GB2490366A - Determining bottleneck information in a cellular network with a relay node - Google Patents
Determining bottleneck information in a cellular network with a relay node Download PDFInfo
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- GB2490366A GB2490366A GB1107282.4A GB201107282A GB2490366A GB 2490366 A GB2490366 A GB 2490366A GB 201107282 A GB201107282 A GB 201107282A GB 2490366 A GB2490366 A GB 2490366A
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W28/00—Network traffic management; Network resource management
- H04W28/02—Traffic management, e.g. flow control or congestion control
- H04W28/08—Load balancing or load distribution
- H04W28/086—Load balancing or load distribution among access entities
- H04W28/0861—Load balancing or load distribution among access entities between base stations
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W28/00—Network traffic management; Network resource management
- H04W28/02—Traffic management, e.g. flow control or congestion control
- H04W28/08—Load balancing or load distribution
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W24/00—Supervisory, monitoring or testing arrangements
- H04W24/10—Scheduling measurement reports ; Arrangements for measurement reports
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- 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
Abstract
A wireless telecommunication system has a base station 10 which communicates with a first relay node 14 via a backhaul link; the first relay node communicating with a mobile phone 16 via an access link. The total bottleneck from the perspective of the user is determined, taking into account the access link and the backhaul link, and this information is transmitted to further node(s) of the system. Ideally the bottleneck information is the physical resource blocks (PRB) usage on the access link or the PRB usage on the backhaul; whichever is greatest. The base station may be a D-eNB and the further nodes may be of Rel-8/9 eNB type. The relay node preferably acquires details of its backhaul link on demand and then determines the bottleneck information. Alternatively the further node could carry out the information determining step after receiving access link PRB data from the relay node. The information can be transmitted to further nodes using the X2 interface or the base stations proxy functionality.
Description
A wireless telecommunications system
Field of the invention
The present invention relates to L2 measurements taken on the relay backhaul of a relay node (especially a Type-i in-band relay) as applicable in the context of 3GPP Long Term Evolution (LTE)-Advanced. The arrangement is particularly useful in relation to cell load-balancing.
Background
The first release of the LIE was referred to as reiease-8, and provided a peak rate of * * 300 Mbps, a radio network delay of less than Sms, an increase in spectrum efficierey and new architecture to reduce cost and simplify operation.
LTE-A or LTE Advanced is currently being standardized by the 3GPP as an enhancement of LTE. LTE mobile communication systems are expected to be deployed from 2010 onwards as a natural evolution of GSM and UIMTS.
Being defined as 3.9G (3G+) technology, LTE does not meet the requirements for 4G, also called IMT Advanced, that has requirements such as peak data rates up to 1 Gbps.
In April 2008, 3GPP agreed to the plans for future work on Long Term Evolution (LTE). A first set of 3GPP requirements on LTE Advanced was approved in June 4 4 2 2008. The standard calls for a peak data rate of 1 Gbps and also targets faster switching between power states and improved performance at the cell edge.
The section below briefly discusses the network architecture of an LTE wireless communications network. Further details may be found at www.3gpp.org.
The base station -or E-UTRAN -for LTE consists of a single node, generally termed the eNodeB (eNB) that interfaces with a given mobile phone (typically termed user equipment, or user terminal). For convenience, the term HE -user equipment -will be used hereafter. The eNB hosts the physical layer (PHY), Medium Access Control layer (MAC), Radio Link Control (RLC) layer, and Packet Data Control Protocol:.
(PDCP) layer; that include the functionality of user-plane header-comprésion and encryption. It also offets. Radio.Resource Control (RFC) functionality corresponding to the control plane. The: evolved RAN performs many functions including radio: resource management, admission control, scheduling, enforcement of negotiated up-link QoS, cell information broadcast, ciphering/deciphering of user and control plane data, and compressionldecompression of down-link/up-link user plane packet headers.
The physical layer is often termed Layer 1. The Medium Access Control layer (MAC), Radio Link Control (RLC) layer, and Packet Data Control Protocol (PDCP) layer are collectively know as Layer 2. The Radio Resource Control is usually termed Later 3.
An LTE network provides two interfaces: Si interface to connect the eNodeBs to the core network gateway, and an X2 interface to perform inter-base station connections.
Relaying is considered as an economical way of extending the coverage of a wireless communication system by improving the cell-edge throughput and system capacity.
