DE3337646C2 - Radio network with a variety of mobile stations - Google Patents

Description

The invention relates to a radio network according to the preamble of claim 1.

In some applications, arrangements of mobile radio stations occur that have the following features:

• - Operation in open terrain or in the forest, on the water or near houses (possibly with inclusion of buildings),
• - Arrangements of many (e.g. 50-100) mobile stations with mostly several end participants,
• - Overall expansion of the tensioned by the participants Network of typically 500 m to 20 km, possibly even more,
• - none for the organization and communication of the Network responsible centralized functions.

Fig. 1 shows an exemplary radio network with Mobilsta tions A, B and C with different numbers of telephone subscribers and data subscribers per station and a connection via station B (as a relay) between telephone 1 of station A and telephone N of station C.

Such radio networks are used for communication made demands, z. B.

• - Availability of all communications that can be implemented with cables cation services, e.g. B. Telephony / writing / copying and data transmission with features that match those correspond with cables,
• - Modular expandability with regard to the transmission capacity citation,
• - digital messaging,
• - alternative transmission rates per channel, e.g. B. 16, 32 or 64 kbit / s,
• - very large possible total data rate (traffic capacity) the channel bundle of the entire radio network of z. B. 512, 1,024, 2,048 or 4,096 Mbit / s,
• - Application of a radio transmission technology, which is only too low emission of signal energy.

Among the known radio systems that comes in IEEE Trans. Comm. Vol.COM-28, No. 9, Sept. 1980, pages 1616-1624 most closely described the invention. Another relevant system is in IEEE Trans. Comm. Vol.COM-27, No. 12, Dec. 1979, pages 1938-1945. The IEEE Trans. Comm. Vol.COM-28, No. 9, Sept. 1980, pages 1616-1624 concept presented as a concept has the following features:

• - Radio network with cm waves (7 GHz) between ground stations for military applications where each station has a transmitter and has a receiver and works half duplex,
• - Bundling transmitting and receiving antennas with 6/10 degrees opening regarding azimuth / elevation,
• - Transmission according to the synchronous time division, where with a network-wide frame takes approx. 65 ms and in 6 Time slots (channels) are divided into 10 ms duration. Each the channel is accessed by each station (after a connection construction procedure) fixed for the connection to a maximum of 6 possible neighboring stations used. Between these 6 Ka Each station can transmit data and also its own data transfer. Between two stations can also be used if necessary two or more channels can be switched. In the Kanä len are after the asynchronous time division multiplexing Da between computer-equipped devices and in a small amount Broad range of packaged language.
• - The maximum possible station throughput is 100 kbit / s.  
• - Each pair of stations communicates with each other using one individual code word for this connection. A Relayed connection uses ver different code words, but the same frequency band. The system So uses code division multiplex.

The object of the invention is to provide a radio network to create the self-organized way and without for the organization and communication of the Net zes responsible centralized functions. There In addition, everyone with cables should be created with the network to be created feasible communication services, e.g. B. Telephony / writing / copying and data transfer are available with features that correspond to those with cables.

The task is with the specified in claim 1 Merk paint solved. The further claims contain advantageous ones Developments or designs of the invention.

The invention is explained in more detail below with reference to the figures explained.  

Fig. 2 shows an example of a radio network with 6 stations S1 to S6, which are not fully meshed with each other (e.g. due to obstacles / distances), but only via the channels Li (i = 1.... 7) are connectable.

• - Only a small number of organizations hidden by code spread traffic. Receiving mode of the stations when there is no transmission wish is present.
• - Time division multiplex transmission via trans parente half duplex channels which for  synchronous (channel switching) and asynchronous (packet mediation) digital transmission are suitable with Data transfer rates that depend on the properties of the Traffic are adapted, e.g. B. 16, 32 or 64 kbit / s per Channel.
• - Switching capacity of each station according to the Sum data rate of a frame, e.g. B. 512, 1024 or 2048 kbit / s.
• - Existence of several mutually synchronous frames in different frequency bands.
• - Operation of the stations half-duplex, i.e. H. Send and Emp catching is not in the same time slot at the same time possible.
• - Addressing procedure: point-to-point, multiple address ressierung (one to more), broadcast (one to all).
• - Use of omnidirectional reception (E) antennas and directional transmit (S) antennas. Possibly. also directed E antennas.
• - Interfaces at each station for multiple telephones and data terminals.
• - Interface at each station with regard to telecommunications Line network with gateway function in the station.
• - Layering of communication and organizational protocols according to the ISO architecture model, cf. Computer Networks 5 ( 1981 ), pages 77-80.

