Classifications

• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04B—TRANSMISSION
  • H04B7/00—Radio transmission systems, i.e. using radiation field
  • H04B7/14—Relay systems
  • H04B7/15—Active relay systems
  • H04B7/155—Ground-based stations
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04B—TRANSMISSION
  • H04B7/00—Radio transmission systems, i.e. using radiation field
  • H04B7/14—Relay systems
  • H04B7/15—Active relay systems
  • H04B7/155—Ground-based stations
  • H04B7/15521—Ground-based stations combining by calculations packets received from different stations before transmitting the combined packets as part of network coding
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04B—TRANSMISSION
  • H04B7/00—Radio transmission systems, i.e. using radiation field
  • H04B7/14—Relay systems
  • H04B7/15—Active relay systems
  • H04B7/155—Ground-based stations
  • H04B7/15528—Control of operation parameters of a relay station to exploit the physical medium
  • H04B7/15542—Selecting at relay station its transmit and receive resources
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04B—TRANSMISSION
  • H04B7/00—Radio transmission systems, i.e. using radiation field
  • H04B7/24—Radio transmission systems, i.e. using radiation field for communication between two or more posts
  • H04B7/26—Radio transmission systems, i.e. using radiation field for communication between two or more posts at least one of which is mobile
  • H04B7/2603—Arrangements for wireless physical layer control
  • H04B7/2606—Arrangements for base station coverage control, e.g. by using relays in tunnels
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
  • H04L27/00—Modulated-carrier systems
  • H04L27/32—Carrier systems characterised by combinations of two or more of the types covered by groups H04L27/02, H04L27/10, H04L27/18 or H04L27/26
  • H04L27/34—Amplitude- and phase-modulated carrier systems, e.g. quadrature-amplitude modulated carrier systems
  • H04L27/3494—Amplitude- and phase-modulated carrier systems, e.g. quadrature-amplitude modulated carrier systems using non - square modulating pulses, e.g. using raised cosine pulses; Partial response QAM, i.e. with partial response pulse shaping
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04W—WIRELESS COMMUNICATION NETWORKS
  • H04W72/00—Local resource management
  • H04W72/04—Wireless resource allocation
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04W—WIRELESS COMMUNICATION NETWORKS
  • H04W84/00—Network topologies
  • H04W84/02—Hierarchically pre-organised networks, e.g. paging networks, cellular networks, WLAN [Wireless Local Area Network] or WLL [Wireless Local Loop]
  • H04W84/04—Large scale networks; Deep hierarchical networks
  • H04W84/042—Public Land Mobile systems, e.g. cellular systems
  • H04W84/047—Public Land Mobile systems, e.g. cellular systems using dedicated repeater stations
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04W—WIRELESS COMMUNICATION NETWORKS
  • H04W16/00—Network planning, e.g. coverage or traffic planning tools; Network deployment, e.g. resource partitioning or cells structures
  • H04W16/24—Cell structures
  • H04W16/26—Cell enhancers or enhancement, e.g. for tunnels, building shadow

Definitions

• the present invention relates generally to relaying information and in particular, to a method and apparatus for relaying information within a communication system.
• Wireless communication systems are known in the art.
• remote communication units (at least some of which may be mobile) communicate with one another and/or with others via system infrastructure such as fixed-location transmitters and receivers.
• system infrastructure such as fixed-location transmitters and receivers.
• wireless communication systems are characterized by a corresponding communication range (typically characterized by either or both of a transmission range and a reception range) beyond which the wireless communications capability of the system infrastructure cannot usefully extend.
• Repeaters are also known in the art. Such devices typically serve to extend the communication range of a given communication system (by extending the transmission and/or reception range). Via this mechanism, for example, a relatively low power remote communication unit can effectively communicate with a relatively distant system receiver notwithstanding that the remote communication unit is otherwise out- of-range of the distant system receiver. Such repeaters often operate in an autonomous automatic mode and repeat whatever transmissions they successfully receive.
• FIG. 1 is a block diagram of a base station and subscriber stations.
• FIG. 2 depicts the possible communication pathways between base stations, subscriber stations, and relays.
• FIG. 3 is a call-flow diagram showing allocation of one or more relays.
• FIG. 4 illustrates resource allocation for relays.
• the present invention provides a method for enabling transparent relaying of data in order to improve the performance of a cellular system.
• one or more relays are deployed in a sector of a cell. These relays will be referred to as transparent relays (TRs) because the present invention enables them to operate in the system in a nearly "transparent" manner from the point of view of the subscriber stations in the cell.
