HK1171313A - Method and apparatus for mitigation of interference due to peer-to peer communication - Google Patents

Description

Method and apparatus for mitigating interference generated by peer-to-peer communication

This application claims priority from U.S. provisional application No.61/227,608, entitled "ad jacent channel protection BY P2P DEVICES," filed on 7, 22/2009, which is assigned to the assignee of the present application and is incorporated herein BY reference.

Technical Field

The present disclosure relates generally to communication, and more specifically to techniques for mitigating interference in a wireless communication network.

Background

Wireless communication networks are widely deployed to provide various communication content such as voice, video, packet data, messaging, broadcast, and so on. These wireless networks may be multiple-access networks capable of supporting multiple users by sharing the available network resources. Examples of such wireless networks include Wireless Wide Area Networks (WWANs) and Wireless Local Area Networks (WLANs).

A wireless communication network may include multiple base stations capable of supporting communication for multiple User Equipments (UEs). A UE may communicate with a base station via the downlink and uplink. The downlink (or forward link) refers to the communication link from the base stations to the UEs, and the uplink (or reverse link) refers to the communication link from the UEs to the base stations.

The UE is also capable of peer-to-peer (P2P) communication with another UE without communicating with a base station in the wireless network. P2P communication may reduce the load on the wireless network for local communication. Further, P2P communication between two UEs may enable a first UE to act as a relay for a second UE. This may allow the second UE to communicate with the wireless network even though the second UE may be outside of the normal coverage of the wireless network. However, P2P communication may cause interference to other UEs (or WWAN UEs) communicating with the base station in the wireless network. It is desirable to mitigate interference to WWAN UEs due to P2P communications.

Disclosure of Invention

Techniques for mitigating interference due to P2P communication are described herein. The P2P UE may communicate peer-to-peer with another UE and may send downlink signals on a particular carrier. The downlink signal may cause interference to WWAN UEs communicating with the base station on the same carrier or different carriers.

In an aspect, a P2P UE may measure the signal strength of downlink signals from a base station on a neighboring carrier and/or its carrier. The P2P UE may set its transmit power based on (e.g., proportional to) the measured signal strength in order to mitigate interference to the WWAN UE. If the measured signal strength is strong enough, the P2P UE may transmit at a higher power because it may have less interference impact on the WWAN UE. Conversely, if the measured signal strength is low, the P2P UE may transmit at a lower power in order to reduce interference to the WWAN UE.

In another aspect, the P2P UE may measure the signal strength of the uplink signal from the WWAN UE on the neighboring carrier and/or its carrier. The P2P UE may set its transmit power based on (e.g., inversely proportional to) the measured signal strength in order to mitigate interference to the WWAN UE. In one design, the P2P UE may measure a signal strength of an uplink signal from the WWAN UE and may determine its transmit power based on the measured signal strength. In one design, the P2P UE may estimate a path loss between the WWAN UE and the P2P UE based on the measured signal strength and the nominal/expected transmit power of the uplink signal. The P2P UE may then determine its transmit power based on the estimated path loss and a target received power at the WWAN UE for the downlink signal from the P2P UE.

The techniques described herein may also be used for other types of base stations and UEs. Various aspects and features of the disclosure are described in further detail below.

Drawings

Fig. 1 illustrates a wireless communication network.

Fig. 2 shows WWAN and P2P communication over different carriers.

Fig. 3 illustrates exemplary spectral mask requirements for a UE.

Fig. 4 illustrates operations by a P2P UE to mitigate interference to WWAN UEs.

Fig. 5 and 6 illustrate a process and apparatus, respectively, for mitigating interference due to P2P communication based on measurements of downlink signals.

Fig. 7 and 8 illustrate a process and apparatus, respectively, for mitigating interference due to P2P communication based on measurements of uplink signals.

Fig. 9 shows a block diagram of a P2P UE and station.

DETAILED DESCRIPTION OF EMBODIMENT (S) OF INVENTION

The techniques described herein may be used for various wireless communication networks, such as WWAN, WLAN, and so on. The terms "network" and "system" are often used interchangeably. The WWAN may be a Code Division Multiple Access (CDMA) network, a Time Division Multiple Access (TDMA) network, a Frequency Division Multiple Access (FDMA) network, an orthogonal FDMA (ofdma) network, a single-carrier FDMA (SC-FDMA) network, or the like. A CDMA network may implement a radio technology such as Universal Terrestrial Radio Access (UTRA), CDMA2000, etc. UTRA includes wideband CDMA (wcdma) and other variants of CDMA. cdma2000 covers IS-2000, IS-95 and IS-856 standards. TDMA networks may implement radio technologies such as global system for mobile communications (GSM). OFDMA networks may implement, for example, evolved UTRA (E-UTRA), Ultra Mobile Broadband (UMB), IEEE 802.16(WiMAX), IEEE 802.20, and,Etc. radio technologies. UTRA and E-UTRA are part of the Universal Mobile Telecommunications System (UMTS). 3GPP Long Term Evolution (LTE) and LTE-advanced (LTE-A) are new versions of UMTS that use E-UTRA. UTRA, E-UTRA, UMTS, LTE-A, and GSM are described in documents of the organization entitled "third Generation partnership project" (3 GPP). Is described in a document of the organization entitled "third Generation partnership project 2" (3GPP2)Cdma2000 and UMB are described. A WLAN may implement one or more standards of the IEEE 802.11 family of standards (also known as Wi-Fi), Hiperlan, etc. The techniques described herein may be used for the wireless networks and radio technologies described above as well as other wireless networks and radio technologies. For clarity, much of the description below is for a WWAN.

