U.S. patent application number 08/952988 was filed with the patent office on 2002-04-11 for mobile radio receiver for cellular radio telecommunications systems.
Invention is credited to MERKER, ANDREAS, WEDI, CHRISTOPH.
Application Number | 20020042272 08/952988 |
Document ID | / |
Family ID | 7763326 |
Filed Date | 2002-04-11 |
United States Patent
Application |
20020042272 |
Kind Code |
A1 |
WEDI, CHRISTOPH ; et
al. |
April 11, 2002 |
MOBILE RADIO RECEIVER FOR CELLULAR RADIO TELECOMMUNICATIONS
SYSTEMS
Abstract
For mobile radio receivers (MT.sub.m) which are used in a
cellular radio telecommunications system, in order to allow
interruption-free relaying of a telecommunications link, in
particular even if stationary radio transmitters (U-BS, H-BS) which
are arranged in the cellular telecommunications system are not
synchronized (asynchronous radio telecommunications system), the
mobile radio receiver (MT.sub.m) has, in particular, first to third
means (FKT, SST, BMC, ZST, .mu.P, SPGM, SWS). Using these means, it
is possible to receive all those radio messages which are
transmitted for possible radio links at frequencies, in time slots
and/or in channels by the radio transmitter (U-BS, H-BS) and allow
radio links to be set up. In consequence, the mobile radio receiver
is able to set up, in addition to a first radio link which is used
as a telecommunications link, at least one second radio link, which
is intended to be used as a telecommunications link, in the
background.
Inventors: |
WEDI, CHRISTOPH; (BOCHOLT,
DE) ; MERKER, ANDREAS; (HORSTMAR, DE) |
Correspondence
Address: |
Schiff Hardin & Waite
Patent Department
6600 Sears Tower
Chicago
IL
60606-6473
US
|
Family ID: |
7763326 |
Appl. No.: |
08/952988 |
Filed: |
November 20, 1997 |
PCT Filed: |
May 29, 1996 |
PCT NO: |
PCT/DE96/00931 |
Current U.S.
Class: |
455/442 ;
455/436 |
Current CPC
Class: |
H04W 36/18 20130101;
H04W 36/0066 20130101 |
Class at
Publication: |
455/442 ;
455/436 |
International
Class: |
H04Q 007/20 |
Foreign Application Data
Date |
Code |
Application Number |
May 31, 1995 |
DE |
19519965.0 |
Claims
1. A mobile radio receiver for cellular radio telecommunications
systems, which (a) can communicate with a large number of (quasi-)
stationary radio transmitters (U-BS, H-BS), the (quasi-)stationary
radio transmitters (U-BS, H-BS) (a1) being arranged in radio cells
of the radio telecommunications system for radio-cell-related
transmission of radio messages which are included in a multiplex
structure (MZR, ZR, ZS) having a plurality of structure elements
(ZS) and allow telecommunications connections to be set up between
the radio transmitters (U-BS, H-BS) and the radio receiver
(MT.sub.m), (a2) are each connected to a telecommunications network
(TKN), synchronously or asynchronously with respect to one another,
via a switching center (PABX), (b) has a functional unit comprising
the following means: (b1) first means (FKT) for receiving and
processing the radio messages, (b2) second means (SST, BMC) for
producing and controlling the radio links to the (quasi-)stationary
radio transmitters (U-BS, H-BS), (b3) third means (ZST, .mu.P,
SPGM, SWS) for detecting and evaluating additional information
(RSSV1, RSSV2, CRCV1, CRCV2) which indicates the radio link quality
and is contained in the radio messages (c) produces and maintains a
first radio link to a first (quasi-)stationary radio transmitter
(U-BS) on the basis of receiving a first radio message which is
included in first structure elements (ZS3, ZS15) of the multiplex
structure (MZR, ZR, ZS), this first radio link being used as a
telecommunications link, characterized in that (d) the first to
third means (FKT, SST, BMC, ZST, .mu.P, SPGM, SWS) are designed and
connected to one another in such a manner that (d1) in addition to
the first radio link, at least one second radio link to at least
one second (quasi-)stationary radio transmitter (H-BS) is produced
and maintained in the background on the basis of receiving radio
messages which are included in the second to n-th structure
elements (ZS1, ZS2, ZS4 . . . ZS14, ZS16 . . . ZS24) of the
multiplex structure (MZR, ZR), which second radio link is intended
to be used as a telecommunications link, (d2) depending on the
comparison between the link quality of the first radio link and the
link quality of the second radio link, the respective link quality
being determined from the evaluation of the respective
radio-link-specific additional information (RSSV1, RSSV2, CRCV1,
CRCV2), either the first radio link continues to be used as the
telecommunications link, or the second radio link is used as a new
telecommunications link. (e) the first to third means (FKT, SST,
BMC, ZST, .mu.P, SPGM, SWS) are designed in such a manner that the
first radio link to the first (quasi-)stationary radio transmitter
(U-BS) is controlled (bearer handover) by a cyclic reception change
from the first radio message, which is included in the first
structure element (ZS3, ZS15) of the multiplex structure (MZR, ZR,
ZS), to one of the radio messages which are included in the second
to n-th structure elements (ZS1, ZS2, ZS4 . . . ZS14, ZS16 . . .
ZS24) of the multiplex structure (MZR, ZR, ZS).
