HK1033734B - Roaming of mobile parts in at least partially asynchronous wireless telecommunications networks, especially dect networks - Google Patents

Description

Roaming of mobile parts in at least partially asynchronous wireless communication networks, in particular DECT networks

Technical Field

The invention relates to roaming of mobile parts in at least partially asynchronous wireless communication networks, in particular DECT networks.

Background

In a communication system with an information transmission line, transmitting and receiving devices are used between an information source and an information sink for the processing and transmission of information, wherein,

1) the information processing and information transmission can take place in one preferred transmission direction (simplex mode) or in both directions (duplex mode),

2) the information is processed in an analog or digital manner,

3) when information transmission is performed by using a long-distance transmission line, the information transmission can be performed according to various information

Methods such as FDMA (frequency division multiple access), TDMA (time division multiple access) and/or CDMA (code division multiple access) -e.g. according to wireless standards such as DECT, GSM, WACS or PACS, IS-54, IS-95, PHS, PDC, etc. [ see IEEE journal of communication, 1 month 1995, pages 50-57; falcon et al: time division multiple access methods for wireless personal communication "], and/or they may also be wired connections. "information" is a generic concept that represents both content (messages) and physical representations (signals). Although the information has the same content-that is to say the messages are identical-different signal forms can be generated. Thus, information about an object may typically be transmitted as follows,

1) in the form of a pattern, the pattern,

2) as a word in the language, the word is,

3) as the recording word, a word is recorded,

4) as a code word or a pattern.

The transmission category according to (1).. to (3) is generally characterized here by continuous (analog) signals, whereas the transmission category according to (4) often results in discontinuous signals (such as pulses, digital signals, etc.).

Starting from this general definition of a communication system, the invention relates to communication systems for at least partially asynchronous wireless communication networks, in particular DECT systems for at least partially asynchronous DECT networks, according to the preamble of claim 1 and the preamble of claim 20.

The above defined kind of communication system may typically be the DECT system [ digital enhanced (early: european) wireless communication; see (1): communications technology electronics 42(1992) month 1/month 2, No. 1, berlin, germany; pilger "structure of DECT-standard", pages 23 to 29, in connection with reference to ETSI-publication ETS 300175-1.. 9, month 10 1992; (2): telecommunication report 16(1993), No. 1, j.h.koch: "digital equipment for cordless communication-new field of use disclosed by the DECT standard", pages 26 and 27; (3): tec 2/93-Ascom engineering journal, "road of global mobile communications", pages 35 to 42; (4): review of philips communications, volume 49, No. 3, 9 months 1991, r.j.mulder: "DECT, a global wireless access system"; (5): WO 93/21719 (FIGS. 1 to 3 and their associated statements) or a GAP system (generic Access Profile; see ETSI-publication ETS 300444, 12.1995, ETSI, FR), which can typically be constructed in the manner shown in FIG. 1.

According to the DECT/GAP standard, a maximum of 12 connections can be formed at the DECT/GAP base station BS by means of a DECT/GAP air interface designed for the frequency domain 1.88-1.90GHz, as shown in fig. 1, which connections are based on the TDMA/FDMA/TDD method (time division multiple access/frequency division multiple access/time division duplex) by which the DECT/GAP mobile unit mt1.. MT12 is connected in parallel to the base station BS. The number 12 is given by "k", which is the number of time slots or communication channels used for the duplex mode of operation of the DECT/GAP system (k 12). The connections here may be internal and/or external connections. Two mobile units registered at the base station BS, such as the mobile unit MT2 and the mobile unit MT3, can communicate with each other by means of an internal connection. In order to form an external connection, the base station BS is connected to the communication network TKN, for example, by a wire connection from a communication connection unit TAE or a private branch exchange NStA to a line-connected communication network, or, according to WO95/05040, wirelessly to a higher-level communication network as a repeater. In the external connection mode, one can communicate with users within the communication network TKN by means of mobile parts, such as the mobile part MT1, via the base station BS, the communication connection unit TAE or the private branch exchange NStA. Since the base station BS, as in the case of the Gigaset 951 (siemens cordless telephone, see telecommunications report 16, (1993) pages 1, 26 and 27), has only one connection to the communication connection unit TAE or the private branch exchange NStA, only one external connection can be formed. In case the base station BS-as in the case of the Gigaset 952 (siemens cordless telephone, cf. telecommunications report 16, (1993) pages 1, 26 and 27) -has two connections to the communication network TKN, the wire-connected communication terminal equipment TKE connected to the base station BS can additionally generate an external connection for an additional external connection with the mobile part MT1. Here, it is also conceivable in principle that a second mobile part, such as the mobile part MT12, can be used instead of the communication terminal device TKE for the second connection of the external connection. During operation of the mobile unit mt1.. MT12 with batteries or with accumulators, the base station BS, which is embodied in the form of a cordless small relay device, is connected to the voltage network SPN via a power supply device NAG.