Fig. 1 shows a wireless communication network 100, which may be a WWAN. Wireless network 100 may include multiple base stations and other network entities capable of supporting communication for multiple UEs. For simplicity, only one base station 110 and three UEs 120, 122, and 124 are shown in fig. 1. A base station 110 may be an entity that communicates with UEs and may also be referred to as a node B, evolved node B (enb), access point, etc. Base stations 110 may provide communication coverage for a particular geographic area and may support communication for UEs located within the coverage area. The term "cell" can refer to a coverage area of a base station 110 and/or a base station subsystem serving the coverage area.

UEs may be dispersed throughout a wireless network, and each UE may be stationary or mobile. A UE may also be referred to as a mobile station, a terminal, an access terminal, a subscriber unit, a station, etc. A UE may be a cellular telephone, a Personal Digital Assistant (PDA), a wireless modem, a wireless communication device, a handheld device, a laptop computer, a cordless telephone, a Wireless Local Loop (WLL) station, a smartphone, a netbook, a smartbook, or the like. The UE may communicate with a base station. Alternatively or in addition, the UE may communicate peer-to-peer with other UEs.

In the example shown in fig. 1, UE 120 may be in communication with base station 110 and may be referred to as a WWAN UE. For WWAN communication between UE 120 and base station 110, UE 120 may receive a WWAN downlink signal from base station 110 and may send a WWAN uplink signal to base station 110. UEs 122 and 124 may communicate peer-to-peer with each other and may be referred to as P2P UEs. For P2P communication between UEs 122 and 124, UE122 may transmit P2P downlink signals to peer UE 124 and may receive P2P uplink signals from peer UE 124.

P2P communication may be supported in various ways. For example, a P2P UE may operate on a separate spectrum that is not used by the wireless network. Alternatively, the P2P UE may utilize the spectrum for the uplink of the wireless network, as using the spectrum for the downlink of the wireless network may be disadvantageous. A P2P UE communicating on the downlink spectrum may be in close proximity to a wwanie communicating with the wireless network. If the downlink spectrum is used, the P2P UE may cause high interference on the downlink to the wwanie, which may result in the WWAN UE not being able to receive downlink signals from the wireless network.

Fig. 2 illustrates WWAN and P2P communications over separate and adjacent carriers. Multiple carriers may be used for communication. Each carrier may be associated with a particular center frequency and a particular bandwidth. These carriers may be defined as not overlapping in frequency.

In the example shown in fig. 2, carrier 212 may be used for WWAN communication on the uplink of the wireless network and may be referred to as a WWAN uplink carrier. Carrier 222 may be used for WWAN communication on the downlink of the wireless network and may be referred to as a WWAN downlink carrier. The carrier 214 may be used for P2P communication on the uplink and may be referred to as a P2P uplink carrier. The carrier 224 may be used for P2P communication on the downlink and may be referred to as a P2P downlink carrier.

Ideally, WWAN communications should not be interfered with from P2P communications, and P2P communications should not be interfered with from WWAN communications. This may be achieved by using separate carriers for WWAN communication and P2P communication, e.g., as shown in fig. 2. This assumes that (i) WWAN communication can be constrained to be entirely within WWAN downlink and uplink carriers, and (ii) P2P communication can be constrained to be entirely within P2P downlink and uplink carriers. However, this assumption is not generally true.

Fig. 3 illustrates exemplary spectral mask requirements for a UE. The spectral mask may specify a certain maximum amount of ripple within the passband and may require a certain minimum amount of attenuation in the cutoff band. The modulated signal transmitted by the UE may be required to comply with spectral mask requirements. The modulated signal may include the most desirable signal components in the passband and typically may include undesirable signal components in the cutoff band. The undesired signal component may be at least Q decibels (dB) lower than the desired signal component, where Q may be a required cutoff band attenuation.

The undesired signal components in the modulated signal from the UE may be due to various phenomena, such as Local Oscillator (LO) leakage, in-phase/quadrature (I/O) imbalance, and non-linearity of the transmitter at the UE. For example, LO leakage may result in a leaked LO signal at the center frequency, and the leaked LO signal may be mixed with a desired signal component to generate an undesired signal component. I/O imbalance may be due to gain errors and/or phase errors between the I and Q paths in the transmitter and may generate undesirable signal components.

As shown in fig. 3, P2P UEs may cause interference on adjacent carriers due to out-of-band emissions from P2P UEs. Such inter-carrier interference can degrade performance of WWAN UEs communicating with the wireless network on the neighboring carrier. From a wireless network perspective, inter-carrier interference may be a greater problem than intra-carrier interference caused by P2P UEs to WWAN UEs. This is because the base station may be able to take corrective action to mitigate the in-carrier interference on its own carrier, for example, by dividing the system bandwidth between WWAN UEs and P2P UEs. However, the base station may have little or no control over the neighboring carriers. Therefore, mechanisms for mitigating inter-carrier interference to WWAN UEs on adjacent carriers from P2P UEs are highly desirable.

