JP3337109B2 - Wireless communication method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radio communication system using a direct spread CDMA system, and more particularly, to easily perform phase estimation on a receiving side and to equalize received power at a base station to improve a bit error rate. Wireless communication system capable of performing transmission power control with high accuracy for the same.

[0002]

2. Description of the Related Art As a practical example of mobile communication to which a direct spread CDMA system is applied, there is a US standard system IS-95. [Document "Mobile Station-Base Station Compat
ibility Standard for Dual-Mode Wideband Spread Spe
ctrum Cellular System ”, TIA / EIA IS-95 (1993 July)
Reference], and in this method, the basic transmission rate is 9600 bits /
s or less (9600 bit / s, 4800 bi
t / s, 2400 bit / s, 1200 bit / s).

The channel configuration of IS-95 has one control channel and 63 traffic channels,
Communication is performed by assigning different spreading codes.
Among them, a signal transmission method on a traffic channel will be described taking an uplink as an example.

FIG. 4 is a diagram showing an example of such a conventional frame structure of the uplink. In the figure, numeral 4-1 denotes a frame configuration at 9600 bit / s, 4-2 denotes a frame configuration at 4800 bit / s, 4-3 denotes a frame configuration at 2400 bit / s, and 4-4 denotes 1200 bit. 4 shows the frame configuration at the time of / s.

As shown in FIG. 1, signal transmission is performed using all slots (16 slots) in one frame at 9600 bits / s, and arbitrary 8 slots in one frame at 4800 bits / s, and similarly 2400 bits / s. A method of transmitting data using 4 slots for s and using 2 slots for 1200 bit / s is adopted.

[0006] The transmission power control bit is 9600 bit / s.
Is transmitted every slot, but in the case of 4800 bit / s or less, it is transmitted only when a slot is transmitted. The phase synchronization in the receiver can be maintained as it is because the signal can be continuously received in the case of 9600 bits / s. The estimation must be repeated.

[0007]

In the DS-CDMA communication system, users use different code codes, respectively.
They are transmitted on the same frequency. Therefore, if the received power at the base station differs depending on the distance between the base station and the partner station, interference occurs between the received powers (far-far problem), and as a result, the user capacity is restricted.

[0008] Therefore, according to an instruction from the base station side,
A technique (TPC) for controlling the transmission power of the partner station is used. (Document "Okazaki et al." Study of Transmission Power Control Method in DS-CDMA System ", IEICE Technical Report, SST 94-94 (19
95) ”)

However, in the conventional signal transmission method as described above, since there is a slot for transmitting a signal and a slot for not transmitting a signal, a control bit for transmission power control cannot be transmitted in all slots. However, there is a problem that the transmission interval of the control bits is extended, the transmission power control error increases, and the user capacity is restricted.

[0010] Further, in the receiver, phase estimation is necessary to establish synchronization. However, if the transmission interval is widened, the phase error between the slots increases. Therefore, it is necessary to perform the phase estimation using the previously received slots. There was also a problem that it became difficult.

The present invention provides a DS-CDMA as described above.
To provide a signal transmission method that can solve a problem that a transmission power control error increases due to a slot to be transmitted and a slot that is not transmitted and a problem that a phase estimation error increases in a communication system. The purpose is.

[0012]

The above-mentioned object is achieved by the means described in the appended claims. That is,
The invention according to claim 1 is a wireless communication method in which one frame is composed of a plurality of slots and a signal is transmitted using a direct spread CDMA communication method. A method of transmitting a K-bit signal per frame with N basic slots and transmitting N basic slots as (K / N) bits continuously is adopted.

When handling a signal having a transmission rate of 1 / M of the maximum transmission rate, (K / N / M) bits are defined as one slot, and the beginning of each slot and a time width equivalent to the basic slot are used. Are sequentially shifted by L bits (L is a natural number) for each slot, and each slot is arranged such that one slot exists within a time width equivalent to each of the basic slots. And the slot is N
This is a wireless communication method for transmitting data continuously.

According to a second aspect of the present invention, in a wireless communication method in which one frame is composed of a plurality of slots and a signal is transmitted using a direct spread CDMA communication system, when a signal having a maximum transmission rate is handled, one frame is used. A frame is composed of N basic slots, a signal of K bits is transmitted per frame, and a method of continuously transmitting N basic slots as (K / N) bits is adopted.

