CN101442357B

CN101442357B - Method and system for wireless transmission adopting Relay supported frame structure

Info

Publication number: CN101442357B
Application number: CN200710177679A
Authority: CN
Inventors: 孙韶辉; 毕海; 谢永斌; 王映民
Original assignee: China Academy of Telecommunications Technology CATT
Current assignee: China Academy of Telecommunications Technology CATT; Datang Mobile Communications Equipment Co Ltd
Priority date: 2007-11-19
Filing date: 2007-11-19
Publication date: 2012-10-10
Anticipated expiration: 2027-11-19
Also published as: CN101442357A

Abstract

The invention provides a method for wireless transmission by adopting a frame structure which supports Relay, which comprises: a time slot of a subframe is divided into an uplink signal area and a downlink signal area, wherein the uplink signal area at least comprises an uplink mixed area, the downlink signal area at least comprises a downlink mixed area, and a relay sends independent synchronous and control information in the downlink signal area; in a downlink direction, the base station sends data to a terminal and the relay respectively in the downlink mixed area in a frequency division multiplexing mode; and in an uplink direction, the base station receives the data which is sent by the terminal and the relay in the frequency division multiplexing mode in the uplink mixed area. The invention also provides a system for the wireless transmission by adopting the frame structure which supports the Relay. The adoption of the method can improve the flexibility of a system and also fully utilize the time-frequency resource of the system. In addition, the method can also sufficiently reduce the cost for the system, improve the utilization rate of resources, and assure enough time of UE used for receiving-sending or sending-receiving conversion at the same time.

Description

Method and system for wireless transmission by adopting frame structure supporting relay

Technical Field

The present invention relates to the field of wireless communication technologies, and in particular, to a method and a system for performing wireless transmission using a frame structure supporting Relay.

Background

Coverage is an important indicator of wireless access systems in both 3G and B3G (Beyond 3 Generation) communication systems, which typically implement coverage to a service area through base stations or access points. However, due to the mobility of the terminal, the terminal is completely possibly out of the service area, so that the wireless access service cannot be obtained; even if the terminal is located within the service area, the transmission of the signal may be obscured by obstacles on the transmission path, resulting in a degradation of the quality of service. In future mobile communication systems, very high-rate data (such as 1 Gbps) needs to be transmitted, and due to the limitation of frequency band allocation conditions, the future mobile communication systems are highly likely to use a higher communication frequency band (such as 5 GHz), both of which cause a sharp reduction in coverage, and the number of base stations/access points greatly affects the construction and operation cost of the network. In view of the above, in order to solve the seamless coverage of the service area and the increase of the system capacity and save the cost as much as possible, it is generally proposed to adopt a "Relay (RS-Relay station)" technique in a future mobile communication solution. When the UE is located outside the service area or the signal quality cannot meet the requirement, the RS may relay the signal, so as to expand the service area or improve the reliability of transmission. The main roles of Relay are to extend coverage and to extend cell capacity.

Relay is one of the key technologies in the B3G system. The introduction of Relay brings about the problems of multiplexing mode and sequence of a Relay link and an access link. The basic structure of the Relay system can be described by fig. 1. Fig. 1 has a total of class 2 links: an Access Link (Access Link) representing a Link between the UE and the BS/RS, and a Relay Link (Relay Link) representing a Link between the BS (base station) and the RS. The access link and the relay link have both a downlink and an uplink. The RS receives the data of the BS through the relay link and then forwards the data to the UE through the access link.

In the prior art, in order to maintain strong compatibility with the existing 3G, a frame structure of B3G is shown in fig. 2. Each frame is 10ms and is divided into 2 subframes of 5ms, and each subframe comprises 1 DL SYNC (downlink synchronization) time slot and 14 data time slots. The DL SYNC slot is used to send synchronization information. There is a guard interval gp (guard period) from downlink to uplink between TS1 (time slot 1, slot 1) and TS 2. The specific parameters are shown in fig. 2.

