CN101159478B

CN101159478B - Physical accidental channel transmitting method

Info

Publication number: CN101159478B
Application number: CN 200710184900
Authority: CN
Inventors: 梁春丽
Original assignee: ZTE Corp
Current assignee: ZTE Corp
Priority date: 2007-10-29
Filing date: 2007-10-29
Publication date: 2012-12-19
Anticipated expiration: 2027-10-29
Also published as: CN101159478A

Abstract

The invention discloses a method of delivering a physical random channel in a time division duplex system, which includes the steps as following: Step 1, the data to be delivered are packaged into the data frame having the preset frame configuration; and Step 2, deliver physical random access channel on a plurality of last uplink symbols in the uplink pilot time slot in the data frame. By using the invention, the number of the uplink symbol delivering PRACH channel in UpPTS is no longer limited within two; therefore, when n is more than 2, the PRACH channel supporting a larger coverage can be delivered on UpPTS.

Description

Physical random channel transmitting method

Technical Field

The invention relates to the field of mobile communication, in particular to a method for transmitting a physical random channel of a time division duplex system.

Background

3GPP(3^rdGeneration Partnership Project, Long Term Evolution (LTE) system defines two types of frame structures, wherein the second type of frame structure (as shown in fig. 1) corresponds to the Long Term Evolution of TD-SCDMA, and adopts TDD (Time Division Duplex) mode. In the second type of frame structure, subframe 0(subframe 0) fixedly transmits downlink data; the first n subframes in the subframes 1-6 are used for transmitting uplink data, and the last 6-n subframes are used for transmitting downlink data (n is more than or equal to 1 and less than or equal to 6); the special Time Slot DwPTS (Downlink Pilot Time Slot) is used for transmitting Downlink synchronization information, GP (Guard Period) is a Guard band, and UpPTS (Uplink Pilot Time Slot) is used for transmitting Uplink synchronization information. Meanwhile, in order to support large cells, the first m subframes of the No. 1-6 subframes can also be used for transmitting uplink synchronization information, and the rest data subframes areThe first n are used to transmit upstream data, and the last 6-m-n are used to transmit downstream data.

The second type of frame structure of the current LTE system has the advantage that the LTE system and the TD-SCDMA system can conveniently realize adjacent frequency coexistence, that is, as long as the uplink and downlink time slot switching ratio of the LTE system is the same as that of the TD-SCDMA system, the mutual interference between the two systems can be effectively avoided. However, the disadvantages of this frame structure are also evident, namely: the setting of GP is very inflexible, in this system, the length of GP slot is equal to 50us, when the system needs to support a wider coverage, the length of GP must be extended, the method for extending GP may be to reserve UpPTS slot as GP slot, or reserve UpPTS slot and TS1 as GP slot (note, part of symbol of TS1 may not be reserved as GP because the uplink control channel is usually on both sides of the system bandwidth, and the duration is one slot, if part of symbol of TS1 is reserved as GP, the receiving performance of uplink control channel will be seriously degraded, or reserve DwPTS and part of symbol of TS0 as GP because P-SCH (primary synchronization channel) is transmitted on DwPTS, S-SCH (secondary synchronization channel) is transmitted on the last 1 symbol of TS0, if part of symbol of DwPTS and TS0 is reserved as GP, the user may not be able to receive P/S-SCH signal, and the P/S-SCH signal is a signal that the user first needs to receive when accessing the system, and the user cannot correctly receive the P/S-SCH signal, i.e., cannot access the system).

The P/S-SCH signal is located at the boundary where the downlink slot is switched to the uplink slot, and as described above, the P/S-SCH signal is a signal that a user access system first needs to receive, so the power of the P/S-SCH signal is usually greater than that of other signals, and in a cellular environment, the reception performance of the uplink slot signal is seriously affected due to the greater power of the P/S-SCH signal;

the DwPTS is not efficiently used, and when the bandwidth of the system is wider, since only the P-SCH signal is transmitted in the middle bandwidth (1.25MHz) of the system bandwidth, the DwPTS is inefficient to use.

