1. Introdução à camada física
RCO2
Introdução à camada física
Lecture slides prepared by Dr Lawrie Brown for “Data and Computer Communications”, 8/e, by William Stallings, Chapter 1 “Data Communications, Data Networks, and the Internet”.

2. Transmissão de uma stream de bits por um meio de transmissão
Camada Física
Transmissão de uma stream de bits por um meio de transmissão

3. Camada Física Atribuições da camada física:
Transmissão de sequências de bits pelo meio físico
Modulação (transmissão analógica)
Codificação (transmissão digital)
Definição das características elétricas e mecânicas do meio físico
Definição das características funcionais e procedurais do acesso ao meio

4. The basic building block of any communications facility is the transmission line.
One of the basic choices facing a business user is the transmission medium. For use within the business premises, this choice is generally completely up to the business. For long-distance communications, the choice is generally but not always made by the long-distance carrier.
In either case, changes in technology are rapidly changing the mix of media used. The ever-increasing capacity of fiber optic channels is making channel capacity a virtually free resource. However, switching is now becoming the bottleneck. The growing use of wireless transmission, is a result of the trend toward universal personal telecommunications and universal access to communications.
Despite the growth in the capacity and the drop in cost of transmission facilities, transmission services remain the most costly component of a communications budget for most businesses. Thus, the manager needs to be aware of techniques that increase the efficiency of the use of these facilities, such as multiplexing and compression.
Camada Física
Posição na arquitetura de redes:

5. The basic building block of any communications facility is the transmission line.
One of the basic choices facing a business user is the transmission medium. For use within the business premises, this choice is generally completely up to the business. For long-distance communications, the choice is generally but not always made by the long-distance carrier.
In either case, changes in technology are rapidly changing the mix of media used. The ever-increasing capacity of fiber optic channels is making channel capacity a virtually free resource. However, switching is now becoming the bottleneck. The growing use of wireless transmission, is a result of the trend toward universal personal telecommunications and universal access to communications.
Despite the growth in the capacity and the drop in cost of transmission facilities, transmission services remain the most costly component of a communications budget for most businesses. Thus, the manager needs to be aware of techniques that increase the efficiency of the use of these facilities, such as multiplexing and compression.
Camada Física
Representação dos bits por um sinal eletromagnético, para poder ser propagado pelo meio de transmissão
Controle da taxa por meio do projeto dos dispositivos da camada física e seus softwares de controle

6. The basic building block of any communications facility is the transmission line.
One of the basic choices facing a business user is the transmission medium. For use within the business premises, this choice is generally completely up to the business. For long-distance communications, the choice is generally but not always made by the long-distance carrier.
In either case, changes in technology are rapidly changing the mix of media used. The ever-increasing capacity of fiber optic channels is making channel capacity a virtually free resource. However, switching is now becoming the bottleneck. The growing use of wireless transmission, is a result of the trend toward universal personal telecommunications and universal access to communications.
Despite the growth in the capacity and the drop in cost of transmission facilities, transmission services remain the most costly component of a communications budget for most businesses. Thus, the manager needs to be aware of techniques that increase the efficiency of the use of these facilities, such as multiplexing and compression.
Camada Física
Fundamental para a correta transmissão dos bits, e feita com mecanismos de clock que controlam transmissor e receptor
Divisão de um link (meio físico) em canais lógicos, para melhorar a eficiência da transmissão.

7. The basic building block of any communications facility is the transmission line.
One of the basic choices facing a business user is the transmission medium. For use within the business premises, this choice is generally completely up to the business. For long-distance communications, the choice is generally but not always made by the long-distance carrier.
In either case, changes in technology are rapidly changing the mix of media used. The ever-increasing capacity of fiber optic channels is making channel capacity a virtually free resource. However, switching is now becoming the bottleneck. The growing use of wireless transmission, is a result of the trend toward universal personal telecommunications and universal access to communications.
Despite the growth in the capacity and the drop in cost of transmission facilities, transmission services remain the most costly component of a communications budget for most businesses. Thus, the manager needs to be aware of techniques that increase the efficiency of the use of these facilities, such as multiplexing and compression.
Camada Física
Método que permite que dois nós fiquem conectados por um link dedicado

