JPH06292251A - Receiver for orthogonal processing spread spectrum signal from plural mobile stations - Google Patents

Abstract

PURPOSE:To allow a base station to receive and demodulate a PN signal received from an optional mobile station while reducing interference of a reception signal from the mobile station closest to the base station in a state that not receiving power control controlling less transmitter output as a mobile station is closer to the base station with respect to the receiver for a PN orthogonal coding spread spectrum signal of a reverse link from plural mobile stations to the base station. CONSTITUTION:All timings obtained by multiplying generated PN orthogonal codes c1-cn for inverse spread demodulation with reception signals s1-sn when a receiver of a base station makes transmission without subject to control of output power of each transmitter from plural (n-sets) mobile stations M1-Mn are set to be those delaying a predetermined time (DELTA) from a point of time (t) of a transmitter of a base station B starting simultaneous transmission to the plural (n-sets) mobile stations M1-Mn. Thus, interference on reception signals s2-sn from mobile stations M2-Mn designated optionally by the base station from a reception signal s2 with a highest level from the mobile station M1 closest to the base station B is reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spread spectrum communication system intended to improve the efficiency of use of a wireless line in wireless communication such as digital mobile communication, and particularly to control from a base station of a cell which is a fixed communication area. A base station that receives a spread signal from each mobile station at a so-called reverse link base station that receives and transmits to each base station. The present invention relates to a receiver of an orthogonalized spread spectrum signal of a base station, which can receive and demodulate by reducing interference of a radio spread spectrum signal from a mobile station located near the station.

[0002]

2. Description of the Related Art A general configuration of a transmitter / receiver of a conventional spread spectrum communication system is shown in FIG. The transmitter uses the output b (t) obtained by code-modulating the information a (t) in the information modulator as one input of the multiplier, which is the spread modulator, and the other input c (t).
_Is the output of the transmitter's time-based clock oscillator f _clock
The two inputs b (t) and c (t) are multiplied by the quadrature phase as the output of the PN code generator having the pseudo noise characteristic which is driven and output by. Then, the multiplication output b (t) xc (t) = s (t), the spread spectrum modulated PN orthogonal code signal is converted by the frequency conversion unit into a frequency spread PN orthogonal signal of a predetermined radio frequency. Then, after the transmission power is set to a predetermined value by the power amplification unit, the wireless frequency spread signal (P
N orthogonal signals). The receiver receives the wireless PN quadrature signal emitted from the transmitter, amplifies it in the RF amplification section, and converts it into the same frequency spread PN orthogonal signal s (t) as in the transmission side in the frequency conversion section. This frequency-converted reception frequency-spread PN orthogonal signal s (t) is input to a spread demodulation unit for despreading, and is synchronized with the reception-input PN orthogonal signal s (t) to generate a PN orthogonal code. It is input to the synchronization unit 10 which outputs the despreading spread demodulation unit that generates and multiplies c (t). Synchronizer 10
Is composed of a time discrimination control circuit 11 and a PN code generator 12, and the time discrimination control circuit 11 refers to FIG.
Timing of N signal s (t) and output c (t) of PN code generator 12
Of the input PN signal s (t) (there is almost no correlation with the shifted PN signal even if the phase is 1 bit Δ), and a value larger than the dotted line is obtained. As shown in (b), the time t ₀ , which finally reaches the maximum value, is pushed into the range and the input signal is advanced by 1/2 bit and the input signal is delayed, and they are obtained by adding them in opposite phases. (C) The time discriminator characteristic is calculated as the center point t ₀ of the S-shaped characteristic with respect to time t. And this time t ₀ at the center of the S-shaped characteristic of the discriminator
The output clock f _clock from the clock oscillator of
By driving the code generator 12, a PN orthogonal code c (t) synchronized with the reception input s (t) is generated and sent to the despreading spread demodulation unit. FIG. 6 shows a detailed circuit of the synchronizing unit 10 of the PN quadrature signal receiver. In the detailed circuit of the synchronization section of FIG.
The time discriminator 11 for the reception input s (t) [P ^1/2 S _PN (t−τ _S ) + n (t)] has two multipliers X surrounded by a dotted line and one adder + And the clock oscillator is a VCC whose control voltage is an integrated output V obtained by integrating the error ε (t) of the output of the time discriminator by a loop filter F (p), and the despreading PN code generator 12 for
Is an n-stage feedback shift register, and the output c (t) of the PN code generator 12 is the n-th stage output AS _PN (t−Δ−
τ _S ) and the output of the (n−2) th stage AS _PN (t + Δ−τ _S ).

