Constellation in LTE In LTE (Long-Term Evolution), the term “constellation” typically refers to the modulation scheme used for transmitting data over the air interface. LTE uses Quadrature Amplitude Modulation (QAM) to encode multiple bits into a single symbol. The constellation diagram visually represents how the amplitude and phase of the modulated signals correspond to specific … 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
Message Transmission Mode MS measures the frame quality and informs the base station to the result i.e. whether it is in the threshold or periodical mode. Base station determines whether to change the forward transmitting power or not. In IS-95 system, the forward power control is slow but in CDMA2000 system it is fast. Forward … Read more
In an actual application, the system implements the modulation in this way: as shown above, I and Q channel sequences in the figure represent two channels of cyclic PN short code sequences. The cyclic period of each channel of PN short codes is 215. For different sectors, there are different starting locations of I … Read more
The 3G LTE uses 3 Quadrature Amplitude Modulations (QAMs) depending on the radio quality. QAM uses both the amplitude and the phase. LTE devices use QPSK, 16QAM and 64QAM to modulate data and control information. The eNodeB supports all of these modulation techniques for the downlink direction. However, 64QAM is optional in the uplink direction. … Read more
A data-modulation scheme defines how the data bits are mixed with the carrier signal, which is always a sine wave. There are three basic ways to modulate a carrier signal in a digital sense: amplitude shift keying (ASK), frequency shift keying (FSK), and phase shift keying (PSK). In ASK the amplitude of the carrier signal … Read more
Transmitting: The process is similar to that of BS. The frequency offset is pre-corrected. The Ranging and BW Request are generated at the physical layer and a code is selected according to the indication at the MAC layer. After the modulation, they are mapped to competitive slots selected at the MAC layer. Later, they are … Read more
Transmitting: After being processed at the MAC layer, the downlink data is sent to the physical layer inthe format of MAC PDU. The MAC PDU arranges the data block size according to the allocation results of radio resources at the MAC layer. After the data packets are processed through the channel coding, modulation, and IFFT … Read more
Reverse power control Open loop power control Closed loop power control Inner loop power control: 800 Hz Outer loop power control Forward power control Message transmission mode: threshold transmission periodic transmission Closed loop power control Reverse open loop power control means that based on the detected signals from a base station, a mobile station … Read more
The long code is a PN sequence with period of 242-1chips The functions of a long code: Scramble the forward CDMA channel Control the insertion of power control bit Spread the information on the reverse CDMA channel to identify the mobile stations In a reverse direction, different long codes are used for the information … Read more