JP2001054162A - Terminal for mobile communication - Google Patents

Abstract

PROBLEM TO BE SOLVED: To minimize a delay buffer to adjust deviation in reception timing of a signal sent from a plurality of base stations in the case of conducting hand-over through site diversity reception with respect to a terminal for mobile communication. SOLUTION: A TDHO calculation section 15 measures a time difference between a transmission timing of a communication channel with a hand-over source base station and a reception timing of a perch channel of a hand-over destination. A Tlast decision section 16 decides a lowest reception timing on the basis of an adjustment value of a delay buffer that adjusts a deviation from reception timings of communication channels from each base station in a site diversity state. A CPU 18 reports a value closer to a slowest retiming Tlast among received signals from each base station in the above time difference TDHO and a value to/from which a round unit by one symbol is added/subtracted as time difference information of the reception timing of the perch channel.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mobile communication terminal device, and more particularly, to adjusting a shift in reception timing of signals transmitted from a plurality of base stations when performing handover by performing site diversity reception. Communication terminal device capable of minimizing a delay buffer for the mobile communication.

[0002] W-CDMA currently under development
In mobile communication systems, mobile stations (MS: Mobile Statio)
n: a base station (BTS: Base Transceiving) currently in communication when a mobile communication terminal device crosses a boundary of a wireless area.
er Station) to a destination base station (BTS), a switching control processing technique called handover is used.

[0003] When a mobile station (MS) crosses a boundary of a radio area, the mobile station (MS) transmits the switching base station (BTS).
1) The transmission signals from both the base station of the switching destination base station (BTS2) and the switching destination base station (BTS2) are temporarily simultaneously received and combined (site diversity reception). BTS) is separated.

In order to perform site diversity reception, a mobile station (MS) delay-adjusts a difference in reception timing from each base station (BTS) in order to combine and receive signals from a plurality of base stations (BTS). After that, it is necessary to synthesize.

[0005] For this reason, it is important for the mobile station (MS) to reduce the time lag of the reception timing from the base station (BTS) to be site-diversified. If the shift time of the reception timing is uncertain, the delay buffer for delay adjustment provided in the mobile station (MS) must be made sufficiently large, leading to an increase in hardware and power consumption.

[0006]

2. Description of the Related Art As a draft standard of IMT-2000, which is currently being drafted by ITU (International Telecommunication Union), Japanese AR
IB (Association of Radio Industries and Business
The procedure for determining the transmission timing of the movement-destination base station (BTS2) at the time of handover studied by es = Japan Radio Industry Association is as follows.

FIG. 6 shows a handover destination base station (BTS).
It is explanatory drawing of the transmission timing determination procedure of 2). The figure shows the timing of signals at each base (BTS) and mobile station (MS), "SFN = 0", "SFN = 1".
, “SFN = 2”, to “SFN = 36863” represent superframe numbers.

FIG. 1A shows a downlink communication channel (DPCH: Dedicated Physic) transmitted from a handover source base station (currently communicating base station BTS1) to a mobile station (MS).
al Channel; transmission timing of a point-to-point dedicated physical channel between a mobile station and a base station), and (b) in the figure represents reception timing of the downlink communication channel (DPCH) at the mobile station (MS). .

As shown in the figure, a mobile station (MS) has a downlink communication channel (DPC) from a base station (BTS1).
The reception timing of H) is delayed from the transmission timing of the base station (BTS1) by the propagation delay time therebetween.

[0010] The mobile station (MS) receives a downlink communication channel (DPCH) from the handover source base station (BTS1) at the reception timing (head superframe (SFN = 0)).
At the start timing position), and as shown in (c) of the figure, a certain time (250 μsec) from this timing
The shifted timing is set as the transmission timing of the uplink communication channel (DPCH) from the mobile station (MS) to the base station (BTS).

The timing shift of the mobile station (MS) for a fixed time (250 μsec) from the reception timing of the downlink communication channel to the transmission timing of the uplink communication channel is called “transmission / reception offset” and is 4.096M.
In the case of a diffusion chip rate of cps, it becomes 1024 chips.

