Relationship between clusters

1. Several digital trunking technologies in China.

Several digital trunking technologies mainly used in China are TETRA in Europe, iDEN in the United States, and GoTa and GT800 with independent intellectual property rights in China.

(1) four

TETRA is a standard recommended by ETSI. TETRA system is an open air interface signaling system, and draws lessons from the concept of GSM. Based on TDMA, it is divided into four channels in the bandwidth of 25kb/s, and adopts advanced ACELP speech coding method and (π/4)QPSK digital modulation technology. Support continuous coverage and large area coverage, and support off-network direct connection and end-to-end encryption functions. TETRA system is perfect in dispatching function, which is very suitable for private network, especially for military, armed police, public security, law enforcement and other units.

(2) Identification

IDEN is introduced by Motorola and also adopts TDMA system, which is divided into 6 time slots on the 25kHz channel (12 time slots have been developed on the 25kHz bandwidth). Its VSELP speech coding and 16QAM modulation technology are advanced. IDEN system was originally designed for * * * network, so it is a working mode integrating command and dispatch, duplex interconnection, packet data and short message.

IDEN system is based on scheduling and is designed according to public network, so its basic scheduling system functions include: group call, private call, call prompt and call display. Advanced dispatching functions include: priority, emergency call, status information, multi-group scanning, area restriction, isolated station operation, dispatching station, etc. IDEN system also has the function of virtual network. Through virtual private network (VPN), end users can manage the terminal configuration of their end users, including opening accounts, adding new services, changing dispatching private numbers, group numbers and telephone numbers, regrouping, and obtaining detailed call lists and usage statistics at any time.

(3)GoTa

Gota (Global Open Cluster Architecture) is a digital trunking communication system independently developed by ZTE. It is based on CDMA 1X technology and faces the evolution of new technologies. Its goal is to meet the needs of * * * network cluster and give consideration to the application of private network cluster.

GoTa system is based on CDMA multiple access mode, adopting modulation mode of 16QAM and QCEP and voice coding technology of QCEP, with frequency division duplex, uplink and downlink bandwidth of 1.25MHz and interval of 45MHz. The air interface of GoTa is optimized and reformed on the basis of cdma2000 technology. The core network adopts independent packet data domain and is based on A8/A9 and A10/A1standard interfaces, which can realize publicity and standardization.

GoTa has certain technical advantages and solves the key technology of realizing trunking service based on CDMA technology. When dealing with communication connection, it also adopts the mode of * * * sharing, which reduces the delay of network processing calls. GoTa has the technical advantages of fast access speed, high channel efficiency and spectrum utilization, high user privacy, easy expansion and support for multiple services.

In the design of GoTa system, the characteristics of digital trunking communication network are fully considered, and the design is oriented to mobile operators and the needs of mobile service users are fully considered. A terminal can integrate a variety of communication services such as trunking dispatching service, ordinary voice service, packet data service and many value-added services (SMS, location) into a network. GoTa system has the characteristics of high flexibility, excellent cost performance and comprehensive functions, which opens up more profit space for operators.

GT800

GT800 system is a digital trunking system based on GSM technology developed by Huawei. GT800 is a system developed based on GPRS and GSMR technology, and its second phase will combine TD-SCDMA technology. The GT800 system developed by Huawei faces the domestic digital trunking market. Referring to the service characteristics of the existing digital trunking system, a lot of work has been done, especially in the aspects of fast calling, group service, priority control, security and confidentiality, fault weakening, etc., which can provide complete trunking scheduling services and meet the needs of domestic professional mobile communication. At the same time, in order to meet the needs of users for high-speed data services, GT800 realizes variable-rate data transmission through GPRS technology. In the second stage of GT800, TD-SCDMA was introduced to further provide data services with the highest rate of 2MB/s. ..

GT800 can provide a wide range of services, including basic call, short message, cluster scheduling, priority preemption, fast connection and location-based routing, as well as data services based on GPRS. GT800 is suitable for the operation of trunking communication network, and also for the self-built private network of civil aviation, railway, water conservancy, municipal administration, transportation, construction, emergency rescue and disaster relief, mining area and other professional departments.

2.3G network PoC service the PoC service standard of 3G network is mainly formulated by OMA, based on the IMS network architecture of 3GPP and 3GPP2.

(1)PoC service concept and service characteristics

PoC is a two-way, instant and multi-party communication mode, which allows users to communicate with one or more users. This service is similar to mobile intercom service-users press a button to talk to a user or broadcast to a group of participants. After receiving the voice, the receiver may not do anything, such as not answering the phone, or be notified and must receive the phone before hearing the voice of the sender. After the initial voice is completed, other participants can reply to the voice message. PoC communication is half-duplex, and at most one person speaks at a time, and others can answer.

The business characteristics of PoC include:

●PoC groups can be predefined, temporary or similar to chat rooms, and users can join the chat groups themselves.

● Users can speak by requesting the right to speak, and the right to speak has a strict control mechanism.

The floor is granted by the PoC business entity. If the user does not speak after a period of time (set by the service provider), the right to speak will expire after the timeout.

The PoC service entity can send instructions to the initiating user before other called users accept the session invitation. If no user receives the media stream, POC participants can be prompted.

●PoC can interact with existing voice-like services on the Internet, such as online games, instant messaging with audio function, etc.

In PoC architecture, the user's right to speak is a very important concept. Based on RTP/RTCP, floor control is mainly completed in the user plane. At the same time, OMA defines the APP application of RTCP, which is called TBCP protocol, thus realizing the distribution and floor control of PoC media streams. For the signaling control of the session, SIP/SDP is mainly used to realize SIP registration, routing and security management, thus ensuring the completion of the PoC session.

