Device and method for assigning spreading code for reverse common channel massage in CDMA communication system

Apparatus and method for allocating spreading codes for reverse common channel messages in code division multiple access communication system

Background of the invention 1. FIELD OF THE INVENTION The present invention generally relates to the field of wireless communication, and more particularly to a device and method for transmitting reverse common channel messages on a temporarily designated collision-free channel (collision-free channel) in a multimedia communication system.

2. Description of related technologies In a communication system based on the TIA/EIA/IS-95 standard, usually on the forward paging channel and the backward access channel in the base station (base station, BS) and mobile station (mobile station, MS) For message communication between them, the channel is a common channel before the voice call is established. In order to communicate with the base station without a dedicated channel connection, the base station must send the message to the paging channel and receive the response on the access channel. From the mobile station's point of view, the mobile station sends a message to the access channel and receives a response on the paging channel. There can be multiple paging and access channels. Each paging channel is distinguished by a unique Walsh code, and each access channel is distinguished by a long code, which is generated using the access channel long code mask.

Figures 1A and 1B show message transmission on a common channel between a base station and a mobile station. 1A, when the base station sends a control message to the paging channel, the correspondingly addressed mobile station sends a response message to the access channel. If the mobile station sends a control message to the access channel, the base station sends a response message for the mobile station to the paging channel. Referring to FIG. 1B, the mobile station sends an access channel message for the base station to the access channel after the message exchange.

The conventional access channel communication method is suitable for processing voice calls under light traffic conditions. If mobile stations sharing the same long code at the same time send messages to the access channel, message contention will occur, resulting in message loss. This mechanism is called contention-based random access.

When such contention for the access channel occurs, the mobile station should try to send the message to the access channel again. In this case, each mobile station uses its assigned long code to send a message to the access channel, and if contention occurs, it captures the message generated within a predetermined time and delays it during the randomization time. Resume message sending afterwards. The mobile station performs an initial trial at a predetermined power level to access the base station. When it does not receive a response message from the base station, it performs the next trial at a power level that is a certain amount higher than the power level of the previous trial. If the predetermined number of repeated attempts to access the access channel proves to be unsuccessful, the process is restarted from the lowest predetermined power level. Information is sent to the access channel in the form of access channel time slots and access channel frames.

Figure 8 describes the message sending process from the mobile station on the access channel. The entire process of sending a message and receiving (or not receiving) a response to the message is called an access trial. Each transmission in an access trial is called an access probe. The access probe is a series of progressively high-power transmissions used when the mobile station tries to access the system for the first time. Each access probe includes a preamble and a message capsule. In the access trial process, access probes constitute an access probe sequence. Each access probe sequence includes a predetermined number (Max_Probe_No) of access probes, and the entire access trial is composed of a predetermined number (Max_Sequence_No) of access probe sequences. First, the first access probe of each access probe sequence is transmitted at relatively low power. Each subsequent access probe is sent at a progressively higher power level than the previous access probe. The time interval RS between access probe sequences is determined by a random function. The time interval TA+RT between each access probe of an access probe sequence is also generated by a random function. After sending each access probe, the mobile station waits for a predetermined period TA to receive an answer signal from the base station. If the response signal is received, the access trial ends successfully. If no response signal is received, the next access probe is sent after a random time RT.

In the above-mentioned long code sharing scheme for common channels, the mobile station uses the Hash function in its initialization state to determine one of all available long codes (access common long codes), so that all mobile stations The long codes of the access channel are shared fairly. To assign the mobile station category, adjust the average of the initial trial time and the next trial time.

According to whether the data service is initiated by the MS or the BS, there are two types of messages sent on the access channel, that is, a message sent spontaneously by the mobile station and a response message as a response to the base station (ie, paging channel) message. These two messages are logically processed at the same level. Both the message initiated by the MS and the paging response message are sent using the access channel long code, which is determined by the mobile station using the Hash function.

The transmission rate of the access channel is determined in a conventional communication system. According to the IS-95 standard, the access channel message is generated in accordance with the upper layer and physical layer protocols. In addition, the message is spread by the access channel long code determined by the mobile station.

However, the mechanism of accessing the common channel of data services in the conventional communication system has the following problems: (1) Random access--because the access channel is obtained through contention-based random access, the same long code is used. The sending of messages can easily cause message contention and cause message loss. When message contention occurs, the mobile station resends the message to the access channel after a predetermined and randomized period of time. It is impossible to estimate the time required to obtain the access channel, thereby increasing the average message transmission time, the variation of the transmission time, and the power consumption of the mobile station; (2) Long code sharing-the mobile station is equally allocated for public use The available long code of the channel makes it impossible to control the individual probability of contention for each mobile station's access channel. Therefore, it is desirable to adopt different procedures for common channel access determined by the data requirements of the mobile station. That is, a mobile station entering data communication with a relatively small time constraint should have a common channel access procedure different from that of a mobile station processing real-time time data such as moving pictures. To achieve this, the long code should be allocated to the latter in a way that allows fast access to the common channel. However, the above-mentioned conventional equivalent long code allocation method cannot provide this special data service; (3) Mobile station category (class) Assignment--it is impossible to assign the mobile station category during access to the common channel, because when the mobile station uses an access channel, the contention probability cannot be controlled; (4) In the control message originating parties ( There is no distinction between MS-originated and BS-originated). In other words, it is impossible to determine whether the access channel request priority should be given to the response message for the base station message, or vice versa, the base station message is a message spontaneously generated from the mobile station; (5) The mobile station can usually pass the service priority However, since the response messages initiated by the base station are processed equally, they cannot be assigned categories; and (6) the fixed transmission rate of the access channel. This increases the transmission time of long messages on the access channel. This results in an increase in the time occupied by the access channel, which in turn increases the probability of contention.

