WO2011123973A1

WO2011123973A1 - Random access method for radio relay communication system and base station thereof

Info

Publication number: WO2011123973A1
Application number: PCT/CN2010/000443
Authority: WO
Inventors: 韩锋; 郑武; 沈钢; 张凯宾; 刘继民
Original assignee: 上海贝尔股份有限公司; 阿尔卡特朗讯
Priority date: 2010-04-06
Filing date: 2010-04-06
Publication date: 2011-10-13
Also published as: CN102783238B; CN102783238A

Abstract

The present invention provides a random access method for a radio relay communication system. The radio relay communication system includes a base station and a relay node associated with the base station. The method includes the following steps: the base station allocates a preamble aggregate dedicated for the relay node; the base station notifies the preamble aggregate to the relay node; when a link between the base station and the relay node is failure, the relay node transmits a random access request to the base station by using a preamble randomly selected from the preamble aggregate. The present invention also provides a base station for realizing the random access method. According to the present invention, by allocating and notifying the dedicated preamble aggregate to the relay node, the base station enables the relay node to recover swiftly to the connection state while the Radio Link Failure (RLF) occurs, and ensures the minimum influence to the ordinary user equipments at the same time.

Description

Random access method and base station for wireless relay communication system

The present invention relates to a random access procedure in an LTE-A (Long Term Evolution Advance) system, and more particularly, to a random access procedure in a scenario in which a Type I relay is deployed. Background technique

In recent years, research on relay technology has gradually attracted people's attention. Relay technology is seen as a good candidate for improving cell capacity and extending coverage to meet LTE-A. In the standardization process, the following rules have been agreed: Type I relays should have their own physical cell ID and be similar to a stand-alone base station (eNB), visible to the user equipment.

FIG. 1 is a schematic diagram showing basic nodes and interfaces in a system in which a Type I relay is deployed, where

Uu (user-user) represents the interface between the user equipment and the relay node, and Un (user-network) represents the interface between the relay node and the base station eNB.

In reference [1], an agreement has been reached on the in-band resource partitioning between the backhaul link and the access link of the Type I relay, which specifies: the link to the relay node to the base station in a single frequency band and The link from the user equipment to the relay node is time division multiplexed, that is, only one link is valid at any time.

Figure 2 shows the basic operation of a wireless communication system in which a Type I relay is deployed. As shown in FIG. 2, in the backhaul DL subframe, a new physical control channel (herein referred to as "R-PDCCH") is used to allocate resources to the RN. In addition, when the relay node RN is in the connected state, it can only receive downlink traffic from the base station (DeNB) through the R-PDCCH. Below, for the sake of simplicity, the RN will serve

The UE is referred to as an RN-UE, and the UE served by the eNB is referred to as a macro-UE.

In general, the Un link maintains relatively good channel quality due to the use of higher antenna strength and advanced antenna technology. However, the Un link may also suffer from Radio Link Failure (RLF), and the relay node must perform the re-establishment process under certain circumstances. For example, in a heterogeneous network, high time-varying interference can degrade the performance of the receiver at the relay node. Another example is: The security of the Un link is not good enough when the relay node moves with the vehicle. When the RLF occurs, considering that one relay node may serve multiple RN-UEs at the same time, it is more desirable that the relay node can quickly recover to the connected state, so as to minimize the impact on the RN-UE.

Some schemes have been proposed so that the relay node performs when RLF occurs on the Un link. The RRC connects to the reestablishment process and initiates a random access procedure. However, in the existing scheme, the relay nodes are all performing contention-based random access. That is, the relay node randomly selects one preamble from the set of preambles previously broadcast by the base station for random access. In this case, the base station cannot distinguish the random access request from the relay node with the normal macro-UE.

