WO2015011557A1

WO2015011557A1 - Method for determining uplink transmission power

Info

Publication number: WO2015011557A1
Application number: PCT/IB2014/001445
Authority: WO
Inventors: Jin Liu; Jianguo Liu; Fang-Chen Cheng
Original assignee: Alcatel Lucent
Priority date: 2013-07-24
Filing date: 2014-07-15
Publication date: 2015-01-29
Also published as: CN104349438A; CN104349438B; TW201513706A

Abstract

The invention provides a new uplink power control scheme. In the scheme, both the useful signal's PSD at the serving cell and the interférence generated by the user equipment to the entire or partial network of neighboring cells are considered. The uplink power control mechanism of the invention has a remarkable performance gain over conventional FPC mechanism in terms of average and cell-edge throughput depending on the adjustment of the compensation factor.

Description

METHOD FOR DETERMINING UPLINK TRANSMISSION POWER

Field of the Invention

The application relates to a communication network, and especially relates to a method for determining uplink (UL) transmission power of a user equipment (UE).

Background of the Invention

In 3 GPP LTE- Advanced Release 12, small cell enhancements for denser and non-uniform distribution of small cells are considered. Due to the irregular deployment and highly overlapped coverage (non-homogeneous network deployment) with non-ideal backhaul, the inter-cell interference (ICI) among the small cells and from the macro-UEs to the small cells becomes a significant limitation to both cell coverage and network capacity.

UL power control is an essential technique to overcome the UL ICI. The conventional power control mechanism was designed for macro cells in homogeneous network. However, the interference distribution characteristics of small cells in heterogeneous networks are very different from the one of macro cells in homogeneous networks. The conventional power control mechanism based on fractional power control (FPC) applied directly to small cell scenarios may face four main challenges, namely low correlation between the generated ICI and the pathloss (PL) to the serving cell, ICI fluctuations due to dynamic scheduling, PL imbalance for the macro-UEs in the vicinity of small cells, and the potential power control avalanche effect resulting from lack of cooperation between neighboring cells for power control.

The conventional UL power control technique, provided by 3GPP LTE Release 8-11, is a combination of open-loop and closed-loop control. In theory, the combination requires less feedback than a purely closed-loop scheme, as the closed-loop feedback is only needed to compensate for cases when the UE's own estimate of the required power setting is not satisfactory (please refer to "S. Sesia, I. Toufik and M. Baker, The UMTS Long Term Evolution: From Theory to Practic, Second Edition" for details).

A typical operation mode for power control in LTE involves setting a coarse operation point for the transmission power spectral density (PSD) by open-loop means, based on the pathloss (PL) estimation from the desired UE to the serving cell. Faster adaptation can then be applied around the open-loop operation point by closed-loop means. This can control interference and fine-tune the power setting to suit the fast varying channel conditions.

The open-loop mechanism in LTE employs a well-known fractional power control (FPC) mechanism, which is composed of a semi-static base level component P₀ , and a fractional PL compensation component, as given by

Basic operation po int = P₀ + ocPL

The semi-static base level component P₀ comprises a nominal power level P_{0 cell} <≡ [-126,+23]ί/β , that is common for all UEs in the cell, and a UE-specific offset ^O_UE≡ [-7,+8] fi , i.e., P₀ = P₀__cell + P₀__UE .

The fractional PL compensation factor can be set on a scale from 0 to 1, corresponding to "no compensation" and "full compensation", respectively.

The potential benefit of FPC is a relatively lower transmit power for UEs closer to the cell border. Thus the cell-edge UEs have less interference to other cells under the assumption that there is a correlation between being close to the serving cell and being far away from its neighboring cells.

However, in heterogeneous networks (HetNet), the assumption that the UEs with large PL generate most of the ICI is not always true. As illustrated in Error! Reference source not found., the macro-UEl with small PL to the macro eNB have a serious interference to the pico-UEl associated with RRHl, which is closer to the macro coverage center.

With the conventional FPC, the power may be set to be higher to those UEs that have the most interference potential. Error! Reference source not found, further shows that the generated ICI follows a different trend than the expected one and that the ICI samples are spread over a range of up to 20dB for the same path gain (please refer to E. Dahlman, S. Parkvall and J. Skold, "4G LTE/LTE- Advanced for Mobile Broadband" for details).

Object and Summary of the Invention

Therefore, it is clear that the requirements for UL interference management in small cells are quite different from those for macro cells in homogeneous networks. This suggests that the UL transmission power should be adjusted so as to compensate for the generated interference to the system rather than the PL to the serving cell only. Based on the above concerns, according to one embodiment of first aspect of the invention, there is provided a method, for use in a serving cell of a communication network, of determining uplink transmission power of a user equipment, the method comprising the steps of:

- determining a common interference PSD Γ_{0 cell} , a first pathloss compensation factor for pathloss from the user equipment to the serving cell and a second pathloss compensation factor β for pathloss from the user equipment to at least one neighboring cell;

- sending the common interference PSD and the first pathloss compensation factor to the user equipment;

- receiving transmission power of each of the at least one neighboring cell, sending measurement configuration to the user equipment to inform the user equipment to conduct reference signal received power measurement of the at least one neighboring cell, and sending downlink reference signals to the user equipment;

- receiving a measurement report from the user equipment, the measurement report including reference signal received power from each of the at least one neighboring cell;

- determining a UE-specific offset Γ_{0 UE} of the user equipment, estimating pathloss

PL_i from each of the at least one neighboring cell to the user equipment based on the reference signal received power from each of the at least one neighboring cell and the received transmission power of each of the at least one neighboring cell and combining all pathlosses from the at least one neighboring cell to the user equipment to obtain interference pathloss PL, ;

- sending the UE-specific offset and product of the second pathloss compensation factor β and the interference pathloss PL, to the user equipment.

