CN100393010C - A method for distinguishing access prefixes by a base station in a wideband code division multiple access system - Google Patents

Abstract

The present invention proposes a method for the base station to distinguish between the access detection prefix and the access conflict prefix in the packet transmission channel of the WCDMA system. The terminal selects available access resources to send APs according to the access resource information broadcast by the common packet channel state indication channel CSICH, Access is required; the base station judges the type of access prefix according to the possible range of the CD prefix recorded in the previous time period. If the received prefix falls within the possible range of the CD prefix, it can be judged as CD, and the others are APs; the base station predicts and Determine the scope of the AP prefixes that will be confused with the CD prefixes to be received, and the system broadcasts the access resources corresponding to these prefix APs as unavailable through the CSICH channel; the base station performs other processing. By adopting the method of the invention, the AP and CD can be distinguished by the base station under the condition of sharing both the scrambling code and the signature, which reduces the confusion of the terminal during the access process by the base station and improves the capacity of the public packet channel.

Description

A method for distinguishing access prefixes by a base station in a wideband code division multiple access system

technical field

The invention relates to a wideband code division multiple access (WCDMA) system in the field of mobile communication, in particular to the process of processing a common packet channel by a base station in the WCDMA system.

Background technique

In the CDMA cellular system, multiple users share the same frequency band for communication. At the transmitting end, the narrowband data signal is spread by a user-specific scrambling code (PN code) to obtain a wideband modulation signal for transmission; while at the receiving end, the receiver uses the same scrambling code as the transmitting end to correlate and despread the received signal , so as to restore the narrowband data signal. The function of the scrambling code is to distinguish different channels during multiplexing.

The Common Packet Channel (CPCH) is an uplink transmission channel in the WCDMA system, used for packet burst data transmission of terminals in a cell. The common packet channel CPCH is mapped to the physical common packet channel (PCPCH), and the message part of the physical common packet channel PCPCH carries packet data. Physical public packet channels PCPCH are distinguished by different scrambling codes, and the base station allocates 64 scrambling codes in each cell, which are shared by terminals in the cell.

In order to prevent conflicts caused by different terminals using the same scrambling code and realize terminal sharing of resources, before the terminal sends data to the base station, it needs to apply for the resource, namely the scrambling code, and release it after the data transmission is completed. The third-generation mobile communication organization 3GPP stipulates that the DSMA-CD (Digital Sense Multiple Access-Collision Detection) method with fast capture indication is used to avoid conflicts and achieve resource sharing. The method includes two processes. First, the terminal obtains the state of the physical common packet channel PCPCH according to the state indicator channel CSICH sent by the base station. After this process, the terminal can know whether a specific PCPCH is occupied, so as to select Idle PCPCH transmission; PCPCH status information will be continuously updated through CSICH broadcast. Then there is the formal process, which is divided into three stages: access contention, conflict detection and data transmission. First, the terminal uses a specific access detection prefix AP to request access to the corresponding PCPCH(s), and the base station uses the corresponding access Incoming prefix AP capture indication channel AP-AICH response is accessible; then, through specific access conflict prefix CD and conflict detection/channel assignment indication channel CD/CA-ICH to confirm or assign specific physical public packet channel PCPCH channel resources; finally, confirm the physical common packet channel PCPCH, and transmit data. The existence of the conflict detection phase is to avoid such a conflict: when two terminals apply for the same physical public packet channel PCPCH with the same access detection prefix AP at the same time, the base station’s positive answer to one of the terminals will also be regarded by the other terminal as Answer affirmatively, thus causing conflicts; in order to avoid conflicts, the terminal will send the access conflict prefix CD in a random way to request confirmation, because the access conflict prefix CD is randomly sent, so the CDs sent by the two terminals will not be the same , so that different terminals are separated by the base station.

