KR100307313B1 - A slotted cdma method using minislots for request accesses in wireless packet network - Google Patents

Abstract

1. TECHNICAL FIELD OF THE INVENTION

The present invention relates to a slot type code division multiple access method using a mini slot in a wireless packet network, and a computer readable recording medium having recorded thereon a program for realizing the method.

2. The technical problem to be solved by the invention

The present invention reduces the probability of request failure by dividing a slot for data transmission into multiple minislots based on the fact that a data packet is considerably longer than a transmission request packet in a wireless packet network. To provide a slot-type code division multiple access method for allocating resources quickly and reducing delay from transmission request to transmission, and a computer-readable recording medium recording a program for realizing the method.

3. Summary of Solution to Invention

In the slot-type code division multiple access method applied to a wireless packet communication system, the present invention selects an arbitrary code from a code set allocated for the transmission request in order to reduce transmission failure in the slot-type code division multiple access scheme. A first step of making; A second step of dividing one slot for transmission of the data packet into several minislots for the transmission request so that the selected arbitrary code is allocated for the transmission request so that the transmission request packet and the data packet can be simultaneously transmitted. ; And a third step of the mobile station transmitting the transmission request packet to the base station simultaneously with the data packet through the divided minislot.

4. Important uses of the invention

The present invention is used in a wireless packet network.

Description

A slotted cdma method using minislots for request accesses in wireless packet network}

In the present invention, a slot-type code division multiple access (CDMA) having a small and flexible overhead is reduced by reducing the probability of transmission request failure due to code collision by using a mini slot in a wireless packet network. And a computer readable recording medium having recorded thereon a program for realizing the method.

A typical medium access control method in a conventional wireless packet network is "DQRUMA / MC-CDMA" based on a multiple code code division access method.

The feature of the DQRUMA / MC-CDMA scheme is that the base station continuously reserves resources without additional transmission requests in case of continuous data transmission using piggybacking, and the base station sends a transmission allowance for each slot. Transmission scheduling is enabled.

However, in this DQRUMA / MC-CDMA scheme, the request packet is transmitted by selecting one of a limited number of codes in a given request allocation time domain, so that the probability of request failure due to collision is large, and the delay from request to response is significantly increased. And the overhead is fixed regardless of the transmission request traffic load. This will be described in more detail with reference to FIG. 1.

Referring to FIG. 1, a transmission request packet 11 and a data packet 13 are transmitted in the uplink 1a, and the request packet 11 and the data packet 13 are transmitted on different time axes.

In the receiver-oriented system, the transmission request packet 11 selects and transmits one of codes allocated to each receiver.

The data packet 13 has a piggybacking area 12, which allows to continuously reserve resources without requiring a new transmission request in the transmission of consecutive data.

On the other hand, in the downlink 1b, the request response 14, the transmission permission 15, and the data packet information 16 are transmitted.

Referring to FIG. 1, the DQRUMA / MC-CDMA protocol, when a mobile station transmits a new data packet, first transmits a transmission request packet 11, and if it does not fail due to collision or multiple access interference, the transmission request from the base station is transmitted. A successful response 14 is received, and if a transmission is possible in the next slot, a transmit permission signal 15 is received. At this time, the mobile station receiving the transmission permission signal 15 transmits the data packet 16 in the next slot. If there is data to be transmitted in the next slot, it may be transmitted after receiving the transmission permission signal 15 without undergoing a transmission request / response process using the piggybacking 12.

In a code division multiple access system, transmission request failure can be caused by multiple access interference as well as collision. Here, the failure due to collision occurs during the collision transmission requests, but when the failure occurs due to multiple access interference, all transmission requests sent at the same time may fail. At this time, the degree of the effect of the multiple access interference is adjusted using the power level and the error correction code.

As described above, the conventional media access control method using the slotted code division multiple access method transmits a request packet with a limited number of codes in a specific time domain. . Therefore, in the related art, there is a problem in that a delay from a transmission request to a response is considerably large, and it is difficult to quickly allocate resources (slots) for real time traffic.

The present invention proposed to solve the problems described above, based on the fact that the data packet in the wireless packet network is significantly longer than the transmission request packet, the transmission request packet is divided into several minislots after the slot for data transmission Slot-type code division multiple access method for fast resource allocation by reducing the probability of request failure by reducing the probability of request failure, and a computer-readable recording of a program for realizing the method. The purpose is to provide a medium.

1 illustrates a conventional DQRUMA / MC-CDMA protocol.

2 is a slot structure diagram of a protocol according to an embodiment of the present invention.

3 is a flowchart illustrating an embodiment of a slot-type code division multiple access method using a minislot according to the present invention.