The following is a detailed analysis of the problems existing in the existing programs:

Since the base station cannot recognize the random access request from the RN or the normal macro-UE, the base station uses the PDCCH to transmit the random access response. If the relay node continues to serve the RN-UE, since it is in in-band operation as described above, the random access response cannot be received. In this case, as a direct solution, the relay node can stop serving the RN-UE and then use the PDCCH to receive the random access response during the RA (random access) response window. Within this window, the relay node cannot send broadcast information, CRS, control signaling, etc. to the RN-UE it serves. At this time, the RN-UE will be in a deep fading state. It can be seen that this scheme has a great impact on the RN-UE. If there is competition, the RN can perform random access again using the random backoff time. Further, when the number of RN-UEs is large, this effect cannot be ignored, for example, more UEs perform RRC re-establishment, or suddenly enter an idle state.

Therefore, a mechanism must be devised to enable the relay node to quickly return to the connected state when RLF occurs on the Un link, while minimizing the impact on the UE served by the relay. This is the object of the present invention.

references

[1]. TR 36.814, "Further advancements for E-UTRA physical layer aspects".

It is an object of the present invention to provide a random access method that enables a relay node to quickly recover from a radio link failure on the Un link to a connected state while ensuring minimal impact on the user equipment.

According to a first aspect of the present invention, a random access method for a wireless relay communication system is provided, the wireless relay communication system comprising a base station and a relay node associated with the base station, the method comprising the following Step: the base station allocates a preamble set dedicated to the relay node; the base station knows the preamble set to the relay node; and when the base station and the relay node When a link between the two links fails, the relay node randomly selects a preamble from the set of preambles to send a random access request to the base station.

Preferably, the base station allocates a preamble set dedicated to the relay node, where: the base station divides the preamble set for random access into a preamble set and a non-contention preamble set, where The preamble set of the preamble is for the user equipment served by the base station itself; the non-contention preamble set is divided into a non-competitive preamble subset for the user equipment served by the station itself and a non-competitive preamble for the relay node a synchronization code subset; and assigning a non-contention preamble subset for the relay node to the relay node.

Preferably, the base station notifying the relay node of the preamble set comprises: the base station notifying the relay node of the preamble set by using broadcast signaling.

Preferably, the notifying the base station of the preamble set by the base station comprises: the base station notifying the relay node of the preamble set by using dedicated signaling.

Preferably, the preamble set is based on a non-contention preamble set.

Preferably, the step of the base station allocating a preamble set dedicated to the relay node is performed based on the following characteristics: the number of relay nodes associated with the base station, the number of user equipments served by the base station, The number of user equipment and wireless link status following the node service.

Preferably, the random access method further comprises: the base station identifying a random access request from the relay node, and transmitting a random access response to the relay node by using the R-PDCCH.

Preferably, the random access method further includes: the relay node receives the random access response, and sends an RRC connection reestablishment message to the base station.

Preferably, the random access method further includes: when the RRC connection reestablishment fails, the relay node sends an RRC connection release message to the user equipment that is served by the RRC connection.

According to another aspect of the present invention, a base station is provided, the base station includes: a random preamble allocation unit, configured to allocate a preamble set dedicated to the relay node, the relay node and the And a preamble set notification unit, configured to notify the relay node of a preamble set dedicated to the relay node, so as to be between the base station and the relay node When the link fails, the relay node randomly selects a preamble from the set of preambles to send a random access request to the base station.

With the present invention, the base station can quickly restore the connection state to the connected state when the RLF occurs by allocating and notifying the relay node to the dedicated preamble set, while ensuring the least impact on the normal user equipment. DRAWINGS

The detailed description of the non-limiting embodiments of the present invention, in accordance with the accompanying drawings, Other objects, features and advantages will become more apparent, in the drawings:

1 shows a schematic diagram of basic nodes and interfaces in a system in which a Type I relay is deployed; FIG. 2 shows communication between a conventional relay node and an RN-UE using normal subframes, and existing An example of communication between a base station and a relay node using a backhaul subframe;

FIG. 3 is a flow chart showing a random access method for a wireless relay communication system according to an embodiment of the present invention; FIG.

