Dr. Beinschróth József Telecommunication informatics I. Part 4
ÓE-KVK Budapest, 2019.
Dr. Beinschróth József: Telecommunication informatics I. Content
Network architectures: collection of recommendations The Physical Layer: transporting bits The Data Link Layer: Logical Link Control and Media Access Control Examles for technologies based on the Data Link Layer The Network Layer 1: functions and protocols The Network Layer 2: routing Examle for technology based on the Network Layer The Transport Layer The Application Layer Criptography IPSec, VPN and border protection QoS and multimedia Additional chapters
Dr. Beinschróth József: Telecommunication informatics I. 2 The content of this chapter
Wired LAN-s
Wireless LAN-s
PLC, BPL (Power Line Communication, Broadband over Power Lines)
DOCSIS
Dr. Beinschróth József: Telecommunication informatics I. 3 The LAN (Local Area Network) architecture covers the first two layer of the model
The LAN technology is very widespread Covers the first two layer of the model, The data link layer plays a decisive role in the LAN architecture.
Wired LAN-s Dr. Beinschróth József: Telecommunication informatics I. 4 The LAN is implemented in buildings or buildings close to each other (1)
Located within a relatively small range of intelligent devices: the physical dimension limit: max. a few km, the transmission time is known in advance (micro, nanosecond scale delays).
Typically is implemented in buildings, buildings close to each other, companies, institutions.
The data transfer is implemented in a communication channel (does not use connected or leased telephone or data networks)
Typically private network - work with one owner and administrative management.
Destination: computers, printers and other shared resources sharing, messaging.
Typically multiple access.
Wired LAN-s Dr. Beinschróth József: Telecommunication informatics I. 5 The LAN is implemented in buildings or buildings close to each other (2)
The stations in the physical layer are shared. (Multiple Access)
The LANs basically differ in media access control solution.
There are various topologies.
10-100-1000Mbps data transfer speed, the transmission time is limited.
The network traffic control is based on the principle of peer communication (no special equipment).
Physical medium: coax (old), UTP, optical fiber, (wireless)
Wired LAN-s Dr. Beinschróth József: Telecommunication informatics I. 6 The LAN is made up of many elements
Computer equipments (servers, workstations, printers, etc.)
Network interface controller
Network elements
• Active elements (repeater, router, HUB, switch…) • Passive elements (cablesystem, connectors, cable organizers…)
Wired LAN-s Dr. Beinschróth József: Telecommunication informatics I. 7 LANs offer many advantages (1)
Distributed data access.
A user can access a file which is stored on another computer or files can be stored on a different machine.
Problem: access at the same time.
Other network resources (typically printers) used by multiple users.
The asset utilization increases (not necessary printer for all the users, every user can access for the expensive printers).
Message forwarding between users.
Wired LAN-s Dr. Beinschróth József: Telecommunication informatics I. 8 LANs offer many advantages (2)
E-mail, messaging commands.
License management optimization.
Appropriate license is required only in the number of concurrent users.
Optimizing operation.
Any available PC configuration databases (user data), remote access.
Fault tolerance, reliability growth.
Achieved by using redundancy to a device failure does not mean a loss of service (printer, server…).
…
Wired LAN-s Dr. Beinschróth József: Telecommunication informatics I. 9 Many standards applies to the LAN IEEE 802 standards 802.1 High level Interface 802.1p General Registration Protocol 802.1q Virtual Bridged LANs 802.2 Logical Link Control 802.3 Carrier Sense Multiple Access/ Collision Detect (CSMA/CD) 802.3u Fast Ethernet 802.4 Token-Passing Bus 802.5 Token-Passing Ring 802.6 Metropolitan Area Networks 802.7 Broadband Technical Advisory Group 802.8 Fiber Optic Technical Advisory Group 802.9a IsoENET 802.9 Integrated Voice and Data Networks 802.10 Network Security (802.11 Wireless LAN-s)
Wired LAN-s Dr. Beinschróth József: Telecommunication informatics I. 10 Special LAN – virtual LAN (vLAN)
• The individual stations are not close to each other, are typically connected via the Internet, but they behave as if they were in a LAN. • The stations are logically organized into a group. (vLAN) • (In case of LAN the together used physical v=virtual medium connected the stations.) • The vLAN is considered to be a broadcast domain. • Logical grouping can be based on MAC address, IP address, protocol type, port number, etc.
Wired LAN-s Dr. Beinschróth József: Telecommunication informatics I. 11 The IEEE LAN standards mapped to the bottom two layers of the OSI model
OSI Reference Contact between IEEE LAN standards and the Model OSI Reference Model Model
Network LAN Architecture
802.2 Logical Link Control Data Link
802.3 802.5 Media Access Media Access Physical Medium Access sublayer Control Control
Physical Physical
Wired LAN-s Dr. Beinschróth József: Telecommunication informatics I. 12 LANs can be either star, ring or bus topology
Structured cabling: apparently star topology
Wired LAN-s Dr. Beinschróth József: Telecommunication informatics I. 13 Several technologies exist for LAN
IEEE Ethernet 802.3
Token Passing
The Ethernet and the IEEE 802.3 are not the same. The Ethernet is a product of XEROX which is practically the implementation of the IEEE 802.3 (apart from minor differences).
Wired LAN-s Dr. Beinschróth József: Telecommunication informatics I. 14 IEEE Ethernet 802.3
Token The Ethernet technology is widely used Passing
Ether: hypothetical medium is necessary for the propagation of electromagnetic waves.
The most common dominant LAN implementation (since 1970)
Reliable, cost-optimized, flexible, requires minimal maintenance.
Well suited to TCP/IP
Reasons for its popularity
• Compatible with different speed limits. • Open standards. • Simple and cheap to implement. • Good fit for data networks.
Wired LAN-s Dr. Beinschróth József: Telecommunication informatics I. 15 IEEE Ethernet Ethernet is continuously evolving 802.3 Token preserving compatibility with old versions Passing
Continuously evolving ,preserving compatibility with old versions.
Development began in the Xerox.
DIX Ethernet standard (Digital, Intel, Xerox): 10 Mbps.
Az IEEE 802.3 came from DIX Ethernet.
Versions (data transfer speeds):
• Classic Ethernet (10Mbps – 1980.; IEEE 802.3 – 1983.). • Fast Ethernet (100Mbps; IEEE 802.3u -1995.). • Gigabit Ethernet (1000Mbps; IEEE 802.3 ab, z – 1998.). • 10 Gigabit Ethernet (10Gbps – IEEE 802.3 ak, ae - 2004.). Ethernet SNAP (SubNetwork Access Protocol) – eliminate the shortcomings of 802.3 – compatible.
Wired LAN-s Dr. Beinschróth József: Telecommunication informatics I. 16 IEEE Ethernet 802.3
Token There are several Ethernet versions Passing Type Denomination Cable Max. length Junction/ Comment segment 10Base5 Thick coaxial 500m 100 Original Traditi- 10Base2 Thin coaxial 185m 30 onal 10BaseT Twisted pair 100m 1024 Cost optimal Ethernet 10BaseF Optical cable 2000m 1024 Between buildings 100BaseT4 Twisted pair 100m 100 Cat3 UTP Fast 100BaseTX Twisted pair 100m 100 Cat5 UTP Ethernet 100BaseFX Optical fiber 2000m 2000 Point-to-point
1000BaseSX Optical fiber 550m
Gigabit 1000BaseLX Optical fiber 5000m Ethernet 1000BaseCX 2 pair STP 25m 1000BaseT 4 pair UTP 100m Cat5 UTP 10 10GBaseCX4 Gigabit 10GBaseT Ethernet 10GBase-LRM
Wired LAN-s Dr. Beinschróth József: Telecommunication informatics I. 17 IEEE Ethernet 802.3
Token 10Base5: classic solution Passing
10Base5: The original Ethernet configuration (thick Ethernet (802.3)– cable diameter: 0,5”)
Wired LAN-s Dr. Beinschróth József: Telecommunication informatics I. 18 IEEE Ethernet 802.3
Token 10Base5: distance up to max. 500m Passing
• Thick Ethernet Name, standard • 10 Mbps, baseband transmission, max. 500 m • IEEE 802.3
• Bus Topology • The transceiver separate unit
• Coax, thick, rigid, 0,5”, close: 50 Ohm Cable, connector • „vampire” connector, 2,5 m per branch is not allowed
• Manchester Coding • Bit period: 100ns
Endpoints • Max. 100
• There are placing signs for the connectors Comment • Outdated solution
Wired LAN-s Dr. Beinschróth József: Telecommunication informatics I. 19 IEEE Ethernet 10Base5: computers connected to networks via 802.3 Token transceiver Passing
Wired LAN-s Dr. Beinschróth József: Telecommunication informatics I. 20 IEEE Ethernet 10Base2: computers connected to the network via 802.3 Token T connectors (1) Passing
Wired LAN-s Dr. Beinschróth József: Telecommunication informatics I. 21 IEEE Ethernet 10Base2: computers connected to the network via 802.3 Token T connectors (2) Passing
Wired LAN-s Dr. Beinschróth József: Telecommunication informatics I. 22 IEEE Ethernet 802.3
Token 10Base2: distance up to cc. 200m Passing
• Thin Ethernet Name, standard • 10 Mbps, baseband transmission, max. 185 m • IEEE 802.3a • Bus Topology • The transceiver unit is not a separate device: the interface card is included.
• Coax, thin 0,25”, close: 50 Ohm Cable, connector • Branch with T connectors
• Manchester Coding • Bit period:100ns
• Max. 30 Endpoints • Can’t connect new endpoint without interruption in operation.