(2)IMS support for PoC

The support of I MS for PoC mainly realizes the registration and security of PoC business, SIP signaling routing, SIP signaling compression, address resolution, identity hiding and billing management.

In the registration of IMS, firstly, the user establishes the PDP context and discovers the P-CSCF in IMS through GPRS request or DNS resolution. P-CSCF forwards the registration request to I-CSCF, and inquires HSS through I-CSCF to find S-CSCF. Implement the registration process in CSCF. In this process, PoC users and S-CSCF realize the authentication and authentication of both parties through AKA algorithm.

When the user registration and authentication are successful, the PoC user can initiate a group call request. Add "+g.poc.talkburst" or "+g.poc.groupad" to the tag of the SIP header contact in the session invitation, thus indicating that this is a poc group session. The P-CSCF forwards the call invitation to the I-CSCF and inquires the address of the S-CSCF to which it belongs, thus forwarding the invitation to the S-CSCF. According to the service trigger point, S-CSCF forwards the session invitation to the responding PoCserver through iFC (Initial Filtering Rule) downloaded from HSS. The PoCserver controls the session and forwards the session invitation to other users in the group through IMS. After media authorization and negotiation, a group call can be established.

The charging of PoC service is based on the charging framework of IMS, which can be based on event charging, group session charging, voice charging and so on.

In addition, the PoC service also applies the SIP signaling compression function in IMS. The purpose of signaling compression is to save link resources and reduce time delay, and realize the compression and decompression of SIP signaling on PoCClient and P-CSCF. At the same time, IMS also supports user identity hiding for other users or some users. In addition, in IMS, considering the response time of PoC session media bearer and the balance of media QoS, the QoS level of SIP signaling is used. 1. Technical differences

Digital trunking needs to share forward and backward resources, that is, all users in the same cluster occupy wireless and wired channels within the coverage of a cell. There is no limit to the number of users carried by a channel, which can greatly increase the carrying capacity of resources. In the case of single-channel resources, it can theoretically support unlimited trunked mobile phones for scheduling.

However, each user in PoC needs to occupy independent wireless and wired resources, which means that the resource occupation will occupy as many channel resources as the users who enter the group call when realizing the service, and the resource occupation will increase exponentially for PTT. If there is only one wireless channel, PoC service cannot be provided, and at least two wireless channels must be provided to ensure one-to-one PoC call.

2. Differences in key indicators

The fundamental difference between digital trunking and PoC lies in its key index-the difference of connection delay.

The connection time of PoC is generally more than 2-3 seconds, and sometimes even more than 10 seconds. If there are more users, the frequency of use increases or the network signal is poor, the connection time will be longer. The connection time of digital trunking is controlled within 1 sec, which is the fundamental reason why digital trunking has not been replaced by mobile public network and also its core competitiveness.

The delay indexes of several foreign digital trunking networks are all within 1 sec, and the general setup delay is 400 ms ~ 700 ms, PTT.

3. Different market positioning

The market positioning of digital trunking can be divided into two types: professional user market and public user market. Professional digital trunking users are generally estimated to be about 10% of mobile users. According to the estimation of 300 million mobile users in China, there is also a digital trunking market space of 30 million users.

PoC services are mainly for individual users, and the dominant voice and integrated services are the main sources of income. At present, the global mobile operators are facing the greatest competitive pressure.

4. Different profit margins

First of all, digital cluster is not very sensitive to price, because its customers are mainly group customers such as government and units. Secondly, any income generated by professional cluster scheduling business is generated under the condition of almost no competition, and the scheduling business is mainly realized in the network, and there is no inter-network settlement cost; In addition, due to professional needs, low product substitutability, high loyalty of these users and low off-network rate all save some operating costs for digital trunking operators.

However, compared with other businesses of operators, PoC business based on mobile public network is basically the same and has the characteristics of substitutability, so the business activities and products of PoC business are facing fierce competition in the market, the prices of products and services are falling, the profit rate is not high, and the settlement cost also accounts for a large proportion, which directly leads to the bottom line that must be considered when pricing products and services.

5. Different coverage priorities

Digital trunking customers mainly work and need effective coverage of work areas, such as outdoor coverage of urban areas and coverage of key areas of work areas. At the same time, cluster users in remote areas such as rural areas basically do not need coverage. The simple coverage requirements of digital trunking can be completely met by mature wireless communication means. For example, all base stations support the construction of large-area networks, which greatly saves the system investment. The coverage means for local key areas, such as government buildings and factory headquarters, are also very mature.

For the dispatching demand brought by unexpected situations, isolated network operation and off-grid direct connection can meet the demand, but the proportion of this situation is extremely low.

For PoC business, because users are highly mobile and widely distributed, it can be said that all the places where people exist need to be covered, so a lot of network investment is needed. Even if only basic coverage is considered, a rough estimate is at least 2-4 times of the investment in digital trunking network coverage.

6. Different capacity requirements

According to the market share analysis, even considering the ratio of 10%, it is enough to show that the demand for capacity of digital trunking is not high, so it is unnecessary to consider the pressure of capacity in the initial stage of digital trunking network construction. It can be understood that the digital trunking system can operate normally only by using the capacity resources of the mobile public network 10% to meet the capacity requirements of digital trunking users, which is undoubtedly a great advantage for building a digital trunking network.

For PoC service, in order to meet the capacity demand, mobile operators have to use the cell system to plan and build the network, and increase the base station density and regional user capacity by reducing the transmission power, pitch angle and antenna height of the base station.