Title of Invention

MULTI-ANTENNA CELLULAR BROADBAND WIRELESS COMMUNICATION SYSTEM WITH INTERFERENCE MITIGATION

Abstract

A multi-antenna cellular broadband wireless communication system with interference mitigation comprises a controller; at least two cells with a possibility of interference between them; a single base-station and a plurality of mobile terminals in each cell;.N<SUB>t</SUB> (Nt &#8805; 2) transmit antennas for each base-station and Nr (N<SUB>r</SUB> &#8805; 1) receiver antennas for each mobile terminal, and each mobile terminal being served by the base-station in its cell, the radio boundary usually exceeding the cell boundary, every mobile terminal estimating a maximum of N<SUB>t</SUB> -1 channel-characteristics parameters (termed as channel state information) per carrier employed by its own base-station (denoted a A for Cell A) and a maximum of N<SUB>t</SUB> -1 parameters per carrier of each interfering base-station (denoted NAB for one interfering base-station B), the said parameters being quantized into bits (called feedback information) and communicated to the respective serving base-station by the mobile terminals in all cells, every base-station then forwarding this feedback information to a controller located at the base-stations via feedback links in the backhaul networks; the input stream at the base-station being modulated (mapped into symbols) onto the carrier taking into account information from the controller, an antenna mapper for transmitting the symbols as such through one antenna and the product of the symbols with functions of the feedback parameters through the other antennas, each mobile terminal receiving the symbols meant for it and processing them to mitigate the channel effect and then decoding the transmitted bit stream

Full Text

This invention relates to multi-antenna cellular broadband wireless communication system with interference mitigation. It is an object of this invention to devise a mobile, cellular wireless communication system which reduces the bit / packet error rate in the down-link (base-station to mobile link), making effective use of channel state information fed back from the receiver to the transmitter to minimize the interference, without significantly increasing the complexity of the mobile terminal equipment. In general this system consists of base-stations with Nt (Nt > 2) transmit antennas and mobile terminals with Nr (Nr ≥ 1) receiver antennas. This invention comprises a controller for multiple base-stations, either located centrally or distributed at the base-station sites, for controlling the space-time-frequency coding and / or carrier allocation in a multi-carrier, broadband wireless communication system. In the present specification two antennas are shown located at the base-station and one antenna in the mobile terminal equipment, as an example. An advantage of this invention is that the system capacity and hence the average aggregate cell throughput increases because of reduced interference amongst users from adjacent cells. The controller co-ordinates among neighboring base-stations and improves the capacity of the system as a whole The earner allocation and / or coding method can be made compatible with existing / emerging cellular wireless standards The multi-antenna cellular broadband wireless communication system with interference mitigation, according to this invention, comprises a controller; at least two cells with a possibility of interference between them; a single base-station and a plurality of mobile terminals in each cell; Nt (Nt >≥2) transmit antennas for each base-station and Nr (Nr ≥ 1) receiver antennas for each mobile terminal, and each mobile terminal being served by the base-station in its cell, the radio boundary usually exceeding the cell boundary, every mobile terminal estimating a maximum of Nt -1 channel-characteristics parameters (termed as channel state information) per carrier employed by its own base-station (denoted A for Cell A) and a maximum of Nt - 1 parameters per carrier of each interfering base-station (denoted җAB for one interfering base-station in Cell B), the said parameters being quantized into bits (called feedback information hereafter) and communicated to the respective serving base-station by the mobile terminals in all cells, every base-station then forwarding this feedback information to a controller located at the base-stations via feedback links in the backhaul networks; the input stream at the base-station being modulated (mapped into symbols) onto the carrier taking into account information from the controller, an antenna mapper for transmitting the symbols as such through one antenna and the product of the symbols with functions of the feedback parameters through the other antennas, each mobile terminal receiving the symbols meant for it and processing them to mitigate the channel effect and then decoding the transmitted bit stream. This invention will now be described with reference to the accompanying drawings which illustrate by way of example and not by way of limitation one of possible embodiments of the system proposed herein, Fig. I illustrating two cells A and B with possibility of interference between them Fig. II illustrating three cells A, B and C also with possibility of interference between them The system is as illustrated in Figures I and II, where users in two and three adjacent cells respectively undergo interference. Each cell consists of a single base-station I, II and III in the respective cells A, B and C along with several mobile terminals (one mobile M1 and M2 each shown in cells A and B of the figures). A base-station in general has Nt transmit antennas and a mobile terminal has Nr receiver antennas. Figures I and II show base-stations with two antennas each (Tx1 and Tx2) and mobile terminals M1 and M2 with one antenna each (Rx) A mobile terminal is served by the base-station in its cell The wireless spectrum allotted to the system is reused fully or partially in all the cells The hexagonal borders indicate the cell boundary and the radical arcs indicate the radio boundary. The radio boundary usually exceeds the cell boundary (as in this case). Since the radio distance overlaps into the adjacent cell, and since the spectrum is re-used, this results in interference caused to the users in the adjacent cells Every mobile terminal estimates a maximum of Nt - 1 channel-characteristic parameters (termed as channel state information) per carrier employed by its own base-station (denoted a) and a maximum of Nt - 1 parameters per carrier of each interfering base-station (denoted N). In Fig. I for the mobile terminal in Cell A, parameter A corresponds to the parameter for a carrier of its own base-station and parameters җAB corresponds to the interference caused on the same carrier by the base-station in Cell B. These parameters are then quantized into bits (called feedback information hereafter) and are communicated to the serving base-station by the mobile. This is done by all mobiles in all cells. Every base-station then forwards this feedback information to a centralized controller, (as in Fig. II) or to the distributed controller located at the base-stations (as in Fig. I) via feedback links in the backhaul networks. At the controller(s), based on the feedback information, each carrier employed by a base-station is associated with a set of optimized parameters (one parameter for the illustrative case with Nt = 2) used to modify the transmission, and each user is also optionally allocated with a set of optimally selected carriers. Optimization of the parameters and carrier selection is done to improve the received signal-to-interference power ratio at the mobile terminals The input bit stream at the base-station is modulated (mapped into symbols) onto the carriers taking into account information from the controller For the system with two base-station antennas (Nt = 2); the symbols are transmitted as such over one of the antennas, and on the other antenna they are modified using the optimized parameter and then transmitted. This is done by the antenna mapper. Each mobile receives the symbol meant for it, and processes it to overcome the channel effect and then decode the transmitted bit stream. This invention: 1. Improves the system performance by reducing the effect of mutual interference among base-stations 2. Enhances system capacity due to improved signal-to-interference power ratio at the mobile stations 3. When used in a mobile communication system decreases the effect of interference, thereby decreasing the bit / packet error rate which results in an increase of the overall system capacity 4. Mitigates interference effects using feedback in a multi-antenna multi-cell scenario 5. Optimizes earner selection / allocation across cell sites in a centralized / distributed controller to minimize the effect of interference 6. Optimizes spatial coding (across antennas) of symbols based on its impact not only for the user the data is meant for, but also for users to whom the coded transmission causes interference The objectives to this invention are realized as follows: 1. Base-stations of the type existing today with available signal processing capability and two transmit antennas are modified. Specifically the antenna mapper will now transmit the symbols as such through one antenna and the product of the symbol with the function of the feedback parameter through the other antenna 2. Mobile terminal equipment with one antenna of the type currently being used, modified to include channel parameter estimation and feedback of parameters 3. Two-way communication link between the base-station and mobile terminal equipment needs to be established for enabling channel state information feedback 4. The mobile terminal should estimate the channel characteristic, optimally code the feedback parameters by compressing the information, and send them via feedback link 5. The base-stations are to be connected using a back-haul network to a controller (centralized or distributed) where the required processing is done viz., selection of carriers / antennas and / or processing the transmit symbols for interference mitigation We claim; 1. A multi-antenna cellular broadband wireless communication system with interference mitigation comprises a controller; at least two cells with a possibility of interference between them; a single base-station and a plurality of mobile terminals in each cell; Nt (Nt > 2) transmit antennas for each base-station and Nr (Nr ≥ 1) receiver antennas for each mobile terminal, and each mobile terminal being served by the base-station in its cell, the radio boundary usually exceeding the cell boundary, every mobile terminal estimating a maximum of Nt -1 channel- characteristics parameters (termed as channel state information) per carrier employed by its own base-station (denoted җ A for Cell A) and a maximum of Nt - 1 parameters per carrier of each interfering base-station (denoted AB for one interfering base-station B), the said parameters being quantized into bits (called feedback information) and communicated to the respective serving base-station by the mobile terminals in all cells, every base-station then forwarding this feedback information to a controller located at the base-stations via feedback links in the backhaul networks; the input stream at the base-station being modulated (mapped into symbols) onto the carrier taking into account information from the controller, an antenna mapper for transmitting the symbols as such through one antenna and the product of the symbols with functions of the feedback parameters through the other antennas, each mobile terminal receiving the symbols meant for it and processing them to mitigate the channel effect and then decoding the transmitted bit stream 2. A Multi-antenna cellular broadband wireless communication system with interference mitigation as claimed in Claim 1 wherein the controller is a single centralized controller 3. A Multi-antenna cellular broadband wireless communication system with interference mitigation as claimed in Claim 1 wherein the controller is a distributed controller located at the base-stations 4. A Multi-antenna cellular broadband wireless communication system with interference mitigation substantially as herein described and illustrated with reference to the accompanying drawings.

