JP2001060894A - Radio communication system with periodic and unique cell bit sequence in local communication signal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To discriminate a true pass and the false pass in spread spectrum communication by selecting a bit sequence so as to include one period of the continuous bit sequences in transmission by a transmitting circuit. SOLUTION: Base stations BST1 and 2 of a cellular communication system 10 respectively execute communication with devices in cells 1 and 2. Communication ranges of the cells 1 and 2 are overlapped. A user station UST is a mobile station. Information in one time slot of a radio frame includes a data symbol group and mid-ambles being the bit sequence. The mid-ambles are used for channel estimation and inserted to each time slot in the frame to be transmitted by a transmitter. The sequence of the plurality of mid-ambles are assigned to the cells 1 and 2 and the transmitter is periodically operated to permit one mid-amble to pass at a time.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to wireless communication systems, and more particularly, to distinguishing between a true cell bit sequence and an error-prone cell bit sequence.

[0002]

BACKGROUND OF THE INVENTION Wireless communication is extremely widespread in business, personal and other applications, and as a result, such communication technology continues to advance in various fields. One such advance involves the use of spread spectrum communication, including the method of code division multiple access (CDMA). In such communications, a user station (eg, a handheld cellular telephone) communicates with a base station, where the base station typically corresponds to a cell. More specifically, CDMA systems are characterized by transmitting different data signals simultaneously over a common channel by assigning a unique code to each signal. This unique code is matched with the code of a given user station in the cell to determine the appropriate recipient of the data signal.

[0003] CDMA is the next generation wideband CDM.
A (WCDMA) continues to evolve with the corresponding standards that spawned it. WCDMA includes another method of data transfer, one method is frequency division duplex (FDD)
Another method is time division duplex (TD).
D) Method. Since the present embodiment has certain advantages in TDD, the TDD will be further introduced herein. The TDD data is transmitted within a data packet of a predetermined time, that is, a time slot, by using a quadrature phase shift key (QPS
K) Sent as a symbol. Two-way communication is possible within a data frame having 15 of these slots. That is, one or more of the slots can accommodate communication from the base station to the user station, and other slots in the same frame can accommodate communication from the user station to the base station.

[0004] Each TDD data packet contains a predetermined training sequence in a time slot. This training sequence is referred to in the art as the mid amble and indicates a known data pattern used to make a channel estimate. In particular, this midamble contains information unique to a given cell and is selected from a predetermined set of 128 possible different bit sequences. Thus, a given cell is assigned a unique sequence, and this information is coded in the midamble of a data frame transmitted by stations in the corresponding cell. Conversely, data packets exchanged for neighboring cells comprise different sets of internally encoded bit sequence sets and have a midamble corresponding to the neighboring cells. Finally, it should be noted that at a given time, the base station can communicate (ie, sectorize) with different cells. In this case, for each different cell, a different unique midamble is encoded in the data frame transmitted for that base station. In the remainder of this specification, for simplicity, each base station will only be associated with one cell, and in this regard the unique midamble of the cell may be considered unique for each corresponding base station. it can. In either case, the basic midamble code can be one of two lengths, which are now 456 bits long basic midamble code and 1
It is described as a short basic midamble code of 92 bits. The basic midamble code consists of the same bit sequence used in communication between the base station and all user stations in the cell corresponding to this base station, but each user station in the cell has the basic midamble code. Each user station can be distinguished from other user stations because different versions are assigned, shifted in time. The allocated shift amount is determined by converting the shift amount into the basic midamble code offset amount. That is, each user station in the cell is assigned its own offset amount indicating the amount of time shift adjustment with respect to the basic midamble code of the user station. For example, if the short length midamble code has a length of 192 bits and eight user stations communicate with one base station, the offset for each of the eight user stations is 2
Only 4 chips can be separated. Therefore, for each user station,
Except for shifting circularly by different multiples of 24 chips to correspond to the offset of a particular user station,
The same basic sequence is used for all of these user stations. After summing the circularly shifted elementary sequences, a period is formed to form a midamble of 256 chips long for a short elementary midamble code and 512 chips long for a long elementary midamble code. Prefix is inserted.

As described above in accordance with the prior art, and as further described below in connection with the preferred embodiment, two related features are obtained for the midamble. The first feature is the channel estimation and the second feature is the delay profile estimation (DPE). Considering first the channel estimation, the signal path is received by the receiver at different times, referred to in the prior art as different chip locations. Responsive to each of these paths that fall within a predetermined time referred to as the channel estimation window, and in particular to the midamble within each path within the channel estimation window, the receiver determines the corresponding channel estimate for each path. Is calculated. This channel estimate can be calculated using a Fourier transform applied to all composite signals present in the channel estimation window. In this case, the composite signal is a function of the midamble of any path occurring within the window. The result of the Fourier transform indicates the chip estimates at each of the chip positions in the window, and the calculated chip estimates are stored relative to the chip position for each estimate. Once the channel estimates are obtained, the receiver also performs a DPE by non-coherently averaging the channel estimates derived from the midamble over a number of frames, and thus, this generally results in each bit in the channel estimation window The respective absolute channel estimates for the location are summed. Thus, the DPE indicates the average power at each bit position over a number of frames, and thus seeks to average out fading and noise. In response to the DPE, the channel estimate corresponding to a bit position having an average power greater than a predetermined threshold is used to generate the channel estimate for further signal processing, for example using a maximum ratio combination (MRC) process. For further use by the receiver.

[0006]

In order to evaluate the contents of the preferred embodiment, the reception by the receiver of both the true path and the false path will be further described. In particular, recall that the midamble used in one cell is different from the midamble used in an adjacent cell. Nevertheless, receivers often receive paths from both stations in the cell where the receiver is located and other stations in one or more neighboring cells.
Thus, each of the receive paths includes either a midamble for the cell in which the receiver is located or a midamble from a different cell. Ideally, the receiver should only attempt to communicate with other stations in the cell where this receiver is located, and if it correctly determines its channel estimate, it will be able to communicate with other stations in the cell where the receiver is located. Should be determined to respond only to the paths (and corresponding midambles), and these paths are referred to as true paths. Even in the ideal case, receivers should ignore paths received from transmitters in other cells, and in the sense that these paths indicate information about receivers that are not from the cell with which they are trying to communicate, Called a fake path.

