KR100842553B1 - Different Ranging Code Set Assignment Method for with the Adjacent Cells in OFDM System - Google Patents

Abstract

The present invention provides a method of allocating ranging codes used by each base station so that terminals registered in each cell can easily distinguish cells registered in the OFDM wireless communication system, and each base station according to a service class of the terminals. It is intended to provide a method for differentially transmitting a ranging response signal to the terminal. By assigning a ranging code set consisting of different ranging codes corresponding to each base station, a ranging response signal is transmitted only to a mobile terminal that makes a ranging request by the ranging code of the ranging code set assigned thereto. Meanwhile, the mobile terminal stores a ranging code set broadcast from a specific base station, makes a ranging request using a ranging code of the ranging code set, and uses a ranging response signal only by an acknowledgment signal of the ranging code. To send. Each base station finds a ranging code from the ranging request signal from the mobile terminal, selects whether there is priority in service, and preferentially sends a ranging response signal to a terminal capable of receiving a high level of service.

OFDM wireless communication system, ranging, ranging code set, ranging code, ranging channel

Description

Different Ranging Code Set Assignment Method for with the Adjacent Cells in OFDM System in Orthogonal Frequency Division Multiple Access wireless communication system             

1 is a view showing a control flow performed for ranging in a conventional base station.

2 is a view showing a control flow performed for ranging in a conventional mobile terminal.

3 is a diagram illustrating a control flow performed for ranging in a base station according to an embodiment of the present invention.

4 is a diagram illustrating a control flow performed for ranging in a mobile terminal according to one embodiment of the present invention;

5 is a diagram illustrating a control flow according to another example of a method of selecting a ranging code of FIG. 4.

6 is a diagram illustrating a control flow performed for ranging in a base station according to another embodiment of the present invention.

7 is a view showing a control flow performed for ranging in a mobile terminal according to another embodiment of the present invention.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to ranging in a wireless communication system of Orthogonal Frequency Division Multiple Access (hereinafter referred to as " OFDMA ") in a broadband wireless access (BWA) system. It is about an allocation method.

In general, in the OFDMA wireless communication system, both a near situation and a non-line-of-sight situation may occur in the same manner as the channel environment as in other modulation and access mobile communication systems. It also includes partial blockage by forests that affect signal attenuation and multipath.

Meanwhile, the OFDMA access method may be defined as a two-dimensional access method combining time division access and frequency division access technology. Each OFDMA symbol is divided into subcarriers and bundled into a predetermined subchannel to transmit data. In the OFDMA wireless communication system, ranging is a process of periodically correcting an accurate time offset between a base station and a subscriber station and correcting power. There are rangings for the following purposes.

Initial Ranging                         

2. Bandwidth Request Ranging

3. Maintenance Ranging

The ranging procedure requires a ranging subchannel and a ranging code. At this time, all base stations use a ranging code in common, and each of the base stations selects subchannels to be used as ranging subchannels according to their traffic environment and broadcasts them as system information. When each base station receives the ranging information transmitted by the terminal, the base station checks whether the received ranging signal meets the criteria. If the test passes, the ranging response message is transmitted to the terminal that transmitted the ranging signal in response to the test. The ranging response signal uses the received ranging code and a ranging subchannel.

1 is a diagram illustrating a control flow performed by a conventional base station for ranging.

Referring to FIG. 1, in step 110, the base station transmits corresponding information for ranging to all mobile terminals in a cell through a broadcast channel. Typically, the base station allocates subchannels to be used as ranging subchannels according to its traffic environment, and transmits the allocated subchannels as corresponding information for the ranging.

In step 112, the base station receives a ranging signal from the mobile terminal corresponding to the corresponding information for the ranging on the allocated subchannels. Upon receiving the ranging signal, the base station proceeds to step 114 to determine whether the ranging by the ranging signal is suitable for a predetermined ranging criterion. If it is determined in step 114 that it does not meet the predetermined ranging criteria, the process proceeds to step 118. However, if it is determined in step 114 that it meets the predetermined ranging criteria, the base station proceeds to step 116 and transmits a ranging response signal to the corresponding mobile terminal. In this case, the base station transmits the ranging response signal using a ranging code and a ranging subchannel received from the corresponding mobile terminal that has transmitted the ranging request signal.