* Explanation of symbols for the main parts of the drawings

2a: uplink 2b: downlink

The present invention for achieving the above object, in the slot-type code division multiple access method applied to a wireless packet communication system, in order to reduce the transmission request failure in the slot-type code division multiple access scheme, a code set allocated for the transmission request Selecting a random code in the first step; A second step of dividing one slot for transmission of the data packet into several minislots for the transmission request so that the selected arbitrary code is allocated for the transmission request so that the transmission request packet and the data packet can be simultaneously transmitted. ; And a third step of the mobile station transmitting the transmission request packet to the base station simultaneously with the data packet through the divided minislot.

In addition, the present invention provides a wireless packet communication system having a processor for a slotted code division multiple access, in order to reduce a transmission request failure in a slotted code division multiple access scheme. A first function of selecting a code; A second function of allocating the selected arbitrary code for a transmission request and dividing one slot for transmission of the data packet into several minislots for the transmission request so that the transmission request packet and the data packet can be simultaneously transmitted. ; And a computer-readable recording medium having recorded thereon a program for realizing a third function of transmitting, by the mobile station, the transmission request packet to the base station simultaneously with the data packet through the divided minislot.

The present invention relates to a media access control scheme in a wireless packet network, and divides one slot for data packet transmission into multiple mini slots by using a transmission request packet having a length much smaller than the data packet length. The transmission request packet is transmitted at the same time as the data packets having a code randomly selected from the code set allocated for the transmission request and coded in a separate code set. At this time, the transmission request packet is sent in any minislot in the slotted Aloha method.

The above objects, features and advantages will become more apparent from the following detailed description taken in conjunction with the accompanying drawings. Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

2 is a slot structure diagram of a protocol according to an embodiment of the present invention.

In order to transmit data in a wireless packet network, a transmission request must be made to obtain a response and a transmission permission. At this time, what is important is the time required for transmission request and response. Since there is little code collision and small overhead, it is necessary to control the medium access, which generates little delay.

The present invention relates to a slot-type code division multiple access method using a mini slot in a wireless packet network, wherein the length of a request packet is much smaller than the data packet length. After dividing into two minislots, the transmission request packet is transmitted simultaneously with data packets that are given codes in a separate code set with one code from among the code sets allocated for the transmission request. At this time, the transmission request packet is sent in any minislot.

Therefore, the present invention can significantly reduce the delay from the transmission request to the response since the code collision is reduced or eliminated by using the mini slot.

In addition, according to the present invention, the transmission request and the data are simultaneously transmitted on the time axis in order to reduce the overhead, and the amount of interference generated at this time is not determined by the number of codes and minislots allocated to the transmission request. Since the interference is caused by, the actual amount of interference due to the transmission request is quite small. In addition, the present invention can easily cope with changes in the transmission request traffic because the number of assigned codes can be easily changed.

In addition, the present invention can eliminate collisions when transmitting a request by using a unique number for each call of each mobile station accommodated in the base station, thereby enabling quick resource (slot) allocation and thus real-time traffic reception.

Now, more specifically, slotted code division multiple access using a minislot in a wireless packet network will be described in more detail.

Referring to FIG. 2, the transmission request packet 21 is transmitted in several minislots in one slot in the slotted Aloha manner simultaneously with the transmission of the data packet 23. Here, the data packet 23 and the request packet 21 are divided into different code sets. One slot can be divided into several minislots because the length of the transmission request packet 21 is much smaller than that of the data packet 23.

As shown in Fig. 2, the slot of the protocol of this embodiment allocates two codes for the transmission request. That is, the transmission request response 24 and the transmission permission 25 of the downlink 2b are matched to the last two minislots of the uplink 2a so that the transmission requests of as many minislots as possible are answered in the corresponding slots. . Of course, the last two minislots can also be used for transmission requirements.

By providing the minislot and the code to the transmission request packet 21 at the same time, the probability of request failure due to collision can be reduced. Therefore, it is possible to reduce the delay from the transmission request to the transmission.

Since it is unknown in advance how many transmission request packets 21 will be transmitted, an appropriate capacity margin is required for them to be transmitted simultaneously with the data packets 23. This capacity margin is determined by the transmission request packet 21 traffic, the number of minislots, the power level of the transmission request packet 21 and the data packet 23, and the error correction coding level. That is, as the number of minislots decreases or the traffic of the transmission request packet 21 increases, the probability of breaking the transmission request packet 21 in a specific mini slot increases. In addition, in order to obtain a probability that a certain level of packet is broken, the error correction coding level may be lowered when the power request packet 21 and the data packet 23 have high power levels. You must raise it to compensate.

For example, by assuming that one virtual terminal is continuously transmitting one data packet 23, it is possible to set as much capacity margin therefor.

