KR20070065101A - Method and apparatus for transmitting/receiving rach preamble in a umts - Google Patents

Abstract

A method and an apparatus for transmitting and receiving RACH(Random Access CHannel) preambles in a UMTS(Universal Mobile Telecommunication System) are provided to increase an existing RACH preamble detection success rate and shorten RACH procedure delay time by enhancing and expanding the structure of an RACH preamble. A mobile terminal selects an arbitrary access slot, and creates an 16-symbol arbitrary basic signature(402). The created basic signature is spread through 256 iterations(404). The mobile terminal creates a 4-symbol supplemental signature(406). The supplemental signature is also iterated 256 times(408). The mobile terminal concatenates the spread basic signatures with the spread supplemental signatures, creates preamble signatures, scrambles the created preamble signatures, and transmits the scrambled preamble signatures through the access slot(410-414). Then the mobile terminal attempts the detection of an AICH(Acquisition Indication CHannel) signature corresponding to the preamble signatures using the basic signatures(416). If the AICH signature is successfully detected, the mobile terminal transmits a preamble message part through an RACH(422).

Description

Method and apparatus for Transmitting / Receiving RACH preamble in WMS {Method and apparatus for Transmitting / Receiving RACH preamble in a UMTS}

1 is a diagram illustrating a conventional RACH transmission process.

2 is an embodiment of a RACH preamble signature configuration of a mobile terminal according to an embodiment of the present invention.

3 is a table of preamble signature symbol sequences constructed in accordance with an embodiment of the invention.

4 is a flowchart illustrating a RACH preamble transmission of a mobile terminal according to an embodiment of the present invention.

5 is a flowchart illustrating a RACH preamble reception of a base station according to an embodiment of the present invention.

6 is a block diagram of a RACH preamble transmitter of a mobile terminal according to an embodiment of the present invention.

7 is a block diagram illustrating a RACH preamble receiver of a base station according to an embodiment of the present invention.

The present invention relates to a universal mobile telecommunication system (UMTS) system, and more particularly, to a method and apparatus for a mobile terminal to access a base station.

In a wireless mobile communication system such as Wideband Code Division Multiple Access (WCDMA) or Code Division Multiple Access 2000 (CDMA2000), the UE randomly accesses the uplink for the purpose of requesting a call connection or transmitting control information such as short user packet transmission. Use a channel. In this case, the random access channel transmitted is composed of two parts, that is, a message part for transmitting information (RACH message part) and a preamble transmitted before the message so that the base station can receive the message.

The mobile terminal transmits a preamble utilized for a special purpose prior to transmitting data through the random access channel. This preamble consists of a signature that uses a spread code of length 256 and contains 16 symbols. Therefore, all of the spread preambles consist of 4096 chips. After the response from the base station for the preamble is received through the AICH, the terminal transmits a message part corresponding to a length of 10 ms or 20 ms. The message part uses spread codes from 256 to 32 depending on the amount of data required. The Acknowledgment Indication Channel (Acquisition Indication Channel) is a channel that informs that the successful reception of the preamble sent from the terminal, the access channel signature (signature) received. The spreading code used for the AICH has a length of 256 and consists of 16 symbols. The signature transmitted in the AICH uses the same signature as the random access preamble received from the UE, and is also spread to 4096 chips.

The random access scheme currently used in the WCDMA system is a slotted-ALOHA scheme that randomly determines an access slot from among predefined slots, and in the determined access slot, transmits a random signature selected from a slot among a plurality of predefined signatures. do. When the base station detects the transmitted preamble above a certain energy, the AICH preamble is transmitted to allow access. Random access procedures in CDMA systems face a near-far problem because they do not have accurate information about the transmission power at the initial transmission. In order to cope with this problem, open-loop power control is applied, which is a method of increasing the power of the RACH a certain number of times before receiving the AICH preamble in downlink after transmitting the RACH preamble at initial power. .

 1 is a diagram illustrating a conventional RACH transmission process.

The mobile station transmits the 4096 chip RACH preamble 102 generated by repeating and scrambling the selected RACH preamble signature to the base station through the RACH. If the response signature corresponding to the RACH preamble 102 is not received through the AICH within a predetermined time after transmitting the RACH preamble 102, the UE increases the transmission power of the RACH and retransmits the RACH preamble 106. . When the base station successfully receives the RACH preamble 106, the base station transmits the AICH preamble 108 including the signature of the RACH preamble 106 to the mobile station. If the mobile station succeeds in receiving the AICH preamble 108, the mobile station transmits the RACH message part 110.

