Ntc362: Analog and Digital Comparison Paper

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Modems are required at both ends of a connection for 56k. When downloads are performed on a 56k modem, they cannot contain any analog to digital conversions. There would be too much noise on the line to complete the transmission. The modulation process for a 56k modem consists of the internet service provider sending a digital signal to the phone company. The digital signal at the phone company is then converted into a digital analog signal which is then relayed back to the customer. (Feibel, 2000)

ADSL

ADSL stands for Asymmetrical Digital Subscriber Line. Asymmetrical means unbalanced or one way. For our purpose it refers to modem sending data faster in one direction rather than in the direction receiving through a copper wire. Throughout time ADSL has been simply referred to as DSL which is the technology mostly used for getting high speed internet access. The line code used for ADSL interface is called the DMT code (discrete multi-tone) which was created in order to be compatible with the twisted-wire pair channel.

Asymmetrical Digital Subscriber Lines utilize existing copper-based and are capable enough to provide LAN access, on-demand video and internet access to its users. LAN also known as Local Area Network most commonly in homes and small businesses where dummy computers are hardwired or directly connected. Modulation in ADSL takes place by the use of Frequency Division Multiplexing (FDM). Frequency division multiplexing separates the frequency bands into upstream and downstream categories. Communication from the user to the telephone central office takes place within the upstream band. The downstream band is used for communication from the central office to the user. Splitters are used when making a ADSL connection. This filter separates the telephone and ADSL signals allowing for phone calls to be placed at the same time that data is being transferred through the line (Alturayef, 2007).

Wi-Fi

There are typically two primary radio transmission techniques. These are the 802.11 b and the 802.11 a and g. The 802.11 b uses the complementary coded keying also known as the (CCK). A special coding is used to process the bit stream and later modulated using the Quadrature Phase Shift Keying which is known as the (QPSK). The other system uses a 64-channel orthogonal frequency division multiplexing also referred to as (OFDM). Within this modulating system, the radio band is divided into multiple sub-channels where each channel sends a portion of the bits. The bit streams are encoded when transmitted using the Binary Phase Shift Keying known as (BPSK). Quadrature Phase Shift Keying also referred to as (QPSK) are another one of the systems used. Although some of the transmitted data is repetitive, the receiver does not need all of the sub-carriers to reconstruct the data. The 802.11 already includes an option for frequency hopping spread spectrum (FHSS) but in large that has been left behind and not too many organizations use that any longer.

In Adaptive Modulation, a WiFi uses a multiple forward error correction to optimize transmission and decrease the error possibilities. This means the transmitter automatically becomes more powerful, when radio signals losses power or interference becomes and obstacle.

SONET

SONET is the American National Standards Institute’s standard for synchronous data when dealing with optical media. It serves as a protocol to transmit speeds at an extremely high rate. Its speed ranges from base rate or OC-1, which provides a connection at 51.84 Mbps to OC-768, which holds a connection of 40 gbps.

T(X)

T(X) is a digital signal that is assigned to a carrier in hierarchy and is used to connect networks. T-1 is the first level category, holds a 1.54 mbps connection. T-2 is the 2nd level category and holds a 6.31 mbps speed. T-3 has the third level in hierarchy and it has a speed of 44 mbps. OC-x carriers replaced T-4 and T5 carriers.

In conclusion, there are so many benefits of using both analog and digital signals and transmissions via telecommunications. In today’s modern technology, telecommunication systems require large volumes of data ranging from voice, radio and television signals to be transmitted over long distances. This paper explained how analog signals are less accepting to noise and interruptions, use good bandwidth and easy to manipulate. However, when trying to convert a system from analog to digital, you may run into issues and even have to change transmitters and receivers. Digital signals are more accepting to noise and can be interrupted with the slightest presence of noise. These types of signals are better in handling standard receivers and transmitters unlike analog transmissions. So, is one better than the other?

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References

Alturayef, M. (2007). ADSL Technology. Retrieved from http://ecee.colorado.edu/~ecen4242/

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http://www.radio-electronics.com/info/rf-technology-design/quadrature-amplitude-modulation-qam

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