GB2496844A - Resource allocation in base stations with shared operating bandwidth and overlapping coverage areas - Google Patents
Resource allocation in base stations with shared operating bandwidth and overlapping coverage areas Download PDFInfo
- Publication number
- GB2496844A GB2496844A GB1119746.4A GB201119746A GB2496844A GB 2496844 A GB2496844 A GB 2496844A GB 201119746 A GB201119746 A GB 201119746A GB 2496844 A GB2496844 A GB 2496844A
- Authority
- GB
- United Kingdom
- Prior art keywords
- base station
- transmission resources
- users
- text
- coverage
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Withdrawn
Links
- 238000013468 resource allocation Methods 0.000 title claims description 13
- 230000005540 biological transmission Effects 0.000 claims abstract description 94
- 238000000034 method Methods 0.000 claims abstract description 57
- 238000004891 communication Methods 0.000 claims description 19
- 239000000969 carrier Substances 0.000 claims description 4
- 238000001228 spectrum Methods 0.000 description 12
- 238000005192 partition Methods 0.000 description 7
- 230000011664 signaling Effects 0.000 description 6
- 238000013459 approach Methods 0.000 description 3
- 230000000116 mitigating effect Effects 0.000 description 3
- 230000001149 cognitive effect Effects 0.000 description 1
- 230000001419 dependent effect Effects 0.000 description 1
- 238000007726 management method Methods 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000013439 planning Methods 0.000 description 1
- 230000008054 signal transmission Effects 0.000 description 1
- 238000000638 solvent extraction Methods 0.000 description 1
- 230000003595 spectral effect Effects 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
Classifications
-
- 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
- H04W16/02—Resource partitioning among network components, e.g. reuse partitioning
- H04W16/10—Dynamic resource partitioning
-
- 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
- H04W16/14—Spectrum sharing arrangements between different networks
- H04W16/16—Spectrum sharing arrangements between different networks for PBS [Private Base Station] arrangements
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W72/00—Local resource management
- H04W72/20—Control channels or signalling for resource management
- H04W72/27—Control channels or signalling for resource management between access points
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W72/00—Local resource management
- H04W72/50—Allocation or scheduling criteria for wireless resources
- H04W72/54—Allocation or scheduling criteria for wireless resources based on quality criteria
- H04W72/541—Allocation or scheduling criteria for wireless resources based on quality criteria using the level of interference
-
- 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
- H04W16/32—Hierarchical cell structures
-
- 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
- H04W84/045—Public Land Mobile systems, e.g. cellular systems using private Base Stations, e.g. femto Base Stations, home Node B
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W92/00—Interfaces specially adapted for wireless communication networks
- H04W92/16—Interfaces between hierarchically similar devices
- H04W92/20—Interfaces between hierarchically similar devices between access points
Landscapes
- Engineering & Computer Science (AREA)
- Computer Networks & Wireless Communication (AREA)
- Signal Processing (AREA)
- Quality & Reliability (AREA)
- Mobile Radio Communication Systems (AREA)
Abstract
A method of operating a heterogeneous network comprising a first and a second base station (BS) which share operating bandwidth, wherein the coverage areas of the two BS at least partially overlap. The second BS determines the number of users in communicative contact with said second BS for which a minimum quality of service, QoS, requirement is not fulfilled. A message comprising said determined number is transmitted to the first BS (or to a control unit controlling the allocation of transmission resources within the first BS). The first BS (or the control unit) prevents the use of a number of transmission resources by the first BS based on the determined number of users for which a minimum quality of service, QoS, requirement at the second base station is not fulfilled. The first BS may be a macro BS and the second BS may be a Femto-cell BS. A further method includes detecting a number of users of a macro BS that are located within the coverage area of a femto-cell BS, randomly selecting a number of transmission resources that would be available to the femto-cell BS for use, and precluding the femto-cell BS from using the selected transmission resources.
Description
Resource Allocation In A Heterogeneous Network
FIELD
Embodiments described herein generally relate to interference management techniques in heterogeneous networks.
BACKGROUND
Femtocell based stations are intended to be plug and play devices that can be deployed by subscribers in a flexible and ad hoc fashion. To allow this flexibility in deployment Femtocell base stations do not normally form part of a network/bandwidth planning exercises. Due to the subscriber deployed nature of Femtocell base stations they can moreover be located anywhere within a macrocell. It is well known that, in network architectures in which one or more Femtocell base stations operate within the coverage area of a macrocell base station data, signal transmission between mobile equipment and the Femtocell base stations and/or between the mobile equipment and the macrocell base station can suffer from significant interference, in particular when both the Femtocell base station(s) and the macrocell base station operate in a co-channel mode.
Figure 1 illustrates this interference problem for the downlink (DL) case.
When a user in active communication with a macrocell base station (labelled macro-cell 68 in Figure 1) approaches the Femtocell base station (labelled Femtocell BS in Figure 1) the user may experience large interference from the Femtocell base station if both the macrocell base station and the Femtocell base station use non-orthogonal radio resources to serve Femtocell users and macrocell users respectively. This interference can compromise the ongoing communication between the user and the macrocell base station if the signal received by the user from the macrocell base station has low power, for example due to high path losses. It will be appreciated that, without interference mitigation, the Femtocell base station creates a coverage hole within the macrocell. Communication between users in communication with the macrocell r 2 base station will be severely interfered with or completely disabled in the coverage hole. Signals emitted by the macrocell base station will equally potentially interfere with signals exchanged between a user and the Femtocell base station.
