JP2002521916A - Method and packet radio system for transmitting modulation and signaling information - Google Patents

Abstract

The present invention comprises at least one base station (112) and a subscriber terminal (150), and a wireless connection (170) between the base station (112) and the subscriber terminal (150). Form a block comprising a burst of symbols, which encodes signaling information in a packet radio system such as comprising a training sequence (302) containing modulation information. A method and a packet radio system. The invention is characterized in that the signaling information is coded together with the modulation information relating to the whole block into a training sequence (302) of the block. This coding allows for a high data transmission rate, for example, because no data bits need to be specified for coding the uplink state flag.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

【Technical field】

The present invention relates to a method and a packet radio system for transmitting signaling and modulation information in a training sequence of a radio system using packet transmission.

[0002]

[Background Art]

The packet radio system refers to a radio system using a packet switching technology known from a fixed network. Packet switching is a method of establishing a connection between users by transmitting data in packets containing address and control information. Multiple connections can use the same outgoing connection simultaneously. In particular,
Since packet switching methods are well suited for data transmission where the data to be transmitted is generated in bursts, research has been conducted on the use of packet switching wireless systems. Therefore, it is not necessary to specify the data transmission connection during the entire transmission time,
It only needs to be specified during transmission of a packet. This can save significant cost and capacity both when configuring and using the network.
When further developing the GSM system (global system for mobile communications),
Research is conducted with particular attention to packet networks, ie, GPRS (general packet radio service) and radio systems that use packet transmission (EGPRS or improved general packet radio service).

One of the main problems in the design of known wireless systems is to guarantee signal quality even when the channel quality is low. When planning a data transmission system, one important parameter is the modulation method to be used in the transmission path. Information symbols to be transmitted cannot be transmitted via the transmission path due to the capacity of the transmission path and the loss on that path. Rather, the symbols must be modulated in an appropriate manner to obtain a satisfactory capacity of the transmission path and the quality of the transmission. Therefore, in the development of known systems and the choice of modulation method,
Guaranteeing the transmission quality is the main problem, in which case the capacity of the modulation method under bad channel conditions is important. As a result, the performance of existing methods of transmitting high data rate signals is slightly reduced. Therefore, there is a need to compromise capacity to guarantee transmission quality.

[0004] One example of a known modulation method is the GMSK used in GSM cellular radio systems.
(Gaussian minimum shift keying). It has a narrow frequency spectrum and good capacity, but the data transmission rate is not very high. One solution for optimizing capacity and transmission rate is to change the modulation method to be used as needed. When good interference tolerance is required, for example, the GMSK method can be used, and when the channel quality is good, for example, the 8-PSK method can be used, which is obtained with GMSK. A data rate three times higher than that can be obtained.

[0005] A problem associated with known wireless systems is how to smoothly change the modulation method during successive connections. Changing the modulation method causes problems, especially for the receiver.
This is because the transmitter can change the modulation method without notifying the receiver in advance. However, for example, the transmission of packet-switched data requires a smooth change in the modulation method. It is known from packet radio systems to transmit bursts, eg blocks consisting of four bursts. Packet radio systems use various burst modulation methods and require a method to identify the modulation method used for the downlink. The modulation is kept the same during one 4-burst block. For example, if one burst of modulation is misinterpreted, the fourth information contained in the block is lost. At most code rates, this prevents reception of the block.

[0006] Multiple subscriber terminals can use the same time slot. The base station sends an uplink status flag on the downlink. These status flags indicate which subscriber terminals are allowed to send signals on the uplink. A time slot can only be used if only one subscriber terminal uses it for data transmission. To achieve this, all subscriber terminals in the time slot must be able to receive the uplink status flag without error. The required detection function is not dependent on modulation or data code rate. For example, in a GPRS system, the uncoded uplink state flag consists of 3 bits for each 4 burst radio block. The uncoded uplink state flag USF is coded into 6 or 12 bits based on the data code rate, and the bits are interleaved into the data.

[0007]

DISCLOSURE OF THE INVENTION

It is an object of the present invention to develop a method for overcoming the above problems and a packet radio system implementing this method. This is achieved by the method and packet radio system described below. The invention comprises at least one base station and a subscriber terminal, wherein the signals to be transmitted over the radio connection between the base station and the subscriber terminal form blocks comprising bursts of symbols, and The burst relates to a method for coding signaling information in a packet radio system including a training sequence including modulation information. In this way, the signaling information is coded into a training sequence for a block along with modulation information associated with the entire block.