Although the above features of channel estimates and DPE provide a certain level of receiver performance in the prior art, but in connection with embodiments of the present invention, such operation is another operation that depends on these earlier operations. It has been determined that the performance of (for example, MRC) can be improved so as to increase. In particular, by identifying paths with relatively high average power, the path with relatively low average power can be considered as a false path while the DPE
Can be understood as trying to identify only the true path received. However, the inventors have recognized that while the DPE process eliminates some spurious paths that occur due to noise or fading, the DPE process cannot reject a significant number of other spurious paths. . Further DP
The inability to reject such spurious paths in E has been observed to occur due to the high cross-correlation between different midamble sequences. In other words, for 128 possible sequences (either 192 bits or 456 bits), there is considerable cross-correlation between the various pairs of these sequences. Thus, these cross-correlations result in spurious paths that conventional DPE processes cannot address. As a result, in the prior art, some of these false paths are
Channel estimates that are accepted by the process as true paths, and thus correspond to these false paths, are used for further processing by the receiver, and such use reduces resources that work better to process the true paths. . Also, by way of example, the channel estimates corresponding to these false paths may be assigned to different fingers at the rake receiver performing the MRC analysis, in which case these fingers are assigned to the true path channel estimates. So better suited. Thus, in the prior art, there is considerable potential for communication from neighboring cells to reduce the user station's ability to perform channel estimation.

In consideration of the above description, there is a problem of improving the DPE in response to the true midamble sequence and the false midamble sequence, and this problem is solved by a preferred embodiment as described below. Will be resolved.

[0009]

SUMMARY OF THE INVENTION In a preferred embodiment, a wireless communication system is provided. The system includes a transmitting circuit that includes a circuit for transmitting a plurality of frames to a receiver in a first cell. Each of the plurality of frames includes one bit group that uniquely distinguishes the first cell from a second cell adjacent to the first cell. The transmitting circuit further includes a circuit for inserting a bit sequence into the bit group, wherein the bit sequence includes a plurality of bits such that a continuous transmission signal from the transmitting circuit includes one period of a continuous bit sequence among the plurality of bit sequences. From the bit sequence. Other circuits, systems and methods are also disclosed and claimed.

[0010]

FIG. 1 shows a diagram of a cellular communication system 10 according to a modern code division multiple access (CDMA) or wideband CDMA (WCDMA) example in which the preferred embodiment can be implemented. Shown in the system 10 are two base stations BST1 and BST2, each base station BST1 and BST2 including a respective antenna AT1 and AT2 from which each station can transmit and receive CDMA signals. The general coverage area intended by each base station defines a corresponding cell. Accordingly, base station BST1 is generally adapted to communicate with cellular devices in cell 1 while base station BST2 is generally adapted to communicate with cellular devices in cell 2. Of course, the communication range of cell 1 and the communication range of cell 2 overlap due to the design that supports continuous communication when the communication station moves from one cell to another. Further in this regard, system 10 also includes a user station UST. This user station is shown in connection with automobile V to indicate that it is a mobile station. Therefore, the vehicle V and the corresponding user station U
The ST is free to move within and between cells 1 and 2 (or other cells). By way of further example, user station UST includes a single antenna ATU for transmitting and receiving cellular communication signals.

In some respects, system 10 includes a CDMA
It can operate in accordance with general known techniques for various types of cellular or other spread spectrum communications, including communications. Such general techniques are known in the art and include initiating a call from a user station UST and handling the call by either or both base stations BST1 and BST2. One skilled in the art would know of other techniques.

One feature of the operation of the system 10, further enhanced in accordance with the preferred embodiment and also shown in the prior art in various respects, is related to a technique known as channel estimation. This channel estimation is used by the receiver, where such a receiver is either in the user station UST or the base station BST and can estimate the effect superimposed on the signal transmitted from the transmitter. For example, referring to FIG.
Are present, when the user station UST receives data frames from the base station BST1, these frames are said to have arrived along the communication channel, and the user station UST attempts to determine the effect of these channels on the communication. . In an attempt to eliminate channel effects by estimating these effects, the received signal or subsequently received signals can be processed by taking into account the channel estimates, thus allowing the true data transmitted by base station BST1 to be correctly interpreted. I can recover. At a similar point, when base station BST1 receives a data frame from user station UST, base station BST1 also attempts to determine the channel effect superimposed on the data frame. In either event, the channel estimation is performed in response to the coded midamble in each data frame received by the receiver, as described in the prior art description herein. The frame and midamble concepts associated with both and the preferred embodiment are further discussed as follows.

FIG. 2 shows a TDD radio frame FR. The midamble of the preferred embodiment can be embedded in this frame, in which case the frame F
The general timing associated with R and the division into parts are known in the art. Frame FR
Is 10 milliseconds long and is divided into fifteen equal-length slots (thus each slot has a length of 667 microseconds). For reference, FIG. 2 shows such slots as SL ₁ to SL ₁₅ , and the slot SL ₁ is enlarged as an example in FIG. 3 to show further details as follows.