The conventional example shown in FIG. 7 is similar to the conventional example shown in FIGS.
Connect the transmitter and receiver of the Quttle spread communication system to mobile
When applied to mobile stations and base stations in the
Of the radio frequency transmitted by each of the n mobile stations in the
A so-called river for receiving and demodulating a transmission wave of a modulated PN orthogonal code
The structure of the receiver of the base station of Slink is shown. 7 conventional
The receiver of the base station is a plurality of mobile stations M (not shown)._iEach of
Information sent from each_iOutput b obtained by code-modulating (t)_ito (t)_,
PN orthogonal code driven by reference clock of base station transmitter
Generator output c_ifrequency spread by multiplying (t)_,Sent
Wireless PN orthogonal signal s₁~ S_nIs received by antenna A,
The frequency conversion unit converts the frequency, and the spreading demodulation unit despreads.
Source information in the information demodulator a_iwhen demodulating (t) it
The above-mentioned time discrimination control circuit 11_iAnd PN * orthogonal code generation
Bowl 12_iEach of the n synchronization units 10 consisting of_i, Independently of each other
Mobile station M_iReceived signal from s₁~ S_nFor each received signal s
₁~ S_nEach time t at which the autocorrelation property of_Ten~ T_n0
PN * orthogonal code generator 12 synchronized with_iOccurred and sent out
PN orthogonal code c (t)_iIs multiplied by to perform spread demodulation for despreading.
It was However, the spread spectrum PN orthogonal using this conventional synchronization unit
In the signal receiver, a plurality of n users (mobile station M₁
~ M_n), Each mobile station M₁~ M_nfrom
Received signal s₁~ S_nFor each synchronization unit 10_iPN for despreading
Quadrature signal c_iTiming t to generate and multiply (t)_Ten~ T_n0
Each mobile station M₁~ M_nSignal modulation method from
And uses an orthogonal code modulation method that is strong against the interference of signals from other stations.
However, as a result, mobile station M₁~ M_nEach received signal from s₁
~ S_nInterference remains between. Mobile station M specified by base station B_nBut
If it is located far from the base station B, its received signal s_n
When t is received_n0PN orthogonal code signal c_ngenerate (t)
Its received signal s_nTo perform despreading demodulation by multiplying
Ming is a mobile station M located near base station B.₁, M₂─
Received signal s₁, s₂Greater than the demodulation timing for
Off the designated mobile station M_nReceived signal from s_nAgainst
Other mobile station M₁~ M_n-1Received signal from s₁~ S_n-1Dried
The amount of communication will increase. To prevent this, the base station
Mobile station M near B₁, M₂--Transmission power attenuation with distance
Less received signal s ₁, s₂Because the level of ─ will increase,
Mobile station M near base station B₁, M₂─ The output power of the transmitter
To do so-called power control to reduce power
From all mobile stations M in the cell₁~ M_nReceived signal from s₁
~ S_nFrom the base station B
Each mobile station M₁~ M_nControl for each mobile station becomes complicated.
The circuit configuration was complicated.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to perform so-called power control on a transmission signal obtained by frequency-spreading station information to each of a plurality of n mobile stations in the cell by using a random PN orthogonal code. When transmitted by a transmitter with a simple structure without any need, the interference of the highest level received signal from the mobile station closest to the base station with respect to the received signal from the mobile station arbitrarily specified by the base station An object of the present invention is to realize a receiver of orthogonalized spread spectrum signals from a plurality of mobile stations, which eliminates the problem of large amount.