In an aspect, a P2P UE may detect downlink signals from a base station on neighboring carriers and/or its carriers and may measure the signal strength of each carrier on which the downlink signals are detected. The signal strength may correspond to received power or received signal quality. The P2PUE may set its transmit power based on (e.g., proportional to) the measured signal strength. In particular, if the measured signal strength is strong enough, the P2P UE may transmit at a higher power because it may have less interference impact on WWAN UEs communicating with the base station. Conversely, if the measured signal strength is low, the P2P UE may transmit at a lower power in order to reduce interference to the WWAN UE.

The P2P UE may detect the downlink signal from the base station in various ways. In one design, the P2P UE may include a WWAN receiver for the radio technology used by the base station. The P2P UE may then use the WWAN receiver to search for an appropriate transmission or signal from a base station. For example, the P2PUE may search for (i) synchronization signals sent by the base station to support cell search and acquisition by WWAN UEs, (ii) reference signals sent by the base station to support channel estimation and channel quality measurement by WWAN UEs, and (iii) other downlink transmissions. The reference signal is a signal known in advance by the transmitter and the receiver, and may also be referred to as a pilot. The P2PUE may search for cell-specific reference signals (CRS) transmitted by base stations in LTE networks, common pilot channels (CPICH) transmitted by base stations in WCDMA networks, pilot channels (PICH) transmitted by base stations in CDMA 1X networks, and so on. The P2P UE may measure the signal strength of a detected signal (e.g., CRS, CPICH, or PICH) on the carrier on which the signal is detected. Alternatively, the P2P UE may measure (i) the signal strength of other transmissions and/or signals on that carrier or (ii) the signal strength of the entire carrier.

In one design, the P2P UE may periodically detect a downlink signal from a base station and may measure the signal strength of each carrier on which the downlink signal is detected. The P2PUE may perform signal detection and measurement during a measurement gap, which may be a communication gap for a P2P UE. The measurement gap may be (i) a period of no communication specified by the radio technology to allow the UE to make measurements; or (ii) periods when the P2P UE is not communicating.

The P2P UE may determine its transmit power based on the measured signal strength on the neighboring carrier and/or its carrier in various ways. In one design, the P2P UE may determine its transmit power based on a function of the measured signal strength as follows:

P_TX＝f(P_RX) Equation (1)

Wherein, P_RXIs the measured signal strength, f (P)_RX) Can be any suitable function, and P_TXIs the transmit power of the P2P UE. The function may be defined based on one or more other parameters than the measured signal strength. In the present description, transmission power and reception power are given in units of decibels (dBm) with respect to one milliwatt, and path loss and offset are given in units of dB.

In one design, the P2P UE may determine its transmit power based on the measured signal strength as follows:

P_TX＝P_RX+Δ_OSequation (2)

Wherein, Delta_OSIs the offset. The offset may be any suitable value that can provide good performance for the P2PUE and WWAN UEs.

In another design, the P2PUE may compare the measured signal strength to different ranges of values, where each range is associated with a different transmit power of the P2P UE. The P2P UE may use a transmit power corresponding to the range within which the measured signal strength falls.

In general, P2P UEs may transmit at progressively higher transmit powers with progressively higher measured signal strengths. The transmit power of the P2P UE may or may not be a linear function of the measured signal strength. In one design, a P2P UE may select a lower than maximum transmit power if the measurement of signal strength on carriers neighboring the carrier and/or the P2P UE is unsuccessful. If no signal from the base station is detected, the base station is not present or the base station is present but too weak to be detected. The P2PUE may assume the latter and may limit its transmit power to an upper limit in order to reduce the impact on base station operation.

In another aspect, the P2P UE may measure the signal strength of the uplink signal from the WWAN UE on the neighboring carrier and/or its carrier. The P2P UE may set its transmit power based on (e.g., inversely proportional to) the measured signal strength in order to reduce interference to the WWAN UE. The operation of the P2P UE may be more clearly described in connection with the following example.

Fig. 4 illustrates operations of a P2P UE for mitigating interference to WWAN UEs. In the example shown in fig. 4, a WWAN UE may communicate with a base station in a wireless network. The P2P UE may communicate peer-to-peer with another UE, which may be referred to as a peer UE.

For WWAN communication, a WWAN UE may receive a WWAN downlink signal from a base station and may send a WWAN uplink signal to the base station. For P2P communication, the P2PUE may transmit P2P downlink signals to peer UEs and may receive P2P uplink signals from peer UEs. The P2P UE and the WWAN UE may be in close proximity to each other. The P2P UE may receive a WWAN uplink signal sent by the WWAN UE to the base station. Accordingly, the WWAN UE may receive a P2P downlink signal transmitted by the P2P UE to the peer UE. At the WWAN UE, the P2P downlink signal from the P2P UE may act as interference to the WWAN downlink signal from the base station and degrade the performance of the WWAN UE.

The base station may transmit at a transmission power P_TX，DL1Sending a WWAN downlink signal. WWAN UE can receive power P_RX，DL1＝P_TX，DL1-X receiving a WWAN downlink signal, wherein X is a path loss from the base station to the WWAN UE. The WWAN UE may estimate the path loss based on the known transmit power and the measured received power of the WWAN downlink signal. WWAN UE can transmit power P_TX，UL1Sending WWAN uplink signals, wherein PT_X，UL1Can be expressed as:

P_TX，UL1＝P₁+ X, equation (3)

Wherein, P₁Is the target received power of the WWAN uplink signal at the base station.