2. A mobile radio receiver for cellular radio telecommunications
systems, which (a) can communicate with a large number of (quasi-)
stationary radio transmitters (U-BS, H-BS), the (quasi-)stationary
radio transmitters (U-BS, H-BS) (a1) being arranged in radio cells
of the radio telecommunications system for radio-cell-related
transmission of radio messages which are included in a multiplex
structure (MZR, ZR, ZS) having a plurality of structure elements
(ZS) and allow telecommunications connections to be set up between
the radio transmitter (U-BS, H-BS) and the radio receiver
(MT.sub.m), (a2) are each connected to a telecommunications network
(TKN), synchronously or asynchronously with respect to one another,
via a switching center (PABX), (b) has a functional unit comprising
the following means: (b1) first means (FKT) for receiving and
processing the radio messages, (b2) second means (SST, BMC) for
producing and controlling the radio links to the (quasi-)stationary
radio transmitters (U-BS, H-BS), (b3) third means (ZST, .mu.P,
SPGM, SWS) for detecting and evaluating additional information
(RSSV1, RSSV2, CRCV1, CRCV2) which indicates the radio link quality
and is contained in the radio messages (c) produces and maintains a
first radio link to a first (quasi-)stationary radio transmitter
(U-BS) on the basis of receiving a first radio message which is
included in first structure elements (ZS3, ZS15) of the multiplex
structure (MZR, ZR, ZS), this first radio link being used as a
telecommunications link, characterized in that (d) the first to
third means (FKT, SST, BMC, ZST, .mu.P, SPGM, SWS) are designed and
connected to one another in such a manner that (d1) in addition to
the first radio link, at least one second radio link to at least
one second (quasi-)stationary radio transmitter (H-BS) is produced
and maintained in the background on the basis of receiving radio
messages which are included in the second to n-th structure
elements (ZS1, ZS2, ZS4 . . . ZS14, ZS16 . . . ZS24) of the
multiplex structure (MZR, ZR), which second radio link is intended
to be used as a telecommunications link, (d2) depending on the
comparison between the link quality of the first radio link and the
link quality of the second radio link, the respective link quality
being determined from the evaluation of the respective
radio-link-specific additional information (RSSV1, RSSV2, CRCV1,
CRCV2), either the first radio link continues to be used as the
telecommunications link, or the second radio link is used as a new
telecommunications link, (e) the second means (SST, BMC) have a
number of counting devices (ZE, ZE.sub.m) corresponding to the
number of radio links.
3. A mobile radio receiver for cellular radio telecommunications
systems, which (a) can communicate with a large number of (quasi-)
stationary radio transmitters (U-BS, H-BS), the (quasi-)stationary
radio transmitters (U-BS, H-BS) (a1) being arranged in radio cells
of the radio telecommunications system for radio-cell-related
transmission of radio messages which are included in a multiplex
structure (MZR, ZR, ZS) having a plurality of structure elements
(ZS) and allow telecommunications connections to be set up between
the radio transmitters (U-BS, H-BS) and the radio receiver (a2) are
each connected to a telecommunications network (TKN), synchronously
or asynchronously with respect to one another, via a switching
center (PABX), (b) has a functional unit comprising the following
means: (b1) first means (FKT) for receiving and processing the
radio messages, (b2) second means (SST, BMC) for producing and
controlling the radio links to the (quasi-)stationary radio
transmitters (U-BS, H-BS), (b3) third means (ZST, .mu.P, SPGM, SWS)
for detecting and evaluating additional information (RSSV1, RSSV2,
CRCV1, CRCV2) which indicates the radio link quality and is
contained in the radio messages (c) produces and maintains a first
radio link to a first (quasi-)stationary radio transmitter (U-BS)
on the basis of receiving a first radio message which is included
in first structure elements (ZS3, ZS15) of the multiplex structure
(MZR, ZR, ZS), this first radio link being used as a
telecommunications link, characterized in that (d) the first to
third means (FKT, SST, BMC, ZST, .mu.P, SPGM, SWS) are designed and
connected to one another in such a manner that (d1) in addition to
the first radio link, at least one second radio link to at least
one second (quasi-)stationary radio transmitter (H-BS) is produced
and maintained in the background on the basis of receiving radio
messages which are included in the second to n-th structure
elements (ZS1, ZS2, ZS4 . . . ZS14, ZS16 . . . ZS24) of the
multiplex structure, which second radio link is intended to be used
as a telecommunications link, (d2) depending on the comparison
between the link quality of the first radio link and the link
quality of the second radio link, the respective link quality being
determined from the evaluation of the respective
radio-link-specific additional information (RSSV1, RSSV2, CRCV1,
CRCV2), either the first radio link continues to be used as the
telecommunications link, or the second radio link is used as a new
telecommunications link, (e) the second means (SST, BMC) have a
counting device (ZE) and an offset store (OSP.sub.m) which is
allocated to this counting device (ZE).
4. The mobile radio receiver for cellular radio telecommunications
systems as claimed in claim 2 or 3, characterized in that the first
to third means (FKT, SST, BMC, ZST, .mu.P, SPGM, SWS) are designed
in such a manner that the first radio link to the first
(quasi-)stationary radio transmitter (U-BS) is controlled (Bearer
Handover) by a cyclic reception change from the first radio
message, which is included in the first structure element (ZS3,
ZS15) of the multiplex structure (MZR, ZR, ZS), to one of the radio
messages which are included in the second to n-th structure
elements (ZS1, ZS2, ZS4 . . . ZS14, ZS16 . . . ZS24) of the
multiplex structure (MZR, ZR, ZS).
5. The mobile radio receiver for cellular radio telecommunications
systems as claimed in claim 1, characterized in that the second
means (SST, BMC) have a number of counting devices (ZE, ZE.sub.m)
corresponding to the number of radio links.
6. The mobile radio receiver for cellular radio telecommunications
systems as claimed in claim 1, characterized in that the second
means (SST, BMC) have a counting device (ZE) and an offset store
(OSP.sub.m) which is allocated to this counting device (ZE).
