AU3131000A

AU3131000A - A transmission system taking account of the requirements of the different kinds of traffic carried, and a corresponding transmitter and receiver

Info

Publication number: AU3131000A
Application number: AU31310/00A
Authority: AU
Inventors: Jean-Pierre Balech; Bertrand Debray; Marc Genot
Original assignee: Alcatel CIT SA; Alcatel SA
Current assignee: Alcatel Lucent SAS
Priority date: 1999-05-11
Filing date: 2000-05-03
Publication date: 2000-11-16
Also published as: EP1052876A1; CN1274206A; CA2308405A1; JP2001016179A

Description

P/00/011 Regulation 3.2

AUSTRALIA

Patents Act 1990

ORIGINAL

0 0 0 :0,90 0 COMPLETE

SPECIFICATION

STANDARD

PATENT

oooe o o oooo oooo "2*2 o O Invention Title: 'A transmission system taking account of the requirements of the different kinds of traffic carried, and a corresponding transmitter and receiver' The following statement is a full description of this invention, including the best method of performing it known to us: FHPSYnDCFrNATP( I121N)\(W36994fL) CE00369932.2 2 A transmission system taking account of the requirements of the different kinds of traffic carried, and a corresponding transmitter and receiver Field of the invention 5 The field of the invention is that of combined telephone and data transmission.

*o More precisely, the present invention relates to a transmission system making it possible to take account of the requirements specific to telephony while also giving high data rate characteristics to data transmission.

Background of the invention 0 In any network, the telephony service is characterized by a flow that is regular and by •oo strict constraints on transmission delays. In contrast, a data transfer service deals with traffic that is erratic, with data rate requirements that are generally higher than for telephony, and with transmission delay requirements that are not so strict.

The following description refers to the down-link direction of a call (from a base station 15 to a terminal) in a transmission network.

A radio transport mechanism carrying both telephone calls and data connections can be implemented, for example, by a base station transmitting a time division multiplex (TDM) frame having certain time slots allocated to telephony and others to data type information. The number of slots allocated to the same user depends on the data rate given to that user. Such a solution is generally used in circuit-oriented communications systems. In packet-oriented communications systems, it is possible to think of carrying telephony as carrying data in asynchronous transfer mode (ATM) cells, with the ATM cells being transmitted in order.

The drawback of the first solution is that it is ill-suited to high data rate data transmission since it was originally designed and dimensioned for telephony. The second solution is well adapted to high data rates, but suffers from the drawback of giving rise to large amounts of delay when carrying telephony. The usual telephony data rate of 64 kbit/s is obtained by transmitting ATM cells containing 48 payload bytes. That means that in order to comply with the data rate of 64 kbit/s, an ATM cell containing telephony is transmitted only once every 6 mins. This situation is contrary to the requirement for short transmission time in CE00369932.2 3 telephony and it makes it necessary to include echo cancellers in the communications system in order to equalize telephone channels so as to ensure good quality communication. In a packetoriented communications system, it is not possible at a base station to know which channel needs to have an activated echo canceller. Under such circumstances, an echo canceller is needed in the receiver terminal, and that represent high cost.

The applicant does not concede that the prior art discussed in this specification forms part of the common general knowledge in the art at the priority date of this application.

Summary of the invention ~An object of the present invention is to propose a transmission system made up of transmitter entities and of receiver entities in which high data rate data transmission and telephone data transmission are mixed while making it possible to satisfy the transmission delay requirements for telephony data.

According to a first aspect of the present invention there is provided a transmission system comprising a transmitter transmitting, to at least one receiver a succession of frames, each having a payload field and a signalling field said payload field including both telephony blocks of predetermined size belonging to at least one telephone call and data type information, said signalling field including indications referencing the type of information contained in each location of said payload field, each telephony block and the data type information being addressed to specific ones of said receivers, wherein in said system any available telephony block is transmitted in said payload field with priority over any data type information.

According to a second aspect of the present invention there is provided a transmitter for a transmission system for transmitting, to at least one receiver, a succession of frames, each having a payload field and a signalling field, said payload field including both telephony blocks of predetermined size belonging to at least one telephone call and data type information, each telephony block and the data type information being addressed to specific ones of said receivers, said transmitter including means for referencing, in said signalling field, the type of information contained in each location of said payload field, wherein said transmitter includes selector means enabling an available telephony block to be transmitted in said payload field with priority over any data type information.

