CN1168330C - A method for configuring downlink offset in CDMA cellular mobile communication system - Google Patents

Abstract

The present invention relates to a method for configuring a downlink offset in a CDMA cellular mobile communication system. The method comprises the steps that the configurable range of the offset is segmented according to sequence numbers, and the sequence number of each offset corresponds to an offset; a database which stores all offset configuring information and can be retrieved through the sequence numbers of the offset is created; frame segment numbers, time slot segment numbers and sub-segment numbers are determined in a delaminated mode, and positions of the offset to be configured are found out; the values of the offset are determined according to the positions of the offset and are output; the database is updated. The present invention expands the pilot frequency signals of different users, dispatches the service of the different users and reduces the peak emission power of the base station and the data processing load of the base station in different time.

Description

A method for configuring downlink offset in CDMA cellular mobile communication system

technical field

The invention relates to a CDMA (Code Division Multiple Access) cellular mobile communication system, in particular to a method for configuring a downlink offset in the CDMA cellular mobile communication system.

Background technique

With the development of mobile communication and the increasing demand for communication, the focus worldwide is on the third generation mobile communication system, such as the Future Public Land Mobile Telecommunications System (FPLMTS) - the 2000 International Mobile Communication System of the ITU ITU communication system (IMT-2000) or the Universal Mobile Telecommunications System (UMTS) in Europe. The use of CDMA technology in the third-generation mobile communication system has also become a consensus. At present, there are three schemes accepted as the choice of IMT-2000 air interface, namely: Wideband CDMA (WCDMA), CDMA 2000 and TD- SCDMA. The new-generation mobile communication system also puts forward higher requirements in terms of multimedia services. In addition to supporting general voice services and low-speed data services, it also needs to support high-speed image communication, high-speed data services, and packet services. Coupled with the large capacity of the system, many users communicate with the base station for various services at the same time, which requires the base station in the system to have a higher load handling capacity to be able to process the uplink and downlink traffic in a timely manner. business data. However, if the data of many users in the cell are transmitted at the same time, the base station may not be able to process such a large amount of data, causing a large processing delay, affecting the communication quality, and reducing the system capacity to a certain extent .

On the other hand, the superiority of the CDMA digital mobile communication system is based on the adoption of many key technologies. If the key technologies of the system cannot be solved well, the high capacity and high quality of the CDMA system cannot be realized. Among them, power control is considered to be the core of all key technologies. Because in the CDMA digital cellular system, due to the cross-correlation of channel address codes, there will be two effects: one is that any channel will be interfered by other channels with different address codes, that is, multiple access interference; The channel will seriously interfere with the channel far from the receiver, so that the near-end strong signal covers the far-end weak signal, which is the near-far effect. The CDMA system is a self-interference system, and the accumulation of various interferences will degrade the capacity and quality of the system. The purpose of power control is to enable the system to maintain high-quality communication without interfering with other code division channels of the same channel. At the same time, there is serious signal fading in the mobile environment, and it is difficult to obtain a phase reference for the correlation detection of the data modulation signal. Therefore, in the CDMA system, user-specific pilot symbols are used as reference signals for channel estimation. User-specific pilot symbols can be time-division multiplexed or code-division multiplexed. For time-division multiplexed pilot symbols, the pilot symbols are at fixed positions in all time slots of the physical frame, and their lengths vary according to the Doppler frequency shift. In order to obtain accurate channel parameter estimation, generally, pilot symbols have higher transmit power than data symbols. Therefore, there may be an extremely unfavorable situation: when the traffic channels of many users and the base station have the same pilot transmission moment (timing relationship), the downlink transmission power of the base station must have a very high peak value, which corresponds to the pilot The time when the frequency symbol is transmitted. On the one hand, this situation increases the ratio of the downlink peak power to the average power of the base station (Crest factor). capacity.

As shown in Figure 1A and Figure 1B, in order to solve the above two problems, an effective method is adopted to control the transmission time of the pilot symbols in the downlink wireless frames corresponding to different users, so that they are extended in the time domain, thereby eliminating The peak transmit power problem caused by the pilot signal (as shown in Figure 1A). At the same time, it is also necessary to schedule the services of different users so that the base station can also process these data in the time domain instead of processing at the same time, thereby reducing the data processing load of the base station (as shown in Figure 1B). This can be achieved by configuring different transmission timings (offsets) for different users' physical channel radio frames.