Individual problems and their solution Establishing and dismantling connections

Communication between two stations goes through three phases: 1) connection establishment, 2) communication and 3) connection establishment. The message transmission during phases 1 ) and 3) is called signaling.

In the radio network, phase 1 ) is processed with datagrams in accordance with the usual signaling methods. For phases 2 ) and 3), the existence of a connection is assumed, via which the connection is cleared after phase 2 ).

Admission and deregistration of newly arriving or outgoing Stations

It is believed that one is for inclusion in the Station advertising the radio network via the network network Conventions such as frequencies, codes, passwords, keys procedure, etc. is informed. Then she is in the state "Canditature". The entire set of rules (protocol) for the Adding a station to the network or deregistering one Station from the network becomes decentralized with the help of Mikropro processor intelligence of the applicant bwz. unsubscribing Station handled. The process is separate ten patent application described.

Switching and transmission technology

Information is transmitted via news channels. To do this, a suitably chosen radio frequency band must be used according to fixed rules. Three methods are common and are used side by side in different embodiments of the invention:

• - synchronous time division (STDM, synchronous time divi multiplex)
• - Frequency division multiplex (FDM)
• - Code division multiplex (CDM).

There are two options for the transmission of information via channels formed using one of these methods:

• - Channel switching (use of transmission capacity on the basis of connection-oriented transparent Channels),
• - packet switching (ATDM, asynchronous time division multiplex). Use of the transmission capacity of a channel-switched connection in the asynchronous time division multiplex method for several different (virtual) connections, cf. CCITT / X.25 and IEEE Project 802 .

Both procedures set according to the number to be sent telender channels and their data transfer rate, med functions as part of the stations ahead. The Ver averaging performance must be the sum bit rate of all at the same time corresponding channels.

Channel switching Use of the synchronous time division multiplex method in the network

The synchronous transmission over a network sets synchronis mus all stations ahead. Not to keep synchronizing It is quartz-sta bilized, periodically synchronized by radio stations used.

The radio network according to the invention uses transmission rates of 16/32 kbit / s according to the recommendation EUROCOM D / 1 or 64 kbit / s according to the CCITT recommendations G. 700 ff for PCM Voice transmission. It uses channels with 64 kbit / s Data rate assumed and the division of each channel in the Time division in n subchannels (n = 2.4) with smaller ones Data rates allowed. Another possible variant goes from 16 kbit / s data rate and forms channels higher Guess by combining n neighboring time slots protect.  

For reasons of efficiency, the Invention with the message length of a time slot 1064 bit chosen significantly larger than with a PCM-Pri March group (8 bit). A channel is through in on each other following frames periodically occurring time slots (slots) formed.

At 32 channels / frames at 64 kbit / s at 1064 bit / slot the frame period 1/60 s. Fig. 3 shows details of such a frame.

Accordingly, are a frame identifier and between the Time slots protection periods are provided. The message within each time slot is a Synchronisa preamble and organizational data, u. a. an identifier bit for the status "Channel occupied / free". The Total bit rate of all channels together is 2,048 Mbit / s and corresponds to that of 32 PCM channels of 64 kbit / s each.

Loop runtime for voice transmission

The message length per time slot takes into account that Voice transmission only loop times below Tolerates 200 ms without significant interference. In every The direction of transmission may therefore be a maximum of 100 ms delayed wearing will be tolerated. Each of an over touched station is either source or sink the connection or relay with switching function.

Protection period

The protection times between time slots are sufficient chosen large, so that runtime differences of different Connections not to overlap time slots being able to lead.  

Synchronization preamble

Despite their own clock standard, stations are only for limited Permanently able to stay in sync with the network. Therefore, the frame password contains a synchronisa tion word.

Relay connections

In each time slot of a frame it is only allowed to be exact send a station. Any connection running through a relay Each section requires an individual channel.