CE00369932.2 4 According to a third aspect of the present invention there is provided a receiver for a transmission system suitable for receiving, from a transmitter frames of predetermined length, each comprising a payload field and a signalling field said payload field including both telephony blocks and data type information, said signalling field including indications accompanying the stream, referencing the type of information contained in each location of said payload field, part of the information contained in said stream being addressed to the receiver, wherein said receiver includes means enabling it to extract the information that is addressed thereto said .ooo.: S telephony blocks belonging to any one telephone call being always transmitted in the 10 same position in the payload field in each frame in which they are present.

An embodiment of the invention is based on the fact that: oolo the telephony blocks making up a telephone call are transmitted in an information stream with priority over any data type information and as soon as a telephony block is available; data type information is transmitted whenever no telephony block is available; and S a the information stream is accompanied by indications making it possible to identify those locations in the stream which are occupied by telephony blocks or by data type information.

The notion of "priority" for telephony blocks must be understood at the scale of telephone calls in progress and not as absolute priority. The system in general is dimensioned in such a manner that some determined passband is reserved for telephony, with the remainder of the passband being reserved for data type information. Thus, if the passband reserved for telephony has been used up, then a newly set up telephone call will not have priority over transmitting data type information. However, for telephone calls in progress, the system ensures that the telephony blocks that belong to them get priority.

Thus, telephone data is no longer tied to the fixed structure of an ATM cell, for example.

Since the telephony blocks belonging to a current telephone call have priority over data, it is possible for the size of the telephony blocks and for their transmission rate to be selected in such a manner as to satisfy the constraints specified above.

CE00369932.2 Brief description of the drawings Other features and advantages of the invention will appear on reading the following description of the preferred embodiment given by way of non-limiting illustration, and from the accompanying drawing, in which: Figure 1 shows a communications system made up of a base station transmitting an 0.0* S information stream together with accompanying indications in accordance with the invention and of terminals receiving the stream and its indications; Figure 2 shows the structure of a transmitter in accordance with the invention; and S* Figure 3 shows a particular implementation of the information stream and of its accompanying indications in the form of frames made up of two fields.

S Detailed description of the embodiments An illustration of the system according to an embodiment of the invention is given with reference to Figure 1: eo A transmitting base station 11 is connected over a radio channel 12 to three receiver stations 13, 14, and 15. The receivers 13 and 14 are capable of receiving telephony type information, the receiver 15 is capable of receiving data type information. The transmitter base station 11 transmits, over the radio channel 12, an information stream 16 containing both telephony blocks and data type information in locations that do not contain telephony blocks.

Accompanying the information stream 16, the base station 11 also transmits accompanying indications 17 over the radio channel 12, which indications contain means 18 for finding within the information stream 16 those locations which are occupied by telephony blocks. Since the stream contains only telephony blocks and/or data type information, the accompanying indications 17 enable the receiver terminals 13, 14, and 15 to determine in satisfactory manner the content of any location in the stream. It is possible to envisage that the information stream and the indications accompanying the stream are transmitted simultaneously or that they are transmitted in alternation, in which case the stream is discontinuous.

In this embodiment, the base station 11 broadcasts the data stream and the indications accompanying the stream to all of the receivers 13, 14, and 15. It is up to each receiver to pick out the information in the stream that is addressed to the receiver, in particular by means of the indications accompanying the stream.

0E00369932.2 6 Details of the transmitter base station 11 are given with reference to Figure 2: The transmitter base station has means 21 and 22 for distinguishing between the types of information to be transmitted. The means 21 can be modelled by a queue that receives the telephony blocks to be transmitted, and the means 22 can be modelled by a queue that receives the data type information to be transmitted. The means 21 and 22 can be put alternately into communication with transmitter means 262 via selector means 24, thereby enabling either telephony or data information to be transmitted. The means 21 receiving the telephony blocks is :%goo in communication with analysis means 23 which, at defined intervals, determines whether a 0 telephony block is available. If so, the analysis means controls the selector means 24 so that the o o 10 telephony block is transmitted by the transmitter means 262. Otherwise, the analysis means controls the selector means 24 so that data type information is transmitted by the transmitter means 262. The analysis means 23 is in communication with means 25 for generating indications that accompany the stream, which means are in turn in communication with transmitter means 261. The transmitter means 261 and 262 are supervised by synchronization 15 means 27 for establishing time correspondence between the indications accompanying the stream and the locations in the stream for which they indicate the type of information contained therein.