When handling a signal having a transmission rate of 1 / M of the maximum transmission rate (M is an integer of 2 or more),
(K / N / M) bits are defined as one slot, and each of the slots is randomly arranged such that one slot exists within a time width equivalent to each of the basic slots. This is a wireless communication method for transmission.

According to a third aspect of the present invention, in the wireless communication method according to the first or second aspect, fixed-length bits are arranged in each basic slot or in a time width equivalent to the basic slot, and the maximum transmission rate is reduced. When handling a signal having a transmission rate of 1 / M, the fixed length bit and the (K / N
/ M) A configuration in which N slots including bit slots are continuously transmitted.

As described above, the present invention is significantly different from the prior art in that signals are continuously transmitted. The invention of claim 1 is a method of shifting the relative position interval between the beginning of a slot and the beginning of a time width equivalent to a basic slot by L bits for each slot. The second invention is a method of randomly arranging the transmission intervals of adjacent slots. Further, the invention of claim 3 establishes reception frame synchronization by transmitting fixed-length bits (for example, a unique word composed of a predetermined bit sequence) instead of transmitting only slots. It's even easier.

In each of the claimed inventions, all the basic slots or a time width equivalent to the basic slot is used.
Since the transmission power control bits can be transmitted, and the transmission interval of the transmission power control bits does not increase as in the related art, it is possible to prevent the transmission power control error from increasing. Further, since the slots are continuously transmitted, there is an effect that the phase estimation for establishing the synchronization on the receiving side is facilitated.

[0019]

FIG. 1 is a diagram showing an example of an embodiment of the present invention. In this example, the transmission speed is 9600 bi
It is intended for a method capable of supporting two speeds of t / s and 2400 bit / s. In the figure, numeral 1-1 indicates a frame configuration at 9600 bit / s, and 1-2a and 1-2b indicate a frame configuration at 2400 bit / s.

At 9600 bit / s, the basic slot is transmitted continuously, and at 2400 bit / s, the transmission is performed while changing the position of the bit (slot position) used within the time width equivalent to the basic slot. As a method of determining the position of the bit to be used (the position of the slot) within the time width equivalent to the basic slot, the method of 1-2a
As shown in the figure, a method of sequentially shifting the relative position interval between the head of the slot and the head of the time width equivalent to the basic slot by several bits for each slot, and the numeral symbol 1-2b in FIG. As shown by, there is a method that follows a random number.

As a method according to a random number, (a) a method of selecting a starting position of a bit to be used from each bit within a time width equivalent to a basic slot using a random number, and (b) a transmission rate of a maximum transmission rate. In the case of 1 / M (M is an integer of 2 or more), a method of dividing a time width equivalent to a basic slot into M small slots and selecting a small slot in which a transmission bit is to be arranged using a random number; (C) A method of selecting, using a random number, a position where a transmission bit is to be arranged from positions where the interference power is lower than the threshold value within a time width equivalent to the basic slot can be adopted.

Since the same frequency band is used in the CDMA system, a transmission signal of a certain user becomes interference power for another user. Therefore, in order to equalize the reception power of the transmission wave from each user in the base station, it is necessary to perform transmission power control, but according to the present invention,
Since the positions of the transmission signals are dispersed, it is possible to prevent the bias of the interference power, and to further suppress a decrease in the user capacity that can be accommodated.

FIG. 3 is a diagram showing an example in which the user capacity is increased by the present invention as compared with the prior art. In the figure, the horizontal axis represents the number of users per unit cell, and the vertical axis represents the frame error rate. The solid line indicates the position of the bit used in the slot,
The characteristics when fixedly arranged from the beginning of the time width equivalent to each basic slot are shown, and the broken lines show the characteristics when the positions of bits to be used within the time width equivalent to each basic slot are determined according to random numbers. I have. When the frame error rate is 10 ^-2 , it can be seen that the user capacity is about 2.3 times as large as when the bits used are fixedly arranged in the method according to the present invention.

