CN101207913A - Network system with coexistence of multiple wireless access systems - Google Patents

Abstract

A network system with coexistence of multiple wireless access systems, including: a first wireless system with multiple base stations supporting a first wireless access system, and the multiple base stations implement continuous coverage in a certain area, and are used to Users who select the first wireless access system in a certain area access the network to provide voice services; the second wireless system has one or more base stations supporting the second wireless access system, and is implemented in a local area of the certain area The continuous coverage is used to connect users in the partial area who select the second wireless access mode to the network to provide data services.

Description

Network system with coexistence of multiple wireless access systems

technical field

The present invention relates to wireless communication technology, in particular to a network system with multiple wireless access systems coexisting.

Background technique

The ultimate goal of the development of mobile communication is to enable anyone, at any time, and anywhere to achieve communication. To achieve this goal, people have proposed that the best ideal solution is to unify the world into one communication standard. However, due to many reasons, there is no unified communication system yet. Therefore, multi-standard, multi-system, and multi-generation system coexistence mixed networking will appear, and it will exist for a long period of time.

In the development of mobile communication services, although data services are gradually increasing, voice is still the main one. The requirement for seamless coverage of the entire network is mainly for voice services. For high-speed data services, such as high-speed data services in the order of more than Mbps, coverage does not require full network coverage. If the high-speed data service requirements are met for full network coverage, the deployment cost of network equipment is very expensive. How to solve the seamless coverage required by the voice service, maximize the capacity required by the hotspot data service, and optimize the performance to meet different service requirements, and realize the minimum network construction cost is the fundamental demand in the current mobile communication field.

Now the world's largest GSM standard mobile network has more than 2 billion users. At present, more than 690 mobile communication network operators in more than 200 countries and regions operate GSM networks. The subsequent development of the GSM network includes equipment manufacturers and operators. hot spots of common concern.

The global CDMA network is the second largest mobile communication network in the 2G era. At present, the follow-up development of many networks is to build CDMA1X. Its support for higher-speed data services in the future is also a hot spot of common concern for equipment manufacturers and operators.

The subsequent evolution of GSM in the industry generally adopts WCDMA technology. At present, 105 network operators in more than 50 countries and regions around the world provide WCDMA commercial services and adopt GSM+WCDMA hybrid networking. Interoperability between WCDMA and GSM enables voice service continuity.

The GSM network mainly provides voice services, supplemented by data services, and the coverage of voice services provided by it is very complete; while the WCDMA system pays equal attention to both voice services and data services, so the area covered by the two systems at the same time obviously has WCDMA voice service bearer Capability and GSM voice service carrying capacity repeated investment construction, the complementarity between the two is not strong, resulting in very high cost.

Although more than 100 WCDMA networks have been built in the world at present, and operators have invested heavily in their networks, it is difficult to find a way to make profits in operation. In addition, because the data service rate provided by the existing WCDMA network carrying capacity is still not high, a higher rate technology needs to be introduced to solve the large-capacity demand in hotspot areas. In short, the existing GSM+WCDMA solution has the disadvantages of redundant construction of investment costs and difficulty in meeting the needs of hotspot high-speed data services.

Contents of the invention

The invention provides a network system with coexistence of multiple wireless access systems, so as to improve the complementarity between voice services and data in the network system composed of multiple wireless networks, and reduce the networking cost.

A network system with multiple wireless access systems coexisting, including:

The first wireless system has multiple base stations supporting the first wireless access system, and the multiple base stations realize continuous service coverage in a certain area, and are used to access the network for users who choose the first wireless access system in the certain area to provide voice services;

The second wireless system has one or more base stations supporting the second wireless access system, and realizes continuous coverage in a partial area in the certain area, and is used to connect users who select the second wireless access system in the partial area Access to the network to provide data services.

A network system with multiple wireless access systems coexisting, including: a long-term evolution LTE system, and other wireless systems that are different from the wireless access standards adopted by the long-term evolution system; wherein,

Multiple base stations in the other wireless system realize continuous coverage in a certain area, and are used to connect users of the other wireless system in the certain area to the network to provide voice services;

The base station of the long-term evolution system implements continuous coverage in a partial area in a certain area, and is used to provide data services to users of the long-term evolution system in the partial area.