8. IA–Interface Analógica
This simple narrative conceals a wealth of technical complexity. To get some idea of the scope of this complexity, Stallings DCC8e Table 1.1 lists a selection of the key tasks that must be performed in a data communications system.
transmission system utilization - need to make efficient use of transmission facilities typically shared among a number of communicating devices
a device must interface with the transmission system
once an interface is established, signal generation is required for communication
there must be synchronization between transmitter and receiver, to determine when a signal begins to arrive and when it ends
there is a variety of requirements for communication between two parties that might be collected under the term exchange management
Error detection and correction are required in circumstances where errors cannot be tolerated
Flow control is required to assure that the source does not overwhelm the destination by sending data faster than they can be processed and absorbed
addressing and routing, so a source system can indicate the identity of the intended destination, and can choose a specific route through this network
Recovery allows an interrupted transaction to resume activity at the point of interruption or to condition prior to the beginning of the exchange
Message formatting has to do with an agreement between two parties as to the form of the data to be exchanged or transmitted
Frequently need to provide some measure of security in a data communications system
Network management capabilities are needed to configure the system, monitor its status, react to failures and overloads, and plan intelligently for future growth
See have gone from the simple idea of data communication between source and destination to a rather formidable list of data communications tasks.
Camada física
Interfaces analógicas (IA) e digitais (ID):
ID – Interface Digital
IA–Interface Analógica
Modem A
Modem B
DTE A
DCE A
DCE B
DTE B
Meio de comunicação
Cabo lógico
Comunicação Física

9. The basic building block of any communications facility is the transmission line.
One of the basic choices facing a business user is the transmission medium. For use within the business premises, this choice is generally completely up to the business. For long-distance communications, the choice is generally but not always made by the long-distance carrier.
In either case, changes in technology are rapidly changing the mix of media used. The ever-increasing capacity of fiber optic channels is making channel capacity a virtually free resource. However, switching is now becoming the bottleneck. The growing use of wireless transmission, is a result of the trend toward universal personal telecommunications and universal access to communications.
Despite the growth in the capacity and the drop in cost of transmission facilities, transmission services remain the most costly component of a communications budget for most businesses. Thus, the manager needs to be aware of techniques that increase the efficiency of the use of these facilities, such as multiplexing and compression.
Camada Física
Transmissão da stream de bits:
Paralela X serial
Half-duplex X Full-duplex
Sincronismo
Taxa de transmissão (bit rate)
Transmissão do sinal:
Meio / fios utilizados
Largura de banda
Modulação / codificação

10. The basic building block of any communications facility is the transmission line.
One of the basic choices facing a business user is the transmission medium. For use within the business premises, this choice is generally completely up to the business. For long-distance communications, the choice is generally but not always made by the long-distance carrier.
In either case, changes in technology are rapidly changing the mix of media used. The ever-increasing capacity of fiber optic channels is making channel capacity a virtually free resource. However, switching is now becoming the bottleneck. The growing use of wireless transmission, is a result of the trend toward universal personal telecommunications and universal access to communications.
Despite the growth in the capacity and the drop in cost of transmission facilities, transmission services remain the most costly component of a communications budget for most businesses. Thus, the manager needs to be aware of techniques that increase the efficiency of the use of these facilities, such as multiplexing and compression.
Camada Física
Transmissão serial X paralela:
Serial: um bit por vez
Paralela: vários bits por vez

11. The basic building block of any communications facility is the transmission line.
One of the basic choices facing a business user is the transmission medium. For use within the business premises, this choice is generally completely up to the business. For long-distance communications, the choice is generally but not always made by the long-distance carrier.
In either case, changes in technology are rapidly changing the mix of media used. The ever-increasing capacity of fiber optic channels is making channel capacity a virtually free resource. However, switching is now becoming the bottleneck. The growing use of wireless transmission, is a result of the trend toward universal personal telecommunications and universal access to communications.
Despite the growth in the capacity and the drop in cost of transmission facilities, transmission services remain the most costly component of a communications budget for most businesses. Thus, the manager needs to be aware of techniques that increase the efficiency of the use of these facilities, such as multiplexing and compression.
Camada Física
Transmissão serial:
Maiores taxas efetivas de transmissão
Maior imunidade a ruído (interferências)
Menor custo
Transmissão paralela:
Menores taxas efetivas de transmissão
Menor imunidade a ruído (interferências)
Maior custo
Conclusão:
Em redes de computadores usa-se transmissão serial