• Easy to use, flexible cable, tear sensitive Comment • Outdated solution
Wired LAN-s Dr. Beinschróth József: Telecommunication informatics I. 23 IEEE Ethernet 802.3
Token 10Base2: cable system components Passing
Thin coaxial cable with Thin coaxial cable with BNC BNC Terminating BNC connector T connector element
Wired LAN-s Dr. Beinschróth József: Telecommunication informatics I. 24 IEEE Ethernet 802.3
Token 10BaseT: apparently a star topology Passing
UTP cables SWITCH/HUB (Implements a logical bus)
Wired LAN-s Dr. Beinschróth József: Telecommunication informatics I. 25 IEEE Ethernet 802.3
Token 10BaseT: Using UTP cable Passing • 10BaseT: 10 Mbps, baseband transmission, T=Twisted Name, standard • Max. 100m • IEEE 802.3i
• Star/Bus Topology • The transceiver unit is not a separate device: the interface card is included
• Cat3 UTP 4x2 pair patch cable (straight and cross Cable, connector link), wiring: TIA/EIA-T568A , illetve T568B • RJ-45 connector, used only 4 pair
• Manchester Coding • Bitperiod:100ns
• Max. 1024 Endpoints • In operation, the new endpoint can be connected without interruption
Comment • Outdated solution
Wired LAN-s Dr. Beinschróth József: Telecommunication informatics I. 26 IEEE Ethernet 10Base-T: The standard included the 802.3 Token connector wiring (1) Passing
RJ-45 wiring (TIA/EIA T568A)
Pin Pair Wire Color
1 3 1 white/green
2 3 2 green
3 2 1 white/orange
4 1 2 blue
5 1 1 white/blue
6 2 2 orange
7 4 1 white/brown
8 4 2 brown
Wired LAN-s Dr. Beinschróth József: Telecommunication informatics I. 27 IEEE Ethernet 10Base-T: The standard included the 802.3 Token connector wiring (2) Passing
RJ-45 wiring (TIA/EIA T568B)
Pin Pair Wire Color
1 2 1 white/orange
2 2 2 orange
3 3 1 white/green
4 1 2 blue
5 1 1 white/blue
6 3 2 green
7 4 1 white/brown
8 4 2 brown
Wired LAN-s Dr. Beinschróth József: Telecommunication informatics I. 28 IEEE Ethernet 10Base-T: the two types of wiring result 802.3 Token different function cable Passing
The 10Base-T hubs and the switches do the transmit on 1 and 2 pins, and do the receive in the 3 and 6 pins, the endpoints do this the other way around. Receive in 1 and 2 pins, transmit 3 and 6 pins.
It follows that when an endpoint must be connected to a hub, switch or patch panel, the straight cable, or the T568A wiring must be chosen.
If the two end point, or a hub / switch and another hub / switch connected to one another, it is the crosslink (crossover) cable, or the T568B wiring must be chosen.
Wired LAN-s Dr. Beinschróth József: Telecommunication informatics I. 29 IEEE Ethernet 802.3
Token 10BaseF: Ethernet optical fiber (802.3i) Passing
• 10 Mbps,baseband transmission, F=Fibre Name, standard • Max. 2000m • IEEE 802.3j
• Star Topology • The transceiver unit(optical processing unit) is not a separate device: the interface card is included
Cable, • Optical cable connector • Optical connectors
• NRZ, NRZI Coding • Bit period:100ns
Endpoints • Max. 1024
Comment • Typically used between buildings.
Wired LAN-s Dr. Beinschróth József: Telecommunication informatics I. 30 IEEE Ethernet 802.3
Token 10Base-F: Special optical connectors Passing
Wired LAN-s Dr. Beinschróth József: Telecommunication informatics I. 31 IEEE Ethernet 802.3
Token 100BaseTX: Fast Ethernet in 2 twisted-pair Passing • 100 Mbps, baseband transmission, T=Twisted, DupleX Name, standard • Max. 100m • IEEE 802.3u • Star/Bus Topology • The transceiver unit is not a separate device: the interface card is included
• Cat5 UTP Cable, connector • RJ-45 connector
• 4B5B Coding • Bit period: 10ns
• In operation, the new endpoint can be connected Endpoints without interruption
• Compared to the 10BaseT to the distinction of Comment being the tenth bit periods is reduced. • Duplex: pair in either direction
Wired LAN-s Dr. Beinschróth József: Telecommunication informatics I. 32 IEEE Ethernet 802.3
Token 100BaseTX: Using CAT5 UTP cable Passing
Wired LAN-s Dr. Beinschróth József: Telecommunication informatics I. 33 IEEE Ethernet 100BaseT2: Fast Ethernet in 4 twisted-pair 802.3 Token (dual-duplex transmission Passing
• 100 Mbps, baseband transmission, T=Twisted Name, standard • Max. 200m • IEEE 802.3y
• Star/Bus Topology • The transceiver unit is not a separate device: the interface card is included
• Cat3 UTP Cable, connector • RJ-45 connector
• PAM5: five-level pulse amplitude modulation – five-level signals Coding • DSP(Digital Signal Processing)application;Bitperiod: 10ns • Max. 1024 Endpoints • In operation, the new endpoint can be connected without interruption • Dual-duplex: each pair two-way traffic Comment • After the fast spread of 100Base-TX is, therefore were not marketed.
Wired LAN-s Dr. Beinschróth József: Telecommunication informatics I. 34 IEEE Ethernet 802.3
Token 100BaseT4: Fast Ethernet in 4 twisted-pair Passing
• 100 Mbps, baseband transmission, T=Twisted Name, standard • Max. 100m • IEEE 802.3u
• Star/Bus Topology • The transceiver unit is not a separate device: the interface card is included
• Cat3 UTP Cable, connector • RJ-45 connector • 4 twisted-pair
• 8B6T Coding • Bit period: 10ns
• Max. 100 Endpoints • In operation, the new endpoint can be connected without interruption
• Early version of the Fast Ethernet is widely used Comment • In both directions a dedicated pair, the other two are dynamically assigned to one direction
Wired LAN-s Dr. Beinschróth József: Telecommunication informatics I. 35 IEEE Ethernet 802.3
Token 100BaseFX: Fast Ethernet in optical fiber Passing
• 100 Mbps, baseband transmission, F=Fibre Name, standard • Max. 400m (half-duplex mode); 2000m (duplex) • IEEE 802.3u
• Star Topology • The transceiver unit is not a separate device: the interface card is included
Cable, • Optical cable connector • Optical connector
• 8B6T, NRZI Coding • Bit period: 10ns
• Max. 2000 Endpoints • In operation, the new endpoint can be connected without interruption
Comment • Not compatible with 10BaseF
Wired LAN-s Dr. Beinschróth József: Telecommunication informatics I. 36 IEEE Ethernet 802.3
Token 100Base-FX: Based on optical cable Passing
Wired LAN-s Dr. Beinschróth József: Telecommunication informatics I. 37 IEEE Ethernet 1000Base-CX: Gigabit Ethernet 802.3 Token twisted-pair (STP) Passing • 1 Gbps, baseband transmission, CX=Shielded Balanced Copper Name, standard • Max. 25m • IEEE 802.3z
Topology • Star
• 2 pair STP Cable, connector • DE9 vagy 8P8C (8Position8Contact, similar to RJ45)
• 8B10B Coding • Bit period: 1ns
Endpoints • n.a.
Comment • Because of 25m practical applicability is limited
Wired LAN-s Dr. Beinschróth József: Telecommunication informatics I. 38 IEEE Ethernet 802.3
Token 1000Base-CX: Special connectors Passing
DE9
8P8C
Wired LAN-s Dr. Beinschróth József: Telecommunication informatics I. 39 IEEE Ethernet 802.3
Token 1000BaseLX: Gigabit Ethernet optical fiber Passing • 1 Gbps, baseband transmission, LX=Long wavelength optical Name, standard • Max. 550m-5km (depending on the cables used) • IEEE 802.3z
Topology • Star
• Optical cable Cable, connector • Optical connector
• 8B10B Coding • Bit period: 1ns
Endpoints • Usually used in backbone applications
• There are several versions, pl. a 1000BaseLX10 – 10km Comment • 1270-1355 nm wavelength
Wired LAN-s Dr. Beinschróth József: Telecommunication informatics I. 40 IEEE Ethernet 802.3
Token 1000BaseSX: Gigabit Ethernet optical fiber Passing
• 1 Gbps, baseband transmission, SX=Short wavelength optical Name, standard • Max. 220m-550m (depending on the cables used) • IEEE 802.3z
Topology • Star
• Optical cable Cable, connector • Optical connector
• 8B10B Coding • Bit period: 1ns
Endpoints • Usually used in backbone applications
• There are several versions, pl. a 1000BaseLX10 – 10km Comment • 770-860nm wavelength
Wired LAN-s Dr. Beinschróth József: Telecommunication informatics I. 41 IEEE Ethernet 1000BaseT: Gigabit Ethernet 802.3 Token twisted-pair (UTP) Passing • 1 Gbps, baseband transmission, T=Twisted Name, standard • Max. 100m • IEEE 802.3ab
Topology • Star
•4 pair UTP Cable, connector •Cat5
• PAM5: five-level pulse amplitude modulation – 5 level signals Coding • DSP (Digital Signal Processing) application • Bit period: 1ns
Endpoints • n.a.
• Using Hybrid circuits each pair two-way traffic Comment • 1000Base-TX version: CAT6 cable
Wired LAN-s Dr. Beinschróth József: Telecommunication informatics I. 42 IEEE Ethernet 1000BaseT: Gigabit Ethernet 802.3 Token twisted-pair (UTP) Passing • 1 Gbps, baseband transmission, T=Twisted Name, standard • Max. 100m • IEEE 802.3ab
Topology • Star
•4 pair UTP Cable, connector •Cat5
• PAM5: five-level pulse amplitude modulation - 5 level signals Coding • DSP (Digital Signal Processing) application • Bit period: 1ns
Endpoints • n.a.
• Using Hybrid circuits each pair two-way traffic Comment • 1000Base-TX version: CAT6 cable
Wired LAN-s Dr. Beinschróth József: Telecommunication informatics I. 43 IEEE Ethernet 10Gigabit Ethernet: Extension of Ethernet technology 802.3 Token for WAN Passing
802.3ae
Distance: More than 10km (depending on version, even 80km) available
Typically optical cable (850, 1310, ill. 1550nm wavelength)
Duplex, no need for CSMA/CD
Coding:8B10B or 64B/66B
Versions • 10GBaseSR (65m) • 10GBaseSW (65m) • 10GBaseLR (10000m) • 10GBaseLW (10000m) • 10GBaseER (40000m ill. 80000m) • 10GBaseEW (40000m ill. 80000m) • 10GBaseLX4 (300m ill. 10000m)
Wired LAN-s Dr. Beinschróth József: Telecommunication informatics I. 44 IEEE Ethernet 802.3
Token 10Broad36: broadband Ethernet Passing
Broad: broadband
802.3b
Used to transmit cable television signals. 75 ohm CATV cable to distance of 3600m signals can be transmitted.