After the base station transmits the ranging response signal, the base station proceeds to step 118. If the base station proceeds to step 118, it is determined whether it is time to transmit system information. If it is determined that the base station is the transmission time point, the base station proceeds to step 110 and repeats the above-described procedures. That is, the base station periodically transmits system information to mobile terminals in the same cell in step 118.

The operation of the mobile terminal corresponding to the ranging process at the base station is shown in FIG. However, the mobile terminals should receive and store system information broadcast from a base station before performing the operation according to FIG. 2.

Referring to FIG. 2, the mobile terminal determines whether ranging is necessary in step 210. If it is determined in step 210 that ranging is not necessary, the mobile terminal proceeds to step 222 to set a data subchannel, and transmits and receives data with the base station through the set subchannel. However, if it is determined in step 210 that ranging is necessary, the mobile terminal proceeds to step 212.

The mobile terminal proceeds to step 212 and checks the reception information related to ranging through previously stored system information. That is, the ranging subchannels to be used for ranging are identified. When the ranging related information is confirmed, the mobile terminal proceeds to step 214 to determine whether the checked ranging information is valid. If it is determined that the ranging information is not valid, the mobile terminal proceeds to step 316 to newly receive ranging related information from the base station and proceeds to step 312 to perform the above-described process again. However, if the ranging information is determined to be valid in step 214, the mobile terminal proceeds to step 218. The mobile terminal proceeds to step 218 and selects any one of ranging codes of the valid ranging information. The mobile terminal also selects any one of ranging subchannels of the valid ranging information. When the mobile station selects the ranging code and the ranging subchannel, the mobile station proceeds to step 220 and transmits a ranging request message requesting the use of the selected ranging code and the ranging subchannel to the base station.

As described above, when ranging is necessary, the mobile station checks the ranging related information in the system information, checks whether the stored ranging related information is valid, and if it is valid, proceeds to the next operation. Receive system information that is broadcast periodically to obtain information. A ranging subchannel is arbitrarily selected from the ranging subchannels found from valid ranging related information, and the ranging request message is transmitted to the base station to which the ranging subchannel is registered.

In the existing ranging procedure, since ranging codes used by each base station are the same and subcarriers used by each base station are the same, if the terminal requesting ranging is located at a cell boundary, the received ranging response signal is received by the terminal. It is unknown whether it belongs to this registered base station or is a signal from a neighboring base station. In addition, the base station cannot know whether the ranging signal received by the base station is from a terminal belonging to its cell or a ranging signal transmitted from a terminal belonging to a neighboring cell. Therefore, if the received ranging signal satisfies the criterion, the base station transmits the ranging response message using the received ranging code.

Accordingly, an object of the present invention is to solve the ranging signal interference between cells in an OFDM wireless communication system, which is caused by all cells using the same ranging code. In providing.

Another object of the present invention is to provide a method for generating a ranging code set for solving ranging signal interference between cells.

Another object of the present invention is to provide a ranging code set allocation and a ranging response signal differential transmission method according to a service level of a mobile terminal.

In a first aspect for achieving the object as described above, the present invention, the ranging code set corresponding to each of the base stations, each of the ranging code set consists of a plurality of different ranging codes In a ranging method at a base station of an OFDMA wireless communication system, a process of broadcasting ranging codes of the allocated ranging code set and corresponding ranging subchannels at a predetermined period, and a ranging request from a predetermined mobile terminal Determining whether the ranging code requested from the predetermined mobile terminal satisfies a predetermined ranging criterion and is present in the allocated ranging code set, and satisfies the predetermined ranging criterion, If present in the set of the code code, the process of transmitting a response signal from the mobile station to the ranging code and the ranging sub-channel required It is characterized by including.

In a second aspect for achieving the object as described above, the present invention relates to an OFDMA that allocates a ranging code set to each of the base stations, and each of the ranging code sets includes a plurality of different ranging codes. A ranging method in a mobile terminal of a wireless communication system, the method comprising: setting a ranging code set corresponding to the base station through system information broadcast from the base station; and when the ranging is requested, the ranging code set. Selecting one ranging code from a randomly or a predetermined process from a predetermined range, and selecting one ranging subchannel among ranging subchannels allocated by the system information; And transmitting the selected ranging code to a channel to the base station.