Summary of the present invention As embodied and mainly described herein, an object of the present invention is to provide a device and method for communicating on a common channel in a communication system, which can reduce the transmission delay of the common channel and Increase its transmission efficiency to support data services.

Another object of the present invention is to provide a common channel access device and method for a communication system, in which user categories are allocated according to user data types in data communication.

Another object of the present invention is to provide a device and method for processing BS-originated data using the priority of MS-originated data in a communication system.

Another object of the present invention is to provide an apparatus and method for continuously sending a common channel message of more than one transmittable length on a designated specific common channel.

Another object of the present invention is to provide an apparatus and method for spreading a reverse common channel message for transmission through a code allocated by a base station in order to prevent message contention.

In order to achieve the above objective of the present invention, a common channel message communication device and method in a CDMA communication system are provided. In the base station of the common channel message communication equipment, the control message generator generates a control message including information indicating the spreading code used to spread the reverse common channel message. The control message is sent to a forward common channel. In the mobile station, the control message analyzer analyzes the information indicating the allocated spreading code included in the control message received from the forward common channel, the spreading code generator generates a spreading code based on the spreading code information, and the channel transmits The receiver uses the spreading code to spread the reverse common channel message and send the spread common channel message.

Brief Description of the Drawings By describing the preferred embodiments of the present invention with reference to the accompanying drawings, the above-mentioned objects and advantages of the present invention will become more apparent. In the accompanying drawings: Figures 1A and 1B show message exchange in a conventional communication system; Figure 2 Figure 3A and 3B show a common channel message communication process between a base station and a mobile station according to an embodiment of the present invention; Figure 4 shows the state transition diagram of the packet service in the communication system; Embodiment of the control message format on the forward link in the communication system; Figure 5 is a block diagram of a mobile station for sending common channel messages in a communication system according to an embodiment of the present invention; Figure 6 is a block diagram of a mobile station used to send common channel messages in a communication system according to an embodiment of the present invention; A block diagram of a base station for sending common channel messages in a communication system according to an embodiment of the invention; FIGS. 7A and 7B respectively illustrate the control message generation and resolution performed in the base station of the communication system according to the embodiment of the invention. The flow chart of the tuner control; Figure 8 shows the message sending process on the common channel shared by multiple mobile stations; Figure 9 shows the message sending process on the common channel designated as dedicated to a specific mobile station;

Figures 10A and 10B are flowcharts of sending common channel messages from a mobile station in the communication system of the present invention; Figure 11 is an implementation of continuous common channel message transmission between a base station and a mobile station in the communication system of the present invention Fig. 12 is a flowchart of another embodiment of continuous common channel message transmission between a base station and a mobile station in the communication system of the present invention; and Fig. 13 is a flowchart of another embodiment in the communication system of the present invention. The unique long code assigned by it is designated as a message transmission on the access channel dedicated to a specific mobile station.

Detailed description of the preferred embodiment The following description of the present invention is directed to the details including the long code, service type and duration used for the access channel, and these details are provided for a comprehensive understanding of the present invention. For any person skilled in the art, it is obvious that the present invention can be implemented even without these details or through modification. Although the description of the embodiments of the present invention is limited to the packet access channel, which is a special form of the access channel, the present invention can be (partly) applied to general access channels, such as circuit voice services in conventional systems.

Terms and definitions 1. The term "data" used here is used in its broadest sense and includes internal alias (alia), packet data, circuit voice, and signaling.

2. The packet common channel is provided as a new common channel to provide fast data transmission in the packet data communication of the communication system. The channel identification code of the packet access channel (that is, the reverse packet common channel) is dynamically allocated to obtain high-speed data services. Here, the channel identification code is assumed to be a long code. The term "packet data" here refers to general data, such as text and real-time data like video data and voice. The packet common channel and the packet access channel are broadly referred to as a common channel and an access channel, respectively, to include conventional (ie, non-packet) access and common control channels.

(1) The high-speed packet data service reduces the transmission delay of the common channel. That is, in order to effectively use resources in high-speed data services, a state transition from a dedicated channel to a common channel occurs regardless of whether the data is sent within a predetermined time. When a call is only established for voice processing between the base station and the mobile station, the common channel is limited to short message service. However, the state transition between the public channel and the dedicated channel frequently occurs in the fast packet data service. Therefore, in the communication mechanism provided by the present invention, the message can be sent to the common channel with reduced transmission delay to realize fast packet data communication in a highly dynamic conversion environment; (2) adjust the user category to control the common channel usage of. In the fast packet data service, various forms of data should be sent, including: A) general data, which requires relatively little real-time processing, but requires high transmission reliability; B) voice, which should be sent in real time, but in transmission Reliability is relatively not very important, and C) image information requires real-time processing and high transmission reliability. Therefore, in order to support various forms of user data, the contention probability, bit rate, and transmission delay of the common channel are individually controlled for each base station; and (3) different common channels are used for the forward service and the reverse service. control. In fast packet data services, the service from the base station to the mobile station is usually heavier than the service from the mobile station to the base station. For example, in providing end users with WWW (World Wide In the case of the Web (World Wide Web) service, a large amount of data for each paging is sent from the base station to the mobile station, but the amount of data sent from the mobile station to the base station is greatly reduced. In view of this inconsistency, the common channel should be used to process BS-originated data with higher priority than MS-originated data.

