KR20070020032A - Power control method and apparatus with inter-link interference prediction for use in cdma wireless communication networks - Google Patents

Abstract

A power control method for use in wireless communication networks: after a receiving node receives radio signal from a transmitting node, the receiving node predicts an inter- link interference power upon itself according to the received radio signal, and sends a power control message to the transmitting node; after the transmitting node receives a power control message from a receiving node, it extracts the inter-link interference power predicted by the receiving node, and adjusts its transmit power according to the predicted inter-link interference power. ® KIPO & WIPO 2007

Description

Power control method and apparatus having an inter-link interference prediction for use in a CDM wireless communication network TECHNICAL FIELD

The present invention relates generally to a power control method and apparatus for use in a wireless communication network, and more particularly to a power control method and apparatus for use in a CDMA wireless communication network.

In modern society, wireless communication networks are playing an increasingly important role in our daily lives by providing an increasing number of rich and fast information services.

Currently, there are two kinds of wireless communication networks: one based on a fixed infrastructure such as a cellular network; The other has a fixed infrastructure, such as an ad hoc network.

In an infrastructure-based network, the size of the cell will be determined by the transmission range of the BS (base station) or AP (access point), and the mobile terminals in the cell will communicate directly with the BS or AP. Can be. However, in an ad hoc network, portable terminals are self-organizing so that two portable terminals can establish communication directly between them, or forwarding of other portable terminals between them (multi-hop). (multi-hop)} to establish mutual communication. With these characteristics, ad hoc networks are applied in many areas such as personal area networks (PANs), military environments, and search and rescue operations.

Over the years, researchers around the world have been working on CDMA-based Ad hoc wireless communications networks in Europe, including "Fleetnet-Internet on the Road" and China's 863 high-tech project "Self-organizing wireless network based on 3G techniques." Various studies have been carried out. As research deepens, CDMA-based ad hoc wireless communication networks have faced more challenging problems such as system architecture, information routing, power control, system synchronization, access control, radio resource allocation, and so on. .

Because of the near-far effect, CDMA systems are self-interfering and interference-limited. Therefore, among the above problems, power control has been a major factor affecting the performance of CDMA-based Ad-hoc wireless communication networks.

Currently, in an ongoing study done on CDMA-based Ad hoc wireless communication networks, a method similar to the open-loop power control or closed-loop power control mechanism used in cellular wireless communication networks is used, i.e. the transmit power of the transmitting node. Is adjusted with reference to history information (e.g., BER of some previous radio frames). "Topology control of multi-hop wireless networks using transmit power adjustment", published in IEEE INFOCOM, Volume 2, by R. Ramanathan and R. Rosales-Hain, September 2002, Eun-Sun Jung and Nitin H. "A Power Control MAC Protocol for Ad Hoc Networks" published by Vaidya at the ACM international Conference on Mobile Computing and Networking (MobiCom), and by IEEE MILCOM, vol. This is described in detail in "Clustering with power control" published in Section 2.

However, due to the dynamic topology of the ad hoc network and the mobility of the nodes in the ad hoc wireless communication network, the inter-link interference at a given receiving node caused by another communication link can vary dramatically. have. If the measurement and interference for the SIR is based on history information at the receiving node, and the derived power control message is fed back to the corresponding transmitting node, then the power control information is potentially interference in the current network. Cannot accurately reflect the effect of As a result, if the transmitting node periodically adjusts its transmit power based on the power control message fed back from the receiving node, the convergence rate of the power control method is very slow, reducing energy efficiency, and causing network interference Increase the performance of the ad hoc wireless communication network.

In order to solve the above problem of system performance degradation, a new power control method is required.

It is an object of the present invention to provide a new power control method and apparatus, with which all nodes in an ad hoc wireless communication network share network resources equally, effectively improve energy efficiency, reduce network interference, Optimize network performance.