In LTE-A, relays are generally defined in two categories: type 1 and type 2. Type 1 relay nodes have their own PCI(Physical Cell ID) and are operable to transmit its common channel/signals. UEs receive scheduling information and HARQ feedback directly from the relay node. It is also possible for type 1 relay nodes to appear differently to eNDs to allow for further performance enhancement.
By contrast, type 2 relay nodes do not have a separate PCI, and are transparent to * UEs * * Each relay in the neto& will hávë a link to* controlling eND. This link is often * * termed the backhaül linl arid is abhiesed b/ ihe Un interface. Each eNB will be *. * linked to the core network, and this link is the eNB's backhaul link. The controlling eNB is sometimes referred to as a donor eND, or D-eNB. A D-eNIB controls network traffic within a domain. Said domain may include a plurality of further nodes. Domains located geographically next to one another may be termed neighbouring domains.
A UE connected directly to a D-eNB is considered to be directly linked, or to comprise a direct link. Such a IJE may be termed a Macro UE, or a M-UE.
A UE's connection to a relay node is termed an access link. A UE connected to a relay node is often termed R-UIE.
In order to support network radio link operations, radio resource management (RRM), network operations and maintenance (OAM), and self-organising networks (SON), generally measurements are taken by an eNB and are transferred over standardised interfaces. In this connection, a number of layer 2 (L2) measurement parameters are defined in TS 36.314. A copy of this documents is available at www.3gpp.org. The contents thereof are hereby incorporated by reference.
For a D-eNB, the L2. measurements have specific significance in the following areas: .. . . * i) Cell load-balancing; *. * ii) OAM perforniance monitoring; and iii) Configuration optimization In current network architectures, some of these L2 measurements are taken by an eNB per quality of service class identifier (QCI) and/or UE. Six different types of measurement parameters have been defined, as specified in TS 36.314 -they consist of: 1. PRB usage: this is to measure the usage of time and frequency resources.
This is measured to perform cell load balancing, where PRB usage is used for information signalled across the X2 interface, and OAM performance monitoring.
2. Received Random Access Preambles: the measured quantity in this case is the number of received Random Access preambles during a time period over all PRACHs configured in a cell. This is used for configuration optimization 3. Number of active liEs: this measures the number of active UBs per QCI for OAM performance monitoring.
4. Packet Delay: this is to measure L2 Packet Delay for OAM performance monitoring.
5. Data Loss: this is to measure packets that are dropped due to congestion, traffic management etc for OAM performance monitoring.
6. Scheduled IP Throughput: this is to measure over Uu the IP throughput * : H H independent of traffic patterns and packet size. This measurement is performed per QCI per UE.
These measurements are executed by the L2 sub-layers, i.e. PDCP, RLC and MAC.
Load balancing is one aspect of SON being built into the design of LTE. The objective of load balancing is to counteract local traffic load imbalance between neighbouring cells with the aim of improving the overall system capacity. In order to detect an imbalance, comparing with neighbouring cell loads is desirable. This is method is typically achieved with the exchange of cell load information via the X2 interface. One way to convey the load is through the periodic measurement of PRB usage.
The present invention seeks advantages in how load balancing within the network is performed.
Disclosure of the Invention
According to a first aspect of the present invention there is provided a wireless telecommunications system comprising: a base station; a first relay node with a backhaul link to the base station, and an access link to one or more user equipments; and one or more further nodS, wherein, the system is operable to detei-min the bottleneck of the overall link consisting of the access* link and backhaul link of the relay node in terms of the load, wherein the said overall link is considered from the perspective of a said user equipment and transmit the determined bottleneck information to each of the one or more further nodes.
Preferably the base station is a D-eNB.
The above arrangement allows for meaningful load-balancing operations to be performed in the system. For example, if the relay node has capacity on its access link, but the backhaul link is exhausted (for example due to encapsulation overhead, increased backhaul signalling, and channel impairments), the present arrangement allows for neighbouring nodes to ascertain that the relay node is not a candidate to receive further wireless communication traffic.
It is preferable that the base station is configured to transmit details of the relay node's backhaul link to the relay node, and that the relay node determines the bottleneck information.
