KR100512354B1 - channel assignment for PAR decrease in base station of CDMA system - Google Patents

Abstract

The present invention enables the allocation of Walsh codes on a call channel with minimal effect on the PAR in the forward link in a CDMA system.

The channel allocation apparatus for PAR reduction in the base station of the CDMA system according to the present invention is characterized in that the peak channel on the forward link, the short PN code, and the open loop power control processing are performed so that the PAR of the multi-channel signal is minimized. And a Walsh code generating means for generating a Walsh code table with a digital gain value and assigning it to a call channel.

The present invention provides a base station capable of transmitting the same output to a low-capacity large power amplifier by minimizing the effect of the PAR to reduce the back off of the large power amplifier.

Description

Channel assignment for PAR decrease in base station of CDMA system {channel assignment for PAR decrease in base station of CDMA system}

The present invention relates to a base station of a code division multiple access (CDMA) system, in particular parameters such as digital channel gain, peak power, and short PN code offset to be assigned to a talk channel in the forward link. The present invention relates to a channel allocation apparatus for reducing PAR at a base station of a code division multiple access system, which can reduce a peak power of a channel by allocating a Walsh code on a traffic channel.

Code division multiple access (CDMA) systems based on the IS-95 standard have different asymmetric link structures on the forward and backward links.

1 is a diagram illustrating a forward and reverse channel structure of a CDMA system.

The forward (base station to terminal) channel is up to one pilot channel, one sync channel, one to seven paging channels, and multiple traffic channels at the same frequency. It consists of 64 channels. These channels are distinguished by different numbers of Walsh codes within the same frequency, and mobile stations use the orthogonal characteristics of Walsh codes to distinguish channels.

The reverse channel structure consists of a plurality of access channels, a plurality of talk channels, and access channels for call channels.

In such a CDMA system, the forward channel is spread by the Walsh code, but the reverse channel is spread by the Long code.

In the IS-95 CDMA system, Walsh codes are generated by the Hadamard matrix (64 x 64), and 64 Walsh codes are generated. The Walsh codes are orthogonal to each other, thereby minimizing interference between channels assigned to the Walsh codes. As a result, the division is made at the mobile station. The orthogonality between codes can be interpreted as meaning that the code does not interfere with each other if the starting point of each code is kept at exactly the same point in time.

The pilot channel is always assigned to Walsh code '0' and is spread modulated with the PN code without any information. Thus, the pilot channel becomes a short PN code itself, providing time and phase reference to the mobile station, and providing reference information (PN offset) for identifying the base station.

The sync channel is assigned to Walsh code '32' at 1.2 Kbps and repeatedly transmitted with specific information. The message transmitted here is common information corresponding to broadcasting rather than information corresponding to a specific mobile station. That is, information required for base station initial synchronization is given to the mobile station, and once the initial synchronization information is obtained through the synchronization channel, the mobile station no longer watches the synchronization channel and proceeds to the next call channel reception state.

The paging channel transmits specific information similar to the sync channel. Unlike synchronous channels, however, they transmit at a higher data rate of 4.8 Kbps or 9.6 Kbps, and are sequentially assigned Walsh codes '1' to '7', depending on the number of call channels used. The message on the calling channel consists of an overhead message for all mobile stations to receive the entire system configuration-related information, and a designated message for receiving specific mobile stations as information such as mobile station calls and responses to mobile station requests. do.

The call channel not only transmits the caller's voice and data, but also sends and receives signaling messages using empty frames during the call. The structure of the forward call channel is very similar to that of the call channel, but with different data rates for each stage and the addition of power control data. That is, the voice or data is mixed using a long code having the same starting point as a specific mobile station so that only a specific mobile station can receive the signal, and then covered by a specific Walsh code assigned to the specific mobile station, and then closed. Loop) is mixed with the power control bit and spread modulated by a short PN code, and then transmitted through a frequency upconversion, a power amplifier (PA), and an antenna.

The allocation of Walsh codes for these call channels is randomly assigned between Walsh codes '8' to '31' or Walsh '33' to '63' except for Walsh codes for pilot, synchronization and calling channels.

There are four channels used in the forward link (base station to mobile terminal): pilot channel, synchronous channel, paging channel, and traffic channel. The division of these channels is called Walsh Code in the forward direction.