FIG. 2 is a diagram showing another example of the embodiment of the present invention. This example shows a case where a unique word is arranged at a fixed position in each slot. In the figure, numeral 2-1 indicates a frame configuration at 9600 bit / s, 2-2 indicates a frame configuration at 2400 bit / s, and 2-3 and 2-4 indicate unique words. By arranging a unique word at a fixed position in this way, slot synchronization becomes very easy.

The transmission power control bits are arranged in the same number of bits in each slot, or 4 bits per slot at 9600 bits / s, 2 bits per slot at 9800 bits / s, depending on the transmission rate. There is a way to change the number.

[0026]

As described above, according to the present invention, in the case of transmitting a signal of a low speed in a direct spread CDMA mobile radio communication system constituted by a frame composed of a plurality of slots and capable of adopting a plurality of transmission speeds. However, a signal is transmitted within a time width equivalent to all basic slots.
Therefore, transmission power control bits can be transmitted within a time width equivalent to all basic slots.

As a result, the transmission power control interval can be shortened as compared with the conventional method, so that the transmission power control error can be reduced. As a result, the user capacity can be increased more than before. In addition, there is an advantage that the phase estimation for establishing synchronization in the receiver is facilitated.

[Brief description of the drawings]

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

FIG. 2 is a diagram showing another example of the embodiment of the present invention.

FIG. 3 is a diagram illustrating an example in which a user capacity is increased according to the present invention.

FIG. 4 is a diagram showing an example of a conventional uplink frame configuration.

[Explanation of symbols]

1-1, 2-1 and 4-1 Frame configuration at 9600 bit / s 1-2, 2-2 and 3-3 Frame configuration at 2400 bit / s 2-3, 2-4 Unique word 4-1 Frame Configuration at 1200 bit / s 4-2 Frame Configuration at 4800 bit / s

────────────────────────────────────────────────── ─── Continuation of the front page (56) References Table 10-505736 (JP, A) Eisuke Kudo (one other), Slot configuration method in multi-rate DS-CDMA system, Proceedings of the Communication Society Conference , IEICE, August 30, 1996, 1, p. 350, B-349 (58) Field surveyed (Int. Cl. ⁷ , DB name) H04J 13/00-13/06 H04B 1/69-1/713

Claims (3)

(57) [Claims] 1. One frame is composed of a plurality of slots,
In a wireless communication method for transmitting a signal using a direct spread CDMA communication method, when a signal having a maximum transmission rate is handled, one frame is composed of N (N is an integer of 2 or more) basic slots; A method of transmitting a signal of K bits (K is an integer of 2 or more) per frame, using a basic slot of (K / N) bits, and continuously transmitting N pieces, is used, and 1 / M of the maximum transmission rate is used. When a signal having a transmission rate of (M is an integer of 2 or more) is handled, (K / N / M) bits are set to one slot, and the beginning of each slot and the beginning of a time width equivalent to the basic slot are set. Are sequentially shifted by L bits (L is a natural number) for each slot, and each slot is arranged such that one slot exists within a time width equivalent to each of the basic slots. Slot Wireless communication method, wherein N packets are continuously transmitted. 2. One frame is composed of a plurality of slots,
In a wireless communication method for transmitting a signal using a direct spread CDMA communication method, when a signal having a maximum transmission rate is handled, one frame is composed of N (N is an integer of 2 or more) basic slots; A signal of K bits (K is an integer of 2 or more) per frame is transmitted, and a method of continuously transmitting N pieces of basic slots as (K / N) bits is employed, and 1 / M (1 / M) of the maximum transmission rate is adopted. When a signal having a transmission rate of (M is an integer of 2 or more) is handled, (K / N / M) bits are set as one slot, and each slot is randomly set within a time width equivalent to each of the basic slots. A wireless communication method comprising arranging one slot at a time and transmitting N slots continuously. 3. A signal having a fixed-length bit arranged at the beginning of each basic slot or a time width equivalent to the basic slot, and having a transmission rate of 1 / M (M is an integer of 2 or more) of a maximum transmission rate. , When fixed length bits and slots are respectively arranged within a time width equivalent to each basic slot, and N fixed length bits and slots are continuously transmitted. The wireless communication method according to claim 2.