WO2001054433A1

WO2001054433A1 - A method relating to a mobile telecommunications system

Info

Publication number: WO2001054433A1
Application number: PCT/SE2001/000099
Authority: WO
Inventors: Rolf Hansson
Original assignee: Telefonaktiebolaget Lm Ericsson (Publ)
Priority date: 2000-01-21
Filing date: 2001-01-19
Publication date: 2001-07-26
Also published as: AU2001228997A1; SE0000181L; SE0000181D0; SE515638C2

Abstract

The present invention relates to a method of handling operator-specific supplementary services in a cellular mobile telecommunications system of the TDMA-type. The invention relates particularly, but not exclusively, to the PDC system used in Japan. According to the invention, operator-specific fields that already exist are divided into different types of elements. Rules that specify how the operator-specific fields shall be used are also set-up, so as to obtain consistent use of the operator-specific fields regardless of the operator used by a subscriber. The invention contributes towards solving the problem of incompatibility between different networks and mobiles occuring when each operator uses the operator-specific fields selectively.

Description

A METHOD RELATING TO A MOBILE TELECOMMUNICATIONS SYSTEM

FIELD OF INVENTION

The present invention relates to the field of mobile telecommunications systems. More specifically, the invention relates to a method concerning operator-specific supplementary services in a cellular mobile communications system.

The invention relates particularly, although not exclusively, to a method of supporting operator-specific supplementary services in a mobile telecommunications system of the PDC- type, Personal Digi tal Cellular .

BACKGROUND OF THE INVENTION

In a digital mobile telecommunications system that uses TDMA, information is transmitted between radio nodes and one or more mobiles, where the effective information may consist of speech information in a speech connection or data information in a data connection. The information transmitted may also consist of control and synchronisation information that is sent over the speech/data channel or over channels that are intended for this purpose , so-called control channels.

Transmission is effected over given radio channels within certain frequency bands that are divided into two parts : uplink when the mobile sends to the radio node and downlink when the radio node sends to the mobile.

PDC (Personal Digital Cellular) used in Japan and described in ARIB standard RCR STD-27 is an example of a digital TDMA system. Networks and signalling systems in a digital mobile telecommunications system of the PDC-type are divided into different layers corresponding to the layers in the so-called OSI architecture. Layer 1 forms the physical link, which in a digital mobile telecommunications system is corresponded by the actual radio air interface. Layer 2 forms the data link, which in a digital mobile telecommunications system manages data transmission with the aid of the physical link in layer 1. Examples of what may be included in layer 2 are frame structures, field formats and procedure descriptions. Layer 3 contains the network, which manages end-to-end transmission with the aid of the data link in layer 2. Layer 3 contains three large blocks: RT, MM and CC . RT includes frequency control, handover and other radio channel administration. MM specifies items related to mobility administration, verification and position registration, and CC manages call control .

It is known, for instance from PCT Application 09853626, to include new fields in the signals with the purpose of providing operator-specific services. This is achieved by expanding the subscriber information with an additional field that includes an intelligent network functionality which supports a further development of the operator-specific services that are already found in the network.

SUMMARY OF THE INVENTION

An existing problem in PDC-type mobile telecommunications systems is that there are no rules or regulations that specify how operator-specific fields shall be used, which results in compatibility problems between different versions of mobile telecommunications networks and mobiles. Because the standard description RCR STD-27 includes no regulations as to how operator-specific fields shall be used, the different mobiles handle these fields in different ways. In this respect, each network operator may use the fields in a manner that is unique to itself. As a result, there is no compatibility whatsoever between different mobile telecommunications networks.

Another problem is that the operator-specific fields may have different lengths, said lengths depending on in which signal the field is included and which service shall be implemented and supported. Consequently, a mobile that does not support a certain service will not be aware of how much information can be ignored by the mobile without losing subsequent information that is required, or run the risk of reading erroneous information.

Accordingly, the object of the present invention is to solve the problems associated with the incompatibility between different networks and mobiles, by introducing rules pertaining to how the operator-specific fields shall be used, and to facilitate subscribers that do not use the service concerned.