Specifically, the above method has two access modes, one is the terminal selection channel mode, and the other is the flexible channel assignment mode, and the access processes are shown in Fig. 1 and Fig. 2 respectively. Taking Figure 1 as an example, the terminal sends the access detection prefix AP to request a specific PCPCH, the base station sends the corresponding access prefix capture indication to respond to whether access is allowed, and then the terminal sends the access conflict prefix CD to perform specific PCPCH collision detection, the base station The collision detection/channel assignment indicates the channel to complete the collision detection, and finally confirms the PCPCH for data transmission. The difference between the two access methods is that in the channel selection mode of the terminal, the terminal selects the physical public packet channel PCPCH within a certain range, while in the flexible channel assignment mode, the base station specifies the PCPCH according to the needs of the terminal.

The expression of access detection prefix AP is:

$C_{c\_\mathrm{accn},\mathrm{the\; s}}\left(k\right)=c_{\mathrm{long},1,\mathrm{no}}\left(i\right)\×C_{\mathrm{sig},\mathrm{the\; s}}\left(k\right)\×e^{j(\frac{\mathrm{\π}}{4}+\frac{\mathrm{\π}}{2}k)},$ k=0, 1, 2, 3, ..., 4095

Wherein, C _{sig, s} (k) is the repeated 16-bit signature signal carried by the prefix, and c _{long, 1, n} (i) is the real part of the uplink long scrambling code.

The expression for accessing the conflict prefix CD is:

$C_{c\_\mathrm{cdn},\mathrm{the\; s}}\left(k\right)=c_{\mathrm{long},1,\mathrm{no}}\left(i\right)\×C_{\mathrm{sig},\mathrm{the\; s}}\left(k\right)\×e^{j(\frac{\mathrm{\π}}{4}+\frac{\mathrm{\π}}{2}k)},$ k=0, 1, 2, 3, ..., 4095

Among them, C _{sig, s} (k) is the repeated 16-bit signature signal carried by the prefix, and the signature is randomly selected by the terminal within a certain range to achieve the purpose of distinguishing different terminals by signature; c _{long, 1, n} (i) is the uplink The real part of the long scrambling code.

It can be seen from the above two equations that the access detection prefix AP and the access collision prefix CD transmitted by the terminal are exactly the same in form. The base station needs to process the channel application of the terminal according to the received access detection prefix AP and access conflict prefix CD. However, since the access detection prefix AP and the access conflict prefix CD are exactly the same in form, the In the case of sharing the scrambling code with the access conflict prefix CD, the base station cannot distinguish between the two, so the base station cannot distinguish the type of application sent by the terminal, and cannot complete the access process.

For the above problem, the existing solution is to assign different access signatures to the access detection prefix AP and the access conflict prefix CD respectively, and guess the type of the prefix by analyzing the obtained signature number. However, this reduces the number of signatures that the terminal can randomly select, making it about half of the original number of signatures. During the access process, different terminals obtain their own different signatures through random selection, and the base station then passes Different signatures distinguish terminals; there are fewer signatures available for random selection, and the chances of different terminals selecting the same signature increase, which will also cause the base station to fail to correctly identify the terminal that initiated the application, especially when there are many applications. This situation.

Contents of the invention

In order to solve the problem that the base station correctly identifies the access detection prefix AP and the access conflict prefix CD under the condition of sharing the scrambling code, the present invention proposes a WCDMA system packet transmission channel CPCH, the base station distinguishes the access detection prefix AP and the access conflict prefix CD Methods.

The method for distinguishing the access prefix of the present invention includes the following steps:

1) The terminal selects available access resources according to the access resource information broadcast by the common packet channel state indicator channel CSICH, and sends an access detection prefix AP to request access;

2) The base station judges the type of access prefix according to the possible range of the CD prefix recorded in the previous time period, and searches the PCPCH corresponding to the prefix signature according to the correspondence table between PCPCH and CD. If the corresponding PCPCH is applied for, the prefix is CD, otherwise the prefix for the AP;

3) The base station predicts the access detection prefix AP that is confused with the access conflict prefix CD to be received, determines its range, and the system broadcasts through the CSICH channel that the access resource corresponding to the above prefix AP is unavailable;

4) The base station performs other processing.

