JP2003060565A - Transmission method of signal and base station - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method and a base station which transmits diversity having adaptability/compatibility to the conventional technique without largely deteriorating performance, in an added white Gaussian noise AWGN state, by using transmitting architecture in which a form of PSTD is assembled. SOLUTION: In the PSTD, a signal and a version of the signal which is subjected to frequency sweeping are transmitted via a diversity antenna by using different power levels. Since the two signals are transmitted by using different power levels, depth of null which is seen in AWGN condition using the PSTD is reduced, and deterioration of performance of the AWGN condition can be restrained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a symmetric phase swept transmission diversity technique.

[0002]

2. Description of the Related Art The performance of a wireless communication system is directly related to the signal strength (statistical value) of a received signal. Third generation wireless communication systems use transmit diversity techniques to improve received signal strength statistics for downstream transmissions (ie, communication links from base stations to mobile stations), resulting in improved performance. is doing. Two transmit diversity techniques are space time spreading (STS) diversity and phase sweep transmit diversity.
diversity, PSTD).

FIG. 1 shows a wireless communication system 10 that employs STS. The wireless communication system 10 has at least one base station 12, which has two antenna elements 14-1 and 14-2, which are spaced apart to perform transmission diversity. Has been done. Base station 1
2 receives signal S for transmission to mobile station 16. The signal S is alternately divided into the signals S _e and S ₀ , the signal s _e includes even-numbered data bits, and the signal s ₀ includes odd-numbered data bits. The signals s _e and s ₀ are processed to generate the signals S ^14-1 and S ^14-2 .

More specifically, s_eThe walsh mark
Issue w₁Multiply with the signal s_ew₁To generate. Signal s₀of
The conjugate is Walsh code w_TwoMultiply with the signal s₀ ^*w_TwoTo
To generate. Signal s₀Walsh code w₁And generate s
₀w₁Generate the signal s_eIs the Walsh code w_Two
Multiply with s_e ^*w_TwoTo generate. Signal s_ew₁The signal
s₀ ^*w_TwoIn addition to the signal S^14-1(Ie S^14-1
= S_ew₁+ S_o ^*w _Two), And the signal s_e ^*w_TwoTo
Signal s₀w₁Subtracted from the signal S^14-2(Ie S
^14-2= S₀w₁-S_e ^*w_Two) Is generated. Signal S
^14-1And S^{14 -2}Antenna element 14-
1,14-2 via almost equal or same power
Send by level. This application smells
Power levels are within 1% of each other herein.
When it is, it is defined as almost equal or identical.

The mobile station 16 uses γ ₁ (S ^14-2 ) + γ ₂
The signal R including (S ^14-2 ) is received. Where γ ₁
And γ ₂ are distortion coefficients associated with the transmission of signals S ^14-1 and S ^14-2 from antenna elements 14-1 and 14-2 to mobile station 16, respectively. The distortion coefficients γ ₁ and γ ₂ are predicted using a pilot signal, which is a known technique in the related art. The mobile station 16 sends the signal R to the Walsh code w ₁ ,
Decode with w ₂ to produce the following outputs, respectively: W ₁ = γ ₁ s _e + γ ₂ s ₀ Formula 1 W ₂ = γ ₁ s ₀ ^* −γ ₂ s _e ^* Formula 1 a

The following equations are used to obtain the predicted values of the signals s _e and s ₀ , that is, the left sides of the equations 2 and 2a, respectively.

[Equation 1] However, STS is a transmit diversity technology that is not compatible / compatible with conventional technology (not compatible / compatible with past products) from the viewpoint of mobile stations. That is, the mobile station 16 needs to add new hardware necessary for decoding the signal R
Or you need to have software. Conventional mobile stations that do not have such hardware and / or software, ie mobile stations before the third generation, cannot decode the signal R.

