1

ĐẠI HỌC QUỐC GIA HÀ NỘI
TRƯỜNG ĐẠI HỌC CÔNG NGHỆ


Hà Minh Toản

NGHIÊN CỨU CÁC CHIẾN LƯỢC
ĐẢM BẢO CHẤT LƯỢNG DỊCH VỤ (QoS)
TRONG CÁC MẠNG KHÔNG DÂY
Ngành: Công Nghệ Thông Tin
Chuyên ngành: Truyền dư
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u va
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Mã số: 60 48 15 LUẬN VĂN THẠC SĨ

 32
CHƢƠNG III. ĐẢM BẢO QoS TRONG CƠ CHẾ EDCA IEEE 802.11e 33
- EDCA 34
 34
- EDCAF 35
 36
 40
 45
CHƢƠNG IV. MÔ PHỎNG VÀ PHÂN TÍCH KẾT QUẢ 46
NS-2 47

3

- 48
 48
 49
 50
 53
 55
 55
 63
KẾT LUẬN VÀ HƢỚNG NGHIÊN CỨU TIẾP THEO 67
 67
 68
TÀI LIỆU THAM KHẢO 69 4

DANH MỤC CÁC KÝ HIỆU, CÁC CHỮ VIẾT TẮT













trong IEEE 802.11
CSMA/CA
Carrier Sense Multiple Access
with Collision Avoidance












C
trung
EDCAF
Enhanced Distributed Channel
Access Function


AIFS
Arbitration Interframe Space



toán quay lui trong EDCAF
TXOP
Transmission Opportunity

NS-2
Network Simulator version 2








2
CBR
Constant Bit Rate


Transmission Control Protocol




giao 

.

6

DANH MỤC CÁC HÌNH VẼ
 21
-hoc 22
 23
 23
 24
Hình  25
 27
 28
 28
 29
 30
 35
 37
Hình 3.3: Contention Free Bursting (CFB) 40
 41
 42
hông tin QoS. 43
 44


7

Hình 4.2b: 































 


. 59
Hình 4.4: 



  




































 


. 61
Hình 4.6: 



  








. 62
 63
Hình 4.8: 





. 64
Hình 4.9: 

  






. 65 8

DANH MỤC CÁC BẢNG
 34
. 36





“Nghiên cứu các chiến lược đảm bảo chất lượng dịch vụ (QoS) trong
các mạng không dây” c
 Chương I:              

các

10



 dây;

 Chương II:             
802.11  
. Chúng ta 
DCF (Distributed Coordination Function)
     PCF (Point Coordination Function). 

, 











.
 Chương III: 

 
cao (Enhanced Distributed Channel Access - EDCA) 
lai (Hybrid Coordination Function - HCF)    Cùng
 
  

 Chương IV: 
-






 , 



  


 k 

























.
 Chương V: 







 Chính vì               
nguyên cho 
 
Vào      i v     
Telecommunication Union - mô hình i là c
(Asynchronous Transfer Mode - ATM) cho 
       B-ISDN (Broadband-Integrated Service Digital
 

kênh,  
khá
 
trong 

12

  
 

. Chính Web ,
          c       
H

       , VoIP,    , P2P (peer-to-
peer
   

datagram 

có 

.
ccd 
Internet.  các gói tin
 (router) Các tvà phát
. Trong hai 
t 
c(processor sharing- PS).
c
    g max-        
; (misbehave);
 - 
 
-in first-out (FIFO) ( first-
come first-serve - FCFS)          andom Early
Detection (RED).V pháp d
d(Integrated services - Intserv), d  (Differentiated
services - Diffserv)



. 4/ M


I.1. Đại lƣợng cần đảm bảo chất lƣợng dịch vụ
 cho  
 chính sau :
1. Băng thông: 
trong m 

14

8 microsecond  s
(p
 
sáng là 3x10
8

trong hàng 
 ch
Ccho
- 

15

. d
150 mili giây

3. Thăng giáng độ trễ: 
 
ph 
 
 
 
 (buffer) 
 
 

 


4. Tỉ lệ mất mát dữ liệu: C nhìn chung 


 







     





I.3. Cơ chế đảm bảo dịch vụ trong mạng có dây

 Ts
              . M   
router, chính
, 

 . M
 
n multi-path routing). 


17

có hop) 


                
router 


18


-effort thông th

cho 
 

               
chính xác.
I.4. Vấn đề phát sinh khi đảm bảo chất lƣợng dịch vụ cho mạng không dây.
          
 
không dây. H 
phát sinh làm cho 
ông dây.
  khi    
,

 c truyn không dây và tính 
tr  (Hidden terminal), tr l (Exposed Terminal), tín hi
truy theo nhi  (multi-path propagation) 
ông dây [1].
   
-lô-mé


xem xét hi sinh  
có 
nào       
            mong
 
            o    
 ph
cph


               
                 



20

CHƢƠNG II. CHUẨN MẠNG LAN KHÔNG DÂY IEEE 802.11
IEEE 802.11 MAC, 
 t 
  
 n tán - DCF (Distributed Coordination
 PCF (Point
 không 

   không  Trong 
tôi trình bày 
 QoS.
II.1. Cấu trúc hệ thống mạng WLAN

             m  


22


k1, 2, 5].
II.1.2. Mạng Ad-hoc
Ad-    d trên 
m có dây  
 Các  -
c nhau
(vùng mà các         
. Chính vì
-

 
hidden terminal) hay exposed terminal),
 [1, 5]. Tuy nhiên, chính
-

        
-hoc.

Hình 2.2: Mạng không dây ad-hoc
II.2. Kiến trúc giao thức
ang  s d ph bi cho
2.3 mô hình 



II.2.1. Tầng vật lý



         

t 
, 5].
II.2.1.1 Kĩ thuật trải phổ nhảy tần FHSS (Frequency Hopping Spread Spectrum) [1,
5, 4]
s d
chung m d tn s 


kênh n


tin -
GFSK (Gaussian shaped Frequency Shift Keying) 

Hình 2.5: Định dạng của một frame quy định trong FHSS 802.11 PHY
Hình 2.5 
PLCP preamble)
 PLCP 
               

7
+z
4




7
+z
4


Hình 2.6: Định dạng của một frame quy định trong DSSS 802.11
2.6, bao
            

 Trường đồng bộ hóa (Synchronization): dài 

sóng mang (cho CCA).
 Đoạn phân cách đầu frame SFD (Start Frame Delimiter): dài 16 bit có 


Trích đoạn III.3. Tóm tắt các đặc điểm chính của chuẩn IEEE 802.11e CHƢƠNG IV. MÔ PHỎNG VÀ PHÂN TÍCH KẾT QUẢ IV.2. Sử dụng NS-2 thiết lập mô phỏng mạng IV.2.1. Thiết lập các lựa chọn, tham số cho mô phỏng IV.2.2. Thiết lập topo và cơ chế định tuyến [14, 15, 16] IV.2.3. Cấu hình trạm tham gia mạng mô phỏng

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