7. The mobile radio receiver for cellular radio telecommunications
systems as claimed in claim 5, characterized in that the counting
devices (ZE, ZE.sub.m) each comprise a bit, time slot and a time
frame counter.
8. The mobile radio receiver for cellular radio telecommunications
systems as claimed in claim 6, characterized in that the counting
device (ZE) is designed as a bit counter, and the offset store
(OSP.sub.m) carries out the functions of a time slot and time frame
counter.
9. The mobile radio receiver for cellular radio telecommunications
systems as claimed in one of claims 5 to 8, characterized in that
the counting device (ZE, ZE.sub.m) and, possibly, the offset store
(OSPM) are designed as software modules.
10. The mobile radio receiver for cellular radio telecommunications
systems as claimed in one of claims 5 to 8, characterized in that
the counting device (ZE, ZE.sub.m) and, possibly, the offset store
(OSP.sub.m) are designed as hardware modules.
11. A mobile radio receiver for cellular radio telecommunications
systems as claimed in one of claims 1 to 10, characterized in that
the first to third means (FKT, SST, BMC, ZST, .mu.P, SPGM, SWS) are
designed and connected to one another in such a manner that the
second radio link or links to the second (quasi-)stationary radio
transmitter or transmitters (H-BS) is or are produced and
maintained as a function of at least one predetermined
additional-information-related threshold value (SW) being exceeded
by an additional information value (RSSV1, CRCV1), which is
obtained from the additional information received with the radio
messages via the first radio link.
12. A mobile radio receiver for cellular radio telecommunications
systems as claimed in one of claims 1 to 10, characterized in that
the first to third means (FKT, SST, BMC, ZST, .mu.P, SPGM, SWS) are
designed and connected to one another in such a manner that the
second radio link or links to the second (quasi-)stationary radio
transmitter or transmitters (H-BS) is or are produced and
maintained as a function of at least one predetermined
additional-information-related threshold value (SW) being undershot
by an additional information value (RSSV1, CRCV1), which is
obtained from the additional information received with the radio
messages via the first radio link.
13. The mobile radio receiver for cellular radio telecommunications
systems as claimed in one of claims 1 to 12, characterized in that
the cellular radio telecommunications system is designed as a
cellular cordless telecommunications system, the (quasi-)stationary
radio transmitter (U-BS, H-BS) is designed as a cordless base
station, and the mobile radio receiver (MT.sub.m) is designed as a
cordless mobile part.
14. The mobile radio receiver for cellular radio telecommunications
systems as claimed in claim 13, characterized in that the cordless
base station (U-BS, H-BS) and the cordless mobile part (MT.sub.m)
are designed as cordless devices for transmitting radio messages in
accordance with the DECT Standard.
15. The mobile radio receiver for cellular radio telecommunications
systems as claimed in one of claims 1 to 12, characterized in that
the cellular radio telecommunications system is designed as a
cellular mobile radio telecommunications system, the
(quasi-)stationary radio transmitter (U-BS, H-BS) is designed as a
mobile radio base station, and the mobile radio receiver (MT.sub.m)
is designed as a mobile radio mobile part.
16. The mobile radio receiver for cellular radio telecommunications
systems as claimed in claim 15, characterized in that the mobile
radio base station (U-BS, H-BS) and the mobile radio mobile part
(MT.sub.m) are designed as mobile radio devices for transmitting
radio messages in accordance with the GSM Standard.
17. The mobile radio receiver for cellular radio telecommunications
systems as claimed in one of claims 1 to 16, characterized in that
the telecommunications network (TKN) is designed as a public
telephone network (PSTN), ISDN network, private telecommunications
network (PTN), mobile radio network or satellite radio network, and
the switching center (PABX) is designed as a private branch
exchange (PABX).
18. The mobile radio receiver for cellular radio telecommunications
systems as claimed in one of claims 1 to 17, characterized in that
the wanted information transmitted in the course of the
telecommunications link represents spoken words, written words
and/or images.
19. The mobile radio receiver for cellular radio telecommunications
systems as claimed in one of claims 1 to 18, characterized in that
the multiplex structure (MZR, ZR, ZS) is designed as an
FDMA/TDMA/TDD structure, and the structure elements (ZS) contained
in the multiplex structure (MZR, ZR, ZS) are designed as time
slots/channels.
Description
[0001] The invention relates to a mobile radio receiver for
cellular radio telecommunications systems according to the
precharacterizing clause of patent claim 1.
[0002] Two of the currently most powerful wire-free
telecommunications systems are the mobile radio system based on the
GSM Standard (Global System for Mobile Communication; see
Informatik Spektrum [Information Spectrum] 14 (June 1991), No. 3,
Berlin; A. Mann: "Der GSM-Standard--Grundlage fur digitale
europische Mobil-funknetze" [The GSM Standard--Basis of European
digital mobile radio networks]; pages 137 to 152) and the cordless
telephone system based on the DECT Standard (Digital Enhanced
(previously: European) Cordless Telecommunications; cf. (1):
Nachrichtentechnik Elektronik [Electronic Information Technology]
42 (Jan/Feb 1992), No. 1, Berlin; U. Pilger: "Struktur des
DECT-Standards" [Structure of the DECT Standard]; pages 23 to 29 in
conjunction with the ETSI Publication ETS 300175-1 . . . 9, October
1992; (2): Siemens Components 31 (1993), No. 6; S. Althammer and D.
Bruckmann: "Hochoptimierte IC's fur DECT-Schnurlos-telefone [Highly
optimized ICs for DECT cordless telephones]", pages 215 to 218;
(3): telecom report 16 (1993), No. 1, J. H. Koch: "Digitaler
Komfort fur schnur-lose Telekommunikation--DECT-Standard eroffnet
neue Nutzungsgebiete [Digital convenience for cordless
telecommunications--DECT Standard opens up new fields of use]",
pages 26 and 27), both of which transmit radio messages inter alia
using the TDMA method (Time Division Multiple Access).