According to printed publication part 31(1993), 6 th edition, pages 215 to 218; s.althammer, d.br u ckmann: "highly optimized IC for DECT-cordless telephones" and according to WO 96/38991 (see fig. 5 and 6 and the related description thereof), fig. 2 shows a schematic circuit diagram of a base station BS and a mobile part MT. For this purpose, the base station BS and the mobile unit MT are provided with a radio element FKT with an antenna ANT for transmitting and receiving radio signals, a signal processing means SVE and a central controller ZST, which are connected to one another in the manner shown in the figure. The wireless element FKT mainly comprises some well-known means, such as a transmitter SE, a receiver EM, a synthesizer SYN, etc. In the signal processing device SVE, an encoding/decoding device CODEC and the like are included. The central controller ZST has a microprocessor μ P for both the base stations BS and the mobile units MT, a memory SP, time counters ZZ, ZZ1, ZZ2 for the timer, a signal control element SST, and a digital signal processor DSP, the processor μ P having a data structure according to the OSI/ISO-layer model [ see (1): teaching pictures-german telecommunications, 48 years, 2/1995, pages 102 to 111; (2): ETSI-printed product ETS 300175-1.. 9, month 10 1992 ], a programming module PGM, a memory SP for storing information intended for the base station BS or the mobile unit MT, and time counters ZZ, ZZ1, ZZ2 for calculating time information specific to the base station or the mobile unit, which are connected to each other as shown in the figure. Among the layers defined according to the layer model, only the four main basic layers directly for the base station BS and the mobile part MT are drawn in the figure. In the base station BS the signal control element SST is implemented as a timing switch controller TSC, and in the mobile part MT it is implemented as an burst mode controller BMC. The main difference between the two types of signaling control elements TSC, BMC is that the base station-specific signaling control element TSC additionally assumes a switching function (switching function) in comparison with the mobile-specific signaling control element BMC. The signaling control elements TSC, BMC each have a counting device ZE with a bit counter, a slot counter and a time frame counter.

The working principle of the above-mentioned circuit unit is typically described in printed matter part 31(1993), 6 th article, pages 215 to 218 cited herein.

The circuit configuration described in fig. 2 can be completed by adding further functional units, depending on the functionality of the base station BS and the mobile part MT in the DECT/GAP system shown in fig. 1.

The base station BS is connected to the communication network TKN via the signal processing means SVE and the communication connection unit TAE or the private branch exchange NStA. The base station BS may optionally also be provided with an operating interface (functional unit shown in dashed lines in fig. 2), which may for example consist of an input device EE formed by a keyboard, a display device AE formed by a display, a speaking/listening device SHE formed by a handset HK with a microphone MIF and an auditory capsule, and a ringing TRK.

The mobile part MT carries an operating interface with some operating elements belonging to it, which has already been described above, which may optionally be employed at the base station BS.

In accordance with the DECT system shown in fig. 1, fig. 3 shows a cellular DECT/GAP-multi-system CMI (wireless multi-cellular integration), in which a plurality of the above-described DECT/GAP-system TKSs each have a base station BS and one/more mobile components MT which are arranged centrally, i.e. in the manner of "radiating points", in an arbitrary geographical location, for example in a management building with large-space multi-floor offices. However, instead of managing a "closed" geographical location such as a building, a cellular DECT/GAP-multi-system CMI may be installed in an "open" geographical location with strategic communication significance, such as in large cities where traffic is high, where commercial units are highly converged, where traffic is heavy, and so on. However, in large-space offices, a part of the deployed base stations BS are constructed as antenna diversity base stations according to WO94/10764, which is different from the base stations in fig. 1 and 2. In this regard, a DECT/GAP-system TKS, when constructed centrally (with complete radio coverage in geographical locations), should be able to operate in the same environment by means of the overlapping cellular DECT/GAP-radio zones FB.

The same environment here means in terms of degree of overlap

a) The first base station BS1 of the first communication system TKS1 is located in the first wireless zone FB1, and the second base station BS2 of the second communication system TKS2 is located in the second wireless zone FB2, and a communication connection is constructed to access at least the mobile part MT_1，2，

b) The third base station BS3 of the third communication system TKS3 and the fourth base station BS4 of the fourth communication system TKS4 are located in a common third wireless zone FB3 and a communication connection is constructed which at least has access to the mobile component MT_3，4，

In the wireless communication scenario shown in fig. 1-3, in which the DECT mobile unit is connected to a private (residential) DECT base station (fig. 1) or to one or more private or public (public) DECT base stations (fig. 3) via a DECT air interface, the wireless communication scenario can now be based on the article of the publication "a.elberse, m.barry, g.fleming zum Thema: "DECT data services-DECT in fixed and mobile networks", 6. 17/18/1996, Hotel Sofitel, paris; pages 1 to 12 and summary "extend so that DECT mobile units connect to private and public DECT base stations via the DECT air interface.