On the other hand, phase-swept transmit diversity (PSTD) is compatible / compatible with the prior art from the viewpoint of mobile stations. FIG. 2 shows a wireless communication system 20 that adopts PSTD. At least one wireless communication system 20
The base station 22 has two antenna elements 24-1 and 24-2.
4-1 and 24-2 are arranged apart from each other in order to perform transmission diversity. The base station 22 receives the signal S for transmission to the mobile station 26.

The signal S is divided into signals s ₁ and s ₂ of equal power, which are processed and signals S ^{2 4-1} and S ^24-2.
, Where s ₁ = s ₂ . Specifically, the signal s ₁ is multiplied by the Walsh code w _k to obtain S
^24-1 = s ₁ w _k is generated. Here, k represents a specific user, that is, a mobile station. The signal s ₂ is the Walsh code w _k
And the phase sweep frequency signal e ^j2πfst to generate a signal S ^24-2 , that is,

[Equation 2] Becomes Where f _s is the phase sweep frequency and t is time.

The signals S ^24-1 and S ^24-2 are transmitted with approximately equal power levels via antenna elements 24-1 and 24-2, respectively. Phase sweep signal e
^{j2πfs t} is a complex baseband representation, ie

[Equation 3] Is. The phase sweep frequency can be applied to an intermediate frequency or a radio frequency.

The mobile station 26 has γ ₁ S ^24-1 + γ ₂ S
A signal R including ^24-2 is received. A simple formula for R is as follows.

[Equation 4] Here, γ _eq is an equivalent channel viewed from the mobile station 26. The distortion factor γ _eq can be predicted using the pilot signal and used in conjunction with Equation 3b to obtain the predicted values for the signals s ₁ and / or s ₂ .

[0011]

In slow fading channel conditions, PSTD improves performance over the case where no transmit diversity technique is used, but this improvement is at the receiver the received signal associated with the slow fading channel. This is done by making the intensity statistic of s to look similar to that of the fast fading channel. However, additional white Gaussian noise (additive whi
te gaussan noise, AWGN)
D can significantly degrade performance. Therefore,
It requires a transmit diversity technique compatible / compatible with the conventional technique without significantly degrading the performance even in the AGWN state.

[0012]

The present invention employs a transmit architecture that incorporates a form of phase sweep transmit diversity (PSTD), referred to herein as biased PSTD, to provide an additional white Gaussian. Provided is a transmit diversity method and apparatus that does not significantly degrade performance in the noise (AWGN) state and is compatible / compatible with the prior art.
Biased PSTD includes transmitting a signal and a frequency swept signal of this same signal at different power levels through a diversity antenna. By transmitting the two signals with different power levels, P
When STD is used, it can reduce the null depth normally found in the AWGN state and reduce performance degradation in the AWGN state.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 3 shows a phase-swept transmit diversity (PS) called a biased PSTD according to the present invention.
1 illustrates a base station 30 that employs the TD) form and CDMA.
The biased PSTD reduces the null depth by transmitting a signal and a frequency swept version of this signal at different power levels through a diversity antenna. The biased PSTD is preferably compatible / compatible with the prior art from the mobile station's perspective and does not degrade the performance of the PSTD in the added white Gaussian noise (AWGN) state. CDMA is a known technique.

The base station 30 provides a mobile station (not shown) with a radio communication service within a cover area, that is, a cell divided into three sectors α, β and γ. Base station 30 has a transmission architecture that incorporates a biased PSTD.

The base station 30 has a processor 32, a splitter 34, multipliers 36 and 38, amplifiers 44 and 46, and a pair of diversity antennas 48 and 50. Base station 3
0 also has splitters, multipliers, amplifiers and antennas for sectors β and γ, which are the same as for sector α. For simplicity of explanation, sectors β and γ
Is not shown. For further discussion, it is assumed that signal S _k is intended for mobile station k, which is in sector α. The invention will be described by way of example of a signal S _k which is processed to be transmitted via sector α.

The processor 32, in accordance with known CDMA techniques and has a software which processes the signals _{S k} generates an output signal _{S k-1.} In other embodiments, the processor 32 is operable to process the signal S _k according to other access techniques than CDMA, such as TDMA or FDMA.