2 is a diagram illustrating a forward link transmission path in a base station of a conventional CDMA system.

Referring to FIG. 2, a first multiplier 101 for multiplying long codes allocated to call channels and traffic channels 1 to N, respectively, and multiplying different Walsh codes to respective channels, respectively. A second multiplier 102, a third multiplier 103 for multiplying each control channel with a power control signal (PC), and a fourth multiplier for multiplying each channel by multiplying each channel by a short PN code; A multiplier 104, a digital-to-analog converter (DAC) 105 for converting the sum of the spread-modulated channel signal into an analog signal, and a mixer unit for up-modulating the analog-converted channel signal by a local oscillation frequency and outputting the same. 106, a power amplifier 107 for amplifying the output power of the mixer section, and a band pass filter 108 for filtering a necessary band from the output of the power amplifier section and radiating it through an antenna.

Here, the first to fourth multipliers 101 to 104 are modems, and the first multiplier 101 multiplies and outputs long codes respectively allocated to the call channel and the call channel, and the second multiplier 102. Is multiplied by the Walsh code as described above by each of the call and talk channels multiplied by the long code in the pilot channel, the synchronization channel, and the first multiplier 101. The third multiplier 103 multiplies each of the call channels multiplied by the Walsh code and outputs a power control signal. The fourth multiplier 104 multiplies each channel multiplied by the Walsh code by a short PN code to spread and output the QPSK. In this way, each channel maintains orthogonality between codes by Walsh codes assigned to channels on a code domain. Each channel given the orthogonality is QPSK spread modulated by a 1.2288 Mbps short PN code, and then the spread modulated channel signals are output.

The digital-to-analog converter 105 converts the channel sum signal into an analog signal and outputs the converted signal. The mixer 106 mixes with the local oscillator frequency (LO) in the mixer 106 and up-converts the frequency to be transmitted. After a large power amplification by the power amplifier (PA) 107, the band amplifier is transmitted to the mobile station through the antenna through the band pass filter 108.

As described above, in the CDMA system, a transmission signal is composed of a pilot channel, a synchronization channel, a call channel, and a call channel, and each channel is classified into covering by a Walsh code according to its use. There are 64 Walsh codes in the IS-95 system, and in the IS-2000 system, the subscriber capacity of the wireless section is increased and can be expanded to 256 by applying the Quasi-Orthogonal Functions (QOF).

However, a transmission signal of a CDMA system composed of multi-channel signals distinguished by Walsh covering shows high peak-to-average rate (PAR) characteristics and is end-to-end for amplification of multi-channel signals having high PAR characteristics. The amplifier must have the same backoff (power margin) as the PAR so that the signal can be amplified without distortion.

In addition, the Walsh code assignment assigned to the call channel affects the PAR of the multichannel signal, which leads to a termination amplifier transient design and the like.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problem. In the CDMA system, a base station of a CDMA system can reduce a PAR by allocating Walsh codes to a call channel on a forward link in consideration of PAR of a multi-channel signal. It is an object of the present invention to provide a channel allocation apparatus for PAR reduction.

An object of the present invention is to reduce the PAR at the base station of the CDMA system to reduce the PAR by assigning a Walsh code to the call channel on the forward link in consideration of the digital channel gain, short PN code, and the current PAR in the CDMA system. It is an object of the present invention to provide a channel allocation apparatus.

A channel allocation apparatus for reducing PAR at a base station of a CDMA system according to the present invention for achieving the above object,

In the forward link path of the base station of the CDMA system,

In order to minimize the PAR of the multi-channel signal, the Walsh code table is used as the peak power by the sum of each channel signal on the forward link, the short PN code to be assigned to the talk channel, and the digital gain value of the talk channel according to the open loop power control processing. And Walsh code generating means for generating and assigning the call channel.

According to an embodiment of the present invention, a channel allocation apparatus for reducing PAR at a base station of a CDMA system detects peak power by detecting an output analog signal of a digital analog converter, which receives a sum of respective talk channels output from a modem. A peak probability calculator that delivers a stochastic distribution, a short PN code generator that tells a short PN code to be assigned to the talk channel, a digital gain controller that delivers the digital gain of the talk channel according to off-loop power control processing; And a call processing processor for controlling the resource allocation and the resource recovery of the Walsh code, and using the resource allocation and resource recovery control signal of the Walsh code from the call processing processor and each parameter transmitted from each part. It characterized in that it comprises a Walsh code generator for generating a code to assign to the call channel do.