Now, such scripts for the "universal mobile telecommunications system" (UMTS) can also be re-expanded according to WO95/05040 (see FIGS. 3 to 8 and their related description), i.e. access to a number of cellular cordless telecommunication systems of the pico-cell type (e.g. DECT systems as discussed so far, which are supported by the CTM-point of view (mobility of the wireless terminal; see ETSI publication (1): IN structure and support capability of CTM; original version 1.10, 1995 month 9; (2): mobility of the wireless terminal (CTM) -phase 1, service description ", draft DE/NA-010039, 6 th edition, 1995 month 10, 2) for access (see ETSI publication" CTM access profile "prETS 300824, 11 th 1996)) IN an upper network infrastructure (e.g. ISDN-, PSTN-, GSM-, and/or satellite-networks). This is achieved according to claim 1 of patent WO95/05040 by a DECT base station in the form of a DECT repeater. In the global system for mobile communications, DECT should first be understood as a "network access technology" for mobile communication services (see article by a. elberse, m.barry, g.fleming: "DECT data services-DECT in fixed and mobile networks", 6. 17/18.1996, Sofitel restaurant, paris; pages 1 to 12 and abstract), instead of the network itself.

As a representative of the script described hereinbefore, fig. 4-from printed matter "communications technology electronics, berlin 45, (1995), pages 1, 21 to 23, pages 3, 29 and 30", and IEE Colloquium1993, 173; (1993) pages 29/1-29/7; hind, f.halsall: "wireless access to the ISDN basic service", based on a DECT/ISDN intermediate system DIIS and according to ETSI publication prETS 300822, 2 months 1997-a communication electronics with ISDN communication subsystem I-TTS [ see printed matter ", berlin 41-43, parts 1 to 10, part 1: (1991) 3 rd, pages 99 to 102; section 2: (1991) 4 th, pages 138 to 143; section 3: (1991) pages 179 to 182 for the 5 th book, and pages 219 to 220 for the 6 th book; section 4: (1991)6 th, pages 220 to 222, (1992)1 st, pages 19 to 20; section 5: (1992) 2 nd book, pages 59 to 62, (1992) 3 rd book, pages 99 to 102; section 6: (1992) 4 th, pages 150 to 153; section 7: (1992) 6 th, pages 238 to 241; section 8: (1993) 1 st book, pages 29 to 33; section 9: (1993) 2 nd, pages 95 to 97, (1993) 3 rd, pages 129 to 135; section 10: (1993) 4 th, page 187 to 190 "] of" ISDN ← → DECT "communication system ID-TS (integration services digital network ← → digitally amplified radio communication) and a DECT communication subsystem D-TTS.

The DECT communication subsystem D-TTS-as will be explained in more detail below-can be a component of the DECT/ISDN intermediate system DIIS or of the RLL/WLL communication subsystem RW-TTS. As in the example shown in fig. 1, the DECT communication subsystem D-TTS is preferably based on the DECT/GAP system, for which purpose the DECT/ISDN intermediate system DIIS or RLL/WLL communication subsystem is also based on it.

The DECT/ISDN intermediate system DIIS or the RLL/WLL communication subsystem RW-TTS can optionally also be built on the basis of the GSM system (group-specific mobile communication or Global System for Mobile communication; cf. information Spectrum 14(1991) 6.3, Berlin, Germany; A.Mann: "GSM Standard-basis for European digital Mobile radio networks", pages 137 to 152). Instead of this, the ISDN communication system I-TTS can also be designed as a GSM system or PSTN system (public switched communication network) within the scope of a hybrid network.

In addition, the systems mentioned at the beginning of the article and in the future also take into account other possibilities for implementing the DECT/ISDN intermediate system DI IS or RLL/WLL communication subsystem RW-TTS or the ISDN communication subsystem I-TTS, which systems are based on the well-known multiple connections FDMA, TDMA, CDMA (frequency division multiple access, time division multiple access, code division multiple access) or on the hybrid multiple connections formed therefrom.

In conventional wire-bound communication systems, such as ISDN, (RLL/WLL scripts), the use of wireless channels (e.g. DECT channels) is becoming more and more important, especially in the context of future selection of network services without their own complex wire networks.

Thus, for example, in an RLL/WLL communications subsystem, in the case of access to a DECT system, the radio connection technology RLL/WLL (radio in the local loop/radio in the local loop) enables ISDN users, i.e. ISDN services, to be used at the standard-ISDN interface.

In the communications system ID-TS "ISDN ← → DECT" shown in fig. 4, on the one hand, it accesses a first communications subscriber (subscriber) TCU1 (communications subscriber) and its terminal equipment TE (terminal; terminal equipment) by means of a standardized S-interface (S-bus) embodied as a local communications loop, preferably defined by DECT and included in the RLL/WLL-communications subsystem RW-TTS, a DECT/ISDN intermediate system DIIS, a further standardized S-interface (S-bus), a network terminal NT (network terminal), and a standardized U-interface of the ISDN communications subsystem I-TTS, and, on the other hand, it also accesses a second communications subscriber TCU2 in the ISDN-field with available services, as an end user of the DECT/ISDN intermediate system DIIS.

The DECT/ISDN intermediate system DIIS is essentially composed of two communication interfaces, the first communication interface being a DIFS (DECT intermediate fixed system) and the second communication interface being a DIPS (DECT intermediate portable system), which can be connected wirelessly to one another, for example, via a DECT air interface. Since the first communication interface DIFS is a quasi-positional connection, the DECT/ISDN intermediate system forms a local communication transmission loop of the above-mentioned relationship. The first communication interface DIFS comprises a radio fixed element RFP (radio fixed element), an adaptation unit IWU1 (interworking unit), and an interface circuit INC1 (interface circuit) connected to the S-interface. The second communication interface DIPS comprises a wireless mobile part RPP (wireless mobile part), an adaptation unit IWU2 (interaction unit) and an interface circuit INC2 (interface circuit) connected to the S-interface. Thus, the radio fixed element RFP and the radio mobile part RPP constitute the well-known DECT/GAP system DGS.