In order to solve the above problem, some companies propose a new frame structure suitable for the TDD model of the LTE system, as shown in fig. 2 (for convenience of description, this frame structure is referred to as a "new frame structure" hereinafter). In this "new frame structure", a 10ms radio frame is divided into two half-frames, each of which is divided into 10 slots (numbered from 0 to 9) of length 0.5ms, the two slots constituting a subframe of length 1ms, and one half-frame containing 5 subframes (numbered from 0 to 4). For short CP (cyclic prefix) with lengths of 5.21us and 4.69us, one slot includes 7 up/down symbols with a length of 66.7us, wherein the first symbol CP has a length of 5.21us, and the remaining 6 symbols have a CP length of 4.69 us; for a long CP of length 16.67us, one slot contains 6 up/down symbols. In addition, in the frame structure, the configuration characteristics of the sub-frame are as follows:

subframe 0 is fixed for downlink transmission;

subframe 1 is a special subframe, which includes 3 special timeslots, which are dwpts (downlink Pilot Time slot), gp (guard period), and uppts (uplink Pilot Time slot). Wherein,

the DwPTS is used for downlink transmission, at least one downlink OFDM symbol is used for transmitting a Primary-Synchronization Channel (P-SCH), and when the DwPTS includes a plurality of OFDM symbols, the P-SCH is placed on a first OFDM symbol (as shown in fig. 2);

GP is protection time and does not transmit any data;

the UpPTS is used for uplink transmission, and at least includes 2 uplink SC-FDMA symbols for transmitting a Physical Random Access Channel (PRACH), and when the number included in the UpPTS is greater than 2, the PRACH is placed on the first two symbols for transmission (as shown in fig. 2).

In the "new frame structure", the PRACH channel is transmitted on the first two symbols of the UpPTS timeslot, and since the duration of the GP may be different depending on the coverage, when the GP needs to satisfy the coverage requirement by dropping the uplink symbol, the position of the PRACH needs to be moved backward correspondingly, that is, the relative position of the PRACH in one frame is actually not fixed, which brings a certain trouble to the detection of the PRACH. In addition, the PRACH channel only occupies 2 symbols, and the length of the preamble (preamble) and the GT (guard time) is relatively short (the preamble length is 133.3us, and the GT length is 9.5us (in short CP time) or 33.5us (in long CP time)), so that the supported coverage is very small, and the application scenario is very limited.

Therefore, there is a need for a solution for transmission of a physical random access signal that can solve the above-mentioned problems in the related art.

Disclosure of Invention

In order to solve the above problems, the present invention proposes a physical random channel transmission method for a tdd system aiming at a new frame structure, which comprises the following steps: step one, encapsulating data to be transmitted into a data frame with a preset frame structure; and step two, sending the physical random access channel on the last plurality of uplink symbols in the uplink pilot frequency time slot in the data frame.

The duration of the uplink pilot time slot is greater than the duration of a plurality of uplink symbols.

When the uplink pilot time slot uses the normal cyclic prefix, the number of the plurality of uplink symbols is greater than or equal to 2 and less than or equal to 14.

When the uplink pilot slot uses the extended cyclic prefix, the number of the plurality of uplink symbols is greater than or equal to 2 and less than or equal to 12.

The predetermined frame structure includes: subframe 0, which is fixedly used for transmitting downlink data; subframe 1, comprising: a downlink pilot time slot field, a guard interval, an uplink pilot time slot field; the first n subframes behind the subframe 1 are used for uplink transmission, wherein n is more than or equal to 1 and less than or equal to 3; and the last 3-n subframes are used for downlink transmission.

In the method, the physical random access channel comprises a cyclic prefix, a preamble symbol and a guard time, and when the duration of a plurality of uplink symbols is 0.5ms, the duration of the cyclic prefix of the physical random access channel is 52.6us, the duration of the preamble symbol is 400us, and the guard time is 47.4 us.