Not widespread in practice
Outdated
Wired LAN-s Dr. Beinschróth József: Telecommunication informatics I. 45 IEEE Ethernet The Ethernet frame format is practically the same 802.3 Token for all version (1) Passing
Ethernet frame format - MAC layer
Destination Source Frame Check Preamble Type Data 46-1500 Address Address Sequence 8 byte 2 byte byte 6 byte 6 byte 4 byte
The time frame decrease in each versions for tenth
Wired LAN-s Dr. Beinschróth József: Telecommunication informatics I. 46 IEEE Ethernet The Ethernet frame format is practically the same 802.3 Token for all version (2) Passing
Field Report Preamble Ethernet: 10101010 … 10101011 (64 bit) Source/Destination Address 6 byte address Type Coding the embedded protocol type Data 46-1500 byte, the MAC frame SDU, the 46 a minimum, necessary for the minimum frame size Frame Check Sum (FCS): Serve for error detection
Similar to the Ethernet SNAP frame format
Wired LAN-s Dr. Beinschróth József: Telecommunication informatics I. 47 IEEE Ethernet The Ethernet frame format is practically the same 802.3 Token for all version (3) Passing
Manufacturers Identifiers
3Com 02-60-8C
Cabletron 00-00-1D
NEC 00-00-4C
NeXT 00-00-0F
Novell 00-00-1B
Western Digital 00-00-C0
Xerox 00-00-AA
Xircom 00-80-C7
Wired LAN-s Dr. Beinschróth József: Telecommunication informatics I. 48 IEEE Ethernet The IEEE 802.3 frame format is almost completely 802.3 Token same as the Ethernet frame format (1) Passing
IEEE 802.3 frame format - MAC layer
IEEE 802.3 keretformátum
Start of Destinati- Data Check Preamble Frame on Address Length 46-1500 Sequence 7 byte Delimiter address 2/6 byte 2 byte byte 4 byte 1 byte 2/6 byte
The time frame decrease in each versions for tenth
Wired LAN-s Dr. Beinschróth József: Telecommunication informatics I. 49 IEEE Ethernet The IEEE 802.3 frame format is almost completely 802.3 Token same as the Ethernet frame format (2) Passing
2 byte Address field 6 byte Address field (Ethernet and IEEE 802.3)
I/G* Address Address I/G* 1 bit U/L 1 bit 1 bit 15 bit 46 bit
I/G: I/G bit: U/L bit: Individual/Group 0 individual 0 unified addressing scheme U/L: Uniform/Local address 1 local (individual) addressing 1 group address scheme
Wired LAN-s Dr. Beinschróth József: Telecommunication informatics I. 50 IEEE Ethernet The IEEE 802.3 frame format is almost completely 802.3 Token same as the Ethernet frame format (3) Passing
Field Report Preamble 10101010 … 10101010 (56 bit)
Start of Frame Delimiter: 802.3: 10101011
Source/Destination Address 6-byte addresses and U / L = 0, the remaining 46 bits to 24 bits (3 bytes) identifies the manufacturer, the remaining 22 bits are distinguished by the manufacturer of the individual cards. Length (802.3): The Data field length in bytes (up to 1500) The embedded protocol (the codes are always greater than 1500)
Data: 46-1500 bytes, the MAC frame SDU,46 is the minimum, this needed for the minimum frame layer
Frame Check Sum (FCS): Serve for error detection
Wired LAN-s Dr. Beinschróth József: Telecommunication informatics I. 51 IEEE Ethernet The Ethernet frame can carry different 802.3 Token embedded protocols Passing
Embedded protocol Hex code X.75 08-01 Address Resolution Protocol 08-06 AppleTalk 80-9B AppleTalk ARM 80-F3 DEC LAT 60-04 IBM SNA 80-DC IP 08-00 Netware IPX/SPX 81-37 SNMP 81-4C X.25 Layer 3 08-05
In case of type interpretation (Ethernet) protocol codes than 1500 (Hex 05-DC) is always greater.
Wired LAN-s Dr. Beinschróth József: Telecommunication informatics I. 52 IEEE Ethernet The common media may report a safety 802.3 Token problem in Ethernet Passing
During transmission of data in all common transmission media connected to the Ethernet device can read the contents of the frame currently being sent, but only after the destination address of an asset will carry on receiving the frame whose address matches the marked.
The only exception is the so-called broadcast address consisting of the 1.which in case of detection the package must be accepted. (The broadcast address is used for all network- connected devices simultaneously "reach out").
Most of today’s used cards know the promiscuous transmission mode, when not only for, but also all the other host receives the packet and forward it to the upper layers.
This opportunity may create a serious safety gap on the network, since with this utilization any of the devices attached to the common medium are immediately capable to intercept any communication between two other devices.
Wired LAN-s Dr. Beinschróth József: Telecommunication informatics I. 53 IEEE Ethernet 802.3
Token There are several types of Ethernet line coding Passing
Traditional • Manchester coding Ethernet • +0,85V, -0,85V
• 8B/6T, 4B/5B redundant codings, depending on Fast used cables • 8B/6T: 8 bit mapped 6 piece 3 signal-level coded signal, 3 data cable), 4B/5B: 5 bit groups, but only Ethernet used 16 bit combination
Gigabit • 8B/10B in case of optical fiber Ethernet • When using copper five-level signals
Wired LAN-s Dr. Beinschróth József: Telecommunication informatics I. 54 IEEE Ethernet 802.3
Token Using special codes Passing
The Fast Ethernet MAC frame format is the same as the 10Mbps Ethernet frame format with the addition of SSD is added to the beginning of the 4bit symbols will frame and the ESD be 5 bit field is added to the symbols. end of the frame.
• Start of Stream Delimiter (SSD): J and K symbols from 4B/5B coded signals • End of Stream Delimiter (ESD): T and R symbols from 4B/5B coded signals
Wired LAN-s Dr. Beinschróth József: Telecommunication informatics I. 55 IEEE Ethernet 802.3
Token The Ethernet topology may be bus, star or mixed Passing
Wired LAN-s Dr. Beinschróth József: Telecommunication informatics I. 56 IEEE Ethernet 802.3
Token What does the oscilloscope show? Passing
Wired LAN-s Dr. Beinschróth József: Telecommunication informatics I. 57 IEEE Ethernet The development of Ethernet standards 802.3 Token is continuous (1) Passing
Standard Introduction Description
Experimental 1972-1978 2.94Mb/s coaxial cable with bus topology. patent Ethernet II 1982 10Mb/s over thick coaxial. Defined type field. The frame format can be (DIX v2.0) used in TCP/IP protocol family all over the medium IEEE 802.3 1983 10BASE5 10Mb/s over thick coaxial; This format is similar to DIX format except that uses length field instead of type field. LLC field performs protocol identification in the data field. 802.3a 1985 10BASE2 10Mb/s over thin coax. 802.3b 1985 10BROAD36. 802.3c 1985 10Mbps repeater. 802.3d 1987 FOIRL (Fiber-Optic between repeater connections). 802.3e 1987 1BASE5 or StarLAN. 802.3i 1990 10BASE-T 10Mb/s over twisted-pair. 802.3j 1993 10BASE-F 10Mbps over fiber. 802.3u 1995 100BASE-TX, 100BASE-T4,and 100BASE-FX Fast Ethernet: 100Mb/s (automatic appointment).
Wired LAN-s Dr. Beinschróth József: Telecommunication informatics I. 58 IEEE Ethernet The development of Ethernet standards 802.3 Token is continuous (2) Passing Standard Introduction Description 802.3x 1997 Full-duplex and process control; DIX framing. It is no longer needed to distinguish the DIX/802.3 framing. 802.3y 1998 100BASE-T2 100Mb/s low reliability over twisted pair. 802.3z 1998 1000BASE-X Gigabit Ethernet over fiber (1Gb/s). 802.3-1998 1998 The basic standard revision to correct the previous errors. 802.3ac 1998 The maximum frame size to 1522 bytes (labeling for A Q). A Q label contains the 802.1Q virtual LAN (VLAN) informations and the 802.1p priority information. 802.3ab 1999 1000BASE-T Gigabit Ethernet over twisted pair (1Gbps). 802.3ad 2000 Parallel connection – connection aggregation. 802.3-2002 2002 Checking the basic standards and change the necessary implementation. 802.3ae 2003 10GBASE-SR, 10GBASE-LR, 10GBASE-ER, 10GBASE-SW, 10GBASE-LW, and 10GBASE-EW 10Gb/s Ethernet over fiber. 802.3af 2003 Power over Ethernet (Ethernet 230-as over network).
802.3ah 2004 Ethernet in the first mile 802.3ak 2004 10GBASE-CX4 10Gbps Ethernet twin axial cable (twinax cable). 802.3-2005 2005 Change the basic standard.
Wired LAN-s Dr. Beinschróth József: Telecommunication informatics I. 59 IEEE Ethernet The development of Ethernet standards 802.3 Token is continuous (3) Passing
Standard Introduction Description
802.3an 10GBASE-T 10Gbps Ethernet over unshielded twisted-pair cable (UTP). 802.3ap Backplane Ethernet (1Gb/s and 10Gb/s over printed circuit board).
802.3aq 10GBASE-LRM 10Gbps Ethernet over multimode cable. 802.3ar Congestion control. 802.3as Frame extension.
Videotorium Wired LAN-s Dr. Beinschróth József: Telecommunication informatics I. 60 IEEE Ethernet 802.3
Token Token Passing Passing
•Token: certainty, token, signal.. •Token Passing: One signal (token – messaging law) moves along the ring from station to station •The token has two stages, free and busy. •If a station receives busy token, it will receive a message and decides to speak with it if yes it will read and forward, if not only forward. •If a station has a message and receive a free token, sets the token to Recommendation: busy then puts the message to the ring together with (up to several frames IEEE 802.5 within a specified timeout interval) if there is no message, itt forwards the (802.4) free state token. •The station can hold the token for no more than the token holding time, during this could send multiple frames. •Get out the message from the ring then set the token to free and forward. •Within a certain period each station will have an opportunity to send a message. •4, 16, 100, 1000Mbps speeds •The Token passing is less widespreadly used than Ethernet.
