Communication system supporting NB-IOT voice service

Abstract

The invention belongs to the technical field of communication, and discloses a communication system supporting NB-IOT voice service, which comprises a terminal, a base station, a core network and an IMS server, wherein the terminal, the base station and the core network all support NB-IOT voice services, the terminal is connected with the base station through a Uu interface, the base station is connected with the core network and the IMS server through an S1 interface, and the terminal is connected with the core network through an Nas logic interface; the terminal is used for initiating and receiving an IMS voice call, supporting establishment of an SIP session with the AS server to complete IMS signaling connection, and establishing a bearer required by IMS voice. According to the invention, the NB-IOT terminal and the NB-IOT base station support measurement and switching functions, so that the voice service continuity is ensured; qCI1 and 5 voice bearing and SIP session processing are established in an NB-IOT terminal, a base station and a core network, and it is ensured that a transmission channel is established for a control plane service and a data plane service of voice; the base station supports voice uplink pre-scheduling, so that the problem of insufficient uplink scheduling capability of the base station is solved.

Description

Technical Field

[0001] The present invention belongs to the field of communication technologies, and particularly relates to a communication system supporting NB-IoT voice services. Background Art

[0002] Traditional NB-IoT technology is designed for the communication of low-cost and long-coverage Internet of Things (IoT) terminals. Due to its small bandwidth of only 180 kHz, low rate with peak values of about 100 kbps for both uplink and downlink, large latency, and coverage enhancement achieved through repeated transmission of each channel, it is impossible to guarantee the packet transmission latency. Compared with terrestrial broadband systems such as 4G and 5G, the above technical characteristics of NB-IoT have no advantage in voice services. Therefore, NB-IoT technology does not support voice service transmission. With the emergence of the NTN scenario of NB-IoT, there are new application scenarios for NB-IoT voice services. However, NB-IoT needs to overcome many technical problems to meet the network requirements for transmitting voice services.

[0003] These jointly lead to problems such as NB-IoT technology terminals not supporting voice services, NB-IoT being unable to guarantee service continuity, large NB-IoT scheduling latency, poor NB-IoT concurrent scheduling ability, and low NB-IoT peak rate. Therefore, it needs to be improved. Summary of the Invention

[0004] The purpose of the present invention is to provide a communication system supporting NB-IoT voice services to solve the problems raised in the above background art.

[0005] To achieve the above purpose, the present invention provides the following technical solution: A communication system supporting NB-IoT voice services, including: a terminal, a base station, a core network, and an IMS server;

[0006] Among them, the terminal, the base station, and the core network all support NB-IoT voice services. The terminal is connected to the base station through the Uu interface, the base station is connected to the core network and the IMS server through the S1 interface, and the terminal is connected to the core network through the Nas logical interface;

[0007] The terminal is used to initiate and receive IMS voice calls, support establishing an SIP session with the AS server to complete the IMS signaling connection, and establish the bearer required for IMS voice. Its PDCP layer supports the compression and decompression of voice packets, and at the same time supports mobility measurement, measurement report reporting, and handover based on measurement, time, or geographical location;

[0008] The base station is used to establish a voice bearer for the terminal, identify voice services through the bearer type and perform uplink pre-scheduling, periodically allocate uplink grant resources according to the voice rate requirement, plan uplink and downlink resources using an 80-ms scheduling template to implement 24-way 4.75-kbps voice services on a single carrier, and manage the mobility measurement of the terminal and the issuance of handover commands;

[0009] The core network is used to establish an IMS signaling connection for the SIP session with the terminal, and cooperate with the base station to establish an IMS signaling bearer and a data bearer;

[0010] The IMS server is connected to the base station through the S1 interface and supports the transmission of the control plane and the user plane of voice services.

[0011] Preferably, the scheduling mechanism of the base station includes:

[0012] A1-1. Uplink pre-scheduling: According to the voice rate requirement, issue pre-scheduling resources of size M for uplink grant every interval of time T, where T is the arrival period of voice packets and M is the minimum resource unit that meets the voice coding rate;

[0013] A1-2. Uplink semi-static scheduling function: According to the voice rate requirement, support the RRC configuration of the uplink semi-static scheduling function, where the scheduling period supports sf20, sf32, sf64, and sf80; the grant obtained by semi-static scheduling is not only used to send the BSR and SPS confirmations, but also can be used to send uplink service data, such as voice data packets; the MCS and Resource assignment of semi-static grants can be dynamically adjusted according to the channel conditions;

[0014] A2. 80-ms scheduling template: Within an 80-ms period, allocate an uplink packet scheduling and a downlink packet scheduling for each terminal in turn, and use the HARQ disabled, NPDCCH format1, and 16QAM modulation methods to improve the scheduling capacity and spectral efficiency.

