JP2962632B2 - Digital mobile phone control system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art Mobile telephone systems have traditionally been viewed as a plurality of layer hierarchies in mobile and base stations. The top layer relates to devices that are processed directly by the user, and the bottom layer relates to protocols that assemble and disassemble messages for transmission between bases. The message is sent from the higher layer of the transmission base to the lowest layer (layer 1) through successive lower layers,
From there it is transmitted by radio to layer 1 of the receiving base and then by successively higher layers to the corresponding upper layer of the receiving base. Layer 1 is a time division multiple access (TDMA) layer, and layer 2 is a link access protocol for a digital mobile channel (LAPDM) layer. The invention relates to the interaction between layer 1 and layer 2.

[0003] Layer 2 defines the frame structure of the message, and layer 1 defines how the frames are divided into units for transmission. It is known that by providing an error recovery system, when an error is detected, a request for retransmission of an information frame is generated. In 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 is proposed to retransmit only the relevant frame parts. 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 rejection 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 a regular field.
In particular, in the partial retransmission system, it is necessary to specify a plurality of parts of a frame that require (a) transmission with a partial rejection REJ 'and (b) retransmission with a partial retransmission I' frame. is there. The frame portion to be retransmitted is specified as a list in the control field. This list employs 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 realized that this creates a problem 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 the information, each frame comprising a frame header with an address / control field. Layer 1 determines the structure. As a result, the frames are broken down into unit structures for transmission and assembled sequentially. The system includes equipment for partially retransmitting an original frame (hereinafter, referred to as an 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 lists identifying multiple units of the original frame for retransmission. In this system, REJ '
And the frame header for the I 'frame may comprise one or more extension units, which or the last extension unit is padded to hold a predetermined layer 1 unit length .

[0005] More preferably, layer 1 comprises provisions for rejecting an entire frame when an error is detected in the first header unit, and layer 2 comprises a facility for rejecting the entire frame when an error is detected in the header extension unit. Provide rejection equipment. More preferably, the digital format for the control field is a control field extension bit EC set to indicate the last part of the control field.
, And the Layer 2 total rejection facility uses an EC bit setting device to perceive the header extension unit.

[0006]

FIG. 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 paging control, mobility management, radio frequency transmission management and the like. Because 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, which specifies frames for 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 of eight data bits.

The main purpose of the LAPDM layer in this embodiment is to provide: 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) 7) Fast appended control channel
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 sizes will be applied.

SCCH, upper, first = 13 octets SCCH, upper = 16 SCCH, lower = 17 FACCH = 11 SACCH, upper = 8 SACCH, lower = 12 For these sizes in layer 1, one octet layer 1 header is included. 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 include message information, and the remaining information is included in a number of information units that follow this first unit. An error recovery system exists to detect unusable transmission of the normal information frame I and ensure retransmission of the frame. However, in this system, the maximum frame length is 200
Exceeds the byte. Retransmission of all frames in the event of an error is time consuming, so detecting units of frames that have become unusable and requesting a partial retransmission using a partially rejected frame REJ 'is not recommended. Proposed. This frame identifies the units to be retransmitted. Thereafter, a retransmission frame I 'containing only the requested information frame is transmitted from the transmitter to the receiver.

[0009] 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 include a header. Layer 1 has an automatic procedure, so that if the header of a frame (ie, the first unit) becomes unusable, all frames are ignored. The absence of an acknowledgment will trigger a retransmission of the frame. 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
L1 header = 1 In such a situation, the maximum length of the I ′ or REJ ′ header can be longer than one layer 1 unit. A problem arises in how to handle such a long header. The proposed solution is to transmit the extended control field using a continuous extension unit and pad the length of the last I 'or REJ' header unit to a standard unit size using dummy octets. It is to be.

Examples of partial retransmission according to the present invention are shown in FIGS. FIG. 2 shows an information flow from the base base B to the mobile M under the FACCH. Here, the header unit size of Layer 1 is 11 octets. In the first example, numbers 0 to 7 are assigned, and one header unit and 7
An original frame I having eight information units and thus a total of eight units is transmitted. This frame has a transmission sequence number N (S) = i and a reception sequence number N
(R) = j. It is assumed that the address field is 5 octets and the control field is 2 octets.
Now assume that in the first transfer, a header unit has been received, but the information units 1-5 have been disabled. The mobile base has a reception sequence number N (R) = i and a list of units to be retransmitted, ie, n (R) =
1, 2, 3, 4, and 5. According 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. Thus, the last octet of the header is located in the second unit of REJ ', which is padded to a standard length of 11 octets with eight dummy octets.

Next, the base station responds to the REJ 'frame by transmitting a partial retransmission frame I'. This gives the parameters 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 seventh unit of the I ′ frame (ie, No. 6) have been correctly received. A reject frame REJ 'is further transmitted from the mobile base having a header of length 5 + 2 + 1 = 8. This is done by using two dummy octets for a total length of 11
It is stored in one padded octet. The parameters of the frame are N (R) = i, n (R) = 5.
The base unit responds with a retransmitted I 'frame with a single unit header and one information request unit.

FIG. 3 shows a format for an original I frame and a continuous I 'frame. Layer 1 is the first
Has an automatic procedure to request the retransmission of the entire frame if that unit is unavailable. This is because it is impossible to process a frame without the address and control fields. However, the first unit received, but received the first I ′ of FIG.
If there are disabled extension units, such as those present in the frame, Layer 1 will be satisfied, even though retransmission is required. Thus, a feature of the present invention is that in this case, layer 2 acts to inhibit acknowledgments, causing retransmission of the entire frame.

FIG. 4 shows two tables for numbered information transfer (I format) and management functions (S format).
Indicates the octet control field format. In each octet following the first control field, an external bit indicates the EC for extension of the control field. If this bit is set to 1, 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 acknowledgments if the extended control unit is disabled.

[Brief description of the drawings]

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

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

FIG. 3 is a diagram showing a frame configuration in the example of FIG. 2;

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

──────────────────────────────────────────────────の Continuing from the front page (56) References Digital Car Phone System Standards (RCR STD-27E) First Volume, The Association of Radio Industries and Businesses (58) Fields surveyed (Int. Cl. ⁶ , DB name) ) H04J 3/00 H04L 1/00 H04L 29/00 H04Q 7/00

Claims (3)

(57) [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. The layer 1 defines the structure, decomposes the frames into unit structures for transmission and assembles them sequentially, and the system comprises several facilities for partial retransmission of the original frames, Are partially rejected REJ 'frames, some are partially retransmitted I' frames, and the R
The control field of the EF 'and I' frames includes a list identifying the units of the original frame for retransmission, and furthermore, the system may include one or two frame headers for the REJ 'and I' frames. A digital mobile telephone control system comprising one or more extension units, wherein the extension unit or the last extension unit is padded to maintain a predetermined layer 1 unit length. 2. The digital mobile telephone control system according to claim 1, wherein said layer 1 has a facility for rejecting an entire frame when an error is detected in a first header unit. 2 is a digital mobile telephone control system having a facility for rejecting an entire frame when an error is detected in the header extension unit. 3. The 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. A digital mobile telephone control system, wherein said all rejection facility at Layer 2 uses an EC bit setting device to perceive a header extension unit.