[0005]

[Means for Solving the Problems] A Book for Achieving this Purpose
The basic idea of the invention is to receive control from a base station within a certain cell.
A transmission signal transmitted to each of the plurality of n mobile stations to the base station
Is a spread spectrum signal using each PN orthogonal code.
Received by the base station, despreading and demodulating the transmitted signal of
The method synchronizes each received signal with a PN orthogonal code for despreading.
Synchronous spread spectrum reception system that generates and multiplies each received signal
Signal from any desired mobile station of the base station, if
Is the amount of interference received from signals received from other than the desired mobile station
Can be almost ignored even if there is a certain level difference in the received signal.
And the mobile station closest to the base station (M₁)from
Highest level received signal (s₁) But its autocorrelation property is
Maximum reception time (t_Ten) Signal from the desired mobile station
PN orthogonal code for despreading is generated and each received signal is multiplied
Then, paying attention to the fact that there is almost no interference, the closest to the base station.
Highest level received signal interference from mobile station
To avoid. The basic configuration of the present invention is shown in FIG.
Referring to the principle diagram corresponding to claim 1, from the base station (B)
Under control, a plurality of mobile stations (M₁~ M_n) of
Each information (a1 ~ a) that each transmits to its base station B_n) Respectively
Code-modulate each output (b1-b_n) To each random PN
Orthogonal code (c1 ~ c_n), Spread modulation, and spread spectrum PN directly
Interchange signal (s1 ~ s_n).
Each received signal (s₁~ S_n) For despreading
Each PN orthogonal code (c1 to c_n) Is generated and multiplied to perform spread demodulation.
Orthogonal code signal (b₁~ B_n) To each of the plurality n of mobile stations
Information (a1 ~ a_n Orthogonalization frequency from multiple mobile stations
In the receiver of the spread spectrum signal, the n mobile stations (M
1 ~ M_n) From each received signal (s₁~ S_n) To each P for despreading
N orthogonal codes (c1 to c_n) To generate and multiply
However, the base station transmitter transmits multiple n mobile stations (M₁~
 M_nOf the mobile stations (M₁) From
Receive the return signal of the received signal (s₁) Has the highest autocorrelation
Time to become large (t_Ten), The base station transmitter is
Several n mobile stations (M₁~ M_n) From the time you start sending
Fixed timing (t1 ~ t) delayed by a fixed time (Δ)
_n), The mobile station arbitrarily specified by the base station
(M₂~ M_n) Received signal from (s ₂~ S_n) Is the base station (B)
Closest mobile station (M₁Highest level reception from
Signal (s₁).
It Or, referring to the principle diagram corresponding to claim 2 of FIG. 2,
The receiver of the base station B has a plurality of n mobile stations (M1 to M)._n) From
Each receiver when transmitting without output power control of each transmitter of
Signal (s₁~ S_n) For each PN orthogonal code (c1
~ C_n) Is generated and multiplied, the timing for
Mobile station (M1 ~ M_nOf the mobile stations closest to the base station (B)
(M₁) Received signal (s₁) Is received (t_Ten)
, Each mobile station (M1 ~ M_n) Original reception time (t_Ten~ T
_n0) Each variable timing advanced by a certain time (Δ)
(t1 ~ t_n), The distance closest to the base station (B)
Remote mobile station (M₁) Other than mobile stations (M₂~ M_n) Is the closest
Mobile station (M₁) Received signal (s₁Interference from
Configure to reduce the amount.

[0006]

In the configuration of FIG. 1 of claim 1 of the present invention, the base station B
Multiple n synchronization units 10 of the receiver_iOf the base station B
N mobile stations M in a fixed radius cell₁~ M_nof
Mobile station M closest to base station B₁Most from
High level received signal S ₁The maximum autocorrelation property of
Time t_TenHowever, the base station B has multiple n mobile stations M₁
~ M_nIs a fixed time Δ from the time t when transmission is started simultaneously
Delayed t_Ten= t + Δ is a fixed time point, and the same t +
Time point Δ₁~ T_nWith mobile station M₁Received signal from S₁Including
Total received signal s₁~ S_nEach PN orthogonal code c for despreading₁~ C
_nAnd mobile station M₁~ M_nEach received signal from s₁~ S_nRiding on
The closest mobile station M₁Highest level receiving from
Signal s₁Is the original reception time t_TenSpread demodulated by
Mobile station M₂~ M_nReceived signal from s₂~ S_nTo the demodulation output of
Is the mobile station M due to its orthogonality.₁Received signal from S₁From
The interference amount of is almost eliminated.

