WO2015198103A1 - Coordination de planification de débit dans un réseau cellulaire sans fil - Google Patents

Coordination de planification de débit dans un réseau cellulaire sans fil Download PDF

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Publication number
WO2015198103A1
WO2015198103A1 PCT/IB2014/062689 IB2014062689W WO2015198103A1 WO 2015198103 A1 WO2015198103 A1 WO 2015198103A1 IB 2014062689 W IB2014062689 W IB 2014062689W WO 2015198103 A1 WO2015198103 A1 WO 2015198103A1
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wireless communication
communication devices
wireless
network node
scheduling
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Andres Reial
Sairamesh Nammi
Yi-Pin Eric Wang
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Telefonaktiebolaget LM Ericsson AB
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Telefonaktiebolaget LM Ericsson AB
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    • 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
    • H04W72/542—Allocation or scheduling criteria for wireless resources based on quality criteria using measured or perceived quality
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W72/00—Local resource management
    • H04W72/12—Wireless traffic scheduling
    • H04W72/121—Wireless traffic scheduling for groups of terminals or users
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W72/00—Local resource management
    • H04W72/12—Wireless traffic scheduling
    • H04W72/1215—Wireless traffic scheduling for collaboration of different radio technologies

Definitions

  • the proposed technology generally relates to scheduling of wireless communication devices in a wireless cellular network, and in particular to rate scheduling coordination of wireless communication devices in a wireless cellular network.
  • a scheduler controls assignment of resources among the users for both uplink and downlink and also determines the appropriate data rate to be used for each transmission.
  • the condition of the channel for each user is a consideration in determining the most efficient allocation of resources.
  • a scheduler may be configured to give scheduling priority to user equipment (UEs) with the highest channel quality.
  • the quality of the signal received by a given user is dependent upon a number of factors, including the channel quality from the serving node, the level of interference from other cells and nodes, and the noise level.
  • a scheduler will typically try to match the modulation, coding, and other signal/protocol parameters to the signal quality. For instance, when signal quality is low, a scheduler may reduce the coding rate or select a lower-order modulation scheme to increase tolerance to interference and raw bit error rates or to otherwise improve robustness.
  • UEs may be configured to report Channel Quality Indicators (CQIs) to assist the scheduler.
  • CQI reports are derived from the downlink received signal quality and are often based on measurements of the downlink reference signals.
  • the LTE standard is primarily designed to operate under the presumption that the entire spectrum is available in each cell; in other words that the same time-frequency resources may be used in neighbouring cells with limited interference. However, this is not always true in practice, particularly at the cell-edge. Transmissions intended for a first user in a first cell are often overheard by a second, unintended user in a second cell.
  • Fig. 1 The stripe-covered region in Fig. 1 is a region between an outer circle and an inner circle around an LPN.
  • the inner circle represents an area where the received power from the LPN is higher than that from the macro base station.
  • the outer circle represents an area where the path loss to the LPN is smaller than that to the macro base station.
  • the stripe-covered area is often referred to as the imbalance area, which potentially could be an LPN range-expansion area because from the uplink perspectives the network still would like the terminal to be served by the LPN within this area.
  • the imbalance area potentially could be an LPN range-expansion area because from the uplink perspectives the network still would like the terminal to be served by the LPN within this area.
  • terminals at the outer edge of such an imbalance zone experience very large received power difference between the macro and LPN layers. For example, if the transmit power levels are 40 watt and 1 watt for the macro and LPN, respectively, such power difference can be as high as 16 dB.
  • the LPN terminal is subject to very severe interference from the Macro base station.
  • Inter-cell interference coordination is supported via the eNodeB-to-eNodeB X2 interface.
  • Each cell can signal the high- power resource blocks in the frequency domain, or time domain, to its neighboring cells. This allows the neighboring cells to schedule cell-edge users avoiding these high-power resource blocks.
  • Such a mechanism can be used to reduce the impact of inter-cell interference.
  • RRS Restricted Resource Subframes
  • RRS Restricted Resource Subframes
  • the idea is to restrict the modulation order and number of High Speed Physical Downlink Shared Channel (HS-PDSCH) channelization codes in special RRS in the macro cell.
  • HS-PDSCH High Speed Physical Downlink Shared Channel
  • Quadrature Phase Shift Keying instead of 16-QAM (Quadrature Amplitude Modulation) makes it easier for the LPN UE to detect the interfering signal more reliably. Once the interfering signal is detected more reliably, better cancellation efficiency can be achieved.
  • using 5 codes instead of 15 HS-PDSCH codes increases the power allocated to each macro HS-PDSCH symbol, resulting in higher detection reliability by the "victim" LPN UE (UE receiving signals intended for another UE) and somewhat improved cancellation efficiency.
  • Rate scheduling coordination has also been proposed where, instead of scheduling the macro UE according to its channel quality towards the macro cell, it is scheduled with a rate that is decodable at the LPN UE location to enable interference cancellation (IC) - typically a rate lower than allowed by conventional scheduling.