FIG. 4 shows an example for the synchronous communication between source and sink via two relays R1, R2. A channel X requires three different time slots on the three subsections.

Properties of the radio channel and consequences

Because of multipath and the resulting run time differences occur with increasing data rate Character dispersion. You can u. U. with echo canceller troubleshoot, but not nearly as large Bit rates as they are aimed for in the present case. Transmission interference due to dispersion can be caused by Eliminate suitable signal coding. That's why it comes STDM method described only within a system with code spread in question.

Narrow-band channels within an STDM system

The previously introduced STDM channels have a bit rate as is required for voice transmission at 64 kbit / s. For some data services and for delta language, channels with lower data rates are sufficient. The proposed frame structure, including the time slot width optimized for the conditions of the radio channel, allows the formation of narrow-band channels in a simple manner without the structure shown in FIG. 3 having to be changed: As FIG. 5 shows, only a reinterpretation of the membership of time slots same number in consecutive frames necessary to get out of a channel with z. B. 64 kbit / s z. B. make three narrowband channels 1.1 , 1.2 and 1.3 , each with 21.3 kbit / s data rate.

The limit of this technology is only given by the tolerable time interval that can be allowed between two successive time slots belonging to the same narrowband channel. For example, with the proposed frame pulse frequency of 60 / s, exactly 120 narrowband channels with the bit rate 532 bit / s can be generated from time slot no. 1. A time slot with 1064 bit content is only used every 2 s per narrowband channel. By combining narrowband channels one can form those with different data rates, e.g. B. two channels with 532 bit / s each result in one with 1064 bit / s. Channels with rates 532 , 1064 , 1596 , 2128 , etc. bit / s could exist side by side, all of which were derived from time slot no. 1.

Use of the frequency multiplex method in the network

The VDM process divides a given frequency band into multiple bands and allows the transmission of one or more channels. However, while the STDM ver driving (within limits) allowed, neighboring time slots to summarize in order to form wider channels and thereby a higher flexibility regarding the transmission rate  enabled per band, the FDM procedure applies for all times the bandwidth and thus the maximum possible transmission rate.

In the radio network according to the invention, a frequency band is followed the STDM process and used in a variant second frequency band for the transmission of an organization channel. Both bands are preferably the same Spread codeword.

Application of code division multiplexing in the network

In the CDM process, the message is sent to a carrier dulated and the resulting, compared to the channel bandwidth B of the system narrowband signal by mod with the help of a code word characterizing the channel tes spectrally spread to the channel bandwidth B. there the clock frequency of the code word is large compared to that Bandwidth b of the message signal. For example, 10 to fall 100 code clocks on a useful bit clock of the message sig nals. One speaks of the chip clock instead of the code clock, to distinguish it from the clock of the useful bits. On each useful bit falls z. B. 10 to 100 chips. After a HF upmixing sends the signal out.

By using different, suitably selected Code words can have a corresponding number of transmission channels in the channel bandwidth B can be accommodated. At the receiver entrance, they are superimposed in the same Frequency band n broadband coded signals (from n sen dern), the performance according to the differ Chen attenuations of the transmission link are damped. The After HF downmixing, the receiver wins for him  certain message from the overlay mixture using of his code word. For this purpose, the received signal with the synchronized code word multiplied. The result spectral compression brings up the desired Signal in frequency from the rest through product formation spectra even further spread out so that it with a bandpass file corresponding to the useful signal bandwidth ter can be screened out.

Synchronization to the chip clock

The synchronization (also acquisition or correlation called) of the code word generated in the receiver on the received code word presents one of the main problems Transmission by code spread represents. It can be different can be implemented in a complex manner and requires a corresponding amount Time, e.g. B. at -20 dB SNR on the receiver about 150 to 1000 times the code word length, correspondingly more at a lower level. The acquisition period depends on the required success probability Pd that the synchronization actually Lich and not only apparently succeeded. One differentiates det serial and parallel acquisition and mixed forms from that.

After successful acquisition, there is a synchronous one Channel for which the preservation of code word synchronism (Tracking) must be guaranteed at all times. This is for each channel that can be operated simultaneously by one station a separate tracking facility is required.

Multiplex capabilities of the CDM process

In the channel of width B there can be as many commu There are nication relationships as there are code words are: The frequency band is therefore repeated several times by code spread used.  