12. The basic building block of any communications facility is the transmission line.
One of the basic choices facing a business user is the transmission medium. For use within the business premises, this choice is generally completely up to the business. For long-distance communications, the choice is generally but not always made by the long-distance carrier.
In either case, changes in technology are rapidly changing the mix of media used. The ever-increasing capacity of fiber optic channels is making channel capacity a virtually free resource. However, switching is now becoming the bottleneck. The growing use of wireless transmission, is a result of the trend toward universal personal telecommunications and universal access to communications.
Despite the growth in the capacity and the drop in cost of transmission facilities, transmission services remain the most costly component of a communications budget for most businesses. Thus, the manager needs to be aware of techniques that increase the efficiency of the use of these facilities, such as multiplexing and compression.
Camada Física
Sentido da transmissão:
Simplex: a transmissão se dá somente em um sentido da comunicação.
Half-duplex (semi-duplex): a transmissão se dá em ambos os sentidos, porém não simultaneamente

13. The basic building block of any communications facility is the transmission line.
One of the basic choices facing a business user is the transmission medium. For use within the business premises, this choice is generally completely up to the business. For long-distance communications, the choice is generally but not always made by the long-distance carrier.
In either case, changes in technology are rapidly changing the mix of media used. The ever-increasing capacity of fiber optic channels is making channel capacity a virtually free resource. However, switching is now becoming the bottleneck. The growing use of wireless transmission, is a result of the trend toward universal personal telecommunications and universal access to communications.
Despite the growth in the capacity and the drop in cost of transmission facilities, transmission services remain the most costly component of a communications budget for most businesses. Thus, the manager needs to be aware of techniques that increase the efficiency of the use of these facilities, such as multiplexing and compression.
Camada Física
Sentido da transmissão:
Full-duplex: a transmissão se dá em ambos os sentidos, e possivelmente ao mesmo tempo
Obs: pode ocorrer de a ID ser half-duplex, e a IA full-duplex, e vice-versa

14. The basic building block of any communications facility is the transmission line.
One of the basic choices facing a business user is the transmission medium. For use within the business premises, this choice is generally completely up to the business. For long-distance communications, the choice is generally but not always made by the long-distance carrier.
In either case, changes in technology are rapidly changing the mix of media used. The ever-increasing capacity of fiber optic channels is making channel capacity a virtually free resource. However, switching is now becoming the bottleneck. The growing use of wireless transmission, is a result of the trend toward universal personal telecommunications and universal access to communications.
Despite the growth in the capacity and the drop in cost of transmission facilities, transmission services remain the most costly component of a communications budget for most businesses. Thus, the manager needs to be aware of techniques that increase the efficiency of the use of these facilities, such as multiplexing and compression.
Camada Física
Sincronismo:
Transmissão assíncrona:
Nem sempre há sinal sendo transmitido
Sincronização na recepção feita para cada palavra transmitida (ex: a cada byte)
Relógios nas ID não estão sincronizados
Sinal transmitido não inclui relógio do transmissor
Transmissão síncrona:
Sinal transmitido inclui relógio do transmissor
Relógios nas ID se mantêm sincronizados
Sempre há sinal sendo transmitido

15. The basic building block of any communications facility is the transmission line.
One of the basic choices facing a business user is the transmission medium. For use within the business premises, this choice is generally completely up to the business. For long-distance communications, the choice is generally but not always made by the long-distance carrier.
In either case, changes in technology are rapidly changing the mix of media used. The ever-increasing capacity of fiber optic channels is making channel capacity a virtually free resource. However, switching is now becoming the bottleneck. The growing use of wireless transmission, is a result of the trend toward universal personal telecommunications and universal access to communications.
Despite the growth in the capacity and the drop in cost of transmission facilities, transmission services remain the most costly component of a communications budget for most businesses. Thus, the manager needs to be aware of techniques that increase the efficiency of the use of these facilities, such as multiplexing and compression.
Camada Física
Transmissão assíncrona:
O sinal de TD na ID indica o início e final de cada caractere (sincronismo de caractere)‏
Uso do protocolo elementar start-stop
Exige somente três fios na ID para uma comunicação full- duplex
Uso de uma UART (Unidade Assíncrona de Recepção e Transmissão) implementada em HW e/ou SW
Custo baixo na ID porém ineficiente