4 is a schematic diagram showing preamble allocation for random access according to an embodiment of the present invention; FIG. 5 shows an example of a random access procedure according to an embodiment of the present invention;

6 shows a modified example of a random access procedure according to an embodiment of the present invention; and FIG. 7 shows a schematic structural diagram of a system for implementing a random access method according to an embodiment of the present invention. Detailed implementation method ^

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the following description, some specific embodiments are for illustrative purposes only and are not to be construed as limiting the invention in any way. It is to be noted that the illustrations are only illustrative of the differences from the prior art, and the conventional structures or structures are omitted so as not to obscure the understanding of the present invention.

In conventional specifications, a base station typically allocates two sets of random access preambles, i.e., a contention based preamble set and a non-contention based preamble set. The former is sent to the user equipment through broadcast signaling for contention-based random access of the user equipment. The latter is allocated by dedicated signaling for user equipment for non-contention based random access, such as handover, downlink data arrival and location, and the like.

The present invention proposes to allocate a non-contention preamble subset from a conventional non-contention based preamble set to a relay node. In this case, there are two non-competitive preamble subsets for the relay node and the macro-UE. The base station further notifies the relay node of the non-contention pre-sync subset assigned to the relay node by broadcast signaling or dedicated signaling. When an RLF occurs on a link between a relay node and a base station, the relay node may perform a random access procedure using a dedicated preamble to enable the base station to recognize an access request from the relay node and utilize the DL Un sub- On the frame

The R-PDCCH sends back a random access response. Thus, the relay node knows where to receive the access response and quickly sends an RRC Connection Reestablishment message.

FIG. 3 shows a flow chart of a random access method for a wireless relay communication system in accordance with an embodiment of the present invention. The wireless relay communication system includes a base station, a user equipment, and a relay node. As shown in FIG. 3, in step S301, the base station allocates a preamble set dedicated to the relay node. Here, the preamble set is based on a non-contention preamble set, and the above allocation may be performed based on the following characteristics: number of relay nodes associated with the base station, number of user equipments served by the base station, relay node service Number of user devices and Un wireless link status, etc. Then, in step S303, the base station notifies the relay node of the preamble set. Here, the base station may perform the above notification by broadcast signaling such as system broadcast information, or may perform directional notification by dedicated signaling. When a link between the base station and the relay node fails, the relay node randomly selects a preamble from the set of preambles for performing random access to the base station (step S305), and then The base station transmits a random access request (step S307). Then, the base station identifies a random access request from the relay node (step S309), and transmits a random access response to the relay node using the R-PDCCH (step S311). Next, in step S313, the relay node receives the random access response and sends an RRC connection reestablishment message to the base station, which is the same as the existing operation. As mentioned above, in the LTE-A in which the relay is deployed, the base station uses the R-PDCCH to allocate resources to the relay node in the backhaul DL subframe, and thus the relay node knows how to receive the response from the base station. Here, the random access procedure between the RRC connection reestablishment messages sent by the base station is completely the same as the random access procedure in the prior art, and thus will not be described again.

In addition, when the relay node fails to perform the RRC connection re-establishment (such as timeout), the relay node actively sends an RRC connection release message (not shown) to the user equipment in the RRC connected state that it serves, thereby avoiding invalid signaling. With data transfer.

It should be noted that although only one relay node is illustrated above, those skilled in the art will appreciate that the above random access method is equally applicable to a wireless relay communication system in which a plurality of relay nodes are deployed.

The application of the random access method shown in FIG. 3 in the LTE-A system will be described in detail below. Of course, this approach also applies to broadband wireless access technologies such as WIMAX.

4 shows a schematic diagram of preamble allocation for random access in accordance with an embodiment of the present invention. As shown in FIG. 4, the base station first divides the entire preamble set into a preamble preamble set (a portion indicated by a left oblique line in FIG. 4) and a non-competitive preamble according to the division in the conventional specification as described above. The set (the portion indicated by the horizontal line in Fig. 4), the two sets being orthogonal to each other (i.e., not associated with each other). Then, the base station further divides the non-contention preamble set into a non-contention preamble subset for the macro-UE and a non-contention preamble subset for the relay node (ie, the relay node-specific preamble) Collection), also the two subsets are also orthogonal to each other. In this way, the impact on the macro-UE can be minimized. The base station can determine based on parameters and configurations of the system (eg, the number of relay nodes associated with the base station, the number of user equipments served by the base station, the number of user equipment served by the relay node, the quality of the radio link channel, etc.) The size of the preamble subset. For example, when the number of relay nodes is small, or only a fixed number of relay nodes are currently used, the size of the non-contention preamble subset for the relay node can be kept very small.