Packet data service status Before describing the method of the present invention, first review the packet data service status to better understand the common channel.

Fig. 2 is a state transition diagram for packet services in a communication system in the prior art. 2, the packet service includes a packet zero state 21, an initialization state 22, a valid state 23, a control hold state 24, a pause state 25, a sleep state 26, and a reconnection state 27. Connect the packet service options in the control hold state, active state, and pause state. Before the packet service is activated, the packet zero state is the default state.

When a packet service is requested in the packet zero state, an initialization state is entered, in which a connection trial of the packet service is performed, and if a dedicated control channel is established, a transition to the control hold state occurs. The dedicated control channel needs to be used to initialize RLP (Radio Link Protocol) and PPP (Point-to-Point Protocol). Then, when entering the active state, the forward and backward dedicated control channels and traffic channels are maintained, and RLP frame communication is performed on these channels. If relatively few invalid time periods are set, the pause state is entered to effectively use wireless resources and save the power of the mobile station. In the suspended state, the dedicated channel is released but can be redistributed in a relatively short time, because both the base station and the mobile station retain state information including RLP state, traffic channel allocation, and encryption variables. If there is no data exchange within a predetermined time, the pause state 25 is converted to the sleep state 26. In the sleep state 26, only the PPP connection is maintained, and if transmission data is generated, the reconnection state 27 is entered. If the dedicated control channel is established, the reconnection state changes to the control hold state 24. While the mobile station is in common channel states such as pause, packet zero, initialization, dormancy, and reconnect states, it monitors the packet paging channel on the forward link. The packet paging channel is usually called the paging channel.

As described above, in a common channel using multiple states, each message is sent to each common channel (ie, paging channel and access channel) between the base station and the mobile station without establishing a dedicated channel. The present invention provides a method for effectively using the access channel on the reverse link in the common channel using multiple states.

3A and 3B show message transmission on the common channel between the base station 34 and the mobile station 36 according to an embodiment of the present invention. The forward control message 31 sent on the common channel includes the access channel information required for the response or system access 32.

Fig. 3A shows an exemplary message exchange performed in the communication system of the present invention. When the base station 34 transmits the control message 31 using the long code information necessary for the response from the mobile station 36, the mobile station 36 transmits the response message 32 to the base station on the dedicated or common channel corresponding to the long code allocated by the control message. . Fig. 3B shows another exemplary message exchange performed in the communication system of the present invention. When the base station 34 transmits the control message using the long code information indicating the access channel, the mobile station 36 transmits the access message 36 to the base station on a dedicated or public channel. If the control message contains long code duration information, the assigned common channel of the long code maintains the timer setting until the duration expires.

It should be noted that the communication system of the present invention supports the conventional message exchange shown in FIGS. 1A and 1B and the message exchange corresponding to the present invention as shown in FIGS. 3A and 3B.

Figure 4 shows the format of the forward control message of the present invention. The control message field 41 contains information corresponding to the purpose of the control message, and the private/public field indicates whether the reverse channel used to send the response message is designated as private or public. A dedicated channel is a channel assigned to a specific mobile station, and a common channel is a channel shared by one or more mobile stations. The parameter presence field 43 indicates the presence or absence of an optional field in the control message. For example, if each field uses 1 bit or 3 bits, the "1" in the first bit indicates the existence of the long code ID field, and the "0" in the first bit indicates the absence of the long code ID field. Similarly, the second bit and the third bit may indicate the presence or absence of the maximum duration field and the presence or absence of the bit rate field, respectively. Therefore, reading the corresponding bit value in the parameter existence field enables the mobile station receiving the control message to determine whether each field exists.

The parameters in the control message of FIG. 4 are the long code ID44, the maximum duration 45, and the bit rate 46. The long code ID field is an optional field and is used to specify the long code used for the mobile station to send the response message. Since the access channel is identified by the access channel long code mask, specifying the long code means specifying the access channel number. The maximum duration field indicates the maximum time period that the allocated long code can maintain. In other words, if the maximum duration is given as T seconds, the mobile station can use the allocated long code to perform an access trial to the access channel within T seconds at most, and the base station should also operate the demodulator to ensure that Receive the reverse channel spread by the long code within seconds. The bit rate field is an optional field used to set the bit rate of the reverse channel for sending a response or access message when a multi-bit rate (multi-bit rate) is used.