In the method, a physical random access channel comprises a preamble symbol and a guard time, and when the duration of a plurality of uplink symbols is 0.5ms, the duration of the preamble symbol of the physical random access channel is 400us, and the guard time is 47.4 us; alternatively, the duration of the preamble symbol is 466.7us and the guard time is 33.3 us.

By adopting the invention, the PRACH channel is sent on the last symbols on the UpPTS. When the number of symbols used for transmitting the PRACH is determined, the position of the PRACH is fixed, and the position of the PRACH does not differ according to different coverage required to be supported by GP, thereby being beneficial to the receiving detection of the PRACH by a receiver. In addition, by adopting the invention, the uplink symbol used for sending the PRACH in the UpPTS is not limited to 2 symbols any more, therefore, when n is more than 2, the PRACH channel supporting larger coverage can be sent on the UpPTS.

Additional features and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.

Drawings

The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the invention and together with the description serve to explain the invention without limiting the invention. In the drawings:

fig. 1 shows a second type frame structure diagram of a conventional LTE system;

FIG. 2 shows a new frame structure diagram;

fig. 3 is a diagram illustrating a transmission method of a physical random channel according to the present invention;

fig. 4 is a flowchart illustrating a transmission method of a physical random channel according to the present invention; and

fig. 5 shows a schematic diagram of a PRACH channel structure according to the present invention.

Detailed Description

Embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

Fig. 4 shows a flowchart of a transmission method of a physical random channel according to the present invention. Referring to fig. 4, the transmission method of a physical random channel according to the present invention includes the steps of: step S402, encapsulating data to be transmitted into a data frame with a preset frame structure; and step S404, sending the physical random access channel on the last plurality of uplink symbols in the uplink pilot time slot in the data frame.

In another embodiment of the present invention, the PRACH channel is sent on the last n uplink symbols in the UpPTS timeslot;

furthermore, the duration of the UpPTS timeslot must be greater than or equal to the duration of n uplink symbols;

further, the value of n is related to a cyclic prefix used by the UpPTS timeslot, and when the UpPTS uses a conventional cyclic prefix, the value of n satisfies: n is more than or equal to 2 and less than or equal to 14; when the extended cyclic prefix is used by the UpPTS, the value of n satisfies the following condition: n is more than or equal to 2 and less than or equal to 12;

further, when n > 2, a PRACH channel supporting greater coverage may be transmitted on the UpPTS;

specifically, the length for the PRACH channel may be 0.5ms, that is, corresponding to the case where n is 7 when UpPTS uses a conventional cyclic prefix, or, corresponding to the case where n is 6 when UpPTS uses an extended cyclic prefix. If order T_RAFor PRACH channel length, T_RA＝T_CP+T_PRE+T_GTWherein T is_CPIs the length of the CP of the preamble, T_PREIs the preamble length, T_GTIs the length of GT (guard time). When the duration of the UpPTS is greater than or equal to 0.5ms, the first PRACH channel may be transmitted within the UpPTS. The structure of the PRACH channel is shown in fig. 5.

Another embodiment is described in detail below with reference again to fig. 1-3. Referring to fig. 1, in the frame structure, a subframe 0 fixedly transmits downlink data; the first n subframes in the subframes 1-6 are used for transmitting uplink data, and the last 6-n subframes are used for transmitting downlink data (n is more than or equal to 1 and less than or equal to 6); the special timeslot dwpts (downlink Pilot Time slot) is used for transmitting downlink synchronization information, gp (guard period) is a guard band, and uppts (uplink Pilot Time slot) is used for transmitting uplink random access information.

