AU6174499A - Method of and components for handing off radio calls in TDMA-based cordless communications systems - Google Patents
Method of and components for handing off radio calls in TDMA-based cordless communications systems Download PDFInfo
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- AU6174499A AU6174499A AU61744/99A AU6174499A AU6174499A AU 6174499 A AU6174499 A AU 6174499A AU 61744/99 A AU61744/99 A AU 61744/99A AU 6174499 A AU6174499 A AU 6174499A AU 6174499 A AU6174499 A AU 6174499A
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- Australia
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- base station
- mobile station
- connection
- cts
- tdma
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- 238000000034 method Methods 0.000 title claims description 27
- 238000004891 communication Methods 0.000 title claims description 22
- 230000005540 biological transmission Effects 0.000 claims description 8
- 230000007423 decrease Effects 0.000 claims 1
- 230000011664 signaling Effects 0.000 description 8
- 102100029290 Transthyretin Human genes 0.000 description 3
- 238000012546 transfer Methods 0.000 description 2
- 230000003247 decreasing effect Effects 0.000 description 1
- 238000010295 mobile communication Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000012360 testing method Methods 0.000 description 1
Classifications
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W36/00—Hand-off or reselection arrangements
- H04W36/16—Performing reselection for specific purposes
- H04W36/18—Performing reselection for specific purposes for allowing seamless reselection, e.g. soft reselection
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W36/00—Hand-off or reselection arrangements
- H04W36/14—Reselecting a network or an air interface
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- Engineering & Computer Science (AREA)
- Computer Networks & Wireless Communication (AREA)
- Signal Processing (AREA)
- Mobile Radio Communication Systems (AREA)
Description
P/00/01Il Regulation 3.2
AUSTRALIA
Patents Act 1990
ORIGINAL
COMPLETE SPECIFICATION STANDARD PATENT a a.
a a a.
a. a a a a. Invention Title: 'Method of and components for handing off radio calls in TDMA-based cordless communications systems' The following statement is a full description of this invention, including the best method of performing it known to us: *b a a a.
A.
Documnents received on: 22 IBatch NO' FHP.'V YrX ATmfl2M9lonIV5, CE\99329005.
1 2 Method of and Components for Handing Off Radio Calls in TDMA-Based Cordless Communications Systems Field of the invention This invention relates to a method of, and components for establishing a connection in TDMA-based communications systems between a mobile station, which is in radio communication with a first base station of a first cordless telephone system, and another, second base station of the same or another, second cordless telephone system.
Background of the invention TDMA (time-division multiple access) is a scheme for accessing a time-division 10 multiplex radio channel using time-selective circuitry with which only the radio signal lying in the corresponding time window or time slot is extracted. Time slots following each other successively in time form a TDMA frame.
In GSM (global system for mobile communications), handoff of the mobile station from one cell to another is controlled by the network side located at the higher level of the system .15 hierarchy, based on data communicated to it by the mobile station.
In a network of cordless telephone systems (CTS) consisting of several cells each having ooooo one base station (CTS-FP: cordless telephone system fixed part), with the base stations being interconnected via a private automatic branch exchange (PABX), mobility for registered mobile 2 stations (CTS-MS: cordless telephone system mobile station), and thus changing of the mobile 20 station between cells of the same network ("reselection" outside a call and "handoff' during a call), is desirable. To achieve high communication quality, seamless handoff should be provided.
Unlike GSM, however, CTS systems that form a network do not have a higher level that could control the handoff of calls.
Summary of the invention It is an object of the present invention to improve a method of the above kind in such a way that the mobile station is in a position to establish a connection to another base station by itself if required, and to provide components for carrying out this method.
OE\99329005.1 3 According to a first aspect of the present invention there is provided a method of establishing a connection in TDMA-based communications systems between a mobile station which is in radio communication with a first base station of a first cordless telephone system and another, second base station of the same or another, second cordless telephone system wherein the mobile station while communicating with the first base station on one time slot attempts to establish a radio link to the second base station on at least one other time slot.
Accordingly, in one embodiment of the invention the mobile station, while being in radio communication with the first base station on one time slot, attempts to establish a connection to the second base station on at least one other time slot.
The invention is predicated on recognition that because of the absence of the higher hierarchy level, during handoff to a neighboring cell, the mobile station itself should initiate the provision of the radio resource, establish a transmission channel (TCH: traffic channel) to the new base station, and, if possible, release the connection to the old base station. The need for handoff to a new cell should be decided by the respective mobile station itself. In addition, the selection of the new cell, if two or more neighboring cells exist, and the handoff procedure can be initiated and controlled by that mobile station.