On the other hand, as shown in FIG. 2D, a perch channel is constantly transmitted from the handover destination base station (BTS2), and the mobile station (MS) is transmitted from the handover destination base station (BTS2). Perch channel at the mobile station (MS) shown in (e) of the figure, and transmission of the uplink communication channel (DPCH) of the mobile station (MS) shown in the above (c). The time difference (T _DHO ) from the timing is measured, and the time difference (T _DHO ) information of the perch channel reception timing is transmitted to the handover source base station (BTS1) via the communication channel (DPC).
Report via H).

The handover source base station (BTS1) notifies the handover destination base station (BTS2) of the time difference (T _DHO ) information via the network. The handover destination base station (BTS2) shifts from the perch channel transmission timing by the time difference (T _DHO ) and further advances the transmission and reception offset by 250 μsec (1024 chips) as shown in FIG. At the timing, a downlink communication channel (DPCH) is transmitted.

The mobile station (MS) provides the handover destination base station (BTS2) at the reception timing shown in FIG.
As can be seen by comparing (b) and (g) in the figure, the reception timing of the downlink communication channel (DPCH) from the handover source base station (BTS1) Downlink communication channel (DPCH) from the handover destination base station (BTS2)
And the base station can be switched with a continuous signal to the mobile station (MS).

The time difference (T _DHO ) information of the perch channel reception timing described above is rounded for each symbol of the uplink communication channel (DPCH) of the mobile station (MS). When the round-off process is performed as a round-off process, the reception timing of the downlink communication channel (DPCH) transmitted from the handover destination base station (BTS2) is advanced by a maximum of one symbol (0 to 255 chips). A deviation occurs from the reception timing from the over source base station (BTS1) (shifts to the left in FIG. 6).

The mobile station (MS) has a handover source base station (BTS1) and a handover destination base station (BTS2).
Simultaneously receive the transmission signals from both base stations, perform site diversity reception, and combine the received signals,
At this time, it is necessary to adjust the difference between the reception timings from the two base stations and make the reception timings of the two base stations coincide.

FIG. 7 is an explanatory diagram of a circuit for adjusting a shift in reception timing in a mobile station (MS). Now, assuming that the received signal from the second base station (BTS2) arrives earlier than the received signal from the first base station (BTS1), the received signal from the second base station (BTS2) is delayed by a delay buffer. The rake combiners 72 ₁ , 7 receive the signals from the base stations (BTS 1, BTS 2) by adjusting the delay amount of the delay buffer 71.
2 ₂ and the rake combining output signal is combined to perform site diversity reception.

Since the delay buffer 71 is configured using a memory, the memory capacity must be increased in order to increase the adjustable delay amount. If the memory capacity is increased, hardware and power consumption increase. Will be invited.

If the capacity of the delay buffer 71 is reduced, it is not possible to perform site diversity reception between base stations (BTS) accompanied by a shift in the reception timing exceeding the capacity, and the site base station ( BT
S) The number decreases, and the communication quality deteriorates.

Then, another third base station (BTS)
When entering the site diversity reception state with 3) added,
The deviation of the reception timing among the three base stations (BTS) is further increased. FIG. 8 shows an example of reception timing in site diversity reception from three base stations (BTS).

FIG. 8A shows the reception timing at the mobile station (MS) of the downlink communication channel from the first handover source first base station (BTS1), and FIG.
Indicates the reception timing at the mobile station (MS) of the downlink communication channel from the second base station (BTS2), which is the first handover destination and the next handover source, and FIG. Mobile station (MS) on the downlink communication channel from the third base station (BTS3)
3 shows the reception timing.

Each base station (BTS1, BTS2, BTS
The difference (Terror1, Terror2) in the reception timing of the downlink communication channel from 3) is obtained by using the time difference (T _DHO ) information of the reception timing of the perch channel from the handover destination base station as one symbol (256 chips).
This is the effect of rounding errors due to truncation in units.

As a rounding process, one symbol (256 ch)
Even if a process of rounding up or down at a certain threshold value is performed instead of the rounding down in units of ip), the same situation occurs if the truncation occurs continuously. This is because the second base station (BTS2) is used as a handover source base station at the time of handover with the third base station (BTS3). There is no rule as to which base station is selected as the handover source base station among the base stations to receive site diversity, and it is necessary to assume that the base station changes depending on the case.