[0003] However, the present invention is not limited either to
these two telecommunications systems or to the TDMA transmission
method. The invention thus also extends to those systems which are
described in the document TIB-R09067 (5)-P. Bauer-Trocheris:
"UMTS-Integrator fur die mobile Kommunikation--ein Ausblick auf die
Mobil-funklandschaft nach dem Jahr 2000 [UMTS integrator for mobile
communications--a summary of the mobile radio situation after the
year 2000]", Report on the Convention "European Mobile Radio, 5th
annual meeting of German and European mobile radio industry, FIBA
Congresses, Munich, Feb. 24 to 26, 1993".
[0004] The GSM mobile radio system is a digital cellular system in
which, according to FIG. 1 (Bee tec 2/93--The technical magazine
Ascom "Wege zur universellen mobilen Telekommunikation" [Ways for
universal mobile telecommunication], pages 35 to 42) a large number
of base stations BST1 . . . BST3 are split into cells in a cellular
supply region. The cells and the base stations BST1 . . . BST3 are
connected to one another and to the outside world via a mobile
switching center MSC1, MSC2 (Mobile Switching Center). For an
efficient network design, usually a number of these mobile
switching centers MSC are combined in a public state-based mobile
network PLMN1, PLMN2 (Public Land Mobile Network). Furthermore, the
mobile switching centers MSC1, MSC2 are linked to a public
telephone network PSTN (Public Switched Telephone Network). A
mobile radio part MFT1 . . . MFT3, from which a call is normally
passed, is, as a rule, operated by that base station with which the
best radio link can be maintained. In GSM mobile radio, the users
under some circumstances move at high speed in the cellular supply
region. This leads to a number of mobile radio cells being
traversed during a call. In order to ensure an interruption-free
handover from one adjacent cell to another adjacent cell (seamless
handover), special protocols are required between the mobile radio
part and the base station.
[0005] The DECT-specific cordless telephone system is a digital
system which, according to FIG. 1 (cf. tec 2/93--Technical Magazine
from Ascom "Wege zur universellen mobilen Telekommunikation [Ways
for universal mobile telephone communication]", pages 35 to 42) can
be used in the private area (for example house, apartment, garden
etc.), in the small public area (for example companies, office
building etc.) and as a telepoint application.
[0006] The basic structure of the cordless telephone system
comprises a base station BS (FP=Fixed Part with FT=Fixed
Termination) and a mobile part MT (PP=Portable Part with
PT=Portable Termination) with the capability for telecommunications
with the base station BS. This basic structure can be extended in
accordance with the DECT Standard in such a manner that up to
twelve such mobile parts MT are assigned to a single base station
BS.
[0007] FIG. 3 shows such a cordless telephone system STS, in which
a maximum of 12 links using the TDMA/FDMA/TDD method (Time Division
Multiple Access/Frequency Division Multiple Access/Time Division
Duplex) are set up on one DECT base station BS in parallel to DECT
mobile parts MT1 . . . MT12 via a DECT radio interface designed for
the frequency band between 1.88 and 1.90 GHz. The FIG. 12 results
from a number "k" of time slots or telecommunications channels
(k=12) available for duplex operation of a DECT system. The links
may in this case be internal and/or external. In the case of an
internal link, two mobile parts registered at the base station BS,
for example the mobile part MT2 and the mobile part MT3, can
communicate with one another. For setting up an external link, the
base station BS is connected to a telecommunications network TKN,
for example in wire-based form via a telecommunications access unit
TAE or a private branch exchange NStA is connected to a wire-based
telecommunications network or, in accordance with WO 95/05040, in
wire-free form as a repeater station to a higher level
telecommunications network. In the case of the external link, it is
possible to communicate with a mobile part, for example with the
mobile part MT1, via the base station BS and the telecommunications
access unit TAE, and for a private branch exchange NStA to
communicate with a subscriber in the telecommunications network
TKN. If, as in the case of the Gigaset 951 (Siemens cordless
telephone, cf. telecom report 16, (1993), issue 1, pages 26 and 27
BS--the base station) has only one connection to the
telecommunications access unit TAE or the private branch exchange
NStA, then only one external link can be set up. If--as in the case
of the Gigaset 952 (Siemens cordless telephone, cf. telecom report
16, (1993), issue 1, pages 26 and 27)--the base station BS has two
connections to the telecommunications network TKN, then, in
addition to the external link to the mobile part MT1, a further
external link is possible from a wire-based telecommunications
terminal TKE connected to the base station BS. In this case, it is
in principle also feasible for a second mobile part, for example
the mobile part MT12, to use the second connection for an external
link, instead of the telecommunications terminal TKE. While the
mobile parts MT1 . . . MT12 are operated using a battery or a
rechargeable battery, base station BS, which is designed as a small
cordless switching system, is connected via a mains connecting unit
NAG to a power network SPN.
[0008] The cordless telephone system according to FIG. 3 is
preferably used in the private area, according to FIG. 2.
[0009] In the small public area--in accordance with FIG. 2--a
plurality of such cordless telephone systems according to FIG. 3
can be operated as a cellular system on a private branch exchange
PABX (Private Automatic Branch EXchange), the private branch
exchange PABX controlling a plurality of base stations A-BS, B-BS,
C-BS and, if required, supporting a handover from one base station
to another. FIG. 2 also shows six mobile parts MT.sub.a . . .
