EP1142388A1

EP1142388A1 - Data transmission method between base station and mobile switching center

Info

Publication number: EP1142388A1
Application number: EP99965648A
Authority: EP
Inventors: Birgitta SJÖQVIST-ERIKSSON; Ingemar Johansson
Original assignee: Telefonaktiebolaget LM Ericsson AB
Current assignee: Telefonaktiebolaget LM Ericsson AB
Priority date: 1998-12-31
Filing date: 1999-12-14
Publication date: 2001-10-10
Also published as: AU2134000A; CN1332941A; WO2000041420A1; KR20010103732A; JP2002534928A

Abstract

The present invention provides a system and method for merging packet data, speech and fax/modem communications within the same communication protocol. According to exemplary embodiments of the present invention, the unused Mode Code values of a conventional TTL frame are tailored so as to allow for the integration of packet data together with speech and fax/modem in a TTL frame. As a result, communication resources are more efficiently utilized.

Description

DATA TRANSMISSION METHOD BETWEEN BASE STATION AND MOBILE SWITCHING CENTER

BACKGROUND

The present invention relates generally to radio communication systems and, more particularly, to a system and method for integrating speech, fax/modem and packet data in a cost-effective manner.

The growth of commercial communication systems and, in particular, the explosive growth of cellular radiotelephone systems, have compelled system designers to search for ways to increase system capacity without reducing communication quality beyond consumer tolerance thresholds. At the same time usage of mobile communication equipment for transmission of data rather than speech has become increasingly popular by consumers. The possibility to send and receive electronic mail and to use a web browser to obtain world-wide-web access is frequently discussed as services that are desirable for wireless communication systems. As a response to this, communication system designers search for ways to efficiently transfer data information to and from mobile users.

There are fundamental differences between requirements for data communication and e.g., speech communication. For example, delay requirements are higher for speech, which is a real time service, and the error requirements are higher for data communications, while the delay constraints are lower. The use of packet data protocols, which are more suitable for transmission of data than circuit-switched protocols, has started to find its way into cellular communication systems. In order to handle frequent traffic of small volumes of data or bursty traffic, such as those associated with browsing the Internet, packet-switched networks are preferred for providing a mobile packet data service, which are defined by such standards as General Packet Radio Service (GPRS), Cellular Digital Packet Data (CDPD) and Personal Digital Cellular (PDC). Unlike circuit- switched data services, the mobile packet data services do not require dedicated use of the radio resources. For example, under the GPRS standard, each packet of data contains a destination address which provides for fast set up and allows multiple users to share a radio resource. Packet service integration in both Global System for Mobile communication

(GSM) cellular systems as well as Digital Advanced Mobile Phone System CD- AMPS) cellular systems is presently being standardized. Today, GSM systems provide a circuit-switched data service, which can be used to interconnect with external data networks. The circuit-switched data service is used for both circuit- switched as well as packet-switched data communication. To make packet- switched data communications more efficient, a new packet-switched data service called General Packet Radio Services (GPRS) has been introduced as a part of GSM. Since GPRS is a GSM service, parts of the GSM infrastructure will be used. Those parts of the GSM communication system are described in European Telecommunication Standard Institute (ETSI) document ETS 300 574 which is incorporated by reference herein.

GPRS will allow for packet-switched communication and will support both a connectionless protocol (e.g., IP) as well as a connection-oriented protocol (e.g., X.25). Every channel is configured for either circuit-switched or packet-switched traffic. One of the advantages with a packet-switched data communication protocol is that a single transmission resource can be shared between a number of users. Thus, in the case of e.g., a GSM cellular system, a timeslot on a radio frequency carrier can be utilized by several mobile users for reception and transmission of data. The shared transmission resource is managed by the network side of the cellular system both for downlink and uplink transmissions.

Figure 1 illustrates an exemplary radio frequency band supporting both circuit-switched and packet-switched traffic in a GPRS system. The exemplary radio frequency band, as illustrated in Figure 1, is divided into 8 timeslots. A timeslot can support a single speech call, a single fax/modem call, or one or more packet data users. For example, timeslot 1 is assigned to speech call 1 and timeslot 2 is shared by GPRS users 1-3.

GPRS is very flexible in that it allows for the integration of both speech and packet data traffic on a single carrier. However, it also requires considerably more bandwidth than other packet data systems. GPRS requires 25 KHz per timeslot compared to 10 KHz per timeslot for other systems (e.g., CDPD).