FIG. 3 shows the structure of a TDD time slot, where slot SL ₁ from FIG. 2 is shown by way of example. Thus, each slot containing a slot SL ₁ is
It is generally divided into what is called a chip in the CDMA technology. In particular, the CDMA communication signal is modulated using a spreading code consisting of a series of binary pulses, and each part of the CDMA signal transmitted according to this code is called a chip. Since the current CDMA transfer rate is 3.84 M chips / sec, the 10 ms frame FR includes 38400 chips (for example, 3.84 M chips / sec × 10 ms = 38400). As a result, each of the 15 slots contains a total of 2560 chips (eg, 3
(8400 chips / 15 slots = 2560) Each of the 160 CDMA signals in one slot is modulated by 16 chips (ie, 2560 chips / slot ÷ 1 slot / 160 symbols = 16). . Considering further division of the information in one time slot as the example of time slot SL ₁ shows, this information comprises a first group 20 of data symbols having 1104 chips. In the example of a spreading factor equal to 16, the first group 20 corresponds to 69 data symbols. First group 20 in time slot SL ₁
Is followed by a midamble 22 having 16 symbols in the example where the spreading factor is equal to 16. As described earlier in the description of the prior art herein, the midamble 22 includes a predetermined training sequence, where the training sequence is used for channel estimation purposes commonly determined using a Fourier transform process. Used for Thus, these midamble signals correspond in some respects to pilot symbols used in frequency division duplex (FDD) systems. The following midamble 22 in time slot SL _1, the second data symbol having 1104 chips
Group 24 follows. It should be noted that the channel estimate derived from midamble 22 preferably applies to both first group 20 of data symbols and second group 24 of data symbols. Finally, the second group 26 in time slot SL ₁
Is followed by a guard time 26. This guard time 26 is 9
It has six chips.

FIG. 4 shows a diagram of one embodiment of a midamble pattern used for channel estimation and further illustrating the use of the midamble pattern for multiple user stations. In particular, FIG. 4 shows a single cell, for example cell 1 in FIG.
Shows four midamble 30 ₁ to 30 ₄ corresponding to the four respective user stations in. Each midamble indicates a cyclic prefix, where each cyclic prefix is a C
They are identified by adding a P subscript (e.g. a cyclic prefix 30 _1CP for midamble 30 _1). Each midamble also includes a circularly shifted basic sequence area, which is identified by adding the suffix BSA to the midamble identifier (eg, midamble 3).
0 ₁ is the basic sequence area _{301 BSA} ). In FIG. 4, the physical gap between each periodic prefix and its basic sequence area is shown for illustration only. Here, the information for the predetermined midamble actually starts from a cyclic prefix,
It should be noted that the information in the circularly shifted elementary sequence area is continuously provided as follows.
Each of these components of the midamble is described further below.

Each circularly shifted elementary sequence area contains a unique elementary sequence of cells, the unique elementary sequence being circularly shifted relative to the elementary sequence for each other user station in the same cell. Located in. To illustrate this feature, FIG. 4 shows diagonal lines within each basic sequence area to indicate the logical starting point of the sequence, and the unshaded areas indicate the rest of the basic sequence. belongs to. For example with respect midamble 30 _1, in its basic sequence area 30 _1BSA, starting point logically located on the left side of the area, another part of the base sequence bit basic sequence is present followed. In contrast, although midamble 30 ₂ comprises the same basic sequence area 30 _2BSA, time to basic sequence area 30 _1BSA starting point of the midamble 30 ₁ with portions thereof hatching basic sequence Shows that it is further shifted to the right. The shift amount of one basic sequence is determined as an offset amount for each user. Other extent that basic sequence area 30 ₁ is shifted to the right, as logical end of the sequence to the beginning of the area 30 _2BSA actually temporally occurs, the ends of the information of the base sequence Note that there is overlap. The same overlap effect occurs for the base sequence as it is when coded in areas _{303 BSA} and _{304 BSA} . The reason for this is that the starting point of the basic sequence within that area (eg, shown diagonally) is continuously shifted further to the right, and thus overlaps, so that the left part of each area has a larger This is because parts remain. Finally, note that for all midambles in FIG. 4, the tail end region 32 is generally defined as the region to the right of the vertical dotted line _32DL . The tail end region 32 is a cyclic prefix for each user station's midamble, and the tail prefix is simply the corresponding tail end region 32 for the midamble.
It is shown to indicate that it is a copy of the bit pattern in. For example to the user 3 and its midamble 30 _3, a part of those skilled in the art starting point of the bit sequence as indicated by the portion to the tail end area 32 marked with diagonal lines for for midamble 30 ₃ shows This part is followed by additional bits of the basic sequence indicated by the unshaded part,
These two parts are also shown to the same extent within the cyclic prefix _303CP .

FIG. 5 relates to the preferred embodiment and shows a conceptual diagram of a number of paths received by a receiver (eg, UST), where, for example, a total of five paths P ₁ -P ₅ are on the horizontal axis. Along the chip location is shown. The apparent vertical axis is not shown, but the relative magnitude of each pass is indicated by the relative height of each pass in FIG. Furthermore, the threshold THR is shown with all paths P ₁ to P ₅ exceeds the threshold THR for explanation. Furthermore, the path P ₂ and P ₄ are hatched marked to indicate that these paths is a true path, this is the path from these paths within the cell user station being received is located Means that On the contrary, the other paths P ₁ , P ₃ and P ₅ are not shaded, indicating a false path. That is, these paths exhibit cross-correlation with midambles from one or more different (ie, potentially adjacent) cells. Of course, the receiver for receiving the path P ₁ to P ₅ is which path is true at the time of reception of these paths, not been informed about which path is false, it can not distinguish between these paths This gives rise to considerations in connection with the preferred embodiment described below.

