Spreading consists of 2 steps: Channelization operation, which transforms data symbols into chips Scrambling operation is applied to the spreading signal Spreading means increasing the bandwidth of the signal beyond the bandwidth normally required to accommodate the information. The spreading process in UTRAN consists of two separate operations: channelization and scrambling. The first operation is … Read more
How Transport Channel Work in LTE? A transport channel defines how and with what characteristics the information is transmitted. Inherited from the WCDMA, data on the transport channel is organized into “Transport Blocks”, TBs. A Transport block can be transmitted every TTI = 1 ms The “Transport Format”, TF, defines how the blocks can be … Read more
How Spreading & Dispreading in WCDMA-3G ? Traditional radio communication systems transmit data using the minimum bandwidth required to carry it as a narrowband signal. CDMA system mix their input data with a fast spreading sequence and transmit a wideband signal. The spreading sequence is independently regenerated at the receiver and mixed with the incoming … Read more
How Correlation works in WCDMA ? Correlation measures similarity between any two arbitrary signals. Identical and Orthogonal signals: Correlation is used to measure similarity of any two arbitrary signals. It is computed by multiplying the two signals and then summing (integrating) the result over a defined time windows. The two signals of figure (a) are … Read more
How Many Logical Channel in LTE ? The following control logical channels have been defined by the 3GPP: BCCH, Broadcast Control Channel, used for the transmission of system control information. A UE needs to decode it before requesting a connection. PCCH, Paging Control Channel, is a downlink channel that transfers paging information and system information … Read more
How WCDMA Interleaving ? Effect Interleaving is used to reduce the probability of consecutive bits error Longer interleaving periods have better data protection with more delay Channel coding works well against random errors, but it is quite vulnerable to bursts of errors, which are typical in mobile radio systems. The especially fast moving UE in … Read more
Effect Enhance the correlation among symbols so as to recover the signal when interference occurs Provides better error correction at receiver, but brings increment of the delay Channel Types No Coding Convolutional Coding (1/2, 1/3) Turbo Coding (1/3) UTRAN employs two FEC schemes: convolutional codes and turbo codes. The idea is to add redundancy … Read more
Block coding is used to detect if there are any uncorrected errors left after error correction. The cyclic redundancy check (CRC) is a common method of block coding. Adding the CRC bits is done before the channel encoding and they are checked after the channel decoding. During the transmission, there are many interferences and fading. … Read more
AMR (Adaptive Multi-Rate) Speech A integrated speech codec with 8 source rates The AMR bit rates can be controlled by the RAN depending on the system load and quality of the speech connections Video Phone Service H.324 is used for VP Service in CS domain Includes: video codec, speech codec, data protocols, multiplexing and etc. … Read more
Processing Procedure of WCDMA System Source coding can increase the transmitting efficiency. Channel coding can make the transmission more reliable. Spreading can increase the capability of overcoming interference. Through the modulation, the signals will transfer to radio signals from digital signals. Bit, Symbol, Chip Bit : data after source coding Symbol: data after channel coding … Read more