Starting from 4G LTE, voice implementation solutions are no longer just 2G/3G networks, but simply provide voice services and other value-added services through circuit domain networks. Instead, they are designed to implement voice services through the IP Multimedia Subsystem (IMS, IP Multimedia Subsystem). The service is carried on the IP network, that is, the way of VoLTE (Voice over LTE), which realizes that all services of the 2G/3G circuit domain are "IPized" on the 4G network. In the process of gradual deployment and expansion of 4G network, it is in the different stages of network development and the consideration of voice service continuity. 4G also proposes such as circuit domain fallback (CSFB, Circuit Switched Fallback) and single wireless voice call continuity (SRVCC, Single Radio Voice Call ConTInuity) and other transition programs.
The 5G NR voice solution design continues the way that 4G LTE carries voice services through the IP network, and carries voice services through the 5G network (wireless network + core network) and the IMS system. This method is called VoNR (Voice over NR). Similarly, considering the different deployment scales of 5G at different stages, 4G networks have been widely deployed and may exist for a long time in the future, and the need for voice service continuity assurance, the design of the fallback scheme is also very necessary. Therefore, the evolution of the packet system has fallen ( EPS fallback) solution is also a kind of 5G voice solution. Here EPS fallback mainly refers to the fallback to 4G and the realization of voice services through VoLTE. However, due to the existence of multiple voice solutions in 4G networks, when the wireless environment of the 4G network is poor, it is inevitable that the UE will complete the voice services by means such as CSFB. .
2 Introduction to 5G Voice Solution2.1 Program introduction
In the overview part, this article briefly introduces possible voice solutions in 5G networks.
(1) VoNR: 5G NR voice solution based on IMS network, the architecture is on 5G NR network, under all IP conditions, an end-to-end voice solution based on IMS server. VoNR can implement concurrent voice services and data services by deploying IMS. All services are carried over the 5G network, but voice services require IMS for service control.
(2) EPS fallback: A solution using 4G network voice services.
1) VoLTE: 5G NR voice solution based on IMS network, the architecture is on 5G NR network, under all IP conditions, an end-to-end voice solution based on IMS server. The VoLTE solution can guarantee voice quality, but requires interoperability between 4G and 5G networks. The launch delay of voice services is longer than that of VoNR, and IMS is also required to be deployed.
2) CSFB: The terminal can initiate CS services such as voice services under LTE access, and receive paging of CS services such as voice, and can correctly process the PS services that the terminal is running in the LTE network. With LTE access, the terminal can initiate CS services such as voice services, and receive paging of CS services such as voice, and can correctly process the PS services that the terminal is in progress in the LTE network. In the current version, 5G does not support interaction with 2/3G networks, so to initiate CSFB, you first need to fall back to 4G networks. In the current version, 5G does not support interaction with 2G/3G networks. Therefore, to initiate CSFB, you first need to fall back to the 4G network. This solution implements voice services with the longest delay, but the solution requires relatively low terminal requirements.
In the initial stage of 5G network deployment, if the 5G network is independently deployed (SA), the EPS fallback method will fall back to 4G, and the voice service can be realized through VoLTE or even CSFB, which can reduce handover and ensure voice continuity. But with the gradual maturity of 5G network deployment, VoNR will gradually become the mainstream 5G voice solution.
2.2 Network architecture
(1) VoNR
Similar to 4G networks, through 5G core network (5GC, 5G core network), the network can meet the business needs of operators, but this kind of business realized through packet switching (PS, Packet Swith) provides a best-effort The service does not guarantee the quality of service, and the voice service has higher requirements for the voice quality, especially compared with the 2/3G through the circuit switch (CS, Circuit Switch) provides a more stable and high-quality service. Therefore, 5G networks also need to provide voice quality assurance for voice services by deploying IMS systems.
In addition to providing quality assurance for services, the IMS system also provides policy and charging control (PCC, Policy and Charging Control). The network architecture of VoNR provided through 5G network is shown in Figure 1:
Figure 1 Connecting to IMS through 5GS to provide voice services
(2) EPS fallback
According to the previous introduction, we know that the EPS fallback method requires interoperability between the 5G network and the 4G network to complete the voice service. Since the CSFB solution is the second fallback of the UE on the basis of falling back to 4G, here we only use the EPS fallback method Falling back to 4G to complete the voice service and introduce the network architecture through VoLTE, as shown in Figure 2:
Figure 2 Network architecture for providing voice services through EPS fallback
Compared with the VoNR network architecture, the voice service is completed through (EPS fallback) VoLTE, and the network still needs to deploy the IMS system. At the same time, a 4G network is required to complete the voice service.
