KR100884699B1 - Method and apparatus for transparent relaying - Google Patents

Abstract

The present invention provides a method capable of transparent relaying of data to improve the performance of a cellular system. In particular, the relay on the uplink is performed by a fixed entity called a transparent relay (TR). The base station assigns one or more TRs for relaying data transmissions in association with a particular CID (eg, a particular subscriber station) on the uplink.

Transparent relays, relay-to-base resources, assigned messages, uplinks, data transmission

Description

Method and apparatus for transparent relay

The present invention relates generally to information relay, and more particularly to a method and apparatus for relaying information in a communication system.

Wireless communication systems are known. In these various systems, the telecommunication units (at least some of which are mobile) communicate with other units and / or with other units via system infrastructure such as fixed-location transmitters and receivers. In general, a wireless communication system is characterized by a corresponding communication range (typically characterized by either or both of the transmission range and the reception range) that the wireless communication capability of the system infrastructure can not be effectively extended and exceeded. do.

Repeaters are also known. Such devices are typically intended to extend the communication range of a given communication system (by extending the transmission and / or reception range). This mechanism allows a relatively low power telecommunication unit to communicate with a relatively far system receiver, for example, even though the telecommunication unit is out of range of another far system receiver. These repeaters sometimes operate in autonomous automatic mode and repeat any transmission they successfully receive.

Unfortunately, despite various improvements to both systems and telecommunications units, there are times and circumstances in which transmission of communication units within the communication range of a given communication system is not reliably received at some desired quality of service level. There are various causes for this result, including but not limited to shadow fading and other propagation problems. Performance requirements may cause conflicts. For example, as the demand for data rates continues to increase (which frequently results in an increase in the corresponding bandwidth), there may be other ranges within the range to successfully achieve the required level of service without a significant increase in transmission power. The ability of a telecommunications unit is generally degraded. Accordingly, what is needed is a method and apparatus for relaying information in a communication system that solves the above problems.

The present invention provides a method for enabling transparent relay of data to improve the performance of a cellular system. In one embodiment, one or more relays are used in the sector of the cell. Such relays are referred to as transparent relays (TRs), because in the present invention they operate in a system in a nearly "transparent" manner in terms of subscriber stations in the cell. As an example, three TRs may be used in a sector in a location selected to provide significant link budget improvement for subscriber stations SS away from the base station BS as shown in FIG. 1.

1 is a block diagram of a base station and subscriber stations.

2 illustrates a possible communication path between a base station, subscriber stations, and relays.

3 is a call-flow diagram illustrating the assignment of one or more relays.

4 illustrates resource allocation for relays.

In one embodiment of the present invention, multiple TRs (eg, more than one, possibly a subset of the total number of TRs in a sector) may be selected and instructed to perform a relay for a particular SS. In this case, the selected TRs monitor (receive and demodulate / decode) uplink data transmissions made by the SS. The selected TRs re-encode and retransmit data on channel resources different from those used by the SS for the original transmission (e.g., different time slots, different subchannels, different extension codes, etc.). In order to provide macro-diversity gain, transmissions from each selected TR can be made on the same channel resource (in this case the TRs are synchronized to BS timing and frequency so that transmissions from the selected TRs are It is desirable to arrive at the BS almost simultaneously).

The method also provides for removing the transmission from any of the selected TRs whenever the selected TRs fail to correctly receive / decode data transmissions from the SS. The method includes maintaining channel resources allocated to TRs for lack of transmission. In this way, all the TRs in a sector can be made up of a single group and assigned a group ID, such as a multicast group ID, and SS monitoring and TR resource allocations are compared to sending separate commands or allocations to each TR. Effective groups can be made. When all the TRs in a sector have been activated for a particular SS transmission, some of the TRs will correctly decode the SS transmission (e.g., close to the SS) and others will not (e.g., away from the SS). It is foreseen. Even in this case, effective macro-diversity can still be provided, since the TRs that correctly decode the SS transmission will be transmitted together, while the TRs that did not successfully decode the SS transmission are in the TR group for transmission of the SS data. This is because it will be silent on the allocated channel resource. A significant advantage of this embodiment is that the SS does not have to "hand off" from one TR to the other and moves across the cell: instead, the present invention provides an efficient way of automatically using the best TRs in the sector. To provide.