Fig. 5 is a block diagram of a mobile station for packet data communication according to an embodiment of the present invention. 5, the receiver 511 converts an RF (Radio Frequency) signal received through an antenna into a baseband signal. The demodulator 513 demodulates the baseband signal received from the receiver 511 into an original signal. The control message analyzer 515 analyzes the fields of the control message received from the demodulator 513 as shown in FIG. 4, and generates information for controlling communication on the corresponding common channel. The information output from the control message analyzer 515 includes bit rate, private/public, long code ID, and maximum duration.

The transmission controller 551 receives the private/public information on the common channel and the response signal ACK from the control message analyzer 515, and determines the message transmission program according to the private/public information. The sending controller 551 sends an access probe sending command (access probe Tx command) for accessing the access channel to the message buffer 553, and powers the access channel power used for the corresponding access probe number. Ping output to the transmitter 533. The transmission controller 551 also generates a control signal for clearing the message buffer 553 when receiving the response signal ACK.

The message buffer 553 stores the higher-layer access channel message to be sent to the access channel. Each time an access probe sending command is generated from the sending controller 551, the internally stored message is sent, and the message is sent from the sending controller. When the clear signal of 551 is used, the internally stored message is cleared.

The transmission rate controller 523 receives the bit rate value from the control message analyzer 515 and generates a transmission rate for controlling the data to be transmitted on the access channel. The memory 519 stores information about private/public, long code ID, and maximum duration. The long code controller 517 receives private/public, long code ID, maximum duration information from the control message analyzer 515, and determines the long code based on the information received from the control message analyzer 515 and the memory 519. The long code generator 521 generates a corresponding long code under the control of the long code controller 517. The time period used to generate the long code is determined by the maximum duration information.

The channel encoder and quadrature modulator 525 subjects the access channel data received from the message buffer 553 to encoding, repetition, and interleaving at the bit rate received from the transmission rate controller 523. Then, the resulting access channel message (reverse common channel message) is orthogonally modulated. The multipliers 527 and 529 multiply the long code received from the long code generator 521 by the PN sequences PN_I and PN_Q, respectively, and generate the PN sequence. The PN spreader 531 multiplies the orthogonally spread access channel signal by the I channel and Q channel spread sequences received from the multipliers 527 and 529. The transmitter 533 up-converts the spread access channel signal received from the PN spreader 531 into an RF signal for transmission.

In operation, the receiver 511 of the mobile station thus constructed receives the RF signal, and the demodulator 513 demodulates the received signal through despreading and decoding processing and generates a control message. Then, the control message analyzer 515 extracts the private/public value from the control message, as shown in Figure 4, by analyzing the content of each field to determine whether there is a long code ID, maximum duration value, and bit rate, and extracts the existence of the field Each value. The control message analyzer 515 sends the private/public value and the response signal ACK to the transmission controller 551, sends the private/public, the long code ID, and the maximum duration value to the long code controller 517, and sends the bit rate value to the transmission controller 551. Rate controller 523.

The transmission controller 551 adopts a different message transmission procedure according to the private/common value received from the control message analyzer 515. In other words, when the private/public value indicates the common channel, multiple mobile stations have to send messages to the common access channel. Therefore, they send the message to the common access channel in the method shown in Figure 8. On the other hand, if the dedicated/common value indicates a dedicated channel, the specific mobile station transmits the message to the dedicated access channel by performing an access trial as shown in FIG. 9. The message buffer 553 transmits an access channel message under the control of the transmission controller 551, and the transmitter 533 outputs the access channel at a power level corresponding to an access probe number under the control of the transmission controller 551 news. The access channel message transmission performed under the control of the transmission controller 551 will be described below with reference to FIGS. 8, 9 and 11.

According to the embodiment of the present invention, the memory 519 stores various parameters necessary for transmission on the access channel. The list of these parameters is as follows. (Table 1)

As shown in Table 1, the memory 519 stores information about the available long code ID, private/public, and maximum duration. The long code controller 517 determines which long code is to be generated in the long code generator 521 based on the private/public, long code ID and maximum duration received from the control message analyzer 515 and the information stored in the memory 519. The function of the memory 519 is to store information about the available long codes. The available long codes include the access channel long code mask allocated by the access channel parameter message in the general communication system, and the additional long code ID allocated by the control message in the communication system of the present invention.

If the private/public value indicates a dedicated channel and there is no long code ID, the long code (generated by the public long code mask) is determined by the unique number of the mobile station (ie, ESN: Electronic Serial Number). Here, it is assumed that the mobile station knows the unique long code of the mobile station according to the previously received message. The unique long code is also used for the traffic channel, but contention is not easy to occur, because the access channel and the traffic channel are not used at the same time. If the dedicated/common value indicates a dedicated channel and a long code ID is given, a spreading code is generated according to the assigned long code ID for spreading the reverse common channel message. Here, if the long code ID represents one of several separately obtained long code masks, the base station does not assign the long code ID to another mobile station, and therefore contention is unlikely to occur.

If the private/public value indicates a common channel and a long code ID is given, the assigned long code is used. When the long code ID does not exist, one of the multiple available long codes stored in the memory 519 is selected by the random number generating function provided to the long code controller 517. When the access trial using the long code received from the control message analyzer 515 fails, the long code generator 517 may use the long code selected from the available long codes in the memory 519 by the random number generating function to perform the access trial again. Therefore, when there is no long code information in the control message, the long code is selected from the available long codes in the memory 519 by the random number generating function.