16. Transmissão assíncrona: comunicação diretamente entre IDs
The basic building block of any communications facility is the transmission line.
One of the basic choices facing a business user is the transmission medium. For use within the business premises, this choice is generally completely up to the business. For long-distance communications, the choice is generally but not always made by the long-distance carrier.
In either case, changes in technology are rapidly changing the mix of media used. The ever-increasing capacity of fiber optic channels is making channel capacity a virtually free resource. However, switching is now becoming the bottleneck. The growing use of wireless transmission, is a result of the trend toward universal personal telecommunications and universal access to communications.
Despite the growth in the capacity and the drop in cost of transmission facilities, transmission services remain the most costly component of a communications budget for most businesses. Thus, the manager needs to be aware of techniques that increase the efficiency of the use of these facilities, such as multiplexing and compression.
Camada Física
Transmissão assíncrona: comunicação diretamente entre IDs

17. Transmissão assíncrona: comunicação usando DCEs
The basic building block of any communications facility is the transmission line.
One of the basic choices facing a business user is the transmission medium. For use within the business premises, this choice is generally completely up to the business. For long-distance communications, the choice is generally but not always made by the long-distance carrier.
In either case, changes in technology are rapidly changing the mix of media used. The ever-increasing capacity of fiber optic channels is making channel capacity a virtually free resource. However, switching is now becoming the bottleneck. The growing use of wireless transmission, is a result of the trend toward universal personal telecommunications and universal access to communications.
Despite the growth in the capacity and the drop in cost of transmission facilities, transmission services remain the most costly component of a communications budget for most businesses. Thus, the manager needs to be aware of techniques that increase the efficiency of the use of these facilities, such as multiplexing and compression.
Camada Física
Transmissão assíncrona: comunicação usando DCEs
Obs: neste caso a comunicação pode ser full-duplex entre IDs, porém half-duplex ou full-duplex entre DCEs

18. The basic building block of any communications facility is the transmission line.
One of the basic choices facing a business user is the transmission medium. For use within the business premises, this choice is generally completely up to the business. For long-distance communications, the choice is generally but not always made by the long-distance carrier.
In either case, changes in technology are rapidly changing the mix of media used. The ever-increasing capacity of fiber optic channels is making channel capacity a virtually free resource. However, switching is now becoming the bottleneck. The growing use of wireless transmission, is a result of the trend toward universal personal telecommunications and universal access to communications.
Despite the growth in the capacity and the drop in cost of transmission facilities, transmission services remain the most costly component of a communications budget for most businesses. Thus, the manager needs to be aware of techniques that increase the efficiency of the use of these facilities, such as multiplexing and compression.
Camada Física
Exemplo de transmissão assíncrona com 8 bits, sem Paridade e estado inicial da linha alto.
Eficiência: Te=100*info/(info+ctle) [%] (máx=80%!)‏
Overhead: Oh=100*(ctle/info) [%]

19. The basic building block of any communications facility is the transmission line.
One of the basic choices facing a business user is the transmission medium. For use within the business premises, this choice is generally completely up to the business. For long-distance communications, the choice is generally but not always made by the long-distance carrier.
In either case, changes in technology are rapidly changing the mix of media used. The ever-increasing capacity of fiber optic channels is making channel capacity a virtually free resource. However, switching is now becoming the bottleneck. The growing use of wireless transmission, is a result of the trend toward universal personal telecommunications and universal access to communications.
Despite the growth in the capacity and the drop in cost of transmission facilities, transmission services remain the most costly component of a communications budget for most businesses. Thus, the manager needs to be aware of techniques that increase the efficiency of the use of these facilities, such as multiplexing and compression.
Camada Física
Exemplo de transmissão assíncrona em uma interface RS-232

