Patent Application
20080032632
The above and other aspects, features and advantages of exemplary embodiments of the present invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings in which:
Throughout the drawings, it should be noted that like reference numbers are used to depict the same or similar elements, features and structures.
The following description with reference to the accompanying drawings is provided to assist in a comprehensive understanding of exemplary embodiments of the invention as defined by the claims and their equivalents. It includes various specific details to assist in that understanding but these are to be regarded as merely exemplary. Accordingly, those of ordinary skill in the art will recognize that various changes and modifications of the embodiments described herein can be made without departing from the scope and spirit of the invention. Also, descriptions of well-known functions and constructions are omitted for clarity and conciseness.
Exemplary embodiments of the present invention provide a technique for canceling interference involved in space-division-based signal transmission and reception in a wireless communication system. Additional exemplary embodiments of the present invention provide a technique for canceling interference from neighbor MSs during SDD communications in a wireless communication system.
Referring to
The transmitter 310 processes a transmission signal and transmits it to an MS through the first antenna 311. The receiver 320 recovers original data by detecting and decoding a signal received though the second antenna 321.
During the transmission and the reception, the transmitter 310 and the receiver 320 use time and frequency resources independently because the downlink and the uplink are separated spatially in SDD.
Therefore, the transmitter 310 continuously transmits signals through the first antenna 311 and the receiver 320 continuously receives signals through the second antenna 321.
In the above-described exemplary embodiment of the present invention, the transmitter 310 and the receiver 320 use different antennas. Meanwhile, it can be further contemplated as another exemplary embodiment that the transmitter 310 and the receiver 320 share one or more antennas.
As described above, an SDD wireless communication system separates the downlink and the uplink by spatial resources. Hence, time and frequency resources are used for the downlink and the uplink, independently, which enables continuous signal transmission/reception on the downlink and the uplink. However, a transmission signal may interfere with a received signal in SDD communications. For instance, a transmission signal directed to the first antenna 311 (i.e. transmit antenna) may be introduced into the second antenna 321 (i.e. receive antenna), acting as noise to a received signal in the BS having the configuration illustrated in
Now, a description will be made of a method for canceling interference between a transmit antenna and a receive antenna residing in the same apparatus in the wireless communication system. While the interference cancellation method is described in the context of an SDD BS, the present invention may be applied to an MS.
Referring to
In order to prevent a signal that is to be transmitted through the first antenna 411 from being introduced into the second antenna 421, the first antenna 411 is configured to be a directional antenna. Also, the second antenna 421 may be positioned opposite to the direction of the first antenna 411, that is, behind the first antenna 411. A directional antenna is defined as an antenna that directs a signal in an intended direction.
Referring to
The transmitter 510 transmits signals through first and second antennas 511 and 513 and the receiver 550 receives signals through third and fourth antennas 551 and 553.
The polarization phase measurer 530 determines the phases of signals received through the third and fourth antennas 551 and 553 by analyzing them. Then the polarization phase measurer 530 controls the phases of signals to be transmitted through the first and second antennas 511 and 513 to be orthogonal to those of the received signals.
For example, the polarization phase measurer 530 determines the polarization phases of signals received on a channel h2 through the third and fourth antennas 551 and 553 and controls the polarization phases of transmission signals directed to the third and fourth antennas 551 and 553 so that the polarization phases of the transmission signals introduced to the third and fourth antennas 551 and 553 on a channel h3 are orthogonal to those of the signals received on the channel h2. As a result, interference between the transmit antennas 511 and 513 and the receive antennas 551 and 553 is cancelled.
An MS 570 includes a transmitter 580, a receiver 590, a fifth antenna 581 and a sixth antenna 591. The transmitter 580 transmits signals through fifth antenna 581 and the receiver 590 receives signals through sixth antenna 591. The fifth and sixth antennas 581 and 591 are polarization antennas. That is, the fifth and sixth antennas 581 and 591 are configured to have mutually orthogonal polarization characteristics for communications between the MS 570 and the BS 500.
Referring to
The transmitter 610 transmits a signal through a first antenna 611 and the interference canceller 660 receives the signal directed to the first antenna 611.
The receiver 650 receives a signal through a second antenna 661. Since the interference canceller 660 has knowledge of the transmission signal to be transmitted through the first antenna 611, it removes the transmission signal from the signal received through the second antenna 661, thus canceling interference between the first and second antennas 611 and 661.
Also, the BS 600 can reduce the interference between the first and second antennas 611 and 661 by positioning them far from each other.
The SDD wireless communication system can cancel interference between a transmit antenna and a receive antenna residing in the same apparatus using the above-described methods. Meanwhile, in the case where a service is provided to multiple users, the MS of a user may be interfered with by other MSs. That is, a signal transmitted from the MS of a first user may interfere with a signal received at the MS of a second user.
Hence, an exemplary technique for canceling interference from transmit antennas of neighbor MSs in the wireless communication system will be described below.