Since one or more time slots within successive TDMA frames are occupied by the •mobile station during the course of a call, handoff can be executed, wholly or in part, on this S• time slot or these time slots, while communications are being conducted on another time slot.
20 If information is transmitted between the mobile station and the base station in TDMA i frames according to a given interleaving scheme, it is advantageous for the mobile station to use at least one TDMA frame of the interleaving scheme of the connection to the first base station CTS-FP1 for establishing the connection to the second base station, to steal at least one frame from the channel time slot TS 1) for a limited period of time.
This is particularly advantageous in that the establishment of the connection to the new, second base station can take place even if the mobile station has previously attempted unsuccessfully to establish a connection to the second base station (CTS-FP2) on another time slot TS2).
According to the GSM standard, any information to be transmitted, both in the downlink direction and in the uplink direction, is distributed over four or eight TDMA frames and transmitted as blocks according to a given interleaving scheme. This interleaving is done in CE\99329005.1 4 such a way that the transmitted information can be completely reconstructed even if individual three out of eight) TDMA frames of an interleaving block are not received.
According to an embodiment of the invention, TDMA frames that are not absolutely necessary to transmit information are "stolen" from the interleaving blocks and are used to execute a handoff to a neighboring cell during the course of a call. Via these stolen TDMA frames of the current traffic channel (TCH), the mobile station can find a new radio resource.
These up to three stolen TDMA frames can also be accumulated over two or more blocks. If the mobile station decides that handoff is to take place, the call in progress will not be interruped and the handoff process will be performed via stolen TDMA frames. The advantageous use of specific sequences for the search for a new CTS and the subsequent registration of the mobile station make it possible to minimize the duration of this process.
Preferably, the connection setup via stolen TDMA frames does not take place before the S mobile station has attempted unsuccessfully to establish a connection to the second base station on another time slot. The method according to the invention can be used both in a system without broadcast signaling (CTS with BCCH-less protocol) and in a system with broadcast signaling (on the broadcast channel BCCH). In addition, these measures can be applied to both Sfull rate traffic and half rate traffic.
The two methods described permit in particular the implementation of seamless handoff S" in a CTS network without the need for a higher-level central mobility management facility. The selected method or methods can be used in a sequential and/or time-division multiplex mode for o two or more adjacent CTSs.
Advantageously, the number of TDMA frames usable for the connection setup is not fixed but depends, for example, on the transmission quality of the radio link existing between the mobile station and the first base station. This ensures that during a connection with poor transmission quality, in which all TDMA frames must be used for the transmission, communication will not collapse due to the stealing a TDMA frame. The better the transmission quality, the more TDMA frames can be stolen from an interleaving block.
During handoff and roaming, the mobile station will attempt to achieve a connection to a second, neighboring base station for signaling purposes. After a change of connection to the second base station has taken place, the mobile station can again establish a connection to the first base station in order to log off or log back on. When the mobile station has executed the CE99329005.1 handoff in whole or in part, it may communicate this information to the old base station, optionally specifiying the identity of the new base station. This enables the old base station to transfer the call in progress directly, and thus, faster, via the private automatic branch exchange to the new base station.
According to a further aspect, the invention relates to a mobile station and a base station comprising a program module for carrying out the proposed method and to a cordless telephone system comprising at least one such mobile station and at least one such base station.
Brief description of the drawings Further advantages of the invention will become apparent from the following description and the accompanying drawings. According to the invention, the aforementioned features and the features described below can be used alone or in arbitrary combinations. While a particular embodiment of the invention is described, it is to be understood that the description is made i only by way of example and not as a limitation to the scope of the invention.
In the drawings: 15 Fig. 1 shows schematically two cordless telephone systems and a mobile station that is moving from one cordless telephone system to the other; Fig. 2 shows schematically the interleaving scheme for communications between mobile 0: 0: station and base station; and Fig. 3 is a flowchart for a software module provided in the mobile station.
Detailed description of the embodiments Fig. 1 shows two adjacent cordless telephone systems CTS1 and CTS2 with base stations CTS-FP1 and CTS-FP2, respectively, whose cells, shown in the form of ellipses, overlap. A mobile station CTS-MS, which is in radio communication Fl with the first base station CTS-FP1 via a time slot TS1, is to be handed off to the adjacent cell. The mobile station CTS-MS itself is to initiate the provision of a radio resource at the new, second base station CTS-FP2, establish a transmission channel to the new base station CTS-FP2, and, if possible, release the connection to the old base station CTS-FP1. The need for handoff to the new cell can be decided by the mobile station CTS-MS or the CTS-FP. In the latter case, the CTS-MS must send its data about the communication quality to the CTS-FP.