Advantageously, the step of combining comprises any one of:

- aggregating all pathlosses from the at least one neighboring cell to the user equipment to obtain the interference athloss PL_l by formula of:

selecting the minimum pathloss from all pathlosses from the at least one neighboring cell to the user equipment to obtain the interference pathloss PL, by formula of:

PL, = min{i^>L₁ , PL₂, · · · , PL_N }

wherein N represents the number of the at least one neighboring cell.

According to another embodiment of first aspect of the invention, there is provided a method, for use in a user equipment of a communication network, of determining uplink transmission power, the method comprising the steps of:

- receiving a common interference PSD Γ_{0 cell} and a first pathloss compensation factor from a serving cell;

- receiving measurement configuration from the serving cell, the measurement configuration being for informing the user equipment to conduct reference signal receiving power measurement of at least one neighboring cell;

- conducting reference signal received power measurement of the serving cell and the at least one neighboring cell respectively;

sending a measurement report to the serving cell, the measurement report including reference signal receiving power from each of the at least one neighboring cell;

- estimating pathloss from the serving cell to the user equipment based on reference signal received power from the serving cell and transmission power of the serving cell to obtain signal pathloss PL_S , and receiving a UE-specific offset Γ_{0 UE} and product of a second pathloss compensation factor β and an interference pathloss PL, from the serving cell;

- obtaining basic operation point based on the received common interference PSD Γ_{0 cell} , the received UE-specific offset Γ_{0 UE} , the received first pathloss compensation factor , the obtained signal pathloss PL_S and the received product of the second pathloss compensation factor β and the interference pathloss PL_l .

Advantageouly, the step of obtaining the basic operation point comprises:

- calculating the basic operation point BOP by formula of:

BOP = Γ_{0 cell} + Γ_{0 UE} + p PL_[ + a- PL_s

According to a further embodiment of first aspect of the invention, there is provided a method, for use in a neighboring cell of a communication network, of assisting a user equipment in determining uplink transmission power, the method comprising the steps of:

- sending transmission power of the neighboring cell to a serving cell of the user equipment;

- sending downlink reference signals to the user equipment.

According to one embodiment of second aspect of the invention, there is provided a method, for use in a serving cell of a communication network, of determining uplink transmission power of a user equipment, the method comprising the steps of:

- sending the common interference PSD, the first pathloss compensation factor and the second pathloss compensation factor to the user equipment;

PL_i from each of the at least one neighboring cell to the user equipment based on the reference signal received power from each of the at least one neighboring cell and the received transmission power of each of the at least one neighboring cell and combining all pathlosses from the at least one neighboring cell to the user equipment to obtain interference pathloss PL_{ ;

- sending the UE-specific offset and the interference pathloss to the user equipment. According to another embodiment of second aspect of the invention, there is provided a method, for use in a user equipment of a communication network, of determining uplink transmission power, the method comprising the steps of:

- receiving a common interference PSD Γ_{0 cell} , a first pathloss compensation factor and a second pathloss compensation factor β from a serving cell;

- receiving measurement configuration from the user equipment, the measurement configuration being for informing the user equipment of at least one neighboring cell to conduct reference signal received power measurement; - conducting reference signal received power measurement with the serving cell and the at least one neighboring cell respectively;

sending a measurement report to the serving cell, the measurement report including reference signal received power from each of the at least one neighboring cell;

- estimating pathloss from the serving cell to the user equipment based on reference signal received power from the serving cell and transmission power of the serving cell to obtain signal pathloss PL_S , and receiving a UE-specific offset Γ_{0 UE} and an interference pathloss PL_j from the serving cell;

- obtaining basic operation point based on the received common interference PSD Γ_{0 cell} , the received UE-specific offset Γ_{0 UE} , the received first pathloss compensation factor , the obtained signal pathloss PL_S , the received second pathloss compensation factor β and the received interference pathloss PL_l .

According to one embodiment of third aspect of the invention, there is provided a method, for use in a serving cell of a communication network, of determining uplink transmission power of a user equipment, the method comprising the steps of:

- sending measurement configuration to the user equipment to inform the user equipment to conduct reference signal received power measurement of the at least one neighboring cell, and sending downlink reference signals to the user equipment;

wherein the method further comprises the step of:

- sending a UE-specific offset Γ_{0 UE} to the user equipment.

Advantageously, the method further comprises the steps of:

- receiving transmission power of each of the at least one neighboring cell;

- sending the received transmission power of each of the at least one neighboring cells to the user equipment.

According to another embodiment of third aspect of the invention, there is provided a method, for use in a user equipment of a communication network, of determining uplink transmission power, the method comprising the steps of:

- receiving measurement configuration from the serving cell, the measurement configuration being for informing the user equipment to conduct reference signal received power measurement of at least one neighboring cell, and receiving transmission power of each of the at least one neighboring cell from the serving cell or the at least one neighboring cell;

- estimating pathloss from the serving cell to the user equipment based on the reference signal received power from the serving cell and transmission power of the serving cell to obtain signal pathloss PL_S , estimating pathloss PL_t from each of the at least one neighboring cell to the user equipment based on the reference signal received power from each of the at least one neighboring cell and the received transmission power of each of the at least one neighboring cell and combining all pathlosses from the at least one neighboring cell to the user equipment to obtain interference pathloss PL_{ ;

- obtaining basic operation point based on the received common interference PSD Γ_{0 cell} , a UE- specific offset Γ_{0 UE} received from the serving cell, the received first pathloss compensation factor , the obtained signal pathloss PL_S , the received second pathloss compensation factor β and the obtained interference pathloss PL_l .

