NZ272933A

NZ272933A - Data transmission in multiframes of cellular radio system for low rate channels using different frame numbers are used for cells using a common frequency

Info

Publication number: NZ272933A
Application number: NZ272933A
Authority: NZ
Inventors: Pierre Dupuy
Original assignee: Alcatel Australia
Priority date: 1994-09-12
Filing date: 1995-09-05
Publication date: 1998-08-26
Also published as: AU687225B2; FR2724509B1; AU3031695A; FR2724509A1

Description

<div class="application article clearfix" id="description"> New Zealand No. 272933 International No. PCT/ TO BE ENTERED AFTER ACCEPTANCE AND PUBLICATION Priority dates: 12.09.1994; Complete Specification Filed: 05.09.1995 Classification:^) H04Q7/20; H04B7/26; H04J3/16; H04L5/22 Publication date: 26 August 1998 Journal No.: 1431 NEW ZEALAND PATENTS ACT 1953 COMPLETE SPECIFICATION Title of Invention: A cellular mobile radio system Name, address and nationality of applicant(s) as in international application form: ALCATEL AUSTRALIA LIMITED (ACN 000 005 363), a company of the State of New South Wales of 280 Botany Road, Alexandria, New South Wales 2015, Australia 2/293 NEW ZEALAND PATENTS ACT 1953 COMPLETE SPECIFICATION "A CELLULAR MOBILE RADIO SYSTEM" WE, ALCATEL AUSTRALIA LIMITED, CAC-n coo 005 3fe^) A Company of the State of New South Wales, of 280 Botany Road, Alexandria, New South Wales, 2015, Australia, hereby declare the invention for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: 1 This invention relates to cellular radio systems, in particular cellular mobile radio systems such as the GSM system. The preseni invention relates more specifically to such systems where data to be transmitted is transmitted according to a time-division multiplex structure, and more specifically according to a time-division multiplex structure including a superframe structure where certain frame numbers are reserved for the transmission of low rate channels. Here are some examples of such low rate channels in the GSM system: the signalling channels referred to as SACCH (Slow Associated Control Channel), the channels reserved for the transmission of "comfort noise" in the absence of voice data, according to the known technique called DTX (Discontinuous Transmission). Hence, in the GSM system, a "26-frame multiframe" has its first 1 2 frames reserved for the transmission of traffic channels, the following frame is reserved for the transmission of SACCH channels, and the next twelve frames are reserved for the transmission of traffic channels. Furthermore, to take into account coding of the data to be transmitted, which in the GSM system, leads to splitting a coded data block into sub-blocks transmitted over two times four consecutive frames, a "104-frame multiframe" must be defined, it is obtained by grouping 4 consecutive "26-frame multiframes". Such a "104-frame multiframe" structure is shown in figure 1, corresponding to a multiframe carrying full rate channels. Indeed, it is reminded that the GSM system caters for two different rates, full rate and half rate respectively, depending on the coding type used to code the data to be transmitted. Figure 1 represents a tabk *<i which the column numbers correspond to the number of frames in a multiframe, 0 to 103 in this instance, and in which the row numbers correspond to the number of time slots in a frame, 0 to 7 in this instance. To keep this figure simple, only those locations occupied by SACCH channels or by channels carrying comfort noise in the absence of voice have been illustrated ; the former being represented by black rectangles occupying, depending on the time slot considered, one of the frame numbers 12, 25, 38, 51, 64, 77, 90, 103, and the latter being represented by hashed rectangles occupying frame numbers 52 to 59. The present invention relates more specifically to such radio communications systems being also of the cellular type (which is the case for the above mentioned GSM system), i.e. where the same carrier frequency can be used in several cells, for instance in seven cells marked CO to C6 when dealing with a seven cell re-utilisation pattern as shown in figure 2. In such systems, interference reduction is a major concern. One method of reducing this interference consists precisely, in the case of the GSM system, of using the discontinuous transmission technique mentioned above. Nevertheless, the actual structure of a "104-frame multiframe" is such that the multifrarnes carried by the same carrier frequency likely to be used in different 5 10 15 2 / 2 y 6 3 cells have the same structure (the structure shown in figure 1). Even when dealing with discontinuous transmission, the risk of interference still remains, especially in synchronous systems, due to the very transmission of the said low rate channels, which indeed continue to be transmitted in such a case. The present invention aims particularly at preventing or reducing these drawbacks. A solution to this problem was suggested in GSM recommendation 03.30 and consists of using a time shift between time bases of base