EP0976230A2 - Device for and method of transmission of digital signals, in particular in dect-type systems - Google Patents
Device for and method of transmission of digital signals, in particular in dect-type systemsInfo
- Publication number
- EP0976230A2 EP0976230A2 EP98925472A EP98925472A EP0976230A2 EP 0976230 A2 EP0976230 A2 EP 0976230A2 EP 98925472 A EP98925472 A EP 98925472A EP 98925472 A EP98925472 A EP 98925472A EP 0976230 A2 EP0976230 A2 EP 0976230A2
- Authority
- EP
- European Patent Office
- Prior art keywords
- transmission
- digital signals
- signals
- hdlc
- transmission channel
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Withdrawn
Links
Classifications
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W88/00—Devices specially adapted for wireless communication networks, e.g. terminals, base stations or access point devices
- H04W88/02—Terminal devices
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L1/00—Arrangements for detecting or preventing errors in the information received
- H04L1/12—Arrangements for detecting or preventing errors in the information received by using return channel
- H04L1/16—Arrangements for detecting or preventing errors in the information received by using return channel in which the return channel carries supervisory signals, e.g. repetition request signals
- H04L1/18—Automatic repetition systems, e.g. Van Duuren systems
- H04L1/1809—Selective-repeat protocols
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L1/00—Arrangements for detecting or preventing errors in the information received
- H04L1/12—Arrangements for detecting or preventing errors in the information received by using return channel
- H04L1/16—Arrangements for detecting or preventing errors in the information received by using return channel in which the return channel carries supervisory signals, e.g. repetition request signals
- H04L1/18—Automatic repetition systems, e.g. Van Duuren systems
- H04L1/1867—Arrangements specially adapted for the transmitter end
- H04L1/187—Details of sliding window management
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L69/00—Network arrangements, protocols or services independent of the application payload and not provided for in the other groups of this subclass
- H04L69/30—Definitions, standards or architectural aspects of layered protocol stacks
- H04L69/32—Architecture of open systems interconnection [OSI] 7-layer type protocol stacks, e.g. the interfaces between the data link level and the physical level
- H04L69/322—Intralayer communication protocols among peer entities or protocol data unit [PDU] definitions
- H04L69/324—Intralayer communication protocols among peer entities or protocol data unit [PDU] definitions in the data link layer [OSI layer 2], e.g. HDLC
Definitions
- the present invention relates in general to the transmission of digital signals and it has been developed with particular attention to its possible application to data transmission within communication systems preferably operating according to DECT (Digital Enhanced Cordless Telecommunications) standard. This statement is not to be taken in a limiting sense since the invention is advantageously applicable to other mobile communication systems. The same invention is also applicable to both the private environment (PABXs) and the public environment.
- POBXs private environment
- DECT standard was developed at the European level in order to facilitate the use, within telecommunication networks, of cordless terminals capable of communicating with respective base stations within a pico-cell system.
- the voice transmission channel of DECT systems proves poorly protected against perturbing phenomena such as the sudden signal attenuation and/or multiple path propagation.
- the aforesaid perturbing phenomena typical of the application context of a mobile communication system such as DECT, are in fact tolerable in voice signal transmission. Though its bandwidth is narrow, the voice signal presents such intrinsic redundancy qualities as to become "robust" against the aforesaid perturbing phenomena, in the sense that such phenomena, as they occur in the current use of the system, usually do not affect the voice signal to such an extent as to make it unintelligible.
- DECT system provides for a specific and more protected channel for data signal transmission, but access to said channel is not provided for in said terminals mainly intended for voice transmission.
- the object of the invention is to overcome the aforesaid drawbacks, by allowing, for instance, the reliable transmission of digital signals such as data signals on the voice channel of a "DECT-type" system.
- DECT-type as it is used in the present application, is to be meant in the sense that the invention applies not only within systems exactly conforming to DECT standard, but also to communication systems operating in essentially similar ways. Such systems suffer, when used for the transmission of digital signals, of the same drawbacks described above.
- the reference to DECT standard made in the present description and, where necessary, in the accompanying claims, is thus to be meant as including within the scope of the invention also such essentially similar systems (e. g., the so called PHS system).
- the invention provides a device for the transmission of digital signals on at least one transmission channel of a mobile communication system where a point-to-point communication protocol is active, comprising conversion means capable of operating in at least one direction of conversion between said digital signals and respective signals suitable for being transmitted on said transmission channel for carrying out the conversion of said digital signals into respective signals suitable for being transmitted on said transmission channel or the opposite conversion, said signals suitable for being transmitted on said transmission channel corresponding to said digital signals organised into HDLC- type frames adapted for error correction on the radio interface.