A power control method for use in a wireless communication network implemented in a receiving node in accordance with the invention comprises the steps of receiving a radio signal from a transmitting node; Predicting inter-link interference power on a receiving node according to the received wireless signal; Sending a power control message to the transmitting node such that the transmitting node can adjust its transmit power according to the predicted inter-link interference power included in the power control message.

A power control method for use in a wireless communication network executed by a transmitting node in accordance with the present invention comprises the steps of: receiving a power control message from a receiving node; Extracting the predicted inter-link interference power on the receiving node from the power control message; Adjusting the transmit power of the transmitting node according to the predicted inter-link interference power.

Other objects and achievements, along with a full understanding of the invention, will be apparent and understood by reference to the following description and claims taken in accordance with the accompanying drawings.

For a detailed description of the preferred embodiment of the present invention, reference will now be made to the drawings.

1 is a schematic diagram illustrating an exemplary Ad hoc wireless communication network.

2 is a flowchart of a power control method in the present invention.

3 is a diagram illustrating an architecture of a mobile terminal for executing a power control method according to an embodiment of the present invention.

Like reference numerals designate the same or corresponding features and functions in all the accompanying drawings.

According to the power control method provided in the present invention: at a given receiving node in a wireless communication network, based on a particular burst and self-similarity of traffic such as voice, image, IP data, etc. Predict the power of inter-link interference on a receiving node caused by another communication link; The transmitting node supplies the predicted interference power back to the transmitting node so that the transmitting node can adjust its power for transmitting the radio signal based on the feedback information.

By illustrating an ad hoc wireless communication network in TDD as shown in FIG. 1, a detailed description will be given below for the power control method of the present invention.

As shown in FIG. 1, in an ad hoc network constituted by a plurality of mobile terminals (mobile terminals), when one node communicates with a neighbor node, a link connection between them will continue. For nodes allocated in different timeslots, the communication links between them do not produce signal interference; Inter-link interference will occur for a pair of transmission modes and receiving nodes assigned in the same timeslot but using different spreading codes for radio signal transmission and reception.

Suppose there is a receiving node i in the network, and this node i receives a radio signal sent from the transmitting node j. In order to satisfy the SIR (Signal Interference Ratio) requirement at the receiving node i, the transmit power of the transmitting node j must satisfy the following equation:

Where G is the processing gain; t is a time slot number set to zero at the beginning of the frame; P _j (t) is the transmit power of the transmit node j expressed in units mW; r _ij (t) is the channel gain from the transmitting node j to the receiving node i; I _inter (t), denoted mW, is the sum of the interference powers generated by the transmission powers of the communication nodes other than the transmitting node j on the receiving node i, that is, the other communication on the receiving node i. It is the sum of the inter-link interferences generated by the links. The propagation channel used by the other nodes is in the same time slot but uses different spreading codes.

N _bk is background noise in units of mW.

SIR _{target ij} (t) is the target SIR at the receiving node i for extracting the signal sent by the transmitting node j. Generally, SIR _{target ij} (t) is set by the radio resource management layer and can be adjusted according to the quality of the communication link. For example, the SIR _{target ij} (t) can be adjusted according to the calculated Bit Error Rate (BER): when the BER is high, the SIR _{target ij} (t) must be increased; When BER is low, SIR _{target ij} (t) must be reduced.

Equation 1 above can also be written as:

Here, E is the same as Equation 3.

The transmit power of the transmit node j may be calculated according to equations (2) and (3).

However, I _inter (t) is inter-link interference at the receiving node i, which is a real-time stochastic process, and inter-link interference I _inter (t) is the variability of the ad hoc network. Because of the dramatic change from time to time, it is not easy to predict the exact information of I _inter (t).

From Equations 2 and 3 above, the main element for the transmitting node j to adjust its transmit power in a timely manner may seem to obtain the current information of I _inter (t).

