DE10015041C2 - Method for signaling the start of a logical channel in a shared physical transmission channel of a radio communication system and device for carrying out the method - Google Patents

Description

The invention relates to a method for signaling the Start of a logical channel in a shared physical transmission channel of a radio communication system stems and a device for performing the method.

In radio communication systems, for example the europi second-generation mobile radio system GSM (Global Sy stem for Mobile Communications), information (at for example, language, image information or other data) Using electromagnetic waves over a radio cut place transferred. The radio interface refers to a connection between a base station and subscriber stations, the subscriber stations for example Mon bil stations or fixed radio stations can be. The The electromagnetic waves are also emitted Carrier frequencies in one for each system seen frequency band lie. For future radio communications tion systems, for example UMTS (Universal Mobile Tele communication system) or other 3rd generation systems frequencies in the frequency band of approx. 2000 MHz are provided. Two modes are provided for the third generation of mobile communications, where one mode is FDD (frequency division duplex) operation and the other mode is TDD (time division duplex) operation designated. These modes can be found in different ones Frequency bands their application. Both modes support one so-called CDMA subscriber separation procedure (Code Divi sion multiple access).  

A proposal for a third generation mobile radio system according to "TD-SCDMA Radio Transmission Technology for IMT-2000", Draft V.0.4, the CATT from September 1998, is based on the be written TDD mode with support of a CDMA Subscriber separation. By using the CDMA subscriber separation procedures can be of several Subscriber stations transmitted in a time slot blocks, which generally consist of a data part and a known training sequence consist of a base station processed in parallel. To do this, you must ensure who that the transmission blocks and in particular the respective training sequences within a certain time frame sters arrive at the location of the base station to get a secured Detection and separation of the different signals währleisten. This problem of synchronization of the Sig nal transmission in the upward direction occurs in known CDMA based radio communication systems in the same way.

The described TD-SCDMA system and the TDD mode of the UMTS mobile radio systems have shared physical Transmission channels, so-called P-CCPCH (Primary Common Con trol Physical Channel), in which, for example, both a general signaling channel BCCH (Broadcast Control Channel) with organizational information as well as a so-called named paging channel PCH (Paging Channel) separated in time be sent out as logical channels. Within the in Time frames (frames) and super so-called superrah With a structured radio interface, the logical Ka channels over a certain number of time frames interleaved. The following is for the number nested time frame for a logical channel also the Term nesting frame used. For the BCCH and the nesting depth corresponds to the PCH, for example four time frames.  

Is a subscriber station receiving the logical channels not knowing what time frame of the nested lo channel receives them, they result from this following disadvantages. On the one hand, the subscriber station must have a so-called try and error technique for determining the start apply a nesting frame. Beats at the Demodulation of the so-called CRC check fails, so the part slave station from another start of a mine framework or from a badly received beginning of a Run out of nesting frames. This disadvantageously reduces the reliability and speed of detection of the logical channel. Furthermore, the subscriber station often has to Detect time frames that lead to an incomplete ver nesting frames, and then again discard. This adversely increases energy consumption as well the time to receive a complete chess development framework.

To avoid the disadvantages described, the following points are desirable from the point of view of the subscriber station:

• - The subscriber station can start a mine Detect lung framework,
• - The subscriber station can change the position of the currently emp caught time frame within a nesting frame determine mens, and
• - The subscriber station can determine the position of the manhole Detect the framework within a superframe.

At the second point, the subscriber station could be at one exemplary detection of a second time frame from one further detection of the still missing time frames.

In the third point, the subscriber station could, for example selectively detect a specific logical channel.  

There is a superframe in the TD-SCDMA system described from 48 time frames. Within this super frame are at for example, two nesting frames, each with four BCCH timeframe arranged. In the event that the part station only wished to detect the BCCH, it can aims to detect those sent in the further time frame Suppress PCHs.

