau a ua tai vi cac giai phap cua mnh. - Thang 05/1987 giai phap TDMA bang hep c la chon, ong thi cac hang khai thac a ky bien ban ghi nh MoU(Memorandem of Understanding) thc hien cac quy nh a ha se co 1 GSM van hanh vao 01/07/91. 1

2. Luan van tot nghiep - Ecrisson vi be day kinh nghiem trong viec thiet ke va san xuat he thong to ong. He thong CME20 cho GSM c thiet ke tren c s chuyen mach so AXE10. nc ta co hai he thong ien thoai di ong la Vinaphone, VMS. - Ve chat lng Chc nang au tien cua CME20 la cung cap mot dch vu ien thoai di ong tin cay va chat lng tot. Cac the he may di ong khac nhau cung s dung nhieu loai dch vu so lieu mi khong can mot modem rieng. GSM viec ang ky thue bao c ghi modem nhan dang thue bao SIM (Subscribe Identity Module) card thue bao co mot kch thc nh mot tam tn phieu. Ban co the cam card thue bao cua mnh vao loai may GSM va ch mnh s dung no. He thong kiem tra la ang ky thue bao ung va card khong b lay cap. Qua trnh nay c t ong thc hien bang mot thu tuc nhan thc thong qua mot trung tam nhan thc. Tnh bao mat cung c tang cng nh viec s dung mot ma so e ngan chan hoan toan viec nghe trom vo tuyen. cac nc ieu kien tng oi tot, chat lng tieng GSM ngang bang vi he thong tng t. Tuy nhien, cac ieu kien toi do tn hieu yeu hay do nhieu giao thoa nang, GSM co chat lng tot hn. Viec s dung cong nghe mi lam cac may ien thoai di ong nho va nhe hn, s dung che ong ngh t ong lam cho tuoi tho ac qui dai hn. Cau truc chung cua he thong GSM 2 3. Luan van tot nghiep NSS: Mang va he thong con chuyen mach BSS: He thong con tram goc OSS: He thong con khai thac MS: Tram di ong Hnh 1.1: Cau truc chung cua GSM 1.1. He thong con chuyen mach (SS) He thong con chuyen mach bao gom cac chc nang chuyen mach chnh cua GSM cung nh c s d lieu can thiet cho so lieu thue bao va quan ly di ong cua thue bao. Chc nang chnh cua SS la quan ly thong tin gia nhng ngi s dung mang GSM vi nhau va vi mang khac. 1.1.1. MSC SS chc nang chuyen mach chnh c MSC thc hien, nhiem vu chnh cua MSC la ieu phoi viec thiet lap cuoc goi en nhng ngi s dung mang GSM. Mot mat MSC giao tiep vi he thong con BSS, mat khac giao tiep vi mang ngoai. MSC lam nhiem vu giao tiep vi mang ngoai goi la MSC cong. Viec giao tiep vi mang ngoai e am bao thong tin cho nhng ngi s dung mang GSM oi hoi cong thch ng (cac chc nang tng tac IWF: interworking function). SS cung can giao tiep vi mang ngoai e s dung cac kha nang truyen tai cua cac mang nay cho viec truyen tai so lieu cua ngi s dung hoac bao hieu gia cac phan t cua mang GSM. Chang han SS co the s dung mang bao hieu kenh chung so 7 (CCS No), mang nay am bao hoat ong tng tac gia cac phan t cua SS trong mot hay nhieu mang GSM. MSC thng la mot tong ai ln ieu khien tram goc (BSC). Mot tong ai MSC thch hp cho mot vung o th va ngoai o co dan c vao khoang mot trieu (vi mat o thue bao trung bnh). e ket noi MSC vi mot so mang khac can phai thch ng vi cac ac iem truyen dan cua GSM vi cac mang nay. Cac thch ng nay c goi la cac chc nang tng tac (IWF: interworking function) bao gom mot thiet b e thch ng giao thc va truyen dan. No cho phep ket noi vi cac mang: PSPDN (mang so lieu cong cong chuyen mach goi) hay CSPDN (mang so lieu cong cong chuyen mach theo mach), no cung ton tai khi cac mang khac ch n thuan la PSTN hay ISDN. IWF co the c thc hien trong cung chc nang MSC hay co the thiet b rieng, trng hp hai giao tiep gia MSC va IWF c e m. 3 4. Luan van tot nghiep 1.1.2. HLR Ngoai MSC, SS bao gom cac c s d lieu. Cac thong tin lien quan en viec cung cap cac dch vu vien thong c lu gi HLR khong phu thuoc vao v tr hien thi cua thue bao. HLR cung cha cac thong tin lien quan en v tr hien thi cua thue bao. Thng HLR la mot may tnh ng rieng khong co kha nang chuyen mach nhng co kha nang quan ly hang tram ngan thue bao. Mot chc nang con cua HLR la nhan dang trung tam nhan thc AUC ma nhiem vu cua trung tam nay quan ly an toan so lieu cua cac thue bao c phep. 1.1.3. VLR VLR la c s d lieu th hai trong mang GSM. No c noi mot hay nhieu MSC va co nhiem vu lu gi tam thi so lieu thue bao cua cac thue bao hien ang nam trong vung phuc vu cua MSC tng ng va ong thi lu gi so lieu ve v tr cua cac thue bao noi tren mc o chnh xac hn HLR. Cac chc nang VLR thng