CN111757427A

CN111757427A - Channel quality evaluation-based selection method for preferred network of wide-narrow convergence terminal

Info

Publication number: CN111757427A
Application number: CN202010504420.9A
Authority: CN
Inventors: 张宗军; 陈池
Original assignee: Eastern Communication Co Ltd
Current assignee: Eastern Communication Co Ltd
Priority date: 2020-06-05
Filing date: 2020-06-05
Publication date: 2020-10-09
Anticipated expiration: 2040-06-05
Also published as: CN111757427B

Abstract

The invention discloses a selection method of a preferred network of a wide and narrow fusion terminal based on channel quality evaluation, which comprises the steps of evaluating the quality of a B-trunk network signal to obtain a CQI value, evaluating the quality of a PDT network signal to obtain a channel path loss parameter C1 value, comparing the CQI value with a C1 value, and selecting one signal as a main network when the signal falls into a judgment range. The invention can reduce the user intervention operation to the maximum extent, improve the convenience of the terminal, expand the use scene of the user for the existing wide and narrow private network, and achieve the purpose of fusing, complementing and multi-guaranteeing the two networks. Meanwhile, for private network users, no matter under a PDT network or a B-Trunc network, the use and operation habits of the private network users do not change greatly, and the internal system and the underlying mechanism of the terminal ensure the smoothness of communication and the optimal signal quality.

Description

Channel quality evaluation-based selection method for preferred network of wide-narrow convergence terminal

Technical Field

The invention relates to the field of wide and narrow converged terminals, in particular to a preferred network selection method of a wide and narrow converged terminal based on channel quality assessment.

Background

PDT is a police digital trunking communication system with independent intellectual property rights in China, has a plurality of advantages in function compared with an analog trunking system, but due to the limitation of a technical system, the processing capability for data services is limited, but the service processing in the aspects of images and videos is basically blank, and along with the deepening of police service work, the improvement of social security requirements and the increase of the matching capability of video services are of great importance.

The PDT police digital trunking communication system is designed for commanding and dispatching, and large-area coverage is realized by using 12.5KHz carrier 2 time slot TDMA technology. The single-slot voice transmission rate is 2.4 Kbps. The data transmission rate is only 4.8 Kbps in the case of two-slot combination.

At present, a pure broadband cluster standard (B-trunk) based on the TD-LTE technology is also established in China, 20 megabandwidths (1447-1467 MHz and 1785-.

In order to achieve the purpose that a PDT private network can be used and a pure broadband cluster standard of a TD-LTE technology can be used, a wide-narrow fusion terminal is designed, namely a PDT + LTE wide-narrow band integrated terminal for police is used, the public security voice and data service fusion mode can be enriched, in the wide-narrow band fusion technology, interconnection of wide and narrow systems is achieved, multiple modes are achieved by an application terminal, and therefore the private network function can be played, the benefit is highlighted, and investment can be saved. The terminal can replace the existing multi-type terminal and is suitable for the multi-form multi-scene use environment of mobile police service.

For a terminal, if two networks meet an access requirement, when a call service is initiated, it is required to determine which network to select for communication, and a simpler method is to specify any one network, but this may result in that the network used is not a physically optimal network, so that simply specifying a network, although simple and easy to use, is not a good method for operation, and if the signal quality is relatively poor at the edge of a network in a certain mode, but other networks may have good signals, at this time, selecting a preferred network as another network may make communication more smooth. Therefore, the mode of the operation of the converged terminal can be more reasonable and feasible by selecting the preferred network through a proper method.

Disclosure of Invention

In order to solve the above technical problems in the prior art, the present invention provides a preferred network selection method for a wide and narrow convergence terminal based on channel quality assessment, which obtains a CQI value for B-Trunc network signal quality assessment, obtains a channel path loss parameter C1 value for PDT network signal quality assessment, compares the CQI value with the C1 value, and selects one of the signals as a master network when the one of the signals falls within a decision range.

Further, in the selection process, if the main network before the conversion is performing the voice or video service, the conversion is performed after the service is completed.

Further, a stable value of the signal lasting for more than 5 seconds is included as a comparison reference.