At present, the specific method of configuring an offset for a new physical channel is to first measure the processing load of the base station at the current moment and the change of the downlink transmission power of the base station, and then determine an appropriate offset according to the measurement results. This method can obtain the required relevant parameters more accurately, and provide a reliable basis for configuring a new offset.

However, when using the method of directly measuring the processing load and downlink transmission power of the base station at a certain moment to determine the offset of the downlink physical channel, the following main parameters need to be directly measured:

1) The change of the load processing of the base station within a certain period of time before and after the current moment, mainly including the change of the occupancy rate of the buffer zone of the base station, and whether the buffer occupancy rate exceeds the maximum value;

2) The distribution of pilot signals of different physical channels in the time domain within a certain period of time at the current moment, that is, the change of the downlink transmission power of the base station in the time domain.

That is to say, if this method is used to configure the offset, the measurement results of the above parameters must first be obtained. This has the following disadvantages:

1) The measurement of base station load and downlink transmission power is an analysis of its changes over a period of time, with a large amount of data processing and high complexity, thus putting forward high data processing capabilities for the specific implementation of the system Require;

2) The measurement of the load condition of the base station and the downlink transmission power is an analysis of its change over a period of time. The measurement must last for a long period of time (up to tens of ms), and the real-time performance is poor, which is not conducive to the offset Quickly respond to traffic configuration requests, thereby affecting the access rate of user services;

3) The measurement of base station load and downlink transmission power is an analysis of their changes over a period of time, and the different lengths of this period (measurement period) will also affect the reliability of the measurement results to a certain extent.

Contents of the invention

The purpose of the present invention is to provide a simple and easy method for configuring the downlink offset in the CDMA cellular mobile communication system, which can provide fast and reliable request response while reducing the data processing load, so as to reduce the processing load of the base station and base station downlink peak transmit power, thereby further improving system capacity and service quality.

The object of the present invention is achieved in that a method for configuring a downlink offset in a CDMA cellular mobile communication system includes the following steps: segmenting the configurable range of the offset by sequence number, and making each subsection The sequence number of the segment corresponds to an offset; when configuring a new offset, the following 'hierarchical' steps are adopted: first, the range of the offset to be configured is determined according to the load processing situation of the base station, and this range is In a time slot segment, it includes the frame segment number where the offset is located and the slot segment number in this frame segment; secondly, according to the offset configuration in the determined time slot segment, the pilot signal When unfolding in the time domain, it can be evenly distributed to determine the sub-segment number; finally, determine the position of the offset, obtain the corresponding offset, and update the database.

In the above method for configuring downlink offsets in a CDMA cellular mobile communication system, the content recorded in the data field corresponding to each offset number in the database is: information about the traffic channel using the offset.

In the method for configuring the downlink offset in the CDMA cellular mobile communication system described above, the process of determining the frame segment number and the time slot segment number and the process of determining the sub-segment number are independent of each other.

The above method for configuring the downlink offset in the CDMA cellular mobile communication system, wherein the configurable range of the offset can be 8 frame segments, each frame segment is 15 time slot segments, each time slot segment Segment for 5 sub-segments.

The method for configuring the downlink offset in the above-mentioned CDMA cellular mobile communication system, wherein, corresponding to the traffic channels of different users, the base station has a specific downlink channel transmission timing, that is, the offset, and these information are stored in the offset In the configuration table, when performing a new offset configuration, the following operations are performed by accessing the data in the offset configuration table: calculate the load in each frame segment, and obtain a minimum value of the load and the corresponding frame segment number ;In the frame segment where the frame segment number corresponding to the minimum load value is located, calculate the load in each time slot segment to obtain the minimum value of the load and the corresponding time slot segment number; in the time slot segment corresponding to the minimum load value In the time slot segment where the number is located, the pilot signal strength in each sub-segment is calculated to obtain the minimum value of the pilot signal strength and the corresponding sub-segment number.

In the above method for configuring downlink offsets in a CDMA cellular mobile communication system, the service channel information includes transmission rate, transmission power and user identifiers using the service.

Since the above method is adopted, that is, the offset configuration of all existing downlink dedicated physical channels in the current cell is used to estimate the transmission load and processing load at the base station at a certain moment, and the pilot signals of all downlink physical channels in the cell The distribution of the distribution of the downlink physical channel, this indirect way to obtain the required parameters, compared with the existing method of directly measuring the base station processing load and the downlink transmission power of the base station to determine the offset of the downlink physical channel, avoids the burden due to measurement requirements. A large amount of complex data processing from the system reduces the requirements for device data processing capabilities when implementing algorithms; avoids data processing delays caused by measurement, and can analyze the database in advance to obtain appropriate values to be configured, further The real-time performance of the configuration is improved; since there is no need to measure the changes of the load of the base station and the downlink transmission power within a period of time, the impact on the reliability of the measurement results caused by the difference in the measurement period is avoided.

