5.2 ?????(WLAN)

1
?5? ???????

• 5.1 ???????

• 5.2 ?????(WLAN)

2
5.1???????
? ???????? 1??? ???????????????????????
?????????,??????????????????????????????? 2?????
3
SNI
UNI
????
PSTN
?? ???
?? ??
??????
?
Internet
??? (??/??)
?
?
????
MAN, LAN WAN
?? ???
?? ??


Umf
? ? ? ? ?
UNI
SNI
4
(1)??? ??????????????,???????????,??????
?????? ????GSM / CDMA?????????????(802.11b)
????????? ???????????(???????)
,????(???) (2)????? ?????????????,??????
5
  ????BS( Base Station , 2G /Second
Generation),Node B (????????? /3G Third
Generation?WCDMA), eNodeB (??4G LTE ??)
(3)??? ???????? / ????????? ??
(SDH)???????????????? ADM,MSTP(???????)
, (IP?ATM?Ethernet) ???
6
(4)?????? ??????????????,????(?????????????????
?),?????????,??????,??????(???)??????????,???????
?????3?(PSTN ,Internet,?????) ????(???,
???,?????),)?
?? 2G?????BSC(BS Controller) 3G???????RNC(Radio
Network Controller,?WCDMA ??) 4G ?????????????EPC
(Evolved Packet Core)
7

• 3?????
• (1)Umf??(User interface for Mobile/Fixed
  terminal)
• ????????????????Um??
• ???????????????????????????,?????
• GSM ?WCDMA?CDMA2000,WLAN?
• (2)SNI??
• ??(?????)????????(V5)?????(Z),??????
  ?????????,? STM-N(IP???ATM??),
  nE1?Ethernet??(100M?1G/10GE)??

8
(3)?????? / ?????????
?????????????,?????????? ??
3G???????????UTRAN (Universal Terrestrial Radio
Access Network)
RNC
Iur

Iu
Iub
Uu (UE User Equipment)
???
RNC
Node B
U E
9
? ????????
1??????? 1)?? ???????????????????????
,???????????
???
PBX / RSU
???
??/CPN
PSTN
? ?
? ? ???  
? ? ?
?

(???) ? ?

(???)
???????,???????
10
2)???? 450MHz?800 /900MHz?1.8
/ 1.9GHz?3.5GHz 3) ?? (1)????????(14,8,
16)??,????????????????(???????2002?)
(2) ?????? ?????,??1990S???PHS??(P
HSPersonal Hand System)
11
(3)???????????
???
PSTN / Internet
???
????
???
???
???
????1.5GHz,1.9GHz,2.4GHz
????560Km,????????600Km
12
2??????? 1)  ??
?????????????????????,????????(10Km/h)???(500Km/h)
????  2) ????
???????????????????LAN???ATM?????(???)?2010???????
???????????????   3)????
13
??
(????????)
???
PSTN/ Internet
???
? ?
????
????
? ?
(1)       ???? S(2/4G)?
C(4/6G)?Ku(11/14G)?Ka(20/30G) (2)       ??
A? GEOGeostationary Earth Orbit (GEO ????????)
??????,35800Km,????,??????????,???,???(260ms
),???????,?????????
14
B? Medium Earth Orbit ???10000Km C? Low
Earth Orbit ???7001500Km,???2070?,?
????,???????,?????(535ms),?????????????,????(???
??????)?????????? D? VAST (Very Small Aperture
Terminal) ????3.58m(Ku)?713m(C??),?????
2.4m ????????GEO/MEO/LEO?????/????,NASA?????????
??-InterPlanet
15
?5? ???????

• 5.1 ???????

• 5.2 ?????(WLAN)

16
5.2 WLAN???

• ??WLAN??
• 1? WLAN
• Wireless Local Area Network,??????????
  ????????????,???????????????????
• 2?????
• ???
• ???????(DSSSDirect Sequence Spread
  Spectrum)
• ? ????(FHSSFrequency Hopped Spread
  Spectrum )
• ? OFDM( Orthogonal FDM),???????