A network system with coexistence of multiple wireless access systems, including: WiMAX system, and other wireless systems different from the wireless access standards adopted by the WiMAX system; wherein,

Multiple base stations in the other wireless system realize continuous coverage in a certain area, and are used to connect users of the other wireless system in the certain area to the network to provide voice services;

The base stations of the WiMAX system implement continuous coverage in a local area within the certain area, and are used to provide data services to users of the WiMAX system in the local area.

A network system with multiple wireless access systems coexisting, including: air interface evolution AIE system, and other wireless systems with different wireless access standards adopted by the AIE system; wherein,

Multiple base stations in the other wireless system realize continuous coverage in a certain area, and are used to connect users of the other wireless system in the certain area to the network to provide voice services;

The base stations of the AIE system implement continuous coverage in a local area within the certain area, and are used to provide data services to users of the AIE system in the local area.

The beneficial effects of the present invention are as follows:

The present invention realizes data service coverage in a partial area in the area where voice services are continuously covered, fully considers the seamless coverage required by voice services, maximizes the demand capacity of hot data services, and satisfies different service requirements on the basis of performance optimization , which improves the complementarity of voice services and data services in the network system, and realizes the minimum cost of network construction.

Description of drawings

FIG. 1 is a schematic structural diagram of an independent LTE system in the prior art;

FIG. 2 is a schematic structural diagram of a network system composed of a GSM system and an LTE system in an embodiment of the present invention;

FIG. 3 is a schematic diagram of an independent core network device in a network composed of a GSM system and an LTE system in an embodiment of the present invention;

FIG. 4 is a schematic diagram of an integrated core network device in a network composed of a GSM system and an LTE system in an embodiment of the present invention;

5 is a schematic structural diagram of a network system composed of a WiMAX system and a GSM system in an embodiment of the present invention;

6 is a schematic structural diagram of a network system composed of an AIE system and a CDMA system in an embodiment of the present invention;

7 is a schematic structural diagram of the integration of the core network of CDMA and AIE in an embodiment of the present invention;

FIG. 8 is a schematic structural diagram of centralized management of wireless resources in an embodiment of the present invention.

Detailed ways

In order to solve the contradiction between seamless coverage and high-capacity demand of hotspots, in this embodiment, under the condition of ensuring the seamlessness of voice service coverage requirements, the high-speed data According to business requirements, a network that mainly provides high-speed data services is used to cover the local area.

In this embodiment, the network system providing voice services and the network system providing high-speed service data may use one of multiple wireless networks with different wireless access standards. Typically, network systems that provide voice services, such as GSM systems, CDMA systems, etc.; network systems that provide high-speed data services, such as Long Term Evolution LTE systems, WiMAX systems, and Air Interface Evolution AIE systems.

The 3GPP standard organization has formulated the WCDMA system development and evolution route as WCDMA->HSPA->EHSPA->LTE. It can be seen that LTE is the evolution direction of WCDMA, and its main purpose is to improve the UMTS (including WCDMA system and CDMA2000 system) system in the future wireless communication market. Competitiveness on the market, to meet the rapid development of various key communication technologies. The LTE system mainly provides high-speed data services. Compared with the WCDMA system, the benefits brought by the LTE system are reduced delay, increased user data rate, improved system capacity and coverage, reduced operator costs, and flexible use of spectrum resources.

Referring to Fig. 1, an independent LTE system network is composed of an LTE base station BTS100 and an LTE access gateway AGW101, and the base stations 100 can interact through the X2 interface. The goal of LTE network carrying capacity is to provide a downlink rate of 100Mbps and an uplink rate of 50Mbps, which has a very strong capacity.

FIG. 2 shows a network system structure in which the LTE system and the GSM system are mixed in this embodiment. The GSM system includes a base station BTS200, a base station controller BSC201 and a GSM core network 203; the LTE system includes a base station 210 and an access gateway AGW211.

Multiple base stations 200 in the GSM system realize continuous coverage in area A, and base station controller 201 controls and manages base stations 200; GSM users in area A access the GSM core network through base station 200 and base station controller 201. The GSM system mainly provides voice services to GSM users in area A.