Thereby reducing base station load and base station downlink transmission peak power, improving system capacity and service quality.

Description of drawings

FIG. 1A is a schematic diagram of an existing configuration using an offset to disperse transmission times of pilot signals;

FIG. 1B is a schematic diagram of an existing division using an offset configuration to balance the processing load of a base station;

Fig. 2 is a schematic diagram of the segmentation division of the offset configurable range in the present invention;

Fig. 3 is the basic flowchart of the offset configuration algorithm of the present invention;

Fig. 4 is a schematic diagram of a user initiating a call in a cell to establish a new service channel;

Fig. 5 is a schematic diagram of a user establishing a traffic channel in a target cell through hard handover.

Detailed ways

The present invention is a method for configuring a downlink offset in a CDMA cellular mobile communication system, the process of which is:

1) The configurable range of the offset (the processing cycle of the base station processing load, that is, the interleaving length) is divided into segments. As shown in Figure 2, it is first divided into 8 "frame segments" in units of frames, and then divided into 15 "slot segments" in units of time slots in each frame segment, and finally each time slot segment is divided into Divided into 5 sub-segments, the resolution of the offset is the length of the sub-segment. The serial number of each sub-segment corresponds to an actual offset (serial number * sub-segment length), for example, the serial number corresponding to the n-th sub-segment in the m-th time slot segment of the first frame segment is: (1*75+m*15+n ), the corresponding offset is (1*75+m*15+n)*subsection length.

2) Establish a database, use it to record the offsets of the downlink dedicated physical channels of all different links in the cell, and retrieve them through the sequence numbers of the offsets, each offset sequence number corresponds to a certain number of used The traffic channel for this offset. The database is dynamically updated during operation, so that it can indirectly reflect the processing load of the base station at different times and the pilot signal distribution of the downlink dedicated physical channel in the cell in real time and accurately: when a newly established traffic channel is configured After the offset, new configuration information is added to the database; similarly, when a service channel is disconnected, corresponding information is released in the database. The service channel information includes transmission rate, transmission power and user identification using the service.

3) When making a new offset configuration, the following 'layered' method is adopted:

As shown in Figure 3, when a new downlink dedicated physical channel needs to be established, that is, an offset configuration request, the range of the offset to be configured is first determined by the load processing situation at the base station, as shown in Figure 2 , this range is based on a slot segment, including the frame segment where the offset is located and the slot segment within this frame segment. When determining this range, it can be realized by different algorithms. The simplest method is to use the information stored in the database to compare the number of dedicated channels contained in different ranges, and find out the least one of them. A more accurate algorithm may also consider other channel information, such as the data transmission rate of each channel. If multiple offsets are available, choose one of them arbitrarily.

Then, in the determined time slot segment, the effect of the configuration of the offset on the expansion of the pilot signal in the time domain is considered to determine the sub-segment number. The simple implementation method is to find the sub-segment number with the least channel in the determined time slot segment, so that the pilot signal can be evenly distributed in the time domain; a more accurate algorithm can also consider other information of the channel , such as the number of pilot bits in each channel, the transmit power of the pilot signal, etc. If there are more than one, choose one of them arbitrarily.

Combining the above two processes, that is, the process of determining the frame segment number, the time slot segment number and the sub-segment number, determine the exact position of the offset, obtain a suitable offset, and update the database.

These two processes are independent of each other, because the transmission of the pilot signal takes a time slot as a period, and its distribution can only be considered in a time slot. Therefore, the present invention determines the sub-section where the offset is located from the perspective of reducing the peak power of the downlink transmission of the base station; and determines the frame segment and time slot segment where the offset is located from the perspective of reducing the processing load of the base station .

As shown in FIG. 4, if a user UEn initiates a call request in a certain cell to establish a traffic channel, at this moment, there are already many other users in the cell communicating with the base station. Corresponding to traffic channels of different users, the base station has a specific downlink channel transmission timing, that is, an offset, and the information is stored in an offset configuration table (database).

