KR100534412B1 - Apparatus of processing Ranging channel for up-link in OFDMA and method therefor - Google Patents

Abstract

The present invention relates to a ranging channel processing apparatus and method for extracting and processing a ranging channel signal from an OFDMA received signal in a base station of an OFDMA communication system.

The ranging channel processing apparatus according to the present invention generates a linear phase with time delay with respect to a reference time of a base station in a linear phase generator, and compensates the phase of the subcarrier of the ranging channel signal in the linear phase multiplier using the linear phase. do. The output signal of the linear phase multiplier performs correlation with the ranging code set used in the ranging code correlator according to the ranging application. Based on the output signal of the ranging code correlator, the received signal power is calculated from the squarer and transmitted to the comparator. The comparator compares this received signal power with a threshold of a specific guard interval that the receiver of the base station can tolerate. Based on the comparison result, a reception signal having a reception signal power included in a specific protection section is selected from the reception signals received by the BS.

According to the present invention, using a ranging channel, it is possible to select a received signal included in the protection interval of the BS from the received signals transmitted by the SS and received by the BS.

Description

Apparatus of processing Ranging channel for up-link in OFDMA and method therefor}

The present invention relates to an apparatus and method for processing an uplink ranging channel in an orthogonal frequency division multiple access scheme.

The orthogonal frequency division multiplexing scheme is a robust modulation scheme for multi-path signals because the high-speed data signal is converted into a low-speed data signal and then loaded on each subcarrier. The orthogonal frequency division multiple access method is an orthogonal frequency division multiple access method (hereinafter, referred to as OFDMA). Specifically, in the OFDMA scheme, each OFDMA symbol is carried on a plurality of subcarriers and grouped into predetermined subchannels. By assigning these subchannels to multiple users, users can share data in the same time zone. In addition, the OFDMA scheme uses frequency-selective fading by employing frequency diversity (Frequency- Diversity), which combines the reception outputs of two communication lines with different frequencies to provide stable and high quality communication. It can have strong characteristics.

In general, in the IEEE 802.16a OFDMA scheme, since downlink is a method in which one base station (hereinafter referred to as BS) transmits a signal to multiple users, multiple user stations (subscriber stations) are used for each subchannel. , Hereinafter referred to as SS) may be used independently. In addition, since downlink uses 2048FFT, a total of 2048 subcarriers are used, and 1696 subcarriers except DC subcarriers and null subcarriers are used for data transmission. In addition, subcarrier allocation of subchannels for data consists of a total of 32 subchannels with 53 subcarriers consisting of one subchannel using a cell ID and a subchannel index.

Meanwhile, since uplink uses 2048FFT in the same way as downlink, a total of 2048 subcarriers are configured. However, in the case of uplink, since each SS has independent time and relative position, each SS received signal arriving at the BS does not have constant time synchronization and power due to its temporal positional difference. As such, when demodulating data whose time synchronization and power are not constant at the same time, the orthogonality of the OFDM signal is lost due to the transmission signal of the SS that exceeds the guard interval allowed by the BS. Will bring.

Therefore, to compensate for this drawback, it is strongly required to measure the time delay and the received signal power of the BS's reference time with respect to the signal transmitted by the SS and to select a signal whose measurement value is within a specific threshold range. In addition, the SS needs to be able to adjust the transmission time and transmission power to be within a certain threshold range allowed by the receiver of the BS when transmitting to the BS.

Therefore, the technical problem of the present invention for solving the above problems is to process the uplink ranging channel in the BS of the OFDMA system by measuring the relative time delay and the received signal power of the SS transmission signal relative to the BS reference time in the BS The present invention provides a ranging channel processing apparatus and method capable of selecting a received signal having a time delay and a received signal power included in a specific protection interval allowed.

A ranging channel processing apparatus according to an aspect of the present invention for solving the technical problem, the linear phase multiplier for compensating the phase of the subcarrier of the ranging channel signal using a specific linear phase; A ranging code correlator receiving the output of the linear phase multiplier and performing correlation with a ranging code set used according to a ranging purpose; A squarer for calculating received signal power based on an output signal of the ranging code correlator; A comparator for comparing the calculated received signal power with a threshold value of a specific protection interval allowed by the receiver of the base station; and sequentially generating the linear phase corresponding to the time delay included in the maximum time delay searchable at the base station. And a linear phase generator provided to the linear phase multiplier as a linear phase of, and based on the result of comparison in the comparator, a received signal having a received signal power included in the specific protection section is selected from the received signals.

The linear phase generator may output a time delay of the linear phase corresponding to the received signal power, and if the received signal power is included in the guard period, the ranging channel processing result signal to be transmitted to the mobile station for the received signal. Can be generated.