It should be noted that although the random access preamble allocation operation as shown in FIG. 4 is performed by the base station in this example, those skilled in the art will appreciate that this operation may also be performed by a superior node having similar functions to the base station. To be done.

FIG. 5 shows an example of a random access procedure according to an embodiment of the present invention, and FIG. 6 shows a modified example of a random access procedure according to an embodiment of the present invention. Both of these cases are performed on the basis of the random access preamble allocation as shown in FIG. 4, that is, the random access procedures shown in FIG. 5 and FIG. 6 are based on the random access in FIG. Preamble allocation.

As shown in FIG. 5, the base station transmits a pre-sync code subset for the relay node as shown in FIG. 4 through the system broadcast information (step S501). Since the preamble subset for the relay node is shared by the plurality of relay nodes at this time, this method can reduce the size of the preamble subset for the relay node, so that the macro-UE can be allocated more. Large non-competitive preamble subsets. When an RLF occurs on the Un link between the base station and the relay node, the relay node randomly selects a preamble from the preamble subset for the relay node to transmit a random access request to the base station (step S503). Then, the base station identifies the random access request from the relay node, and transmits a random access response to the relay node using the R-PDCCH (step S505). The relay node receives the random access response and transmits an RRC Connection Reestablishment message to the base station (step S507). The next process is exactly the same as the existing random access procedure, so it will not be described here.

A schematic configuration of elements of system broadcast information dedicated to the relay node is given below.

SystemlnformationBlockType-RN ::= SEQUENCE {

RACH- RACH-ConfigCommon-RN

RACH-ConfigCommon-RN ::= SEQUENCE {

numberOfRA-Preambles-RN ENUMERATED {

N4, n8, nl2, nl6, n20, n24, n28, N32, n36, n40, n44, n48, n52, n56

N60, n64},

As indicated above, numberOfRA -Preambles-RN represents the size of the preamble subset for the relay node. After receiving the system broadcast information as shown, the relay node can infer that the preamble uses numberO TiA-Preambles to numberOfRA-Preambles-RN-1, where numberOfRA-Preambles is based on the size of the non-contention preamble.

Of course, in this example, if two relay nodes select the same preamble from the set of preambles for the relay node, then competition may still occur. However, considering that the RLF on the Un link does not appear so frequently, this problem is not serious.

As an improvement to the random access procedure shown in Fig. 5, the relay node is notified of the preamble subset for it mainly by dedicated signaling in Fig. 6. As shown in FIG. 6, the base station sends a preamble subset for the relay node as shown in FIG. 4 through dedicated signaling (step S601), that is, the RRC connection reconfiguration message is directed to each relay node. A subset of preambles for the relay node shown in 4. In this case, if each relay node is assigned a different preamble within the subset of preambles for the relay node, it may be avoided between the relay nodes that may occur in the example shown in FIG. competition. Of course, different relay nodes can also be assigned the same preamble. In step S603, the relay node sends an R C connection reconfiguration complete message to the base station to indicate that the preamble is received. Then, when an RLF occurs on the Un link between the base station and the relay node, the relay node transmits a random access request to the base station using the received preamble (step S605). The base station identifies the random access request from the relay node and transmits a random access response to the relay node using the R-PDCCH (step S607). The relay node receives the random access response and transmits an RRC Connection Reestablishment message to the base station (step S609). The next process is exactly the same as the existing random access process, so it will not be described here.

A schematic configuration of an information element dedicated to dedicated signaling of a relay node is also given.

