MAKING CONNECTIONS EFFICIENT; TRANSMISSION ERRORS
- Multiplexing technique and it is application within the cellular device network
Multiplexing is the combination of several different signals and their transmission over a single transmission medium. For example, in telecommunications, several telephone calls may be carried using one wire. There are different types of multiplexing technologies used for example, frequency division multiplexing (FDM), time division multiplexing (TDM), code division multiplexing (CDM), Space division multiplexing among others.
Frequency division multiplexing, as the name suggests, involves transmitting data over a single medium by dividing the signals into different distinct frequencies. A good example is radio and television broadcasting whereby different stations use different frequencies.
Time division multiplexing involves allocating every signal a time slice on the transmission media. The result is, every signal is sent and received separately.
Space division multiplexing is used in wired communication channels. It implies different point-to-point wires for different signals. For example, an stereo audio cable, with one pair of wires for the left speaker and another for the right speaker.
- Compare and contrast how the problem of communication interference of noise and cross among others would manifest for analog data transmitted with an analog signal, for analog data transmitted with a digital signal, for digital data transmitted with an analog signal, and for digital data transmitted with a digital signal in addition to the impact on quality.
Noise is interference or distortion of data transmission resulting in receiving unwanted data that is, “noise”. Whereas crosstalk results when two or more cables transmitting data interfere with each other for example in the case of twisted pair cables. When analogue data is transmitted over an analogue signal, the data becomes very susceptible to noise and cross talk. However, the data is not greatly distorted.
On the other hand, if digital data is transmitted over an analog signal, the data becomes susceptible to interference, noise and cross talk and the distortion becomes great. There is also signal attenuation therefore resulting in an extra cost of setting up amplification stations.
Digital data can also be transmitted in digital signals such as the fiber optic cables. This technology goes a long way to prevent noise and cross talk since light cannot be affected y radio frequencies or electromagnetic fields.
- Compare and contrast parity check, checksum, and hamming code. Include both error detection and error correction considerations
A checksum or hash sum is a small piece of data extracted from a large chunk of data in order to detect errors that may have occurred during transmission or storage. The correctness of the data can be tested at any time by regenerating the checksum and comparing it with the current one. If the checksums match, the data is correct.
Hamming code is a set of error-correction codes that can be used to detect and correct bit errors that may have occurred when computer data is being transmitted or stored. Hamming codes can detect up to two-bit errors or correct one-bit errors without detection of uncorrected errors. The simple parity code, on the other hand, cannot correct errors. It can only detect an odd number of bits in an error.
Parity check is the simplest method of error detection. It involves addition of a bit to the end of a string of binary codes that show whether the number of bits in the string has a value that’s either odd or even. If the bits (including the parity bit) are incorrectly transmitted, the parity bit will be incorrect, thus indicating that an error occurred. This method is only used for detecting errors since it’s impossible to determine which bit has the error.
Therefore, in comparison, the best method to use is the hamming code which can not only detect but correct errors unlike the checksum and the parity check. The checksum method has its efficiency in detecting errors for a large chuck of data. The parity check can be used to check for errors especially during transmission. And the hamming code can be used to correct the errors as detected by the other two methods.