In view of the above it is desirable to find a way of ensuring that communication with the macrocell base station is free from interference from Femtocell base stations, or at least to ensure that any residual interference is acceptable or even negligible.
It is equally desirable that the Femtocell base stations deployed within a macrocell reliably provide a desired network access in addition to the connectivity provided by the macrocell base station.
BRIEF DESCRIPTION OF THE DRAWINGS
Embodiment of the present invention will now be described by way of example only and with reference to the accompanying drawings, in which: Figure 1 illustrates downlink interference suffered by user equipment in active communication with a macrocell base station when approaching a Femtocell; Figure 2 shows a known heterogeneous macrocell-Femtocell network architecture; Figure 3 illustrates a known method of frequency allocation to Fenitocell and macrocell base stations; Figure 4 illustrates a method of reserving spectral bandwidth for use by Femtocell base stations; Figure 5 shows an example of spectrum partition for a Femtocell base station and a macrocell base station; Figure 7 shows an example of a spectrum allocation technique; Figure 8 shows an example of subcarrier allocation for a heterogeneous network comprising a macrocell base station and three Femtocell base stations located with the macrocell; r 3 Figure 9 shows an averaged cell throughput comparison; Figure 10 shows an averaged user throughput comparison; and Figure 11 shows the architecture of a Femtocell base station that may be used in an embodiment.
DETAILED DESCRIPTION
According to an embodiment there is provided a method of operating a heterogeneous network comprising a first base station with a first area of coverage and a second base stations with a second area of coverage. The first and second areas of coverage at least partially overlap. The first and second base stations share operating bandwidth. The method comprises determining, within the second base station, a number of users in communicative contact with the second base station for which a minimum quality of service, hereinafter referred to as QoS, requirement is not fulfilled and transmitting a message comprising the determined number to the first base station or to a control unit controlling the allocation of transmission resources within the first base station.
The method further comprises, within the first base station or the control unit, receiving the message, determining based on the determined number of users a number of transmission resources and preventing the use of the number of transmission resources by the first base station.
The first base station or the control unit may transmit a message identifying the reserved resources to the second base station.
The reserved transmission resources may be reserved sub-carriers or reserved sub-channels.
Determining the number of transmission resources may include determining a percentage that the received number of users of the second base station represents out of a sum of the total number of users of the first base station and of the received number of users of the second base station and calculating the determined number of transmission resources to be a fraction of the total number of available transmission resources that is substantially equal to the determined percentage. r 4
The second base station may determine the number of users by comparing, for each user in communicating with the second base station, the signal to interference noise ration, hereinafter referred to as SINR, across the transmission resources used by the user with and without interference from the first base station and may include a user in the number of users if the SINR is below a predetermined threshold if there is interference from the first base station and above the threshold if there is no interference from the first base station.
The network may comprise one or more further base stations with coverage areas that at least partially overlap with the first coverage area. The first base station may share operating bandwidth with the one or more further base stations. The method may further comprise determining, within each of the one or more further base stations, a number of users in communicative contact with the further base station for which a minimum quality of service requirement is not fulfilled and transmitting a message comprising the determined number to the first base station or to a control unit controlling the allocation of transmission resources within the first base station. The first base station or the control unit may determine the number of transmission resources to be reserved based the highest determined number received from any of the second and one or more further base stations.
According to another embodiment there is provided a method of operating a second base station having a coverage area that is at least partially located within the coverage area of a first base station. The first and second base stations share operating bandwidth. The method comprises determining a number of users in communicative contact with the second base station for which a minimum quality of service requirement is not fulfilled and transmitting a message comprising the determined number onto a data path, receiving a message indicating transmission resources that the first base station has been precluded from using and allocating reserved transmission resources to users for which the minimum quality of service requirement is not fulfilled.
According to another embodiment there is provided a method of operating a transmission resource allocation apparatus for a base station that r 5 shares coverage area and operating bandwidth with a further base station. The method comprises receiving a message indicating a number of users of the other base station and reserving transmission resources for use by the other base station based on the number.
According to another embodiment there is provided a base station comprising a transceiver connectable to a transmission path and a microprocessor, The microprocessor is operative to determine whether or not communication sessions with users of the base station fulfil a minimum quality of service requirement, to transmit, using said transceiver, a message onto the transmission path indicating a number of users for which the minimum quality of service requirement is not fulfilled and to re-allocate transmission resources to the users for which the minimum quality of service requirement is not fulfilled following receipt of an indication of the reserved transmission resources.
According to another embodiment there is provided a transmission resource allocation apparatus for a base station that shares coverage area and operating bandwidth with a further base station. The apparatus comprises an interface operative to receive a message indicating an number of users of the other base station, block a number of transmission resources from use by the base station based on the number and transmit a message identifying the blocked transmission resources.
According to another embodiment there is provided a system comprising one of the above discussed transmission resource allocation apparatus, configured to allocate the transmission resources of a first base station, and one or more of the above discussed further base stations.
According to another embodiment there is provided a method of operating a heterogeneous network comprising a first base station with a first area of coverage and a second base stations with a second area of coverage.