In a further embodiment, one or more TRs are instructed to monitor data transmissions of multiple SSs. For example, the selected TRs may be a list of given connection IDs (CIDs), which means that the selected TRs are directed to monitor uplink data transmission on all uplink channel resources assigned to these CIDs. . The selected TRs are also given uplink channel resource allocation to be used by the TRs to transmit data received from the SSs (eg, retransmit data from the SSs). By providing an efficient allocation scheme, block resource allocation can be provided to the TRs, and the TRs are all TRs to ensure that transmissions from multiple TRs provide macro-diversity combining at the BS rather than interfere with each other. Use a predetermined data ordering convention, which ensures that the transmissions from the two transmit exactly the same data portion (eg, data segment from other SSs) on the corresponding resource. A further aspect of the present invention is that the data rate may differ from other SSs and that the data rate used by the TRs may differ from the SSs. In this case, the BS can calculate the total required channel resource allocation required for the TRs by considering the demodulation and coding rate to be used by the SSs to be relayed and the demodulation and coding rate to be used by the TRs (see later example in the specification). have. In this case, each of the selected TRs preferably uses the same demodulation and coding rate to maintain macro-diversity gain.

In a further embodiment, the method is provided with selecting and adjusting the demodulation and coding rate used for transmission.

In a further embodiment, the BS will store the received signal from the SS received on one channel resource set and combine the stored signal with the received signal from the TR on another channel resource set. This provides an additional form of macro-diversity, since signals from SS and TR are combined within the BS according to the signal processing step.

The above embodiments can be combined to provide the greatest overall functionality. Various aspects of these embodiments as well as aspects of additional embodiments are described below.

The above-described embodiments provided below are described within the background of IEEE 802.16e where standardization efforts are underway. The detailed solution is presented for the OFDMA mode of 802.16e, but the present invention is applicable to other systems. Table 1 lists the acronyms used herein.

Table 1. Acronym List

UL_MAP is a message specifying resource allocation on the uplink. This message may be extended to carry other information relative to resource allocation, such as, for example, information related to suitable antenna processing or uplink relay.

The REG_REQ message is a 'registration request'. This is a message transmitted by the SS after performing initial ranging. This message is a pre-requisite before any data transmission and is recognized by the BS by sending a REG-RSP, or 'Registration Response' message.

The above relay technique can be applied to the uplink for IEEE 802.16e OFDMA. This is a serious link budget problem on the uplink that significantly reduces the uplink data rate and system throughput, even for a reasonable cell radius (2 km). The solution presented here allows for the seamless introduction of a simple one-hop relay on the uplink that addresses this issue. The downlink transmission is not relayed at all, which greatly reduces the complexity of the relay.

The solution presented here has the following advantages:

Transparent relays (T-relays) are simplified units that only need to perform a few layer-one operations and a minimum set of two layer-two tasks. In addition, the relay does not need to be connected to the network.

• The relay process is a transparent process that does not require a change in the SS and requires minimal signal processing changes to adjust the process available relay.

One or more T-relays may be placed in each sector. A particular T-relay does not need to recognize other T-relays.

BS always remains within transmission control, resulting in increased transmission reliability.

The architecture still allows hybrid-ARQ (HARQ) to be performed on the uplink.

The imbalance in PA power between the SS and BS can be customized to provide the necessary cooperation for the uplink while not included in the downlink. As a result, cost efficiency can be achieved by creating a load relationship between the relay and the BS, allowing a low cost of the relay while ensuring a robust and reliable transmission supervised by central authority. Cost effectiveness can be realized by reducing relay complexity by focusing on only one layer operation and a minimum of two layer task sets. In addition, control messages need not be relayed-only bearer data. Transparent relay (T-relay) configuration also simplifies system deployment. This T-relay can be placed in an existing cell addressing an uplink range issue without having to have a re-address cell plan to be required when adding a microcell to achieve the same purpose.

