Key Technologies of CDMA2000-1X

1. Forward Fast power control technology

CDMA2000 adopts fast power control method. The method is that the mobile station measure receives the eb/nt of the service channel, and compares with the threshold value, according to the comparison result, sends to the base station to adjust the base station transmit power the instruction, the power control rate can reach 800b/s.

Due to the use of fast power control, can reduce the base station transmission power, reduce the total interference level, thereby reducing the mobile station signal-to-noise ratio requirements, and eventually increase the system capacity.

2. Forward Fast Paging channel technology

This technology has two uses:

(1) Selection of paging or sleep status

Because the base station uses the fast paging channel to send the instruction to the mobile station, decides that the mobile station is in the listening paging channel or is in the low power state sleep state, so the mobile station does not need to continuously monitor the forward paging channel for a long time, can reduce activates the mobile station activation time and saves the mobile

(2) Configuration change

Through the forward fast paging channel, the base station sends the system parameter message in the last few minutes to the mobile station, which makes the mobile station deal with the new message accordingly.

3. Forward Link transmit Diversity technology

CDMA2000-1X adopts direct spread spectrum transmit diversity technology, it has two kinds of ways:

(1) A kind of orthogonal transmit diversity method

The method is to separate the data streams and then use different orthogonal Walsh codes to spread the two data streams, and launch them through the high two transmitting antennas.

(2) The other is the space-time extended diversity method

Using a space of two separate antennas to transmit the interleaved data, the same original Walsh code channel is used.

The use of forward link emission diversity technology can reduce transmission power, anti Rayleigh fading, increase system capacity.

4, Reverse coherent demodulation

The base station uses the reverse guide frequency channel to emit the spread spectrum signal to capture the mobile station's launch, then uses the comb (Rake) receiver to realize the coherent demodulation, and compared with the IS-95 demodulation, it improves the reverse link performance, reduces the transmitting power of the mobile station and improves the system capacity. (Computer science)

5, continuous reverse air interface waveform

In the reverse link, the data adopts the continuous pilot frequency to make the data waveform continuous on the channel, this measure can reduce the external electromagnetic interference, improve the search performance, support the forward power fast control and the reverse power control continuous monitoring.

6, the use of turbo code

Turbo code has excellent error-correcting performance, suitable for high speed data transmission service with low decoding delay, and can reduce the requirement of transmitting power and increase system capacity, in cdma2000-1x, the turbo code is only used in forward supplementary channel and reverse supplementary channel.

The Turbo encoder consists of two RSC encoders (one type of convolutional code), a interleaving device, and a deletion device. Each RSC has two-way output, two output after the deletion of multiplexing to form a turbo code.

The Turbo decoder is composed of two soft input, soft output decoder, interleaving device and interleaving device, and decoding output is obtained after alternating decoding of input signals, multiple-wheel decoding of soft output and over 0 judgments.

7. Flexible frame length

Unlike IS-95, CDMA2000-1X supports a variety of frame lengths for 5ms, 10ms, 20ms, 40ms, 80ms, and 160ms, and different types of channels support different frame lengths respectively. The forward basic channel, the forward dedicated control channel, the reverse basic channel, the reverse special control channel adopts 5ms or 20ms frame, the forward supplementary channel, the reverse supplementary channel adopts 20ms, 40ms or 80ms frame, and the voice channel adopts 20ms frame.

The shorter frame can reduce the delay, but the demodulation performance is lower, and the longer frame can reduce the transmission power requirement.

8, enhance the media access control function

The media access control sub layer controls a variety of service access physical layer to ensure the realization of multimedia. It realizes voice, packet data and circuit data service, simultaneously processing, providing sending, reusing and QoS control, providing access program. Compared with IS-95, it can meet the requirements of more broadband and more business.