SPREAD SPECTRUM COMMUNICATION IN FEMTOCELL NETWORKS, AND ASSOCIATED DEVICES, SYSTEMS, AND METHODS
Various embodiments relate to spread spectrum modulation. A device may include a processor and at least one transmitter. The device may be configured to add a cyclic prefix (CP) to each block of a number of blocks of a direct sequence spread spectrum (DSSS) signal to generate a cyclic prefix-direct sequence spread spectrum (CP-DSSS) signal. Further, the device may be configured to transmit, via a channel, the CP-DSSS signal. Associated methods and communications systems are also disclosed.
1 . A device including a processor and at least one transmitter, the device configured to:
add a cyclic prefix (CP) to each block of a number of blocks of a direct sequence spread spectrum (DSSS) signal to generate a cyclic prefix-direct sequence spread spectrum (CP-DSSS) signal; and
transmit, via a channel, the CP-DSSS signal.
2 . The device of claim 1 , wherein the device is configured to modulate a set of orthogonal vectors that are cyclically shifted versions of a root sequence to add the CP to each block of the number of blocks of the DSSS signal.
3 . The device of claim 1 , wherein the device is configured to transmit the CP-DSSS signal, via the channel, to a femtocell gateway (FGW) within a first network.
4 . The device of claim 3 , wherein the device is further configured to at least one of:
synchronize signaling with the FGW via downlink synchronization of a long-term evolution (LTE) network including the first network; and
share spectrum resources with the LTE network.
5 . The device of claim 1 , wherein the device is further configured to transmit the CP-DSSS signal via the channel at a power level less than a noise floor of the channel.
6 . The device of claim 1 , wherein the device includes a user equipment (UE) of a femtocell.
7 . A method, comprising:
adding a cyclic prefix (CP) to each block of a number of blocks of a first direct sequence spread spectrum (DSSS) signal to generate a first cyclic prefix-direct sequence spread spectrum (CP-DSSS) signal; and
transmitting, via a first device of a number of devices of a first network, the first CP-DSSS signal to a base station of the first network.
8 . The method of claim 7 , further comprising synchronizing signaling between the base station and at least some of the number of devices via downlink synchronization of a long-term evolution (LTE) network including the first network.
9 . The method of claim 7 , wherein adding the CP comprises modulating a set of orthogonal vectors that are cyclically shifted versions of a root sequence.
10 . The method of claim 9 , further comprising:
receiving the first CP-DSSS signal at a receiver;
removing, via the receiver, the CP from each block of the number of blocks of the first CP-DSSS signal to generate a received signal vector; and
despreading the received signal vector via a Hermitian of the cyclically shifted versions of the root sequence.
11 . The method of claim 10 , wherein receiving the first CP-DSSS signal comprises receiving the first CP-DSSS signal via a plurality of antennas of the receiver.
12 . The method of claim 10 , further comprising extracting information from the despread received signal vector via one of a matched filer (MF) detector, a zero-forcing (ZF) detector, a minimum mean square (MMSE) detector, and a detector configured to extract log-likelihood ratio (LLR) values.
13 . The method of claim 7 , further comprising:
adding another cyclic prefix (CP) to each block of another number of blocks of another DSSS signal to generate a second CP-DSSS signal; and
transmitting, via a second device of the number of devices of the first network, the second CP-DSSS signal to the base station of the first network;
wherein the first CP-DSSS signal and the second CP-DSSS signal are transmitted to the base station substantially simultaneously via one of space division multiplexing and frequency division multiplexing.
14 . The method of claim 7 , further comprising transmitting, substantially simultaneously, downlink information from the base station to a plurality of devices of the number of devices via one of space division multiplexing and frequency division multiplexing.
15 . A communication system, comprising:
a primary network including:
a base station; and
a femtocell configured to share a spectrum with the primary network such that at least some communications in the primary network and the femtocell occur substantially simultaneously on the same spectrum, the femtocell including:
a number of user equipment (UEs); and
a gateway configured to communicate with each UE of the number of UEs.
16 . The communication system of claim 15 , wherein the primary network comprises a long-term evolution (LTE) network.
17 . The communication system of claim 15 , wherein the gateway comprises a femtocell gateway including multiple antennas.
18 . The communication system of claim 17 , wherein the femtocell gateway includes a 32 or more antennas and wherein at least one UE of the number of UEs is configured to transmit a CP-DSSS signal via the channel at a power level less than a noise floor of the channel.
19 . The communication system of claim 15 , wherein at least one UE of the number of UEs is configured to:
add a cyclic prefix (CP) to each block of a number of blocks of a direct sequence spread spectrum (DSSS) signal to generate a CP-DSSS signal; and
transmit the CP-DSSS signal within the femtocell.
20 . The communication system of claim 19 , wherein the gateway is configured to:
receive the CP-DSSS signal; and
demodulate the CP-DSSS signal via a Hermitian of cyclically shifted versions of a root sequence.
21 . The communication system of claim 15 , wherein at least one UE of the number of UEs is configured to synchronize in time and frequency with the gateway via a downlink signal from the base station.
22 . The communication system of claim 15 , wherein at least one UE of the number of UEs and the gateway are configured to process signals in the frequency domain in a per-tone manner.