The base station 210 in the LTE system realizes service coverage in the hotspot area in area A, that is, local area A1 and local area A2 (of course, it can also be three or more local areas, or even only one local area), access The gateway 211 controls and manages the base station 210 ; the LTE users in the local area A1 and the local area A2 access the access gateway 211 in the packet core network 213 through the base station 210 . The LTE system mainly provides high-speed data services to LTE users in local areas A1 and A2.

In the local area A1 and the local area C, base stations of the GSM system and the LTE system may be deployed in various manners. For example, LTE base stations and GSM base stations are set separately for overlapping coverage; LTE base stations and GSM base stations are set up in a co-site manner to cover the site together; base station processing boards supporting LTE are directly inserted into existing GSM network base station equipment; new forms of GSM +LTE dual-mode base station, etc. Base stations in local areas A1 and A2 can be deployed in different ways. For example, LTE base stations and GSM base stations are installed separately in local area A1, and a new form of GSM+LTE dual-mode base station is installed in local area A2.

In the network system shown in FIG. 2 , the packet core network 213 and the GSM core network 203 are independent from each other and interoperate through the communication interface 204 . For example, the GSM core network forwards data service requests to the LTE network for bearer; another example, performs unified radio resource management (RRM), quality of service (QoS) control, and maintenance function O&M.

Figure 3 shows a simplified network system structure diagram. In this network system, the base stations in the four local areas adopt different deployment methods (of course, all of them can be the same, or the local areas are the same, and some local areas are different. Deployment method); LTE core network and GSM core network are independent of each other and interoperate through communication interfaces. In this network system, by upgrading the existing GSM core network equipment, the upgraded GSM core network can realize the AGW interoperability function with the LTE system, and support unified RRM, QoS, O&M between the LTE system and the GSM system Function. Interoperability satisfies the harmonious and unified resource management mechanism between the two generation-separation standards, and realizes that the networks of different standards form the same network, which can realize terminal access requests, service distribution, and information identification between the core networks of the two standards Interaction, to make full use of the advantages of different wireless access systems, that is, the GSM network provides voice services, and the LTE network provides high-speed wireless data services, so as to realize the best bearing strategy for services between the two systems and improve complementarity.

The base station in the hotspot area carries different user services through the GSM network or the LTE network according to the service type initiated by the user equipment UE. When the service initiated by the GSM user is a voice service, for the circuit-switched voice service, the service request is forwarded to the GSM core network, which is directly managed by the GSM core network, and the service bearer is completed through the GSM network. When the service initiated by a GSM user is a data service in the packet domain, if the rate is relatively low, the request initiated by the user can be carried by the GSM network, or the interoperability function between the GSM core network and the AGW will be implemented. The bearer of the service is allocated to the LTE network bearer; if the rate is relatively high, the GSM core network directly implements the request initiated by the user through the LTE network bearer through the interoperability function between it and the AGW.

Fig. 4 shows another network system structure of the hybrid network of the GSM system and the LTE system in this embodiment. The difference from the network system shown in Fig. 3 is that in the network system shown in Fig. 4 , the core network device 400 is A new form of GSM/LTE integrated core network equipment includes three parts: MSC function entity 4000, GSM packet domain entity 4001 and LTE access gateway entity 4002. Among them, the MSC entity 4000 completes the circuit domain core network function of the GSM network for voice and circuit data services. The main functions include voice services and basic circuit data bearer services, system roaming and switching between GSM and LTE, and guarantee Network security features, support for relocation between GSM access network and LTE base station, etc. The GSM packet domain entity 4001 mainly completes the functions of GGSN and SGSN of GPRS, and its main functions include resource admission control, routing selection and forwarding functions, mobility management functions, user data management functions, logical link management functions, etc. The access gateway entity 4002 supports the LTE core network access gateway function.

The integrated GSM and LTE core network shown in Figure 4 has the advantages of strong network capabilities, good system coordination, flexible deployment, simple architecture, easy transplantation, and unified and coordinated radio resource management.

Using the above-mentioned GSM system and LTE system integration mode to form a network, according to the different types of service requests initiated by user terminals, high-speed data services can be carried on access network equipment implemented by LTE technology, voice services can be carried on GSM equipment, and through The unified management and optimization mechanism for different standards can ensure that different standards will not affect each other within the same coverage area, and can meet the optimization of wireless resource utilization. The above networking method also breaks the gradual evolution steps of GSM->GPRS->EDGE->WCDMA->HSPA->EHSPA->LTE, and utilizes the capacity of LTE based on the perfect coverage of the existing GSM network capabilities to complement voice and data services. Adopting this new model of intergenerational networking avoids the problem of high cost caused by the construction of a simple data network.