The P2P UE may receive power P_RX，UL1＝P_TX，UL1Y receives the WWAN uplink signal, where Y is the path loss from the WWAN UE to the P2P UE. The P2P UE may not know the transmit power of the WWAN uplink signal, and may estimate the "corrected" path loss by assuming the nominal/expected transmit power of the WWAN uplink signal as follows:

Z＝P_{TX，UL1，NOM}-P_RX，UL1equation (4)

＝P_{TX，UL1，NOM}-(P_TX，UL1-Y)，

Wherein, P_{TX，UL1，NOM}Is the nominal transmit power of the WWAN uplink signal and Z is the corrected path loss.

The P2P UE may transmit at a power P_TX，UL2Sending P2P downlink signals, wherein PT_X，UL2Can be expressed as:

P_TX，DL2＝P₂+Z

equation (5)

＝P₂+P_{TX，UL1，NOM}-(P_TX，UL1-Y)，

Wherein, P₂Is the target received power of the P2P downlink signal at the WWAN UE.

WWAN UE can receive power P_RX，DL2Receiving P2P downlink signals, wherein P_RX，DL2Can be expressed as:

P_RX，DL2＝P_TX，DL2-Y

＝P₂+ Z-Y equation (6)

＝P₂+P_{TX，UL1，NOM}-P₁-X。

The signal-to-noise-and-interference ratio (SINR) of the WWAN downlink signal at the WWAN UE may be expressed as:

SINR＝P_RX，DL1-P_RX，DL2

＝(P_TX，DL1-X)-(P₂+P_{TX，UL1，NOM}-P₁-X) equation (7)

＝(P_TX,DL1-P_{TX，UL1，NOM})+P₁-P₂。

Equation (7) assumes that the path loss from the WWAN UE to the P2P UE is approximately equal to the path loss from the P2P UE to the WWAN UE. Equation (7) also assumes that all or most of the interference observed by the WWAN UEs is due to P2P downlink signals from P2P UEs.

As an example, the transmission power, the reception power, and the path loss of each signal in fig. 4 may have the following values:

for WWAN downlink and uplink:

P_TX，DL1＝+43dBm，P_RX，DL1＝-42dBm，X＝85dB，

P_TX，UL1＝-15dBm，P₁＝-100dBm，

for the link between the WWAN UE and the P2P UE:

P_TX，UL1＝-15dBm， P_RX，UL1＝-50dBm，Y＝35dB，

P_{TX，UL1，NOM}＝-10dBm，P₂＝-60dBm， Z＝40dB，

P_TX，DL2＝-20dBm， P_RX，DL2＝-55dBm。

for the example given above, the base station may transmit the WWAN downlink signal at a transmit power of +43 dBm. The WWAN UE may receive the WWAN downlink signal at a received power of-42 dBm, with a path loss of 85 dB. The target received power of the WWAN uplink signal at the base station may be-100 dBm. The WWAN UE may transmit the WWAN uplink signal at-15 dBm transmit power due to an 85dB path loss. The path loss from the WWAN UE to the P2P UE may be 35dB, and the P2P UE may receive the WWAN uplink signal with a received power of-50 dBm. The nominal/expected transmit power of the WWAN uplink signal may be-10 dBm and the corrected path loss may be 40 dB. The target received power of the P2P downlink signal at the WWAN UE may be-60 dBm, and the P2P UE may send the P2P downlink signal at a power level of-20 dBm. The received power of the P2P downlink signal at the WWAN UE may be-55 dBm. The SINR of the WWAN downlink signal at the WWAN UE may be-42 + 55-13 dB.

As shown in equation (7), the WWAN UE may observe SINR, which may be independent of the location of the WWAN UE and the P2P UE. Specifically, the SINR does not depend on the path loss X of the WWAN link or the path loss Y of the P2P link. The target SINR for the WWAN UE may be determined based on the appropriate values of the parameters shown in the last row of equation (7). For example, can be to P₂A selection is made to obtain a target SINR for the WWAN UE.

In the design shown in equation (3), the WWAN UE may perform path loss inversion (inversion) and may set its transmit power in proportion to the path loss between the WWAN UE and the base station. In a second design, the transmit power of the WWAN UE may be adjusted using power control. In this design, the transmit power of the WWAN uplink signal from the WWAN UE may be expressed as:

P_TX，UL1＝P₁+ g (X), equation (8)

Where g (x) may be any suitable function of path loss.

For the second design, the P2P UE may set its transmit power for its P2P downlink signal as described above for fig. 4. The SINR of the WWAN UE may then be expressed as:

SINR＝(P_TX，DL1-P_{TX，UL1，NOM})+P₁-P₂-X + g (X). Equation (9)

For the second design, the SINR of the WWAN UE may depend on the path loss X between the WWAN UE and the base station, and the path loss may depend on the location of the WWAN UE. A conservative estimate of the smallest possible value of g (X) -X may be used, and P may be considered₂The selection is made to take into account g (X) -X and obtain a target SINR for the WWAN UE. Can also be used for P₂The selection is made to compensate for link imbalance between the downlink and uplink, calibration errors, etc.

