SPD-2000 digital trunking system is all digital wireless communication system , face to public security ,armed police , customs , airport , railway ,etc.,the important department of city meet an urgent that need communication .SPD-2000 also supports the speed to reach 19.2Kbps besides offering the digital speech communication, realize to transmit for the information of monitor controlling , text and static picture . The pronunciation and data communication, adopt figures to secret, it is up to 96 degrees, have very high private communication. Support the function of communication to jump frequency, have higher communication privacy and anti-interference ability . System installation is easy, network is convenient.

SPD-2000 digital trunking system is a own intellectual property right of our company, it is a kind of trunking communication system for large district and low density users. Thank to trunking system that have network convenient, dispose flexible, monitor controlling management of all none digits. it can realize many base stations networked that needn’t rely on the transmission of wired or other ways, and can cooperate with terminal to realize jump frequent communication for the whole system, so it has the special status of application itself.
The comparative analysis of SPD-2000 and other trunking system is as follows :

First. Main function of SPD-2000

1. The section (group ) call out, personal call out, urgent call out etc..
2. Wireless dispatcher, the function of monitor controlling management , monitor controlling and managing themselves according to the different of user group(different ID)
3. set frequency parameters with wireless way in the air.
4. data communication (include the transmissions of static picture , text file , short news , controlling instructions)function
5. The spoken and data communication adopt 96 digits to private
6. Jumping frequency of communication function, higher communicative privacy and anti-interference ability
7. networking convenient, can organize the single base station and many base stations network
8. Realize to switch over between the digital spoken and simulative spoken
9. Extend network
10. network of E1/T1 way.
11. E1/T1 accesses PSTN

Second. SPD-2000 network component

1. Single base station and single channel
   Can’t control channel, take distance-turn directly.
2. Single base station and large channels
   divide into control-channel and spoken-channel, while calling out urgentlyand ,if the spoken-channels are all taken up, the control-channel can be used in the spoken-channel temporarily.
3. Many base stations and many channels
   to many base stations and many channel situations, consider the need of responding communication ,network must simple and flexible, basic group-network way adopt the concept of wireless to extend the network , sketch map of group-network., see Fig. 1.
   Network structure is the hierarchical structure, the whole network has base station of a centre, extend several first class stations downwards, each first class station continues extending several second class downwards, the base station of each class is extended downwards in theory.

fig.1 Many base stations and many channels

1. E1/T1 group-network
According to actual state of communication every region, can choose E1/T1 group-network, or extended and mixed group-network with E1/T1 , is usually suitable for telecommunication or busy frequent point .

Clock synchronization of E1/T1 group-network, take primary and secondary synchronous way, only limited to base stations of direct networking for simultaneous chain only, including control information and spoken information. So, E1/T1 group-network can be compatible with the wireless extension network . And simple E1/T1 group-network, limited to primary and secondary synchronous way, groupping network isn’t flexible, but can economize the spoken transmission channel of extended station. So local network which is small capacity (channel little) adopt wireless extended network to recommend, large capacity (channel more) or when terms convenient, adopt E1/T1 group-network auxiliary.

2. E1/T1 access
Access such wired networks as PSTN , PABX ,etc. through E1/T1, support wireless- wire and wire- wireless call, selective support China No.1 or No.7 signal etc..

Third. SPD-2000 air chain

Under many base stations and many channels situation, control channel of base station adopt time-divide control channel, control-signal frame launchs every 50ms downwards or upwards.

By Fig. 1, the central station controls f1 which is launching frequency of channe, receiving frequency f2,controlling chain extend separately to first class 1 and 2 downwards, first class 1 extend to second class 2 downwards, the time sequence of control-chain see Fig. 2.

Communicative speed of control-signal is 9.6k/s,frame length is 15Bytes (120bit ),time-length is 30ms every frame of air, launch up/down row control-siginal every 50ms jump-frequency, in 20ms interval privide enough time for synchronic search and steady jump-frequency among base stations. Because the synchronism among the base stations is just to controlling the chain, the spoken channel does not need clock synchronization, it is very simple, reckon by time according to the base of higher authorities of down row control-chain signal of synchronous head of reach-time.

Every spoken channel of transmission in the central station takes up only one channel, it of extended station takes up two channels.