stations relating to cells likely to use at least one common frequency. Nevertheless, this solution presents some drawbacks, two of which are to be noted: • time sharing of frequencies between cells cannot be used efficiently with a different time base in each base station. • synchronous handover between different base stations becomes impossible. The present invention permits in particular to avoid these drawbacks. Hence, an object of the present invention is a cellular mobile radio system where data to be transmitted is transmitted according to a time-division multiplex structure including a multiframe structure where certain frame numbers are reserved for the transmission of low rate channels, this system being essentially characterised in that, all or some of these numbers are different for the various cells within this system which are likely to use at least one common frequency. 4 Another object of the invention is a transmitting or receiving device for such a system. In order that the invention may be readily carried into effect, embodiments thereof will now be described in relation to the accompanying drawings, in which: • Figure 1, previously described, illustrates a multiframe structure in accordance with the previous art, for a multiframe carrying full rate channels. • Figure 2, previously described, is a reminder of the structure of a cellular radio system. • Figures 3, 4 and 5 respectively illustrate a first, a second and a third example of multiframe structure in accordance with the present invention, when dealing with a multiframe carrying half rate channels. • Figure 6 is a schematic illustration of a means to generate a multiframe structure for a system in accordance with the present invention. Figures 3, 4 and 5 show, for one example and for a given time slot, the frame number of a "104-frame multiframe" in which are transmitted the SACCH channels (shown as black rectangles) and the channels carrying data relating to comfort noise (shown as hashed rectangles). Figures 3, 4 and 5 are represented in table form, the frame numbers from 0 to 103 appearing as column headings while the cell numbers appear as row headings. 5 10 In the example illustrated in figures 3, 4 and 5, cell numbers may vary from 0 to 7. This numerical example corresponds in particular to the case whereby, in order to differentiate the various cells likely to use at least one common frequency, we use a parameter already used in the GSM system, such as the parameter called BSIC (Base Station Identity Code), as described for instance in the book "The GSM System for Mobile Communications" Michel MO'JLY, Marie-Bernadette PAUTHET (p. 336-339), or the parameter consisting of the type of training sequence used, as described for instance in pages 232 to 234 of the above mentioned book. When the cells to be differentiated consist of the 7 cells CO to C6 of a re-utilisation pattern such as shown in figure 2, one of the 8 rows numbered 0 to 7 in figures 3 and 4 tables is not used. Nevertheless, there are other ways of differentiating the various cells likely to use at least one common frequency. The first row (not numbered) in figures 3 and 4 tables reminds us the frame numbers within a "104-frame multiframe" in which are transmitted the low rate channels considered, when dealing with a multiframe carrying full rate channels, and as an example when dealing with time slot number 0. In figure 3, the multiframe structures relating to the various cells likely to use at least one common frequency have been optimised such that a minimum number of low rate channels relating to these various cells be transmitted in the same frame number. In the selected GSM system example, with "104-frame multiframes" and cell 6 2/2933 numbers likely to vary from 0 to 7, it is indeed impossible for all low rate channels to be transmitted in different frame numbers. Nevertheless, it is conceivable to envisage other examples where the said low rate channels would all be transmitted in different frame numbers. In figure 4, the multiframe structures relating to the various cells have been optimised such that no low rate channel relating to a multiframe carrying half rate channels be transmitted in a frame number already occupied by a low rate channel relating to a multiframe carrying full rate channels. When dealing with systems where multiframes carrying full rate channels coexist with multiframes carrying half rate channels, figure 4 example could be a better choice. When dealing with systems where the only existing multiframes are multiframes carrying half rate channels, figure 3 example could be a better choice. The structure of multiframes relating to the various cells likely to use at least one common frequency, as shown in figure 5, are a compromise between the goals sought in figures 3 and 4 and a greater evenness in the distribution of frames. It is reminded that in the GSM system, a half rate channel is split into two sub-channels, respectively called sub-channel 0 and sub-channel 1. Thus, as an example, in figure 3, the SACCH channels occupy: • For cell 0: Frames 8, 34, 60, 86, for sub-channel 0 Frames 21, 47, 73, 99, for sub-channel 1 For cell 1: Frames 9, 35, 61, 87, for sub-channel 0 Frames 22, 48, 74, 100, for sub-channel 1 For cell 2: Frames 10, 36, 62, 88, for sub-channel 0 Frames 23, 49, 75, 101, for sub-channel 1 For cell 3: Frames 11, 37, 63, 89, for sub-channel 0 Frames 24, 50, 76, 102, for sub-channel 1 For cell 4: Frames 7, 33, 59, 85, for sub-channel 0 Frames 20, 46, 72, 98, for sub-channel 1 For cell 5: Frames 0, 26, 52, 78, , for sub-channel 0 Frames 13, 39, 65, 91, for sub-channel 1 For cell 6: Frames 1, 27, 53, 79, for sub-channel 0 Frames 14, 40, 66, 92, for sub-channel 1 For cell 7: Frames 2, ^8, 54, 80, for sub-channel 0 / k. y Frames 15, 41, 67, 93, for sub-channel 1 Thus, as an example, in figure 3, the channels carrying data relating to comfort noise in the absence of voice activity occupy: • For cell 0: Frames 91, 93, 95, 97, for sub-channel 0 Frames 92, 94, 96, 98, for sub-channel 1 • For cell 1: Frames 79, 81, 83, 85, for sub-channel 0 Frames 80, 82, 84, 86, for sub-channel 1 • For cell 2: Frames 67, 69, 71, 73, for sub-channel 0 Frames 68, 70, 72, 74, for sub-channel 1 • For cell 3: Frames 3, 5, 7, 9, for sub-channel 0 Frames 4, 6, 8, 10, for sub-channel 1 • For cell 4: Frames 99, 101,103, 1, for sub-channel 0 Frames 100, 102, 0, 2, for sub-channel 1 • For cell 5: Frames 44, 46, 48, 50, for sub-channel 0 Frames 45, 47, 49, 51, for sub-channel 1 2/293 For cell 6: Frames 19, 21, 23, 25, for sub-channel 0 Frames 20, 22, 24, 26, for sub-channel 1 For cell 7: Frames 29, 31, 33, 35, for sub-channel 0 Frames 30, 32, 34, 36, for sub-channel 1 As an example, in figure 4, the SACCH channels occupy: For cells 0 to 3: the same frame numbers as in figure 3 For cells 4 to 7: the same frame numbers as for cells 0 to 3 respectively As an example, in figure 4, the channels carrying data relating to comfort the absence of voice activity occupy: For cell 0: Frames 0, 2, 4, 6, for sub-channel 0 Frames 1, 3, 5, 7, for sub-channel 1 For cell 1: Frames 14, 16, 18, 20, for sub-channel 0 Frames 15, 17, 19, 21, for sub-channel 1 For cell 2: Frames 28, 30, 32, 34, for sub-channel 0 Frames 29, 31, 33, 35, for sub-channel 1 For cell 3: 10 2~/' L ) li ' ! T / l b J 0 Frames 42, 44, 46, 48, for sub-channel 0 Frames 43, 45, 47, 49, for sub-channel 1 • For cell 4: Frames 65, 67, 69, 71, for sub-channel 0 Frames 66, 68, 70, 72, for sub-channel 1 • For cell 5: Frames 79, 81, 83, 85, for sub-channel 0 Frames 80, 82, 84, 86, for sub-channel 1 • For cell 6: Frames 93, 95, 97, 99, for sub-channel 0 Frames 94, 96, 98, 100, for sub-channel 1 • For cell 1\ Frames 3, 5, 7, 9, for sub-channel 0 Frames 4, 6, 8, 10, for sub-channel 1 To take into account the shift of 13 which exists, in the multiframe structure carrying full rate channels, between frame numbers occupied by the SACCH channels for consecutive time slots, a similar shift shall be applied to figure 4 SACCH channels. In figure 5, for cell number n, the SACCH channels occupy as an example the frames numbered FN-1 -n, where FN designates the frame numbers occupied by the SACCH channel relating to a multiframe carrying full rate channels. In 11 5 10 15 272933 relation with the case whereby they would occupy the frames numbered FN-n, this makes it possible to prevent interference between SACCH channels relating to multiframes carrying full rate channels and multiframes carrying half rate channels. In figure 5, for cell number n, the channels carrying comfort noise in the absence of voice activity occupy for instance: • for sub-channel 0: frames 12 + 13n, 14+13n, 16+1 3n, 18+ 13n • for sub-channel 1: frames 13+13n, 15+1 3n, 17+1 3n, 19+ 1 3n Another objective of the present invention is a transmitting or receiving device for such a system. A transmitting or receiving device for a system where data to be transmitted is transmitted according to a time-division multiplex structure including a multiframe structure, is conventionally fitted with some means of generating a multiframe structure, these means generally consisting of a set of counters incremented by a clock signal characteristic of the transmitted data rate. In a transmitting or receiving device in accordance with the invention, these means of generating a multiframe structure are such that all or some of the frame numbers reserved for the transmission of low rate channels are different for the various cells likely to use at least one common frequency, as described previously. As previously mentioned, in the GSM system, an advantageous way of differentiating the various cells likely to use at least one common frequency consists of using an already existing parameter, such as the Base Station Identity Code 12 27^9 33 (BSIC) or the parameter consisting of the type of training sequence used. As shown in figure 6, the means of generating a multiframe structure (M), which can still consist of a set of counters, then receives one of these parameters (N), in addition 5 to the said clock signal (H), to supply a multiframe structure (S). 13 </div>