Further, the decision rule is specifically as follows:

(1) when PDT network 10 is less than or equal to C1 and less than 20, if the B-Trunc network can carry out 64QAM communication and CQI is more than or equal to 10, selecting the B-Trunc network as a preferred network, and if the CQI of the B-Trunc network is less than or equal to 10, still using the PDT network;

(2) when PDT network 5< C1 is less than or equal to 10, if the CQI of the B-Trunc network is detected to be more than or equal to 7 and the B-Trunc network can carry out 16QAM communication, selecting the B-Trunc network as a preferred network, and if the CQI of the B-Trunc network is less than 7, still using the PDT network;

(3) when PDT network 0< C1 is less than or equal to 5, if the CQI of the B-trunk network is detected to be more than or equal to 3 and the B-trunk network can carry out qpsk communication, selecting the B-trunk network as a preferred network, and if the CQI of the B-trunk network is less than 3, still using the PDT network.

Further, in the case of rule (3), the wireless signal of the network is constantly monitored, and the network is immediately accessed as soon as improvement.

Further, the CQI of the C1 of the PDT network and the CQI of the B-Trunc network are taken as two-dimensional parameters, and a working state diagram of the fusion terminal is given on a coordinate axis to compare and judge.

Furthermore, the CQI value is measured and reported by the user equipment UE, and the eNodeB selects a proper downlink scheduling algorithm and a downlink data block size according to the CQI information.

Further, the CQI value is related to SINR of downlink reference signal, sensitivity of UE receiver, MIMO transmission mode and radio link characteristics.

Further, the path loss parameter C1 is calculated as follows:

C1 = A-B-Max (0，C-D )

a: RSSI = average signal strength of the downlink signal received by the mobile station from the cell base station;

b: MIN _ RXLEV = minimum allowed signal reception strength of the mobile station within the cell;

c: MAX _ TXPWR = maximum allowed signal transmission strength of the mobile station in the cell;

d: PMS = maximum emission level value of the mobile station itself;

wherein Max (0, C-D) is the maximum value between 0 and C-D;

the higher the value of C1, the better the field strength signal of the serving cell of the mobile station, when the value of C1 fades to a certain threshold, the mobile station starts to measure and calculate the values of the neighboring cells, continuously compares the values with the value of C1 of the serving cell, and switches according to the actual situation in combination with the cell reselection parameters preset in the system.

Further, when the wide-narrow converged terminal is in a dual coverage network of PDT and B-trunk, after the wide-narrow converged terminal is started, the PDT network needs to be searched, the B-trunk network also needs to be searched, and after the two networks meet the network access conditions of the terminal, the terminal can be registered in the corresponding PDT and B-trunk networks in sequence.

The invention provides a selection method of a preferred network of a wide and narrow converged terminal, which is based on dynamic evaluation of signal quality of a B-trunk network and a PDT network, samples evaluation values into different quantization spaces, compares the channel signal evaluation values of the two networks, selects one signal as a main network when one signal falls into a judgment range based on the method, and simultaneously, in the selection process, if the main network before conversion is in voice or video service, the conversion must be carried out after the service is finished, and in order to avoid accidental signal interference or sudden change, a stable value which can last for more than 5 seconds is required to be ensured for a measured value of the signal to be included into a comparison reference.

The invention provides a feasible network selection method for the converged multimode private network terminal by adopting a signal dynamic evaluation method based on the converged terminal, can reduce user intervention operation to the maximum extent, improves the convenience of the terminal, expands the use scene of a user for the existing wide and narrow private network, and achieves the purposes of convergence, complementation and multiple guarantee of the two networks. Meanwhile, for private network users, no matter under a PDT network or a B-trunk network, the use and operation habits of the private network users do not change greatly, only the use of the terminal needs to be concerned, the selection of different networks does not need to be concerned, and the internal system and the bottom layer mechanism of the terminal ensure the smoothness and the optimal signal quality of communication.

Drawings

FIG. 1 is a flow chart of a terminal network access process of a B-trunk network;

fig. 2 is a flow chart of a PDT terminal network access process;

fig. 3 is a graph of PDT parameters C1 and CQI values versus network selection;

fig. 4 is a schematic diagram of a preferred network decision tree.

Detailed Description

The invention will be further explained with reference to the drawings.