The CDPD system, which is part of D-AMPS, and the PDC system set forth different approaches than that described above for providing packet data communications. In the CDPD system, specific base stations are dedicated to handling packet data transmissions. As such, speech and packet data traffic are not mixed. In the PDC system, a base station comprises separate transceivers for handling packet data communications. As with the CDPD system, speech and packet data traffic are not mixed. Conventional approaches for providing packet data have failed to efficiently integrate packet data, speech and fax/modem traffic. In an attempt to provide both packet data and speech communications, conventional system have dedicated specific base stations, transceivers and channels for handling packet data transmissions. As a result, communication resources are inefficiently utilized. Moreover, since the cost of a transmission channel is often expensive, these conventional approaches have resulted in systems which are not cost-effective.

There exists a need for a system which integrates speech, fax/modem and packet data communications in a cost-effective manner.

SUMMARY The present invention seeks to overcome the above-identified deficiencies by providing a system and method for merging packet data, speech and fax/modem communications within the same communication protocol. According to exemplary embodiments of the present invention, the unused Mode Code values of a conventional TTL frame are tailored so as to allow for the integration of packet data together with speech and fax/modem in a TTL frame. As a result, communication resources are more efficiently utilized.

BRIEF DESCRIPTION OF THE DRAWINGS

The above objects and features of the present invention will be more apparent from the following description of the preferred embodiments with reference to the accompanying drawings, wherein:

Figure 1 illustrates an exemplary radio frequency band supporting both circuit-switched and packet-switched traffic in a GPRS system;

Figure 2 illustrates a conventional PDC radio communication system; Figure 3 illustrates the base station 210 and MSC 220 of Figure 2 in more detail;

Figure 4 illustrates a conventional TTL frame which can contain either speech and/or fax/modem information or packet data information; and

Figure 5 illustrates a base station and MSC according to exemplary embodiments of the present invention.

DETAILED DESCRIPTION

In the following description, for purposes of explanation and not limitation, specific details are set forth, such as particular circuits, circuit components, techniques, etc. in order to provide a thorough understanding of the present invention. However, it will be apparent to one skilled in the art that the present invention may be practiced in other embodiments that depart from these specific details. In other instances, detailed descriptions of well-known methods, devices, and circuits are omitted so as not to obscure the description of the present invention. The exemplary radio communication systems discussed herein are described as using the TRA-TRX Link (TTL) protocol, in which communication between the base station and the mobile services switching center is performed over a TTL frame. However, those skilled in the art will appreciate that the concepts disclosed herein is equally applicable to other protocols. Likewise, some of the exemplary embodiments provide illustrative examples relating to the PDC system, however, the techniques described herein are equally applicable to radio base stations in any system.

Figure 2 illustrates a conventional PDC radio communication system. In Figure 2, the conventional system includes a plurality of mobile stations (MS)

200,-200_N, a base station (BS) 210, a mobile services switching center (MSC) 220, a packet mobile services switching center (PMSC) 230 which is connected to a packet network 250, such as the Internet, and a public switched telephone network (PSTN) 240. In operation, the plurality of mobile stations 200_r200_N communicate with base station 210 in a well known manner. Each of mobile stations 200,-200_N is capable of transmitting speech, fax/modem data and/or packet data. The base station 210 receives information from the mobile stations via transceivers, processes the information and forwards the processed information to the MSC 220. One skilled in the art will appreciate that the base station 210 also receives information from MSC 220 and transfers such information to one or more mobile stations. According to this conventional system, the base station comprises separate transceivers for handling speech and fax/modem communications and for handling packet data communications.

At the MSC 220, information from the base station 210 is routed to its destination (i.e., the PSTN 240 when the information is speech or fax/modem data and through the PMSC 230 to its destination on the packet data network 250 when the information is packet data). One skilled in the art will appreciate that the network illustrated in Figure 2 would typically include other components, such as routers (not shown), which aid in the reception, processing and transmission of information in the network. Moreover, the number of components depicted in Figure 2 is provided merely for the sake of simplicity. Radio communication systems generally include multiple base stations, MSCs, PMSCs, etc. Figure 3 illustrates the base station 210 and MSC 220 of Figure 2 in more detail. In Figure 3, the base station 210 comprises two transceivers, TRX 212 and TRX 213, which receive information from and transmit information to mobile stations 200 200_N via antennas 215 and 216, respectively. One of the transceivers, for example TRX 212, handles only packet data communications while the other transceiver, TRX 213, handles communications which involve speech and fax/modem transmissions. Base station 210 also comprises a control unit (CU) 214 for controlling the routing of information over the wire line 250 that connects the base station 210 and the MSC 220.