[0015] Preferably, the mobility management of the base station includes:

[0016] B1. Send a location reporting request to the terminal and receive location information;

[0017] B2. Calculate the service time and the handover target cell based on the terminal location and the satellite ephemeris;

[0018] B3. Interact with the target cell through the X2 / S1 interface to complete handover preparation, and issue a conditional handover command, which includes measurement Gap configuration, target cell ephemeris information, and RACH-Skip parameters;

[0019] The RACH-Skip parameters include: reference time of resource information (HSFN, SFN, subframe); Doppler frequency offset information of the terminal relative to the satellite at the reference time of resource information, including (instantaneous value, first-order rate of change over time, second-order rate of change over time); time advance of the terminal relative to the satellite at the reference time of resource information, including (instantaneous value, first-order rate of change over time, second-order rate of change over time); pre-allocated uplink msg3 resources starting from the reference time of resource information, including (start subframe, msg3 period, msg3 scheduling number, msg3 grant);

[0020] Among them, the reference time of resource information is the time corresponding to the instantaneous values of Doppler frequency offset and time offset, and is also the starting time of the pre-allocated msg3 resources.

[0021] Preferably, the mobility measurement configuration of the terminal includes:

[0022] The measurement object is based on the target cell information of the satellite ephemeris, and is reconfigured and sent through MeasObjectEUTRA or SIB31.

[0023] Preferably, the IMS signaling bearer established between the core network and the base station includes:

[0024] Transmit SIP session control signaling through the S1 interface, and ensure low latency of signaling transmission based on the QCI5 priority.

[0025] Preferably, the establishment of the voice bearer of the terminal includes:

[0026] C1. Request the allocation of dedicated bearer resources for QCI1 and QCI5 from the core network through the NAS logical interface to distinguish voice control plane and user plane data;

[0027] C2. Support 4.75 kbps voice service with AMR-NB coding, and a single carrier can accommodate up to 24 concurrent voice channels.

[0028] Preferably, the period of the measurement Gap configuration is 80 ms, 160 ms or 320 ms, and the measurement duration is 40 ms, 60 ms, 80 ms or 160 ms.

[0029] Preferably, the conditional handover command of the base station includes:

[0030] Calculate the service end time and arrival time based on the terminal location and the satellite ephemeris of the target cell, and the RACH-Skip information is used for the terminal to quickly access the target cell.

[0031] The beneficial effects of the present invention are as follows:

[0032] 1. The present invention enables measurement and handover functions through an NB-IoT terminal and an NB-IoT base station to ensure the continuity of voice services.

[0033] 3. The present invention establishes QCI1 and 5 voice bearers and processes SIP sessions in the NB-IoT terminal, base station, and core network to ensure the establishment of transmission channels for the control plane and data plane services of voice.

[0034] 3. The present invention solves the problem of insufficient uplink scheduling capacity of the base station by supporting uplink voice pre-scheduling in the base station.

[0035] 4. The present invention uses an 80ms uplink and downlink scheduling template in the base station, and can support up to 24 channels of 4.75kbps voice services at most. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 It is a schematic diagram of the technical process of the present invention;

[0037] Figure 2 It is a schematic diagram of the AMR-NB and AMR-WB coding rates of the present invention;

[0038] Figure 3 It is a schematic diagram of the IMS network framework of the present invention;

[0039] Figure 4 It is a schematic diagram of the IMS call flow of the present invention;

[0040] Figure 5 It is a schematic diagram of the method for improving the uplink rate of the present invention;

[0041] Figure 6 It is a schematic diagram of the first uplink and downlink scheduling timing template of the present invention;

[0042] Figure 7 It is a schematic diagram of the second uplink and downlink scheduling timing template of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0043] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0044] As Figures 1 - 7 shown, the embodiment of the present invention provides a communication system supporting NB-IoT voice services, including: a terminal, a base station, a core network, and an IMS server;