The first and second areas of coverage at least partially overlap. The first and second base stations share operating bandwidth. The method comprises, within the second base station, detecting a number of users of the first base station that are located within the coverage area of the second base station, randomly r 6 selecting a number of transmission resources that would be available to the second base station and preventing the second base station from using the selected transmission resources. The number of selected transmission resources is the sum of all transmission resources required by the users of the first base station to communicate with the first base station, The method may further comprise receiving at the second base station from the first base station a number of transmission resources required by a user of the first base station and multiplying the received number of required transmission resources with the determined number of users.
According to another embodiment there is provided a method of operating a base station with a coverage area that is at least partially inside the coverage area of another base station. The base station and the other base station share operating bandwidth. The method comprises detecting a number of users of the other base station that are located within the coverage area of the base station, randomly selecting a number of transmission resources that would be available to the base station for use and precluding the base station from using the selected transmission resources. The number of selected transmission resources is the sum of all transmission resources required by the users of the other base station for communication with the other base station.
According to another embodiment there is provided a heterogeneous network comprising a first base station with a first area of coverage and a second base stations with a second area of coverage, wherein the first and second areas of coverage at least partially overlap and wherein the first and second base stations share operating bandwidth. The second base station is operative to detect a number of users of the first base station that are located within the coverage area of the second base station, randomly select a number of transmission resources that would be available to the second base station and prevent the second base station from using the selected transmission resources. The number of selected transmission resources is the sum of all transmission resources required by the users of the first base station to communicate with the first base station. r 7
According to another embodiment there is provided a base station comprising a transceiver and a controller. The controller is operative to, using the transceiver, detect a number of users of another base station that are located within the coverage area of the base station, in use. The controller is further operative to randomly select a number of transmission resources that would be available to the base station for use and to preclude the base station from using the selected transmission resources. The number of selected transmission resources is the sum of all transmission resources required by the users of the other base station for communication with the other base station, A given Femtocell base station can suffer from interference based on signals originating at neighbouring Femtocell base stations and at rracrocell base stations. As discussed above, subscriber to network services are free to acquire Femtocell base stations and to set these Femtocell base stations up in an ad-hoc fashion at his or her home, benefiting from plug-and-play nature of Femtocell base stations. The subscriber, however, will often not be aware of the nature of the macrocell network coverage in the location of deployment before setting up the Femtocell base station. If the deployment location is close to a macrocell base station interference from the macrocell base station can be sufficiently strong to effectively disable the Femtocell. Alternatively or additionally there may be plenty of neighbouring Femtocell base stations, resulting in severe interference.
To address interference problems, routines for handing over ongoing communication from one base station (be that a macrocell base station or a Femtocell base station) to another base station (which may again be either a macrocell base station or a Femtocell base station) have been devised. Such handover routines may be efficient but are not practicable in situations where macrocell users do not belong to the Femtocell or are not allowed to access the Femtocell.
Power control routines, in which the Femtocell base station can adjust its transmit power to reduce the interference to macrocell users or to neighbouring Femtocell users, are also known. A result of adjusting the Femtocell base station's transmit power as a macrocell user approaches the Femtocell is that r 8 the Femtocell shrinks with the power reduction. This is undesirable, in particular if the size of the Femtocell shrinks considerably, dependent on how far the rriacrocell user approaches the Femtocell base station.
A heterogeneous macrocell-Femtocell network architecture is known from LIE. An example of this architecture is provided in Figure 2. As shown in Figure 2 there are no direct interface between the macrocell base stations (labelled eNB in Figure 2) and the Femtocell base stations (labelled HeNB in Figure 2). In the Figure 2 architecture macrocell base stations communicate with Femtocell base stations via gateways (labelled GW in Figure 2). Such communication may have to be delay-resistant. At the same time, if several Femtocell base stations are operated in one macrocell there is a danger that the backhaul may be overburden with exchanged information unless information exchange between macrocell base stations and Femtocell base stations is kept as low as possible.
In OFDM-based macrocell-Femtocell systems, spectrum or frequency allocation can be utIlized so that different subcarriers are allocated to different users to tackle interference problems. One straightforward way of achieving this is to partition the totality of the subcarriers into two non-overlay groups and to allocate one of the groups for use by Femtocell base stations and the other one of the groups for use by macrocell base stations respectively. This is illustrated in Figure 3. This technique eliminates interference between the macrocell layer and the Femtocell layer but is highly inefficient.
Alternatively, Femtocell base stations and macrocell base stations could use the same subcarriers but allocate subcarriers to their users dynamically. To reduce interference and achieve higher system throughput in such dynamic allocation, it may be necessary to exchange instantaneous SINR information of users among Femtocell and macrocell base stations through the backhaul. The resulting network is likely to exhibit very low delay-tolerance. There is then a danger that such a network is rendered impractical, since there are no direct connections between macrocell base stations and Femtocell base station.
Moreover, the overhead created by such exchange of information will be considerable if the Femtocell base stations are deployed in large numbers. r
A new resource allocation method, the above discussed interference problem for heterogeneous networks is discussed in the following. In heterogeneous network there may not be a direct link between the infrastructural system (for example the macrocell base stations) and the distributed system (for example the Femtocell base station). In this case any communication between these two systems is routed via the backhaul and has to be delay-resistant. Meanwhile, if a large number of distributed systems are deployed, the transmission overheads via the backhaul should be kept as low as possible. The resource allocation method uses a dynamic frequency reuse and a dynamic resource allocation scheme to attempt to meet the delay-resistance and low overhead requirement, while tackling the interference problem.