  • IC interference cancellation
  • ICIC or RRS may be seen as a trivial form of rate coordination, where however the scheduled macro rate is lowered or zeroed without regard to its instantaneous interference impact towards the LPN UE. Furthermore, both have a negative impact on the macro throughput.
  • the macro rate is lowered adaptively to enable a LPN rate increase.
  • the macro average rate is decreased compared to the conventional scheduling solution and thus the sum rate of macro and LPN UEs does not improve in many scenarios.
  • An aspect of the embodiments relates to a method performed by a wireless network node for scheduling wireless communication devices in a wireless cellular network.
  • the method comprises the step of selecting, at each scheduling instant, and based on scheduled transmission rates for the wireless communication devices, at least one first wireless communication device from a first set of wireless communication devices being served by a first wireless network node in the wireless cellular network, and at least one second wireless communication device from at least one second set of wireless communication devices, each second set of wireless communication devices being served by a respective second wireless network node in the wireless cellular network, and each of the second wireless communication devices being capable of interference cancellation, where the selected wireless communication devices are to be co-scheduled at each respective scheduling instant.
  • the wireless communication devices are selected such that a rate metric for the selected wireless communication devices is maximized over one or more scheduling instants, where the rate metric is a combination of achievable rates for the selected wireless communication devices, the achievable rates being based on achievable interference cancellation efficiency of signals from the first wireless network node causing interference at the at least one second wireless communication device.
  • the achievable interference cancellation efficiency is determined based on link quality information from the at least one second wireless communication device representing link quality between the at least one second wireless communication device and the first wireless network node, and scheduled transmission rate for the at least one first wireless communication device.
  • the wireless network node configured to enable scheduling of wireless communication devices in a wireless cellular network.
  • the wireless network node is configured to select, at each scheduling instant, and based on scheduled transmission rates for the wireless communication devices, at least one first wireless communication device from a first set of wireless communication devices being served by a first wireless network node in the wireless cellular network, and at least one second wireless communication device from at least one second set of wireless communication devices, each second set of wireless communication devices being served by a respective second wireless network node in the wireless cellular network, and each of the second wireless communication devices being capable of interference cancellation, where the selected wireless communication devices are to be co-scheduled at each respective scheduling instant.
  • the wireless communication devices are selected such that a rate metric for the selected wireless communication devices is maximized over one or more scheduling instants, wherein the rate metric is a combination of achievable rates for the selected wireless communication devices, the achievable rates being based on achievable interference cancellation efficiency of signals from the first wireless network node causing interference at the at least one second wireless communication device.
  • the achievable interference cancellation efficiency is determined based on link quality information from the at least one second wireless communication device representing link quality between the at least one second wireless communication device and the first wireless network node, and scheduled transmission rate for the at least one first wireless communication device.
  • Yet another aspect of the embodiments relates to a computer program comprising instructions, which when executed by at least one processor, cause the processor or processors to select, at each scheduling instant, and based on scheduled transmission rates for the wireless communication devices, at least one first wireless communication device from a first set of wireless communication devices being served by a first wireless network node in the wireless cellular network, and at least one second wireless communication device from at least one second set of wireless communication devices, each second set of wireless communication devices being served by a respective second wireless network node in the wireless cellular network, and each of the second wireless communication devices being capable of interference cancellation, where the selected wireless communication devices are to be co- scheduled at each respective scheduling instant.
  • the wireless communication devices are selected such that a rate metric for the selected wireless communication devices is maximized over one or more scheduling instants, where the rate metric is a combination of achievable rates for the selected wireless communication devices, the achievable rates being based on achievable interference cancellation efficiency of signals from the first wireless network node causing interference at the at least one second wireless communication device.
  • the achievable interference cancellation efficiency is determined based on link quality information from the at least one second wireless communication device representing link quality between the at least one second wireless communication device and the first wireless network node, and scheduled transmission rate for the at least one first wireless communication device.
  • the wireless network node comprises a selecting module configured to select, at each scheduling instant, and based on scheduled transmission rates for the wireless communication devices, at least one first wireless communication device from a first set of wireless communication devices being served by a first wireless network node in the wireless cellular network, and at least one second wireless communication device from at least one second set of wireless communication devices, each second set of wireless communication devices being served by a respective second wireless network node in the wireless cellular network, and each of the second wireless communication devices being capable of interference cancellation, where the selected wireless communication devices are to be co-scheduled at each respective scheduling instant.
  • the wireless communication devices are selected such that a rate metric for the selected wireless communication devices is maximized over one or more scheduling instants, where the rate metric is a combination of achievable rates for the selected wireless communication devices, the achievable rates being based on achievable interference cancellation efficiency of signals from the first wireless network node causing interference at the at least one second wireless communication device.
  • the achievable interference cancellation efficiency is determined based on link quality information from the at least one second wireless communication device representing link quality between the at least one second wireless communication device and the first wireless network node, and scheduled transmission rate for the at least one first wireless communication device.
  • An advantage of the proposed technology is that increased interference cancellation efficiency is achieved together with improved transmission rates for the scheduled wireless devices.
  • Fig. 1 is an illustration of an example of inter-cell interference in a heterogeneous network.