For clarity, the above description assumes that the P2P UE transmits the P2P downlink signal on the same carrier used by the base station to transmit the WWAN downlink signal. If the P2P UE and the base station transmit on adjacent carriers, the transmit power of the P2P downlink signal may be determined as follows:

P_TX，DL2＝P₂+Z+δ_OS

equation (10)

＝P₂+P_{TX，UL1，NOM}-(P_TX，UL1-Y)+δ_OS，

Wherein, delta_OSIs an offset or adjustment. Offset delta_OSMay depend on the cutoff-band attenuation requirements for P2P UEs. For example, if the cutoff band attenuation is 30dB, the offset may be equal to 30 dB. The transmit power of the P2P UE may be increased by 30dB due to operation on the adjacent carrier rather than on the same carrier as the base station.

In one design, the P2P UE may autonomously measure the received power of the WWAN uplink signal from the WWAN UE and may adjust its transmit power for the P2P downlink signal based on the received power of the WWAN uplink signal to mitigate interference to the WWAN UE. The P2P UE may be provided with values of relevant parameters to calculate its transmit power, e.g., as shown in equation (5) or (10). The WWAN UE and the base station may not need to be aware of the existence of the P2P UE. In another design, the P2P UE may autonomously measure the total received power on the uplink. This design may be used, for example, when the P2P UE does not have information about the WWAN UE and cannot measure the received power of the WWAN UE.

In another design, the P2P UE may be provided with information that may be used to improve interference mitigation for the WWAN UE. For example, a P2P UE may be provided with information for one or more of the following:

● used by WWAN UEs, which may replace the nominal transmit power P_{TX，UL1，NOM}And an

●, which may be used to search for WWAN uplink signals from the WWAN UE.

In one design, the P2P UE may always perform interference mitigation for WWAN UEs. In another design, the P2P UE may perform interference mitigation when required. For example, the WWAN UE may observe poor channel conditions on the WWAN downlink and may report this to the base station. The base station may then send information regarding the poor channel conditions observed by the WWAN UE. The P2P UE may receive the information from the base station and may perform interference mitigation in response to receiving the information.

Fig. 5 shows a design of a process 500 for mitigating interference due to peer-to-peer communication. Process 500 may be performed by a UE (as described below) or by some other entity. The UE may detect for a downlink signal from a base station based on at least one synchronization signal, or at least one reference signal, and/or some other transmission or signal sent by the base station. The UE may communicate peer-to-peer with another UE and may not communicate with the base station. The UE may measure a signal strength (e.g., received power) of a downlink signal from the base station (block 512). The UE may determine its transmit power based on the measured signal strength of the downlink signal (block 514). In one design, the UE may determine its transmit power based on a function of the measured signal strength of the downlink signal, e.g., as shown in equation (1). In another design, the UE may determine its transmit power based on the measured signal strength of the downlink signal and an offset, e.g., as shown in equation (2).

The UE may receive a downlink signal from a base station on a first carrier. In one design, the UE may transmit on the first carrier and may determine its transmit power for the carrier. In another design, the UE may transmit on a second carrier different from the first carrier (e.g., adjacent to the first carrier) and may determine its transmit power for the second carrier.

Fig. 6 shows a design of an apparatus 600 for mitigating interference due to peer-to-peer communication. The apparatus 600 includes a module 612 for measuring a signal strength of a downlink signal from a base station, and a module 614 for determining a transmit power of the UE based on the measured signal strength of the downlink signal. The UE may communicate peer-to-peer with another UE and may not communicate with the base station.

Fig. 7 shows a design of a process 700 for mitigating interference to a first UE due to peer-to-peer communication by a second UE. The first UE may communicate with a base station and the second UE may communicate peer-to-peer with a third UE. Process 700 may be performed by a second UE (as described below) or by some other entity. The second UE may measure a signal strength (e.g., received power) of at least the uplink signal from the first UE (block 712). In one design, the second UE may measure the signal strength of the uplink signal from only the first UE. In another design, the second UE may measure a total signal strength on the uplink that will include uplink signals from the first UE and possibly uplink signals from other UEs. In either case, the second UE may determine its transmit power based on the measured signal strength of at least the uplink signal from the first UE (block 714).

The first UE may receive a downlink signal from a base station on a first carrier. In one design, the second UE may transmit on the first carrier and may determine its transmit power for the first carrier based on at least the measured signal strength of the uplink signal from the first UE. In another design, the second UE may transmit on a second carrier that is different from (e.g., adjacent to) the first carrier, and may determine its transmit power for the second carrier based on at least the measured signal strength of the uplink signal from the first UE.

In one design of block 714, the second UE may be based on the measured signal strength (e.g., P) of the uplink signal from the first UE_RX，UL1) To estimate the path loss (e.g., Z) between the first UE and the second UE. The nominal/expected transmit power (e.g., P) of the uplink signal from the first UE may also be based on_{TX，UL1，NOM}) The path loss is estimated, for example, as shown in equation (4). The second UE may then target received power (e.g., P) at the first UE based on the estimated path loss and a downlink signal from the second UE₂) To determine its transmit power, e.g., as shown in equation (5). The second UE may also be further based on the offset (e.g., δ)_OS) To determine its transmit power, where the offset may be determined by the amount of attenuation of the out-of-band emissions from the second UE, e.g., as shown in equation (10).

The target received power of the downlink signal from the second UE may be selected to provide desired performance for the first UE and possibly to account for other factors. In one design, the uplink signal from the first UE may be determined based on a function of path loss between the first UE and the base station, e.g., as shown in equation (8). In this case, a target received power of the downlink signal from the second UE at the first UE may be determined based on the function of the path loss.

