Transmit emission control in a wireless transceiver

Abstract

Methods and apparatus for control of uplink resource allocation and undesirable transmit emissions from a wireless transceiver in a frequency division duplex (FDD) or hybrid frequency division duplex (H-FDD) wireless system. The bandwidths spanned by the receive band and the transmit band may be symmetric or asymmetric. Additionally, each of the receive band or the transmit band may be contiguous or may be an aggregate of multiple discontinuous frequency bands. The wireless transceiver can control undesirable transmit emissions from occurring in a predetermined frequency band by using an offset LO frequency and restricting transmit signals to frequencies away from the predetermined frequency band. Alternatively, in an asymmetric FDD system where a receive band is larger than a transmit band, the transceiver can limit transmit signal allocation to the transmit band. The transceiver can further limit out of band transmit emissions using an offset LO frequency.

1 . A method of transmit emission control in a wireless transceiver, the method comprising:
 receiving a downlink Orthogonal Frequency Division Multiplex (OFDM) symbol in a downlink frequency band; and   determining an uplink allocation in an uplink OFDM symbol of an uplink frequency band wherein the uplink frequency band is distinct from the downlink frequency band and wherein the uplink OFDM symbol includes a number of uplink subcarriers distinct from a number of downlink subcarriers in the downlink OFDM symbol.   
     
     
         2 . The method of  claim 1 , further comprising:
 remapping the uplink allocation to a remapped allocation in a reduced uplink frequency band that is narrower than the uplink frequency band;   generating the uplink OFDM symbol based on the remapped allocation; and   transmitting the uplink OFDM symbol.   
     
     
         3 . A wireless apparatus with transmit emission control, the apparatus comprising:
 a receiver configured to receive wireless downlink signals in a downlink frequency band, the wireless signals including a virtual uplink resource allocation;   a channel index remapper coupled to the receiver and configured to remap the virtual uplink resource allocation to an uplink resource allocation;   a signal mapper configured to map uplink information to a plurality of uplink subcarriers based on the uplink resource allocation; and   a transmitter configured to transmit the plurality of uplink subcarriers in an uplink frequency band distinct from the downlink frequency band.   
     
     
         4 . The apparatus of  claim 3 , further comprising a filter configured to filter a signal mapper output based on a bandwidth of the uplink resource allocation, and couple a filtered uplink signal to the transmitter. 
     
     
         5 . The apparatus of  claim 4 , wherein the filter comprises a programmable digital filter. 
     
     
         6 . The apparatus of  claim 4 , wherein the filter comprises an analog variable filter. 
     
     
         7 . The apparatus of  claim 4 , further comprising a bandwidth controller configured to vary a bandwidth of the filter based on the uplink resource allocation. 
     
     
         8 . The apparatus of  claim 3 , wherein the receiver is configured to receive the wireless downlink signals during a downlink subframe that is time division duplexed with an uplink subframe during which the transmitter transmits the plurality of uplink subcarriers. 
     
     
         9 . The apparatus of  claim 3 , wherein the receiver is configured to receive the wireless downlink signals in a plurality of OFDM symbols having a downlink subcarrier spacing that is substantially the same as an uplink subcarrier spacing. 
     
     
         10 . The apparatus of  claim 9 , wherein a number of downlink subcarriers is the same as a number of subcarriers in a virtual uplink bandwidth. 
     
     
         11 . The apparatus of  claim 9 , wherein a number of downlink subcarriers is the greater than a number of subcarriers in the uplink frequency band. 
     
     
         12 . The apparatus of  claim 4 , further comprising a local oscillator (LO) and wherein the channel index remapper is configured to program a LO frequency at a frequency offset from a nominal LO frequency for a virtual uplink band, and remapping the virtual uplink resource allocation based on the frequency offset. 
     
     
         13 . A wireless apparatus with transmit emission control, the apparatus comprising:
 a receiver configured to receive in a downlink frequency band a plurality of downlink Orthogonal Frequency Division Multiplex (OFDM) symbols including a virtual uplink resource allocation; and   a transmitter configured to transmit a plurality of uplink OFDM symbols based on the virtual uplink resource allocation and in an uplink frequency band distinct from the downlink frequency band, wherein the uplink frequency band has a second bandwidth distinct from a first bandwidth of the downlink frequency band.   
     
     
         14 . The apparatus of  claim 13 , wherein the second bandwidth is narrower than the first bandwidth. 
     
     
         15 . The apparatus of  claim 13 , wherein a downlink subcarrier spacing is substantially identical to a virtual uplink subcarrier spacing. 
     
     
         16 . The apparatus of  claim 13 , wherein the receiver receives the OFDM symbols in a downlink subframe that is time division duplexed with an uplink subframe during which the transmitter is configured to transmit. 
     
     
         17 . The apparatus of  claim 13 , further comprising a channel index remapper coupled to the receiver and configured to remap the virtual uplink resource allocation to an uplink resource allocation in the uplink frequency band. 
     
     
         18 . The apparatus of  claim 17 , wherein the channel index remapper remaps the virtual uplink resource allocation based in part on a difference in a number of subcarriers in a virtual uplink frequency band and a number of subcarriers in the uplink frequency band. 
     
     
         19 . The apparatus of  claim 13 , further comprising:
 a local oscillator (LO) common to the receiver and the transmitter; and   a LO controller configured to control a frequency of the LO based on a time division duplexed transmit and receive timing.   
     
     
         20 . The apparatus of  claim 19 , wherein the LO controller is further configured to control a frequency of the LO based on a state of a reduced emissions mode.