[0045] Among them, the terminal, the base station, and the core network all support NB-IoT voice services. The terminal is connected to the base station through the Uu interface. The base station is connected to the core network and the IMS server through the S1 interface. The terminal is connected to the core network through the Nas logical interface;

[0046] The terminal is used to initiate and receive IMS voice calls, support establishing an SIP session with the AS server to complete the IMS signaling connection, and establish the bearers required for IMS voice. Its PDCP layer supports compression and decompression of voice packets, and at the same time supports mobility measurement, measurement report reporting, and handover based on measurement, time, or geographical location;

[0047] The base station is used to establish a voice bearer for the terminal, identify the voice service through the bearer type and implement uplink pre-scheduling, periodically allocate uplink grant resources according to the voice rate requirement, use an 80ms scheduling template to plan uplink and downlink resources to achieve 24-way 4.75kbps voice services on a single carrier, and manage the mobility measurement of the terminal and the issuance of handover commands;

[0048] The core network is used to establish an IMS signaling connection for the SIP session with the terminal, and cooperate with the base station to establish an IMS signaling bearer and a data bearer;

[0049] The IMS server is connected to the base station through the S1 interface and supports the transmission of the control plane and user plane of the voice service.

[0050] Through the NB-IoT terminal and the NB-IoT base station supporting measurement and handover functions, the continuity of voice services is ensured.

[0051] By establishing QCI1 and 5 voice bearers and processing SIP sessions in the NB-IoT terminal, base station, and core network, the transmission channels for the control plane and data plane services of voice are ensured.

[0052] By the base station supporting voice uplink pre-scheduling, the problem of insufficient uplink scheduling capacity of the base station is solved.

[0053] By the base station using an 80ms uplink and downlink scheduling template, up to 24-way 4.75kbps voice services can be achieved.

[0054] As Figure 1 shown, the scheduling mechanism of the base station includes:

[0055] A1-1. Uplink pre-scheduling: According to the voice rate requirement, uplink grant resources of size M are issued once every interval time T, where T is the arrival period of voice packets and M is the minimum resource unit that meets the voice coding rate;

[0056] A1-2. Uplink semi-static scheduling function: According to the voice rate requirement, it supports RRC configuration of the uplink semi-static scheduling function, where the scheduling period supports sf20, sf32, sf64, sf80; the authorization obtained by semi-static scheduling is not only used to send BSR and SPS confirmations, but also can be used to send uplink service data, such as voice data packets; the MCS and Resource assignment of semi-static authorization can be dynamically adjusted according to the channel conditions.

[0057] A2. 80ms scheduling template: Within an 80ms cycle, each terminal is allocated an uplink packet scheduling and a downlink packet scheduling in turn, and the HARQ is disabled, NPDCCH format1 and 16QAM modulation mode are adopted to improve the scheduling capacity and spectrum efficiency.

[0058] Among them, uplink pre-scheduling avoids the delay of dynamic resource requests, adapts to the periodic characteristics of voice services, and enables efficient use of resources; the 80ms template combines HARQ disabling and 16QAM modulation, and a single carrier supports 24 concurrent voice calls, increasing the spectrum utilization rate by more than 30%.

[0059] As Figure 1 shown, the mobility management of the base station includes:

[0060] B1. Sending a location reporting request to the terminal and receiving location information;

[0061] B2. Calculating the service time and the target handover cell based on the terminal location and satellite ephemeris;

[0062] B3. Interacting with the target cell through the X2 / S1 interface to complete handover preparation, and sending a conditional handover command, which includes measurement Gap configuration, target cell ephemeris information, and RACH-Skip parameters;

[0063] The RACH-Skip parameters include: resource information reference time (HSFN, SFN, subframe); the Doppler frequency offset information of the terminal relative to the satellite at the resource information reference time point, including (instantaneous value, first-order change rate with time, second-order change rate with time); the time advance of the terminal relative to the satellite at the resource information reference time point, including (instantaneous value, first-order change rate with time, second-order change rate with time); the uplink msg3 pre-allocated resources starting from the resource information reference time point, including (startsubframe, msg3 period, msg3 scheduling number, msg3 grant);

[0064] Among them, the resource information reference time is the time corresponding to the instantaneous values of Doppler frequency offset and time offset, and it is also the starting time of the msg3 pre-allocated resources.

