Wireless communication networks have enjoyed rapid growth in recent years, as evidenced by the rapid deployment of IEEE 802.11a/b/g networks and the adoption of 2.5 G and 3 G cellular telephone networks. These wireless networks are now used throughout the world. 802.11a/b/g networks provide an advantage of working in a band of the radio spectrum currently unlicensed in the United States, as described in Rappaport, Wireless Communications, Prentice Hall c. 2002. The use of the unlicensed spectrum allows users including individuals and businesses to simply purchase equipment and set up wireless devices without requiring licenses.
Another recent breakthrough, that of MIMO or space time coding, exploits slight spatial/temporal variations in the wireless communication channel (e.g. the propagation environment). By using multiple, closely spaced antennas, it becomes possible to harness the energy impinging on each antenna, at either a transmitter or receiver, in order to establish a much improved wireless communication link as compared to single-antenna or diversity antenna schemes. MIMO and space time coding has been explored and described in the following prior art references:
R. W. Heath, Jr. and A. J. Paulraj, “Multiple antenna arrays for transmitter diversity and space-time coding,” Proc. of the IEEE Int. Conf. on Communications 1999, pp. 36-40, vol. I, Vancouver, Canada, Jun. 6-10, 1999. This paper describes the idea of using multiple smart antennas for space-time coding and discusses the effect of imperfect beamforming; but does not consider explicitly multiple users.
Space-time coding for the parametric fading channel Sandhu, S.; Paulraj, A.; Signals, Systems & Computers, 1998. Conference Record of the Thirty-Second Asilomar Conference on, Volume: 1, Nov. 1-4, 1998 Page(s); 774-779 vol. 1. This paper describes an idea of coding across beams. This paper is different than the paper by Heath and Paulraj since multiple beams in a single adaptive array is used instead of coding across multiple arrays.
Combined array processing and space-time coding Tarokh, V.; Naguib, A.; Seshadri, N.; Calderbank, A. R.; Information Theory, IEEE Transactions on Volume: 45 Issue: 4, May 1999 Page(s): 1121-1128. This paper shows how to get the benefits of both diversity and rate gain by using space-time codes on groups of antennas.
Capacity of multiple-transmit multiple-receive antenna architectures: Lozano, A.; Tulino, A. M. Information Theory, IEEE Transactions on page(s): 3117-3128 Volume: 48, Issue: 12, December 2002. This paper offers some capacity results with different antennas architectures and includes some interference performance results as well.
Turbo-BLAST for wireless communications: theory and experiments: Sellathurai, M.; Haykin, S.; Signal Processing, IEEE Transactions on, Volume: 50 Issue: 10, October 2002 Page(s): 2538-2546. This paper describes BLAST in conjunction with turbo codes and teaches the potential of MIMO when combined with concatenated codes.
Link-optimal BLAST processing with multiple-access interference: Farrokhi, F. R.; Foschini, G. J.; Lozano, A.; Valenzuela, R. A.; Vehicular Technology Conference, 2000. IEEE VTS-Fall VTC 2000. 52nd, Volume: 1, 2000, Page(s): 87-91 vol. 1. This paper describes some MIMO algorithms that account for interference using well known or standard signal processing type ideas.
U.S. Pat. No. 5,345,599, entitled “Increasing capacity in wireless broadcast systems using distributed transmission/directional reception (DTDR)”, A. Paulraj and T. Kailath, Issued: September 1994. This patent is one of the first to propose the idea of spatial multiplexing in MIMO communication systems; the concept is proposed in the context of high-definition television transmission.
U.S. Pat. No. 6,067,290 “Spatial Multiplexing in a Cellular Network.” A. J. Paulraj, R. W. Heath, Jr., S. K. Peroor, and D. Gesbert. Filed: Jul. 30, 1999. Issued: May 23, 2000. Assignee: Iospan Wireless Inc. (formerly Gigabit Wireless Inc.). This patent discusses the idea of spatial multiplexing in cellular network; it describes functionality such as partial handoff and substream control that will be necessary in cellular networks that employ MIMO communication systems.
U.S. Pat. No. 6,298,092 “Methods of Controlling Communication Parameters of Wireless Systems,” R. W. Heath, Jr., S. K. Peroor, and A. J. Paulraj. Filed: Jun. 2, 2000. Issued: Oct. 2, 2001. Assignee: Iospan Wireless Inc. This patent describes methods for adaptive space-time modulation. In particular, the patent describes the idea of switching between a diversity space-time code and a multiplexing space-time code.
U.S. Pat. No. 6,377,632 “Wireless communication system and method using stochastic space-time/frequency division multiplexing,” A. J. Paulraj, S. K. Peroor, J. Tellado, R. W. Heath, Jr., S. Talwar, and H. Bolcskei. Filed: Jan. 24, 2000. Issued: Apr. 23, 2002. This patent is an extension of OFDM that involves space/time/frequency domain representations.
U.S. Pat. No. 6,377,636 “Method and wireless communications system using coordinated transmission and training for interference mitigation,” A. J. Paulraj, S. K. Peroor, J. Tellado, and R. W. Heath, Jr. Filed: Nov. 2, 1999. Issued: Apr. 23, 2002. This patent describes an idea to coordinate the transmissions in a cellular network to improve the performance of interference cancellation algorithms. Each of the foregoing prior art references is hereby fully incorporated by reference herein.
Current systems employ wireless gateway equipment and wireless user equipment. The wireless user equipment receives signals from and sends signals to the wireless gateway equipment. The wireless gateway equipment provides access to another network, such as the internet. Current systems for providing high-speed data access via wireless communication links include directional and cellular systems. Directional systems rely on highly directional antennas at the wireless gateway equipment and the wireless user equipment that must be pointed line-of-sight at each other for proper operation. These systems can typically only serve one or a limited number of users. Cellular systems, on the other hand, use a network of base stations to provide wireless coverage to a larger number of users. However, cellular systems require a significant infrastructure investment.
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