  • Fig. 2 is a schematic illustration of a simulation scenario for analysis of network assisted interference cancellation.
  • Fig. 3 is a schematic illustration of some examples of paring arrangements according to some example embodiments.
  • Fig. 4 is a schematic flow diagram illustrating an example of a method performed by a wireless network node for scheduling wireless communication devices in a wireless cellular network according to an embodiment.
  • Fig. 5 is a schematic diagram illustrating an example of a wireless network node configured to enable scheduling of wireless communication devices in a wireless cellular network according to an embodiment.
  • Fig. 6 is a schematic block diagram illustrating an example of a wireless network node configured to enable scheduling of wireless communication devices in a wireless cellular network according to an alternative embodiment.
  • downlink data throughput in a wireless network may be limited by inter-cell interference.
  • the effect of inter-cell interference is more pronounced for users at the edge of the serving cell or when a user is in the so-called low-power node (LPN) range expansion area, in which the received power level from the macro node may be higher than that from the serving LPN.
  • LPN low-power node
  • Rate scheduling coordination has been previously proposed where, instead of scheduling the macro UE according to its channel quality towards the macro cell, it is scheduled with a rate that is decodable at the LPN UE location to enable interference cancellation (IC) - typically a rate lower than allowed by conventional scheduling.
  • IC interference cancellation
  • the impact of inter-cell interference depends closely on the interfered (or "victim") terminal's ability to mitigate interference.
  • the LPN UE may attempt to first decode the macro signal and cancel it before decoding its desired signal. A strong interference signal can thus be harmless provided that it can be decoded correctly and removed at a victim terminal.
  • Network assisted interference cancellation (NAIC) is being considered in 3GPP for both LTE and High Speed Packet Access (HSPA). The concept is to have the network send assistance information to the UE to enable the UE to perform efficient interference cancellation. The concept was first described in Refs. [1 ] and [2].
  • y is the macro interfering signal and y is the reconstructed signal at the victim UE after decoding and reconstruction.
  • the victim UE can achieve cancellation efficiency close to 1 .
  • Fig. 1 illustrates a scenario where NAIC could be beneficial.
  • a wireless communication device 300 such as a UE, served by a wireless network node 30, such as an LPN, in the range expansion area (stripe covered area) experiences strong interference from another wireless network node 20, such as a macro node.
  • the network provides certain information about the interference signal, e.g. UE ID, modulation format, transport block size, etc., to the victim UE, the victim UE may be able to cancel the interfering macro signal and boost its achievable data rate in the LPN downlink.
  • the interference signal e.g. UE ID, modulation format, transport block size, etc.
  • Fig. 2 shows a simplified heterogeneous networks model with one LPN and one dominant macro. This is a simplified layout of a heterogeneous network of 57 macro cells. The other macro and LPN cells are not shown, but their interference is captured as described below.
  • UE locations Twelve possible UE locations are created and shown in Fig. 2 (marked from L1 to L12).
  • ISD inter-site distance
  • Received signal power levels at each of the 12 UE locations are shown in Table 1 , where macro 2 (not shown in Fig. 2) is the strongest received macro power level among those 56 macros not shown in Fig. 2 (lor is defined as the total transmit power at the eNodeB antenna connector and loc is defined as the total noise power at UE antenna connector). Interference from other macros and LPNs not listed in Table 1 is included in loc. According to Fig. 2 and Table 1 , UE at location L7 sees its received signal dominated by the macro, where UE at e.g. location L6 sees its received signal dominated by the LPN.
  • Table 2 shows the gains of NAIC over blind IC in terms of LPN UE throughput.
  • the LPN UE is at location 1
  • the scheduled macro UE is at location L12
  • the LPN UE enjoys a high NAIC benefit (50% gain in UE throughput).
  • the scheduled macro UE is at location L7
  • the LPN UE sees a small NAIC benefit (5% in UE throughput).
  • scheduling coordination may improve NAIC gains.
  • ICIC or RRS may be seen as a trivial form of rate coordination, where however the scheduled macro rate is not dynamically chosen based on the decodability at the LPN UE and the cancellation efficiency is not maximized. Furthermore, both have a negative impact on the macro throughput. In Ref. [4], it was shown that up to 67% loss in macro UE throughput could be a result of RRS.
  • SINR Signal to Interference plus Noise Ratio
  • the increase of the LPN rate is offset by the decrease of the macro rate and the sum rate of macro and LPN UEs does not improve in many scenarios.
  • the transmission data rate to a scheduled user in a given cell may be reduced to ensure effective interference cancellation performance at the receiver of a co-scheduled user in another cell.
  • the rates of the co-scheduled users are selected in order to enable the UEs to completely cancel interference caused by the unintended signal.
  • Fig. 4 is a schematic flow diagram illustrating an example of a method performed by a wireless network node for scheduling wireless communication devices in a wireless cellular network according to an embodiment.