The long code is fed from the long code generator 521 to the PN spreader 531. In the case where the maximum duration value is assigned to the long code ID, the corresponding long code is used, and is no longer used when the timeout indicated by the maximum duration value has passed. This can be done by setting a timer in the long code controller 517. The bit rate controller 523 controls the channel encoder and the quadrature modulator 525 according to the received bit rate value so as to transmit data at a designated bit rate. Therefore, in order to send the response message or access message for the forward control message to the access channel, the information about the long code, bit rate, and maximum duration in the forward control message is reflected as the reverse channel parameters.

Fig. 6 is a block diagram of a base station for data communication according to an embodiment of the present invention.

Referring to FIG. 6, the control message generator 612 generates control message data including access channel related information. The modulator 616 modulates the transmission signal and transmits the modulated signal as an RF signal to a forward common channel (for example, a paging channel or a forward common control channel). The control message generator 612 feeds the access channel related information (ie, long code ID, private/public, maximum duration, and bit rate) to the demodulation controller 620. The demodulation controller 620 controls the demodulation unit 624 according to the information to demodulate the signal received from the receiver 626. The first memory 614 stores information about the provided service and the long code ID assigned to each mobile station, as shown in Table 2, for providing parameters to the control message generator 612. The first memory 614 also retains information about the type of the long code (private or public), the mobile station number of the available long code when the long code is public, and the like. The second memory 622 stores the long code allocation and the expiration time in the respective demodulators 651 to 65N so that the demodulation controller 620 can refer to this information. (Table 2)

(table 3)

The first memory 614 stores information about the type of service in which the mobile station is engaged and the current long code ID is assigned, as shown in Table 2. The service type represents QOS (Quality Of Service, quality of service). The second memory 622 stores information about the long code ID, private/public, maximum duration, and bit rate used by the demodulators 651 to 65N, as shown in Table 3. The control message generator 612 determines the long code to be allocated based on the information in the first memory 614, and loads information about the long code ID, private/public, maximum duration, and bit rate of the control message to be sent.

As a way to specify the spreading code used to spread the reverse common channel message dedicated to a specific mobile station, as shown in Figure 4, the base station sets the private/public field of the control message to private, and lets the long code ID The field is empty so that the mobile station can use the public long code determined by its own ESN. When receiving the control message, the mobile station uses its ESN to generate a public long code mask, and spreads the reverse common channel message by using the long code generated by the public long code mask. This long code is dedicated to the mobile station and does not generate message contention.

Another method of assigning a dedicated long code to a mobile station is that the base station selects a long code ID in the pool of long code IDs. The long code ID is a long code ID that has not been previously assigned to a different mobile station. Long code ID, and send the selected long code ID to the mobile station through a control message. In order to allow the corresponding mobile station to send reverse common channel messages without signal contention with other mobile stations, the selected long code ID will not be allocated to another mobile station during its use. While the mobile station uses the long code ID, the base station does not allocate the same long code ID to different mobile stations, effectively making the long code ID dedicated to the mobile station.

In order to allocate the long code as public to the mobile station, the base station sets the private/public field of the control message as shown in Fig. 4 to public, and loads the long code ID with a long code selected from the long code ID obtained separately Field, but not designated as dedicated to a specific mobile station. When the base station wants to allocate the common long code to another mobile station, the occupied long code can be re-allocated to the mobile station. By controlling the number of mobile stations that use the same long code, the contention probability caused by the allocation of the same long code varies with the type of mobile station and the quality of service.

The allocation of the common long code can be obtained by sending a forward common channel message including the identifier of the existing access channel. That is to say, if it is not notified that there is no additional access channel number, the private/public field is set to public, and the long code ID field is vacant, and the mobile station determines that the access channel long code is in use in a conventional manner. This method can be designated as a semi-private public long code using the method described above. In addition, by allocating a long code to a mobile station within a predetermined time while avoiding other mobile stations from using the same long code, the common long code can be used as a dedicated mode.

The demodulation controller 620 receives the access channel related information from the control message generator 612, allocates long codes to the demodulators 651 to 65N if necessary, and stops the operation of a demodulator using the expired long codes. The long code demodulation time period is checked by setting a timer in the demodulation controller 620. The demodulation controller 620 controls the operation of the demodulators 651 to 65N in accordance with the receivable bit rate so that the signal received from the receiver 626 can be reliably demodulated.

7A and 7B are flowcharts respectively illustrating the operations of the control message generator 612 and the demodulation controller 620 in the base station of FIG. 6.

Referring to FIG. 7A, in the communication in step 711, the control message generator 612 determines whether the long code allocated to the access channel needs to be changed for a mobile station. The long code changes in the following situations: when entering the common channel state, the long code allocation changes, the response message long code changes, or the maximum duration of the response message long code is extended. In step 713, if there is a reason for changing the long code, the control message generator 612 determines the type of long code to be newly allocated. The long code types are classified into private, high-level public, and normal-level public. In step 715, the control message generator 612 determines whether there is an available long code. In step 717, when there is an available long code, the long code is determined to be allocated. In step 723, when there is no available long code, a long code is allocated to designate the general public access channel. In step 719, after the corresponding long code is determined, the parameters including the long code information are sent to the modulator 616. In step 721, the control message generator 612 also sends the long code information to the demodulation controller 620 and ends the process.