Assuming that a receiver can receive both true and false paths, both the prior art and the preferred embodiment will reduce the effects of false paths during receiver processing and operation. And strive. Thus, there is a goal in the prior art for receivers to reject false paths, and this concept is sometimes referred to as inter-cell reject. That is, the receiver attempts to reject paths from cells other than the cell in which the receiver is located. More specifically, as relevant to the present embodiment, each path further indicates the reception of a frame including a slot and a corresponding midamble. Generally related to the same that receivers attempt to improve inter-cell rejection, and particularly as related to the description herein, the receiver seeks to improve mid-amble inter-cell rejection. That is, it rejects the false path with the corresponding midamble and tries to prevent the channel estimate from that midamble from being used for further processing, such as a maximum ratio combination (MRC) operation. Further in this regard, FIG. 6 shows a plot of an example of the cumulative distribution of inter-cell rejects according to the prior art. In particular, FIG. 6 illustrates the case where a receiver (eg, UST) receives two paths within a channel estimation window of 24 chips, each path having a respective midamble of the same power of length 256. Where one of the midambles is considered to be a true midamble (eg, from base station BST1),
The other midamble is considered to be a fake midamble (eg, from base station BST2). An inter-cell jam rejection rate of 6 dB means that the strongest false path caused by cross-correlation from the jamming base station is 6 dB lower in power than the true base station strongest path. Therefore, the strongest path from the true base station is amplitude 1 (ie, 0d
B power), the strongest false path has an amplitude of 0.
5 (that is, -6 dB power).

Assuming the cumulative distribution of FIG. 6, D is generally an attempt to distinguish between true and false paths.
In the PE process, the threshold is used by the receiver. In this case, this threshold can be conceptually recognized as threshold THR in FIG.
However, if the threshold THR is set to a relatively low value to increase the likelihood of including the true path, those skilled in the art will recognize that the false path can be thresholded by the relatively large cross-correlation from the jamming transmitter. Understand that there is a possibility that If this occurs, the receiver responds to both the true path midamble and the false path midamble above the threshold THR, for example in the MRC operation described above, and performs further operations. Thus, false paths introduce additional noise into the signal processing and reduce the signal-to-noise ratio. Alternatively, the threshold THR can be set very high, but this also eliminates weak true paths. Such alternatives result in a loss of diversity and a loss of signal power, which degrades signal-to-noise performance.

FIG. 7 is a block diagram of a base station BST1 (or BST2) according to a preferred embodiment for a transmitter / receiver, where various features associated with midamble transmission are described with reference to FIG. This can be realized as described in more detail below. Next, the structure of the base station BST1 according to the present invention will be described with reference to FIG. Those skilled in the art will appreciate that this particular architecture is merely illustrative and that other base station architectures may be used within the scope of the present invention. Further, as will be described in more detail below, the structure of FIG. 7 differs from a base station and can be easily modified to show a preferred embodiment of a transmitter / receiver for use at a user station (eg, UST). .

As shown in FIG. 7, base station BST1 drives the amplified transmission signal through base station antenna AT1 (or multiple antennas), and transmits antenna A
It includes an amplifier 42 for amplifying the signal received from T1. RF interface function circuitry 44 includes appropriate transmit / receive formatting and filtering circuitry. Further, the RF interface function circuit 44 includes an analog-to-digital converter for digitizing the amplified received signal and a digital-to-analog converter for converting the transmitted signal into an analog domain. Thus RF
The interface function circuit 44 communicates digitally with the baseband interface 45, and the baseband interface 45 communicates with the RF interface function circuit 44.
And the baseband device 40 performs appropriate signal formatting.

The baseband device 40 communicates by way of a physical layer interface 55 and a network interface adapter 56 with a packet network as shown in FIG. Physical layer interface 55 and network interface adapter 56 are conventional subsystems selected according to the type of network and corresponding interface desired for base station BST1.

The baseband device 40 is a base station BST
1 performs a digital signal processing function when processing a wireless communication signal, and the base station generates a midamble according to a preferred embodiment as described later, among other functions, among other functions. And
There is a function of embedding these in a frame time slot. In order to perform these functions, the baseband device 40 includes a TMS320 available from Texas Instruments, with appropriate memory and external functions suitable for handling the digital processing conditions of the base station BST1.
one or more high performance digital signal processors (DS) such as c5x and TMS320c6x class DSPs
P) It is a subsystem including a device. In FIG. 7, an implementation of baseband device 40 is described according to various functions, rather than its structure, and those skilled in the art will be able to describe this function and base station BST.
The baseband device 40 could easily be implemented using such a conventional integrated circuit according to the capacity desired in (1).

On the transmitting side, the baseband device 40 includes a coding and modulation function circuit 54 coupled between the physical layer interface 55 and the baseband interface 45 as shown in FIG. This coding and modulation function circuit 54 receives digital data from the physical layer interface 55 and, for a particular protocol,
Perform appropriate digital processing functions. For example, the coding and modulation function circuit 54 can first code the received digital data into symbols. As another example, the encoding and modulation function circuit 54 can position these symbols in frame time slots, each time slot having a midamble inserted between data symbols as previously shown in FIG. . Next, all symbols are spread into chips of a certain sequence by a spreading code according to a predetermined chip rate. This spreading may also include spreading the symbols over multiple subchannels.
In general, a cell-specific scramble signal is added to the spread symbol so that the radio unit on the receiving side can distinguish the transmission signal generated by the base station BST1 from the transmission signal of an adjacent cell. Next, modulation of the spreading symbol is performed.
In general, a number of sub-channels are divided into an in-phase group (I) and a quadrature group (Q), so that the resulting modulated signal contains both components. The spread spectrum signal is then applied to the baseband interface 45 and, after appropriate filtering and pre-equalization for channel distortion, is transmitted from the antenna AT1 via the RF interface function circuit 44 and the amplifier 42.