The form of the indications accompanying the stream must be such that, after acquiring the predefined time correspondence between the stream and the accompanying indications, the receivers are capable of determining the content of any location in the information stream in sufficient manner.

The data type information received in the means 22 can be structured in the form of packets, e.g. Internet protocol (IP) packets or ATM cells. The constraint consisting in transmitting telephony blocks with priority over data type information implies that a transmitted packet is broken up into pieces if, during transmission of the packet, the analysis means 23 detects that a telephony block must be transmitted. It is up to the transmission system to provide the receiver terminals with means enabling them to recognize and reconstruct the packet. To this end, it is possible to envisage data-packet-defining mechanisms that are used for reconstituting the packets with the help of check sums, header error codes, or cyclic redundancy codes.

CE00369932.2 7 In a preferred embodiment, the information stream and the indications accompanying the stream can be combined in such a manner that together they are structured in the form of frames of constant length, each frame containing at least one payload field and at least one signalling field. Every payload field contains information of the information stream, i.e. telephony blocks and data type information, and every signalling field contains indications accompanying the stream. The signalling field can also contain synchronization information enabling the receiver to determine the structure of the frame.

An illustration of this embodiment is given in Figure 3. This figure shows a succession of three frames T1, T2, and T3 of identical length and structure. The content of frame T2 is S 10 shown in detail. The signalling field 31 is made up of a sequence of bits, it may also contain a single word (not shown in the figure) enabling the receiver to find frame synchronization. The S payload field 32 is subdivided into time slots I1, 116 of identical length and selected to be equal to the length of a telephony block. The slots 2, 4, and 8 contain telephony blocks. The other slots in the payload field contain data type information. The bits of the signalling field are 15 such that the nth bit of the field represents the content of slot In in the payload field. A signalling field bit at 1 represents a telephony block and a bit at 0 represents a slot containing data type information. It is possible to envisage that the content of the signalling field of a frame qualifies the content of the payload field in the same frame or the content of the payload field in any other frame, providing means exist that enable the receiver to determine the relationship associating signalling fields with payload fields in the succession of frames.

As described above, the data type information situated in the locations of the payload field of the frame other than those locations which are occupied by telephony blocks can correspond to the content of packets that have been broken up in pieces, e.g. IP packets or ATM cells. It is then possible for the content of a packet to be transmitted while it is spread out over more than one frame.

In order to reduce the quantity of accompanying indications, it is possible to envisage defining a multiframe structure containing a defined number of frames that all possess the same organization in terms of telephony blocks and data type information. The content of the signalling fields for the frames of the multiframe defines the composition of the payload field of one frame in the multiframe and it applies to all of the payload fields in the frames of the multiframe.

CE00369932.2 8 In a particular embodiment, it is possible to envisage dimensioning the frame in such a manner that for a traditional telephone call having a data rate of 64 kbit/s, the telephony blocks of predetermined length belonging to said call are transmitted in each frame and always at the same location within the frame. This amounts to using a TDM frame structure for transmitting telephony blocks. If the telephony block is one byte long, the length of the frame must be 1.25 ps so as to achieve the data rate of 64 kbit/s. Under such circumstances, telephony is provided at a regular transmission rate and the delay of telephony blocks is compatible with the absence of an echo canceller in the transmission system.

°It will be understood that the invention disclosed and defined herein extends to all S 10 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 Sthe 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 15 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.

Claims

7. A transmission system substantially as hereinbefore described with reference to the accompanying drawings. o S
8. A receiver substantially as hereinbefore described with reference to the accompanying drawings. S
9. A transmitter substantially as hereinbefore described with reference to the accompanying drawings. Dated this 3rd day of April 2000 ALCATEL by its attorneys Freehills Carter Smith Beadle