In current and future wireless communication networks, voice, image and IP data are the main traffic delivered on the network. For such traffic, burst and self-similarity are the most important statistical properties, meaning that inter-link interference at the receiving node i is correlated from one time slot to the next. According to the time correlation of the I _inter (t), since the Kalman filter (Kalman filter) is used to detect a radio signal received from the receiving node (i), it may be possible to predict the value of I _inter (t) . When the predicted I _inter (t) is obtained, Equation 3 may be changed as follows:

는 I_inter(t)의 예측된 값이다. here

Is the predicted value of I _inter (t).

If I _inter (t) is defined as:

,

,

The dynamic process of inter-link interference power (in dBm) can be expressed by the first Markov process as follows:

Where α is the weighting factor, 0 <α <1, and α is defined as:

Where ν is the speed of the receiving node i, η is the power control rate, c and Δ are constant coefficients, each defined by a high layer.

W (t) in Equation 5 is a zero mean Gaussian white noise sequence, and has a variance of σ ² _W (t).

The variance of i _inter (t) can be written as:

Let Y (t) be the interference power measured in timeslot t:

Y (t-1) = i _inter (t-1) + U (t-1)

Where U (t) is measurement noise and measurement noise which is zero mean Gaussian white noise with a dispersion of variance σ ² u.

Since i _inter (t) is independent of U (t), the variance of Y (t) is:

When the Kalman filter is employed to process the interfering signal on the receiving node i, the Kalman filter equation can be expressed as follows:

및

는 i_inter(t)의 후순위우선(posteriori) 및 선 순위우선(priori) 추정치를 각각 나타낸다. 즉, i_inter(t)의 검출 및 예측된 값; K(t)는 칼만 이득;

및

는 선순위우선 및 후순위우선 추정된 에러 분산이다. here

And

Denotes the posteriori and priori estimates of i _inter (t), respectively. That is, the detected and predicted value of i _inter (t); K (t) is Kalman gain;

And

Is the first and second priority estimated error variances.

It is estimated that ± 4dB of measurement accuracy for the measured i _inter (t) is required under normal conditions. If we estimate σ _U = 3dB, σ ² _U = 9 according to equations (7) and (9), the following equations can be obtained.

의 추정치

을 얻을 수 있다. Based on the interference measurements of the last L timeslots, according to equations 16 and 18

Estimate of

Can be obtained.

을 위한 수학식 16 및 수학식 18의 입력으로서 사용된다. 추정치

및 현재의 간섭 측정치는 간섭 전력

을 예측하기 위해 칼만 필터 수학식 10 및 수학식 14의 입력으로서 사용된다. Receiving node (i) measures the interference for each timeslot, and these interference measurements are estimated

It is used as the input of equations (16) and (18) for Estimate

And current interference measurements are interference power

Are used as inputs to the Kalman filter equations (10) and (14).

을 dBm로 산출한다.

는 mW 단위로 다음식으로서 얻을 수 있다. In fact, Equation 11 is

Is calculated in dBm.

Can be obtained in the following units in mW.

는 계산된 후, 송신 노드(j)의 송신 전력 P_j을 계산하기 위해서 수학식 4 및 수학식 2에서 예측된 간섭 전력으로서 사용될 수 있을 것이다.

May be used as the predicted interference power in equations (4) and (2) to calculate the transmit power P _j of transmit node j.

을 예측하는데 도움을 줄 수 있는 것처럼 보일 수 있다. 수신 노드가 네트워크에서 예측된 인터-링크 간섭 전력을 송신 노드로 다시 보낸 후에, 전송 노드는 피드백 정보에 따라 자신의 송신 전력을 조정할 수 있다. From the above description, the burst and self-similarity of the data traffic is determined by the receiving node as inter-link interference power, i.e.

It may seem to be able to help predict this. After the receiving node sends back the inter-link interference power predicted in the network to the transmitting node, the transmitting node can adjust its transmit power according to the feedback information.

The following description will be given to the transmission power control method to be executed between the transmitting node j and the corresponding receiving node i in the Ad hoc network according to FIG. 2.