Here, the ranging channel processing apparatus is a ranging channel processing apparatus that processes initial ranging, periodic ranging, or bandwidth-request ranging.

According to another aspect of the present invention, there is provided a ranging channel processing method comprising: a) sequentially generating a linear phase corresponding to a time delay included in a maximum time delay searchable at a base station; b) compensating for a phase of a subcarrier of the ranging channel signal using the generated linear phase; c) performing correlation with a ranging code set used according to a ranging purpose for a phase compensated ranging channel signal; d) calculating received signal power based on an output signal of the ranging code correlator; e) comparing the calculated received signal power with a threshold of a specific guard interval allowed by the receiver of the base station; And f) selecting a reception signal having a reception signal power included in the specific protection interval from among the reception signals based on the comparison result.

After the step e), the method may further include outputting a time delay of a linear phase corresponding to the received signal power. In addition, the step e) may include the case where the received signal power is included in the protection period. And generating a ranging channel processing result signal to be transmitted to the mobile station with respect to the received signal.

Hereinafter, with reference to the accompanying drawings will be described in detail a preferred embodiment of the present invention.

First, the ranging channel and the processing method of the ranging channel of the present invention will be described generally.

The ranging channel used in the uplink according to the present invention is composed of one or more adjacent subchannel pairs, and depending on the purpose of use, initial ranging, periodic ranging, and band It is divided into three types of request ranging (Bandwidth-Request Ranging). The use of the ranging channel is distinguished using a set of M (= 48) ranging codes having a length of L (= 106) generated using a ranging code generator. In this case, it is determined by the BS how much M ranging code sets are allocated for what use.

As such, the allocation result determined by the BS is transmitted to the SS using a MAC management message, and each SS uses the ranging code randomly selected from among codes allocated for each purpose when attempting ranging. It will send a signal to. Therefore, the BS processes the ranging channel, such as identifying which ranging code set each SS attempts to perform ranging, and measures the relative time delay and received signal power information of the BS's reference time, and the ranging The channel processing result is transmitted to the SS.

1 is a block diagram schematically illustrating a structure of a base station for processing an uplink ranging channel according to the present invention.

As shown in FIG. 1, the base station according to the present invention includes an FFT 100, a ranging channel signal extractor 200, an initial ranging processor 300, a periodic ranging processor 400, and a band request ranging processor ( 500).

The FFT 100 receives the data transmitted by the SS in the OFDMA system, performs fast Fourier transform on the received signal, and outputs the received signal to the ranging channel signal extracting unit 200. In general, a channel consists of subchannels (for example 32 subchannels) consisting of a number of subcarriers (eg 53 subcarriers), ranging from one or more adjacent subchannel pairs of the subchannels. Since the channel is used, the ranging channel signal must be extracted from the channel signal output from the FFT 100. The ranging channels thus extracted are input to the initial ranging processing unit 300, the periodic ranging processing unit 400, and the band request ranging processing unit 500, respectively. The initial ranging processing unit 300, the periodic ranging processing unit 400, and the band request ranging processing unit 500 may perform initial ranging signals and periodic rangings among the ranging channel signals extracted by the ranging channel signal extractor 200. Signal and band request ranging signal, respectively.

Hereinafter, an apparatus for processing each ranging signal according to the present invention will be described in more detail. However, the apparatus for processing the initial ranging signal, the periodic ranging signal, and the band request ranging signal may all be applied in the same structure, and may be processed by the same method. Only the method will be described as an example.

2 is a block diagram showing in detail the structure of the initial ranging processing unit 300 of FIG. Here, two lines of signal lines connecting each block mean a complex signal.

As shown in FIG. 2, the initial ranging processing unit 300 includes a linear phase multiplier 310, a linear phase generator 350, a ranging code correlator 320, a squarer 330, and a comparator 340. .

The linear phase multiplier 310 performs a function of changing the phase of the subcarrier signal of the ranging channel extracted and transmitted from the ranging channel signal extractor 200.

The ranging code correlators 320-1 to 320 -N are provided with the same number as the ranging code set N used according to each ranging application. Each ranging code correlator 320-1 to 320 -N performs auto-correlation or cross-correlation with a ranging code.

The squarers 320-1 to 320 -N are provided with the same number as the ranging code correlators. Each of the squarers 330-1 to 330 -N receives a complex signal output from the ranging code correlators 320-1 to 320 -N, and calculates a reception power.

The comparator 340 compares an arbitrary threshold value, which is the minimum value of the received signal power corresponding to the guard interval allowed by the BS, with the received power calculated by the squarers 330-1 to 330 -N. Do this.

The linear phase generator 350 generates a linear phase according to each time delay with respect to the reference time of the BS.