- the invention also provides a method of transmission of digital signals on at least one transmission channel of a mobile communication system where a point-to-point communication protocol is active, comprising the operation of effecting a conversion, in at least one direction, between said digital signals and respective signals suitable for being transmitted on said transmission channel, said signals suitable for being transmitted on said transmission channel corresponding to said digital signals organised in HDLC-type frames adapted for error correction at the radio interface.
- Figure 1 shows, in the form of a block diagram, the general structure of a terminal of a DECT system, capable of operating in accordance with the solution according to the invention
- Figure 2 shows, in greater detail and also in the form of a block diagram, the embodiment of the invention within a terminal such as the one shown in Figure 1
- Figure 3 shows additional embodiment details of the invention.
- terminal 1 (which is derived from the paper by Werbus et al. mentioned in the introductory part of the present description) indicates in its entirety a mobile terminal of a telecommunications system operating according to DECT standard or the like.
- Terminal 1 is essentially a conventional cordless telephone capable of communicating with a base station to which one or more mobile terminals can be connected.
- terminal 1 The basic components of terminal 1 are: unit 2 for coding/decoding the voice signal (ADPCM coding/decoding), which unit is connected respectively to a microphone 3 and to a loudspeaker 4, controller 5, tasked with dialling and signalling and usually associated with a keyboard and a display unit (not shown), - unit 6 acting as management logic of the MAC (Medium Access Control) layer and as DECT frame generator and decoder, modulator 7 (usually operating according to a GMSK or ⁇ /4-DQPSK modulation technique, with different choices, for instance, in the European and in the US standard), radio frequency synthesizer 8, radio frequency transmission stage 9a, radio frequency reception stage 9b, and - antenna unit 10.
- unit 2 for coding/decoding the voice signal ADPCM coding/decoding
- ADPCM coding/decoding voice signal
- controller 5 tasked with dialling and signalling and usually associated with a keyboard and a display unit (not shown)
- - unit 6 acting as management logic of the MAC (Med
- Such units can be integrated, at least in part, into the processing means (typically a personal computer) employed by the user to transmit data over the system.
- Units 12, 13 communicate with block 11 through two bi-directional communication lines 120, 130, for instance two RS232 V.24 serial interface lines. It is in any case evident that the aforesaid lines may be of a wholly different kind, providing, for instance, for the parallel byte transmission over eight wires.
- Communication between units 12 and 13 and block 11 could also take place by using a single interface, for instance with a single RS232/V.24 line, able to convey both signalling information and user information.
- the use of two interfaces has however proved preferable, in that block 11 is able to implement the entire DECT protocol up to the MAC layer on the terminal.
- block 11 and unit 12 - separated from the functions of the U-plane, preferably located on the user's portable computer and maintained insofar as possible under the control of the applications of the user's computer.
- unit 13 in Figure 2 can be implemented entirely on the user's computer or split between the latter and a dedicated intermediate apparatus (adapter) or also located on the terminal (blocks 11 and 13 in Figure 2 partially integrated).
- the procedures described hereafter for dividing the functions should thus not be taken in a limiting sense.
- unit 12 For communication through communication line 120, unit 12 uses a management module 122 (implementing the functions of the so-called Lower Layer Management Entity of the protocol) which cooperates, according to a typical stack configuration, with a structure with three layers, indicated as DLC, NTW and IWU respectively. These layers and the related interface at the MAC layer (included in block 11 in Figure 2) are used to make voice and/or data calls.
- a management module 122 implementing the functions of the so-called Lower Layer Management Entity of the protocol
- Layer DLC Data Link Control
- Upper layer NTW Network Engineering Layer
- Uppermost layer IWU manages user interface functions: essentially this layer is the interworking layer at the application level and is employed for accessing functionalities not described in the DECT standard and made available by the exchange devices.
- Unit 13 instead is connected to line 130 through a driving unit 132 which interfaces a corresponding stack structure comprising three layers: PPP+, IP and TCP.
- Layer PPP+ is essentially tasked with managing the point-to-point protocol and it is based on PPP (Point to Point Protocol) standard.
- Layer IP Internet Protocol
- Layer TCP Transmission Control Protocol
- Reference numerals 121, 131 denote co-ordination entities of the C- plane and U-plane, respectively; said entities are known in se and have no interest for the invention.
- Figure 3 shows in the form of a functional diagram the criteria implemented at layer PPP+ within unit 13.
- layer PPP+ accomplishes communication between the IP layer and lines 130 through driving unit 132.
- the digital signals exiting the terminal pass into a module 201, acting essentially as a multiplexer, which arranges the data signals originally organised into IP frames into lower level frames which can essentially be assimilated to HDLC frames (High Level Data Link Control - see ISO/IEC 3309 standard).