MT.sub.f which are assigned to the three base stations A-BS, B-BS,
C-BS. This results in a cellular cordless telephone system in which
the telecommunications link as a rule passes via that base station
A-BS, B-BS, C-BS with which the mobile part MT.sub.a . . . MT.sub.f
has the best radio contact.
[0010] Based on the document "Nachrichtentechnik Elektronik
[Electronic Information Technology]" 42 (1992) Jan/Feb, No. 1,
Berlin, DE; U. Pilger: "Struktur des DECT-Standards [Structure of
the DECT Standard]", pages 23 to 29 in conjunction with the ETS 300
175-1 . . . 9, October 1992 FIG. 4 shows the TDMA structure of the
DECT system STS. In terms of multiple access methods, the DECT
system is a hybrid system in which radio messages can be
transmitted on ten frequencies in the frequency band between 1.88
and 1.90 GHz using the FDMA principle and, according to FIG. 4, in
a predetermined time sequence using the TDMA principle, from the
base station BS to the mobile part MT and from the mobile part MT
to the base station BS (duplex operation). The time sequence is in
this case governed by a multiple time frame MZR, which occurs every
160 ms and which has 16 time frames ZR, each having a time duration
of 10 ms. Information is transmitted separately in these time
frames ZR to the base station BS and to the mobile part MT, this
information relating to a C, M, N, P and Q channel defined in the
DECT Standard. If information for a number of these channels is
transmitted in one time frame ZR, then the transmission takes place
based on a priority list where M>C>N and P>N. Each of the
16 time frames ZR in the multiple time frame MZR is in turn split
into 24 time slots ZS each having a time duration of 417 .mu.s, of
which 12 time slots ZS (time slots 0 . . . 11) are reserved for the
transmission direction "base station BS--mobile part MT" and a
further 12 time slots ZS (time slots 12 . . . 23) are reserved for
the transmission direction "mobile part MT.fwdarw.base station BS".
Information having a bit length of 480 bits is transmitted in each
of these time slots ZS, in accordance with the DECT Standard. Of
these 480 bits, 32 bits are transmitted as synchronization
information in a SYNC field, and 388 bits as wanted information in
a D field. The remaining 60 bits are transmitted as additional
information in a Z field and as guard information in a "Guard Time"
field. The 388 bits in the D field transmitted as wanted
information are in turn split into a 64-bit long A field, and a
320-bit long B field and a 4-bit long "X-CRC" word. The 64-bit long
A field is composed of an 8-bit long data header, a 40-bit long
data set with data for the C, Q, M, N and P channels and a 16-bit
long "A-CRC" word.
[0011] Based on the document Components 31 (1993), Issue 6, pages
215 to 218; S. Althammer, D. Bruckman: "Hochoptimierte IC's fur
DECT-Schnurlostelefone [Highly optimized ICs for DECT cordless
telephones]", FIG. 5 shows the basic circuit layout of the base
station BS and of the mobile part MT. According to this, the base
station BS and the mobile part MT have a radio section FKT with an
antenna ANT which is associated with transmission and reception of
radio signals, a signal processing device SVE and a central
controller ZST, these items being linked to one another in the
manner illustrated. The radio section FKT essentially contains
known devices such as the transmitter SE, receiver EM and
synthesizer SYN as well as a field strength measuring device RSSI
(Radio Signal Strength Indicator), which are linked with one
another in a known manner. The signal processing device SVE
contains, inter alia, an encoder/decoder device CODEC. The central
controller ZST has a microprocessor .mu.P both for the base station
BS and for the mobile part MT, with a program module PGM designed
in accordance with the OSI/ISO layer model (cf. (1): Information
leaflets--Deutsche Telekom year 48, 2/1995, pages 102 to 11; (2):
ETSI Publication ETS 300175-1 . . . 9, October 1992), a signal
control section SST and a digital signal processor DSP, which are
linked to one another in the manner illustrated. Of the layers
defined in the layer model only the first four layers, which are
absolutely essential for the base station BS and the mobile part MT
are illustrated. The signal control section SST in the base station
BS is designed as a Time Switch Controller TSC, and that in the
mobile part MT is designed as a Burst Mode Controller BMC. The
major difference between the two signal control sections TSC, BMC
is that the base-station-specific signal control section TSC also
carries out switching functions (switch functions) in comparison
with the mobile-unit-specific signal control section BMC. The
signal control sections TSC, BMC each contain a counting device ZE
with a bit, time slot and time frame counter.
[0012] The basic method of operation of the circuit units mentioned
above is described, for example, in the document cited above,
Components 31 (1993), Issue 6, pages 215 to 218.
[0013] The described circuit layout according to FIG. 5 in the base
station BS and the mobile part MT is supplemented by additional
functional units in accordance with their function in the DECT
system according to FIG. 3.
[0014] The base station BS is connected to the telecommunications
network TKN via the signal processing device SVE and the
telecommunications access unit TAE or the private branch exchange
NStA. As an option, the base station BS may also have an operator
interface (functional units shown by dashed lines in FIG. 5), which
comprises, for example, an input device EE designed as a keypad, an
indicating device AE designed as a display, and speech/listening
device SHE designed as a handset with microphone MIF and an
earpiece HK, as well as a ringer bell TRK.
[0015] The mobile part MT has the operator interface (which is
possible as an option for the base station BS) with the control
elements which are part of this operator interface and are
described above.
[0016] Like the base station BS in the private area, the private
branch exchange PABX according to FIG. 2 is connected to the
wire-based public telephone network PSTN (Public Switched Telephone
Network). In this way, anyone can become his own network operator
by obtaining a cordless telecommunications system comprising the
private branch exchange PABX and the cordless telephones A-BS,
B-BS, C-BS, MT.sub.a . . . MT.sub.f connected to it.