It is preferable that the relay node is configured to acquire details of it's backhaul link from the base station on demand, if required, and that the relay node use such details to calculate its combined load condition Preferably, the relay node is operable to transmit the the determined bottleneck information toihe one or more further nodes using the X2 interface. If the relaynode does not maintain an X2 interface with each of the one or more further nodes, it preferred that the relay nodeuses the base statibq's proxy functionality to transmit the determined bottleneck information to theoneor more further nodes. --. --It is preferable that the one or more further nodes is/are of Rel-8/9 eNB type.
Preferably the bottleneck information of the relay node is calculated using its usage of physical resource blocks (PRB). In wireless communication systems, the total number of available subcarriers depends on the overall transmission bandwidth of the system. LTE systems define bandwidths from I.25 MHz to 20 MHz. A PRB is defined as consisting of 12 consecutive subcarriers for one slot (0.5 msec) in duration.
A PRE is the smallest element of resource allocation assigned by a base station. It is preferred that the bottleneck information is determined by the following operation: PRB usage to be disseminated to the one or more further nodes max { PRB usage on access link, PRB usage on backhaul}.
The arrangement looks to find the highest PRB usage on either the backhaul link and the access link, and use this value as a load condition of a relay node. If one of the two links is at or close to capacity, it does not matter if the other link has capacity; the relay will be at or close to capacity. The bottleneck information is based on the load condition.
It is preferred that the PRB usage may be calculated as a percentage of total available resource (ie if the usage on the backhaul link is 10mb, and the total bandwidth of the link is 5 0mb, then the link is at 20% capacity).
Preferably the system further. comprises one or more user equipments directly linked to the base statiom It is preferred that if the relay node shares radio resources with H said one or more directly linked user equipments, the relay node is operable to directly obtain details of its backhaul link from the base station.
It is preferred that if the relay node does not share radio resource with said one or more directly linked user equipments, the relay node is operable to demand information regarding its backhaul link from the base station.
In a second aspect of the present invention of the present invention there is provided a wireless telecommunications system comprising: a base station; and a relay node and a further node, said relay node comprising a backhaul link to the base station, and respective access link to one or more user equipments, wherein, the relay node is operable to make a measurement of its PRB usage on the access link and transmit measured PRB usage to the further node, the further node is operable to obtain information regarding the relay node's PRB usage on the backhaul link and collate a load condition for the relay node in order to determine the bottleneck of the overall link consisting of the access link and the backhaul link from the perspective of a said user equipment.
It is preferable that the further node is a base station that has capabilities as stipulated byRel-lO.
In! another preferred arrangement the. further node is a relay node.
In this arrangement neighbouring nodes are operable to determine the load condition for relay nodes. It will be appreciated that in arrangements with multiple relay nodes associated with a D-eNB, a relay node will disseminate its access link load information to each of the relay nodes.
Preferably the load condition is determined by the following protocol: PRB usage to be disseminated to the one or more further nodes = max { PRB usage on access link, PRB usage on backhaul}, According to the present invention there is provided a wireless telecommunications system that is operable to selectively implement the first aspect of the present invention and the second aspect of the present invention.
In order that the present invention be more readily understood, specific embodiments thereof will now be described with reference to the accompanying drawings.
Description of the Drawings
Figure 1 shows an example of part of a network architecture.
Figure 2 shows a sequence involved in disseminating a relay node's load to neighbouring nodes in accordance with a first embodiment.
Figure 3 illustrates how PRB usage measurements from a relay node are interpreted by a neighbour node in accordance with a second embodiment.
Description of preferred embodiments
The present arrangement relates to a wireless telecommunications system. Such systems generally comprise one or more base stations. In long term evolution systems these are termed eNBs. Each eNB will be linked to the core network. The controlling eNB is generally referred to as a D-eNB. A D-eNB controls network traffic originating from or destined to one or more relays within a domain. Said domain may include a plurality of further nodes. Domains located geographically next to one another may be termed neighbouring domains.
In LTE Rel-lO and further future releases D-eNBs will have capabilities to serve both UEs and relay nodes. Under such circumstances, a D-eNB will maintain a direct link with a M-UE, which it serves via the Uu interface and a backhaul link to serve a relay node via the Un interface. A relay node will maintain an access link to a UE (termed R-UE) that is connected via the Uu interface.