In an embodiment the Femtocell base stations keeps the macrocell base station informed of either the Femtocell base station's channel information status (CSI; in terms of SINR) or of the Femtocell base station's required quality of service (QoS). Based on the CSIs or QoS requirements, the macrocell base station can then act as a central control unit and allocate frequency spectrum for itself and for the Femtocell base stations it is in communication with over the backhaul. It is emphasised that, while the following description is based on the sub-carrier level, this is only be way of example. Embodiments are also applicable to the sub-channel level, where sub-channels are composed of a set of subcarriers and are the units to be allocated to users. In embodiments using sub-channels, the signal to interference noise ratio used for determining whether or not a minimum quality of service required by a user is met can an effective signal to interference noise ratio determined, for example as the average of power signal to interference and noise over the subcarriers in a sub channel. Alternatively the signal to interference noise ratio may be judged to fulfil the minimum quality of service requirement if the signal to interference noise ratio of each sub-carrier in a sub-channel is above a predetermined threshold. This predetermined threshold can be the same threshold used for determining whether or not a minimum quality of service is achieved for a user in the sub-channel example discussed above or a lower threshold. r 10
DYNAMIC FREQUENCY REUSE
In the proposed dynamic frequency reuse technique each Femtocell base station averages the SINRs across the subcarriers for its fttb Femtocell user with and without the macro interference in a given time duration T as: _______ N vT S/NP1 (1 SINE' -£ajLat1 * ftJxT * E7=1Er=sJNRZ.t) (2) NcT where SINR.kQJt) is the SINR on the F subcarrier at the kth Femtocell user in the n Femtocell S1]VR" is the SINR without macro interferences on the subcarrier at the ktb Femtocell user in the th Femtocell, and N is the number of the total subcarriers used for the kth Femtocell user.
Each Femtocell base station can then separate its users into two set, a first set composed of the outage users of the zfemtocell, whose averaged SINR with macro interference cannot meet the minimal QoS requirement, while their averaged SINR without macro interference meets the minimal QoS requirement, and a second set including other users of the ttbfemtocell The Femtocell base station thus counts the number of outage users. This is illustrated in step 510 in Figure 4. The Femtocell base station then reports the number of "outage" users in the set to the macrocell base station, as illustrated in step S20 of Figure 4.
The macrocell base station is configured to allocate subcarriers for the macrocell and the Femtocells by partitioning the frequency spectrum into two parts Fl and P2, for example as shown in Figure 7. In the example shown in Figure 7 n is a set of subcarriers reserved for the exclusive use by Femtocefl base stations and is intended to be used for the Femtocell users of the set, as illustrated by steps S30 and S40 in Figure 4. The the number of reserved subcarriers in Fl can be derived as: r 11 max(I (3) Flceil N max(lf D÷K And P2 iS F1=N-F2 (4) max(lFl).
where is the largest number of the users of the sets i among the Fenitocell base stations, ceii(x) rounds the elements of x to the nearest integers towards infinity, K is the number of the macro users and N is the total number of available subcarriers.
It can be seen that El is calculated based on the number of the outage users from the one Femtocell most affected by macrocell interference. Since the outage number of Femtocell users from each Femtocell only relies on the averaged SINR across the time duration 7' , the partition scheme can be rendered quasi-static or indeed more dynamic and delay-tolerant by changing the time duration T As shown in Figure 7, the frequency band reserved based on the number Ft can be a contiguous frequency band. Alternatively, the resources reserved based on Fl can be distributed throughout the remaining frequency band.
The spectrum allocation is a frequency reuse scheme among the macrocell base station and the Femtocell base station operating within the area covered by the macroceil, as illustrated in Figure 8. The frequency reuse scheme merely requires each Femtocell base station to communicate the number of outage users in the first set to the macrocell base station.
The macrocell base station in contrast does not have to keep the Femtocell base stations informed of which individual subcarriers have been reserved for use by the Femtocell base stations when reserved subcarriers are contiguous. Instead the macrocell base station may only broadcast the partition to the Femtocell base stations operating within the coverage area of the macrocell base station, as shown as step S50 in Figure 4. It will be appreciated that communicating this partition to the Femtocell base stations will give rise to a very small amount of signalling overhead only. The partition pattern can be predefined, for example, the F] can be composed of the reserved subcarriers with index from 1 to a number, which is broadcasted by the macrocell base station and once the broadcasted number is known, then the femtocell base station can know what exactly the part El is. Alternatively, the Macrocell base station does not need to broadcast the number of reserved subcarriers in El (this is why step S50 is indicated as being optional in Figure 4). Instead the users of the Femtocell or the Femtocell base station can detect these reserved interference free subcarriers in F! through the measurement of the interference, as indicated by step S80 in Figure 4. Signalling overhead can be further reduced in this manner.