Forth. SPD-2000 network management

Each wireless user terminal has one"s own independent ID, every user"s unit, according to different users" ID, safeguarded operating system manage users that carried on different ranks or all of them in grouping through the controller.

The substance included monitor-control information the identity of the wireless user terminal, user"s rank, set of group-call, set of channel-frequency , long-distance-locking, terminal equipment state etc..
Fifth. Jump-frequency communication

It takes the technology of SPD-2000,be used in private military affairs and anti-interference communication. SPD-2000-HF network made up of single base station or many base stations group, many base station network adopt extended wireless station or many base stations through E1/T1 network.
Many channel in base station take asynchronous group-network , realize many group-call according to different jump-frequency map,which depend on the choice of frequency list and jump the choice of pursueing to depend on the frequency form frequently and frequency alignment(namely secret-key).

Sixth. SPD-2000 calls deal with

1. The spoken call
It including section-call(group ),person-call. section-call(group) is use often, namely is initiated by one wireless user, call out the members of this group.person-call is to call some specific ID , the special case belonging to the group-call.

The course of call-continue follow Fig.2.terminal user 2 call out, under the simultaneity of the second class stand of down row control-chain ,send call-respect to the base station with frequency f3 , second class station 1 check the legitimacy of calling, distribute the spoken channel , namely receive and dispatch frequency-point with VF8/VF7,respect spoken-road frequency-point to first class station 1 through control-channel at the same time (fix-chain frequency-point or dynamical distribution frequency-point),the call-deal process of first class station 1 is same as second class station 1, distribute the spoken channel, namely receive and dispatch frequency-point with VF4/VF3, continue and apply to central station for meanwhile frequently to receive and dispatch , until all base stations of the network .

2. The data-call
It is usually belong to point-to-point call , and broadcast-call through manage center too, the process of call is similar to spoken-call, take up the spoken channel . Can also transmit text file, short news, controll-instruction.

3. The urgent-call
It includes spoken-call and data-call, belonging to the highest call, when distribute channels,it have the highest priority , control-channel be used in the spoken-channel temporarily in case of necessity.
Seventh. SPD-2000 hardware-structure and function

SPD-2000 digital communication system is divided into four parts: The base station controller (BSC ), the base tunnel station (BTS), the wireless user terminal (RU ), safeguard-operating system (O&M ) and platform for command and dispatch.

The base tunnel station (BTS) includes information machine of receiving and dispatching and antenna and cable system.

Controller and receive-dispatcher of base station are in the standard cabinet of 42”, increasing and decreasing expanding according to the scale of channel. Single-board base station controller support （1-8） channel, single base station scale can reach 32 channels most, namely the base station controller of four single-boards , is linked and expanded by RS232 .

Hardware structure function of the single-board base station controller (BSC ):

1. Support the wireless channel 1-8
2. Let the any-channel monitor
3. Independent double RS232 interface.
4. double E1/T1 interface .
5. The network card is supported.

Eighth. SPD-2000 software function.

1. Section(group )-call ,person-call
2. Data call
3. Urgent call
4. wireless monitor-control and dispatcher
5. wireless-wire call
6. wire-wireless call

Ninth. The trouble weakens

the weaken of system trouble in several aspects:

1. The base station distributes control-channel arbitrarily, while the control-channel that is appointed to is in trouble ,we can appoint the other channel to be the control-channel; if there has one spoken-channel only, appoint spoken-channel to be control-channel temporarily, control-channel returns to be spoken-channel after conversing.
2. When some base station is in trouble, the other base station can change the set of group-network temporarily , reduce the influence that some base station trouble brings in other base stations.
3. The technology of air-wireless set , under such situations as base station group-network , base station trouble , frequency-band interference of base station ,etc., offered the flexible , simple and convenient set means for frequency-band parameter of every base station.
4. Take off the network way

Tenth. Main technical indicators:

1. Work frequency: 138-170 MHz 350-390 MHz 403-470 MHz
2. Temperature of work circumstance: -20℃～+60℃
3. frequent stability: ：±1PPm
4. Launch power： 40W
5. receive sensitivity:digit≤-118dBM
   simulation≤-119dBM
6. wireless-transmission speed ： 9.6Kbps 19.2Kbps
7. the average-continuity time of spanning the base stations: ： ≤300ms
   Eleventh. Running example