Figure 1 shows an example of part of an LTE network architecture. Here, D-eNB, maintains a direct link withmacro,UE (M-IJE) 12. ..This link is supported by the. H Uu interface. DTeNB. 10 is also conncted.to. a re1ay node 14. This.connection is supported by the Un interface, and is termed the relay nod&s backhaul link. .. . . . . Type 1 Relay nodes are operable to support a communication link to a UE 16 in the same manner as a D-eNB. The link between a relay node 14 and a UE is via the Uu interface. UBs connected to a relay node are termed relay-UEs, or R-TJEs.
The 3GPP agreed that relay nodes should perform the L2 measurements on the Uu in the same way as an eNB does without any consideration of the Un. Thus, a relay node is required to take L2 measurements on its access link and report to its OAM, whereas the D-eNB 10 has to take measurements on the relay node's backhaul and report to its respective OAM. This type of independent operation will not cause undesirable effect in terms of the way they are interpreted by different entities/nodes in the network in the case of many of the L2 measurement metrics/parameters as listed above. However, the measurement of PRB usage, if taken and treated independently, will create a wrong picture, especially to the neighbour nodes of a relay node, and thereby will lead to undesirable effects. This is because when considering load balancing, the resource status of the relay node's backhaul is an important input to the calculation of the total relay node resource status. Thus, if either a relay node's 14 access link or backhaul link resources are exhausted, that relay node 14 will not be in a position to serve further R-UEs.
A relay differs from other E-UTRAN nodes in that it needs to maintain two independent wireless links simultaneously. Either or both of these links maybe 1w band. The backhaul link is as important as the access link in the operation of a relay node. Applying a strict modular principle, and thereby treating these links independently for L2 measurement purposes may give a false result. Applying optimisations independently on each link will not bear what L2 measurements are trying to achieve: if there is capacity on the access, but the backhaul link is exhausted namely due to increased backhaul signalling, encapsulation overhead and channel impairments the relay is effectively at its full operating capacity. Thus the result regarding the indication that the access link is able to support further wireless communication sessions is potentially misleading.
Optimisation operations have to be coordinated together on the access and backhaul links for an effective relay load-balancing operation. Although it is important that a relay node is treated differently to a D-eNB, if measurements are taken on the Uu interface and the Un interface independently, conveying the appropriate information of a relay node to neighbouring nodes for them to use these measurements in their load-balancing and handover decisions is important. Further constrains are that OAMs of a relay node and its D-eNB can have limited interactions -whether or not this limited number of interactions is enough to achieve the necessary OAM/SON and other optimisations and load-balancing is questionable, because constant interactions are preferred.
The PRB usage of an access link cannot serve its purpose unless combined with the associated measurement of backhaul link. The L2. measurement on the Uu interface: is not sufficient to perform meaningful relay node load-balancing. Relying ow the J.u interface measurements that are not representative of a specific relay node 14 will compromise the usefulness/accuracies of the measurements; $ According to a first embodiment there is provided a wireless telecommunications system comprising a base station -which is preferably a D-eNB -, a first relay node with a backhaul link to the base station, and an access link to one or more user equipments. Also provided is one or more further nodes. The system is operable to assess a combined load condition for the access link and backihaul link of the relay node and transmit same to each of the one or more further nodes. Thus, the system is operable to determine the bottleneck of the of the overall link consisting of the access link and backhaul link of the relay node in terms of the load, wherein the said overall link is considered from the perspective of a said user equipment and transmit the determined bottleneck information to each of the one or more further nodes.
According to this embodiment, it is disclosed that before disseminating the PRB usage measurement to neighbouring nodes, a relay node has to consider the combined PRB usage of both the access and backhaul links. This can be performed by the following operation: The PRB usage to be disseminated to neighbouring nodes by a relay node = max{ PRB usage on Uu, PRB usage on backhaul} ----(1) The above operation is governed by a maximization protocol. . . The PP.2 usage may be calculated as a petcentagé of the total available resource: . . . -It will be appreciated that the maximisation protocol needs to be performed irrespective of whether or not a relay node 14 is treated differently from M-UEs 12 by the D-eNB 10 for L2 measurements. This is also true no matter whether or not a relay node uses a specific set of radio resources that is different from that being used by a M-UE.
