MXPA97002008A

MXPA97002008A - Control signal transmission in radiotelefonia digi

Info

Publication number: MXPA97002008A
Application number: MXPA/A/1997/002008A
Authority: MX
Inventors: John Albrow Richard; Maxwell Martin Paul
Original assignee: Ionica L3 Limited
Priority date: 1994-09-16
Filing date: 1997-03-17
Publication date: 1998-04-01

Abstract

The present invention relates to the transmission between a base station and a subscriber station, the system control signals are sent in seconds of time within time frames of fixed length. The control signals of the system are fragmented, each fragment being sent in a time segment different from a quad

Description

CONTROL SIGNAL TRANSMISSION IN DIGITAL RADIOTELEPHONY This invention relates to the transmission of system control signals in time segments within time frames of fixed length. In time division / time division multiple access (TDM / TDMA) multiple systems, the system control signals are transmitted from a base station to associated subscriber units. These system control signals may be warning messages directed to a specific subscriber unit. They can be messages that host traffic channels in response to a request from a subscriber unit to establish a call. The system control signals may include specific user messages, directed and sent to a specific subscriber unit even though the traffic channel has not been housed. The control messages may include a list (Aloha segment list) of channels available for subscriber units for the transmission of call set-up requests. In conventional TDM / TDMA systems such as GSM systems (Global System for Mobile communications), the system control signals are sent on a dedicated channel, i.e., a segment in each TDM box from the base station to the unit Subscriber is dedicated to such signage. This is known as a Transmission channel. The present invention is defined in the claims to which reference should now be made. The present invention preferably provides a method of transmitting system control signals between a base station and the subscriber units in a TDM / TDMA system, the control signals comprising data units, in which each data unit is fragmented, each fragment being sent in a different time segment of a frame. The transmission is preferably from a base station to the subscriber units. The present invention also relates to a method of receiving control signals from a base station in a subscriber unit in a TDM / TDMA system, wherein the fragments of control signal data are received in a subscriber unit during the time for recombination to provide control signals, each fragment having been sent in a different time segment of a TDM frame. The present invention also relates to a base station including operational control signal fragmentation means for fragmenting control signals into predetermined portions of different TDM time segments for transmission and transmission means. The present invention preferably further provides a subscriber unit that includes reception means operative to receive signals from a base station, operational selection means to distinguish fragments of system control signal, and recombination means to recombine the fragments to provide the signals of system control in the subscribing unit. The present invention has the advantage of avoiding the need for a dedicated transmission channel. Preferably, the control fragments of the system are of a predetermined length and take a predetermined position within each segment. The fragments can be of equal fixed length. Each segment may also include other data such as spoken data. A TDM frame, preferably of ten segments, includes a fragment in each segment. Accordingly, the control signals of the system that are encoded in standard length data units are fragmented so that each data unit provides ten fragments of equal length. Each data unit may include a header and error correction data in addition to the system control signaling. The error correction data can be cyclic redundancy check (CRC) data. The correct transmission of control signals of the system is further preferably protected by forward error correction (FEC) in the TDM frame. The system control data units are preferably duplicated on all radiofrequency carriers transmitted from a base station; and the transmission of TDM frames over all those radiofrequency carriers are synchronized. Accordingly, a subscriber unit can correctly receive control signaling from the system regardless of which RF carrier is received. A preferred embodiment of the present invention will now be described, by way of example, with reference to the drawings in which: Figure 1 is a schematic diagram illustrating the system including a base station (BTE-Base Terminal Equipment) and a subscriber unit (NTE-Network Terminal Equipment); Figure 2 is a diagram illustrating the frame structure and time control for a double link; Figure 3 is a block diagram illustrating the basic equipment for the communication of control signals; and Figure 4 is a diagram illustrating the fragmentation of control signals (BROADCAST DATA) in a control signaling data unit (PDU) for transmission in predetermined portions of the segments within a TDM frame. downlink and, subsequent recombination.

