KR20020015086A - Method for orthogonal transmit diversity using differential code in radio communication - Google Patents

Abstract

PURPOSE: An orthogonal transmit diversity method using a differential coding in wireless communication is provided to apply the differential coding in a transmitter of a base station and to apply the differential coding in a receiver of a mobile station, so as to perform diversity via one path. CONSTITUTION: A transmitter performs a differential coding for message columns to be transmitted to modulate the message columns to two channels, and transmits signals through assigned antennas(ST11-ST13). A receiver receives the signals through one antenna to separate the signals into two channels, and demodulates the signals to perform a differential coding(ST14-ST17). The signals differentially coded by each channel are coupled by a rake receiver(ST18).

Description

Orthogonal transmit diversity method using differential coding in wireless communication {Method for orthogonal transmit diversity using differential code in radio communication}

The present invention relates to orthogonal transmit diversity (orthogonal transmit diversity), in particular orthogonal transmission using orthogonal transmission using differential coding in the wireless communication to be suitable for improving the performance of the receiver by applying differential coding (differential coding) to the orthogonal transmission diversity Diversity method.

In general, in the transmission and reception of a radio signal through an antenna, the diversity scheme combines signals received through two or more lines or channels, thereby preventing fading and improving diversity gain.

Hereinafter, the prior art for the diversity scheme will be described.

First, FIG. 1A is a block diagram of a transmitter in a diversity scheme according to the prior art, and FIG. 1B is a block diagram of a receiver in a diversity scheme according to the prior art.

In FIG. 1A, the transmitter has two transmission channels, and the signals to be transmitted are divided into two, and the signals having 1/2 energy are transmitted through separate paths. At this time, the signal for each channel is independently adjusted the chip energy, becomes the only Walsh code, then spread according to the spreading factor (Spreading Factor) is transmitted through each antenna.

If the input of each channel is Ec, the chip energy adjustment is Each channel Wow Walsh code conversion takes place. Diffusion factor after Walsh transcoding Is spread, filtered and modulated before being transmitted.

The signal transmitted by the diversity transmitter operating in this manner is received by the diversity receiver. As shown in FIG. 1B, the diversity receiver operates inversely with the diversity transmitter to combine received signals received through two antennas.

That is, in the diversity receiver, a signal received at each antenna is demodulated and filtered and then a spreading factor Spreading to Wow After Walshcode conversion is performed The chip energy is adjusted. Diversity gain is improved by combining the signal with chip energy adjustment into one received signal.

The conventional diversity method described above is mainly applied to the receiver and research and development has been conducted to improve the performance of the system. Current code division multiple access (CDMA) systems include a time diversity scheme using interleaving and coding, a path diversity scheme using a multipath, and a spatial diversity scheme using multiple reception antennas.

On the other hand, recently, the orthogonal transmit diversity scheme for transmitting signals through two transmission antennas is used for the base station transmitter, and the spatial diversity scheme for the receiver has been proposed.

However, in the above-described prior art, the orthogonal transmit diversity scheme in which a base station transmits signals to multiple transmitting antennas has advantages in that the structure of the mobile base station can be easily maintained and the performance of the forward link can be effectively improved. The station had to use two receivers.

As such, since two receivers are required in the terminal station, the receiving circuit is complicated and the device volume is increased.

Accordingly, the present invention has been proposed to solve the above-mentioned conventional problems, and an object of the present invention is to apply a differential coding to orthogonal transmit diversity to improve the performance of a receiver. To provide orthogonal transmit diversity method using differential coding in.

In order to achieve the above object, in the orthogonal transmit diversity method using differential coding in wireless communication according to the present invention, an antenna allocated to each channel after separate modulation and modulation into a plurality of channels by differentially encoding a message sequence to be transmitted from a transmitter Transmitting through; A technical feature of the present invention is that the receiver receives, demodulates and differentially decodes a signal transmitted from the transmitter by one antenna.

Figure 1a is a block diagram of a transmitter in the diversity method according to the prior art,

1B is a block diagram of a receiver in a diversity scheme according to the related art.

2 is a flowchart of an orthogonal transmit diversity method using differential coding in wireless communication according to the present invention;

3A is a block diagram of a base station transmitter according to the present invention;

3B is a block diagram of a terminal station receiver for receiving the transmission signal of FIG. 3A.

Hereinafter, the configuration and operation of the present invention will be described in detail based on an embodiment of the present invention in the orthogonal transmit diversity method using differential coding in the wireless communication.

First, FIG. 2 is a flowchart of an orthogonal transmit diversity method using differential coding in wireless communication according to the present invention, FIG. 3A is a block diagram of a base station transmitter according to the present invention, and FIG. 3B shows the transmission signal of FIG. It is a block diagram of a terminal station receiving section.

As shown in FIG. 2, a suitable embodiment of the present invention includes the steps of differentially coding a message string to be transmitted by a transmitter and then modulating the message string into two channels and transmitting the signals through an antenna allocated to each channel (ST11 to ST13); Receiving, by the receiver, a signal transmitted from the transmitter by one antenna, separating the signal into two channels, demodulating and differentially decoding each of the signals (ST14 to ST17); In the steps ST14 to ST17, rake-coupling the differentially decoded signal for each channel (ST18) is performed.

The operation of the method configured as described above is as follows.