Advantageously, the step of combining comprises any one of:

selecting the minimum pathloss from all pathlosses from the at least one neighboring cell to the user equipment to obtain the interference pathloss PL_{ by formula of:

PL_j = miniPL_j , PL₂ , · · · , PL_N } ; wherein N represents the number of the at least one neighboring cell.

Advantageously, the step of obtaining comprises:

- calculating the basic operation point BOP by formula of:

BOP = Γ_{0 cell} + Γ_{0 UE} + p PL_[ + a- PL_s

According to one embodiment of fourth aspect of the invention, there is provided a method, for use in a serving cell of a communication network, of determining uplink transmission power of a user equipment, the method comprising the steps of:

- sending downlink reference signals to the user equipment;

- estimating transmission power of the user equipment;

- receiving uplink reception power at each of the at least one neighboring cell from the at least one neighboring cell respectively, and estimating pathloss PL_t from the user equipment to each of the at least one neighboring cell based on the received uplink reception power at each of the at least one neighboring cell and the estimated transmission power of the user equipment and combining all pathlosses from the user equipment to the at least one neighboring cell to obtain interference pathloss PL_{ ;

sending a UE-specific offset Γ_{0 UE} and product of the second pathloss compensation factor and the interference pathloss to the user equipment.

According to another embodiment of fourth aspect of the invention, there is provided a method, for use in a user equipment of a communication network, of determining uplink transmission power, the method comprising the steps of:

- receiving a common interference PSD Γ_{0 cell} and a first pathloss compensation factor from a serving cell ;

- conducting reference signal received power measurement of the serving cell;

- estimating pathloss from the serving cell to the user equipment based on reference signal received power from the serving cell and transmission power of the serving cell to obtain signal pathloss PL_S ;

- sending uplink reference signal or uplink data;

- receiving a UE-specific offset and product of the second pathloss compensation factor and the interference pathloss;

- obtaining basic operation point based on the received common interference PSD

Γ_{0 cell} , the received UE-specific offset Γ_{0 UE} , the received first pathloss compensation factor , the obtained signal pathloss PL_S and the received product of the second pathloss compensation factor β and the interference pathloss PL_l .

According to a further embodiment of fourth aspect of the invention, there is provided a method, for use in a neighboring cell of a communication network, of assisting a user equipment in determining uplink transmission power, the method comprising the steps of:

- receiving uplink reference signal or uplink data from the user equipment;

- estimating uplink reception power at the neighboring cell based on the received uplink reference signal or uplink data;

- sending the uplink reception power at the neighboring cell to the serving cell.

According to one embodiment of fifth aspect of the invention, there is provided a method, for use in a serving cell of a communication network, of determining uplink transmission power of a user equipment, the method comprising the steps of:

- sending downlink reference signals to the user equipment;

estimating transmission power of the user equipment, and informing the transmission power of the user equipment to each of the at least one neighboring cell;

- receiving pathloss PL_i from the user equipment to each of the at least one neighboring cell from each of the at least one neighboring cell respectively, and combining all pathlosses from the user equipment to the at least one neighboring cell to obtain interference pathloss PL_{ ; sending a UE-specific offset Γ_{0 UE} and product of the second pathloss compensation factor and the interference pathloss to the user equipment.

According to another embodiment of fifth aspect of the invention, there is provided a method, for use in a neighboring cell of a communication network, of assisting a user equipment in determining uplink transmission power, the method comprising the steps of:

- receiving uplink reference signal or uplink data from the user equipment;

- estimating uplink reception power at the neighboring cell based on the received uplink reference signal or uplink data, and estimating pathloss PL_{ from the user equipment to the neighboring cell based on the estimated uplink reception power at the neighboring cell and the informed transmission power of the user equipment;

- informing to the serving cell the estimated pathloss PL_t from the user equipment to the neighboring cell.

According to one embodiment of sixth aspect of the invention, there is provided a method, for use in a serving cell of a communication network, of determining uplink transmission power of a user equipment, the method comprising the steps of:

- sending the common interference PSD to the user equipment;

- receiving transmission power of each of the at least one neighboring cell from the at least one neighboring cell respectively, sending measurement configuration to the user equipment to inform the user equipment to conduct reference signal received power measurement of the at least one neighboring cell, and sending downlink reference signals to the user equipment;

- receiving a measurement report from the user equipment, the measurement report including reference signal received power from the serving cell and reference signal received power from each of the at least one neighboring cell;

- determining a UE-specific offset Γ_{0 UE} of the user equipment, estimating pathloss from the serving cell to the user equipment based on the reference signal received power from the serving cell and transmission power of the serving cell to obtain signal pathloss PL_S , estimating pathloss PL_{ from each of the at least one neighboring cell to the user equipment based on the reference signal received power from each of the at least one neighboring cell and the received transmission power of each of the at least one neighboring cell and combining all pathlosses from the at least one neighboring cell to the user equipment to obtain interference pathloss PL_l ;

- sending the UE-specific offset, product of the first pathloss compensation factor and the signal pathloss PL_S and product of the second pathloss compensation factor β and the interference pathloss PL_{ to the user equipment.