In the base station connection by the RACH according to the prior art operating as described above, the time taken for the entire random access procedure depends heavily on the initial power setting of the RACH preamble. From the point of view of the UE, the more minimal the RACH procedure delay is, the better the success rate is. To this end, the initial power of the RACH preamble transmitted by the UE may be increased, but this has a problem in that the capacity of the entire system is reduced by immediately increasing the interference of the uplink.

Accordingly, the present invention, which is designed to solve the problems of the prior art operating as described above, provides a method and apparatus for transmitting and receiving a new RACH or AICH preamble signature to improve the RACH or AICH preamble signature detection capability.

The present invention provides a method and apparatus for transmitting and receiving a new RACH or AICH preamble signature to shorten the time for detecting the RACH or AICH.

The present invention provides a method and apparatus for transmitting and receiving a new RACH or AICH preamble signature to reduce power consumption of a mobile terminal.

According to an embodiment of the present invention, in a method for transmitting a RACH preamble to a base station by a mobile terminal,

Generating a first signature of any of the available signatures;

Generating a second signature indicative of the index of the first signature;

Combining the first signature and the second signature to generate a preamble signature;

RACH preamble transmission method comprising the step of transmitting the generated preamble signature;

According to another embodiment of the present invention, in a method for receiving a RACH preamble at a base station,

Detecting a RACH preamble signature using first stored signatures;

Generating and transmitting an AICH using the detected preamble signature when the RACH preamble signature is detected as a result of the detection;

Detecting a signature of the received preamble using the first signatures and second signatures stored in advance when the RACH preamble signature is not detected as a result of the detection;

If a signature is detected using the first signatures and the second signatures, generating and transmitting an AICH using the detected signature.

Hereinafter, with reference to the accompanying drawings will be described in detail the operating principle of the preferred embodiment of the present invention. In the following description of the present invention, detailed descriptions of well-known functions or configurations will be omitted if it is determined that they may unnecessarily obscure the subject matter of the present invention. Terms to be described later are terms defined in consideration of functions in the present invention, and may be changed according to intentions or customs of users or operators. Therefore, the definition should be made based on the contents throughout the specification.

In the following description, the asynchronous wideband code division multiple access (WCDMA) system will be used. However, the base station access time shortening method, which is a basic object of the present invention, can be applied to other mobile communication systems having similar technical backgrounds and channel types with a slight modification without departing from the scope of the present invention. It will be possible at the discretion of those skilled in the art.

The main subject of the present invention described below is to transmit additional information such as a signature index to a signature of 16 symbols during RACH or AICH preamble transmission.

In the conventional RACH_preamble, a signature having a length of 16 symbols is spread to a length corresponding to a total of 4096 chips by using a 256 length spread code. In WCDMA, since one slot is 2560 chips long, the total length of the RACH preamble corresponds to 1.6 slots, which is less than 2 slots. The total number of symbols corresponding to 2 slots corresponds to 20 symbols since 256 length spread codes are used, and no signals are actually transmitted during the remaining 4 symbol intervals except for the 16 symbol length signature. In the preferred embodiment of the present invention, additional information is sent in the four symbol intervals which are not used. In this case, the preamble signature used in the previous 16 symbol intervals is used without change.

2 is an embodiment of a RACH preamble signature configuration of a mobile terminal according to an embodiment of the present invention. As shown, an additional signature of 4 symbols is added to the basic signature of 16 symbols to generate the signature of the RACH preamble.

3 illustrates preamble signature symbol sequences constructed in accordance with an embodiment of the invention.

Each of the sixteen preamble signatures is composed of a predetermined 16-symbol length basic signature and an additional signature of four symbols representing the index of the basic signature. An operation of generating the preamble signatures is described below.