Relay nodes differ from other E-UTRAN nodes in that they have a wireless backhaul. By contrast an eNB typically maintains a wired backhaul. This link would typically comprise one or more optical fibres. In certain scenarios, an eNB backhaul can be a point-to-point out-of-band microwave link. Therefore, bandwidth is generally freely available on an eNB's backhaul due to the massive amount of data that can be transmitted through an optical fibre.
By contrast, bandwidth can be very limited in a wireless relay node backhaul. In the ease of an in-band relay node, the capacity and quality of the backhaul link is not better than those of the access link. Consider a scenario: a relay node disseminates its PRB usage to its neighbours, and suppose the load on access link is low, whereas the load on the backhaul is at capacity. Such dissemination may invite neighbouring nodes with a load-imbalance, or high capacity access links to consider handing over some of the cell edge traffic to the relay node as a way to redress the lad imbalance problem. Given the exhausted backhaul link, the relay.
node will not be able to accept such handovers, and such an attempt will likely lead:.
to a failed handover or unnecessary wasteful load balancing operations. The likelihood for this to happen in the case of an eNB is very minimal, as its backhaul:-capacity is much higher than that of a relay backhaul (due to the presence of a wired backhaul). Load balancing through handover rejection may work in the case of cNB, but not with a relay node without wasting resources and incurring latency.
Hence, if the load balancing is left to be effected through handover rejection, the cost and adverse effect would be high.
The problem gets aggravated when one of the neighbouring nodes is a legacy node, such as a Rel-819 eNB. This is because such an eNB does not perceive a relay node as a relay node, but as an eNB. In other words, it cannot determine whether the relay node comprises a wired or wireless backhaul link.
Any relay node, or its respective D-eNB, can perform the maximum-operation as set out in equation (1). However, it is preferred that the relay node performs the operation. It is particularly preferred that the base station is configured to transmit details of the relay node's backhaul link to the relay node, and that the relay node determines the bottleneck information.
If a relay node and M-UE share the same radio resources, the load information of D-eNB is readily available to the relay node -hence it is straightforward for the relay node to obtain the information. This is because a relay node can get the load information of the D-eNB ift ith cäaCity as a neighbour of the D-eNB. Thus, it is preferred that'th system further c'ompties' one' or'rnbre user equipments directly linked to the base' station; and further Wherein if the relay node shares radio resources with said one bt more direcily linked User equipments, the relay node is.
operable to directly obtain details of its backhaul link from the base station.
If the relay node uses a different set of radio resources than that being used by any active M-UEs, the D-eNBs are required to measure this separately and distribute the information to each associated relay node to allow for each of them to do the maximum-operation (equation 1 above). This is also true irrespective of whether each RN uses a specific set of resources or shares resources with other relays served by the same D-eNB.
The relay node is configured to acquire details of its backhaul link from the base station on demand. Thus, if the relay node does not share radio resource with said one or more directly linked user equipments, the relay node is operable to request information regarding its backhaul link from the base station on demand.
A relay node does not necessarily maintain the X2 interface with every neighbouring node. However, as it uses the D-eNB's proxy functionality, the D-eNB can also perform the above maximum operation after having performed the Deep Packet Inspection (DPI) operation when a load information packet of a relay node traverses via the. D-eNB. , ( "The D-eNB can take a conim6ñ Un PRB usage measurement for all of the relay.
nodes that it serves, Or itake a specific Un PRB measurement and transmit it to the relevant relay node. In either case, it is preferred that corrective measures are taken for a relay node to disseminate the combined PRB usage (load information) after performing the above-mentioned maximum-operation.
Figure 1 illustrates a process of disseminating the load information of a relay node to its neighbours. Initially the D-eNB 10 indicates its load information via the X2 interface to each of its neighbours. If the load indication message is specific to relays, the D-eNB 10 has to additionally pass that load indication information to each of the relay nodes under its control. In case the relay nodes and M-UEs use the same set of radio resources, the current load indication mechanism is sufficient.
Once a relay node acquires its backhaul-specific load, it is in a position to perform the maximum operation (as formulated by equation (1)). Once this is performed, the given relay node can disseminate the combined load to its neighbouring nodes.
If the relay node does not maintain an X2 interface with each neighbouring node, it can use the D-eNB's proxy functionality for such load indication dissemination.
In a second embodiment, a neighbouring node performs the maximum operation (as formulated by equation (1)) for a given relay node. This method is facilitated when all neighbouring nodes are operable to interpret a relay node as a relay node (as opposed to an eNB). Accordingly, a relay node takes the PRB usage measurement (or load information) on thç access link and disseminates the data to its neighbours.