The Basic System As shown in Fig. 1, the preferred system is part of a telephone system in which the local wired circuit from the switch to the subscriber has been replaced by a full double radio link between a base station fixed and a fixed subscriber unit. The preferred system includes the double radio link and the transmitters and receivers to implement the necessary protocol. There are similarities between the preferred system and digital cellular mobile phone systems such as GSM that are known in the art. This system uses a protocol based on a layered model, in particular, the following layers: PHY (Physical), -MAC (Medium Access Control), DLC (Data Link Control), NWK (Network). One difference compared to GSM is that, in the preferred system, the subscriber units are in fixed locations and there is no need for loose layouts or other features that relate to mobility. This means, for example, that directional antenna and main electricity can be used in the preferred system. Each base station in the preferred system provides six double radio links on twelve frequencies selected from the general frequency housing, to minimize interference between nearby base stations. The frame structure and time control for the double link are shown in Figure 2. Each double radio link comprises an uplink from a subscriber unit to a base station and, in a fixed frequency offset, a downlink from the base station to the subscribing unit. The downlinks are TDM and the uplinks are TDMA. The modulation of all the links is p / 4 - DPQPSK and the basic structure for all the links is ten segments per frame of 2560 bits, that is 256 bits per segment. The bit rate is 512 kbps. The downlinks are continuously transmitted and incorporate a transmission channel for system information. When there is no user information to be transmitted, the downlink transmissions continue to use the basic frame and segment structure and contain an adequate fill pattern. For both downlink and uplink transmissions, there are two types of segments, normal segments that are used after call establishment and, pilot segments that are used during call set-up. Each normal downlink segment comprises 8 bits of synchronization information followed by 24 bits designated S-field including an 8-bit header, followed by 160 bits designated D-field these are followed by 24 bits of Forward Error Correction and an end of 8-bit pulse, followed by 12 bits of transmission channel. The ten transmission channel segments in each of the time slots of a frame together form the common signaling channel that is transmitted by the base station and contains control messages that contain link information such as segment lists. , multiple frame and superframe information, offline messages and other basic information for the operation of the system. During call set-up, each downlink pilot segment contains frequency correction data and a frame-forming sequence for initializing the receiver with only a short S-field and no D-field information. Uplink segments basically contain two different types of data packets. The first type of packet, called a pilot packet, is used before a connection is established, for example, for an Aloha call request and to allow adaptive time alignment. The other type of data packet, called the normal packet, is used when a call has been established and is a larger data packet, due to the use of adaptive time alignment. Each normal uplink packet contains a 244-bit data packet that is preceded and followed by a 4-bit duration ramp. The ramps and the remaining bits outside the 256-bit segment provide a guard space against interference from nearby segments due to time control errors. Each subscriber unit adjusts the time control of its segment transmission to compensate for the time the signals take to reach the base station. Each normal uplink data packet comprises 24 bits of synchronization data followed by an S-field and a D-field of the same number of bits as in each normal downlink segment. Each uplink pilot segment contains a pilot data packet that is 192 bits in length preceded and followed by 4-bit ramps that define an extended 60-bit guard space. This larger guard space is necessary since there is no time control information available and without it the propagation delays would cause nearby segments to interfere. The pilot packet comprises 64 synchronization bits followed by 104 bits of the S-field that start with an 8 bit header and end with a Cyclic Redundancy Check of 16 bits, 2 reserved bits, 14 FEC bits and 8 bits of end of pulse . There is no D-field. The S-fields in the aforementioned data packets can be used for the two types of signaling. The first type is MAC (MS) signaling and is used for signaling between the MAC layer of the base station and the MAC layer of a subscriber unit, so time control is important. The second type is called associated signaling, which can be slow or fast and is used for signaling between the base station and the subscriber units in the DLC or NWK layers. The D-field is the largest data field and, in the case of normal telephony, it contains digitized spoken samples, although they may also contain samples of non-spoken data.

In the preferred system, the subscriber unit authentication using a polling response protocol is provided. General coding is provided by the combination of speech or data with an unpredictable sequence of digit bits produced by a key current generator that is synchronized to the transmitted superframe number. In addition, the transmitted signal is mixed to remove the components.

Distributed System Control Signaling The system control signaling, ie the transmission signaling, is transmitted downlink as shown in Figures 3 and 4. The control data is fragmented so that each part of the signal Transmission takes a predetermined part of a respective segment within a downlink TDM frame. There are processing means 2 and fragmentation / transmission means 4 in the base station 6. In each of the plurality of subscriber units 8, there are corresponding reception / recombination means 10 and processing means 12. In operation, the signals control are fragmented for transmission and recombined after receipt in a subscriber unit. In the base station as shown in Figure 4, the control signaling of the system is first coded in so-called service data units consisting of 104 bit transmission data. The forward error correction data (FEC-B) is added together with 2 bits that are held in reserve to provide a standard length data unit of 120 bits. As shown in Figure 4, the data unit is fragmented into ten 12-bit fragments. The first fragment is sent in the transmission field of the downlink physical packet in the zero time segment of the TDM box, the second in segment 1 and so on, until the last piece of data in that data unit is sent in the physical packet transmitted in segment 9. Therefore, it will be noted that the transmission field is a predetermined portion of each physical downlink packet, a physical downlink packet being transmitted in a time slot. Accordingly, an individual data unit is sent in each complete TDM frame. In the subscriber unit, the 12 bit transmission fields from each of the downlink physical packets are received, stored and recombined to form a complete reconstituted data unit of transmission signals.