RRCConnectionReconfiguration ::= SEQUENCE {

RACH-ConfigDedicated }

RACH-ConfigDedicated: — SEQUENCE {

ra-Preamblelndex INTEGER (0..63

}

As indicated above, the base station assigns a dedicated preamble to the relay node in the form - e _a We/mfec, where - /^^6/e/«ife represents the sequence number of the dedicated preamble assigned to the relay node.

Figure 7 shows a block diagram of a system implementing a random access method in accordance with an embodiment of the present invention, the system comprising a base station 10 and a relay node 20 associated with the base station.

As shown in FIG. 7, the base station 10 includes: a random preamble allocation unit 101, configured to allocate a preamble set dedicated to a relay node, the preamble set is based on a non-contention preamble set, and The allocation is performed based on the following characteristics: the number of relay nodes associated with the base station, the number of user equipments served by the base station, the number of user equipments served by the relay node, and the state of the radio link; and the preamble set The notifying unit 103 is configured to notify the relay node of the preamble 专门A dedicated to the relay node.

Stay Π

Preferably, the random preamble allocation unit 101 is configured to: divide the preamble set for random access into a preamble set and a non-contention preamble set, where the preamble set of the preamble is for the base station itself a user equipment of the service; dividing the non-contention preamble set into a non-contention preamble subset for the user equipment served by the base station itself and a non-contention preamble subset for the relay node; A subset of the non-contention preamble of the relay node is allocated to the relay node.

The preamble set notification unit 103 notifies the relay node by broadcast signaling such as system broadcast information or by dedicated signaling.

Optionally, the base station 10 further includes: a random access request receiving unit 105, configured to receive a random access request from the relay node; and a random access request identifying unit 107, configured to identify a random access request from the relay node. And a random access response transmitting unit 109, which transmits a random access response to the relay node by using the R-PDCCH.

In this embodiment, the relay node 20 is the same as the existing type I relay node, and the main difference is: when the relay node 20 performs the RRC connection reestablishment failure, such as timeout, the relay node 20 actively The user equipment in the RRC connected state sends an RRC connection release message, thereby avoiding invalid signaling and data transmission.

Although a system in which one relay node is deployed is illustrated as an example in FIG. 7, those skilled in the art should understand that the random access method according to an embodiment of the present invention is also applicable to deploying more than one relay. The system of the node.

In summary, the present invention provides a random preamble allocation mechanism and a notification mechanism for a random preamble conforming to the current specification, which is used to allocate and notify a dedicated preamble to a relay node, so that the relay node is in the RLF. Quickly return to the connected state when it appears.

Compared with the existing scheme, the proposed mechanism has the following advantages: When RLF occurs, it provides a very fast recovery mechanism; has the least impact on RN-UE and macro-UE; and has good scalability and can be easily Expand to multi-hop scenarios (ie multiple relay nodes).

Although the above description relates to a plurality of units, the present invention can also be implemented by dividing one unit into a plurality of units or combining a plurality of units into one unit as long as it can still perform the corresponding functions. In addition, although the present invention has been specifically described by taking the type I relay as an example, those skilled in the art should understand that the present invention is also applicable to other systems of LTE-A in which a relay node similar to the type I relay is deployed.

Those skilled in the art will readily recognize that the different steps of the above methods can be implemented by a programmed computer. Herein, some embodiments also include a machine readable or computer readable program storage device (eg, a digital data storage medium) and encoding machine executable or computer executable program instructions, wherein the instructions perform some of the above methods or All steps. For example, the program storage device can be a digital memory, a magnetic storage medium (such as a disk and tape), a hardware or an optically readable digital data storage medium. The implementation also includes a programming computer that performs the steps of the above method.

The description and drawings merely illustrate the principles of the invention. It will be appreciated that those skilled in the art are able to devise various structures, and the various structures are not described or illustrated herein, but are intended to be within the spirit and scope of the invention. In addition, all of the examples mentioned herein are explicitly used primarily for teaching purposes to assist the reader in understanding the principles of the present invention and the concepts promoted by the inventors, and should be construed as not to the specific examples. And conditional restrictions. In addition, all statements herein reciting principles, aspects, and embodiments of the invention, as well as the specific examples thereof,

The above description is only used to implement the embodiments of the present invention, and those skilled in the art should understand that any modifications or partial substitutions without departing from the scope of the present invention should fall within the scope defined by the claims of the present invention. The scope of the invention should be determined by the scope of the claims.