2 shows a possible communication path between BS, SS, and T-relay. 2A illustrates a typical communication path in a cellular system that is not T-relay capable. The BS coordinates resources within the cell by distributing control information and mediating access requests. In addition, the BS sends the transport data directly to the SS and receives the transport data directly from the SS. 2B shows that the communication path with the T-relay is enabled. In this case, the BS still coordinates resources within the cell by distributing control information and arbitrating access requests. In addition, the BS continues to send the transport data directly to the SS. However, uplink carrier data from the SS follows a triangular pass that is first received and detected by the T-relay and then re-encoded and transmitted by the T-relay to the BS. 2C and 2D show two variations in the T-relay configuration. 2C shows multiple active s-relays that simultaneously repeat SS carry data to the BS. 2D illustrates simultaneous coexistence of relayed and unrelayed uplink communications. The key and highly beneficial aspect of T-relay configuration is that the SS does not fully know the presence of relays in the system. Other controls related to uplink functionality, such as ranking and bandwidth requests, are still handled by the direct SS to BS pass to simplify the relaying scheme.

In the broadest sense, the above procedure is the minimum required to increase the uplink carry data rate. If no T-relay can be employed, the data rate cannot take into account the relay. If a T-relay can be employed, then the data rate can take into account the T-relay so that the data rate is higher. Since each data transmission depends on the proper channel state, the channel state may even be employed in T-relay and may not be employed if the direct link to the BS is of sufficient quality. Typically, the decision to employ a T-relay is made by each transmission, but in the long run it may be made with an average channel quality criterion (e.g., adopting shadows but not considering fast fading). The T-relay (more generally one or more T-relays) is a lower relay because the resource allocation for the SS to T-relay link is provided by the BS.

Action to be performed

As mentioned above, the relay process is completely transparent to the SS and therefore does not require additional operation to be performed. However, the link between the T-relay and the BS is necessary for deployment and maintenance. The implementation of the various tasks required to perform is as follows.

Network entry and initialization

The network entry and initialization process is identical to the conventional SS except for one point (registration process), the unit must be identified as a T-relay.

Relay assignment for connection (listening)

The relay assignment process is done on a frame-by-frame basis. Each T-relay (or group of T-relays) is assigned a transmission of the CID necessary to monitor in the uplink portion of the current frame. Thus, by UL_MAP decoding, each T-relay knows all the resources needed to listen and to attempt detection. The T-relay may monitor one or more connections (eg one or more SSs) and may be part of one or more multicast groups. For example, a T-Relay can be assigned to two different connections and addressed by a different CID (e.g., a specific CID if the T-Relay is active, as well as a multicast CID if it is part of a relay group). Can be.

Alternatively, instead of being performed on a per frame basis, the assignment may remain valid until future assignment or non-allocation is received. Or it may be valid for a predetermined total amount of time (eg 10 frames).

Communication of relay assignment (transmission)

Resource allocation for transmission from T-Relay to BS is also done on a frame by frame basis. Each T-relay (or T-relay group) is assigned via an existing UL-MAP_IE message. Each T-relay only relays to a connection that has successfully decoded data.

Modulation / coding Scheme  Selection

Since the T-Relay only relays back to the connection with successfully decoded data, the BS can initially initiate a high MCS assignment for the SS. T-relay monitors the link. If the data cannot be successfully decoded, nothing is sent to the BS. The BS that receives none knows that the selected MCS is too high and assigns the lower MCS to the SS until it receives something from one or more T-relays. This process enables initial MCS selection. After this initial MCS selection, the HARQ process can fine tune the MCS selection.

Alternatively, blind AMC selection may be made by the BS based on some open-loop approximation. The simplest method of MCS selection is to use an aggressive default value with the hope that the SS is close to either relay or BS. The system may rely on hybrid ARQ and retransmission to mitigate all insufficiently selected AMC levels.

Alternatively, the relay may eavesdrop on the ranking channel and then report the information to the base. The relay may use the ranking channel to report this information. Alternatively, dedicated resources (referred to as 1 RE) may be reserved by the BS for this process. To prevent conflicts between all relays, each relay is assigned a Walsh code and develops a report with the assigned code.