DE 37 35 377 A1 describes a method of a time multiple plexsystems for a more uniform transmission of packets Length known at which by detecting the start of the Packet misdirection of packets is avoided.

The object of the invention is a method and a front to indicate the direction that a secure signaling of the Allow beginning of a logical channel. This task will by the method with the features of claim 1 and solved by the base station system of claim 17. before partial developments of the invention are dependent Claims.

Embodiments of the invention are based on the enclosed ing drawings explained in more detail.

Show

Fig. 1 is a block diagram of a radio communication system.

Fig. Merseparierungsverfahren 2 is a schematic illustration of the frame structure of a radio interface with a TD-SCDMA parti,

Fig. 3 shows a detail of the framework in Fig. 3, and

Fig. 4 is a schematic representation of the coding of a radio block.

Fig. 1 shows part of a mobile radio system as an example for the structure of a radio communication system. A mobile radio system in each case consists of a plurality of mobile switching centers MSC, which belong to a switching network (SSS - Switching Subsystem) and are networked with one another or provide access to a fixed network, and one or more base station systems BSS (connected to these mobile switching centers MSC) BSS - Base Station Subsystem). A base station system BSS in turn has at least one device RNC (RNC - Radio Network Controller) for assigning radio resources and at least one base station NB (NB - Node B) connected to it.

A base station NB can connect via a radio interface on subscriber stations UE (UE - User Equipment) build and maintain. Each base station NB becomes least one radio cell Z is formed. The size of the radio cell Z is usually determined by the range of a general sig Broadcast Control Channel (BCCH), the from the base stations NB with a maximum and constant transmission power is determined. More lo signaling channels, such as a paging Channel (PCH - Paging Channel), a notification channel (NCH - Notification Channel) or an access confirmation channel (AGCH - Access Grant Channel) are together with the Signa BCCH lization channel separated in time in one physical P-CCPCH transmission channel. Continue to be from the base station NB in a pilot channel Pilot Synchroni Sationssequenzen sent that a synchronization of the Subscriber station UE on the time base of the base station NB serve.

With sectorization or with hierarchical cell structure Ren can also use several radio cells Z per base station NB be worried. The functionality of this structure is on other radio communication systems in which the Er can be used.

The example in FIG. 1 shows a subscriber station UE which is located in the radio cell Z of a base station NB. The subscriber station UE has established a communication link to the base station NB, on which a signal transmission of a selected service takes place in the upward UL and downward direction DL. The communication link is separated by one or more spreading codes assigned to the subscriber station UE from communication connections set up in parallel in the radio cell Z, the subscriber station UE each partly or all spreading codes currently assigned in the radio cell Z for receiving the signals according to the own communication link uses the well-known joint detection method.

The frame structure of the radio transmission of the TD-SCDMA mobile radio system is shown in FIG. 2. The radio interface is a broadband radio interface with a frequency band B = 1.6 MHz (thus three frequency bands per 5 MHz), with a time frame duration of 5 ms (thus two time frames for each UTRA time frame), with 7 time slots ts one each length of 675 us for traffic channels, as well as with CDMA subscriber separation using 16 different spreading codes c0 to c15.

Corresponds to the TDD transmission method shown the frequency band B for the upward direction UL the frequency band B for the downward direction DL. The same thing is repeated for further carrier frequencies. Through the variable assignment of the time slots ts for the upward or downward direction UL, DL can prescribe a variety of asymmetrical resource allocations be taken. Part of the time slots td0. , , tdn is ent speaking for the signal transmission in the downlink DL (Downlink) and the remaining time slots tu0. , , tum for the Si Signal transmission in the upward direction UL (uplink) used. The Parameters n, m and thus the switchover point SP (switching Point) are individually adapted to current needs bar, where the relationship n + m + 2 = 7 applies. In time  Connection to the first time slot td0 for the downward direction tung DL follows a protection period to separate the transmission directions DL and UL, which represent the switchover point SP provides.