• TRs transparent relays
• three TRs can be deployed in a sector in locations that are selected to provide significant link budget improvements to subscriber stations (SSs) located far from the base station (BS), as shown in FIG. 1.
• multiple TRs may be selected and instructed to perform relaying (or be activated) for a particular SS.
• the selected TRs monitor (receive and demodulate/decode) the uplink data transmissions made by the SS. Then the selected TRs re-encode and re-transmit the data on a different channel resource than was used by the SS for the original transmission (e.g., a different time slot, a different subchannel, a different spreading code, etc.).
• the transmissions from each of the selected TRs can be made on the same channel resource (in this case the TRs are preferably synchronized to the BS timing and frequency so that the transmissions from the selected TRs arrive at the BS approximately synchronously).
• a method is also provided to eliminate transmissions from any of the selected TRs whenever a selected TR fails to correctly receive/decode the data transmission from the SS.
• This method involves leaving the channel resource assigned to the TR for the transmission empty.
• all TRs in a sector can be made into a single group, assigned a group ID such as a multicast group ID, and then the SS monitoring and TR resource assignments can be made very efficiently to the group as compared to sending separate commands or assignments to each TR.
• all TRs in a sector are activated for a particular SS transmission, it is expected that some of the TRs will correctly decode the SS transmission (e.g., close to the SS) and others will not (e.g., far from the SS).
• a significant advantage of this embodiment is that there is no need for a SS to "handoff ' from one TR to another as is moves across the cell: instead, the present invention provides an effective method for automatically using the best TRs in the sector.
• one or more TRs are instructed to monitor the data transmissions of multiple SSs.
• the selected TRs can be given a list of connection IDs (CIDs), and this means that the selected TRs are being instructed to monitor the uplink data transmissions on all of the uplink channel resources that are allocated to those CIDs.
• the selected TRs are also given an uplink channel resource allocation that will be used by the TRs to transmit (e.g., retransmit the data from the SSs) the data received from the SSs.
• An efficient assignment method is provided whereby a block resource assignment can be provided to the TRs and the TRs use a predetermined data ordering rule to insure that transmissions from all TRs send the same data portions (e.g., data segments from different SSs) on exactly the same corresponding resources to insure that the transmissions from multiple TRs provide macro-diversity combining at the BS rather than interfering with each other.
• An additional aspect of the invention is that the data transmission rates can be different from different SSs, and the data transmission rate used by the TRs can be different from the SSs.
• the BS can calculate the total necessary channel resource allocation needed for the TRs by taking into account the modulation and coding rates being used by the SSs being relayed and the modulation and coding rate being used by the TRs (see example later in the document).
• each of the selected TRs preferably uses the same modulation and coding rate to preserve the macro-diversity benefit.
• a method for selecting and adjusting the modulation and coding rate used for the transmissions.
• the BS will store the received signal from an SS that was received on one set of channel resources and will combine the stored signal with a received signal from a TR on a different set of channel resources. This provides an additional form of macro-diversity since signals from the SS and the TR are being combined within the BS as a signal processing step.
• the ULJVlAP is the message that specifies the resource assignment on the uplink. This message can be extended to convey other information than the resource assignment, such as e.g., information relative to adaptive antenna processing or uplink relaying.
• REG-REQ message is the 'registration request' message. It is a message that the SS sends after performing the initial ranging. This message is a pre-requisite before any data transmission, and is acknowledged by the BS by sending a REG-RSP, or 'registration response' message.
• the above-relaying technique can be applied to the uplink for IEEE 802.16e OFDMA.
• There is a serious link budget problem on the uplink that drastically reduces the uplink data rates and the system throughput, even for reasonable cell radii (2 km).
• the solution presented here enables the seamless introduction of simple one-hop relaying on the uplink to deal with this issue. Downlink transmissions are not relayed at all, thereby drastically reducing the complexity of the relay.
• the transparent relay (T-relay) is a simplified unit that only needs to perform a few layer-one operations and a minimal set of layer-two tasks. Moreover, the relay does not need to wired to the network.
• the relaying process is a transparent process that requires no changes in the SS and very minimal signaling changes to accommodate the relay enabling process.
• T-relays can be deployed in each sector. A particular T-relay does not need to be aware of other T-relays.
• the BS always remains in control of the transmission, thereby resulting in increased transmission reliability.
• the architecture still permits hybrid- ARQ (HARQ) to be performed on the uplink.
• HARQ hybrid- ARQ
• T-relay transparent relay
• FIG. 2 depicts the possible communication pathways between BSs, SS, and T- relays.