When a neighbour node receives the PRB usage measurement from one. of its ¶ neighbouring relay nodes, it will await a PRB measurement pertaining tO:. the; backhaul from the respective D-eNB, if it has not already received it. If required, ¶ the neighbour node can obtain such a measurement from the D-eNB on-demand.
In this embodiment there is thus provided a wireless telecommunications system comprising a base station (typically a D-eNB), a relay node and a further node. The further node is preferably a base station that has capabilities as stipulated by Rel-lO (and ideally configured to support future releases). Alternatively, the further node may be a relay node. The relay node comprising a backhaul link to the base station, and respective access link to one or more user equipments. The relay node is operable to make a measurement of its PRB usage on the access link and transmit same to the further node, and the further node is operable to obtain information regarding the relay node's PRB usage on the backhaul link and collate a load condition for the relay node. The present system thus permits the determination of a bottleneck of the overall link consisting of the access link and the backhaul link from the perspective of a said user equipment.
If the D-eNB 10 treats the relay node 14 as an M-UE 12 from the perspectives of L2 measurements, the D-eNB takes the combined PRB usage measurement (considering relay node and M-UIE) and disseminates it as required by the legacy Rel-819 L2 measurement mechanism. This is applicable when relay nodes and M-liEs share the same set of radio resources... . . Situations where relay nodes uses a specific set of radio resources that differs from. . .; those being used by M-UEs, it is preferable for the D-eNB to take separate FF3: . usage measurements different. from that of the M-UEs. In one embodiment, the D-eNB can treat each relay node it controls differently, and take relay node specific PRB usage measurement pertaining to the respective backhaul links.
Irrespective of how the D-eNB obtains PRB usage measurements, neighbouring nodes have to wait for such a measurement and combine the data with that received from a given relay node. Once a neighbour node has received the PRB usage measurement pertaining to an access link and the backhaul link of a relay node from a given relay node and the D-eNB respectively, the neighbour node has to perform the maximum operation. The neighbour node is required to take the PRB usage measurement resulting from the maximum operation into consideration for any of its load balancing or handover related operations involving a respective relay node.
The PRB usage in the above context means the downlink PRB usage for traffic, uplink PRB usage for traffic, downlink Total PRB usage, and uplink Total PRB usage.
The overall idea is to determine the bottleneck of the overall link consisting of the access link and backhaul link of the relay node in terms of the load. The overall link is considered from the perspective of an R-1JE. The load condition on either the* . access link or the backhaul link is preferably measured in terms of the PRB usage:.
* * This PRB usage of thther the access link orl the hackhaul link can. preferabiy;b& a. . . . . reiative measure in that it is. the Tatio or. percehtage of used P to the overall: . . ...
capacity.
The total PRB usage may be calculated based on the following equations: total PRB usage (RN PRBs + UE PRBs) / total PRBs where, RN PRBs indicate the PRB used for info to/from a relay node connected to the D-cNB; UE PRBs indicate the PRB used for info to/from a UE connected to the D-eNB; and total PRBs indicate the total PRB capacity (used and unused PRBs). Also: Total PRB usage per RN = RN PRBs / total PRBs.
Further, if needed, the PRB usage can be measured seperately per different QCIs.
In this connection the following two statements apply: i) R14 PRBs for a certain QCI / total PRBs; ii) (RN PRB + UE PRBs) for a certain QCI / total PRBs.
In the case of Received Random Access Preambles, given that a Rel-10 relay node can access the network in the capacity of a TIE, a single measurement is sufficient by treating a relay node as a M-UE. If a relay node uses a different sets of preambles (either on the same PRACH being used by M-UEs or on a different relay specific R-PRACH) from those used by M-UEs, a separate L2 measurement for Received Random Acces Preamblésthas tO be taken by the fl-eThB. . t.: H., Figure 2' illustrates the equence inolvèd in disseminating the load of an RN 14 to.
bne or more further nodes (i.e., ny of its heighbour) as per the first embodiment; H' .: 1'.