In one design, the second UE may perform interference mitigation at all times. In another design, the second UE may perform interference mitigation only when required or indicated. In this design, the second UE may receive information indicating that the first UE observed poor channel conditions. In response, the second UE may determine its transmit power based on the measured signal strength of the uplink signal from the first UE to mitigate interference to the first UE.

In one design, the second UE may autonomously perform interference mitigation based on information known and/or collected by the second UE. In another design, the second UE may receive information related to an uplink signal transmitted by the first UE and may perform interference mitigation based on the received information. The information may be received from the first UE and/or a base station in communication with the first UE. The second UE may measure the signal strength of the uplink signal based on received information, which may include information about a sequence used by the first UE, and the like. The second UE may also determine its transmit power based on received information, which may include the transmit power of the first UE, etc.

Fig. 8 shows a design of an apparatus 800 for mitigating interference to a first UE due to peer-to-peer communication by a second UE. The apparatus 800 may be for a second UE. The apparatus 800 comprises: means 812 for measuring a signal strength of an uplink signal at a second UE from at least a first UE, wherein the first UE is in communication with a base station and the second UE is in peer-to-peer communication with a third UE; and a module 814 for determining a transmit power of the second UE based on the measured signal strength of at least the uplink signal from the first UE.

The modules in fig. 6 and 8 may comprise processors, electronics devices, hardware devices, electronics components, logic circuits, memories, software codes, firmware codes, etc., or any combination thereof.

Fig. 9 shows a block diagram of a design of the sta 112 and the P2P UE 122. Station 112 may be base station 110 or UE 120 in fig. 1. A station 112 may be equipped with T antennas 934a through 934T, and UE122 may be equipped with R antennas 952a through 952R, where typically T ≧ 1 and R ≧ 1.

At station 112, a transmit processor 920 may receive data from a data source 912 and control information from a controller/processor 940. Processor 920 may process (e.g., encode and modulate) the data and control information to obtain data symbols and control symbols, respectively. Processor 920 may also generate reference symbols corresponding to one or more reference signals and/or one or more synchronization signals. A Transmit (TX) multiple-input multiple-output (MIMO) processor 930 may perform spatial processing (e.g., precoding) on the data symbols, the control symbols, and/or the reference symbols, if applicable, and may provide T output symbol streams to T Modulators (MODs) 932a through 932T. Each modulator 932 may process a respective output symbol stream (e.g., for OFDM, SC-FDMA, etc.) to obtain an output sample stream. Each modulator 932 may further process (e.g., analog convert, amplify, filter, and upconvert) the output sample stream to obtain a modulated signal. T modulated signals from modulators 932a through 932T may be transmitted via T antennas 934a through 934T, respectively.

At UE122, antennas 952a through 952r may receive the modulated signals from station 112 and other stations (e.g., peer UEs 124, other UEs, and/or base stations), and may provide received signals to demodulators (DEMODs) 954a through 954r, respectively. Each demodulator 954 may condition (e.g., filter, amplify, downconvert, and digitize) a respective received signal to obtain input samples. Each demodulator 954 may further process the input samples (e.g., for OFDM, SC-FDMA, etc.) to obtain received symbols. A MIMO detector 956 may obtain received symbols from all R demodulators 954a through 954R, perform MIMO detection on the received symbols, if applicable, and provide detected symbols. A receive processor 958 may process (e.g., demodulate and decode) the detected symbols, provide decoded data for UE122 to a data sink 960, and provide decoded control information to a controller/processor 980.

At the UE122, a transmit processor 964 may receive data from a data source 962 and control information from a controller/processor 980. A processor 964 may process (e.g., encode and modulate) the data and control information to obtain data symbols and control symbols, respectively. The processor 964 may also generate reference symbols corresponding to one or more reference signals and/or one or more synchronization signals. The symbols from transmit processor 964 may be processed by a TX MIMO processor 966, further processed by modulators 954a through 954r (e.g., for SC-FDM, OFDM, etc.), and transmitted back to peer UE 124 and/or other stations, if applicable. Station 112 may receive the modulated signal transmitted by UE 122.

At station 112, the modulated signals from UE122 and other stations (e.g., other UEs and/or base stations) may be received by antennas 934, processed by demodulators 932, detected by a MIMO detector 936 if applicable, and further processed by a receive processor 938 to obtain decoded data and control information sent to station 112. Processor 938 may provide the decoded data to a data sink 939 and the decoded control information to controller/processor 940.

Controllers/processors 940 and 980 may direct operation at station 112 and UE122, respectively. Memories 942 and 982 may store data and program codes for station 112 and UE122, respectively. Demodulator 954 and/or processor 980 may detect for signals from base stations and/or UEs and may measure signal strengths of the detected signals. As described above, the processor 980 may determine the transmit power of the UE122 based on the measured signal strength. Processor 980 and/or other processors and modules at UE122 may perform or direct process 500 in fig. 5, process 700 in fig. 7, and/or other processes for the techniques described herein.

Those of skill in the art would understand that information and signals may be represented using any of a variety of different technologies and techniques. For example, data, instructions, commands, information, signals, bits, symbols, and chips that may be referenced throughout the above description may be represented by voltages, currents, electromagnetic waves, magnetic fields or particles, optical fields or particles, or any combination thereof.