- the HDLC-type frame length (and in particular, the information field length) preferably is fixed and is suited to protocol PPP+ described herein.
- the experiments conducted so far by the Applicants have indicated as particularly advantageous the choice of a length of less than 240 bytes.
- the sizes of the frames can in any case be varied upon setting up the data connection.
- the HDLC-type frames thus obtained are then associated in module 202 with a cyclic redundancy control (CRC) code and then are made to pass, through a transmitter module 203 whose function shall be described better farther on, to a location in a memory 204 which is essentially to serve as buffer memory for communication with line 130 through unit 132.
- CRC cyclic redundancy control
- the digital signals coming from line 130 arrive at buffer memory 204 to be extracted, also in the form of non-formatted frames, in view of their passage to a receiver module 206 which reconfigures them as HDLC-type frames and passes such frames to an error control module 207.
- the digital signals subjected to error control with positive outcome still in the form of HDLC-type frames, pass to a demultiplexer module 208 which reconstitutes IP frames destined to propagate towards the IP layer.
- Error control module 207 presents a feedback on transmitter module 203.
- the feedback function is to allow transmission, towards the source of the received data, of messages indicating the correctness or incorrectness, respectively, of the data received.
- the data source is activated (in a way widely known in itself) to re-transmit the signals perturbed during transmission.
- a re- transmission mechanism is performed based on a selective repetition principle, which provides for the re-transmission solely of those HDLC-type frames where the presence of errors has been detected within windows comprising a number of HDLC-type frames that can be configured so as to optimise the system performance.
- the experiments conducted so far by the Applicants have shown that the choice of a value ranging from 16 to 32 for this parameter is particularly advantageous.
- a segmentation and re-assembly (SAR) function is performed which allows using IP frame lengths exceeding the HDLC-type frame length (for instance, HDLC-type frames can be 4 to 8 times shorter than IP frames) thereby increasing the exploitation efficiency of the DECT channel.
- SAR segmentation and re-assembly
- the aforesaid SAR function is managed at the transmission side by module 203, which acts according to indications contained in the HDLC- type frames received by module 207.
- the frames received also provide information about the status of the frames received at the other end of the communication system, through a mechanism commonly denominated "piggy backing". Such information, together with the aforesaid indications, is transmitted from module 207 to module 203.
- the aforesaid segmentation and re-assembly mechanism is also effected, in an obviously complementary manner, at the receiving side, in module 206.
- module 207 notifies module 203 that a PPP+ frame considered erroneous must be re-transmitted and - to that end - module 203 temporarily retains within it all PPP+ frames into which one IP frame has been segmented.
- the HDLC-type frames resulting from the correction are sent towards demultiplexer module 208 in the terms described above.
- the latter entity accomplishes IP frame extraction from the HDLC-type frames by eliminating the HDLC flags, the FCSs (frame control sequences), the address and control fields, and then passes the information field, in the IP frame format, to layer IP.
- driving unit 132 Upon reception of a data packet (DECT frame) from line 130, driving unit 132 copies that packet into a location of upper level memory 204 and notifies also the reception of a packet.
- Protocol PPP+ accepts the data (at the receiver module level) and identifies the start of the HDLC-type frame. This is done since the channel used procedures do not guarantee constant start and stop positions for all HDLC-type frames received.
- multiplexer module 201 receives IP frames from upper layer IP and multiplexes them, according to HDLC rules, thereby forming HDCL frames. It then informs transmitter module 203 of the availability of the data to be sent. Transmitter module 203 at the same time detects whether a message has been received from error control module 207. In the negative, it sends the data to driving unit 132 (through memory 204) thereby informing the physical layer of the existence of data to be transmitted.
- the set of the PPP+ modules integrate a protocol which in transmission performs the segmentation of the upper level frames (for instance IP frames) into lower level HDLC-type frames and autonomously manages the possible re-transmission of said frames in accordance with a correction mechanism.
- the set of the PPP+ modules effects, starting from the HDLC-type frames received, the reconstruction of the upper level frame (for instance an IP frame), in a manner that is totally transparent to layer IP. This function has been denoted segmentation and re-assembly (SAR).
- SAR segmentation and re-assembly
- the operating modalities described above it is advantageous for the operating modalities described above to have sufficiently large window sizes when the selective repetition mode is used.
- the window sizes indicated above ranging from 16 to 32 frames, have proven particularly advantageous. The reference to such lengths must not however be interpreted as limiting the scope of the invention. It is in any case preferable that the window sizes are configurable, so that it is possible to suit to specific service requirements and to the environmental conditions in which the underlying access system and the mechanism described herein are to operate. This can be effected upon setting up the data transfer connection.