Wired LAN-s Dr. Beinschróth József: Telecommunication informatics I. 61 IEEE Ethernet 802.3
Token Logical topology: ring Passing
In case of physical and logical ring topology: Token Ring
In case of physical bus and logical ring: Token Bus, but often also used Token Ring name
Wired LAN-s Dr. Beinschróth József: Telecommunication informatics I. 62 IEEE Ethernet 802.3
Token The exceptions of treatment is complicated Passing
The token processing and monitoring is difficult There are several exceptions to handle
• Recovery – new ring • Station exit/entry • Race condition unlock several stations simultaneously ring entry • Ring broken • Lost token • Orphaned frame • … Solution: To solve the above things is the task of the monitor station. If the monitor station fails, the stations choose a new monitor. The monitor station examines the frame formats, CRC etc..
Wired LAN-s Dr. Beinschróth József: Telecommunication informatics I. 63 IEEE Ethernet 802.3
Token Based on physical ring Token Passing: Token Ring Passing
• Physical ring. Each station receives and regenerates the binary sequence – each Topology station is a repeater.
• Coax (75 Ohm), 1 or 2 cable (in each direction) versions. Physical • Differential Manchester coding (+/- 3,5-4,5V) • Physical layer violation: Applied fouls (physical layer layer coding fouls) in the Differential Manchester coding. (J and K types)
Wired LAN-s Dr. Beinschróth József: Telecommunication informatics I. 64 IEEE Ethernet 802.3
Token The J and K symbols performing the frame limitation Passing
J K
J K
The J and K symbols non-standard Differential Manchester codes, use them to the frame sync. (Starting Delimiter, Ending Delimiter)
A variation of this framing: the physical layer fouls, so called the symbols J and K.
Wired LAN-s Dr. Beinschróth József: Telecommunication informatics I. 65 IEEE Ethernet 802.3
Token The ring initialization Passing
When turn on the first station, it notices there is no traffic
Sends Claim token frame. (claim)
Because not noticing other competing token partner, it creates a token and a ring which will be a member of this station
In systematic intervals ask offer entry to new stations
Wired LAN-s Dr. Beinschróth József: Telecommunication informatics I. 66 IEEE Ethernet 802.3
Token The token frame Passing
Many frames are possible. Token frame (if no traffic, this orbit in the ring)
Starting delimiter (8bit) Access Control (8bit) Ending delimiter (8bit)
P P P T M R R R
Wired LAN-s Dr. Beinschróth József: Telecommunication informatics I. 67 IEEE Ethernet 802.3
Token The fields of the token frame (1) Passing
• Determination of the Differential Manchester encoding is in breach of the Starting rules Delimiter • Starting Delimiter coding: JK0JK000
• Determination of the Differential Manchester encoding is in breach of the rules • Ending Delimiter coding: JK1JK1IE • I bit meaning: Intermediate Frame Bit (I): Ending • 0 last frame; Delimiter • 1 intermediate frame • E bit meaning: Error Bit (E): • The transmitter starts the frame with E=0 • All stations in the ring check the frame (format, CRC, etc.) if an error detected sets E=1
Wired LAN-s Dr. Beinschróth József: Telecommunication informatics I. 68 IEEE Ethernet 802.3
Token The fields of the token frame(2) Passing
Access Control (Here we can see for example if the token is free,busy or transmitting):
T: • 0: Token frame; 1: Data frame (All the frames begin Token with the same sequence.) bit
• (Each ring has a monitor station. It handles the token M: loss, broken ring, defective frames etc.) Monitor • The frame sending station starts with M=0 when it arrives to the station, it sets to M=1 (If for example the bit monitor station arrived with M=1 the frame deletes it)
Wired LAN-s Dr. Beinschróth József: Telecommunication informatics I. 69 IEEE Ethernet 802.3
Token The fields of the token frame (3) Passing
Access Control (Here we can see for example if the token is free,busy or transmitting.):
• If a station wants to send a P-priority frame, you will have to wait until a frame is given to less than or equal to p. • Frame allocation: the station set to what priority frame it want to send • There are priority classes. A station at its discretion, determine the P:Priority priorities on the basis of their status(real time applications) management • PPP: Priority field • 0,1,2,3 : Normal user priorities • 4: Bridge • 5,6: Reserved Station management
• RRR: Reservation – token reservation RRR: • The station sets the current priority value to the RRR field for reserving Reservation the token. If there is no higher priority request it receives the token. (Even if there are lower priority claimants.)
Wired LAN-s Dr. Beinschróth József: Telecommunication informatics I. 70 LAN archtectures IEEE Ethernet 802.3
Token The data frame Passing
Infor- Starting Access Frame Destination Source mation Ending Frame CRC Delimiter Control Control Address Address (variable, Delimiter Status (32bit) (8bit) (8bit) (8bit) (48bit) (48bit) no upper (8bit) (8bit) limit)
P P P T M R R R
Wired LAN-s Dr. Beinschróth József: Telecommunication informatics I. 71 IEEE Ethernet 802.3
Token The data frame fields (1) Passing
Frame Control field (FFZZZZZZ bits) • FF bits: • 00: MAC frame; 01: LLC frame • ZZZZZZ bits: In the case of FF=00 the normal data and the different token functions. Coding the frames in the case of FF=00 the normal data or a variety of control function. Example: • Initialization • Station sign out/login • Etc. Frame Status field (at the end of the frame): • Format: ACrrACrr (The 4-4 bit used the same content) • Informs the sending host from the status of the frame after the frame take on rotation in the ring. • rr : Reserved • A: Address Recognized Bit: Address recognition is done • C: Frame Copied bit: the receiver has the frame • A=0, C=0: The destination does not exist or not activated. • A=1, C=0: The destination exits but did not accept the frame. • A=1, C=1: The destination exits and received the frame.
Wired LAN-s Dr. Beinschróth József: Telecommunication informatics I. 72 IEEE Ethernet 802.3
Token The data frame fields (2) Passing
Information • Info field length: • In case of 4Mbps implementation max. 4,5kbyte; • In case of 16Mbps implementation max. 18kbyte Source/Destination Address: 6 byte
CRC
There are other frames, for example: abort token frame (the token is lost)
Wired LAN-s Dr. Beinschróth József: Telecommunication informatics I. 73 IEEE Ethernet What is the length of a bit in the ring? How does the 802.3 Token ring and the frame length compare to each other? Passing
For example: 16mbps, 2000m
1 bit duration: 1/16X(10exp6)=0,0625us
1 frame minimum time: tmin=10,5us (min. 21 byte*8bit – data frame – if the info field is 0 length)
Arriving time of the sign: 2000/2X(10exp8)=10exp(-5) (s) =10us
The smallest data frame as long as the ring (There are longer frames)
About 160 bit fit on the ring!
Wired LAN-s Dr. Beinschróth József: Telecommunication informatics I. 74 There are several types of wireless network
System networks (system interconnection), body surface networks
• Connects each parts of the computer, for example: Bluetooth mouse, keyboard, substitue printer cables, master- slave layout
Wireless local area networks (wireless LANs, WLAN),
• Antennas in machines, which are in contact with the access point, replaced wired LANs, IEEE 802.11
Wireless WANs, low speed networks
• Radio network for mobile network • 1. generation: analog, audio only • 2. generation: digital, audio only; • 2.5 generation, able to transfer data, but only in audio • 3. generation: able to transmit voice and data High speed network: IEEE 802.16 local multipoint distribution service,high speed network Internet access, which bypasses the telephone system
(Mostly all of the wireless networks are connected to a wired network somewhere)
Wirless LAN-s Dr. Beinschróth József: Telecommunication informatics I. 75 What are the general characteristics of WLANs? (1)
Portable devices: demand for wireless and mobile connections (dynamic, easily scalable, cheap, quickly implement, infrastructure for movement).
Standard, anywhere easily accessible wireless computer network system.
Wireless connectivity to LAN : WLAN (Wireless LAN).
Interoperable implementation for wired LAN.
(The WLAN should have wired parts, typically integrated to wired networks)
The connection electromagnetic might infrared: The transmission is through electromagnetic or infrared waves in the physical medium.
Distances: outdoors cc. 300m, within the building cc. 30 m.
Wirless LAN-s Dr. Beinschróth József: Telecommunication informatics I. 76 What are the general characteristics of WLANs? (2)
Can be used while moving (v<8km/h)
Public access connection options: Hot Spots
Implemented in unlicensed frequency. (Free to use everywhere in the world, which creates an extraordinary opportunity, standard and anywhere easily accessible wireless computer networking system. However, unregulated.) (100mW- 1W)
• 2.4 GHz band - ISM (Industrial, Scintific and Medical ), industrial, scientific and medical application 2,4-2.4835GHz, 14 pre-assigned carrier. (Different by geographical regions.) (cc. 80MHz) • 5 GHz band – UNII (Unlicenced National Information Infrastructure). 5.150- 5.250GHz, 12 pre-assigned carrier. (Different by geographical regions.) (cc. 100MHz)
Wirless LAN-s Dr. Beinschróth József: Telecommunication informatics I. 77 The main problems of WLANs
• The wireless connection is defenseless against external signals, noisy and unreliable. The medium is characterized by a much less reliable than in the case of guided wave connection, time dependent, asymmetric propagation properties. Problems (other systems, microwave oven, Bluetooth) • The wireless networks can interfere with each other. • Security problem: illegal connection, can be listened – „The wireless network does not end at the entrance of the company!”
Wirless LAN-s Dr. Beinschróth József: Telecommunication informatics I. 78 Example
Wirless LAN-s Dr. Beinschróth József: Telecommunication informatics I. 79 WLANs commonly used (1)
Searching WLAN
Wirless LAN-s Dr. Beinschróth József: Telecommunication informatics I. 80 WLANs commonly used (2)
Wirless LAN-s Dr. Beinschróth József: Telecommunication informatics I. 81 WLANs have many features (1)
Wirless LAN-s Dr. Beinschróth József: Telecommunication informatics I. 82 WLANs have many features (2)
Wirless LAN-s Dr. Beinschróth József: Telecommunication informatics I. 83 WLANs are cell structured (1)
Base station Connection to wired network
Wireless network based on base station Ad hoc network
Wirless LAN-s Dr. Beinschróth József: Telecommunication informatics I. 84 WLANs are cell structured (2)
Connection to wired network
Some elements of WLANs are forming confusing signals to each other , thus increasing the noise on the channel
Wirless LAN-s Dr. Beinschróth József: Telecommunication informatics I. 85 WLANs are cell structured (3)
Cell structured like the GSM.