7B, the figure shows demodulation control in the base station. In step 751, the demodulation controller 620 determines whether long code information is received from the control message generator 612. When the long code information is received, in step 753, the demodulation controller 620 specifies a demodulator for demodulating the long code. Then, in step 755, the demodulation controller 620 checks the timer or state transition. If the timer expires or a state transition occurs, then in step 757, the allocated long code is discarded and the demodulator operation is stopped.

To send a message from the mobile station to the access channel, different procedures are performed depending on the private/public field of the received control message. Figure 8 shows how the access channel message is sent to the access channel designated as common. If the access channel is designated as dedicated, the procedure follows the method shown in Figure 9.

Figures 10A and 10B illustrate the access channel message transmission according to the private/public field.

With reference to FIGS. 8-10B below, a description will be provided of an access channel message sending procedure according to an embodiment of the present invention.

Figures 8 and 9 generally describe the sending of messages from the mobile station to the access channel. The process of sending a message and receiving (or not receiving) a response for the message is called an access trial. Each transmission in the access trial is called an access probe. Each access probe includes a preamble and a message capsule. In the access trial, the access probe is composed of an access probe sequence. Each access probe sequence is composed of a predetermined number of access probes, and the entire access trial is composed of a predetermined number of access probe sequences. The first access probe of each access probe sequence is sent at the initial power level, and each subsequent access probe is sent at a gradually higher power level than the previous access probe.

According to the type of the access channel, that is, according to whether the access channel is designated as dedicated or public, the time interval RS between the access probe sequences is set differently. In the case of a common access channel, the time interval is determined by a random function (ie, RT) as shown in FIG. 8. In the case of a dedicated access channel, the time interval is a constant as shown in FIG. 9 (ie, TA). The time (TA+RT) between access probes of an access probe sequence varies with the type of access channel. For the public access channel, it is determined by the random function as shown in Fig. 8, while for the dedicated access channel, it is determined as a constant, which can be zero. Referring to FIG. 8, after transmitting each access probe, the mobile station waits for a certain period of time TA to receive the response signal. If the response signal is received, the access trial ends successfully. If the response signal is not received, the next access probe is sent after an additional backup delay (backoff delay) RT. The backup delay is defined here as the interval between access probes. To avoid endless contention, this value should be a random value. In Fig. 8, RT and RS are respectively given as the first and second waiting periods. In addition, it is also assumed that the respective constants specifying the first and second waiting periods are the first and second constants.

Fig. 10 is a flowchart illustrating the steps of the method for performing message transmission according to Figs. 8 and 9. 10, the transmission controller 551 determines in step 1002 whether a private/public field value is received from the control message analyzer 515, and if such a value is received, it stores the received parameter in step 1004. In step 1006, the transmission controller 551 determines whether a transmission ready signal, that is, Tx Ready, is generated from the message buffer 553. When a message to be sent from a higher layer to the access channel is generated, the message buffer 553 stores the access channel message and informs the sending controller 553 that it is ready to be sent.

When the transmission ready signal Tx Ready is received, in step 1008, the transmission controller 551 initializes the probe number Probe_No and the sequence number Sequence_No to zero, and initializes the power level to the initial power level to transmit the access channel message . Then, in step 1010, the transmission controller 551 outputs the access probe transmission command to the message buffer 553, and outputs the current power level to the transmitter 533. In step 1012, the transmission controller 551 increments the probe number by 1, sets an acknowledgment (ACK) timer to check the acknowledgment period, and waits for a response from the base station. The response timer is set to TA, which is the period during which the mobile station waits for a response after sending an access channel message.

Then, the message buffer 553 outputs the currently stored access channel message, the channel encoder and quadrature modulator 525 subjects the access channel message to channel coding and orthogonal spreading, and the PN spreader 531 passes through the long code generator The long code and PN spreading sequence generated by 521 spread the spread spectrum of the access channel message. The transmitter 533 transmits the access channel message in the form of an RF signal at a power level specified by the transmission controller 551.

When receiving the access channel message in the access channel receiver of the base station, its paging channel transmitter sends a response message. In step 1014, the transmission controller 551 determines whether a response is received from the control message generator 515. When the response is received, in step 1016, the transmission controller 551 outputs a clear signal to the message buffer 553. Then, the message buffer 553 clears the internally stored messages in response to the clear signal, and is ready for the next state.

If no response is received until the timer expires in steps 1014 and 1018, the transmission controller 551 considers that the base station has not received the access channel message, and tries to resend the access channel message. In step 1020, the sending controller 551 determines whether the current probe sequence number is greater than the maximum probe number in the access probe sequence. If the current probe sequence number is within the current access probe sequence, then in step 1022, the sending controller 551 determines, according to the parameters stored in step 1004, that the access channel to which the current access channel message is to be sent is designated as Private or public, to set a random time RT, after the random time RT, the access channel message will be retransmitted.