2.3 Basic process
For a user terminal (UE, User Equipment), no matter what kind of service it wants to initiate, it must go through processes such as network registration, service initiation, and resource release, and the same is true for voice services. For a 5G UE, if it wants to initiate a voice service on the 5G network, it needs to go through 5G network registration (5GC RegistraTIon), IMS system registration (IMS Register), service initiation, resource allocation, resource release and other processes. The following will introduce the implementation of 5G voice from the registration process (including 5G network registration and IMS system registration), service initiation and resource allocation.
2.4 Registration process
(1) 5G system registration
For any user terminal, when it is turned on, it needs to be attached to the 5G network first so that it can obtain the corresponding service. During the initial access process, the network will obtain PEI() from the UE, and AMF will use EIR() to detect the PEI of the UE and send the PEI to UDM, SMF, PCF, etc. During the network registration process, the UE will also send information about the registration type, UE capabilities, and security parameters to the network. According to the information provided by the UE, the network performs identity verification and access control on the UE. When the network accepts the UE, it will feed back a RegistraTIon Accept message to the UE. This information will include such as 5G-GUTI, registration area, mobility restriction conditions, PDU session presence, word order NSSAI, registration update timing Device cycle, LADN information and MICO mode, and whether to support IMS voice instructions through PS sessions, and whether the network supports interoperability when the N26 interface is supported. Among them, whether to support the indication of IMS voice through the PS session, and whether the network supports the N26 interface interoperability will have a certain impact on the UE's choice of voice implementation. Figure 3 is a 5G system registration flow chart.
Figure 3 5G system registration flow chart
Here, "Whether to support the indication of IMS voice through PS session" is set by AMF based on the matching of UE capabilities and network capabilities. In order to set this value, AMF will initiate a UE capability and compatibility query process, and AMF sets this After the value is set, the value can be updated periodically. Specifically, AMF will set the indication to "support" when any one of the following conditions is met.
1) The network can provide successful IMS voice on the PS session through the 5G QoS stream that supports voice in the current registration area;
2) If the network cannot provide successful IMS voice through the PS session on the NR-RAN connected to the 5GC, but can perform one of the following operations:
â—†If E-UTRA connected to 5GC supports IMS voice, and NG-RAN supports handover or redirection to E-UTRA connected to 5GC, the UE does not establish a QoS flow for IMS voice;
â—†If the UE supports switching to EPS, EPS supports IMS voice, and NG-RAN supports switching to EPS, and establishes a QoS flow for the UE for IMS voice;
â—†If the UE supports redirection to EPS, EPS supports IMS voice, and NG-RAN supports redirection to EPS, and establishes QoS flow establishment for IMS voice for the UE.
Different from the 4G network attach process, the network does not establish a default bearer for the UE to provide always-on services during the 5G network registration process. Therefore, if the UE is still an IMS user, after the UE completes the registration, since the IMS domain registration is still required, a corresponding bearer/QoS flow needs to be established to carry the registration signaling.
(2) IMS domain registration
As a relatively independent system, IMS requires users to perform authentication and authorization before IMS services. Therefore, similar to the registration of the 5G system, the registration process of the IMS domain is also a two-way authentication process between the network and the UE.
In this process, the UE initiates the registration process of the IMS domain by sending a Register (registration request) message. The registration request message will include user representation, user information, session description information, etc. The registration request message will first reach the P-CSCF; then, the P-CSCF obtains the I-CSCF of the user’s home network through DNS and forwards the registration message to the I -CSCF; by querying the HSS, the I-CSCF will select an S-CSCF for the UE and forward the message to the S-CSCF, and then the S-CSCF will use the user authentication information (such as subscription information, security information, etc.) obtained from the HSS, and The UE performs the calculation and feedback of the authentication data; only here, the UE will initiate a second registration and feed back the calculated data. The S-CSCF confirms that the UE is a legitimate user and then sends a message to inform the UE that the registration is successful. Figure 4 is a flowchart of IMS registration.
Figure 4 IMS registration flow chart
2.5 Business initiation and resource allocation
Generally speaking, when a UE completes 5GS registration and IMS domain registration without service initiation, it will release the connection and enter the idle state, but for a UE, it is possible to initiate a service from the connected state or the idle state. Here, we assume that when the UE enters the idle state after completing the registration described in 2.3.1, it will go through the following stages when it wants to initiate a voice service as a calling user: 1) voice domain selection; 2) voice plan determination.