The terminal obtains additional information of 4 symbols by representing the index of one basic signature randomly selected from among the basic signatures allowed by the base station in binary. For example, all default signatures are indexed from 0 to 15 times. If the index of the selected default signature is 5, this value can be converted to binary and displayed as 0x0101, and each bit is converted to a symbol. The symbols are assigned as 1, -1, 1, -1. Since the number of basic signatures specified in the WCDMA system are all 16, the index of the basic signature can be represented by all four bits. 'Bit 0' is '1' and 'Bit 1' is '-'. Replace it with the 1 'value to make it an additional signature. In this way, the additional signature is added to the basic signature to generate the final preamble signature. A variety of information can be used as the additional signature, which is the additional information of the basic signature. In the above example, the binary signature of the signature index is used. If the number of basic signatures allowed in the cell is 16 or less, the preamble signature may be configured by repeating the basic signature.

4 is a flowchart illustrating a RACH preamble transmission of a mobile terminal according to an embodiment of the present invention.

The mobile terminal selects any access slot among the currently available access slots in step 402, and then generates any base signature of all 16 symbols of the transmittable base signatures. In step 404, the generated default signature is spread through 256 iterations. In step 406, the UE generates an additional signature of 4 symbols, which is additional information that can be additionally applied to the detection of the preamble signature. As an example, the additional signature represents an index of the generated basic signature. In step 408, the additional signature is repeated 256 times as the basic signature. In step 410, the mobile terminal concatenates the spread basic signature and the spread additional signature to generate a preamble signature. In step 412, the preamble signature is scrambled. In step 414, the scrambled preamble signature is transmitted through the access slot of the RACH.

After transmitting the scrambled preamble signature, the mobile terminal attempts to detect the AICH signature corresponding to the preamble signature in step 416 using only the generated default signature after a predetermined time. In step 418, the mobile station determines whether AICH detection using the basic signature is successful. If the AICH detection is successful as a result of the determination, the preamble message part is transmitted through the RACH in step 422. If the AICH detection fails in step 418, the AICH is attempted again using the base signature and the additional signature in step 420. If the AICH detection is successful in step 424 and the detection is successful, the preamble message part is transmitted in step 422.

5 is a flowchart illustrating a RACH preamble reception of a base station according to an embodiment of the present invention.

The base station receives the RACH preamble from the mobile terminal in step 502. In step 504, the received preamble is descrambled and combined to be received as a preamble signature. In step 506, the received preamble signature is detected using basic signatures stored in advance. In operation 508, the base signatures stored in advance are compared with the received preamble signatures to determine whether there is a signature corresponding to the received preamble signature and the base signatures, and thus whether the preamble signature is detected. . If the detection of the preamble signature fails in step 508, the RACH preamble signature is detected again using the base signatures and additional signatures corresponding to the base signatures in step 510. In step 512, it is determined whether the detection in step 510 is successful. If the RACH preamble is detected successfully in step 508 or step 512, the AICH preamble including the detected basic signature and the corresponding additional signature is generated in step 514. In step 516, the generated AICH preamble is transmitted to the mobile station through the AICH.

6 is a block diagram of a RACH preamble transmitter of a mobile terminal according to an embodiment of the present invention.

In FIG. 6, the generation unit 602 selects an arbitrary basic signature among all valid signatures stored in advance, generates an additional signature indicating the index of the selected basic signature, and transmits a final preamble signature to be transmitted as a RACH preamble. To generate The basic signature selected by the generation unit 602 is repeated according to a constant repetition rate in the first iteration unit 604, and the additional signature generated by the generation unit 602 is a constant repetition rate in the second iteration unit 606. Will be repeated. The signatures repeated in each of the first and second repeaters 604 and 606 are combined in the combiner 608 to generate a preamble signature, and the scrambler 610 scrambles the preamble signature to the transceiver 612. By the RACH to the base station.

7 is a block diagram of a RACH preamble receiver of a base station according to an embodiment of the present invention.

The base station receiver 702 receives the RACH preamble from the mobile terminal and descrambles the RACH preamble by the descrambler 704. The descrambled signal is combined as many times as repeated in the mobile terminal in the combiner 706 and then output as a sequence of preamble signatures. The preamble signature is divided into a basic signature that is an upper 16 symbol and an additional signature that is a lower 4 symbol in the divider 708. The detector 710 attempts to detect the received preamble signature using the basic signatures stored in advance. If the detection fails using the basic signature information, the preamble signature is attempted again using the basic signatures and the additional signatures. As a result of the detection, when the RACH preamble is detected successfully, the AICH preamble including the signature of the detected RACH preamble is transmitted to the mobile terminal.