c lien ket vi cac chc nang MSC. 1.1.4. GMSC SS co the cha nhieu MSC, VLR, HLR. e thiet lap mot cuoc goi en ngi s dung GSM, trc het cuoc goi phai c nh tuyen en mot tong ai cong c goi la GMSC ma khong can biet en hien thi thue bao ang au. - Cac tong ai cong co nhiem vu lay thong tin ve v tr cua thue bao va nh tuyen cuoc goi en tong ai ang quan ly thue bao thi iem hien thi (MSC tam tru). - e vay, trc het cac tong ai cong phai da tren so thoai danh ba cua thue bao e tm ung HLR can thiet va hoi HLR nay. Tong ai cong co mot giao dien vi cac mang ben ngoai thong qua giao dien nay no lam nhiem vu cong e ket noi cac mang ben ngoai vi mang GSM. Ngoai ra tong ai nay cung co giao dien bao hieu so 7 (CCS No7) e co the tng tac phan t khac cua SS. Ve phng dien kinh te khong phai bao gi tong ai cong cung ng rieng ma thng c ket hp vi MSC. 4 5. Luan van tot nghiep 1.2. He thong con BSS Co the noi BSS la mot he thong cac thiet b ac thu rieng cho cac tnh chat to ong vo tuyen cua GSM. BSS giao dien trc tiep vi cac tram di ong (MS) thong qua giao dien vo tuyen, v the no bao gom cac thiet b phat va thu ng vo tuyen va quan ly cac chc nang nay. Mat khac BSS thc hien giao dien vi cac tong ai SS. Tom lai BSS thc hien au noi cac MS vi cac ngi s dung vien thong khac. BSS cung phai c ieu khien va v vay no c au noi vi CSS. Cac giao dien ben ngoai cua BSS cho hnh 1.2. NSS: Mang va he thong con chuyen mach BSS: He thong con tram goc OSS: He thong con khai thac MS: Tram di ong Hnh 1.2: Cac giao dien ngoai BSS BSS bao gom hai loai thiet b: BTS giao dien vi MS va BSC giao dien vi MSC. Cau truc ben trong BSS c cho hnh 1.3. Luong ieu khien Luong lu lng OSS MS BSS NSS 5 6. Luan van tot nghiep OSS BSC NSS BTS BTS BTS BSS Giao dien Abis Giao dien A Giao dien Vo tuyen Hnh 1.3: Cac phan t cua BSS 1.2.1. BTS Mot BTS bao gom cac thiet b phat thu, anten va x ly tn hieu ac thu cho giao dien vo tuyen. Co the coi BTS la cac modem vo tuyen phc tap co them mot so cac chc nang khac. Mot bo phan quan trong cua BTS la TRAU (Transcoder and rate adapter unit: khoi chuyen oi ma va thch ng toc o). TRAU la thiet b ma o qua trnh ma hoa va giai ma tieng ac thu rieng cho GSM c tien hanh, ay cung thc hien thch ng toc o trong trng hp truyen so lieu. TRAU la mot bo 6 7. Luan van tot nghiep phan cua BTS, nhng cung co the at no cach xa BTS va tham ch trong nhieu trng hp c at gia cac BSC va MSC. 1.2.2. BSC BSC co nhiem vu qua ly tat ca giao dien vo tuyen thong qua cac lenh ieu khien t xa BTS va MS. Cac lenh nay chu yeu la cac lenh an nh, giai phong kenh vo tuyen va quan ly chuyen giao (handover). Mot pha BSC c noi vi BTS con pha kia noi vi MSC cua SS. Trong thc te BSC la mot tong ai nho co kha nang tnh toan ang ke. Vai tro chu yeu cua no la quan ly cac kenh giao dien vo tuyen va chuyen giao (handover). Mot BSC trung bnh co the quan ly ti vai chuc BTS phu thuoc vao lu lng cua cac BTS nay. Giao dien gia BSC vi MSC c goi la giao dien A, con giao dien gia no vi BTS c goi la giao dien Abis. 1.3. Tram di ong MS Tram di ong la thiet b duy nhat ma ngi s dung co the thng xuyen nhn thay cua he thong. MS co the la thiet b at trong o to, thiet b xach tay hoac thiet b cam tay. Loai thiet b cam tay se la thiet b tram di ong pho bien nhat. Ngoai viec cha cac chc nang vo tuyen chung va x ly cho giao dien vo tuyen MS con phai cung cap cac giao dien vi ngi s dung (nh: micro, loa, man hien th, ban phm e quan ly cuoc goi) hoac giao dien vi mot so thiet b khac (nh: giao dien vi may tnh ca nhan, fax). Hien nay ngi ta ang co gang san xuat cac thiet b au cuoi gon nhe e au noi vi tram di ong. Viec la chon cac thiet b au cuoi hien e m cho cac nha san xuat, ta co the liet ke ba chc nang chnh: - Thiet b au cuoi thc hien cac chc nang khong lien quan en mang GSM: Fax. - Ket cuoi tram di ong thc hien cac chc nang lien quan en truyen dan giao dien vo tuyen. - Bo thch ng au cuoi lam viec nh mot ca noi thong thiet b au cuoi vi ket cuoi di ong. Can s dung bo thch ng au cuoi khi giao dien ngoai tram di 7 8. Luan van tot nghiep ong tuan theo tieu chuan ISDN e au noi au cuoi, con thiet b au cuoi lai co the giao dien au cuoi modem. Cau truc chc nang cua tram di ong cho hnh 1.4. au cuoi di ong au cuoi di ong Thch ng au