Abstract
Description
Claims
Applications Claiming Priority (3)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
ITTO970311 | 1997-04-14 | ||
IT97TO000311A IT1293882B1 (en) | 1997-04-14 | 1997-04-14 | DEVICE AND PROCEDURE FOR THE TRANSMISSION OF DIGITAL SIGNALS, ESPECIALLY ON DECT SYSTEMS. |
PCT/EP1998/002151 WO1998047256A2 (en) | 1997-04-14 | 1998-04-12 | Device for and method of transmission of digital signals, in particular in dect-type systems |
Publications (1)
Publication Number | Publication Date |
---|---|
EP0976230A2 true EP0976230A2 (en) | 2000-02-02 |
Family
ID=11415639
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP98925472A Withdrawn EP0976230A2 (en) | 1997-04-14 | 1998-04-12 | Device for and method of transmission of digital signals, in particular in dect-type systems |
Country Status (4)
Country | Link |
---|---|
EP (1) | EP0976230A2 (en) |
AR (1) | AR012401A1 (en) |
IT (1) | IT1293882B1 (en) |
WO (1) | WO1998047256A2 (en) |
Families Citing this family (8)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPH11340956A (en) * | 1998-05-26 | 1999-12-10 | Alps Electric Co Ltd | Data transmitter-receiver |
US6442169B1 (en) | 1998-11-20 | 2002-08-27 | Level 3 Communications, Inc. | System and method for bypassing data from egress facilities |
US6614781B1 (en) | 1998-11-20 | 2003-09-02 | Level 3 Communications, Inc. | Voice over data telecommunications network architecture |
KR20010090794A (en) * | 1999-08-19 | 2001-10-19 | 롤페스 요하네스 게라투스 알베르투스 | Automatic repeat request protocol |
DE10007012B4 (en) | 2000-02-16 | 2010-07-01 | Ipcom Gmbh & Co. Kg | Method for bidirectional data transmission via a packet-oriented network device |
US7324635B2 (en) | 2000-05-04 | 2008-01-29 | Telemaze Llc | Branch calling and caller ID based call routing telephone features |
JP4197266B2 (en) * | 2003-04-10 | 2008-12-17 | 株式会社エヌ・ティ・ティ・ドコモ | Radio control apparatus and handover control method |
US8218580B2 (en) | 2008-07-15 | 2012-07-10 | Intel Corporation | Managing timing of a protocol stack |
Family Cites Families (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
FI98027C (en) * | 1995-01-10 | 1997-03-25 | Nokia Telecommunications Oy | Packet radio system and terminal equipment for a packet radio system |
AU6721096A (en) * | 1995-08-14 | 1997-03-19 | Ericsson Inc. | Method and apparatus for modifying a standard internetwork protocol layer header |
GB9518540D0 (en) * | 1995-09-11 | 1995-11-08 | Nokia Mobile Phones Ltd | Radio telephones and methods of operation |
-
1997
- 1997-04-14 IT IT97TO000311A patent/IT1293882B1/en active IP Right Grant
-
1998
- 1998-04-12 EP EP98925472A patent/EP0976230A2/en not_active Withdrawn
- 1998-04-12 WO PCT/EP1998/002151 patent/WO1998047256A2/en not_active Application Discontinuation
- 1998-04-13 AR ARP980101678A patent/AR012401A1/en not_active Application Discontinuation
Non-Patent Citations (1)
Title |
---|
See references of WO9847256A3 * |
Also Published As
Publication number | Publication date |
---|---|
IT1293882B1 (en) | 1999-03-11 |
WO1998047256A3 (en) | 1999-01-28 |
ITTO970311A1 (en) | 1998-10-14 |
WO1998047256A2 (en) | 1998-10-22 |
AR012401A1 (en) | 2000-10-18 |
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Legal Events
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PUAI | Public reference made under article 153(3) epc to a published international application that has entered the european phase |
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17P | Request for examination filed |
Effective date: 19991112 |
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AK | Designated contracting states |
Kind code of ref document: A2 Designated state(s): DE FI FR SE |
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RAP1 | Party data changed (applicant data changed or rights of an application transferred) |
Owner name: MORENA, GAETANO Owner name: GOBBI, ROBERTA Owner name: FERRARI, GIANFRANCO Owner name: BETTI, ALESSANDRO Owner name: ITALTEL S.P.A. Owner name: TELECOM ITALIA S.P.A. |
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17Q | First examination report despatched |
Effective date: 20050118 |
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STAA | Information on the status of an ep patent application or granted ep patent |
Free format text: STATUS: THE APPLICATION IS DEEMED TO BE WITHDRAWN |
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18D | Application deemed to be withdrawn |
Effective date: 20050729 |