Initially the D-eNB 10 is supposed: to indicate its load via the X2 interface to its neighbours. If the load indication message is specific to relays 14, the D-eNB 10 has to additionally pass the details of the backhaul link of an RN 14 in question, especially the load indication information, on to every RN 14 it serves. On the other hand, in case relays 14 and M-UEs 12 use the same set of radio resources, the current load indication mechanism is suffice -hence, in this case the D-eNB 10 does not need to pass the backhaul-spebific details of an RN 14 in question to that particular RN 14. In other words, such information is directly and automatically available from the D-eNB 10. M-UEs 12 are one or more user equipments directly linked to the base station D-eNB 10.
In case an RN 14 has not received the details of the backhaul link from the D-eNB 10 or if an RN 14 does not share radio resource with one or more directly linked user equipments (i.e., M-UEs 12), the RN 14 in question can request information regarding its backhaul link from the base station, D-eNB 10, on demand.
Once an RN 14 has got to know its backhaul specific load, it has to perform the maximum operation as formulated by equation (1) in order to assess a combined load condition considering the access link and the backhaul link. Once this is performed, the given RN 14 can disseminate the details of its load condition (i.e., combined load considering both the access link and the backhaul link) to one or more further nodes (i.e., any of its neighbdurs);Incáse it does flOt maintain the X2 interface with every: neighbour; it can use the D-eNB's 10 proxy functionality for such load indicatiorc dissemination. -. : . Figure 3 illustrates how PRB usage measurements from a relay node 14 are interpreted by a further node (i.e., a neighbour node of an RN 14 in question) in accordance with a second embodiment. In operation (1), an RN 14 disseminates the RN-specific load information to its neighbours via X2 interface. For this purpose, an RN 14 in question makes a measurement of its PRB usage on the access link and transmit measured PRB usage to the further node (i.e., a neighbour node of an RN 14 in question).
A D-eNB 10 will receive such information because of its capacity as a neighbour node. If an RN 14 does not maintain an X2 interface with all of its neighbours, it can use the proxy functionality of the D-eNB 10 to disseminate the load information as indicated by operation (2). With the operation (3), a further node (i.e., a neighbour node of an R1'.T 14 in question) requests to obtain information regarding the relay node's PRB usage on the backhaul link (especially the load information) from the D-eNB 10 of an RN 14 in question on demand (i.e., pull approach from the perspective of a neighbour node) in response to operation (2) and the D-eNB will supply such information as indicated by operation (4). In case the RN 14 in question and all M-UEs 12 share the same physical radio resources, the D-eNB's load information (i.e., total PRB usage) is enough without having to consider relay-specific PRB usage on the backhaul.
The operation of (3) to send the: RESOURCE STATUS REQUEST message by a neighboUr node for the purpose of. requesting the corresponding PRE usage measurement from the respective D-eNB of the RN in question on demand as indicated in Figure 3-may not be needed in case D-eNB periodically sends (e.g., push: approach from the perspective of the D-eNB) the PRB usage measurement to its neighbour node. Based on the obtained information, a neighbour node will determine the bottleneck of a relay node by considering the loads of both the access link and the baclchaul link as indicated by operation (5).
As will be understood, a wireless telecommunications system can selectively implement the solutions as proposed by first embodiment or the solutions as proposed by second embodiment depending on the capabilities of one or more further nodes (i.e., a neighbour node of an RN 14 in question). In case a further node is a legacy node whose operations are govemed as stipulated by Rel-8/9, the solutions as proposed by first embodiment need to be implemented -in this case the solutions of the second embodiment cannot work at all. On the other hand, a fUrther node is built in accordance with Rel-10 or future releases, the solutions as proposed by second embodiment can preferably implemented although the solutions of the first embodiment can still work.
The above described specific embodiments are described by way of example only, and many variations and modifications are available within the scope of the present invention.
Priority Applications (2)
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| GB1107282.4A GB2490366A (en) | 2011-04-28 | 2011-04-28 | Determining bottleneck information in a cellular network with a relay node |
| PCT/JP2012/061932 WO2012148009A1 (en) | 2011-04-28 | 2012-05-01 | A wireless telecommunications system |
Applications Claiming Priority (1)
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| GB1107282.4A GB2490366A (en) | 2011-04-28 | 2011-04-28 | Determining bottleneck information in a cellular network with a relay node |
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| GB201107282D0 (en) | 2011-06-15 |
| WO2012148009A1 (en) | 2012-11-01 |
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