Claims

1 . A method of transmitting system control signals in time segments within time frames of fixed length, the control signals comprising data units, in which each data unit is fragmented, each fragment being sent in a segment of different time of a frame, the transmission of the system control signals is from a base station to at least one subscriber unit and, the system control signals comprise at least one of: a warning message addressed to a specific subscriber unit, a message that hosts traffic channels in response to a request from a subscriber unit to establish a call, a message directed and sent to a specific subscriber unit even though no traffic channels have been hosted, a list of channels available to subscriber units, and a list of available time segments for call set-up requests .

2. A method of transmitting system control signals according to claim 1, by radio.

3. A method according to claim 1 or claim 2, wherein the frame comprises one fragment per time segment.

4. A method of transmitting system control signals according to any preceding claim, wherein each subscriber unit is in a fixed location.

5. A method according to any preceding claim, wherein the fragments are of predetermined length and take a predetermined position within each segment.

6. A method according to any preceding claim, wherein the fragments are equal fixed length.

7. A method according to any preceding claim, wherein each segment also transports other data such as spoken data. A method according to any preceding claim, wherein each data unit includes a header and error correction data in addition to the system control signaling. 9. A method according to claim 8, wherein the error correction data comprises cyclic redundancy check (CRC) data. 10. A method according to claim 9, wherein the error correction data comprises forward error correction data (FEC). eleven . A method according to any preceding claim, wherein the system control data units are preferably transmitted on all radio frequency carrier signals transmitted from a base station and the transmission of the frames on all those radiofrequency carriers are synchronized to allow a subscriber unit to correctly receive the system control signaling from any of the radiofrequency carriers received. 12. A method according to any preceding claim, wherein the system control signals comprise a warning message addressed to a specific subscriber unit. 13. A method according to any preceding claim, wherein the system control messages comprise messages that host traffic channels in response to a request from the subscriber unit to establish a call. 14. A method according to any preceding claim, wherein the system control signals include messages addressed and sent to a specific subscriber unit even though no traffic channels have been accommodated. 15. A method according to any preceding claim, wherein the system control messages include a list of available channels for the subscriber units. 16. A method according to any preceding claim, wherein the system control messages include a list of available time segments for the call set-up requests. 17. A method of receiving system control signals received in predetermined time segments within time frames of fixed length, wherein the fragments of control signal data are received in a subscriber unit during the time for recombination to provide control signals, each fragment having been sent in a different time segment of a frame, the control signals, comprising at least one of: a message that hosts traffic channels in response to a request from a subscriber unit to establish a call, a message directed and sent to a specific subscriber unit even though no traffic channels have been hosted, list of available channels for subscriber units, and a list of available time segments for call set-up requests. 1

8. A method of receiving system control signals according to claim 17, received in a subscriber unit from a base station, the base station transmitting multiple frames by time division (TDM). 1

9. A base station including operational control signal fragmentation means for fragmenting system control signals into predetermined portions of different time segments within fixed-length time frames for transmission and, operational transmission means for transmitting the fragmented system control signals, system control signals comprising at least one of: a warning message addressed to a specific subscriber unit, a message that hosts traffic channels in response to a request from a subscriber unit to establish a call, a message addressed and sent to a specific subscriber unit even though no traffic channels have been hosted, a list of available channels for subscriber units, and a list of available time segments for call set-up requests. 20. A subscriber unit including operating reception means for receiving signals from a base station sent in predetermined time segments within fixed-length time frames, operational identification means for identifying fragments of system control signal, each fragment having sent in a time segment different from a frame, and operational recombination means for recombining said fragments to provide system control signals in the subscriber unit, the system control signals comprising at least one of: a warning message directed to a specific subscriber unit, a message that hosts traffic channels in response to a request from a subscriber unit to establish a call, a message directed and sent to a specific subscriber unit even though no traffic channels have been hosted, a list of available channels for your units crypto, and a list of available time segments for call set-up requests. SUMMARY In the transmission between a base station and a subscriber station, the system control signals are sent in time segments within fixed-length time frames. The control signals of the system are fragmented, each fragment being sent in a different time segment of a frame.