Referring to fig. 2, in the frame structure, a 10ms radio frame is divided into two half-frames, each of which is divided into 10 slots (numbered from 0 to 9) of length 0.5ms, the two slots constitute a subframe of length 1ms, and one half-frame includes 5 subframes (numbered from 0 to 4). For short CP (Cyclic Prefix) with lengths of 5.21us and 4.69us, one slot contains 7 uplink/downlink symbols with a length of 66.7us, wherein the CP length of the first symbol is 5.21us, and the CP length of the remaining 6 symbols is 4.69 us; for a long CP of length 16.67us, one slot contains 6 up/down symbols. In the "new frame structure", the PRACH channel is transmitted on the first two symbols of the UpPTS timeslot, and since the duration of the GP may be different depending on the coverage, when the GP needs to satisfy the coverage requirement by dropping the uplink symbol, the position of the PRACH needs to be moved backward correspondingly, that is, the relative position of the PRACH in one frame is actually not fixed, which brings a certain trouble to the detection of the PRACH. In addition, the PRACH channel only occupies 2 symbols, and the length of the preamble and the GT (guard time) is relatively short (the preamble length is 133.3us, and the GT length is 9.5us (in the case of short CP) or 33.5us (in the case of long CP)), so that the supported coverage is very small, and the application scenario is very limited.

Referring to fig. 3, PRACH signals are transmitted on the last n uplink symbols of the UpPTS;

further, when n > 2, a PRACH channel supporting greater coverage may be transmitted on UpPTS.

Several embodiments of RACH channels with a length of 0.5ms are given below. Similarly, let T_RAIs the PRACH channel length, and T_RA＝T_CP+T_PRE+T_GTWherein T is_CPIs the length of the CP of the preamble, T_PREIs the length of the preamble, T_GTLength of gt (guard time):

(1)T_CP＝52.6us，T_PRE＝400us，T_GT＝47.4us；

(2)T_CP＝0us，T_PRE＝400us，T_GT＝100us；

(3)T_CP＝0us，T_PRE＝466.7us，T_GT＝33.3us。

for the PRACH channel design with the cyclic prefix in the step (1), frequency domain detection can be supported, so that the complexity of a receiver is reduced, and the detection performance is improved. For (2) this PRACH design without cyclic prefix and increasing the length of the GT, the PRACH coverage is increased from the GT perspective. For (3) the PRACH design without cyclic prefix and with increased Preamble length, the detection performance of the Preamble is improved under the same coverage condition, or the coverage is improved under the same detection performance requirement.

The above is only a preferred embodiment of the present invention, and is not intended to limit the present invention, and various modifications and changes will occur to those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A physical random channel transmission method is used for a time division duplex system, and is characterized by comprising the following steps:

step one, encapsulating data to be transmitted into a data frame with a preset frame structure; and

and step two, sending a physical random access channel on the last plurality of uplink symbols in the uplink pilot frequency time slot in the data frame.

2. The method as claimed in claim 1, wherein the duration of the uplink pilot time slot is greater than the duration of the plurality of uplink symbols.

3. The method as claimed in claim 2, wherein the number of the plurality of uplink symbols is greater than or equal to 2 and less than or equal to 14 when the uplink pilot slot uses a normal cyclic prefix.

4. The method as claimed in claim 2, wherein when the uplink pilot slot uses an extended cyclic prefix, the number of the plurality of uplink symbols is greater than or equal to 2 and less than or equal to 12.

5. The physical random channel transmission method as claimed in claim 4, wherein the predetermined frame structure comprises:

subframe 0, which is fixedly used for transmitting downlink data;

subframe 1, comprising: a downlink pilot time slot field, a guard interval, an uplink pilot time slot field;

the first n subframes behind the subframe 1 are used for uplink transmission, wherein n is more than or equal to 1 and less than or equal to 3;

and the last 3-n subframes are used for downlink transmission.

6. The method as claimed in claim 1, wherein the physical random access channel includes a cyclic prefix, a preamble symbol and a guard time.

7. The method as claimed in claim 6, wherein when the duration of the plurality of uplink symbols is 0.5ms, the duration of the cyclic prefix of the physical random access channel is 52.6us, the duration of the preamble symbol is 400us, and the guard time is 47.4 us.

8. The method as claimed in claim 1, wherein the physical random access channel comprises a preamble symbol and a guard time.

9. The method as claimed in claim 8, wherein when the duration of the plurality of uplink symbols is 0.5ms, the duration of the preamble symbol of the physical random access channel is 400us and the guard time is 47.4us, or the duration of the preamble symbol is 466.7us and the guard time is 33.3 us.