In the process of the TD-SCDMA system evolving to the wideband TDD system, it is more necessary to add a radio communication technology, called Relay, to improve the capacity, the frequency band utilization rate, and the coverage capability of the system. For TD-SCDMA systems, the frame structure consists of 10ms radio frames, each of which is divided into two 5ms radio subframes. As shown in fig. 3, each radio subframe is composed of 7 normal slots (TS 0 to TS 6) and three special slots; the common time slot is used for transmitting data, and the time slots with corresponding proportion can be distributed according to the proportion of the uplink and downlink services for uplink and downlink service data transmission; the three special time slots are DwPTS (downlink pilot channel for sending downlink synchronization information of the system), UpPTS (uplink pilot channel for sending uplink synchronization information accessed by a user), and GP (transition protection time slot for providing a time interval for transition of the downlink sending time slot to the uplink sending time slot), respectively.

At present, the frame structure of fig. 3 has been used as a frame structure of an air interface of a new generation wireless broadband LTE TDD (long term evolution time division duplex) system, thereby ensuring strong compatibility with a TD-SCDMA frame structure, ensuring smooth upgrade of the system, and reducing interference with an original system. Meanwhile, for an IMT-Advanced (intelligent multimode terminal evolution) system, in order to improve the system of the system, key technologies such as Relay need to be introduced. For a wireless communication device based on the frame structure of fig. 3, when used in an IMT-Advanced system, if Relay is introduced, it will inevitably cause a large impact on the signal processing flow and timing of the frame structure shown in fig. 3. Because Relay adds a new device between the original wireless links of the base station and the terminal, in order to support Relay, the multiplexing mode and transmission sequence of the Relay link and the access link need to be arranged reasonably.

In order to support relay, the multiplexing mode and transmission sequence of the relay link and the access link need to be arranged reasonably. In the existing TDD system supporting Relay, a downlink subframe and an uplink subframe are generally divided into an Access Zone and a Relay Zone, where the Access Zone and the Relay Zone are respectively used for Access link and Relay link transmission, and the Access Zone and the Relay Zone use a time division multiplexing method, which is specifically shown in fig. 4.

The existing TDD (Time Division Duplex) system supporting Relay only considers the Time Division multiplexing of the Relay link and the Access link, that is, the Access Zone and the Relay Zone adopt the Time Division multiplexing mode. The bandwidth of the future B3G system will be very large, possibly reaching 100MHz, for such large bandwidth, if only the time division multiplexing of the relay link and the access link is considered, when the relay traffic is light, the resource will be greatly wasted, and the single multiplexing mode is not favorable for the flexible use of the system. Considering that the TD SCDMA compatible B3G system still adopts the timeslot structure, i.e. the position and length of the relay zone are configured by using the timeslot as the length. Therefore, if the Access Zone and the Relay Zone still use time division multiplexing with time slot granularity, it is easy to cause inflexible resource scheduling and waste of resources due to too large granularity. Therefore, a more reasonable multiplexing method of the relay link and the access link is required for the B3G system using the time slot structure. The main disadvantages of the existing TDD system for supporting the relay frame structure are as follows:

(1) the delay is increased. Taking BS sending downlink service as an example, when downlink service arrives at BS, BS can send at the beginning of downlink subframe under the original system frame structure, but can only send in DL Access Zone (downlink Access Zone) area under B3G frame structure supporting Relay, which increases time delay virtually, and it is difficult to meet the harsh requirement of B3G time delay. As shown in particular in fig. 5.

(2) The resources are wasted, and if the original Relay frame structure is adopted, the bandwidth of the whole Relay zone needs to be distributed to the Relay links under the condition that the traffic of the Relay links is small and a small bandwidth is needed, which is a great waste of the resources. As shown in particular in fig. 6.

Disclosure of Invention

In view of this, the problem to be solved by the present invention is to provide a method and a system for performing wireless transmission by using a frame structure supporting Relay, which effectively utilize frequency resources and time resources, improve the utilization rate of resources, and reduce the signal transmission delay caused by introducing Relay into the system.

In order to solve the above problems, the technical scheme provided by the invention is as follows:

a method for wireless transmission using a Relay-capable frame structure, the method comprising:

dividing a time slot of a subframe into an uplink signal area and a downlink signal area, wherein the uplink signal area at least comprises an uplink mixed area, the downlink signal area at least comprises a downlink mixed area, and a relay sends independent synchronization and control information in the downlink signal area;

in the downlink direction, the base station respectively sends data to the terminal and the relay in a downlink mixed region in a frequency division multiplexing mode;

in the uplink direction, the base station receives data sent by the terminal and the relay in a frequency division multiplexing mode in an uplink mixed area;

and multiplexing the relay link and the access link together in a frequency division multiplexing mode in the mixed area.