In a third aspect for achieving the above object, the present invention allocates a ranging code set to each of the base stations, and each of the ranging code sets includes a plurality of different ranging codes. A ranging method in a base station of a wireless communication system, the method comprising: broadcasting ranging codes of the allocated ranging code set and corresponding ranging subchannels at predetermined periods, and ranging requests from a plurality of mobile terminals. Determining whether a request for the use of the same ranging code that satisfies a predetermined ranging criterion from the plurality of mobile terminals and that satisfies a condition present in the allocated ranging code set is requested. If the use of the same ranging code that satisfies the above condition is requested from the mobile terminals, Determining a service rates, and characterized in that it comprises the step of transmitting a response signal to the ranging code and the ranging sub-channel service is requested from the most mobile terminals.

In a fourth aspect for achieving the above object, the present invention allocates a ranging code set to each of the base stations, and each of the ranging code sets includes a plurality of different ranging codes. In a ranging method in a mobile terminal of a wireless communication system, a process of pre-setting a ranging code set corresponding to the base station through system information broadcast from the base station, and when the ranging is required, Selecting any one ranging code from the corresponding ranging code set, selecting one ranging subchannel among ranging subchannels allocated by the system information, and the selected lane And transmitting the selected ranging code to a base channel to the base station.

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

3 shows a ranging procedure in a base station according to the present invention.

Referring to FIG. 3, base stations corresponding to each cell periodically broadcast a ranging code set, which is a set of ranging codes to be used, and uplink channels to be used as ranging subchannels through a predetermined message as system information. Mobile terminals registered to their base stations can be used for ranging.

4 shows a ranging procedure in a mobile terminal according to the present invention.

Referring to FIG. 4, the terminal receives and stores system information broadcast from a base station. When ranging is necessary, the system checks the ranging information in the system information, checks whether the stored ranging information is valid, and if so, proceeds to the next operation and if it is not valid, periodically broadcasts to obtain new ranging related information. Receive system information again. Subchannels allocated to a ranging subchannel by selecting one ranging code through the following equation in order to avoid collision with another terminal in the same cell arbitrarily or in a ranging code set found from valid ranging related information. Randomly selects a ranging subchannel. The terminal transmits the ranging request message to the base station registered with the selected ranging code by carrying the selected ranging code on the selected ranging subchannel.

Ranging code index = terminal's unique ID mod number of ranging codes received on ranging code set

In order to avoid a collision caused by two or more terminals selecting the same ranging code in the same cell, a ranging code selectable by one terminal is limited as described above. In the above formula, the ranging code index indexes the ranging codes of the ranging code set received from the system information in order.

The service provider may classify the mobile terminals into different classes of service. Thus, each mobile terminal will belong to one of several service classes. In this case, it is assumed that a high service class can write high-speed data, and gives priority to data transmission.

When the mobile station performs ranging for network access or channel allocation request, the mobile station receives the ranging response signal by priority corresponding to the service class. That is, it is possible to receive the ranging response signal differentially according to the service level for the terminals requesting the same channel.

In order to enable the ranging response signal transmission according to the above-described service class, when the terminal's own service class is SG _E (g = 1,2, ..., G), the following Equation 2 is given. The ranging code index selectable by the terminal is selected. In Equation 2, SG _g has a higher priority because a smaller variable g indicates a higher grade of service. The lowest grade of service in a system is SG _G.

According to Equation 2, terminals having a low service level are limited to a ranging code that can be selected by the user, and a terminal having a high service level, for example, SG ₁ , selects all ranging codes allowed by a base station. Will be used. Therefore, terminals with a higher service class have a lower probability of collision in ranging signal requests than terminals having a low service class.

Meanwhile, when several classes of terminals simultaneously transmit a ranging request signal, a ranging request signal from one or more terminals satisfies a ranging criterion, and even when the terminals request the same channel, the base station may provide a terminal with a high service grade. The ranging response signal can be sent first.