The signal S _k-1 is separated into signals S _k-1 (a) and S _k-1 (b) by the splitter 34, and along the paths A and B, respectively, the multiplier 36 according to the added PSTD technique. , 38 and amplifiers 44, 46. Here, the signal S _k-1 (a) and the signal S _k-1 (b)
Are identical in terms of data. In one embodiment of the present invention, signals _{S k-1} are unevenly power split by splitter 34, the power level signal _{S k-1} power level (b) of the resulting signal _{S k-1} (a) Higher than. For example, the signal S _k-1 is power-divided, so that the signal S _k-1 (a) is 5/8 of the power of the signal S _k-1.
, The signal S _k-1 (b) takes 3/8 of the power of the signal S _k-1 , that is, S _k-1 (a) = √5 / 8 (S
_k−1 ) and S _{k− 1} (b) = √3 / 8 (S _k−1 ).

In another embodiment of the invention, the signal S
_k-1 is power-divided and the resulting signal S _k-1 (a)
Takes the power 2/3 of the signal S _k−1 ,
_k-1 (b) takes 1/3 of the power of the signal S _k-1 .
In one embodiment of the invention, the signal S _{k -1} is non-uniformly power separated by the splitter 34, resulting in the signal S _{k -1.}
The power level of _k-1 (b) is made higher than that of the signal S _k-1 (a), or
_k-1 is equally power-divided into signals S _k-1 (a) and S _k-1 (b). The signal S _k-1 (a) and the carrier signal e ^j2πfct are given as inputs to the multiplier ₃₆ to generate the signal S ₃₆ . here,

[Equation 5] Is. Here, f _c represents a carrier frequency and t represents time.

The signal S _k-1 (b), the phase sweep frequency signal e ^{j Θs (t)} and the carrier signal e ^{j 2πfct} are input to the multiplier 38, where the signal S _k-1 (b) is the signal e.
^The frequency phase is swept with ^{jΘs (t)} and modulated onto the carrier frequency e ^j2πfct to obtain the signal

[Equation 6] And where

[Equation 7] And f _c represents the phase sweep frequency.

Signal S₃₆, S₃₈Are amplifiers 4
Amplified by 4,46, signal S ₄₄And S₄₆Generate a
Then, it is transmitted via the antennas 48 and 50. here,

[Equation 8] Is. A ₄₄ represents the gain amount of the amplifier 44, and A ₄₆
Represents the gain amount of the amplifier 46.

In one embodiment of the present invention, the gain amount A
₄₄ and A ₄₆ are equal. In this embodiment, S
_k-1 is separated by the splitter 34, so that the power level of the signal S _k-1 (a) can be greater than that of the signal S _k-1 (b) or vice versa, and the result signal S _k The difference in power levels between ₄₄ and S ₄₆ is not significant when compared to the equal power separation of signal S _k-1 .

In another embodiment of the invention, the gain quantities A ₄₄ , A ₄₆ are different and this is the splitter 34.
Relates to how to power separate the signal S _k-1 . For example, signals _{S 36, S} gain amount _A 44 applied to _{38, A 46} should be an amount such substantially equal the power level of the signal _{S 4 4} and _{S 46.} For purposes of this specification, power levels being substantially equal are defined to be within 10% of each other. In other embodiments of the invention, the higher power level signal S ₃₆ or S ₃₈ is amplified more than the other signals.

The signal S _α-1 and / or the signals S ₃₆ , S
_{If 40} is biased, unequally separated, or unequally amplified, STS performance will degrade. The reason is that signal S ₄₄ is transmitted at about 1/3 the power of signal S ₄₆ . Preferably, the biased or unequal separated signal S _α-1 and / or the biased or unequal amplified signal S ₃₆ , S ₄₀ is the signal S _{α-. 1} and signals S ₃₆ , S
_{All of the 40} suppress this degradation to STS performance when compared to the case where they are not biased, ie, unequally separated / amplified.