  • the method comprises the step S10 of selecting, at each scheduling instant, and based on scheduled transmission rates for the wireless communication devices, at least one first wireless communication device from a first set of wireless communication devices being served by a first wireless network node in the wireless cellular network, and at least one second wireless communication device from at least one second set of wireless communication devices, each second set of wireless communication devices being served by a respective second wireless network node in the wireless cellular network, and each of the second wireless communication devices being capable of interference cancellation, where the selected wireless communication devices are to be co- scheduled at each respective scheduling instant.
  • the wireless communication devices are selected such that a rate metric for the selected wireless communication devices is maximized over one or more scheduling instants, where the rate metric is a combination of achievable rates for the selected wireless communication devices, the achievable rates being based on achievable interference cancellation efficiency of signals from the first wireless network node causing interference at the at least one second wireless communication device.
  • the achievable interference cancellation efficiency is determined based on link quality information from the at least one second wireless communication device representing link quality between the at least one second wireless communication device and the first wireless network node, and scheduled transmission rate for the at least one first wireless communication device.
  • the wireless communication devices are selected for co-scheduling in order to maximize the transmission rates for the co-scheduled wireless communication devices, without necessarily achieving complete cancellation of the interfering signal.
  • the rate for the at least one second wireless communication device may for instance be calculated by taking into account the achievable interference cancellation efficiency, which may for instance be determined based on the scheduled transmission rate for the at least one first wireless communication device together with link quality information regarding link quality between the at least one second wireless communication device and the first wireless network node.
  • the link quality information comprises channel quality indicator, CQI, information
  • the rate metric may be calculated in one of the following manners:
  • the wireless cellular network is a heterogeneous network
  • each of the respective second wireless network nodes 30; 40 is a low power node, LPN
  • the first wireless network node 20 is a macro node.
  • LPN low power node
  • the LPN cell may then be interpreted more generally as a cell serving victim UEs and the macro cell as an interfering neighbour cell.
  • the wireless communication devices are user equipment, UE.
  • the wireless cellular network is a Long Term Evolution, LTE, network.
  • the rate metric is further based on duration of time that at least one of the selected wireless communication devices has been waiting in a scheduling queue at the first and second wireless network nodes.
  • the rate metric is further based on a proportional-fair criterion for the selected wireless communication devices.
  • the selecting is based on forming a group comprising one wireless communication device from the first set of wireless communication devices, and one out of several wireless communication devices from each of the at least one second set of wireless communication devices, at each scheduling instant.
  • the selecting is based on forming a group comprising one wireless communication device from each of the at least one second set of wireless communication devices, and one out of several wireless communication devices from the first set of wireless communication devices, at each scheduling instant.
  • the selecting is based on forming a group comprising one out of several wireless communication devices from the first set of wireless communication devices, and one out of several wireless communication devices from each of the at least one second set of wireless communication devices, at each scheduling instant.
  • the selecting is based on forming several groups comprising one out of several wireless communication devices from the first set of wireless communication devices, and one out of several wireless communication devices from each of the at least one second set of wireless communication devices, to be used respectively at several scheduling instants.
  • the above described embodiments of selection strategies are illustrated in Fig. 3, and will also be further exemplified below.
  • a UE pair is selected out of M 1 ⁇ 1 LPN UEs and 0 > 1 macro UEs available, where M 1 + M 0 > 2.
  • the pair ⁇ n 0 *, n ⁇ ) may be scheduled such that
  • a penalty function may in one embodiment be added to the rate metric that penalizes long waiting time in the priority queue:
  • ⁇ n 0 *, n ) arg max p ⁇ (t - t ⁇ p ⁇ ft - t ⁇ R t ⁇ n 0 , n ⁇ , n 0 G t/[ 0) n x G t/[ 1 ⁇
  • the penalty function is preferably a monotonically non-decreasing function and may be UE-specific, to account e.g. for different subscription types or Quality of Service (QoS) requirements.
  • QoS Quality of Service
  • a proportional-fair criterion can be used, for example the sum proportional fairness metric as illustrated below:
  • J (n 0 ) and ⁇ n-J are the average throughputs, measured at time t, of UEs with indices and m ⁇ , respectively.
  • the actual throughput A k n 0 ) is 0, if UE n 0 is not scheduled in the macro cell during time instant t-k, and equal to R ⁇ n 0 , if UE n 0 is scheduled during time instant t-k.
  • the actual throughput is 0, if UE n x is not scheduled during time instant t-k, and equal to R ⁇ k (n 0 , if UE n is scheduled during time instant t-k.
  • one of the UE groups may be eliminated and a fixed UE from that cell selected instead, e.g. the UE that would have been scheduled according to a state-of-the-art scheduling approach at time t.
  • Typical scheduling patterns from this scheduling approach are that if the macro cell Channel Quality Indicator (CQI) with respect to the LPN UE is high, a low-to-medium- rate macro UE is selected for pairing, since full decoding of the interferer is possible. If the macro CQI is low, a high-rate macro UE is selected, since the interferer cannot be decoded at any rate.
  • CQI Channel Quality Indicator
  • the pairwise rate is some combination of macro and LPN rates that may be decoded simultaneously at the macro and LPN UEs respectively.