Hereinafter, an operation relationship of the initial ranging processing unit 300 according to the present embodiment will be described in detail.

The ranging channel signal extractor 200 (refer to FIG. 1) receives a complex signal of which the OFDMA received signal is fast Fourier transformed, extracts the ranging channel signal, and delivers the ranging channel signal to the linear phase multiplier 310. The linear phase multiplier 310 performs a phase compensation of the laser complex signal by performing a complex product of the linear channel signal and the specific linear phase generated by the linear phase generator 350.

The phase-compensated complex signal has a ranging code PRBS (Psuedo Random Binary Sequence, PRBS) according to the ranging purpose in each of the N ranging code correlators 320-1 to 320-N allocated according to each ranging purpose. Autocorrelation or cross-correlation is performed to the squarer (330-1 ~ 330-N).

The squarers 330-1 to 330 -N square the complex signals output from the ranging code correlators 320-1 to 320 -N, and calculate a received signal power. In this way, the received signal power for the ranging channel signal multiplied by the PRBS code is calculated and transmitted to the comparator 340.

The comparator 340 compares the received signal power with a threshold in order to determine the validity of the calculated received signal power. Here, the threshold is a value representing the minimum received signal power that the BS receiver can tolerate and is a value input to the comparator 340 from the outside. The comparator 340 compares the threshold with the received signal power, and outputs the received signal power when the received signal power is greater than the threshold. In addition, a ranging channel processing result signal to be transmitted to the SS may be generated corresponding to the received signal power. However, when the received signal power is smaller than the threshold value, the corresponding received signal power is not output, and therefore the ranging channel processing result signal is not generated.

By doing so, a threshold value is compared with the calculated received signal power, and based on the result of the comparison, the received signal having the received signal power included in the guard interval allowed by the receiver of the BS is selected from the received signals received by the BS. It will be possible. In addition, as a signal for transmitting to the SS, a ranging channel processing result signal corresponding to a reception signal having a reception signal power included in a guard interval allowed by the receiver of the BS may be transmitted to the SS.

On the other hand, the linear phase generator 350 generates a linear phase for the maximum time delay from the linear phase with a time delay of 0 with respect to the BS reference time. Specifically, when the N-point FFT is used as the FFT 100, the total number of linear phases that the linear phase generator can generate is N, but in the present linear phase generator 350, BS among the N linear phases is shown. Create a linear phase (hereinafter referred to as the maximum linear phase) for a time delay (called the maximum time delay) that allows searching. Accordingly, the linear phase generator 350 determines whether the search has been performed for all the linear phases allowed by the BS, and then generates a linear phase to be searched next if there are more linear phases to be searched. This process is repeated to continuously generate linear phases until the maximum linear phase is reached. The generated linear phase is transferred to the linear phase multiplier 310 to be used for phase compensation of the ranging channel signal, and the time delay of the linear phase is output.

As described above, the ranging channel processing apparatus according to the present invention measures the time delay and the received signal power of the received signal by processing the ranging channel of the received signals transmitted to the BS and received through the uplink in each SS. Among the signals, the received signal whose time delay and received signal power are included in the protection interval allowed by the BS is selected.

On the other hand, when the received signal power in the comparator 340 is smaller than the threshold value and the value is not output and is discarded, the SS cannot receive the ranging channel processing result signal from the BS. In this case, the SS can transmit by adjusting the transmission power when transmitting the next OFDM signal.

Hereinafter, a method of processing a ranging channel according to the present invention will be described in detail with reference to FIG. 3.

3 is a diagram illustrating a method of processing a ranging channel according to the present invention in order.

First, the ranging channel signal extracting unit 200 (FIG. 1) receives an OFDMA reception signal, receives a fast Fourier transformed signal, and extracts the ranging channel signal (S100).

Next, the linear phase generator 350 generates a linear phase having a time delay of "0" (S200).

The extracted ranging channel signal and the linear phase are transmitted to the linear phase multiplier 310, and the linear phase multiplier 310 performs complex compensation of both signals to perform phase compensation (S300).

Next, the N ranging code correlators 320-1 to 320-N allocated according to the ranging purpose perform autocorrelation or cross-correlation of the complex signal with the ranging code PRBS according to the ranging purpose. (S400).

Next, the squarers 330-1 to 330 -N receive output complex signals of the ranging code correlators 320-1 to 320 -N, respectively, and calculate received signal power based on the complex signal. (S500).

The received signal power thus calculated is input to the comparator 340. The comparator 340 compares the received signal power with a threshold value that is the minimum received signal power that the BS receiver can tolerate. Based on the result of the comparison, among the received signals transmitted from the SS and received by the BS, a received signal having a received signal power larger than a threshold value that is the minimum received signal power that the BS receiver can allow is selected (S600). In this step S600, a ranging channel processing result signal to be transmitted to the mobile station can be generated.