Correspondingly, at least one time slot in the subframe is set as a mixing zone.

Correspondingly, the uplink signal area may further include an uplink access area, and the downlink signal area may further include a downlink access area.

Correspondingly, the uplink access zone is before the uplink mixed zone and the downlink access zone is before the downlink mixed zone according to the signal timing sequence.

Accordingly, two reception/transmission switching intervals and one transmission/reception switching interval are inserted in the subframe of the relay terminal.

Correspondingly, a part of time slot resources are reserved according to the distance between the relay and the base station for uplink access delay.

A system for carrying out wireless transmission by adopting a frame structure supporting Relay comprises a base station, a Relay and a terminal, wherein a time slot of a subframe is divided into an uplink signal area and a downlink signal area, the uplink signal area at least comprises an uplink mixed area, the downlink signal area at least comprises a downlink mixed area, and data transmission is carried out by carrying out a Relay link and an access link in a frequency division multiplexing mode in the mixed area of the subframe;

for the base station, a mixed area is set in each subframe, namely a receiving mixed area is used for replacing a relay area, so that each subframe consists of a first downlink access area, an uplink mixed area, an uplink access area, a downlink mixed area and a second downlink access area;

for relay, each subframe consists of a first downlink access area, an uplink relay area, an uplink access area, a downlink relay area and a second downlink access area; wherein,

the base station is used for respectively sending data to the terminal and the relay in a downlink mixed region in a frequency division multiplexing mode, and receiving the data sent by the terminal and the relay in the frequency division multiplexing mode in the uplink mixed region;

the relay is used for sending self-independent synchronization and control information in the first downlink access area, and sending data to the base station in the uplink relay area according to the frequency distributed by the base station after receiving the data sent by the terminal in the uplink access area;

and the terminal is used for sending data to the base station in the uplink access area and sending the data to the base station after frequency division multiplexing with the relay.

It can be seen that, by adopting the method and system of the invention, the data transmission is realized by frequency division multiplexing the access link and the relay link in the mixed region of the subframe, thereby improving the utilization rate of system resources, further improving the performance of the system, and being compatible with the TD _ SCDMA system; meanwhile, the flexibility of system resource scheduling is improved by adopting frequency division multiplexing, the resource scheduling with the minimum granularity can be realized, and the signal transmission delay caused by the introduction of a relay into the system can be effectively reduced.

Drawings

FIG. 1 is a schematic diagram of the basic structure of a Relay system in the prior art;

fig. 2 is a schematic diagram of a B3G frame structure compatible with TD _ SCDMA in the prior art;

fig. 3 is a prior art LTE TDD frame structure compatible with TD _ SCDMA;

fig. 4 is a diagram illustrating a frame structure of a TDD system supporting relay in the prior art;

fig. 5 is a schematic diagram of increasing delay of a frame structure of a TDD system supporting relay in the prior art;

FIG. 6 is a diagram of a frame structure of a TDD system supporting relay in the prior art for wasting resources;

FIG. 7 is a flow chart of the method of the present invention;

fig. 8 is a schematic diagram of a TDD frame structure supporting in-band non-transparent relay in embodiment 1 of the present invention;

fig. 9 is a schematic diagram of reducing delay of a frame structure supporting that a relay link and an access link may be frequency division multiplexed in embodiment 1 of the present invention;

fig. 10 is a schematic diagram of reasonable resource allocation of a frame structure supporting that a relay link and an access link can perform frequency division multiplexing in embodiment 1 of the present invention;

fig. 11 is a signal flow diagram of supporting in-band non-transparent relay in embodiment 1 of the present invention;

fig. 12 is a schematic diagram of a TDD frame structure supporting in-band non-transparent relay according to embodiment 2 of the present invention;

fig. 13 is a schematic time slot diagram of a signal early-transmission Δ t time in embodiment 2 of the present invention.