On the receiving side, the baseband device 40
After digitizing the received signal in the F interface function circuit 44, the incoming digital signal from the baseband interface 45 is received. These signals are applied to a chip rate demodulation and despreading function circuit 48, which derives transmitted symbols from the digitized received data. Considering that base station BST1 receives signals from multiple wireless user stations in a cell over multiple channels, channel estimation function circuit 46 estimates random channel changes. Channel estimation function circuit 46 and chip rate demodulation and despreading function circuit 48
Provide an output to a symbol user detection and combination function circuit 50, in which the demodulated data is associated with a respective channel. Furthermore, recalling earlier that the block diagram of FIG. 7 could easily be modified to be a block diagram of the user station, such changes can be made by further including a joint detection function in block diagram 50. You can further understand that In this case, the joint detector is TDD
Provide a preferred multi-user detection function for the system.
The reason is that the spreading factor is relatively small (eg, 16) and there is considerable interference from other users. Thus, the joint detector works to offset interference from other users. Returning to general block 50, after the demodulated data has been associated with each channel, the symbol decode function circuit 52 transmits the received symbols to the physical layer interface 55 and the network for each channel, and thus for each conversation. Decoding into a bit stream suitable for communication with the network via the interface function 56.

FIG. 8 shows an example of a base station BST1 or BS
FIG. 3 shows a state diagram of a preferred embodiment method for operating a transmitter (either in T2 or in a user station UST) and cycling the midamble the transmitter includes during transmission. To focus on the preferred features, FIG.
The state diagram of FIG. 7 relates only to the insertion of the midamble into the frame (ie, its time slot) by the transmitter, and such operation can be performed through the coding and modulation function circuit 54 of FIG. However, those skilled in the art will appreciate that the transmitter (and its associated receiving circuitry)
Perform a number of other functions not described with reference to FIG. 8 at the same time. Looking at this state, the transmitter starts to operate in the first state S _1. Next, the operation continues from the state S ₁ to state S _2, the transition indicates a formation of the first frames F ₁ to be transmitted by the transmitter. In particular for each time slot in the first frame F _1, the first midamble M ₁ is inserted into the time slots for the first frame F ₁ (in FIG. 8 M ₁ →
Shown as F _1). The operation then shifts from state S ₂ to state S _3. This transition denotes the formation of a second frame F ₂ to be transmitted by the transmitter. For each time slot in this second frame F ₂ , a second midamble M ₂ is inserted into the time slot for the second frame F ₂ (ie, M ₂ → F ₂ ). Furthermore, each separate change the state in FIG. 8, the operation of passing the state S ₃ is repeated, thus the frame F _K final state S _K indicating the formation of a
It is shown. Here, for that frame, the transmitter inserts a midamble M _K into each time slot for that frame F _K.

The first sequence in the state shown in FIG. 8 will be described.
Then, the next of these states (and another successive)
Pay attention to the sequence. First, state S_KReach
And midamble M_KWith frame F_KWas sent
Later, frame F₁To F_KThe midamble corresponding to
Midamble M₁To M_KEach sequence up to
Can be interpreted as circulating. Frame F_KAnd its mi
Doamble M_KAfter the transmission of the state S, the flow of FIG.₁To
Return. Therefore, the next frame that the transmitter should transmit is F
_{K + 1}Can be displayed. Therefore, the miss for this frame
Doamble M₁To M _KPeriodic sequence to the
-Start with the first midamble in Kens
Is repeated. Therefore, the frame F is next transmitted by the transmitter.
_{K + 1}Within M₁Is inserted. Each additional frame is created
As the period passes through the midamble sequence,
Each additional state occurs so that it is continuous, and thus the frame
F_{K + 2}Midamble M_TwoIs inserted and the frame F_{K + 3}
Hemid Amble M_ThreeIs inserted, and finally the frame F_2K
Midamble M_KThe same insertion is repeated until
Will be returned. Finally, the state diagram in Figure 8 can be repeated many times.
Can be. Where each iteration of all states is
Complete through the midamble sequence for the station
Corresponds to the cycle.

From the above description, it will be appreciated by those skilled in the art that in the preferred embodiment, the transmitter transmits only one assigned midamble corresponding to the cell in which the transmitter resides, as in the prior art case. I can understand that there is no. Instead, in the preferred embodiment, the cells are assigned a sequence of K midambles,
Transmitters communicating within this sequence operate periodically so that they only pass through these midambles one at a time. In the preferred embodiment, this periodic operation is such that a different midamble is used for each successive frame transmitted by the transmitter until all midambles in the period have been transmitted. Assuming such operation, various additional observations can be made in relation to a particular implementation. Those skilled in the art can select the value of K in FIG. 8 according to various considerations as a first observation. For example, during the development of the preferred embodiment, a value of K of 18 was found, resulting in a midamble of a periodic sequence having a total of 18 different midambles. More recently, as will be explained in more detail below, the preferred embodiment is to complete the operation over the prior art when K is a number less than 18, and to obtain significant advantages when K is equal to 2 or 4. Have been observed. As a second observation, those skilled in the art will be able to select a mechanism for implementing the sequence operation and its repetition. Note that in the preferred embodiment, the communication of the base stations in the TDD system is synchronized so that each frame includes the frame number of the system. Thus, tracking the change of each different midamble in the midamble of the periodic sequence can be correlated with the change in frame number of the system. In a preferred embodiment, for example, where the periodic sequence includes two different midambles (eg, K = 2), if the base station system has an odd frame number, the first midamble is inserted into the frame and transmitted. The second midamble can be inserted into the frame when the base station has an even frame number, and can be transmitted by the transmitter. As another example,
In a preferred embodiment where the periodic sequence has three or more different midambles (ie, K> 2), a modulo counter can be triggered each time the base station's system frame number increments,
With each change in the counter, a different next successive one of the midambles in the periodic sequence can be inserted into the frame and transmitted by the transmitter. One skilled in the art will be able to ascertain further examples.