According to another embodiment of sixth aspect of the invention, there is provided a method, for use in a user equipment of a communication network, of determining uplink transmission power, the method comprising the steps of:

- receiving a common interference PSD Γ_{0 cell} from a serving cell;

- receiving measurement configuration from the serving cell, the measurement configuration being for informing the user equipment to conduct reference signal received power measurement of at least one neighboring cell;

sending a measurement report to the serving cell, the measurement report including reference signal received power from the serving cell and reference signal received power from each of the at least one neighboring cell;

- receiving a UE-specific offset Γ_{0 UE} , product of a first pathloss compensation factor and a signal pathloss PL_S and product of a second pathloss compensation factor β and an interference pathloss PL_l from the serving cell;

- obtaining basic operation point based on the received common interference PSD Γ_{0 cell} , the received UE-specific offset Γ_{0 UE} , the received product of the first pathloss compensation factor and the signal pathloss PL_S and the received product of the second pathloss compensation factor β and the interference pathloss PL_{ .

According to one embodiment of seventh aspect of the invention, there is provided a method, for use in a serving cell of a communication network, of determining uplink transmission power of a user equipment, the method comprising the steps of:

- sending the UE-specific offset, the signal pathloss and the interference pathloss to the user equipment.

According to another embodiment of seventh aspect of the invention, there is provided a method, for use in a user equipment of a communication network, of determining uplink transmission power, the method comprising the steps of:

- receiving measurement configuration from the user equipment, the measurement configuration being for informing the user equipment of at least one neighboring cell to conduct reference signal received power measurement;

- conducting reference signal received power measurement with the serving cell and the at least one neighboring cell respectively; sending a measurement report to the serving cell, the measurement report including reference signal received power from the serving cell and reference signal received power from each of the at least one neighboring cell;

- receiving a UE-specific offset Γ_{0 UE} , a signal pathloss PL_S and an interference pathloss PL_l from the serving cell;

- obtaining basic operation point based on the received common interference PSD Γ_{0 cell} , the received UE-specific offset Γ_{0 UE} , the received first pathloss compensation factor , the received signal pathloss PL_S , the received second pathloss compensation factor β and the received interference pathloss PL_{ .

Brief Description of the Drawings

The invention is explained in further detail, and by way of example, with reference to the accompanying drawings wherein:

Fig. 1 shows an uplink transmission in HetNet;

Fig. 2 shows a diagram of interference density versus path-gain to serving cell;

Fig. 3 shows a flow chart of a method of determining uplink transmission power according to one embodiment of the invention;

Fig. 4 shows a flow chart of a method of determining uplink transmission power according to another embodiment of the invention;

Fig. 5 shows a diagram of IoT distribution for macro-only scenario;

Fig. 6 shows a diagram of normalized user throughput performance for macro-only scenario;

Fig. 7 shows a diagram of IoT distribution for HetNet scenario; and

Fig. 8 shows a diagram of normalized user throughput performance for HetNet scenario.

Throughout the above drawings, like reference numerals will be understood to refer to like, similar or corresponding features or functions.

Detailed Description

Illustrative embodiments are described below. In the interest of clarity, not all features of an actual implementation are described in this specification. It will of course be appreciated that in the development of any such actual embodiment, numerous implementation- specific decisions should be made to achieve the developers' specific goals, such as compliance with system-related and business-related constraints, which will vary from one implementation to another. Moreover, it will be appreciated that such a development effort might be complex and time-consuming, but would nevertheless be a routine undertaking for those of ordinary skill in the art having the benefit of this disclosure.

The disclosed subject matter will now be described with reference to the attached figures. Various structures, systems and devices are schematically depicted in the drawings for purposes of explanation only and so as to not obscure the description with details that are well known to those skilled in the art. Nevertheless, the attached drawings are included to describe and explain illustrative examples of the disclosed subject matter. The words and phrases used herein should be understood and interpreted to have a meaning consistent with the understanding of those words and phrases by those skilled in the relevant art. No special definition of a term or phrase, i.e., a definition that is different from the ordinary and customary meaning as understood by those skilled in the art, is intended to be implied by consistent usage of the term or phrase herein. To the extent that a term or phrase is intended to have a special meaning, i.e., a meaning other than that understood by skilled artisans, such a special definition will be expressly set forth in the specification in a definitional manner that directly and unequivocally provides the special definition for the term or phrase.

Hereinafter, the embodiments of the invention will be described with reference to figures. The embodiments of the invention can be applicable to both homogeneous network and heterogeneous network.

the first embodiment

Referring to Fig. 3, first in step 301, the serving cell determines a common interference PSD (power spectral density) Γ_{0 cell} , a first pathloss compensation factor for pathloss from the user equipment to the serving cell and a second pathloss compensation factor β for pathloss from the user equipment to at least one neighboring cell. Then, in step 302, the serving cell sends the common interference PSD Γ_{0 cell} and the first pathloss compensation factor to the user equipment through a broadcast signaling.

Then, in step 303, the serving cell receives transmission power of each of the at least one neighboring cell from each of the at least one neighboring cell through a X2 signaling.

Meanwhile, the serving cell sends measurement configuration to the user equipment to inform the user equipment to conduct reference signal received power measurement of the at least one neighboring cell, and sends downlink reference signals to the user equipment. Likewise, each of the at least one neighboring cell also sends downlink reference signals to the user equipment.

After receiving the measurement configuration from the serving cell, in step 304, the user equipment conducts reference signal received power measurement of the serving cell and the at least one neighboring cell respectively to obtain the reference signal received power from the serving cell and the reference signal received power from each of the at least one neighboring cell.

Then, in step 305, the user equipment sends a measurement report to the serving cell. The measurement report includes the reference signal received power from each of the at least one neighboring cell.