FIG. 9 is an explanatory diagram of a circuit for adjusting a shift in reception timing of signals from three base stations. In the case where the reception timing of signals from three base stations is shifted as shown in FIG. 8, the second and third base stations (BTS2, BT2)
The signals from S3) are transferred to delay buffers 91 and 92, respectively.
To the first, second and third base stations (BTS1, BTS1).
, BTS3), the first, second and third rake combining units 93, 94, 9
Enter 5

However, since it is not actually determined which base station is the first handover source, each base station (B
It is necessary to treat the received signals from TS1, BTS2, and BTS3) equally, and the actual circuit configuration is as shown in FIG.

In FIG. 10, each delay buffer 101, 1
02 and 103 have the same capacity. The received signal is usually AD
Since conversion is performed, a delay buffer capacity (number of bits) equal to the number of quantization bits × the number of delay-adjustable chips × the maximum number of site diversity receiving base stations is required.

[0027]

In such a state, for example, the signal from the second base station (BTS2) becomes weak, is separated from the mobile station (MS), and is further replaced by a new fourth base station (BTS4). When a handover situation occurs, there is a possibility that a delay buffer for adjusting the deviation of a larger reception timing is required in order to perform site diversity reception.

Further, when the third base station (BTS3) is disconnected and a new handover to the fifth base station (BTS5) occurs, a larger delay buffer is required. FIG. 11 shows a state in which a plurality of handovers are performed as described above.

As shown in FIG. 11, a first base station (BT
When handover to another new base station is repeated while leaving the link by the communication channel with S1), any number of first base station (BTS1) and other base station (BTS) are repeated.
4, BTS 5).

In order for the mobile station (MS) to obtain the maximum site diversity effect, a delay for accumulating received signals from all base stations other than the first base station (BTS1) and adjusting a shift in reception timing. You need to have a buffer.

If the deviation of the reception timing of the received signal from each base station is large, the capacity of the delay buffer for adjusting the deviation must be increased, which causes the hardware and power consumption of the mobile station (MS) to increase. This causes disadvantages such as a reduction in talk time, an increase in battery capacity, and an increase in terminal weight.

According to the present invention, the reception timing of the communication channel from the handover destination base station is set to be the minimum deviation from the reception timing of the communication channel from the base station to which the site diversity is to be received. It is an object of the present invention to obtain the maximum site diversity effect while keeping the buffer to a minimum, to reduce the hardware and power consumption of the mobile communication terminal device, and to improve the reception quality by the site diversity effect.

[0033]

A mobile communication terminal according to the present invention comprises: (1) a mobile communication terminal used as a mobile station in a CDMA cellular system; Means for measuring the time difference between the reception timing of the mobile station or the transmission timing of the mobile station and the reception timing of the perch channel of the handover destination, and the time difference based on the shift of the reception timing of the communication channel from each base station at the time of site diversity reception. And means for reporting the corrected time difference to the base station.

[0034] (2) The means for correcting the time difference includes the step of receiving the communication channel from the handover destination base station based on the latest timing of receiving the communication channel from each base station at the time of site diversity reception. A value obtained by adding or subtracting a rounded amount in a specific unit to or from the time difference or a time difference value not performing the addition / subtraction so that the timing is the timing closest to the timing within a range not exceeding the latest timing. , To correct the time difference. (3) The corrected time difference is rounded in a specific unit before being reported to the base station.

[0035]

FIG. 1 is a diagram showing a configuration example of an embodiment of the present invention. As shown in the figure, the mobile terminal device of the present invention includes a perch channel receiving unit 1 via a receiving unit Rx.
1 by receiving the perch channel from the handover destination base station, the receiving timing measuring section 13 ₁ measures the reception timing of the perch channel, the reception timing information in the perch channel reception timing time difference (T _DHO) calculator 15 Output.

Further, receiving a signal from the handover source base station by a communication channel (DPCH) receiver 12 _1, to measure the reception timing at the receiving timing measuring section 13 _2, it transmits the measured value timing determination unit 14 is output.