When the target Eb / Io of the transmission request packet 21 is gamma_ {r}, the target Eb / Io of the data packet 23 is gamma _ {d} and the processing gain G is the processing request packet 21. The relative channel capacity ratio (varphi) of the data packet 23 to Let's define If varphi = 0.5, that is, suppose that the power level that appears when two transmission request packets 21 are transmitted during one mini slot is equal to the power level that appears when one data packet 23 is transmitted. The target Eb / Io of the transmission request packet 21 can be determined. Therefore, the method mentioned above after estimating the number of transmission request packets 21 occurring in one minislot from the traffic of the transmission request packet 21 and the number of minislots during one time slot and determining the error correction coding level Therefore, the capacity margin may be determined in consideration of the power levels of the transmission request packet 21 and the data packet 23. This value is considered overhead since the data transfer is reduced by this capacity margin.

As an example of eliminating collisions for fast resource allocation, collisions can be avoided by assigning different code / minislot pairs with unique numbers for each mobile station call.

By using this method, since the base station requires as many codes / minislot pairs as the number of calls of the mobile station subjected to call admission control, the number of codes required for the actual transmission request is small.

The operation of the multiple access protocol proposed in this embodiment is shown in FIG.

3 is a flowchart illustrating an embodiment of a slot-type code division multiple access method using a minislot according to the present invention.

The present invention divides the slot for data transmission into several minislots based on the fact that the data packet is considerably longer than the request packet, so that the request packet is transmitted to this minislot. At this time, the transmission request packet selects a code at random from a code set allocated for the transmission request. Therefore, the transmit request packets are transmitted simultaneously without collision with the data packet using the code set for data transmission.

The present invention can reduce the transmission request failure due to a collision and reduce the delay from the transmission request to the response by allocating a mini slot to the transmission request packet together with the code. By allocating the code / minislot pairs of, avoiding code conflicts allows for faster resource allocation.

As shown in FIG. 3, the slotted code division multiple access method using minislot in a wireless packet network, if there is a data packet (N) to be transmitted to the mobile station (301), the mobile station has already successfully responded to the transmission request. Received (302).

As a result of the analysis, if the mobile station has not received a successful response yet, after increasing (N + 1) the number of transmission requests (N) by the mobile station (303), there is a 1 / N probability of transmitting the request packet to the base station. Transmit (304). Subsequently, the mobile station can receive a successful response unless a plurality of transmission request packets are transmitted in the same minislot with the same code or if the transmission request packet is damaged due to multiple access interference and cannot be corrected. If the transmission request packet transmission failure occurs (305) and waits for one slot (306) to increase the number of transmission requests (N) by one (N + 1) in the next slot (303), 1 The transmission request packet is retransmitted to the base station with a probability of / N (304).

Meanwhile, the base station notifies the mobile station of the result of the transmission request (307) and at the same time determines the priority for the successfully received transmission request (308) and transmits a transmission permission signal only to the corresponding mobile stations (309). At this time, the mobile stations which have received the transmission permission signal determine whether they can transmit (310), and if not possible, wait for one slot (311), and if possible, check whether there is a data packet to be transmitted further in the next slot ( 312).

As a result of the check, if there is a data packet to be transmitted in the next slot, it is indicated in the piggybacking bit (313), and then data is transmitted to the base station (314).

Transmission allowance is made to satisfy all required error performances of packets to be transmitted in the next slot, but transmission failure due to multiple access interference can be probabilistic due to uncertainty of transmission request packet arrival and interference from other cells. Therefore, in the transmission failure 315, after receiving the transmission permission signal later, it transmits (310 to 314).

On the other hand, when the base station is notified of the data reception result from the mobile station (316), it is checked whether a piggybacking indication exists in the received data (317), and if a piggybacking indication exists in the received data, the base station determines whether to allow transmission in the next slot. (308) The result is notified to the mobile station (309), and the mobile station can transmit the data without the transmission request and response process.

As described above, in the case of randomly selecting a code / minislot pair, there is a possibility of collision, and a failure due to multiple access interference also exists.

To accommodate traffic requiring fast resource allocation, first assign a unique code / minislot pair to each mobile's call to avoid collisions. Thus, a particular code / minislot pair ensures there is no conflict by allowing only one mobile station's call to be assigned to a cell, and making use of only that mobile station's call while in the cell.

Secondly, in order to reduce the failure due to multiple access interference, the mobile station needs to allocate a higher power than other transmission request packets to a transmission request packet of a mobile station which requires fast resource allocation to obtain a higher E _b / Io level, or a stronger error correction code Apply to compensate for more errors. In this case, the actual overhead can be increased.

In order to reduce the delay from the transmission request response to the transmission allowance, priority may be given to calls requiring rapid resource allocation when scheduling the transmission of the packets that have undergone the transmission request response at the base station.