Meanwhile, in the detailed description of the present invention, specific embodiments have been described, but various modifications are possible without departing from the scope of the present invention. Therefore, the scope of the present invention should not be limited to the described embodiments, but should be defined not only by the scope of the following claims, but also by those equivalent to the scope of the claims.

In the present invention operating as described in detail above, the effects obtained by the representative ones of the disclosed inventions will be briefly described as follows.

According to the present invention, by improving and extending the structure of the RACH preamble in the WCDMA system, it is possible to increase the success rate of the existing RACH preamble detection and reduce the RACH procedure delay time. Moreover, simple modifications can increase call success rates and ultimately help increase system capacity, without any changes to the existing RACH procedure structure. Another effect of being an extension of the existing structure is that it can be applied to the present WCDMA system to which the present invention is not applied. That is, the terminal or system to which the structure of the present invention is applied can benefit from the RACH procedure compared to the existing terminal or system, thereby increasing the overall system capacity.

Claims (22)

A method for transmitting a RACH preamble to a base station by a mobile terminal, Generating a first signature of any of the available signatures; Generating a second signature indicative of the index of the first signature; Combining the first signature and the second signature to generate a preamble signature; RACH preamble transmission method comprising the step of transmitting the generated preamble signature. 2. The method of claim 1, further comprising: detecting an AICH using first signatures; If the AICH is detected, transmitting a RACH message part; If the AICH is not detected, detecting the AICH using first signatures and second signatures; If the AICH is additionally detected using the second signature, transmitting the RACH message part. The method of claim 1, wherein the second signature is configured by converting each bit into a symbol in a binary number by converting an index of the first signature into a binary number. 2. The method of claim 1, wherein the first signature consists of 16 symbols. 2. The method of claim 1, wherein the second signature consists of four symbols. 2. The method of claim 1, wherein the available signatures consist of sixteen types. In the method for receiving a RACH preamble at the base station, Detecting a RACH preamble signature using first stored signatures; Generating and transmitting an AICH using the detected preamble signature when the RACH preamble signature is detected as a result of the detection; Detecting a signature of the received preamble using the first signatures and second signatures stored in advance when the RACH preamble signature is not detected as a result of the detection; If a signature is detected using the first signatures and the second signatures, generating and transmitting an AICH using the detected signature. 8. The method of claim 7, wherein the preamble signature comprises a first signature of 16 symbols and a second signature of 4 symbols. 9. The method of claim 8, wherein the second signature is configured by converting each bit into a symbol in a binary number by converting an index of the first signature into a binary number. 8. The method of claim 7, wherein the first signatures are of 16 types. 8. The method of claim 7, wherein the second signatures are of 16 types. An apparatus for transmitting a RACH preamble to a base station by a mobile terminal, A generation unit for generating any first signature among the available signatures and generating a second signature using the index of the first signature; A first repeating unit repeating the generated first signature; A second repeater for repeating the generated second signature; A combining unit combining the repeated first signature and the second signature to generate a preamble signature; A scrambler that scrambles the generated preamble signature; And a transmitter / receiver for transmitting the scrambled preamble signature. The apparatus of claim 12, wherein the second signature is configured by converting each bit into a symbol in a binary number by converting an index of the first signature into a binary number. 13. The apparatus of claim 12, wherein the first signature consists of 16 symbols. 13. The apparatus of claim 12, wherein the second signature consists of four symbols. 13. The apparatus of claim 12, wherein the available signatures are of 16 types. An apparatus for receiving a RACH preamble at a base station, A receiver for receiving a RACH preamble from the base station; A descrambler for descrambling the received RACH preamble; A combiner for combining the descrambled RACH preamble to obtain a RACH preamble signature; A divider for dividing the preamble signature into a first signature and a second signature; A detector for detecting the preamble signature using first signatures or detecting the preamble signature using first signatures and second signatures;  And generating and transmitting an AICH using the detected preamble signature. 18. The apparatus of claim 17, wherein the second signature is configured by converting each bit into a symbol in a binary number by converting an index of the first signature into a binary number. 18. The apparatus of claim 17, wherein the first signature consists of 16 symbols. 18. The apparatus of claim 17, wherein the second signature consists of four symbols. 18. The apparatus of claim 17, wherein the first signatures are of 16 types. 18. The apparatus of claim 17, wherein the second signatures are of 16 types.

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