After receiving the measurement report from the user equipment, in step 306, the serving cell determines a UE-specific offset Γ_{0 UE} of the user equipment and estimates pathloss PL_i from each of the at least one neighboring cell to the user equipment based on the reference signal received power from each of the at least one neighboring cell and the received transmission power of each of the at least one neighboring cell.

After estimating pathloss PL_i from each of the at least one neighboring cell to the user equipment, the serving cell combines all pathlosses from the at least one neighboring cell to the user equipment to obtain interference pathloss PL_{ . Then, in step 307, the serving cell sends the UE-specific offset Γ_{0 UE} and the product of the second pathloss compensation factor β and the interference pathloss PL_l to the user equipment.

In one example, the serving cell may aggregate all pathlosses from the at least one neighboring cell to the user equi ment to obtain interference pathloss PL_l by formula of:

where N represents the number of the at least one neighboring cell. For simplification purpose, we could only consider the interference to three neighboring cell (i.e., N=3), because the interference of the user equipment to these three closest neighboring cells dominates the most interference to the entire system.

In another example, the serving cell may select the minimum pathloss from all pathlosses from the at least one neighboring cell to the user equipment to obtain the interference pathloss PL, by formula of:

PL^ miniPL, , PL₂, ···, PL_N}.

At the same time, in step 308, the user equipment receives the UE-specific offset Γ_{0 UE} and the product of the second pathloss compensation factorβ and the interference pathloss PL_l from the serving cell, and estimates pathloss from the serving cell to the user equipment based on the reference signal received power from the serving cell and the transmission power of the serving cell to obtain signal pathloss PL_S .

Then, in step 309, the user equipment obtains basic operation point based on the received common interference PSD Γ_{0 cell} , the received UE-specific offset Γ_{0 UE} , the received first pathloss compensation factor , the obtained signal pathloss PL_S and the received product of the second pathloss compensation factor β and the interference pathloss PL, . To be specific, the user equipment calculates the basic operation point BOP by formula of:

B P = Γ_{0 cell} + Γ_{0 UE} +p PL_l+a-PL_s

Based on the basic operation point, the user equipment can obtain the power spectral density (PSD) of the transmission power of the user equipment by the following formula:

PSD = min{P SL , Γ_{0 cell} + Γ_{0 UE} +β■ PL, +a■ PL_S +A_MCS + δ) where PSD_^ is the maximum PSD of the transmission power of the user equipment, Γ_{0 cell} + Γ_{0 UE} +β■ PL, +a■ PL_S is the basic operation point and corresponds to the open loop control part, and A_MCS + δ corresponds to the close loop control part, which is similar to that of the fractional power control in the art.

Advantageously, β - 1 -a .

the second embodiment

The technical solution of the second embodiment differs from that of the first embodiment in that the serving cell sends the second pathloss compensation factor β and the interference pathloss PL_{ to the user equipment respectively instead of sending the product of the second pathloss compensation factor β and the interference pathloss PL_l to the user equipment.

the third embodiment

In the first and second embodiments, the user equipment estimates pathloss from the serving cell to the user equipment based on the reference signal received power from the serving cell and the transmission power of the serving cell to obtain the signal pathloss PL_S . However, in alternative embodiments, the serving cell can estimate pathloss from the serving cell to the user equipment based on the received reference signal received power from the serving cell and the transmission power of the serving cell to obtain signal pathloss PL_S , and then send the signal pathloss PL_S to the user equipment.

the fourth embodiment

In aforesaid embodiments, the interference pathloss PL_l is calculated at the user equipment side. However, in alternative embodiments, the interference pathloss PL_{ can also be calculated at the serving cell side.

To be specific, referring to Fig. 4, first in step 401, the serving cell determines a common interference PSD Γ_{0 cell} , a first pathloss compensation factor for pathloss from the user equipment to the serving cell and a second pathloss compensation factor β for pathloss from the user equipment to at least one neighboring cell. Then, in step 402, the serving cell sends the common interference PSD Γ_{0 cell} , the first pathloss compensation factor and the second pathloss compensation factor β to the user equipment.

Then in step 403, the serving cell sends measurement configuration to the user equipment to inform the user equipment to conduct reference signal received power measurement of the at least one neighboring cell, and sends downlink reference signals to the user equipment. Likewise, each of the at least one neighboring cell also sends downlink reference signals to the user equipment.

After receiving the measurement configuration from the serving cell, in step 404, the user equipment conducts reference signal received power measurement of the serving cell and the at least one neighboring cell respectively to obtain the reference signal received power from the serving cell and the reference signal received power from each of the at least one neighboring cell. At the same time, the user equipment receives the transmission power of each of the at least one neighboring cell from the at least one neighboring cell respectively.

Then in step 405, the user estimates pathloss from the serving cell to the user equipment based on the reference signal received power from the serving cell and transmission power of the serving cell to obtain signal pathloss PL_S , and estimates pathloss

PL_i from each of the at least one neighboring cell to the user equipment based on the reference signal received power from each of the at least one neighboring cell and the received transmission power of each of the at least one neighboring cell.

After estimating pathloss PL_i from each of the at least one neighboring cell to the user equipment, the user equipment combines all pathlosses from the at least one neighboring cell to the user equipment to obtain interference pathloss PL_{ .