20. The basic building block of any communications facility is the transmission line.
One of the basic choices facing a business user is the transmission medium. For use within the business premises, this choice is generally completely up to the business. For long-distance communications, the choice is generally but not always made by the long-distance carrier.
In either case, changes in technology are rapidly changing the mix of media used. The ever-increasing capacity of fiber optic channels is making channel capacity a virtually free resource. However, switching is now becoming the bottleneck. The growing use of wireless transmission, is a result of the trend toward universal personal telecommunications and universal access to communications.
Despite the growth in the capacity and the drop in cost of transmission facilities, transmission services remain the most costly component of a communications budget for most businesses. Thus, the manager needs to be aware of techniques that increase the efficiency of the use of these facilities, such as multiplexing and compression.
Camada Física
Comunicação síncrona
O sinal de TD/RD na ID necessita de um sinal adicional separado para dar o compasso da amostragem dos bits de dados. Não há start/stop.
Todos os bits de TD são bits de dados
Exige 5 fios na ID para uma comunicação full-duplex
Uso de uma USART (Unidade Síncrona Assíncrona de Recepção e Transmissão) implementada em HW e/ou SW
Custo elevado na ID porém é possível conseguir índices de eficiência mais próximos de 100%

21. The basic building block of any communications facility is the transmission line.
One of the basic choices facing a business user is the transmission medium. For use within the business premises, this choice is generally completely up to the business. For long-distance communications, the choice is generally but not always made by the long-distance carrier.
In either case, changes in technology are rapidly changing the mix of media used. The ever-increasing capacity of fiber optic channels is making channel capacity a virtually free resource. However, switching is now becoming the bottleneck. The growing use of wireless transmission, is a result of the trend toward universal personal telecommunications and universal access to communications.
Despite the growth in the capacity and the drop in cost of transmission facilities, transmission services remain the most costly component of a communications budget for most businesses. Thus, the manager needs to be aware of techniques that increase the efficiency of the use of these facilities, such as multiplexing and compression.
Camada Física
Comunicação síncrona:
Conexão FÍSICA da ID em modo síncrono duplex. Por padrão universal o ECD é o equipamento que deve gerar o sincronismo de TD e RD. TD TD ID ID TC TC RD RD
ETD
ECD RC RC
MEIO
GND
GND
TC – TRANSMITER CLOCK
RC – RECEIVER CLOCK

22. The basic building block of any communications facility is the transmission line.
One of the basic choices facing a business user is the transmission medium. For use within the business premises, this choice is generally completely up to the business. For long-distance communications, the choice is generally but not always made by the long-distance carrier.
In either case, changes in technology are rapidly changing the mix of media used. The ever-increasing capacity of fiber optic channels is making channel capacity a virtually free resource. However, switching is now becoming the bottleneck. The growing use of wireless transmission, is a result of the trend toward universal personal telecommunications and universal access to communications.
Despite the growth in the capacity and the drop in cost of transmission facilities, transmission services remain the most costly component of a communications budget for most businesses. Thus, the manager needs to be aware of techniques that increase the efficiency of the use of these facilities, such as multiplexing and compression.
Camada Física
Taxa de transmissão (taxa de bits, ou bit rate):
Quantidade de bits transmitidos sem interrupção por unidade de tempo
Inverso do tempo de duração de um bit na linha
Obs: não confundir com frequência do sinal !!!

23. The basic building block of any communications facility is the transmission line.
One of the basic choices facing a business user is the transmission medium. For use within the business premises, this choice is generally completely up to the business. For long-distance communications, the choice is generally but not always made by the long-distance carrier.
In either case, changes in technology are rapidly changing the mix of media used. The ever-increasing capacity of fiber optic channels is making channel capacity a virtually free resource. However, switching is now becoming the bottleneck. The growing use of wireless transmission, is a result of the trend toward universal personal telecommunications and universal access to communications.
Despite the growth in the capacity and the drop in cost of transmission facilities, transmission services remain the most costly component of a communications budget for most businesses. Thus, the manager needs to be aware of techniques that increase the efficiency of the use of these facilities, such as multiplexing and compression.
Camada Física
Interface Analógica (IA): pares de fios metálicos
1 par: transmissão física half-duplex
2 pares: transmissão física half-duplex ou full-duplex