[0017] In order to make it possible to dispense with network
coordination in this case, according to the DECT Standard, the
Dynamic Channel Allocation method (DCA method) is provided. If, for
example, a DECT link is being set up, a search is carried out for
that frequency and that time window having the least interference.
The level (intensity) of the interference depends primarily on
whether
[0018] (a) a conversation is already being carried out on another
base station, or
[0019] (b) as a result of movement, a mobile part comes into visual
contact with a base station that was previously screened.
[0020] Any increase in interference resulting from this can be
countered using the TDMA transmission method on which the DECT
cordless telephone system is based. According to the TDMA method,
only one time slot is used for the actual transmission; the other
eleven time slots can be used for measurements. In consequence, it
is possible to determine an alternative frequency/time slot pair,
to which the link can be switched. This is done in the course of
adaptive channel allocation in accordance with the DECT Standard
(cf. (1) Nachrichtentechnik Elektronik [Electronic Information
Technology] 42 (Jan/Feb 1992), No. 1, Berlin; U. Pilger: "Struktur
des DECT-Standards [Structure of the DECT Standard]"; page 28,
paragraph 3.2.6) and (2) EP-0 576 079 A1) by means of a "Connection
Handover" (Intra-Cell Handover).
[0021] In addition to this "Intra-Cell Handover", the "Inter-Cell
Handover" or the seamless handover may also be mentioned, which is
likewise possible in the course of DECT-specific adaptive channel
allocation.
[0022] In order now to address in particular the "Inter-Cell
Handover" problem which occurs regularly in cellular wire-free
telecommunications systems according to EP-0 577 322 A1, the mobile
radio receiver (mobile part) provided for such cellular radio
telecommunications systems, must be able to change the base
station, subject to a cell change within the cellular radio system,
at any time during an active telecommunications link to a (quasi-)
stationary radio transmitter (base station) (setting up a
telecommunications link to another base station) while, at the same
time, passing on the already existing active telecommunications
link without any interruption (seamlessly) to the other base
station (seamless handover). In this context, EP-0 577 322 A1
discloses the "handover" being controlled by base stations involved
and/or by a central mobile switching center (Mobile Switching
Center MSC) connected to the base stations and, alternatively, by
the relevant mobile part itself.
[0023] According to the document Nachrichtentechnik Electronik
[Electronic Information Technology] 42 (Jan/Feb 1992) No. 1,
Berlin; U. Pilger: "Struktur des DECT-Standards [Structure of the
DECT Standard]"; page 28, paragraph 3.2.6, the DECT Standard
provides for this purpose that the mobile part autonomously sets up
a second telecommunications link, in parallel with the existing
link, in the event of any deterioration in the transmission quality
of the existing telecommunications link, on the basis of indicators
of the transmission quality (for example signal field strength, CRC
values, etc.). In the case of this "Inter-Cell Handover" procedure,
the fact that DECT mobile parts are continuously informed of the
status of the channels available in the current environment in the
course of the dynamic, decentralized channel allocation process
(DCA method), is used in such a manner that the second link is set
up on the basis of the entry in a channel list.
[0024] An interruption-free handover is possible using the above
procedure only if the mobile part is located in a cellular radio
system with synchronized base stations. In such a synchronous
cellular radio system, the mobile part can then, in addition to the
already existing telecommunications link to a base station
(originating base station), set up at least one further link to
another base station in another radio cell without losing the
synchronism with the originating base station in the process. Such
a synchronous cellular radio system can, however, be implemented
only with considerable system complexity (cable or radio
synchronization).
[0025] The object on which the invention is based is to provide
mobile radio receivers for cellular radio telecommunications
systems which allow interruption-free intercellular relaying
(seamless "intercell-Handover") in particular even when
(quasi-)stationary radio transmitters arranged in the cellular
radio telecommunications system are not synchronized (asynchronous
radio telecommunications system).
[0026] This object is achieved, on the basis of the mobile radio
receiver defined in the precharacterizing clause of patent claim 1,
by the features specified in the characterizing part of patent
claim 1.
[0027] By contrast with previously known mobile radio receivers,
described initially, the mobile radio receiver which achieves the
object according to the invention is able (at any time and as a
result of the fact that, in particular, the first to third means
can receive all the radio messages transmitted for possible radio
links on frequencies, in time slots and/or in channels by a radio
transmitter and allow radio links to be set up) to set up in the
background (in addition to a first radio link used as a
telecommunications link to a first (quasi-)stationary radio
transmitter) at least one second radio link, which is intended to
be used as a telecommunications link, to at least one second
(quasi-)stationary radio transmitter, in particular within an
asynchronous cellular radio telecommunications system. In this
case, it is irrelevant for the proposed solution principle
whether
[0028] (1) the cellular wire-free telecommunications system is a
radio system in accordance with the DECT Standard or the GSM
Standard,
[0029] (2) the radio messages which are transmitted from the
stationary radio transmitters to the mobile radio receivers and
allow radio links to be set up between the radio transmitter and
the radio receiver are transmitted in accordance with the TDMA
method, the CDMA method or a hybrid (for example FDMA/TDMA/CDMA
method) access method.
[0030] In this case, it is advantageous according to claim 1 (claim
4) if the mobile radio receiver carries out a DECT-specific "Bearer
Handover" in order to prevent the masking (concealment), which
occurs according to static viewpoints, of other radio messages by
the radio link, which is used as a telecommunications link.
[0031] In addition, according to claim 2 (claim 5), it is
advantageous if the mobile radio transmitter/radio receiver has a
number of counting devices intended to match the number of radio
links and telecommunications links to be set up. In the normal case
(handover case), two counting devices are provided in the mobile
radio receiver (mobile part) according to FIGS. 7 and 8, these
being required to set up telecommunications links to two
(quasi-)stationary radio transmitters (base stations).
