JP3860652B2 - Packet data communication method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to packet data communication in a telecommunications system, and more particularly to packet data communication related to, but not limited to, an RCR-27 personal digital cellular system.
[0002]
[Prior art]
In a cellular communication system consisting of a base station and a subscriber mobile station, many packet transactions between the subscriber mobile station and the base station use a large amount of downlink, but the base station and the mobile station The uplink between is relatively low in usage. Internet applications correspond to this example in that most data flows are done via the downlink from the Internet to the subscriber.
[0003]
[Problems to be solved by the invention]
In view of this, it is an object of the present invention to provide a method and a telecommunication system in which the format of a channel for packet communication changes according to the nature of the packet transaction.
[0004]
[Means for Solving the Problems]
The present invention allows a communication system to optimally manage packet channel characteristics to its needs, within the limits of a given system protocol and system specific hardware.
[0005]
Exemplary embodiments of the invention are described below with reference to the accompanying drawings.
[0006]
DETAILED DESCRIPTION OF THE INVENTION
The Japanese RCR-27 personal digital cellular system is a time division multiple access (TDMA) system. In order to facilitate understanding of the present invention, an outline of the RCR-27 system is shown below. For details on how to operate this system, please refer to the following standard specifications: Reference 1-RCR STD-27D (Packet Revised) Layer 1 Standard and Reference 2-RCR STD-27D (Packet Revised) Layer 3 standards.
[0007]
As shown in FIG. 1, communication between the base station BS and the mobile station MS includes a downlink reserved for communication from the base station BS to the mobile station MS, and communication from the mobile station MS to the base station BS. This is done via two discrete frequency bands with the reserved uplink. In the example of FIG. 1, the uplink uses 641 filled carrier at intervals of 25kHz between 810MHz and 826MHz. For each filled carrier in the uplink, there is a real carrier corresponding to the downlink. In the downlink , the real carrier is also located between 940 MHz and 956 MHz with 25 kHz spacing.
[0008]
Each real carrier has data transmitted to it in the form of a superframe. Referring to FIG. 2, each superframe 100 is composed of 36 (0... 35) frames 20 ms long, and each frame 102 is 3 (0... 2) slots 104 each 6.6 ms long. Consists of. The superframe lasts 720 ms. Each frame can be assigned the role of either the user traffic channel TCH or the control channel CCH. Superframes in the uplink and downlink are transmitted with a small temporal offset. The uplink control channel is common access and in any case any mobile station MS can connect to the base station using that channel.
[0009]
In order to register with the base station BS, the mobile station MS scans a subset of the downlink real carriers predefined by the network operator as perch channels. The signal strength of each perch channel is confirmed and sorted in the order of signal strength. Starting with the perch channel with the maximum received signal strength, the mobile station MS attempts to tune and decode the data in slot 2 of the perch channel. This slot is assigned to the control channel, more specifically to the broadcast control channel BCCH. The broadcast control channel BCCH has information about the cell or zone including, for example, the control channel structure, network identity, location area, adjacent zone, usage restrictions, etc. The BCCH information includes information indicating which slot is reserved for the role of the user packet channel UPCH. This UPCH information is a data format indicating a real carrier and a slot of a superframe transmitted on the real carrier.
[0010]
If the BCCH information cannot be decoded from the perch channel with the highest received signal strength, the mobile station MS will try the perch channel with the next highest received signal strength, and so on.
[0011]
After decoding the BCCH information, the mobile station MS can request registration into the cell or zone. After registering with the base station BS, the mobile station MS is in standby mode. In the standby mode, the mobile station MS is in the slots of the control channel CCH superframe that has been given the role of the call channel PCH to monitor whether the station has been called for a packet or voice transaction from the base station BS. Operates only during
[0012]
Packet transactions can either be initiated from the mobile station MS (“mobile station originated transaction”) or from the base station (“mobile station incoming transaction”).
[0013]
A mobile station originated packet transaction is initiated as follows. The mobile station MS tunes in the downlink to one of the dedicated user packet channels UPCH (since it was previously decoded from the BCCH information as described above). The mobile station MS makes a request for packet communication via the corresponding uplink slot. As part of that request, the mobile station MS presents whether it wants a fast or slow packet channel and can support full-duplex communication. In the high-speed packet channel, two or three slots (0..2) out of the three slot frames allocated to the user packet channel UPCH are used to carry packet data ("multi-multiple"). slot"). In the slow packet channel, one slot of the frame allocated to the user packet channel UPCH is used to carry packet data (“single slot”). Via the assigned downlink slot, the mobile station MS can be approved for either multi-slot or single-slot channel.
[0014]
As described above, the mobile station incoming packet data transaction is started when the mobile station itself detects that the mobile station MS is being called via the call channel PCH. Thereafter, the procedure for transmitting a transaction is the same as that for a mobile station-originated transaction.
[0015]
The packet data is transmitted as a series of I frames or layer 2 LAPDm units (in the standard OSI 7 layer model). As shown in FIG. 3, each I frame 50 includes a head unit 52, an end unit 54, and several intermediate units 53. Each unit occupies one slot of the user packet channel UPCH.
[0016]
FIG. 4 shows an example of a packet transaction in which both multi-slot and single-slot user packet channel UPCH formats are adopted.
[0017]
First, the base station BS transmits three I frames, I _d1 , I _d2 , and I _d3 in the frames 0 to 4 via the downlink. The mobile station MS does not transmit during this interval, but receives in the continuous reception mode (see section 4.1.10.2.2.2.2 of Reference 1). I _d1 includes a head unit 52, two intermediate units 53a and 53b, and an end unit 54, and is transmitted in slot 0. I _d2 includes a head unit 52, an intermediate unit 53 a, and an end unit 54, and is transmitted in slot 1. I _d3 is composed of a head unit 52, an intermediate unit 53 a, and an end unit 54, and is transmitted in slot 2. These initial frames employ a multi-slot user packet channel UPCH format when packet data is sent in one direction via the downlink, with a maximum of 3 slots per packet • Allocated to carry data.
[0018]
On slot 0 of frame 4, a unit 60 that does not go to the mobile station MS appears, giving the mobile station MS an opportunity to attempt uplink access. Since the uplink control channel including the user packet channel UPCH is common access, it is necessary to adopt a collision control mechanism (between mobile stations). The mobile station MS decodes the idle / busy (idle / busy) flag for slot 0 in the current frame of the downlink indicating whether the corresponding uplink slot is currently in use (arrow 62). If, as in this case it is "empty", the mobile station MS sends a head unit 52 of the I-frame I _t1 on the corresponding uplink slot. The MS station then waits for a base station BS response on slot 0 of frame 5. The base station BS transmits a partial echo PE and a reception / non-reception or R / N flag (arrow 64). Partial echo is the sum of CRC checks. As in this case, if the partial echo PE matches the partial echo of the transmitted head unit 52 and the R / N flag indicates that the head unit 52 has been successfully “received”, the mobile station MS Is estimated to have been allocated slot 0 for subsequent unit uplink transmission of I frame _It1 in the following frame and switched to single slot user packet channel UPCH format. Upon receiving a decodable head unit 52 from the mobile station MS, the base station BS assumes that the mobile station MS is switched to a single slot user packet channel UPCH format and operates accordingly. For example, if uplink access cannot be obtained due to a collision with another mobile station MS (not shown), the mobile station MS may use the random number specified in FIG. 4.1.13.1-2 of Reference 1. Continue the multi-slot user packet channel UPCH format during the retransmission interval. In the subsequent frame, the intermediate unit 53a of the I-frame _{I t1,} 53b, 53c and end unit 54 is transmitted onto the slot 0. From frame 5 onwards, the downlink user packet channel takes a single slot format, where only slot 0 is used. In frames 5 and 6, an I frame I _d4 (unit length = 2) composed of the head unit 52 and the end unit 54 is transmitted to the mobile station MS. Next, in slot 0 , an I frame I _d5 (unit length = 1) composed only of the head / end unit 52/54 is transmitted to the mobile station MS.
[0019]
The time offset of the uplink and downlink channels allows for half-duplex communication between the same logical slots via the uplink and downlink while using a mobile station MS that cannot transmit and receive simultaneously. It will be understood that it can be realized.
[0020]
In the example of FIG. 4, the mobile station MS is receiving in the continuous reception mode using the multi-slot user packet channel UPCH format. Even when switching to the single slot user packet channel UPCH format, the mobile station MS remains in the continuous reception mode. Similarly, if the mobile station is initially intermittent reception, superframe intermittent reception, or hyperframe intermittent reception as defined in section 4.1.1.1.10.2.2.2.2 of reference 1, The mobile station MS will keep the same reception mode when switching between multi-slot and single-slot user packet channel UPCH formats.
[0021]
Since the format of the user packet channel is switched in the manner described above, half-duplex mobile stations may not have a low data rate if circumstances permit (ie, no uplink communication is required for a given leg). However, the throughput of the downlink can be maximized (up to 28.8 kbps) while still being able to handle communication via both the uplink and the downlink. Moreover, since the change in user packet channel format has the effect of being constrained by a given frame, full-duplex and half-duplex mobile stations can easily coexist on the same network.
[Brief description of the drawings]
FIG. 1 is a diagram showing frequency distribution in an 800 MHz frequency band in an RCR system.
FIG. 2 is a diagram illustrating a superframe structure in an RCR system.
FIG. 3 is a diagram showing the structure of an I frame or layer 2 unit.
FIG. 4 is a diagram showing an example of a packet transaction between a base station and a mobile station.
[Explanation of symbols]
BS ... Base station MS ... Mobile station 100 ... Super frame 102 ... Frame 104 ... Slot