Detailed Description

The basic idea of the invention is to adopt a multiplexing mode of combining time division and frequency division in a broadband TDD system, so that the time-frequency resources of the system can be fully utilized.

In order that those skilled in the art will better understand the technical solution of the present invention, the following detailed description of the present invention is provided in conjunction with the accompanying drawings and embodiments. As shown in fig. 7, the method of the present invention includes:

step 701: dividing a time slot of a subframe into an uplink signal area and a downlink signal area, wherein the uplink signal area at least comprises an uplink mixed area, the downlink signal area at least comprises a downlink mixed area, and a relay sends independent synchronization and control information in the downlink signal area;

step 702: in the downlink direction, the base station respectively sends data to the terminal and the relay in a downlink mixed region in a frequency division multiplexing mode;

step 703: in the uplink direction, the base station receives data sent by the terminal and the relay in a frequency division multiplexing mode in an uplink mixed area.

Specifically, in embodiment 1 of the present invention, a frame structure compatible with TD-SCDMA and LTE TDD systems is adopted, and the frame structure supporting Relay still has a length of 10ms per frame and is divided into 2 subframes. Each subframe includes 7 service timeslots and 3 special timeslots (in some cases, the position of the UpPTS timeslot may be changed or even cancelled, so that GP is increased, and thus the requirement of large coverage of the system can be satisfied), and this embodiment makes corresponding changes to the frame structure on this basis:

wherein, for non-transparent relays, as shown in fig. 8: for a Base Station (BS), one radio frame includes two subframes, and a Hybrid Zone is set in each subframe, i.e., a Relay Zone is replaced by a Hybrid Zone; each subframe includes a first downlink Access Zone (DL Access Zone), an uplink reception mixed Zone (UL Hybrid Zone), an uplink Access Zone (UL Access Zone), a downlink transmission mixed Zone (DL Hybrid Zone) and a second downlink Access Zone (DL Access Zone) in a signal timing sequence. In this embodiment there are two special areas: an uplink receiving mixed area and a downlink sending mixed area. For an uplink receiving mixed area, a terminal and a relay station can occupy uplink sending resources in a Frequency Division Multiplexing (FDM) mode and are accessed to a base station, because the maximum bandwidth requirement of an IMT-Advanced system reaches 100MHz, and the bandwidth of most relay stations is less than 100MHz, if the bandwidth required by the relay station in the system is less than the system bandwidth, the terminal and the relay station can occupy the uplink sending resources in the FDM mode, and therefore the utilization rate of system resources is improved. In the same way, the base station in the downlink transmission hybrid region can simultaneously transmit data and control signaling for the terminal and the relay station in an FDM manner. Only the terminal can transmit data to the base station using the slot resource in the uplink access zone. And the base station in the second downlink access area sends data and control signaling to the mobile station through the time slot resource. In the downlink reception mixed region, the base station also transmits a synchronization signal and control signaling to the relay.

Since the system still needs to be forward compatible after the Relay is introduced, and the TS0 of the original system must be a downlink timeslot, the base station end frame structure supporting the in-band non-transparent Relay in this embodiment is designed such that the first downlink access area only includes the TS0 timeslot. Meanwhile, the original system specifies that TS1 must be an uplink timeslot, so this embodiment divides the timeslots TS1 to TS6 in the subframe into an uplink signal region and a downlink signal region, where the uplink signal region is divided into an uplink receiving mix region and an uplink access region. The uplink reception mix area is located in front of the uplink access area, and is arranged such that when the relay station transmits uplink data to the base station, the amount of data transmission is not reduced due to a delay in the time for transmitting the data in the uplink reception mix area. The relay station can transmit data in advance using the previous GP without interfering with data reception of the uplink access zone. Meanwhile, the interior of the downlink signal area is divided into a downlink sending mixed area and a second downlink access area. Of course, those skilled in the art understand that there may be no access area in the uplink and downlink signal areas, and the description thereof is omitted here. In order to ensure the minimization of the signal transmission delay, the downlink transmission mixing area must be located in front of the second downlink access area, which will reduce the delay of the signal transmitted from the base station to the relay station, so that the signal transmission delays of the base station and the terminal, and the base station and the relay station are more balanced. For the frame structure of the base station, there is a transition point GP from downlink to uplink between DwPTS and UpPTS.