(1) Access Domain Selection
The basis discussed in this article is that the UE registers and resides in the 5G network. Generally speaking, the UE should also implement voice services through the 5G system. However, there are some situations where the 5G network cannot provide voice services for the UE, and the UE needs to be reselected or reselected. Directed to a 4G or 2G/3G cell, the voice domain selection process is to solve this problem.
The UE will consider the following factors when selecting an access domain:
1) The status of the UE in the IMS domain: registered or unregistered;
2) The above-mentioned "Whether to support the instruction of IMS voice through PS session";
3) The UE wants to access the 5G system through the "voice service-centric" or "data service-centric" approach;
4) UE's ability to support IMS PS voice;
5) The ability of the UE to perform the session conversion of the selected PDU in the dual registration mode;
6) Whether 3GPP PS Data Off is activated and whether IMS voice is included in 3GPP PS Data Off Exempt Services.
If the UE cannot use IMS for voice services in the 5G system, for example, because the "Does it support IMS voice through PS session" is "not supported", that is, the 5G system does not support voice services, the UE will follow the "voice service as the center "Or "data business as the center" to choose whether to stay in the 5G system.
For UEs that set the 5G system as "voice service-centric", he will try his best to ensure voice services. For such a UE, if it supports both 5GC capability and EPC capability, but cannot obtain voice service in the 5G system, he will not select a cell that can only be connected to 5GC when selecting a cell (5G supports and connects to 5GC at the same time. To the EPC cell). The UE will disable the 5GC capability, and then perform cell reselection, and choose the LTE cell that is connected to the EPC as much as possible, and implement voice services such as voice domain selection and program selection according to the 4G voice plan;
As for the UE with the 5G system set to "data service as the center", even if the current cell does not have the time voice service, the cell reselection will not be performed.
(2) Confirmation of the voice plan
Different from the 4G voice solution, the UE can initiate VoLTE or CSFB according to its own choice (differentiated by sending Service Request or Extended Service Request). In the 5G system, the UE only informs the network that it needs to initiate a voice service by sending a Service Request. The implementation method is determined by the network. Figure 5 shows the UE voice solution determination process:
1) The UE resides on the NG-RAN of the 5G system and initiates the establishment of the MO/MT IMS voice session, that is, the UE will send Invite signaling to the IMS domain.
2) The network initiates the PDU session modification process in order to establish a QoS flow for the voice realized through NG-RAN.
3) If the NG-RAN configuration supports EPS fallback for IMS voice, the RAN side will review the UE capabilities, AMF on whether to support voice services initiated through redirection, network configuration (such as whether the N26 interface is configured), and current wireless conditions. Based on comprehensive considerations, it is decided whether to initiate EPS fallback for the UE or provide VoNR through the 5G system. In order to make this determination, the RAN side may perform measurement on the LTE cell.
4) If the wireless side decides to implement voice services through EPS fallback, the wireless side will reject the PDU session correction process to establish a QoS flow for IMS voice, and inform SMF and PGW-C that mobility will occur due to IMS fallback. UE capabilities, network configuration, etc., initiate a handover or redirection process. When the UE accesses the EPS, the SMF/PGW re-initiates the dedicated bearer establishment process, establishes the bearer for the voice service, and then performs the IMS session establishment process; if the wireless side determines that the voice service can be provided through the 5G system, it will receive the PDU session modification Request, establish the corresponding QoS flow/bearer through RRC reconfiguration, and then proceed to IMS session establishment and other processes.
Whether it is through VoNR or VoLTE to complete the voice service, the process of IMS session establishment is similar, just because the 5G core network and 4G core network architecture and network element function allocation are slightly different, we will not introduce it here.
3 Optimization direction of voice solutionThrough the introduction of the voice solution in the 5G system above, it can be found that compared with the 4G network, the 5G network has more possibilities in terms of architecture. If there is a 4G base station accessing the 5G core network, this is 5G voice The realization of the business provides more diversity; in addition, the 5G voice solution itself has inherited and improved the 4G solution, and there are more possibilities for solution selection. The existence of these diversity on the one hand provides a guarantee for ensuring that users complete voice services in the 5G system, and on the other hand it also brings some problems.