CE\99329005.1 6 While being in radio communication Fl with the first base station CTS-FP1 on the time slot TS1, the mobile station CTS-MS attempts to set up a radio link F2 to the second base station CTS-FP2 on another time slot TS2. On time slot TS2, handoff can be attempted, while on slot TS 1, the call is being made.
If, however, the mobile station CTS-MS, in order to establish the connection to the second base station CTS-FP2, must use the same channel time slot TS1) as for the call in progress, it can, for the duration of the establishment of the connection to the second base station CTS-FP2, steal at least one TDMA frame of the interleaving scheme and use it for signaling purposes.
For the TDMA channel in the time slot TS1, an interleaving scheme with two times eight TDMA frames fl to f8 is shown in Fig. 2. Let us assume that of the respective eight TDMA frames, the respective first three TDMA frames fl, f2, and f can be stolen, and that the connection with the first base station CTS-FP1 can be maintained via the other TDMA frames.
Via the stolen TDMA frames, the mobile station CTS-MS establishes a connection to the second base station CTS-FP2 if required, in case of decreasing communication quality, as is indicated in Fig. 2 by the assignment of the frames fl to f3 to the new radio link with the Ssecond base station CTS-FP2.
These measures, which have been described as applied to a GSM CTS, can be applied to TDMA systems in general.
20 Fig. 3 shows an exemplary flowchart for the method according to the invention, illustrating, on the one hand, the case for a BCCH-less protocol and, on the other hand, the case for the use of a BCCH. Let us assume that the mobile station CTS-MS is communicating with the first base station CTS-FP1 on time slot TS1. After the start of the program at step 1, at step 2, the quality of the communication between the mobile station CTS-MS and the first station CTS-FP1 is continuously checked. If the communication quality is sufficient, there is not need for a change of connection, and the program remains in a wait loop. If the communication quality is no longer sufficient, the mobile station CTS-MS will set up a connection to another, second base station CTS-FP2. The time slot on which this is done is specified by the base station CTS-FP2. If there is no BCCH, the connection will be established on another time slot, on time slot TS2. The program then branches from step 2 to steps 3 and 4. The connection setup occurs parallel with the connection existing with the first base station CTS-FP1.
CE\99329005.1 7 If the establishment of the connection to the second base station CTS-FP2 must take place on the same time slot TS 1 as the connection existing with the first base station CTS-FP1, for example because this time slot represents a BCCH, the program will branch to step 5. At step 5, the mobile station sends on time slot TS1, on which it is communicating with the first base station CTS-FP1, a signal for establishing the connection to the other, second base station CTS-FP2. For this signaling, TDMA frames stolen from the interleaving scheme of the connection between mobile station CTS-MS and first base station CTS-FP1 are used. At step 6, a test is made to determine whether the connection setup was successful. In this case, the connection setup was successful and the program progresses to step 7, at which further signaling from the mobile station CTS-MS to the second base station CTS-FP2 takes place via stolen TDMA frames. If the connection setup is not successful, a branch will be made from step back to step 2 in order to attempt to establish a connection to another base station.
e °After the establishment of the connection to the second base station CTS-FP2 (step 4 or the second base station CTS-FP2 can assign another time slot for the further signaling and the transfer of the connection between the mobile station CTS-MS and the first base station CTS-FP1.
If the establishment of the connection to the second base station CTS-FP2 was successful, the mobile station CTS-MS may send an identification to this second base station and subsequently signal to the first base station CTS-FP1 the successful establishment of the connection to the second base station CTS-FP2. The first base station CTS-FP1 then routes the call via the private automatic branch exchange PABX to the second base station CTS-FP2, transmitting the same identification to the second base station CTS-FP2 by suitable signaling.
Based on this identification, the second base station CTS-FP2 can check whether the redirected call originates from the mobile station CTS-MS. The call from the mobile station CTS-MS is then switched from the second base station CTS-FP2 through to the private automatic branch exchange PABX.
The above-described stealing of individual TDMA frames is independent of whether a broadcast channel BCCH is used or not. If a BCCH is used, this channel must be established on a fixed radio frequency; the other channels for communication (traffic channels TCH) should preferably be established on changing radio frequencies ("frequency hopping") to avoid interferences between the CTSs.
CE\99329005.1 8 It will be understood that the invention disclosed and defined herein extends to all alternative combinations of two or more of the individual features mentioned or evident from the text or drawings. All of these different combinations constitute various alternative aspects of the invention.
The foregoing describes embodiments of the present invention and modifications, obvious to those skilled in the art can be made thereto, without departing from the scope of the present invention.
