SYSTEM AND METHOD FOR
INTERFERENCE MITIGATION FOR
This application is a continuation of Ser. No. 10/730,649, 5 filed Dec. 8, 2003, now U.S. Pat. No. 7,366,202.
The present invention is related to co-pending and com- io monly assigned U.S. patent application Ser. No. 10/306,972 entitled "Space-Time-Power Scheduling for Wireless Networks," filed Nov. 27,2002, the disclosure of which is hereby incorporated herein by reference.
The invention relates generally to wireless communication and, more particularly, to interference mitigation for wireless communication. 20
BACKGROUND OF THE INVENTION
The use of wireless communication links, whether for video, voice, or data, have become prevalent in recent years, 25 particularly in light of the widespread adoption of mobile technology, such as cellular telephones, laptop computers, personal digital assistants (PDAs), pagers, and the like. Wireless communication links are particularly desirable with respect to some situations, such as to avoid obstacles associ- 30 ated with laying cable between communication nodes, providing freedom of movement, etcetera. Accordingly, wireless communication links have been given much consideration by communication infrastructure providers. However, deploying wireless communication links is not without difficulty. In 35 particular, wireless spectrum is often highly regulated and may be prone to interference.
Wireless broadband access has been considered quite extensively in recent years. Although multiple solutions have been experimented with, attempts at providing wireless 40 broadband access, particularly widespread access, has generally not met with commercial success due to inadequate economical conditions, i.e., high cost without sufficient demand. In particular, the need for licensed spectrum in which to provide wireless links has typically resulted in high costs to 45 wireless broadband access providers. Moreover, past wireless broadband access solutions have typically implemented nonstandard or application specific equipment, due to each provider developing a unique solution tailored to their particular solution, circumstances, and spectrum, thereby preventing 50 economies of scale and compatibility.
Demand for such wireless broadband access has generally been associated with applications and appears to be correlated to at least some degree to the cost of the service and equipment, the complexity of the implementation, and the 55 reliability of the links. The proliferation of wired broadband access, such as via cable modem and digital subscriber line (DSL), is stimulating the creation of applications requiring relatively large amounts of bandwidth, such as music downloading, video streaming, multi-media presentations, etcet- 60 era. However, a large number of nodes desirous of implementing such emerging applications are not yet wired for broadband access and, therefore, cannot adequately access such applications.
Two related wireless technologies are beginning to gain 65 acceptance in providing at least some level of wireless broadband access, these being wireless technologies based on the
Institute of Electronic and Electrical Engineers (IEEE) 802.11 and 802.16standards.The 802.11 standard is directed toward indoor applications and sets forth asynchronous protocols for short range communications, while the 802.16 standard is directed toward outdoor applications and sets forth synchronous protocols for longer range communications, each being operable in unlicensed spectrum such as within the 2 to 11 GHz range. Implementation of such standards facilitates equipment cost reduction by providing for compatibility and economy of scale. However, technologies adopting the foregoing standards heretofore have not adequately addressed the issues associated with commercial or economic deployment of wireless broadband access. For example, although addressing aspects such as communication protocols, the standards alone do not provide for spectrum utilization suitable for reliable or large scale wireless broadband access.
Traditional wireless services rely upon licensed spectrum, in which the use of the spectrum is highly regulated such that sources of interference are avoided, in order to provide for spectrum utilization suitable for reliable or large scale access. However, that spectrum is expensive and is very difficult to obtain. Unlicensed bands, although providing a readily available and inexpensive alternative, present a cost in that the spectrum is open to many simultaneous uses and thus prone to interference leading to link degradation and even blocking. Such disadvantages are particularly prevalent in outdoor applications, where interference from uncontrolled sources can travel long distances, substantially unimpeded.
Accordingly, a need exists in the art for systems and methods providing for utilization of spectrum suitable for reliable and/or large scale wireless access. Particularly, a need exists in the art for systems and methods which mitigate interference with respect to wireless communication links, such as those operable in unlicensed bands.
BRIEF SUMMARY OF THE INVENTION
The present invention is directed to systems and methods which provide interference mitigation by making alternative resources available within areas served by wireless communication links. Embodiments of the invention provide multiple channel availability in establishing wireless communication links to facilitate interference mitigation. For example, systems of the present invention may use time synchronous transmissions and scheduling to allow all or a plurality of available channels to be used throughout a service area and/or the network, thereby eliminate the need for cellular frequency planning according to some embodiments. Accordingly, communication between nodes can be carried out over multiple channels and/or dynamically selected channels to provide for channel diversity. Channel diversity according to preferred embodiments provides strong immunity to interference providing desired levels of quality of service (QoS) and enables utilization of spectrum suitable for reliable and/or large scale wireless access. Embodiments of the present invention are well suited for providing the aforementioned advantages with respect to the use of unlicensed spectrum in providing wireless communication links, and particularly in providing wireless broadband access using unlicensed spectrum.
Preferred embodiments of the present invention implement time domain techniques (such as may include transmission scheduling, high rank modulation, and coding), spatial processing techniques (such as may include grouping nodes by spatial attributes), as well as frequency domain techniques for spectrum management. Implementation of embodiments of