를 예측하기 위해서 여기서 칼만 필터를 사용한다(단계 S10).First, as FIG. 2 illustrates, after receiving a wireless signal from transmitting node j, receiving node i detects background noise of the wireless signal, and inter-link interference power.

The Kalman filter is used here to predict (step S10).

Second, a receiving node (i) is the estimated bit error rate of the received channel in a conventional manner according to the received signal, and the _target SIR according to the following equation: Adjust _ij (step S20):

Where Δ is a fixed power control step and BER _req is the BER required to satisfy QoS.

The receiving node i then generates a Target SIR Control (TSC) in the usual way and transmits it to the corresponding transmitting node j according to the following equation (step S30):

Next, the receiving node i calculates E according to equation (4) (step S40).

Later, the receiving node i broadcasts a power control message containing the calculated E value for its neighboring node via the control channel (step S50). The corresponding transmitting node j may adjust its transmit power according to the power control message, and other neighbors may also use this broadcast message for channel estimation to obtain access information and route information. .

After receiving the power control message from the receiving node i, the transmitting node j extracts the information of E from the power control message (step S60).

The transmitting node j then receives the SIR _target according to the TSC command from the receiving node i and according to the following rules. Adjust _ij (t) (step S70):

Next, the transmitting node j predicts the channel gain r _ij in a conventional manner (step S80).

The transmitting node j is the adjusted SIR _{target ij} (t) and predicted channel gain r _ij Calculate the transmit power P _j according to Equation 2 according to the extracted E, and then adjust its transmit power (step S90).

은 칼만 필터를 사용해서 예측된다. 그러므로, 송신 노드(j)가 수신된 전력 제어 메시지로부터 E를 추출하고, E를 가지고 수학식 2로부터 계산된 전력 P_j에 따라 송신 전력을 조정할 때, 송신 노드(j)는 통상적인 모드에서 히스토리 정보에 기초하여 송신전력을 조정하기보다는 수신 모드에서 간섭 전력의 현재 예측 정보를 사용한다.As can be seen from the description above with FIG. 2, when the receiving node i calculates E through Equation 2, inter-link interference power

Is predicted using the Kalman filter. Therefore, when the transmitting node j extracts E from the received power control message and adjusts the transmit power according to the power P _j calculated from Equation 2 with E, the transmitting node j has a history in the normal mode. Rather than adjusting the transmit power based on the information, it uses the current prediction information of the interference power in the receive mode.

The power control method for use in the CDMA wireless communication system of the present invention may be implemented in computer software or computer hardware, or a combination of both.

3 illustrates a hardware architecture of a mobile terminal for implementing power control in a CDMA wireless communication system according to an embodiment of the present invention, and the same elements as those in the existing mobile terminal are not shown here.

As shown in FIG. 3, as the transmitting node j in the above, the transmitting unit 40 in the mobile terminal 10 is wireless to the another mobile terminal 10 operating as the receiving node i in the above. If the receiving unit 20 of another mobile terminal 10 receives the wireless signal as the receiving node i after receiving the wireless signal, the prediction unit 30 is here receiving node i. In order to predict the inter-link interference power, the Kalman filter above is used to process the radio signal. Then, at the receiving node i, the transmitting unit 40 sends a power control message to the transmitting node j so that the transmitting node j transmits its own according to the predicted inter-link interference power included in the power control message. Power can be adjusted.

When the receiving unit 20 at the transmitting node j receives the power control message from the receiving node i, the extracting unit 50 extracts the inter-link interference power predicted on the receiving node i, By providing the background noise included in the power control message to the adjustment unit 60, the adjustment unit 60 transmits the transmission unit at the transmitting node j with the above equation 2 according to the predicted inter-link power and the background noise. The transmit power of 40 can be adjusted.