FIG. 5 shows a network system structure composed of a mixture of a WiMAX system and a GSM system in this embodiment. GSM system includes base station BTS500, base station controller BSC501 and GSM core network 512; WiMAX system includes base station BS510 and access service network-gateway ASN-AGW511.

Multiple base stations 500 in the GSM system realize continuous coverage in area M, and base station controller 501 controls and manages base stations 500; GSM users in area M access GSM core network 512 through base station 500 and base station controller 501. The GSM system mainly provides voice services to GSM users in area M.

The base station BS 510 in the WiMAX system realizes service coverage in the hotspot area in the area M, that is, the local area M1 (certainly, it can also be two or more local areas), and the access service network-gateway 511 controls and communicates with the base station 510. Management: WiMAX users in the local area M1 access the service network (such as the Internet network) through the base station 510 and the access service network-gateway 511 . The WiMAX system mainly provides high-speed data services to WiMAX users in the local area M1.

In the local area M1, the deployment of the base station BS in the WiMAX system and the base station in the GSM system can adopt the above-mentioned various manners.

In the network system shown in FIG. 5 , the base station controller 501 of the GSM system and the access service network-gateway ASN-GW in the WiMAX system are respectively connected to entities in the packet domain network to unify WiMAX users and GSM users. Management, for example, the information of WiMAX users and GSM users is uniformly stored on the HSS, and the unified AAA server performs authentication and billing processing for WiMAX users and GSM users, thereby ensuring the continuity of WiMAX and GSM services and supporting the connection between WiMAX and GSM mobility between.

The above-mentioned GSM+WiMAX networking method can not only make full use of the existing perfect coverage characteristics of the GSM network, but also give full play to the high-speed data service capability of WiMAX.

FIG. 6 shows a network system structure in which the AIE system and the CDMA system are mixed in this embodiment. It includes the base station BTS600 of the CDMA system, the base station NodeB601 of the AIE system, the base station controller 602 and the core network 603.

Multiple base stations 600 in the CDMA system realize continuous coverage in area X, and base stations 601 in the AIE system realize service coverage in the hotspot area in area X, that is, local area X1 (of course, it can also be two or more local areas) , the base station controller and the core network equipment of the CDMA system and the AIE system are all in one structure. As shown in Figure 7, the core network supporting the integration of CDMA and AIE includes: packet data serving node PDSN (Packet Data Serving Node), mobile switching center MSC, service control point SCP, AAA server and home location register HLR. The information of CDMA users and AIE users is uniformly stored on the HLR, and the AAA server performs unified authentication, billing and other processing on CDMA users and AIE users.

The CDMA system is mainly used to provide voice services to CDMA users in area X; the AIE system uses advanced air interface technology in the base station, OFDM and MIMO technology in the uplink and downlink, and can provide broadband mobile network data at a data rate of up to 210Mbps within a 20MHz bandwidth Therefore, the AIE mainly provides data services to the AIE users in the local area X1. Since the core network equipment is integrated, the service request initiated by the user, whether it is a voice service or a data service, has the same message flow. Therefore, in this system, the voice service is mainly allocated to the CDMA base station according to the type of service request. The data service is carried on the AIE base station.

In the local area X1, the base stations in the AIE system and the base stations in the CDMA system can be deployed in the aforementioned multiple manners.

The base station controller and core network equipment of the CDMA system and the AIE system adopt an integrated structure, which is easy to realize the unified management of the CDMA users and the AIE users, and the unified control and management of the wireless resources of the CDMA system and the AIE system. Of course, the corresponding base station controllers and core networks of the CDMA system and the AIE system can also be set independently, and the core networks are interoperable through communication interfaces, and its implementation is similar to the implementation of the network system shown in Figure 2.

The networking method in Figure 6 also breaks the gradual evolution steps of CDMA->CDMA2000lx->CDMA2000EV-DO->CDMA2000EV-DV->AIE, and skips the stages of EV-DO and EV-DV. This networking method fully considers how to solve the seamless coverage required by the voice service, maximize the capacity required by the hotspot data service, and realize the minimum network construction cost on the basis of performance optimization that meets different service requirements.