For the public access channel, the random time RT is determined by a random function, while for the dedicated access channel, the random time RT is set to a predetermined constant, which can be zero. On the common access channel, the access channel message is repeatedly sent every RT time interval. The TA is defined to avoid continuous message contention, because multiple mobile stations are likely to try to obtain a common access channel. In contrast, since a specific mobile station or a few mobile stations try to use the dedicated access channel, there is no need to delay the transmission for a random time after the response period, so the random time RT is set to a predetermined constant. The random time RT may be randomly determined by a random function, and the function may be a Hash function. The random time RT for the common channel and the dedicated channel are determined in steps 1024 and 1026, respectively, and the probing standby timer for RT is determined in step 1028.

The transmission controller 551 waits for the time TA+RT, and then increases the power level in step 1032. Then, return to step 1010, where the access channel message is sent again. While repeating the above process to send the access channel message, if the response is not received within the corresponding access probe sequence in step 1020, then in step 1034, the sending controller 551 sets the probe number to 0 and sets The access probe sequence number is increased by 1, and the transmission power level is set to the initial value (see FIG. 10B).

In step 1036 of FIG. 10B, the transmission controller 551 determines whether the access channel to which the current access channel message is to be transmitted is designated as dedicated or public to determine the time interval RS between access probe sequences. This determination process is performed through the parameters obtained in step 1004. For the common access channel, the transmission controller 551 sets the RS to the time period obtained by the random function in step 1038. For the dedicated access channel, the RS is set as a constant in step 1040. In general, in the case of a common access channel, RT and RS are obtained through a random function, and in the case of a dedicated access channel, RT and RS are predetermined constants (RT may be 0).

Then, the transmission controller 551 sets the sequence standby timer [WHAT IS THIS?] for the RS in steps 1042 and 1044, and waits for the elapse of the time RS. When the time RS has passed, in step 1046, the transmission controller 551 determines whether the current sequence number is less than the maximum sequence number. If it is less than, in step 1010, the next sequence of access channel messages is sent. If the current sequence number is not less than the maximum sequence number, an access failure flag is set in step 1048 to announce the failure of sending the access channel message, and the process ends.

As described above, RS and RT are randomly determined or predetermined constants according to whether the access channel is designated as dedicated or public. Therefore, the efficiency of the access channel increases and its transmission delay decreases.

The following will describe in detail the access channel using the above-mentioned scheme, that is, the long code allocation.

Multiple long codes can be allocated to the access channel. Simultaneous message transmission from mobile stations using different long codes will not experience contention for access channels. However, multiple mobile stations sharing the same long code may lose their messages due to message contention when they transmit at the same time. Therefore, there is a need for an effective method for allocating access channel long codes to mobile stations.

There are three situations in which the base station additionally allocates the common channel long code to a mobile station: (1) In the packet service, it is converted from the dedicated channel state to the common channel state; (2) The previously allocated access channel long code is changed in the common channel state. And allow to continue to use the newly allocated long code; (3) Change the previously allocated access channel long code and allow the newly allocated long code to be used within a limited time.

When entering the common channel state, the long code allocation is also applied to the mobile station that initiates communication with the base station. Shortly before the state of the dedicated channel is converted to the state of the common channel, the access channel parameters are sent through a forward control message. That is, at the point of time when the state of the dedicated channel is switched to the state of the common channel (access channel), the base station allocates the long code to the mobile station. Although the base station can allocate the long code through the control message of FIG. 4, this is not always necessary. Whether this additional long code allocation should be performed is determined according to the type and quality of service provided to the mobile station. The mobile station stores the long code information in the memory 519 for the access trial. If the communication on the access channel to which the long code is allocated fails, the access channel corresponding to the conventionally allocated long code previously used in the initial stage of call establishment can be reused.

In an embodiment of the present invention, in the common channel state of the packet service, the base station can change the access channel long code previously allocated to the mobile station through a forward control message. In this case, since the newly allocated long code is retained for as long as the packet service is retained in the common channel state, the maximum duration is not specified.

The long code may be allocated for a limited duration to transmit the response message for the base station message received on the paging channel. When the base station requests a response message from the mobile station in the common channel state, it allocates a long code indicating the access channel to which the response message is sent through the forward control message. Then, the mobile station sends the response message to the dedicated or public access channel specified by the control message. In this case, set the maximum duration so that the allocated long code is used within the time period required for sending the response message. If the response message exceeds one access channel time slot in length, the long code for the subsequent access channel time slot can be allocated by indicating the continuous demand in the response process of the previous time slot.

FIG. 11 illustrates the transmission of the response message in three time slots by the continuous indication in the response message. That is to say, the long code allocation for the subsequent access channel time slots is completed by replacing the long code information with the continuous indication in the forward response message, which is used to allocate the previous access channel when the forward response message is sent. Gap.

There are two types of long code allocation.

One is to designate the long code as dedicated. For this reason, the private/public field is set to private. If the long code ID field has a specific long code, the mobile station uses its unique long code (obtained from the common long code mask determined by the reordered ESN) or the long code allocated by the long code ID field for private access Channel long code. In the latter case, the specific long code ID is no longer allocated to another mobile station while the mobile station occupies the long code ID. This solution provides a contention-free access channel and reduces the transmission delay without increasing the complexity of the base station and mobile station. In addition, the demodulator pool of the demodulation unit 624 in the base station is also well used. Only when the packet service is in a state where the corresponding unique long code is reserved or the base station is notified of the unique long code information on the access channel, it is effective to use the unique long code of the mobile station to spread the access channel message. . When a dedicated code channel is used, the time interval between access probes used to send the access channel message to the base station can be set to a constant, as shown in FIG. 9.

