JPH0653921A - Control system of digital mobile telephone - Google Patents

Abstract

PURPOSE: To improve partial re-transmission of a message. CONSTITUTION: For partially-e-transmitting the frame I of an original layer 2, a digital mobile telephone control system is provided. The layer 1 unit of the frame I required for re-transmission can be identified with error restoration. The control field of a frame header can occupy one or more than two header extension units with a partial rejection frame REJ' and a partial re-transmission frame I'. The last header extension unit is padded in a standard unit length. A control field extension bit EC identifies the extension header unit and it is used for realizing all rejections in a layer 2 level when such unit cannot be used.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION This invention relates to digital mobile telephone control systems, and more particularly to partial retransmission of messages in such systems.

[0002]

BACKGROUND OF THE INVENTION Mobile telephone systems have traditionally been viewed as multiple layer hierarchies at mobile and base stations. The top layer relates to the devices that are processed directly by the user, and the bottom layer relates to the protocol that assembles and disassembles messages for transmission between bases. The message is sent from the upper layer of the transmission base to the lowest layer (layer 1) through successive lower layers.
Further from there it is transmitted by radio to layer 1 of the receiving base and then by successive higher layers to the corresponding upper layers of the receiving base. Layer 1 is the Time Division Multiple Access (TDMA) layer and Layer 2 is the link access protocol for the Digital Mobile Channel (LAPDM) layer. The present invention relates to the interaction between Layer 1 and Layer 2.

Layer 2 defines the frame structure of the message and layer 1 defines the method of unitizing the frame for transmission. It is known to provide an error recovery system to generate a request for retransmission of an information frame when an error is detected. On some systems, the frame can be relatively large, and to save the time required for retransmission, instead of detecting the erroneous frame portion and retransmitting the entire frame, , It has been proposed to retransmit only the relevant frame part. The first part of the frame comprises an address field and a control field. In a normal frame, it is possible to predict the maximum length of the address and control fields. The reject frame REJ requires the transmission of a complete frame and the length of the address and control fields will correspond to the normal frame length. However, in some situations, the address field may be longer than the regular field.
Further, in particular, the partial retransmission system needs to specify a plurality of parts of the frame that require (a) transmission with partial rejection REJ ′ and (b) retransmission with partial retransmission I ′ frame. is there. The frame parts to be retransmitted are specified as a list in the control field. This list adopts a combination of address and control field length on a normal Layer 2 boundary. This overflow may be due to a combination of list size and oversized address fields. The present invention has found that this causes problems at layer 1 and has proposed a solution.

[0004]

SUMMARY OF THE INVENTION In accordance with the present invention, there is provided a digital mobile telephone control system having a LAPDM layer 2 interfaced to a TDMA layer 1. Layer 2
Determines the frame structure for information, each frame comprising a frame header with address / control fields. Also, layer 1 determines the structure. As a result, the frames are decomposed into unitary structures for transmission and assembled sequentially. The system comprises equipment for partial retransmission of the original frame (hereinafter referred to as the original frame). Some frames are partially rejected REJ 'frames and some frames are partially retransmitted I'frames. The control fields of the REJ 'and I'frames comprise a list identifying multiple units of the original frame for retransmission. In this system, REJ '
And the frame header for the I'frame can comprise one or more expansion units, which or the last expansion unit is padded to hold a predetermined Layer 1 unit length. .

More preferably, Layer 1 comprises equipment for rejecting the entire frame when an error is detected in the first header unit and Layer 2 discards the entire frame when an error is detected in the header extension unit. Equipped with facilities to reject. More preferably, the digital format for the control field is a control field extension bit EC set to display the last part of the control field.
And the Layer 2 all reject facility uses the EC bit setter to perceive the header extension unit.

[0006]

1 shows a multi-layer mobile telephone system. The mobile unit M and the base unit B have the same hierarchical structure. Layer 3 entities are protocol entities for call control, mobility management, radio frequency transmission management, etc. Since the system is digital,
If the original signal is analog, such as a telephone, it is converted to digital form. Layer 3 is interfaced with layer 2. Layer 2 is the LAPDM layer and specifies the frame for the information to be transmitted. Layer 2 is interfaced with layer 1. Layer 2 establishes a physical (actually wireless) connection between the bases and manages, for example, communication in a TDMA system in which frame data is divided into unit sizes. Each unit is a specific number of octets that collects eight data bits.

The LAPDM layer in this embodiment is mainly intended to provide the following. 1) Connection between mobile bases on user / network interface 2) Multi-layer 3 entity 3) Information transfer by broadcast channel (BCCH) 4) Information transfer by paging channel (PCH) 5) Information using single cell signal generation channel Transfer (S
CCH) 6) Slow appended control channel
channel) (SACCH) information transfer 7) Fast appended control channel
channel) (SACCH) information transfer 8) Information transfer using packet channel (UPCH) The unit size of Layer 1 differs depending on the type and direction of information to be transmitted. If the direction “up” indicates transmission from the mobile base M to the base base B and the direction “down” is the reverse, the following basic size will apply.