Abbreviations and terms used in the present invention are explained:

PDT: police Digital Trunking

SIC: system Information Code, System Information codeword

TDMA: time division multiple access

LTE: long Term Evolution, Long Term Evolution

MME: mobile Management Entity

TD-LTE: time Division LTE

B-Trunc: broadband Trunking Communication

CQI: channle Quality Indication, channel Quality Indication

UE: user Equipment, User machine

QAM: quadrature Amplitude Modulation

QPSK: quadrature Phase Shift Keying (QPSK) modulation

PDSCH: physical Downlink Shared Channel (pdcch)

BLER: block Error Rate, decoded Block Error Rate

SINR: signal to Interference plus Noise Ratio

PRB：Physical Resource Block

RE: resource Element, Resource Element

Physical Downlink Control Channel (PDCCH), Downlink Control Channel

MIMO: multi Input Multi Output, multiple Input multiple Output

TBS: transport Block Size, Transport Block Size

CFI: control Format indicator, Control Format indication

DwPTS: downlink Pilot Time Slot, Downlink Pilot Time Slot

C1: channel path loss parameter

IMSI: international Mobile Subscriber Identity (IMSI)

eNodeB: evolved Node B, Evolved base station

eNB: evolved Node B, Evolved base station

EPC: evolved Packet Core, Evolved Packet Core network

TM: transfer Mode, antenna port Transfer Mode

GUTI: global Unique temporal UE Identity, Globally Unique Temporary UE Identity

RRC: radio Resource Control, Radio Resource Control

TAU: tracking Area Update

NAS: Non-Access Stratum, Non-Access Stratum

MCS: modulation and Coding Scheme, Modulation and Coding strategy

E-UTRAN: E-UTRAN evolution type Universal Terrestrial Radio Access Network

GSM: global System for Mobile Communication

Enhanced Data Rate for GSM Evolution for Enhanced Data Rate for GSM Evolution

GERAN: GSM EDGE Radio Access Network, GSM/EDGE wireless communication Network

S1: the interface between EPC and E-UTRAN is called S1 interface

MNC: mobile Network Code, Mobile area Code

RSSI: received Signal Strength Indication, the mobile station receives the Signal Strength Indication.

MIN _ RXLEV: minimum Received signal level, Minimum allowed signal Received strength.

MAX _ TXPWR: maximum Transmission Power, the Maximum allowable signal Transmission strength of a mobile station in a cell.

PMS: power of Mobile Station, maximum transmission level value of the mobile Station itself.

Terminal network access process of network

As shown in fig. 1, when a user equipment UE is just powered on, the UE firstly performs physical downlink synchronization, searches for measurement to perform cell selection, and after selecting a suitable or acceptable cell, resides and performs an attachment process, which is specifically as follows:

1) the steps 1 to 5 establish RRC connection, and the steps 6 and 9 establish S1 connection, and completing these procedures indicates that the NAS signaling connection is completed.

2) Description of message 7: the user and the UE are just started and attached for the first time, the IMSI is used, and the verification process is not needed; subsequently, if there is a valid GUTI, the core network will initiate the validation procedure (for uplink and downlink direct transfer messages) using the GUTI attach.

3) Description of messages 10-12: if the message 9 carries the UE wireless capability information, the eNB cannot send the UE capability query message to the UE, namely 10-12 processes do not exist; otherwise, the UE sends the wireless capability information, and the eNB sends the UE capability information indication again to report the wireless capability information of the UE to the core network. To reduce air interface overhead, the MME may store UE radio capability information in the EPC in idle, and the initial context setup request message may be brought to the eNB unless the UE performs an attach or "first TAU with GERAN/UTRAN attach" or "UE radio capability update" TAU procedure (i.e., these procedures the MME will not bring UE radio capability information to the eNB and will delete locally stored UE radio capability information, and the eNB may query the UE capability information and report it to the MME in the EPC). The E _ UTRAN radio capability information of the UE needs to be attached first and then attached if changed.

4) Description of messages 13-15: the eNB has finished sending the message 13 and does not need to wait for the message 14 to be received and sends the message 15 directly.

5) If the IMSI of a UE is duplicated with the IMSI of another UE when the IMSI attach is initiated, and other UEs are already attached, the core network releases the previous UE. If the MNC in the IMSI is inconsistent with the configuration of the core network, the core network replies attachment rejection.