The guard time consists of a downward pilot time slot DPTS (Downlink Pilot Time Slot) with a length of 75 us for Sending through a set of so-called gold codes below different synchronization sequences, from a protection time GP (Guard Period) with a length of 75 us for the switchover between sending and receiving in the base station NB, as well as from an UPTS time slot UPTS (Uplink Pilot Time slot) with a length of 125 us for sending a syn chronization sequence when trying to establish a connection a subscriber station UE with a subsequent signal RACH random access channel. To the sub separation of several subscriber stations UE in this case a set of gold codes is used.

Information of several connections is transmitted in radio blocks within the time slots ts. The data d are connection-specific with a fine structure, a spreading code c0, c1. , , cn spread so that, for example, n connections can be separated at the receiving end by this CDMA component. The spreading of individual symbols of the data d causes T _sym Q chips of the duration Tc to be transmitted within the symbol duration. The Q chips form the connection-individual spreading code c. A channel measurement sequence tseq is also embedded in the radio blocks for a channel estimate at the receiving end. A radio block is completed with a protection time gp.

The parameters of the radio interface used for the described TD-SCDMA system are advantageously:
Chip rate: 1.28 Mchip / s
Frame duration: 5 ms
Number of time slots: 7
Duration of a time slot: 675 µs
Spread factor: 1 to 16
Bandwidth: 1.6 MHz

These parameters enable the best possible harmonization with the UTRA TDD and FDD mode (FDD frequency division du plex) and the well-known GSM mobile radio system.

The method according to the invention for signaling the start of a time frame within an interleaving frame, for signaling the position of a time frame within an interleaving frame or for signaling the position of the interleaving frame within a superframe is based on modulating the phase of the pilot channel pilot in the downward pilot time slot DPTS. For this purpose, according to the invention, the midamble, also referred to as the training sequence tseq, of the shared physical transmission channel P-CCPCH is used as a reference value for determining the phase difference. Using this channel as a reference value has the advantage that it is sent in every time frame for and the midamble always corresponds to the first derivative of the midamble basic code used in the radio cell. This is known per se to the subscriber station UE. Furthermore, as shown in FIGS . 2 and 3, the P-CCPCH is always sent in the last time slot td0 for the downward direction DL, so that a minimum distance a between the center of the middle tseq0 and the center of the sync sequence sync Pilot channel pilot is given. The distance a between the midamble tseq0 and the synchronization sequence sync in the TD-SCDMA system is 393.75 us or 31.5 symbols, for example, and determines the effects of the time variation and frequency offset on the detection algorithm used.

To detect the modulation of the pilot channel pilot, ver Different algorithms can be used, the following put algorithms themselves in the complexity and reliability differentiate.

In a first algorithm, the midamble of the P-CCPCH and the region around the DPTS is detected. Then one Channel estimation in the channel estimation window for the P-CCPCH carried out. The strongest channel impulse taps are with a Channel impulse response post processing algorithm that works for one known joint detection process is used. The content of the DPTS is subsequently described using a so-called Matched Filters detected (folded with the channel pulse answer) and the output signal of the matched filter demodu profiled.

With other algorithms, for example:

• - The frequency offset by means of the midamble tseq0 and / or the synchronization sequence determines sync,
• - The information of the frequency tracking algorithm for the Frequency offset used, this can be used for a double check during the detection of the P- CCPCH are performed
• - an adaptive equalization to update the channel im pulse response used, with the channel impulse response at the end of the P-CCPCH radio block as a reference for determining the Modulation of the pilot channel pilot is taken into account, and
• A channel estimate using the last detek symbol of the P-CCPCH.

Different signals according to the invention are described below strategies described.  

In the case of 4PSK modulation for the DPTS, two bits per time frame. These are two bits sufficient for signaling the Posi, for example tion of the current time frame within a mine development framework. More than one time frame is necessary for the Si gnalization of further information.