By adopting the method of the present invention, compared with the prior art, the access detection prefix AP and the access conflict prefix CD can be distinguished by the base station under the condition that both the scrambling code and the signature are shared, which reduces the number of problems in the access process of the base station. In the case of terminal confusion, the capacity of the common packet channel CPCH is improved.

Description of drawings

FIG. 1 is a schematic diagram of an access process for a terminal to select a channel mode.

Fig. 2 is a schematic diagram of the access process in the flexible channel assignment mode.

Figure 3 is a flow chart of the method of the present invention.

Detailed ways

The implementation of the technical solution will be further described in detail below in conjunction with the accompanying drawings.

FIG. 1 and FIG. 2 have already been described in the background technology, and will not be repeated here.

Fig. 3 is the basic flow of the method of the present invention. Each time before the terminal sends out the application, it will know the busy status information of the PCPCH channel to be applied for from the CSICH channel, and decide whether to send out the AP. Each PCPCH channel has three states: unapplied, applied, and occupied. For the applied and occupied PCPCH channels, it is marked as busy. According to the PCPCH channel marked as busy, it can be inferred that the prefix CD that may be received, And mark the PCPCH channel corresponding to the AP that can be confused with it as busy in the next time slot, so that the AP that may be confused with the CD will not be sent out. If the prefix received by the base station falls within the possible range of the CD prefix, it is judged as the prefix CD, and the rest is the prefix AP. The base station sends information according to different prefixes, performs collision detection, and finally confirms the required PCPCH channel to complete data transmission. At the same time, if the original access application is in the conflict detection stage, it is necessary to issue a CD for conflict detection, and the corresponding PCPCH channel also needs to be displayed as being occupied. From this point, the correspondence table between PCPCH and AP and CD can be as consistent as possible, so that The number of PCPCHs additionally marked as busy for distinguishing between AP and CD will be small.

The specific implementation process is as follows: Initialize the correspondence table between PCPCH and AP, CD, so that the AP and CD corresponding to the same PCPCH are as similar as possible; initialize the busy-idle state table of PCPCH, each PCPCH channel has 3 states, unapplied, applied, occupied. The state of the PCPCH channel is broadcast in the cell through the CSICH, and the PCPCH channel that has been applied for and occupied is marked as busy. The terminal sends the access detection prefix AP according to the status of the PCPCH channel to request access, the base station receives the prefix signature, and searches the PCPCH corresponding to the prefix signature from the correspondence table between PCPCH and CD. If the corresponding PCPCH is applied for, the prefix is CD, and other prefixes are AP. If it is an AP, for the acceptable application, set the corresponding PCPCH channel as applied, and at the same time find out that the PCPCH channel corresponding to the AP that may be confused with the CD to be received is also marked as applied, and clear the outdated application , to mark the PCPCH resource as unapplied. Then the CPCH channel performs other processing. The new state of the PCPCH channel is re-broadcasted.

Claims (2)

1. the method for base station resolution prefixing in the broadband CDMA system is characterized in that, may further comprise the steps:

1) terminal is chosen available access-in resource and is sent access detection prefix (AP) according to the access-in resource information of CPCH state indicating channel (CSICH) broadcasting, requires to insert;

2) type of Access Preamble is differentiated in the base station according to the possible scope of the access interference prefix (CD) of previous time period record, search the corresponding PCPCH of prefix signature according to physical common grouped channels (PCPCH) and the correspondence table of CD, PCPCH as correspondence is applied, then prefix is CD, otherwise prefix is AP;

3) the base station prediction detects prefix (AP) with the access that the access interference prefix (CD) that will receive is obscured mutually, determines its scope, and system is unavailable by the CSICH channel radio access-in resource corresponding with these prefixes AP;

4) other processing is carried out in the base station.

2. the method for claim 1, it is characterized in that: described access-in resource information is the busy-idle condition of physical common grouped channels (PCPCH).

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