When there is only one relay, the relay can piggyback MCS information with the relayed data. When multiple relays and RF are combined, this solution does not apply. The relay may send an MCS increase request on the ranking channel. Alternatively, the above-described CDMA embodiment is also applicable. In addition, some types of analog feedback (eg, by changing the transmit power) may be used to notify the base that a high MCS may be supported.

The relay can also send a beacon at a given time, the SS can measure the received power, and make its own MCS request.

hybrid ARQ  process

This structure can be harmonized with HARQ on the uplink. The T-Relay (or T-Relay Group) buffers the data received from the SS. When the T-Relay successfully decodes the packet, it transmits data to the BS at the resource explicitly allocated on the uplink. If the decoding is not successful, the T-Relay (or T-Relay Group) sends nothing. If none is received, the BS knows that the transmission is unsuccessful and sends control for the next HARQ transmission.

Text Changes to Be Configured as IEEE 802.16

[In section 6.1, After third paragraph, add the following paragraph]

In addition, to improve the uplink data rate, transparent relays on the uplink are enabled. Transparent relays (TRs) can be used to provide higher data rates and / or capabilities on the uplink, or on an "as-beneficial" basis when the SS to BS link is of unacceptable quality. A BS link is placed in the cell to intercept the SS to TR link and the TR to BS link. This process is completely transparent to the SS: it does not know to be relayed.

[In Section 6.3.2.3.7 Registration request (REG-REQ) message, Just before 6.3.2.3.8 insert the following bolded text]

The REG-REQ may include the following TLVs:

(...)

Transparent Relay Capability (11.7.19)

[In Section 6.3.2.3.8 Registration response (REG-RSP) message, Just before 6.3.2.3.9 insert the following bolded text]

The REG-RSP may include the following TLVs:

(...)

Transparent Relay Capability (11.7.19)

[Add a new section 6.3.2.3.43.7.8]

Section 6.3.2.3.43.7.8 Compact_UL_MAP Transparent Relay Monitor

The transparent relay monitor information element provides a transmission list of SS CIDs to be monitored (detected) and relayed in the next frame during the UL portion of the current frame.

[Add a new section 6.3.2.3.57]

Section 6.3.2.3.57 Transparent Relay CID Assignment (TR-CID) Messages

The base will assign one or more second relay CIDs to the transparent relay to send relay monitor commands and allocate resources for retransmission of the monitored SS data. This relay CID can be assigned to only one transparent relay or multiple transparent relays. Upon receipt, the SS will delete all previously assigned relay CIDs and apply their new assignment.

The parameters are as follows;

CID (usually MAC header)

SS's primary maintenance CID.

Transaction ID

Unique identifier for this transaction assigned by the sender

All other parameters are coded according to the TLV tuple.

Relay CID (see 11.16)

Section 6.3.2.3.58 Transparent Relay CID Assignment ACK (TR-ACK) Messages

This message is transmitted according to the TR-CID assignment message.

The parameters are as follows:

CID (usually MAC header)

SS's primary maintenance CID.

Transaction ID

Unique identifier for this transaction assigned by the sender

Verification code

Zero indicates that the request was successful. Non-zero indicates failure.

[Add a new section 11.7.19]

Section 11.7.19 Transparent Relay Capabilities

This field indicates whether the unit is a regular SS or a transparent relay.

[Add a new section 6.3.18]

Section 6.3.18 Transparent Relay Operation

To improve the data rate on the uplink, relaying some uplink transmissions have advantages. The relay on the uplink is performed by a fixed entity called a transparent relay (TR). The BS allocates one or more TRs to relay data transmissions associated with a particular CID (eg, a particular SS) on the uplink. This process is shown in FIG. For UL_MAP, uplink resource allocation is sent to the transmitting SS and UL_TR_MONITOR_IE is included to command a TR or TR group to monitor uplink transmissions associated with one or more SS CIDs. In the uplink, the SS transmits and the TR monitors the transmission assigned to the monitor. The monitored transmission is demodulated and decoded by the TR to be re-encoded and retransmitted (relayed) in the next frame. In the next frame, in the second UL_MAP message, each activation TR receives a resource allocation for relay transmission. This resource allocation is made either per TR CID or for a multicast group TR CID. When assignment is made per multicast group TR CID, this is a T-relay that is foreseen to simultaneously relay monitored transmissions that provide macro-diversity gain.