  • the details of how the rate metric is formed depend on the rate optimization criterion. Some examples are:
  • the post-IC SINR estimate for the victim UE is obtained by removing the corresponding fraction of macro interference in the serving-cell SINR computation. In one embodiment, it is obtained as:
  • the LPN UE rate is determined as:
  • the macro UE rate is chosen so that it may be fully decoded at the LPN UE (and of course at the macro UE):
  • the post-IC SINR estimate for the victim UE is obtained by fully removing the macro interference in the serving-cell SINR computation. In one embodiment, it is obtained as
  • the sum rate may be maximized by the macro-optimized rate combination above, the LPN-optimized rate combination above, or by some rate combination where the macro rate lies between the two bounds.
  • the sum rate is optimized by the following sequence:
  • some mechanisms for providing the network with CQI information for estimating the IC impact may be for example legacy or new modes of CQI reporting, or standard UE measurement reports, such as for example Received Signal Code Power (RSCP), Received Signal Strength Indicator (RSSI), or SINR.
  • RSCP Received Signal Code Power
  • RSSI Received Signal Strength Indicator
  • SINR SINR
  • the LPN have 3 active UEs, out of which UE has been selected for scheduling at time t.
  • the network will then select one out of the 20 macro UEs to be scheduled together with the LPN UE ⁇ so as to maximize the sum rate, subject to the scheduling delay penalty term.
  • ⁇ (At) At 1 - 5 .
  • the LPN interference to macro UEs is negligible and the macro rate does not depend on the simultaneously scheduled LPN rate.
  • At t - as used below, and 3 ⁇ 4 .is known to the scheduler at run time as the time instant the UE first appeared in the priority queue.
  • the different rates are determined by the transport block length in the chosen modulation and coding scheme (MCS), i.e. to get a certain rate, the scheduler selects the appropriate transport format/MCS.
  • MCS modulation and coding scheme
  • the LPN UE ⁇ CQI with respect to the LPN cell may be SINR ⁇ m ⁇ and with respect to the macro cell
  • the last CQI quantity is not required in legacy implementations.
  • the current embodiment if we don't assume new CQI signalling, it may be estimated e.g. from the average SINR that the LPN UE has reported with respect to the macro cell as part of its mobility measurements.
  • the rate terms of interest are then fetched from a pre-computed lookup table L as and where SINR w ' mod (m ⁇ in turn is estimated based on the SINR without cancellation and the anticipated cancellation efficiency when the macro rate is i? t 0) ⁇ n 0) ): i? t (0) ⁇ n )) )
  • the LUT L is part of legacy scheduler design where the MCS (transport format) is selected as a function of the CQI (essentially SINR) report.
  • F(-) and ?( ⁇ ) may be implemented as lookup tables or closed-form expressions.
  • the macro UE k * maximizing the sum rate metric is selected to be scheduled together with the LPN UE
  • the LPN UE then performs IC of the macro cell signal scheduled for UE k * as part of the process of demodulating and decoding its signal from the LPN
  • the victim UE is assumed to employ an IC receiver.
  • Preferably post-decoding IC is used to maximize performance, and some form of network assistance or related signalling is provided for the UE to obtain interfering signal transport format information required for decoding.
  • the invention is also applicable to scenarios where the victim UE applies pre-decoding IC.
  • the IC type is reflected in the IC efficiency lookup table (LUT), containing the ⁇ values.
  • the idea of the invention may be naturally applied to scenarios with more than one LPN cell per macro cell.
  • the configuration B(LPN) with a fixed macro UE is particularly amenable to such scenarios, since the search for a proper LPN UE pairing may be done on a per-LPN cell basis by searching over each of the K LPN cells and the sets
  • Scheduling and CQI information communication between the cells may be implemented using e.g. the X2 interface or a proprietary interface in a main-remote configuration.
  • the invention has been illustrated using the example of a heterogeneous network where a macro cell is the dominant interferer towards one or more LPN cells.
  • the concept of the invention also applies to other deployment scenarios.
  • the LPN cell may then be interpreted more generally as a cell serving victim UEs and the macro cell as an interfering neighbour cell.
  • the non-limiting terms "User Equipment” and “wireless communication device” may refer to a mobile phone, a cellular phone, a Personal Digital Assistant, PDA, equipped with radio communication capabilities, a smart phone, a laptop or Personal Computer, PC, equipped with an internal or external mobile broadband modem, a tablet PC with radio communication capabilities, a target device, a device to device UE, a machine type UE or UE capable of machine to machine communication, i PAD, customer premises equipment, CPE, laptop embedded equipment, LEE, laptop mounted equipment, LME, USB dongle, a portable electronic radio communication device, a sensor device equipped with radio communication capabilities or the like.
  • UE and the term “wireless communication device” should be interpreted as non-limiting terms comprising any type of wireless device communicating with a wireless network node in a cellular or mobile communication system or any device equipped with radio circuitry for wireless communication according to any relevant standard for communication within a cellular or mobile communication system.
  • wireless network node may refer to base stations, network control nodes such as network controllers, radio network controllers, base station controllers, and the like.