According to a first embodiment of the invention The position of the current time frame becomes internal half of a nesting frame in each time frame signa lisiert. This is done according to the exemplary table 1 the respective time frame number of a specific phase dif reference compared to a previously determined phase orderly. The phase difference is, for example, in each Time frame determined.

Table 1

The minimum number of time frames to be detected to determine the Po position within the nesting frame bears in this configuration is one. For example assign a BCCH timeframe within a superframe of 48 timeframes need to determine at least 4 timeframes can be detected.

The position of the Timeframe within a nesting frame directly encoded, after only one detection of a DPTS is the position  determinable. For a double check during the emp Starting with a nesting frame, further steps can be taken be performed. In the event of a strong frequency Offsets are the first and third time frames of a ver nesting framework without possible ambiguity difference encoded, and the second and fourth time frames are with a encoded double ambiguity.

According to a second embodiment of the method according to the invention The beginning of a nesting frame will differ tial and the position within a superframe directly in the first and third time frames of a nesting frame mens signals.

For the exemplary case that the start of the mine is only signaled differentially, the direct signaling for specifying, for example, the Be of the next BCCH nesting frame the. The P-CCPCH, for example, has two equidistant BCCH- Nesting frame within 12 nesting frames of a super frame. For the signaling of the Be the next BCCH nesting frame will follow of the scheme given in Table 2 used. Doing so the phase for the first time frame within chess defined according to the following rule.

Table 2

In this example, the phase is for the third time frame within the nesting frame 90 ° larger. The he time frame is within the nesting frame by a phase difference of 0 or + 90 ° compared to the Phase of the previous time frame. The third time frame is within the nesting frame accordingly characterized by a phase difference of -90 ° net. In the event that a phase offset of 225 ° or 315 ° is detected, the subscriber station can the first Time frame of the nesting frame within two or four timeframes and then determine if this nesting frame is a BCCH delt, or only one of the following nesting frames corresponds to the BCCH.

The minimum number of time frames to be detected for the determination The position of the nesting frame is at this method 2 to 3. The minimum number to detect the time frame for determining the BCCH nesting frame mens is 2 to 4 accordingly.

In addition to the advantages mentioned in the first description NEN execution can be the position of a Nesting frame advantageous with ambiguity si be signaled.

According to a third embodiment of the invention Procedure will both start a nesting frame mens as well as its position within a superframe signaled directly. In this version, for example the phase 45 ° to mark the beginning of a chess frame reserved. For the further timeframes of The nesting frame is the respective phase 135 °, 225 ° and 315 ° only to determine the position within the Super frame used. To avoid detection errors between  45 ° symbols and the other symbols indicate the white phase quadruples as many 225 ° symbols as possible. The 180 ° phase difference results in a one clear assignment. The closer a BCCH nesting frame more 225 ° symbols are used. This Relationships are shown in Table 3 below.

To determine the position within the superframe the four phases (phase quadruples) of an interleaving frame mens evaluated. With a length of a super frame of 48 This allows 12 nesting frames, each with time frames because 4 time frames can be distinguished.

Table 3

The minimum number of time frames to be detected for the determination position within a nesting frame carries 1 to 3 in this version. The minimum number increases detecting time frame for determining the BCCH and the Super frame is 3 to 4.

This inventive method is advantageous ben already advantages of the previous procedure ren the beginning of a nesting frame advantageous di right coded. Furthermore, the temporal structure of the Su signaled in just four time frames. The order and the phase quadruple used can be opti be mated that a differential decoding of four or five successive DPTS also a detection of the position inside half of the superframe for large frequency offsets. Detection under poor transmission conditions This version enables reliable detection of the Super frame.

The case can occur in poor transmission conditions ten that a subscriber station is unable to BCCH or another logical channel to be clearly identified due to the fact that several logical channels are combined on one used physical transmission channel P-CCPCH mapped become. In the known GSM mobile radio system, the BCCH using a synchronization channel SCH (synchronization  Channel) signals. Such a channel is in the described TD-SCDMA system is not provided. This information mation is implicit in the phase difference.