MAC PDUs are modulated and coded with a modulation coding scheme (MCS, UIUC based) specified in UL_MAP_IE addressed by TR and transmitted from TR in exactly the same relative order as they were received. For each SS relayed, the MAC PDUs of each SS are encoded separately as if the BS sent separate assignments. If the TR did not correctly decode the data from a particular user (CID), it does not relay the data and keeps part of this assignment empty.

An example of TR resource allocation is given in FIG. In the example described, the TR must relay three transmissions: MAC PDU S1, MAC PDU S2, MAC PDU S3, and their assignments appear in the same relative order as in the previous frame. The TR receives the resource allocation (for UL_MAP_IE) for relaying three transmissions with 64-QAM R = 1/2 and the total amount of subchannels needed to perform the relay operation. The first PDU to be relayed, MAC PDU S1 is modulated and encoded into a new MCS and mapped to the first resource. Since the TR could not correctly receive the MAC PDU S2, it does not transmit anything for S2, but leaves a portion of the allocated resources that should have relayed this PDU. The resources for the MAC PDU S3 relay are allocated after the resources are prepared for MAC PDU S2. This TR resource allocation process allows the BS to know where to look for relayed data for each MAC PDU, even through relays using SS and other MCS. Macro-diversity is also provided when multiple TRs are assigned to relay the same CID.

[Add a new section 8.4.5.4.15]

Section 8.4.5.4.15 UL_MAP Transparent Relay Monitor

 The transparent relay monitor information element provides a transmission list of SS CIDs to be monitored (detected) and relayed in the next frame during the UL portion of the current frame.

Table XYZ-OFDMA UL-MAP Transparent Relay Monitor IE Format

[Add a new section 11.17]

Section 11.16 Assigning Transparent Relay CIDs

The value of this field specifies the CID assigned by the BS to a specific transparent relay. This field will be provided in the TR-CID assignment message. The BS will use the assigned values for the UL_MAP Transparent Relay Monitor IE and the Compact_UL_MAP Transparent Relay Monitor IE to command the relay to monitor a particular uplink assignment. The BS will use the value assigned in the UL_MAP IE to allocate resources for retransmission of the monitored SS data.

While the invention has been shown and described with particular reference to specific embodiments, those skilled in the art will understand that various changes in form and detail may be made without departing from the spirit and scope of the invention. It is intended that such changes be within the scope of the following claims.

Claims (7)

A method for a relay device to relay information in a communication system, the method comprising: Receiving a message indicating subscriber stations to be monitored; Receiving an allocation message indicating a relay-to-base resource; Receiving transmissions from the subscriber stations; Demodulating and decoding the transmissions of the subscriber stations; Remodulating and re-encoding the transmissions of the subscriber stations; And Relaying the remodulated and re-encoded transmissions via the relay to base resource, wherein the transmissions are relayed in a predetermined order. The method of claim 1, Relaying the transmissions in the predetermined order comprises relaying the transmissions in the order in which the transmissions were received. The method of claim 1, Relaying the transmissions in the predetermined order includes ordering the transmissions in the same relative order as the transmissions relayed in a previous frame. The method of claim 1, Relaying the transmissions comprises relaying only correctly demodulated and decoded transmissions by not transmitting a transmission that has not been correctly decoded. The method of claim 1, Relaying the remodulated and re-encoded transmissions through the relay to base resource includes relaying the remodulated and re-encoded transmissions through a relay to base resource used substantially simultaneously by another relay device. Information relay method. The method of claim 1, Determining a modulation and coding rate to use when remodulating and re-encoding transmissions of the one or more subscriber stations. The method of claim 1, Sending a message indicating relay capability prior to relaying transmissions from the one or more subscriber stations.

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