(1) Ability matching problem
Different from the implementation of voice services in the 4G network, there are multiple voice solutions in the 5G network, which also means that the network and the UE supported or preferred voice solutions may be different, resulting in a mismatch between the network and the terminal capabilities; in addition, according to As mentioned above, since the 5G network supports the LTE connection to the 5G core network, and due to the widespread deployment of 4G base stations, this architecture will most likely also be widely used in future 5G networks. The existence of multiple architectures has also exacerbated the ambiguity of "whether to support IMS voice instructions through PS sessions". The UE cannot clarify the degree of matching between the current network status and its own capabilities based on the instructions as in the 4G network. Cause UE voice service to be unable to realize or increase the delay of realization.
To solve the above problems, you can start with the clarity of "whether to support IMS voice instructions through PS sessions", and you can also avoid this problem through more detailed capability matching judgments during UE registration or service initiation. Early detection of capacity mismatches allows the UE to select a suitable radio cell to initiate services.
(2) Delay optimization problem
In the capacity mismatch problem, we mentioned the problem that the UE may increase the delay in launching the voice service due to the capacity mismatch, which will not be repeated one by one.
In addition, through the introduction of the previous program, we can find that compared with the 4G voice solution, the decision-making power of the 5G voice solution is on the network side. Although this can ensure the controllability of the network, it can also be found by carefully studying the existing process. In the current process, the decision time of the network is relatively late. Before that, there will be many interactions between the UE and the 5G network and IMS, which also increases the UE’s voice service initiation delay to a certain extent, especially when the network decides to let the UE perform In the case of EPS fallback. For this problem, we can consider ways to learn from the way in which the UE initiates different voice solutions in LTE and advance the network decision point to solve it.
(3) Continuity of voice services
The continuity of the voice service is an important indicator of the voice service. It is very necessary to ensure the continuity of the voice service and provide a high user experience. Since the current protocol version does not support interoperability between 5G and 2G/3G, it does not support the use of SRVCC to complete voice services in UTRAN. In some scenarios, voice continuity problems may occur when mobility occurs. 6 shows a scenario where there may be discontinuous voice services in a centralized manner:
Scenario 1 is in the network where the UE is located, and the operator supports VoNR and VoLTE, but due to imperfect deployment, when mobility occurs, the UE moves to a VoNR and VoLTE hole, causing call drop; Scenario 2 is deployed for the operator VoNR and LTE, but VoLTE is not configured in the LTE network. When the UE moves from the 5G network to the 4G network, a call will occur; Scenario 3 is that in some countries and regions, 4G is not deployed but only 2G/3G is deployed , The subsequent deployment of 5G directly, and the interoperability between 5G and 2G/3G networks is not supported, when the UE moves out of the 5G network, call drops will occur.
To solve this problem, the most straightforward solution is to support the interoperability between 5G and 2G/3G networks, avoid the holes caused by the deployment of 4G and 5G networks, or consider methods such as D2D and V2X to make up for it.
4 ConclusionAccording to the progress of the existing protocol standards, this article introduces the 5G network voice solution, and explains the voice solution from the network architecture and workflow. After that, based on the understanding and understanding of the existing process, it analyzed the aspects of capability matching, delay optimization, voice service continuity, etc., explored the problems of the current voice solution, and proposed some possible optimization directions for the follow-up 5G voice The optimization and implementation of the plan pointed out the direction.
Best Budget I7 Laptop is everyone eager to. Laptop Intel Core i7 is the No. 1 processor clients choose when they are searching for a performance Gaming Laptop,cause it`s of excellent powering, bigger Solid State Drive, usually 512GB based, full HD 16:9 aspect ratio slimmer display bezels, bigger battery-12000mAh-no need to worry lack of power, fingerprint reader, backlight keyboard, etc. What is intel Core I7 Laptop Price? Usually 300-400usd. You can get Intel i7 11th Generation Laptop, Intel i7 10th Generation Laptop, Intel I5 11th Generation Laptop, Laptop I3 11th Generation,etc. 15.6 or 14 inch all available for i7 processor.
Cooperating with us, you just need to share all your requirements details, like size, cpu, ram, rom, battery, fingerprint, backlight, enter button numbers, SSD+HDD or only SSD ok, if need oem service, if need logo position, special apps preinstall if need, etc. Can provide matched and value feedback in 1-2 working days.
The reason why clients choose us is that just half of DOA than others, longer warranty time, smaller MOQ, fast delivery, competitive cost, good after-sale service, etc.
Laptop Intel Core I7,Intel Core I7 Laptop Price,Best Budget I7 Laptop,Intel I7 11th Generation Laptop,Intel I7 10th Generation Laptop
Henan Shuyi Electronics Co., Ltd. , https://www.sycustomelectronics.com