In fig. 4, which was already mentioned, as a typical RLL/WLL scenario, the DECT/ISDN intermediate system DIIS located in the range of the RLL/WLL communication subsystem RW-TTS is connected in the form of a local communication transmission loop to the ISDN communication subsystem I-TTS, on the one hand (possibility 1), while on the other hand (possibility 2), the DECT/ISDN intermediate system DIIS supported by the CAP point of view (mobile radio access profile) is connected to the ISDN communication subsystem I-TTS only on the network side. In the case of possibility 2, the second communication interface DIPS, whose interface circuit INC2 is used to connect the S-interface, will not function, or will not function at all. To graphically illustrate and demonstrate this together, the interface circuit INC2 of the second communication interface DIPS is indicated by a dashed line. In the case of possibility 1, the second communication interface DIPS is implemented without a moving part feature, i.e. it only carries an operating interface, whereas in the case of possibility 2, the second communication interface DIPS is implemented with a typical moving part carrying an operating interface.

According to the printed matter "communications technology electronics 42(1992) month 1/month 2, No. 1, berlin, germany; pilger "structure of DECT-standard", pages 23 to 29, in connection with reference ETS 300175-1.. 9, month 10 1992 ", fig. 5 shows the TDMA-structure of the DGS of the DECT/GAP system. The DECT/GAP system is a hybrid system with respect to the multiple access method, for which the FDMA principle is established on 10 frequencies lying in the frequency band 1.88-1.9GHz, so that radio messages according to the TDMA principle can be transmitted from the base station BS to the mobile part MT and from the mobile part MT to the base station BS in a predetermined time sequence according to fig. 5 (time division duplex). The time sequence here is determined by a multi-time frame MZR, which amounts to 160ms and the duration of 16 time frames ZR is 10ms each. The discrete messages in the time frame ZR are transmitted to the base station BS and the mobile unit MT, and these discrete messages involve a C-, M-, N-, P-, Q-channel defined by the DECT standard. If information is transmitted to a plurality of such channels within a time frame ZR, the priority of the transmission should be M > C > N, P > N. Of the 16 time frames ZR of the multi-time frame MZR, each time frame is subdivided into 24 time slots ZS of 417 μ s duration, 12 time slots ZS (time slots 0.. 11) being used in the transmission direction "base station BS → mobile unit MT", and the other 12 time slots ZS (time slots 12.. 23) being used in the transmission direction "mobile unit MT → base station BS". According to the DECT standard, the length of the information bits transmitted in each such time slot ZS is 480 bits. Of the 480 bits, 32 bits are used as synchronization information in the SYNC field, and 388 bits are used as valid information in the D field. The remaining 60 bits are used as additional information in the Z zone and guard information in the "guard time" zone. The 388 bits of the D field, which is used for the effective information transmission, are subdivided into an A field 64 bits long, a B field 320 bits long, and an "X-CRC" word 4 bits long. The 64-bit long A field consists of an 8-bit long data pointer (pointer), a 40-bit data statement with C-, Q-, M-, N-, P-channel data, and a 16-bit long "A-CRC" word.

In the DECT system shown in fig. 1 to 5, the following steps can typically be taken in accordance with the DECT standard in order to construct a communication connection between the base station BS and the mobile component MT.

The base station BS (radio fixed part RFP) according to fig. 1 to 5 transmits broadcast information via the DECT air interface, in which transmission the time slots on the simplex transmission line, the so-called virtual bearer, are evenly distributed, and which broadcast information is received by the mobile part MT (radio mobile part RPP) in fig. 1 to 5 and serves the synchronization of the mobile part and the connection of the mobile part to the base station. The broadcast information does not necessarily have to be transmitted over a virtual transmission line (virtual carrier).

The virtual transmission line may also be dispensed with, since at least one communication connection, a so-called communication transmission line (communication carrier), is present between the base station and the other mobile components, so that the base station can transmit the necessary broadcast information on this line. In this case, if there is a communication connection between the mobile part MT, RPP and the base station BS, RFP, they can receive broadcast information-as well as transmit it over the virtual transmission line.

Broadcast information includes-according to ETSI publication ETS 300175-3, month 10 1992, chapter 9.1.1.1-information beyond access rights, system information and paging information, etc.

In a global system for mobile communications, DECT-already mentioned-is first to be understood as a "network access technology" for mobile communication services (see article by a. elberse, m.barry, g.fleming: "DECT data services-DECT in fixed and mobile networks", 1996, 6. 17/18, Sofitel restaurant, paris; pages 1 to 12 and abstract), instead of the network itself. However, as discussed above with respect to various communication systems, each can purchase DECT systems of various features for their own network services as needed.

In order to dispense with the use of network location functions, a dynamic channel allocation method (DCA method) can be provided according to the DECT standard. For example, if a DECT connection is constructed, the frequency and time slots with the least interference can be found. The magnitude (intensity) of the interference depends on whether or not

(a) A call has been made at another base station, or

(b) The moving part is moved into visual contact with the previously concealed base station.

