Method and apparatus for managing transmit power for device-to-device communication
A method and apparatus for managing transmit power for device-to-device communication is provided. According to an embodiment of the invention, a UE uses a component carrier of one cell to engage in D2D communication. In parallel with its D2D communication, the UE uses one or more other component carriers of one or more other cells to engage in cellular communication. The UE configures its D2D transmit power as well as its cellular transmit power so that its total transmit power does not exceed the UEs maximum power limit, and so that the transmit power on a component carrier of a cell does not exceed the maximum power limit for the cell that provides the component carrier.
1. A method, on a first UE, for managing transmit power in device-to-device communication and cellular communication, the method comprising:
determining a first configured maximum output power, wherein the first configured maximum output power is based on a configuration of a first cell;
determining a second configured maximum output power, wherein the second configured maximum output power is based on the configuration of the first cell and a configuration of a second cell;
determining whether a total transmit power would exceed the second configured maximum output power; and
if it is determined that the total transmit power would exceed the second configured maximum output power, performing steps comprising:
determining a cellular transmit power based on one or more of a plurality of factors, the plurality comprising: the first configured maximum output power, the second configured maximum output power, and the relative priority of service of device-to-device communication and cellular communication;
transmitting a cellular signal on a carrier of the first cell at the determined cellular transmit power;
determining a device-to-device transmit power based on one or more of a plurality of factors, the plurality comprising: the first configured maximum output power, the second configured maximum output power, and the relative priority of service of device-to-device communication and cellular communication; and
transmitting a device-to-device signal to a second UE on a carrier of the second cell at the determined device-to-device transmit power; wherein:
w 2 ( i )· {circumflex over (P)} D2D ( i )+ w 3 ( i )· {circumflex over (P)} PUSCH,k ( i )+ w 4 ( i )· {circumflex over (P)} PUCCH ( i )≦ {circumflex over (P)} CMAX ( i );
{circumflex over (P)} D2D (i) is the linear value of power setting of device-to-device signal transmission from the first UE to the second UE without power scaling;
{circumflex over (P)} PUSCH,k (i) is the linear value of power setting of cellular uplink data channel signal transmission from the first UE to a primary cell k without power scaling;
{circumflex over (P)} PUCCH (i) is the linear value of power setting of cellular uplink control channel signal transmission from the first UE without power scaling;
{circumflex over (P)} CMAX,k (i) is the linear value of the first configured maximum output power level;
{circumflex over (P)} CMAX (i) is the linear value of the second configured maximum output power level;
{circumflex over (P)} PUSCH,k ( i )+ {circumflex over (P)} PUCCH ( i )≦ {circumflex over (P)}CMAX,k ( i );
w 2 (i), w 3 (i) and w 4 (i) are power scaling factors; and
the determined device-to-device transmit power and the determined cellular transmit power are:
{tilde over (P)} D2D ( i )= w 2 ( i )· {circumflex over (P)} D2D ( i ),
{tilde over (P)} PUSCH,k ( i )= w 3 ( i )· {circumflex over (P)} PUSCH,k ( i ),
{tilde over (P)} PUCCH ( i )= w 4 ( i )· {circumflex over (P)} PUCCH ( i ), and
0≦ w 2 ( i ), w 3 ( i ), w 4 ( i )≦1.
2. A method for transmitting over a plurality of uplink carriers, the method comprising:
receiving an indication, from a network entity, to perform device-to-device communication on a first uplink carrier of the plurality of uplink carriers;
determining a total configured maximum output power, the total configured maximum output power being based on maximum power requirements for a plurality of configured serving cells associated with the plurality of uplink carriers;
transmitting a device-to-device signal on the first uplink carrier at a first transmit power level if the total transmit power of the UE would exceed the total configured maximum output power, or at a second transmit power level if the total transmit power of the UE would not exceed the total configured maximum output power; and
transmitting a set of cellular signals on one or more uplink carriers of the plurality of uplink carriers other than the first uplink carrier at a first set of transmit power levels if the total transmit power of the UE would exceed the total configured maximum output power, or at a second set of transmit power levels if the total transmit power of the UE would not exceed the total configured maximum output power;
wherein the total configured maximum output power is a first total configured maximum output power, the method further comprising:
determining a second total configured maximum output power, the second total configured maximum output power being based on the maximum power requirements for the plurality of configured serving cells except a cell associated with the first uplink carrier;
wherein the first set of transmit power levels of the set of cellular signals is based on one or more of the first and second total configured maximum output powers;
wherein the first transmit power level of the device-to-device signal, {tilde over (P)} D2D (i), and the first set of transmit power levels of the set of cellular signals, {tilde over (P)} PUCCH (i), {tilde over (P)} PUSCH,k (i), and {tilde over (P)} PUSCH,c (i), for subframe i satisfy inequalities comprising:
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wherein:
{circumflex over (P)} PUSCH,c (i) is the linear value of power setting of cellular uplink data channel signal transmission from the first UE to a serving cell c and that does not include uplink control information without power scaling;
{circumflex over (P)} D2D (i) is the linear value of power setting of device-to-device signal transmission from the first UE to the second UE without power scaling;
{circumflex over (P)} PUSCH,k (i) is the linear value of power setting of cellular uplink data channel signal transmission from the first UE to a serving cell k and that may include uplink control information without power scaling;
{circumflex over (P)} PUCCH (i) is the linear value of power setting of cellular uplink control channel signal transmission from the first UE over an uplink control channel without power scaling;
{circumflex over (P)} CMAX, (i) is the linear value of the first total configured maximum output power level;
{circumflex over (P)} CMAX,-j (i) is the linear value of the second total configured maximum output power level; and
w 1 (i), w 2 (i), w 3 (i) and w 4 (i) are power scaling coefficients, wherein:
{tilde over (P)} PUSCH,c ( i )= w 1 ( i )· {circumflex over (P)} PUSCH,c ( i );
{tilde over (P)} D2D ( i )= w 2 ( i )· {circumflex over (P)} D2D ( i );
{tilde over (P)} PUSCH,k ( i )= w 3 ( i )· {circumflex over (P)} PUSCH,k ( i );
{tilde over (P)} PUCCH ( i )= w 4 ( i )· {circumflex over (P)} PUCCH ( i ); and
0≦ w 1 (), w 2 ( i ), w 3 ( i ), w 4 ( i )≦1.