24. The basic building block of any communications facility is the transmission line.
One of the basic choices facing a business user is the transmission medium. For use within the business premises, this choice is generally completely up to the business. For long-distance communications, the choice is generally but not always made by the long-distance carrier.
In either case, changes in technology are rapidly changing the mix of media used. The ever-increasing capacity of fiber optic channels is making channel capacity a virtually free resource. However, switching is now becoming the bottleneck. The growing use of wireless transmission, is a result of the trend toward universal personal telecommunications and universal access to communications.
Despite the growth in the capacity and the drop in cost of transmission facilities, transmission services remain the most costly component of a communications budget for most businesses. Thus, the manager needs to be aware of techniques that increase the efficiency of the use of these facilities, such as multiplexing and compression.
Camada Física
Largura de banda: dela depende a taxa de transmissão
Nyquist: C = 2B log2M (Obs: M = níveis de sinal)
Shannon: SNR = 10 log10 (sinal/ruído)
C = B log2 (1 + SNR)

25. The basic building block of any communications facility is the transmission line.
One of the basic choices facing a business user is the transmission medium. For use within the business premises, this choice is generally completely up to the business. For long-distance communications, the choice is generally but not always made by the long-distance carrier.
In either case, changes in technology are rapidly changing the mix of media used. The ever-increasing capacity of fiber optic channels is making channel capacity a virtually free resource. However, switching is now becoming the bottleneck. The growing use of wireless transmission, is a result of the trend toward universal personal telecommunications and universal access to communications.
Despite the growth in the capacity and the drop in cost of transmission facilities, transmission services remain the most costly component of a communications budget for most businesses. Thus, the manager needs to be aware of techniques that increase the efficiency of the use of these facilities, such as multiplexing and compression.
Camada Física
Modulação
Modificação de uma portadora para representar um sinal
Características modificáveis:
Amplitude, frequência ou fase
Necessário para transmissão analógica
Portadora é um sinal base com frequência apropriada para o meio de transmissão (i.e.: baixa atenuação)

26. The basic building block of any communications facility is the transmission line.
One of the basic choices facing a business user is the transmission medium. For use within the business premises, this choice is generally completely up to the business. For long-distance communications, the choice is generally but not always made by the long-distance carrier.
In either case, changes in technology are rapidly changing the mix of media used. The ever-increasing capacity of fiber optic channels is making channel capacity a virtually free resource. However, switching is now becoming the bottleneck. The growing use of wireless transmission, is a result of the trend toward universal personal telecommunications and universal access to communications.
Despite the growth in the capacity and the drop in cost of transmission facilities, transmission services remain the most costly component of a communications budget for most businesses. Thus, the manager needs to be aware of techniques that increase the efficiency of the use of these facilities, such as multiplexing and compression.
Camada Física
Modulação
ASK: amplitude
FSK: frequência
PSK: fase

27. The basic building block of any communications facility is the transmission line.
One of the basic choices facing a business user is the transmission medium. For use within the business premises, this choice is generally completely up to the business. For long-distance communications, the choice is generally but not always made by the long-distance carrier.
In either case, changes in technology are rapidly changing the mix of media used. The ever-increasing capacity of fiber optic channels is making channel capacity a virtually free resource. However, switching is now becoming the bottleneck. The growing use of wireless transmission, is a result of the trend toward universal personal telecommunications and universal access to communications.
Despite the growth in the capacity and the drop in cost of transmission facilities, transmission services remain the most costly component of a communications budget for most businesses. Thus, the manager needs to be aware of techniques that increase the efficiency of the use of these facilities, such as multiplexing and compression.
Camada Física
Codificação
Tradução da stream de bits para um código digital
Necessária para transmissão digital
Código resulta em um sinal com características para o meio de transmissão

28. The basic building block of any communications facility is the transmission line.
One of the basic choices facing a business user is the transmission medium. For use within the business premises, this choice is generally completely up to the business. For long-distance communications, the choice is generally but not always made by the long-distance carrier.
In either case, changes in technology are rapidly changing the mix of media used. The ever-increasing capacity of fiber optic channels is making channel capacity a virtually free resource. However, switching is now becoming the bottleneck. The growing use of wireless transmission, is a result of the trend toward universal personal telecommunications and universal access to communications.
Despite the growth in the capacity and the drop in cost of transmission facilities, transmission services remain the most costly component of a communications budget for most businesses. Thus, the manager needs to be aware of techniques that increase the efficiency of the use of these facilities, such as multiplexing and compression.
Camada Física
Codificação
Vários tipos de codificação