It should be noted that where in the specification or claims the terms "comprised" or "comprising" are used those terms should be interpreted inclusively rather than exclusively.
a a
Claims (11)
1. A method of establishing a connection in TDMA-based communications systems between a mobile station which is in radio communication with a first base station of a first cordless telephone system and another, second base station of the same or another, second cordless telephone system wherein the mobile station while communicating with the first base station on one time slot attempts to establish a radio link to the second base station on at least one other time slot
2. A method as claimed in claim 1, wherein information distributed over several TDMA frames according to a predeterminable interleaving scheme is transmitted between the mobile station and the base stations, and at least one TDMA frame of the interleaving scheme is used by the mobile station to establish the connection to the second base station as*:
3. A method as claimed in claim 2, wherein the number of TDMA frames used for the establishment of the connection is determined based on the transmission quality of the radio link existing between the mobile station and the first base station
4. A method as claimed in claim 2, wherein the number of TDMA frames used for the establishment of the connection is determined based on the traffic carried by the second base station **see: e 05. A method as claimed in any one of the preceding claims, wherein, if the transmission quality of the radio link existing with the first base station decreases, the mobile station S 20 attempts by itself to establish a connection to the other, second base station S• A method as claimed in any one of the preceding claims, wherein, if a handoff to the second base station was successful, the connection to the first base station is established in order to log off at the first base station
7. A method as claimed in any one of the preceding claims, wherein in the first and second cordless telephone systems, broadcast signals are signaled on the same radio channel, and wherein on other radio channels, information is transmitted in a frequency-hopping mode.
8. A mobile station comprising a program module for carrying out the method claimed in any one of claims I to 7.
9. A base station comprising a program module for carrying out the method claimed in any one of claims 1 to 7. CE\99329005.1 A cordless telephone system comprising at least one mobile station as claimed in claim 8 and at least one base station as claimed in claim 9.
11. A method substantially as hereinbefore described with reference to the accompanying drawings.
12. A mobile station substantially as hereinbefore described with reference to the accompanying drawings.
13. A base station substantially as hereinbefore described with reference to the accompanying drawings.
14. A cordless telephone system substantially as hereinbefore described with reference to the accompanying drawings. Dated this 25th day of November 1999 *ALCATEL by its attorneys Freehills Patent Attorneys
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE19854618A DE19854618A1 (en) | 1998-11-26 | 1998-11-26 | Methods and components for handing over radio connections in TDMA-based cordless communication systems |
| DE19854618 | 1998-11-26 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| AU6174499A true AU6174499A (en) | 2000-06-01 |
Family
ID=7889131
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| AU61744/99A Abandoned AU6174499A (en) | 1998-11-26 | 1999-11-26 | Method of and components for handing off radio calls in TDMA-based cordless communications systems |
Country Status (5)
| Country | Link |
|---|---|
| EP (1) | EP1005246A3 (en) |
| JP (1) | JP2000165929A (en) |
| AU (1) | AU6174499A (en) |
| CA (1) | CA2289238A1 (en) |
| DE (1) | DE19854618A1 (en) |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE10008058C1 (en) * | 2000-02-22 | 2001-08-09 | Siemens Ag | Preparation of a call forwarding between two radio communication systems |
| JP3870761B2 (en) | 2001-09-07 | 2007-01-24 | 松下電器産業株式会社 | Wireless telephone equipment |
| JP3712996B2 (en) * | 2002-07-19 | 2005-11-02 | 松下電器産業株式会社 | Communication terminal apparatus and handover method |
Family Cites Families (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6018661A (en) * | 1995-10-18 | 2000-01-25 | Telefonaktiebolaget Lm Ericsson | Inhibiting and controlling signal strength measurements by a mobile station in a wireless communication system |
| US5822313A (en) * | 1996-05-24 | 1998-10-13 | National Semiconductor Corporation | Seamless handover in a cordless TDMA system |
| SE506816C2 (en) * | 1996-06-20 | 1998-02-16 | Ericsson Telefon Ab L M | A method and a communication unit for the rapid identification of base stations in a communication network |
-
1998
- 1998-11-26 DE DE19854618A patent/DE19854618A1/en not_active Ceased
-
1999
- 1999-11-10 CA CA002289238A patent/CA2289238A1/en not_active Abandoned
- 1999-11-18 JP JP11327724A patent/JP2000165929A/en active Pending
- 1999-11-19 EP EP99440322A patent/EP1005246A3/en not_active Withdrawn
- 1999-11-26 AU AU61744/99A patent/AU6174499A/en not_active Abandoned
Also Published As
| Publication number | Publication date |
|---|---|
| EP1005246A2 (en) | 2000-05-31 |
| CA2289238A1 (en) | 2000-05-26 |
| EP1005246A3 (en) | 2003-01-15 |
| DE19854618A1 (en) | 2000-06-08 |
| JP2000165929A (en) | 2000-06-16 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MK1 | Application lapsed section 142(2)(a) - no request for examination in relevant period |