FIG. 4 illustrates a 30a that employs CDMA and split shift phase-swept transmit diversity PSTD according to the present invention. Split-shifted PSTD comprises transmitting at least two phase swept versions of a signal using a diversity antenna, where the two phase swept versions of the signal have different phases. In one embodiment of the invention, the signal is split into a first signal and a second signal.

The first and second signals are phase swept in equal but opposite directions using different phase swept frequency signals, so that the energy of the transmitted signal is concentrated near the carrier frequency. According to another embodiment of the invention, the phase swept frequency signal has a constant or varying phase shift rate, has the same or different phase shift rates, or has a phase shift in the same or opposite directions. . Preferable for split shift
The STD is compatible / compatible with the prior art as seen from the mobile station. CDMA technology is known.

The base station 30a has three sectors α, β and γ.
A mobile station (not shown) is provided with a wireless communication service which is within a cover area, that is, within a cell. Base station 30a
Has a transmission architecture that incorporates a split-shift PSTD.

The base station 30a includes a processor 32a, a splitter 34a, and multipliers 36a, 38a, 40a and 42a.
And amplifiers 44a and 46a and a pair of diversity antennas 48a and 50a. Base station 30a also has splitters, multipliers, amplifiers and antennas for sectors β and γ, which are the same as for sector α.
To simplify the description, the configurations of the sectors β and γ are not shown. For further discussion, it is assumed that signal S _k is intended for mobile station k in sector α. The present invention provides a signal S _k that is processed to be transmitted via sector α.
Will be described as an example.

The processor 32a is in accordance with known CDMA techniques and has a software that generates an output signal _{S k-1} processes the signal _{S k.} In other embodiments, the processor 32a is operable to process the signal S _k according to other access techniques than CDMA, such as TDMA or FDMA.

The signal S _k-1 is separated into signals S _k-1 (a) and S _k-1 (b) by the splitter 34a, and along the paths A and B, respectively, the multiplier 36a is added in accordance with the added PSTD technique. , 38a, 40a, 42a and amplifier 44
a, 46a. Where the signal S
_{The k-1} (a) and the signal S _k-1 (b) are the same in terms of data. In one embodiment of the invention, the signal S
_{The power of k-1} is unevenly divided by the splitter 34a, so that the power level of the signal S _{k -1} (a) is higher than that of the signal S _{k- 1} (b). For example, the signal S _k-1 is power-divided, resulting in the signal S _k
k-1 (a), the signal _{S k-1} of the take 5/8 of the power, the signal _{S k-1} (b) is the signal _{S k-1} of the power 3 /
8, that is, S _k-1 (a) = √5 / 8 (S _k-1 )
And S _k−1 (b) = √3 / 8 (S _k−1 ).

In another embodiment of the invention, the signal S
_k-1 is power-divided and the resulting signal S _k-1 (a)
Takes the power 2/3 of the signal S _k−1 ,
_k-1 (b) takes 1/3 of the power of the signal S _k-1 .
In one embodiment of the present invention, signals _{S k -1} is unevenly power separated by the splitter 34a, the power level of the result signal _{S k-1} (b), the signal _{S k-1} (a)
Above the power level of S or signal S
_k-1 is equally power-divided into signals S _k-1 (a) and S _k-1 (b).

The signal S _k-1 (a) and the phase sweep frequency signal e ^{jΘs (t)} are given as inputs to the multiplier 36a,
Here, the signal S _k-1 (a) is the phase sweep frequency signal e
Phase swept with ^{jΘs (t)} to produce signal S _36a .

[Equation 9] here,

[Equation 10] Where f _s represents the phase sweep frequency and t represents time.

The signal S _k-1 (b) and the phase sweep frequency signal e ^{-jΘs (t)} are provided as inputs to the multiplier 38a, where the signal S _k-1 (b) is the signal e ^{-jΘs (t).}
Thus, the frequency and phase are swept to generate the signal S _38a .