6) Description of message 9: the message is an initial context establishment request initiated by the MME to the eNB, requests the eNB to establish bearer resources, and simultaneously has security context and possibly parameters such as user wireless capability, a handover restriction list and the like. The security capability parameters of the UE are brought to the core network via the attach request message, which is then sent to the eNB via the message. The TAU needs to be initiated if the network capability (security capability) information of the UE changes.

Network access process of terminal

After the mobile station is started, the mobile station firstly scans to a PDT network to obtain system access information including access parameters, system access authority, system codes and the like, then the mobile station sends an access signaling to start a registration process, the level parameters include 16 bits lower than a network address, a system information code SIC of the network where the mobile station is located is filled, 8 bits higher than the network address is all 0, and whether a security module is carried or not is indicated.

During registration, the base station may perform a device number query for the mobile station.

Message process of registration as shown in fig. 2, after the registration is successful, the terminal can initiate PDT cluster service.

When the terminal accesses the PDT network, the signal measurement is continuously carried out, and the current channel path loss parameter C1 value is obtained according to the measurement result, and the value is used as the quality basis for the terminal to evaluate the current PDT network.

B-Trunc network signal quality evaluation method

CQI value determination

The quality of the B-trunk network uses CQI as a channel quality evaluation parameter, the CQI is measured by UE, and the CQI refers to the quality of a downlink channel. Since the B-Trunc network is physically the same as the LTE network, but the cluster function is expanded, the CQI parameter is used in the B-Trunc network for network quality evaluation. And the eNodeB selects a proper scheduling algorithm and the size of the downlink data block according to the CQI information so as to ensure that the UE obtains the optimal downlink performance under different wireless environments. The eNodeB selects a proper downlink scheduling algorithm and a transmission coding mode according to the CQI information, different channel conditions also have different choices for modulation modes, and the higher the coding mode is (QPSK <16QAM <64 QAM), the higher the requirement on the channel conditions is.

Since the downlink scheduling is determined by the eNodeB, which is the transmitting end and does not know the quality of the channel, the quality of the channel is measured by the UE. The eNodeB determines what coding method to use, and needs the UE to feed back the quality of the channel, and the LTE protocol quantizes the quality of the channel into a sequence of 0 to 15 (4 bits for carrying), and defines the channel as CQI.

The CQI value is measured and reported by the UE. The CQI selection criterion in the LTE specification is to ensure that the decoding error rate (i.e., BLER) of the PDSCH is less than 10% of the CQI value used. That is, the UE needs to evaluate the downlink characteristics according to the measurement result (such as SINR), determine the BLER value that can be obtained under this SINR condition, and report the corresponding CQI value according to the limitation that BLER is less than 10%. The CQI values and coding schemes used are shown in table 1.

Table 1 CQI values and corresponding coding schemes

The modulation scheme determines the modulation order, which represents the number of bits transmitted in each 1 symbol. QPSK corresponds to a modulation order of 2, 16QAM of 4 and 64QAM of 6. The code rate is the ratio of the number of information bits in the transport block to the total number of physical channel bits, i.e.:

code rate = number of information bits in transport block/total number of physical channels = number of information bits/(total number of symbols of physical channels) = modulation order) = efficiency/modulation order

Therefore, different values of the CQI determine the difference between the downlink modulation mode and the transport block size. The larger the CQI value is, the higher the modulation and coding scheme used is, the higher the efficiency is, and the larger the corresponding transport block is, so that the higher the downlink peak throughput provided is, the better the quality of the radio channel is.

CQI influencing factor

The UE determines the available CQI from the measured SINR value and reports to the eNodeB, so the CQI value is mainly related to the SINR of the downlink reference signal.

The CQI is related to, among other things, the UE receiver sensitivity, MIMO transmission mode and radio link characteristics. The concrete expression is as follows:

under the same channel quality condition, the higher the sensitivity of the UE receiver, the higher the measured SINR value, and therefore the larger the reported CQI value.

MIMO mode, number of retransmissions and number of antennas all affect BLE performance. Since the CQI corresponds to the SINR value required for 10% BLER, the CQI value is higher for 3 retransmissions than for 0 retransmissions, TM3/4 is higher than for TM2, and 4 antennas is higher than for 2 antennas under the same SINR condition.