Each cells are BSS (Basic Service Set) .
The BSS consits of a set of ESS-t (Extended Service Set).
The communication between the BSS is done via DS (Distribution System) (DS: for example Ethernet LAN).
Simplex (half duplex) connections
BSS versions
• Peer-to-peer stations mesh network (ad-hoc network, IBSS – Independent BSS, ad-hoc mode.) • Star topology, where the stations transmission is made by a distinguished co-operation station (infrastructure mode). The control station is an AP (Access Point).
Wirless LAN-s Dr. Beinschróth József: Telecommunication informatics I. 86 The WLAN standards in the OSI network architecture cover the first two layers
OSI LAN WLAN
LLC Logical link control 802.2
Data Link layer MAC (Media CSMA/CA versions (DCF) or polling procedures(PCF) Access Control) (decision from the channel allocation)
Physical layer Physical layer 802.11 802.11 802.11 802.11a 802.11b 802.11g Infra FHSS DSSS OFDM HR- OFDM DSSS
Wirless LAN-s Dr. Beinschróth József: Telecommunication informatics I. 87 Example: IEEE 802.11 architecture
Physical Media Dependent (PMD) sublayer: Physical Layer Convergence Procedure Includes the specific characteristics of the (PLCP) sublayer: electromagnetic signal transmission. The physical layer and MAC nested frames, segmentation.
LLC sublayer
MAC sublayer
Physical sublayer
Each layers data units Layers
Wirless LAN-s Dr. Beinschróth József: Telecommunication informatics I. 88 There are many standards for WLANs (1)
Standard Year of Carrier Speed Transfer Transmi Comment publi- (GHZ) (Mbps) process ssion cation distance (m)
IEEE 1997 2,4 1 or 2 Infra, 300 Common name WiFi – Wireless 802.11 FHSS, Fidelity –basic version DSSS IEEE 1999 5 54 OFDM 200 The advantage of the higher 802.11a bandwidth, but typically only used for point-to-point connections and the tools used for this are usually more expensive. Especially important is the optical line of sight between the two points. IEEE 1999 2,4 5,5 or HR- 100 The operational range varies widely, 802.11b 11 DSSS depending on the terrain, the case is significantly smaller than 802.11a. Point-to-multipoint connections within 1km radius circle custom design.
Wirless LAN-s Dr. Beinschróth József: Telecommunication informatics I. 89 There are many standards for WLANs (2)
Standard Year of Carrier Speed Transfer Transmi Comment publi- (GHZ) (Mbps) process ssion cation distance (m)
IEEE 2003 2,4 54 OFDM 200 Same as 802.11b, most routers 802.11g support both. Its benefit is more bandwith, disadvantage is that with the distance growth the efficiency significantly deteriorates, and it is sensitive to interference.
IEEE 2009 2,4 or Max OFDM 300 Using 4 p 40 MHz speed channel (4 802.11n 5 150/ antenna) ,max. 600mbps data chann transfer rate can be achieved. el Multiple input/output (MIMO)
Wirless LAN-s Dr. Beinschróth József: Telecommunication informatics I. 90 There are many standards for WLANs (3)
Standard Year of Carrier Speed Transfer Transmission Comment publi- (GHZ) (Mbps) process distance (m) cation
IEEE 2008 3,7 54 OFDM 50 Higher transmit performance. 802.11y 5000 m outdoors range. Used in the U.S.
Home RF 1998 2,4 1,6 FHSS 130 Wifi competing solution, but the professional organization disbanded (2003).
Home 2,4 10 FHSS 15 RF+
Bluetooth 1998 2,4 1 FHSS 1-9 http://www.bluetooth.com/Blueto oth/SIG/ Hyper 2003 5 54 OFDM 100 ETSI. WIFI competing solution. LAN/2
Wirless LAN-s Dr. Beinschróth József: Telecommunication informatics I. 91 Transmission method exists as infrared (IR) transmission, but not widespread
Using infrared light to transfer
Direct line of sight is required for the IR transmission.
The infrared signal does not pass through the objects (example: walls)
The infrared signal is sensitive to sunlight
Applied wavelength: 0,85, 0, 95 µ.
Baseband signal transmission
The method is commonly used (remote control, cordless telephone etc.)
In case of 1Mbps • 4 bits per 16 bit codewords are formed (1 out of the n, Gray code) In case of 2Mbps • 2 bits per 4 bit codewords are formed (1 out of the n, Gray code)
Wirless LAN-s Dr. Beinschróth József: Telecommunication informatics I. 92 IrDA: The use of infrared light
IrDA (Infrared Data Association)
(Option of IEEE 802.11, but significantly reduced.)
Used for short range data transmission (computer-printer, cell phone-computer).
Simple, cheap, long time ago used in remote controls
Range max. 1m.
Transfer rate: max. 16Mbps. Does not pass through solid objects– can be used only in local premises, optic angle about 30°. Monitoring is problematic.
It does not require frequency licenses.
Not widespread
Wirless LAN-s Dr. Beinschróth József: Telecommunication informatics I. 93 Most of the procedures used in WLAN are based on spread spectrum method (1)
The Spread Spectrum Radio communications (such as broadband RF transmission method), were originally intended for military applications of high reliability, secure communication systems.
Uses specific coding for transmitting signals and uses a much wider frequency band than the normal transmission procedures.
The useful signal hardly stands out from the background noise, difficult to discover
Knowing the coding pattern the useful signal can be recovered safely.
It is important to choose highly redundant encoding method, the coded signal is noise-like.
In practice, two solutions are widespread
• FHSS (Frequency Hopping Spread Spectrum) • DSSS (Direct Sequence Spread Spectrum).
Wirless LAN-s Dr. Beinschróth József: Telecommunication informatics I. 94 Most of the procedures used in WLAN are based on spread spectrum method (2)
The frequency hopping (Frequency-Hopping Spread Spectrum - FHSS) is a type of spectrum extension procedures in radio technology.
The broadcast spectrum extension methods the transmission of information by the Shannon formula specified minimum required bandwidth is much higher frequency, but it is not useless while it decreases the load per unit frequency band.
This direct sequential transmission mode in the frequency band per unit decrease in power level is manifested,the jump frequency and duration of each specific transmission frequency band is reduced drastically.
The primary frequency jump sequence in frequency domain is called broadcast sequence.
The frequency hopping radio’s "soul" is a sequence generator, which is better when the longer code repetition between the time.
Among the modern conditions this time has a measurable million years, that is mathematically proven to be said after "infinite" long-term observation does not know where will be the next sign.
Wirless LAN-s Dr. Beinschróth József: Telecommunication informatics I. 95 Example: Jump between channels
Data series for transmission
2 0 1 0 1 0 2 5 d u
1.ch. f 2 h 1 a a 2 n 1 g 2.ch. 2 4 j r u a j z 3 j 3.ch. 4 a h g 1 b l 5 6 3 4.ch. g n 1 n d f c c o 6 5.ch. f 0 n m f i f v j n 6.ch. 5 l h d h 0 c b w i 7.ch. h i 7 v r n h j d 5 8.ch. t b q 0 o n o f v h 9.ch. v r s b d n 1 5 x 9 10.ch. n i l d 5 i 9 g 3 u
Code:25483619710 – the sequence of jumps
Wirless LAN-s Dr. Beinschróth József: Telecommunication informatics I. 96 Transfer procedures
FHSS DSSS
OFDM
Wirless LAN-s Dr. Beinschróth József: Telecommunication informatics I. 97 FHSS DSSS FHSS transfer process (1) OFDM
Submit a frequency by a pseudo-random generator then continued on a different frequency to the next stage.
If the receiver is provided with the same parameter pseudo-random generator then the receiver will switch to the same frequency, so the receiver intermediate frequency part will "see" a continuous spectrum.
It can be seen that the average energy per unit frequency due to the constant migration also in this case may be a value below the noise level.
Shares the used frequency for 79 pcs 1 MHz bandwith channels.
The carrier "bounces" from one channel to a pseudo-random sequence.
A jump during a period, the signal can be interpreted as a narrow band signal.
Wirless LAN-s Dr. Beinschróth József: Telecommunication informatics I. 98 FHSS DSSS FHSS transfer process (2) OFDM
The spent time in each channel (dwell time) is fixed, bounded (max 400ms).
The transmitter and receiver are using the same pseudo random generation procedure and using the same initial value, so they stay in sync with each other.
Feasible, two or more networks operating with FHSS using the same channel, in such a way that the frequency hopping rate and sequence is not synchronized.
The FHSS provides reasonable spectrum utilization in the unregulated ISM band.
Security: The transmission interception is problematic.
Not very sensitive to the radio interference (path difference), so it can be used between buildings.
Wirless LAN-s Dr. Beinschróth József: Telecommunication informatics I. 99 FHSS DSSS DSSS transfer process(1) OFDM DSSS - Direct Sequence Spread Spectrum
The spread spectrum signal is not generated with frequency hopping but also generated with spreading the modulation signal (data to be transferred). A bit is simultaneously transmitted in multiple channels. All bits we want to transfer are replaced with a redundant bit pattern (chips). The bits in each bit pattern are transmitted at different frequencies. The longer this bit pattern is, the greater probability we have to restore the original signal, despite of transmission distortion. (The chips are much shorter than bits.)
The data scattering is a code of 11 chip, with this chip code the data bits are to be sent each contacting the 11 bit chip code to a XOR.
The chip code is a pseudo random sequence which ensures that the resulting signal is as smooth as possible.
The chip bits are transmitted at different frequencies (channels). Data rate concerning chips of the original data rate are much higher.
Wirless LAN-s Dr. Beinschróth József: Telecommunication informatics I. 100 FHSS DSSS DSSS transfer process (2) OFDM
The receiver knows the chip code
Modulation: PM
Interception is problematic: The DSSS signal is a broadband low power noise for an unauthorized monitor.