[Equation 11] In another embodiment of the invention, the phase sweep frequency signal e
^{-JΘs (t)}Using the signal S_k-1Phase sweep of (a)
Phase sweep frequency signal e^{jΘs (t)}Is the signal S _k-1
Phase sweep is performed using (b).

Phase-swept frequency signal e ^{j Θs (t)} , e
^{−jΘs (t)} is the signal S _k−1 (a), S
Phase sweep _k-1 (b) with equal amplitude in opposite directions.
Preferably, the phase sweep frequency signal e ^{j Θs (t)} , e
The carrier frequency f _c by the selection of ^{-jΘs (t)} or to concentrate the energy of the transmission signal at the mobile station in the vicinity thereof.

In another embodiment of the invention, S _k-1.
(A), S _k-1 (b) The phase sweep frequency signals used to phase sweep have a constant or varying phase shift rate, have the same or different phase shift rates, or are offset from each other. Phase shift in the same or opposite direction.

The signal S _36a and the carrier signal e
^j2πfct is input to the multiplier 40a, where the signal S
_40a is generated. here,

[Equation 12] Is. Similarly, signal S _38a and carrier signal e
^j2πfct is input to the multiplier 42a, where the signal S
_42a is generated. here,

[Equation 13] Is.

The signals S _40a and S _42a are amplified by amplifiers 44a and 46a, respectively, to obtain signals S _44a and S _42a.
46a is generated and transmitted via the antennas 48a and 50a. here,

[Equation 14] Is. A _44a represents the gain amount of the amplifier 44a, and
_46a represents the gain amount of the amplifier 46a.

In one embodiment of the present invention, the gain amount A
_44a, A_46aAre equal. In this embodiment, S
_k-1Is separated by the splitter 34a and the resulting signal is
Issue S _k-1The power level of (a) is the signal S_k-1(B)
Can be greater than the power level of vice versa or vice versa
Yes, resulting signal S_44aAnd S_46aPower between
Bell difference is signal S_k-1Compared to the equal power separation of
Not big. Alternatively, the signal S_k-1Is the splitter
Equally separated by 34a.

In another embodiment of the present invention, the gain quantities A _44a , A _46a are different, and this is related to how the splitter 34a power splits the signal S _k-1 . For example, the signal _{S 36a,} the gain amount _A 44a applied to the _{S 38a, A 46 a,} the signal _{S 44a} and S
The power level of _46a should be approximately equal. In this specification, the power levels are substantially equal to each other when the power levels are within 10% of each other. In another embodiment of the invention, the higher power level signal S _36a or S _38a is amplified more than the other signals.

The above description relates to one embodiment of the present invention, and those skilled in the art can think of various modifications of the present invention, but they are all within the technical scope of the present invention. Included in. It should be noted that any reference numbers in the claims are not to be construed as limiting the technical scope thereof, for easy understanding of the invention.

【The invention's effect】 [Brief description of drawings]

FIG. 1 is a diagram showing a wireless communication system using a conventional space-time spreading technique.

FIG. 2 is a diagram showing a wireless communication system adopting phase-swept transmission diversity according to the related art.

FIG. 3 is a phase-swept transmit diversity (PSTD) configuration called Biased PSTD and CDM according to the present invention.
Diagram showing the base station that adopted A

FIG. 4 is a diagram illustrating a base station that employs split-shift phase-swept transmission diversity (PSTD) and CDMA according to the present invention.