For cancellation of interference from transmit antennas of neighbor MSs, the wireless communication system may use a frame configured as illustrated in
Referring to
In the first region 700, the BS transmits the control information to the MSs within its service area. The control information includes the positions of the MSs, a pilot signal, and time allocation information for each MS.
In the second region 710, the BS and the MSs exchange signals in SDD. As will be illustrated in
Referring to
At time T(K+1) 870, the BS transmits a signal to MS 2 through the transmit antenna 800 according to time allocation information, while receiving a signal from MS 1 through a receive antenna 801. That is, at time T(K+1) 870, MS 1 transmits the signal to the BS through a transmit antenna 810 and MS 2 receives the signal from the BS through the receive antenna 821. Simultaneously, the BS cancels interference introduced to the receive antenna 801 from the transmit antenna 800 using an exemplary method as illustrated in
The signal transmitted from the transmit antenna 810 of MS 1 interferes with the signal received at the receive antenna 821 of MS 2. Thus, MS 2 cancels the interference from MS 1 using status information about MS 1 received from the BS at time T(K) 860.
Finally at time T(K+2) 880, the BS transmits a signal to MS 1 through the transmit antenna 800 and receives a signal from MS 2 through the receive antenna 801. That is, at time T(K+2) 880, MS 2 transmits the signal to the BS through the transmit antenna 820 and MS 1 receives the signal from the BS through the receive antenna 811.
The signal transmitted from the transmit antenna 820 of MS 2 interferes the signal received at the receive antenna 811 of MS 1. Thus, MS 1 cancels the interference from MS 2 using status information about MS 2 received from the BS at time T(K) 860.
Operations of a BS and an MS that transmit and receive signals in a frame configured as illustrated in
Referring to
The BS transmits signals to the MSs through a transmit antenna in step 905 and receives signals from the MSs through a receive antenna in step 907. Since the downlink and the uplink are separated by spatial resources, signals are transmitted and received at the same time using time and frequency resources independently on the downlink and the uplink. When the BS provides a service to a plurality of MSs, it transmits and receives signals according to the time allocation information of each MS. For example, the BS transmits a signal to a first MS through the transmit antenna and receives a signal from a second MS through the receive antenna during a first time interval.
Then the BS ends the algorithm.
Referring to
Upon receipt of the control information, the MS monitors reception of a downlink signal from the BS in step 1003. Upon receipt of the downlink signal, the MS cancels interference from the neighbor MSs included in the received signal based on the status information of the neighbor MSs in step 1005.
Then, the MS ends the algorithm.
Now a description will be made below of exemplary structures of the BS and the MS for canceling interference from neighbor MSs in the wireless communication system.
Referring to
The scheduler 1105 provides a timing signal to the transmitter 310, for transmitting a signal to an MS. For example, the scheduler 1105 provides a timing signal to the transmitter 310 so that the transmitter 310 transmits control information about information about the statuses of neighbor MSs at time T(K) 860 in
While not shown, the scheduler 1105 provides timing signals to the receiver 320 so that the receiver 320 can receive signals from MSs. For example, the scheduler 1105 provides a timing signal to the receiver 320 so that the receiver 320 receives a signal from MS 1 at time T(K+1) 870 and from MS 2 at time T(K+2) 880 in
The MS status monitor 1101 acquires the status information of MSs within the service area of the BS and provides it to the transmitter 1103.
The transmitter 1103 transmits a signal through a transmit antenna under the control of the scheduler 1105. For instance, the transmitter 1103 transmits the control information including information about the statuses of the neighbor MSs at time T(K) 860 in accordance with a timing signal received from the scheduler 1105. The transmitter 310 also transmits a signal to MS 2 at time T(K+1) 870 and to MS 1 at time T(K+2) 880 in accordance with timing signals received from the scheduler 1105.
Referring to
The receiver 1201 monitors a signal received from a receive antenna and provides the signal to the MS status information storage 1203 or the interference canceller 1205. For example, if communications are conducted in the manner illustrated in
The MS status information storage 1203 stores the status information received from the receiver 1201 and later provides it to the interference canceller 1205 so as to cancel the neighbor MSs′ interference from a received signal.
The interference canceller 1205 cancels the neighbor MSs′ interference from the downlink signal received from the receiver 1201 based on the status information received from the MS status information storage 1203.
While communications between an SDD BS and SDD MSs have been described above, communications can be conducted and interference can be cancelled in the same manner between an SDD BS and TDD or FDD MSs in other exemplary embodiments of the present invention. For example, the SDD BS uses time and frequency resources independently for a transmit antenna and a receive antenna. Therefore, when the SDD BS communicates with TDD MSs, it carries out transmission and reception independently in time. When the SDD BS communicates with FDD MSs, it carries transmission and reception independently in frequency.
As is apparent from the above description, exemplary embodiments of the present invention advantageously cancel interference from neighbor MSs based on information about the statuses of the neighbor MSs by providing the status information from a BS to each MS in an SDD wireless communication system.
While the invention has been shown and described with reference to certain exemplary embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims and their equivalents.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2006-0074091 | Aug 2006 | KR | national |