By increasing the above-mentioned interference, it is possible to use a TDMA transmission method based on the DECT cordless telephone system. According to the TDMA method, only one time slot is required for the original transmission; the remaining 11 slots are used for measurements. Thus, the connection can be switched to the selected frequency/time slot pair and then measured. This is a suitable frequency allocation according to the DECT standard (cf. communications technology electronics 42 (1/2.1992), No. 1, berlin; u.pilger "architecture of the DECT standard", page 28, item 3.2.6) by means of "wire transfer" (mesh internal transfer).

In addition to this "intra-cell handover", there are also "inter-cell handover" or seamless handover, etc., which are also suitable frequency allocations specific to DECT.

In order to be able to handle the problem of "handover" which occurs uniformly in cellular radio communication systems, it is necessary for the mobile radio receiver (mobile part) provided for such a cellular radio communication system to have the ability to change a base station (to communicate with another base station) by means of a mesh change in the cellular radio system, as the case may be, at each point in time of an active communication connection with a (quasi-) stationary radio terminal (base station) and thus to transfer the already active communication connection to (seamlessly transfer) the other base station without interruption (seamlessly).

For this purpose, the DECT standard is based on the printed matter "communications technology electronics 42 (month 1/2 1992), No. 1, berlin; u.pilger "structure of the DECT standard", page 28, item 3.2.6) "provides that, when a mobile component recognizes a deterioration of the transmission quality of an existing communication connection on the basis of transmission quality indicators (e.g. signal field strength, CRC values, etc.), it itself merges into a second communication connection on the basis of the existing connection. In this "mesh internal handover" procedure, the DECT mobile units belonging to the dynamically decentralized channel allocation are constantly informed of the channel used in the current environment, and by using this fact, the second connection can be constructed on the basis of the entries in the channel table.

The uninterrupted transition of the above process occurs only when the mobile unit is within a cellular radio system with a synchronized base station. In such synchronous cellular radio systems, the mobile unit can, in addition to the existing communication connection with the base station (original base station), additionally at least constitute a connection to another base station in another radio network without losing synchronization with the original base station. However, when implementing such a synchronous cellular radio system, the system outlay (cable-or radio synchronization) is high.

When the cost of implementing a synchronous cellular radio system is not satisfactory, one can forego synchronization and use an asynchronous relationship.

Fig. 6 shows an at least partially asynchronous wireless communication network TKN, which is preferably implemented as a DECT network, comprising a number of communication systems tks1.. TKSn, which are preferably implemented as DECT systems (see fig. 1 to 5). The TKSn has a number of base stations BS, RFP, DIFS placed in the wireless mesh FZ, to which the base stations can be connected by means of wireless communication (e.g. according to DECT air interface protocol), in the communication system tks1.. TKSn and in the communication network TKN for mobile parts MT, RPP, DIPS (roaming wireless mobile parts; roaming mobile parts) that move or remain freely in position. The communication system tks1.. TKSn comprises several wireless grids FZ connected to a so-called radio group, which preferably consists of mutually synchronized base stations BS, RFP, DIFS. In order to be able to graphically draw one hundred percent of radio coverage and also to obtain a perspective view, the radio mesh FZ is here represented by a hexagon (honeycomb). In ideal geographical and physical conditions, the base station should have a circular radio space around it, i.e. the radio mesh FZ', instead of the radio mesh FZ. In the figure, overlapping or intersecting wireless regions (overlapping or intersecting regions) are generated. Within such overlapping or intersecting areas, the "roaming" mobile unit makes wireless connections with multiple base stations, depending on the size of the overlapping or intersecting wireless area, and maintains the wireless connections as necessary.

The communication network TKN in the figure is peculiar in that although the base stations BS, RFP, DIFS within a single communication system tks1.. TKSn are mutually synchronized, the single communication system tks1.. TKSn is not synchronized at all or is only partially synchronized (at least partially asynchronous communication network TKN). For this practical situation in the figure, the first communication system TKS1.. TKS7 is unsynchronized, i.e. asynchronous to each other, whereas the second communication system TKSn-2, TKSn-1, TKSn is synchronized to each other. For this purpose, the current communication network TKN has base stations in the edge area of the first communication system TKS1.. TKS7, of which at least one neighboring base station is out of synchronization, i.e. asynchronous, with the associated base station. The "roaming" of the mobile parts MT, RPP, DIPS in such an at least partially asynchronous communication network TKN will now be described as follows:

for mobile parts currently available on the market (such as the siemens mobile part "Gigaset 1000C or 1000S", or other DECT/GAP terminals), the IDLE LOCKED-mode (see ETSI publication ETS 300175-3, month 10 1992, chapter 4.3.1) is typically employed to assign a base station with the highest field strength from all base stations that can be received at one location. A transmit CRC value or a combination of both possibilities may also optionally be provided as a decision criterion for assigning a base station. If a mobile unit has been assigned one base station and the reception quality of the assigned base station has deteriorated, the mobile unit may be assigned to another base station. When allocating a new base station, there are two different scenarios:

1. the reception quality of the active base station becomes so bad that the mobile part loses radio contact with the assigned base station and the deteriorated reception quality is no longer able to maintain synchronization with the base station. In this case, the mobile unit enters a so-called "free motion scan mode" and attempts to maintain synchronization with the best receiving base station of all receiving base stations.