The transmission timing determination unit 14 determines the transmission timing of the uplink communication channel shifted from the reception timing by a predetermined time (250 μsec), and uses the transmission timing information to determine the time difference (T
_DHO ) Output to the calculation unit 15.

The perch channel reception timing time difference (T _DHO ) calculator 15 calculates the perch channel reception timing difference (T _DHO ) from the perch channel reception timing information and the uplink communication channel transmission timing information.
_DHO ). At this time, the perch channel reception timing difference (T _DHO ) is truncated for each symbol of the uplink communication channel.

The perch channel reception timing time difference (T _DHO ) calculation unit 15 inputs the calculated time difference (T _DHO ) information to the CPU 18 and _{adds the} rounding unit R (the symbol unit of the communication channel symbol unit) to the time difference (T _DHO ) information. The added value (T _DHO + R) is input to the CPU 18 through the adding unit 17 for adding the time length.

On the other hand, a signal received from the other base station is performing a site diversity reception, received by the communication channel (DPCH) receiver 12 ₂ measures the reception timing at the reception timing measurement unit 13 ₃ .

Each of the two communication channel (DPCH) receivers 12 ₁ and 12 ₂ performing site diversity reception from two base stations has a delay buffer, and adjusts the adjustment value by the delay buffer to the last reception timing (T
_last ) Output to the determination unit 16.

Last reception timing (T _last ) determination unit 1
6 includes two communication channel (DPCH) receiving units 12 ₁ ,
From the delay buffer adjustment value input from the 12 _2, it determines the slowest reception timing, and outputs the timing (T _last) information to CPU 18.

The CPU 18 has a reception timing measuring section 13 ₂
And reception timing information of the communication channel of the handover source base station to be output, perch channel reception timing time difference (T _DHO) perch channel reception timing time difference output from the calculating unit 15 (T _DHO) and unit R rounding it added from and the value (T _DHO + R), inputs the latest reception timing (T _{la st)} information outputted from the last reception timing (T _last) determining unit 16, to report to the handover source base station on the basis of their The perch channel reception timing difference (T _DHO ) is corrected by the method described below, and the corrected perch channel reception timing difference (T _DHO ) is corrected to the uplink communication channel (D _DHO ).
(PCH) frame generating section 19 and transmitting section Tx to the handover source base station.

FIG. 2 is an explanatory diagram of the means for correcting the perch channel reception timing difference (T _DHO ) according to the present invention. Here, the perch channel reception timing from the handover destination base station is _defined as T _PERCH, and the perch channel reception timing time difference T _DHO is truncated in symbol units as [T _DHO ]. Let R and the transmission / reception offset be T _offset .

If the perch channel reception timing difference (T _DHO ) is simply reported to the base station as in the prior art, the reception timing T _BTS3DPCH of the downlink communication channel from the handover destination base station is _{ΔT PERCH} + [T _DHO ]. -T
_offset ｝.

If the reception timing T _BTS3DPCH of the downlink communication channel from the handover destination base station is _closest to the above-mentioned T _last , the necessary capacity of the delay adjustment buffer becomes the minimum. The reception timing T _BTS3DPCH corresponds to the mobile station (M
It can be predicted on the side of S).

Therefore, the handover destination base station
Communication channel reception timing T _BTS3DPCHAs
｛T_PERCH+ [T_DHO] -T_offset｝ And ｛T_PERCH+
[T_{DH O}+ Rounding unit R] -T_offsetCalculate two values of｝
And T_lastChoose the timing closer to
This ensures that the delay buffer is always kept to a minimum.
You.

If a timing later than T _last is selected, the delay amount of the delay buffer must be set to a negative value, so that a timing later than T _last cannot be selected. That is, when the value of {T _PERCH + [T _DHO + rounding unit R] −T _offset } exceeds the value of T _last ,
Select the value of {T _PERCH + [T _DHO ] -T _offset }, otherwise {T _PERCH + [T _DHO + Rounding unit R]
-T _offset Select the value of｝.

Thus, the reception timing T of the downlink communication channel from the handover destination base station is
_BTS3DPCH can be set only in the shaded area in FIG.
The delay adjustment amount by the delay buffer can always be made equal to or less than the rounding unit R.