• FIG. 2a shows the typical communication paths in a cellular system with the T-relay disabled.
• a BS coordinates the resources in the cell by distributing control information and arbitrating access requests.
• the BS transmits bearer data directly to the SS and receives bearer data directly from an SS.
• FIG. 2b shows the communication paths with the T-relay enabled. In this case, the BS still coordinates resources in the cell by distributing control information and arbitrating access requests. Additionally, the BS continues to transmit bearer data directly to the SS.
• the uplink bearer data from the SS follows a triangular path first being received and detected by the T-relay then re-encoded and transmitted to the BS by the T-relay.
• FIG. 2c and FIG. 2d show two variations on the T-relay configuration.
• FIG. 2c shows multiple active s-relays simultaneously repeating the SS bearer data to the BS.
• FIG. 2d shows the simultaneous co-existence of a relayed and non-relayed uplink communication.
• a key and highly beneficial aspect of the T-relay configuration is that the SS may be completely unaware of the existence of a relay within in the system. Other control-related uplink functions, such as ranging and bandwidth request, are still handled by the direct SS-to-BS path in order to simplify the relaying scheme.
• the above procedure is the minimum required to increase uplink bearer data transmissions rates.
• the data rate cannot take into account the relay.
• the data rate can take into account the T-relay and be such that the data rate is much higher.
• the determination of whether a T-relay is to be employed is made for each transmission, but may also be made on a longer term average channel quality basis (e.g., taking shadowing but not fast fading into account).
• the T-relay (more generally, one or more T-relays) is a subordinate relay because the resource allocation for the SS to T-relay link is provided by the BS.
• the relaying process is completely transparent to the SS, thereby requiring no additional operations to be performed.
• the link between the T-relay and the BS needs to be established and maintained. An implementation of the various tasks that need to be performed is detailed below.
• the network entry and initialization process is the same as for a conventional
• the unit must identify itself as a T-relay.
• the relay assignment process is done on a frame-by-frame basis.
• Each T-relay (or group of T-relays) is assigned the CIDs whose transmissions it needs to monitor in the uplink portion of the current frame. Therefore, by decoding the UL_MAP, each T- relay knows every resource it needs to listen to and attempt to detect.
• a T- relay may monitor one or more connections (e.g., one or more SSs) and may be part of one or more multicast groups.
• a T-relay may be assigned to monitor two different connections and may be addressed by different CIDs (e.g., a special CID if the T-relay being activated, or even a multicast CID if it is part of a group of relays being activated).
• the assignment could remain valid until a future assignment or a de-assignment is received. Or, the assignment could be valid for a pre-determined amount of time (e.g., 10 frames).
• the assignment of resources for the transmission from the T-relay(s) to the BS is also done on a frame-by-frame basis.
• Each T-relay (or group of T-relays) is assigned resources via the existing UL-MAP-IE message.
• Each T-relay only relays connections for which it has successfully decoded the data.
• the BS can initially start assigning a high MCS to the SS.
• the T-relay monitors the link. If it cannot successfully decode the data, it does not send anything to the BS.
• the BS not receiving anything, knows that the chosen MCS is too high, and then assigns a lower MCS to the SS until it receives something from one or more T- relays. The process would allow an initial MCS selection. After this initial MCS selection, the HARQ process can fine-tune the MCS selection.
• a blind AMC selection could be made by the BS based on some open-loop approximation.
• the simplest method of MCS selection would be to use an aggressive default value with the hope that the SS is close to either one of several relays or the BS.
• the system may rely on Hybrid ARQ and retransmission to mitigate all poorly chosen AMC levels.
• the relay may eavesdrop on the ranging channel, then report information to the base.
• the relay could use the ranging channel to report this information.
• dedicated resources (Say 1 RE) could be reserved by the BS for this process.
• each relay is assigned a Walsh code and spreads the report with the assigned code.
• the relay can piggyback the MCS information with the relayed data.
• the relays could send an MCS increase request on the ranging channel.
• the CDMA embodiment mentioned above is applicable as well.
• it might be possible to use some type of analog feedback e.g., by modifying the transmit power to notify the base that a higher MCS could be supported.
• the relays can also transmit beacons at given times, the SS can measure received power, and makes its own MCS request.
• the T-relay (or group of T-relays) buffer the data received from the SS.
• a T-relay successfully decodes the packet, it sends the data to the BS on the resources explicitly assigned on the uplink. If the decoding is not successful, the T-relay (or group of T-relays) does not transmit anything. Not receiving anything, the BS knows that the transmission was not successful, and sends the control for the next HARQ transmission.