The invention also comprises a block comprising at least one base station and a subscriber terminal, wherein the signal to be transmitted over the wireless connection between the base station and the subscriber terminal comprises a burst of symbols. And this burst also pertains to a packet radio system that includes a training sequence with modulation information. The packet radio system is configured to code the signaling information into a block training sequence with modulation information associated with the entire block.

[0009] Preferred embodiments of the invention are set out in the dependent claims. The training sequence means a group of predetermined symbols known to the receiver.
By comparing a received training sequence according to a method to a known training sequence, the receiver can determine what kind of distortion the received signal contains from a non-ideal wireless connection between the base station and the subscriber terminal. , And this information can be used to easily demodulate the received signal.

[0010] In other words, the present invention relates to a method and a packet radio system for transmitting signaling and modulation information in a training sequence of a radio system using packet transmission. The same modulation is used for each burst of the block, thus:
It is not necessary to include modulation information separately in each training sequence. Thus, according to the present invention, the training sequence can be used to transmit signaling information in addition to modulation information. In the method according to the invention, the training sequence to be used can be detected, for example, by comparing channel estimates calculated with different training sequences.

[0011] The methods and systems of the present invention provide a number of advantages. The method according to the invention comprises:
Particularly suitable for coding the uplink state flag. The coding is efficient because a very large number of symbols are used to code the uplink state flags. Also, the encoding allows for a high data transmission rate since there is no need to specify data bits for the encoding of the uplink state flag, and thus,
The coding preferably saves, for example, three symbols per burst. Coding can be easily implemented for different code rates and modulations. or,
The coding, by its efficiency, allows the same time slot to be assigned to both the subscriber terminal near the base station and the terminal far from it. The effect of the system according to the invention is the same as that described for the method. Obviously, the preferred and detailed embodiments can be combined with one another to achieve the desired technical effect.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. The method of the present invention is a wireless system that uses digital packet transmission, wherein the signal to be transmitted includes a burst of symbols, the burst includes a known training sequence, and the burst is transmitted in blocks. Applicable to systems. The present invention is preferably applicable to networks developed from GSM-based cellular radio networks, where data is transmitted using packet radio services (EGPRS, an improved general packet radio service). In this case, the data is transmitted in packets.

An exemplary structure of a cellular wireless network according to the present invention and its connection to a switched telephone network and a packet transmission network will be described with reference to FIG. Although FIG. 1 shows only those elements relevant to describing the present invention, it will be apparent to those skilled in the art that conventional cellular wireless networks also include other features and structures that need not be described in detail here. Would. The cellular radio network comprises network portions 100, 102, 132, 1
40 and a subscriber terminal 150. Network part 100, 1
02, 132 and 140 include the base station 100. There is a two-way wireless connection 170 between the base station 100 and the subscriber terminal 150;
After this, the radio signal is transmitted at a certain carrier frequency. Subscriber terminal 150
May be fixed, mounted on a vehicle, or portable.
A number of base stations 100 are centrally controlled by a base station controller 102 that communicates with these base stations. Base station 100 includes transceiver 114. Base station 100 is typically
It includes one to sixteen transceivers 114. One transceiver 114 has one
It provides radio capacity for one TDMA frame, typically eight time slots.

The base station 100 includes a control unit 1 for controlling the function of the transceiver.
18 and a multiplexer 116. Multiplexer 116 is used to send traffic and control channels used by multiple transceivers 114 to one transmission connection 160. The structure of the outgoing connection 160 is strictly defined and is called the Abis interface. Outgoing connection 160 is typically 2
It is implemented using an Mbit / s connection, ie a PCM (pulse code modulation) link. Antenna unit 112 from transceiver 114 of base station 100
And the antenna unit is used to implement a two-way wireless connection 170 to the subscriber terminal 150. Two-way wireless connection 170 is used to establish a connection and perform packet transmission. The structure of the frame to be transmitted over the two-way wireless connection 170 is also strictly defined and is referred to as the air interface.

The subscriber terminal 150 is, for example, a conventional GSM mobile station to which a portable computer 152 can be connected using an expansion card. This computer can be used for processing and contracting packets in packet transmission.
The protocol processing may be performed on the subscriber terminal 150 and / or the subscriber terminal 150
Is connected to the computer 152 connected to. Base station controller 102 establishes a connection to subscriber terminal 150 by requesting base station 100 to send a message to subscriber terminal 150 to establish a connection. The base station controller 102 includes a group switching field 120 and a control unit 124. The group switching field 120 is used to connect speech and data as well as to connect signaling circuits.
The base station subsystem BSS formed by the base station 100 and the base station controller 102 includes a transcoder 122,
It also has a speech codec called RAU (Transcoder and Rate Adapter Unit). Transcoder 122 is typically located as close as possible to mobile services switching center 132. This is because speech can be transmitted between the transcoder 122 and the base station controller 102 in the form of a cellular wireless network, saving transmission capacity.