Each Femtoceu base stations allocates it frequency resources to its users. The outage users will be assigned to the frequency resources/sub-carriers reserved by the macrocell base station for this purpose in Ft. Since El is computed based on the number of the outage users in the Femtocell that comprises the largest number of users affected by interference from the macrocell base station, those Femtocell base stations that have a number of outage users that is lower than the maximum number of outage users of any Femtocell base station will have fewer outage users to allocate frequency resources/sub-carriers to than reserved frequency resources. It is consequently not necessary for each Femtocell base station to allocate the all of Fl to its outage users. The number of resources up to a maximum number of resourcesn that will be allocated to the Femtocell base station's outage users therefore depends on the number of the Femtocell base station's outage users.
Through the above described spectrum partition method, interference from the macrocell base station to the Femtocell base station is mitigated. While the described method may degrade macrocell throughput to some degree, the overall system throughput can be improved by offloading communication traffic from the macrocell base station to Femtocell base stations. Moreover, the Femtocell users can benefit from a predetermined QOS level. This is advantageous in situations where numerous Femtocell base stations are close to the macrocell base station. r 13
It will be appreciated that, while the above description focuses on the macrocell base station performing the role of a central control unit that is responsible for allocating spectrum for itself and the reporting Femtocell base stations, this function could alternatively be fulfilled by a control unit located in the backhaul, such as MME in LTE.
It will also be appreciated that, while the above description relates to a scenario in which a number of Femtocell base stations is deployed within a rnacrocell the described dynamic frequency reuse scheme is also useable in networks in which only a single Femtocell base station is deployed within the macrocell. It will be appreciated that in this situation the function niax(l does not need to be computed. Instead only a single set -would exist and the number of outage users within this set would simply be used instead of the max(l t I) number
DYNAMIC RESOURCE ALLOCATION
In the following a way of mitigating interference to signal exchange between a user and a macrocell base station created by a Femtocell base station is discussed.
Suppose any user in communication with a macrocell base station enters the territory of any Femtocell and, as a consequence, experiences severe interferences from signals emitted by the Femtocell base station. In this situation the macrocell user reports the experienced interference level in term of SINR to the macrocell base station with which it is in communicative contact.
One method of mitigating the interference the macrocell user experiences from the Femtocell base station is to keep the Femtocell base station informed not to use the resource used by the macrocell user. It will, however, be appreciated that this method would result in large signalling overhead since the macrocell base station has to inform the Femtocell base stations individually. r
In another simple method the macrocell base station could accumulate how many resources all of the macrocell users experiencing interference from Femtocell base stations need and allocates an exclusive resource part/frequency spectrum to the macrocell users experiencing interference from Femtocell base stations and broadcast this exclusive pad to all its Femtocell base stations to prevent the Femtocell base stations from using this exclusive resource part. Such a method would reduce the signalling overhead, but at the cost of lower spectrum efficiency.
The following method provides low signalling overhead with high spectrum efficiency.
Assume a is the required number of interference free subcarriers to meet the minimal QoS requirement with which a macrocell user experiencing interference from a Femtocell base station can communicate with the macrocell base station. In the first step (step S100 in Figure 6), the macrocell base station broadcasts the number a to the all of the Femtocell base stations operating within the macrocell.
In a second step (step 5110 in Figure 6) each Femtocell base station detects the number of the macrocell users in its vicinity/within the Femtocell and calculates (step 5120 in Figure 6) the resources needed for the macrocell users in its vicinity as a,=axr,, where i is the number of macro users falling into the vicinity of the e" Femtocell base station. Depending on the capability of the Femtocell base station, the femtocell base station might not be able to detect the macrocell users in its vicinity and in this case, the macrocell base station will keep the fentocell base station informed of the number z. After that, each Femtocell base station will individually reserve (step 5130 in Figure 6) a number of a. subcarriers (with a, being specific to the Femtocell base station, based on the number of macrocell users within the Femtocell) for the macrocell users.
The Femtocell base station randomly selects the a, subcarriers that are to remain unused.
The macrocell user suffering from interference by the Femtocell base station can detect the unused subcarriers by estimating the SINR across the r 15 subcarriers. Subcarriers that have been identified as having a high SINR (or as having the maximum SINR out of all subcarriers considered) are identified by the macrocell user to the rnacrocell base station. The macrocell base station then assigns the resources that remain unused by the Femtocell base station (as identified in the feedback received from the macrocell users) to those macro users that have suffered interference from the Femtocell base station.
By using randomly distributed unused subcarriers in the above mechanism, there is no need to inform each individual Femtocell base station which part of subcarriers should be reserved for the macrocell users that suffer from interference. The above discussed method can thus greatly reduce signalling overhead as well as interference Femtocell base stations cause macro cell users.
EXAM PLE
Figure 9 shows an example of subcarrier allocation for a heterogeneous network comprising a macrocell base station and three Femtocell base stations located with the macrocell. The illustrated subcarrier allocation reduces interferences Femtocell base stations cause macrocell users as well as interference niacrocell base stations cause users of the Femtocells. As discussed above, interference rnacrocell base stations cause users of the Femtocells is reduced or avoided by splitting the available subcarriers into parts Fl and F2, wherein part Fl is reserved for use by Femtocell base stations. The result of this reserving of subcarriers in part Fl is illustrated in Figure 9. The fact that in the example the same subcarriers are reserved for all Femtocell base stations does not diminish the interference reduction capability if the Femtocells created by the Femtocell base stations do not overlap.