Problem:
• Low bandwidth(1 or 2 Mbps)
Wirless LAN-s Dr. Beinschróth József: Telecommunication informatics I. 101 FHSS DSSS The implementation of the DSSS encoding OFDM
Wirless LAN-s Dr. Beinschróth József: Telecommunication informatics I. 102 FHSS DSSS Example for DSSS transmission method OFDM
Let the transmitted data be 9. (Binary: 1001)
The binary code of 1: 11001100100 - 11 channels required
The binary code of 0: 00110011011 - 11 channels required
The transmitted code: 11001100100 00110011011 00110011011 11001100100
1 11.ch 0 11.ch 0 11.ch 1 1.ch 1.ch 1.ch 1.ch 11.ch
Wirless LAN-s Dr. Beinschróth József: Telecommunication informatics I. 103 FHSS DSSS DSSS spectrum OFDM
Channel carrier
Channels
Wirless LAN-s Dr. Beinschróth József: Telecommunication informatics I. 104 DSSS spectrum: wider than the original FHSS DSSS signal spectrum OFDM Original signal’s spectrum Eredeti, withoutDSSS eljárásDSSS nélküli jel Power
The figure demonstrates the Shannon thesis very well
Noise level DSSS spectrum
Frequency Same performance – are under the curve
Wirless LAN-s Dr. Beinschróth József: Telecommunication informatics I. 105 The transmitter and receiver use the same chip FHSS DSSS code OFDM
Much faster than the stream (e.g. 11) obtained with pseudo random generator code XORed the binary data stream and this "noise" will be transferred to the channel.
On the receiver side the same pseudo-random generator parameters back XORed received the "noise" we get the bitstream.
Meanwhile, the RF signal energy in this case became a 11 times larger smeared spectrum.
Wirless LAN-s Dr. Beinschróth József: Telecommunication informatics I. 106 FHSS DSSS HR-DSSS process OFDM
HR-DSSS (High Rate - Direct Sequence Spread Spectrum – high-speed direct sequence spread spectrum
Compatible with DSSS
The further development of DSSS to higher data rates (11Mbps). )
11 million chip/s
Supports several data transmission rate, the data transmission rate can be changed dynamically in progress (based on the current load and noise quality).
Wirless LAN-s Dr. Beinschróth József: Telecommunication informatics I. 107 The OFDM process (1)
OFDM (Orthogonal Frequency Division Multiplexing )
Motif: A high-speed data stream can be divided into several smaller streams. These unique subcarrier modulation, independent of the others, and at the same. (parallel transmission)
In each channels the bit periods are increased from the original, the data rate is reduced, so the transfer is more resistant to the radio interference and other noise.
Divided and transferred the signal in more narrow frequency band (sub carriers apart from 300 KHz)
In practice, 100 ... 10000 carriers are used.
The transmission happens at the same time on more than one frequency band (e.g. 48 for transmission, 4 for the carriers phase synchronization).
Wirless LAN-s Dr. Beinschróth József: Telecommunication informatics I. 108 FHSS DSSS The OFDM process (2) OFDM
The sub carriers are mutually orthogonal to each other, "put together" the subcarriers and the sub carriers in medium frequency the rest of the signal takes the 0 value. (two function is orthogonal if the scalar product is zero.)
Higher data rate ( e.g. 54Mbps).
Modulation process: PSK, QAM (BPSK - Binary Phase Shift Keying), QPSK… …64QAM
Wirless LAN-s Dr. Beinschróth József: Telecommunication informatics I. 109 FHSS DSSS The OFDM process (3) OFDM
The orthogonal frequency division multiplexing (OFDM) signal spectrum
Wirless LAN-s Dr. Beinschróth József: Telecommunication informatics I. 110 FHSS DSSS The OFDM process (4) OFDM
V data transfer
speed 1 0 1 1 0 1 1 1
Channel 1: 1
Channel 2: 0
Channel 3 : 1 V/8 data transfer speed in one Channel 4 : 1 channel. Sum of data transfer speed Channel 5: 0 is V. Channel 6 : 1
Channel 7 : 1
Channel 8 : 1 t
Wirless LAN-s Dr. Beinschróth József: Telecommunication informatics I. 111 Modulation and speed used in the FHSS DSSS OFDM process OFDM
Modulation Speed (Mbps) BPSK 6 BPSK 9 QPSK 12 QPSK 18 16QAM 24 16QAM 36 16QAM 48 16QAM 54
Wirless LAN-s Dr. Beinschróth József: Telecommunication informatics I. 112 FHSS DSSS Example of OFDM spectrum: 802.11g (1) OFDM
The channels may overlap, 22 MHz wide.
The carriers 5 MHz close to each other, the channel is in the frequency range’s center, could interfere with 8 other channels.
The 14th channel placement doesn't follow this regularity.
Not all channels are used in all geographical regions.
Wirless LAN-s Dr. Beinschróth József: Telecommunication informatics I. 113 FHSS DSSS Example of OFDM spectrum: 802.11g (2) OFDM
Wirless LAN-s Dr. Beinschróth József: Telecommunication informatics I. 114 Media access: Special problems occur in the case of WLAN radio connection (1)
WLAN stations in a half-duplex communication channel capable of, or during transmission can not pay attention to the physical media, when there has been a collision. (When using a radio connection while you are listening to a broadcast transmitter channels, the transmission signal strength overwhelms all others, so the traffic is not detected.)
Another problem is the "hidden terminal" problem and the "visible terminal." (Applicable to the CSMA / CD process?)
Wirless LAN-s Dr. Beinschróth József: Telecommunication informatics I. 115 Media access: Special problems occur in the case of WLAN radio connection (2)
The hidden and the visible terminal problem
E
The surrounding areas of the individual stations are the stations rays
Wirless LAN-s Dr. Beinschróth József: Telecommunication informatics I. 116 Media access: Special problems occur in the case of WLAN radio connection (3)
• A would like to send to B, but do not hear that C sends a Hidden terminal message to B, and therefore does not know that B is busy. • (A start sending, so B will impact, but at least unnecessarily disturbed the channel, B is not able to receive.)
• B would like to give to C, but because A sending a message (a fourth station) B detected the channel is busy, but C could Visible terminal receive. • (B not begin to broadcast, but it could do it and C would be able to receive. Deferred option: waste the channel capacity.)
Wirless LAN-s Dr. Beinschróth József: Telecommunication informatics I. 117 WLAN medium access method versions
For these reasons, the CSMA / CD medium access method is not applicable, other medium access procedure is required.
PCF DCF
DCF and PCF can work at a BSS at the same time.
Wirless LAN-s Dr. Beinschróth József: Telecommunication informatics I. 118 PCF DCF PCF: Central station necessary
PCF (Point Coordination Function) - Centralized collision-free medium access control – Access point necessary • All activities will be controlled by using a base station, can be used only in infrastructure mode. • The base station polling the stations: is there another frame? • Collision can not happen.
All stations able to see the Access Point.
The Access Point has a polling list. The stations are added for their request.
The Access Point has a higher priority in the communication then the other stations.
Wirless LAN-s Dr. Beinschróth József: Telecommunication informatics I. 119 PCF DCF The central station polls the other stations
The Access Point called Polling Request messages to individual stations to send information (beacon frame).
The beacon frame contains the specific parameters of the communication (eg clock sync, jumping series and stay time for the FHSS, etc and give instruction to the station, for example., Go stand-by mode and remain in that state until such. Put the user not awaken.)
The beacon frame calls the new stations to subscribe for the polling list.
The polled station must respond immediately.
In the stand-by mode stations send frames, which are temporarily stored in the Access Point.
Implementation is optional
Wirless LAN-s Dr. Beinschróth József: Telecommunication informatics I. 120 There is no central station in case of DCF PCF DCF
DCF (Distributed Coordination Function). • Does not use central control, the stations are competing for transmission time. • CSMA/CA (Carrier Sense Multipple Access/Collision Avoidance ) process variant. • Not at the same time transmissions are eliminated, but also acknowledgments are introduced. (Transmissions occur at the same time, but not destroy mutually each other, but only one will actually receive.) • Delivering required. • Can be used in ad-hoc and infrastructure mode.
Wirless LAN-s Dr. Beinschróth József: Telecommunication informatics I. 121 Optional: MACAW PCF DCF
Optional possibility (MACA – Multiple Access with Collision Avoidance; MACAW – MACA for Wireless) (Reserving a time interval) • The MACAW handle the problem of hidden and visible station. • The sending station can send an RTS (Request To Send) frame before release the data frames, to which the receiving station responds with a CTS (Clear To Send) frame. • The RTS and CTS frames contain the information, the next data frame and the following frame ACK release will take much time. • Those stations, which are close to the sending station, but are hidden for the receiving station, from the RTS frame, those stations which are close to the receiving station, will known that from the CTS frame how long the channel flow .
Wirless LAN-s Dr. Beinschróth József: Telecommunication informatics I. 122 MACAW data frame PCF DCF
There are three different frame class: data, control and management frame. (The control and the management frame are similar to the data frame, but some fields are obviously missing.
Data Frame Address Preamble Period Address1 Address2 Address3 Number (0- CRC control 4 (1Byte) (2Byte) (6Byte) (6Byte) (6Byte) (2Byte) 2312 (4Byte) (2Byte) (6Byte) Byte)
Resub Compl. From Version Type Subtype To DS missio MF Further W(EP) (O)rder DS admini (2bit) (2bit) (4bit) (1bit) n (1bit) (1bit) (1bit) (1bit) (1bit) strator (1bit) (1bit)
Wirless LAN-s Dr. Beinschróth József: Telecommunication informatics I. 123 MACAW data frame fields (1) PCF DCF
Field Size Explanation name Preamble More Beginning of the frame, but also transfer information to the physical layer. (speed is versions (Synchronization, enter the rest bit rate of the frame, Specify the number of always data bits in the MAC, information of the modulation method) 1 Mbps)
Frame 2 Byte See: the following table control
Period 2 Byte How long will allocate the channel the frame and the corresponding ACK.