In the configuration of FIG. 2 according to claim 2 of the present invention, the timing of each output of each time discrimination control circuit 11 _i of each of the plurality n of synchronization units 10 _i of the receiver is set to the distance of the distance closest to the base station B. It becomes closer as the reception time t ₁₀ of the received signal s ₁ from the mobile station M _1, the original of each reception time of the received signal s ₂ ~s _n from another mobile station M ₂ ~M _n t ₂₀ ~t _n0 The closest mobile station M ₁
Since the variable timings t ₁ to t _n are advanced by a fixed time (Δ) so as to be close to the reception time t ₁₀ of the reception signal s ₁ from, the reception signals from other mobile stations M ₂ to M _n s ₂ to the demodulation output of ~s _n is interference from the received signals S ₁ from the mobile station M ₁ of outermost close distance almost eliminated.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The principle diagram of the present invention in FIG. 1 is shown as it is, and shows the configuration of a receiver for orthogonalized spread spectrum signals from a plurality of mobile stations according to an embodiment corresponding to claim 1 of the present invention. The receiver of the base station B of a micro cell with a radius of about 100 m in a cell of a constant radius has the shortest distance from the base station B among a plurality of n mobile stations M ₁ to M _n in the cell. Therefore _, for example, the original reception in which the autocorrelation characteristic of the reception signal s ₁ determined by the time discrimination control circuit 11 ₁ of the synchronization unit 10 ₁ for demodulating the reception signal s ₁ of the highest level from the mobile station M ₁ becomes the maximum value Time point t ₁₀ (determined by the sum of the signal processing time at the mobile station M ₁ and the delay due to the transmission distance to the base station B) At fixed time points t ₁ to t _n , each PN orthogonal code c ₁ to for despreading It raises the c _n to the spread demodulation despreading by multiplying each received signal s ₁ ~ s _n from the mobile stations M ₁ ~ M _n. Then, the received signal from the mobile station M _n arbitrarily designated by the base station B
For s _n , received signals S ₁ ~ from other mobile stations M ₁ ~ M _n-1
The interference of S _n-1 is reduced, especially the interference of the received signal s ₁ from the mobile station M ₁ closest to the base station B ₁ . The method of FIG. 1 is effective when the cell radius is sufficiently smaller than the transmission rate (chip rate) of the spread code. The cell radius being sufficiently smaller than the chip rate means that the SIR (signal-to-interference ratio) of the received signal does not deteriorate even if the timing of synchronization for demodulating the received signal deviates somewhat. .

The principle diagram of FIG. 2 shows the structure of a receiver for orthogonalized spread spectrum signals from a plurality of mobile stations in an embodiment corresponding to claim 2 of the present invention. As in the case of Figure 1,
Multiple n mobile stations M ₁ in a microcell with a radius of around 100 m
~ Receiver of the base station B that receives the frequency spread PN quadrature signals s ₁ - s _n from M _n despreading demodulation at each timing t ₁₀ ~t _n0 synchronized with each received signal s ₁ - s _n having each synchronization unit 10 _i for generating the PN orthogonal code c ₁ to c _n for.
However, demodulation timing of the received signal to provide a significant interference in the received signal of the desired, i.e. the mobile station M closest to the base station B when the transmitter output of each mobile station M ₁ ~ M _n is not a power control Highest level received signal from ₁
The timing of multiplying another received signal by the PN spreading code is advanced by a certain time Δt so as to approach the synchronization timing t ₁₀ of s ₁ and does not cause significant interference with other received signals s ₂ to s _n. Is being done. Therefore, other received signals s ₂ to s _n
The timing t _{2 to} t _n of the output from each time discrimination control circuit 11 _{2 to} 11 _n to each PN orthogonal code generator 12 _{2 to} 12 _n is more than the original synchronization timing t ₀ 2 to t _0n. Time Δt
Each received signal s ₂
It is possible to improve the SIR of ~ s _n. Received signal s ₁ ~
The operation of shifting the synchronization timings t _{01 to} t _0n of s _n by the time Δt is performed by the synchronization unit 10 _{i as} shown in the detailed circuit of the synchronization unit of FIG.
Input signal of the cross-correlation network, which is the time discriminator 11 of
s (t) is bifurcated into the n-th output of the PN code generator 12 and the n-th output.
Output error Eε of two multipliers X that take the product of two-stage output
The error E is added to the input side of the adder + that adds (t) and Lε (t).
By providing an attenuator ATT that attenuates ε (t) or Lε (t), the output ε (t) of the adder + is changed so that the phase of the output clock of the VCC, which is the clock generator, is delayed or advanced. do it.