First do the following definition:

Load-F ₁ : load in the frame segment, which refers to the load caused by all traffic channels in the first frame segment in the offset configurable range to the base station;

Load-S _{1, m} : The load in the time slot segment refers to the load caused by all traffic channels in the mth time slot in the first frame segment to the base station;

Load-T _{1, m, n} : sub-segment load, refers to the load on the base station caused by all traffic channels corresponding to the n-th offset in the m-th time slot segment of the first frame segment. in:

The relationship is as follows: Load-F ₁ =∑Load-S _{1, m} m=0～14

Load-S _{1, m} ＝∑Load-T _{1, m, n} n=0～4

Load-F-min: the minimum value of Load-F ₁ ;

Load-S-min: Load-S _{1, the minimum value of m} ;

N-Load-F-min: the frame segment number corresponding to Load-F-min;

N-Load-S-min: the slot segment number corresponding to Load-S-min;

PilotStrength _n : the pilot signal strength on the sub-segment, that is, the pilot signal strength generated by all links in the cell at the nth offset.

PilotStrength-min: the minimum value of PilotStrength _n (n=0～4)

N-PilotStrength-min: corresponds to the subsection number of PilotStrength-min.

When performing a new offset configuration, the following operations are performed by accessing the data in the offset configuration table:

1) Calculate the Load-F1 of each frame segment within the configurable range of the offset to obtain the minimum Load-F-min and the corresponding N-Load-F-min;

2) Calculate the Load-S _1,m of each time slot in the frame segment corresponding to N-Load-F-min to obtain the minimum Load-S-min and the corresponding N-Load-S-min;

3) Calculate the PilotStrength _n corresponding to the offset of each sub-segment in the time slot segment corresponding to N-Load-S-min, and obtain the minimum value PilotStrength-min and the corresponding N-PilotStrength-min;

4) Combine the results of the above three steps to get the exact offset.

As shown in FIG. 5 , when a mobile user establishes a new traffic channel in the target cell through hard handover during the moving process, a new offset configuration should also be performed for it. The configuration method and process are the same as those in Embodiment 1, and will not be repeated here.

Claims (6)

1. the method for a configurating offset of down link in the cdma cellular mobile communication system is characterized in that, comprises the following steps:

By sequence number the configurable range of side-play amount is carried out segmentation, and make corresponding side-play amount of sequence number of each son section;

When carrying out new side-play amount configuration, adopt the step of following ' layering ':

At first, determine the scope of the side-play amount that will dispose according to the load disposition of base station, this scope is a unit with a time slot section, comprises the time slot segment number in the residing frame segment number of this side-play amount and this frame section; Secondly, the configuration according to side-play amount in the time slot section of determining makes pilot signal can evenly distribute when launching on time domain, determines sub-segment number; At last, determine the position of side-play amount, obtain corresponding offset, more new database.

2. according to claim 1 a kind of in the cdma cellular mobile communication system method of configurating offset of down link, it is characterized in that the content of the data field of each side-play amount sequence number correspondence record is in database: the traffic channel information that uses this side-play amount.

3. according to claim 1 a kind of in the cdma cellular mobile communication system method of configurating offset of down link, it is characterized in that, determine that the process of frame segment number, time slot segment number and the process of determining sub-segment number are separate.

4. according to claim 1 a kind of in the cdma cellular mobile communication system method of configurating offset of down link, it is characterized in that, can be that 15 time slot sections, each time slot section are that 5 son sections are carried out segmentation by 8 frame sections, each frame section to the configurable range of side-play amount.

5. according to claim 1 a kind of in the cdma cellular mobile communication system method of configurating offset of down link, it is characterized in that, the Traffic Channel of corresponding different user, the base station has specific down channel emission regularly, it is side-play amount, these information all are kept in the side-play amount allocation list, when carrying out new side-play amount configuration, are done as follows by the visit to data in the side-play amount allocation list:

Calculate the load in each frame section, obtain the minimum value and the corresponding frame segment number of a load;

In the frame section at the frame segment number place of this load minimum value correspondence, calculate the load in each time slot section, obtain the minimum value and the time slot corresponding segment number of load;

In the time slot section at this load minimum value time slot corresponding segment number place, calculate the pilot signal strength in each son section, obtain the minimum value and the corresponding sub-segment number of pilot signal strength.

6. according to claim 2 a kind of in the cdma cellular mobile communication system method of configurating offset of down link, it is characterized in that described traffic channel information comprises transmission rate, transmitting power and uses this professional user ID.

Images