2. The quality of the distribution base station has deteriorated but its radio contact with the existing distribution base station has not been separated, i.e. the mobile part receives the base station's signal with a poor quality and still remains synchronized with the distribution base station. In this case, the mobile component finds nearby base stations that are bit-, time-burst-, and/or time-frame-synchronized with the assigned base station and have better reception quality with the mobile component. If the mobile unit cannot find a better base station according to a given synchronization criterion, the mobile unit remains on the existing allocated base station even if the reception quality of the allocated base station has deteriorated.

The disadvantage of the second scenario is that if there is an asynchronous base station in the vicinity and the mobile unit can receive it with a better quality, the mobile unit cannot find the asynchronous base station according to the given synchronization criterion, because it can only find the location of the synchronous base station as long as contact with the allocated base station is still present.

WO97/15160 discloses a communication system with a base station and at least one mobile element, wherein the radio environment is scanned on the basis of synchronous or asynchronous radio connections. The transfer of the synchronous connection is seamless, and during the transfer in an asynchronous wireless environment, the connection of the mobile station to the first base station is changed to a connection with the second base station by interrupting the transmission of the mobile station over the first wireless connection, but maintaining the transmission of the first base station over the first wireless connection, subsequently establishing a second wireless connection between the mobile station and the second base station, and continuing to extend the second wireless connection after the first base station releases the first wireless connection.

In US 5448569 a method or arrangement is disclosed for use in a wireless communication network having mobile stations and base stations, by which patent the mobile station is able to obtain, on the one hand, the quality of the connection with the first base station, and, on the other hand, if the obtained quality is below a predetermined value, the connection is transferred to the second base station using the procedures or methods provided in the patent.

Disclosure of Invention

To this end, the invention is based on the object of improving the roaming quality of a mobile unit in an at least partially asynchronous wireless communication network.

The communication system according to the invention for a wireless, at least partially asynchronous communication network, in particular a DECT system for an at least partially asynchronous DECT network, having a first base station which is synchronized with a first mobile unit and, in the vicinity of the first base station, at least one second base station which is asynchronous with respect to the first base station, wherein the base stations are connected to the first mobile unit by wireless transmission of information, is characterized in that a first message with first information of at least one component of the first base station is at least temporarily transmittable and the first message is transmitted to at least one of the first mobile units, wherein the message contains the content that the first base station is always surrounded by at least one second base station.

The invention is based on the idea of improving the "roaming" quality of mobile units in at least partly asynchronous radio communication networks with a plurality of communication systems with base stations of the kind described at the beginning, which are arranged in a radio network, and in the vicinity of a first base station or a part of such a base station, at least one asynchronous second base station, which transmits information to a first mobile unit in communication connection with the first base station, and which information is given such that each first base station transmitting information is surrounded by at least one second base station.

These transmitted messages are, for example, RFP status signals transmitted over a broadcast channel-at the DECT base station (see ETSI publication ETS-300175-3, month 10 1992, chapter 7.2.4.3.9), which contain corresponding signal information.

If the first mobile unit, based on the information obtained, concludes that the reception quality has deteriorated and, for a short time (for a predetermined short time), leaves the wireless contact or is synchronized, it may preferably seek an asynchronous base station, thereby improving the quality of the wireless contact. In this way, the first mobile unit can know that, in addition to the synchronous first base station, there is at least one asynchronous second base station or only one asynchronous second n base station in its vicinity.

If the connection to the assigned first base station has become poor and the first mobile unit detects the presence of an RFP status signal "asynchronous second base station", then the algorithm within the first mobile unit may operate as per WO 96/38991:

with wireless information transmission, the first base station charges the time counter of the first mobile unit for a predetermined time interval as an initial value.

The first base station has a memory in which time intervals are stored.

The time interval may be accessed to the first base station on the network side.

If the first mobile unit does not find a better first synchronous base station and the connection has become worse for a certain time, e.g. the reception value for a certain time slot is below a predetermined threshold, the mobile unit enters a so-called "free motion scanning mode" to find a nearby second asynchronous base station or base station with the highest field strength. If the search for other base stations is unsuccessful, the mobile unit returns to the original base station, since the original base station always appears to be the best receiving base station. The search for the second asynchronous base station can typically take another 5 minutes, depending on the running course of the first time counter (timer).

In case the search for the second base station is unsuccessful, the first mobile part repeats the search again at regular time intervals.

Assuming that the mobile unit has found a second asynchronous base station, although the radio contact still exists, if the quality of the newly allocated base station is degraded, the second asynchronous base station will find another second asynchronous base station again, typically within 5 seconds, according to the running process of the second time counter (timer). Or, in other words, after the first mobile unit finds the second base station, it interrupts the search for another predetermined time interval. For the second time counter, it should be possible to avoid the mobile part from moving back and forth at the radio coverage limits of the asynchronous base station, which means that the signal load of the network coupled at the base station can be increased.