17

• ? ??????(?????,???????)
• ???????
• ???IR(Infra Red)
• DSSS?FHSS??ISM (Industrial Scientific
  Medical)??(2.4 GHz),????

3?  ???? (1) ??? ??????????10-4 -
10-5,????????10-8 (2) ??? ?????????????
(3)????????1-10Mbps??,?????600Mbps,???1000Mbps
(4)???? ??????(DSSS)???????????
18
(5) ????????????????? (6)??????????????,???
???????,??,???????WSN (7) ????????????????EMC(
????)?

• 4???????
• (1)IEEE 802.11
• ??802.11
• ???,Barker??? ,2.4 GHz,???????????????(1Mbps
  ?2Mbps),lt100m

19

• 802.11b
• ???,Barker,2.4 GHz,CCK (????? Complimentary
  Code Keying),??????????PBCC(Packet Binary
  Conventional Code),(1,2,5.5,11)Mbps,??????,lt100m

• 802.11a
• ???,OFDM,(6,9,12,18,36,48,54)Mbps,5 GHz
  (5.155.25 GHz?5.255.35 GHz ? 5.7255.825 GHz
  ????),??????????,510Km

• 802.11g
• ???????,CCK,PBCC,OFDM,(5.5,6,9,11,12,18,22,24,
  33,36,48,54)Mbps,???????????????,??????????,2.4GHz
  , (outstanding feature)?802.11b??

20
(2)   Bluetooth ?? 2.4 GHz(ISM)
????1.152Mbps/piconet (?????)
?? 10m100m,8??/piconet,???? (3)   HomeRF
?? 2.4 GHz,??????? MAC ????CSMA/CA,??TDMA
?? 50100m, ??? 12Mbps11Mbps
21
IEEE 802.11????
?? ??(RF) ???(IR) ???? ????(Mb/s)
802.11 2.4GHz DSSS 2
802.11 2.4GHz FHSS 2
802.11 850-950nm Diffuse IR 2
802.11a 5GHz OFDM 54
802.11b 2.4GHz DSSS 11
802.11g 2.4GHz ???802.11b/a?? OFDM , DSSS 54
Diffuse?????
22
IEEE?WLAN?????, WWW.Ieee.org, WWW.anywlan.com??8
02.16 (?WiMAX World Interoperability for
Microwave Access,???????????, Wireless MAN)
PHY
MAC
802.11(1/2 Mbps)
802.11/11a/11b MAC
802.11b(5.5/11 Mbps)
802.11e---QoS
802.11g(gt20 Mbps)
802.11f--?????
802.11a(??54 Mbps)
802.11i ????
802.11h ???? ???????
23
??802.11?????? 1?  ????
(1)PMD PMDPhysical Media Dependent
(??????) ??????????(Modem)
(2)PLCPPhysical Layer Convergence Protocol
??MAC-PDU?PMD-PDU???,????MAC?PMD??????,????
PLCP????MAC PDU?????(PLCP???????,???ATM???????TC?
?????) (3)MACMedium Access Control
?????????? (4) LLC (Logic Link Control,
specified by IEEE 802.2), a subset of HDLC
24
2? PMD ????DSSS?FHSS?OFDM (1) CCK?????
(???,M-ary Orthogonal Keying Modulation,
I/O Modulation ,?Barker????)?????????? (2)
FHSS ????,????? (3) OFDM??FDM,?????
3?PLCP (1) ????
25
Preamble
???????????(??,bit??) Start Frame
Delimiter(??????) ???
Signal ??????
Service ????????? Length
MAC-PDU??
26
(2)DSSS?HR/DSSS?PLCP(High Rate)
SYNC128 bits ???1bit (Scrambled) SFD 0XF3A
(Start Frame Delimiter) Signal 0X0A 1
Mbps 0X14 2 Mbps 0X37
5.5 Mbps 0X6E 11 Mbps
27
Service ?????CCK/PBCC???PBCC??????? Length
MAC PDU?? CRC ?PLCP???? MPDU MAC PDU
(3)FHSS?PLCP
PSDU PHY Service Data Unit(MAC PDU????????MAC
PDUs ) SYNC 80 bits (0,1)??,???0,??1
SFD 0000 1100 1011 1101 PLW PSDU Length Word
28
PSFPLCP Signaling Field,?????,14.5Mbps,????0.5
Mbps
(4)  OFDM?PLCP
12 4 1
1 6 16
bits
Preamble ??10?????2???? Rate
????????????? Tail ???????Byte
Alignment(?????)
29
Rate code 1011 1111 1010
1110 1001 1101 1000 1100 Mbps 6
9 12 18 24 36 48
54
??802.11 MAC 1??????? ESS ( extended
services set)??
30
Distribution System (Ethernet?SDH?ATM)
PSTN
BSS-b