The MSC 220 comprises a transcoder and rate adapter board (TRAB) 222 which processes information received in the MSC 220 in a well known manner. TRAB 222 is associated with transceiver 213. As a result, TRAB 222 processes speech and modem/fax information and transfers and receives information from the PSTN 240. TRX 212, on the other hand, is not associated with a TRAB. As such, TRX 212 is almost directly connected to the PMSC 230. The MSC 220 also includes exchange terminal circuits 221, 224 and 225 which operate as switches for transferring data to its appropriate destination. One skilled in the art will appreciate that a typical base station and MSC would generally include more components than those illustrated in Figure 3 that aid in receiving, transmitting, and processing of information. As indicated above, base station 210 comprises a transceiver, TRX 213, for handling speech and fax/modem communications and a transceiver, TRX 212, for handling packet data communications. Transceivers 212 and 213 communicate with MSC via wire line 250. Communications between TRX 213 and TRAB 222 are made using the TTL protocol. The TTL protocol is described in detail in the document entitled "Signal Description, TRA-TRX with IMUX/HR," 10/15 14- ANT 244 02, Rev. A, which is incorporated by reference herein and attached as Appendix A. Communications between the TRX 212 and the PMSC 230, on the other hand, are made using a different protocol (referred to hereinafter as the

"Conventional Packet Data Protocol"). This protocol requires a separate channel on the wire line 250.

Figure 4 illustrates a conventional TTL frame which can contain speech and/or fax/modem information. In Figure 4, the conventional TTL frame comprises a header field which contains, among other things, synchronization information, two sub-frames and a tail frame. Each sub-frame comprises three TTL-individuals and an extension field. The term "TTL-individual" is used to designate the TTL resource being allocated to a particular TRX and TRAB pair. Each TTL-individual comprises a data field and a control field. Each data field of a particular frame includes, as set forth above, speech and/or fax/modem information. Each control field of a TTL-individual comprises the following sub- fields: a Quality Information sub-field, a Dummy Data Indication sub-field, a Mode Code sub-field, and a Cyclic Redundancy Check (CRC) sub-field.

Conventionally, the Mode Code sub-field was used in the TTL protocol to identify /distinguish between different types and rates of service. The coding of the conventional Mode Code sub-field is provided below in Table 1. As illustrated, the conventional TTL protocol does not make use of Mode Code values 8-14. As a result, these values are available for adapting the TTL protocol for future services. Table 1

In Table 1, "A-S/FR" indicates an Active-Speech full rate mode, "A-S/HR" indicates an Active-Speech half rate mode, "T-C/FR" indicates a Through-Connect full rate mode, "T-C/HR" indicates a Through-Connect half rate mode, "N-S/FR" indicates a Non-Speech full rate mode and "N-S/HR" indicates a Non-Speech half rate mode. As indicated above, the conventional TTL protocol does not provide the ability to integrate speech and packet data information in a single TTL frame. As such, TTL frames are dedicated to speech and/or fax/modem information resulting in transceivers, which act together with TRABs, being dedicated to only speech and/or fax/modem information. One skilled in the art will appreciate that, due to this constraint, instances exist where conventional TTL frames are transmitted with unoccupied TTL individuals thereby wasting valuable communication resources. For example, consider that speech information, which would occupy the data fields of four TTL individuals, and packet data, with an information bandwidth which would fit into the data fields of two TTL individuals, are to be transferred from a base station to a MSC. Using the conventional TTL protocol, speech information may, for example, be transferred in TTL individuals 0, 1, 3 and 4 of a TTL frame which would leave TTL individual 2 and 5 unoccupied. Even though the packet data could be transmitted in the data fields of two TTL individuals and thus occupy TTL individuals 2 and 5, the conventional TTL protocol would have refused that packet data transmission, and thus required the packet data to be transferred via the Conventional Packet Data Protocol, using a separate MSC-to-BS channel.

Thus, conventional attempts to provide packet data communications in a radio communication environment have resulted in specific base stations, transceivers or channels being dedicated for handling such communications. These conventional approaches make inefficient use of communication resources. The present invention provides a method and system for integrating packet data communications with speech and fax/modem communications in a cost-effective manner. Figure 5 illustrates a base station 310 and MSC 320 according to exemplary embodiments of the present invention. As illustrated, the base station 310 includes two transceivers TRX 312 and TRX 313, which communicate with one or more mobile stations via antennas 315 and 316, respectively. According to the present invention, both transceivers 312 and 313 are capable of handling packet data, speech and fax/modem communications. Similar to the system illustrated in Figure 3 above, the control unit (CU) 314 controls the transfer of information over the wire line 250 that connects the base station 310 and the MSC 320. The exemplary MSC 320 comprises two transcoder and rate adapter boards, TRAB 322 and TRAB 323. According to the present embodiment, both TRAB 322 and TRAB 323 are capable of handling packet data, speech and fax/modem information. As such, each TRAB is connected to both the PMSC 230 and the PSTN 240. For speech and/or fax/modem transmissions, as set forth above, the TRABs process the information in a well known manner. For packet data transmissions, on the other hand, the TRAB simply routes the data to its intended destination. The conventional TRAB could be modified to perform the above-identified functionality via software reprograrnming.