Figure 9 also indicates unused suboarriers in the spectra of the respective Femtocell base stations. As shown in Figure 9, the locations of the unused subcarriers are random as a result of the random allocation of these unused subcarriers by the individual Femtocell base stations. These unused subcarriers are reserved for use by the macrocell base station and can be detected by the macrocell users, as discussed above. r
Discussing the example in more detail now, Figure 9 is based on the assumption that three Fentocell base stations within the macrocell comprise macrocell users that suffer from interference caused by the Femtocell base station. The first Femtocell base station causes undue interference to the communication two users undergo with the macrocell base station. The second and third Femtocell base stations each cause undo interference for one macrocell user. Each 1nterfered macrocell user required two subearriers to communicated with the macrocell base station to meet the least QoS requirement of the macrocell user. As discussed above, this number of required subcarriers has been broadcasted from the macrocell base station to all the Femtocell base station, either through the backhaul or over air.
Femtocell base station #1 has randomly reserved four subcarriers for use by the macrocell base station, while Femtocell base stations #2 and #3 have randomly reserved two subcarriers each for use by the macrocell base station.
In practice, the number of subcarriers required to meet the least QoS requirement of a macrocell user will be much less than the number of subcarriers within F2. Consequently, the likelihood that two Ferntocell base stations reserve the same subcarriers for use by macrocell users is acceptably low.
Figure 10 shows a performance comparison for a heterogeneous network comprising 40 Femtocell base stations in a macrocell. 50% of the Femtocell base stations are assumed to be within 100 m from the macrocell base station. Two Femtocell users are moreover assumed to be present within each Femtocell. Ten macrocell users are assumed to be served by the macrocell base station. 20% of the macrocell users are assumed to be located within a Femtocell, Both of Figures 8 and 9 show performance criteria for a first method of operating this homogeneous network, wherein the above discussed methods are not used and a second method in which the above discussed methods are used, Figure 10 plots CDF over average cell throughput and Figure 10 plots CDF over average user throughput. As can be seen from these two figures, r both the averaged cell throughput and the averaged user throughput improve significantly when the disclosed methods are used.
Figure 11 shows the structure of a Femtocell base station 200 suitable for use in a preferred embodiment. The Femtocell base station 200 comprises an interface 210 to the backhaul via which it can communicate with the macrocell base station or with a control unit that is responsible for allocating transmission resources of the macrocell base station. The Femtocell base station moreover comprises a transceiver 220 for communicating with Femtocell users as well as a processor 230. The processor 230 and the transceiver 220 can jointly evaluate QoS for individual Femtocell users or determine the number of macrocell users within the coverage area of the Femtocell. The processor can moreover determine, based on information received from the macrocell base station or its resource allocation control unit, how many transmission resources are to be blocked for use by the macrocell base station and to randomly select these transmission resources.
It will be appreciated that, although the above discussed methods are discussed with reference to Femtocell base stations deployed in a macrocell base station, it is also applicable to other network architectures, for example network architectures in which cognitive radio is deployed within a macrocell.
While certain embodiments have been described, the embodiments have been presented by way of example only, an area not intended to limit the scope of the inventions. Indeed, the novel methods, apparatus and systems described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the methods and systems described herein may be made without departing from the spirit of the inventions. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the inventions. r 16
Claims (1)
- <claim-text>CLAIMS: 1. A method of operating a heterogeneous network comprising a first base station with a first area of coverage and a second base stations with a second area of coverage, wherein the first and second areas of coverage at least partially overlap and wherein the first and second base stations share operating bandwidth, the method comprising: determining, within the second base station, a number of users in communicative contact with the second base station for which a minimum quality of service, hereinafter referred to as QoS, requirement is not fulfilled and transmitting a message comprising the determined number to the first base station or to a control unit controlling the allocation of transmission resources within the first base station; within the first base station or the control unit receiving the message, determining based on the determined number of users of the reserved transmission resources and preventing the use of the reserved transmission resources by the first base station.</claim-text> <claim-text>2. A method according to Claim 1, further comprising, within the first base station or the control unit, transmitting a message identifying the reserved transmission resources to the second base station.</claim-text> <claim-text>3. A method according to Claim 1 or 2, wherein the reserved transmission resources are reserved sub-carriers or reserved sub-channels.</claim-text> <claim-text>4. A method according to Claim 1, 2 or 3, wherein determining the number of transmission resources includes: determining a percentage that the received number of users of the second base station represents out of a sum of the total number of users of the first base station and of the received number of users of the second base station; and calculating the determined number of transmission resources tc be a fraction of the total number of available transmission resources that is substantially equal to the determined percentage.</claim-text> <claim-text>S. A method according to any preceding claim, wherein the second base station determines the said number of users by comparing, for each user in communicating with the second base station, the signa$ to interference noise ration, hereinafter referred to as SINR, across the transmission resources used by the user with and without interference from the first base station and includes a user in the number of users if the SINR is below a predetermined threshold if there is interference from the first base station and above the threshold if there is no interference from the first base station.