  • base station may encompass different types of radio base stations including standardized base stations such as Node Bs, or evolved Node Bs, eNBs, and also macro/micro/pico radio base stations, home base stations, also known as femto base stations, relay nodes, repeaters, radio access points, base transceiver stations, BTSs, and even radio control nodes controlling one or more Remote Radio Units, RRUs, or the like.
  • base stations may encompass different types of radio base stations including standardized base stations such as Node Bs, or evolved Node Bs, eNBs, and also macro/micro/pico radio base stations, home base stations, also known as femto base stations, relay nodes, repeaters, radio access points, base transceiver stations, BTSs, and even radio control nodes controlling one or more Remote Radio Units, RRUs, or the like.
  • Particular examples include one or more suitably configured digital signal processors and other known electronic circuits, e.g. discrete logic gates interconnected to perform a specialized function, or Application Specific Integrated Circuits (ASICs).
  • digital signal processors and other known electronic circuits, e.g. discrete logic gates interconnected to perform a specialized function, or Application Specific Integrated Circuits (ASICs).
  • ASICs Application Specific Integrated Circuits
  • At least some of the steps, functions, procedures, modules and/or blocks described above may be implemented in software such as a computer program for execution by suitable processing circuitry including one or more processing units.
  • processing circuitry includes, but is not limited to, one or more microprocessors, one or more Digital Signal Processors, DSPs, one or more Central Processing Units, CPUs, video acceleration hardware, and/or any suitable programmable logic circuitry such as one or more Field Programmable Gate Arrays, FPGAs, or one or more Programmable Logic Controllers, PLCs.
  • At least some of the steps, functions, procedures, modules and/or blocks described herein are implemented in a computer program, which is loaded into the memory for execution by processing circuitry including one or more processors.
  • the processor(s) and memory are interconnected to each other to enable normal software execution.
  • An optional input/output device may also be interconnected to the processor(s) and/or the memory to enable input and/or output of relevant data such as input parameter(s) and/or resulting output parameter(s).
  • processor' should be interpreted in a general sense as any system or device capable of executing program code or computer program instructions to perform a particular processing, determining or computing task.
  • the processing circuitry including one or more processors is thus configured to perform, when executing the computer program, well-defined processing tasks such as those described above.
  • a wireless network node 10 is configured to enable scheduling of wireless communication devices in a wireless cellular network.
  • the wireless network node is configured to select, at each scheduling instant, and based on scheduled transmission rates for the wireless communication devices, at least one first wireless communication device from a first set of wireless communication devices being served by a first wireless network node in the wireless cellular network, and at least one second wireless communication device from at least one second set of wireless communication devices, each second set of wireless communication devices being served by a respective second wireless network node in the wireless cellular network, and each of the second wireless communication devices being capable of interference cancellation, where the selected wireless communication devices are to be co-scheduled at each respective scheduling instant.
  • the wireless communication devices are selected such that a rate metric for the selected wireless communication devices is maximized over one or more scheduling instants, wherein the rate metric is a combination of achievable rates for the selected wireless communication devices, the achievable rates being based on achievable interference cancellation efficiency of signals from the first wireless network node causing interference at the at least one second wireless communication device.
  • the achievable interference cancellation efficiency is determined based on link quality information from the at least one second wireless communication device representing link quality between the at least one second wireless communication device and the first wireless network node, and scheduled transmission rate for the at least one first wireless communication device.
  • the link quality information comprises channel quality indicator, CQI, information
  • the rate metric may be calculated in one of the following manners:
  • the wireless cellular network is a heterogeneous network, and each of the respective second wireless network nodes 30; 40 is a low power node, LPN, and the first wireless network node 20 is a macro node.
  • the wireless cellular network is a Long Term Evolution, LTE, network.
  • the rate metric is further based on duration of time that at least one of the selected wireless communication devices has been waiting in a scheduling queue at the first and second wireless network nodes. An example of an implementation of such an embodiment has been described above.
  • the rate metric is further based on a proportional-fair criterion for the selected wireless communication devices.
  • a proportional-fair criterion for the selected wireless communication devices An example of an implementation of such an embodiment has been described above.
  • the wireless network node is configured to select the wireless communication devices based on forming a group comprising one wireless communication device from the first set of wireless communication devices, and one out of several wireless communication devices from each of the at least one second set of wireless communication devices, at each scheduling instant.
  • the wireless network node is configured to select the wireless communication devices based on forming a group comprising one wireless communication device from each of the at least one second set of wireless communication devices, and one out of several wireless communication devices from the first set of wireless communication devices, at each scheduling instant.
  • the wireless network node is configured to select the wireless communication devices based on forming a group comprising one out of several wireless communication devices from the first set of wireless communication devices, and one out of several wireless communication devices from each of the at least one second set of wireless communication devices, at each scheduling instant.
  • the wireless network node is configured to select the wireless communication devices based on forming several groups comprising one out of several wireless communication devices from the first set of wireless communication devices, and one out of several wireless communication devices from each of the at least one second set of wireless communication devices, to be used respectively at several scheduling instants.
  • Fig. 5 is a schematic diagram illustrating an example of a wireless network node 10 operative to enable scheduling of wireless communication devices in a wireless cellular network according to an embodiment.