The present invention performs differential coding on two paths for transmit diversity to overcome a mobile communication channel environment such as multipath fading, path loss, and reflected wave generated in a wireless channel environment (ST11 to ST12). In the transmit diversity, a signal transmitted after differential coding arrives at a receiver while covering different channel environments.

That is, as shown in FIG. 3A, the differentially coded and modulated transmission signals of the transmitter are transmitted at half power through two antennas (ST13). In this case, the transmission signal is Walsh-coded independently in each channel path of the transmitter divided into two channels.

And each antenna has a unique Walsh code Wow By spreading, signals transmitted through two antennas are mutually orthogonal.

The chip energy adjustment, Walsh coding and chip energy adjustment operations for the signal on which differential coding is performed are the same as in the related art.

Then, the receiver divides the signal received through one antenna into two channels, demodulates each of them, and then performs rake combining to realize the reception diversity effect.

That is, as shown in FIG. 3B, the signal transmitted and received by the transmitter is oversampled by an integer multiple of the chip rate, passes through a digital matched filter that matches the chip pulse, and then the inputs of the respective fingers are (ST14 to ST15).

Each finger demodulates, differentially decodes the multipath signal of the corresponding channel, and passes it to a Rake receiver (ST16 to ST18). In this case, the rake receiver uses a receiver of maximum ratio combining. Thus, the rake receiver receives signals from the fingers, which are guaranteed the magnitude, phase and delay of each channel path, and combines them.

Therefore, two signals each transmitted to the terminal station through two transmitters Wow In the receiver, the pilot signal is divided and rake-coupled independently of each other, thereby performing the maximum ratio combining method.

The differential coding applied to the present invention will be described in detail.

The receiving circuit of the receiver causes phase ambiguity on the restored carrier.

That is, the restored carrier is It may be a 180 degree phase error Phase ambiguity may be obtained. Therefore, the detection signal of the receiver has an error probability of 100%.

The present invention can solve the above error probability by differential coding and differential decoding.

Differential coding is a process of encoding data differentially. The determination of 0 or 1 does not end with only the symbol, but is compared with the previous symbol.

The error probability solving process by differential coding is expressed as the following equation.

{ }: Differentially coded columns,

{ }: Message column to send

Speaking of

Current differential coded bit Is the current message bit And previous differential coded bits It is obtained by comparing. At this time Is usually an exclusive OR, Or Exclusive NOR.

In other words,

Differential coding is performed by constructing the logic circuit of. At this time { } Any reference bit can be used as the initial value of the column.

The source coded differentially coded above

If the phase of the carrier,

Become,

( : Receive bit, same as following method)

Decoded according to the rules.

So by some cause When the carrier with offset and phase ambiguity is recovered again, the differentially coded signal is

Same as

In the case of the encoded signal, The carrier recovery shifted by [rad] occurs, but the phase shift can be eliminated as follows through differential decoding. In other words,

Message bits currently received by differential decoding that perform an exclusive OR between the currently received differential encoding bits and the previously received differential encoding bits. Source bits with phase shift removed It can be confirmed that.

Therefore, the differentially coded signal is a differential coded sequence { } Can be detected without error at the receiver even with phase ambiguity.

As described above, the present invention performs independent differential coding for each channel in a transmission path of a transmitter, transmits the signal, and performs differential decoding by receiving a signal transmitted from the transmitter in a receiver path of the receiver, thereby achieving a reception diversity effect without a reception diversity circuit. You can have it.

Although the preferred embodiment of the present invention has been described above, the present invention may use various changes, modifications, and equivalents. It is clear that the present invention can be applied in the same manner by appropriately modifying the above embodiments. Accordingly, the above description does not limit the scope of the invention as defined by the limitations of the following claims.

As described above, in the orthogonal transmit diversity method using differential coding in wireless communication according to the present invention, unlike the diversity scheme using two paths in the terminal station receiver in the prior art, the differential coding is applied to the transmitter portion of the base station. And differential decoding is applied to the terminal station receiver to enable diversity with only one path.

Therefore, since the receiving circuit can be designed to have the receiving diversity effect with only one path without configuring the receiving diversity circuit in the terminal station receiving section, the circuit configuration of the receiving section can be simplified and the receiving performance of the system can be improved.

Claims (3)

Differentially encoding the message string to be transmitted by the transmitter and transmitting the signal string through an antenna allocated to each channel after the modulation and modulation are performed on a plurality of channels; Orthogonal transmission diversity method using differential coding in the wireless communication, characterized in that for performing the step of receiving, demodulating and differential decoding the signal transmitted from the transmitter by a single antenna. The method of claim 1, wherein the demodulation and differential decoding of the receiver comprises: Demodulating the received signals through separate paths by the number of separately transmitted channels, and differentially decoding the demodulated signals; In the step, rake-coupling the differentially decoded signal for each channel to restore the transmission message sequence of the transmitter, orthogonal transmission diversity method using differential coding in a wireless communication, characterized in that the step. The method of claim 1, The differential coding performs an exclusive logical sum operation on a current message bit and a previous differential coded bit to generate a current differential coded bit, and the differential decoding on the differentially coded signal is performed on the currently received differential coded bit and the previously received differential coded bit. Orthogonal transmit diversity method using differential coding in a wireless communication, comprising extracting the current received message bit by performing an exclusive OR operation on the encoded differential encoded bits.