1-4. title 4X6 The 802 format appropriate addresses, source and destination addresses or Byte the cell leaving (eg. Ethernet or crossing to another wireless network) necessary for the traffic Number 2 Byte Numbering the frames
Data Variable Transferred data (Max. 2312 Byte) CRC 4 Byte Checksum
Wirless LAN-s Dr. Beinschróth József: Telecommunication informatics I. 124 MACAW data frame fields (2) PCF DCF
Field Size Explanation name (Frame Control) Protocol v. 2 bit Protocols identification – distinguish between different versions
Type 2 bit Differentiation between data, control, management frame Subtype 4 bit Wide range of subtypes exist: eg. RTS, CTS, ACK, DATA… To DS 1 bit The frame (distribution system between cells) on the way to DS (eg. To Ethernet) From DS 1 bit The frame (distribution system between cells) coming from DS (eg. From Ethernet) Resubmis 1 bit (Retry) Resending the previously sent frame sion MF 1 bit (More Fragment) Other parts (fragments) follow Telj. gazd. 1 bit Management the station standby status (Pwr) Further 1 bit (More) More frames to the transmitter W (EP) 1 bit Wired Equivalent Privacy algorithm
O(rder) 1 bit The resulting frames must be processed strictly in the order
Wirless LAN-s Dr. Beinschróth József: Telecommunication informatics I. 125 Example of access point locations
Wirless LAN-s Dr. Beinschróth József: Telecommunication informatics I. 126 WLANs major problem is the security
The wireless networks are based on broadcast. It also follows, very easy to listen to the networks. Solutions: (how to prevent/complicate the listening): • Managed access point • Only the necessary performance • Encrypt • Wired Equivalent Privacy, WEP: weak • Wi-Fi Protected Access, WPA: medium • Wi-Fi Protected Access 2, WPA2: acceptable
Wirless LAN-s Dr. Beinschróth József: Telecommunication informatics I. 127 Bluetooth describes a complete system from the physical to the application layer (1)
Broadcast network
Bluetooth Dr. Beinschróth József: Telecommunication informatics I. 128 Bluetooth describes a complete system from the physical to the application layer (2)
Bluetooth Dr. Beinschróth József: Telecommunication informatics I. 129 Bluetooth is built on the IEEE 802.15, which describes the physical and the data link layer
The Bluetooth Special Interest Group developed (IBM, Intel, Nokia, Toshiba), describes the entire system from the physical to the application layer. The layer structure is not entirely like known models (OSI, TCP/IP, IEEE 802…). The physical radio the baseband transmission and the L2CAP covers the physical and the MAC layer more or less. The IEEE 802.15 is not all the layers, only the physical and data link layers are standardized.
Handles low power communication devices.
Developed for short distances (about 10 meter)
Works on ISM frequency range, transfer rate max. 1Mbps.
Point-to-point, point-to-multipoint connects.
Typically used between computers and handheld devices (eg. computer – cellular phone, cellular phone -headset).
http://www.bluetooth. com/Bluetooth/SIG/). Bluetooth Dr. Beinschróth József: Telecommunication informatics I. 130 The Bluetooth is a piconetwork
The Bluetooth is a main unit of piconetwork, which means there are 8 devices (1 master and 7 slave). The slaves are very simple, cheap devices, the piconetwork can be connected to each other. In the piconetwork there may be even beyond the eight active devices, up to 255 waiting devices. (In this state (parked) waiting for the activation signal from the master)
The piconetwork is a centralized TDM system, in which the master decides which device can be communicated in the time slot.
In the piconetwork the communication is always between the master and the slave, the slaves don't communicate directly with each other.
FHSS technique used in a time slot, the master determines the pseudo random jump sequence.
A device may also participate in other piconetworks with time multiplexing, so the master of a piconetwork can be a slave to another piconetwork. Diffused network can be formed.
Bluetooth Dr. Beinschróth József: Telecommunication informatics I. 131 The Bluetooth is a broadcast network
Bluetooth Dr. Beinschróth József: Telecommunication informatics I. 132 The Bluetooth’s layer structure is not completely following original models
Application Applications/profiles layer
Other RFcomm Telephony Service discovery Intermediate LLC layer Sound Control Logical Link Control Adaption Protocol (L2CAP) Data Link Connection manager layer
Baseband
Physical radio Physical 802.15 layer
Bluetooth Dr. Beinschróth József: Telecommunication informatics I. 133 The Bluetooth layers functions
Layer Function Physical radio More or less same as physical layer, the design was intended mainly to optimize costs.. Baseband layer The time slots controls organized into frames. Connection manager, Builds up logical channels between devices, authentication, quality Logical Link Control assurance. Adaption Protocol Like the LLC layer hides the transfer details from the upper layers.(L2CAP - Logical Link Control Adaptation Protocol). Sound and control Deals with voice and control, the applications can be independently protocol accessed from L2CAP LLC In order for the other 802 network cooperation Rfcomm Radio Frequency communication- the PC keyboard, mouse, modem connection makes it possible to wireless Telephony Real time protocol for speech transmission. Service discovery Discovering services on the network. Applications/Profiles Each application has its own set of protocols. The individual devices (slaves) know only protocol elements necessary for a particular application.
Bluetooth Dr. Beinschróth József: Telecommunication informatics I. 134 The Bluetooth application independent layers (802.15)
L2CAP
Baseband
Physical radio
Bluetooth Dr. Beinschróth József: Telecommunication informatics I. 135 L2CAP Physical radio- FHSS Baseband
Physical radio 79 pcs 1 MHz channel in the 2,4 GHz ISM band.
FHSS 1600 jumps/second, 625µs residence time.
802.11 and Bluetooth radios can interfere with each other!
Bluetooth Dr. Beinschróth József: Telecommunication informatics I. 136 L2CAP Baseband – frame treatment Baseband
Physical radio
Settles the bitstream to frames, the master defines 625 µs time slots.
The length of the frames is 1, 3, or 5 time slots.
The logical channels for the transmission can not guarantee quality (frames may be lost, causing retransmissions may be required) or using real time.
Bluetooth Dr. Beinschróth József: Telecommunication informatics I. 137 L2CAP – Treatment of logical channels L2CAP
Control Adaptation Protocol Baseband
Physical radio
(Logical link control adaptation protocol)
Multiplexing/demultiplexing (for multi source package).
Quality of service treatment needs (e.g. to determine the maximum size of a data field.)
Bluetooth Dr. Beinschróth József: Telecommunication informatics I. 138 Bluetooth frame : The header is consecutively transmitted 3 times
There are several possible frames
Access code Header Data field
Title Type F A S CRC
Bluetooth Dr. Beinschróth József: Telecommunication informatics I. 139 Bluetooth frame fields
Field Length Interpretation (bit)
Access code 72 Identification of the master (the slave stay in the masters broadcast)
Header 54 MAC sublayer appropriate field Data field Max. 5 timeslot frame: 2744 bit, 1 timeslot frame (240 bit) 2744 Title 3 For addressing the 8 active device. Type 4 Type of the frame (e.g. query, real time data transmission etc.) F(low) 1 Traffic control: the slave is set when the buffer is full and can not accept more data. A(ck) 1 Receipt S(equence) 1 Number: The frame numbering for re-transmission detection. CRC 8 Checksum
Bluetooth Dr. Beinschróth József: Telecommunication informatics I. 140 Bluetooth technology is widespread
Bluetooth Dr. Beinschróth József: Telecommunication informatics I. 141 Data transmission over power network (1)
Parctically available High noise anywhere
General cathegories: Power Line Communication (PLC) Broadband over Power Lines (BPL)
Examlpes: SOHO Internet connection
PLC, BPL Dr. Beinschróth József: Telecommunication informatics I. 142 Data transmission over power network (2)
HomePlug® Auto MDI / X HomePlug® AV HomePlug® AV sTANDARD AV 1.1 HomePlug AV 1.1 1.0 1.0
Rate* 200 Mbps 200 Mbps 200 Mbps 200 Mbps
Frequency 2 - 30 MHz 2 - 30 MHz 2 - 30 MHz 2 - 30 MHz
Medium access CSMA/CA CSMA/CA CSMA/CA CSMA/CA procedure
Cryptographí 128-bit AES 128-bit AES 128-bit AES 128-bit AES Coding OFDM OFDM OFDM OFDM procedure Efficient distance 300m 300m 300m 300m Example for Sharp Devolo dLAN 200 Belkin Sunvalleyus practical product HN-VA100U AVsmart+ Powerline AV+ 200Mbps
*Newer trens: 500Mbps, 1Gbps
PLC, BPL Dr. Beinschróth József: Telecommunication informatics I. 143 DOCSIS: Data Over Cable Service Interface Specifications
A Data Over Cable Service Interface Specification (DOCSIS): telecommunication standard using cable TV network for high rate data transmission. It was developed by CableLabs. It is developing continuously.
It is a data transmission procedure optimised for calble TV network. (CableLab, Cisco, Intel, Motorola, Broadcom…)
It uses difficult digital modulations (high level PM, QAM)
It realises OSI L1 and L2
Timing in the centre, no collision protocol
Starting point: In cable TV nerwork, the highest frequency is 1GHz. (It depends on elements of network)
Separated upstream band an downstream band (US: 5- 65 MHz, DS: 550-862 MHz) – in newer version they are wider.
DOCSIS Dr. Beinschróth József: Telecommunication informatics I. 144 A kábel TV spektrum és a DOCSIS
EuroDocsis: DS: 8MHz (USA: 6MHz) – FDMA channels, but in a unique channel: TDMA established
In US és DS direction the operation is quite different. DS direction: useful data and control messages tranmitted.
In DS direction contol messages contains licences: when a distinguished cable moden can start sending messages. There is a time slot for new entering equipment to connect.
A CMTS (Cable Modem Termination System, central element – head station) controls transmitting level using continouos messages and time delaying derived from delaying of cable.