Effect of CQI on Performance

As can be seen from the above analysis, the CQI plays a very critical role in downlink scheduling. The UE estimates CQI according to the SINR value and reports the CQI in a periodic or aperiodic mode, and the eNodeB extracts corresponding broadband or sub-band CQI information according to different CQI modes to obtain the interference situation of the UE on a specific frequency band and realize frequency selective or non-selective scheduling. Importantly, the eNodeB acquires MCS and TBS information according to CQI and PRB information, directly affecting downlink throughput.

The CQI evaluation and measurement mechanism in the UE and eNodeB scheduling algorithms has a direct impact on system performance. If the CQI reported by the UE is low but the system erroneously sends a large TBS, the UE may fail to decode and send acknowledgement information, thereby generating a retransmission and affecting the resource utilization of the system. On the contrary, if the actual radio environment is poor but the CQI value reported by the UE is high, the network selects a larger TBS according to the CQI, which may also cause the UE to fail decoding, resulting in a decrease in the utilization of system resources.

PDT network signal quality evaluation method

PDT refers to the practice of general networks. I.e. the parameter determining the signal quality of the mobile station cell is the current path loss parameter C1. Here, C1 also represents to some extent the signal quality of the current cell.

The path loss parameter C1 is calculated by the following method:

C1 = A-B-Max (0，C-D )

a: RSSI = average signal strength of the downlink signal received by the mobile station from the base station of the cell.

B: MIN _ RXLEV = minimum allowed signal reception strength of the mobile station in the cell.

C: MAX _ TXPWR = maximum allowed signal transmission strength of the mobile station in the cell.

D: PMS = maximum emission level value of the mobile station itself.

Where Max (0, C-D) is the maximum between 0 and C-D.

The specific value of a is measured by the mobile station.

The specific values of B and C are preset by the system and are given by the broadcast form through the cell base station. The specific value of D is given by the mobile station itself.

The units of C1 are dB and the units of all parameters in the C1 calculation are dBm.

In summary, the higher the value of C1, the better the field strength signal representing the serving cell of the mobile station. The value of C1 provides a basis for the field strength for cell reselection by the mobile station. No matter the mobile station is in an idle state or a call state, the mobile station can constantly monitor the downlink signals of the base stations of the serving cell and the adjacent cells, when the C1 value is faded to a certain threshold value, the mobile station starts to measure and calculate the values of the adjacent cells, constantly compares the values with the C1 value of the serving cell, and switches according to actual conditions and cell reselection parameters preset in the system.

When the converged terminal is under a dual-coverage network of PDT and B-trunk, for the terminal, after the terminal is started, not only the PDT network but also the B-trunk network are searched, and after the two networks both meet the network access conditions of the terminal, the terminal is registered under the corresponding PDT and B-trunk networks in sequence.

PDT and B-Trunc network selection criteria

As shown in fig. 3 and 4, for the convergence terminal, based on the selection principle of signal quality and network preference, the preferred network selection method of the wide-narrow convergence terminal based on channel quality evaluation is proposed:

when C1 of PDT network is more than or equal to 20, PDT network is selected as the preferred network for communication.

When PDT network 10 is less than or equal to C1<20, and B-trunk network can carry out 64QAM communication, CQI is more than or equal to 10, B-trunk network is selected as preferred network, if terminal is carrying out voice call through PDT network at the moment, then corresponding preferred network mode switching process can be carried out after the call is finished. If the B-Trunc network or the CQI is less than or equal to 10 at the moment, the PDT network is used;

when PDT network 5< C1 is less than or equal to 10, detecting that CQI of B-trunk network is more than or equal to 7, the B-trunk network can carry out 16QAM communication, selecting the B-trunk network as a preferred network, if the terminal is carrying out voice call through PDT network at the moment, then carrying out corresponding preferred network mode switching process after the call is finished. If the B-Trunc network is also CQI <7 at the time, the PDT network is used;

when PDT network 0< C1 is less than or equal to 5, detecting that CQI of the B-trunk network is more than or equal to 3, the B-trunk network can carry out qpsk communication, selecting the B-trunk network as a preferred network, and if the terminal is carrying out voice call through the PDT network at the moment, carrying out corresponding preferred network mode switching process after the call is finished. If the B-Trunc network is also CQI <3 at this time and the PDT network is still used, the radio signals of the network are constantly monitored even if communication has hardly been possible at this time, an improved immediate access network.