[0032] As an alternative to the solution according to claim 2
(claim 6), it is also possible to provide a single counting device
in conjunction with an offset store, which is allocated to this
counting device, in the mobile radio transmitter/radio receiver,
for setting up the telecommunications links.
[0033] Patent claims 7 to 10 relate to advantageous developments of
the counting devices according to claims 1 and 2 (claims 5 and
6).
[0034] According to claims 11 and 12, it is advantageous to set up
the second telecommunications link at least after exceeding a
threshold value defined with respect to reciprocal signal field
strength values and/or CRC values or after undershooting at least
one threshold value defined with respect to signal field strength
values and/or reciprocal CRC values.
[0035] Patent claims 13 to 16 specify, in particular, advantageous
developments of the invention with respect to the statements
relating to paragraph (1). Patent claims 17 and 18 relate to
advantageous developments of the telecommunications network (claim
12) and to the wanted information transmitted in the course of
telecommunications links (claim 18).
[0036] Further advantageous developments of the invention are
specified in the other dependent claims.
[0037] The invention will be explained in the following text with
reference to a DECT-specific exemplary embodiment, using FIGS. 6 to
9, in which:
[0038] based on FIG. 5, FIG. 6 shows a modified mobile part,
designed as a multisynchronization mobile part (multisync mobile
part) for operation in radio telecommunications systems, in
particular asynchronous systems,
[0039] FIG. 7 shows the setting up of a telecommunications link
between the multisync mobile part according to FIG. 6 and the base
station according to FIG. 5 during the "multisync mobile part in
the search state" situation,
[0040] FIG. 8 shows the setting up of two telecommunications links
between the multisync mobile part according to FIG. 6 and an
originating base station, as well as a handover base station
according to FIGS. 2 and 5 during the "multisync mobile part during
handover" situation.
[0041] FIG. 9 shows a function flow chart of the multisync mobile
part according to FIG. 6 for setting up the two radio links
according to FIG. 8.
[0042] Based on FIG. 5, FIG. 6 shows a modified mobile part
MT.sub.m designed as a multisynchronization mobile part (multisync
mobile part) for operation in radio telecommunications systems, in
particular asynchronous systems. In comparison with the mobile part
MT according to FIG. 5, the multisync mobile part MT.sub.m
contains, in the signal control section SST, BMC and in addition to
the counting device ZE, a further counting device ZE.sub.m or,
alternatively, an offset store SP designed, for example, as a bit
register. The two counting devices ZE, ZE.sub.m or the counting
device ZE and the offset store SP are driven by a control program
module SPGM in the microprocessor .mu.P in the central controller
ZST. This drive by the control program module SPGM is dependent on
the comparison between a field strength value RSSV1, RSSV2 (Radio
Signal Strength Value) (which is measured by the field strength
measuring device RSSI and is subsequently converted from analog to
digital form) and a threshold value SW1 which is stored in the
threshold value store SWS and is related to the field strength
value.
[0043] The two counting devices ZE, ZE.sub.m or the counting device
ZE and the offset store SP can be driven by the control program
module SPGM alternatively either as a function of the comparison
between a CRC value CRCV1, CRCV2 (Cycle Redundancy Check Value)
contained in the received radio message and a threshold value SW2
stored in the threshold value memory SWS and related to the CRC
value, or, in addition, as a function of the comparison between the
CRC value CRCV1, CRCV2 and the threshold value SW2. There is a
reciprocal relationship between the CRC value and the field
strength value which are contained as additional information in the
radio message transmitted between the base station BS and the
multisync mobile part MT.sub.m. As the transmission distance
between the base station BS and the multisync mobile part MT.sub.m
increases, the field strength value RSSV1, RSSV2 becomes smaller
while the CRC value CRCV1, CRCV2 becomes larger.
[0044] By virtue of the two counting devices ZE, ZE.sub.m and their
drive by the control program module SPGM, the multisync mobile part
MT.sub.m is able to set up two telecommunications links to two base
stations independently of one another, which belong, for example
according to FIG. 2, to different radio cells. This allows an
interruption-free radio cell change during a call. For example, it
is possible to maintain a voice link to an originating base station
U-BS and at the same time, to set up a handover link to a handover
base station H-BS in the background. With regard to setting up
telecommunications links in this way, it is irrelevant whether the
two base stations are or are not synchronized. In other words, a
multisync mobile part MT.sub.m is able to set up the
telecommunications links both in a synchronous, wire-free, cellular
telecommunications system and in an asynchronous wire-free,
cellular telecommmunications system.
[0045] The search for the handover base station H-BS can be
initiated in an advantageous manner as a function of a threshold
value SW, which is defined with respect to reciprocal signal field
strength values and/or CRC values, being exceeded, or after
undershooting a threshold value SW, which is defined with respect
to signal field strength values and/or reciprocal CRC values.
[0046] This results in the following advantages. It is possible to
use standard base stations without any radio or cable
synchronization. Furthermore, a system extension with a multisync
mobile part can be achieved retrospectively, without having to
replace or adapt already existing systems. Users of such a mobile
part, who need a cell change during the call, can be equipped with
such a multisync mobile part without the rest of the system being
influenced.
[0047] The way in which the multisync mobile part MT.sub.m sets up
these telecommunications links will be explained in detail on the
basis of FIG. 4 and with reference to FIGS. 7 to 9.
[0048] FIG. 7 shows the situation when the multisync mobile part
MT.sub.m is searching for the handover base station H-BS during the
call link to the originating base station U-BS.