SCCH, upper, first = 13 octet SCCH, upper = 16 SCCH, lower = 17 FACCH = 11 SACCH, upper = 8 SACCH, lower = 12 These octets in Layer 1 have one octet Layer 1 header included. Therefore, their size in layer 2 is one octet smaller. Each layer 2 frame has a header that occupies the first unit of the frame. The first unit may also contain message information, the rest of the information being contained in a number of information units following this first unit. Error recovery systems exist to detect unusable transmissions of normal information frame I and ensure frame retransmissions. However, in this system, the maximum frame length is 200
It exceeds the byte. Retransmitting all frames in the event of an error is time consuming, so it is possible to detect a unit of a dead frame and request a partial retransmission with a partial reject frame REJ '. Proposed. This frame identifies multiple units to retransmit. Then, a retransmitted frame I ′ containing only the requested frame of information is transmitted from the transmitter to the receiver.

The header for each frame includes an address field and a control field. Since the address / control field space is typically smaller than one Layer 1 unit, the first unit of the frame is considered to contain the header. Layer 1 has an automatic procedure so that if the frame's header (ie the first unit) becomes unavailable, all frames are ignored. The absence of acknowledgment will result in the retransmission of the frame being triggered. The lengths of the I and I'headers in this system are: I: address field = 1-5 octets control field = 2 I ': address field = 1-5 control field = 2 + k (k is not received L
Amount of 1 unit) L1 header = 1 In such a situation, it is possible to make the maximum length of the I'or REJ 'header longer than one layer 1 unit. The problem arises of how to handle such long headers. The proposed solution is to send the extended control field with consecutive extension units and use dummy octets to pad the length of the last I'or REJ 'header unit to the standard unit size. It is to be.

An example of partial retransmission according to the present invention is shown in FIGS. FIG. 2 shows the information flow from base base B to mobile M under FACCH. Here, the header unit size of layer 1 is 11 octets. In the first example, the numbers 0 to 7 are added, and one header unit and 7
An original frame I is transmitted, which has information units, and thus a total of 8 units. This frame has a transmission sequence number N (S) = i and a reception sequence number N.
(R) = j. The address field is assumed to be 5 octets and the control field is assumed to be 2 octets.
Now assume that in the first transfer, the header unit was received, but the information units 1-5 were disabled. This mobile base has a reception sequence number N (R) = i and a list of units to retransmit, ie n (R) =.
1, 2, 3, 4, 5. Corresponding to the length of the n (R) list, the total length of the header required for REJ 'is 5 + 2 +
5 = 12. This is more than twice the header allocation for FACCH. Therefore, the last octet of the header is placed in the second unit of REJ ', which is padded to a standard length of 11 octets with 8 dummy octets.

The base station then responds to the REJ 'frame by transmitting a partial retransmit frame I'. This is the parameter N (S) = i, N (R) = j,
n (S) = 1, 2, 3, 4, 5. Also, the header is sent to two units, and the second unit is padded to eight dummy octets. Now assume that all but the 7th unit of the I'frame (ie No6) has been received correctly. A further reject frame REJ ′ is transmitted from the mobile base with a header of length 5 + 2 + 1 = 8. This is a total length of 11 using 2 dummy octets
It is housed in one padded octet. The parameters of the frame are N (R) = i and n (R) = 5.
The base unit responds with a retransmitted I'frame with a single unit header and one information request unit.

FIG. 3 is a format for the original I frame and successive I'frames. Layer 1 is the first
Has an automatic procedure that requests retransmission of the entire frame if the unit is unavailable. This is because it is impossible to process a frame without address and control fields. However, the first unit received but for the control frame the first I'of FIG.
If there are disabled extension units present in the frame, Layer 1 will be filled in despite the need for retransmission. Therefore, a feature of the invention is that in this case, Layer 2 acts to prohibit acknowledgments, causing retransmission of the entire frame.

FIG. 4 shows two for numbered information transfer (I format) and management function (S format).
The octet control field format is shown. In each octet that follows the first control field, an external 1 bit indicates an EC for extension of the control field. If this bit is set to 1, then it is known that this is the last octet of the control field. According to a feature of the invention, this EC indication is used by layer 2 to inhibit acknowledgment if the extended control unit is disabled.

[Brief description of drawings]

FIG. 1 is a diagram showing a hierarchical structure of a mobile telephone system.

FIG. 2 is a diagram showing the flow of information in the system according to the present invention.

3 is a diagram showing a frame structure in the example of FIG.

FIG. 4 is a diagram showing a bit pattern of a control field for the system.

Claims (3)

[Claims] 1. A digital mobile telephone control system comprising a LAPDM layer 2 interfaced to a TDMA layer 1, said layer 2 defining a frame structure for information, each frame comprising a frame header having an address / control field. , Layer 1 defines a structure, decomposes and sequentially assembles the frame into unitary structures for transmission, and the system includes equipment for partial retransmission of the original frame, Are partially rejected REJ 'frames, some are partially retransmitted I'frames, and
The control field of the EF 'and I'frames contains a list identifying the units of the original frame for retransmission, and the system further provides one or two frame headers for the REJ' and I'frames. A digital mobile telephone control system comprising one or more expansion units, the expansion unit or the last expansion unit being padded to maintain a predetermined Layer 1 unit length. 2. The digital mobile telephone control system according to claim 1, wherein the layer 1 comprises equipment for rejecting an entire frame when an error is detected in the first header unit. 2 is a digital mobile telephone control system equipped with equipment for rejecting the entire frame when an error is detected in the header extension unit. 3. A digital mobile telephone control system according to claim 2, wherein the digital format for the control field comprises a control field extension bit EC set to indicate the last part of the control field, The Layer 2 all reject facility is a digital mobile telephone control system that uses an EC bit setter to perceive a header extension unit.