For Relay, one radio frame also includes two subframes, and each subframe is composed of a first downlink access Zone, an uplink Relay Zone (UL Relay Zone), a downlink access Zone, a downlink Relay Zone (DL Relay Zone), and a downlink access Zone. The first downlink access zone contains only TS0 time slots, while the other zones consist of one or more remaining time slots. In the first downlink access zone, the RS transmits its own synchronization information and control information. Corresponding to the time slot division of the BS, dividing the TS 1-TS 6 time slots into an uplink signal area and a downlink signal area, wherein the uplink signal area is divided into an uplink relay area and an uplink access area; in the uplink relay zone, the RS forwards the data of the UE to the BS, and the UE can send the data to its host RS in the uplink access zone. The downlink signal area is divided into a downlink relay area and a second downlink access area; in the downlink relay zone, the RS may receive data from the BS and forward to the UE in the second downlink access zone. Between DwPTS and UpPTS is a downlink-to-uplink transition point GP, a transmission/reception transition gap (TTG) is inserted between an uplink relay zone and an uplink access zone, and a reception/transmission transition gap (RTG) is inserted between a downlink relay zone and a second downlink access zone.

With the above frame structure, although the time division multiplexing mode is still adopted between the zones, in the areas of the ul Hybrid Zone and the DL Hybrid Zone, the relay link and the access link adopt the frequency division multiplexing mode. Meanwhile, the frequency domain resource allocation of the relay link and the access link of each time slot in the Hybrid Zone may be different, which is determined by scheduling. When the traffic of the relay link is very small, that is, the relay does not occupy a large bandwidth, a part of frequency resources can be taken out from the UL Hybrid Zone or the DL Hybrid Zone to be used by the UE, so that resource waste caused by allocating all the bandwidth of one timeslot to the relay link is avoided. Meanwhile, the flexibility of system resource transfer is improved by adopting frequency reuse. By adopting the frame structure, the resource scheduling with smaller granularity and the time delay reduction can be realized.

Specifically, as shown in fig. 9, taking the BS sending downlink traffic as an example: when downlink traffic reaches the BS, because the relay link and the access link in the Hybrid zone may be frequency division multiplexed, the BS may transmit data to the terminal in the downlink sub-frame Hybrid zone area under the system frame structure supporting the Hybrid zone, which is the same as the transmission time of the frame structure not supporting the relay, so that the delay may not be increased. Similarly, as shown in fig. 10, for the case that the traffic of the relay link is small and a small bandwidth is needed, a frame structure supporting frequency division multiplexing of the relay link and the access link is adopted, so that a part of the bandwidth of the hybrid zone can be distributed to the relay link, which reduces the waste of resources.

Accordingly, as shown in fig. 11, when the above frame structure is adopted, the system works as follows: in the downlink direction, the BS respectively sends data to the UE and the RS within the coverage of the BS in an FDM mode at the DL Access Zone, and the RS demodulates and decodes the data of the BS after receiving the data of the BS at the corresponding frequency resource, judges the corresponding destination address, codes and modulates the data at the proper position of the DL Access Zone and forwards the modulated data to the corresponding UE; in the uplink aspect, the UE sends data to the RS in the UL Access, the RS performs demodulation and decoding after receiving the data, determines a corresponding destination address, and sends the frequency resource allocated to the RS in the BS of the UL Hybrid Zone to the BS, and the UE also sends data to the BS in frequency division multiplexing of the UL Hybrid Zone and the RS.

As shown in fig. 12, based on the above change of the frame structure of the base station, the uplink access zone may be divided before the uplink reception mixed zone and the second downlink access zone may be divided before the downlink transmission mixed zone in the signal sequence order in each subframe; the function of each region and the transmission or reception flow of signals therein are the same as those described above, and are not described herein again. Correspondingly, for the frame structure of the relay, the uplink access zone can be divided before the uplink relay zone and the second downlink access zone can be divided before the downlink relay zone in each subframe according to the signal timing sequence; in order to convert the RS from the receiving mode to the transmitting mode, the frame structure of the relay end includes two receiving/transmitting conversion intervals (RTGs), which are RTG1 and RTG 2; meanwhile, in order to guarantee the conversion of transmission and reception, a transmission/reception conversion interval (TTG) needs to be inserted.