The transcoder 122 converts the digital code formats of the speech used between the public switched telephone network and the mobile telephone network into compatible formats, for example, fixed network formats (64
kbit / s) to the format of the cellular wireless network (eg, 13k
Bits / s) and vice versa. The control unit 124 is responsible for call control, mobility management, collecting statistical information and signaling. As is evident from FIG. 1, the group switching field 120 passes through the mobile services switching center 132 to the public switched telephone network (PSTN)
And to establish a connection to the packet transmission network 142 (indicated by the black dot). In the public switched telephone network 134, a typical terminal 136 is a conventional telephone or an ISDN (Integrated Services Digital Network) telephone.

The connection between the packet transmission network 142 and the group switching field 120 is established by a support node 140 (SGSN = Service GPRS support node). The support node 140 is responsible for transmitting packets between the base station system and the gateway support node 144 (GGSN = Gateway GPRS support node) and keeping a record of the location of the subscriber terminal 150 in its area. The gateway support node 144 includes a public packet transmission network 146.
And the packet transmission network 142 are connected. At the interface, for example, Internet Protocol or X.400. Twenty-five protocols can be used. The gateway support node 144 communicates with the packet transmission network 1
42 is hidden from the public packet transmission network 146 by encapsulating the structure, so that the public packet transmission network 146
The packet transmission network 142 is considered a sub-network for the subscriber terminal 150 where the public packet transmission network 146 can specify and receive packets.

Packet transmission network 142 is a private network that typically uses the Internet Protocol and carries signaling and tunneled user data. The structure of the network 142, both its architecture and protocol, can be changed by the operator under the Internet Protocol layer. Public packet transmission network 146 may be, for example, a global Internet network. A terminal 148, eg, a server computer, in communication with the network desires to send a packet to the subscriber terminal 150.

The portable computer 152 is connected to the subscriber terminal 152. Data to be transmitted is carried from portable computer 152 to server computer 148. Of course, the data can also be sent in the opposite direction,
That is, it can be transmitted from the server computer 148 to the portable computer 152. Data is transmitted to the antenna 112 at the air interface 170.
From the system to the transceiver 114 and from there to the group switching field 120 along the transmit connection 160 in multiplexed form provided by the multiplexer 116. In the group switching field, a connection to the output towards the support node 140 is established, from which:
The data is provided in the packet transmission network 142 via the gateway support node 144 to a server computer 148 connected to the public packet transmission network 146.

In a digital radio system, a signal burst can be provided with a predetermined symbol sequence or training sequence, which can be used, for example, to calculate an impulse response. FIG. 2 shows a typical burst of a digital GSM cellular radio system as an example. A typical burst in a GSM system contains symbols consisting of bits or combinations of bits. The burst symbol is the start symbol 200
, An information symbol 202, a training symbol 204, an information symbol 206, and a stop symbol 208.

Hereinafter, the method of the present invention will be described. This can be used in digital wireless systems that use packet transmission to signal between base station 110 and subscriber terminal 150. The signal to be transmitted over wireless connection 170 between base station 110 and subscriber terminal 150 includes a burst of symbols, and the burst includes a known training sequence 204. If there are two different training sequences 204 for the connection 170 between the base station 110 and the subscriber terminal 150,
The symbol indicating the data to be transmitted has two different values, for example, 0 and 1. If two or more different training sequences 204 are used,
The symbols indicating the data to be transmitted are available training sequences 2
Receives the same number of different values as 04. The method of the invention is characterized in that the training sequence is not completely known, but rather there are a number of alternatives. One of the known groups of training sequences is used as the training sequence, but it is unknown which sequence it is.

It is already known to include the modulation information in the training sequence 204 contained in the burst, ie to transmit the information with the modulation used in the training sequence 204. In the method according to the invention, the same modulation is used for all blocks. The modulation information is preferably coded only into one training sequence, and the signaling is preferably coded into another training sequence. Different bursts of blocks include different numbers of training sequence alternatives 204.

Each training sequence may include log ₂ n information bits.
Here, n means the number of available training sequence alternatives. In the most preferred embodiment, three training sequences are used to transmit block coded uplink state flags. The structure of the block code is determined by the variable n, ie the structure is based on the number of different training sequences available. In this case, each training sequence is one of the predetermined alternatives. For example, when n = 2, a 3-bit USF can be transmitted without a code.