[0065] Among them, the RACH-Skip parameter pre-allocates access resources, reducing the handover delay to within 40 ms; the real-time calculation of Doppler frequency offset and time offset ensures signal synchronization in the scenario of high-speed satellite movement.

[0066] As Figure 1 shown, the mobility measurement configuration of the terminal includes:

[0067] The measurement object is based on the target cell information of the satellite ephemeris, and is reconfigured and sent through MeasObjectEUTRA or SIB31.

[0068] Among them, the target cell coverage range is predicted in combination with the satellite ephemeris to reduce invalid measurements; the measurement object is dynamically adjusted through SIB31 or MeasObjectEUTRA to support the hybrid networking of multi-orbit satellites.

[0069] As Figure 1 shown, the IMS signaling bearer established between the core network and the base station includes:

[0070] The SIP session control signaling is transmitted through the S1 interface, and the low latency of signaling transmission is guaranteed based on the QCI5 priority.

[0071] Among them, the high-priority bearer of QCI5 ensures the improvement of the SIP session establishment success rate; the standardized design of the S1 interface is used to be compatible with the existing 4G / 5G core network architecture.

[0072] As Figure 1 shown, the establishment of the voice bearer of the terminal includes:

[0073] C1. Request the allocation of dedicated bearer resources for QCI1 and QCI5 from the core network through the NAS logical interface to distinguish the voice control plane and user plane data;

[0074] C2. Support the 4.75 kbps voice service with AMR-NB coding, and a single carrier can accommodate up to 24 concurrent voices at most.

[0075] Among them, the separation of the QCI1 / QCI5 bearer controls the control plane and the user plane to avoid service interference; the AMR-NB 4.75 kbps coding matches the NB-IOT narrowband characteristics, reducing the bandwidth occupancy by 50%.

[0076] As Figure 1 shown, the period of the measurement Gap configuration is 80 ms, 160 ms or 320 ms, and the measurement duration is 40 ms, 60 ms, 80 ms or 160 ms.

[0077] Among them, the Gap period is dynamically selected according to the satellite movement speed to balance the measurement accuracy and service continuity; short-period measurement (such as 40 ms) reduces the terminal power consumption and extends the battery life.

[0078] As shown in Figure 1 , the conditional handover command of the base station includes:

[0079] Calculation of the service end time and arrival time based on the terminal location and the target cell ephemeris, and RACH-Skip information for the terminal to quickly access the target cell.

[0080] Among them, for the predictive handover based on the ephemeris, the service interruption time is less than 10 ms; it is applicable to different orbit satellites such as GEO / LEO, and supports global coverage voice services.

[0081] Working principle and usage process:

[0082] Embodiment 1: Uplink and downlink scheduling template for voice mode

[0083] AMR-NB voice has different coding rates, the lowest is 4.75 kbps, and the number of users that can be accommodated will also increase accordingly. The packet arrival interval is 80 ms, and 380 bits need to be scheduled each time, (MCS21, SF1, TB488), 24 channels.

[0084] Uplink and downlink scheduling timing template: NPDCCH-->NPDSCH, subframe of n + 5 + k0 (after n + 4, there is an interval of k0 downlink subframes); k0 = 0 4 8 12 16 32 64 128

[0085] NPDSCH-->NPUSCH type2, subframe of n + k0 + koffset; k0 = 1 3 15 17 18

[0086] NPDCCH-->NPUSCH type1, subframe of n + k0 + 1 + koffset; k0 = 8 16 32 64

[0087] Koffset = 12

[0088] Enable HARQ disabled

[0089] Search space configuration: The search space period T*G = 16 ms; the least common multiple with SFN 10 ms is 80 ms, that is, the search space repeats according to an 80 ms cycle. Design the uplink and downlink scheduling timing template according to an 80 ms cycle as Figure 6 .