Another type of long code allocation is to allocate access channels based on channel types. This long code allocation scheme limits and changes the number of mobile stations used for each long code, and thus the channel category changes with the type of service. In other words, the contention probability is proportional to the number of mobile stations using a channel, and the channel type is determined based on the contention probability. In an extreme case, the channel allocated to a single mobile station is used as a dedicated channel, and the channel shared by all mobile stations becomes a common channel in this sense as it is used in a conventional system. For example, channels of a higher category are assigned to services that require real-time or immediate processing (such as video signals), while channels of a lower category are assigned to services that allow less time delay or have lower processing priority (e.g., email) service.

The access efficiency of the access channel is increased by setting the bit rate. This is called multi-bit rate access channel allocation. The bit rate of the access channel is controlled by setting the desired bit rate for sending data to the access channel in the forward control message field, thereby providing the advantages of accelerated response message transmission and reducing response time changes , And increase the use efficiency of the mobile station modulator. Here, the bit rate setting can be independent of the long code allocation type.

Now turn to the continuous message transmission on the common channel. In some cases, the access channel message can exceed the transmittable length at one time. As a result, it is easy to conflict with another access channel message. In other words, when a mobile station wants to send an access channel message in multiple time slots, the message transmission is delayed due to message contention with other mobile stations, resulting in the loss of the access channel message in severe cases. Therefore, when the access channel message is sent in multiple time slots, the continuous flag is inserted into the current access channel message to indicate that there are other continuous messages to be sent. This access channel message has the following format: (Table 4) <tables id="table1" num="004"> <table>message type continuous flag designation request flag data</table> </tables> where the message type indicates For response or access channel messages, the continuation flag indicates the presence or absence of the next message to be sent, the channel specification request flag (des_req_flag) indicates the presence or absence of the channel specification request, and the data is response data or from the mobile station The data sent to the base station is used as the actual data of the access channel message.

The continuous message transmission from the mobile station to the base station on the access channel will be described below. The control message generator 612 of the base station generates a control message when receiving an access channel message from the demodulation unit 624 or a mobile station paging message from a higher-level message processor, and sends the control message to the mobile station. Then, the control message analyzer 515 of the mobile station analyzes the control message and sends a response message to the base station on the access channel.

If the response message is too long to be sent at one time, the continuation flag of the response message frame is set as shown in Table 4. Then, the control message generator 612 and the modulation controller 620 in the base station control the transmission of the access channel message from the mobile station according to the procedures shown in FIGS. 7A and 7B.

Figures 11 and 12 show the continuous transmission of multiple message frames from the mobile station to the base station on the access channel. In Figure 11, the mobile station uses the same long code ID to send response messages to the access channel in multiple time slots. The access channel can be designated as public or private. On the initial access channel allocated by the base station, the mobile station continuously sends multiple access channel message frames to the same allocated access channel. Alternatively, a different long code ID can be used to send a long response message. As shown in Figure 12, when a handover occurs from one base station to another base station, the base station can assign an access channel to the mobile station. In FIGS. 11 and 12, part 1, part 2, and part 3 indicate continuous messages, where it is assumed that the access channel message sent from the mobile station occupies 3 frames. The base station extends the channel duration by assigning the long code ID, and changes the maximum duration for sending the multi-frame access channel message from the mobile station.

As described above, the base station determines whether there is a next message to be received by analyzing the continuation flag of the message received from the mobile station. If there is another message to receive, it determines whether the current long code should be changed. If after analyzing the current long code, it is considered that there is an available long code, then the corresponding long code ID is loaded into the response message. Each time a message is received from the mobile station, the above process is executed. Therefore, the channels allocated for receiving messages can be the same or different. In other words, the base station specifies the same or different channels as needed.

If the base station independently allocates the designated access channel as a dedicated long code ID, the mobile station can use the access channel alone as a dedicated, without the need for the base station to allocate the long code. Figure 13 shows message communication between a base station and a mobile station. Referring to FIG. 13, the mobile station sends an access channel message including its unique long code information to the base station, and then the base station sets the private/public field of the control message as shown in FIG. 4 to private and does not have a long code ID. The mobile station sends the response message to the dedicated access channel designated by the unique long code. Here, the only long code is determined by the ESN of the mobile station.

The access channel data communication device of the present invention as described above provides the advantages of controllable contention probability, fast response, and multi-bit rate access channel. In the case that the message is too long to be sent to the access channel at one time, multiple time slots are required, and a specific access channel for continuous message transmission is designated, so that the message transmission is delayed. It is not necessary for the base station to assign a long code ID to the mobile station, and the mobile station can send the access channel message to the dedicated access channel designated by its unique long code.

Although the invention has been described with reference to specific embodiments of the invention, these embodiments are merely exemplary applications. Therefore, it should be clearly understood that any person of ordinary skill in the art can make many changes to the present invention within the spirit and scope of the present invention.