Patent Application
20080096546
This invention describes a method that reduces interference and enhances signal strength for a wireless cellular network. The following merely illustrates various embodiments of the present invention for purposes of explaining the principles thereof. It is understood that people skilled in the art will be able to devise various equivalents that, although not explicitly described herein, embody the principles of this invention.
The BTS's are also linked to an element management system (EMS) that controls the BTS's to form uplinks and downlinks with the MS's, using a beam forming technology. For example, a MS located at the boundary of cells deployed with BTS 1, BTS2, and BTS 3 transmits/receives signals to/from BST 1 as a primary source, with BTS 2 and BTS 3 as secondary sources if certain criteria. Beam forming will be performed for BTS 1, BTS 2 and BTS 3, such that BTS 2 and BTS 3 become signal sources that strengthen the signals received by the MS, instead of sources of interference as they would have been, had they functioned according to conventional schemes.
At step 206, the MS transmits signals containing information indicating the selected candidate serving BTS's to a first group of serving BTS's that currently form downlinks with the MS. These current serving BTS's may not be the same as the selected candidate serving BTS's. At step 208, the information indicating the selected serving BTS's is forwarded by the current downlink serving BTS's to the EMS. For example, although the MS may select BTS 1, BTS 2, and BTS 3 as the candidates, it may transmit the indicating signals to BTS 1, BTS 3, and BTS 4 that currently communicate with the MS through downlink channels. BTS 1, BTS 3 and BTS 4 then forward the information indicating that BTS 1, BTS 2 and BTS 3 have been selected as candidate serving BTS's to the MS.
At step 210, the EMS selects a second group of serving BTS's from the candidate serving BTS's based on the information forwarded by the current serving BTS's and on its own selection criteria, such as balancing system resources. The ESM also determines beam forming weighing factors for the selected second group of serving BTS's. For example, the MS may select BTS 1 and BTS 2 as the second group of serving BTS's and disregard BTS 3, even though it is also one of the selected candidate serving BTS's.
At step 214, the EMS transmits control signals containing information of the second group of the serving BTS's and their corresponding beam forming weighing factors to the current serving and candidate serving BTS's in order for rearranging the first group of the current serving BTS's into the second group of the selected serving BTS's for establishing new downlinks with the MS. For example, the control signals are transmitted from the EMS to BTS 1, BTS 3, and BTS 4, the first group of current serving BTS's, and to BTS 2 and BTS 3, the selected candidate serving BTS's. Since the second group of BTS's only includes BTS 1 and BTS 2, the current serving BTS 3 and BTS 4 that do not belong to the second group are deactivated from serving the MS though downlink channels upon receiving the control signals. The BTS that belongs to the second group of serving BTS's, but do not belong to the first group of current serving BTS's, such as BTS 2, is activated to form downlink channels with the MS upon receiving the control signals. A beam forming technology is performed for BTS 1 and BTS 2 to form downlink channels with the MS simultaneously, using the beam forming weighing factors determined by the EMS. It is understood that various implementations the beam forming schemes can be made without undue experimentation by people skilled in the art of telecommunications. As such, detailed description of such implementations is omitted from the present disclosure.
In this embodiment, the second group of serving BTS's then notify the MS of the rearrangement of BTS's through downlink channels. This can be done by transmitting one bit in the downlink message, using “1” to indicate that collaborative beam forming is employed, and “0” to indicate that only one BTS is serving the MS. It is noted that, as an alternative, the second group of serving BTS's can be simply activated to form downlink channels with the MS without utilization of any notification bit.
This method is a multi-cell interference reduction and signal enhancement technique based on adaptive collaborative BTS beam forming and dynamic BTS selection. It is applicable to any multiple access technologies, such as FDD, TDD, FDMA, TDMA, MC-CDMA, OFDM-MA and any combination of them.
The above illustration provides many different embodiments or embodiments for implementing different features of the invention. Specific embodiments of components and processes are described to help clarify the invention. These are, of course, merely embodiments and are not intended to limit the invention from that described in the claims.
Although the invention is illustrated and described herein as embodied in one or more specific examples, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims. Accordingly, it is appropriate that the appended claims be construed broadly and in a manner consistent with the scope of the invention, as set forth in the following claims.
| Number | Date | Country | |
|---|---|---|---|
| 60853848 | Oct 2006 | US |