  • the wireless network node 10 basically comprises a processor 1 1 , an associated memory 12 and optional communication circuitry 13.
  • the optional communication circuitry 13 is adapted for wireless and/or wired communication with one or more other nodes, including transmitting and/or receiving information. As indicated in the specific example of Fig.
  • the wireless network node 10 comprises a processor 1 1 and a memory 12, wherein the memory 12 comprises instructions executable by the processor 1 1 to perform operations of the wireless network node 10.
  • the processor is operative to select, at each scheduling instant, and based on scheduled transmission rates for the wireless communication devices, at least one first wireless communication device from a first set of wireless communication devices being served by a first wireless network node in the wireless cellular network, and at least one second wireless communication device from at least one second set of wireless communication devices, each second set of wireless communication devices being served by a respective second wireless network node in the wireless cellular network, and each of the second wireless communication devices being capable of interference cancellation, where the selected wireless communication devices are to be co-scheduled at each respective scheduling instant.
  • the wireless communication devices are selected such that a rate metric for the selected wireless communication devices is maximized over one or more scheduling instants, wherein the rate metric is a combination of achievable rates for the selected wireless communication devices, the achievable rates being based on achievable interference cancellation efficiency of signals from the first wireless network node causing interference at the at least one second wireless communication device.
  • the achievable interference cancellation efficiency is determined based on link quality information from the at least one second wireless communication device representing link quality between the at least one second wireless communication device and the first wireless network node, and scheduled transmission rate for the at least one first wireless communication device.
  • the wireless network node 10 may also include communication circuitry 13 for communication with one or more other nodes, including transmitting and/or receiving information.
  • the wireless network node 10 comprises communication circuitry 13 configured to receive link quality information from the at least one second wireless communication device representing link quality between the at least one second wireless communication device and the first wireless network node.
  • communication circuitry 13 configured to receive link quality information from the at least one second wireless communication device representing link quality between the at least one second wireless communication device and the first wireless network node.
  • a computer program comprises instructions, which when executed by at least one processor, cause the processor(s) to select, at each scheduling instant, and based on scheduled transmission rates for the wireless communication devices, at least one first wireless communication device from a first set of wireless communication devices being served by a first wireless network node in the wireless cellular network, and at least one second wireless communication device from at least one second set of wireless communication devices, each second set of wireless communication devices being served by a respective second wireless network node in the wireless cellular network, and each of the second wireless communication devices being capable of interference cancellation, where the selected wireless communication devices are to be co-scheduled at each respective scheduling instant.
  • the wireless communication devices are selected such that a rate metric for the selected wireless communication devices is maximized over one or more scheduling instants, wherein the rate metric is a combination of achievable rates for the selected wireless communication devices, the achievable rates being based on achievable interference cancellation efficiency of signals from the first wireless network node causing interference at the at least one second wireless communication device.
  • the achievable interference cancellation efficiency is determined based on link quality information from the at least one second wireless communication device representing link quality between the at least one second wireless communication device and the first wireless network node, and scheduled transmission rate for the at least one first wireless communication device.
  • the proposed technology also provides a carrier comprising the computer program, wherein the carrier is one of an electronic signal, an optical signal, an electromagnetic signal, a magnetic signal, an electric signal, a radio signal, a microwave signal, or a computer-readable storage medium.
  • the software or computer program may be realized as a computer program product, which is normally carried or stored on a computer-readable medium, in particular a non-volatile medium.
  • the computer-readable medium may include one or more removable or non-removable memory devices including, but not limited to a Readonly Memory (ROM), a Random Access Memory (RAM), a Compact Disc (CD), a Digital Versatile Disc (DVD), a Blueray disc, a Universal Serial Bus (USB) memory, a Hard Disk Drive (HDD) storage device, a flash memory, a magnetic tape, or any other conventional memory device.
  • the computer program may thus be loaded into the operating memory of a computer or equivalent processing device for execution by the processing circuitry thereof.
  • a corresponding wireless network node may be defined as a group of function modules, where each step performed by the processor corresponds to a function module.
  • the function modules are implemented as a computer program running on the processor.
  • the wireless network node may alternatively be defined as a group of function modules, where the function modules are implemented as a computer program running on at least one processor.
  • Fig. 6 is a schematic block diagram illustrating an example of a wireless network node for enabling scheduling of wireless communication devices in a wireless cellular network.
  • the wireless network node in this example comprises a selecting module 100 configured to select, at each scheduling instant, and based on scheduled transmission rates for the wireless communication devices, at least one first wireless communication device from a first set of wireless communication devices being served by a first wireless network node in the wireless cellular network, and at least one second wireless communication device from at least one second set of wireless communication devices, each second set of wireless communication devices being served by a respective second wireless network node in the wireless cellular network, and each of the second wireless communication devices being capable of interference cancellation, where the selected wireless communication devices are to be co- scheduled at each respective scheduling instant.
  • the wireless communication devices are selected such that a rate metric for the selected wireless communication devices is maximized over one or more scheduling instants, wherein the rate metric is a combination of achievable rates for the selected wireless communication devices, the achievable rates being based on achievable interference cancellation efficiency of signals from the first wireless network node causing interference at the at least one second wireless communication device.