In the network system of the above-mentioned various hybrid networks, when the core networks of different wireless systems are set independently, the wireless resources of the multi-standard communication network can be managed by setting a centralized radio resource management (Centralized Radio Resource Management, CRRM) unit . An implementation manner in this embodiment is shown in FIG. 8 . The CRRM unit is connected to the radio resource management unit 1 and the radio resource management unit 2 (not limited to 2 radio resource management units, for example, there may be 3 or more), and the radio resource management units 1 and 2 are single-mode communication networks The unit that performs radio resource management in the CRRM unit is used to report the radio resource information of each single-mode communication network to the CRRM unit (the radio resource information can be load information, cell information, radio parameters, access parameters, etc.), such as BSC in GSM, AGW in LTE. The CRRM unit is used to uniformly manage the wireless resources of the multi-standard communication network according to the wireless resource information reported by the wireless resource management unit; CRRM performs interface adaptation on the information of various wireless access standards, that is, The information reported by the radio resource management unit is converted into a format that can be recognized, and the delivered information is converted into a format that can be recognized by the radio resource management unit of the corresponding wireless access standard; The physical entity, which can also be a logical functional entity, is set together with an existing network element in the multi-standard communication network. The unified management of radio resources that can be realized by CRRM may include centralized load control, centralized power control, centralized switching control, and the like. In addition, in order to maximize the use of the wireless resource information reported by each single-standard communication network in the multi-standard communication network, and perform unified wireless resource management on the multi-standard communication network, CRRM conducts unified radio resource management for the entire multi-standard communication network according to the received wireless resource information. Optimizing wireless resources, for example, CRRM configures and adjusts relevant parameters of wireless resources of communication networks of each standard according to the configured optimization algorithm and wireless resource information, so as to realize the optimization of multi-standard communication networks.

Using the above-mentioned hybrid networking and similar networking methods can realize the lowest network construction cost under the premise of seamless coverage meeting the requirements of voice services, maximizing the demand capacity of hotspot data services, and optimizing performance meeting different service requirements demand.

Take the GSM network of a typical city as an example: the GSM network now has 1,000 GSM base stations, and supports a network capacity of 8 million users. At present, the voice traffic accounts for 95% of the network, and the data traffic is 5%. It is assumed that the voice traffic will only account for 70% in the next 5 years, and the data traffic will increase by 30%. In order to meet the future market demand. The traditional evolution method in the industry is to build a hybrid network of GSM+WCDMA. Considering that the coverage of WCDMA is weaker than that of GSM, it is estimated that more than 1,000 base stations will be invested in the WCDMA network to achieve continuous coverage of WCDMA. If the above-mentioned GSM+LTE networking solution is adopted, only a small number of LTE base stations need to be built for hotspot areas with data service requirements, and the number of base stations is about 200 to 300. It can be seen that it not only avoids the duplication of the voice service carrying capacity of the WCDMA network with the existing GSM network voice carrying capacity, but also saves huge investment expenditures and greatly reduces the network construction cost.

Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and equivalent technologies, the present invention also intends to include these modifications and variations.

Claims (19)