As another method for transmitting the ranging response signal according to the service class, when the terminal unique ID is assigned to each terminal, the terminal uniqueness is considered in consideration of the ranging code index according to Equation 1 according to the service class. Give an ID. The terminal unique ID may correspond to a MAC address of the terminal. Therefore, the system classifies the ranging code index according to the service class in advance, and each base station receives this information, detects the ranging code indexes of the terminals that have sent the ranging request signal, and then performs the ranging response Prioritize signal transmissions. The method does not have to broadcast the classification information according to the service class of the ranging code index to each terminal.

Hereinafter, an operation according to an embodiment of the present invention will be described in detail with reference to the above-described drawings.                     

First, in the present invention, the ranging code set used in each base station should use a ranging code set different from the ranging code sets used in adjacent cells. Therefore, if the maximum number of cells that can be adjacent in one cell of an OFDMA wireless communication system is K, the ranging code sets used in one OFDMA system should be at least K + 1. This is referred to as " ranging code reuse coefficient " for convenience and denoted by k (K + 1). That is, any one base station will use a different ranging code set than the base stations of immediately adjacent cells.

Therefore, in the OFDMA wireless communication system, the ranging code reuse coefficient, k is determined in consideration of the cell arrangement in the system, and at least k ranging code sets, which are sets of ranging codes to be used by the base stations, must be defined and allocated to each cell. . Therefore, the base station of each cell uses the ranging code set allocated by the OFDMA wireless communication system, and broadcasts it as system information periodically so that terminals registered in its cell can use it.

When the ranging signal is input to the channel designated as the ranging subchannel, the ranging request signal is checked whether the received signal size satisfies the criterion, and if appropriate, the ranging code of the ranging code set used by the ranging subchannel is checked. If the ranging code is used, the ranging response signal is transmitted to the corresponding terminal using the same ranging code. If the ranging code is not used, the ranging response signal is not sent even if the received ranging request signal satisfies the criteria.

Referring to FIG. 3, the base station transmits corresponding information for ranging to all mobile terminals in a cell through a broadcast channel in step 310. At this time, the base station transmits a ranging code set previously allocated by the OFDMA wireless communication system and corresponding ranging subchannel sets.

The base station receives a ranging signal from the mobile terminal corresponding to the corresponding information for the ranging on the allocated subchannels in step 312. After receiving the ranging signal, the base station proceeds to step 314 to determine whether the ranging by the ranging signal is suitable for the ranging criteria. If it is determined in step 314 that it does not meet the ranging criteria, the process proceeds to step 320. However, if it is determined in step 314 that the ranging criteria are satisfied, the base station proceeds to step 316 to determine whether a ranging code suitable for the ranging criteria exists in the ranging code set assigned to the base station. If the ranging code suitable for the criterion does not exist in the ranging code set assigned to the base station, the base station proceeds to step 320. However, if a ranging code suitable for the ranging criteria exists in the ranging code set, the base station proceeds to step 318 and transmits a ranging response signal to the corresponding mobile terminal. In this case, the base station transmits the ranging response signal using a ranging code and a ranging subchannel received from the corresponding mobile terminal that has transmitted the ranging request signal.

The base station transmits the ranging response signal and then proceeds to step 320. In step 320, the base station determines whether a time point for transmitting system information has arrived, and when it is determined that the base station transmits the system information, the base station proceeds to step 310 and repeats the above-described procedures. That is, the base station periodically transmits system information to mobile terminals in the same cell in step 320.

On the other hand, referring to Figure 4 described in detail the operation of the mobile terminal according to an embodiment of the present invention, the mobile terminal determines whether the ranging is necessary in step 410. If it is determined in step 410 that ranging is not necessary, the mobile terminal proceeds to step 424 to set a data subchannel, and transmits and receives data with the base station through the set subchannel. However, if it is determined in step 410 that ranging is necessary, the mobile terminal proceeds to step 412.

