Telecommunication systems potx

Telecommunication systems Lecturer: M.Eng. P.T.A.Quang Quality of service and telecommunication impairments 1. Quality of service: voice, data, and image 2. The three basic impairments and how they affect the end-user 3. Level 4. Echo and singing Quality of service : voice, data, and image  SNR  Voice transmission  Data circuits  Video Signal-to-Noise ratio  Measure signal quality  S/N requirement (@ receivers):  Voice: 40 dB  Video (TV): 45 dB  Data: 15dB (depend on modulation type and specified error performance) N S SNR  Voice transmission Data circuits  BER : basic QoS parameter for data circuits.  CCITT/ITU-T recommends BER: 1x10 -6 for at least 80% of a month Ex: 1500-byte ethernet packets transmit through the cables have -BER: 5x10 -7 Determine the packet error rate? Video (television) CCIR TASO Impairments  Amplitude (or attenuation) distortion and Phase distortion  Noise Amplitude and phase distortion  Amplitude distortion:  Voice channel occupies the band from 300 to 3400 Hz  Some frequencies are attenuated more than others  Phase distortion  Velocity of propagation varies with frequency  Filter: increase toward band center and decrease toward band edge Amplitude and phase distortion [...]... Caused by:     Electrical coupling between transmission media, such as between wire pairs on a voice-frequency (VF) cable system and on digital (PCM) cable systems Poor control of frequency response Nonlinear performance in analog (FDM) multiplex systems Types:   Intelligible (4 words are intelligible to the listener from extraneous conversation(s) in a 7-second period) Unintelligible Level & Echo . Telecommunication systems Lecturer: M.Eng. P.T.A.Quang Quality of service and telecommunication impairments 1. Quality. and on digital (PCM) cable systems.  Poor control of frequency response  Nonlinear performance in analog (FDM) multiplex systems  Types:  Intelligible