Then in step 406, the user equipment obtains basic operation point based on the received common interference PSD Γ_{0 cell} , a UE-specific offset Γ_{0 UE} received from the serving cell, the received first pathloss compensation factor , the obtained signal pathloss PL_S , the received second pathloss compensation factor β and the obtained interference pathloss PL_l . To be specific, the user equipment calculates the basic operation point BOP by formula of:

B P = Γ_{0 cell} + Γ_{0 UE} + 0- PL_{I +} a- PL_s

PSD = min{P SL , Γ_{0 cell} + Γ_{0 UE} + β · PL_[ + cc■ PL_S + A_MCS + S] the fifth embodiment

The technical solution of the fifth embodiment differs from that of the fourth embodiment in that each of the at least one neighboring cell sends its transmission power to the serving cell and then the serving cell forwards the transmission power of each of the at least one neighboring cell to the user equipment in the fifth embodiment.

the sixth embodiment

In this embodiment, first, the serving cell determines a common interference PSD Γ_{0 cell} , a first pathloss compensation factor for pathloss from the user equipment to the serving cell and a second pathloss compensation factor β for pathloss from the user equipment to at least one neighboring cell. Then, the serving cell sends the common interference PSD Γ_{0 cell} and the first pathloss compensation factor to the user equipment.

Then the serving cell sends downlink reference signals to the user equipment. Correspondingly, the user equipment conducts reference signal received power measurement of the serving cell, and then estimates pathloss from the serving cell to the user equipment based on reference signal received power from the serving cell and transmission power of the serving cell to obtain signal pathloss PL_S .

Meanwhile, the user equipment sends uplink reference signal or uplink data. After receiving the uplink reference signal or uplink data from the user equipment, the neighboring cell estimates the uplink reception power at the neighboring based on the received uplink reference signal or uplink data, and then sends the uplink reception power at the neighboring to the serving cell.

The serving cell estimates transmission power of the user equipment, and then estimates pathloss PL_t from the user equipment to each of the at least one neighboring cell based on the received uplink reception power at each of the at least one neighboring cell and the estimated transmission power of the user equipment.

After estimating pathloss PL_t from the user equipment to each of the at least one neighboring cell, the serving cell combines all pathlosses from the user equipment to the at least one neighboring cell to obtain interference pathloss PL_l .

Then, the serving cell sends a UE-specific offset Γ_{0 UE} and product of the second pathloss compensation factor β and the interference pathloss PL_{ to the user equipment.

Then, the user equipment obtains basic operation point based on the received common interference PSD Γ_{0 cell} , the received UE-specific offset Γ_{0 UE} , the received first pathloss compensation factor , the obtained signal pathloss PL_S and the received product of the second pathloss compensation factor β and the interference pathloss PL_{ . To be specific, the user equipment calculates the basic operation point BOP by formula of:

B P = Γ_{0 cell} + Γ_{0 UE} + p PL_[ + a- PL_s

Based on the basic operation point, the user equipment can obtain the power spectral density (PSD) of the transmission power of the user equipment by the following formula: PSD = min{PSD_max , Γ_{0 cell} + Γ_{0 UE} + β^■ PL, + a- PL_S + A_MCS + δ)

the seventh embodiment

In the sixth embodiment, the serving cell receives uplink reception power of each of the at least one neighboring cell from the at least one neighboring cell respectively, and estimates pathloss PL_t from the user equipment to each of the at least one neighboring cell based on the received uplink reception power at each of the at least one neighboring cell and the estimated transmission power of the user equipment. However, in an alternative embodiment, each neighboring cell estimates pathloss PL_i from the user equipment to the neighboring cell and sends the estimated pathloss PL_i to the serving cell. Correspondingly, the serving cell receives the estimated pathloss PL_{ from each neighboring cell and then combines all pathlosses from the user equipment to the at least one neighboring cell to obtain interference pathloss PL, .

In the following, some simulation results are provided to demonstrate the performance advantages of the proposed uplink power control mechanism. The simulation assumptions and parameters are summarized in Table 1.

Table 1 Simulation Assumptions and Parameters

Carrier frequency 2GHz

System bandwidth 10MHz [50 PRBs]

Duplex method FDD

Network Synchronized

synchronization

System Handover margin ldB

Parameters Network topology 1. Macro only

2. HetNet: 2 small cells with fixed

positions in the macro coverage area

UE number 25 UEs/sector

Thermal noise per -116 dBm

PRB

Scheduler Traffic model Full buffer

Parameters UL Scheduler PF Scheduling granularity 5 PRBs

UL link adaptation Non-idea link adaption with 7ms delay

BLER target 10%

UL HARQ Synchronous HARQ with max. 4 transmissions for CC

UL receiver MMSE

Propagation scenario 3 GPP case 1 [ISD 500m]

Channel model SCM urban macro high spread

Channel Pathloss As defined in 3 GPP TS 36.814

Parameters Penetration loss 20dB

ICI modeling Explicitly

Channel estimation ideal

Macro cell layout Hexagonal grid, 7 macro eNB sites, 3 sectors/site, wrap-around

DL maximum Tx 46dBm

Macro eNB power

Antenna configuration 2 Rx antennas with antenna pattern defined in TS36.814

BS antenna downtilt 3 GPP Case 1 2D: N/A

Small cell layout 0 or 2 small cells/sector

DL maximum Tx 30dBm

power

Small Cell

Bias 9dB

Antenna configuration 2 Rx antennas with antenna pattern defined in TS36.814

UE maximum Tx 23dBm

power

UL transmission 1x2 SIMO

UE

scheme

Antenna configuration 1 Tx antenna (0 dBi antenna gain, omni-directional)

UL power 0.1, 0.6 control P_c for FPC -64dBm

parameters r§ for new PC [-111, -110, -108] dBm depending on a

The simulations are conducted for macro-only scenario and HetNet scenario respectively to investigate the performances of the proposed uplink power control mechanism. The conventional FPC mechanism is also evaluated as a benchmark.