Claims

Rights request

A random access method for a wireless relay communication system, the wireless relay communication system comprising a base station and a relay node associated with the base station, the method comprising the steps of:

The base station allocates a preamble set dedicated to the relay node;

The base station notifying the relay node of the preamble set;

When the link between the base station and the relay node fails, the relay node randomly selects a preamble from the set of preambles to send a random access request to the base station.

2. The random access method according to claim 1, wherein the base station allocates a preamble set dedicated to the relay node, comprising:

The base station divides the preamble set for random access into a preamble set and a non-contention preamble set, where the preamble set is a user equipment served by the base station itself;

Dividing the non-contention preamble set into a non-contention preamble subset for the user equipment served by the base station itself and a non-contention preamble subset for the relay node;

A subset of non-contention preambles for the relay node is assigned to the relay node.

The random access method according to claim 1, wherein the notifying the base station of the preamble set to the relay node comprises: the base station notifying the relay node by using broadcast signaling Preamble collection.

The random access method according to claim 1, wherein the base station notifying the relay node of the preamble set comprises: the base station notifying the relay node by using dedicated signaling The same weight collection before.

The random access method according to any one of claims 1 to 3, wherein the preamble set is based on a non-contention preamble set.

The random access method according to any one of claims 1 to 4, wherein the step of the base station assigning a preamble set dedicated to the relay node is performed based on the following characteristics:

The number of relay nodes associated with the base station, the number of user equipments served by the base station, the number of user equipments served by the relay node, and the radio link status.

The random access method according to any one of claims 1 to 4, further comprising: the base station identifying a random access request from the relay node, and transmitting a random access response to the relay node by using the R-PDCCH.

The random access method according to any one of claims 1 to 4, further comprising: The relay node receives the random access response and transmits an RRC connection reestablishment message to the base station.

9. The random access method of claim 8, further comprising:

When the RRC connection reestablishment fails, the relay node sends an RRC Connection Release message to the user equipment it is serving and is in the RRC connection.

10. A base station, the base station comprising:

a random preamble allocation unit, configured to allocate a preamble set specifically for the relay node, the relay node being associated with the base station;

a preamble set notification unit, configured to notify the relay node of a preamble set dedicated to the relay node, so that when a link between the base station and the relay node fails, The relay node randomly selects a preamble from the set of preambles to send a random access request to the base station.

11. The base station according to claim 10, wherein: assigning a pre-identical weight set specifically for the relay node comprises:

The preamble set for random access is divided into a preamble preamble set and a non-contention preamble set, where the competing preamble set is for a user equipment served by the base station itself;

12. The base station according to claim 10, wherein notifying the relay node of a preamble set specifically for the relay node comprises:

The preamble set notification unit notifies the relay node of the preamble set by broadcast signaling.

13. The base station according to claim 10, wherein notifying the relay node of a preamble set specifically for the relay node comprises:

The preamble set notification unit notifies the relay node of the preamble set by dedicated signaling.

The base station according to any one of claims 10 and 12 to 13, wherein the preamble set is based on a non-contention preamble set.

The random access method according to any one of claims 10 to 13, wherein the predetermined characteristic includes a number of relay nodes associated with a base station, a number of user equipments served by the base station, and a relay section. The number of user equipments and wireless link status of the point service.

The base station according to any one of claims 10 to 13, further comprising:

a random access request receiving unit, configured to receive a random access request from the relay node; a random access request identifying unit, configured to identify a random access request from the relay node; and a random access response sending unit, using the R The PDCCH transmits a random access response to the relay node that transmitted the random access request.

The base station according to claim 10, wherein the relay node is configured to: send an RRC connection release message to a user equipment that is served by the relay node and is in an RRC connection when performing an RRC connection reestablishment failure .