초록 ▼

The present disclosure provides a method for transmitting a signal to multiple User Equipments (UEs) utilizing reciprocity of a wireless channel. In this method, a vector channel from the base station to each UE can be converted into an equivalent Single Input Single Output (SISO) channel having a s

The present disclosure provides a method for transmitting a signal to multiple User Equipments (UEs) utilizing reciprocity of a wireless channel. In this method, a vector channel from the base station to each UE can be converted into an equivalent Single Input Single Output (SISO) channel having a strong Light-of-Sight (LOS) component using channel feedback. In this way, a reliable signal transmission to multiple UEs can be achieved with little channel training overhead. The present disclosure has prominent advantages such as simplicity in implementation, low processing complexity and very low channel training overhead and is particularly applicable in low-speed transmission of broadcast signaling in a massive MIMO system and scenarios where the base station is to page inactive UEs.

대표청구항 ▼

1. A method for signal transmission, applied in a multi-user, multi-antenna system operating in a Time Division Duplex (TDD) mode and comprising a base station and a number, K, of User Equipments (UEs), the base station being configured with M antennas, each UE being configured with one receiving an

1. A method for signal transmission, applied in a multi-user, multi-antenna system operating in a Time Division Duplex (TDD) mode and comprising a base station and a number, K, of User Equipments (UEs), the base station being configured with M antennas, each UE being configured with one receiving antenna or configured to combine signals from a plurality of receiving antennas to obtain one scalar channel output, each UE maintaining synchronization with the base station, one downlink transmission period being discretized into T timeslots, reciprocal uplink and downlink channels remaining unchanged during the T timeslots, an uplink channel from a UE k to the base station being denoted as hk, a downlink channel from the base station to the UE k being denoted as hk†, where † denotes conjugate transpose, the method comprising: S1: in the first timeslot, transmitting, by the UE k, a constant signal to the base station, such that a signal received by the base station is a simple addition of an uplink channel from the UE to the base station and a noise, i.e., yBS[1]=Σk=1Khk+zBS[1], where yBS[1] denotes a signal received by the base station in the first timeslot and zBS[1] denotes a noise at the base station;S2: in the second timeslot, multiplying, by the base station, the signal yBS[1] received in the first timeslot with a power adjustment factor a and feeding ayBS[1] back to all the UEs by means of broadcast, such that a signal received by a UE j in the second timeslot is yj[2]=hj†ayBS[1]+zj[2]≙gj+zj[2], where zj[2] is a noise at the UE j and gj=a(hj†Σk=1Khk+hj†zBS[1]), and the UE j estimates gj based on the signal yj[2] received in the second timeslot to obtain an estimated value ĝj; andS3: in the t-th timeslot, where t=3, . . . , T, precoding, by the base station, a signal xBS[t] to be broadcasted to the UEs in the t-th timeslot based on ayBS[1], and broadcasting axBS[t]yBS[1] to all the UEs, such that a signal received by the UE j in the t-th timeslot is yj[t]=gjxBS[t]+zj[t], where zj[t] is a noise at the UE j, and the UE j demodulates xBS[t] based on ĝj. 2. The method of claim 1, wherein in the step S1, the constant signal is normalized to a transmission power of the UE. 3. The method of claim 1, wherein in the step S1, the noise zBS[1] at the base station is an independent and identically distributed Gaussian noise, i.e., zBS[1]˜CN (0,σBS2IM), where σBS2 is a noise power at the base station, IM is an M-dimensional identity matrix, and CN (0,σBS2IM) denotes an M-dimensional cyclically symmetric complex Gaussian distribution having a mean value of 0 and a covariance matrix of σBS2IM. 4. The method of claim 1, wherein in the step S2, the power adjustment factor a satisfies a=1/√{square root over (MK)}. 5. The method of claim 1, wherein in the step S2, the noise zj[2] at the UE j is a Gaussian noise, i.e., zj[2]˜CN (0,σUE2), where σUE2 is a noise power at the UE, and CN (0,σUE2) denotes a cyclically symmetric complex Gaussian distribution having a mean value of 0 and a covariance matrix of σUE2. 6. The method of claim 1, wherein in the step S2, ĝj is estimated using a least square method, i.e., ĝj=yj[2]. 7. A method for signal transmission, applied in a multi-user, multi-antenna system comprising a base station and a plurality of User Equipments (UEs), the UEs being divided into a number of groups, the UEs in different groups occupying different sub-carriers and the UEs in each group transmitting signals according to the method of claim 1. 8. A method for signal transmission, applied in a multi-user, multi-antenna system operating in a Time Division Duplex (TDD) mode and comprising a base station and a number, K, of User Equipments (UEs), the base station being configured with M antennas, each UE being configured with one receiving antenna or configured to combine signals from a plurality of receiving antennas to obtain one scalar channel output, each UE maintaining synchronization with the base station, one downlink transmission period being discretized into T timeslots, reciprocal uplink and downlink channels remaining unchanged during the T timeslots, an uplink channel from a UE k to the base station being denoted as hk, a downlink channel from the base station to the UE k being denoted as hk†, the method comprising: S1: in the first timeslot, transmitting, by the UE k, a constant signal to the base station, such that a signal received by the base station is a simple addition of an uplink channel from the UE to the base station and a noise, i.e., yBS[1]=Σk=1Khk+zBS[1], where yBS[1] denotes a signal received by the base station in the first timeslot and zBS[1] denotes a noise at the base station; andS2: in the t-th timeslot, where t=2, . . . , T, applying, by the base station, a differential modulation to data to be broadcasted to the UEs in the t-th timeslot, so as to obtain a modulated signal xBS[t] first, then multiplying the signal yBS[1] received in the first timeslot with a power adjustment factor a, precoding xBS[t] based on ayBS[1], and broadcasting axBS[t]yBS[1] to all the UEs, such that a signal received by a UE j in the t-th timeslot is yj[t]=hj†ayBS[1]xBS[t]≙gjxBS[t]+zj[t], where zj[t] is a noise at the UE j, gj=a(hj†Σk=1Khk+hj†zBS[1]), and the UE j applies incoherent differential demodulation to the signal broadcasted from the base station without performing any explicit channel estimation. 9. The method of claim 8, wherein in the step S1, the constant signal is normalized to a transmission power of the UE. 10. The method of claim 8, wherein in the step S1, the noise zBS[1] at the base station is an independent and identically distributed Gaussian noise, i.e., zBS[1]˜CN (0,σBS2IM), where σBS2 is a noise power at the base station, IM is an M-dimensional identity matrix, and CN (0,σBS2IM) denotes an M-dimensional cyclically symmetric complex Gaussian distribution having a mean value of 0 and a covariance matrix of σBS2IM. 11. The method of claim 8, wherein in the step S2, the power adjustment factor a satisfies a=1/√{square root over (MK)}. 12. The method of claim 8, wherein in the step S2, the noise zj[2] at the UE j is a Gaussian noise, i.e., zj[2]˜CN (0,σUE2), where σUE2 is a noise power at the UE, and CN (0,σUE2) denotes a cyclically symmetric complex Gaussian distribution having a mean value of 0 and a covariance matrix of σUE2. 13. A method for signal transmission, applied in a multi-user, multi-antenna system comprising a base station and a plurality of User Equipments (UEs), the UEs being divided into a number of groups, the UEs in different groups occupying different sub-carriers and the UEs in each group transmitting signals according to the method of claim 8.