As described above, the present invention can reduce the collision time in transmission request by using the mini slot in the wireless packet network, which can significantly reduce the time taken from the transmission request to the response, and reduce the overhead by simultaneously transmitting the transmission request and the data transmission. It is possible to construct an efficient network, and to avoid collisions when transmitting requests by using unique numbers for each mobile station call, so that the allocation of resources (slots) is possible quickly. The slot type code division multiple access method can be used as a medium access control method.

The method of the present invention as described above may be implemented as a program and stored in a computer-readable recording medium (CD-ROM, RAM, ROM, floppy disk, hard disk, magneto-optical disk, etc.).

The present invention described above is capable of various substitutions, modifications, and changes without departing from the spirit of the present invention for those skilled in the art to which the present invention pertains, and the above-described embodiments and accompanying It is not limited to the drawing.

The present invention as described above allows the transmission request packet to be selected simultaneously with the data packet by selecting a code and minislot pair, thereby greatly reducing the delay from the transmission request to the data transmission with the use of the minislot, making it small and flexible. Because of the overhead, the system efficiency is increased, and the quick resource allocation is easy, which makes it easy to construct a system suitable for a multimedia environment in which real-time traffic coexists.

Claims (9)

A slot type code division multiple access method applied to a wireless packet communication system, Selecting a random code from a code set allocated for the transmission request in order to reduce transmission request failure in the slotted code division multiple access scheme; A second step of dividing one slot for transmission of the data packet into several minislots for the transmission request so that the selected arbitrary code is allocated for the transmission request so that the transmission request packet and the data packet can be simultaneously transmitted. ; And A third step of the mobile station transmitting the transmission request packet to the base station simultaneously with the data packet through the divided minislot; Slot type code division multiple access method using a mini slot in a wireless packet network comprising a. The method of claim 1, In the transmission request packet, A slot-type code division multiple access method using minislots in a wireless packet network, wherein code / minislot pairs are allocated and transmitted simultaneously with the data packet. The method according to claim 1 or 2, The third step, If the mobile station has data to transmit and has not already received a successful response to the transmission request, after increasing the transmission request number N by one (N + 1), there is a probability of 1 / N (N is a natural number) for transmission. A fourth step of transmitting a request packet to a base station; In response to the transmission request result notification from the base station, when the transmission failure of the transmission request packet occurs, the mobile station repeatedly performs the third step for the next slot; A sixth step of determining a priority of the transmission request successfully received by the base station and transmitting a transmission permission signal only to corresponding mobile stations; A seventh step of confirming whether there is a data packet to be transmitted further in the next slot transmittable by the mobile stations which have received the transmit permission signal; An eighth step of transmitting data to the base station after indicating the piggybacking bit if there is a data packet to be transmitted in the next slot as a result of the checking of the seventh step; A ninth step of transmitting data to the base station after receiving the transmission permission signal again when the transmission fails after performing the eighth step; A tenth step of checking whether a piggybacking indication is present in the data received at the base station; And As a result of the check of the tenth step, if a piggybacking indication is present in the received data, the next slot is notified to the mobile station of the result through a transmission allowance determination, so that the mobile station can transmit data without a transmission request and response process. 11th Step Slot type code division multiple access method using a mini slot in a wireless packet network comprising a. The method of claim 3, wherein The transmission request packet, A slot type code division multiple access method using a mini slot in a wireless packet network, characterized in that a capacity margin considering interference is required to be transmitted simultaneously with the data packet. The method of claim 3, wherein The transmission request packet, In the case of transmitting the data packet at the same time, slot type code division multiple access method using a mini slot in a wireless packet network, characterized in that the power is reduced to transmit in order to reduce the interference and the required capacity margin. The method of claim 3, wherein The mobile station, A slot-type code division multiple access method using minislots in a wireless packet network, characterized by assigning unique code / minislot pairs to each call for fast resource (slot) allocation. The method of claim 3, wherein The mobile station, Slot type code division multiple access method using a mini slot in a wireless packet network, characterized in that to reduce the failure caused by multiple access interference by allocating a higher power level than other transmission request packets to the transmission request packet. The method of claim 3, wherein The mobile station, Slot type code division multiple access method using a mini-slot characterized in that to reduce the failure caused by multiple access interference by applying a stronger error correction code to the transmission request packet than other transmission request packets. In a wireless packet communication system having a processor for slot type code division multiple access, A first function of selecting an arbitrary code from a code set allocated for a transmission request in order to reduce a transmission request failure in a slotted code division multiple access scheme; A second function of allocating the selected arbitrary code for a transmission request and dividing one slot for transmission of the data packet into several minislots for the transmission request so that the transmission request packet and the data packet can be simultaneously transmitted. ; And A third function of transmitting, by the mobile station, the transmission request packet to the base station simultaneously with the data packet through the divided minislot; A computer-readable recording medium having recorded thereon a program for realizing this.