The mobile terminal proceeds to step 412 and checks the reception information related to ranging through previously stored system information. That is, the ranging code set and the ranging subchannel to be used for ranging are identified. The ranging code set means a ranging code set composed of different ranging codes for each base station. That is, the ranging code set is comprised of ranging codes uniquely assigned to a specific base station. When the ranging related information is confirmed, the mobile terminal proceeds to step 414 to confirm the ranging code set. When the confirmation is made, the mobile terminal proceeds to step 416 to determine whether the checked ranging information is valid. . If it is determined that the ranging information is not valid, the mobile terminal proceeds to step 418 and newly receives ranging related information from the base station, and proceeds to step 412 to perform the above-described process again. However, if the ranging information is determined to be valid in step 416, the mobile terminal proceeds to step 420. The mobile terminal proceeds to step 420 and selects any one of the ranging codes in the valid ranging code set. In addition, the mobile station selects any one of ranging subchannels of the valid ranging information. When the mobile station selects the ranging code and the ranging subchannel, the mobile terminal proceeds to step 422 and transmits a ranging request message requesting the use of the selected ranging code and the ranging subchannel to the base station.

Meanwhile, as another method of selecting a ranging code in step 420, the operation of the mobile terminal according to an embodiment of the present invention will be described in detail with reference to FIG. 5. To judge. If it is determined in step 510 that the ranging is not necessary, the mobile terminal proceeds to step 526 to set a data subchannel, and transmits and receives data with the base station through the set subchannel. However, if it is determined in step 510 that ranging is necessary, the mobile terminal proceeds to step 512.

The mobile terminal proceeds to step 512 and checks the reception information related to ranging through previously stored system information. That is, the ranging code set and the ranging subchannel to be used for ranging are identified. The ranging code set means a ranging code set composed of different ranging codes for each base station. That is, the ranging code set is comprised of ranging codes uniquely assigned to a specific base station. When the ranging related information is confirmed, the mobile terminal proceeds to step 514 to confirm the ranging code set. When the confirmation is made, the mobile terminal proceeds to step 516 to determine whether the checked ranging information is valid. . If it is determined that the ranging information is not valid, the mobile terminal proceeds to step 518 and newly receives ranging related information from the base station, and then proceeds to step 512 to perform the above process again. However, if the ranging information is determined to be valid in step 516, the mobile terminal proceeds to step 520. The mobile terminal proceeds to step 520 to avoid a collision caused by the ranging request signal of other terminals existing in the same cell randomly selecting the same ranging code among the ranging codes in the valid ranging code set. Through the process of Equation 1, the ranging code selectable by the terminal is limited. That is, each mobile terminal that needs ranging finds the number of ranging codes from the ranging code set of the received system information, and divides the unique ID of the terminal by the number of ranging codes, thereby ranging the index corresponding to the remaining number. Select the code. In addition, the mobile terminal proceeds to step 522 to select an arbitrary one from ranging subchannels of the valid ranging information. When the mobile station selects the ranging code and the ranging subchannel, the mobile station proceeds to step 524 and transmits a ranging request message requesting the use of the selected ranging code and the ranging subchannel to the base station. If there is no response to the ranging signal by the ranging code selection, the ranging signal is retransmitted with a time offset change by random backoff as in the conventional method.

Therefore, whenever the base station receives a signal on the ranging subchannel, only the ranging codes of the ranging code set used by the base station checks only the ranging signals from the terminals in the cell. Even if the registered terminal receives the ranging signal transmitted, the ranging response to these signals can be blocked. In addition, the terminal receiving the ranging response signal from the base station, even if the received ranging response signal from the base station of the adjacent cells can easily determine whether or not their ranging response signal due to the difference in the ranging code set to use the adjacent cells. have.

Hereinafter, an operation according to another embodiment of the present invention will be described in detail with reference to the above-described drawings. Another embodiment of the present invention to be described below relates to a limitation of ranging code selection according to a service class and a method for differential transmission in a ranging response signal.

6 is a diagram illustrating a control flow for ranging in a base station according to another embodiment of the present invention.

Referring to FIG. 6, in step 610, the base station transmits corresponding information for ranging to all mobile terminals in a cell through a broadcast channel. At this time, the base station transmits a ranging code set previously allocated by the OFDMA wireless communication system and corresponding ranging subchannel sets.