The invention involves the use of existing operator-specific fields and dividing these fields into different types of elements. Rules that determine how the operator-specific fields shall be used are also set up, and different codes indicate which type of element is used. The codes also specify indirectly the size of the operator-specific fields.

One advantage afforded by the invention is that incompatibility problems no longer occur in use, as a result of the introduction of rules specifying how the operator- specific fields shall be used in general . Another advantage is that each network operator may have its own services and other network operators or subscribers that do not wish to use, or cannot use, the service concerned simply skip over the operator-specific field. This is readily achieved by virtue of the invention making it possible to read-off the number of octets that the operator-specific field will take-up in respect of the application in question. BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described in more detail with reference to the accompanying drawings, in which

Figure 1 illustrates a system that includes cells, mobiles and nodes;

Figure 2 illustrates the channel structure over the air interface of a PDC system;

Figure 3 is an overall view of layers 1-3 according to OSI;

Figure 4 illustrates more clearly a physical control channel in a PDC system;

Figure 5 illustrates an example of using a one octet element in an operator-specific field;

Figure 6 illustrates an example of using two octet elements in an operator-specific field; and

Figure 7 illustrates the use of multi-octet elements in an operator-specific field.

DESCRIPTION OF PREFERRED EMBODIMENTS

The inventive method is intended for a mobile telecommunications system of the TDMA-type. An example of one such system is PDC, described in ARIB standard RCR STD-27 found in Japan. Such a system includes one or more radio nodes and one or more mobiles, which communicate with each other over a given radio channel .

Figure 1 shows part of such a system, which includes the radio nodes BTS1-BTS3 and the mobiles MS1-MS3, where the mobile MS3 is situated in cell C3 covered by the radio node BTS3. The communication between the mobile MS3 and the radio node BTS3 is divided into two parts, i.e. uplink UL when the mobile transmits to the radio node and downlink DL when the radio node transmits to the mobile.

Figure 2 shows the channel structure of the air interface in respect of the aforementioned PDC system. The channel structure includes a physical control channel CCH over which control signals are sent between radio nodes and mobiles. The control channel also includes a physical traffic channel TCH, over which utility signals (speech and/or data) are transmitted. This traffic channel will not, however, be used for the transmission of the operator-specific fields in accordance with the invention.

As will be apparent from Figure 2, the control channel CCH consists of a number of special control channels, namely the broadcast control channel BCCH used to send information to all mobiles in a cell, for instance system information and channel structure information.

When transmitting the operator-specific fields in accordance with the invention, it is the aforesaid control channels BCCH and UPCH that are particularly concerned.

An example of a signal sent on downlink DL is the broadcast signal that is sent from a radio node, for instance radio node BTS1, to all mobiles that can receive the signal on the broadcast control channel BCCH. The broadcast control channel BCCH is used by the network to send different types of information to channel structures for instance, and system information.

Figure 3 shows the signal structure for the air interface in PDC, said interface consisting of three layers corresponding to the layers in the OSI model. Layer 3 in Figure 3 is responsible for functions concerning call control CC , mobile management or administration MM and radio frequency administration RT . The messages sent on the broadcast control channel BCCH include several defined fields. For instance, the messages include fields for network identity, frequency codes and other control information.

Figure 4 illustrates in more detail the signalling format for a physical control channel CCH. The whole format is 280 bits long and includes the following:

G Security bit

R = Ramping-up security time (ramp time)

P = Preamble

SW = Synchronisation word

CC = Colour code CAC = Actual control signal, e.g. PCH. BCCH, UPCH

E = Collision control bit

The word in the format relevant to the present invention is primarily the CAC word that contains the control signal, which in this example is comprised of the BCCH signalling.

The messages also include definitions of operator-specific fields, i.e. fields described in the standard description RCR STD-27. Operator-specific fields are also included in other signals, i.e. in messages pertaining to radio channel allocation sent on a packet data channel such as UPCH.