Since it u. There may be a large number of code words (= channels) difficult for a station S2 newly joining the network noticeable:

For this it is necessary that an already existing one Station S1, which is also within reception range of S2, just tried the code word used by S2. Open then it is obviously useful to register Reserve codeword and make all stations mandatory constantly concerned with acquisition of synchronism this To try code word.

It is also for stations that are already part of the network time consuming to connect with other stations because the target station (or a relay on the Route there) must refer to the broadcast codeword synchronize, which is very much with a large number of code words can be time consuming.

Therefore, in a preferred embodiment of the invention dispense with code multiplex and code spread with only a code word applied.

Each station only broadcasts in the time allocated to it slot, while receiving stations for the sake of Listen to synchronization whenever possible, but the message useful only in its receive time slot nal evaluate. As there is only one valid code at a time word in the system, a pair of Modulators or demodulators.

In systems with a large spectral spread you have to use considerable fluctuations in the level of the various connections calculations on the receiver, which are separated per time slot must be taken into account. Therefore, in continuing education  the invention each station its receiver for everyone Channel regarding the reception level dynamics and other channel properties on the in the previous frame set level.

The main effort for the transmission of code spread ter signals is in the receiver. If you strive for minimal S / E effort, so is the use of only one code word optimal in all bands. However, the solution is not very economical in terms of frequency, but what with the low Range with mm waves in the upper frequency range less is significant.

Application of the packet switching procedure in the network

The asynchronous time division multiplex method ATDM has become proven in many applications for radio networks. It is typical that the total bit rate available in the transmission channel each connection is available for a limited time stands so that the transmission duration of a fixed data quantity is significantly shorter than with FDM or STDM systems with the same total data transfer rate. Within Packets have bit synchronism.

Instead of channel-oriented (switched) connections between message source and sink, as with STDM or FDM, are mostly virtual connections at ATDM used only for the duration of the transfer access physical transmission capacity. An ATDM Variant also works without virtual connections and uses datagrams instead. In a training course the invention takes advantage of the possibility in each of the channel obtained using the STDM or FDM method to transfer the ATDM process.  

Characteristic of the radio network according to the invention is under other that signaling and network management are processed according to the ATDM process, while the Message transmission is channel-switched.

Mediation effort in each station

The switching between incoming and outgoing channels at a station requires, as part of the station, internal computer-controlled connection paths used according to the time-division multiplex method. The coupling arrangement KA of each station can switch between any incoming and outgoing channels, cf. Fig. 6. A connection is made up of two channels, one for each direction of transmission. In Fig. 6, for example, a station switches connections a, b and c.

In the radio network according to the invention, all stations have the same frame rate, so that at one station in time slot Z1 received data only in one time later timeslot are conveyed. Deviating of exchanges of wired networks are in Stations not timeslot contents of the incoming frame mediated in the subsequent time frame, but in the next free time slot (mostly the same Frame).

Gateway functions of the network

There is none especially for connecting the network with gateway sta equipped with differently organized networks ions. Instead, each station is sufficiently out equips to make the transition to the line network itself reali to be able to. Each station therefore has a suitable one  Cable interface (typically 6-wire, 4-wire and E u. M). Connections to other networks are over suitable line networks implemented.

Interfaces to the station's own participants

Each station has several interfaces to the Connection of digital telephones and also over several Interfaces for connecting data-oriented devices ten, e.g. B. teletype, visual display, facsimile, etc.

Signaling

Signaling, d. H. Transmission of connection or degradation information, is abge according to the ATDM process wraps. It can be used as an in-channel or off-channel signal be realized. In-channel signaling is used det when stations about the busy state of everyone in their S / E area available channels are informed. The one for that necessary information is in a form of the Erfin distribution through a channel management network, in one another form through decentralized information acquisition won by the stations themselves. The Outer Channel Signa lization is based on standard procedures. she is according to CCITT recommendation SS.7 or EUROCOM D / 1 (IIA3), is implemented and will be implemented for the entire channel bundle if necessary, handled via a separate sewer network.