As mentioned above, for the power control method and apparatus provided herein, the receiving node may use a Kalman filter to predict and calculate inter-link interference power according to the inherent burst and self-similarity of the data traffic. In this case, all nodes in a CDMA-based Ad hoc network can share network resources fairly. Thus, the corresponding transmitting node adjusts its transmit power using current prediction information of the interference power at the receiving node rather than based on historical information in a conventional manner. Therefore, the power control method in the present invention enables higher energy efficiency, lower interference and better system performance compared to the conventional method.

Although the present invention has been illustrated and described with respect to exemplary embodiments, power control methods and apparatus for use in the CDMA wireless communication network disclosed herein may be variously modified without departing from the spirit and scope of the present invention. It should be understood by those skilled in the art.

The present invention relates generally to a power control method and apparatus for use in a wireless communication network, and is particularly applicable to a power control method and apparatus for use in a CDMA wireless communication network.

Claims (18)

A power control method for use in a wireless communication network executed by a receiving node, the method comprising: (a) receiving a radio signal from a transmitting node; (b) predicting inter-link interference power on a receiving node according to the received wireless signal; (c) sending a power control message to the transmitting node such that the transmitting node can adjust its transmit power according to the predicted inter-link interference power included in the power control message. Comprising a power control method. The power control method according to claim 1, wherein the inter-link interference power is a total sum of interference powers generated by transmission powers of other communication nodes except for the transmitting node on the receiving node. 3. The method of claim 2, wherein the power control message further comprises background noise. 4. The method of any one of the preceding claims, wherein the predicted inter-link interference power can be obtained through processing the radio signal by using a Kalman filter. 5. The method of claim 4, wherein the power control message is broadcast over a control channel. 6. The method of claim 5, further comprising: generating a TSC command in accordance with the received wireless signal; Sending the TSC command to the transmitting node; A power control method for use in a wireless communication network executed by a transmitting node, the method comprising: (a) receiving a power control message from a receiving node; (b) extracting predicted inter-link interference power on a receiving node from the power control message; (c) adjusting the transmit power of the transmitting node according to the predicted inter-link interference power Comprising a power control method. 8. The method of claim 7, wherein the inter-link interference power is a total sum of interference power generated by transmission powers of other communication nodes except for the transmitting node on the receiving node. 10. The method of claim 8, wherein the power control message further comprises background noise, further comprising adjusting the transmit power of the transmitting node in accordance with the background noise. 10. The method of any one of claims 7 to 9, wherein the predicted inter-link interference power is obtained by the receiving node processing the radio signal through a Kalman filter. 11. The method of claim 10, wherein the transmitting node receives the power control message via a control channel. 12. The method of claim 11, further comprising: receiving a TSC command from the receiving node; Adjusting the transmit power of the transmitting node in accordance with the TSC command. 13. The method of claim 12, further comprising: measuring channel gain between the transmitting node and the receiving node; Adjusting the transmit power of the transmitting node in accordance with the channel gain. As a mobile terminal, A receiving unit for receiving a radio signal sent from another mobile terminal; A prediction unit, for predicting inter-link interference power on the mobile terminal according to the received wireless signal; A sending unit, for sending a power control message to the another mobile terminal such that another mobile terminal can adjust the transmit power according to the predicted inter-link interference power included in the power control message. Including, a mobile terminal. 15. The mobile terminal of claim 14, wherein the inter-link interference power is a total sum of interference power generated by transmission powers of other communication mobile terminals other than the other mobile terminal on the mobile terminal. 16. The mobile terminal of claim 15, wherein the prediction unit processes the wireless signal with a Kalman filter to obtain predicted inter-link interference power. A mobile terminal, comprising: a receiving unit for receiving a power control message from another mobile terminal; An extraction unit for extracting predicted inter-link interference power on the another mobile terminal from the power control message; Adjusting the transmit power of the mobile terminal according to the predicted inter-link interference power. 18. The mobile terminal of claim 17, wherein the inter-link interference power is a total sum of interference power generated by transmission powers of other communication mobile terminals except the mobile terminal on the another mobile terminal.

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