Hereinafter, with reference to the accompanying drawings as follows.

3 is a diagram illustrating a channel allocation apparatus for reducing PAR in a base station of a CDMA system according to the present invention.

Referring to FIG. 3, a peak probability calculator 209 that detects peak power by detecting an output analog signal of a digital analog converter 205 receiving a sum of respective talk channels, and delivers a probability distribution. ), A digital gain control unit 210 for transmitting the digital gain value of the call channel according to off-loop power control processing, a short PN code generator 211 for indicating a short PN code to be allocated to the call channel, and a Walsh code. A Walsh code for generating and assigning a Walsh code for call channel allocation by using a call processing processor 212 for controlling resource allocation and resource recovery of the call processor, and a control signal from the call processing processor and each parameter transmitted from each unit. It characterized in that it comprises a generator 213.

Referring to the accompanying drawings, a channel allocation apparatus for reducing PAR in a base station of a CDMA system according to the present invention as described above is as follows.

The Walsh code assigned to each channel in the CDMA system is generated by the base station and the mobile station, respectively, and the base station informs the Walsh code available as a traffic channel through the call channel to the mobile station.

The Walsh codes for the remaining channels except for the Walsh codes allocated to the call channels are standardized and fixed by IS-95, but the Walsh codes assigned to each call channel are randomly assigned to 55 code notes according to the connection environment. Losing code will be used.

The Walsh code assigned to each of these call channels affects the PAR of the multi-channel signal. These PARs are generated differently according to the composition of each channel signal according to the mixing of the multi-channel signals, but in the CDMA system, the size of the PAR due to the multi-channel signals is generated around 12 dB, which is very large. . Due to the PAR of the multi-channel signal, the terminating amplifier requires a back-off as large as PAR for distortion-free large power amplification, which requires an expensive large-capacity amplifier.

In order to solve this problem, the present invention can maintain the minimum PAR to reduce the required capacity of the termination power amplifier. For example, a 3dB reduction in PAR reduces the backoff of the termination amplifier by 3dB, which can reduce the required capacity of the termination amplifier by half.

To this end, a call channel allocation apparatus for reducing PAR will be described with reference to FIG. 3.

First, a traffic channel signal (Traffic 1 ch data to 4 ch data) input to the first to fourth multipliers 201 to 204 of a modem is a long code, a Walsh code, Multiplied by a power control signal (PC) and a short PN code (Short PN), each is output as a call channel signal of a QPSK spread-modulated modem, and these call channel signals are summed into one multi-channel signal and then converted into a digital analog converter. Here, the long code is a code used by the base station to distinguish each mobile station and spread a voice signal, and the Walsh code is an arbitrary Walsh code that is not used when a call is set, and a call price is released. In this case, the Walsh code used by the call becomes available, and the resource allocation and retrieval operation is performed while repeating the call setup and release. The short PN code is used to distinguish the base station, that is, the mobile station can easily synchronize. The digital-to-analog converter (DAC) 205 converts the input multi-channel signal into an analog signal, The mixer unit 206 multiplies the local oscillation frequency LO and converts the signal to an uplink frequency. The mixer unit 206 is multiplied by the power amplifier 207 and amplified by the power amplifier 207 to radiate the antenna through the band pass filter 208.

At this time, the peak probability calculator 209 detects the peak power by detecting the multi-channel signal output from the digital analog converter 205 and calculates the probability distribution to calculate the Walsh code generator 213. To pass.

The short PN code generator 211 generates and assigns a short PN code to be assigned to a communication channel (Traffic 1 to 4ch data) of the first to fourth multipliers 201 to 204. The Walsh code generator 213 informs the Walsh code generator 213 of a short PN code to be allocated to the talk channel. The digital gain controller 214 performs a digital gain value of the talk channel according to open loop power control processing. This is predicted and transmitted to the Walsh code generator 213.

Here, in the open loop power control scheme of the forward link, the base station predicts the forward loss based on the reception power of the terminal when the terminal (mobile station) is connected, and adjusts the initial digital gain of each talk channel based on the predicted value. The base station initially allocates a reference gain for each channel.