Claims

<div class="application article clearfix printTableText" id="claims"> 10 15 What we claim is:

1. A cellular mobile radio system where data to be transmitted is transmitted according to a time-division multiplex structure including a multiframe structure where certain frame numbers are reserved for the transmission of low rate channels, wherein all or some of these numbers are different for the various cells within this system which are likely to use at least one common frequency.

2. A cellular mobile radio system as claimed in claim 1, wherein said low rate channels are signalling channels.

3. A cellular mobile radio system as claimed in claim 1, wherein said low rate channels are channels carrying data relating to comfort noise in the absence of voice activity, when dealing with discontinuous transmission.

4. A cellular mobile radio system as claimed in any one of claims 1 to 3, where .r, multiframe structures within each cell can be of two types, one type carrying half rate channels, the other type carrying full rate channels, furthermore, all or some of the said numbers being different for these two possible types of multiframe.

5. A cellular mobile radio system as claimed in any one of the preceding claims of the GSM type, wherein various cells likely to use at least one common frequency are differentiated by means of a paramefer called Base Station Identity Code.

6. A cellular mobile radio system as claimed in any one of claims 1 to 4, of the GSM type, wherein various cells likely to use at least one common frequency are differentiated by means of a parameter consisting of the type of training sequence used.

7. A transmitting or receiving device for a cellular radio system, where data to be transmitted is transmitted according to a time-division multiplex structure including a multiframe structure where certain frame numbers are reserved for the transmission of low rate channels, the device being fitted with means for generating 14 a multiframe structure, wherein means of generating a multiframe structure are such that all or some of these numbers are different for the various cells within this system which are likely to use at least one common frequency.

8. A device as claimed in claim 7, for a GSM type system, wherein said means for generating a multiframe structure receives a parameter called Base Station Identity Code, in order to differentiate the various cells likely to use ai least one common frequency.

9. A device as claimed in claim 7, for a GSM type system, wherein said means for generating a multiframe structure receives a parameter comprising a type of training sequence used, in order to differentiate the various cells likely to use at least one common frequency.

10. A cellular mobile radio system substantially as herein described with reference to Figures 3-6 of the accompanying drawings.

11. A device substantially as herein described with reference to Figures 3 - 6 of the accompanying drawings. ALCATEL AUSTRALIA LIMITED B. O'Connor Authorized Agent P5/1/1 703 15 </div>