FIG. 3 is a flowchart for correcting the perch channel reception timing difference (T _DHO ) by the CPU of the present invention. The CPU 18 shown in FIG. 1 checks the latest reception timing (T _last ) from the input reception timings (3-1), and T ₀ = ｛T _PERCH + [T
_DHO ] −T _offset } and T ₁ = {T _PERCH + [T _DHO + rounding unit R] −T _offset } are calculated (3-2). Note that the larger the numerical value representing the timing, the more delayed the timing, and each timing can be represented in a chip unit. FIG. 4 shows the timing relationship between T _last , T ₀ , and T ₁ .

Then, the CPU 18 compares the magnitudes of T ₀ and T _last (3-3), and as shown in FIG.
_{If 0} exceeds T _last , a perch channel reception timing time difference (T _DHO ) setting error process (3-5) is performed.

In the comparison of the above (3-3), T
₀Is T_lastT if₁And T _lastCompare size with
(3-4), and as shown in FIG.₁Is T
_lastExceeds the perch channel reception timing
Time difference (T_DHO) Is reported (3-6), and FIG.
As shown, T₁Is T_lastIn the following cases,
Time difference (T_DHO) With rounding unit R
Report the obtained value (3-7).

In the above determination (3-3), T ₀ is equal to T
_The error processing is performed when the value exceeds _last , because the perch channel reception timing time difference (T _DHO ) is properly measured and rounded off by truncation, and the communication channel of the reference handover source base station (BTS) is used. (DP
This is because the reception timing of the communication channel (DPCH) of the handover destination base station can never be later than the reception timing of (CH).

Of course, the processing shown in FIG. 3 may be performed by hardware instead of the CPU. Also,
The processing in the range indicated by the dotted line in FIG. 1 can be performed by software processing by the CPU. When the rounding process is a truncation process, the above calculation in [] can be performed by a simple bit shift operation.

As described above, the mobile station (MS) is connected to the base station (B)
TS) Perch channel reception timing time difference (T
_DHO ) When information is reported, by adding a rounding unit R to the measured perch channel reception timing time difference (T _DHO ) and reporting, the reception of the communication channel from the base station (BTS) targeted for site diversity reception is performed. The maximum site diversity effect can be obtained while minimizing the timing shift and minimizing the size of the delay buffer in the mobile station (MS).

Furthermore, when the perch channel reception timing difference (T _DHO ) may be rounded up in symbol units, the rounding unit R is generally increased or decreased by the following method to increase or decrease the perch channel reception timing difference (T _DHO ). T _DHO ) to the base station (BTS).

FIG. 5 is a flow diagram of a general modification of the perch channel reception timing difference (T _DHO ) according to the present invention. As shown in the figure, first, at the mobile station (MS), the reception timing is currently adjusted by the delay buffer, and the latest reception timing among the reception timings of the communication channel (DPCH) performing the site diversity reception. And its timing is set as T _last (5-1).

Next, the handover from the handover destination base station
T _PERCHIs measured, and T
_PERCHBased on the following T₀, T₊, T_-Is calculated (5-
2). T₀= T_PERCH+ [T_DHO] -T_offset T₊= T_PERCH+ [T_DHO+ Rounding unit R] -T_offset T_-= T_PERCH+ [T_DHO-Rounding unit R] -T_offset

[0059] Then, the T _0, T _+, T _- from among, for selecting the timing of the closest to T _last. However, a timing that is later than T _last is not selected even if it is the nearest timing (5-3). Such timing is excluded as a candidate. The reason is as described above.

Then, [T _DHO ], [T _DHO + rounding unit R] or [T _{DHO -rounding} unit R] corresponding to one of the selected timings T ₀ , T ₊ , and T _- is determined by the perch channel reception timing. As the time difference (T _DHO ), the base station (B
TS) (5-4).

[0061] Incidentally, in the flow shown in FIG. 5, if rounding is only truncation, the T _- Calculation may disconnect from the object. If the rounding process is only rounding up, the calculation of T ₊ may be excluded from the target. If the rounding truncation or rounding up is carried out by comparison with the certain threshold, the T _0, T _+, T _- be compared to calculate all.