In contrast, if the network consists of only second asynchronous base stations, e.g. at one S₀Multiple "residential" ISDN base stations on a bus [ see WO 96/38990 (FIGS. 5 and 6 and their associated description)]The mobile unit can then be constructed, for example, by means of an internal menu (menu point: multi-grid structure) in such a way that if the connection is bad and the radio connection or the synchronization with the assigned base station has not been lost, the mobile unit is always in the so-called "free-motion scanning mode" in order to detect and assign nearby asynchronous base stations.

The invention also comprises a preferred extension based on the system described above.

Drawings

FIG. 1 shows a DECT/GAP system of the prior art;

FIG. 2 shows a circuit configuration of the DECT/GAP system of FIG. 1;

FIG. 3 shows a cellular DECT/GAP-multisystem CMI;

fig. 4 shows "ISDN ← → DECT" communication system ID-TS;

FIG. 5 shows the TDMA structure of the DGS of the DECT/GAP system;

fig. 6A and 6B show an at least partially asynchronous wireless communication network TKN;

fig. 7A and 7B show an embodiment of an at least partially asynchronous wireless communication network TKN according to the invention.

Detailed Description

An exemplary embodiment of the invention is illustrated with the aid of fig. 7A and 7B.

Starting from fig. 6, fig. 7A and 7B show an at least partially asynchronous wireless communication network TKN, which is preferably embodied as a DECT network and in particular comprises a plurality of first wireless communication systems TKS1.. TKS7 (see fig. 1 to 5), which are preferably embodied as DECT systems, which are not synchronized, i.e. are asynchronous with respect to one another. In the first communication system TKS1.. TKS7, many locations in the communication network TKN are represented in the figure by two cases (I) and (II) -with the first base station BS1, RFP1, DIFS1 (radio grid FZ indicated by diagonal hatching upwards), for which at least one of the nearby base stations (radio grid FZ indicated by horizontal hatching) of the nearby second base stations BS2, RFP2, DIFS2 (radio grid FZ indicated by horizontal and vertical hatching) remains out of sync with the first base station BS1, RFP1, DIFS1, that is asynchronous, at the same time the second base station remains in sync with the first mobile component MT1, RPP1, DIPS1, or-is completely universally compiled with other words-the information is communicated with the first mobile component (e.g. publication information according to the DECT air interface protocol; see DECT et MT 175. si 175. t.s.1992.) in the same year as the first mobile component or with the DECT 175. ETS 175. ets.s.10, RPP1, DIPS 1. Typically, synchronization here means that the first mobile part MT1, RPP1, DIPS1 can be in idle LOCKED-mode and/or ACTIVE LOCKED-mode according to DECT standard. The first base stations BS1, REP1, DIFS1, which are denoted by "triangular symbols", are characterized by a natural number whose value is the number of second base stations BS2, REP2, DIFS2 located in the vicinity of the first base stations BS1, REP1, DIFS 1. In the first scenario (I), the number of the second base stations BS2, REP2, DIFS2 is "3", and in the second scenario (II), the number of the second base stations BS2, REP2, DIFS2 is "1". This information is transmitted as first information "at least one asynchronous base station is present" from the first base station BS1, REP1, DIFS1 to the first mobile part MT1, RPP1, DIPS 1-in the case of DECT base stations via an RFP-status signal (see ETSI publication ETS-300175-3, month 10 1992, chapter 7.2.4.3.9) transmitted via a broadcast channel.

The first message N1 (the RFP-state signal with the first information "at least one asynchronous base station present") can be sent controllably in a more preferred manner using the communication network TKN and/or using the respective communication systems TKS1.. TKS7 and/or in an automatic way with uniform time slots.

With this method the first mobile part MT1, RPP1, DIPS1 can know that there is at least one further asynchronous second base station BS2, RFP2, DIFS2, or only one asynchronous second base station BS2, RFP2, DIFS2, in the vicinity of the first synchronous base station.

In case the connection with the allocated first base station BS1, RFP2, DIFS2 has become bad and the first mobile means MT1, RPP1, DIPS1 detect the presence of the RFP-state signal "second asynchronous base station", the following algorithm can be performed inside the first mobile means MT1, RPP1, DIPS1, typically according to WO 96/38991 (see fig. 9 and claims 1 to 3):

if the first mobile unit does not find a better first synchronous base station and the connection has become worse for a certain time, e.g. the reception value for a certain time slot is below a predetermined threshold, the mobile unit enters a so-called "free motion scanning mode" to find a nearby second asynchronous base station or base station with the highest field strength. If the search for other base stations is unsuccessful, the mobile unit returns to the original base station, since the original base station always appears to be the best receiving base station. The search for the second asynchronous base station can typically take another 5 minutes, depending on the running course of the first time counter (timer). The threshold value of the received field strength defined by the position of the mobile element is equal to the initialization threshold value for switching between grids.

With wireless information transmission, the first base station charges the time counter of the first mobile part for a predetermined time interval as an initial value. The first base station is provided with a memory, wherein a time interval is stored; and, the time interval can be accessed to the first base station at the network side.