Similar to the conventional system, base station 310 and MSC 320 communicate using the TTL protocol. However, according to the present invention, the TTL protocol allows for packet data, speech and fax/modem communications to be integrated within a single TTL frame. The present invention utilizes the unused Mode Code values 8-13 of a TTL-individual control field to indicate packet data information. Table 2 illustrates new Mode Codes for values 8-13 of the TTL protocol.

Table 2

One skilled in the art will appreciate that the above-identified Mode Codes are merely exemplary and that the Mode Codes could be tailored in other ways so as to meet specific network needs.

The following example illustrates the benefits of the present invention.

Suppose once again that a base station wants to transfer speech information, which would occupy the data fields of four TTL individuals, and packet data, with an information bandwidth which would fit into the data fields of two TTL individuals, to the MSC. According to conventional techniques, the speech information and packet data would have to be transferred in separate MSC-to-BS channels, where one TRAB-TRX pair is involved in the speech transmission and another TRX is involved in the packet data transmission. However, according to the present invention, a single TRX-TRAB pair and a single MSC-to-BS channel can be used to transmit both the speech information and the packet data. Moreover, the modification to the TTL protocol would allow for the transmission of packet data along with speech and/or fax/modem information in a TTL frame. As a result, valuable communication resources are more efficiently utilized. The above-described system and method for integrating packet data, speech and fax/modem communications within a single TTL frame is both easy to implement and cost-effective. This packet data/speech/fax/modem integration procedure can be implemented through software programming without the need for replacing hardware components. By integrating packet data, speech and fax/modem communications within a single TTL frame, the present invention makes more efficient use of information bandwidth. The present invention also allows for a single transceiver to be configured to handle packet data, speech and fax/modem communications, thereby eliminating the need for dedicated transceivers. As a result, the present invention makes efficient use of communication resources.

The foregoing has described the principles, preferred embodiments and modes of operation of the present invention. However, the invention should not be construed as being limited to the particular embodiments discussed above. Thus, the above-described embodiments should be regarded as illustrative rather than restrictive, and it should be appreciated that variations may be made in those embodiments by workers skilled in the art without departing from the scope of the present invention as defined by the following claims.

Claims

IN THE CLAIMS:

1. A method for transmitting both data and non-data information between a base station and a mobile services switching center using a communication protocol, said method comprising the step of: transmitting both said data and said non-data information within a single frame of said communications protocol.

2. The method of claim 1 wherein said non-data information is speech information.

3. The method of claim 1 wherein said non-data information is fax/modem information.

4. The method of claim 1 wherein said communications protocol is a TTL protocol.

5. The method of claim 4 wherein said single frame includes a plurality of individuals, at least one of said individuals carrying said data and at least one of said individuals carrying said non-data information.

6. The method of claim 5 wherein each individual includes a plurality of sub-fields at least one of which identifies the individual as carrying data or non- data information.

7. A system comprising: means for transmitting data and non-data information within a single frame of a communications protocol; means for receiving said single frame and for routing said data to a first destination and for routing said non-data information to a second destination.

8. The system of claim 7 wherein said non-data information is speech information.

9. The system of claim 7 wherein said non-data information is fax/modem information.

10. The system of claim 7 wherein said non-data information is both speech and fax/modem information.

11. The system of claim 7 wherein said communications protocol is a TTL protocol.

12. The system of claim 11 wherein said single frame includes a plurality of individuals, at least one of said individuals carrying said data and at least one of said individuals carrying said non-data.

13. The system of claim 12 wherein each individual includes a plurality of sub-fields at least one of which identifies the individual as carrying data or non- data information.

14. The system of claim 7 wherein said first destination is a packet data network and said second destination is a telephone network.

15. A base station comprising: at least one transceiver for handling data and non-data information and for routing said data and non-data information according to a communications protocol, wherein data and non-data information are routed by said at least one transceiver within a single frame of said communications protocol.

16. The base station of claim 15 wherein said communications protocol is a TTL protocol.

17. The base station of claim 16 wherein said single frame includes a plurality of individuals, at least one of said individuals carrying said data and at least one of said individuals carrying said non-data.

18. The system of claim 17 wherein each individual includes a plurality of sub-fields at least one of which identifies the individual as carrying data or non- data information.