[0090] Downlink TBsize table

[0091]

[0092]

[0093] Uplink TBsize table

[0094]

[0095]

[0096] Example 2: NB-IOT mobility enhancement function, conditional handover message measurement gap configuration, period 80ms / 160ms / 320ms, measurement duration 40ms / 60ms / 80ms / 160ms

[0097]

[0098]

[0099]

[0100]

[0101] Example 3: RACH-Skip information in the conditional handover message

[0102]

[0103] Among them, ul-ConfigInfo-r14:

[0104] ul-ConfigInfo-r14 SEQUENCE{

[0105] Startsubframe ENUMERATED{sf0,sf1,sf2,sf3,sf4,sf5,sf6,sf7,sf8,sf9},

[0106] ul-SchedInterval-r14 ENUMERATED{sf10,sf40,sf80,sf160,sf320,sf640},

[0107] ul-SchedNum ENUMERATED{n1,n4,n8,n16,n32,n64,n128,n320},

[0108] ul-Grant-r14 BIT STRING(SIZE(15))

[0109] Among them, nta-dedicatedParameters:

[0110] nta-dedicatedParameters SEQUENCE{

[0111] nta-dedicated-r17 INTEGER(0..8316827)OPTIONAL,--Need OP

[0112] nta-dedicatedDrift-r17 INTEGER(-261935..261935)OPTIONAL,--Need OP

[0113] nta-dedicatedDriftVariation-r17 INTEGER(0..29479)OPTIONAL--Need OP

[0114] Among them, ndopplerfreq-dedicatedParameters:

[0115] ndopplerfreq-dedicatedParameters SEQUENCE{

[0116] ndopplerfreq-dedicated INTEGER(0..8316827)OPTIONAL,--Need OP

[0117] ndopplerfreq-dedicatedDrift INTEGER(-261935..261935)OPTIONAL,--Need OP

[0118] ndopplerfreq-dedicatedDriftVariation INTEGER(0..29479)OPTIONAL--Need OP

[0119] When the minimum coverage inclination angle is 10° at different satellite altitudes, the maximum Doppler frequency offset:

[0120]

[0121] Example 4: Support the uplink pre-authorization function for NB-IOT terminals and base stations, which can be implemented through the uplink semi-static scheduling function or the uplink pre-scheduling

[0122] Uplink pre-scheduling: According to the voice rate requirement, send the pre-scheduling resources of size M for uplink authorization every interval time T, where T is the arrival period of voice packets and M is the minimum resource unit that meets the voice coding rate;

[0123] Uplink semi-static scheduling function: According to the voice rate requirement, it supports the RRC configuration of the uplink semi-static scheduling function, where the scheduling period supports sf20, sf32, sf64, sf80; the authorization obtained by semi-static scheduling is not only used to send BSR and SPS acknowledgments, but also can be used to send uplink service data, such as voice data packets; the MCS and Resource assignment of semi-static authorization can be dynamically adjusted according to the channel conditions.

[0124]

[0125] In the prior art of NB-IOT semi-static scheduling, the MCS is fixed at 0000 and the Resource assignment is fixed at 000, corresponding to a TBsize of 16bit, which is sufficient for transmitting only BSR, but far from enough for transmitting voice packets. A method is proposed in which the MCS and Resource assignment of semi-static scheduling can be dynamically adjusted according to the channel conditions, and the MCS and Resource assignment fields sent by the NPDCCH scrambled by SPS C-RNTI are dynamically adjusted according to the requirements of voice packets and the channel conditions. For example, when the requirement of the voice packet is a TBsize of 488bit, the MCS takes 21 and the Resource assignment takes 0 when the channel quality is good, corresponding to a TBsize of 488bit; when the channel quality is poor, the MCS takes 3 and the Resource assignment takes 7, corresponding to a TBsize of 568bit.

[0126]

[0127]

[0128] It should be noted that in this article, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the term "comprising", "including" or any other variant thereof is intended to cover non-exclusive inclusion, so that a process, method, article or device comprising a series of elements not only includes those elements, but also includes other elements not expressly listed, or elements inherent to such process, method, article or device.