Error! Reference source not found, and Error! Reference source not found, show the performance advantages of the proposed uplink power control mechanism in the macro-only scenario, in terms of IoT (interference over thermal noise) control and throughput performance. Error! Reference source not found, reveals that the proposed uplink power control mechanism has a more controlled IoT level, since the slope of the new PC (power control) curves is steeper than that of FPC curve regardless the value of .

The normalized user throughput performance for macro-only scenario is illustrated in Error! Reference source not found.. The comparison is conducted under the assumption of similar IoT level. Compared to the conventional FPC case, the new PC with a— 0.6 has better coverage performance while the case with a = Q.l has better capacity performance, which is obtained at the cost of suppressing the uplink transmission power of the user equipments closed to the cell-edge more significantly.

Table 2 Gains of New PC over FPC for Macro-only Scenario

IoT level Normalized User Throughput

(dB) (bps/Hz/User)

5% Gains Mean Gains

Conventional FPC, 7.2984 0.0178 - 0.0410

P₆ = - 64dB.ii., . = 0.6

New PC, Γ_{0 cell} = -111.5i¾m , 0.0182 2.2% 0.0480 17.1% a = Θ.1

As shown in Table 2, with the proposed new PC when = 0.6, the cell-edg throughput performance can be increased up to 34.8% while keeping the same averag throughput performance, compared to conventional FPC. The new PC with = 0.1 exhibits 17.1% gains on average throughput performance while still having marginal cell-edge performance gain over FPC.

Error! Reference source not found, and Error! Reference source not found, investigate the performances of proposed uplink power control mechanism in HetNet scenario, in terms of IoT distribution and throughput performance. The steeper slope of IoT distribution curves of new PC in Error! Reference source not found, demonstrates again that the new mechanism has a better IoT control than conventional FPC in HetNet scenario.

Table 3 Gains of New PC over FPC for HetNet Scenario

IoT level (dB) Normalized User Throughput

(bps/Hz/User)

Macro Small 5% Gains Mean Gains cell

Conventional FPC, 9.3204 8.1924 0.0194 - 0.1371

New PC, Γ_{0 cell} = -U0dBm , 8.6783 6.9457 0.0105 -45.9% 0.1759 28.3% a— 8.1

Table 3 exhibits the throughput performance of new PC with different compensation factors under the assumption of similar IoT levels. In the case of a = 0,6, the new PC could achieve 29.4% cell-edge performance gain over FPC while have a little performance gain on average throughput performance. In the case of «: = 0,1, the new PC has a remarkable performance gain in terms of average throughput at the cost of significant decreasing in cell-edge performance up to -45.9%. It can be seen that the compensation factor has more effects on the tradeoff between cell-edge and average performances for HetNet scenario.

It should be noted that the above described embodiments are given for describing rather than limiting the invention, and it is to be understood that modifications and variations may be resorted to without departing from the spirit and scope of the invention as those skilled in the art readily understand. Such modifications and variations are considered to be within the scope of the invention and the appended claims. The protection scope of the invention is defined by the accompanying claims. In addition, any of the reference numerals in the claims should not be interpreted as a limitation to the claims. Use of the verb "comprise" and its conjugations does not exclude the presence of elements or steps other than those stated in a claim. The indefinite article "a" or "an" preceding an element or step does not exclude the presence of a plurality of such elements or steps.

Claims

What is claimed is:

1. A method, for use in a serving cell of a communication network, of determining uplink transmission power of a user equipment, the method comprising the steps of:

sending the UE-specific offset Γ_{0 UE} and product of the second pathloss compensation factor β and the interference pathloss PL_l to the user equipment.

2. The method of claim 1, wherein the step of combining comprises any one of:

PL, = min{i^>L₁ , PL₂, · · · , PL_N }

wherein N represents the number of the at least one neighboring cell.

3. A method, for use in a user equipment of a communication network, of determining uplink transmission power, the method comprising the steps of:

- estimating pathloss from the serving cell to the user equipment based on reference signal received power from the serving cell and transmission power of the serving cell to obtain signal pathloss PL_S , and receiving a UE-specific offset Γ_{0 UE} and product of a second pathloss compensation factor β and an interference pathloss PL_l from the serving cell;

4. The method of claim 3, wherein the step of obtaining the basic operation point comprises:

- calculating the basic operation point BOP by formula of:

BOP = r₀__cell + Γ₀__υΕ + p PL_[ + a- PL_s

5. A method, for use in a neighboring cell of a communication network, of assisting a user equipment in determining uplink transmission power, the method comprising the steps of:

- sending downlink reference signals to the user equipment.

6. A method, for use in a serving cell of a communication network, of determining uplink transmission power of a user equipment, the method comprising the steps of:

- determining a UE-specific offset Γ_{0 UE} of the user equipment, estimating pathloss PL_i from each of the at least one neighboring cell to the user equipment based on the reference signal received power from each of the at least one neighboring cell and the received transmission power of each of the at least one neighboring cell and combining all pathlosses from the at least one neighboring cell to the user equipment to obtain interference pathloss PL_{ ;

- sending the UE-specific offset Γ_{0 UE} and the interference pathloss PL_{ to the user equipment.

7. A method, for use in a user equipment of a communication network, of determining uplink transmission power, the method comprising the steps of:

- conducting reference signal received power measurement with the serving cell and the at least one neighboring cell respectively;

- sending a measurement report to the serving cell, the measurement report including reference signal received power from each of the at least one neighboring cell;

- estimating pathloss from the serving cell to the user equipment based on reference signal received power from the serving cell and transmission power of the serving cell to obtain signal pathloss PL_S , and receiving a UE-specific offset Γ_{0 UE} and an interference pathloss PL_l from the serving cell;

- obtaining basic operation point based on the received common interference PSD Γ_{0 cell} , the received UE-specific offset Γ_{0 UE} , the received first pathloss compensation factor , the obtained signal pathloss PL_S , the received second pathloss compensation factor β and the received interference pathloss PL_{ .

