All posts by Azar
DOES UPLINK TIME ALIGNMENT REMAIN VALID FOR THE UE ALL THE TIME?
Once uplink time alignment has been achieved for the UE, as long as a UE keeps on carrying out uplink data transmission, time alignment will continue to take place for the UE. The continuous transmission can be used by the receiving cell site to estimate the uplink receive timing and can be used as a […]
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HOW IS UPLINK TRANSMIT-TIMING CONTROL HANDLED IN LTE?
Different UEs within a cell will experience different propagation delay to/from the cell site, depending on their exact position within the cell coverage area. If UEs set their transmit timing based only on the timing of the received downlink timing, their corresponding uplink transmissions will arrive at the cell site with potentially very different timing. […]
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WHAT UPLINK L1/L2 CONTROL SIGNALLING IS DEFINED FOR LTE?
In LTE, Uplink L1/L2 control signaling consists of one (or more) of the following pieces of information: Hybrid-ARQ acknowledgements related to reception of DL-SCH transport blocks. CQI (Channel-Quality Indicator) indicating the instantaneous downlink channel quality perceived by the terminal. CQI reports can be used by the network for downlink channel-dependent scheduling and rate control. LTE CQI reports indicate […]
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WHAT REFERENCE SIGNALS ARE DEFINED FOR LTE UPLINK TRANSMISSION?
There are two types of uplink reference signals in LTE: Reference signals for channel estimation to support coherent uplink transmission and Sounding reference signals. Reference signals for channel estimation As illustrated in Figure below, the uplink reference signals used for channel estimation are transmitted within the fourth block of each uplink slot and with an […]
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HOW IS LINK ADAPTATION USED IN LTE UPLINK?
Uplink link adaptation, i.e., selection of modulation and channel coding, is controlled by the network. The eNodeB measures the uplink channel quality and orders the UE to use a specific modulation and coding scheme (MCS) based on this. Other parameters may also be taken into account, such as UE power headroom, scheduled bandwidth, buffer content […]
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