[0129] Although the embodiments of the present invention have been shown and described, those of ordinary skill in the art can understand that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present invention, and the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A communication system supporting NB-IOT voice services, characterized in that, It includes: a terminal, a base station, a core network, and an IMS server; Among them, the terminal, the base station, and the core network all support NB-IoT voice services. The terminal is connected to the base station through the Uu interface. The base station is connected to the core network and the IMS server through the S1 interface. The terminal is connected to the core network through the Nas logical interface; The terminal is used to initiate and receive IMS voice calls, support establishing an SIP session with the AS server to complete the IMS signaling connection, and establish the bearers required for IMS voice. Its PDCP layer supports the compression and decompression of voice packets, and also supports mobility measurement, measurement report reporting, and handover based on measurement, time, or geographical location; The base station is used to establish a voice bearer for the terminal, identify the voice service through the bearer type and implement uplink pre-scheduling, periodically allocate uplink authorization resources according to the voice rate requirement, use an 80ms scheduling template to plan uplink and downlink resources to achieve 24 channels of 4.75kbps voice services on a single carrier, and manage the mobility measurement of the terminal and the issuance of handover commands; The core network is used to establish an IMS signaling connection for the SIP session with the terminal, and cooperate with the base station to establish an IMS signaling bearer and a data bearer; The IMS server is connected to the base station through the S1 interface and supports the transmission of the control plane and the user plane of the voice service.

2. The communication system for supporting NB-IoT voice service according to claim 1, wherein: The scheduling mechanism of the base station includes: A1-1. Uplink pre-scheduling: According to the voice rate requirement, issue pre-scheduling resources of size M for uplink authorization once every interval time T, where T is the arrival period of the voice packet and M is the minimum resource unit that meets the voice coding rate; A1-2. Uplink semi-static scheduling function: According to the voice rate requirement, support RRC configuration of the uplink semi-static scheduling function, where the scheduling period supports sf20, sf32, sf64, sf80; The authorization obtained by semi-static scheduling is not only used to send BSR and SPS confirmations, but also can be used to send uplink service data, such as voice data packets; The MCS and Resource assignment of semi-static authorization can be dynamically adjusted according to the channel conditions; A2. 80ms scheduling template: Within an 80ms cycle, allocate an uplink packet scheduling and a downlink packet scheduling for each terminal in turn, and use the HARQ disabled, NPDCCH format1, and 16QAM modulation methods to improve the scheduling capacity and spectrum efficiency.

3. A communication system supporting NB-IoT voice services according to claim 1, characterized in that: The mobility management of the base station includes: B1. Send a location reporting request to the terminal and receive location information; B2. Calculate the service time and the handover target cell based on the terminal location and the satellite ephemeris; B3. Interact with the target cell through the X2 / S1 interface to complete the handover preparation, and issue a conditional handover command, which includes measurement Gap configuration, target cell ephemeris information, and RACH-Skip parameters; The RACH-Skip parameters include: the resource information reference time; the Doppler frequency offset information of the terminal relative to the satellite at the resource information reference time; the time advance of the terminal relative to the satellite at the resource information reference time; the pre-allocated resources for uplink msg3 starting from the resource information reference time; The reference time of the resource information is the time corresponding to the instantaneous values of the Doppler frequency offset and the timing offset, and is also the start time of the pre-allocated resources for msg3.

4. A communication system supporting NB-IoT voice services according to claim 1, characterized in that: The mobility measurement configuration of the terminal includes: The measurement object is based on the target cell information of the satellite ephemeris, and is reconfigured and sent through MeasObjectEUTRA or SIB31.

5. A communication system supporting NB-IoT voice service according to claim 1, characterized in that: The IMS signaling bearer established between the core network and the base station includes: Transmitting SIP session control signaling through the S1 interface, and ensuring low latency for signaling transmission based on the QCI5 priority.

6. A communication system supporting NB-IoT voice services according to claim 1, characterized in that: The establishment of the voice bearer of the terminal includes: C1. Requesting the allocation of dedicated bearer resources for QCI 1 and QCI5 from the core network through the NAS logical interface to distinguish voice control plane and user plane data; C2. Supporting 4.75 kbps voice services with AMR-NB coding, and a single carrier can accommodate up to 24 concurrent voice channels at most.

7. A communication system supporting NB-IoT voice services according to claim 3, characterized in that: The period of the measurement Gap configuration is 80 ms, 160 ms, or 320 ms, and the measurement duration is 40 ms, 60 ms, 80 ms, or 160 ms.

8. A communication system supporting NB-IoT voice services according to claim 1, characterized in that: The conditional handover command of the base station includes: Calculating the service end time and arrival time based on the terminal location and the target cell ephemeris, and the RACH-Skip information is used for the terminal to quickly access the target cell.

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