  • the achievable interference cancellation efficiency is determined based on link quality information from the at least one second wireless communication device representing link quality between the at least one second wireless communication device and the first wireless network node, and scheduled transmission rate for the at least one first wireless communication device.
  • the link quality information comprises channel quality indicator, CQI, information.
  • the rate metric may be calculated in one of the following manners:
  • the wireless cellular network is a heterogeneous network, and each of the respective second wireless network nodes 30; 40 is a low power node, LPN, and the first wireless network node 20 is a macro node.
  • the wireless cellular network is a Long Term Evolution, LTE, network.
  • the rate metric is further based on duration of time that at least one of the selected wireless communication devices has been waiting in a scheduling queue at the first and second wireless network nodes.
  • the rate metric is further based on a proportional-fair criterion for the selected wireless communication devices.
  • a proportional-fair criterion for the selected wireless communication devices An example of an implementation of such an embodiment has been described above.
  • the selecting module 100 is configured to select the wireless communication devices based on forming a group comprising one wireless communication device from the first set of wireless communication devices, and one out of several wireless communication devices from each of the at least one second set of wireless communication devices, at each scheduling instant.
  • the selecting module 100 is configured to select the wireless communication devices based on forming a group comprising one wireless communication device from each of the at least one second set of wireless communication devices, and one out of several wireless communication devices from the first set of wireless communication devices, at each scheduling instant. In yet another particular embodiment, the selecting module 100 is configured to select the wireless communication devices based on forming a group comprising one out of several wireless communication devices from the first set of wireless communication devices, and one out of several wireless communication devices from each of the at least one second set of wireless communication devices, at each scheduling instant.
  • the selecting module 100 is configured to select the wireless communication devices based on forming several groups comprising one out of several wireless communication devices from the first set of wireless communication devices, and one out of several wireless communication devices from each of the at least one second set of wireless communication devices, to be used respectively at several scheduling instants.
  • the present embodiments aim to provide an improved scheduling coordination in a wireless network by selecting LPN and macro UEs in a manner that achieves improved cancellation efficiency without having to lower the macro scheduled rate compared to the conventional scheduling.
  • a LPN UE and a macro UE is scheduled so as to create UE pairs maximizing a per-pair scheduled rate metric (e.g. sum rate, LPN rate or macro rate), taking into account the IC efficiency at the LPN UE for the different rate and channel conditions combinations.
  • the rate metric may also account for individual UE priorities, accumulated scheduling delays, etc.
  • Variants of the invention are also applicable to handling more than one LPN cells per macro cell, i.e. creating groups of more than 2 UEs.
  • An advantage of the disclosed embodiments is that rate scheduling coordination and LPN and/or sum rate improvement is achieved without lowering the macro UE rate at each scheduling instant. Since the rate remains the same as without coordination, rate scheduling coordination may be used to improve overall NW capacity.
  • macro rate is lowered or zeroed without regard to its instantaneous interference impact towards the LPN UE.
  • the macro rate is lowered adaptively to enable a LPN rate increase.
  • the invention has been illustrated using the example of a heterogeneous network where a macro cell is the dominant interferer towards one or more LPN cells. The concept of the invention also applies to other deployment scenarios.
  • the LPN cell may then be interpreted more generally as a cell serving victim UEs and the macro cell as an interfering neighbour cell.

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

Abstract

La présente invention concerne des procédés et des nœuds de réseau sans fil pour planifier des dispositifs de communication sans fil dans un réseau cellulaire sans fil. Par exemple, un procédé exécuté par un nœud de réseau sans fil (10) comprend l'étape (S10) consistant à sélectionner pour une co-planification, à chaque instant de planification et sur la base de débits de transmission planifiée pour les dispositifs de communication sans fil, au moins un premier dispositif de communication sans fil (200), qui est desservi par un premier nœud de réseau sans fil (20), et au moins un second dispositif de communication sans fil à circuit intégré (IC) (300), qui est desservi par un second nœud de réseau sans fil (30 ; 40) respectif. Les dispositifs de communication sans fil sont sélectionnés de telle sorte qu'une métrique de débit pour les dispositifs de communication sans fil sélectionnés est rendue maximale au cours d'un ou de plusieurs instants de planification, la métrique de débit étant fondée sur une efficacité pouvant être atteinte d'annulation de brouillage de signaux provenant du premier nœud de réseau sans fil (20) provoquant un brouillage au niveau du ou des seconds dispositifs de communication sans fil (300). L'efficacité pouvant être atteinte d'annulation de brouillage est déterminée sur la base d'une qualité de liaison entre le ou les seconds dispositifs de communication sans fil (300) et le premier nœud de réseau sans fil (20), et du débit de transmission planifiée pour le ou les premiers dispositifs de communication sans fil (200).
PCT/IB2014/062689 2014-06-27 2014-06-27 Coordination de planification de débit dans un réseau cellulaire sans fil Ceased WO2015198103A1 (fr)

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