8. A method, for use in a serving cell of a communication network, of determining uplink transmission power of a user equipment, the method comprising the steps of:

- sending measurement configuration to the user equipment to inform the user equipment to conduct reference signal received power measurement of the at least one neighboring cell, and sending downlink reference signals to the user equipment; wherein the method further comprises the step of:

- sending a UE-specific offset Γ_{0 UE} to the user equipment.

9. The method of claim 8, further comprising the steps of:

- receiving transmission power of each of the at least one neighboring cell from the at least one neighboring cell respectively;

10. A method, for use in a user equipment of a communication network, of determining uplink transmission power, the method comprising the steps of:

- obtaining basic operation point based on the received common interference PSD Γ_{0 cell} , a UE-specific offset Γ_{0 UE} received from the serving cell, the received first pathloss compensation factor , the obtained signal pathloss PL_S , the received second pathloss compensation factor β and the obtained interference pathloss PL_l .

11. The method of claim 10, wherein the step of combining comprises any one of:

PL^ miniPL, , PL₂, · · · , PL_N };

wherein N represents the number of the at least one neighboring cell.

12. The method of claim 10, wherein the step of obtaining the basic operation point comprises:

- calculating the basic operation point BOP by formula of:

B P = r₀__cell + Γ₀__υΕ + p PL_[ + a- PL_s

13. A method, for use in a serving cell of a communication network, of determining uplink transmission power of a user equipment, the method comprising the steps of:

- sending downlink reference signals to the user equipment;

- estimating transmission power of the user equipment;

- receiving uplink reception power at each of the at least one neighboring cell from the at least one neighboring cell respectively, estimating pathloss PL_i from the user equipment to each of the at least one neighboring cell based on the received uplink reception power at each of the at least one neighboring cell and the estimated transmission power of the user equipment and combining all pathlosses from the user equipment to the at least one neighboring cell to obtain interference pathloss PL_{ ;

sending a UE-specific offset Γ_{0 UE} and product of the second pathloss compensation factor β and the interference pathloss PL_l to the user equipment.

14. A method, for use in a user equipment of a communication network, of determining uplink transmission power, the method comprising the steps of:

- conducting reference signal received power measurement of the serving cell;

- sending uplink reference signal or uplink data;

- receiving a UE-specific offset Γ_{0 UE} and product of the second pathloss compensation factor β and the interference pathloss PL_l from the serving cell;

- obtaining basic operation point based on the received common interference PSD Γ_{0 cell} , the received UE-specific offset Γ_{0 UE} , the received first pathloss compensation factor , the obtained signal pathloss PL_S and the received product of the second pathloss compensation factor β and the interference pathloss PL_{ .

15. A method, for use in a neighboring cell of a communication network, of assisting a user equipment in determining uplink transmission power, the method comprising the steps of:

- receiving uplink reference signal or uplink data from the user equipment;

16. A method, for use in a serving cell of a communication network, of determining uplink transmission power of a user equipment, the method comprising the steps of: - determining a common interference PSD Γ_{0 cell} , a first pathloss compensation factor for pathloss from the user equipment to the serving cell and a second pathloss compensation factor β for pathloss from the user equipment to at least one neighboring cell;

- sending downlink reference signals to the user equipment;

- receiving pathloss PL_i from the user equipment to each of the at least one neighboring cell from each of the at least one neighboring cell respectively, and combining all pathlosses from the user equipment to the at least one neighboring cell to obtain interference pathloss PL_l ;

sending a UE-specific offset Γ_{0 UE} and product of the second pathloss compensation factor β and the interference pathloss PL_{ to the user equipment.

17. A method, for use in a neighboring cell of a communication network, of assisting a user equipment in determining uplink transmission power, the method comprising the steps of:

- receiving uplink reference signal or uplink data from the user equipment;

- informing the serving cell the estimated pathloss PL_t from the user equipment to the neighboring cell.

18. A method, for use in a serving cell of a communication network, of determining uplink transmission power of a user equipment, the method comprising the steps of:

- sending the common interference PSD to the user equipment;

19. A method, for use in a user equipment of a communication network, of determining uplink transmission power, the method comprising the steps of:

- receiving a common interference PSD Γ_{0 cell} from a serving cell;

- receiving a UE-specific offset Γ_{0 UE} , product of a first pathloss compensation factor and a signal pathloss PL_S and product of a second pathloss compensation factor β and an interference pathloss PL_{ from the serving cell;

- obtaining basic operation point based on the received common interference PSD Γ_{0 cell} , the received UE-specific offset Γ_{0 UE} , the received product of the first pathloss compensation factor and the signal pathloss PL_S and the received product of the second pathloss compensation factor β and the interference pathloss PL_l .

20. A method, for use in a serving cell of a communication network, of determining uplink transmission power of a user equipment, the method comprising the steps of:

21. A method, for use in a user equipment of a communication network, of determining uplink transmission power, the method comprising the steps of:

- receiving a UE-specific offset Γ_{0 UE} , a signal pathloss PL_S and an interference pathloss PL_{ from the serving cell;

- obtaining basic operation point based on the received common interference PSD Γ_{0 cell} , the received UE-specific offset Γ_{0 UE} , the received first pathloss compensation factor , the received signal pathloss PL_S , the received second pathloss compensation factor β and the received interference pathloss PL_l .