Having described the transmission of a midamble for one cell through one period in accordance with the preferred embodiment, those skilled in the art will now briefly describe the corresponding operation by a receiver in a given cell, as will be briefly described below. Should be easily understood. In general, the operation of the receiver is parallel to the operation of the state diagram of FIG. 8, and for each successive state change, the receiver measures the channel estimate in response to the midamble for the current state. For example, in frame F ₁ , the midamble M ₁ is transmitted and is responsive to the frame number of the system and is selected from one period of this midamble, so that when the frame F ₁ is received, the receiver will receive the same system using the frame number by using the same midamble M _1, measuring channel estimation value, i.e., to evaluate the correlation between the midamble in the path and the received midamble M _1. Accordingly, such periodic operation at the receiver also continues for successive frames as indicated by the frame number of the system.
Therefore, when the next frame F ₂ are received by the receiver, the receiver uses the frame number of the system, using the midamble M ₂ to determine the channel estimation value, and displays the receiver . Thus, this process continues periodically for frame F _K until the use of midamble M _K to measure the channel estimate, after which the process is repeated with midamble M ₁ and a similar process continues.

To further illustrate the operation of the receiver in accordance with the preferred embodiment, FIGS. 9a-9d illustrate a receiver for a system using a system of _four midambles M ₁ -M ₄ (ie, K = 4). An example of each of the consecutive frames is shown. The general format of FIGS. 9a-9d corresponds to FIG. 5 in that each figure shows a conceptual diagram of the multiple paths received by the receiver at the indicated chip locations, and these figures show four mid-points. indicate the path identified by the receiver to perform channel estimation by using the period of the amble M ₁ ~M ₄ it is, could further understood with respect to these figures.
Thus, for FIG. 9a, the receiver is the midamble M ₁
To determine the channel estimate and respond to it,
Identifying the six paths P ₁₀ to P _15. Similarly, with respect to FIG. 9b, the receiver channel estimation value determined using midamble M _2, in response to which the four paths P ₂₀ to P ₂₃
Identify. It relates identifying diagram 9c path P ₃₀ to P ₃₆ in response to a channel estimate based on midamble M _3, diagram identifies the path P ₄₀ to P ₄₅ in response further to the channel estimate based on midamble M ₄ Similar observations can be made for 9d.

Turning now to FIGS. 9a-9d as a whole, the results of the preferred embodiment of a midamble that is periodic for transmitting and receiving signals can be understood. More specifically,
The receiver performing the DPE in the preferred embodiment performs the DPE by evaluating the channel estimate through successive frames using different midambles in the period as described above, and then the receiver performs , Further enhance this process by identifying paths that occur at the same bit position as true paths. In other words, for each of the individual FIGS. 9a-9d, according to the prior art, only the relative size of each path is not a basis on which to distinguish a true path from a false path. However, since the preferred embodiment uses different midambles for successive frames, only paths that occur at the same bit position over successive frames are likely to be true paths. To further understand this point, by contrast, when using the same midamble as in the prior art, one of ordinary skill in the art will appreciate that due to the cross-correlation from one or more other midambles, FIGS. Could estimate paths that exist at different locations, such as However, since the preferred embodiment uses a periodically changing midamble, paths occurring at the same bit position in successive frames are likely to deviate from strong autocorrelation for each different midamble in the period. Similarly, located paths are more likely to indicate true paths than fake paths. As a specific example, comparing FIGS. 9a and 9b, it can be seen that three paths occur at similar locations. That is, the paths P ₁₂ and P ₂₁ occur at the position 14 and the position 16
, Paths P ₁₃ and P ₂₂ occur, and path P ₁₄ and P ₂₃ occur at position 20. Various circuits, such as matching filters, can be used to identify these similarly located paths. In each case, FIG.
If there are only two midambles a and 9b, each of the three paths having a common bit position can be assumed to be a true path and the remaining paths can be estimated as false paths. However, by adding to analyze the Figure 9c and its midamble M _3, position 20 in the path is not identified, in the position 14 and 16 two paths (i.e. the path P ₃₃ and P ₃₄₎ is still present, these positions to 14 and 16, it will be appreciated that the path for the midamble M ₁ and M ₂ in FIG. 9a and 9b are present, respectively. Finally, once again examining FIG. 9d, it can be seen that there are paths at positions 14 and 16 (ie, _P42 and _P44 ). Thus, in the preferred embodiment, by further examining paths at similar locations,
The DPE of the receiver can be assisted, so that after a periodic operation through the midambles M ₁ -M ₄ , the paths at positions 14 and 16 by the receiver are the true paths (thus in the representation of FIG. Attached), while
It can be concluded that the remaining paths shown in FIGS. 9a-9d are fake paths (and thus are not shaded in the convention of FIG. 5).

FIG. 10 shows a plot of the cumulative distribution of the inter-cell rejection rate in response to a periodically operating midamble according to the preferred embodiment. More specifically, FIG.
0 indicates the rejection rate between cells in the case where K = 18, ie, the midamble operates periodically with frame transmissions in one of 18 different sequences before returning again to repeat the sequence. . Therefore, the graph of FIG. 10 can be compared with the conventional plot of FIG. In FIG. 10, the minimum inter-cell reject rate is 9 dB, and the intermediate reject rate is 11 dB.
It is. Thus, inter-cell rejection is generally greater than prior art rejection rates, and therefore has a greater tendency to reject false paths. This results in a DPE
To improve the operation of the receiver further, the true path can be determined more accurately while improving the detection of the true path.

FIG. 11 shows another diagram comparing the results of the prior art and the preferred embodiment with respect to distinguishing between true paths and false paths. In particular, FIG. 11 shows the cumulative distribution of the midamble, in which FIG. 11 shows a plot 6 corresponding to the case where the midamble does not circulate.
Shown is a plot 62 corresponding to the case of operating periodically between two different midambles as well as a plot 62 and a plot 64 corresponding to the case of operating periodically between four different midambles. The vertical axis in FIG. 11 indicates the number of spurious paths with values greater than -10 dB, and paths below 10 dB are ignored. Plot 60 is 50 when the midamble is not periodic.
% Time indicates that more than eight spurious paths of -10 dB or more occur. In contrast, plot 62 performs midamble periodicization in FIG. 8 and, in the case where only two midambles are used (ie, K = 2), a much smaller number of false This indicates that only the path will occur. Further, plot 64 performs midamble periodicization in FIG. 8 and uses four midambles (ie, K =
4) indicates that no fake path is detected in more than 85% of the time.