Documents:

298-CHE-2007 AMENDED CLAIMS 07-11-2012.pdf

298-CHE-2007 AMENDED PAGES OF SPECIFICATION 07-11-2012.pdf

298-CHE-2007 POWER OF ATTORNEY 07-11-2012.pdf

298-CHE-2007 CORRESPONDENCE OTHERS 15 -11-2012.pdf

298-CHE-2007 EXAMINATION REPORT REPLY RECEIVED 07-11-2012.pdf

298-CHE-2007 FORM-3 15 -11-2012.pdf

298-CHE-2007 POWER OF ATTORNEY 15 -11-2012.pdf

298-CHE-2007 AMENDED PAGES OF SPECIFICATION 15 -11-2012.pdf

298-CHE-2007 AMENDED CLAIMS 15 -11-2012.pdf

298-CHE-2007 CORRESPONDENCE OTHERS 14 -11-2012.pdf

298-CHE-2007 CORRESPONDENCE OTHERS 19-11-2012.pdf

298-CHE-2007 POWER OF ATTORNEY 14 -11-2012.pdf

298-CHE-2007 POWER OF ATTORNEY 19-11-2012.pdf

298-CHE-2007 POWER OF ATTORNEY 22-11-2012.pdf

298-CHE-2007 CORRESPONDENCE OTHERS 22-11-2012.pdf

298-CHE-2007 CORRESPONDENCE OTHERS. 17-07-2012.pdf

298-CHE-2007 FORM-13 17-07-2012.pdf

298-CHE-2007 POWER OF ATTORNEY 17-07-2012.pdf

298-che-2007-abstract.pdf

298-che-2007-claims.pdf

298-che-2007-correspondnece-others.pdf

298-che-2007-description(complete).pdf

298-che-2007-drawings.pdf

298-che-2007-form 1.pdf

298-che-2007-form 18.pdf

298-che-2007-form 26.pdf

3701CHENP2007.pdf