The call processing processor 212 controls the Walsh code generator 213 for resource allocation and retrieval of Walsh codes allocated to the call channel. That is, if the call channel is set, the Walsh code assignment is not controlled, and if the call channel is released, the Walsh code used by the call is recovered to the available state.

Then, the Walsh code generator 213 receives the control signal for the Walsh code allocation and release of the call processing processor 212 and the current PAR from the peak probability calculator 209. A Walsh code that can reduce the PAR is generated and assigned to each talk channel of the multipliers 201-204. To this end, the Walsh code generator 213 generates a Walsh code table having a minimum PAR by using the digital channel gain and the short PN code transmitted from the digital gain controller 210 and the short PN code generator 211. By using the generated Walsh code table, Walsh codes maintaining a minimum PAR are allocated to each call channel (traffic 1 ~ 4ch data) of multipliers 201 to 214 and released.

That is, the Walsh code generator 213 calculates the peak rate to be calculated at the next output of the digital analog change unit 205 in consideration of the digital channel gain and the short PN code by the open loop power control of the call channel to which each code is assigned. We will assign Walsh codes so that the probability of distribution is kept to a minimum PAR.

In other words, the call channel on the forward link at the base station is digitally connected through Open Loop Power Control when the initial call is set up for a mobile station far from the base station for the same quality of service regardless of the position of the mobile station. The channel gain is higher and the talk channel with high digital channel gain has a greater impact on the PAR of the multichannel signal according to the Walsh code assignment.

At this time, the Walsh code generator 213 generates and manages a Walsh code table having a minimum PAR by monitoring digital channel gain parameters, short PN codes, and peak power distribution probabilities of multi-channel signals in each case. The multiplier allocates and releases Walsh codes for each talk channel.

As a result, the PAR of the multichannel signal can be reduced, and the reduced PAR can reduce the required backoff of the end-to-end power amplifier of the base station, thereby enabling the use of a low cost low capacity amplifier.

As described above, according to the channel allocation apparatus for reducing the PAR at the base station of the CDMA system according to the present invention, the PAR of the multi-channel signal can be reduced, and the reduced PAR reduces the required backoff of the end-to-power amplifier of the base station. The low cost enables the use of low-cost, low-capacity amplifiers, which contributes to base station cost reduction and size reduction.

1 is a forward and reverse channel structure of a CDMA system.

2 is a diagram illustrating a transmission path of a base station forward link of a conventional CDMA system.

3 is a block diagram illustrating a channel allocation apparatus for reducing PAR in a base station according to the present invention.

<Description of the symbols for the main parts of the drawings>

201,202,203,204 ... Multiplier 205 ... Digital-Analog Converter

206 Mixer 207 Power Amplifier

208 Band pass filter 209 Peak probability calculation unit

210 Digital gain control 211 Short PN code generator

Call processing processor ...

Claims (2)

delete In the forward link path of the base station of the CDMA system, A modem having a multiplier for multiplying a multi-call channel by a long code, a Walsh code, a power control, and a short PN code, respectively, and mixing them into one multi-channel signal; A digital analog converter for converting a multi-channel signal output from the modem into an analog signal; A mixer unit for up-converting and outputting the analog-converted multi-channel signal; A power amplifier for power amplifying the up-converted multi-channel signal; A peak probability calculator which detects the analog-converted multi-channel signal, detects current peak power, and transmits a probability distribution (PAR); A short PN code generator for assigning a short PN code to each call channel and indicating a short PN code assigned to each call channel; A digital gain control unit for transmitting the digital gain value of the call channel according to the open loop power control processing; A call processing processor for controlling resource allocation and resource recovery of Walsh codes to be allocated to each call channel according to call establishment and release; Receiving the Walsh code resource allocation and resource recovery control signal, the probabilistic distribution value of the current peak power of the multi-channel signal, the short PN code allocated to the communication channel, and the digital gain value of the communication channel from the respective units. Generate and manage a Walsh code table that maintains a PAR at which the probabilistic distribution value of the next peak power output from the analog converter is minimized, and assign a Walsh code generated from the Walsh code table to each talk channel of the multiplier; And a Walsh code generator for releasing the channel allocation apparatus for reducing the PAR at the base station of the CDMA system.