KR20000045008A - Slot type cdma method using mini slot in wireless packet network - Google Patents

Abstract

PURPOSE: A slot type CDMA method is provided to reduce a transmission request failure ratio and a delay from a transmission request to a transmission by dividing a slot for a data transmission into a multiple of mini slots and making a transmission request packet transmitted in the mini slot based on the fact that the data packet is much larger than the a transmission request packet. CONSTITUTION: A slot type CDMA method comprises steps of checking if a data packet(N) for transmission to a mobile station exists(301), checking if the mobile station receives a successful response to a transmission request(302), increasing the number of the transmission request by one if the mobile station does not receive the successful request(303), transmitting a transmission request packet to a base station with a ratio of 1/N(304), checking if the transmission request is successful(305), waiting one slot if a transmission failure occurs(306), informing a result on a transmission request of the mobile station(307), determining a priority on the transmission request(308), transmitting a permission signal to just corresponding mobile station(309), checking if a transmission to the permitted mobile station is possible(310), waiting one slot if not(311), certifying if more data packets exist(312), displaying the more data packet at a piggy backing bit(313), transmitting the data packet to the base station(314).

Description

Slot-type Code Division Multiple Access Using Minislot in Wireless Packet Network

According to the present invention, a slot-type code division multiple access (CDMA) having a small and flexible overhead is reduced by using a mini slot in a wireless packet network to reduce a transmission request failure probability due to a code collision, thereby reducing delay from transmission request to transmission. Access) method and a computer-readable recording medium recording a program for realizing the same.

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 it is possible to continuously reserve resources without additional transmission requests in case of continuous data transmission using piggybacking, and the base station sends a transmission permission per slot to efficiently 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 very 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.

In order to solve the above problems, the present invention is based on the fact that a data packet is considerably longer than a transmission request packet in a wireless packet network. Slot-type code division multiple access method for allocating resources by reducing the probability of request failure by reducing the probability of request failure and quickly allocating a resource, and a computer-readable recording medium recording a program for realizing the same. The purpose is to provide.

1 illustrates a conventional DQRUMA / MC-CDMA protocol.

2 is a slot structure diagram of a protocol according to 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

In order to achieve the above object, the present invention provides a slot type code division multiple access method applied to a wireless packet communication system. A first step of dividing a slot for transmitting the data packet into several minislots so that a packet and a data packet of another terminal are simultaneously transmitted; And a second step of causing the transmission request packet to be transmitted to the minislot at the same time as the transmission of the data packet.

In addition, the present invention, in the wireless packet communication system having a processor, to allocate a number of codes for the transmission request to reduce the request failure in the code division multiple access so that the transmission request packet and the data packet of the other terminal is transmitted at the same time Partitioning one slot into several minislots for the data packet transmission; And a computer readable recording medium having recorded thereon a program for realizing a function of causing the transmission request packet to be transmitted to the minislot simultaneously with the transmission of the data packet.

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 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, which requires a medium access control in which a code collision is small and a small overhead causes 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 reduces or eliminates code collisions by using minislots, thereby significantly reducing the delay from the transmission request to the response.

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 with 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. do. 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.

For example, assuming that one virtual terminal is continuously transmitting one data packet 23, a capacity margin can be set for it. 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.

According to the present invention, a minislot is allocated to a request packet along with a code, thereby reducing a transmission request failure due to a collision, and reducing a delay from a transmission request to a response. By allocating unique code / minislot pairs, there is no code conflict to allow fast 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 that have received the transmission permission signal determine whether they can transmit (310), waits for one slot if they cannot transmit (311), and if it is possible to transmit, 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 case of transmission failure (315), it is transmitted after receiving the transmission permission signal later (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 that when a call of one mobile station is allowed to a cell, it is assigned only to that mobile station's call and only uses that mobile station's call during a call in that cell, thereby avoiding a conflict.

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, significantly reducing the time taken from the transmission request to the response, and reduce the overhead by simultaneously transmitting the transmission request and 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 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 at the same time as the data packet by selecting a code and minislot pair, so that the use of mini slots can greatly reduce the delay from the transmission request to the data transmission. 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, In order to reduce request failure in code division multiple access, several mini slots are allocated to one slot for transmitting the data packet so that several codes are allocated for the transmission request so that the transmission request packet and the data packet of another terminal can be transmitted simultaneously. A first step of dividing into; And A second step of causing the transmission request packet to be transmitted to the minislot simultaneously with the transmission of the data packet Slot type code division multiple access method using a mini-slot comprising a. The method of claim 1, The transmission request packet, A slot-type code division multiple access method using minislots, wherein code / minislot pairs are allocated and transmitted simultaneously with the data packet. The method according to claim 1 or 2, The second 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. Transmitting a request packet to a base station; A fourth step of repeating, by the mobile station, the third step for the next slot when a transmission failure of the transmission request packet occurs in response to the transmission request result notification from the base station; A fifth step of determining a priority for the transmission request successfully received by the base station and transmitting a transmission permission signal only to corresponding mobile stations; A sixth step of checking 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; A seventh 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 sixth step; An eighth step of, after performing the seventh step, retransmitting data to the base station after receiving the transmission permission signal upon transmission failure; A ninth 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 ninth 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 permission determination so that the mobile station can transmit data without a transmission request and response process. Tenth step Slot type code division multiple access method using a mini-slot comprising a. The method of claim 3, wherein The transmission request packet, In order to be transmitted simultaneously with the data packet, slot type code division multiple access method using a mini slot, characterized in that the capacity margin considering the interference. 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 characterized in that the power is transmitted to reduce the interference and to reduce the required capacity margin. The method of claim 3, wherein The mobile station, A slot-type code division multiple access method using a mini slot, characterized by assigning unique code / minislot pairs to each call so as to allocate resources (slots) quickly. The method of claim 3, wherein The mobile station, Slot type code division multiple access method using a mini-slot characterized in that the transmission request packet is assigned a higher power level than other transmission request packets to reduce the failure due to multiple access interference. 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, In order to reduce request failure in code division multiple access, several mini slots are allocated to one slot for transmitting the data packet so that several codes are allocated for the transmission request so that the transmission request packet and the data packet of another terminal can be transmitted simultaneously. Dividing into; And The transmission request packet is transmitted to the minislot at the same time as the transmission of the data packet A computer-readable recording medium having recorded thereon a program for realizing this.