In addition, the linear phase generator 350 may further include outputting a time delay of the linear phase corresponding to the received signal power calculated by the comparator 340.

Next, the linear phase generator 350 determines whether the generated linear phase is the maximum linear phase (S700). As a result, if the generated linear phase is not the maximum linear phase, the next linear phase is generated (S800), and the steps S200 to S600 are repeatedly performed. On the other hand, when the generated linear phase corresponds to the maximum linear phase, the ranging channel processing is terminated.

As described above, according to the ranging channel processing method according to the present invention, a received signal having a received signal power and a time delay larger than a threshold value allowed by the BS can be selected from among the received signals transmitted by the SS and received by the BS.

Although the invention has been described with reference to the most practical and preferred embodiments, the invention is not limited to the embodiments disclosed above but also encompasses various modifications and equivalents which fall within the scope of the following claims.

According to the present invention, a reception signal having a received signal power and a time delay larger than an arbitrary threshold value allowed by the BS can be selected from among the received signals transmitted by the SS using the ranging channel.

In addition, if the received signal power is greater than the threshold value during the ranging channel processing, the corresponding ranging channel processing result signal is transmitted to the SS. If the received signal power is less than the threshold value, the corresponding ranging channel processing result signal is SS. Since it is not transmitted to the SS, the SS cannot receive the corresponding ranging channel processing result signal for the transmission signal. Therefore, when the SS transmits the next ranging signal, the SS adjusts and transmits the transmission power. If it is determined that the result of performing the ranging channel processing by receiving the transmission power having the adjusted value is greater than the threshold value, the SS can receive the ranging channel processing result signal of the BS for the next ranging signal. do.

1 is a block diagram schematically illustrating a structure of a base station for processing an uplink ranging channel according to the present invention.

2 is a block diagram showing in detail the structure of the initial ranging processing unit 300 of FIG.

3 is a diagram illustrating a method of processing a ranging channel according to the present invention in order.

Claims (9)

A ranging channel processing apparatus provided in a base station of an OFDMA communication system and processing a ranging channel signal extracted from a received signal transmitted by a mobile station, A linear phase multiplier for compensating the phase of a subcarrier of the ranging channel signal using a specific linear phase; A ranging code correlator receiving the output of the linear phase multiplier and performing correlation with a ranging code set used according to a ranging purpose; A squarer for calculating received signal power based on an output signal of the ranging code correlator; A comparator for comparing the calculated received signal power with a threshold of a specific protection interval allowed by the receiver of the base station: and Linear phase generator which sequentially generates linear phases corresponding to the time delays included in the maximum time delay searchable by the base station and provides the linear phase multipliers as the specific linear phases. Including, Selecting a received signal having a received signal power included in the specific protection period from the received signals based on a result of comparison by the comparator; Ranging channel processing apparatus, characterized in that. The ranging channel processing apparatus according to claim 1, wherein the linear phase generator outputs a time delay of a linear phase corresponding to the received signal power. The ranging channel processing apparatus according to claim 1 or 2, wherein when the received signal power is included in the guard period, a ranging channel processing result signal to be transmitted to the mobile station is generated for the received signal. . The ranging channel processing apparatus of claim 1 or 2, wherein the ranging channel processing apparatus processes initial ranging. The ranging channel processing apparatus of claim 1 or 2, wherein the ranging channel processing apparatus performs periodic ranging. 3. The ranging channel processing apparatus according to claim 1 or 2, wherein the ranging channel processing apparatus processes bandwidth-request ranging. A ranging channel processing method for processing a ranging channel signal of a received signal received from a mobile station at a base station of an OFDMA communication system, a) sequentially generating linear phases corresponding to time delays included in a maximum time delay searchable at a base station; b) compensating for a phase of a subcarrier of the ranging channel signal using the generated linear phase; c) performing correlation with a ranging code set used according to a ranging purpose for a phase compensated ranging channel signal; d) calculating received signal power based on an output signal of the ranging code correlator; e) comparing the calculated received signal power with a threshold of a specific guard interval allowed by the receiver of the base station; And f) selecting a reception signal having a reception signal power included in the specific protection section from the reception signals based on the comparison result; Ranging channel processing method comprising a. 8. The ranging channel processing method according to claim 7, further comprising, after step e), outputting a time delay of a linear phase corresponding to the received signal power. The method of claim 7 or 8, wherein the step e) includes generating a ranging channel processing result signal to be transmitted to the mobile station with respect to the received signal when the received signal power is included in the guard period. Ranging channel processing method.