Decentralized network management

Network management functions are

• - Registering and deregistering stations from the network,
• - Administration of the directory of participants, d. H. Assignment from station names to network addresses,  
• - management of the list of station characteristics,
• - Monitoring of the stations with regard to their function and compliance of regulations and rights,
• - Reconfiguration of the network and preparation / control of relocation of stations for maintenance / improvement connectivity,
• - Key resource management etc.

So far it has been common to use such functions as temporary assign to the master declared station and provide that other stations can take over these functions (Master transfer). In the network under consideration, these are Decentralized functions using in-station software executed.

Organizational network and communication network

The radio network can be logically divided into a communication system KOMSYS and an organization system ORGSYS. channels can optionally be sent to KOMSYS or ORGSYS be classified. Channels assigned to KOMSYS are only for message transmission (telephony / writing / co pieren and data transfer) used. All for them Management of the KOMSYS necessary traffic such as signaling tion, login / logout, network management, synchronization, etc. are processed via channels of the ORGSYS. Channels of the ORGSYS do not differ in their characteristics dig from those of the KOMSYS.

Separate ORGSYS channel for new registrations

The first contact of a new station with the radio network is particularly difficult for stations that are not synchronized. For this reason, a separate FDM channel with a data rate of approximately 16 kbit / s is preferably provided for this, cf. Fig. 7. Otherwise there is a risk of disturbance of normal network traffic by newly arriving stations.

System variants

The radio network should be able to be used in different applications with regard to the requirements for channel capacity and the concealment of radio traffic. Therefore, a distinction is made between variants that differ in the concealment of parts of radio communications. The message transmission in KOMSYS takes place in all variants with the help of code-spread signals, whereby

• - only one code word is used system-wide,
• - tapes are made available according to the FDM method,
• - Channels can be used synchronously or asynchronously as required.

The variants differ in which traffic at new registration or signaling open or through Spread code spread hidden. The open traffic is published in an FDM volume different from the KOMSYS on the ORGSYS transferred.

Claims (9)

1. Radio network for digital message transmission in the mm-Wel len frequency range with a plurality of half-duplex mobile stations, to which one or more end users are connected, in which radio network

• - The mobile stations are designed so that they can connect one or more of their own end users via radio channels with other end users;
• - Each mobile station is able to act as a relay (relay) directly or with the interposition of further relays of the mobile stations between many pairs of the mobile stations to act;
• - Each mobile station, in its simultaneously feasible function as a mobile station and relay for digital message transmission, can establish communication connections with corresponding terminals of other mobile stations via transparent time multiplex channels and can act as a switch for a large number of channels from neighboring mobile stations;

characterized by

• - That the neighboring mobile stations in radio range receive a transmission channel only for the duration of a communication connection or, alternatively, always right, in the latter case to use the transmission channels once set up between mobile stations as required for further communication connections,
• - That the switching takes place within each mobile station from a time slot (channel) of a system-wide synchronous frame in the next free time slot (channel) of the same or the subsequent frame;
• - That synchronous narrowband channels are formed by not allocating all the time associated with a channel to a narrowband channel, but only assigning time slots every nth of the consecutive frames (n = 2, 3,...), and
• - That the narrowband channels are routed through relays.

2. Radio network according to claim 1, characterized in that all also over different frequency bands used in the network transmitted messages with the same codeword spectrally be spread. 3. Radio network according to claim 1 with use different code words, so that a code division multiplex system arises, characterized in that codewords connections be assigned between end devices. 4. Radio network according to claim 1, characterized in that the connections assigned to the code words via relays be performed. 5. Radio network according to one of claims 2 to 4, characterized in that each mobile station with the help of a computer control Receiver for each channel regarding the reception level dynamics and the channel properties to those in the previous frame established values. 6. Radio network according to one of the preceding claims, characterized characterized in that   the synchronous digital transmission channels are used according to the asynchronous time division multiplex method for packet-oriented communication in such a way that many mobile stations share the transmission capacity of a channel or narrowband channel using a random access protocol,

• - Channels used in this way can also be routed via relays.

7. Radio network according to one of the preceding claims, characterized characterized in that each mobile station has one or more Interfaces that you connect to the Line selection network enables (gateway function). 8. Radio network according to one of the preceding claims, characterized characterized in that each mobile station one or more Interfaces for connecting telephones and owns data-oriented devices.