[0049] By means of the counting device ZE in the signal control
section SST, BMC according to FIG. 5, the multisync mobile part
MT.sub.m has a duplex telecommunications link to the originating
base station U-BS in the time slots 3 and 15.
[0050] By means of the further counting device ZE.sub.m in the
signal control section SST, BMC according to FIG. 5, the multisync
mobile part MT.sub.m has the capability to search for the handover
base station H-BS in the remaining time slots--these being the time
slots 1, 2, 4 to 14 and 16 to 24. In this case, apart from the two
time slots allocated to the dedicated link, all the remaining time
slots are switched to receive by the multisync mobile part
MT.sub.m, in order to make it possible to receive a second radio
cell, irrespective of the timing. Since other radio cells, whose
carriers are transmitted during the dedicated time slot, cannot be
received, overlapping of the time slots can be prevented by
appropriate control of the dedicated link. This can be controlled
by a corresponding time slot change of the dedicated link by the
multisync mobile part MT.sub.m (bearer handover).
[0051] FIG. 8 shows the situation when the multisync mobile part
MT.sub.m carries out a handover link to the handover base station
H-BS during the call link to the originating base station U-BS. The
time bases of the two base stations U-BS, H-BS drift apart from one
another (time difference between the time frames). In other words,
the base stations U-BS, H-BS are asynchronous. In the present case,
a duplex telecommunications link between the handover base station
H-BS and the multisync mobile part MT.sub.m is produced using the
counting device ZE.sub.m, for example in the time slots 4 and
16.
[0052] The production of the duplex telecommunications link to the
handover base station H-BS can once again be carried out in an
advantageous manner related to threshold values. In principle,
there are two possible options for this.
[0053] The first option is for the duplex telecommunications link
to be produced as a function of the threshold value SW defined with
respect to reciprocal signal field strength values and/or CRC
values being exceeded, or after a threshold value SW defined with
respect to signal field strength values and/or reciprocal CRC
values is undershot.
[0054] The second option is for the duplex telecommunications link
to be produced as a function of a further threshold value SW
defined with respect to reciprocal signal field strength values
and/or CRC values being exceeded, or after a further threshold
value SW defined with respect to signal field strength values
and/or reciprocal CRC values is undershot.
[0055] On the basis of FIGS. 6 to 8 and with the alternatives
outlined above, FIG. 9 shows one possible flow chart for the
multisync mobile part MT.sub.m for searching of the handover base
station H-BS and for producing the duplex telecommunications link
to this handover base station H-BS.
[0056] While the search mode is active, all the RF and DECT control
signals are derived from the counting device ZE.sub.m and the
associated control registers with the exception that, for the
active link channel on the counting device ZE, for example time
slot 3 and 15, a change is made to the counting device ZE and the
RF and DECT control signals are derived from the counting device ZE
and its control signals. If the search mode is inactive, all the RF
and DECT control signals are derived exclusively from the counting
device ZE and its control signals. In principle, the counting
device ZE.sub.m comprises bit, time slot and time frame counters
(bits 0 to 480, time slots 1 to 24, time frames 0 to 15), it being
possible by an offset control of the software to allow the time
frame counter or the time slot and time frame counter to be
omitted.
[0057] As an alternative to the embodiment described above, the
following embodiment is also possible on the basis of FIG. 6, in
which the counting device ZE.sub.m is replaced by an offset store
OSP.sub.m designed as a register.
[0058] If a mobile part is synchronized when searching for a
handover base station, then the current bit value of the counting
device ZE is saved in the register OSP.sub.m. Theoretically, this
register has to have a size of 9 bits in order to allow the maximum
bit counter value of a time slot (480 bits) to be stored. However,
since a synchronization window of less than .+-.32 bits is normally
used, it is, alternatively, sufficient to save the last 6 bits of
the counting device ZE. The normal synchronization position is at
the end of the sync word, at the bit position 32 (decimal) or
000100000 (binary). There is normally a synchronization window (for
example .+-.4 bits or .+-.8 bits) around this position now, in
which synchronization is allowed. If synchronization takes place
now, within this window, to another base station (handover base
station), then the mobile part experiences a shift with respect to
the originating base station. If, for example, the synchronization
takes place at bit position 28 (decimal) or 011100 (binary), then
these values are written to the 6 registers. The mobile part now
has a shift of 4 bits with respect to the originating base station.
The old sync position stored in the register OSP.sub.m, in the
example the value 28 (decimal) or 01100 (binary), can now be
back-loaded to the counting device ZE at a fixed defined point of
the counting device ZE at which the last 6 bits once again assume
the value 32 (decimal) or 10000000 (binary). This can be done, for
example, in the guard field (guard time) at bit position 464
(decimal) 1110100000 (binary), in the same time slot. If, for
example, a "slow hopping" radio section is used, which can fill
only every other time slot in any case, back-synchronization is
also possible in the directly following inactive time slot, for
example at the expected sync position.
[0059] In a time-slot-related register, it is possible to use a bit
to designate the time slot in which synchronization is intended to
have a long-term effect on the counting device ZE, and the time
slot in which back-synchronization to the old bit value of the
counting device ZE is intended to take place.
[0060] Instead of a 6-bit register, it is likewise possible to
allow a 9-bit counter (up to 480 decimal) to run in parallel with
the counting device ZE. This counter may run on without
resynchronization in a time slot in which long-term synchronization
is not intended to take place. This count can be back-loaded to the
counting device ZE at a suitable point, for example in the guard
field (guard time). This counter is resynchronized to the counting
device ZE again, and by the reception of the sync word, in a time
slot to be synchronized.
[0061] In both cases, the result is thus that the mobile part
maintains the synchronization position of the originating base
station even in the event of multiple synchronization within the
sync window within one time frame.
* * * * *