</claim-text> <claim-text>6. A method according to any preceding claim, wherein the network comprises one or more further base stations with coverage areas that at least partially overlap with the first coverage area, the first base station sharing operating bandwidth with the one or more further base stations, the method comprising: determining, within each of the one or more further base stations, a number of users in communicative contact with the further base station for which a minimum quality of service requirement is not fulfilled and transmitting a message comprising the determined number to the first base station or to a control unit controlling the allocation of transmission resources within the first base station; wherein the first base station or the control unit determines the transmission resources to be reserved based the highest determined number received from any of the second and one or more further base stations.</claim-text> <claim-text>7. A method of operating a second base station having a coverage area that is at least partially located within the coverage area of a first base station, wherein the first and second base stations share operating bandwidth, the method comprising: determining a number of users in communicative contact with the second base station for which a minimum quality of service requirement is not fulfilled and transmitting a message comprising the determined number onto a data path; and receiving a message indicating the transmission resources that the first base station has been precluded from using and allocating reserved transmission resources to users for which the minimum quality of service requirement is not fulfilled.</claim-text> <claim-text>8. A method of operating a transmission resource allocation apparatus for a base station that shares coverage area and operating bandwidth with a further base station, the method comprising: r 20 receiving a message indicating an number of users of the other base station and reserving transmission resources for use by the other base station based on the number.</claim-text> <claim-text>9. A base station comprising a transceiver connectable to a transmission path and a microprocessor, the microprocessor operative to: determine whether or not communication sessions with users of the base station fulfil a minimum quality of service requirement; transmit, using said transceiver, a message onto the transmission path indicating a number of users for which the minimum quality of service requirement is not fulfilled; and re-allocate transmission resources to the users for which the minimum quality of service requirement is not fulfilled following receipt of an indication of the reserved transmission resources.</claim-text> <claim-text>10. A transmission resource allocation apparatus for a base station that shares coverage area and operating bandwidth with a further base station, the apparatus comprising: an interface operative to: receive a message indicating an number of users of the other base station; block a number of transmission resources from use by the base station based on the number; and transmit a message identifying the blocked transmission resources.</claim-text> <claim-text>11. A system comprising a transmission resource allocation apparatus according to Claim 10, configured to allocate the transmission resources of a first base station, and a further base station according to Claim 9.</claim-text> <claim-text>12. A method of operating a heterogeneous network comprising a first base station with a first area of coverage and a second base stations with a second area of coverage, wherein the first and second areas of coverage at least partially overlap and wherein the first and second base stations share operating bandwidth, the method comprising: within the second base station: r 21 detecting a number of users of the first base station that are located within the coverage area of the second base station; randomly selecting a number of transmission resources that would be available to the second base station; and preventing the second base station from using the selected transmission resources; wherein the number of selected transmission resources is the sum of all transmission resources required by the users of the first base station to communicate with the first base station.</claim-text> <claim-text>13. A method according to Claim 12, further comprising, receiving at the second base station from the first base station a number of transmission resources required by a user of the first base station and multiplying the received number of required transmission resources with the determined number of users.</claim-text> <claim-text>14. A method of operating a base station with a coverage area that is at least partially inside the coverage area of another base station, the base station and the other base station sharing operating bandwidth, the method comprising: detecting a number of users of the other base station that are located within the coverage area of the base station; and randomly selecting a number of transmission resources that would be available to the base station for use; and precluding the base station from using the selected transmission resources; wherein the number of selected transmission resources is the sum of all transmission resources required by the users of the other base station for communication with the other base station.</claim-text> <claim-text>15. A method according to Claim 14, further comprising receiving a message from the other base station comprising an indication of the number of transmission resources required by a user of the other base station and calculating the number of transmission resources by multiplying the received number of required transmission resources with the detected number of users of the other base station.</claim-text> <claim-text>16. A heterogeneous network comprising a first base station with a first area of coverage and a second base stations with a second area of coverage, wherein the first r 22 and second areas of coverage at least partialiy overlap and wherein the first and second base stations share operating bandwidth, wherein the second base station is operative to: detect a number of users of the first base station that are located within the coverage area of the second base station; randomly select a number of transmission resources that would be available to the second base station; and prevent the second base station from using the selected transmission resources; wherein the number of selected transmission resources is the sum of all transmission resources required by the users of the first base station to communicate with the first base station.</claim-text> <claim-text>17. A base station comprising a transceiver and a controller, the controller operative to, using the transceiver, detect a number of users of another base station that are located within the coverage area of the base station, in use; the controller further operative to randomly select a number of transmission resources that would be available to the base station for use and to preclude the base station from using the selected transmission resources; wherein the number of selected transmission resources is the sum of all transmission resources required by the users of the other base station for communication with the other base station.</claim-text>