Further, the mobile station (MS) transmits the information to the base station (BT).
S) to T _DHO , (T _DHO + rounding unit R) or (T _DHO
The base station (BTS) may report the rounding unit R), and the base station (BTS) may perform the rounding process. However, the mobile station (MS) performs the rounding process and sends the rounded value to the base station (BTS). With the configuration for reporting, the rounding processing at the base station (BTS) becomes unnecessary, and the mobile station (MS) and the base station (BT
The amount of information transmitted during S) can be reduced.

[0063]

As described above, according to the present invention,
Mobile station (MS) is base station (BTS) during handover
When reporting the perch channel reception timing time difference (T _DHO ), the value of the time difference (T _DHO ) is increased or decreased before reporting, so that the size of the delay buffer for adjusting the reception timing in site diversity reception is minimized. In this case, the maximum site diversity effect can be obtained, the hardware and power consumption of the mobile communication terminal device can be reduced, and the reception quality can be improved by the site diversity effect.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a configuration example of an embodiment of the present invention.

FIG. 2 is an explanatory diagram of means for correcting a perch channel reception timing difference (T _DHO ) according to the present invention.

FIG. 3 is a flow chart for correcting a perch channel reception timing time difference (T _DHO ) by the CPU of the present invention.

FIG. 4 is a diagram showing a timing relationship between T _last , T ₀ , and T _{1 in} the present invention.

FIG. 5 is a flow diagram of a general modification of the perch channel reception timing difference (T _DHO ) according to the present invention.

FIG. 6 is an explanatory diagram of a procedure for determining a transmission timing of a handover destination base station (BTS2).

FIG. 7 is an explanatory diagram of a circuit that adjusts a reception timing shift in a mobile station (MS).

FIG. 8 is a diagram illustrating an example of reception timing in site diversity reception from three base stations (BTS).

FIG. 9 is an explanatory diagram of a circuit that adjusts a shift in reception timing of signals from three base stations.

FIG. 10 is an explanatory diagram of a general circuit that adjusts a shift in reception timing of signals from three base stations.

FIG. 11 is a diagram illustrating a state when a plurality of handovers are performed.

[Explanation of symbols]

Reference Signs List 11 Perch channel receiving unit 12 ₁ , 12 ₂ Communication channel (DPCH) receiving unit 13 ₁ , 13 ₂ , 13 ₃ Receiving timing measuring unit 14 Transmission timing determining unit 15 Perch channel receiving timing time difference (T _DHO ) calculating unit 16 Last receiving timing (T _last ) determination unit 17 addition unit 18 CPU 19 communication channel (DPCH) frame generation unit Rx reception unit Tx transmission unit

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Makoto Uchijima 4-1-1, Kamiodanaka, Nakahara-ku, Kawasaki-shi, Kanagawa F-term within Fujitsu Limited (reference) 5K059 AA14 CC03 DD33 EE02 5K067 AA23 BB04 BB21 CC10 CC24 DD42 EE02 EE10 EE24 EE32 HH11 HH21 KK01 KK13 KK15 LL11

Claims (3)

[Claims] 1. A mobile communication terminal device in a CDMA cellular system, comprising: a reception timing of a communication channel of a handover source base station at a mobile station, or a time difference between a transmission timing of the mobile station and a reception timing of a perch channel of a handover destination. Means for measuring the time difference, means for correcting the time difference based on a shift in the reception timing of the communication channel from each base station at the time of site diversity reception, and means for reporting the corrected time difference to the base station. A mobile communication terminal device characterized by the above-mentioned. 2. The means for correcting the time difference, wherein the reception timing of the communication channel from the handover destination base station is based on the latest timing of the reception timing of the communication channel from each base station at the time of site diversity reception.
A value obtained by adding or subtracting a rounded amount in a specific unit to or from the time difference or a time difference value not performing the addition / subtraction so as to be a timing closest to the timing within a range not exceeding the latest timing. 2. The mobile communication terminal device according to claim 1, wherein 3. The mobile communication terminal device according to claim 1, wherein the corrected time difference is reported to a base station after being rounded in a specific unit in advance.