From the foregoing, it can be seen that the above embodiments can be used in a wireless system to provide a transmitter for periodicizing the midamble to improve the inter-cell rejection rate. Furthermore, although this embodiment has been described in detail, various substitutions, modifications or changes can be made to the above description without departing from the scope of the present invention. A variety of different embodiments have been described that help elucidate this invention. Furthermore, other modifications are possible with respect to the content of the present invention. For example, the transmitter of FIG. 7 is but one example of a number of transmitters capable of periodicizing a midamble in accordance with the teachings herein. As another example, while the midamble has been shown to be periodic on a frame-by-frame basis, in other embodiments these midambles may be periodic according to other groups of data (eg, every time slot, every many frames). Is also good. As another example, while the preferred embodiment has been described in connection with a TDD CDMA implementation, other wireless systems, such as time division multiple access (TDMA), may be used in this context.
Let's enjoy the benefits. As yet another example, while the midamble has been described as a preferred group of bits that can be periodized, those skilled in the art will appreciate that a period of time may be improved by passing a set of bits through a sequence of two or more different sets of bits. Other sets of bits that are unique to the cell as having undesirable cross-correlation can be similarly identified so that the cross-correlation and the negative consequences of these cross-correlations can be reduced. Therefore, from the above description, those skilled in the art should be able to understand the scope of the invention described in the claims.

With respect to the above description, the following items are further disclosed. (1) a transmission circuit including a circuit for transmitting a plurality of frames to a receiver in a first cell, wherein each of the plurality of frames includes a bit group, and the bit group includes a first cell; The transmitting circuit further includes a circuit for uniquely distinguishing a second cell adjacent to the first cell and for inserting a bit sequence into a bit group, wherein the continuous transmission by the transmitting circuit includes a plurality of bit sequences. A wireless communication system, wherein a bit sequence is selected from the plurality of bit sequences so as to include one cycle of the continuous bit sequence.

(2) The system according to claim 1, wherein each of the plurality of frames includes a midamble, and the midamble includes a bit group.

(3) The system according to claim 2, wherein said plurality of bit sequences comprises two bit sequences.

(4) The system according to (3), wherein each of the plurality of frames has a frame number of a corresponding system, and selects a bit sequence from the plurality of bit sequences in response to the frame number of the system. .

(5) The system according to (4), wherein a bit sequence is selected from the plurality of bit sequences according to whether the system frame number is odd or even.

(6) The system according to (2), wherein said plurality of bit sequences comprises four bit sequences.

(7) The system of claim 1, wherein said plurality of bit sequences comprises four bit sequences.

(8) The system of claim 1, wherein said plurality of bit sequences comprises two bit sequences.

(9) The system according to (8), wherein each of the plurality of frames has a corresponding system frame number, and selects a bit sequence from the plurality of bit sequences in response to the system frame number. .

(10) The system according to (9), wherein a bit sequence is selected from the plurality of bit sequences according to whether the system frame number is odd or even.

(11) Each of the plurality of frames includes one midamble, the midamble includes a bit group, the plurality of bit sequences includes two bit sequences, and the transmission circuit includes a CDMA transmission circuit. The system of claim 1, comprising:

(12) The system according to claim 1, wherein each of the plurality of frames has a corresponding system frame number, and selects a bit sequence from the plurality of bit sequences in response to the frame number of the system. .

(13) The system according to (1), wherein said transmission circuit includes a CDMA transmission circuit.

(14) The system according to (1), wherein said transmission circuit includes a TDMA transmission circuit.

(15) The apparatus further includes a receiver, wherein the receiver includes:
A circuit for receiving the plurality of frames, and a path resulting from a measurement of a continuous correlation between a continuous bit sequence of the plurality of bit sequences in a period and a group of bits in each of the plurality of frames. And circuitry responsive to the position comparison for identifying a path in the plurality of frames as a true path.

(16) A circuit for identifying a path in the plurality of frames as a true path identifies the path as a true path in response to a path in the plurality of frames having a similar chip position. 16. The system of claim 15, wherein:

(17) A receiving circuit including a circuit for receiving a plurality of frames from a transmitter in the first cell, wherein each of the plurality of frames includes a bit group including a bit sequence, and the bit group includes Uniquely distinguishing a first cell from a second cell adjacent to the first cell;
The receiving circuit is responsive to a comparison of path positions resulting from a measurement of successive correlations between successive bit sequences of the plurality of bit sequences in a period and bit groups in each of the plurality of frames; The wireless communication system further includes circuitry for identifying a path in the plurality of frames as a true path.

(18) The circuit for identifying a path may identify a path as a true path in response to a path in the plurality of frames having a similar chip position.
The system described in the section.

The system of claim 17, wherein each of the plurality of frames includes a midamble, and wherein the midamble includes a bit sequence.

(20) The plurality of bit sequences are 2
20. The system of claim 19, comprising a single bit sequence.

(21) transmitting a plurality of frames by a transmitting circuit to a receiver in a first cell, wherein each of the plurality of frames includes a bit group, wherein the bit group is composed of the first cell and the first cell; Wherein the transmitting step includes inserting a bit sequence in a bit group to uniquely distinguish a second cell adjacent to one cell, wherein the successive transmissions by the transmitting circuit comprise successive bits of a plurality of bit sequences. A method of operating a wireless communication system, wherein a bit sequence is selected from a plurality of bit sequences to include one cycle of the sequence.

22. The method according to claim 21, wherein each of the plurality of frames includes a midamble, and the midamble includes a bit group.

(23) The plurality of bit sequences are 2
23. The method of claim 22, comprising one group of bits.

24. The method of claim 23, wherein each of said plurality of frames has a corresponding system frame number and selects a bit sequence from said plurality of bit sequences in response to said system frame number. .