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB1119746.4A GB2496844A (en) | 2011-11-15 | 2011-11-15 | Resource allocation in base stations with shared operating bandwidth and overlapping coverage areas |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB1119746.4A GB2496844A (en) | 2011-11-15 | 2011-11-15 | Resource allocation in base stations with shared operating bandwidth and overlapping coverage areas |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| GB201119746D0 GB201119746D0 (en) | 2011-12-28 |
| GB2496844A true GB2496844A (en) | 2013-05-29 |
Family
ID=45444197
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB1119746.4A Withdrawn GB2496844A (en) | 2011-11-15 | 2011-11-15 | Resource allocation in base stations with shared operating bandwidth and overlapping coverage areas |
Country Status (1)
| Country | Link |
|---|---|
| GB (1) | GB2496844A (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103906218A (en) * | 2014-04-04 | 2014-07-02 | 东南大学 | Service resource control method in heterogeneous network convergence system |
| CN111093210A (en) * | 2013-07-17 | 2020-05-01 | 三菱电机株式会社 | Communication system |
Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20090131065A1 (en) * | 2007-11-16 | 2009-05-21 | Qualcomm Incorporated | Time reservation for a dominant interference scenario in a wireless communication network |
| WO2009077519A1 (en) * | 2007-12-19 | 2009-06-25 | Nokia Siemens Networks Oy | Radio system configuration |
| US20090221295A1 (en) * | 2008-03-03 | 2009-09-03 | Ntt Docomo Inc. | OFDMA-based co-channel femtocell |
| WO2009129413A2 (en) * | 2008-04-16 | 2009-10-22 | Qualcomm Incorporated | Methods and apparatus for uplink and downlink inter-cell interference coordination |
| EP2224766A1 (en) * | 2009-02-27 | 2010-09-01 | Industrial Technology Research Institute | Method, apparatus and system for interference avoidance in a femtocell network |
| US20110034174A1 (en) * | 2009-08-04 | 2011-02-10 | Motorola, Inc. | In a radio network environment, reducing interference among overlapping cells |
-
2011
- 2011-11-15 GB GB1119746.4A patent/GB2496844A/en not_active Withdrawn
Patent Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20090131065A1 (en) * | 2007-11-16 | 2009-05-21 | Qualcomm Incorporated | Time reservation for a dominant interference scenario in a wireless communication network |
| WO2009077519A1 (en) * | 2007-12-19 | 2009-06-25 | Nokia Siemens Networks Oy | Radio system configuration |
| US20090221295A1 (en) * | 2008-03-03 | 2009-09-03 | Ntt Docomo Inc. | OFDMA-based co-channel femtocell |
| WO2009129413A2 (en) * | 2008-04-16 | 2009-10-22 | Qualcomm Incorporated | Methods and apparatus for uplink and downlink inter-cell interference coordination |
| EP2224766A1 (en) * | 2009-02-27 | 2010-09-01 | Industrial Technology Research Institute | Method, apparatus and system for interference avoidance in a femtocell network |
| US20110034174A1 (en) * | 2009-08-04 | 2011-02-10 | Motorola, Inc. | In a radio network environment, reducing interference among overlapping cells |
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN111093210A (en) * | 2013-07-17 | 2020-05-01 | 三菱电机株式会社 | Communication system |
| CN111093210B (en) * | 2013-07-17 | 2023-02-17 | 三菱电机株式会社 | Communication system |
| CN103906218A (en) * | 2014-04-04 | 2014-07-02 | 东南大学 | Service resource control method in heterogeneous network convergence system |
| CN103906218B (en) * | 2014-04-04 | 2017-04-05 | 东南大学 | Service resources control method in isomerization network fusion system |
Also Published As
| Publication number | Publication date |
|---|---|
| GB201119746D0 (en) | 2011-12-28 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| JP6686034B2 (en) | Bandwidth Occupancy Techniques for Transmission in Unlicensed Spectrum | |
| Mao et al. | Adaptive soft frequency reuse for inter-cell interference coordination in SC-FDMA based 3GPP LTE uplinks | |
| KR101498293B1 (en) | Method of allocating radio resource and transmitting neighbor information in wireless communication system | |
| EP3094123B1 (en) | Measurement-assisted dynamic frequency-reuse in cellular telecommuncations networks | |
| CN101854635B (en) | The sending method of inter cell interference coordination indication information and device | |
| US7912475B2 (en) | Dynamic allocation of radio resources | |
| JP5496406B2 (en) | Base station and processor | |
| US9526108B2 (en) | Apparatus and method for mitigation/removal of interference between macro-cell and femto-cell | |
| US9844048B2 (en) | Resource allocation system and control method | |
| CN101827370A (en) | Frequency reuse control method, system and base station equipment based on OFDM (Orthogonal Frequency Division Multiplexing) | |
| US8483038B2 (en) | Radio communication apparatus and radio communication method | |
| CN104938008A (en) | Resource allocation in radio communication network | |
| US20130172001A1 (en) | Method for inter-cell interference coordination in a cellular communication network, network element of a cellular communication network, and cellular communication network | |
| US10477570B2 (en) | Advance communication resource notification in wireless communication systems having overlapping service areas | |
| US9674742B2 (en) | Exploiting almost blank subframes for inter-cell scheduling | |
| GB2496844A (en) | Resource allocation in base stations with shared operating bandwidth and overlapping coverage areas | |
| Kuo et al. | Adaptive Smart Power Control Algorithm for LTE downlink cross-tier interference avoidance | |
| JP5712328B2 (en) | Wireless communication system, base station and control method thereof | |
| KR20120105918A (en) | Method for sharing radio resources between femtocells and macrocells in mobile wireless access systems | |
| Eguizábal et al. | Throughput gain by hybrid TDM/FDM & spatial reuse of resources among nodes and links for inband relaying | |
| Eguizábal-Alonso et al. | Joint Spatial Relay Distribution and Resource Allocation & ICIC Strategies for Performance Enhancement for Inband Relay LTE–A Systems | |
| Cao et al. | Downlink Spectrum Allocation for Macro-Femto Networks |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| WAP | Application withdrawn, taken to be withdrawn or refused ** after publication under section 16(1) |