In step 614, the base station waits for reception of ranging request signals from the mobile terminal corresponding to the corresponding information for the ranging on the allocated subchannels. If there is no ranging request signal received in step 616, the base station continuously waits for reception of the ranging request signals in step 614. However, the base station that receives the ranging request signals in step 618 proceeds to step 620 and determines whether the ranging by the ranging request signal is suitable for a predetermined tolerable limit of the base station. If it is determined in step 620 that it does not meet the predetermined ranging criteria, the process proceeds to step 630. However, if it is determined in step 620 that it meets the ranging criteria, the base station determines in step 622 whether the code used for the ranging request signal suitable for the ranging criteria exists in the ranging code set assigned to the base station. do. If the ranging code suitable for the criterion does not exist in the ranging code set assigned thereto, the base station proceeds to step 630. However, if the ranging code used by the ranging request signal suitable for the ranging criteria exists in the ranging code set, the base station determines whether there are two or more ranging request signals requesting the same channel in step 624. . If two or more ranging request signals select the same channel, the base station determines the service level of the corresponding terminals from the ranging code used by the ranging request signal and proceeds from step 626 to determine from the terminal having the highest service level. Selects a ranging request signal. The highest service grade means the highest priority. When the ranging request signal having the highest priority is selected, the ranging response signal corresponding to the selected ranging request signal is transmitted. In this case, the base station transmits the ranging response signal using a ranging code and a ranging subchannel received from the corresponding mobile terminal that has transmitted the ranging request signal. If the corresponding mobile stations have the same service class or two or more ranging signals requesting the same channel, the base station uses the existing ranging response signal transmission criteria.

After the base station transmits the ranging response signal, the base station proceeds to step 630. If the base station proceeds to step 630, it is determined whether the time to transmit system information has arrived. That is, the base station periodically transmits system information to mobile terminals in the same cell in step 630.

7 is a diagram illustrating a control flow for ranging in a mobile terminal according to another embodiment of the present invention.

Referring to FIG. 7, the mobile terminal determines whether ranging is necessary in step 710. If it is determined in step 710 that ranging is not necessary, the mobile terminal proceeds to step 726 to set a data subchannel, and transmits and receives data with the base station through the set subchannel. However, if it is determined in step 710 that ranging is necessary, the mobile terminal proceeds to step 712.

The mobile terminal proceeds to step 712 and checks the reception information related to ranging through previously stored system information. That is, the ranging code set and the ranging subchannel to be used for ranging are identified. The ranging code set means a ranging code set composed of different ranging codes for each base station. That is, the ranging code set is comprised of ranging codes uniquely assigned to a specific base station. When the ranging related information is confirmed, the mobile terminal proceeds to step 714 to confirm the ranging code set. When the check is performed, the mobile terminal proceeds to step 716 to determine whether the checked ranging information is valid. . If it is determined that the ranging information is not valid, the mobile terminal proceeds to step 718 and newly receives ranging related information from the base station, and then proceeds to step 712 to perform the aforementioned process again. However, if the ranging information is determined to be valid in step 716, the mobile terminal proceeds to step 720. The mobile terminal proceeds to step 720 and selects one ranging code among ranging code indices of the ranging code set selectable by Equation 2 according to its service level. This limits the number of ranging codes that can be selected based on their service class. In step 722, the mobile terminal selects any one subchannel among ranging subchannels.

When the mobile station selects the ranging code and the ranging subchannel, the mobile terminal proceeds to step 724 and transmits a ranging request message requesting the use of the selected ranging code and the ranging subchannel to the base station. If there is no response to the ranging signal by the ranging code selection, the ranging signal is retransmitted with a time offset change by random backoff as in the conventional method.

Therefore, in the ranging operation, the number of ranging codes that the terminal can select according to the service class of the terminal that can only occur within the same cell is different, and accordingly different collision possibilities, thereby distinguishing the service. Can be. In addition, the base station can differentiate the service by preferentially transmitting a ranging response signal to a terminal having a high service grade according to the service grade of terminals requesting the same channel.

The present invention can be applied to a ranging procedure of an OFDMA wireless communication system. In Mode B _L of IEEE802.16a, which is currently enacted, the base station provides uplink and downlink map information as one of broadcast system information through UL-MAP_Information_Element and DL_MAP_Information_Element of UL-MAP message and DL-MAP message, respectively. do. In the UL-MAP_Information_Element, information necessary when the terminal performs ranging includes an element for indicating which subchannels are currently used as ranging subchannels in the base station. Table 1 below shows the configuration of a ranging related information message in the existing IEEE802.16a.