(25) The method according to (24), wherein a bit sequence is selected from a plurality of bit sequences according to whether the system frame number is odd or even.

(26) The plurality of bit sequences are 4
23. The method according to claim 22, comprising two bit sequences.

(27) The plurality of bit sequences are 4
22. The method of claim 21, comprising a single bit sequence.

(28) When the plurality of bit sequences are 2
22. The method of claim 21, comprising a single bit sequence.

29. The method of claim 28, wherein each of said plurality of frames has a corresponding system frame number and selects a bit sequence from said plurality of bit sequences in response to said system frame number. .

(30) The method according to (29), wherein a bit sequence is selected from the plurality of bit sequences according to whether the system frame number is odd or even.

(31) Each of the plurality of frames includes one midamble, the midamble includes a bit group, the plurality of bit sequences includes two bit sequences, and the transmission circuit includes a CDMA transmission circuit. 22. The method of claim 21.

(32) The method according to claim 21, wherein each of the plurality of frames has a frame number of a corresponding system, and a bit sequence is selected from the plurality of bit sequences in response to the frame number of the system. .

(33) The method according to item 21, wherein the transmitting circuit includes a CDMA transmitting circuit.

(34) The method according to item 21, wherein the transmission circuit includes a TDMA transmission circuit.

(35) a step of receiving the plurality of frames at a receiving station in a first cell; and a step of: selecting a continuous bit sequence of the plurality of bit sequences in a cycle and a bit group in each of the plurality of frames. Responsive to a comparison of path locations resulting from successive correlation measurements between the plurality of frames, identifying paths within the plurality of frames as true paths.

(36) The method of paragraph 35, comprising applying a channel estimate corresponding to a true path to a maximum ratio combination circuit.

(37) receiving a plurality of frames from a transmitter in a first cell, wherein each of the plurality of frames includes a bit group having a bit sequence;
A bit group uniquely distinguishes between a first cell and a second cell adjacent to the first cell, further comprising a continuous bit sequence of the plurality of bit sequences within a period, and a bit in each of the plurality of frames. A method of operating a wireless communication system, further comprising identifying a path in said plurality of frames as a true path in response to a comparison of path positions resulting from a measurement of successive correlations with a group.

38. The method of claim 37, wherein said identifying step comprises responding to a path in said plurality of frames having similar chip locations and identifying the path as a true path.

(39) A radio communication system (10), wherein the transmission circuit (B) includes a circuit for transmitting a plurality of frames to a receiver in a first cell (cell 1).
ST1). Each of the plurality of frames includes one bit group (22) that uniquely distinguishes a first cell from a second cell (cell 2) adjacent to the first cell. The transmission circuit further includes a circuit (54) for inserting the bit sequence into the bit group. A bit sequence is selected from the plurality of bit sequences (S _{1 to} S _K ) so that the continuous transmission by the transmission circuit includes one cycle of the continuous bit sequence among the plurality of bit sequences.

(Mutual Reference with Related Application) This application is based on U.S. Provisional Patent Application Ser. No. 60 / 143,574 (TI-29425PS), filed July 13, 1999, U.S. Pat. ) Claims the rights under paragraph (1).

[Brief description of the drawings]

FIG. 1 shows a diagram of a cellular communication system according to a modern code division multiple access (CDMA) example in which the preferred embodiment can be implemented.

FIG. 2 shows a TDD radio frame in which the preferred embodiment can be embedded.

FIG. 3 shows a time slot in the radio frame of FIG.

FIG. 4 shows the structure of the midamble for different users in the same cell with the basic sequence of the midamble time-shifted for different users.

FIG. 5 shows a conceptual diagram of a set of paths received by a receiver.

FIG. 6 shows a plot of the cumulative distribution of inter-cell rejects in response to a midamble according to the prior art.

FIG. 7 shows a block diagram of a circuit of a base station as an example of a transmitter / receiver according to a preferred embodiment.

FIG. 8 shows a state diagram of a method for periodicizing a midamble in a cell transmission signal according to a preferred embodiment;

FIG. 9 shows an example of a receiver channel estimate with periodicization over a sequence of four midambles.

FIG. 10 shows a plot of the cumulative distribution of inter-cell rejects in response to midamble periodicization according to a preferred embodiment.

FIG. 11 shows another diagram comparing the results of detecting true and false paths between the prior art and the preferred embodiment.

[Explanation of symbols]

 Reference Signs List 10 communication system BST1 transmission circuit 22 bit group cell 1 first cell cell 2 second cell 54 insertion circuit

 ──────────────────────────────────────────────────の Continued on front page (72) Inventor Anand Zee, Davak United States Texas, Plano, Kendal Drive 8625

Claims (2)

[Claims] 1. A transmission circuit comprising: a circuit for transmitting a plurality of frames to a receiver in a first cell, wherein each of the plurality of frames includes a bit group, wherein the bit group comprises a first cell and a first cell. Wherein the transmitting circuit further comprises a circuit for uniquely distinguishing a second cell adjacent to the first cell, wherein the transmitting circuit further includes a bit sequence in a bit group, wherein the continuous transmission by the transmitting circuit comprises a plurality of bit sequences. Selecting a bit sequence from the plurality of bit sequences so as to include one cycle of the continuous bit sequence. 2. Transmitting a plurality of frames by a transmission circuit to a receiver in a first cell, wherein each of the plurality of frames includes a bit group, wherein the bit group comprises a first cell and the first cell. Wherein the transmitting step comprises inserting a bit sequence in a bit group, wherein the transmitting step comprises inserting a bit sequence in a bit group, wherein the continuous transmission by the transmitting circuit is a continuous bit sequence of a plurality of bit sequences. A method for operating a wireless communication system, wherein a bit sequence is selected from a plurality of bit sequences so as to include one cycle of the wireless communication system.