In addition, since the uplink access zone is placed in the uplink relay zone, in addition to receiving the transition time of transmission, a certain resource needs to be reserved in RTG1 for the advance of data transmission; therefore, it is necessary to set aside a delay for uplink access of a part of slot resources in the uplink relay zone or the uplink access zone, and the delay time is determined by the distance from the RS to the BS. Specifically, as shown in fig. 13, due to the delay of the RS transmitting signal to the BS, the data of the RS needs to be transmitted earlier by a time Δ t, which is determined by the distance between the RS and the BS.

Therefore, the method of the invention improves the utilization rate of system resources, and further improves the performance of the system; meanwhile, the flexibility of system resource scheduling is improved by adopting frequency division multiplexing, the resource scheduling with the minimum granularity can be realized, and the signal transmission delay caused by the introduction of a relay into the system can be effectively reduced.

It will be understood by those skilled in the art that all or part of the steps in the method for implementing the above embodiments may be implemented by hardware associated with program instructions, and the program is stored in a specific storage medium.

The following introduces a specific embodiment of the system for implementing wireless transmission by using a frame structure supporting Relay according to the present invention, and the system includes a base station, a Relay, and a terminal;

For the base station, a mixed area is set in each subframe, namely a Relay Zone is replaced by a Hybrid Zone, so that each subframe consists of a first DL Access Zone, a UL Relay Zone, a UL Access Zone, a DL Relay Zone and a second DL Access Zone; for the Relay, each subframe consists of a first DL Access Zone, a UL Relay Zone, a UL Access Zone, a DL Relay Zone, and a DL Access Zone.

Specifically, in the downlink direction, the BS may perform frequency division multiplexing on the DL Hybrid Zone relay link and the access link, that is, the BS divides part of the bandwidth of the Hybrid Zone to the relay link; therefore, the BS can respectively send data to the UE and the RS within the coverage of the BS in an FDM mode in the DL Access Zone, and the RS demodulates and decodes the data of the BS after receiving the data of the BS in the corresponding frequency resource, judges the corresponding destination address, codes and modulates the data at the proper position of the DL Access Zone and forwards the modulated data to the corresponding UE; in the uplink direction, the UE sends data to the RS in UL Access, the RS demodulates and decodes after receiving the data, a corresponding destination address is judged, the data is sent to the BS by the frequency resources which are allocated to the RS by the BS of the UL Hybrid Zone, and meanwhile, the UE also sends the data to the BS in the UL Hybrid Zone and the RS frequency division multiplexing.

It can be seen that, by adopting the above system, the high bandwidth of the B3G system is fully utilized, and the data transmission is realized by frequency division multiplexing the access link and the relay link in the mixed region of the sub-frame, thereby not only improving the flexibility of the system, but also fully utilizing the time-frequency resources of the system; meanwhile, when the system has a plurality of relays, the multi-hop relay can be supported.

The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.

Claims

1. A method for wireless transmission using a frame structure that supports relaying, the method comprising:

2. The method of claim 1, wherein:

at least one slot in the subframe is set as a mixing zone.

3. The method of claim 1, wherein:

the uplink signal area also comprises an uplink access area, and the downlink signal area also comprises a downlink access area.

4. The method of claim 3, wherein:

according to the signal time sequence, the uplink access area is before the uplink mixed area, and the downlink access area is before the downlink mixed area.

5. The method of claim 4, wherein:

two reception/transmission switching intervals and one transmission/reception switching interval are inserted in a subframe of the relay terminal.

6. The method of claim 5, wherein:

and reserving part of time slot resources for uplink access delay according to the distance between the relay and the base station.

7. A system for wireless transmission using a frame structure supporting relaying, comprising a base station, a relay and a terminal, characterized in that: dividing a time slot of a subframe into an uplink signal area and a downlink signal area, wherein the uplink signal area at least comprises an uplink mixed area, the downlink signal area at least comprises a downlink mixed area, and transmitting data by using a relay link and an access link in a frequency division multiplexing mode in the mixed area of the subframe;