Syntax Size Notes UL-MAP_Information_Element () { CID 16 bits Connection Identifier UIUC 4 bits Purpose of use of burst OFDMA Symbol Offset 10 bits Offset to indicate the start of the burst Sub-Channel Offset 6 bits Index of the first subchannel of the OFDMA subchannels used to transmit the burst No. OFDMA Symbols 10 bits Number of OFDMA Symbols Used to Transmit Uplink Bursts No. Sub-Channels 6 bits Number of OFDMA Subchannels Used to Send Bursts    }

In Table 1, the UIUC value has a value from '0' to '15', and indicates the purpose of the burst. When this UIUC value is '12', this indicates that the corresponding burst is used as a ranging subchannel. Therefore, in the conventional method, information required for ranging received from the base station is which subchannel is used as the ranging subchannel, and the ranging codes are the PN code generator, 1 + X ¹ + X ⁴ + X ⁷ + X ¹⁵ A total of 48 ranging codes created by cutting the PN code sequence generated by the first bit by 53 bits are used in all cells. Therefore, even if a base station receives a ranging request signal from a terminal registered to neighboring cells, the base station cannot detect whether the signal is from a terminal registered in its cell.

Table 2 below shows a structure of a UCD message in which the base station broadcasts periodically. In Table 2, it can be seen that there is no information indicating the ranging code set used by the base station.

Syntax Size Notes UCD-Message_Format () {    Management Message Type = 0 8 bits    Uplink channel ID 8 bits    Configuration Change Count 8 bits    Mini-slot size 8 bits    Ranging Backoff Start 8 bits    Ranging Backoff End 8 bits    Request Backoff Start 8 bits    Request Backoff End 8 bits    Request Backoff Start 8 bits    TLV Encoded Information for the overall channel Variable    Begin PHY Specific Section {      for (i = 1; i <n; i + n)    Uplink_Burst_Descriptor Variable      }    } }

However, if a different ranging code set is used for each base station as proposed in the present invention, the base station can avoid interference caused by ranging request signals from terminals registered in neighboring cells. The ranging code set information used by the base station includes all elements belonging to the cell by adding one element to an uplink channel descriptor message, which is one of system information messages periodically broadcasted by the base station, as shown in Table 3 below. It can inform the terminals. The UCD message shown in Table 3 below contains information on uplink channels.

Syntax Size Notes UCD-Message_Format () {    Management Message Type = 0 8 bits    Uplink channel ID 8 bits    Configuration Change Count 8 bits    Mini-slot size 8 bits    Ranging Backoff Start 8 bits    Ranging Backoff End 8 bits    Request Backoff Start 8 bits    Request Backoff End 8 bits    Request Backoff Start 8 bits    Ranging Code Set 4 bits Ranging Code Set Index Used in Cells    TLV Encoded Information for the overall channel Variable    Begin PHY Specific Section {      for (i = 1; i <n; i + n)    Uplink_Burst_Descriptor Variable      }    } }

The number of ranging code sets must be equal to or larger than the ranging code reuse coefficient as described above, and the number of ranging codes belonging to each ranging code set is one or more. Therefore, if the ranging code reuse coefficient is 7 and the ranging code uses the IEEE802.16a / D1 standard PRBS code, the 53-bit long ranging code, R _i (i = 0,1, ..., Up to 618).

In addition, IEEE802.16a / D1 assumes 48 ranging codes per ranging code set because the total number of ranging codes used for ranging is 48, and the ranging code index, j (0, 1) , ..., 47). Therefore, if a ranging code of IEEE802.16a / D1 is used, up to 12 ranging code sets, RS _r (r = 0, 1, ..., 11) can be created. r is the index of the ranging code set, appended in order of generation.

RS _r (r = 0,1, ..., 11)

Therefore, the "Ranging Code Set" element of Table 3 may be represented by 4 bits that may represent an index value of the ranging code set. Since the terminal already knows the ranging code generation polynomial, and since the ranging code generation polynomial is one, the terminal can know which ranging codes are used even if the base station only provides the ranging code set index. In the existing IEEE802.16a / D1, only an index, a ranging code set with r of 0, and RS ₀ were used for the ranging procedure of the system.

In addition, the ranging code used may use other codes having good correlation characteristics in addition to the above-described PRBS code, and may only broadcast ranging code set information for knowing ranging codes used in a cell.