145 DOCSIS Dr. Beinschróth József: Telecommunication informatics I. DOCSIS evolution
DOCSIS Year ITU-T Modulations Theoretical Properties (CableLab) Standard rates 1.0 199 J.112 DS:64QAM, DS: 42,88Mbps First version, best effort 7 (DOC-SIS 256QAM (57,2Mbps- data transmission 1.1) US:QPSK, 16QAM EuroDocsis) (1.1: QOS, VoIP support) US:10,24Mbps 2.0 200 J122 DS:64QAM, DS: 42,88Mbps Higher data transsmission 1 256QAM (57,2Mbps- rate and noise tolerancy in US: 32QAM, EuroDocsis) US direction 64QAM, 128QAM US:30,72Mbps 3.0 200 DS:64QAM, DS:>480Mbps (Channel-bonding) –IPv6 6 256QAM US:>120Mbps support, higher secutity US: 64QAM (AES) 3.1 201 4096QAM DS:>10Gbps Wider spectrum (200MHz 3 US:>1Gbps US, 1.2 GHz DS) OFDM
Practical data transmission rates are always lower tha theoretical ones.
DOCSIS Dr. Beinschróth József: Telecommunication informatics I. 146 DOCSIS architecture (1)
Service provider Cable Subscriber
CMTS: WAN Cable CM: Cable Modem HFC Modem Termination System Hybrid Fiber Coaxial CPE: Customer Premises Equipment In a network at least one CMTS - CMI: CMTS and more CM-s exist. Network Customer So US is problematic: there Side Premises can be collisions. Interface Equipment Interface
DOCSIS Dr. Beinschróth József: Telecommunication informatics I. 147 DOCSIS architecure (2)
SATELITE
Service
CTMS
Filters, distributros, amplifyers…
DOCSIS Dr. Beinschróth József: Telecommunication informatics I. 148 DOCSIS protocol stack
802.2 LLC 802.2 LLC 802.2 LLC
DOCSYS MAC 802.3 MAC
DOCSYS PHY Ethernet
Cable interface Customer interface
DOCSIS Dr. Beinschróth József: Telecommunication informatics I. 149 Process of US (1)
• All the US data unit transmitted inside one or more minislots. (Longness of minislots are different in different networks). US channels • Mini-slot: 62,5µs. Contains 16-48 byte data, devided od necessary in US direction minislots • A CM asks timeframe from (minislot) • A minislots are enapmed by CTMS (MAP- Mini-slot Allocation Packet)
• Mini-slots can be asked in certaint times • The cable delay causes: CM-s sense in different CMTS time, but every CM can count its distance from periodically CTMS, so every CM can count the starting time of declares new minislots. minislots groups • Every CM has a special minislot which can be used requiring bandwidth. More CM has the same minislot so collisions can be appeared.
DOCSIS Dr. Beinschróth József: Telecommunication informatics I. 150 Process of US (2)
• If CTMS accepted requeset, send ACK which contain the desiganated minislosts for CM. ACK/ Collision • Collision: CM waitin during random time. In case os collision the time is duplicated.
• After then CM sends data units in the designated mini-slots. Data uploading In the header of minislot CM can require another minislots.
• Ranging: CM (Cable Modem) measures the distance from CMTS. • CM-s sense in different time, but every CM can count its Modem distance from CMTS, so every CM can count the starting time measures the of minislots. distance form CMTS • CMTS time by time appies special time slots: advertises system parameters and waits for new CM logins. CM login: special data unit – CM measures the time until answer arrives.
DOCSIS Dr. Beinschróth József: Telecommunication informatics I. 151 Process of US (3)
Slotted ALOHA
DOCSIS Dr. Beinschróth József: Telecommunication informatics I. 152 Process of DS (1)
In DS direction no collisions
• DS channels handled different method compairing US channels. • Why? In this case there are only one sender (CMTS), so no race situation no need for minislots. And in generally US speed is by far lower than DS speed. • DS is a broadcast. Channel contanis all the data units.
DOCSIS Dr. Beinschróth József: Telecommunication informatics I. 153 Process of DS (2)
DOCSIS Dr. Beinschróth József: Telecommunication informatics I. 154 Logical cahnnels during US and DS
Coax cable DS channel, no race situation, 27Mb/s QAM-64 and 184 byte-user data field
Data unit US channel, race situation, 9Mb/s QPSK and 8 byte-minislost USA
DOCSIS Dr. Beinschróth József: Telecommunication informatics I. 155 Access procedures
TDMA S-CDMA
• Time Division Multiple • Synchronous Code Access Division Multiple • Time division. Time Access slots are devided • Same-time dinamically they are trasmission in the requested by CM-s same channel and time slot: They can be separated becouse of orthogaonal coding (Mthelatical and DSP procedures)
DOCSIS Dr. Beinschróth József: Telecommunication informatics I. 156 Cable modems
DOCSYS Dr. Beinschróth József: Telecommunication informatics I. 157 Questions (1)
1. How large is the data field in the Ethernet frame?
2. What kind of modulation scheme is used in the Ethernet?
3. What codings are used in the Ethernet?
4. What versions do you know in the token ring technology?
5. What bridged distances are characterized in the WLAN?
6. What transmission procedures are used in WLAN?
7. What is the ISM band?
8. What does the base station and the ad-hoc networks mean in the WLANs?
9. What is the BSS and the ESS?
10. What is the visible and the hidden terminal problems?
11. In what kind of frequency band does the Bluetooth work? How large data transfer rate characterize it?
12. How large is the data field in the Bluetooth frame? +1: Write five questions
Dr. Beinschróth József: Telecommunication informatics I. 158 Questions (2)
DSSS (11 channel)
(11) (25) FHSS (79 channel) (8) 1:11001100100 Code:3,5,1,6,4,7,9,21,23,17,2,15, 8,9,11,19 OFDM (52 channel)
0:00110011011
Channel
Channel
Channel
1 2 3 4 5 6 7 8 9 10 10 9 8 7 6 5 4 3 2 1
1 2 3 4 5 6 7 8 9 10 10 9 8 7 6 5 4 3 2 1 1 2 3 4 5 6 7 8 9 10 10 9 8 7 6 5 4 3 2 1 t t 1 0 0 1 0 0 0 1 1 0 1 0 1 0 1 0 t 1 0 0 1 0 0 0 1 1 0 1 0 1 0 1 0 1 0 0 1 0 0 0 1 1 0 1 0 1 0 1 0
Dr. Beinschróth József: Telecommunication informatics I. 159 Test worksheet (1)
1. The Ethernet a. implements each layers of the OSI._____ b. all versions data transfer rate higher than in the case of modems available data rates._____ c. using PM and QAM modulation._____ d. in case of wiring still using unshielded twisted-pair (UTP) cable._____ 2. Ethernet card address is the following: 8:0:20:F1:G1:1.3_____ 3. The Ethetnet frame a. The type field defines that how many fields are in the frame._____ b. contains the serial number of the frame._____ c. belongs to the MAC sublayer._____ d. belongs to the LLC sublayer._____
Dr. Beinschróth József: Telecommunication informatics I. 160 Test worksheet (2)
4. The Ethernet line coding a. AMI or HDB-3._____ b. in case of 10BASE is Manchester coding._____ c. In case of Fast Ethernet can be a variety of encoding symbols._____ d. Gigabit Ethernet based on copper wire in case of NRZ._____ 5. In case of Token Ring a. Only the station can take a frame from the ring, which made it._____ b. The token frame means erasure rights._____ c. The token in the ring is going from station to station._____ d. The station can hold the token up to the token holding time. _____ e. The token frame and the data field in the Access Control is same._____ f. The starting and the ending delimiter includes physical layer coding violations._____
Dr. Beinschróth József: Telecommunication informatics I. 161 Test worksheet (3)
6. VLAN and WLAN are the same_____ 7. In case of WLAN a. only wireless connections used._____ b. the maximum effective range is several hundred meters._____ c. the maximum data transfer rate is several hundred mbps._____ d. the devices can be used without transmitting license in the ISM and the UNI band._____ e. the devices can't be used in movement._____ f. FHSS, DSSS or OFDM modulations are used._____ 8. In WLAN terminology the BSS means: a. Backup Slave System. _____ b. Blocks of Standard Service._____ c. Basic Service Set._____ d. Block of Source Station._____
Dr. Beinschróth József: Telecommunication informatics I. 162 Test worksheet (4)
9. In case of FHSS the carriers are in different frequencies, the spent time in each channel is the dwell time._____ 10. In case of DSSS splits a chip to chips and transfer the chips at the same time but at different frequencies._____ 11. In case of OFDM each bit periods in the channels are growing compared to the original._____ 12. Visible terminal problem a. the final cause is the limited range of the radio station._____ b. exist for wired networks._____ c. In case of wireless local area networks can't use CSMA/CD method._____ d. because not use the whole bandwidth._____
Dr. Beinschróth József: Telecommunication informatics I. 163 Test worksheet (5)
13. The hidden terminal problem a. In case of wireless networks will not occur_____ b. each transmits unreasonably interfere with each other._____ c. In case of wireless local area networks can't use CSMA/CD method._____ d. is rooted in the transmitter is not available for the required information._____ 14. The WLAN multiple access a. can be PCF and DCF procedures_____ b. always using centralized control_____ c. in one case, when a base station coordinates the communication._____ d. in each case the beacon frame invites the new stations to subscribe for the polling list._____ e. In each case using the CSMA/CA version._____ f. In each case there is no elimination of same time transmissions, but acknowledgments are introduced._____
Dr. Beinschróth József: Telecommunication informatics I. 164 Test worksheet (6)
15. THE MACAW a. Uses RTS and CTS frames._____ b. One of the special version of CSMA/CA._____ c. Is the Many Agent of Communcation All Wireless device._____ d. In case of the RTS and CTS frames contain the information that the next data frame and the subsequent release of ACK frame will take much time._____ 16. The MACA frame a. Is always the same length._____ b. Have several types._____ c. Contains only control data._____ d. Contains timing data._____
Dr. Beinschróth József: Telecommunication informatics I. 165 Test worksheet (7)
17. Bluetooth is developing criterion taken into consideration, that a. low power devices can be connected to each other._____ b. the distance between the devices can not be more than 100m._____ c. up to four devices can be simultaneously connected to another._____ d. the slave can only connect to a master._____ e. the architecture follows the OSI model._____ f. can be more than one master in the pico network._____ 18. The Bluetooth a. Physical layer is the physical radio, which is using FHSS modulation._____ b. only bitstream in case of connection, can not speak about frames._____ c. The audio connection is always real time._____ d. Due to the short distances does not apply redundant transmission._____
+1: Write five test questions
Dr. Beinschróth József: Telecommunication informatics I. 166