Assuming that the mobile unit has found a second asynchronous base station, although the radio contact still exists, if the quality of the newly allocated base station is degraded, the second asynchronous base station will find another second asynchronous base station again, typically within 5 seconds, according to the running process of the second time counter (timer). That is, in case the search for the second asynchronous base station is unsuccessful, the mobile part repeats the search again at even time intervals. After the mobile component finds the second asynchronous base station, it interrupts the search for another predetermined time interval. For the second time counter, it should be possible to avoid the mobile part from moving back and forth at the radio coverage limits of the asynchronous base station, which means that the signal load of the network coupled at the base station can be increased.

In contrast, if the network consists of only second asynchronous base stations, such as a plurality of "residential" ISDN base stations on an SO bus [ see WO 96/38990 (fig. 5 and 6 and the related description) ], the mobile unit can be configured-for example by means of an internal menu (menu point: multiple grid structure) -in such a way that if the connection is bad and the radio connection or synchronization with the assigned base station has not been lost, the mobile unit is always in the SO-called "free motion scan mode" to detect and assign nearby asynchronous base stations.

Claims (19)

1. Communication system for a wireless, at least partially asynchronous communication network, in particular a DECT system for an at least partially asynchronous DECT network, with a first base station (BS1, RFP1, DIFS1) which is synchronized with a first mobile component (MT1, RPP1, DIPS1), and, in the vicinity of the first base station, at least one second base station (BS2, RFP2, DIFS2) which is asynchronous with respect to the first base station (BS1, RFP1, DIFS1), wherein the base stations (BS1, RFP1, DIFS1, BS2, RFP2, DIFS2) are connected to the first mobile component (MT1, RPP1, DIPS1) by wireless transmission of information,

a first message (N1) with first information of at least one component of a first base station (BS1, RFP1, DIFS1) is at least temporarily transmittable, and said first message is transmitted to at least one of said first mobile components, wherein said message contains the fact that the first base station (BS1, RFP1, DIFS1) is always surrounded by at least one second base station (BS2, RFP2, DIFS 2).

2. The communication system of claim 1,

the synchronization between the first base station (BS1, RFP1, DIFS1) and the first mobile part (MT1, RPP1, DIPS1) is in IDLE LOCKED-mode of the first mobile part (MT1, RPP1, DIPS 1).

3. The communication system of claim 1,

the synchronization between the first base station (BS2, RFP2, DIFS2) and the first mobile part (MT1, RPP1, DIPS1) is in the ACTIVE LOCKED-mode of the first mobile part (MT1, RPP1, DIPS 1).

4. The communication system of claim 1,

the communication system (TKS1.. TKS7) is a TDMA-based communication system.

5. The communication system according to claim 4,

the first base station (BS1, RFP1, DIFS1) is asynchronous with respect to the second base station (BS2, RFP2, DIFS2) with respect to bit-, slot-and/or time frame synchronization.

6. The communication system of claim 1,

the one component of the first base station (BS1, RFP1, DIFS1) uniformly transmits the first message (N1) with the first information.

7. The communication system of claim 1,

the one component of the first base station (BS1, RFP1, DIFS1) automatically transmits a first message (N1) with first information.

8. Communication system according to one of the claims 1 to 6,

the one component of the first base station (BS1, RFP1, DIFS1) which is used to transmit the first message (N1) with the first information is located in the vicinity of the network side.

9. The communication system according to claim 8,

after receiving the first information, the first mobile unit (MT1, RPP1, DIPS1) generates asynchronization with the first base station (BS1, RFP1, DIFS1) to find the second base station (BS2, RFP2, DIFS2) according to a predetermined time interval defined by the mobile unit location.

10. The communication system according to claim 4 or 9,

the first mobile part (MT1, RPP1, DIPS1) is asynchronous with respect to bit-, slot-and/or time frame synchronization with the first base station (BS1, RFP1, DIFS 1).

11. The communication system according to claim 9,

after the first mobile part (MT1, RPP1, DIPS1) finds the second base station (BS2, RFP2, DIFS2), it interrupts the search for another predetermined time interval.

12. The communication system according to claim 11,

the first mobile part (MT1, RPP1, DIPS1) is provided with a time counter (ZZ) for acquiring a time interval.

13. The communication system according to claim 12,

by wireless information transmission, the first base station (BS1, RFP1, DIFS1) charges the time counter (ZZ) of the first mobile unit (MT1, RPP1, DIPS1) for a predetermined time interval as an initial value.

14. The communication system according to claim 13,

the first base station (BS1, RFP1, DIFS1) has a memory (SP) in which time intervals are stored.

15. The communication system according to claim 13 or 14,

the time interval allows access to the first base station (BS1, RFP1, DIFS1) on the network side.

16. A communication system according to claim 9, characterized in that the time intervals are multiples of a time slot or a time frame.

17. The communication system according to claim 9,

in case of an unsuccessful search for the second base station (BS2, RFP2, DIFS2), the first mobile part (MT1, RPP1, DIPS1) repeats the search again at uniform time intervals.

18. The communication system according to claim 9,

the reception value specified by the position of the moving part does not exceed the reception field strength threshold specified by the position of the moving part.

19. The communication system according to claim 18,

the receiving field strength threshold value specified by the position of the moving part is equal to the initialization threshold value of switching between grids.