In order to avoid frequent mode switching of the convergence terminal, it is set that when the stabilization time of the detection value is not less than 5 seconds, that is, for the PDT network, the C1 value in a certain range is required to satisfy 5 seconds of duration, and correspondingly the corresponding CQI of the B-trunc network is also required to last 5 seconds, which can be measured by setting a duration timer.

In the above process, if the converged terminal operates in the B-Trunc mode, when the preferred network is switched to the PDT mode, if the terminal is performing the voice or video service, the terminal may switch the PDT mode only if the current service state is ended, so as to ensure the smoothness of the ongoing service.

According to the principle, the CQI of the C1 and the B-Trunc of PDT can be used as two-dimensional parameters, the working state diagram of the converged terminal is given on the coordinate axis, the problem of the network selection principle in practical work is solved by optimizing the signal quality of PDT and the B-Trunc network, and meanwhile, by the method, the main network can be dynamically selected according to the signal quality of the two networks, the conversation effect is improved, and the communication quality is ensured.

Claims

1. A preferred network selection method of a wide and narrow converged terminal based on channel quality assessment is characterized by comprising the following steps: and obtaining CQI values for the signal quality evaluation of the B-trunk network, obtaining a channel path loss parameter C1 value for the signal quality evaluation of the PDT network, comparing the CQI values with the C1 value, and selecting one of the signals as the master network when the one of the signals falls into a judgment range.

2. The channel quality estimation-based selection method for a preferred network of a wide-narrow convergence terminal according to claim 1, characterized in that: in the selection process, if the main network before conversion is performing voice or video service, the conversion is performed after the service is completed.

3. The method for selecting a preferred network of a wide-narrow converged terminal based on channel quality assessment according to claim 1 or 2, wherein: the steady value of the signal lasting more than 5 seconds is taken as a measured value and is included as a comparison reference.

4. The method for selecting a preferred network of a wide-narrow converged terminal based on channel quality assessment according to claim 1 or 2, wherein: the decision rule is as follows:

5. The method for selecting a preferred network of a wide-narrow converged terminal based on channel quality assessment according to claim 4, wherein: in the case of rule (3), the wireless signals of the network are constantly monitored, and the network is immediately accessed as soon as improvement.

6. The channel quality estimation-based selection method for a preferred network of a wide-narrow convergence terminal according to claim 1, characterized in that: and taking the CQI of the C1 of the PDT network and the CQI of the B-Trunc network as two-dimensional parameters, and giving a working state diagram of the convergence terminal on a coordinate axis to compare and judge.

7. The channel quality estimation-based selection method for a preferred network of a wide-narrow convergence terminal according to claim 1, characterized in that: and the CQI value is measured and reported by the user equipment UE, and the eNodeB selects a proper downlink scheduling algorithm and a downlink data block size according to the CQI information.

8. The channel quality estimation-based selection method for a preferred network of a wide-narrow convergence terminal according to claim 7, wherein: the CQI value is related to the SINR of the downlink reference signal, the sensitivity of the UE receiver, the MIMO transmission mode and the radio link characteristics.

9. The channel quality estimation-based selection method for a preferred network of a wide-narrow convergence terminal according to claim 1, characterized in that: the path loss parameter C1 is calculated as follows:

C1 = A-B-Max (0，C-D )

d: PMS = maximum emission level value of the mobile station itself;

wherein Max (0, C-D) is the maximum value between 0 and C-D;

10. The channel quality estimation-based selection method for a preferred network of a wide-narrow convergence terminal according to claim 1, characterized in that: when the wide-narrow converged terminal is in a dual coverage network of PDT and B-Trunc, after the wide-narrow converged terminal is started, a PDT network needs to be searched, a B-Trunc network needs to be searched at the same time, and after the two networks meet the network access conditions of the terminal, the terminal can be registered under the corresponding PDT and B-Trunc networks in sequence.