• Transparent relays are deployed in a cell in order to break the SS to BS link into a SS to TR link and a TR to BS link on an "as-beneficial" basis in order to provide higher data rates and/or capacity on the uplink, or when the SS to BS link is of unacceptable quality. This process is completely transparent for the SS: it is not aware that it is being relayed.
• the REG-REQ may contain the following TLVs:
• TLVs :
• Fixed Transparent Relay Capabilities (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 contain the following TLVs:
• the Transparent Relay Monitor Information Element provides the list of SS CIDs whose transmissions are to be monitored (detected) during the UL part of the current frame and relayed in the next frame.
• the base will assign one or more secondary relay CIDs to a transparent relay for the purpose of sending relay monitor command and allocating resource for a retransmission of the monitored SS(s) data.
• the relay CID may be assigned to only one transparent relay or multiple transparent relays.
• a SS Upon reception, a SS will delete all previously assigned relay CIDs and adopt those newly assigned.
• This message is sent in response to a TR-CID assignment message.
• This field indicates whether the unit is a re ular SS or a trans arent rela .
• the BS may allocate one or more TR to relay the data transmissions associated with a particular CID (e.g., a particular SS) on the uplink.
• a particular CID e.g., a particular SS
• the process is shown in FIG. 3.
• the uplink resource allocations are sent to the transmitting SSs and an UL TR MONITOR IE is included to instruct a TR or a group of TRs to monitor the uplink transmissions associated with one or more SS CIDs.
• the SSs transmit, and the TRs monitor the transmissions they were assigned to monitor.
• each active TR receives its resource assignment for the relaying transmission. This resource assignment is made per TR CID, or for a multicast group TR CID. When the assignment is made per a multicast group TR CID, these are T-relays are expected to simultaneously relay the monitored transmission providing a macro diversity gain.
• the MAC PDUs are transmitted from a TR in exactly the same relative order as they were received and are modulated and coded with the Modulation Coding Scheme (MCS, based on the UIUC) specified in the UL_MAP_IE addressed to the TR.
• MCS Modulation Coding Scheme
• the MAC PDUs of each respective SS are encoded separately as if the BS had sent separate allocations for each SS that is being relayed. If the TR did not correctly decode the data from a particular user (CID), it does not relay that data and leaves this portion of the assignment empty.
• TR resource allocation is given in FIG. 4.
• the TR has to relay three transmissions: MAC PDU Sl, MAC PDU S2, MAC PDU S3, whose assignments appeared in this same relative order in the previous frame.
• the first PDU to be relayed, MAC PDU Sl is modulated and encoded with the new MCS and mapped onto the first resources.
• the TR was not able to receive correctly MAC PDU S2, therefore it does not transmit anything for S2, but leaves blank the portion of the assignment resources where it should have relayed this PDU.
• Resources for relaying MAC PDU S3 are assigned after the resources that were provisioned for MAC PDU S2. This TR resource assignment process enables the BS to know where to find the relayed data for each MAC PDU even though the relay uses a different MCS than the SSs. Macro-diversity is also provided when multiple TRs are assigned to relay the same CIDs.
• the Transparent Relay Monitor Information Element provides the list of SS CIDs whose transmissions are to be monitored (detected) during the UL part of the current frame and relayed in the next frame.
• the value of this field specifies the CID assigned by the BS to a particular transparent relay. This field shall be present in the TR-CID assignment message.
• the BS shall use the assigned value in the ULJvIAP Transparent Relay Monitor IE and Compact UL MAP Transparent Relay Monitor IE to instruct the relay to monitor particular uplink allocations.
• the BS shall use the assigned value in ULJVIAP IE to allocate resources for the retransmission of monitored SS data.

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• Engineering & Computer Science (AREA)
• Computer Networks & Wireless Communication (AREA)
• Signal Processing (AREA)
• Mobile Radio Communication Systems (AREA)
• Radio Relay Systems (AREA)

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• 2005
  • 2005-08-18 JP JP2007528057A patent/JP4615566B2/ja not_active Expired - Lifetime
  • 2005-08-18 CN CNA2005800279201A patent/CN101006660A/zh active Pending
  • 2005-08-18 KR KR1020077004008A patent/KR100884699B1/ko not_active Expired - Fee Related
  • 2005-08-18 WO PCT/US2005/029624 patent/WO2006023771A2/en not_active Ceased
  • 2005-08-18 EP EP05785534A patent/EP1784931A4/de not_active Withdrawn

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