To ensure a safe De in bad transmission conditions tection of the BCCH, for example uncoded radio block of the logical channel a status indicator f (flag) added, which consists of one or more bits or Symbols to distinguish the different logical Ka can exist. The binary state of this status indicator f defines which logical channel it is delt.

A correct detection of the logical channel is made possible by the in-band signaling of the status indicator f described below in relation to FIG. 4. The method described above using the phase difference can thus be used without thinking, since the correct channel for determining the phase difference is always referenced in the detection.

FIG. 4 shows the inventive expansion of a radio block to a status indicator f. An encoder is in a first step 1 a radio block with, for example, 184 bits or data symbols d. In a second step 2, a further bit for the status indicator f is added to this radio block. According to an exemplary third step 3 , a CRC checksum (Cyclic Redundancy Check) is added to the expanded radio block by block coding, and in a fourth step 4 there is finally a folding coding of the radio block.

The status indicator f is therefore double for the transmission Protected via the radio interface and can safely detec be animals. A binary state of the status indicator f of 1  can, for example, identify the BCCH while the other logical channels identified by the binary state 0 are drawn. When using multiple bits for the status on pointer is also a distinction between the other logical ones Channels possible.

Claims (17)

1. Method of signaling the start of a logical Channel (BCCH) in a shared physical Transmission channel (P-CCPCH) of a radio communication system, in which the beginning by means of a phase relationship between the logi channel (BCCH) and another physical transmission channel (pilot) is signaled. 2. The method according to claim 1, wherein a phase difference between symbols of the logical channel (BCCH) and symbols of further physical transmission channel (pilot) signals the start. 3. The method according to any preceding claim, in which through a phase modulation of the symbols of the further physika The transmission channel (pilot) signals the start becomes. 4. The method according to the preceding claim, wherein the phase of the logical channel (BCCH) as a reference to the Be mood of the phase difference is used. 5. The method according to any preceding claim, in which the logical channel (BCCH) nested over several time frames men (fr) within the shared physical Transmission channel (P-CCPCH) is transmitted. 6. The method according to any preceding claim, in which in the shared physical transmission channel (P-CCPCH) at least one further logical channel (PCH) via will wear. 7. The method according to any preceding claim, in which  the logical channel (BCCH) in a number of time frames (fr) within a su consisting of several time frames (fr) per frame is sent out. 8. The method according to the preceding claim, in which through the phase relationship a position of the respective time frames (fr) within the nested time frames (fr) is defined for the logical channel (BCCH). 9. The method according to any one of claims 1 to 7, in which a position of the beginning of the ver nested timeframes (fr) within a superframe si is signaled. 10. The method according to the preceding claim, in which the position of the respective time frame (fr) within the nested time frame (fr) for the logical channel (BCCH) defined by a differential phase relationship becomes. 11. The method according to any one of claims 1 to 7, in which the position of the respective time frame (fr) within the nested time frame (fr) for the logical channel (BCCH) and the position of the start of the nested Time frame (fr) within a super frame by one each defined constellation of several phase relationships becomes. 12. The method according to any preceding claim, in which the logical channel (BCCH) by a status indicator (f) of distinguishable at least one further logical channel (PCH) is. 13. The method according to any preceding claim, in which  a physical transmission channel (P-CCPCH, pilot) at least one frequency band (B) and one connection individual ellen spreading code (c) is defined. 14. The method according to the preceding claim, in which a physical transmission channel (P-CCPCH, pilot) too is additionally defined by a time slot (ts). 15. The method according to claim 6 or 7, wherein the radio interface of the radio communication system according to is organized in a time-division duplex process. 16. The method according to any preceding claim, in which the signal transmission in a downward direction (DL) from one Base station (NB) of the radio communication system at least a subscriber station (UE) is carried out. 17. Base station system (BSS) of a radio communication system stems for performing the method according to claim 1.