BSS-a
Internet
APb
APa
Intranet
?Bn
?B1
?a1
?a2
Server
?an
31
(1)  ????(ad hoc network) BSS ( Basic Service
Set) ??????????(?)??,????????????,?
????server/client??? ad hoc network?IBSS
(Independent Basic Service Set)
????????,?????????????(peer-to-peer) ?
AP/RAP(Radio Access Point,?????)
?????????????LAN/?????????, ?
1)???????(?????)???????????? 2) ?????????
(2) ESS (extended services set) ???(
Distribution)????????????BSSs?
32
2?MAC ???????CSMA/CA (Collision
Avoidance),?????????CA???
MAC Sublayer Architecture
Contention free ????
33
802.11????? (1)DCF(Distributed Coordination
Function???????) ??CSMA/CA,????????,
????RTS/CTS??????????? (2)PCF(Point Coordination
Function,?????) ??????????,???DCF????PCF
?,PCF????????????????????????? (3) IFS
(Interframe Space,???)
?????IFS????????
34
SIFS Short IFS ? ?
PIFS PCF IFS ? ?
DIFS DCF IFS ? ?
?
? The SIFS Interval is the
smallest IFS, followed by PIFS and DIFS,
respectively   (4) Hidden Node
Problem (??????)
35
?B A?????
Data request Let
stations A and C be transmitting to stations B
and D, respectively. If station As and Cs
transmissions overlap in time, it is possible
that station B will not receive the packets from
A reliably, since the interference from C is too
strong. How can avoid this situation?
36
hidden node problem described in the
Networking Dictionary The hidden node
problem occurs in the wireless networking when a
node is visible from a wireless hub, but not from
other nodes communicating with said hub. This
leads to difficulties in media access control.
Hidden nodes in a wireless network refer to nodes
which are out of range of other nodes or a
collection for nodes. Take a physical star
topology with an Access Point with many nodes
surrounding it in a circular fashion each node
is within the communication range of the Access
Point, however, not each node can communicate
with each other.
???? ?A?B??RTS (Request to
send),??C???A???????,????RTS ?B??CTS (Clear to
send),?C???, ??????? ????????????????????????? ?
37
(5) ???? (??P61,Book entitledwireless
LAN standards APP) NAV The Network
Allocation Vector (NAV) is virtual carrier
sensing mechanism used with wireless network
protocols such as IEEE 802.11 and IEEE 802.16
(WiMax). how long the channel is occupied.
????random0, slot-time
ranf() 0,1????, RTS20 bytes, CTS14
Bytes CW contention window
(a) Without handshaking
(b) RTS/CTS ??
NAV ??? NAV??????,?????????????????(?????????)
38
???????????????? 1. ???????1)???????,?????????
?2)??MTU(maximum transfer Unit)??? 2. How to
fragment? ?? ????Fragmentation threshold
Fragment 1
Fragment 2
39
??????
??(????)????????????????????????????
????,?????word???????????PPT??,???????????? ??
??????????????
??????PPT,?20??,???30 slides
?????????word??(tutorial,overview),???????????????
???????????? ??????PPT?????tutorial??
You could request/ recommend other issues if I
agree with. Note Each group consists of one
student only ( but student tutored by Prof. Xu
should attend different group, i.e., it is not
allowed that two or more students attend the
same group). I can provide the necessary
materials for those issues like 3G WCDMA if
needed.
39
Dr. Zhanqi XU, National Key Lab on ISN, Xidian
University
2016/8/6