[0010]

As described above, according to the present invention, in a receiver of a base station in a microcell having a cell radius of about 100 m, mutual interference of received signals from a plurality of mobile stations controlled by the base station. In particular, the interference due to the strongest received signal from the mobile station closest to the base station is reduced, and the effect of improving the utilization efficiency of the wireless line in the cell can be obtained.

[Brief description of drawings]

FIG. 1 is a principle diagram showing a basic configuration of a receiver for orthogonalized spread spectrum signals from a plurality of mobile stations according to claim 1 of the present invention;

FIG. 2 is a principle diagram showing a basic configuration of a receiver for orthogonalized spread spectrum signals from a plurality of mobile stations according to claim 2 of the present invention;

FIG. 3 is a circuit diagram of a detailed circuit of a synchronization unit of the receiver for explaining the operation of the receiver according to the exemplary embodiment of the present invention.

FIG. 4 is a basic configuration diagram of a conventional spread spectrum communication system.

FIG. 5 is a diagram of autocorrelation characteristics of a PN signal and time discriminator characteristics.

FIG. 6 is a circuit diagram of a detailed circuit of a synchronizing unit of a conventional PN signal receiver.

FIG. 7 is a block diagram of a conventional receiver for orthogonalized spread spectrum signals from a plurality of mobile stations.

[Description of Codes] M ₁ to M _n are a plurality of n mobile stations in a fixed cell _, M ₁ is a mobile station closest to the base station B, and s ₁ to s _n are base stations B
Receivers receive signals from _n mobile stations M ₁ to M _n , and t _{10 to} t _n0 are reception signals s ₁ to s ₁ to M _n from the mobile stations M ₁ to M _n.
It is the original reception timing synchronized with s _n .

Claims (2)

[Claims] [Claim 1] Each information (a1 to a _n) respectively code modulation to the base station the mobile station of a plurality n of transmitting under the control of the _{(B) (M 1 ~ M} n) Each of the base stations Each output (b ₁ ~ b _n )
Random Each PN orthogonal code (c1~c _n) obtained by multiplying spreading modulation frequency spread PN quadrature signals (s1 to s _n) a plurality n received its respective received signal a transmission signal which is sent as the the (s ₁ ~ s each information of the mobile station of the plurality n of synchronization with the PN orthogonal codes (C1 to c _n) to generate multiplied by orthogonal code signal despread demodulation (b ₁ ~ b _n) in _n) (A1 to _n In the receiver of the orthogonalized spread spectrum signal from a plurality of mobile stations that demodulates), the transmission power from each of the plurality of mobile stations (M1 to _Mn ) is controlled without being controlled. All timing multiplying by generating each PN orthogonal codes (C1 to c _n) for despreading the received signals (s ₁ ~ s _n), the transmitter of the base station has multiple n mobile stations (M ₁ ~
By setting a timing that is further delayed by a fixed time (Δ) from the time point (t) at which transmission is simultaneously started to M _n ),
The received signal (s ₂ to s _n ) from the mobile station (M _{2 to} M _n ) arbitrarily specified by the base station is the mobile station (M ₂ ) whose distance is closest to the base station (B).
The highest levels receiver of an orthogonal frequency spread signal from a plurality of mobile stations, characterized in that it has to eliminate the interference amount received from the received signal (s ₁₎ of from _1). 2. The base station receiver comprises a plurality of n mobile stations.
(M1 to M _n) Each PN orthogonal code despreading for each received signal (s ₁ ~ s _n) in the case where the transmission is not controlled in the output power of each transmitter from (C1 to c _n) reception time of each timing multiplying generate respective received signal _{(s 1 ~s n) (t} 10
~ T _n0 ), the amount of interference received from the received signal from the mobile station close to the base station (B) is made smaller by setting the timing earlier than the fixed time (Δ) by a certain time (Δ). Receiver for orthogonalized spread spectrum signals from mobile stations.