As described above, the present invention is different from the conventional ranging procedure described in the prior art by changing the ranging code used for each adjacent cell to determine whether the ranging signal received from the cell is a signal of a terminal belonging to its own cell. It can be easily seen to prevent the ranging success probability lowered by the ranging signal detection error. In addition, when the terminal moves to the neighboring cell, the ranging code set and the ranging subchannel information used by the base station of the neighboring cell are received in advance from the connected base station, so that handover to the neighboring cell can be performed quickly.                     

In addition, when the mobile terminal selects the ranging code, by limiting the number of ranging codes that can be selected according to the service class, the collision probability and the service provision according to the service class can be discriminated. Alternatively, by setting the ranging code index that the mobile device can select according to the unique MAC address of the mobile station and the number of ranging codes, the collision probability can be somewhat lower than that of the conventional random selection.

Claims (10)

In the ranging method in the base station of the OFDMA wireless communication system for assigning a ranging code set corresponding to each of the base stations, each of the ranging code set comprises a plurality of different ranging codes, Broadcasting ranging codes of the allocated ranging code set and corresponding ranging subchannels at a predetermined period; Determining whether a ranging code requested from the predetermined mobile terminal satisfies a predetermined ranging criterion and exists in the assigned ranging code set when a ranging request is received from a predetermined mobile terminal; And transmitting a response signal from the mobile terminal to the requested ranging code and a ranging subchannel if the predetermined ranging criterion is satisfied and is present in the allocated ranging code set. . The method of claim 1, And if the ranging code requested from the mobile terminal does not exist in the allocated ranging code set, transmitting the response signal. In the ranging method in the mobile terminal of the OFDMA wireless communication system for assigning a ranging code set corresponding to each of the base stations, each ranging code set comprises a plurality of different ranging codes, Setting a ranging code set corresponding to the base station in advance through system information broadcast from the base station; Selecting any one ranging code from the ranging code set when the ranging is required, and selecting one ranging subchannel among ranging subchannels allocated by the system information; and, And loading the selected ranging code on the selected ranging subchannel and transmitting the selected ranging code to the base station. The method of claim 3, Receiving a response signal from the base station and terminating the ranging code when the ranging code used in the response signal is present in the ranging code set. The method of claim 1, The ranging code is selected using a unique identifier of the mobile terminal, that is, a MAC address. The method of claim 5, When the base station receiving the request signal to the mobile station transmits the response signal, the base station knows the service level of the mobile terminal from the ranging code used for the request signal, and discriminates the response signal transmission according to the service level The method characterized in that it comprises a. In the ranging method in the base station of the OFDMA wireless communication system for assigning a ranging code set corresponding to each of the base stations, each of the ranging code set comprises a plurality of different ranging codes, Broadcasting ranging codes of the allocated ranging code set and corresponding ranging subchannels at a predetermined period; When there are ranging requests from a plurality of mobile terminals, use of the same ranging code satisfying a predetermined ranging criterion from the plurality of mobile terminals and satisfying a condition present in the allocated ranging code set is requested. The process of determining whether If the use of the same ranging code that satisfies the condition is requested from the plurality of mobile terminals, the service classes of the plurality of mobile terminals are determined, and the ranging code and ranging requested from the mobile terminal having the highest service grade are determined. And transmitting a response signal through a subchannel. The method of claim 7, wherein If a request for use of a different ranging code is satisfied from the plurality of mobile terminals, but a response signal is transmitted from each of the plurality of mobile terminals to the ranging code and the ranging subchannel. The method characterized in that. In the ranging method in the mobile terminal of the OFDMA wireless communication system for assigning a ranging code set corresponding to each of the base stations, each ranging code set comprises a plurality of different ranging codes, Setting a ranging code set corresponding to the base station in advance through system information broadcast from the base station; When the ranging is required, any one ranging code is selected from the ranging code set corresponding to its service class, and any one of the ranging subchannels allocated by the system information is selected. Selecting a subchannel And loading the selected ranging code on the selected ranging subchannel and transmitting the selected ranging code to the base station. The method as claimed in claim 9, wherein the ranging code is selected by Equation 3 below.

Here, SG _g represents its service class, and SG _G represents the lowest service class in a system.

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