When an operator-specific service shall be used, the number of octets that shall be used is first determined on the basis of how much information space is required for the service concerned. Subsequent to having determined the number of octets required, these octets are allocated in the message to be sent and the operator-specific field is divided into elements, either one-octet elements El, E2 which contain one octet (8 bits), two-octet elements E3 which contain two octets (16 bits) or multi-octet elements E4 that contain more than two octets. The field is then coded to show which type of elements have been used for the service concerned. Figures 5a and 5b illustrate two examples of the use of one- octet elements El, E2 in the operator-specific fields. The code 01 or 10 in the two most significant bits B8 , B7 indicate that a one-octet element El, E2 has been used. The most significant bits B8 , B7 are followed by identification bits I which identify the intended use of the operator- specific field, for instance the service that shall be supported. The most significant bits B8, B7 are also followed by parameter bits P which include relevant parameters for the service to be supported, for instance.

Figure 6 illustrates an example of the use of two-octet elements E3 in the operator-specific fields. The code 11 in the two most significant bits B8 , B7 indicates that it is precisely a two-octet element E3 that is used. Identification bits I and parameter bits P are also included in the example. Element E3 thus takes-up two full octets in the operator- specific fields, i.e. one octet that includes element type coding, additional bits S for future use, and identification bits I, and also one octet that includes parameter bits P.

Figure 7 illustrates an example of the use of multi-octet elements E4 in the operator-specific fields. The code 00 in the two most significant bits B8 , B7 indicates that a multi- octet element E4 has been used. A length field LEN is used to define the size of the element E4. LEN tells the number of octets that follow the length field LEN in the operator- specific field. This enables the size of a multi-octet element E4 to be calculated, by adding LEN+2 where the two additional bits are represented by the length field LEN itself and the first octet including the coding bits B8 , B7 , additional bits S for future use, and information bits I.

In other cases where the length field LEN is not found, the size of the coding in the most significant bits B8 , B7 is given where the code 01 or 10 corresponds to a one-octet size and the code 11 corresponds to a two-octet size. It will be understood that the invention is not limited to the aforedescribed and illustrated embodiments thereof and that modifications can be made within the scope of the accompanying Claims .

Claims

1. A method relating to a mobile telecommunications system that includes a number of radio nodes (BTSl, BTS2...) adapted to communicate with mobiles (MSI, MS2...) by means of message signalling, wherein at least one signal includes predefined operator-specific fields, characterised by using the procedure according to the following steps in order to obtain rules that specify how said operator-specific fields shall be used: determining the number of octets that said operator- specific field shall include, and allocating said octets; dividing said operator-specific field into one of given type of elements: one-octet (El, E2 ) , two-octet (E3) or multi-octet (E4) ; and coding said operator-specific fields in accordance with the type of elements (El, E2 , E3...) to be used.

2. A method according to Claim 1, characterised in that when operator-specific fields occur, said message signalling consists in one case of the broadcasting signal transmitted on the broadcast control channel (BCCH) .

3. A method according to Claim 1, characterised in that when operator-specific fields occur, said message signalling is comprised in one case of messages that are sent on a packet data channel (UPCH) .

4. A method according to any one of Claims 1-3, characterised by using the binary codes 01 or 10 to show that a one-octet element (El,E2) has been used.

5. A method according to any one of Claims 1-3, characterised by using the code.11 to show that two-octet elements (E3) have been used.

6. A method according to any one of Claims 1-3, characterised by using the code 00 to show that multi-octet elements (E4) have been used.

7. A method according to any one of Claims 1-3 or Claim 6, characterised in that when multi-octet elements (E4) are used, there is included a length field (LEN) that tells the number of following elements included in the message.

8. A method according to any one of Claims 1-7, characterised by using the two most significant bits (B8, B7 ) in the operator-specific fields in said coding, to determine which type of element (El, E2 , E3...) shall be used.

9. A method according to Claim 8, characterised in that the two most significant bits (B8, B7 ) in the operator-specific fields are followed by identification bits (I) that identify the operator-specific service.

10. A method according to any one of Claims 8-9, characterised in that the two most significant bits (B8, B7 ) in the operator-specific fields are followed by parameter bits (P) that include parameters for operator-specific services .