Mobile Communication: Physical Layer and Channel Measurement, Slides of Mobile Communication Systems

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MOBILE COMMUNICATION PHYSICAL LAYER

TODAY’S LECTURE

 Channel Measurement

 IDE Mode  During Connection  Services

 Speech coding, source coding

IDLE MODE

 629 values are measured for selection of highest RXLEVEL  Frequency with highest RXLEVEL is selected, which is BCCH most likely  FB (Frequency Burst on FCCH) is searched and MS attempts to synchronize  Task becomes easy with stored list of BCCH channels

DURING CONNECTION

 Parameters measured

 RXLEV

 RXQUAL

 Channels

 SACCH

 SDACCH

 Measurements are made during SACCH interval and are sent on SACCH

 Hand off measurements

 RXLEV and RXQUAL of 6 neighboring cells are also reported  This information is gathered during idle slots  MS has to synchronize with these cells to find their IDs, these IDs are also sent with report  Synchronization steps : Find BCCHFCCH Next frame would be SCH, use SCH

TRANSMISSION POWER CONTROL

 MS and BSS both follow 16 step power control table

 A threshold for each side is defined

 Each power step is of 2 dbm

 Measurements are sent to network, orders are received from BSS

CHANNEL CODING, SOURCE AND SPEECH CODING,

 sender

 Sample speech, compress  Add error correction codes, interleaving codes  Encrypt  Form burst  Modulate

 Receiver

 Inverse the operations

SPEECH PROCESSING

 VAD

 Voice Activity Detectors  Differentiates between speech data and pauses

 DTX mode

 Discontinue transmission

 Comfort noise

 Synthetic background noise

 SID

 Silence descriptor is measured and transmitted at the source  Based on background acoustics and noise