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T Carriers and Multiplexing
Transcript of T Carriers and Multiplexing
Transmission voltages and DC components
Unipolar (UP)- involves the transmission of only a single nonzero voltage level
Bipolar(BP)- two nonzero voltages are involved.
Digital Carrier Line Encoding
Error Detection- with UPNRZ, BPNRZ, UPRZ AND BPRZ encoding, there is no way to determine if the received data have errors. However, with BPRZ-AMI encoding, an error in any bit will cause a bipolar Violation.
Nonreturn to zero (NRZ)- binary pulse is maintained for the entire bit time
Return to Zero (RZ)- active time of the binary pulse is less than 100% of the bit time.
Transmission medium- may be metallic wire pair, a coaxial cable, a PCS mobile telephone, a terrestrial microwave radio system, or an optical fiber cable.
Phase-division multiplexing(PDM)- two data channels modulated the same carrier frequency that has been 90◦ in phase.
involves converting standard logic levels(TTL, CMOS, etc) to form more suitable to telephone line transmission.
Space-division multiplexing(SDM)- unsophisticated form of multiplexing that simply constitute propagating signals from different source on different cables that are contained within the same trench.
1. Transmission voltages and DC components
2. Duty Cycle
3. Bandwidth considerations
4. Clock and framing bit recovery
5. Error detection
6. Ease of detection and decoding
Multiplexing- the transmission of information(in any form) from one or more source to one or more destination over the same transmission medium(facility).
Bandwidth Requirements- to determine the minimum bandwidth required to propagate a line-encoded digital signal, you must determine the highest fundamental frequency associated with the signal. The highest fundamental frequency is determined from the worst-case (fastest transition) binary bit sequence
Time division Multiplexing (TDM)- transmission from multiple sources occur on the same facility but not at the same time.
T1 Digital Carrier- a communication system that uses digital pulse rather than analog signals to encode information.
Super TDM Format- 8 kbps designating rate used with the early digital channel banks was excessive for signaling on standard telephone voice circuit.
Extended Superframe Format- consist of 24 193-bit frames totaling 4632 bits, of which 24 are framing bits.
Fractional T Carriers Service- it emerged because standard T1 carriers provide a higher capacity than most user require.Fractional T1 distribute the channels in standard T1 system among more than one user, allowing several subcribers is share one T1 line.
Clock and Framing Recovery- to recover and maintain clock and framing bit synchronization from the received data, there must be sufficient transitions in the data waveform.(BPRZ-AMI encoding provides sufficient transition to ensure clock synchronization)
Digital Biphase- (sometimes called Manchester code or diphase)- a popular type of line encoding that produces a strong timing component for clock recovery and does not cause dc wandering.
• Biphase M- used to encode SMPTE(Society of Motion Picture and Television Engineers) time code data for recording on videotapes.
• Biphase L(manchester code)-specified by IEEE standard 802.3 for Ethernet local networks
• Miller Code- forms of delay-modulated codes where logic1 condition produces a transition in the middle of the clock pulse, and a logic 0 produces no transition at the end of the clock intervals unless followed by another logic 0
Dicode- multilevel binary code that use more than two voltage levels to represent the data.
T carrier system- used for the transmission of PCM-encoded time division multiplexed digital signals
Utilize special line-encoded signals and metallic cable that have been conditioned to meet relatively high bandwidths required for high speed digital tansmission.
T1 carrier system- designed to combined PCM and TDM techniques for short-haul transmission of 24 64-kbps channels with each channel capable of carrying digitally encoded voice band telephone signals or data.
T2 carrier system- T2 carriers time division multiplex 96 64-kbps voice or data channels into single 6.312-Mbps data signal for transmission over twisted-pair copper wire up to 500 miles over a special LOCAP (low capacity) metallic cable.
T3 carrier system- T3 carriers time-division multiplex 672 64-kbps voice or data channels for transmission over a single 3A-RDS coaxial cable. The transmission bit rate for T3 signals is 44.736Mbps
T4M Carrier system- T4M carriers time-division Multiples 4032 64-kbps voice or data channels for transmission over a single T4M coaxial cable up to 500 miles. The transmission rate ias sufficiently high that substitute patterns are impractical.
T5 Carrier System- T5 carrier time division multiplex 8064 64-kbps voice or data channels and transmit them at a 506.16 Mbps rate over a single coaxial cable.
Frequency-Division Multiplexing (FDM)- multiple sources that originally occupied the same frequency spectrum are each converted to a different frequency band and transmitted simultaneously over a single transmission medium, which can be physical cable or the earth’s atmosphere.
Wavelenght-Divison Multiplexing- as network mechanism for telecommunications routing, switching, and selection based on wavelength . it vastly increases the bandwidth capacity of optical transmission media
WDM vs FDM- the basic principle of WDM is essentially the same as FDM, where several signals are transmitted using different carriers, occupying nonoverlapping bands of a frequency or wavelength spectrum.