Different bursts of blocks may include different numbers of possible training sequence alternatives. FIG. 3 shows a burst structure for a USF code according to the present invention. Four bursts of blocks are shown. This burst structure is divided into sequences. First and last sequence of modulation information 300 and 304
Contains a data sequence. The center sequence 302 includes a training sequence. Each training sequence is one of n alternatives. The training sequence of the central sequence 302 includes, for example, a training / modulation indicator 306, which is preferably the first sequence, and
Coded USF Part 1 (Coded USF Training / Part 1) 308
And Coded USF Part 2 (Coded USF Training / Part 2) 3
10 and Coded USF Part 3 (Coded USF Training / Part 3
) 312.

The coding of the uplink status flag according to the method of the present invention has the following effects, for example. Coding is relatively efficient because a large number of symbols are used to code the uplink state flag. Due to its efficiency, this coding allows the same time slot to be assigned to both the subscriber terminal close to the base station and the terminal far from it. Also, this encoding allows for good throughput since there is no need to specify data bits for the encoding of the uplink state flags, and thus preferably saves, for example, approximately 3 symbols per burst. Coding can also be easily implemented for different code rates and modulations. As described above, the present invention has been described by way of example with reference to the accompanying drawings. However, the present invention is not limited thereto, and various modifications may be made without departing from the concept of the present invention described in the claims. It is clear that this can be done.

[Brief description of the drawings]

FIG. 1 is a block diagram of a cellular wireless network showing how a base station and a base station controller are connected to a packet transmission network.

FIG. 2 is a diagram showing the structure of a normal GSM burst in which a training sequence is provided at the center.

FIG. 3 is a diagram illustrating a burst structure of a USF code according to the present invention.

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Claims (16)

[Claims] An apparatus comprising at least one base station (112) and a subscriber terminal (150), the base station (112) and the subscriber terminal (150).
The signal to be transmitted over the wireless connection (170) to and from forms a block comprising a burst of symbols, which burst comprises a training sequence (302) containing modulation information. A method for coding signaling information in a wireless system, the method comprising coding the signaling information together with modulation information associated with all blocks into a training sequence (302) for a block. 2. The modulation information associated with the entire block is included in only a part of the training sequence (302) included in the burst of the block of the packet radio system, and the signaling information is included in another training sequence of the block. The method of claim 1 coded into (302). 3. The method of claim 1, wherein the uplink status flag is coded in a packet radio system training sequence (302). 4. The method of claim 2, wherein the modulation information is included in only a first burst of a block. 5. The method according to claim 1, wherein the bursts are demodulated immediately after they are received. 6. The method according to claim 1, wherein the burst following the first burst is demodulated using the same modulation method as the demodulation of the first burst. 7. A training sequence for a burst following the first burst.
The method according to any of the preceding claims, wherein (302) is used for transmitting a block coded uplink status flag. 8. A training sequence for a burst following the first burst.
The method according to claim 1, 2, 3 or 4, wherein (302) is used for signaling other than burst modulation. 9. At least one base station (112) and a subscriber terminal (150), the base station (112) and the subscriber terminal (150).
The signal to be transmitted over the wireless connection (170) to and from forms a block comprising a burst of symbols, which burst comprises a training sequence (302) containing modulation information. A packet radio system in a wireless system configured to encode signaling information into a block training sequence (302) with modulation information associated with all blocks. 10. The packet radio system is configured to include modulation information related to the entire block in only a portion of the training sequence (302) included in a burst of the block, and the packet radio system includes: The packet radio system of claim 9, wherein the packet radio system is configured to encode signaling information into another training sequence (302) of the block. 11. The packet radio system of claim 9, wherein the packet radio system is configured to code an uplink status flag in a training sequence of the packet radio system. 12. The packet radio system according to claim 10, wherein the packet radio system is configured to include modulation information only in a first burst of a block. 13. The packet radio system according to claim 9, wherein the system is configured to demodulate the burst immediately after the burst is received. 14. The system of claim 9, wherein the system is configured to demodulate a burst following the first burst using the same modulation method as in the demodulation of the first burst.
14. The packet radio system according to any one of claims 13 to 13. 15. A training sequence of a burst following the first burst (3
The packet radio system according to any one of claims 9 to 14, wherein 02) is configured to transmit a block coded uplink status flag. 16. The packet according to claim 9, 10, 11 or 12, wherein the packet radio system is configured to use a training sequence (302) of a burst following the first burst for signaling other than burst modulation. Wireless system.