Claims (5)

In a method for performing a transaction between a mobile station and a base station in a cellular radio system using a communication channel comprising a number of time division multiplexed frames, each frame having a number of consecutive slots,
The base station can switch between downlink transmission in a multi-slot format having more than one slot per frame and downlink transmission in a single slot format having one slot per frame. And
When the base station is performing downlink transmission in the multi-slot format,
When the mobile station is estimated that performs uplink transmission in the single-slot format, the base station switches the downlink transmission in the multi-slot format to downlink transmission in the single slot formats A method characterized by that. The method of claim 1, wherein
A method wherein the base station switches from the multi-slot format to the single-slot format to allow the mobile station to perform uplink transmissions. The method according to claim 1 or claim 2, wherein
The method, wherein the mobile station starts uplink transmission after the end of downlink transmission in the multi-slot format. In a system in which the method according to claims 1 to 3 is used,
The mobile station is
A transmitter performing uplink transmission in the single slot format;
And a receiver that performs downlink reception by the multi-slot or the single slot format,
The corresponding uplink and downlink slots in the system are substantially spaced from each other in frequency and spaced from each other by less than the length of one slot;
The mobile station, and means for attempting an uplink access via the uplink slot, and means for estimating said uplink access by via the corresponding downlink slot message is approved The system further comprising:   A mobile station for performing the method according to any one of claims 1 to 3.

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