Tag Archives: qpsk

Specifications of WCDMA

Channel Bandwidth  5 MHz Duplex Mode  FDD and TDD Downlink RF Channel Structure  Direct Spread (DS) Chip Rate  3.84 Mcps Frame Length  10 ms Spreading Modulation  Balanced QPSK (downlink) Dual-channel

Types of Power Control in CDMA

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

Long Code & Short Code In CDMA

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

Interleaving in CDMA

It can be seen from the figure that the data are read row by row into an interleaver at the transmit end,read column by column out (this process is called

WCDMA Modulation

Different modulation methods corresponding to different transmitting abilities in air interface. R99/R4: QPSK HSDPA: QPSK or 16QAM The UTRAN air interface uses QPSK modulation in the downlink, although HSDPA may

Soft/Softer Handoff in CDMA

Multi-path combination in the BSC during soft handoffMulti-path combination in the BTS during softer handoffs       Soft handoff means that during the handoff of a mobile station at the coverage

Forward Power Control in CDMA

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 

Scrambling (M) sequence in CDMA

  Two points are important here:  Maximum number of shift register (N)  Mask The period of out put sequence is 2N-1 bits Only sequence offset is change when the mask

Constellation in LTE

The QPSK is the most robust modulation. It can be represented by a constellation: The radius, R, represents the amplitude. The angle, ?, represents the phase. There are 1 amplitude

How Modulation-QPSK in CDMA ?

     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

How to LTE Radio Air Interface?

The state-of-the-art design of the LTE air interface is characterised by OFDMA (DL) and SC-FDMA (UL) together with MIMO. The downlink modulation is based on OFDMA (Orthogonal Frequency Division Multiple