Those of skill would further appreciate that the various illustrative logical blocks, modules, circuits, and algorithm steps described in connection with the disclosure herein may be implemented as electronic hardware, computer software, or combinations of both. To clearly illustrate this interchangeability of hardware and software, various illustrative components, blocks, modules, circuits, and steps have been described above generally in terms of their functionality. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the overall system. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present disclosure.

The various illustrative logical blocks, modules, and circuits described in connection with the disclosure herein may be implemented or performed with the following components: a general purpose processor, a Digital Signal Processor (DSP), an Application Specific Integrated Circuit (ASIC), a Field Programmable Gate Array (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination of these components designed to perform the functions described herein. A general purpose processor may be a microprocessor, but in the alternative, the processor may be any conventional processor, controller, microcontroller, or state machine. A processor may also be implemented as a combination of computing devices, e.g., a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration.

The steps of a method or algorithm described in connection with the disclosure herein may be embodied directly in hardware, in a software module executed by a processor, or in a combination of the two. A software module may reside in RAM memory, flash memory, ROM memory, EPROM memory, EEPROM memory, registers, hard disk, a removable disk, a CD-ROM, or any other form of storage medium known in the art. An example storage medium may be coupled to the processor such the processor can read information from, and write information to, the storage medium. In the alternative, the storage medium may be integral to the processor. The processor and the storage medium may reside in an ASIC. The ASIC may reside in a user terminal. In the alternative, the processor and the storage medium may reside as discrete components in a user terminal.

In one or more example designs, the functions may be implemented in hardware, software, firmware, or any combination thereof. If implemented in software, the functions may be stored on or transmitted over as one or more instructions or code on a computer-readable medium. Computer-readable media includes both computer storage media and communication media including any medium that facilitates transfer of a computer program from one place to another. A storage media may be any available media that can be accessed by a general purpose or special purpose computer. By way of example, and not limitation, such computer-readable media can comprise RAM, ROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other medium which can be used to carry or store desired program code means in the form of instructions or data structures and which can be accessed by a general-purpose or special-purpose computer, or a general-purpose or special-purpose processor. Also, any connection is properly termed a computer-readable medium. For example, if the software is transmitted from a website, server, or other remote source using a coaxial cable, fiber optic cable, twisted pair, Digital Subscriber Line (DSL), or wireless technologies such as infrared, radio, and microwave, then the coaxial cable, fiber optic cable, twisted pair, DSL, or wireless technologies such as infrared, radio, and microwave are included in the definition of medium. Disk and disc, as used herein, includes Compact Disc (CD), laser disc, optical disc, Digital Versatile Disc (DVD), floppy disk, blu-ray disc where disks usually reproduce data magnetically, while discs reproduce data optically with lasers. Combinations of the above should also be included within the scope of computer-readable media.

The previous description of the disclosure is provided to enable any person skilled in the art to make or use the disclosure. Various modifications to the disclosure will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other variations without departing from the spirit or scope of the disclosure. Thus, the disclosure is not intended to be limited to the examples and designs described herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims (35)

1. A method for wireless communication, comprising:

measuring a signal strength of a downlink signal from a base station; and

determining a transmit power of a User Equipment (UE) based on the measured signal strength of the downlink signal, the UE communicating peer-to-peer with another UE and not communicating with the base station.

2. The method of claim 1, further comprising:

detecting the downlink signal from the base station based on at least one synchronization signal, or at least one reference signal, or both, transmitted by the base station.

3. The method of claim 1, wherein the determining the transmit power of the UE comprises: determining a transmit power of the UE based on a function of the measured signal strength of the downlink signal.

4. The method of claim 1, wherein the determining the transmit power of the UE comprises: determining a transmit power of the UE based on the measured signal strength of the downlink signal and an offset.

5. The method of claim 1, further comprising:

receiving the downlink signal from the base station on a first carrier, and wherein the transmit power of the UE is for a second carrier different from the first carrier.

6. The method of claim 1, further comprising:

receiving the downlink signal from the base station on a first carrier, and wherein the transmit power of the UE is for the first carrier.

7. An apparatus for wireless communication, comprising:

means for measuring a signal strength of a downlink signal from a base station; and

means for determining a transmit power of a User Equipment (UE) in peer-to-peer communication with another UE and not in communication with the base station based on the measured signal strength of the downlink signal.

8. The apparatus of claim 7, further comprising:

means for detecting the downlink signal from the base station based on at least one synchronization signal, or at least one reference signal, or both transmitted by the base station.

9. The apparatus of claim 7, wherein the means for determining the transmit power of the UE comprises: means for determining a transmit power of the UE based on a function of the measured signal strength of the downlink signal.

10. The apparatus of claim 7, further comprising:

means for receiving the downlink signal from the base station on a first carrier, and wherein the transmit power of the UE is for a second carrier different from the first carrier.

11. An apparatus for wireless communication, comprising:

at least one processor configured to measure a signal strength of a downlink signal from a base station; and determining a transmit power of a User Equipment (UE) based on the measured signal strength of the downlink signal, the UE communicating peer-to-peer with another UE and not communicating with the base station.

12. The apparatus of claim 11, wherein the at least one processor is configured to: detecting the downlink signal from the base station based on at least one synchronization signal, or at least one reference signal, or both, transmitted by the base station.