1. A network system with multiple wireless access systems coexisting, characterized in that it comprises: The first wireless system has multiple base stations supporting the first wireless access system, and the multiple base stations realize continuous coverage in a certain area, and are used to access the network for users who select the first wireless access system in the certain area to Provide voice services; The second wireless system has one or more base stations supporting the second wireless access system, and realizes continuous coverage in a partial area in the certain area, and is used to connect users who select the second wireless access system in the partial area Access to the network to provide data services. 2. The network system according to claim 1, characterized in that, the base station in the first wireless system and the base station in the second wireless system are set independently; or, the base station in the second wireless system and the base station in the first wireless system The base station is set up in a co-site manner; or, the base station in the second wireless system is embedded in the base station in the first wireless system; or, the base station in the partial area is a dual-mode wireless access system supporting the first wireless access system and the second wireless system base station. 3. The network system according to claim 1, wherein the network system has an entity for centralized management of wireless resources, and the entity manages the wireless resources of the first wireless system and the second wireless system in a unified manner. 4. The network system according to any one of claims 1 to 3, wherein the core networks of the first wireless system and the second wireless system are independent of each other and interoperate through interfaces; or, the first wireless system and the second wireless system The core network of the second wireless system has an integrated structure. 5. A network system with multiple wireless access systems coexisting, characterized in that it includes a long-term evolution LTE system, and other wireless systems that are different from the wireless access standards adopted by the long-term evolution system; wherein, Multiple base stations in the other wireless system realize continuous coverage in a certain area, and are used to connect users of the other wireless system in the certain area to the network to provide voice services; The base station of the long-term evolution system implements continuous coverage in a partial area in a certain area, and is used to provide data services to users of the long-term evolution system in the partial area. 6. The network system according to claim 5, wherein the base station in the long-term evolution system is set independently from the base stations in the other wireless systems; or, the base station in the long-term evolution system is set independently from the other base stations The base stations in the wireless system are set up in a co-site manner; or, the base stations of the long-term evolution system are embedded in the base stations of the other wireless systems; or, the base stations in the partial area support the wireless access adopted by the long-term evolution system standard and the dual-mode base station of the wireless access standard adopted by the other wireless systems. 7. The network system according to claim 5, wherein the network system has an entity for centralized management of wireless resources, and the entity manages the wireless resources of the long term evolution system and the other wireless systems in a unified manner. 8. The network system according to any one of claims 5 to 7, wherein the core networks of the long-term evolution system and the other wireless systems are independent of each other and interoperate through interfaces; or, the long-term evolution The evolved system has an integral structure with the core network of the other wireless system. 9. The network system according to claim 5, characterized in that, the other network systems are GSM systems. 10. A network system with multiple wireless access systems coexisting, characterized in that it includes a WiMAX system and other wireless systems that are different from the wireless access standards adopted by the WiMAX system; wherein, Multiple base stations in the other wireless system realize continuous coverage in a certain area, and are used to connect users of the other wireless system in the certain area to the network to provide voice services; The base stations of the WiMAX system implement continuous coverage in a local area within the certain area, and are used to provide data services to users of the WiMAX system in the local area. 11. The network system according to claim 10, characterized in that, the base station in the WiMAX system is set independently from the base stations in the other wireless systems; or, the base station in the WiMAX system is set independently from the base stations in the other wireless systems The base stations in the WiMAX system are set up in a co-site manner; or, the base stations of the WiMAX system are embedded in the base stations of other wireless systems; The dual-mode base station of the wireless access system adopted by other wireless systems. 12. The network system according to claim 10, characterized in that, there is an entity for centralized management of wireless resources in the network system, and the entity manages the wireless resources of the WiMAX system and the other wireless systems in a unified manner. 13. The network system according to any one of claims 10 to 12, wherein the core networks of the WiMAX system and the other wireless systems are independent of each other and interoperate through interfaces; or, the WiMAX system It has an integral structure with the core network of the other wireless systems. 14. The network system according to claim 10, characterized in that, said other network system is a GSM system. 15. A network system with multiple wireless access systems coexisting, characterized in that it includes an air interface evolution AIE system, and other wireless systems that are different from the wireless access standards adopted by the AIE system; wherein, Multiple base stations in the other wireless system realize continuous coverage in a certain area, and are used to connect users of the other wireless system in the certain area to the network to provide voice services; The base stations of the AIE system implement continuous coverage in a local area within the certain area, and are used to provide data services to users of the AIE system in the local area. 16. The network system according to claim 15, characterized in that, the base station in the AIE system is set independently from the base stations in the other wireless systems; or, the base station in the AIE system is set independently from the base stations in the other wireless systems The base stations in the AIE system are set up in a co-site manner; or, the base stations of the AIE system are embedded in the base stations of the other wireless systems; or, the base stations in the partial area support the wireless access system adopted by the AIE system and the The dual-mode base station of the wireless access system adopted by other wireless systems. 17. The network system according to claim 15, wherein the network system has an entity for centralized management of wireless resources, and the entity manages the wireless resources of the AIE system and the other wireless systems in a unified manner. 18. The network system according to any one of claims 15 to 17, wherein the core network of the AIE system and the other wireless systems is independent of each other, and interoperates through an interface; or, the AIE system It has an integral structure with the core network of the other wireless systems. 19. The network system according to claim 15, wherein the other network systems are CDMA systems.

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