[Explanation of symbols]

10, 20 Wireless communication system 12,22,30 base stations 14,24 Antenna element 16,26 Mobile station 32 processors 34,35 splitter 36,38,40,41 Multiplier 42,43 adder 44,46 Amplifier 48 main antenna 50 diversity antenna

   ─────────────────────────────────────────────────── ─── Continued front page    (71) Applicant 596077259             600 Mountain Avenue,             Murray Hill, New Je             rsey 07974-0636U. S. A. (72) Inventor Roger David Benin             New Jersey, United States             07853, Long Barry, Stoney             Look road 11 (72) Inventor Earl Michael Bjeller             New Jersey, United States             07960, Morristown, Longview             Russ 1 (72) Inventor Robert Art Maran Sony             New Jersey, United States             07950, Morris Plains, Fernck             Riff 30 F term (reference) 5K059 CC02                 5K067 CC24 EE02 EE10 GG08

Claims (10)

[Claims] 1. (A) The signal s ₁ is replaced with the signals s ₁ (a) and s
₁ (b), the signal s ₁ is non-uniformly separated such that the signal s ₁ (a) has a power level greater than that of the signal s ₁ (b); 1 phase-swept signal s ₁ (b) or s
₁ (a) to frequency sweep one of said signal s ₁ (b) or signal s ₁ (a) using a first phase swept frequency signal. Signal transmission method. To 2. A (C) for generating an amplified signal _s 1 (a) or _s 1 (b), not phase sweep of the signals _s 1 (a) or _s 1 (b) the other And (D) the amplified first phase-swept signal s
Amplifying the first phase sweep signal s ₁ (b) or s ₁ (a) to produce ₁ (b) or s ₁ (a). Method. 3. The amplified signal s ₁ (a) or s
₁ (b) and the amplified first phase-swept signal s
The method of claim 2, wherein the power levels of ₁ (b) and s ₁ (a) are equal. 4. The other signal of the signals s ₁ (a) or s ₁ (b) is greater than the amount by which the first phase-swept signal s ₁ (b) or s ₁ (a) is amplified. The method according to claim 2, wherein the method is greatly amplified. 5. (E) a second phase swept signal s ₁
(A) or to produce _s 1 to (b), the signal _s 1 using the second phase sweep frequency signal (a) or s
₁ (b), the other phase-unswept signal is phase-swept, the first phase-swept signal s ₁ (b) or s
_{1 (a)} The method of claim 1, wherein the second signal s ₁ that is phase-swept _(a) or s _{1 (b)} is characterized by having a different phase. 6. (A) The signal s ₁ is replaced with the signals s ₁ (a) and s
₁ (b) and the signal s ₁ is split unequally so that the signal s ₁ (a) has a power level greater than that of the signal s ₁ (b), (B) 1 phase-swept signal s ₁ (b) or s
To generate the _{1 (a),} and characterized by having a first multiplier for frequency sweep one of signals s _{1 (b)} or a signal s _{1 (a)} using a first phase-sweep frequency signal Base station to do. 7. A (C) for generating an amplified signal _s 1 (a) or _s 1 (b), not phase sweep of the signals _s 1 (a) or _s 1 (b) the other A first amplifier for amplifying the signal, and (D) the amplified first phase-swept signal s
_A second phase amplifying signal s ₁ (b) or s ₁ (a) to produce ₁ (b) or s ₁ (a)
The base station according to claim 6, further comprising an amplifier. 8. The first and second amplifiers include an amplified signal s ₁ (a) or s ₁ (b) and an amplified first phase-swept signal s ₁ (b) and s ₁ 7. The base station according to claim 6, wherein the signal is amplified so that the power levels of (a) are equal. 9. The first amplifier and the second amplifier are provided with a signal s.
The other signal of ₁ (a) or s ₁ (b) is the signal such that the first phase-shifted signal s ₁ (b) or s ₁ (a) is amplified more than it is amplified. 7. The base station according to claim 6, wherein the base station is amplified. 10. (E) a second phase swept signal s
₁ (a) or s ₁ (b) using the second phase swept frequency signal to generate the signal s ₁ (a) or s
_A second amplifier that phase-sweeps the other signal of ₁ (b) that has not been phase-swept, and the first phase-swept signal s ₁ (b) or s
_{. 1 (a),} the base station according to claim 6, characterized in that it comprises a second signal s ₁ that is phase-swept _(a) or s _{1 (b)} is different phases.