13. The apparatus of claim 11, wherein the at least one processor is configured to: determining a transmit power of the UE based on a function of the measured signal strength of the downlink signal.

14. The apparatus of claim 11, wherein the at least one processor is configured to: receiving the downlink signal from the base station on a first carrier and determining a transmit power of the UE for a second carrier different from the first carrier.

15. A computer program product, comprising:

a non-transitory computer-readable medium comprising:

code for causing at least one computer to measure a signal strength of a downlink signal from a base station; and

code for causing the at least one computer to determine a transmit power of a User Equipment (UE) based on the measured signal strength of the downlink signal, the UE communicating peer-to-peer with another UE and not communicating with the base station.

16. A method for wireless communication, comprising:

measuring a signal strength of an uplink signal at a second User Equipment (UE) from at least a first UE in communication with a base station, the second UE in peer-to-peer communication with a third UE; and

determining a transmit power of the second UE based on at least the measured signal strength of the uplink signal from the first UE.

17. The method of claim 16, wherein the step of measuring signal strength comprises: measuring signal strength of the uplink signal from only the first UE, and wherein the step of determining the transmit power of the second UE comprises: determining a transmit power of the second UE based on the measured signal strength of the uplink signal from only the first UE.

18. The method of claim 16, wherein the step of measuring signal strength comprises: measuring a total signal strength of an uplink at the second UE, and wherein the step of determining the transmit power of the second UE comprises: determining a transmit power of the second UE based on the measured total signal strength of the uplink.

19. The method of claim 17, wherein the determining the transmit power of the second UE comprises: estimating a path loss between the first UE and the second UE based on the measured signal strength of the uplink signal from only the first UE, and determining a transmit power of the second UE based on the estimated path loss.

20. The method of claim 19, wherein the path loss between the first UE and the second UE is estimated further based on a nominal transmit power of the uplink signal from the first UE.

21. The method of claim 16, wherein the transmit power of the second UE is determined based further on a target received power of a downlink signal from the second UE at the first UE.

22. The method of claim 21, wherein the transmit power of the uplink signal from the first UE is determined based on a function of a path loss between the first UE and a base station, and wherein the target received power of a downlink signal from the second UE at the first UE is determined based on the function of the path loss.

23. The method of claim 16, wherein the transmit power of the second UE is determined based further on an offset determined by an amount of attenuation of out-of-band emissions from the second UE.

24. The method of claim 16, further comprising:

receiving information indicating that the first UE observes poor channel conditions, and wherein a transmit power of the second UE is determined based on at least the measured signal strength of the uplink signal from the first UE in response to receiving the information.

25. The method of claim 17, further comprising:

receiving information related to the uplink signal from the first UE, and wherein only a signal strength of the uplink signal from the first UE is measured based on the received information, or a transmit power of the second UE is determined based on the received information, or both.

26. The method of claim 16, wherein the first UE receives a downlink signal from a base station on a first carrier, and wherein a transmit power of the second UE on a second carrier is determined based on at least the measured signal strength of the uplink signal from the first UE, the second carrier being different from the first carrier.

27. The method of claim 16, wherein the first UE receives a downlink signal from a base station on a first carrier, and wherein a transmit power of the second UE on the first carrier is determined based on at least the measured signal strength of the uplink signal from the first UE.

28. An apparatus for wireless communication, comprising:

means for measuring a signal strength of an uplink signal at a second User Equipment (UE) from at least a first UE in communication with a base station, the second UE in peer-to-peer communication with a third UE; and

means for determining a transmit power of the second UE based on at least the measured signal strength of the uplink signal from the first UE.

29. The apparatus of claim 28, wherein the means for measuring signal strength comprises: means for measuring a signal strength of the uplink signal from only the first UE, and wherein the means for determining the transmit power of the second UE comprises: means for determining a transmit power of the second UE based on the measured signal strength of the uplink signal from only the first UE.

30. The apparatus of claim 29, wherein the means for determining the transmit power of the second UE comprises:

means for estimating a path loss between the first UE and the second UE based on measured signal strength of the uplink signal from only the first UE, an

Means for determining a transmit power of the second UE based on the estimated path loss.

31. The apparatus of claim 28, wherein the transmit power of the second UE is determined based further on a target received power of a downlink signal from the second UE at the first UE.

32. The apparatus of claim 28, wherein the transmit power of the second UE is determined based further on an offset determined by an amount of attenuation of out-of-band emissions from the second UE.

33. The apparatus of claim 28, wherein the first UE receives a downlink signal from a base station on a first carrier, and wherein a transmit power of the second UE on a second carrier is determined based on at least the measured signal strength of the uplink signal from the first UE, the second carrier being different from the first carrier.

34. An apparatus for wireless communication, comprising:

at least one processor configured to measure a signal strength of an uplink signal at a second User Equipment (UE) from at least a first UE in communication with a base station, the second UE in peer-to-peer communication with a third UE, and determine a transmit power of the second UE based on the measured signal strength of the uplink signal from at least the first UE.

35. A computer program product, comprising:

a non-transitory computer-readable medium comprising:

code for causing at least one computer to measure a signal strength of an uplink signal at a second User Equipment (UE) from at least a first UE in communication with a base station, the second UE in peer-to-peer communication with a third UE, and

code for causing the at least one computer to determine a transmit power of the second UE based on at least the measured signal strength of the uplink signal from the first UE.